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.

The Prevalence of CYP2B6 Gene Polymorphisms in Malaria-endemic Population of Timor in East Nusa Tenggara Indonesia

OBJECTIVES: The CYP2B6 is one of the most polymorphic CYP genes in humans that has the potential to modify the pharmacological and toxicological responses to clinically important drugs such as antimalarial artemisinin and its derivatives. The aim of the study was to determine the frequency of CYP2B6 polymorphisms in Timor malaria endemic area, East Nusa Tenggara, Indonesia where Artemisin-based Combination Therapy (ACT) has been used to treat uncomplicated malaria. METHODS: A total of 109 healthy subjects were participated in this study. CYP2B6*4, *6 and *9 polymorphisms were analyzed using PCR-RFLP to confirm the SNPs prevalence of 516G>T and 785A>G in exon 4 and 5. RESULTS: There were 96 subjects included in the analysis. In the exon 4 of CYP2B6 516G>T, the frequency of the T mutation was 37.5% (39/96), and the wildtype 27.1% (26/96). In the exon 5, CYP2B6 785A>G mutant was detected in 29.2% (28/96) of individuals, and the wildtype allele in 35.4% (34/96). The frequency of CYP2B6*9 (516G>T), CYP2B6*4 (785A>G) and CYP2B6*6 (516G>T and 785A>G) were 40.6%, 29.2% and 22.9%, respectively. The prevalence of these CYP2B6 gene polymorphisms in Timorian ethnic were higher than that in Malay, Han Chinese, Indian, and Egyptian populations. CONCLUSION: The prevalence of these CYP2B6 516G>T and 785A>G polymorphisms in Timorian ethnic is higher than that in other populations. These polymorphisms may affect the metabolism of artemisinin and its derivatives.

CYP2B6 516 G>T polymorphism and side effects of the central nervous system in HIV-positive individuals under Efavirenz treatment: Study of a sample from southern Brazil

ABSTRACT This study aimed to identify the 516 G>T polymorphism of the CYP2B6 gene and evaluate its influence on central nervous system (CNS) side effect development in HIV-positive individuals undergoing Efavirenz (EFV) treatment in a population from southern Brazil. Additionally, we performed a survey on the clinical and epidemiological characteristics of our sample. In addition to medical records evaluation, whole blood of 89 individuals was analyzed for viral load, T lymphocyte count (CD4+ and CD8+), and the polymorphism. Considering the side effects of the CNS reported by individuals but without considering the genetic variables, no statistically significant association was noted between the adverse effects and the antiretroviral treatment (including or not EFV). In addition, no statistically significant difference was noted for the influence of genotype on the viral load or the number of T lymphocytes (CD4+ and CD8+) among individuals undergoing EFV treatment. This is the first study that investigated the impact of the 516 G>T polymorphism of the CYP2B6 gene among HIV-positive individuals from southern Brazil. Its clinical significance indicates the need for prospective studies in this population.

Effect of Shenmai Iniection on isoforms of cytochrome P450 enzymes in rats / 中草药

Objective: To investigate the effects of Shenmai Injection (SMI) on activities of six isoforms of cytochrome P450 (CYP450) by Cocktail probe drugs in rats. Methods: SD rats were randomly divided into SM group and blank control group, which were given SMI (10 mL/kg) or normal saline for 7 d. Phenacetin, bupropion, tolbutamide, omeprazole, metoprolol, and midazolam were used as probe drugs for CYP1A2, CYP2B1, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. The UPLC-MS/MS method was used to determine the concentration of probe drugs in rat plasma, and the pharmacokinetic parameters were estimated by DAS3.0. Results: Compared with the blank control group, AUC0~∞, CL, and Cmax of phenacetin, bupropion, and omeprazole were significantly decreased (P < 0.05). However, no significant difference of plasma concentration and pharmacokinetics for tolbutamide, metoprolol, and midazolam was shown between SMI group and the blank control group. Conclusion: SMI can inhibit CYPlA2, CYP2B1, and CYP2C19 activities significantly, but has no effect on the activities of CYP2C9, CYP2D6, and CYP3A4.

In vivo effect of arecoline hydrobromide on rat hepatic CYP2B expression and its mechanism / 中草药

Objective: To study the effect of arecoline hydrobromide (AH) on rat hepatic CYP2B expression/activity, as well as the underlying regulation mechanism in vivo. Methods: After oral administration of AH (4, 20, and 100 mg/kg/d) to rats for 7 consecutive days, the hepatic CYP2B activity was detected by LC-MS/MS method, the protein levels of hepatic CYP2B, total CAR, and endonuclear CAR were detected by Western blotting, and the hepatic CYP2B1 mRNA level was detected by real-time PCR. Results: AH treatment had no effect on rat hepatic CYP2B protein level, but the hepatic CYP2B1 mRNA level was dose-dependently increased. Additionally, although the hepatic CYP2B activity was induced by AH treatment, the induction was weakened with the dose increase of AH. Furthermore, the protein content of hepatic endonuclear CAR was increased while the total CAR protein remained unchanged following AH treatment. Conclusion: AH induces rat hepatic CYP2B by promoting nuclear translocation of CAR. The regulation of AH on rat hepatic CYP2B largely involve transcriptional activation of the gene, partially involve the post-translational modification of CYP2B protein. Our results also suggest that the risk of metabolic interaction could be existed when the substrate drugs of CYP2B are administered in betel-quid used human.

A brief history of the discovery of PXR and CAR as xenobiotic receptors

The nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) were cloned and/or established as xenobiotic receptors in 1998. Due to their activities in the transcriptional regulation of phase I and phase II enzymes as well as drug transporters, PXR and CAR have been defined as the master regulators of xenobiotic responses. The discovery of PXR and CAR provides the essential molecular basis by which drugs and other xenobiotic compounds regulate the expression of xenobiotic enzymes and transporters. This article is intended to provide a historical overview on the discovery of PXR and CAR as xenobiotic receptors.

Frequencies of Cytochrome P450 2B6 and 2C8 Allelic Variants in the Mozambican Population

Background: The cytochrome P450 enzymes (CYP) play an important role in the metabolism of many therapeutic agents. The activities of different enzymes exhibit variability in different populations, which causes variations in drug response or toxicity. The CYP2B6 and CYP2C8 enzymes are encoded by polymorphic genes characterised by different single nucleotide polymorphisms (SNPs). Several of these CYP variants are often associated with slow metabolism phenotypes. This study aimed to analyse the frequencies of allelic variants of CYP2B6 and CYP2C8 in the Mozambican population. Methods: Using a polymerase chain reaction and restriction fragment length polymorphism assay (PCR-RFLP), the frequencies of the allelic variants of CYP2B6 (c.64C>T, c.516G>T, c.777C>A, c.785A>G, c.1459C>T) and CYP2C8 (c.805A>T, c.416G>A, c.1196A>G, c.792C>G) were determined in 360 Mozambican blood donors. Results: The frequencies of the allelic variants of the CYP2B6 gene were 0.057, 0.426, 0.0, 0.410, and 0.004. For the CYP2C8 gene, the frequencies of the allelic variants were 0.160, 0.048, 0.0, and 0.005. No significant differences were observed between the gender and geographic distribution of volunteers around the country. Conclusion: The frequencies of the allelic variants of the CYP2B6 and CYP2C8 genes were found to be homogeneously distributed in the Mozambican population and were comparable to other African populations. Further studies are required to explore the impact of these variants on the clinical response (efficacy and toxicity) of drugs, including antimalarials.

Correlation analysis of CYP2B6 gene polymorphisms and pharmacokinetic parameters of isotretinoin in healthy human volunteers / 中华皮肤科杂志

Objective To evaluate the association between isotretinoin pharmacokinetic parameters and CYP2B6 (cytochrome p-450) gene polymorphisms. Methods Blood samples were collected at different time points from 21 healthy male volunteers who received a single 40-rng oral dose of isotretinoin. High performance liquid chromatography-electrospray ionization mass spectrometry (LC-MS) was used for the quantification of isotretinoin in plasma samples which were standardized by dosage and body weight. PCR and restriction fragment length polymorphism (RFLP) analysis were performed to detect the G516T mutation in exon 4 as well as A785G mutation in exon 5 of CYP2B6 gene in these subjects. Results There was an obvious genetic linkage imbalance in exon 4 and 5 of CYP2B6 gene among these volunteers. In the case of CYP2B6*4 allele,3 (14.29%) people were CYP2B6*4/*4 homozygotes, 6 (28.57%) CYP2B6*1/*4 heterozygotes, and 12 (57.14%) CYP2B6*1/*1 wild-type homogygotes, while as far as CYP2B6*6 allele was concerned, 3 (14.29%)people were CYP2B6*6/*6 homozygotes, 5 (23.81%) CYP2B6*1/*6 heterozygotes, and 13 (61.90%)CYP2B6*1/*1 wild-type homozygotes. The reaction half-time (t1/2) and mean residence time (MRT) of isotretinoin were longer in volunteers carrying wild-type CYP2B6*4 allele than those of CYP2B6*4/*4 homozygotes (both P ＜ 0.05 ), while no significant difference was observed in maximum concentration (Cmax), peak time (Tmax) or area under the plasma concentration time (AUC) between the two groups of volunteers. There was no statistical difference in any of the above parameters between subjects carrying wild type CYP2B6*6 allele and those of CYP2B6 *6/*6 homozygotes (all P ＞ 0.05 ). Conclusions The mutation of CYP2B6*4 allele ia relevant to the metabolism of isotretinoin, which seems to be more rapid in CYP2B6*4/*4 homozygotes.

The Construction of Eukaryotic Expression Vector Containing CYP2B1 Suicide Gene / 中国医师杂志

Objective To construct an expression vector harboring CYP2B1 suicide gene, and detect its expressions in tumor cell lines. Methods PCR amplification was performed using primers based on murine CYP2B1 gene sequence from gene bank and pc3/2B1 as template. PCR product was directly inserted an eukaryotic expression plasmid pcDNA3.0. The recombinants were analyzed and identified by restriction enzyme analysis, PCR and sequencing. Then the recombinant vector pcDNA3.0/CYP2B1 was transfected into three tumor cell lines by liposome-mediated method. The expressions of CYP2B1 gene in all the cell lines were detected by RT-PCR method. Results pCDNA3.0/CYP2B1 vector was successfully constructed, and could express CYP2B1 mRNA in the three tumor cell lines. Conclusion Eukaryotic expression vector pcDNA3.0/CYP2B1 containing CYP2B1 gene under the control of a CMV promoter is an novel effective expression vector for tumor gene therapy.

Correlation between the alleles polymorphism of CYP2A6 and CYP2B6 and blood concentration of Valproate sodium / 临床神经病学杂志

Objective To investigate the correlation between the alleles polymorphism of CYP2A6 and CYP2B6 and blood concentration of Valproate sodium(VPA).Methods The 165 epilepsy patients received simplex VPA and without dysfunction of liver and kidney were chose in this study.The alleles polymorphism of CYP2A6 in 95 cases and CYP2B6 in 70 cases were detected by polymerase chain reaction(PCR).Fluorescence polarization immunoassay(FPIA) was used to measure the blood concentration of VPA.Results The frequence of allele CYP2A6*4 in 95 cases was 13.2%.The blood concentration of VPA in patients with allele CYP2A6*4[(4.23?0.27)mg/ml]was significantly higher than that in patients without allele CYP2A6*4[(3.35?0.38)mg/ml](P