ROLE OF INTESTINAL UGT IN DRUG DISPOSITION

描述(由申请人提供)：UGTS的葡萄糖醛酸化作用是一个主要阶段 代谢途径，广泛分布于体内，负责 多种药物、其他外源物质和内源性底物的偶联。 葡萄糖醛酸化通常是一种解毒过程，尽管有值得注意的 例外情况。葡萄糖醛酸化作用还能引导 外源生物，例如结合物通常是主动转运的底物 进入尿液和胆汁中排泄。胆汁排泄是 肠肝循环(EHC)的药物是葡萄糖醛酸化的，它具有 降低表观清除量和增加肠道暴露的效果 为毒品干杯。胆汁排泄与促进肠道功能有关 细胞毒性药物，如抗肿瘤药物伊立替康。上一首 结合药物整合解决肠道毒性问题的途径 新陈代谢、胆汁排泄和EHC已经取得了一些成功，尽管是预测性的 减少肠道毒性的关系或方法通常仍然是 难以捉摸。是药物引起的肠道毒性的关键成分，具有 到目前为止还没有被纳入方案，是肠道的能力 上皮细胞形成葡萄糖醛酸苷并将其排泄出来，从而提供 在细胞水平上对毒性的内在抗性。霉酚酸(Mpa， 免疫抑制剂)和SN-38(抗肿瘤)是来源于 前药MMF和伊立替康分别依赖于葡萄糖醛酸化和伊立替康 胆汁排泄物用于排出。这两种药物都是细胞毒性药物，具有很高的 以腹泻表现的肠道毒性的发生率通常限制在 有效的治疗。 肠道UGT正在积极研究中，以确定其潜在作用 外源性毒素的防护及识别和测量方法 UGT的特定人类亚型的表达正从 无数实验室的努力。患者间的巨大变异性和潜力 人类中UGT的多态性也不完全清楚。一些实验室有 根据定性RT-PCR鉴定UGT亚型的组织分布， 然而，这些措施并没有提供有关数量方面的信息 这些酶的表达和功能能力。在此，我们建议 通过以下方法研究MPA和SN38对人和动物的肠道毒性 肠道UGT毒代动力学与蛋白质表达的整合及其作用机制 直接催化底物形成葡萄糖醛酸苷。以下是全球 假说将被解决：肠道UGT在 调节肠上皮细胞对药物的暴露，从而影响 他们的胃肠道毒性。细胞培养和人的一系列体外研究 组织，在Gunn和tr大鼠模型中的活体研究将使用 甲孕酮和SN-38葡萄糖醛酸化反应的特异性检测及特异性Western 免疫印迹法检测大鼠与人UGT同工酶的关系 葡萄糖醛酸化和毒性。对接受这些治疗的患者的翻译性研究 药物也将用于评估人类的肠道葡萄糖醛酸化反应。 并检验了局部组织特异性UGT可能调节 对人类的肠道毒性。

DESCRIPTION (provided by applicant): Glucuronidation by UGTs is a major Phase II metabolic pathway, widely distributed in the body, responsible for conjugation of numerous drugs, other xenobiotics and endogenous substrates. Glucuronidation is generally a detoxification process, though there are notable exceptions. Glucuronidation also directs the excretion and distribution of xenobiotics such that the conjugates are often substrates for active transport into the urine and excretion in bile. Biliary excretion is one step in the enterohepatic recycling (EHC) of drugs that are glucuronidated and it has the effects of reducing the apparent clearance and increasing intestinal exposure to drugs. Biliary excretion has been implicated as enhancing intestinal toxicity by cytotoxic drugs such as the antitumor agent irinotecan. Previous approaches to the problem of intestinal toxicity, with the integration of drug metabolism, biliary excretion and EHC have had some success, though predictive relationships or approaches to reduce intestinal toxicity are often still elusive. A critical component of drug-induced intestinal toxicity that has heretofore not been incorporated into the scheme, is the ability of intestinal epithelial cells to form glucuronides and excrete them, thus providing intrinsic resistance to toxicity at the cellular level. Mycophenolic acid (MPA, immunosuppressant) and SN-38 (antitumor), are active compounds derived from prodrugs MMF and irinotecan, respectively, that rely upon glucuronidation and biliary excretion for elimination. Both are cytotoxic drugs that have a high incidence of intestinal toxicity manifested by diarrhea that often limits effective therapy. Intestinal UGT is under active investigation to characterize its potential role in protection from exogenous toxins and methods to identify and measure expression of specific human isoforms of UGT are developing rapidly from the efforts of numerous labs. Large interpatient variability and potential polymorphisms of UGTs in humans are also not fully understood. Some labs have identified tissue distributions of UGT isoforms based upon qualitative RT-PCR, however, these measures do not provide information on the quantitative expression and functional capacity of these enzymes. Here we propose to investigate the intestinal toxicity of MPA and SN38, in humans and animals, by integrating toxicokinetics with protein expression of intestinal UGTs and their direct catalysis of substrates to form glucuronides. The following global hypothesis will be addressed: Intestinal UGTs have a critical role in modulating exposure of intestinal epithelial cells to drugs, thus influencing their of gi toxicity. A series of in vitro studies with cell culture and human tissues, and in vivo studies in Gunn and TR- rat models will be conducted using specific assays of MPA and SN-38 glucuronidation together with specific Western blots of rat and human UGT isozymes to determine the relationship between glucuronidation and toxicity. Translational studies to patients receiving these drugs will also be conducted to evaluate intestinal glucuronidation in humans and examine the hypothesis that local tissue specific UGTs may modulate intestinal toxicity in humans.