Mitochondrial Mechanism Of JAK2-STAT3 Signaling Pathway In Reversing Myocardial Ischemia/Reperfusion Injury In Diabetic Rats By Sevoflurane Postconditioning

Objective:Cardiovascular disease is a prominent social issue in the world.The incidence of cardiovascular diseases in China has been on the rise.The incidence of diabetes is rising year by year and tends to be younger.It has become a worldwide public health problem that poses serious threats to human health.Myocardial ischemic reperfusion?I/R?injury occurs in diabetes patients,and the complication rate and mortality rate obviously increase with serious consequences.Sevoflurane Postconditioning?SPostC?has a myocardial protective effect similar to that of ischemic preconditioning,but myocardial protection of SpostC disappears in the diabetic state,and insulin can not restore the cardioprotective effect of SPostC in diabetic rats.How to restore the clinically existing myocardial protection measures and restore the protective effect on diabetic myocardium is an important clinical problem to be solved urgently.Based on the previous studies,this study focused on myocardial cell signaling pathway and HIF-1?,mitochondria and other key targets,and hope to restore the myocardial protection of SpostC in diabetic condition.Methods:An adult male Sprague-Dawley?SD?rat model of myocardial ischemia/reperfusion?I/R?injury was established using the Langendorff apparatus.The initial of reperfusion,2.4%sevoflurane alone or in combination with AG490?a JAK2 selective inhibitor?was used as a postconditioning treatment.The cardiac function indicators,myocardial infarct size,lactic dehydrogenase?LDH?release,mitochondrial ultrastructure,mitochondrial reactive oxygen species?ROS?generation rates,ATP content,protein expression of p-JAK,p-STAT3,Bcl-2 and Bax were measured.A rat model of type II diabetes mellitus and Langendorff isolated cardiac ischemia-reperfusion model were established and treated with sevoflurane?2.4%?for post-treatment.Randomized vehicle treatment or Cobaltous Chloride?CoCl₂??30mg/Kg?treatment,or in combination with HIF-1?blocker 2-Methoxyestradiol?2ME2?.The cardiac function,infarct size,mitochondria morphology,nitric oxide?NO?,ROS,HIF-1protein levels,vascular endothelial growth factor?VEGF?,endothelial nitric oxide synthase?eNOS?,mitochondrial respiration Function and enzyme activity.And determine the application of insulin to reduce the impact of blood glucose on SPostC.To establish a rat model of type II diabetes mellitus and the left anterior descending coronary artery?LAD?was ligated to prepare a myocardial I/R injury model.Desferrioxamine?DFO?was injected intraperitoneally 24 hours before the experiment and 2ME2 was injected intraperitoneally before LAD was ligated.The SpostC implementation gave 2.4%sevoflurane 15minutes prior to the start of reperfusion.Myocardial infarct size,cardiac function,myocardial ultrastructure,mitochondrial respiratory function,respiratory chain enzyme activity,ROS production,expression of HIF-1?and VEGF protein were detected after I/R injury.Results:In isolated rat myocardial I/R model,compared with the I/R group,S-post significantly increased the expression of p-JAK,p-STAT3 and Bcl-2 and reduced the protein expression of Bax,which markedly decreased the myocardial infarction areas,improved the cardiac function indicators and the mitochondrial ultrastructure,decreased the mitochondrial ROS and increased the ATP content.However,the cardioprotective effects of S-post were abolished by treatment with a JAK2 selective inhibitor?P<0.05?.Loss of SPostC protection in diabetic conditions and impaired HIF-1?expression.However,CoCl₂ treatment restored the protective effect of SPostC,stabilized the activity of enzymes and improved cardiac function and mitochondrial respiratory function?P<0.05?.The area of myocardial infarction was reduced to 25.08±3.87%?P<0.05?,and this effect was dependent on HIF-1?stable expression?P<0.05?.In addition,blood glucose levels had no effect on the above effects?P<0.05?.After DFO activated HIF-1 in diabetic myocardium,SpostC significantly up-regulated the protein expression of HIF-1?and its downstream VEGF,thereby improving myocardial mitochondrial respiration and respiratory chain enzyme activity,decreasing ROS production and decreasing Caspase 3 and Bax protein Decreased expression;thereby reducing myocardial infarction area,improve cardiac function and mitochondrial ultrastructure.Conclusion:This study demonstrates that the cardioprotective effects of S-post are associated with the activation of JAK2-STAT3.The mechanism may be related to an increased expression of p-JAK2 and p-STAT3 after S-post,which reduced ROS generation of mitochondrial and increased ATP content,thereby reducing myocardial infarct size.The protective effects of SPostC on diabetic myocardium were weakened.Combined with CoCl₂ could reverse the damage of HIF-1?and restore the protective effect of SPostC.The main mechanism is to improve cardiac function,NO,mitochondrial respiratory function by up-regulating the expression of HIF-1?,VEGF,eNOS and enzyme activity,ultimately reduce ROS production and reduce infarct size.Also confirmed that,DFO can activate HIF-1 can restore myocardial SpostC diabetic state of protection.The intrinsic protective effect of diabetic myocardium has nothing to do with blood glucose levels.