Arsenic Exposure and Immunotoxicity: a Review Including the Possible Influence of Age and Sex

Integration of proteomics and metabolomics analysis investigate mechanism of As-induced immune injury in rat spleen

Arsenic (As) is a widespread metalloid and human carcinogen found in the natural environment, and multiple toxic effects have been shown to be associated with As exposure. As can be accumulated in the spleen, the largest peripheral lymphatic organ, and long-term exposure to As can lead to splenic injury. In this study, a Sprague-Dawley (SD) rat model of As-poisoned was established, aiming to explore the molecular mechanism of As-induced immune injury through the combined analysis of proteomics and metabolomics of rats' spleen. After feeding the rats with As diet (50 mg/kg) for 90 days, the spleen tissue of the rats in the As-poisoned group was damaged, the level of As was significantly higher than that of the control group (P < 0.001), and the level of inflammatory cytokine interleukin-6 (IL-6) was decreased (P < 0.01). Proteomics and metabolomics results showed that a total of 134 differentially expressed proteins (DEPs) (P < 0.05 and fold change > 1.2) and 182 differentially expressed metabolites (DEMs) (VIP >1 and P < 0.05) were identified in the spleens of the As poisoned group compared to the control group (As/Ctrl). The proteomic results highlight the role of hypoxia-inducible factors (HIF), natural killer cell mediated cytotoxicity, and ribosomes. The major pathways of metabolic disruption included arachidonic acid (AA) metabolism, glycerophospholipid metabolism and folate single-carbon pool. The integrated analysis of these two omics suggested that Hmox1, Stat3, arachidonic acid, phosphatidylcholine and leukotriene B4 may play key roles in the mechanism of immune injury to the spleen by As exposure. The results indicate that As exposure can cause spleen damage in rats. Through proteomic and metabolomic analysis, the key proteins and metabolites and their associated mechanisms were obtained, which provided a basis for further understanding of the molecular mechanism of spleen immune damage caused by As exposure.

The mitochondria-targeted antioxidant MitoQ ameliorates inorganic arsenic-induced DCs/Th1/Th2/Th17/Treg differentiation partially by activating PINK1-mediated mitophagy in murine liver

Inorganic arsenic is a well-established environmental toxicant linked to acute liver injury, fibrosis, and cancer. While oxidative stress, pyroptosis, and ferroptosis are known contributors, the role of PTEN-induced kinase 1 (PINK1)-mediated mitophagy in arsenic-induced hepatic immunotoxicity remains underexplored. Our study revealed that acute arsenic exposure prompts differentiation of hepatic dendritic cells (DCs) and T helper (Th) 1, Th2, Th17, and regulatory T (Treg) cells, alongside increased transcription factors and cytokines. Inorganic arsenic triggered liver redox imbalance, leading to elevated alanine transaminase (ALT), hydrogen peroxide (H2O2), malondialdehyde (MDA), and activation of nuclear factor erythroid 2-related factor (Nrf2)/heme oxygenase-1 (HO-1) pathway. PINK1-mediated mitophagy was initiated, and its inhibition exacerbates H2O2 accumulation while promoting DCs/Th1/Th2/Treg differentiation in the liver of arsenic-exposed mice. Mitoquinone (MitoQ) pretreatment relieved arsenic-induced acute liver injury and immune imbalance by activating Nrf2/HO-1 and PINK1-mediated mitophagy. To our knowledge, this is the first report identifying PINK1-mediated mitophagy as a protective factor against inorganic arsenic-induced hepatic DCs/Th1/Th2 differentiation. This study has provided new insights on the immunotoxicity of inorganic arsenic and established a foundation for exploring preventive and therapeutic strategies targeting PINK1-mediated mitophagy in acute liver injury. Consequently, the application of mitochondrial antioxidant MitoQ may offer a promising treatment for the metalloid-induced acute liver injury.

Arsenic exposure is associated with alterations to multiple red blood cell parameters among adults in rural Bangladesh

Chronic arsenic exposures are associated with multiple hematologic disturbances, including anemia. The goal of this study was to evaluate associations between arsenic exposures and hematological parameters among men and women who are chronically exposed to elevated levels of arsenic from drinking water. Hematologic analyses were performed on blood collected from 755 participants (45% male and 54% female) in the Health Effects of Arsenic Longitudinal Study (HEALS) cohort, Bangladesh. Herein, we used linear regression models to estimate associations between red blood cell (RBC) parameters (i.e., RBC counts, hematocrit (HCT), hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)) and measurements of arsenic exposure (urinary arsenic and urinary arsenic metabolites). Arsenic exposures showed trending associations with decreased RBC counts in both men and women, a positive association with MCV in males, and an inverse association with MCHC among males, but not among non-smoking females. Among men, those who smoked had stronger associations between arsenic exposures and MCHC than non-smoking males. Collectively, our results show that arsenic exposures affect multiple RBC parameters and highlight potentially important sex differences in arsenic-induced hematotoxicity.

An in vitro medium for modeling gut dysbiosis associated with cystic fibrosis

The gut physiology of pediatric and adult persons with cystic fibrosis (pwCF) is altered relative to healthy persons. The CF gut is characterized, in part, as having excess mucus, increased fat content, acidic pH, increased inflammation, increased antibiotic perturbation, and the potential for increased oxygen availability. These physiological differences shift nutritional availability and the local environment for intestinal microbes, thus likely driving significant changes in microbial metabolism, colonization, and competition with other microbes. The impact of any specific change in this physiological landscape is difficult to parse using human or animal studies. Thus, we have developed a novel culture medium representative of the CF gut environment, inclusive of all the aforementioned features. This medium, called CF-MiPro, maintains CF gut microbiome communities, while significantly shifting nonCF gut microbiome communities toward a CF-like microbial profile, characterized by low Bacteroidetes and high Proteobacteria abundance. This medium is able to maintain this culture composition for up to 5 days of passage. Additionally, microbial communities passaged in CF-MiPro produce significantly less immunomodulatory short-chain fatty acids (SCFA), including propionate and butyrate, than communities passaged in MiPro, a culture medium representative of healthy gut physiology, confirming not only a shift in microbial composition but also altered community function. Our results support the potential for this in vitro culture medium as a new tool for the study of CF gut dysbiosis. IMPORTANCE Cystic fibrosis is an autosomal recessive disease that disrupts ion transport at mucosal surfaces, leading to mucus accumulation and altered physiology of both the lungs and the intestines, among other organs, with the resulting altered environment contributing to an imbalance of microbial communities. Culture media representative of the CF airway have been developed and validated; however, no such medium exists for modeling the CF intestine. Here, we develop and validate a first-generation culture medium inclusive of features that are altered in the CF colon. Our findings suggest this novel medium, called CF-MiPro, as a maintenance medium for CF gut microbiome samples and a flexible tool for studying key drivers of CF-associated gut dysbiosis.

Association of arsenic exposure with measles antibody titers in US children: Influence of sex and serum folate levels

Exposure to arsenic during childhood is associated with various adverse health conditions. However, little is known about the effect of arsenic exposure on vaccine-related humoral immunity in children. We analyzed data from the National Health and Nutrition Examination Survey (2003-2004 and 2009-2010) to study the relationship between urinary arsenic and measles antibody levels in 476 US children aged 6-11. Multivariable linear regression was used to evaluate the association, adjusting for cycle, age, race, body mass index (BMI), serum cotinine, poverty index ratio, and vitamin B12 and selenium intakes. Stratified analyses were conducted by sex and serum folate levels using the median as cutoff (18.7 ng/mL). The measles antibody concentrations in the 3rd and 4th quartiles were found to have significantly decreased by 28.5 % (95 % Confidence Interval (CI) -47.6, -2.28) and 36.8 % (95 % CI -50.2, -19.5), compared to the lowest quartile among boys with serum folate levels lower than 18.7 ng/ml. The serum measles antibody titers significantly decreased by 16.7 % (95 %CI -25.0, -7.61) for each doubling of creatinine-corrected urinary total inorganic arsenic concentrations in the same group. No associations were found in boys with high serum folate levels or in girls. Further prospective studies are needed to validate these findings and develop interventions to protect children from infectious diseases.

Mechanisms of genotoxicity and proteotoxicity induced by the metalloids arsenic and antimony

Arsenic and antimony are metalloids with profound effects on biological systems and human health. Both elements are toxic to cells and organisms, and exposure is associated with several pathological conditions including cancer and neurodegenerative disorders. At the same time, arsenic- and antimony-containing compounds are used in the treatment of multiple diseases. Although these metalloids can both cause and cure disease, their modes of molecular action are incompletely understood. The past decades have seen major advances in our understanding of arsenic and antimony toxicity, emphasizing genotoxicity and proteotoxicity as key contributors to pathogenesis. In this review, we highlight mechanisms by which arsenic and antimony cause toxicity, focusing on their genotoxic and proteotoxic effects. The mechanisms used by cells to maintain proteostasis during metalloid exposure are also described. Furthermore, we address how metalloid-induced proteotoxicity may promote neurodegenerative disease and how genotoxicity and proteotoxicity may be interrelated and together contribute to proteinopathies. A deeper understanding of cellular toxicity and response mechanisms and their links to pathogenesis may promote the development of strategies for both disease prevention and treatment.

Trimester-specific effects of maternal exposure to single and mixed metals on cord serum inflammatory cytokines levels: A prospective birth cohort study

BACKGROUND

Cord blood inflammatory cytokines are vital in early-life programming. An increasing number of studies concern the effect of maternal exposure to different metal elements during pregnancy on inflammatory cytokines, but limited studies have explored the association between maternal exposure to mixed metals and cord blood inflammatory cytokine levels.

METHODS

We measured serum concentrations of vanadium (V), copper (Cu), arsenic (As), cadmium (Cd), and barium (Ba) in the first, second, and third trimesters and eight cord serum inflammatory cytokines (IFN-γ, IL-1β, IL-6, IL-8, IL-10, IL-12p70, IL-17A, and TNF-α) in 1436 mother-child dyads from the Ma'anshan Birth Cohort. Generalized linear models and Bayesian kernel machine regression (BKMR) were performed to assess the association of single and mixed metal exposure during each trimester with cord serum inflammatory cytokine levels, respectively.

RESULTS

Regarding metal exposure in the first trimester, V was positively associated with TNF-α (β = 0.33, 95 % CI: 0.13, 0.53); Cu was positively associated with IL-8 (β = 0.23, 95 % CI: 0.07, 0.39); Ba was positively associated with IFN-γ and IL-6; As was negatively associated with IFN-γ and IL-17A; and Cd was negatively associated with IFN-γ, IL-1β, IL-12p70, IL-17A, and TNF-α. BKMR revealed that exposure to metal mixtures in the first trimester was positively associated with IL-8 and TNF-α but negatively associated with IL-17A. Moreover, V contributed the most to these associations. Interaction effects were observed between Cd and As and between Cd and Cu with IL-8, and between Cd and V with IL-17A. Among males, As decreased inflammatory cytokines; among females, Cu increased inflammatory cytokine levels, whereas Cd decreased inflammatory cytokine concentrations.

CONCLUSIONS

Maternal exposure to metal mixtures in the first trimester interfered with cord serum inflammatory cytokine levels. The associations of maternal exposure to As, Cu and Cd with inflammatory cytokines showed sex differences. Further studies are warranted to support the findings and explore the mechanism of the susceptibility window and sex-specific disparity.

Comparison of circulating and excreted metals and of autoimmunity between two Great Plains Tribal communities

Metals contaminants of the environment from mine waste have been implicated as contributing agents in autoimmune disease. The current study compares metals and autoimmunity in two Tribal communities residing in the Black Hills and the Bighorn Mountains geographical regions that are scattered with extant hard rock mines. With documented drinking water contamination in both communities, in vivo levels of more than half of the measured serum and urine metals differed between the two communities and were substantially different from their national median values. Serum autoantibodies associated with systemic autoimmune disease were rare or at low-level, but antibodies to denatured (single-stranded) DNA and thyroid-specific autoantibodies were commonly elevated, especially in women. A three-tier statistical modeling process was carried out to examine individual metals exposure as predictors of autoantibody levels. For the most part only weak positive associations between individual metals and systemic autoantibodies were found, although univariate quantile regression analysis showed positive statistical associations of serum lead and antimony with anti-chromatin and anti-histone autoantibodies. Using age and gender-adjusted multivariable statistical models, metals did not predict anti-thyroglobulin or -thyroid peroxidase significantly and metals were generally negative predictors of the other autoantibodies. Overall these results suggest that elevated levels of environmental metals and metalloids in these communities may result in suppression of autoantibodies associated with systemic autoimmune disease.

An In Vitro Medium for Modeling Gut Dysbiosis Associated with Cystic Fibrosis

The gut physiology of pediatric and adult persons with cystic fibrosis (pwCF) is altered relative to healthy persons. The CF gut is characterized, in part, as having excess mucus, increased fat content, acidic pH, increased inflammation, increased antibiotic perturbation and the potential for increased oxygen availability. These physiological differences shift nutritional availability and the local environment for intestinal microbes, thus likely driving significant changes in microbial metabolism, colonization and competition with other microbes. The impact of any specific change in this physiological landscape is difficult to parse using human or animal studies. Thus, we have developed a novel culture medium representative of the CF gut environment, inclusive of all the aforementioned features. This medium, called CF-MiPro, maintains CF gut microbiome communities, while significantly shifting non-CF gut microbiome communities toward a CF-like microbial profile, characterized by low Bacteroidetes and high Proteobacteria abundance. This medium is able to maintain this culture composition for up to 5 days of passage. Additionally, microbial communities passaged in CF-MiPro produce significantly less immunomodulatory short chain fatty acids (SCFA), including propionate and butyrate, than communities passaged in MiPro, a culture medium representative of healthy gut physiology, confirming not only a shift in microbial composition but altered community function. Our results support the potential for this in vitro culture medium as a new tool for the study of gut dysbiosis in CF.

Transcriptomic Effects of Low-Dose Inorganic Arsenic Exposure on Murine Bone Marrow-Derived Macrophages

Both tissue-resident macrophages and monocytes recruited from the bone marrow that transform into tissue-resident cells play critical roles in mediating homeostasis as well as in the pathology of inflammatory diseases. Inorganic arsenic (iAs) is the most common drinking water contaminant worldwide and represents a major public health concern. Several diseases that macrophages have implicated involvement in are caused by iAs exposure, including cardiovascular disease, cancer, and increased risk of infectious disease. Therefore, understanding the effects of iAs exposure on macrophages can help us better grasp the full range of arsenic immunotoxicity and better design therapeutic targets for iAs-induced diseases particularly in exposed populations. In this study, we analyzed the transcriptome of low dose iAs-exposed male and female murine bone marrow-derived macrophages (BMDMs) with either M0, M1, or M2 stimulation. We identified differentially expressed genes by iAs in a sex- and stimulation-dependent manner and used bioinformatics tools to predict protein-protein interactions, transcriptional regulatory networks, and associated biological processes. Overall, our data suggest that M1-stimulated, especially female-derived, BMDMs are most susceptible to iAs exposure. Most notably, we observed significant downregulation of major proinflammatory transcription factors, like IRF8, and its downstream targets, as well as genes encoding proteins involved in pattern recognition and antigen presentation, such as TLR7, TLR8, and H2-D1, potentially providing causal insight regarding arsenic's role in perturbing immune responses to infectious diseases. We also observed significant downregulation of genes involved in processes crucial to coordinating a proinflammatory response including leukocyte migration, differentiation, and cytokine and chemokine production and response. Finally, we discovered that 24 X-linked genes were dysregulated in iAs-exposed female stimulation groups compared to only 3 across the iAs-exposed male stimulation groups. These findings elucidate the potential mechanisms underlying the sex-differential iAs-associated immune-related disease risk.

Early Environment and Telomeres: a Long-Term Toxic Relationship

PURPOSE OF REVIEW

Telomere length (TL) shortening is a hallmark of biological aging. While studies have extensively focused on the impact of environmental exposures on TL in older populations, consistent evidence indicates that prenatal environmental exposures to air pollutants, polycyclic aromatic hydrocarbons, metals, and endocrine-disrupting chemicals influence TL shortening. Here, we summarize evidence linking prenatal environmental exposures with children's TL and discuss potential long-term effects.

RECENT FINDINGS

Current evidence shows that prenatal environmental exposures alter TL and identify pregnancy as a critical window of susceptibility for telomere damage in children. However, results vary across studies, possibly depending on the source, exposure time window, and stage evaluated. Additional research is needed to investigate whether early TL alterations mediate long-term health effects of offspring. Prenatal environmental exposures induce early childhood changes in TL. Based on known links between TL and biological aging, these alterations may have long-term impact on individuals' health throughout life.

Trace elements in Foodstuffs from the Mediterranean Basin-Occurrence, Risk Assessment, Regulations, and Prevention strategies: A review

Trace elements (TEs) are chemical compounds that naturally occur in the earth's crust and in living organisms at low concentrations. Anthropogenic activities can significantly increase the level of TEs in the environment and finally enter the food chain. Toxic TEs like cadmium, lead, arsenic, and mercury have no positive role in a biological system and can cause harmful effects on human health. Ingestion of contaminated food is a typical route of TEs intake by humans. Recent data about the occurrence of TEs in food available in the Mediterranean countries are considered in this review. Analytical methods are also discussed. Furthermore, a discussion of existing international agency regulations will be given. The risk associated with the dietary intake of TEs was estimated by considering consumer exposure and threshold values such as Benchmark dose lower confidence limit and provisional tolerable weekly intake established by the European Food Safety Authority and the Joint FAO/WHO Expert Committee on Food Additives, respectively. Finally, several remediation approaches to minimize TE contamination in foodstuffs were discussed including chemical, biological, biotechnological, and nanotechnological methods. The results of this study proved the occurrence of TEs contamination at high levels in vegetables and fish from some Mediterranean countries. Lead and cadmium are more abundant in foodstuffs than other toxic trace elements. Geographical variations in TE contamination of food crops clearly appear, with a greater risk in developing countries. There is still a need for the regular monitoring of these toxic element levels in food items to ensure consumer protection.

Epidemiological evidence for the effect of environmental heavy metal exposure on the immune system in children

Heavy metals exist widely in daily life, and exposure to heavy metals caused by environmental pollution has become a serious public health problem worldwide. Due to children's age-specific behavioral characteristics and imperfect physical function, the adverse health effects of heavy metals on children are much higher than in adults. Studies have found that heavy metal exposure is associated with low immune function in children. Although there are reviews describing the evidence for the adverse effects of heavy metal exposure on the immune system in children, the summary of evidence from epidemiological studies involving the level of immune molecules is not comprehensive. Therefore, this review summarizes the current epidemiological study on the effect of heavy metal exposure on childhood immune function from multiple perspectives, emphasizing its risks to the health of children's immune systems. It focuses on the effects of six heavy metals (lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), nickel (Ni), and manganese (Mn)) on children's innate immune cells, lymphocytes and their subpopulations, cytokines, total and specific immunoglobulins, and explores the immunotoxicological effects of heavy metals. The review finds that exposure to heavy metals, particularly Pb, Cd, As, and Hg, not only reduced lymphocyte numbers and suppressed adaptive immune responses in children, but also altered the innate immune response to impair the body's ability to fight pathogens. Epidemiological evidence suggests that heavy metal exposure alters cytokine levels and is associated with the development of inflammatory responses in children. Pb, As, and Hg exposure was associated with vaccination failure and decreased antibody titers, and increased risk of immune-related diseases in children by altering specific immunoglobulin levels. Cd, Ni and Mn showed activation effects on the immune response to childhood vaccination. Exposure age, sex, nutritional status, and co-exposure may influence the effects of heavy metals on immune function in children.

Arsenite Methyltransferase Is an Important Mediator of Hematotoxicity Induced by Arsenic in Drinking Water

Chronic arsenic exposures via the consumption of contaminated drinking water are clearly associated with many deleterious health outcomes, including anemia. Following exposure, trivalent inorganic arsenic (As^III) is methylated through a series of arsenic (+III oxidation state) methyltransferase (As3MT)-dependent reactions, resulting in the production of several intermediates with greater toxicity than the parent inorganic arsenicals. The extent to which inorganic vs. methylated arsenicals contribute to As^III-induced hematotoxicity remains unknown. In this study, the contribution of As3MT-dependent biotransformation to the development of anemia was evaluated in male As3mt-knockout (KO) and wild-type, C57BL/6J, mice following 60-day drinking water exposures to 1 mg/L (ppm) As^III. The evaluation of hematological indicators of anemia revealed significant reductions in red blood cell counts, hemoglobin levels, and hematocrit in As^III-exposed wild-type mice as compared to unexposed controls. No such changes in the blood of As3mt-KO mice were detected. Compared with unexposed controls, the percentages of mature RBCs in the bone marrow and spleen (measured by flow cytometry) were significantly reduced in the bone marrow of As^III-exposed wild-type, but not As3mt-KO mice. This was accompanied by increased levels of mature RBCS in the spleen and elevated levels of circulating erythropoietin in the serum of As^III-exposed wild-type, but not As3mt-KO mice. Taken together, the findings from the present study suggest that As3MT-dependent biotransformation has an essential role in mediating the hematotoxicity of As^III following drinking water exposures.

Arsenic Ingested Early in Life Is More Readily Absorbed: Mechanistic Insights from Gut Microbiota, Gut Metabolites, and Intestinal Morphology and Functions

Early-life arsenic (As) exposure is a particular health concern. However, it is unknown if As ingested early in life is more readily absorbed from the gastrointestinal (GI) tract, i.e., higher in oral bioavailability. Here, weanling (3-week) and adult (6-week-old) female mice were exposed to arsenate in the diet (10 μg g^-1) over a 3-week period with As oral bioavailability estimated using As urinary excretion as the bioavailability endpoint. The As urinary excretion factor was 1.54-fold higher in weanling mice compared to adult mice (82.2 ± 7.29 versus 53.1 ± 3.73%), while weanling mice also showed 2.28-, 1.50-, 1.48-, and 1.89-fold higher As concentration in small intestine tissue, blood, liver, and kidneys, demonstrating significantly higher As oral bioavailability of early-life exposure. Compared to adult mice, weanling mice significantly differed in gut microbiota, but the difference did not lead to remarkable differences in As biotransformation in the GI tract or tissue and in overall gut metabolite composition. Although the expression of several metabolites (e.g., atrolactic acid, hydroxyphenyllactic acid, and xanthine) was up-regulated in weanling mice, they had limited ability to elevate As solubility in the intestinal tract. Compared to adult mice, the intestinal barrier function and intestinal expression of phosphate transporters responsible for arsenate absorption were similar in weanling mice. However, the small intestine of weanling mice was characterized by more defined intestinal villi with greater length and smaller width, providing a greater surface area for As to be absorbed across the GI barrier. The results highlight that early-life As exposure can be more readily absorbed, advancing the understanding of its health risk.

Arsenic exposure and prevalence of human papillomavirus in the US male population

Arsenic is a known carcinogen and is naturally available in earth's crust. Inorganic arsenic is an environmental pollutant with immunosuppressive properties. Human papillomavirus (HPV) is considered one of the most common sexually transmitted diseases in the United States. HPV is linked to several types of cancers in males, including oral, anal, and penile cancer. However, limited information is available on the effect of arsenic on HPV in males. The purpose of this study was to examine the association of urinary arsenic species (speciated and total) and the prevalence of HPV infection in the male population. HPV prevalence in males was analyzed using the 2013-2014 and 2015-2016 National Health and Nutrition Examination Survey (NHANES) dataset. Logistic regression analysis was used to examine associations of seven types of urinary arsenic species (arsenous acid, arsenic acid, arsenobetaine, arsenocholine, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), total arsenic acid) with HPV risk for male participants aged 18-59 years (N = 1516). Demographic characteristics were included in the logistic regression model for each arsenic variable. All statistical analyses were conducted by using the software R (version 4.2.0). Increasing DMA was positively associated with the prevalence of low-risk HPV (odds ratio (OR): 1.075, 95% confidence interval (CI): 1.025, 1.128) in addition to the sum of total toxic arsenic species (TUA1) including arsenous acid, arsenic acid, DMA, and MMA (OR: 1.068, 95% CI: 1.022, 1.116). High-risk HPV strains were found to be positively associated with arsenic acid (OR: 1.806, 95% CI: 1.134, 2.876) and total arsenic minus the sum of the two organic arsenic species arsenobetaine and arsenocholine (TUA2) at quartile 3 (Q3) level (OR: 1.523, 95% CI: 1.102, 2.103). The logistic regression models also showed that race and marital status were significant factors related to high-risk HPV. Our study reported that DMA and TUA1 are associated with low-risk HPV and arsenic acid is associated with high-risk HPV infections in males. Future research is required to confirm or refute this finding.

Association between arsenic exposure and inflammatory cytokines and C-reaction protein: A systematic review and meta-analysis

BACKGROUND

Previous studies have reported controversial results on levels of inflammatory cytokines in patients with arsenic exposure. This study aims to evaluate the associations between arsenic exposure and inflammatory cytokines and C-reaction protein (CRP).

METHODS

We searched the databases including PubMed, Embase, Web of Science, and China national knowledge infrastructure (CNKI) for studies reporting levels of cytokines and CRP in patients with arsenic exposure compared to the controls. The retrieval time was from January 2000 to September 2022.

RESULTS

13 observational studies involving 1665 arsenic exposed and 1091 unexposed individuals were included. Among these studies, 6 from China, 4 from India, 2 from Bangladesh and 1 from Turkey. Our result showed that interleukin (IL)-6, IL-8, and IL-12 levels were significantly higher in arsenic-exposed individuals compared to the control group, IL-2 level was significantly lower, and Tumor necrosis factor-α, Interferon-γ, CRP, and IL-10 levels were not changed. After sensitivity analyses, tumor necrosis factor-α and Interferon-γ levels were significantly higher in arsenic-exposed individuals compared to the control group. High heterogeneity was detected in most studies.

CONCLUSION

Many cytokines (such as IL-6, IL-8, and IL-12) have altered in individuals with arsenic exposure, this indicates arsenic exposure could trigger the cell-mediated inflammatory response. Regular examining immune function (such as inflammatory cytokines) in individuals with the risk of arsenic exposure is important to human health.

Exploring the relationship between blood toxic metal(oid)s and serum insulin levels through benchmark modelling of human data: Possible role of arsenic as a metabolic disruptor

The major goal of this study was to estimate the correlations and dose-response pattern between the measured blood toxic metals (cadmium (Cd), mercury (Hg), chromium (Cr), nickel (Ni))/metalloid (arsenic (As)) and serum insulin level by conducting Benchmark dose (BMD) analysis of human data. The study involved 435 non-occupationally exposed individuals (217 men and 218 women). The samples were collected at health care institutions in Belgrade, Serbia, from January 2019 to May 2021. Blood sample preparation was conducted by microwave digestion. Cd was measured by graphite furnace atomic absorption spectrophotometry (GF-AAS), while inductively coupled plasma-mass spectrometry (ICP-MS) was used to measure Hg, Ni, Cr and As. BMD analysis of insulin levels represented as quantal data was done using the PROAST software version 70.1 (model averaging methodology, BMD response: 10%). In the male population, there was no correlation between toxic metal/metalloid concentrations and insulin level. However, in the female population/whole population, a high positive correlation for As and Hg, and a strong negative correlation for Ni and measured serum insulin level was established. BMD modelling revealed quantitative associations between blood toxic metal/metalloid concentrations and serum insulin levels. All the estimated BMD intervals were wide except the one for As, reflecting a high degree of confidence in the estimations and possible role of As as a metabolic disruptor. These results indicate that, in the case of As blood concentrations, even values higher than BMD (BMDL): 3.27 (1.26) (male population), 2.79 (0.771) (female population), or 1.18 (2.96) μg/L (whole population) might contribute to a 10% higher risk of insulin level alterations, meaning 10% higher risk of blood insulin increasing from within reference range to above reference range. The obtained results contribute to the current body of knowledge on the use of BMD modelling for analysing human data.

Chronic Community Exposure to Environmental Metal Mixtures Is Associated with Selected Cytokines in the Navajo Birth Cohort Study (NBCS)

Many tribal populations are characterized by health disparities, including higher rates of infection, metabolic syndrome, and cancer-all of which are mediated by the immune system. Members of the Navajo Nation have suffered chronic low-level exposure to metal mixtures from uranium mine wastes for decades. We suspect that such metal and metalloid exposures lead to adverse health effects via their modulation of immune system function. We examined the relationships between nine key metal and metalloid exposures (in blood and urine) with 11 circulating biomarkers (cytokines and CRP in serum) in 231 pregnant Navajo women participating in the Navajo Birth Cohort Study. Biomonitored levels of uranium and arsenic species were considerably higher in participants than NHANES averages. Each biomarker was associated with a unique set of exposures, and arsenic species were generally immunosuppressive (decreased cellular and humoral stimulating cytokines). Overall, our results suggest that environmental metal and metalloid exposures modulate immune status in pregnant Navajo women, which may impact long-term health outcomes in mothers and their children.

Non-essential heavy metals and protective effects of selenium against mercury toxicity in endangered Australian sea lion (Neophoca cinerea) pups with hookworm disease

The endangered Australian sea lion, Neophoca cinerea, faces ongoing population decline. Identification of key threats to N. cinerea population recovery, including disease and pollutants, is an objective of the species' recovery plan. Previous studies have identified Uncinaria sanguinis, an intestinal nematode, as a significant cause of disease and mortality in N. cinerea pups. Given the impact of heavy metals on the immune response, investigation of these pollutants is critical. To this end, the concentrations of arsenic (As), total mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb) and selenium (Se) were determined in blood collected from N. cinerea pups sampled during the 2017/18, 2019 and 2020/21 breeding seasons at Seal Bay Conservation Park, South Australia. Significant differences (p < 0.05) in Hg, As, Cr, and Se concentrations and molar ratio of Se:Hg were seen between breeding seasons. Pup age, maternal parity and inter-individual foraging behaviour were considered factors driving these differences. The concentrations of Hg (357, 198 and 241 µg/L) and As (225, 834 and 608 µg/L) were high in 2017/18, 2019 and 2020/21 respectively with Hg concentrations in the blood of N. cinerea pups above toxicological thresholds reported for marine mammals. The concentration of Se (1332, 647, 763 µg/L) and molar ratio of Se:Hg (9.47, 7.98 and 6.82) were low compared to other pinniped pups, indicating potential vulnerability of pups to the toxic effects of Hg. Significant (p < 0.05) negative associations for Pb and Cd with several red blood cell parameters suggest they could be exacerbating the anaemia caused by hookworm disease. Temporal (age-related) changes in element concentrations were also seen, such that pup age needs to be considered when interpreting bioaccumulation patterns. Further investigation of the role of elevated heavy metal concentrations on N. cinerea pup health, disease and development is recommended, particularly with respect to immunological impacts.

Urinary Arsenic Concentration and Its Relationship with Bronchial Asthma in Children from Arica, Chile

In the city of Arica, northern Chile, the population has been involuntarily exposed to arsenic of natural and anthropogenic origin. This study aims to evaluate the association between urinary arsenic concentration and bronchial asthma diagnosis in the children of Arica. A cross-sectional analysis of a database of 1892 subjects under 18 years of age enrolled in the Environmental Health Centre between 2009 and 2021 was carried out. Arsenic exposure was obtained from a urine sample and bronchial asthma diagnosis from the database of the system for the management of explicit health guarantees. Logistic regression models were used to assess the association between inorganic arsenic and asthma. The median inorganic arsenic was 15 μg/L, and the prevalence of asthma was 7.4%. After adjusting for sex, age, ethnicity, and urinary creatinine, children with the highest tertile of urinary arsenic concentration (≥21.4 μg/L) had a greater chance of developing asthma (odds ratio (OR) 1.90; 95% confidence interval (CI) [1.13-3.18]). When exploring the modifying effect of ethnicity, the association increased among children belonging to any ethnic group (OR 3.51, 95%CI [1.43-8.65]). These findings suggest a relationship between arsenic exposure and bronchial asthma in children. While further studies are needed to assess the impact of arsenic on respiratory health, mitigation efforts to reduce arsenic exposure should be maintained.

Arsenic exposure and respiratory outcomes during childhood in the INMA study

Ingested inorganic arsenic (iAs) is a human carcinogen that is also linked to other adverse health effects, such as respiratory outcomes. Yet, among populations consuming low-arsenic drinking water, the impact of iAs exposure on childhood respiratory health is still uncertain. For a Spanish child study cohort (INfancia y Medio Ambiente—INMA), low-arsenic drinking water is usually available and ingestion of iAs from food is considered the major source of exposure. Here, we explored the association between iAs exposure and children’s respiratory outcomes assessed at 4 and 7 years of age (n = 400). The summation of 4-year-old children’s urinary iAs, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) was used as a biomarker of iAs exposure (∑As) (median of 4.92 μg/L). Children’s occurrence of asthma, eczema, sneeze, wheeze, and medication for asthma and wheeze at each assessment time point (i.e., 4- and 7-year) was assessed with maternal interviewer-led questionnaires. Crude and adjusted Poisson regression models using Generalized Estimating Equation (GEE) were performed to account for the association between natural logarithm transformed (ln) urinary ∑As in μg/L at 4 years and repeated assessments of respiratory symptoms at 4 and 7 years of age. The covariates included in the models were child sex, maternal smoking status, maternal level of education, sub-cohort, and children’s consumption of vegetables, fruits, and fish/seafood. The GEE—splines function using Poisson regression showed an increased trend of the overall expected counts of respiratory symptoms with high urinary ∑As. The adjusted expected counts (95% confidence intervals) at ln-transformed urinary ∑As 1.57 (average concentration) and 4.00 (99^th percentile concentration) were 0.63 (0.36, 1.10) and 1.33 (0.61, 2.89), respectively. These exploratory findings suggest that even relatively low-iAs exposure levels, relevant to the Spanish and other populations, may relate to an increased number of respiratory symptoms during childhood.

The fate of inhaled uranium-containing particles upon clearance to gastrointestinal tract

Uranium-bearing respirable dust can cause various health problems, such as cardiovascular and neurological disorders, cancers, immunosuppression, and autoimmunity. Exposure to elevated levels of uranium is linked to many such health conditions in Navajo Nation residents in northwestern New Mexico. Most studies have focused on the fate of inhaled dust particles (<4 μm) in the lungs. However, larger-sized inhaled particles (10-20 μm) can be cleared to the human gastrointestinal tract (GIT), thereby enabling them to interact with stomach and intestinal fluids. Despite the vital importance of understanding the fate of uranium-bearing solids entering the human GIT and their impact on body tissues, cells, and gut microbiota, our understanding remains limited. This study investigated uranium solubility from dust and sediment samples collected near two uranium mines in the Grants Mining District in New Mexico in two simulated gastrointestinal fluids representing fasting conditions in the GIT: Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF). The dissolution of uranium from dust depends on its mineralogy, fluid pH, and composition. The dust samples from the Jackpile mine favored higher solubility in the SIF solution, whereas the sediment samples from the St. Anthony Mine favored higher solubility in the SGF solution. Further, geochemical calculations performed with the PHREEQC modeling program suggested that samples rich in the minerals andersonite, tyuyamunite, and/or autunite have higher uranium dissolution in the SIF solution than in the SGF solution. We also tested the effect of added kaolinite and microcline, which are both present in some samples. The ratio of dissolved uranium in SGF relative to SIF decreases with the addition of kaolinite for all mineral phases but andersonite. With the addition of microcline, the ratio of dissolved uranium in SGF relative to SIF decreases for all the tested uranium minerals. The most prevalent oxidation state of dissolved uranium was computationally determined as +6, U(VI). The geochemical calculations made with PHREEQC agree with the experimentally observed results. Therefore, this study gives insight into the mineralogy-controlled toxicological assessment of uranium-containing inhaled dust cleared to the gastrointestinal tract.

Role of N6-methyladenosine RNA modification in the imbalanced inflammatory homeostasis of arsenic-induced skin lesions

This study aimed to investigate the effect of N6-methyladenosine (m⁶ A) modification in modulating inflammatory homeostasis of arsenic (As)-induced skin lesions. Our bioinformatic analysis revealed abnormal expression of m⁶ A RNA methylation regulators and cytokines in the arsenic-exposed population. In human keratinocytes, arsenite increased the levels of m⁶ A methylation by upregulating the RNA methyltransferase like 3 (METTL3), mediating the disordered secretion of indicators that reflect inflammatory homeostasis (IL-6, IL-17, and IL-10). The indicators reflecting arsenic-induced skin lesions (Krt1 and Krt10) were also significantly elevated, which contributed to the occurrence of skin lesions. Our results also confirmed the association between METTL3 with inflammatory homeostasis and arsenic-induced skin lesions using arsenic-exposed human skin samples. In the arsenic-exposed group, the upregulation of METTL3 exacerbated the increase in cytokine levels (IL-6, IL-17, and IL-10), which was associated with the upregulation of keratins (Krt1 and Krt10). In addition, significant correlations among these factors corroborate the theoretical links. Finally, alteration of the m⁶ A levels via knockdown or enhancement of the METTL3 protein could antagonize or aggravate arsenite-induced imbalanced inflammatory homeostasis and human keratinocyte damage in HaCaT cells. Collectively, our study reveals some evidence that regulation of m⁶ A modification plays an important role in arsenic-induced skin lesions, which provide a new perspective on the mechanism of arsenite-induced imbalanced inflammatory homeostasis in the field of RNA epigenetics.

Harmonization of transcriptomic and methylomic analysis in environmental epidemiology studies for potential application in chemical risk assessment

Recent efforts have posited the utility of transcriptomic-based approaches to understand chemical-related perturbations in the context of human health risk assessment. Epigenetic modification (e.g., DNA methylation) can influence gene expression changes and is known to occur as a molecular response to some chemical exposures. Characterization of these methylation events is critical to understand the molecular consequences of chemical exposures. In this context, a novel workflow was developed to interrogate publicly available epidemiological transcriptomic and methylomic data to identify relevant pathway level changes in response to chemical exposure, using inorganic arsenic as a case study. Gene Set Enrichment Analysis (GSEA) was used to identify causal methylation events that result in concomitant downstream transcriptional deregulation. This analysis demonstrated an unequal distribution of differentially methylated regions across the human genome. After mapping these events to known genes, significant enrichment of a subset of these pathways suggested that arsenic-mediated methylation may be both specific and non-specific. Parallel GSEA performed on matched transcriptomic samples determined that a substantially reduced subset of these pathways are enriched and that not all chemically-induced methylation results in a downstream alteration in gene expression. The resulting pathways were found to be representative of well-established molecular events known to occur in response to arsenic exposure. The harmonization of enriched transcriptional patterns with those identified from the methylomic platform promoted the characterization of plausibly causal molecular signaling events. The workflow described here enables significant gene and methylation-specific pathways to be identified from whole blood samples of individuals exposed to environmentally relevant chemical levels. As future efforts solidify specific causal relationships between these molecular events and relevant apical endpoints, this novel workflow could aid risk assessments by identifying molecular targets serving as biomarkers of hazard, informing mechanistic understanding, and characterizing dose ranges that promote relevant molecular/epigenetic signaling events occuring in response to chemical exposures.

Environmental-level exposure to metals and metal-mixtures associated with spirometry-defined lung disease in American Indian adults: Evidence from the Strong Heart Study

BACKGROUND

American Indians have a higher burden of chronic lung disease compared to the US average. Several metals are known to induce chronic lung disease at high exposure levels; however, less is known about the role of environmental-level metal exposure. We investigated respiratory effects of exposure to single metals and metal-mixtures in American Indians who participated in the Strong Heart Study.

METHODS

We included 2077 participants with data on 6 metals (As, Cd, Mo, Se, W, Zn) measured from baseline urine samples (1989-1991) and who underwent spirometry testing at follow-up (1993-1995). We used generalized linear regression to assess associations of single metals with spirometry-defined measures of airflow limitation and restrictive ventilatory pattern, and continuous spirometry. We used Bayesian Kernel Machine Regression to investigate the joint effects of the metal-mixture. Sensitivity analyses included stratifying by smoking status and diabetes.

RESULTS

Participants were 40% male, with median age 55 years. 21% had spirometry-defined airflow limitation, and 14% had a restrictive ventilatory pattern. In individual metal analyses, Cd was associated with higher odds of airflow limitation and lower FEV1 and FEV1/FVC. Mo was associated with higher odds of restrictive ventilatory pattern and lower FVC. Metal-mixtures analyses confirmed these models. In smoking stratified analyses, the overall metal-mixture was linearly and positively associated with airflow limitation among non-smokers; Cd was the strongest contributor. For restrictive ventilatory pattern, the association with the overall metal-mixture was strong and linear among participants with diabetes and markedly attenuated among participants without diabetes. Among those with diabetes, Mo and Zn were the major contributors.

CONCLUSIONS

Environmental-level exposure to several metals was associated with higher odds of spirometry-defined lung disease in an American Indian population. Exposure to multiple metals, including Cd and Mo, may have an under-recognized adverse role on the respiratory system.

Arsenic Induces Continuous Inflammation and Regulates Th1/Th2/Th17/Treg Balance in Liver and Kidney In Vivo

Numerous studies on arsenic-induced hepatonephric toxicity including cancer have been reported. Given that chronic inflammatory response and immune imbalance are associated with oncogenesis, we investigated whether arsenic could influence the hepatic and nephritic expression of inflammatory factors and the differentiation of T cells. Mice were exposed to NaAsO₂ (0, 25, and 50 mg/L) for 1 and 3 months. Our data showed the destruction of the structure and inflammatory infiltration in the liver. The arsenic markedly increased the activity of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The myeloperoxidase (MPO) activities increased in the liver at 25 and 50 mg/L arsenic for 3 months as well as in the kidney at both 1 and 3 months. An increased expression of inflammatory indicators (IL-1β, IL-12, and TNF-α) at 25 and 50 mg/L arsenic for 1 and 3 months in the liver and kidney, as well as IL-1β in the liver for 3 months and in the kidney at 50 mg/L for 1 and 3 months were demonstrated in our experiments. Besides, a definite tendency toward Th1/Th17 cytokines in the liver while Th2/Th17 cytokines in kidney was also observed by arsenic. Moreover, arsenic enhanced the expression of MAPK/Nrf2/NF-κB signaling molecules. In conclusion, the results of the study suggested that arsenic induces continuous immune-inflammatory responses in the liver and kidney.

Arsenic-Induced Sex Hormone Disruption: An Insight into Male Infertility

Arsenic (As) is one of the most potent natural as well as anthropogenic metalloid toxicants that have various implications in the everyday life of humans. It is found in several chemical forms such as inorganic salt, organic salt, and arsine (gaseous form). Although it is mostly released via natural causes, there are many ways through which humans come in contact with As. Drinking water contamination by As is one of the major health concerns in various parts of the world. Arsenic exposure has the ability to induce adverse health effects including reproductive problems. Globally, around 15% of the couples are affected with infertility, of which about 20-30% are attributed to the male factor. Arsenic affects the normal development and function of sperm cells, tissue organization of the gonads, and also the sex hormone parameters. Stress induction is one of the implications of As exposure. Excessive stress leads to the release of glucocorticoids, which impact the oxidative balance in the body leading to overproduction of reactive oxygen species (ROS). This may in turn result in oxidative stress (OS) ultimately interfering with normal sperm and hormonal parameters. This study deals with As-induced OS and its association with sex hormone disruption as well as its effect on sperm and semen quality.

Arsenite exposure inhibits the erythroid differentiation of human hematopoietic progenitor CD34+ cells and causes decreased levels of hemoglobin

Arsenic exposure poses numerous threats to human health. Our previous work in mice has shown that arsenic causes anemia by inhibiting erythropoiesis. However, the impacts of arsenic exposure on human erythropoiesis remain largely unclear. We report here that low-dose arsenic exposure inhibits the erythroid differentiation of human hematopoietic progenitor cells (HPCs). The impacts of arsenic (in the form of arsenite; As3+) on red blood cell (RBC) development was evaluated using a long-term culture of normal human bone marrow CD34+-HPCs stimulated in vitro to undergo erythropoiesis. Over the time course studied, we analyzed the expression of the cell surface antigens CD34, CD71 and CD235a, which are markers commonly used to monitor the progression of HPCs through the stages of erythropoiesis. Simultaneously, we measured hemoglobin content, which is an important criterion used clinically for diagnosing anemia. As compared to control, low-dose As3+ exposure (100 nM and 500 nM) inhibited the expansion of CD34+-HPCs over the time course investigated; decreased the number of committed erythroid progenitors (BFU-E and CFU-E) and erythroblast differentiation in the subsequent stages; and caused a reduction of hemoglobin content. These findings demonstrate that low-dose arsenic exposure impairs human erythropoiesis, likely by combined effects on various stages of RBC formation.

Arsenite and monomethylarsonous acid disrupt erythropoiesis through combined effects on differentiation and survival pathways in early erythroid progenitors

Strong epidemiological evidence demonstrates an association between chronic arsenic exposure and anemia. We recently found that As+3 impairs erythropoiesis by disrupting the function of GATA-1; however the downstream pathways impacted by the loss of GATA-1 function have not been evaluated. Additionally, our previous findings indicate that the predominant arsenical in the bone marrow of mice exposed to As+3 in their drinking water for 30 days was MMA+3, but the impacts of this arsenical on erythorpoisis also remain largely unknown. The goal of this study was to address these critical knowledge gaps by evaluating the comparative effects of arsenite (As+3) and the As+3 metabolite, monomethyarsonous acid (MMA+3) on two critical regulatory pathways that control the differentiation and survival of early erythroid progenitor cells. We found that 500 nM As+3 and 100 and 500 nM MMA+3 suppress erythropoiesis by impairing the differentiation of early stage erythroid progenitors. The suppression of early erythroid progenitor cell development was attributed to combined effects on differentiation and survival pathways mediated by disruption of GATA-1 and STAT5. Our results show that As+3 primarily disrupted GATA-1 function; whereas, MMA+3 suppressed both GATA-1 and STAT5 activity. Collectively, these findings provide novel mechanistic insights into arsenic-induced dyserythropoiesis and suggest that MMA+3 may be more toxic than As+3 to early developing erythroid cells.

Prenatal arsenic exposure interferes in postnatal immunocompetence despite an absence of ongoing arsenic exposure

Arsenic (As) readily crosses the placenta and exposure of the fetus may cause adverse consequences later in life, including immunomodulation. In the current study, the question was asked how the immune repertoire might respond in postnatal life when there is no further As exposure. Here, pregnant mice (Balb/c [H-2^d]) were exposed to arsenic trioxide (As₂O₃) through their drinking water from time of conception until parturition. Their offspring, 4-week-old mice who had not been exposed again to As, were used for functional analyses of innate, humoral and cellular immunity. Compared to cells from non-As-exposed dam offspring, isolated peritoneal macro-phages (Mϕ) displayed no differences in T-cell stimulating ability. Levels of circulating IgG_2a but not IgG₁ were decreased in As-exposed dam offspring as compared to control offspring counterparts. Mixed-leukocyte reactions (MLR) indicated that CD4⁺ T-cells from the prenatal As-exposed mice were significantly less responsive to allogenic stimulation as evidenced by decreases in interferon (IFN)-γ and IL-2 production and in expression of CD44 and CD69 (but not CD25) activation markers. Interestingly, the Mϕ from the prenatal As-exposed mice were capable of stimulating normal allogenic T-cells, indicating that T-cells from these mice were refractory to allogenic signals. There was also a significant decrease in absolute numbers of splenic CD4⁺ and CD8⁺ T-cells due to prenatal As exposure (as compared to control). Lastly, the impaired immune function of the prenatal As-exposed mice was correlated with a very strong susceptibility to Escherichia coli infection. Taken together, the data from this study clearly show that in utero As exposure may continue to perpetuate a dampening effect on the immune repertoire of offspring, even into the early stages of postnatal life.

Investigating Molecular Mechanisms of Immunotoxicity and the Utility of ToxCast for Immunotoxicity Screening of Chemicals Added to Food

The development of high-throughput screening methodologies may decrease the need for laboratory animals for toxicity testing. Here, we investigate the potential of assessing immunotoxicity with high-throughput screening data from the U.S. Environmental Protection Agency ToxCast program. As case studies, we analyzed the most common chemicals added to food as well as per- and polyfluoroalkyl substances (PFAS) shown to migrate to food from packaging materials or processing equipment. The antioxidant preservative tert-butylhydroquinone (TBHQ) showed activity both in ToxCast assays and in classical immunological assays, suggesting that it may affect the immune response in people. From the PFAS group, we identified eight substances that can migrate from food contact materials and have ToxCast data. In epidemiological and toxicological studies, PFAS suppress the immune system and decrease the response to vaccination. However, most PFAS show weak or no activity in immune-related ToxCast assays. This lack of concordance between toxicological and high-throughput data for common PFAS indicates the current limitations of in vitro screening for analyzing immunotoxicity. High-throughput in vitro assays show promise for providing mechanistic data relevant for immune risk assessment. In contrast, the lack of immune-specific activity in the existing high-throughput assays cannot validate the safety of a chemical for the immune system.

Experimental acute arsenic toxicity in Balb/c mice: organic markers and splenic involvement

Introduction: Arsenic is an environmental toxic present worldwide. In men and animals, various organs and tissues are targets of its deleterious effects including those of the immune system. Objective: To determine acute arsenic toxicity in tissues and target cells of Balb/c mice using an in vivo methodology. Materials and methods: We injected Balb/c mice intraperitoneally with 9.5 or 19 mg/kg of sodium arsenite (NaAsO2), or an equivalent volume of physiological solution as a control (with 3 per experimental group). After 30 minutes, the animals were sacrificed to obtain spleen, thymus, liver, kidneys, and blood. We determined arsenic, polyphenols, and iron concentrations in each sample and we evaluated the oxidative markers (peroxides, advanced products of protein oxidation, and free sulfhydryl groups). In splenocytes from the spleen, cell viability and mitochondrial potential were also determined. Results: The exposure to an acute dose of NaAsO2 reduced the mitochondrial function of splenocytes, which resulted in cell death. Simultaneously, the confirmed presence of arsenic in spleen samples and the resulting cytotoxicity occurred with a decrease in polyphenols, free sulfhydryl groups, and an alteration in the content and distribution of iron, but did not increase the production of peroxides. Conclusion: These findings provide scientific evidence about changes occurring in biomarkers involved in the immunotoxicity of arsenic and offer a methodology for testing possible treatments against the deleterious action of this compound on the immune system.

Zinc offers splenic protection through suppressing PERK/IRE1-driven apoptosis pathway in common carp (Cyprinus carpio) under arsenic stress

Arsenic (As) occurs naturally and concentrations in water bodies can reach high levels, leading to accumulation in vital organs like the spleen. Being an important organ in immune response and blood development processes, toxic effects of As on the spleen could compromise immunity and cause associated disorders in affected individuals. Splenic detoxification is key to improving the chances of survival but relatively little is known about the mechanisms involved. Essential trace elements like zinc have shown immune-modulatory effects humans and livestock. This study aimed to investigate the mechanisms involved in As-induced splenic toxicity in the common carp (Cyprinus carpio), and the protective effects of zinc (Zn). Our findings suggest that environmental exposure to As caused severe histological injuries and Ca²⁺ accumulation in the spleen of common carp. Additionally, transcriptional and translational profiles of endoplasmic reticulum stress, apoptosis and autophagy-related genes of the spleen showed upward trends under As toxicity. Treatment with Zn appears to offer protection against As-induced splenic injury in common carp and the pathologic changes above were alleviated. Our results provide additional insight into the mechanism of As toxicity in common carp while elucidating the role of Zn, a natural immune-modulator, as a potential antidote against As poisoning.

Maternal and childhood exposure to inorganic arsenic and airway allergy - A 15-Year birth cohort follow-up study

BACKGROUND

The prevalence of allergic diseases in children has increased globally. Early-life exposure to inorganic arsenic has been found to be associated with impaired immune function and decreased lung function in children; however, the results are inconsistent. We aimed to evaluate the effect of prenatal and childhood exposure to inorganic arsenic on allergic diseases in children, through a 15-year follow-up birth cohort study, conducted in central Taiwan.

METHODS

Children born to women enrolled in the Taiwan Maternal and Infant Cohort Study (TMICS-pilot) from December 2000 to November 2001 were recruited and followed every 2-3 years until the age of 14 years. Urinary specimens were collected in the pregnant women during the 3rd trimester and the followed children. Diagnoses of allergic diseases were based on physician diagnoses using the International Study of Asthma and Allergies in Childhood questionnaire. Urinary arsenic speciation was performed using high-performance liquid chromatography and inductively coupled plasma dynamic reaction cell mass spectrophotometry.

RESULTS

Of the 261 children from 358 mother-infant pairs for this study, those with asthma and allergic rhinitis reported a higher prevalence of maternal allergy (49.47%) than did non-allergic children (29.81%). In the fully adjusted model, levels of maternal urine (iAs + MMA + DMA) greater than the median were found to be significantly associated with an increased risk of asthma (OR = 4.28; 95% CI 1.32, 13.85). Levels of urinary (iAs + MMA + DMA) in children higher than the median were associated with an increased risk of allergic rhinitis (OR = 2.26; 95% CI 1.20, 4.26).

CONCLUSION

Prenatal and childhood exposure to inorganic arsenic were found to be significantly associated with the occurrence of asthma and allergic rhinitis in children, respectively. Further large cohort follow-up studies are important to validate the association between inorganic arsenic exposure and allergic diseases in children.

Arsenic Exposure and Cancer-Related Proteins in Urine of Indigenous Bolivian Women

Indigenous people living in the Bolivian Andes are exposed through their drinking water to inorganic arsenic, a potent carcinogen. However, the health consequences of arsenic exposure in this region are unknown. The aim of this study was to evaluate associations between arsenic exposure and changes in cancer-related proteins in indigenous women (n = 176) from communities around the Andean Lake Poopó, Bolivia. Arsenic exposure was assessed in whole blood (B-As) and urine (as the sum of arsenic metabolites, U-As) by inductively coupled plasma-mass spectrometry (ICP-MS). Cancer-related proteins (N = 92) were measured in urine using the proximity extension assay. The median B-As concentration was 2.1 (range 0.60-9.1) ng/g, and U-As concentration was 67 (12-399) μg/L. Using linear regression models adjusted for age, urinary osmolality, and urinary leukocytes, we identified associations between B-As and four putative cancer-related proteins: FASLG, SEZ6L, LYPD3, and TFPI2. Increasing B-As concentrations were associated with lower protein expression of SEZ6L, LYPD3, and TFPI2, and with higher expression of FASLG in urine (no association was statistically significant after correcting for multiple comparisons). The associations were similar across groups with different arsenic metabolism efficiency, a susceptibility factor for arsenic toxicity. In conclusion, arsenic exposure in this region was associated with changes in the expression of some cancer-related proteins in urine. Future research is warranted to understand if these proteins could serve as valid biomarkers for arsenic-related toxicity.

Toxic metal exposure as a possible risk factor for COVID-19 and other respiratory infectious diseases

Multiple medical, lifestyle, and environmental conditions, including smoking and particulate pollution, have been considered as risk factors for COronaVIrus Disease 2019 (COVID-19) susceptibility and severity. Taking into account the high level of toxic metals in both particulate matter (PM2.5) and tobacco smoke, the objective of this review is to discuss recent data on the role of heavy metal exposure in development of respiratory dysfunction, immunotoxicity, and severity of viral diseases in epidemiological and experimental studies, as to demonstrate the potential crossroads between heavy metal exposure and COVID-19 severity risk. The existing data demonstrate that As, Cd, Hg, and Pb exposure is associated with respiratory dysfunction and respiratory diseases (COPD, bronchitis). These observations corroborate laboratory findings on the role of heavy metal exposure in impaired mucociliary clearance, reduced barrier function, airway inflammation, oxidative stress, and apoptosis. The association between heavy metal exposure and severity of viral diseases, including influenza and respiratory syncytial virus has been also demonstrated. The latter may be considered a consequence of adverse effects of metal exposure on adaptive immunity. Therefore, reduction of toxic metal exposure may be considered as a potential tool for reducing susceptibility and severity of viral diseases affecting the respiratory system, including COVID-19.

Differential response of human T-lymphocytes to arsenic and uranium

Elevated levels of arsenic and uranium have been detected in water sources near abandoned uranium mines in the Southwest. Evidence suggests uranium exposure increases the likelihood of immune dysfunction and this study investigates the impact of arsenic and uranium on human immune cell lines. Concentration-dependent cytotoxicity occurred following exposure to arsenite, whereas cells remained viable after 48 -h treatment with up to 100 μM uranyl acetate despite uptake of uranium into cells. Arsenite stimulated an oxidative stress response as detected by Nrf-2 nuclear accumulation and induction of HMOX-1 and NQO1, which was not detected with up to 30 μM uranyl acetate. Cellular oxidative stress can promote DNA damage and arsenite, but not uranium, stimulated DNA damage as measured by pH2AX. Arsenic enhanced the cytotoxic response to etoposide suggesting an inhibition of DNA repair, unlike uranium. Similarly, uranium did not inhibit PARP-1 activity. Because uranium reportedly stimulates oxidative stress, DNA damage and cytotoxicity in adherent epithelial cells, the current study suggests distinct cell type differences in response to uranium that may relate to generation of oxidative stress and associated downstream consequences. Delineating the actions of uranium across different cell targets will be important for understanding the potential health effects of uranium exposures.

Cellular and Molecular Mechanisms of Environmental Pollutants on Hematopoiesis

Hematopoiesis is a complex and intricate process that aims to replenish blood components in a constant fashion. It is orchestrated mostly by hematopoietic progenitor cells (hematopoietic stem cells (HSCs)) that are capable of self-renewal and differentiation. These cells can originate other cell subtypes that are responsible for maintaining vital functions, mediate innate and adaptive immune responses, provide tissues with oxygen, and control coagulation. Hematopoiesis in adults takes place in the bone marrow, which is endowed with an extensive vasculature conferring an intense flow of cells. A myriad of cell subtypes can be found in the bone marrow at different levels of activation, being also under constant action of an extensive amount of diverse chemical mediators and enzymatic systems. Bone marrow platelets, mature erythrocytes and leukocytes are delivered into the bloodstream readily available to meet body demands. Leukocytes circulate and reach different tissues, returning or not returning to the bloodstream. Senescent leukocytes, specially granulocytes, return to the bone marrow to be phagocytized by macrophages, restarting granulopoiesis. The constant high production and delivery of cells into the bloodstream, alongside the fact that blood cells can also circulate between tissues, makes the hematopoietic system a prime target for toxic agents to act upon, making the understanding of the bone marrow microenvironment vital for both toxicological sciences and risk assessment. Environmental and occupational pollutants, therapeutic molecules, drugs of abuse, and even nutritional status can directly affect progenitor cells at their differentiation and maturation stages, altering behavior and function of blood compounds and resulting in impaired immune responses, anemias, leukemias, and blood coagulation disturbances. This review aims to describe the most recently investigated molecular and cellular toxicity mechanisms of current major environmental pollutants on hematopoiesis in the bone marrow.

Exposures to uranium and arsenic alter intraepithelial and innate immune cells in the small intestine of male and female mice

Human exposures to environmental metals, including uranium (U) and arsenic (As) are a global public health concern. Chronic exposures to U and As are linked to many adverse health effects including, immune suppression and autoimmunity. The gastrointestinal (GI) tract is home to many immune cells vital in the maintenance of systemic immune health. However, very little is known about the immunotoxicity of U and As at this site. The present study examined the burden of U and As exposure in the GI tract as well as the resultant immunotoxicity to intraepithelial lymphocytes (IELs) and innate immune cells of the small intestine following chronic drinking water exposures of male and female mice to U (in the form of uranyl acetate, UA) and As (in the form of sodium arsenite, As3+). Exposure to U or As3+ resulted in high levels of U or As in the GI tract of male and female mice, respectively. A reduction of small intestinal CD4+ IELs (TCRαβ+, CD8αα+) was found following As3+ exposure, whereas U produced widespread suppression of CD4- IEL subsets (TCRαβ+ and TCRγδ+). Evaluation of innate immune cell subsets in the small intestinal lamina propria revealed a decrease in mature macrophages, along with a corresponding increase in immature/proinflammatory macrophages following As3+ exposures. These data show that exposures to two prevalent environmental contaminants, U and As produce significant immunotoxicity in the GI tract. Collectively, these findings provide a critical framework for understanding the underlying immune health issues reported in human populations chronically exposed to environmental metals.

Arsenic induces mTOR-dependent autophagy, whereas it impairs the autophagy-lysosome pathway and the potential role of TFEB in cultured dendritic cells

Arsenic is a toxic metalloid, which also compromises immunity and causes various immunological disorders. Exposure to arsenic exerts the immunosuppressive properties of dendritic cells (DCs). Autophagy is a self-renewal process of cells, which degrades damaged macromolecules and organelles through the lysosomal pathway. Thus, herein, we attempt to clarify the impacts of autophagy and the autophagy-lysosome pathway on arsenic-exposed DCs. Bone marrow-derived dendritic cells (BMDCs) were exposed to different concentrations of arsenic (0.25, 0.5 and 1 μM) with or without LPS stimulation. Initially, we observed that arsenic induced autophagosome accumulation, significantly enhanced the LC3 II and p62 expressions and down-regulated the p-mTOR protein levels. We also determined that arsenic-induced autophagy occurred via an mTOR pathway. The results further revealed that arsenic inhibited autophagic flux in LPS-stimulated BMDCs using the autophagy inhibitor chloroquine (CQ). Meanwhile, arsenic significantly decreased the number of lysosomes, protein expression of lysosomal-specific markers LAMP1 and LAMP2, and the protein levels of lysosomal cysteine cathepsins (CTSD and CTSL). Moreover, the overexpression of transcription factor EB (TFEB), the master transcriptional regulator of autophagy and lysosome biogenesis, partially relieved arsenic-inhibited lysosomal CTSD and CTSL expressions, recovered the disorder of autophagic flux, promoted the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-12, and reduced anti-inflammatory cytokine IL-10 secretion. In summary, our results support the idea that arsenic induces autophagy through an mTOR-dependent pathway in cultured BMDCs. Meanwhile, arsenic weakens the process of autophagic flux, which may be partially due to lysosomal dysfunction. Furthermore, we also suggest that TFEB can positively act on the autophagy-lysosome pathway and influence the expression of immunocytokines in DCs.

Arsenite induces dysfunction of regulatory T cells through acetylation control of the Foxp3 promoter

Arsenic is known to cause damage to the body's immune system by inducing epigenetic changes. However, the molecular mechanism of this damage remains elusive. Here, we report that arsenic disrupts the morphology of lymphocytes, decreases cell viability, and results in abnormal proportions of T lymphocyte subsets. Moreover, our results revealed that arsenic can reduce global acetylation of histone H4 at K16 (H4K16 ac) in lymphocytes via decreasing the level of males absent on the first but upregulates mRNA and protein levels of the forkhead/winged-helix box P3 (Foxp3) gene by increasing the acetylation of histone H4 at K16 (H4K16) at the promoter of Foxp3. Finally, arsenic-induced dysfunction of regulatory T cells (Tregs) could be ameliorated by trichostatin A. Our research indicates that arsenic-induced immunosuppressive effect in human lymphocytes may be related to the acetylation of H4K16 at the promoter of Foxp3 and that histone deacetylase inhibitors may play a role in the prevention and treatment of immune injury caused by arsenic.

Chronic arsenic exposure induces the time-dependent modulation of inflammation and immunosuppression in spleen

Background

Arsenic exposure has become a matter of worldwide concern, which is associated with immune-related diseases. However, little is known about its effect on inflammatory immune-related homeostasis. The purpose of our study was to understand the potential tuning of above responses exerted by chronic arsenic exposure.

Methods

Kunming mice were treated with 25 and 50 mg/L sodium arsenite for 1, 3 and 12 months via drinking water. At different endpoints of arsenic exposure, all animals and the whole spleen of the mice were weighed. The total arsenic levels of spleen were determined by the HPLC-HG-AFS method. Splenic NF-κB, MAPK and NRF2 protein levels by treatment of 25 mg/L NaAsO₂ for 1, 3 and 12 months and 25 mg/L and 50 mg/L NaAsO₂ for 12 months were assessed by western blot. Total RNA of spleen was isolated and relative mRNA levels of Foxp3, Il-10, Tnf-α, Il-6, Ifn-γ, Il-1β and Il-12 were measured by real-time PCR.

Results

Our results shown that NF-κB were continuously activated with treatment of 25 mg/L arsenic from 1, 3 to 12 months and 50 mg/L arsenic for 12 months. The transcription factor Foxp3 increased at 1 month but decreased at 3 and 12 months no matter 25 or 50 mg/L arsenic exposure. However, cytokine Il-10 always showed increased trend in mice treated with 25 or 50 mg/L arsenic for 1, 3 and 12 months. The transcriptional profiles of Tnf-α, Il-1β, Il-6, Ifn-γ and Il-12 revealed transient elevation at 1 and 3 months but shown significant decrease at 12 months on the whole. In addition, the sustained activation of inflammatory MAPK and anti-oxidative Nrf2 signaling pathways were observed in mice exposed to arsenic for 1, 3 and 12 months.

Conclusion

In summary, our experiment in vivo suggested chronic arsenic exposure induces the time-dependent modulation of the inflammation and immunosuppression in spleen, which may be related to the activation of Tregs induced by MAPK/NF-κB as well as the increased transcription level of Foxp3 and Il-10.

Effect of arsenic trioxide on the Tregs ratio and the levels of IFN-γ, IL-4, IL-17 and TGF-β1 in the peripheral blood of severe aplastic anemia patients

Previous studies have suggested that the anticancer agent, arsenic trioxide (ATO), could attenuate T cell mediated immunity by not only inhibiting the proliferative response of T cells but by also increasing the frequency of regulatory T cells (Tregs). Furthermore, ATO represents a reasonable salvage treatment in some patients with refractory severe aplastic anemia (SAA). The current study aimed to evaluate the function of ATO on the Tregs percentage and cytokines changes in the peripheral blood mononuclear cells (PBMCs) of SAA patients.PBMCs were collected from 20 newly diagnosed SAA patients in Henan Cancer Hospital and treated with different concentrations of ATO (0, 1, 2.5, and 5 μmol/L). Then we investigated the efficacy of ATO on Tregs ratio and the levels of interferon (IFN)-γ, interleukin (IL)-4, IL-17 and transforming growth factor (TGF)-β1 in the peripheral blood of SAA patients in vitro.The results showed that ATO significantly increased the proportion of Tregs (P < .001) at 2.5 and 5 μmol/L concentrations, and the proportion of Tregs was increased with increasing ATO concentration (r = 0.524). At 1 (P = .03), 2.5 (P < .001) and 5 μmol/L (P < .001), ATO significantly up-regulated the expression levels of Foxp3 mRNA, which was positively and linearly correlated with the increase of Tregs cell-frequency (r = 0.52, 95%CI, 0.37-0.67). In addition, ATO significantly reduced the levels of IFN-γ (at 1, 2.5 and 5 μmol/L, P < .001), IL-4 (at 2.5 μmol/L, P = .009; at 5 μmol/L, P < .001), and IL-17 (at 2.5, P = .016; at 5 μmol/L, P < .001). ATO significantly reduced the levels of TGF-β1 at 5 μmol/L (P = .03), but showed no significant effects at 1 and 2.5 μmol/L (P > .05).ATO could mediate the immune regulation, which might contribute to improve hematopoietic recovery in SAA patients.

Beyond the looking glass: recent advances in understanding the impact of environmental exposures on neuropsychiatric disease

The etiologic pathways leading to neuropsychiatric diseases remain poorly defined. As genomic technologies have advanced over the past several decades, considerable progress has been made linking neuropsychiatric disorders to genetic underpinnings. Interest and consideration of nongenetic risk factors (e.g., lead exposure and schizophrenia) have, in contrast, lagged behind heritable frameworks of explanation. Thus, the association of neuropsychiatric illness to environmental chemical exposure, and their potential interactions with genetic susceptibility, are largely unexplored. In this review, we describe emerging approaches for considering the impact of chemical risk factors acting alone and in concert with genetic risk, and point to the potential role of epigenetics in mediating exposure effects on transcription of genes implicated in mental disorders. We highlight recent examples of research in nongenetic risk factors in psychiatric disorders that point to potential shared biological mechanisms-synaptic dysfunction, immune alterations, and gut-brain interactions. We outline new tools and resources that can be harnessed for the study of environmental factors in psychiatric disorders. These tools, combined with emerging experimental evidence, suggest that there is a need to broadly incorporate environmental exposures in psychiatric research, with the ultimate goal of identifying modifiable risk factors and informing new treatment strategies for neuropsychiatric disease.

Lung Function and Respiratory Symptoms after Tuberculosis in an American Indian Population. The Strong Heart Study

Rationale: Permanent lung function impairment after active tuberculosis infection is relatively common. It remains unclear which spirometric pattern is most prevalent after tuberculosis.Objectives: Our objective was to elucidate the impact of active tuberculosis survival on lung health in the Strong Heart Study (SHS), a population of American Indians historically highly impacted by tuberculosis. As arsenic exposure has also been related to lung function in the SHS, we also assessed the joint effect between arsenic exposure and past active tuberculosis.Methods: The SHS is an ongoing population-based, prospective study of cardiovascular disease and its risk factors in American Indian adults. This study uses tuberculosis data and spirometry data from the Visit 2 examination (1993-1995). Prior active tuberculosis was ascertained by a review of medical records. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC were measured by spirometry. An additional analysis was conducted to evaluate the potential association between active tuberculosis and arsenic exposure.Results: A history of active tuberculosis was associated with reduced percent predicted FVC and FEV1, an increased odds of airflow obstruction (odds ratio = 1.45, 95% confidence interval = 1.08-1.95), and spirometric restrictive pattern (odds ratio = 1.73, 95% confidence interval = 1.24-2.40). These associations persisted after adjustment for diabetes and other risk factors, including smoking. We also observed the presence of cough, phlegm, and exertional dyspnea after a history of active tuberculosis. In the additional analysis, increasing urinary arsenic concentrations were associated with decreasing lung function in those with a history of active tuberculosis, but a reduced odds of active tuberculosis was found with elevated arsenic.Conclusions: Our findings support existing knowledge that a history of active tuberculosis is a risk factor for long-term respiratory impairment. Arsenic exposure, although inversely associated with prior active tuberculosis, was associated with a further decrease in lung function among those with a prior active tuberculosis history. The possible interaction between arsenic and tuberculosis, as well as the reduced odds of tuberculosis associated with arsenic exposure, warrants further investigation, as many populations at risk of developing active tuberculosis are also exposed to arsenic-contaminated water.

Exposure to low-dose arsenic in early life alters innate immune function in children

Early-life exposure to arsenic (As) increases risks of respiratory diseases/infections in children. However, data on the ability of the innate immune system to combat bacterial infections in the respiratory tracts of As-exposed children are scarce. To evaluate whether persistent low-dose As exposure alters innate immune function among children younger than 5 years-of-age, mothers and participating children (N = 51) that were members of the Health Effects of Arsenic Longitudinal Study (HEALS) cohort in rural Bangladesh were recruited. Household water As, past and concurrent maternal urinary As (U-As) as well as child U-As were all measured at enrollment. In addition, U-As metabolites were evaluated. Innate immune function was examined via measures of cathelicidin LL-37 in plasma, ex vivo monocyte-derived-macrophage (MDM)-mediated killing of Streptococcus pneumoniae (Spn), and serum bactericidal antibody (SBA) responses against Haemophilus influenzae type b (Hib). Cyto-/chemokines produced by isolated peripheral blood mononuclear cells (PBMC) were assayed using a Multiplex system. Multivariable linear regression analyses revealed that maternal (p < 0.01) and child (p = 0.02) U-As were positively associated with plasma LL-37 levels. Decreased MDM-mediated Spn killing (p = 0.05) and SBA responses (p = 0.02) were seen to be each associated with fractions of mono-methylarsonic acid (MMA; a U-As metabolite) in the children. In addition, U-As levels were seen to be negatively associated with PBMC formation of fractalkine and IL-7, and positively associated with that for IL-13, IL-17 and MIP-1α. These findings suggested that early-life As exposure may disrupt the innate host defense pathway in these children. It is possible that such disruptions may have health consequences later in life.

Low-moderate arsenic exposure and respiratory in American Indian communities in the Strong Heart Study

BACKGROUND

Arsenic exposure through drinking water is an established lung carcinogen. Evidence on non-malignant lung outcomes is less conclusive and suggests arsenic is associated with lower lung function. Studies examining low-moderate arsenic (< 50 μg/L), the level relevant for most populations, are limited. We evaluated the association of arsenic exposure with respiratory health in American Indians from the Northern Plains, the Southern Plains and the Southwest United States, communities with environmental exposure to inorganic arsenic through drinking water.

METHODS

The Strong Heart Study is a prospective study of American Indian adults. This analysis used urinary arsenic measurements at baseline (1989-1991) and spirometry at Visit 2 (1993-1995) from 2132 participants to evaluate associations of arsenic exposure with airflow obstruction, restrictive pattern, self-reported respiratory disease, and symptoms.

RESULTS

Airflow obstruction was present in 21.5% and restrictive pattern was present in 14.4%. The odds ratio (95% confidence interval) for obstruction and restrictive patterns, based on the fixed ratio definition, comparing the 75th to 25th percentile of arsenic, was 1.17 (0.99, 1.38) and 1.27 (1.01, 1.60), respectively, after adjustments, and 1.28 (1.02, 1.60) and 1.33 (0.90, 1.50), respectively, based on the lower limit of normal definition. Arsenic was associated with lower percent predicted FEV1 and FVC, self-reported emphysema and stopping for breath.

CONCLUSION

Low-moderate arsenic exposure was positively associated with restrictive pattern, airflow obstruction, lower lung function, self-reported emphysema and stopping for breath, independent of smoking and other lung disease risk factors. Findings suggest that low-moderate arsenic exposure may contribute to restrictive lung disease.

Transcriptome-wide analysis of changes in the fetal placenta associated with prenatal arsenic exposure in the New Hampshire Birth Cohort Study

BACKGROUND

Increasing evidence suggests that prenatal exposure to arsenic, even at common environmental levels, adversely affects child health. These adverse effects include impaired fetal growth, which can carry serious health implications lifelong. However, the mechanisms by which arsenic affects fetal health and development remain unclear.

METHODS

We addressed this question using a group of 46 pregnant women selected from the New Hampshire Birth Cohort Study (NHBCS), a US cohort exposed to low-to-moderate arsenic levels in drinking water through the use of unregulated private wells. Prenatal arsenic exposure was assessed using maternal urine samples taken at mid-gestation. Samples of the fetal portion of the placenta were taken from the base of the umbilical cord insertion at the time of delivery, stored in RNAlater and frozen. We used RNA sequencing to analyze changes in global gene expression in the fetal placenta associated with in utero arsenic exposure, adjusting for maternal age. Gene set enrichment analysis and enrichment mapping were then used to identify biological processes represented by the differentially expressed genes. Since our previous analyses have identified considerable sex differences in placental gene expression associated with arsenic exposure, we analyzed male and female samples separately.

RESULTS

At FDR < 0.05, no genes were differentially expressed in female placenta, while 606 genes were differentially expressed in males. Genes showing the most significant associations with arsenic exposure in females were LEMD1 and UPK3B (fold changes 2.51 and 2.48), and in males, FIBIN and RANBP3L (fold changes 0.14 and 0.15). In gene set enrichment analyses, at FDR < 0.05, a total of 211 gene sets were enriched with differentially expressed genes in female placenta, and 154 in male placenta. In female but not male placenta, 103 of these gene sets were also associated with reduced birth weight.

CONCLUSIONS

Our results reveal multiple biological functions in the fetal placenta that are potentially affected by increased arsenic exposure, a subset of which is sex-dependent. Further, our data suggest that in female infants, the mechanisms underlying the arsenic-induced reduction of birth weight may involve activation of stress response pathways.