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(Circulation Research. 1999;85:e70.)
© 1999 American Heart Association, Inc.

Circulation Research Electronic Pages

ARC Inhibits Cytochrome c Release From Mitochondria and Protects Against Hypoxia-Induced Apoptosis in Heart-Derived H9c2 Cells

Daryoush Ekhterae, Zhiwu Lin, Martha S. Lundberg, Michael T. Crow, Frank C. Brosius, III, Gabriel Núñez

From the Department of Pathology and Comprehensive Cancer Center (D.E., G.N.), Departments of Internal Medicine (Z.L., F.C.B.) and Physiology (F.C.B.), University of Michigan Medical School, Ann Arbor, Mich; Veterans Affairs Hospital (F.C.B.), Ann Arbor, Mich; and Laboratory of Cardiovascular Science (M.S.L., M.T.C.), National Institute on Aging, National Institutes of Health, Baltimore, Md.

Correspondence to Gabriel Núñez, University of Michigan Cancer Center, 1500 E Medical Center Dr, 4215 CCGC, Ann Arbor, MI 48109-0938. E-mail gabriel.nunez{at}umich.edu

Abstract—Ischemia induces apoptosis as well as necrosis of cardiac myocytes. We recently reported the cloning of a cDNA that encodes an apoptotic inhibitor, ARC, that is expressed predominantly in cardiac and skeletal muscle. In the present study, we examined the ability of ARC to protect rat embryonic heart–derived H9c2 cells from apoptosis induced by hypoxia, a component of ischemia. We found that H9c2 cells express ARC and that exposure to hypoxia substantially reduces ARC expression while inducing apoptosis. Transfected H9c2 cells in which cytosolic ARC protein levels remain elevated during hypoxia were significantly more resistant to hypoxia-induced apoptosis than parental H9c2 cells or H9c2 cells transfected with a control vector. Loss of endogenous ARC in the cytosol of H9c2 cells was associated with translocation of ARC from the cytosol to intracellular membranes, release of cytochrome c from the mitochondria, activation of caspase-3, poly(ADP-ribose)polymerase (PARP) cleavage, and DNA fragmentation. All of these events were inhibited in H9c2 cells overexpressing ARC when compared with control cells. In contrast, caspase inhibitors prevented PARP cleavage but not cytochrome c release, suggesting that exogenously expressed ARC acts upstream of caspase activation in this model of apoptosis. These results demonstrate that ARC can protect heart myogenic H9c2 cells from hypoxia-induced apoptosis, and that ARC prevents cytochrome c release by acting upstream of caspase activation, perhaps at the mitochondrial level. The full text of this article is available at http://www.circresaha.org.

Key Words: apoptosis • ARC • hypoxia • cardiomyocyte • cytochrome c

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