Transactivation Assays that Identify Indirect and Direct Activators of Human Pregnane X Receptor (PXR, NR1I2) and Constitutive Androstane Receptor (CAR, NR1I3)
| Autor: | Marija Pinne, Judy L. Raucy, Elsa Ponce |
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| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Transcriptional Activation Receptors Steroid Clinical Biochemistry Pharmaceutical Science Receptors Cytoplasmic and Nuclear Ligands digestive system 03 medical and health sciences Transactivation Constitutive androstane receptor Drug Discovery Humans Pharmacology (medical) Receptor Promoter Regions Genetic Transcription factor Constitutive Androstane Receptor Pregnane X receptor Chemistry Ligand binding assay Biochemistry (medical) Pregnane X Receptor Hep G2 Cells Ligand (biochemistry) Staurosporine digestive system diseases Cell biology 030104 developmental biology Nuclear receptor Phenobarbital Biological Assay |
| Zdroj: | Drug metabolism letters. 11(2) |
| ISSN: | 1874-0758 |
| Popis: | Background Nuclear Receptors (NRs), including PXR and CAR, are presumed to be ligand-dependent transcription factors, but ligand binding is not an absolute requirement for activation. Indeed, many compounds activate PXR and CAR by indirect mechanisms. Detecting these indirect activators of specific nuclear receptors in vitro has been difficult. As NR activation of either or both PXR and CAR can lead to drug-drug interactions and adverse drug effects, false negatives obtained with screening tools incapable of detecting indirect activators could present liabilities. Objective The aim of this study was to establish assays that identify indirect activators of human PXR and CAR. Methods Commercially available human PXR and CAR transactivation assays were used for analyses. Results We show that transactivation assays containing full-length nuclear receptors with native promoters can identify indirect activators of human CAR and PXRwhen compared to those of commercially available assays containing only the LBD of PXR and CAR. Of these two assay systems, only human PXR and CAR1 assays with full-length receptors and native promoters are capable of detecting indirect and ligand activators. With this capability, several kinase inhibitors were identified that activate PXR and CAR by indirect mechanisms. Furthermore by using both the LBD and full-length receptors, phenobarbital and midostaurin were found to be direct and indirect activators of PXR while human CAR activation by phenobarbital occurs by indirect mechanisms only. Conclusion Cell based transactivation assays employing the full-length receptors and native promoters identify both direct and indirect activators of either or both human PXR and CAR. |
| Databáze: | OpenAIRE |
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