Association of inorganic arsenic exposure with liver cancer mortality: A meta-analysis

Occupational arsenic exposure and digestive and head and neck cancers: A systematic review and meta-analysis

Arsenic is a known carcinogen for the lungs, the bladder, and the skin, while systematic evidence on other cancer types is lacking, especially for occupational exposure. Thus, we aimed to systematically summarize current evidence on the association between occupational arsenic exposure and digestive cancers, including head and neck cancer (HNC). We conducted a systematic review on Pubmed, Web of Science, and Embase search engines. We computed pooled relative risks (RRs) and corresponding 95% confidence intervals (CIs) using DerSimonian and Laird random-effects model. Occurrence of publication bias was assessed using contour-enhanced funnel plots and Egger's test. Twenty-two studies on digestive cancers and 11 on HNC were included in the meta-analysis. RRs for the association with occupational exposure to arsenic of 1.23 (95% CI: 1.07-1.40; I2 = 72.3%, p < 0.001) and 1.08 (95% CI: 0.76-1.53; I2 = 76.6%, p < 0.001) for digestive cancer and HNC, respectively, were observed. As for specific cancer types, arsenic was associated with rectal cancer (RR: 1.51; 95% CI: 1.003-2.28; I2 = 37.0%, p = 0.174), but not with other investigated cancer types. No clear evidence of publication bias was found. The results of our study suggest that the observed association between occupational arsenic exposure and digestive cancer might be mainly driven by a positive association for rectal cancer, while arsenic exposure did not appear to be associated with HNC. However, further high-quality studies with detailed assessment of arsenic exposure are warranted to clarify the potential association of arsenic with digestive cancers and HNC.

Predictors of Toxic Metal/Metalloid Exposures Among Mexican Americans in Starr County, Texas

BACKGROUND

Arsenic, cadmium, and lead are toxic elements that widely contaminate our environment. These toxicants are associated with acute and chronic health problems, and evidence suggests that minority communities, including Hispanic/Latino Americans, are disproportionately exposed. Few studies have assessed culturally specific predictors of exposure to understand the potential drivers of racial/ethnic exposure disparities.

OBJECTIVE

We sought to evaluate acculturation measures as predictors of metal/metalloid (hereafter "metal") concentrations among Mexican American adults to illuminate potential exposure sources that may be targeted for interventions.

METHODS

As part of a longitudinal cohort, 510 adults, aged 35 to 69 years, underwent baseline interview, physical examination, and urine sample collection. Self-reported acculturation was assessed across various domains using the Short Acculturation Scale for Hispanics (SASH). Multivariable linear regression was used to assess associations between acculturation and urinary concentrations of arsenic, cadmium, and lead. Ordinal logistic regression was utilized to assess associations between acculturation and a metal mixture score. Lastly, best subset selection was used to build a prediction model for each toxic metal with a combination of the acculturation predictors.

RESULTS

After adjustment, immigration factors were positively associated with arsenic and lead concentrations. For lead alone, English language and American media and food preferences were associated with lower levels. Immigration and parental heritage from Mexico were positively associated with the metal mixture, while preferences for English language, media, and food were negatively associated.

CONCLUSION

Acculturation-related predictors of exposure provide information about potential sources of toxic metals, including international travel, foods, and consumer products. The findings in this research study provide information to empower future efforts to identify and address specific acculturation-associated toxicant exposures in order to promote health equity through clinical guidance, patient education, and public policy.

An overview of the Be Well Home Health Navigator Program to reduce contaminants in well water: Design and methods

BACKGROUND

The Be Well Home Health Navigator Program is a prospective, randomized controlled trial (RCT) implemented to compare a community health navigator program to usual care program to reduce contaminants in drinking water.

DESIGN AND SETTING

This 4-year two-armed RCT will involve well owners in Oregon that have private drinking water wells that contain arsenic, nitrate, or lead above maximum contaminant levels.

INTERVENTION

The intervention leverages the trusted relationship between Cooperative Extension Service (CES) Community Educators and rural well owners to educate, assist and motivate to make decisions and set actionable steps to mitigate water contamination. In this study, CES will serve as home health navigators to deliver: 1) individualized feedback, 2) positive reinforcement, 3) teach-back moments, 4) decision-making skills, 5) navigation to resources, 6) self-management, and 7) repeated contact for shaping and maintenance of behaviors. Usual care includes information only with no access to individual meetings with CES.

MEASURABLE OUTCOMES

Pre-specified primary outcomes include 1) adoption of treatment to reduce exposure to arsenic, nitrate, or lead in water which may include switching to bottled water and 2) engagement with well stewardship behaviors assessed at baseline, and post-6 and 12 months follow-up. Water quality will be measured at baseline and 12-month through household water tests. Secondary outcomes include increased health literacy scores and risk perception assessed at baseline and 6-month surveys.

IMPLICATIONS

The results will demonstrate the efficacy of a domestic well water safety program to disseminate to other CES organizations.

TRIAL REGISTRATION NUMBER

NCT05395663.

Race/ethnicity and sex differences in the association between area-level arsenic exposure concentration and hepatocellular carcinoma (HCC) incidence rates in Texas. An ecological study

INTRODUCTION

Texas has the highest rates of hepatocellular carcinoma (HCC) in the United States. Exposure to toxicants may play a role in liver disease. Several mechanisms of arsenic carcinogenesis have been proposed, however, the evidence in human populations is limited to associations between HCC and ingestion of arsenic-contaminated drinking water. Through an ecological study, we examined associations between ambient arsenic and HCC incidence rates.

METHODS

Primary outcome was HCC incidence rates based on Texas Cancer Registry (TCR) data. Primary exposure of interest was the simulated census-tract level estimate of arsenic exposure concentration (EC) from the U.S. Environmental Protection Agency 2011 National Air Toxics Assessment (NATA). We analyzed the association between the arsenic EC and HCC using the negative binomial Poisson regression model separately for six study groups that were based on race/ethnicity and sex. We adjusted the main analyses for selected characteristics.

RESULTS

Texas has 5265 census tracts and TCR reported 18,235 new ≥20 years old HCC diagnoses between 2007 and 2015. We observed significant differences along racial-ethnic and sex groups while accounting for socioeconomic deprivation, urban/rural residency, and senior residents' health insurance status. Census tracts with the highest arsenic EC had elevated rates of HCC among NH black men (Quintile 5 vs. Quintile 1: IRR = 2.18, 95% CI: 1.66-2.86), NH black women (Quintile 5 vs. Quintile 1: IRR = 1.72, 95% CI: 1.33-2.22) and NH white men (Quintile 5 vs. Quintile 1: IRR = 1.38, 95% CI: 1.24-1.54). The associations in the remaining study groups were either inconsistent or attenuated.

CONCLUSIONS

Our finding suggests a potential inhalation pathway for the Arsenic-HCC association; however, the ecological nature of our study precludes the interpretation of a causal link between exposure to aerial arsenic and HCC. This finding needs to be further examined in cohort studies.

Arsenic and UVR co-exposure results in unique gene expression profile identifying key co-carcinogenic mechanisms

Changes in gene expression underlie many pathogenic endpoints including carcinogenesis. Metals, like arsenic, alter gene expression; however, the consequences of co-exposures of metals with other stressors are less understood. Although arsenic acts as a co-carcinogen by enhancing the development of UVR skin cancers, changes in gene expression in arsenic UVR co-carcinogenesis have not been investigated. We performed RNA-sequencing analysis to profile changes in gene expression distinct from arsenic or UVR exposures alone. A large number of differentially expressed genes (DEGs) were identified after arsenic exposure alone, while after UVR exposure alone fewer genes were changed. A distinct increase in the number of DEGs was identified after exposure to combined arsenic and UVR exposure that was synergistic rather than additive. In addition, a majority of these DEGs were unique from arsenic or UVR alone suggesting a distinct response to combined arsenic-UVR exposure. Globally, arsenic alone and arsenic plus UVR exposure caused a global downregulation of genes while fewer genes were upregulated. Gene Ontology analysis using the DEGs revealed cellular processes related to chromosome instability, cell cycle, cellular transformation, and signaling were targeted by combined arsenic and UVR exposure, distinct from UVR alone and arsenic alone, while others were related to epigenetic mechanisms such as the modification of histones. This result suggests the cellular functions we identified in this study may be key in understanding how arsenic enhances UVR carcinogenesis and that arsenic-enhanced gene expression changes may drive co-carcinogenesis of UVR exposure.

Exposome and unhealthy aging: environmental drivers from air pollution to occupational exposures

The aging population worldwide is facing a significant increase in age-related non-communicable diseases, including cardiovascular and brain pathologies. This comprehensive review paper delves into the impact of the exposome, which encompasses the totality of environmental exposures, on unhealthy aging. It explores how environmental factors contribute to the acceleration of aging processes, increase biological age, and facilitate the development and progression of a wide range of age-associated diseases. The impact of environmental factors on cognitive health and the development of chronic age-related diseases affecting the cardiovascular system and central nervous system is discussed, with a specific focus on Alzheimer's disease, Parkinson's disease, stroke, small vessel disease, and vascular cognitive impairment (VCI). Aging is a major risk factor for these diseases. Their pathogenesis involves cellular and molecular mechanisms of aging such as increased oxidative stress, impaired mitochondrial function, DNA damage, and inflammation and is influenced by environmental factors. Environmental toxicants, including ambient particulate matter, pesticides, heavy metals, and organic solvents, have been identified as significant contributors to cardiovascular and brain aging disorders. These toxicants can inflict both macro- and microvascular damage and many of them can also cross the blood-brain barrier, inducing neurotoxic effects, neuroinflammation, and neuronal dysfunction. In conclusion, environmental factors play a critical role in modulating cardiovascular and brain aging. A deeper understanding of how environmental toxicants exacerbate aging processes and contribute to the pathogenesis of neurodegenerative diseases, VCI, and dementia is crucial for the development of preventive strategies and interventions to promote cardiovascular, cerebrovascular, and brain health. By mitigating exposure to harmful environmental factors and promoting healthy aging, we can strive to reduce the burden of age-related cardiovascular and brain pathologies in the aging population.

Suppressed Histone H3 Lysine 18 Acetylation Is Involved in Arsenic-Induced Liver Fibrosis in Rats by Triggering the Dedifferentiation of Liver Sinusoidal Endothelial Cells

Arsenic pollution is a global environmental concern. Arsenic-induced chronic liver injury and its irreversible outcomes, including liver cirrhosis and liver cancer, threaten the health of residents in arsenic-contaminated areas. Liver fibrosis is a reversible pathological stage in the progression of arsenic-induced chronic liver injury to cirrhosis and liver cancer. The aim of this study is to identify the epigenetic mechanism of arsenic-induced liver fibrosis based on the dedifferentiation of liver sinusoidal endothelial cells (LSECs). Rats were treated with 0.0, 2.5, 5.0, or 10.0 mg/kg sodium arsenite for 36 weeks. Marked fibrotic phenotypes were observed in the rat livers, manifested by hepatic stellate cell activation and an increased extracellular matrix, as well as the deposition of collagen fibers. The reduced fenestrations on the cells' surface and the increased expression of the dedifferentiation marker CD31 corroborated the LSECs' dedifferentiation in the liver tissue, which was also found to be significantly associated with fibrotic phenotypes. We further revealed that arsenic exposure could inhibit the enrichment of histone H3 lysine 18 acetylation (H3K18ac) in the promoters of Fcgr2b and Lyve1, two key genes responsible for maintaining the differentiation phenotype of LSECs. This inhibition subsequently suppressed the genes' expression, promoting LSEC dedifferentiation and subsequent liver fibrosis. In conclusion, arsenic can trigger liver fibrosis by inhibiting H3K18ac-dependent maintenance of LSEC differentiation. These findings uncover a novel mechanism of arsenic-induced liver fibrosis based on a new insight into epigenetically dependent LSEC dedifferentiation.

The association of arsenic exposure with mortality due to cancer, diabetes, Alzheimer's and congenital anomalies using Poisson regression

The present study aims to determine the relationship between the concentration of arsenic in the groundwater of Hamadan province and the mortality rate due to various types of malignancies, congenital anomalies, diabetes mellitus and Alzheimer's. Mortality data due to various causes of death in Hamadan province were collected for five years (2016-2020). Sampling of drinking water was determined in the reference laboratory using polarography method. Poisson regression was used to investigate the relationship between arsenic level and the death rate due to various types of disease, at a significant level (p value < 0.05). According to the results of Poisson regression, among the various causes of death (N = 8042), Alzheimer's 5.94 (3.67-9.61), diabetes mellitus 4.05 (3.5-5.37), congenital malformations 2.98 (1.88-4.72), breast cancer 2.72 (1.56-4.71), leukemia 1.90 (1.24-2.92), stomach cancer 1.64 (1.28-2.10), Liver cancer 1.58 (1.58-2.30), other digestive organs 5.86 (3.38-10.16), meninges and brain cancer 1.57 (1.02-2.41) showed the highest relationship with arsenic contamination. The results of this study could be evidence for a positive and significant relationship between arsenic concentrations and mortality rates due to cancers, diabetes mellitus, Alzheimer disease, and congenital malformations. Therefore, it's necessary to use appropriate water treatment methods to remove arsenic at the source in contaminated areas.

Genotoxicity and mutagenicity in blood and drinking water induced by arsenic in an impacted gold mining region in Colombia

Arsenic (As) is one of the most dangerous substances that can affect human health and long-term exposure to As in drinking water can even cause cancer. The objective of this study was to investigate the concentrations of total As in the blood of inhabitants of a Colombian region impacted by gold mining and to evaluate its genotoxic effect through DNA damage by means of the comet assay. Additionally, the concentration of As in the water consumed by the population as well as the mutagenic activity of drinking water (n = 34) in individuals were determined by hydride generator atomic absorption spectrometry and the Ames test, respectively. In the monitoring, the study population was made up of a group of 112 people, including inhabitants of four municipalities: Guaranda, Sucre, Majagual, and San Marcos from the Mojana region as the exposed group, and Montería as a control group. The results showed DNA damage related to the presence of As in blood (p < 0.05) in the exposed population, and blood As concentrations were above the maximum allowable limit of 1 μg/L established by the ATSDR. A mutagenic activity of the drinking water was observed, and regarding the concentrations of As in water, only one sample exceeded the maximum permissible value of 10 μg/L established by the WHO. The intake of water and/or food containing As is potentially generating DNA damage in the inhabitants of the Mojana region, which requires surveillance and control by health entities to mitigate these effects.

Independent, modified, and interacting effects of long-term noise, extremely low-frequency electromagnetic fields, and shift work exposures on liver enzymes

To quantify long-term independent, modified, and interacting effects of noise, extremely low-frequency electromagnetic fields (ELF-EMFs), and shift work exposures on liver enzymes, a four-year repeated measures study was performed among male workers in a thermal power plant industry from 2016 to 2020. The 8-h equivalent sound pressure levels (Leq) were measured at weighting channels of Z, A, and C for octave-band frequencies. The 8-h time-weighted average of ELF-EMFs levels was measured for each participant. Shift work schedule was determined based on job titles, including 3-rotating night shift work and fixed day shift work schedules. The fasting blood samples were taken to determine liver enzymes (AST, Aspartate transaminase; ALT, Alanine transaminase). The percentage change (PC) and 95% confidence interval (CI) of AST and ALT enzymes were estimated by the different bootstrapped-mixed-effects linear regression models. Per 10-dB noise increase, we found a significantly higher PC (95% CI) of AST and ALT (only LAeq) levels in all regression models with the highest changes for LAeq. For the octave-band noise analysis, there was an upward trend from 31.5 Hz to 1 kHz frequencies and a downward trend from 1 to 8 kHz frequencies. Per 1 mG ELF-EMFs increase, we observed a significantly higher PC (95% CI) of AST and ALT enzymes in the main adjusted and the main adjusted + shift work models. The 3-rotating night than fixed day shift workers had a significant PC in the unadjusted model for AST enzyme and the fully adjusted and the main adjusted + ELF-EMFs models for ALT enzyme. Significant negative two-way or/and three-way interaction effects among the noise, ELF-EMFs, and shift work were observed for both AST and ALT enzymes. Our findings indicated long-term noise, ELF-EMFs, and 3-rotating night shift work exposures may be significantly associated with changes in the levels of liver enzymes.

Carcinogen sodium arsenite disrupts antioxidant and redox homeostasis in Drosophila melanogaster

OBJECTIVES

The inadvertent exposure to environmental contaminants has been reported to induce cancer in different animal models. Here, we investigated the toxicity of Sodium Arsenite (SA), a Class I Carcinogen in Drosophila melanogaster.

METHODS

Harwich fly strain (1-3 days old) of both sexes were orally exposed to SA (0, 0.0312, 0.0625 and 0.125 mM) for 14 days for survival study. Thereafter, 5 days exposure period was selected to assess the toxic effects of SA on oxidative stress and antioxidant markers.

RESULTS

The results indicated that SA induced significant reduction in survival and emergence rate of flies. Furthermore, SA significantly increased Nitric Oxide (NO, nitrite and nitrate) and Hydrogen Peroxide (H2O2) levels in flies compared with control (p<0.05). In addition, SA inhibited catalase and glutathione-S-transferase (GST) activities, and depleted total thiol and glutathione (GSH) contents. Moreover, acetylcholinesterase activity significantly increased in flies treated with SA when compared with control.

CONCLUSIONS

Sodium arsenite-induced reduction in survival and emergence rates of flies occurred via the disruption of oxidative stress-antioxidant homeostasis in D. melanogaster.

Somatic loss of the Y chromosome is associated with arsenic exposure among Bangladeshi men

BACKGROUND

Arsenic exposure increases the risk of several cancers in humans and contributes to genomic instability. Somatic loss of the Y chromosome (LoY) is a potential biomarker of genomic instability and cancer risk. Smoking is associated with LoY, but few other carcinogens have been investigated. We tested the cross-sectional association between arsenic exposure and LoY in leukocytes among genotyped Bangladeshi men (age 20-70 years) from the Health Effects of Arsenic Longitudinal Study.

METHODS

We extracted the median of logR-ratios from probes on the Y chromosome (mLRR-chrY) from genotyping arrays (n = 1364) and estimated the percentage of cells with LoY (% LoY) from mLRR-chrY. We evaluated the association between arsenic exposure (measured in drinking water and urine) and LoY using multivariable linear and logistic regression models. The association between LoY and incident arsenic-induced skin lesions was also examined.

RESULTS

Ten percent of genotyped men had LoY in at least 5% of cells and % LoY increased with age. Among men randomly selected for genotyping (n = 778), higher arsenic in drinking water, arsenic consumed and urinary arsenic were associated with increased % LoY (P = 0.006, P = 0.06 and P = 0.13, respectively). LoY was associated with increased risk of incident skin lesions (P = 0.008).

CONCLUSION

Arsenic exposure was associated with increased LoY, providing additional evidence that arsenic contributes to genomic instability. LoY was associated with developing skin lesions, a risk factor for cancer, suggesting that LoY may be a biomarker of susceptibility in arsenic-exposed populations. The effect of arsenic on somatic events should be further explored in cancer-prone tissue types.

Use of Microbial Consortia in Bioremediation of Metalloid Polluted Environments

Metalloids are released into the environment due to the erosion of the rocks or anthropogenic activities, causing problems for human health in different world regions. Meanwhile, microorganisms with different mechanisms to tolerate and detoxify metalloid contaminants have an essential role in reducing risks. In this review, we first define metalloids and bioremediation methods and examine the ecology and biodiversity of microorganisms in areas contaminated with these metalloids. Then we studied the genes and proteins involved in the tolerance, transport, uptake, and reduction of these metalloids. Most of these studies focused on a single metalloid and co-contamination of multiple pollutants were poorly discussed in the literature. Furthermore, microbial communication within consortia was rarely explored. Finally, we summarized the microbial relationships between microorganisms in consortia and biofilms to remove one or more contaminants. Therefore, this review article contains valuable information about microbial consortia and their mechanisms in the bioremediation of metalloids.

Smoking and passive smoking increases mortality through mediation effect of cadmium exposure in the United States

Cigarette smoking is one of the leading causes of preventable and premature death worldwide. Even worse, many people are generally exposed to passive smoking, which leads to several respiratory diseases and related mortalities. Considering, more than 7000 compounds are included in cigarettes, their combustion results intoxicants that have deleterious effects on health. However, there is a lack of research analyzing the effects of smoking and passive smoking on all-cause and disease-specific mortality through its chemical compounds including heavy metals. Thus, this study aimed to evaluate the effect of smoking and passive smoking on all-cause and disease-specific mortality mediated by cadmium, one of the representative smoking-related heavy metals using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2018 in the United States. We found that current smoking and passive smoking was related to increased risk of all-cause, CVD-related, and cancer-related mortality. Notably, passive smoking showed a synergistic effect with smoking status on the risk of mortality. In particular, current smokers with passive smoking had the highest risk of all-cause and disease-specific deaths. In addition, the accumulation of cadmium in the blood due to smoking and passive smoking mediates the increased risk of all-cause mortality. Further studies are needed to monitor and treat cadmium toxicity to improve smoking-related mortality rates.

Malignant growth of arsenic-transformed cells depends on activated Akt induced by reactive oxygen species

Arsenic is an identified carcinogen for humans.In this study, chronic exposure of human hepatocyte L-02 to low-doses of inorganic arsenic caused cell malignant proliferation. Meanwhile, compared with normal L-02 cells, arsenic-transformed malignant cells, L-02-As displayed more ROS and significantly higher Cyclin D1 expression as well as aerobic glycolysis. Moreover, Akt activation is followed by the upregulation of Cyclin D1 and HK2 expression in L-02-As cells, since inhibition of Akt activity by Ly294002 attenuated the colony formation in soft agar and decreased the levels of Cyclin D1 and HK2. In addition, scavenging of ROS by NAC resulted in a decreased expression of phospho-Akt, HK2 and Cyclin D1, and attenuates the ability of anchorage-independent growth ofL-02-As cells, suggested that ROS mediated the Akt activation in L-02-As cells. In summary, our results demonstrated that ROS contributes to the malignant phenotype of arsenic-transformed human hepatocyte L-02-As via the activation of Akt pathway.

Hyperphosphorylation of EGFR/ERK signaling facilitates long-term arsenite-induced hepatocytes epithelial-mesenchymal transition and liver fibrosis in sprague-dawley rats

Arsenic is a well known environmental hazardous material, chronic arsenic exposure results in different types of liver damage. Among them, liver fibrosis has become a research hotspot because of its reversibility, while the underlying mechanism is still unclear. Previous studies revealed that EGFR/ERK signaling appears to play an important role in fibrosis diseases. In this study, sprague-dawley rats were exposed to different doses of arsenite for 36 weeks to investigate the roles of EGFR/ERK signaling on arsenite-induced liver fibrogenesis. Our results showed that long-term arsenite exposure induced liver fibrosis, accompanied by hepatic stellate cells (HSCs) activation, excessive serum secretion of extracellular matrix (ECM), and hepatocytes epithelial-mesenchymal transformation (EMT). In addition, arsenite exposure caused hyperphosphorylation of EGFR/ERK signaling in liver tissue of rats, indicating that EGFR/ERK signaling may be involved in arsenite-induced liver fibrosis. Indeed, erlotinib (a specific phosphorylation inhibitor of EGFR) intervention significantly decreased arsenite induced hyperphosphorylation of EGFR/ERK signaling, thereby suppressed hepatocytes EMT process and alleviated liver fibrogenesis in arsenite exposed rats. In summary, the present study provides evidences showing that hyperphosphorylation of EGFR/ERK signaling facilitates long-term arsenite-induced hepatocytes EMT and liver fibrosis in rats, which brings new insights into the pathogenesis of arsenic-induced liver injury.

Arsenic and cadmium leaching in co-contaminated agronomic soil and the influence of high rainfall and amendments

Arsenic (As) and cadmium (Cd) co-contaminate agricultural systems worldwide and threaten water resources, food security and human health. This column leaching study examined As and Cd mobility in an acidic sandy loam Alfisol soil collected from the dry zone of Sri Lankafor four co-contaminant concentration combinations (spiked and 1 year aged As at 20 & 100 mg kg^-1 with co-added Cd at 3 & 20 mg kg^-1) i, and under the influence of high rainfall (RF), phosphorus fertilizer (P) and lime amendments. In almost all treatments a synergistic co-contaminant adsorption effect was evident which reduced leaching of both elements, significantly in the higher spiked soil concentration treatments. The magnitude of leaching decrease varied with treatment but was greater for As due to its weaker retention in the soil. The co-sorbing effects, evident even under RF, were attributed to electrostatic sorption interactions, the formation of ternary bridging complexes and surface precipitation at higher concentrations. Liming significantly retarded mobilisation of both elements in all treatments, whereas P enhanced As leaching but suppressed Cd leaching, and both amendments moderated co-contaminant effects. An antagonistic effect of Cd on As sorption was evident in two treatments which showed increased As leaching with added Cd: the RF low spike concentration treatment, accredited to washout of stable As-Cd soluble complexes; the P high concentration treatment considered due to P disruption of As-Cd bridging complexes. This work is important for effective risk mitigation in these widely occurring co-contaminated agronomic systems, and demonstrates a strong system effect on synergistic or antagonistic co-contaminant interactions.

Contemporary Comprehensive Review on Arsenic-Induced Male Reproductive Toxicity and Mechanisms of Phytonutrient Intervention

Arsenic (As) is a poisonous metalloid that is toxic to both humans and animals. Drinking water contamination has been linked to the development of cancer (skin, lung, urinary bladder, and liver), as well as other disorders such as diabetes and cardiovascular, gastrointestinal, neurological, and developmental damage. According to epidemiological studies, As contributes to male infertility, sexual dysfunction, poor sperm quality, and developmental consequences such as low birth weight, spontaneous abortion, and small for gestational age (SGA). Arsenic exposure negatively affected male reproductive systems by lowering testicular and accessory organ weights, and sperm counts, increasing sperm abnormalities and causing apoptotic cell death in Leydig and Sertoli cells, which resulted in decreased testosterone synthesis. Furthermore, during male reproductive toxicity, several molecular signalling pathways, such as apoptosis, inflammation, and autophagy are involved. Phytonutrient intervention in arsenic-induced male reproductive toxicity in various species has received a lot of attention over the years. The current review provides an in-depth summary of the available literature on arsenic-induced male toxicity, as well as therapeutic approaches and future directions.

PIN1-mediated ROS production is involved in antagonism of N-acetyl-L-cysteine against arsenic-induced hepatotoxicity

Arsenic, a widely existing environmental contaminant, is recognized to be toxic to multiple organs. Exposure to arsenic results in liver damage via excessive production of reactive oxidative species (ROS). PIN1 regulates the levels of ROS. N-acetyl-L-cysteine (NAC) is an ROS scavenger that protects the hepatic functions. Whether PIN1 plays a regulatory role in NAC-mediated antagonism against arsenic hepatotoxicity remains largely unknown. In our study, the protective effects of NAC against arsenic (NaAsO2)-induced hepatotoxicity were evaluated in vitro and in vivo. Arsenic exposure induced cytotoxicity by increasing the intracellular ROS production, impairing mitochondrial function and inducing apoptosis in L02 hepatocytes. Overexpression of PIN1 markedly protected against arsenic cytotoxicity, decreased ROS levels, and mitigated mitochondrial dysfunction and apoptosis in L02 cells. However, loss of PIN1 further aggravated arsenic-induced cytotoxicity and abolished the protective effects of NAC in L02 cells. An in vivo study showed that pretreatment with NAC rescued arsenic-induced liver injury by restoring liver function and suppressing hepatic oxidative stress. Overexpression of PIN1 in mice transfected with AAV-Pin1 relieved arsenic-induced liver dysfunction and hepatic oxidative stress. Taken together, our study identified PIN1 as a novel intervention target for antagonizing arsenic-induced hepatotoxicity, highlighting a new pharmacological mechanism of NAC targeting PIN1 in antagonism against arsenic toxicity.

Toenail speciation biomarkers in arsenic-related disease: a feasibility study for investigating the association between arsenic exposure and chronic disease

Long-term exposure to environmental arsenic has been associated with many chronic diseases, including several cancers, and diabetes. Urinary studies have implicated arsenic speciation as an important risk factor, however, such associations have not been replicated using toenail samples: a relatively new biosample for estimating long-term internal dose-exposure to arsenic. Despite having several advantages over conventional biosamples such as ease of collection and storage, standard methods for arsenic speciation analysis in toenails have not yet been established. The primary objectives of this study were to 1) establish an analytical method for arsenic speciation analysis in toenails, 2) describe preliminary arsenic speciation profiles of toenail samples from individuals with skin, lung, bladder, and kidney cancer, type II diabetes, and no known disease, and 3) determine if these speciation patterns differ between disease groups to inform the feasibility of subsequent research. A small cross-sectional feasibility study was carried out using 60 toenail samples and baseline questionnaire data from the Atlantic Partnership for Tomorrow's Health (Atlantic PATH) study. Arsenic speciation profiles were determined using high performance liquid chromatography (HPLC) paired with inductively coupled plasma-mass spectrometry (ICP-MS). While no differences in total arsenic were found, arsenic speciation profiles were significantly different between certain cancer groups and the reference group with no known disease. Specifically, the percentage of monomethylarsonic acid (%MMA) was found to be significantly higher in the toenails of individuals with lung cancer and kidney cancer, compared to healthy individuals with similar total arsenic exposure. To the best of our knowledge, this is the first study to describe arsenic speciation patterns in individuals with several arsenic-related diseases using toenails: a convenient, non-invasive, biobankable sample capable of longer-term exposure estimation than conventional biosamples. These preliminary data provide evidence that toenail arsenic speciation patterns differ between groups with arsenic-related disease, and those with no known disease. Toenail arsenic speciation analysis is feasible and could potentially have important implications for research on arsenic-related diseases. Further investigation is warranted and would benefit from including detailed arsenic exposure data to explore the observed heterogeneity in arsenic speciation profiles.

Nanomaterials as adsorbents for As(III) and As(V) removal from water: A review

Freshwater demand will rise in the next couple of decades, with an increase in worldwide population growth and industrial development. The development activities, on one side, have increased the freshwater demand. However, the ground water has been degraded. Among the various organic and inorganic contaminants, arsenic is one of the most toxic elements. Arsenic contamination in ground waters is a major issue worldwide, especially in South and Southeast Asia. Various methods have been applied to provide a remedy to arsenic contamination, including adsorption, ion exchange, oxidation, coagulation-precipitation and filtration, and membrane filtration. Out of these methods, adsorption of As(III)/As(V) using nanomaterials and biopolymers has been used on a wide scale. The present review focuses on recently used nanomaterials and biopolymer composites for As(III)/As(V) sorptive removal. As(III)/As(V) adsorption mechanisms have been explored for various sorbents. The impacts of environmental factors such as pH and co-existing ions on As(III)/As(V) removal, have been discussed. Comparison of various nanosorbents and biopolymer composites for As(III)/As(V) adsorption and regeneration of exhausted materials has been included. Overall, this review will be useful to understand the sorption mechanisms involved in As(III)/As(V) removal by nanomaterials and biopolymer composites and their comparative sorption performances.

Assessing heavy metal contamination in soils using improved weighted index (IWI) and their associated human health risks in urban, wetland, and agricultural soils

Contamination of nine heavy metals (HMs) Zn, Pb, Cu, Cd, As, Co, Cr, Mo, and Ni in agricultural, urban, and wetland soils from Western and Rift Valley parts of Kenya was assessed using improved weighted index (IWI) and pollution loading index (PLI). Non-carcinogenic risks posed by the HMs were assessed using hazard quotients (HQ) and hazard index (HI), while carcinogenic risks were assessed using cancer risks (CR) and total cancer risks (TCR). The average concentration of Zn, Cr, Ni, Pb, Co, Cu, As, Mo, and Cd was 94.7 mg/kg, 43.6 mg/kg, 22.3 mg/kg, 21.0 mg/kg, 19.8 mg/kg, 18.0 mg/kg, 16.3 mg/kg, 1.83 mg/kg, and 1.16 mg/kg, respectively. IWI ranged from 0.57 to 6.04 and categorized 6.82% of the study sites as not polluted, 27.3% as slightly polluted, 43.2% as moderately polluted, and 22.7% as seriously polluted. PLI ranged from 0.38 to 3.95 and classified 15.9% of the sites as not polluted, 61.4% as slightly polluted, 20.5% as moderately polluted, and only 2.3% as seriously polluted. Wetlands retained more HMs from both urban and agricultural runoff and were therefore the most polluted. The heavy metals did not pose any risks via inhalation and dermal contact, but HQingestion for As for children was >1 in 2.3% of the sites studied. CR via ingestion and TCR for As were above the allowable limits for children and adults indicating high risks of cancer. Intensive agriculture and urbanization should be closely monitored to prevent further HM pollution.

Combined pollution of arsenic and Polymyxin B enhanced arsenic toxicity and enriched ARG abundance in soil and earthworm gut microbiotas

Polymyxin B (PMB) is considered as the last line of antibiotic defense available to humans. The environmental effects of the combined pollution with PMB and heavy metals and their interaction mechanisms are unclear. We explored the effects of the combined pollution with PMB and arsenic (As) on the microbial composition of the soil and in the earthworm gut, as well as the spread and transmission of antibiotic resistance genes (ARGs). The results showed that, compared with As alone, the combined addition of PMB and As could significantly increase the bioaccumulation factor and toxicity of As in earthworm tissues by 12.1% and 16.0%, respectively. PMB treatment could significantly increase the abundance of Actinobacteria in the earthworm gut (from 35.6% to 45.2%), and As stress could significantly increase the abundance of Proteobacteria (from 19.8% to 56.9%). PMB and As stress both could significantly increase the abundance of ARGs and mobile genetic elements (MGEs), which were positively correlated, indicating that ARGs might be horizontally transferred. The inactivation of antibiotics was the main resistance mechanism that microbes use to resist PMB and As stress. Network analysis showed that PMB and As might have antagonistic effects through competition with multi-drug resistant ARGs. The combined pollution by PMB and As significantly promoted the relative abundance of microbes carrying multi-drug resistant ARGs and MGEs, thereby increasing the risk of transmission of ARGs. This research advances the understanding of the interaction mechanism between antibiotics and heavy metals and provides new theoretical guidance for the environmental risk assessment and combined pollution management.

Integration of Epigenetic Mechanisms into Non-Genotoxic Carcinogenicity Hazard Assessment: Focus on DNA Methylation and Histone Modifications

Epigenetics involves a series of mechanisms that entail histone and DNA covalent modifications and non-coding RNAs, and that collectively contribute to programing cell functions and differentiation. Epigenetic anomalies and DNA mutations are co-drivers of cellular dysfunctions, including carcinogenesis. Alterations of the epigenetic system occur in cancers whether the initial carcinogenic events are from genotoxic (GTxC) or non-genotoxic (NGTxC) carcinogens. NGTxC are not inherently DNA reactive, they do not have a unifying mode of action and as yet there are no regulatory test guidelines addressing mechanisms of NGTxC. To fil this gap, the Test Guideline Programme of the Organisation for Economic Cooperation and Development is developing a framework for an integrated approach for the testing and assessment (IATA) of NGTxC and is considering assays that address key events of cancer hallmarks. Here, with the intent of better understanding the applicability of epigenetic assays in chemical carcinogenicity assessment, we focus on DNA methylation and histone modifications and review: (1) epigenetic mechanisms contributing to carcinogenesis, (2) epigenetic mechanisms altered following exposure to arsenic, nickel, or phenobarbital in order to identify common carcinogen-specific mechanisms, (3) characteristics of a series of epigenetic assay types, and (4) epigenetic assay validation needs in the context of chemical hazard assessment. As a key component of numerous NGTxC mechanisms of action, epigenetic assays included in IATA assay combinations can contribute to improved chemical carcinogen identification for the better protection of public health.

Health Effects Associated With Pre- and Perinatal Exposure to Arsenic

Inorganic arsenic is a well-established human carcinogen, able to induce genetic and epigenetic alterations. More than 200 million people worldwide are exposed to arsenic concentrations in drinking water exceeding the recommended WHO threshold (10μg/l). Additionally, chronic exposure to levels below this threshold is known to result in long-term health effects in humans. The arsenic-related health effects in humans are associated with its biotransformation process, whereby the resulting metabolites can induce molecular damage that accumulates over time. The effects derived from these alterations include genomic instability associated with oxidative damage, alteration of gene expression (including coding and non-coding RNAs), global and localized epigenetic reprogramming, and histone posttranslational modifications. These alterations directly affect molecular pathways involved in the onset and progression of many conditions that can arise even decades after the exposure occurs. Importantly, arsenic metabolites generated during its biotransformation can also pass through the placental barrier, resulting in fetal exposure to this carcinogen at similar levels to those of the mother. As such, more immediate effects of the arsenic-induced molecular damage can be observed as detrimental effects on fetal development, pregnancy, and birth outcomes. In this review, we focus on the genetic and epigenetic damage associated with exposure to low levels of arsenic, particularly those affecting early developmental stages. We also present how these alterations occurring during early life can impact the development of certain diseases in adult life.

Main nitric oxide (NO) hallmarks to relieve arsenic stress in higher plants

Arsenic (As) is a toxic metalloid that adversely affects plant growth, and poses severe risks to human health. It induces disturbance to many physiological and metabolic pathways such as nutrient, water and redox imbalance, abnormal photosynthesis and ATP synthesis and loss of membrane integrity. Nitric oxide (NO) is a free radical molecule endogenously generated in plant cells which has signalling properties. Under As-stress, the endogenous NO metabolism is significantly affected in a clear connection with the metabolism of reactive oxygen species (ROS) triggering nitro-oxidative stress. However, the exogenous NO application provides beneficial effects under As-stress conditions which can relieve oxidative damages by stimulating the antioxidant systems, regulation of the expression of the transporter and other defence-related genes, modification of root cell wall composition or the biosynthesis of enriched sulfur compounds such phytochelatins (PCs). This review aims to provide up-to-date information on the key NO hallmarks to relieve As-stress in higher plants. Furthermore, it will be analyzed the diverse genetic engineering techniques to increase the endogenous NO content which could open new biotechnological applications, especially in crops under arsenic stress.

Liver cancer mortality over six decades in an epidemic area: what we have learned

BACKGROUND AND AIMS

Liver cancer is one of the most dominant malignant tumors in the world. The trends of liver cancer mortality over the past six decades have been tracked in the epidemic region of Qidong, China. Using epidemiological tools, we explore the dynamic changes in age-standardized rates to characterize important aspects of liver cancer etiology and prevention.

METHODS

Mortality data of liver cancer in Qidong from 1958 to 1971 (death retrospective survey) and from 1972 to 2017 (cancer registration) were tabulated for the crude rate (CR), and age-standardized rate and age-birth cohorts. The average annual percentage change was calculated by the Joinpoint Regression Program.

RESULTS

The natural death rate during 1958-2017 decreased from 9‰ to 5.4‰ and then increased to 8‰ as the population aged; cancer mortality rates rose continuously from 57/105 to 240/105. Liver cancer mortality increased from 20/105 to 80/105, and then dropped to less than 52/105 in 2017. Liver cancer deaths in 1972-2017 accounted for 30.53% of all cancers, with a CR of 60.48/105, age-standardized rate China (ASRC) of 34.78/105, and ASRW (world) of 45.71/105. Other key features were the CR for males and females of 91.86/105 and 29.92/105, respectively, with a sex ratio of 3.07:1. Period analysis showed that the ASRs for mortality of the age groups under 54 years old had a significant decreasing trend. Importantly, birth cohort analysis showed that the mortality rate of liver cancer in 40-44, 35-39, 30-34, 25-29, 20-24, 15-19 years cohort decreased considerably, but the rates in 70-74, and 75+ increased.

CONCLUSIONS

The crude mortality rate of liver cancer in Qidong has experienced trends from lower to higher levels, and from continued increase at a high plateau to most recently a gradual decline, and a change greatest in younger people. Many years of comprehensive prevention and intervention measures have influenced the decline of the liver cancer epidemic in this area. The reduction of intake levels of aflatoxin might be one of the most significant factors as evidenced by the dramatic decline of exposure biomarkers in this population during the past three decades.

Spatial assessment of heavy metals contamination in household garden soils in rural Limpopo Province, South Africa

Heavy metal pollution in soil poses a serious health threat to humans living in close proximity and in contact with contaminated soil. Exposure to heavy metals can result in a range of adverse health effects, including skin lesions, cardiovascular effects, lowering of IQ scores and cancers. The main objectives of this study were to (1) use a portable XRF spectrophotometer to measure concentrations of lead (Pb), arsenic (As), mercury (Hg) and cadmium (Cd) in residential soils in rural Giyani in the Limpopo province of South Africa; (2) to assess the spatial distribution of soil metal concentrations; and (3) to assess pollution levels in residential soils. There were elevated levels of As at one of the sites where 54% of soil samples exceeded the Canadian reference levels for As of 20 mg/kg. Using the geoaccumulation index (I_geo) to determine contamination levels of As, 57% of soil samples from the most polluted site were found to be moderately to heavily and extremely contaminated with As (I_geo class 2-5). The site is located near the Giyani Greenstone Belt, which is characterized by abandoned mines and artisanal mining activities. Gold ores are closely associated with sulphide minerals such as arsenopyrite, and these have been found to contain high amounts of As. This study highlighted the potential for soil contamination and the importance of site-specific risk assessment in the context of environment and health impact assessments prior to major developments, including human settlement developments.

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.

Epigenetic effects of low-level sodium arsenite exposure on human liver HepaRG cells

Chronic exposure to inorganic arsenic is associated with a variety of adverse health effects, including lung, bladder, kidney, and liver cancer. Several mechanisms have been proposed for arsenic-induced tumorigenesis; however, insufficient knowledge and many unanswered questions remain to explain the integrated molecular pathogenesis of arsenic carcinogenicity. In the present study, using non-tumorigenic human liver HepaRG cells, we investigated epigenetic alterations upon prolonged exposure to a noncytotoxic concentration of sodium arsenite (NaAsO₂). We demonstrate that continuous exposure of HepaRG cells to 1 µM sodium arsenite (NaAsO₂) for 14 days resulted in substantial cytosine DNA demethylation and hypermethylation across the genome, among which the claudin 14 (CLDN14) gene was hypermethylated and the most down-regulated gene. Another important finding was a profound loss of histone H3 lysine 36 (H3K36) trimethylation, which was accompanied by increased damage to genomic DNA and an elevated de novo mutation frequency. These results demonstrate that continuous exposure of HepaRG cells to a noncytotoxic concentration of NaAsO₂ results in substantial epigenetic abnormalities accompanied by several carcinogenesis-related events, including induction of epithelial-to-mesenchymal transition, damage to DNA, inhibition of DNA repair genes, and induction of de novo mutations. Importantly, this study highlights the intimate mechanistic link and interplay between two fundamental cancer-associated events, epigenetic and genetic alterations, in arsenic-associated carcinogenesis.

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.

Effect of Indigenous Microbial Consortium on Bioleaching of Arsenic from Contaminated Soil by Shewanella putrefaciens

The effects of indigenous microbial consortium on removal of As from As-contaminated soil using an Fe(III)-reducing bacterium Shewanella putrefaciens were investigated under circumneutral pH condition. Sequential extraction of As revealed that more than 30% of As was associated with Fe(III)-(oxy)hydroxides in the soil. Bioleaching experiments were conducted anaerobically with a supply of lactate as a carbon source. The highest As removal efficiency (57.5%) was obtained when S. putrefaciens and indigenous bacterial consortium coexisted in the soil. S. putrefaciens and indigenous bacteria solely removed 30.1% and 16.4% of As from the soil, respectively. The combination of S. putrefaciens and indigenous bacteria led to a higher amount of labile As after microbial dissolution of Fe(III)-(oxy)hydroxides. After microbial treatment, soil quality represented by pH and organic content appeared to be preserved. The results indicated that the ecological and physiological understanding of the indigenous microbiome might be important for the efficient application of bioleaching technology to remove As from contaminated soils.

Assessment of risk factors, and racial and ethnic differences in hepatocellular carcinoma

Despite improved screening and surveillance guidelines, significant race/ethnicity‐specific disparities in hepatocellular carcinoma (HCC) continue to exist and disproportionately affect minority and disadvantaged populations. This trend indicates that social determinants, genetic, and environmental factors are driving the epidemic at the population level. Race and geography had independent associations with risk of mortality among patients with HCC. The present review discusses the risk factors and issues related to disparities in HCC. The underlying etiologies for these disparities are complex and multifactorial. Some of the risk factors for developing HCC include hepatitis B (HBV) and hepatitis C (HCV) viral infection, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, smoking and alcohol consumption. In addition, population genetics; socioeconomic and health care access; treatment and prevention differences; and genetic, behavioral, and biological influences can contribute to HCC. Acculturation of ethnic minorities, insurance status, and access to health care may further contribute to the observed disparities in HCC. By increasing awareness, better modalities for screening and surveillance, improving access to health care, and adapting targeted preventive and therapeutic interventions, disparities in HCC outcomes can be reduced or eliminated.

Positive Association of Cardiovascular Disease (CVD) with Chronic Exposure to Drinking Water Arsenic (As) at Concentrations below the WHO Provisional Guideline Value: A Systematic Review and Meta-Analysis

To the best of our knowledge, a dose-response meta-analysis of the relationship between cardiovascular disease (CVD) and arsenic (As) exposure at drinking water As concentrations lower than the WHO provisional guideline value (10 µg/L) has not been published yet. We conducted a systematic review and meta-analyses to estimate the pooled association between the relative risk of each CVD endpoint and low-level As concentration in drinking water both linearly and non-linearly using a random effects dose-response model. In this study, a significant positive association was found between the risks of most CVD outcomes and drinking water As concentration for both linear and non-linear models (p-value for trend < 0.05). Using the preferred linear model, we found significant increased risks of coronary heart disease (CHD) mortality and CVD mortality as well as combined fatal and non-fatal CHD, CVD, carotid atherosclerosis disease and hypertension in those exposed to drinking water with an As concentration of 10 µg/L compared to the referent (drinking water As concentration of 1 µg/L) population. Notwithstanding limitations included, the observed significant increased risks of CVD endpoints arising from As concentrations in drinking water between 1 µg/L and the 10 µg/L suggests further lowering of this guideline value should be considered.

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.

The Azorean edible abalone Haliotis tuberculata, an alternative heavy metal-free marine resource?

Abalones are considered a delicacy and exploited for food worldwide. In many places, overfishing has led to the decimation of wild stocks and many are now reared in aquaculture systems. In the Azores, there is no tradition of eating abalones and Haliotis tuberculata stocks are still virtually untouched. However, as tourism in the islands grows and the stocks of other shellfish diminish, there is an increasing pressure to find alternative edible resources, leading to a rising interest in abalones. According to previous studies performed in the region, other edible species, including the local highly appreciated limpets and the giant barnacle, present high concentration levels of some heavy metals, which has been attributed to the volcanic origin of the islands. Here we analysed the metal content in the edible tissue of Haliotis tuberculata from São Miguel Island, Azores. The potential human health risks due to its consumption was assessed by estimating the average daily intake (EDI) and target hazard quotient (THQ) of metals. Similarly to other organisms in the Azores, abalones have higher than normal levels of some heavy metals, particularly cadmium, reflecting a local natural source that should be closely monitored from a public health point of view.

SO2 derivatives and As co-exposure promote liver cancer metastasis through integrin αvβ3 activation

Arsenic (As) and sulfur dioxide (SO₂) are two environmental pollutants that have been shown to promote the development of human cancer. In recent years, due to increased pollution, humans are often exposed to SO₂, in addition to As. Despite the development and implementation of standards for environment and air quality, cases of disease caused by As or SO₂ continue to rise alarmingly. It is currently unknown whether simultaneous exposure to As and SO₂ results in increased cancer promoting activity. In this study, concentrations of As and SO₂ below the limits established by the world health organization (WHO) in force environmental standards (concentrations of As should be lower than 1×10^-2 mg/L and SO₂ should be lower than 50 μg/m³), were employed to investigate possible, long-term, synergistic effects of As and SO₂, by using cell-based assays. We found that co-exposure to these pollutants significantly promotes HepG2 cancer cell migration, while As or SO₂ alone have no remarkable effects. Integrins αvβ3 play a key role in this process, as cilengitide, an integrin αvβ3 inhibitor, substantially prevented As and SO₂-induced cell migration. MMPs, IL-8, and TGF-β were also involved in the induced cell migration. In summary, combined exposure to As and SO₂ promotes integrin-dependent cell migration and may be of relevance for the activation of mechanisms underlying liver cancer progression.

Akt Regulated Phosphorylation of GSK-3β/Cyclin D1, p21 and p27 Contributes to Cell Proliferation Through Cell Cycle Progression From G1 to S/G2M Phase in Low-Dose Arsenite Exposed HaCat Cells

Arsenic is a toxic environmental contaminant. Long-term exposure to arsenic through drinking water induces human cancers. However, it is as yet uncertain about the mechanisms of arsenic induced carcinogenesis. Although the effects of low-dose arsenicals on proliferation and cell cycle have been revealed by short time exposure, the evidences for long-term exposure were seldom reported. The detailed mechanism has been unclear and supplemented constantly. In the present study, we used normal human keratinocytes (HaCat) to study the effects of long-term, low-dose sodium arsenite (NaAsO₂) exposure on cell proliferation with emphasis on the Akt regulated cell cycle signaling pathways. Treatment of NaAsO₂ resulted in increased cell proliferation and promotion of cell cycle progression from G1 to S/G2M phase, both of which could be attenuated by MK2206, a highly selective inhibitor of Akt. Along with the increased expression of phospho-Akt (p-Akt, Ser 473), increased expression of p-GSK-3β (Ser 9), p-p21 (Thr 145), p-p27 (Thr 157) and total cyclin D1, and decreased expression of p-cyclin D1 (Thr 286), p21 and p27 were also found in the NaAsO₂ exposed cells. Treatment of MK2206 markedly reversed the expression of all of the above proteins. Our findings indicated that the phosphorylated activation of Akt played a role in the proliferation of HaCat cells upon long-term, low-dose NaAsO₂ exposure through the phosphorylative regulation of its downstream cell cycle regulating factors of GSK-3β/cyclin D1, p21 and p27, which could induce the promotion of cell cycle progression from G1 to S/G2M phase.

Using disability-adjusted life years to estimate the cancer risks of low-level arsenic in drinking water

Recent studies have shown that long-term exposure to low-level arsenic (<10 μg/L) may cause human health problems. However, the induced cancer risks and differences among multisite cancers have not been well-understood. In this study, the concentrations of low-level arsenic in drinking water in XP city, Northwest China were investigated. A health risk assessment was carried out for different age groups and exposure pathways based on Monte Carlo simulations and disability-adjusted life years (DALYs). The measured arsenic levels were in the range of 7.61-9.25 μg/L with a mean of 8.23 μg/L. For the public, the average total lifetime cancer risk was 3.87 × 10^-4, and the total DALYs estimation for all age groups was 20.58 person-year. The average individual DALYs lost was 3.35 × 10^-5 per person-year (ppy), which was 33.5 times the reference value (1.00 × 10^-6 ppy). The mortality burden had a considerably larger contribution (97.31%) to the total disease burden, and the 60-65-year age group exhibited the largest DALYs lost. Skin cancer exhibited the largest burden of 2.15 × 10^-5 ppy, followed by lung cancer (1.20 × 10^-5 ppy). This study might be useful for potential strategies of risk control and management in XP drinking water.

Arsenic and sulfur dioxide co-exposure induce renal injury via activation of the NF-κB and caspase signaling pathway

Although emerging evidence suggests positive association of arsenic (As) or sulfur dioxide (SO₂) exposure with human diseases, reports concerning the effects of co-exposure of As and SO₂ are lacking. Moreover, there is insufficient information in the literature about As and SO₂ co-exposure to renal injury. In this study, we focus on the environmental problems of excessive As and SO₂ that co-exist in many coal consumption areas. We used both C57BL/6 mice and 293T cells to detect toxicities of As and SO₂ exposure alone or in combination. Our results showed that co-exposure significantly increased the hazard compared with exposure to As or SO₂ alone. Mouse kidney tissue slices showed that co-exposure caused more severe diffuse sclerosing glomerulonephritis than As and SO₂ exposure alone. Meanwhile experiments showed that apoptosis was aggravated by co-exposure of As and SO₂ in 293T cells. Because As and SO₂ cause cell toxicity through increasing oxidative stress, next we detected ROS and other oxidative stress parameters, and the results showed oxidative stress was increased by co-exposure compared with the other three groups. The expression levels of downstream genes in the NF-κB and caspase pathways were higher in the co-exposure group than in the groups of As or SO₂ exposure alone in mice and 293T cells. Based on the above results, co-exposure could induce higher toxicity in vitro and in vivo compared with single exposure to As or SO₂, indicating that people living in places that contaminated by As and SO₂ may have higher chance to get renal injury.

Chronic Oral Arsenic Exposure and Its Correlation with Serum S100B Concentration

Arsenic is one of the most important environmental pollutants especially in drinking water. The S100B protein is presented as a sensitive biomarker for assessment of the blood-brain barrier integrity previously. The objective of this study was to determine the impact of chronic arsenic exposure in drinking water and serum S100B correlation. Fifty-four male BALB/c mice were randomly divided into three groups. Group I and II subjects were treated with arsenic trioxide (1 ppm and 10 ppm, respectively), while the rest received normal drinking water. Arsenic concentration in serum and brain was measured by an atomic absorption spectrometer (Varian model 220-Z) conjugated with a graphite furnace atomizer (GTA-110). Also, a serum S100B protein concentration was determined using commercial ELISA kit during different times of exposure. It was observed that body weight gain was significantly lower from the 10th week onwards in arsenic-treated subjects. However, it did not induce any visible clinical signs of toxicity. Measured arsenic level in serum and brain was higher in espoused groups as compared to the control subjects (p < 0.001 and p < 0.0001, respectively). In addition, serum S100B content was increased over a period of 3 months and had significant differences as compared to the control and 1-ppm group especially after 3 months of exposure in the 10-ppm group (p < 0.0001). In conclusion, it could be inferred that long-term arsenic exposure via drinking water leads to brain arsenic accumulation with serum S100B elevated concentration as a probable BBB disruption consequence.

Cellular and Molecular Effects of Prolonged Low-Level Sodium Arsenite Exposure on Human Hepatic HepaRG Cells

Inorganic arsenic is a human carcinogen associated with several types of cancers, including liver cancer. Inorganic arsenic has been postulated to target stem cells, causing their oncogenic transformation. This is proposed to be one of the key events in arsenic-associated carcinogenesis; however, the underlying mechanisms for this process remain largely unknown. To address this question, human hepatic HepaRG cells, at progenitor and differentiated states, were continuously treated with a noncytotoxic concentration of 1 μM sodium arsenite (NaAsO2). The HepaRG cells demonstrated active intracellular arsenite metabolism that shared important characteristic with primary human hepatocytes. Treatment of proliferating progenitor-like HepaRG cells with NaAsO2 inhibited their differentiation into mature hepatocyte-like cells, up-regulated genes involved in cell growth, proliferation, and survival, and down-regulated genes involved in cell death. In contrast, treatment of differentiated hepatocyte-like HepaRG cells with NaAsO2 resulted in enhanced cell death of mature hepatocyte-like cells, overexpression of cell death-related genes, and down-regulation of genes in the cell proliferation pathway, while biliary-like cells remained largely unaffected. Mechanistically, the cytotoxic effect of arsenic on mature hepatocyte-like HepaRG cells may be attributed to arsenic-induced dysregulation of cellular iron metabolism. The inhibitory effect of NaAsO2 on the differentiation of progenitor cells, the resistance of biliary-like cells to cell death, and the enhanced cell death of functional hepatocyte-like cells resulted in stem-cell activation. These effects favored the proliferation of liver progenitor cells that can serve as a source of initiation and driving force of arsenic-mediated liver carcinogenesis.

Chronic low dose arsenic exposure preferentially perturbs mitotic phase of the cell cycle

Environmental pollution is a big challenge for human survival. Arsenic compounds are well-known biohazard, the exposure of which is closely linked to onsets of various human diseases, particularly cancers. Upon chronically exposing to arsenic compounds, genomic integrity is often disrupted, leading to tumor development. However, the underlying mechanisms by which chronic, low dose arsenic exposure targets genetic stability to initiate carcinogenesis still remain not fully understood. In this study, human lung epithelial BEAS-2B cells and keratinocytes were treated with 0.5 μM of sodium arsenite for one month (designated as BEAS-2B-SA cells or keratinocytes-SA), and its effect on cell cycle responses was analyzed. After being arrested in mitotic phase of the cell cycle by nocodazole treatment, BEAS-2B-SA cells or keratinocytes-SA were delayed to enter next cytokinesis. The lagging exit of the cells from mitosis was accompanied by a sustained Plk1 phosphorylation, which led to a persistent activation of the mitotic regulators BubR1 and Cdc27. As the result, cyclin B1 (clnB1) degradation was attenuated. BEAS-2B-SA cells or keratinocytes-SA also expressed a constitutively active Akt. The cytogenetic analysis showed an increased numbers of aneuploidy in these cells. The suppression of Akt reversed the aberrant expressions of the mitotic regulators, delay of mitotic exit as well as chromosomal aberrations. Our findings suggest that a long-term exposure to low dose sodium arsenite aberrantly retains the catenation of mitosis, which facilitates establishing genetic instability and predisposes the cells to tumorigenesis.

Estimating and comparing the cancer risks from THMs and low-level arsenic in drinking water based on disability-adjusted life years

To determine the priority hazard in drinking water, disability-adjusted life years (DALYs) method was used to evaluate the disease burden induced by trihalomethanes (THMs) and low-level arsenic through multiple exposure routes based on the two-year sampling from drinking water in Xi'an city, Northwest China. The average concentrations of chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), bromoform (TBM) and arsenic were 12.67 μg/L, 1.42 μg/L, 0.60 μg/L, 0.13 μg/L and 1.00 μg/L, respectively, and the total lifetime cancer risks for all THMs and arsenic were 8.54 × 10^-6 and 4.02 × 10^-5, which were 8.54 and 40.2 times of the negligible risk level (1.00 × 10^-6), respectively. The DALYs estimation showed that the total DALYs lost for all age groups was 32.62 person-year, and the average individual DALYs lost was 4.77 × 10^-6 per person-year (ppy), which was 4.77 times of the reference level (1.00 × 10^-6 ppy). About 72.07% of the total disease burden was due to arsenic, which was considered to be the priority hazard in Xi'an drinking water. The age group of 75-80 years was found to be most vulnerable to the induced cancer risk, and skin cancer had the highest disease burden (2.24 × 10^-6 ppy). Due to the relatively high incidence rates of lung cancer and skin cancer, most DALYs lost for males were 2-4 times to that for females in the same age group. Oral ingestion made the most contribution (88.58%) to the total disease burden, followed by inhalation of THMs (11.30%), whereas dermal absorption showed negligible risk (0.12%). As the first to compare the cancer risks of arsenic and THMs to the public in DALYs in China, this study might be useful for potential strategies of risk control and management of hazardous agents in drinking water.

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

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

Bioaccumulation of As, Hg, and Se in tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific: tissue distribution and As speciation

With the aim of knowing the distribution of As, Hg, and Se in skipjack (Katsuwonus pelamis, Linnaeus, 1758) and yellowfin tuna (Thunnus albacares, Bonnaterre, 1788) from the Eastern Pacific, elemental concentrations were determined in the muscle and liver; As species were also analyzed in the stomach content. Additionally, health risk for consumers was assessed. For both tunas, levels of As and Se were significantly higher (p < 0.05) in the liver than in the muscle. In K. pelamis, Hg concentrations in the muscle were significantly higher (p < 0.05) than those in the liver. In T. albacares, As, Hg, and Se showed a trend to increase with fish dimensions. Arsenic extractability was better in the muscle than in the liver of both species; in K. pelamis, As species were better extracted than in T. albacares. In both tuna species, the most extractable arsenic was arsenobetaine (AsB) and a minor part was dimethylarsinic acid (DMA). The liver contained mainly AsB with some DMA and arsenocholine (AsC). Hazard indexes (HI) indicated no risk from Hg and Se intake through these tuna species. Considering the individual contribution to the HI, Hg contributed more (80 to 86%) than Se. In the context of health risk, none of the As and Hg values were above the permissible limits; however, two samples of T. albacares (9%) and three samples of K. pelamis (12%) had Se concentrations over the limits. If Hg and Se in the edible portion of tuna are considered under the approach of the HBV_Se, tuna consumption is beneficial.

Alleviation of Arsenic-Induced Pulmonary Oxidative Damage by GSPE as Shown during In vivo and In vitro Experiments

A long-term exposure to arsenic may lead to lung damage due to oxidative stress. In this context, GSPE can play a major role as a strong antioxidant. Our study attempted to reveal the connection between arsenic-induced lung injury and the antagonistic effect of GSPE. For this purpose, BEAS-2B cells and Kunming mice were exposed to different dosages of As₂O₃ and GSPE. Oxidative stress indicators were detected both in vivo and in vitro. Cell survival rate and morphological changes in the lung tissue (H&E staining) were evaluated as well. It was exhibited that As₂O₃ increased oxidative stress both in vivo and in vitro and decreased cells viability. In contrast, higher cell survival rate was revealed in the group treated with arsenic plus GSPE after 24 h as compared to that in the arsenic group. GSPE effectively reduced oxidative stress levels, along with increasing antioxidant capacity. In vivo experiments in arsenic-exposed group showed alveolar septum to be significantly thickened with considerable capillary congestion and invasion by inflammatory cells. After the intervention with GSPE, there seemed to be a dramatic reversal of morphology with thinning of the alveolar septum, decrease in capillary congestion, and number of inflammatory cells. This had shown that GSPE can effectively reduce the levels of oxidative stress, induced by arsenic in mice lung tissue. Conversely, antioxidant enzymes or products were increased. The experiment proved that GSPE can protect the lungs from oxidative damage induced by arsenic, and it may also be used as an antagonist against arsenic injuries.