Enantioselective Metabolism Influences PCB Developmental Neurotoxicity

对映选择性代谢影响 PCB 发育神经毒性

• 批准号: 7788064
• 负责人: HANS-JOACHIM LEHMLER
• 金额: $ 42.39万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-26 至 2014-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7788064
• 关键词: Address; Binding; Biochemical; Chlorine; Coculture Techniques; Complex; Cytochrome P450; Cytochromes; Data; Development; Dose; Elements; Enzymes; Exhibits; Exposure to; Future; Genes; Genetic Polymorphism; Goals; Growth; Hippocampus (Brain); Human; Immunophilins; In Vitro; Interdisciplinary Study; Intravenous; Investigation; Light; Link; Liver; Mediating; Metabolic Biotransformation; Metabolism; Microsomes; Molecular; Morphology; Mus; Nervous system structure; Neurodevelopmental Disorder; Neuroglia; Neurons; Oral; Outcome; Parents; Perinatal; Perinatal Exposure; Pesticides; Plasticizers; Polychlorinated Biphenyls; Population; Predisposition; Process; Protein Isoforms; Public Health; Rattus; Recombinants; Research; Risk; Role; RyR1; RyR2; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptors; Site-Directed Mutagenesis; Slice; Tacrolimus Binding Protein 1A; Testing; Tissues; Toxic effect; Transport Process; base; clinically relevant; developmental neurotoxicity; enantiomer; exposed human population; gene environment interaction; human CYP2B6 protein; in vitro Model; in vivo; inhibitor/antagonist; insight; metabolic abnormality assessment; neurotoxicity; novel; offspring; pharmacokinetic model; pollutant; pregnant; protein expression; public health relevance; receptor binding; receptor expression

DESCRIPTION (provided by applicant): Polychlorinated biphenyl (PCB) congeners with multiple ortho chlorine substituents are potent sensitizers of the ryanodine receptor (RyR) and this activity is thought to contribute to the developmental neurotoxicity associated with perinatal PCB exposure. Many of these congeners display axial chirality and are present in industrial PCB mixtures as a racemate (a 1:1 ratio of both atropisomers). However, the ratio of the two enantiomers changes in vivo, probably due to enantioselective processes involving cytochrome (CYP) P450 enzymes. Emerging data suggest significant variability in the enantiomeric enrichment of chiral PCBs in the human population. This, when considered in light of our preliminary data demonstrating that PCB atropisomers differentially sensitize the ryanodine receptor (RyR), raises the question of whether enantiomeric enrichment influences the risk for adverse neurodevelopmental outcomes following PCB exposure. We propose three specific aims to test the hypothesis that chiral PCB congeners undergo enantioselective biotransformation catalyzed by P450 enzymes and that these differences in biotransformation influence neurodevelopmental endpoints. In Aim 1, the enantiospecificity of RyR-mediated mechanisms of developmental neurotoxicity will be characterized in vitro. The effects of pure PCB atropisomers on dendritic morphology will be quantified in primary rat hippocampal neuron-glia co-cultures and correlated with cellular PCB levels. The molecular mechanisms responsible for enantiospecific activation of RyR1 and RyR2 channel complexes will be investigated using biochemical, biophysical and cellular analyses. In Aim 2, the species and isoform-dependent enantioselective binding and metabolism of pure PCB atropisomers by P450 enzymes will be investigated using murine and human microsomes and tissue slices, as well as recombinant human P450 enzymes. The P450 isoforms responsible for the enantioselective metabolism of PCBs in microsomes will be identified using P450 inhibitors. Aim 3 will confirm, in vivo, that metabolism by P450 enzymes is responsible for enantiomeric enrichment of PCBs and that PCB 136 atropisomers cause enantioselective RyR-mediated developmental neurotoxicity. First, a pharmacokinetic model will be developed, in mice, to examine the role of metabolism in the enantioselective disposition of PCBs. Subsequent studies will determine whether perinatal exposure to chiral PCBs causes enantiomeric enrichment-dependent effects on hippocampal expression and function of RyR and dendritic arborization. These studies will make a fundamental contribution to understanding the risk associated with human exposure to chiral PCB congeners that are highly toxic to the developing nervous system and will provide an insight into the role of chirality in the disposition and toxicity of many chiral pollutants, such as pesticides and plasticizers. Given the extensive polymorphism in human CYP genes, the proposed studies may also suggest future investigations into gene-environment interactions that modulate susceptibility to PCB developmental neurotoxicity. PUBLIC HEALTH RELEVANCE: Developmental exposures to chiral polychlorinated biphenyls (PCBs) may cause neurodevelopmental toxicity by interfering with dendritic growth and plasticity via mechanisms involving the enantiospecific sensitization of ryanodine receptors. The goal of the proposed research is to investigate how differences in the enantioselective disposition of chiral PCBs in pregnant mice influence neurodevelopmental endpoints in exposed offspring. Because the enantiomer ratio of chiral PCBs is highly variable in human populations, the proposed studies will make a fundamental contribution to understanding the risk associated with human exposure to chiral PCB congeners that are highly toxic to the developing nervous system and will provide an insight into the role of chirality in the disposition and toxicity of a broad range of other organic pollutants, such as many pesticides and plasticizers.

描述（由申请人提供）：具有多个邻氯取代基的多氯联苯 (PCB) 同系物是兰尼碱受体 (RyR) 的有效致敏剂，并且这种活性被认为会导致与围产期 PCB 暴露相关的发育神经毒性。其中许多同源物表现出轴向手性，并作为外消旋体存在于工业 PCB 混合物中（两种阻转异构体的比例为 1:1）。然而，两种对映体的比例在体内发生变化，可能是由于涉及细胞色素 (CYP) P450 酶的对映选择性过程。新数据表明，人群中手性 PCB 的对映体富集存在显着差异。考虑到我们的初步数据表明 PCB 阻转异构体对兰尼碱受体 (RyR) 具有不同的敏感性，这就提出了一个问题：对映体富集是否会影响 PCB 暴露后不良神经发育结果的风险。我们提出了三个具体目标来检验以下假设：手性 PCB 同系物经历 P450 酶催化的对映选择性生物转化，并且生物转化的这些差异影响神经发育终点。在目标 1 中，将在体外表征 RyR 介导的发育神经毒性机制的对映特异性。纯 PCB 阻转异构体对树突形态的影响将在原代大鼠海马神经元-神经胶质细胞共培养物中进行量化，并与细胞 PCB 水平相关。将使用生化、生物物理和细胞分析来研究负责 RyR1 和 RyR2 通道复合物对映特异性激活的分子机制。在目标 2 中，将使用鼠类和人类微粒体和组织切片以及重组人类 P450 酶来研究 P450 酶对纯 PCB 阻转异构体的物种和异构体依赖性对映选择性结合和代谢。将使用 P450 抑制剂来鉴定负责微粒体中 PCB 对映选择性代谢的 P450 亚型。目标 3 将在体内证实 P450 酶的代谢导致 PCB 对映体富集，而 PCB 136 阻转异构体会导致对映选择性 RyR 介导的发育神经毒性。首先，将在小鼠中开发药代动力学模型，以检查代谢在 PCB 对映选择性处置中的作用。后续研究将确定围产期接触手性 PCB 是否会对海马表达以及 RyR 和树突状树枝化功能产生对映体富集依赖性影响。这些研究将为了解人类接触对发育中的神经系统具有剧毒的手性 PCB 同系物相关的风险做出根本性贡献，并将深入了解手性在许多手性污染物的处置和毒性中的作用，例如农药和增塑剂。鉴于人类 CYP 基因的广泛多态性，拟议的研究还可能建议未来对调节 PCB 发育神经毒性易感性的基因-环境相互作用进行研究。 公共健康相关性：发育过程中接触手性多氯联苯 (PCB) 可能会通过涉及兰尼碱受体对映特异性敏化的机制干扰树突生长和可塑性，从而导致神经发育毒性。拟议研究的目的是调查怀孕小鼠手性 PCB 的对映选择性配置差异如何影响暴露后代的神经发育终点。由于手性 PCB 的对映体比例在人群中变化很大，因此拟议的研究将为了解人类接触对发育中的神经系统具有剧毒的手性 PCB 同系物相关的风险做出根本性贡献，并将提供对手性在许多其他有机污染物（例如许多农药和增塑剂）的处置和毒性中的作用。