脑缺血预处理及HSP70表达对大鼠脑梗死的保护作用

Protective effects of focal ischemic preconditioning and HSP70 expression on middle cerebral artery occlusion in rats

目的建立局灶性可重复性大鼠脑缺血动物模型,探讨蛋白合成在脑缺血预处理(PC)诱导脑缺血耐受(IT)中的作用。方法应用改进的Longa’s法建立局灶脑缺血(MCAO)模型,短暂性脑缺血20min作为PC,PC 后24h给予永久性MCAO(PMCAO),并与未进行PC者比较。免疫印记法测量PC后24h及给予蛋白合成抑制剂放线菌酮后HSP70的变化,PMCAO24h后观察脑梗死的大小,神经功能评分;同时观察在PC前或PC后PMCAO 前给予蛋白合成抑制剂放线菌酮对上述指标的影响。结果 PC后24h行PMCAO,脑梗死体积明显减小(P<0．01), 神经功能评分减低(P<0．05);PC前给予放线菌酮消除了以上影响,但在PC后较长时间而在PMCAO之前给予则没有以上影响;HSP70在PC后24h明显表达,而在PC前30min给予防线菌酮抑制了HSP70的表达。结论 PC能够通过减少脑组织损伤和神经功能缺损对之后发生的脑缺血产生脑保护作用。PC诱导脑缺血耐受有赖于新蛋白的合成。

Objective To systematically evaluate the importance of protein synthesis in ischemic preeonditioning（PC）-induced ischemic tolerance （IT）. Methods Temporary middle cerebral artery occlusion（MCAO） by Longa （20 minutes） was used for PC （ischemic precondioning）. 24h of reperfusion was allowed after PC and before permanent MCAO to establish ischemic tolerance （IT） compared with non-PC （sham-operated） rats （n=5 per group）. Infarct size ,neurological deficits were measured 24h after PMCAO. Samples of brain were taken for the determination of HSP70 expression by Western blot analysis. The effects of the protein synthesis inhibitor （cycloheximide administered just before PC or administered long after PC but just before PMCAO on IT ） were also determined （n=5 per group）. Results Hemispheric infarct was significantly （P〈0.01） reduced only if PC was performed 24h,and PC significantly（P〈0.05） reduced neurological deficits （similar to reductions in infarct size）. Cycloheximide eliminated ischemic PC-induced IT effects on both brain injury and neurological deficits if administered before PC but not if administered long after PC but before PMCAO. PC produced no brain injury but did increased HSP70 protein at 24h. Cycloheximide eliminated that effects. Conclusions The results suggest that PC is a powerful inducer of ischemic brain tolerance as reflected by the preservation of brain tissue and motor function. PC inducing IT is dependent on de novo protein synthesis.