Experimental Study On The Neuroprotective Mechanism Of AMPK-mTOR Mediated Autophagy In Bradykinin Postconditioning After Cardiac Arrest In Rats

Objective To observe the effect of bradykinin postconditioning on the impro vement of total cerebral ischemia and hypoxia injury and explore its possible me chanism。Methods Forty adult male Sprague-Dawley rats were divided into five groups randomly:sham operation group,cardiac arrest(CA)group,bradykinin treatment(BK)group,Compound C+bradykinin treatment(CP+BK)group,rapamycin+bradykinin treatment(Ra+BK)group,8 rats in each group,30 minutes before cardiac arrest,rats in CP + BK group were intraperitoneally injected with Compound C(250 ug/kg),Rats in the Ra+BK group were intraperitoneally injected with rapamycin(1mg/kg),and rats in the remaining groups were injected with the same dose of DMSO.After ROSC,rats in the BK group,CP+BK group and Ra+BK group were intraperitoneally injected with bradykinin(150ug/kg),and rats in the remaining groups were injected with the same dose of normal saline.72 h after ROSC was the observation point.After 72 h,the nerve function of rats in each group was evaluated with neurological deficit score(NDS),and then the mice in each group were selected.The IHC(immunohistochemistry)was conducted to examine the expression of AMPK-mTOR pathway related proteins(AMPK,p-AMPK,mTOR,p-mTOR)and autophagy-related proteins(LC3,P62)in hippocampal tissues,formation of autophagosomes and ultrastructure of neuronal cells was observed with transmission electron microscopy、The TUNEL method was uesed to detect the apoptosis rate of hippocampal nerve cells.Results(1)compared with sham group:the neurological deficit score of CA group was decreased,the expression levels of LC3,P62,AMPK,p-AMKP,mTOR,p-mTOR and the number of apoptotic cells were increased.(2)Compared with the BK group:(1)the neurological deficit score of the CA group decreased,the expression levels of AMPK and p-AMPK decreased,the expression levels of mTOR and p-mTOR increased,the expression levels of autophagy-related protein LC3 decreased,the expression levels of P62 increased,and the number of apoptotic cells increased;(2)the neurological deficit score of CP+BK group was decreased,the expression of AMPK and p-AMPK decreased,the expression of mTOR and p-mTOR increased,the expression of autophagy-related protein LC3 decreased,the expression of P62 increased,and the number of apoptotic cells increased;(3)the neurological deficit score of Ra+BK group was increased,the expression of AMPK and p-AMPK increased,the expression of mTOR and p-mTOR decreased,the expression of LC3 increased,the expression of P62 decreased,and the number of apoptotic cells decreased.The differences between the above groups were statistically significant(P<0.05).(3)Autophagosomes were observed by transmission electron microscopy in each group: no autophagosomes were observed in sham group,autophagosomes were observed in other groups,and multiple fields were observed under the same power microscope.Comparatively,the number of autophagosomes in Ra+BK group was the largest,followed by BK group,and there was no significant difference in the number of autophagosomes in CA group and CP+BK group.Conclusion Bradykinin postconditioning play a neuroprotective role in cardiopulmonary resuscitation(CPR)rats by activating AMPK-mTOR pathway mediated autophagy and reducing hippocampal nerve cell apoptosis.