title: In vivo induction of human cytochrome P450 3A4 by rifabutin in chimeric mice with humanized liver.
abstract: The induction of human cytochrome P450 enzymes (CYPs) often poses a serious problem in clinical practice. The induction of CYP3A leads to a decrease in the pharmacological potency of drugs, since many drugs are substrates of CYP3A. The present study examined the in vivo induction potency of human CYP3A in chimeric mice with humanized liver, recently established in Japan, by a specific inducer of human CYP3A enzyme activity in this experimental condition, rifabutin, which is an analogue of rifampicin. The chimeric mice were treated intraperitoneally daily for 4 days with rifabutin (50 mg kg(-1) day(-1)). The mRNA, protein and enzyme activity in liver of the chimeric mice were measured by reverse-transcriptase polymerase chain reaction, Western blot analysis and high-performance liquid chromatography, respectively. In the chimeric mice, the human CYP3A4 mRNA expression, CYP3A4 protein content, testosterone 6ss-hydroxylase activity and dexamethasone 6-hydroxylase activity were increased 7.4-, 3.0-, 2.4- and 1.9-fold, respectively, by treatment with rifabutin. The mRNA expression of other human CYPs, transporters and nuclear receptors was not significantly changed by rifabutin. On the other hand, rifabutin was demonstrated not to increase the murine Cyp3a enzyme activities in the control mice. It was demonstrated that human CYP3A4 expressed in the chimeric mice with humanized liver was induced by rifabutin, suggesting that human CYP3A4 in the chimeric mice had induction potency. This chimeric mouse model may be a useful animal model to estimate and predict the in vivo induction of CYPs in human.
authors.affiliation: Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Katoh
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Tabata
authors.forename: Y
authors.initials: Y
authors.lastname: Sato
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: M
authors.initials: M
authors.lastname: Nishimura
authors.forename: S
authors.initials: S
authors.lastname: Naito
authors.forename: C
authors.initials: C
authors.lastname: Tateno
authors.forename: K
authors.initials: K
authors.lastname: Iwasaki
authors.forename: K
authors.initials: K
authors.lastname: Yoshizato
authors.forename: T
authors.initials: T
authors.lastname: Yokoi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D022781:Hepatocytes / Q000201:enzymology* / Q000637:transplantation; D006801:Humans; D008099:Liver / Q000201:enzymology*; D051379:Mice; D016513:Mice, SCID; D017828:Rifabutin / Q000008:administration & dosage*; D018183:Transplantation Chimera / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D017828:Rifabutin; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human