AP-1 and SP1 trans-activate the expression of hepatic CYP1A1 and CYP2A6 in the bioactivation of AFB1 in chicken.

Dietary exposure to aflatoxin B1 (AFB1) is harmful to the health and performance of domestic animals. The hepatic cytochrome P450s (CYPs), CYP1A1 and CYP2A6, are the primary enzymes responsible for the bioactivation of AFB1 to the highly toxic exo-AFB1-8,9-epoxide (AFBO) in chicks. However, the transcriptional regulation mechanism of these CYP genes in the liver of chicks in AFB1 metabolism remains unknown. Dual-luciferase reporter assay, bioinformatics and site-directed mutation results indicated that specificity protein 1 (SP1) and activator protein-1 (AP-1) motifs were located in the core region -1,063/-948, -606/-541 of the CYP1A1 promoter as well as -636/-595, -503/-462, -147/-1 of the CYP2A6 promoter. Furthermore, overexpression and decoy oligodeoxynucleotide technologies demonstrated that SP1 and AP-1 were pivotal transcriptional activators regulating the promoter activity of CYP1A1 and CYP2A6. Moreover, bioactivation of AFB1 to AFBO could be increased by upregulation of CYP1A1 and CYP2A6 expression, which was trans-activated owing to the upregulalion of AP-1, rather than SP1, stimulated by AFB1-induced reactive oxygen species. Additionally, nano-selenium could reduce ROS, downregulate AP-1 expression and then decrease the expression of CYP1A1 and CYP2A6, thus alleviating the toxicity of AFB1. In conclusion, AP-1 and SP1 played important roles in the transactivation of CYP1A1 and CYP2A6 expression and further bioactivated AFB1 to AFBO in chicken liver, which could provide novel targets for the remediation of aflatoxicosis in chicks.

Identification of non-adherence to adjuvant letrozole using a population pharmacokinetics approach in hormone receptor-positive breast cancer patients.

BACKGROUND: Letrozole, an aromatase inhibitor metabolised via CYP2A6 and CYP3A4/5 enzymes, is used as adjuvant therapy for women with hormone receptor (HR)-positive early breast cancer. The objective of this study was to quantify the impact of CYP2A6 genotype on letrozole pharmacokinetics (PK), to identify non-adherent patients using a population approach and explore the possibility of a relationship between non-adherence and early relapse. METHODS: Breast cancer patients enrolled in the prospective PHACS study (ClinicalTrials.gov NCT01127295) and treated with adjuvant letrozole 2.5 mg/day were included. Trough letrozole concentrations (Css,trough) were measured every 6 months for 3 years by a validated LC-MS/MS method. Concentration-time data were analysed using non-linear mixed effects modelling. Three methods were evaluated for identification of non-adherent subjects using the base PK model. RESULTS: 617 patients contributing 2534 plasma concentrations were included and led to a one-compartment PK model with linear absorption and elimination. Model-based methods identified 28 % of patients as non-adherent based on high fluctuations of their Css,trough compared to 3 % based on patient declarations. The covariate analysis performed in adherent subjects revealed that CYP2A6 intermediate (IM) and slow metabolisers (SM) had 21 % (CI95 % = 12 - 30 %) and 46 % (CI95 % = 41 - 51 %) lower apparent clearance, respectively, compared to normal and ultrarapid metabolisers (NM+UM). Early relapse (19 patients) was not associated with model-estimated, concentration-based or declared adherence in the total population (p = 0.41, p = 0.37 and p = 0.45, respectively). CONCLUSIONS: These findings will help future investigations focusing on the exposure-efficacy relationship for letrozole in adjuvant setting.

Identification of New Substrates and Inhibitors of Human CYP2A7.

CYP2A7 is one of the most understudied human cytochrome P450 enzymes and its contributions to either drug metabolism or endogenous biosynthesis pathways are not understood, as its only known enzymatic activities are the conversions of two proluciferin probe substrates. In addition, the CYP2A7 gene contains four single-nucleotide polymorphisms (SNPs) that cause missense mutations and have minor allele frequencies (MAFs) above 0.5. This means that the resulting amino acid changes occur in the majority of humans. In a previous study, we employed the reference standard sequence (called CYP2A7*1 in P450 nomenclature). For the present study, we created another CYP2A7 sequence that contains all four amino acid changes (Cys311, Glu169, Gly479, and Arg274) and labeled it CYP2A7-WT. Thus, it was the aim of this study to identify new substrates and inhibitors of CYP2A7 and to compare the properties of CYP2A7-WT with CYP2A7*1. We found several new proluciferin probe substrates for both enzyme variants (we also performed in silico studies to understand the activity difference between CYP2A7-WT and CYP2A7*1 on specific substrates), and we show that while they do not act on the standard CYP2A6 substrates nicotine, coumarin, or 7-ethoxycoumarin, both can hydroxylate diclofenac (as can CYP2A6). Moreover, we found ketoconazole, 1-benzylimidazole, and letrozole to be CYP2A7 inhibitors.

Impact of CYP2A6 Gene Polymorphism on the Efficacy and Safety of S-1 Therapy in Patients with Gastric Cancer: A Systematic Review and Meta-Analysis.

INTRODUCTION: The relationship of CYP2A6 polymorphisms with S-1 therapy outcomes in gastric cancer is unclear. This review aimed to assess the association between CYP2A6 gene polymorphisms (CYP2A6*4, *7, *9, *10) and S-1 therapy outcomes in gastric cancer, aiming to identify predictive markers for S-1 efficacy and adverse reactions. METHODS: We searched seven databases, using random or fixed-effect models to calculate hazard ratio (HR) and 95% confidence interval (CI) based on study heterogeneity. RESULTS: A total of 1,143 articles were retrieved from multiple online databases as of March 28, 2023. After screening, seven articles containing seven investigations were included in the meta-analysis. Our results revealed a significant association between the CYP2A6 polymorphism site and the overall survival (OS) of variant/variant group (V/V) patients compared to wild-type/wild-type (W/W) or wild-type/variant (W/V) patients (HR = 2.73, 95% CI: 1.45-5.14, p = 0.002). S-1 was more beneficial for W/W or W/V patients than V/V patients in terms of progression-free survival (PFS) (HR = 3.15, 95% CI: 1.47-6.75, p = 0.003). There was no association between CYP2A6 polymorphism and hematological adverse reactions (OR = 0.52, 95% CI: 0.23-1.15, p = 0.104). CONCLUSION: CYP2A6 polymorphisms correlate with S-1 efficacy (OS and PFS) in gastric cancer, suggesting their potential as predictive markers. However, the generalizability of findings is limited by the small number of studies from Eastern countries and variations in chemotherapy regimens and detection methods. Further, large-scale studies are needed to confirm these associations.

Circadian rhythms in CYP2A5 expression underlie the time-dependent effect of tegafur on breast cancer.

The chemotherapeutic agent tegafur, a prodrug that prolongs the half-life of fluorouracil (5-FU), exerts antitumor effects against various cancers. Since tegafur is metabolized to 5-FU by CYP2A6 in the liver, the expression of CYP2A6 determines the effect of tegafur. Here, we report that the expression rhythm of Cyp2a5, a homolog of human CYP2A6, in female mice causes dosing time-dependent differences in tegafur metabolism. In the livers of female mice, CYP2A5 expression showed a circadian rhythm, peaking during the dark period. This rhythm is regulated by RORA, a core clock component, and abrogation of the CYP2A5 activity abolished the time-dependent difference in the rate of tegafur metabolism in female mice. Furthermore, administration of tegafur to mice transplanted with 4T1 breast cancer cells during the dark period suppressed increases in tumor size compared to female mice treated during the light period. Our findings reveal a novel relationship between 5-FU prodrugs and circadian clock machinery, potentially influencing antitumor effects, and contributing to the development of time-aware chemotherapy regimens for breast cancer.

CYP2A6 associates with respiratory disease risk and younger age of diagnosis: a phenome-wide association Mendelian Randomization study.

CYP2A6, a genetically variable enzyme, inactivates nicotine, activates carcinogens, and metabolizes many pharmaceuticals. Variation in CYP2A6 influences smoking behaviors and tobacco-related disease risk. This phenome-wide association study examined associations between a reconstructed version of our weighted genetic risk score (wGRS) for CYP2A6 activity with diseases in the UK Biobank (N = 395 887). Causal effects of phenotypic CYP2A6 activity (measured as the nicotine metabolite ratio: 3'-hydroxycotinine/cotinine) on the phenome-wide significant (PWS) signals were then estimated in two-sample Mendelian Randomization using the wGRS as the instrument. Time-to-diagnosis age was compared between faster versus slower CYP2A6 metabolizers for the PWS signals in survival analyses. In the total sample, six PWS signals were identified: two lung cancers and four obstructive respiratory diseases PheCodes, where faster CYP2A6 activity was associated with greater disease risk (Ps < 1 × 10-6). A significant CYP2A6-by-smoking status interaction was found (Psinteraction < 0.05); in current smokers, the same six PWS signals were found as identified in the total group, whereas no PWS signals were found in former or never smokers. In the total sample and current smokers, CYP2A6 activity causal estimates on the six PWS signals were significant in Mendelian Randomization (Ps < 5 × 10-5). Additionally, faster CYP2A6 metabolizer status was associated with younger age of disease diagnosis for the six PWS signals (Ps < 5 × 10-4, in current smokers). These findings support a role for faster CYP2A6 activity as a causal risk factor for lung cancers and obstructive respiratory diseases among current smokers, and a younger onset of these diseases. This research utilized the UK Biobank Resource.

Cigarette Smoking and Intracranial Aneurysms: A Pilot Analysis of SNPs in the CYP2A6 Gene in the Italian Population.

BACKGROUND: Cigarette smoking is a modifiable risk factor associated with formation and rupture of intracranial aneurysms (IAs). Cytochrome P450 2A6 (CYP2A6) is the main enzyme implied in catabolism of nicotine and xenobiotics, giving rise to oxidative stress products. Our study investigated the associations between specific single-nucleotide polymorphisms (SNPs) in the CYP2A6 gene and the presence of sporadic IAs in a cluster of Italian patients, as well as their rupture regarding cigarette smoking habit. METHODS: Three hundred and thirty-one Italian patients with sporadic IAs were recruited in a single institution. We recorded data on clinical onset with subarachnoid hemorrhage (SAH) and smoking habit. Genetic analysis was performed with a standard procedure on peripheral blood samples: CYP2A6 ∗1B2, CYP2A6 ∗2, and CYP2A6 ∗14 SNPs were analyzed in the study group along with 150 healthy control subjects. Statistical analysis was conducted according to genetic association study guidelines. RESULTS: In the patient cohort, the frequency of aSAH was significantly higher in current smokers (P < 0.001; OR=17.45), regardless of the pattern of CYP2A6 SNPs. There was a correlation between IA rupture and cigarette smoking in patients with the heterozygous CYP2A6 ∗1B2 allele (P < 0.001; OR=15.47). All patients carrying the heterozygous CYP2A6 ∗14 allele had an aSAH event (100%), regardless of smoking habit, although this correlation was not statistically significant (P = 1). CONCLUSIONS: According to our findings, a cigarette smoker carrying a fully active CYP2A6 enzyme (heterozygous ∗1B2 allele) may have an increased risk of IA rupture compared to those with functionally less active variants: further investigation on a larger sample is needed to verify this result. The role of the heterozygous CYP2A6 ∗14 allele in aSAH is yet to be clarified.

Tratamiento del tabaquismo guiado por marcadores genéticos

Introducción: Entre las adicciones por drogas, el tabaquismo ocupa el primer lugar como causa de morbimortalidad y es factor de riesgo para seis de las ocho principales causas de muerte en el mundo. La nicotina es el principal componente adictivo del tabaco. En la terapia de reemplazo con nicotina (TRN), la vareniclina y el bupropion son los medicamentos aprobados para tratamiento del tabaquismo, pero los resultados de las clínicas de dejación del tabaquismo sugieren que aún se desconoce muchas variables influyentes en la respuesta al tratamiento. Objetivo: Determinar la adherencia, la tolerabilidad y la efectividad de un programa de dejación de tabaquismo basado en nicotina o bupropion, en pacientes con dependencia al tabaco, seleccionados según los genotipos de las enzimas que metabolizan los dos fármacos. Hallazgos clínicos: Se incluyeron en esta serie 21 fumadores, 67% hombres, con edad promedio de 46,2±11,7 años. Su tabaquismo comenzó a los 17,8±6 años y llevaban fumando 28±13 años. Al inicio del estudio fumaban 17±12 cigarrillos por día (CPD), habían hecho 3,7±2 intentos de dejar de fumar y el puntaje NDSS (escala breve de evaluación de dependencia de la nicotina, por sus siglas en inglés) fue de 22±5 (punto de corte para dependencia a nicotina: 11 o más puntos). Tratamiento: Los pacientes tenían libre acceso telefónico al médico tratante y, cada semana, una consulta consistente en consejería y control del tratamiento farmacológico prescrito según los genotipos CYP2A6 (que codifica la enzima que metaboliza la nicotina) y CYP2B6 (que codifica la enzima que metaboliza el bupropion). Se empleó nicotina en parches transdérmicos de 14 mg el primer mes y luego de 7 mg el segundo mes, complementados con chicles para manejo del síndrome de abstinencia y bupropion en forma de liberación regulada por 300 mg, 1-2 veces al día. Resultados: Después de 8 semanas de tratamiento y 4 de observación, 15 sujetos (71,4%) respondieron en forma parcial/total. El consumo de CPD bajó de 17±12 al inicio del estudio, a 2,2±3,5 al final del estudio, que corresponde a una reducción de 195 cigarrillos/día. Siete de ocho pacientes tratados con bupropion (87,5%) y siete de trece tratados con nicotina (54%) tuvieron respuesta parcial/total. Solo un paciente formulado con nicotina suspendió el medicamento por intolerancia gastrointestinal (náusea y vómito). La tasa de recaídas, evaluada un mes después del tratamiento farmacológico, fue de cero. Se encontró buena correlación genotipo-fenotipo en los individuos tratados con bupropion, pero no en los tratados con nicotina. Relevancia clínica: La inclusión de marcadores farmacogenéticos para la elección de nicotina o bupropion en un programa de dejación de tabaquismo puede mejorar la adherencia, la tolerabilidad al fármaco y la efectividad del tratamiento.

Introduction: Among drug addictions, smoking ranks first as a cause of morbidity and mortality and is a risk factor for six of the eight leading causes of death in the world. Nicotine is the main addictive component of tobacco. In nicotine replacement therapy (NRT), varenicline and bupropion are the approved medications for smoking cessation, but results from smoking cessation clinics suggest that many variables influencing response to treatment remain unknown. Objective: To determine the adherence, tolerability and effectiveness of a smoking cessation program based on nicotine or bupropion, in patients with tobacco dependence, selected according to the genotypes of the enzymes that metabolize the two drugs. Clinical findings: Twenty-one smokers were included in this series, 67% men, with a mean age of 46.2 ± 11.7 years. Their smoking began at 17.8±6 years and they had been smoking for 28±13 years. At baseline, they smoked 17±12 cigarettes per day (CPD), had made 3.7±2 quit attempts, and the NDSS score it was 22±5 (cut-off point for nicotine dependence: 11 or more points). Treatment: The patients had free telephone access to the treating physician and, every week, a consultation consisting of counseling and control of the pharmacological treatment prescribed according to the CYP2A6 genotypes (encoding the enzyme that metabolizes nicotine) and CYP2B6 (coding for the enzyme that metabolizes bupropion). Nicotine was used in transdermal patches of 14 mg the first month and then 7 mg the second month, supplemented with gum to manage the withdrawal syndrome and bupropion in the form of controlled release 300 mg, 1-2 times a day. Results: After 8 weeks of treatment and 4 weeks of observation, 15 subjects (71.4%) responded partially/totally. CPD consumption dropped from 17±12 at the beginning of the study to 2.2±3.5 at the end of the study, which corresponds to a reduction of 195 cigarettes/day. Seven of eight patients treated with bupropion (87.5%) and seven of thirteen treated with nicotine (54%) had a partial/total response. Only one patient receiving nicotine discontinued the medication due to gastrointestinal intolerance (nausea and vomiting). The relapse rate, assessed one month after drug treatment, was zero. Good genotype-phenotype correlation was found in individuals treated with bupropion, but not in those treated with nicotine. Clinical relevance: The inclusion of pharmacogenetic markers for the choice of nicotine or bupropion in a smoking cessation program may improve adherence, drug tolerability, and treatment effectiveness.

Recurrent CYP2A6 gene mutation in biphasic hyalinizing psammomatous renal cell carcinoma: Additional support of three cases.

Biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC) with NF2 gene mutations is a newly described provisional category of renal cell carcinoma (RCC). Here we described three additional cases of BHP RCC with CYP2A6 gene mutation besides NF2 gene. The carcinomas were predominantly unencapsulated, and two of them had a rounded, nodular interface with the native kidney while one had perirenal adipose tissue invasion. Histopathologically, all neoplasms had a characteristic biphasic appearance of smaller cells clustering around basement membrane material within larger acini, forming pseudorosettes or a glomeruloid pattern. The smaller cells were focally spindle-shaped in two carcinomas. Psammoma bodies were shown in two carcinomas. Cellular necrosis and perineural invasion was identified in one case. Immunohistochemically, Vimentin, EMA, P504s were extensively expressed while RCC and CD10 were only expressed in larger cells. CK7 was positive in one tumor. CYP2A6 gene mutation (CYP2A6 NM_000762.6: exon4:c.A580G:p.K194E) was revealed in three tumors by Whole-genome exome sequencing, which was further confirmed by Sanger sequencing. Only one case harbored a somatic termination mutation in NF2 gene. NF2 promoter methylation was observed in the other two cases. Clinically, one patient died of disease with widespread bone metastases confirmed by biopsy at the ninth month after surgery but the other two patients had no evidence of recurrence or metastases (follow-up period 9-90 months). Our findings validated previously described clinicopathological features and NF2 gene mutation or promoter methylation of BHP RCC. In addition, we reported different IHC pattern of BHP RCC and further revealed the recurrent CYP2A6 genetic alteration.

A computational study on the biotransformation of alkenylbenzenes by a selection of CYPs: Reflections on their possible bioactivation.

Alkenylbenzenes are aromatic compounds found in several vegetable foods that can cause genotoxicity upon bioactivation by members of the cytochrome P450 (CYP) family, forming 1'-hydroxy metabolites. These intermediates act as proximate carcinogens and can be further converted into reactive 1'-sulfooxy metabolites, which are the ultimate carcinogens responsible for genotoxicity. Safrole, a member of this class, has been banned as a food or feed additive in many countries based on its genotoxicity and carcinogenicity. However, it can still enter the food and feed chain. There is limited information about the toxicity of other alkenylbenzenes that may be present in safrole-containing foods, such as myristicin, apiole, and dillapiole. In vitro studies showed safrole as mainly bioactivated by CYP2A6 to form its proximate carcinogen, while for myristicin this is mainly done by CYP1A1. However, it is not known whether CYP1A1 and CYP2A6 can activate apiole and dillapiole. The present study uses an in silico pipeline to investigate this knowledge gap and determine whether CYP1A1 and CYP2A6 may play a role in the bioactivation of these alkenylbenzenes. The study found that the bioactivation of apiole and dillapiole by CYP1A1 and CYP2A6 is limited, possibly indicating that these compounds may have limited toxicity, while describing a possible role of CYP1A1 in the bioactivation of safrole. The study expands the current understanding of safrole toxicity and bioactivation and helps understand the mechanisms of CYPs involved in the bioactivation of alkenylbenzenes. This information is essential for a more informed analysis of alkenylbenzenes toxicity and risk assessment.

Synthesis and biological evaluation of coumarin derivatives as selective CYP2A6 inhibitors.

Cytochrome P450 2A6 (CYP2A6) inhibitors are expected to be suitable as smoking cessation aids and for cancer prevention. Because the typical coumarin-based CYP2A6 inhibitor methoxsalen also inhibits CYP3A4, unintended drug-drug interactions are still a concern. Therefore, the development of selective CYP2A6 inhibitors is desirable. In this study, we synthesized coumarin-based molecules, determined the IC50 values for CYP2A6 inhibition, verified the possibility of mechanism-based inhibition, and compared the selectivity for CYP2A6 versus CYP3A4. The results demonstrated that we developed CYP2A6 inhibitors that were more potent and selective than methoxsalen.

A Computational Inter-Species Study on Safrole Phase I Metabolism-Dependent Bioactivation: A Mechanistic Insight into the Study of Possible Differences among Species.

Safrole, a 162.2 Da natural compound belonging to the alkenylbenzenes class, is classified as a possible carcinogen to humans by IARC (group IIB) and has proven to be genotoxic and carcinogenic to rodents. Despite its use as a food or feed additive, it is forbidden in many countries due to its documented toxicity; yet, it is still broadly present within food and feed and is particularly abundant in spices, herbs and essential oils. Specifically, safrole may exert its toxicity upon bioactivation to its proximate carcinogen 1'-hydroxy-safrole via specific members of the cytochrome P450 protein family with a certain inter/intra-species variability. To investigate this variability, an in-silico workflow based on molecular modelling, docking and molecular dynamics has been successfully applied. This work highlighted the mechanistic basis underpinning differences among humans, cats, chickens, goats, sheep, dogs, mice, pigs, rats and rabbits. The chosen metric to estimate the likeliness of formation of 1'-hydroxy-safrole by the species-specific cytochrome P450 under investigation allowed for the provision of a knowledge-based ground to rationally design and prioritise further experiments and deepen the current understanding of alkenylbenzenes bioactivation and CYPs mechanics. Both are crucial for a more informed framework of analysis for safrole toxicity.

Mining of molecular insights of CYP2A6 and its variants complex with coumarin (CYP2A6*-coumarin) using molecular dynamics simulation.

CYP2A6 is a very important enzyme that plays a crucial role in nicotine compounds and is responsible for the metabolism of more than 3% drugs of total metabolized drugs by the CYP family and reported as one of very important pharmacogenes. CYP2A6 is highly polymorphic in nature and reported with more than 40 variants, most of these variants are SNPs originated and population specific. It has been well observed and reported that the presence of these population-specific non-synonymous SNPs in CYP2A6 alters the rate of drug metabolism and as a functional consequence, drugs produce an abnormal response. Though genomics and pharmacogenomics studies are there, very less is known about the structural effects of these SNPs on molecular-interaction and folding of CYP2A6. To fill the knowledge gap, SNPs based four variants, i.e., CYP2A6*2, CYP2A6*18, CYP2A6*21, and CYP2A6*35, which are frequently reported in the South Asian population, were considered for the study. Coumarin (DB04665), a well reported drug, is considered as a model substance, and the effect of all four variants on 'CYP2A6*-coumarin' complex was studied. MD simulation-based analysis (at 200 ns) was performed and comparative analysis with respect to wild type 'CYP2A6-coumarin' complex was done. Though observation didn't find any global effect on complete complex but found some crucial minor-local alteration in interaction and folding process. It is assumed that the change due to SNPs in the single amino acid did not bring global change in physiochemical properties of CYP2A6* but caused local-trivial changes which are very crucial for its metabolic activity.Communicated by Ramaswamy H. Sarma.

CYP2A6 and GABRA2 Gene Polymorphisms are Associated With Dexmedetomidine Drug Response.

Background: Dexmedetomidine is a commonly used clinical sedative; however, the drug response varies among individuals. Thus, the purpose of this study was to explore the association between dexmedetomidine response and gene polymorphisms related to drug-metabolizing enzymes and drug response (CYP2A6, UGT2B10, UGT1A4, ADRA2A, ADRA2B, ADRA2C, GABRA1, GABRB2, and GLRA1). Methods: This study was a prospective cohort study. A total of 194 female patients aged 18-60 years, American Society of Anesthesiologists (ASA) score I-II, who underwent laparoscopy at the Third Xiangya Hospital of Central South University, were included. The sedative effect was assessed every 2 min using the Ramsay score, and the patient's heart rate decrease within 20 min was recorded. Peripheral blood was collected from each participant to identify genetic variants in the candidate genes of metabolic and drug effects using the Sequenom MassARRAY® platform. Furthermore, additional peripheral blood samples were collected from the first 99 participants at multiple time points after dexmedetomidine infusion to perform dexmedetomidine pharmacokinetic analysis by Phoenix® WinNonlin 7.0 software. Results: Carriers of the minor allele (C) of CYP2A6 rs28399433 had lower metabolic enzyme efficiency and higher plasma concentrations of dexmedetomidine. In addition, the participants were divided into dexmedetomidine sensitive or dexmedetomidine tolerant groups based on whether they had a Ramsay score of at least four within 20 min, and CYP2A6 rs28399433 was identified to have a significant influence on the dexmedetomidine sedation sensitivity by logistic regression with Plink software [p = 0.003, OR (95% CI): 0.27 (0.11-0.65)]. C allele carriers were more sensitive to the sedative effects of dexmedetomidine than A allele carriers. GABRA2 rs279847 polymorphism was significantly associated with the degree of the heart rate decrease. In particular, individuals with the GG genotype had a 4-fold higher risk of heart rate abnormality than carriers of the T allele (OR = 4.32, 95% CI: 1.96-9.50, p = 0.00027). Conclusion: CYP2A6 rs28399433 polymorphism affects the metabolic rate of dexmedetomidine and is associated with susceptibility to the sedative effects of dexmedetomidine; GABRA2 rs279847 polymorphism is significantly associated with the degree of the heart rate decrease.

Genetic influences impacting nicotine use and abuse during adolescence: Insights from human and rodent studies.

Nicotine use continues to be a major public health concern, with an alarming recent rise in electronic cigarette consumption. Heritability estimates of nicotine use and abuse range from 40% to 80%, providing strong evidence that genetic factors impact nicotine addiction-relevant phenotypes. Although nicotine use during adolescence is a key factor in the development of addiction, it remains unclear how genetic factors impact adolescent nicotine use and abuse. This review will discuss studies investigating genetic factors impacting nicotine use during adolescence. Evidence from both rodent and human studies will be summarized and integrated when possible. Human adolescent studies have largely included candidate gene studies for genes identified in adult populations, such as genes involved in nicotine metabolism, nicotinic acetylcholine receptor signaling, dopaminergic signaling, and other neurotransmitter signaling systems. Alternatively, rodent studies have largely taken a discovery-based approach identifying strain differences in adolescent nicotine addiction-relevant behaviors. Here, we aim to answer the following three questions by integrating human and rodent findings: (1) Are there genetic variants that uniquely impact nicotine use during adolescence? (2) Are there genetic variants that impact both adolescent and adult nicotine use? and (3) Do genetic factors in adolescence significantly impact long-term consequences of adolescent nicotine use? Determining answers for these three questions will be critical for the development of preventative measures and treatments for adolescent nicotine use and addiction.

Influence of nicotine dependence, current smoking status and gender on CYP1A1, CYP1B1 and CYP2A6 expression in oral squamous cell carcinoma / Influência da dependência nicotínica, parâmetros de consumo de tabaco e gênero na expressão de CYP1A1, CYP1B1 e CYP2A6 em carcinoma de células escamosas oral

Objective: Tobacco smoke is composed of cancer-causing chemicals referred to as carcinogens. These carcinogens are metabolized by the enzymes of the cytochrome P450 (CYP) family. Our objective was to evaluate the correlation of tobacco consumption parameters with CYP1A1, CYP1B1 and CYP2A6 expression using qRT-PCR in samples of oral squamous cell carcinoma (OSCC). Material and Methods: The sample was divided into 2 groups: Cancer (36 subjects) and non-Cancer (12 subjects). The smokers' participants (36) were evaluated regarding their Nicotine dependence (ND) was assessed by the Fagerström test for cigarette dependence (FTCD). Questions regarding tobacco consumption like the number of cigarettes/day (CPD), duration of use, and pack-years were also evaluated. The Mann-Whitney and Spearman correlation tests were used at a significance level of 5%. Results: 48 participants were included, 32 men (66.7%), 36 smokers (75%) and 27 smokers with OSCC (56.3%). Samples of OSCC expressed more CYP1A1, CYP1B1, and CYP2A6. Especially, the CYP1B1 gene was significantly expressed in OSCC samples, regardless gender or tobacco use. No women expressed CYP2A6, as well as, non-smokers did not express the CYP1A1 and CYP2A6 genes. CYP1A1 gene was higher among men (P = 0.021). Conclusion: Lack of exposure to tobacco may justify the absence of CYP1A1 and CYP2A6 expression in non-smokers. The CYP1B1 gene was significantly expressed in the cancer presence despite gender or tobacco use. The assessment of ND and quantification of tobacco consumption are important instruments in monitoring smokers with benign oral lesions and, especially, in the presence of cancer.(AU)

Objetivo: A fumaça do tabaco é composta de substâncias químicas cancerígenas conhecidas como carcinógenos. Esses carcinógenos são metabolizados pelas enzimas da família do citocromo P450 (CYP). Nosso objetivo foi avaliar a correlação dos parâmetros do consumo de tabaco com a expressão de CYP1A1, CYP1B1 e CYP2A6 por qRT-PCR em amostras de carcinoma de células escamosas bucal (CCEB). Material e Métodos: A amostra foi dividida em 2 grupos: Câncer (36 indivíduos) e sem Câncer (12 indivíduos). Os participantes fumantes (36) foram avaliados quanto à dependência nicotínica (DN) pelo teste de Fagerström para dependência de cigarro (TFDC). Questões relacionadas ao consumo de tabaco como número de cigarros / dia (CPD), tempo de uso e anos-maço também foram avaliadas. Os testes de correlação de Mann-Whitney e Spearman foram utilizados com nível de significância de 5%. Resultados: foram incluídos 48 participantes, 32 homens (66,7%), 36 fumantes (75%) e 27 fumantes com CCEB (56,3%). Amostras de CCEB expressaram mais CYP1A1, CYP1B1 e CYP2A6. Especialmente, o gene CYP1B1 foi significativamente expresso em amostras de CCEB, apesar do sexo ou uso de tabaco. Nenhuma mulher expressou CYP2A6, assim como, não fumantes não expressaram os genes CYP1A1 e CYP2A6. O gene CYP1A1 foi maior entre os homens (P = 0,021). Conclusão: A falta de exposição pode justificar a ausência da expressão dos genes CYP1A1 e CYP2A6 entre não fumantes. O gene CYP1B1 foi significativamente expresso na presença de câncer, independentemente do sexo ou do uso de tabaco. A avaliação da DN e a quantificação do consumo de tabaco são importantes instrumentos no acompanhamento de fumantes com lesões bucais benignas e, principalmente, na presença de câncer (AU)

Polymorphism in cytochrome P4502A6 reduces the risk to head and neck cancer and modifies the treatment outcome.

The present case-control study consisting of 1300 cases of head and neck squamous cell carcinoma (HNSCC) and the equal number of controls aimed to investigate the association of functionally important polymorphisms in cytochrome P4502A6 (CYP2A6*1B, CYP2A6*4C, CYP2A6*9-rs28399433) with HNSCC and the treatment response in cases receiving a combination of chemotherapy/radiotherapy (CT/RT). A significant decrease in risk to HNSCC was observed in the cases with deletion (CYP2A6*4B and CYP2A6*4C) or reduced activity genotypes (CYP2A6*9) of CYP2A6. This risk to HNSCC was further reduced significantly in tobacco users among the cases when compared to nontobacco users among the cases. The risk was also reduced to a slightly greater extent in alcohol users among the cases when compared to nonalcohol users among the cases. In contrast with decreased risk to HNSCC, almost half of the cases with variant genotypes of CYP2A6 (CYP2A6*1A/*4C+*1B/*4C+*4C/*4C and *9/*9) did not respond to the treatment. Likewise, the survival rate in cases receiving the treatment, after 55 months of follow-up was significantly lower in cases with deletion (6.3%) or reduced activity (11.9%) allele than in the cases with common alleles (41%). The present study has shown that CYP2A6 polymorphism significantly reduces the risk to HNSCC. Our data further suggested that CYP2A6 polymorphism may worsen the treatment outcome in the cases receiving CT/RT.

Roles of cytochrome P450 2A6 in the oxidation of flavone, 4'-hydroxyflavone, and 4'-, 3'-, and 2'-methoxyflavones by human liver microsomes.

Nine forms of recombinant cytochrome P450 (P450 or CYP) enzymes were used to study roles of individual P450 enzymes in the oxidation of flavone and some other flavonoids, 4'-hydroxyflavone and 4'-, 3'-, and 2'-methoxyflavones, by human liver microsomes using LC-MS/MS analysis.As has been reported previously , 4'-, 3'-, and 2'-methoxyflavones were preferentially O-demethylated by human liver P450 enzymes to form 4'-, 3'-, and 2'-hydroxylated flavones and also 3',4'-dihydroxyflavone from the former two substrates.In comparisons of product formation by oxidation of these methoxylated flavones, CYP2A6 was found to be a major enzyme catalysing flavone 4'- and 3'-hydroxylations by human liver microsomes but did not play significant roles in 2'-hydroxylation of flavone, O-demethylations of three methoxylated flavones, and the oxidation of 4'-hydroxyflavone to 3',4'-dihydroxyflavone.The effects of anti-CYP2A6 IgG and chemical P450 inhibitors suggested that different P450 enzymes, as well as CYP2A6, catalysed oxidation of these flavonoids at different positions by liver microsomes.These studies suggest that CYP2A6 catalyses flavone 4'- and 3'-hydroxylations in human liver microsomes and that other P450 enzymes have different roles in oxidizing these flavonoids.

Accurate transcriptome assembly by Nanopore RNA sequencing reveals novel functional transcripts in hepatocellular carcinoma.

The long reads of Nanopore sequencing permit accurate transcript assembly and ease in discovering novel transcripts with potentially important functions in cancers. The wide adoption of Nanopore sequencing for transcript quantification, however, is largely limited by high costs. To address this issue, we developed a bioinformatics software, NovelQuant, that can specifically quantify long-read-assembled novel transcripts with short-read sequencing data. Nanopore Direct RNA Sequencing was carried out on three hepatocellular carcinoma (HCC) patients' tumor, matched portal vein tumor thrombus, and peritumor to reconstruct the HCC transcriptome. Then, based on the reconstructed transcriptome, NovelQuant was applied on Illumina RNA sequencing data of 59 HCC patients' tumor and paired peritumor to quantify novel transcripts. Our further analysis revealed 361 novel transcripts dysregulated in HCC and that 101 of them were significantly associated with prognosis. There were 19 novel prognostic transcripts predicted to be long noncoding RNAs (lncRNAs), and some of them had regulatory targets that were reported to be associated with HCC. Additionally, 42 novel prognostic transcripts were predicted to be protein-coding mRNAs, and many of them could be involved in xenobiotic metabolism. Moreover, the tumor-suppressive roles of two representative novel prognostic transcripts, CDO1-novel (lncRNA) and CYP2A6-novel (protein-coding mRNA), were further functionally validated during HCC progression. Overall, the current study shows a possibility of combining long- and short-read sequencing to explore functionally important novel transcripts in HCC with accuracy and cost-efficiency, which expands the pool of molecular biomarkers that could enhance our understanding of the molecular mechanisms of HCC.

Genetic Variants in Smoking-Related Genes in Two Smoking Cessation Programs: A Cross-Sectional Study.

Previous studies have identified variants in genes encoding proteins associated with the degree of addiction, smoking onset, and cessation. We aimed to describe thirty-one single nucleotide polymorphisms (SNPs) in seven candidate genomic regions spanning six genes associated with tobacco-smoking in a cross-sectional study from two different interventions for quitting smoking: (1) thirty-eight smokers were recruited via multimedia to participate in e-Decídete! program (e-Dec) and (2) ninety-four attended an institutional smoking cessation program on-site. SNPs genotyping was done by real-time PCR using TaqMan probes. The analysis of alleles and genotypes was carried out using the EpiInfo v7. on-site subjects had more years smoking and tobacco index than e-Dec smokers (p < 0.05, both); in CYP2A6 we found differences in the rs28399433 (p < 0.01), the e-Dec group had a higher frequency of TT genotype (0.78 vs. 0.35), and TG genotype frequency was higher in the on-site group (0.63 vs. 0.18), same as GG genotype (0.03 vs. 0.02). Moreover, three SNPs in NRXN1, two in CHRNA3, and two in CHRNA5 had differences in genotype frequencies (p < 0.01). Cigarettes per day were different (p < 0.05) in the metabolizer classification by CYP2A6 alleles. In conclusion, subjects attending a mobile smoking cessation intervention smoked fewer cigarettes per day, by fewer years, and by fewer cumulative pack-years. There were differences in the genotype frequencies of SNPs in genes related to nicotine metabolism and nicotine dependence. Slow metabolizers smoked more cigarettes per day than intermediate and normal metabolizers.