缺血后适应对脑缺血树鼩海马TLR4表达的影响

摘要

目的:观察血栓性脑缺血树鼩海马Toll 样受体4(TLR4)表达的改变,进一步探讨缺血后适应对海马TLR4表达的影响.方法:用光化学法建立血栓性脑缺血模型;并于缺血4 h夹闭缺血侧颈总动脉5 min,再通5 min,重复3个循环,实施后适应处理.用HE染色观察海马组织学改变,Western blotting测定海马TLR4蛋白表达,RT-PCR测定海马TLR4 mRNA.结果:脑缺血4、24、72 h海马神经元损伤进行性加重,24 h达高峰,后适应后损伤减轻.脑缺血海马TLR4蛋白表达明显增强(P＜0.05).与脑缺血组比较,后适应4 h及24 h TLR4蛋白表达减少(P＜0.05),后适应72 h TLR4蛋白表达增加(P＜0.05).海马TLR4 mRNA的表达趋势与蛋白表达基本一致.结论:脑缺血时海马TLR4表达明显增强,缺血后适应的脑保护机制可能与调控TLR4表达有关.%AIM : To observe the effects of thrombotic cerebral ischemia and postconditioning on the expression of toll - like receptor 4 ( TLR4 ) in hippocampus of tree shrews.METHODS : The model of thrombotic focal cerebral ischemia was established by photochemical reaction.Four hours after the onset of photochemical reaction, ischemic postconditioning was induced by 3 repeated cycles of carotid artery occlusion for 5 min and reperfusion for 5 min.The histological changes of hippocampus ( by HE staining ), TLR4 protein level ( by Western blotting ) and TLR4 mRNA expression ( by semiquantitative RT - PCR ) were observed.RESULTS: The extensive neuronal degeneration in hippocampus was observed from 4 h to 72 h and peaked at 24 h after cerebral ischemia, but was significantly attenuated after postconditioning.Cerebral ischemia caused a progressive increase in the expression of TLR4 protein at 4 h and 24 h ( P ＜ 0.05 ), and decreased at 72 h ( P ＜ 0.05 ).In contrast to ischemia groups, postconditioning decreased the expression of TLR4 protein at 4 h and 24 h ( P ＜0.05 ), but an increase in the expression of TLR4 at 72 h ( P ＜0.05 ) was observed.Simultaneously,the level of TLR4 mRNA in hippocampus showed the tendency of approximate variation in accordance with the protein expression.CONCLUSION : The expression of TLR4 increases by cerebral ischemia.The protection mechanisms of postconditioning may be associated with modulating TLR4 expression.