神经元内铁聚积与外泌体α突触核蛋白传播相互促进在帕金森病疾病进展中的作用及机制研究

Alpha-synuclein (α-syn) is the key player in the pathogenesis and progression of Parkinson’s disease (PD). Aggregated α-syn is the major components of Lewy bodies, together with iron deposit in the same region, which are two neuropathological hallmarks in PD. Following the extensive focus on iron metabolism disturbance in PD for a long time, in our pilot study, interactions between iron deposition and α-syn pathology in dopaminergic neurons have been accentuated. We also found iron promotes exosomal α-syn release into the surroundings. However, how this occurred and what happens next has not been fully elucidated. In the proposed study, we adopted animal models and cell cultures triggered by environmental insults or genetic factors to investigate neuronal iron deposit modulates Rab family members and promotes α-syn phosphorylation and aggregation, and thus facilitate exosomal α-syn release from neurons in iron-binding, phosphorylated, oligomeric forms; to investigate exosomal α-syn internalizations by recipient neurons and neuroglia trigger endoplasmic reticulum stress, activate intracellular iron regulatory factors (iron regulatory proteins) via pCREB and aggravate iron deposit and damages by affecting iron transport and storage. Then we are interested in whether it could be beneficial for disease progression by modulation of the above processes from the perspectives of both neurons and neuroglia, using knockout mice and blocking reagents. Taken together, we propose to uncover the reciprocal relations between exosomal α-syn propagation among neighboring cells and iron deposit, thus provide novel evidence on PD pathogenesis and possible therapeutic strategies.

Alpha-突触核蛋白（α-syn）是帕金森病（PD）发病及进展的关键因素，其聚集形成的路易小体及伴随的铁聚积是PD两大神经病理学表现。前期工作在多巴胺能神经元内阐明铁聚积促进α-syn病理，且初步发现铁促进外泌体α-syn向细胞外释放增强，然而机制和后续过程仍不明确。本研究将在PD动物和细胞模型（环境/遗传因素）中，阐明神经元内铁聚积通过调控Rab家族分子及诱导α-syn聚集和磷酸化并结合铁，促进外泌体α-syn释放并改变其形式；明确外泌体α-syn被神经元和胶质细胞再摄取后易诱发内质网应激，通过pCREB调控铁调节蛋白IRPs的亚细胞定位及表达，导致接受细胞内铁聚积和损伤；利用基因敲除小鼠和阻断剂探讨调控上述过程是否可能从神经元和胶质细胞的双重角度延缓疾病进程。本研究将揭示神经元内铁聚积与外泌体α-syn细胞间传播相互促进导致疾病进展的分子机制，为PD疾病机制和治疗策略提供新证据。

Alpha-突触核蛋白（α-syn）被认为是帕金森病（PD）发病的核心因素，其聚集形成的路易小体及伴随的铁沉积是PD两大神经病理学表现。前期工作发现α-syn聚集和铁沉积在多巴胺能神经元内具有重要联系，然而α-syn在细胞间的传播与PD铁代谢异常间的关系尚不清楚。本项目研究结果揭示了（1）细胞内铁负载可显著促进细胞内α-syn表达和聚集，同时显著降低外泌体释放的数目，且外泌体释放的减少与细胞内α-syn表达水平并无关联；但以外泌体形式释放的α-syn和铁显著增多，且不依赖于外泌体释放的调控机制如Rab蛋白家族、ATP13A2等分子。（2）细胞外α-syn单体和预制原纤维（PFFs）能够调控体外培养的神经元铁代谢、诱导原代星形胶质细胞促炎反应，但在小鼠模型中，侧脑室或脑区注射α-syn单体和PFFs并不影响黑质和纹状体铁代谢相关蛋白的表达，提示在体情况下细胞间传播的α-syn对铁代谢的调控可能存在更多影响因素。（3）细胞间传播的α-syn被摄取后可抑制自噬并介导细胞损伤，这将使得一些自噬激活为关键靶点的神经保护因素无法发挥作用。上述结果针对PD发病中铁和α-syn两大因素，探讨了细胞外（外泌体）α-syn与铁沉积的相互作用和分子机制，从细胞间信息传递的角度出发，提示其是细胞内两者之间紧密关系的重要补充。此外，本研究探讨了铁、 细胞外（外泌体）α-syn和自噬之间的联系，提出α-syn被摄取后可抑制自噬且不能被激活，从而为探索新的神经保护策略提供了理论基础和实验依据。