Translocation of phospholipase A 2 to membranes by oxidized LDL and hydroxyoctadecadienoic acid to contribute to cholesteryl ester formation

Abstract

We examined the mechanisms underlying the activation of group IVA cytosolic phospholipase A 2 (cPLA 2α) contributing to the supply of fatty acids required for the formation of cholesteryl ester in oxidized low-density lipoprotein (oxLDL)-stimulated macrophages. The possible involvement of oxidized lipids was also examined. In [ 3H]arachidonic acid-labeled mouse peritoneal macrophages, oxLDL stimulated the release of arachidonic acid, which was suppressed by methyl arachidonyl fluorophosphonate (MAFP), a cPLA 2α inhibitor. oxLDL induced an increase in PLA 2α levels in the membrane fraction without affecting those in whole cells or the activity in the lysate. Among 13-hydroxyoctadecadienoic acid (13-HODE), 7-ketocholesterol, and 25-hydroxycholesterol, oxidized lipids present in oxLDL particles, only 13-HODE induced the release of arachidonic acid, which was also sensitive to MAFP. Under conditions where addition of Ca 2+ to the cell lysate induced an increase in cPLA 2α protein in the membrane fraction, preincubation with 13-HODE facilitated the Ca 2+-dependent translocation of cPLA 2α. Furthermore, 13-HODE increased cholesteryl ester formation in the presence of [ 3H]cholesterol. These results suggest that 13-HODE mediates the oxLDL-induced activation of cPLA 2α through an increase in cPLA 2α protein in the membranes, thus contributing, in part, to the supply of fatty acids required for the esterification of cholesterol in macrophages.