Atrial Natriuretic Peptide Induces Apoptosis in Neonatal Rat Cardiac Myocytes*
- From the ‡Falk Cardiovascular Research Center, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California 94305 and the ¶Molecular Cardiology Laboratory, Stanford Research Institute International, Menlo Park, California 94025
Abstract
Early heart failure is characterized by elevated plasma atrial natriuretic peptide (ANP) levels, but little is known about the direct effects of ANP on cardiac myocytes. In neonatal rat cardiac myocytes, ANP induced apoptosis in a dose-dependent and cell type-specific manner. Maximum effects occurred at 1 μm ANP, with a 4–5-fold increase in apoptotic cells, reaching a maximum apoptotic index of 19%. In contrast, the maximum apoptotic index of ANP-treated non-myocytes was 1.1 ± 0.2%, equivalent to control cultures. ANP treatment also sharply reduced levels of Mcl-1 mRNA, a Bcl-2 homologue, coincident with the increase in the incidence of apoptosis. ANP induction of apoptosis was receptor-dependent and mediated by cyclic GMP: the effect was mimicked by 8-bromo-cGMP, a membrane-permeable analog, and by sodium nitroprusside, an activator of soluble guanylyl cyclase, and was potentiated by a cGMP-specific phosphodiesterase inhibitor, zaprinast. Interestingly, norepinephrine, a myocyte growth factor, inhibited ANP-induced apoptosis via activation of the β-adrenergic receptor and elevation of cyclic AMP. These results show that ANP is a specific effector of cardiac myocyte apoptosis in culture via receptor-mediated elevation of cGMP. Furthermore, at least in this model, ANP and norepinephrine may have opposing roles in the modulation of cardiac myocyte growth and survival.
Footnotes
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↵* This work was presented in part at the American College of Cardiology National Meeting, Orlando, FL, March 24–27, 1996, and the American Heart Association Scientific Sessions, New Orleans, LA, November 10–13, 1996. This work was supported by National Institutes of Health Grants HL42663 (to R. E. P.) and HL49891 (to N. H. B.) and Training Grant HL07708 for Vascular Medicine and Biology.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ Current address: Cardiovascular Research Dept., Genentech, Inc., 460 Point San Bruno Blvd., South San Francisco, CA 94080.
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↵‖ Current address: Dept. of Molecular and Cellular Pharmacology, University of Miami School of Medicine (R-189), P. O. Box 016189, Miami, FL 33101. E-mail: nhb{at}chroma.med.miami.edu.
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↵** To whom correspondence should be addressed. Current address: Laboratory of Genetic Physiology, Cardiovascular Research, Thorn-12, Brigham and Women’s Hospital, 75 Francis St., Boston, MA 00000. Tel.: 617-732-8799; Fax: 617-975-0995; E-mail: rpratt{at}bustoff.bwh.harvard.edu.
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↵1 The abbreviations used are: ANP, atrial natriuretic peptide; RT-PCR, reverse transcription-polymerase chain reaction; DIG, digoxigenin; cGMP, cyclic GMP; FITC, fluorescein isothiocyanate; Bt2cAMP, dibutyryl cyclic AMP.
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↵2 N. H. Bishopric, unpublished data.
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- Received December 16, 1996.
- Revision received March 19, 1997.
