Angiotensin II type 2 receptor antagonizes angiotensin ii type 1 receptor-mediated cardiomyocyte autophagy

Abstract

Autophagy has emerged as an important process in the pathogenesis of cardiovascular diseases, but the proximal triggers for autophagy are unknown. Angiotensin II plays a central role in the pathogenesis of cardiac hypertrophy and heart failure. In this study, we used angiotensin II type 1 (AT 1) and type 2 (AT 2) receptor-expressing adenoviruses in cultured neonatal cardiomyocytes to provide the first demonstration that neonatal cardiomyocyte autophagic activity is differentially modulated by AT 1 and AT 2 receptor subtypes. Angiotensin II stimulation (48 hours) of neonatal cardiomyocytes expressing the AT 1 receptor alone (Ad-AT 1; 10 multiplicities of infection) induced a significant increase in the number of HcRed-LC3 autophagosomes per cell (17.3±1.6 versus 33.3±4.1 autophagosomes per cell; P<0.05). Coexpression of a high ratio of AT 2:AT 1 (Ad-AT 2:Ad-AT 1 multiplicity of infection ratio: 20:5) receptors completely abrogated the AT 1-mediated increase in autophagy (9.3±1.4 versus 33.3±4.1 autophagosomes per cell; P<0.05). Treatment with the AT 2 receptor antagonist PD123319 did not reverse the AT 2-mediated antiautophagic effect. AT 1- and AT 2-mediated autophagic responses were also assessed in cardiomyocytes from a genetic model that exhibits neonatal myocardial growth suppression. In these neonate myocyte cultures, AT 1 receptor activation induced a marked increase in the number of myocytes containing cytoplasmic vacuoles compared with the control (22.7±4.1% versus 1.1 ±0.6%; P<0.001) and was characterized by a nonapoptotic autophagic phenotype. The incidence of cardiomyocyte autophagic vacuolization in this myocyte population decreased dramatically to only 0.4±0.2% in myocytes infected with a high ratio of Ad-AT 2: Ad-AT 1. This study provides the first description of reciprocal regulation of cardiomyocyte autophagic induction by the AT 1 and AT 2 receptor subtypes. © 2009 American Heart Association, Inc.