PURPOSE: Although sister-P-glycoprotein (SPGP, BSEP) is closely related to P-glycoprotein, it is much more selective in distribution and substrate recognition. Moreover, because inhibition or lack of BSEP function has severe consequences including cholestasis, hepatotoxicity, exposure to toxic xenobiotics, and drug interactions, in vitro methods are necessary for quantifying and characterizing specific inhibition of BSEP. Therefore, the objective is to discern a method and quantitatively characterize several example BSEP inhibitors. METHODS: With fluorescent markers having been used successfully to evaluate and quantify inhibition of P-gp-mediated transport, this study evaluates several compounds for specific cell retention caused by BSEP inhibitors. In addition to the several compounds asserted to be BSEP inhibitors, the compounds suggested to be BSEP substrates might also inhibit BSEP competitively. Retained fluorescence of possible BSEP substrates was measured by a flow cell cytometer using transfected cells presenting the BSEP transporter specifically and abundantly. RESULTS: Several compounds were shown to inhibit BSEP active transport of the fluorescent substrates dihydrofluorescein and bodipy. The inhibition potency was quantified (i.e., cyclosporin A IC50 approximately 7 microM), revealing incongruent relative sensitivities among the substrate markers, with H2FDA generally the most sensitive of the series of substrate markers evaluated. CONCLUSIONS: The inconsistent sensitivities of the transport markers (H2FDA and bodipy) were reminiscent of the apparent multiple binding site behaviors observed for P-gp and could indicate opposing and unequal yet interacting binding sites akin to those of P-gp. Nonetheless, notable differences between P-gp and BSEP in marker substrate recognition/transport were apparent despite the observed overlap in xenobiotic recognition and transport. Thus far the most potent inhibitors seem to be cyclosporin, tamoxifen, and valinomycin. There are likely to be much more potent inhibitors, and other substrates also may be more sensitive to inhibition of transport.
PURPOSE: Although sister-P-glycoprotein (SPGP, BSEP) is closely related to P-glycoprotein, it is much more selective in distribution and substrate recognition. Moreover, because inhibition or lack of BSEP function has severe consequences including cholestasis, hepatotoxicity, exposure to toxic xenobiotics, and drug interactions, in vitro methods are necessary for quantifying and characterizing specific inhibition of BSEP. Therefore, the objective is to discern a method and quantitatively characterize several example BSEP inhibitors. METHODS: With fluorescent markers having been used successfully to evaluate and quantify inhibition of P-gp-mediated transport, this study evaluates several compounds for specific cell retention caused by BSEP inhibitors. In addition to the several compounds asserted to be BSEP inhibitors, the compounds suggested to be BSEP substrates might also inhibit BSEP competitively. Retained fluorescence of possible BSEP substrates was measured by a flow cell cytometer using transfected cells presenting the BSEP transporter specifically and abundantly. RESULTS: Several compounds were shown to inhibit BSEP active transport of the fluorescent substrates dihydrofluorescein and bodipy. The inhibition potency was quantified (i.e., cyclosporin A IC50 approximately 7 microM), revealing incongruent relative sensitivities among the substrate markers, with H2FDA generally the most sensitive of the series of substrate markers evaluated. CONCLUSIONS: The inconsistent sensitivities of the transport markers (H2FDA and bodipy) were reminiscent of the apparent multiple binding site behaviors observed for P-gp and could indicate opposing and unequal yet interacting binding sites akin to those of P-gp. Nonetheless, notable differences between P-gp and BSEP in marker substrate recognition/transport were apparent despite the observed overlap in xenobiotic recognition and transport. Thus far the most potent inhibitors seem to be cyclosporin, tamoxifen, and valinomycin. There are likely to be much more potent inhibitors, and other substrates also may be more sensitive to inhibition of transport.
Authors: V E Kostrubsky; M Vore; E Kindt; J Burliegh; K Rogers; G Peter; D Altrogge; M W Sinz Journal: Drug Metab Dispos Date: 2001-12 Impact factor: 3.922
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Authors: Richard J Weaver; Eric A Blomme; Amy E Chadwick; Ian M Copple; Helga H J Gerets; Christopher E Goldring; Andre Guillouzo; Philip G Hewitt; Magnus Ingelman-Sundberg; Klaus Gjervig Jensen; Satu Juhila; Ursula Klingmüller; Gilles Labbe; Michael J Liguori; Cerys A Lovatt; Paul Morgan; Dean J Naisbitt; Raymond H H Pieters; Jan Snoeys; Bob van de Water; Dominic P Williams; B Kevin Park Journal: Nat Rev Drug Discov Date: 2019-11-20 Impact factor: 84.694
Authors: Andrea Testa; Sergio Dall'Angelo; Marco Mingarelli; Andrea Augello; Lutz Schweiger; Andrew Welch; Charles S Elmore; Dana Dawson; Pradeep Sharma; Matteo Zanda Journal: Contrast Media Mol Imaging Date: 2018-07-30 Impact factor: 3.161
Authors: Tristan M Sissung; Arun Rajan; Gideon M Blumenthal; David J Liewehr; Seth M Steinberg; Arlene Berman; Giuseppe Giaccone; William D Figg Journal: PLoS One Date: 2019-02-28 Impact factor: 3.240