Lovastatin induced cytokine‐mediated inducible nitric oxide synthase (INOS) expression in brain transformed cell lines

Nitric oxide (NO) produced by inducible nitric‐oxide synthase (iNOS) in different cells including brain cells in response to proinflammatory cytokines plays an important role in the pathophysiology of neurodegenerative diseases. The present study underlines the involvement of RhoA protein in the expression of iNOS via NF‐κB in transformed brain cell lines [rat C6 glioma, human astrocytoma (T98G and A172) and immortal rat astrocytes]. Treatment of C6 glioma cells with lovastatin resulted in the induction of iNOS mRNA and increased NO production in a dose and time dependent manner. Addition of mevalonate and geranylgeranylpyrophosphate reversed the lovastatin‐mediated effect. A selective inhibitor of geranylgeranyltransferase inhibitor (GGTI 298) further enhanced the lovastatin as well as cytokine‐mediated iNOS expression suggesting the involvement of geranylgeranylated proteins in the down regulation of iNOS expression. Inactivators of Rho A family (bacterial toxin B), Rho A protein (C3 toxin from C. botulinum ) and Rho A associated kinases (Y‐27632) increased the iNOS expression. Lovastatin induced NO production mediated by increasing IkB? degradation and NF‐κB translocation via inactivation of Rho A protein. Co‐transfection studies using dominant negative form of RhoA along with iNOS luciferase and NF‐κB luciferase reporter constructs further supported these observations. Taken together, these studies document a role for Rho A in lovastatin mediated induction of iNOS expression in brain glial cell lines. Acknowledgements:  Supported by NIH grants NS‐22576, NS‐34741 and NS‐37766.