人参皂甙Rg1通过P38信号通路影响帕金森病MPTP模型小鼠黑质COX-2的表达

Ginsenoside Rg1 modulates COX-2 expression in the substantia nigra of mice with MPTP-induced Parkinson disease through the P38 signaling pathway

目的研究P38信号通路在1-甲基-4-苯基-1,2,3,6-四氢吡啶(MPTP)所致小鼠帕金森病(PD)模型中对环氧合酶-2(COX-2)的表达调控作用,以探讨导致多巴胺(DA)能神经元变性失活的可能机制,以及人参皂甙Rg1对P38信号通路的影响和对多巴胺神经元的保护作用。方法采用MPTP制备亚急性PD小鼠模型,用免疫组织化学和免疫蛋白印记法,观察小鼠黑质酪氨酸羟化酶(TH),COX-2,前列腺素E2(PGE2)以及磷酸化P38(p-P38)的表达变化;并观察给予人参皂甙Rg1对上述变化的影响。结果与对照组小鼠相比,模型组小鼠出现典型PD症状,在MPTP第3次注射后6 h,黑质区p-P38,COX-2,PGE2阳性细胞显著增加(P<0.01)。在MPTP第5次注射后24 h,黑质区TH阳性神经元显著丢失60%(P<0.01);经人参皂甙Rg1处理后,模型小鼠PD症状减轻,与模型组比较,在MPTP第3次注射后6 h,黑质区p-P38,COX-2,PGE2阳性细胞明显减少(P<0.01),在MPTP第5次注射后24 h,TH阳性细胞数较对照组仅下降30%。结论P38通路在亚急性PD模型早期对黑质COX-2表达可能起重要调控作用;人参皂甙Rg1可影响P38信号通路及C0X-2的表达而对小鼠多巴胺神经元起到一定保护作用。

Objective To investigatc the role of P38 signaling pathway in modulating the expression of cyclooxygenase-2 （COX-2） in the substantia nigra （SN） of mice with 1-mcthyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine （MPTP）-induced Parkinson disease （PD）, and explore the possible mechanism of the dopaminergic （DA） neuron death in PD and the effects ofginsenoside Rgl on the P38 signaling pathway and DA neurons. Methods C57BL6 mice were treated with MPTP to produce the subacute PD model, and the behavioral changes were observed. Immunohistochemistry and Western blotting for tyrosine hydroxylase （TH）, COX-2, prostaglandin E2 （PGE2） and phosphorylated P38 （p-P38） were used to observe the changes of positive cell number in the midbrain after treatment with ginsenoside Rgl. Results Compared with the control mice, the mice with PD presented with typical symptoms of PD. The number of p-P38-, COX-2-, and PGE2-positive cells significantly increased in the SN area 6 h after the 3rd injection of 30 mg/kg MPTP （P〈0.01）. The number of TH-positive neurons in the PD model group was substantially reduced by about 60% （P〈0.01） in 24 h after the 5th injection of MPTP. In mice with ginsenoside Rgl treatment, the number of p-P38-, COX-2-, and PGE2-positive cells was reduced obviously 6 h after the 3rd injection of MPTP as compared with that in the model group （P〈0.01）. The number of TH-positive neurons in the SN was decreased by only 30% （P〈0.01 vs control group） 24h after the 5th injection of MPTP. Conclusion P38 signaling pathway may play an important role in modulating COX-2 expression in the SN in the early stage of MPTP-induced subacute PD, and ginsenoside Rgl may act on the P38 signaling pathway to protect the DA neurons in PD.