RT Journal Article
SR Electronic
T1 REGULATION OF CYP2B6 IN PRIMARY HUMAN HEPATOCYTES BY PROTOTYPICAL INDUCERS
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 348
OP 358
DO 10.1124/dmd.32.3.348
VO 32
IS 3
A1 Faucette, Stephanie R.
A1 Wang, Hongbing
A1 Hamilton, Geraldine A.
A1 Jolley, Summer L.
A1 Gilbert, Darryl
A1 Lindley, Celeste
A1 Yan, Bingfang
A1 Negishi, Masahiko
A1 LeCluyse, Edward L.
YR 2004
UL http://dmd.aspetjournals.org/content/32/3/348.abstract
AB The objectives of this study were to evaluate the ability of 14 compounds, which differentially activate human pregnane X receptor (hPXR), to induce CYP2B6 expression and to compare CYP2B6 and CYP3A4 concentration- and time-dependent induction by select inducers. Three primary human hepatocyte preparations were treated daily for 3 days with three concentrations of all compounds. Additional concentration- and/or time-response studies were conducted with clotrimazole, phenytoin, phenobarbital, and rifampin in six preparations. CYP2B6 and CYP3A4 protein and activities were assessed by Western blotting, bupropion hydroxylation, and testosterone 6β-hydroxylation, respectively. To evaluate hPXR activation by the 14 compounds, reporter gene assays were conducted using Huh7 cells cotransfected with hPXR and a CYP2B6 (NR1)5-LUC reporter plasmid. Clotrimazole, phenobarbital, rifampin, and ritonavir strongly induced CYP2B6 and activated hPXR; dexamethasone t-butylacetate and sulfinpyrazone induced CYP2B6 weakly and activated hPXR moderately; paclitaxel strongly activated hPXR but did not increase CYP2B6 expression; carbamazepine and phenytoin moderately or strongly increased CYP2B6 expression but weakly activated hPXR; and dexamethasone, methotrexate, probenecid, sulfadimidine, and troleandomycin demonstrated weak or negligible effects on CYP2B6 and hPXR. EC50 values for CYP2B6 and CYP3A4 induction by clotrimazole, phenobarbital, phenytoin, and rifampin were strongly correlated (r2 = 0.99) and were statistically indistinguishable for clotrimazole, phenytoin, and rifampin. Kinetic constants governing time-dependent induction by phenobarbital and rifampin were also similar between CYP2B6 and CYP3A4. These results indicate that CYP2B6 is highly inducible by known CYP3A4 inducers and suggest that hPXR is a major determinant of CYP2B6-inducible expression for many, but not all, compounds evaluated in this study. The American Society for Pharmacology and Experimental Therapeutics