Arsenic toxicity, mutagenesis, and carcinogenesis--a health risk assessment and management approach

Association of low-level inorganic arsenic exposure from rice with age-standardized mortality risk of cardiovascular disease (CVD) in England and Wales

Adverse health outcomes, including death from cardiovascular disease (CVD), arising from chronic exposure to inorganic arsenic (iAs) are well documented. Consumption of rice is a major iAs exposure route for over 3 billion people, however, there is still a lack of epidemiological evidence demonstrating the association between iAs exposure from rice intake and CVD risks. We explored this potential association through an ecological study using data at local authority level across England and Wales. Local authority level daily per capita iAs exposure from rice (E-iAs_ing,rice) was estimated using ethnicity as a proxy for class of rice consumption. A series of linear and non-linear models were applied to estimate the association between E-iAs_ing,rice and CVD age-standardized mortality rate (ASMR), using Akaike's Information Criterion as the principle model selection criterion. When adjusted for significant confounders, notably smoking prevalence, education level, employment rate, overweight percentage, PM2.5, female percentage and medical and care establishments, the preferred non-linear model indicated that CVD risks increased with iAs exposure from rice at exposures above 0.3 μg/person/day. Also, the best-fitted linear model indicated that CVD ASMR in the highest quartile of iAs exposure (0.375-2.71 μg/person/day) was 1.06 (1.02, 1.11; p-trend <0.001) times higher than that in the lowest quartile (<0.265 μg/person/day). Notwithstanding the well-known limitations of ecological studies, this study further suggests exposure to iAs, including from rice intake, as a potentially important confounder for studies of the factors controlling CVD risks.

Effect of applying calcium peroxide on the accumulation of arsenic in rice plants grown in arsenic-elevated paddy soils

Water management such as drainage for creating aerobic conditions is considered to be an adequate method for reducing the accumulation of arsenic (As) in rice grains; however, it is difficult to conduct drainage operations in some areas that experience a lengthy rainy season as well as in soils with poor drainage. In this regard, application of oxygen-releasing compounds (ORCs) may be an alternative method for maintaining aerobic conditions even under flooding in paddy soils. Therefore, a pot experiment was conducted to investigate the effects of application of an ORC, calcium peroxide (CaO₂), on the growth and accumulation of As in rice plants grown in As-contaminated paddy soils. The rice plants were grown in two soils with different characteristics and As levels, and all of the tested soils were treated with 0, 5, 10, and 20 g CaO₂ kg^-1. Results revealed that the concentration of As and the distribution of arsenite in the pore water of all tested soils was reduced by CaO₂ application. In addition, the grain yields increased and the concentration of inorganic As in brown rice decreased by 25-45% upon CaO₂ treatment of low-As-level soils (<16 mg kg^-1). However, the effect of CaO₂ application on the accumulation of inorganic As in brown rice in As-enriched soils (>78 mg kg^-1) could not found in this study, due to the rice plant suffered from serious As phytotoxicity. It suggests that CaO₂ amendment may be suitable for reducing the As concentration of rice grains grown in low-As-level paddy soils, but for As-enriched soils, the proposed CaO₂ application method is not feasible.

Chemical identity and cardiovascular toxicity of hydrophobic organic components in PM2.5

Numerous experimental and epidemiological studies have demonstrated that exposure to PM_2.5 may result in pathogenesis of several major cardiovascular diseases (CVDs), which can be attributed to the combined adverse effects induced by the complicated components of PM_2.5. Organic materials, which are major components of PM_2.5, contain thousands of chemicals, and most of them are environmental hazards. However, the contamination profile and contribution to overall toxicity of PM_2.5-bound organic components (OCs) have not been thoroughly evaluated yet. Herein, we aim to provide an overview of the literature on PM_2.5-bound hydrophobic OCs, with an emphasis on the chemical identity and reported impairments on the cardiovascular system, including the potential exposure routes and mechanisms. We first provide an update on the worldwide mass concentration and composition data of PM_2.5, and then, review the contamination profile of PM_2.5-bound hydrophobic OCs, including constitution, concentration, distribution, formation, source, and identification. In particular, the link between exposure to PM_2.5-bound hydrophobic OCs and CVDs and its possible underlying mechanisms are discussed to evaluate the possible risks of PM_2.5-bound hydrophobic OCs on the cardiovascular system and to provide suggestions for future studies.

Density Functional Theory Investigation of As(III) S-Adenosylmethionine Methyltransferase

Arsenic is one of the most pervasive environmental toxins. It enters our water and food supply through many different routes, including the burning of fossil fuels, the application of arsenic-based herbicides, and natural sources. Using a density functional theory (DFT) cluster approach, the mechanism of arsenic (III) S-adenosylmethionine methyltransferases and various selenium-containing analogues was investigated. Notably, the methylation of arsenic by arsenic (III) S-adenosylmethionine is proposed to be a way to remove arsenic from contaminated water or soil. From the DFT cluster results, it was found that the selective substitution of the active-site Cys44, Cys72, and Cys174 residues with selenocysteines had a marginal effect on the barrier for CH₃ transfer. Specifically, the average Gibbs activation energy was calculated to be only 4.2 kJ mol^-1 lower than the Gibbs activation energy of 107.4 kJ mol^-1 for the WT enzyme. However, importantly, it was found that with selective mutation, the methylation process becomes considerably more exergonic, where the methylation reaction can be made to be 26.4 kJ mol^-1 more exergonic than the reaction catalyzed by the WT enzyme. Therefore, we propose that the selective substitution of the active-site Cys44, Cys72 and Cys174 residues with selenocysteines could make the process of methylation and volatilization more advantageous for bioremediation.

Status of arsenic accumulation in agricultural soils across China (1985-2016)

Based on 1677 published studies, 1648 sites across China collected from 1985 to 2016 were used to research the concentrations of arsenic in agricultural soils. In order to understand the status of arsenic pollution in agricultural soils in China over the past three decades, and to learn about the arsenic stocks in agricultural soils in various regions, and compared the relationship with annual arsenic emissions in China, and finally evaluated the potential ecological risks and human health risks. The median arsenic concentration in the surface agricultural soils of China was 10.40 mg Kg^-1, and it ranged from 0.4 mg Kg^-1 to 175.8 mg Kg^-1. The inventory of arsenic in Chinese agricultural surface soils was estimated to be 3.71 × 10⁶ t. In this study, the arsenic concentrations were found to be higher in Central, South, and Southwest China than those in other regions. The trend of arsenic pollution in agricultural soils has gradually increased over the past three decades. However, the growth rate of arsenic concentrations pollution in farmlands agricultural in China slowed during 2012-2016. The ecological risk index and geoaccumulation index revealed that arsenic in Chinese agricultural soil poses a low risk to the ecosystem. For human health assessment, the dietary pathway was the main pathway of exposure to arsenic in farmland soil of China. However, children's soil intake also contributed 34.48% to the exposure to arsenic, owing to their behavior. This study can provide a reference for the management of arsenic agricultural pollution in farmland soils in China.

Pollution characteristics and chronic health risk assessment of metals and metalloids in ambient PM2.5 in Licheng District, Jinan, China

PM_2.5 samples were collected at the Wangsheren primary school site in Licheng District of Jinan, China, during 2016. Eleven metals and metalloids including Al, As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sb and Se in PM_2.5 were measured by inductively coupled plasma-mass spectroscopy. The annual average mass concentration of PM_2.5 was found to be 88.7 μg m^-3. The highest PM_2.5 concentrations were obtained during the heating seasons of winter and spring. The concentrations of metals and metalloids in PM_2.5 were in a descending order of Al, Pb, Mn, As, Se, Cr, Sb, Ni, Cd, Hg and Be. The enrichment factors showed that Pb, Mn, As, Se, Cr, Sb, Ni, Cd, Hg originated from anthropogenic sources. Factor analysis indicated that the main sources of the metals were coal combustion dust, soil dust, metallurgical industry, brake abrasion of vehicles and other mixed sources. Coal combustion dust was the primary source of metal pollution in PM_2.5. Non-carcinogenic risks associated with exposure through the respiratory system were between 6.30 × 10^-4 and 7.62 × 10^-1, which were lower than the safe limit (1). The carcinogenic risks of Cr, As and Cd were 3.17 × 10^-5, 1.52 × 10^-5, 2.22 × 10^-6, respectively, which were higher than the precautionary criterion (10^-6/year). This study indicates that the air pollution of PM_2.5 is of public health concern in Licheng District of Jinan, particularly related to potential carcinogenic metals of As, Cr and Cd. Intervention action is needed to reduce the emission sources of these elements, especially coal combustion in winter heating season.

Characterization of Nitrate-Dependent As(III)-Oxidizing Communities in Arsenic-Contaminated Soil and Investigation of Their Metabolic Potentials by the Combination of DNA-Stable Isotope Probing and Metagenomics

Arsenite (As(III)) oxidation has important environmental implications by decreasing both the mobility and toxicity of As in the environment. Microbe-mediated nitrate-dependent As(III) oxidation (NDAO) may be an important process for As(III) oxidation in anoxic environments. Our current knowledge of nitrate-dependent As(III)-oxidizing bacteria (NDAB), however, is largely based on isolates, and thus, the diversity of NDAB may be underestimated. In this study, DNA-stable isotope probing (SIP) with ¹³C-labeled NaHCO₃ as the sole carbon source, amplicon sequencing, and shotgun metagenomics were combined to identify NDAB and investigate their NDAO metabolism. As(III) oxidation was observed in the treatment amended with nitrate, while no obvious As(III) oxidation was observed without nitrate addition. The increase in the gene copies of aioA in the nitrate-amended treatment suggested that As(III) oxidation was mediated by microorganisms containing the aioA genes. Furthermore, diverse putative NDAB were identified in the As-contaminated soil cultures, such as Azoarcus, Rhodanobacter, Pseudomonas, and Burkholderiales-related bacteria. Metagenomic analysis further indicated that most of these putative NDAB contained genes for As(III) oxidation and nitrate reduction, confirming their roles in NDAO. The identification of novel putative NDAB expands current knowledge regarding the diversity of NDAB. The current study also suggests the proof of concept of using DNA-SIP to identify the slow-growing NDAB.

Arsenic exposure and perception of health risk due to groundwater contamination in Majuli (river island), Assam, India

Island populations are rarely studied for risk of arsenic (As) poisoning. As poisoning, multimetal contamination and people's perceptions of health risks were assessed on India's Majuli Island, the largest inhabited river island in the world. This holistic approach illustrated the association of groundwater contamination status with consequent health risk by measuring levels of inorganic arsenic (iAs) in groundwater, borehole sediment and biological samples (hair, nails and urine). Piper and Gibbs's plots discerned the underlying hydrogeochemical processes in the aquifer. Demographic data and qualitative factors were evaluated to assess the risks and uncertainties of exposure. The results exhibited significant enrichment of groundwater with As, Mn and Fe along with significant body burden. Maximum Hazard Index values indicated severe non-carcinogenic health impacts as well as a significantly elevated risk of cancer for both adults and children. Most (99%) of the locally affected population did not know about the adverse health impacts of metal contamination, and only 15% understood bodily ailments and health issues. Various aspects of the island environment were used to elucidate the status of contamination and future risk of disease. A projection showed adverse health outcomes rising significantly, especially among the young population of Majuli, due to overexposure to not only As but also Ba, Mn and Fe.

Arsenic hampered embryonic development: An in vivo study using local Bangladeshi Danio rerio model

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Exposure to arsenic results delayed and deformed embryonic development.

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Arsenic exposure increased the mortality rate of embryos.

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Arsenic exposure may increase miscarriage or abortion rate in the pregnant mother.

Zebrafish (Danio rerio) has appeared as a valuable and popular model species to study the developmental and toxicological impact of environmental pollutants. To get insights on the toxicological effect of arsenic on early embryonic development, a controlled breeding of local Bangladeshi zebrafish followed by comprehensive microscopic analysis was conducted to study the embryonic development after exposure to different concentrations of arsenic ranges from 4−120 h post-fertilization. Zebrafish embryos exposed to 2 mM of arsenic displayed distinguishable developmental delay compared to control. At three days post-fertilization, a distinct phenotype appears in arsenic-treated embryos, which can be characterized by dechorionated embryos, larger egg mass, pericardial edema, abnormal heart rate, and abnormal head development. Remarkably, the death rate of the arsenic-treated embryos was significantly higher compared to control. Collectively, these findings indicate that exposure to arsenic may result in abnormal embryonic development. These results suggest for proper management of the pregnant mother in the arsenic-exposed area, and may also explain the incidence of increased miscarriage/abortion rate in arsenic water drinking pregnant mother.

Heavy metal content and health risk assessment of commonly patronized herbal medicinal preparations from the Kumasi metropolis of Ghana

PURPOSE

To address the question of whether users of herbal products (HPs) are exposed to harmful contaminants, we evaluated six HPs mostly patronized in Kumasi for heavy metal contamination and assessed the health risk associated with their use. This study is one of the first safety evaluation studies on finished multiherbal products in the region.

METHOD

Three antimalarial, two antidiabetic and one antihypertensive HPs were selected after a mini-survey and coded randomly as HP A-F. The HPs were acid digested for quantitative analysis of heavy metals using Inductively Coupled Plasma Mass Spectrometer. Hg quantification was carried out using cold vapour atomic absorption spectroscopy.

RESULTS

The cancer risk estimation values for the carcinogenic metals ranged between 1.54 × 10^-9 to 3.73 × 10^-4 and were all within acceptable limits. The non-cancer health risk evaluation revealed that, some of the products pose health risk to consumers. The estimated daily intake (EDI) for As in HPF was 2.48 × 10^-4 mg/kg/day compared to the reference limit of 1.67 × 10^-4 mg/kg/day. HPF also had high hazard index (HI) of 5.70 (HI >1) in children as compared to 1.68 (HI >1) in adults showing a 3.4 folds increase in the health risk among the former.

CONCLUSION

The six polyherbal products exhibited carcinogenic risk within acceptable limits. Although, the non-carcinogenic risk assessment of products HPA to HPE suggests safety, this can only be ascertained after further characterization of their health risks in detailed chronic toxicity studies. The high HI for product HPF suggests health risk for consumers of this product.

A Comprehensive Review of Microfluidic Water Quality Monitoring Sensors

Water crisis is a global issue due to water contamination and extremely restricted sources of fresh water. Water contamination induces severe diseases which put human lives at risk. Hence, water quality monitoring has become a prime activity worldwide. The available monitoring procedures are inadequate as most of them require expensive instrumentation, longer processing time, tedious processes, and skilled lab technicians. Therefore, a portable, sensitive, and selective sensor with in situ and continuous water quality monitoring is the current necessity. In this context, microfluidics is the promising technology to fulfill this need due to its advantages such as faster reaction times, better process control, reduced waste generation, system compactness and parallelization, reduced cost, and disposability. This paper presents a review on the latest enhancements of microfluidic-based electrochemical and optical sensors for water quality monitoring and discusses the relative merits and shortcomings of the methods.

Determination of polycyclic aromatic hydrocarbons and potentially toxic metals in commonly consumed beef sausage roll products in Nigeria

Levels of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic metals (PTMs) were determined in the commonly consumed beef sausage roll products (coded BS1 - BS6) in Nigeria. This was done in order to assess the safety of regular consumption of these products with respect to the substances determined. Three batches of six samples of beef sausage roll products were collected from Ile-Ife, Osun sate, Nigeria. A part of the pretreated sample was Soxhlet extracted using n-hexane and analyzed with Gas Chromatography coupled with Flame Ionization Detector (GC-FID) to identify and quantify each of the PAHs in the sample, while Atomic Absorption Spectrometer (AAS) was used to profile the concentrations of As, Cd, Co, Cu, Pd, Mn and Zn in the digested sausage roll samples. Levels of PAHs in the samples ranged from 1.84 μg/g of Acenaphthylene in BS5 to 282.83 μg/g of Benzo[k]fluoranthene in BS1. Concentrations of benzo[a]pyrene in all the samples were higher than the guideline value of 0.003 mg/kg/day. For PTMs, a range of 0.075 μg/g As in both BS1 and BS6 to 2.950 μg/g Cu in BS3 was obtained. The study concluded that both PAHs and PTMs occurred in the samples at levels that called for caution on the part of consumers to prevent health infarctions that might be associated with prolonged regular and large consumption of beef sausage roll products.

Prenatal toxicity of the environmental pollutants on neuronal and cardiac development derived from embryonic stem cells

Pesticides, antibiotics, and industrial excipients are widely used in agriculture, medicine, and chemical industry, respectively. They often end up in the environment, not only being not easily decomposed but also being accumulated. Moreover, they may cause serious toxic problems such as reproductive and developmental defects, immunological toxicity, and carcinogenesis. Hence, they are called environmental pollutants. It is known that the environmental pollutants easily enter the body through various channels such as respiration, ingestion of food, and skin contact etc. in everyday life. If they enter the mother through the placenta, they can cause the disturbance in embryo development as well as malfunction of organs after birth because early prenatal developmental process is highly sensitive to toxic chemicals and stress. Embryonic stem cells (ESCs) that consist of inner cell mass of blastocyst differentiate into distinct cell lineages via three germ layers such as the ectoderm, mesoderm, and endoderm due to their pluripotency. The differentiation process initiated from ESCs reflects dynamic nature of embryonic development. Therefore, ESCs have been used as a useful tool to investigate early developmental toxicities of a variety of stress. Based on relatively recent scientific results, this review would address toxicity of a few chemical substances that have been widely used as pesticide, antibiotics, and industrial excipient on ESCs based-prenatal developmental process. This review further suggests how they act on the viability of ESCs and/or early stages of cardiac and neuronal development derived from ESCs as well as on expression of pluripotency and/or differentiation markers through diverse mechanisms.

Realgar and cinnabar are essential components contributing to neuroprotection of Angong Niuhuang Wan with no hepatorenal toxicity in transient ischemic brain injury

Realgar and cinnabar are commonly used mineral medicine containing arsenic and mercury in Traditional Chinese Medicine (TCM). Angong Niuhuang Wan (AGNHW) is a representative realgar- and cinnabar-containing TCM formula for treating acute ischemic stroke, but its toxicology and neuropharmacological effects are not well addressed. In this study, we compared the neuropharmacological effects of AGNHW and modified AGNHW in an experimental ischemic stroke rat model. Male SD rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus 22 h of reperfusion. Although oral administration of AGNHW for 7 days in the rats increased arsenic level in the blood and liver tissue, there were no significant changes in the arsenic level in kidney, mercury level in the blood, liver and kidney as well as hepatic and renal functions in MCAO rats. AGNHW revealed neuroprotective properties by reducing infarction volume, preserving blood-brain barrier integrity and improving neurological functions against cerebral ischemia-reperfusion injury. Interestingly, removing realgar and/or cinnabar from AGNHW abolished the neuroprotective effects. Meanwhile, AGNHW could scavenge peroxynitrite, down-regulate the expression of p47_phox, 3-NT and MMP-9 and up-regulate the expression of ZO-1 and claudin-5 in the ischemic brains, which were abolished by removing realgar and/or cinnabar from AGNHW. Notably, realgar or cinnabar had no neuroprotection when used alone. Taken together, oral administration of AGNHW for one week should be safe for treating ischemic stroke with neuroprotective effects. Realgar and cinnabar are necessary elements with synergetic actions with other herbal materials for the neuroprotective effects of AGNHW against cerebral ischemia-reperfusion injury.

A systematic review on global pollution status of particulate matter-associated potential toxic elements and health perspectives in urban environment

Airborne particulate matter (PM) that is a heterogeneous mixture of particles with a variety of chemical components and physical features acts as a potential risk to human health. The ability to pose health risk depends upon the size, concentration and chemical composition of the suspended particles. Potential toxic elements (PTEs) associated with PM have multiple sources of origin, and each source has the ability to generate multiple particulate PTEs. In urban areas, automobile, industrial emissions, construction and demolition activities are the major anthropogenic sources of pollution. Fine particles associated with PTEs have the ability to penetrate deep into respiratory system resulting in an increasing range of adverse health effects, at ever-lower concentrations. In-depth investigation of PTEs content and mode of occurrence in PM is important from both environmental and pathological point of view. Considering this air pollution risk, several studies had addressed the issues related to these pollutants in road and street dust, indicating high pollution level than the air quality guidelines. Observed from the literature, particulate PTEs pollution can lead to respiratory symptoms, cardiovascular problems, lungs cancer, reduced lungs function, asthma and severe case mortality. Due to the important role of PM and associated PTEs, detailed knowledge of their impacts on human health is of key importance.

Arsenite malignantly transforms human prostate epithelial cells in vitro by gene amplification of mutated KRAS

Inorganic arsenic is an environmental human carcinogen of several organs including the urinary tract. RWPE-1 cells are immortalized, non-tumorigenic, human prostate epithelia that become malignantly transformed into the CAsE-PE line after continuous in vitro exposure to 5μM arsenite over a period of months. For insight into in vitro arsenite transformation, we performed RNA-seq for differential gene expression and targeted sequencing of KRAS. We report >7,000 differentially expressed transcripts in CAsE-PE cells compared to RWPE-1 cells at >2-fold change, q<0.05 by RNA-seq. Notably, KRAS expression was highly elevated in CAsE-PE cells, with pathway analysis supporting increased cell proliferation, cell motility, survival and cancer pathways. Targeted DNA sequencing of KRAS revealed a mutant specific allelic imbalance, ‘MASI’, frequently found in primary clinical tumors. We found high expression of a mutated KRAS transcript carrying oncogenic mutations at codons 12 and 59 and many silent mutations, accompanied by lower expression of a wild-type allele. Parallel cultures of RWPE-1 cells retained a wild-type KRAS genotype. Copy number analysis and sequencing showed amplification of the mutant KRAS allele. KRAS is expressed as two splice variants, KRAS4a and KRAS4b, where variant 4b is more prevalent in normal cells compared to greater levels of variant 4a seen in tumor cells. 454 Roche sequencing measured KRAS variants in each cell type. We found KRAS4a as the predominant transcript variant in CAsE-PE cells compared to KRAS4b, the variant expressed primarily in RWPE-1 cells and in normal prostate, early passage, primary epithelial cells. Overall, gene expression data were consistent with KRAS-driven proliferation pathways found in spontaneous tumors and malignantly transformed cell lines. Arsenite is recognized as an important environmental carcinogen, but it is not a direct mutagen. Further investigations into this in vitro transformation model will focus on genomic events that cause arsenite-mediated mutation and overexpression of KRAS in CAsE-PE cells.

Heavy metals detoxification: A review of herbal compounds for chelation therapy in heavy metals toxicity

Some heavy metals are nutritionally essential elements playing key roles in different physiological and biological processes, like: iron, cobalt, zinc, copper, chromium, molybdenum, selenium and manganese, while some others are considered as the potentially toxic elements in high amounts or certain chemical forms. Nowadays, various usage of heavy metals in industry, agriculture, medicine and technology has led to a widespread distribution in nature raising concerns about their effects on human health and environment. Metallic ions may interact with cellular components such as DNA and nuclear proteins leading to apoptosis and carcinogenesis arising from DNA damage and structural changes. As a result, exposure to heavy metals through ingestion, inhalation and dermal contact causes several health problems such as, cardiovascular diseases, neurological and neurobehavioral abnormalities, diabetes, blood abnormalities and various types of cancer. Due to extensive damage caused by heavy metal poisoning on various organs of the body, the investigation and identification of therapeutic methods for poisoning with heavy metals is very important. The most common method for the removal of heavy metals from the body is administration of chemical chelators. Recently, medicinal herbs have attracted the attention of researchers as the potential treatments for the heavy metals poisoning because of their fewer side effects. In the present study, we review the potential of medicinal herbs such as: Allium sativum (garlic), Silybum marianum (milk thistle), Coriandrum sativum (cilantro), Ginkgo biloba (gingko), Curcuma longa (turmeric), phytochelatins, triphala, herbal fibers and Chlorophyta (green algae) to treat heavy metal poisoning.

State of the science review of the health effects of inorganic arsenic: Perspectives for future research

Human exposure to inorganic arsenic (iAs) is a global health issue. Although there is strong evidence for iAs-induced toxicity at higher levels of exposure, many epidemiological studies evaluating its effects at low exposure levels have reported mixed results. We comprehensively reviewed the literature and evaluated the scientific knowledge on human exposure to arsenic, mechanisms of action, systemic and carcinogenic effects, risk characterization, and regulatory guidelines. We identified areas where additional research is needed. These priority areas include: (1) further development of animal models of iAs carcinogenicity to identify molecular events involved in iAs carcinogenicity; (2) characterization of underlying mechanisms of iAs toxicity; (3) assessment of gender-specific susceptibilities and other factors that modulate arsenic metabolism; (4) sufficiently powered epidemiological studies to ascertain relationship between iAs exposure and reproductive/developmental effects; (5) evaluation of genetic/epigenetic determinants of iAs effects in children; and (6) epidemiological studies of people chronically exposed to low iAs concentrations.

Interaction landscape of a 'CαNN' motif with arsenate and arsenite: a potential peptide-based scavenger of arsenic

Arsenic (As) is a toxic metalloid that has drawn immense attention from the scientific community recently due to its fatal effects through its unwanted occurrence in ground water around the globe. The presence of an excess amount of water soluble arsenate and/or arsenite salt (permissible limit 10 μg L-1 as recommended by the WHO) in water has been correlated with several human diseases. Although arsenate (HAsO4 2-) is a molecular analogue of phosphate (HPO4 2-), phosphate is indispensable for life, while arsenic and its salts are toxic. Therefore, it is worthwhile to focus on the removal of arsenic from water. Towards this end, the design of peptide-based scaffolds for the recognition of arsenate and arsenite would add a new dimension. Utilizing the stereochemical similarity between arsenate (HAsO4 2-) and phosphate (HPO4 2-), we successfully investigated the recognition of arsenate and arsenite with a naturally occurring novel phosphate binding 'CαNN' motif and its related designed analogues. Using computational as well as biophysical approaches, for the first time, we report here that a designed peptide-based scaffold based on the 'CαNN' motif can recognize anions of arsenic in a thermodynamically favorable manner in a context-free system. This peptide-based arsenic binding agent has the potential for future development as a scavenger of arsenic anions to obtain arsenic free water.

Multiple Bowen's diseases and basal cell carcinomas in a patient with acute promyelocytic leukemia treated with arsenic trioxide: A case report and effective treatment with photodynamic therapy

It is very rare that multiple Bowen's disease (BD) and basal cell carcinoma (BCC) lesions develop in a single patient. Routine therapy for the multiple lesions is not satisfactory. The present authors report on a patient who had developed multiple BD and BCC lesions for 12 years after arsenic trioxide treatment for his acute promyelocytic leukemia 20 years before. The patient with multiple lesions was successfully treated with photodynamic therapy.

Reactive oxygen species (ROS) activity of ambient fine particles (PM2.5) measured in Seoul, Korea

Substantial increase in level of particulate matter has raised concerns in South Korea recently. Ambient particulate matter is classified as Group I carcinogen (IARC, 2013) and multiple epidemiological studies has demonstrated adverse health effects due to exposure of particulate matter. Fine particulate matter (PM_2.5) which has a diameter <2.5 μm is likely to penetrate deeply into lung and is known to be eliciting adverse health effects. A number of epidemiological studies have been conducted on adverse health effects of PM-related diseases and mortality rate, yet particulate matter (PM)-induced reactive oxygen species (ROS) activity at the cellular level has not been actively studied in Korea. This study assessed PM-induced oxidative potential by exposure of collected ambient PM_2.5 samples to the rat alveolar macrophage cell line. The characteristics of PM_2.5 in Korea were further characterized by linking chemical constituents and contributing sources to ROS. PM_2.5 mass concentration during the cold season was relatively higher than mass concentration during the warm season and chemical constituents except for Secondary Organic Carbon (SOC) and SO₄^2- which both showed similar trends in both the cold and cold seasons. The concentration of crustal elements was especially high during the cold season which can be an indication of long range transport of Asian dust. Water soluble organic carbon and water soluble transition metals (Cr and Zn) were also shown to be correlated to oxidative potential and metals such as As and V were shown to have a high contribution to ROS activity according to stepwise multiple linear regression. Principal Component Analysis (PCA) results identified six factors that can be interpreted as soil, mobile, industry, secondary inorganic aerosol, secondary organic aerosol and oil combustion. Moreover, through Principal Component Regression (PCR), industry, soil, mobile and SIA were shown to be statistically significant sources in a relation to ROS activity.

Ethnic, Geographic, and Genetic Differences in Arsenic Metabolism at Low Arsenic Exposure: A Preliminary Analysis in the Multi-Ethnic Study of Atherosclerosis (MESA)

We investigated the effect of candidate variants in AS3MT (arsenic (III) methyltransferase) with urinary arsenic metabolites and their principal components in a subset of 264 participants in the Multi-Ethnic Study of Atherosclerosis (MESA). Urinary arsenic species, including inorganic arsenic (iAs), monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenobetaine (Ab), were measured using high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) and corrected for organic sources from seafood consumption by regressing Ab on arsenic species using a validated method. Principal components of arsenic metabolism were also used as independent phenotypes. We conducted linear regression of arsenic traits with allelic dosage of candidate single nucleotide polymorphisms (SNPs) rs12768205 (G > A), rs3740394 (A > G), and rs3740393 (G > C) measured using Illumina MetaboChip. Models were stratified by non-Hispanic white vs. all other race/ethnicity and adjusted for age, sex, arsenic exposure, study site, and population stratification. Consistent with previous studies, rs12768205 showed evidence for strongest association (non-Hispanic white: iAs% -0.14 (P 0.83), MMA% -0.66 (0.49), DMA% 0.81(0.49); other race/ethnicity: 0.13 (0.71), -1.21 (0.09), 1.08 (0.20)). No association, however, passed the strict Bonferroni p-value. This was a novel study among an ethnically diverse population exposed to low arsenic levels.

Carcinogenic and non-carcinogenic risk assessments of arsenic contamination in drinking water of Ardabil city in the Northwest of Iran

Based on the environmental health assessment framework of the United State Environmental Protection Agency, a quantitative health risk assessment of arsenic in contaminated drinking water in a city in the northwest of Iran has been carried out. In the exposure assessment step, arsenic concentrations in drinking water were determined during four seasons. In addition, the water ingestion rate for different age groups in this region was determined. The concentration of arsenic in 163 collected samples from different locations during four seasons ranged from 0 to 99 μg L^-1. Furthermore, a high percentage of the samples manifested higher levels than the permissible limit of 10 μg L^-1. The total daily water intake rates of four age groups 1 to <2 (group 1), 2 to <6 (group 2), 6 to <16 (group 3), and ≥16 years (group 4) were estimated as 0.86, 1.49, 2.00, and 2.33 L day^-1, respectively. Calculating the lifetime average daily dose of arsenic indicated that adults (group 4) had the highest and children (group 1) had the lowest daily intake of arsenic in their entire life. The results of risk characteristic showed that the order of excess lifetime cancer risk via arsenic exposure in the four groups was 4 > 3 > 2 > 1. The estimated risks for all age groups were higher than the acceptable range (1E-6 to 1E-4). The hazard quotient values for all of the classified groups were lower than the recommended limit values (<1), but it cannot be concluded that potential non-carcinogenicity risks are non-existent since the possible exposure to arsenic via food and skin may also pose the risk.

Bacillus cereus AR156 Activates Defense Responses to Pseudomonas syringae pv. tomato in Arabidopsis thaliana Similarly to flg22

Bacillus cereus AR156 (AR156) is a plant growth-promoting rhizobacterium capable of inducing systemic resistance to Pseudomonas syringae pv. tomato in Arabidopsis thaliana. Here, we show that, when applied to Arabidopsis leaves, AR156 acted similarly to flg22, a typical pathogen-associated molecular pattern (PAMP), in initiating PAMP-triggered immunity (PTI). AR156-elicited PTI responses included phosphorylation of MPK3 and MPK6, induction of the expression of defense-related genes PR1, FRK1, WRKY22, and WRKY29, production of reactive oxygen species, and callose deposition. Pretreatment with AR156 still significantly reduced P. syringae pv. tomato multiplication and disease severity in NahG transgenic plants and mutants sid2-2, jar1, etr1, ein2, npr1, and fls2. This suggests that AR156-induced PTI responses require neither salicylic acid, jasmonic acid, and ethylene signaling nor flagella receptor kinase FLS2, the receptor of flg22. On the other hand, AR156 and flg22 acted in concert to differentially regulate a number of AGO1-bound microRNAs that function to mediate PTI. A full-genome transcriptional profiling analysis indicated that AR156 and flg22 activated similar transcriptional programs, coregulating the expression of 117 genes; their concerted regulation of 16 genes was confirmed by real-time quantitative polymerase chain reaction analysis. These results suggest that AR156 activates basal defense responses to P. syringae pv. tomato in Arabidopsis, similarly to flg22.

Arsenic in agricultural soils across China: Distribution pattern, accumulation trend, influencing factors, and risk assessment

Arsenic (As) in the environment is of concern due to its strong toxicity and high risks to the ecosystems and humans. In this study, soil samples across China collected in 2011 and 2016 were used to determine the concentrations of arsenic in arable soils. The median concentration of arsenic in surface soils was 9.7mg/kg. The inventory of arsenic in the Chinese agricultural surface soils was estimated to be 3.7×10⁶tons. In general, arsenic contamination was found higher in South and Northeast China than in other regions, with means of 18.7 and 15.8mg/kg, respectively. Vertically, arsenic concentrations were higher in top layer (0-15cm) soils (median of 9.8mg/kg) and decreased with soil depth (medians of 8.9mg/kg at 15-30cm and 8.0mg/kg at 30-45cm). By comparing with published data, an increasing accumulation trend over the past decades was found and this enhancement was positively related with the long-term application of fertilizers in agricultural practice, especially phosphate fertilizers. Soil pH was found to affect the movement of arsenic in soil, and high-pH conditions enhanced the pool of arsenic. The ecological risk assessment revealed that arsenic in Chinese agricultural soil posed a low risk to the ecosystem. Regarding human health, the mean hazard indices (HIs) of arsenic were below 1, suggesting an absence of non-carcinogenic risks. In addition, the cancer risks of arsenic in all soil samples were within the acceptable range (below 1×10^-4), indicating low to very low risks to the exposed population. Findings from this study are valuable to provide effective management options for risk avoidance and to control the persistent accumulation of arsenic in the agriculture sector across the world.

Preremedial assessment of the municipal landfill pollution impact on soil and shallow groundwater in Subotica, Serbia

Most regional municipal solid waste landfills in Serbia are operated without control of landfill leachate and gas or with no regard for implementation of national and European legislation. For the first time in Serbia, groundwater and soil at a landfill were subject to systematic annual monitoring according to national, European legislation and adopted methodologies. Characterisation of the groundwater and soil samples from the landfill included ten metals (Fe, Mn, As, Zn, Cd, Pb, Ni, Cr, Cu and Hg), 16 EPA PAHs, nutrients and certain physicochemical parameters, in order to assess the risks such poorly controlled landfills pose to the environment. This impact assessment was performed using specially adapted pollution indices: LWPI, the Single factor pollution index and the Nemerow index for groundwater, and geo-accumulation index, ecological risk factor and selected rations of PAHs for soil. The data analysis included multivariate statistical methods (factor analysis of principal component analysis (PCA/FA)) in order to assess the extent of the contaminants detected in the groundwater and soil samples. The pollution indices (LWPI: 3.56-8.89; Nemerow index: 2.02-3.78) indicate the quality of the groundwater at the landfill is degrading over time, with PAH₁₆, TOC, Cr, Cu, Pb and Zn as the substances of greatest concern. Heavy metals Hg (I_geo≤3.14), Pb (I_geo≤2.22), Cr (I_geo≤3.31) and Cu (I_geo≤2.16) represent the worst soil contamination. Hg has moderate (52.9) to very high (530.0) potential ecological risk, demonstrating the long-term potential effects of bioaccumulation and biomagnification. The results of this work indicate that Cr and Cu should possibly be added to the EU Watch List of emerging substances. This proposition is substantiated by relevant state and alike environmental information from nations in the region. This study demonstrates the need to develop a model for prioritization of landfill closure and remediation based on environmental risk assessment.

Whole blood and hair trace elements and minerals in children living in metal-polluted area near copper smelter in Karabash, Chelyabinsk region, Russia

The primary aim of the study is assessment of hair and whole blood trace element and mineral levels in children living in a polluted area near a copper smelter (Karabash) and two control locations (Varna, Tomino) using inductively coupled plasma mass spectrometry. The obtained data indicates that both blood and hair As, Pb, and Fe levels in children living in Karabash significantly exceeded the control values. Whole blood levels of copper in children living in Varna exceeded that in Tomino (p = 0.155) and Karabash (p < 0.001) by 16 %. Oppositely, hair concentration of Cu was maximal in children from Karabash. Blood Ca and Mg content in children from Varna exceeded the respective values from Tomino and Karabash by 32 % (p = 0.021) and 42 % (p < 0.001), and 19 % (p < 0.001) and 9 % (p < 0.001), respectively. Similar differences were observed in hair mineral content. Oppositely, children living in Tomino and Karabash were characterized by 10 (p = 0.002) and 23 % (p < 0.001) higher levels of blood phosphorus. At the same time, hair P content was maximal in a polluted area. Therefore, children living in a polluted area near a copper smelter had significantly higher values of heavy metals and decreased Mg and Ca content in biosamples. It is supposed that adverse health effects in persons living near a copper smelter may be associated not only with toxic metal overexposure but also with altered mineral homeostasis.

Aqueous Extract of Carica Papaya Linn Roots Halts Sodium Arsenite-Induced Renal Inflammation through Inhibiting Adenosine Deaminase, 8-Hydroxy-2′-Deoxyguanosine, C-Reactive Protein and Inducible Nitric Oxide Synthase Activity

Objectives: Inflammation plays a crucial role in many of the metabolic abnormalities. The prototypic marker of inflammation is C-reactive protein (CRP), Nitric Oxide (NO), inducible nitric oxide synthase (iNOS) and their inhibition is considered a promising strategy to combat inflammation. Here, we report the anti-inflammatory mechanism of Carica papaya root aqueous extract in sodium arsenic-induced renal dysfunction.

Methodology: Thirty-five rats were used for the experiments. Griess assay was used to evaluate the inhibitory effect of Carica papaya roots aqueous extract on the overproduction of nitric oxide (NO). ELISA was used to determine the level of pro-inflammatory markers including c-reactive protein (CRP). ELISA was used to analyze 8-OHdG. The inhibitory effect on the enzymatic activity of inducible nitric oxide synthase (iNOS), adenosine deaminase (ADA), malondialdehyde (MDA) was tested by enzyme activity assay kits.

Results: Carica papaya roots aqueous extract suppressed sodium arsenite-stimulated NO production and proinflammatory secretion, such as CRP. Carica papaya roots aqueous extract significantly (p < 0.05) decrease the activities of iNOS, 8-OHdG, ADA and MDA.

Conclusion: These results indicated that potent inhibition on CRP, NO, iNOS, ADA, 8-OHdG might constitute the anti-inflammatory mechanism of Carica papaya roots aqueous extract.

Combination of HPLC with organic and inorganic mass spectrometry to study the metabolic response of the clam Scrobicularia plana to arsenic exposure

Arsenic is a toxic element extensively studied in the marine environment due to differential toxicological effects of inorganic and organic species. In the present work, the bivalve Scrobicularia plana was exposed to As^V (10 and 100 μg/L) for 14 days to evaluate the metabolic perturbations caused by this element. Arsenic speciation and metabolomic analysis were performed in the digestive gland of the bivalve using two complementary analytical platforms based on inorganic and organic mass spectrometry. It has been observed the greater presence of the innocuous specie arsenobetaine produced in this organism as defense mechanism against arsenic toxicity, although significant concentrations of methylated and inorganic arsenic were also present, depending on the level of arsenic in aqueous media. Complementarily, a metabolomic study based on mass spectrometry and statistical discriminant analysis allows a good classification of samples associated to low and high As(V) exposure in relation to controls. About 15 metabolites suffer significant changes of expression by the presence of As(V): amino acids, nucleotides, energy-related metabolites, free fatty acids, phospholipids and triacylglycerides, which can be related to membrane structural and functional damage. In addition, perturbation of the methylation cycle, associated with the increase of homocysteine and methionine was observed, which enhance the methylation of toxic inorganic arsenic to less toxic dimethylarsenic.

Trace element occurrence in the Pacific oyster Crassostrea gigas from coastal marine ecosystems in Italy

The Pacific oyster is one of the world's most widespread bivalves and a suitable species for biomonitoring trace elements in marine environments thanks to its bioaccumulation ability. As it is also an edible mollusc, concentrations of harmful elements in its tissues must be monitored. For these purposes, 464 wild individuals were collected from 12 sites along the Italian coasts. The concentration of fourteen trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sn, Tl, and Zn) in their tissues was quantified. Among the three heavy metals, cadmium, lead, and mercury, none exceeded the maximum limit for in food set by European Union regulations but Cd in one sample from the Varano Lagoon resulted extremely close to this value. Contamination by Hg of the northern Adriatic and Orbetello Lagoons was also observed. Moreover, there was a positive association between the lagoon's environmental conditions and the bioaccumulation of this element in oysters. Despite the ban instituted 15 years ago on the use of Sn in antifouling paints, this element is still present in several marine environments, as demonstrated in the oysters sampled from harbour areas. Samples collected from harbours also showed very high concentrations of Cu and Zn due to the ability of oysters to accumulate these elements, which have replaced Sn in antifouling paints. Analysis of the samples from most sites indicated a low risk of human exposure to harmful elements through oyster consumption; nonetheless, chemical sanitary controls should focus primarily on Cd, Cu, and Zn.

Speciation analysis of six arsenic species in marketed shellfish: Extraction optimization and health risk assessment

A comparative study between microwave assisted and sonication methods was carried out to extract arsenic (As) species in shellfish samples using different extractants. Six As species including arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC) were simultaneously separated and determined by the HPLC-ICP-MS method. The microwave assisted method exhibited higher efficiency than sonication, especially using diluted HNO₃ as extractant. By compromising extraction efficiency, pretreatment time and stability of As species, the microwave assisted method using 1% HNO₃ at 100°C for 1.5h was selected to extract As from real samples. The proposed method has been applied to extract and determine As species in shellfish samples. The result of correlation analysis indicated that the proportion of AsB in the shellfish samples was decreased with total As concentration increasing due to the biotransformation threshold from inorganic As to AsB.

Environmental epigenetics in zebrafish

It is widely accepted that the epigenome can act as the link between environmental cues, both external and internal, to the organism and phenotype by converting the environmental stimuli to phenotypic responses through changes in gene transcription outcomes. Environmental stress endured by individual organisms can also enforce epigenetic variations in offspring that had never experienced it directly, which is termed transgenerational inheritance. To date, research in the environmental epigenetics discipline has used a wide range of both model and non-model organisms to elucidate the various epigenetic mechanisms underlying the adaptive response to environmental stimuli. In this review, we discuss the advantages of the zebrafish model for studying how environmental toxicant exposures affect the regulation of epigenetic processes, especially DNA methylation, which is the best-studied epigenetic mechanism. We include several very recent studies describing the state-of-the-art knowledge on this topic in zebrafish, together with key concepts in the function of DNA methylation during vertebrate embryogenesis.

Arsenic-contaminated freshwater: assessing arsenate and arsenite toxicity and low-dose genotoxicity in Gammarus elvirae (Crustacea; Amphipoda)

Arsenic (As) contamination of freshwater is largely due to geogenic processes, but As is also released into the environment because of improper anthropic activities. The European regulatory limits in drinking water are of 10 μg L^-1 As. However, knowledge of the genotoxic effects induced by low doses of As in freshwater environments is still scanty. This study was designed to investigate arsenate (As(V)) and arsenite (As(III)) toxicity and low-dose genotoxicity in Gammarus elvirae, which has proved to be a useful organism for genotoxicity assays in freshwater. As(V) and As(III) toxicity was assessed on the basis of the median lethal concentration, LC(50), while estimates of DNA damage were based on the Comet assay. The G. elvirae LC (50-240 h) value we calculated was 1.55 mg L^-1 for As(V) and 1.72 mg L^-1 for As(III). Arsenic exposure (240 h) at 5, 10, and 50 µg L^-1 of As in assays with either arsenate or arsenite-induced DNA damage in hemocytes of G. elvirae in a concentration-dependent manner. Our study provides a basis for future genotoxic research on exposure to freshwater that contains low levels of arsenic.

Arsenic speciation and heavy metal distribution in polished rice grown in Guangdong Province, Southern China

Arsenic speciation and heavy metal distributions have been investigated in locally grown rice grains from Guangdong Province, Southern China. A total of 41 polished rice grain samples were collected throughout Guangdong Province. Arsenite (As(III)), as the predominant form found in the rice, was positively correlated (p<0.01) with total As (tAs) concentration. However, the percentage of As(III) reduced while tAs concentration increased (r=-0.361, p<0.05), due to restricted accumulation and translocation of As(III) in rice grains at high level of tAs. Statistical and geostatistical analyses were applied to investigate potential origins of heavy metals in rice. Only Cd, Cu and Ni were identified as influenced by anthropogenic sources such as industrial and commercial activities. As and Pb were primarily controlled by natural occurrence. The results of health risk assessment implied that continuous intake of rice grown in Guangdong Province could cause considerably non-carcinogenic and carcinogenic risk to local inhabitants.

Developmental exposure to heavy metals alters visually-guided behaviors in zebrafish

This laboratory-based study determined the consequences of heavy metal exposure using zebrafish Danio rerio. Embryos were transiently exposed to environmentally-relevant concentrations of cadmium or nickel until 72 h postfertilization (hpf), then they were returned to system water and allowed to grow until 7, 9, and 11 days postfertilization (dpf), when they were examined morphologically and behaviorally. Morphological measures of notochord length, eye diameter, and inter-eye distance were not different across treatments; however, significant differences in optomotor responses were observed in treated larvae at all ages tested. These results suggest that initial developmental exposure to cadmium and nickel significantly impacts visually-guided larval behavior. The absence of significant differences in gross morphology suggests that the effects of these metals are subtle and may occur at the cellular level. By using this ecologically relevant model and pollutant type, this study has broad application and implications with regard to safe levels of contaminant in drinking water and freshwater ecosystems.

Sustained Early Disruption of Mitochondrial Function Contributes to Arsenic-Induced Prostate Tumorigenesis

Arsenic is a well-known human carcinogen that affects millions of people worldwide, but the underlying mechanisms of carcinogenesis are unclear. Several epidemiological studies have suggested increased prostate cancer incidence and mortality due to exposure to arsenic. Due to lack of an animal model of arsenic-induced carcinogenesis, we used a prostate epithelial cell culture model to identify a role for mitochondria in arsenic-induced prostate cancer. Mitochondrial morphology and membrane potential was impacted within a few hours of arsenic exposure of non-neoplastic prostate epithelial cells. Chronic arsenic treatment induced mutations in mitochondrial genes and altered mitochondrial functions. Human non-neoplastic prostate epithelial cells continuously cultured for seven months in the presence of 5 µM arsenite showed tumorigenic properties in vitro and induced tumors in SCID mice, which indicated transformation of these cells. Protein and mRNA expression of subunits of mtOXPHOS complex I were decreased in arsenic-transformed cells. Alterations in complex I, a main site for reactive oxygen species (ROS) production as well as increased expression of ROS-producing NOX4 in arsenic-transformed cells suggested a role of oxidative stress in tumorigenic transformation of prostate epithelial cells. Whole genome cGH array analyses of arsenic-transformed prostate cells identified extensive genomic instability. Our study revealed mitochondrial dysfunction induced oxidative stress and decreased expression of p53 in arsenic-transformed cells as an underlying mechanism of the mitochondrial and nuclear genomic instability. These studies suggest that early changes in mitochondrial functions are sustained during prolong arsenic exposure. Overall, our study provides evidence that arsenic disruption of mitochondrial function is an early and key step in tumorigenic transformation of prostate epithelial cells.

Zebrafish: A Model for the Study of Toxicants Affecting Muscle Development and Function

The rapid progress in medicine, agriculture, and allied sciences has enabled the development of a large amount of potentially useful bioactive compounds, such as drugs and pesticides. However, there is another side of this phenomenon, which includes side effects and environmental pollution. To avoid or minimize the uncontrollable consequences of using the newly developed compounds, researchers seek a quick and effective means of their evaluation. In achieving this goal, the zebrafish (Danio rerio) has proven to be a highly useful tool, mostly because of its fast growth and development, as well as the ability to absorb the molecules diluted in water through its skin and gills. In this review, we focus on the reports concerning the application of zebrafish as a model for assessing the impact of toxicants on skeletal muscles, which share many structural and functional similarities among vertebrates, including zebrafish and humans.

Chronic Arsenic Exposure and Risk of Post Kala-azar Dermal Leishmaniasis Development in India: A Retrospective Cohort Study

Background

Visceral leishmaniasis (VL), with the squeal of Post-kala-azar dermal leishmaniasis (PKDL), is a global threat for health. Studies have shown sodium stibogluconate (SSG) resistance in VL patients with chronic arsenic exposure. Here, we assessed the association between arsenic exposure and risk of developing PKDL in treated VL patients.

Methods

In this retrospective study, PKDL patients (n = 139), earlier treated with SSG or any other drug during VL, were selected from the study cohort. Trained physicians, unaware of arsenic exposure, interviewed them and collected relevant data in a questionnaire format. All probable water sources were identified around the patient’s house and water was collected for evaluation of arsenic concentration. A GIS-based village-level digital database of PKDL cases and arsenic concentration in groundwater was developed and individual point location of PKDL cases were overlaid on an integrated GIS map. We used multivariate logistic regression analysis to assess odds ratios (ORs) for association between arsenic exposure and PKDL development.

Results

Out of the 429 water samples tested, 403 had arsenic content of over 10 μg/L, with highest level of 432 μg/L among the seven study villages. Multivariate adjusted ORs for risk of PKDL development in comparison of arsenic concentrations of 10.1–200 μg/L and 200.1–432.0 μg/L were 1.85 (1.13–3.03) and 2.31 (1.39–3.8) respectively. Interestingly, similar results were found for daily dose of arsenic and total arsenic concentration in urine sample of the individual. The multivariate-adjusted OR for comparison of high baseline arsenic exposure to low baseline arsenic exposure of the individuals in the study cohort was 1.66 (95% CI 1.02–2.7; p = 0.04).

Conclusion

Our findings indicate the need to consider environmental factors, like long time arsenic exposure, as an additional influence on treated VL patients towards risk of PKDL development in Bihar.

Post-kala-azar dermal leishmaniasis (PKDL) is a sequela of visceral leishmaniasis (VL) that appears after patients have apparently been cured of visceral leishmaniasis; even been reported in patients without a history of VL. Previous clinical and epidemiological data ascertains the main risk factor associated with the development of PKDL is previous treatment for VL with antimonials (SSG); however, PKDL also occurs after treatment with other drugs like paromomycin, miltefosine etc. Here, in light of the risk of arsenic-associated dermal manifestations, we hypothesized that the long term exposure to groundwater arsenic acts as an additional risk factor for development of PKDL in patients treated for VL with SSG or other drugs. Using a cohort, we retrospectively assessed the risk of arsenic in development of PKDL in treated VL patients. Our findings support a significant association and prompts parasites might persist successfully in individuals over-exposed to arsenic and may exhibit features of dermatotropism leading to development of PKDL after treatment for VL. Further research is needed to dissect the mechanistic role of arsenic on VL, as well as PKDL development.

Hormesis effect of trace metals on cultured normal and immortal human mammary cells

An in vitro study was conducted to determine the effects of variable concentrations of trace metals on human cultured mammary cells. Monolayers of human mortal (MCF-12A) and immortal (MDAMB231) mammary epithelial cells were incubated in the absence or presence of increasing concentrations of arsenic (As), mercury (Hg) and copper (Cu) for 24-h, 72-h, 4-d, and 7-d. The MTT assay was used to assess viability for all time periods and cell proliferation was monitored for 4-d and 7-d studies. Monolayers were also labeled with rhodamine-110 (R-6501), Sytox green®, and Celltiter blueTM fluorescent dyes as indicators for intracellular esterase activity, nucleic acid staining, and cell reduction/viability, respectively. Total incubation time with chemical plus dyes was 24 h. For 24-h and 72-h studies, cells were seeded in 96-well plates, after which confluent monolayers were exposed to increasing concentrations of chemicals. For 4-d and 7-d studies, cells were seeded in 12-well plates at 1/3 confluent density (day 0) and exposed to increasing concentrations of metals on day 1. All cells were counted on days 4 and 7. In addition, test medium was removed from select groups of cultures on day 4, replaced with fresh medium in the absence of chemical (recovery studies), and assays were performed on day 7 as above. The data suggest that there is a consistent protective and/or stimulating effect of metals at the lowest concentrations in MCF-12A cells that is not observed in immortal MDA-MB231 cells. In fact, cell viability of MCF-12A cells is stimulated by otherwise equivalent inhibitory concentrations of As, Cu, and Hg on MDA-MB231 cells at 24-h. Whereas As and Hg suppress proliferation and viability in both cell lines after 4-d and 7-d of exposure, Cu enhances cell proliferation and viability of MCF-12A cells. MDA-MB231, however, recover better after 4-days of toxic insult. In addition, nutritional manipulation of media between the cell lines, or pretreatment with penicillamine, did not alter the hormesis effect displayed by MCF- 12A. Growth of these cells however was not maintained in the alternative medium. The study demonstrates that a hormesis effect from trace metals is detectable in cultured mammary cells; fluorescent indicators, however, are not as sensitive as cell proliferation or MTT in recognizing the subtle responses. Also, sensitivity of mammary cells to lower concentrations of Cu, a biologically important trace metal, may play an important role in controlling cellular processes and proliferation. The ability to detect this in vitro phenomenon implies that similar processes, occurring in vivo, may be responsible for the development, induction, or enhancement of human cancers.