Epidemiological and clinical studies have long shown that exposure to high levels of heavy metals are associated with increased risks of neurodegenerative diseases. It is widely accepted that autophagic dysfunction is involved in pathogenesis of various neurodegenerative disorders; however, the role of heavy metals in regulation of macroautophagy/autophagy is unclear. Here, we show that manganese (Mn) induces a decline in nuclear localization of TFEB (transcription factor EB), a master regulator of the autophagy-lysosome pathway, leading to autophagic dysfunction in astrocytes of mouse striatum. We further show that Mn exposure suppresses autophagic-lysosomal degradation of mitochondria and induces accumulation of unhealthy mitochondria. Activation of autophagy by rapamycin or TFEB overexpression ameliorates Mn-induced mitochondrial respiratory dysfunction and reactive oxygen species (ROS) generation in astrocytes, suggesting a causal relation between autophagic failure and mitochondrial dysfunction in Mn toxicity. Taken together, our data demonstrate that Mn inhibits TFEB activity, leading to impaired autophagy that is causally related to mitochondrial dysfunction in astrocytes. These findings reveal a previously unappreciated role for Mn in dysregulation of autophagy and identify TFEB as a potential therapeutic target to mitigate Mn toxicity.

Abbreviations

BECN1: beclin 1; CTSD: cathepsin D; DMEM: Dulbecco’s Modified Eagle Medium; GFAP: glial fibrillary acid protein; GFP: green fluorescent protein; HBSS: hanks balanced salt solution; LAMP: lysosomal-associated membrane protein; LDH: lactate dehydrogenase; Lys Inh: lysosomal inhibitors; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; Mn: manganese; MTOR: mechanistic target of rapamycin kinase; OCR: oxygen consumption rate; PBS: phosphate-buffered saline; PFA: paraformaldehyde; PI: propidium iodide; ROS: reactive oxygen species; s.c.: subcutaneous; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TFEB: transcription factor EB

中文翻译：

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TFEB的失调导致星形胶质细胞中锰诱导的自噬失败和线粒体功能障碍。

流行病学和临床研究早已表明，暴露于高水平的重金属与神经退行性疾病的风险增加有关。自噬功能障碍与多种神经退行性疾病的发病机理有关，这一点已被广泛接受。然而，重金属在调控巨噬细胞自噬中的作用尚不清楚。在这里，我们显示锰（Mn）诱导自噬-溶酶体途径的主要调节剂TFEB（转录因子EB）的核定位下降，导致小鼠纹状体星形胶质细胞的自噬功能障碍。我们进一步表明，锰暴露抑制线粒体的自噬溶酶体降解并诱导不健康的线粒体积累。雷帕霉素或TFEB过表达激活自噬可改善星形胶质细胞中Mn诱导的线粒体呼吸功能障碍和活性氧（ROS）生成，提示Mn毒性中自噬失败与线粒体功能障碍之间存在因果关系。两者合计，我们的数据表明Mn抑制TFEB活性，导致自噬受损，这与星形胶质细胞中的线粒体功能障碍有因果关系。这些发现揭示了锰在自噬失调中的前所未有的作用，并将TFEB鉴定为减轻锰毒性的潜在治疗靶标。导致自噬功能受损，这与星形胶质细胞中的线粒体功能障碍有因果关系。这些发现揭示了锰在自噬失调中的前所未有的作用，并将TFEB鉴定为减轻锰毒性的潜在治疗靶标。导致自噬功能受损，这与星形胶质细胞中的线粒体功能障碍有因果关系。这些发现揭示了锰在自噬失调中的前所未有的作用，并将TFEB鉴定为减轻锰毒性的潜在治疗靶标。

缩略语

BECN1：beclin 1；CTSD：组织蛋白酶D；DMEM：Dulbecco的改良Eagle培养基；GFAP：神经胶质纤维酸性蛋白；GFP：绿色荧光蛋白；HBSS：需要平衡盐溶液；LAMP：溶酶体相关膜蛋白；LDH：乳酸脱氢酶；Lys Inh：溶酶体抑制剂；MAP1LC3 / LC3：微管相关蛋白1轻链3；MAPK：有丝分裂原激活的蛋白激酶；Mn：锰；MTOR：雷帕霉素激酶的机制靶标；OCR：耗氧率；PBS：磷酸盐缓冲盐水；PFA：多聚甲醛；PI：碘化丙啶；ROS：活性氧；sc：皮下；SQSTM1 / p62：螯合体1；TEM：透射电子显微镜；TFEB：转录因子EB