The role of prostaglandin E2 and nitric oxide in cell death in J774 murine macrophages

We investigated the role of prostaglandin E-2 (PGE(2)) and its interactions with nitric oxide (NO) on cell death and NO-mediated cytotoxicity in the murine macrophage cell line J774. Stimulation of the J774 cells with lipopolysaccharide together with interferon-gamma resulted in a dose-dependent cytotoxicity and production of PGE(2) and NO, measured as nitrite. Our results showed a linear correlation between PGE(2) release and cytotoxicity. The cyclooxygenase (COX) inhibitor indomethacin completely inhibited PGE(2) biosynthesis, without affecting NO production or cell death. This supports previous reports suggesting that overproduction of endogenous PGE(2) is mainly the consequence of cell death and does not cause it. In contrast, the NO synthase inhibitor N-omega-monomethyl-L-arginine (L-NMMA) gave a significant, though incomplete suppression of NO release and cell death. This points to the presence of other cytotoxic factors besides NO. To evaluate the toxic effect 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) release were both reversed by indomethacin. In conclusion, PGE(2) biosynthesis may represent a mechanism by which inflammatory macrophages protect themselves against the cytotoxic effects of NO. (C) 1998 Elsevier Science B.V. All rights reserved.