ReferenceID 3679
Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo
Br J Pharmacol
BACKGROUND AND PURPOSE: Chalepensin is a pharmacologically active furanocoumarin compound found in rue, a medicinal herb. Here we have investigated the inhibitory effects of chalepensin on cytochrome P450 (CYP) 2A6 in v
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- Reference Id
- 3679
- Evidence Id
- 20269
- Core Evidence Id
- 20269
- Source Reference Id
- 646
- Herb2 Reference Id
- HBREF001085
- Subject Paper Key
- HBIN020196_21418183
- Pubmed Id
- 21418183
- Doi
- 10.1111/j.1476-5381.2011.01341.x
- Paper Title
- Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo
- Paper Abstract
- BACKGROUND AND PURPOSE: Chalepensin is a pharmacologically active furanocoumarin compound found in rue, a medicinal herb. Here we have investigated the inhibitory effects of chalepensin on cytochrome P450 (CYP) 2A6 in vitro and in vivo. EXPERIMENTAL APPROACH: Mechanism-based inhibition was studied in vitro using human liver microsomes and bacterial membranes expressing genetic variants of human CYP2A6. Effects in vivo were studied in C57BL/6J mice. CYP2A6 activity was assayed as coumarin 7-hydroxylation (CH) using HPLC and fluorescence measurements. Metabolism of chalepensin was assessed with liquid chromatography/mass spectrometry (LC/MS). KEY RESULTS: CYP2A6.1, without pre-incubation with NADPH, was competitively inhibited by chalepensin. After pre-incubation with NADPH, inhibition by chalepensin was increased (IC(50) value decreased by 98%). This time-dependent inactivation (k(inact) 0.044 min(-1) ; K(I) 2.64 M) caused the loss of spectrally detectable P450 content and was diminished by known inhibitors of CYP2A6, pilocarpine or tranylcypromine, and by glutathione conjugation. LC/MS analysis of chalepensin metabolites suggested an unstable epoxide intermediate was formed, identified as the corresponding dihydrodiol, which was then conjugated with glutathione. Compared with the wild-type CYP2A6.1, the isoforms CYP2A6.7 and CYP2A6.10 were less inhibited. In mouse liver microsomes, pre-incubation enhanced inhibition of CH activity. Oral administration of chalepensin to mice reduced hepatic CH activity ex vivo. CONCLUSIONS AND IMPLICATIONS: Chalepensin was a substrate and a mechanism-based inhibitor of human CYP2A6. Formation of an epoxide could be a key step in this inactivation. 'Poor metabolizers' carrying CYP2A6*7 or *10 may be less susceptible to inhibition by chalepensin. Given in vivo, chalepensin decreased CYP2A activity in mice.
- Journal
- Br J Pharmacol
- Publish Year
- 2011
- Experiment Subject
- mouse
- Experiment Type
- Animal Experiment
- Phenotype Related
- Paper Title Cn
- Paper Title En
- Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo
- Bilingual Status
- semi_complete