Role of DNA damage response in Mn-induced neurotoxicity in C. elegans

锰是人体必需的微量元素，对人体健康具有重要的生理功能。然而，环境或职业的过度暴露可能会导致一种被称为锰中毒的不可逆转的疾病，这种疾病与帕金森病(PD)有着相似的神经病理，与运动和认知障碍的表现相关的显性多巴胺(DA)能细胞丢失。尽管潜在的机制尚不清楚，但最近我们发现DNA损伤相关的信号反应聚(ADP-核糖基)对体外锰暴露高度敏感。对DNA损伤的缺陷反应已被证明在包括帕金森病在内的一系列神经疾病的病因学中发挥作用，强调了DNA修复在神经动态平衡中的重要性。因此，本研究旨在利用体内模式生物秀丽线虫(C.elegans)来评估DNA损伤反应在锰诱导的神经毒性中的作用，特别是DNA反应基因与锰的相互作用。项目研究的第一部分将确定是否在DNA损伤反应(PME-1、PME-2、PME-3、PME-4(人类PAPS的秀丽线虫同源))缺失突变体中加剧了锰诱导的毒性。毒性终点将包括致命性、细胞应激和DNA损伤，同时将评估锰含量及其对其他金属动态平衡的影响，如铁、铜、锌和钙，以将观察到的影响与生理相关浓度联系起来。将锰暴露后的多巴胺能神经退行性变、多巴胺能信号和功能与DNA损伤反应相关信号联系起来，将为理解锰的神经毒性提供新的见解。此外，DNA损伤反应基因PME-1与各种修复途径的基因之间的相互作用还知之甚少。对选定的DNA修复基因的研究将在功能丧失的PME-1的背景下进行，并在锰的存在下进行，以指导未来对与锰诱导的神经毒性最相关的通路的研究。此外，还将研究锰暴露是否抑制野生型蠕虫以及与PME-1相关的基因(如sirtuins、PINK1、α-突触核蛋白)的转基因突变株的DNA损伤反应。为了进一步确定锰诱导毒性的新靶点，将对PME-1缺失突变体中的GABA能神经变性及其对MAPK信号的影响进行研究。识别新的锰诱导神经毒性的潜在机制将为治疗策略提供新的靶点，并可能为确定神经保护策略，包括食物成分对锰诱导的神经毒性的神经保护特性奠定基础。

Manganese (Mn) is an essential trace element occupying important physiological functions for human health. However, environmental or occupational overexposure may result in an irreversible condition known as manganism that shares similar neuropathology with Parkinson disease (PD), with overt dopaminergic (DAergic) cell loss associated with the presentation of motor and cognitive deficits. Although the underlying mechanism remains unclear, recently we identified the DNA damage related signaling reaction poly(ADP-ribosyl)ation to be highly sensitive to in vitro Mn exposure. A defective response to DNA damage has been shown to play a role in the etiology of a host of neurological disorders, including Parkinson disease, emphasizing the importance of DNA repair in neural homeostasis. Accordingly, this study is designed to assess the role of the DNA damage response in Mn-induced neurotoxicity with a special focus on interactions of DNA response genes and Mn using the in vivo model organism Caenorhabditis elegans (C. elegans). The first part of the project studies will determine if Mn-induced toxicity is exacerbated in DNA damage response (pme-1, pme-2, pme-3, pme-4 (C. elegans orthologs of human PARPs)) deletion mutants. Toxicity endpoints will include lethality, cellular stress and DNA damage, while in parallel the Mn content and the impact on other metal homeostasis e.g. Fe, Cu, Zn and Ca will be assessed to link the observed effects with physiologically relevant concentrations. Correlating dopaminergic (DAergic) neurodegeneration, DAergic signaling and function with DNA damage response related signaling following Mn exposure will provide novel insights in understanding Mn-induced neurotoxicity. Additionally, the interaction of the DNA damage response gene pme-1 with genes of various repair pathways is poorly understood. Studies on selected DNA repair genes will be carried out in the background of a loss-of-function pme-1 and in the presence of Mn to guide future studies on the most relevant pathways that are involved in Mn-induced neurotoxicity. Moreover, it will be investigated whether Mn exposure is inhibiting DNA damage response in wildtype worms as well as transgenic mutants of genes related to pme-1 (e.g. sirtuins, pink1, alpha-synuclein). To further identify novel targets of Mn-induced toxicity GABAergic neurodegeneration and the effect on MAPK signaling in the pme-1 deletion mutants will be studied. Identifying novel underlying mechanisms of Mn-induced neurotoxicity will provide novel targets for therapy strategies and may lay the foundation to identify neuroprotective strategies including neuroprotective properties of food constituents against Mn-induced neurotoxicity.