TRANSGENIC MICE, GENE KNOCKOUT MICE, AND CYTOCHROME P450 FUNCTION

转基因小鼠、基因敲除小鼠和细胞色素 P450 功能

• 批准号: 3752741
• 负责人: F J GONZALEZ
• 金额: --
• 依托单位: DIVISION OF CANCER EPIDEMIOLOGY AND GENETICS
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3752741
• 关键词: NAD(P)H oxidoreductase; aflatoxins; alleles; benzene; catalyst; cell transformation; chemical carcinogen; chemical carcinogenesis; complementary DNA; cytochrome P450; drug metabolism; drug receptors; enzyme activity; gene expression; gene mutation; genetic promoter element; genetically modified animals; heterocyclic compounds; hormone metabolism; human genetic material tag; isozymes; laboratory mouse; ligands; nitrogenous heterocyclic compound; nitrosamines; pancreatic islets; peroxisome; tissue /cell culture; tumor promoters

Two major questions in the cytochrome P450 field remain unanswered. First, are P450s required for the process of chemical carcinogenesis in an intact animal? Only studies done in vitro and in cell culture infer the importance of these enzymes. Second, do xenobiotic-metabolizing P450s also have an important, physiologically-relevant role in metabolism of endogenous hormones or other chemicals in animals? Are these enzymes required for development and survival? These questions can be answered by constructing mice that lack a functional P450 by the "gene knockout" strategy. We have focused on two P450s, CYP1A2 and CYP2E1 that are among the most well conserved in animals and that metabolically activate known chemical carcinogens. CYP1A2 is the principal P450 responsible for metabolic activation of arylamine and heterocyclic arylamine carcinogens and the most potent human hepatocarcinogen aflatoxin B1. CYP2E1 activates low molecular weight nitrosamines and a number of low molecular weight cancer suspect chemicals including benzene and vinyl halides. We are also studying receptors for foreign chemicals. These have no known function in animals and no clearly defined endogenous ligands. Therefore, the xenobiotic-receptor genes encoding the peroxisome proliferator-activated receptor, PPAR, and the Ah receptor are being subjected to the gene knockout strategy. Peroxisome proliferators are tumor promoters in rodents and also activate genes encoding P450s and peroxisomal enzymes. Many inducers that require the Ah receptor are known carcinogens and tumor promoters. Thus, the gene knockout studies can yield insight into the endogenous function and role in disease of receptors that bind foreign chemicals. These receptors are also highly conserved in mammals indicating a possible critical function. Their binding of carcinogens and tumor promoters might be required for the process of chemical carcinogenesis. Germ line transmissions of damaged alleles for CYP1A2, PPAR and the Ah receptor have been obtained. The progeny mice containing only one copy of each gene appear to be normal. The heterozygotes are currently being mated to produce homozygous mice lacking the genes.

细胞色素 P450 领域的两个主要问题仍未得到解答。 首先，化学致癌过程是否需要P450？ 完整的动物？ 只有在体外和细胞培养中进行的研究才能推断 这些酶的重要性。 其次，进行异生素代谢 P450 在新陈代谢中也具有重要的生理相关作用 动物内源性激素或其他化学物质？ 这些是酶吗 发展和生存所需要的？ 这些问题都可以得到解答 通过“基因敲除”构建缺乏功能性 P450 的小鼠 战略。 我们重点关注两个 P450：CYP1A2 和 CYP2E1，它们属于 在动物中保存最完好，并且已知能代谢激活 化学致癌物。 CYP1A2 是主要的 P450 负责 芳胺和杂环芳胺致癌物的代谢激活 以及最强效的人类肝癌物质黄曲霉毒素B1。 CYP2E1 活化低分子量亚硝胺和许多低分子 体重致癌的可疑化学物质包括苯和卤乙烯。 我们 还在研究外来化学物质的受体。 这些都无人知晓 在动物中发挥作用，并且没有明确定义的内源性配体。 因此，编码过氧化物酶体的异生物质受体基因 增殖物激活受体、PPAR 和 Ah 受体 进行基因敲除策略。 过氧化物酶体增殖剂是 啮齿类动物的肿瘤促进剂，还激活编码 P450 和 过氧化物酶体酶。 许多需要 Ah 受体的诱导剂是 已知的致癌物和肿瘤促进剂。 因此，基因敲除研究 可以深入了解疾病的内源性功能和作用 结合外来化学物质的受体。 这些受体也高度 在哺乳动物中保守，表明可能具有关键功能。 他们的 致癌物和肿瘤促进剂的结合可能是 化学致癌过程。 受损的种系传播 CYP1A2、PPAR 和 Ah 受体的等位基因已获得。 这 每个基因仅含有一个拷贝的子代小鼠似乎是正常的。 目前正在将杂合子交配以产生纯合子小鼠 缺乏基因。