INDUCTION OF CYCLOOXYGENASE AND NITRIC-OXIDE SYNTHASE IN ENDOTOXIN-ACTIVATED J774 MACROPHAGES IS DIFFERENTIALLY REGULATED BY INDOMETHACIN -ENHANCED CYCLOOXYGENASE-2 PROTEIN EXPRESSION BUT REDUCTION OF INDUCIBLE NITRIC-OXIDE SYNTHASE

The involvement of prostaglandins in feedback modulation of the lipopo lysaccharide-inducible isoforms of cyclooxygenase and nitric oxide was studied, This was done by testing the effects of arachidonic acid and indomethacin in the murine macrophage cell line J774, When added befo re lipopolysaccharide, arachidonic acid (10(-6)-10(-4) M) dose-depende ntly reduced inducible nitric oxide synthase and cyclooxygenase-2 acti vity as well as reducing the expression of both enzyme proteins, Indom ethacin (10(-7)-10(-4) M) suppressed prostaglandin E(2) release into t he medium and reduced cyclooxygenase-2 activity inversibly, as expecte d, but the amount of cyclooxygenase 3 protein was increased (because i ndomethacin removes the inhibitory effect of prostaglandins on cycloox ygenase-2 expression). However, the same doses of indomethacin also in hibited the release of nitric oxide into the medium, This was accompan ied by a reduction in the amount of inducible nitric oxide synthase pr otein, The drug was not cytotoxic, Thus these results show that pharma cological treatments can have opposing actions on inducible nitric oxi de synthase and cyclooxygenase-2 induction, with indomethacin showing an additional unexpected action in macrophages which may diminish thei r cytotoxic potential.