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 (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.

MiR‐144 protects the heart from hyperglycemia‐induced injury by regulating mitochondrial biogenesis and cardiomyocyte apoptosis

“…Previous findings demonstrated that mitochondrial structure and function are significantly impaired in the islets and muscles of diabetic animals. [28][29][30] Mitochondria also exhibited diminished biogenesis; defective oxidative phosphorylation (OXPHOS); and reduced expression of complexes I, III, and V of the electron transport chain in STZ-treated myocardium tissue or HG-induced cardiomyocytes, [30][31][32] suggesting the impairment and dysfunction of mitochondria in hyperglycemic hearts. Based on TEM analysis, we found that the mitochondrial volume density was not remarkably altered, but that the mitochondria from HG-induced H9c2 cells exhibited significant morphological defects, including mitochondrial vacuolization and destroyed cristae and membranes ( Figure 1E).…”

Upregulation of CFTR Protects against Palmitate-Induced Endothelial Dysfunction by Enhancing Autophagic Flux

“…The mitochondrial apoptotic signaling pathway is associated with mitochondrial dysfunction: decreased mitochondrial membrane potential, and proapoptotic Bcl-2 family member translocation from cytosol to mitochondria leading to the release of Cyt C, and subsequently causes the activation of caspase 9 apoptotic caspase cascade [ 45 ]. It was reported that PA induced endothelial cell apoptosis by stimulating the death receptor pathway mediated by the TNF-R1/TNFR1-associated death domain protein (TRADD)/caspase 8 pathway [ 46 ], whereas most studies showed that PA led to mitochondrial dysfunction and increased the protein levels of Bax, Cyt C, and cleaved caspase 9 but reduced Bcl-2 protein expression [ 13 , 47 – 49 ]. In our previous study, we found that PA induced apoptosis in HUVECs through the mitochondria-mediated signaling pathway showing as a decrease of mitochondrial membrane potential and the ratio of Bcl-2/Bax [ 6 ].…”

“…Palmitate, a prominent component of FFAs, is widely utilized in in vitro experiments to mimic the effects of FFAs. Palmitate, in combination with high glucose impaired autophagosome formation and decreased autophagic flux participating in endothelial dysfunction [ 13 ]. Improvement of autophagic flux might serve as a critical approach to protect endothelial cells against injury induced by FFAs.…”

Hydrogen sulfide and vascular regulation – An update

“…H 2 S is reported to either promote or inhibit autophagy depending on the different pathological process [69] , [70] . NaHS was shown to activate mitophagy in rat aortic endothelial cells (RAECs) [71] . Mechanistically, NaHS facilitates Parkin recruited by PTEN induced putative kinase 1 (PINK1), and then ubiquitylates mitofusin 2 (Mfn2), leading to the upregulation of mitophagy [71] .…”

“…NaHS was shown to activate mitophagy in rat aortic endothelial cells (RAECs) [71] . Mechanistically, NaHS facilitates Parkin recruited by PTEN induced putative kinase 1 (PINK1), and then ubiquitylates mitofusin 2 (Mfn2), leading to the upregulation of mitophagy [71] . However, several studies showed that both supplementation of H 2 S and the overexpression of its synthetases mitigated mitophagy [72] .…”