Hydrogen sulfide protects neurons against hypoxic injury via stimulation of ATP-sensitive potassium channel/protein kinase C/extracellular signal-regulated kinase/heat shock protein90 pathway

Cerebral hypoxia is one of the main causes of cerebral injury. This study was conducted to investigate the potential protective effect of H₂S in in vitro hypoxic models by subjecting SH-SY5Y cells to either oxygen–glucose deprivation or Na₂S₂O₄ (an oxygen scavenger) treatment. We found that treatment with NaHS (an H₂S donor, 10–100 μM) 15 min prior to hypoxia increased cell viability in a concentration-dependent manner. Time-course study showed that NaHS was able to exert its protective effect even when added 8 h before or less than 4 h after hypoxia induction. Interestingly, endogenous H₂S level was markedly reduced by hypoxia induction. Over-expression of cystathionine-β-synthase prevented hypoxia induced cell apoptosis. Blockade of ATP-sensitive K⁺ (K_ATP) channels with glibenclamide and HMR-1098, protein kinase C (PKC) with its three specific inhibitors (chelerythrine, bisindolylmaleide I and calphostin C), extracellular signal-regulated kinase 1/2 (ERK1/2) with PD98059 and heat shock protein 90 (Hsp90) with geldanamycin and radicicol significantly attenuated the protective effects of NaHS. Western blots showed that NaHS significantly stimulated ERK1/2 activation and Hsp90 expression. In conclusion, H₂S exerts a protective effect against cerebral hypoxia induced neuronal cell death via K_ATP/PKC/ERK1/2/Hsp90 pathway. Our findings emphasize the important neuroprotective role of H₂S in the brain during cerebral hypoxia.