Prostaglandins prevent inducible nitric oxide synthase protein expression by inhibiting nuclear factor-κB activation in J774 macrophages

We investigated the effect of PGE(2) and iloprost (a prostacyclin analogue) on inducible nitric oxide synthase (iNOS) protein expression and nuclear factor-kappa B (NF-kappa B) activation in lipopolysaccharide (LPS)-stimulated J774 macrophages. Incubation of J774 cells with LPS (10 mu g/ml) caused an increase of iNOS protein expression which was prevented in a concentration-dependent fashion by PGE(2) (0.1, 1, 10 mu M) and iloprost (0.01, 0.1, 1 mu M). Electrophoretic mobility shift assay indicated that both prostanoids blocked the activation of NF-kappa B, a transcription factor necessary for NO synthase induction. PGE(2) and iloprost also blocked disappearance of I kappa B-alpha from cytosolic fraction and nuclear translocation of NF-kappa B subunits p50 and p65. These results show for the first time that PGE(2) and iloprost down-regulate iNOS protein expression by inhibiting NF-kappa B activation and suggest a negative feed-back mechanism that may be important for limiting excessive or prolonged NO production in pathological events. (C) 1998 Federation of European Biochemical Societies.