Suppression of endothelial nitric oxide production after withdrawal of statin treatment is mediated by negative feedback regulation of rho GTPase gene transcription

Background-Statins improve endothelial function by upregulating endothelial nitric oxide (NO) production that is mediated by inhibiting the isoprenyla tion of rho GTPase. Withdrawal of statin treatment could suppress endotheli al NO production and may impair vascular function. Methods and Results-To test this hypothesis, mice were treated for 14 days with 10 mg/kg atorvastatin per day; this led to the upregulation of endothe lial NO synthase expression and activity by 2.3- and 3-fold, respectively. Withdrawal of statins resulted in a dramatic, 90% decrease of NO production after 2 days. In mouse aortas and cultured endothelial cells, statins upre gulated the expression of rho GTPase in the cytosol, but statins blocked is oprenoid-dependent rho membrane translocation and GTP-binding activity. Inh ibiting the downstream targets of rho showed that rho expression is control led by a negative feedback mechanism mediated by the actin cytoskeleton. Me asuring rho mRNA half-life and nuclear run-on assays demonstrated that stat ins or disruption of actin stress fibers increased rho gene transcription b ut not rho mRNA stability. Therefore, treatment with statins leads to the a ccumulation of nonisoprenylated rho in the cytosol. Withdrawing statin trea tment restored the availability of isoprenoids and resulted in a massive me mbrane translocation and activation of rho, causing downregulation of endot helial NO production. Conclusions-Withdrawal of statin therapy in normocholesterolemic mice resul ts in a transient increase of rho activity, causing a suppression of endoth elial NO production. The underlying molecular mechanism is a negative feedb ack regulation of rho gene transcription mediated by the actin cytoskeleton .