摘要目的 观察局灶脑缺血预处理对核因子-κB(NF-κB)及其靶基因诱导型一氧化氮合酶(iNOS)mRNA表达的影响并初步探讨NF-κB/iNOS在诱导脑缺血耐受中的意义.方法 SD大鼠随机分为4组,IPC+SS组在假手术(SS)前3天给予10 min的缺血预处理(IPC),SS+MCAO组和IPC+MCAO组分别在2 h大脑中动脉缺血(MCAO)及22 h再灌注前3天给予SS或IPC,SS+SS组仅给予2次相隔3 d的假手术,采用透射电镜观察各组超微结构变化,免疫组织化学和逆转录-聚合酶链反应(RT-PCR)技术比较各组NF-κB活化及iNOS mRNA的转录水平.结果 IPC+SS组有低水平的NF-κB活化和中等程度的iNOS mRNA转录,但无明显超微结构改变;IPC+MCAO组NF-κB活化和iNOS的mRNA转录水平显著低于SS+MCAO组(P＜0.01),超微结构改变也明显轻于后者.结论 局灶性IPC所诱导的NF-κB活化减少和iNOS基因转录下调,可能是脑缺血耐受产生的重要分子机制之一,NF-κB/iNOS信号通路在IPC诱导的内源性神经保护中可能扮演了双重角色.

abstractsObjective To investigate the effect of focal cerebral ischemic preconditioning on the expression of nuclear factor kappa B(NF-κB)and its target gene inducible nitric oxide synthase(iNOS)and to explore its role in ischemic tolerance in rats.Methods A total of 32 SD rats were divided into 4 groups.The control group received sham surgery(SS)twice only.The IPC +SS group received 10 minutes of ischemic preconditioning(IPC)followed by SS 3 days later.And the other two groups received 2 hours of middle cerebral artery occlusion(MCAO)followed by 22 hours of reperfusion with or without IPC 3 days before.The ultrastructure, NF-κB activation and iNOS mRNA transcription were evaluated in each group by electron microscope, immunohistochemistry staining and reverse transcriptase polymerase chain reaction (RT-PCR)respectively.Results(1)In contrast with the SS + SS group, there was a lower NF-κB immunoreactivity(57.3 ±6.3)and iNOS mRNA level(29.1% ±3.1%)in the IPC +SS group while no ultrastructural abnormality was identified.(2)The expression of NF-κB/iNOS was down-regulated in the IPC + MCAO group(81.2% ±7.3%/89.0% ± 5.3%)than in the SS + MCAO group(98.9% ±9.4%/132.8% ± 7.9%, P ＜ 0.01)with minor ultrastructure abnormality.Conclusion A down-regulated expression of NF-κB/iNOS is a key event in the molecular mechanism of cerebral ischemic tolerance.And the NF-κB/iNOS pathway might play a dual role in endogenous neuroprotection induced by focal IPC.