Defining the cellular and molecular mechanisms of how toxicants disrupt mitochondrial DNA homeostasis

项目概要/摘要 药物和污染物对线粒体的毒性作用的认识正在增长。我们的长期目标是 了解污染物诱导线粒体功能障碍的分子机制，并将其应用于 新的治疗策略的发展信息。将军的广泛曝光 邻苯二甲酸盐的危害引起了公众的极大关注。邻苯二甲酸酯被广泛添加到塑料中， 食品包装、玩具、医疗器械、药品、家具和化妆品， 产品进入食物，水和空气。邻苯二甲酸二（2-乙基己基）酯（DEHP）被大量使用，在肠道内， 它被水解成活性代谢物邻苯二甲酸单（2-乙基己基）酯（MEHP）。最近的证据表明， 邻苯二甲酸酯是改变线粒体DNA拷贝数的线粒体DNA（mtDNA）毒物。有毒污染物， 破坏线粒体功能可能导致线粒体疾病或使个体具有遗传变异 影响线粒体的风险更大这是一个非常重要的问题，因为成人线粒体疾病影响 每4,300人中有1人。此外，用于治疗人类肿瘤的核苷逆转录酶抑制剂（NRTI）， 免疫缺陷病毒感染引起线粒体毒性并通过引起 线粒体DNA严重缺失拟议的工作将解决我们对分子生物学知识的空白。 这些mtDNA毒物诱导线粒体功能障碍的机制。该项目的目标是 确定驱动毒物诱导的mtDNA降解变异的分子机制， 在我们对用NRTI 2 '，3'- 双脱氧胞苷（ddC）。器官中未分化细胞的功能是替换在稳定条件下丢失的细胞- 状态条件和组织修复期间。我们预测线粒体污染物可以触发或促成 针对未分化的细胞。我们假设，当暴露于mtDNA毒物时， 线粒体自噬介导的mtDNA降解途径在未分化细胞中特异性上调， 与分化的细胞相比，线粒体DNA消耗显著更高。有两个具体目标， 这项工作首先，在分别用MEHP或MEHP处理的细胞中， ddC将被量化。在毒物暴露后，我们将确定未分化的细胞是否具有 相对于其分化的对应物，线粒体DNA降解和生物能量缺陷增加。还 将确定毒物诱导的mtDNA缺失和突变的程度。第二，分子 毒物诱导的线粒体DNA稳态破坏的机制将通过测量 自噬/线粒体自噬和降解体类型的机制的组件的表达水平， 未分化和分化的细胞。这项工作是有意义的，因为它将阐明的机制， 毒物介导的mtDNA降解，从而为未来的污染物研究奠定了基础。从长远来看， 这项工作可能形成治疗或预防毒物诱导的线粒体损伤的策略的框架。

Project summary/abstract Awareness of the toxic effects of drugs and pollutants on mitochondria is growing. Our long-term goal is to understand the molecular mechanisms by which pollutants induce mitochondrial dysfunction and to apply this information to the development of new therapeutic strategies. The widespread exposure of the general population to phthalates has raised significant public concern. Phthalates are added to plastics widely found in food packaging, toys, medical devices, pharmaceuticals, furniture, and cosmetics and they leach out of these products into the food, water, and air. Di-2-ethylhexyl phthalate (DEHP) is abundantly used, and inside the gut, it is hydrolyzed to the active metabolite mono-(2-ethylhexyl) phthalate (MEHP). Recent evidence indicates that phthalates are mitochondrial DNA (mtDNA) toxicants that alter mtDNA copy number. Toxic contaminants that disrupt mitochondrial function may cause mitochondrial disease or place individuals with genetic variants affecting mitochondria at greater risk. This is a very significant concern, as adult mitochondrial disease affects 1 in 4,300 individuals. Furthermore, nucleoside reverse transcriptase inhibitors (NRTIs) used to treat human immunodeficiency virus infection cause mitochondrial toxicity and mimic mitochondrial disease by causing severe mtDNA depletion. The proposed work will address gaps in our knowledge about the molecular mechanisms by which these mtDNA toxicants induce mitochondrial dysfunction. The goal of this project is to determine the molecular mechanisms driving the toxicant-induced variability in mtDNA degradation that we have observed in our preliminary studies of undifferentiated and differentiated cells treated with the NRTI 2',3'- dideoxycytidine (ddC). The function of undifferentiated cells in an organ is to replace cells lost under steady- state conditions and during tissue repair. We predict that mitochondrial pollutants can trigger or contribute to disease by targeting undifferentiated cells. We hypothesize that upon exposure to a mtDNA toxicant, a mitophagy-mediated mtDNA degradation pathway is specifically up-regulated in undifferentiated cells causing significantly higher mtDNA depletion compared to that in differentiated cells. There are two specific aims for this work. First, the disruption of mitochondrial homeostasis in cells treated separately with either MEHP or ddC will be quantified. Following toxicant exposures, we will determine whether undifferentiated cells have increased mtDNA degradation and bioenergetic defects relative to their differentiated counterparts. Also, the extent of toxicant-induced mtDNA deletions and mutations will be determined. Second, the molecular mechanism of toxicant-induced disruption of mtDNA homeostasis will be determined by measuring the expression levels of components of the autophagy/mitophagy and degradosome types of machinery in undifferentiated and differentiated cells. This work is significant because it will elucidate the mechanism of toxicant-mediated mtDNA degradation and thus lay the foundation for future pollutant studies. In the long-term, this work may form the framework for strategies to treat or prevent toxicant-induced mitochondrial damage.