Cellular mechanisms and ecophysiological consequences of selenium toxicity in fish

目前，在包括加拿大在内的世界许多地区，硒被认为是一种优先的水污染物。硒被有效地结合到水生食物网中，并可作为一种发育毒物(致畸剂)，导致幼鱼畸形。然而，导致畸形的生化/细胞机制以及畸形的长期生理和生态后果尚不清楚。这项研究的总体目标是研究硒对鱼类发育毒性的机制及其与鱼类的生理和生态相关性。我们将通过下列方法检验这一假设：(1)在抗氧化剂和抗氧化剂抑制剂的存在下孵育胚胎，(2)阻止抗氧化状态的关键介质的表达，(3)对整条鱼进行染色以确定活性氧物种的产生和细胞死亡，(4)确定氧化细胞膜损伤的程度，以及(5)确定不同身体组织中硒的浓度和形态(分子形式)的差异。在单独的实验中，暴露在Se中的胚胎将被培养到幼年和成年阶段。在这些实验中，我们将检验这样一种假设，即硒诱导的畸形会导致不可逆的生理后果，从而对个体鱼类的适应性产生负面影响。这些实验将包括(1)游泳表现，(2)能量储存/动员能力，(3)生理应激反应挑战，以及(4)繁殖能力。这些综合实验将解决我们对Se的水生生态毒理学知识中的几个主要数据空白，即(1)氧化应激在Se诱导的仔鱼畸形中的作用，(2)亚致死性Se暴露的生理后果，(3)对Se暴露的反应的种类和生命阶段的差异，以及(4)Se在鱼类组织中的分布和形态。这项研究计划的目标与我的长期研究目标非常吻合，即研究优先水生污染物对鱼类的发育和生殖毒性的机制。

Selenium (Se) is currently recognized as a priority aquatic pollutant in many areas of the world, including Canada. Selenium is efficiently incorporated into aquatic food webs and can act as a developmental toxicant (teratogen) causing deformities in larval fish. However the biochemical/cellular mechanisms that cause deformities, and the long-term physiological and ecological consequences of deformities, are not well understood. The overall objective of this proposed research is to investigate mechanisms of developmental toxicities caused by Se and their physiological and ecological relevance to fish. We will test the hypothesis that oxidative stress resulting from Se exposure plays a key role in causing deformities using the following approaches: (1) incubating embryos in the presence of antioxidants and inhibitors of antioxidants, (2) blocking expression of key mediators of antioxidant status, (3) staining whole fish to identify production of reactive oxygen species and cell death, (4) determining the extent of oxidative cell membrane damage, and (5) determining differences among body tissues in the concentration and speciation (molecular form) of Se. In separate experiments, embryos exposed to Se will be raised to the juvenile and adult stages. In these experiments, we will test the hypothesis that Se-induced deformities cause irreversible physiological consequences that negatively affect fitness of individual fish. These experiments will include (1) swim performance, (2) energy storage/mobilization capacity, (3) physiological stress response challenges, and (4) reproductive capacity. These integrated experiments will address several major data gaps in our knowledge of the aquatic ecotoxicology of Se, namely (1) the role of oxidative stress in Se-induced larval deformities, (2) the physiological consequences of sublethal Se exposure, (3) species and life stage differences in responses to Se exposure, and (4) Se distribution and speciation in fish tissues. The objectives of this research proposal fit closely with my long term research goal, which is to investigate mechanisms of developmental and reproductive toxicities in fish exposed to priority aquatic pollutants.