Effect of hepatic cytochrome P450 oxidoreductase deficiency on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adduct formation in P450 reductase conditional null mice.

2.50
Hdl Handle:
http://hdl.handle.net/10146/189938
Title:
Effect of hepatic cytochrome P450 oxidoreductase deficiency on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adduct formation in P450 reductase conditional null mice.
Authors:
Arlt, Volker M.; Singh, Rajinder; Stiborova, Marie; Gamboa da Costa, Goncalo; Frei, Eva; Evans, James D.; Farmer, Peter B.; Wolf, C. Roland; Henderson, Colin J.; Phillips, David H.
Abstract:
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), formed during the cooking of foods, induces colon cancer in rodents. PhIP is metabolically activated by cytochrome P450s (CYPs). In order to evaluate the role of hepatic CYPs in the bioactivation of PhIP, we used Reductase Conditional Null (RCN) mice, in which cytochrome P450 oxidoreductase (POR), the unique electron donor to CYPs, can be specifically deleted in hepatocytes by pretreatment with 3-methylcholanthrene (3-MC), resulting in the loss of essentially all hepatic CYP function. RCN mice were treated orally with 50 mg/kg body weight PhIP daily for 5 days, with and without 3-MC pretreatment. PhIP-DNA adducts (i.e. N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [dG-C8-PhIP]), measured by liquid chromatography-tandem mass spectrometry, were highest in colon (1362 adducts per 10(8) deoxynucleosides), while adduct levels in liver were ~3.5-fold lower. While no differences in PhIP-DNA adduct levels were found in livers with active POR versus inactivated POR, adduct levels were on average ~2-fold lower in extra-hepatic tissues of mice lacking hepatic POR. Hepatic microsomes from RCN mice with or without 3-MC pretreatment were also incubated with PhIP and DNA in vitro. PhIP-DNA adduct formation was ~8-fold lower with hepatic microsomes from POR-inactivated mice than with those with active POR. Most of the hepatic microsomal activation of PhIP in vitro was attributable to CYP1A. Our results show that PhIP-DNA adduct formation in colon involves hepatic N-oxidation, circulation of activated metabolites via the bloodstream to extra-hepatic tissues and further activation resulting in the formation of dG-C8-PhIP. Besides hepatic CYPs, PhIP may be metabolically activated mainly by a non-CYP pathway in liver.
Citation:
Drug Metab. Dispos. 2011, 39 (12):2169-2173
Journal:
Drug Metabolism and Disposition
Issue Date:
22-Sep-2011
URI:
http://hdl.handle.net/10146/189938
DOI:
10.1124/dmd.111.041343
PubMed ID:
21940903
Additional Links:
http://dmd.aspetjournals.org/content/early/2011/09/22/dmd.111.041343.long
Type:
Article
Language:
en
ISSN:
1521-009X
Sponsors:
This work was supported by Environmental Cancer Risk, Nutrition and Individual Susceptibility (ECNIS) as part of the European Union 6 th Framework, Priority 5: ‘Food Quality and Safety’ [Contract No. 513943]; Cancer Research UK; and the Grant Agency of the Czech Republic [Grant P301/10/0356]
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Full metadata record

DC FieldValue Language
dc.contributor.authorArlt, Volker M.en
dc.contributor.authorSingh, Rajinderen
dc.contributor.authorStiborova, Marieen
dc.contributor.authorGamboa da Costa, Goncaloen
dc.contributor.authorFrei, Evaen
dc.contributor.authorEvans, James D.en
dc.contributor.authorFarmer, Peter B.en
dc.contributor.authorWolf, C. Rolanden
dc.contributor.authorHenderson, Colin J.en
dc.contributor.authorPhillips, David H.en
dc.date.accessioned2011-11-18T12:27:44Z-
dc.date.available2011-11-18T12:27:44Z-
dc.date.issued2011-09-22-
dc.identifier.citationDrug Metab. Dispos. 2011, 39 (12):2169-2173en
dc.identifier.issn1521-009X-
dc.identifier.pmid21940903-
dc.identifier.doi10.1124/dmd.111.041343-
dc.identifier.urihttp://hdl.handle.net/10146/189938-
dc.description.abstract2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), formed during the cooking of foods, induces colon cancer in rodents. PhIP is metabolically activated by cytochrome P450s (CYPs). In order to evaluate the role of hepatic CYPs in the bioactivation of PhIP, we used Reductase Conditional Null (RCN) mice, in which cytochrome P450 oxidoreductase (POR), the unique electron donor to CYPs, can be specifically deleted in hepatocytes by pretreatment with 3-methylcholanthrene (3-MC), resulting in the loss of essentially all hepatic CYP function. RCN mice were treated orally with 50 mg/kg body weight PhIP daily for 5 days, with and without 3-MC pretreatment. PhIP-DNA adducts (i.e. N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [dG-C8-PhIP]), measured by liquid chromatography-tandem mass spectrometry, were highest in colon (1362 adducts per 10(8) deoxynucleosides), while adduct levels in liver were ~3.5-fold lower. While no differences in PhIP-DNA adduct levels were found in livers with active POR versus inactivated POR, adduct levels were on average ~2-fold lower in extra-hepatic tissues of mice lacking hepatic POR. Hepatic microsomes from RCN mice with or without 3-MC pretreatment were also incubated with PhIP and DNA in vitro. PhIP-DNA adduct formation was ~8-fold lower with hepatic microsomes from POR-inactivated mice than with those with active POR. Most of the hepatic microsomal activation of PhIP in vitro was attributable to CYP1A. Our results show that PhIP-DNA adduct formation in colon involves hepatic N-oxidation, circulation of activated metabolites via the bloodstream to extra-hepatic tissues and further activation resulting in the formation of dG-C8-PhIP. Besides hepatic CYPs, PhIP may be metabolically activated mainly by a non-CYP pathway in liver.en
dc.description.sponsorshipThis work was supported by Environmental Cancer Risk, Nutrition and Individual Susceptibility (ECNIS) as part of the European Union 6 th Framework, Priority 5: ‘Food Quality and Safety’ [Contract No. 513943]; Cancer Research UK; and the Grant Agency of the Czech Republic [Grant P301/10/0356]en
dc.languageENG-
dc.language.isoenen
dc.relation.urlhttp://dmd.aspetjournals.org/content/early/2011/09/22/dmd.111.041343.longen
dc.subject2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridineen
dc.subjectHeterocyclic aromatic amineen
dc.subjectCytochrome P450 oxidoreductaseen
dc.subjectDNA adducten
dc.subjectHepatic P450 Reductase Nullen
dc.subjectReductase Conditional Nullen
dc.subject.meshAnimalsen
dc.subject.meshBlotting, Westernen
dc.subject.meshChromatography, Liquiden
dc.subject.meshDNA Adductsen
dc.subject.meshImidazolesen
dc.subject.meshMiceen
dc.subject.meshMice, Inbred C57BLen
dc.subject.meshMice, Knockouten
dc.subject.meshMicrosomes, Liveren
dc.subject.meshNADPH-Ferrihemoprotein Reductaseen
dc.subject.meshSpectrometry, Mass, Electrospray Ionizationen
dc.titleEffect of hepatic cytochrome P450 oxidoreductase deficiency on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adduct formation in P450 reductase conditional null mice.en
dc.typeArticleen
dc.identifier.journalDrug Metabolism and Dispositionen

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