LIPID HYDROPEROXIDE-INDUCED PEROXIDATION AND TURNOVER OF ENDOTHELIAL-CELL PHOSPHOLIPIDS

The effects of lipid peroxidation on rabbit aortic endothelial cell ph ospholipid turnover was studied using linoleic acid hydroperoxide (LOO H). Following treatments with 20-40 mu M LOOH, cells prelabeled with e ither arachidonic acid (20:4) or oleic acid (18:1) showed a movement o f these fatty acids out of the phospholipids and into neutral lipid an d free fatty acid pools. There was also a release of radioactive free fatty acids and phospholipids into the media, which was significantly increased as compared to cells maintained under standard culture condi tions. Fatty acid uptake and distribution among phospholipid pools was also affected by LOOH treatment where incorporation of 20:4 and 18:1 into phosphatidylcholine (PC) decreased, while uptake into phosphatidy linositol (PI) increased after 1 h of incubation with 40 mu M LOOH. Th ese effects were also inhibited by vitamin E. In cells prelabeled with 20:4 or 18:1 under conditions where approximately 99% of the fatty ac ids were incorporated into neutral and phospholipid pools, LOOH treatm ent produced a decrease in radioactivity associated with PC, while the specific activity of PI increased. The extent of these changes was gr eater for 20:4 than 18:1. but in each case the effects were inhibited by Vitamin E. The temporal pattern of uptake for labeled choline and i nositol after LOOH treatments paralleled those found for fatty acid in corporation. These cell responses indicate that induction of lipid per oxidation produces rapid fatty acid release and phospholipid turnover involving repair as well as de novo synthesis. The implications of the se effects on turnover of specific phospholipids and cell responses to oxidative stress are discussed.