人参皂苷Rg1对Aβ_(25-35)诱导大鼠海马神经元tau蛋白异常磷酸化的影响

The effect of Ginsenoside Rg1 on abnormal phosphorylation of tau in rat’s hippocampal neurons induced by aggregated Aβ_(25-35)

目的探讨人参皂苷Rg1对Aβ2535所致大鼠海马神经tau蛋白异常磷酸化的抑制作用及其可能机制。方法应用脑立体定向技术向成年大鼠海马背侧注射凝聚态Aβ25355nmol制备AD样大鼠模型,术后分别给予腹腔内注射不同浓度的人参皂苷Rg1(625、125、25μmol·kg-1)处理,14d后处死,采用镀银染色方法观察海马组织神经元病理改变;免疫组织化学染色方法和免疫蛋白印迹技术显示大鼠脑内[pS396]tau、[pSpS199/202]tau、[pT231]tau的表达水平情况,以及总tau蛋白的水平(tau5);免疫蛋白印迹技术检测海马组织中GSK3β和磷酸化GSK3β的水平变化。结果凝聚态Aβ2535注射组神经元纤维走行紊乱,增粗、肿胀密集成宽带状,轴突深染;而人参皂苷Rg1对神经元具有明显的保护作用,脑内总tau的水平下降,[pS396]tau、[pSpS199/202]tau、[pT231]tau的表达明显低于Aβ2535注射组(P<001),以25μmol·kg-1保护作用最明显;GSK3β和磷酸化GSK3β的水平亦明显低于Aβ2535注射组,与正常和假注射组差异无显著性(P>005),以25μmol·kg-1作用最明显。结论人参皂苷Rg1对Aβ2535诱导的AD样大鼠海马神经元具有保护作用,其机制可能是通过阻断GSK3β的活性而降低磷酸化tau蛋白的表达而实现的。

Aim To explore the effect and mechanism of Gensenoside Rg1 on abnormal phosphorylation of tau in rats hippocampal neurons induced by aggregated Aβ_~25-35 .Methods The rats were administered with different doses of Rg1(6.25,12.5,25 μmol·kg^-1 ,ip) for 14 days,after dorsal hippocampus microinjection of 5 nmol aggregated Aβ_~25-35 was performed by stereotaxic technique.The pathological changes in rat hippocampal neurons were observed by Bielschowsky stain;the expressions of PS^396 -tau,PS^199 PS^202 -tau and PT^231 -tau were observed by immunohistochemical and Western blotting detection;the expressions of tau 5,GSK-3β and phosphorylating GSK-3β were measured by western blot.Results The neurofibrils were found fused,disordered,thickened and crowded together into broad band,and the neurites were deeply stained in the group of aggregated Aβ_~25-35 .Ginsenoside Rg1 had evident protective effect on the hippocampal neurons;the expressions of PS^396 -tau,PS^199PS202 -tau,PT^231 -tau(P<0.01)and GSK-3β,phosphorylating GSK-3β in Rg1 treatment groups significantly decreased as compared with aggregated Aβ_~25-35 microinjected groups. And the effective dose of Ginsenoside Rg1 had abrrevant difference;the dose of 25 μmol·kg^-1 were especially significant in Rg1 treatment groups (P<0.01).Conclusions Ginsenoside Rg1 had protective effect on Aβ_~25-35 induced pathology of AD in rat hippocampal neurons, and the mechanism may due to decrease in the levels of phosphorylation of tau by inhibiting the GSK-3β’ activation.