Chronic low level arsenic exposure evokes inflammatory responses and DNA damage

Association of arsenic exposure with PDGF-BB in vitro and in a South Texas population exposed through drinking water

Exposure to arsenic (As) from drinking water is a global public health concern, as As is a recognized carcinogen. Groundwater in South Texas, particularly in areas with Gulf Coast aquifers, contains high levels of As. Private wells are neither regulated nor regularly monitored, leaving residents vulnerable to arsenic exposure. This study aimed to investigate potential biomarkers of health effects for long-term, low-level As exposure among private well users in South Texas and to cross-validate findings using an in vitro model. Among 74 private well users, the association between urinary As levels and urinary LDH and 16 cytokine levels was assessed. After adjusting for covariates, linear regression analysis showed weak but significant associations between urinary total inorganic As levels and LDH (β = 0.37, p < 0.01, R2 = 0.23) and PDGF-BB (β = 0.22, p = 0.02, R2 = 0.17). However, no significant associations were found with other cytokines. To compare findings from the population study, SV-HUC-1 uroepithelial cells were exposed to 0.1 or 0.5 μM NaAsO₂ subchronically for 5 weeks, corresponding to total arsenic levels of 7.5 and 37.5 μg/L in drinking water. As exposure was not cytotoxic at either dose, as indicated by lactate dehydrogenase (LDH) activity. However, platelet-derived growth factor (PDGF)-BB protein levels showed a statistically significant increase at a lower concentration of 0.1 μM. These findings suggest that PDGF-BB may serve as a potential biomarker for low-level As exposure, but further studies are required for confirmation.

Health risk assessment upon exposure to groundwater arsenic among individuals of different sex and age groups of Vaishali district, Bihar (India)

Availability of safe drinking water is one of the requirements for maintaining good health. Unfortunately, inhabitants of many nations suffer from adverse health effects due to the intake of arsenic-contaminated groundwater. The Vaishali district of Bihar (India) is the part of Ganga River Basin, a hotspot of arsenic contamination and hence, risk assessment among its individuals is highly pertinent. This study aimed to evaluate the extent of arsenic contamination in the ground waters of Bidupur block under Vaishali district, followed by an assessment of health risk, both non-cancer and cancer, within the arsenic-exposed adult females, adult males and children. Estimation of groundwater arsenic was done in 68 duplicate samples through an MQuant test kit (Merck, Germany). For this, Microsoft Office Excel and ArcGIS software were used as a tool. The results showed that only one-fourth of the groundwater samples exceeded the WHO permissible limit of arsenic with a high contamination factor. The total hazard index (HI), representing the non-cancer risk, was found above the threshold value (>1) among all individuals, which was high among the adults, more in adult females (3.21) than adult males (2.97), and low among the children (2.02). The cancer risk, expressed in terms of cancer index (CI), was also beyond the acceptable limit (10-4 to 10-6) among all sex and age groups, ranging from 0.91 × 10-3 to 1.45 × 10-3. Conclusively, arsenic was found to pose both high non-cancer and cancer risks in the population even at its low level due to long-term exposure.

Unveiling the interaction and combined effects of multiple metals/metalloids exposure to TNF-α and kidney function in adults using bayesian kernel machine regression and quantile-based G-computation

BACKGROUND

Exposure to multiple metals may cause adverse effects, particularly in the kidneys. However, studies on the combined and interaction effects of metal mixtures on human health remain limited.

OBJECTIVE

The study aims to evaluate the interaction between metals and assess the combined effects of exposure to metal mixtures on tumor necrosis factor-alpha (TNF-α) levels and kidney function METHODS: Particular emphasis has been placed on the impact of various metals, including arsenic (As), cadmium (Cd), lead (Pb), as well as essential trace elements, such as cobalt (Co), copper (Cu), selenium (Se), and zinc (Zn), on human health and their potential collective influence on both TNF-α and kidney function. This cross-sectional study analyzed the data of 421 adults who underwent a health examination. Generalized linear model (GLM), Bayesian kernel machine regression (BKMR), and quantile-based G-computation (qgcomp) were used to evaluate the association and joint effects between the metals and TNF-α, as well as kidney function.

RESULTS

Increased concentrations of As (β = 0.11, 95 % CI = 0.05, 0.17) and Pb (β = 0.30, 95 % CI = 0.23, 0.37) in the blood were associated with elevated levels of TNF-α, while elevated Cu (β = -0.42, 95 % CI = -0.77, -0.07) levels were linked to a significant reduction in TNF-α. The overall effect of metals mixture showed a significant association with a decline in eGFR and an increase TNF-α in the BKMR model. Qgcomp analysis of the metals mixture (β = -0.06, 95 % CI = -0.07, -0.05) indicated that As, Pb, and Zn were the primary contributors to the reduction in eGFR, while As and Pb were the major contributors in metals mixture (β = 0.12, 95 % CI = 0.08, 0.15) to the elevation of TNF-α levels.

CONCLUSION

Exposure to multiple metals could have joint association with the TNF-α levels and kidney function. Furthermore, TNF-α could act as a mediator between metal mixtures and eGFR.

The Role of Copper in Alzheimer's Disease Etiopathogenesis: An Updated Systematic Review

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia and cognitive decline in the elderly. Although the etiology of AD is unknow, an increase in amyloid precursor protein (APP) leads to the toxic aggregation of Aβ plaques. Several factors, such as hypertension, diabetes, dyslipidemia, smoking, hormonal changes, and metal exposure, could increase the risk of developing AD. In this review, we will examine the role of copper (Cu) in the pathophysiology of AD, as well as the mechanisms involved in neurotoxicity and cognitive decline.

METHODS

This review was conducted in accordance with PRISMA guidelines. We performed a comprehensive literature analysis over the last ten years on AD and Cu. Only late-onset Alzheimer's disease was considered; only studies on elderly people of both sexes were included.

RESULTS

A total of seven articles were picked for this review, three studies focused on non-ceruloplasmin-bound Copper (non-Cp-Cu) and four on ceruloplasmin-bound Copper (Cp-Cu). The results showed higher Cu concentrations in patients compared to healthy controls.

CONCLUSIONS

Elevated concentrations of Cu may contribute to the progression of AD, potentially interacting with ATP7B mutations, oxidative stress (OS), and amyloid-β plaques. Future research is needed to provide more robust evidence and better characterize the relationship between AD and Cu.

Inflammation in Metal-Induced Neurological Disorders and Neurodegenerative Diseases

Essential metals play critical roles in maintaining human health as they participate in various physiological activities. Nonetheless, both excessive accumulation and deficiency of these metals may result in neurotoxicity secondary to neuroinflammation and the activation of microglia and astrocytes. Activation of these cells can promote the release of pro-inflammatory cytokines. It is well known that neuroinflammation plays a critical role in metal-induced neurotoxicity as well as the development of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Initially seen as a defense mechanism, persistent inflammatory responses are now considered harmful. Astrocytes and microglia are key regulators of neuroinflammation in the central nervous system, and their excessive activation may induce sustained neuroinflammation. Therefore, in this review, we aim to emphasize the important role and molecular mechanisms underlying metal-induced neurotoxicity. Our objective is to raise the awareness on metal-induced neuroinflammation in neurological disorders. However, it is not only just neuroinflammation that different metals could induce; they can also cause harm to the nervous system through oxidative stress, apoptosis, and autophagy, to name a few. The primary pathophysiological mechanism by which these metals induce neurological disorders remains to be determined. In addition, given the various pathways through which individuals are exposed to metals, it is necessary to also consider the effects of co-exposure to multiple metals on neurological disorders.

Mediation analysis for TNF-α as a mediator between multiple metal exposure and kidney function

The association between metal mixtures and kidney function has been reported. However, reports on the mechanism of metal toxicity were limited. Oxidative stress was reported as a possible cause. This study aimed to determine the association between of kidney function and metals, such as arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), lead (Pb), selenium (Se), and zinc (Zn), and to explore the possible mediating role of tumor necrosis factor alpha (TNF-α) between metal toxicity and kidney function. In this study, we recruited 421 adults from a health examination. The concentration of blood metals was analyzed using inductively coupled plasma mass spectrometry. We used linear regression models to assess the association between metals and TNF-α. Then, mediation analysis was applied to investigate the relationship between metal exposure, TNF-α, and kidney function. In univariate linear regression, blood As, Cd, Co, Cu, Pb, and Zn levels significantly increased TNF-α and decreased kidney function. Higher blood As and Pb levels significantly increased TNF-α in multivariable linear regressions after adjusting for covariates. We found that blood levels of As (coefficients = -0.021, p = 0.011), Pb (coefficients = -0.060, p < 0.001), and Zn (coefficients = -0.230, p < 0.001) showed a significant negative association with eGFR in the multiple-metal model. Furthermore, mediation analysis showed that TNF-α mediated 41.7 %, 38.8 %, and 20.8 % of blood Cd, As and Pb, respectively. Among the essential elements, TNF-α mediated 24.5 %, 21.5 % and 19.9 % in the effects of blood Co, Cu, and Zn on kidney function, respectively. TNF-α, acting as a mediator, accounted for 20.1 % of the contribution between the WQS score of metal mixtures and the eGFR (p < 0.001). This study suggested that TNF-α may be a persuasive pathway mediating the association between metals and kidney function. Inflammation and kidney injury could be the underlying mechanisms of metal exposure. However, there is still a need to clarify the biochemical mechanism in follow-up studies.

Metabolic and Environmental Biomarkers in Mild Cognitive Impairment and Dementia: An Exploratory Study

Objective: To determine the frequency with which suspected pathogenic factors, including metals and metabolites that might contribute to Alzheimer's disease (AD), may be found in patients with cognitive impairment through commonly available blood tests. Methods: A variety of serum studies, including metals, ammonia, homocysteine, vitamin B12, folate, thyroid tests, metabolic products, and inflammatory markers, were measured in two cohorts: one meeting mild cognitive impairment (MCI) criteria and the other meeting mild-to-moderate dementia (DE) criteria. Medications these patients received were reviewed. Results: Metal abnormalities were detected in over half the subjects, including evidence of mercury, lead, and arsenic elevation as well as instances of excessive essential metals, iron (Fe), and copper. Some metal aberration was detected in 64% of the DE group and 66% of the MCI group. Females were more likely to have elevated copper, consistent with hormonal effects on copper excretion. Homocysteinemia was the most common abnormality, detected in 71% with DE and 67% with MCI, while methylmalonic acid was not elevated. Slight hyperammonemia was moderately common (38%) suggesting a hepatic factor in this subset. Findings of moderate insulin resistance were present in nearly half (44% DE, 52% MCI). Sixty of 65 (92%) had at least one abnormal biomarker and 60% had two or more. The most common drug taken by the total cohort was proton pump inhibitors at 22% DE and 38% MCI. Conclusions: This study suggests that both toxic metals and excessive vital metals such as copper and iron, as well as common metabolic and hepatic factors are detectable at both stages of MCI and DE. There appears to be a multiplicity of provocative factors leading to DE. Individualized interventions based on these parameters may be a means to reduce cognitive decline leading to DE. A more comprehensive prospective study of these environmental and metabolic factors with corrective early interventions appears warranted.

Unlocking the potential of flavonoids: Natural solutions in the fight against colon cancer

Colorectal cancer (CRC) is a major cause of cancer-related deaths worldwide, underscoring the importance of understanding the diverse molecular and genetic underpinnings of CRC to improve its diagnosis, prognosis, and treatment. This review delves into the adenoma-carcinoma-metastasis model, emphasizing the "APC-KRAS-TP53" signature events in CRC development. CRC is categorized into four consensus molecular subtypes, each characterized by unique genetic alterations and responses to therapy, illustrating its complexity and heterogeneity. Furthermore, we explore the role of chronic inflammation and the gut microbiome in CRC progression, emphasizing the potential of targeting these factors for prevention and treatment. This review discusses the impact of dietary carcinogens and lifestyle factors and the critical role of early detection in improving outcomes, and also examines conventional chemotherapy options for CRC and associated challenges. There is significant focus on the therapeutic potential of flavonoids for CRC management, discussing various types of flavonoids, their sources, and mechanisms of action, including their antioxidant properties, modulation of cell signaling pathways, and effects on cell cycle and apoptosis. This article presents evidence of the synergistic effects of flavonoids with conventional cancer therapies and their role in modulating the gut microbiome and immune response, thereby offering new avenues for CRC treatment. We conclude by emphasizing the importance of a multidisciplinary approach to CRC research and treatment, incorporating insights from genetic, molecular, and lifestyle factors. Further research is needed on the preventive and therapeutic potential of natural compounds, such as flavonoids, in CRC, underscoring the need for personalized and targeted treatment strategies.

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.

Update of the risk assessment of inorganic arsenic in food

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 μg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

The Therapeutic Application of Hydrogen in Cancer: The Potential and Challenges

Hydrogen therapy has emerged as a possible approach for both preventing and treating cancer. Cancers are often associated with oxidative stress and chronic inflammation. Hydrogen, with its unique physiological functions and characteristics, exhibits antioxidant, anti-inflammatory, and anti-apoptotic properties, making it an attractive candidate for cancer treatment. Through its ability to mitigate oxidative damage, modulate inflammatory responses, and sustain cellular viability, hydrogen demonstrates significant potential in preventing cancer recurrence and improving treatment outcomes. Preclinical studies have shown the efficacy of hydrogen therapy in several cancer types, highlighting its ability to enhance the effectiveness of conventional treatments while reducing associated side effects. Furthermore, hydrogen therapy has been found to be safe and well-tolerated in clinical settings. Nonetheless, additional investigations are necessary to improve a comprehensive understanding of the mechanisms underlying hydrogen's therapeutic potential and refine the administration and dosage protocols. However, further clinical trials are still needed to explore its safety profile and capacity. In aggregate, hydrogen therapy represents an innovative and promising treatment for several malignancies.

The disruption of blood-brain barrier induced by long-term arsenic exposure is associated with the increase of MMP-9 and MMP-2: The characteristics are similar to those caused by senescence

Accumulating evidence suggests that Matrix metalloproteinase-9 (MMP-9) and -2 (MMP-2) are involved in the neuropathological processes by contributing to breaking the extracellular matrix and the tight junctions that constitute the blood-brain barrier (BBB). However, the influences of arsenic (As) on these two MMPs were inconsistent. In the cross-sectional study of 500 adults, serum MMP-2 and MMP-9 positively correlated with urine arsenic. And the positive correlation between urine tAs and serum MMP-9/2 was found in people older than 59 years. In vivo studies, we found that arsenic exposure or senescence might decrease number of neurons and neuritic density and increase serum and cortical MMP-9/2 levels. Furthermore, arsenic exposure or senescence could disrupt the tight junction of BBB and elevate MMP-9 and MMP-2 expression in the cerebral microvascular endothelium. The MMP-9 and MMP-2 are of particular interest when researching the link between arsenic exposure and nerve damage.

Systemic impact of heavy metals and their role in cancer development: a review

Heavy metals are well-recognised as environmental hazards due to their toxicity, environmental persistence, and bioaccumulation in living organisms. Human health is a crucial concern related to terrestrial and aquatic ecosystems poisoned by harmful heavy metals. Most heavy metals pollute the air, water, and soil, which can be fatal to humans. Humans and other species can be exposed to heavy metals through the food chain if the metals oxidise or combine with other environmental elements (such as water, soil, or air). Their entry into the food chain assures interactions with biological macromolecules in living systems, including humans, resulting in undesirable outcomes. Human poisonings have typically been caused by mercury, lead, chromium, cadmium, and arsenic. The build-up of these metals in living organisms causes various harmful consequences on different organs and tissues. The gravitas of heavy metal toxicity regarding molecular impact and carcinogenesis needs in-depth understanding despite the plethora of available data. Hence, additionally, we attempt to elaborate on the multi-level impact of five heavy metals and emphasise their role in cancer development. The rationale of this essay is thus to understand the role of five heavy metals, viz., lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg), in carcinogenesis. Heavy metals interfere with various biological functions, including proliferation, differentiation, repair of damage, and apoptosis. By comparing their modes of action, we see that these metals share common mechanisms for inducing toxicity, such as reactive oxygen species (ROS) production, antioxidant defence weakening, enzyme inactivation, and oxidative stress.

Food-grade xylitol production from corncob biomass with acute oral toxicity studies

Xylitol, a sugar substitute, is widely used in various food formulations and finds a steady global market. In this study, xylitol crystals were produced from corncob by fermentation (as an alternative to the chemical catalytic process) by a GRAS yeast Pichia caribbica MTCC 5703 and characterized in detail for their purity and presence of any possible contaminant that may adversely affect mammalian cell growth and proliferation. The acute and chronic oral toxicity trials demonstrated no gross pathological changes with average weekly weight gain in female Wistar rats at high xylitol loading (LD₅₀ > 10,000 mg/kg body weight). The clinical chemistry analysis supported the evidence of no dose-dependent effect by analyzing blood biochemical parameters. The finding suggests the possible application of the crystals (> 98% purity) as a food-grade ingredient for commercial manufacture pending human trials.

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.

Influence of differential arsenic exposure on cellular redox homeostasis of exposed rural women of West Bengal

The metalloid arsenic (As) induces oxidative stress is a well-known fact. However, the extent of variation of oxidative stress according to different exposure levels of As in groundwater and the mechanism responsible for As mediated oxidative stress is yet to be elucidated in a human population of West Bengal. In the present study, we have investigated the impact of low level (> 10 ≤ 50 µg/L) and high-level groundwater As (> 50 µg/L) on cellular redox status, DNA damage, and repair mechanisms in chronically exposed rural women of West Bengal. Prediction models of ordinary least square regression of nail As, forced vital capacity (FVC) %, and that of forced expiratory volume during the first one second (FEV1) % deciphered that accumulation of As in nails may predict hemoglobin deficiency. Moreover, consumption of As-laced water tends to decrease FEV1% and FVC%. A strong positive correlation was observed between water and nail As level and reactive oxygen species (ROS) generation. ROS, perturbed nuclear factor erythroid 2-related factor 2(Nrf2)/ Kelch-like ECH-associated protein 1 (Keap1) redox regulation, compromised antioxidant defense machinery-superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione transferase (GST), induced DNA damage, and suppressed DNA repair proteins-poly ADP ribose polymerase1(PARP1)/ X-ray repair cross-complementing protein 1(XRCC1)/ 8-oxoguanine glycosylase (OGG1) in a dose-dependent manner. All the low and high As areas had very high cancer risk values for the exposed population. It has been predicted that if the As level in the drinking water of a 40-year adult increases by 2 ug/L, the likelihood of the cancer risk will increase by 10%, keeping the body weight and amount of water intake constant. Thus, long-term exposure to either low or high As is seriously affecting the lives of asymptomatic women who are vulnerable to developing carcinogenic changes after a period of latency.

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.

Arsenic Induces M2 Macrophage Polarization and Shifts M1/M2 Cytokine Production via Mitophagy

Arsenic is an environmental factor associated with epithelial-mesenchymal transition (EMT). Since macrophages play a crucial role in regulating EMT, we studied the effects of arsenic on macrophage polarization. We first determined the arsenic concentrations to be used by cell viability assays in conjunction with previous studies. In our results, arsenic treatment increased the alternatively activated (M2) macrophage markers, including arginase 1 (ARG-1) gene expression, chemokine (C-C motif) ligand 16 (CCL16), transforming growth factor-β1 (TGF-β1), and the cluster of differentiation 206 (CD206) surface marker. Arsenic-treated macrophages promoted A549 lung epithelial cell invasion and migration in a cell co-culture model and a 3D gel cell co-culture model, confirming that arsenic treatment promoted EMT in lung epithelial cells. We confirmed that arsenic induced autophagy/mitophagy by microtubule-associated protein 1 light-chain 3-II (LC3 II) and phosphor-Parkin (p-Parkin) protein markers. The autophagy inhibitor chloroquine (CQ) recovered the expression of the inducible nitric oxide synthase (iNOS) gene in arsenic-treated M1 macrophages, which represents a confirmation that arsenic indeed induced the repolarization of classically activated (M1) macrophage to M2 macrophages through the autophagy/mitophagy pathway. Next, we verified that arsenic increased M2 cell markers in mouse blood and lungs. This study suggests that mitophagy is involved in the arsenic-induced M1 macrophage switch to an M2-like phenotype.

Study on the Mechanism of Arsenic-Induced Lung Injury Based on SWATH Proteomics Technology

Chronic arsenic poisoning is a global health problem that affects millions of people, and studies have found that long-term ingestion of arsenic-containing compounds can lead to lung damage, but the exact mechanism is unknown. In this study, Sprague-Dawley (SD) rats were used as the research object, and the proteomic analysis method based on sequential window acquisition of all theoretical fragment ions (SWATH) was used to detect the changes in the expression levels of related proteins in the lung tissue of arsenic-exposed rats, and to explore the mechanism of arsenic compound-induced lung injury. The results showed that arsenic exposure resulted in the abnormal expression of collagen type III and proteins involved in metabolic, immune, and cellular processes, leading to the dysfunction of important pathways associated with these proteins, resulting in lung injury. It suggested that the underlying mechanism of arsenic-induced lung injury may be related to oxidative stress, immune injury, cell junction, and collagen type III. This result provides a new research idea for revealing the mechanism of lung injury caused by arsenic exposure.

Indoor dryness and humidification-induced arsenic inhalation exposure above 4200 m in Ngari, China

Ngari Prefecture, Tibet, China, features its ultrahigh altitude above 4200 m, very little annual precipitation and extremely low relative humidity. Residents who have migrated to Tibet from the plains use indoor humidification to reduce the respiratory discomfort caused by prolonged exposure to dry indoor air. In this study, field investigations and analysis of residential indoor environments and humidification methods in Ngari Prefecture revealed that ninety-eight percent of humidifier consumers in the prefecture used low-cost ultrasonic humidifiers filled with indoor tap water. The results revealed that the arsenic (As) concentration of the tap water was 41.6 μg/L, over four times China's standards for drinking water quality (10 μg/L). The source As concentration in the air humidified by the tap water-filled ultrasonic humidifier is (619.8 ± 59.1) (ng/m³ ·air), while no As was detected in the air humidified by the evaporative humidifier. For ultrasonic humidifier with tap water-filled, the inhalation dose of a healthy adult was 45.4 ng/d. The minute ventilation volume of migrated residents who had been in Ngari for less than two years (12.5 ± 4.3 L/min) was greater than those of the long-term residents (10.0 ± 4.5 L/min), which may exacerbate the short-term inhalation exposure risk for migrated residents. To reduce the health risks associated with As exposure, evaporative humidifiers are recommended for households using domestic water. If ultrasonic humidifiers are used, the tap water must be purified with terminal filters.

Arsenic and cancer: Evidence and mechanisms

Arsenic is a potent carcinogen and poses a significant health concern worldwide. Exposure occurs through ingestion of drinking water and contaminated foods and through inhalation due to pollution. Epidemiological evidence shows arsenic induces cancers of the skin, lung, liver, and bladder among other tissues. While studies in animal and cell culture models support arsenic as a carcinogen, the mechanisms of arsenic carcinogenesis are not fully understood. Arsenic carcinogenesis is a complex process due its ability to be metabolized and because of the many cellular pathways it targets in the cell. Arsenic metabolism and the multiple forms of arsenic play distinct roles in its toxicity and contribute differently to carcinogenic endpoints, and thus must be considered. Arsenic generates reactive oxygen species increasing oxidative stress and damaging DNA and other macromolecules. Concurrently, arsenic inhibits DNA repair, modifies epigenetic regulation of gene expression, and targets protein function due its ability to replace zinc in select proteins. While these mechanisms contribute to arsenic carcinogenesis, there remain significant gaps in understanding the complex nature of arsenic cancers. In the future improving models available for arsenic cancer research and the use of arsenic induced human tumors will bridge some of these gaps in understanding arsenic driven cancers.

Arsenic as an immunotoxicant

Arsenic is world-wide contaminant to which millions of people are exposed. The health consequences of arsenic exposure are varied, including cancer, cardiometabolic disease, and respiratory disorders. Arsenic is also toxic to the immune system, which may link many of the pathologies associated with arsenic exposure. The immune system can be classified into two interconnected arms: the innate and the adaptive immune responses. Herein, we discuss the effects of arsenic on key cell types within each of these arms, highlighting both in vitro and in vivo responses. These cells include macrophages, neutrophils, dendritic cells, and both B and T lymphocytes. Furthermore, we will explore data from human populations where altered immune status is implicated in disease and identify several data gaps where research is needed to complete our understanding of the immunotoxic effects of arsenic.

Non-malignant respiratory illness associated with exposure to arsenic compounds in the environment

Arsenic (As), a toxic metalloid, primarily originates from both natural and anthropogenic activities. Reports suggested that millions of people globally exposed to high levels of naturally occurring As compounds via inhalation and ingestion. There is evidence that As is a well-known lung carcinogen. However, there has been relatively little evidence suggesting its non-malignant lung effects. This review comprehensively summarises current experimental and clinical studies implicating the association of As exposure and the development of several non-malignant lung diseases. Experimental studies provided evidence that As exposure induces redox imbalance, apoptosis, inflammatory response, epithelial-to-mesenchymal transition (EMT), and affected normal lung development through alteration of the components of intracellular signaling cascades. In addition, we also discuss the sources and possible mechanisms of As influx and efflux in the lung. Finally, current experimental studies on treatment strategies using phytochemicals and our perspective on future research with As are also discussed.

Use of Generalized Weighted Quantile Sum Regressions of Tumor Necrosis Factor Alpha and Kidney Function to Explore Joint Effects of Multiple Metals in Blood

Exposure to heavy metals could lead to adverse health effects by oxidative reactions or inflammation. Some essential elements are known as reactors of anti-inflammatory enzymes or coenzymes. The relationship between tumor necrosis factor alpha (TNF-α) and heavy metal exposures was reported. However, the interaction between toxic metals and essential elements in the inflammatory response remains unclear. This study aimed to explore the association between arsenic (As), cadmium (Cd), lead (Pb), cobalt (Co), copper (Cu), selenium (Se), and zinc (Zn) in blood and TNF-α as well as kidney function. We enrolled 421 workers and measured the levels of these seven metals/metalloids and TNF-α in blood; kidney function was calculated by CKD-EPI equation. We applied weighted quantile sum (WQS) regression and group WQS regression to assess the effects of metal/metalloid mixtures to TNF-α and kidney function. We also approached the relationship between metals/metalloids and TNF-α by generalized additive models (GAM). The relationship of the exposure−response curve between Pb level and TNF-α in serum was found significantly non-linear after adjusting covariates (p < 0.001). Within the multiple-metal model, Pb, As, and Zn were associated with increased TNF-α levels with effects dedicated to the mixture of 50%, 31%, and 15%, respectively. Grouped WQS revealed that the essential metal group showed a significantly negative association with TNF-α and kidney function. The toxic metal group found significantly positive associations with TNF-α, serum creatinine, and WBC but not for eGFR. These results suggested Pb, As, Zn, Se, and mixtures may act on TNF-α even through interactive mechanisms. Our findings offer insights into what primary components of metal mixtures affect inflammation and kidney function during co-exposure to metals; however, the mechanisms still need further research.

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.

Do urinary metals associate with the homeostasis of inflammatory mediators? Results from the perspective of inflammatory signaling in middle-aged and older adults

OBJECTIVE

We aimed to investigate whether urinary metal mixtures are associated with the homeostasis of inflammatory mediators in middle-aged and older adults.

METHODS

A four-visit repeated-measures study was conducted with 98 middle-aged and older adults from five communities in Beijing, China. Only one person was lost to follow-up at the third visit. Ultimately, 391 observations were included in the analysis. The urinary concentrations of 10 metals were measured at each visit using inductively coupled plasma mass spectrometry (ICP-MS) with a limit of detection (LOD) ranging from 0.002 to 0.173 µg/L, and the detection rates were all above 84%. Similarly, 14 serum inflammatory mediators were measured using a Beckman Coulter analyzer and the Bio-Plex MAGPIX system. A linear mixed model (LMM), LMM with least absolute shrinkage and selection operator regularization (LMMLASSO), and Bayesian kernel machine regression (BKMR) were adopted to explore the effects of urinary metal mixtures on inflammatory mediators.

RESULTS

In LMM, a two-fold increase in urinary cesium (Cs) and chromium (Cr) was statistically associated with -35.22% (95% confidence interval [CI]: -53.17, -10.40) changes in interleukin 6 (IL-6) and -11.13% (95 %CI: -20.67, -0.44) in IL-8. Urinary copper (Cu) and selenium (Se) was statistically associated with IL-6 (88.10%, 95%CI: 34.92, 162.24) and tumor necrosis factor-alpha (TNF-α) (22.32%, 95%CI: 3.28, 44.12), respectively. Similar results were observed for the LMMLASSO and BKMR. Furthermore, Cr, Cs, Cu, and Se were significantly associated with other inflammatory regulatory network mediators. For example, urinary Cs was statistically associated with endothelin-1, and Cr was statistically associated with endothelin-1 and intercellular adhesion molecule 1 (ICAM-1). Finally, the interaction effects of Cu with various metals on inflammatory mediators were observed.

CONCLUSION

Our findings suggest that Cr, Cs, Cu, and Se may disrupt the homeostasis of inflammatory mediators, providing insight into the potential pathophysiological mechanisms of metal mixtures and chronic diseases.

Arsenic exposure and human blood DNA methylation and hydroxymethylation profiles in two diverse populations from Bangladesh and Spain

BACKGROUND

Associations of arsenic (As) with the sum of 5-mC and 5-hmC levels have been reported; however, As exposure-related differences of the separated 5-mC and 5-hmC markers have rarely been studied.

METHODS

In this study, we evaluated the association of arsenic exposure biomarkers and 5-mC and 5-hmC in 30 healthy men (43-55 years) from the Aragon Workers Health Study (AWHS) (Spain) and 31 healthy men (31-50 years) from the Folic Acid and Creatinine Trial (FACT) (Bangladesh). We conducted 5-mC and 5-hmC profiling using Infinium MethylationEPIC arrays, on paired standard and modified (ox-BS in AWHS and TAB in FACT) bisulfite converted blood DNA samples.

RESULTS

The median for the sum of urine inorganic and methylated As species (ΣAs) (μg/L) was 12.5 for AWHS and 89.6 for FACT. The median of blood As (μg/L) was 8.8 for AWHS and 10.2 for FACT. At a statistical significance p-value cut-off of 0.01, the differentially methylated (DMP) and hydroxymethylated (DHP) positions were mostly located in different genomic sites. Several DMPs and DHPs were consistently found in AWHS and FACT both for urine ΣAs and blood models, being of special interest those attributed to the DIP2C gene. Three DMPs (annotated to CLEC12A) for AWHS and one DHP (annotated to NPLOC4) for FACT remained statistically significant after false discovery rate (FDR) correction. Pathways related to chronic diseases including cardiovascular, cancer and neurological were enriched.

CONCLUSIONS

While we identified common 5-hmC and 5-mC signatures in two populations exposed to varying levels of inorganic As, differences in As-related epigenetic sites across the study populations may additionally reflect low and high As-specific associations. This work contributes a deeper understanding of potential epigenetic dysregulations of As. However, further research is needed to confirm biological consequences associated with DIP2C epigenetic regulation and to investigate the role of 5-hmC and 5-mC separately in As-induced health disorders at different exposure levels.

Arsenic and Human Health: Genotoxicity, Epigenomic Effects, and Cancer Signaling

Arsenic is a well-known element because of its toxicity. Humans as well as plants and animals are negatively affected by its exposure. Some countries suffer from high levels of arsenic in their tap water and soils, which is considered a primary arsenic-linked risk factor for living beings. Humans generally get exposed to arsenic by contaminated drinking waters, resulting in many health problems, ranging from cancer to skin diseases. On the other hand, the FDA-certified drug arsenic trioxide provides solutions for various diseases, including several types of cancers. This issue emphasizes the importance of speciation of the metalloid elements in terms of impacts on health. When species get exposed to arsenic, it affects the cells altering their involvement. It can lead to abnormalities in inflammatory mechanisms and the immune system which contribute to the negative impacts generated on the body. The poisoning originating from arsenic gives rise to various biological signs on the body which can be useful for the diagnosis. It is important to find true biomarkers for the detection of arsenic poisoning. In view of its application in medicine and biology, studies on understanding the biological activity of arsenic have increased. In this review, we aim at summarizing the current state of knowledge of arsenic and the mechanism behind its toxicity including genotoxicity, oxidative insults, epigenomic changes, and alterations in cellular signaling.

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 co-carcinogenesis: Inhibition of DNA repair and interaction with zinc finger proteins

Arsenic is widely present in the environment and is associated with various population health risks including cancers. Arsenic exposure at environmentally relevant levels enhances the mutagenic effect of other carcinogens such as ultraviolet radiation. Investigation on the molecular mechanisms could inform the prevention and intervention strategies of arsenic carcinogenesis and co-carcinogenesis. Arsenic inhibition of DNA repair has been demonstrated to be an important mechanism, and certain DNA repair proteins have been identified to be extremely sensitive to arsenic exposure. This review will summarize the recent advances in understanding the mechanisms of arsenic carcinogenesis and co-carcinogenesis, including DNA damage induction and ROS generation, particularly how arsenic inhibits DNA repair through an integrated molecular mechanism which includes its interactions with sensitive zinc finger DNA repair proteins.

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.

Amelioration potential of Moringa oleifera extracts against sodium arsenate induced embryotoxicity and genotoxicity in mouse (Mus musculus)

Previous studies have suggested that arsenic crosses the placenta and affects the fetus development. The study under consideration aims to show comparative ameliorative effect of Moringa oleifera leaf and flower extracts against sodium arsenate induced fetus toxicity of mice. Pregnant mice (N=44) were kept in lab and divided into eleven group from (A to K) and were orally administered the doses 6 mg/kg, 12 mg/kg for sodium arsenate, 150 mg/kg and 300 mg/kg for Moringa oleifera leaf extracts (MOLE) and 150 mg/kg and 300 mg/kg for Moringa oleifera flower extracts (MOFE) comparing with control. The investigation revealed evident reduction in the fetuses weight, hind limb, fore limb, tail and snout length, crown rump and head circumferences well as malformations in tail, feet, arms, legs, skin and eyes in the negative control group (only administered with sodium arsenate). Co-administration of sodium arsenate with MOLE and MOFE ameliorate the reversed effect of sodium arsenate on the shape, length, body weight and DNA damage of fetus significantly at 95% confidence interval. However, Moringa oleifera leaf extract showed more significant results in comparison to Moringa oleifera flower extract. Hence concluded that Moringa oleifera leaf extract ameliorated the embryo toxic effects of sodium arsenate and can be used against environmental teratogens.

Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and Arsenic

The industrial activities of the last century have caused massive increases in human exposure to heavy metals. Mercury, lead, chromium, cadmium, and arsenic have been the most common heavy metals that induced human poisonings. Here, we reviewed the mechanistic action of these heavy metals according to the available animal and human studies. Acute or chronic poisonings may occur following exposure through water, air, and food. Bioaccumulation of these heavy metals leads to a diversity of toxic effects on a variety of body tissues and organs. Heavy metals disrupt cellular events including growth, proliferation, differentiation, damage-repairing processes, and apoptosis. Comparison of the mechanisms of action reveals similar pathways for these metals to induce toxicity including ROS generation, weakening of the antioxidant defense, enzyme inactivation, and oxidative stress. On the other hand, some of them have selective binding to specific macromolecules. The interaction of lead with aminolevulinic acid dehydratase and ferrochelatase is within this context. Reactions of other heavy metals with certain proteins were discussed as well. Some toxic metals including chromium, cadmium, and arsenic cause genomic instability. Defects in DNA repair following the induction of oxidative stress and DNA damage by the three metals have been considered as the cause of their carcinogenicity. Even with the current knowledge of hazards of heavy metals, the incidence of poisoning remains considerable and requires preventive and effective treatment. The application of chelation therapy for the management of metal poisoning could be another aspect of heavy metals to be reviewed in the future.

Association between arsenic exposure, DNA damage, and urological cancers incidence: A long-term follow-up study of residents in an arseniasis endemic area of northeastern Taiwan

Arsenic is a well-established human carcinogen and is considered a health risk worldwide, especially where groundwater is consumed as drinking water. In 2018, bladder and kidney cancers were the 14th and 17th leading causes of global cancer mortality, respectively. Our aim was to investigate the association between arsenic exposure, DNA damage, and the incidence of bladder and kidney cancers. A total of 788 participants aged ≥40 years were enrolled in a prospective cohort study in Taiwan between 1991 and 1994, with follow-up between 2011 and 2014. Well-water and first-morning spot urine samples were collected between 1991 and 1994 to estimate arsenic exposure, and the baseline urinary levels of 8-Oxo-2'-deoxyguanosine (8-OHdG) and N7-methylguanine (N7-MeG) were quantified to assess DNA lesions. The Cox proportional hazard model was used to estimate the effects of arsenic exposure and DNA adduct levels on the risk of bladder or kidney cancer. Urinary arsenic species were associated with significantly increased 8-OHdG and N7-MeG after adjusting for age, sex, and cigarette smoking. Only non-statistically significant mediation effects of 8-OHdG were observed. In a fully adjusted Cox model, participants with arsenic exposure and urinary 8-OHdG levels higher than the median had a higher risk of bladder cancer (HR = 4.60, confidence interval: 1.43-14.85). Overall, the combined effects of high cumulative arsenic exposure from artesian well-water and advanced DNA damage predicted the risk of bladder cancer.

Flavonoids Regulate Inflammation and Oxidative Stress in Cancer

Cancer is the second leading cause of death globally. Millions of persons die due to cancer each year. In the last two decades, the anticancer effects of natural flavonoids have become a hot topic in many laboratories. Meanwhile, flavonoids, of which over 8000 molecules are known to date, are potential candidates for the discovery of anticancer drugs. The current review summarizes the major flavonoid classes of anticancer efficacy and discusses the potential anti-cancer mechanisms through inflammation and oxidative stress action, which were based on database and clinical studies within the past years. The results showed that flavonoids could regulate the inflammatory response and oxidative stress of tumor through some anti-inflammatory mechanisms such as NF-κB, so as to realize the anti-tumor effect.

Association of arsenic exposure and cognitive impairment: A population-based cross-sectional study in China

BACKGROUND

The influence of chronic arsenic exposure on cognitive impairment has been explored broadly by previous studies. However, most of them focused mainly on children rather than adults. In addition, in China, studies in this field are not sufficient. To illustrate how long-term arsenic exposure affects cognitive function, we designed a cross-sectional study involving 1556 adults.

METHODS

All of them came from three locations around the Realgar Plant. The cognitive function of the participants was evaluated using a Chinese version of the Mini-mental state Examination (MMSE). The participants' internal arsenic exposure status (hair arsenic concentrations) and the external arsenic exposure status (the distance between the participants' location of residence and the Realgar Plant) were measured.

RESULTS

Our research revealed that both of hair arsenic concentrations and the prevalence of arsenicosis, two important indexes, were significantly higher in the cognitive-impaired (CI) group than in the cognitive-normal (CN) group (P < 0.05). In addition, distance from the Realgar Plant was positively correlated with the MMSE scores and was negatively correlated with the prevalence of cognitive impairment. Moreover, our results demonstrated that there was a negative correlation between hair arsenic concentrations and MMSE scores. We conducted a two-level Logistic regression analysis and further confirmed that even after adjusting for potential confounding variables, arsenicosis retained a risk factor for cognitive impairment (odds ratio (OR) = 1.84, P < 0.05).

CONCLUSIONS

Our results indicated that chronic arsenic exposure could impair adults' cognitive function in a dose-dependent manner. Additionally, arsenicosis could be an independent risk factor for cognitive impairment.

Grape seed proanthocyanidin extract alleviates arsenic-induced lung damage through NF-κB signaling

IMPACT STATEMENT

Arsenic-induced respiratory inflammatory damage is an important occupational hazard in many areas of the world, particularly in underdeveloped and developing countries. Effective treatments are lacking and expensive. Therefore, the aim of the study was to examine the anti-inflammatory effects of proanthocyanidin (PC) and the molecular mechanisms in vivo and in vitro. The present study showed that PC extracted from grape seed could attenuate the lung damage in a mouse model of arsenic poisoning. The effects were observed at the level of lung histology and inflammasome expression. This study suggests that a natural compound is effective in mitigating the toxic effects of arsenic in the lungs, providing an inexpensive and more readily accessible method for treating arsenic exposure in some parts of the world.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Identification of environmental chemicals targeting miscarriage genes and pathways using the comparative toxicogenomics database

BACKGROUND

Miscarriage is a prevalent public health issue and many events occur before women are aware of their pregnancy, complicating research design. Thus, risk factors for miscarriage are critically understudied. Our goal was to identify environmental chemicals with a high number of interactions with miscarriage genes, based on known toxicogenomic responses.

METHODS

We used miscarriage (MeSH: D000022) and chemical gene lists from the Comparative Toxicogenomics Database in human, mouse, and rat. We assessed enrichment for gene ontology biological processes among the miscarriage genes. We prioritized chemicals (n = 25) found at Superfund sites or in the blood or urine pregnant women. For chemical-disease gene sets of sufficient size (n = 13 chemicals, n = 20 comparisons), chi-squared enrichment tests and proportional reporting ratios (PRR) were calculated. We cross-validated enrichment results.

RESULTS

Miscarriage was annotated with 121 genes and overrepresented in inflammatory response (q = 0.001), collagen metabolic process (q = 1 × 10-13), cell death (q = 0.02), and vasculature development (q = 0.005) pathways. The number of unique genes annotated to a chemical ranged from 2 (bromacil) to 5607 (atrazine). In humans, all chemicals tested were highly enriched for miscarriage gene overlap (all p < 0.001; parathion PRR = 7, cadmium PRR = 6.5, lead PRR = 3.9, arsenic PRR = 3.5, atrazine PRR = 2.8). In mice, highest enrichment (p < 0.001) was observed for naphthalene (PRR = 16.1), cadmium (PRR = 12.8), arsenic (PRR = 11.6), and carbon tetrachloride (PRR = 7.7). In rats, we observed highest enrichment (p < 0.001) for cadmium (PRR = 8.7), carbon tetrachloride (PRR = 8.3), and dieldrin (PRR = 5.3). Our findings were robust to 1000 permutations each of variable gene set sizes.

CONCLUSION

We observed chemical gene sets (parathion, cadmium, naphthalene, carbon tetrachloride, arsenic, lead, dieldrin, and atrazine) were highly enriched for miscarriage genes. Exposures to chemicals linked to miscarriage, and thus linked to decreased probability of live birth, may limit the inclusion of fetuses susceptible to adverse birth outcomes in epidemiology studies. Our findings have critical public health implications for successful pregnancies and the interpretation of adverse impacts of environmental chemical exposures on pregnancy.

Ginkgo biloba extract attenuates the disruption of pro-and anti-inflammatory T-cell balance in peripheral blood of arsenicosis patients

Endemic arsenicosis is a public health problem that affects thousands of people worldwide. However, the biological mechanism involved is not well characterized, and there is no specific treatment. Exposure to arsenic may be associated with immune-related problems. In the present work, we performed an investigation to determine whether the Th17/Treg balance was abnormal in peripheral blood mononuclear cells (PBMCs) of patients with arsenicosis caused by burning coal. Furthermore, we investigated the effect of Ginkgo biloba extract (GBE) on the Th17/Treg imbalance in patients with arsenicosis. In this trial, 81 arsenicosis patients and 37 controls were enrolled. The numbers of Th17 and Treg cells, as well as related transcription factors and serum cytokines, were determined at the beginning and end of the study. Patients with arsenicosis exhibited higher levels of Th17 cells, Th17-related cytokines (IL-17A and IL-6), and the transcription factor RORγt. There were lower levels of Treg cells, a Treg-related cytokine (IL-10), and the transcription factor Foxp3 as compared with controls. There was a positive correlation between the levels of Th17 cells and IL-17A and the levels of arsenic in hair. Arsenicosis patients were randomly assigned to a GBE treatment group or a placebo group. After 3 months of follow-up, 74 patients completed the study (39 cases in the GBE group and 35 in the placebo group). Administration of GBE to patient upregulated the numbers of Treg cells and the level of IL-10 and downregulated the numbers of Th17 cells and the levels of cytokines associated with Th17 cells. The mRNA levels of Foxp3 and RORγt were increased and decreased, respectively. These results indicated that exposure to arsenic is associated with immune-related problems. The present investigation describes a previously unknown mechanism showing that an imbalance of pro- and anti-inflammatory T cells is involved in the pathogenesis of arsenicosis and that a GBE exerts effects on arsenicosis through regulation of the pro- and anti-inflammatory T cell balance.

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.

Health effects inflicted by chronic low-level arsenic contamination in groundwater: A global public health challenge

Groundwater arsenic (As) contamination is a global public health concern. The high level of As exposure (100-1000 μg/L or even higher) through groundwater has been frequently associated with serious public health hazards, e.g., skin disorders, cardiovascular diseases, respiratory problems, complications of gastrointestinal tract, liver and splenic ailments, kidney and bladder disorders, reproductive failure, neurotoxicity and cancer. However, reviews on low-level As exposure and the imperative health effects are far less documented. The World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA) has set the permissible standard of As in drinking water at 10 μg/L. Considering the WHO and USEPA guidelines, most of the developed countries have established standards at or below this guideline. Worldwide many countries including India have millions of aquifers with low-level As contamination (≤50 μg/L). The exposed population of these areas might not show any As-related skin lesions (hallmark of As toxicity particularly in a population consuming As contaminated groundwater >300 μg/L) but might be subclinically affected. This review has attempted to encompass the wide range of health effects associated with chronic low-level As exposure ≤50 μg/L and the probable mechanisms that might provide a better insight regarding the underlying cause of these clinical manifestations. Therefore, there is an urgent need to create mass awareness about the health effects of chronic low-level As exposure and planning of proper mitigation strategies.

A single or short time repeated arsenic oral exposure in mice impacts mRNA expression for signaling and immunity related genes in the gut

Arsenic is prevalent in contaminated drinking water and affects more than 140 million people in 50 countries. While the wide-ranging effects of arsenic on neurological development and cancer draw the majority of concern, arsenic's effects on the gut mucosa-associated immune system are often overlooked. In this study, we show that 24 h after a single dose [low dose (50 μg/kg bw), medium dose (100 μg/kg bw) or high dose (200 μg/kg bw)] of arsenic by oral gavage, mice show significantly reduced gut mucosa-associated mRNA expression for the key genes involved in the signaling pathways central to immune responses, such as Nuclear factor κB (NFκB), Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), p38 and Myeloid differentiation protein 88-dependent (Myd88) pathways. Additionally, mRNA expression of apoptosis, inflammasomes and inflammatory response genes are significantly downregulated in the animals exposed to arsenic. Comparisons of time-dependent effects (24 h vs 48 h) from low dose arsenic exposed animals showed a significant shift in expression of Myd88 alone, suggesting that the down regulation was sustained for the key genes/signaling pathway. An extended eight-day exposure to arsenic showed a decreased state of immune preparedness, though not as diminished as seen in the single dose exposure.

Association of Arsenic Exposure with Whole Blood DNA Methylation: An Epigenome-Wide Study of Bangladeshi Adults

BACKGROUND

Arsenic exposure affects [Formula: see text] people worldwide, including [Formula: see text] in Bangladesh. Arsenic exposure increases the risk of cancer and other chronic diseases, and one potential mechanism of arsenic toxicity is epigenetic dysregulation.

OBJECTIVE

We assessed associations between arsenic exposure and genome-wide DNA methylation measured at baseline among 396 Bangladeshi adults participating in the Health Effects of Arsenic Longitudinal Study (HEALS) who were exposed by drinking naturally contaminated well water.

METHODS

Methylation in whole blood DNA was measured at [Formula: see text] using the Illumina InfiniumMethylationEPIC (EPIC) array. To assess associations between arsenic exposure and CpG methylation, we used linear regression models adjusted for covariates and surrogate variables (SVs) (capturing unknown technical and biologic factors). We attempted replication and conducted a meta-analysis using an independent dataset of [Formula: see text] from 400 Bangladeshi individuals with arsenical skin lesions.

RESULTS

We identified 34 CpGs associated with [Formula: see text] creatinine-adjusted urinary arsenic [[Formula: see text]]. Sixteen of these CpGs annotated to the [Formula: see text] array, and 10 associations were replicated ([Formula: see text]). The top two CpGs annotated upstream of the ABR gene (cg01912040, cg10003262 ). All urinary arsenic-associated CpGs were also associated with arsenic concentration measured in drinking water ([Formula: see text]). Meta-analysis ([Formula: see text] samples) identified 221 urinary arsenic-associated CpGs ([Formula: see text]). The arsenic-associated CpGs from the meta-analysis were enriched in non-CpG islands and shores ([Formula: see text]) and depleted in promoter regions ([Formula: see text]). Among the arsenic-associated CpGs ([Formula: see text]), we observed significant enrichment of genes annotating to the reactive oxygen species pathway, inflammatory response, and tumor necrosis factor [Formula: see text] ([Formula: see text]) signaling via nuclear factor kappa-B ([Formula: see text]) hallmarks ([Formula: see text]).

CONCLUSIONS

The novel and replicable associations between arsenic exposure and DNA methylation at specific CpGs observed in this work suggest that epigenetic alterations should be further investigated as potential mediators in arsenic toxicity and as biomarkers of exposure and effect in exposed populations. https://doi.org/10.1289/EHP3849.

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.

A review on arsenic carcinogenesis: Epidemiology, metabolism, genotoxicity and epigenetic changes

Long-term exposure to arsenic (inorganic arsenic) is a world-wide environmental health concern. Arsenic is classified as the Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). Epidemiological studies have established a strong association between inorganic arsenic (iAs) exposure in drinking water and an increased incidence of cancer including bladder, liver, lung, prostate, and skin cancer. iAs also increases the risk of other diseases such as cardiovascular disease, hypertension and diabetes. The molecular mechanisms of carcinogenesis of iAs remain poorly defined, several mechanisms have been proposed, including genotoxicity, altered cell proliferation, oxidative stress, changes to the epigenome, disturbances of signal transduction pathways, cytotoxicity and regenerative proliferation. In this article, we will summarize current knowledge on the mechanisms of arsenic carcinogenesis and focus on integrating all these issues to garner a broader perspective.

Developing robust arsenic awareness prediction models using machine learning algorithms

Arsenic awareness plays a vital role in ensuring the sustainability of arsenic mitigation technologies. Thus far, however, few studies have dealt with the sustainability of such technologies and its associated socioeconomic dimensions. As a result, arsenic awareness prediction has not yet been fully conceptualized. Accordingly, this study evaluated arsenic awareness among arsenic-affected communities in rural India, using a structured questionnaire to record socioeconomic, demographic, and other sociobehavioral factors with an eye to assessing their association with and influence on arsenic awareness. First a logistic regression model was applied and its results compared with those produced by six state-of-the-art machine-learning algorithms (Support Vector Machine [SVM], Kernel-SVM, Decision Tree [DT], k-Nearest Neighbor [k-NN], Naïve Bayes [NB], and Random Forests [RF]) as measured by their accuracy at predicting arsenic awareness. Most (63%) of the surveyed population was found to be arsenic-aware. Significant arsenic awareness predictors were divided into three types: (1) socioeconomic factors: caste, education level, and occupation; (2) water and sanitation behavior factors: number of family members involved in water collection, distance traveled and time spent for water collection, places for defecation, and materials used for handwashing after defecation; and (3) social capital and trust factors: presence of anganwadi and people's trust in other community members, NGOs, and private agencies. Moreover, individuals' having higher social network positively contributed to arsenic awareness in the communities. Results indicated that both the SVM and the RF algorithms outperformed at overall prediction of arsenic awareness-a nonlinear classification problem. Lower-caste, less educated, and unemployed members of the population were found to be the most vulnerable, requiring immediate arsenic mitigation. To this end, local social institutions and NGOs could play a crucial role in arsenic awareness and outreach programs. Use of SVM or RF or a combination of the two, together with use of a larger sample size, could enhance the accuracy of arsenic awareness prediction.

Arsenite exposure potentiates apoptosis-inducing effects of tumor necrosis factor-alpha- through reactive oxygen species

Tumor necrosis factor-alpha (TNF-α) is a proinflammatory cytokine released by immune cells during inflammation process. Sodium arsenite (NaAsO₂) is an environmental toxic metal. The effects of excess NaAsO₂ on TNF-α response and its intracellular signaling are not well understood. We hypothesized that NaAsO₂ exposure might affect cellular response to TNF-α. Using HeLa cell model, we found that the combination of NaAsO₂ and TNF-α clearly decreased cell viability and mitochondrial membrane potential, but increased percentage of early and late apoptotic cells and cleaved-poly (ADP-ribose) polymerase (PARP). Moreover, the combination prolonged the phosphorylation of mitogen-activated protein kinase (MAPK) members, including c-Jun-N-terminal kinase (JNK), p38, and extracellular signal related kinases (ERK), and increased intracellular reactive oxygen species (ROS), in comparison to treatment of NaAsO₂ or TNF-α alone. We further investigated the role of ROS and MAPK signaling on this event by inhibiting ROS production and MAPK. An antioxidant N-acetylcysteine pretreatment diminished the apoptosis-inducing effect of NaAsO₂ and TNF-α combination and also inhibited MAPK signaling. Using specific inhibitor of p38 (SB203580) and siRNA-p38 surprisingly increased cell apoptosis and this effect was not observed by JNK and ERK inhibition. This study suggests that p38 may possibly be a survival mediator in response to environmental toxicant-related inflammation. In conclusion, NaAsO₂ exposure might amplify inflammation-related tissue injury by potentiating the apoptosis-inducing effect of TNF-α through ROS-dependent mechanism.