Arachidonate Products and CYP1A in Dioxin Toxicity

二恶英毒性中的花生四烯酸产品和 CYP1A

• 批准号: 7880924
• 负责人: ARLEEN B. RIFKIND
• 金额: $ 52.12万
• 依托单位: WEILL MEDICAL COLL OF CORNELL UNIV
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-30 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7880924
• 关键词: Affect; Age; Animal Model; Arachidonic Acids; Aryl Hydrocarbon Receptor; Binding; CYP1A2 gene; Caloric Restriction; Carbohydrates; Cardiac; Cardiotoxicity; Cardiovascular Diseases; Cardiovascular system; Cells; Cessation of life; Chick Embryo; Cultured Cells; Cyclic AMP-Dependent Protein Kinases; Cytochrome P450; Data; Depressed mood; Development; Diabetes Mellitus; Dioxins; Disease; Eating; Energy Metabolism; Energy-Generating Resources; Environment; Enzyme Induction; Enzymes; Epoxy Compounds; Failure; Fatty Acids; Figs - dietary; Food; Functional disorder; Funding; Gallus gallus CYP1A5 protein; Gene Targeting; Genes; Genetic Transcription; Gluconeogenesis; Glucose; Grant; Heart; Hepatic; Hepatocyte; Human; Immune System and Related Disorders; Ion Channel; Ischemia; Lead; Learning; Ligands; Lipids; Literature; Liver; Malignant Neoplasms; Mammalian Cell; Mammals; Mediating; Membrane Lipids; Metabolic; Metabolism; Methods; Mitochondria; Modeling; Molecular; Mus; Muscle function; Myocardium; NADP; Nutrient; Organ; Orthologous Gene; Pathologic; Pathway interactions; Phosphoenolpyruvate Carboxylase; Physiological; Physiology; Primordium; Process; Production; Progress Reports; Public Health; Rattus; Reactive Oxygen Species; Receptor Activation; Regulatory Pathway; Reliance; Reperfusion Therapy; Research; Research Design; Retroviral Vector; Role; Route; Scheme; Signal Pathway; Signal Transduction; Source; Staging; Study models; Techniques; Testing; Tetrachlorodibenzodioxin; Toxic Environmental Substances; Toxic effect; Tumor Promotion; Vertebrates; Wasting Syndrome; activating transcription factor; arachidonate; base; fatty acid oxidation; follow-up; glucose-6-phosphatase; hatching; hepatic gluconeogenesis; human disease; improved; in vivo; lipid metabolism; novel; novel strategies; nutrient metabolism; overexpression; oxidation; receptor; response; tool

DESCRIPTION (provided by applicant): Binding and activation of the Ah receptor (AhR) is required for the environmental toxin 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD, dioxin) to produce its toxic effects. TCDD toxicity includes a lethal wasting syndrome and cardiovascular dysfunction, but it is not known how TCDD activation of the AhR produces those effects. This research seeks to understand how TCDD activation of the AhR leads to suppression of gluconeogenesis, energy failure and death and to identify contributions of cytochrome P450 (CYP) 1A enzymes, the major transcriptional products of AhR activation, to the toxicity. The following hypothesis will be tested: (1) Transcriptional and posttranslational effects of TCDD on signaling pathways converging on PGC1?, i.e. Akt, AMPK, PKA and Sirt1, contribute to suppression of gluconeogensis by TCDD. PGC1? governs transcription of PEPCK and glucose 6-phosphatase, regulators of flux through the gluconeogenic pathway; (2) Suppression of gluconeogenesis forces reliance on lipids for energy but also limits availability of lipids as a fuel source; (3) Effects of TCDD on CYP-dependent metabolism of the membrane lipid arachidonic acid (aa) contribute to energy failure in liver and heart. The research will follow up on discoveries under prior funding periods of the grant that TCDD causes cardiac contractile dysfunction and increases hepatic formation of CYP-dependent aa epoxides, EETs, and decreases formation of 20-HETE, aa products with major physiologic cardiovascular regulatory effects, to examine their involvement in nutrient metabolism. TCDD will be used as a tool to learn how AhR activation and changes in CYP-dependent aa metabolism can lead to physiologic disturbances in glucose and lipid metabolism involved in the wasting syndrome (specific aim (SA) 1) and in ion channel and cardiac muscle function (SA2). Studies in SA2 will also determine whether increased production of EETs in liver affect the heart and are cardioprotective or cardiotoxic. The chick embryo close to hatching will continue to be used as the major model based on its track record in studying TCDD toxicity, its similarity to humans with respect to aa metabolism and its special utility for this research in permitting hepatic metabolic effects to be studied independently of confounding effects of food intake. Findings will be confirmed in mammalian cells. Definitive evidence for or against a role of CYP1A in AhR effects will be sought by silencing or overexpressing CYP1A4 and CYP1A5 in chick embryo hepatocytes and by a novel molecular approach in which sense and antisense CYP1A gene constructs in retroviral vectors will be targeted to liver or heart in chick embryos at early stages of development and the effects examined at a later stages. This research is expected to show that CYP1A enzymes contribute to metabolic and cardiovascular regulatory pathways, to improve understanding about relationships between glucose and lipid metabolism and the role of the AhR in regulating physiologic and pathologic responses to changes in nutrient availability, and to have implications for common related diseases, cardiovascular disease and diabetes. Relevance: Responses to changes in nutrient supply and metabolism contribute to aging and common human diseases including diabetes, cardiovascular disease and cancer. The environmental toxin, TCDD, by the single action of binding to the aryl hydrocarbon receptor (AhR), which is present in all our cells, initiates a lethal wasting syndrome characterized by a failure to synthesize glucose and leading to energy failure and death. By learning how TCDD activation of the AhR produces massive dysregulation of nutrient responses we expect to learn more about how the body normally orchestrates responses to changing levels of nutrients and how normal regulatory processes can spin out of control, with implications for common human diseases as well as normal physiology.

描述（由申请人提供）：环境毒素2，3，7，8-四氯二苯并-对-二恶英（TCDD，二恶英）产生毒性作用需要Ah受体（AhR）的结合和激活。TCDD毒性包括致命的消耗综合征和心血管功能障碍，但目前尚不清楚TCDD如何激活AhR产生这些影响。本研究旨在了解TCDD激活AhR如何导致细胞异生抑制、能量衰竭和死亡，并确定细胞色素P450（P450）1A酶（AhR激活的主要转录产物）对毒性的贡献。本研究将验证以下假设：（1）TCDD对聚集于PGC 1？的信号通路的转录和翻译后影响，即Akt、AMPK、PKA和Sirt 1有助于TCDD抑制糖异生。PGC1？控制PEPCK和葡萄糖-6-磷酸酶的转录，这些酶是通过脂质生成途径的流量调节剂;（2）抑制脂质生成迫使依赖脂质提供能量，但也限制了脂质作为燃料来源的可用性;（3）TCDD对CYP依赖的膜脂质花生四烯酸（aa）代谢的影响导致肝脏和心脏的能量衰竭。该研究将跟进在先前资助期间的发现，即TCDD导致心脏收缩功能障碍，并增加CYP依赖性aa环氧化物，雌二醇的肝脏形成，并减少20-HETE的形成，aa产品具有主要的生理心血管调节作用，以检查它们参与营养代谢。TCDD将被用作一种工具，以了解AhR激活和CYP依赖性aa代谢的变化如何导致消耗综合征（特异性目标（SA）1）和离子通道和心肌功能（SA 2）中涉及的葡萄糖和脂质代谢的生理紊乱。对SA 2的研究还将确定肝脏中雌二醇的产生增加是否会影响心脏，以及是否具有心脏保护作用或心脏毒性。接近孵化的鸡胚将继续被用作主要模型的基础上，其跟踪记录在研究TCDD毒性，其相似性与人类方面的AA代谢和其特殊用途，这项研究允许肝脏代谢的影响进行研究独立的食物摄入的混杂效应。研究结果将在哺乳动物细胞中得到证实。通过在鸡胚肝细胞中沉默或过表达CYP 1A 4和CYP 1A 5，以及通过一种新的分子方法，其中逆转录病毒载体中的正义和反义CYP 1A基因构建体将在发育的早期阶段靶向鸡胚的肝脏或心脏，并在后期阶段检查影响，将寻求支持或反对CYP 1A在AhR效应中的作用的证据。这项研究预计将表明CYP 1A酶有助于代谢和心血管调节途径，提高对葡萄糖和脂质代谢之间关系的理解，以及AhR在调节营养物质可利用性变化的生理和病理反应中的作用，并对常见相关疾病，心血管疾病和糖尿病产生影响。相关性：对营养供应和新陈代谢变化的反应有助于衰老和常见的人类疾病，包括糖尿病，心血管疾病和癌症。环境毒素TCDD通过与存在于我们所有细胞中的芳香烃受体（AhR）结合的单一作用，引发致命的消耗综合征，其特征在于不能合成葡萄糖并导致能量衰竭和死亡。通过了解AhR的TCDD激活如何产生营养反应的大规模失调，我们希望更多地了解身体通常如何协调对营养水平变化的反应，以及正常的调节过程如何失控，这对常见的人类疾病以及正常的生理学都有影响。