摘要:

A C825T polymorphism was recently identified in the gene for the G-protein β3 subunit, the T-allele being associated with hypertension. To better understand the underlying pathophysiological mechanisms, we compared the haemodynamics of young healthy males with and without the T-allele. In three studies, subjects were investigated with regard to cardiac and vascular function at rest and following intravenous administration of the β-adrenoceptor antagonist, propranolol, and the α2-adrenoceptor agonist, α-methylnoradrenaline, and with regard to local venous vasoconstriction in the dorsal hand veinin situfollowing infusion of the α2-adrenoceptor agonist, azepexol. α2-Adrenoceptor agonists were chosen as vasoconstrictor drugs since α2-adrenoceptors couple to pertussis toxin (PTX)-sensitive G-proteins and since in-vitro studies have demonstrated enhanced signal transduction of PTX-dependent pathways in the presence of the T-allele. Total peripheral resistance was determined as a parameter of vasoconstrictor tone and heart rate, stroke volume and systolic time intervals for cardiac function. T-allele carriers had a significantly elevated stroke volume and lower total peripheral resistance at baseline. After propranolol, their fall in stroke volume was significantly greater. During α-methylnoradrenaline infusion, elevation of total peripheral resistance was not increased relative to controls. Similarly, the constriction response of the dorsal hand vein to azepexol was not different. Our study does not support the idea of increased vasoconstrictor tone in T-allele carriers either at rest or during stimulation of α2-adrenoceptors. However, this allele may be associated with elevated cardiac stroke volume.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Serotonin receptor type 3 is a ligand-gated ion channel implicated in behavioural disorders. Our objective was to identify nucleotide variants in a specific portion of the 5′ region of the serotonin receptor gene(HTR3A) containing upstream open reading frames (uORFs) and to investigate their effect on bipolar disease. Mutations in uORFs have been recently shown to cause disease by changing expression on the translational level. We identified one polymorphism, C195T, and one missense mutation, C178T (Pro16Ser) within an upstream open reading frame. No significant association was found between the C195T polymorphism and bipolar affective disorder. A significant association was, however, found between the variant C178T in 156 patients with bipolar disorder compared to 156 healthy controls (P= 0.00016). To investigate the relevance of this variant on gene expression, luciferase reporter constructs containing the C178T (Pro16Ser) allele were established and compared to the C178T plus C195T and wild-type alleles. Reporter constructs containing the C178T (Pro16Ser) allele drove 245% and 138% expression compared to the wild-type allele. These findings show that the C178T(Pro16Ser) variant inHTR3Amay represent a functional variant and affect the susceptibility to bipolar disorder.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

CYP2D6 is involved in the metabolism of several classes of drugs, including tricyclic antidepressants, selective serotonin reuptake inhibitors and various amphetamines.CYP2D6*10is an allelic variant, producing an enzyme with Pro34Ser and Ser486Thr amino acid substitutions. Approximately 75% of Asians possess the*10allele. We sought to further characterize CYP2D6.10 catalyticallyin vitroin a baculovirus expression system using various substrates and inhibitors, in comparison to CYP2D6.1 (wild-type). Using dextromethorphan (DEX),P-methoxyamphetamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and (±)3,4-methylenedioxymethamphetamine (MDMA), the ratios of intrinsic clearance (Vmax/Km) of *1 to *10 were 50, 34, 22 and 123, respectively. The CYP2D6 substrates amitriptyline, and (+) and (−) methamphetamine (MAMP) are bothp-hydroxylated andN-demethylated (NDM). The intrinsic clearance*1/*10ratios were 42, 30 and 67 for thep-hydroxylation; and 60, 120 and 157 for the NDM, respectively, illustrating chemical pathway and enantiomeric selectivity for MAMP. It was apparent that (+) and (−) MAMP NDM and MDMA demethylenation were most significantly different in CYP2D6.10. Using DEX as the substrate, the ratios ofKi(*10)/Ki(*1) for inhibitors were: budipine (1.3), sparteine (1.6), debrisoquine (8.1), fluoxetine (16), norfluoxetine (30), paroxetine (14), MDMA (21) and MMDA-2 (7.1), indicating that CYP2D6.10 shows drug-specific altered susceptibility to inhibition. Taken together, these data suggest thatCYP2D6*10/*10individuals may be expected to require different drug doses; and show altered susceptibility to toxicity, interaction risk and, in the case of the amphetamines, drug dependence and toxicity compared toCYP2D6*1/*1individuals.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Despite its importance in drug metabolism and disease susceptibility, CYP2D6 activity and genetic polymorphism have rarely been investigated in African-American populations. In order to bridge this gap, we examined the genotype and phenotype of the enzyme in 154 African-American (AA) and 143 Caucasian (C) normal volunteers. AAs are significantly more likely to possess *17and *5, but less likely to have *4. Overall, the two groups were similar in their CYP2D6 activity as measured with dextromethorphan as the probe (metabolic ratio 2.21±0.78 for AAs; 2.11±0.86 for Cs;t= 1.02, NS). Two of four AAs and six of seven Cs were classified as poor metabolizers and have two nonfunctioning alleles. CYP2D6 activity is determined by *17, *4, *5and age in AAs (r2= 0.33,f= 18.8,P<0.001) and by *4and *XNin Cs (r2= 0.14,f= 10.8,P<0.001). These results support previous findings demonstrating the importance of *17in determining CYP2D6 activity in AAs.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Induction of a polycyclic aromatic hydrocarbon-metabolizing cytochrome P450 isoform CYP1A1 is regulated by aromatic hydrocarbon receptor (AHR). High inducibility of CYP1A1, possibly due to genetic polymorphisms, has been considered to be a risk factor for lung cancer in tobacco smokers. The relationship between low or high pulmonary expression of CYP1A1 and polymorphic genotypes ofCYP1A1andAHRwas investigated in 73 active smokers. CYP1A1 expression was determined in surgical lung samples by measuring ethoxyresorufinO-deethylase (EROD) activity and by immunostaining for CYP1A1 protein. The most common allelic variants ofCYP1A1andAHRin Finns, i.e. theMspI variant (CYP1A1*2A), I462V variant (CYP1A1*2B), and−459C to T variant ofCYP1A1and the R554K variant (AHR*2) ofAHRwere studied using polymerase chain reaction based methods. EROD activity correlated positively with the daily cigarette consumption (r= 0.45). There was additional variation in EROD activity independent of the amount of smoking e.g. among those who smoked one pack per day until the day of operation, EROD activity ranged from 4–142 (median 48) pmol/min/mg. The frequencies of theMspI, 462V, and−459T variant alleles ofCYP1A1and 554K variant allele ofAHRwere 0.158, 0.055, 0.055 and 0.075, respectively. No differences were observed in the frequencies of polymorphic genotypes between the smokers with low and those with high expression, when the relationship was studied using a regression analysis adjusted for cigarette consumption. Our results thus indicate that the interindividual variation of CYP1A1 levels in smokers’ lung tissue is not attributable to genetic polymorphisms ofCYP1A1orAHRtested in this study.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

N-acetyltransferase 1 (NAT1) catalyses the activation and/or deactivation of aromatic and heterocyclic amine carcinogens. A genetic polymorphism inNAT1is associated with an increased risk of various cancers and drug toxicities, but epidemiological investigations are severely compromised by a poor understanding of the relationship betweenNAT1genotype and phenotype. Human referenceNAT1*4and 12 known humanNAT1allelic variants possessing nucleotide polymorphisms in theNAT1coding region were cloned and expressed in yeast (Schizosaccharomyces pombe). Large reductions inN-andO-acetyltransferase catalytic activities were observed for recombinant NAT1 allozymes encoded byNAT1*14B, NAT1*15, NAT1*17, NAT1*19andNAT1*22.Each of these alleles exhibited NAT1 protein expression levels below the limit of detection as measured by Western blot. No differences between high and low activityNAT1alleles were observed in relative mRNA expression or relative transformation efficiency. The recombinant NAT1 17 and NAT1 22 allozymes showed reduced intrinsic stability when compared with NAT1 4. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)N-acetylation was not catalysed by any of the NAT1 allozymes. Large differences in the metabolic activation viaO-acetylation of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP) were noted forNAT1allelic variants. The results of these studies suggest an important role for theNAT1genetic polymorphism in metabolism of aromatic and heterocyclic amine carcinogens. Furthermore, these results suggest that low NAT1 phenotype results fromNAT1allelic variants that encode reduced expression of NAT1 and/or less-stable NAT1 protein.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

The von Hippel-Lindau (VHL) tumour suppressor gene is commonly mutated in renal cell carcinoma of clear cell type (CCRCC). We investigated the possible relationship betweenVHLmutations in sporadic CCRCC and polymorphism of genes encoding enzymes involved in carcinogen metabolism: two cytochrome P450 monooxygenases (CYP1A1andCYP2D6), one NAD[P]H:quinone oxidoreductase (NQO1), three glutathioneS-transferases (GSTM1,GSTT1andGSTP1) and two arylamineN-acetyltransferases (NAT1andNAT2). We analysed DNA from tumour and nontumoural kidney tissue from 195 CCRCC patients. SingleVHLmutations were identified in 88 patients and double mutations were present in two patients. Nine of 18 transversions were GC to TA, four were AT to TA, four were GC to CG and one was AT to CG. Ten of 19 transitions were GC to AT and nine were AT to GC. We also identified 53 frameshifts and two GC to AT at CpG. An excess of transversions was observed in a subset of patients with active GSTT1 [GSTT1(+) genotype] and probably defective NAT1 (NAT1S/R variant genotype). All 18 transversions were inGSTT1(+) patients, whereas only 76% of transitions (P= 0.05) and 81% of the other mutations (P= 0.06) occurred in this genotype. We found that 28% of the transversions were in theNAT1S/R genotype versus 12% of the transitions (P= 0.40) and 4% of the other mutations (P= 0.01). This suggests that pharmacogenetic polymorphisms may be associated with the type of acquiredVHLmutation, which may modulate CCRCC development.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

The cellular response to DNA damage is often a p53-mediated cell cycle arrest to provide time for DNA repair or to direct damaged cells into apoptosis. In this study, the impact of glutathione-S-transferase M1 (GSTM1) on DNA damage and subsequent p53-protein accumulation was examined in lymphocytes of healthy volunteersin vitroexposed to benzo[a]pyrene-diol-epoxide (BPDE) and in skin of atopic eczema patients topically treated with coal tar. DNA adducts were determined by immunocytochemical staining (ICC) and32P-postlabelling, P53 accumulation was studied by ICC and theGSTM1genotype was assessed by polymerase chain reaction. In cultured lymphocytes treated with 2.5 μm BPDE for 18 h, increased levels of p53 were found, which were positively related to BPDE-DNA adduct levels assessed by ICC (rs= 0.66,P< 0.001) and32P-postlabelling (rs= 0.56,P< 0.001) and appeared to be higher inGSTM1(–/–) than inGSTM1(+) subjects (P= 0.003). In skin biopsies of coal tar treated eczema patients, p53 levels were elevated in 7/10 patients and a correlation was observed between p53 and DNA adduct levels (rs= 0.50,P= 0.029).GSTM1(–/–) subjects contained higher levels of p53 in the stratum basale thanGSTM1(+) individuals (P= 0.026), but no influence ofGSTM1on DNA adduct levels was observed. Thus, P53 accumulates in human skin and lymphocytes as a protective mechanism against polycyclic aromatic hydrocarbon induced DNA damage, and this is more pronounced inGSTM1(–/–) compared toGSTM1(+) individuals.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Previous studies have demonstrated a lower density of dopamine D2receptor (DRD2) in subjects withoutDelalleles of the −141CIns/Delpolymorphism inDRD2gene promoter region than in those with one or twoDelalleles. The present study aimed to examine whether the −141CIns/DelDRD2promoter polymorphism is related to therapeutic response to selective DRD2antagonists in the treatment of schizophrenia. Subjects consisted of 49 acutely exacerbated schizophrenic inpatients treated with bromperidol (30 cases, mean dose ± SD: 11.4 ± 4.8 mg/day) or nemonapride (19 cases, 18 mg/day). Clinical symptoms were evaluated by the Brief Psychiatric Rating Scale (BPRS) before and 3 weeks after the treatment. The −141CIns/DelDRD2genotypes, theInsandDelalleles, were determined by a polymerase chain reaction method. Thirty-five patients were homozygous for theInsallele and 14 were heterozygous for theDelandInsalleles. The patients withoutDelallele showed a higher percentage of improvement in anxiety–depression symptoms than those withDelallele (58.5 ± 44.5% versus 24.1 ± 48.2%) after 3 weeks of treatment while percentage improvement in total BPRS or other subgrouped symptoms (positive, negative, excitement and cognitive symptoms) was similar between the two genotype groups. The present results suggest that the −141CIns/DelDRD2polymorphism is associated with anxiolytic and antidepressive effects of neuroleptic treatment in schizophrenic patients.

ISSN:0960-314X    

出版商:OVID    

年代:2001

数据来源: OVID