title: Evaluation of the endothelin receptor antagonists ambrisentan, darusentan, bosentan, and sitaxsentan as substrates and inhibitors of hepatobiliary transporters in sandwich-cultured human hepatocytes.
abstract: To evaluate potential mechanisms of clinical hepatotoxicity, 4 endothelin receptor antagonists (ERAs) were examined for substrate activity and inhibition of hepatic uptake and efflux transporters in sandwich-cultured human hepatocytes. The 4 transporters studied were sodium-dependent taurocholate cotransporter (NTCP), organic anion transporter (OATP), bile salt export pump (BSEP), and multidrug resistance-associated protein 2 (MRP2). ERA transporter inhibition was examined using the substrates taurocholate (for NTCP and BSEP), [(3)H]estradiol-17beta-D-glucuronide (for OATP), and [2-D-penicillamine, 5-D-penicillamine]enkephalin (for MRP2). ERA substrate activity was evaluated using probe inhibitors ritonavir (OATP and BSEP), bromosulfalein (OATP), erythromycin (P-glycoprotein), probenecid (MRP2 and OATP), and cyclosporin (NTCP). ERAs were tested at 2, 20, and 100 micromol*L-1 for inhibition and at 2 micromol*L-1 as substrates. OATP, NTCP, or BSEP transport activity was not reduced by ambrisentan or darusentan. Bosentan and sitaxsentan attenuated NTCP transport at higher concentrations. Only sitaxsentan decreased OATP transport (52%), and only bosentan reduced BSEP transport (78%). MRP2 transport activity was unaltered. OATP inhibitors decreased influx of all ERAs. Darusentan influx was least affected (84%-100% of control), whereas bosentan was most affected (32%-58% of control). NTCP did not contribute to influx of ERAs. Only bosentan and darusentan were shown as substrates for both BSEP and P-glycoprotein efflux. All ERAs tested were substrates for at least one hepatic transporter. Bosentan and sitaxsentan, but not ambrisentan and darusentan, inhibited human hepatic transporters, which provides a potential mechanism for the increased hepatotoxicity observed for these agents in the clinical setting.
authors.affiliation: Gilead Sciences Inc., Foster City, CA 94404, USA. craig.hartman@gilead.com
authors.forename: J Craig
authors.initials: JC
authors.lastname: Hartman
authors.forename: Kenneth
authors.initials: K
authors.lastname: Brouwer
authors.forename: Arun
authors.initials: A
authors.lastname: Mandagere
authors.forename: Lawrence
authors.initials: L
authors.lastname: Melvin
authors.forename: Richard
authors.initials: R
authors.lastname: Gorczynski
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D000077300:Bosentan; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D065128:Endothelin Receptor Antagonists; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007555:Isoxazoles / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D027361:Organic Anion Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D029363:Organic Anion Transporters, Sodium-Dependent / Q000037:antagonists & inhibitors / Q000378:metabolism; D010666:Phenylpropionates / Q000378:metabolism* / Q000494:pharmacology; D011724:Pyridazines / Q000378:metabolism* / Q000494:pharmacology; D011743:Pyrimidines / Q000378:metabolism* / Q000494:pharmacology; D013449:Sulfonamides / Q000378:metabolism* / Q000494:pharmacology; D027981:Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D013656:Taurocholic Acid / Q000378:metabolism; D013876:Thiophenes / Q000378:metabolism* / Q000494:pharmacology; D055815:Young Adult
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; D000959:Antihypertensive Agents; D000077300:Bosentan; D065128:Endothelin Receptor Antagonists; D020881:Enkephalin, D-Penicillamine (2,5)-; D004958:Estradiol; D007555:Isoxazoles; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D027361:Organic Anion Transporters; D029363:Organic Anion Transporters, Sodium-Dependent; D010666:Phenylpropionates; D011724:Pyridazines; D011743:Pyrimidines; D013449:Sulfonamides; D027981:Symporters; D013656:Taurocholic Acid; D013876:Thiophenes; C093491:ABCB11 protein, human; C000715087:ABCC2 protein, human; C512988:SLCO1A2 protein, human; C071908:sodium-bile acid cotransporter; C014529:estradiol-3-glucoside; C107831:darusentan; C467894:ambrisentan; C106276:sitaxsentan