局灶性脑缺血神经细胞DNA损伤与修复机制探讨

目的:观察脑缺血后半胱氨酸蛋白酶3(caspase-3)和脱嘌呤/脱嘧啶核酸内切酶(APE/Ref-1)的表达, 探讨脑缺血损伤与修复机制。方法: 采用大鼠大脑中动脉阻塞脑缺血模型, 应用免疫组化染色观察caspase-3和APE/Ref-1的表达, 应用TUNEL染色观察神经细胞DNA损伤, 采用免疫双标染色观察APE/Ref-1与DNA损伤的关系。结果:Caspase-3的活性单位P₂₀蛋白主要在半暗带表达, 表达高峰时间早于DNA损伤最高峰的时间。随着缺血时间延长, 缺血周边区APE/Ref-1免疫阳性细胞数量逐渐减少。结论:脑缺血后半胱氨酸蛋白酶级联反应启动, 促使DNA破坏, 同时, DNA损伤的修复分子表达水平下降, DNA修复失败, 进一步加速了细胞凋亡。

The mechanism of neuronal injury and repair after focal cerebral ischemia

AIM: To explore the mechanism of neuronal injury and repair by investigating the expression of caspase-3 and apurinic/apyrimidinic endonuclease (APE/Ref-1) after focal cerebral ischemia. METHODS: A model of middle cerebral artery occlusion in rats was performed . The expression of caspase-3P 20 and APE/Ref-1 was examined by immunohistochemistry staining, TUNEL was applied to detected DNA damage, and double labeling with TUNEL and APE/Ref-1 was used to determine the relationship between APE/Ref-1 and DNA damage. RESULTS: The active subunit P 20 of caspase-3 was predominantly expressed within ischemic penumbra. The peak time of caspase-3P 20 positive cells preceded the appearance of TUNEL. With aggravation of cerebral ischemia, APE/Ref-1 immunoreactive cells in penumbra were significantly decreased. CONCLUSION: The activation of caspase enzymatic cascade following cerebral ischemia leads to degradation in DNA, meanwhile, decrease in DNA repair molecules or the failure of DNA repair may deteriorate the course.