INTESTINAL AND COLONIC CYTOCHROME P450 GENE EXPRESSION

小肠和结肠的上皮细胞 暴露于许多摄入的外源性物质，包括药物， 环境致癌物。 细胞色素P450同工酶， 由一个大的相关基因超家族编码的基因， 在外源性物质的代谢和激活中的作用- 致癌物质。 初步数据显示苯巴比妥- 诱导型P450基因在小肠中的调节不同 和肝脏，有一个复杂的调节模式沿着 小肠的长度和隐窝-绒毛轴内 这一建议是基于这样的假设，即基因的表达 在肝脏、小肠和结肠中表达的P450形式中， 确定单个组织对毒素的反应，或 对致癌物的敏感性。 该提案将解决几个 关于P450基因表达的问题，包括1）如何 这些基因的表达和诱导模式 在肝脏、肠和结肠中的不同？2)是不同的成员 这些高度同源的基因家族在这三个 纸巾？3)是什么样的分子机制 这些基因的表达是由化合物诱导的吗？和 4)哪些生理因素调控着这种表达 沿着小肠和结肠的P450基因的分布 大鼠P450主要同工酶可被多种药物诱导， 将在结肠粘膜和直肠粘膜中研究外源性物质 用cDNA和寡核苷酸检测特异性P450 mRNA， 探针和P450脱辅基蛋白。 分布 研究P450 mRNA在小肠隐窝绒毛轴中的表达 使用原位杂交。 P450表达于 小肠和结肠将使用 互补DNA克隆 P450的诱导机制 将通过测量化学诱导剂的表达来评估。 基因的转录速率和mRNA的半衰期 肠细胞 最后，生理因素如胆汁和 胃肠道激素，这可能是负责维持 P450基因在小肠和结肠中的表达将是 评估。 这些研究在几个领域具有潜在的重要性。 第一、 P450基因在小细胞肺癌中的差异表达及诱导 肠和结肠可能会对反应产生影响， 这些组织的化学致癌物，这可能有助于 在这些组织的敏感性显着差异， 癌症的发展。 第二，表达方式的差异 肝脏和肠道中的这些基因可以提供进一步的了解， 组织特异性基因调控的分子机制 表情 P450基因的表达 沿着肠上皮细胞的成熟沿着 隐窝-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.