VTA多巴胺能神经元中CDK5激活参与抑郁症导致帕金森病易感的神经环路和分子机制

Parkinson disease (PD) and depression have comorbidity. Nearly 40% PD patients are accompanied by depressive symptoms. In the meantime, the risk of PD is 3 times higher than that of the normal population after the diagnosis of depression. Depression after PD has been widely studied, but the structural basis of neural circuits and molecular mechanism of depression-induced susceptibility to PD has not been reported. In the current study, new technologies and methods, including animal behavior tests, chemogenetics (DREADD), optigenetics, anterograde and retrograde virus tracing techniques, electrophysiology using MED64, in vivo calcium imaging and molecular biology, were designed to study the structural basis of neural circuits, functional characteristics and molecular mechanism in depression-induced PD. 1) to find the behavioral and histological evidences to prove that depression leads to the susceptibility to PD by environmental or genetic factors. 2) prove that the dopaminergic neurons in VTA are involved in depression-induced PD using the methods of animal behavior, DREADD and optigenetics t; 3) to explore the structural basis of VTA/SNr neural circuits using whole brain mapping and anterograde/retrograde virus tracing techniques; 4) to study the role of CDK5 and its phospholated target ANK2 in the regulation of VTA/SNr neural circuit in depression-induced PD. The aim of the study is to provide a new perspective and target for understanding the pathogenesis and clinical treatment of depression and PD.

帕金森病（PD）和抑郁症存在共病现象，40%的PD患者伴有抑郁症状，而抑郁症确诊后患PD的几率比正常人群高3倍。PD后抑郁已被广泛研究，但抑郁诱发PD易感的机制尚无实验报道。本课题拟在抑郁叠加PD的小鼠模型中研究抑郁诱发PD的环路和分子机制，为预防和临床治疗PD提供新靶点：①整体水平：行为学和组织学证实抑郁小鼠对诱发PD的环境或遗传因素易感；②细胞水平：光/化学遗传学验证腹侧被盖区（VTA）的多巴胺能神经元（DA）激活参与上述过程；③环路水平：神经示踪验证抑郁导致VTA向黑质网状区（SNr）GABA能神经元的DA投射增加；电生理和钙成像检测抑郁小鼠SNr的抑制性放电上调；化学遗传学验证特异性抑制VTA/SNr环路可逆转抑郁诱发的PD易感；④分子水平：证明抑郁小鼠VTA向SNr投射的DA中CDK5激活并磷酸化其突触底物ANK2，上调VTA/SNr投射的突触功能，介导SNpc对MPTP易感。

大量临床研究表明，运动活动减少是重度抑郁症（MDD）以及其他精神疾病的常见症状，抑郁也与帕金森病的发病有明确的共病现象。在MDD中，中脑腹侧被盖区（VTA）多巴胺（DA）神经元与调节奖赏、动机、认知和厌恶的信息处理密切相关。然而，VTA-DA神经元与MDD相关运动损伤（尤其是运动能力低下）之间关系的神经回路机制在很大程度上仍然是未知的。依托本项目，我们研究了VTA-DA神经元如何在慢性社交失败应激（CSDS）诱发抑郁的状态下导致运动能力低下，并研究抑郁对帕金森氏毒素1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）诱导的运动障碍和黑质致密部（SNc）多巴胺能（DA）神经元丢失的影响。结果表明，CSDS可影响小鼠的自发运动活动，但不影响握力和强迫运动能力。VTA-DA神经元的化学遗传学激活减轻了CSDS诱导的运动减退。随后，定量全脑标测显示，在CSDS治疗后，VTA-DA神经元向黑质网状部（SNr）的投射减少。通过阶段性放电刺激（而非强直性放电），多巴胺能从VTA投射到SNr的光遗传学激活可以显著增加小鼠的运动活动。此外，CSDS小鼠VTA-SNr多巴胺能回路的化学遗传学激活也可以挽救运动活动的下降。我们研究发现，在MPTP给药后，CSDS小鼠表现出比对照小鼠更差的运动表现和更多的SNcDA神经元丢失。CSDS小鼠的中央杏仁核（CeA）向SNcDA的投射显著增加。在CSDS小鼠中，SNc投射的CeA神经元的活性增强。激活或抑制CeA-SNcDA途径可以模拟或阻断CSDS诱导的MPTP敏感性。总之，我们的数据表明VTA-SNr多巴胺能投射介导CSDS诱导的运动减退，而CeA-SNcDA神经投射参与CSDS诱导的小鼠对MPTP的易感性，这为MDD加重运动障碍和帕金森病发病率提供了理论基础和潜在的治疗靶点。.