Sulforaphane and quercetin modulate PhIP-DNA adduct formation in human HepG2 cells and hepatocytes

James R. Bacon, Gary Williamson, R. Colin Garner, Graham Lappin, Sophie Langouët, Yongping Bao

Research output: Contribution to journalArticleResearchpeer-review

92 Citations (Scopus)

Abstract

The formation of DNA adducts in human HepG2 cells and human hepatocytes exposed to 14C-labelled 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was examined using Accelerator Mass Spectrometry (AMS). PhIP generated DNA adducts in a linear dose-dependent manner between 100 pM and 20 μM. Co-treatment with the dietary isothiocyanate, sulforaphane (SFN, 1-10 μM), or the flavonoid, quercetin (5-20 μM), significantly reduced the level of PhIP-DNA adducts in a dose-dependent manner. The degree of protection was dependent on PhIP concentration, i.e. after 100 pM PhIP exposure, SFN or quercetin reduced adduct levels to below the limit of detection (0.15 amol PhIP/μg DNA) but at higher PhIP exposure (10 nM and 1 μM), the protection was 60 and 10%, respectively. The involvement of phase I, phase II and DNA repair enzymes in this protection against PhIP-DNA adduct formation was investigated using real-time RT-PCR and enzyme activity assays. In intact HepG2 cells, quercetin inhibited cytochrome P450 (CYP)1A2, the main phase I enzyme responsible for PhIP bioactivation. In contrast, SFN induced phase II detoxification enzymes, UDP-glucuronosyltransferase 1A1 and glutathione S-transferase A1 mRNA expression. SFN and quercetin showed no effect on DNA repair, neither in terms of the level of PhIP-DNA adducts, when cells were treated with phytochemicals after the carcinogen exposure, nor the regulation of mRNA expression of two DNA repair enzymes, apurinic endonuclease and DNA polymerase β. This study indicates that dietary isothiocyanates and flavonoids modulate phase I and phase II enzyme expression, hence increasing the rate of detoxification of the dietary carcinogen PhIP in human HepG2 cells but do not affect the rate of PhIP-DNA adduct repair. The formation of PhIP-DNA adducts in human hepatocytes was also dose-dependent with PhIP-concentration and the levels of protection by SFN or quercetin were up to 60% after 10 nM PhIP treatment, but showed large inter-individual variation with no observed protection in some individuals.

Original languageEnglish
Pages (from-to)1903-1911
Number of pages9
JournalCarcinogenesis
Volume24
Issue number12
DOIs
Publication statusPublished - 1 Dec 2003
Externally publishedYes

Cite this

Bacon, James R. ; Williamson, Gary ; Garner, R. Colin ; Lappin, Graham ; Langouët, Sophie ; Bao, Yongping. / Sulforaphane and quercetin modulate PhIP-DNA adduct formation in human HepG2 cells and hepatocytes. In: Carcinogenesis. 2003 ; Vol. 24, No. 12. pp. 1903-1911.
@article{68c06ae604114b6492ea9b20851eeba1,
title = "Sulforaphane and quercetin modulate PhIP-DNA adduct formation in human HepG2 cells and hepatocytes",
abstract = "The formation of DNA adducts in human HepG2 cells and human hepatocytes exposed to 14C-labelled 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was examined using Accelerator Mass Spectrometry (AMS). PhIP generated DNA adducts in a linear dose-dependent manner between 100 pM and 20 μM. Co-treatment with the dietary isothiocyanate, sulforaphane (SFN, 1-10 μM), or the flavonoid, quercetin (5-20 μM), significantly reduced the level of PhIP-DNA adducts in a dose-dependent manner. The degree of protection was dependent on PhIP concentration, i.e. after 100 pM PhIP exposure, SFN or quercetin reduced adduct levels to below the limit of detection (0.15 amol PhIP/μg DNA) but at higher PhIP exposure (10 nM and 1 μM), the protection was 60 and 10{\%}, respectively. The involvement of phase I, phase II and DNA repair enzymes in this protection against PhIP-DNA adduct formation was investigated using real-time RT-PCR and enzyme activity assays. In intact HepG2 cells, quercetin inhibited cytochrome P450 (CYP)1A2, the main phase I enzyme responsible for PhIP bioactivation. In contrast, SFN induced phase II detoxification enzymes, UDP-glucuronosyltransferase 1A1 and glutathione S-transferase A1 mRNA expression. SFN and quercetin showed no effect on DNA repair, neither in terms of the level of PhIP-DNA adducts, when cells were treated with phytochemicals after the carcinogen exposure, nor the regulation of mRNA expression of two DNA repair enzymes, apurinic endonuclease and DNA polymerase β. This study indicates that dietary isothiocyanates and flavonoids modulate phase I and phase II enzyme expression, hence increasing the rate of detoxification of the dietary carcinogen PhIP in human HepG2 cells but do not affect the rate of PhIP-DNA adduct repair. The formation of PhIP-DNA adducts in human hepatocytes was also dose-dependent with PhIP-concentration and the levels of protection by SFN or quercetin were up to 60{\%} after 10 nM PhIP treatment, but showed large inter-individual variation with no observed protection in some individuals.",
author = "Bacon, {James R.} and Gary Williamson and Garner, {R. Colin} and Graham Lappin and Sophie Langou{\"e}t and Yongping Bao",
year = "2003",
month = "12",
day = "1",
doi = "10.1093/carcin/bgg157",
language = "English",
volume = "24",
pages = "1903--1911",
journal = "Carcinogenesis",
issn = "0143-3334",
publisher = "Oxford University Press",
number = "12",

}

Sulforaphane and quercetin modulate PhIP-DNA adduct formation in human HepG2 cells and hepatocytes. / Bacon, James R.; Williamson, Gary; Garner, R. Colin; Lappin, Graham; Langouët, Sophie; Bao, Yongping.

In: Carcinogenesis, Vol. 24, No. 12, 01.12.2003, p. 1903-1911.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Sulforaphane and quercetin modulate PhIP-DNA adduct formation in human HepG2 cells and hepatocytes

AU - Bacon, James R.

AU - Williamson, Gary

AU - Garner, R. Colin

AU - Lappin, Graham

AU - Langouët, Sophie

AU - Bao, Yongping

PY - 2003/12/1

Y1 - 2003/12/1

N2 - The formation of DNA adducts in human HepG2 cells and human hepatocytes exposed to 14C-labelled 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was examined using Accelerator Mass Spectrometry (AMS). PhIP generated DNA adducts in a linear dose-dependent manner between 100 pM and 20 μM. Co-treatment with the dietary isothiocyanate, sulforaphane (SFN, 1-10 μM), or the flavonoid, quercetin (5-20 μM), significantly reduced the level of PhIP-DNA adducts in a dose-dependent manner. The degree of protection was dependent on PhIP concentration, i.e. after 100 pM PhIP exposure, SFN or quercetin reduced adduct levels to below the limit of detection (0.15 amol PhIP/μg DNA) but at higher PhIP exposure (10 nM and 1 μM), the protection was 60 and 10%, respectively. The involvement of phase I, phase II and DNA repair enzymes in this protection against PhIP-DNA adduct formation was investigated using real-time RT-PCR and enzyme activity assays. In intact HepG2 cells, quercetin inhibited cytochrome P450 (CYP)1A2, the main phase I enzyme responsible for PhIP bioactivation. In contrast, SFN induced phase II detoxification enzymes, UDP-glucuronosyltransferase 1A1 and glutathione S-transferase A1 mRNA expression. SFN and quercetin showed no effect on DNA repair, neither in terms of the level of PhIP-DNA adducts, when cells were treated with phytochemicals after the carcinogen exposure, nor the regulation of mRNA expression of two DNA repair enzymes, apurinic endonuclease and DNA polymerase β. This study indicates that dietary isothiocyanates and flavonoids modulate phase I and phase II enzyme expression, hence increasing the rate of detoxification of the dietary carcinogen PhIP in human HepG2 cells but do not affect the rate of PhIP-DNA adduct repair. The formation of PhIP-DNA adducts in human hepatocytes was also dose-dependent with PhIP-concentration and the levels of protection by SFN or quercetin were up to 60% after 10 nM PhIP treatment, but showed large inter-individual variation with no observed protection in some individuals.

AB - The formation of DNA adducts in human HepG2 cells and human hepatocytes exposed to 14C-labelled 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was examined using Accelerator Mass Spectrometry (AMS). PhIP generated DNA adducts in a linear dose-dependent manner between 100 pM and 20 μM. Co-treatment with the dietary isothiocyanate, sulforaphane (SFN, 1-10 μM), or the flavonoid, quercetin (5-20 μM), significantly reduced the level of PhIP-DNA adducts in a dose-dependent manner. The degree of protection was dependent on PhIP concentration, i.e. after 100 pM PhIP exposure, SFN or quercetin reduced adduct levels to below the limit of detection (0.15 amol PhIP/μg DNA) but at higher PhIP exposure (10 nM and 1 μM), the protection was 60 and 10%, respectively. The involvement of phase I, phase II and DNA repair enzymes in this protection against PhIP-DNA adduct formation was investigated using real-time RT-PCR and enzyme activity assays. In intact HepG2 cells, quercetin inhibited cytochrome P450 (CYP)1A2, the main phase I enzyme responsible for PhIP bioactivation. In contrast, SFN induced phase II detoxification enzymes, UDP-glucuronosyltransferase 1A1 and glutathione S-transferase A1 mRNA expression. SFN and quercetin showed no effect on DNA repair, neither in terms of the level of PhIP-DNA adducts, when cells were treated with phytochemicals after the carcinogen exposure, nor the regulation of mRNA expression of two DNA repair enzymes, apurinic endonuclease and DNA polymerase β. This study indicates that dietary isothiocyanates and flavonoids modulate phase I and phase II enzyme expression, hence increasing the rate of detoxification of the dietary carcinogen PhIP in human HepG2 cells but do not affect the rate of PhIP-DNA adduct repair. The formation of PhIP-DNA adducts in human hepatocytes was also dose-dependent with PhIP-concentration and the levels of protection by SFN or quercetin were up to 60% after 10 nM PhIP treatment, but showed large inter-individual variation with no observed protection in some individuals.

UR - http://www.scopus.com/inward/record.url?scp=0346888660&partnerID=8YFLogxK

U2 - 10.1093/carcin/bgg157

DO - 10.1093/carcin/bgg157

M3 - Article

C2 - 12949046

AN - SCOPUS:0346888660

VL - 24

SP - 1903

EP - 1911

JO - Carcinogenesis

JF - Carcinogenesis

SN - 0143-3334

IS - 12

ER -