Hydrogen Sulfide Protects against Rat Ischemic Brain Injury by Promoting RhoA Phosphorylation at Serine 188

The protective role of hydrogen sulfide against cerebral ischemia-reperfusion injury involves the inhibition of the RhoA-/Rho-associated coiled-coil kinase (ROCK) pathway. However, the specific mechanism remains elusive. This study investigates the impact of hydrogen sulfide on RhoA phosphorylation at serine 188 (Ser188) in vivo, aiming to test the hypothesis that hydrogen sulfide exerts neuroprotection by enhancing RhoA phosphorylation at Ser188, subsequently inhibiting the RhoA/ROCK pathway. Recombinant RhoA^wild-pEGFP-N1 and RhoA^S188A-pEGFP-N1 plasmids were constructed and administered via stereotaxic injection into the rat hippocampus. A rat global cerebral ischemia-reperfusion model was induced by bilateral carotid artery ligation to elucidate the neuroprotective mechanisms of hydrogen sulfide. Both RhoA^wild-pEGFP-N1 and RhoA^S188A-pEGFP-N1 plasmids expressed RhoA^wild and RhoA^S188A proteins, respectively, in rat hippocampal tissues, alongside the intrinsic RhoA protein. Systemic administration of the exogenous hydrogen sulfide donor sodium hydrosulfide led to an increase in Ser188 phosphorylation of transfected RhoA^wild and intrinsic RhoA protein within the hippocampus. However, this effect was not observed in tissues transfected with RhoA^S188A. Sodium hydrosulfide-mediated RhoA phosphorylation correlated with decreased RhoA and ROCK₂ activity in rat hippocampal tissues. Furthermore, sodium hydrosulfide administration reduced cerebral ischemia-reperfusion-induced neuronal damage and apoptosis in rat hippocampal tissues transfected with RhoA^wild. However, this neuroprotective effect was attenuated in rats transfected with RhoA^S188A. These findings suggest that the neuroprotective mechanism of hydrogen sulfide against cerebral ischemia/reperfusion injury involves increased RhoA phosphorylation at Ser188. Promoting this phosphorylation may represent a potential intrinsic therapeutic target for ischemic stroke.