In vitro formation of activators for prostaglandin synthesis by neutrophils and macrophages from humans and guinea pigs.

Prostaglandin H synthase, the primary enzyme in the pathway to the prostaglandins, requires the continued presence of a hydroperoxide activator for its enzyme activity. Phagocytic leukocytes from either humans or guinea pigs produced activator hydroperoxides in quantities sufficient to enhance prostaglandin synthesis in cells. Compounds that stimulated the oxidative burst (e.g., phorbol myristate acetate, opsonized zymosan, and N-formyl-L-methionyl-L-leucyl-L-phenylalanine) enhanced the overall production of the activators. Accumulation of activator(s) was promoted by exogenous Fe+3 (2 mumol/L), adenosine diphosphate (10 mumol/L), and unsaturated fatty acids (1 to 30 mumol/L) and was completely inhibited by glutathione peroxidase (0.5 U/ml). Catalase (500 U/ml) decreased the amount of activator by 70% when added during the incubation but by only 40% when added after the incubation. Thus, the activator appeared to be partly H2O2 and partly a lipid hydroperoxide. The addition of H2O2 in quantities similar to those produced by phagocytes increased prostaglandin formation by twofold in incubations with U937 cells and carbon 14-labeled arachidonic acid (2 mumol/L). These results indicate a new role for the oxygen metabolites from leukocytes in providing an intercellular signal that can stimulate prostaglandin synthesis.