ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Infliximab induces remission in 30–40% of patients with active Crohn's disease. Treatment response is a stable trait over repeated doses yet the clinical predictors of response are still unknown. Recently, three variants in the CARD15 gene have been identified as major genetic risk factors for Crohn's disease. Single nucleotide polymorphisms (SNPs) 8, 12 and 13, have been shown to be independently associated with Crohn's disease susceptibility. The aim of the present study was to investigate these variants in relation to the therapeutic efficacy of infliximab. SNPs were genotyped (TaqMan) in two cohorts (n= 90 andn= 444 (ACCENT I)) of active Crohn's disease patients (CDAI 220–450). The patients were recruited from independent multicenter trials conducted according to GCP. At the start of both trials, patients received a single infusion of open label infliximab (5 mg/kg bodyweight). The genotypic and allelic frequencies of each SNP were significantly associated with Crohn's disease in comparison to 370 healthy controls as reported previously. Response to infliximab (drop in CDAI>70 points or remission, respectively) was not associated with the genetic variants in the CARD15 gene in either cohort. The subsequent negative findings in a two-cohort model exclude SNPs 8, 12 and 13 of the CARD15 gene as predictors for therapeutic response to infliximab treatment.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The major detoxification pathway of the carcinogenic catechol estrogens is methylation by catechol-O-methyltransferase (COMT). It has been hypothesized that the enzyme encoded by the low-activity allele (COMTL) has a lower catalytic activity for catechol estrogen methylation than that encoded by the high activity allele (COMTH). We expressed and purified human soluble (S)-COMTHand S-COMTLinEscherichia coliand characterized the methylation of 2- and 4-hydroxyestradiol (2- and 4-OH-E2). There were no differences between the kinetic parameters for COMTHand COMTL. The kinetic parameters forS-adenosylmethionine (SAM), the methyl donor in these reactions, also did not differ for COMTHand COMTL.S-adenosylhomocysteine, the demethylated SAM metabolite, inhibited methylation of the catechol estrogens in a non-competitive manner similarly for COMTHand COMTL. Each COMT substrate tested inhibited the methylation of other substrates in a mixed competitive and non-competitive fashion similarly for COMTHand COMTL. Furthermore, in cytosolic fractions ofCOMTHH(MCF-10A and ZR-75–1) andCOMTLL(MCF-7 and T47D) human breast epithelial cell lines, no differences were detected between the kinetic parameters of COMT with respect to 2- and 4-OH-E2 methylation; nor were COMT protein levels associated with the COMT genotype. These data suggest that the decreased COMT enzymatic activity that has been detected in human tissue in association with theCOMTLallele is not reflected by differences in the affinity or capacity of COMTHand COMTLfor catechol estrogen methylation. These results raise the question of what accounts for the difference in COMT activity associated with theCOMTHHandCOMTLLgenotypes in human tissue.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Because drug transporters such as P-glycoprotein, the product of the multidrug resistance (MDR1) gene, contribute to the function of the blood–brain barrier, we hypothesized that differences in their expression could affect the uptake of neurotoxic xenobiotics, thereby modulating interindividual susceptibility for neurological disorders such as Parkinson's disease. In a pilot case–control study comprising 95 Parkinson's disease patients (25 early-onset patients with onset age ⩽ 45 years) and 106 controls we analysed the three commonMDR1polymorphisms, 3435C>T in exon 26, 2677G>T,A in exon 21, and −129T>C in exon 1b. There were no statistically significant associations between any of these polymorphisms and Parkinson's disease. However, a distribution pattern consistent with our hypothesis was observed in that the frequency of the 3435T/T genotype, which had previously been associated with decreased P-glycoprotein expression and function, was highest in the early-onset Parkinson's disease group (36.0%), second-highest in the late-onset Parkinson's disease group (22.9%), and lowest in the control group (18.9%). Furthermore, we confirmed that theMDR1exon 21 and exon 26 polymorphisms are in significant linkage disequilibrium since the [2677G, 3435C] and [2677T, 3435T] haplotypes were far more frequently observed than expected. In conclusion,MDR1and other drug transporters represent plausible candidates as Parkinson's disease risk genes. Larger studies are required to confirm this role in the etiology of Parkinson's disease.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Deposition of the β-amyloid peptide (Aβ) in the brain occurs during normal ageing and is substantially accelerated in patients with Alzheimer's disease. Since Aβ is continuously produced in the brain, it has been suggested that a clearance mechanism should exist to prevent its accumulation and subsequent aggregation. Until now, little attention has been paid to the possible role of P-glycoprotein (P-gp), a member of the ATP binding cassette superfamily of transporter proteins, in the pathogenesis of Alzheimer's disease. A recent study demonstratedin vitrothat Aβ40 and Aβ42 interact directly with P-gp. We therefore hypothesized that Aβ accumulation in the brain would correlate inversely with the degree of vascular P-gp expression. To study early pathogenetic factors that influence the deposition of Aβ, at routine autopsies, brain tissue samples were taken from 243 non-demented subjects who died between the ages of 50 and 91 years. Vascular P-gp expression and the number of Aβ40- and Aβ42-positive senile plaques were assessed immunohistochemically in the medial temporal lobe. In addition, the apolipoprotein E (apoE) genotypes, as well as multiple drug resistance gene 1 (MDR1) polymorphisms (exon 2, G–1A; exon 21, G2677T/A; exon 26, C3436T), were also determined for each case. P-gp expression was not correlated withMDR1genotypes, but we found a significant inverse correlation between P-gp expression and the deposition of both Aβ40 and Aβ42 in the medial temporal lobe. Our results provide the first evidence in human brain tissue that the accumulation of Aβ may be influenced by the expression of P-gp in blood vessels, and suggest that P-gp may influence the elimination of Aβ from brain.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The polymorphic human GSTP1 gene locus encodes proteins that differentially metabolize electrophilic substrates, including, many chemotherapeutic agents used in clinical cancer therapy. In this study, we usedEscherichia coliXL1-Blue MRF′strain, transformed with phagemid expression vectors carrying cDNAs of three GSTP1 alleles, to investigate the cytoprotective abilities of the different GSTP1 alleles against four clinically active anticancer agents, namely, carboplatin, cisplatin, thiotepa, and 4-hydroperoxyifosfamide. Following induction of protein expression with isopropyl-β-d-thiogalactoside, the cells were treated with each drug for 3 h (1 h for 4-hydroperoxyifosfamide). Surviving fractions were determined and used to compute a cytoprotective factor for each allele against each drug. The results showed all the GSTP1 alleles to be cytoprotective, albeit, to different degrees. For cisplatin and carboplatin, theGSTP1*Callele was most protective, with CPs of 5.58 and 3.76, respectively, compared with 1.21 and 1.61 forGSTP1*Aand 2.50 and 2.79 forGSTP1*B. In contrast, protection against thiotepa was highest for theGSTP1*Aallele, with a cytoprotective factor of 1.56, compared to 1.32 forGSTP1*Band 1.1 forGSTP1*C. For 4-hydroperoxyifosfamide, the CP forGSTP1*BandGSTP1*Cwas the same, 1.45, compared with 1.18 forGSTP1*A. These data demonstrate significant differences in the ability of the different GSTP1 alleles to protect against the cytotoxicity of electrophilic anticancer agents. The level of protection differs significantly between different GSTP1 alleles, and between different anticancer agents. The optimized prokaryotic system described provides a useful and rapid tool for pharmacogenetic analysis of the effects of genes on drug sensitivity.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (5FU) and a DPD deficiency is increasingly being recognized as an important pharmacogenetic factor in the aetiology of severe 5FU-associated toxicity. In this study, we evaluated the DPD activity and the prevalence of the common splice site mutation IVS14 + 1G>A in tumour patients suffering from severe grade 3–4 toxicity after the administration of 5FU. DPD activity was measured with a radiochemical assay and screening for the presence of the IVS14 + 1G>A mutation was performed by restriction fragment length polymorphism. A decreased DPD activity could be detected in peripheral blood mononuclear cells in 60% of the cases. Furthermore, a high prevalence of the IVS14 + 1G>A mutation was noted as 28% of all patients were heterozygous or homozygous for this mutation. In patients with a low DPD activity, 42% were heterozygous and one patient (3%) was homozygous for the IVS14 + 1G>A mutation. In contrast, the IVS14 + 1G>A mutation could be detected in only one out of 24 (4%) patients with a normal DPD activity. Our study demonstrates that a DPD deficiency is the major determinant of 5FU-associated toxicity. The apparently high prevalence of the IVS14 + 1G>A mutation warrants genetic screening for this mutation in cancer patients before the administration of 5FU.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The slow arylamineN-acetyltransferase 2 (NAT2) phenotype frequently has been assumed to be associated with an elevated risk to develop a lupus-like syndrome after administration of drugs such as procainamide or hydralazine. Moreover, there are conflicting data on the role of acetylator phenotype as a susceptibility factor for systemic lupus erythematosus (SLE). Because most investigations have previously been conducted with relatively small sample sizes, the present study was performed to clarify the possible association betweenNAT2genotypes and SLE among a large European cohort. In a case–control study, 209 patients with SLE (194 women, 15 men) were enrolled and matched by gender to 209 controls without clinical signs of inflammatory diseases. All SLE patients fulfilled at least four of the revised American College of Rheumatology classification criteria of SLE.NAT2was genotyped for seven known mutations by polymerase chain reaction/restriction fragment length polymorphism. The frequency of slow acetylation genotypes in SLE patients (59.8%) did not differ significantly from controls (56.5%). The adjusted odds ratio (OR) was 0.95 (95% confidence interval, 0.59–1.53). Further differentiation to gender, cigarette consumption, allergic disorders and specific SLE manifestations revealed an equal distribution ofNAT2genotypes in all subgroups. We conclude that this large genotyping study in a Caucasian population demonstrated a lack of evidence for an association of the slow acetylator genotype with SLE.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

CysLT1antagonists are effective for a subset of patients with asthma; however, there has been no good way to predict a given patient's response. We examined the interaction between the clinical response to a cysLT1antagonist, pranlukast, and DNA sequence variant A(-444)C in leukotriene C4synthase (LTC4S) gene in Japanese patients with moderate asthma. The frequency of LTC4S C(-444) allele was 21.6% in the Japanese general population (n= 171) and 19.4% in the asthmatic subjects (n= 349). A 4-week prospective, open trial of pranlukast (225 mg twice daily) was performed in 50 patients with moderate asthma who had been well controlled with inhaled corticosteroid (beclomethasone 400–800 μg/day or fluticasone 200–400 μg/day). The C(-444) allele carriers (n= 16) responded better to pranlukast compared to the A(-444) allele homozygotes (n= 31) [14.3±5.3% vs. 3.1±2.4% improvement of forced expiratory volume in one second (FEV1),P<0.01], while LTC4S genotype-stratified response to inhaled β-agonist salbutamol (200 μg) was not observed (17.5±2.1% vs. 18.7±2.2% improvement of FEV1). Univariate analysis demonstrated that the better response to pranlukast (more than 10% improvement of FEV1) was correlated with LTC4S genotype (P<0.01) and pretreatment airway reversibility to salbutamol (P<0.01), but not with sex, age, atopic status, urinary leukotriene E4excretion rate, or daily dose of inhaled corticosteroid. Furthermore, multivariate regression analysis suggested that LTC4S genotype and the bronchodilatory effect of salbutamol were independent variables to predict the clinical response to pranlukast (P<0.05). We conclude that LTC4S genotype is predictive of the clinical response to a cysLT1antagonist, pranlukast, in Japanese patients with moderate asthma.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

In-vitro data indicated a contribution of cytochrome P450 enzymes 1A2, 3A4, 2C9, 2C19 and 2D6 to biotransformation of doxepin. We studied the effects of genetic polymorphisms in CYP2D6, CYP2C9 and CYP2C19 on E- and Z-doxepin pharmacokinetics in humans. Doxepin kinetics was studied after a single oral dose of 75 mg in healthy volunteers genotyped as extensive (EM), intermediate (IM) and poor (PM) metabolizers of substrates of CYP2D6 and of CYP2C19 and as slow metabolizers with the CYP2C9 genotype *3/*3. E-, Z-doxepin andN-desmethyldoxepin were quantified in plasma by HPLC. Data were analyzed by non-parametric pharmacokinetics and statistics and by population pharmacokinetic modeling considering effects of genotype on clearance and bioavailability. Mean E-doxepin clearance (95% confidence interval) was 406 (390–445), 247 (241–271), and 127 (124–139) l h–1in EMs, IMs and PMs of CYP2D6. In addition, EMs had about 2-fold lower bioavailability compared with PMs indicating significant contribution of CYP2D6 to E-doxepin first-pass metabolism. E-doxepin oral clearance was also significantly lower in carriers of CYP2C9*3/*3 (238 l h–1). CYP2C19 was involved in Z-doxepin metabolism with 2.5-fold differences in oral clearances (73 l h–1in CYP2C19 PMs compared with 191 l h–1in EMs). The area under the curve (0–48 h) of the active metaboliteN-desmethyldoxepin was dependent on CYP2D6 genotype with a median of 5.28, 1.35, and 1.28 nmol l h–1in PMs, IMs, and EMs of CYP2D6. The genetically polymorphic enzymes exhibited highly stereoselective effects on doxepin biotransformation in humans. The CYP2D6 polymorphism had a major impact on E-doxepin pharmacokinetics and CYP2D6 PMs might be at an elevated risk for adverse drug effects when treated with common recommended doses.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID