title: Human pregnane X receptor is activated by dibenzazepine carbamate-based inhibitors of constitutive androstane receptor.
abstract: Unintentional activation of xenosensing nuclear receptors pregnane X receptor (PXR) and/or constitutive androstane receptor (CAR) by clinical drug use is known to produce severe side effects in patients, which may be overcome by co-administering antagonists. However, especially antagonizing CAR is hampered by the lack of specific inhibitors, which do not activate PXR. Recently, compounds based on a dibenzazepine carbamate scaffold were identified as potent CAR inhibitors. However, their potential to activate PXR was not thoroughly investigated, even if the lead compound was named "CAR inhibitor not PXR activator 1" (CINPA1). Thus, we performed a comprehensive analysis of the interaction of CINPA1 and four analogs with PXR. Cellular assays were used to investigate intra- and intermolecular interactions and transactivation activity of PXR as a function of the compounds. Modulation of PXR target gene expression was analyzed in primary human hepatocytes. Ligand binding to PXR was investigated by molecular docking and limited proteolytic digestion. We show here that CINPA1 induced the assembly of the PXR ligand-binding domain, released co-repressors from and recruited co-activators to the receptor. CINPA1 and its analogs induced the PXR-dependent activation of a CYP3A4 reporter gene and CINPA1 induced the expression of endogenous cytochrome P450 genes in primary hepatocytes, while not consistently inhibiting CAR-mediated induction. Molecular docking revealed favorable binding of CINPA1 and analogs to the PXR ligand-binding pocket, which was confirmed in vitro. Altogether, our data provide consistent evidence that compounds with a dibenzazepine carbamate scaffold, such as CINPA1 and its four analogs, bind to and activate PXR.
authors.affiliation: Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology Stuttgart and University of Tübingen, Tübingen, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Jeske
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Hamburg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Windshügel
authors.affiliation: Department of General, Visceral, and Transplantation Surgery, Hospital of the Ludwig-Maximilians University, Munich, Germany.
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Thasler
authors.affiliation: Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology Stuttgart and University of Tübingen, Tübingen, Germany.|Department of Clinical Pharmacology, Institute of Experimental and Clinical Pharmacology and Toxicology, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwab
authors.affiliation: Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology Stuttgart and University of Tübingen, Tübingen, Germany. oliver.burk@ikp-stuttgart.de.
authors.forename: Oliver
authors.identifier: http://orcid.org/0000-0001-8990-9656
authors.initials: O
authors.lastname: Burk
mesh_terms: D001552:Benzazepines / Q000737:chemistry / Q000494:pharmacology*; D000090702:Constitutive Androstane Receptor; D015870:Gene Expression / Q000187:drug effects; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D062105:Molecular Docking Simulation; D000077297:Pregnane X Receptor; D061251:Primary Cell Culture; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors*; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*
chemical_list: D001552:Benzazepines; D000090702:Constitutive Androstane Receptor; D008024:Ligands; D000077297:Pregnane X Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; C000611514:ethyl (5-(diethylglycyl)-10,11-dihydro-5H-dibenzo(b,f)azepin-3-yl)carbamate
keywords: CINPA1; Constitutive androstane receptor; Dibenzazepine carbamate; Molecular docking; Pregnane X receptor; Primary human hepatocytes