Regulation of delayed prostaglandin production in activated P388D1 macrophages by Group IV cytosolic and Group V secretory phospholipase A2s

Group V secretory phospholipase A(2) (sPLA(2)) rather than Group IIA sPLA(2) is involved in short term, immediate arachidonic acid mobilization and prostaglandin E-2 (PGE(2)) production in the macrophage-like cell line P388D(1). When a new clone of these cells, P388D(1)/MAB, selected on the basis of high responsivity to lipopolysaccharide plus platelet-activating factor, was studied, delayed PGE(2) production (6-24 h) in response to lipopolysaccharide alone occurred in parallel with the induction of Group V sPLA(2) and cyclooxygenase-a (COX-2), No changes in the level of cytosolic phospholipase A(2) (cPLA(2)) or COX-1 were observed, and Group IIA sPLA(2) was not detectable. Use of a potent and selective sPLA(2) inhibitor, 3-(3-acetamide 1-benzyl-2-ethylindolyl-5-oxy)-propanesulfonic acid (LY311727), and an antisense oligonucleotide specific for Group V sPLA(2) revealed that delayed PGE, was largely dependent on the induction of Group V sPLA(2). Also, COX-2, not COX-1, was found to mediate delayed PGE(2) production because the response was completely blocked by the specific COX-2 inhibitor NS-398, Delayed PGE(2) production and Group V sPLA(2) expression were also found to be blunted by the inhibitor methylarachidonyl fluorophosphonate, Because inhibition of Ca2+-independent PLA(2) by an antisense technique did not have any effect on the arachidonic acid release, the data using methylarachidonyl fluorophosphonate suggest a key role for the cPLA(2) in the response as well. Collectively, the results suggest a model whereby cPLA(2) activation regulates Group V sPLA(2) expression, which in turn is responsible for delayed PGE(2) production via COX-2.