Characterization of human cytochrome P450 isoforms involved in the metabolism of 7-<i>epi</i>-paclitaxel

Zhang, Y.-Y.; Liu, Yan; Zhang, J.-W.; Ge, Guang-Bo; Wang, L.-M.; Sun, Jie; Yang, Ling

doi:10.1080/00498250802714907

Cited by 25 publications

(24 citation statements)

References 32 publications

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“…All incubations were performed for 10 min using a concentration of 0.1 mg of protein/ml. The IC 50 , representing the concentration that inhibits 50% of control activity, was determined by nonlinear curve fitting with Origin (OriginLab Corporation, Northampton, MA), as described previously (Zhang et al, 2009). For comparison of the inhibitory effects of phenylbutazone and mefenamic acid among different species, experiments with several concentrations of phenylbutazone (50 and 500 M) and mefenamic acid (10 and 100 M) in pooled liver microsomes from humans, rats, and minipigs were conducted to investigate their inhibitory effects on daphnetin glucuronidation.…”

Section: Methodsmentioning

confidence: 99%

Identification and Characterization of Human UDP-Glucuronosyltransferases Responsible for the In Vitro Glucuronidation of Daphnetin

Liang

Ge²,

Liu³

et al. 2010

Drug Metab Dispos

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ABSTRACT:Daphnetin has been developed as an oral medicine for treatment of coagulation disorders and rheumatoid arthritis in China, but its in vitro metabolism remains unknown. In the present study, the UDP-glucuronosyltransferase (UGT) conjugation pathways of daphnetin were characterized. Two metabolites, 7-Omonoglucuronide daphnetin (M-1) and 8-O-monoglucuronide daphnetin (M-2), were identified by liquid chromatography/mass spectrometry and NMR when daphnetin was incubated, respectively, with liver microsomes from human (HLM), rat (RLM), and minipig (PLM) and human intestinal microsomes (HIM) in the presence of UDP-glucuronic acid. Screening assays with 12 human recombinant UGTs demonstrated that the formations of M-1 and M-2 were almost exclusively catalyzed by UGT1A9 and UGT1A6, whereas M-1 was formed to a minor extent by UGT1A3, 1A4, 1A7, 1A8, and 1A10 at a high substrate concentration. Kinetics studies, chemical inhibition, and correlation analysis were used to demonstrate that human UGT1A9 and UGT1A6 were major isoforms involved in the daphnetin glucuronidations in HLM and HIM. By in vitro-in vivo extrapolation of the kinetic data measured in HLM, the hepatic clearance and the corresponding hepatic extraction ratio were estimated to be 19.3 ml/min/kg b.wt. and 0.93, respectively, suggesting that human clearance of daphnetin via the glucuronidation is extensive. Chemical inhibition of daphnetin glucuronidation in HLM, RLM, and PLM showed large species differences although the metabolites were formed similarly among the species. In conclusion, the UGT conjugation pathways of daphnetin were fully elucidated and its C-8 phenol group was more selectively catalyzed by UGTs than by the C-7 phenol.

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Section: Methodsmentioning

confidence: 99%

Identification and Characterization of Human UDP-Glucuronosyltransferases Responsible for the In Vitro Glucuronidation of Daphnetin

Liang

Ge²,

Liu³

et al. 2010

Drug Metab Dispos

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“…The concentrations of positive inhibitors used were as follows: 10 mM furafylline for CYP1A2, 2.5 mM 8-methoxypsoralen for CYP2A6, 1 mM ketoconazole for CYP3A4, 10 mM sulfaphenazole for CYP2C9, 10 mM quinidine for CYP2D6, 50 mM clomethiazole for CYP2E1, and 5 mM montelukast for CYP2C8. For CYP isoforms that were strongly inhibited, half inhibition concentration (IC50) values were determined using various concentrations of noscapine (50, 20, 10, 5, 2, 1, 0.5, 0.2, 0 mM for CYP3A4 and 100, 50, 20, 10, 5, 2, 1, 0 mM for CYP2C9) as previously reported [12]. The Ki value was obtained by incubating various probe substrates (5-30 mM diclofenac and 30-100 mM testosterone) and 0-50 mM noscapine.…”

Section: Enzyme Inhibition Experimentsmentioning

confidence: 99%

Time‐dependent inhibition (TDI) of CYP3A4 and CYP2C9 by noscapine potentially explains clinical noscapine–warfarin interaction

Fang

Zhang

et al. 2010

Brit J Clinical Pharma

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WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Clinical cases reported to the Swedish adverse drug interactions register (SWEDIS) indicated that drug-drug interaction (DDI) existed when warfarin was co-administered with noscapine.• In vitro testing with recombinant human enzyme showed that noscapine inhibited CYP3A4 and CYP2C9 with an IC50 of around 1 mM.• However, the clinical relevance of these in vitro data remains to be explored. WHAT THIS STUDY ADDS• Noscapine was demonstrated to be both a reversible inhibitor and a time-dependent inhibitor to CYP3A4 and CYP2C9.• DDI magnitude predicted from reversible inhibition and time-dependent inhibition (TDI) kinetic parameters showed that the TDI might be a noteworthy factor resulting in clinical noscapine-warfarin interaction. AIMSTo investigate the inhibition potential and kinetic information of noscapine to seven CYP isoforms and extrapolate in vivo noscapine-warfarin interaction magnitude from in vitro data. METHODSThe activities of seven CYP isoforms (CYP3A4, CYP1A2, CYP2A6, CYP2E1, CYP2D6, CYP2C9, CYP2C8) in human liver microsomes were investigated following co-or preincubation with noscapine. A two-step incubation method was used to examine in vitro time-dependent inhibition (TDI) of noscapine. Reversible and TDI prediction equations were employed to extrapolate in vivo noscapine-warfarin interaction magnitude from in vitro data. RESULTSAmong seven CYP isoforms tested, the activities of CYP3A4 and CYP2C9 were strongly inhibited with an IC50 of 10.8 Ϯ 2.5 mM and 13.3 Ϯ 1.2 mM. Kinetic analysis showed that inhibition of CYP2C9 by noscapine was best fit to a noncompetitive type with Ki value of 8.8 mM, while inhibition of CYP3A4 by noscapine was best fit to a competitive manner with Ki value of 5.2 mM. Noscapine also exhibited TDI to CYP3A4 and CYP2C9. The inactivation parameters (KI and kinact) were calculated to be 9.3 mM and 0.06 min -1 for CYP3A4 and 8.9 mM and 0.014 min -1 for CYP2C9, respectively. The AUC of (S)-warfarin and (R)-warfarin was predicted to increase 1.5% and 1.1% using Cmax or 0.5% and 0.4% using unbound Cmax with reversible inhibition prediction equation, while the AUC of (S)-warfarin and (R)-warfarin was estimated to increase by 110.9% and 48.9% using Cmax or 41.8% and 32.7% using unbound Cmax with TDI prediction equation. CONCLUSIONSTDI of CYP3A4 and CYP2C9 by noscapine potentially explains clinical noscapine-warfarin interaction.

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“…Preliminary investigation on the epimeric interactions between paclitaxel and its degradant, 7-epipaclitaxel (Figure 1, III), has also raised the importance of the C-7 configuration for the substrate stereoselectivity of CYP2C8 (Zhang et al 2009b). In addition, CYP3A4/5 exhibited a two-fold lower activity in the hydroxylation of 7-epi-docetaxel (Figure 1, IV) in comparison with docetaxel (Shou et al 1998).…”

Section: Introductionmentioning

confidence: 97%

C-7 configuration as one of determinants in taxanes metabolism by human cytochrome P450 enzymes

Zhang¹,

Liu²,

Zhang³

et al. 2009

Xenobiotica

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Taxanes exhibit a high tendency to epimerize at C-7 under physiological conditions. This study aimed to investigate the composite effect of C-7 configuration and other substructural elements on the metabolic properties of taxanes. Cephalomannine, 7-epi-cephalomannine, 10-deacetyl-paclitaxel, and 7-epi-10-deacetyl-paclitaxel were chosen as model compounds. In human liver microsomes, 7-epi-cephalomannine was subject to C-13 lateral chain (M-1) and diterpenoid core monohydroxylation (M-2), mediated by cytochrome P450 (CYP) 3A4 and CYP2C8, respectively. However, only one 7-epi-10-deacetyl-paclitaxel metabolite (M), monohydroxylated at taxane ring by CYP2C8, was detected. In comparison with cephalomannine, the catalytic efficiency of CYP2C8 for 7-epi-cephalomannine was about five-fold higher due to the decreased K(m). Although CYP2C8 showed a high capacity for metabolizing 7-epi-10-deacetyl-paclitaxel, 10-deacetyl-paclitaxel was hardly metabolized under the identical incubation conditions. In conclusion, C-7 configuration represents one of the most important structural determinants in taxanes metabolism.

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Characterization of human cytochrome P450 isoforms involved in the metabolism of 7-epi-paclitaxel

Cited by 25 publications

References 32 publications

Identification and Characterization of Human UDP-Glucuronosyltransferases Responsible for the In Vitro Glucuronidation of Daphnetin

Identification and Characterization of Human UDP-Glucuronosyltransferases Responsible for the In Vitro Glucuronidation of Daphnetin

Time‐dependent inhibition (TDI) of CYP3A4 and CYP2C9 by noscapine potentially explains clinical noscapine–warfarin interaction

C-7 configuration as one of determinants in taxanes metabolism by human cytochrome P450 enzymes

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