Department of Biomedical and Pharmaceutical Sciences (S.E.L, K.S., E.S., R.D., F.C.-P, E.L.W.), Center for Environmental Health Sciences (S.E.L., F.C.-P.), Center for Biomolecular Structure and Dynamics (E.L.W.), Department of Chemistry (J.N.G., K.D.S.), University of Montana, Missoula, Montana; and Department of Pediatrics, University of Utah, Salt Lake City, Utah (C.M.T.S.).
J Pharmacol Exp Ther. 2014 Feb;348(2):336-45. doi: 10.1124/jpet.113.209791. Epub 2013 Dec 2.
Genetic variation in the multidrug resistance gene ABCB1, which encodes the efflux transporter P-glycoprotein (P-gp), has been associated with Parkinson disease. Our goal was to investigate P-gp transport of paraquat, a Parkinson-associated neurotoxicant. We used in vitro transport models of ATPase activity, xenobiotic-induced cytotoxicity, transepithelial permeability, and rhodamine-123 inhibition. We also measured paraquat pharmacokinetics and brain distribution in Friend leukemia virus B-type (FVB) wild-type and P-gp-deficient (mdr1a(-/-)/mdr1b(-/-)) mice following 10, 25, 50, and 100 mg/kg oral doses. In vitro data showed that: 1) paraquat failed to stimulate ATPase activity; 2) resistance to paraquat-induced cytotoxicity was unchanged in P-gp-expressing cells in the absence or presence of P-gp inhibitors GF120918 [N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide] and verapamil-37.0 [95% confidence interval (CI): 33.2-41.4], 46.2 (42.5-50.2), and 34.1 µM (31.2-37.2)-respectively; 3) transepithelial permeability ratios of paraquat were the same in P-gp-expressing and nonexpressing cells (1.55 ± 0.39 and 1.39 ± 0.43, respectively); and 4) paraquat did not inhibit rhodamine-123 transport. Population pharmacokinetic modeling revealed minor differences between FVB wild-type and mdr1a(-/-)/mdr1b(-/-) mice: clearances of 0.47 [95% confidence interval (CI): 0.42-0.52] and 0.78 l/h (0.58-0.98), respectively, and volume of distributions of 1.77 (95% CI: 1.50-2.04) and 3.36 liters (2.39-4.33), respectively; however, the change in clearance was in the opposite direction of what would be expected. It is noteworthy that paraquat brain-to-plasma partitioning ratios and total brain accumulation were the same across doses between FVB wild-type and mdr1a(-/-)/mdr1b(-/-) mice. These studies indicate that paraquat is not a P-gp substrate. Therefore, the association between ABCB1 pharmacogenomics and Parkinson disease is not attributed to alterations in paraquat transport.
多药耐药基因 ABCB1 中的遗传变异，该基因编码外排转运蛋白 P-糖蛋白（P-gp），与帕金森病有关。我们的目标是研究与帕金森病相关的神经毒性剂百草枯的 P-gp 转运。我们使用了 ATP 酶活性、外源生物诱导的细胞毒性、跨上皮通透性和罗丹明 123 抑制的体外转运模型。我们还测量了 10、25、50 和 100mg/kg 口服剂量后，在 Friend 白血病病毒 B 型（FVB）野生型和 P-gp 缺陷型（mdr1a(-/-)/mdr1b(-/-)）小鼠中的百草枯药代动力学和脑分布。体外数据表明：1）百草枯未能刺激 ATP 酶活性；2）在不存在或存在 P-gp 抑制剂 GF120918[N-(4-[2-(1,2,3,4-四氢-6,7-二甲氧基-2-异喹啉基)乙基]-苯基)-9,10-二氢-5-甲氧基-9-氧代-4-吖啶羧酸酰胺]和维拉帕米-37.0[95%置信区间（CI）：33.2-41.4]、46.2（42.5-50.2）和 34.1µM（31.2-37.2）时，百草枯诱导的细胞毒性的抗性保持不变；3）在表达和不表达 P-gp 的细胞中，百草枯的跨上皮通透性比值相同（分别为 1.55±0.39 和 1.39±0.43）；4）百草枯不抑制罗丹明 123 的转运。群体药代动力学模型显示 FVB 野生型和 mdr1a(-/-)/mdr1b(-/-) 小鼠之间存在微小差异：清除率分别为 0.47[95%置信区间（CI）：0.42-0.52]和 0.78l/h（0.58-0.98），分布容积分别为 1.77[95%置信区间（CI）：1.50-2.04]和 3.36 升（2.39-4.33）；然而，清除率的变化与预期的相反。值得注意的是，百草枯脑-血浆分配比和总脑积累在 FVB 野生型和 mdr1a(-/-)/mdr1b(-/-) 小鼠之间，各剂量下均相同。这些研究表明，百草枯不是 P-gp 的底物。因此，ABCB1 药物基因组学与帕金森病之间的关联并非归因于百草枯转运的改变。
