摘要:

To assess the effects of Ile359to Leu359change on CYP2C9-mediated metabolism, we performed site-directed mutagenesis and cDNA expression in yeast for CYP2C9 and examined in detail the kinetics of seven metabolic reactions by wild-type CYP2C9 (Ile359) and its Leu359variant. For the metabolism of all the substrates studied, the Leu359variant exhibited smallerVmax/Kmvalues than did the wild-type. The differences in theVmax/Kmvalues between the wild-type and the Leu359variant varied from 3.4-fold to 26.9-fold. The Leu359variant had higherKmvalues than did the wild-type for all the reactions studied. Among the seven reactions studied, the greatest difference in theVmaxvalues between the wild-type and the Leu359variant was for piroxicam 5′-hydroxylation (408 versus 19 pmol/min/nmol P450), whereas there were no differences in theVmaxvalues between the wild-type and the Leu359variant for diclofenac 4′-hydroxylation and tolbutamide methylhydroxylation. These results indicate that the Ile359to Leu359change significantly decreases the catalytic activity of all the CYP2C9-mediated metabolisms studied, whereas the extent of the reduction in activity and changes of the kinetic parameters varies between substrates. Moreover, the amino acid substitution decreased the enantiomeric excess in the formation of 5-(4-hydroxyphenyl)-5-phenylhydantoin from phenytoin.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

To examine the risk of lung cancer associated with theMspI-restriction fragment length polymorphism and Exon7-Val polymorphisms ofCYP1A1, a meta-analysis of published case–control studies was undertaken using a random effects model. The principal outcome measure was the odds ratio for the risk of lung cancer, using homozygosity of the `wild-type allele' as the reference group. Fifteen reports detailing the relationship between the lung cancer and theMspI andIle-Valpolymorphisms ofCYP1A1were identified. The odds ratio of lung cancer associated with theMspI combined variant and homozygous genotypes were 1.09 (0.94–1.25) and 1.27 (0.91–1.77), respectively. The odds ratio of lung cancer associated with theIle-Valcombined variant and homozygous genotypes were 1.16 (0.92–1.48) and 1.62 (0.93–2.82), respectively. The hypothesis that the modulation of carcinogen metabolism is under genetic control is a plausible and attractive mechanism for explaining inter-individual susceptibility of lung cancer. However, the results from this analysis provide little support for the role of variation in theCYP1A1gene defined by either polymorphisms represents as lung cancer risk factor. Additional well-designed studies based on sample sizes commensurate with the detection of small genotypic risks may allow a more definitive conclusion.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

TheNAT2gene is involved in phase II detoxification of aromatic monoamines, a class of known bladder carcinogens. Certain allelic combinations result in the slow acetylation phenotype, which is thought to increase bladder cancer risk. We conducted a meta-analysis of all identifiable published case–control studies conducted in the general population that had examined the relationship of acetylation status and bladder cancer risk (22 studies, 2496 cases, 3340 controls). Using meta-analysis techniques that employed weighting based on individual-study variation, slow acetylators had an approximately 40% increase in risk compared with rapid acetylators [odds ratio (OR) 1.4, 95% confidence interval (CI) 1.2–1.6]. Statistical tests indicated, however, that pooling of all studies, or of studies conducted in Caucasian populations, hid potentially important heterogeneity in the individual study results, and suggested that the relationship of NAT2 slow acetylation and bladder cancer risk might differ by geographical region. Studies conducted in Asia generated a summary OR of 2.1 (CI 1.2–3.8), in Europe, a summary OR of 1.4 (CI 1.2–1.6), and in the USA, a summary OR of 0.9 (CI 0.7–1.3). Among European studies, the relationship between NAT2 slow acetylation and bladder cancer risk did not differ by method used to assess acetylation status (older drug-based phenotyping methods: 10 studies, OR 1.5, CI 1.2–1.8; more recentNAT2 genotyping methods: four studies, OR 1.4, CI 1.1–1.7). Our results suggest that in most populations studied to date, NAT2 slow acetylation status is associated with a modest increase in bladder cancer risk.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Two members of the mu class of glutathioneS-transferase (GST) genes,GSTM1andGSTM3, have polymorphic alleles which have been associated with altered levels of GST μ protein expression and may be linked to increased risk for several tobacco-related cancers. Oral cancer is a tobacco-related disease that affects African-American men at a significantly higher incidence than Caucasian men. To examine the potential role of GSTM polymorphisms in risk for oral cancer in African-Americans and Caucasians, the prevalences of theGSTM1null andGSTM3intron 6 polymorphisms were examined in 63 African-American and 101 Caucasian patients with histologically confirmed primary oral cancer, as well as in 133 African-American and 213 Caucasian matched control subjects. In African-Americans, the odds ratio for oral cancer associated with theGSTM1(0/0) genotype was 3.1 [95% confidence interval (CI) = 1.1–8.5], with the association between theGSTM1(0/0) genotype and oral cancer risk strongest in heavy smokers [i.e. > 24 pack-years; odds ratio (OR) = 5.4, 95% CI = 1.2–24]. Using the potentially most protectiveGSTM1[+]/GSTM3(B/B) genotype as the reference group, increased risk for oral cancer was observed in African-Americans with theGSTM1[+]/GSTM3[(A/A) + (A/B)] (OR = 2.2, 95% CI = 0.82–6.0),GSTM1(0/0)/GSTM3(B/B) (OR = 4.3, 95% CI = 1.1–16), andGSTM1(0/0)/GSTM3[(A/A) + (A/B)] (OR = 6.6, 95% CI = 1.2–38) genotypes (P< 0.01, trend test). No significant associations were observed betweenGSTMgenotype and oral cancer risk in Caucasians. These results suggest that theGSTM1null andGSTM3intron 6 polymorphisms play an important role in risk for oral cancer among African-Americans and implicates the mu class of GSTs as important tobacco carcinogen detoxifying enzymes in this population.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Endothelial nitric oxide synthase (eNOS) plays a key role in vascular homeostasis. Because its product, nitric oxide, possesses vasodilatory and antiatherogenic properties, an altered eNOS function might promote atherosclerosis. We investigated the association between variations in CA repeat copy number [(CA)npolymorphism] in intron 13 of theeNOSgene and the risk of coronary artery disease. (CA)npolymorphism was investigated in 1000 consecutive patients with angiographically confirmed coronary artery disease and 1000 age- and gender-matched control subjects by a PCR-based fragment length calculation. Twenty-eight different alleles were identified containing 17–44 CA repeats. The presence of one allele containing ⩾ 38 repeats was associated with an excess risk of coronary artery disease (odds ratio 1.94, 95% confidence interval 1.31–2.86,P= 0.001). Carriers of alleles containing ⩾ 38 CA repeats were, in particular, overrepresented in the subgroup without common cardiovascular risk factors (odds ratio 3.39, 95% confidence interval 1.30–8.86,P= 0.009). Logistic regression analysis revealed that the (CA)npolymorphism proved to be an independent risk factor (relative risk 2.17, 95% confidence interval 1.44–3.27,P= 0.0002). Our findings indicate that high numbers of CA repeats in intron 13 of theeNOSgene are associated with an excess risk of coronary artery disease.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Cadmium (Cd++) is a widespread environmental pollutant and classifed as an IARC `Category I' human carcinogen. Cd++can also cause severe renal toxicity and may be involved clinically in cardiovascular disease and osteoporosis. Genetic differences in sensitivity to cadmium toxicity have been noted in humans, whereas, among inbred mouse strains, unequivocal genetic data exist. Resistance to cadmium-induced testicular damage was reported in 1973 to be associated with a single major recessive gene, namedCdm, which has now been localized to mouse chromosome (Chr) 3. Using polymorphic microsatellite markers and semiquantitative histological parameters, we have corroborated the original 1973 data concerning mendelian inheritance and have further refined the region containing theCdmgene from more than 24 cM to 0.64 cM (estimated 40–80 genes). We phenotyped 26 recombinant inbred lines generated from C57BL/6 J (B6, resistant) and DBA/2 J (D2, sensitive) inbred mice, and determined that theCdmgene maps between microsatellite markers D3Mit110 and D3Mit255. Although toxicity to numerous heavy metals is well known, virtually no molecular mechanisms have yet been uncovered either in humans or laboratory animals. Identification and characterization of the mouseCdmgene should enhance our understanding of heavy metal toxicity by identifying and characterizing, for the first time, a major mammalian gene responsible for susceptibility to diseases caused by heavy metal toxicity.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The β-adrenoceptor agonist, isoprenaline, inhibited the immunoglobulin E-mediated release of histamine from human lung mast cells (HLMC). Long-term (24 h) exposure of HLMC to isoprenaline reduced the subsequent effectiveness of isoprenaline to inhibit histamine release. The extent of this functional desensitization was variable with some HLMC preparations resistant and others highly susceptible. We sought to determine whether the variability in the degree of functional desensitization was influenced by genetic polymorphisms in the β2-adrenoceptor. HLMC preparations were genotyped at two polymorphic loci, positions 16 (arg to gly) and 27 (gln to glu), and the effect of desensitizing conditions (24 h with 10−6m isoprenaline) on the subsequent ability of isoprenaline (10−7m) to inhibit histamine release from HLMC was determined (n= 72). In HLMC preparations expressing β2-adrenoceptors with arg (wild-type) or gly (mutant) at position 16, desensitization was 71 ± 5% (n= 18) or 43 ± 5% (n= 26), respectively, whereas the desensitization was 59 ± 6% (n= 28) for heterozygotes at this position. In HLMC preparations expressing β2-adrenoceptors with gln (wild-type) or glu (mutant) at position 27, desensitization was 65 ± 5% (n= 25) or 28 ± 7% (n= 17), respectively, whereas the desensitization was 61 ± 5% (n= 30) for heterozygotes at this position. These data suggest that mutant (gly16and glu27) forms of the receptor are resistant to desensitization compared to wild-type (arg16and gln27) forms. However, analyses to determine the relative contributions of positions 16 and 27 suggest that position 27 is more important in influencing the degree of functional desensitization.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Three human phenol sulfotransferases, provisionally named SULT1A1, 1A2 and 1A3, show 91–96% homology of their amino acid sequences and are encoded by neighbouring gene loci. Functional genetic polymorphisms are known for two of these sulfotransferases. InSULT1A1, a G to A transition leads to an Arg213to His exchange and eliminates aBsp143II restriction site. SULT1A1*His shows lower enzyme activity and thermostability than SULT1A1*Arg. InSULT1A2, an A to C transversion causes an Asn235to Thr exchange and introduces aBpiI restriction site. Enzyme SULT1A2*Thr is less active than SULT1A2*Asn. These substitutions were detected by restriction fragment length polymorphism analyses of genomic sequences amplified by polymerase chain reaction. Despite the high similarity between the different humanSULT1Agenes, it was possible to amplify specifically the polymorphic parts of eitherSULT1A1or1A2, but not the homologous sequences of the otherSULT, by setting the forward primer into intron 6. DNA from 300 adult male Caucasian subjects was analysed. Allele frequencies were 0.63 and 0.37 forSULT1A1*Argand*His, and 0.62 and 0.38 forSULT1A2*Asnand*Thr, respectively. The frequency of the haplotypeSULT1A1*Arg/SULT1A2*Asn(0.61) was nearly as high as the allele frequencies of its components. The same was observed for the haplotypeSULT1A1*His/SULT1A2*Thr, whose frequency was 0.35. In contrast, haplotypes1A1*Arg/1A2*Thrand1A1*His/1A2*Asnwere very rare. Their frequencies (0.02 each) were less than 10% of the figures expected in an independent distribution. The results demonstrate a strong association of the alleles producing the more active enzyme variants (SULT1A1*Arg and SULT1A2*Asn) and of those encoding the less active variants (SULT1A1*His and SULT1A2*Thr).

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The acetylator phenotype and genotype of AIDS patients, with and without an acute illness, was compared with that of healthy control subjects (30 per group). Two probe drugs, caffeine and dapsone, were used to determine the phenotype in the acutely ill cohort. Polymerase chain reaction amplification and restriction fragment length polymorphism analysis served to distinguish between the 26 knownNAT2alleles and the 21 most commonNAT1alleles. The distribution (%) of slow:rapid acetylator phenotype seen among acutely ill AIDS patients differed with the probe substrate used: 70:30 with caffeine versus 53:47 with dapsone. Phenotype assignment differed considerably between the two methods and there were numerous discrepancies between phenotype and genotype. TheNAT2genotype distribution was 45:55 slow:rapid. Control subjects, phenotyped only with caffeine, were 67:33 slow:rapid versus 60:40 genotypically. Stable AIDS patients, phenotyped only with dapsone, were 55:45 slow:rapid versus 46:54 genotypically. Following resolution of their acute infections, 12 of the acutely ill subjects were rephenotyped with dapsone. Phenotype assignment remained unchanged in all cases. The distribution ofNAT1alleles was similar in all three groups. It is evident from the amount of discordance between caffeine phenotype and dapsone phenotype or genotype that caution should be exercised in the use of caffeine as a probe for NAT2 in acutely ill patients. It is also clear that meaningful study of the acetylation polymorphism requires both phenotypic and genotypic data.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID