| These years,the cerebrovascular disease,especially the ischemic cerebrovascular disease,becomes one of the common diseases which can seriously threaten the human health and affect the life quality.The main characteristics of cerebrovascular disease are high incidence rate,high disability rate,high mortality rate,high recurrence rate and many complications.Thus,this disease often causes a heavy burden to the society and family.The traditional treatments contain dredging the blocked blood-vessels and improving the blood supply in the lesion region.However,these methods only focus on protecting the nerves or blood-vessels and have little effect on the interaction and signal transmission between cells.In addition,reperfusion injury is more likely to occur for these methods when the blood supply in the ischemic region is improved.Under the condition of ischemia and hypoxia,improving the tolerance ability to cerebral ischemia helps to essentially solve the problem.Some studies show that the transient ischemic attack is closely related to the severity of the following cerebral infarction.Therefore,studying an effective method which can improve the tolerance ability to cerebral ischemia becomes a difficult problem before us.These years,the phenomenon of ischemic tolerance caused by cerebral ischemic preconditioning(CIPC)is widely studied by the researchers at home and abroad.With a very complex mechanism of action,CIPC has the treatment advantages of multi-mechanism and multi-target.Thus,it becomes one of the hot study topics in the life science field [1].The pathophysiologicalmechanism of cell injury after the cerebral ischemia is extremely complex.There is a series of cascade reactions about injuries and these reactions which eventually lead to the cell death are interrelated and reciprocal causation.Oxidative stress injury and free radical chain reaction are the core pathology links of ischemia reperfusion injury.Therefore,earlier antioxidant therapy,blocking the cascade reactions of cerebral ischemia injury and reducing the neuronal damage in the ischemic penumbra are the important points in the treatment of ischemic cerebrovascular disease.In addition,nuclear factor erythroid 2-related factor 2 / antioxidant response element(Nrf2/ARE)signal pathway is one of the important pathways for endogenous antioxidant injury in the cell [2,3].Considering these points,our r experiment will build the transient right middle cerebral artery occlusion(MCAO)model and observe the effect of CIPC on the nerve function of MCAO rats,the volume of cerebral infarction,the volume of cerebral infarction,the histopathology morphology change,the expression of Nrf2 and quinone oxidoreductase 1(NQO-1)in the ischemic brain tissue,the malondialdehyde(MDA)content of ischemic brain homogenate and the activity of superoxide dismutase(SOD)to study whether CIPC can protect the nerves by activating the Nrf2/ARE signal pathway.In the experiment,225 male Sprague-Dawley rats with a weight of 250 ~ 280 g are randomly divided into three groups: control group,model group and experiment group.In each group,subgroups with 6h,12 h,24h,48 h and 72 h after reperfusion are set respectively.In the model group,the Zea-Longa middle cerebral artery suture method [4] is used to build the MCAO model.In the experiment group,the blood flow of right internal carotid artery is blocked for 10 min and the MCAO model is built with the same method as the model group after 3 days.In the control group,the cervical vessels are separated and the external carotid artery is ligated,while the suture is not inserted.At the time when the rats are clear-headed after the operation and the times of 6h,12 h,24h,48 h,72h after the operation,score the neurological function of rats with the Zea-Longa score criterion [4] and observe the praxiology change of rats.Measure the volume of cerebral infarction with the 2,3,5-triphenyltetrazolium chloride(TTC)staining method.Observe the pathological change of brain tissue with the optical microscope after implementing hematoxylin and eosin(HE)staining on the brain tissue.Observe the Nrf2 nucleus transfer with the immunohistochemistry(IHC)method,and check the expression of Nrf2 and NQO-1 mRNA in the ischemic cerebral cortex with the quantitative reverse transcription PCR(qRT-PCR)method.Measure the SOD activity with the water-soluble tetrazolium-1(WST-1)method and measure the MDA content with the thiobarbituric acid(TBA)method in the brain homogenate.Compared with the control group,the rats showed obvious nerve function vitium symptom after the ischemia reperfusion injury in the model group(P<0.01).Ischemic preconditioning can remarkably improve the histopathological injury after the ischemia reperfusion injury.The behavioral score of experiment group are much lower than that of the model group at 24 h,48h and 72 h after the reperfusion(P<0.05).The infarction volumes of experiment group and model group are respectively(21.4±4.48)% and(33.2±7.48)%(P<0.01).The nuclear expression of Nrf2 is not obvious in the control group,while the number of positive cells with Nrf2 nuclear staining begins to increase at 6h,reaches the peak at 24 h and begins to decrease at 48 h in the model group and experiment group.The number of positive cells with Nrf2 nuclear transfer in the experiment group is much higher than that in the model group all the time(P<0.05,P<0.01).The expression of Nrf2 and NQO-1 mRNA is low and has no obvious change as time goes on in the control group.Meantime,the expression of Nrf2 and NQO-1 mRNA is obvious in the model group and experiment group.The expression begins to increase at 6h after the ischemia and reaches the peak at 24 h.The peak continues to 48 h,and the expression begins to decrease at 72 h.The expression of Nrf2 and NQO-1 mRNA in the mode group and experiment group is much higher than that in the control group all the time.Compared with the model group,the experiment group can further improve the expression of Nerf2 and NQO-1 mRNA.The SOD activity of brain tissue is highest in the control group,and it has no obvious change as time goes on.In the experiment group and model group,the SOD activity begins to decrease at 6h after the reperfusion,decreases most obviously at 24 h and increases at 48 h and 72 h.The SOD activity in the experiment group at 24 h and 48 h are respectively(269.83±42.41,271.50±55.73)U/mgprot.The SOD activity in the model group at 24 h and 48 h are respectively(189.50±37.57,193.83±44.21)U/mgprot.The SOD activity in the experiment group is higher than that in the model group(P<0.05).The MDA content of brain tissue is low in the control group and it has no obvious change as time goes on.The MDA content of brain tissue begins to increase at 6h after the reperfusion,increases most obviously at 24 h and decreases at 48 h and 72 h in the experiment group and model group.The MDA contents in the experiment group and model group are respectively(25.43±8.68)nmol/mgprot and(39.91±7.10)nmol/mgprot at 24 h.The MDA content in the experiment group is lower than that in the model group(P<0.05,P<0.01).In summary,CIPC can observably reduce the nerve function score of rats with cerebral ischemia reperfusion injury,decrease the volume of cerebral infarction,improve the SOD activity and reduce the MDA content.Thus,it can adjust the antioxidant stress capacity,clear a large number of oxygen free radicals in the body and reduce the ischemic brain tissue injury.CIPC can increase the Nrf2 nuclear translocation rate and improve the expression of Nrf2 mRNA and NQO-1 mRNA,so that it can restrain the brain tissue injury caused by the ischemia and hypoxia.This may be one of the antioxidant effect mechanisms caused by the ischemic preconditioning. |
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