多巴胺D2受体（DRD2）对星形胶质细胞自噬的调控及其在帕金森病发病中的作用

Parkinson disease (PD) is a common neurodegenerative disease, but its etiology and pathogenesis are still not clear. Astrocyte activation and its functional changes play an important role in the development of PD, such as chronic neuroinflammation,, reduced secretion of neurotrophic factors, and transmission of prion-like pathological changes. Activation of astrocytic dopamine receptor subtype 2 (DRD2) plays a role in inhibiting inflammation in the brain, and DRD2 deficiency or down-regulation accelerates the neuroinflammatory responses; however, whether this is associated with autophagic activity changes in astrocytes is not clear yet. Moreover, it remains poorly understood how the autophagy activity is altered in astrocyte and whether the astrocytic autophagy dysfunction participates in PD development. It warrants intensive study. Recently, our group found that DRD2 receptor agonists, in addition to enhancing autophagy activity in DA neurons, also affect the autophagy processes in astrocytes. But This is limited to the in vitro study at the cellular level using the DRD2 receptor agonist/antagonist. Therefore, this project will investigate the potential role and molecular mechanism of DRD2 in regulating the autophagy activity in astrocytes, and define whether it is involved in the inhibition by DRD2 signaling on neuroinflammation using the astrocytic Atg7 conditional knockout mouse from the animal, cellular to molecular levels. The Research results will not only help to clarify the effect of DRD2 signaling on autophagy, and may also shed light on the regulation of astrocytic autophagy on neuroinflammation during PD progression. This may lead to a better understanding of PD pathogenesis from a new point of view.

帕金森病（PD）是常见的神经变性疾病，但其病因和发病机制仍未明确。自噬异常和星形胶质细胞功能改变在PD发生中都扮演了重要角色。最近有文献报道激活星形胶质细胞多巴胺D2受体（DRD2）能抑制脑内炎症，DRD2表达下调或缺失加重神经炎症反应。我们最近发现DRD2受体激动剂能上调星形胶质细胞自噬，且自噬底物蛋白P62敲减能抑制炎症反应；然而，星形胶质细胞自噬是否介导DRD2对炎症反应的调控、并且星形胶质细胞自噬是否及如何参与PD发病都未明，亟待深入研究。因此，本项目将从动物、细胞和分子水平，研究DRD2对星形胶质细胞自噬的调控，分别运用星形胶质细胞Atg7条件性敲除小鼠和Atg7过表达研究星形胶质细胞自噬在DRD2抑制神经炎症反应中的作用和分子机制。研究成果将有助于明确DRD2途径对细胞自噬的作用，揭示星形胶质细胞自噬对神经炎症等PD病理过程的调控，阐明PD发病新机制。

星形胶质细胞上多巴胺受体DRD2能抑制脑内炎症，该受体表达下调或缺失加重神经炎症反应，是帕金森病（PD）进行性进展的重要病理机制。然而，多巴胺受体调控神经炎症的分子机制仍未完全阐明。细胞自噬紊乱被认为参与帕金森病发病的细胞与分子机制。我们课题组既往研究发现，多巴胺受体激动（DRD2、DRD3）经c-fos/Beclin-1依赖的通路上调多巴胺神经元自噬活性，减少PD关键病理蛋白--共核蛋白病理性蓄积。星形胶质细胞中多巴胺受体激动是否也能激活自噬并调控神经炎症？这个问题尚未明确。因此，本课题围绕此科学问题，从分子、细胞到动物实验，运用多种生物学技术探索，并发现：（1）激动原代星形胶质细胞DRD2受体可以抑制促炎症因子转录，但是该过程不依赖于自噬；（2）激动DRD3受体对星形胶质细胞促炎症因子转录无明显抑制，但是可以抑制NLRP3炎症小体活化，以及IL-1β生成与分泌；（3）激动DRD3可以促进星形胶质细胞自噬、且自噬抑制剂可以阻断DRD3激动剂对NLRP3炎症小体和IL-1β的抑制作用；（4）DRD3激动剂普拉克索腹腔注射可以缓解细菌脂多糖纹状体定位注射诱导的PD相关脑区IL-1β增加，该作用在星型胶质细胞Atg5特异性缺失小鼠不明显。上述研究成果充分表明：星形胶质细胞多巴胺受体可以通过不同的分子机制调节神经炎症；DRD3受体激活可以经Beclin-1依赖的自噬途径减少NLRP3炎症小体活化，降低IL-1β生成而缓解脑内炎症。本项目揭示了星形胶质细胞内自噬对神经炎症的调节，阐明了DRD3受体激动调控神经炎症的细胞与分子机制，为我们认识PD复杂的病理机制开拓了新思路。项目执行过程中，培养了3名硕博士研究生、在FASEB J等已发表3篇SCI二区论文，尚有部分成果正在整理投稿。