Arsenic speciation transported through the placenta from mother mice to their newborn pups

Recent developments in speciation and determination of arsenic in marine organisms using different analytical techniques. A review

Marine organisms play a vital role as the main providers of essential and functional food. Yet they also constitute the primary pathway through which humans are exposed to total arsenic (As) in their diets. Since it is well known that the toxicity of this metalloid ultimately depends on its chemical forms, speciation in As is an important issue. Most relevant articles about arsenic speciation have been investigated. This extended not only from general knowledge about As but also the toxicity and health related issues resulting from exposure to these As species from the food ecosystem. There can be enormous side effects originating from exposure to As species that must be measured quantitatively. Therefore, various convenient approaches have been developed to identify different species of As in marine samples. Different extraction strategies have been utilized based on the As species of interest including water, methanol and mixtures of both, and many other extraction agents have been explained in this article. Furthermore, details of hyphenated techniques which are available for detecting these As species have been documented, especially the most versatile and applied technique including inductively coupled plasma mass spectrometry.

Prenatal influences on postnatal neuroplasticity: Integrating DOHaD and sensitive/critical period frameworks to understand biological embedding in early development

Early environments can have significant and lasting effects on brain, body, and behavior across the lifecourse. Here, we address current research efforts to understand how experiences impact neurodevelopment with a new perspective integrating two well-known conceptual frameworks - the Developmental Origins of Health and Disease (DOHaD) and sensitive/critical period frameworks. Specifically, we consider how prenatal experiences characterized in the DOHaD model impact two key neurobiological mechanisms of sensitive/critical periods for adapting to and learning from the postnatal environment. We draw from both animal and human research to summarize the current state of knowledge on how particular prenatal substance exposures (psychoactive substances and heavy metals) and nutritional profiles (protein-energy malnutrition and iron deficiency) each differentially impact brain circuits' excitation/GABAergic inhibition balance and myelination. Finally, we highlight new research directions that emerge from this integrated framework, including testing how prenatal environments alter sensitive/critical period timing and learning and identifying potential promotional/buffering prenatal exposures to impact postnatal sensitive/critical periods. We hope this integrative framework considering prenatal influences on postnatal neuroplasticity will stimulate new research to understand how early environments have lasting consequences on our brains, behavior, and health.

Evidence of reduced gestational age in response to in utero arsenic exposure and implications for aging trajectories of the newborn

Arsenic exposure is associated with a plethora of age-related health outcomes of disparate etiology. However, evidence of the impact of arsenic on aging remains limited. Here, we investigated the utility of epigenetic clocks in two different populations and the impact of maternal arsenic exposure during pregnancy on epigenetic gestational age at birth. To do this, we examined publicly available DNA methylation data and estimated gestational age across five gestational clocks in two unrelated human populations. These populations also differ in the extent of arsenic exposure and the targeted tissue of analysis (cord blood and placental tissue). Our results indicate that same-tissue clocks produce gestational age estimates that are more highly correlated with clinical gestational age. Interestingly, our results also indicate that arsenic exposure is associated with gestational age, with higher arsenic exposures associated with decreased gestational age. We also applied two pediatric clocks to evaluate infant biological age in the same samples. The data is suggestive of higher pediatric age in infants exposed to higher arsenic levels during gestation. Taken altogether, our findings are consistent with past work indicating that that in utero arsenic exposure is associated with decreased gestational maturity as characterized by infant outcomes such as low birthweight and lung underdevelopment and dysfunction in arsenic exposed infants. The findings are also consistent with arsenic exposure setting infants on a trajectory of accelerated epigenetic aging that starts at birth.

AsHC 360 Exposure Influence on Epileptiform Discharges in Hippocampus of Infantile Male Rats In Vitro

Arsenic-containing hydrocarbons (AsHCs) are typical arsenolipids found in various marine organisms. They can penetrate the blood-brain barrier, specifically affecting synaptic plasticity and the learning and memory ability of hippocampal neurons. Temporal lobe epilepsy often occurs in the hippocampus. Thus, the possible influence of AsHCs exposure to temporal lobe epilepsy garnered attention. The present study investigated the effects of epileptiform discharges (EDs) signals introduced by low-magnesium ACSF in the hippocampus of infantile male rats in vitro, using electrophysiological techniques with multi-electrode arrays under AsHC 360 exposure. In our study of the effects of AsHC 360 on EDs signals, we found that inter-ictal discharges (IIDs) were not significantly impacted. When AsHC 360 was removed, any minor effects observed were reversed. However, when we examined the impact of AsHC 360 on ictal discharges (IDs), distinct patterns emerged based on the concentration levels. For low-concentration groups (5, 20, 60 μg As L-1), both the frequency and duration effects on IDs returned to normal post-elimination of AsHC 360. However, this recovery was not evident for concentrations of 100 μg As L-1 or higher. IDs were only observed in EDs signals during exposures to AsHC 360 concentrations up to 60 μg As L-1. In these conditions, ID frequencies significantly enhanced with the increased of AsHC 360 concentration. At high concentrations of AsHC 360 (≥100 μg As L-1), the transition from IIDs or pre-ictal discharges (PIDs) to IDs was notably inhibited. Additional study on co-exposure of AsHC 360 (100 μg As L-1) and agonist (10 nM (S)-(-)-Bay-K-8644) indicated that the regulation of EDs signals under AsHC 360 exposure could be due to directly interference with the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR) expression which influences the binding of excitatory glutamate neurotransmitter to AMPAR. The results suggest that EDs activities in the hippocampus of infantile Sprague Dawley rats are concentration-dependent on AsHC 360 exposure. Thus, it provides a basis for the seafood intake with AsHCs for epileptic patients and those with potential seizures.

Genetic Susceptibility to Neurotoxicity Related to Prenatal Inorganic Arsenic Exposure in Young Spanish Children

We explored the influence of child and maternal single nucleotide polymorphisms (SNPs) in genes related to neurological function and arsenic metabolism (i.e., ABCA1, ABCB1, PON1, CYP3A, BDNF, GSTP1, MT2A, and APOE as well as AS3MT) on the association between prenatal arsenic (As) exposure and methylation efficiency and neuropsychological development in 4-5-year-old children. Participants were 549 mother-child pairs from the INMA (Environment and Childhood) Spanish Project. We measured inorganic arsenic (iAs) and the metabolites monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine samples collected during pregnancy. Neuropsychological development was assessed at the age of 4-5 years using the McCarthy Scales of Children's Abilities (MSCA). Several SNPs were determined in maternal and child DNA; AS3MT and APOE haplotypes were inferred. The median ∑As (sum of iAs, DMA, and MMA) was 7.08 μg/g creatinine. Statistically significant interactions for children's APOE haplotype were observed. Specifically, ε4-carrier children had consistently lower MSCA scores in several scales with increasing ∑As and MMA concentrations. These results provide evidence regarding the neurotoxic effects of early life exposure to As, observing that the APOE ε4 allele could make children more vulnerable to this exposure.

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

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

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.

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

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

Prenatal arsenic exposure induces immunometabolic alteration and renal injury in rats

Arsenic (As) exposure is progressively associated with chronic kidney disease (CKD), a leading public health concern present worldwide. The adverse effect of As exposure on the kidneys of people living in As endemic areas have not been extensively studied. Furthermore, the impact of only prenatal exposure to As on the progression of CKD also has not been fully characterized. In the present study, we examined the effect of prenatal exposure to low doses of As 0.04 and 0.4 mg/kg body weight (0.04 and 0.4 ppm, respectively) on the progression of CKD in male offspring using a Wistar rat model. Interestingly, only prenatal As exposure was sufficient to elevate the expression of profibrotic (TGF-β1) and proinflammatory (IL-1α, MIP-2α, RANTES, and TNF-α) cytokines at 2-day, 12- and 38-week time points in the exposed progeny. Further, alteration in adipogenic factors (ghrelin, leptin, and glucagon) was also observed in 12- and 38-week old male offspring prenatally exposed to As. An altered level of these factors coincides with impaired glucose metabolism and homeostasis accompanied by progressive kidney damage. We observed a significant increase in the deposition of extracellular matrix components and glomerular and tubular damage in the kidneys of 38-week-old male offspring prenatally exposed to As. Furthermore, the overexpression of TGF-β1 in kidneys corresponds with hypermethylation of the TGF-β1 gene-body, indicating a possible involvement of prenatal As exposure-driven epigenetic modulations of TGF-β1 expression. Our study provides evidence that prenatal As exposure to males can adversely affect the immunometabolism of offspring which can promote kidney damage later in life.

Salix subserrata Bark Extract-Loaded Chitosan Nanoparticles Attenuate Neurotoxicity Induced by Sodium Arsenate in Rats in Relation with HPLC-PDA-ESI-MS/MS Profile

Pollution is a worldwide environmental risk. Arsenic (As) is an environmental pollutant with a major health concern due to its toxic effects on multiple body organs, including the brain. Humans are exposed to As through eating contaminated food and water or via skin contact. Salix species (willow) are plants with medicinal efficacy. Salix subserrata Willd bark extract-loaded chitosan nanoparticles (SBE.CNPs) was formulated, characterized, and evaluated against As-induced neurotoxicity. The stem bark was selected for nanoparticle formulation based on HPLC-PDA-ESI-MS/MS profiling and in vitro antioxidant assessment using free radical scavenging activity. SBE.CNPs demonstrated an average un-hydrated diameter of 193.4 ± 24.5 nm and zeta potential of + 39.6 ± 0.4 mV with an encapsulation efficiency of 83.7 ± 4.3%. Compared to As-intoxicated rats, SBE.CNP-treated rats exhibited anxiolytic activity and memory-boosting as evidenced in open field test, light-dark activity box, and Y-maze. Also, it increased the antioxidant biomarkers, including superoxide dismutase and glutathione peroxidase associated with reducing the malondialdehyde levels and apoptotic activity. Besides this, SBE.CNPs maintained the brain architecture and downregulated both nuclear factor-kappa B and heme oxygenase-1 expression. These results suggest that SBE.CNP administration showed promising potent neuroprotective and antioxidative efficiencies against arsenic-induced oxidative threats.

Determination of toxic metal burden and related risk factors in pregnant women: a biological monitoring in Sabzevar, Iran

Nowadays, the adverse effect of toxic metals on humans is well known, especially in the fetal period such as preventing cognitive development and congenital abnormalities of the central nervous system. Hence, this study aims to evaluate the toxic metal burden in mothers and newborns in Sabzevar. Obtained data can be useful for authorities in public health issues. To determine heavy metals in placental blood and umbilical cord blood, one hundred eighty blood samples were taken from ninety mothers referred to Shahidan Mobini Hospital for delivery. The amount of metals in samples was analyzed using inductively coupled plasma optical emission spectrometry (ICP OES). The results of this study revealed that 21.52%, 26.19%, and 60.71% of maternal blood samples (placental blood) and 16.47%, 56.47%, and 20% of umbilical cord blood samples were higher than the US center for disease control (CDC) recommended levels for Pb, Cd, and As respectively. According to the multiple linear regression analysis, the Pb (p = 0.054), As (p < 0.001), and Se (p < 0.001) levels had an association with the mother's living area. Also, there was a significant association between Se (0.021) and the age of the mother. However, the Se values in its optimum concentrations in the blood (60-140 μg/L) can decrease the adverse effects of toxic metals, 72.5% of the pregnant women had Se values below the 60 μg/L and only 6% of pregnant women had Se levels higher than 140 μg/L. We concluded that the mothers inhabiting the rural areas need more Se sources in their diets.

Alzheimer's Disease Association with Metals and Metalloids Concentration in Blood and Urine

As there is some evidence that the risk for Alzheimer’s disease (AD) is partially attributable to environmental exposure to some metals and metalloids, we examined an association between AD and arsenic, chromium, and selenium in 53 AD patients and 217 controls. Urinary arsenic, blood chromium, and selenium were determined by inductively coupled plasma mass spectrometry. Logistic regression models calculating odds ratios (ORs) and 95% confidence intervals (CI) were used to estimate AD association with arsenic, chromium, and selenium. In AD patients, urinary arsenic and blood chromium were significantly higher, while blood selenium was significantly lower compared to controls. Increased blood selenium was related to a significant decrease in the odds of AD after adjustment for risk factors. Blood selenium per 1 kg × 10⁻⁹/m³ × 10⁻⁴ increment was associated with 1.4 times lower risk of AD (OR = 0.71; 95% CI 0.58–0.87). A significant increase in the odds of AD associated with increased blood chromium was also seen in the adjusted model: the OR per 1 kg × 10⁻⁹/m³ × 10⁻³ chromium increment was 2.39 (95% CI 1.32–4.31). The association of urinary arsenic with the risk of AD was not significant. The data obtained provide evidence that selenium reduces the risk of Alzheimer’s disease, while chromium increases it.

Associations among prenatal and postnatal arsenic, lead, and cadmium exposures and motor development in 3-year-old children: a longitudinal birth cohort study in Taiwan

Prenatal and postnatal exposures to heavy metals have been suggested to interfere with neurodevelopment, but the neurotoxicity of lead (Pb), arsenic (As), and cadmium (Cd) is still unclear. In this study, we aimed to assess the associations between the levels of As, Cd, and Pb and children's neurodevelopment. A total of 299 mother-infant pairs were recruited in this study and their meconium were collected. After three years, 53 children underwent the Bayley Scales of Infant and Toddler Development (Bayley-III) examinations and provided hair and fingernail specimens. The levels of As, Cd, and Pb in the meconium, hair, and fingernail were measured by inductively coupled plasma mass spectrometry; the median levels were the following: meconium, 42.7, 5.57, and 25.6 ng/g, respectively; hair, 0.19, 0.05, and 3.61 μg/g, respectively; and fingernail, 0.29, 0.04, and 0.84 μg/g, respectively. After adjusting for potential confounding factors, we found that the log-transformed levels of As in the hair samples was negatively associated with gross motor development (β =  - 0.032; 95% confidence interval: - 0.061 to - 0.004). We conclude that postnatal exposure to As is a crucial period for gross motor development in children, while the effects of Cd and Pb on neurodevelopment are less clear.

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.

Arsenic exposure via drinking water during pregnancy and lactation induces autism-like behaviors in male offspring mice

Exposure to arsenic (As), an environmental toxicant, causes damages to the central nervous system (CNS) structure and function. Emerging epidemiological studies support that exposure to As, especially during the critical periods of the CNS development, may act as an environmental risk factor of autism spectrum disorders (ASD), which is characterized by behavioral changes, including abnormal social behaviors, restricted interests and repetitive behaviors. However, direct evidence supporting the cause-effect relationship between As exposure and the risk of ASD is still missing. Thus, we aimed to investigate whether As exposure during pregnancy and lactation led to autism-like behaviors in offspring mice in the present study. We established a mice model of exposure to As via drinking water during pregnancy and lactation and conducted a battery of behavioral tests to evaluate social behaviors, repetitive behaviors, anxiety behaviors and learning and memory ability in offspring mice. We found that perinatal exposure to As caused autism-like behaviors in male offspring, which demonstrated by abnormal social behaviors and repetitive behaviors. Anxiety-like behaviors, and learning and memory impairments, known as concomitant behavioral phenotypes in mice with autism-like behaviors, were also observed. Decreases of synaptic density, especially in cortex, hippocampus and cerebellum, are extensively observed in both ASD patients and animal models of ASD. Thus, immunofluorescence staining and western blotting were used to observe the expression of PSD-95 and SYP, well-known markers for presynaptic and postsynaptic membranes, to assess the synaptic density in offspring cortex, hippocampus and cerebellum. We found perinatal exposure to As decreased the expression of PSD-95 and SYP in these brain regions. This indicated that perinatal exposure to As caused decreases of synaptic density, a typical autism-like cellular alteration in brains, which may contribute to autism-like behaviors in offspring.

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.

The neuroprotective effect of curcumin against ATO triggered neurotoxicity through Nrf2 and NF-κB signaling pathway in the brain of ducks

Arsenic trioxide (ATO) has confirmed as a global pollutant, the toxic effect of which was not fully understood and lack effective therapies to against its associated toxicities. Curcumin (Cur) is a beneficial natural pigment for its antioxidant and anti-inflammatory properties. The purpose of this paper was to illustrate the antagonism of Cur against ATO-induced neurotoxicity. A total of 40 ducks were divided randomly into 4 groups and conducted via bite and sup for 28 days: control group (Control); 2 mg/kg ATO group (Low ATO); 4 mg/kg ATO group (Middle ATO); 8 mg/kg ATO group (High ATO); 400 mg/kg Cur group + 8 mg/kg ATO (Cur+ATO). The results showed that ATO exposure can hinder the duck growth and arsenic element accumulation rate increased in a dose-dependent manner. We observed neuronal shrinkage and vacuolize of HE staining in the ATO-treated group. In addition, SOD activity and T-AOC level reduced while MDA content increased in the ATO-exposed group. ATO exposure can decrease the expression of anti-oxidation related mRNA and proteins (Nrf2, SOD-1, GPX-1, CAT, Trx and HO-1) and anti-inflammatory makers (IL-4, IL-10), increased the expression of Keap1, NF-κB and pro-inflammatory makers (TNF-α, IL-1β, IL-18, IL-2, IL-6, INOS and COX-2). ATO treated might cause blood-brain barrier (BBB) damage through degradation of the tight junction proteins (TJs) occludin and ZO-1. Importantly, the experimental results also showed that Cur can alleviate oxidative stress, inflammatory response and BBB injury caused by ATO exposure through Nrf2 and NF-κB signaling pathway. The results suggested Cur exerted as a food additive and provided novel potential benefits of ATO toxicology in inflammation of the brain.

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.

Transgenerational effects in DNA methylation, genotoxicity and reproductive phenotype by chronic arsenic exposure

An emerging concern is the influences of early life exposure to environmental toxicants on offspring characteristics in later life. Since recent evidence suggests a transgenerational transference of aberrant phenotypes from exposed-parents to non-exposed offspring related to adult-onset diseases including reproductive phenotype. The transgenerational potential of arsenic a well know genotoxic and epigenetic modifier agent has not been assessed in mammals until now. In this experimental study, we evaluated the transgenerational effects of arsenic in a rat model with chronic exposure to arsenic. Rats chronically exposed to arsenic in drinking water (1 mg As₂O₃/mL) (F0) were mated to produce the arsenic lineage (F1, F2, and F3). The arsenic toxic effects on were evaluated over the four generations by analyzing the DNA methylation percentage, genotoxicity in WBC and physical and reproductive parameters, including sperm quality parameters and histopathological evaluation of the gonads. Chronic exposure to arsenic caused genotoxic damage (F0-F3) different methylation patterns, alterations in physical and reproductive parameters, aberrant morphology in the ovaries (F0 and F1) and testicles (F1-F3), and a decrease in the quality of sperm (F0-F3, except F2). Parental chronic arsenic exposure causes transgenerational genotoxicity and changes in global DNA methylation which might be associated with reproductive defects in rats. Combined with recent studies reveal that disturbances in the early life of an individual can affect the health of later generations.

Effects of maternal exposure to arsenic on social behavior and related gene expression in F2 male mice

Background

Arsenic is a developmental neurotoxicant. It means that its neurotoxic effect could occur in offspring by maternal arsenic exposure. Our previous study showed that developmental arsenic exposure impaired social behavior and serotonergic system in C3H adult male mice. These effects might affect the next generation with no direct exposure to arsenic. This study aimed to detect the social behavior and related gene expression changes in F2 male mice born to gestationally arsenite-exposed F1 mice.

Methods

Pregnant C3H/HeN mice (F0) were given free access to tap water (control mice) or tap water containing 85 ppm sodium arsenite from days 8 to 18 of gestation. Arsenite was not given to F1 or F2 mice. The F2 mice were generated by mating among control F1 males and females, and arsenite-F1 males and females at the age of 10 weeks. At 41 weeks and 74 weeks of age respectively, F2 males were used for the assessment of social behavior by a three-chamber social behavior apparatus. Histological features of the prefrontal cortex were studied by ordinary light microscope. Social behavior-related gene expressions were determined in the prefrontal cortex by real time RT-PCR method.

Results

The arsenite-F2 male mice showed significantly poor sociability and social novelty preference in both 41-week-old group and 74-week-old group. There was no significant histological difference between the control mice and the arsenite-F2 mice. Regarding gene expression, serotonin receptor 5B (5-HT 5B) mRNA expression was significantly decreased (p < 0.05) in the arsenite-F2 male mice compared to the control F2 male mice in both groups. Brain-derived neurotrophic factor (BDNF) and dopamine receptor D1a (Drd1a) gene expressions were significantly decreased (p < 0.05) only in the arsenite-F2 male mice of the 74-week-old group. Heme oxygenase-1 (HO-1) gene expression was significantly increased (p < 0.001) in the arsenite-F2 male mice of both groups, but plasma 8-hydroxy-2′-deoxyguanosine (8-OHdG) and cyclooxygenase-2 (COX-2) gene expression were not significantly different. Interleukin-1β (IL-1β) mRNA expression was significantly increased only in 41-week-old arsenite-F2 mice.

Conclusions

These findings suggest that maternal arsenic exposure affects social behavior in F2 male mice via serotonergic system in the prefrontal cortex. In this study, COX-2 were not increased although oxidative stress marker (HO-1) was increased significantly in arsnite-F2 male mice.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparative efficacy of Nano and Bulk Monoisoamyl DMSA against arsenic-induced neurotoxicity in rats

Chelation therapy is considered as a safe and effective strategy to combat metal poisoning. Arsenic is known to cause neurological dysfunctions such as impaired memory, encephalopathy, and peripheral neuropathy as it easily crosses the blood-brain barrier. Oxidative stress is one of the mechanisms suggested for arsenic-induced neurotoxicity. We prepared Solid Lipid nanoparticles loaded with Monoisoamyl 2, 3-dimercaptosuccinic acid (Nano-MiADMSA), and compared their efficacy with bulk MiADMSA for treating arsenic-induced neurological and other biochemical effects. Solid lipid nanoparticles entrapping MiADMSA were synthesized and particle characterization was carried out by transmission electron microscopy (TEM) and dynamic light scattering (DLS). An in vivo study was planned to investigate the therapeutic efficacy of MiADMSA-encapsulated solid lipid nanoparticles (Nano-MiADMSA; 50 mg/kg orally for 5 days) and compared it with bulk MiADMSA against sodium meta-arsenite exposed rats (25 ppm in drinking water, for 12 weeks) in male rats. The results suggested the size of Nano-MiADMSA was between 100-120 nm ranges. We noted enhanced chelating properties of Nano-MiADMSA compared with bulk MiADMSA as evident by the reversal of oxidative stress variables like blood δ-aminolevulinic acid dehydratase (δ-ALAD), Reactive Oxygen Species (ROS), Catalase activity, Superoxide Dismutase (SOD), Thiobarbituric Acid Reactive Substances (TBARS), Reduced Glutathione (GSH) and Oxidized Glutathione (GSSG), Glutathione Peroxidase (GPx), Glutathione-S-transferase (GST) and efficient removal of arsenic from the blood and tissues. Recoveries in neurobehavioral parameters further confirmed nano-MiADMSA to be more effective than bulk MiADMSA. We conclude that treatment with Nano-MiADMSA is a better therapeutic strategy than bulk MiADMSA in reducing the effects of arsenic-induced oxidative stress and associated neurobehavioral changes.

Environmental toxins and Alzheimer's disease progression

Alzheimer's disease (AD) is the most common form of dementia, which causes progressive memory loss and cognitive decline. Effective strategies to treat or prevent remains one of the most challenging undertakings in the medical field. AD is a complex and multifactorial disease that involves several risk factors. Aging and genetic factors both play important roles in the onset of the AD, however; certain environmental factors have been reported to increase the risk of AD. Chronic exposure to toxins has been seen as an environmental factor that may increase the risk of developing a neurodegenerative disease such as AD. Exposure to metals and biotoxins produced by bacteria, molds, and viruses may contribute to the cognitive decline and pathophysiology associated with AD. Toxins may contribute to the pathology of the disease through various mechanisms such as deposition of amyloid-beta (Aβ) plaques and tangles in the brain, induction of apoptosis, inflammation, or oxidative damage. Here, we will review how toxins affect brain physiology with a focus on mechanisms by which toxins may contribute to the development and progression of AD. A better understanding of these mechanisms may help contribute towards the development of an effective strategy to slow the progression of AD.

Comparative Cytotoxicity of Inorganic Arsenite and Methylarsenite in Human Brain Cells

The overall goal of this study is to elucidate the potential effect(s) of arsenic on a variety of human brain cells. Arsenic is the most pervasive Group A human environmental carcinogen. Long-term exposure to arsenic is associated with human diseases including cancer, cardiovascular disease, and diabetes. More immediate are the health effects on neurological development and associated disorders in infants and children exposed to arsenic in utero. Arsenic is metabolized in various organs and tissues into more toxic methylated species, including methylarsenite (MAs(III)), so the question arises whether the methylate species are responsible for the neurological effects of arsenic. Arsenic enters the brain through the blood-brain barrier and produces toxicity in the brain microvascular endothelial cells, glia (astrocytes and microglia), and neurons. In this study, we first assessed the toxicity in different types of brain cells exposed to either inorganic trivalent As(III) or MAs(III) using both morphological and cytotoxicity cell-based analysis. Second, we determined the methylation of arsenicals and the expression levels of the methylation enzyme, As(III) S-adenosylmethionine (SAM) methyltransferase (AS3MT), in several types of brain cells. We showed that the toxicity to neurons of MAs(III) was significantly higher than that of As(III). Interestingly, the differences in cytotoxicity between cell types was not due to expression of AS3MT, as this was expressed in neurons and glia but not in endothelial cells. These results support our hypothesis that MAs(III) is the likely physiological neurotoxin rather than inorganic arsenic species.

Organoarsenicals in Seafood: Occurrence, Dietary Exposure, Toxicity, and Risk Assessment Considerations - A Review

Diet, especially seafood, is the main source of arsenic exposure for humans. The total arsenic content of a diet offers inadequate information for assessment of the toxicological consequences of arsenic intake, which has impeded progress in the establishment of regulatory limits for arsenic in food. Toxicity assessments are mainly based on inorganic arsenic, a well-characterized carcinogen, and arsenobetaine, the main organoarsenical in seafood. Scarcity of toxicity data for organoarsenicals, and the predominance of arsenobetaine as an organic arsenic species in seafood, has led to the assumption of their nontoxicity. Recent toxicokinetic studies show that some organoarsenicals are bioaccessible and cytotoxic with demonstrated toxicities like that of pernicious trivalent inorganic arsenic, underpinning the need for speciation analysis. The need to investigate and compare the bioavailability, metabolic transformation, and elimination from the body of organoarsenicals to the well-established physiological consequences of inorganic arsenic and arsenobetaine exposure is apparent. This review provides an overview of the occurrence and assessment of human exposure to arsenic toxicity associated with the consumption of seafood.

Gestational Arsenic Trioxide Exposure Acts as a Developing Neuroendocrine-Disruptor by Downregulating Nrf2/PPARγ and Upregulating Caspase-3/NF-ĸB/Cox2/BAX/iNOS/ROS

The goal of this investigation was to evaluate the effects of gestational administrations of arsenic trioxide (ATO; As₂O₃) on fetal neuroendocrine development (the thyroid-cerebrum axis). Pregnant Wistar rats were orally administered ATO (5 or 10 mg/kg) from gestation day (GD) 1 to 20. Both doses of ATO diminished free thyroxine and free triiodothyronine levels and augmented thyrotropin level in both dams and fetuses at GD 20. Also, the maternofetal hypothyroidism in both groups caused a dose-dependent reduction in the fetal serum growth hormone, insulin growth factor-I (IGF-I), and IGF-II levels at embryonic day (ED) 20. These disorders perturbed the maternofetal body weight, fetal brain weight, and survival of pregnant and their fetuses. In addition, destructive degeneration, vacuolation, hyperplasia, and edema were observed in the fetal thyroid and cerebrum of both ATO groups at ED 20. These disruptions appear to depend on intensification in the values of lipid peroxidation, nitric oxide, and H₂O₂, suppression of messenger RNA (mRNA) expression of nuclear factor erythroid 2-related factor 2 and peroxisome proliferator-activated receptor gamma, and activation of mRNA expression of caspase-3, nuclear factor kappa-light-chain-enhancer of activated B cells, cyclooxygenase-2, Bcl-2–associated X protein, and inducible nitric oxide synthase in the fetal cerebrum. These data suggest that gestational ATO may disturb thyroid-cerebrum axis generating fetal neurodevelopmental toxicity.

Arsenic-Induced Neurotoxicity by Dysfunctioning Cholinergic and Dopaminergic System in Brain of Developing Rats

Chronic exposure to arsenic via drinking water throughout the globe is assumed to cause a developmental neurotoxicity. Here, we investigated the effect of perinatal arsenic exposure on the neurobehavioral and neurochemical changes in the corpus striatum, frontal cortex, and hippocampus that is critically involved in motor and cognition functions. In continuation of previous studies, this study demonstrates that perinatal exposures (GD6-PD21) to arsenic (2 or 4 mg/kg body weight, p.o.) cause hypo-activity in arsenic-exposed rats on PD22. The hypo-activity was found to be linked with a decrease in the mRNA and protein expression of the DA-D2 receptor. Further, a protein expression of tyrosine hydroxylase (TH), levels of dopamine, and its metabolites were also significantly impaired in corpus striatum. The arsenic-exposed groups showed spatial learning and memory significantly below the average in a dose-dependent manner for the controls. Here, we evaluated the declined expression of CHRM2 receptor gene and protein expression of ChAT, PKCβ-1 in the frontal cortex and hippocampus, which are critically involved in cognition functions including learning and memory. A trend of recovery was found in the cholinergic and dopaminergic system of the brain, but changes remained persisted even after the withdrawal of arsenic exposure on PD45. Taken together, our results indicate that perinatal arsenic exposure appears to be critical and vulnerable as the development of cholinergic and dopaminergic system continues during this period.

Impact of prenatal arsenate exposure on gene expression in a pure population of migratory cranial neural crest cells

Prenatal exposure to arsenic, a naturally occurring toxic element, causes neural tube defects (NTDs) and, in animal models, orofacial anomalies. Since aberrant development or migration of cranial neural crest cells (CNCCs) can also cause similar anomalies within developing embryos, we examined the effects of in utero exposure to sodium arsenate on gene expression patterns in pure populations of CNCCs, isolated by fluorescence activated cell sorting (FACS), from Cre/LoxP reporter mice. Changes in gene expression were analyzed using Affymetrix GeneChip^® microarrays and expression of selected genes was verified by TaqMan quantitative real-time PCR. We report, for the first time, arsenate-induced alterations in the expression of a number of novel candidate genes and canonical cascades that may contribute to the pathogenesis of orofacial defects. Ingenuity Pathway and NIH-DAVID analyses revealed cellular response pathways, biological themes, and potential upstream regulators, that may underlie altered fetal programming of arsenate exposed CNCCs.

Perinatal Exposure to Arsenic in Drinking Water Alters Glutamatergic Neurotransmission in the Striatum of C57BL/6 Mice

Although exposure to arsenic (As) induces developmental neurotoxicity, there is a lack of data regarding its specific effects on glutamatergic neurotransmission in offspring from dams exposed to As during gestation and lactation. In this study, the body weight, glutamate content, and expression of vesicular glutamate transporter 2 (VGLUT2) and metabotropic glutamate receptors mGluR2 and mGluR3 was examined in the striatum of offspring following treatment of the dams with As (10 or 100 mg/L NaAsO₂ in drinking water). At postnatal day 21, body weight was decreased significantly, whereas the glutamate content in the striatum of offspring in the 100-mg/L As group were not significantly different from those in the control group. Although mGluR3 expression was not significantly different, VGLUT2 and mGluR2 expression was significantly lower in the striatum of offspring of As-exposed dams. These data indicate that altered glutamatergic neurotransmission may contribute to As-induced developmental neurotoxic effects.

WITHDRAWN: Toxic effects of gestational arsenic trioxide on the neuroendocrine axis of developing rats

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Arsenic-Induced Autophagy in the Developing Mouse Cerebellum: Involvement of the Blood-Brain Barrier's Tight-Junction Proteins and the PI3K-Akt-mTOR Signaling Pathway

This study was designed to determine whether the tight-junction (TJ) proteins of the blood-brain barrier (BBB) and the PI3K-Akt-mTOR signaling pathway are involved during arsenic (As)-induced autophagy in developing mouse cerebella after exposure to different As concentrations (0, 0.15, 1.5, and 15 mg/L As(III)) during gestational and lactational periods. The dosage was continually given to the pups until postnatal day (PND) 42. Studies conducted at different developmental age points, like PND21, 28, 35, and 42, showed that exposure to As led to a significant decrease in the mRNA-expression levels of TJ proteins (occludin, claudin, ZO-1, and ZO-2), PI3K, Akt, mTOR, and p62, with concomitant increases in Beclin1, LC3I, LC3II, Atg5, and Atg12. Also, As significantly downregulated occludin and mTOR protein-expression levels with concomitant upregulation of Beclin1, LC3, and Atg12 at all the developmental age points. However, no significant alterations were observed in low- and medium-dose-exposed groups at PND42. Histopathological analysis revealed the irregular arrangement of the Purkinje cell layer in the As-exposed mice. Ultrastructural analysis by transmission electron microscopy (TEM) revealed the occurrence of autophagosomes and vacuolated axons in the cerebella of the mice exposed to high doses of As at PND21 and 42, respectively. Finally, we conclude that developmental As exposure significantly alters TJ proteins, resulting an increase in BBB permeability, facilitating the ability of As to cross the BBB and induce autophagy, which might be partly the result of inhibition of the PI3K-Akt-mTOR signaling pathway, in an age-dependent manner (i.e., PND21 mice were found to be more vulnerable to As-induced neurotoxicity), which could be due to the immature BBB allowing As to cross through it. However, the effect was not significant in PND42, which could be due to the developed BBB.

Effects of developmental arsenite exposure on hippocampal synapses in mouse offspring

arsenite. The thickness of the postsynaptic density (PSD) decreased, whereas the width of the synaptic cleft widened significantly in arsenite exposure groups. Moreover, protein expression of both PSD-95 and SYP decreased significantly in arsenite exposure groups. In conclusion, the results of this study demonstrated that developmental arsenite exposure could depress the expression of synaptic proteins, subsequently cause alteration in synaptic structures, and finally contribute to arsenite-induced deficits in spatial learning and memory ability in mouse offspring.

Metabolism and disposition of arsenic species after repeated oral dosing with sodium arsenite in drinking water. II. Measurements in pregnant and fetal CD-1 mice

Arsenic is ubiquitous in the earth's crust, and human diseases are linked with exposures that are similar to dietary intake estimates. Metabolic methylation of inorganic arsenic facilitates excretion of pentavalent metabolites and decreases acute toxicity; however, tissue binding of trivalent arsenic intermediates is evidence for concomitant metabolic activation. Pregnant and fetal CD-1 mice comprise a key animal model for arsenic carcinogenesis since adult-only exposures have minimal effects. This study evaluated inorganic arsenic and its metabolites in pentavalent and trivalent states in blood and tissues from maternal and fetal CD-1 mice after repeated administration of arsenite through drinking water. After 8 days of exposure, DMA species were ubiquitous in dams and fetuses. Despite the presence of MMA^III in dams, none was observed in any fetal sample. This difference may be important in assessing fetal susceptibility to arsenic toxicity because MMA production has been linked with human disease. Binding of DMA^III in fetal tissues provided evidence for metabolic activation, although the role for such binding in arsenic toxicity is unclear. This study provides links between administered dose, metabolism, and internal exposures from a key animal model of arsenic toxicity to better understand risks from human exposure to environmental arsenic.

Ellagic acid attenuates arsenic induced neuro-inflammation and mitochondrial dysfunction associated apoptosis

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Ellagic acid mitigates arsenic mediated genotoxicity in rat brain hippocampi.

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Ellagic acid ameliorates arsenic induced exacerbation in levels of ROS and pro-inflammatory cytokines in rat brain hippocampi.

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Ellagic acid has the propensity to modulate mRNA expression of BAX, Bcl₂ and caspase3, suggestive of its neuroprotective efficacy.

Arsenic, being a global pollutant needs a potential remedy which could fight against its associated toxicities. Ellagic acid (EA) is a known agent for its anti-inflammatory, antioxidant and antiapoptotic effects, and it is commonly found in fruits. The present study is designed to determine protective efficacy of EA against arsenic induced toxicity with special mention to inflammation and mitochondrial dysfunction in hippocampi of wistar rats. Rats were pre-treated with EA (20 and 40 mg/kg b.wt; p.o. for 11 days) along with arsenic (10 mg/kg; p.o. for 8 days). Total reactive oxygen species level and mitochondrial membrane potential were analyzed using flow cytometry. Protein and mRNA expression of apoptotic and inflammatory markers were also evaluated in rat hippocampus. Our results show that arsenic exposure increased total ROS generation and DNA fragmentation, decreased mitochondrial membrane potential alongwith an increase in expression of pro-apoptotic and inflammatory markers. suggesting that EA complementation downregulated total ROS generation dose dependently. Apoptotic markers, BAX and Bcl₂ as well as inflammatory markers, IL-1β, TNFα, INFγ got altered significantly on its administration. Moreover, it also attenuated effects on mitochondrial membrane potential. Based on our findings, EA might substantiate to be a budding therapeutic candidate against arsenic induced neurotoxicity.

Heavy metals exposure levels and their correlation with different clinical forms of fetal growth restriction

Background

Prenatal heavy metals exposure has shown a negative impact on birth weight. However, their influence on different clinical forms of fetal smallness was never assessed.

Objectives

To investigate whether there is a differential association between heavy metals exposure and fetal smallness subclassification into intrauterine growth restriction (IUGR) and small-for-gestational age (SGA).

Method

In this prospective case-control study, we included 178 mother–infant pairs; 96 of appropriate for gestational age (AGA) and 82 of small fetuses diagnosed in third trimester. The small ones were further subclassified into IUGR, n = 49 and SGA, n = 33. Cadmium (Cd), mercury (Hg), lead (Pb), arsenic (As) and zinc (Zn) levels were measured in the maternal and cord serum, and in the placentas of the three groups.

Results

Maternal serum level of Cd (p<0.001) was higher in the small fetuses compared to AGA. Fetal serum level of Cd (p<0.001) was increased in the small fetuses compared to AGA. Fetal serum level of Hg (p<0.05) showed an increase in SGA compared to both IUGR and AGA. Fetal serum level of Zn was increased in the AGA (p < 0.001) compared to each of the small fetuses groups. Only differences in the levels between the small fetuses’ subgroups were detected in the fetal serum levels of Cd and Hg. Fetal birth weight was negatively correlated with the fetal serum level of Cd (p < 0.001). No differences in the placental heavy metal levels were observed among the groups.

Conclusion

Fetal serum levels of Cd showed differential correlation between small fetuses' clinical subclassification, which together with the increased Cd levels in both maternal and fetal serum of the small fetuses reinforce the negative influence of heavy metals on birth weight. These findings provide more opportunities to verify the role of heavy metals exposure in relation to small fetuses’ subclassification.

Tissue-specific distributions of inorganic arsenic and its methylated metabolites, especially in cerebral cortex, cerebellum and hippocampus of mice after a single oral administration of arsenite

Groundwater contaminated with inorganic arsenic (iAs) is the main source of human exposure to arsenic and generates a global health issue. In this study, the urinary excretion, as well as the time-course distributions of various arsenic species in murine tissues, especially in different brain regions were determined after a single oral administration of 2.5, 5, 10 and 20mg/kg sodium arsenite (NaAsO₂). Our data showed that the peak times of urinary, hepatic and nephritic total arsenic (TAs) were happened at about 1h, then TAs levels decreased gradually and almost could not be observed after 72h. On contrast, the time course of TAs in lung, urinary bladder and different brain regions exhibited an obvious process of accumulation and elimination,and the peak times were nearly at 6h to 9h. TAs levels of 10 and 20mg/kg NaAsO₂ groups were significantly higher than 2.5 and 5mg/kg groups, and the amounts of TAs in 5mg/kg groups were in the order of liver>lung>kidney>urinary bladder>hippocampus>cerebral cortex>cerebellum. In addition, iAs was the most abundant species in liver and kidney, while lung and urinary bladder accumulated the highest concentrations of dimethylated arsenicals (DMA). What's more, the distributions of arsenic species were not homogeneous among different brain regions, as DMA was the sole species in cerebral cortex and cerebellum, while extremely high concentrations and percentages of monomethylated arsenicals (MMA) were found in hippocampus. These results demonstrated that distributions of iAs and its methylated metabolites were tissue-specific and even not homogeneous among different brain regions, which must be considered as to the tissue- and region-specific toxicity of iAs exposure. Our results thus provide useful information for clarifying and reducing the uncertainty in the risk assessment for this metalloid.

Mechanism of arsenite toxicity in embryonic stem cells

Environmental arsenite exposure has been linked to cancer as well as other diseases, presenting an important and serious public health problem. Toxicity of inorganic arsenite (iAs) has been investigated using animal models and cell culture, yet its developmental effects are poorly understood. This study investigated the molecular mechanism of iAs toxicity to ascertain insight into development and differentiation processes using mouse embryonic stem cells (ESCs). The results showed that iAs exposure affected morphology and integrity of ESC colonies as well as inhibited cell growth in a concentration-dependent manner, excluding concentrations <1 μM iAs which stimulated ESC growth. ESCs self-renewal and pluripotency was also affected as evident from the downregulation of transcription circuitry, Oct4, Nanog, Sox2 and Klf4 resulting in non-specific differentiation. ESCs exposed to iAs randomly differentiated into three germ layers, mesoderm, endoderm and ectoderm, as judged by transcriptional expression of Brachyury, Gata4 and FGF2, as well as translational expression of BRACHYURY, GATA4 and TUJ1 respectively. The differentiated cells represented osteogenic, chondrogenic, myogenic and neurogenic lineages as evident from upregulation of Col1, Sox9, Col2, Myog, Notch, Nes and Nef. Although iAs caused slight apoptosis with a concomitant increase in ROS levels, the exposed ESCs had significant Bcl2 expression, which could be involved in the protection against apoptosis. Further analysis revealed upregulation of Jun and P38 in ESCs with an increase in iAs concentration. These observations indicated that iAs stress caused random differentiation of ESCs via JNK/P38 pathways. These findings suggest that iAs exposure may cause teratogenicity during early fetal development. Copyright © 2017 John Wiley & Sons, Ltd.

Influence of age on arsenic-induced behavioral and cholinergic perturbations: Amelioration with zinc and α-tocopherol

This study was planned to determine arsenic (As) (10 mg/kg body weight given through oral gavage) induced behavioral and cholinergic perturbations in three different age groups of rats; young (postnatal day 21), adult (3 months), and aged (18 months) at 7 days post-acute exposure ( n = 6 for each of the four groups of all three age points). Further, we also evaluated the ameliorative effect of essential metal zinc (Zn; 0.02% through drinking water) and an antioxidant, α-tocopherol (vitamin E; 125 mg/kg body weight through oral gavage) against As-induced neurotoxicity. As exposure showed significant alterations in behavioral functions (open-field behavior, total locomotor activity, grip strength, exploratory behavior, and water maze learning). Cholinergic studies in three brain regions (cerebral cortex, cerebellum, and hippocampus) of different age groups also showed significant increase in acetylcholine levels and a decrease in acetylcholinesterase activity. These effects were more pronounced in hippocampus followed by cerebral cortex and cerebellum. Among the three different age points, aged animals were found to be more vulnerable to the As-induced toxicity as compared to young and adult animals suggesting that As neurotoxicity is age dependent. These As-induced alterations were significantly reversed following supplementation with Zn or vitamin E. However, vitamin E was found to elicit greater protection as compared to Zn in restoring the altered behavioral and cholinergic perturbations, providing evidence for As-induced oxidative damage.

Metabolism and toxicity of arsenicals in mammals

Arsenic (As) is a metalloid usually found in organic and inorganic forms with different oxidation states, while inorganic form (arsenite As-III and arsenate As-v) is considered to be more hazardous as compared to organic form (methylarsonate and dimethylarsinate), with mild or no toxicity in mammals. Due to an increasing trend to using arsenicals as growth promoters or for treatment purposes, the understanding of metabolism and toxicity of As gets vital importance. Its toxicity is mainly depends on oxi-reduction states (As-III or As-v) and the level of methylation during the metabolism process. Currently, the exact metabolic pathways of As have yet to be confirmed in humans and food producing animals. Oxidative methylation and glutathione conjugation is believed to be major pathways of As metabolism. Oxidative methylation is based on conversion of Arsenite in to mono-methylarsonic acid and di-methylarsenic acid in mammals. It has been confirmed that As is only methylated in the presence of glutathione or thiol compounds, suggesting that As is being methylated in trivalent states. Subsequently, non-conjugated trivalent arsenicals are highly reactive with thiol which converts the trivalent arsenicals in to less toxic pentavalent forms. The glutathione conjugate stability of As is the most important factor for determining the toxicity. It can lead to DNA damage by alerting enzyme profile and production of reactive oxygen and nitrogen species which causes the oxidative stress. Moreover, As causes immune-dysfunction by hindering cellular and humeral immune response. The present review discussed different metabolic pathways and toxic outcomes of arsenicals in mammals which will be helpful in health risk assessment and its impact on biological world.

Assessment of arsenic in colostrum and cord serum and risk exposure to neonates from an island population in China

Arsenic (As) has been proven to be highly toxic to humans, but limited attention has focused on exposure levels and potential risks to mother-neonate pairs of coastal populations. This study was conducted by examining the As concentration in colostrum and umbilical cord serum collected from 106 mother-neonate pairs living on Shengsi Island, facing the Yangtze River estuary and Hangzhou Bay in China. Average concentrations of total As in colostrum and cord serum were 18.51 ± 7.00 and 19.83 ± 10.50 μg L^-1. One-way ANOVA analysis showed delivered ages and source of drinking water played significant roles in influencing the maternal exposure patterns. Correlation analysis indicated a significantly positive association between As concentrations in colostrum and cord serum. Multivariable linear regression models adjusted for other confounders clarified the dose-response relationship with a coefficient value of 0.23 and a 95 % confidence interval of (0.006, 0.492); p < 0.05. The calculated daily intake of total As for neonates through breastfeeding was in the range from 0.413 to 3.65 μg kg^-1 body weight, and colostrum As, especially the most toxic species, inorganic arsenic (iAs), would pose a risk to neonates.

Arsenic Exposure Induces Unscheduled Mitotic S Phase Entry Coupled with Cell Death in Mouse Cortical Astrocytes

There is serious concern about arsenic in the natural environment, which exhibits neurotoxicity and increases the risk of neurodevelopmental disorders. Adverse effects of arsenic have been demonstrated in neurons, but it is not fully understood how arsenic affects other cell types in the brain. In the current study, we examined whether sodium arsenite (NaAsO₂) affects the cell cycle, viability, and apoptosis of in vitro-cultured astrocytes isolated from the cerebral cortex of mice. Cultured astrocytes from transgenic mice expressing fluorescent ubiquitination-based cell cycle indicator (Fucci) were subjected to live imaging analysis to assess the effects of NaAsO₂ (0, 1, 2, and 4 μM) on the cell cycle and number of cells. Fucci was designed to express monomeric Kusabira Orange2 (mKO2) fused with the ubiquitylation domain of hCdt1, a marker of G1 phase, and monomeric Azami Green (mAG) fused with the ubiquitylation domain of hGem, a marker of S, G2, and M phases. NaAsO₂ concentration-dependently decreased the peak levels of the mAG/mKO2 emission ratio when the ratio had reached a peak in astrocytes without NaAsO₂ exposure, which was due to attenuating the increase in the mAG-expressing cell number. In contrast, the mAG/mKO2 emission ratio and number of mAG-expressing cells were concentration-dependently increased by NaAsO₂ before their peak levels, indicating unscheduled S phase entry. We further examined the fate of cells forced to enter S phase by NaAsO₂. We found that most of these cells died up to the end of live imaging. In addition, quantification of the copy number of the glial fibrillary acidic protein gene expressed specifically in astrocytes revealed a concentration-dependent decrease caused by NaAsO₂. However, NaAsO₂ did not increase the amount of nucleosomes generated from DNA fragmentation and failed to alter the gene expression of molecules relevant to unscheduled S phase entry-coupled apoptosis (p21, p53, E2F1, E2F4, and Gm36566). These findings suggest that NaAsO₂ adversely affects the cell cycle and viability of astrocytes by inducing unscheduled S phase entry coupled with cell death that may be caused by mechanisms other than apoptosis.

Neurological Toxicity of Individual and Mixtures of Low Dose Arsenic, Mono and Di (n-butyl) Phthalates on Sub-Chronic Exposure to Mice

The objective of this study was to evaluate the toxicity of individual and mixtures of di(n-butyl) phthalates (DBP) and their active metabolite monobutyl phthalate (MBP) and arsenic (As) on spatial cognition associated with hippocampal apoptosis in mice. Mice were exposed, individually or in combination, to DBP (50 mg/kg body weight, intragastrically), MBP (50 mg/kg body weight, intragastrically), and As (10 mg/L, per os) for 8 weeks. The Morris water maze test showed that mice exposed to DBP/MBP combined with As exhibited longer escape latencies and the lower average number of crossing the platform. The As content in the hippocampus after As exposure increased as compared to those without As exposure. In mice exposed to DBP/MBP combined with As, pathological alterations and oxidative damage to the hippocampus were found. Expression of apoptosis-related protein: Bax and caspase-3 were significantly increased in the hippocampus, while there was no significant change in expression of Bcl-2. The results suggested that DBP and MBP combined with As can induce spatial cognitive deficits through altering the expression of apoptosis-related protein and As played a critical role in cognition impairments. And the joint exposure has antagonistic effect.

Arsenic inhibits stem cell differentiation by altering the interplay between the Wnt3a and Notch signaling pathways

data indicates that arsenic exposure inhibits stem cell differentiation. This study investigated whether arsenic disrupted the Wnt3a signaling pathway, critical in the formation of myotubes and neurons, during the differentiation in P19 mouse embryonic stem cells. Cells were exposed to 0, 0.1, or 0.5 μM arsenite, with or without exogenous Wnt3a, for up to 9 days of differentiation. Arsenic exposure alone inhibits the differentiation of stem cells into neurons and skeletal myotubes, and reduces the expression of both β-catenin and GSK3β mRNA to ~55% of control levels. Co-culture of the arsenic-exposed cells with exogenous Wnt3a rescues the morphological phenotype, but does not alter transcript, protein, or phosphorylation status of GSK3β or β-catenin. However, arsenic exposure maintains high levels of Hes5 and decreases the expression of MASH1 by 2.2-fold, which are anti- and pro-myogenic and neurogenic genes, respectively, in the Notch signaling pathway. While rescue with exogenous Wnt3a reduced Hes5 levels, MASH1 levels stay repressed. Thus, while Wnt3a can partially rescue the inhibition of differentiation from arsenic, it does so by also modulating Notch target genes rather than only working through the canonical Wnt signaling pathway. These results indicate that arsenic alters the interplay between multiple signaling pathways, leading to reduced stem cell differentiation.

Do the Levels of Maternal Plasma Trace Elements Affect Fetal Nuchal Translucency Thickness?

OBJECTIVE

Fetal nuchal translucency (NT) thickness is an important marker for prenatal screening; however, studies focusing on the correlation between maternal trace element levels and NT thickness are limited. The aim of this study was to evaluate maternal trace element levels during the first trimester and to investigate the association between maternal trace element levels and fetal NT thickness.

METHODS

In total, 113 samples were obtained from singleton pregnant women. Maternal plasma samples were collected in the first trimester of gestation. Plasma trace element levels were measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Nuchal translucency thickness was measured using ultrasonography at 10-14 weeks of gestation.

RESULTS

We found that maternal plasma potassium (K) levels had a significant negative correlation with both NT (r = -0.230, p < 0.05) and NT Multiples of the Median (NT MoM) (r = -0.206, p < 0.05). After adjustment for potential confounders, log-transformed maternal plasma potassium levels in the first trimester were significantly associated with fetal NT (NT MoM: β = -0.68, p < 0.05; NT: β = -1.20, p < 0.01). Although not statistically significant, the As, Hg and Pb levels in maternal plasma were positively correlated with NT, and the Mg, Cu, Zn, Na and Ca levels were negatively correlated with NT.

CONCLUSION

Maternal plasma K levels during the first trimester appeared to be associated with NT thickness. The essential elements tended to decrease NT thickness, and non-essential elements tended to increase it.

Arsenic and Its Methylated Metabolites Inhibit the Differentiation of Neural Plate Border Specifier Cells

Exposure to arsenic in food and drinking water has been correlated with adverse developmental outcomes, such as reductions in birth weight and neurological deficits. Additionally, studies have shown that arsenic suppresses sensory neuron formation and skeletal muscle myogenesis, although the reason why arsenic targets both of these cell types in unclear. Thus, P19 mouse embryonic stem cells were used to investigate the mechanisms by which arsenic could inhibit cellular differentiation. P19 cells were exposed to 0, 0.1, or 0.5 μM sodium arsenite and induced to form embryoid bodies over a period of 5 days. The expression of transcription factors necessary to form neural plate border specifier (NPBS) cells, neural crest cells and their progenitors, and myocytes and their progenitors were examined. Early during differentiation, arsenic significantly reduced the transcript and protein expression of Msx1 and Pax3, both needed for NPBS cell formation. Arsenic also significantly reduced the protein expression of Sox 10, needed for neural crest progenitor cell production, by 31-50%, and downregulated the protein and mRNA levels of NeuroD1, needed for neural crest cell differentiation, in a time- and dose-dependent manner. While the overall protein expression of transcription factors in the skeletal muscle lineage was not changed, arsenic did alter their nuclear localization. MyoD nuclear translocation was significantly reduced on days 2-5 between 15 and 70%. At a 10-fold lower concentration, monomethylarsonous acid (MMA III) appeared to be just as potent as inorganic arsenic at reducing the mRNA levels Pax3 (79% vs84%), Sox10 (49% vs 65%), and Msx1 (56% vs 56%). Dimethylarsinous acid (DMA III) also reduced protein and transcript expression, but the changes were less dramatic than those with MMA or arsenite. All three arsenic species reduced the nuclear localization of MyoD and NeuroD1 in a similar manner. The early changes in the differentiation of neural plate border specifier cells may provide a mechanism for arsenic to suppress both neurogenesis and myogenesis.