Cellular mechanisms and ecophysiological consequences of selenium toxicity in fish

硒（Se）是目前世界上许多地区（包括加拿大）公认的优先水生污染物。硒被有效地纳入水生食物网，并可作为一种发育毒物（致畸剂），导致仔鱼畸形。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，还没有得到很好的理解。本研究的总体目标是探讨硒对鱼类发育毒性的机制及其与鱼类生理和生态的相关性。我们将使用以下方法检验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）在存在抗氧化剂和抗氧化剂抑制剂的情况下孵育胚胎，（2）阻断抗氧化状态的关键介质的表达，（3）染色整条鱼以鉴定活性氧物质的产生和细胞死亡，（4）确定氧化性细胞膜损伤的程度，和（5）确定身体组织中Se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培养到幼年和成年阶段。在这些实验中，我们将测试的假设，硒引起的畸形造成不可逆转的生理后果，负面影响个别鱼的健身。这些实验将包括（1）游泳能力，（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几个主要的数据差距，在我们的知识硒的水生生态毒理学，即（1）硒诱导的幼虫畸形的氧化应激的作用，（2）亚致死硒暴露的生理后果，（3）物种和生命阶段的差异，在响应硒暴露，（4）硒在鱼组织中的分布和形态。这项研究计划的目的与我的长期研究目标密切相关，即研究鱼类暴露于优先水生污染物的发育和生殖毒性机制。

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.