Xin-Xue Liao

The roles of hydrogen sulfide (H₂S) and endoplasmic reticulum (ER) stress in doxorubicin (DOX)-induced cardiotoxicity are still unclear. This study aimed to dissect the hypothesis that H₂S could protect H9c2 cells against DOX-induced cardiotoxicity by inhibiting ER stress. Our results showed that exposure of H9c2 cells to DOX significantly inhibited the expression and activity of cystathionine-γ-lyase (CSE), a synthetase of H₂S, accompanied by the decreased cell viability and the increased reactive oxygen species (ROS) accumulation. In addition, exposure of cells to H₂O₂ (an exogenous ROS) mimicked the inhibitory effect of DOX on the expression and activity of CSE. Pretreatment with N-acetyl-l-cysteine (NAC) (a ROS scavenger) attenuated intracellular ROS accumulation, cytotoxicity, and the inhibition of expression and activity of CSE induced by DOX. Notably, the ER stress-related proteins, including glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were obviously upregulated in DOX-treated H9c2 cells. Pretreatment with sodium hydrosulfide (NaHS, a H₂S donor) before DOX exposure markedly suppressed DOX-induced overexpressions of GRP78 and CHOP, cytotoxicity and oxidative stress. In conclusion, we have demonstrated that ROS-mediated inhibition of CSE is involved in DOX-induced cytotoxicity in H9c2 cells, and that exogenous H₂S can confer protection against DOX-induced cardiotoxicity partly through inhibition of ER stress.

Hydrogen sulfide (H₂S) has been shown to exert cardioprotective effects. However, the roles of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in H₂S-induced cardioprotection have not been completely elucidated. In this study, cobalt chloride (CoCl₂), a chemical hypoxia mimetic agent, was applied to treat H9c2 cells to establish a chemical hypoxia-induced cardiomyocyte injury model. The results showed that pretreatment with NaHS (a donor of H₂S) before exposure to CoCl₂ attenuated the decreased cell viability, the increased apoptosis rate, the loss of mitochondrial membrane potential (ΔΨm), and the intracellular accumulation of reactive oxygen species (ROS) in H9c2 cells. Exposure of H9c2 cells to CoCl₂ or hydrogen peroxide (H₂O₂) upregulated expression of phosphorylated (p) ERK1/2, which was reduced by pretreatment with NaHS or N-acetyl-l-cysteine, a ROS scavenger. More importantly, U0126, a selective inhibitor of ERK1/2, mimicked the above cytoprotection of H₂S against CoCl₂-induced injury in H9c2 cells. In conclusion, these results indicate that H₂S protects H9c2 cells against chemical hypoxia-induced injury partially by inhibiting ROS-mediated activation of ERK1/2.