Protection against Hypoxia-Reoxygenation Injury of Hippocampal Neurons by H2S via Promoting Phosphorylation of ROCK2 at Tyr722 in Rat Model

The RhoA-ROCK signaling pathway is associated with the protective effects of hydrogen sulfide (H2S) against cerebral ischemia. H2S protects rat hippocampal neurons (RHNs) against hypoxia-reoxygenation (H/R) injury by promoting phosphorylation of RhoA at Ser188. However, effect of H2S on the phosphorylation of ROCK2-related sites is unclear. The present study was designed to investigate whether H2S can play a role in the phosphorylation of ROCK2 at Tyr722, and explore whether this role mediates the protective effect of H/R injury in RHNs. Prokaryotic recombinant plasmids ROCK2wild-pGEX-6P-1 and ROCK2Y722F-pGEX-6P-1 were constructed and transfected into E. coli in vitro, and the expressed protein, GST-ROCK2wild and GST-ROCK2Y722F were used for phosphorylation assay in vitro. Eukaryotic recombinant plasmids ROCK2Y722-pEGFP-N1 and ROCK2Y722F-pEGFP-N1 as well as empty plasmid were transfected into the RHNs. Western blot assay and whole-cell patch-clamp technique were used to detect phosphorylation of ROCK2 at Tyr722 and BKCa channel current in the RHNs, respectively. Cell viability, leakages of intracellular enzymes lactate dehydrogenase (LDH), and nerve-specific enolase (NSE) were measured. The H/R injury was indicated by decrease of cell viability and leakages of intracellular LDH and NSE. The results of Western blot have shown that NaHS, a H2S donor, significantly promoted phosphorylation of GST-ROCK2wild at Tyr722, while no phosphorylation of GST-ROCK2Y722F was detected. The phosphorylation of ROCK2wild promoted by NaHS was also observed in RHNs. NaHS induced more potent effects on protection against H/R injury, phosphorylation of ROCK2 at Tyr722, inhibition of ROCK2 activity, as well as increase of the BKCa current in the ROCK2Y722-pEGFP-N1-transfected RHNs. Our results revealed that H2S protects the RHNs from H/R injury through promoting phosphorylation of ROCK2 at Tyr722 to inhibit ROCK2 activity and potentially by opening channel currents.

Automated summary

The present study demonstrates that H2S protects rat hippocampal neurons against hypoxia-reoxygenation injury by promoting the phosphorylation of ROCK2 at Tyr722. This phosphorylation inhibits ROCK2 activity and potentially contributes to the protective effects against H/R injury by opening channel currents.