The Effect And Mechanism Of Limb Ischemic Postconditioning(LPostC) On Cerebral Ischemia And Reperfusion Injury In The Mice

Ischemic cerebral apoplexy is a cerebrovascular disease with high incidence, mortality and disability rate.To clearify pathogenesis and to seek the effective way for prevent and treatment are still very important problems in neuroscience.Many studies have shown that improving cerebral ischemic tolerance reduce ischemia-reperfusion(I/R) injury.After myocardial ischemia,a brief subcritical limb ischemic challenge could reduced myocardial I/R injury,which defined as limb ischemic postconditionin(LPostC). However,whether brief limb ischemia has the similar effect on cerebral ischemia has not been reported up to now.Aim To study the effect and feature of LPostC on cerebral I/R injury and evaluate relationship between applying opportunity of LPostC and cerebral ischemic times,as well as detect changes of MDA content,SOD activity,expression of HSP70 in brain after LPostC.To discuss the mechanism of LPostC neuroprotection and provide new idea and experimental basis for clinical prevention and treatment of Ischemic cerebral apoplexy.METHODS Ischemia-reperfusion(I/R) model was made by middle cerebral artery occlusion(MCAO).Male mice were randomly divided into nine groups,which were sham group,I/R groups(0.5h,1h,1.5h,2h) and LPostC+I/R groups (0.5h+L,1h+L,1.5h+L,2h+L).The reperfusion was made after LPostC for 24 hours,and then the neurologic deficit scores were recorded according to Longa standard.The brains were taken out for measure the infarct volumes by TTC staining or for pathological observation by HE staining.The apoptotic neurons were checked-by TUNEL staining.Subsequently,Male mice were divided randomly into 4 groups, which were sham-operated control group,I/R group,I/R+transient cerebral ischemia (PostC) group and IR+LPostC group.For the PostC group,after 90 minutes of MACO at the beginning of reperfusion,Postcond was performed as 3 cycles of 20 sec reperfusion(withdrawing the nylon 2 mm)/20 sec ischemia(inserting the nylon 2 mm). For LPostC group,after 90 minutes of MACO at the beginning of reperfusion,Postcond was performed as 3 cycles of 5 mins limb ischemia(occluding the femoral artery by 4-0 silk thread)/5 mins reperfusion(releasing the silk thread).Then we used kits to detect MDA content and SOD activity of brain tissue and immune-histochemistry method to analyse expression of brain HSP70.RESULTS The duration of ischemia is related to the motor behavior and degree of brain injury.The ischemic duration was longer,the reperfusion injury was more severe in behavior changes and brain pathology.Compared with the I/R groups,each indexes of LPostC groups were significantly lower,including neurologic deficit scores,the infarct volumes,brain injury degree and TUNEL-positive cell numbers.LPostC applied at 1h and 1.5h after MCAO have shown more obvious effect than that of 2h.LPostC can obviously decrease MDA content,and increase SOD activity of mice brain.LPostC also can obviously increase the expression of brain HSP70.CONCLUSION 1.Brain I/R injury was attenuated by LPostC in certain time of ischemia in mice brain.LPostC improves neurprotective ability.2.LPostC inhabits generation of free radical by increased SOD and decreased MDA in brain and achieves neuroprotective effect.3.HSP70 is induced by LPostC and relates to the mechanism of LPost against brain I/R injury.