LysoPC(0:0/18:1(9Z)) is a lysophosphatidylcholine, which is a lysophospholipid. The term 'lysophospholipid' (LPL) refers to any phospholipid that is missing one of its two O-acyl chains. Thus, LPLs have a free alcohol in either the sn-1 or sn-2 position. The prefix 'lyso-' comes from the fact that lysophospholipids were originally found to be hemolytic however it is now used to refer generally to phospholipids missing an acyl chain. LPLs are usually the result of phospholipase A-type enzymatic activity on regular phospholipids such as phosphatidylcholine or phosphatidic acid, although they can also be generated by the acylation of glycerophospholipids or the phosphorylation of monoacylglycerols. Lysophosphatidylcholine is found in small amounts in most tissues. It is formed by hydrolysis of phosphatidylcholine by the enzyme phospholipase A2 as part of the de-acylation/re-acylation cycle that controls its overall molecular species composition. It can also be formed inadvertently during extraction of lipids from tissues if the phospholipase is activated by careless handling. There is also a phospholipase A1, which is able to cleave the sn-1 ester bond. Lysophosphatidylcholine has pro-inflammatory properties in vitro and it is known to be a pathological component of oxidized lipoproteins (LDL) in plasma and of atherosclerotic lesions. Recently, it has been found to have some functions in cell signalling, and specific receptors (coupled to G proteins) have been identified. It activates the specific phospholipase C that releases diacylglycerols and inositol triphosphate with resultant increases in intracellular Ca2+ and activation of protein kinase C. It also activates the mitogen-activated protein kinase in certain cell types. Lysophosphatidylcholines can have different combinations of fatty acids of varying lengths and saturation attached at the C-1 (sn-1) or C-2 (sn-2) position. LysoPC(0:0/18:1(9Z)), in particular, consists of one chain of oleic acid at the C-2 position.