Urinary arsenic profile affects the risk of urothelial carcinoma even at low arsenic exposure

Matrine Suppresses Arsenic-Induced Malignant Transformation of SV-HUC-1 Cells via NOX2

Arsenic (As) has been classified as a carcinogen for humans. There is abundant evidence indicating that arsenic increases the risk of bladder cancer among human populations. However, the underlying mechanisms have yet to be fully understood and elucidated. NADPH oxidases (NOXs) are the main enzymes for ROS production in the body. NADPH Oxidase 2 (NOX2), which is the most distinctive and ubiquitously expressed subunit of NOXs, can promote the formation and development of tumors. The utilization of NOX2 as a therapeutic target has been proposed to modulate diseases resulting from the activation of NOD-like receptor thermal protein domain associated protein 3 (NLRP3). Matrine has been reported to exhibit various pharmacological effects, including anti-inflammatory, antifibrotic, antitumor, and analgesic properties. However, it has not been reported whether matrine can inhibit malignant transformation induced by arsenic in uroepithelial cells through NOX2. We have conducted a series of experiments using both a sub-chronic NaAsO2 exposure rat model and a long-term NaAsO2 exposure cell model. Our findings indicate that arsenic significantly increases cell proliferation, migration, and angiogenesis in vivo and in vitro. Arsenic exposure resulted in an upregulation of reactive oxygen species (ROS), NOX2, and NLRP3 inflammasome expression. Remarkably, both in vivo and in vitro, the administration of matrine demonstrated a significant improvement in the detrimental impact of arsenic on bladder epithelial cells. This was evidenced by the downregulation of proliferation, migration, and angiogenesis, as well as the expression of the NOX2 and NLRP3 inflammasomes. Collectively, these findings indicate that matrine possesses the ability to reduce NOX2 levels and inhibit the transformation of bladder epithelial cells.

Urinary and household chemical exposures in pet dogs with urothelial cell carcinoma

Urothelial cell carcinoma (UCC) has been linked to environmental chemical exposures in people, but these risk factors are not well understood in dogs with UCC. We hypothesised that household chemical exposures contribute to the risk of UCC in pet dogs. This prospective cross-sectional case-control study included 37 dogs with UCC and 37 unaffected breed-, sex-, and age-matched controls. Dog owners completed an environmental questionnaire and household samples were collected and analysed for arsenic (in tap water and room dust) and acrolein (in room air). Urine samples from UCC dogs, control dogs, and consenting owners were analysed for inorganic arsenic species, the acrolein metabolite 3-HPMA, and the phenoxy herbicide 2,4-D. Public data on chlorination byproducts (total trihalomethanes) in municipal drinking water were also compared between case and control households. Dogs with UCC were more likely to swim in a pool (15.2%) compared with control dogs (0%) (OR 1.69, 95% CI = 1.69-∞; p = .02). Dogs with UCC also had more than 4-fold higher reported municipal water concentrations of chlorination byproducts (median 28.0 ppb) compared with controls (median 6.9 ppb; p < .0001). Dust arsenic concentrations were unexpectedly lower in case households (median 0.277 ng/cm2) compared with control households (median 0.401 ng/cm2; p = .0002). Other outcomes were not significantly different between groups. These data suggest that dog owners, especially those of breeds known to be at higher risk for UCC, consider limiting access to swimming pools and installing water filtration units that remove total trihalomethanes.

Low-to-Moderate Arsenic Exposure and Urothelial Tract Cancers with a Long Latent Period of Follow-Up in an Arseniasis Area

BACKGROUND

Arsenic exposure can cause adverse health effects. The effects of long-term low-to-moderate exposure and methylations remain unclear.

OBJECTIVE

This study aims to examine the association between low-to-moderate arsenic exposure and urothelial tract cancers while considering the effects of methylation capacity.

METHODS

In this study, 5,811 participants were recruited from an arseniasis area in Taiwan for inorganic arsenic metabolite analysis. This follow-up study was conducted between August 1995 and December 2017. We identified 85 urothelial tract cancers in these participants, including 49 bladder and 36 upper urothelial tract cancer cases. A Cox proportional hazards model was employed.

RESULTS

The analyses revealed a significant association between concentrations of inorganic arsenic in water > 100 ug/L and bladder cancer occurrence, with a hazard ratio (HR) of 4.88 (95% CI 1.35-17.61). A monotonic trend was observed between concentrations of inorganic arsenic in water (from 0 to > 100 ug/L) and the incidence of urothelial tract cancer, including bladder cancer (p < 0.05) and upper urothelial tract cancers (p < 0.05). Participants with a lower primary methylation index or higher secondary methylation index had a prominent effect.

CONCLUSIONS

Rigorous regulations and active interventions should be considered for populations with susceptible characteristics.

Determination of potential sources of heavy metals in patients with urothelial carcinoma in central Taiwan: a biomonitoring case-control study

The clarification of possible exposure sources of multiple metals to identify associations between metal doses and urothelial carcinoma (UC) risk is currently limited in the literature. We sought to identify the exposure sources of 10 metals (Vanadium, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, cadmium, and lead) using principal component analysis (PCA) and then linked various principal component (PC) scores with environmental characteristics, including smoking-related indices, PM2.5, and distance to the nearest bus station. In addition, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and DNA hypomethylation markers (5-methyl-2'-deoxycytidine levels; %5-MedC) were investigated in combination with UC risks. We conducted this hospital-based case control study in 359 UC patients with histologically confirmed disease and 718 controls. All data were collected from face-to-face interviews and medical records. Approximately 6 mL blood was collected from participants for analysis of multiple heavy metal and DNA methylation in leukocyte DNA. Further, a 20 mL urine sample was collected to measure urinary cotinine and 8-OHdG levels. In addition, average values for PM2.5 for individual resident were calculated using the hybrid kriging/land-use regression model. In UC patients, significantly higher cobalt, nickel, copper, arsenic, and cadmium (μg/L) levels were observed in blood when compared with controls. Three PCs with eigenvalues > 1 accounted for 24.3, 15.8, and 10.7% of UC patients, and 26.9, 16.7, and 11.1% of controls, respectively. Environmental metal sources in major clusters were potentially associated with industrial activities and traffic emissions (PC1), smoking (PC2), and food consumption, including vitamin supplements (PC3). Multiple metal doses were linked with incremental urinary 8-OHdG and DNA hypomethylation biomarkers. For individuals with high PC1 and PC2 scores, both displayed an approximate 1.2-fold risk for UC with DNA hypomethylation.In conclusion, we provide a foundation for health education and risk communication strategies to limit metal exposure in environment, so that UC risks can be improved potentially.

The Folic Acid and Creatine Trial: Treatment Effects of Supplementation on Arsenic Methylation Indices and Metabolite Concentrations in Blood in a Bangladeshi Population

BACKGROUND

Chronic arsenic (As) exposure is a global environmental health issue. Inorganic As (InAs) undergoes methylation to monomethyl (MMAs) and dimethyl-arsenical species (DMAs); full methylation to DMAs facilitates urinary excretion and is associated with reduced risk for As-related health outcomes. Nutritional factors, including folate and creatine, influence one-carbon metabolism, the biochemical pathway that provides methyl groups for As methylation.

OBJECTIVE

Our aim was to investigate the effects of supplementation with folic acid (FA), creatine, or the two combined on the concentrations of As metabolites and the primary methylation index (PMI: MMAs/InAs) and secondary methylation index (SMI: DMAs/MMAs) in blood in Bangladeshi adults having a wide range of folate status.

METHODS

In a randomized, double-blinded, placebo (PBO)-controlled trial, 622 participants were recruited independent of folate status and assigned to one of five treatment arms: a) PBO (n = 102 ), b) 400 μ g FA/d (400FA; n = 153 ), c) 800 μ g FA/d (800FA; n = 151 ), d) 3 g creatine/d (creatine; n = 101 ), or e) 3 g  creatine + 400 μ g  of FA / d (creatine + 400 FA ; n = 103 ) for 12 wk. For the following 12 wk, half of the FA participants were randomly switched to the PBO while the other half continued FA supplementation. All participants received As-removal water filters at baseline. Blood As (bAs) metabolites were measured at weeks 0, 1, 12, and 24.

RESULTS

At baseline, 80.3% (n = 489 ) of participants were folate sufficient (≥ 9  nmol / L in plasma). In all groups, bAs metabolite concentrations decreased, likely due to filter use; for example, in the PBO group, blood concentrations of MMAs (bMMAs) (geometric mean ± geometric standard deviation ) decreased from 3.55 ± 1.89 μ g / L at baseline to 2.73 ± 1.74 at week 1. After 1 wk, the mean within-person increase in SMI for the creatine + 400 FA group was greater than that of the PBO group (p = 0.05 ). The mean percentage decrease in bMMAs between baseline and week 12 was greater for all treatment groups compared with the PBO group [400FA: - 10.4 (95% CI: - 11.9 , - 8.75 ), 800FA: - 9.54 (95% CI: - 11.1 , - 7.97 ), creatine: - 5.85 (95% CI: - 8.59 , - 3.03 ), creatine + 400 FA : - 8.44 (95% CI: - 9.95 , - 6.90 ), PBO: - 2.02 (95% CI: - 4.03 , 0.04)], and the percentage increase in blood DMAs (bDMAs) concentrations for the FA-treated groups significantly exceeded that of PBO [400FA: 12.8 (95% CI: 10.5, 15.2), 800FA: 11.3 (95% CI: 8.95, 13.8), creatine + 400 FA : 7.45 (95% CI: 5.23, 9.71), PBO: - 0.15 (95% CI: - 2.85 , 2.63)]. The mean decrease in PMI and increase in SMI in all FA groups significantly exceeded PBO (p < 0.05 ). Data from week 24 showed evidence of a reversal of treatment effects on As metabolites from week 12 in those who switched from 800FA to PBO, with significant decreases in SMI [- 9.0 % (95% CI: - 3.5 , - 14.8 )] and bDMAs [- 5.9 % (95% CI: - 1.8 , - 10.2 )], whereas PMI and bMMAs concentrations continued to decline [- 7.16 % (95% CI: - 0.48 , - 14.3 ) and - 3.1 % (95% CI: - 0.1 , - 6.2 ), respectively] for those who remained on 800FA supplementation.

CONCLUSIONS

FA supplementation lowered bMMAs and increased bDMAs in a sample of primarily folate-replete adults, whereas creatine supplementation lowered bMMAs. Evidence of the reversal of treatment effects on As metabolites following FA cessation suggests short-term benefits of supplementation and underscores the importance of long-term interventions, such as FA fortification. https://doi.org/10.1289/EHP11270.

Effect of Arsenic Exposure and Cigarette Smoking on Total and Cause-Specific Mortality: An Occupational Cohort With 27 Follow-up Years

BACKGROUND

The relationship between arsenic exposure and all-cause mortality and the joint effects of arsenic exposure and smoking have been poorly described in previous studies.

METHODS

After 27 years of follow-up, a total of 1738 miners were included in the analysis. Different statistical methods were used to explore the relationship between arsenic exposure and smoking and the risk of all-cause mortality and various causes of death.

RESULTS

A total of 694 deaths occurred during the 36,199.79 person-years of follow-up. Cancer was the leading cause of death, and arsenic-exposed workers had significantly higher mortality rates for all-cause, cancer, and cerebrovascular disease. All-cause, cancer, cerebrovascular disease, and respiratory disease increased with cumulative arsenic exposure.

CONCLUSIONS

We demonstrated the negative effects of smoking and arsenic exposure on all-cause mortality. More effective actions should be taken to reduce arsenic exposure in miners.

The Duality of Arsenic Metabolism: Impact on Human Health

Arsenic is a naturally occurring hazardous element that is environmentally ubiquitous in various chemical forms. Upon exposure, the human body initiates an elimination pathway of progressive methylation into relatively less bioreactive and more easily excretable pentavalent methylated forms. Given its association with decreasing the internal burden of arsenic with ensuing attenuation of its related toxicities, biomethylation has been applauded for decades as a pure route of arsenic detoxification. However, the emergence of detectable trivalent species with profound toxicity has opened a long-standing debate regarding whether arsenic methylation is a detoxifying or bioactivating mechanism. In this review, we approach the topic of arsenic metabolism from both perspectives to create a complete picture of its potential role in the mitigation or aggravation of various arsenic-related pathologies.

Metabolic Changes and Their Associations with Selected Nutrients Intake in the Group of Workers Exposed to Arsenic

Arsenic (As) exposure causes numerous adverse health effects, which can be reduced by the nutrients involved in the metabolism of iAs (inorganic As). This study was carried out on two groups of copper-smelting workers: WN, workers with a urinary total arsenic (tAs) concentration within the norm (n = 75), and WH, workers with a urinary tAs concentration above the norm (n = 41). This study aimed to analyze the association between the intake level of the nutrients involved in iAs metabolism and the signal intensity of the metabolites that were affected by iAs exposure. An untargeted metabolomics analysis was carried out on urine samples using liquid chromatography-mass spectrometry, and the intake of the nutrients was analyzed based on 3-day dietary records. Compared with the WN group, five pathways (the metabolism of amino acids, carbohydrates, glycans, vitamins, and nucleotides) with twenty-five putatively annotated metabolites were found to be increased in the WH group. In the WN group, the intake of nutrients (methionine; vitamins B2, B6, and B12; folate; and zinc) was negatively associated with six metabolites (cytosine, D-glucuronic acid, N-acetyl-D-glucosamine, pyroglutamic acid, uridine, and urocanic acid), whereas in the WH group, it was associated with five metabolites (D-glucuronic acid, L-glutamic acid, N-acetyl-D-glucosamine, N-acetylneuraminic acid, and uridine). Furthermore, in the WH group, positive associations between methionine, folate, and zinc intake and the signal intensity of succinic acid and 3-mercaptolactic acid were observed. These results highlight the need to educate the participants about the intake level of the nutrients involved in iAs metabolism and may contribute to further considerations with respect to the formulation of dietary recommendations for people exposed to iAs.

Evaluation of low-to-moderate arsenic exposure, metabolism and skin lesions in a Turkish rural population exposed through drinking water

BACKGROUND

There is no human data regarding the exposure, metabolism and potential health effects of arsenic (As) contamination in drinking water in the Central Anatolian region of Turkey.

METHODS

Residents in ten villages with drinking water of total As (T-As) level >50 μg L^-1 and 10-50 μg L^-1 were selected as an exposed group (n = 420) and <10 μg L^-1 as an unexposed group (n = 185). Time-weighted average-As (TWA-As) intake was calculated from T-As analysis of drinking water samples. Concentrations of T-As in urine and hair samples, urinary As species [i.e., As(III), As(V), MMA(V) and DMA(V], and some micronutrients in serum samples of residents of the study area were determined. Primary and secondary methylation indices (PMI and SMI, respectively) were assessed from urinary As species concentrations and the presence of skin lesion was examined.

RESULTS

TWA-As intake was found as 75 μg L^-1 in the exposed group. Urinary and hair T-As and urinary As species concentrations were significantly higher in the exposed group (P < 0.05). The PMI and SMI values revealed that methylation capacities of the residents were efficient and that there was no saturation in As metabolism. No significant increase was observed in the frequency of skin lesions (hyperpigmentation, hypopigmentation, keratosis) of the exposed group (P > 0.05). Only frequency of keratosis either at the hand or foot was higher in individuals with hair As concentration >1 μg g^-1 (P < 0.05).

CONCLUSIONS

Individuals living in the study area were chronically exposed to low-to-moderate As due to geological contamination in drinking water. No significant increase was observed in the frequency of skin lesions. Because of the controversy surrounding the health risks of low-to-moderate As exposure, it is critical to initiate long-term follow-up studies on health effects in this region.

Human adaptation to arsenic in Bolivians living in the Andes

Humans living in the Andes Mountains have been historically exposed to arsenic from natural sources, including drinking water. Enzymatic methylation of arsenic allows it to be excreted more efficiently by the human body. Adaptation to high-arsenic environments via enhanced methylation and excretion of arsenic was first reported in indigenous women in the Argentinean Andes, but whether adaptation to arsenic is a general phenomenon across native populations from the Andes Mountains remains unclear. Therefore, we evaluated whether adaptation to arsenic has occurred in the Bolivian Andes by studying indigenous groups who belong to the Aymara-Quechua and Uru ethnicities and have lived in the Bolivian Andes for generations. Our population genetics methods, including genome-wide selection scans based on linkage disequilibrium patterns and allele frequency differences, in combination with targeted and whole-genome sequencing and genotype-phenotype association analyses, detected signatures of positive selection near the gene encoding arsenite methyltransferase (AS3MT), the main arsenic methylating enzyme. This was among the strongest selection signals (top 0.5% signals via locus-specific branch length and extended haplotype homozygosity tests) at a genome-wide level in the Bolivian study groups. We found a large haplotype block of 676 kb in the AS3MT region and identified candidate functional variants for further analysis. Moreover, our analyses revealed associations between AS3MT variants and the fraction of mono-methylated arsenic in urine and showed that the Bolivian study groups had the highest frequency of alleles associated with more efficient arsenic metabolism reported so far. Our data support the idea that arsenic exposure has been a driver for human adaptation to tolerate arsenic through more efficient arsenic detoxification in different Andean populations.

Provision of folic acid for reducing arsenic toxicity in arsenic-exposed children and adults

BACKGROUND

Arsenic is a common environmental toxin. Exposure to arsenic (particularly its inorganic form) through contaminated food and drinking water is an important public health burden worldwide, and is associated with increased risk of neurotoxicity, congenital anomalies, cancer, and adverse neurodevelopment in children. Arsenic is excreted following methylation reactions, which are mediated by folate. Provision of folate through folic acid supplements could facilitate arsenic methylation and excretion, thereby reducing arsenic toxicity.

OBJECTIVES

To assess the effects of provision of folic acid (through fortified foods or supplements), alone or in combination with other nutrients, in lessening the burden of arsenic-related health outcomes and reducing arsenic toxicity in arsenic-exposed populations.

SEARCH METHODS

In September 2020, we searched CENTRAL, MEDLINE, Embase, 10 other international databases, nine regional databases, and two trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing the provision of folic acid (at any dose or duration), alone or in combination with other nutrients or nutrient supplements, with no intervention, placebo, unfortified food, or the same nutrient or supplements without folic acid, in arsenic-exposed populations of all ages and genders.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included two RCTs with 822 adults exposed to arsenic-contaminated drinking water in Bangladesh. The RCTs compared 400 µg/d (FA400) or 800 µg/d (FA800) folic acid supplements, given for 12 or 24 weeks, with placebo. One RCT, a multi-armed trial, compared FA400 plus creatine (3 g/d) to creatine alone. We judged both RCTs at low risk of bias in all domains. Due to differences in co-intervention, arsenic exposure, and participants' nutritional status, we could not conduct meta-analyses, and therefore, provide a narrative description of the data. Neither RCT reported on cancer, all-cause mortality, neurocognitive function, or congenital anomalies. Folic acid supplements alone versus placebo Blood arsenic. In arsenic-exposed individuals, FA likely reduces blood arsenic concentrations compared to placebo (2 studies, 536 participants; moderate-certainty evidence). For folate-deficient and folate-replete participants who received arsenic-removal water filters as a co-intervention, FA800 reduced blood arsenic levels more than placebo (percentage change (%change) in geometric mean (GM) FA800 -17.8%, 95% confidence intervals (CI) -25.0 to -9.8; placebo GM -9.5%, 95% CI -16.5 to -1.8; 1 study, 406 participants). In one study with 130 participants with low baseline plasma folate, FA400 reduced total blood arsenic (%change FA400 mean (M) -13.62%, standard error (SE) ± 2.87; placebo M -2.49%, SE ± 3.25), and monomethylarsonic acid (MMA) concentrations (%change FA400 M -22.24%, SE ± 2.86; placebo M -1.24%, SE ± 3.59) more than placebo. Inorganic arsenic (InAs) concentrations reduced in both groups (%change FA400 M -18.54%, SE ± 3.60; placebo M -10.61%, SE ± 3.38). There was little to no change in dimethylarsinic acid (DMA) in either group. Urinary arsenic. In arsenic-exposed individuals, FA likely reduces the proportion of total urinary arsenic excreted as InAs (%InAs) and MMA (%MMA) and increases the proportion excreted as DMA (%DMA) to a greater extent than placebo (2 studies, 546 participants; moderate-certainty evidence), suggesting that FA enhances arsenic methylation. In a mixed folate-deficient and folate-replete population (1 study, 352 participants) receiving arsenic-removal water filters as a co-intervention, groups receiving FA had a greater decrease in %InAs (within-person change FA400 M -0.09%, 95% CI -0.17 to -0.01; FA800 M -0.14%, 95% CI -0.21 to -0.06; placebo M 0.05%, 95% CI 0.00 to 0.10), a greater decrease in %MMA (within-person change FA400 M -1.80%, 95% CI -2.53 to -1.07; FA800 M -2.60%, 95% CI -3.35 to -1.85; placebo M 0.15%, 95% CI -0.37 to 0.68), and a greater increase in %DMA (within-person change FA400 M 3.25%, 95% CI 1.81 to 4.68; FA800 M 4.57%, 95% CI 3.20 to 5.95; placebo M -1.17%, 95% CI -2.18 to -0.17), compared to placebo. In 194 participants with low baseline plasma folate, FA reduced %InAs (%change FA400 M -0.31%, SE ± 0.04; placebo M -0.13%, SE ± 0.04) and %MMA (%change FA400 M -2.6%, SE ± 0.37; placebo M -0.71%, SE ± 0.43), and increased %DMA (%change FA400 M 5.9%, SE ± 0.82; placebo M 2.14%, SE ± 0.71), more than placebo. Plasma homocysteine: In arsenic-exposed individuals, FA400 likely reduces homocysteine concentrations to a greater extent than placebo (2 studies, 448 participants; moderate-certainty evidence), in the mixed folate-deficient and folate-replete population receiving arsenic-removal water filters as a co-intervention (%change in GM FA400 -23.4%, 95% CI -27.1 to -19.5; placebo -1.3%, 95% CI -5.3 to 3.1; 1 study, 254 participants), and participants with low baseline plasma folate (within-person change FA400 M -3.06 µmol/L, SE ± 3.51; placebo M -0.05 µmol/L, SE ± 4.31; 1 study, 194 participants). FA supplements plus other nutrient supplements versus nutrient supplements alone In arsenic-exposed individuals who received arsenic-removal water filters as a co-intervention, FA400 plus creatine may reduce blood arsenic concentrations more than creatine alone (%change in GM FA400 + creatine -14%, 95% CI -22.2 to -5.0; creatine -7.0%, 95% CI -14.8 to 1.5; 1 study, 204 participants; low-certainty evidence); may not change urinary arsenic methylation indices (FA400 + creatine: %InAs M 13.2%, SE ± 7.0; %MMA M 10.8, SE ± 4.1; %DMA M 76, SE ± 7.8; creatine: %InAs M 14.8, SE ± 5.5; %MMA M 12.8, SE ± 4.0; %DMA M 72.4, SE ±7.6; 1 study, 190 participants; low-certainty evidence); and may reduce homocysteine concentrations to a greater extent (%change in GM FA400 + creatinine -21%, 95% CI -25.2 to -16.4; creatine -4.3%, 95% CI -9.0 to 0.7; 1 study, 204 participants; low-certainty evidence) than creatine alone.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that FA supplements may benefit blood arsenic concentration, urinary arsenic methylation profiles, and plasma homocysteine concentration versus placebo. There is low-certainty evidence that FA supplements plus other nutrients may benefit blood arsenic and plasma homocysteine concentrations versus nutrients alone. No studies reported on cancer, all-cause mortality, neurocognitive function, or congenital anomalies. Given the limited number of RCTs, more studies conducted in diverse settings are needed to assess the effects of FA on arsenic-related health outcomes and arsenic toxicity in arsenic-exposed adults and children.

Arsenic Secondary Methylation Capacity Is Inversely Associated with Arsenic Exposure-Related Muscle Mass Reduction

Skeletal muscle mass reduction has been implicated in insulin resistance (IR) that promotes cardiometabolic diseases. We have previously reported that arsenic exposure increases IR concomitantly with the reduction of skeletal muscle mass among individuals exposed to arsenic. The arsenic methylation capacity is linked to the susceptibility to some arsenic exposure-related diseases. However, it remains unknown whether the arsenic methylation capacity affects the arsenic-induced reduction of muscle mass and elevation of IR. Therefore, this study examined the associations between the arsenic methylation status and skeletal muscle mass measures with regard to IR by recruiting 437 participants from low- and high-arsenic exposure areas in Bangladesh. The subjects' skeletal muscle mass was estimated by their lean body mass (LBM) and serum creatinine levels. Subjects' drinking water arsenic concentrations were positively associated with total urinary arsenic concentrations and the percentages of MMA, as well as inversely associated with the percentages of DMA and the secondary methylation index (SMI). Subjects' LBM and serum creatinine levels were positively associated with the percentage of DMA and SMI, as well as inversely associated with the percentage of MMA. HOMA-IR showed an inverse association with SMI, with a confounding effect of sex. Our results suggest that reduced secondary methylation capacity is involved in the arsenic-induced skeletal muscle loss that may be implicated in arsenic-induced IR and cardiometabolic diseases.

Nutrition, one-carbon metabolism and arsenic methylation

Exposure to arsenic (As) is a major public health concern globally. Inorganic As (InAs) undergoes hepatic methylation to form monomethyl (MMAs)- and dimethyl (DMAs)-arsenical species, facilitating urinary As elimination. MMAsIII is considerably more toxic than either InAsIII or DMAsV, and a higher proportion of MMAs in urine has been associated with risk for a wide range of adverse health outcomes. Efficiency of As methylation differs substantially between species, between individuals, and across populations. One-carbon metabolism (OCM) is a biochemical pathway that provides methyl groups for the methylation of As, and is influenced by folate and other micronutrients, such as vitamin B12, choline, betaine and creatine. A growing body of evidence has demonstrated that OCM-related micronutrients play a critical role in As methylation. This review will summarize observational epidemiological studies, interventions, and relevant experimental evidence examining the role that OCM-related micronutrients have on As methylation, toxicity of As, and risk for associated adverse health-related outcomes. There is fairly robust evidence supporting the impact of folate on As methylation, and some evidence from case-control studies indicating that folate nutritional status influences risk for As-induced skin lesions and bladder cancer. However, the potential for folate to be protective for other As-related health outcomes, and the potential beneficial effects of other OCM-related micronutrients on As methylation and risk for health outcomes are less well studied and warrant additional research.

Arsenic Exposure, Arsenic Metabolism, and Glycemia: Results from a Clinical Population in New York City

Little information is available regarding the glycemic effects of inorganic arsenic (iAs) exposure in urban populations. We evaluated the association of total arsenic and the relative proportions of arsenic metabolites in urine with glycemia as measured by glycated blood hemoglobin (HbA1c) among 45 participants with prediabetes (HbA1c ≥ 5.7-6.4%), 65 with diabetes (HbA1c ≥ 6.5%), and 36 controls (HbA1c < 5.7%) recruited from an academic medical center in New York City. Each 10% increase in the proportion of urinary dimethylarsinic acid (DMA%) was associated with an odds ratio (OR) of 0.59 (95% confidence interval (CI): 0.28-1.26) for prediabetes, 0.46 (0.22-0.94) for diabetes, and 0.51 (0.26-0.99) for prediabetes and diabetes combined. Each 10% increase in the proportion of urinary monomethylarsonic acid (MMA%) was associated with a 1.13% (0.39, 1.88) increase in HbA1c. In contrast, each 10% increase in DMA% was associated with a 0.76% (0.24, 1.29) decrease in HbA1c. There was no evidence of an association of total urinary arsenic with prediabetes, diabetes, or HbA1c. These data suggest that a lower arsenic methylation capacity indicated by higher MMA% and lower DMA% in urine is associated with worse glycemic control and diabetes. Prospective, longitudinal studies are needed to evaluate the glycemic effects of low-level iAs exposure in urban populations.

Additive Effects of Arsenic and Aristolochic Acid in Chemical Carcinogenesis of Upper Urinary Tract Urothelium

BACKGROUND

Aristolochic acids (AA) and arsenic are chemical carcinogens associated with urothelial carcinogenesis. Here we investigate the combined effects of AA and arsenic toward the risk of developing upper tract urothelial carcinoma (UTUC).

METHODS

Hospital-based (n = 89) and population-based (2,921 cases and 11,684 controls) Taiwanese UTUC cohorts were used to investigate the association between exposure to AA and/or arsenic and the risk of developing UTUC. In the hospital cohort, AA exposure was evaluated by measuring aristolactam-DNA adducts in the renal cortex and by identifying A>T TP53 mutations in tumors. In the population cohort, AA exposure was determined from prescription health insurance records. Arsenic levels were graded from 0 to 3 based on concentrations in well water and the presence of arseniasis-related diseases.

RESULTS

In the hospital cohort, 43, 26, and 20 patients resided in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Aristolactam-DNA adducts were present in >90% of these patients, indicating widespread AA exposure. A>T mutations in TP53 were detected in 28%, 44%, and 22% of patients residing in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Population studies revealed that individuals who consumed more AA-containing herbs had a higher risk of developing UTUC in both arseniasis-endemic and nonendemic areas. Logistic regression showed an additive effect of AA and arsenic exposure on the risk of developing UTUC.

CONCLUSIONS

Exposure to both AA and arsenic acts additively to increase the UTUC risk in Taiwan.

IMPACT

This is the first study to investigate the combined effect of AA and arsenic exposure on UTUC.

Use of study-specific MOE-like estimates to prioritize health effects from chemical exposure for analysis in human health assessments

There are unique challenges in estimating dose-response with chemicals that are associated with multiple health outcomes and numerous studies. Some studies are more suitable than others for quantitative dose-response analyses. For such chemicals, an efficient method of screening studies and endpoints to identify suitable studies and potentially important health effects for dose-response modeling is valuable. Using inorganic arsenic as a test case, we developed a tiered approach that involves estimating study-specific margin of exposure (MOE)-like unitless ratios for two hypothetical scenarios. These study-specific unitless ratios are derived by dividing the exposure estimated to result in a 20% increase in relative risk over the background exposure (RRE20) by the background exposure, as estimated in two different ways. In our case study illustration, separate study-specific ratios are derived using estimates of United States population background exposure (RRB-US) and the mean study population reference group background exposure (RRB-SP). Systematic review methods were used to identify and evaluate epidemiologic studies, which were categorized based on study design (case-control, cohort, cross-sectional), various study quality criteria specific to dose-response analysis (number of dose groups, exposure ascertainment, exposure uncertainty), and availability of necessary dose-response data. Both case-control and cohort studies were included in the RRB analysis. The RRE20 estimates were derived by modeling effective counts of cases and controls estimated from study-reported adjusted odds ratios and relative risks. Using a broad (but not necessarily comprehensive) set of epidemiologic studies of multiple health outcomes selected for the purposes of illustrating the RRB approach, this test case analysis would suggest that diseases of the circulatory system, bladder cancer, and lung cancer may be arsenic health outcomes that warrant further analysis. This is suggested by the number of datasets from adequate dose-response studies demonstrating an effect with RRBs close to 1 (i.e., RRE20 values close to estimated background arsenic exposure levels).

Joint effects of genomic markers and urinary methylation capacity associated with inorganic arsenic metabolism on the occurrence of cancers among residents in arseniasis-endemic areas: A cohort subset with average fifteen-year follow-up

Background

Chronic exposure to inorganic arsenic results in many cancers in susceptible persons. The metabolism of inorganic arsenic and genomic susceptibility are thought to be associated with cancer occurrence.

Methods

This study aims to examine the interaction of genomic susceptibility markers and urinary methylation capacity indicators involved in inorganic arsenic metabolism with all-cancer occurrence. This study conducted a follow-up on 96 residents to determine their urinary inorganic arsenic metabolites and genomic assay from an arseniasis area. Among them, 24 cancer developed. Multivariable Cox proportional hazards model was used to determine and estimate the candidate independent variables for cancer development.

Results

The residents with high inorganic arsenic exposure, high primary methylation index (PMI; MMA/InAs) (but lower secondary methylation index (SMI)), and non-heterogeneity type of genomic markers, including GSTO1, AS3MT, and MPO, tend to develop cancers. Subjects with higher PMI are at higher risk of developing cancers (HR = 1.66; 95% CI = 1.30–2.12). Cancer occurrence was greater among the CC type of GSTO1 (HR = 3.33; 95% CI = 1.11–10.00), CC type of AS3MT (HR = 19.21; 95% CI = 1.16–318.80), and AA type of MPO (HR = 13.40; 95% CI = 1.26–142.40). After adjusting confounders, a mutually moderating effect was revealed between genomic markers and methylation capacity on cancer occurrence.

Conclusions

This study found the hypermethylation responses to inorganic arsenic exposure and an array of genomic markers may increase the susceptibility of a wide range of organ cancers. The findings indicated a high-risk arsenic-exposed population to develop cancers. The phenotype of arsenic metabolism and genomic polymorphism suggested a potential preventive strategy for arsenic carcinogenesis.

Executive functions in school children from Montevideo, Uruguay and their associations with concurrent low-level arsenic exposure

OBJECTIVE

Arsenic is a known childhood neurotoxicant, but its neurotoxicity at low exposure levels is still not well established. The aim of our cross-sectional study was to test the association between low-level arsenic exposure and executive functions (EF) among children in Montevideo. We also assessed effect modification by arsenic methylation capacity, a susceptibility factor for the health effects of arsenic, and by B-vitamin intake, which impacts arsenic methylation.

METHODS

Arsenic exposure was assessed as the specific gravity-adjusted sum of urinary arsenic metabolites (U-As) among 255 ~ 7 year-old children, and methylation capacity as the proportion of urinary monomethylarsonic acid (%MMA). Arsenic concentrations from kitchen water samples at participants' homes were assessed. B-vitamin intake was calculated from the average of two 24-hour dietary recalls. EF was measured using three tests from the Cambridge Neuropsychological Test Automated Battery- Stockings of Cambridge (SOC), Intra-dimensional/extra-dimensional shift task (IED), and Spatial Span (SSP). Generalized linear models assessed the association between U-As and EF measures; models were adjusted for age, sex, maternal education, possessions score, Home Observation for Measurement of the Environment Inventory score, season, and school clusters. Additional analyses were conducted to address issues of residual confounding and sample size. A "B-vitamin index" was calculated using principal component analysis. Effect modification by the index and urinary %MMA was assessed in strata split at the respective medians of these variables.

RESULTS

The median (range) U-As and water arsenic levels were 9.9 µg/L (2.2, 47.7) and 0.45 µg/L (0.1, 18.9) respectively, indicating that exposure originated mainly from other sources. U-As was inversely associated with the number of stages completed (β = -0.02; 95% CI: -0.03, -0.002) and pre-executive shift errors (β = -0.08; 95% CI: -0.14, -0.02) of the IED task, and span length of the SSP task (β = -0.01; 95% CI: -0.02, -0.004). There was no clear pattern of effect modification by B-vitamin intake or urinary %MMA.

CONCLUSION

Low-level arsenic exposure may adversely affect executive function among children but additional, including longitudinal, studies are necessary to confirm these findings.

Factors Affecting Arsenic Methylation in Contaminated Italian Areas

Chronic arsenic (As) exposure is a critical public health issue. The As metabolism can be influenced by many factors. The objective of this study is to verify if these factors influence As metabolism in four Italian areas affected by As pollution. Descriptive analyses were conducted on 271 subjects aged 20-49 in order to assess the effect of each factor considered on As methylation. Percentages of metabolites of As in urine, primary and secondary methylation indexes were calculated as indicators for metabolic capacity. The results indicate that women have a better methylation capacity (MC) than men, and drinking As-contaminated water from public aqueducts is associated with poorer MC, especially in areas with natural As pollution. In areas with anthropogenic As pollution occupational exposure is associated with a higher MC while smoking with a poorer MC. Dietary habits and genetic characteristics are probably implicated in As metabolism. BMI, alcohol consumption and polymorphism of the AS3MT gene seem not to influence As MC. Arsenic metabolism may be affected by various factors and in order to achieve a comprehensive risk assessment of As-associated disease, it is crucial to understand how these factors contribute to differences in As metabolism.

Biotransformation of dietary inorganic arsenic in a freshwater fish Carassius auratus and the unique association between arsenic dimethylation and oxidative damage

The metabolic process and toxicity mechanism of dietary inorganic arsenic (iAs) in freshwater fish remain unclear to date. The present study conducted two iAs [arsenate (As(V)) and arsenite (As(III))] dietary exposures in freshwater fish crucian carp (Carassius auratus). The fish were fed on As supplemented artificial diets at nominal concentrations of 50 and 100 μg As(III) or As(V) g^-1 (dry weight) for 10 d and 20 d. We found that the liver, kidney, spleen, and intestine of fish accumulated more As in As(V) feeding group than that in As(III), while the total As levels in muscle were similar between As(V) and As(III) group at the end of exposure. Reduction of As(V) to As(III) and oxidation of As(III) to As(V) occurred in fish fed with As(V) and As(III), respectively, indicating that toxicity of iAs was likely elevated or reduced when iAs was absorbed by fish before entering into human body through diet. Biomethylation to monomethylarsonic acid and dimethylarsinic acid and transformation to arsenocholine and arsenobetaine were also found in the fish. The linear regression analysis showed a positive correlation between secondary methylation index and the malondialdehyde content in tissues, highlighting the vital role of arsenic dimethylation in the oxidative damages in fish.

Vitamin B-6 Intake Is Modestly Associated with Arsenic Methylation in Uruguayan Children with Low-Level Arsenic Exposure

BACKGROUND

Detoxification of inorganic arsenic (iAs) occurs when it methylates to form monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Lower proportions of urinary iAs and MMA, and higher proportions of DMA indicate efficient methylation. The role of B-vitamins in iAs methylation in children with low-level arsenic exposure is understudied.

OBJECTIVES

Our study objective was to assess the association between B-vitamin intake and iAs methylation in children with low-level arsenic exposure (<50 µg/L in water; urinary arsenic 5-50 µg/L).

METHODS

We conducted a cross-sectional study in 290 ∼7-y-old children in Montevideo. Intake of thiamin, riboflavin, niacin, vitamin B-6, and vitamin B-12 was calculated by averaging 2 nonconsecutive 24-h recalls. Total urinary arsenic concentration was measured as the sum of urinary iAs, MMA, and DMA, and adjusted for urinary specific gravity; iAs methylation was measured as urinary percentage As, percentage MMA, and percentage DMA. Arsenic concentrations from household water sources were assessed. Linear regressions tested the relationships between individual energy-adjusted B-vitamins and iAs methylation.

RESULTS

Median (range) arsenic concentrations in urine and water were 9.9 (2.2-48.7) and 0.45 (0.1-18.9) µg/L, respectively. The median (range) of urinary percentage iAs, percentage MMA, and percentage DMA was 10.6% (0.0-33.8), 9.7% (2.6-24.8), and 79.1% (58.5-95.4), respectively. The median (range) intake levels of thiamin, riboflavin, niacin, and vitamin B-6 were 0.81 (0.19-2.56), 1.0 (0.30-2.24), 8.6 (3.5-23.3), and 0.67 (0.25-1.73) mg/1000 kcal, respectively, whereas those of folate and vitamin B-12 were 216 (75-466) and 1.7 (0.34-8.3) µg/1000 kcal, respectively. Vitamin B-6 intake was inversely associated with urinary percentage MMA (β = -1.60; 95% CI: -3.07, -0.15). No other statistically significant associations were observed.

CONCLUSIONS

Although vitamin B-6 intake was inversely associated with urinary percentage MMA, our findings suggest limited support for a relation between B-vitamin intake and iAs methylation in children exposed to low-level arsenic.

Arsenic Exposure and Risk of Urothelial Cancer: Systematic Review and Meta-Analysis

Background: Arsenic is a toxic metalloid element widely distributed throughout the environment. Arsenic contaminated water has become an ongoing public health issue affecting hundred million people worldwide. The aim of this paper was to summarize the evidence in the association between arsenic metabolites and urinary tract cancer risk. Methods: A systematic review was conducted searching for observational studies that evaluated the association of arsenic metabolites and urinary tract cancer. Risk estimates from individual studies were pooled by using random effects models. Results: All the metabolites considered in this study resulted to be significantly associated to urothelial cancer, respectively: IA% 3.51 (1.21-5.82) (p = 0.003), MMA with WMD = 2.77 (1.67-3.87) (p < 0.001) and DMA with WMD = -4.56 (-7.91-1.22) (p = 0.008). Conclusions: Arsenic metabolites are significantly associated to urothelial cancer. Future studies will help to verify the independent association(s) between arsenic metabolites and urothelial cancer.

Impact of arsenic exposure on clinicopathological characteristics of bladder cancer: A comparative study between patients from an arsenic-exposed region and nonexposed reference sites

BACKGROUND

Beyond exposure to arsenic in drinking-water, there is few information about demographic and clinicopathological features of patients with bladder cancer living in arsenic-exposed regions. The aim of the study was to assess the impact of arsenic exposure on clinicopathological characteristics in patients with bladder cancer from a contaminated region compared to those of 2 reference areas.

METHODS

Data of 285 patients with bladder cancer (83 with arsenic exposure from Antofagasta and 202 controls from 2 different sites in Santiago) were obtained through personal interviews and from review of medical records. Demographic, clinicopathological parameters, and information on relevant environmental risk factors were compared with parametric and nonparametric tests as needed. Multivariable analysis was performed to identify independent predictors for high grade and muscle-invasive disease (T2-4).

RESULTS

We found no significant differences between groups regarding age at presentation (66.4 vs. 66.5 and 67.2 years; P = 0.69, for exposed vs. the 2 nonexposed groups, respectively) and female gender (28.9% vs. 29.8% and 26.2%; P = 0.84). Proportion of current smokers was significantly lower in the exposed population (10.7% vs. 38.6% and 26.9%; P < 0.001). There was a significantly higher proportion of locally advanced (10.8 vs. 1.8 and 0.7% T3/4; P = 0.002) and high-grade tumors (79.5% vs. 63.2% and 64.1%; P = 0.001) within arsenic-exposed patients. Arsenic exposure was the only significant predictor for the presence of high-grade tumors (adjusted OR: 5.10; 95%CI: 2.03-12.77) on multivariable analysis.

CONCLUSIONS

Our study revealed relevant clinical differences in bladder cancer patients with a history of arsenic exposure as compared to nonexposed cases. The more aggressive phenotype associated to arsenic-related bladder cancer should be considered when designing efficient screening strategies for this high-risk population.

Low level arsenic exposure, B-vitamins, and achievement among Uruguayan school children

OBJECTIVES

Millions of children globally, including the U.S., are exposed to low levels of arsenic from water and food. Arsenic is a known neurotoxicant at high levels but its effects at lower exposure levels are understudied. Arsenic methylation capacity, influenced by B-vitamin intake and status, potentially influences arsenic toxicity. In a cross-secitonal study of 5-8 year-old children from Montevideo, we assessed the relationship between urinary arsenic (U-As) and academic achievement, and tested for effect modification by B-vitamin intake, status, and arsenic methylation capacity.

METHODS

Broad math and reading scores were calculated based on six subtests (calculation, math facts fluency, applied problems, sentence reading fluency, letter word identification, passage comprehension) from the Woodcock-Muñoz Achievement Battery. B-vitamin intake was assessed from two non-consecutive 24-h dietary recalls, serum folate and vitamin B-12 levels were measured in a subset of participants. Arsenic methylation capacity was measured as the proportion of urinary monomethylarsonic acid (%MMA). Multiple imputation using chained equations was conducted to account for missing covariate and exposure data. Ordinal regressions assessed associations between U-As and achievement score tertiles in the complete case and imputed samples. A "B-vitamin index" was calculated using principal component analysis. Interactions by urinary %MMA and the B-vitamin index were assessed.

RESULTS

Median specific gravity adjusted U-As was 11.7 μg/L (range: 2.6, 50.1). We found no association between U-As and broad math and reading scores, nor effect modification by %MMA or B-vitamins.

CONCLUSION

At low-levels of exposure, U-As does not appear to affect children's academic achievement.

Measurement of urinary arsenic profiles and DNA hypomethylation in a case-control study of urothelial carcinoma

Environmental exposure to arsenic may be involved in the disturbance of DNA hypomethylation. The aim of this study is the first to explore the effect of interactions of urinary total arsenic levels, arsenic methylation capacity, 8-hydroxy-2'-deoxyguanosine (8-OHdG), plasma folate, and global 5-methyl-2'-deoxycytidine (5-MedC) levels on the risk of urothelial carcinoma (UC). A hospital-based case-control study was constructed. The research involved the histological recruitment and pathological verification of 178 UC patients and 356 age-/sex-matched controls without prior history of cancer. Arsenic species were determined by high-performance liquid chromatography (HPLC)-hydride generation and atomic absorption. 5-MedC levels were detected by HPLC and triple-quadrupole mass spectrometry (MS). 8-OHdG was processed by an online solid-phase extraction LC-MS/MS. Plasma folate levels were measured using the chemiluminescent technology. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by multiple logistic regression analysis. Results indicate that the high levels of total urinary arsenic, inorganic arsenic percentage, and 8-OHdG and the low levels of DMA % and plasma folate were independent factors of UC. In addition, global 5-MedC levels in the first quartile versus fifth quartile significantly increased the twofold OR of UC after potential factors were adjusted (95% CI:1.10-4.03). The interaction of 5-MedC level and high total arsenic level, insufficient arsenic capacity, high 8-OHdG, and low folate levels was insignificant. Results of stepwise logistic regression analysis indicate that high total urinary arsenic levels (Q3 versus Q1), low plasma folate level, and low global 5-MedC (Q4 versus Q5) significantly increased the ORs of UC. The above results suggest that high total arsenic, low plasma folate, and 5-MedC levels affect the ORs of UC independently.

Analysis of the association between bladder carcinoma and arsenic concentration in soil and water in southeast Brazil

In approximately 50% of cases of bladder carcinoma, an associated predisposing factor can be established. The main factors are exposure to tobacco, arsenic (As) ore and aromatic compounds. Arsenic is a metalloid with a low average concentration in the earth's crust, and one of the most dangerous substances for human health. The present study aims to evaluate the incidence of hospitalization and mortality from bladder neoplasia and its possible association with As concentration in water and soil in two of the most critical regions of Brazil: the states of São Paulo and Minas Gerais. We have investigated bladder cancer hospitalization and mortality in the states of São Paulo and Minas Gerais during 2010-2014. Water and soil samples were analyzed and As concentrations were established. Data were obtained through the Department of Informatics of the Brazilian Unified Health System. Correlation was made with water samples from São Paulo and with data on soil analysis from Minas Gerais. The results revealed no direct association in the distinctive municipalities. Areas with high environmental As concentration had a low bladder cancer rate, while areas with normal as levels had similar cancer rates. The quantitative variables did not present a normal distribution (p < 0.05). In conclusion, we did not observe a correlation between as concentration in water or soil and bladder cancer's hospitalization and mortality rates in the states of São Paulo and Minas Gerais.

Potential effect modifiers of the arsenic-bladder cancer risk relationship

Populations exposed to arsenic in drinking water have an increased bladder cancer risk and evidence suggests that several factors may modify arsenic metabolism, influencing disease risk. We evaluated whether the association between cumulative lifetime arsenic exposure from drinking water and bladder cancer risk was modified by factors that may impact arsenic metabolism in a population-based case-control study of 1,213 cases and 1,418 controls. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between cumulative arsenic intake and bladder cancer stratified by age, sex, smoking status, body mass index (BMI), alcohol consumption and folate intake. P-values for interaction were computed using a likelihood ratio test. We observed no statistically significant multiplicative interactions although some variations in associations were notable across risk factors, particularly for smoking and BMI. Among former smokers and current smokers, those with the highest cumulative arsenic intake had elevated risks of bladder cancer (OR = 1.4, 95% CI: 0.96-2.0 and OR = 1.6, 95% CI: 0.91-3.0, respectively; while the OR among never smokers was 1.1, 95% CI: 0.6-1.9, p-interaction = 0.49). Among those classified as normal or overweight based on usual adult BMI, the highest level of cumulative arsenic intake was associated with elevated risks of bladder cancer (OR = 1.3, 95% CI: 0.89-2.0 and OR = 1.6, 95% CI: 1.1-2.4, respectively), while risk was not elevated among those who were obese (OR = 0.9, 95% CI: 0.4-1.8) (p-interaction = 0.14). Our study provides some limited evidence of modifying roles of age, sex, smoking, BMI, folate and alcohol on arsenic-related bladder cancer risk that requires confirmation in other, larger studies.

Gut microbiome disruption altered the biotransformation and liver toxicity of arsenic in mice

The mammalian gut microbiome (GM) plays a critical role in xenobiotic biotransformation and can profoundly affect the toxic effects of xenobiotics. Previous in vitro studies have demonstrated that gut bacteria have the capability to metabolize arsenic (As); however, the specific roles of the gut microbiota in As metabolism in vivo and the toxic effects of As are largely unknown. Here, we administered sodium arsenite to conventionally raised mice (with normal microbiomes) and GM-disrupted mice with antibiotics to investigate the role of the gut microbiota in As biotransformation and its toxicity. We found that the urinary total As levels of GM-disrupted mice were much higher, but the fecal total As levels were lower, than the levels in the conventionally raised mice. In vitro experiments, in which the GM was incubated with As, also demonstrated that the gut bacteria could adsorb or take up As and thus reduce the free As levels in the culture medium. With the disruption of the gut microbiota, arsenic biotransformation was significantly perturbed. Of note, the urinary monomethylarsonic acid/dimethylarsinic acid ratio, a biomarker of arsenic metabolism and toxicity, was markedly increased. Meanwhile, the expression of genes of one-carbon metabolism, including folr2, bhmt, and mthfr, was downregulated, and the liver S-adenosylmethionine (SAM) levels were significantly decreased in the As-treated GM-disrupted mice only. Moreover, As exposure altered the expression of genes of the p53 signaling pathway, and the expression of multiple genes associated with hepatocellular carcinoma (HCC) was also changed in the As-treated GM-disrupted mice only. Collectively, disruption of the GM enhances the effect of As on one-carbon metabolism, which could in turn affect As biotransformation. GM disruption also increases the toxic effects of As and may increase the risk of As-induced HCC in mice.

A cross-sectional study of general cognitive abilities among Uruguayan school children with low-level arsenic exposure, potential effect modification by methylation capacity and dietary folate

BACKGROUND

Few studies have evaluated the association between low-level arsenic (As) exposure and cognitive performance among children.

OBJECTIVES

In this cross-sectional study, we assessed the association between low-level As exposure and cognitive performance among 5-8 year-old children in Montevideo, and tested effect modification by As methylation capacity and children's dietary folate intake.

METHODS

We measured total urinary As (UAs) concentrations and the proportion of monomethylarsonic acid (MMA) in the urine of 328 children. Seven subtests of the standardized Woodcock-Muñoz cognitive battery were used to assess cognitive performance, from which, the general intellectual abilities (GIA) score was derived. Total folate intake was estimated from two 24-h dietary recalls. Linear regression analyses were performed. Effect modification was assessed by stratifying at the median %MMA value and tertiles of total folate intake calculated as micrograms (µg) of dietary folate equivalents (dfe).

RESULTS

The median UAs was 11.9 µg/l (range = 1.4-93.9), mean folate intake was 337.4 (SD = 123.3) µg dfe, and median %MMA was 9.42 (range = 2.6-24.8). There was no association between UAs and cognitive abilities, and no consistent effect modification by %MMA. UAs was associated inversely with concept formation, and positively with cognitive efficiency and numbers reversed subtest in the lowest folate intake tertile; UAs was also positively associated with sound integration in the second tertile and concept formation in the highest tertile of folate intake. There was no consistent pattern of effect modification by %MMA or folate intake.

CONCLUSION

There was no association between low-level As exposure and general cognitive abilities.

Comparison of arsenic methylation capacity and polymorphisms of arsenic methylation genes between bladder cancer and upper tract urothelial carcinoma

Arsenic exposure is an environmental risk factor for urothelial carcinoma (UC). The natural history of upper tract urothelial carcinoma (UTUC) differs from that of bladder cancer (BC). However, the risk factors of BC and UTUC are not exactly the same and should be discussed separately. The aims of this study were to evaluate 1) the association between arsenic methylation capacity and UTUC and/or BC, separately, and 2) the association between polymorphisms of the arsenic metabolism-related genes AS3MT, GSTOs, and PNP against BC and/or UTUC, separately. We conducted a hospital-based study and collected 216 BC and 212 UTUC cases, and 813 healthy controls, from September 2007 to October 2011. Urinary arsenic profiles were measured using high-performance liquid chromatography-hydride generator-atomic absorption spectrometry. The polymorphisms of AS3MT, GSTO, and PNP were identified using the Sequenom MassARRAY platform with iPLEX Gold chemistry. We found that inefficient arsenic methylation capacity was associated with BC in a significant dose-response relationship, but only found that high urinary total arsenic concentration was related to the risk of UTUC, also in a significant dose-response manner. Those with a total urinary arsenic level of > 30.28 μg/L compared to ≤ 9.78 μg/L, had a odds ratio (OR), and 95% confidence interval (CI) of UTUC, of 4.80 (2.22-10.39). The polymorphisms of AS3MT rs11191438, AS3MT rs10748835, and AS3MT rs1046778 were related to the risk of BC and UTUC, while the polymorphisms of AS3MT rs3740393, AS3MT rs11191453, and AS3MT rs11191454 were associated with arsenic methylation capacity. The AS3MT gene polymorphisms and arsenic methylation capacity appear to independently affect the risk of BC and UTUC.

Nutritional Influences on One-Carbon Metabolism: Effects on Arsenic Methylation and Toxicity

Exposure to inorganic arsenic (InAs) via drinking water and/or food is a considerable worldwide problem. Methylation of InAs generates monomethyl (MMAs^III+V)- and dimethyl (DMAs^III+V)-arsenical species in a process that facilitates urinary As elimination; however, MMAs is considerably more toxic than either InAs or DMAs. Emerging evidence suggests that incomplete methylation of As to DMAs, resulting in increased MMAs, is associated with increased risk for a host of As-related health outcomes. The biochemical pathway that provides methyl groups for As methylation, one-carbon metabolism (OCM), is influenced by folate and other micronutrients, including choline and betaine. Individuals and species differ widely in their ability to methylate As. A growing body of research, including cell-culture, animal-model, and epidemiological studies, has demonstrated the role of OCM-related micronutrients in As methylation. This review examines the evidence that nutritional status and nutritional interventions can influence the metabolism and toxicity of As, with a primary focus on folate.

Nutrients in one-carbon metabolism and urinary arsenic methylation in the National Health and Nutrition Examination Survey (NHANES) 2003-2004

Exposure to inorganic arsenic (inAs), a potent toxicant, occurs primarily through ingestion of food and water. The efficiency with which it is methylated to mono and dimethyl arsenicals (MMA and DMA) affects toxicity. Folate, vitamins B12 and B6 are required for 1C metabolism, and studies have found that higher levels of these nutrients increase methylation capacity and are associated with protection against adverse health effects from inAs, especially in undernourished populations. Our aim was to determine whether 1C-related nutrients are associated with greater inAs methylation capacity in a general population sample with overall adequate nutrition and low levels of As exposure. Univariate and multivariable regression models were used to evaluate the relationship of dietary and blood nutrients to urinary As methylation in the National Health and Nutrition Examination Survey (NHANES) 2003-2004. Outcome variables were the percent of the sum of inAs and methylated As species (inAs+MMA+DMA) excreted as inAs, MMA, and DMA, and the ratio of MMA:DMA. In univariate models, dietary folate, vitamin B6 and protein intake were associated with lower urinary inAs% and greater DMA% in adults (≥18years), with similar trends in children (6-18). In adjusted models, vitamin B6 intake (p=0.011) and RBC folate (p=0.036) were associated with lower inAs%, while dietary vitamin B12 was associated with higher inAs% (p=0.002) and lower DMA% (p=0.030). Total plasma homocysteine was associated with higher MMA% (p=0.004) and lower DMA% (p=0.003), but not with inAs%; other blood nutrients showed no association with urinary As. Although effect size is small, these findings suggest that 1C nutrients can influence inAs methylation and potentially play an indirect role in reducing toxicity in a general population sample.

The Association of Arsenic Metabolism with Cancer, Cardiovascular Disease, and Diabetes: A Systematic Review of the Epidemiological Evidence

BACKGROUND

The available evidence on the role of arsenic metabolism in individual susceptibility to the development of cancer, cardiovascular disease, and diabetes has not been formally and comprehensively reviewed.

OBJECTIVES

Our goal was to systematically investigate the association of arsenic metabolism with cancer, cardiovascular disease, and diabetes-related outcomes in epidemiologic studies. As a secondary objective, we characterized the variation of arsenic metabolism in different populations worldwide.

METHODS

We searched Medline/PubMed and EMBASE from inception to January 2016 and applied predetermined exclusion criteria. Compositional data analysis was used to describe the distribution of arsenic metabolism biomarkers and evaluate the association between arsenic exposure and metabolism.

RESULTS

Twenty-eight studies met the inclusion criteria, 12 on cancer, nine on cardiovascular disease, and seven on diabetes-related outcomes. The median (interquartile range) for mean iAs%, MMA%, and DMA% was 11.2 (7.8-14.9)%, 13.0 (10.4-13.6)%, and 74.9 (69.8-80.0)%, respectively. Findings across studies suggested that higher arsenic exposure levels were associated with higher iAs% and lower DMA% and not associated with MMA%. For cancer, most studies found a pattern of higher MMA% and lower DMA% associated with higher risk of all-site, urothelial, lung, and skin cancers. For cardiovascular disease, higher MMA% was generally associated with higher risk of carotid atherosclerosis and clinical cardiovascular disease but not with hypertension. For diabetes-related outcomes, the pattern of lower MMA% and higher DMA% was associated with higher risk of metabolic syndrome and diabetes.

CONCLUSIONS

Population level of iAs% and DMA%, but not MMA%, were associated with arsenic exposure levels. Overall, study findings suggest that higher MMA% was associated with an increased risk of cancer and cardiovascular disease, while lower MMA% was associated with an increased risk of diabetes and metabolic syndrome. Additional population-based studies and experimental studies are needed to further evaluate and understand the role of arsenic exposure in arsenic metabolism and the role of arsenic metabolism in disease development. https://doi.org/10.1289/EHP577.

Arsenic metabolism and cancer risk: A meta-analysis

OBJECTIVE

To describe the studies that have reported association measures between risk of cancer and the percentage distribution of urinary inorganic arsenic (iAs) metabolites by anatomical site, in non-ecological epidemiological studies.

METHODS

Studies were identified in the PubMed database in the period from 1990 to 2015. Inclusion criteria were: non-ecological epidemiological study, with histologically confirmed cancer cases, reporting the percentage distribution of inorganic arsenic (iAs), monomethylated (MMA) and dimethylated (DMA) metabolites, as well as association measures with confidence intervals (CI) between cancer and %iAs and/or %MMA and/or %DMA. A descriptive meta-analysis was performed by the method of the inverse of the variance for the fixed effects model and the DerSimonian and Laird's method for the random effects model. Heterogeneity was tested using the Q statistic and stratifying for epidemiological design and total As in urine. The possibility of publication bias was assessed through Begg's test.

RESULTS

A total of 13 eligible studies were found, most of them were performed in Taiwan and focused on skin and bladder cancer. The positive association between %MMA and various types of cancer was consistent, in contrast to the negative relationship between %DMA and cancer that was inconsistent. The summary risk of bladder (OR=1.79; 95% CI: 1.42, 2.26, n=4 studies) and lung (OR=2.44; 95% CI: 1.57, 3.80, n=2 studies) cancer increased significantly with increasing %MMA, without statistical heterogeneity. In contrast, lung cancer risk was inversely related to %DMA (OR=0.58; 95% CI: 0.36, 0.93, n=2 studies), also without significant heterogeneity. These results were similar after stratifying by epidemiological design and total As in urine. No evidence of publication bias was found.

CONCLUSION

These findings provide additional support that methylation needs to be taken into account when assessing the potential iAs carcinogenicity risk.

Relationships between arsenic concentrations in drinking water and lung and bladder cancer incidence in U.S. counties

Increased risks of lung and bladder cancer have been observed in populations exposed to high levels of inorganic arsenic. However, studies at lower exposures (i.e., less than 100 μg/l in water) have shown inconsistent results. We therefore conducted an ecological analysis of the association between historical drinking water arsenic concentrations and lung and bladder cancer incidence in U.S. counties. We used drinking water arsenic concentrations measured by the U.S. Geological Survey and state agencies in the 1980s and 1990s as proxies for historical exposures in counties where public groundwater systems and private wells are important sources of drinking water. Relationships between arsenic levels and cancer incidence in 2006-2010 were explored by Poisson regression analyses, adjusted for groundwater dependence and important demographic covariates. The median and 95th percentile county mean arsenic concentrations were 1.5 and 15.4 μg/l, respectively. Water arsenic concentrations were significant and positively associated with female and male bladder cancer, and with female lung cancer. Our findings support an association between low water arsenic concentrations and lung and bladder cancer incidence in the United States. However, the limitations of the ecological study design suggest caution in interpreting these results.

Dose-Response Relationship between Inorganic Arsenic Exposure and Lung Cancer among Arseniasis Residents with Low Methylation Capacity

Background: Exposure to inorganic arsenic (InAs) has been documented as a risk factor for lung cancer. This study examined the association between InAs exposure, its metabolism, and lung cancer occurrence.Methods: We followed 1,300 residents from an arseniasis area in Taiwan, determined urinary InAs metabolites, and identified 39 lung cancer cases. Cox proportional hazards model was performed.Results: The results demonstrated that participants with either the primary methylation index [monomethylarsonic acid (MMA)/InAs] or the secondary methylation index [dimethylarsenic acid (DMA)/MMA] lower than their respective median values were at a higher risk of lung cancer (HRs from 3.41 to 4.66) than those with high methylation capacity. The incidence density of lung cancer increased from 79.9/100,000 (year^-1) to 467.4/100,000 (year^-1) for residents with low methylation capacity and from 0 to 158.5/100,000 (year^-1) for residents with high methylation capacity when the arsenic exposure dose increased from 2 to 10 ppb to ≥200 ppb, respectively. The analyses revealed a dose-response relationship between lung cancer occurrence and increasing arsenic concentrations in drinking water as well as cumulative arsenic exposure (monotonic trend test; P < 0.05 and P < 0.05, respectively) among the residents with low methylation capacity. The relationship between arsenic exposure and lung cancer among high methylators was not statistically significant.Conclusions: Hypomethylation responses to InAs exposure may dose dependently increase lung cancer occurrence.Impact: The high-risk characteristics observed among those exposed should be considered in future preventive medicine and research on arsenic carcinogenesis. Cancer Epidemiol Biomarkers Prev; 26(5); 756-61. ©2016 AACR.

Association between polymorphisms in arsenic metabolism genes and urinary arsenic methylation profiles in girls and boys chronically exposed to arsenic

Disease manifestations or susceptibilities often differ among individuals exposed to the same concentrations of arsenic (As). These differences have been associated with several factors including As metabolism, sex, age, genetic variants, nutritional status, smoking, and others. This study evaluated the associations between four As metabolism-related gene polymorphisms/null genotypes with urinary As methylation profiles in girls and boys chronically exposed to As. In a total of 332 children aged 6-12 years, the frequency of AS3MT, GSTO1, GSTT1, and GSTM1 polymorphisms/null genotypes and As urinary metabolites were measured. The results revealed that total As and monomethyl metabolites of As (MMA) levels were higher in boys than in girls. No differences in the frequency of the evaluated polymorphisms were found between girls and boys. In AS3MT-Met287Thr carriers, %MMA levels were higher and second methylation levels (defined as dimethylarsinic acid divided by MMA) were lower. In children with the GSTM1 null genotype, second methylation levels were higher. In boys, a positive association between the AS3MT-Met287Thr polymorphism with %MMA and between the GSTO1-Glu155del and As(v) was found; whereas, a negative relationship was identified between AS3MT-Met287Thr and second methylation profiles. In girls, a positive association was found between the GSTO1-Ala140Asp polymorphism with second methylation levels. In conclusion, our data indicate that gender, high As exposure levels, and polymorphisms in the evaluated genes negatively influenced As metabolism. Environ. Mol. Mutagen. 57:516-525, 2016. © 2016 Wiley Periodicals, Inc.

Arsenic Metabolites and Methylation Capacity Among Individuals Living in a Rural Area with Endemic Arseniasis in Inner Mongolia, China

More than 0.3 million individuals are subject to chronic exposure to arsenic via their drinking water in Inner Mongolia, China. To determine arsenic methylation capacity profiles for such individuals, concentrations of urinary arsenic metabolites were measured for 548 subjects using high-performance liquid chromatography and a hydride generator combined with inductively coupled plasma-mass spectrometry. Mean urinary concentrations of dimethylarsonic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenic (iAs), and total arsenic (TAs) were 200.50, 46.71, 52.96, and 300.17 μg/L, respectively. The %iAs, %DMA, and %MMA were 15.98, 69.72, and 14.29%. Mean urinary %iAs and %MMA were higher in males, while urinary %DMA was higher in females. There was a strong positive correlation between %iAs and %MMA, with negative correlations between %iAs and %DMA, and %iAs and %MMA. In addition, %iAs and %MMA were positively associated with total arsenic in drinking water (WAs), while %DMA was negatively related with WAs. Regression analysis indicated that the primary methylation index (PMI) and secondary methylation index (SMI) generally decreased with increasing WAs. Females had a higher arsenic methylation capacity compared to males. Younger subjects had lower primary arsenic methylation capacity. However, the secondary arsenic methylation capacity was hardly affected by age. Moreover, both primary and secondary arsenic methylation capacities were negatively related to WAs.

Joint Effect of Urinary Total Arsenic Level and VEGF-A Genetic Polymorphisms on the Recurrence of Renal Cell Carcinoma

The results of our previous study suggested that high urinary total arsenic levels were associated with an increased risk of renal cell carcinoma (RCC). Germline genetic polymorphisms might also affect cancer risk and clinical outcomes. Vascular endothelial growth factor (VEGF) plays an important role in vasculogenesis and angiogenesis, but the combined effect of these factors on RCC remains unclear. In this study, we explored the association between the VEGF-A -2578C>A, -1498T>C, -1154G>A, -634G>C, and +936C>T gene polymorphisms and RCC. We also evaluated the combined effects of the VEGF-A haplotypes and urinary total arsenic levels on the prognosis of RCC. This case-control study was conducted with 191 RCC patients who were diagnosed with renal tumors on the basis of image-guided biopsy or surgical resections. An additional 376 age- and gender-matched controls were recruited. Concentrations of urinary arsenic species were determined by a high performance liquid chromatography-linked hydride generator and atomic absorption spectrometry. Genotyping was investigated using fluorescent-based TaqMan allelic discrimination. We observed no significant associations between VEGF-A haplotypes and RCC risk. However, the VEGF-A ACGG haplotype from VEGF-A -2578, -1498, -1154, and -634 was significantly associated with an increased recurrence of RCC (OR = 3.34, 95% CI = 1.03–10.91). Urinary total arsenic level was significantly associated with the risk of RCC in a dose-response manner, but it was not related to the recurrence of RCC. The combination of high urinary total arsenic level and VEGF-A risk haplotypes affected the OR of RCC recurrence in a dose-response manner. This is the first study to show that joint effect of high urinary total arsenic and VEGF-A risk haplotypes may influence the risk of RCC recurrence in humans who live in an area without obvious arsenic exposure.

Association between levels of urinary heavy metals and increased risk of urothelial carcinoma

OBJECTIVES

To evaluate possible sources of exposure to heavy metals in the general population, and to determine the association between urinary heavy metals and urothelial carcinoma risk.

METHODS

We recruited 205 patients with urothelial carcinoma and 406 control participants for a case-control study between June 2011 and December 2013. The control participants were frequency-matched with cases according to sex and age. We measured the urinary levels of arsenic, cadmium, chromium, nickel and lead by using inductively coupled plasma mass spectrometry. We collected environmental exposure-related information through questionnaires. Multivariate logistic regression and 95% confidence intervals were applied to estimate the urothelial carcinoma risk and potential effects of urothelial carcinoma-related risk factors on the levels of urinary heavy metals.

RESULTS

Patients with urothelial carcinoma showed higher urinary levels of arsenic, cadmium, chromium, nickel and lead than the controls. After considering other potential risk factors, a significantly increased risk for urothelial carcinoma was observed in patients with increased urinary levels of cadmium, chromium, nickel and lead. Smokers showed a high urinary cadmium level. In addition to cadmium, a high urinary lead level was associated with cumulative cigarette smoking and herbal medicine use.

CONCLUSION

Environmental factors might contribute to higher urinary levels of heavy metals and ultimately result in urothelial carcinoma carcinogenesis. These findings can promote proper environmental surveillance of exposure to heavy metals in the general population.

Polymorphisms of human 8-oxoguanine DNA glycosylase 1 and 8-hydroxydeoxyguanosine increase susceptibility to arsenic methylation capacity-related urothelial carcinoma

Arsenic causes oxidative stress in cultured animal and human cells, and it is a well-documented human carcinogen. We conducted a hospital-based case-control study including 167 cases of urothelial carcinoma (UC) and 334 age- and gender-matched healthy controls to evaluate the relationships between urinary arsenic profiles, urinary 8-hydroxydeoxyguanosine (8-OHdG) levels, and human 8-oxoguanine DNA glycosylase (hOGG1) genotypes and UC. The urinary arsenic species were analyzed by high-performance liquid chromatography and hydride generator-atomic absorption spectrometry. Genotyping for hOGG1 (Ser326Cys) and hOGG1 (-15C>G) was performed using the Sequenom MassARRAY platform with iPLEX Gold chemistry. Urinary 8-OHdG was measured with high-sensitivity enzyme-linked immunosorbent assay kits. The results indicated that the hOGG1 326 Cys/Cys genotype and the hOGG1 -15C>G G/G genotype were associated with an increased risk of UC (OR [95 % CI] 1.57 [1.04-2.35] and 1.57 [1.04-2.35], respectively). Participants with high urinary total arsenic, regardless of the haplotype of hOGG1 Ser326Cys and the -15C>G polymorphism, had significantly higher urinary 8-OHdG compared to participants with low urinary total arsenic. This is the first study to investigate the joint effects of high urinary total arsenic or inefficient arsenic methylation capacity indices, and the high-risk G-G haplotype of hOGG1 on the risk of UC. The findings are especially meaningful for participants with risk factors such as high urinary total arsenic, inefficient arsenic methylation indices, high urinary 8-OHdG, and the high-risk G-G haplotype of hOGG1 which are all associated with an increased UC risk.

XRCC1 Polymorphisms and Urinary 8-Hydroxydeoxyguanine Levels Are Associated with Urothelial Carcinoma

The aim of this study was to examine the associations between the combined effects of urinary 8-Hydroxydeoxyguanine (8-OHdG) level and polymorphisms of XRCC1 Arg194Trp and XRCC1 Arg399Gln on the risk of urothelial carcinoma (UC). We conducted a hospital-based case-control study that included 168 cases of UC and 336 age- and gender-matched healthy controls. We used polymerase chain reaction and restriction fragment length polymorphism analyses to examine the genotypes of XRCC1 Arg194Trp and XRCC1 Arg399Gln. We used a competitive in vitro enzyme-linked immunosorbent assay to determine urinary 8-OHdG levels. The XRCC1 399 Gln/Gln genotype and the XRCC1 194 Arg/Arg genotype were positively correlated to UC (OR [95%CI] = 2.27 [1.20-4.27] and 1.59 [1.06-2.36], respectively). Urinary 8-OHdG levels were associated with UC in a dose-dependent manner. Participants with the XRCC1 (Arg399Gln) Gln/Gln genotype or the G-C/A-C haplotype of XRCC1 and a high urinary 8-OHdG level had a significantly higher risk of UC than those with the Arg/Arg + Arg/Gln genotype or the G-T haplotype and a low urinary 8-OHdG level. This is the first study to investigate the combined effect of urinary 8-OHdG level and XRCC1 polymorphisms on UC risk. The findings are especially meaningful for participants with XRCC1 399Gln or XRCC1 Arg194 genotypes and a high urinary 8-OHdG level, since these variables are associated with an increased risk of UC.

A potential synergy between incomplete arsenic methylation capacity and demographic characteristics on the risk of hypertension: findings from a cross-sectional study in an arsenic-endemic area of inner Mongolia, China

Inefficient arsenic methylation capacity has been associated with various health hazards induced by arsenic. In this study, we aimed to explore the interaction effect of lower arsenic methylation capacity with demographic characteristics on hypertension risk. A total of 512 adult participants (126 hypertension subjects and 386 non-hypertension subjects) residing in an arsenic-endemic area in Inner Mongolia, China were included. Urinary levels of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured for all subjects. The percentage of urinary arsenic metabolites (iAs%, MMA%, and DMA%), primary methylation index (PMI) and secondary methylation index (SMI) were calculated to assess arsenic methylation capacity of individuals. Results showed that participants carrying a lower methylation capacity, which is characterized by lower DMA% and SMI, have a higher risk of hypertension compared to their corresponding references after adjusting for multiple confounders. A potential synergy between poor arsenic methylation capacity (higher MMA%, lower DMA% and SMI) and older age or higher BMI were detected. The joint effects of higher MMA% and lower SMI with cigarette smoking also suggest some evidence of synergism. The findings of present study indicated that inefficient arsenic methylation capacity was associated with hypertension and the effect might be enhanced by certain demographic factors.

Arsenic induced overexpression of inflammatory cytokines based on the human urothelial cell model in vitro and urinary secretion of individuals chronically exposed to arsenic

Chronic persistent inflammation could play an important role in the pathogenesis of some malignancies, and inflammation is a critical factor for bladder cancer development. In this study, we measured urine levels of transforming growth factor-α (TGF-α), tumor necrosis factor-α (TNF-α), and IL-8 in arsenic exposure workers and expressions of inflammatory cytokines in human urothelial cells in vivo and in vitro. We found the concentrations of IL-8, TNF-α, and TGF-α presented in urine were significantly elevated in the high urinary arsenic workers compared with the low urinary arsenic workers. Multiple regression analysis showed that the urinary IL-8 level was significantly positively associated with urinary iAs concentration after adjusting for the confounding effects of age, employed years, body mass index (BMI), smoking, alcohol, and seafood consumption in recent 3 days. Urinary TNF-α and TGF-α levels were also significantly positively associated with urinary iAs concentration, and SMI. TGF-α level was negatively associated with age after adjusting for the confounding effects. Consistent with the results in vivo, mRNA expressions of TNF-α, TGF-α, and IL-8 and protein expressions of TGF-α, TGF-β1, and IL-8 were significantly elevated in SV-HUC-1 cells after exposure to lower concentrations of arsenite for 24h as compared to the control group. These data indicated that arsenic increased the secretion of inflammatory factors and IL-8, TNF-α, and TGF-α expression may be a useful biomarker of the effect of arsenic exposure.