Cellular mechanisms and ecophysiological consequences of selenium toxicity in fish

硒（Se）目前在包括加拿大在内的世界许多地区被认为是一种优先的水生污染物。硒被有效地纳入水生食物网，并可作为一种发育毒物（致畸原）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。本研究旨在探讨硒对鱼类发育毒性的作用机制及其生理生态学意义。我们将通过以下方法验证硒暴露引起的氧化应激在导致畸形中起关键作用的假设：(1)在抗氧化剂和抗氧化剂抑制剂存在的情况下培养胚胎，(2)阻断抗氧化状态关键介质的表达，(3)对全鱼进行染色，以鉴定活性氧的产生和细胞死亡，(4)确定氧化细胞膜损伤的程度，(5)确定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，暴露于硒的胚胎将被饲养到幼年和成年阶段。在这些实验中，我们将验证硒诱导的畸形会导致不可逆的生理后果，从而对鱼类个体的健康产生负面影响的假设。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)生殖能力。这些综合实验将解决我们在硒的水生生态毒理学知识方面的几个主要数据缺口，即(1)氧化应激在硒诱导的幼虫畸形中的作用，(2)亚致死硒暴露的生理后果，(3)对硒暴露的反应的物种和生命阶段差异，以及(4)硒在鱼类组织中的分布和物种形成。这项研究计划的目标与我的长期研究目标密切相关，即研究暴露于重点水生污染物的鱼类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.