MOLECULAR REGULATION OF INDUCIBLE NITRIC OXIDE SYNTHASE GENE EXPRESSION IN MACROPHAGES : (ROLE OF H₂O₂ AND NITRIC OXIDE (NO) IN NO PRODUCTION)

다국어 초록 (Multilingual Abstract)

Macrophages produce the reactive small molecules H₂O₂ and NO following of exposure to LPS. We investigated the biological function of these molecules on iNOS gene expression and NO production in LPS-stimulated macrophages. The macrophage cell line RAW264.7 stimulated with LPS produced NO. The NO production was inhibited by NOS inhibitor NMA and anti-oxidative enzymes, horseradish peroxidase(HRP), and myeloperoxidase(MPG), but nor by superoxide-scavenging proteins superoxide dismutase(SOD) or cytochrome c. In contrast, the NO-producing activity of LPS-stimulated RAW264.7 cells was enhanced by the NO scavengers hemoglobin(Hb) and myoglobin(Mb). Anti-oxidative enzymes decreased cellular levels of iNOS mRNA and protein in LPS-stimulated RAW264.7 cells, whereas NMA and Hb increased the level of iNOS protein, but not mRNA, indication that NO inhibits iNOS· protein expression. NF-ĸB was activated in LPS-stimulated RAW264.7 cells and the activation was significantly_inhibited by anti-oxidative enzymes, but not by Hb. The anti-oxidative enzymes and Hb similarly regulated iNOS gene expression and NO production from LPS-stimulated peritoneal macrophages as they did from LPS-stimulated RAW264.7 cells. Furthermore, H₂O₂ synergistically induced iNOS gene expression and NO production in peritoneal macrophages with IFNγ treatment and the effects of H₂O₂ were inhibited by catalase and pyrroline dithiocarbamate(PDTC). H₂O₂ production from LPS-stimulated macrophages is a trigger for transcriptional induction iNOS gene expression via NFĸB activation and that NO is a translational negative feedback modulator for suppression of excessive NO production.