Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)

Xiaochao Ma, Jeffrey R. Idle, Michael A. Malfatti, Kristopher W. Krausz, Daniel W. Nebert, Chong Sheng Chen, James S. Felton, David J. Waxman, Frank J. Gonzalez

Research output: Contribution to journalArticle

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Abstract

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis is initiated by N2-hydroxylation, mediated by several cytochromes P450, including CYP1A1. However, the role of CYP1A1 in PhIP metabolic activation in vivo is unclear. In this study, Cyp1a1-null and wild-type (WT) mice were used to investigate the potential role of CYP1A1 in PhIP metabolic activation in vivo. PhIP N2-hydroxylation was actively catalyzed by lung homogenates of WT mice, at a rate of 14.9 ± 5.0 pmol/min/g tissue, but <1 pmol/min/g tissue in stomach and small intestine, and almost undetectable in mammary gland and colon. PhIP N2-hydroxylation catalyzed by lung homogenates of Cyp1a1-null mice was ∼10-fold lower than that of WT mice. In contrast, PhIP N2-hydroxylation activity in lung homogenates of Cyp1a2-null versus WT mice was not decreased. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin increased lung Cyp1a1 mRNA and lung homogenate PhIP N2-hydroxylase activity ∼50-fold in WT mice, where the activity was substantially inhibited (70%) by monoclonal antibodies against CYP1A1. In vivo , 30 min after oral treatment with PhIP, PhIP levels in lung were similar to those in liver. After a single dose of 0.1 mg/kg [14C]PhIP, lung PhIP-DNA adduct levels in Cyp1a1-null mice, but not in Cyp1a2-null mice, were significantly lower (P = 0.0028) than in WT mice. These results reveal that mouse lung has basal and inducible PhIP N2-hydroxylase activity predominantly catalyzed by CYP1A1. Because of the high inducibility of human CYP1A1, especially in cigarette smokers, the role of lung CYP1A1 in PhIP carcinogenesis should be considered. (237 words).

Original languageEnglish (US)
Pages (from-to)732-737
Number of pages6
JournalCarcinogenesis
Volume28
Issue number3
DOIs
StatePublished - Mar 2007
Externally publishedYes

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Cytochrome P-450 CYP1A1
Lung
Hydroxylation
Mixed Function Oxygenases
Metabolic Activation
2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine
Carcinogenesis
Human Mammary Glands
Tobacco Products
Cytochrome P-450 Enzyme System
Small Intestine
Stomach
Colon

ASJC Scopus subject areas

  • Cancer Research

Cite this

Ma, X., Idle, J. R., Malfatti, M. A., Krausz, K. W., Nebert, D. W., Chen, C. S., ... Gonzalez, F. J. (2007). Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Carcinogenesis, 28(3), 732-737. https://doi.org/10.1093/carcin/bgl184

Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). / Ma, Xiaochao; Idle, Jeffrey R.; Malfatti, Michael A.; Krausz, Kristopher W.; Nebert, Daniel W.; Chen, Chong Sheng; Felton, James S.; Waxman, David J.; Gonzalez, Frank J.

In: Carcinogenesis, Vol. 28, No. 3, 03.2007, p. 732-737.

Research output: Contribution to journalArticle

Ma, X, Idle, JR, Malfatti, MA, Krausz, KW, Nebert, DW, Chen, CS, Felton, JS, Waxman, DJ & Gonzalez, FJ 2007, 'Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)', Carcinogenesis, vol. 28, no. 3, pp. 732-737. https://doi.org/10.1093/carcin/bgl184
Ma, Xiaochao ; Idle, Jeffrey R. ; Malfatti, Michael A. ; Krausz, Kristopher W. ; Nebert, Daniel W. ; Chen, Chong Sheng ; Felton, James S. ; Waxman, David J. ; Gonzalez, Frank J. / Mouse lung CYP1A1 catalyzes the metabolic activation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). In: Carcinogenesis. 2007 ; Vol. 28, No. 3. pp. 732-737.
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abstract = "2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis is initiated by N2-hydroxylation, mediated by several cytochromes P450, including CYP1A1. However, the role of CYP1A1 in PhIP metabolic activation in vivo is unclear. In this study, Cyp1a1-null and wild-type (WT) mice were used to investigate the potential role of CYP1A1 in PhIP metabolic activation in vivo. PhIP N2-hydroxylation was actively catalyzed by lung homogenates of WT mice, at a rate of 14.9 ± 5.0 pmol/min/g tissue, but <1 pmol/min/g tissue in stomach and small intestine, and almost undetectable in mammary gland and colon. PhIP N2-hydroxylation catalyzed by lung homogenates of Cyp1a1-null mice was ∼10-fold lower than that of WT mice. In contrast, PhIP N2-hydroxylation activity in lung homogenates of Cyp1a2-null versus WT mice was not decreased. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin increased lung Cyp1a1 mRNA and lung homogenate PhIP N2-hydroxylase activity ∼50-fold in WT mice, where the activity was substantially inhibited (70{\%}) by monoclonal antibodies against CYP1A1. In vivo , 30 min after oral treatment with PhIP, PhIP levels in lung were similar to those in liver. After a single dose of 0.1 mg/kg [14C]PhIP, lung PhIP-DNA adduct levels in Cyp1a1-null mice, but not in Cyp1a2-null mice, were significantly lower (P = 0.0028) than in WT mice. These results reveal that mouse lung has basal and inducible PhIP N2-hydroxylase activity predominantly catalyzed by CYP1A1. Because of the high inducibility of human CYP1A1, especially in cigarette smokers, the role of lung CYP1A1 in PhIP carcinogenesis should be considered. (237 words).",
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AU - Ma, Xiaochao

AU - Idle, Jeffrey R.

AU - Malfatti, Michael A.

AU - Krausz, Kristopher W.

AU - Nebert, Daniel W.

AU - Chen, Chong Sheng

AU - Felton, James S.

AU - Waxman, David J.

AU - Gonzalez, Frank J.

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N2 - 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis is initiated by N2-hydroxylation, mediated by several cytochromes P450, including CYP1A1. However, the role of CYP1A1 in PhIP metabolic activation in vivo is unclear. In this study, Cyp1a1-null and wild-type (WT) mice were used to investigate the potential role of CYP1A1 in PhIP metabolic activation in vivo. PhIP N2-hydroxylation was actively catalyzed by lung homogenates of WT mice, at a rate of 14.9 ± 5.0 pmol/min/g tissue, but <1 pmol/min/g tissue in stomach and small intestine, and almost undetectable in mammary gland and colon. PhIP N2-hydroxylation catalyzed by lung homogenates of Cyp1a1-null mice was ∼10-fold lower than that of WT mice. In contrast, PhIP N2-hydroxylation activity in lung homogenates of Cyp1a2-null versus WT mice was not decreased. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin increased lung Cyp1a1 mRNA and lung homogenate PhIP N2-hydroxylase activity ∼50-fold in WT mice, where the activity was substantially inhibited (70%) by monoclonal antibodies against CYP1A1. In vivo , 30 min after oral treatment with PhIP, PhIP levels in lung were similar to those in liver. After a single dose of 0.1 mg/kg [14C]PhIP, lung PhIP-DNA adduct levels in Cyp1a1-null mice, but not in Cyp1a2-null mice, were significantly lower (P = 0.0028) than in WT mice. These results reveal that mouse lung has basal and inducible PhIP N2-hydroxylase activity predominantly catalyzed by CYP1A1. Because of the high inducibility of human CYP1A1, especially in cigarette smokers, the role of lung CYP1A1 in PhIP carcinogenesis should be considered. (237 words).

AB - 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis is initiated by N2-hydroxylation, mediated by several cytochromes P450, including CYP1A1. However, the role of CYP1A1 in PhIP metabolic activation in vivo is unclear. In this study, Cyp1a1-null and wild-type (WT) mice were used to investigate the potential role of CYP1A1 in PhIP metabolic activation in vivo. PhIP N2-hydroxylation was actively catalyzed by lung homogenates of WT mice, at a rate of 14.9 ± 5.0 pmol/min/g tissue, but <1 pmol/min/g tissue in stomach and small intestine, and almost undetectable in mammary gland and colon. PhIP N2-hydroxylation catalyzed by lung homogenates of Cyp1a1-null mice was ∼10-fold lower than that of WT mice. In contrast, PhIP N2-hydroxylation activity in lung homogenates of Cyp1a2-null versus WT mice was not decreased. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin increased lung Cyp1a1 mRNA and lung homogenate PhIP N2-hydroxylase activity ∼50-fold in WT mice, where the activity was substantially inhibited (70%) by monoclonal antibodies against CYP1A1. In vivo , 30 min after oral treatment with PhIP, PhIP levels in lung were similar to those in liver. After a single dose of 0.1 mg/kg [14C]PhIP, lung PhIP-DNA adduct levels in Cyp1a1-null mice, but not in Cyp1a2-null mice, were significantly lower (P = 0.0028) than in WT mice. These results reveal that mouse lung has basal and inducible PhIP N2-hydroxylase activity predominantly catalyzed by CYP1A1. Because of the high inducibility of human CYP1A1, especially in cigarette smokers, the role of lung CYP1A1 in PhIP carcinogenesis should be considered. (237 words).

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