Release of arachidonate and reduction of oxygen. Independent metabolic bursts of the mouse peritoneal macrophage.

Abstract

Diverse particulate and soluble stimuli trigger two metabolic bursts in mouse peritoneal macrophages important in the inflammatory and/or cytotoxic actions of the cells: release, oxygenation, and further metabolism of arachidonic acid from endogenous phospholipids and reduction of molecular oxygen to reactive intermediates. We tested the hypothesis that the release of arachidonic acid or formation of its metabolites are obligatory intermediate steps in triggering the NADPH oxidase that reduces O2 to O-2. With phorbol diesters as stimuli, the following inhibitors of phospholipase A2 and lipoxygenase suppressed release of H2O2 at nontoxic concentrations (microM range): p-bromophenacyl bromide, quinacrine, eicosatetraenoic acid, nordihydroguaiaretic acid, and phenidone. Indomethacin and acetylsalicylic acid were ineffective. However, the suppressive effect of the first five agents on H2O2 release could be attributed to their suppression of macrophage glucose uptake at the same concentrations, a previously unrecognized effect of these compounds. Further, concanavalin A, wheat germ agglutinin, and thrombin each stimulated abundant arachidonate release without H2O2 release. Finally, noncytolytic concentrations of cycloheximide and/or emetine suppressed arachidonate release without affecting H2O2 secretion triggered either by phorbol esters or zymosan. Release and metabolism of arachidonic acid and secretion of reactive oxygen intermediates appear to be two frequently coincident but mutually independent metabolic pathways in the mouse peritoneal macrophage.