Involvement of Rho GTPases in the transcriptional inhibition of preproendothelin-1 gene expression by simvastatin in vascular endothelial cells

Endothelial dysfunction is characterized by an impaired vasodilatory response to endothelial agonists as well. as by alterations in adhesion and coagulation processes. 3-Hydroxy-3-methylglutaryl-CoA reductase inhibitors (statins) have been shown to be useful in the reversal of endothelial dysfunction, an effect that may be independent of the reduction in cholesterol levels. Both the L-arginine-nitric oxide-cGMP and endothelin pathways are involved in the regulation of vascular tone. Here, we show that the basal transcription rate of the preproendothelin-l gene was decreased by simvastatin (10 mu mol/L) in bovine aortic endothelial cells. Transfection studies with the preproendothelin-l gene promoter showed that mevalonate (100 mu mol/L) was able to prevent the inhibitory effect mediated by simvastatin. Protein geranylgeranylation, but not farnesylation, proved to be crucial for a correct expression of the preproendothelin-1 gene. The C3 exotoxin from Clostridium botulinum that selectively inactivates Rho GTPases, the processing of which involves geranylgeranylation, reproduced the inhibitory effect of simvastatin on the expression of preproendothelin-1. Overexpression of dominant-negative mutants of RhoA and RhoB led to a significant reduction in the preproendothelin-l promoter activity, whereas the expression of wild-type and constitutively active forms of these proteins resulted in an increase, in support that Rho proteins are required for the basal expression of the preproendothelin-l gene. Finally, we show that the Rho-dependent activation of the preproendothelin-l gene transcription was inhibited by simvastatin. Thus, the control of vascular tone and proliferative response mediated by endothelin-l is regulated at multiple levels, among which the Rho proteins play an essential role.