Polycyclic aromatic hydrocarbons present in cigarette smoke cause endothelial cell apoptosis by a phospholipase A2-dependent mechanism

Smoking is a major risk factor for endothelial cell injury and subsequent coronary artery disease. Epidemiological studies implicate the phospholipase A(2)/arachidonic acid cascade in the mechanism by which smoking causes heart disease. However, specific components of cigarette smoke that activate this pathway have not been identified. The purpose of this study was to investigate the effects of polycyclic aromatic hydrocarbons contained in cigarette smoke on phospholipase A(2) (PLA(2)) activity and apoptosis of human coronary artery endothelial cells. 1-methylanthracene (1-MA), phenanthrene (PA), and benzo(a)pyrene (B(a)P) caused significant release of H-3-arachidonate from endothelial cells. 1-MA and PA, but not B(a)P, also caused significant release of H-3-linoleic acid. Release of fatty acids from membrane phospholipids preceded the onset of apoptosis. 3 H-arachidonate release and apoptosis induced by 1-MA, B(a)P, and PA were inhibited by methylarachidonoyl-fluorophosphonate, an inhibitor of Groups IV and VI PLA(2)s. Bromoenol lactone, an inhibitor of Group VI enzymes, inhibited both H-3-arachidonate release and apoptosis induced by 1-MA and PA, but not B(a)P. MJ33, an inhibitor of the acidic calcium-independent PLA(2), attenuated H-3-arachidonate release and apoptosis by PA, but not 1-MA or B(a)P. The presence of Groups IV and VI and the acidic iPLA(2) in endothelial cells was demonstrated by reverse transcriptase-polymerase chain reaction and Western analysis. These data suggest that 1-MA, B(a)P and PA induce apoptosis of endothelial cells by a mechanism that involves activation of these three distinct isoforms of PLA(2).