Endothelial cell dysfunction is one of the main reasons for type II diabetes vascular complications. Hydrogen sulphide (H2S) has antioxidative effect, but its regulation on mitochondrial dynamics and mitophagy in aortic endothelial cells under hyperglycaemia and hyperlipidaemia is unclear. Rat aortic endothelial cells (RAECs) were treated with 40 mM glucose and 200 μM palmitate to imitate endothelium under hyperglycaemia and hyperlipidaemia, and 100 μM NaHS was used as an exogenous H2S donor. Firstly, we demonstrated that high glucose and palmitate decreased H2S production and CSE expression in RAECs. Then, the antioxidative effect of H2S was proved in RAECs under high glucose and palmitate to reduce mitochondrial ROS level. We also showed that exogenous H2S inhibited mitochondrial apoptosis in RAECs under high glucose and palmitate. Using Mito Tracker and transmission electron microscopy assay, we revealed that exogenous H2S decreased mitochondrial fragments and significantly reduced the expression of p‐Drp‐1/Drp‐1 and Fis1 compared to high‐glucose and high‐palmitate group, whereas it increased mitophagy by transmission electron microscopy assay. We demonstrated that exogenous H2S facilitated Parkin recruited by PINK1 by immunoprecipitation and immunostaining assays and then ubiquitylated mitofusin 2 (Mfn2), which illuminated the mechanism of exogenous H2S on mitophagy. Parkin siRNA suppressed the expression of Mfn2, Nix and LC3B, which revealed that it eliminated mitophagy. In summary, exogenous H2S could protect RAECs against apoptosis under high glucose and palmitate by suppressing oxidative stress, decreasing mitochondrial fragments and promoting mitophagy. Based on these results, we proposed a new mechanism of H2S on protecting endothelium, which might provide a new strategy for type II diabetes vascular complication.

Background/Aim: Autophagy plays an important role in cellular homeostasis through the disposal and recycling of cellular components. Hydrogen sulphide (H₂S) is the third endogenous gas that has been shown to confer cardiac protective effects. Given the regulation of autophagy in cardioprotection, this study aimed to investigate the protective effects of H₂S via autophagy during high glucose treatment. Methods: This study investigated the content of H₂S in the plasma as well as myocardial, ultrastructural changes in mitochondria and autophagosomes. This study also investigated the apoptotic rate using Hoechst/PI as well as expression of autophagy-associated proteins and mitochondrial apoptotic proteins in H9C2 cells treated with or without GYY4137. Mitochondria of cardiac tissues were isolated and RCR and ADP/O were also detected. AMPK knockdown was performed with siRNA transfection. Results: In a STZ-induced diabetic model, NaHS treatment not only increased the expression of p-AMPK in diabetic group but further activated cell autophagy. Following 48h high glucose, autophagosomes and cell viability were reduced. The present results showed that autophagy could be induced by H₂S, which was verified by autophagic ultrastructural observation and LC3-I/LC3-II conversion. In addition, the mitochondrial membrane potential (MMP) was significantly decreased. The expressions levels of autophagic-related proteins were significantly elevated. Moreover, H₂S activated the AMPK/rapamycin (mTOR) signalling pathway. Conclusions: Our findings demonstrated that H₂S decreases oxidative stress and protects against mitochondria injury, activates autophagy, and eventually leads to cardiac protection via the AMPK/mTOR pathway.

HS regulated the acetylation level and activities of enzymes in fatty acid oxidation and glucose oxidation in cardiac tissues of db/db mice. Exogenous HS decreased mitochondrial acetylation level through upregulating the expression and activity of SIRT3 in vivo and in vitro. HS induced a switch in cardiac energy substrate utilization from fatty acid oxidation to glucose.

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes. Hydrogen sulphide (H2S), a newly found gaseous signalling molecule, has an important role in many regulatory functions. The purpose of this study is to investigate the effects of exogenous H2S on autophagy and its possible mechanism in DCM induced by type II diabetes (T2DCM). In this study, we found that sodium hydrosulphide (NaHS) attenuated the augment in left ventricular (LV) mass and increased LV volume, decreased reactive oxygen species (ROS) production and ameliorated H2S production in the hearts of db/db mice. NaHS facilitated autophagosome content degradation, reduced the expression of P62 (a known substrate of autophagy) and increased the expression of microtubule-associated protein 1 light chain 3 II. It also increased the expression of autophagy-related protein 7 (ATG7) and Beclin1 in db/db mouse hearts. NaHS increased the expression of Kelch-like ECH-associated protein 1 (Keap-1) and reduced the ubiquitylation level in the hearts of db/db mice. 1,4-Dithiothreitol, an inhibitor of disulphide bonds, increased the ubiquitylation level of Keap-1, suppressed the expression of Keap-1 and abolished the effects of NaHS on ubiquitin aggregate clearance and ROS production in H9C2 cells treated with high glucose and palmitate. Overall, we concluded that exogenous H2S promoted ubiquitin aggregate clearance via autophagy, which might exert its antioxidative effect in db/db mouse myocardia. Moreover, exogenous H2S increased Keap-1 expression by suppressing its ubiquitylation, which might have an important role in ubiquitin aggregate clearance via autophagy. Our findings provide new insight into the mechanisms responsible for the antioxidative effects of H2S in the context of T2DCM.