Deficiency in E3 Ubiquitin Ligase Parkin Exacerbates Chronic Alcohol Intake-Induced Cardiomyopathy through an Ambra1-Dependent Mechanism.

BACKGROUND AND PURPOSE Chronic alcohol consumption contributes to contractile dysfunction and unfavorable geometric changes in myocardium, accompanied with altered autophagy and disturbed mitochondrial homeostasis. The E3 ubiquitin ligase Parkin encoded by PARK2 gene maintains a fundamental role in regulating mitophagy and mitochondrial homeostasis although little is known for its role in the etiology of alcoholic cardiomyopathy. EXPERIMENTAL APPROACH This study aimed to discern the impact of Parkin deletion in chronic alcohol-evoked cardiotoxicity. Following alcohol (4%) or control diet intake for 8 weeks, adult male wild-type (WT) and PARK2 knockout (Parkin-/- ) mice were examined using echocardiography. Cardiomyocyte mechanical properties, morphology of myocardium and mitochondrial damage were also evaluated. Besides, autophagy and mitophagy levels were assessed by LC3B and GFP-LC3 puncta, whereas lysosome-dependent autophagic flux was scrutinized using GFP-mRFP-LC3 puncta and Bafilomycin A1 treatment. KEY RESULTS Our data indicated that chronic alcohol exposure provoked unfavorable geometric changes in myocardium, including enlarged left ventricles, increased cell size, worsened interstitial fibrosis and mitochondrial swelling. Moreover, alcohol intake led to mitochondrial dysfunction and cardiac contractile defects, such as decreased ejection fraction, fractional shortening, peak shortening, velocity of shortening and relengthening, and prolonged relengthening duration, the effects of which were further exacerbated by Parkin knockout. Chronic alcohol exposure provoked autophagy and PINK1/Parkin-mediated mitophagy without affecting lysosome-dependent autophagic flux, the effects of which were diminished by Parkin ablation. Parkin adenovirus infection in neonatal rat cardiomyocytes further increased autophagy and protected against alcohol-induced myocardial injury, the effect of which was negated by Ambra1 (Autophagy and Beclin1 regulator 1) silencing by siRNA. Immunofluorescence staining and co-immunoprecipitation assay denoted evident interaction between Parkin and Ambra1. CONCLUSIONS AND IMPLICATIONS In conclusion, our results revealed that Parkin is obligatory to the cardiac homeostasis in alcohol challenge, likely due to promotion of autophagy/mitophagy and maintenance of mitochondrial integrity through its interaction with Ambra1.