Transcriptional Regulation of Human <i>CYP2A13</i> Expression in the Respiratory Tract by CCAAT/Enhancer Binding Protein and Epigenetic Modulation

Ling, Guoyu; Wei, Yuan; Ding, Xinxin

doi:10.1124/mol.106.031104

Cited by 33 publications

(40 citation statements)

References 37 publications

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“…The genetic, epigenetic, and environmental factors that influence CYP2A expression in the lung are subjects of ongoing studies in the Ding laboratory. In this regard, we have identified a CYP2A13 7520CϾG variation that is associated with decreased CYP2A13 expression in human lung (Zhang et al, 2004), and we have also obtained evidence supporting the involvement of epigenetic factors in CYP2A13 regulation (Ling et al, 2007).…”

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confidence: 78%

CYP2A13: Variable Expression and Role in Human Lung Microsomal Metabolic Activation of the Tobacco-Specific Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone

Zhang¹,

D’Agostino²,

Wu³

et al. 2007

J Pharmacol Exp Ther

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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, ϳ90% had detectable CYP2A6, whereas only 12% had detectable CYP2A13 with a detection limit of ϳ2 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 (ϳ20 fmol/mg protein) was ϳ10-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.The human cytochrome P450 (P450) CYP2A gene subfamily is known to have two functional members, CYP2A6 and CYP2A13 (Fernandez-Salguero et al., 1995;Su et al., 2000). Previous studies on CYP2A mRNA expression in human tissues indicated that CYP2A6 is expressed in the lung at much lower levels than in the liver, whereas CYP2A13 is selectively expressed in the respiratory tract (Koskela et al., 1999;Su et al., 2000). A more recent study indicated that CYP2A13 is also expressed in the bladder (Nakajima et al., 2006). Heterologously expressed CYP2A6 and CYP2A13 enzymes are both active in the metabolic activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a lung procarcinogen, which is found in cigarettes (Hecht, 1998) and can also be produced endogenously from nicotine metabolites (Hecht et al., 2000). NNK metabolic activation involves P450-catalyzed hydroxylation at one of the two ␣ carbons to the N-nitroso group, leading to the formation of reactive intermediates that can form either DNA adducts or else stable metabolites, including 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) and 4-oxo-1-(3-pyridyl)-1-butanone (OPB) (Hecht, 1998). Although multiple human P450 enzymes, including CYP1A1, CYP1A2, CYP2A6, CYP2A13, CYP2B6, CYP2E1, and CYP...

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confidence: 78%

CYP2A13: Variable Expression and Role in Human Lung Microsomal Metabolic Activation of the Tobacco-Specific Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone

Zhang¹,

D’Agostino²,

Wu³

et al. 2007

J Pharmacol Exp Ther

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“…Mouse genomic DNA was isolated from frozen thymus samples, whereas human genomic DNA was isolated from frozen lung tissues from an 18-year-old, black, male donor (Ling et al, 2007). HindIIIdigested genomic DNA was fractionated through electrophoresis on 0.7% agarose gels, transferred to nylon membranes, and analyzed by using a 32 Plabeled, 864-bp, DNA probe corresponding to CYP2A13 exon 2 (positions ϩ593 to ϩ1456).…”

Section: Methodsmentioning

confidence: 99%

Generation and Characterization of aCYP2A13/2B6/2F1-Transgenic Mouse Model

Wei

Lei

et al. 2012

Drug Metab Dispos

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ABSTRACT:CYP2A13, CYP2B6, and CYP2F1, which are encoded by neighboring cytochrome P450 genes on human chromosome 19, are active in the metabolic activation of many drugs, respiratory toxicants, and chemical carcinogens. To facilitate studies on the regulation and function of these human genes, we have generated a CYP2A13/2B6/2F1-transgenic (TG) mouse model (all *1 alleles). Homozygous transgenic mice are normal with respect to gross morphological features, development, and fertility. The tissue distribution of transgenic mRNA expression agreed well with the known respiratory tract-selective expression of CYP2A13 and CYP2F1 and hepatic expression of CYP2B6 in humans. CYP2A13 protein was detected through immunoblot analyses in the nasal mucosa (NM) (ϳ100 pmol/mg of microsomal protein; similar to the level of mouse CYP2A5) and the lung (ϳ0.2 pmol/mg of microsomal protein) but not in the liver of the TG mice. CYP2F1 protein, which could not be separated from mouse CYP2F2 in immunoblot analyses, was readily detected in the NM and lung but not the liver of TG/Cyp2f2-null mice, at levels 10-and 40-fold, respectively, lower than that of mouse CYP2F2 in the TG mice. CYP2B6 protein was detected in the liver (ϳ0.2 pmol/mg of microsomal protein) but not the NM or lung (with a detection limit of 0.04 pmol/mg of microsomal protein) of the TG mice. At least one transgenic protein (CYP2A13) seems to be active, because the NM of the TG mice had greater in vitro and in vivo activities in bioactivation of a CYP2A13 substrate, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (a lung carcinogen), than did the NM of wild-type mice.

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“…Drug-metabolizing capability and specificity of dog CYP2A enzymes have not been characterized as extensively as the human and rodent isoforms. Human CYP2A6 is mainly expressed in human liver and contributes ϳ4% of total hepatic P450 (Martignoni et al, 2006), whereas human CYP2A13 is primarily expressed in the respiratory tract (Ling et al, 2007). Both dog CYP2A13 and CYP2A25 are present predominantly in liver tissues (Martignoni et al, 2006).…”

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confidence: 99%

Expression and Characterization of Dog Cytochrome P450 2A13 and 2A25 in Baculovirus-Infected Insect Cells

Zhou¹,

Linnenbach²,

Liu³

et al. 2010

Drug Metab Dispos

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ABSTRACT:Dog CYP2A13 and CYP2A25 were coexpressed with dog NADPHcytochrome P450 reductase (OR) in baculovirus-infected Sf9 insect cells. CYP2A13 effectively catalyzed 7-ethoxycoumarin (7EC) deethylation and coumarin hydroxylation with apparent K m values of 4.8 and 2.1 M, respectively, similar to those observed using dog liver microsomes (7.5 and 0.75 M, respectively). CYP2A25 exhibited much lower affinity toward 7EC, with an apparent K m value of 150 M, which indicates that CYP2A13 plays a more significant role in the metabolism of these CYP2A substrates. Similar to the dog CYP1A2 enzyme, CYP2A13 efficiently catalyzed phenacetin deethylation with a K m value of 3.9 M, which suggests that phenacetin is not a selective probe for dog CYP1A2 activity. Both dog CYP2A13 and CYP2A25 exhibited little or no catalytic activity toward other common cytochrome P450 probe substrates, including bupropion, amodiaquine, diclofenac, S-mephenytoin, bufuralol, dextromethorphan, midazolam, and testosterone. These results provided additional information about the selectivity of these commonly used probe substrates.

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Transcriptional Regulation of Human CYP2A13 Expression in the Respiratory Tract by CCAAT/Enhancer Binding Protein and Epigenetic Modulation

Cited by 33 publications

References 37 publications

CYP2A13: Variable Expression and Role in Human Lung Microsomal Metabolic Activation of the Tobacco-Specific Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone

CYP2A13: Variable Expression and Role in Human Lung Microsomal Metabolic Activation of the Tobacco-Specific Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone

Generation and Characterization of aCYP2A13/2B6/2F1-Transgenic Mouse Model

Expression and Characterization of Dog Cytochrome P450 2A13 and 2A25 in Baculovirus-Infected Insect Cells

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