MiR-34a modulates angiotensin II-induced myocardial hypertrophy by direct inhibition of ATG9A expression and autophagic activity.

Jionghua Huang,Wen Sun,Xiangyu You,Shiming Liu,Longgen Xiong,Benrong Liu,Chuanfang Cheng,He Huang,Jing Ye,Yun Zhong,Wei Pan,Sharmila Shankar

doi:10.1371/journal.pone.0094382

Jionghua Huang, Wen Sun + Show 10 more

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https://doi.org/10.1371/journal.pone.0094382

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Abstract

Cardiac hypertrophy is characterized by thickening myocardium and decreasing in heart chamber volume in response to mechanical or pathological stress, but the underlying molecular mechanisms remain to be defined. This study investigated altered miRNA expression and autophagic activity in pathogenesis of cardiac hypertrophy. A rat model of myocardial hypertrophy was used and confirmed by heart morphology, induction of cardiomyocyte autophagy, altered expression of autophagy-related ATG9A, LC3 II/I and p62 proteins, and decrease in miR-34a expression. The in vitro data showed that in hypertrophic cardiomyocytes induced by Ang II, miR-34a expression was downregulated, whereas ATG9A expression was up-regulated. Moreover, miR-34a was able to bind to ATG9A 3′-UTR, but not to the mutated 3′-UTR and inhibited ATG9A protein expression and autophagic activity. The latter was evaluated by autophagy-related LC3 II/I and p62 levels, TEM, and flow cytometry in rat cardiomyocytes. In addition, ATG9A expression induced either by treatment of rat cardiomyocytes with Ang II or ATG9A cDNA transfection upregulated autophagic activity and cardiomyocyte hypertrophy in both morphology and expression of hypertrophy-related genes (i.e., ANP and β-MHC), whereas knockdown of ATG9A expression downregulated autophagic activity and cardiomyocyte hypertrophy. However, miR-34a antagonized Ang II-stimulated myocardial hypertrophy, whereas inhibition of miR-34a expression aggravated Ang II-stimulated myocardial hypertrophy (such as cardiomyocyte hypertrophy-related ANP and β-MHC expression and cardiomyocyte morphology). This study indicates that miR-34a plays a role in regulation of Ang II-induced cardiomyocyte hypertrophy by inhibition of ATG9A expression and autophagic activity.

Highlights

Cardiac hypertrophy refers to a thickening myocardium, resulting in a decrease in size of the heart chamber
We first produced a rat model of myocardial hypertrophy using the transverse abdominal aortic constriction (TAAC) operation and an in vitro cardiomyocytes hypertrophic model using Angiotensin II (Ang II) treatment, ATG9A cDNA transfection, or lentiviral infection of miR-34a inhibitor, or miR-34a mimics, or ATG9A siRNA
We found that the rat myocardial hypertrophy heart tissues increased autophagic activity and upregulated expression of autophagy-related ATG9A and LC3 II/I proteins, but reduced p62 and miR-34a expression

Summary

Introduction

Cardiac hypertrophy refers to a thickening myocardium, resulting in a decrease in size of the heart chamber. A common cause of cardiac hypertrophy is hypertension or heart valve stenosis. Cardiac hypertrophy is generally characterized by an increase in the size of cardiomyocytes, without increase in cell numbers, and by cytoskeletal reorganization. Cardiac hypertrophy shows an increased expression of fetal-type genes [1,2]. Cardiac hypertrophy is initially an adaptive response to stress overload. The continued presence of hypertrophic growth often carries a poor prognosis that may result in heart failure and sudden death of patients [3,4]

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