Angiotensin II Type 2 Receptor Antagonizes Angiotensin II Type 1 Receptor-Mediated Cardiomyocyte Autophagy

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 AT2 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, AT1 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. (Hypertension. 2009;53:1032-1040.)