INHIBITION OF HUMAN CYTOCHROME P450 1A2 BY FURAFYLLINE

呋喃茶碱对人细胞色素 P450 1A2 的抑制作用

• 批准号: 3469031
• 负责人: KENT L KUNZE
• 金额: $ 9.53万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3469031
• 关键词: aflatoxins; biotransformation; chemical carcinogenesis; cytochrome P450; drug metabolism; environmental contamination; enzyme activity; enzyme inhibitors; gas chromatography; high performance liquid chromatography; human tissue; isozymes; liver neoplasms; mutagen testing; spectrometry

The first long term goal of this proposal is to provide a firm foundation for the use of furafylline in vivo and in vitro as a highly specific probe for studying the role of human cytochrome P450 1A2 in chemical carcinogenesis and toxicity and in drug metabolism. Human cytochrome P450 1A2 is a major constitutive liver enzyme whose levels are induced by exposure to environmental agents such as drugs and constituents of cigarette smoke. Cytochrome P450 1A2 plays an important role in the bioactivation of chemicals and environmental contaminants to mutagenic and carcinogenic compounds. Preliminary data indicates that furafylline is a mechanism based inhibitor (suicide substrate) for 1A2 and an ineffective inhibitor of most other major forms of human hepatic P450. The mechanism and specificity of furafylline will be confirmed and extended in this proposal. Further studies using promutagenic agents activated by human liver preparations to mutagens will be conducted using furafylline and the Ames mutagenicity assay to specifically identify the contribution of 1A2 activation to these processes. The second major goal of this proposal is to make use of furafylline's inhibitory properties to investigate the role of 1A2 in the bioactivation of the potent hepatic carcinogen aflatoxin. Aflatoxin contamination of the human diet is believed to be an important causative agent in human liver cancer, especially in Asia and Africa, and estimates of 250,000 deaths per year have been attributed to it's toxic effects. The mutagenic and carcinogenic properties of aflatoxin appear to be due to activation by hepatic cytochrome P450 isozymes to the 8,9 epoxide metabolite which binds to DNA- Considerable confusion exists over which forms of P450 are involved in the initial premutagenic epoxidation event. Preliminary in vitro data within this application using furafylline as an inhibitor of 1A2 confirms that multiple P450 isoforms are involved in epoxidation. Furthermore, the relative importance of each P450 isoform on aflatoxin epoxidation appears to be dependent on the concentration of aflatoxin. The striking and highly significant observations were made that (1) furafylline almost completely inhibits microsomal epoxidation at low concentrations of aflatoxin and (2) the formation of other major non- mutagenic aflatoxin metabolites is not inhibited by furafylline. Proposed studies designed to confirm these findings may also provide a rationale for the use of furafylline as a safe and potent chemoprotective agent against toxicities caused by metabolic processing of environmental contaminants such as aflatoxin by cytochrome P450 1A2.

该提案的第一个长期目标是提供牢固的基础 用于在体内和体外用作高度特异性探针的使用 用于研究人细胞色素P450 1A2在化学中的作用 癌变和毒性以及药物代谢。人细胞色素P450 1A2是一种主要的组成型肝酶，其水平是由 暴露于毒品和成分等环境因素 香烟烟。细胞色素P450 1A2在 化学物质和环境污染物对诱变和环境污染物的生物活化和 致癌化合物。 初步数据表明furafylline是一个 基于机理的抑制剂（自杀底物）的1A2和无效的 大多数其他主要形式的人肝P450的抑制剂。机制 在此中，将确认并扩展Furafylline的特异性 提议。进一步的研究使用人类激活的正面剂 将使用Furafylline和 AMES诱变测定法以特异性确定1a2的贡献 激活这些过程。 该提案的第二个主要目标是利用furafylline的 抑制性能研究1a2在生物活化中的作用 有效的肝癌黄曲霉毒素。黄曲霉毒素的污染 人饮食被认为是人肝脏中重要的病因 癌症，尤其是在亚洲和非洲，估计每人25万人死亡 一年归因于其有毒作用。诱变和 黄曲霉毒素的致癌特性似乎是由于激活 肝细胞色素P450同工酶至8,9的环氧代谢产物，该代谢产物结合 在哪种形式的p450中存在很大的混乱 参与初始前食氧化事件。初步 该应用程序中使用furafylline作为抑制剂的体外数据 1A2证实了多种P450同工型与环氧化有关。 此外，每个P450同工型在黄曲霉毒素上的相对重要性 环氧化似乎取决于黄曲霉毒素的浓度。这 提出了惊人的观察结果（1） Furafylline几乎完全抑制了低的微粒体环氧化 黄曲霉毒素的浓度和（2）其他主要非主要非 Furafylline不会抑制诱变的黄曲霉毒素代谢产物。建议的 旨在确认这些发现的研究也可能提供理由 用于使用富拉菲林作为安全且有效的化学保护剂 抵抗由环境的代谢加工引起的毒性 细胞色素P450 1A2等污染物，例如黄曲霉毒素。