Dataset Information

Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo.

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?µM) 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.

SUBMITTER: Ueng YF

PROVIDER: S-EPMC3144538 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Publications

Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo.

Ueng Yune-Fang YF Chen Chien-Chih CC Chung Yu-Ting YT Liu Tsung-Yun TY Chang Yu-Ping YP Lo Wei-Sheng WS Murayama Norie N Yamazaki Hiroshi H Souček Pavel P Chau Gar-Yang GY Chi Chin-Wen CW Chen Ruei-Ming RM Li Ding-Tzai DT

British journal of pharmacology 20110701 6

<h4>Background and purpose</h4>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.<h4>Experimental approach</h4>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 cou ...[more]

PMID: 21418183

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Project description:Gingerols, mainly [6]-gingerol (6G), [8]-gingerol (8G), and [10]-gingerol (10G), are the functional and specific pungent phytochemicals in ginger. However, poor oral bioavailability limits their applications owing to extensive metabolism. The present study aims to characterize the cytochrome P450 (CYP) metabolic characteristics of 6G, 8G, and 10G by using pooled human liver microsomes (HLM), different animal liver microsomes, and the expressed CYP enzymes. It is shown that NADPH-dependent oxidation and hydrogenation metabolisms of gingerols are the main metabolic types in HLM. With the increase of the carbon chain, the polarity of gingerols decreases and the formation of hydrogenated metabolites is more efficient (CLint: 1.41 μL min-1 mg-1 for 6G, 7.79 μL min-1 mg-1 for 8G and 14.11 μL min-1 mg-1 for 10G), indicating that the phase I metabolism of gingerols by HLM varied with the chemical structure of the substrate. The phase I metabolism of gingerols revealed considerable species variations, and compared to HLM, novel metabolites such as (3S,5S)-gingerdiols and demethylated metabolites are generated in some animal liver microsomes. The primary enzymes involved in the oxidized and demethylated metabolism of these gingerols are CYP1A2 and CYP2C19, but their affinities for gingerols are not the same. CYP2D6 and CYP2B6 contributed significantly to the formation of (3R,5S)-[8]-gingerdiol and (3R,5S)-[10]-gingerdiol, respectively; however, the enzyme responsible for the production of (3R,5S)-[6]-gingerediol is yet to be identified. Some metabolites in microsomes cannot be detected by the 12 investigated CYP enzymes, which may be related to the combined effects of multiple enzymes in microsomes, the different affinity of mixed liver microsomes and CYP enzymes, gene polymorphisms, etc. Overall, this work provides a deeper knowledge of the influence of CYP metabolism on the gingerols, as well as the mode of action and the possibility for drug-herbal interactions.

Dataset Information

Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo.

Background and purpose

Experimental approach

Key results

Conclusions and implications

Publications

Mechanism-based inhibition of cytochrome P450 (CYP)2A6 by chalepensin in recombinant systems, in human liver microsomes and in mice in vivo.

Similar Datasets

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