Effects of acid and lactone forms of statins on S-warfarin 7-hydroxylation catalyzed by human liver microsomes and recombinant CYP2C9 variants (CYP2C9.1 and CYP2C9.3).

The inhibition of CYP2C9-mediated warfarin metabolism by acid or lactone forms of statin converted in the body and effects of CYP2C9 genetic variants on their inhibition are not fully understood. Here, the effects of acid and lactone forms of statins on S-warfarin 7-hydroxylation were investigated in vitro. S-Warfarin 7-hydroxylase activities of human liver microsomes (HLMs), recombinant CYP2C9.1 (rCYP2C9.1), and rCYP2C9.3 (Ile359Leu variant) in the presence of statins were determined by high-performance liquid chromatography. Lactone forms of atorvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin inhibited the activity of HLMs more potently than the corresponding acid forms, whereas fluvastatin acid showed stronger inhibition than fluvastatin lactone. When the effects of statins on rCYP2C9 variants were examined, inhibition profiles of acid versus lactone forms of statins except for fluvastatin were similar between rCYP2C9.1 and rCYP2C9.3. However, the degrees of inhibition by atorvastatin lactone, fluvastatin acid, fluvastatin lactone, lovastatin lactone, and pitavastatin lactone (Ki values) were significantly different between these variants. These results indicated that lactone forms of statins other than fluvastatin showed more potent inhibition of CYP2C9-catalyzed S-warfarin 7-hydroxylation than the corresponding acid forms. Furthermore, our results indicated that Ile359Leu substitution in CYP2C9 affected the inhibitory potencies of statins.

Predictive Value of FMO3 Variants on Plasma Disposition and Adverse Reactions of Oral Voriconazole in Febrile Neutropenia.

BACKGROUND AND OBJECTIVES: With the increasing number of patients with febrile neutropenia (FN), voriconazole (VRC) has been widely used in hospitals for first-line treatment of FN. The study was designed for evaluating the influence of FMO3 mutation on the plasma disposition and adverse reactions of VRC in FN. MATERIALS AND METHODS: A single-center observational study was conducted in the inpatient ward for 4 years. The genotypes of FMO3 and cytochrome P450 (CYP) 2C19 were detected by PCR-restriction fragment length polymorphism. Patients with neutropenia were screened according to the CYP2C19 metabolic phenotype and other inclusion criteria. Five days after empirical administration of VRC, blood concentrations of VRC and nitrogen oxides in patients' blood were determined by liquid chromatography-electrospray tandem mass spectrometry (LC-ESI MS/MS). Serum parameters and clinical adverse reaction symptoms in the medical records were collected and statistically analyzed. RESULTS: A total of 165 patients with neutropenia with the intermediate metabolic phenotype of CYP2C19 were screened. At the initial stage of oral VRC treatment, patients with the FMO3 E308G genotype had a poorer plasma disposal ability to VRC than those with the wide type of FMO3 (WT) genotype (p = 0.0005). Moreover, patients with the FMO3 E308G genotype were more likely to have adverse drug reactions and abnormal serum parameters after receiving VRC treatment. For example, the serum potassium level in the FMO3 E308G genotype group was significantly lower than that in the WT group (p = 0.028), the abnormal level of total bilirubin in the FMO3 E308G genotype group was significantly higher than that in the WT group (p = 0.049), and the aspartate aminotransferase level in the E308G group was significantly higher than that in the WT group (p = 0.05). The incidence of atopic dermatitis and visual impairment in the FMO3 E308G genotype group was 67 and 75%, respectively, and the incidences of peripheral neuroedema, headache, and diarrhea were 57, 50, and 60%, respectively, which were significantly different from those in the WT group. CONCLUSION: FMO3 E308G reduces the activity of the FMO3 enzyme by decreasing the metabolic ability of VRC, which increases the plasma concentration of VRC and may also lead to adverse reactions in patients with FN.

Association between polymorphisms in microRNA seed region and warfarin stable dose.

BACKGROUND: The optimal dose of anticoagulant warfarin varies among patients to achieve the target international normalised ratio. Although genetic variations related to warfarin pharmacokinetics and vitamin K cycle are important factors associated with warfarin dose requirements, these variations do not completely explain the large interindividual variability observed in the most populations, suggesting that additional factors may contribute to this variability. microRNAs have recently been introduced as regulators of drug function genes, and therefore, may be involved in drug responses. In this study, we aimed to evaluate the possible association between variants in the seed region of microRNAs, which target the genes involved in the action of warfarin and warfarin dose requirement. METHODS: 526 samples were collected from Iranian patients. Four selected polymorphisms in the seed region of microRNAs (rs2910164, rs66683138, rs12416605 and rs35770269 in miR-146a, miR-3622a, miR-938 and miR-449c, respectively) were genotyped by PCR-restriction fragment length polymorphism method. RESULTS: rs2910164 C/G in the seed region of miR-146a was associated with warfarin dose requirement (p<0.001); the patients with GG genotype had the higher mean dose of warfarin (40.6 mg/week, compared with 33.9 and 31.8 mg/week for GC and CC genotypes, respectively). The association of other polymorphisms with warfarin dose requirement was not statistically significant. CONCLUSION: rs2910164 C/G in the seed region of miR-146a is associated with warfarin maintenance dose, likely by disrupting interaction between miR-146a and ATP-binding cassette subfamily B member 1 gene, ABCB1. Therefore, this polymorphism may possibly be a potential factor for assessment of warfarin dose requirements.

Hereditary component of variation in 90Sr deposition in inbred mice under exogenous conditions that affect bone formation.

Bone-seeking radionuclides (specifically 90Sr) accumulate in the bone tissue and act as a long-term source of internal irradiation. Their behaviour in the body has been studied in detail, while the impact of inheritance has not been established. On one hand, the genetic determination of both skeletal morphology and calcium metabolism is indirect evidence that the kinetics of deposition of alkaline-earth radioisotopes in the skeleton also have a hereditary component. On the other hand, analysis of 90Sr kinetics in different inbred mouse strains did not reveal any differences between the mice. This study used a classical approach to evaluating the hereditary component of variation in quantitative traits, namely, a variant of familial analysis (the method of twin families). The growth of the skeleton is known to be accompanied by distinct changes in 90Sr accumulation. That is why the hereditary (familial) component of variation in 90Sr kinetics in the bone tissue of CBA mice was analyzed under the influences that modify growth processes Individual parameters of 90Sr accumulation differed between experimental groups by a factor of 2-4.5. At the same time, features of 90Sr accumulation proved to be characteristic of entire families. The results show that the intrafamilial correlation in 90Sr deposition in the skeleton is highly significant (R = 0.542, P ≤ 0.0001) and comparable to that of morphological parameters (R = 0.532-0.546, P ≤ 0.0001). The results confirm the existence of statistically significant intrafamilial correlations of weight and metabolic parameters, which is similarly expressed in different families, thereby providing evidence for hereditary determination of 90Sr metabolism. At the same time, the stability of 90Sr metabolism inheritance to changes in morphophysiology and environmental influences (including those close to pathogenic ones) is shown. This is evidence of its authenticity and significance. The results obtained can be extrapolated to humans instead of directly analyzing the role of hereditary factors in the metabolism of toxic compounds, which are difficult and unethical to perform in human subjects.

Critical Issues and Optimized Practices in Quantification of Protein Abundance Level to Determine Interindividual Variability in DMET Proteins by LC-MS/MS Proteomics.

Protein quantification data on drug metabolizing enzymes and transporters (collectively referred as DMET proteins) in human tissues are useful in predicting interindividual variability in drug disposition. While targeted proteomics is an emerging technique for quantification of DMET proteins, the methodology involves significant technical challenges especially when multiple samples are analyzed in a single study over a long period of time. Therefore, it is important to thoroughly address the critical variables that could affect DMET protein quantification.

Truncated µ-Opioid Receptors With 6 Transmembrane Domains Are Essential for Opioid Analgesia.

BACKGROUND: Most clinical opioids act through µ-opioid receptors. They effectively relieve pain but are limited by side effects, such as constipation, respiratory depression, dependence, and addiction. Many efforts have been made toward developing potent analgesics that lack side effects. Three-iodobenzoyl-6ß-naltrexamide (IBNtxA) is a novel class of opioid active against thermal, inflammatory, and neuropathic pain, without respiratory depression, physical dependence, and reward behavior. The µ-opioid receptor (OPRM1) gene undergoes extensive alternative precursor messenger ribonucleic acid splicing, generating multiple splice variants that are conserved from rodents to humans. One type of variant is the exon 11 (E11)-associated truncated variant containing 6 transmembrane domains (6TM variant). There are 5 6TM variants in the mouse OPRM1 gene, including mMOR-1G, mMOR-1M, mMOR-1N, mMOR-1K, and mMOR-1L. Gene-targeting mouse models selectively removing 6TM variants in E11 knockout (KO) mice eliminated IBNtxA analgesia without affecting morphine analgesia. Conversely, morphine analgesia is lost in an exon 1 (E1) KO mouse that lacks all 7 transmembrane (7TM) variants but retains 6TM variant expression, while IBNtxA analgesia remains intact. Elimination of both E1 and E11 in an E1/E11 double KO mice abolishes both morphine and IBNtxA analgesia. Reconstituting expression of the 6TM variant mMOR-1G in E1/E11 KO mice through lentiviral expression rescued IBNtxA but not morphine analgesia. The aim of this study was to investigate the effect of lentiviral expression of the other 6TM variants in E1/E11 KO mice on IBNtxA analgesia. METHODS: Lentiviruses expressing 6TM variants were packaged in HEK293T cells, concentrated by ultracentrifugation, and intrathecally administered 3 times. Opioid analgesia was determined using a radiant-heat tail-flick assay. Expression of lentiviral 6TM variant messenger ribonucleic acids was examined by polymerase chain reaction (PCR) or quantitative PCR. RESULTS: All the 6TM variants restored IBNtxA analgesia in the E1/E11 KO mouse, while morphine remained inactive. Expression of lentiviral 6TM variants was confirmed by PCR or quantitative PCR. IBNtxA median effective dose values determined from cumulative dose-response studies in the rescued mice were indistinguishable from wild-type animals. IBNtxA analgesia was maintained for up to 33 weeks in the rescue mice and was readily antagonized by the opioid antagonist levallorphan. CONCLUSIONS: Our study demonstrated the pharmacological relevance of mouse 6TM variants in IBNtxA analgesia and established that a common functional core of the receptors corresponding to the transmembrane domains encoded by exons 2 and 3 is sufficient for activity. Thus, 6TM variants offer potential therapeutic targets for a distinct class of analgesics that are effective against broad-spectrum pain models without many side effects associated with traditional opioids.

Pharmacogenetic implications in the management of metabolic diseases in Brazilian populations

Dyslipidemia, diabetes, obesity and hypertension are common metabolic diseases. In the last decades, unhealthy lifestyle and aging have leads to an increased incidence of these diseases, increasing morbidity and mortality by cardiovascular causes. The treatment of metabolic diseases includes life-style interventions as healthy diet and physical exercise, as well as pharmacological interventions. Several drugs are available for the management of metabolic diseases including among others lipid-lowering antidiabetics and antihypertensive drugs. Variability in response to these drugs is influenced by both genetic and non-genetic factors. Polymorphisms in genes related to drug pharmacokinetics and pharmacodynamics have been shown to influence drug efficacy and safety. This review is focused on pharmacogenetic studies related to the management of metabolic diseases in samples of the Brazilian population. Associations of variants in drug metabolizing enzymes and transporters, drug target and metabolism-related genes with the efficacy and safety of lipid-lowering, antidiabetic and antihypertensive drugs are described. Most pharmacogenetic studies in Brazil have focused in pharmacological response to a small group of drugs, as statins and some antihypertensives, while there are almost no studies on antidiabetic and antiobesity drugs. Some studies reported significant associations of gene polymorphisms with drug response confirming previous data from other populations, whereas other works did not replicate, which may relay on the genetic admixture of our population. In conclusion, further studies are necessary considering larger sample sizes, new unexplored drugs and more genetic variants to obtain stronger conclusions to explore clinical applications of pharmacogenetic studies in our population.

Function of 38 variants CYP2C9 polymorphism on ketamine metabolism in vitro.

BACKGROUND: Cytochrome P450 proteins (CYP 450) is the most important enzyme system of drug phase I metabolism in liver. In previous reports, reduced efficiency or increased risk of adverse events can be affected by primary sequence mutation in CYP450. AIM: To investigate the effect of gene polymorphism on the metabolism of ketamine in vitro, including the new alleles: 2C9*58, *59 and *60. METHOD: Incubation system which was contained insect microsome, b5, NADPH and 1M PBS incubated 10 µM-1000 µM ketamine in 37 °C for 40 min concentration of norketamine was analyzed by ultra-performance liquid chromatography-tandem mass spectrometry system (UPLC-MS/MS). RESULT: Catalytic activity of thirty-eight CYP2C9 alleles on ketamine metabolism to norketamine was surveyed. Compared with 2C9*1, three alleles (2C9*40, *49 and *51) was demonstrated dramatically increased intrinsic clearance (1.2-fold-3.75-fold); four subtypes (2C9*27, *31, *41 and *56) exhibited no significantly change on enzyme activity. The resting 31 alleles expressed different degrees of reduction compared with wild type. CONCLUSION: The result of research warns that attention should be more paid on individual who carry on the special 2C9 alleles under the situation of administrating ketamine.

Variant Inosine Triphosphatase Phenotypes Are Associated With Increased Ribavirin Triphosphate Levels.

Individuals with lower inosine triphosphatase (ITPA) enzyme activity have a reduced likelihood of experiencing hemolytic anemia during hepatitis C virus (HCV) treatment containing ribavirin (RBV). Because ITPA degrades purines and RBV is a purine analogue, it is conceivable that ITPA activity may affect intracellular RBV concentrations. Here we assessed the association between ITPA activity phenotype and concentrations of RBV triphosphate (RBV-TP) in red blood cells (RBCs) during HCV treatment. RBV-TP was quantified in the RBCs of 177 HCV-infected individuals at a median (range) of 84 (19 to 336) days into HCV treatment that included RBV. Mean (SD) RBV-TP concentrations were 92.8 (51.6), 101.3 (53.5), 184.8 (84.5), and 197.7 (64.6) pmol/106 cells for 100%, 60%, 30%, and ≤10% ITPA activity groups, respectively. Overall, RBV-TP was approximately 2-fold higher in patients with ≤30% ITPA activity compared to 100% activity (P < .0001). Despite higher RBV-TP levels, individuals with variant ITPA phenotypes had less anemia. The 100% activity group had, on average, a -2.20 g/dL drop in hemoglobin vs -1.43 g/dL (P = .04) for 60% activity, -1.14 g/dL (P = .008) for 30% activity, and -0.70 g/dL (P = .06) for ≤10% activity. This finding of higher RBV-TP concentrations in RBCs in ITPA variants was unexpected given that ITPA activity-deficient individuals have a reduced likelihood of RBV-induced anemia. It also refutes the hypothesis that the mechanism by which ITPA variants are protected against anemia is due to lower RBV-TP levels in RBCs.