IL-17A经小胶质细胞外泌体ciRS-7机制促进帕金森病模型鼠的神经退变

Neuroinflammation has been considered as an important factor promoting the occurrence and development of Parkinson's disease (PD). Interleukin (IL)-17A, a proinflammatory cytokine principally released from T-helper (Th)17 cells, has been associated with autoimmune diseases and inflammatory diseases. Over the recent years, the role of neuroinflammation in Parkinson's disease (PD) has gained increasing attention. We have recently reported that Th17 cells infiltrate into the brain in PD model mice and induce neuroinflammation and neurodegeneration. Our further investigation found that IL-17A exerted the toxic effect to dopaminergic neurons only in the presence of microglia. Herein, we are planning to explore the molecular mechanism underlying that microglia promote neurodegeneration of PD in response to IL-17A. Firstly, we employ PD mice with IL-17 receptor A conditional knockout in microglia and PD cell model with the co-culture of ventral mesencephalic neurons and microglia that have the silenced IL-17 receptor A gene to identify that microglia are the major target cells directly responsive to IL-17A in promoting neurodegeneration of PD. Secondly, by analysis of a particular type of circular RNA (circRNA) ciRS-7 in exosome released from microglia and its effects on a microRNA (miRNA) miR-7, the α-synuclein gene SNCA, and α-synuclein aggregation in dopaminergic neurons, we clarify the circRNA-miRNA-mRNA regulatory mechanism underlying that IL-17A promotes microglial exosome release and leads to neurodegeneration of PD. These studies will provide novel mechanism for neurodegeneration of PD induced by T lymphocyte-mediated immune inflammation and also provide a new insight into potential anti-inflammatory therapy for PD.

近年来神经炎症被视为促进帕金森病（PD）发生发展的重要因素。白介素-17A（IL-17A）是由Th17淋巴细胞释放的促炎细胞因子，我们已报道Th17细胞渗入PD小鼠脑实质内诱发神经炎症及促进神经退变，我们预实验还发现IL-17A只有在小胶质细胞存在下才能发挥对多巴胺能神经元的损伤作用。本项目拟在我们以前工作的基础上，利用条件性敲除小胶质细胞IL-17A受体的PD小鼠及体外沉默IL-17A受体的小胶质细胞与中脑神经元共培养体系，说明小胶质细胞是IL-17A促进PD神经退变的中介细胞；然后通过分析小胶质细胞外泌体circRNA(ciRS-7)及其对多巴胺能神经元miRNA-7、SNCA表达和α-突触核蛋白积聚的影响，阐明IL-17A促进小胶质细胞外泌体释放进而导致PD神经退变的circRNA-miRNA-mRNA调节机制。为PD的T细胞炎性致病机制提供新视角，为潜在的PD抗炎治疗提供实验资料。

帕金森病（Parkinson’s disease，PD）是一种神经系统退行性疾病，主要表现为黑质多巴胺神经元变性缺失所导致的运动行为异常。近10多年来的研究发现，脑内小胶质细胞介导的神经炎症参与了PD的发病机制，但对于T淋巴细胞在PD中的作用还知之甚少。本项目在前一项目的基础上，进一步研究Th17细胞所释放的促炎细胞因子白细胞介素-17A（interleukin-17A）对PD神经炎症和神经退变的影响及其机制。获得的重要结果和关键数据如下：① PD小鼠和大鼠的血清、脑脊液和黑质中的IL-17A水平升高，但黑质以外的脑区如大脑皮层、海马和纹状体内的IL-17A水平均没有明显改变。② IL-17A中和抗体可减轻PD大鼠的小胶质细胞激活、多巴胺神经元丢失及运动行为障碍。③ IL-17A基因敲除也减轻了PD小鼠的神经炎症和神经退变。④ 小胶质细胞表达IL-17受体（IL-17RA），沉默小胶质细胞的IL-17RA基因可抑制IL-17A对小胶质细胞的激活作用及对多巴胺神经元的损伤作用。⑤ 多巴胺神经元不表达IL-17RA，IL-17A对多巴胺神经元没有直接的影响，而是由小胶质细胞介导IL-17A对多巴胺神经元的损伤作用。⑥ IL-17A增强小胶质细胞释放外泌体并上调外泌体表达ciRS-7。⑦ 小胶质细胞来源的外泌体可被多巴胺神经元所摄取，该外泌体的ciRS-7可下调神经元的miR-7表达进而上调SNCA表达，促进多巴胺神经元的死亡。⑧ IL-17A处理的小胶质细胞所释放的外泌体加重了PD的神经退变，而ciRS-7-shRNA处理的小胶质细胞所释放的外泌体减轻了PD的神经退变。这种小胶质细胞外泌体与多巴胺神经元之间的ciRS-7-miR-7-SNCA通信为神经炎症促进PD神经退变的机制提供了全新的数据，也为靶向调节ciRS-7-miR-7-SNCA分子链来减缓PD神经退变提供基础实验资料。

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