Expression of a dominant-negative mutant of p21(ras) inhibits induction ofnitric oxide synthase and activation of nuclear factor-kappa B in primary astrocytes

The present study underlines the importance of p21(ras) in regulating the i nducible nitric oxide synthase (iNOS) in primary astrocytes. Bacterial lipo polysaccharides induced the GTP loading of p21(ras), and the expression of a dominant-negative mutant of p21(ras) (Delta p21(ras)) inhibited lipopolys accharide-induced GTP loading in rat primary astrocytes. To delineate the r ole of p21(ras) in the induction of iNOS, we examined the effect of Delta p 21(ras) on the expression of iNOS and the production of nitric oxide. It is interesting that expression of Delta p21(ras) markedly inhibited the produ ction of nitric oxide and the expression of iNOS in lipopolysaccharide- and proinflammatory cytokine (tumor necrosis factor-alpha, interleukin-1 beta; interferon-gamma)-stimulated rat and human primary astrocytes. Inhibition of iNOS promoter-derived chloramphenicol acetyltransferase activity by Delt a p21(ras) suggests that p21(ras) is involved in the transcription of iNOS. As activation of nuclear factor-kappa-B (NF-kappa B) is necessary for the transcription of iNOS, we examined the effect of Delta p21(ras) on the acti vation of NF-kappa B. Expression of Delta p21(ras) inhibited the DNA bindin g as well as the transcriptional activity of NF-kappa B in activated astroc ytes, suggesting that Delta p2(ras) inhibits the expression of iNOS by inhi biting the activation of NF-kappa B. These studies also suggest that inhibi tors of p21(ras) may be used as therapeutics in nitric oxide- and cytokine- mediated neuroinflammatory diseases.