Search

This study aimed to investigate whether the water-soluble pharmaceutical form of phosphatidylcholine nanoparticles (wPC) stimulated the catalytic activity of CYP enzymes 2C9 and 2D6. We have shown that electroenzymatic CYP2C9 catalysis to nonsteroidal anti-inflammatory drug naproxen as a substrate was enhanced from 100% to 155% in the presence of wPC in media. Electroenzymatic CYP2D6 activity in the presence of the adrenoceptor-blocking agent bisoprolol as a substrate was elevated significantly from 100% to 144% when wPC was added to potassium phosphate buffer solution. These results indicate the ability of wPC in the form of the phospholipid ultra-small nanoparticles to work as a membrane additive and crowding agent to accelerate the electroenzymatic reactions of cytochrome P450. [ABSTRACT FROM AUTHOR]

Cytochrome P450 2D6 (CYP2D6) is a key enzyme that mediates the metabolism of various drugs and endogenous substances in humans. However, its biological role in drug‐drug interactions especially mechanism‐based inactivation (MBI), and various diseases remains poorly understood, owing to the lack of molecular tools suitable for selectively monitoring CYP2D6 in complex biological systems. Herein, using a tailored molecular strategy, we developed a fluorescent probe BDPM for CYP2D6. BDPM exhibits excellent specificity and imaging capability for CYP2D6, making it suitable for the real‐time monitoring of endogenous CYP2D6 activity in living bio‐samples. Therefore, our tailored strategy proved useful for constructing the highly selective and enzyme‐activated fluorescent probes. BDPM as a molecular tool to explore the critical roles of CYP2D6 in the pathogenesis of diseases, high‐throughput screening of inhibitors and intensive investigation of CYP2D6‐induced MBI in natural systems. [ABSTRACT FROM AUTHOR]

Background: The Val66Met single nucleotide polymorphism (SNP) of the brain-derived growth factor (BDNF) and deletional mutation of the cytochrome P4502D6 (CYP2D6) have been reported to be linked to the etiology and severity of depressive disorders (DD) in a variable manner among different ethnicities and populations. Aims: The present study was aimed to find the relationship of mutational variations of these two neurotrophins with the severity of DD and their serum cortisol levels as a marker of the stress factor. Methods: In 104 drug-naïve newly diagnosed cases of DD and 106 control subjects, the severity of depression was assessed using the HAM-D score. Val66Met SNP of the BDNF was analyzed in them using restriction digestion of its polymerase chain reaction (PCR) product. CYP2D6 deletional variants were detected by the absence of their PCR products. Serum cortisol levels were measured by the enzyme-linked immunosorbent assay (ELISA) technique. Results: The Chi-square test (χ² = 1.42, P = 0.49) did not show any higher prevalence of Val66Met SNP of the BDNF gene in the case group. A correlation coefficient (R) of --0.14 for HAM-D score with a P value of 0.29 signified no direct link of the severity of DD with this SNP. However, a χ² of 12.68 with P < 0.001 indicated a significantly higher prevalence of the CYP2D6 deletional mutants in DD cases, whereas an R-value of 0.39 for HAM-D score with P < 0.001 suggested a significantly higher severity of DD having with them. Serum cortisol level showed a significant positive correlation with the deletional variants of CYP2D6 (R = 0.198, P = 0.04) and the HAM-D score (R = 0.22, P = 0.025). Conclusion: We conclude that CYP2D6 deletion significantly contributes to the severity and stress factor in the DD patients in our study population. Early identification of these mutations may provide important molecular and cellular predisposition for the disease and may lay the ground for possible more effective measures of intervention. [ABSTRACT FROM AUTHOR]

Background: The modified Xiang Bei Yang Rong Tang (XBYRT) is a Chinese herbal medicine formulated to mitigate symptoms of cancer-related fatigue. XBYRT comprises of 15 herbal components which are commonly used in traditional Chinese medicine. Objectives: In this study, the in vitro inhibition of cytochrome P450 3A4 (CYP3A4) and cytochrome P450 2D6 (CYP2D6) activities, along with the in vitro liver cell toxicity were evaluated for XBYRT and the individual herbal components. Materials and Methods: CYP3A4 and CYP2D6 inhibitions were assayed using the Vivid® CYP450 screening kits and liver cell toxicity in L-02 cells was analyzed using the 3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl) -2-(4-sulfophenyl)-2H-tetrazolium cell viability kit. The half maximal inhibitory concentrations (IC50) for CYP450 inhibition and cell viability were determined using the non-linear regression from GraphPad Prism. Results: The IC50 for CYP3A4 and CYP2D6 activities were 980 (942–1019) μg/ml and 1159 (1066–1261) μg/ml, respectively, for the XBYRT. The herbal components with the lowest IC50 values for CYP3A4 activity were Radix Paeoniae Alba (144 μg/ml) and Rhizoma Cyperi (278 μg/ml), while herbal components with the lowest IC50 values for CYP2D6 activity were Radix Codonopsis pilosulae (437 μg/ml) and Fructus Ligustri Lucidi (447 μg/ml). At the concentration of 256 μg/ml, XBYRT did not exhibit liver cell toxicity, with a 100% cell viability. Conclusion: The herbal components assessed did not demonstrate potent inhibitions of CYP3A4 and CYP2D6; however, precaution is recommended for breast cancer patients taking tamoxifen as the long-term impact of the herb-drug interaction is unclear. Further, in vivo and pharmacokinetic studies are required to ascertain the actual clinical significance of potential herb–drug interactions. [ABSTRACT FROM AUTHOR]

Autoimmune hepatitis (AIH) is a severe and chronic liver disease, and its incidence has increased worldwide in recent years. Research into the pathogenesis of AIH remains limited largely owing to the lack of suitable mouse models. The concanavalin A (ConA) mouse model is a typical and well-established model used to investigate T cell-dependent liver injury. However, ConA-induced hepatitis is acute and usually disappears after 48 h; thus, it does not mimic the pathogenesis of AIH in the human body. Several studies have explored various AIH mouse models, but as yet there is no widely accepted and valid mouse model for AIH. Immunosuppression is the standard clinical therapy for AIH, but patient side effects and recurrence limit its use. Regulatory T cells (Tregs) play critical roles in the maintenance of immune homeostasis and in the prevention of autoimmune diseases, which may provide a potential therapeutic target for AIH therapy. However, the role of Tregs in AIH has not yet been clarified, partly because of difficulties in diagnosing AIH and in collecting patient samples. In this review, we discuss the studies related to Treg in various AIH mouse models and patients with AIH and provide some novel insights for this research area.

Concetta Dagostino,1,2 Massimo Allegri,2–4 Valerio Napolioni,5 Simona D’Agnelli,1 Elena Bignami,1 Antonio Mutti,1 Ron HN van Schaik6 1Department of Medicine and Surgery, University of Parma, Parma 43126, Italy; 2Study In Multidisciplinary Pain Research (SIMPAR), Milan 20100, Italy; 3Anesthesia and Intensive Care Department, IRCCS Multi Medica Hospital, Milan 20099, Italy; 4Italian Pain Institute, Milan 20100, Italy; 5Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; 6Department of Clinical Chemistry, Erasmus MC, 3000 Rotterdam, The Netherlands Background: Opioids are widely used for chronic low back pain (CLBP); however, it is still unclear how to predict their effectiveness and safety. Codeine, tramadol and oxycodone are metabolized by CYP/CYP450 2D6 (CYP2D6), a highly polymorphic enzyme linked to allele-specific related differences in metabolic activity.Purpose: CYP2D6 genetic polymorphisms could potentially help to predict the effectiveness and safety of opioid-based drugs in clinical practice, especially in the treatment of CLBP.Patients and methods: A cohort of 224 Italian patients with CLBP treated with codeine or oxycodone was retrospectively evaluated to determine whether adverse reactions and effectiveness were related to CYP2D6 single-nucleotide polymorphisms. CYP2D6 genotyping was performed using the xTAG® CYP2D6 Kit v3 (Luminex) to determine CYP2D6 metabolizer phenotype (poor, intermediate, rapid and ultrarapid). Subjects from the cohort were categorized into two groups according to the occurrence of side effects (Case) or benefit (Control) after chronic analgesic treatment. The impact of CYP2D6 polymorphism on treatment outcome was tested at the metabolizer phenotype, diplotype and haplotype levels.Results: CYP2D6 polymorphism was significantly associated with opioid treatment outcome (Omnibus P=0.018, for both global haplotype and diplotype distribution test). CYP2D6*6 and *9 carriers, alleles characterized by a reduced (*9) or absent (*6) enzymatic activity, were significantly (P

Autoimmune hepatitis (AIH) is a severe and chronic liver disease, and its incidence has increased worldwide in recent years. Research into the pathogenesis of AIH remains limited largely owing to the lack of suitable mouse models. The concanavalin A (ConA) mouse model is a typical and well-established model used to investigate T cell-dependent liver injury. However, ConA-induced hepatitis is acute and usually disappears after 48 h; thus, it does not mimic the pathogenesis of AIH in the human body. Several studies have explored various AIH mouse models, but as yet there is no widely accepted and valid mouse model for AIH. Immunosuppression is the standard clinical therapy for AIH, but patient side effects and recurrence limit its use. Regulatory T cells (Tregs) play critical roles in the maintenance of immune homeostasis and in the prevention of autoimmune diseases, which may provide a potential therapeutic target for AIH therapy. However, the role of Tregs in AIH has not yet been clarified, partly because of difficulties in diagnosing AIH and in collecting patient samples. In this review, we discuss the studies related to Treg in various AIH mouse models and patients with AIH and provide some novel insights for this research area. [ABSTRACT FROM AUTHOR]

Background: The β‐blockers and antidepressants are two of the most commonly prescribed drug classes in the United States. Several antidepressants are potent inhibitors of cytochrome P450 2D6 liver enzymes (CYP2D6) and can increase the plasma concentrations of certain β‐blockers when administered concomitantly, potentially leading to serious medical consequences such as hypotension, bradycardia, and falls. Objective: The primary objective of this investigation was to determine whether initiating an antidepressant in patients receiving β‐blockers increased the risk of hemodynamic adverse events. Our primary outcome was time to hospital admissions or emergency department (ED) visits for an International Classification of Diseases‐9 diagnosis suggestive of excessive β‐blockade. Methods: We conducted a survival analysis for adults continuously enrolled in the California Medicaid system (Medi‐Cal) between 2004 and 2012. Eligible patients were required to be receiving β‐blocker medications that are primarily CYP2D6 substrates (e.g., metoprolol, propranolol, or carvedilol). Univariate and multivariable analyses were performed for patients who concurrently received antidepressants with β‐blockers. An additional multivariable analysis analyzed the association of this combination upon hospitalizations or ED visits for all causes. Results: A total of 21,292 beneficiaries met the inclusion criteria, and 4.3% of patients required hospitalization or ED visits within 30 days of co‐medication. In multivariable analysis, patients receiving antidepressants with moderate to strong CYP2D6 inhibitory potential (fluoxetine, paroxetine, duloxetine, or bupropion) had a greater risk for hospitalization or ED visits for hemodynamic events than those initiated on antidepressants with weak CYP2D6 inhibition for 30 days or less when each was compared with patients receiving no antidepressants (hazard ratio [HR] 1.53, 95% confidence interval [CI] 1.03–2.81; p=0.04 vs HR 1.24; 95% CI 0.82–1.88; p=0.30). Other demographic variables associated with increased morbidity included advanced age, male sex, higher β‐blocker doses, and African American race or Hispanic ethnicity. Conclusions: Results of this analysis suggest that initiation of certain antidepressants was associated with an increased risk for serious medical sequelae among patients concurrently receiving β‐blockers. Greater risk was observed with antidepressants that potently inhibit the CYP2D6 enzyme, implying that increased morbidity may be mediated by a metabolic drug interaction. [ABSTRACT FROM AUTHOR]

OBJECTIVES: Cytochrome P450 2D6 (CYP2D6) enzyme metabolizes a quarter of prescription drugs. Polymorphisms of CYP2D6 gene and resultant phenotypic variations in metabolic activity have been described in various populations. We assessed the prevalence of CYP2D6 activity phenotypes, employing dextromethorphan (DXM) as probe drug in subjects with at least two parental generations residing in eastern India. MATERIALS AND METHODS: Unrelated healthy subjects took 60 mg DXM after fasting overnight. Blood samples were collected 3 h after dosing and plasma separated. DXM and its primary metabolite dextrorphan (DXT) were measured by liquid chromatography with tandem mass spectrometry. The DXM-to-DXT metabolic ratio (MR) was obtained for each subject. Histogram of MR values suggested bimodal distribution. A polynomial regression equation derived through probit analysis was solved to identify the antimode of the MR values. Subjects with log(MR) < antimode were extensive metabolizers (EMs). Log(MR) = antimode indicated poor metabolizers (PMs). RESULTS: We evaluated the results from 97 participants. The median MR was 0.209 (interquartile range: 0.090-0.609), while the antimode for MR was 3.055. From these, it was inferred that three subjects were PMs, while the rest were EMs. CYP2D6 polymorphism prevalence is low (3.09%; 95% confidence interval: 0.35%-6.54%) in the population of eastern India and matches the prevalence in other zones of the country. CONCLUSIONS: Differences in CYP2D6 activity has treatment implications and may lead to adverse events or therapeutic failure. Phenotyping of subjects receiving CYP2D6 metabolized drugs may help clinicians personalize treatment and avert adverse drug-drug interactions. However, the frequency of the PM phenotype is low in India, and routinely phenotyping for CYP2D6 activity will not be cost-effective. We cannot recommend it at this stage. [ABSTRACT FROM AUTHOR]

Maribavir is an investigational drug being evaluated in transplant recipients with cytomegalovirus infection. To understand potential drug‐drug interactions, we examined the effects of multiple doses of maribavir on cytochrome P450 (CYP) 2D6 and P‐glycoprotein (P‐gp) activity using probe substrates in healthy volunteers. During this phase 1 open‐label study (NCT02775240), participants received the probe substrates digoxin (0.5 mg) and dextromethorphan (30 mg) before and after maribavir (400 mg twice daily for 8 days). Serial plasma samples were analyzed for digoxin, dextromethorpha, dextrorphan, and maribavir concentrations. Pharmacokinetic parameters were calculated (noncompartmental analysis) and analyzed with a linear mixed‐effects model for treatment comparison to estimate geometric mean ratios (GMRs) and 90% confidence intervals (CIs). CYP2D6 polymorphisms were genotyped using polymerase chain reaction. Overall, 17 of 18 participants (94.4%) completed the study. All participants were genotyped as CYP2D6 intermediate/extensive metabolizers. GMR (90%CI) of digoxin Cmax, AUClast, and AUC0‐∞ with and without maribavir was 1.257 (1.139‐1.387), 1.187 (1.088‐1.296), and 1.217 (1.110‐1.335), respectively, outside the "no‐effect" window (0.8‐1.25). GMR (90%CI) of dextromethorphan AUClast and AUClast ratio of dextromethorphan/dextrorphan were 0.877 (0.692‐1.112) and 0.901 (0.717‐1.133), respectively, marginally outside the no‐effect window, although large variability was observed in these pharmacokinetic parameters. Pharmacokinetic parameters of dextrorphan were unaffected. Maribavir inhibited P‐gp activity but did not affect CYP2D6 activity. Maribavir's effect on the pharmacokinetics of P‐gp substrates should be evaluated individually, and caution should be exercised with P‐gp substrates with narrow therapeutic windows. [ABSTRACT FROM AUTHOR]

One major source of inter-individual variability in drug pharmacokinetics is genetic polymorphism of the cytochrome P450 (CYP) genes. This study aimed to elucidate the enzyme kinetic and molecular basis for altered activity in three major alleles of CYP2D6, namely CYP2D6*2, CYP2D6*10 and CYP2D6*17. The E. coli-expressed allelic variants were examined using substrate (venlafaxine and 3-cyano-7-ethoxycoumarin[CEC]) and inhibitor (quinidine, fluoxetine, paroxetine, terbinafine) probes in enzyme assays as well as molecular docking. The kinetics data indicated that R296C and S486T mutations in CYP2D6*2 have caused enhanced ligand binding (enhanced intrinsic clearance for venlafaxine and reduced IC50 for quinidine, paroxetine and terbinafine), suggesting morphological changes within the active site cavity that favoured ligand docking and binding. Mutations in CYP2D6*10 and CYP2D6*17 tended to cause deleterious effect on catalysis, with reduced clearance for venlafaxine and CEC. Molecular docking indicated that P34S and T107I, the unique mutations in the alleles, have negatively impacted activity by affecting ligand access and binding due to alteration of the substrate access channel and active site morphology. IC50 values however were quite variable for quinidine, fluoxetine and terbinafine, and a general decrease in IC50 was observed for paroxetine, suggesting ligand-specific altered susceptibility to inhibition in the alleles. This study indicates that CYP2D6 allele selectivity for ligands was not solely governed by changes in the active site architecture induced by the mutations, but that the intrinsic properties of the substrates and inhibitors also played vital role. [ABSTRACT FROM AUTHOR]

Cytochrome P450 2D6 (CYP2D6) is an important drug metabolizing enzyme involved in the pharmacokinetic metabolism of drugs. CYP2D6 gene is highly polymorphic, and the combination of its different alleles yields different phenotypes including extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), and ultrarapid metabolizer (UM). Genotyping of the important alleles for this gene in different ethnicities is of particular importance for assessing the efficacy of various drugs. In this study, we reviewed the CYP2D6 allele and phenotype frequencies predicted from the genotypes of CYP2D6 in the Middle East area. Regardless of different ethnicities, the CYP2D6*41 allele frequency was shown to be higher than that of other reduced functional alleles. In addition, CYP2D6*4 was the most frequent nonfunctional allele in all studied populations in the Middle East. Taken together, our findings illustrated that the frequencies of PM or IM alleles and different genotypes harboring these alleles are relatively high in the Middle Eastern countries. Therefore, the study of CYP2D6 alleles for each patient to detect those that are at risk is of great importance to prevent adverse drug reactions through individualization therapy. [ABSTRACT FROM AUTHOR]

Paul Y Takahashi,1 Euijung Ryu,2 Jyotishman Pathak,2 Gregory D Jenkins,2 Anthony Batzler,2 Matthew A Hathcock,2 John Logan Black,3 Janet E Olson,2 James R Cerhan,2 Suzette J Bielinski2 1Division of Primary Care Internal Medicine, Department of Medicine, 2Department of Health Sciences Research, 3Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA Background: Cytochrome P450 2D6 (CYP2D6) is responsible for the metabolism of clinically used drugs and other environmental exposures, but it is unclear whether the CYP2D6 phenotype is associated with adverse health outcomes. The aim was to determine the association of CYP2D6 phenotype with the risk of hospitalization or an emergency department (ED) visit among a group of primary care patients. Methods: In this study, 929 adult patients underwent CYP2D6 testing. The primary outcome was risk of hospitalization or an ED visit from January 2005 through September 2014. CYP2D6 genotypes were interpreted as 1 of 7 clinical phenotypes, from ultrarapid to poor metabolizer, and patients with the extensive metabolizer phenotype were used as the reference group. The hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for finding the association of CYP2D6 phenotypes with the risk of hospitalization or an ED visit by using Cox proportional hazard models and adjusting for age and sex. Results: The median age was 49 years (interquartile range, 46–52 years); 74% of patients had 3 or fewer chronic conditions, 285 had at least 1 hospitalization, and 496 had at least 1 ED visit. The risk of hospitalization was higher among patients who were ultrarapid metabolizers compared to extensive metabolizers (47% vs 30%; HR, 1.69; 95% CI, 1.11–2.57), as was the risk of an ED visit (62% vs 49%; HR, 1.50; 95% CI, 1.05–2.14). For poor metabolizers compared to extensive metabolizers, there was no difference in the risk of hospitalization (HR, 0.95; 95% CI, 0.58–1.56), but there was an increase in the risk of an ED visit (HR, 1.38; 95% CI, 0.96–1.98) (the difference was not statistically significant). Conclusion: We found an increased risk of hospitalization or an ED visit among ultrarapid compared to extensive CYP2D6 metabolizers. Further research identifying the mechanisms of the association and ultimate clinical utility is warranted. Keywords: cohort study, pharmacogenomics, emergency department, hospitalization

My research focused on the effects of various drugs on (1) dopamine formation from p-tyramine catalyzed by polymorphic cytochrome P450 (CYP or P450) 2D6 variants and (2) endogenous steroid hormone hydroxylation catalyzed by CYP3A subfamily members (CYP3A4, CYP3A5, CYP3A7). The activation (cooperativity) of metabolic reactions catalyzed by P450s was especially emphasized. The effects of various psychotropic agents on dopamine formation from p-tyramine, catalyzed by wild-type CYP2D6.1 and CYP2D6 variants, including CYP2D6.2 (Arg296Cys;Ser486Thr), CYP2D6.10 (Pro34Ser;Ser486Thr), and CYP2D6.39 (Ser486Thr) were compared. Michaelis (K m ) and inhibition (K i ) constants of the psychotropic agents in the presence of CYP2D6.10 were higher than those observed in the presence of other CYP2D6 variants. Fluvoxamine, fluoxetine, milnacipran, and haloperidol activated CYP2D6-catalyzed dopamine formation [decreasing the K m and/or increasing the maximal velocity (k cat )], and this activation was CYP2D6 variant-dependent. Regarding the CYP3A subfamily, the effects of various compounds including endogenous steroid hormones on the 6β-hydroxylation of steroid hormones, such as testosterone, progesterone, and cortisol, were determined; it was found that testosterone, dehydroepiandrosterone, and/or α-naphthoflavone activated 6β-hydroxylation of cortisol and/or progesterone, but the effects varied in the presence of different CYP3A subfamily members. Further studies are required to confirm the mechanisms and therapeutic relevance of these activation phenomena.

Graphical abstract Abstract We investigate the mechanism of time-dependent inhibition (TDI) of human cytochrome P450 2D6 (CYP2D6) by 3,4-methylenedioxymethamphetamine (MDMA, ecstasy), one of the most widespread recreational drugs of abuse. In an effort to unravel the kinetic mechanism of the formation of metabolic inhibitory complex (MIC) of CYP2D6 with MDMA-derived carbene we carried out a series of spectrophotometric studies paralleled with registration of the kinetics of time-dependent inhibition (TDI) in CYP2D6-incorporated proteoliposomes. The high amplitude of spectral signal in this system allowed us to characterize the spectral properties of the formed MIC in details and obtain an accurate spectral signature of MIC formation. This information was then used in the studies with CYP2D6-containing microsomes of insect cells (CYP2D6 Supersomes™). Our results demonstrate that in both systems the formation of the ferrous carbene-derived MIC is relatively slow, reversible and is not associated with the accumulation of the ferric carbene intermediate, as takes place in the case of CYP3A4 and podophylotoxin. Furthermore, the limited amplitude of MIC formation suggests that only a fraction (∼50%) of spectrally detectable CYP2D6 in both proteoliposomes and Supersomes participates in the formation of MIC and is therefore involved in the MDMA metabolism. This observation reveals yet another example of a cytochrome P450 that exhibits persistent functional heterogeneity of its population in microsomal membranes. Our study provides a solid methodological background for further mechanistic studies of MIC formation in human liver microsomes and demonstrates that the potency and physiological relevance of MDMA-dependent TDI of CYP2D6 may be overestimated. [ABSTRACT FROM AUTHOR]

Methamphetamine (MA) is an illicit stimulant that affects the central nervous system. Cytochrome P450 2D6 (CYP2D6) plays an important role in MA metabolism. Numerous allelic variants confer substantial variation in CYP2D6 activity among individuals. In the present study, we examined the frequencies of CYP2D6 alleles, including CYP2D6*1, *2, *4, *5, *10, *14A, *14B, *18, and *36, and multiplication, in 82 forensic autopsy cases of MA abusers and 567 autopsy cases in which MA was not detected (controls). Ultrarapid metabolizer (UM), extensive metabolizer (EM), intermediate metabolizer (IM), and poor metabolizer (PM) phenotypes were predicted from CYP2D6 genotypes. Of MA abusers, 64 subjects were predicted to be EM, 17 were IM, and 1 was UM. No MA abuser had the predicted PM phenotype. No significant differences in CYP2D6 phenotype frequencies were found between MA abusers and controls. MA and amphetamine (AMP) concentrations were measured in the right heart blood, left heart blood, peripheral external iliac blood, urine, pericardial fluid, and bone marrow of MA abusers. MA concentrations in urine and bone marrow were significantly higher in IM than in EM. AMP concentration was not associated with CYP2D6 phenotype in any body fluid. These results suggest that the MA concentration in body fluids is influenced by CYP2D6 phenotypes in the Japanese population. [ABSTRACT FROM AUTHOR]

Objective: Many studies have shown the association of susceptibility to several cancers with gene encoding enzymes' polymorphisms which engage in xenobiotics' biotransformation. In this study, the main purpose is to search the relation between cytochrome P450 (CYP) 2D6* 4 polymorphisms and Polycythemia vera (PV) incidence in Turkish population. Materials and Methods: In this research article, 80 Polycthemia vera (PV) cases and 76 control samples have been used for the analysis of CYP 2D6* 4 polymorphism. The research has been performed by the methods of polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Results: As a result, when patients and controls were compared in terms of CYP 2D6* 4 poor metabolizer (PM) and heterozygous extensive metabolizer (HEM) genotype frequency, it has been found that the patients have 1.35% PM and 32.43% HEM frequency, and controls have 2.63% PM and 21.05% HEM frequency. The correlation between the results of CYP 2D6 genotype analysis and the risk of disease in patients and controls was examined. We found that PM, HEM and extensive metabolizer (EM) genotypes were unrelated with the risk of PV (OR 0.51, 95% CI 0.04-5.71, OR 1.80, 95% CI 0.86-3.75, χ² 1.93, P: 0.164, OR 0.61, 95% CI 0.30-1.24, χ² 1.40, P: 0.235). Conclusion: Our results suggested that the CYP 2D6* 4 polymorphism, in the studied population, does not play an important role in PV etiology. [ABSTRACT FROM AUTHOR]

The CYP2D6 enzyme is crucial for the metabolism of tamoxifen. The CYP2D6 gene is highly polymorphic, and individuals can be extensive, intermediate, or poor tamoxifen metabolizers. The aim of this study was to determine the frequencies of the CYP2D6 *3, *4, and *10 alleles in women with breast cancer who were treated with tamoxifen and analyze the association of enzyme activity with prognostic factors and disease-free survival. We observed a high frequency of CYP2D6 *10, with an allelic frequency of 0.14 (14.4%). The *3 allele was not present in the studied population, and *4 had an allelic frequency of 0.13 (13.8%). We conclude that patients with reduced CYP2D6 activity did not present worse tumor characteristics or decreased disease-free survival than women with normal enzyme activity, as the difference was not statistically significant. We also observed a high frequency of CYP2D6 *10, which had not been previously described in this specific population. This study is the first in north-northeastern Brazil that aimed to contribute to the knowledge of the Brazilian regional profile for CYP2D6 polymorphisms and their phenotypes. These findings add to the knowledge of the distribution of different polymorphic CYP2D6 alleles and the potential role of CYP2D6 genotyping in clinical practice prior to choosing therapeutic protocols.

CYP2D6 and SULT1A1 occasionally show copy number variations (CNVs), with a larger number generally indicating greater enzymic activity. However, those variations are difficult to calculate using standard methods. With digital PCR, a recently introduced method for CNV analysis, DNA molecules are subjected to limited dilution and separated into nanoscale droplets prior to a PCR assay. Absolute quantitation of copy number can then be performed with high accuracy and sensitivity by determining the number of droplets showing an amplified signal for the target gene. This is the first report of analyses of CYP2D6 and SULT1A1 CNVs using a digital PCR method with blood sample from Japanese subject. Primers and probes were synthesized for the target and reference genes, and copy number calculation was performed using a QX200 Droplet Digital PCR System. Our results showed that the copy numbers in CYP2D65 hetero, non-CNV, and CYP2D6xN subjects were 1, 2, and 3 to 4, respectively. In addition, in non-CNV and multiplication subjects, the number of copies for SULT1A1 was 2 and 3 to 6, respectively. We found that the present digital PCR method was useful as well as accurate. In the future, a combined genotyping, allele distinction, and copy number calculation technique will be helpful for analysis of enzymic activity. [ABSTRACT FROM AUTHOR]

Autoimmune hepatitis (AIH) is defined as a chronic liver inflammation with loss of tolerance against hepatocytes. The etiology and pathophysiology of AIH are still poorly understood because reliable animal models are limited. Therefore, we recently introduced a model of experimental murine AIH by a self-limited adenoviral infection with the AIH type 2 antigen formiminotransferase cyclodeaminase (FTCD). We could demonstrate that break of humoral tolerance towards liver specific autoantigens like FTCD and cytochrome P450 2D6 (CYP2D6) is not dependent on the genetic background. However, the development of AIH in autoantibody positive animals is determined by genetic background genes. We could also show that the break of humoral tolerance is necessary but not sufficient for the development of AIH. In contrast the break of tolerance against the ubiquitously expressed nuclear antigens (ANAs) is strictly dependent on genetic predisposition. Priming with the UGA suppressor tRNA-associated protein (soluble liver antigen; SLA) is a strong inducer of ANA reactivity, but not sufficient to cause AIH development thereby questioning the importance of anti-SLA immune response as an important driver in AIH. Monogenetic mutations such as Aire-deficiency can cause AIH in otherwise genetically resistant strains. Conclusion The results have important implications for our understanding of the pathophysiology of AIH development and for the interpretation of humoral antibody responses in AIH. [ABSTRACT FROM AUTHOR]

The organic cation transporter 1 (OCT1) mediates the cell uptake and cytochrome P450 2D6 (CYP2D6) the metabolism of many cationic substrates. Activities of OCT1 and CYP2D6 are affected by enormous genetic variation and frequent drug-drug interactions. Single or combined deficiency of OCT1 and CYP2D6 might result in dramatic differences in systemic exposure, adverse drug reactions, and efficacy. Thus, one should know what drugs are affected to what extent by OCT1, CYP2D6 or both. Here, we compiled all data on CYP2D6 and OCT1 drug substrates. Among 246 CYP2D6 substrates and 132 OCT1 substrates, we identified 31 shared substrates. In OCT1 and CYP2D6 single and double-transfected cells, we studied which, OCT1 or CYP2D6, is more critical for a given drug and whether there are additive, antagonistic or synergistic effects. In general, OCT1 substrates were more hydrophilic than CYP2D6 substrates and smaller in size. Inhibition studies showed unexpectedly pronounced inhibition of substrate depletion by shared OCT1/CYP2D6 inhibitors. In conclusion, there is a distinct overlap in the OCT1/CYP2D6 substrate and inhibitor spectra, so in vivo pharmacokinetics and -dynamics of shared substrates may be significantly affected by frequent OCT1- and CYP2D6-polymorphisms and by comedication with shared inhibitors. [Display omitted] • About 50 % of cationic drugs are either substrates of OCT1 or CYP2D6 or of both. • These substrates may be affected by the OCT1 or CYP2D6 genetic polymorphisms. • CYP2D6 substrates are more lipophilic and larger in molecular weight than OCT1 substrates. • There were additive effects and complex interactions between OCT1 and CYP2D6. [ABSTRACT FROM AUTHOR]

In this work, a simple and accurate in vitro drug metabolism strategy was proposed by using macroporous ordered siliceous foam (MOSF) as a nanoreactor for confining the nanohybrid of CdTe quantum dots (QDs) and cytochrome P450 2D6 (CYP2D6). After CYP2D6 was coupled to QDs through the carbodiimide coupling chemistry, the resulting nanohybrid of CYP2D6/QDs exhibited fluorescence emission at 645 nm, which could be used as a photocatalyst for drug metabolism. The energy level of CYP2D6 was located between the conduction band (CB) and valence band (VB) of QDs, which provided the possibility of the electron transferring from the CB of QDs to CYP2D6. Tramadol was chosen as the model substrate. Under the irradiation of a white-light, the photocurrent increased with the addition of tramadol in a wide linear range from 4.0 μM to 100 μM. The apparent Michaelis–Menten constant was measured to be 3.6 μM. The high performance liquid chromatography coupled with mass spectrometry (HPLC–MS) confirmed the production of metabolite of o -desmethyltramadol. Such nanoreactor provided a suitable environment to confine a mass of enzyme, as well as to maintain their catalytic activities for highly effective drug metabolic reactions. This showed promising potential for immobilizing various enzymes and other biomolecules in biomimetic metabolism study. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the catalytic activity of 22 novel CYP2D6 allelic variants (2D6*87-*98, R25Q, F164L, E215K, F219S, V327M, D336N, V342M, R344Q, R440C and R497C) to olanzapine in vitro. Their protein products expressed in Spodoptera frugiperda 21 (Sf21) insect cells were incubated with olanzapine 100-2,000 µmol/l for 30 min. The kinetic parameters of Km, Vmax and intrinsic clearance were determined by 2-hydroxymethylolanzapine, the metabolite of olanzapine mediated by CYP2D6, using ultra-performance liquid chromatography tandem mass spectrometry. Results showed that the kinetic parameters of 2 alleles, CYP2D6*92 and 2D6*96, could not be detected; 17 allelic variants, CYP2D6*87-*88, 2D6*90-*91, 2D6*93-*95, 2D6*97, R25Q, F164L, E215K, F219S, V327M, V342M, R344Q, R440C and R497C, significantly reduced the intrinsic clearance of olanzapine; 2 variants, CYP2D6*89 and 2D6*98, increased the intrinsic clearance of olanzapine; no difference was found in intrinsic clearance of D336N. Furthermore, 6 alleles, CYP2D6*87, 2D6*88, 2D6*91, 2D6*93, 2D6*97 and R497C, exhibited high er Km values in a range of 120.80-217.56% relative to wildtype CYP2D6*1. The research demonstrated the metabolic phenotype of the 22 novel CYP2D6 variants for olanzapine that were different from probe drugs we used previously and might provide beneficial information to the personalized medicine of olanzapine. [ABSTRACT FROM AUTHOR]

• A new approach to prepare TTF–TCNQ/IL gel. • MWNT/IL gel is used as the matrix of TTF–TCNQ/IL gel. • The synergetic effect of MWNT/IL and TTF–TCNQ/IL promote the catalysis of CYP2D6. • Low detection limit for perphenazine. A cytochrome P450 2D6 (CYP2D6) biosensor was developed with the incorporation of multi-walled carbon nanotube/ionic liquid and tetrathiafulvalene-tetracyanoquinodimethane salt/ionic liquid (MWNT/IL-[TTF–TCNQ]/IL) gels. The MWNT/IL-[TTF–TCNQ]/IL gels were characterized using Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, and scanning electron microscopy. Utilizing the excellent stability of the MWNT/IL gel and the unique structure of the [TTF–TCNQ]/IL gel, CYP2D6 was immobilized on the screen-printed electrode with high bioactivity. Moreover, the CYP2D6 catalytic effect was highly promoted upon application of MWNT/IL-[TTF–TCNQ]/IL gels as the mediating system. The proposed MWNT/IL-[TTF–TCNQ]/IL gel-based CYP2D6 biosensor was used to detect perphenazine via voltammetry and amperometry. The calibration of perphenazine ranged from 6 × 10−8 to 1.6 × 10−5 M with a detection limit of 2.05 × 10−8 M. It is expected that the MWNT/IL-[TTF–TCNQ]/IL gel-based CYP2D6 biosensor opens new avenues for promising advances in the analysis of drugs. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently an iterative method was proposed to enhance the accuracy and efficiency of ligand-protein binding affinity prediction through linear interaction energy (LIE) theory. For ligand binding to flexible Cytochrome P450s (CYPs), this method was shown to decrease the rootmean- square error and standard deviation of error prediction by combining interaction energies of simulations starting from different conformations. Thereby, different parts of protein-ligand conformational space are sampled in parallel simulations. The iterative LIE framework relies on the assumption that separate simulations explore different local parts of phase space, and do not show transitions to other parts of configurational space that are already covered in parallel simulations. In this work, a method is proposed to (automatically) detect such transitions during the simulations that are performed to construct LIE models and to predict binding affinities. Using noise-canceling techniques and splines to fit time series of the raw data for the interaction energies, transitions during simulation between different parts of phase space are identified. Boolean selection criteria are then applied to determine which parts of the interaction energy trajectories are to be used as input for the LIE calculations. Here we show that this filtering approach benefits the predictive quality of our previous CYP 2D6-aryloxypropanolamine LIE model. In addition, an analysis is performed of the gain in computational efficiency that can be obtained from monitoring simulations using the proposed filtering method and by prematurely terminating simulations accordingly. [ABSTRACT FROM AUTHOR]

Aims: Cytochrome P450 (CYP450) 2D6 is an important member of the P450 enzyme superfamily and responsible for clearing 25% of clinically important drugs. The aim of this study was to assess the catalytic characteristics of 24 CYP2D6 allelic isoforms found in the Chinese population and their effects on the metabolism of risperidone in vitro. Methods: Insect microsomes expressing wild-type CYP2D6 and 24 CYP2D6 allelic variants were incubated with 20-1,000 μmol/l risperidone for 40 min at 37°C. After termination, risperidone and 9-OH risperidone, the metabolite of risperidone, were precipitated and used for signal collection by ultra-performance liquid-chromatography tandem mass spectrometry. Results: Among 24 CYP2D6 variants tested, 2 variants (CYP2D6*92 and CYP2D6*96) were found to be with no detectable activity. Two variants (E215K and R440C) exhibited higher intrinsic clearance values than the wild-type protein, while the remaining 20 CYP2D6 allelic variants exhibited significantly decreased clearance values (2.01-87.56%) compared to CYP2D6*1. Conclusion: These findings suggest that more attention should be directed to subjects carrying these infrequent CYP2D6 alleles when administering risperidone in the clinic. This is the first report of all these novel alleles for risperidone metabolism, providing fundamental data for further clinical studies on CYP2D6 alleles. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

To report a sinus bradycardia induced by metoprolol and terbinafine drug-drug interaction and its management. A 63 year-old Caucasian man on metoprolol 200 mg/day for stable coronary artery disease was prescribed a 90-day course of oral terbinafine 250 mg/day for onychomycosis. On the 49th day of terbinafine therapy, he was brought to the emergency room for a decrease of his global health status, confusion and falls. The electrocardiogram revealed a 37 beats/min sinus bradycardia. A score of 7 on the Naranjo adverse drug reaction probability scale indicates a probable relationship between the patient's sinus bradycardia and the drug interaction between metoprolol and terbinafine. The heart rate ameliorated first with a decrease in the dose of metoprolol. It was subsequently changed to bisoprolol and the heart rate remained normal. By inhibiting the cytochrome P450 2D6, terbinafine had decreased metoprolol's clearance, leading in metoprolol accumulation which has resulted in clinically significant sinus bradycardia. [ABSTRACT FROM AUTHOR]

Objective: Tramadol is a synthetic opioid which has analgesic efficacy in the postoperative pain. It is metabolized by polymorphic enzyme cytochrome P450 ( CYP2D6). Patients with different CYP2D6 genotypes would have different responses to tramadol in pain relief. The CYP2D6* 10 allele is the most common allele in a Chinese population. The aim of this study was to evaluate whether the different CYP2D6* 10 genotypes have an effect on the postoperative tramadol analgesia in the Chinese population after elective nephrectomy. Methods: One hundred and twenty patients after performed elective nephrectomy were enrolled in this study after being approved by the local Ethics Committee. The patients were given patient-controlled analgesia (PCA) which included 10 mg/ml tramadol after receiving a loading dose of 100 mg tramadol and 1 mg granisetron intravenously. Blood samples were collected after induction of anesthesia. The CYP2D6* 10 polymorphism was analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). According to the results, the patients were divided into three groups ( CYP2D6* 1/* 1, n = 33; CYP2D6* 1/* 10, n = 28; CYP2D6* 10/* 10, n = 50). The total consumption of tramadol, visual analogue scale (VAS) score, and PCA control times among the three genotype groups for 2, 4, 24, 48, and 72 h after operation were compared. Results: Nine out of 120 patients were dropped out of the study; 111 patients completed the study. The frequency of CYP2D6* 10 allele was 57.7 %. The demographic data among the three groups were comparable. The consumption of tramadol, patient self-control times of pump, and VAS score in CYP2D6* 10/* 10 group were significantly higher than that in CYP2D6* 1/* 1 or CYP2D6* 1/* 10 group at 2 and 4 h ( P < 0.05), while it did not differ between CYP2D6* 1/* 1 and CYP2D6* 1/* 10 group ( P > 0.05). There was no difference in the incidence of nausea and vomiting among the three groups ( P > 0.05). No sever apnea was recorded in these groups. Conclusions: Different CYP2D6* 10 genotypes have an influence on the analgesic effect of tramadol in Han nationality patients after elective nephrectomy. [ABSTRACT FROM AUTHOR]

In this work, nanohybrids of CdTe quantum dots (QDs) and cytochrome P450 2D6 (CYP2D6) prepared by covalent binding of CYP2D6 to QDs were used as photocatalysts for drug metabolism. As a proof-of-concept of the light-driven drug metabolism, tramadol was chosen as the substrate. As control, the high performance liquid chromatography coupled with mass spectrometry (HPLC–MS) was used to confirm the production of metabolites. Under irradiation with a white-light, the catalytic cycle of P450-mediated oxygenation reactions occurred with the formation of radical species on QDs, which immediately activated the proximity of the bound P450 enzyme and transferred electrons from the conduction band (CB) of CdTe QDs to CYP2D6. This light-driven catalytic reaction via nanohybrids was comparable to the native biological metabolism by CYP2D6 isozyme microsomes with CYP reductase (CPR) using the enzyme cofactor nicotinamide-adenine dinucleotide phosphate (NADPH) as electron donor. Furthermore, a photoelectrochemical platform was designed for in-situ monitoring the metabolic reactions. Upon addition of tramadol, the photocurrent increased due to the electron transfer from the CB of CdTe QDs to CYP2D6. The apparent Michaelis–Menten constant was thus easily measured to be 1.35 μM. This enzyme-based photoelectrochemical platform showed accepted stability and great potential for studies on drug metabolism in vitro. [ABSTRACT FROM AUTHOR]

Considering the enzymatic activity of the cytochrome P450 2D6 on substrates such as codeine, the current paper includes the development of an enzymatic biosensor for detection of this drug. Home-made screen-printed electrodes were used as electrochemical transducers of the biosensor, in which the enzyme was covalently attached to the carbon surface of the working electrode, this type of modification being the most suitable for the immobilization of the biological element. Chronoamperometric measurements were carried out under optimum conditions of pH and working potential, pH 7 and +200 mV vs. screen-printed Ag/AgCl electrode, giving a reduction signal related to the concentration of codeine in solution. Consecutive additions of a solution of codeine were performed to obtain calibration curves in order to validate the electrochemical method in terms of precision and calculate its capability of detection. These biosensors were used for the determination of codeine in urine and commercial pharmaceutical samples. [ABSTRACT FROM AUTHOR]

Background: Cytochrome P450 2D6 (CYP2D6) metabolizes around 25% of the drugs used in therapeutics and different polymorphisms have been identified in various populations. This study aimed at finding the prevalence of CYP2D6 polymorphisms using dextromethorphan as a probe drug. Materials and Methods: Healthy participants were administered 60 mg dextromethorphan after an overnight fast and 5 ml of blood was collected 3 h postdose. A validated laboratory method was used to measure both dextromethorphan and its active metabolite, dextrorphan from plasma. Metabolic ratio (MR) of dextromethorphan to dextrorphan was calculated for each of the participants. Probit analysis was done and antimode was defined. Individuals with log MR equal to or higher than the antimode were classified as poor metabolizers (PMs) and those with values less than antimode were categorized as extensive metabolizers (EMs). Results: Data from a total of 149 participants were evaluated and the median (range) of MR was 0.25 (0.03-3.01). The polynomial equation obtained in probit analysis gave an antimode for MR of 1.39. Five (3.36%) participants were PMs and 144 (96.64%) were found to be EMs. One participant had reported mild drowsiness 2 h postdose that subsided spontaneously without any intervention. Conclusion: The prevalence of CYP2D6 polymorphism in Western Indian population is low (3.36%) and is similar to other populations. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether breast cancer (BC) patients with CYP2D6 gene variation have different clinical tamoxifen (TAM) treatment outcomes to those with normal function of CYP2D6. Methods: Systematic searches of the PubMed up to February 21, 2013, were retrieved. The study end points were disease-free survival (DFS) and overall survival (OS). Fixed or random-effects meta-analytical models were used to calculate summary hazard ratio (HR) and corresponding 95 % confidence intervals (CIs). Meta-regression, Galbraith plots, subgroup analysis, and sensitivity analysis were also performed. Results: A total of 11,701 BC patients from 20 trials were included. Compared with reduced CYP2D6 function, normal function was associated with a trend toward improved DFS (HR = 1.37, 95 % CI 1.12-1.69, P = 0.002) and OS (HR = 1.25, 95 % CI 1.03-1.50, P = 0.021). We found significant heterogeneity between studies. When the analysis was stratified into subgroups, significantly worse DFS was found in the groups of intermediate metabolizer versus extensive metabolizer (HR = 1.65, 95 % CI 1.04-2.64, P = 0.035), Asian population (HR = 3.29, 95 % CI 1.64-6.63, P = 0.001), 5 years TAM treatment duration (HR = 1.59; 95 % CI 1.14-2.22, P = 0.006), concomitant chemotherapy (HR = 1.35, 95 % CI 1.04-1.76, P = 0.025), and TAM alone (HR = 1.44, 95 % CI 1.44-2.06, P = 0.045). With respect to OS, no significant association was demonstrated in stratified analyses. Conclusions: We concluded that CYP2D6 polymorphisms may influence tamoxifen treatment outcomes of DFS in BC patients. [ABSTRACT FROM AUTHOR]

Chemotherapy-induced nausea and vomiting is one of the most concerning adverse drug effects from cytotoxic chemotherapy. Despite appropriate use of antiemetic guidelines, 20-30 % of patients experience breakthrough nausea and vomiting secondary to chemotherapy. To assess the variability of 5-hydroxytryptamine type 3 receptor antagonist efficacy caused by genetic variation, a review of the available literature was conducted. From the literature, three sources of pharmacogenomic variability were identified: polymorphisms associated with 5-hydroxytryptamine type 3 receptor subunits, drug metabolism via cytochromes P450, and drug transport in the body. Testing for receptor subunit polymorphisms is not applicable to a clinical setting at this time; however, cytochrome P450 2D6 testing is FDA-approved and widely accessible. Cytochrome P450 2D6 ultrarapid metabolizers and poor metabolizers displayed altered antiemetic efficacy when compared with intermediate metabolizers and extensive metabolizers. We postulate that testing for cytochrome P450 2D6 phenotypes may be the most accessible way to provide individualized antiemetic therapy in the future. [ABSTRACT FROM AUTHOR]

Abstract: CYP2D6 (cytochrome P450 2D6) is one of the most important enzymes involved in drug metabolism, and CYP2D6 gene variants may cause toxic effects of therapeutic drugs or treatment failure. In this research, a rapid and simple method for genotyping the most common mutant alleles in the Asian population (CYP2D6*1/*1, CYP2D6*1/*10, CYP2D6*10/*10, CYP2D6*1/*5, CYP2D6*5/*10, and CYP2D6*5/*5) was developed by allele-specific polymerase chain reaction (AS-PCR) combined with capillary electrophoresis (CE). We designed a second mismatch nucleotide next to the single nucleotide polymorphism (SNP) site in allele-specific primers to increase the difference in PCR amplification. Besides, we established simulation equations to predict the CYP2D6 genotypes by analyzing the DNA patterns in the CE chromatograms. The multiplex PCR combined with CE method was applied to test 50 patients, and all of the test results were compared with the DNA sequencing method, long-PCR method and real-time PCR method. The correlation of the analytical results between the proposed method and other methods were higher than 90%, and the proposed method is superior to other methods for being able to simultaneous detection of SNPs and copy number variations (CNV). Furthermore, we compared the plasma concentration of aripiprazole (a CYP2D6 substrate) and its major metabolites with the genotype of 25 patients. The results demonstrate the proposed genotyping method is effective for estimating the activity of the CYP2D6 enzyme and shows potential for application in personalized medicine. Similar approach can be applied to simultaneous detection of SNPs and CNVs of other genes. [Copyright &y& Elsevier]

Patients with infectious viral or toxic cirrhosis of the liver participated in complex clinical pathomorphological and molecular-genetic study aimed at the search for markers of predisposition to accelerated liver fibrosis, in which the xenobiotic biotransformation system is involved. The results demonstrate association between CYP2D6 (1846 G/A) genotype and rapid cirrhosis development and indicate the necessity of studying the mechanisms underlying this association. [ABSTRACT FROM AUTHOR]

Adjuvant tamoxifen therapy of breast cancer patients with estrogen receptor-positive tumors reduces the rate of breast cancer recurrence by approximately a half. Tamoxifen is metabolized by several polymorphic enzymes, including cytochrome P450 2D6 (CYP2D6), to more active metabolites. We have reviewed the clinical pharmacology of tamoxifen and evaluated the evidence from clinical epidemiology studies regarding the association between CYP2D6 inhibition and tamoxifen effectiveness. We conclude that the impact of CYP2D6 inhibition on tamoxifen effectiveness is likely to be null or small, at least in the populations studied so far. Understanding the effect of variations in tamoxifen metabolism on breast cancer outcomes, if any, will likely require a broader perspective, including examination of the complete metabolic pathway and subgroups of patients with other markers of potentially poor tamoxifen response. [ABSTRACT FROM AUTHOR]

Variations in cytochrome P450 (CYP) genes have been shown to be associated with both accelerated and delayed pharmacokinetic clearance of many psychotropic medications. Citalopram is metabolized by three CYP enzymes. CYP2C19 and CYP3A4 play a primary role in citalopram metabolism, whereas CYP2D6 plays a secondary role.The Sequenced Treatment Alternatives to Relieve Depression sample was used to examine the relationship between variations in the CYP2C19 and CYP2D6 genes and remission of depressive symptoms and tolerance to treatment with citalopram. The primary analyses were of the White non-Hispanic patients adherent to the study protocol (n=1074).Generally, patients who had CYP2C19 genotypes associated with decreased metabolism were less likely to tolerate citalopram than those with increased metabolism, although this difference was not statistically significant (P=0.06). However, patients with the inactive 2C19∗2 allele had significantly lower odds of tolerance (P=0.02). Patients with the poor metabolism CYP2C19 genotype-based category who were classified as citalopram tolerant were more likely to experience remission (P=0.03). No relationship between CYP2D6 genotype-based categories and either remission or tolerance was identified, although exploratory analyses identified a potential interaction between CYP2C19 and CYP2D6 effects.Despite several limitations including the lack of serum drug levels, this study showed that variations in CYP2C19 were associated with tolerance and remission in a large sample of White non-Hispanic patients treated with citalopram. [ABSTRACT FROM AUTHOR]

Pharmacological evidence shows that cytochrome P450 2D6 (CYP2D6) function is important in the conversion of tamoxifen to its active metabolites. Many retrospective analyses have assessed the role of both CYP2D6 genotype and concurrent administration of drug inhibitors of CYP2D6 on outcome of tamoxifen therapy. These studies have frequently been of small size and their data highly variable. A published data meta-analysis of trials evaluating outcomes of tamoxifen therapy in early breast cancer was undertaken. Hazard ratios (HRs) were extracted for disease-free survival (DFS) and overall survival (OS). Pooled estimates were computed using inverse-variance and random-effect modeling. Data from 10 studies assessing CYP2D6 genotype were included in a meta-analysis. There was significant heterogeneity in the definition of comparison groups between studies. When compared to reduced CYP2D6 function, normal function was associated with a trend toward improved DFS (HR 2.07, 95% CI 0.96–4.49, P = 0.06) but not OS (HR 1.36, 95% CI 0.73–2.52, P = 0.34). Pooling of data from two studies evaluating CYP2D6 drug inhibitors showed that concomitant administration of these with tamoxifen was associated with a non-significant association with DFS (HR 1.37, 95% CI 0.69–2.73, P = 0.37). Analysis of the effect of CYP2D6 drug inhibitors on OS was not possible. The effect of CYP2D6 genotype on breast cancer seems to be relatively small and may not warrant testing of CYP2D6 genotype in all women with hormone receptor positive breast cancer. The effect of CYP2D6 genotype on outcome in low-risk patients may not be clinically relevant, while the upfront use of aromatase inhibitors is a reasonable alternative to tamoxifen in high-risk post-menopausal women, irrespective of CYP2D6 genotype. There are limited data supporting the association of potent inhibitors of CYP2D6 and detrimental outcome, but avoidance of such drugs seems reasonable. [ABSTRACT FROM AUTHOR]

Copy number variations (CNVs) in the CYP2D6 gene contribute to interindividual variation in drug metabolism. As the most common duplicated allele in Asian populations is the nonfunctional CYP2D6∗36 allele, the goal of this study was to identify CNV assays that can differentiate between multiple copies of the CYP2D6∗36 allele and multiple copies of other CYP2D6 alleles. We determined CYP2D6 gene copy numbers in 32 individuals with known CYP2D6 CNVs from the Coriell Japanese-Chinese panel using four quantitative real-time PCR assays. These assays target different regions of the CYP2D6 gene: 5′-flanking region, intron 2, intron 6, and exon 9 (Ex9). The specific target site of the Ex9 assay was verified by sequencing the PCR amplicon. Three of the CYP2D6 CNV assays (5′-flanking region, intron 2, and intron 6) estimated CYP2D6 copy numbers that were concordant for all 32 individuals. However, the Ex9 assay was concordant in only 10 of 32 samples. The 10 concordant samples did not contain any CYP2D6∗36 alleles and the 22 discordant samples contained at least one CYP2D6∗36 allele. In addition, the Ex9 assay accurately quantified all of the non-CYP2D6∗36 alleles in all samples. Ex9 amplicon sequencing indicated that it targets a region of CYP2D6 exon 9 that undergoes partial gene-conversion in the CYP2D6∗36 allele. In conclusion, CYP2D6 Ex9 CNV assay can be used to determine the copy number of non-CYP2D6∗36 alleles. Selective amplification of non-CYP2D6∗36 sequence by the Ex9 assay should be useful in determining the number of functional copies of CYP2D6 in Asian populations. [ABSTRACT FROM AUTHOR]

Cytochrome P450 (CYP) 2D6 is an enzyme that is expressed in liver and brain. It can inactivate neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1,2,3,4-tetrahydroisoquinoline and β-carbolines. Genetically slow CYP2D6 metabolizers are at higher risk for developing Parkinson’s disease, a risk that increases with exposure to pesticides. The goal of this study was to investigate the neuroprotective role of CYP2D6 in an in-vitro neurotoxicity model. SH-SY5Y human neuroblastoma cells express CYP2D6 as determined by western blotting, immunocytochemistry and enzymatic activity. CYP2D6 metabolized 3-[2-( N, N-diethyl- N-methylammonium)ethyl]-7-methoxy-4-methylcoumarin and the CYP2D6-specific inhibitor quinidine (1 μm) blocked 96 ± 1% of this metabolism, indicating that CYP2D6 is functional in this cell line. Treatment of cells with CYP2D6 inhibitors (quinidine, propanolol, metoprolol or timolol) at varying concentrations significantly increased the neurotoxicity caused by 1-methyl-4-phenylpyridinium (MPP+) at 10 and 25 μm by between 9 ± 1 and 22 ± 5% ( P < 0.01). We found that CYP3A is also expressed in SH-SY5Y cells and inhibiting CYP3A with ketoconazole significantly increased the cell death caused by 10 and 25 μm of MPP+ by between 8 ± 1 and 30 ± 3% ( P < 0.001). Inhibiting both CYP2D6 and CYP3A showed an additive effect on MPP+ neurotoxicity. These data further support a possible role for CYP2D6 in neuroprotection from Parkinson’s disease-causing neurotoxins, especially in the human brain where expression of CYP2D6 is high in some regions (e.g. substantia nigra). [ABSTRACT FROM AUTHOR]

Abstract: A rapid and sensitive method using liquid chromatography–tandem mass spectrometry (LC–MS/MS) for enantiomeric determination of tramadol and its primary phase metabolite O-desmethyltramadol in human plasma has been developed. Tramadol hydrochloride –13C, d3, was used as an isotopic labeled internal standard for quantification. The method involves a simple solid phase extraction. The analytes and internal standard were separated on Lux Cellulose-2 packed with cellulose tris(3-chloro-4-methylphenylcarbamate) using isocratic elution with hexane/isopropanol/diethylamine (90:10:0.1, v/v/v) at a flow rate of 1.3mL/min. The APCI positive ionization mass spectrometry was used with multiple reaction monitoring of the transitions at m/z 264.2→58.2 for tramadol, m/z 250.1→58.2 for O-desmethyltramadol and m/z 268.2→58.2 for internal standard. Linearity was achieved between 1–800ng/mL and 1–400ng/mL (R 2 ≥0.999) for each enantiomer of tramadol and O-desmethyltramadol, respectively. Intra-day accuracies ranged among 98.2–102.8%, 97.1–109.1% and 97.4–102.9% at the lower, intermediate, and high concentration for all analytes, respectively. Inter-day accuracies ranged among 95.5–104.1%, 99.2–104.7%, and 94.2–105.6% at the lower, intermediate, and high concentration for all analytes, respectively. This assay was successfully used to determine the concentration of enantiomers of tramadol and O-desmethyltramadol in a pharmacogenetic study. [Copyright &y& Elsevier]

Abstract: We report an autopsy case of a man who died 2days after taking an overdose of vegetamin. The autopsy findings were as follows: the epidermis on the axillary fossa and the inguinal skin had become macerated. Skeletal muscle was discolored. Concentrations of urea nitrogen, creatinine and urine myoglobin were 1.95g/day, 0.66g/day and 1100ng/mL, respectively. Immunohistochemically, myoglobin was strongly stained at the Bowman’s capsule, and tubular lumen and epithelium. 8-OH-dG was strongly stained in renal tubular epithelium in which cell nuclei were strongly stained. ORP-150 was observed in intraglomerular cells and renal tubular epithelium. The concentrations of phenobarbital, promethazine and chlorpromazine ranged from therapeutic to toxic levels, from toxic to lethal levels and toxic level, respectively. His cause of death was considered to be vegetamin-induced rhabdomyolysis. In genetic analysis of this subject, there were two heterozygous silent mutations in the three hot-spot regions in the RYR1 gene. In the CPT II gene, the subject was found to be heterozygous for an amino acid substitution in exon 4, 1203G>A causing a 368Val>Ile amino acid substitution. There was no mutation in the VLCAD gene or CYP2C19 gene. The subject was heterozygous for CYP2D6*1 and CYP2D6*2. [Copyright &y& Elsevier]

The selective estrogen receptor modulator tamoxifen is routinely used for treatment and prevention of estrogen-receptor-positive breast cancer. Studies of tamoxifen adherence suggest that over half of patients discontinue treatment before the recommended 5 years. We hypothesized that polymorphisms in CYP2D6, the enzyme responsible for tamoxifen activation, predict for tamoxifen discontinuation. Tamoxifen-treated women (n=297) were genotyped for CYP2D6 variants and assigned a ‘score’ based on predicted allele activities from 0 (no activity) to 2 (high activity). Correlation between CYP2D6 score and discontinuation rates at 4 months was tested. We observed a strong nonlinear correlation between higher CYP2D6 score and increased rates of discontinuation (r2=0.935, P=0.018). These data suggest that presence of active CYP2D6 alleles may predict for higher likelihood of tamoxifen discontinuation. Therefore, patients who may be most likely to benefit from tamoxifen may paradoxically be most likely to discontinue treatment prematurely.The Pharmacogenomics Journal (2009) 9, 258–264; doi:10.1038/tpj.2009.14; published online 5 May 2009 [ABSTRACT FROM AUTHOR]