Effect of Antioxidants and Dexamethasone on inducible Nitric Oxide Synthase Expression and Nitric Oxide Production in Murine Macrophage Cells / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Nitric oxide(NO) plays a role in a number of physiologic functions and may be cytotoxic in high concentrations. Some kinds of cells including macrophage are known to produce large quantities of NO in response to inflammatory stimuli such as cytokines and lipopolysaccharide(LPS). Reactive oxygen species are also known to be important in the pathogenesis of cell and tissue injury such as otitis media with effusions. Using the macrophage RAW 264.7 cell, we have examined the ability of oxidant hydrogen peroxide (H2O2) to stimulate NO production and inducible nitric oxide synthase(iNOS) mRNA expression. Also, we have examined the effects of Dexamethasone(DEX) and antioxi- dants on H2O2 induced NO production. MATERIALS AND METHOD: Macrop- hages were cultured with LPS and H2O2 in the presence or absence of DEX or antioxidants for 24 hr. The effect of DEX and antioxidants on NO production and iNOS mRNA expression was examined by assaying the culture supernatant for oxidation product nitrite(NO-2) and nitrate (NO-3) content and Northern blot analysis. The effect of DEX on NO production when added at different stages of activation was determined. RESULTS: DEX significantly inhibited the formation of NO2- and NO3- and iNOS mRNA expression in cells stimulated with LPS and H2O2. Antioxid- ants significantly inhibited the H2O2-induced augmentation of LPS induced NO2- and NO3- formation and iNOS mRNA expression. CONCLUSION: H2O2 contributes to inflammatory process by augmenting the iNOS mRNA expression and NO synthesis induced by LPS, and DEX and anti- oxidants inhibits NO synthesis by inhibition of iNOS mRNA expression.