Exogenous HS Promoted USP8 Sulfhydration to Regulate Mitophagy in the Hearts of db/db Mice.

Hydrogen sulfide (HS), an important gasotransmitter, regulates cardiovascular functions. Mitochondrial damage induced by the overproduction of reactive oxygen species (ROS) results in myocardial injury with a diabetic state. The purpose of this study was to investigate the effects of exogenous HS on mitophagy formation in diabetic cardiomyopathy. In this study, we found that exogenous HS could improve cardiac functions, reduce mitochondrial fragments and ROS levels, enhance mitochondrial respiration chain activities and inhibit mitochondrial apoptosis in the hearts of db/db mice. Our results showed that exogenous HS facilitated parkin translocation into mitochondria and promoted mitophagy formation in the hearts of db/db mice. Our studies further revealed that the ubiquitination level of cytosolic parkin was increased and the expression of USP8, a deubiquitinating enzyme, was decreased in db/db cardiac tissues. S-sulfhydration is a novel posttranslational modification of specific cysteine residues on target proteins by HS. Our results showed that the S-sulfhydration level of USP8 was obviously decreased in vivo and in vitro under hyperglycemia and hyperlipidemia, however, exogenous HS could reverse this effect and promote USP8/parkin interaction. Dithiothreitol, a reducing agent that reverses sulfhydration-mediated covalent modification, increased the ubiquitylation level of parkin, abolished the effects of exogenous HS on USP8 deubiquitylation and suppressed the interaction of USP8 with parkin in neonatal rat cardiomyocytes treated with high glucose, oleate and palmitate. Our findings suggested that HS promoted mitophagy formation by increasing S-sulfhydration of USP8, which enhanced deubiquitination of parkin through the recruitment of parkin in mitochondria.