title: Influence of sildenafil and tadalafil on the enzyme- and transporter-inducing effects of bosentan and ambrisentan in LS180 cells.
abstract: The combinations of the endothelin-1 receptor antagonists bosentan or ambrisentan with the phosphodiesterase 5 inhibitors sildenafil or tadalafil are current standard therapies of advanced pulmonary arterial hypertension. However, these drugs have a number of drug interactions. Changes of bosentan pharmacokinetics by sildenafil are attributed to reduced hepatic uptake as a consequence of inhibition of organic anion transporting polypeptides. We therefore tested in vitro the hypothesis that sildenafil and tadalafil reduce the enzyme- and transporter-inducing effects of bosentan or ambrisentan by preventing cellular access. Although intracellular concentrations of bosentan and ambrisentan (measured by high pressure liquid chromatography coupled with tandem mass-spectrometry) after four days of incubation of LS180 cells were lower when sildenafil or tadalafil were present, quantification of mRNA expression in these cells by real-time reverse transcription polymerase chain reaction revealed that bosentan and ambrisentan-mediated induction was stable or even increased in combination with sildenafil or tadalafil. For the drug transporter P-glycoprotein this was confirmed at the protein and functional level with highly significant correlations between P-gp mRNA, protein, and function. Moreover, using a reporter gene assay in LS180 cells, our study demonstrates for the first time that tadalafil is a potent, ambrisentan a weak, and sildenafil no activator of pregnane X receptor. In conclusion, our study demonstrates that although sildenafil and tadalafil indeed reduce intracellular concentrations of bosentan and ambrisentan in LS180 cells, they do not mitigate the inducing effects of these endothelin-1 receptor antagonists.
authors.affiliation: Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany. johanna.weiss@med.uni-heidelberg.de
authors.forename: Johanna
authors.initials: J
authors.lastname: Weiss
authors.forename: Dirk
authors.initials: D
authors.lastname: Theile
authors.forename: Adriana
authors.initials: A
authors.lastname: Spalwisz
authors.forename: Jürgen
authors.initials: J
authors.lastname: Burhenne
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Riedel
authors.forename: Walter Emil
authors.initials: WE
authors.lastname: Haefeli
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000959:Antihypertensive Agents / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport; D000077300:Bosentan; D002243:Carbolines / Q000009:adverse effects / Q000494:pharmacology*; D045744:Cell Line, Tumor; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D004347:Drug Interactions; D065130:Endothelin A Receptor Antagonists; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects* / Q000201:enzymology; D000074435:Peroxisome-Targeting Signal 1 Receptor; D010666:Phenylpropionates / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000009:adverse effects / Q000494:pharmacology*; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011687:Purines / Q000009:adverse effects / Q000494:pharmacology; D011724:Pyridazines / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D000068677:Sildenafil Citrate; D013449:Sulfonamides / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D013450:Sulfones / Q000009:adverse effects / Q000494:pharmacology*; D000068581:Tadalafil
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000959:Antihypertensive Agents; D002243:Carbolines; D065130:Endothelin A Receptor Antagonists; D000074435:Peroxisome-Targeting Signal 1 Receptor; D010666:Phenylpropionates; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D000077297:Pregnane X Receptor; D011687:Purines; D011724:Pyridazines; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D013449:Sulfonamides; D013450:Sulfones; D000068581:Tadalafil; D000068677:Sildenafil Citrate; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; C467894:ambrisentan; D000077300:Bosentan