The role of ERR-gamma in the developmental toxicity of bisphenol A

描述（由申请人提供）：摘要在美国人群中检测到低水平的双酚A （BPA; 2,2-双（4-羟基苯基）丙烷）。这些低水平的接触是否会对人类健康构成风险仍然存在争议和不确定。在中枢神经系统（CNS）发育的关键时期，暴露在相当低水平的双酚a会导致成年啮齿动物的行为异常，导致国家毒理学计划最近报道低剂量双酚a暴露会损害中枢神经系统发育。BPA通过雌激素受体（ER）激活发挥其中枢神经系统作用的主流假设不太可能，因为BPA对经典ER的结合亲和力较弱。然而，BPA对雌激素相关受体γ (ERR3)的结合亲和力要高100到10000倍。ERR3是一种核受体，在发育的关键时期在大脑和胎盘中高度表达，没有已知的内源性配体，在雌激素反应元件（estrogen response elements, EREs）中具有组成性活性。本研究将验证低剂量双酚a暴露会在发育的关键窗口期维持ERR3组成活性，从而导致含有EREs或ERREs的基因异常表达，从而干扰中枢神经系统的发育和行为。为支持这项为期两年的探索性资助而进行的初步研究表明，发育过程中暴露于非致畸性、低浓度（<1<M）的双酚a会增加斑马鱼幼虫和成年斑马鱼的运动活性。为了确定ERR3在介导低剂量BPA的生理和行为影响中的作用，已经制定了两个具体目标。在第一个特定目标中，我们将确定环境相关浓度的双酚a是否会影响暴露于低浓度双酚a的斑马鱼的神经系统发育和功能。ERR3在产生这些反应中的作用将通过在BPA暴露窗口期间特异性抑制ERR3表达来确定。在第二个特定目标中，比较基因表达研究将用于鉴定体内功能生物标志物并确定ERR3在其表达中的作用。我们还将利用一种强大的、新描述的转基因甲基化反应鱼来研究BPA暴露在大脑中的表观遗传效应。这些实验将首次探讨低浓度BPA暴露损害中枢神经系统功能的潜在表观遗传机制，并确定ERR3在这些影响中的介导作用。ERR3在介导低剂量BPA对中枢神经系统的影响中所起的作用尚未被研究过。斑马鱼模型非常适合快速和明确地回答ERR3是否在BPA作用于发育中的中枢神经系统的机制中起核心作用。该提案将通过确定最可能的候选受体ERR3是否介导BPA对中枢神经系统发育和行为的低剂量影响，从而使科学界、工业界和公众受益。

DESCRIPTION (provided by applicant): Abstract Low levels of bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl)propane) are detectable throughout the US population. Whether these low levels of exposure pose a human health risk remain controversial and uncertain. Comparable low levels of BPA cause behavioral abnormalities in adult rodents exposed during critical periods of central nervous system (CNS) development, leading the National Toxicology Program to recently report concern that low dose BPA exposure can impair CNS development. The predominant assumption that BPA exerts its CNS effects through estrogen receptor (ER) activation is unlikely due to BPA's weak binding affinity for classical ERs. However, BPA exhibits 100- to 10,000-fold greater binding affinity for estrogen related receptor gamma (ERR3). ERR3 is a nuclear receptor that is highly expressed in the brain and placenta during critical periods of development, has no known endogenous ligand, and is constitutively active at estrogen response elements (EREs). This proposal will test the hypothesis that low dose developmental BPA exposure perturbs CNS development and behavior by maintaining ERR3 constitutive activity during critical windows of development resulting in abnormal expression of genes containing EREs or ERREs. Preliminary studies conducted to support this two year exploratory grant suggest that developmental exposure to non-teratogenic, low concentrations (<1<M) of BPA increases motor activity in larval and adult zebrafish. Two specific aims have been developed to define the role of ERR3 in mediating the physical and behavioral effects of low dose BPA. In the first Specific Aim, we will determine whether environmentally relevant concentrations of BPA affect nervous system development and functions in zebrafish developmentally exposed to low concentrations of BPA. The role of ERR3 in producing these responses will be determined by repressing ERR3 expression specifically during the BPA exposure window. In the second Specific Aim, comparative gene expression studies will be used to identify in vivo functional biomarkers and determine the role of ERR3 in their expression. We will also utilize a powerful, newly described transgenic methylation-responsive fish to investigate epigenetic effects of BPA exposure specifically in the brain. These experiments will probe for the first time a potential epigenetic mechanism by which low concentration BPA exposure impairs CNS function, and define the role of ERR3 in mediating these effects. The role of ERR3 in mediating low dose BPA effects on the CNS has not been previously investigated. The zebrafish model is ideally suited to quickly and definitively answer whether ERR3 is central to the mechanism of BPA's action on the developing CNS. This proposal will benefit the scientific community, industry, and the public by defining whether the most likely candidate receptor, ERR3, mediates BPA's low dose effects on CNS development and behavior. PUBLIC HEALTH RELEVANCE: In recent years the public and the scientific community have become concerned with the risk that bisphenol A (BPA) may pose to human health. This project will use the unique advantages of the embryonic zebrafish model to dissect the mechanism by which low concentrations of BPA interact with and perturb central nervous development and function.