The role of the aryl hydrocarbon receptor in persistent effects of toxicants in fish

常见的环境污染物，二恶英和石油碳氢化合物，主要通过在心脏和血管中造成严重缺陷来杀死非常年轻的鱼。这些污染物通过改变心脏发育过程中重要部位的基因表达而起作用，但所有相关基因的身份仍不清楚。该实验室最近的研究表明，即使接触到低水平的这些污染物（低于杀死幼鱼所需的水平）也会损害鱼的健康。具体来说，我们已经发现，在发育过程中，非常短暂的暴露会影响鱼类成年后的游泳水平，并导致过量的脂肪。从我们之前的工作来看，目前还不清楚是否有足够的污染物在鱼的体内停留到成年，从而导致这些持续的影响。另一种可能是，心脏和血管缺陷导致血液循环不畅，导致肌肉力量下降，脂肪组织中脂肪的清除能力下降。最后一种可能性是，某些东西正在改变基因制造蛋白质的方式。我们对分子生物学的最新理解表明，大多数生物体的DNA具有通过所谓的“表观遗传机制”沉默或增强某些基因的机制。因此，本提案的主要目标是确定对鱼类造成持续影响所需的最低污染物水平。我们还想确定产生污染效应的重要蛋白质，以及表观遗传机制是否起作用。该实验将使用高分辨率微超声、三维图像分析软件和共聚焦显微镜，以及先进的分子技术（绿色荧光血管转基因鱼、qPCR和敲低技术）来评估斑马鱼（Danio rerio）的心血管结构和功能。我们的目标是证明，如果这些污染物发生在鱼很小的时候，那么它们在一次接触后就会影响至关重要的游泳能力。这些信息将使政府能够改变环境法规，以更好地保护加拿大和其他地方的野生鱼类种群。

The common environmental contaminants, dioxins and petroleum hydrocarbons, kill very young fish mainly by causing severe defects in the heart and blood vessels. These pollutants work by changing gene expression at important points while the heart is developing, but the identity of all the genes involved is still unclear. Recent work from this laboratory suggests that exposure to even low levels of these contaminants (lower than what is needed to kill young fish) hampers fish health. Specifically, we have found that a very brief exposure during development affects how well exposed fish swim in adulthood and leads to excess fattiness. From our previous work, it is unclear if enough of the pollutant simply stays in the bodies of the fish until adulthood to cause these persistent effects. Another possibility is that the heart and blood vessel defects cause poor blood circulation, leading to poor muscle strength and poor removal of fat from fatty tissues. The final possibility is that something is changing how genes are being allowed to make proteins. Recent advances in our understanding of molecular biology show that DNA in most organisms possesses mechanisms where certain genes can be silenced or enhanced through so-called 'epigenetic mechanisms'. Thus, the major goal of this proposal is to determine the lowest level of pollutant needed to cause persistent effects in fish. We also want to identify important proteins that produce the pollutant effects and whether epigenetic mechanisms are responsible. The proposed experiments will assess cardiovascular structure and function using high resolution micro-ultrasound, 3-D image analysis software with confocal microscopy, and advanced molecular techniques (transgenic fish with green fluorescent vasculature, qPCR and knock down techniques) in zebrafish (Danio rerio). Our goal is to show that these pollutants affect the critically important ability of fish to swim after a single exposure if that exposure occurs when they are very young. This information will allow the government to change environmental regulations to better protect wild fish populations in Canada and elsewhere.