Significantly increased risk of carotid atherosclerosis with arsenic exposure and polymorphisms in arsenic metabolism genes

Individual susceptibility to arsenic-induced carotid atherosclerosis might be associated with genetic variations in arsenic metabolism. The purpose of this study is to explore the interaction effect on risk of carotid atherosclerosis between arsenic exposure and risk genotypes of purine nucleoside phosphorylase (PNP), arsenic (+3) methyltransferase (As3MT), and glutathione S-transferase omega 1 (GSTO1) and omega 2 (GSTO2). A community-based case-control study was conducted in northeastern Taiwan to investigate the arsenic metabolic-related genetic susceptibility to carotid atherosclerosis. In total, 863 subjects, who had been genotyped and for whom the severity of carotid atherosclerosis had been determined, were included in the present study. Individual well water was collected and arsenic concentration determined using hydride generation combined with flame atomic absorption spectrometry. The result showed that a significant dose–response trend (P=0.04) of carotid atherosclerosis risk associated with increasing arsenic concentration. Non-significant association between genetic polymorphisms of PNP Gly51Ser, Pro57Pro, As3MT Met287Thr, GSTO1 Ala140Asp, and GSTO2 A-183G and the risk for development of carotid atherosclerosis were observed. However, the significant interaction effect on carotid atherosclerosis risk was found for arsenic exposure (>50 μg/l) and the haplotypes of PNP (p=0.0115). A marked elevated risk of carotid atherosclerosis was observed in subjects with arsenic exposure of >50 μg/l in drinking water and those who carried the PNP A–T haplotype and at least either of the As3MT risk polymorphism or GSTO risk haplotypes (OR, 6.43; 95% CI, 1.79–23.19). In conclusion, arsenic metabolic genes, PNP, As3MT, and GSTO, may exacerbate the formation of atherosclerosis in individuals with high levels of arsenic concentration in well water (>50 μg/l).     

Comparison of health effects between individuals with and without skin lesions in the population exposed to arsenic through drinking water in West Bengal, India

A study was conducted to explore the effect of arsenic causing conjunctivitis, neuropathy and respiratory illness in individuals, with or without skin lesions, as a result of exposure through drinking water, contaminated with arsenic to similar extent. Exposed study population belongs to the districts of North 24 Parganas and Nadia, West Bengal, India. A total of 725 exposed (373 with skin lesions and 352 without skin lesions) and 389 unexposed individuals were recruited as study participants. Participants were clinically examined and interviewed. Arsenic content in drinking water, urine, nail and hair was estimated. Individuals with skin lesion showed significant retention of arsenic in nail and hair and lower amount of urinary arsenic compared to the group without any skin lesion. Individuals with skin lesion also showed higher risk for conjunctivitis ((odd's ratio) OR: 7.33, 95% CI: 5.05-10.59), peripheral neuropathy (OR: 3.95, 95% CI: 2.61-5.93) and respiratory illness (OR: 4.86, 95% CI: 3.16-7.48) compared to the group without any skin lesion. The trend test for OR of the three diseases in three groups was found to be statistically significant. Again, individuals without skin lesion in the exposed group showed higher risk for conjunctivitis (OR: 4.66, 95% CI: 2.45-8.85), neuropathy (OR: 3.99, 95% CI: 1.95-8.09), and respiratory illness (OR: 3.21, 95% CI: 1.65-6.26) when compared to arsenic unexposed individuals. Although individuals with skin lesions were more susceptible to arsenic-induced toxicity, individuals without skin lesions were also subclinically affected and are also susceptible to arsenic-induced toxicity and carcinogenicity when compared to individuals not exposed to arsenic.     

Association between GSTO2 polymorphism and the urinary arsenic profile in copper industry workers

Two members of the recently identified Omega class glutathione S-transferase enzymes (GSTO1 and GSTO2) have been proposed to play a role in the response to arsenic exposure. Therefore, polymorphisms in these genes could be related with variations in the arsenic excretion profile and, consequently, with the individual response to chronic exposure. Exons and flanking regions of GSTO2 gene have been screened in two different ethnic groups (20 Europeans and 20 Chilean Indians), and the urinary arsenic patterns and the GSTO2 Asn142Asp polymorphism have been investigated in 207 copper mine workers occupationally exposed to arsenic. Three polymorphisms of GSTO2 already described were detected in Europeans and Chilean Indians, although with significant different allele frequencies. The genotyping for the Asn142Asp polymorphism revealed that almost no significant association exists between this change and the arsenic excretion profile. However, 142Asp change seems to be correlated with an increase in DMA excretion after age and total urinary arsenic adjustment (OR=3.61; P=0.05). Altogether, our findings indicate that ethnical differences should be taken into account for correlation studies between GST Omega polymorphisms and arsenic susceptibility, and that the 142Asp allozyme could modulate arsenic biotransformation and thereby arsenic toxicity.     

GSTO基因多态性与燃煤污染型砷中毒易感性的关系

[目的]探讨GSTO基因多态性与燃煤污染型砷中毒易感性的关系.[方法]应用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)技术检测130名燃煤型砷中毒患者和140名健康个体GSTO1 Ala140Asp和GSTO2Asn142Asp基因两个位点的多态性,并分析不同基因型与砷中毒发病风险的关系.[结果]病例组中携带GSTO2 142Asn/Asp Asp/Asp(杂合型 突变纯合型)基因型个体的比例显著高于对照组,携带该基因型的个体较携带GSTO2 142Asn/Asn(野生纯合型)基因型个体发生砷中毒的风险升高1.18倍(ORadj=1.18,95%CI:1.02～1.37);而病例组中携带GSTO1140Ala/Asp Asp/Asp(杂合型 突变纯合型)基因型个体的比例仅略高于对照组,差异无统计学意义(ORadj=0.98,95%CI:0.51～1.91);但同时携带GSTO1 140Ala/Asp Asp/Asp和GSTO2 142Asn/Asp Asp/Asp基因型的个体砷中毒的发病风险显著增加(ORadj=2.48,95%CI:1.14～5.40).[结论]携带GSTO2Asn142Asp基因型个体有较高的砷中毒发病风险;而同时携带GSTO1 140Ala/Asp Asp/Asp和GSTO2 142Asn/Asp Asp/Asp的个体可能更容易发生砷中毒.     

5,10-亚甲基四氢叶酸还原酶基因C677T位点突变与地方性砷中毒皮肤病变发生关系的研究

目的　 5 ,10- 亚甲基四氢叶酸还原酶 (MTHFR)是叶酸代谢关键酶 ,旨在了解该酶基因C6 77T位点突变是否是地方性砷中毒皮肤病变发生的遗传易感因素。方法　选择 5 0名出现砷性皮肤病变居民作为皮肤病变组 ,以同地区饮水砷浓度相近的 35名正常人作为对照 ,进行MTHFR基因C6 77T位点多态性分析(PCR- RFLP法 )、血清叶酸测定 (微生物法 )和维生素B1 2 测定 (电化学发光法 )。结果　皮肤病变组MTHFR基因C6 77T位点TT基因型占 34. 0 % ,T等位基因频率为 5 6 . 0 %。皮肤病变组和对照组基因型构成和等位基因频率差异无显著性。两组血清叶酸、VitB1 2 水平差异均无显著性。以血清叶酸水平≥ 10. 5nmol L且CC基因型作为参照 ,其它组粗OR值和经Logistic回归分析控制性别、年龄、水砷浓度、吸烟后的校正OR值均大于 1,但 95 %CI包含 1。结论　MTHFR基因C6 77T位点多态性与地方性砷中毒皮肤病变的发生无明显关联。     

Genetic polymorphisms influencing arsenic metabolism: evidence from Argentina

The susceptibility to arsenic-induced diseases differs greatly between individuals, possibly due to interindividual variations in As metabolism that affect retention and distribution of toxic metabolites. To elucidate the role of genetic factors in As metabolism, we studied how polymorphisms in six genes affected the urinary metabolite pattern in a group of indigenous women (n = 147) in northern Argentina who were exposed to approximately 200 microg/L As in drinking water. These women had low urinary percentages of monomethylated As (MMA) and high percentages of dimethylated As (DMA). MMA has been associated with adverse health effects, and DMA has the lowest body retention of the metabolites. The genes studied were arsenic(+III)methyltransferase (AS3MT), glutathione S-transferase omega 1 (GSTO1), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), methylenetetrahydrofolate reductase (MTHFR), and glutathione S-transferases mu 1 (GSTM1) and theta 1 (GSTT1). We found three intronic polymorphisms in AS3MT (G12390C, C14215T, and G35991A) associated with a lower percentage of MMA (%MMA) and a higher percentage of DMA (%DMA) in urine. The variant homozygotes showed approximately half the %MMA compared with wild-type homozygotes. These polymorphisms were in strong linkage, with high allelic frequencies (72-76%) compared with other populations. We also saw minor effects of other polymorphisms in the multivariate regression analysis with effect modification for the deletion genotypes for GSTM1 (affecting %MMA) and GSTT1 (affecting %MMA and %DMA). For pregnant women, effect modification was seen for the folate-metabolizing genes MTR and MTHFR. In conclusion, these findings indicate that polymorphisms in AS3MT-and possibly GSTM1, GSTT1, MTR, and MTHFR-are responsible for a large part of the interindividual variation in As metabolism and susceptibility.     

Nutritional factors and susceptibility to arsenic-caused skin lesions in West Bengal, India

There has been widespread speculation about whether nutritional deficiencies increase the susceptibility to arsenic health effects. This is the first study to investigate whether dietary micronutrient and macronutrient intake modulates the well-established human risk of arsenic-induced skin lesions, including alterations in skin pigmentation and keratoses. The study was conducted in West Bengal, India, which along with Bangladesh constitutes the largest population in the world exposed to arsenic from drinking water. In this case-control study design, cases were patients with arsenic-induced skin lesions and had < 500 microg/L arsenic in their drinking water. For each case, an age- and sex-matched control was selected from participants of a 1995-1996 cross-sectional survey, whose drinking water at that time also contained < 500 microg/L arsenic. Nutritional assessment was based on a 24-hr recall for major dietary constituents and a 1-week recall for less common constituents. Modest increases in risk were related to being in the lowest quintiles of intake of animal protein [odds ratio (OR) = 1.94; 95% confidence interval (CI), 1.05-3.59], calcium (OR = 1.89; 95% CI, 1.04-3.43), fiber (OR = 2.20; 95% CI, 1.15-4.21), and folate (OR = 1.67; 95% CI, 0.87-3.2). Conditional logistic regression suggested that the strongest associations were with low calcium, low animal protein, low folate, and low fiber intake. Nutrient intake was not related to arsenic exposure. We conclude that low intake of calcium, animal protein, folate, and fiber may increase susceptibility to arsenic-caused skin lesions. However, in light of the small magnitude of increased risks related to these dietary deficiencies, prevention should focus on reducing exposure to arsenic.     

砷代谢相关酶及其基因多态性研究进展

地方性砷中毒是一种严重危害健康的地方病,研究发现,高砷暴露环境下的个体并不都患病,提示除环境因素外,个体的遗传易感性在砷中毒的发病过程中可能也起着重要作用。砷在体内的代谢过程涉及许多酶促和/或非酶促反应过程,现在研究较多的砷代谢酶促反应3种相关酶是谷胱甘肽S转移酶(GSTO 1-1)、嘌呤核苷磷酸化酶(PNP)、三价砷甲基转移酶(CYT19/AS3MT),围绕上述酶及其基因多态性展开综述。     

Genetic variation in genes associated with arsenic metabolism: glutathione S-transferase omega 1-1 and purine nucleoside phosphorylase polymorphisms in European and indigenous Americans

Individual variability in human arsenic metabolism has been reported frequently in the literature. This variability could be an underlying determinant of individual susceptibility to arsenic-induced disease in humans. Recent analysis revealing familial aggregation of arsenic metabolic profiles suggests that genetic factors could underlie interindividual variation in arsenic metabolism. We screened two genes responsible for arsenic metabolism, human purine nucleoside phosphorylase (hNP), which functions as an arsenate reductase converting arsenate to arsenite, and human glutathione S-transferase omega 1-1 (hGSTO1-1), which functions as a monomethylarsonic acid (MMA) reductase, converting MMA(V) to MMA(III), to develop a comprehensive catalog of commonly occurring genetic polymorphisms in these genes. This catalog was generated by DNA sequencing of 22 individuals of European ancestry (EA) and 24 individuals of indigenous American (IA) ancestry. In (Italic)hNP(/Italic), 48 polymorphic sites were observed, including 6 that occurred in exons, of which 1 was nonsynonymous (G51S). One intronic polymorphism occurred in a known enhancer region. In hGSTO1-1, 33 polymorphisms were observed. Six polymorphisms occurred in exons, of which 4 were nonsynonymous. In contrast to hNP, in which the IA group was more polymorphic than the EA group, in hGSTO1-1 the EA group was more polymorphic than the IA group, which had only 1 polymorphism with a frequency > 10%. Populations representing genetic admixture between the EA and IA groups, such as Mexican Hispanics, could vary in the extent of polymorphism in these genes based upon the extent of admixture. These data provide a framework in which to conduct genetic association studies of these two genes in relevant populations, thereby allowing hNP and hGSTO1-1 to be evaluated as potential susceptibility genes in human arsenicism.     

Association of genetic variation in cystathionine-β-synthase and arsenic metabolism

Variation in individual susceptibility to arsenic-induced disease may be partially explained by genetic differences in arsenic metabolism. Mounting epidemiological evidence and in vitro studies suggest that methylated arsenic metabolites, particularly monomethylarsonic (MMA3), are more acutely toxic than inorganic arsenic; thus, MMA3 may be the primary toxic arsenic species. To test the role of genetic variation in arsenic metabolism, polymorphisms in genes involved in one-carbon metabolism [methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), cystathionine-β-synthase (CBS), thymidylate synthase (TYMS), dihydrofolate reductase (DHFR), serine hydroxymethyltransferase 1 (SHMT1)] and glutathione biosynthesis [glutathione-S-transferase omega 1 (GSTO1)] were examined in an arsenic-exposed population to determine their influence in urinary arsenic metabolite patterns. In 142 subjects in Cordoba Province, Argentina, variant genotypes for CBS rs234709 and rs4920037 SNPs compared with wild-type homozygotes were associated with 24% and 26% increases, respectively, in the mean proportion of arsenic excreted as monomethylarsonic acid (%MMA). This difference is within the range of differences in %MMA seen between people with arsenic-related disease and those without such disease in other studies. Small inverse associations with CBS rs234709 and rs4920037 variants were also found for the mean levels of the proportion of arsenic excreted as dimethylarsinous acid (%DMA). No other genetic associations were found. These findings are the first to suggest that CBS polymorphisms may influence arsenic metabolism in humans and susceptibility to arsenic-related disease.     

Metabolism of low-dose inorganic arsenic in a central European population: influence of sex and genetic polymorphisms

BACKGROUND: There is a wide variation in susceptibility to health effects of arsenic, which, in part, may be due to differences in arsenic metabolism. Arsenic is metabolized by reduction and methylation reactions, catalyzed by reductases and methyltransferases. OBJECTIVES: Our goal in this study was to elucidate the influence of various demographic and genetic factors on the metabolism of arsenic. METHODS: We studied 415 individuals from Hungary, Romania, and Slovakia by measuring arsenic metabolites in urine using liquid chromatography with hydride generation and inductively coupled plasma mass spectrometry (HPLC-HG-ICPMS). We performed genotyping of arsenic (+III) methyltransferase (AS3MT), glutathione S-transferase omega 1 (GSTO1), and methylene-tetrahydrofolate reductase (MTHFR). RESULTS: The results show that the M287T (T-->C) polymorphism in the AS3MT gene, the A222V (C-->T) polymorphism in the MTHFR gene, body mass index, and sex are major factors that influence arsenic metabolism in this population, with a median of 8.0 microg/L arsenic in urine. Females < 60 years of age had, in general, higher methylation efficiency than males, indicating an influence of sex steroids. That might also explain the observed better methylation in overweight or obese women, compared with normal weight men. The influence of the M287T (T-->C) polymorphism in the AS3MT gene on the methylation capacity was much more pronounced in men than in women. CONCLUSIONS: The factors investigated explained almost 20% of the variation seen in the metabolism of arsenic among men and only around 4% of the variation among women. The rest of the variation is probably explained by other methyltransferases backing up the methylation of arsenic.     

Decrements in lung function related to arsenic in drinking water in West Bengal, India

During 1998-2000, the authors investigated relations between lung function, respiratory symptoms, and arsenic in drinking water among 287 study participants, including 132 with arsenic-caused skin lesions, in West Bengal, India. The source population involved 7,683 participants who had been surveyed for arsenic-related skin lesions in 1995-1996. Respiratory symptoms were increased among men with arsenic-caused skin lesions (versus those without lesions), particularly "shortness of breath at night" (odds ratio (OR) = 2.8, 95% confidence interval (CI): 1.1, 7.6) and "morning cough" (OR = 2.8, 95% CI: 1.2, 6.6) in smokers and "shortness of breath ever" (OR = 3.8, 95% CI: 0.7, 20.6) in nonsmokers. Among men with skin lesions, the average adjusted forced expiratory volume in 1 second (FEV1) was reduced by 256.2 ml (95% CI: 113.9, 398.4; p < 0.001) and the average adjusted forced vital capacity (FVC) was reduced by 287.8 ml (95% CI: 134.9, 440.8; p < 0.001). In men, a 100-microg/liter increase in arsenic level was associated with a 45.0-ml decrease (95% CI: 6.2, 83.9) in FEV1 (p = 0.02) and a 41.4-ml decrease (95% CI: -0.7, 83.5) in FVC (p = 0.054). Women had lower risks than men of developing skin lesions and showed little evidence of respiratory effects. In this study, consumption of arsenic-contaminated water was associated with respiratory symptoms and reduced lung function in men, especially among those with arsenic-related skin lesions.     

不同人群GSTO1 mRNA表达及与砷甲基化关系

目的 观察谷胱甘肽-S-转移酶(GSTO1)mRNA在砷中毒患者、病区对照和非病区对照人群中的表达及其与尿砷甲基化水平的关系.方法 选取饮水型砷中毒重度患者、轻度患者、病区对照和非病区对照各6例,采用实时定量RT-PCR技术测定研究对象的淋巴细胞中GSTO1 mRNA表达,采用AFS-9130、SAP-10检测尿无机砷(iAS)、一甲基胂酸(MMA)、二甲基胂酸(DMA)、尿总砷TAs含量.结果 中重度组,轻度组、病区对照组人群iAs,MMA,DMA,TAs一甲基化指数(PMI)均明显高于非病区对照人群(P<0.05);中重度组(P_(50)=1.96),轻度组(P_(50)=1.31)、病区对照组人群(P_(50)=1.23)GSTO1mRNA表达高于非病区对照人群(P_(50)=1.015)(P<0.05);GSTO1 mRNA表达与MMA%(r=0.206,P=0.112)、DMA%(r=0.098,P:0.700),PMI(r=0.127,P=0.615)和SMI(r=0.192,P=0.445)无相关性.结论 GSTO1 mRNA表达与砷甲基化无明显关系,砷中毒引起的损伤可能与砷暴露引起GSTO1mRNA表达增高,并将五价砷化物还原为三价砷化物增多有关.     

A prospective study of arsenic exposure from drinking water and incidence of skin lesions in Bangladesh

Elevated concentrations of arsenic in groundwater pose a public health threat to millions of people worldwide. The authors aimed to evaluate the association between arsenic exposure and skin lesion incidence among participants in the Health Effects of Arsenic Longitudinal Study (HEALS). The analyses used data on 10,182 adults free of skin lesions at baseline through the third biennial follow-up of the cohort (2000-2009). Discrete-time hazard regression models were used to estimate hazard ratios and 95% confidence intervals for incident skin lesions. Multivariate-adjusted hazard ratios for incident skin lesions comparing 10.1-50.0, 50.1-100.0, 100.1-200.0, and ≥200.1 μg/L with ≤10.0 μg/L of well water arsenic exposure were 1.17 (95% confidence interval (CI): 0.92, 1.49), 1.69 (95% CI: 1.33, 2.14), 1.97 (95% CI: 1.58, 2.46), and 2.98 (95% CI: 2.40, 3.71), respectively (P(trend) = 0.0001). Results were similar for the other measures of arsenic exposure, and the increased risks remained unchanged with changes in exposure in recent years. Dose-dependent associations were more pronounced in females, but the incidence of skin lesions was greater in males and older individuals. Chronic arsenic exposure from drinking water was associated with increased incidence of skin lesions, even at low levels of arsenic exposure (<100 μg/L).     

The impact of diet and betel nut use on skin lesions associated with drinking-water arsenic in Pabna, Bangladesh

An established exposure-response relationship exists between water arsenic levels and skin lesions. Results of previous studies with limited historical exposure data, and laboratory animal studies suggest that diet may modify arsenic metabolism and toxicity. In this study, we evaluated the effect of diet on the risk of arsenic-related skin lesions in Pabna, Bangladesh. Six hundred cases and 600 controls loosely matched on age and sex were enrolled at Dhaka Community Hospital, Bangladesh, in 2001-2002. Diet, demographic data, and water samples were collected. Water samples were analyzed for arsenic using inductively coupled plasma mass spectroscopy. Betel nut use was associated with a greater risk of skin lesions in a multivariate model [odds ratio (OR) = 1.67; 95% confidence interval (CI), 1.18-2.36]. Modest decreases in risk of skin lesions were associated with fruit intake 1-3 times/month (OR = 0.68; 95%CI, 0.51-0.89) and canned goods at least 1 time/month (OR = 0.41; 95% CI, 0.20-0.86). Bean intake at least 1 time/day (OR = 1.89; 95% CI, 1.11-3.22) was associated with increased odds of skin lesions. Betel nut use appears to be associated with increased risk of developing skin lesions in Bangladesh. Increased intake of fruit and canned goods may be associated with reduced risk of lesions. Increased intake of beans may be associated with an increased risk of skin lesions. The results of this study do not provide clear support for a protective effect of vegetable and overall protein consumption against the development of skin lesions, but a modest benefit cannot be excluded.     

Arsenic in drinking water and the prevalence of respiratory effects in West Bengal, India

BACKGROUND: A large population in West Bengal, India has been exposed to naturally occurring inorganic arsenic through their drinking water. A cross-sectional survey involving 7683 participants of all ages was conducted in an arsenic-affected region between April 1995 and March 1996. The main focus of the study was skin keratoses and pigmentation alterations, two characteristic signs of ingested inorganic arsenic. Strong exposure-response gradients were found for these skin lesions. The study also collected limited information concerning respiratory system signs and symptoms, which we report here because increasing evidence suggests that arsenic ingestion also causes pulmonary effects. METHODS: Participants were clinically examined and interviewed, and the arsenic content in their current primary drinking water source was measured. There were few smokers and analyses were confined to non-smokers (N = 6864 participants). RESULTS: Among both males and females, the prevalence of cough, shortness of breath, and chest sounds (crepitations and/or rhonchi) in the lungs rose with increasing arsenic concentrations in drinking water. These respiratory effects were most pronounced in individuals with high arsenic water concentrations who also had skin lesions. Prevalence odds ratio (POR) estimates were markedly increased for participants with arsenic-induced skin lesions who also had high levels of arsenic in their current drinking water source (> or = 500 microg/l) compared with individuals who had normal skin and were exposed to low levels of arsenic (<50 microg/l). In participants with skin lesions, the age-adjusted POR estimates for cough were 7.8 for females (95% CI : 3.1-19.5) and 5.0 for males (95% CI : 2.6-9.9); for chest sounds POR for females was 9.6 (95% CI : 4.0-22.9) and for males 6.9 (95% CI : 3.1-15.0). The POR for shortness of breath in females was 23.2 (95% CI : 5.8-92.8) and in males 3.7 (95% CI : 1.3-10.6). CONCLUSION: These results add to evidence that long-term ingestion of inorganic arsenic can cause respiratory effects.     

Resistance to Fluoroquinolone by a Combination of Efflux and Target Site Mutations in Enteroaggregative Escherichia coli Isolated in Korea

ObjectivesEnteroaggregative Escherichia coli (EAEC) was recently reported as a major diarrheagenic pathogen in infant and adult travelers, both in developing and developed countries. EAEC strains are known to be highly resistant to antibiotics including quinolones. Therefore in this study we have determined the various mechanisms of quinolone resistance in EAEC strains isolated in Korea.MethodsFor 26 EAEC strains highly resistant to fluoroquinolone, minimal inhibitory concentrations for fluoroquinolones were determined, mutations in the quinolone target genes were identified by PCR and sequencing, the presence of transferable quinolone resistance mechanism were identified by PCR, and the contribution of the efflux pump was determined by synergy tests using a proton pump inhibitor. The expression levels of efflux pump-related genes were identified by relative quantification using real-time PCR.ResultsApart from two, all tested isolates had common mutations on GyrA (Ser83Leu and Ser87Gly) and ParC (Ser80Gln). Isolates EACR24 and EACR39 had mutations that have not been reported previously: Ala81Pro in ParC and Arg157Gly in GyrA, respectively. Increased susceptibility of all the tested isolates to ciprofloxacin and norfloxacin in the presence of the pump inhibitor implies that efflux pumps contributed to the resistance against fluoroquinolones. Expression of the efflux pump-related genes, tolC, mdfA, and ydhE, were induced in isolates EACR 07, EACR 29, and EACR 33 in the presence of ciprofloxacin.ConclusionThese results indicate that quinolone resistance of EAEC strains mainly results from the combination of mutations in the target enzyme and an increased expression of efflux pump-related genes. The mutations Ala81Pro in ParC and Arg157Gly in GyrA have not been reported previously; the exact influence of these mutations should be investigated further.     

A pathway-based analysis of urinary arsenic metabolites and skin lesions

Inorganic arsenic is metabolized to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Limited evidence suggests that the ability to fully metabolize arsenic into DMA influences susceptibility to disease. To determine whether percentage of MMA was predictive of disease, the authors used data from a case-control study conducted in Bangladesh (2001-2003). Persons who were diagnosed with keratosis, melanosis, Bowen's disease, or squamous cell carcinoma were matched on age, sex, and village to persons without these conditions. This analysis was restricted to persons who had no missing data on covariates (859 cases, 868 controls). A path analysis was used to evaluate simultaneously the association between the percentage of all urinary arsenic metabolites and the odds of skin lesions using PROC CALIS in SAS, version 9.1 (SAS Institute, Inc., Cary, North Carolina) and Mplus, version 6.1 (Muthén & Muthén, Los Angeles, California). The odds of skin lesions were significantly associated with log(10) percentage of MMA (adjusted odds ratio (OR(adj)) = 1.56, 95% confidence interval (CI): 1.15, 2.12) but not log(10) percentage of inorganic arsenic (OR(adj) = 1.06, 95% CI: 0.75, 1.50) or log(10) percentage of DMA (OR(adj) = 1.07, 95% CI: 0.33, 3.46). This novel analysis confirmed that persons who excrete a higher proportion of MMA have a greater risk of skin lesions after data are adequately controlled for urinary arsenic metabolites, current arsenic exposure, and other risk factors.     

Pregnancy outcomes, infant mortality, and arsenic in drinking water in West Bengal, India

Between 2001 and 2003, the authors studied pregnancy outcomes and infant mortality among 202 married women in West Bengal, India. Reproductive histories were ascertained using structured interviews. Arsenic exposure during each pregnancy, including all water sources used, was assessed; this involved measurements from 409 wells. Odds ratios for spontaneous abortion, stillbirth, neonatal mortality, and infant mortality were estimated with logistic regression based on the method of generalized estimating equations. Exposure to high concentrations of arsenic (> or =200 microg/liter) during pregnancy was associated with a sixfold increased risk of stillbirth after adjustment for potential confounders (odds ratio (OR) = 6.07, 95% confidence interval (CI): 1.54, 24.0; p = 0.01). Arsenic-related skin lesions were found in 12 women who had a substantially increased risk of stillbirth (OR = 13.1, 95% CI: 3.17, 54.0; p = 0.002). The odds ratio for neonatal death was 2.81 (95% CI: 0.73, 10.8). No association was found between arsenic exposure and spontaneous abortion (OR = 1.01, 95% CI: 0.38, 2.70) or overall infant mortality (OR = 1.33, 95% CI: 0.43, 4.04). This study adds to the limited evidence that exposure to high concentrations of arsenic during pregnancy increases the risk of stillbirth. However, there was no indication of the increased rates of spontaneous abortion and overall infant mortality that have been reported in some studies.     

Developmentally restricted genetic determinants of human arsenic metabolism: association between urinary methylated arsenic and CYT19 polymorphisms in children

We report the results of a screen for genetic association with urinary arsenic metabolite levels in three arsenic metabolism candidate genes, PNP, GSTO, and CYT19, in 135 arsenic-exposed subjects from the Yaqui Valley in Sonora, Mexico, who were exposed to drinking water concentrations ranging from 5.5 to 43.3 ppb. We chose 23 polymorphic sites to test in the arsenic-exposed population. Initial phenotypes evaluated included the ratio of urinary inorganic arsenic(III) to inorganic arsenic(V) and the ratio of urinary dimethylarsenic(V) to monomethylarsenic(V) (D:M). In the initial association screening, three polymorphic sites in the CYT19 gene were significantly associated with D:M ratios in the total population. Subsequent analysis of this association revealed that the association signal for the entire population was actually caused by an extremely strong association in only the children (7-11 years of age) between CYT19 genotype and D:M levels. With children removed from the analysis, no significant genetic association was observed in adults (18-79 years). The existence of a strong, developmentally regulated genetic association between CYT19 and arsenic metabolism carries import for both arsenic pharmacogenetics and arsenic toxicology, as well as for public health and governmental regulatory officials.