CYP2A13: Variable expression and role in human lung microsomal metabolic activation of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone

Xiuling Zhang, Jaime D'Agostino, Hong Wu, Qing Yu Zhang, Linda B von Weymarn, Sharon E Murphy, Xinxin Ding

Research output: Contribution to journalArticle

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Abstract

CYP2A13 is the most efficient cytochrome P450 enzyme in the metabolic activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific lung carcinogen. The aims of this study were to determine the levels of CYP2A13 protein in human lung microsomes and to ascertain whether CYP2A13 plays any role in lung microsomal NNK metabolic activation. The expression of CYP2A6 and CYP2A13 was examined using a high-resolution immunoblotting method, following immunopurification with an anti-CYP2A5 antibody. We found that, of 116 human lung microsomal samples analyzed, ∼90% had detectable CYP2A6, whereas only 12% had detectable CYP2A13 with a detection limit of ∼2 fmol of CYP2A/mg protein. For the majority of microsomal samples analyzed, the level of CYP2A13 was found to be lower than the level of CYP2A6; overall, the highest level of CYP2A13 found (∼20 fmol/mg protein) was ∼10-fold lower than the highest level of CYP2A6 detected. Quantitative RNA-polymerase chain reaction analysis confirmed that the highly variable expression of the CYP2A proteins was consistent with variations in the levels of the corresponding CYP2A mRNAs in the same tissue samples. It is noteworthy that the level of CYP2A13, but not CYP2A6, was correlated with lung microsomal NNK metabolic activation activity. Furthermore, the addition of 8-methoxypsoralen, a CYP2A inhibitor, led to greater inhibition of NNK metabolic activation in microsomes containing relatively high levels of CYP2A13 than in samples containing no detectable CYP2A13. Taken together, these data indicate that human lung microsomal CYP2A13 is active in NNK metabolic activation. Therefore, individuals having relatively high levels of CYP2A13 expression will likely have an increased risk of developing smoking-related lung cancer.

Original languageEnglish (US)
Pages (from-to)570-578
Number of pages9
JournalJournal of Pharmacology and Experimental Therapeutics
Volume323
Issue number2
DOIs
StatePublished - Nov 1 2007

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Carcinogens
Tobacco
Lung
Microsomes
Cytochrome P-450 Enzyme System
Methoxsalen
Proteins
DNA-Directed RNA Polymerases
Immunoblotting
Limit of Detection
Metabolic Activation
4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone
Anti-Idiotypic Antibodies
Lung Neoplasms
Smoking
Polymerase Chain Reaction
Messenger RNA
steroid hormone 7-alpha-hydroxylase

Cite this

CYP2A13 : Variable expression and role in human lung microsomal metabolic activation of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone. / Zhang, Xiuling; D'Agostino, Jaime; Wu, Hong; Zhang, Qing Yu; von Weymarn, Linda B; Murphy, Sharon E; Ding, Xinxin.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 323, No. 2, 01.11.2007, p. 570-578.

Research output: Contribution to journalArticle

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abstract = "CYP2A13 is the most efficient cytochrome P450 enzyme in the metabolic activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific lung carcinogen. The aims of this study were to determine the levels of CYP2A13 protein in human lung microsomes and to ascertain whether CYP2A13 plays any role in lung microsomal NNK metabolic activation. The expression of CYP2A6 and CYP2A13 was examined using a high-resolution immunoblotting method, following immunopurification with an anti-CYP2A5 antibody. We found that, of 116 human lung microsomal samples analyzed, ∼90{\%} had detectable CYP2A6, whereas only 12{\%} had detectable CYP2A13 with a detection limit of ∼2 fmol of CYP2A/mg protein. For the majority of microsomal samples analyzed, the level of CYP2A13 was found to be lower than the level of CYP2A6; overall, the highest level of CYP2A13 found (∼20 fmol/mg protein) was ∼10-fold lower than the highest level of CYP2A6 detected. Quantitative RNA-polymerase chain reaction analysis confirmed that the highly variable expression of the CYP2A proteins was consistent with variations in the levels of the corresponding CYP2A mRNAs in the same tissue samples. It is noteworthy that the level of CYP2A13, but not CYP2A6, was correlated with lung microsomal NNK metabolic activation activity. Furthermore, the addition of 8-methoxypsoralen, a CYP2A inhibitor, led to greater inhibition of NNK metabolic activation in microsomes containing relatively high levels of CYP2A13 than in samples containing no detectable CYP2A13. Taken together, these data indicate that human lung microsomal CYP2A13 is active in NNK metabolic activation. Therefore, individuals having relatively high levels of CYP2A13 expression will likely have an increased risk of developing smoking-related lung cancer.",
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AU - Ding, Xinxin

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