Effects Of Ischemic Preconditioning On Myocardical Ischemia-reperfusion Injury In Mice

In recent years,with the establishment and application of coronary angioplasty,artery bypass surgery,thrombolytic therapy,cardiac surgery extracoporeal circulation,which makes the tissues and organs receive blood reperfusion after ischemia.Under most circumstances,the organ which is in ischemia can be restored,the structures which is damaged can be repaired,and patients can recover.But sometimes ischemic reperfusion can not make the organs or the tiusse recover.Instead,it can aggravate organizations' and organs' function disorder and structure injury.The phenomenon that the damage of ischemic tiusse is worse after reperfusion,or causes irreversible damage is known as ischemia reperfusion injury.Ischemic preconditioning refers to that after one or more brief ischemia,then heart have a long time ischemia reperfusion,it can reduce the damage which caused by ischemia reperfusion.To explore the effects of ischemic-preconditioning on myocardial ischemic-reperfusion injury,the myocardial ischemia-perfusion model was established in C57/B6 male mice aged 6-8 weeks.Thirty-six mice were randomly divided into three groups:Sham group(Sham,n=12),ischemia-reperfusion group(I/R,n= 12)and ischemic preconditioning group(Ipost,n=12).The hematoxylin-eosin staining(HE),TUNEL,immunohistochemical staining,and Western-blot were used to detect the changes in myocardial tissues from three groups.Compared with the Sham group,the histopathological changes,including myocardial tissue edema and inflammatory cell infiltration,were obviously serious in the I/R group.However,Ipost group was improved significantly compared with the I/R group.TUNEL results showed that the myocardial apoptosis rate in Ipost group was significantly lower than that in I/R group(P<0.01),though higher than that in the Sham group.In Ipost group,the number of capillaries on the edge of myocardial infarction area was significantly higher than that in I/R group(P<0.01).Western-blot results indicated that the expression of PTEN protein in the myocardial tissue in Ipost group was down-regulated,whereas the AMPK phosphorylation and LC3I/II expressions were increased.Taken together,ischemic preconditioning may have protective effects on I/R injury,and could reduce the infarct area.The protective mechanism of Ipost may be related to reduction of myocardial cell apoptosis,down-regulation of PTEN,enhancement of the phosphorylation level of AMPK and enhancement of myocardial cell autophagy in ischemic infarcted myocardium after pretreatment.