| Background and Objective: Apoptosis after cerebral ischemia-reperfusion injury is an important way to nerve cell death. Apoptosis is the result of apoptosis-related gene expression, but also by many internal and external factors conditioning. lysosome Cathepsin B (Cathepsin B, CB) involved in the initial part of apoptosis and it plays an important role in cerebral ischemia and reperfusion neuronal apoptosis, It is currently relatively rare ischemia-reperfusion model in the Cathepsin-B-mediated apoptosis pathway. In order to investigate the role of CB in cerebral ischemia injury and the molecular mechanism of CB in cell apoptosis , we explore the correlation between CB and Caspase-9 which was important to start the mitochondrial pathway in cerebral ischemia injury . and used the application of inhibitor, CA-074Me, to observe its influence of CB and Caspase-9 and the neuronal apoptosis as well as its neuroprotective effects. for clinical treatment of cerebral ischemia and thus provide a theoretical basis and treatment ideas.Methods: 145 healthy male Sprague-Dawley rats weighing 250-300g were randomly divided into four groups: normal group (n = 10), sham-operated group (n = 15), cerebral ischemia-reperfusion model group (the model group n = 60), and CA-074Me intraperitoneal injection of the treatment group (treated group n = 60). Temporary middle cerebral artery occlusion (MCAO) model was applied.Reperfusion at the time of 2 hours after ischemia. Immediately, Rats received intraperitoneal injections of CA-074Me for the treated group and same volume physiological saline for the other groups, Then, neurolgical behavior evaluation were evaluated by the methods of Longa's scoring. Rats were sacrificed respectively at 1h, 6h, 24h, 48h after reperfusion. The cerebal infarction volume were evaluated by the methods of TTC staining.The expression of CB,Caspase-9 mRNA and protein were measured by the method of reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. The neuronal apoptosis was detected by the method of terminal deoxynucleotidy transferase-mediated dUTP-biotin nick end labeling(TUNEL).Results: (1) 70.1% rats were induced ischemic neurological deficits. Compared With the rats of model group, CA-074Me could reduce neurological deficits significantly beginning at 24h after reperfusion(P <0.05). (2)TTC staining showed: normal and sham-operated rats were no infarction and also The TUNEL positive cells were hardly found . The cerebral infarction volume and apoptosis cell counting were increasing gradually with the advance of time after cerebral ischemia-reperfusion and reach a peak at 48h after reperfusion. Compared with the rats of model group, CA-074Me could reduce those damage (P <0.05). (3) A certain amount of CB mRNA and protein was detected in the cerebral cortex of sham and normal rats.The expression of CB mRNA and protein in the model group were present dynamic changed.The expression level of CB mRNA and protein all increased significantly at 1h after reperfusion, peaked at 6h .The changes of the CA -074Me -treated group was similar with the model group,but the amount reduced remarkably(P<0.05) . (4)The active Caspase-9 protein and positive cells were hardly detected in normal and sham rats.The expression changes of Caspase-9 mRNA and protein in the model group were consistently, all increased significantly at 6h after reperfusion, peaked at 24h, Compared with the model group,the expressions of Caspase-9 mRNA and protein were lower in the CA -074Me -treated group at same time point (P<0.05).Conclusions: (1) The upregulation of the protein CB after cerebral ischemia and reperfusion. may be involved in cell apoptosis through mitochondrial pathway. (2) CA -074Me could reduce neurological deficits and cell apoptosis and cerebral infarction volume after cerebral ischemia reperfusion in rats.
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