Metabolism of arsenic and its toxicological relevance

Microbial arsenic methylation in soil-water systems and its environmental significance

In this review, we have summarized the current knowledge about the environmental importance, relevance, and consequences of microbial arsenic (As) methylation in various ecosystems. In this regard, we have presented As biomethylation in terrestrial and aquatic ecosystems particularly in rice paddy soils and wetlands. The functions of As biomethylation by microbial consortia in anaerobic and aerobic conditions are extensively discussed. In addition, we have tried to explain the interconnections between As transformation and carbon (C), such as microbial degradation of organic compounds and methane (CH4) emission. These processes can cause As release because of the reduction of arsenate (As(V)) to the more mobile arsenite (As(III)) as well as As methylation and the formation of toxic trivalent methylated As species in anaerobic conditions. Furthermore, the sulfur (S) transformation can form highly toxic thiolated As species owing to its interference with As biomethylation. Besides, we have focused on many other mutual interlinks that remain elusive between As and C, including As biomethylation, thiolation, and CH4 emission, in the soil-water systems. Recent developments have clarified the significant and complex interactions between the coupled microbial process in anoxic and submerged soils. These processes, performed by little-known/unknown microbial taxa or well-known members of microbial communities with unrecognized metabolic pathways, conducted several concurrent reactions that contributed to global warming on our planet and have unfavorable impacts on water quality and human food resources. Finally, some environmental implications in rice production and arsenic removal from soil-water systems are discussed. Generally, our understanding of the ecological and metabolic evidence for the coupling and synchronous processes of As, C, and S are involved in environmental contamination-caused toxicity in human food, including high As content in rice grain, water resources, and global warming through methanogenesis elucidate combating global rice safety, drinking water, and climate changes.

Hepatoprotective effects of zingerone on sodium arsenite-induced hepatotoxicity in rats: Modulating the levels of caspase-3/Bax/Bcl-2, NLRP3/NF-κB/TNF-α and ATF6/IRE1/PERK/GRP78 signaling pathways

OBJECTIVE

Long-term exposure to arsenic has been linked to several illnesses, including hypertension, diabetes, hepatic and renal diseases and cardiovascular malfunction. The aim of the current investigation was to determine whether zingerone (ZN) could shield rats against the hepatotoxicity that sodium arsenite (SA) causes.

METHODS

The following five groups of thirty-five male Sprague Dawley rats were created: I) Control; received normal saline, II) ZN; received ZN, III) SA; received SA, IV) SA + ZN 25; received 10 mg/kg body weight SA + 25 mg/kg body weight ZN, and V) SA + ZN 50; received 10 mg/kg body weight SA + 50 mg/kg body weight ZN. The experiment lasted 14 days, and the rats were sacrificed on the 15th day. While oxidative stress parameters were studied by spectrophotometric method, apoptosis, inflammation and endoplasmic reticulum stress parameters were measured by RT-PCR method.

RESULTS

The SA disrupted the histological architecture and integrity of the liver and enhanced oxidative damage by lowering antioxidant enzyme activity, such as those of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH) level and increasing malondialdehyde (MDA) level in the liver tissue. Additionally, SA increased the mRNA transcript levels of Bcl2 associated x (Bax), caspases (-3, -6, -9), apoptotic protease-activating factor 1 (Apaf-1), p53, tumor necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB), interleukin-1β (IL-1β), interleukin-6 (IL-6), c-Jun NH2-terminal kinase (JNK), mitogen-activated protein kinase 14 (MAPK14), MAPK15, receptor for advanced glycation endproducts (RAGE) and nod-like receptor family pyrin domain-containing 3 (NLRP3) in the liver tissue. Also produced endoplasmic reticulum stress by raising the mRNA transcript levels of activating transcription factor 6 (ATF-6), protein kinase RNA-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and glucose-regulated protein 78 (GRP-78). These factors together led to inflammation, apoptosis, and endoplasmic reticulum stress. On the other hand, liver tissue treated with ZN at doses of 25 and 50 mg/kg showed significant improvement in oxidative stress, inflammation, apoptosis and endoplasmic reticulum stress.

CONCLUSIONS

Overall, the study's data suggest that administering ZN may be able to lessen the liver damage caused by SA toxicity.

Arsenic inorganic exposure, metabolism, genetic biomarkers and its impact on human health: A mini-review

Inorganic arsenic species exist in the environment as a result of both natural sources, such as volcanic and geothermal activities, and geological formations, as well as anthropogenic activities, including smelting, exploration of fossil fuels, coal burning, mining, and the use of pesticides. These species deposit in water, rocks, soil, sediments, and the atmosphere. Arsenic-contaminated drinking water is a global public health issue because of its natural prevalence and toxicity. Therefore, chronic exposure to arsenic can have deleterious effect on humans, including cancer and other diseases. This work describes the mechanisms of environmental exposure to arsenic, molecular regulatory factors involved in its metabolism, genetic polymorphisms affecting individual susceptibility and the toxic effects of arsenic on human health (oxidative stress, DNA damage and cancer). We conclude that the role of single nucleotide variants affecting urinary excretion of arsenic metabolites are highly relevant and can be used as biomarkers of the intracellular retention rates of arsenic, showing new avenues of research in this field.

Bioaccessibility and human health risks of arsenic from geological origin in lateritic red soil on construction land

Current human health risk assessments of soil arsenic (As) contamination rarely consider bioaccessibility (IVBA), which may overestimate the health risks of soil As. The IVBA of As (As-IVBA) may differ among various soil types. This investigation of As-IVBA focused As from geological origin in a typical subtropical soil, lateritic red soil, and its risk control values. The study used the SBRC gastric phase in vitro digestion method and As speciation sequential extraction based upon phosphorus speciation extraction method. Two construction land sites (CH and HD sites) in the Pearl River Delta region were surveyed. The results revealed a high content of residual As (including scorodite, mansfieldite, orpiment, realgar, and aluminum arsenite) in the lateritic red soils at both sites (CH: 84.9%, HD: 91.7%). The content of adsorbed aluminum arsenate (CH: 3.24%, HD: 0.228%), adsorbed ferrum arsenate (CH: 8.55%, HD: 5.01%), and calcium arsenate (CH: 7.33%, HD: 3.01%) were found to be low. The bioaccessible As content was significantly positively correlated with the As content in adsorbed aluminum arsenate, adsorbed ferrum arsenate, and calcium arsenate. A small portion of these sequential extractable As speciation could be absorbed by the human body (CH: 14.9%, HD: 3.16%), posing a certain health risk. Adsorbed aluminum arsenate had the highest IVBA, followed by calcium arsenate, and adsorbed ferrum arsenate had the lowest IVBA. The aforementioned speciation characteristics of As from geological origin in lateritic red soil contributed to its lower IVBA compared to other soils. The oxidation state of As did not significantly affect As-IVBA. Based on As-IVBA, the carcinogenic and non-carcinogenic risks of soil As in the CH and HD sites decreased greatly in human health risk assessment. The results suggest that As-IVBA in lateritic red soil should be considered when assessing human health risks on construction land.

Effect of Gentianella acuta (Michx.) Hulten against the arsenic-induced development hindrance of mouse oocytes

The current study was designed to investigate the alleviative effect of Gentianella acuta (Michx.) Hulten (G. acuta) against the sodium arsenite (NaAsO2)-induced development hindrance of mouse oocytes. For this purpose, the in vitro maturation (IVM) of mouse cumulus-oocyte complexes (COCs) was conducted in the presence of NaAsO2 and G. acuta, followed by the assessments of IVM efficiency including oocyte maturation, spindle organization, chromosome alignment, cytoskeleton assembly, cortical granule (CGs) dynamics, redox regulation, epigenetic modification, DNA damage, and apoptosis. Subsequently, the alleviative effect of G. acuta intervention on the fertilization impairments of NaAsO2-exposed oocytes was confirmed by the assessment of in vitro fertilization (IVF). The results showed that the G. acuta intervention effectively ameliorated the decreased maturation potentials and fertilization deficiency of NaAsO2-exposed oocytes but also significantly inhibited the DNA damages, apoptosis, and altered H3K27me3 expression level in the NaAsO2-exposed oocytes. The effective effects of G. acuta intervention against redox dysregulation including mitochondrial dysfunctions, accumulated reactive oxygen species (ROS) generation, glutathione (GSH) deficiency, and decreased adenosine triphosphate (ATP) further confirmed that the ameliorative effects of G. acuta intervention against the development hindrance of mouse oocytes were positively related to the antioxidant capacity of G. acuta. Evidenced by these abovementioned results, the present study provided fundamental bases for the ameliorative effect of G. acuta intervention against the meiotic defects caused by the NaAsO2 exposure, benefiting the future application potentials of G. acuta intervention in these nutritional and therapeutic research for attenuating the outcomes of arseniasis.

Chronic Exposure to Arsenic and Fluoride Starting at Gestation Alters Liver Mitochondrial Protein Expression and Induces Early Onset of Liver Fibrosis in Male Mouse Offspring

The presence of arsenic (As) and fluoride (F-) in drinking water is of concern due to the enormous number of individuals exposed to this condition worldwide. Studies in cultured cells and animal models have shown that As- or F-induced hepatotoxicity is primarily associated with redox disturbance and altered mitochondrial homeostasis. To explore the hepatotoxic effects of chronic combined exposure to As and F- in drinking water, pregnant CD-1 mice were exposed to 2 mg/L As (sodium arsenite) and/or 25 mg/L F- (sodium fluoride). The male offspring continued the exposure treatment up to 30 (P30) or 90 (P90) postnatal days. GSH levels, cysteine synthesis enzyme activities, and cysteine transporter levels were investigated in liver homogenates, as well as the expression of biomarkers of ferroptosis and mitochondrial biogenesis-related proteins. Serum transaminase levels and Hematoxylin-Eosin and Masson trichrome-stained liver tissue slices were examined. Combined exposure at P30 significantly reduced GSH levels and the mitochondrial transcription factor A (TFAM) expression while increasing lipid peroxidation, free Fe 2+, p53 expression, and serum ALT activity. At P90, the upregulation of cysteine uptake and synthesis was associated with a recovery of GSH levels. Nevertheless, the downregulation of TFAM continued and was now associated with a downstream inhibition of the expression of MT-CO2 and reduced levels of mtDNA and fibrotic liver damage. Our experimental approach using human-relevant doses gives evidence of the increased risk for early liver damage associated with elevated levels of As and F- in the diet during intrauterine and postnatal period.

Dimethylmonothioarsinic acid (DMMTAV) differentially modulates the expression of AHR-regulated cytochrome P450 1A enzymes in vivo and in vitro

Dimethylmonothioarsinic acid (DMMTAV), a pentavalent thio-arsenic derivative, has been found in bodily fluids and tissues including urine, liver, kidney homogenates, plasma, and red blood cells. Although DMMTAV is a minor metabolite in humans and animals, its substantial toxicity raises concerns about potential carcinogenic effects. This toxicity could be attributed to arsenicals' ability to regulate cytochrome P450 1 A (CYP1A) enzymes, pivotal in procarcinogen activation or detoxification. The current study investigates DMMTAV's impact on CYP1A1/2 expression, individually and in conjunction with its inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). C57BL/6 mice were intraperitoneally injected with 6 mg/kg DMMTAV, alone or with 15 μg/kg TCDD, for 6 and 24 h. Similarly, Hepa-1c1c7 cells were exposed to DMMTAV (0.5, 1, and 2 μM) with or without 1 nM TCDD for 6 and 24 h. DMMTAV hindered TCDD-induced elevation of Cyp1a1 mRNA, both in vivo (at 6 h) and in vitro, associated with reduced CYP1A regulatory element activation. Interestingly, in C57BL/6 mice, DMMTAV boosted TCDD-induced CYP1A1/2 protein and activity, unlike Hepa-1c1c7 cells where it suppressed both. DMMTAV co-exposure increased TCDD-induced Cyp1a2 mRNA. While Cyp1a1 mRNA stability remained unchanged, DMMTAV negatively affected protein stability, indicated by shortened half-life. Baseline levels of CYP1A1/2 mRNA, protein, and catalytic activities showed no significant alterations in DMMTAV-treated C57BL/6 mice and Hepa-1c1c7 cells. Taken together, these findings indicate, for the first time, that DMMTAV differentially modulates the TCDD-mediated induction of AHR-regulated enzymes in both liver of C57BL/6 mice and murine Hepa-1c1c7 cells suggesting that thio-arsenic pentavalent metabolites are extremely reactive and could play a role in the toxicity of arsenic.

Exploring ecological effects of arsenic and cadmium combined exposure on cropland soil: from multilevel organisms to soil functioning by multi-omics coupled with high-throughput quantitative PCR

Arsenic (As) and cadmium (Cd) pose potential ecological threats to cropland soils; however, few studies have investigated their combined effects on multilevel organisms and soil functioning. Here, we used collembolans and soil microbiota as test organisms to examine their responses to soil As and Cd co-contamination at the gene, individual, and community levels, respectively, and further uncovered ecological relationships between pollutants, multilevel organisms, and soil functioning. At the gene level, collembolan transcriptome revealed that elevated As concentrations stimulated As-detoxifying genes AS3MT and GST, whereas the concurrent Cd restrained GST gene expression. At the individual level, collembolan reproduction was sensitive to pollutants while collembolan survival wasn't. At the community level, significant but inconsistent correlations were observed between the biodiversity of different soil keystone microbial clusters and soil As levels. Moreover, soil functioning related to nutrient (e.g., carbon, nitrogen, phosphorus, and sulfur) cycles was inhibited under As and Cd co-exposure only through the mediation of plant pathogens. Overall, these findings suggested multilevel bioindicators (i.e., AS3MT gene expression in collembolans, collembolan reproduction, and biodiversity of soil keystone microbial clusters) in cropland soils co-contaminated with As and Cd, thus improving the understanding of the ecotoxicological impact of heavy metal co-contamination on soil ecosystems.

Translocation, enzymatic reduction and toxicity of dimethylarsenate in rice

Dimethylarsenate [DMAs(V)] can be produced by some soil microorganisms through methylation of inorganic arsenic (As), especially in anoxic paddy soils. DMAs(V) is more phytotoxic than inorganic As and can cause the physiological disorder straighthead disease in rice. Rice cultivars vary widely in the resistance to DMAs(V), but the mechanism remains elusive. Here, we investigated the differences in DMAs(V) uptake, translocation, and reduction to dimethylarsenite [DMAs(III)], as well as the effects on the metabolome, between two rice cultivars Mars and Zhe733. We found that Mars was 11-times more resistant to DMAs(V) than Zhe733. Mars accumulated more DMAs(V) in the roots, whereas Zhe733 translocated more DMAs(V) to the shoots and reduced more DMAs(V) to DMAs(III). DMAs(III) was more toxic than DMAs(V). Using heterologous expression and in vitro enzyme assays, we showed that the glutathione-S-transferases OsGSTU17 and OsGSTU50 were able to reduce DMAs(V) to DMAs(III). The expression levels of OsGSTU17 and OsGSTU50 were higher in the shoot of Zhe733 compared to Mars. Metabolomic analysis in rice shoots showed that glutathione (GSH) metabolism was perturbed by DMAs(V) toxicity in Zhe733. Application of exogenous GSH significantly alleviated the toxicity of DMAs(V) in Zhe733. Taken together, the results suggest that Mars is more resistant to DMAs(V) than Zhe733 because of a lower root-to-shoot translocation and a smaller capacity to reduce DMAs(V) to DMAs(III).

Transcriptomic and metabolomic analysis of the mechanisms underlying stress responses of the freshwater snail, Pomacea canaliculata, exposed to different levels of arsenic

Arsenic (As) pollution poses an important problem, but limited information is available about the physiological effects of As on freshwater invertebrates. Here, we investigated the physiological effects of chronic As exposure on Pomacea canaliculata, a freshwater invertebrate. High level of As (Ⅲ, 5 mg/L) inhibited the growth of P. canaliculata, whereas low level of As (Ⅲ, 2 mg/L) promoted growth. Pathological changes in shell and cellular ultrastructure due to As accumulation likely explain the growth inhibition at high As level. Low level of As simulated the expression of genes related to DNA replication and chitosan biosynthesis, potentially accounting for the growth promotion observed. High level of As enrichment pathways primarily involved cytochrome P450, glutathione, and arachidonic acid-mediated metabolism of xenobiotics. ATP-binding cassette (ABC) transporters, specifically the ABCB and ABCC subfamilies, were involved in As transport. Differential metabolites were mainly associated with the metabolism and biosynthesis of amino acids. These findings elucidate the dose-dependent effects of As stress on P. canaliculata growth, with low levels promoting and high levels inhibiting. Additionally, our findings also provide insights into As metabolism and transport in P. canaliculata.

Mixed effects and co-transfer of CeO2 NPs and arsenic in the pakchoi-snail food chain

Nanomaterial application in agriculture offers novel solutions for soil arsenic (As) pollution control, yet safety along the food chain is of concern. We comprehensively assessed CeO2 nanoparticles (NPs) foliar application effects on As uptake by pakchoi and their presence in the pakchoi-snail food chain. CeO2 NPs reduced As transfer from pakchoi roots to shoots by 37.9%, lowered As in snail foot by 39%, and halved human As exposure risk. The NPs alleviated pakchoi shoot As toxicity by regulating antioxidants, enhancing water use efficiency, and photosynthesis. CeO2 +As treatment raised GSH/GSSG ratios by 38.92%- 167.54%, leading to an increased AsIII/AsV ratio and inorganic As detoxification compared to As alone. Metabolomics revealed CeO2's rapid As response via phosphatidylinositol signaling. The enzyme-like activity of CeO2 NPs may drive these effects. While CeO2 foliar application accumulated Ce on pakchoi leaves, > 99% of Ce was excreted following snail consumption. Ce transfer from pakchoi leaves to snail foot was minimal (trophic transfer factor ∼0.00007) due to limited bioavailability. The target hazard quotient of Ce in pakchoi shoot (1.21 ± 0.18) and snails (0.0016 ± 0.0004) indicated low exposure risk, suggesting a 'risk filter' effect for CeO2. Our results contribute to the safe and sustainable application of CeO2 NPs in the future implication.

Arsenic induces metabolome remodeling in mature human adipocytes

Human lifetime exposure to arsenic through drinking water, food supply or industrial pollution leads to its accumulation in many organs such as liver, kidneys, lungs or pancreas but also adipose tissue. Recently, population-based studies revealed the association between arsenic exposure and the development of metabolic diseases such as obesity and type 2 diabetes. To shed light on the molecular bases of such association, we determined the concentration that inhibited 17% of cell viability and investigated the effects of arsenic acute exposure on adipose-derived human mesenchymal stem cells differentiated in vitro into mature adipocytes and treated with sodium arsenite (NaAsO2, 10 nM to 10 µM). Untargeted metabolomics and gene expression analyses revealed a strong dose-dependent inhibition of lipogenesis and lipolysis induction, reducing the cellular ability to store lipids. These dysregulations were emphasized by the inhibition of the cellular response to insulin, as shown by the perturbation of several genes and metabolites involved in the mentioned biological pathways. Our study highlighted the activation of an adaptive oxidative stress response with the strong induction of metallothioneins and increased glutathione levels in response to arsenic accumulation that could exacerbate the decreased insulin sensitivity of the adipocytes. Arsenic exposure strongly affected the expression of arsenic transporters, responsible for arsenic influx and efflux, and induced a pro-inflammatory state in adipocytes by enhancing the expression of the inflammatory interleukin 6 (IL6). Collectively, our data showed that an acute exposure to low levels of arsenic concentrations alters key adipocyte functions, highlighting its contribution to the development of insulin resistance and the pathogenesis of metabolic disorders.

Biomonitoring of inorganic arsenic species in pregnancy

Exposure assessment of inorganic arsenic is challenging due to the existence of multiple species, complexity of arsenic metabolism, and variety of exposure sources. Exposure assessment of arsenic during pregnancy is further complicated by the physiological changes that occur to support fetal growth. Given the well-established toxicity of inorganic arsenic at high concentrations, continued research into the potential health effects of low-level exposure on maternal and fetal health is necessary. Our objectives were to review the value of and challenges inherent in measuring inorganic arsenic species in pregnancy and highlight related research priorities. We discussed how the physiological changes of pregnancy influence arsenic metabolism and necessitate the need for pregnancy-specific data. We reviewed the biomonitoring challenges according to common and novel biological matrices and discussed how each matrix differs according to half-life, bioavailability, availability of laboratory methods, and interpretation within pregnancy. Exposure assessment in both established and novel matrices that accounts for the physiological changes of pregnancy and complexity of speciation is a research priority. Standardization of laboratory method for novel matrices will help address these data gaps. Research is particularly lacking in contemporary populations of pregnant women without naturally elevated arsenic drinking water concentrations (i.e. <10 µg/l).

In utero arsenic exposure and early childhood motor development in the New Hampshire Birth Cohort Study

Introduction

High-level prenatal and childhood arsenic (As) exposure characteristic of several regions in Asia (e.g., Bangladesh), may impact motor function. However, the relationship between lower-level arsenic exposure (characteristic of other regions) and motor development is largely unstudied, despite the potential for deficient motor skills in childhood to have adverse long-term consequences. Thus, we sought to investigate the association between prenatal As exposure and motor function among 395 children in the New Hampshire Birth Cohort Study, a rural cohort from northern New England.

Methods

Prenatal exposure was estimated by measuring maternal urine speciated As at 24-28 weeks of gestation using high-performance liquid chromatography (HPLC) inductively coupled plasma mass spectrometry (ICP-MS) and summing inorganic As, monomethylarsonic acid, and dimethylarsinic acid to obtain total urinary As (tAs). Motor function was assessed with the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition (BOT-2) at a mean (SD) age of 5.5 (0.4) years.

Results

Children who completed this exam were largely reported as white race (97%), born to married mothers (86%) with a college degree or higher (67%). The median (IQR) gestational urine tAs concentration was 4.0 (5.0) µg/L. Mean (SD) BOT-2 scores were 48.6 (8.4) for overall motor proficiency and 48.2 (9.6) for fine manual control [standard score = 50 (10)], and were 16.3 (5.1) for fine motor integration and 12.5 (4.1) for fine motor precision [standard score = 15 (5)]. We found evidence of a non-linear dose response relationship and used a change-point model to assess the association of tAs with overall motor proficiency and indices of fine motor integration, fine motor precision, and their composite, fine manual control, adjusted for age and sex. In models adjusted for potential confounders, each doubling of urine tAs decreased overall motor proficiency by -3.3 points (95% CI: -6.1, -0.4) for tAs concentrations greater than the change point of 9.5 µg/L and decreased fine motor integration by -4.3 points (95% CI: -8.0, -0.6) for tAs concentrations greater than the change point of 17.0 µg/L.

Discussion

In summary, we found that levels of prenatal As exposure above an empirically-derived threshold (i.e., the change point) were associated with decrements in childhood motor development in a US population.

Individual, Independent, and Joint Associations of Toxic Metals and Manganese on Hypertensive Disorders of Pregnancy: Results from the MIREC Canadian Pregnancy Cohort

BACKGROUND

Toxic metals, such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg), may be associated with a higher risk of gestational hypertension and preeclampsia, whereas manganese (Mn) is an essential metal that may be protective.

OBJECTIVES

We estimated the individual, independent, and joint associations of Pb, Cd, As, Hg, and Mn on the risk of developing gestational hypertension and preeclampsia in a cohort of Canadian women.

METHODS

Metal concentrations were analyzed in first and third trimester maternal blood (n=1,560). We measured blood pressure after 20 wk gestation to diagnose gestational hypertension, whereas proteinuria and other complications defined preeclampsia. We estimated individual and independent (adjusted for coexposure) relative risks (RRs) for each doubling of metal concentrations and examined interactions between toxic metals and Mn. We used quantile g-computation to estimate the joint effect of trimester-specific exposures.

RESULTS

Each doubling of third trimester Pb (RR=1.54; 95% CI: 1.06, 2.22) and first trimester blood As (RR=1.25; 95% CI: 1.01, 1.58) was independently associated with a higher risk of developing preeclampsia. First trimester blood As (RR=3.40; 95% CI: 1.40, 8.28) and Mn (RR=0.63; 95% CI: 0.42, 0.94) concentrations were associated with a higher and lower risk, respectively, of developing gestational hypertension. Mn modified the association with As such that the deleterious association with As was stronger at lower concentrations of Mn. First trimester urinary dimethylarsinic acid concentrations were not associated with gestational hypertension (RR=1.31; 95% CI: 0.60, 2.85) or preeclampsia (RR=0.92; 95% CI: 0.68, 1.24). We did not observe overall joint effects for blood metals.

DISCUSSION

Our results confirm that even low blood Pb concentrations are a risk factor for preeclampsia. Women with higher blood As concentrations combined with lower Mn in early pregnancy were more likely to develop gestational hypertension. These pregnancy complications impact maternal and neonatal health. Understanding the contribution of toxic metals and Mn is of public health importance. https://doi.org/10.1289/EHP10825.

Independent and combined associations of urinary arsenic exposure and serum sex steroid hormones among 6-19-year old children and adolescents in NHANES 2013-2016

Arsenic exposure may disrupt sex steroid hormones, causing endocrine disruption. However, human evidence is limited and inconsistent, especially for children and adolescents. To evaluate the independent and combined associations between arsenic exposure and serum sex steroid hormones in children and adolescents, we conducted a cross-sectional analysis of data from 1063 participants aged 6 to 19 years from the 2013-2016 National Health and Nutrition Examination Survey (NHANES). Three urine arsenic metabolites were examined, as well as three serum sex steroid hormones, estradiol (E₂), total testosterone (TT), and sex hormone-binding globulin (SHBG). The ratio of TT to E₂ (TT/E₂) and the free androgen index (FAI) generated by TT/SHBG were also assessed. Linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were used to evaluate the associations of individual or arsenic metabolite combinations with sex steroid hormones by gender and age stratification. Positive associations were found between total arsenic and arsenic metabolites with TT, E₂, and FAI. In contrast, negative associations were found between arsenic metabolites and SHBG. Furthermore, there was an interaction after gender-age stratification between DMA and SHBG in female adolescents. Notably, based on the WQS and BKMR model results, the combined association of arsenic and its metabolites was positively associated with TT, E₂, and FAI and negatively associated with SHBG. Moreover, DMA and MMA dominated the highest weights among the arsenic metabolites. Overall, our results indicate that exposure to arsenic, either alone or in mixtures, may alter sex steroid hormone levels in children and adolescents.

Improvement of Arsenic Tolerance and Removal Ability of Multi-stress-tolerant Pichia kudriavzevii A16 by Salt Preincubation

Arsenic (As) exists widely in the environment and its strong toxicity endangers human health, causing widespread concern. Microbial adsorption technology plays an important role in As removal due to its advantages of high safety, low pollution, and low cost. The removal of As by active microorganisms requires not only good accumulation characteristics but also high As tolerance. The effect of salt preincubation on arsenate [As(V)] tolerance and bioaccumulation of Pichia kudriavzevii A16 and the possible mechanisms were studied. Salt preincubation improved the As(V) tolerance and bioaccumulation ability of the yeast. After Na₅P₃O₁₀ preincubation, the proportion of dead cells and cells with high reactive oxygen species (ROS) accumulation decreased from 50.88% and 16.54% to 14.60% and 5.24%, respectively. In addition, the As removal rate significantly increased from 26.20% to 57.98%. The preincubated cells showed stronger As(V) tolerance and removal ability. The potential of use in complex environment to remove As(V) as well as the mechanisms involved in As(V) tolerance by yeast will be discussed.

Selenium attenuates the association of co-exposure to arsenic, cadmium, and lead with cognitive function among Chinese community-dwelling older adults

The effects of interactions between the toxic and essential metal mixtures on cognitive function are poorly understood. This study aims to identify the joint association of arsenic (As), cadmium (Cd), and lead (Pb) with cognitive function in older adults and the moderating role of selenium (Se), zinc (Zn), and copper (Cu) in this association. This study included 1000 community-dwelling older adults. Cognitive function was assessed by the Mini-Mental State Examination (MMSE). Blood concentrations of As, Cd, Pb, Se, Zn, and Cu were measured using inductively coupled plasma mass spectrometry. Linear regression and Bayesian kernel machine regression (BKMR) models were applied to assess the individual and joint associations of As, Cd, and Pb with cognitive function and to examine whether Se, Zn, and Cu (individually and as a mixture) modified these associations. In the adjusted single-metal models, both Cd (β = - 0.37, 95% CI: - 0.73 to - 0.01) and Pb (β = - 0.44, 95% CI: - 0.86 to - 0.02) were associated with MMSE scores, while Se (β = 0.71, 95% CI: 0.30 to 1.13) exhibited a positive relationship with MMSE scores. Univariate exposure-response functions from BKMR models showed similar results. Moreover, the toxic metal mixture (As, Cd, and Pb) exhibited a significant negative association with MMSE scores in a dose-response pattern, with Pb being the greatest contributor within the mixture. The negative association of Pb alone or the toxic metal mixture with MMSE scores became weaker at higher concentrations of Se within its normal range, especially when Se levels were greater than the median (89.18 μg/L). Our findings support that Se can attenuate the negative associations of exposure to single Pb or the As, Cd, and Pb mixtures with cognitive function. Future prospective studies are needed to replicate our findings.

The relevance of arsenic speciation analysis in health & medicine

Long term exposure to arsenic through consumption of contaminated groundwater has been a global issue since the last five decades; while from an alternate standpoint, arsenic compounds have emerged as unparallel chemotherapeutic drugs. This review highlights the contribution from arsenic speciation studies that have played a pivotal role in the progression of our understanding of the biological behaviour of arsenic in humans. We also discuss the limitations of the speciation studies and their association with the interpretation of arsenic metabolism. Chromatographic separation followed by spectroscopic detection as well as the utilization of biotinylated pull-down assays, protein microarray and radiolabelled arsenic have been instrumental in identifying hundreds of metabolic arsenic conjugates, while, computational modelling has predicted thousands of them. However, these species exhibit a variegated pattern, which supports more than one hypothesis for the metabolic pathway of arsenic. Thus, the arsenic species are yet to be integrated into a coherent mechanistic pathway depicting its chemicobiological fate. Novel biorelevant arsenic species have been identified due to significant evolution in experimental methodologies. However, these methods are specific for the identification of only a group of arsenicals sharing similar physiochemical properties; and may not be applicable to other constituents of the vast spectrum of arsenic species. Consequently, the identity of arsenic binding partners in vivo and the sequence of events in arsenic metabolism are still elusive. This resonates the need for additional focus on the extraction and characterization of both low and high molecular weight arsenicals in a combinative manner.

Arsenic exposure and its implications in male fertility

Arsenic exposure is a global health concern. This toxic metalloid is ubiquitous in the environment and contaminates food and drinking water. Once ingested, it undergoes a complex metabolic process within the body, which contributes to its accumulation and reactivity. Arsenic toxicity stems from the induction of oxidative stress, inhibition of thiol-containing proteins, and mimicry of inorganic phosphates. Arsenic poisoning is associated with the development of reproductive disorders. In males, arsenic causes a reduction in testicular weight and alterations in steroidogenesis and spermatogenesis. Moreover, it reduces the number and quality of spermatozoa harvested from the cauda epididymis. The mitochondria are targets of arsenic toxicity because of the production of free radicals and their high content of cysteine-rich proteins and fatty acids. Mitochondrial dysfunction may contribute to reproductive disorders because this organelle is crucial for controlling testicular and epididymal events related to sperm production and maturation. All of these alterations mediated by arsenic exposure contribute to the failure of male reproductive competence by reducing gamete viability. This review describes the potential mechanisms of arsenic toxicity, its detrimental effects on male reproductive organs, and consequences on sperm fertility.

The Duality of Arsenic Metabolism: Impact on Human Health

Arsenic is a naturally occurring hazardous element that is environmentally ubiquitous in various chemical forms. Upon exposure, the human body initiates an elimination pathway of progressive methylation into relatively less bioreactive and more easily excretable pentavalent methylated forms. Given its association with decreasing the internal burden of arsenic with ensuing attenuation of its related toxicities, biomethylation has been applauded for decades as a pure route of arsenic detoxification. However, the emergence of detectable trivalent species with profound toxicity has opened a long-standing debate regarding whether arsenic methylation is a detoxifying or bioactivating mechanism. In this review, we approach the topic of arsenic metabolism from both perspectives to create a complete picture of its potential role in the mitigation or aggravation of various arsenic-related pathologies.

A comprehensive review on bio-stimulation and bio-enhancement towards remediation of heavy metals degeneration

Pollution of heavy metals is one of the risky contaminations that should be managed for all intents and purposes of general well-being concerns. The bioaccumulation of these heavy metals inside our bodies and pecking orders will influence our people in the future. Bioremediation is a bio-mechanism where residing organic entities use and reuse the squanders that are reused to one more form. This could be accomplished by taking advantage of the property of explicit biomolecules or biomass that is equipped for restricting by concentrating the necessary heavy metal particles. The microorganisms can't obliterate the metal yet can change it into a less harmful substance. In this unique circumstance, this review talks about the sources, poisonousness, impacts, and bioremediation strategies of five heavy metals: lead, mercury, arsenic, chromium, and manganese. The concentrations here are the ordinary strategies for bioremediation such as biosorption methods, the use of microbes, green growth, and organisms, etc. This review demonstrates the toxicity of heavy metal contamination degradation by biotransformation through bacterioremediation and biodegradation through mycoremediation.

Gene expression analysis of antioxidant and DNA methylation on the rat liver after 4-week wood preservative chromated copper arsenate exposure

Our previous 4-week repeated dose toxicity study showed that wood preservative chromated copper arsenate (CCA) induced hepatocellular hypertrophy accompanied by biochemical hepatic dysfunction and an increase in oxidative stress marker, 8-hydroxydeoxyguanosine, in female rats. To further explore the molecular mechanisms of CCA hepatotoxicity, we analyzed 10%-buffered formalin-fixed liver samples from female rats for cell proliferation, apoptosis, and protein glutathionylation and conducted microarray analysis on frozen liver samples from female rats treated with 0 or 80 mg/kg/day of CCA. Chemical analysis revealed that dimethylated arsenical was the major metabolite in liver tissues of male and female rats. CCA increase labeling indices of proliferating cell nuclear antigen and decrease terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling accompanied with increased expression of protein glutathionylation, indicating a decrease in glutathione (GSH) in hepatocytes of female rats. Microarray analysis revealed that CCA altered gene expression of antioxidants, glutathione-S-transferase (GST), heat shock proteins and ubiquitin-proteasome pathway, cell proliferation, apoptosis, DNA methylation, cytochrome P450, and glucose and lipid metabolism in female rats. Increased expression of GSTs, including Gsta2, Gsta3, Mgst1, and Cdkn1b (p27), and decreased expression of the antioxidant Mt1, and DNA methylation Dnmt1, Dnmt3a, and Ctcf were confirmed in the liver of female rats in a dose-dependent manner. Methylation status of the promoter region of the Mt1 was not evidently changed between control and treatment groups. The results suggested that CCA decreased GSH and altered the expression of several genes, including antioxidants, GST, and DNA methylation, followed by impaired cell proliferation in the liver of female rats.

Arsenic exposure promotes the emergence of cardiovascular diseases

A large number of studies conducted in the past decade 2010-2020 refer to the impact of arsenic (As) exposure on cardiovascular risk factors. The arsenic effect on humans is complex and mainly depends on the varying individual susceptibilities, its numerous toxic expressions and the variation in arsenic metabolism between individuals. In this review we present relevant data from studies which document the association of arsenic exposure with various biomarkers, the effect of several genome polymorphisms on arsenic methylation and the underling molecular mechanisms influencing the cardiovascular pathology. The corresponding results provide strong evidence that high and moderate-high As intake induce oxidative stress, inflammation and vessel endothelial dysfunction that are associated with increased risk for cardiovascular diseases (CVDs) and in particular hypertension, myocardial infarction, carotid intima-media thickness and stroke, ventricular arrhythmias and peripheral arterial disease. In addition, As exposure during pregnancy implies risks for blood pressure abnormalities among infants and increased mortality rates from acute myocardial infarction during early adulthood. Low water As concentrations are associated with increased systolic, diastolic and pulse pressure, coronary heart disease and incident stroke. For very low As concentrations the relevant studies are few. They predict a risk for myocardial infarction, stroke and ischemic stroke and incident CVD, but they are not in agreement regarding the risk magnitude.

Impact of mining on the metal content of dust in indigenous villages of northern Chile

Indigenous communities from northern Chile have historically been exposed to the impacts of massive copper industrial activities conducted in the region. Some of the communities belonging to the Alto El Loa Indigenous Development Area are located less than 10 km from the "Talabre'' tailings dam, which contains residues from copper production and other metals that can be toxic to human health (e.g., As, Sb, Cd, Mo, Pb). Given the increasing demand of copper production to achieve net-zero emission scenarios and concomitant expansions of the tailings, the exposure to toxic metals is a latent risk to local communities. Despite the impact that copper production could generate on ancestral communities from northern Chile, studies and monitoring are limited and the results are often not made accessible for local communities. Here, we evaluate such risks by characterizing metal concentrations in dust collected from roofs and windows of houses from the Alto El Loa area. Our results showed that As, Sb, Cd, Cu, Mo, Ag, S, and Pb concentrations in these matrices can be connected to local copper mining activities. Additionally, air transport models indicate that high concentrations of toxic elements (As, Sb, and Cd) can be explained by the atmospheric transport of particles from the tailings in a NE direction up to 50 km away. Pollution indices and Health Risk Assessment suggested a highly contaminated region with a health risk for its inhabitants. Our analysis on a local scale seeks to make visible the case of northern Chile as a critical territory where actions should be taken to mitigate the effects of mining in the face of this new scenario of international demand for the raw materials necessary for the transition to a net-zero carbon global society.

Protective efficacy of Coriandrum sativum seeds against arsenic induced toxicity in Swiss albino mice

Arsenic poisoning in ground water is one of the most sensitive environmental pollutant causing serious pollution all over the world. Chronic arsenic exposure through drinking water to humans leads to major public health related issues. There have been very meagre studies which reported that, the plant constituents proved to exhibit protective effect from arsenicosis. Therefore, the present study aims to evaluate the protective efficacy of Coriandrum sativum seeds extract against sodium arsenite induced toxicity in Swiss albino mice. In the present study twenty-four male healthy Swiss albino mice (30 ± 5 g) were divided into four groups (n = 6), where the control group received normal diet and water; group II and group III treated with sodium arsenite (2 mg per kg body weight per day) for 2 and 4 weeks respectively. The group IV mice were administered with C.sativum seeds extract at the dose of 150 mg per kg body weight per day for 4 weeks upon sodium arsenite pretreated (2 mg/kg body weight for 4 weeks per day) mice. After the complete dose duration, all the treatment group animals were sacrificed same day for haematological, biochemical and histopathological study. In the arsenic treated mice, there were significant (p < 0.0001) changes in the serum levels of ALT, AST, ALP, urea, uric acid and creatinine as well as in the haematological parameters. In contrast, after the administration with C.sativum seeds extract upon arsenic pretreated mice, there was significant (p < 0.0001) improvement observed in the hepatic and renal biomarker parameters as well as haematological variables. In the arsenic intoxicated mice,  after administration with C.sativum seeds extract there was significant (p < 0.0001) reduction in the arsenic concentration in blood, liver and kidney tissues as well as in the serum LPO levels. Furthermore, the histopathological study showed that, C.sativum seeds extract administrated group of mice significantly restored the liver and kidney at cellular level against arsenic induced toxicity. The entire study concludes that C.sativum seeds extract possesses the ameliorative effect against arsenic induced liver and kidney intoxication.

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.

Layered Double Hydroxide-Based Micro "Chemical Factory" with Arsenic Processing and Screening Functions on Nitinol for Gallbladder Cancer Treatment

Gallbladder cancer is a common malignant tumor of the biliary system with a high fatality rate. Nitinol (Ni-Ti) stents, a standard treatment for prolonging patients' lives, are susceptible to reocclusion and cannot inhibit tumor recurrence because they lack antitumor and antibacterial activity. Herein, an arsenic-loaded layered double-hydroxide film is constructed on Ni-Ti, forming a micro "chemical factory." The LDH plays the role of a "processer" which absorbs highly toxic trivalent arsenic (As(III)) and processes it into lowly toxic pentavalent arsenic (As(V)). It also acts as a "quality-inspector," confining As(III) in the interlayer and releasing only As(V) (the finished product) to the outside. This control mechanism minimizes the toxicity during contact with normal tissue. The acidic microenvironment and overexpression of glutathione in tumor tissues not only accelerates the release of arsenic from the platform but also triggers the in situ transformation of arsenic from lowly toxic As(V) to highly toxic As(III), exerting a strong arsenic-mediated antineoplastic effect. Such a microenvironment-responsive "chemical factory" with arsenic processing and screening functions is expected to prevent tumor overgrowth, metastasis, and bacterial infection and provide new insights into the design of Ni-Ti drug-eluting stents for gallbladder cancer treatment.

Arsenic Exposure through Dietary Intake and Associated Health Hazards in the Middle East

Dietary arsenic (As) contamination is a major public health issue. In the Middle East, the food supply relies primarily on the import of food commodities. Among different age groups the main source of As exposure is grains and grain-based food products, particularly rice and rice-based dietary products. Rice and rice products are a rich source of core macronutrients and act as a chief energy source across the world. The rate of rice consumption ranges from 250 to 650 g per day per person in South East Asian countries. The source of carbohydrates through rice is one of the leading causes of human As exposure. The Gulf population consumes primarily rice and ready-to-eat cereals as a large proportion of their meals. Exposure to arsenic leads to an increased risk of non-communicable diseases such as dysbiosis, obesity, metabolic syndrome, diabetes, chronic kidney disease, chronic heart disease, cancer, and maternal and fetal complications. The impact of arsenic-containing food items and their exposure on health outcomes are different among different age groups. In the Middle East countries, neurological deficit disorder (NDD) and autism spectrum disorder (ASD) cases are alarming issues. Arsenic exposure might be a causative factor that should be assessed by screening the population and regulatory bodies rechecking the limits of As among all age groups. Our goals for this review are to outline the source and distribution of arsenic in various foods and water and summarize the health complications linked with arsenic toxicity along with identified modifiers that add heterogeneity in biological responses and suggest improvements for multi-disciplinary interventions to minimize the global influence of arsenic. The development and validation of diverse analytical techniques to evaluate the toxic levels of different As contaminants in our food products is the need of the hour. Furthermore, standard parameters and guidelines for As-containing foods should be developed and implemented.

Cortex metabolome and proteome analysis reveals chronic arsenic exposure via drinking water induces developmental neurotoxicity through hnRNP L mediated mitochondrial dysfunction in male rats

Lots of people are at the risk of arsenic-contaminated drinking water. Arsenic exposure was confirmed to be closely linked to neurocognitive deficits, particularly during childhood. The multi-omics approaches are known be well suitable for toxicological research. Thus, this study aimed to explore the molecular mechanisms of arsenic-induced learning and memory function impairments through the integrative proteome and metabolome analysis of cortex in rats. The weaned rats were exposed to arsenic-contaminated drinking water for six months to mimic the developmental exposure. 220 differential proteins and 19 differential metabolites were identified in the cortex, and nine potential biomarkers were found to be related to impaired Morris water maze (MWM) indicators. Chronic arsenic exposure affected the cognitive function by inducing the overproduction of amyloid-β (Aβ) peptides and the redox imbalance in the mitochondria. Glycolysis and tricarboxylic acid (TCA) cycle enhancement driven by the increased heterogeneous nuclear ribonucleoprotein L (hnRNP L) is a low-dose protective mechanism against arsenic-induced ATP deficiency and oxidative stress. Moreover, apoptosis is another important pathway of arsenic-induced neurotoxicity. This study provides new evidence about the alterations of proteins and metabolites in the cortex of the exposed rats under arsenic toxicity. These findings suggest hnRNP L could be a potential target for the treatment of arsenic-induced neurotoxicity.

Effects of carnosic acid on arsenic-induced liver injury in mice: A comparative transcriptomics analysis

BACKGROUND

Long-term chronic exposure to arsenic can cause different degrees of liver injury. Till date, its molecular mechanism has not meant fully elucidated. Evidence indicates that Carnosic acid (CA) has a protective role in arsenic-induced liver injury. This study aimed to reveal the potential targets and evaluate the potential effect of CA intervention at transcriptional level, and provide reference for the intervention of arsenic-induced liver injury.

METHODS

Arsenic-induced liver injury and CA intervention models were established in C57BL/6 mice. RNA sequencing technique was carried out to obtain the differentially expressed gene (DEG) profiles. The common covariant DEGs between arsenic induction and CA intervention was screened by comparative transcriptomic analysis methods. QRT-PCR was used to verify the covariant DEGs.

RESULTS

Transcriptome results showed that 220 DEGs were identified after arsenic induction. 267 DEGs were identified after CA intervention (|fold change| > 2.0 and adjusted P < 0.05). 42 covariant DEGs were discovered between the comparison of "AS vs Control" and "AS & CA vs AS". In addition, hub gene analysis revealed a total of 8 covariant DEGs (Ehhadh, Fgf21, Cyp2b10, Plin2, Aacs, Cyp7a1, Per2 and Mylip). The mRNA expressions of Fgf21 and Plin2 were significantly increased (P < 0.05) and the mRNA expressions of Cyp2b10, Cyp7a1, Per2 and Mylip were significantly decreased (P < 0.05) after arsenic induction. On the contrary, the changes of these DEGs were reversed after CA intervention.

CONCLUSION

The present study would be helpful to understand the potential health effects of arsenic-induced liver injury and identify new potential targets, and provide a reference for the intervention of CA.

Preclinical In Vitro Model to Assess the Changes in Permeability and Cytotoxicity of Polarized Intestinal Epithelial Cells during Exposure Mimicking Oral or Intravenous Routes: An Example of Arsenite Exposure

The gastrointestinal tract (GIT) is exposed to xenobiotics, including drugs, through both: local (oral) and systemic routes. Despite the advances in drug discovery and in vitro pre-clinical models, there is a lack of appropriate translational models to distinguish the impact of these routes of exposure. Changes in intestinal permeability has been observed in different gastrointestinal and systemic diseases. This study utilized one such xenobiotic, arsenic, to which more than 200 million people around the globe are exposed via their food, drinking water, work environment, soil, and air. The purpose of this study was to establish an in vitro model to mimic gastrointestinal tract exposure to xenobiotics via oral or intravenous routes. To achieve this, we compared the route (mimicking oral and intravenous exposure to GIT and the dose response (using threshold approach) of trivalent and pentavalent inorganic arsenic species on the permeability of in vitro cultured polarized T84 cells, an example of intestinal epithelial cells. Arsenic treatment to polarized T84 cells via the apical and basolateral compartment of the trans-well system reflected oral or intravenous routes of exposure in vivo, respectively. Sodium arsenite, sodium arsenate, dimethyl arsenic acid sodium salt (DMA^V), and disodium methyl arsonate hydrate (MMA^V) were assessed for their effects on intestinal permeability by measuring the change in trans-epithelial electrical resistance (TEER) of T-84 cells. Polarized T-84 cells exposed to 12.8 µM of sodium arsenite from the basolateral side showed a marked reduction in TEER. Cytotoxicity of sodium arsenite, as measured by release of lactate dehydrogenase (LDH), was increased when cells were exposed via the basolateral side. The mRNA expression of genes related to cell junctions in T-84 cells was analyzed after exposure with sodium arsenite for 72 h. Changes in TEER correlated with mRNA expression of focal-adhesion-, tight-junction- and gap-junction-related genes (upregulation of Jam2, Itgb3 and Notch4 genes and downregulation of Cldn2, Cldn3, Gjb1, and Gjb2). Overall, exposure to sodium arsenite from the basolateral side was found to have a differential effect on monolayer permeability and on cell-junction-related genes as compared to apical exposure. Most importantly, this study established a preclinical human-relevant in vitro translational model to assess the changes in permeability and cytotoxicity during exposure, mimicking oral or intravenous routes.

Removal of dimethylarsinic acid (DMA) in the Fe/C system: roles of Fe(II) release, DMA/Fe(II) and DMA/Fe(III) complexation

Methylated arsenic species are ubiquitous in the environment and resistant to removal by conventional treatment technologies. This study addressed this challenge based on the examination of the removal of dimethylarsinic acid (DMA) in a system that combines zerovalent iron (ZVI) and powdered activated carbon (PAC). The removal of DMA in the ZVI/PAC system was compared to that by coagulation, adsorption, electrochemical and Fenton oxidations, and other conventional methods. While only the electrochemical oxidation using a PbO2/Sb-SnO2/Ti anode allowed removing up to 60% DMA at several hours-long treatment times, the removal of DMA in the ZVI/PAC system containing 10 g/L ZVI and 2.5 g/L PAC with an initial pH of 2.0 was 95% for a 30 min reaction time. Specific roles of PAC, ZVI and its oxidation products in DMA removal were examined based on the spectroscopic data and quantum chemical modeling for the DMA/Fe(II) and DMA/Fe(III) systems. These methods demonstrated the formation of moderately strong DMA/Fe(II) and DMA/Fe(III) complexation. These results and relevant kinetic data were interpreted to indicate that the removal of DMA is governed by the rapid generation of Fe2+ ions released as a result of accelerated ZVI corrosion in the galvanic ZVI/PAC microcells and ensuing formation of DMA/ Fe2+ complexes that are readily adsorbed by PAC.

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.

Nephroprotective effect of magnesium isoglycyrrhizinate against arsenic trioxide‑induced acute kidney damage in mice

Magnesium isoglycyrrhizinate (MgIG) has anti-inflammatory, antioxidative, antiviral and anti-hepatotoxic effects. However, protective effects of MgIG against renal damage caused by arsenic trioxide (ATO) have not been reported. The present study aimed to clarify the protective function of MgIG on kidney damaged induced by ATO. Other than the control group and the group treated with MgIG alone, mice were injected intraperitoneally with ATO (5 mg/kg/day) for 7 days to establish a mouse model of kidney damage. On the 8th day, blood and kidney tissue were collected and the inflammatory factors and antioxidants levels in the kidney tissue and serum were measured. The expression of protein levels of caspase-3, Bcl-2, Bax, Toll-like receptor-4 (TLR4) and nuclear factor-κB (NF-κB) were determined via western blot analysis. In the renal tissue of mice, ATO exposure dramatically elevated markers of oxidative stress, apoptosis and inflammation. However, MgIG could also restore the activities of urea nitrogen and creatinine to normal levels, decrease the malondialdehyde level and reactive oxygen species formation and increase superoxide dismutase, catalase and glutathione activities. MgIG also ameliorated the morphological abnormalities generated by ATO, reduced inflammation and apoptosis and inhibited the TLR4/NF-κB signaling pathway. In conclusion, MgIG may mitigate ATO-induced kidney damage by decreasing apoptosis, oxidative stress and inflammation and its mechanism may be connected to the inhibition of TLR4/NF-κB signaling.

Arsenic-Related Health Risk Assessment of Realgar-Containing NiuHuangJieDu Tablets in Healthy Volunteers Po Administration

Realgar, an arsenic-containing traditional Chinese medicine of As₂S₂, has significant therapeutic effects for hundreds of years. NiuHuangJieDu tablets (NHJDT) is one of the most commonly prescribed realgar-containing preparations for the treatment of sore throat, swelling, and aching of gums. However, realgar-containing TCMs raise great safety concerns due to the adverse effects reported by arsenic poisoning. In this study, the arsenic-related health risk assessment of NHJDT was conducted in healthy volunteers after single and multiple doses oral administration. Blood, plasma, and urine samples were collected after dosing at predetermined time points or periods. Simple, rapid, and sensitive methods were established for the quantification of total arsenic and arsenic speciation in biological samples. The total arsenic and arsenic speciation were determined by hydride generation-atomic fluorescence spectrometry (HG-AFS) and high-performance liquid chromatography–hydride generation–atomic fluorescence spectrometry (HPLC-HG-AFS), respectively. No significant fluctuation of total arsenic was observed in human blood, and no traces of arsenic speciation were found in human plasma. Dimethylarsenic acid was detected as the predominated arsenic species in human urine after dosing. Therapeutic dose administration of NHJDT was relatively safe in single dose for the limited blood arsenic exposure, but long-term medication may still pose health risks due to the accumulation of arsenics in blood and its extremely slow excretion rate. Therefore, arsenic exposure should be carefully monitored during realgar-containing TCM medication, especially for long-term regimen. The results obtained in this study will provide scientific references for the clinical application of realgar and its-containing TCMs.

Is Arsenic Exposure a Risk Factor for Metabolic Syndrome? A Review of the Potential Mechanisms

Exposure to arsenic in drinking water is a worldwide health problem. This pollutant is associated with increased risk of developing chronic diseases, including metabolic diseases. Metabolic syndrome (MS) is a complex pathology that results from the interaction between environmental and genetic factors. This condition increases the risk of developing type 2 diabetes, cardiovascular diseases, and cancer. The MS includes at least three of the following signs, central obesity, impaired fasting glucose, insulin resistance, dyslipidemias, and hypertension. Here, we summarize the existing evidence of the multiple mechanisms triggered by arsenic to developing the cardinal signs of MS, showing that this pollutant could contribute to the multifactorial origin of this pathology.

The associations between urinary metals and metal mixtures and kidney function in Chinese community-dwelling older adults with diabetes mellitus

BACKGROUND

Previous studies have found associations between single toxic metals, such as arsenic and cadmium, and kidney function in adults with diabetes. However, studies with regards to other metals and metal mixtures are still limited.

OBJECTIVE

Our study aimed to investigate the associations between urinary concentrations of 5 selected metals and metal mixtures and kidney function using a sample of older adults with diabetes mellitus in Chinese communities.

METHODS

In a sample of older adults (n = 5186), 592 eligible subjects were included in this study. Urinary concentrations of 5 metals, i.e., arsenic (As), cadmium (Cd), vanadium (V), cobalt (Co), and thallium (Tl), were measured by inductively coupled plasma mass spectrometer (ICP-MS). Estimated glomerular filtration rate (eGFR) was calculated and dichotomized into indicator of chronic kidney disease (CKD). Logistic analysis and Bayesian kernel machine regression (BKMR) were used to explore the associations between single metals and metal mixtures and CKD, respectively.

RESULTS

Urinary levels of As and V were positively correlated with CKD (OR=2.37, 95% CI: 1.31-4.30 for As; OR=2.24, 95% CI: 1.25-4.03 for V), when compared the 4th quartile with the 1st quartile. After adjustment for potential confounders, the significant association between As and CKD still existed (OR=2.73, 95% CI: 1.23-6.07). BKMR analyses showed strong linear positive associations between As and V and CKD. Higher urinary levels of the mixture were significantly associated with higher odds of CKD in a dose-response pattern. As and V showed the highest posterior inclusion probabilities.

CONCLUSION

Urine As and V were positively associated with CKD in older adults with diabetes mellitus, separately and in a mixture. The metals mixture showed a linear dose-response association with the odds of CKD. The analyses of mixtures, rather than of single metals, may provide a real-world perspective on the relationship between metals and kidney function.

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.

Changes in metabolomics and lipidomics in brain tissue and their correlations with the gut microbiome after chronic food-derived arsenic exposure in mice

Arsenic can cause neurodegenerative diseases of the brain, but the definite mechanism is still unknown. In this study, to discuss the disturbances on brain metabolome and lipidome under subchronic arsenic exposure, we treated mice with the arsenic-containing feed (concentration of total arsenic = 30 mg/kg) prepared in accordance with the proportion of rice arsenicals for 16 weeks and performed metabolomics and lipidomics studies respectively using UHPLC-Triple-TOF-MS/MS and UHPLC-Q Exactive Focus MS/MS on mice brain. In addition, the distributions of arsenical metabolites along the feed-gut-blood-brain chain were analyzed by ICP-MS and HPLC-ICP-MS, and fecal microbial variations were investigated by 16 s sequencing. The data showed that although only a tiny amount of arsenic (DMA=0.101 mg/kg, uAs=0.071 mg/kg) enters the brain through the blood-brain barrier, there were significant changes in brain metabolism, including 118 metabolites and 17 lipids. These different metabolites were involved in 30 distinct pathways, including glycometabolism, and metabolisms of lipid, nucleic acid, and amino acid were previously reported to be correlated with neurodegenerative diseases. Additionally, these different metabolites were significantly correlated with 12 gut bacterial OTUs, among which Lachnospiraceae, Muribaculaceae, Ruminococcaceae, and Erysipelotrichaceae were also previously reported to be related to the distortion of metabolism, indicating that the disturbance of metabolism in the brain may be associated with the disturbance of gut microbes induced by arsenic. Thus, the current study demonstrated that the brain metabolome and lipidome were significantly disturbed under subchronic arsenic exposure, and the disturbances also significantly correlated with some gut microbiome and may be associated with neurodegenerative diseases. Although preliminary, the results shed some light on the pathophysiology of arsenic-caused neurodegenerative diseases.

Arsenic exposure and metabolism in relation to blood pressure changes in pregnant women

Arsenic is concerned with cardiovascular diseases including hypertension, atherosclerosis, and endothelial dysfunction. However, what effects the arsenic exposure and the arsenic metabolism have on hypertensive disorders of pregnancy (HDP) and blood pressure changes during pregnancy remain largely unknown. Our goal was to assess the associations of arsenic exposure and arsenic metabolism with HDP and blood pressure changes in pregnant women through a prospective birth cohort study. A total of 1038 women who were pregnant (52 HDP, 986 non-HDP participants) were included. Arsenic species of spot urine samples collected at three trimesters were measured, which included inorganic arsenic (iAs), monomethylated arsenic (MMA), and dimethylated arsenic (DMA). Arsenic metabolism was evaluated as the percentages of iAs, MMA, and DMA respectively (i.e., iAs%, MMA%, and DMA%). Outcomes were HDP and systolic, diastolic, and mean arterial pressure changes during pregnancy. We employed mixed linear models to investigate the relationships between arsenic exposure and arsenic metabolism with changes in blood pressure during pregnancy. Poisson regression with a robust error variance with generalized estimating equations (GEE) estimation was used so that the associations of arsenic exposure and arsenic metabolism with HDP could be estimated. In this study, there was a significant relationship between the concentrations of urinary DMA and the weekly change in systolic blood pressure (SBP) (β = -0.10; 95% CI: -0.15, -0.05), diastolic blood pressure (DBP) (β = -0.07; 95% CI: -0.11, -0.02) and mean arterial pressure (MAP) (β = -0.08; 95% CI: -0.12, -0.04). Higher DMA% was accompanied with lesser weekly increase in SBP (β = -0.05; 95% CI: -0.10, 0.00), DBP (β = -0.06; 95% CI: -0.10, -0.01) and MAP (β = -0.06; 95% CI: -0.09, -0.01) during pregnancy. There was a positive association with the highest tertile of iAs% and weekly change of SBP (β = 0.08; 95% CI: 0.03, 0.13), DBP (β = 0.07; 95% CI: 0.03, 0.11) and MAP (β = 0.07; 95% CI: 0.03, 0.11). No association was found between each arsenic specie and arsenic metabolism marker in the first trimester and risk of HDP. Arsenic exposure and arsenic metabolism during pregnancy potentially change blood pressure of pregnant women. These findings may be significance as even modest elevation of blood pressure can increase the risk of cardiovascular disease.

Arsenic Secondary Methylation Capacity Is Inversely Associated with Arsenic Exposure-Related Muscle Mass Reduction

Skeletal muscle mass reduction has been implicated in insulin resistance (IR) that promotes cardiometabolic diseases. We have previously reported that arsenic exposure increases IR concomitantly with the reduction of skeletal muscle mass among individuals exposed to arsenic. The arsenic methylation capacity is linked to the susceptibility to some arsenic exposure-related diseases. However, it remains unknown whether the arsenic methylation capacity affects the arsenic-induced reduction of muscle mass and elevation of IR. Therefore, this study examined the associations between the arsenic methylation status and skeletal muscle mass measures with regard to IR by recruiting 437 participants from low- and high-arsenic exposure areas in Bangladesh. The subjects' skeletal muscle mass was estimated by their lean body mass (LBM) and serum creatinine levels. Subjects' drinking water arsenic concentrations were positively associated with total urinary arsenic concentrations and the percentages of MMA, as well as inversely associated with the percentages of DMA and the secondary methylation index (SMI). Subjects' LBM and serum creatinine levels were positively associated with the percentage of DMA and SMI, as well as inversely associated with the percentage of MMA. HOMA-IR showed an inverse association with SMI, with a confounding effect of sex. Our results suggest that reduced secondary methylation capacity is involved in the arsenic-induced skeletal muscle loss that may be implicated in arsenic-induced IR and cardiometabolic diseases.

Arsenic: A Global Environmental Challenge

Arsenic is a naturally occurring metalloid and one of the few metals that can be metabolized inside the human body. The pervasive presence of arsenic in nature and anthropogenic sources from agricultural and medical use have perpetuated human exposure to this toxic and carcinogenic element. Highly exposed individuals are susceptible to various illnesses, including skin disorders; cognitive impairment; and cancers of the lung, liver, and kidneys. In fact, across the globe, approximately 200 million people are exposed to potentially toxic levels of arsenic, which has prompted substantial research and mitigation efforts to combat this extensive public health issue. This review provides an up-to-date look at arsenic-related challenges facing the global community, including current sources of arsenic, global disease burden, arsenic resistance, and shortcomings of ongoing mitigation measures, and discusses potential next steps.

Tobacco smoking induces metabolic reprogramming of renal cell carcinoma

BACKGROUNDClear cell renal cell carcinoma (ccRCC) is the most common histologically defined renal cancer. However, it is not a uniform disease and includes several genetic subtypes with different prognoses. ccRCC is also characterized by distinctive metabolic reprogramming. Tobacco smoking (TS) is an established risk factor for ccRCC, with unknown effects on tumor pathobiology.METHODSWe investigated the landscape of ccRCCs and paired normal kidney tissues using integrated transcriptomic, metabolomic, and metallomic approaches in a cohort of white males who were long-term current smokers (LTS) or were never smokers (NS).RESULTSAll 3 Omics domains consistently identified a distinct metabolic subtype of ccRCCs in LTS, characterized by activation of oxidative phosphorylation (OXPHOS) coupled with reprogramming of the malate-aspartate shuttle and metabolism of aspartate, glutamate, glutamine, and histidine. Cadmium, copper, and inorganic arsenic accumulated in LTS tumors, showing redistribution among intracellular pools, including relocation of copper into the cytochrome c oxidase complex. A gene expression signature based on the LTS metabolic subtype provided prognostic stratification of The Cancer Genome Atlas ccRCC tumors that was independent of genomic alterations.CONCLUSIONThe work identified the TS-related metabolic subtype of ccRCC with vulnerabilities that can be exploited for precision medicine approaches targeting metabolic pathways. The results provided rationale for the development of metabolic biomarkers with diagnostic and prognostic applications using evaluation of OXPHOS status. The metallomic analysis revealed the role of disrupted metal homeostasis in ccRCC, highlighting the importance of studying effects of metals from e-cigarettes and environmental exposures.FUNDINGDepartment of Defense, Veteran Administration, NIH, ACS, and University of Cincinnati Cancer Institute.

Early Low-Level Arsenic Exposure Impacts Post-Synaptic Hippocampal Function in Juvenile Mice

Arsenic is a well-established carcinogen known to increase mortality, but its effects on the central nervous system are less well understood. Epidemiological studies suggest that early life exposure is associated with learning deficits and behavioral changes. Studies in arsenic-exposed rodents have begun to shed light on potential mechanistic underpinnings, including changes in synaptic transmission and plasticity. However, previous studies relied on extended exposure into adulthood, and little is known about the effect of arsenic exposure in early development. Here, we studied the effects of early developmental arsenic exposure in juvenile mice on synaptic transmission and plasticity in the hippocampus. C57BL/6J females were exposed to arsenic (0, 50 ppb, 36 ppm) via drinking water two weeks prior to mating, with continued exposure throughout gestation and parturition. Electrophysiological recordings were then performed on juvenile offspring prior to weaning. In this paradigm, the offspring are exposed to arsenic indirectly, via the mother. We found that high (36 ppm) and relatively low (50 ppb) arsenic exposure both decreased basal synaptic transmission. A compensatory increase in pre-synaptic vesicular release was only observed in the high-exposure group. These results suggest that indirect, ecologically relevant arsenic exposure in early development impacts hippocampal synaptic transmission and plasticity that could underlie learning deficits reported in epidemiological studies.

Arsenic: Various species with different effects on cytochrome P450 regulation in humans

Arsenic is well-recognized as one of the most hazardous elements which is characterized by its omnipresence throughout the environment in various chemical forms. From the simple inorganic arsenite (iAsIII) and arsenate (iAsV) molecules, a multitude of more complex organic species are biologically produced through a process of metabolic transformation with biomethylation being the core of this process. Because of their differential toxicity, speciation of arsenic-based compounds is necessary for assessing health risks posed by exposure to individual species or co-exposure to several species. In this regard, exposure assessment is another pivotal factor that includes identification of the potential sources as well as routes of exposure. Identification of arsenic impact on different physiological organ systems, through understanding its behavior in the human body that leads to homeostatic derangements, is the key for developing strategies to mitigate its toxicity. Metabolic machinery is one of the sophisticated body systems targeted by arsenic. The prominent role of cytochrome P450 enzymes (CYPs) in the metabolism of both endobiotics and xenobiotics necessitates paying a great deal of attention to the possible effects of arsenic compounds on this superfamily of enzymes. Here we highlight the toxicologically relevant arsenic species with a detailed description of the different environmental sources as well as the possible routes of human exposure to these species. We also summarize the reported findings of experimental investigations evaluating the influence of various arsenicals on different members of CYP superfamily using human-based models.

Analyzing liver protein-bound DMAV by using size exclusion and ion exchange HPLC combined with ICP-MS and MRM mode in rats exposed to AS4S4

Long-term exposure to high levels of arsenic (As) will result in damage to organs. Compared with free arsenic, protein-bound arsenic are more difficult to be excreted from the bodies due to their complexation with biological macromolecules. We developed a method of size exclusion chromatography (SEC) and ion exchange chromatography (IEC) combined with inductively coupled plasma-mass spectrometry (ICP-MS) and multiple reaction monitoring (MRM) mode, which was used to determine bound-arsenic species. DMA^V was identified as bound arsenic species in rat livers after As4S4 overexposure. Subsequent proteomics analysis showed the potential binding partners included hemoglobin, glutathione S-transferases, superoxide dismutase [Cu-Zn] & [Mn], thiosulfate sulfurtransferase, and metallothionein-2. The method developed here was sensitive, repeatable, and conducive to arsenic analysis, especially for toxicity evaluation of arsenic-containing substances in vivo.

Evaluation of arsenic species in leukocytes and granulocytes of acute promyelocytic leukemia patients treated with arsenic trioxide

Concentrations of arsenic metabolites were important to clarify the sensitivity and resistance of APL (acute promyelocytic leukemia) patients to arsenic trioxide (As₂O₃). Our purpose was to evaluate levels and distributions of arsenic species in leukocytes and granulocytes of APL patients. Inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured by high performance liquid chromatography coupled inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Leukocytes were collected from 21 patients treated with As₂O₃ during induction, consolidation, and drug-withdrawal period. The upregulation of granulocytes in induction period was closely related to the differentiation of promyelocytes. Therefore, granulocytes were collected during induction period from 4 APL patients and purified by flow cytometry sorting using a panel of monoclonal antibodies specific for CD45, CD3, CD14, and CD19. The developed HPLC-ICP-MS method was precise and accurate with the limit of quantification of 0.5 ng/mL. During induction, consolidation, and drug-withdrawal period, the general trend of arsenic species was iAs > MMA > DMA (P < 0.05) in leukocytes. iAs was predominant arsenic species with median concentration of 10.84 (6.03-14.62) ng/mL. MMA was major methylated metabolite with median concentration of 0.94 (0.60-2.50) ng/mL. Moreover, arsenicals were detected in leukocytes during drug-withdrawal. In granulocytes, iAs was found during induction period with median concentration of 1.08 ng/mL, while MMA and DMA were not detected. These results showed that iAs was the primary arsenic species in leukocytes and granulocytes from APL patients treated with As₂O₃. This study suggested that iAs might play a dominant therapeutic role during the whole treatment process of APL.

The gut microbiome and arsenic-induced disease-iAs metabolism in mice

PURPOSE OF REVIEW

This review summarizes inorganic arsenic (iAs) metabolism and toxicity in mice and the gut microbiome and how iAs and the gut microbiome interact to induce diseases.

RECENT FINDINGS

Recently, a variety of studies have started to reveal the interactions between iAs and the gut microbiome. Evidence shows that gut bacteria can influence iAs biotransformation and disease risks. The gut microbiome can directly metabolize iAs, and it can also indirectly be involved in iAs metabolism through the host, such as altering iAs absorption, cofactors, and genes related to iAs metabolism. Many factors, such as iAs metabolism influenced by the gut microbiome, and microbiome metabolites perturbed by iAs can lead to different disease risks. iAs is a widespread toxic metalloid in environment, and iAs toxicity has become a global health issue. iAs is subject to metabolic reactions after entering the host body, including methylation, demethylation, oxidation, reduction, and thiolation. Different arsenic species, including trivalent and pentavalent forms and inorganic and organic forms, determine their toxicity. iAs poisoning is predominately caused by contaminated drinking water and food, and chronic arsenic toxicity can cause various diseases. Therefore, studies of iAs metabolism are important for understanding iAs associated disease risks.