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

Abstract

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