REGULATION OF INDUCIBLE NITRIC-OXIDE SYNTHASE GENE BY INTERLEUKIN-1-BETA IN RAT VASCULAR ENDOTHELIAL-CELLS

To elucidate the regulation of endothelial inducible nitric oxide synthase (iNOS), we studied the effects of interleukin (IL)-1 beta on production of nitric oxide (NO) and expression of iNOS mRNA and iNOS protein in cultured rat aortic endothelial cells (ECs) by measurement of NO2-/NO3- (NOx) and Northern blot and Western blot analyses. Among several cytokines and bacterial lipopolysaccharide tested, IL-1 beta most effectively stimulated NOx production. IL-1 beta dose and time dependently stimulated NOx production. Northern blot analysis using cDNA for mouse liver iNOS as a probe showed that IL-1 beta induced expression of iNOS mRNA and stimulated NOx production in a dose- and time-dependent manner. Transforming growth factor (TGF)-beta and dexamethasone blocked the IL-1 beta-induced NOx production as well as expression of iNOS mRNA and protein. TGF-beta dose dependently inhibited the IL-1 beta-induced NOx production and iNOS mRNA expression. Northern blot analysis for the decay of the IL-1 beta-induced iNOS mRNA. revealed the approximate half-life of 4 h. These data indicate that IL-1 beta induces iNOS gene expression and de novo synthesis of iNOS and subsequent NO generation in vascular endo thelium and that TGF-beta and glucocorticoid block iNOS gene expression at the transcriptional level.