细胞外信号调节激酶在NGF/VEGF介导的神经保护作用中的动态变化及其调控机制

Extracellular signal-regulated kinase involved in NGF/VEGF-induced neuroprotective effect

目的探讨细胞外信号调节激酶1（ERK1）在局灶性脑缺血/再灌注不同时间、不同脑区的动态时空变化,以及其在NGF/VEGF介导的神经保护作用中的调控表达机制。方法采用兔大脑中动脉阻断（MCAO）局灶性脑缺血再灌注模型,所有动物随机分为假手术组（n=6）、缺血/再灌注组（n=60）、因子干预组（n=40）。应用免疫组化检测ERK1在脑缺血/再灌注损伤不同脑区的动态表达,同时,应用免疫组化、流式细胞术和电镜检测caspase-3表达、凋亡和超微结构的变化。结果免疫组化分析显示,再灌注损伤1hERK1首先在海马CA3和齿状回（DG）表达增加,6h后其它脑区也相继增加,随再灌注时间延长而加剧,1-3d达高峰。再灌注1hcaspase-3活性表达在各脑区迅速增加,3d达高峰。应用神经保护剂（NGF/VEGF）后各脑区ERK1表达呈明显抑制,caspase-3表达同时被抑制。结论ERK信号通路可能通过调节死亡受体途径介导神经保护作用,抑制ERK信号途径可能是减轻脑缺血损伤过程中神经细胞死亡的有效方法。

Objective To investigate the effect of the expression of extracellular signal-regulated kinase 1 （ ERK1 ） on cerebral ischemic injury, temporospatial alterations of ERK1 immunoreactivity in bippocampus and perifocal cortex and the expression involved in NGF/VEGF-induced neuroprotective effect were examined. Methods Focal cerebral ischemia/ reperfusion model in rabbits was induced by transient occlusion of middle cerebral artery （MCAO）. All rabbits were randomly divided into three groups： sham-operated group （n = 6）, ischemia/reperfusion group （n = 60）, factor-treated group （n =40）. We measured the dynamic expression of ERK1 in hippocampus and perifocal cortex in rabbits exposed to focal cerebral ischemia and reperfusion by immuohistochemistry. Expression of caspase-3, apoptosis and ultrastructure were also evaluated by immunohistochemistry, flow cytometry analysis and electron microscopy. Results ERK1 expression was first increased in hippoeampal CA3/DG 1 hours after reperfusion. At 6 hours after reperfusion ERK1 expression was also in- creased in other brain regions, with peak formed at day 1 to day 3, and then gradually decreased to basal level at day 14 af- ter reperfusion. The expression of caspase-3 also was strongly activated 1 h after reperfusion, with peak demonstrated at 3 days. NGF/VEGF significantly inhibited the expression of ERK1 and caspase-3. Conclusions These results suggest that ERK signaling pathway was involved in neuronal cell death and NGF/VEGF-induced neuroprotective effect by modifying death receptor pathway. Inhibition of ERK signaling pathway might therefore provide an efficient way for preventing neuronal cell death after cerebral ischemia.