Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson’s disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain. aSYN PFFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell-type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser-scanning microscopy of genetically encoded sensors for bioenergetic and redox status. In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure. Taken together, our findings suggest that disruption of mitochondrial function, and the subsequent bioenergetic deficit, is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD.

中文翻译：

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α-突触核蛋白病理学破坏帕金森病中高危多巴胺能和胆碱能神经元的线粒体功能


聚集的 α-突触核蛋白 （aSYN） 的病理性积累是帕金森病 （PD） 的常见特征。然而，细胞内 aSYN 病理导致大脑神经元功能障碍和变性的机制仍不清楚。aSYN 的一个潜在相关靶标是线粒体。为了检验这一假设，使用遗传和生理学方法监测黑质致密部 （SNc） 多巴胺能和花梗孔板核 （PPN） 胆碱能神经元的线粒体功能在立体定位注射 aSYN 预制原纤维 （PFF） 到小鼠大脑中。将 aSYN PFFs 立体定向注射到小鼠的 SNc 或 PPN 中。12 周后，使用多种方法组合研究小鼠，包括免疫细胞化学分析、细胞类型特异性转录组学分析、电子显微镜、电生理学和基因编码传感器的双光子激光扫描显微镜检查生物能量和氧化还原状态。除了诱导显着的神经元丢失外，SNc 注射 PFFs 还选择性地诱导了多巴胺能神经元中细胞内磷酸化 aSYN 聚集体的形成。在这些神经元中，PFF 暴露降低了线粒体基因表达，减少了线粒体的数量，增加了氧化应激，并严重破坏了线粒体三磷酸腺苷的产生。与 aSYN 诱导的生物能量缺陷一致，多巴胺能神经元的自主尖峰减慢或停止。PFF 还上调溶酶体基因表达并增加溶酶体丰度，导致形成 Lewy 样包涵体。在 aSYN PFF 暴露后，在 PPN 胆碱能神经元中观察到类似的变化。 综上所述，我们的研究结果表明，线粒体功能的破坏和随后的生物能量缺陷是 aSYN 病理诱导的事件级联反应中的近端步骤，导致 PD 中高危神经元功能障碍和变性。