CYP1A1 GENE AND ENVIRONMENTAL TOXICITY

CYP1A1 基因和环境毒性

• 批准号: 6476273
• 负责人: Daniel W. Nebert
• 金额: $ 34.12万
• 依托单位: UNIVERSITY OF CINCINNATI
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2005-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6476273
• 关键词: aromatic hydrocarbon receptor; benzanthracenes; bone marrow; cytochrome P450; dioxins; embryogenesis; environmental contamination; environmental toxicology; enzyme mechanism; gene environment interaction; gene targeting; genetically modified animals; genome; hazardous substances; hepatotoxin; laboratory mouse; liver; mitochondrial membrane; protein structure function; receptor binding; toxin metabolism

The long-term goal of this project is to understand the role of cytochrome P450 1A1 (CYP1A1) in toxicity caused by environmental pollutants. Cyp1a1 has a broad tissue distribution, is expressed very early in gestation, and is transcriptionally regulated by the Ah receptor (AHR). The environmental contaminants benzo[a]pyrene (BaP) and dioxin are ligands for the AHR. Toxicity caused by these pollutants is known to be AHR-mediated, BaP requiring metabolic activation and dioxin negligibly metabolized. Evidence is accumulating that CYP1A1 also mediates the toxicity of dioxin. It is increasingly clear that, in the most basic of terms, environmental toxicity of chemicals occurs via two routes: [a] covalent binding of reactive intermediates to cellular macromolecules and/or [b] activation of signal transduction pathways that ultimately influence the fate of specific cell types. With our recent success in making the Cyp1a1 (-/-) knockout mouse line, we are now in the unique position to delineate tissue- and cell type-specific CYP1A1- versus AHR-dependent and - independent modes of toxicity elicited by metabolized (BaP) and nonmetabolized (dioxin) AHR ligands. The work of others has unequivocally shown that about 15% to more than 25% (depending on the tissue) of CYP1A1 is located in the inner mitochondrial membrane (mt1A1), the remaining in the endoplasmic reticulum, i.e. microsomes (mc1A1), and that clear differences in the inducibility profile and substrate specificity exist between mt1A1 and mc1A1. Events very early in the apoptosis cascade (cytochrome c release, BCL2 function) also occur in the inner mitochondrial membrane. Thus, CYP1A1-dependent toxicity may be largely ascribed to one subcellular location of the enzyme versus another. Our hypothesis is that Bap and dioxin-induced toxicity of various tissues is primarily he result of CYP1A1 function. For the next funding period we therefore will [1] assess in the Cyp1a1 (-/-) knockout mouse, compared with the Cyp1a1 (+/+) wild-type, differential toxicity induced by BaP versus dioxin in the [a] bone marrow, [b] liver, and [c]developing embryo; and [2] generate exclusively mitochondrial CYP1A1-containing (mt1A1) and exclusively microsomal CYP1A1 - containing (mc1A1) knock-in mouse lines to dissect the mechanism of liver toxicity further. These studies will greatly enhance our understanding of mtCYP1A1 versus mcCYP1A1- mediated toxicity caused by environmental pollutants and perhaps lead to the design of drugs to shield against such toxicity of CYP1A1 substrates and AHR ligands, in the diet and especially for cigarette smokers and occupationally-exposed workers.

本项目的长期目标是了解细胞色素P450 1A 1（CYP 1A 1）在环境污染物引起的毒性中的作用。Cyp 1a 1具有广泛的组织分布，在妊娠早期表达，并受Ah受体（AHR）的转录调节。环境污染物苯并[a]芘（BaP）和二恶英是AHR的配体。已知这些污染物引起的毒性是由AHR介导的，BaP需要代谢活化，而二恶英的代谢可以忽略不计。越来越多的证据表明，CYP 1A 1也介导二恶英的毒性。越来越清楚的是，在最基本的术语中，化学品的环境毒性通过两种途径发生：[a]活性中间体与细胞大分子的共价结合和/或[B]最终影响特定细胞类型命运的信号转导途径的激活。随着我们最近成功地使Cyp 1A 1（-/-）敲除小鼠系，我们现在在独特的位置，以描绘组织和细胞类型特异性CYP 1A 1与AHR依赖性和非依赖性模式引起的代谢（BaP）和非代谢（二恶英）AHR配体的毒性。其他人的工作明确表明，约15%至超过25%（取决于组织）的CYP 1A 1位于线粒体内膜（mt 1A 1）中，其余位于内质网，即微粒体（mc 1A 1），并且mt 1A 1和mc 1A 1之间存在明显的诱导性特征和底物特异性差异。细胞凋亡级联中非常早期的事件（细胞色素c释放，BCL 2功能）也发生在线粒体内膜中。因此，CYP 1A 1依赖性毒性可能主要归因于酶的一个亚细胞位置与另一个亚细胞位置。我们的假设是Bap和二恶英诱导的各种组织毒性主要是CYP 1A 1功能的结果。因此，在下一个资助期内，我们将[1]在Cyp 1a 1（-/-）基因敲除小鼠中，与Cyp 1a 1（+/+）野生型小鼠相比，评估BaP与二恶英在[a]骨髓、[B]肝脏和[c]发育胚胎中诱导的不同毒性;和[2]产生仅含线粒体CYP 1A 1（mt 1A 1）和仅含微粒体CYP 1A 1（mc 1A 1）的基因敲入小鼠品系，以进一步剖析肝毒性的机制。这些研究将极大地提高我们对环境污染物引起的mtCYP 1A 1与mcCYP 1A 1介导的毒性的理解，并可能导致药物的设计，以屏蔽CYP 1A 1底物和AHR配体在饮食中的毒性，特别是对于吸烟者和职业暴露的工人。