Prostaglandin Synthesis in Human Cell Lines Mechanism of Stimulation by Human Interferon of Updated Version

Human interferon ß(IFN-/Î) stimulated the synthesis of prostaglandin E (PGE) and prostaglandin F2o in IFN-sensitive RSa and GM258 cell lines, but not in IFN-resistant HEC-1 cells. IFN-/S at a concentration of 1000 units/ml elicited 2to 3-fold increases in PGE production in these cell lines. In the presence of exogenous arachidonic acid (1 jug/ml), IFN-pretreated cells produced 5-fold more PGE compared to the cell cultures in the absence of arachidonic acid. Prednisolone, an inhibitor of phospholipase A2, at a concentration of 2 ¿ig/mlinhibited the enhanced synthesis of PGE by IFN-pretreated cells. Indomethacin (4 ftg/ml), a potent fatty acid cyclooxygenase inhibitor, also inhibited the increased synthesis of PGE. IFN stimulated the release of [14C]arachidonic acid from phospholipids but did not stimulate the activity of fatty acid cyclooxygenase. These data suggest that IFN stimulates prostaglandin synthesis by promoting the release of arachidonic acid from phospholipids. Since cycloheximide and actinomycin D inhibited the stimula tion of PGE synthesis, the stimulation of prostaglandin synthe sis by IFN seemed to be due to de novo enzyme synthesis which catalyzes the release of fatty acid. Addition of exogenous PGE suppressed the growth of RSa and GM258 cells. Prednisolone and iodomethacin partially inhibited anti-cell growth activity of IFN, suggesting a possibility that IFN-inhibited cell growth was partly mediated by prosta-