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: 8600678
• 负责人: HANS-JOACHIM LEHMLER
• 金额: $ 40.3万
• 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 2015-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8600678
• 关键词: Address; Beryllium; Binding; Biochemical; Chlorine; Coculture Techniques; Complex; Cytochrome P450; Cytochromes; Data; Development; Dose; 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; 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

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.

描述（由申请人提供）：具有多个邻氯取代基的多氯联苯（PCB）同源物是瑞氨烷受体（RYR）的有效敏化剂，并且该活性被认为有助于与围产期PCB暴露有关的发育神经毒性。这些同类物中的许多人都表现出轴向手性，并以种族酸盐的形式出现在工业PCB混合物中（两个阿托波异构体的比例为1：1）。但是，两个对映异构体的比率改变了体内，这可能是由于涉及细胞色素（CYP）P450酶的对映选择过程所致。新兴数据表明，人口中手性PCB的对映体富集的差异很大。鉴于我们的初步数据考虑，这表明PCB抗叶剂会差异化Ryanodine受体（RYR），这提出了一个问题，即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。我们提出了三个特定的目的，旨在检验手性PCB同源物经历P450酶催化的对映选择性生物转化的假设，并且生物转化的这些差异会影响神经发育终点。在AIM 1中，将在体外表征RYR介导的发育神经毒性机制的对映体特异性。纯PCB阿托比异构体对树突形态的影响将在原发性大鼠海马神经元 - 糖培养中进行量化，并与细胞PCB水平相关。将使用生化，生物物理和细胞分析研究负责RYR1和RYR2通道复合物的映体激活的分子机制。在AIM 2中，将使用鼠类和人类的微粒体和组织切片以及重组人类P450酶对P450酶进行纯PCB阿托比异构体的物种和同工型的对映选择性结合和代谢。使用P450抑制剂鉴定出负责PCB的对映选择性代谢的P450同工型。 AIM 3将在体内证实，P450酶的代谢负责PCB的对映体富集，并且PCB 136阿托波异构体引起对映射RyR介导的发育神经毒性。首先，将在小鼠中开发出一种药代动力学模型，以检查代谢在PCB的对映选择性处置中的作用。随后的研究将确定围产期暴露于手性PCB是否会导致对映体富集依赖性对海马表达和RYR和树突含量的功能的作用。这些研究将为了解与人类对发展神经系统剧毒的手性PCB同类物相关的风险做出基本贡献，并将洞悉手性在许多手动污染物（例如农药和塑料化剂）的处置和毒性中的作用。鉴于人CYP基因的广泛多态性，拟议的研究还可能表明对基因环境相互作用的未来研究调节了PCB发育神经毒性的易感性。