The Effects And Mechanisms Of Ischemic Postconditioning Prolong Time Window On Cerebral Ischemia/reperfusion Injury In Rats

Objective To study the effects of ischemic postconditioning prolong time window and investigate the possible mechanism.Method There are three parts in this experiment. The first part:middle cerebral artery occlusion model was stablished and ischemic postconditioning was implemented in the beginning of reperfusion. Adult male SD rats were randomly divided into ischemia/reperfusion groups and ischemia/reperfusion with ischemic postconditioning groups at2h,3h,4h,4.5h,6h ischemic time points. The effects of ischemic postconditioning were evaluated by neurological score, infarct volume, brain edema and found out the best time window. To select one time point that neurological score and infarct volume is no difference compared to2h, then continuing the following experiments. The second part:the pathological changes of brain tissue in rats were observed by HE staining; the expression of TLR2and TLR4in ischemic cortex in ischemia/reperfusion groups and ischemia/reperfusion with ischemic postconditioning groups at2h and4.5h ischemic time points were measured through immunohistochemistry. The third part:the expression of TLR2, TLR4, IRAK4, IL-1β and apoptosis in ischemic cortex in ischemia/reperfusion groups and ischemia/reperfusion with ischemic postconditioning groups at2h and4.5h ischemic time points were measured through flow cytometry, qRT-PCR and Western-Blotting.Result Neurological score of ischemic postconditioning groups at2h,3h,4h ischemic time points were improved by the same time points ischemic groups and4.5h,6h postconditioning groups in reperfusion24h and48h(p<0.05). Infarct volume and brain edema of ischemic postconditioning groups at2h,3h,4h ischemic time points were reduced by the same time points ischemic groups and4.5h,6h postconditioning groups in reperfusion48h(p<0.05). The number of TLR2and TLR4positive cells in ischemic cortex at2h postconditioning group during reperfusion48h were reduced by2h ischemic group and4.5h postconditioning group (p<0.05); the number of TLR4positive cells was reduced at4.5h postconditioning group by4.5h ischemic group. The apoptosis in ischemic cortex at2h postconditioning group during reperfusion48h were reduced by2h ischemic group and4.5h postconditioning group (p<0.05). The expression of TLR2, TLR4, IL-1βmRNA and protein as well as IRAK4mRNA in ischemic cortex at2h postconditioning group during reperfusion48h were decreased by2h ischemic group (p<0.05); the expression of TLR2, IL-1βmRNA and protein as well as TLR4protein decreased by4.5h postconditioning group (p<0.05)Conclusion Ischemic postconditioning significantly attenuated the cerebral ischemia/reperfusion injury by neurological score, infarct volume, brain edema improved. The best time window is within4.5h. Ischemic postconditioning significantly attenuated apoptosis and inflammation caused by cerebral ischemia/reperfusion injury. The expression of TLR2, TLR4, IRAK4, IL-1βand apoptosis in ischemic cortex at2h postconditioning group significantly were inhibited.