218 Myocardial protection by ischaemic preconditioning and K(ATP) channels opening in the rat heart: evidence for involvement of tyrosine kinase and p38 MAPK

Abstract

Background: Reactive oxygen species (ROS) contribute to the pathophysiology of chronic heart failure. A potential source of myocardial ROS may be the NAD(P)H oxidase. The small GTP-binding protein rac1 is a necessary regulator of the NAD(P)H oxidase. Thus, we examined ROS and rac1 in failing human myocardium and tested their regulation by statins in vivo. Methods and Results: Experiments were performed on human left ventricular myocardium from patients with ischemic (ICM) or dilated cardiomyopathy (DCM), compared to nonfailing controls (NF), n=8 per group. Furthermore, right atrial myocardium from patients undergoing cardiac surgery was used who were prospectively treated with atorvastatin or pravastatin (40 mg/day, respectively) or without statin, n=8 per group. Compared to NF, NAD(P)H oxidase activity was increased to 151 ± 28% in ICM and 153.9 ± 13% in DCM (p<0.05). Similarly, intracellular oxidative stress determined by aconitase activity assays was significantly increased in failing ventricles. This correlated (r=-0.69, p<0.001) with increased translocation of rac1 GTPase from the cytosol to the membrane in western-blot experiments (ICM, 142 ± 16%; DCM, 193 ± 19%, p<0.05 vs. NF). Pull-down assays showed a 3-fold increase of rac1 activity in ICM and DCM compared to NF myocardium (p<0.05). In parallel, membrane expression of the NAD(P)H oxidase subunit p47phox, but not p67phox, was upregulated in failing compared to nonfailing myocardium. In patients treated with statins, rac1 activity was decreased by 33 ± 12% (atorvastatin) and 35 ± 9% (pravastatin) compared to controls (p<0.05). Statin treatment did not alter basal NAD(P)H oxidase activity but significantly inhibited angiotensin II induced ROS release. Conclusions: In failing human myocardium, upregulation of NAD(P)H oxidase mediated ROS release is associated with increased rac1 membrane expression and activity, which can be reduced by oral statin treatment. These mechanisms may contribute to beneficial effects of statins in patients with chronic heart failure.