Hydrogen Sulphide modulating mitochondrial morphology to promote mitophagy in endothelial cells under high-glucose and high-palmitate

Abstract

Endothelial cell dysfunction is one of the main reasons for type II diabetes vascular complications. Hydrogen sulphide (H₂ S) 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 H₂ S donor. Firstly, we demonstrated that high glucose and palmitate decreased H₂ S production and CSE expression in RAECs. Then, the antioxidative effect of H₂ S was proved in RAECs under high glucose and palmitate to reduce mitochondrial ROS level. We also showed that exogenous H₂ S inhibited mitochondrial apoptosis in RAECs under high glucose and palmitate. Using Mito Tracker and transmission electron microscopy assay, we revealed that exogenous H₂ S 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 H₂ S facilitated Parkin recruited by PINK1 by immunoprecipitation and immunostaining assays and then ubiquitylated mitofusin 2 (Mfn2), which illuminated the mechanism of exogenous H₂ S on mitophagy. Parkin siRNA suppressed the expression of Mfn2, Nix and LC3B, which revealed that it eliminated mitophagy. In summary, exogenous H₂ S 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 H₂ S on protecting endothelium, which might provide a new strategy for type II diabetes vascular complication.

Keywords: Parkin; diabetes; hydrogen sulphide; mitochondrial fission/fusion; mitophagy.