Polyunsaturated fatty acids potentiate interleukin-1-stimulated arachidonic acid release by cells overexpressing type IIA secretory phospholipase A2

By analyzing human embryonic kidney 293 cell transfectants stably overexpressing various types of phospholipase A2 (PLA2), we have shown that polyunsaturated fatty acids (PUFAs) preferentially activate type IIA secretory PLA2 (sPLA2-IIA)-mediated arachidonic acid (AA) release from interleukin-1 (IL-1)-stimulated cells. When 293 cells prelabeled with [3H]AA were incubated with exogenous PUFAs in the presence of IL-1 and serum, there was a significant increase in [3H]AA release (in the order AA>linoleic acid>oleic acid), which was augmented markedly by sPLA2-IIA and modestly by type IV cytosolic PLA2 (cPLA2), but only minimally by type VI Ca2+-independent PLA2, overexpression. Transfection of cPLA2 into sPLA2-IIA-expressing cells produced a synergistic increase in IL-1-dependent [3H]AA release and subsequent prostaglandin production. Our results support the proposal that prior production of AA by cPLA2 in cytokine-stimulated cells destabilizes the cellular membranes, thereby rendering them more susceptible to subsequent hydrolysis by sPLA2-IIA.