Novel Antioxidant Defenses and Redox Maintenance Systems in Bdelloid Rotifers

描述（由申请人提供）：活性氧（ROS）的损伤和硫醇氧化还原循环的扰动在衰老、衰老和细胞凋亡中起着重要作用，并推动抗氧化防御（AOD）系统的进化。然而，AOD和氧化还原维持需要代谢和生理成本，并且在损伤成本和修复成本之间存在平衡。经常经历高压力和诱变环境的生物正在选择增加投资，以开发新的AOD和氧化还原维持手段。蛭形轮虫是一种小型水生无脊椎动物，其复杂程度与线虫相似，就是这样一种动物。蛭形虫栖息在短暂的水生环境中，可以在反复的干燥中存活，而不会减少水分寿命。在一些物种中，经历过干燥的雌性延长了寿命和繁殖力。蛭形虫也是已知最耐辐射的动物之一，在暴露于电离辐射（IR）水平后，能够修复数百条DNA双链断裂，而电离辐射（IR）会使任何已建立的动物模型物种绝育或死亡。蛭形虫对IR的极端抗性几乎肯定是它们在干燥期间和从干燥中恢复时耐受氧化应激的能力的结果。这进一步支持了观察，蛭形线虫对过氧化氢有很强的抵抗力，在过氧化氢浓度对线虫致死时没有观察到的影响。暴露在浓度高于LC50的H2O2下，线虫的寿命和繁殖力会增加。基因组和转录组的分析表明，蛭形虫表达合成和还原谷胱甘肽样多胺二硫醇、锥虫硫酮的基因的多个拷贝，否则只在锥虫等动质体原生动物中被发现。这个r21规模的项目将描述这种新的硫醇氧化还原系统，并评估其对轮虫和模式生物氧化应激后不同寿命和繁殖力的贡献。指导假设是，研究一种新的动物群体，其中氧化还原维持AOD系统最大化，将为延长寿命和健康寿命提供新的见解和方法。第一个目标是通过一系列的遗传和生化分析，验证锥虫硫酮在胶质细胞AOD和氧化应激和衰老的氧化还原维持反应中起主要作用的假设。第二个目标将测试假设，即锥虫硫酮系统足以增强对氧化应激的抵抗力，并且在一定程度上负责观察寿命和繁殖力的增加，使用RNAi来降低轮虫中的锥虫硫酮合成酶，并通过在大肠杆菌和秀丽线虫中表达合成酶和还原酶，然后暴露于氧化应激。这项工作的长期目标是建立蛭形轮虫作为一个特别有利的模型，用于氧化还原维持和AOD系统的比较研究，因为它们与衰老有关，目标是开发方法来增强其他物种的这些系统，包括标准衰老模型。

DESCRIPTION (provided by applicant): Damage from reactive oxygen species (ROS) and perturbations in thiol redox cycling play a major role in aging, senescence, and apoptosis and drive the evolution of antioxidant defense (AOD) systems. However, AOD and redox maintenance incur metabolic and physiological costs, and a balance exists between the cost of damage and the cost of repair. Organisms that routinely experience highly stressful and mutagenic environments are under selection for an increased investment in developing novel means of AOD and redox maintenance. Bdelloid rotifers, small aquatic invertebrates of similar complexity to nematodes, are one such group. Bdelloids inhabit ephemerally aquatic environments and can survive repeated rounds of desiccation without a decrease in hydrated lifespan. In some species, females that have been through desiccation have increased lifespan and fecundity. Bdelloids are also among the most radiation resistant animals known, capable of repairing many hundreds of DNA double strand breaks after exposure to levels of ionizing radiation (IR) that would sterilize or kill any established animal model species. The extreme resistance of bdelloids to IR is almost certainly a consequence of their ability to tolerate the oxidative stress incurred during and recovering from desiccation. This is further supported by the observation that bdelloids are very resistant to hydrogen peroxide, with no observable effect at concentrations of H2O2 lethal to nematodes. Exposure to H2O2 at concentrations above the LC50 for nematodes increases lifespan and fecundity in bdelloids. Analysis of genomes and transcriptomes has revealed that bdelloids express multiple copies of genes for the synthesis and reduction of a glutathione-like polyamine dithiol, trypanothione, otherwise known only from kinetoplastid protozoans such as trypanosomes. This R21-scale project will characterize this novel thiol redox system and assess its contribution to different lifespan and fecundity outcomes after oxidative stress in rotifers and model organisms. The guiding hypothesis is that investigating a novel group of animals where redox maintenance AOD systems are maximized will provide new insights and approaches to increasing lifespan and healthspan. The first aim will test the hypothesis that trypanothione plays a major role in the bdelloid AOD and redox maintenance response to oxidative stress and aging, using a series of genetic and biochemical analyses. The second aim will test the hypothesis that the trypanothione system is sufficient to confer enhanced resistance to oxidative stress and is in part responsible for the observation of increased lifespan and fecundity, using RNAi to knock down trypanothione synthase in rotifers and by expressing the synthase and reductase in E. coli and C. elegans followed by exposure to oxidative stress. The long-term objective of this work is to establish bdelloid rotifers as a particularly advantageous model for comparative studies of redox maintenance and AOD systems as they relate to aging, with the goal of developing methods for enhancing these systems in other species, including standard aging models.