Volatile anesthetics differentially affect immunostimulated expression of inducible nitric oxide synthase - Role of intracellular calcium

Background Nitric oxide released by inducible nitric oxide synthase (iNOS) plays an important role in immune responses and systemic vasodilation in se ptic shock. Volatile anesthetics have been reported to interfere with signa l transduction and gene expression. We studied the effect of volatile anest hetics on activity and expression of iNOS and potential mechanisms of actio n. Methods: Nitrite release and iNOS expression were determined using the Grie ss reaction and Western and Northern blot techniques, respectively, in J774 murine macrophages stimulated with lipopolysaccharide and gamma-interferon in the absence and presence of various concentrations (0.25-2.0 minimum al veolar concentration [MAC]) of volatile anesthetics (i.e., halothane, enflu rane, isoflurane, desflurane). Furthermore, potential interference of volat ile anesthetics with specific signal transduction pathways was investigated . Results: All volatile anesthetics, studied in a time- and dose-dependent ma nner, suppressed nitrite production and iNOS expression in J774 macrophages stimulated by lipopolysaccharide or gamma-interferon at clinically relevan t concentrations. The inhibition was completely antagonized by ionomycin bu t unaffected by diacylglycerol, phorbol myristate acetate, and C2-ceramide. in contrast, in cells costimulated by lipopolysaccharide plus gamma-interf eron, volatile anesthetics significantly increased nitrite production and i NOS expression independent of ionomycin and other mediators studied. Conclusions: Volatile anesthetics strongly reduced the mRNA and protein lev els of iNOS and NOS activity after a single stimulation with lipopolysaccha ride or gamma-interferon, most Likely by attenuating intracellular calcium increase. Costimulation with lipopolysaccharide plus gamma-interferon, howe ver, results in maximum iNOS expression and activity, which are no longer i nhibited but are potentiated by volatile anesthetics by unidentified mechan isms.