摘要:

Polymorphisms of N-acetyltransferase type 2 (NAT2) conferring the slow acetylator phenotype have been linked to increased susceptibility to arylamine-induced bladder cancer in Caucasians. Genes for NAT2, the other NAT isozyroe, NAT1, and a NAT pseudogene (NATP) are found on 8p22, a region displaying loss of heteroiygosity, particularly in invasive bladder tumours. A restriction enzyme digestion map has defined the relative positions of the NAT genes to each other and to adjacent CpG islands. NAT2, as a polymorphic gene of known function, is a potentially valuable marker for the detection of loss of hetennygosity in 8p22. Two approaches to investigate loss of heterozygosity at the NAT2 focus in bladder tumours have been used. (1) A cosmid containing NAT2 has been used in fluorescence in-situ hybridization on human exfoliated bladder cells collected from unselected bladder cancer outpatients. Loss of signal from the NAT2 cosmid was found in nine of the 20 patients. (2) A panel of 13 human bladder tumours was investigated for loss of heterozygosity using the polymorphism in the NAT2 gene as a marker. Loss of heterozygosity at the NAT2 locus has been compared with loss of heterozygosity at adjacent microsatellite marker sites known to be located on 8p. There is agreement between loss of heterozygosity at the NAT2 locus and adjacent microsatellite marker loci in 11 of the tumours but two of the tumours appear to show retention at the NAT2 locus. More extensive mapping of the region around the NAT loci, particularly on the centromeric side, is important to pinpoint possible tumour suppressor genes or their modifiers in the region. There are no other expressed sequences known in this region and therefore NAT genes are important genetic landmarks. Pharmacogentics 9:1–8 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The importance of environmental aggression and individual susceptibility to develop Alzheimer's Disease (AD) has been suggested by epidemiological studies on both typical familial and sporadic AD cases. In order to elucidate functions that can influence the susceptibility to AD pathogenesis, we genotyped a group of 53 sporadic late-onset AD patients, matched control individuals and a larger randomly selected non-demented population for theN-acetyltransferase (NAT2). We determined the relative frequencies of individual allele combinations that define a broad range of acetylator phenotypes. Inter-individual variability in the cytotoxic and genotoxic responses to a wide diversity of environmental chemicals is known to result from the polymorphism ofNAT2as well as other drug-metabolizing-enzyme genes. The results presented are the first to demonstrate a significant difference in theNAT2genotype profiles of sporadic AD patients compared with the healthy population. A lower frequency of the recessive allelesNAT2*6(chi-squared 1 d.f. = 12.56,P< 0.0004) andNAT2*5B(chi-squared 1 d.f. = 6.72,P< 0.01) was found among the AD population compared with control indivduals, which was concomitant with a significantly higher number ofNAT2*4fully active allele homozygotes and heterozygotes (chi-squared 1 d.f. = 5.69,P= 0.017). The most notable observation was the absence ofNAT2*5B/NAT2*6heterozygotesamong cases while being present in 22.5% of control individuals (chi-squared 1 d.f. = 13.08,P= 0.0003). These observations indicate thatNAT2is a potential low-penetrance gene in AD pathogenesis, determining an individual susceptibility trait predisposing to this degenerative disease. Pharmacogenetics 9:9–15 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Neuroleptics, or antipsychotics, are widely used for the treatment of psychotic symptoms such as hallucinations and delusions in schizophrenia and other psychiatric disorders. Pharmacotherapy of these diseases is frequently complicated by a great variability in the clinical response to neuroleptics and by the development of serious and potentially life-threatening side-effects. Brain D2dopamine receptors are one of the major targets of neuroleptic treatment. The human D2dopamine receptor (DRD2) gene has three variants predicting the amino acid substitutions Ser311Cys, Pro310Ser and Val96Ala in the receptor protein. We show that several typical and atypical neuroleptics commonly used in the treatment of psychotic disorders have differences in binding affinities and potencies for the D2dopamine receptor variants. Functional differences between dopamine receptor variants might be related to genetically determined differences in response to neuroleptic treatment. Pharmacogenetics 9:17–23 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The human alcohol dehydrogenase 4 gene (ADH4) encodes the human π-alcohol dehydrogenase (π-ADH), which can contribute to ethanol metabolism at moderate and high concentrations of ethanol. There are no known structural variants of π-ADH in humans. We report the first polymorphisms in theADH4gene, at three sites in the promoter:-192 bp, −159 bp and −75 bp, respectively. To determine whether these variations affected promoter function, different haplotypes of theADH4proximal promoter were subcloned into a luciferase reporter vector, and the relative promoter activity analysed in hepatoma cells. One of the three sites had a dramatic effect on promoter activity, while the others did not detectably affect activity. The −75A allele had promoter activity more than twice that of the −75C allele. Alcohol dehydrogenase activity is rate limiting for ethanol oxidation. We hypothesize that the differentADH4alleles lead to different amounts of π-ADH in liver, which affects the risk for alcoholism by modulating alcohol metabolism. Pharmacogenetics 9:25–30 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The similarities between the clinical and pathological findings of dementia with Lewy Bodies (DLB) with Alzheimer's disease and Parkinson's disease are complex, and their significance for pathogenesis is unresolved. It is likely that DLB shares common disease determinants with both Alzheimer's disease and Parkinson's disease. Clinically DLB shows the presence of dementia similar, though not identical, to that found in Alzheimer's disease. A parkinsonian movement disorder is present in a proportion of DLB cases. Pathologically DLB shows senile plaques, as with Alzheimer's disease, and also substantia nigra neurone loss and Lewy bodies, as with Parkinson's disease. At a genetic level, DLB shows an elevated Apolipoprotein E & epsilon4 frequency as described in Alzheimer's disease, but this is absent in Parkinson's disease. An elevated frequency of theCYP2D6*4allele has been found in Parkinson's disease and we have therefore genotyped a large series of clinically and neuropathologically confirmed cases of DLB, Alzheimer's disease, Parkinson's disease and age-matched control individuals for theCYP2D6*4allele. Whilst an elevated frequency of theCYP2D6*4allele was found in Parkinson's disease, no such elevations were found in DLB or Alzheimer's disease. Stratification of theCYP2D6*4allele with respect to the Apolipoprotein E & epsilon4 also did not show any significant associations with theCYP2D6*4allele. TheCYP2D6*4allele is not a major genetic determinant of DLB and the results place DLB with Alzheimer's disease rather than Parkinson's disease on a genetic level. Pharmacogenetics 9:31–35 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Thiopurine methyltransferase metabolizes 6-mercaptopurine, thioguanine and azathioprine, thereby regulating cytotoxicity and clinical response to these thiopurine drugs. In healthy Caucasian populations, 89–94% of individuals have high thiopurine methyltransferase activity, 6–11% intermediate and 0.3% low, resulting from genetic polymorphism. Four variant thiopurine methyltransferase alleles were detected in over 80% of individuals with low or intermediate thiopurine methyltransferase activity. The wild-type allele is defined asTPMT*1and the mutant alleles areTPMT*2(G238C),TPMT*3A(G460A and A719G),TPMT*3B(G460A) andTPMT*3C(A719G). The frequency of these alleles in different ethnic groups is not well defined. In this study, DNA from 199 British Caucasian, 99 British South West Asian and 192 Chinese individuals was analysed for the presence of these variant alleles using polymerase chain reaction-restriction fragment length polymorphism and allele-specific polymerase chain reaction based assays. The frequency of individuals with a variant thiopurine methyltransferase genotype was: Caucasians 10.1% (20/199), South West Asians 2.0% (2/99) and Chinese 4.7% (9/192). TwoTPMT*2heterozygotes were identified in the Caucasian population, but this allele was not found in the two Asian populations.TPMT*3Awas the only mutant allele found in the South West Asians (two heterozygotes). This was also the most common mutant allele in the Caucasians (16 heterozygotes and one homozygote) but was not found in the Chinese. All mutant alleles identified in the Chinese population wereTPMT*3C(nine heterozygotes). This allele was found at a low frequency in the Caucasians (one heterozygote). This suggests that A719G is the oldest mutation, with G460A being acquired later to form theTPMT*3Aallele in the Caucasian and South West Asian populations.TPMT*2appears to be a more recent allele, which has only been detected in Caucasians to date. These ethnic differences may be important in the clinical use of thiopurine drugs. Pharmacogenetics 9:37–42 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Sulphamethoxazole undergoes CYP2C9-mediated bioactivation to a hydroxylamine. In this study, we investigated the effect of the CYP2C9Arg144to Cys (CYP2C9*2) and CYP2C9Ile359to Leu (CYP2C9*3) polymorphisms on sulphamethoxazole N-hydroxylation. Human livers were genotyped using polymerase chain reaction amplification and restriction fragment length polymorphism analysis. Formation of sulphamethoxazole hydroxylamine and methylhydroxy tolbutamide in microsomes prepared from cell lines and the genotyped human livers was determined by high-pressure liquid chromatography. Microsomes prepared from the cell line expressing the allelic variants CYP2C9-Cys144and CYP2C9-Leu359displayed a threefold and 20-fold decrease in intrinsic clearance (Clint) for sulphamethoxazole, respectively, when compared with the wild-type, CYP2C9-Arg144. A significant decrease (P< 0.05) in Clintwas also observed with tolbutamide for both mutations. Of the 26 human livers genotyped, 61.5% were homozygous wild-type, 26.9% were heterozygotes forCYP2C9*2and 15.4% were heterozygotes forCYP2C9*3. No homozygous mutant livers were detected. There was a good correlation between sulphamethoxazole N-hydroxylation and tolbutamide methyl hydroxylation (r= 0.825). However, there was no difference in the kinetic parameters for either sulphamethoxazole N-hydroxylation or tolbutamide methyl hydroxylation between the wild type livers (n= 6) and either the livers heterozygous for theCYP2C9*2(n= 5) or the livers heterozygous for theCYP2C9*3mutation (n= 3). TheCYP2C9*2andCYP2C9*3polymorphisms may have some influence on the bioactivation of sulphamethoxazole, particularly in individuals who are homozygous mutants, and this could act as a protective factor against sulphamethoxazole hypersensitivity. However, given the rarity of homozygous mutants, it is likely that other metabolic and immunological risk factors will dominate individual susceptibility. Pharmacogenetics 9:43–53 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The selective serotonin reuptake inhibitor fluoxetine is administered as a racemic mixture, and R- and S-fluoxetine are metabolized in the liver by N-demethylation to R- and S-norfluoxetine, respectively. R- and S-fluoxetine and S-norfluoxetine are equally potent selective serotonin reuptake inhibitors, but R-norfluoxetine is 20-fold less potent in this regard. Racemic fluoxetine and norfluoxetine are potent inhibitors of cytochrome P450 (CYP) 2D6in vivoandin vitroand recent studiesin vivohave shown that racemic fluoxetine is metabolized by CYP2D6. The primary aim of the present study was to investigate the stereoselective metabolism of fluoxetine and norfluoxetine by CYP2D6in vivo.A single oral dose of fluoxetine (60 mg) was administered to six poor and six extensive metabolizers of sparteine. Blood samples were collected during 6 weeks for poor metabolizers and 3 weeks for extensive metabolizers. Once a week a sparteine test was performed. The R- and S-enantiomers of fluoxetine and norfluoxetine were determined by a stereoselective gas chromatography-mass spectroscopy method. In the poor metabolizers, the oral clearance of R- and S-fluoxetine was 3.0 1/h and 17 1/h, respectively, the corresponding values in the extensive metabolizers were 36 1/h and 40 1/h, respectively. For both enantiomers, the phenotype difference was statistically significant. In poor metabolizers, the elimination half-lives were 6.9 days and 17.4 days for R- and S-norfluoxetine, respectively, and in the extensive metabolizers it was 5.5 days for both enantiomers, a significant phenotypical difference only for S-norfluoxetine. For fluoxetine the elimination half-lives were 9.5 and 6.1 days in poor metabolizers for the R- and S-enantiomer, respectively. The corresponding values in the extensive metabolizers were 2.6 and 1.1 days, respectively. Also for this parameter, the differences were statistically significant. This study shows that CYP2D6 catalyses the metabolism of R- and S-fluoxetine and most likely the further metabolism of S-norfluoxetine but not of R-norfluoxetine. Pharmacogenetics 9:55–60 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

P450 S12, an engineered human P450 1A2 containing the 88-first amino-acids of the P450 1A1, demonstrates particularly high expression level in yeast while exhibiting catalytic properties very similar to the moderately expressed natural human P450 1A2. To facilitate P450 purification by nickel chelate chromatography, C-terminal extensions including histidine tags were tested. The -G(H)4extension was found to be particularly efficient for permitting high expression levels without any catalytic alteration. This engineered P450 was purified to electrophoretic homogeneity (18 nmol/mg of protein) at a very high yield (87%) without any detectable formation of P420. P450 S12 activities were reconstituted in the presence of yeast andArabidopsis thaliana(ATR1) NADPH-P450 reductases. The plant reductase supported better ethoxyresorufin-, methoxyresorufin- and phenacetin-O-dealkylase activities than the yeast reductase in reconstituted systems. Interestingly, polyclonal antibodies raised against purified P450 S12 selectively recognized in Western blot and fully immuno-inhibited the natural or recombinant P450 1A2 with very limited or no cross-reaction with P450 1A1 and other isoenzymes. Pharmacogenetics 9:61–70 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Genetic polymorphisms in the cytochrome P450 (CYP) family are widely known to contribute to interindividual differences in the pharmacokinetics of many drugs. Several alleles for theCYP2C9gene have been reported. Individuals homozygous for the Leu359variant (CYP2C9*3) have been shown to have significantly lower drug clearances compared with Ile359(CYP2C9*1) homozygous individuals. A male Caucasian who participated in six bioavailability studies in our laboratory over a period of several years showed extremely low clearance of two drugs: phenytoin and glipizide (both substrates of CYP2C9), but not for nifedipine (a CYP3A4 substrate) and chlorpheniramine (a CYP2D6 substrate). His oral clearance of phenytoin was 21% of the mean of the other 11 individuals participating in the study, and his oral clearance of glipizide, a second generation sulfonylurea structurally similar to tolbutamide, was only 18% of the mean of the other 10 individuals. However, his oral clearance of nifedipine and chlorpheniramine did not differ from individuals in other studies performed at our laboratories. An additional blood sample was obtained from this individual to determine if he possessed any of the knownCYP2C9orCYP2C19allelic variants that would account for his poor clearance of the CYP2C9 substrates (phenytoin and glipizide) compared with the CYP3A4 (nifedipine) and CYP2D6 (chlorpheniramine) substrates. The results of the genotype testing showed that this individual was homozygous for theCYP2C9*3allele and did not possess any of the known defectiveCYP2C19alleles. This study establishes that the Leu359mutation is responsible for the phenytoin and glipizide/tolbutamide poor metabolizer phenotype. Pharmacogenetics 9:71–80 © 1999 Lippincott Williams & Wilkins

ISSN:0960-314X    

出版商:OVID    

年代:1999

数据来源: OVID