The Significance of the Homozygous CYP2A6 Deletion on Nicotine Metabolism: A New Genotyping Method of CYP2A6 Using a Single PCR–RFLP

doi:10.1006/bbrc.1999.1182

Biochemical and Biophysical Research Communications

Volume 262, Issue 1, 19 August 1999, Pages 146-151

https://doi.org/10.1006/bbrc.1999.1182 Get rights and content

Abstract

A convenient and specific CYP2A6 genotyping method was developed in this study. This method consisting of a single PCR–RFLP is capable of resolving the genotype into either CYP2A6*1 (wild type), CYP2A6*2, or CYP2A6*3. Among 252 Japanese persons genotyped, 241 were genotyped as the wild type, 1 as an unknown variant, and none as either CYP2A6*2 or CYP2A6*3. A homozygous deletion was found in the 10 remaining subjects. To clarify the metabolic significance of this deletion in the whole human body, urinary cotinine, the principal metabolite of nicotine, was analyzed subsequent to smoking. Cumulated urinary cotinine excretion in the homozygously CYP2A6-deleted individuals was about one-seventh compared to the control group (wild type). This study provides a firm experimental basis for correlating genotypic characterization of CYP2A6 with phenotypic expression of nicotine metabolism.

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Pharmacogenetics in psychiatry: study of allelic variants of CYP450 in chilean patients with psychiatric disease
2022, Revista Medica Clinica Las Condes
: Los trastornos psiquiátricos forman parte de las enfermedades más frecuentes en la población chilena y, a pesar de que la mayoría de estos cuadros son tratables farmacológicamente de manera eficaz, hay un porcentaje de pacientes que no responden adecuadamente, o presentan severos efectos adversos que obligan a la discontinuidad de su tratamiento. En la actualidad, no existe ningún método fiable para predecir qué tratamiento farmacológico será el mejor para un determinado paciente
El metabolismo de los psicofármacos está mediado, principalmente, por el complejo enzimático Citocromo P450 (CYP450), que incluye las isoformas 1A2, 2C9, 2C19, 2D6, 3A4 y 3A5. Los genes que codifican para estas enzimas, presentan variantes polimórficas que influyen en la actividad enzimática. La identificación de estos polimorfismos del CYP450, nos permite clasificar a los pacientes como metabolizadores lentos, intermedios, normales o ultrarrápidos, facilitando el diseño de una estrategia farmacológica personalizada predeciblemente eficaz para el paciente
: Genotipificar las variantes alélicas más relevantes del CYP450 1A2, 2C9, 2C19, 2D6, 3A4 y 3A5 en pacientes chilenos que consultan por trastornos psiquiátricos
: En este estudio observacional, descriptivo y exploratorio se evaluaron las variantes genéticas de 6 enzimas del CYP450 mediante RFLP y secuenciación en 158 pacientes chilenos, consultantes por trastornos psiquiátricos, cuyo rango etario es de 6-74 años (mediana de 35 años), siendo 66 hombres y 92 mujeres. Las frecuencias alélicas obtenidas mostradas como alelo silvestre/alelo polimórfico fueron las siguientes: 1A2 (1A/1F 0,290/0,710); 2C9 (1A/2A 0,880/0,120); 2C19 (1A/2A 0,885/0,115); 2D6*2 (1/2 0,590/0,410); 2D6*3 (1/30,985/0,0015); 2D6*4 (1/4 0,910/0,090); 3A4 (1A/1B 0,935/0,065); y 3A5 (1A/3A 0,115/0,885). En nuestro estudio, las frecuencias genotípicas para todos los polimorfismos estudiados en la población estaban en equilibrio de Hardy-Weinberg
: Las frecuencias alélicas obtenidas para el grupo de estudio son similares a las descritas por otros autores tanto para población chilena como de otros países del mundo y por tanto permite ajustar las dosis de los medicamentos de acuerdo a las pautas internacionales en concordancia con el uso de una medicina personalizada. En psiquiatría, contar con un examen que nos permita implementar, desde el comienzo, una terapia predeciblemente eficaz para el paciente, puede hacer una gran diferencia en la práctica clínica
: Psychiatric disorders are one of the most frequent illnesses in the Chilean population and, even though most of these conditions are effectively pharmacologically treatable, there is a percentage of patients who do not respond adequately or have severe adverse effects that require patients to discontinue their treatment. At present, there is no reliable method to predict which drug treatment will be the best for a given patient.
The metabolism of psychotropic drugs is mainly mediated by the enzyme complex Cytochrome P450 (CYP450), which includes the isoforms 1A2, 2C9, 2C19, 2D6, 3A4, and 3A5. The genes that code for these enzymes have polymorphic variants that influence enzyme activity. Identification of these CYP450 polymorphisms allows us to classify patients as poor, intermediate, normal, or ultra-rapid metabolizers, facilitating the design of a personalized drug strategy that is predictably effective for the patient.
: Genotyping the most relevant allelic variants of CYP450 1A2, 2C9, 2C19, 2D6, 3A4, and 3A5 in Chilean patients consulting for psychiatric disorders.
: In this observational, descriptive and exploratory study, the genetic variants of 6 CYP450 enzymes were evaluated by RFLP and sequencing in 158 Chilean patients, consulting for psychiatric disorders whose age range was 6-74 years (median of 35 years), being 66 men and 92 women. The allele frequencies obtained shown as wild allele/polymorphic allele were the following: 1A2 (1A/1F 0.290/0.710); 2C9 (1A/2A 0.880/0.120); 2C19 (1A/2A 0.885/0.115); 2D6 * 2 (1/2 0.590/0.410); 2D6 * 3 (1/3 0.985/0.0015); 2D6 * 4 (1/4 0.910/0.090); 3A4 (1A/1B 0.935/0.065); and 3A5 (1A/3A 0.115/0.885). In our study, the genotype frequencies for all the polymorphisms studied in the population were in Hardy-Weinberg equilibrium.
: The allelic frequencies obtained for the study group are similar to those described by other authors for both the Chilean population and those of other countries in the world and therefore allow adjusting the drugs doses according to international guidelines on personalized medicine. In psychiatry, having a test that allows us to implement a predictably effective therapy for the patient right from the start can make a big difference in clinical practice.
Association between CYP2A6 genotypes and smoking behavior in Lebanese smokers
2020, Meta Gene
Citation Excerpt :
Concerning CYP2A6 polymorphisms, our data demonstrates a higher rate of the CYP2A6*2 allele variant in Lebanese as compared to other populations, Table 5. CYP2A6*2 is rare in Asian populations such as the Koreans, Japanese and Chinese (Chen et al., 1999; Kitagawa et al., 1999; Oscarson et al., 1999a; Oscarson et al., 1999b; Kwon et al., 2001; Nakajima et al., 2001). An allelic frequency of around 1% was found in Swedes, Finns, Brazilians and African North Americans (Oscarson et al., 1998; Schoedel et al., 2004; Vasconcelos et al., 2005; Djordjevic et al., 2013).
With the absence of effective reinforcement of tobacco control laws in the country, the Lebanese population has been vulnerable to the health burden of smoking. Smoking and quitting behaviors are influenced by genetic factors, mainly CYP2A6 polymorphisms. To date, the assessment of the genetic profile and its effect on the behavior of Lebanese smokers has not yet been studied. The aim of this study was to determine the CYP2A6 polymorphisms and its relation to smoking and quitting behavior in a cohort of Lebanese smokers.
Healthy adult Lebanese smokers were recruited from the American University of Beirut and its Medical Center. Their nicotine metabolite (NM) levels and CYP2A6 alleles (2, 4, 9 and 12) were determined. The smoking behavior, Nicotine Dependence Score (NDS) and quitting behavior of the participants were assessed after filling a “smoking assessment questionnaire”.
53 healthy adult smokers participated in our study (M: F = 4:1, median age = 38.47 +/− 14.15 years). Mutated CYP* 2 was present in 33.9% (18/53 cases), CYP* 4 in 11.3% (6/53 cases), CYP* 9 in 100% (53/53 cases) and CYP* 12 in 86.7% (46/53 cases). Slow metabolizers constituted 90.6% of our group while 9.4% were intermediate metabolizers. Slow metabolizers smoked a smaller number of cigarettes per day (CPD) (median = 15 CPD vs 25 CPD) and had higher NM levels (median = 23 ng/mL vs 10 ng/mL or undetectable) than intermediate metabolizers. A statistically significant correlation with NDS and quitting behavior was not found in either group.
In this first study from Lebanon, a unique distribution of CYP2A6 alleles (high prevalence of CYP2A6*9 and CYP2A6*12) was detected. In accordance with previously published data, slow metabolizers smoked a lower number of CPD and had higher NM levels in their serum. Larger studies are required to fully elucidate the CYP2A6 polymorphisms of Lebanese smokers and include them in personalized smoking cessation programs.
Exploring QSAR and QAAR for inhibitors of cytochrome P450 2A6 and 2A5 enzymes using GFA and G/PLS techniques
2009, European Journal of Medicinal Chemistry
Citation Excerpt :
According to the World Health Organization (WHO), use of tobacco is responsible for causing disease burden measured in disability adjusted life years in developed countries and one of the top 10 health risk factors even in the poorest developing regions. Individuals having deficient CYP2A6 enzyme function display a decreased capacity for nicotine metabolism, and these individuals may be less likely to become smokers than those having the active enzyme functions [20–26]. An effective inhibitor of P450 2A6 could be used to diminish smoking and tobacco-related cancers.
A series of naphthalene and non-naphthalene derivatives (n = 42) having cytochrome P450 2A6 and 2A5 inhibitory activities, reported by Rahnasto et al., were subjected to QSAR and QAAR studies. The analyses were performed using electronic, spatial, shape and thermodynamic descriptors to develop quantitative models for prediction of the inhibitory activities and to explore importance of different descriptors for the responses. The data set was divided into training and test sets (with test set size being approximately 25% of the full data set size) based on K-means clustering applied on the standardized descriptor matrix. Genetic function approximation (GFA) and genetic partial least-squares (G/PLS) were used as chemometric tools for modeling, and the derived equations were of acceptable statistical and prediction (both internal and external) qualities although different equations varied in quality in a wide range (R²: 0.561–0.898, R_a²: 0.508–0.870, Q²: 0.495–0.814, R_pred²: 0.615–0.914, r²: 0.679–0.905, r₀²: 0.639–0.904, r_m²: 0.494–0.876). In the case of CYP2A5 inhibition, the GFA derived QSAR model is better than the G/PLS derived model considering both internal and external validations. In the case of CYP2A6 inhibitory potency data, the GFA derived QSAR model is better than the G/PLS model considering internal validation whereas the latter is better in external validation (which is more important) than the former. The model development process was subjected to randomization test at 90% confidence level by taking into account the whole pool of descriptors, while the developed models were also subjected to randomization test (99% confidence level) for validation. Based on the randomization test results, GFA models are found to be superior to the G/PLS models. Among the parameters, which were found important in modeling both the responses, were different Jurs descriptors, electronic descriptors (like Sr, Apol), steric descriptors (like shadow indices, Molref), shape descriptors (like COSV, Fo) and lipophilicity descriptors. This indicates that the CYP2A5 and CYP2A6 inhibition of these compounds is related to charge distribution, surface area, electronic, hydrophobic and spatial properties of the molecules.
Association of genetic polymorphisms CYP2A6*2 rs1801272 and CYP2A6*9 rs28399433 with tobacco-induced lung Cancer: Case-control study in an Egyptian population
2018, BMC Cancer
Distribution of polymorphic variants of CYP2A6 and their involvement in nicotine addiction
2017, EXCLI Journal
Nicotine metabolism and smoking: Ethnic differences in the role of P450 2A6
2017, Chemical Research in Toxicology

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¹: Present address: Division of Molecular Epidemiology, NCTR, 3900 NCTR Drive, Jefferson, AR 72079.

²: To whom correspondence should be addressed. Fax: +81-93-691-9341. E-mail: [email protected].

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Biochemical and Biophysical Research Communications

Abstract

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Cited by (81)

Pharmacogenetics in psychiatry: study of allelic variants of CYP450 in chilean patients with psychiatric disease

Association between CYP2A6 genotypes and smoking behavior in Lebanese smokers

Exploring QSAR and QAAR for inhibitors of cytochrome P450 2A6 and 2A5 enzymes using GFA and G/PLS techniques

Association of genetic polymorphisms CYP2A62 rs1801272 and CYP2A69 rs28399433 with tobacco-induced lung Cancer: Case-control study in an Egyptian population

Distribution of polymorphic variants of CYP2A6 and their involvement in nicotine addiction

Nicotine metabolism and smoking: Ethnic differences in the role of P450 2A6

Regular ArticleThe Significance of the Homozygous CYP2A6 Deletion on Nicotine Metabolism: A New Genotyping Method of CYP2A6 Using a Single PCR–RFLP

Abstract

Toxicol. Appl. Pharmacol.

FEBS Lett.

FEBS Lett.

Lancet

J. Mol. Evol.

Cancer Res.

Eur. J. Clin. Pharmacol.

Arch. Environ. Contam. Toxicol.

Arch. Environ. Contam. Toxicol.

Proc. Natl. Acad. Sci. USA

Carcinogenesis

Drug Metab. Dispos.

J. Pharmacol. Exp. Ther.

Arch. Toxicol.

Pharmacogenetics

Regular Article
The Significance of the Homozygous CYP2A6 Deletion on Nicotine Metabolism: A New Genotyping Method of CYP2A6 Using a Single PCR–RFLP