Angiotensin II Plays a Critical Role in Alcohol-Induced Cardiac Nitrative Damage, Cell Death, Remodeling, and Cardiomyopathy in a Protein Kinase C/Nicotinamide Adenine Dinucleotide Phosphate Oxidase–Dependent Manner

Abstract

The purpose of this study was to examine the cellular and molecular mechanisms underlying alcoholic cardiomyopathy. The mechanism for alcoholic cardiomyopathy remains largely unknown. The chronic cardiac effects of alcohol were examined in mice feeding with alcohol or isocaloric control diet for 2 months. Signaling pathways of alcohol-induced cardiac cell death were examined in H9c2 cells. Compared with controls, hearts from alcohol-fed mice exhibited increased apoptosis, along with significant nitrative damage, demonstrated by 3-nitrotyrosine abundance. Alcohol exposure to H9c2 cells induced apoptosis, accompanied by 3-nitrotyrosine accumulation and nicotinamide adenine dinucleotide phosphate oxidase (NOX) activation. Pre-incubation of H9c2 cells with urate (peroxynitrite scavenger), N(G)-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor), manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (a superoxide dismutase mimetic), and apocynin (NOX inhibitor) abrogated alcohol-induced apoptosis. Furthermore, alcohol exposure significantly increased the expression of angiotensin II and its type 1 receptor (AT1). A protein kinase C (PKC)-α/β1 inhibitor or PKC-β1 small interfering RNA and an AT1 blocker prevented alcohol-induced activation of NOX, and the AT1 blocker losartan significantly inhibited the expression of PKC-β1, indicating that alcohol-induced activation of NOX is mediated by PKC-β1 via AT1. To define the role of AT1-mediated PKC/NOX-derived superoxide generation in alcohol-induced cardiotoxicity, mice with knockout of the AT1 gene and wild-type mice were simultaneously treated with alcohol for 2 months. The knockout AT1 gene completely prevented cardiac nitrative damage, cell death, remodeling, and dysfunction. More importantly, pharmacological treatment of alcoholic mice with superoxide dismutase mimetic also significantly prevented cardiac nitrative damage, cell death, and remodeling. Alcohol-induced nitrative stress and apoptosis, which are mediated by angiotensin II interaction with AT1 and subsequent activation of a PKC-β1-dependent NOX pathway, are a causal factor in the development of alcoholic cardiomyopathy.