FURANOCOUMARINS AND DRUGS EFFECT ON CYP3A4

CYP 3A 4是存在于人类肝脏和小肠中的主要P450 上皮细胞（肠上皮细胞）。 肠上皮细胞CYP 3A 4的作用 对药物消除的影响是巨大的。然而，在这方面， 区分肠酶和肝酶的贡献， 以及转运蛋白P-糖蛋白的作用， 有问题 我们已经开发出实验技术， 使我们能够安全地研究活体肝脏和肠上皮细胞CYP 3A 4。 我们已经证明，存在显著的个体间和个体内 肠上皮细胞CYP 3A 4活性的变化。 我们还表明， 一般来说， 肝脏和肠道中CYP 3A 4的相对活性。 进一步 研究这些变化的机制，我们选择了 深入研究我们的观察，一些果汁（葡萄柚 果汁和塞维利亚橙子汁）引起显著和相对快速的损失 肠上皮细胞CYP 3A 4的机制，似乎并不涉及损失 CYP3A4 mRNA。 我们已经表明，2果汁衍生的呋喃香豆素（FC s），6 '，7'-二羟基佛手柑素（DHB）和相关的二聚体（FC 726），导致 新型人肠（Caco-2）细胞中CYP 3A 4的选择性丢失 单层培养系统，DHB是一种基于机理灭活剂 CYP3A4 然而，DHB和FC 726不能完全解释这种效应 它们的作用可能不是CYP 3A 4选择性的。 我们将 测试假设，多个FC，这是相当普遍的， 水果和蔬菜，导致基于机制的失活， 加速细胞内CYP 3A 4降解。 为此我们将 表征选定FC对CYP 3A 4影响的时间过程 和人肠微粒体中其他主要肠上皮细胞P450， 我们的Caco-2细胞系统和健康志愿者。 我们还将 确定所选FC对合成速率的影响， CYP 3A 4在我们培养的细胞中的降解。 最后，我们将测试 假设一些导致临床上 肝脏中CYP 3A 4的重要诱导不会诱导肝脏中的酶。 肠细胞。 从拟议研究中获得的数据应提供 对CYP 3A 4活性变化基础的实质性了解 人与人之间，人与人之间，以及肝脏与 肠子 此外，口服FC的鉴别 特异性消除肠上皮细胞中的CYP 3A 4活性（但不 肝脏），或选择性诱导肝脏中的CYP 3A 4（但不诱导肝脏中的CYP 3A 4）的药物。 肠上皮细胞）将提供强大的研究工具，以评估 肠上皮细胞和肝脏CYP 3A 4对 异生物质在活人体内的分布。

CYP3A4 is the major P450 present in human liver and small bowel epithelial cells (enterocytes). The contribution of enterocyte CYP3A4 to drug elimination is believed to be substantial. However, distinguishing the contributions of the intestinal vs. the liver enzyme, as well as the role of the transporter P-glycoprotein, has been problematic. We have developed experimental techniques that have enabled us to safely study liver and enterocyte CYP3A4 in living people. We have shown that there exists marked inter- and intraindividual variation in the activity of enterocyte CYP3A4. We have also shown that there is generally not a good intraindividual correlation between the relative activities of CYP3A4 in liver and intestine. To further investigate the mechanisms underlying these variations, we have chosen to intensively pursue our observation that some fruit juices (grapefruit juice and Seville orange juice) cause a marked and relatively rapid loss of enterocyte CYP3A4 by a mechanism that does not appear to involve loss of CYP3A4 mRNA. We have shown that 2 juice-derived furanocoumarins (FC s), 6',7'-dihydroxybergamottin (DHB) and a related dimer (FC726), cause selective loss of CYP3A4 in a novel human intestinal (Caco-2) cell monolayer culture system, and that DHB is a mechanism-based inactivator of CYP3A4. However, DHB and FC726 can not fully account for the effects of whole juice, and their effects may not be CYP3A4 selective. We will test the hypothesis that multiple FC s, which are quite ubiquitous in fruits and vegetables, cause mechanism-based inactivation and accelerated intracellular degradation of CYP3A4. To this end, we will characterize the time course of the effects of selected FC s on CYP3A4 and on other major enterocyte P450s in human intestinal microsomes, in our Caco-2 cell system, and in healthy volunteers. We will also determine the effects of selected FC s on rates of synthesis and degradation of CYP3A4 in our cultured cells. Finally, we will test the hypothesis that some oral medication regimens that result in clinically important induction of CYP3A4 in liver do not induce the enzyme in enterocytes. The data obtained from the proposed studies should provide substantial insight into the basis for variations in CYP3A4 activity between people, within a person over time, and between liver and intestine. In addition, the identification of orally administered FC s that specifically ablate CYP3A4 activity in enterocytes (but not liver), or drugs that selectively induce CYP3A4 in liver (but not in enterocytes) would provide powerful research tools to assess the relative contributions of enterocyte and hepatic CYP3A4 to the disposition of xenobiotics in living people.