Role of platelet-activating factor acetylhydrolase on the inflammatory and apoptotic processes in atherosclerosis

Plasma platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme that belongs to group VII PLA2. Plasma PAF-AH circulates mostly bound to lipoproteins. Two-thirds of the enzyme are associated with low-density lipoprotein (LDL), whereas the rest is associated with high-density lipoprotein (HDL), and only a minor part is carried by very low-density lipoprotein (VLDL) and lipoprotein(a) (Lp(a)). PAF-AH hydrolyzes the acetyl or acyl groups at the sn-2 position of bioactive phospholipids, such as the platelet-activating factor (PAF), and of oxidized phosphatidylcholines. As a result, different biologically inactive (lyso-PAF, acetate) or active (lysophosphatidylcholine, oxidized fatty acids) products are produced. PAF-AH is involved in the inflammatory and apoptotic processes associated with atherosclerosis. However, there is no clear consensus regarding whether its role is protective or, on the contrary, accelerates the arteriosclerotic process. The present chapter discusses the main features of PAF-AH and its putative role in inflammation and apoptosis in atherosclerosis.