老龄大鼠局灶性脑缺血后DNA修复蛋白:增生细胞核抗原表达的研究

Changes in PCNA, a protein involved in DNA repair, in the neurons following focal cerebral ischemia in age rats

目的 :探讨增生细胞核抗原 ( Proliferating cell nuclearantigen PCNA)在老龄大鼠局灶性脑缺血后不同时空表达改变的规律。方法 :采用 2 6月龄 Wistar大鼠 ,在光化学诱导局灶性脑缺血后 ,应用免疫组织化学和原位杂交的方法从蛋白质和 m RNA水平观察不同时间和空间状态下 PCNA表达的改变。结果 :缺血 4小时缺血周边区有少许核染色为棕褐色颗粒的神经元和大量的胶质细胞 ;缺血 2 4小时在缺血中心区仍无 PCNA的表达 ,在缺血周边区则 PCNA表达较 4小时组增强 ( P<0 .0 1 )。缺血 5天组缺血周边区 PCNA表达则较 4小时明显减弱 ( P<0 .0 5)。除了缺血 4小时组缺血中心区及周边区其 m RNA水平较对照组增加 ( P<0 .0 5)外 ,其余各时间点基本和蛋白表达水平的改变相一致。结论 :脑缺血后衰老神经细胞 DNA损伤后存在切除修复现象 ,其修复能力的减弱参与了衰老神经元缺血后的死亡机制。

Objective: Proliferating cell nuclear antigen(PCNA) is required for completion of the DNA synthesis step of DNA replication as well as nucleotide excision repair(NER) of damaged DNA. We investigated the expression of PCNA mRNA and the levels of PCNA protein in the aged rats following focal ischemia . Methods: By the immunohistochemistry and in situ hybridization, the protein and mRNA of PCNA were analyzed constitutively in the aged rats(26 months) following focal ischemia induced by photochemistry. Results: The expression of PCNA mRNA and protein at the border area of infarct were up-regulation at 24 hours following focal cerebral ischemia than at 4 hours( P <0.01), while after 5 days following ischemia, a decrease of protein expression was observed ( P <0.05). No expression of PCNA protein and mRNA had been detected at the core of the infarction until ischemia for 5 days.Conclusion:Our findings indicate an altered functional state of PCNA protein and mRNA in the ischemic neurons suggesting that DNA repair processes are affected in post-mitotic cells following ischemia. Impaired DNA repair may play a role in the development of aged postischemic neuronal damage.