Hydrogen sulfide ameliorated endothelial dysfunction in hyperhomocysteinemia rats: Mechanism of IRE1α/JNK pathway-mediated autophagy

Previous studies showed that hyperhomocysteinemia (HHcy) induced endothelial dysfunction by endoplasmic reticulum (ER) stress induction and autophagy stimulation. This study aimed to determine the effect of hydrogen sulfide (H₂S) in homocysteine (Hcy)-induced endothelial dysfunction and observe the possible mechanism involved. Male Wistar rats (160–180g) were used and randomly divided into four groups: Control group, HHcy group, HHcy+Sodium hydrosulfide (NaHS) group and NaHS group. Rats were fed with 2% high methionine diet for 8 weeks to set up HHcy model. Plasma concentration of Hcy was measured by ELISA. Endothelium-dependent and non-endothelium-dependent vasodilation of rat renal arteries were determined by myograph. The protein expression of cystathionine-γ-lyase (CSE), ER stress- and autophagy-related proteins in renal arteries or human umbilical vein endothelial cells (HUVECs) were analyzed by western blotting. The endothelial function was impaired in HHcy rats and HUVECs. NaHS supplementation could improve the ACh-induced vasodilation, however it was eliminated by ER stress inducer Tunicamycin (TM) or autophagy inducer Rapamycin. Western blotting in renal arteries showed that Glucose-regulated protein 78 (GRP78) and three branches of ER stress (p-IRE1α, p-PERK, ATF6) , p-JNK1+p-JNK2 were downregulated, simultaneously the autophagy marker Beclin1, LC3BII/LC3BI ratio were decreased and p62 was increased with NaHS treatment in HHcy rats. In HUVECs, IRE1α-JNK induced autophagy was involved in HHcy-induced endothelial dysfunction, while NaHS stimulation reversed the protein expression in IRE1α/JNK-autophagy pathway with Hcy incubation. This study might suggest that endothelial dysfunction induced by HHcy might be correlated with IRE1α-JNK-autophagy axis pathway, which was suppressed by exogenous supplementation of H₂S donor, NaHS.