Abstract P051: Induction of Cardiac Nitrosative Stress and Cell Death by Chronic Alcohol Consumption in an Angiotensin II-, PKC-, and NOX-Dependent Manner

Abstract

Alcohol induced cardiac cell death is causative of cardiomyopathy, but the mechanisms responsible for alcoholic cardiac cell death remain largely unknown. We hypothesize that alcohol-induced Ang II plays a critical role in cardiac nitrosative stress, cell death and cardiomyopathy. To test this hypothesis, male C57BL/6 mice were pair-fed an alcohol or isocaloric maltose dextrin liquid diet for 2 months. Alcohol feeding caused significant cardiac cell death and nitrosative damage (shown by TUNEL positive cells, caspase-3 activation and protein nitration) and cardiac remodeling (shown by hypertrophy and fibrosis) along with increases in serum Ang II and cardiac AT1 expression. Mechanistic study in which cardiac H9c2 cells were treated with 100–400 mM alcohol for 24h revealed that alcohol exposure induced cell death, nitrosative damage and fibrosis, along with NADPH oxidase p47 phox (NOX) activation in a dose-dependent manner. Pre-treatment of alcohol-treated cells with NOX inhibitor (apycinin), peroxynitrite scavenger (urate), NOS inhibitor (L-NAME) and superoxide dismutase mimic (MnTMPyP) significantly abolished alcohol induced cell death. Furthermore, exposure to alcohol significantly up-regulated the expression of angiotensin II (Ang II) and its type 1 receptor (AT1) in these cultured cardiac cells. Either PKCα/β1 inhibitor or AT1 blocker completely prevented alcoholic NOX activation, and AT1 blocker inhibited the expression of PKCβ1, implying that alcoholic NOX activation is dependent of PKCα/β1 activation via AT1. To validate the in vitro findings, alcohol-fed and pair-fed mice were treated with MnTMPyP (5 mg/Kg) daily for 2 months, which did not change blood pressure, alcohol-induced cardiac PKC and NOX activation, but significantly prevented alcohol-induced cardiac nitrosative damage and cell death, along with a prevention of cardiac fibrosis and dysfunction. These results suggest that alcohol-induced cardiac cell death is mediated by up-regulated Ang II that via AT1 induces PKCα/β1-dependent NOX activation. The cardiac cell death plays a critical role in the development of alcoholic cardiomyopathy.