ALTERED HEPATIC DISPOSITION OF ANIONIC DRUGS-MECHANISMS

描述（由申请方提供）：继发于药物相互作用、化学暴露、疾病状态或遗传易感性的阴离子药物的肝脏处置改变具有重要的治疗意义。全身暴露量以及药理学反应的幅度和持续时间可能受到药物肝移位变化的显著影响。同样，肝脏转运的扰动可影响全身、肠道以及可能最重要的肝毒性。这项正在进行的研究计划的长期目标是发展一个机制的理解，如何改变肝脏转运影响整体肝胆处置的阴离子药物和衍生代谢物。结合相关体外表达系统的多实验方法（Sf 9细胞，非洲爪蟾卵母细胞）;一种新的体外培养（SC）的原代肝细胞模型，其保留了肝转运机制，提供了关于胆汁和基底外侧排泄的定量数据，并且易于通过RNAi敲低转运蛋白;使用TR-大鼠（Mrp 2缺陷模型）分离的灌注肝;并且将采用体内人类研究来阐明模型阴离子底物的改变的肝脏转运的机制和后果。将测试多种Mrp亚型有助于阴离子药物和代谢物从肝脏基底外侧排泄的假设，将鉴定对该过程有显著贡献的蛋白质，并确定模型底物的转运动力学。据称，肝小管转运的“特异性”抑制剂可能与基底外侧转运蛋白相互作用，导致以前未认识到的药物相互作用类别。这些抑制剂调节基底外侧排泄的能力，以及这种调节对肝胆处置的后果，将进行探讨。将评估肝脏反应机制（基底外侧输出细胞、其他小管转运蛋白和肝脏II相酶）补偿受损Mrp 2功能的假设;将定义核激素受体在这些补偿反应中的作用以及这种补偿的动力学后果。最后，将采用一种新的临床方案评估人SC肝细胞预测模型阴离子在人体中肝胆处置的能力，该方案允许定量健康人体中的胆汁排泄。阐明肝脏转运的机制，并确定这些过程中的改变的功能后果，是理解决定外源性物质全身暴露（最终生物反应）的多种因素的重要一步，也是利用这些过程实现理想治疗结果的先决条件。

DESCRIPTION (provided by applicant): Altered hepatic disposition of anionic drugs secondary to drug interactions, chemical exposure, disease states or genetic predisposition has important therapeutic implications. Systemic exposure, and therefore the magnitude and duration of pharmacologic response, may be affected substantially by changes in hepatic translocation of drugs. Likewise, perturbations in hepatic transport can influence systemic, intestinal and, perhaps most importantly, hepatic toxicity. The long-term objective of this ongoing research program is to develop a mechanistic understanding of how alterations in hepatic transport influence overall hepatobiliary disposition of anionic drugs and derived metabolites. A multiexperimental approach incorporating relevant in vitro expression systems (Sf9 cells, Xenopus laevis oocytes); a novel sandwich-cultured (SC) primary hepatocyte model that retains hepatic transport mechanisms, provides quantitative data on biliary and basolateral excretion, and is amenable to transporter knockdown by RNAi; isolated perfused livers using TR- rats, a model of Mrp2 deficiency; and an in vivo human study will be employed to elucidate mechanisms and consequences of altered hepatic transport of model anionic substrates. The hypothesis that multiple Mrp isoforms contribute to basolateral excretion of anionic drugs and metabolites from the liver will be tested, proteins that contribute significantly to this process will be identified, and kinetics of transport will be determined for model substrates. Purportedly "specific" inhibitors of hepatic canalicular transport may interact with basolateral transport proteins, resulting in a previously unrecognized category of drug-drug interactions. The ability of these inhibitors to modulate basolateral excretion, and the consequences of such modulation on hepatobiliary disposition, will be explored. The hypothesis that hepatic response mechanisms (basolateral exporters, other canalicular transporters, and hepatic Phase II enzymes) compensate for impaired Mrp2 function will be evaluated; the role of nuclear hormone receptors in these compensatory responses, and the kinetic consequences of such compensation, will be defined. Finally, the ability of human SC hepatocytes to predict hepatobiliary disposition of a model anion in humans will be assessed with a novel clinical protocol that allows quantitation of biliary excretion in healthy humans. Elucidating mechanisms of hepatic transport, and identifying functional consequences of alterations in these processes, is an important step in understanding the multiplicity of factors that determine systemic exposure (and ultimately biologic response) to xenobiotics, and is prerequisite to exploiting these processes to achieve desirable therapeutic outcomes.