Induction of human CYP2C9 by rifampicin, hyperforin, and phenobarbital is mediated by the pregnane X receptor.
Human CYP2C9 is important in the metabolism of numerous clinically used drugs such as the anticoagulant warfarin, the anticonvulsant phenytoin, antidiabetic drugs such as tolbutamide and glipizide, the hypertensive agent losartan, and numerous nonsteroidal anti-inflammatory drugs. Several studies have reported that certain drugs such as rifampicin and phenobarbital induce CYP2C9, but the molecular basis for this induction remains unknown. In the present study, we demonstrate that the human pregnane X receptor (hPXR) mediates induction of CYP2C9 by the prototype drugs rifampicin, hyperforin (found in St. John's Wart), and phenobarbital. Deletion and mutagenesis studies with luciferase reporter constructs showed that a functional PXR-responsive element located -1839/-1824 base pairs upstream from the translation start site was the primary binding site mediating the rifampicin induction of CYP2C9. This site was previously described as a constitutive androstane receptor-responsive element (CAR-RE). Mutational analysis of 3- and 12-kilobase CYP2C9 promoter fragments indicated that this proximal binding site was essential for rifampicin inducibility, although a cooperative effect could be attributed to a second CAR-RE located at -2899/-2883. In summary, we have demonstrated rifampicin induction of CYP2C9 promoter constructs that is consistent with the magnitude of induction of CYP2C9 protein and mRNA reported in vivo and in primary human hepatocytes, and we have identified the cis-element essential for this response. This is the first report to demonstrate that the nuclear receptor PXR mediates induction of CYP2C9 with rifampicin, phenobarbital, and hyperforin.
Chen
Yuping
Y
Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Ferguson
Stephen S
SS
Negishi
Masahiko
M
Goldstein
Joyce A
JA
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics; D001665:Binding Sites; D001643:Bridged Bicyclo Compounds; D065729:Cytochrome P-450 CYP2C9; D004790:Enzyme Induction; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D010634:Phenobarbital / Q000494:pharmacology*; D010696:Phloroglucinol / Q000031:analogs & derivatives; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic / Q000187:drug effects; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D011987:Receptors, Steroid / Q000502:physiology*; D012293:Rifampin / Q000494:pharmacology*; D013729:Terpenes / Q000494:pharmacology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D000900:Anti-Bacterial Agents; D001643:Bridged Bicyclo Compounds; D018691:Excitatory Amino Acid Antagonists; D000077297:Pregnane X Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D013729:Terpenes; D010696:Phloroglucinol; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C001654:hyperforin; D012293:Rifampin; D010634:Phenobarbital