Increased basal contractility of cardiomyocytes overexpressing protein kinase C epsilon and blunted positive inotropic response to endothelin-1

Abstract

Objective: Protein kinase C (PKC) is thought to be involved in the regulation of the mammalian cardiac excitation-contraction coupling process by vasoactive peptides Like endothelin-1 (ET-1). However, the demonstration of a causal link between activation of specific PKC isoforms and the increase in contractility mediated by ET-1 is still inferential. Methods: By means of adenovirus-mediated gene transfer, we specifically overexpressed PKC epsilon in cultured adult rabbit Ventricular myocytes (Ad-PKC epsilon). Myocyte shortening and [Ca2+](i) transients under basal and ET-1-stimulated conditions were measured in Ad-PKC epsilon and Ad-LacZ control transfected cells. Results: Infection with Ad-PKC epsilon resulted in a strong, virus dose-dependent increase in PKC epsilon protein Levels, whereas protein expression of other PKC isoforms remained unchanged. Using a multiplicity of infection of 100 plaque-forming units/myocyte, basal and cofactor-dependent PKC epsilon kinase activity was increased 28- and 90-fold, respectively, when compared to control. Myocyte basal fractional shortening and [Ca2+](i), transient amplitude were both increased by 21% (P<0.05 each) in Ad-PKC<epsilon> transfected myocytes when compared to Ad-LacZ transfected control myocytes. The positive Inotropic effect of ET-1 in control myocytes was markedly blunted in PKC epsilon -overexpressing myocytes. Conclusion: Specific overexpression of PKC epsilon in rabbit ventricular myocytes increases basal myocyte contractility and [Ca2+](i) transients, and modifies their responsiveness to ET-1. (C) 2001 Elsevier Science B.V. AII rights reserved.