title: Effects of atorvastatin metabolites on induction of drug-metabolizing enzymes and membrane transporters through human pregnane X receptor.
abstract: OBJECTIVE
  Atorvastatin metabolites differ in their potential for drug interaction because of differential inhibition of drug-metabolizing enzymes and transporters. We here investigate whether they exert differential effects on the induction of these genes via activation of pregnane X receptor (PXR) and constitutive androstane receptor (CAR).
  
  
  METHODS
  Ligand binding to PXR or CAR was analysed by mammalian two-hybrid assembly and promoter/reporter gene assays. Additionally, surface plasmon resonance was used to analyse ligand binding to CAR. Primary human hepatocytes were treated with atorvastatin metabolites, and mRNA and protein expression of PXR-regulated genes was measured. Two-hybrid co-activator interaction and co-repressor release assays were utilized to elucidate the molecular mechanism of PXR activation.
  
  
  RESULTS
  All atorvastatin metabolites induced the assembly of PXR and activated CYP3A4 promoter activity. Ligand binding to CAR could not be proven. In primary human hepatocytes, the para-hydroxy metabolite markedly reduced or abolished induction of cytochrome P450 and transporter genes. While significant differences in co-activator recruitment were not observed, para-hydroxy atorvastatin demonstrated only 50% release of co-repressors.
  
  
  CONCLUSIONS
  Atorvastatin metabolites are ligands of PXR but not of CAR. Atorvastatin metabolites demonstrate differential induction of PXR target genes, which results from impaired release of co-repressors. Consequently, the properties of drug metabolites have to be taken into account when analysing PXR-dependent induction of drug metabolism and transport. The drug interaction potential of the active metabolite, para-hydroxy atorvastatin, might be lower than that of the parent compound.
authors.affiliation: Dr Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tübingen, Tübingen, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Hoffart
authors.forename: L
authors.initials: L
authors.lastname: Ghebreghiorghis
authors.forename: A K
authors.initials: AK
authors.lastname: Nussler
authors.forename: W E
authors.initials: WE
authors.lastname: Thasler
authors.forename: T S
authors.initials: TS
authors.lastname: Weiss
authors.forename: M
authors.initials: M
authors.lastname: Schwab
authors.forename: O
authors.initials: O
authors.lastname: Burk
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000069059:Atorvastatin; D045744:Cell Line, Tumor; D056970:Co-Repressor Proteins / Q000378:metabolism; D000090702:Constitutive Androstane Receptor; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D004347:Drug Interactions; D017930:Genes, Reporter / Q000187:drug effects; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006538:Heptanoic Acids / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D008024:Ligands; D026901:Membrane Transport Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic; D011758:Pyrroles / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011987:Receptors, Steroid / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism
chemical_list: D056970:Co-Repressor Proteins; D000090702:Constitutive Androstane Receptor; D006538:Heptanoic Acids; D008024:Ligands; D026901:Membrane Transport Proteins; D000077297:Pregnane X Receptor; D011758:Pyrroles; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D003577:Cytochrome P-450 Enzyme System; D000069059:Atorvastatin; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating