人参皂苷Rb1对β-淀粉样蛋白25-35诱导神经干细胞分化过程中Tau蛋白过度磷酸化的影响

Ginsenoside Rb1 reduced beta-amyloid peptide 25-35-induced hyperphosphorylation of Tau protein during the differentiation of neural stem cells

背景:前期研究发现,人参皂苷Rb1和β-淀粉样蛋白25-35可调节神经干细胞分化过程中Tau蛋白的磷酸化水平。蛋白磷酸酯酶2A与Tau蛋白过度磷酸化密切相关。目的:观察β-淀粉样蛋白25-35和人参皂苷Rb1对神经干细胞分化过程中Tau蛋白磷酸化水平和蛋白磷酸酯酶2A活性的影响。方法:分离、培养新生大鼠海马神经干细胞,诱导第3代神经干细胞分化1周后分组:①空白组:不加其他处理因素继续培养36h。②β-淀粉样蛋白组:培养24h后,加入β-淀粉样蛋白25-35继续培养12h。③预处理组:先加入人参皂苷Rb1预处理24h,再加入β-淀粉样蛋白25-35继续培养12h。分别采用免疫荧光细胞化学法和western-blot法检测各组细胞Tau[pS396]、Tau[pS262]表达以及蛋白磷酸酯酶2A活性。结果与结论:正常神经干细胞分化过程中有Tau[pS396]和Tau[pS262]的表达;β-淀粉样蛋白组细胞的Tau[pS396]和Tau[pS262]表达上调,蛋白磷酸酯酶2A活性无明显变化;预处理组Tau[pS396]和Tau[pS262]表达下调且蛋白磷酸酯酶2A活性显著增强。提示正常神经干细胞分化过程中Tau蛋白表达一定程度的磷酸化水平,人参皂苷Rb1可通过提高蛋白磷酸酯酶2A活性来减轻β-淀粉样蛋白25-35诱导的神经干细胞分化过程中Tau蛋白过度磷酸化。

BACKGROUND：Previous studies have demonstrated that ginsenoside Rb and beta-amyloid peptide 25-35（Aβ25-35） can regulate the phospholation of Tan protein during the differentiation of neural stem cells（NSCs）.Protein phosphatase 2A（PP2A） is closely related to hyperphosphorylation of Tau protein.OBJECTIVE：To investigate the effects of Aβ25-35 and ginsenoside Rb1 on phosphorylation level of Tau protein and activity of PP2A during the differentiation of NSCs.METHODS：NSCs were isolated from newborn rat hippocampus.After culture for 1 week,passage 3 NSCs were divided into three groups.In the control group,NSCs were further cultured for 36 hours without any medium added.In the Aβ group,after 24 hours of culture,Aβ25-35 was added for another 12 hours of culture.In the ginsenoside Rb1 froup,ginsenoside Rb1 was added for 24 hour pretreatment,and Aβ25-35 was added for another 12 hours of culture.The expression of Tau[pS396] and Tau[pS262] was tested by the immunofluorescent cytochemical staining and western blot method,and PP2A activity was tested by ELISA.RESULTS AND CONCLUSION：Cellular expression of Tau[pS396] and Tau[pS262] was detected during the differentiation of NSCs.In the Aβ group,cellular expression of Tau[pS396] and Tau[pS262] was up-regulated,and PP2A activity was not altered obviously.In the ginsenoside Rb1 group,cellular expression of Tau[pS396] and Tau[pS262] was down-regulated and PP2A activity was significantly increased.These findings suggest that during normal differentiation of NSCs,Tau protein was phosphorylated at a certain level,and ginsenoside Rb1 can alleviate Aβ25-35-induced hyperphosphorylation of Tau protein during the differentiation of NSCs by increasing PP2A activity.