Qin Zifei, Zhang Beibei, Yang Jing, Li Shishi, Xu Jinjin, Yao Zhihong, Zhang Xiaojian, Gonzalez Frank J, Yao Xinsheng
Department of Pharmacy, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
Henan Key Laboratory of Precision Clinical Pharmacy, Zhengzhou University, Zhengzhou, China.
Front Pharmacol. 2019 May 7;10:496. doi: 10.3389/fphar.2019.00496. eCollection 2019.
Fraxetin, a natural compound present in many dietary supplements and herbs, is useful in the treatment of acute bacillary dysentery and type 2 diabetes. Previously, several metabolic studies have revealed extensive first-pass metabolism causing formation of fraxetin--glucuronides (G1 and G2), resulting in poor bioavailability of fraxetin. Active transport processes play an important role in the excretion of fraxetin--glucuronides. Nevertheless, the transporters involved are yet to be elucidated. In this study, we aimed to determine the active efflux transporters, including breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), involved in the excretion of fraxetin--glucuronides. A chemical inhibitor, MK571 (5 and 20 μM), a pan-MRP inhibitor, led to a significant decrease in excreted G1 (maximal 59.1%) and G2 levels (maximal 42.4%), whereas Ko143 (5 and 20 μM), a selective BCRP inhibitor, caused moderate downregulation of excreted G1 (maximal 29.4%) and G2 (maximal 28.5%). Furthermore, MRP3 silencing resulted in a marked decrease of excretion rates (by 29.1% for G1 and by 21.1% for G2) and of fraction metabolized ( ; by 24.1% for G1 and by 18.6% for G2). Similar results, i.e., a significant reduction in excretion rates (by 34.8% for G1 and by 32.3% for G2) and in (by 22.7% for G1 and by 23.1% for G2) were obtained when MRP4 was partially silenced. No obvious modifications in the excretion rates, intracellular levels, and values of glucuronides were observed after short hairpin RNA (shRNA)-mediated silencing of transporters BCRP and MRP1. Taken together, our results indicate that MRP3 and MRP4 contribute more to the excretion of fraxetin--glucuronides than the other transporters do.
秦皮素是一种存在于多种膳食补充剂和草药中的天然化合物，可用于治疗急性细菌性痢疾和2型糖尿病。此前，多项代谢研究表明，广泛的首过代谢会导致秦皮素 - 葡萄糖醛酸苷（G1和G2）的形成，从而使秦皮素的生物利用度较低。主动转运过程在秦皮素 - 葡萄糖醛酸苷的排泄中起重要作用。然而，其中涉及的转运蛋白尚未阐明。在本研究中，我们旨在确定参与秦皮素 - 葡萄糖醛酸苷排泄的主动外排转运蛋白，包括乳腺癌耐药蛋白（BCRP）和多药耐药相关蛋白（MRP）。化学抑制剂MK571（5和20 μM），一种泛MRP抑制剂，导致排泄的G1（最大59.1%）和G2水平显著降低（最大42.4%），而选择性BCRP抑制剂Ko143（5和20 μM）导致排泄的G1（最大29.4%）和G2（最大28.5%）适度下调。此外，MRP3沉默导致排泄率显著降低（G1降低29.1%，G2降低21.1%）以及代谢分数降低（G1降低24.1%，G2降低18.6%）。当MRP4部分沉默时，获得了类似的结果，即排泄率显著降低（G1降低34.8%，G2降低32.3%）以及代谢分数降低（G1降低22.7%，G2降低23.1%）。在短发夹RNA（shRNA）介导的转运蛋白BCRP和MRP1沉默后，未观察到葡萄糖醛酸苷的排泄率、细胞内水平和代谢分数值有明显变化。综上所述，我们的结果表明，MRP3和MRP4对秦皮素 - 葡萄糖醛酸苷排泄的贡献比其他转运蛋白更大。
