Lipoprotein-Associated Phospholipase A2, Platelet-Activating Factor Acetylhydrolase, Is Expressed by Macrophages in Human and Rabbit Atherosclerotic Lesions

Abstract—We studied the expression of lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzyme capable of hydrolyzing platelet-activating factor (PAF), PAF-like phospholipids, and polar-modified phosphatidylcholines, in human and rabbit atherosclerotic lesions. Oxidative modification of low-density lipoprotein, which plays an important role in atherogenesis, generates biologically active PAF-like modified phospholipid derivatives with polar fatty acid chains. PAF is known to have a potent proinflammatory activity and is inactivated by its hydrolysis. On the other hand, lysophosphatidylcholine and oxidized fatty acids released from oxidized low-density lipoprotein as a result of Lp-PLA2 activity are thought to be involved in the progression of atherosclerosis. Using combined in situ hybridization and immunocytochemistry, we detected Lp-PLA2 mRNA and protein in macrophages in both human and rabbit atherosclerotic lesions. Reverse transcriptase—polymerase chain reaction analysis indicated an increased ex...