Dose-response relationship between peripheral vascular disease and ingested inorganic arsenic among residents in blackfoot disease endemic villages in Taiwan

Arsenic exposure from drinking water and endothelial dysfunction in Bangladeshi adolescents

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, with ∼80% of CVD-related deaths occurring in low- and middle-income countries. Growing evidence suggests that chronic arsenic exposure may contribute to CVD through its effect on endothelial function in adults. However, few studies have examined the influence of arsenic exposure on cardiovascular health in children and adolescents. To examine arsenic's relation to preclinical markers of endothelial dysfunction, we enrolled 200 adolescent children (ages 15-19 years; median 17) of adult participants in the Health Effects of Arsenic Longitudinal Study (HEALS), in Araihazar, Bangladesh. Participants' arsenic exposure was determined by recall of lifetime well usage for drinking water. As part of HEALS, wells were color-coded to indicate arsenic level (<10 μg/L, 10-50 μg/L, >50 μg/L). Endothelial function was measured by recording fingertip arterial pulsatile volume change and reactive hyperemia index (RHI) score, an independent CVD risk factor, was calculated from these measurements. In linear regression models adjusted for participant's sex, age, education, maternal education, land ownership and body weight, individuals who reported always drinking water from wells with >50 μg/L arsenic had a 11.75% lower level of RHI (95% CI: -21.26, -1.09, p = 0.03), as compared to participants who drank exclusively from wells with ≤50 μg/L arsenic. Sex-stratified analyses suggest that these associations were stronger in female participants. As compared to individuals who drank exclusively from wells with ≤50 μg/L arsenic, the use of wells with >50 μg/L arsenic was associated with 14.36% lower RHI (95% CI: -25.69, -1.29, p = 0.03) in females, as compared to 5.35% lower RHI (95% CI: -22.28, 15.37, p = 0.58) in males for the same comparison. Our results suggest that chronic arsenic exposure may be related to endothelial dysfunction in adolescents, especially among females. Further work is needed to confirm these findings and examine whether these changes may increase risk of later adverse cardiovascular health events.

Effects of heavy metals in acute ischemic stroke patients: A cross-sectional study

Cerebrovascular disease is the second commonest cause of mortality globally and among the commonest causes of disability. However, research executed to probe the heavy metal exposure-stroke incidence relationship is scarce. Accordingly, we executed our study to probe the relationship of heavy metal concentrations (ie, concentrations of lead [Pb], mercury [Hg], cadmium [Cd], and arsenic) in the serum and urine of acute ischemic stroke (AIS) patients with several patient variables.For enrollment, we chose patients who had a first AIS within 7 days after the onset of a stroke. Thus, 33 newly diagnosed patients with AIS were recruited. We determined the aforementioned metals' concentrations by executing inductively coupled plasma mass spectrometry. We also gauged the association between such metal concentrations and patient variables by employing Spearman correlation coefficient. To examine the differences in metal concentrations between the different variables, we implemented an independent Mann-Whitney U test.In our cohort analysis, we noted serum Pb and Cd concentrations to be positively correlated with serum creatinine and hemoglobin. Serum and urine Cd concentrations had a negative correlation with impaired HbA1c in AIS patients. Urine Hg had a positive correlation with C-reactive protein in the participants. Participants who smoked or consumed alcohol had significantly higher Pb and Cd levels in serum than did those who neither smoked nor drank. Patients with AIS who smoked or consumed alcohol had high levels of serum Pb and serum Cd than did those who did not. Patients with AIS who consumed alcohol had significantly higher Pb and Hg urine concentrations than did those who did not.Our study indicated that serum Cd and Pb elevation increased the AIS risk in southern Taiwan patients.

Selective removal of arsenic in water: A critical review

Selective removal of arsenic (As) is the key challenge for any of As removal mechanisms as this not only increases the efficiency of removal of the main As species (neutral As(III) and As(V) hydroxyl-anions) but also allows for a significant reduction of waste as it does not co-remove other solutes. Selective removal has a number of benefits: it increases the capacity and lifetime of units while lowering the cost of the process. Therefore, a sustainable selective mitigation method should be considered concerning the economic resources available, the ability of infrastructure to sustain water treatment, and the options for reuse and/or safe disposal of treatment residuals. Several methods of selective As removal have been developed, such as precipitation, adsorption and modified iron and ligand exchange. The biggest challenge in selective removal of As is the presence of phosphate in water which is chemically comparable with As(V). There are two types of mechanisms involved with As removal: Coulombic or ion exchange; and Lewis acid-base interaction. Solution pH is one of the major controlling factors limiting removal efficiency since most of the above-mentioned methods depend on complexation through electrostatic effects. The different features of two different As species make the selective removal process more difficult, especially under natural conditions. Most of the selective As removal methods involve hydrated Fe(III) oxides through Lewis acid-base interaction. Microbiological methods have been studied recently for selective removal of As, and although there have been only a small number of studies, the method shows remarkable results and indicates positive prospects for the future.

Arsenic-induced changes in miRNA expression in cancer and other diseases

miRNAs (miRNA) are essential players regulating gene expression affecting cellular processes contributing to disease development. Dysregulated miRNA expression has been observed in numerous diseases including hepatitis, cardiovascular diseases and cancers. In cardiovascular diseases, several miRNAs function as mediators of pathogenic stress-related signaling pathways that may lead to an excessive extracellular matrix production and collagen deposition causing cardiac stress resulting in fibrosis. In cancers, many miRNAs function as oncogenes or tumor suppressors facilitating tumor growth, invasion and angiogenesis. Furthermore, the association between distinct miRNA profile and tumor development, progression and treatment response has identified miRNAs as potential biomarkers for disease diagnosis and prognosis. Growing evidence demonstrates changes in miRNA expression levels in experimental settings or observational studies associated with environmental chemical exposures such as arsenic. Arsenic is one of the most well-known human carcinogens. Long-term exposure through drinking water increases risk of developing skin, lung and urinary bladder cancers, as well as cardiovascular disease. The mechanism(s) by which arsenic causes disease remains elusive. Proposed mechanisms include miRNA dysregulation. Epidemiological studies identified differential miRNA expression between arsenic-exposed and non-exposed individuals from India, Bangladesh, China and Mexico. In vivo and in vitro studies have shown that miRNAs are critically involved in arsenic-induced malignant transformation. Few studies analyzed miRNAs in other diseases associated with arsenic exposure. Importantly, there is no consensus on a consistent miRNA profile for arsenic-induced cancers because most studies analyze only particular miRNAs. Identifying miRNA expression changes common among humans, rodents and cell lines might guide future miRNA investigations.

Positive Association of Cardiovascular Disease (CVD) with Chronic Exposure to Drinking Water Arsenic (As) at Concentrations below the WHO Provisional Guideline Value: A Systematic Review and Meta-Analysis

To the best of our knowledge, a dose-response meta-analysis of the relationship between cardiovascular disease (CVD) and arsenic (As) exposure at drinking water As concentrations lower than the WHO provisional guideline value (10 µg/L) has not been published yet. We conducted a systematic review and meta-analyses to estimate the pooled association between the relative risk of each CVD endpoint and low-level As concentration in drinking water both linearly and non-linearly using a random effects dose-response model. In this study, a significant positive association was found between the risks of most CVD outcomes and drinking water As concentration for both linear and non-linear models (p-value for trend < 0.05). Using the preferred linear model, we found significant increased risks of coronary heart disease (CHD) mortality and CVD mortality as well as combined fatal and non-fatal CHD, CVD, carotid atherosclerosis disease and hypertension in those exposed to drinking water with an As concentration of 10 µg/L compared to the referent (drinking water As concentration of 1 µg/L) population. Notwithstanding limitations included, the observed significant increased risks of CVD endpoints arising from As concentrations in drinking water between 1 µg/L and the 10 µg/L suggests further lowering of this guideline value should be considered.

Circulating miRNAs Associated with Arsenic Exposure

Arsenic (As) is a toxic metalloid. Inorganic arsenic (iAs) is a form of As commonly found in drinking water and in some foods. Overwhelming evidence suggests that people chronically exposed to iAs are at risk of developing cancer or cardiovascular, neurological, and metabolic diseases. Although the mechanisms underlying iAs-associated illness remain poorly characterized, a growing body of literature raises the possibility that microRNAs (miRNAs), post-transcriptional gene suppressors, may serve as mediators and/or early indicators of the pathologies associated with iAs exposure. To characterize the circulating miRNA profiles of individuals chronically exposed to iAs, samples of plasma were collected from 109 healthy residents of the city of Zimapán and the Lagunera area in Mexico, the regions with historically high exposures to iAs in drinking water. These plasma samples were analyzed for small RNAs using high-throughput sequencing and for iAs and its methylated metabolites. Associations between plasma levels of arsenic species and miRNAs were evaluated. Six circulating miRNAs (miRs-423-5p, -142-5p -2, -423-5p +1, -320c-1, -320c-2, and -454-5p), two of which have been previously linked to cardiovascular disease and diabetes (miRs-423-5p, -454-5p), were found to be significantly correlated with plasma MAs. No miRNAs were associated with plasma iAs or DMAs after correction for multiple testing. These miRNAs may represent mechanistic links between iAs exposure and disease or serve as markers of disease risks associated with this exposure.

Blood pressure in indoor and outdoor workers

INTRODUCTION

The aim of our study is to evaluate the changes in systolic and diastolic blood pressure in two occupational categories: outdoor workers (traffic policemen and environment technicians) and indoor workers.

MATERIALS AND METHODS

The study was conducted comparing the results obtained from three samples of male workers: 175 outdoor traffic policemen, 175 outdoor environment technicians and 175 indoor workers. The outdoor and indoor groups were made comparable by age, length of service, body mass index, alcohol consumption, smoking status.

RESULTS

The mean values of systolic and diastolic blood pressure were found higher in traffic policemen and technicians than in indoor workers, as well as higher values of systolic blood pressure in traffic policemen than in technicians.

CONCLUSIONS

The results suggest that outdoor working affects the blood pressure, contributing to an increased cardiovascular risk.

Removal of Arsenic (V) from Aqueous Solutions Using Chitosan-Red Scoria and Chitosan-Pumice Blends

In different regions across the globe, elevated arsenic contents in the groundwater constitute a major health problem. In this work, a biopolymer chitosan has been blended with volcanic rocks (red scoria and pumice) for arsenic (V) removal. The effect of three blending ratios of chitosan and volcanic rocks (1:2, 1:5 and 1:10) on arsenic removal has been studied. The optimal blending ratio was 1:5 (chitosan: volcanic rocks) with maximum adsorption capacity of 0.72 mg/g and 0.71 mg/g for chitosan: red scoria (Ch–Rs) and chitosan: pumice (Ch–Pu), respectively. The experimental adsorption data fitted well a Langmuir isotherm (R² > 0.99) and followed pseudo-second-order kinetics. The high stability of the materials and their high arsenic (V) removal efficiency (~93%) in a wide pH range (4 to 10) are useful for real field applications. Moreover, the blends could be regenerated using 0.05 M NaOH and used for several cycles without losing their original arsenic removal efficiency. The results of the study demonstrate that chitosan-volcanic rock blends should be further explored as a potential sustainable solution for removal of arsenic (V) from water.

Arsenic Exposure and Type 2 Diabetes: MicroRNAs as Mechanistic Links?

PURPOSE OF REVIEW

The goal of this review is to delineate the following: (1) the primary means of inorganic arsenic (iAs) exposure for human populations, (2) the adverse public health outcomes associated with chronic iAs exposure, (3) the pathophysiological connection between arsenic and type 2 diabetes (T2D), and (4) the incipient evidence for microRNAs as candidate mechanistic links between iAs exposure and T2D.

RECENT FINDINGS

Exposure to iAs in animal models has been associated with the dysfunction of several different cell types and tissues, including liver and pancreatic islets. Many microRNAs that have been identified as responsive to iAs exposure under in vitro and/or in vivo conditions have also been shown in independent studies to regulate processes that underlie T2D etiology, such as glucose-stimulated insulin secretion from pancreatic beta cells. Defects in insulin secretion could be, in part, associated with aberrant microRNA expression and activity. Additional in vivo studies need to be performed with standardized concentrations and durations of arsenic exposure in order to evaluate rigorously microRNAs as molecular drivers of iAs-associated diabetes.

Effects of Arsenic in Drinking Water on Risk of Hepatitis or Cirrhosis in Persons With and Without Chronic Viral Hepatitis

BACKGROUND & AIMS

Arsenic in drinking water is associated with hepatomegaly and death from liver cancer. However, confounding factors related to liver diseases have not been carefully studied. We examined associations between exposure of arsenic in drinking water and risk of hepatitis and cirrhosis, and the interaction with chronic viral hepatitis, in people living in the Lanyang Basin of northeastern Taiwan, where well water has an arsenic content that ranges from undetectable to 3590 μg/L.

METHODS

We tested blood samples from 4387 people who lived in arseniasis-endemic areas in northeastern Taiwan from 1991 through 1994 for hepatitis B virus DNA, hepatitis B surface antigen (HBsAg), and antibodies against hepatitis C virus (anti-HCV). We measured arsenic concentrations in well water and collected information on residents' histories of major chronic diseases. Reports of chronic hepatitis or cirrhosis were ascertained using the Taiwan National Health Insurance database. Reports of liver cancer were ascertained using the Taiwan National Cancer Registry.

RESULTS

Prevalence odds ratios in the overall study population for chronic hepatitis or cirrhosis for well water arsenic concentrations of ≤10 μg/L were 1.00 (reference), 0.93 for 10.1-49.9 μg/L (95% confidence interval [CI], 0.57-1.52), 1.24 for 50.0-99.9 μg/L (95% CI, 0.68-2.23), 0.98 for 100.0-299.9 (95% CI, 0.52-1.85), and 1.86 for ≥300.0 μg/L (95% CI, 1.08-3.20). Increasing levels of arsenic in drinking water were associated with increasing prevalence of chronic hepatitis or cirrhosis in residents who were seronegative for HBsAg and seronegative for anti-HCV, but not for seropositive for either HBsAg or anti-HCV. In individuals who were seropositive for HBsAg or anti-HCV, we observed an inverse association between hepatitis or cirrhosis and consumption of water with levels of arsenic ≥100.0 μg/L. Among participants who were seropositive for HBsAg or anti-HCV, consumption of water with levels of arsenic ≥100.0 μg/L was associated with a reduced risk of liver cancer (multivariate-adjusted hazard ratio, 0.29; 95% CI, 0.09-0.95; P < .05). A higher proportion of individuals exposed to cumulative arsenic level >14,000 μg/L ×year were carriers of inactive hepatitis B virus (DNA <10,000 copies/mL) and were positive for HBsAg (60%) than individuals exposed to water below this arsenic level (35%).

CONCLUSIONS

Concentrations of arsenic concentration in drinking water ≥300.0 μg/L significantly increase risk of hepatitis or cirrhosis in people without chronic viral hepatitis. However, in people with chronic viral hepatitis, levels of arsenic ≥100.0 μg/L in drinking water significantly reduce the risk of chronic hepatitis or cirrhosis.

Requirements for a Biologically Realistic Cancer Risk Assessment for Inorganic Arsenic

A remarkable feature of the carcinogenicity of inorganic arsenic (As,) is the observation that human exposures to Asi have been strongly associated with increases in skin, lung, and internal cancers, but As, does not typically cause tumors in standard laboratory animal test protocols. Considerable controversy has centered on whether there is epidemiological evidence of a “threshold” for the carcinogenic effects of Asi, or at least of a highly nonlinear dose–response. Saturation of metabolism in the dose-range associated with tumors does not appear to be adequate to produce a major impact on the dose-response for carcinogenicity. If there is a strong nonlinearity, it results from the nature of the carcinogenic mechanism(s) of Asi. However, no single hypothesis for the mechanism of Asi carcinogenicity has widespread support. A biologically realistic cancer risk assessment for Asi would requirea quantitative description of the dose of active arsenic species in target tissues, the interactions between active arsenic and tissue constituents, and the manner in which these interactions result in tumor formation in multiple organs in humans, but not in experimental animals. Although Asi has only infrequently been associated with tumors in animal studies, it has repeatedly been shown to act as a comutagen in vitro and as a cocarcinogen in vivo. Asi is clastogenic, producing chromatid aberrations, but does not produce point mutations at single gene loci. Of particular interest, Asi has been shown to inhibit repair of DNA single-strand breaks, a possible mechanism for its observed comutagenicity and cocarcinogenicity. We propose a cocarcinogenic mode of action in which Asi acts primarily on intermediate cells deficient in cell cycle control at a late stage in a preexisting carcinogenic process. This interaction enhances ge-nomic fragility and accelerates conversion of premalignant lesions to more aggressive, clinically observable tumors. An indirect effect of As, on DNA repair is consistent with the expectation of a nonlinear dose-response rather than the linear dose-response traditionally assumed for mutagenic carcinogens. However, defining the exact nature of this tumor dose-response will require further experimental data on the dose-response for the cellular effects of Asi. Because Asi carcinogenicity is unlikely to be observed in normal experimental animals not exposed to other carcinogens, studies in animals and cell lines deficient in cell cycle control should also be considered. Experimental studies specifically designed to address the key mechanistic and dose-response issues for Asi carcinogenicity are critically needed to support public health policy decisions regarding current environmental exposures to Asi.

Arsenic speciation in rice and risk assessment of inorganic arsenic in Taiwan population

This study assessed the total arsenic content and arsenic speciation in rice to determine the health risks associated with rice consumption in various age-gender subgroups in Taiwan. The average total arsenic levels in white rice and brown rice were 116.6 ± 39.2 and 215.5 ± 63.5 ng/g weight (n = 51 and 13), respectively. The cumulative cancer risk among males was 10.4/100,000. The highest fraction of inorganic/total arsenic content in white rice ranged from 76.9 to 88.2 % and from 81.0 to 96.5 % in brown rice. The current study found different arsenic speciation of rice in southern Taiwan, where the famous blackfoot disease has been reported compared with arsenic speciation from other Taiwan areas. Therefore, rice and other grains should be further monitored in southern Taiwan to evaluate whether arsenic contamination is well controlled in this area.

Arsenic and human health effects: A review

Arsenic (As) is ubiquitous in nature and humans being exposed to arsenic via atmospheric air, ground water and food sources are certain. Major sources of arsenic contamination could be either through geological or via anthropogenic activities. In physiological individuals, organ system is described as group of organs that transact collectively and associate with other systems for conventional body functions. Arsenic has been associated with persuading a variety of complications in body organ systems: integumentary, nervous, respiratory, cardiovascular, hematopoietic, immune, endocrine, hepatic, renal, reproductive system and development. In this review, we outline the effects of arsenic on the human body with a main focus on assorted organ systems with respective disease conditions. Additionally, underlying mechanisms of disease development in each organ system due to arsenic have also been explored. Strikingly, arsenic has been able to induce epigenetic changes (in utero) and genetic mutations (a leading cause of cancer) in the body. Occurrence of various arsenic induced health effects involving emerging areas such as epigenetics and cancer along with their respective mechanisms are also briefly discussed.

Association between Arsenic Exposure from Drinking Water and Longitudinal Change in Blood Pressure among HEALS Cohort Participants

BACKGROUND

Cross-sectional studies have shown associations between arsenic exposure and prevalence of high blood pressure; however, studies examining the relationship of arsenic exposure with longitudinal changes in blood pressure are lacking.

METHOD

We evaluated associations of arsenic exposure in relation to longitudinal change in blood pressure in 10,853 participants in the Health Effects of Arsenic Longitudinal Study (HEALS). Arsenic was measured in well water and in urine samples at baseline and in urine samples every 2 years after baseline. Mixed-effect models were used to estimate the association of baseline well and urinary creatinine-adjusted arsenic with annual change in blood pressure during follow-up (median, 6.7 years).

RESULT

In the HEALS population, the median water arsenic concentration at baseline was 62 μg/L. Individuals in the highest quartile of baseline water arsenic or urinary creatinine-adjusted arsenic had a greater annual increase in systolic blood pressure compared with those in the reference group (β = 0.48 mmHg/year; 95% CI: 0.35, 0.61, and β = 0.43 mmHg/year; 95% CI: 0.29, 0.56 for water arsenic and urinary creatinine-adjusted arsenic, respectively) in fully adjusted models. Likewise, individuals in the highest quartile of baseline arsenic exposure had a greater annual increase in diastolic blood pressure for water arsenic and urinary creatinine-adjusted arsenic, (β = 0.39 mmHg/year; 95% CI: 0.30, 0.49, and β = 0.45 mmHg/year; 95% CI: 0.36, 0.55, respectively) compared with those in the lowest quartile.

CONCLUSION

Our findings suggest that long-term arsenic exposure may accelerate age-related increases in blood pressure. These findings may help explain associations between arsenic exposure and cardiovascular disease.

Association between arsenic exposure and thyroid function: data from NHANES 2007-2010

The association of arsenic variables in urine, total arsenic (UAS), arsenobetaine (UAB), dimethylarsinic acid (UDMA), and arsenic adjusted for arsenobetaine (UAAS) with thyroid-stimulating hormone (TSH), free and total serum thyroxine (FT4, TT4), free and total triiodothyronine (FT3, TT3), and thyroglobulin (TGN) was evaluated by analyzing data from 2007-2010 National Health and Nutrition Examination Survey. For iodine deficient males, there was a positive association between TSH and UDMA (p < 0.01) and a negative association between the levels of TT4 and UDMA (p < 0.01). Levels of UAAS were inversely associated with the levels of TT4 for both iodine-deficient (p = 0.054) and iodine-replete females (p < 0.01). For iodine-replete females, levels of both TSH and TGN increased with decrease in the levels of both UAB (p < 0.01) and UAS (p < 0.01). There was also a negative association between TSH and UAB as well as UAS (p < 0.01). For iodine-replete males, increased levels of UDMA were associated with decreasing levels of FT4 (p = 0.03).

Cardiovascular disease and arsenic exposure in Inner Mongolia, China: a case control study

BACKGROUND

Millions of people are at risk from the adverse effects of arsenic exposure through drinking water. Increasingly, non-cancer effects such as cardiovascular disease have been associated with drinking water arsenic exposures. However, most studies have been conducted in highly exposed populations and lacked individual measurements.

OBJECTIVE

To evaluate the association between cardiovascular disease and well-water arsenic exposure.

METHODS

We conducted a hospital based case control study in Inner Mongolia, China. Cases and controls were prospectively identified and enrolled from a large hospital in the Hangjin Hou area. Cases were patients diagnosed with cardiovascular disease and controls were patients free from cardiovascular disease, admitted for conditions unrelated to arsenic exposure. Water from the primary water source and toenail samples were collected from each subject and tested for inorganic arsenic.

RESULTS

Arsenic exposures were moderate with mean and median arsenic exposures of 8.9 μg/L and 13.1 μg/L, respectively. A total of 298 cases and 275 controls were enrolled. The adjusted odds ratio (AOR) and corresponding 95% confidence interval (95% CI) for a 10 μg/L increase in water arsenic were 1.19 (95% CI: 1.03, 1.38). Compared to exposures less than 10 μg/L, the AOR for water arsenic exposures above 40 μg/L was 4.05 (95% CI: 1.1-14.99, p = 0.04). Nail arsenic above 1.38 μg/g was also associated with an increased risk of cardiovascular disease.

CONCLUSIONS

By using standardized case definitions and collecting individual measurements of arsenic, this study addressed several limitations of previous studies. The results provide further evidence of the association between cardiovascular disease and arsenic at moderate exposures.

Association of hypothyroidism with low-level arsenic exposure in rural West Texas

It has been reported recently that a higher airborne arsenic level was correlated with higher urinary arsenic concentration and lower serum thyroxin level among urban policemen and rural highway workmen in Italy. The current study was to determine whether exposure to low-level arsenic groundwater (2-22µg/L) is associated with hypothyroidism among 723 participants (118 male and 267 female Hispanics; 108 male and 230 female non-Hispanic whites, NHW) living in rural West Texas counties. Arsenic and iodine levels in their groundwater used for drinking and or cooking were estimated by the inverse distance weighted (IDW) interpolation technique. Groundwater arsenic was ≥8µg/L in 36% of the subjects' wells while iodine concentration was <1µg/L in 91% of their wells. Logistic regression analysis showed that arsenic in groundwater ≥8µg/L and cumulative arsenic exposure (groundwater arsenic concentration multiplied by the number of years living in the current address) but not groundwater iodine concentration were significant predictors for hypothyroidism among Hispanics (p<0.05) but not NHW after adjusting for covariates such as age, gender, annual household income and health insurance coverage. The ethnic difference may be due to a marginally higher percentage of Hispanics (p=0.0622) who lived in areas with groundwater arsenic ≥8µg/L compared with NHW. The prevalence of hypothyroidism was significantly higher in Hispanics or NHW of this rural cohort than the national prevalence. Measures should be taken to reduce arsenic in drinking water in order to prevent hypothyroidism in rural areas.

Associations of total arsenic in drinking water, hair and nails with serum vascular endothelial growth factor in arsenic-endemic individuals in Bangladesh

Arsenic exposure is associated with cancer and vascular diseases. Angiogenesis is an important step for the pathological development of cancer and vascular diseases. Vascular endothelial growth factor (VEGF) is a specific marker for angiogenesis. However, human study showing the association between arsenic exposure and serum VEGF levels has not yet been documented. This study was aimed to investigate the association between arsenic exposure and serum VEGF levels in the arsenic-endemic individuals in Bangladesh. A total of 260 individuals were recruited for this study. Arsenic exposure levels were measured by ICP-MS and VEGF levels were quantified using VEGF immunoassay kit. The study subjects were stratified into tertile (low, medium and high) groups based on the arsenic in water, hair and nails. Serum VEGF levels were correlated with water (rs = 0.363, p < 0.001), hair (rs = 0.205, p < 0.01) and nail (rs = 0.190, p < 0.01) arsenic. Further, VEGF levels showed dose-response relationships with water, hair and nail arsenic. Mean VEGF levels in ⩽ 10 μg L(-1), 10.1-50 μg L(-1) and > 50 μg L(-1) groups were 91.84, 129.54, and 169.86 pg mL(-1), respectively, however, significant (p < 0.01) difference in VEGF levels was only found in > 50 μg L(-1) versus ⩽ 10 μg L(-1) groups. Significant associations of arsenic exposure with VEGF levels were found even after adjusting with relevant covariates. Therefore, these results provide evidence that arsenic exposure has a pro-angiogenic effect on humans, which may be implicated in arsenic-induced tumorigenesis and vascular diseases.

Metal pollutants and cardiovascular disease: mechanisms and consequences of exposure

INTRODUCTION

There is epidemiological evidence that metal contaminants may play a role in the development of atherosclerosis and its complications. Moreover, a recent clinical trial of a metal chelator had a surprisingly positive result in reducing cardiovascular events in a secondary prevention population, strengthening the link between metal exposure and cardiovascular disease (CVD). This is, therefore, an opportune moment to review evidence that exposure to metal pollutants, such as arsenic, lead, cadmium, and mercury, is a significant risk factor for CVD.

METHODS

We reviewed the English-speaking medical literature to assess and present the epidemiological evidence that 4 metals having no role in the human body (xenobiotic), mercury, lead, cadmium, and arsenic, have epidemiologic and mechanistic links to atherosclerosis and CVD. Moreover, we briefly review how the results of the Trial to Assess Chelation Therapy (TACT) strengthen the link between atherosclerosis and xenobiotic metal contamination in humans.

CONCLUSIONS

There is strong evidence that xenobiotic metal contamination is linked to atherosclerotic disease and is a modifiable risk factor.

Embryonic exposure to sodium arsenite perturbs vascular development in zebrafish

Exposure to arsenic in its inorganic form, arsenite, causes adverse effects to many different organs and tissues. Here, we have investigated arsenite-induced adverse effects on vascular tissues in the model organism zebrafish, Danio rerio. Zebrafish embryos were exposed to arsenite at different exposure windows and the susceptibility to vascular tissue damage was recorded at 72hours post fertilization (hpf). Intersegmental vessel sprouting and growth was most perturbed by exposure to arsenite during the 24-48hpf window, while disruption in the condensation of the caudal vein plexus was more often observed at the 48-72hpf exposure window, reflecting when these structures develop during normal embryogenesis. The vascular growth rate was decreased by arsenite exposure, and deviated from that of control embryos at around 24-26.5hpf. We further mapped changes in expression of key regulators of angiogenesis and vasculogenesis. Downregulation of vascular endothelial growth factor receptor 1/fms-related tyrosine kinase 1 (vegfr1/flt1) expression was evident already at 24hpf, coinciding with the decreased vascular growth rate. At later time points, matrix metalloproteinase 9 (mmp9) expression was upregulated, suggesting that arsenite affects the composition of the extracellular matrix. In total, the expression of eight key factors involved in different aspects of vascularization was significantly altered by arsenic exposure. In conclusion, our results show that arsenite is a potent vascular disruptor in the developing zebrafish embryo, a finding that calls for an evaluation of arsenite as a developmental vascular toxicant in mammalian model systems.

Molecular features in arsenic-induced lung tumors

Arsenic is a well-known human carcinogen, which potentially affects ~160 million people worldwide via exposure to unsafe levels in drinking water. Lungs are one of the main target organs for arsenic-related carcinogenesis. These tumors exhibit particular features, such as squamous cell-type specificity and high incidence among never smokers. Arsenic-induced malignant transformation is mainly related to the biotransformation process intended for the metabolic clearing of the carcinogen, which results in specific genetic and epigenetic alterations that ultimately affect key pathways in lung carcinogenesis. Based on this, lung tumors induced by arsenic exposure could be considered an additional subtype of lung cancer, especially in the case of never-smokers, where arsenic is a known etiological agent. In this article, we review the current knowledge on the various mechanisms of arsenic carcinogenicity and the specific roles of this metalloid in signaling pathways leading to lung cancer.

Arsenic exposure and cardiovascular disease: an updated systematic review

In epidemiologic studies, high-chronic arsenic exposure has been associated with cardiovascular disease, despite methodological limitations. At low-moderate arsenic levels, the evidence was inconclusive. Here, we update a previous systematic review (Am J Epidemiol 2005;162:1037-49) examining the association between arsenic exposure and cardiovascular disease. Eighteen studies published since 2005 were combined with 13 studies from the previous review. We calculated pooled relative risks by comparing the highest versus the lowest exposure category across studies. For high exposure (arsenic in drinking water > 50 μg/L), the pooled relative risks (95 % confidence interval) for cardiovascular disease, coronary heart disease, stroke, and peripheral arterial disease were 1.32 (95 % CI:1.05-1.67), 1.89 (95 % CI:1.33-2.69), 1.08 (95 % CI:0.98-1.19), and 2.17 (95 % CI:1.47-3.20), respectively. At low-moderate arsenic levels, the evidence was inconclusive. Our review strengthens the evidence for a causal association between high-chronic arsenic exposure and clinical cardiovascular endpoints. Additional high quality studies are needed at low-moderate arsenic levels.

Association between arsenic exposure from drinking water and plasma levels of cardiovascular markers

The authors conducted a cross-sectional study to assess the relation between arsenic exposure from drinking water and plasma levels of markers of systemic inflammation and endothelial dysfunction (matrix metalloproteinase-9, myeloperoxidase, plasminogen activator inhibitor-1, soluble E-selectin, soluble intercellular adhesion molecule-1 (ICAM-1), and soluble vascular adhesion molecule-1 (VCAM-1)) using baseline data from 668 participants (age, >30 years) in the Health Effects of Arsenic Longitudinal Study in Bangladesh (2007-2008). Both well water arsenic and urinary arsenic were positively associated with plasma levels of soluble VCAM-1. For every 1-unit increase in log-transformed well water arsenic (ln μg/L) and urinary arsenic (ln μg/g creatinine), plasma soluble VCAM-1 was 1.02 (95% confidence interval: 1.01, 1.03) and 1.04 (95% confidence interval: 1.01, 1.07) times greater, respectively. There was a significant interaction between arsenic exposure and higher body mass index, such that the increased levels of plasminogen activator inhibitor-1 and soluble VCAM-1 associated with arsenic exposure were stronger among people with higher body mass index. The findings indicate an effect of chronic arsenic exposure from drinking water on vascular inflammation and endothelial dysfunction that could be modified by body mass index and also suggest a potential mechanism underlying the association between arsenic exposure and cardiovascular disease.

Increased serum level of epidermal growth factor receptor in liver cancer patients and its association with exposure to arsenic

Arsenic is a human carcinogen and can activate epidermal growth factor receptor (EGFR) in human cell lines. As EGFR is associated with the occurrence of cancers, we conducted a study to evaluate whether serum EGFR may increase in liver cancer patients, particularly in those with exposure to arsenic. We recruited 100 patients of liver cancer and 100 age- and sex-matched controls in Taiwan and determined EGFR levels in sera by enzyme-linked immunosorbent assay. The patients had higher EGFR levels (668.1 vs. 243.1 fmol/mL, p<0.01), and after adjusting for hepatitis B and C, they still had an average EGFR level 406.1 fmol/mL higher than that of the controls (p<0.01). When we compared 22 patients residing in an endemic area of arsenic intoxication to 22 age- and sex-matched patients residing outside the area, we found that patients from the endemic area had higher EGFR levels (882.8 vs. 511.6 fmol/mL, p = 0.04). We concluded that EGFR is over-expressed in patients of liver cancer, particularly in those with exposure to arsenic, and therefore, serum EGFR level is not only a potential biomarker of liver cancer, but also a potential biomarker of cancers associated with arsenic exposure.

Use of chitosan and chitosan-derivatives to remove arsenic from aqueous solutions--a mini review

Arsenic removal has become a relevant concern due to the final confirmation of its behaviour as chronic human carcinogen, corresponding to an ever-increasing contamination of water, soil and crops in many parts of the world. Developing easily accessible removal strategies is therefore a primary environmental matter. Chitosan and chitosan derivatives show good adsorption performances against arsenic removal and are considered low cost products, easily obtainable. This review provides a summary of recent advances of the application of these compounds in the area of sorption sciences for arsenate and arsenite removal from water, focusing on equilibrium and kinetic mechanisms.

Arsenic promotes ubiquitinylation and lysosomal degradation of cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels in human airway epithelial cells

Arsenic exposure significantly increases respiratory bacterial infections and reduces the ability of the innate immune system to eliminate bacterial infections. Recently, we observed in the gill of killifish, an environmental model organism, that arsenic exposure induced the ubiquitinylation and degradation of cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel that is essential for the mucociliary clearance of respiratory pathogens in humans. Accordingly, in this study, we tested the hypothesis that low dose arsenic exposure reduces the abundance and function of CFTR in human airway epithelial cells. Arsenic induced a time- and dose-dependent increase in multiubiquitinylated CFTR, which led to its lysosomal degradation, and a decrease in CFTR-mediated chloride secretion. Although arsenic had no effect on the abundance or activity of USP10, a deubiquitinylating enzyme, siRNA-mediated knockdown of c-Cbl, an E3 ubiquitin ligase, abolished the arsenic-stimulated degradation of CFTR. Arsenic enhanced the degradation of CFTR by increasing phosphorylated c-Cbl, which increased its interaction with CFTR, and subsequent ubiquitinylation of CFTR. Because epidemiological studies have shown that arsenic increases the incidence of respiratory infections, this study suggests that one potential mechanism of this effect involves arsenic-induced ubiquitinylation and degradation of CFTR, which decreases chloride secretion and airway surface liquid volume, effects that would be proposed to reduce mucociliary clearance of respiratory pathogens.

Global gene expression changes in human urothelial cells exposed to low-level monomethylarsonous acid

Bladder cancer has been associated with chronic arsenic exposure. Monomethylarsonous acid [MMA(III)] is a metabolite of inorganic arsenic and has been shown to transform an immortalized urothelial cell line (UROtsa) at concentrations 20-fold less than arsenite. MMA(III) was used as a model arsenical to examine the mechanisms of arsenical-induced transformation of urothelium. A microarray analysis was performed to assess the transcriptional changes in UROtsa during the critical window of chronic 50nM MMA(III) exposure that leads to transformation at 3 months of exposure. The analysis revealed only minor changes in gene expression at 1 and 2 months of exposure, contrasting with substantial changes observed at 3 months of exposure. The gene expression changes at 3 months were analyzed showing distinct alterations in biological processes and pathways such as a response to oxidative stress, enhanced cell proliferation, anti-apoptosis, MAPK signaling, as well as inflammation. Twelve genes selected as markers of these particular biological processes were used to validate the microarray and these genes showed a time-dependent changes at 1 and 2 months of exposure, with the most substantial changes occurring at 3 months of exposure. These results indicate that there is a strong association between the acquired phenotypic changes that occur with chronic MMA(III) exposure and the observed gene expression patterns that are indicative of a malignant transformation. Although the substantial changes that occur at 3 months of exposure may be a consequence of transformation, there are common occurrences of altered biological processes between the first 2 months of exposure and the third, which may be pivotal in driving transformation.

Arsenic exposure and toxicology: a historical perspective

The metalloid arsenic is a natural environmental contaminant to which humans are routinely exposed in food, water, air, and soil. Arsenic has a long history of use as a homicidal agent, but in the past 100 years arsenic, has been used as a pesticide, a chemotherapeutic agent and a constituent of consumer products. In some areas of the world, high levels of arsenic are naturally present in drinking water and are a toxicological concern. There are several structural forms and oxidation states of arsenic because it forms alloys with metals and covalent bonds with hydrogen, oxygen, carbon, and other elements. Environmentally relevant forms of arsenic are inorganic and organic existing in the trivalent or pentavalent state. Metabolism of arsenic, catalyzed by arsenic (+3 oxidation state) methyltransferase, is a sequential process of reduction from pentavalency to trivalency followed by oxidative methylation back to pentavalency. Trivalent arsenic is generally more toxicologically potent than pentavalent arsenic. Acute effects of arsenic range from gastrointestinal distress to death. Depending on the dose, chronic arsenic exposure may affect several major organ systems. A major concern of ingested arsenic is cancer, primarily of skin, bladder, and lung. The mode of action of arsenic for its disease endpoints is currently under study. Two key areas are the interaction of trivalent arsenicals with sulfur in proteins and the ability of arsenic to generate oxidative stress. With advances in technology and the recent development of animal models for arsenic carcinogenicity, understanding of the toxicology of arsenic will continue to improve.

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 (>50μg/l) and the haplotypes of PNP (p=0.0115). A marked elevated risk of carotid atherosclerosis was observed in subjects with arsenic exposure of >50μg/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 (>50μg/l).

Genetic polymorphisms in glutathione S-transferase (GST) superfamily and risk of arsenic-induced urothelial carcinoma in residents of southwestern Taiwan

Background

Arsenic exposure is an important public health issue worldwide. Dose-response relationship between arsenic exposure and risk of urothelial carcinoma (UC) is consistently observed. Inorganic arsenic is methylated to form the metabolites monomethylarsonic acid and dimethylarsinic acid while ingested. Variations in capacity of xenobiotic detoxification and arsenic methylation might explain individual variation in susceptibility to arsenic-induced cancers.

Methods

To estimate individual susceptibility to arsenic-induced UC, 764 DNA specimens from our long-term follow-up cohort in Southwestern Taiwan were used and the genetic polymorphisms in GSTM1, GSTT1, GSTP1 and arsenic methylation enzymes including GSTO1 and GSTO2 were genotyped.

Results

The GSTT1 null was marginally associated with increased urothelial carcinoma (UC) risk (HR, 1.91, 95% CI, 1.00-3.65), while the association was not observed for other GSTs. Among the subjects with cumulative arsenic exposure (CAE) ≥ 20 mg/L*year, the GSTT1 null genotype conferred a significantly increased cancer risk (RR, 3.25, 95% CI, 1.20-8.80). The gene-environment interaction between the GSTT1 and high arsenic exposure with respect to cancer risk was statistically significant (multiplicative model, p = 0.0151) and etiologic fraction was as high as 0.86 (95% CI, 0.51-1.22). The genetic effects of GSTO1/GSTO2 were largely confined to high arsenic level (CAE ≥ 20). Diplotype analysis showed that among subjects exposed to high levels of arsenic, the AGG/AGG variant of GSTO1 Ala140Asp, GSTO2 5'UTR (-183)A/G, and GSTO2 Asn142Asp was associated with an increased cancer risk (HRs, 4.91, 95% CI, 1.02-23.74) when compared to the all-wildtype reference, respectively.

Conclusions

The GSTs do not play a critical role in arsenic-induced urothelial carcinogenesis. The genetic effects of GSTT1 and GSTO1 on arsenic-induced urothelial carcinogenesis are largely confined to very high exposure level.

Arsenic exposure from drinking water and mortality from cardiovascular disease in Bangladesh: prospective cohort study

OBJECTIVE

To evaluate the association between arsenic exposure and mortality from cardiovascular disease and to assess whether cigarette smoking influences the association.

DESIGN

Prospective cohort study with arsenic exposure measured in drinking water from wells and urine.

SETTING

General population in Araihazar, Bangladesh.

PARTICIPANTS

11,746 men and women who provided urine samples in 2000 and were followed up for an average of 6.6 years.

MAIN OUTCOME MEASURE

Death from cardiovascular disease.

RESULTS

198 people died from diseases of circulatory system, accounting for 43% of total mortality in the population. The mortality rate for cardiovascular disease was 214.3 per 100,000 person years in people drinking water containing <12.0 µg/L arsenic, compared with 271.1 per 100,000 person years in people drinking water with ≥ 12.0 µg/L arsenic. There was a dose-response relation between exposure to arsenic in well water assessed at baseline and mortality from ischaemic heart disease and other heart disease; the hazard ratios in increasing quarters of arsenic concentration in well water (0.1-12.0, 12.1-62.0, 62.1-148.0, and 148.1-864.0 µg/L) were 1.00 (reference), 1.22 (0.65 to 2.32), 1.35 (0.71 to 2.57), and 1.92 (1.07 to 3.43) (P = 0.0019 for trend), respectively, after adjustment for potential confounders including age, sex, smoking status, educational attainment, body mass index (BMI), and changes in urinary arsenic concentration since baseline. Similar associations were observed when baseline total urinary arsenic was used as the exposure variable and for mortality from ischaemic heart disease specifically. The data indicate a significant synergistic interaction between arsenic exposure and cigarette smoking in mortality from ischaemic heart disease and other heart disease. In particular, the hazard ratio for the joint effect of a moderate level of arsenic exposure (middle third of well arsenic concentration 25.3-114.0 µg/L, mean 63.5 µg/L) and cigarette smoking on mortality from heart disease was greater than the sum of the hazard ratios associated with their individual effect (relative excess risk for interaction 1.56, 0.05 to 3.14; P = 0.010).

CONCLUSIONS

Exposure to arsenic in drinking water is adversely associated with mortality from heart disease, especially among smokers.

Arsenic induces apoptosis of human umbilical vein endothelial cells through mitochondrial pathways

To clarify the molecular mechanisms through which arsenic causes injuries to blood vessels, we analyzed the effects of sodium arsenite (NaAsO(2)) on the apoptosis of human umbilical vein endothelial cells (HUVECs), mitochondrial membrane potential (Delta Psi m), intracellular reactive oxygen species (ROS), and the expression of the related genes. HUVECs apoptosis increased and Delta Psi m decreased in a dose-dependent manner following arsenic treatment. Intracellular ROS showed 2 phase alterations: a slight decrease with low levels of arsenic (5 and 10 microM) treatment; but a sharp increase at higher concentrations (>or=20 microM). The arsenic-induced cell apoptosis and intracellular ROS were blocked by the addition of the antioxidant N-acetyl-L-cysteine (NAC). The mRNAs of superoxide dismutase 2 (SOD2) and NAD(P)H:quinone oxidoreductase 1 (NQO1) increased strikingly when cells were treated with a low concentration of NaAsO(2) (5 microM) and the level of induction was decreased with higher concentrations of arsenic treatment. Based on the results, we suggest that the decrease of Delta Psi m caused by arsenic and the resulting cell apoptosis may contribute to the injuries of blood vessel in arsenism. The decrease in intracellular ROS and the increase in SOD2 and NQO1 expressions observed when HUVECs were treated with low concentration of NaAsO(2), suggest the role of the two enzymes in protecting HUVECs from injuries of arsenic exposure.

Potential molecular mechanisms for combined toxicity of arsenic and alcohol

Arsenic is a ubiquitous environmental factor that has been identified as a risk factor for a wide range of human diseases. Alcohol is clearly a toxic substance when consumed in excess. Alcohol abuse results in a variety of pathological effects, including damages to liver, heart, and brain, as well as other organs, and is associated with an increased risk of certain types of cancers. In history, arsenic-contaminated beers caused severe diseases. There are populations who are exposed to relatively high levels of arsenic in their drinking water and consume alcohol at the same time. In this focused review, we aim to discuss important molecular mechanisms responsible for arsenic toxicity and potential combined toxic effects of alcohol and arsenic.

Arsenic exposure from drinking water, and all-cause and chronic-disease mortalities in Bangladesh (HEALS): a prospective cohort study

BACKGROUND

Millions of people worldwide are chronically exposed to arsenic through drinking water, including 35-77 million people in Bangladesh. The association between arsenic exposure and mortality rate has not been prospectively investigated by use of individual-level data. We therefore prospectively assessed whether chronic and recent changes in arsenic exposure are associated with all-cause and chronic-disease mortalities in a Bangladeshi population.

METHODS

In the prospective cohort Health Effects of Arsenic Longitudinal Study (HEALS), trained physicians unaware of arsenic exposure interviewed in person and clinically assessed 11 746 population-based participants (aged 18-75 years) from Araihazar, Bangladesh. Participants were recruited from October, 2000, to May, 2002, and followed-up biennially. Data for mortality rates were available throughout February, 2009. We used Cox proportional hazards model to estimate hazard ratios (HRs) of mortality, with adjustment for potential confounders, at different doses of arsenic exposure.

FINDINGS

407 deaths were ascertained between October, 2000, and February, 2009. Multivariate adjusted HRs for all-cause mortality in a comparison of arsenic at concentrations of 10.1-50.0 microg/L, 50.1-150.0 microg/L, and 150.1-864.0 microg/L with at least 10.0 microg/L in well water were 1.34 (95% CI 0.99-1.82), 1.09 (0.81-1.47), and 1.68 (1.26-2.23), respectively. Results were similar with daily arsenic dose and total arsenic concentration in urine. Recent change in exposure, measurement of total arsenic concentrations in urine repeated biennially, did not have much effect on the mortality rate.

INTERPRETATION

Chronic arsenic exposure through drinking water was associated with an increase in the mortality rate. Follow-up data from this cohort will be used to assess the long-term effects of arsenic exposure and how they might be affected by changes in exposure. However, solutions and resources are urgently needed to mitigate the resulting health effects of arsenic exposure.

FUNDING

US National Institutes of Health.

Inhibition of liver x receptor/retinoid X receptor-mediated transcription contributes to the proatherogenic effects of arsenic in macrophages in vitro

OBJECTIVE

To determine whether arsenic inhibits transcriptional activation of the liver X receptor (LXR)/retinoid X receptor (RXR) heterodimers, thereby impairing cholesterol efflux from macrophages and potentially contributing to a proatherogenic phenotype.

METHODS AND RESULTS

Arsenic is an important environmental contaminant and has been linked to an increased incidence of atherosclerosis. Previous findings showed that arsenic inhibits transcriptional activation of type 2 nuclear receptors, known to heterodimerize with RXR. Environmentally relevant arsenic doses decrease the LXR/RXR ligand-induced expression of the LXR target genes (ABCA1 and SREBP-1c). Arsenic failed to decrease cAMP-induced ABCA1 expression, suggesting a selective LXR/RXR effect. This selectivity correlated with the ability of arsenic to decrease LXR/RXR ligand-induced, but not cAMP-induced, cholesterol efflux. By using chromatin immunoprecipitation assays, we found that arsenic inhibits the ability of LXR/RXR ligands to induce activation markers on the ABCA1 and SREBP-1c promoters and blocks ligand-induced release of the nuclear receptor coexpressor (NCoR) from the promoter. Arsenic did not alter the ability of LXR to transrepress inflammatory gene transcription, further supporting our hypothesis that RXR is the target for arsenic inhibition.

CONCLUSIONS

Exposure to arsenic enhances the risk of atherosclerosis. We present data that arsenic inhibits the transcriptional activity of the liver X receptor, resulting in decreased cholesterol-induced gene expression and efflux from macrophages. Therefore, arsenic may promote an athersclerotic environment by decreasing the ability of macrophages to efflux excess cholesterol, thereby favoring increased plaque formation.

Chronic exposure of arsenic via drinking water and its adverse health impacts on humans

Worldwide chronic arsenic (As) toxicity has become a human health threat. Arsenic exposure to humans mainly occurs from the ingestion of As contaminated water and food. This communication presents a review of current research conducted on the adverse health effects on humans exposed to As-contaminated water. Chronic exposure of As via drinking water causes various types of skin lesions such as melanosis, leucomelanosis, and keratosis. Other manifestations include neurological effects, obstetric problems, high blood pressure, diabetes mellitus, diseases of the respiratory system and of blood vessels including cardiovascular, and cancers typically involving the skin, lung, and bladder. The skin seems to be quite susceptible to the effects of As. Arsenic-induced skin lesions seem to be the most common and initial symptoms of arsenicosis. More systematic studies are needed to determine the link between As exposure and its related cancer and noncancer end points.

Risk of carotid atherosclerosis is associated with low serum paraoxonase (PON1) activity among arsenic exposed residents in Southwestern Taiwan

To understand whether human paraoxonase 1 (PON1) would modulate the risk for arsenic-related atherosclerosis, we studied 196 residents from an arseniasis-endemic area in Southwestern Taiwan and 291 age- and sex-matched residents from a nearby control area where arsenic exposure was found low. Carotid atherosclerosis was defined by a carotid artery intima-media wall thickness (IMT) of >1.0 mm. Prevalence of carotid atherosclerosis was increased in the arseniasis-endemic area as compared to the control area after adjustment for conventional risk factors (OR=2.20, p<0.01). The prevalence was positively associated with cumulative arsenic exposure (mg/L-year) in a dose-dependent manner. Multiple logistic regression analysis showed that in the endemic group, low serum PON1 activity was an independent risk factor for atherosclerosis (OR=4.18 low vs. high, p<0.05). For those of low PON1 activity and high cumulative arsenic exposure, the odds ratio for the prevalence of atherosclerosis was further increased up to 5.68 (p<0.05). No significant association was found between atherosclerosis and four polymorphisms of the PON gene cluster (PON1 -108C/T, PON1 Q192R, PON2 A148G, PON2 C311S). However, genetic frequencies of certain alleles including PON1 Q192, PON2 G148 and PON2 C311 were found increased in the endemic group as compared to the controls and a general Chinese population, indicating a possible survival selection in the endemic group after a long arsenic exposure history. Our results showed a significant joint effect between arsenic exposure and serum PON1 activity on carotid atherosclerosis, suggesting that subjects of low PON1 activity may be more susceptible to arsenic-related cardiovascular disease.

Increased aquaglyceroporin 9 expression disrupts arsenic resistance in human lung cancer cells

Resistance to chemotherapy is one of the major problems in treatment responses of lung cancer. This study explored the mechanism underlying the arsenic resistance of lung cancer. Four lung cancer cells with different proliferation activity were characterized for cytotoxicity, arsenic influx/efflux, and arsenic effects on intracellular glutathione and 8-hydroxy-2'-deoxyguanosine (8-OHdG) production. Our data revealed that relative proliferation potency of these cells was H1299>A549>CL3>H1355. Moreover, A549, H1299, and H1355 were markedly resistant to As(2)O(3) with IC50 approximately 100 microM, whereas CL3 was sensitive to As(2)O(3) with IC50 approximately 11.8 microM. After treatment with the respective As(2)O(3) at IC50, arsenic influx/efflux activity in CL3 was comparable to those in the other three arsenic-resistant cells. However, differences in glutathione levels and 8-OHdG production were also detected either before or after arsenic treatment, indicating that a certain degree of variation in anti-oxidative systems and/or 8-OHdG repair activity existed in these cell lines. By transfection of an aquaglyceroporin 9 (AQP9) gene, we showed that increased AQP9 expression significantly enhanced arsenic uptake and disrupted arsenic resistance of A549. The present study strongly suggests that membrane transporters responsible for arsenic uptake, such as AQP9, may play a critical role in development of arsenic resistance in human lung cancer cells.

Arsenic in groundwaters in the Northern Appalachian Mountain belt: a review of patterns and processes

Naturally occurring arsenic in the bedrock of the Northern Appalachian Mountain belt was first recognized in the late 19th century. The knowledge of the behavior of arsenic in groundwater in this region has lagged behind nearly a century, with the popular press reporting on local studies in the early 1980s, and most peer-reviewed research articles on regional patterns conducted and written in the late 1990s and early 2000s. Research reports have shown that within this high arsenic region, between 6% and 22% of households using private drinking water wells contain arsenic in excess of 10 microg/L, the United States Environmental Protection Agency's maximum contaminant level. In nearly all reports, arsenic in drinking water was derived from naturally occurring geologic sources, typically arsenopyrite, substituted sulfides such as arsenian pyrite, and nanoscale minerals such as westerveldite. In most studies, arsenic concentrations in groundwater were controlled by pH dependent adsorption to mineral surfaces, most commonly iron oxide minerals. In some cases, reductive dissolution of iron minerals has been shown to increase arsenic concentrations in groundwater, more commonly associated with anthropogenic activities such as landfills. Evidence of nitrate reduction promoting the presence of arsenic(V) and iron(III) minerals in anoxic environments has been shown to occur in surface waters, and in this manuscript we show this process perhaps applies to groundwater. The geologic explanation for the high arsenic region in the Northern Appalachian Mountain belt is most likely the crustal recycling of arsenic as an incompatible element during tectonic activity. Accretion of multiple terranes, in particular Avalonia and the Central Maine Terrane of New England appear to be connected to the presence of high concentrations of arsenic. Continued tectonic activity and recycling of these older terranes may also be responsible for the high arsenic observed in the Triassic rift basins, e.g. the Newark Basin. There are only two well-known cases of anthropogenic contamination of the environment in the northern Appalachian Mountain belt, both of which are industrial sites with surface contamination at that infiltrated the local groundwater.

Environmental risk factors for heart disease

In this review, we discuss current evidence linking environmental pollutants to cardiovascular disease (CVD). Extensive evidence indicates that environmental factors contribute to CVD risk, incidence, and severity. Migrant studies show that changes in the environment could substantially alter CVD risk in a genetically stable population. Additionally, CVD risk is affected by changes in nutritional and lifestyle choices. Recent studies in the field of environmental cardiology suggest that environmental toxins also influence CVD. Exposure to tobacco smoke is paradigmatic of such environmental risk and is strongly and positively associated with increased cardiovascular morbidity and mortality. In animal models of exposure, tobacco smoke induces endothelial dysfunction and prothrombotic responses and exacerbates atherogenesis and myocardial ischemic injury. Similar mechanism may be engaged by other pollutants or food constituents. Several large population-based studies indicate that exposure to fine or ultrafine particulate air pollution increases CVD morbidity and mortality, and the plausibility of this association is supported by data from animal studies. Exposure to other chemicals such as polyaromatic hydrocarbons, aldehydes, and metals has also been reported to elevate CVD risk by affecting atherogenesis, thrombosis, or blood pressure regulation. Maternal exposure to drugs, toxins, and infection has been linked with cardiac birth defects and premature CVD in later life. Collectively, the data support the notion that chronic environmental stress is an important determinant of CVD risk. Further work is required to assess the magnitude of this risk fully and to delineate specific mechanisms by which environmental toxins affect CVD.

Associations between arsenic in drinking water and pterygium in southwestern Taiwan

BACKGROUND

Pterygium is a fibrovascular growth of the bulbar conjunctiva and underlying subconjunctival tissue that may cause blindness. The mechanism of pterygium formation is not yet fully understood, but pterygium has some tumorlike features.

OBJECTIVES

The objective of this study was to evaluate the association between arsenic exposure through drinking water and the occurrence of pterygium in southwestern Taiwan.

METHODS

We recruited participants > 40 years of age from three villages in the arseniasis-endemic area in southwestern Taiwan (exposure villages) and four neighboring nonendemic villages (comparison villages). Each participant received an eye examination and a questionnaire interview. Photographs taken of both eyes were later graded by an ophthalmologist to determine pterygium status.

RESULTS

We included 223 participants from the exposure villages and 160 from the comparison villages. The prevalence of pterygium was higher in the exposure villages across all age groups in both sexes and increased with cumulative arsenic exposure. We found a significant association between cumulative arsenic exposure and the prevalence of pterygium. After adjusting for age, sex, working under sunlight, and working in sandy environments, we found that cumulative arsenic exposure of 0.1-15.0 mg/L-year and > or = 15.1 mg/L-year were associated with increased risks of developing pterygium. The adjusted odds ratios were 2.04 [95% confidence interval (CI), 1.04-3.99] and 2.88 (95% CI, 1.42-5.83), respectively.

CONCLUSIONS

Chronic exposure to arsenic in drinking water was related to the occurrence of pterygium, and the association was still observed after adjusting for exposures to sunlight and sandy environments.

The role of Akt on arsenic trioxide suppression of 3T3-L1 preadipocyte differentiation

The present study investigates the molecular details of how arsenic trioxide inhibits preadipocyte differentiation and examines the role of Akt/PKB in regulation of differentiation and apoptosis. Continual exposure of arsenic trioxide, at the clinic achievable dosage that does not induce apoptosis, suppressed 3T3-L1 cell differentiation into fat cells by inhibiting the expression of PPARgamma and C/EBPalpha and disrupting the interaction between PPARgamma and RXRalpha, which determines the programming of the adipogenic genes. Interestingly, if we treated the cells for 12 or 24 h and then withdrew arsenic trioxide, the cells were able to differentiate to the comparable levels of untreated cells as assayed by the activity of GAPDH, the biochemical marker of preadipocyte differentiation. Long term treatment blocked the differentiation and the activity of GAPDH could not recover to the comparable levels of untreated cells. Continual exposure of arsenic trioxide caused accumulation in G2/M phase and the accumulation of p21. We found that arsenic trioxide induced the expression and the phosphorylation of Akt/PKB and it inhibited the interaction between Akt/PKB and PPARgamma . Akt/PKB inhibitor appears to block the arsenic trioxide suppression of differentiation. Our results suggested that Akt/PKB may play a role in suppression of apoptosis and negatively regulate preadipocyte differentiation.