Hydrogen Sulfide Combined With Mild Hypothermia Can Selectively Activating Synaptic NMDARs And Triggering The CREB Signaling Pathway

Objective To evaluate the effects of hydrogen sulfide combined with mild hypothermia on the expression of NR2A, NR2B, phospho-cAMP response element binding protein (p-CREB) and mRNA of brain-derived-neurotrophic factor(BDNF mRNA) in the rats hippocampus following global cerebral ischemia-reperfusion (I/R) injury, so as to speculate the underlying possible mechanisms of neuroresuscitation.Methods One hundred male SD rats, aged 3 months, weighing 250-300 g, were randomly divided into five groups with 20 each:sham operation group (groupⅠ), cerebral ischemia-reperfusion group (groupⅡ), mild hypothermia group (groupⅢ), sodium hydrogen sulfide group (groupⅣ), sodium hydrogen sulfide+mild hypothermia group (groupⅤ). In groupⅡto V cerebral I/R was induced by 15 min ligation of bilateral carotid artery followed by reperfusion. In group IV and V intraperitoneal sodium hydrogen sulfide 14μM/kg was injected immediately after reperfusion, while the equal volume of normal saline was injected in the other three groups. At the same time, the rectal temperature was reduced to 32-33℃within 15 min, lasting for 6 h, in groupⅢandⅤ, while it was maintained at 36-37℃by lamp in other groups. Sixteen rats of each group were sacrificed after 6 h of reperfusion, and then the hippocampus was removed for microscopic examination. The content of H2S in hippocampus was measured by spectrophotometer. The expression of NR2A, NR2B and p-CREB were detected by western blotting, while BDNF mRNA was measured by RT-PCR. Four rats of each group were sacrificed after 72 h of reperfusion to evaluate the pathological changes of pyramidal neurons by HE staining.Results The cerebral I/R injury was attenuated in groupⅢ, IVand V compared with groupⅡ, with the best effect in group V. The content of H2S was increased in groupⅡ,Ⅲ,ⅣandⅤthan in groupⅠ(P<0.05). It was significantly higher in groupⅣandⅤthan in groupⅡandⅢ(P<0.05). There was no significant difference between groupⅡandⅢ, group IVandⅤ, respectively (P>0.05). The lever of NR2B was greater than NR2A in groupⅡandⅢ, which was opposite in groupⅣandⅤ. The expression of p-CREB and BNDF mRNA were both up-regulated in groupⅡtoⅤthan in groupⅠ(P<0.05). They were also significantly elevated in groupⅢto V than in groupⅡ(P< 0.05). The expression of p-CREB was no statistical difference in group V than groupⅢandⅣ(P>0.05), while the level of BDNF mRNA was significantly higher(P<0.05). The difference in the expression of p-CREB and BDNF mRNA between groupⅢand IV was no statistical meaning (P>0.05).Conclusion Hydrogen sulfide combined with mild hypothermia could alleviate the cerebral I/R injury by selectively activating synaptic NMDARs and triggering the CREB signaling pathway.