Angiotensin-(1-7) inhibits growth of cardiac myocytes through activation of the mas receptor |
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Authors: | Tallant E Ann Ferrario Carlos M Gallagher Patricia E |
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Institution: | Hypertension and Vascular Disease Center, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1032, USA. atallant@wfubmc.edu |
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Abstract: | Peptide hormones such as ANG II and endothelin contribute to cardiac remodeling after myocardial infarction by stimulating myocyte hypertrophy and myofibroblast proliferation. In contrast, angiotensin-(1-7) ANG-(1-7)] infusion after myocardial infarction reduced myocyte size and attenuated ventricular dysfunction and remodeling. We measured the effect of ANG-(1-7) on protein and DNA synthesis in cultured neonatal rat myocytes to assess the role of the heptapeptide in cell growth. ANG-(1-7) significantly attenuated either fetal bovine serum- or endothelin-1-stimulated (3)H]leucine incorporation into myocytes with no effect on (3)H]thymidine incorporation. d-Ala(7)]-ANG-(1-7), the selective ANG type 1-7 (AT(1-7)) receptor antagonist, blocked the ANG-(1-7)-mediated reduction in protein synthesis in cardiac myocytes, whereas the AT(1) and AT(2) angiotensin peptide receptors were ineffective. Serum-stimulated ERK1/ERK2 mitogen-activated protein kinase activity was significantly decreased by ANG-(1-7) in myocytes, a response that was also blocked by d-Ala(7)]-ANG-(1-7). Both rat heart and cardiac myocytes express the mRNA for the mas receptor, and a 59-kDa immunoreactive protein was identified in both extracts of rat heart and cultured myocytes by Western blot hybridization with the use of an antibody to mas, an ANG-(1-7) receptor. Transfection of cultured myocytes with an antisense oligonucleotide to the mas receptor blocked the ANG-(1-7)-mediated inhibition of serum-stimulated MAPK activation, whereas a sense oligonucleotide was ineffective. These results suggest that ANG-(1-7) reduces the growth of cardiomyocytes through activation of the mas receptor. Because ANG-(1-7) is elevated after treatment with angiotensin-converting enzyme inhibitors or AT(1) receptor blockers, ANG-(1-7) may contribute to their beneficial effects on cardiac dysfunction and ventricular remodeling after myocardial infarction. |
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