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 (H 2 S) 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, GRP78) and p-JNK1+p-JNK2 was downregulated by NaHS administration, simultaneously the autophagy marker Beclin1, LC3BII/LC3BI ratio was decreased and p62 was increased in HHcy rats. In HUVECs, IRE1α-JNK induced autophagy was involved in HHcy-induced endothelial dysfunction, while NaHS stimulation decreased the protein expression in IRE1α/JNK-autophagy pathway with Hcy incubation. This study might suggest that endothelial dysfunction induced by HHcy might be correlate with IRE1α-JNK-autophagy axis pathway, which was suppressed by exogenous supplementation of H 2 S donor NaHS.
Excessive accumulation of cadmium (Cd) in retina plays an important role in tobacco smoking-associated age-related macular degeneration (AMD). Plenty of evidence has revealed that the retinal pigment epithelium (RPE) is the primary site of pathology in AMD. Our current study demonstrated that Cd induced apoptosis in a human RPE cell line ARPE-19 cells, as it dose-dependently caused cell viability loss and activated caspase-3. The reactive oxygen species (ROS) were confirmed to be important mediators for Cd-triggered cell death in ARPE-19 cells. We found that endoplasmic reticulum (ER) stress was activated as its marker BiP was remarkably upregulated by Cd-exposure. Whereas the antioxidants N-acetylcysteine (NAC) and Tempol significantly suppressed the expression of BiP and CHOP, suggesting that ROS generation is an early trigger of Cd-activated ER stress. Furthermore, we found that Cd-induced oxidative stress significantly increased autophagic flux and p62 expression. A temporal impact of Cd exposure is possibly existed in p62 expression in ARPE-19 cells. Moreover, an ER stress inhibitor salubrinal diminished Cd-induced LC3BII expression and attenuated cytotoxicity, indicating that ER stress mediates autophagy and was implicated in apoptosis of Cd-exposed ARPE-19 cells. However, CHOP expression may not exert impact on the regulation of Cd-caused autophagy. Additionally, inhibition of autophagy with si-Beclin 1 and 3-Methyladenine significantly ameliorated Cd-induced CHOP expression and cytotoxicity, indicating that autophagy was detrimental in Cd-accumulated ARPE-19 cells, and a positive feedback regulation mechanism may exist between Cd-triggered ER stress and autophagy. Taken together, these results suggest that Cd-caused ER stress and autophagy are implicated in RPE cell death associated retinopathies especially related to smoking.
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