Objective: To investigate the effect of ischemic preconditioning on chaperone hsp70 expression and protein aggregation in the CA1 neurons of rats, and to further explore its potential neuroprotective mechanism.
Methods: Two-vesseloccluded transient global ischemia rat model was used. The rats were divided into sublethal 3-min ischemia group, lethal 10-min ischemia group and ischemic preconditioning group. Neuronal death in the CA1 region was observed by hematoxylineosin staining, and number of live neurons was assessed by cell counting under a light microscope. Immunochemistry and laser scanning confocal microscopy were used to observe the distribution of chaperone hsp70 in the CA1 neurons. Differential centrifuge was used to isolate cytosol, nucleus and protein aggregates fractions. Western blot was used to analyze the quantitative alterations of protein aggregates and inducible chaperone hsp70 in cellular fractions and in protein aggregates under different ischemic conditions.
Results: Histological examination showed that ischemic preconditioning significantly reduced delayed neuronal death in the hippocampus CA1 region (P < 0.01 vs 10-min ischemia group). Sublethal ischemic preconditioning induced chaperone hsp70 expression in the CA1 neurons after 24 h reperfusion following 10-min ischemia. Induced-hsp70 combined with the abnormal proteins produced during the secondary lethal 10-min ischemia and inhibited the formation of cytotoxic protein aggregates (P < 0.01 vs 10-min ischemia group).
Conclusion: Ischemic preconditioning induced chaperone hsp70 expression and inhibited protein aggregates formation in the CA1 neurons when suffered secondary lethal ischemia, which may protect neurons from death.
目的: 研究预缺血对蛋白伴侣hsp70表达和蛋白聚集物形成的影响, 探讨其可能的脑保护机制。
方法: 采用大鼠双侧颈总动脉暂时夹闭法建立全脑缺血模型。 大鼠分为3 min 缺血组, 10 min缺血组以及预缺血组。 苏木素-伊红染色, 光镜下随机计数分析预缺血后海马CA1区死亡神经元数量变化。 免疫组织化学及激光扫描共聚焦显微镜法观察蛋白伴侣hsp70 在CA1区神经元内的分布。 差速离心分离细胞浆、 细胞核及蛋白聚集物。 蛋白印迹法检测不同缺血状态下海马CA1神经元内蛋白聚集物含量的变化, 以及胞浆、 胞核及蛋白聚集物内蛋白伴侣hsp70含量的变化。
结果: 组织学检查显示预缺血能够显著减少海马CA1区神经元死亡数量。 预缺血诱导海马CA1区神经元内蛋白냩侣hsp70 在再灌注后24 h表达。 预缺血处理后, 海马CA1区神经元内蛋白聚集物显著减少。 预缺血诱导的蛋白伴侣hsp70与再缺血形成的异常蛋白结合在一起并防止其聚集。
结论: 预缺血可能通过诱导蛋白伴侣hsp70的表达和抑制再缺血后蛋白聚集物的形成, 减少再缺血引起的神经元死亡。