Oxidized LDL activates phospholipase A2 to supply fatty acids required for cholesterol esterification

We examined the roles of phospholipase A2 (PLA2) in oxidized LDL (oxLDL)-induced cholesteryl ester formation in macrophages. In [3H]oleic acid-labeled RAW264.7 cells and mouse peritoneal macrophages, oxLDL induced [3H]cholesteryl oleate formation with an increase in free [3H]oleic acid and a decrease in [3H]phosphatidylcholine. The changes in these lipids were suppressed by methyl arachidonyl fluorophosphonate (MAFP), a cytosolic PLA2 (cPLA2) inhibitor. However, MAFP had no effect on the ACAT activity or the binding and/or uptake of oxLDL. Stimulation with oxLDL in the presence of [3H]cholesterol increased [3H]cholesteryl ester bearing fatty acyl chains derived from cellular and/or exogenous (oxLDL) lipids. The formation of cholesteryl ester under this condition was also inhibited by MAFP, and the inhibitory effect was reversed by adding oleic acid. While oxLDL did not affect the activity or amounts of cPLA2, preincubation with oxLDL enhanced the release of oleic acid and arachidonic acid induced by ionomycin in RAW264.7 cells. 13(S)-hydroxyoctadecadienoic acid, but not 7-ketocholesterol, also enhanced ionomycin-induced oleic acid release. These results suggest that oxLDL induces cPLA2 activation, which contributes, at least in part, to the supply of fatty acids required for the cholesteryl esterification, probably through the acceleration by oxidized lipids of the catalytic action of cPLA2 in macrophages.