Department of Environmental Health Sciences, Florida International University, Miami, USA.
Peninsula Schools of Medicine and Dentistry, Plymouth University, Plymouth, UK.
Acta Neuropathol Commun. 2019 Nov 19;7(1):184. doi: 10.1186/s40478-019-0821-4.
Targeting alpha-synuclein (α-syn) as a therapeutic strategy for Parkinson's disease (PD) has been intensively pursued largely due to its well-recognized pathogenic role. Since its discovery as the first familial link to PD over two decades ago, this protein has been associated with multiple neurotoxic mechanisms, such as mitochondrial dysfunction and impaired autophagic flux. We report here that blocking dynamin-related protein 1 (Drp1) improved both mitochondrial function and autophagic flux in experimental models of α-syn. Using rat dopaminergic neuronal cells with inducible wild-type human α-syn, we observed excessive mitochondrial fragmentation and increased Drp1 levels 48 h after gene induction. Functionally, these cells exhibited lower mitochondrial membrane potential, reduced ATP production rate and mitochondrial spare respiratory capacity, as well as increased levels of mitochondrial reactive oxygen species. To evaluate the protective role of Drp1 inhibition, we used three complementary approaches: gene silencing mediated by siRNA, overexpression of Drp1-dominant negative and the small molecule mitochondrial division inhibitor-1 (mdivi-1). Both morphological and functional defects induced by α-syn were attenuated by these strategies. Importantly, Drp1 inhibition reduced proteinase K-resistant α-syn aggregates. Based on that observation, we investigated the involvement of autophagy. Through a combination of stable autophagy reporter cells and immunoreactivity for LC3 and p62 in neuronal cells with either α-syn overexpression or treatment of human α-syn preformed fibrils (PFF), we observed that Drp1 inhibition abolished autophagic impairment induced by α-syn. Consistent with its role in improving autophagy function, Drp1 inhibition reduced exosome release and spread of α-syn pathology from neurons to neurons and from microglia to neurons. In summary, this study highlights new insights that Drp1 inhibition confers neuroprotection through both mitochondrial and autophagy-lysosomal pathways, further strengthening the therapeutic potential of targeting Drp1.
靶向α-突触核蛋白（α-syn）作为治疗帕金森病（PD）的策略已被广泛研究，主要是因为它的致病性作用得到了广泛认可。自二十多年前发现其与 PD 的第一个家族性联系以来，这种蛋白质与多种神经毒性机制有关，如线粒体功能障碍和自噬通量受损。我们在此报告，阻断动力相关蛋白 1（Drp1）可改善α-syn 实验模型中的线粒体功能和自噬通量。使用诱导型野生型人α-syn 的大鼠多巴胺能神经元细胞，我们观察到基因诱导后 48 小时内线粒体过度碎片化和 Drp1 水平升高。功能上，这些细胞表现出更低的线粒体膜电位、降低的 ATP 产生率和线粒体备用呼吸能力，以及更高水平的线粒体活性氧。为了评估 Drp1 抑制的保护作用，我们使用了三种互补方法：siRNA 介导的基因沉默、Drp1 显性负性的过表达和小分子线粒体分裂抑制剂-1（mdivi-1）。这些策略均减弱了由α-syn 诱导的形态和功能缺陷。重要的是，Drp1 抑制减少了蛋白水解酶抗性α-syn 聚集体。基于这一观察，我们研究了自噬的参与。通过稳定自噬报告细胞与神经元细胞中 LC3 和 p62 的免疫反应性的结合，我们观察到 Drp1 抑制消除了α-syn 诱导的自噬损伤。与改善自噬功能的作用一致，Drp1 抑制减少了外体释放和α-syn 病理学从神经元到神经元以及从小胶质细胞到神经元的传播。总之，这项研究强调了新的见解，即 Drp1 抑制通过线粒体和自噬溶酶体途径提供神经保护，进一步加强了靶向 Drp1 的治疗潜力。
