Induction of nitric oxide synthase by lipopolysaccharide and its inhibition by auranofin in RAW 264.7 cells.

In RAW 264.7 cells, a murine macrophage cell line, treatment with lipopolysaccharide (1 to 10 ng/ml) stimulated production of nitric oxide (NO), which was inhibited by L-N(G)-monomethyl-L-arginine acetate, an inhibitor of NO synthase. Auranofin, an orally active chrysotherapeutic agent, also inhibited the lipopolysaccharide-induced NO production in a concentration-dependent manner (0.3 to 3 microM). Other gold salts such as aurothioglucose and aurothiomalate had no effect. Western blot analysis demonstrated that the lipopolysaccharide (10 ng/ml)-induced expression of inducible NO synthase protein was inhibited by auranofin as well as by the protein synthesis inhibitor cycloheximide. In addition, the lipopolysaccharide-induced increase in the level of mRNA for inducible NO synthase was also lowered by auranofin. Furthermore, auranofin showed no direct effect on the conversion of [3H]arginine to [3H]citrulline by the cell lysate. These findings indicate that auranofin inhibits lipopolysaccharide-induced NO production by suppressing the expression of inducible NO synthase.