Environmental arsenic exposure and its contribution to human diseases, toxicity mechanism and management

Calcitriol Inhibits NaAsO2 Triggered Hepatic Stellate Cells Activation and Extracellular Matrix Oversecretion by Activating Nrf2 Signaling Pathway Through Vitamin D Receptor

Previous studies, including our own, have demonstrated that arsenic exposure can induce liver fibrosis, while the underlying mechanism remains unclear and there is currently no effective pharmacological intervention available. Recent research has demonstrated that vitamin D supplementation can ameliorate liver fibrosis caused by various etiologies, potentially through modulation of the Nrf2 signaling pathways. However, it remains unclear whether vitamin D intervention can mitigate arsenic-caused liver fibrosis. As is known hepatic stellate cells (HSCs) activation and extracellular matrix (ECM) deposition are pivotal in the pathogenesis of liver fibrosis. In this study, we investigated the intervention effect of calcitriol (a form of active vitamin D) on arsenite-triggered Lx-2 cells (a human hepatic stellate cell line) activation and ECM oversecretion. Additionally, we also elucidated the role and mechanism of Nrf2 antioxidant signaling pathway. Our results demonstrated that calcitriol intervention significantly inhibits Lx-2 cell activation and ECM oversecretion induced by arsenite exposure. Additionally, calcitriol activates Nrf2 and its downstream antioxidant enzyme expression in Lx-2 cells, thereby reducing ROS overproduction caused by arsenite exposure. Further investigation reveals that calcitriol activates the Nrf2 signaling pathway and inhibits arsenite-triggered Lx-2 cell activation and ECM oversecretion by targeting vitamin D receptor (VDR). In conclusion, this study has demonstrated that vitamin D intervention can effectively inhibit HSC activation and ECM oversecretion triggered by arsenite exposure through its antioxidant activity. This provides a novel strategy for targeted nutritional intervention in the treatment of arsenic-induced liver fibrosis.

Reductive dissolution of As-bearing iron oxides: Mediating mechanism of fulvic acid and dissimilated iron reducing bacteria

Fulvic acid (FA) and iron oxides often play regulating roles in the geochemical behavior and ecological risk of arsenic (As) in terrestrial ecosystems. FA can act as electron shuttles to facilitate the reductive dissolution of As-bearing iron (hydr)oxides. However, the influence of FA from different sources on the sequential conversion of Fe/As in As-bearing iron oxides under biotic and abiotic conditions remains unclear. In this work, we exposed prepared As-bearing iron oxides to FAs derived from lignite (FAL) and plant peat (FAP) under anaerobic conditions, tracked the fate of Fe and As in the aqueous phase, and investigated the reduction transformation of Fe(III)/As(V) with or without the presence of Shewanella oneidensis MR-1. The results showed that the reduction efficiency of Fe(III)/As(V) was increased by MR-1, through its metabolic activity and using FAs as electron shuttles. The reduction of Fe(III)/As(V) was closely associated with goethite being more conducive to Fe/As reduction compared to hematite. It is determined that functional groups such as hydroxy, carboxy, aromatic, aldehyde, ketone and aliphatic groups are the primary electron donors. Their reductive capacities rank in the following sequence: hydroxy> carboxy, aromatic, aldehyde, ketone> aliphatic group. Notably, our findings suggest that in the biotic reduction, Fe significantly reduction precedes As reduction, thereby influencing the latter's reduction process across all incubation systems. This work provides empirical support for understanding iron's role in modulating the geochemical cycling of As and is of significant importance for assessing the release risk of arsenic in natural environments.

Effects of water-table changes following rainfall events on arsenic fate and transport in groundwater-surface water mixing zones

This study investigated the effects of groundwater-surface water (GW-SW) interactions on the fate and transport of arsenic (As) following rainfall events and subsequent water-table changes in GW-SW mixing zones, comprising the riparian and hyporheic zones, near an abandoned gold mine. During the dry and wet periods, stream conditions changed from flow-through to gaining, respectively. Water-table changes caused by rainfall events controlled flow paths between riparian zones and the stream, affecting spatiotemporal variation in the redox and pH conditions of the aquatic environment. Subsequently, the fate and transport of As in GW-SW mixing zones was responsive to variations in redox and pH conditions. Through the oxidative dissolution of As-bearing sulfide minerals and the reductive dissolution of iron (Fe) oxides with adsorbed As, As was released into the groundwater in the riparian zones and transported to the stream and streambed along the baseflow discharge. However, As was also immobilized in the sediment through adsorption onto Fe-oxides and coprecipitation with calcium (Ca) and zinc (Zn), suggesting that the sediment acts as a sink-and-source of As in aquatic environments. Therefore, water-table changes and GW-SW interactions could play an important role in the fate and transport of As in aquatic environments, specifically groundwater-riparian-streambed-stream systems. The findings of this study will provide scientific insights into the mechanisms of As in aquatic environments, aiding in improved decision-making to ensure safe and sustainable water management in response to future climate change.

Essential and Non-Essential Elements Levels in Fish Species Highly Consumed in the Middle Miranda River, Brazilian Pantanal

The present study investigated the levels of As, Ag, Al, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Se, and Zn in muscle samples of six fish species (Pygocentrus nattereri, Serrasalmus marginatus, Mylossoma duriventre, Leporinus friderici, Pimelodus argenteus, and P. pantaneiro) highly consumed by local riverine and non-resident people in middle Miranda River, southern Brazilian Pantanal. Significant differences were detected for Ba, Fe, Mn, and Zn levels among the analyzed species. Pairwise comparison detected significant differences in element levels between species with similar diets, which implies that other factors, instead of species' feeding habits, could be involved in distinct levels of element bioaccumulation. Significant correlations between body size and concentrations were found for Ba in P. nattereri (moderate positive correlation), and for Mn in M. duriventre (weak positive correlation) and P. argenteus (moderate negative correlation). Levels exceeding tolerable daily intake (TDI) were found for Pb maximum concentrations in P. nattereri, M. duriventre, L. friderici, P. argenteus, and P. pantaneiro, and for Cd maximum concentration in P. argenteus. Health risk assessment indicated considerable risk only for the worst-case scenario (calculated from maximum concentrations) for all species. Adopting a Pb monitoring program in biotic and abiotic compartments in Miranda River is strongly recommended.

Maternal diet quality during pregnancy and biomarkers of potentially toxic trace element exposure: Data from the ELFE cohort

The contribution of the diet to potentially toxic trace element exposure in pregnancy has been rarely addressed. The objective of the present study was to determine the association between the maternal diet during pregnancy and biomarkers of exposure for arsenic (As), mercury (Hg) and lead (Pb) at delivery. As was assessed in maternal urine, Hg in maternal hair, and Pb in cord blood, as a proxy for in utero exposure. Based on 2995 women from the ELFE nationwide birth cohort, higher scores for dietary patterns considered healthy were associated with higher concentrations of As and Hg in maternal matrices. Levels of cord blood Pb were inconsistently associated with dietary patterns considered healthy, and lower with a dietary pattern driven by milk and breakfast cereals. Lower levels of Hg were associated with higher Western dietary pattern scores. In conclusion, higher levels of maternal urinary As and hair Hg are associated with diets considered as "Healthy", while cord blood Pb was not strongly correlated with dietary exposure.

Arsenic exposure induced renal fibrosis via regulation of mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling pathway

Environmental arsenic exposure is one of the major global public health problems. Studies have shown that arsenic exposure can cause renal fibrosis, but the underlying mechanism is still unclear. Integrating the in vivo and in vitro models, this study investigated the potential molecular pathways for arsenic-induced renal fibrosis. In this study, SD rats were treated with 0, 5, 25, 50, and 100 mg/L NaAsO2 for 8 weeks via drinking water, and HK2 cells were treated with different doses of NaAsO2 for 48 h. The in vivo results showed that arsenic content in the rats' kidneys increased as the dose increased. Body weight decreased and kidney coefficient increased at 100 mg/L. As a response to the elevated NaAsO2 dose, inflammatory cell infiltration, renal tubular injury, glomerular atrophy, tubulointerstitial hemorrhage, and fibrosis became more obvious indicated by HE and Masson staining. The kidney transcriptome profiles further supported the protein-protein interactions involved in NaAsO2-induced renal fibrosis. The in vivo results, in together with the in vitro experiments, have revealed that exposure to NaAsO2 disturbed mitochondrial dynamics, promoted mitophagy, activated inflammation and the TGF-β1/SMAD signaling pathway, and finally resulted in fibrosis. In summary, arsenic exposure contributed to renal fibrosis via regulating the mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling axis. This study presented an adverse outcome pathway for the development of renal fibrosis due to arsenic exposure through drinking water.

Urea cycle promotion via ammonia-upregulated CPS1 is involved in arsenite-induced pulmonary fibrosis through enhancing collagen synthesis

Arsenic exposure is connected with lung toxicity and is related to lung fibrotic changes. Idiopathic pulmonary fibrosis (IPF) is characterized by extracellular matrix (ECM) deposition. Various genetic mechanisms and environmental factors induce or exacerbate pulmonary fibrosis. Collagen synthesis induced by sodium arsenite (NaAsO2) is closely associated with IPF. Fibroblasts tend to fine-tune their metabolic networks to support their synthetic requirements in response to environmental stimuli. Alterations in metabolism have an influential role in the pathogenesis of IPF. However, it is unclear how arsenic affects the metabolism in IPF. The urea cycle (UC) is needed for collagen formation, which provides adequate levels of proline (Pro) for biosynthesis of collagen. Carbamoyl phosphate synthetase 1 (CPS1) converts the ammonia to carbamoyl phosphate, which controls the first reaction of the UC. We show that, in arsenite-exposed mice, high amounts of ammonia in the lung microenvironment promotes the expression levels of CPS1 and the Pro metabolism. Reduction of ammonia and CPS1 ablation inhibit collagen synthesis and ameliorate IPF phenotypes induced by arsenite. This work takes advantage of multi-omics data to enhance understanding of the underlying pathogenic mechanisms, the key molecules and the complicated cellular responses to this pollutant, which provide a target for the prevention of pulmonary fibrosis caused by arsenic.

Retinal toxicity of heavy metals and its involvement in retinal pathology

The objective of the present review is to discuss epidemiological evidence demonstrating the association between toxic metal (Cd, Pb, Hg, As, Sn, Ti, Tl) exposure and retinal pathology, along with the potential underlying molecular mechanisms. Epidemiological studies demonstrate that Cd, and to a lesser extent Pb exposure, are associated with age-related macular degeneration (AMD), while the existing evidence on the levels of these metals in patients with diabetic retinopathy is scarce. Epidemiological data on the association between other toxic metals and metalloids including mercury (Hg) and arsenic (As), are limited. Clinical reports and laboratory in vivo studies have shown structural alterations in different layers of retina following metal exposure. Examination of retina samples demonstrate that toxic metals can accumulate in the retina, and the rate of accumulation appears to increase with age. Experimental studies in vivo and in vitro studies in APRE-19 and D407 cells demonstrate that toxic metal exposure may cause retinal damage through oxidative stress, apoptosis, DNA damage, mitochondrial dysfunction, endoplasmic reticulum stress, impaired retinogenesis, and retinal inflammation. However, further epidemiological as well as laboratory studies are required for understanding the underlying molecular mechanisms and identifying of the potential therapeutic targets and estimation of the dose-response effects.

Down-regulation of O-GlcNAcylation alleviates insulin signaling pathway impairment following arsenic exposure via suppressing the AMPK/mTOR-autophagy pathway

Impairment of the insulin signaling pathway is a key contributor to insulin resistance under arsenic exposure. Specifically, O-GlcNAcylation, an important post-translational modification, plays a crucial role in insulin resistance. Nevertheless, the concrete effect and mechanism of O-GlcNAcylation in arsenic-induced impairment of the insulin signaling pathway remain elusive. Herein, C57BL/6 mice were continuously fed arsenic-containing food, with a total arsenic concentration of 30 mg/kg. We observed that the IRS/Akt/GSK-3β insulin signaling pathway was impaired, and autophagy was activated in mouse livers and HepG2 cells exposed to arsenic. Additionally, O-GlcNAcylation expression in mouse livers and HepG2 cells was elevated, and the key O-GlcNAcylation homeostasis enzyme, O-GlcNAc transferase (OGT), was upregulated. In vitro, non-targeted metabolomic analysis showed that metabolic disorder was induced, and inhibition of O-GlcNAcylation restored the metabolic profile of HepG2 cells exposed to arsenic. In addition, we found that the compromised insulin signaling pathway was dependent on AMPK activation. Inhibition of AMPK mitigated autophagy activation and impairment of insulin signaling pathway under arsenic exposure. Furthermore, down-regulation of O-GlcNAcylation inhibited AMPK activation, thereby suppressing autophagy activation, and improving the impaired insulin signaling pathway. Collectively, our findings indicate that arsenic can impair the insulin signaling pathway by regulating O-GlcNAcylation homeostasis. Importantly, O-GlcNAcylation inhibition alleviated the impaired insulin signaling pathway by suppressing the AMPK/mTOR-autophagy pathway. This indicates that regulating O-GlcNAcylation may be a potential intervention for the impaired insulin signaling pathway induced by arsenic.

D-Limonene Alleviates Oxidative Stress Injury of the Testis Induced by Arsenic in Rat

Long-term exposure to arsenic can lead to testicular damage and lower sperm quality in males, which is mediated by increased arsenic-induced oxidative stress and other damage mechanisms. D-Limonene, which is rich in oranges, lemons, oranges, grapes and other natural fruits, can relieve doxorubicin (DOX)-induced kidney injury and CCL4-induced cardiac toxicity by inhibiting oxidative stress and inflammatory response. The antioxidant and anti-inflammatory properties of D-limonene motivate us to further explore whether it can reduce arsenic-induced testicular injury. To verify this scientific hypothesis, testicular pathology, testicular oxidative stress levels and sperm motility were determined after intervention with D-limonene in rats chronically exposed to arsenic. As expected, long-term arsenic exposure caused testicular tissue structure disturbances, increased levels of oxidative stress, and decreased sperm activation, all of which were significantly inhibited due to treatment with D-limonene. In conclusion, our data reveal a previously unproven beneficial effect of D-limonene, namely that D-limonene can inhibit arsenic-induced testicular injury, and also provide theoretical and experimental basis for the application of D-limonene in the treatment of arsenic-induced testicular injury.

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

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

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

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

Simultaneous stabilization of particulate and bioavailable arsenic in soils from the realgar mining area by polyacrylamide, nano-SiO2, and ferrihydrite composite materials

Arsenic (As) contamination in realgar mining areas poses a severe environmental and health risk, highlighting the critical need for effective strategies to manage As migration, particularly in its particulate and bioavailable states. Soil erosion and water leaching serve as significant pathways for spreading As, emphasizing the imperative to curtail its mobility. In the present study, we proposed an effective strategy that combines the utilization of polyacrylamide (PAM), nano-SiO2 (NS), and ferrihydrite (Fh) to elevate the stability of As in soils from a realgar mining area. The results show that this composite material demonstrates the capability to concurrently regulate soil erosion and mitigate the leaching of bioavailable As. The combination of the three materials in the proportion of 0.5 % PAM +0.1 % NS + 1.0 % Fh can reduce the soil particulate and bioavailable As content by 99.11 % and 93.98 %, respectively. The unconfined compressive strength of the soil can be increased by about 30 % under this condition. The SEM analyses show that the addition of PAM and NS can significantly enhance the aggregation of soil particles and then reduce the soil erosion rate. These findings highlight the significant potential of the proposed approach in mitigating As contamination in soil within mining environments. The approach offers a sustainable and comprehensive solution to address the transport of heavy metal contaminants in both particulate and bioavailable states in mining areas.

Can Sb(III)-oxidizing prokaryote also oxidize As(III) under aerobic and anaerobic conditions, and vice versa?

Sb(III) and As(III) share similar chemical features and coexist in the environment. However, their oxidase enzymes have completely different sequences and structures. This raises an intriguing question: Could Sb(III)-oxidizing prokaryotes (SOPs) also oxidize As(III), and vice versa? Regarding this issue, previous investigations have yielded unclear, incorrect and even conflicting data. This work aims to address this matter. First, we prepared an enriched population of SOPs that comprises 55 different AnoA genes, lacking AioAB and ArxAB genes. We found that these SOPs can oxidize both Sb(III) and As(III) with comparable capabilities. To further confirm this finding, we isolated three cultivable SOP strains that have AnoA gene, but lack AioAB and ArxAB genes. We observed that they also oxidize both Sb(III) and As(III) under both anaerobic and aerobic conditions. Secondly, we obtained an enriched population of As(III)-oxidizing prokaryotes (AOPs) from As-contaminated soils, which comprises 69 different AioA genes, lacking AnoA gene. We observed that the AOP population has significant As(III)-oxidizing activities, but lack detectable Sb(III)-oxidizing activities under both aerobic and anaerobic conditions. Therefore, we convincingly show that SOPs can oxidize As(III), but AOPs cannot oxidize Sb(III). These findings clarify the previous ambiguities, confusion, errors or contradictions regarding how SOPs and AOPs oxidize each other's substrate.

Assessment of the stabilization effect of ferrous sulfate for arsenic-contaminated soils based on chemical extraction methods and in vitro methods: Methodological differences and linkages

Stabilization of arsenic-contaminated soils with ferrous sulfate has been reported in many studies, but there are few stabilization effects assessments simultaneously combined chemical extraction methods and in vitro methods, and further explored the corresponding alternative relationships. In this study, ferrous sulfate was added at FeAs molar ratio of 0, 5, 10 and 20 to stabilize As in 10 As spiked soils. Stabilization effects were assessed by 6 chemical extraction methods (toxicity characteristic leaching procedures (TCLP), HCl, diethylenetriamine pentaacetic acid (DTPA), CaCl2, CH3COONH4, (NH4)2SO4), and 4 in vitro methods (physiologically based extraction test (PBET), in vitro gastrointestinal method (IVG), Solubility Bioaccessibility Research Consortium (SBRC) method, and the Unified Bioaccessibility Research Group of Europe method (UBM)). The results showed that the HCl method provides the most conservative assessment results in non-calcareous soils, and in alkaline calcareous soils, (NH4)2SO4 method provides a more conservative assessment. In vitro methods provided significantly higher As concentrations than chemical extraction methods. The components of the simulated digestion solution as well as the parameters may have contributed to this result. The small intestinal phase of PBET and SBRC method produced the highest and lowest ranges of As concentrations, and in the range of 127-462 mg/kg and 68-222 mg/kg when the FeAs molar ratio was 5. So the small intestinal phase of PBET method may provide the most conservative assessment results, while the same phase of SBRC may underestimate the human health risks of As in stabilized soil by 51 %(at a FeAs molar ratio of 5). Spearman correlation analysis indicated that the small intestinal phase of PBET method correlated best with HCl method (correlation coefficient: 0.71). This study provides ideas for the assessment of stabilization efforts to ensure that stabilization meets ecological needs while also being less harmful to humans.

Overexpression of OsTIP1;2 confers arsenite tolerance in rice and reduces root-to-shoot translocation of arsenic

Tonoplast Intrinsic Proteins (TIPs) are vital in transporting water and solutes across vacuolar membrane. The role of TIPs in the arsenic stress response is largely undefined. Rice shows sensitivity to the arsenite [As[III]] stress and its accumulation at high concentrations in grains poses severe health hazards. In this study, functional characterization of OsTIP1;2 from Oryza sativa indica cultivar Pusa Basmati-1 (PB-1) was done under the As[III] stress. Overexpression of OsTIP1;2 in PB-1 rice conferred tolerance to As[III] treatment measured in terms of enhanced shoot growth, biomass, and shoot/root ratio of overexpression (OE) lines compared to the wild-type (WT) plants. Moreover, seed priming with the IRW100 yeast cells (deficient in vacuolar membrane As[III] transporter YCF1) expressing OsTIP1;2 further increased As[III] stress tolerance of both WT and OE plants. The dithizone assay showed that WT plants accumulated high arsenic in shoots, while OE lines accumulated more arsenic in roots than shoots thereby limiting the translocation of arsenic to shoot. The activity of enzymatic and non-enzymatic antioxidants also increased in the OE lines on exposure to As[III]. The tissue-specific localization showed OsTIP1;2 promoter activity in root and root hairs, indicating its possible root-specific function. After As[III] treatment in hydroponic medium, the arsenic translocation factor (TF) for WT was around 0.8, while that of OE lines was around 0.2. Moreover, the arsenic content in the grains of OE lines reduced significantly compared to WT plants.

Sources and human health risks associated with potentially toxic elements (PTEs) in urban dust: A global perspective

Long-term exposure to urban dust containing potentially toxic elements (PTEs) poses detrimental impacts on human health. However, studies estimating human health risks in urban dusts from a global perspective are scarce. We evaluated data for twelve PTEs in urban dusts across 59 countries from 463 published articles, including their concentrations, input sources, and probabilistic risks to human health. We found that 34.1 and 60.3% of those investigated urban dusts have been heavily contaminated with As and Cd, respectively. The input of PTEs was significantly correlated with economic structure due to emissions of industrial activities and traffic emissions being the major sources. Based on the Monte Carlo simulation, we found that the mean hazard index below the safe threshold (1.0) could still cause non-negligible risks to human health. Arsenic and Cr were the major PTEs threatening human health, and relatively high risk levels were observed in cities in China, Korea, Chile, Malaysia, and Australia. Importantly, our analysis suggested that PTEs threaten the health of approximately 92 million adults and 280 million children worldwide. Overall, our study provides important foundational understanding and guidance for policy decision-making to reduce the potential risks associated with PTE exposure and to promote sustainable development of urban economies.

Metabolic Derangement by Arsenic: a Review of the Mechanisms

Studies have implicated arsenic exposure in various pathological conditions, including metabolic disorders, which have become a global phenomenon, affecting developed, developing, and under-developed nations. Despite the huge risks associated with arsenic exposure, humans remain constantly exposed to it, especially through the consumption of contaminated water and food. This present study provides an in-depth insight into the mechanistic pathways involved in the metabolic derangement by arsenic. Compelling pieces of evidence demonstrate that arsenic induces metabolic disorders via multiple pathways. Apart from the initiation of oxidative stress and inflammation, arsenic prevents the phosphorylation of Akt at Ser473 and Thr308, leading to the inhibition of PDK-1/Akt insulin signaling, thereby reducing GLUT4 translocation through the activation of Nrf2. Also, arsenic downregulates mitochondrial deacetylase Sirt3, decreasing the ability of its associated transcription factor, FOXO3a, to bind to the agents that support the genes for manganese superoxide dismutase and PPARg co-activator (PGC)-1a. In addition, arsenic activates MAPKs, modulates p53/ Bcl-2 signaling, suppresses Mdm-2 and PARP, activates NLRP3 inflammasome and caspase-mediated apoptosis, and induces ER stress, and ox-mtDNA-dependent mitophagy and autophagy. More so, arsenic alters lipid metabolism by decreasing the presence of 3-hydroxy-e-methylglutaryl-CoA synthase 1 and carnitine O-octanoyl transferase (Crot) and increasing the presence of fatty acid-binding protein-3 mRNA. Furthermore, arsenic promotes atherosclerosis by inducing endothelial damage. This cascade of pathophysiological events promotes metabolic derangement. Although the pieces of evidence provided by this study are convincing, future studies evaluating the involvement of other likely mechanisms are important. Also, epidemiological studies might be necessary for the translation of most of the findings in animal models to humans.

Epigallocatechin-3-gallate attenuates arsenic-induced fibrogenic changes in human kidney epithelial cells through reversal of epigenetic aberrations and antioxidant activities

Renal fibrosis is a pathogenic intermediate stage of chronic kidney disease (CKD). Nephrotoxicants including arsenic can cause kidney fibrosis through induction of oxidative stress and epigenetic aberrations. Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, is known to have antioxidant and epigenetic modulation properties. Whether EGCG, through its antioxidant and epigenetic modulating activities, can attenuate fibrogenesis is not known. Therefore, the objective of this study was to determine whether EGCG can attenuate arsenic-induced acute injury and long-term exposure associated fibrogenicity in kidney epithelial cells. To address this question, two human kidney epithelial cell lines Caki-1 and HK-2 exposed to arsenic for both acute and long-term durations were treated with EGCG. The protective effect of EGCG on arsenic-induced cytotoxicity and fibrogenicity were evaluated by measuring the cell growth, reactive oxygen species (ROS) production, genes expression, and epigenetic changes in histone marks. Results revealed that EGCG has a protective effect in arsenic-induced acute cytotoxicity in these cells. EGCG scavenges the increased levels of ROS in arsenic exposed cells. Aberrant expression of fibrogenic genes in arsenic exposed cells were restored by EGCG. Abrogation of arsenic-induced fibrogenic changes was also associated with EGCG-mediated restoration of arsenic-induced aberrant expression of epigenetic regulatory proteins and histone marks. Novel findings of this study suggest that EGCG, through its antioxidant and epigenetic modulation capacities, has protective effects against arsenic-induced cytotoxicity and fibrogenic changes in kidney epithelial cells.

Multilevel Regulation of Membrane Proteins in Response to Metal and Metalloid Stress: A Lesson from Yeast

In the face of flourishing industrialization and global trade, heavy metal and metalloid contamination of the environment is a growing concern throughout the world. The widespread presence of highly toxic compounds of arsenic, antimony, and cadmium in nature poses a particular threat to human health. Prolonged exposure to these toxins has been associated with severe human diseases, including cancer, diabetes, and neurodegenerative disorders. These toxins are known to induce analogous cellular stresses, such as DNA damage, disturbance of redox homeostasis, and proteotoxicity. To overcome these threats and improve or devise treatment methods, it is crucial to understand the mechanisms of cellular detoxification in metal and metalloid stress. Membrane proteins are key cellular components involved in the uptake, vacuolar/lysosomal sequestration, and efflux of these compounds; thus, deciphering the multilevel regulation of these proteins is of the utmost importance. In this review, we summarize data on the mechanisms of arsenic, antimony, and cadmium detoxification in the context of membrane proteome. We used yeast Saccharomyces cerevisiae as a eukaryotic model to elucidate the complex mechanisms of the production, regulation, and degradation of selected membrane transporters under metal(loid)-induced stress conditions. Additionally, we present data on orthologues membrane proteins involved in metal(loid)-associated diseases in humans.

Transgenerational Effects of Arsenic Exposure on Learning and Memory in Rats: Crosstalk between Arsenic Methylation, Hippocampal Metabolism, and Histone Modifications

Arsenic (As) is widely present in the natural environment, and exposure to it can lead to learning and memory impairment. However, the underlying epigenetic mechanisms are still largely unclear. This study aimed to reveal the role of histone modifications in environmental levels of arsenic (sodium arsenite) exposure-induced learning and memory dysfunction in male rats, and the inter/transgenerational effects of paternal arsenic exposure were also investigated. It was found that arsenic exposure impaired the learning and memory ability of F0 rats and down-regulated the expression of cognition-related genes Bdnf, c-Fos, mGlur1, Nmdar1, and Gria2 in the hippocampus. We also observed that inorganic arsenite was methylated to DMA and histone modification-related metabolites were altered, contributing to the dysregulation of H3K4me1/2/3, H3K9me1/2/3, and H3K4ac in rat hippocampus after exposure. Therefore, it is suggested that arsenic methylation and hippocampal metabolism changes attenuated H3K4me1/2/3 and H3K4ac while enhancing H3K9me1/2/3, which repressed the key gene expressions, leading to cognitive impairment in rats exposed to arsenic. In addition, paternal arsenic exposure induced transgenerational effects of learning and memory disorder in F2 male rats through the regulation of H3K4me2 and H3K9me1/2/3, which inhibited c-Fos, mGlur1, and Nmdar1 expression. These results provide novel insights into the molecular mechanism of arsenic-induced neurotoxicity and highlight the risk of neurological deficits in offspring with paternal exposure to arsenic.

Nod-like receptor protein 3 inflammasome-mediated pyroptosis contributes to chronic NaAsO2 exposure-induced fibrotic changes and dysfunction in the liver of SD rats

The metalloid arsenic, known for its toxic properties, is widespread presence in the environment. Our previous research has confirmed that prolonged exposure to arsenic can lead to liver fibrosis injury in rats, while the precise pathogenic mechanism still requires further investigation. In the past few years, the Nod-like receptor protein 3 (NLRP3) inflammasome has been found to play a pivotal role in the occurrence and development of liver injury. In this study, we administered varying doses of sodium arsenite (NaAsO2) and 10 mg/kg.bw MCC950 (a particular tiny molecular inhibitor targeting NLRP3) to Sprague-Dawley (SD) rats for 36 weeks to explore the involvement of NLRP3 inflammasome in NaAsO2-induced liver injury. The findings suggested that prolonged exposure to NaAsO2 resulted in pyroptosis in liver tissue of SD rats, accompanied by the fibrotic injury, extracellular matrix (ECM) deposition and liver dysfunction. Moreover, long-term NaAsO2 exposure activated NLRP3 inflammasome, leading to the release of pro-inflammatory cytokines in liver tissue. After treatment with MCC950, the induction of NLRP3-mediated pyroptosis and release of pro-inflammatory cytokines were significantly attenuated, leading to a decrease in the severity of liver fibrosis and an improvement in liver function. To summarize, those results clearly indicate that hepatic fibrosis and liver dysfunction induced by NaAsO2 occur through the activation of NLRP3 inflammasome-mediated pyroptosis, shedding new light on the potential mechanisms underlying arsenic-induced liver damage.

Pollution levels and probability risk assessment of potential toxic elements in soil of Pb-Zn smelting areas

Soil pollution around Pb-Zn smelters has attracted widespread attention around the world. In this study, we compiled a database of eight potentially toxic elements (PTEs) Pb, Zn, Cd, As, Cr, Ni, Cu, and Mn in the soil of Pb-Zn smelting areas by screening the published research papers from 2000 to 2023. The pollution assessment and risk screening of eight PTEs were carried out by geo-accumulation index (Igeo), potential ecological risk index (PERI) and health risk assessment model, and Monte Carlo simulation employed to further evaluate the probabilistic health risks. The results suggested that the mean values of the eight PTEs all exceeded the corresponding values in the upper crust, and more than 60% of the study sites had serious Pb and Cd pollution (Igeo > 4), with Brazil, Belgium, China, France and Slovenia having higher levels of pollution than other regions. Besides, PTEs in smelting area caused serious ecological risk (PERI = 10912.12), in which Cd was the main contributor to PREI (86.02%). The average hazard index (HI) of the eight PTEs for adults and children was 7.19 and 9.73, respectively, and the average value of total carcinogenic risk (TCR) was 4.20 × 10-3 and 8.05 × 10-4, respectively. Pb and As are the main contributors to non-carcinogenic risk, while Cu and As are the main contributors to carcinogenic risk. The probability of non-carcinogenic risk in adults and children was 84.05% and 97.57%, while carcinogenic risk was 92.56% and 79.73%, respectively. In summary, there are high ecological and health risks of PTEs in the soil of Pb-Zn smelting areas, and Pb, Cd, As and Cu are the key elements that cause contamination and risk, which need to be paid attention to and controlled. This study is expected to provide guidance for soil remediation in Pb-Zn smelting areas.

Fast and efficient As(III) removal from water by bifunctional nZVI@NBC

As a notable toxic substance, metalloid arsenic (As) widely exists in water body and drinking As-contaminated water for an extended period of time can result in serious health concerns. Here, the performance of nanoscale zero-valent iron (nZVI) modified N-doped biochar (NBC) composites (nZVI@NBC) activated peroxydisulfate (PDS) for As(III) removal was investigated. The removal efficiencies of As(III) with initial concentration ranging from 50 to 1000 μg/L were above 99% (the residual total arsenic below 10 μg/L, satisfying the contaminant limit for arsenic in drinking water) within 10 min by nZVI@NBC (0.2 g/L)/PDS (100 μM). As(III) removal efficiency influenced by reaction time, PDS dosage, initial concentration, pH, co-existing ions, and natural organic matter in nZVI@NBC/PDS system were investigated. The nZVI@NBC composite is magnetic and could be conveniently collected from aqueous solutions. In practical applications, nZVI@NBC/PDS has more than 99% As(III) removal efficiency in various water bodies (such as deionized water, piped water, river water, and lake water) under optimized operation parameters. Radical quenching and EPR analysis revealed that SO4·- and ·OH play important roles in nZVI@NBC/PDS system, and the possible reaction mechanism was further proposed. These results suggest that nZVI@NBC activated peroxydisulfate may be an efficient and fast approach for the removal of water contaminated with As(III).

Iron-lanthanum supported on graphite sheets for As(III) removal from aqueous solution: kinetics, thermodynamic and ecotoxicity assessment

Graphene-based material is widely used to remove arsenic from water due to its layered structure with high surface area. Here, we have successfully synthesized Fe-La bimetallic modified graphite sheet materials to more efficiently remove As(III) from aqueous solution. The results showed that Fe-La-graphite sheets (FL-graphite sheets) have a larger specific surface area (194.28 m2·g-1) than graphite sheets (2.80 m2·g-1). The adsorption capacity of FL-graphite sheets for As(III) was 51.69 mg·g-1, which was higher than that of graphite sheets (21.91 mg·g-1), La-graphite sheets (26.06 mg·g-1), and Fe-graphite sheets (40.26 mg·g-1). The FL-graphite sheets conformed to the Freundlich and Dubinin-Radushkevich isotherm, and the maximum adsorption capacity was 53.62 mg·g-1. The removal process obeys intra-particle diffusion and pore diffusion for As(III). The results of batch adsorption experiments and characterization analyses demonstrated that oxidation, ligand exchange, and inner sphere complexation mechanisms involved in the adsorption of FL-graphite sheets to As(III) in comparison with graphite sheets. In addition, electrostatic attraction mechanism was found vital in the adsorption. Ecotoxicity assessment revealed that FL-graphite sheets have little influence on rice germination and growth, but reduced the toxicity of As(III) to rice. Therefore, the FL-graphite sheets have good practical application value in purifying As(III) polluted water with litter ecotoxicity.

Silicon reduces toxicity and accumulation of arsenic and cadmium in cereal crops: A meta-analysis, mechanism, and perspective study

Arsenic (As) and cadmium (Cd) are two toxic metal(loid)s that pose significant risks to food security and human health. Silicon (Si) has attracted substantial attention because of its positive effects on alleviating the toxicity and accumulation of As and Cd in crops. However, our current knowledge of the comprehensive effects and detailed mechanisms of Si amendment is limited. In this study, a global meta-analysis of 248 original articles with over 7000 paired observations was conducted to evaluate Si-mediated effects on growth and As and Cd accumulation in rice (Oryza sativa L.), wheat (Triticum aestivum L.), and maize (Zea mays L.). Si application increases the biomass of these crops under As and/or Cd contamination. Si amendment also decreased shoot As and Cd accumulation by 24.1 % (20.6 to 27.5 %) and 31.9 % (29.0 to 31.9 %), respectively. Furthermore, the Si amendment reduced the human health risks posed by As (2.6 %) and Cd (12.9 %) in crop grains. Si-induced inhibition of Cd accumulation is associated with decreased Cd bioavailability and the downregulation of gene expression. The regulation of gene expression by Si addition was the driving factor limiting shoot As accumulation. Overall, our analysis demonstrated that Si amendment has great potential to reduce the toxicity and accumulation of As and/or Cd in crops, providing a scientific basis for promoting food safety globally.

Biological oxidation of As(III) and Sb(III) by a novel bacterium with Sb(III) oxidase rather than As(III) oxidase under anaerobic and aerobic conditions

Sb and As are chemically similar, but the sequences and structures of Sb(III) and As(III) oxidase are totally distinct. It is thus interesting to explore whether Sb(III) oxidase oxidizes As(III), and if so, how microbial oxidations of Sb(III) and As(III) influence one another. Previous investigations have yielded ambiguous or even erroneous conclusions. This study aimed to clarify this issue. Firstly, we prepared a consortium of Sb(III)-oxidizing prokaryotes (SOPs) by enrichment cultivation. Metagenomic analysis reveals that SOPs with the Sb(III) oxidase gene, but lacking the As(III) oxidase gene are predominant in the SOP community. Despite this, SOPs exhibit comparable Sb(III) and As(III)-oxidizing activities in both aerobic and anaerobic conditions, indicating that at the microbial community level, Sb(III) oxidase can oxidize As(III). Secondly, we isolated a representative cultivable SOP, Ralstonia sp. SbOX with Sb(III) oxidase gene but without As(III) oxidase gene. Genomic analysis of SbOX reveals that this SOP strain has a complete Sb(III) oxidase (AnoA) gene, but lacks As(III) oxidase (AioAB or ArxAB) gene. It is interesting to discover that, besides its Sb(III) oxidation activities, SbOX also exhibits significant capabilities in oxidizing As(III) under both aerobic and anaerobic conditions. Moreover, under aerobic conditions and in the presence of both Sb(III) and As(III), SbOX exhibited a preference for oxidizing Sb(III). Only after the near complete oxidation of Sb(III) did SbOX initiate rapid oxidation of As(III). In contrast, under anaerobic conditions and in the presence of both Sb(III) and As(III), Sb(III) oxidation notably inhibited the As(III) oxidation pathway in SbOX, while As(III) exhibited minimal effects on the Sb(III) oxidation. These findings suggest that SOPs can oxidize As(III) under both aerobic and anaerobic conditions, exhibiting a strong preference for Sb(III) over As(III) oxidation in the presence of both. This study unveils a novel mechanism of interaction within the Sb and As biogeochemical cycles.

Isolation, characterization, identification, genomics and analyses of bioaccumulation and biosorption potential of two arsenic-resistant bacteria obtained from natural environments

Arsenic (As) is a significant contaminant whose unrestrained entrance into different ecosystems has created global concern. At the cellular level, As forms unsteady intermediates with genetic materials and perturbs different metabolic processes and proper folding of proteins. This study was the first in this region to explore, isolate, screen systematically, and intensively characterize potent As-tolerant bacterial strains from natural environments near Raiganj town of Uttar Dinajpur, West Bengal. In this study, two potent Gram-negative bacterial strains with high tolerance to the poisonous form of As, i.e., As(III) and As(V), were obtained. Both the isolates were identified using biochemical tests and 16S rRNA gene sequencing. These bacteria oxidized toxic As(III) into less poisonous As(V) and depicted tolerance towards other heavy metals. Comparative metabolic profiling of the isolates in control and As-exposed conditions through Fourier-transform infrared spectroscopy showed metabolic adjustments to cope with As toxicity. The metal removal efficiency of the isolates at different pH showed that one of the isolates, KG1D, could remove As efficiently irrespective of changes in the media pH. In contrast, the efficiency of metal removal by PF14 was largely pH-dependent. The cell mass of both the isolates was also found to favourably adsorb As(III). Whole genome sequence analysis of the isolates depicted the presence of the arsRBC genes of the arsenic operon conferring resistance to As. Owing to their As(III) oxidizing potential, high As bioaccumulation, and tolerance to other heavy metals, these bacteria could be used to bioremediate and reclaim As-contaminated sites.

Rice tonoplast intrinsic protein member OsTIP1;2 confers tolerance to arsenite stress

The International Agency for Research on Cancer categorizes arsenic (As) as a group I carcinogen. Arsenic exposure significantly reduces growth, development, metabolism, and crop yield. Tonoplast intrinsic proteins (TIPs) belong to the major intrinsic protein (MIP) superfamily and transport various substrates, including metals/metalloids. Our study aimed to characterize rice OsTIP1;2 in As[III] stress response. The gene expression analysis showed that the OsTIP1;2 expression was enhanced in roots on exposure to As[III] treatment. The heterologous expression of OsTIP1;2 in S. cerevisiae mutant lacking YCF1 (ycf1∆) complemented the As[III] transport function of the YCF1 transporter but not for boron (B) and arsenate As[V], indicating its substrate selective nature. The ycf1∆ mutant expressing OsTIP1;2 accumulated more As than the wild type (W303-1A) and ycf1∆ mutant strain carrying the pYES2.1 vector. OsTIP1;2 activity was partially inhibited in the presence of the aquaporin (AQP) inhibitors. The subcellular localization studies confirmed that OsTIP1;2 is localized to the tonoplast. The transient overexpression of OsTIP1;2 in Nicotiana benthamiana leaves resulted in increased activities of enzymatic and non-enzymatic antioxidants, suggesting a potential role in mitigating oxidative stress induced by As[III]. The transgenic N. tabacum overexpressing OsTIP1;2 displayed an As[III]-tolerant phenotype, with increased fresh weight and root length than the wild-type (WT) and empty vector (EV line). The As translocation factor (TF) for WT and EV was around 0.8, while that of OE lines was around 0.4. Moreover, the OE line bioconcentration factor (BCF) was more than 1. Notably, the reduced TF and increased BCF in the OE line imply the potential of OsTIP1;2 for phytostabilization.

Gut microbiota deficiency aggravates arsenic-induced toxicity by affecting bioaccumulation and biotransformation in C57BL/6J mice

Gut microbiome can influence the arsenic metabolism in mammals. Confusingly, gut microbiome was found to both mitigate and exacerbate arsenic toxicity. In this study, the role of gut microbiota in arsenic bioaccumulation, biotransformation, and organ toxicity in C57BL/6J mice was investigated. Gut microbiota deficiency model was established by antibiotics (Ab) cocktail AVNM. Conventional and gut microbiota deficiency mice were exposed to NaAsO2 for 4 weeks. Comparing with Ab-treated mice, the total arsenic (tAs) in the tissues was significantly reduced in conventional mice, which was opposed to the results of those in feces. Interestingly, dimethyl arsenite (DMA) was the most abundant metabolite in the feces of Ab-treated mice, while arsenic acid (AsV) had the highest proportion in the feces of conventional mice with approximately 16-fold than that in Ab-treated mice, indicating the critical role of gut microbiota in metabolizing arsenious acid (AsIII) to AsV. Additionally, the liver and kidney in Ab-treated mice showed more severe pathological changes and apoptosis. The significant increased level of ionized calcium-binding adapter molecule 1 (IBA-1) was also found in the brains of Ab-treated mice. Our results indicated that gut microbiota protected the host from arsenic-induced toxicity in liver, kidney, and brain by reducing the arsenic accumulation.

Research progress on arsenic, arsenic-containing medicinal materials, and arsenic-containing preparations: clinical application, pharmacological effects, and toxicity

Introduction: The toxicity of arsenic is widely recognized globally, mainly harming human health by polluting water, soil, and food. However, its formulations can also be used for the clinical treatment of diseases such as leukemia and tumors. Arsenic has been used as a drug in China for over 2,400 years, with examples such as the arsenic-containing drug realgar mentioned in Shennong's Herbal Classic. We have reviewed references on arsenic over the past thirty years and found that research has mainly focused on clinical, pharmacological, and toxicological aspects. Results and Discussion: The finding showed that in clinical practice, arsenic trioxide is mainly used in combination with all-trans retinoic acid (ATRA) at a dose of 10 mg/d for the treatment of acute promyelocytic leukemia (APL); realgar can be used to treat acute promyelocytic leukemia, myelodysplastic syndrome, and lymphoma. In terms of pharmacology, arsenic mainly exerts anti-tumor effects. The dosage range of the action is 0.01-80 μmol/L, and the concentration of arsenic in most studies does not exceed 20 μmol/L. The pharmacological effects of realgar include antiviral activity, inhibition of overactivated lactate dehydrogenase, and resistance to malaria parasites. In terms of toxicity, arsenic is toxic to multiple systems in a dose-dependent manner. For example, 5 μmol/L sodium arsenite can induce liver oxidative damage and promote the expression of pro-inflammatory factors, and 15 μmol/L sodium arsenite induces myocardial injury; when the concentration is higher, it is more likely to cause toxic damage.

Potential of oligonucleotide- and protein/peptide-based therapeutics in the management of toxicant/stressor-induced diseases

Exposure to toxicants/stressors has been linked to the development of many human diseases. They could affect various cellular components, such as DNA, proteins, lipids, and non-coding RNAs (ncRNA), thereby triggering various cellular pathways, particularly oxidative stress, inflammatory responses, and apoptosis, which can contribute to pathophysiological states. Accordingly, modulation of these pathways has been the focus of numerous investigations for managing related diseases. The involvement of various ncRNAs, such as small interfering RNA (siRNA), microRNAs (miRNA), and long non-coding RNAs (lncRNA), as well as various proteins and peptides in mediating these pathways, provides many target sites for pharmaceutical intervention. In this regard, various oligonucleotide- and protein/peptide-based therapies have been developed to treat toxicity-induced diseases, which have shown promising results in vitro and in vivo. This comprehensive review provides information about various aspects of toxicity-related diseases including their causing factors, main underlying mechanisms and intermediates, and their roles in pathophysiological states. Particularly, it highlights the principles and mechanisms of oligonucleotide- and protein/peptide-based therapies in the treatment of toxicity-related diseases. Furthermore, various issues of oligonucleotides and proteins/peptides for clinical usage and potential solutions are discussed.

Chronic arsenite exposure induced skeletal muscle atrophy by disrupting angiotensin II-melatonin axis in rats

Arsenic is a well-known environmental toxicant and emerging evidence suggests that arsenic exposure has potential skeletal muscle toxicity; however, the underlying mechanism has not yet been clarified. The aim of this study was to investigate the correlation among adverse effects of subchronic and chronic environmental arsenic exposure on skeletal muscle as well as specific myokines secretion and angiotensin II (AngII)-melatonin (MT) axis in rats. Four-week-old rats were exposed to arsenite (iAs) in drinking water at environmental relevant concentration of 10 ppm for 3 or 9 months. Results indicated that the gastrocnemius muscle had atrophied and its mass was decreased in rats exposed to arsenite for 9 months, whereas, they had no significant changes in rats exposed to arsenite for 3 months. The levels of serum-specific myokine irisin and gastrocnemius muscle insulin-like growth factor-1 (IGF-1) were increased in 3-month exposure group and decreased in 9-month exposure group, while serum myostatin (MSTN) was increased significantly in 9-month exposure group. In addition, serum AngII level increased both in 3- and 9-month exposure groups, while serum MT level increased in 3-month exposure group and decreased in 9-month exposure group. Importantly, the ratio of AngII to MT level in serum increased gradually with the prolongation of arsenite exposure. It showed a certain correlation between AngII-MT axis and gastrocnemius muscle mass, gastrocnemius muscle level of IGF-1 or serum levels of irisin and MSTN. In conclusion, the disruption of AngII-MT axis balance may be a significant factor for skeletal muscle atrophy induced by chronic environmental arsenic exposure.

Arsenic-induced IGF-1 signaling impairment and neurite shortening: The protective roles of IGF-1 through the PI3K/Akt axis

We recently reported that arsenic caused insulin resistance in differentiated human neuroblastoma SH-SY5Y cells. Herein, we further investigated the effects of sodium arsenite on IGF-1 signaling, which shares downstream signaling with insulin. A time-course experiment revealed that sodium arsenite began to decrease IGF-1-stimulated Akt phosphorylation on Day 3 after treatment, indicating that prolonged sodium arsenite treatment disrupted the neuronal IGF-1 response. Additionally, sodium arsenite decreased IGF-1-stimulated tyrosine phosphorylation of the IGF-1 receptor β (IGF-1Rβ) and its downstream target, insulin receptor substrate 1 (IRS1). These results suggested that sodium arsenite impaired the intrinsic tyrosine kinase activity of IGF-1Rβ, ultimately resulting in a reduction in tyrosine-phosphorylated IRS1. Sodium arsenite also reduced IGF-1 stimulated tyrosine phosphorylation of insulin receptor β (IRβ), indicating the potential inhibition of IGF-1R/IR crosstalk by sodium arsenite. Interestingly, sodium arsenite also induced neurite shortening at the same concentrations that caused IGF-1 signaling impairment. A 24-h IGF-1 treatment partially rescued neurite shortening caused by sodium arsenite. Moreover, the reduction in Akt phosphorylation by sodium arsenite was attenuated by IGF-1. Inhibition of PI3K/Akt by LY294002 diminished the protective effects of IGF-1 against sodium arsenite-induced neurite retraction. Together, our findings suggested that sodium arsenite-impaired IGF-1 signaling, leading to neurite shortening through IGF-1/PI3K/Akt.

Didactical approaches and insights into environmental processes and cardiovascular hazards of arsenic contaminants

Arsenic, as a metalloid, has the ability to move and transform in different environmental media. Its widespread contamination has become a significant environmental problem and public concern. Arsenic can jeopardize multiple organs through various pathways, influenced by environmental bioprocesses. This article provides a comprehensive overview of current research on the cardiovascular hazards of arsenic. A bibliometric analysis revealed that there are 376 papers published in 145 journals, involving 40 countries, 631 institutions, and 2093 authors, all focused on arsenic-related concerns regarding cardiovascular health. China and the U.S. have emerged as the central hubs of collaborative relationships and have the highest number of publications. Hypertension and atherosclerosis are the most extensively studied topics, with redox imbalance, apoptosis, and methylation being the primary mechanistic clues. Cardiovascular damage caused by arsenic includes arrhythmia, cardiac remodeling, vascular leakage, and abnormal angiogenesis. However, the current understanding is still inadequate over cardiovascular impairments, underlying mechanisms, and precautionary methods of arsenic, thus calling an urgent need for further studies to bridge the gap between environmental processes and arsenic hazards.

Genotoxicity in humans exposed to arsenic, lithium, and boron in drinking water in the Bolivian Andes-A cross sectional study

Elevated concentrations of arsenic, lithium and boron in drinking water have already been reported in Bolivia. Arsenic is known to cause genotoxicity but that caused by lithium and boron is less well known. The aim of the present cross-sectional study was to evaluate potential genotoxic effects of exposure to arsenic, while considering exposure to lithium and boron and genetic susceptibility. Women (n = 230) were recruited in villages located around Lake Poopó. Exposure to arsenic was determined as the sum of concentrations of arsenic metabolites inorganic arsenic, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in urine. Exposure to lithium and boron was determined based on their concentrations in urine. Genetic susceptibility was determined by GSTM1 (glutathione S-transferase-mu-1) and GSTT1 (glutathione S-transferase-theta-1) null genotypes and AS3MT (Arsenite Methyltransferase) rs3740393. Genotoxicity was measured in peripheral blood leukocytes using the comet assay. The geometric means of arsenic, lithium, and boron concentrations were 68, 897, and 3972 μg/L, respectively. GSTM1 and GSTT1 null carriers had more DNA strand breaks than gene carriers (p = .008, p = .005). We found no correlation between urinary arsenic and DNA strand breaks (rS = .03, p = .64), and only a weak non-significant positive association in the adjusted multivariate analysis (β = .09 [-.03; .22], p = .14). Surprisingly, increasing concentrations of lithium in urine were negatively correlated with DNA strand breaks (rS = -.24, p = .0006), and the association persisted in multivariate analysis after adjusting for arsenic (β = -.22 [-.36; -.08], p = .003). We found no association between boron and DNA strand breaks. The apparent protective effect of lithium merits further investigation.

Heavy metals/-metalloids (As) phytoremediation with Landoltia punctata and Lemna sp. (duckweeds): coupling with biorefinery prospects for sustainable phytotechnologies

Heavy metals/-metalloids can result in serious human health hazards. Phytoremediation is green bioresource technology for the remediation of heavy metals and arsenic (As). However, there exists a knowledge gap and systematic information on duckweed-based metal phytoremediation in an eco-sustainable way. Therefore, the present review offers a critical discussion on the effective use of duckweeds (genera Landoltia and Lemna)-based phytoremediation to decontaminate metallic contaminants from wastewater. Phytoextraction and rhizofiltration were the major mechanism in 'duckweed bioreactors' that can be dependent on physico-chemical factors and plant-microbe interactions. The biotechnological advances such as gene manipulations can accelerate the duckweed-based phytoremediation process. High starch and protein contents of the metal-loaded duckweed biomass facilitate their use as feedstock in biorefinery. Biorefinery prospects such as bioenergy production, value-added products, and biofertilizers can augment the circular economy approach. Coupling duckweed-based phytoremediation with biorefinery can help achieve Sustainable Development Goals (SDGs) and human well-being.

Functional features of a novel Sb(III)- and As(III)-oxidizing bacterium: Implications for the interactions between bacterial Sb(III) and As(III) oxidation pathways

Antimony (Sb) and arsenic (As) share similar chemical characteristics and commonly coexist in contaminated environments. It has been reported that the biogeochemical cycles of antimony and arsenic affect each other. However, there is limited understanding regarding microbial coupling between the biogeochemical processes of antimony and arsenic. Here, we aimed to solve this issue. We successfully isolated a novel bacterium, Shinella sp. SbAsOP1, which possesses both Sb(III) and As(III) oxidase, and can effectively oxidize both Sb(III) and As(III) under aerobic and anaerobic conditions. SbAsOP1 exhibits greater aerobic oxidation activity for the oxidation of As(III) or Sb(III) compared to its anaerobic activity. SbAsOP1 also significantly catalyzes the oxidative mobilization of solid-phase Sb(III) under aerobic conditions. The activity of SbAsOP1 in oxidizing solid Sb(III) is 3 times lower than its activity in oxidizing soluble form. It is noteworthy that, in the presence of both Sb(III) and As(III) under aerobic conditions, either As(III) or Sb(III) significantly inhibits the oxidation of Sb(III) or As(III), respectively. In comparison, under anaerobic conditions and in the coexistence of Sb(III) and As(III), As(III) significantly inhibits Sb(III) oxidation, whereas Sb(III) almost completely inhibits As(III) oxidation. These findings suggest that under both aerobic and anaerobic conditions, SbAsOP1 demonstrates a partial preference for Sb(III) oxidation. Additionally, bacterial oxidations of Sb(III) and As(III) mutually inhibit each other to varying degrees. These observations gain a novel understanding of the interplay between the biogeochemical processes of antimony and arsenic.

Assessing the mechanisms and adjunctive therapy for arsenic-induced liver injury in rats

Environmental arsenic exposure is a significant global public health concern. Previous studies have demonstrated the association between arsenic-induced liver injury and oxidative stress as well as ferroptosis. However, the knowledge of the interactions among these mechanisms remains limited. Moreover, there is a lack of research on potential therapeutic interventions for liver injury resulting from arsenic exposure. To address these limitations, we established a rat model with liver injury caused by arsenic exposure and investigated the impact of the nuclear factor E2-related factor 2 (Nrf2)/glutathione peroxidase 4 (GPx4) signaling pathway and ferroptosis on arsenic-induced liver injury. Our findings revealed that arsenic increased Nrf2 expression and decreased GPx4 expression in the rat liver. This was accompanied by a substantial generation of reactive oxygen species and disruption of the antioxidant defense system, ultimately promoting liver injury through ferroptosis. Subsequently, we conducted intervention experiments using Rosa roxburghii Tratt (RRT) in rats exposed to arsenic. The results showed that the detrimental effects mentioned earlier were partially alleviated following RRT intervention. This study offers preliminary evidence that persistent activation of Nrf2 by arsenic triggers an adaptive antioxidant response, leading to liver injury through the promotion of ferroptosis. Additionally, we discovered that RRT inhibits Nrf2-mediated adaptive antioxidant responses by reducing hepatic ferroptosis, thereby mitigating liver injury caused by arsenic exposure in rats. Our study contributes to a deeper understanding of the molecular mechanisms underlying liver injury resulting from arsenic exposure. Furthermore, our findings may facilitate the identification of a potential edible and medicinal plant extracts that could be utilized to develop a more effective adjunctive treatment approach.

Detection of Arsenic(V) by Fluorescence Sensing Based on Chlorin e6-Copper Ion

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu2+) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu2+, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu2+, As(III), and As(V), respectively. The developed method can be used to determine Cu2+ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu2+ was obtained from the Job plot that was developed from UV-visible spectra. The binding constants for Cu2+ and As(V) were established to be 1.248 × 105 M-1 and 2.35 × 1012 M-2, respectively, using B-H (Benesi-Hildebrand) plots. Fluorescence lifetimes, B-H plots, FT-IR, and 1H-NMR were used to postulate the mechanism of Cu2+ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule.

Association between Heavy Metals and Trace Elements in Cancerous and Non-cancerous Tissues with the Risk of Colorectal Cancer Progression in Northwest China

Alterations in heavy metals and trace element levels may be associated with various cancers. However, the role of this interaction in colorectal cancer (CRC) progression is unclear. In recent years, Principal Component Analysis (PCA) and Bayesian Kernel Machine Regression (BKMR) models have provided new ideas for analyzing the effects of metal mixtures on CRC progression. Herein, we assessed the differences in the levels of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), selenium (Se), and zinc (Zn) in tumors and adjacent healthy tissues, to investigate the relationship between heavy metals/trace elements and CRC progression. Surgical samples of CRC and noncancerous tissues were collected, and trace metal levels were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Logistic regression, PCA, and BKMR models were used to investigate the relationship between heavy metals and trace elements and the degree of tumor differentiation and lymph node metastasis in CRC. Cancer tissues showed lower As, Cd, Co, and Cr concentrations, and higher Se concentrations than healthy tissues (P < 0.05). In addition, CRC patients with poorly differentiated tumors and/or positive lymph node metastases had lower levels of Cd, Zn, Cu, and Se (P < 0.05). Logistic regression showed that single metal concentration was negatively correlated with CRC progression. PCA and BKMR models also showed that the metal mixture concentration was negatively correlated with CRC progression, with Cd contributing the most. Overall, changes in heavy metal and trace element levels may be related to the development of CRC; however, further mechanistic studies are required.

A review of metallurgical slags as catalysts in advanced oxidation processes for removal of refractory organic pollutants in wastewater

With the rapid growth of the metallurgical industry, there is a significant increase in the production of metallurgical slags. The waste slags pose significant challenges for their disposal because of complex compositions, low utilization rates, and environmental toxicity. One promising approach is to utilize metallurgical slags as catalysts for treatment of refractory organic pollutants in wastewater through advanced oxidation processes (AOPs), achieving the objective of "treating waste with waste". This work provides a literature review of the source, production, and chemical composition of metallurgical slags, including steel slag, copper slag, electrolytic manganese residue, and red mud. It emphasizes the modification methods of metallurgical slags as catalysts and the application in AOPs for degradation of refractory organic pollutants. The reaction conditions, catalytic performance, and degradation mechanisms of organic pollutants using metallurgical slags are summarized. Studies have proved the feasibility of using metallurgical slags as catalysts for removing various pollutants by AOPs. The catalytic performance was significantly influenced by slags-derived catalysts, catalyst modification, and process factors. Future research should focus on addressing the safety and stability of catalysts, developing green and efficient modification methods, enhancing degradation efficiency, and implementing large-scale treatment of real wastewater. This work offers insights into the resource utilization of metallurgical slags and pollutant degradation in wastewater.

Mediating Role of Liver Dysfunction in the Association between Arsenic Exposure and Diabetes in Chinese Adults: A Nationwide Cross-Sectional Study of China National Human Biomonitoring (CNHBM) 2017-2018

Inconsistent results have been reported regarding the association between low-to-moderate arsenic (As) exposure and diabetes. The effect of liver dysfunction on As-induced diabetes remains unclear. The cross-sectional study included 10,574 adults from 2017-2018 China National Human Biomonitoring. Urinary total As (TAs) levels were analyzed as markers of As exposure. Generalized linear mixed models and restricted cubic splines models were used to examine the relationships among TAs levels, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) concentrations, and diabetes prevalence. Mediating analysis was performed to assess whether liver dysfunction mediated the association between TAs and diabetes. Overall, the OR (95% CI) of diabetes in participants in the second, third, and fourth quartiles of TAs were 1.08 (0.88, 1.33), 1.17 (0.94, 1.45), and 1.52 (1.22, 1.90), respectively, in the fully adjusted models compared with those in the lowest quartile. Serum ALT was positively associated with TAs and diabetes. Additionally, mediation analyses showed that ALT mediated 4.32% of the association between TAs and diabetes in the overall population and 8.86% in the population without alcohol consumption in the past year. This study suggested that alleviating the hepatotoxicity of As could have implications for both diabetes and liver disease.

Concentration of heavy metals in pasteurized and sterilized milk and health risk assessment across the globe: A systematic review

OBJECTIVE

Although milk and dairy products are almost complete food, they can contain toxic heavy elements with potential hazards for consumers. This review aims to provide a comprehensive report on the occurrence, concentration, and health risks of selected heavy metals in pasteurized and sterilized milk recorded worldwide.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) was used to develop this systematic review. Databases included the Web of Knowledge, Scopus, Scientific Information Database, Google Scholar, and PubMed from inception until January 2023. Keywords related to the terms "Heavy metals", "Arsenic" and "Pasteurized and sterilized milk" and "Risk Assessment" were used. The potential health risks to human health from milk daily consumption were estimated using extracted data on heavy metals concentration based on metal estimated daily intake, target hazard quotient, and carcinogenic risk.

RESULTS

A total of 48 potentially relevant articles with data on 981 milk samples were included in the systematic review. Atomic Absorption Spectroscopy, atomic absorption spectroscopy, inductively coupled plasma-mass spectrometry, and inductively coupled plasma-optical emission spectrometry were the most common valid methods to measure heavy metals in milk samples. Following the initial evaluation, Cu, Cd, Zn, and Pb were the most contaminants, which exceeded the maximum permissible criteria in 94%, 67%, 62%, and 46% of the milk samples tested. Relying on target hazard quotient and carcinogenic risk results, milk consumers in 33(68.75%) and 7 (14.5%) studies were exposed to moderate to high levels of carcinogenic and non-carcinogenic risk, respectively. The highest level of risk is due to the consumption of pasteurized and sterilized milk detected in Pakistan, Brazil, Egypt, Slovakia, and Turkey.

CONCLUSION

The elevated levels of heavy metals in milk samples, especially Pb and Cd is a public health concern; therefore, maximum control and strict regulations must be adopted to decrease heavy metals contaminants in the dairy industry. Further studies are required to develop safe milk processing and handling methods for the decontamination of heavy metals in milk and its products.

Interaction mechanism of water-soluble inorganic arsenic onto pristine nanoplastics

Nanoplastics (NPLs) persist in aquatic habitats, leading to incremental research on their interaction mechanisms with metalloids in the environment. In this regard, it is known that plastic debris can reduce the number of water-soluble arsenicals in contaminated environments. Here, the arsenic interaction mechanism with pure NPLs, such as polyethylene terephthalate (PET), aliphatic polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and polystyrene (PS) is evaluated using computational chemistry tools. Our results show that arsenic forms stable monolayers on NPLs through surface adsorption, with adsorption energies of 9-24 kcal/mol comparable to those on minerals and composite materials. NPLs exhibit varying affinity towards arsenic based on their composition, with As(V) adsorption showing higher stability than As(III). The adsorption mechanism results from a balance between electrostatics and dispersion forces (physisorption), with an average combined contribution of 87%. PA, PET, PVC, and PS maximize the electrostatic effects over dispersion forces, while PE and PP maximize the dispersion forces over electrostatic effects. The electrostatic contribution is attributed to hydrogen bonding and the activation of terminal O-C, C-H, and C-Cl groups of NPLs, resulting in several pairwise interactions with arsenic. Moreover, NPLs polarity enables high mobility in aqueous environments and fast mass transfer. Upon adsorption, As(III) keeps the NPLs polarity, while As(V) limits subsequent uptake but ensures high mobility in water. The solvation process is destabilizing, and the higher the NPL polarity, the higher the solvation energy penalty. Finally, the mechanistic understanding explains how temperature, pressure, pH, salinity, and aging affect arsenic adsorption. This study provides reliable quantitative data for sorption and kinetic experiments on plastic pollution and enhances our understanding of interactions between water contaminants.

Arsenic toxicity: sources, pathophysiology and mechanism

Background

Arsenic is a naturally occurring element that poses a significant threat to human health due to its widespread presence in the environment, affecting millions worldwide. Sources of arsenic exposure are diverse, stemming from mining activities, manufacturing processes, and natural geological formations. Arsenic manifests in both organic and inorganic forms, with trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) being the most common inorganic forms. The trivalent state, in particular, holds toxicological significance due to its potent interactions with sulfur-containing proteins.

Objective

The primary objective of this review is to consolidate current knowledge on arsenic toxicity, addressing its sources, chemical forms, and the diverse pathways through which it affects human health. It also focuses on the impact of arsenic toxicity on various organs and systems, as well as potential molecular and cellular mechanisms involved in arsenic-induced pathogenesis.

Methods

A systematic literature review was conducted, encompassing studies from diverse fields such as environmental science, toxicology, and epidemiology. Key databases like PubMed, Scopus, Google Scholar, and Science Direct were searched using predetermined criteria to select relevant articles, with a focus on recent research and comprehensive reviews to unravel the toxicological manifestations of arsenic, employing various animal models to discern the underlying mechanisms of arsenic toxicity.

Results

The review outlines the multifaceted aspects of arsenic toxicity, including its association with chronic diseases such as cancer, cardiovascular disorders, and neurotoxicity. The emphasis is placed on elucidating the role of oxidative stress, genotoxicity, and epigenetic modifications in arsenic-induced cellular damage. Additionally, the impact of arsenic on vulnerable populations and potential interventions are discussed.

Conclusions

Arsenic toxicity represents a complex and pervasive public health issue with far-reaching implications. Understanding the diverse pathways through which arsenic exerts its toxic effects is crucial to developing effective mitigation strategies and interventions. Further research is needed to fill gaps in our understanding of arsenic toxicity and to inform public health policies aimed at minimising exposure.Arsenic toxicity is a crucial public health problem influencing millions of people around the world. The possible sources of arsenic toxicity includes mining, manufacturing processes and natural geological sources. Arsenic exists in organic as well as in inorganic forms. Trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) are two most common inorganic forms of arsenic. Trivalent oxidation state is toxicologically more potent due to its potential to interact with sulfur containing proteins. Humans are exposed to arsenic in many ways such as environment and consumption of arsenic containing foods. Drinking of arsenic-contaminated groundwater is an unavoidable source of poisoning, especially in India, Bangladesh, China, and some Central and South American countries. Plenty of research has been carried out on toxicological manifestation of arsenic in different animal models to identify the actual mechanism of aresenic toxicity. Therefore, we have made an effort to summarize the toxicology of arsenic, its pathophysiological impacts on various organs and its molecular mechanism of action.

Baicalein Alleviates Arsenic-induced Oxidative Stress through Activation of the Keap1/Nrf2 Signalling Pathway in Normal Human Liver Cells

BACKGROUND

Oxidative stress is a key mechanism underlying arsenicinduced liver injury, the Kelch-like epichlorohydrin-related protein 1 (Keap1)/nuclear factor E2 related factor 2 (Nrf2) pathway is the main regulatory pathway involved in antioxidant protein and phase II detoxification enzyme expression. The aim of the present study was to investigate the role and mechanism of baicalein in the alleviation of arsenic-induced oxidative stress in normal human liver cells.

METHODS

Normal human liver cells (MIHA cells) were treated with NaAsO2 (0, 5, 10, 20 μM) to observe the effect of different doses of NaAsO2 on MIHA cells. In addition, the cells were treated with DMSO (0.1%), NaAsO2 (20 μM), or a combination of NaAsO2 (20 μM) and Baicalein (25, 50 or 100 μM) for 24 h to observe the antagonistic effect of Baicalein on NaAsO2. Cell viability was determined using a Cell Counting Kit- 8 (CCK-8 kit). The intervention doses of baicalein in subsequent experiments were determined to be 25, 50 and 100μM. The intracellular content of reactive oxygen species (ROS) was assessed using a 2',7'-dichlorodihydrofluorescein diacetate (DCFHDA) probe kit. The malonaldehyde (MDA), Cu-Zn superoxide dismutase (Cu-Zn SOD) and glutathione peroxidase (GSH-Px) activities were determined by a test kit. The expression levels of key genes and proteins were determined by real-time fluorescence quantitative polymerase chain reaction (qPCR) and Western blotting.

RESULTS

Baicalein upregulated the protein expression levels of phosphorylated Nrf2 (p-Nrf2) and nuclear Nrf2, inhibited the downregulation of Nrf2 target genes induced by arsenic, and decreased the production of ROS and MDA. These results demonstrate that baicalein promotes Nrf2 nuclear translocation by upregulating p-Nrf2 and inhibiting the downregulation of Nrf2 target genes in arsenic-treated MIHA cells, thereby enhancing the antioxidant capacity of cells and reducing oxidative stress.

CONCLUSION

Baicalein alleviated arsenic-induced oxidative stress through activation of the Keap1/Nrf2 signalling pathway in normal human liver cells.

Dissolved black carbon mediated photo-oxidation of arsenic(III) to arsenic(V) in water: The key role of triplet states

Arsenic is a common contaminant found in natural waters, and has raised significant environmental concerns due to its toxicity and carcinogenicity. In this study, we investigated the mediated photo-oxidation of arsenite (As(III)) under simulated sunlight by dissolved black carbon (DBC), an important dissolved organic matter (DOM) constituent released from black carbon. Five DBC were collected from the water extracts of black carbons that were derived by pyrolyzing different biomass (i.e., bamboo, rice, peanuts, corn, and sorghum stalks), and four well-studied dissolved humic substances (DHS) were selected for benchmarking. The presence of DBC (i.e., 5 mg C-1) significantly accelerated the photo-oxidation of As(III) to arsenate (As(V)), with the observed pseudo-first-order rate constant of reaction increased by 5∼11 times. Quenching experiments of photochemically produced reactive intermediates suggested that As(III) was mainly oxidized by triplet-excited DBC (3DBC*, contribution of 48%), singlet oxygen (1O2, 18%) and superoxide anions (O2•-, 28%) in sunlight-irradiated DBC solutions. The average apparent quantum yield of As(III) photo-oxidation for DBC was found to be more than 4 times higher in comparison with DHS. Such a strong mediation efficiency of DBC was due to its smaller molecular size and higher aromaticity than DHS, which facilitated the non-charge-transfer process to produce triplet-excited states and their sensitized 1O2. Consistently, DBC exhibited a higher apparent quantum yield and a longer lifetime of triplet states as compared with DHS. The results imply that DBC may play a previously unrecognized important role in the fate of arsenic in aquatic environments.

The role of thioredoxin and glutathione systems in arsenic-induced liver injury in rats under glutathione depletion

Antioxidant systems like thioredoxin (Trx) and glutaredoxin (Grx) maintain oxidative stress balance. These systems have cross-talk supported by some in vitro studies. We investigated the underlying mechanisms of arsenic-induced liver injury in glutathione-deficient rats and whether there was any cross-talk between the Trx and Grx systems. The rats in arsenic-treated groups were administered with sodium arsenite (10, 20 mg/kg b w/d) for four weeks. In buthionine sulfoximine (BSO, an inhibitor of GSH) and 20 mg/kg arsenic combined groups, rats were injected with 2 mmol/kg BSO intraperitoneally twice per week. BSO exacerbated arsenic-induced liver injury by increasing arsenic accumulation in urine, serum, and liver while decreasing glutathione activity and resulting in upregulated mRNA expression of the Trx system and downregulation of Grx mRNA expression. The impact of Trx lasted longer than that of the Grx. The Trx system remained highly expressed, while GSH, Grx1, and Grx2 levels were decreased. The inhibitory effect of only BSO treatment on Grx1 and Grx2 was not pronounced. However, the combined impact of arsenic and BSO upregulated Trx expression, primarily related to further reduction of GSH. As a result, the suppressed Grxs were protected by the upregulated Trxs, which serve as a backup antioxidant defense system in the liver.

MicroRNA-195-5p mediates arsenic-induced cytotoxicity in human lung epithelial cells: Beneficial role of plant-derived tannic acid

Arsenic (As), a highly toxic metalloid, which causes environmental lung diseases and affects millions of people worldwide. Respiratory epithelial cells are essential for maintaining lung homeostasis, aberrant epithelial damage and death due to exposure to a wide range of environmental pollutants, which are considered to be the initial trigger for many pulmonary diseases. Accumulating evidence has shown that microRNAs (miRNAs) appear to be important players in various normal physiological and pathological processes. Therefore, the present study was carried out to examine the cytotoxic effects of a trivalent form of As (As3+) in normal human bronchial (BEAS-2B) and adenocarcinoma alveolar basal (A549) epithelial cells and the role of miR-195-5p. Further, we also explored the protective effects of a natural dietary polyphenol tannic acid (TA). As3+ (1 μM) treatment in BEAS-2B cells for 24 h induced cytotoxicity by decreasing the cell viability, mitochondrial membrane potential (ΔΨm) and inducing reactive oxygen species (ROS) generation, lipid peroxidation (LPO), cell cycle arrest, and apoptosis, which was associated with a significantly higher level of miR-195-5p expression compared with vehicle control. Forced expression of miR-195-5p alone suppressed cell survival, ΔΨm, regulated cell cycle distribution and induced ROS generation in BEAS-2B cells. As expected, miR-195-5p inhibition effectively rescued BEAS-2B cells from As3+-mediated toxicity, confirming the involvement of miR-195-5p in the cytotoxic effects of As3+. Further, TA pre-treatment expressively alleviated As3+-induced toxicity by suppressing ROS production, miR-195-5p expression, and increasing ΔΨm. These in vitro results indicate that miR-195-5p may be useful as a therapeutic target for treating As3+ toxicity.