Arsenic immunotoxicity: a review

Thermodynamic parameters for the protonation and the interaction of arsenate with Mg2+, Ca2+ and Sr2+: Application to natural waters

Thermodynamic parameters for the protonation of AsO₄^3- and for the interaction with Mg²⁺, Ca²⁺ and Sr²⁺ were reported, comprehensive also of their dependence on ionic strength, considering the 0.1 ≤ I ≤ 1 M range and using NaCl as background salt. The same speciation models were obtained for Mg²⁺, Ca²⁺ and Sr²⁺ systems, with the formation of three different species: ML, MLH and MLH₂ (L = AsO₄^3-). Mono- and di-protonated species were very weak, with formation constant values (log K) ranging from 1.45 to 3.23. In order to have a complete picture of thermodynamic properties of the systems under study and to fill the shortage of thermodynamic data on arsenate complex systems, the ligand protonation and metal complex enthalpies were also determined by calorimetric titrations, at t = 25 °C and in NaCl at I = 0.7 M (for H⁺-AsO₄^3- species also at I = 0.1 M). On the light of the proposed speciation models, examples of As(V) distribution in some natural waters are reported.

Imbalanced immune responses involving inflammatory molecules and immune-related pathways in the lung of acute and subchronic arsenic-exposed mice

Inorganic arsenic has been claimed to increase the risk of pulmonary diseases through ingestion, as opposed to inhalation, which makes it a unique and intriguing environmental toxicant. However, the immunotoxic effects of lung, one of the targets of arsenic exposure, have not been extensively investigated in vivo. In the present study, we first confirmed that 2.5, 5 and 10mg/kg NaAsO₂ orally for 24h dose-dependently triggered the infiltration of neutrophils, lymphocytes and macrophages in BALF. Not only the transcription activity, but also the secretion of proinflammatory cytokines IL-1β, IL-6 and TNF-α were consistently raised in the lung and BALF of acute arsenic-exposed mice. Acute oral administration of NaAsO₂ also raised pulmonary MPO activity and mRNA levels of chemokine Mip-2 and Mcp-1. Meanwhile, obvious histopathological damages with inflammatory cells infiltration and erythrocyte aggregation around the capillaries were verified in the lung of mice drank arsenic-rich water freely for 3 months. Furthermore, we affirmed notable disturbance of CD4⁺ T-cell differentiation in the lung of acute arsenic-exposed mice, as demonstrated by up-regulated mRNA levels of regulator Gata3 and cytokine Il-4 of Th2, enhanced Foxp3 and Il-10 of Treg, down-regulated T-bet and Ifn-γ of Th1, as well as lessened Ror-γt and Il-23 of Th17. However, impressive elevation of cytokine Ifn-γ and Il-23, as well as moderate enhancement of Il-4 and Il-10 were found in the lung by subchronic arsenic administration. Finally, our present study demonstrated that both a single and sustained arsenic exposure prominently increased the expression of immune-related p38, JNK, ERK1/2 and NF-κB proteins in the lung tissue. While disrupting the pulmonary redox homeostasis by increasing MDA levels, exhausting GSH and impaired enzyme activities of CAT and GSH-Px, antioxidant regulator NRF2 and its downstream targets HO-1 and GSTO1/2 were also up-regulated by both acute and subchronic arsenic treatment. Conclusively, our present study demonstrated both acute and subchronic oral administration of arsenic triggers multiple pulmonary immune responses involving inflammatory molecules and T-cell differentiation, which might be closely associated with the imbalanced redox status and activation of immune-related MAPKs, NF-κB and anti-inflammatory NRF2 pathways.

Inhibition of early T cell cytokine production by arsenic trioxide occurs independently of Nrf2

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a stress-activated transcription factor that induces a variety of cytoprotective genes. Nrf2 also mediates immunosuppressive effects in multiple inflammatory models. Upon activation, Nrf2 dissociates from its repressor protein, Keap1, and translocates to the nucleus where it induces Nrf2 target genes. The Nrf2-Keap1 interaction is disrupted by the environmental toxicant and chemotherapeutic agent arsenic trioxide (ATO). The purpose of the present study was to determine the effects of ATO on early events of T cell activation and the role of Nrf2 in those effects. The Nrf2 target genes Hmox-1, Nqo-1, and Gclc were all upregulated by ATO (1–2 μM) in splenocytes derived from wild-type, but not Nrf2-null, mice, suggesting that Nrf2 is activated by ATO in splenocytes. ATO also inhibited IFNγ, IL-2, and GM-CSF mRNA and protein production in wild-type splenocytes activated with the T cell activator, anti-CD3/anti-CD28. However, ATO also decreased production of these cytokines in activated splenocytes from Nrf2-null mice, suggesting the inhibition is independent of Nrf2. Interestingly, ATO inhibited TNFα protein secretion, but not mRNA expression, in activated splenocytes suggesting the inhibition is due to post-transcriptional modification. In addition, c-Fos DNA binding was significantly diminished by ATO in wild-type and Nrf2-null splenocytes activated with anti-CD3/anti-CD28, consistent with the observed inhibition of cytokine production by ATO. Collectively, this study suggests that although ATO activates Nrf2 in splenocytes, inhibition of early T cell cytokine production by ATO occurs independently of Nrf2 and may instead be due to impaired AP-1 DNA binding.

Arsenic and Immune Response to Infection During Pregnancy and Early Life

PURPOSE OF REVIEW

Arsenic, a known carcinogen and developmental toxicant, is a major threat to global health. While the contribution of arsenic exposure to chronic diseases and adverse pregnancy and birth outcomes is recognized, its ability to impair critical functions of humoral and cell-mediated immunity-including the specific mechanisms in humans-is not well understood. Arsenic has been shown to increase risk of infectious diseases that have significant health implications during pregnancy and early life. Here, we review the latest research on the mechanisms of arsenic-related immune response alterations that could underlie arsenic-associated increased risk of infection during the vulnerable periods of pregnancy and early life.

RECENT FINDINGS

The latest evidence points to alteration of antibody production and transplacental transfer as well as failure of T helper cells to produce IL-2 and proliferate. Critical areas for future research include the effects of arsenic exposure during pregnancy and early life on immune responses to natural infection and the immunogenicity and efficacy of vaccines.

PKC θ-mediated Ca2+/NF-AT signalling pathway may be involved in T-cell immunosuppression in coal-burning arsenic-poisoned population

Arsenic poisoning is a worldwide endemic disease that affects thousands of people. Growing evidence from animal, cell, and human studies indicates that arsenic has deleterious effects on the immune system. The present investigation is a population-based study that observed changes in the proliferation of human T-cells and IL-2 and INF-γ mRNA expression. Our results show that coal-burning arsenic can cause T-cell immunosuppression in the population, and participates in the occurrence and development of arsenic poisoning. In addition, we analyzed the intracellular calcium index, expression of protein kinase C theta (PKC θ) and phosphorylated PKC θ, and the DNA-binding activity of NF-AT in peripheral blood mononuclear cells (PBMCs). Our analysis demonstrates that the PKC θ-mediated Ca²⁺/NF-AT signalling pathway may be involved in the T-cell immunosuppression of coal-burning arsenic-poisoned population. This study provides important data for a mechanistic understanding of endemic arsenic poisoning.

The 9th Conference on Metal Toxicity and Carcinogenesis: The conference overview

Heavy metals, such as arsenic, chromium, cadmium, nickel, mercury, and uranium are known to cause many human diseases and health complications after occupational or environmental exposure. Consequently, metals are environmental health concerns. This manuscript is an overview of the 9th Conference on Metal Toxicity and Carcinogenesis held in October 2016 in Lexington, Kentucky. Since 2000, this biennial meeting brings together experts in the field to discuss current and prospective research in an effort to advance research pertaining to metal toxicity and carcinogenesis. In this review we summarize the major topics discussed and provide insight regarding current research in the field and an account of the direction in which the field is progressing.

Arsenic exposure impels CD4 commitment in thymus and suppress T cell cytokine secretion by increasing regulatory T cells

Arsenic is globally infamous for inducing immunosuppression associated with prevalence of opportunistic infection in exposed population, although the mechanism remains elusive. In this study, we investigate the effect of arsenic exposure on thymocyte lineage commitment and the involvement of regulatory T cells (T_reg) in arsenic-induced immunosuppression. Male Balb/c mice were exposed to 0.038, 0.38 and 3.8 ppm sodium arsenite for 7, 15 and 30 days through oral gavage. Arsenic exposure promoted CD4 lineage commitment in a dose dependent manner supported by the expression of ThPOK in thymus. Arsenic also increased splenic CD4⁺ T cells and promoted their differentiation into T_reg cells. In parallel, arsenic exposure induced immunosuppression characterized by low cytokine secretion from splenocytes and increased susceptibility to Mycobacterium fortuitum (M. fortuitum) infection. Therefore, we linked arsenic-induced rise in T_reg cells with suppressed T_h1 and T_h2 related cytokines, which has been reversed by inhibition of T_reg cells in-vivo using wortmannin. Other parameters like body weight, kidney and liver function, histoanatomy of thymus and spleen as well as thymocyte and splenocytes viability were unaltered by arsenic exposure. Taken together our findings indicated that environmentally relevant dose of arsenic enhanced differentiation of T_reg cells which in turn induce immunosuppression in experimental animals.

Effects of Inorganic Arsenic, Methylated Arsenicals, and Arsenobetaine on Atherosclerosis in the Mouse Model and the Role of As3mt-Mediated Methylation

BACKGROUND

Arsenic is metabolized through a series of oxidative methylation reactions by arsenic (3) methyltransferase (As3MT) to yield methylated intermediates. Although arsenic exposure is known to increase the risk of atherosclerosis, the contribution of arsenic methylation and As3MT remains undefined.

OBJECTIVES

Our objective was to define whether methylated arsenic intermediates were proatherogenic and whether arsenic biotransformation by As3MT was required for arsenic-enhanced atherosclerosis.

METHODS

We utilized the apoE^−/− mouse model to compare atherosclerotic plaque size and composition after inorganic arsenic, methylated arsenical, or arsenobetaine exposure in drinking water. We also generated apoE^−/−/As3mt^−/− double knockout mice to test whether As3MT-mediated biotransformation was required for the proatherogenic effects of inorganic arsenite. Furthermore, As3MT expression and function were assessed in in vitro cultures of plaque-resident cells. Finally, bone marrow transplantation studies were performed to define the contribution of As3MT-mediated methylation in different cell types to the development of atherosclerosis after inorganic arsenic exposure.

RESULTS

We found that methylated arsenicals, but not arsenobetaine, are proatherogenic and that As3MT is required for arsenic to induce reactive oxygen species and promote atherosclerosis. Importantly, As3MT was expressed and functional in multiple plaque-resident cell types, and transplant studies indicated that As3MT is required in extrahepatic tissues to promote atherosclerosis.

CONCLUSION

Taken together, our findings indicate that As3MT acts to promote cardiovascular toxicity of arsenic and suggest that human AS3MT SNPs that correlate with enzyme function could predict those most at risk to develop atherosclerosis among the millions that are exposed to arsenic. https://doi.org/10.1289/EHP806.

Elements of kitchen toxicology to exploit the value of traditional (African) recipes: The case of Egusi Okra meal in the diet of HIV+/AIDS subjects

The Egusi Okra soup is a traditional African meal that is considered of high nutritional value and protective against weight loss. We introduce the concept of "kitchen toxicology" to analyse the recipe of the Egusi Okra soup and highlight possible mitigation measures for toxic and/or antinutritional effects in the wide spectrum of health and nutritional needs of HIV+/AIDS subjects. In particular, we focus on toxicants (environmental contaminants, process contaminants, substances leaching from food contact materials) dysregulating the immune status, as well as on interactions between nutrients, contaminants, and/or antinutrients which may lead to secondary/conditioned nutritional deficiencies or imbalances; in their turn, these can modulate the ability to cope with toxicants, and increase nutritional requirements. Recommendations are given for practices preserving the Egusi Okra soup from such risk factors, identifying points of particular attention during meal preparation, from purchase of raw ingredients through to food handling, cooking, storage, and consumption. The Egusi Okra soup is discussed in the context of a diet that is asked to mitigate complications (weight loss, opportunistic infections) and support antiretroviral therapy in African countries with high HIV/AIDS prevalence. The paper discusses how nutritional interventions benefit of the integration of kitchen toxicology practices in everyday life. Toxicological risk assessment is crucial to understand the history and status of the person exposed to or affected by infectious diseases.

Cord blood T cell subpopulations and associations with maternal cadmium and arsenic exposures

Background

Arsenic and cadmium are environmental pollutants, and although the evidence for adverse immune effects after prenatal arsenic and cadmium exposures is increasing, little is known about the underlying immunological mechanisms.

Methods

We investigated the relationship between prenatal arsenic and cadmium exposures and a variety of T cell subpopulations measured in cord blood for 63 participants in the New Hampshire Birth Cohort Study. Post-partum toenail concentrations of arsenic and cadmium were used as an estimate of maternal exposure during pregnancy. The characteristics of cord blood proportions of T lymphocytes and subpopulations (expression of markers for Th1, Th2, Th17, Th1Th17, induced and natural regulatory T cells and NKTs) are presented.

Results

In regression analyses, maternal arsenic exposure levels were inversely associated with cord blood T helper memory cells (-21%, 95% CI: -36%, -3%) and the association was found to be stronger in females. They were also inversely associated with activated T helper memory cells, particularly in males (-26%, 95% CI: -43%, -3%). Similarly, inverse associations were observed between cadmium exposure levels and activated T helper memory cells (-16%, 95% CI: -30%, -1%) and also for T helper memory cells in females (-20%, 95% CI: -35%, -3%).

Conclusion

The results suggest that prenatal exposures to relatively low levels of arsenic and cadmium may contribute to altered distribution of T cell populations at birth. These changes in theory, could have contributed to the previously reported immunosuppressive effects observed later in infancy/childhood.

Humoral Immunity in Arsenic-Exposed Children in Rural Bangladesh: Total Immunoglobulins and Vaccine-Specific Antibodies

BACKGROUND

Early-life arsenic exposure has been associated with reduced cell-mediated immunity, but little is known about its effects on humoral immunity.

OBJECTIVE

We evaluated whether prenatal and childhood arsenic exposure was associated with humoral immune function in school-aged children.

METHODS

Children born in a prospective mother–child cohort in rural Bangladesh were immunized with measles, mumps, and rubella (MMR) vaccines at 9 years of age (n=525). Arsenic exposure was assessed in urine (U-As), from mothers during pregnancy and their children at 4.5 and 9 years of age. Total IgG (tIgG), tIgE, tIgA, and MMR-specific IgG concentrations were measured in plasma using immunoassays.

RESULTS

Arsenic exposure was positively associated with child tIgG and tIgE, but not tIgA. The association with tIgG was mainly apparent in boys (p for interaction=0.055), in whom each doubling of maternal U-As was related to an increase in tIgG by 28 mg/dL. The associations of U-As at 9 years with tIgG and tIgE were evident in underweight children (p for interaction <0.032). Childhood arsenic exposure tended to impair mumps-specific vaccine response, although the evaluation was complicated by high preimmunization titers. Postimmunization mumps–specific IgG titers tended to decrease with increasing U-As at 4.5 and 9 years of age [regression coefficient (β)=−0.16; 95% confidence interval (CI): −0.33, 0.01; p=0.064 and β=−0.12; 95% CI: −0.27, −0.029; p=0.113, respectively) in 25% children with the lowest preexisting mumps-specific IgG titers.

CONCLUSIONS

Arsenic exposure increased tIgG and tIgE in plasma, and tended to decrease mumps-specific IgG in children at 9 years of age. https://doi.org/10.1289/EHP318.

Chronic early childhood exposure to arsenic is associated with a TNF-mediated proteomic signaling response

Exposure to inorganic arsenic (iAs) in drinking water is a global public health concern and is associated with a range of health outcomes, including immune dysfunction. Children are a particularly sensitive population to the effects of inorganic arsenic, yet the biological mechanisms underlying adverse health outcomes are understudied. Here we used a proteomic approach to examine the effects of iAs exposure on circulating serum protein levels in a cross-sectional children's cohort in Mexico. To identify iAs-associated proteins, levels of total urinary arsenic (U-tAs) and its metabolites were determined and serum proteins assessed for differences in expression. The results indicate an enrichment of Tumor Necrosis Factor-(TNF)-regulated immune and inflammatory response proteins that displayed decreased expression levels in relation to increasing U-tAs. Notably, when analyzed in the context of the proportions of urinary arsenic metabolites in children, the most robust response was observed in relation to the monomethylated arsenicals. This study is among the first serum proteomics assessment in children exposed to iAs.

Mining and Environmental Health Disparities in Native American Communities

PURPOSE OF REVIEW

More than a century of hard rock mining has left a legacy of >160,000 abandoned mines in the Western USA that are home to the majority of Native American lands. This article describes how abrogation of treaty rights, ineffective policies, lack of infrastructure, and a lack of research in Native communities converge to create chronic exposure, ill-defined risks, and tribal health concerns.

RECENT FINDINGS

Recent results show that Native Americans living near abandoned uranium mines have an increased likelihood for kidney disease and hypertension, and an increased likelihood of developing multiple chronic diseases linked to their proximity to the mine waste and activities bringing them in contact with the waste. Biomonitoring confirms higher than expected exposure to uranium and associated metals in the waste in adults, neonates, and children in these communities. These sites will not be cleaned up for many generations making it critical to understand and prioritize exposure-toxicity relationships in Native populations to appropriately allocate limited resources to protect health. Recent initiatives, in partnership with Native communities, recognize these needs and support development of tribal research capacity to ensure that research respectful of tribal culture and policies can address concerns in the future. In addition, recognition of the risks posed by these abandoned sites should inform policy change to protect community health in the future.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide "hot spots" where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide.

Cancer Immunoprevention and Public Health

The power of cancer immune surveillance has been documented beyond doubt, and the successful exploitation of immune response to cancer has started a new era in the war against cancer. Cancer biologists have recognized immunoevasion as an emerging hallmark in addition to the six hallmarks of cancer. Besides the natural connection between the immune system and cancer development, most established environmental risk factors are now known to interfere with immune surveillance mechanisms. Genetic variations regulating immunity may also modulate cancer susceptibility, but evidence for this is currently limited. Molecular cross talk linking “immune” and “genomic” surveillance pathways has been characterized. It appears that immune mechanisms may contribute to the effects of common cancer risk factors. We provide an updated overview of evidence for cancer immune surveillance, cancer risk factors interfering with it, and interventions to enhance cancer immune surveillance as tools to complement ongoing vaccine development efforts for cancer immunoprevention. Although there is a lot of support for cancer immunoprevention with simple lifestyle modifications from observational studies, there is an urgent need for clinical trials to establish the effectiveness of this approach for public health benefits.

Arsenic exposure alters lung function and airway inflammation in children: A cohort study in rural Bangladesh

Exposure to arsenic has been associated with increased risk of reduced lung function in adults, but the adverse impacts in early life are unclear. We aim to examine whether prenatal and childhood arsenic exposure is associated with reduced lung function and increased airway inflammation in school-aged children. Children born in the MINIMat cohort in rural Bangladesh were evaluated at 9years of age (n=540). Arsenic exposure was assessed in urine (U-As) that was collected from mothers during early pregnancy and their children aged 4.5 and 9years. In the 9-year-old children, lung function was assessed using spirometry and airway inflammation was assessed by the NIOX MINO system. C-reactive protein (CRP) and Clara cell secretory protein (CC16) concentrations were measured in plasma by immunoassays. The U-As concentrations in 9-year-old children were lower (median 53μg/l) compared to their mothers (median 76μg/l). Maternal U-As (log₂ transformed) was inversely associated with forced vital capacity (FVC) and forced expiratory volume at 1s (FEV1) (β=-12; 95% CI: -22, -1.5; p=0.031 and β=-12; 95% CI: -22, -1.9; p=0.023, respectively) in all children, and the associations were stronger in boys and among children with adequate height and weight, as well as among those whose mothers had higher percentages of methylarsonic acid (MMA) and lower percentages of dimethylarsinic acid (DMA). U-As (log₂ transformed) at 4.5 and 9years was positively associated with fractional exhaled nitric oxide (FE_NO) concentrations in boys (β=0.89; 95% CI: 0.13, 1.66; p=0.022 and β=0.88; 95% CI: 0.16, 1.61; p=0.017, respectively) but not in girls. Increased CC16 concentrations were associated with higher lung function indices. In conclusion, our findings suggest that prenatal arsenic exposure is related to impaired lung function, while childhood exposure may increase airway inflammation, particularly in boys.

Low-level arsenic causes chronic inflammation and suppresses expression of phagocytic receptors

The impact of chronic low-level groundwater arsenic (As) exposure [in the range above the WHO-recommended limit of 10 μg/L but ≤50 μg/L (permissible limit of As for many Asian countries)] was investigated for cross talk of inflammatory changes and expression of phagocytic receptors of exposed rural women (N, 45) from districts of 24 Parganas (south) and in matched control groups (N, 43) [As ≤10 μg/L] from the same district. Systemic inflammation was evident from the upregulated levels of pro-inflammatory mediators like tumor necrosis factor-α (TNF-α); interleukins (ILs) like IL-6, IL-8, and IL-12; and C-reactive protein (CRP) in the sera and upregulated expression of protein kinase B phosphorylated at ser473 (pAKTser473)/nuclear factor-κB (NF-κB)/TNF-α axis in the leukocytes of exposed women with respect to control. We found that low-dose As exposure apart from inflicting inflammation altered the expression of phagocytic receptors-Fcγ receptors (FcγRs) and complement receptors (CRs). The leukocytes of the low-As-exposed women exhibited suppression of CD64, CD35, and CD11b and increased expression of CD16 with respect to control. Groundwater As showed a negative correlation with CD64 expression on monocytes [Pearson's r, -0.8205; 95% confidence interval (CI), -0.8789 to -0.7379] and granulocytes [r, -0.7635; 95% CI, -0.8388 to -0.6595] and a positive correlation with CD16 on granulocytes [r, 0.8363; 95% CI, 0.7599 to 0.8899]. A negative correlation of groundwater As was also observed with expression of CD35 on granulocytes [r, -0.8780; 95% CI, -0.9185 to -0.8192] and monocytes [r, -0.7778; 95% CI, -0.8490 to -0.6790] and CD11b on monocytes [r, -0.6035; 95% CI, -0.7218 to -0.4511]. Therefore, it may be indicated that chronic low-level As exposure (11-50 μg/L) not only evoked chronic inflammatory changes but also suppressed the expression of FcγRs and CRs in the exposed women. This, in turn, may lead to susceptibility towards pathogenic infections or in long run may even contribute towards chronic inflammatory diseases including cancer.

Arsenic exposure from drinking water is associated with decreased gene expression and increased DNA methylation in peripheral blood

BACKGROUND

Exposure to inorganic arsenic increases the risk of cancer and non-malignant diseases. Inefficient arsenic metabolism is a marker for susceptibility to arsenic toxicity. Arsenic may alter gene expression, possibly by altering DNA methylation.

OBJECTIVES

To elucidate the associations between arsenic exposure, gene expression, and DNA methylation in peripheral blood, and the modifying effects of arsenic metabolism.

METHODS

The study participants, women from the Andes, Argentina, were exposed to arsenic via drinking water. Arsenic exposure was assessed as the sum of arsenic metabolites in urine (U-As), using high performance liquid-chromatography hydride-generation inductively-coupled-plasma-mass-spectrometry, and arsenic metabolism efficiency was assessed by the urinary fractions (%) of the individual metabolites. Genome-wide gene expression (N=80 women) and DNA methylation (N=93; 80 overlapping with gene expression) in peripheral blood were measured using Illumina DirectHyb HumanHT-12 v4.0 and Infinium Human-Methylation 450K BeadChip, respectively.

RESULTS

U-As concentrations, ranging 10-1251μg/L, was associated with decreased gene expression: 64% of the top 1000 differentially expressed genes were down-regulated with increasing U-As. U-As was also associated with hypermethylation: 87% of the top 1000CpGs were hypermethylated with increasing U-As. The expression of six genes and six individual CpG sites were significantly associated with increased U-As concentration. Pathway analyses revealed enrichment of genes related to cell death and cancer. The pathways differed somewhat depending on arsenic metabolism efficiency. We found no overlap between arsenic-related gene expression and DNA methylation for individual genes.

CONCLUSIONS

Increased arsenic exposure was associated with lower gene expression and hypermethylation in peripheral blood, but with no evident overlap.

Identification of novel signature genes attesting arsenic-induced immune alterations in adult zebrafish (Danio rerio)

Arsenic poisoning is a serious global issue. Apart from causing developmental and systemic toxicity, arsenic has recently been reported for its ability to hinder immune responses. The present study is designed to identify the global expression profile associated with arsenic-induced immune alterations at the organismic level. Adult zebrafish (Danio rerio) were exposed to 20, 40 and 80ppb of arsenic trioxide for 30days, sacrificed and global gene expression profile studied. Microarray data suggested 65 immune related genes were commonly affected in the three treatment regimens. The expression profile of key immune related genes (tlr1, nitr1f, nitr1c, crfb8, socs7, socs3b, abcb3/1, mch1uja, ifnγ1-2, cxcl12b and crlf1a) was validated by qPCR. Pathway analysis suggested the major involvement of JAK-STAT circuit in the process. The expression of these marker genes was also studied in arsenic exposed and bacteria (Aeromonas hydrophila) challenged zebrafish. Increase in bacterial colony forming units (CFU) coupled with gross histopathology of kidney in arsenic exposed-bacteria challenged fish suggested profound immuno-compromised condition. We propose that chronic arsenic exposure leads to hyperactivation of the immune system as a consequence when exposed to further stress (microbial) it induces immuno-suppression with pathological implications. The study provides a molecular snap shot for predicting arsenic immuno-toxicity.

The Association of Arsenic Exposure and Metabolism With Type 1 and Type 2 Diabetes in Youth: The SEARCH Case-Control Study

OBJECTIVE

Little is known about arsenic and diabetes in youth. We examined the association of arsenic with type 1 and type 2 diabetes in the SEARCH for Diabetes in Youth Case-Control (SEARCH-CC) study. Because one-carbon metabolism can influence arsenic metabolism, we also evaluated the potential interaction of folate and vitamin B12 with arsenic metabolism on the odds of diabetes.

RESEARCH DESIGN AND METHODS

Six hundred eighty-eight participants <22 years of age (429 with type 1 diabetes, 85 with type 2 diabetes, and 174 control participants) were evaluated. Arsenic species (inorganic arsenic [iAs], monomethylated arsenic [MMA], dimethylated arsenic [DMA]), and one-carbon metabolism biomarkers (folate and vitamin B12) were measured in plasma. We used the sum of iAs, MMA, and DMA (∑As) and the individual species as biomarkers of arsenic concentrations and the relative proportions of the species over their sum (iAs%, MMA%, DMA%) as biomarkers of arsenic metabolism.

RESULTS

Median ∑As, iAs%, MMA%, and DMA% were 83.1 ng/L, 63.4%, 10.3%, and 25.2%, respectively. ∑As was not associated with either type of diabetes. The fully adjusted odds ratios (95% CI), rescaled to compare a difference in levels corresponding to the interquartile range of iAs%, MMA%, and DMA%, were 0.68 (0.50-0.91), 1.33 (1.02-1.74), and 1.28 (1.01-1.63), respectively, for type 1 diabetes and 0.82 (0.48-1.39), 1.09 (0.65-1.82), and 1.17 (0.77-1.77), respectively, for type 2 diabetes. In interaction analysis, the odds ratio of type 1 diabetes by MMA% was 1.80 (1.25-2.58) and 0.98 (0.70-1.38) for participants with plasma folate levels above and below the median (P for interaction = 0.02), respectively.

CONCLUSIONS

Low iAs% versus high MMA% and DMA% was associated with a higher odds of type 1 diabetes, with a potential interaction by folate levels. These data support further research on the role of arsenic metabolism in type 1 diabetes, including the interplay with one-carbon metabolism biomarkers.

Inorganic Arsenic Determination in Food: A Review of Analytical Proposals and Quality Assessment Over the Last Six Years

Here we review recent developments in analytical proposals for the assessment of inorganic arsenic (iAs) content in food products. Interest in the determination of iAs in products for human consumption such as food commodities, wine, and seaweed among others is fueled by the wide recognition of its toxic effects on humans, even at low concentrations. Currently, the need for robust and reliable analytical methods is recognized by various international safety and health agencies, and by organizations in charge of establishing acceptable tolerance levels of iAs in food. This review summarizes the state of the art of analytical methods while highlighting tools for the assessment of quality assessment of the results, such as the production and evaluation of certified reference materials (CRMs) and the availability of specific proficiency testing (PT) programmes. Because the number of studies dedicated to the subject of this review has increased considerably over recent years, the sources consulted and cited here are limited to those from 2010 to the end of 2015.

Differential modulation of cellular antioxidant status in zebrafish liver and kidney exposed to low dose arsenic trioxide

Zebrafish were exposed to a nonlethal dose (1/350LC₅₀; 50µg/L) of As₂O₃ and sampled at 7, 15, 30, 60 and 90 days of treatment. The oxidative stress response was assessed in terms of time-dependent histopathological changes, lipid peroxidation, GSH status, activities of detoxification enzymes and expression of antioxidant genes in liver and kidney. As₂O₃ treatment enhanced lipid peroxidation except at day 90 in liver and day 30 in kidney. Glutathione depleted significantly in the liver except on day 30; whereas in kidney, it increased initially but thereafter depleted significantly. The liver GST activity was high until day 30, low on day 60 and high on day 90. On the other hand, activity of GST in kidney remained high throughout the exposure. GR activity in liver decreased initially but augmented from 30 days onwards whereas in kidney it remained high until 30 days of exposure. Significant increase in GPx and CAT activities in liver and kidney confirmed oxidative stress in zebrafish which correlated with mRNA expression of antioxidant genes. Upregulation in mRNA level of Cu-Zn Sod in liver and kidney was prominent. Gpx1 upregulation was more conspicuous in kidney as compared to liver while the pattern of Cat expression was almost similar in both the organs. Among the mitochondrial genes, expression of Cox1 was significantly high only after 90 days in liver, while in kidney it enhanced at 7, 30 and 60 days of arsenic exposure. Ucp2 was upregulated in liver after 15 days of exposure but significantly downregulated at day 90; in kidney it remained unchanged at other time points except at day 90. An overall increased expression of Bcl2 further confirmed As₂O₃ induced oxidative stress in zebrafish liver and kidney. The pattern of mRNA expression of Nrf2 was not uniform and was in accordance to its downstream antioxidant genes. Present findings elucidate that low dose of As₂O₃ exposure induces a time dependent differential modulation of antioxidant status in liver and kidney of zebrafish in a tissue-specific manner.

Investigating Susceptibility to Diabetes Using Features of the Adipose Tissue in Response to In Utero Polycyclic Aromatic Hydrocarbons Exposure

BACKGROUND

In recent times, there has been an increase in the incidence of type 2 diabetes mellitus (T2DM) particularly in children. Adipocyte dysfunction provide a critical link between obesity and insulin resistance resulting in diabetes outcome. Further, environmental chemical exposure during early years of life might be a significant contributing factor to the increase in the incidence of T2DM. This study tests the idea that exposure to environmental contaminants (2-aminoanthracene [2AA]) in utero will show effects in the adipose tissue (AT) that signify T2DM vulnerability. 2AA is a polycyclic aromatic hydrocarbon found in a variety of products.

METHODS

To accomplish the study objective, pregnant dams were fed various amounts of 2AA adulterated diets from gestation through postnatal period. The neonates and older offspring were analyzed for diabetic-like genes in the ATs and analysis of serum glucose. Furthermore, weight monitoring, histopathology and immunohistochemical (IHC) staining for CD68 in AT, adipocyte size determination and adiponectin amounts in serum were undertaken.

RESULTS

Up-regulation of adiponectin and interleukin-6 genes were noted in the pups and older rats. Combination of intrauterine 2AA toxicity with moderate high fat diet exhibited gene expression patterns similar to those of the neonates. Elevated serum glucose levels were noted in treated groups. IHC of the AT indicated no significant malformations; however, CD68+ cells were greater in the animals treated to 2AA. Similarly, mean sizes of the adipocytes were larger in treated and combined 2AA and moderate high fat animals. Adiponectin was reduced in 2AA groups.

CONCLUSION

From the preceding, it appears intrauterine 2AA disturbance, when combined with excess fat accumulation will lead to greater risk for the diabetic condition.

Transcriptomics and methylomics of CD4-positive T cells in arsenic-exposed women

Arsenic, a carcinogen with immunotoxic effects, is a common contaminant of drinking water and certain food worldwide. We hypothesized that chronic arsenic exposure alters gene expression, potentially by altering DNA methylation of genes encoding central components of the immune system. We therefore analyzed the transcriptomes (by RNA sequencing) and methylomes (by target-enrichment next-generation sequencing) of primary CD4-positive T cells from matched groups of four women each in the Argentinean Andes, with fivefold differences in urinary arsenic concentrations (median concentrations of urinary arsenic in the lower- and high-arsenic groups: 65 and 276 μg/l, respectively). Arsenic exposure was associated with genome-wide alterations of gene expression; principal component analysis indicated that the exposure explained 53% of the variance in gene expression among the top variable genes and 19% of 28,351 genes were differentially expressed (false discovery rate <0.05) between the exposure groups. Key genes regulating the immune system, such as tumor necrosis factor alpha and interferon gamma, as well as genes related to the NF-kappa-beta complex, were significantly downregulated in the high-arsenic group. Arsenic exposure was associated with genome-wide DNA methylation; the high-arsenic group had 3% points higher genome-wide full methylation (>80% methylation) than the lower-arsenic group. Differentially methylated regions that were hyper-methylated in the high-arsenic group showed enrichment for immune-related gene ontologies that constitute the basic functions of CD4-positive T cells, such as isotype switching and lymphocyte activation and differentiation. In conclusion, chronic arsenic exposure from drinking water was related to changes in the transcriptome and methylome of CD4-positive T cells, both genome wide and in specific genes, supporting the hypothesis that arsenic causes immunotoxicity by interfering with gene expression and regulation.

Cumulative arsenic exposure is associated with fungal infections: Two cohort studies based on southwestern and northeastern basins in Taiwan

Long-term arsenic exposure results in atherosclerosis and cancers, along with aberrant immune responses. Animal-based and epidemiological studies indicate that arsenic exposure increases susceptibility to viral and bacterial infections. This study aimed to assess whether arsenic exposure is associated with the development of fungal infection, which is substantially attributed to as a cause of aberrant immunity. Based on two well-established cohorts from two basins in southwestern (SW; high arsenic area) and northeastern (NE; low arsenic area) Taiwan (n=297 and 2738, respectively), the arsenic exposure in well water was estimated using HPLC-ICP-MS. Fungal infections were defined via clinical and mycological assessments (PCR of fungal 18S rRNA) of nail samples. Individuals in SW cohort with cumulative arsenic exposure >10,000μg/L∗years had a higher risk of developing fungal infections (OR=1.57, 95% CI=1.08-1.92) after adjusting for diabetes and occupation. In NE cohort, female sex, alcohol consumption, and chronic kidney diseases were associated with toenail infections. In contrast, fingernail infections (OR=1.33, 95% CI=1.05-1.68) were highly associated with arsenic exposure in a dose-dependent manner. We are the first to report palmar and plantar hyperkeratosis upon low arsenic exposure in 3.9% and 6.7% individuals, respectively. This is the first large-scale study showing arsenic exposure is associated with fungal infections in a dose-dependent manner.

Developmental Windows of Susceptibility to Inorganic Arsenic: A Survey of Current Toxicologic and Epidemiologic Data

Globally, millions of people are exposed to elevated levels of inorganic arsenic (iAs) via drinking water. Exposure to iAs is associated with a wide range of negative health outcomes, including cancers, skin lesions, neurological impairment, cardiovascular diseases, and an increased susceptibility to infection. Among those exposed to iAs, the developing fetus and young children represent particularly sensitive subpopulations. Specifically, it has been noted in animal models and human populations that prenatal and early life iAs exposures are associated with diseases occurring during childhood and later in life. Recent epidemiologic and toxicologic studies have also demonstrated that epigenetic alterations may play a key mechanistic role underlying many of the iAs-associated health outcomes, including the carcinogenic and immunologic effects of exposure. This review summarizes some of the key studies related to prenatal and early life iAs exposure and highlights the complexities in isolating the precise developmental windows of exposure associated with these health outcomes.

Effect of Terminalia arjuna bark powder on some diagnostic enzymes in buffalo (Bubalus bubalis) ingesting arsenic contaminated water and fodder

Aim:

The study investigated the effect of Terminalia arjuna bark powder on some diagnostic enzymes related to hepatic and muscle function in buffaloes ingesting arsenic contaminated water and fodder in an arsenic affected area.

Materials and Methods:

A total of 25 samples of tube well water, fodder and buffalo blood were collected through a survey from arsenic contaminated areas and 20 samples from the uncontaminated, i.e., control areas of Ludhiana district, Punjab for determination of arsenic concentration. A total of 30 buffaloes (selected from above 45 animals) were divided into three groups of 10 each on the basis of blood arsenic level, viz., control group: Clinically healthy buffaloes from the uncontaminated area with the blood arsenic level within the normal limit (0-0.05 ppm); Arsenic exposed group: Buffaloes exposed to arsenic through intake of contaminated water and fodder in the arsenic affected area with the blood arsenic level above the normal limit of 0-0.05 ppm; treatment group: Arsenic exposed buffaloes treated with T. arjuna bark powder orally at 42 mg/kg b.w. OD for 30 days. Single blood samples were collected from control and arsenic exposed groups. Blood samples from the treatment group were collected on 0, 15^th, and 30^th day of treatment along with one sample on the 45^th day, i.e., after withdrawal of treatment. Activities of alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), and creatine kinase (CK) were assayed in plasma.

Results:

Significantly (p<0.05) higher arsenic concentration was observed in tube well water, fodder and buffalo blood samples collected from the arsenic contaminated area. A significant positive correlation was noticed between arsenic concentrations of tube well water, fodder and untreated buffalo blood samples, collected from the arsenic affected area. ALP, GGT, LDH, and CK activities were significantly (p<0.05) increased in the arsenic exposed buffaloes compared to control. Treatment with T. arjuna bark powder reduced the plasma levels of ALP, GGT, LDH, and CK in arsenic exposed buffaloes comparable to that of control.

Conclusion:

Exposure to arsenic altered the hepatic and muscle function enzymes in buffaloes. T. arjuna bark powder supplementation lowered the ALP, GGT, LDH, and CK activities in arsenic exposed buffaloes toward the values exhibited by the control group.

Dietary exposure of the Italian population to inorganic arsenic: The 2012-2014 Total Diet Study

Dietary exposure of the Italian population to inorganic arsenic has been assessed in the national Total Diet Study (TDS) carried out in 2012-2014. Within the TDS, food samples (>3000) were collected to be representative of the whole diet of the population, prepared as consumed, and pooled into 51 food groups, thus modelling the Italian diet. Inorganic arsenic was determined by HPLC-ICP-MS after chemical extraction and quantified in all samples. Occurrence data were combined with national individual consumption data to estimate mean and high level dietary exposure of the general population and of population subgroups according to age and gender, both at the national level and for each of the four main geographical areas of Italy. The intakes assessed are in the lower range of iAs exposure estimates in other European countries carried out without the support of the TDS approach. However, taking the lower limit of the BMDL₀₁ range established by the EFSA as reference point, the margins of exposure are <2 for the mean intake in infants and toddlers and <1 for the 95th percentile intakes in all younger age groups. Our results indicate the goal to check and further reduce the dietary exposure to inorganic arsenic.

Assessing multimedia/multipathway exposures to inorganic arsenic at population and individual level using MERLIN-Expo

In this study, we report on model simulations performed using the newly developed exposure tool, MERLIN-Expo, in order to assess inorganic arsenic (iAs) exposure to adults resulting from past emissions by non-ferrous smelters in Belgium (Northern Campine area). Exposure scenarios were constructed to estimate external iAs exposure as well as the toxicologically relevant As (tAs, i.e., iAs, MMA and DMA) body burden in adults living in the vicinity of the former industrial sites as compared to adults living in adjacent areas and a reference area. Two scenarios are discussed: a first scenario studying exposure to iAs at the aggregated population level and a second scenario studying exposure at the individual level for a random sub-sample of subjects in each of the three different study areas. These two scenarios only differ in the type of human related input data (i.e., time-activity data, ingestion rates and consumption patterns) that were used, namely averages (incl. probability density functions, PDFs) in the simulation at population level and subject-specific values in the simulation at individual level. The model predictions are shown to be lower than the corresponding biomonitoring data from the monitoring campaign. Urinary tAs levels in adults, irrespective of the area they lived in, were under-predicted by MERLIN-Expo by 40% on average. The model predictions for individual adults, by contrast, under-predict the biomonitoring data by 7% on average, but with more important under-predictions for subjects at the upper end of exposure. Still, average predicted urinary tAs levels from the simulations at population level and at individual level overlap, and, at least for the current case, lead to similar conclusions. These results constitute a first and partial verification of the model performance of MERLIN-Expo when dealing with iAs in a complex site-specific exposure scenario, and demonstrate the robustness of the modelling tool for these situations.

The hypothetical roles of arsenic in multiple sclerosis by induction of inflammation and aggregation of tau protein: A commentary

Multiple sclerosis (MS) is a disease which manifests demyelination of neuronal cells in the brain. Despite extensive research on the mechanisms of disease development and progression, the exact mechanism is not elucidated yet, which has hampered drug development and subsequent treatment of the disease. We have recently shown that the serum levels of arsenic and malondialdehyde, a lipid peroxidation marker, are high in MS patients. In this article, we would like to formulate the hypothesis that arsenic may cause MS by induction of inflammation, degeneration, and apoptosis in neuronal cells. The induction of ROS generation in cells upon exposure to arsenic as a heavy metal may be involved in the pathogenesis of MS. Tau protein, a member of the family of microtubule-associated proteins, is mainly expressed in neurons and contribute to the assembly of neuronal microtubules network. Arsenic may affect the hyperphosphorylation and aggregation of tau proteins and may be involved in the cascade leading to deregulation of tau function associated with neurodegeneration. For validation of this hypothesis, studies might be conducted to evaluate the association of arsenic levels and tau protein levels in MS patients. Further studies might also focus on the trafficking along microtubules in neurons of MS patient with regard to hyperphosphorylation of tau protein. This hypothesis may add a new dimension to the understanding of MS etiology and help to design novel therapeutic agents against potential targets that might be discovered. If this hypothesis proves to be true, tau phosphorylation inhibitors can be potential candidates for MS drug development.

Chronic Ingestion of Coal Fly-Ash Contaminated Prey and Its Effects on Health and Immune Parameters in Juvenile American Alligators (Alligator mississippiensis)

Coal-burning power plants supply approximately 37 % of the electricity in the United States. However, incomplete combustion produces ash wastes enriched with toxic trace elements that have historically been disposed of in aquatic basins. Organisms inhabiting such habitats may accumulate these trace elements; however, studies investigating the effects on biota have been primarily restricted to shorter-lived, lower-trophic organisms. The American alligator (Alligator mississippiensis), a long-lived, top-trophic carnivore, has been observed inhabiting these basins, yet the health or immune effects of chronic exposure and possible accumulation remains unknown. In this study, we investigated how chronic dietary ingestion of prey contaminated with coal combustion wastes (CCWs) for 25 months, and subsequent accumulation of trace elements present in CCWs, affected juvenile alligator immune function and health. Alligators were assigned to one of four dietary-treatment groups including controls and those fed prey contaminated with CCWs for one, two, or three times a week. However, no effect of Dietary Treatment (p > 0.05) was observed on any immune parameter or hematological or plasma analyte we tested. Our results suggest that neither exposure to nor accumulation of low doses of CCWs had a negative effect on certain aspects of the immune and hematological system. However, future studies are required to elucidate this further.

The immune responses and expression of metallothionein (MT) gene and heat shock protein 70 (HSP 70) in juvenile rockfish, Sebastes schlegelii, exposed to waterborne arsenic (As3+)

Juvenile rockfish, Sebastes schlegelii (mean length 16.4±1.9cm, and mean weight 71.6±6.4g) were exposed for 20days with the different levels of waterborne arsenic concentration (0, 50, 100, 200 and 400μg/L). The plasma cortisol of S. schlegelii was significantly increased by the waterborne arsenit exposure. In the immune responses, the immunoglobulin M (Ig M) and lysozyme activity of S. schlegelii were significantly increased by the waterborne arsenic exposure. The acetylcholinesterase (AChE) activity of S. schlegelii was inhibited by the waterborne arsenic exposure. The substantial increases in the gene expression such as metallothionein (MT) and heat shock protein 70 (HSP 70) were observed by the waterborne arsenic exposure. The results demonstrated that waterborne arsenic exposure can induce the significant alterations in the immune responses and specific gene expression of S. schlegelii.

Assessment of health risks due to arsenic from iron ore lumps in a beach setting

In 2011, an artificial hook-shaped peninsula of 128ha beach area was created along the Dutch coast, containing thousands of iron ore lumps, which include arsenic from natural origin. Elemental arsenic and inorganic arsenic induce a range of toxicological effects and has been classified as proven human carcinogens. The combination of easy access to the beach and the presence of arsenic raised concern about possible human health effects by the local authorities. The objective of this study is therefore to investigate human health risks from the presence of arsenic-containing iron ore lumps in a beach setting. The exposure scenarios underlying the human health-based risk limits for contaminated land in The Netherlands, based on soil material ingestion and a residential setting, are not appropriate. Two specific exposure scenarios related to the playing with iron ore lumps on the beach ('sandcastle building') are developed on the basis of expert judgement, relating to children in the age of 2 to 12years, i.e., a worst case exposure scenario and a precautionary scenario. Subsequently, exposure is calculated by the quantification of the following factors: hand loading, soil-mouth transfer effectivity, hand-mouth contact frequency, contact surface, body weight and the relative oral bioavailability factor. By lack of consensus on a universal reference dose for arsenic for use in the stage of risk characterization, three different types of assessments have been evaluated: on the basis of the current Provisional Tolerable Daily Intake (PTWI), on the basis of the Benchmark Dose Lower limit (BMDL), and by a comparison of exposure from the iron ore lumps with background exposure. It is concluded, certainly from the perspective of the conservative exposure assessment, that unacceptable human health risks due to exposure to arsenic from the iron ore lumps are unlikely and there is no need for risk management actions.

Anticancer effect of arsenite on cell migration, cell cycle and apoptosis in human pancreatic cancer cells

The standard treatment for advanced pancreatic cancer is chemotherapy, but its clinical outcome remains unsatisfactory. Therefore, the development of novel treatments for this malignancy is urgently required. In the present study, the anticancer effect of arsenite on platelet-derived growth factor (PDGF)-BB-induced migration, cell cycle and apoptosis was investigated in pancreatic cancer cells (AsPC-1 and BxPC-3), and compared with the effect on normal pancreatic epithelial (PE) cells. In the cell migration assay, arsenite clearly inhibited PDGF-BB-induced cell migration in AsPC-1 cells, but not in BxPC-3 or PE cells. Arsenite also caused cell apoptosis in AsPC-1 cells, but not in BxPC-3 or PE cells. In AsPC-1 cells, the levels of cyclin D1 and phosphorylated retinoblastoma protein decreased following treatment with arsenite, but this was not observed in BxPC-3 cells. To further examine the differences between these two cell lines, the effect of arsenite on upstream p44/p42 mitogen-activated protein kinase (MAPK) and Akt was investigated. PDGF-BB caused phosphorylation of p44/p42 MAPK and Akt in both cell lines. Pretreatment with arsenite significantly suppressed PDGF-BB-induced phosphorylation of Akt, but not of p44/p42 MAPK in AsPC-1 cells. By contrast, arsenite did not affect these molecules in BxPC-3 cells. Since the inhibition of the Akt signaling pathway markedly reduced PDGF-BB-induced migration in AsPC-1 cells, the present results strongly suggest that arsenite inhibits PDGF-BB-induced migration by suppressing the Akt signaling pathway in AsPC-1 cells. Therefore, arsenite may be a useful tool for the treatment of patients with certain types of pancreatic cancer, without causing adverse effects on normal pancreatic cells.

Arsenic-induced dose-dependent modulation of the NF-κB/IL-6 axis in thymocytes triggers differential immune responses

Arsenic contamination of drinking water is a matter of global concern. Arsenic intake impairs immune responses and leads to a variety of pathological conditions including cancer. In order to understand the intricate tuning of immune responses elicited by chronic exposure to arsenic, a mouse model was established by subjecting mice to different environmentally relevant concentrations of arsenic in drinking water for 30days. Detailed study of the thymus, a primary immune organ, revealed arsenic-mediated tissue damage in both histological specimens and scanning electron micrographs. Analysis of molecular markers of apoptosis by Western blot revealed a dose-dependent activation of the apoptotic cascade. Enzymatic assays supported oxidative stress as an instigator of cell death. Interestingly, assessment of inflammatory responses revealed disparity in the NF-κB/IL-6/STAT3 axis, where it was found that in animals consuming higher amounts of arsenic NF-κB activation did not lead to the classical IL-6 upregulation response. This deviation from the canonical pathway was accompanied with a significant rise in numbers of CD4+ CD25+ FoxP3 expressing cells in the thymus. The cytokine profile of the animals exposed to higher doses of arsenic also indicated an immune-suppressed milieu, thus validating that arsenic shapes the immune environment in context to its dose of exposure and that at higher doses it leads to immune-suppression. Our study establishes a novel role of arsenic in regulating immune homeostasis in context to its dose, where, at higher doses, arsenic related upregulation of NF-κB cascade takes on an alternative role that is correlated with increased immune-suppression.

Infant Infections and Respiratory Symptoms in Relation to in Utero Arsenic Exposure in a U.S. Cohort

BACKGROUND

Arsenic has been linked to disrupted immune function and greater infection susceptibility in highly exposed populations. Well arsenic levels above the U.S. EPA limit occur in our U.S. study area and are of particular concern for pregnant women and infants.

OBJECTIVES

We investigated whether in utero arsenic exposure affects the risk of infections and respiratory symptoms over the first year of life.

METHODS

We prospectively obtained information on infant infections and symptoms, including their duration and treatment (n = 412) at 4, 8, and 12 months using a parental telephone survey. Using generalized estimating equation models adjusted for potential confounders, we evaluated the association between maternal pregnancy urinary arsenic and infant infections and symptoms over the first year.

RESULTS

Each doubling of maternal urinary arsenic was related to increases in the total number of infections requiring prescription medication in the first year [relative risk (RR) = 1.1; 95% CI: 1.0, 1.2]. Urinary arsenic was related specifically to respiratory symptoms (difficulty breathing, wheezing, and cough) lasting ≥ 2 days or requiring prescription medication (RR = 1.1; 95% CI: 1.0, 1.2; and RR = 1.2; 95% CI: 1.0, 1.5, respectively), and wheezing lasting ≥ 2 days, resulting in a doctor visit or prescription medication treatment (RR = 1.3; 95% CI: 1.0, 1.7; RR = 1.3; 95% CI: 1.0, 1.8, and RR = 1.5; 95% CI: 1.0, 2.2, respectively). Associations also were observed with diarrhea (RR = 1.4; 95% CI: 1.1, 1.9) and fever resulting in a doctor visit (RR = 1.2; 95% CI: 1.0, 1.5).

CONCLUSIONS

In utero arsenic exposure was associated with a higher risk of infection during the first year of life in our study population, particularly infections requiring medical treatment, and with diarrhea and respiratory symptoms.

CITATION

Farzan SF, Li Z, Korrick SA, Spiegelman D, Enelow R, Nadeau K, Baker E, Karagas MR. 2016. Infant infections and respiratory symptoms in relation to in utero arsenic exposure in a U.S.

COHORT

Environ Health Perspect 124:840-847; http://dx.doi.org/10.1289/ehp.1409282.

Arsenic Trioxide Attenuates NF-κB and Cytokine mRNA Levels in the Livers of Cocks

Arsenic (As) is a trace element widely found in nature. It exists in several forms, including organic arsenic, inorganic arsenic, and trivalent arsenic, the most toxic. Arsenic trioxide (As2O3) is widespread in nature. This form tends to accumulate in animals and humans and therefore has a potential harm for them. Cytokines play essential roles in the immune response and inflammation. Although the importance of cytokines in the responses to arsenic exposure has been demonstrated in many types of mammals, the function of these in poultry, especially in chickens, remains unclear. The purpose of the present study was to examine the effect of As2O3 exposure on cytokines in cock livers. In this study, 72 1-day-old male Hy-line cocks were randomly divided into four groups including the control group, low-As group, middle-As group, and high-As group. The livers were collected on days 30, 60, and 90 of the experiment. The levels of nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-12 beta (IL-12β), and interleukin-1 beta (IL-1β) mRNA in the livers of the cocks were measured using real-time PCR. The results showed that the expression levels of IL-6, IL-8, TNF-α, and NF-κB which seemed to be a critical mediator in the inflammatory response tended to increase in the birds chronically treated with As2O3. However, the mRNA expression levels of IL-4, IL-12β, and IL-1β were decreased in the experiment. The information regarding the effects of As2O3 on cytokine mRNA expression generated in this study will be important information for arsenic toxicology evaluation.

A possible new mechanism and drug intervention for kidney damage due to arsenic poisoning in rats

Arsenic poisoning is a worldwide endemic disease that affects thousands of people. Currently, the aetiology of the disease is known, but its pathogenesis is uncharacterized and there is no specific treatment. We established a rat model of coal-burning arsenic poisoning by feeding the animals corn powder baked with high arsenic coal. By observing subsequent changes in kidney and immune function, we found that arsenic induces both kidney and immune damage. Furthermore, there is a significant correlation between kidney and immune damage. Moreover, Ginkgo biloba, a known immune enhancer, was used as an intervention agent in arsenic poisoned rats to validate the relationship between kidney and immune damage. Meanwhile, we also explored the mechanism of Ginkgo biloba treatment of kidney damage in burning-coal arsenic poisoned rats. We found that Ginkgo biloba enhanced immune function in rats with arsenic poisoning and ameliorated arsenic-induced kidney damage. These results suggest that immune suppression may be one of the mechanisms underlying arsenic-induced kidney damage and that Ginkgo biloba might relieve kidney damage by enhancing immune function.

Heat Shock Protein Alteration in the Gastrointestinal Tract Tissues of Chickens Exposed to Arsenic Trioxide

Arsenic (As) is widely distributed in our living environment and is useful for industry, agriculture, medical treatment, and other fields. Arsenic trioxide (As2O3) is an existing form of As. Exposure to As2O3 has a toxic effect on humans and animals. It not only leads to skin cancer, peripheral vascular disease, hyperkeratosis, etc. but also interferes with the functioning of the gastrointestinal tract. The gastrointestinal tract is an important organ for animals to transform the food they eat into the nutrients their body needs for maintenance and growth. Heat shock proteins (Hsps) exist in the non-stress normal cells and their expression increases under stimuli. Therefore, we wonder whether the "stimulus" of As2O3 could change the messenger RNA (mRNA) abundance and expression level of Hsps in the gastrointestinal tract of birds. To investigate the relation between arseniasis and Hsp alterations in the chicken's gastrointestinal tract induced by an As2O3-supplemented diet, we selected 72 one-day-old male Hy-line chickens and randomly divided them into four groups. They were fed either a commercial diet or an As2O3-supplemented diet containing 7.5, 15, and 30 mg/kg As2O3. The experiment lasted for 90 days, and gastrointestinal tract tissue samples (gizzard, glandular stomach, duodenum, jejunum, ileum, cecum, and rectum) were collected at 30, 60, and 90 days. The mRNA contents of Hsps (including Hsp27, Hsp40, Hsp60, Hsp70, and Hsp90) were examined by real-time PCR (RT-PCR). The correlation between As2O3 and Hsp genes was assessed. In addition, the protein expression levels of Hsp60 and Hsp70 in the gastrointestinal tract tissue samples were measured by western blot. The results indicated that the mRNA expression levels and the Hsp expression levels in the gastrointestinal tract tissues of chickens with As2O3 supplementation increased at different time points in a dose-dependent manner (p < 0.05 or p < 0.01). These data suggested that arseniasis influenced the mRNA abundance of Hsp27, Hsp40, Hsp60, Hsp70, and Hsp90 and the protein expression levels of Hsp60 and Hsp70 in the chicken's gastrointestinal tract tissues.

Environmentally relevant concentrations of arsenite and monomethylarsonous acid inhibit IL-7/STAT5 cytokine signaling pathways in mouse CD3+CD4-CD8- double negative thymus cells

Environmental arsenic exposure is a public health issue. Immunotoxicity induced by arsenic has been reported in humans and animal models. The purpose of this study was to evaluate mechanisms of As(+3) and MMA(+3) toxicity in mouse thymus cells. Because we know that MMA(+3) inhibits IL-7 signaling in mouse bone marrow pre-B cells, we studied the influence of As(+3) and MMA(+3) on T cell development in the thymus at the earliest stage of T cell development (CD4-CD8-, double negative, DN) which requires IL-7 dependent signaling. We found in a DN thymus cell line (D1) that a low concentration of MMA(+3) (50 nM) suppressed IL-7 dependent JAK1, 3 and STAT5 signaling. As(+3) suppressed STAT5 and JAK3 at higher concentrations (500 nM). Cell surface expression of the IL-7 receptor (CD127) was also suppressed by 50 nM MMA(+)3, but was increased by 500 NM As(+3), indicating possible differences in the mechanisms of action of these agents. A decrease in cyclin D1 protein expression was observed in D1 cells exposed to As(+3) at 500 nM and MMA(+3) starting at 50 nM, suggesting that arsenic at these environmentally-relevant doses suppresses early T cell development through the inhibition of IL-7 signaling pathway.

Mechanisms Underlying Latent Disease Risk Associated with Early-Life Arsenic Exposure: Current Research Trends and Scientific Gaps

BACKGROUND

Millions of individuals worldwide, particularly those living in rural and developing areas, are exposed to harmful levels of inorganic arsenic (iAs) in their drinking water. Inorganic As exposure during key developmental periods is associated with a variety of adverse health effects, including those that are evident in adulthood. There is considerable interest in identifying the molecular mechanisms that relate early-life iAs exposure to the development of these latent diseases, particularly in relationship to cancer.

OBJECTIVES

This work summarizes research on the molecular mechanisms that underlie the increased risk of cancer development in adulthood that is associated with early-life iAs exposure.

DISCUSSION

Epigenetic reprogramming that imparts functional changes in gene expression, the development of cancer stem cells, and immunomodulation are plausible underlying mechanisms by which early-life iAs exposure elicits latent carcinogenic effects.

CONCLUSIONS

Evidence is mounting that relates early-life iAs exposure and cancer development later in life. Future research should include animal studies that address mechanistic hypotheses and studies of human populations that integrate early-life exposure, molecular alterations, and latent disease outcomes.

Arsenic exposure and the seroprevalence of total hepatitis A antibodies in the US population: NHANES, 2003-2012

We evaluated the association between urinary arsenic and the seroprevalence of total hepatitis A antibodies (total anti-HAV: IgG and IgM) in 11 092 participants aged ⩾6 years using information collected in the US National Health and Nutrition Examination Survey (2003–2012). Multivariate logistic regression models evaluated associations between total anti-HAV and total urinary arsenic defined as the sum of arsenite, arsenate, monomethylarsonate and dimethylarsinate (TUA1). Effect modification by self-reported HAV immunization status was evaluated. Total anti-HAV seroprevalence was 35·1% [95% confidence interval (CI) 33·3–36·9]. Seropositive status was associated with higher arsenic levels and this association was modified by immunization status (P = 0·03). For participants that received ⩾2 vaccine doses or did not know if they had received any doses, a positive dose-response association was observed between increasing TUA1 and odds of total anti-HAV [odds ratio (OR) 1·42, 95% CI 1·11–1·81; and OR 1·75, 95% CI 1·22–2·52], respectively. A positive but not statistically significant association was observed in those who received <2 doses (OR 1·46, 95% CI 0·83–2·59) or no dose (OR 1·12, 95% CI 0·98–1·30). Our analysis indicates that prevalent arsenic exposure was associated with positive total anti-HAV seroprevalence. Further studies are needed to determine if arsenic increases the risk for incident hepatitis A infection or HAV seroconversion.

Lysosomal membrane response of the earthworm, Eisenia fetida, to arsenic species exposure in OECD soil

The NRRT assay was sensitive for toxicity assessment of inorganic arsenic pollution and it was affected more by As(iii) than by As(v).

Implications of the Differential Toxicological Effects of III-V Ionic and Particulate Materials for Hazard Assessment of Semiconductor Slurries

Because of tunable band gaps, high carrier mobility, and low-energy consumption rates, III-V materials are attractive for use in semiconductor wafers. However, these wafers require chemical mechanical planarization (CMP) for polishing, which leads to the generation of large quantities of hazardous waste including particulate and ionic III-V debris. Although the toxic effects of micron-sized III-V materials have been studied in vivo, no comprehensive assessment has been undertaken to elucidate the hazardous effects of submicron particulates and released III-V ionic components. Since III-V materials may contribute disproportionately to the hazard of CMP slurries, we obtained GaP, InP, GaAs, and InAs as micron- (0.2-3 μm) and nanoscale (<100 nm) particles for comparative studies of their cytotoxic potential in macrophage (THP-1) and lung epithelial (BEAS-2B) cell lines. We found that nanosized III-V arsenides, including GaAs and InAs, could induce significantly more cytotoxicity over a 24-72 h observation period. In contrast, GaP and InP particulates of all sizes as well as ionic GaCl3 and InCl3 were substantially less hazardous. The principal mechanism of III-V arsenide nanoparticle toxicity is dissolution and shedding of toxic As(III) and, to a lesser extent, As(V) ions. GaAs dissolves in the cell culture medium as well as in acidifying intracellular compartments, while InAs dissolves (more slowly) inside cells. Chelation of released As by 2,3-dimercapto-1-propanesulfonic acid interfered in GaAs toxicity. Collectively, these results demonstrate that III-V arsenides, GaAs and InAs nanoparticles, contribute in a major way to the toxicity of III-V materials that could appear in slurries. This finding is of importance for considering how to deal with the hazard potential of CMP slurries.

A Community-Driven Intervention in Tuftonboro, New Hampshire, Succeeds in Altering Water Testing Behavior

Maximum contaminant levels created by the U.S. Environmental Protection Agency under the Safe Drinking Water Act do not apply to private wells. Rather, the onus is on individual households to undertake regular water testing. Several barriers exist to testing and treating water from private wells, including a lack of awareness about both well water as a potential source of contaminants and government-recommended water testing schedules; a health literacy level that may not be sufficient to interpret complex environmental health messages; the inconvenience of water testing; the financial costs of testing and treatment; and a myriad of available treatment options. The existence of these barriers is problematic because well water can be a source of hazardous contaminants. This article describes an initiative--undertaken by the Tuftonboro (New Hampshire) Conservation Commission, with support from state agencies and a research program at Dartmouth College--to increase water testing rates in a rural region with a relatively high number of wells. The project prompted more water tests at the state laboratory in one day than in the prior six years. This suggests that community-driven, collaborative efforts to overcome practical barriers could be successful at raising testing rates and ultimately improving public health.

Monomethylarsonous Acid (MMAIII) Has an Adverse Effect on the Innate Immune Response of Human Bronchial Epithelial Cells to Pseudomonas aeruginosa

Arsenic is the number one contaminant of concern with regard to human health according to the World Health Organization. Epidemiological studies on Asian and South American populations have linked arsenic exposure with an increased incidence of lung disease, including pneumonia, and chronic obstructive pulmonary disease, both of which are associated with bacterial infection. However, little is known about the effects of low dose arsenic exposure, or the contributions of organic arsenic to the innate immune response to bacterial infection. This study examined the effects on Pseudomonas aeruginosa (P. aeruginosa) induced cytokine secretion by human bronchial epithelial cells (HBEC) by inorganic sodium arsenite (iAs^III) and two major metabolites, monomethylarsonous acid (MMA^III) and dimethylarsenic acid (DMA^V), at concentrations relevant to the U.S. population. Neither iAs^III nor DMA^V altered P. aeruginosa induced cytokine secretion. By contrast, MMA^III increased P. aeruginosa induced secretion of IL-8, IL-6 and CXCL2. A combination of iAs^III, MMA^III and DMA^V (10 pbb total) reduced IL-8 and CXCL1 secretion. These data demonstrate for the first time that exposure to MMA^III alone, and a combination of iAs^III, MMA^III and DMA^V at levels relevant to the U.S. may have negative effects on the innate immune response of human bronchial epithelial cells to P. aeruginosa.

Nrf2-dependent repression of interleukin-12 expression in human dendritic cells exposed to inorganic arsenic

Inorganic arsenic, a well-known Nrf2 inducer, exerts immunosuppressive properties. In this context, we recently reported that the differentiation of human blood monocytes into immature dendritic cells (DCs), in the presence of low and noncytotoxic concentrations of arsenic, represses the ability of DCs to release key cytokines in response to different stimulating agents. Particularly, arsenic inhibits the expression of human interleukin-12 (IL-12, also named IL-12p70), a major proinflammatory cytokine that controls the differentiation of Th1 lymphocytes. In the present study, we determined if Nrf2 could contribute to these arsenic immunotoxic effects. To this goal, human monocyte-derived DCs were first differentiated in the absence of metalloid and then pretreated with arsenic just before DC stimulation with lipopolysaccharide (LPS). Under these experimental conditions, arsenic rapidly and stably activates Nrf2 and increases the expression of Nrf2 target genes. It also significantly inhibits IL-12 expression in activated DCs, at both mRNA and protein levels. Particularly, arsenic reduces mRNA levels of IL12A and IL12B genes which encodes the p35 and p40 subunits of IL-12p70, respectively. tert-Butylhydroquinone (tBHQ), a reference Nrf2 inducer, mimics arsenic effects and potently inhibits IL-12 expression. Genetic inhibition of Nrf2 expression markedly prevents the repression of both IL12 mRNA and IL-12 protein levels triggered by arsenic and tBHQ in human LPS-stimulated DCs. In addition, arsenic significantly reduces IL-12 mRNA levels in LPS-activated bone marrow-derived DCs from Nrf2+/+ mice but not in DCs from Nrf2-/- mice. Finally, we show that, besides IL-12, arsenic significantly reduces the expression of IL-23, another heterodimer containing the p40 subunit. In conclusion, our study demonstrated that arsenic represses IL-12 expression in human-activated DCs by specifically stimulating Nrf2 activity.

Environmentally Relevant Concentrations of Arsenite Induce Dose-Dependent Differential Genotoxicity Through Poly(ADP-Ribose) Polymerase Inhibition and Oxidative Stress in Mouse Thymus Cells

Inhibition of DNA repair and oxidative stress are 2 common mechanisms associated with arsenic-induced genotoxicity. The purpose of this study was to examine mechanisms of genotoxicity induced by environmentally relevant doses of arsenite (As(+3)) in mouse thymus cells. An increase in DNA damage and a decrease in poly(ADP-ribose) polymerase (PARP) activity were seen in vitro following exposure to 50 nM As(+3) in primary mouse thymus cells and a murine thymus pre-T cell line, D1. 3,4-Dihydro-5[4-(1-piperindinyl) butoxyl]-1(2H)-isoquinoline, a well-characterized PARP inhibitor, also produced DNA damage in D1 cells, confirming the correlation between PARP inhibition and DNA damage increase. As(+3) at 500 nM induced double strand breaks (DSBs) in DNA and oxidative stress at 4 h in D1 cells, which was reversed at 18 h. No apoptosis or decrease of viability was observed in these exposures. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, a widely-used antioxidant, was utilized to confirm that oxidative stress is partially responsible for the increase of strand breaks in 500 nM As(+3) exposure at 4 h. Expression of As(+3) exporters, Mdr1 and Mrp1, were found to be induced by 500 nM As(+3) in D1 cells, suggesting a possible mechanism for reversal of oxidative stress and DSBs at the 18-h timepoint. Finally, we showed that DNA damage and PARP inhibition by As(+3) were reversed by zinc (Zn(+2)) at approximate equimolar doses. Collectively, these results demonstrate that As(+3) at doses within the nanomolar range induce genotoxicity by inhibiting PARP, and produces oxidative stress at higher concentrations, which can be reversed by a Zn(+2) treatment.