NITROSAMINE ACTIVATION AND EXTRAHEPATIC P450S

描述：亚硝胺对动物有很强的致癌性， 据信对人类也有致癌作用。在大鼠身上，食道 对亚硝胺诱发肿瘤最敏感的器官。这个 亚硝胺诱导肿瘤的特异性被认为是由于 P-450酶的组织特异性激活(a-羟基化) 食道，如NNN和NBzMA的有效激活所示 (分别为N‘-亚硝基烟碱和N-亚硝基苄基甲胺)。这个 本项目的目标是分离和鉴定猪P450酶(S)。 对亚硝胺有特异性激活的大鼠食道。初步 用人P450、大鼠鼻粘膜和大鼠食道微粒体进行研究， 提示P4502A酶在肌动蛋白的激活过程中起重要作用。 亚硝胺。这个项目中的工作假设是亚硝胺 大鼠食道和鼻腔组织中的激活是由于2A的P450 一家人。从大鼠食道和鼻黏膜组织中提取的cdna文库将 产生，文库将用一个或多个P450 2A基因进行筛选 碎片。得到的cDNA将被测序，并将在 昆虫细胞使用杆状病毒表达系统。表达的P450蛋白 将测试NNN和NBzMA的羟化活性。使用这些P450 和各种相关的亚硝胺，这一假说将得到检验 亚硝胺是强致癌物质，是预防食道癌的良好底物。 已分离的组织特异性P450。根据这一点 假设，结构的改变降低了致癌性， 也会导致P450介导的激活减少。最后，人类 将对食道进行分析，以确定类似的P450酶是否具有特异性 对于亚硝胺来说，存在活化。

DESCRIPTION: Nitrosamines are strongly carcinogenic in animals and are believed to be carcinogenic in humans as well. In rats, the esophagus is the most susceptible organ to tumor induction by nitrosamines. The specificity of tumor induction of nitrosamines is believed to be due to tissue-specific activation (a-hydroxylation) by P-450 enzymes localized in the esophagus, as shown by the efficient activation of both NNN and NBzMA (N'-Nitrosonornicotine and N-Nitrosobenzylmethylamine, respectively). The goal of this project is to isolate and characterize the P450 enzyme(s) in rat esophagus that are specific for nitrosamine activation. Preliminary studies with human P450s, rat nasal mucosa and rat esophageal microsomes, indicate that P450 2A enzymes play an important role in the activation of nitrosamines. The working hypothesis in this project is that nitrosamine activation in rat esophagus and nasal tissue is due to P450s of the 2A family. A cDNA library from rat esophagus and nasal mucosa tissue will be generated, and the library will be screened with one or more P450 2A gene fragments. The resulting cDNAs will be sequenced and will be expressed in insect cells using the baculovirus expression system. The expressed P450s will be tested for NNN and NBzMA hydroxylation activity. Using these P450s and various related nitrosamines, the hypothesis will be tested that nitrosamines which are strong esophageal carcinogens are good substrates for the tissue specific P450s that have been isolated. According to this hypothesis, a change in the structure which decreases the carcinogenicity, will also result in a decreased P450-mediated activation. Finally, human esophagus will be analyzed to determine if a similar P450 enzyme specific for nitrosamine activation is present.