CYP1A1 GENE AND ENVIRONMENTAL TOXICITY

CYP1A1 基因和环境毒性

• 批准号: 6283567
• 负责人: Daniel W. Nebert
• 金额: $ 34.14万
• 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/6283567
• 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.

该项目的长期目标是了解细胞色素P450 1A1 （CYP1A1）在环境污染物引起的毒性中的作用。Cyp1a1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ahr介导的，BaP需要代谢激活，二恶英的代谢可以忽略不计。越来越多的证据表明，CYP1A1也介导二恶英的毒性。越来越清楚的是，用最基本的术语来说，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。随着我们最近在Cyp1a1（-/-）敲除小鼠系上的成功，我们现在处于独特的位置，可以描绘组织和细胞类型特异性Cyp1a1 -与代谢（BaP）和非代谢（二oxin） AHR配体引起的AHR依赖性和非依赖性毒性模式。其他人的工作明确表明，大约15%至25%以上的CYP1A1（取决于组织）位于线粒体内膜（mt1A1），其余的位于内质网，即微粒体（mc1A1），并且mt1A1和mc1A1在诱导谱和底物特异性方面存在明显差异。凋亡级联的早期事件（细胞色素c释放，BCL2功能）也发生在线粒体内膜。因此，cyp1a1依赖性毒性可能主要归因于该酶的一个亚细胞位置相对于另一个亚细胞位置。我们的假设是，Bap和二恶英引起的各种组织毒性主要是CYP1A1功能的结果。因此，在下一个资助期，我们将在Cyp1a1（-/-）敲除小鼠中，与Cyp1a1（+/+）野生型小鼠相比，[1]评估BaP与二恶英在[a]骨髓、[b]肝脏和[c]发育中的胚胎中诱导的差异毒性；和[2]产生纯线粒体含CYP1A1 （mt1A1）和纯微粒体含CYP1A1 （mc1A1）敲入小鼠系，进一步解剖肝毒性机制。这些研究将极大地增强我们对环境污染物引起的mtCYP1A1与mcCYP1A1介导的毒性的理解，并可能导致设计药物来屏蔽CYP1A1底物和AHR配体的毒性，特别是对于吸烟者和职业暴露的工人。