Effects of ACE inhibitor and AT1 blocker on dystrophin-related proteins and calpain in failing heart

Objectives : Genetic depletion of dystrophin-related protein (DRP) complex causes cardiomyopathy in animals and humans. We found in a previous study that some types of DRP were degraded and that calpain content was increased in rats with non-genetically induced heart failure. The present study was aimed at examining the effects of an angiotensin-I-converting enzyme inhibitor (ACEI) trandolapril (Tra) or an angiotensin II type 1 receptor blocker (ARB) candesartan (Can), both of which are known to improve the pathophysiology of chronic heart failure (CHF) on degradation of DRP in failing hearts. Methods : Coronary artery-ligated (CAL) and sham-operated rats (Sham rats) were treated orally with 3 mg/kg/day trandolapril (Tra) or 1 mg/kg/day candesartan (Can) from the 2nd to 8th week after surgery. Results : Hemodynamic parameters of CAL rats at the 8th week after CAL (8w-CAL) indicated heart failure. α-Sarcoglycan (SG) and dystrophin in the surviving left ventricle (surviving LV) of 8w-CAL rats decreased, whereas β-, γ-, and δ-SGs remained unchanged. Calcium-activated neutral proteases μ-calpain and m-calpain increased in the surviving LV at the 8th week of postmyocardial infarction. Proteolytic activity in the presence of 5 mM Ca2+ markedly increased at the 2nd and 8th weeks, whereas 50 μM Ca2+ slightly but significantly increased proteolysis of casein. Tra or Can treatment improved the hemodynamic parameters, attenuated changes in α-SG and dystrophin, and reversed both calpain contents and activities of the failing heart back to sham levels. Conclusion : These results suggest that attenuation in calpain-induced degradation of DRP complex is a possible mechanism for the Tra- or Can-mediated improvement of the pathogenesis of CHF following myocardial infarction.