Arsenic exposure through drinking water increases the risk of liver and cardiovascular diseases in the population of West Bengal, India

Recyclable Au@R-Fe3O4/g-C3N4 substrates for rapid SERS detection and degradation of multiple pollutants

Developing a Surface-enhanced Raman spectroscopy (SERS) method with excellent detecting ability, good recyclability and analyzing multiple pollutants rapidly are critical for evaluation of water quality in emergency pollution affairs. While constructing a multifunctional substrate with these characteristics to realize the application of SERS in water quality monitoring remains a challenge. In this work, a reusable Au@R-Fe3O4/g-C3N4 SERS substrate is prepared by loading Au nanoparticles (Au NPs) on Fe3O4 nanorings (R-Fe3O4) and the formed Au@R-Fe3O4 is further combined with g-C3N4 nanosheets through a simple electrostatic assembly method. The Au@R-Fe3O4/g-C3N4 nanocomposite presents multifunction of magnetic enrichment, SERS signal enhancement, multiple pollutants analyzing, and photocatalytic activity, which achieves quantitative detection of rhodamine B (RhB), tetracycline hydrochloride (TC), and 4-chlorophenol (4-CP), with detection limits of 5.30 × 10-9, 7.50 × 10-8, 7.69 × 10-8 mol/L, respectively. Furthermore, the recyclable detection capability of Au@R-Fe3O4/g-C3N4 for multi components is demonstrated by the strong SERS signal after 9 cycles of "detection-degradation" processes. Combined with good uniformity and stability, this SERS method based on Au@R-Fe3O4/g-C3N4 substrate provides a new strategy for the multi-pollutants detection and degradation in water environment.

Copper, Iron, Cadmium, and Arsenic, All Generated in the Universe: Elucidating Their Environmental Impact Risk on Human Health Including Clinical Liver Injury

Humans are continuously exposed to various heavy metals including copper, iron, cadmium, and arsenic, which were specifically selected for the current analysis because they are among the most frequently encountered environmental mankind and industrial pollutants potentially causing human health hazards and liver injury. So far, these issues were poorly assessed and remained a matter of debate, also due to inconsistent results. The aim of the actual report is to thoroughly analyze the positive as well as negative effects of these four heavy metals on human health. Copper and iron are correctly viewed as pollutant elements essential for maintaining human health because they are part of important enzymes and metabolic pathways. Healthy individuals are prepared through various genetically based mechanisms to maintain cellular copper and iron homeostasis, thereby circumventing or reducing hazardous liver and organ injury due to excessive amounts of these metals continuously entering the human body. In a few humans with gene aberration, however, liver and organ injury may develop because excessively accumulated copper can lead to Wilson disease and substantial iron deposition to hemochromatosis. At the molecular level, toxicities of some heavy metals are traced back to the Haber Weiss and Fenton reactions involving reactive oxygen species formed in the course of oxidative stress. On the other hand, cellular homeostasis for cadmium and arsenic cannot be provided, causing their life-long excessive deposition in the liver and other organs. Consequently, cadmium and arsenic represent health hazards leading to higher disability-adjusted life years and increased mortality rates due to cancer and non-cancer diseases. For unknown reasons, however, liver injury in humans exposed to cadmium and arsenic is rarely observed. In sum, copper and iron are good for the human health of most individuals except for those with Wilson disease or hemochromatosis at risk of liver injury through radical formation, while cadmium and arsenic lack any beneficial effects but rather are potentially hazardous to human health with a focus on increased disability potential and risk for cancer. Primary efforts should focus on reducing the industrial emission of hazardous heavy metals.

Arsenic and adipose tissue: an unexplored pathway for toxicity and metabolic dysfunction

Arsenic-contaminated drinking water can induce various disorders by disrupting lipid and glucose metabolism in adipose tissue, leading to insulin resistance. It inhibits adipocyte development and exacerbates insulin resistance, though the precise impact on lipid synthesis and lipolysis remains unclear. This review aims to explore the processes and pathways involved in adipogenesis and lipolysis within adipose tissue concerning arsenic-induced diabetes. Although arsenic exposure is linked to type 2 diabetes, the specific role of adipose tissue in its pathogenesis remains uncertain. The review delves into arsenic's effects on adipose tissue and related signaling pathways, such as SIRT3-FOXO3a, Ras-MAP-AP-1, PI(3)-K-Akt, endoplasmic reticulum stress proteins, CHOP10, and GPCR pathways, emphasizing the role of adipokines. This analysis relies on existing literature, striving to offer a comprehensive understanding of different adipokine categories contributing to arsenic-induced diabetes. The findings reveal that arsenic detrimentally impacts white adipose tissue (WAT) by reducing adipogenesis and promoting lipolysis. Epidemiological studies have hinted at a potential link between arsenic exposure and obesity development, with limited research suggesting a connection to lipodystrophy. Further investigations are needed to elucidate the mechanistic association between arsenic exposure and impaired adipose tissue function, ultimately leading to insulin resistance.

Arsenic exposure and increased C-reactive protein are independently associated with lower erythrocyte glutathione peroxidase activity in Bangladeshi children

Toxic metal contaminants present in food and water have widespread effects on health and disease. Chalcophiles, such as arsenic, cadmium, and mercury, show a high affinity to selenium and exposure to these metals could have a modulating effect on enzymes dependent on selenocysteine in their active sites. The aim of this study was to assess the influence of these metals on the activity of the selenoprotein glutathione peroxidase 1 (GPX1) in erythrocytes of 100 children residing in rural Bangladesh, where drinking water often contains arsenic. GPX1 expression, as measured using high-throughput immunoblotting, showed little correlation with GPX activity (rs = 0.02, p = 0.87) in blood samples. Toxic metals and selenium measured in erythrocytes using inductively coupled plasma mass spectrometry (ICP-MS) and C-reactive protein (CRP) measured in plasma, were all considered as effectors of this divergence in GPX enzymatic activity. Arsenic concentrations in erythrocytes were most influential for GPX1 activity (rs = -0.395, p < 0.0001), and CRP levels also negatively impacted GPX1 activity (rs = -0.443, p < 0.0001). These effects appear independent of each other as arsenic concentrations and CRP showed no correlation (rs = 0.124, p = 0.2204). Erythrocyte selenium, cadmium, and mercury did not show any correlation with GPX1 activity, nor with CRP or arsenic. Our findings suggest that childhood exposure to inorganic arsenic, as well as inflammation triggering the release of CRP, may negatively affect GPX1 activity in erythrocytes.

Long-term effects of prenatal arsenic exposure from gestational day 9 to birth on lung, heart, and immune outcomes in the C57BL/6 mouse model

Prenatal arsenic exposure is a major public health concern, associated with altered birth outcomes and increased respiratory disease risk. However, characterization of the long-term effects of mid-pregnancy (second trimester) arsenic exposure on multiple organ systems is scant. This study aimed to characterize the long-term impact of mid-pregnancy inorganic arsenic exposure on the lung, heart, and immune system, including infectious disease response using the C57BL/6 mouse model. Mice were exposed from gestational day 9 till birth to either 0 or 1000 µg/L sodium (meta)arsenite in drinking water. Male and female offspring assessed at adulthood (10-12 weeks of age) did not show significant effects on recovery outcomes after ischemia reperfusion injury but did exhibit increased airway hyperresponsiveness compared to controls. Flow cytometric analysis revealed significantly greater total numbers of cells in arsenic-exposed lungs, lower MHCII expression in natural killer cells, and increased percentages of dendritic cell populations. Activated interstitial (IMs) and alveolar macrophages (AMs) isolated from arsenic-exposed male mice produced significantly less IFN-γ than controls. Conversely, activated AMs from arsenic-exposed females produced significantly more IFN-γ than controls. Although systemic cytokine levels were higher upon Mycobacterium tuberculosis (Mtb) infection in prenatally arsenic-exposed offspring there was no difference in lung Mtb burden compared to controls. This study highlights significant long-term impacts of prenatal arsenic exposure on lung and immune cell function. These effects may contribute to the elevated risk of respiratory diseases associated with prenatal arsenic exposure in epidemiology studies and point to the need for more research into mechanisms driving these maintained responses.

Route of Arsenic Exposure Differentially Impacts the Expression of Genes Involved in Gut-Mucosa-Associated Immune Responses and Gastrointestinal Permeability

First-pass metabolism alters arsenic biotransformation and its immunomodulatory activities. This study aims to determine the mRNA expression of intestinal-immunity- and permeability-associated genes, levels of cytokine/chemokines and levels of immunoglobulin isotypes when CD-1 mice were exposed to a single dose of intravenous (IV) sodium arsenite (50 µg/kg body weight (BW)) and to compare these responses to exposure via oral gavage (OG) (50 µg/kg BW). Samples were collected at 1, 4, 24 and 48 h post IV exposure and 24 and 48 h post OG. Sodium arsenite IV exposure led to a transient modulation of mRNA expression and protein levels of immunity-related genes involved in inflammation/apoptotic pathways and production of cytokines/chemokines, whereas it also led to downregulated expression of genes encoding tight junction, focal adhesion, and gap junction proteins, which are responsible for maintaining cell permeability. Oral exposure perturbed fewer cell-permeability-related genes at 24 and 48 h post exposure. At 24 h post exposure, OG decreased IgA and IgG2b levels; however, IV exposure significantly increased IgG2b, IgG3 and IgA in ileal tissue. Earlier, we showed significant downregulation of mRNA expression of genes involved in the immune-related pathways during OG in the intestinal mucosa of the same animals. Cumulatively, these results provide evidence that the exposure route of a xenobiotic can differentially impact the intestinal responses due to the impact of first-pass metabolism.

Intestinal homeostasis disruption in mice chronically exposed to arsenite-contaminated drinking water

Chronic exposure to inorganic arsenic [As(III) and As(V)] affects about 200 million people, and is linked to a greater incidence of certain types of cancer. Drinking water is the main route of exposure, so, in endemic areas, the intestinal mucosa is constantly exposed to the metalloid. However, studies on the intestinal toxicity of inorganic As are scarce. The objective of this study was to evaluate the toxicity of a chronic exposure to As(III) on the intestinal mucosa and its associated microbiota. For this purpose, BALB/c mice were exposed during 6 months through drinking water to As(III) (15 and 30 mg/L). Treatment with As(III) increased reactive oxygen species (43-64%) and lipid peroxidation (8-51%). A pro-inflammatory response was also observed, evidenced by an increase in fecal lactoferrin (23-29%) and mucosal neutrophil infiltration. As(III) also induced an increase in the colonic levels of pro-inflammatory cytokines (24-201%) and the activation of some pro-inflammatory signaling pathways. Reductions in the number of goblet cells and mucus production were also observed. Moreover, As(III) exposure resulted in changes in gut microbial alpha diversity but no differences in beta diversity. This suggested that the abundance of some taxa was significantly affected by As(III), although the composition of the population did not show significant alterations. Analysis of differential taxa agreed with this, 21 ASVs were affected in abundance or variability, especially ASVs from the family Muribaculaceae. Intestinal microbiota metabolism was also affected, as reductions in fecal concentration of short-chain fatty acids were observed. The effects observed on different components of the intestinal barrier may be responsible of the increased permeability in As(III) treated mice, evidenced by an increase in fecal albumin (48-66%). Moreover, serum levels of Lipopolysaccharide binding proteins and TNF-α were increased in animals treated with 30 mg/L of As(III), suggesting a low-level systemic inflammation.

Arsenic and Diabetes Mellitus: A Putative Role for the Immune System

Diabetes mellitus (DM) is an enormous public health issue worldwide. Recent data suggest that chronic arsenic exposure is linked to the risk of developing type 1 and type 2 DM, albeit the underlying mechanisms are unclear. This review discusses the role of the immune system as a link to possibly explain some of the mechanisms of developing T1DM or T2DM associated with arsenic exposure in humans, animal models, and in vitro studies. The rationale for the hypothesis includes: (1) Arsenic is a well-recognized modulator of the immune system; (2) arsenic exposures are associated with increased risk of DM; and (3) dysregulation of the immune system is one of the hallmarks in the pathogenesis of both T1DM and T2DM. A better understanding of DM in association with immune dysregulation and arsenic exposures may help to understand how environmental exposures modulate the immune system and how these effects may impact the manifestation of disease.

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.

Hypermethylation of Mig-6 gene promoter region inactivates its function, leading to EGFR/ERK signaling hyperphosphorylation, and is involved in arsenite-induced hepatic stellate cells activation and extracellular matrix deposition

Arsenic is a widespread naturally contaminant. Previous studies have highlighted the issue of liver fibrosis induced by arsenic exposure, while the exact mechanisms are not yet fully understood. Recent studies suggest that Mig-6/EGFR/ERK signaling appear to play important roles in fibrosis caused by various factors. In this study, we focused on the epigenetic modification combined with the signaling dysregulation to validate the role of Mig-6 in regulating EGFR/ERK signaling in arsenite-induced human hepatic stellate cells (HSCs) activation. Our results revealed that arsenite exposure induced HSCs activation and extracellular matrix (ECM) deposition. The EGFR/ERK signaling was significantly hyperphosphorylated in arsenite-exposed HSCs, and Mig-6 inactivation was involved in arsenite induced hyperphosphorylation of EGFR and activation of HSCs. Additionally, we further illustrated that hypermethylation of Mig-6 gene promoter region was responsible for the downregulation of Mig-6 induced by arsenite exposure. Moreover, 5-Aza-dC (a DNA methyltransferase inhibitor) can efficiently rescue hypermethylation of Mig-6 gene, decrease the hyperphosphorylation of EGFR/ERK signaling, then reverse arsenite induced HSCs activation. Taken together, the present study strongly suggests that inactivating of Mig-6 function by hypermethylation of its promoter region leading to hyperphosphorylation of EGFR/ERK signaling, and is involved in arsenite-induced HSCs activation and ECM deposition.

LC/MS/MS-Based Liver Metabolomics to Identify Chronic Liver Injury Biomarkers Following Exposure to Arsenic in Rats

Arsenic is a widespread natural metalloid element. Long-term chronic exposure to arsenic can lead to different degrees of liver injury. Although the etiology of this disease is well known, to date, the underlying mechanism of arsenic-induced liver injury remains unclear, and no specific treatment exists because of the complexity of arsenic. In the present study, potential biomarkers and metabolic pathways in the livers of Wistar rats treated with arsenic for 24 weeks were investigated using an integrated metabolic approach with an LC-Orbitrap Q Exactive™ HF-X mass spectrometer. Markedly increased liver levels of arsenic, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total bile acid (TBA) were detected in the arsenic treatment groups (P < 0.05). Furthermore, histopathological examination of liver tissues showed obviously swollen, loose cytoplasm and increased necrosis in the arsenic treatment groups compared with those in the control group (P < 0.05). Metabonomics results showed that 109 metabolites (variable importance in the projection (VIP) > 1; fold change > 2 or < 0.5; P adjusted < 0.05) changed significantly after exposure to arsenic and included 71 upregulated metabolites and 38 downregulated metabolites. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that 6 metabolic pathways with statistical significance-phenylalanine metabolism, pyruvate metabolism, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), thiamine metabolism, and vitamin B6 metabolism-were selected, and 13 differential metabolites were detected to be involved in regulating these metabolic pathways. The present study could help identify potential biomarkers and their functions, as well as metabolic pathways, likely providing evidence for the early diagnosis, prevention, and mechanistic study of arsenism.

Combined effects of arsenic and 2,2-dichloroacetamide on different cell populations of zebrafish liver

Arsenic (As) and disinfection by-products are important health risk factors in the water environment. However, their combined effects on different cell populations in the liver are not well known. Here, zebrafish were exposed to 100 μg/L As, 300 μg/L 2,2-dichloroacetamide (DCAcAm), and their combination for 23 days. Then transcriptome profiles of cell populations in zebrafish liver were analyzed by single-cell RNA sequencing (scRNA-seq). A total of 13,563 cells were obtained, which were identified as hepatocytes, hepatic duct cells, endothelial cells and macrophages. Hepatocytes were the main target cell subtype of As and DCAcAm exposures. DCAcAm exposure induced higher toxicity in male hepatocytes, which specifically changed amino acid metabolism, response to hormone and cofactor metabolism. However, As exposure caused higher toxicity in female hepatocytes, which altered lipid metabolism, carbon metabolism, and peroxisome. Combined exposure to As and DCAcAm decreased toxicities in hepatocytes compared to each one alone. Female hepatocytes had higher tolerance to co-exposure of As and DCAcAm than male hepatocytes. Further, combined exposure to As and DCAcAm induced functional changes in macrophages similar to As alone groups, which mainly altered the transfer of sterol and cholesterol. Hepatic duct cells and endothelial cells were not influenced by exposures to As and DCAcAm. This study for the first time highlights the cell-specific combined responses of As and DCAcAm in zebrafish liver, which provide useful information for their health risk assessment in a co-exposure environment.

The Effect of Broccoli Extract in Arsenic-Induced Experimental Poisoning on the Hematological, Biochemical, and Electrophoretic Parameters of the Liver and Kidney of Rats

Heavy metals such as arsenic contribute to environmental pollution that can lead to systemic effects in various body organs. Some medicinal plants such as broccoli have been shown to reduce the harmful effects of these heavy metals. The main aim of the present study is to evaluate the effects of broccoli extract on liver and kidney toxicity, considering hematological and biochemical changes. The experimental study was performed in 28 days on 32 male Wistar rats classified into four groups: the control group (C), a group receiving 5 mg/kg oral arsenic (AS), a group receiving 300 mg/kg broccoli (B), and a group receiving arsenic and broccoli combination (AS + B). Finally, blood samples were taken to evaluate the hematological and biochemical parameters of the liver and kidney, as well as serum proteins' concentration. Liver and kidney tissue were fixed and stained by H&E and used for histopathological diagnosis. The results demonstrated a significant decrease in white blood cells (WBC), red blood cells (RBC), and hemoglobin (Hb) in the AS group compared to other groups. However, in the B group, a significant increase in RBC and WBC was observed compared to the AS and C groups (P < 0.05). Moreover, RBC and WBC levels increased significantly in the AS + B group compared to the AS group (P = 0.046). However, in the AS group, aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine levels increased, while total protein, albumin, and globulin decreased. This can be a result of liver and kidney damage, which was observed in the AS group. Furthermore, the increase in the concentration of albumin and globulin in the AS + B group was higher than that in the AS group. Infiltration of inflammatory cells and necrosis of the liver and kidney tissue in the pathological evaluation of the AS group were significantly higher than other groups. There was an increase in superoxide dismutases (SOD), glutathione peroxidase (GPx), and total antioxidant capacity (TAC); however, a decrease in malondialdehyde (MDA) concentration was seen in the AS + B group compared to the AS group. It seems that broccoli is highly effective at reducing liver and kidney damage and improving the hematological and biochemical factors in arsenic poisoning conditions.

Mitochondrial Dysfunction in Arsenic-Induced Hepatotoxicity: Pathogenic and Therapeutic Implications

Mitochondria are vital cellular organelles associated with energy production as well as cell signaling pathways. These organelles, responsible for metabolism, are highly abundant in hepatocytes that make them key players in hepatotoxicity. The literature suggests that mitochondria are targeted by various environmental pollutants. Arsenic, a toxic metalloid known as an environmental pollutant, readily contaminates drinking water and exerts toxic effects. It is toxic to various cellular organs; among them, the liver seems to be most affected. A growing body of evidence suggests that within cells, arsenic is highly toxic to mitochondria and reported to cause oxidative stress and alter an array of signaling pathways and functions. Hence, it is imperative to highlight the mechanisms associated with altered mitochondrial functions and integrity in arsenic-induced liver toxicity. This review provides the details of mechanistic aspects of mitochondrial dysfunction in arsenic-induced hepatotoxicity as well as various ameliorative measures undertaken concerning mitochondrial functions.

Biochemical Investigation of Therapeutic Potential of Resveratrol Against Arsenic Intoxication

Arsenic has been reported to cause damaging effects on different body organs. This study was designed to evaluate the protective effect of resveratrol (RSV) against arsenic trioxide (ATO)–induced intoxication in experimental animals. Twenty-four Wistar rats were allocated in 4 groups: group 1: control group, received normal diet; group 2: received ATO (3 mg/kg); group 3: received RSV (8 mg/kg) 30 minutes before administration of ATO; and group 4: received ascorbic acid (25 mg/kg) 30 minutes before administration of ATO. Treatments were given to experimental rats daily for consecutive 8 days. At the end of experimental period, bioaccumulation of arsenic in liver and kidney was assessed by hydride generation-atomic absorption spectrophotometer to investigate the association of arsenic accumulation with histological aberrations. Following parameters were also investigated: serum biochemical profile (alanine aminotransferase, aspartate transaminase, alkaline phosphatase, blood urea nitrogen, and creatinine) for evaluation of liver and kidney functions and lipid peroxidation and oxidative stress (malondialdehyde, glutathione, superoxide dismutase, catalase, and glutathione peroxidase) in tissue homogenates of liver and kidney for estimation of oxidative status. The findings of this study indicate that RSV remarkably ameliorated the hepatic and renal toxicity in arsenic-exposed rat model due to its strong antioxidant potential.

Environmental arsenic exposure and its contribution to human diseases, toxicity mechanism and management

Arsenic is a well-recognized environmental contaminant that occurs naturally through geogenic processes in the aquifer. More than 200 million people around the world are potentially exposed to the elevated level of arsenic mostly from Asia and Latin America. Many adverse health effects including skin diseases (i.e., arsenicosis, hyperkeratosis, pigmentation changes), carcinogenesis, and neurological diseases have been reported due to arsenic exposure. In addition, arsenic has recently been shown to contribute to the onset of non-communicable diseases, such as diabetes mellitus and cardiovascular diseases. The mechanisms involved in arsenic-induced diabetes are pancreatic β-cell dysfunction and death, impaired insulin secretion, insulin resistance and reduced cellular glucose transport. Whereas, the most proposed mechanisms of arsenic-induced hypertension are oxidative stress, disruption of nitric oxide signaling, altered vascular response to neurotransmitters and impaired vascular muscle calcium (Ca²⁺) signaling, damage of renal, and interference with the renin-angiotensin system (RAS). However, the contributions of arsenic exposure to non-communicable diseases are complex and multifaceted, and little information is available about the molecular mechanisms involved in arsenic-induced non-communicable diseases and also no suitable therapeutic target identified yet. Therefore, in the future, more basic research is necessary to identify the appropriate therapeutic target for the treatment and management of arsenic-induced non-communicable diseases. Several reports demonstrated that a daily balanced diet with proper nutrient supplements (vitamins, micronutrients, natural antioxidants) has shown effective to reduce the damages caused by arsenic exposure. Arsenic detoxication through natural compounds or nutraceuticals is considered a cost-effective treatment/management and researchers should focus on these alternative options. This review paper explores the scenarios of arsenic contamination in groundwater with an emphasis on public health concerns. It also demonstrated arsenic sources, biogeochemistry, toxicity mechanisms with therapeutic targets, arsenic exposure-related human diseases, and onsets of cardiovascular diseases as well as feasible management options for arsenic toxicity.

Assessment of hypertension association with arsenic exposure from food and drinking water in Bihar, India

Epidemiological studies have associated chronic exposure to arsenic (As) from drinking water with increased risk of hypertension. However, evidence of an association between As exposure from food and hypertension risks is sparse. To quantify the association between daily As intake from both food (rice, wheat and potatoes) and drinking water (As_water) along with total exposure (As_total) and hypertension risks in a study population in Bihar, India, we conducted an individual level cross-sectional analysis between 2017 and 2019 involving 150 participants. Arsenic intake variables and three indicators of hypertension risks (general hypertension, low-density lipoprotein (LDL) and high-density lipoprotein (HDL)) were derived, and any relationship was quantified using a series of crude and multivariable log-linear or logistic regression models. The prevalence of general hypertension was 40% for the studied population. The median level of HDL was 45 mg/dL while median value of LDL was 114 mg/dL. Apart from a marginally significant positive relationship between As intake from rice and the changes of LDL (p-value = 0.032), no significant positive association between As intake and hypertension risks could be ascertained. In fact, As_total was found to be associated with lower risks of general hypertension and higher levels of HDL (p-value = 0.020 and 0.010 respectively) whilst general hypertension was marginally associated with lower As_water (p-value = 0.043). Due to limitations regarding study design and residual confounding, all observed marginal associations should be treated with caution.

Imbalanced inflammatory response in subchronic arsenic-induced liver injury and the protective effects of Ginkgo biloba extract in rats: Potential role of cytokines mediated cell-cell interactions

Arsenic is a well-known environmental toxicant and carcinogen, which has been epidemiologically proved related to the increased hepatic disorders. Researches have shown that aseptic inflammation and abnormal immune response are associated with arsenic-induced liver injury. However, the immunotoxic effects of liver have not been extensively characterized. Ginkgo biloba extract (GBE), a natural products of G. biloba leaves with proven anti-inflammatory and potential immunoregulatory activities, was used as intervention agent to explore its protective effects on arsenic-induced hepatotoxicity. Thus, the underlying mechanism of the immunotoxic effects on arsenic-induced liver injury were investigated in 2.5, 5.0, and 10.0 mg/kg NaAsO₂ of Wistar rats for 16 weeks. Subsequently, GBE was used as intervention agent in 50 mg/kg for 6 weeks after cessation of arsenic exposure. The ratio of Th17 to Treg cells in peripheral blood as well as the secretion of inflammatory cytokines IL-17A, IL-6, TGF-β1, and IL-10 in serum and liver were detected. Meanwhile, the notable activation of aseptic inflammation-related molecule TLR4 and its downstream targets MyD88 and NF-κB in the liver were observed. In this work, we confirmed that subchronic exposed to arsenic triggered the infiltration of inflammatory cells in rat liver, coupled with obvious histopathological changes and aberrant hepatic serum biochemical parameters. Meanwhile, imbalanced immune response was verified by the notable abnormal ratio of Th17 to Treg cells in peripheral blood as well as the secretion of inflammatory cytokines IL-17A, IL-6, TGF-β1, and IL-10 in serum and liver of arsenic exposed rats. Further, the level of TLR4, MyD88, and NF-κB in liver both transcription and translation activity were raised. Subsequently, GBE markedly mitigated arsenic-induced liver injury, most impressively, post treatment with GBE prominently suppressed the overactivated inflammatory-related TLR4-MyD88-NF-κB pathway and evidently decreased the secretion of inflammation cytokines. Meanwhile, the disturbance of pro- and anti-inflammatory response was reversed. We concluded that the disruption of pro- and anti-inflammatory T-cells balance caused by cytokines mediated cell-cell interactions may be one of the mechanisms underlying arsenic-induced liver injury and that GBE intervention exerts an evidence protective effects, which might be closely associated with the suppression of inflammatory-related TLR4 pathway.

Occupational exposure of rural workers to pesticides in a vegetable-producing region in Brazil

The health of family farmers is at risk due to occupational exposure to pesticides. The aims of the current study were to investigate the level of farmers' perception of risks associated with pesticide use and to assess their health condition based on biochemical and immunological tests. Family farmers living in a vegetable-producing region in Southern Brazil were selected to participate in the study. More than 70% of the family farmers were often exposed to more than one type of pesticides; 41.2% were intensively using several pesticides for more than one decade and 74.4% were not using personal protective equipment (PPE) at the time of pesticide handling due to low perception of the risks posed by these chemicals. Enzymatic analysis performed in participants' blood samples showed changes in catalase (CAT) and glutathione reductase (GR) activity, in lipid peroxidation (TBARS) and carbonylated protein levels, as well as in chemoattractant (IL-8) and anti-inflammatory (IL-10) interleukin expression. Low perception of health-related risks posed by pesticides can be attributed to factors such as low schooling and lack of information, which put farmers' health at risk, as evidenced by blood biochemical and immunological changes.

Arsenic Stress-Related F-Box (ASRF) gene regulates arsenic stress tolerance in Arabidopsis thaliana

Arsenic (As), a non-biodegradable contaminant, is extremely toxic to plants and animals in its inorganic form. As negatively affects plant growth and development, primarily by inducing oxidative stress through redox imbalance. Here we characterized the Arabidopsis F-box protein gene AT2G16220 (Arsenic Stress-Related F-box (ASRF)) that we identified in the genome-wide association study. The asrf mutant seedlings showed high sensitivity to arsenate (As^V) stress. As^V significantly affected asrf seedling growth when germinated on or exposed to As^V-supplemented growth regimes. As^V stress significantly induced production of reactive oxygen species and proline accumulation in asrf, so the asrf maintained high proline content, possibly for cellular protection and redox homeostasis. Heterozygous seedlings (Col-0 x asrf, F1 progeny) were relatively less affected by As^V stress than asrf mutant but showed slightly reduced growth compared with the Col-0 wild type, which suggests that the homozygous ASRF locus is important for As^V stress resistance. Transcriptome analysis involving the mutant and wild type revealed altered phosphate homeostasis in asrf seedlings, which implies that ASRF is required for maintaining phosphate and cellular- homeostasis under excess As^V. Our findings confirm the roles of ASRF in As stress tolerance in plants, for a novel way to mitigate arsenic stress.

Associations between and risks of trace elements related to skin and liver damage induced by arsenic from coal burning

Long-term exposure to high levels of arsenic has been documented to induce skin and liver damage, affecting hundreds of millions of people. While arsenic-induced skin and liver damage and trace element alterations have been studied, their correlations and risks have not been explained. Based on the above premise, this study included a total of 172 subjects from a coal-burning arsenic poisoning area. The levels of 18 trace elements in hair and six liver function indices in serum were detected, and the associations between and risks of trace elements related to skin and liver damage were analyzed. Finally, the receiver operating characteristic (ROC) curve and areas under the curve (AUC) were used to analyze the diagnostic values of certain trace elements for arsenic-induced skin and liver damage. The results found that a decrease in Se was a risk factor for arsenic-induced skin and liver damage (OR = 8.33 and 1.92, respectively). Furthermore, increases in Al and V were risk factors for arsenic-induced skin damage (OR = 1.05) and liver damage (OR = 13.16), respectively. In addition, the results found that Se and Al possessed certain diagnostic values for arsenic-induced skin damage (AUC = 0.93, 0.80), that Se possessed a diagnostic value for liver damage (AUC = 0.93), and that the combination of Se and Al increased the diagnostic value for skin damage (AUC = 0.96). This study provides an important research basis for further understanding the reasons for arsenic-induced skin and liver damage, for screening and identifying candidate diagnostic biomarkers, and for improving prevention and control strategies for arsenism.

Pentoxifylline Attenuates Arsenic Trioxide-Induced Cardiac Oxidative Damage in Mice

This study was undertaken to evaluate the therapeutic potential effect of pentoxifylline (PTX) against arsenic trioxide (ATO)-induced cardiac oxidative damage in mice. Thirty-six male albino mice were divided into six groups and treated intraperitoneally with normal saline (group 1), ATO (5 mg/kg; group 2), PTX (100 mg/kg; group 3), and different doses of PTX (25, 50, and 100 mg/kg; groups 4, 5, and 6, respectively) with ATO. After four weeks, the blood sample was collected for biochemical experiments. In addition, cardiac tissue was removed for assessment of oxidative stress markers and histopathological changes (such as hemorrhage, necrosis, infiltration of inflammatory cells, and myocardial degeneration). The findings showed that ATO caused a significant raise in serum biochemical markers such as lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and troponin-I (cTnI), glucose, total cholesterol (TC), and triglyceride (TG) levels. In addition to histopathological changes in cardiac tissue, ATO led to the significant increase in cardiac lipid peroxidation (LPO) and nitric oxide (NO); remarkable decrease in the activity of cardiac antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx); and the depletion of the total antioxidant capacity (TAC) and total thiol groups (TTGs). PTX was able to reduce the increased levels of serum cardiac markers (LDH, CPK, cTnI, TC, and TG), cardiac LPO, and improve antioxidant markers (TAC, TTGs, CAT, SOD, and GPx) alongside histopathologic changes. However, no significant changes were observed in elevated serum glucose and cardiac NO levels. In conclusion, the current study showed the potential therapeutic effect of PTX in the prevention of ATO-induced cardiotoxicity via reversing the oxidative stress.

Biochemical and histological effects of five weeks ingestion of Zamzam water on the liver and kidneys of Wistar rats

Zamzam water is a natural alkaline water which has become alkaline as a result of the natural environment. It comes from what is considered as one of the oldest springs in the world. The water contains high concentrations of alkaline minerals as well as trace and heavy metals. The aim of the current study is to evaluate the effects of five weeks ingestion of Zamzam water on the liver and kidney functions of rats. Adult female Wistar rats weighing 150-200 g were divided into two groups, with 15 rats in each. The control group was supplied daily by bottled water and the Zamzam water group was supplied daily by 500 ml of Zamzam water for five weeks. The rats were weighed weekly and, at the end of the experiment, blood samples were collected from all rats for the biochemical determination of serum levels of aspartate transaminase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), urea, creatinine, albumin, and uric acid, using calorimetric methods. Liver and kidney tissues were fixed in 10% neutral buffered-formalin solution and further embedded in wax blocks for routine hematoxylin and eosin (H&E) staining and were examined for histopathological changes using a light microscope. The results of the current study showed that there was a significant increase (P < 0.05) in the weight of the Zamzam group when compared to the control group after five weeks of ingestion. Liver and kidney function tests did not show any significant difference when compared with the controls (P > 0.05). In addition, histological examination of the liver and kidney tissues did not show any toxicological changes. In conclusion, the results showed that the ingestion of Zamzam water did not alter serum levels of kidney function tests and liver enzymes; and did not result in a noticeable change in the liver and kidney histology. Thus, the high concentrations of elements in Zamzam water do not induce hepatotoxicity or nephrotoxicity and the water is considered safe for long-term consumption.

MicroRNA-15b in extracellular vesicles from arsenite-treated macrophages promotes the progression of hepatocellular carcinomas by blocking the LATS1-mediated Hippo pathway

Arsenic, a human carcinogen, causes various human cancers, including those of the skin, lung, and liver. Hepatocellular carcinomas (HCCs), which have high mortality, are common malignancies worldwide. Tumor-associated macrophages (TAMs), which are considered to be similar to M2-polarized macrophages, promote tumor invasion and progression. Small non-coding RNAs (miRNAs) regulate expression of genes involved in progression of various malignancies. Extracellular vesicles (EVs), as mediators of cell communication, pass specific miRNAs directly from TAMs to tumor cells, promoting tumor pathogenesis and metastasis. In HCCs, large tumor suppressor kinase 1 (LATS1), functions as a tumor suppressor. However, the molecular mechanism by which miRNA modulates LATS1 expression in HCCs remains unclear. The results show that exposure to arsenite, increased miR-15b levels and induced M2 polarization of THP-1 cells. Elevated levels of miR-15b were transferred from arsenite-treated-THP-1 (As-THP-1) cells to HCC cells via miR-15b in EVs inhibited activation of the Hippo pathway by targeting LATS1, and was involved in promoting the proliferation, migration, and invasion of HCC cells. In conclusion, miR-15b in EVs from As-THP-1 cells is transferred to HCC cells, in which it targets and downregulates LATS1 expression and promotes the proliferation, migration, and invasion of HCC cells.

Protective effect of Mucuna pruriens against arsenic-induced liver and kidney dysfunction and neurobehavioral alterations in rats

BACKGROUND AND AIM

Intoxication of arsenic in rats is known to result in neurological effects as well as liver and kidney dysfunction. Mucuna pruriens has been identified for its medicinal properties. The aim of the study was to investigate the protective effect of aqueous seed extract of M. pruriens on sodium arsenite-induced memory impairment, liver, and kidney functions in rats.

MATERIALS AND METHODS

The experiment was divided into short-term treatment (45 days) and long-term treatment (90 days), with each group divided into nine sub-groups consisting of six animals each. Sub-groups 1 and 2 served as normal, and N-acetylcysteine (NAC) controls, respectively. Sub-groups 3-9 received sodium arsenite in drinking water (50 mg/L). In addition, sub-group 4 received NAC (210 mg/kg b.wt) orally once daily, sub-groups 5-7 received aqueous seed extract of M. pruriens (350 mg/kg b.wt, 530 mg/kg b.wt, and 700 mg/kg b.wt) orally once daily and sub-groups 8 and 9 received a combination of NAC and aqueous seed extract of M. pruriens (350 mg/kg b.wt and 530 mg/kg b.wt) orally once daily. Following the treatment, the blood was drawn retro-orbitally to assess the liver (serum alanine transaminase [ALT], serum aspartate transaminase, and serum alkaline phosphatase) and kidney (serum urea and serum creatinine) functions. Learning and memory were assessed by passive avoidance test. Animals were sacrificed by an overdose of ketamine, and their Nissl stained hippocampal sections were analyzed for alterations in neural cell numbers in CA1 and CA3 regions.

RESULTS

In the short-term treatment, groups administered with M. pruriens 530 mg/kg b.wt alone and combination of NAC + M. pruriens 350 mg/kg b.wt exhibited a significant improvement in memory retention, less severe neurodegeneration, and decrease in serum ALT levels. In long-term treatment, groups administered with M. pruriens 700 mg/kg b.wt alone and combination of NAC+M. pruriens 350 mg/kg b.wt, respectively, showed better memory retention, decreased neural deficits, and reduced levels of kidney and liver enzymes.

CONCLUSION

The seed extract of M. pruriens showed significant enhancement in memory and learning. The number of surviving neurons in the CA1 and CA3 regions also increased on treatment with M. pruriens. Serum ALT, serum urea, and serum creatinine levels showed significant improvement on long-term treatment with M. pruriens.

Urinary Metals Concentrations and Biomarkers of Autoimmunity among Navajo and Nicaraguan Men

Metals are suspected contributors of autoimmune disease among indigenous Americans. However, the association between metals exposure and biomarkers of autoimmunity is under-studied. In Nicaragua, environmental exposure to metals is also largely unexamined with regard to autoimmunity. We analyzed pooled and stratified exposure and outcome data from Navajo (n = 68) and Nicaraguan (n = 47) men of similar age and health status in order to characterize urinary concentrations of metals, compare concentrations with the US National Health and Nutrition Examination Survey (NHANES) male population, and examine the associations with biomarkers of autoimmunity. Urine samples were analyzed for metals via inductively coupled plasma mass spectrometry (ICP-MS) at the US Centers for Disease Control and Prevention. Serum samples were examined for antinuclear antibodies (ANA) at 1:160 and 1:40 dilutions, using an indirect immunofluorescence assay and for specific autoantibodies using enzyme-linked immunosorbent assay (ELISA). Logistic regression analyses evaluated associations of urinary metals with autoimmune biomarkers, adjusted for group (Navajo or Nicaraguan), age, and seafood consumption. The Nicaraguan men had higher urinary metal concentrations compared with both NHANES and the Navajo for most metals; however, tin was highest among the Navajo, and uranium was much higher in both populations compared with NHANES. Upper tertile associations with ANA positivity at the 1:160 dilution were observed for barium, cesium, lead, strontium and tungsten.

Understanding the mechanistic insight of arsenic exposure and decoding the histone cipher

BACKGROUND

The study of heritable epigenetic changes in arsenic exposure has intensified over the last decade. Groundwater arsenic contamination causes a great threat to humans and, to date, no accurate measure has been formulated for remediation. The fascinating possibilities of epi-therapeutics identify the need for an in-depth mechanistic understanding of the epigenetic landscape.

OBJECTIVE

In this comprehensive review, we have set to analyze major studies pertaining to histone post-translational modifications in arsenic-mediated disease development and carcinogenesis during last ten years (2008-2018).

RESULTS

The role of the specific histone marks in arsenic toxicity has been detailed. A comprehensive list that includes major arsenic-induced histone modifications identified for the last 10 years has been documented and details of different states of arsenic, organisms, exposure type, study platform, and findings were provided. An arsenic signature panel was suggested to help in early prognosis. An attempt has been made to identify the grey areas of research.

PROSPECTS

Future prospective multi-target analyses of the inter-molecular crosstalk among different histone marks are needed to be explored further in order to understand the mechanism of arsenic toxicity and carcinogenicity and to confirm the suitability of these epi-marks as prognostic markers.

An assessment of arsenic hazard in groundwater-soil-rice system in two villages of Nadia district, West Bengal, India

The present study measured arsenic (As) concentrations in soil, groundwater and rice grain samples in two villages, Sarapur and Chinili, under Chakdaha block, Nadia district, West Bengal, India. This study also included a survey of the two villages to understand the knowledge among villagers about the As problem. Soil and groundwater samples were collected from fields in two villages while rice grain samples were collected from villagers' houses. The results revealed the presence of As in higher concentrations than the maximum permissible limit of As in drinking water (10 µg L^-1 and 50 µg L^-1 by WHO and Indian standard, respectively) in groundwater [124.50 ± 1.11 µg L^-1 (Sarapur) and 138.20 ± 1.34 µg L^-1 (Chinili)]. The level of As in soil was found to range from 47.7 ± 0.14 to 49.3 ± 0.19 mg Kg^-1 in Sarapur and from 57.5 ± 0.25 to 62.5 ± 0.44 mg Kg^-1 in Chinili which are also higher than European Union maximum acceptable limit in agricultural soil (i.e. 20 mg Kg^-1). The analysis of As in rice grains of five varieties, collected from residents of two villages, showed the presence of higher than recommended safe level of As in rice by FAO/WHO (0.2 mg Kg^-1). The As concentration order was Gosai (0.95 ± 0.044 mg kg^-1), Satabdi (0.79 ± 0.038 mg kg^-1), Banskathi (0.60 ± 0.026 mg kg^-1), Kunti (0.47 ± 0.018 mg kg^-1) and Ranjit (0.29 ± 0.021 mg kg^-1). Importantly, Gosai and Satabdi were the most popular varieties being consumed by local people. The data of consumption of rice per day in the survey was used for the measurement of average daily dose and hazard quotient. It was seen that the As hazard was negatively correlated to the age of residents. Therefore, children and toddlers were at higher risk of As exposure than elderly people. In addition, people with skin related As toxicity symptoms were also cited in the two villages. The study emphasized the severity of As problem in remote areas of West Bengal, India where people consume As tainted rice due to lack of awareness about the As problem and associated health issues.

Application of water quality index, synthetic pollution index, and geospatial tools for the assessment of drinking water quality in the Indus Delta, Pakistan

Seawater intrusion into the Indus Delta, Pakistan, has spoiled groundwater aquifers in the area. In the delta, the groundwater is widely used by residents for drinking. Considering the gravity of the problem, and concerns expressed by affected communities, the present study was conducted to assess and map the quality of groundwater, based on the physico-chemical properties of 180 samples, using two standard numerical indices, geospatial and statistical techniques. The analysis of water samples revealed that several parameters exceeded the drinking water quality guidelines suggested by the World Health Organization (WHO). The water quality index (WQI) identified that about 1.7%, 1.1%, 27.8%, 42.8%, and 26.6% of the water samples were excellent, good, poor, very poor, and unsuitable for drinking purposes, respectively. However, the synthetic pollution index (SPI) ranked the quality of 2.8%, 2.2%, 23.9%, 41.7%, and 29.4% as suitable, slightly polluted, moderately polluted, highly polluted, and unsuitable, respectively. Though the numerical model's input is different, the proportionate ranking revealed a fair correlation (R² = 0.75) between the outcomes of both indices. The results of the numerical indices and the interpolated geographical information system (GIS) mapping revealed that the quality of groundwater in most of the delta does not meet WHO guidelines for potable water. Hence, it is recommended that the groundwater of the delta should be properly treated before its use for domestic purposes. The study highlights the significance of using numerical indices and geospatial techniques for water quality evaluation in the Indus Delta and similar deltaic regions throughout the world.

MicroRNAs play an important role in contributing to arsenic susceptibility in the chronically exposed individuals of West Bengal, India

Arsenic exposure by groundwater contamination is a menace which threatens more than 26 million individuals of West Bengal. Interestingly, with similar levels of arsenic exposure, only 15-20% of the population show arsenic-induced skin lesions, the hallmarks of chronic arsenic toxicity, but the rest do not. In this study, our aim was to identify whether microRNAs (miRNA) have any role to play in causing such arsenic susceptibility. Global plasma miRNA profiling was done in 12 arsenic-exposed individuals with skin lesions and 12 exposed individuals without skin lesions. Two hundred two miRNAs were found to be differentially regulated between the two study groups. Results were validated by quantitative real-time PCR in 30 exposed subjects from each of the groups, which showed that among others miR-21, miR-23a, miR-27a, miR-122, miR-124, miR-126, miR-619, and miR-3613 were significantly upregulated and miR-1282 and miR-4530 were downregulated in the skin lesion group compared with the no skin lesion group. Bioinformatic analyses predicted that these altered miRNAs have targets in 7 different biochemical pathways, including glycerophospholipid metabolism, colorectal cancer, glycosphingolipid biosynthesis, T cell receptor signaling, and neurotrophin signaling pathways; glycerophospholipid metabolism pathway being the most enriched pathway. Association study show that these microRNAs contribute significantly to the increased prevalence of other non-dermatological health effects like conjunctival irritations of the eyes and respiratory distress in the study subjects. To our knowledge, this is the first study of its kind involving miRNA expressions contributing to arsenic susceptibility in the exposed population of West Bengal.

Thyroid hormones and neurobehavioral functions among adolescents chronically exposed to groundwater with geogenic arsenic in Bangladesh

Groundwater, the major source of drinking water in Bengal Delta Plain, is contaminated with geogenic arsenic (As) enrichment affecting millions of people. Children exposed to tubewell water containing As may be associated with thyroid dysfunction, which in turn may impact neurodevelopmental outcomes. However, data to support such relationship is sparse. The purpose of this study was to examine if chronic water As (WAs) from Holocene alluvial aquifers in this region was associated with serum thyroid hormone (TH) and if TH biomarkers were related to neurobehavioral (NB) performance in a group of adolescents. A sample of 32 healthy adolescents were randomly drawn from a child cohort in the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh. Half of these participants were consistently exposed to low WAs (<10 μg/L) and the remaining half had high WAs exposure (≥10 μg/L) since birth. Measurements included serum total triiodothyronine (tT₃), free thyroxine (fT₄), thyrotropin (TSH) and thyroperoxidase antibodies (TPOAb); concurrent WAs and urinary arsenic (UAs); and adolescents' NB performance. WAs and UAs were positively and significantly correlated with TPOAb but were not correlated with TSH, tT₃ and fT₄. After accounting for covariates, both WAs and UAs demonstrated positive but non-significant relationships with TSH and TPOAb and negative but non-significant relationships with tT₃ and fT₄. TPOAb was significantly associated with reduced NB performance indicated by positive associations with latencies in simple reaction time (b = 82.58; p < 0.001) and symbol digit (b = 276.85; p = 0.005) tests. TSH was significantly and negatively associated with match-to-sample correct count (b = -0.95; p = 0.05). Overall, we did not observe significant associations between arsenic exposure and TH biomarkers although the relationships were in the expected directions. We observed TH biomarkers to be related to reduced NB performance as hypothesized. Our study indicated a possible mechanism of As-induced neurotoxicity, which requires further investigations for confirmatory findings.

South Asian Health: Inflammation, Infection, Exposure, and the Human Microbiome

This paper presents the results of the literature review conducted for the working group topic on inflammation, infection, exposure, and the human microbiome. Infection and chronic inflammation can elevate risk for cardiovascular disease and cancer. Environmental exposures common among South Asian (SA) subgroups, such as arsenic exposure among Bangladeshis and particulate matter air pollution among taxi drivers, also pose risks. This review explores the effects of exposure to arsenic and particulate matter, as well as other infections common among SAs, including human papillomavirus (HPV) and hepatitis B/C infection. Emerging research on the human microbiome, and the effect of microbiome changes on obesity and diabetes risk among SAs are also explored.

Socioeconomic status and the association between arsenic exposure and type 2 diabetes

OBJECTIVE

Evaluate whether arsenic-related diabetes risks differ between people of low and high socioeconomic status (SES).

METHODS

We used data collected between October 2007-December 2010 from a population-based cancer case-control study (N = 1301) in Northern Chile, an area with high arsenic water concentrations (>800 µg/L) and comprehensive records of past exposure. Information on lifetime exposure and potential confounders were obtained using structured interviews, questionnaires, and residential histories. Type 2 diabetes was defined as physician-diagnosed diabetes or oral hypoglycemic medication use. SES was measured using a 14-point scale based on ownership of household appliances, cars, internet access, or use of domestic help. Logistic regression was used to assess the relationship between arsenic and diabetes within strata of SES.

RESULTS

Among those with low SES, the odds ratio (OR) for diabetes comparing individuals in the highest to lowest tertile of lifetime average arsenic exposure was 2.12 (95% confidence interval (CI) 1.29-3.49, p = 0.004). However, those in the high SES group were not at increased risk (OR = 1.12 [95% CI = 0.72-1.73]).

CONCLUSIONS

Our findings provide evidence that risks of arsenic-related diabetes may be higher in Chile in people with low versus high SES.

Inorganic arsenic exposure induces sex-disparate effects and exacerbates ischemia-reperfusion injury in the female heart

Arsenic is a common contaminant in drinking water throughout the world, and recent studies support a link between inorganic arsenic (iAS) exposure and ischemic heart disease in men and women. Female hearts exhibit an estrogen-dependent reduction in susceptibility to myocardial ischemic injury compared with males, and as such, female hearts may be more susceptible to the endocrine-disrupting effects of iAS exposure. However, iAS exposure and susceptibility to ischemic heart injury have not been examined in mechanistic studies. Male and female mice (8 wk) were exposed to environmentally relevant concentrations of sodium arsenite (0, 10, 100, and 1,000 parts/billion) via drinking water for 4 wk. Pre- and postexposure echocardiography was performed, and postexposure plasma was collected for 17β-estradiol measurement. Hearts were excised and subjected to ischemia-reperfusion (I/R) injury via Langendorff perfusion. Exposure to 1,000 parts/billion iAS led to sex-disparate effects, such that I/R injury was exacerbated in female hearts but unexpectedly attenuated in males. Assessment of echocardiographic parameters revealed statistically significant structural remodeling in iAS-treated female hearts with no change in function; males showed no change. Plasma 17β-estradiol levels were not significantly altered by iAS in male or female mice versus nontreated controls. Although total eNOS protein levels did not change in whole heart homogenates from iAS-treated male or female mice, eNOS phosphorylation (Ser¹¹⁷⁷) was significantly elevated in iAS-treated male hearts. These results suggest that iAS exposure can induce sex-disparate effects and modulate susceptibility to ischemic heart injury by targeting distinct sex-dependent pathways. NEW & NOTEWORTHY This is the first mechanistic study examining iAS exposure on myocardial ischemia-reperfusion injury in male and female mice. Following iAS exposure, ischemia-reperfusion injury was exacerbated in female hearts but attenuated in males. iAS treatment induced statistically significant cardiac remodeling in females, with no change in males. iAS treatment also enhanced phosphorylated eNOS levels at Ser¹¹⁷⁷, but only in male hearts. These results suggest that iAS alters susceptibility to myocardial I/R injury through distinct sex-dependent pathways.

Regulation of gasdermin D by miR-379-5p is involved in arsenite-induced activation of hepatic stellate cells and in fibrosis via secretion of IL-1β from human hepatic cells

Arsenic is an environmental toxicant and human carcinogen.

Effect of Curcumin and N-Acetylcysteine on Brain Histology and Inflammatory Factors (MMP-2, 9 and TNF-α) in Rats Exposed to Arsenic

Background: Arsenic is a toxic element that widely widespread in environment. Inflammation is now considered as one of the major mechanisms implicated in arsenic poisoning. Curcumin (Cur) and N-acetylcysteine (NAC) are potential antioxidants that protect cells against inflammation. This study aimed to compare the protective effect of Cur and NAC on brain histology and inflammatory factors, including matrix metalloproteinases-2, -9 (MMP-2, 9) and tumor necrosis factor-α (TNF-α) in rats exposed to single dose of arsenic. Methods: Rats were exposed to single dose of arsenic (20mg/kg, by gavage) for 30 days and then treated with 300mg/kg NAC (by gavage) and 100mg/kg Cur (by gavage), individually. Serum level of TNF-α was measured using specific ELISA kits. MMP2 and MMP9 contents were measured using Gelatin Zymography method. Brain samples were collected for histopathological and morphological examinations. Results: Arsenic treatment induced white matter lesions and cellular damages at hippocampal CA1 area of the brain. The number of hippocampal CA1 pyramidal cells was significantly declined in arsenic exposed rats (p<0.05). Treatment with NAC and Cur improved these abnormalities. The mean levels of MMP2, MMP9 and TNF-α inflammatory biomarkers were slightly declined after treatment with NAC and Cur (p>0.05). Conclusion: NAC and Cur play an important role in protecting the hippocampal CA1 cells injury induced by arsenic.

Amelioration of arsenic-induced toxic effects in mice by dietary supplementation of Syzygium cumini leaf extract

Arsenic created a serious public health problem in Bangladesh due to its presence in groundwater and dissemination of the toxic effects to millions of people. The scarcity of the treatment options to manage this affected population has made the situation much worse. To find a promising treatment option, this study was undertaken to examine the ameliorating roles of Syzygium cumini leaf extract (SLE) against arsenic-induced toxic effects in mice. Swiss albino mice were divided into four groups where ‘control’ group received pure water + normal feed, ‘arsenic (As)’ group received sodium arsenite (NaAsO₂)-containing water (10 μg/g body weight/day) + normal feed, ‘As+SLE’ group received NaAsO₂-containing water + feed supplemented with SLE (50 µg/g body weight/day) and finally the ‘SLE’ group received pure water + feed supplemented with SLE. A gradual increase in body weight gain was observed in control mice; however, the body weight gain in As-exposed mice was decreased. This decrease in body weight gain was prevented in As+SLE group mice that received SLE supplemented feed. Arsenic showed a secondary effect by causing enlargement of spleen, kidney and liver of ‘As’ group mice and this enlargement of the organs was minimized with SLE supplementation. In addition, SLE abrogated arsenic-mediated elevation of serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), uric acid and glucose. These results, therefore, suggest that SLE might have future therapeutic value for preventing or reducing arsenic-induced toxic effects.

Obesity and increased susceptibility to arsenic-related type 2 diabetes in Northern Chile

BACKGROUND

The prevalence of type 2 diabetes (T2D) has nearly doubled since 1980. Elevated body mass index (BMI) is the leading risk factor for T2D, mediated by inflammation and oxidative stress. Arsenic shares similar pathogenic processes, and may contribute to hyperglycemia and β-cell dysfunction.

OBJECTIVES

We assessed a unique situation of individuals living in Northern Chile with data on lifetime arsenic exposure to evaluate the relationship between arsenic and T2D, and investigate possible interactions with BMI.

METHODS

We analyzed data collected from October 2007-December 2010 from an arsenic-cancer case-control study. Information on self-reported weight, height, smoking, diet, and other factors were obtained. Diabetes was defined by self-reported physician-diagnoses or use of hypoglycemic medication. A total of 1053 individuals, 234 diabetics and 819 without known diabetes were included.

RESULTS

The T2D odds ratio (OR) for cumulative arsenic exposures of 610-5279 and ≥ 5280 μg/L-years occurring 40 years or more before interview were 0.97 (95% CI: 0.66-1.43) and 1.53 (95% CI: 1.05-2.23), respectively. Arsenic-associated T2D ORs were greater in subjects with increased BMIs. For example, the ORs for past cumulative exposures ≥ 5280 μg/L-years was 1.45 (95% CI: 0.74-2.84) in participants with BMIs < 25 kg/m² but 2.64 (95% CI: 1.14-6.11) in those with BMIs ≥ 30 kg/m² (synergy index = 2.49, 95% CI: 0.87-7.09). Results were similar when people with cancer were excluded.

CONCLUSIONS

These findings identify increased odds of T2D with arsenic exposure, which are significantly increased in individuals with excess BMI.

Taurine Ameliorates Arsenic-Induced Apoptosis in the Hippocampus of Mice Through Intrinsic Pathway

Our group previously reported that arsenic (As) exposure induced apoptosis in hippocampus neurons. The aim of the present study was to clarify the protective capacity of taurine (Tau) on As-induced neuronal apoptosis and the related mechanism in mouse hippocampus. Mice were divided into: control group, Tau control group, As exposure group and Tau protective group, randomly. The apoptotic rate of mouse hippocampus was determined by TUNEL staining. The levels of Bcl-2 and Bax gene and protein were analyzed by real time RT-PCR and WB, respectively. Furthermore, cytochrome c (Cyt C) release, and the activity of caspase-8 and caspase-3 were also determined. The results showed that Tau treatment induced the decrease of TUNEL-positive cells, prohibited the disturbance of Bcl-2 and Bax expression, and inhibited Cyt C release and caspase-8 and caspase-3 activation significantly. The results indicated that Tau supplement markedly ameliorates As-induced apoptosis by mitochondria-related pathway in mouse hippocampus.

Taurine attenuates arsenic-induced pyroptosis and nonalcoholic steatohepatitis by inhibiting the autophagic-inflammasomal pathway

Arsenic exposure causes nonalcoholic steatohepatitis (NASH). Inflammation is a key contributor to the pathology of nonalcoholic fatty liver disease (NAFLD), including NASH. However, it is unclear how arsenic induces inflammation. In mouse livers, we show that arsenic trioxide (As₂O₃) induced NASH, increased autophagy and NLRP3 inflammasome activation, increased lipid accumulation, and resulted in dysregulation of lipid-related genes. Supplemented with taurine (Tau) attenuated the inflammation and autophagy caused by As₂O₃. In HepG2 cells, we found that As₂O₃-induced pyroptotic cell death was dependent upon the activation of NLRP3 inflammasome, which was CTSB-dependent. In addition, inhibiting autophagy alleviated the As₂O₃-induced increase of cytosolic CTSB expression and subsequent release of LDH, activation of the NLRP3 inflammasome, and pyroptosis. Moreover, we found that Tau alleviated As₂O₃-induced elevation of autophagy, CTSB expression, and activation of the NLRP3 inflammasome, and reduced the release of LDH, pyroptotic cell death, and inflammation. Interestingly, As₂O₃-induced lipid accumulation could not be alleviated by either inhibition of autophagy nor by inhibition of CTSB. Additionally, neither inhibition of the NLRP3 inflammasome or Tau treatment could alleviate lipid accumulation. These results demonstrated that As₂O₃-induced pyroptosis involves autophagy, CTSB, and the NLRP3 inflammasome cascade, and that Tau alleviates As₂O₃-induced liver inflammation by inhibiting the autophagic-CTSB-NLRP3 inflammasomal pathway rather than decreasing lipid accumulation. These findings give insight into the association of autophagy, inflammation, pyroptosis, and NASH induced by As₂O₃.

DNA methylation 101: what is important to know about DNA methylation and its role in SLE risk and disease heterogeneity

SLE is a complex autoimmune disease that results from the interplay of genetics, epigenetics and environmental exposures. DNA methylation is an epigenetic mechanism that regulates gene expression and tissue differentiation. Among all the epigenetic modifications, DNA methylation perturbations have been the most widely studied in SLE. It mediates processes relevant to SLE, including lymphocyte development, X-chromosome inactivation and the suppression of endogenous retroviruses. The establishment of most DNA methylation marks occurs in utero; however, a small percentage of epigenetic marks are dynamic and can change throughout a person’s lifetime and in relation to exposures. In this review, we discuss the current understanding of the biology of DNA methylation and its regulators, the measurement and interpretation of methylation marks, the effects of genetics on DNA methylation and the role of environmental exposures with relevance to SLE. We also summarise research findings associated with SLE disease risk and heterogeneity. The robust finding of hypomethylation of interferon-responsive genes in patients with SLE and new associations beyond interferon-responsive genes such as cell-specific methylation abnormalities are described. We also discuss methylation changes associated with lupus nephritis, autoantibody status and disease activity. Lastly, we explore future research directions, emphasising the need for longitudinal studies, cell tissue and context-specific profiling, as well as integrative approaches. With new technologies, DNA methylation perturbations could be targeted and edited, offering novel therapeutic approaches.

Inorganic arsenic causes fatty liver and interacts with ethanol to cause alcoholic liver disease in zebrafish

The rapid increase in fatty liver disease (FLD) incidence is attributed largely to genetic and lifestyle factors; however, environmental toxicants are a frequently overlooked factor that can modify the effects of more common causes of FLD. Chronic exposure to inorganic arsenic (iAs) is associated with liver disease in humans and animal models, but neither the mechanism of action nor the combinatorial interaction with other disease-causing factors has been fully investigated. Here, we examined the contribution of iAs to FLD using zebrafish and tested the interaction with ethanol to cause alcoholic liver disease (ALD). We report that zebrafish exposed to iAs throughout development developed specific phenotypes beginning at 4 days post-fertilization (dpf), including the development of FLD in over 50% of larvae by 5 dpf. Comparative transcriptomic analysis of livers from larvae exposed to either iAs or ethanol revealed the oxidative stress response and the unfolded protein response (UPR) caused by endoplasmic reticulum (ER) stress as common pathways in both these models of FLD, suggesting that they target similar cellular processes. This was confirmed by our finding that arsenic is synthetically lethal with both ethanol and a well-characterized ER-stress-inducing agent (tunicamycin), suggesting that these exposures work together through UPR activation to cause iAs toxicity. Most significantly, combined exposure to sub-toxic concentrations of iAs and ethanol potentiated the expression of UPR-associated genes, cooperated to induce FLD, reduced the expression of as3mt, which encodes an arsenic-metabolizing enzyme, and significantly increased the concentration of iAs in the liver. This demonstrates that iAs exposure is sufficient to cause FLD and that low doses of iAs can potentiate the effects of ethanol to cause liver disease.

This article has an associated First Person interview with the first author of the paper.

Summary: Using zebrafish, the authors show that exposure to a common environmental contaminant, inorganic arsenic, increases the risk of alcoholic liver disease.

Role of microRNAs in senescence and its contribution to peripheral neuropathy in the arsenic exposed population of West Bengal, India

Arsenic induced senescence (AIS) has been identified in the population of West Bengal, India very recently. Also there is a high incidence of arsenic induced peripheral neuropathy (PN) throughout India. However, the epigenetic regulation of AIS and its contribution in arsenic induced PN remains unexplored. We recruited seventy two arsenic exposed and forty unexposed individuals from West Bengal to evaluate the role of senescence associated miRNAs (SA-miRs) in AIS and their involvement if any, in PN. The downstream molecules of the miRNA associated with the disease outcome, was also checked by immuoblotting. In vitro studies were conducted with HEK 293 cells and sodium arsenite exposure. Our results show that all the SA-miRs were upregulated in comparison to unexposed controls. miR-29a was the most significantly altered, highest expression being in the arsenic exposed group with PN, suggesting its association with the occurrence of PN. We looked for the expression of peripheral myelin protein 22 (PMP22), a specific target of miR-29a associated with myelination and found that both in vitro and in vivo results showed over-expression of the protein. Since this was quite contrary to miRNA regulation, we checked for intermediate players β-catenin and GSK-3β upon arsenic exposure which affects PMP22 expression. We found that β-catenin was upregulated in vitro and was also highest in the arsenic exposed group with PN while GSK-3β followed the reverse pattern. Our findings suggest that arsenic exposure alters the expression of SA-miRs and the mir-29a/beta catenin/PMP22 axis might be responsible for arsenic induced PN.

Arsenic Induces Thioredoxin 1 and Apoptosis in Human Liver HHL-5 Cells

To further characterize the mechanisms underlying liver toxicity induced by arsenic, we examined in this study the effect of arsenic on thioredoxin (Trx) and the apoptotic signaling pathways in human liver HHL-5 cells. The cells were treated with 0, 2, 5, and 10 μM of sodium arsenite for 24 h, and the changes of Trx1 and thioredoxin reductase (TrxR1) as well as intracellular ROS and apoptosis were examined. A concentration-dependent increase in mRNA and protein levels of Trx1 and TrxR1 was observed in arsenic-treated cells. Intracellular ROS levels and apoptosis were also significantly increased in a concentration-dependent manner. In line with this, protein levels of Bax and cytochrome C were increased and Bcl-2 was decreased by arsenic treatments. Increases in caspase 3 activity were observed. These results indicate that Trx is involved in arsenic-induced liver cell injury, probably through the apoptotic signaling pathway. However, further studies are needed to elucidate on these findings.

Arsenic in groundwater of West Bengal, India: A review of human health risks and assessment of possible intervention options

This paper reviews how active research in West Bengal has unmasked the endemic arsenism that has detrimental effects on the health of millions of people and their offspring. It documents how the pathways of exposure to this toxin/poison have been greatly expanded through intensive application of groundwater in agriculture in the region within the Green Revolution framework. A goal of this paper is to compare and contrast the similarities and differences in arsenic occurrence in West Bengal with those of other parts of the world and assess the unique socio-cultural factors that determine the risks of exposure to arsenic in local groundwater. Successful intervention options are also critically reviewed with emphasis on integrative strategies that ensure safe water to the population, proper nutrition, and effective ways to reduce the transfer of arsenic from soil to crops. While no universal model may be suited for the vast areas of the world affected with by natural contamination of groundwater with arsenic, we have emphasized community-specific sustainable options that can be adapted. Disseminating scientifically correct information among the population coupled with increased community level participation and education are recognized as necessary adjuncts for an engineering intervention to be successful and sustainable.

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.