Alamandine acts via MrgD to induce AMPK/NO activation against ANG II hypertrophy in cardiomyocytes

Abstract

The renin-angiotensin system (RAS) plays a pivotal role in the pathogenesis of cardiovascular diseases. New members of this system have been characterized and shown to have biologically relevant actions. Alamandine and its receptor MrgD are recently identified components of RAS. In the cardiovascular system, alamandine actions included vasodilation, antihypertensive, and antifibrosis effects. Currently, the actions of alamandine on cardiomyocytes are unknown. Here our goal was twofold: 1) to unravel the signaling molecules activated by the alamandine/MrgD axis in cardiomyocytes; and 2) to evaluate the ability of this axis to prevent angiotensin II (ANG II)-induced hypertrophy. In cardiomyocytes from C57BL/6 mice, alamandine treatment induced an increase in nitric oxide (NO) production, which was blocked by d-Pro-ANG-(1-7), a MrgD antagonist. This NO rise correlated with increased phosphorylation of AMPK. Alamandine-induced NO production was preserved in Mas myocytes and lost in MrgD cells. Binding of fluorescent-labeled alamandine was observed in wild-type cells, but it was dramatically reduced in MrgD myocytes. We also assessed the consequences of prolonged alamandine exposure to cultured neonatal rat cardiomyocytes (NRCMs) treated with ANG II. Treatment of NRCMs with alamandine prevented ANG II-induced hypertrophy. Moreover, the antihypertrophic actions of alamandine were mediated via MrgD and NO, since they could be prevented by d-Pro-ANG-(1-7) or inhibitors of NO synthase or AMPK. β-Alanine, a MrgD agonist, recapitulated alamandine's cardioprotective effects in cardiomyocytes. Our data show that alamandine via MrgD induces AMPK/NO signaling to counterregulate ANG II-induced hypertrophy. These findings highlight the therapeutic potential of the alamandine/MrgD axis in the heart.

Counter-regulatory renin–angiotensin system in cardiovascular disease

“…Alternatively , angiotensin II can be processed by aspartate decarboxylase (AD) to produce angiotensin A , which can be converted to alamandine by ACE2. Upon binding to the Mas-related G protein-coupled receptor member D (MRGD), alamandine can promote the same effects reported for angiotensin 1-7 5,67,190 , with the exception of natriuresis. RAS, renin-angiotensin system.…”

“…This mechanism might contribute to the anti hypertrophic properties of angiotensin 1-7, given that neither activation of the AT 1 R nor the proto oncogene Mas receptor antagonists prevented the bene ficial effects of this peptide 4 . Alamandine activates the AMPactivated protein kinase (AMPK)-nitric oxide (NO) pathway via the Mas related G protein coupled recep tor member D (MRGD), which prevents angiotensin II induced hypertrophy 5 . By contrast, angiotensin 1-9 stimulates the AT 2 R-AKT signalling pathway to pro tect the myocardium against reperfusion induced cell death 6 .…”

“…80. Flores-Munoz, M. et al Angiotensin- (1)(2)(3)(4)(5)(6)(7)(8)(9) attenuates cardiac fibrosis in the stroke-prone spontaneously hypertensive rat via the angiotensin type 2 receptor. Hypertension 59, 300-307 (2012 Inflammatory processes in cardiovascular disease:…”

AMPK: a balancer of the renin–angiotensin system

“…Alamandine acts on the MrgD and expresses similar effects to Ang (1-7) [128,136]. Recent research claimed that alamandine could activate AMPK in ventricular cardiomyocytes via MrgD [89]. Alamandine also induced a significant increase in LKB1 phosphorylation.…”

“…Chen et al [88] reported that when H9C2 cells were co-cultured with 5 μM of AngII for 12, 24, or 48 h, autophagy was enhanced, while AMPKα/mTOR signaling or cellular ADP/ATP ratio was not impacted. In another study, neonatal rat cardiomyocytes (NRCMs) were treated with AngII (100 nmol/l) for 36 h. The results showed that AngII did not affect the phosphorylation of AMPK [89]. Kim et al [90] claimed that by activating the AT1R-calcium-AMPK-JNK axis pathway, AngII induces inflammation in atrial cells.…”