Drug Interactions

啮齿动物血脑屏障（BBB）P-糖蛋白（P-gp; MDR 1）的遗传或化学敲除 显著增加（10至30倍）P-gp底物药物在脑中的分布。基于 根据这些数据，人们普遍认为P-gp在限制药物在人体内分布方面起着至关重要的作用。 在人血脑屏障中基于P-gp的药物相互作用可能是深刻的。我们的假设 挑战这一既定的范式，并声称这种互动将是适度的，因为 潜在P-gp抑制剂药物的治疗血浆浓度将不足以显著抑制P-gp 在人的血脑屏障上此外，我们假设这种药物相互作用可以定量地 通过体外细胞模型和大鼠体内研究预测。我们实验室对一部小说的研究 和创新的非侵入性正电子发射断层扫描（PET）成像方法来测量P-gp活性 将使我们能够验证这些假设。由于P-gp可以显示变构激活， 和多个结合位点，基于P-gp的药物相互作用的预测可能会因这些而复杂化。 现象。因此，我们的具体目标是： 1.体外研究：我们将确定各种药物抑制P-gp外排的效力（EC 50）。 通过表达MDR 1基因的LLCPK 1细胞或空载体（对照细胞）进行维拉帕米-博迪比。 2.体内啮齿动物研究：对于所研究的药物（目的1），我们将确定治疗剂量的比例。 最大血浆浓度（Cmax）和EC 50（Cmax/EC 50）以及未结合的最大浓度 血浆浓度（Cmaxu）和EC 50（Cmaxu/EC 50）。对于强效药物（n=4） P-gp抑制剂在其治疗浓度（最高比例）时，我们将测定其体内EC 50 在大鼠血脑屏障使用[3 H]-维拉帕米作为P-gp底物。 人体体内研究：将测试从大鼠研究中鉴定的两种最有效的抑制剂（在 通过使用PET测量它们对P-gp活性的影响， [11 C]-维拉帕米在脑中的分布。 4.体外-体内相关性：我们将确定（a）上述体外EC 50和体内EC 50值是否与体外EC 50和体内EC 50值一致。 （B）体外和体内啮齿类动物数据是否可预测 在抑制剂Cmax时在人BBB中观察到的相互作用幅度。 5. P-QD变构和多结合位点：我们将确定P-gp与其药物的相互作用是否 底物显示变构和多个结合位点。如果是这样，这些现象将需要 在预测体内基于P-gp的药物相互作用时要考虑。

Genetic or chemical knock-out of P-glycoprotein (P-gp; MDR1) at the rodent blood-brain barrier (BBB) significantly increases (by 10 to 30-fold) the distribution of P-gp substrate drugs into the brain. Based on these data, it has been widely postulated that P-gp plays a vital role in limiting drug distribution at the human BBB and that P-gp based drug interactions at the human BBB are likely to be profound. Our hypothesis challenges this well-established paradigm and claims that such interactions will be modest because therapeutic plasma concentrations of potential P-gp inhibitor drugs will be insufficient to profoundly inhibit Pgp at the human BBB. Moreover, we hypothesize that such drug interactions can be quantitatively predicted by in vitro cell models and in vivo studies in the rat. The development by our laboratory of a novel and innovative non-invasive, Positron Emission Tomography (PET) imaging method to measure P-gp activity at the human BBB will allow us to test these hypotheses. Since P-gp can demonstrate allosteric activation and multiple binding sites, predictions of P-gp based drug interactions can be complicated by these phenomena. Therefore, our specific aims will be: 1. In vitro studies: We will determine the potency of a variety of drugs (EC50) to inhibit P-gp efflux of verapamil-bodipy by LLCPK1 cells expressing the MDR1 gene or an empty vector (control cells). 2. In vivo rodent studies: For the drugs studied (aim 1), we will determine the ratio of the therapeutic maximum plasma concentration (Cmax) and EC50 (Cmax/ECso) as well as the unbound maximum plasma concentration (Cmaxu) and EC5o(Cmaxu/EC5o). For those drugs (n=4) that are potent inhibitors of P-gp at their therapeutic concentrations (highest ratios), we will determine their in vivo EC50 at the rat BBB using [3H]-verapamil as the P-gp substrate. In vivo human studies: The two most potent inhibitors identified from the rat studies will be tested (at Cmax) for their ability to inhibit P-gp activity at the human BBB by measuring, using PET, their effect on the distribution of [11C]-verapamil into the brain. 4. In vitro-vivo correlation: We will determine (a) if the above in vitro EC50 and in vivo ECso values in the rat are correlated; and (b) whether the in vitro and in vivo rodent data are predictive of the magnitude of interaction observed at the human BBB at the Cmax of the inhibitor. 5. P-QD allosterism and multiple binding sites: We will determine if the interaction of P-gp with its drug substrates demonstrates allosterism and multiple binding sites. If it does, these phenomena will need to be taken into consideration when predicting in vivo P-gp based drug interactions.