NMDA受体的激活在帕金森病黑质铁聚集中的作用机制研究

A growing body of evidence shows that the elevated iron levels in the substantia nigra pars compacta (SNpc) play a key role in the degeneration of dopamine neurons in Parkinson's disease (PD). The previous study in our laboratory showed that the misregulation of iron import protein divalent metal transporter 1 (DMT1) and iron export protein Ferroportin 1 (FPN1) were involved in this nigral iron accumulation in PD. Evidence also showed that the activation of NMDA recepter could up-regulate DMT1 in hippocampal neurons. However, the relationship between the activation of NMDA recepter and iron accumulation in the substantial nigra in PD was unknown. In this study, using MPTP-induced PD models, NR1 knockout mice and cultured dopamine neurons, we will explore the role of the activation of NMDA recepter in the expression of iron transporters DMT1, FPN1 and the function of iron transport in dopamine neurons, as well as the underlying mechanisms. We hypothesize that the stimulation of NMDA receptors could up-regulate DMT1 via NO-IRPs/IRE pathway or activating NF-κB or affecting the activity of parkin, enhance iron uptake via NO-Dexras1-DMT1 signaling cascade, and down regulate FPN1 via NO-IRPs/IRE pathway. This leads to the ultimate nigral iron accumulation in PD. This will provide new research results and strategies for the prevention and treatment of PD.

研究已证实黑质铁聚集是帕金森病（PD）多巴胺能神经元损伤的原因之一。我们发现PD黑质铁聚集与铁转入蛋白二价金属离子转运蛋白1（DMT1）及铁转出蛋白Ferroportin 1 (FPN1)的表达异常有关。文献报道NMDA受体的激活可以上调海马神经元的DMT1，但在PD的病理状态下，NMDA受体的激活与黑质铁聚集之间的关系如何尚不清楚。本项目应用多种技术方法，在MPTP制备的PD动物模型，NR1条件基因敲除小鼠及体外培养的多巴胺能神经元中，研究NMDA受体的激活对多巴胺能神经元DMT1，FPN1的表达及铁转运功能的影响，并深入探讨其机制，证实NMDA受体激活能够通过IRPs/IRE，NF-κB及Parkin等因素增加DMT1的表达，通过NO-Dexras1通路的激活增强DMT1的摄铁功能，还可以通过IRPs/IRE系统下调FPN1。本研究将为NMDA受体参与PD的发病机制提供全新的理论依据。

越来越多的证据证实黑质（substantia nigra, SN）铁聚集及N-甲基-D-天冬氨酸（N-methyl-D-aspirate，NMDA）受体激活是帕金森病（Parkinson’s disease, PD）多巴胺(dopamine, DA)能神经元损伤的重要因素。但是NMDA受体激活与PD SN区铁聚集的关系至今尚无报道。本项目在PD动物模型及体外培养的神经元中，应用多种技术方法深入探讨NMDA受体激活在PD SN区铁聚集中的作用及机制。实验结果证实NMDA受体激活可以通过铁调节蛋白/铁反应元件（iron regulatory proteins/iron responsive element, IRPs/IRE）通路上调铁转入蛋白“+IRE”型二价金属离子转运蛋白1（divalent metal transporter 1, DMT1)，并下调铁转出蛋白ferroportin 1（Fpn1）的表达，导致DA神经元的铁聚集及细胞损伤。在体实验证实NMDA受体抑制剂MK-801或AP5预处理能够改善6-羟基多巴(6-hydroxydopamine, 6-OHDA)诱导的PD模型大鼠的行为学，拮抗6-OHDA诱导的SN区酪氨酸羟化酶（tyrosine hydroxylase, TH）阳性细胞数量及蛋白表达的降低及纹状体DA释放的减少；MK-801或AP5预处理可以通过抑制SN区DMT1的蛋白表达，降低SN区铁水平而发挥其对PD大鼠模型的保护作用。体外实验表明NMDA受体异常激活导致6-OHDA诱导的MES23.5细胞铁聚集的机制可能是NMDA受体激活后活化神经元型一氧化氮合酶（neuronal nitric oxide synthase, nNOS）并合成一氧化氮(nitric oxide, NO)，从而上调IRP1的表达，进而通过IRPs/IRE机制上调DMT1，下调Fpn1的表达，最终造成细胞内铁聚集，并加重铁诱导的神经元损伤。本研究结果将为NMDA受体参与PD的发病机制及PD的防治提供全新的理论依据。