THE ROLE OF PROSTAGLANDIN E-2 AND NITRIC-OXIDE IN CELL-DEATH IN J774 MURINE MACROPHAGES

We investigated the role of prostaglandin E-2 (PGE(2)) and its interac tions with nitric oxide (NO) on cell death and NO-mediated cytotoxicit y in the murine macrophage cell line J774. Stimulation of the J774 cel ls with lipopolysaccharide together with interferon-gamma resulted in a dose-dependent cytotoxicity and production of PGE(2) and NO, measure d as nitrite. Our results showed a linear correlation between PGE(2) r elease and cytotoxicity. The cyclooxygenase (COX) inhibitor indomethac in completely inhibited PGE(2) biosynthesis, without affecting NO prod uction or cell death. This supports previous reports suggesting that o verproduction of endogenous PGE(2) is mainly the consequence of cell d eath and does not cause it. In contrast, the NO synthase inhibitor N-o mega-monomethyl-L-arginine (L-NMMA) gave a significant, though incompl ete suppression of NO release and cell death. This points to the prese nce of other cytotoxic factors besides NO. To evaluate the toxic effec t solely due to NO, macrophages were exposed to the NO donor S-nitroso -N-acetyl-D,L-penicillamine (SNAP). Incubation with SNAP also resulted in a concentration-dependent cell injury and PGE(2) production. When exogenously added, PGE(2) protected against SNAP-mediated cytotoxicity and simultaneously increased PGE(2) release into the medium, without inducing COX-2. The cytoprotection and the stimulation of PGE(2) relea se were both reversed by indomethacin. In conclusion, PGE(2) biosynthe sis may represent a mechanism by which inflammatory macrophages protec t themselves against the cytotoxic effects of NO. (C) 1998 Elsevier Sc ience B.V. All rights reserved.