Possible involvement of Janus kinase Jak2 in interferon-γ induction of nitric oxide synthase in rat glial cells

Abstract

To clarify the induction pathway of inducible nitric oxide (NO) synthase in the brain, we examined the effects of interferon-γ and lipopolysaccharide on the induction of inducible NO synthase in glial cells cultured from neonatal rats, compared to those in the macrophage cell line RAW264.7 which was derived from Abelson leukemia virus-induced BALB/c lymphocytic lymphoma. NO synthase activity (NO − 2 accumulation) and 130 kDa protein of inducible NO synthase were induced 24 h after treatment with interferon-γ or lipopolysaccharide in both glial cells and RAW264.7 macrophages. These induction activities were inhibited by a tyrosine kinase inhibitor, herbimycin A. Immunoprecipitation assay using antibodies against Janus kinases, and the signal transducer and activator of transcription-1 (STAT1), revealed that interferon-γ induced tyrosine phosphorylation of the just another kinase-2 (Jak2) and STAT1 α but did not induced the phosphorylation of Jak1, the non-receptor tyrosine kinase-2 (Tyk2) and STAT1 β. Tyrosine phosphorylation of Jak2 and STAT1 α induced by interferon-γ was also inhibited by herbimycin A, while lipopolysaccharide did not induce any tyrosine phosphorylation of Janus kinases and STAT1 at all. These results suggest that the interferon-γ-induced inducible NO synthase induction involves activation of Jak2-STAT1 α pathway in both glial cells and macrophages.