title: The hepatobiliary disposition of timosaponin b2 is highly dependent on influx/efflux transporters but not metabolism.
abstract: The purpose of this study was to characterize the hepatobiliary disposition of timosaponin B2 (TB-2), a natural saponin. Although TB-2 has multiple pharmacologic activities, the mechanism of its hepatobiliary disposition has not been explored. Because the metabolism of TB-2 is limited and the accumulation of TB-2 in primary hepatocytes is highly temperature dependent (93% of its accumulation is due to active uptake), the contribution of hepatic transporters was investigated. Organic anion-transporting polypeptide (OATP) 1B1- and OATP1B3-transfected human embryonic kidney 293 cells were employed. TB-2 serves as a substrate for OATP1B1 and OATP1B3, with the former playing a predominant role in the hepatic uptake of TB-2. An inhibition study in sandwich-cultured rat hepatocytes suggested that TB-2 is a substrate for both breast cancer resistance protein (Bcrp) and multidrug resistance-associated protein 2 (Mrp2), consistent with its high biliary excretion index (43.1-44.9%). This hypothesis was further verified in BCRP and MRP2 membrane vesicles. The cooperation of uptake and efflux transporters in TB-2 hepatic disposition could partially explain the double-peak phenomenon observed in rat plasma and liver and biliary clearance, which accounted for 70% of the total TB-2 clearance. Moreover, TB-2 significantly increased the rosuvastatin concentration in rat plasma in a concentration-dependent manner and decreased its biliary excretion, which corresponded to reductions in rosuvastatin accumulation in hepatocytes and the biliary excretion index in sandwich-cultured rat hepatocytes, representing a perfect example of a potential saponin-statin drug-drug interaction. These studies demonstrate that transporters (Oatp, Bcrp/Mrp2), but not metabolism, contribute significantly to rat TB-2 hepatobiliary disposition.
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Jingjing
authors.initials: J
authors.lastname: Sheng
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Tian
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Guanglin
authors.initials: G
authors.lastname: Xu
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Le
authors.initials: L
authors.lastname: Wang
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.).
authors.forename: Lili
authors.initials: L
authors.lastname: Pan
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.) gypan@cdser.simm.ac.cn cghuang@simm.ac.cn.
authors.forename: Chenggang
authors.initials: C
authors.lastname: Huang
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (X.T., Z.W., L.W., C.H., G.P.); Key Laboratory for Molecular and Medical Biotechnology, College of Life Science, Nanjing Normal University, Nanjing, China (J.S., G.X., L.P.); and Institute of Life Sciences, Jiangsu University, Zhenjiang, People's Republic of China (C.C.) gypan@cdser.simm.ac.cn cghuang@simm.ac.cn.
authors.forename: Guoyu
authors.initials: G
authors.lastname: Pan
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D001646:Bile / Q000378:metabolism*; D002460:Cell Line; D004347:Drug Interactions / Q000502:physiology; D005464:Fluorobenzenes / Q000378:metabolism / Q000494:pharmacology; D057809:HEK293 Cells; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D029362:Organic Anion Transporters, Sodium-Independent / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000068718:Rosuvastatin Calcium; D012503:Saponins / Q000378:metabolism*; D013256:Steroids / Q000378:metabolism*; D013449:Sulfonamides / Q000378:metabolism / Q000494:pharmacology; D014162:Transfection / Q000379:methods
chemical_list: D018528:ATP-Binding Cassette Transporters; D005464:Fluorobenzenes; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D029362:Organic Anion Transporters, Sodium-Independent; D011743:Pyrimidines; D000068718:Rosuvastatin Calcium; D012503:Saponins; D013256:Steroids; D013449:Sulfonamides; C000715087:ABCC2 protein, human; C523027:timosaponin B-II