Polymorphism of human cytochrome P450 enzymes and its clinical impact

Phenotyping and genotyping of CYP2C19 using comparative metabolism of proguanil in sickle-cell disease patients and healthy controls in Nigeria

Polymorphic expression of metabolic enzymes have been identified as one of the key factors responsible for the interindividual/ethnic/racial variability in drug metabolism and effect. In Nigeria, there is a disproportionately high incidence of sickle-cell disease (SCD), a condition characterized by painful crisis frequently triggered by malaria. Proguanil, a substrate of the polymorphic CYP2C19, is a chemoprophylactic antimalarial drug widely used among SCD patients in Nigeria. This study aimed to conduct a comparative CYP2C19 phenotyping among SCD patients and healthy controls and to compare the results with those previously reported. One hundred seventy-seven unrelated subjects comprising 131 SCD patients and 46 non-SCD volunteers were phenotyped. This was carried out by collecting pooled urine samples over 8 h following PG administration. Proguanil and its major CYP2C19-dependent metabolites were measured by high-performance liquid chromatography. Metabolic ratios (MRs) were computed and employed in classifying subjects into poor or extensive metabolizers. Among SCD group, 130 (99.2%) were extensive metabolizers (EMs) and 1 (0.8%) was poor metabolizer (PM) of PG, while 95.7 and 4.3% non-SCDs were EMs and PMs, respectively. MRs ranged from 0.02 to 8.70 for SCD EMs and from 0.22 to 8.33 for non-SCD EMs . Two non-SCDs with MRs of 18.18 and 25.76 and the SCD with MR of 16.77 regarded as PMs had earlier been genotyped as CYP2C19*2/*2. Poor metabolizers of proguanil in SCD patients are reported for the first time. Regardless of clinical significance, a difference in metabolic disposition of proguanil and CYP2C19 by SCDs and non-SCDs was established.

Inhibition of cytochrome P450 3A by acetoxylated analogues of resveratrol in in vitro and in silico models

Many dietary compounds, including resveratrol, are potent inhibitors of CYP3A4. Here we examined the potential to predict inhibition capacity of dietary polyphenolics using an in silico and in vitro approaches and synthetic model compounds. Mono, di, and tri-acetoxy resveratrol were synthesized, a cell line of human intestine origin and microsomes from rat liver served to determine their in vitro inhibition of CYP3A4, and compared to that of resveratrol. Docking simulation served to predict the affinity of the synthetic model compounds to the enzyme. Modelling of the enzyme’s binding site revealed three types of interaction: hydrophobic, electrostatic and H-bonding. The simulation revealed that each of the examined acetylations of resveratrol led to the loss of important interactions of all types. Tri-acetoxy resveratrol was the weakest inhibitor in vitro despite being the more lipophilic and having the highest affinity for the binding site. The simulation demonstrated exclusion of all interactions between tri-acetoxy resveratrol and the heme due to distal binding, highlighting the complexity of the CYP3A4 binding site, which may allow simultaneous accommodation of two molecules. Finally, the use of computational modelling may serve as a quick predictive tool to identify potential harmful interactions between dietary compounds and prescribed drugs.

Correlation of CpG Island Methylation of the Cytochrome P450 2E1/2D6 Genes with Liver Injury Induced by Anti-Tuberculosis Drugs: A Nested Case-Control Study

This study investigated the role of CpG island methylation of the CYP2E1 and CYP2D6 genes in liver injury induced by anti-TB drugs from an epigenetic perspective in a Chinese cohort. A 1:1 matched nested case-control study design was applied. Pulmonary tuberculosis (TB) patients, who underwent standard anti-TB therapy and developed liver injury were defined as cases, while those who did not develop liver injury were defined as control. The two groups were matched in terms of sex, treatment regimen, and age. In 114 pairs of cases, CpG island methylation levels of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA were found to be significantly correlated with the occurrence of anti-TB drug-induced liver injury (ADLI), with odds ratio (OR) values of 2.429 and 3.500, respectively (p < 0.01). Moreover, through multivariate logistic regression analysis, CpG island methylation of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA were found to be significantly correlated with the occurrence of ADLI, with adjusted OR values of 4.390 (95% confidence interval (CI): 1.982–9.724) and 9.193 (95% CI: 3.624–25.888), respectively (p < 0.001). These results suggest that aberrantly elevated methylation of CpG islands of the CYP2E1 and CYP2D6 genes in plasma cell-free DNA may increase the risk of ADLI in Chinese TB patients.

Engineering a perfusable 3D human liver platform from iPS cells

In vitro models of human tissue are crucial to our ability to study human disease as well as develop safe and effective drug therapies. Models of single organs in static and microfluidic culture have been established and shown utility for modeling some aspects of health and disease; however, these systems lack multi-organ interactions that are critical to some aspects of drug metabolism and toxicity. Thus, as part of a consortium of researchers, we have developed a liver chip that meets the following criteria: (1) employs human iPS cells from a patient of interest, (2) cultures cells in perfusable 3D organoids, and (3) is robust to variations in perfusion rate so as to be compatible in series with other specialized tissue chips (e.g. heart, lung). In order to achieve this, we describe methods to form hepatocyte aggregates from primary and iPS-derived cells, alone and in co-culture with support cells. This necessitated a novel culture protocol for the interrupted differentiation of iPS cells that permits their removal from a plated surface and aggregation while maintaining phenotypic hepatic functions. In order to incorporate these 3D aggregates in a perfusable platform, we next encapsulated the cells in a PEG hydrogel to prevent aggregation and overgrowth once on chip. We adapted a C-trap chip architecture from the literature that enabled robust loading with encapsulated organoids and culture over a range of flow rates. Finally, we characterize the liver functions of this iHep organoid chip under perfusion and demonstrate a lifetime of at least 28 days. We envision that such this strategy can be generalized to other microfluidic tissue models and provides an opportunity to query patient-specific liver responses in vitro.

Monkey-based research on human disease: the implications of genetic differences

Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90-93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimer's disease, Parkinson's disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology - there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists.

Pharmacodynamics, pharmacokinetics, and safety of ticagrelor in Chinese patients with stable coronary artery disease

AIM

The aim of the study was to assess ticagrelor's effects on inhibition of platelet aggregation (IPA), P2Y12 reaction units (PRU, measure of platelet P2Y12 receptor blockade), pharmacokinetic (PK) parameters and safety in Chinese patients with stable coronary artery disease (CAD).

METHODS

This was an open label, single centre, randomized study. Thirty-six patients on low dose aspirin (75-100 mg day(-1) ) received ticagrelor 45, 60 or 90 mg (single dose, days 1 and 7; twice daily, days 3-6). IPA (final extent), PRU and ticagrelor and AR-C124910XX plasma concentrations were determined.

RESULTS

On day 1, peak IPA >80% occurred 2-6 h post-dose (all doses). PRU was markedly reduced at 1 h vs. baseline (all doses). With ticagrelor 45 and 90 mg twice daily, maximum IPA (mean, SD) was 91% (13%), and 99% (3%), and maximum PRU reduction from baseline (mean, SD) was 82% (17%) and 92% (9%), respectively. Approximate dose-proportional increases (mean [%CV]; 45 vs. 90 mg twice daily) in ticagrelor Cmax (616 [37] vs. 1273 [43] ng ml(-1) ) and AUC (3882 [42] vs. 8206 [51] ng ml(-1) h) and AR-C124910XX parameters were seen. Pharmacodynamic and PK differences between 45 and 60 mg were small. No safety issues were identified.

CONCLUSIONS

In Chinese patients with CAD, ticagrelor (45, 60 and 90 mg) markedly reduced platelet aggregation. The IPA and PRU magnitude increased generally with increasing doses. However, the mean pharmacodynamic differences between 45 and 60 mg doses were small. Following single and multiple doses, the mean Cmax and AUC values of ticagrelor and AR-C124910XX increased approximately dose proportionally between 45 and 90 mg doses.

Role of cytochrome P450 2D6 genetic polymorphism in carvedilol hydroxylation in vitro

Cytochrome P450 2D6 (CYP2D6) is a highly polymorphic enzyme that catalyzes the metabolism of a great number of therapeutic drugs. Up to now, >100 allelic variants of CYP2D6 have been reported. Recently, we identified 22 novel variants in the Chinese population in these variants. The purpose of this study was to examine the enzymatic activity of the variants toward the CYP2D6 substrate carvedilol in vitro. The CYP2D6 proteins, including CYP2D6.1 (wild type), CYP2D6.2, CYP2D6.10, and 22 other novel CYP2D6 variants, were expressed from insect microsomes and incubated with carvedilol ranging from 1.0 μM to 50 μM at 37°C for 30 minutes. After termination, the carvedilol metabolites were extracted and detected using ultra-performance liquid chromatography tandem mass-spectrometry. Among the 24 CYP2D6 variants, CYP2D6.92 and CYP2D6.96 were catalytically inactive and the remaining 22 variants exhibited significantly decreased intrinsic clearance values (ranging from ~25% to 95%) compared with CYP2D6.1. The present data in vitro suggest that the newly found variants significantly reduced catalytic activities compared with CYP2D6.1. Given that CYP2D6 protein activities could affect carvedilol plasma levels, these findings are greatly relevant to personalized medicine.

Emerging In Vitro Liver Technologies for Drug Metabolism and Inter-Organ Interactions

In vitro liver models provide essential information for evaluating drug metabolism, metabolite formation, and hepatotoxicity. Interfacing liver models with other organ models could provide insights into the desirable as well as unintended systemic side effects of therapeutic agents and their metabolites. Such information is invaluable for drug screening processes particularly in the context of secondary organ toxicity. While interfacing of liver models with other organ models has been achieved, platforms that effectively provide human-relevant precise information are needed. In this concise review, we discuss the current state-of-the-art of liver-based multiorgan cell culture platforms primarily from a drug and metabolite perspective, and highlight the importance of media-to-cell ratio in interfacing liver models with other organ models. In addition, we briefly discuss issues related to development of optimal liver models that include recent advances in hepatic cell lines, stem cells, and challenges associated with primary hepatocyte-based liver models. Liver-based multiorgan models that achieve physiologically relevant coupling of different organ models can have a broad impact in evaluating drug efficacy and toxicity, as well as mechanistic investigation of human-relevant disease conditions.

Effects of CYP2C19 variants on methadone metabolism in vitro

CYP2C19 is an important member of the cytochrome P450 (CYP450) enzyme super family and is responsible for clearing approximately 10% of commonly used clinical drugs that undergo phase I metabolism. Genetic polymorphisms of CYP2C19 significantly influence the efficacy and safety of some drugs, which might cause undesirable adverse effects or cure failure at standard dosages. The aim of this study was to clarify the catalytic activities of 31 CYP2C19 alleles on the oxidative in vitro metabolism of methadone. Insect microsomes expressing the CYP2C19 alleles were incubated with 50-2000 μM methadone for 30 min at 37 °C and terminated by cooling to -80 °C immediately. Methadone and its metabolite EDDP were analyzed by an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) system. Of the 31 tested CYP2C19 allelies variants, CYP2C19*1 is the wild-type. Compared with CYP2C19*1, two CYP2C19 variants (CYP2C19*3 and *35FS) had no detectable enzyme activity, one variant L16F exhibited slightly increased intrinsic clearance values, and one variant N277K showed no significant difference. In addition, 26 variants exhibited significantly decreased values (from 1.48% to 80.40%). These findings suggest that more attention should be paid in clinical administration of methadone to individuals carrying these CYP2C19 alleles. Copyright © 2016 John Wiley & Sons, Ltd.

In vitro metabolism of l-corydalmine, a potent analgesic drug, in human, cynomolgus monkey, beagle dog, rat and mouse liver microsomes

l-Corydalmine (l-CDL) was under development as an oral analgesic agent, exhibiting potent analgesic activity in preclinical models. The objective of this study was to compare metabolic profiles of l-CDL in liver microsomes from mouse, rat, monkey, dog and human. Six metabolites (M1-M6) were identified using LC-Q/TOF in liver microsomes from the five species. The metabolism of l-CDL included O-demethylation (M1-3) and hydroxylation (M4-6). The desmethyl metabolites were the major ones among the five species, which accounted for more than 84%. Data from chemical inhibition in human liver microsomes (HLM) and human recombinant CYP450s demonstrated that CYP2D6 exhibited strong catalytic activity towards M1 and M2 formations, while CYP2C9 and CYP2C19 also catalyzed M2 formation. Formations of M3 and hydroxyl metabolites (M4 and M5) were mainly catalyzed by CYP3A4. Further studies showed that M1 and M2 were main metabolites in HLM. The kinetics of M1 and M2 formations in HLM and recombinant CYP450s were also investigated. The results showed that M1 and M2 formations in HLM and recombinant CYP2D6 characterized biphasic kinetics, whereas sigmoid Vmax model was better used to fit M2 formation by recombinant CYP2C9 and CYP2C19. The contributions of CYP2D6 to M1 and M2 formations in HLM were estimated to be 75.3% and 50.7%, respectively. However, the contributions of CYP2C9 and CYP2C19 to M2 formation were only 5.0% and 4.1%, respectively. All these data indicated that M1 and M2 were main metabolites in HLM, and CYP2D6 was the primary enzyme responsible for their formations.

Prevalence and implications of cytochrome P450 substrates in Massachusetts hospital discharges

The cytochrome P450 (CYP450) system of drug-metabolizing enzymes may contribute to individual variation in drug response. We examined prevalence of CYP450 substrates at hospital discharge for patients in two cohorts: insurance claims of Massachusetts residents and the medical records of two academic medical centers. The claims cohort included 47 473 individuals (38.2%) treated with at least one CYP450 2D6, 2C19, 3A4 or 1A2 substrate. The electronic medical records cohort included 45 905 individuals (57.4%) treated with at least one substrate. In adjusted models, substrates of CYP450 2D6 and 2C19 were associated with greater risk for 90-day readmission in both cohorts (odds ratios of 1.104 and 1.128 (P<0.001), respectively). Presence of any CYP450 substrate was associated with increased monthly medical costs (+$397, P<0.003). These analyses of more than 300 000 admissions using two different cohorts and data types indicate that CYP450 substrates are associated with greater readmission rates and greater health-care cost.

Challenges, Solutions, and Quality Metrics of Personal Genome Assembly in Advancing Precision Medicine

Even though each of us shares more than 99% of the DNA sequences in our genome, there are millions of sequence codes or structure in small regions that differ between individuals, giving us different characteristics of appearance or responsiveness to medical treatments. Currently, genetic variants in diseased tissues, such as tumors, are uncovered by exploring the differences between the reference genome and the sequences detected in the diseased tissue. However, the public reference genome was derived with the DNA from multiple individuals. As a result of this, the reference genome is incomplete and may misrepresent the sequence variants of the general population. The more reliable solution is to compare sequences of diseased tissue with its own genome sequence derived from tissue in a normal state. As the price to sequence the human genome has dropped dramatically to around $1000, it shows a promising future of documenting the personal genome for every individual. However, de novo assembly of individual genomes at an affordable cost is still challenging. Thus, till now, only a few human genomes have been fully assembled. In this review, we introduce the history of human genome sequencing and the evolution of sequencing platforms, from Sanger sequencing to emerging "third generation sequencing" technologies. We present the currently available de novo assembly and post-assembly software packages for human genome assembly and their requirements for computational infrastructures. We recommend that a combined hybrid assembly with long and short reads would be a promising way to generate good quality human genome assemblies and specify parameters for the quality assessment of assembly outcomes. We provide a perspective view of the benefit of using personal genomes as references and suggestions for obtaining a quality personal genome. Finally, we discuss the usage of the personal genome in aiding vaccine design and development, monitoring host immune-response, tailoring drug therapy and detecting tumors. We believe the precision medicine would largely benefit from bioinformatics solutions, particularly for personal genome assembly.

CYP1A1 MspI polymorphism and the risk of oral squamous cell carcinoma: Evidence from a meta-analysis

Numerous case-control studies have investigated whether the CYP1A1 gene polymorphism is involved in the occurrence of oral squamous cell carcinoma (OSCC); however, the conclusions are inconsistent. In order to further explore the correlation and obtain a strong conclusion, a meta-analysis was performed to systematically assess the association between the CYP1A1 MspI polymorphism and risk of OSCC. In the present meta-analysis, the odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were used to assess the association. The statistical analyses were performed with STATA 11.0 software. The heterogeneity was assessed by Q test and I²test. The final analysis included 10 studies of 1,505 cases and 1,967 controls. The overall results suggested that the CYP1A1 MspI polymorphism was significantly associated with an increased risk of OSCC (CC+TC vs. TT: OR, 1.31; 95% CI, 1.01-1.70; P=0.043; CC vs. TC+TT: OR, 2.38; 95% CI, 1.58-3.58; P<0.001; CC vs. TT: OR, 2.52; 95% CI, 1.60-3.96; P<0.001; and C vs. T: OR, 1.45; 95% CI, 1.15-1.83; P<0.001). In a stratified analysis by ethnicity, a statistically significant correlation existed in the Asian population, but not mixed-race and Caucasian populations. In conclusion, despite several limitations, the present meta-analysis established that the CYP1A1 MspI polymorphism may be a risk factor for OSCC, particularly among the Asian population.

Coumarin Derivatives as Substrate Probes of Mammalian Cytochromes P450 2B4 and 2B6: Assessing the Importance of 7-Alkoxy Chain Length, Halogen Substitution, and Non-Active Site Mutations

Using a combined structural and biochemical approach, the functional importance of a recently described peripheral pocket bounded by the E-, F-, G-, and I-helices in CYP2B4 and 2B6 was probed. Three series of 4-substituted-7-alkoxycoumarin derivatives with -H, -CH3, or -CF3 at the 4 position of the coumarin core were used initially to monitor functional differences between CYP2B4 and 2B6. 7-Ethoxy-4-(trifluoromethyl)coumarin (7-EFC) displayed the highest catalytic efficiency among these substrates. Mutants were made to alter side-chain polarity (V/E194Q) or bulk (F/Y244W) to alter access to the peripheral pocket. Modest increases in catalytic efficiency of 7-EFC O-deethylation by the mutants were magnified considerably by chlorination or bromination of the substrate ethoxy chain. A structure of CYP2B6 Y244W in complex with (+)-α-pinene was solved at 2.2 Å and showed no CYMAL-5 in the peripheral pocket. A ligand free structure of CYP2B4 F244W was solved at 3.0 Å with CYMAL-5 in the peripheral pocket. In both instances, comparison of the respective wild-type and mutant CYP2B enzymes revealed that CYMAL-5 occupancy of the peripheral pocket had little effect on the topology of active site residue side-chains, despite the fact that the peripheral pocket and active site are located on opposite sides of the I-helix. Analysis of available CYP2B structures suggest that the effect of the amino acid substitutions within the peripheral pocket derive from altered interactions between the F and G helices.

Association of CYP2C19*2 and associated haplotypes with lower norendoxifen concentrations in tamoxifen-treated Asian breast cancer patients

AIM

The aim was to examine the influence of CYP2C19 variants and associated haplotypes on the disposition of tamoxifen and its metabolites, particularly norendoxifen (NorEND), in Asian patients with breast cancer.

METHODS

Sixty-six CYP2C19 polymorphisms were identified in healthy Asians (n = 240), of which 14 were found to be tightly linked with CYP2C19*2, CYP2C19*3 and CYP2C19*17. These 17 SNPs were further genotyped in Asian breast cancer patients receiving tamoxifen (n = 201). Steady-state concentrations of tamoxifen and its metabolites were quantified using liquid chromatography–mass spectrometry. Non-parametric tests and regression methods were implemented to evaluate genotypic–phenotypic associations and haplotypic effects of the SNPs.

RESULTS

CYP2C19 functional polymorphisms and their linked SNPs were not significantly associated with plasma concentrations of tamoxifen and its main metabolites N-desmethyltamoxifen, (Z)-4-hydroxytamoxifen and (Z)-Endoxifen. However, CYP2C19*2 and its seven linked SNPs were significantly associated with lower NorEND concentrations, MRNorEND/NDDM and MRNorEND/(Z)-END. Specifically, patients carrying the CYP2C19*2 variant allele A had significantly lower NorEND concentrations [median (range), GG vs. GA vs. AA: 1.51 (0.38–3.28) vs. 1.28 (0.30–3.36) vs. 1.15 ng ml−1 (0.26–2.45, P = 0.010)] as well as significantly lower MRNorEND/(Z)-END [GG vs. GA vs. AA: 9.40 (3.27–28.35) vs. 8.15 (2.67–18.9) vs. 6.06 (4.47–14.6), P < 0.0001] and MRNorEND/NDDM [GG vs. GA vs. AA: 2.75 (0.62–6.26) vs. 2.43 (0.96–4.18) vs. 1.75 (1.10–2.49), P < 0.00001]. CYP2C19 H2 haplotype, which included CYP2C19*2, was also significantly associated with lower NorEND concentrations (P = 0.0020), MRNorEND/NDDM (P < 0.0001) and MRNorEND/(Z)-END (P < 0.0001), indicating significantly lower formation rates of NorEND.

CONCLUSION

These data highlight the potential relevance of CYP2C19 pharmacogenetics in influencing NorEND concentrations in tamoxifen-treated patients, which may influence treatment outcomes.

Investigating the impact of missense mutations in hCES1 by in silico structure-based approaches

Genetic variations in drug-metabolizing enzymes have been reported to influence pharmacokinetics, drug dosage, and other aspects that affect therapeutic outcomes. Most particularly, non-synonymous single-nucleotide polymorphisms (nsSNPs) resulting in amino acid changes disrupt potential functional sites responsible for protein activity, structure, or stability, which can account for individual susceptibility to disease and drug response. Investigating the impact of nsSNPs at a protein's structural level is a key step in understanding the relationship between genetic variants and the resulting phenotypic changes. For this purpose, in silico structure-based approaches have proven their relevance in providing an atomic-level description of the underlying mechanisms. The present review focuses on nsSNPs in human carboxylesterase 1 (hCES1), an enzyme involved in drug metabolism. We highlight how prioritization of functional nsSNPs through computational prediction techniques in combination with structure-based approaches, namely molecular docking and molecular dynamics simulations, is a powerful tool in providing insight into the underlying molecular mechanisms of nsSNPs phenotypic effects at microscopic level. Examples of in silico studies of carboxylesterases (CESs) are discussed, ranging from exploring the effect of mutations on enzyme activity to predicting the metabolism of new hCES1 substrates as well as to guiding rational design of CES-selective inhibitors.

Effects of 22 novel CYP2D6 variants found in Chinese population on the metabolism of dapoxetine

Background

CYP2D6 is one of the most important members of the cytochrome P450 superfamily. Its genetic polymorphism significantly influences the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure.

Methods and results

The aim of this research was mainly to explore the catalytic activities of 22 newly reported CYP2D6 isoforms (2D6*87, *88, *89, *90, *91, *92, *93, *94, *95, *96,*97, *98, *R25Q, F164L, E215K, F219S, V327M, D336N, V342M, R344Q, R440C, R497C) on dapoxetine in vitro. The research was designed with an appropriate incubation system in test tubes and carried out in the constant temperature water. Through detecting its two metabolites desmethyldapoxetine and dapoxetine-N-oxide, the available data were obtained to explain the influence of CYP2D6 polymorphism on the substrate drug dapoxetine. As a result, the intrinsic clearance (V_max/K_m) values of most variants were significantly altered when compared with the counterpart of CYP2D6*1, with most of these variants exhibiting either reduced V_max and/or increased K_m values. For dapoxetine demethylation pathway (which produces desmethyldapoxetine), 2D6*89 and E215K exhibited no markedly decreased relative clearance of 92.81% and 97.70%, respectively. The relative clearance of rest 20 variants exhibited decrease in different levels, ranging from 20.44% to 90.90%. For the dapoxetine oxidation pathway (which produces dapoxetine-N-oxide), the relative clearance values of three variants, 2D6*90, *94, and V342M, exhibited no markedly increased relative clearance of 106.17%, 107.78%, and 109.98%, respectively; the rest 19 variants exhibited significantly decreased levels ranging from 27.56% to 84.64%. In addition, the kinetic parameters of two CYP2D6 variants (2D6*92 and 2D6*96) could not be detected, due to the defect of the CYP2D6 gene.

Conclusion

As the first report of all aforementioned alleles for dapoxetine metabolism, these data may help in the clinical assessment of the metabolic elimination of dapoxetine and may provide fundamental information for further clinical studies.

The pharmacogenomics of pain management: prospects for personalized medicine

Pain is a common symptom that can be complex to treat. Analgesic medications are the mainstay treatment, but there is wide interindividual variability in analgesic response and adverse effects. Pharmacogenomics is the study of inherited genetic traits that result in these individual responses to drugs. This narrative review will attempt to cover the current understanding of the pharmacogenomics of pain, examining common genes affecting metabolism of analgesic medications, their distribution throughout the body, and end organ effects.

Deterministically patterned biomimetic human iPSC-derived hepatic model via rapid 3D bioprinting

The functional maturation and preservation of hepatic cells derived from human induced pluripotent stem cells (hiPSCs) are essential to personalized in vitro drug screening and disease study. Major liver functions are tightly linked to the 3D assembly of hepatocytes, with the supporting cell types from both endodermal and mesodermal origins in a hexagonal lobule unit. Although there are many reports on functional 2D cell differentiation, few studies have demonstrated the in vitro maturation of hiPSC-derived hepatic progenitor cells (hiPSC-HPCs) in a 3D environment that depicts the physiologically relevant cell combination and microarchitecture. The application of rapid, digital 3D bioprinting to tissue engineering has allowed 3D patterning of multiple cell types in a predefined biomimetic manner. Here we present a 3D hydrogel-based triculture model that embeds hiPSC-HPCs with human umbilical vein endothelial cells and adipose-derived stem cells in a microscale hexagonal architecture. In comparison with 2D monolayer culture and a 3D HPC-only model, our 3D triculture model shows both phenotypic and functional enhancements in the hiPSC-HPCs over weeks of in vitro culture. Specifically, we find improved morphological organization, higher liver-specific gene expression levels, increased metabolic product secretion, and enhanced cytochrome P450 induction. The application of bioprinting technology in tissue engineering enables the development of a 3D biomimetic liver model that recapitulates the native liver module architecture and could be used for various applications such as early drug screening and disease modeling.

Influence of CYP2B6 and CYP2C19 polymorphisms on sertraline metabolism in major depression patients

BACKGROUND

Genetic polymorphisms in CYP2B6 and CYP2C19 may cause variability in the metabolism of sertraline, a widely used antidepressant in major depressive disorder treatment.

OBJECTIVE

This study investigates the impact of CYP2B6*4 (785A > G), CYP2B6*9 (516G > T), CYP2B6*6 (516G > T + 685G > A) CYP2C19*2 (685G > A), CYP2C19*17 (-3402C > T) polymorphisms on plasma concentrations of sertraline and N-desmethyl sertraline in major depression patients treated with sertraline [n = 50].

SETTING

Participants were patients who admitted to an adult psychiatry outpatient unit at a university hospital. These were DSM-IV major depression diagnosed patients with a stable sertraline medication regimen [for at least one month].

METHODS

CYP2B6*4 (rs 2279343; 785A > G), CYP2B6*9 (516G > T; rs 3745274), CYP2B6*6 (516G > T + 685G > A) CYP2C19*2 (rs 4244285; 685G > A), CYP2C19*17 (rs 11188072; -3402C > T), polymorphisms were analyzed by polymerase chain reaction and restriction fragment length polymorphism. Plasma concentrations were measured by high-performance liquid chromatography in patients treated with SERT.

MAIN OUTCOME MEASURE

The distribution of CYP2B6*4, *6, *9 and CYP2C19*2, *17 among patient group and the association between genotype and sertraline metabolism.

RESULTS

Sertraline, N-desmethyl sertraline, N-desmethyl sertraline/sertraline and dose-adjusted plasma concentrations were statistically compared between individuals with wild-type and variant alleles both for CYP2B6 and CYP2C19 enzymes. The mean N-desmethyl sertraline/sertraline value, was significantly lower in all subgroups with *6 and *9 variant alleles (p < 0.05). Sertraline/C values were significantly higher (p < 0.05) and N-desmethyl sertraline/C values were lower in all subgroups with *6 and *9 variant alleles compared to wild-type subgroup.

CONCLUSION

CYP2B6*6 and *9 variant alleles had a significant decreasing effect on sertraline metabolism in major depression patients which might result as variations in sertraline therapy.

Sphingolipids and Epoxidized Lipid Metabolites in the Control of Gut Immunosurveillance and Allergy

The intestinal immune system ingeniously balances the distinct responses of elimination and tolerance of non-self-substances for the creation and maintenance of homeostatic environments. Accumulating evidence has recently shown that various lipids, including dietary one, are involved in the regulation of intestinal immunity and are associated with biophylaxis and immune disorders. Recent advances in the lipidomics allow the identification of novel pathways of lipid metabolism and lipid metabolites for the control of intestinal immunity. In this paper, we describe the effects and functions of lipids, especially sphingolipids and new lipid metabolites originated from dietary oil on the immunomodulation and on the development and pathogenesis of allergic diseases in the intestine.

Effect of CYP2D6 genetic polymorphism on the metabolism of citalopram in vitro

Genetic polymorphisms of CYP2D6 significantly influence the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure. We aimed at investigating the role of CYP2D6 in the metabolism of citalopram and identifying the effect of 24 CYP2D6 allelic variants we found in Chinese Han population on the metabolism of citalopram in vitro. These CYP2D6 variants expressed by insect cells system were incubated with 10-1000 μM citalopram for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Citalopram and its metabolites were analyzed by high-performance liquid chromatography (HPLC). The intrinsic clearance (Vmax/Km) values of the variants toward citalopram metabolites were significantly altered, 38-129% for demethylcitalopram and 13-138% for citalopram N-oxide when compared with CYP2D6*1. Most of the tested rare alleles exhibited significantly decreased values due to increased Km and/or decreased Vmax values. We conclude that recombinant system could be used to investigate the enzymes involved in drug metabolism and these findings suggest that more attention should be paid to subjects carrying these CYP2D6 alleles when administering citalopram in the clinic.

Associations of CYP1A2 Polymorphisms with the Risk Haplotypes in Lung Cancer in the Slovak Population

Phase I enzymes, including cytochrome P450, family 1, subfamily A, and polypeptide 2 (CYP1A2), are involved in the activation of carcinogens to reactive intermediates that are capable of binding covalently to DNA to form DNA adducts, potentially initiating the carcinogenic process. The aim of present study was to investigate the association of CYP1A2 gene polymorphisms and haplotypes with lung cancer risk. A case-control study was carried out on 105 lung cancer patients and 189 controls. To investigate three CYP1A2 polymorphisms: rs2472299, rs2470890, rs11072508 we used a high resolution melting analysis. We found significant allele associations (rs2470890 and rs2422299) with lung cancer risk. We searched for meaningful associations for all variants in the dominant, recessive, and additive genetic models. Genotype associations in the recessive model were of marginal significance for the same single nucleotide polymorphisms. A haplotype analysis included five variants with the frequency higher than 1 %. The haplotype "acc", present with the highest frequency, was associated with increased lung cancer risk (38.7 % vs. 31.5 %; OR 1.38; 95 %CI 0.95-2.01). On the contrary, rare haplotype "gtc" was significantly associated with decreased lung cancer risk in the Slovak population. In conclusion, the present study identified the risk alleles and haploid genotype associations of the CYP1A2 gene in lung cancer.

Polymorphisms of pesticide-metabolizing genes in children living in intensive farming communities

Polymorphisms in genes encoding xenobiotic-metabolizing enzymes (XME) are important parameters accounting for the wide inter-individual variability to environmental exposures. Paraoxonase-1 (PON1), butyrylcholinesterase (BChE) and Cytochrome-P450 constitute major classes of XME involved in the detoxification of pesticide chemicals, in particular organophosphates. This study explored the allelic frequency, linkage disequilibrium and haplotype analysis of ten common polymorphic variants of seven key genes involved in organophosphate metabolism (BCHE-K, BCHE-A, PON1 Q192R, PON1 L55M, PON1 -108C/T, CYP2C19 G681A, CYP2D6 G1846A, CYP3AP1 -44G/A, GSTM1∗0 and GSTT1∗0) in a children population living near an intensive agriculture area in Spain. It was hypothesized that individuals with unfavorable combinations of gene variants will be more susceptible to adverse effects from organophosphate exposure. Genomic DNA from 496 healthy children was isolated and amplified by PCR. Hydrolysis probes were used for the detection of eight specific SNPs and two copy number variants (CNVs) by using TaqMan® Assay-based real-time PCR. Frequencies of SNPs and CNVs in the target genes were in Hardy-Weinberg equilibrium and broadly consistent with European populations. Linkage disequilibrium was found between the three PON1 genetic polymorphisms studied and between BCHE-K and BCHE-A. The adverse genotype combination (unusual BCHE variants, PON1 55MM/-108TT and null genotype for both GSTM1 and GSTT1) potentially conferring a greater genetic risk from exposure to organophosphates was observed in 0.2% of our study population. This information allows broadening our knowledge about differential susceptibility toward environmental toxicants and may be helpful for further research to understand the inter-individual toxicokinetic variability in response to organophosphate pesticides exposure.

Pharmacogenetic comparison of CYP2D6 predictive and measured phenotypes in a South African cohort

The relationship between genetic variation in CYP2D6 and variable drug response represents a potentially powerful pharmacogenetic tool. However, little is known regarding this relationship in the genetically diverse South African population. The aim was therefore to evaluate the relationship between predicted and measured CYP2D6 phenotype. An XL-PCR+Sequencing approach was used to determine CYP2D6 genotype in 100 healthy volunteers and phenotype was predicted using activity scores. With dextromethorphan as the probe drug, metabolic ratios served as a surrogate measure of in vivo CYP2D6 activity. Three-hour plasma metabolic ratios of dextrorphan/dextromethorphan were measured simultaneously using semi-automated online solid phase extraction coupled with tandem mass spectrometry. Partial adaptation of the activity score system demonstrated a strong association between genotype and phenotype, as illustrated by a kappa value of 0.792, inter-rater discrepancy of 0.051 and sensitivity of 72.7%. Predicted phenotype frequencies using the modified activity score were 1.3% for poor metabolisers (PM), 7.6% for intermediate metabolisers (IM) and 87.3% for extensive metabolisers (EM). Measured phenotype frequencies were 1.3% for PM, 13.9% for IM and 84.8% for EM. Comprehensive CYP2D6 genotyping reliably predicts CYP2D6 activity in this South African cohort and can be utilised as a valuable pharmacogenetic tool.

microRNAs as pharmacogenomic biomarkers for drug efficacy and drug safety assessment

Much evidence has documented that microRNAs (miRNAs) play an important role in the modulation of interindividual variability in the production of drug metabolizing enzymes and transporters (DMETs) and nuclear receptors (NRs) through multidirectional interactions involving environmental stimuli/stressors, the expression of miRNA molecules and genetic polymorphisms. MiRNA expression has been reported to be affected by drugs and miRNAs themselves may affect drug metabolism and toxicity. In cancer research, miRNA biomarkers have been identified to mediate intrinsic and acquired resistance to cancer therapies. In drug safety assessment, miRNAs have been found associated with cardiotoxicity, hepatotoxicity and nephrotoxicity. This review article summarizes published studies to show that miRNAs can serve as early biomarkers for the evaluation of drug efficacy and drug safety.

Interethnic differences in pharmacokinetics of antibacterials

BACKGROUND

Optimal antibacterial dosing is imperative for maximising clinical outcome. Many factors can contribute to changes in the pharmacokinetics of antibacterials to the extent where dose adjustment may be needed. In acute illness, substantial changes in important pharmacokinetic parameters such as volume of distribution and clearance can occur for certain antibacterials. The possibility of interethnic pharmacokinetic differences can further complicate attempts to design an appropriate dosing regimen. Factors of ethnicity, such as genetics, body size and fat distribution, contribute to differences in absorption, distribution, metabolism and elimination of drugs. Despite extensive previous work on the altered pharmacokinetics of antibacterials in some patient groups such as the critically ill, knowledge of interethnic pharmacokinetic differences for antibacterials is limited.

OBJECTIVES

This systematic review aims to describe any pharmacokinetic differences in antibacterials between different ethnic groups, and discuss their probable mechanisms as well as any clinical implications.

METHODS

We performed a structured literature review to identify and describe available data of the interethnic differences in the pharmacokinetics of antibacterials.

RESULTS

We found 50 articles that met our inclusion criteria and only six of these compared antibacterial pharmacokinetics between different ethnicities within the same study. Overall, there was limited evidence available. We found that interethnic pharmacokinetic differences are negligible for carbapenems, most β-lactams, aminoglycosides, glycopeptides, most fluoroquinolones, linezolid and daptomycin, whereas significant difference is likely for ciprofloxacin, macrolides, clindamycin, tinidazole and some cephalosporins. In general, subjects of Asian ethnicity achieve drug exposures up to two to threefold greater than Caucasian counterparts for these antibacterials. This difference is caused by a comparatively lower volume of distribution and/or drug clearance.

CONCLUSION

Interethnic pharmacokinetic differences of antibacterials are likely; however, the clinical relevance of these differences is unknown and warrants further research.

Use of In Vitro and Predictive In Silico Models to Study the Inhibition of Cytochrome P4503A by Stilbenes

CYP3A4 is recognized as the main enzyme involved in the metabolism of drugs and xenobiotics in the human body and its inhibition may lead to undesirable consequences. Stilbenes, including resveratrol, belong to a group of dietary health-promoting compounds that also act as inhibitors of CYP3A4. The aim of this study was to examine the use of computer modeling of enzyme-ligand interactions to analyze and predict the inhibition of structurally related compounds. To this end, an aldehyde group was attached to resveratrol and the interactions of CYP3A4 with resveratrol, its aldehyde analogue (RA) and a known synthetic inhibitor were studied and compared in two biological models. Specifically, the metabolism of testosterone was examined in a human intestine cell line (Caco-2/TC7) and in rat liver microsomes (RLM). The results demonstrated a weak inhibitory effect of RA on CYP3A4, as compared to resveratrol itself, in both biological models. Human CYP3A4 was more susceptible to inhibition than the commonly used model isozyme from rat. Modeling of the binding site of CYP3A4 revealed a combination of three types of interactions: hydrophobic interactions, electrostatic interactions and hydrogen bonds. A docking simulation revealed that the RA lacked an important binding feature, as compared to resveratrol, and that that difference may be responsible for its lower level of affinity for CYP3A4. Software analysis of binding affinity may serve as a predictive tool for designing new therapeutic compounds in terms of inhibition of CYP3A4 and help to reveal the biochemical nature of the interactions of dietary compounds, herbal compounds and drugs whose metabolism is mediated by this enzyme.

Molecular Targets of Cannabidiol in Neurological Disorders

Cannabis has a long history of anecdotal medicinal use and limited licensed medicinal use. Until recently, alleged clinical effects from anecdotal reports and the use of licensed cannabinoid medicines are most likely mediated by tetrahydrocannabinol by virtue of: 1) this cannabinoid being present in the most significant quantities in these preparations; and b) the proportion:potency relationship between tetrahydrocannabinol and other plant cannabinoids derived from cannabis. However, there has recently been considerable interest in the therapeutic potential for the plant cannabinoid, cannabidiol (CBD), in neurological disorders but the current evidence suggests that CBD does not directly interact with the endocannabinoid system except in vitro at supraphysiological concentrations. Thus, as further evidence for CBD's beneficial effects in neurological disease emerges, there remains an urgent need to establish the molecular targets through which it exerts its therapeutic effects. Here, we conducted a systematic search of the extant literature for original articles describing the molecular pharmacology of CBD. We critically appraised the results for the validity of the molecular targets proposed. Thereafter, we considered whether the molecular targets of CBD identified hold therapeutic potential in relevant neurological diseases. The molecular targets identified include numerous classical ion channels, receptors, transporters, and enzymes. Some CBD effects at these targets in in vitro assays only manifest at high concentrations, which may be difficult to achieve in vivo, particularly given CBD's relatively poor bioavailability. Moreover, several targets were asserted through experimental designs that demonstrate only correlation with a given target rather than a causal proof. When the molecular targets of CBD that were physiologically plausible were considered for their potential for exploitation in neurological therapeutics, the results were variable. In some cases, the targets identified had little or no established link to the diseases considered. In others, molecular targets of CBD were entirely consistent with those already actively exploited in relevant, clinically used, neurological treatments. Finally, CBD was found to act upon a number of targets that are linked to neurological therapeutics but that its actions were not consistent withmodulation of such targets that would derive a therapeutically beneficial outcome. Overall, we find that while >65 discrete molecular targets have been reported in the literature for CBD, a relatively limited number represent plausible targets for the drug's action in neurological disorders when judged by the criteria we set. We conclude that CBD is very unlikely to exert effects in neurological diseases through modulation of the endocannabinoid system. Moreover, a number of other molecular targets of CBD reported in the literature are unlikely to be of relevance owing to effects only being observed at supraphysiological concentrations. Of interest and after excluding unlikely and implausible targets, the remaining molecular targets of CBD with plausible evidence for involvement in therapeutic effects in neurological disorders (e.g., voltage-dependent anion channel 1, G protein-coupled receptor 55, CaV3.x, etc.) are associated with either the regulation of, or responses to changes in, intracellular calcium levels. While no causal proof yet exists for CBD's effects at these targets, they represent the most probable for such investigations and should be prioritized in further studies of CBD's therapeutic mechanism of action.

Modulation of ALDH5A1 and SLC22A7 by microRNA hsa-miR-29a-3p in human liver cells

Observed variations in drug responses among patients may result from differences in heritable genetic traits or from alterations in the epigenetic regulation of drug metabolizing enzymes and transporters (DMETs). MicroRNAs (miRNAs), a group of small non-coding RNAs, provide an epigenetic mechanism for fine-tuning the expression of targeted DMET genes by regulating the efficiency of protein translation and by decreasing mRNA stability via enhanced degradation. In the current study we systematically screened 374 important genes encoding DMETs for potential response elements to hsa-miR-29a-3p, a highly abundant miRNA in human liver. RNA electrophoresis mobility shift assays displayed direct interactions between hsa-miR-29a-3p and its cognate targets within the mRNA transcripts for the ABCC6, SLC22A7 and ALDH5A1 genes. The expression of luciferase reporter genes containing the 3'-UTRs of SLC22A7 or ALDH5A1 and the expression of endogenous SLC22A7 and ALDH5A1 were each suppressed by transfection with hsa-miR-29a-3p mimics. Importantly, chemically-induced up-regulation of hsa-miR-29a-3p correlated inversely with the expression of SLC22A7 and ALDH5A1. However, our studies failed to detect suppressive effects of hsa-miR-29a-3p on ABCC6 expression, which might be explained by the notion that the interaction of hsa-miR-29a-3p and ABCC6 mRNA was unable to recruit ribonucleoproteins to form a RNA-induced silencing complex.

Opioid Analgesics and Nicotine: More Than Blowing Smoke

Practitioners are highly likely to encounter patients with concurrent use of nicotine products and opioid analgesics. Smokers present with more severe and extended chronic pain outcomes and have a higher frequency of prescription opioid use. Current tobacco smoking is a strong predictor of risk for nonmedical use of prescription opioids. Opioid and nicotinic-cholinergic neurotransmitter systems interact in important ways to modulate opioid and nicotine effects: dopamine release induced by nicotine is dependent on facilitation by the opioid system, and the nicotinic-acetylcholine system modulates self-administration of several classes of abused drugs-including opioids. Nicotine can serve as a prime for the use of other drugs, which in the case of the opioid system may be bidirectional. Opioids and compounds in tobacco, including nicotine, are metabolized by the cytochrome P450 enzyme system, but the metabolism of opioids and tobacco products can be complicated. Accordingly, drug interactions are possible but not always clear. Because of these issues, asking about nicotine use in patients taking opioids for pain is recommended. When assessing patient tobacco use, practitioners should also obtain information on products other than cigarettes, such as cigars, pipes, smokeless tobacco, and electronic nicotine delivery systems (ENDS, or e-cigarettes). There are multiple forms of behavioral therapy and pharmacotherapy available to assist patients with smoking cessation, and opioid agonist maintenance and pain clinics represent underutilized opportunities for nicotine intervention programs.

Characterization of the Gly45Asp variant of human cytochrome P450 1A1 using recombinant expression

Cytochrome P450 1A1 (CYP1A1) is a heme-containing enzyme involved in metabolism of xenobiotics. CYP1A1 containing a Gly45Asp substitution has not yet been characterized. Escherichia coli expressing the Gly45Asp variant, as well as the purified variant protein, had lower CYP (i.e., holoenzyme) contents than their wild-type (WT) equivalents. The purified variant protein had reduced heme contents compared with their WT equivalents. Enhanced supplementation of a heme precursor during culture did not increase CYP content in E. coli expressing the variant, but did for the WT. Substitution of Gly45 with other residues, especially those having large side chains, decreased CYP contents of E. coli expressing the variants to a considerable extent. A 3D structure of CYP1A1 indicates that Gly45, along with other residues of the PR region, interacts with Arg77 of β- strand 1-1, which indirectly interacts with heme. Substitution analyses suggest the importance of residues of the PR region and Arg77 in holoenzyme expression. E. coli membrane and mammalian microsomes expressing the Gly45Asp variant, as well as the purified variant protein, had reduced ethoxyresorufin O-dealkylation activities, compared with the WT equivalents. These findings suggest the Gly45Asp substitution results in a structural disturbance of CYP1A1, reducing its holoenzyme formation and catalytic activity.

Functional importance of a peripheral pocket in mammalian cytochrome P450 2B enzymes

The functional importance of a peripheral pocket found in previously published X-ray crystal structures of CYP2B4 and CYP2B6 was probed using a biophysical approach. Introduction of tryptophan within the pocket of CYP2B4 at F202 or I241 leads to marked impairment of 7-ethoxy-4-(trifluoromethyl)coumarin (7-EFC) or 7-benzyloxyresorufin O-dealkylation efficiency; a similar substitution at F195, near the surface access to the pocket, does not affect these activities. The analogous CYP2B6 F202W mutant is inactive in the 7-EFC O-dealkylation assay. The stoichiometry of 7-EFC deethylation suggested that the decreased activity of F202W and I241W in CYP2B4 and lack of activity of F202W in CYP2B6 coincided with a sharp increase in the flux of reducing equivalents through the oxidase shunt to produce excess water. The results indicate that the chemical identity of residues within this peripheral pocket, but not at the mouth of the pocket, is important in substrate turnover and redox coupling, likely through effects on active site topology.

Atomoxetine pharmacogenetics: associations with pharmacokinetics, treatment response and tolerability

Atomoxetine is indicated for the treatment of attention deficit hyperactivity disorder and is predominantly metabolized by the CYP2D6 enzyme. Differences in pharmacokinetic parameters as well as clinical treatment outcomes across CYP2D6 genotype groups have resulted in dosing recommendations within the product label, but clinical studies supporting the use of genotype guided dosing are currently lacking. Furthermore, pharmacokinetic and clinical studies have primarily focused on extensive as compared with poor metabolizers, with little information known about other metabolizer categories as well as genes involved in the pharmacodynamics of atomoxetine. This review describes the pharmacogenetic associations with atomoxetine pharmacokinetics, treatment response and tolerability with considerations for the clinical utility of this information.

Long-term maintenance of a microfluidic 3D human liver sinusoid

The development of long-term human organotypic liver-on-a-chip models for successful prediction of toxic response is one of the most important and urgent goals of the NIH/DARPA's initiative to replicate and replace chronic and acute drug testing in animals. For this purpose, we developed a microfluidic chip that consists of two microfluidic chambers separated by a porous membrane. The aim of this communication is to demonstrate the recapitulation of a liver sinusoid-on-a-chip, using human cells only for a period of 28 days. Using a step-by-step method for building a 3D microtissue on-a-chip, we demonstrate that an organotypic in vitro model that reassembles the liver sinusoid microarchitecture can be maintained successfully for a period of 28 days. In addition, higher albumin synthesis (synthetic) and urea excretion (detoxification) were observed under flow compared to static cultures. This human liver-on-a-chip should be further evaluated in drug-related studies.

CYP2D6 genetic polymorphisms in Southern Mexican Mayan Lacandones and Mestizos from Chiapas

AIM

In previous CYP2D6 genotyping studies in Mexican-Amerindians a very low frequency of poor metabolizers (PMs) has been reported. Moreover, ultrarapid metabolizers (UMs) status has only been analyzed in some groups from Northern Mexico.

MATERIALS & METHODS

In the present study we evaluated the hypothesis of low frequency of PMs in Mexican-Amerindians in Southern Mexican populations from Chiapas (Lacandones [ML] vs Mestizos [MM]). The frequency of UMs is also reported. CYP2D6 alleles *2, *3, *4, *5, *6, *10, *17, *35 and *41 and copy number variations were analyzed in 154 ML and 100 MM healthy volunteers.

RESULTS

The PM frequency was 0% in MLs and 1% in MMs, and for UMs was 2.6% in MLs and 3% in MMs.

CONCLUSION

The present data support previous findings reporting a very low frequency of CYP2D6 PMs in Mexican-Amerindians. Furthermore, the predicted UM phenotype in both MMs and MLs was lower than those reported for most Mexican populations.

Tobacco carcinogen-metabolizing genes CYP1A1, GSTM1, and GSTT1 polymorphisms and their interaction with tobacco exposure influence the risk of head and neck cancer in Northeast Indian population

Genetic polymorphisms in tobacco-metabolizing genes may modulate the risk of head and neck cancer (HNC). In Northeast India, head and neck cancers and tobacco consumption remains most prevalent. The aim of the study was to investigate the combined effect of cytochrome P450 1A1 (CYP1A1) T3801C, glutathione S-transferases (GSTs) genes polymorphisms and smoking and tobacco-betel quid chewing in the risk of HNC. The study included 420 subjects (180 cases and 240 controls) from Northeast Indian population. Polymorphisms of CYP1A1 T3801C and GST (M1 & T1) were studied by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and multiplex PCR, respectively. Logistic regression (LR) and multifactor dimensionality reduction (MDR) approach were applied for statistical analysis. LR analysis revealed that subjects carrying CYP1A1 TC/CC + GSTM1 null genotypes had 3.52-fold (P < 0.001) increase the risk of head and neck squamous cell carcinoma (HNSCC). Smokers carrying CYP1A1 TC/CC + GSTM1 null and CYP1A1 TC/CC + GSTT1 null genotypes showed significant association with HNC risk (odds ratio [OR] = 6.42; P < 0.001 and 3.86; P = 0.005, respectively). Similarly, tobacco-betel quid chewers carrying CYP1A1 TC/CC + GSTM1 null genotypes also had several fold increased risk of HNC (P < 0.001). In MDR analysis, the best model for HNSCC risk was the four-factor model of tobacco-betel quid chewing, smoking, CYP1A1 TC/CC, and GSTM1 null genotypes (testing balance accuracy [TBA] = 0.6292; cross-validation consistency [CVC] = 9/10 and P < 0.0001). These findings suggest that interaction of combined genotypes of carcinogen-metabolizing genes with environmental factors might modulate susceptibility of HNC in Northeast Indian population.

Clinical Utility of Combinatorial Pharmacogenomics-Guided Antidepressant Therapy: Evidence from Three Clinical Studies

DNA of 258 patients with treatment-resistant depression was collected in three 8-10 week, two-arm, prospective clinical trials. Forty-four allelic variations were measured in genes for the cytochrome P450 (CYP) enzymes CYP2D6, CYPC19, and CYP1A2, the serotonin transporter (SLC6A4), and the 5-HT2A receptor (HTR2A). The combinatorial pharmacogenomic (CPGx™) GeneSight test results were provided to clinicians to support medication changes from baseline (guided arm), or they were provided at the end of each study to clinicians of unguided patients who were treated as usual (TAU). TAU subjects who at baseline were prescribed medications genetically discordant for them showed only a 12% symptom improvement, far less than the 32.5% or 28.5% improvements of the TAU subjects on yellow-category ('use with caution'; p = 0.002) or green-category medications ('use as recommended'; p = 0.02), respectively. The odds of a clinical response were increased 2.3-fold among all GeneSight-guided compared to all TAU subjects (p = 0.004), and overall, the guided group had a 53% greater improvement in depressive symptoms (p = 0.0002), a 1.7-fold relative improvement in response (p = 0.01), and a number needed to treat for one clinical response above that seen in the TAU group of 6.07.

In vitro functional analysis of 24 novel CYP2C19 variants recently found in the Chinese Han population

1. CYP2C19 is a highly polymorphic enzyme responsible for the metabolism of a wide range of clinical drugs. Alterations to the CYP2C19 gene contribute to the variability of CYP2C19 enzyme activity, which causes pharmacokinetics and drug efficacies to vary and adverse drug reactions to occur in different persons. Recently, we identified 24 novel CYP2C19 allelic variants in the Chinese Han population. The purpose of present study is to assess the impact of these newly found nucleotide mutations on the enzymatic activity of the CYP2C19 protein. 2. Dual-expression vectors were constructed and transiently transfected into 293FT cells. Forty-eight hours after transfection, cells were re-suspended and incubated with two typical probe substrates, omeprazole and S-mephenytoin, to determine the activities of each variant relative to the wild-type protein. 3. Immunoblotting results showed that the protein expression levels of the CYP2C19 variants were diverse. Enzymatic ability analysis showed that the variant 35FS exhibited no functional activity, and most of the other variants showed significantly decreased metabolic activities toward both omeprazole and S-mephenytoin compared with wild-type. 4. These findings greatly enrich the knowledge of biological effects of these newly found CYP2C19 mutations and aid the application of this knowledge to future individualized drug therapy in clinic.

Effect of kanglaite on rat cytochrome P450

CONTEXT

Kanglaite (KLT) is an oily substance extracted from Coix lacryma-jobi Linn. (Cramineae) and has been proved to significantly improve the life span and quality of life of patients, when combined with chemotherapy, radiotherapy, or surgery.

OBJECTIVE

The purpose of this study was to find out whether KLT influences the effect on rat cytochrome P450 (CYP) enzymes (CYP1A2, CYP2B6, CYP2C9, CYP2C19, and CYP3A4) by using cocktail probe drugs in vivo.

MATERIALS AND METHODS

A cocktail solution at a dose of 5 mL/kg, which contained phenacetin (20 mg/kg), bupropion (20 mg/kg), tolbutamide (5 mg/kg), omeprazole (20 mg/kg), and midazolam (10 mg/kg), was given as oral administration to rats treated with 7 d intraperitoneal injection of KLT. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by HPLC-MS/MS. The corresponding pharmacokinetic parameters were calculated by the software of DAS 2.0 (SPPS Inc., Chicago, IL).

RESULTS

In the experiment, there was a statistically significant difference in the t1/2, Cmax, AUC(0-∞), and CL for phenacetin, bupropion, tolbutamide, omeprazole, and midazolam. Our study showed that treatment with multiple doses of KLT had induction effect on rat CYP1A2, while CYP2B6, CYP2C9, CYP2C19, and CYP3A4 enzyme activities had been inhibited after multiple doses of KLT treatment.

CONCLUSIONS

KLT can either induce or inhibit activities of CYP. Therefore, caution is needed when KLT is co-administration with some CYP substrates in clinic, which may result in herb-drug interactions.