Hydrogen sulfide (H2S), 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 H2S on mitophagy formation in diabetic cardiomyopathy. In this study, we found that exogenous H2S 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 H2S 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 H2S. Our results showed that the S-sulfhydration level of USP8 was obviously decreased in vivo and in vitro under hyperglycemia and hyperlipidemia, however, exogenous H2S 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 H2S 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 H2S promoted mitophagy formation by increasing S-sulfhydration of USP8, which enhanced deubiquitination of parkin through the recruitment of parkin in mitochondria.

Hydrogen sulfide (H2S), a gaseous molecule, is involved in modulating multiple physiological functions, such as antioxidant, antihypertension, and the production of polysulfide cysteine. H2S may inhibit reactive oxygen species generation and ATP production through modulating respiratory chain enzyme activities; however, the mechanism of this effect remains unclear. In this study, db/db mice, neonatal rat cardiomyocytes, and H9c2 cells treated with high glucose, oleate, and palmitate were used as animal and cellular models of type 2 diabetes. The mitochondrial respiratory rate, respiratory chain complex activities, and ATP production were decreased in db/db mice compared with those in db/db mice treated with exogenous H2S. Liquid chromatography with tandem mass spectrometry analysis showed that the acetylation level of proteins involved in the mitochondrial respiratory chain were increased in the db/db mice hearts compared with those with sodium hydrosulfide (NaHS) treatment. Exogenous H2S restored the ratio of NAD+/NADH, enhanced the expression and activity of sirtuin 3 (SIRT3) and decreased mitochondrial acetylation level in cardiomyocytes under hyperglycemia and hyperlipidemia. As a result of SIRT3 activation, acetylation of the respiratory complexe enzymes NADH dehydrogenase 1 (ND1), ubiquinol cytochrome c reductase core protein 1, and ATP synthase mitochondrial F1 complex assembly factor 1 was reduced, which enhanced the activities of the mitochondrial respiratory chain activity and ATP production. We conclude that exogenous H2S plays a critical role in improving cardiac mitochondrial function in diabetes by upregulating SIRT3.

Background and Purpose Hydrogen sulfide (H2S) plays important roles as a gasotransmitter in pathologies. Increased expression of the E3 ubiquitin ligase, muscle RING finger‐1 (MuRF1), may be involved in diabetic cardiomyopathy. Here we have investigated whether and how exogenous H2S alleviates cardiac muscle degradation through modifications of MuRF1 S‐sulfhydration in db/db mice. Experimental Approach Neonatal rat cardiomyocytes were treated with high glucose (40 mM), oleate (100 μM), palmitate (400 μM), and NaHS (100 μM) for 72 hr. MuRF1 was silenced with siRNA technology and mutation at Cys44. Endoplasmic reticulum stress markers, MuRF1 expression, and ubiquitination level were measured. db/db mice were injected with NaHS (39 μmol·kg−1) for 20 weeks. Echocardiography, cardiac ultrastructure, cystathionine‐γ‐lyase, cardiac structure proteins expression, and S‐sulfhydration production were measured. Key Results H2S levels and cystathionine‐γ‐lyase protein expression in myocardium were decreased in db/db mice. Exogenous H2S reversed endoplasmic reticulum stress, including impairment of the function of cardiomyocytes and structural damage in db/db mice. Exogenous H2S could suppress the levels of myosin heavy chain 6 and myosin light chain 2 ubiquitination in cardiac tissues of db/db mice, and MuRF1 was modified by S‐sulfhydration, following treatment with exogenous H2S, to reduce the interaction between MuRF1 and myosin heavy chain 6 and myosin light chain 2. Conclusions and Implications Our findings suggest that H2S regulates MuRF1 S‐sulfhydration at Cys44 to prevent myocardial degradation in the cardiac tissues of db/db mice. Linked Articles This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc

The in situ nano Ta4HfC5 reinforced SiBCN-Ta4HfC5 composite ceramics were prepared by a combination of two-step mechanical alloying and reactive hot-pressing sintering. The microstructural evolution and mechanical properties of the resulting SiBCN-Ta4HfC5 were studied. After the first-step milling of 30 h, the raw materials of TaC and HfC underwent crushing, cold sintering, and short-range interdiffusion to finally obtain the high pure nano Ta4HfC5. A hybrid structure of amorphous SiBCN and nano Ta4HfC5 was obtained by adopting a second-step ball-milling. After reactive hot-pressing sintering, amorphous SiBCN has crystallized to 3C-SiC, 6H-SiC, and turbostratic BN(C) phases and Ta4HfC5 retained the form of the nanostructure. With the in situ generations of 2.5 wt% Ta4HfC5, Ta4HfC5 is preferentially distributed within the turbostratic BN(C); however, as Ta4HfC5 content further raised to 10 wt%, it mainly distributed in the grain-boundary of BN(C) and SiC. The introduction of Ta4HfC5 nanocrystals can effectively improve the flexural strength and fracture toughness of SiBCN ceramics, reaching to 344.1 MPa and 4.52 MPa·m1/2, respectively. This work has solved the problems of uneven distribution of ultra-high temperature phases in the ceramic matrix, which is beneficial to the real applications of SiBCN ceramics.

Hydrogen sulfide (H2S) plays physiological roles in vascular tone regulation, cytoprotection, and ATP synthesis. HMG-CoA reductase degradation protein (Hrd1), an E3 ubiquitin ligase, is involved in protein trafficking. H2S may play a role in controlling fatty acid uptake in diabetic cardiomyopathy (DCM) in a manner correlated with modulation of Hrd1 S-sulfhydration; however, this role remains to be elucidated. The aim of the present study was to examine whether H2S can attenuate lipid accumulation and to explain the possible mechanisms involved in the regulation of the H2S-Hrd1/VAMP3 pathway. Db/db mice and neonatal rat cardiomyocytes treated with high glucose, palmitate and oleate were used as animal and cellular models of type 2 diabetes, respectively. The expression of cystathionine-γ-lyase (CSE), Hrd1, CD36 and VAMP3 was detected by Western blot analysis. In addition, Hrd1 was mutated at Cys115, and Hrd1 S-sulfhydration was examined using an S-sulfhydration assay. VAMP3 ubiquitylation was investigated by immunoprecipitation. Lipid droplet formation was tested by TEM, BODIPY 493/503 staining and oil red O staining. The expression of CSE and Hrd1 was decreased in db/db mice compared to control mice, whereas CD36 and VAMP3 expression was increased. NaHS administration reduced droplet formation, and exogenous H2S restored Hrd1 expression, modified Ssulfhydration, and decreased VAMP3 expression in the plasma membrane. Using LC-MS/MS analysis, we identified 85 proteins with decreased ubiquitylation, including 3 vesicle-associated membrane proteins, in the cardiac tissues of model db/db mice compared with NaHS-treated db/db mice. Overexpression of Hrd1 mutated at Cys115 diminished VAMP3 ubiquitylation, whereas it increased CD36 and VAMP3 expression and droplet formation. siRNA-mediated Hrd1 deletion increased the expression of CD36 in the cell membrane. These findings suggested that H2S regulates VAMP3 ubiquitylation via Hrd1 S-sulfhydration at Cys115 to prevent CD36 translocation in diabetes.