A Novel Single Nucleotide Polymorphism Altering Stability and Activity of CYP2A6

doi:10.1006/bbrc.2001.4422

Biochemical and Biophysical Research Communications

Volume 281, Issue 3, 2 March 2001, Pages 810-814

https://doi.org/10.1006/bbrc.2001.4422 Get rights and content

Abstract

CYP2A6 is known as a major cytochrome P450 (CYP) responsible for the oxidation of nicotine and coumarin in humans. In this study, we explored genetic polymorphisms, which reduce CYP2A6 activity in Japanese. Two novel mutations in exon 9 of the CYP2A6 gene were found. A single nucleotide polymorphism of T1412C and G1454T resulted in Ile471Thr and Arg485Leu substitution, respectively. The frequency of the former variant allele was considerably high (15.7%), while the latter variant appeared to be a rare polymorphism. Heterologous expression of CYP2A6 using a cDNA possessing C instead of T-base at codon 471 in Escherichia coli caused remarkable reduction of the stability of holoenzyme at 37°C. Furthermore, this variant enzyme almost lacked nicotine C-oxidase activity, although coumarin 7-hydroxylase activity was still observed. These data suggest that individuals homozygous for the T1412C variant allele or heterozygous for this and a defect allele such as the CYP2A6*4 may be poor metabolizer of nicotine, but not coumarin.

References (18)

M. Oscarson et al.
FEBS Lett.
(1998)
M. Oscarson et al.
FEBS Lett.
(1999)
M. Miyamoto et al.
Biochem. Biophys. Res. Commun.
(1999)
H. Iwata et al.
Biochem. Pharmacol.
(1998)
T. Omura et al.
J. Biol. Chem.
(1964)
M. Nakajima et al.
Drug Metab. Dispos.
(1996)
E.S. Messina et al.
J. Pharmacol. Exp. Ther.
(1997)
M.L. Pianezza et al.
Nature
(1998)

There are more references available in the full text version of this article.

Cited by (88)

How can we Improve on Modeling Nicotine Addiction to Develop Better Smoking Cessation Treatments?
2016, International Review of Neurobiology
Citation Excerpt :
Altered activity of CYP2A6 would clearly affect the bioavailability of nicotine in the systemic circulation and therefore would be a key factor involved with the addictive properties of nicotine itself. Several genetic single nucleotide polymorphisms (SNPs) have been identified that reduce function of CYP2A6*2, *4, and *5, which would lead to a prolonged effect of nicotine in the body, as well as increased gene replication of CYP2A6 in some individuals which would lead to lower sensitivity to the effects of nicotine (Ariyoshi, Sawamura, & Kamataki, 2001; Benowitz, Tyndale, Jacob, & Swan, 2002; Hadidi, Zahlsen, Idle, & Cholerton, 1997; Tyndale & Sellers, 2001). SNPs in the choline acetyltransferase (ChAT) gene (rs1880676, rs3810950, and rs868750) were also significantly associated with level of nicotine dependence (allele p-values were 0.01, 0.02, and 0.04, respectively).
Clinically effective smoking cessation treatments are few in number, mainly varenicline, bupropion, and nicotine replacement therapy being prescribed by health organizations. Of the many compounds tested for smoking cessation, a good proportion fail in human trials despite positive findings in rodents. This chapter aims to cover the uses and some pit falls of current methodologies employed to discover clinical treatments in the laboratory. Complicating factors include the complex nature of genetics in tobacco smoking and the comorbidity associated with other psychiatric disorders, which has not been addressed fully in the rodent laboratory. This chapter reviews the evidence from intravenous nicotine self-administration studies and proposes modifications on how we can improve the validity of the animal models by incorporating clinically relevant factors considered to be critical in tobacco smoking. For example, choice procedures that incorporate alternative reinforcers, use of reinstatement models, and second-order schedules of reinforcement are proposed to have better scientific validity that may lead to better clinical outcomes. Furthermore, improved experimental methods will also improve our chances of discovering effective treatments that ultimately may mitigate the effects of tobacco smoking with regard to health worldwide.
CYP2A6 genetic polymorphism is associated with decreased susceptibility to squamous cell lung cancer in Japanese smokers
2015, Drug Metabolism and Pharmacokinetics
Citation Excerpt :
Among CYP isozymes, CYP2A6 responds to the metabolism of nicotine and to the metabolic activation of a number of procarcinogens, including the tobacco-specific N-nitrosamines, N-nitrosonornicotine (NNN), and 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK); this can ultimately lead to development of lung cancer [4,5]. Since the first discovery that CYP2A6 genetic polymorphism was associated with differences in the capacity of coumarin 7-hydroxylation, there have been several studies describing CYP2A6 polymorphisms and their association with tobacco-related cancer and smoking habits [6–12]. We reported previously that Japanese subjects harboring the homozygous CYP2A6*4 allele have a low risk of lung cancer [13].
Cytochrome P450 2A6 (CYP2A6) is an enzyme involved in the metabolism of tobacco carcinogens, which are important risk factors in lung cancer. We and others have previously reported that CYP2A6*4, a whole-gene deletion polymorphism, is associated with lower risk of lung cancer than the wild-type allele. However, the genotyping method used in these previous studies considered only the CYP2A6*4 allele; this lead to insufficient classification of the CYP2A6 genotype, thereby underestimating the frequencies of the deficient alleles. In this study, CYP2A6 genotypes of Japanese smokers (110 individuals with squamous cell lung cancer (SQCC) and 132 sex-matched cancer-free controls) were determined using a sequencing-based approach to determine CYP2A6 haplotypes. The risk of SQCC was evaluated using the activity score (AS) system to predict CYP2A6 phenotype from its genotype. The risk of developing SQCC was significantly lower in the poor metabolizers assigned as AS 0.5 (adjusted odds ratio [OR] = 0.13, 95% CI = 0.04–0.45, P = 0.001) and AS 0 (adjusted OR = 0.15, 95% CI = 0.03–0.82, P = 0.028) than in the extensive metabolizers assigned as AS 2.0. In conclusion, CYP2A6 genetic polymorphisms may play important roles in the development of SQCC in Japanese smokers.
Nicotine, cotinine, and β-nicotyrine inhibit NNK-induced DNA-strand break in the hepatic cell line HepaRG
2014, Toxicology in Vitro
Citation Excerpt :
The coumarin 7-hydroxylation activity that was recorded in our study contrasted with the low CYP2A6 mRNA expression at 7 days in HepaRG. This could be attributed to post-transcriptional regulation of CYP2A6 which has been described previously at the mRNA and enzymatic level (Ariyoshi et al., 2001; Gilmore et al., 2001). In addition to a favorable CYP profile, HepaRG cells are grown as a monolayer which is important for the consistency of COMET results and thus offer an advantage.
Recent in vitro work using purified enzymes demonstrated that nicotine and/or a nicotine metabolite could inhibit CYPs (CYP2A6, 2A13, 2E1) involved in the metabolism of the genotoxic tobacco nitrosamine NNK. This observation raises the possibility of nicotine interaction with the mechanism of NNK bioactivation. Therefore, we hypothesized that nicotine or a nicotine metabolite such as cotinine might contribute to the inhibition of NNK-induced DNA strand breaks by interfering with CYP enzymes. The effect of nicotine and cotinine on DNA strand breaks was evaluated using the COMET assay in CYP competent HepaRG cells incubated with bioactive CYP-dependent NNK and CYP-independent NNKOAc (4-(acetoxymethylnitrosoamino)-1-(3-pyridyl)-1-butanone). We report a dose-dependent reduction in DNA damage in hepatic-derived cell lines in the presence of nicotine and cotinine. Those results are discussed in the context of the in vitro model selected.
Optimization of cancer chemotherapy on the basis of pharmacokinetics and pharmacodynamics: From patients enrolled in clinical trials to those in the 'real world'
2014, Drug Metabolism and Pharmacokinetics
Cytotoxic anticancer drugs are the most challenging therapeutic agents among all medicines with relatively narrow efficacy profiles. Therefore, medical oncologists have to practically manage the risk of severe toxic effects to optimize treatment outcomes. Dose and treatment-schedule recommendations for cytotoxic anticancer agents are determined on the basis of clinical trials. Patients enrolled in clinical trials are those likely to receive the drug in clinical practice, excluding those with conditions such as organ dysfunction, obesity, advanced age, or comorbidity. On the other hand, the ‘real world’ includes large numbers of such patients who do not meet the eligibility criteria of clinical trials. However, there is a paucity of data from sufficiently powered pharmacokinetic and pharmacodynamic studies to support dosage recommendations in such patients. Consequently, dose levels and treatment schedules for chemotherapy in these subjects are somewhat arbitrary and not evidence-based. Pharmacokinetic and pharmacodynamic studies of patients in the ‘real world’ are needed to address this issue. In this review article, we describe general aspects of clinical pharmacology in cancer patients enrolled in clinical trials and those in the ‘real world,’ and introduce recent findings regarding the pharmacokinetic and pharmacodynamic properties of irinotecan and S-1 in ‘real world’ cancer patients.
Advances in molecular modeling of human cytochrome P450 polymorphism
2013, Journal of Molecular Biology
Cytochrome P450 (CYP) is a supergene family of metabolizing enzymes involved in the phase I metabolism of drugs and endogenous compounds. CYP oxidation often leads to inactive drug metabolites or to highly toxic or carcinogenic metabolites involved in adverse drug reactions (ADR). During the last decade, the impact of CYP polymorphism in various drug responses and ADR has been demonstrated. Of the drugs involved in ADR, 56% are metabolized by polymorphic phase I metabolizing enzymes, 86% among them being CYP. Here, we review the major CYP polymorphic forms, their impact for drug response and current advances in molecular modeling of CYP polymorphism. We focus on recent studies exploring CYP polymorphism performed by the use of sequence-based and/or protein-structure-based computational approaches. The importance of understanding the molecular mechanisms related to CYP polymorphism and drug response at the atomic level is outlined.
Impact of Genetic Variants in the Nicotine Metabolism Pathway on Nicotine Metabolite Levels in Smokers
2023, Cancer Epidemiology Biomarkers and Prevention

View all citing articles on Scopus

^☆: Abbreviations used: SNP, single nucleotide polymorphism; UTR, untranslated region; PCR-SSCP, polymerase chain reaction-single strand conformation polymorphism.

¹: To whom correspondence should be addressed at Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, N12W6, Kita-ku, Sapporo, 060-0812, Japan. Fax: +81-11-706-4978. E-mail: [email protected].

View full text

Regular ArticleA Novel Single Nucleotide Polymorphism Altering Stability and Activity of CYP2A6☆

Abstract

FEBS Lett.

FEBS Lett.

Biochem. Biophys. Res. Commun.

Biochem. Pharmacol.

J. Biol. Chem.

Drug Metab. Dispos.

J. Pharmacol. Exp. Ther.

Nature

Regular Article
A Novel Single Nucleotide Polymorphism Altering Stability and Activity of CYP2A6☆