Cytochrome P450 in Nicotine Metabolism

尼古丁代谢中的细胞色素 P450

• 批准号: 7561024
• 负责人: SHARON E MURPHY
• 金额: $ 19.79万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2012-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7561024
• 关键词: Affect; Apoproteins; Biological Models; Butanones; Carcinogens; Cessation of life; Cotinine; Cytochrome P450; Data; Disease; Enzyme Inhibitor Drugs; Enzyme Inhibitors; Enzymes; Exposure to; Extrahepatic; Figs - dietary; Goals; Grant; Half-Life; Heme; Hepatic; Human; Individual Differences; Ions; Laboratories; Lung; Mass Spectrum Analysis; Mediating; Medical; Metabolic; Metabolic Activation; Metabolism; Minor; Modification; Nicotine; Nicotine Dependence; Nitrosamines; Outcome; Outcome Study; Pathway interactions; Pharmaceutical Preparations; Play; Rattus; Reaction; Reporting; Research Personnel; Role; Smoker; Smoking Behavior; Specificity; Tissues; Tobacco; Tobacco smoking; United States; analog; base; carbene; carcinogenesis; carcinogenicity; catalyst; design; enzyme activity; enzyme structure; in vivo; inhibitor/antagonist; oxidation; programs; research study; smoking cessation; success; suicide inhibitor; tobacco abuse

DESCRIPTION (provided by applicant): Tobacco smoking is responsible for more than 400,000 deaths annually in the United States. Nicotine is the major addictive agent in tobacco, the key ingredient that maintains smoking behavior. Individual differences in nicotine metabolism affect smoking behavior and potentially nicotine addiction. Nicotine is primarily metabolized by 5'-oxidation. P450 2A6 is the major hepatic catalyst of this reaction, and we recently reported that P450 2A13, a lung P450, is also a good catalyst. An unexpected and exciting outcome of these studies was that nicotine was a mechanism-based (suicide) inhibitor of P450 2A6 and P450 2A13. Determining the mechanism of this inhibition is the primary goal of this grant. However, to begin to investigate the impact of nicotine-mediated inactivation on whole tissue metabolism, we will study P450 2A3 inactivation in the perfused rat lung. P450 2A3 (89% identical to P450 2A13) is an excellent catalyst of nicotine metabolism. Our hypothesis is that inactivation of P450 2A6, P450 2A13 and P450 2A3 occurs through a common mechanism and that any differences in inactivation are due to differences in the specificity and catalytic efficiency of these enzymes. Nicotine 5'-oxidation, as well as minor pathways of 2'- and methyl oxidation, generates reactive iminium ions, all possible inactivating molecules. However, preliminary data support a metabolite of the ?5'(1') iminium ion, as the inactivating species. This grant will investigate what pathway of nicotine metabolism is responsible for enzyme inactivation and how P450 2A3 inactivation affects the metabolic capacity of the rat lung. The Specific aims are: 1. To characterize the secondary products of nicotine metabolism and determine their role in inactivation. 2. To determine if modification of the heme and/or apoprotein occurs during nicotine-mediated inactivation of P450 2A enzymes, both Mass Spectrometry and NMR analyses will be carried out. 3. To establish the rat lung as a model system in which to investigate potential in vivo effects of nicotine-mediated P450 2A inactivation. The characterization of nicotine-mediated inactivation of P450 2A6 and 2A13 is critical to an accurate and complete understanding of nicotine metabolism in smokers. In addition, identifying the mechanism by which this occurs will aid in the design of nicotine analogs as enzyme inhibitors and potential medications for treatment of nicotine addiction. Also of key importance, is that the inactivation of P450 2A enzymes will impact the metabolism of the tobacco specific carcinogens, NNK and NNN.

描述（由申请人提供）：在美国，吸烟每年导致超过 400,000 人死亡。尼古丁是烟草中的主要成瘾剂，是维持吸烟行为的关键成分。尼古丁代谢的个体差异会影响吸烟行为和潜在的尼古丁成瘾。尼古丁主要通过 5'-氧化代谢。 P450 2A6 是该反应的主要肝催化剂，我们最近报道了 P450 2A13（肺 P450）也是良好的催化剂。这些研究的一个意外且令人兴奋的结果是，尼古丁是 P450 2A6 和 P450 2A13 的基于机制的（自杀）抑制剂。确定这种抑制的机制是本次资助的主要目标。然而，为了开始研究尼古丁介导的失活对整个组织代谢的影响，我们将研究灌注大鼠肺中 P450 2A3 失活。 P450 2A3（与 P450 2A13 89% 相同）是尼古丁代谢的优异催化剂。我们的假设是，P450 2A6、P450 2A13 和 P450 2A3 的失活通过共同机制发生，失活的任何差异都是由于这些酶的特异性和催化效率的差异造成的。尼古丁 5'-氧化，以及 2'- 和甲基氧化的次要途径，产生活性亚胺离子，所有可能的失活分子。然而，初步数据支持α5'(1')亚胺离子的代谢物作为失活物质。这笔赠款将研究尼古丁代谢的哪种途径导致酶失活以及 P450 2A3 失活如何影响大鼠肺部的代谢能力。具体目标是： 1. 表征尼古丁代谢的次级产物并确定其在灭活中的作用。 2. 为了确定在尼古丁介导的 P450 2A 酶失活过程中是否发生血红素和/或脱辅基蛋白的修饰，将进行质谱和 NMR 分析。 3. 建立大鼠肺作为模型系统，研究尼古丁介导的 P450 2A 失活的潜在体内效应。尼古丁介导的 P450 2A6 和 2A13 失活的特征对于准确、完整地了解吸烟者的尼古丁代谢至关重要。此外，确定这种情况发生的机制将有助于设计尼古丁类似物作为酶抑制剂和治疗尼古丁成瘾的潜在药物。同样重要的是，P450 2A 酶的失活将影响烟草特定致癌物 NNK 和 NNN 的代谢。