JNK介导帕金森病神经炎症发生的亚型作用及其机制

Parkinson’s disease (PD) is a common neurodegenerative disease whose cardinal symptoms are due to the progressive loss of dopamine neurons of the substantia nigra. A crucial goal of PD-related research is the development of a neuroprotective treatment that delays disease progression. It has been established that JNK is a critical regulator of dopamine neuron death in PD by us and others. Further, we found in a mouse model of PD: i) JNK is activated predominantly and earliest in dopamine neurons; ii) dopaminergic neurotoxin-induced neuroinflammation is blocked in global JNK1-, JNK2- or JNK3-knockout mice; iii) JNK2/3-mediated activation of ATF2 contributes to dopaminergic neurodegeneration while functional loss of ATF2 in dopamine neurons has no effect on neuroinflammation. We hypothesize that JNKs of dopamine neurons play a role in neuroinflammation and mediate dopaminergic neurodegeneration via a non-cell-autonomous mechanism. We propose to clarify whether it is the JNKs of dopamine neurons and which isoform(s) are involved in neuroinflammation; whether JNKs-mediating neuroinflammation is c-Jun-dependent; whether Mmp3 is the downstream target of JNK/c-Jun to induce neuroinflammaiton, by using dopamine neuron-specific JNK1-，JNK2-, JNK3- or c-Jun-knockout mice. This proposal will provide scientific evidence of elucidation of the mechanism of JNKs-mediated neuroinflammaiton and establishment of JNK as the target for neuroprotective therapy for PD.

帕金森病（PD）的发病本质是中脑黑质多巴胺（DA）神经元死亡，目前尚无有效的神经保护手段。神经炎症是DA神经元进行性死亡的重要原因。我们和其他实验室已证明JNK是介导DA神经元死亡的关键激酶。我们在PD小鼠模型中进一步发现：JNK主要在DA神经元内激活；JNK三个亚型（JNK1、JNK2、JNK3）分别全身敲除均抑制黑质局部神经炎症发生；JNK下游转录因子ATF2介导DA神经元死亡（Exp Neurol 2016第一作者）但不调控神经炎症。那么，关键问题是：是否DA神经元内的JNK介导神经炎症发生？哪个JNK亚型起关键作用？此过程是否下游转录因子c-Jun依赖、通过转录上调MMP3所介导？本项目拟采用DA神经元选择性的JNK各亚型及c-Jun基因敲除小鼠进行研究以回答这些问题，为阐明JNK介导神经炎症的机制、解析DA神经元损伤/死亡与神经炎症的关系、确立JNK为PD治疗靶标提供科学依据。

帕金森病(PD)的重要病理特征是黑质多巴胺能(DA)神经元死亡，伴随脑内神经炎症的发生。我们的前期研究证明JNK是介导神经元死亡的关键激酶，并观察到：JNK各亚型全身敲除均可显著抑制PD小鼠黑质局部炎症的发生，且JNK及其下游转录因子c-Jun主要在DA神经元激活，提出DA神经元内JNK以细胞非自主形式调控神经炎症发生的科学假说。针对此科学假说及项目的研究目标，我们按计划获得了JNK三个亚型及c-Jun的DA神经元特异条件性敲除鼠，利用MPTP诱导的PD小鼠模型：1)证实了DA神经元JNK3介导死亡(JNK1、JNK2不介导)；2)证明了DA神经元中JNK三个亚型均不参与调控神经炎症的发生；3)获得了DA神经元中c-Jun促进PD小鼠神经退化的可靠证据；4)阐明了DA神经元中c-Jun通过转录激活BH3-only促凋亡蛋白Bim介导神经元死亡；5) 发现转录因子Egr-1在MPTP造模早期在黑质星形胶质细胞转录上调并介导神经炎症的发生和DA神经元胞体丢失；6) 观察到基质金属蛋白酶MMP-3 (可能的c-Jun靶基因)在MPTP模型中表达上调，定位于星形胶质细胞而非DA神经元；7) 发现DA神经元内GSK-3β介导神经元死亡且以细胞非自主形式调控小胶质细胞激活。在本项目的资助下，我们完成了申请书中的全部研究内容，在体准确阐明了DA神经元内JNK3/c-Jun/Bim通路介导PD模型神经元死亡，证明了DA神经元内JNK各亚型不参与细胞非自主调控胶质细胞活化，发现Egr-1在星形胶质细胞中激活并介导PD神经炎症发生和神经元死亡，为寻找和确立PD神经保护治疗靶点提供了思路和线索。