Effects Of Acid-sensing Ion Channel La In Global Cerebral Ischemia-reperfusion Injury In Rats

Objective To evaluate the effect of acid sensing ion channel la on the expression of Caspase-3, Bcl-2, Bax, mRNA of brain-derived-neurotrophic factor(BDNF mRNA) and mRNA of Tyrosine kinase B(TrKB mRNA) in the rats hippocampus following global cerebral ischemia-reperfusion (I/R) injury, so as to speculate whether acid-sensing ion channel la(ASICla) induces global cerebral ischemia-reperfusion injury in rats and validate the neuroprotective effect of ASIC1a suppression in global cerebral ischemia-reperfusion (I/R) injury in rats.Methods Seventy-two male SD rats weighing250～300g were randomly divided into4groups (n=18each):sham operation group (group S), cerebral ischemia-reperfusion group (group I/R), vehicle group (group V) and group PcTXl (a ASICla blocker, group P). Global cerebral ischemia-reperfusion was induced by four-vessel occlusion. In groups I/R, V and P cerebral ischemia-reperfusion was induced by15min ligation of bilateral carotid artery followed by reperfusion.PcTX1(500ng/ml)6μl or vehicle6μl were injected into the cerebral ventricular in groups P and V respectively. Six rats of each group were sacrificed after6h of reperfusion, and then the hippocampus was removed for biochemical testing. The level of BDNF mRNA and TrKB mRNA were detected by using RT-PCR method. Twelve rats were sacrificed at24h of reperfusion, and then the hippocampus was removed for biochemical testing and microscopic examination. The expression of Caspase-3was detected by western blotting, while Bcl-2and Bax protein expression and pathological changes of pyramidal neurons were evaluated in hippocampal CA1 region by using immunocytochemiatry and HE staining.Results Compared with group S, the expression of BDNF mRNA and TrKB mRNA was up-regulated in group I/R,V and P at6h of reperfusion (P<0.05); the expression of Caspase-3, Bcl-2and Bax protein was up-regulated in groups I/R, V and P at24h of reperfusion (P<0.05).Compared with groups I/R, the expression of BDNF mRNA and TrKB mRNA were significantly higher in group P at6h of reperfusion (P<0.05); the expression of Caspase-3and Bax was down-regulated, and the expression of Bcl-2up-regulated in group P at24h of reperfusion (P<0.05). There was no significant difference in BDNF mRNA, TrKB mRNA, Caspase-3, Bcl-2and Bax protein expression between groups I/R and V (P>0.05). The histopathologic damage was ameliorated in group P as compared with group I/R.Conclusion ASIC1a can induce global cerebral ischemia-reperfusion injury in rats by up-regulating Caspase-3and Bax expression, and down-regulating Bcl-2expression and inducing apoptosis. PcTXl can alleviate the cerebral I/R injury by up-regulation of the expression of BDNF mRNA and TrKB mRNA.