INTESTINAL AND COLONIC CYTOCHROME P450 GENE EXPRESSION

排列在小肠和结肠内的上皮细胞是 接触到许多摄入的外来物质，包括药物和 环境致癌物质。细胞色素P450同工酶，它们是 由一个相关基因的大超家族编码，发挥着重要的作用 在外源生物的新陈代谢和激活- 致癌物质。初步数据表明，苯巴比妥- 可诱导的P450基因在小肠中的不同调控 和肝脏之间存在着一种复杂的调节模式 小肠和隐窝绒毛轴内的长度 这一建议是基于这样一个假设，即基因的表达 在杠杆、小肠和结肠表达的P450形式中， 确定单个组织对毒素或 对致癌物的易感性。这项提案将解决几个问题 关于P450基因表达的问题，包括1)如何表达 这些基因的表达模式和可诱导性 肝、肠、结肠不同？2)是不同的成员 在这些高度同源的基因家族中表达在这三个 组织？，3)分子机制是什么？ 这些基因的表达是由化合物诱导的吗？和 4)调节表达的生理因素是什么？ P450基因在小肠和结肠长度上的分布情况？ 大鼠体内主要的P450同工酶可被不同种类的药物诱导 将在肠道和结肠粘膜中研究外源物质 用c DNA和寡核苷酸检测特异性P450 m RNA 用免疫印迹法检测探针和P450载脂蛋白。分布情况 将对肠道隐绒毛轴内的P450 mRNA进行研究 采用原位杂交技术。P450，其表达形式为 小肠和结肠将被确定为使用 互补DNA克隆。P450的诱导机制 化学诱导剂的表达将通过测量 基因的转录速率和mRNA的半衰期 肠道细胞。最后，胆汁和胆汁等生理因素 胃肠激素，这可能是维持 P450基因在小肠和结肠中的表达将是 已评估。 这些研究在几个领域具有潜在的重要性。第一, 小鼠P450基因的差异表达及诱导性 肠道和结肠可能会对反应产生影响 这些组织中的化学致癌物，这可能有助于 这些组织的敏感性有显著差异 癌症的发展。表达的第二个差异 肝脏和肠道中的这些基因可能提供进一步的洞察 调控组织特异性基因的分子机制 表情。最后，P450基因的表达和表达 沿着肠道的长度，随着肠道细胞的成熟 地穴-绒毛轴。

The epithelial cells lining the small intestine and colon are exposed to many ingested xenobiotics including drugs and environmental carcinogens. Cytochrome P450 isoenzymes, which are encoded by a large superfamily of related genes play an important role in the metabolism of xenobiotics and in the activation of- carcinogens. Preliminary data has indicated that phenobarbital- inducible P450 genes are regulated differently in small intestine and liver and that there is a complex pattern of regulation along the length of the small intestine and within the crypt-villus axis This proposal is based on the hypothesis that expression of genes in the P450 forms expressed in lever, small intestine and colon may determine the response of the individual tissues to toxins or susceptibility to carcinogens. This proposal will address several questions concerning the expression of P450 genes including 1) How are the patterns of expression and inducibility of these genes different in liver, intestine and colon?, 2) Are different members of these highly homologous gene families express in these three tissues?, 3) What are the molecular mechanisms by which the expression of these genes are induced by chemical compounds? and 4) What are the physiologic factors which regulate the expression of P450 genes along the length of small intestine and colon? The major P450 isoenzymes in rat which are inducible by various xenobiotics will be studied in intestinalesinal and colonic mucosa by measuring specific P450 mRNA with cDNA and oligonucleotide probes and P450 apoproteins using immunoblots. The distribution of P450 mRNA within the intestinal cryptvillus axis will be studied using in situ hybridization. P450 from which are expressed in small intestine and colon will be definitively identified using complementary DNA cloning. The mechanism for the induction of P450 expression by chemical inducers will be evaluated by measuring the rate of transcription of the genes and the half-life of mRNA in enterocytes. Finally, physiologic factors such as bile and gastrointestinal hormones, which may be responsible for maintaining expression of P450 genes in the small intestine and colon will be evaluated. These studies have potential importance in several areas. First, differential expression and inducibility of P450 genes in small intestine and colon may have ramifications regarding the response of these tissues to chemical carcinogens this may contribute to the marked difference in the susceptibility of these tissues to the development of cancer. Second differences in the expression of these genes in liver and intestine may provide further insight into the molecular mechanisms which regulate tissue-specific gene expression. And finally, the expression of P450 genes expression along the length of the intestine and as enterocytes mature along the crypt-villus axis.