Antisense inhibition of group II phospholipase A2 expression blocks the production of prostaglandin E2 by P388D1 cells.

Macrophage-like P388D1 cells release [3H]arachidonic acid and produce prostaglandin E2 (PGE2) upon stimulation with bacterial lipopolysaccharide (LPS) and platelet-activating factor (PAF). To determine whether group II phospholipase A2 (PLA2) is involved in this release, we treated P388D1 cells with antisense inhibitors specific for group II PLA2 RNA. Treatment with oligonucleotide ASGII decreased PLA2 activity in P388D1 cell homogenates by approximately 60% and reduced the release of [3H]arachidonic acid and PGE2 from activated cells to nearly resting cell levels. The inhibition by antisense oligonucleotide ASGII was blocked when its sense complement, SGII, was included in the incubation mixture. Stably transfected P388D1 cells expressing an antisense construct for group II PLA2 also produced reduced quantities of PGE2 in response to LPS and PAF. These data suggest that prostaglandin production by activated P388D1 cells involves phospholipid hydrolysis by group II PLA2. Oligonucleotide ASGII also blocked the appearance of a heparin-releasable group II PLA2 in the culture supernatants of P388D1 cells. The disappearance of this protein correlated with reduced PGE2 production by activated cells, indicating that an extracellular heparin-associated pool of group II PLA2 is involved in prostaglandin production by P388D1 cells.