Ischemic Postconditioning Ameliorates Cerebral Ischemia-reperfusion Injury Through Activating Autophagy Flux During Early Reperfusion

Recently stroke has become the first cause of mortality of residents,and Ischemic stroke accounted for 70% of all new diagnosed patients.The treatment for acute ischemic stroke(AIS)is closely related to the health of our residents.At present,Intravenous thrombolysis followed by intra-arterial thrombolysis is the most effective treatment for AIS which can significantly improve the prognosis of patients through opening vessels.However,this treatment may result in re-injury to the brain tissue to induce ischemic/reperfusion(I/R)injury.Ischemic postconditioning(IpostC)treatment has been shown to have neuroprotective effects but the protective mechanisms remains unclear.Autophagy is an evolutionarily conserved catabolic process that promotes ATP production and maintains intracellular stability.Previous literatures suggest that autophagy activation occurs after cerebral ischemia,but its function in cerebral ischemia received no consensus.In this present study,SD rats were used to establish local cerebral ischemia-reperfusion models by Doppler detection of regional cerebral blood flow before and after surgery,neuroethology test and cerebral infarction area evaluation.On the basis this model,we further established and optimized post-ischemic Processing Model,which turns out to show a good neuroprotective effect.The expression of autophagy-related proteins Beclin1,LC3,and p62 at 1,6,12,24,and 48 h after reperfusion in I/R rats and Ipost C rats were detected by western blot.Results showed that autophagy in both I/R and IpostC were activated.The activation of autophagy was earlier in IpostC,and the degradation of p62 was more pronounced in IpostC,suggesting that the effect of IpostC on autophagy is to maintain a complete autophagic process instead of just activating autophagy.What’s more,results using autophagy-inducing drug rapamycin in I/R rats further confirmed that promoting autophagy formation alone in I/R cannot lead to improvement in neurological function.Results of western blot,immunohistochemistry and transmission electron microscopy showed that the expression of lysosome-associated protein LAMP2 in IpostC rats was higher than that in I/R rats,while expression of Cathepsin B protein was lower than that of I/R rats.Results also suggest that IpostC can promote nuclear transcription of nuclear transcription factor EB.The electron microscopy results showed that the number of autolysosomes in IpostC rats was more than that in I/R rats,indicating that IpostC promoted the autophagy pathway.However,the neuroprotective effect of IpostC was inhibited after treated with autophagy inhibition drug 3MA.After that we further explored the relationship between I/R,IpostC and apoptosis and found that compared with I/R,cytochrome c release,Bax translocation and TUNEL positive cells and mitochondrial damage was reduced in IpostC,and 3MA inhibited the neuroprotective effect of IpostC.In conclusion,this study showed that IpostC has a certain neuroprotective effect on cerebral ischemia-reperfusion injury,which is related to the promotion of autophagy pathway and may become a new target in the clinical treatment of acute ischemic stroke in the future.