OXIDANT-INDUCED ARACHIDONIC-ACID RELEASE AND IMPAIRMENT OF FATTY-ACIDACYLATION IN VASCULAR SMOOTH-MUSCLE CELLS

Oxidative damage, which plays a major role in the early stages of athe rosclerosis, is associated with arachidonic acid (AA) release in vascu lar smooth muscle cells (VSMC) as in other cell types. In this study, H2O2 was used to investigate mechanisms of AA release from VSMC on oxi dative stress. Cell treatment with H2O2 inhibited AA incorporation in an inverse relationship to prolonged H2O2-induced AA release. Identica l kinetics of inhibition of AA incorporation and AA release were obser ved after cell treatment with AlF4-, a process not involving phospholi pase A(2) (PLA(2)) activation as recently described (A. Cane, M. Breto n, G. Bereziat, and O. Colard. Biochem. Pharmacol. 53: 327-337, 1997). AA release was not specific, since oleic acid also increased in the e xtracellular medium of cells treated with H2O2 or AlF4- as measured by gas chromatography-mass spectrometry. In contrast, AA and oleic acid cell content decreased after cell treatment. Oleoyl and arachidonoyl a cyl-CoA synthases and acyltransferases, assayed using a cell-free syst em, were not significantly modified. In contrast, a good correlation w as observed between decreases in AA acylation and cell ATP content. Th e decrease in ATP content is only partially accounted for by mitochond rial damage as assayed by rhodamine 123 assay. We conclude that oxidan t-induced arachidonate release results from impairment of fatty acid e sterification and that ATP availability is probably responsible for fr ee AA accumulation on oxidative stress by preventing its reesterificat ion and/or transmembrane transport.