School of Pharmacy, China Medical University, Taichung 404, Taiwan.
Department of Pharmacy, China Medical University Hospital, Taichung 404, Taiwan.
J Food Drug Anal. 2018 Apr;26(2S):S133-S140. doi: 10.1016/j.jfda.2017.11.006. Epub 2017 Dec 14.
Indican (indoxyl-β-D-glucoside) is present in several Chinese herbs e.g. Isatis indigotica, Polygonum tinctorium and Polygonum perfoliatum. The major metabolite of indican was indoxyl sulfate (IS), an uremic toxin which was a known substrate/inhibitor of organic anion transporter (OAT) 1, OAT 3 and multidrug resistance-associated protein (MRP) 4. Methotrexate (MTX), an important immunosuppressant with narrow therapeutic window, is a substrate of OAT 1, 2, 3, 4 and MRP 1, 2, 3, 4. We hypothesized that IS, the major metabolite of oral indican, might inhibit the renal excretion of MTX mediated by OAT 1, OAT 3 and MRP 4. Therefore, this study investigated the effect of oral indican on the pharmacokinetics of MTX. Rats were orally given MTX with and without indican (20.0 and 40.0 mg/kg) in a parallel design. The serum MTX concentration was determined by a fluorescence polarization immunoassay. For mechanism clarification, phenolsulfonphthalein (PSP, 5.0 mg/kg), a probe substrate of OAT 1, OAT 3, MRP 2 and MRP 4, was intravenously given to rats with and without a intravenous bolus of IS (10.0 mg/kg) to measure the effect of IS on the elimination of PSP. The results indicated that 20.0 and 40.0 mg/kg of oral indican significantly increased the area under concentration-time curve (AUC) of MTX by 231% and 259%, prolonged the mean residence time (MRT) by 223% and 204%, respectively. Furthermore, intravenous IS significantly increased the AUC of PSP by 204% and decreased the Cl by 68%. In conclusion, oral indican increased the systemic exposure and MRT of MTX through inhibition on multiple anion transporters including OAT 1, OAT 3 and MRP 4 by the major metabolite IS.
靛基质（吲哚基-β-D-葡糖苷酸）存在于多种中草药中，如板蓝根、大青叶和贯叶连翘。靛基质的主要代谢产物是吲哚硫酸酯（IS），一种尿毒症毒素，是有机阴离子转运体（OAT）1、OAT3 和多药耐药相关蛋白（MRP）4 的已知底物/抑制剂。甲氨蝶呤（MTX）是一种具有较窄治疗窗的重要免疫抑制剂，是 OAT1、2、3、4 和 MRP1、2、3、4 的底物。我们假设口服靛基质的主要代谢产物 IS 可能通过 OAT1、OAT3 和 MRP4 抑制 MTX 的肾脏排泄。因此，本研究探讨了口服靛基质对 MTX 药代动力学的影响。采用平行设计，大鼠口服给予 MTX 并同时给予靛基质（20.0 和 40.0mg/kg）。采用荧光偏振免疫分析法测定血清 MTX 浓度。为了阐明机制，采用酚磺酞（PSP，5.0mg/kg）作为 OAT1、OAT3、MRP2 和 MRP4 的探针底物，静脉给予大鼠，并同时静脉给予 IS（10.0mg/kg）以测量 IS 对 PSP 消除的影响。结果表明，20.0 和 40.0mg/kg 的口服靛基质分别使 MTX 的 AUC 增加 231%和 259%，MRT 延长 223%和 204%。此外，静脉内 IS 使 PSP 的 AUC 增加 204%，Cl 降低 68%。结论：口服靛基质通过其主要代谢产物 IS 抑制包括 OAT1、OAT3 和 MRP4 在内的多种阴离子转运体，增加 MTX 的全身暴露量和 MRT。
