淀粉样β蛋白1～40对胚胎大鼠皮质神经前体细胞毒性损伤的c-Jun氨基端激酶信号转导的影响

背景淀粉样β蛋白是阿尔茨海默病致病关键因素之一.近来的研究证明在成人中枢神经系统内存在能不断自我更新、多向分化潜能、终身神经修复的神经干细胞.但是在阿尔茨海默病脑内却未见到这些神经前体细胞的起到有效作用,其机制尚未清楚.淀粉样β蛋白1～40是否通过c-Jun氨基端激酶信号转导通路对胚胎大鼠皮质神经前体细胞造成神经毒性损害尚不清楚.目的体外实验淀粉样β蛋白1～40对胚胎中皮质神经前体细胞毒性作用中c-Jun氨基端激酶信号转导通路的可能作用机制,探讨c-Jun氨基端激酶抑制剂SP600125对淀粉样β蛋白1～40致胚胎中皮质神经前体细胞神经毒性作用的保护作用.设计以细胞为观察对象,随机对照实验.单位中国医科大学附属第一医院神经内科.材料实验于2005-05/10在中国医科大学中心实验室完成.选用10只孕14 d Wistar大鼠,取其胚胎以备实验.方法取Wistar大鼠胚胎脑皮质组织神经前体细胞,体外培养、传代、鉴定.将生长状态良好的胚胎大鼠皮质神经前体细胞随机分为4组淀粉样β蛋白1～40组(每孔加入10 nmol/L β淀粉样蛋白1～40);SP600125+淀粉样β蛋白1～40组(每孔先加入10 μmol/L SP600125培养30 min后再加入10 nmol/L淀粉样β蛋白1～40);SP600125组(每孔加入10 μmol/L SP600125培养);生理盐水组(每孔加入等体积的生理盐水),每组分别培养0,2,4,6,12,24 h,每个时间点设8个孔.采用α甲基偶氮唑蓝法测定细胞生存率.流式细胞分析术检测细胞凋亡率.免疫印迹法检测c-Jun氨基端激酶,p-c-Jun氨基端激酶,c-Jun,p-c-Jun表达.计量资料差异比较采用t检验.主要观察指标①Wistar大鼠胚胎皮质神经前体细胞细胞生存率.②胚胎中皮质神经前体细胞细胞凋亡率.③胚胎中皮质神经前体细胞c-Jun氨基端激酶,p-c-Jun氨基端激酶,c-Jun,p-c-Jun表达结果.结果①淀粉样β蛋白1～40组和SP600125+淀粉样β蛋白1～40组细胞生存率随培养时间延长而下降,4 h时下降最明显;培养0,2,4,6,12,24 h时淀粉样β蛋白1～40组明显低于其他3组(P＜0.01),SP600125+淀粉样β蛋白1～40组培养2,4,6,12,24 h明显低于SP600125组和生理盐水组(P＜0.01).SP600125组细胞生存率无时间依赖性,与生理盐水组相比,差异不明显(P＞0.05).②淀粉样β蛋白1～40组和SP600125+淀粉样β蛋白1～40组细胞凋亡率随培养时间延长而上升,4 h时上升最明显;培养0,2,4,6,12,24 h时淀粉样β蛋白1～40组明显高于其他3组(P＜0.01),SP600125+淀粉样β蛋白1～40组培养2,4,6,12,24 h明显高于SP600125组和生理盐水组(P＜0.01).SP600125组细胞生存率无时间依赖性,与生理盐水组相比,差异不明显(P＞0.05).③淀粉样β蛋白组c-Jun氨基端激酶和c-Jun在培养0,2,4,6,12,24 h均有表达,但无变化;p-c-Jun氨基端激酶和p-c-Jun在淀粉样β蛋白1～40作用0 h时即有表达,逐渐增高,4 h时达高峰,以后逐渐减少.结论淀粉样β蛋白1～40能明显抑制胚胎中皮质神经前体细胞细胞活性,降低细胞生存率,导致细胞凋亡,c-Jun氨基端激酶信号转导通路参与了此过程,这可能是阿尔茨海默病不能启动自我救活机制原因之一;使用SP600125,可抑制c-Jun氨基端激酶和c-Jun激活,明显减轻淀粉样β蛋白1～40对胚胎中皮质神经前体细胞的神经毒性作用.

Signal transduction of c-Jun N-terminal kinase against beta-amyloid protein 1-40 induced neuronal toxicity to cortical progenitor cells of embryonic rats

BACKGROUND: The primary pathophysiology of Alzheimer disease (AD) is linked to β-amyloid (Aβ)protein. Neural progenitor cells (NPCs), which have the ability of multipotency, self-renewal and repair,have been detected in the central nerve system (CNS) of adult rat recently. But effective function of these neural progenitor cells are not seen in the AD brain ,which mechanism is unclear.It is unclear if Aβ1-40protein is compromised by the signal pathway of c-Jun N-termial kinase associated with the neurotoxicity to the progenitor cells on the cortex of embryonic rats.OBJECTIVE: To investigate the mechanism of c-Jun N-terminal kinase signal transduction pathway of Aβ1-40 protein, which has neuronal toxicity to progenitor cells(CPC)on the cortex of embryonic rats . To detect the neuroprotective effects of c-Jun N-termial kinase inhibitor (SP600125) against Aβ1-40-induced neuronal toxicity to the cortical progenitor cells on the cortex of embryonic rats.DESIGN: A randomized and controlled trial with cells as objects.SETTING: Department of Neurology, First Hospital Affiliated to China Medical UniversityMATERIALS: This experiment was carried out at the Central Laboratory,China Medical University from May to October 2005. Embryos at age of 14 days from Wistar rats were used in this experiment.METHODS: Cortical progenitor cells harvested from Wistar embryonic rats were cultured in vitro, passaged and identified. Embryonic rat cortical progenitor cells of rats with good growth state were randomly divided into 4groups:Aβ1-40 group (10 nmol/L Aβ1-40 in each well);SP600125+Aβ1-40group (10 μmol/L SP600125 for 30 minutes and then with 10 nmol/L Aβ1-40 in each well); SP600125 group ( 10 μmol/L SP600125 in each well); Normal saline group (same volume of normal saline). The incubated durations were 0,2 hours, 4 hours, 6 hours, 12 hours, 24 hours respectively,8 wells for each time point. The cell survival rate was measured by MTF assay (The concentration of cortical progenitor cells on the cortex was 1×10s L-1 in each group), the apoptosis rate was detected by flow cytometer (The concentration of cortical progenitor cells on the cortex was 1 ×1010 L-1in each group) and the expression of c-Jun N-termial kinase and p-c-Jun N-termial kinase, c-Jun,p-c-Jun were measured by Western Blot(The concentration of cortical progenitor cells on the cortex was 1×1013 L-1 in each group). t test was adopted for the comparison of difference in measurement data.sion of c-Jun N-terminal kinase, p-c-Jun N-termial kinase ,c-Jun and p-c-Jun of embryonic rat CPC .ture time in Aβ group and SP600125 +Aβ group, decreased obviously at 4hours; cellular survival rate in Aβ1-40 group was lower obviously than that in the other 3 groups at 0,2,4,6,12,24 hours (P ＜ 0.01); Cellular survival rate in SP60025 +Aβ1-40 group was lower obviously than that in SP600125 group and normal saline group at 2,4,6,12,24 hours (P ＜ 0.01);Compared with normal saline group, the difference of cell survival rate was not significant without time-dependent manner in SP600125 group (P＞ 0.05).amyloid protein group and SP600125 +Aβ group, increased obviously at 4hours; cell apoptosis rate in Aβ1-40 group was higher obviously than that of the other 3 groups at 0,2,4,6,12,24 hours(P ＜ 0.01); Cellular apoptosis rate in SP60025+Aβ1-40 group was higher obviously than that in the SP600125 group and normal saline group at 2,4,6,12,24 hours (P ＜ 0.01);Compared with normal saline group, the difference of cellular apoptosis rate was not significant without time-dependent manner in SP600125 group 12,24 hours without changes in Aβ1-40 group; the expression of p-c-Jun N-terminal kinase and p-c-Jun in Aβ1-40 group were seen at 0hour ,increased gradually, reached to the peak at hour 4 and decreased gradually.CONCLUSION: Aβ1-40 could inhibit the cell activity of CPC , reduce cellular survival rate and induce cellular apoptosis. c-Jun N-terminal kinase signal transduction pathway may mediate the Aβ1-40 inducd neurnal apoptosis in AD which may be one reason for unseen rescue mechanism in AD. SP600125 (c-Jun N-terminal kinase inhibitor) could inhibit the activation of c-Jun N-terminal kinase and c-Jun and protect the embryonic rats CPC from the Aβ1-40-induced neurotoxicity.