CYP3A4 induction by drugs: correlation between a pregnane X receptor reporter gene assay and CYP3A4 expression in human hepatocytes.
Induction of cytochrome P450 3A4 (CYP3A4) is determined typically by employing primary culture of human hepatocytes and measuring CYP3A4 mRNA, protein and microsomal activity. Recently a pregnane X receptor (PXR) reporter gene assay was established to screen CYP3A4 inducers. To evaluate results from the PXR reporter gene assay with those from the aforementioned conventional assays, 14 drugs were evaluated for their ability to induce CYP3A4 and activate PXR. Sandwiched primary cultures of human hepatocytes from six donors were used and CYP3A4 activity was assessed by measuring microsomal testosterone 6beta-hydroxylase activity. Hepatic CYP3A4 mRNA and protein levels were also analyzed using branched DNA technology/Northern blotting and Western blotting, respectively. In general, PXR activation correlated with the induction potential observed in human hepatocyte cultures. Clotrimazole, phenobarbital, rifampin, and sulfinpyrazone highly activated PXR and increased CYP3A4 activity; carbamazepine, dexamethasone, dexamethasone-t-butylacetate, phenytoin, sulfadimidine, and taxol weakly activated PXR and induced CYP3A4 activity, and methotrexate and probenecid showed no marked activation in either system. Ritonavir and troleandomycin showed marked PXR activation but no increase (in the case of troleandomycin) or a significant decrease (in the case of ritonavir) in microsomal CYP3A4 activity. It is concluded that the PXR reporter gene assay is a reliable and complementary method to assess the CYP3A4 induction potential of drugs and other xenobiotics.
Luo
Gang
G
Drug Metabolism and Pharmacokinetics, Bristol-Myers Squibb Pharma Company, Newark, Delaware, USA. gang.luo@bms.com
Cunningham
Mark
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Kim
Sean
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Burn
Tim
T
Lin
Jianrong
J
Sinz
Michael
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Hamilton
Geraldine
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Rizzo
Christopher
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Jolley
Summer
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Gilbert
Darryl
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Downey
April
A
Mudra
Daniel
D
Graham
Richard
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Carroll
Kathy
K
Xie
Jindong
J
Madan
Ajay
A
Parkinson
Andrew
A
Christ
Dave
D
Selling
Bernard
B
LeCluyse
Edward
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Gan
Liang-Shang
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D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D002648:Child; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004790:Enzyme Induction / Q000187:drug effects / Q000502:physiology; D005260:Female; D017930:Genes, Reporter / Q000187:drug effects / Q000502:physiology*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D004364:Pharmaceutical Preparations / Q000378:metabolism; D000077297:Pregnane X Receptor; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*
D004364:Pharmaceutical Preparations; D000077297:Pregnane X Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human