新生大鼠缺氧缺血性脑损伤后caspase-3蛋白表达与神经元变性的关系

Relationship between caspase-3 level and neurodegeneration in neonatal rats with hypoxic-ischemic brain damage

目的探讨新生大鼠缺氧缺血性脑损伤（hypoxic ischemic brain damage，HIBD）后半胱氨酸天冬氨酸特异性蛋白酶-3（cysteinyl asparate-specific proteinase-3，caspase-3）蛋白表达及其与神经元变性的关系。方法将35只7日龄Wistar大鼠随机分为正常对照组、假手术组、HIBD后6、12、24、72和120h组，每组5只。HIBD组按Rice法制成模型。采用免疫组化法及Fluoro-Jade B（FJB）荧光染色分别观察caspase-3蛋白表达及神经元变性情况。结果缺氧缺血（hypoxic ischemia，HI）后12h皮质caspase-3表达（0．405±0．021）高于正常对照组（0．367±0．023）（P〈0．05），HI后24h皮质、纹状体及海马caspase-3表达达高峰（P〈0．05）；至HI后120h皮质、纹状体和海马caspase-3表达均与对照组差异无统计学意义（P〉0．05）。正常对照组大鼠各脑区内FJB阳性细胞罕见，HI后24h各部位脑组织FJB阳性细胞明显增多（P〈0．05），72h进一步增多（P〈0．05），120h时FJB阳性细胞数达高峰（P〈0．05）。结论新生大鼠HIBD后脑caspase-3蛋白表达与变性神经元在空间与时间分布上存在一致性，但变性神经元分布得更广泛、更持久。提示caspase-3蛋白可能在缺氧缺血所致神经元变性中起到一定作用。

Objective To explore the relationship between caspase-3 level and neurodegeneration in neonatal rats with hypoxic ischemic brain damage （HIBD）. Methods Thirty-five 7-day-old Wistar rats were randomly assigned into normal group （n = 5）, sham-operation group （n = 5） and HIBD group （n= 25）. HIBD model was established by ligating the right carotid artery and exposing to 8% oxygen for 2 hours. The rats were killed at 6, 12, 24, 72 and 120 hours after hypoxic ischemia （HI）. Caspase-3 level and neuronal degeneration were detected by immunohistochemistry and Fluoro Jade B （FJB） staining. Results Caspase-3 expression was weak in the normal neonatal rat brain. The number of caspase-3 positive cells and staining intensity increased significantly at 12 h after HI in the cortex of right side （0. 405 ± 0.021） （P〈0.05）, and reached a peak at 24 hours in all of ipsilateral cortex （0. 427±0. 032）, striatum （0. 432±0. 033） and hippocampus （0. 458±0. 047） （P〈0.05）. In the normal neonatal rats brain, FJB positive cells were rare. Twenty-four hours after HI, the number of FJB positive cells significantly increased in ipsilateral cortex, striatum and hippocampus（P〈0.05）, and kept increasing during the next two days and peaked at 120 hours after HI（P〈0. 05）. Conclusions The regional and temporal patterns of caspase-3 expression corresponded well to FJB staining for the degenerating neurons after HIBD. But the distribution of degenerating neurons was more extensive and the degeneration was more persistent. It is suggested that caspase-3 may partly contribute to the neuronal degeneration of neonatal rats with HIBD.