Impact of HMG CoA reductase inhibition on small GTPases in the heart

Objective: Members of the Rho GTPase family, Rac1 and RhoA have been suggested to be mediators of cardiac hypertrophy in mice. Rho proteins are posttranslationally isoprenylated. In addition to cholesterol-lowering, statins inhibit the isoprenylation of small G proteins. Therefore, it was tested if these drugs inhibit Rac1 and RhoA activity in cardiomyocytes and, thereby, prevent angiotensin II-mediated expression of atrial natriuretic factor (ANF) and myosin light chain (MLC)-2 in the heart. Methods and results: Western and Nor-them analysis of rat neonatal cardiomyocytes and H9C2 cells showed inhibition of basal and angiotensin-stimulated Rac1 expression, membrane-translocation and activity after statin treatment. Similarly, basal and stimulated RhoA membrane expression was inhibited. Statins concentration- and time-dependently downregulated basal as well as angiotensin-induced expression of ANF by 86+/-2.3% and 89+/-1.7%, as well as MLC-2 by 75+/-4.1% and 84+/-6%, respectively. Direct inhibition of Rac GTPase by overexpression of the dominant negative mutant RacN17 or by Clostridium sordelli lethal toxin in rat H9C2 cells inhibited ANF expression by 70+/-4.9% and 78+/-10%, respectively. Inhibition of RhoA by Clostridium botulinum C3 transferase or the dominant negative mutant RhoN19 reduced ANF mRNA by 19+/-11% and 23+/-8%, respectively. To test these findings in vivo, spontaneously hypertensive rats were treated with atorvastatin, leading to a decrease in cardiac Rac1 and RhoA activity as determined by [S-35]-GTPgammaS-binding assays by 61+/-16% and 72+/-24%, and downregulation of MLC-2 as well as ANF mRNA expression by 31+/-16% and 80+/-24%, respectively. Conclusions: (1) Statins downregulate the activity of small G proteins in cardiomyocytes in culture as well as in vivo. (2) Inhibition of Rac I and RhoA by statins reduces myocardial expression of ANF and MLC-2. (3) Targeting myocardial Rho GTPases by statins may be a novel treatment strategy to prevent cardiac hypertrophy. (C) 2002 Elsevier Science BY All rights reserved.