Fumagillin blocks blood vessel formation (angiogenesis) by inhibiting the enzyme methionine aminopeptidase 2. This prevents angiogenesis by arresting endothelial cells in the G1 phase of the cell cycle. Inhibition of angiogenesis can suppress tumor growth and metastasis. Methionine aminopeptidase 2 inhibition also blocks Wnt signaling, which plays a critical role in development, cell differentiation, and tumorigenesis. (A3059, A3060)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. (A2976)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. (A2976)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. (A2976)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. (A2976)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. (A2976)
The neurological effects of Lolitrem B are a result of its ability to inhibit large conductance calcium-activated potassium channels (BK channels). Lolitrem B binds to the alpha subunit of the BK channel, inhibiting channel potassium currents. This causes tremorgenic effects either by directly affecting channels in the muscle or by acting on channels in the central nervous system. (A3066, A3067)
Luteoskyrin is hepatotoxic. It is thought that this is a result of its metabolic reduction to the semiquinone radical catalyzed by NADPH-dependent cytochrome reductases in the liver, leading to the generation of active oxygen species in redox systems. This causes the induction of lipid peroxidation, hepatocellular membrane damage, and elevation of serum transaminase activities, resultin in liver injuries. Luteoskyrin is also hepatocarcinogenic, possibly a result of its ability to induce DNA fragmentation. It is able to bind to DNA, forming chelate-complexes with nucleic acids and select metal ions. Luteoskyrin inhibits the replication, transcription and repair of DNA, which is at least partially because it inhibits RNA polymerase and ribonuclease H. (A2955, A3042, A3070, A3071, A3072)
Kojic acid acts as a competitive and reversible inhibitor of animal and plant polyphenol oxidases (tyrosinases), xanthine oxidase, and D- and some L-amino acid oxidases. Inhibition of tyrosinases prevents melanosis, while inhibition of the oxidases prevents metabolism of certain amino acids. Kojic acid also reversibly affects thyroid function by inhibiting iodine uptake, leading to decreases in thyroid hormones T3 and T4 and increases in thyroid-stimulating hormone (TSH). Increased TSH from pituitary gland in turn stimulates thyroid hyperplasia. (A3073, A3074)
Moniliformin reversibly inhibits the enzymes pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase by competing for the binding site of pyruvate. This interferes with the tricarboxylic acid cycle by preventing the necessary incorporation of pyruvate and oxidation of the alpha-ketoglutarate intermediate. Moniliformin has also been shown to interfere with carbohydrate metabolism by inhibiting transketolase and aldose reductase. 

Moniliformin causes the necrosis of human chondrocytes in cartilage. It does so by increasing the expression of matrix catabolic enzymes, such as MMP-1 and MMP-13, and decreasing the syntheses of extracellular matrix components such as aggrecan and type II collage. This accelerates the catabolism of the extracellular matrix in articular cartilages, inducing a loss of cartilage function and eventually leading to cartilage degradation. Moniliformin is also known to cause DNA damage, inducing chromatid breaks, chromosome breaks, and chromatid exchanges. (A3075, A3076, A3077)
Secalonic acid D (SAD) is though to induce cleft palate by causing the formation of smaller palatal shelves that fail to elevate and fuse. This inhibited palatal shelf growth is a result of the of SAD causing reduced proliferation of embryonic palatal mesenchymal (HEPM) cells. SAD binds to and phosphorylates cAMP response element binding protein (CREB), an important transcription factor required for the expression of numerous genes including proliferating cell nuclear antigen (PCNA) gene. The phosphorylation of CREB by SAD prevents it from forming the necessary transcription factor-cAMP response element complex at transcription start sites, so these genes are not expressed. This leads to reduced palatal mesenchymal cell number causing reduced palatal shelf growth and thus cleft palate. (A3088, A3089, A3090)
Slaframine is a parasympathomimetic compound and causes increased secretion by salivary glands, pancreas, and other exocrine and endocrine glands. This is due to its activity as a cholingergic agonist. Slaframine has a high affinity for muscarinic receptors, especially in the gastrointestinal tract, and it stimulates these to produce its parasympathomimetic effects. Slaframine is also known to affect the concentration of circulating metabolic hormones, though the mechanism of this is unknown. (A3091, A3092)
Sporidesmin and its reduced (dithiol) form undergo cyclic reduction/autoxidation reactions with glutathione and other thiols, generating toxic superoxide radicals, hydrogen peroxide, and hydroxy radicals. It targets the liver, causing pericholangitis and the occlusion of bile ducts, which leads to the accumulation of bile constitutents in the bloodstream. In livestock, this results in a build up of phylloerythrin, a photodyamic metabolite produced by the microbial degradation of chlorophyll in the rumen. High plasma levels of phylloerythrin cause the animals to become sensitive to sunlight. (A3097, A3098)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. In addition, paspalitrem A inhibits presynaptic high-conductance Ca+2 activated maxi-K+ channels in the smooth muscle. (A2976, A2993)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. In addition, paspalitrem B inhibits presynaptic high-conductance Ca+2 activated maxi-K+ channels in the smooth muscle. (A2976, A2993)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. In addition, paspalicine inhibits presynaptic high-conductance Ca+2 activated maxi-K+ channels in the smooth muscle. (A2976, A2993)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. In addition, paxilline inhibits presynaptic high-conductance Ca+2 activated maxi-K+ channels in the smooth muscle. Paxilline is also genotoxic and causes DNA damage. (A2976, A2993, A3026)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. Verrucosidin is also genotoxic and causes DNA damage. (A2976, A3026)
Tremorgenic mycotoxins exert their toxic effects by interfering with neurotransmitter release, possibly by causing degeneration of nerve terminals. They are thought to inhibit gamma-aminobutyric acid (GABA) receptors, both pre- and postsynaptic, as well as inhibit transmitter breakdown at the GABA-T receptors. This would initially increase neurotransmitter levels, potentiating the GABA-induced chloride current, then lead to decreased levels of neurotransmitter in the synapse. In addition, verruculogen inhibits presynaptic high-conductance Ca+2 activated maxi-K+ channels in the smooth muscle. Verruculogen is also genotoxic and causes DNA damage. (A2976, A2993, A3026)
Not known.
Acephate is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
The pharmacological activity of amitraz includes different mechanisms of action leading to toxic effects in humans as well as in animals. Many of these effects and most of the effects on humans are caused by its alpha-adrenergic agonist activity. Furthermore amitraz inhibits prostaglandin synthesis, interacts with the octopamine receptors of the central nervous system and inhibits monoamine oxidases. Animal studies revealed that damages due to amitraz poisoning can be recovered even after exposure to a potentially lethal dose. This could mean that amitraz' effects are reversible or at least are recoverable. When an amitraz poisoning is lethal, death results from respiratory depression. (Wikipedia)
Anilazine was found to be mutagenic.
Azamethiphos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Bensulide is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Chlorpyrifos-methyl is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Cinmethylin is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
AR binding was observed for clorophene, which were both associated with delays in sexual development and decrements in reproductive performance.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Dicrotophos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Difenzoquat metilsulfate is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Ethephon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Fenamiphos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Fenitrothion is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
'EP A does not have, at this time, available data to determine whether flufenpyr-ethyl has a common mechanism of toxicity with other substances.' (L2089)
Flusilazole has a dose-related inhibition of serum testosterone and estradiol concentrations in rats. This inhibition of testosterone and estradiol biosynthesis may disrupt the hypothalamus–pituitary–testis axis, resulting in overstimulation of the testicular endocrine tissues and increase the risk of Leydig-cell tumours.
Fosthiazate is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
2,2-bis(p-hydroxyphenyl)-1,1, 1-trichloroethane (HPTE), acts as an estrogen analogue. HPTE is an estrogen receptor alpha agonist, and also acts as an antagonist at the estrogen receptor beta and androgen receptor. HPTE specifically inhibits the P450 cholesterol side-chain cleavage enzyme (P450scc, CYP11A1) resulting in decreased androgen production testicular Leydig cells along with decreased progesterone production by ovarian cells (A7861).  HPTE directly inhibit human CYP17A1 activity (17α-hydroxylase/17,20-lyase). The IC50 value of HPTE is 1.13±0.10 uM.  The observed changed in EEG patterns as well as tremors, convulsion and seizures with acute methoxychlor/HPTE exposure may be due to the inhibition of key sodium/potassium and calcium channels by HPTE.
It is thought that indoxacarb's aromatic metabolites biotransform to active intermediates that produce methemoglobin (A15207). The mechanism of indoxacarb-induced renal injury and metabolic acidosis in humans remains unclear. (A15207) It has been suggested that acute kidney injury results from indoxacarb-induced circulatory shock (A15206). Rhabdomyolysis may have been induced by methemoglobinemia (A15206).
Malathion is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
(±)-Methamidophos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Methidathion is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Mevinphos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
(E)-Monocrotophos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Niclosamide works by killing tapeworms on contact. Adult worms (but not ova) are rapidly killed, presumably due to uncoupling of oxidative phosphorylation or stimulation of ATPase activity. The killed worms are then passed in the stool or sometimes destroyed in the intestine. Niclosamide may work as a molluscicide by binding to and damaging DNA.
'Oxadiazon is a member of the oxadiazole class of herbicides. While current data are limited, EPA has evidence that compounds within a class may share a common mechanism of toxicity. At this time, the Agency does not have sufficient data concerning common mechanism issues to determine whether or not oxadiazon shares a common mechanism of toxicity with other substances, including other oxadiazoles or other probable human carcinogens.' (L2081)
2-Phenoxyethanol is a glycol ether. Glycol ethers can produce toxicity following oxidation to the corresponding aldehyde and alkoxyacetic acid by alcohol dehydrogenase (ADH; EC 1.1.1.1) and aldehyde dehydrogenase (ALDH; EC 1.2.1.3), respectively. (A15201) 2-Phenoxyethanol causes reduction of NMDA-induced membrane currents, indicating a neurotoxic potential for 2-phenoxyethanol. (A15202)
Phosalone is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Prochloraz acts in vitro as a an aromatase inhibitor, aryl hydrocarbon receptor agonist, androgen receptor antagonist, and estrogen receptor antagonist. (A15203)
Propetamphos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Propiconazole can decrease cholesterol levels that may cause polyploidy and disruption of mitotic cell cycling. It down-regulates the PTEN pathway and up-regulates the WNT-beta-catenin signaling pathway, that would stimulate cell proliferation and may lead to the tumorigenic outcome. (A15329)
Tebupirimfos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
The precise mode of action of thiabendazole on the parasite is unknown, but it most likely inhibits the helminth-specific enzyme fumarate reductase.
Tralkoxydim is structurally a cyclohexanedione, but because it does not appear to produce a toxic metabolite produced by other substances, the EPA has not assumed that tralkoxydim has a common mechanism of toxicity with other substances (L2079).
Trichlorfon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
At in-use concentrations, triclosan acts as a biocide, with multiple cytoplasmic and membrane targets. At lower concentrations, however, triclosan appears bacteriostatic and is seen to target bacteria mainly by inhibiting fatty acid synthesis. Triclosan binds to bacterial enoyl-acyl carrier protein reductase enzyme (ENR), which is encoded by the gene FabI. This binding increases the enzyme's affinity for nicotinamide adenine dinucleotide (NAD+). This results in the formation of a stable ternary complex of ENR-NAD+-triclosan, which is unable to participate in fatty acid synthesis. Fatty acids are necessary for reproducing and building cell membranes. Humans do not have an ENR enzyme, and thus are not affected.
Vinclozolin and some of its metabolites have antiandrogenic activity. Vinclozolin's main toxic effects are related to its antiandrogenic activity. They compete with androgens for the androgen receptor, inhibit androgen receptor-DNA binding, and alter androgen-dependent gene expression.
Tetracyclines target the 28S small subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result tetracyclines are cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of most tetracyclines is the 12S rRNA molecule in the mitochondrial ribosome, which is analogous to the 16S rRNA in bacterial ribosomes.
Tetracyclines target the 28S small subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result tetracyclines are cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of most tetracyclines is the 12S rRNA molecule in the mitochondrial ribosome, which is analogous to the 16S rRNA in bacterial ribosomes.
Tetracyclines target the 28S small subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result tetracyclines are cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of most tetracyclines is the 12S rRNA molecule in the mitochondrial ribosome, which is analogous to the 16S rRNA in bacterial ribosomes.
Tetracyclines target the 28S small subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result tetracyclines are cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of most tetracyclines is the 12S rRNA molecule in the mitochondrial ribosome, which is analogous to the 16S rRNA in bacterial ribosomes.
Chloramphenicol targets the large 39S subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result chloramphenicol is cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of chloramphenicol is the 16S rRNA molecule in the mitochondrial ribosome, which is analogous to the 23S rRNA in bacterial ribosomes.
Tetracyclines target the 28S small subunit of the mitochondrial ribosome thereby deactivation mitochondrial protein synthesis. As a result tetracyclines are cytotoxic to the most metabolically active cells or tissues including the heart, liver, thymus and bone-marrow. (A7823).  The likely target of most tetracyclines is the 12S rRNA molecule in the mitochondrial ribosome, which is analogous to the 16S rRNA in bacterial ribosomes.
High levels of molybdenum can interfere with the body's uptake of copper, producing copper deficiency. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted in urine. Molybdenum dusts and fumes, which can be generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in the sinuses and later swallowed). (Wikipedia)
Diethylthiophosphate (DETP) induces DNA damage only in the hepatic cell lines, and this effect could be related to a secondary non-diffusible metabolite generated by the activity of P450 enzymes since P450 enzyme inhibitors also inhibited the induction of DNA damage in hepatic cells. This organophosphorous (OP) metabolite has shown some toxicity in human peripheral blood mononucleated cells (PBMC). DETP is a cytotoxic compound in human PBMC. A relationship between urinary levels of DETP and the number of sperm susceptible to chromatin alteration has been reported among rural agricultural workers. In addition, a correlation between the frequency of aneuploidy in sperm and the levels of DETP in urine was identified in a rural population exposed to OP pesticides, indicating that the potential for genotoxicity following OP exposure may depend on the type and quantity of specific metabolites produced, such as DETP. (A15411)
Tungsten oxide (or tungsten trioxide: WO3) is a chemical compound containing oxygen and the transition metal tungsten. Possible health impact of WO3 nanoparticles (NPs) upon introduction into the body is of great interest. Cytotoxicity, inflammation and increased oxidative stress through reactive oxygen species (ROS) formation are prominently discussed to be relevant factors regarding the safety of small particles down to the nano-range. It has been reported that different sizes and morphologies of NPs have the potential to influence the interaction with many kind of biomolecules, including proteins, enzymes and DNA. The liver was considered as a target site for nanotoxicity due to its accumulative properties after ingestion, inhalation or absorption. (L2144) Tungsten interferes with molybdenum and copper metabolism and is somewhat toxic to animal life. (Wikipedia)
Phthalates are synthetic industrial compounds capable of disrupting the endocrine system. The phthalates have been the most common chemical compounds with the ability to disrupt the endocrine system. Phthalates, when acting in a critical period of the development of genital tract, lead to disturbances in the androgen-signaling pathway. Fetal testicular dysgenesis syndrome, otherwise known as the ”phthalate syndrome” in rodents, is a consequence of reduced level of fetal testosterone, insulin-like growth factor-3 (IGF-3) and follicule stimulating hormone (FSH). A negative correlation between levels in breast milk and free testosterone of babies was observed, while there was a positive correlation between mono-ethyl phthalate (MEP) and mono-butyl (MBP) with sex hormone bingind globuline (SHBG) and mono-metyl phthalate (MMP) and MEP and MBP with the ratio of lutenzing hormone (LH) and free testosterone. Exposure to phthalates is significantly associated with the duration of pregnancy. According to some studies, the chemical structure of some phthalates and prostaglandin/thromboxane, interleukin-1 connects the phthalates with induction of intrauterine inflammatory processes as well as shortening of pregnancy. (A15412)
O-desmethylangolensin (ODMA) exerts androgen receptor antagonistic activity and agonistic activity towards estrogen receptor (ER)-α and ERβ. The structure of ODMA is somewhat similar to estrogen. (A15413)
1-Naphthol is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
S-Ethylisothiouronium diethylphosphate is a specific inhibitor of inducible NO synthase on hepatic NO production level. S-Ethylisothiouronium diethylphosphate affects systemic hemodynamic indices in the following way: the peripheral vascular resistance increases, the stroke volume and central blood volume increase, and the work of the left ventricle improves. (Wikipedia)
Thallium(I) compounds have a high aqueous solubility and are readily absorbed through the skin. Part of the reason for thallium's high toxicity is that, when present in aqueous solution as the univalent thallium(I) ion (Tl+), it exhibits some similarities with essential alkali metal cations, particularly potassium (due to similar atomic radii). It can thus enter the body via potassium uptake pathways. Other aspects of thallium's chemistry differ strongly from that of the alkali metals, such its high affinity for sulfur ligands. Thus this substitution disrupts many cellular processes (for instance, thallium may attack sulfur-containing proteins such as cysteine residues and ferredoxins). (Wikipedia) A 2013 study found evidence that the thallium(I)-induced liver toxicity is a result of the disruptive effect of this metal on the mitochondrial respiratory complexes (I, II, and IV), which are the obvious causes of metal-induced reactive oxygen species formation and ATP depletion. The latter two events, in turn, trigger cell death signaling via opening of mitochondrial permeability transition pore and cytochrome c expulsion. (A15464)
Benzophenone is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
2,5-Dimethylfuran plays a role in the mechanism for the neurotoxicity of hexane in humans. Together with hexane-2,5-dione and 4,5-dihydroxy-2-hexanone, it is one of the main metabolites of hexane. (Wikipedia)
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a substrate of UDP-glucuronyl transferase, leading to the formation of [4-(methylnitrosamino)-1-(3-pyridyl)but-1-yl]-b-O-D-glycopyranosiduronic acid. (A15414)
9-Hydroxyfluorene is a weak dopamine reuptake inhibitor. (Wikipedia)
The antitumor activity of Vincristine is thought to be due primarily to inhibition of mitosis at metaphase through its interaction with tubulin. Like other vinca alkaloids, Vincristine may also interfere with: 1) amino acid, cyclic AMP, and glutathione metabolism, 2) calmodulin-dependent Ca<sup>2+</sup>-transport ATPase activity, 3) cellular respiration, and 4) nucleic acid and lipid biosynthesis.
The antitumor activity of vinblastine is thought to be due primarily to inhibition of mitosis at metaphase through its interaction with tubulin. Vinblastine binds to the microtubular proteins of the mitotic spindle, leading to crystallization of the microtubule and mitotic arrest or cell death.
Ouabain inhibits the Na-K-ATPase membrane pump, resulting in an increase in intracellular sodium and calcium concentrations. Increased intracellular concentrations of calcium may promote activation of contractile proteins (e.g., actin, myosin). Ouabain also acts on the electrical activity of the heart, increasing the slope of phase 4 depolarization, shortening the action potential duration, and decreasing the maximal diastolic potential.
Paclitaxel interferes with the normal function of microtubule growth. Whereas drugs like colchicine cause the depolymerization of microtubules in vivo, paclitaxel arrests their function by having the opposite effect; it hyper-stabilizes their structure. This destroys the cell's ability to use its cytoskeleton in a flexible manner. Specifically, paclitaxel binds to the &beta; subunit of tubulin. Tubulin is the 'building block' of mictotubules, and the binding of paclitaxel locks these building blocks in place. The resulting microtubule/paclitaxel complex does not have the ability to disassemble. This adversely affects cell function because the shortening and lengthening of microtubules (termed dynamic instability) is necessary for their function as a transportation highway for the cell. Chromosomes, for example, rely upon this property of microtubules during mitosis. Further research has indicated that paclitaxel induces programmed cell death (apoptosis) in cancer cells by binding to an apoptosis stopping protein called Bcl-2 (B-cell leukemia 2) and thus arresting its function.
Colchicine inhibits microtubule assembly in various cells, including leukocytes, probably by binding to and interfering with polymerization of the microtubule subunit tubulin. Although some studies have found that this action probably does not contribute significantly to colchicine's antigout action, a recent in vitro study has shown that it may be at least partially involved.
Digitoxin inhibits the Na-K-ATPase membrane pump, resulting in an increase in intracellular sodium and calcium concentrations. Increased intracellular concentrations of calcium may promote activation of contractile proteins (e.g., actin, myosin). Digitoxin also acts on the electrical activity of the heart, increasing the slope of phase 4 depolarization, shortening the action potential duration, and decreasing the maximal diastolic potential.
Sanguinarine, at micromolar concentrations, imparts cell growth inhibitory response in human squamous carcinoma (A431) cells via an induction of apoptosis. This is while sanguinarine treatment did not result in apoptosis of the normal human epidermal keratinocytes at similar dose. Sanguinarine [0.1 (M-2 (M)] treatment to HaCaT cells was found to inhibit in a dose-dependent manner the cell proliferation and induce apoptosis, as measured by 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and ELISA, respectively. Sanguinarine treatment also resulted in a significant cleavage of poly(ADP-ribose) polymerase in HaCaT cells. Sanguinarine treatment to HaCaT cells resulted in a dose-dependent (a) increase in the level of Bax with a concomitant decrease in Bcl-2 levels and (b) increase in Bax/Bcl-2 ratio. Sanguinarine also resulted in significant increases in the proapoptotic members of Bcl-2 family proteins, i.e., Bak and Bid. This was accompanied by increase in (a) protein expression of cytochrome c and apoptotic protease-activating factor-1 and (b) activity and protein expression of caspase-3, caspase-7, caspase-8, and caspase-9. This indicates the involvement of mitochondrial pathway and Bcl-2 family proteins during sanguinarine-mediated apoptosis of immortalized keratinocytes. (A15415)
Neosaxitoxin (NSTX) blocks the extracellular portion, the outer vestibule, of some voltage gated sodium channels in a very powerful and reversible manner, without affection of other ion channels. NSTX and other site 1 blockers (i.e., tetrodotoxin and saxitoxin) have high affinity (very low dissociation constant) and high specificity for Nav channels ("Voltage gated", also called "voltage sensitive" and "voltage dependant" sodium channel also known as "VGSCs" or "Nav channel"). The action of NSTX produces minimal effect on cardiac Nav, where it exhibits about 20_60 fold lesser affinity than in Nav channels from rat skeletal muscle and rat brain. Toxins such as neosaxitoxin and tetrodotoxin have less affinity for most cardiac Nav channels than for most Nav channels in nerve tissue. Moreover, NSTX is so active on nerve Nav channel than is roughly a million-fold more potent than lidocaine. (Wikipedia)
Generally, hypoglycin is an amino acid and chemically related to lysine. It competitively binds to enzymes used in the catabolism of lysine and is the reason why it and its metabolitemethylene cyclopropyl acetic acid (MCPA) are toxic. The metabolite MCPA also is a potent inhibitor of acyl CoA dehydrogenase, preventing the metabolism of fatty acids. It has been shown that oxidation of leucine is inhibited by hypoglycin A. In contrast, oxidation of valine and isoleucine are not significantly inhibited by this compound. However, the specific step in the pathway of leucine metabolism that is inhibited by hypoglycin A has not been precisely identified. Hypoglycemia and depletion of glycogen were due to the decreased gluconeogenesis resulting from impairment of long chain fatty acid metabolism after injection of hypoglycin A. Hypoglycin A or its metabolite, methylenecyclopropylacetic acid, and also 4-pentenoic acid (4-PE) were shown to inhibit long-chain fatty acid oxidation; whereas oxidation of straight short chain fatty acids including butyrate, hexanoate, and octanoate was not inhibited. Hypolglycin A inhibits dehydrogenation of isovaleryl-CoA and alpha-methylbutyryl-CoA by liver slices in vitro, and that it induces isovaleric and alpha-methylbutyric acidemias in experimental animals in vivo. (PMID: 4636318; PMID:5276292)
Generally, hypoglycin is an amino acid and chemically related to lysine. It competitively binds to enzymes used in the catabolism of lysine and is the reason why it and its metabolitemethylene cyclopropyl acetic acid (MCPA) are toxic. The metabolite MCPA also is a potent inhibitor of acyl CoA dehydrogenase, preventing the metabolism of fatty acids.
Isocorydine induces G2/M phase arrest by increasing cyclin B1 and p-CDK1 expression levels, which was caused by decreasing the expression and inhibiting the activation of Cdc25C. The phosphorylation levels of Chk1 and Chk2 were increased after ICD treatment. Furthermore, G2/M arrest induced by ICD can be disrupted by Chk1 siRNA but not by Chk2 siRNA. In addition, isocorydine treatment led to a decrease in the percentage of CD133+ PLC/PRF/5 cells. Interestingly, isocorydine treatment dramatically decreased the tumorigenicity of SMMC-7721 and Huh7 cells. (A15211)
(S)-2-Propylpiperidine is a neurotoxin which disrupts the peripheral nervous system. It is toxic to humans and all classes of livestock; less than 0.2g is fatal to humans, with death caused by respiratory paralysis. Propylpiperidine has a nicotine-like action in first stimulating and then depressing autonomic ganglia, and a curare-like effect in paralysing the motor nerve endings to the skeletal muscles.
Okadaic acid (OA) dramatically increases both nerve growth factor (NGF) mRNA content (50-fold) and NGF secretion (100-fold) in astrocytes. Okadaic acid also activated NGF gene transcription, which was preceded by an induction of c-fos and c-jun gene transcription. The induction of NGF expression by okadaic acid appeared independent from protein kinase C activity because down-regulating protein kinase C activity failed to decrease the okadaic acid stimulation. Results indicate that okadaic acid profoundly stimulates NGF expression in astrocytes mainly by enhancing NGF mRNA stability and suggest important roles for phosphoprotein phosphatases in regulating NGF production. Instead of activating protein kinase C like the phorbol ester tumor promoters, OA specifically inhibits phosphoprotein phosphatases 1 and 2A leading to an increase in the phosphorylation state of many cellular proteins. Interestingly, OA treatment of fibroblasts mimicked the effects of IL-1 on protein phosphorylation, suggesting that one cellular action of IL-1 might be to inhibit phosphoprotein phosphatase activity. OA has also been found to increase NGF mRNA content in mixed glial-neuronal hippocampal cell cultures similar to IL-1. The toxic potency of this phycotoxin is highly associated with the presence of the free carboxylic acid. Therefore, the toxin forms where the carboxylic acid is acylated are less toxic. However, it is clear that enzymatic hydrolisis after consumption of contaminated shellfish can occur, therefore liberating the free acid. (PMID: 19925818; PMID: 7890729)
Dinophysistoxin 1 (DTX1) is the analogue of okadaic acid causing diarrheic shellfish poisoning (DSP) in humans shortly after the ingestion of contaminated seafood. DTX1 is able to disrupt the integrity of Caco-2 monolayer cells at concentrations above 50 nM. In addition, confocal microscopy imaging confirmed that the tight-junction protein, occludin, was affected by DTX1. Permeability assays revealed that only DTX1 was able to significantly cross the intestinal epithelium at concentrations above 100 nM. The mechanism of action of this group of toxins is mainly the potent inhibition of serine/threonine protein phosphatases 1 (PP1) and 2A (PP2A). DTX1-treated Caco-2 monolayers could damage tight-junctions among cells. Tight-junctions form the physical barrier to the diffusion of substances through the paracellular space.
Cyclochlorotine (CC) causes hepatic necrosis and has carcinogenic properties. The in vitro application of CC on myocytes induced disruption of myofibrils and large accumulations of actin, myosin, alpha-actinin, and vinculin at the cellular processes. This agent also induced the formation of islands of myosin and alpha-actinin aggregates. Actin filament bundles in fibroblasts were either unaffected or disrupted completely. CC damage was dose-dependently reversible. Acute administration of CC by intraperitoneal injection to rats caused degeneration and necrosis in hepatocytes revealing that the liver was a specific target. CC poisoning has shown to induce the formation of large accumulations of actin, myosin, _-actinin and vinculin at the cellular processes. It also induces the extensive formation of islands of myosin and _-actinin aggregates, scattered within the cytoplasm. The desmin distribution is changed from a loosely to a densely arranged filament network. Cytoplasmic microtubules remained normal and could not be distinguished from their usual pattern. Thus, the degree of CC influence on myofibrillar and cytoskeletal proteins seems to be in the order of actin, myosin/a-actinin/vinculin, desmin and tubulin. This order is proportional to the proximity of proteins to actomyosin of myofibrils. CC, in some as yet unknown manner, appeares to dismantle previously assembled myofibrils and to form aggregates of myofibrillar and cytoskeletal proteins. The accumulation of myoproteins, particularly actin, at the cellular peripheries was characteristic of CC treatment, but its mechanism remains to be clarified. Two different responses of fibroblasts were noted after CC treatment, i.e., actin filament bundles were either unaffected or were disrupted completely to result in the formation of actin islands. Also, cell damage caused by CC treatment is reversible. (A15416)
The gonyautoxin toxicity is caused by the reversibly binding to its receptor site on the voltage-gated sodium channel on excitable cells, thus blocking the influx of Na+ ions and preventing nerve and muscle cells from producing action potentials, therefore, blocking neuronal transmission, which results in a temporary paralysis of muscles. Gonyautoxin paralyzes the injected sphincter reducing anal tone, leaving the other muscles unaffected. The paretic effect lasts for more than one week. Its effect is dose-dependent and the binding to its receptor site is only regulated by affinity.(A3261)
The gonyautoxin toxicity is caused by the reversibly binding to its receptor site on the voltage-gated sodium channel on excitable cells, thus blocking the influx of Na+ ions and preventing nerve and muscle cells from producing action potentials, therefore, blocking neuronal transmission, which results in a temporary paralysis of muscles. Gonyautoxin paralyzes the injected sphincter reducing anal tone, leaving the other muscles unaffected. The paretic effect lasts for more than one week. Its effect is dose-dependent and the binding to its receptor site is only regulated by affinity.(A3261)
Domoic acid acts as a neurotoxin. It induces excitotoxicity by an integrative action on ionotropic glutamate receptors at both sides of the synapse for which it has high affinity, preferentially the KA subtype, coupled with an effect that prevents the channel from rapid desensitization. DOM crosses the placenta and can be detected in milk, opening the possibility of a risk for fetal and neonatal exposure.
Solanum glycoalkaloids can inhibit cholinesterase, disrupt cell membranes, and be teratogenic (cause birth defects). One study suggests that the toxic mechanism of solanine is caused by the chemical's interaction with mitochondrial membranes. Experiments show that solanine exposure opens the potassium channels of mitochondria, decreasing their membrane potential. This in turn leads to Ca2+ being transported from the mitochondria into the cytoplasm, and it is this increased concentration of Ca2+ in the cytoplasm that triggers cell damage and apoptosis. (Wikipedia)
Alpha-Chaconine has inhibitory effect on lung adenocarcinoma cell metastasis in vitro. Alpha-chaconine could inhibit phosphorylation of c-Jun N-terminal kinase (JNK) and Akt, whereas it did not affected phosphorylation of extracellular signal regulating kinase (ERK) and p38. In addition, alpha-chaconine significantly decreased the nuclear level of nuclear factor kappa B (NF-_B) and the binding ability of NF-_B. Therefore, alpha-chaconine inhibited A549 cell metastasis by a reduction of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) activities involving suppression of phosphoinositide 3-kinase/Akt/NF-_B (PI3K/Akt/NF-_B) signaling pathway. Alpha-chaconine has exhibited its antiproliferative and apoptotic effects on the growth of cancer cells originating from human skin, liver, prostate, breast, and colon. In addition to the cytotoxicity in various cancer cells, R-chaconine induces significant cytotoxicity in Chang, normal human liver cells. (A15417)
Gymnodimine exerts its toxic effects via binding to nicotinic acetylcholine receptors with picomolar affinities with no sign of apparent reversibility in short time frames. The toxicity of gymnodimine has been attributed, at least in part, to the imine functionality as its reduction leads to a non-toxic derivative. Gymnodimine and 13-desmethyl spirolide C bound to acetylcholine binding proteins. (A15418)
Debromoaplysiatoxin have the ability to evoke biological and biochemical responses in cells, and belong to the TPA (12-O-tetradecanoylphorbol 13-acetate) type tumor promoters. Debromoaplysiatoxin is a typical tumor promoter. Debromoaplysiatoxin inhibited the binding of [3H]PDBu or 125I-EGF to their cell receptors in MEM containing 2 mg/ml ovalbumin. Debromoaplysiatoxin also inhibited the binding of [3H]PDBu in MEM containing sera from eight mammalian species tested. (A15421)
Senecionine is classified as a pyrrolizidine alkaloid (PA). Unsaturated pyrrolizidine alkaloids are hepatotoxic, that is, damaging to the liver. PAs also cause hepatic veno-occlusive disease and liver cancer. PAs are tumorigenic. Disease associated with consumption of PAs is known as pyrrolizidine alkaloidosis. (Wikipedia) The pyrrolizidine alkaloid senecionine has been shown to produce an increase in cytosolic free Ca2+ concentration in isolated hepatocytes that correlated with an increase in cellular toxicity. The cytotoxicity was greater in the absence of extracellular Ca2+ than in its presence, suggesting that alterations in intracellular Ca2+ distribution, and not an influx of extracellular Ca2+, were responsible for the senecionine-induced hepatotoxicity. Senecionine has been shown to be hepatotoxic, genotoxic, and cytotoxic. Senecionine has been shown to produce peroxidation of membrane lipids in a dose-related manner in isolated rat hepatocytes. Alterations in intracellular Ca2+ concentration also were examined as a possible primary mechanism of cellular toxicity. (A15422) Substantial research has revealed that senecionine-induced hepatotoxicity is associated with lipid peroxidation, intracellular Ca2+ alteration, and intercellular glutathione depletion. (A15423)
Retronecine is classified as a pyrrolizidine alkaloid (PA). Unsaturated pyrrolizidine alkaloids are hepatotoxic, that is, damaging to the liver. PAs also cause hepatic veno-occlusive disease and liver cancer. PAs are tumorigenic. Disease associated with consumption of PAs is known as pyrrolizidine alkaloidosis. (Wikipedia)
Veratridine is a steroid-derived alkaloid from plants in the Liliaceae family that functions as a neurotoxin by abolishing inactivation of sodium ion channels. It binds to intramembrane receptor site 2 and increases intracellular Ca2+ concentration. It acts by preferentially binding to activated Na+ channels causing persistent activation that leads to increased nerve excitability. (Wikipedia) The activation of the action potential Na+ ionophore by veratridine is time- and concentrationdependent and completely reversible. (A15424)
Ranunculin (RAN) inhibited the incorporation of 3H-labeled precursors into DNA and RNA of L1210 cells. RAN (15 mumol/L) markedly decreased DNA synthesis catalyzed by DNA polymerase I and promoted the generation of superoxide anions in DMSO/KO2 system. In the meantime, SOD and CAT were shown to partly revoke the inhibitory effects of RAN upon the incorporation of 3H-TdR into DNA. The cytotoxicity of RAN in vitro may be due to inhibition of DNA polymerase and increase of oxygen free radicals. (A15425)
Lycorine is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Mesaconitine (MA) is one of the Aconitum sp. alkaloids. The primary toxicity of Aconitum sp. alkaloids is on the heart and the central nervous system. They can induce cardiac flutter or fibrillation, ventricular arrhythmias, and repetitive after-potentials and oscillations following nerve stimulation. The electrophysiological mechanism of the arrhythmogenic effect of aconitine is a delay in the final repolarization phase of the action potential, which initiates premature or triggered excitations. These are due to a removal of inactivation of voltage-dependent Na+ channels. Due to the massive influx of Na+, the excitation is followed by complete inexcitability of nerve cells. Aconitum sp. alkaloids evoke dopamine release from dopaminergic neurons; then excessive extracellular dopamine creates stresses on cellular antioxidant systems and induces neuron apoptosis. They are known cardiotoxins and neurotoxins, and also have embryotoxicity and cytotoxicity. (A15426) Mesaconitine activates inhibitory noradrenergic neurones of descending inhibitory pathways. Mesaconitine is capable of evoking a long-lasting excitatory action at a low concentration, a depressant action at high concentrations and biphasic effects in an intermediate concentration range, probably via the involvement of the noradrenergic system. The biphasic effect observed during application of 30 and 100 nM mesaconitine is similar to the action of noradrenaline in the rat hippocampal CA1 region. The fact that the two different kinds of actions evoked by 30 and 100 nM mesaconitine in a biphasic manner are selectively prevented by pretreatment with a- and b-adrenoceptor antagonists provides evidence that the effects involve activation of a- and b-receptors. (A15427)
Ryanodine has extremely high affinity to the open-form ryanodine receptor, a group of calcium channels found in skeletal muscle, smooth muscle, and heart muscle cells. It binds with such high affinity to the receptor that it was used as a label for the first purification of that class of ion channels and gave its name to it. At nanomolar concentrations, ryanodine locks the receptor in a half-open state, whereas it fully closes them at micromolarconcentration. The effect of the nanomolar-level binding is that ryanodine causes release of calcium from calcium stores as thesarcoplasmic reticulum in the cytoplasm, leading to massive muscular contractions. (Wikipedia)
Convallatoxin (CNT) is classified as a cardiac glycoside. Cardiac glycosides are well known Na+/K+-ATPase inhibitors, and some of them are used to treat congestive heart failure and atrial arrhythmias. Recent studies have reported that cardiac glycosides have potential as anticancer agents. CNT exerts cytotoxic effects on a number of cancer and normal cell lines and induces apoptosis by increasing caspase-3 and poly ADP ribose polymerase (PARP) cleavage. Moreover, dose- and time-dependent autophagic activity was detected in CNT-treated cells, and mammalian target of rapamycin (mTOR)/p70S6K signal pathway inhibition was observed. Notably, CNT inhibits human umbilical vein endothelial cell (HUVEC) growth and exerts anti-angiogenic activity in vitro and in vivo. (A15340)
It has been prpoposed that surarine speeds up destruction of chemical transmitter, and raises the threshold point at which excess of the transmitter is able to exert its depressant power. (A15428)
Gelsemine has convulsant effects with a similar mechanism of action to strychnine. Strychnine is a neurotoxin which acts as an antagonist of glycine and acetylcholine receptors. It primarily affects the motor nerves in the spinal cord which control muscle contraction. An impulse is triggered at one end of a nerve by the binding of neurotransmitters to the receptors. In the presence of a neuroinhibitor, such as glycine, a greater quantity of excitatory neurotransmitters must bind to receptors before there will be an action potential generated. Glycine acts primarily as an agonist of the glycine receptor, which is a ligand-gated chloride channel in neurons located in the spinal cord and in the brain. This chloride channel will allow the negatively charged chloride ions into the neuron, causing a hyperpolarization which pushes the membrane potential further from threshold. Strychnine is an antagonist of glycine, which means it binds to the same receptor, preventing the inhibitory effects of glycine on the postsynaptic neuron. Therefore, action potentials are triggered with lower levels of excitatory neurotransmitters. When the inhibitory signals are prevented, the motor neurons do will be more easliy activated and the victim will have spastic muscle contractions. Structure of strychnine in complex with ACh binding protein (AChBP). Strychnine is also an antagonist for acetylcholine receptors, which is known to be homologous to the glycine receptor. (Wikipedia)
The action of bicuculline is primarily on the ionotropic GABAA receptors, which are ligand-gated ion channels concerned chiefly with the passing of chloride ions across the cell membrane, thus promoting an inhibitory influence on the target neuron. These receptors are the major targets for benzodiazepines and related anxiolytic drugs. The half-maximal inhibitory concentration (IC50) of bicuculline on GABAA receptors is 3 μM. In addition to being a potent GABAA receptor antagonist, bicuculline can be used to block Ca2+-activated potassium channels. Sensitivity to bicuculline is defined by IUPHAR as a major criterion in the definition of GABAA receptors.
Coriamyrtin has inhibitory activity when modulating receptors of the central nervous system. In other words, coriamyrtin, as a picrotoxin-like sesquiterpene lactones found in Anamirta paniculata and A. cocculus, has a mode of anticonvulsive action as potent transmission inhibitors in the central nervous system. The presence of a hydroxyl group at C-6 could have a significant affinity for a γ-aminobutyric acid (GABA) effector chloride channel, an antagonist to the effects observed on γ-aminobutyric acid but not on alanine or taurine. These experiments were tested on primary afferent terminals and for the antagonism of presynaptic inhibition. Picrotoxin is a known antagonist of GABA-R in all its protein isoforms and R-Gly in the homomeric form. (A15430)
Lasiocarpine is toxic to liver cells but not to lung cells, which is unable to metabolize the pyrrolizidine alkaloids to pyrroles. The application of lasiocarpine to human liver cells in culture is followed by inhibition of DNA, RNA and protein synthesis; vacuolation of the cells, the prevention of mitosis and the formation of giant cells (“megalocytes”). (A15431) Effects on the liver include hemorrhagic necrosis of parenchymal cells, marked enlargement of parenchymal cells and of their nuclei and nucleoli, fibrosis or cirrhosis, depression of cell division, and possibly neoplasia. (A15432) The inducibility of tryptophan pyrrolase activity by hydrocortisone, in the livers of rats treated chronically with lasiocarpine is an indication that translational mechanisms are intact. However, the increased uptake of 3H-thymidine by megalocytes, in the absence of observable mitotic activity, suggests that these cells are in the process of hypertrophy. They may act as prolonged, potent inhibitors of mitosis in hepatocytes, they are mutagenic in Drosophila and cause chromosome breakage in leukocytes. One of the unusual results of chronic poisoning by lasiocarpine and other members of the pyrrolizidine alkaloids is progressive enlargement of liver cells to up to three times the normal diameter, with an accompanying proportionate increase in nuclear diameter. The term megalocytosis has been applied to this abnormality which may be associated with mild fibrosis of central veins and proliferation of bile ducts. The prominence of rough ER in enlarged hepatocytes is s a sign of increased metabolic activity. (A15433)
Dictamnine has been shown to be phototoxic to human cell lines (namely Jurkat T cells and HaCaT keratinocytes). Although it is less phototoxic than the structurally related furocoumarins 5-methoxypsoralen and 8-methoxypsoralen, "it may play a major role in the elicitation of phytophotodermatitis because of its abundance in plants of the Rutaceae family." (A15434)
The nervous system is the main target organ by the toxicity of matrine. Morphological observation revealed degenerative changes of the nerve cells in the brain tissue of the mice. (A15436) Matrine has a variety of pharmacological effects, including anti-cancer effects, and action as a kappa opioid receptor and µ-receptor agonist. Matrine possesses strong antitumor activities in vitro and in vivo. Inhibition of cell proliferation and induction of apoptosis are the likely mechanisms responsible for matrine's antitumor activities. (Wikipedia)
Cyclopamine causes usually fatal birth defects. It can prevent the fetal brain from dividing into two lobes (holoprosencephaly) and cause the development of a single eye (cyclopia). It does so by inhibiting the hedgehog pathway (Hh). Cyclopamine inhibits the Hh by influencing the balance between the active and inactive forms of the smoothened protein. Cyclopamine is useful in studying the role of Hh in normal development, and as a potential treatment for certain cancers in which Hh is overexpressed. Cyclopamine acts as a primary inhibitor of the hedgehog signaling pathway in cells. This pathway named for the ligand for the signal protein, is used by cells to help them react to external chemical signals. The pathway carries out important functions in embryonic development and when it goes awry, deformities can occur. However, errant activation of the pathway can also trigger cancer in adult humans, leading to basal cell carcinoma, medulloblastoma, rhabdomyosarcoma, and prostate, pancreatic and breast cancers. A way of controlling the pathway using cyclopamine could turn this problem on its head and provide a way to treat cancer. (Wikipedia) Cyclopamine inhibits the Hh pathway by binding to and preventing the activation of Smoothened (Smo), preventing downstream target gene regulation. (A15437)
Jervine's biological activity is mediated via its interaction with the 7 pass trans membrane protein smoothened. Jervine binds with and inhibits smoothened, which is an integral part of the hedgehog signaling pathways. With smoothened inhibited, the GLI1 transcription cannot be activated and hedgehog target genes cannot be transcribed. (Wikipedia) It is now known that the teratogenic effects of jervine and cyclopamine are due to their specific inhibition of vertebrate cellular responses to the Hedgehog (Hh) family of secreted growth factors. (A15438) In cultures with cyclopamine, jervine, or blocking antibody, fungiform papilla numbers doubled on the dorsal tongue with a distribution that essentially eliminated inter-papilla regions, compared with tongues in standard medium or solanidine. (A15439)
Veratramine produces a characteristic excitatory action on the central nervous system, producing both tremor and a characteristic "struggling" behavior. This behavioral excitation is accompanied by changes in serotonin content in hypothalamus. The central serotonin agonist methysergide in doses of 5--15 mg per kg produces a dose-dependent inhibition of veratramine's action, while parachlorophenylalanine has no effect. (A15440)
Chelerythrine is a potent, selective, and cell-permeable protein kinase C (PKC) inhibitor. It is also the major active natural product found in the plant Zanthoxylum clava-herculis, exhibiting anti-bacterial activity against Staphylococcus aureus. (Wikipedia) Chelerythrine is a selective inhibitor of group A and B PKC isoforms with an antitumor activity. Inhibition of PKC with chelerythrine chloride induces apoptosis by activation of a neutral sphingomyelinase, accumulation of ceramide, and depletion of sphingomyelin. Chelerythrine is at least 100-fold more selective for PKCs than for other kinases. Chelerythrine competes for the conserved catalytic sites of PKC and seems to be a potent and specific inhibitor of the group A and group B kinases. Chelerythrine exhibited cytotoxic activity against nine human tumor cell lines tested in vitro. Radioresistant and chemoresistant squamous cell carcinoma lines (HNSCC) undergo apoptosis rapidly after treatment with chelerythrine in vitro. Chelerythrine treatment of nude mice bearing SQ-20B HNSCC cells is associated with significant tumor growth delay. Also, treatment with chelerythrine resulted in minimal toxicity. (A15441)
Lyngbyatoxin A is a tumor promoter. Lyngbyatoxin A and related compounds bind to the cysteine-rich C1 domains (C1A and C1B) of protein kinase C (PKC) isozymes to activate them, possibly leading to tumor formation (A15358). In cancer cells, PKC isozymes are involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and anticancer drug resistance through their increased or decreased participation in various cellular signaling pathways (L2138). Lyngbyatoxin A also induces ornithine decarboxylase (A3219). The ornithine decarboxylation reaction catalyzed by ornithine decarboxylase (ODC) is the first and committed step in the synthesis of polyamines, particularly putrescine, spermidine and spermine. ODC is upregulated in a wide variety of cancers. The mechanism by which ODC promotes carcinogenesis is complex and not entirely known. Along with their direct effect on DNA stability, polyamines also upregulate gap junction genes and downregulate tight junction genes. Gap junction genes are involved in communication between carcinogenic cells and tight junction genes act as tumor suppressors. (Wikipedia)
Dicentrine was found to be a potent alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of noradrenaline- (pA2 = 8.19 +/- 0.09) or phenylephrine (pA2 = 9.01 +/- 0.10)-induced vasoconstriction. These effects still persisted in denuded aorta. Dicentrine inhibited platelet aggregation and release reaction through the suppression of thromboxane formation and elevation of adenosine 3': S'-cyclic monophosphate. (A15323) d-Dicentrine significantly inhibits the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. (A15341) Dicentrine is also a selective α1-adrenoceptor antagonist with potent antiarrhythmic and antihypertensive activities. (A15324)
Nantenine is an antagonist at both the α1 adrenergic receptor and the 5-HT2A serotonin receptor, and blocks both the behavioural and physiological effects of MDMA in animals (Wikipedia). Nantenine is reported to have 5-HT2A antagonist properties (A15342).
The carcinogenic and mutagenic effects associated with the binding of metabolites of ingested aristolochic acid (AA) to DNA have been extensively described in vitro and in vivo, resulting in the classification of AA as a genotoxic carcinogen. AA-derived DNA adducts in renal cortical and urothelial tumor tissue of patients with documented BEN, associated with the dominance of the A:T to T:A transversions in the p53 tumor suppressor gene mutational spectrum. (A15444) AA is a nephrotoxic and carcinogenic compound, which has been demonstrated to be genotoxic and mutagenic both in vitro and in vivo. Toxicity and carcinogenicity of the nephrotoxic compound aristolochic acid between rodents and humans suggest a species-dependent mechanism of action. AA had a comparable effect on the cell cycle in primary human and porcine cells and the rat NRK-52E cell line following 48 h exposure, also corroborated by the reduced 3H-thymidine incorporation in NRK-52E cells. In addition, DNA unwinding, suggestive of enhanced DNA damage, was observed in primary porcine cells. (A15445)
Anatoxin-a is an agonist of both neuronal α4β2 and α4 nicotinic acetylcholine receptors present in the CNS as well as the α12βγδ muscle-type nAchRs that are present at the neuromuscular junction. Anatoxin-a has an affinity for these receptors that is about 20 times greater than that of acetylcholine. Anatoxin-a also shows much less potency in the CNS than in neuromuscular junctions. In hippocampal and brain stem neurons, a 5 to 10 times greater concentration of anatoxin-a was necessary to activate nAchRs than what was required in the PNS. Anatoxin-a binding is irreversible, and the anatoxin-a nAchR complex cannot be broken down by acetylcholinesterase. Thus, the nAchR is temporarily locked open and after a period of time becomes desensitized. In this desensitized state the nAchRs no longer let cations pass through, which ultimately leads to a blockage of neuromuscular transmission.
Brevetoxins are neurotoxins that bind to voltage-gated sodium channels in nerve cells, leading to disruption of normal neurological processes and causing the illness clinically described as neurotoxic shellfish poisoning (NSP). Brevetoxins bind to site 5 on the alpha-subunit of voltage sensitive sodium channels (VSSCs), which serve as key proteins in the structure of the cell membrane. Pulmonary receptors associated with ligand-gated epithelial Na+ channels and cathepsin inhibition in macrophages have been reported to be effected by brevetoxin exposure. (Wikipedia)
Anatoxin-a(s) is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Uremic toxins such as dimethylamine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869)
Uremic toxins such as guanidinoacetic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869)
Hypoxanthine is a poorly soluble compound.  As a result high concentrations of serum hypoxanthine can lead to the formation of kidney stones which can, over the long term, induce kidney failure.
Uremic toxins such as methylamine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869)
Uremic toxins such as indole-3-acetic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869)
Uremic toxins such as phenylacetic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869)
Uremic toxins such as noradrenalin are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869). Norepinephrine functions as a peripheral vasoconstrictor by acting on alpha-adrenergic receptors. It is also an inotropic stimulator of the heart and dilator of coronary arteries as a result of it's activity at the beta-adrenergic receptors.
Uremic toxins such as indican are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as Indoxyl sulfate are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as hippuric acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as kynurenic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as neopterin are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as trimethylamine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as TMAO are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (5). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO. KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (6). TMAO appears to contribute to the development of atherosclerosis in part by promoting cholesterol accumulation within macrophages, perhaps by inducing scavenger receptors such as CD36 and SRA1, both of which are involved in the uptake of modified lipoproteins (A15344).
Uremic toxins such as anthranilic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as spermine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869). 
Spermine is derived from spermidine by spermine synthase. Spermine is a polyamine, a small organic cations that is absolutely required for eukaryotic cell growth. Spermine, is normally found in millimolar concentrations in the nucleus. Spermine functions directly as a free radical scavenger, and forms a variety of adducts that prevent oxidative damage to DNA. Oxidative damage to DNA by reactive oxygen species is a continual problem that cells must guard against to survive. Hence, spermine is a major natural intracellular compound capable of protecting DNA from free radical attack. Spermine is also implicated in the regulation of gene expression, the stabilization of chromatin, and the prevention of endonuclease-mediated DNA fragmentation.
Uremic toxins such as spermidine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as nicotinamide are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as putrescine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as methylguanidine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as asymmetric dimethylarginine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as guaniidine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as arginic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as guanidinosuccinic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 8-Hydroxy-2Х-deoxyguanosine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as symmetric dimethylarginine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as pentosidine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as N-methyl-2-pyridone-5-carboxamide are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as N-methyl-4-pyridone-3-carboxamide are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 4-Hydroxynonenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as hexanal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as malondialdehyde are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as decanal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as p-Cresol sulfate are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as ethylamine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 2-Octenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 2-Nonenall are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as heptanal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 2-Hexenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 2-Heptenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 4-Decenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as nonanal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 4-Hydroxydecenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 4-Hydroxyhexenall are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 4-Hydroxyoctenal are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as alpha-keto-delta-guanidinoacetic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as 3-Carboxy-4-methyl-5-propyl-2-furan-propanoic acid are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as carboxymethyllysine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as dihydroxyphenylalanine are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Uremic toxins such as indoxyl-beta-D-glucuronide are actively transported into the kidneys via organic ion transporters (especially OAT3). Increased levels of uremic toxins can stimulate the production of reactive oxygen species. This seems to be mediated by the direct binding or inhibition by uremic toxins of the enzyme NADPH oxidase (especially NOX4 which is abundant in the kidneys and heart) (A7868). Reactive oxygen species can induce several different DNA methyltransferases (DNMTs) which are involved in the silencing of a protein known as KLOTHO.  KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. A number of studies have indicated that KLOTHO mRNA and protein levels are reduced during acute or chronic kidney diseases in response to high local levels of reactive oxygen species (A7869).
Carbamic acid is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Alkylating agents work by three different mechanisms: 1) attachment of alkyl groups to DNA bases, resulting in the DNA being fragmented by repair enzymes in their attempts to replace the alkylated bases, preventing DNA synthesis and RNA transcription from the affected DNA, 2) DNA damage via the formation of cross-links (bonds between atoms in the DNA) which prevents DNA from being separated for synthesis or transcription, and 3) the induction of mispairing of the nucleotides leading to mutations. Mechlorethamine is cell cycle phase-nonspecific.
Ethylene oxide is an alkylating agent. The addition of alkyl groups to proteins, DNA, and RNA by binding to the sulfhydryl and hydroxyl, amino, and carboxyl groups, prevents normal cellular metabolism and ultimately kills cells.  It is likely that the carcinogenicity of ethylene oxide in laboratory animals arises primarily as a result of its direct alkylation of DNA and RNA. In vivo exposure to ethylene oxide induced mutations (5- to 5.6-fold) at the Hprt locus in splenic T-lymphocytes in rats and mice.
Treatment of AS52 cells with N-OH-2,6-dimethylaniline (2,6-DMA) and 2,6-DMAP led to intracellular production of reactive oxygen species (ROS). DNA strand breaks were observed in a dose-dependent manner in AS52 cells when treated with each of the N-OH-2,6-DMA and 2,6-DMAP. Comparative evaluation of the results indicates that the principal mechanism of mutagenic action is likely to be through redox cycling of intracellularly bound aminophenol/quinone imine structures to generate ROS rather than through formation of covalent DNA adducts. These considerations do not rule out DNA adduct formation by monocyclic nitrenium ions because it has been established that the free nitrenium ion derived from 2,6-DMA can form under aqueous conditions. (A15447)
Aplysiatoxin is a 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoter that activates protein kinase C (PKC) (A15358). In cancer cells, PKC isozymes are involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and anticancer drug resistance through their increased or decreased participation in various cellular signaling pathways (L2138).
Androstenedione is converted to testosterone and estrogen, and when taken in sufficient quantities androstenedione can cause unwanted masculinizing and feminizing effects.  Androstenedione is considered an androgenic steroid precursor because testosterone is an androgen or male hormone. In males, conversion of androstenedione to testosterone requires the enzyme 17β-hydroxysteroid dehydrogenase. In females, conversion of androstenedione to estrogen (e.g., estrone and estradiol) requires the enzyme aromatase.
Although it predominantly functions as an endogenous precursor to more potent androgens such as testosterone and dihydroxytestosterone, DHEA (which is produced from DHEAS) has been found to possess some degree of androgenic activity in its own right, acting as a low affinity (Ki = 1 μM), weak partial agonist of the androgen receptor. DHEA has also been found to bind to and activate the ERα and ERβ estrogen receptors with Ki values of 1.1 μM and 0.5 μM, respectively. When taken in sufficient quantities DHEAS can cause masculinizing effects.  DHEAS is considered an androgenic steroid precursor because testosterone (its product) is an androgen or male hormone. In males and females, conversion of DHEAS to testosterone requires the enzyme 17β-hydroxysteroid dehydrogenase. Testosterone plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair. High levels of testosterone can lead to masculinization in females or premature puberty in young boys.  Chronically high levels in adults increase the incidence of heart attack, stroke and blood clots by lowering the level of HDL (good cholesterol). The development of breast tissue in males, a condition called gynecomastia (which is usually caused by high levels of circulating estradiol), arises because of increased conversion of testosterone to estradiol by the enzyme aromatase. Reduced sexual function and temporary infertility can also occur in males.
2-hydroxyglutarate is an oncometabolite. It is a competitive inhibitor of multiple α-ketoglutarate-dependent dioxygenases, including histone demethylases and the TET family of 5-methlycytosine (5mC) hydroxylases. As a result, high levels of 2-hydroxyglutarate lead to genome-wide histone and DNA methylation alterations, which in turn lead to mutations that ultimately cause cancer. L-2-hydroxyglutarate mediates its neurotoxicity through activation of N-methyl-D-aspartate receptors. L-2-hydroxyglutarate is structurally similar to the excitatory amino acid glutamate and stimulates neurodegeneration by mechanisms well-known for glutamate, NMDA or mitochondrial toxins (A15198).
2-hydroxyglutarate is an oncometabolite. It is a competitive inhibitor of multiple α-ketoglutarate-dependent dioxygenases, including histone demethylases and the TET family of 5-methlycytosine (5mC) hydroxylases. As a result, high levels of 2-hydroxyglutarate lead to genome-wide histone and DNA methylation alterations, which in turn lead to mutations that ultimately cause cancer.  High L-2-Hydroxyglutarate levels are associated with gliomas and acute myeloid leukemia. L-2-Hydroxyglutarate can reversibly promote leukemogenesis in vitro. D-2-hydroxyglutarate mediates its neurotoxicity through activation of N-methyl-D-aspartate receptors. D-2-hydroxyglutarate is structurally similar to the excitatory amino acid glutamate and stimulates neurodegeneration by mechanisms well-known for glutamate, NMDA or mitochondrial toxins (A15198).
Accumulation of L-lactic acid in the body has been shown to be toxic. At times of lactic acidosis, when excess intracellular lactate is released into the blood, maintenance of electroneutrality of the blood requires that a cation be released into the blood, as well. This can reduce blood pH. Lactate may exert a strong action over GABAergic networks in the developing brain, making them more inhibitory than it was previously assumed, acting either through better support of metabolites, or alterations in base intracellular pH levels, or both. (Wikipedia)
In the matrix of mitochondria, 2-oxoadipate is decarboxylated to glutaryl-CoA by the 2-oxoadipate dehydrogenase complex and then converted to acetyl-CoA. Accumulation of oxoadipic acid in the body has been shown to be toxic.
2-Hydroxyadipic acid is a hydroxy-dicarboxylic acid formed by the reduction of 2-ketoadipic acid. Deficiency of 2-ketoadipic dehydrogenase causes 2-ketoadipic acidemia, a condition characterized by accumulation and excretion of 2-hydroxyadipic acid (with 2-ketoadipic and 2-aminoadipic) probably without adverse phenotypic effects.
3-Hydroxyisovaleric acid is a normal human metabolite excreted in the urine. Elevated levels of this compound are found in several disorders due to impairment of renal reclamation of biotin. Levels may also be increased from prolonged consumption of raw egg-whites.
Accumulation of 3-methylglutaconic acid in the body has been shown to be toxic. 3-methylglutaconyl-CoA hydratase is involved in the metabolism process of 3-methylglutaconic acid. 3-Methylglutaconic acid accumulates in patients with a deficiency of this enzyme and a large amount of 3-methylglutaconic acid appear in urine. (Wikipedia).
GHB reaches much higher concentrations in the brain and activates GABAB receptors, which are primarily responsible for its sedative effects. GHB receptors are densely expressed in many areas of the brain, including the cortex and hippocampus, and these are the receptors that GHB displays the highest affinity for. There has been somewhat limited research into the GHB receptor; however, there is evidence that activation of the GHB receptor in some brain areas results in the release of glutamate, the principal excitatory neurotransmitter.
Activation of both the GHB receptor and GABA(B) is responsible for the addictive profile of GHB. GHB's effect on dopamine release is biphasic,[19] low concentrations stimulate dopamine release via the GHB receptor.[20] Higher concentrations inhibit dopamine release via GABA(B) receptors as do other GABA(B) agonists such as baclofen and phenibut.[21] After an initial phase of inhibition, dopamine release is then increased via the GHB receptor. This explains the paradoxical mix of sedative and stimulatory properties of GHB, as well as the so-called "rebound" effect, experienced by individuals using GHB as a sleeping agent, wherein they awake suddenly after several hours of GHB-induced deep sleep. That is to say that, over time, the concentration of GHB in the system decreases below the threshold for significant GABAB receptor activation and activates predominantly the GHB receptor, leading to wakefulness.
5-Oxoprolinuria develops in moderate to severe cases of glutathione synthetase deficiency. The deficiency in glutathione synthetase leads to the accumulation of γ-glutamylcysteine, which is converted into 5-oxoproline by the action of γ-glutamyl cyclotransferase. The excessive formation of 5-oxoproline exceeds the capacity of 5-oxoprolinase, leading to accumulation of 5-oxoproline in body fluids causing metabolic acidosis and 5-oxoprolinuria. 5-Oxoproline accumulation is thought to be the cause of metabolic acidosis in Hawkinsinuria. 5-Oxoprolinase deficiency also leads to decreased conversion of 5-oxoproline to glutamate, resulting in elevated levels of 5-oxoproline in body fluids. 5-Oxoprolinuria has also been described in patients with urea cycle defects, such as ornithine transcarbamoylase deficiency or homocystinuria. In nephropathic cystinosis 5-oxoprolinuria may occur because of secondary impairment of the γ-glutamyl cycle resulting from decreased availability of free cysteine and can be corrected through cysteamine therapy. Transient 5-oxoprolinuria of unknown cause has been reported in very preterm infants. Limited availability of glycine in malnutrition and pregnancy as well as increased turnover of collagen, fibrinogen and other proteins containing considerable amounts of 5-oxoproline in patients with severe burns or Stevens-Johnson syndrome may lead to 5-oxoprolinuria. In addition, certain drugs, such as paracetamol, vigabatrin or some antibiotics (flucloxacillin, netimicin), are known to induce 5-oxoprolinuria, probably through interaction with the γ-glutamyl cycle. Particular infant formulas and tomato juice may contain modified proteins with increased content of 5-oxoproline. (T527)
According to the presumed mechanism of action, photosensitization following application of aminolevulinic acid (ALA) topical solution occurs through the metabolic conversion of ALA to protoporphyrin IX (PpIX), which accumulates in the skin to which aminolevulinic acid has been applied. When exposed to light of appropriate wavelength and energy, the accumulated PpIX produces a photodynamic reaction, a cytotoxic process dependent upon the simultaneous presence of light and oxygen. The absorption of light results in an excited state of the porphyrin molecule, and subsequent spin transfer from PpIX to molecular oxygen generates singlet oxygen, which can further react to form superoxide and hydroxyl radicals. Photosensitization of actinic (solar) keratosis lesions using aminolevulinic acid, plus illumination with the BLU-UTM Blue Light Photodynamic Therapy Illuminator (BLU-U), is the basis for aminolevulinic acid photodynamic therapy (PDT).
Adenosine slows conduction time through the AV node and can interrupt the reentry pathways through the AV node, resulting in the restoration of normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with Wolff-Parkinson-White Syndrome. This effect may be mediated through the drug's activation of cell-surface A<sub>1</sub> and A<sub>2</sub> adenosine receptors. Adenosine also inhibits the slow inward calcium current and activation of adenylate cyclase in smooth muscle cells, thereby causing relaxation of vascular smooth muscle. By increasing blood flow in normal coronary arteries with little or no increase in stenotic arteries (with little to no increase in stenotic arteries), adenosine produces a relative difference in thallous (thallium) chloride TI 201 uptake in myocardium supplied by normal verus stenotic coronary arteries.
ATP is able to store and transport chemical energy within cells. ATP also plays an important role in the synthesis of nucleic acids. ATP can be produced by various cellular processes, most typically in mitochondria by oxidative phosphorylation under the catalytic influence of ATP synthase. The total quantity of ATP in the human body is about 0.1 mole. The energy used by human cells requires the hydrolysis of 200 to 300 moles of ATP daily. This means that each ATP molecule is recycled 2000 to 3000 times during a single day. ATP cannot be stored, hence its consumption must closely follow its synthesis.
Adenine forms adenosine, a nucleoside, when attached to ribose, and deoxyadenosine when attached to deoxyribose, and it forms adenosine triphosphate (ATP), a nucleotide, when three phosphate groups are added to adenosine. Adenosine triphosphate is used in cellular metabolism as one of the basic methods of transferring chemical energy between reactions. In older literature, adenine was sometimes called Vitamin B4Not Available
Testosterone is considered an anabolic steroid. It plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair. High levels of testosterone can lead to masculinization in females or premature puberty in young boys.  Chronically high levels in adults increase the incidence of heart attack, stroke and blood clots by lowering the level of HDL (good cholesterol) and increasing the level of LDL (bad cholesterol). Chronic high use of anabolic steroids (such as testosterone) appears to lead to cardiac myopathy and weakening the left ventricle. The development of breast tissue in males, a condition called gynecomastia (which is usually caused by high levels of circulating estradiol), arises because of increased conversion of testosterone to estradiol by the enzyme aromatase. Reduced sexual function and temporary infertility can also occur in males. 
The mechanism of testosterone’s action is as follows: Free testosterone is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5-alpha reductase. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of testosterone. Once bound, the ligand-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects.
18-Hydroxycorticosterone is a derivative of corticosterone. It serves as an intermediate in the synthesis of aldosterone by the enzyme aldosterone synthase in the zona glomerulosa. (Wikipedia) 18-Hydroxycorticosterone (18OHB) has low affinity for the mineralocorticoid receptor and mainly originates from the conversion of corticosterone by the aldosterone synthase, although small amounts may be produced by the 11β-hydroxylase. Serum concentrations of 18OHB increase with increased aldosterone synthesis due to sodium depletion and angiotensin II infusion. (A15449) Accumulation of 18-hydroxycorticosterone in a given organ has been shown to be toxic for the body.
Adrenoleukodystrophy (ALD) is caused by mutations in ABCD1, a gene located on the X chromosome that codes for ALD, a peroxisomal membrane transporter protein. The exact mechanism of the pathogenesis of the various forms of ALD is not known. Biochemically, individuals with ALD show very high levels of unbranched, saturated, very long chain fatty acids, particularly cerotic acid (26:0). The level of cerotic acid in plasma does not correlate with clinical presentation. (Wikipedia)
Extremely high levels of homogentisic acid are found in patients with the inborn error of metabolism (IEM) called Alkaptonuria. Homogentisic acid spontaneously undergoes oxidation into benzoquinone acetic acid (BQA), which polymerizes forming plasma soluble melanins (PSM).  The PSM darkens many tissues (ochronosis - as the tissue looks like ochre), and produces widespread degenerative changes in cartilage and other connective tissues, joints, blood vessels, heart valves and the kidneys.  Ochronotic tissue is stiff and unusually brittle. The accumulation of PSM in chondrocytes (the cells that form cartilage) leads to profound alterations in the levels of proteins involved in cell defense, protein folding, and cell organization. An increased post-translational oxidation of proteins, which also involved high molecular weight protein aggregates, has been found to be particularly evident in chondrocytes from patients with alkaptonuria.
In the muscles, a fraction of the total creatine binds to phosphate - forming creatine phosphate. The reaction is catalysed by creatine kinase, and the result is phosphocreatine (PCr). Phosphocreatine binds with adenosine diphosphate to convert it back to ATP (adenosine triphosphate), an important cellular energy source for short term ATP needs prior to oxidative phosphorylation.
Glutamate activates both ionotropic and metabotropic glutamate receptors. The ionotropic ones being non-NMDA (AMPA and kainate) and NMDA receptors. Free glutamic acid cannot cross the blood-brain barrier in appreciable quantities; instead it is converted into L-glutamine, which the brain uses for fuel and protein synthesis. It is conjectured that glutamate is involved in cognitive functions like learning and memory in the brain, though excessive amounts may cause neuronal damage associated in diseases like amyotrophic lateral sclerosis, lathyrism, and Alzheimer's disease. Also, the drug phencyclidine (more commonly known as PCP) antagonizes glutamate at the NMDA receptor, causing behavior reminiscent of schizophrenia. Glutamate in action is extremely difficult to study due to its transient nature.
5-Hydroxy-L-tryptophan is the immediate precursor of the neurotransmitter serotonin. An accumulation of 5-hydroxy-L-tryptophan in cerebrospinal fluid occurs in aromatic L-amino acid decarboxylase deficiency, accompanied by an increased excretion in the urine of the patients, which are indicative of the disorder. 5-Hydroxy-L-tryptophan easily crosses the blood-brain barrier and effectively increases central nervous system (CNS) synthesis of serotonin. Supplementation with 5-hydroxy-L-tryptophan is hypothesized to normalize serotonin synthesis, which is putatively related to its antidepressant properties.
Dopamine is a precursor to norepinephrine in noradrenergic nerves and is also a neurotransmitter in certain areas of the central nervous system. Dopamine produces positive chronotropic and inotropic effects on the myocardium, resulting in increased heart rate and cardiac contractility. This is accomplished directly by exerting an agonist action on beta-adrenoceptors and indirectly by causing release of norepinephrine from storage sites in sympathetic nerve endings. In the brain, dopamine actas as an agonist to the five dopamine receptor subtypes (D!, D2, D3, D4, D5).
3-hydroxypropionic acid (3HP) toxicity is mediated by 3-hydroxypropionic aldehyde (reuterin). 3HP toxicity is also proposed to be related to inhibition of the chorismate and threonine super-pathways. Generally, the toxicity mechanism of 3HP is not understood at the molecular level. (A15450)
The primary proposed functions of N-acetylaspartic acid include: 1) A neuronal osmolyte that is involved in fluid balance in the brain; 2) a source of acetate for lipid and myelin synthesis in oligodendrocytes, the glial cells that myelinate neuronal axons; 3) a precursor for the synthesis of the important neuronal dipeptide N-acetylaspartylglutamate; 4) N-acetylaspartic acid may also be involved in energy production from the amino acid glutamate in neuronal mitochondria. Excess amounts of N-acetyl-L-aspartic acid accumulated in plasma, spinal fluid, and urine have been found to be toxic. On the other hand, decreased concentration of N-acetyl-L-aspartic acid according to the in vivo spectrum of the brain has been related to disorders such as hypoacetylaspartia.
Cholesterol is essential for life. However, chronically high levels (from diet or from genetic predisposition or from diseases such as hyperlipidemia) of cholesterol and cholesterol esters lead to an excess of low-density lipoprotein (LDL) particles. In healthy individuals the LDL particles are large and relatively few in number. In contrast, large numbers of small LDL particles are strongly associated with promoting atheromatous disease within the arteries. In conditions with elevated concentrations of oxidized LDL particles, especially small LDL particles, cholesterol promotes atheroma plaque deposits in the walls of arteries, a condition known as atherosclerosis, which is a major contributor to coronary heart disease and other forms of cardiovascular disease. Resistin, a protein secreted by fat tissue, has been shown to increase the production of LDL in human liver cells and also degrades LDL receptors in the liver. As a result, the liver is less able to clear cholesterol from the bloodstream. Resistin accelerates the accumulation of LDL in arteries, increasing the risk of heart disease.
In the CNS, there exist strychnine-sensitive glycine binding sites as well as strychnine-insensitive glycine binding sites. The strychnine-insensitive glycine-binding site is located on the NMDA receptor complex. The strychnine-sensitive glycine receptor complex is comprised of a chloride channel and is a member of the ligand-gated ion channel superfamily. The putative antispastic activity of supplemental glycine could be mediated by glycine's binding to strychnine-sensitive binding sites in the spinal cord. This would result in increased chloride conductance and consequent enhancement of inhibitory neurotransmission. The ability of glycine to potentiate NMDA receptor-mediated neurotransmission raised the possibility of its use in the management of neuroleptic-resistant negative symptoms in schizophrenia. <br/>Animal studies indicate that supplemental glycine protects against endotoxin-induced lethality, hypoxia-reperfusion injury after liver transplantation, and D-galactosamine-mediated liver injury. Neutrophils are thought to participate in these pathologic processes via invasion of tissue and releasing such reactive oxygen species as superoxide. In vitro studies have shown that neutrophils contain a glycine-gated chloride channel that can attenuate increases in intracellular calcium and diminsh neutrophil oxidant production. This research is ealy-stage, but suggests that supplementary glycine may turn out to be useful in processes where neutrophil infiltration contributes to toxicity, such as ARDS.
L-Alanine is a non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases immunity, and provides energy for muscle tissue, brain, and the central nervous system. BCAAs are used as a source of energy for muscle cells. During prolonged exercise, BCAAs are released from skeletal muscles and their carbon backbones are used as fuel, while their nitrogen portion is used to form another amino acid, Alanine. Alanine is then converted to Glucose by the liver. This form of energy production is called the Alanine-Glucose cycle, and it plays a major role in maintaining the body's blood sugar balance.
Pyruvate serves as a biological fuel by being converted to acetyl coenzyme A, which enters the tricarboxylic acid or Krebs cycle where it is metabolized to produce ATP aerobically. Energy can also be obtained anaerobically from pyruvate via its conversion to lactate. Pyruvate injections or perfusions increase contractile function of hearts when metabolizing glucose or fatty acids. This inotropic effect is striking in hearts stunned by ischemia/reperfusion. The inotropic effect of pyruvate requires intracoronary infusion. Among possible mechanisms for this effect are increased generation of ATP and an increase in ATP phosphorylation potential. Another is activation of pyruvate dehydrogenase, promoting its own oxidation by inhibiting pyruvate dehydrogenase kinase. Pyruvate dehydrogenase is inactivated in ischemia myocardium. Yet another is reduction of cytosolic inorganic phosphate concentration. Pyruvate, as an antioxidant, is known to scavenge such reactive oxygen species as hydrogen peroxide and lipid peroxides. Indirectly, supraphysiological levels of pyruvate may increase cellular reduced glutathione.
The mechanism of the possible anti-hepatotoxic activity of L-methionine is not entirely clear. It is thought that metabolism of high doses of acetaminophen in the liver lead to decreased levels of hepatic glutathione and increased oxidative stress. L-methionine is a precursor to L-cysteine. L-cysteine itself may have antioxidant activity. L-cysteine is also a precursor to the antioxidant glutathione. Antioxidant activity of L-methionine and metabolites of L-methionine appear to account for its possible anti-hepatotoxic activity. Recent research suggests that methionine itself has free-radical scavenging activity by virtue of its sulfur, as well as its chelating ability.
Glyceric acid is a compound that is secreted excessively in the urine by patients suffering from D-glyceric aciduria and D-glycerate anemia. Deficiency of human glycerate kinase leads to D-glycerate acidemia/D-glyceric aciduria. Accumulation of glyceric acid in the body has been shown to be toxic.
Dihydropyrimidine dehydrogenase catalyzes the reduction of thymine to 5, 6-dihydrothymine then dihydropyrimidinase hydrolyzes 5, 6-dihydrothymine to N-carbamyl-b-alanine. Finally, beta-ureidopropionase catalyzes the conversion of N-carbamyl-b-alanine to beta-alanine. Accumulation of dihydrothymine in the body has been shown to be toxic.
Accumulation of galactitol in the body has been shown to be toxic. Accumulation of galactitol in the lens causes the osmotic phenomena and results in cataract formation. It may form in excess in the lens of the eye in galactosemias, a deficiency of galactokinase.
Glutathione (GSH) participates in leukotriene synthesis and is a cofactor for the enzyme glutathione peroxidase. It is also important as a hydrophilic molecule that is added to lipophilic toxins and waste in the liver during biotransformation before they can become part of the bile. Glutathione is also needed for the detoxification of methylglyoxal, a toxin produced as a by-product of metabolism. This detoxification reaction is carried out by the glyoxalase system. Glyoxalase I catalyzes the conversion of methylglyoxal and reduced glutathione to S-D-Lactoyl-glutathione. Glyoxalase II catalyzes the conversion of S-D-Lactoyl Glutathione to Reduced Glutathione and D-lactate. GSH is known as a cofactor in both conjugation reactions and reduction reactions, catalyzed by glutathione S-transferase enzymes in cytosol, microsomes, and mitochondria. However, it is capable of participating in non-enzymatic conjugation with some chemicals, as it is hypothesized to do to a significant extent with n-acetyl-p-benzoquinone imine (NAPQI), the reactive cytochrome P450 reactive metabolite formed by toxic overdose of acetaminophen. Glutathione in this capacity binds to NAPQI as a suicide substrate and in the process detoxifies it, taking the place of cellular protein sulfhydryl groups which would otherwise be toxically adducted. The preferred medical treatment to an overdose of this nature, whose efficacy has been consistently supported in literature, is the administration (usually in atomized form) of N-acetylcysteine, which is used by cells to replace spent GSSG and allow a usable GSH pool.
Very high serum levels of glucose are found in untreated diabetic (type I or type II) patients. Glucose in chronic excess causes toxic effects on the structure and function of many cells and organs, including the pancreas and pancreatic islet cells. Multiple biochemical pathways and mechanisms of action for glucose toxicity have been suggested. These include glyceraldehyde auto-oxidation, protein kinase C activation, methylglyoxal formation and glycation, hexosamine metabolism, sorbitol formation, and oxidative phosphorylation. All these pathways have in common the formation of reactive oxygen species that, in excess and over time, cause chronic oxidative stress, which in turn causes defective insulin gene expression and insulin secretion as well as increased apoptosis.   Exposure of endothelial cells to high glucose causes GAPDH inhibition through reactive oxygen species-activated poly(ADP-ribosyl)ation of GAPDH by poly(ADP-ribose) polymerase. Three products from glucose metabolism (glyoxal, methylglyoxal, and 3-deoxyglucosone) form advanced glycation end products (AGEs) by reacting with amino groups on intracellular and extracellular proteins. AGEs play important roles in the pathogenesis of secondary complications of diabetes, especially with regard to microvascular disease in the retina, nerves, and kidney and likely islets. Glycated hemoglobin is a particularly important AGE. A 1% increase in absolute concentrations of glycated hemoglobin is associated with about 10-20% increase in cardiovascular disease risk.
Accumulating trans-glutaconic (TG) acids has been proposed to be involved in the development of the striatal degeneration seen in children with glutaric acidemia type 1 (GA1) via an excitotoxic mechanism. TG is neurotoxic and neurotoxicity is thought to be caused by an excitotoxic mechanism in which TG overactivates N-methyl-D-aspartate (NMDA) receptors. (A15451) In glutaric aciduria type 1, glutaconic acid accumulates, resulting in brain damage. (Wikipedia)
Accumulation of glutaric acid in the body has been shown to be toxic. The accumulation of glutaric acid ranging from slightly or intermittently elevated urinary glutaric acid to gross organic aciduria occurs in glutaric aciduria. Glutaric aciduria type 1 is an autosomal-recessive disorder resulting from a deficiency of mitochondrial glutaryl-CoA dehydrogenase which is involved in the metabolism of lysine, hydroxylysine, and tryptophan.
Asparagine, a non-essential amino acid is important in the metabolism of toxic ammonia in the body through the action of asparagine synthase which attaches ammonia to aspartic acid in an amidation reaction. Asparagine is also used as a structural component in many proteins.
(Applies to Valine, Leucine and Isoleucine) <br/>This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates. <br/>The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic. <br/>There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.
This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates. The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic. There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.
Extremely high serum levels of phenylalanine are found in patients with the inborn error of metabolism (IEM) called Phenylketonuria (PKU). At pathological concentrations typical of PKU, phenylalanine self-assembles into fibrils with amyloid-like morphology and well-ordered electron diffraction. These fibrils and their resulting amyloid deposits that localize to the brain appear to be partially responsible for the neural tissue damage seen in PKU patients (A8160).  It has also been suggested that very high plasma phenylalanine concentrations can increase phenylalanine entry into brain and thereby restrict the entry of other large neutral amino acids. The lack of large neutral amino acids may lead to disturbed cerebral protein synthesis, which is particularly important for young children (A8162). The mechanism of L-phenylalanine's putative antidepressant activity may be accounted for by its precursor role in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects. <br/>The mechanism of L-phenylalanine's possible antivitiligo activity is not well understood. It is thought that L-phenylalanine may stimulate the production of melanin in the affected skin.
L-Serine plays a role in cell growth and development (cellular proliferation). The conversion of L-serine to glycine by serine hydroxymethyltransferase results in the formation of the one-carbon units necessary for the synthesis of the purine bases, adenine and guanine. These bases when linked to the phosphate ester of pentose sugars are essential components of DNA and RNA and the end products of energy producing metabolic pathways, ATP and GTP. In addition, L-serine conversion to glycine via this same enzyme provides the one-carbon units necessary for production of the pyrimidine nucleotide, deoxythymidine monophosphate, also an essential component of DNA.
L-Threonine is a precursor to the amino acids glycine and serine. It acts as a lipotropic in controlling fat build-up in the liver. May help combat mental illness and may be very useful in indigestion and intestinal malfunctions. Also, threonine prevents excessive liver fat. Nutrients are more readily absorbed when threonine is present.
A number of important side reactions occur during the catabolism of tryptophan on the pathway to acetoacetate. The first enzyme of the catabolic pathway is an iron porphyrin oxygenase that opens the indole ring. The latter enzyme is highly inducible, its concentration rising almost 10-fold on a diet high in tryptophan. Kynurenine is the first key branch point intermediate in the pathway. Kynurenine undergoes deamniation in a standard transamination reaction yielding kynurenic acid. Kynurenic acid and metabolites have been shown to act as antiexcitotoxics and anticonvulsives. A second side branch reaction produces anthranilic acid plus alanine. Another equivalent of alanine is produced further along the main catabolic pathway, and it is the production of these alanine residues that allows tryptophan to be classified among the glucogenic and ketogenic amino acids. The second important branch point converts kynurenine into 2-amino-3-carboxymuconic semialdehyde, which has two fates. The main flow of carbon elements from this intermediate is to glutarate. An important side reaction in liver is a transamination and several rearrangements to produce limited amounts of nicotinic acid, which leads to production of a small amount of NAD<sup>+</sup> and NADP<sup>+</sup>.
(Applies to Valine, Leucine and Isoleucine) <br/>This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates. <br/>The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic. <br/>There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.
Tyrosine is produced in cells by hydroxylating the essential amino acid phenylalanine. This relationship is much like that between cysteine and methionine. Half of the phenylalanine required goes into the production of tyrosine; if the diet is rich in tyrosine itself, the requirements for phenylalanine are reduced by about 50%. The mechanism of L-tyrosine's antidepressant activity can be accounted for by the precursor role of L-tyrosine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.
Methylmalonic acid is a vital intermediate in the metabolism of fat and protein. Abnormalities in methylmalonic acid metabolism lead to methylmalonic aciduria. This metabolic disease is attributed to a block in the enzymatic conversion of methylmalonyl CoA to succinyl CoA. Accumulation of Methylmalonic acid in the body has been shown to be toxic.
Calcium plays a vital role in the anatomy, physiology and biochemistry of organisms and of the cell, particularly in signal transduction pathways. More than 500 human proteins are known to bind or transport calcium.   The skeleton acts as a major mineral storage site for the element and releases Ca2+ ions into the bloodstream under controlled conditions. Circulating calcium is either in the free, ionized form or bound to blood proteins such as serum albumin. Parathyroid hormone (secreted from the parathyroid gland) regulates the resorption of Ca2+ from bone. Calcitonin stimulates incorporation of calcium in bone, although this process is largely independent of calcitonin. Although calcium flow to and from the bone is neutral, about 5 mmol is turned over a day. Bone serves as an important storage point for calcium, as it contains 99% of the total body calcium.  Low calcium intake may also be a risk factor in the development of osteoporosis.  The best-absorbed form of calcium from a pill is a calcium salt like carbonate or phosphate. Calcium gluconate and calcium lactate are absorbed well by pregnant women. Seniors absorb calcium lactate, gluconate and citrate better unless they take their calcium supplement with a full breakfast. The currently recommended calcium intake is 1,500 milligrams per day for women not taking estrogen and 800 milligrams per day for women on estrogen. There is close to 300 milligrams of calcium in one cup of fluid milk. Calcium carbonate is currently the best and least expensive form of calcium supplement available.
Xanthine is a poorly soluble compound.  As a result high concentrations of serum xanthine can lead to the formation of kidney stones (xanthine kidney stones) which can, over the long term, induce kidney failure.
Glycogenic, by L-Proline oxidase in the kidney, it is ring-opened and is oxidized to form L-Glutamic acid. L-Ornithine and L-Glutamic acid are converted to L-Proline via L-Glutamic acid-gamma-semialdehyde. It is contained abundantly in collagen, and is intimately involved in the function of arthrosis and chordae.
3-Methyl-2-oxovaleric acid is produced from isoleucine by cytosolic branched chain aminotransferase 1, whereupon it is further degraded by branched chain keto acid dehydrogenase E1 to 2-methyl-1-hydroxybutyl-ThPP. It is used as a clinical marker for maple syrup urine disease (MSUD). MSUD is caused by a deficiency of the branched-chain -keto acid dehydrogenase complex resulting in an accumulation of branched-chain amino acids and the corresponding -keto-and -hydroxy acids in blood, urine and cerebrospinal fluid causing neurological damage and mental retardation.
Ketoleucine is a metabolite that accumulates in Maple Syrup Urine Disease (MSUD) and shown to compromise brain energy metabolism by blocking the respiratory chain.
Deoxyuridine triphosphate (dUTP) can be misincorporated into DNA and cause DNA damage. The extent of DNA damage caused by dUTP is dependent on the levels of the pyrophosphatase dUTPase and uracil-DNA glycosylase (UDG). DNA damage due to dUTP misincorporation is highly dependent on the levels of the pyrophosphatase dUTPase, which limits intracellular accumulation of dUTP. (A4337) Also, loss of viability following thymidylate synthase (TS) inhibition occurs as a consequence of accumulation of dUTP in some cell lines and subsequent misincorporation of uracil into DNA. (PMCID: PMC2364072)
S-Sulfocysteine (SSC) is a very potent NMDA-receptor agonist. Electrophysiological studies have shown that SSC displays depolarizing properties similar to glutamate. Subcutaneous and intracerebral administration of SSC to infant rats induces brain damage. Apart from activating NMDA receptors, elevated SSC could also be neurotoxic by inhibition of the rate-limiting enzyme in glutathione synthesis (A15403), thereby reducing the intracellular levels of free radical scavengers. (A15402)
Tyramine is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
In healthy individuals, the enzyme propionyl CoA carboxylase converts propionyl CoA to methylmalonyl CoA. This is one step in the process of converting certain amino acids and fats into sugar for energy. Individuals with propionic acidemia cannot perform this conversion because the enzyme propionyl CoA carboxylase is nonfunctional. The essential amino acids; isoleucine, valine, threonine, and methionine and odd-chain fatty acids are simply converted to propionyl CoA, before the process stops, leading to a buildup of propionyl CoA. Instead of being converted to methylmalonyl CoA, propionyl CoA is then converted into propionic acid, which builds up in the bloodstream. Propionyl-CoA, propionic acid, ketones, ammonia, and other toxic compounds accumulate in the blood, causing the signs and symptoms of propionic acidemia. Propionate acts as a metabolic toxin in liver cells by accumulating in mitochondria. Propanoate is metabolized oxidatively by glia, which suggests astrocytic vulnerability in propanoic acidemia when intramitochondrial propionyl-CoA may accumulate. Propanoic acidemia may alter both neuronal and glial gene expression by affecting histone acetylation (A15452, A15453). (Wikipedia)
In propionic aciduria, propionyl CoA accumulates within the mitochondria in massive quantities; free carnitine is then esterified, creating propionyl carnitine, which is then excreted in the urine. Because the supply of carnitine in the diet and from synthesis is limited, such patients readily develop carnitine deficiency as a result of the increased loss of acylcarnitine derivatives.
Succinate can inhibit the activities of α-KG–dependent oxygenases (KDMs) and the TET family of 5-methlycytosine (5mC) hydroxylases. Succinate also mediates allosteric inhibition of hypoxia inducible factor (HIF) prolyl hydroxylases (PHDs). Inhibition of HIF PHDs leads to activation of HIF-mediated pseudohypoxic response, whereas inhibition of KDMs and TET family of 5mC hydroxylases causes epigenetic alterations that ultimately cause cancer. Succination of KEAP1 in FH deficiency results in the constitutive activation of the antioxidant defense pathway mediated by NRF2, conferring a reductive milieu that promotes cell proliferation. Succination of the Krebs cycle enzyme Aco2 impairs aconitase activity in Fh1-deficient MEFs.  Succination also causes irreversible inactivation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH).
S-Adenosylmethionine (SAMe) is a natural substance present in the cells of the body. It is a direct metabolite of the essential amino acid L-methionine. SAMe plays a crucial biochemical role in the body by donating a one-carbon methyl group in a process called transmethylation. SAMe, formed from the reaction of L-methionine and adenosine triphosphate catalyzed by the enzyme S-adenosylmethionine synthetase, is the methyl-group donor in the biosynthesis of both DNA and RNA nucleic acids, phospholipids, proteins, epinephrine, melatonin, creatine and other molecules.
Sarcosine is an oncometabolite. Sarcosine appears to upregulate the expression of the potent oncoprotein called human epidermal growth factor receptor 2 (HER2/neu) in androgen-dependent prostate cancer cells upon exposure to exogenous sarcosine. Thus, sarcosine may induce prostate cancer progression by increased HER2/neu expression.
Ethylmalonic acid is identified in the urine of patients with short-chain acyl-coenzyme A dehydrogenase deficiency, which is a fatty acid metabolism disorder.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Chlorethoxyfos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Chlorpyrifos oxon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Clomazone induces oxidative stress and AChE inhibition in human erythrocytes (in vitro), suggesting a role for reactive oxygen species in the toxicity mechanism induced by clomazone in humans. (A15208)
Coumaphos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Diazoxon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Diphenylamine uncouples mitochondrial oxidative phosphorylation, resulting in a decrease in hepatocellular ATP content and consequently hepatocyte injury (A15350). Short-term and long-term exposure in animal models results in altered haematological parameters, splenic erythropoiesis, splenic congestion and haemosiderosis (L2078).
Diuron has been reported to bind to androgen receptors. This suggests that diuron may block the receptors and result in the toxicity on the reproductive system.
Fenarimol is an antiandrogen. It has effects on the reproductive organs and prostate gene expression levels. Studies suggested that the adverse effects of Fenarimol in males are mediated at least partialy via antagonism or androgen receptor.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
ACCLAIM is a proprietary combination of nitrate and L-arginine that provides the beneficial cardiovascular effects of nitrates. Combining L-arginine with organic nitrates prevents the endothelial cell's depletion of L-arginine and the associated problem of nitrate tolerance. By eliminating nitrate tolerance, ACCLAIM allows patients to receive the continuous, 24-hour benefit of a potent nitrate product, thus sustaining the desired vasodilation effect.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Isazofos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Linuron is a weak competitive inhibitor of androgen receptor binding and it inhibits androgen-induced gene expression in vitro. This may partially contribute to the malformations of androgen-dependent tissues in male rats. (A9961)
Malaoxon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Pirimiphos-methyl is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Profenofos is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
The US EPA has found no information indicating thidiazuron shares a common mechanism of toxicity with other substances. (L2080)
Like other antihistamines, doxylamine acts by competitively inhibiting histamine at H1&nbsp;receptors. It also has substantial sedative and anticholinergic effects.
The mechanism of action of Eszopiclone is not completely understood. It is thought that Eszopiclone acts on the benzodiazepine receptors as an agonist and interacts with GABA-receptor complexes.
Carbinoxamine competes with free histamine for binding at HA-receptor sites. This antagonizes the effects of histamine on HA-receptors, leading to a reduction of the negative symptoms brought on by histamine HA-receptor binding. Carbinoxamine's anticholinergic action appears to be due to a central antimuscarinic effect, which also may be responsible for its antiemetic effects, although the exact mechanism is unknown.
Brompheniramine works by acting as an antagonist of the H1 histamine receptors. It also functions as a moderately effective anticholingeric agent, likely an antimuscarinic agent similar to other common antihistamines such as diphenhydramine. Its effects on the cholinergic system may include side-effects such as drowsiness, sedation, dry mouth, dry throat, blurred vision, and increased heart rate.
Pseudoephedrine acts directly on both alpha- and, to a lesser degree, beta-adrenergic receptors. Through direct action on alpha-adrenergic receptors in the mucosa of the respiratory tract, pseudoephedrine produces vasoconstriction. Pseudoephedrine relaxes bronchial smooth muscle by stimulating beta2-adrenergic receptors. Like ephedrine, pseudoephedrine releasing norepinephrine from its storage sites, an indirect effect. This is its main and direct mechanism of action. The displaced noradrenaline is released into the neuronal synapse where it is free to activate the postsynaptic adrenergic receptors.
Guaifenesin may act as an irritant to gastric vagal receptors, and recruit efferent parasympathetic reflexes that cause glandular exocytosis of a less viscous mucus mixture. Cough may be provoked. This combination may flush tenacious, congealed mucopurulent material from obstructed small airways and lead to a temporary improvement in dyspnea or the work of breathing.
Like other H1-blockers, Desloratadine competes with free histamine for binding at H<sub>1</sub>-receptors in the GI tract, uterus, large blood vessels, and bronchial smooth muscle. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms (eg. nasal congestion, watery eyes) brought on by histamine.
Azelastine competes with histamine for the H1-receptor sites on effector cells and acts as an antagonist by inhibiting the release of histamine and other mediators involved in the allergic response.
Like other H1-antagonists, promethazine competes with free histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. The relief of nausea appears to be related to central anticholinergic actions and may implicate activity on the medullary chemoreceptor trigger zone.
Amobarbital (like all barbiturates) works by binding to the GABAA receptor at either the alpha or the beta sub unit.  These are binding sites that are distinct from GABA itself and also distinct from the benzodiazepine binding site. Like benzodiazepines, barbiturates potentiate the effect of GABA at this receptor.  This GABAA receptor binding decreases input resistance, depresses burst and tonic firing, especially in ventrobasal and intralaminar neurons, while at the same time increasing burst duration and mean conductance at individual chloride channels; this increases both the amplitude and decay time of inhibitory postsynaptic currents.  In addition to this GABA-ergic effect, barbiturates also block the AMPA receptor, a subtype of glutamate receptor. Glutamate is the principal excitatory neurotransmitter in the mammalian CNS.  Amobarbital also appears to bind neuronal nicotinic acetylcholine receptors.
Heroin is a mu-opioid agonist. It acts on endogenous mu-opioid receptors that are spread in discrete packets throughout the brain, spinal cord and gut in almost all mammals. Heroin, along with other opioids, are agonists to four endogenous neurotransmitters. They are beta-endorphin, dynorphin, leu-enkephalin, and met-enkephalin. The body responds to heroin in the brain by reducing (and sometimes stopping) production of the endogenous opioids when heroin is present. Endorphins are regularly released in the brain and nerves, attenuating pain. Their other functions are still obscure, but are probably related to the effects produced by heroin besides analgesia (antitussin, anti-diarrheal).
Methylphenidate blocks dopamine uptake in central adrenergic neurons by blocking dopamine transport or carrier proteins. Methylphenidate acts at the brain stem arousal system and the cerebral cortex and causes increased sympathomimetic activity in the central nervous system.
Methylphenidate is a catecholamine reuptake inhibitor that indirectly increases catecholaminergic neurotransmission by inhibiting the dopamine transporter (DAT) and norepinephrine transporter (NET), which are responsible for clearing catecholamines from the synapse, particularly in the striatum and meso-limbic system.
Clobazam binds at distinct binding sites associated with the chloride ionopore at the post-synaptic GABA receptor. These GABA receptors are in various locations in the CNS (limbic, reticular formation) and clobazam increases the duration of time for which the chloride ionopore is open. As a result, hyper polarization and stabilization of the membrane occur as the post-synaptic inhibitory effect of GABA is enhanced.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Camazepam has been shown to bind competitively to benzodiazepine receptors in the brain with a relatively low affinity in animal models. This binding of benzodiazepine receptors by camazepam and its active metabolites is responsible for its anticonvulsant effects. Notably, only three metabolites were shown to exert anticonvulsant activity, temazepam, oxazepam, and hydroxy camazepam. The anxiolytic properties of camazepam are also attributed to their ability to bind benzodiazepine receptors, also known as GABA receptors.  When benzodiazepines bind to GABA receptors they increase the efficiency with which the inhibitory neurotransmitter GABA binds.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Cloxazolam is a long acting benzodiazepine. It acts as a prodrug, with pharmacologically active metabolites, which bind to to the GABAa receptor, which other benzodiazepines bind to, to illicit a physiological response.
Fludiazepam has similar action to diazepam, but binds with four times more affinity to benzodiazepine receptors than diazepam.
Benzodiazepines share a similar chemical structure and their effects in humans are mainly produced by the allosteric modification of a specific kind of neurotransmitter receptor, the GABAA receptor, which increases the conductance of this inhibitory channel; this results in the various therapeutic effects as well as adverse effects of benzodiazepines. Binding of benzodiazepines to this receptor complex promotes binding of GABA, which in turn increases the conduction of chloride ions across the neuronal cell membrane. This increased conductance raises the membrane potential of the neuron resulting in inhibition of neuronal firing. In addition, different GABAA receptor subtypes have varying distributions within different regions of the brain and therefore control distinct neuronal circuits. Hence, activation of different GABAA receptor subtypes by benzodiazepines may result in distinct pharmacological actions.
Tofisopam does not bind to the benzodiazepine binding site of the gamma-aminobutyric acid receptor. One study (Rundfeldt C. et al.) has shown that tofisopam acts as an isoenzyme-selective inhibitor of phosphodiesterases (PDEs) with highest affinity to PDE-4A1 (0.42 _Мц_M) followed by PDE-10A1 (0.92 _Мц_M), PDE-3 (1.98 _Мц_M) and PDE-2A3 (2.11 _Мц_M).
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Quinone is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Ethyl carbamate is genotoxic and a potent carcinogen.  It exerts its effects through the formation of DNA adducts (via its vinyl carbamate epoxide metabolite) that induce choromosomal aberrations, micronuclei and sister chromatid exchange. It also tends to induce specific mutations in the Kras oncogene in codon 61 of exon 2 including A:T transversions and A-->G transitions in the second base and A-->T transversions in the third base.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Butyric acid is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
It has been demonstrated that octanoic (OA) and decanoic (DA) acids compromise the glycolytic pathway and citric acid cycle functioning, increase oxygen consumption in the liver and inhibit some activities of the respiratory chain complexes and creatine kinase in rat brain (A15454, A15455). These fatty acids were also shown to induce oxidative stress in the brain (A15456). Experiments suggest that OA and DA impair brain mitochondrial energy homeostasis that could underlie at least in part the neuropathology of MCADD. (A15457)
Etoposide, a semisynthetic derivative of podofilox, induces DNA breakage through its inhibition of topoisomerase II. The drug is most active in the late S and early G2 phases of the cell cycle. Teniposide is an analog with very similar pharmacologic characteristics. Podofilox derivatives display binding activity to the enzyme topoisomerase II during the late S and early G2 stage. For instance, etoposide binds and stabilizes the temporary break caused by the enzyme, disrupts the reparation of the break through which the double-stranded DNA passes, and consequently stops DNA unwinding and replication. Mutants resistant to either podofilox, or to its topoisomerase II inhibitory derivatives such as etoposide (VP-16), have been described in Chinese hamster cells. The mutually exclusive cross-resistance patterns of these mutants provide a highly specific mean to distinguish the two kinds of podofilox derivatives. Mutant Chinese hamster cells resistant to podofilox are affected in a protein P1 that was later identified as the mammalian HSP60 or chaperonin protein. (Wikipedia)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
1,2-Naphthoquinone is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
A high salt diet disrupts the natural sodium balance in the body. This causes fluid retention which increases the pressure exerted by the blood against blood vessel walls leading to high blood pressure or hypertension. It has been estimated that a reduction in salt intake from 10g a day to 6g could reduce blood pressure sufficiently that it would lead to a 16% reduction in deaths from strokes and a 12% reduction in deaths from coronary heart disease.
Estradiol enters target cells freely (e.g., female organs, breasts, hypothalamus, pituitary) and interacts with a target cell receptor. When the estrogen receptor has bound its ligand it can enter the nucleus of the target cell, and regulate gene transcription which leads to formation of messenger RNA. The mRNA interacts with ribosomes to produce specific proteins that express the effect of estradiol upon the target cell. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary.
After 4,4'-Methylenedianiline enters to our body, it is transported in the blood or stored in tissues. The N-N-acetylation of the compound leads to the formation of some toxic derivatives. The liver and thyroid are the targets of 4,4'-methylenedianiline in animals.
Mechanistically, adapalene binds to specific retinoic acid nuclear receptors (gamma and beta) and retinoid X receptors but does not bind to the cytosolic receptor protein. Although the exact mode of action of adapalene is unknown, it is suggested that topical adapalene may normalize the differentiation of follicular epithelial cells resulting in decreased microcomedone formation.
Amsacrine binds to DNA through intercalation and external binding. It has a base specificity for A-T pairs. Rapidly dividing cells are two to four times more sensitive to amsacrine than are resting cells. Amsacrine appears to cleave DNA by inducing double stranded breaks. Amsacrine also targets and inhibits topoisomerase II. Cytotoxicity is greatest during the S phase of the cell cycle when topoisomerase levels are at a maximum.
Arecoline is the primary active ingredient responsible for the central nervous system effects of the areca nut. Arecoline has been compared to nicotine; however, nicotine acts primarily on the nicotinic acetylcholine receptor. Arecoline is known to be a partial agonist of muscarinic acetylcholine M1, M2, M3 receptors and M4, which is believed to be the primary cause of its parasympathetic effects (such as pupillary constriction, bronchial constriction, etc.). (Wikipedia) Arecoline is cytotoxic to human gingival fibroblasts at a concentration higher than 50 μg/ml by depleting intracellular thiols and inhibiting mitochondrial activity (P<0.05). In addition, the cells displayed a marked arrest at G2/M phase in a dose-dependent manner. (A15351)
Azacitidine (5-azacytidine) is a chemical analogue of the cytosine nucleoside used in DNA and RNA. Azacitidine is thought to induce antineoplastic activity via two mechanisms; inhibition of DNA methyltransferase at low doses, causing hypomethylation of DNA, and direct cytotoxicity in abnormal hematopoietic cells in the bone marrow through its incorporation into DNA and RNA at high doses, resulting in cell death. As azacitidine is a ribonucleoside, it incoporates into RNA to a larger extent than into DNA. The incorporation into RNA leads to the dissembly of polyribosomes, defective methylation and acceptor function of transfer RNA, and inhibition of the production of protein. Its incorporation into DNA leads to a covalent binding with DNA methyltransferases, which prevents DNA synthesis and subsequent cytotoxicity.
Azathioprine antagonizes purine metabolism and may inhibit synthesis of DNA, RNA, and proteins. It may also interfere with cellular metabolism and inhibit mitosis. Its mechanism of action is likely due to incorporation of thiopurine analogues into the DNA structure, causing chain termination and cytotoxicity.
Carmustine causes cross-links in DNA and RNA, leading to the inhibition of DNA synthesis, RNA production and RNA translation (protein synthesis). Carmustine also binds to and modifies (carbamoylates) glutathione reductase. This leads to cell death.
Alkylating agents work by three different mechanisms: 1) attachment of alkyl groups to DNA bases, resulting in the DNA being fragmented by repair enzymes in their attempts to replace the alkylated bases, preventing DNA synthesis and RNA transcription from the affected DNA, 2) DNA damage via the formation of cross-links (bonds between atoms in the DNA) which prevents DNA from being separated for synthesis or transcription, and 3) the induction of mispairing of the nucleotides leading to mutations.
Alkylating agents work by three different mechanisms: 1) attachment of alkyl groups to DNA bases, resulting in the DNA being fragmented by repair enzymes in their attempts to replace the alkylated bases, preventing DNA synthesis and RNA transcription from the affected DNA, 2) DNA damage via the formation of cross-links (bonds between atoms in the DNA) which prevents DNA from being separated for synthesis or transcription, and 3) the induction of mispairing of the nucleotides leading to mutations.
Alkylating agents work by three different mechanisms: 1) attachment of alkyl groups to DNA bases, resulting in the DNA being fragmented by repair enzymes in their attempts to replace the alkylated bases, preventing DNA synthesis and RNA transcription from the affected DNA, 2) DNA damage via the formation of cross-links (bonds between atoms in the DNA) which prevents DNA from being separated for synthesis or transcription, and 3) the induction of mispairing of the nucleotides leading to mutations.
The mechanism of action is not known, but appears to exert cytotoxic effects via its action as an alkylating agent. Other theories include DNA synthesis inhibition by its action as a purine analog, and interaction with SH groups. Dacarbazine is not cell cycle-phase specific.
The dichloroacetate ion stimulates the activity of the enzyme pyruvate dehydrogenase by inhibiting the enzyme pyruvate dehydrogenase kinase. Thus, it decreases lactate production by shifting the metabolism of pyruvate from fermentation towards oxidation in the mitochondria. (Wikipedia)
Estrogens enter the cells of responsive tissues (e.g., female organs, breasts, hypothalamus, pituitary) where they interact with a protein receptor, subsequently increasing the rate of synthesis of DNA, RNA, and some proteins. Estrogens decrease the secretion of gonadotropin-releasing hormone by the hypothalamus, reducing the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary.
Etoposide inhibits DNA topoisomerase II, thereby inhibiting DNA re-ligation. This causes critical errors in DNA synthesis at the premitotic stage of cell division and can lead to apoptosis of the cancer cell. Etoposide is cell cycle dependent and phase specific, affecting mainly the S and G2 phases of cell division. Inhibition of the topoisomerase II alpha isoform results in the anti-tumour activity of etoposide. The drug is also capable of inhibiting the beta isoform but inhibition of this target is not associated with the anti-tumour activity. It is instead associated with the carcinogenic effect.
Griseofulvin is fungistatic, however the exact mechanism by which it inhibits the growth of dermatophytes is not clear. It is thought to inhibit fungal cell mitosis and nuclear acid synthesis. It also binds to and interferes with the function of spindle and cytoplasmic microtubules by binding to alpha and beta tubulin. It binds to keratin in human cells, then once it reaches the fungal site of action, it binds to fungal microtubes thus altering the fungal process of mitosis.
Iron is necessary for the production of hemoglobin. Iron-deficiency can lead to decreased production of hemoglobin and a microcytic, hypochromic anemia.
Lomustine is a highly lipophilic nitrosourea compound which undergoes hydrolysis in vivo to form reactive metabolites. These metabolites cause alkylation and cross-linking of DNA (at the O6 position of guanine-containing bases) and RNA, thus inducing cytotoxicity. Other biologic effects include inhibition of DNA synthesis and some cell cycle phase specificity. Nitrosureas generally lack cross-resistance with other alkylating agents. As lomustine is a nitrosurea, it may also inhibit several key processes such as carbamoylation and modification of cellular proteins.
Alkylating agents work by three different mechanisms: 1) attachment of alkyl groups to DNA bases (primarily at the N-7 position of guanine and to a lesser extent, at the N-3 position of adenine), forming monoadducts and resulting in the DNA being fragmented by repair enzymes in their attempts to replace the alkylated bases, preventing DNA synthesis and RNA transcription from the affected DNA, 2) DNA damage via the formation of cross-links (bonds between atoms in the DNA) which prevents DNA from being separated for synthesis or transcription, and 3) the induction of mispairing of the nucleotides leading to mutations.
Metronidazole is a prodrug. Unionized metronidazole is selective for anaerobic bacteria due to their ability to intracellularly reduce metronidazole to its active form. This reduced metronidazole then covalently binds to DNA, disrupt its helical structure, inhibiting bacterial nucleic acid synthesis and resulting in bacterial cell death.
Phenacetin's analgesic effects are due to its actions on the sensory tracts of the spinal cord. In addition, phenacetin has a depressant action on the heart, where it acts as a negative inotrope. It is an antipyretic, acting on the brain to decrease the temperature set point. It is also used to treat rheumatoid arthritis (subacute type) and intercostal neuralgia.
Prednisone is a glucocorticoid receptor agonist. It is first metabolized in the liver to its active form, prednisolone. Prednisolone crosses cell membranes and binds with high affinity to specific cytoplasmic receptors. The result includes inhibition of leukocyte infiltration at the site of inflammation, interference in the function of mediators of inflammatory response, suppression of humoral immune responses, and reduction in edema or scar tissue. The antiinflammatory actions of corticosteroids are thought to involve phospholipase A2 inhibitory proteins, lipocortins, which control the biosynthesis of potent mediators of inflammation such as prostaglandins and leukotrienes. Prednisone can stimulate secretion of various components of gastric juice. Suppression of the production of corticotropin may lead to suppression of endogenous corticosteroids. Prednisone has slight mineralocorticoid activity, whereby entry of sodium into cells and loss of intracellular potassium is stimulated. This is particularly evident in the kidney, where rapid ion exchange leads to sodium retention and hypertension.
The precise mode of cytotoxic action of procarbazine has not been clearly defined. There is evidence that the drug may act by inhibition of protein, RNA and DNA synthesis. Studies have suggested that procarbazine may inhibit transmethylation of methyl groups of methionine into t-RNA. The absence of functional t-RNA could cause the cessation of protein synthesis and consequently DNA and RNA synthesis. In addition, procarbazine may directly damage DNA. Hydrogen peroxide, formed during the auto-oxidation of the drug, may attack protein sulfhydryl groups contained in residual protein which is tightly bound to DNA.
Propylthiouracil binds to thyroid peroxidase and thereby inhibits the conversion of iodide to iodine. Thyroid peroxidase normally converts iodide to iodine (via hydrogen peroxide as a cofactor) and also catalyzes the incorporation of the resulting iodide molecule onto both the 3 and/or 5 positions of the phenol rings of tyrosines found in thyroglobulin. Thyroglobulin is degraded to produce thyroxine (T4) and tri-iodothyronine (T3), which are the main hormones produced by the thyroid gland. Therefore propylthiouracil effectively inhibits the production of new thyroid hormones.
Tamoxifen is a nonsteroidal agent that binds to estrogen receptors (ER), inducing a conformational change in the receptor. This results in a blockage or change in the expression of estrogen dependent genes. The prolonged binding of tamoxifen to the nuclear chromatin of these results in reduced DNA polymerase activity, impaired thymidine utilization, blockade of estradiol uptake, and decreased estrogen response. It is likely that tamoxifen interacts with other coactivators or corepressors in the tissue and binds with different estrogen receptors, ER-alpha or ER-beta, producing both estrogenic and antiestrogenic effects.
The mechanism of action appears to be related to the inhibition of type II topoisomerase activity since teniposide does not intercalate into DNA or bind strongly to DNA. Teniposide binds to and inhibits DNA topoisomerase II. The cytotoxic effects of teniposide are related to the relative number of double-stranded DNA breaks produced in cells, which are a reflection of the stabilization of a topoisomerase II-DNA intermediate.
The alkyl group is attached to the guanine base of DNA, at the number 7 nitrogen atom of the imidazole ring. They stop tumor growth by crosslinking guanine nucleobases in DNA double-helix strands, directly attacking DNA. This makes the strands unable to uncoil and separate. As this is necessary in DNA replication, the cells can no longer divide. These drugs act nonspecifically.
After activation, it binds preferentially to the guanine and cytosine moieties of DNA, leading to cross-linking of DNA, thus inhibiting DNA synthesis and function.
Zalcitabine is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Within cells, zalcitabine is converted to its active metabolite, dideoxycytidine 5'-triphosphate (ddCTP), by the sequential action of cellular enzymes. ddCTP interferes with viral RNA-directed DNA polymerase (reverse transcriptase) by competing for utilization of the natural substrate deoxycytidine 5'-triphosphate (dCTP), as well as incorpating into viral DNA. Due to it's lack of a 3'-OH group, the formation of a 5' to 3' phosphodiester linkage that is necessary for DNA chain elongation is inhibited, thus leading to the termination of viral DNA growth.
Zidovudine, a structural analog of thymidine, is a prodrug that must be phosphorylated to its active 5ду_-triphosphate metabolite, zidovudine triphosphate (ZDV-TP). It inhibits the activity of HIV-1 reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue. It competes with the natural substrate dGTP and incorporates itself into viral DNA. It is also a weak inhibitor of cellular DNA polymerase ‘± and ‘_.
Ozone is a strong oxidant and reacts directly with organic double bonds. When ozone breaks down to dioxygen it gives rise to oxygen free radicals, which are highly reactive and capable of damaging many organic molecules. Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation. When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques. These metabolites have been confirmed as naturally occurring in human atherosclerotic arteries and are categorized into a class of secosterols termed atheronals, generated by ozonolysis of cholesterol's double bond to form a 5,6 secosterol.  Ozone has also been shown to form the suspected carcinogen bromate when it is introduced to source water with high bromide concentrations. Studies have also demonstrated an increase in collagen, a structural protein involved in fibrosis, following prolonged ozone exposure. Acute and short-term exposure studies have demonstrated ozone’s effects on lung lipids which include an increase in arachidonic acid (a pro-inflammatory molecule).
The antiinflammatory effects of diclofenac are believed to be due to inhibition of both leukocyte migration and the enzyme cylooxygenase (COX-1 and COX-2), leading to the peripheral inhibition of prostaglandin synthesis. As prostaglandins sensitize pain receptors, inhibition of their synthesis is responsible for the analgesic effects of diclofenac. Antipyretic effects may be due to action on the hypothalamus, resulting in peripheral dilation, increased cutaneous blood flow, and subsequent heat dissipation.
Progestins diffuse freely into target cells in the female reproductive tract, mammary gland, hypothalamus, and the pituitary and bind to the progesterone receptor. Once bound to the receptor, progestins slow the frequency of release of gonadotropin releasing hormone (GnRH) from the hypothalamus and blunt the pre-ovulatory LH surge.
Supplemental potassium in the form of high potassium food or potassium chloride may be able to restore normal potassium levels.
The mechanism of action of tacrolimus in atopic dermatitis is not known. While the following have been observed, the clinical significance of these observations in atopic dermatitis is not known. It has been demonstrated that tacrolimus inhibits T-lymphocyte activation by first binding to an intracellular protein, FKBP-12. A complex of tacrolimus-FKBP-12, calcium, calmodulin, and calcineurin is then formed and the phosphatase activity of calcineurin is inhibited. This prevents the dephosphorylation and translocation of nuclear factor of activated T-cells (NF-AT), a nuclear component thought to initiate gene transcription for the formation of lymphokines. Tacrolimus also inhibits the transcription for genes which encode IL-3, IL-4, IL-5, GM-CSF, and TNF-, all of which are involved in the early stages of T-cell activation. Additionally, tacrolimus has been shown to inhibit the release of pre-formed mediators from skin mast cells and basophils, and to downregulate the expression of FceRI on Langerhans cells.
There are two isoforms of ACE: the somatic isoform, which exists as a glycoprotein comprised of a single polypeptide chain of 1277; and the testicular isoform, which has a lower molecular mass and is thought to play a role in sperm maturation and binding of sperm to the oviduct epithelium. Somatic ACE has two functionally active domains, N and C, which arise from tandem gene duplication. Although the two domains have high sequence similarity, they play distinct physiological roles. The C-domain is predominantly involved in blood pressure regulation while the N-domain plays a role in hematopoietic stem cell differentiation and proliferation. ACE inhibitors bind to and inhibit the activity of both domains, but have much greater affinity for and inhibitory activity against the C-domain. Quinaprilat, the principle active metabolite of quinapril, competes with ATI for binding to ACE and inhibits and enzymatic proteolysis of ATI to ATII. Decreasing ATII levels in the body decreases blood pressure by inhibiting the pressor effects of ATII as described in the Pharmacology section above. Quinaprilat also causes an increase in plasma renin activity likely due to a loss of feedback inhibition mediated by ATII on the release of renin and/or stimulation of reflex mechanisms via baroreceptors.
Salmeterol's long, lipophilic side chain binds to exosites near beta(2)-receptors in the lungs and on bronchiolar smooth muscle, allowing the active portion of the molecule to remain at the receptor site, continually binding and releasing. Beta(2)-receptor stimulation in the lung causes relaxation of bronchial smooth muscle, bronchodilation, and increased bronchial airflow.
Salbutamol is a beta(2)-adrenergic agonist and thus it stimulates beta(2)-adrenergic receptors. Binding of albuterol to beta(2)-receptors in the lungs results in relaxation of bronchial smooth muscles. It is believed that salbutamol increases cAMP production by activating adenylate cyclase, and the actions of salbutamol are mediated by cAMP. Increased intracellular cyclic AMP increases the activity of cAMP-dependent protein kinase A, which inhibits the phosphorylation of myosin and lowers intracellular calcium concentrations. A lowered intracellular calcium concentration leads to a smooth muscle relaxation and bronchodilation. In addition to bronchodilation, salbutamol inhibits the release of bronchoconstricting agents from mast cells, inhibits microvascular leakage, and enhances mucociliary clearance.
Fludarabine phosphate is rapidly dephosphorylated to 2-fluoro-ara-A and then phosphorylated intracellularly by deoxycytidine kinase to the active triphosphate, 2-fluoro-ara-ATP. This metabolite appears to act by inhibiting DNA polymerase alpha, ribonucleotide reductase and DNA primase, thus inhibiting DNA synthesis. The mechanism of action of this antimetabolite is not completely characterized and may be multi-faceted.
The antiarrhythmic effect of amiodarone may be due to at least two major actions. It prolongs the myocardial cell-action potential (phase 3) duration and refractory period and acts as a noncompetitive a- and b-adrenergic inhibitor.
Encainide is a sodium channel blocker, binding to voltage gated sodium channels. It stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses. Ventricular excitability is depressed and the stimulation threshold of the ventricle is increased during diastole.
Imipenem acts as an antimicrobial through the inhibition of cell wall synthesis of various gram-positive and gram-negative bacteria. This inhibition of cell wall synthesis in gram-negative bateria is attained by binding to pencillin binding proteins (PBPs). In E. coli and selected strains of P. aeruginosa, imipenem has shown to have the highest affinity to PBP-2, PBP-1a, and PBP-1b. This preferential binding to PBP-2 and PBP-1b results in the direct conversion of the individual cell to a spheroblast, which leads to rapid cell lysis and death without filament formation.
Aminopterin is an amino derivative of folic acid which binds competitively to the dihydrofolate reductase enzyme to block tetrahydrofolate synthesis. Tetrahydrofolate is essential in the production of purines and pyrimadines, thus it's deficiency results in a reduction of DNA, RNA and protein synthesis.
Sodium tetradecyl sulfate is a potent toxin for endothelial cells in that brief exposure to even low concentrations are effective in stripping endothelium over a considerable distance and exposing highly thrombogenic endothelium in the process. Diluted sodium tetradecyl sulfate is also able to induce a hypercoagulable state, possibly by selective inhibition of protein C, and can also promote platelet aggregation.
Estrogens diffuse into their target cells and interact with a protein receptor. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary. This cascade is initiated by initially binding to the estrogen receptors. The combination of an estrogen with a progestin suppresses the hypothalamic-pituitary system, decreasing the secretion of gonadotropin-releasing hormone (GnRH).
Estrogens diffuse into their target cells and interact with a protein receptor, the estrogen receptor. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. The effect of Estrogen binding their receptors causes downstream increases the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary. The combination of an estrogen with a progestin suppresses the hypothalamic-pituitary system, decreasing the secretion of gonadotropin-releasing hormone (GnRH).
Progestins diffuse freely into target cells and bind to the progesterone receptor. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Once bound to the receptor, progestins slow the frequency of release of gonadotropin releasing hormone (GnRH) from the hypothalamus and blunt the pre-ovulatory LH surge.
Estrogens enter the cells of responsive tissues (e.g. female organs, breasts, hypothalamus, pituitary) where they interact with estrogen receptors. Hormone-bound estrogen receptors dimerize, translocate to the nucleus of cells and bind to estrogen response elements (ERE) of genes. Binding to ERE alters the transcription rate of affected genes. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) release from the anterior pituitary.
The direct antiandrogenic effect of cyproterone is blockage of the binding of dihydrotestosterone to the specific receptors in the prostatic carcinoma cell. In addition, cyproterone exerts a negative feed-back on the hypothalamo-pituitary axis, by inhibiting the secretion of luteinizing hormone resulting in diminished production of testicular testosterone.
The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5&alpha;-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5&alpha;-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects.
Binds to the progesterone and estrogen receptors. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Once bound to the receptor, progestins like levonorgestrel will slow the frequency of release of gonadotropin releasing hormone (GnRH) from the hypothalamus and blunt the pre-ovulatory LH (luteinizing hormone) surge.
Busulfan is an alkylating agent that contains 2 labile methanesulfonate groups attached to opposite ends of a 4-carbon alkyl chain. Once busulfan is hydrolyzed, the methanesulfonate groups are released and carbonium ions are produced. These carbonium ions alkylate DNA, which results in the interference of DNA replication and RNA transcription, ultimately leading to the disruption of nucleic acid function. Specifically, its mechanism of action through alkylation produces guanine-adenine intrastrand crosslinks. This occurs through an SN2 reaction in which the relatively nucleophilic guanine N7 attacks the carbon adjacent to the mesylate leaving group. This kind of damage cannot be repaired by cellular machinery and thus the cell undergoes apoptosis.
The exact mechanism of action is unknown. Nitrofurazone inhibits several bacterial enzymes, especially those involved in the aerobic and anaerobic degradation of glucose and pyruvate. This activity is believed also to affect pyruvate dehydrogenase, citrate synthetase, malate dehydrogenase, glutathione reductase, and pyruvate decarboxylase.
Spironolactone is a specific pharmacologic antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone-dependent sodium-potassium exchange site in the distal convoluted renal tubule. Spironolactone causes increased amounts of sodium and water to be excreted, while potassium is retained. Spironolactone acts both as a diuretic and as an antihypertensive drug by this mechanism. It may be given alone or with other diuretic agents which act more proximally in the renal tubule. Aldosterone interacts with a cytoplasmic mineralocorticoid receptor to enhance the expression of the Na+, K+-ATPase and the Na+ channel involved in a Na+ K+ transport in the distal tubule . Spironolactone bind to this mineralcorticoid receptor, blocking the actions of aldosterone on gene expression. Aldosterone is a hormone; its primary function is to retain sodium and excrete potassium in the kidneys.
The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5&alpha;-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5&alpha;-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects.
The antiinflammatory actions of corticosteroids are thought to involve lipocortins, phospholipase A2 inhibitory proteins which, through inhibition of arachidonic acid, control the biosynthesis of prostaglandins and leukotrienes. Firstly, however, these glucocorticoids bind to the glucocorticoid receptors which translocate into the nucleus and bind DNA (GRE) and change genetic expression both positively and negatively. The immune system is suppressed by corticosteroids due to a decrease in the function of the lymphatic system, a reduction in immunoglobulin and complement concentrations, the precipitation of lymphocytopenia, and interference with antigen-antibody binding.
Fulvestrant competitively and reversibly binds to estrogen receptors present in cancer cells and achieves its anti-estrogen effects through two separate mechanisms. First, fulvestrant binds to the receptors and downregulates them so that estrogen is no longer able to bind to these receptors. Second, fulvestrant degrades the estrogen receptors to which it is bound. Both of these mechanisms inhibit the growth of tamoxifen-resistant as well as estrogen-sensitive human breast cancer cell lines.
Quercetin is a specific quinone reductase 2 (QR2) inhibitor, an enzyme (along with the human QR1 homolog) which catalyzes metabolism of toxic quinolines. Inhibition of QR2 in plasmodium may potentially cause lethal oxidative stress. The inhibition of antioxidant activity in plasmodium may contribute to killing the malaria causing parasites.
The hormones, T<sub>4</sub> and T<sub>3</sub>, are tyrosine-based hormones produced by the thyroid gland. Iodine is an important component in their synthesis. The major form of thyroid hormone in the blood is thyroxine (T<sub>4</sub>). This is converted to the more active liothyronine form by deiodinases in peripheral tissues. Liothyronine acts on the body to increase the basal metabolic rate, affect protein synthesis and increase the body's sensitivity to catecholamines (such as adrenaline). The thyroid hormones are essential to proper development and differentiation of all cells of the human body. To various extents T<sub>4</sub> and T<sub>3</sub> regulate protein, fat and carbohydrate metabolism. Their most pronounced effect is on how human cells use energetic compounds. The thyroid hormone derivatives bind to the thyroid hormone receptors initially to initiate their downstream effects.
Erythromycin acts by penetrating the bacterial cell membrane and reversibly binding to the 50 S subunit of bacterial ribosomes or near the &ldquo;P&rdquo; or donor site so that binding of tRNA (transfer RNA) to the donor site is blocked. Translocation of peptides from the &ldquo;A&rdquo; or acceptor site to the &ldquo;P&rdquo; or donor site is prevented, and subsequent protein synthesis is inhibited. Erythromycin is effective only against actively dividing organisms. The exact mechanism by which erythmromycin reduces lesions of acne vulgaris is not fully known: however, the effect appears to be due in part to the antibacterial activity of the drug.
Sulfonylureas likely bind to ATP-sensitive potassium-channel receptors on the pancreatic cell surface, reducing potassium conductance and causing depolarization of the membrane. Depolarization stimulates calcium ion influx through voltage-sensitive calcium channels, raising intracellular concentrations of calcium ions, which induces the secretion, or exocytosis, of insulin.
Hydroxyurea is converted to a free radical nitroxide (NO) in vivo, and transported by diffusion into cells where it quenches the tyrosyl free radical at the active site of the M2 protein subunit of ribonucleotide reductase, inactivating the enzyme. The entire replicase complex, including ribonucleotide reductase, is inactivated and DNA synthesis is selectively inhibited, producing cell death in S phase and synchronization of the fraction of cells that survive. Repair of DNA damaged by chemicals or irradiation is also inhibited by hydroxyurea, offering potential synergy between hydroxyurea and radiation or alkylating agents. Hydroxyurea also increases the level of fetal hemoglobin, leading to a reduction in the incidence of vasoocclusive crises in sickle cell anemia. Levels of fetal hemoglobin increase in response to activation of soluble guanylyl cyclase (sGC) by hydroxyurea-derived NO.
Flutamide is a nonsteroidal antiandrogen that blocks the action of both endogenous and exogenous testosterone by binding to the androgen receptor. In addition Flutamide is a potent inhibitor of testosterone-stimulated prostatic DNA synthesis. Moreover, it is capable of inhibiting prostatic nuclear uptake of androgen.
Thioguanine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is itself converted to 6-thioguanilyic acid (TGMP), which reaches high intracellular concentrations at therapeutic doses. TGMP interferes with the synthesis of guanine nucleotides by its inhibition of purine biosynthesis by pseudofeedback inhibition of glutamine-5-phosphoribosylpyrophosphate amidotransferase, the first enzyme unique to the de novo pathway of purine ribonucleotide synthesis. TGMP also inhibits the conversion of inosinic acid (IMP) to xanthylic acid (XMP) by competition for the enzyme IMP dehydrogenase. Thioguanine nucleotides are incorporated into both the DNA and the RNA by phosphodiester linkages, and some studies have shown that incorporation of such false bases contributes to the cytotoxicity of thioguanine. Its tumor inhibitory properties may be due to one or more of its effects on feedback inhibition of de novo purine synthesis; inhibition of purine nucleotide interconversions; or incorporation into the DNA and RNA. The overall result of its action is a sequential blockade of the utilization and synthesis of the purine nucleotides.
The mechanism of action of celecoxib is believed to be due to inhibition of prostaglandin synthesis. Unlike most NSAIDs, which inhibit both types of cyclooxygenases (COX-1 and COX-2), celecoxib is a selective noncompetitive inhibitor of cyclooxygenase-2 (COX-2) enzyme. It binds with its polar sulfonamide side chain to a hydrophilic side pocket region close to the active COX-2 binding site. Both COX-1 and COX-2 catalyze the conversion of arachidonic acid to prostaglandin (PG) H2, the precursor of PGs and thromboxane.
Stavudine inhibits the activity of HIV-1 reverse transcriptase (RT) both by competing with the natural substrate dGTP and by its incorporation into viral DNA.
It has been demonstrated that octanoic (OA) and decanoic (DA) acids compromise the glycolytic pathway and citric acid cycle functioning, increase oxygen consumption in the liver and inhibit some activities of the respiratory chain complexes and creatine kinase in rat brain (A15454, A15455). These fatty acids were also shown to induce oxidative stress in the brain (A15456). Experiments suggest that OA and DA impair brain mitochondrial energy homeostasis that could underlie at least in part the neuropathology of MCADD. (A15457)
Cladribine is structurally related to fludarabine and pentostatin but has a different mechanism of action. Although the exact mechanism of action has not been fully determined, evidence shows that cladribine is phosphorylated by deoxycytidine kinase to the nucleotidecladribine triphosphate (CdATP; 2-chloro-2ду_-deoxyadenosine 5ду_-triphosphate), which accumulates and is incorporated into DNA in cells such as lymphocytes that contain high levels of deoxycytidine kinase and low levels of deoxynucleotidase, resulting in DNA strand breakage and inhibition of DNA synthesis and repair. High levels of CdATP also appear to inhibit ribonucleotide reductase, which leads to an imbalance in triphosphorylated deoxynucleotide (dNTP) pools and subsequent DNA strand breaks, inhibition of DNA synthesis and repair, nicotinamide adenine dinucleotide (NAD) and ATP depletion, and cell death. Unlike other antimetabolite drugs, cladribine has cytotoxic effects on resting as well as proliferating lymphocytes. However, it does cause cells to accumulate at the G1/S phase junction, suggesting that cytotoxicity is associated with events critical to cell entry into S phase. It also binds purine nucleoside phosphorylase (PNP), however no relationship between this binding and a mechanism of action has been established.
Fenofibrate exerts its therapeutic effects through activation of peroxisome proliferator activated receptor a (PPARa). This increases lipolysis and elimination of triglyceride-rich particles from plasma by activating lipoprotein lipase and reducing production of apoprotein C-III. The resulting fall in triglycerides produces an alteration in the size and composition of LDL from small, dense particles, to large buoyant particles. These larger particles have a greater affinity for cholesterol receptors and are catabolized rapidly.
The precise mechanism of action has not been fully determined, but the main mechanism of fluorouracil is thought to be the binding of the deoxyribonucleotide of the drug (FdUMP) and the folate cofactor, N5дус10-methylenetetrahydrofolate, to thymidylate synthase (TS) to form a covalently bound ternary complex. This results in the inhibition of the formation of thymidylate from uracil, which leads to the inhibition of DNA and RNA synthesis and cell death. Fluorouracil can also be incorporated into RNA in place of uridine triphosphate (UTP), producing a fraudulent RNA and interfering with RNA processing and protein synthesis.
Isoniazid is a prodrug and must be activated by bacterial catalase. Specficially, activation is associated with reduction of the mycobacterial ferric KatG catalase-peroxidase by hydrazine and reaction with oxygen to form an oxyferrous enzyme complex. Once activated, isoniazid inhibits the synthesis of mycoloic acids, an essential component of the bacterial cell wall. At therapeutic levels isoniazid is bacteriocidal against actively growing intracellular and extracellular <i>Mycobacterium tuberculosis</i> organisms. Specifically isoniazid inhibits InhA, the enoyl reductase from <i>Mycobacterium tuberculosis</i>, by forming a covalent adduct with the NAD cofactor. It is the INH-NAD adduct that acts as a slow, tight-binding competitive inhibitor of InhA.
Pyrimethamine inhibits the dihydrofolate reductase of plasmodia and thereby blocks the biosynthesis of purines and pyrimidines, which are essential for DNA synthesis and cell multiplication. This leads to failure of nuclear division at the time of schizont formation in erythrocytes and liver.
Theophylline relaxes the smooth muscle of the bronchial airways and pulmonary blood vessels and reduces airway responsiveness to histamine, methacholine, adenosine, and allergen. Theophylline competitively inhibits type III and type IV phosphodiesterase (PDE), the enzyme responsible for breaking down cyclic AMP in smooth muscle cells, possibly resulting in bronchodilation. Theophylline also binds to the adenosine A2B receptor and blocks adenosine mediated bronchoconstriction. In inflammatory states, theophylline activates histone deacetylase to prevent transcription of inflammatory genes that require the acetylation of histones for transcription to begin.
Hydrochlorothiazide, a thiazide diuretic, inhibits water reabsorption in the nephron by inhibiting the sodium-chloride symporter (SLC12A3) in the distal convoluted tubule, which is responsible for 5% of total sodium reabsorption. Normally, the sodium-chloride symporter transports sodium and chloride from the lumen into the epithelial cell lining the distal convoluted tubule. The energy for this is provided by a sodium gradient established by sodium-potassium ATPases on the basolateral membrane. Once sodium has entered the cell, it is transported out into the basolateral interstitium via the sodium-potassium ATPase, causing an increase in the osmolarity of the interstitium, thereby establishing an osmotic gradient for water reabsorption. By blocking the sodium-chloride symporter, hydrochlorothiazide effectively reduces the osmotic gradient and water reabsorption throughout the nephron.
Nilutamide competes with androgen for the binding of androgen receptors, consequently blocking the action of androgens of adrenal and testicular origin that stimulate the growth of normal and malignant prostatic tissue. This blockade of androgen receptors may result in growth arrest or transient tumor regression through inhibition of androgen-dependent DNA and protein synthesis.
Clofibrate increases the activity of extrahepatic lipoprotein lipase (LL), thereby increasing lipoprotein triglyceride lipolysis. Chylomicrons are degraded, VLDLs are converted to LDLs, and LDLs are converted to HDL. This is accompanied by a slight increase in secretion of lipids into the bile and ultimately the intestine. Clofibrate also inhibits the synthesis and increases the clearance of apolipoprotein B, a carrier molecule for VLDL. Also, as a fibrate, Clofibrate is an agonist of the PPAR-‘± receptor[4] in muscle, liver, and other tissues. This agonism ultimately leads to modification in gene expression resulting in increased beta-oxidation, decreased triglyceride secretion, increased HDL, increased lipoprotein lipase activity.
Didanosine (ddI) is metabolized intracellularly by a series of cellular enzymes to its active moiety, dideoxyadenosine triphosphate (ddATP), which inhibits the HIV reverse transcriptase enzyme competitively by competing with natural dATP. It also acts as a chain terminator by its incorporation into viral DNA as the lack of a 3'-OH group in the incorporated nucleoside analogue prevents the formation of the 5' to 3' phosphodiester linkage essential for DNA chain elongation, and therefore, the viral DNA growth is terminated.
Lovastatin is structurally similar to the HMG, a substituent of the endogenous substrate of HMG-CoA reductase. Lovastatin is a prodrug that is activated <i>in vivo</i> via hydrolysis of the lactone ring to form the ‘_-hydroxyacid. The hydrolyzed lactone ring mimics the tetrahedral intermediate produced by the reductase allowing the agent to bind to HMG-CoA reductase with 20,000 times greater affinity than its natural substrate. The bicyclic portion of lovastatin binds to the coenzyme A portion of the active site.
Simvastatin is a prodrug in which the 6-membered lactone ring of simvastatin is hydrolyzed <i>in vivo</i> to generate the beta,delta-dihydroxy acid, an active metabolite structurally similar to HMG-CoA (hydroxymethylglutaryl CoA). Once hydrolyzed, simvastatin competes with HMG-CoA for HMG-CoA reductase, a hepatic microsomal enzyme. Interference with the activity of this enzyme reduces the quantity of mevalonic acid, a precursor of cholesterol.
Troglitazone is a thiazolidinedione antidiabetic agent that lowers blood glucose by improving target cell response to insulin. It has a unique mechanism of action that is dependent on the presence of insulin for activity. Troglitazone decreases hepatic glucose output and increases insulin dependent glucose disposal in skeletal muscle. Its mechanism of action is thought to involve binding to nuclear receptors (PPAR) that regulate the transcription of a number of insulin responsive genes critical for the control of glucose and lipid metabolism. Troglitazone is a ligand to both PPAR‘± and PPAR‘_, with a highter affinity for PPAR‘_. The drug also contains an ‘±-tocopheroyl moiety, potentially giving it vitamin E-like activity. Troglitazone has  been shown to reduce inflammation, and is associated with a decrase in nuclear factor kappa-B (NF-‘_B) and a concomitant increase in its inhibitor (I‘_B). NF-‘_B is an important cellular transcription regulator for the immune response. Unlike sulfonylureas, troglitazone is not an insulin secretagogue.
Estriol levels can be measured to give an indication of the general health of the fetus. DHEA-S is produced by the adrenal cortex of the fetus. This is converted to estriol by the placenta. If levels of "unconjugated estriol" are abnormally low in a pregnant woman, this may indicate a problem with the development of the child. The drug interacts with a target cell receptor. When the estrogen receptor has bound its ligand it can enter the nucleus of the target cell, and regulate gene transcription which leads to formation of messenger RNA. The mRNA interacts with ribosomes to produce specific proteins that express the effect of estriol upon the target cell. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary.
Mestranol is the 3-methyl ether of ethinylestradiol. Ethinylestradiol, is a synthetic derivative of estradiol. Ethinylestradiol is orally bio-active and the estrogen used in almost all modern formulations of combined oral contraceptive pills.  It binds to (and activates) the estrogen receptor. Mestranol is a biologically inactive prodrug of ethinylestradiol to which it is demethylated in the liver with a conversion efficiency of 70%.



Estrogens diffuse into their target cells and interact with a protein receptor. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary. The combination of an estrogen with a progestin suppresses the hypothalamic-pituitary system, decreasing the secretion of gonadotropin-releasing hormone (GnRH).
Anastrozole selectively inhibits aromatase. The principal source of circulating estrogen (primarily estradiol) is conversion of adrenally-generated androstenedione to estrone by aromatase in peripheral tissues. Therefore, aromatase inhibition leads to a decrease in serum and tumor concentration of estrogen, leading to a decreased tumor mass or delayed progression of tumor growth in some women. Anastrozole has no detectable effect on synthesis of adrenal corticosteroids, aldosterone, and thyroid hormone. Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
The exact mechanism of action of azelaic acid is not known. It is thought that azelaic acid manifests its antibacterial effects by inhibiting the synthesis of cellular protein in anaerobic and aerobic bacteria, especially <i>Staphylococcus epidermidis</i> and <i>Propionibacterium acnes</i>. In aerobic bacteria, azelaic acid reversibly inhibits several oxidoreductive enzymes including tyrosinase, mitochondrial enzymes of the respiratory chain, thioredoxin reductase, 5-alpha-reductase, and DNA polymerases. In anaerobic bacteria, azelaic acid impedes glycolysis. Along with these actions, azelaic acid also improves acne vulgaris by normalizing the keratin process and decreasing microcomedo formation. Azelaic acid may be effective against both inflamed and noninflamed lesions. Specifically, azelaic acid reduces the thickness of the stratum corneum, shrinks keratohyalin granules by reducing the amount and distribution of filaggrin (a component of keratohyalin) in epidermal layers, and lowers the number of keratohyalin granules.
Letrozole is a nonsteroidal competitive inhibitor of the aromatase enzyme system; it inhibits the conversion of androgens to estrogens. In adult nontumor- and tumorbearing female animals, letrozole is as effective as ovariectomy in reducing uterine weight, elevating serum Leuteinizing hormone (LH), and causing the regression of estrogen-dependent tumors. In contrast to ovariectomy, treatment with letrozole does not lead to an increase in serum (folicile stimulating hormone (FSH). Letrozole selectively inhibits gonadal steroidogenesis but has no significant effect on adrenal mineralocorticoid or glucocorticoid synthesis. Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
Aminoglutethimide reduces the production of D5-pregnenolone and blocks several other steps in steroid synthesis, including the C-11, C-18, and C-21 hydroxylations and the hydroxylations required for the aromatization of androgens to estrogens, mediated through the binding of aminoglutethimide to cytochrome P-450 complexes. Specifically, the drug binds to and inhibits aromatase which is essential for the generation of estrogens from androstenedione and testosterone. A decrease in adrenal secretion of cortisol is followed by an increased secretion of pituitary adrenocorticotropic hormone (ACTH), which will overcome the blockade of adrenocortical steroid synthesis by aminoglutethimide. The compensatory increase in ACTH secretion can be suppressed by the simultaneous administration of hydrocortisone. Since aminoglutethimide increases the rate of metabolism of dexamethasone but not that of hydrocortisone, the latter is preferred as the adrenal glucocorticoid replacement. Although aminoglutethimide inhibits the synthesis of thyroxine by the thyroid gland, the compensatory increase in thyroid-stimulating hormone (TSH) is frequently of sufficient magnitude to overcome the inhibition of thyroid synthesis due to aminoglutethimide. In spite of an increase in TSH, aminoglutethimide has not been associated with increased prolactin secretion.
Oxybenzone absorbs UV-A ultraviolet rays, preventing them from reaching the skin.
Fluorescein sodium is used extensively as a diagnostic tool in the field of ophthalmology. Fluorescein is a fluorescent compound or fluorophore having a maximum absorbance of 494 m and an emission maximum of 521 nm. The yellowish-green fluorescence of the compound  can be used to demarcate the vascular area under observation, distinguishing it from adjacent areas. It is applied topically in the form of a drop or it can be injected intravenously to produce a fluorescein angiogram. Topical fluorescein is a useful tool in the diagnosis of corneal abrasions, corneal ulcers, herpetic corneal infections, and dry eye. Fluorescein angiography is used to diagnose and categorize macular degeneration, diabetic retinopathy, inflammatory intraocular conditions, and intraocular tumors.
Gemfibrozil increases the activity of extrahepatic lipoprotein lipase (LL), thereby increasing lipoprotein triglyceride lipolysis. It does so by activating Peroxisome proliferator-activated receptor-alpha (PPAR‘±) 'transcription factor ligand', a receptor that is involved in metabolism of carbohydrates and fats, as well as adipose tissue differentiation. This increase in the synthesis of lipoprotein lipase thereby increases the clearance of triglycerides. Chylomicrons are degraded, VLDLs are converted to LDLs, and LDLs are converted to HDL. This is accompanied by a slight increase in secretion of lipids into the bile and ultimately the intestine. Gemfibrozil also inhibits the synthesis and increases the clearance of apolipoprotein B, a carrier molecule for VLDL.
Alpha Linolenic Acid or ALA is considered an essential fatty acid because it is required for human health, but cannot be synthesized by humans. It is in fact  a plant-derived fatty acid. Humans can synthesize other omega-3 fatty acids from ALA, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA is a precursor of the series-3 prostaglandins, the series-5 leukotrienes and the series-3 thromboxanes. These eicosanoids have anti-inflammatory and anti-atherogenic properties. ALA metabolites may also inhibit the production of the pro-inflammatory eicosanoids, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4), as well as the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). Omega-3 fatty acids like ALA and its byproducts can modulate the expression of a number of genes, including those involved with fatty acid metabolism and inflammation. They regulate gene expression through their effects on the activity of transcription factors including NF-kappa B and members of the peroxisome proliferator-activated receptor (PPAR) family. Incorporation of ALA and its metabolites in cell membranes can affect membrane fluidity and may play a role in anti-inflammatory activity, inhibition of platelet aggregation and possibly in anti-proliferative actions of ALA. ALA is first metabolized by delta6 desaturease into steridonic acid.
Although the exact mechanism of action is not known, studies have shown that masoprocol is a potent 5-lipoxygenase inhibitor and has antiproliferative activity against keratinocytes in tissue culture, but the relationship between this activity and its effectiveness in actinic keratoses is unknown. Masoprocol also inhibits prostaglandins but the significance of this action is not yet known.
Salicylic acid directly and irreversibly inhibits the activity of both types of cyclo-oxygenases (COX-1 and COX-2) to decrease the formation of precursors of prostaglandins and thromboxanes from arachidonic acid.  Salicylate may competitively inhibit prostaglandin formation. Salicylate's antirheumatic (nonsteroidal anti-inflammatory) actions are a result of its analgesic and anti-inflammatory mechanisms. Salicylic acid is a key ingredient in many skin-care products for the treatment of acne, psoriasis, calluses, corns, keratosis pilaris, and warts. It works by causing the cells of the epidermis to slough off more readily, preventing pores from clogging up, and allowing room for new cell growth. Because of its effect on skin cells, salicylic acid is used in several shampoos used to treat dandruff. Salicylic acid is also used as an active ingredient in gels which remove verrucas (plantar warts). Salicylic acid inhibits the oxidation of uridine-5-diphosphoglucose (UDPG) competitively with nicotinamide adenosine dinucleotide (NAD) and noncompetitively with UDPG. It also competitively inhibits the transferring of glucuronyl group of uridine-5-phosphoglucuronic acid (UDPGA) to the phenolic acceptor. The wound-healing retardation action of salicylates is probably due mainly to its inhibitory action on mucopolysaccharide synthesis.
Binds to riboflavin hydrogenase, riboflavin kinase, and riboflavin synthase. Riboflavin is the precursor of flavin mononucleotide (FMN, riboflavin monophosphate) and flavin adenine dinucleotide (FAD). The antioxidant activity of riboflavin is principally derived from its role as a precursor of FAD and the role of this cofactor in the production of the antioxidant reduced glutathione. Reduced glutathione is the cofactor of the selenium-containing glutathione peroxidases among other things. The glutathione peroxidases are major antioxidant enzymes. Reduced glutathione is generated by the FAD-containing enzyme glutathione reductase.
Bicalutamide competes with androgen for the binding of androgen receptors, consequently blocking the action of androgens of adrenal and testicular origin which stimulate the growth of normal and malignant prostatic tissue. Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)
The mechanism of action of Finasteride is based on its preferential inhibition of Type II 5a-reductase through the formation of a stable complex with the enzyme. Inhibition of Type II 5a-reductase blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations, minimal to moderate increase in serum testosterone concentrations, and substantial increases in prostatic testosterone concetrations. As DHT appears to be the principal androgen responsible for stimulation of prostatic growth, a decrease in DHT concentrations will result in a decrease in prostatic volume (approximately 20-30% after 6-24 months of continued therapy). In men with androgenic alopecia, the mechanism of action has not been fully determined, but finasteride has shown to decrease scalp DHT concentration to the levels found in hairy scalp, reduce serum DHT, increase hair regrowth, and slow hair loss.
Gentian Violet is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
CP-122721 is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
4-Tert-butylphenol is structurally similar to the melanin precursor tyrosine, and acts as a substrate for tyrosinase. Tyrosinase oxidizes 4-tert-butylphenol to a quinone (4-tert-butylcyclohexa-3,5-diene-1,2-dione) which in turn rapidly reacts with glutathione (GSH). A depletion of the GSH defence system may allow the quinone to generate reactive oxygen species that damage melanocytes and induce apoptosis, leading to leukoderma/vitiligo. (A15209, A15210)
BHT is metabolized to quinone methides (QMs) which are responsible for promoting tumor formation in many animal models. One example of a QM is 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM). QMs are strongly electrophilic and readily form adducts with proteins. Some of the QM targets include redox proteins such as glutathione S-transferase P1 (GST-P1), peroxiredoxin 6 (Prx6), Cu,Zn-superoxide dismutase (SOD1), carbonyl reductase, and selenium-binding protein 1, which have direct or indirect antioxidant functions. (A15087, A15355). The modification of these proteins leads to decreased cellular protection from electrophiles and oxidants. Alkylation also may interfere with GSTP1 regulation of stress kinases, thereby influencing phosphorylation and cell growth.  BHT also binds to the retinoic acid receptor which can lead to changes in cell development.
Paraoxon is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death.  Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.
One of the metabolites of diflubenzuron, PCA, is a proximate carcinogen. It is conjugated to form the carcinogen that can ionize and reat with DNA to form adducts which result in splenic tumor formation.
1-Nitronaphthalene and its reactive products specifically targets the airway epithelium. Its toxicity is synergized by prior long-term ozone exposure. 1-NN appears to specifically target peroxiredoxin 6 and biliverdin reductase as well as the N-terminal region of calreticulin.
Tritium is an isotope of hydrogen, which allows it to readily bind to hydroxyl radicals, forming tritiated water (HTO), and to carbon atoms. Since tritium is a low energy beta emitter, it is not dangerous externally (its beta particles are unable to penetrate the skin), but it is a radiation hazard when inhaled, ingested via food or water, or absorbed through the skin. Beta particles are able to penetrate living matter to a certain extent and can change the structure of struck molecules. In most cases, such change can be considered to be damage, with results possibly as severe as cancer or death. If the struck molecule is DNA, it can cause spontaneous mutation. (Wikipedia)
Acts as a neurotransmitter mimic , having both excitatory and depressant effects, eventually blocking postsynaptic nicotinic receptors. (T10)
Both hydrogen chloride gas and hydrochloric acid are highly corrosive.  Many strong acids cause tissue burns through the denaturation of proteins and partial hydrolysis of proteins. Most proteins denature at pH values of less than 3-4.  The large-scale denaturation of proteins, de-esterification of lipids and subsequent desiccation of tissues leads to chemical burns. Symptoms include itching, bleaching or darkening of skin or tissues, blistering and burning sensations.
Sodium hypochlorite is a strong oxidizer. Oxidation reactions are corrosive, solutions burn skin and cause eye damage, especially when used in concentrated forms. In particular, hypochorite (HOCl) is known to cause post-translational modifications to amino acids in proteins, the notable ones being cysteine and methionine oxidation. These oxidation reactions can lead to widespread protein aggregation and denaturation, leading to cell death and tissue damage.  It is estimated that there are about 3300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes. A recent European study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated volatile organic compounds (VOCs). Some of these VOCs are toxic and probable human carcinogens. The study showed that indoor air concentrations significantly increase (8-52 times for chloroform and 1-1170 times for carbon tetrachloride, respectively, above baseline quantities in the household) during the use of bleach containing products.  Sodium Hypochlorite reacts violently with amines and ammonium salts. Solutions are reactive with common cleaning products such as toilet bowl cleaners, rust removers, vinegar, acids, organics and ammonia products to produce hazardous gases such as chlorine and other chlorinated species.
The bromide ion is also known to affect the central nervous system, causing bromism. This is believed to be a result of bromide ions substituting for chloride ions in the in actions of neurotransmitters and transport systems, thus affecting numerous synaptic processes. (L626, L627, A543)
Chlorine is a strong oxidizer that hydrolyzes in water forming hydrochloric and hypochlorous acids. In this form, it can penetrate the cell and form N-chloro-derivatives that can damage cellular integrity. Chlorine reacts with water in the epithelial lining of the upper respiratory airways. The mechanism of toxicity of aqueous chlorine or a hypochlorous acid/sodium hypochlorite is basically the same as that for chlorine gas. However, hypochlorous acid is a stronger oxidant than chlorine gas as reflected by its higher redox potential. Damage to the upper gastrointestinal tract, as may occur following ingestion of sodium hypochlorite bleach, is likely the result of oxidation reactions of hypochlorous acid with a range of biological molecules.
Cobalt is believed to exhibit its toxicity through a oxidant-based and free radical-based processes. It produces oxygen radicals and may be oxidized to ionic cobalt, causing increased lipid peroxidation, DNA damage, and inducing certain enzymes that lead to cell apoptosis. Cobalt has also been shown to block inorganic calcium channels, possibly impairing neurotransmission. Cobalt can also chelate lipoic acids, impairing oxidation of pyruvate or fatty acids. In addition, cobalt may inhibit DNA repair by interacting with zinc finger DNA repair proteins, and has also been shown to inhibit heme synthesis and glucose metabolism. Cobalt may activate specific helper T-lymphocyte cells and interact directly with immunologic proteins, such as antibodies (IgA and IgE) or Fc receptors, resulting in immunosensitization. Radioactive cobalt damages DNA, RNA, and lipids through ionizing events. (L29)
Clomifene has both estrogenic and anti-estrogenic properties, but its precise mechanism of action has not been determined. Clomifene appears to stumulate the release of gonadotropins, follicle-stimulating hormone (FSH), and leuteinizing hormone (LH), which leads to the development and maturation of ovarian follicle, ovulation, and subsequent development and function of the coprus luteum, thus resulting in pregnancy. Gonadotropin release may result from direct stimulation of the hypothalamic-pituitary axis or from a decreased inhibitory influence of estrogens on the hypothalamic-pituitary axis by competing with the endogenous estrogens of the uterus, pituitary, or hypothalamus. Clomifene has no apparent progestational, androgenic, or antrandrogenic effects and does not appear to interfere with pituitary-adrenal or pituitary-thyroid function.
The pharmacologic effects of edetate calcium disodium are due to the formation of chelates with divalent and trivalent metals. A stable chelate will form with any metal that has the ability to displace calcium from the molecule, a feature shared by lead, zinc, cadmium, manganese, iron and mercury. The amounts of manganese and iron metabolized are not significant. Copper is not mobilized and mercury is unavailable for chelation because it is too tightly bound to body ligands or it is stored in inaccessible body compartments. The excretion of calcium by the body is not increased following intravenous administration of edetate calcium disodium, but the excretion of zinc is considerably increased.
Cytarabine acts through direct DNA damage and incorporation into DNA. Cytarabine is cytotoxic to a wide variety of proliferating mammalian cells in culture. It exhibits cell phase specificity, primarily killing cells undergoing DNA synthesis (S-phase) and under certain conditions blocking the progression of cells from the G1 phase to the S-phase. Although the mechanism of action is not completely understood, it appears that cytarabine acts through the inhibition of DNA polymerase. A limited, but significant, incorporation of cytarabine into both DNA and RNA has also been reported.
The pharmacologic effects of isoproterenol are at least in part attributable to stimulation through beta-adrenergic receptors of intracellular adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic AMP. Increased cyclic AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells.
Atorvastatin selectively and competitively inhibits the hepatic enzyme HMG-CoA reductase. As HMG-CoA reductase is responsible for converting HMG-CoA to mevalonate in the cholesterol biosynthesis pathway, this results in a subsequent decrease in hepatic cholesterol levels. Decreased hepatic cholesterol levels stimulates upregulation of hepatic LDL-C receptors which increases hepatic uptake of LDL-C and reduces serum LDL-C concentrations.
Pioglitazone acts as an agonist at peroxisome proliferator activated receptors (PPAR) in target tissues for insulin action such as adipose tissue, skeletal muscle, and liver. Activation of PPAR-gamma receptors increases the transcription of insulin-responsive genes involved in the control of glucose production, transport, and utilization. In this way, pioglitazone both enhances tissue sensitivity to insulin and reduces hepatic gluconeogenesis. Thus, insulin resistance associated with type 2 diabetes mellitus is improved without an increase in insulin secretion by pancreatic β cells.
Dexamethasone is a glucocorticoid agonist. Unbound dexamethasone crosses cell membranes and binds with high affinity to specific cytoplasmic glucocorticoid receptors. This complex binds to DNA elements (glucocorticoid response elements) which results in a modification of transcription and, hence, protein synthesis in order to achieve inhibition of leukocyte infiltration at the site of inflammation, interference in the function of mediators of inflammatory response, suppression of humoral immune responses, and reduction in edema or scar tissue. The antiinflammatory actions of dexamethasone are thought to involve phospholipase A<sub>2</sub> inhibitory proteins, lipocortins, which control the biosynthesis of potent mediators of inflammation such as prostaglandins and leukotrienes.
Tiratricol is a naturally occurring metabolite of T4 (thyroxine) and a structural analog of T3 (triiodothyronine). Low concentrations of tiratricol are found in plasma, but tiratricol has no known role in thyroid physiology. Tiratricol has a high affinity for T3 receptors and suppresses thyroid stimulating hormone (TSH) secretion at therapeutic doses without causing significant peripheral effects, such as increased basal metabolism rate and heart rate. Tiratricol might lower total and LDL cholesterol, and stimulate bone formation. About 67% of an oral dose of tiratricol is absorbed; the half-life is 6 hours. (L2139) Serum sex hormone-binding globulin levels increased 55 +/- 13% with tiratricol, indicating an augmented hepatic response to tiratricol. Tiratricol had effected the cardiovascular function. Tiratricol has distinct augmented hepatic and skeletal thyromimetic actions of potential therapeutic value. (A15458)
Aniline induces lipid peroxidation and protein oxidation in the spleen and that oxidative stress plays a role in the splenic toxicity of aniline. The hematopoietic system is the primary target of aniline insult in rats which is characterized by methemoglobinemia, hemolysis, and hemolytic anemia and by the development of splenic hyperplasia, siderosis, fibrosis, a variety of sarcomas, and, most commonly, fibrosarcomas on prolonged exposure. Many of the characteristics of splenotoxicity in rats, such as hyperplasia, hyperpigmentation, and/or formation of highly malignant tumors such as fibrosarcomas, are not restricted to aniline exposure, but also occur when animals are exposed to substituted anilines such as chloroaniline. Studies with aniline hydrochloride in rats indicate an association between erythrocyte damage and the severity of the splenotoxicity. Since one of the major functions of the spleen is to remove damaged erythrocytes, aniline-damaged erythrocytes would be expected to be scavenged by the spleen, especially by phagocytes. The deposition and subsequent breakdown of damaged erythrocytes will not only release aniline and/or its metabolites, but, most importantly, will also result in accumulation of iron in the spleen which may catalyze the generation of tissue-damaging oxygen radicals which can subsequently cause oxidation of biomolecules and result in lipid peroxidation and protein oxidation. It is also possible that during the scavenging of damaged erythrocytes, the splenic phagocytes, especially macrophages themselves, can become activated and release reactive oxygen species (ROS) which could further contribute to the oxidation of biomolecules leading to tissue injury. (A15460)
Cinnamaldehyde is an allergen. The physiologic effect of cinnamaldehyde is by means of increased histamine release and cell-mediated immunity.
p-Anisidine reacts with secondary oxidation products such as aldehydes and ketones in fats and oils. (Wikipedia)
9-phenanthrol is a recently identified inhibitor of the transient receptor potential melastatin (TRPM) 4 channel, a Ca(2+) -activated non-selective cation channel whose mechanism of action remains to be determined. 9-phenanthrol modulates a variety of physiological processes through TRPM4 current inhibition. 9-Phenanthrol modulates smooth muscle contraction in bladder and cerebral arteries, affects spontaneous activity in neurons and in the heart, and reduces lipopolysaccharide-induced cell death. 9-phenanthrol exerts cardioprotective effects against ischaemia-reperfusion injuries and reduces ischaemic stroke injuries. (A15462) The most specific inhibitor of TRPM4 channels currently available is 9-phenanthrol, which abolishes arrhythmias induced by hypoxia and reoxygenation in the mouse ventricle. TRPM4 has been linked to diverse physiological functions such as protection against Ca2+ overload, regulating the levels of intracellular ATP and reactive oxygen species, and cell death. TRPM4 in neurons contributes toward inflammation-induced neurodegeneration by mediating cell death, which corresponds to the cardioprotective effect of 9-phenanthrol. Damage induced by ischemia/reperfusion (I/R) was caused by TPRM4-dependent cell death and that 9-phenanthorol induces cardioprotection by blocking this pathway. (A15463)
The liver damage caused in rats by 1,3-dichlorobenzene is accompanied by induction of xenobiotic metabolizing enzymes of the phenobarbital type. In rats, a disturbance in thyroid homoeostasis can develop by hepatic enzyme induction: 1,3-dichlorobenzene induces glucuronosyl transferases. The conjugation of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) is increased by the induction of glucuronosyl transferases. This leads to an increased release of T4 and T3 in the thyroid follicles.
Hydroxyflutamide is an antiandrogen. Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting androgen production. Antiandrogens are classified as steroidal or nonsteroidal. Steroidal antiandrogens not only counter androgens, but also affect secondary sex characteristics. Steroidal antiandrogens directly affect gene expression due to their fat-soluble nature that allows them to diffuse through the plasma membrane's phospholipid bilayer and prevent the binding of testosterone and dihydrotestosterone (DHT) to the androgen receptor. Inhibition of androgen production occurs through a unique mechanism for each antiandrogen. (Wikipedia)
Ivermectin binds selectively and with high affinity to glutamate-gated chloride ion channels in invertebrate muscle and nerve cells of the microfilaria. This binding causes an increase in the permeability of the cell membrane to chloride ions and results in hyperpolarization of the cell, leading to paralysis and death of the parasite. Ivermectin also is believed to act as an agonist of the neurotransmitter gamma-aminobutyric acid (GABA), thereby disrupting GABA-mediated central nervous system (CNS) neurosynaptic transmission. Ivermectin may also impair normal intrauterine development of O. volvulus microfilariae and may inhibit their release from the uteri of gravid female worms. It has low solubility in water and extensive non-specific binding. It opens GABA-insensitive chloride channels, reducing membrane resistance and increasing conductance inward. (T10)
Ivermectin binds selectively and with high affinity to glutamate-gated chloride ion channels in invertebrate muscle and nerve cells of the microfilaria. This binding causes an increase in the permeability of the cell membrane to chloride ions and results in hyperpolarization of the cell, leading to paralysis and death of the parasite. Ivermectin also is believed to act as an agonist of the neurotransmitter gamma-aminobutyric acid (GABA), thereby disrupting GABA-mediated central nervous system (CNS) neurosynaptic transmission. Ivermectin may also impair normal intrauterine development of O. volvulus microfilariae and may inhibit their release from the uteri of gravid female worms. It has low solubility in water and extensive non-specific binding. It opens GABA-insensitive chloride channels, reducing membrane resistance and increasing conductance inward. (T10)
Many strong acids cause tissue burns through the denaturation of proteins and partial hydrolysis of proteins.  Most proteins denature at pH values of less than 3-4.  The large-scale denaturation of proteins, de-esterification of lipids and subsequent desiccation of tissues leads to chemical burns.  Symptoms include itching, bleaching or darkening of skin or tissues, blistering and burning sensations. More specifically, sulfuric acid readily decomposes proteins and lipids through amide hydrolysis and ester hydrolysis upon contact with living tissues. In addition, it exhibits a strong dehydrating property on carbohydrates, liberating extra heat and causing secondary thermal burns. The strong oxidizing property may also extend its corrosiveness on the tissue. Because of such reasons, damage posed by sulfuric acid is potentially more severe than that caused by other comparable strong acids, such as hydrochloric acid and nitric acid.