Arsenobetaine Research Articles

Integrating Transcriptome and Metabolome Analyses Revealed Salinity Induces Arsenobetaine Biosynthesis in Marine Medaka (Oryzias melastigma).

Marine fish exhibit elevated levels of arsenobetaine (AsB), while the impact and underlying mechanism of salinity on AsB biosynthesis remain inadequately explored. In this study, marine medaka (Oryzias melastigma), typically inhabiting 30‰ high salinity, were gradually acclimated to low salinities of 20, 10, and 0‰. Following acclimation, the fish were exposed to arsenate (As(V)) in their diet for 30 days. Results showed a significant accumulation of total arsenic (As) and AsB concentrations in the muscle and head tissues of the exposed fish, with these accumulations exhibiting a positive correlation with water salinity. Transcriptome analyses revealed that exposure to As(V) at low salinity may disrupt membrane components and induce cytoskeletal injuries, while at high salinity, it triggered oxidoreductase activity and transmembrane transport. Metabolome analyses indicated that low salinity induced osmotic stress, resulting in an increased requirement for amino acids to upload intracellular osmotic equilibrium in O. melastigma. Furthermore, the key organic osmolytes and amino acids, including taurine, l-methionine, guanidinoethyl sulfonate, and N-acetyl-l-aspartic acid, exhibited a negative correlation with the AsB concentration. These findings indicated that salinity can regulate osmotic balance by influencing amino acid synthesis under low salinity and stimulating AsB synthesis under high salinity conditions in O. melastigma. This study provides insights into the impact of high salinity on AsB biosynthesis, the underlying regulatory mechanisms, and implications for managing As(V) risk.

Microplastics and arsenic speciation in edible bivalves from the coast of China: Distribution, bioavailability, and human health risk

Bivalves, such as oysters and mussels, are exposed to environmental pollutants, like microplastics (MPs) and arsenic (As). This study investigated co-existence and interaction of MPs and As (total As and As species) in two bivalve species from the Chinese coastline. Smaller MPs (20–100 μm) averaged 30.98 items/g, while larger MPs (100–500 μm) averaged 2.98 items/g. Oysters contained more MPs (57.97 items/g) in comparison to mussels (11.10 items/g). In Contrast, mussels had a higher As concentrations (8.36–23.65 mg/kg) than oysters (4.97–11.02 mg/kg). The size and composition of MPs influenced As uptake and speciation in bivalves, with inorganic arsenic (iAs) and methylated arsenic (MMA and DMA) correlating with larger-sized MPs. Polyethylene (PE) may interact with the formation of arsenobetaine (AsB) in oyster. This study provides valuable insights into the interaction of MPs and As in marine ecosystems and highlights their implications for food safety.

Total arsenic and arsenic species in selected seafoods: Analysis using high-performance liquid chromatography- inductively coupled plasma mass spectrometry and health risk assessment

The objective of the present study was to determine the inorganic and organic arsenic species and assess the actual risk of selected seafood produced in Sri Lanka in terms of inorganic arsenic species. A total of 80 samples, comprising 75 seafood samples and 5 freshwater samples, including mollusks, echinoderms, and crustaceans, were analyzed for their total arsenic (TA) levels and arsenic species. TA levels in seafood were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after microwave digestion. Arsenic species, including arsenobetaine (AsB), arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA), were selectively separated and quantified using High-Performance Liquid Chromatography (HPLC) coupled to ICP-MS, following water bath extraction with 30 mmol/L nitric acid. The TA levels in seafood ranged from 0.036 to 11.686 mg kg-1. The spike recovery values for the five arsenic species lay within 80 % to 120 %, and the chromatographic recovery percentages ranged from 85.5 % to 123.6 %. In most samples, 100 % AsB was detected. Sea cucumber and both marine and freshwater giant river prawns showed AsB percentages of the total arsenicals at 83.2 %, 39.7 %, and 21.3 %, respectively. DMA was found in sea cucumber and marine giant river prawn at levels of 0.065 mg kg-1 and 0.048 mg kg-1, respectively, while MMA was not detected in any samples. AsIII was found in marine water giant river prawn and freshwater giant river prawn at levels of 0.010 mg kg-1 and 0.044 mg kg-1, respectively. AsV was only found in marine giant river prawn at a concentration of 0.193 mg kg-1. No other samples contained detectable levels of inorganic arsenicals. The Target Hazard Quotient (THQ) values for marine and freshwater giant river prawn were 0.90 and 0.2, respectively, indicating no significant health risks since the THQ values were <1. Therefore, our study suggests that consuming the studied seafood does not pose any health risks in terms of arsenic.

Metabolome analysis revealed the critical role of betaine for arsenobetaine biosynthesis in the marine medaka (Oryzias melastigma)

Arsenobetaine (AsB), a non-toxic arsenic (As) compound found in marine fish, structurally resembles betaine (GB), a common methyl donor in organisms. This study investigates the potential role of GB in AsB synthesis in marine medaka (Oryzias melastigma) using metabolomic analysis. Dietary exposure to arsenate (As(V)) and varying GB concentrations (0.05% and 0.1% in diets) increased total As and AsB bioaccumulation, particularly in marine medaka muscle. Metabolomic analysis revealed that GB played a crucial role in promoting up-regulation in methylthioadenosine (MTA) by modulating the methionine cycle and down-regulation in glutathione (GSH) by modulating the glutathione cycle. Methionine metabolism and GSH, potentially binding again to exogenous GB, could synchronously produce more non-toxic AsB. Combining verification experiments of differential metabolites of Escherichia coli in vitro, GB, GSH, S-adenosylmethionine (SAM), and arsenocholine (AsC) entered methionine and glutathione metabolism pathways to generate more AsB. These findings underscore the GB's crucial regulatory role in modulating the synthesis of AsB. This study provides vital insights into the interplay between the structural analogs GB and AsB, offering specific strategies to enhance the detoxification mechanisms of marine fish in As-contaminated environments.

Alleviative effects of C60 fullerene nanoparticles on arsenate transformation and toxicity to Danio rerio

Widely-used C60 fullerene nanoparticles (C60) result in their release into the aquatic environment, which may affect the distribution and toxicity of pollutants such as arsenic (As), to aquatic organism. In this study, arsenate (As(V)) accumulation, speciation and subcellular distribution was determined in Danio rerio (zebrafish) intestine, head and muscle tissues in the presence of C60. Meanwhile we compared how single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO) and graphene (GN) nanoparticles alter the behaviors of As(V). Results showed that C60 significantly inhibited As accumulation and toxicity in D. rerio, due to a decrease in total As and monomethylarsonic acid (MMA) and As(V) species concentrations, a lower relative distribution in the metal-sensitive fraction (MSF). It was attributed that C60 may coat As(V) ion channels and consequently, affect the secretion of digestive enzymes in the gut, favoring As excretion and inhibiting As methylation. Similarly, MWCNTs reduced the species concentration of MMA and As(V) in the intestines, low GSH (glutathione) contents in the intestine. Due to the disparity of other carbon-based nanomaterial morphologies, SWCNTs, GO and GN exhibited the various effects on the toxicity of As(V). In addition, the possible pathway of arsenobetaine (AsB) biosynthesis included migration from the intestine to muscle in D. rerio, with the precursor of AsB likely to be 2-dimethylarsinylacetic acid (DMAA). The results of this study suggest that C60 is beneficial for controlling As(V) pollution and reducing the impact of As(V) biogeochemical cycles throughout the ecosystem.

Bio-accessibility and bio-availability evaluation of each arsenic species existing in various edible seaweeds in vitro and in vivo for arsenic risk assessment

Seaweeds consumption is one of main internal exposure sources of arsenic for human. However, the absence of representative bio-availabilities of arsenic species makes the accurate assessment of arsenic health risk originating from seaweeds consumption impossible. Herein, the arsenic species in various seaweeds collected from Fujian of China were investigated, and the bio-accessibilities/bio-availabilities of arsenic species existing in seaweeds were evaluated in vitro and in vivo. Results revealed that in vitro bio-availabilities of arsenic species presenting in seaweeds, which obtained with Caco-2 cells, were lower than those of pure arsenic standards, and varied with order of inorganic arsenic (iAs) > dimethylarsinic acid (DMA) ≈ arsenobetaine (AsB) > arsenosugars. During gastrointestinal digestion of mice, As5+ was partly methylated into monomethylarsonic acid (MMA) and DMA, which makes the in vivo bioavailability of iAs (⁓31.8 %) obtained with mouse metabolic experiment is much higher than its in vitro bio-availability (⁓10.3 %). The in vivo bio-availabilities of DMA and total arsenic (tAs) are similar to their in vitro bio-availabilities. As the dominant arsenic species in most seaweeds, arsenosugars have an ⁓0.0 % of in vivo bioavailability and only a ⁓3.7 % of in vitro bioavailability. The simulated calculation of target hazard quotient (THQ) and target cancer risk (TR) revealed that the arsenic risk originating from seaweeds was greatly degraded by taking into consideration of arsenic species and bio-availabilities, and all seaweeds collected from Fujian are safety for consumption. The simulated calculation also revealed that arsenic risk of seaweeds can be also more accurately assessed based on tAs together with bioavailability, which provides a simple but accurate and protective method for the risk assessment of arsenic originating from seaweeds. Our work provides the possible representative bio-availabilities of arsenic species presenting in seaweeds for accurately assessing arsenic risk of seaweeds, and novel insights into the bio-availabilities of arsenic in animal.

A review of arsenic speciation in freshwater fish: Perspectives on monitoring approaches and analytical methods

Arsenic accumulation in fish poses concerns for subsistence and recreational fishers worldwide. However, the toxicity of arsenic to consumers strongly depends on the chemical forms, or species, present. Risk assessments often rely on total arsenic concentrations ([As]), adjusting for assumed small percentages of the most harmful inorganic species. While studies on arsenic speciation in marine fish are widespread, and commonly report less toxic arsenobetaine (AsB) as the dominant form, fewer studies have been conducted on freshwater fish, where arsenic speciation may be more variable. To assess these findings, we conducted a systematic literature review on arsenic speciation in freshwater fish using Covidence© review management software. From over 1100 screened studies, 41 were selected for inclusion based on predefined criteria. These studies reported highly variable arsenic speciation patterns in freshwater fish, calling into question the assumption that AsB is the dominant form present. Sites with suspected or known arsenic contamination issues were prominent, with &gt;50% of data reviewed originating from a contaminated river or lake, but the effect of contamination on arsenic speciation was variable. Although AsB and other organic forms typically dominated, some studies (6/41; 15%) identified fish with elevated concentrations of inorganic arsenic (&gt;1 mg/kg dry wt.), most often corresponding to over 20% of total arsenic. Furthermore, arsenic speciation results accounted for a highly variable proportion of total [As] in fish, often less than 50%. Assuming 20% inorganic arsenic appears to be a poor approximation that cannot be applied to all fish. Based on this considerable variability, we recommend the direct measurement of arsenic species whenever possible, especially when total [As] is elevated above relevant guidelines for the most toxic species (e.g., 0.1-2 mg/kg inorganic arsenic wet wt.). We also recommend future works communicate their results in more detail, including complete description of QAQC protocols, to improve the potential for future meta-analyses. Additional work is needed to characterize arsenic speciation in freshwater fish and assess the toxicity of various arsenic species to accurately evaluate the environmental and human health risks associated with arsenic in fish.

Arsenic bioaccumulation and biotransformation in the marine copepod Tigriopus japonicus under chronic dietborne and waterborne exposure

Arsenic (As) can be transferred along the food chain, while little is known about the toxic effects of dietborne As on marine copepods. In this study, we investigated the short-term and long-term effects of waterborne and dietborne As exposure on the bioaccumulation and biotransformation, as well as developmental toxicity of Tigriopus japonicus. Under acute As exposure, As bioaccumulation increased and reached a plateau with increasing exposure concentration. Moreover, As accumulation at dietborne exposure was 4.3 and 5.7 times greater than that at control group for AsIII and AsV, respectively. At chronic As exposure, As accumulation increased continuously with exposure time, with a 2.8-day extension of development time and a 45% reduction in 10-d fecundity under dietborne exposure compared to control, whereas 2.3-day extension of development time and a 20% reduction in 10-d fecundity were observed under waterborne exposure. Among As species, inorganic As had the highest concentrations, but the proportion of inorganic As decreased from 89% to 63% during 4 to 21 d of exposure, suggesting the conversion of inorganic As to organic As. The organic As was dominated by arsenobetaine (AsB, 13–25%), followed by monomethylarsenic (MMA, 8–25%). These results suggest that dietborne exposure has more pronounced toxic effects on T. japonicus, but the toxicity of As could be reduced through biotransformation under chronic exposure. Therefore, the arsenic species should be considered when assessing As toxicity.

Arsenic bioaccumulation and biotransformation in different tissues of Nile tilapia (Oreochromis niloticus): A comparative study between As(III) and As(V) exposure and evaluation of antagonistic effects of selenium

The speciation of arsenic in fish has been widely investigated, but bioaccumulation and biotransformation of inorganic As in different tissues of Nile tilapia (Oreochromis niloticus) are not fully understood. The present study aimed to investigate the bioaccumulation of As in Nile tilapia, as well as to evaluate the distribution of the main arsenic species (As(III), As(V), MMA, DMA, and AsB) in liver, stomach, gill, and muscle, after controlled exposures to As(III) and As(V) at concentrations of 5.0 and 10.0 mg L−1 during periods of 1 and 7 days. Total As was determined by inductively coupled plasma mass spectroscopy (ICP-MS). For both exposures (As(III) and As(V)), the total As levels after 7-day exposure were highest in the liver and lowest in the muscle. Overall, the Nile tilapia exposed to As(III) showed higher tissue levels of As after the treatments, compared to As(V) exposure. Speciation of arsenic present in the tissues employed liquid chromatography coupled to ICP-MS (LC-ICP-MS), revealing that the biotransformation of As included As(V) reduction to As(III), methylation to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), and subsequent conversion to nontoxic arsenobetaine (AsB), which was the predominant arsenic form. Finally, the interactions and antagonistic effects of selenium in the bioaccumulation processes were tested by the combined exposure to As(III), the most toxic species of As, together with tetravalent selenium (Se(IV)). The results indicated a 4–6 times reduction of arsenic toxicity in the tilapia.

Speciation of arsenic in milk from cows fed seaweed.

Including seaweed in cattle feed has gained increased interest, but it is important to take into account that the concentration of toxic metals, especially arsenic, is high in seaweed. This study investigated the arsenic species in milk from seaweed-fed cows. Total arsenic in milk of control diets (9.3 ± 1.0 μg As kg-1, n = 4, dry mass) was significantly higher than seaweed-based diet (high-seaweed diet: 7.8 ± 0.4 μg As kg-1, P < 0.05, n = 4, dry mass; low-seaweed diet: 6.2 ± 1.0 μg As kg-1, P < 0.01, n = 4, dry mass). Arsenic speciation showed that the main species present were arsenobetaine (AB) and arsenate (As(V)) (37% and 24% of the total arsenic, respectively). Trace amounts of dimethylarsinic acid (DMA) and arsenocholine (AC) have also been detected in milk. Apart from arsenate being significantly lower (P < 0.001) in milk from seaweed-fed cows than in milk from the control group, other arsenic species showed no significant differences between groups. The lower total arsenic and arsenate in seaweed diet groups indicates a possible competition of uptake between arsenate and phosphate, and the presence of AC indicates that a reduction of AB occurred in the digestive tract. Feeding a seaweed blend (91% Ascophyllum nodosum and 9% Laminaria digitata) does not raise As-related safety concerns for milk. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Arsenic speciation in low-trophic marine food chain – An arsenic exposure study on microalgae (Diacronema lutheri) and blue mussels (Mytilus edulis L.)

Microalgae and blue mussels are known to accumulate undesirable substances from the environment, including arsenic (As). Microalgae can biotransform inorganic As (iAs) to organoarsenic species, which can be transferred to blue mussels. Knowledge on As uptake, biotransformation, and trophic transfer is important with regards to feed and food safety since As species have varying toxicities. In the current work, experiments were conducted in two parts: (1) exposure of the microalgae Diacronema lutheri to 5 and 10 μg/L As(V) in seawater for 4 days, and (2) dietary As exposure where blue mussels (Mytilus edulis L.) were fed with D. lutheri exposed to 5 and 10 μg/L As(V), or by aquatic exposure to 5 μg/L As(V) in seawater, for a total of 25 days. The results showed that D. lutheri can take up As from seawater and transform it to methylated As species and arsenosugars (AsSug). However, exposure to 10 μg/L As(V) resulted in accumulation of iAs in D. lutheri and lower production of methylated As species, which may suggest that detoxification mechanisms were overwhelmed. Blue mussels exposed to As via the diet and seawater showed no accumulation of As. Use of linear mixed models revealed that the blue mussels were gradually losing As instead, which may be due to As concentration differences in the mussels’ natural environment and the experimental setup. Both D. lutheri and blue mussels contained notable proportions of simple methylated As species and AsSug. Arsenobetaine (AB) was not detected in D. lutheri but present in minor fraction in mussels. The findings suggest that low-trophic marine organisms mainly contain methylated As species and AsSug. The use of low-trophic marine organisms as feed ingredients requires further studies since AsSug are regarded as potentially toxic, which may introduce new risks to feed and food safety.

Association between mediterranean diet and metal(loid) exposure in 4-5-year-old children living in Spain.

Even relatively low levels of metals exposure may impact health, particularly among vulnerable populations such as infants and young children. However, little is known about the interplay between simultaneous metal exposures, common in real-life scenarios, and their association with specific dietary patterns. In this study, we have evaluated the association between adherence to Mediterranean diet (MD) and urinary metal concentrations individually and as an exposure mixture in 713 children aged 4-5-years from the INMA cohort study. We used a validated food frequency questionnaire to calculate two MD indexes scores: aMED and rMED. These indexes gather information on various food groups within the MD and score differently. To measure urinary concentrations of cobalt, copper, zinc, molybdenum, selenium, lead, and cadmium as exposure biomarkers, we used inductively coupled plasma mass spectrometry (ICP-MS), coupled with an ion chromatography (IC) equipment for arsenic speciation analysis. We applied linear regression and quantile g-computation, adjusted for confounders, to analyse the association between MD adherence and exposure to the metal mixture. High adherence to MD such as the quintile (Q) 5 MD was associated with higher urinary arsenobetaine (AsB) levels than Q1, with β values of 0.55 (confidence interval - CI 95% 0.01; 1.09) for aMED and 0.73 (CI 95% 0.13; 1.33) for rMED. Consumption of fish was associated with increased urinary AsB but reduced inorganic arsenic concentrations. In contrast, the aMED vegetables consumption increased urinary inorganic arsenic content. A moderate level of adherence to MD (Q2 and Q3) was associated with lower copper urinary concentrations than Q1, with β values of −0.42 (CI 95% −0.72; −0.11) for Q2 and -0.33 (CI 95% −0.63; −0.02) for Q3, but only with aMED. Our study, conducted in Spain, revealed that adhering to the MD reduces exposure to certain metals while increasing exposure to others. Specifically, we observed increase in exposure to non-toxic AsB, highlighting the significance of consuming fish/seafood. However, it is crucial to emphasize the necessity for additional efforts in reducing early-life exposure to toxic metals, even when adhering to certain food components of the MD.

Chemical Speciation of Arsenic and Chromium in Seafood by LC-ICP-MS

Two methods were developed for the As and Cr species determination in different kinds of seafood, exploring the LC-ICP-MS potential and chemometric approach to define the extraction conditions. Adequates separation and sensitivity data by LC-ICP-MS were obtained with 0.01 mol L-1 (NH4)2HPO4 in 1% ethanol (pH 8.0) for arsenic, and 0.015 mol L-1 Na2SO4, 0.005 mol L-1 EDTA, and 0.005 mol L-1 NaH2PO4 (pH 7.0) for chromium. The Doehlert matrix and Box-Behnken design defined the ideal extraction conditions for arsenic and chromium species. For As extraction, the optimized conditions employed 0.1 g of sample and 30 mmol L-1 HNO3 at 90°C for 45 min, and Cr, 0.1 g of sample and 0.045 mol L-1 [EDTA] at 90°C for 40 min. Recoveries from 88 to 106% of arsenobetaine (AsB), arsenite [As(III)], dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenate [As(V)], Cr(III) and Cr(VI) were obtained for all evaluated samples. The limits of quantification provided by the proposed methods were 5.3; 52.1; 16.4; 2.8; 83.3; 113.8; 53.9 ng g-1 for AsB, As(III), DMA, MMA, As(V), Cr(III) and Cr(VI) respectively. The trueness was evaluated using certified reference materials and addition and recovery procedures. The sum of the species agreed with the total concentration of arsenic and chromium contents.

Prenatal arsenic exposure, arsenic metabolism and neurocognitive development of 2-year-old children in low-arsenic areas

BackgroundThere is limited evidence on the effects of arsenic species and metabolic capacity on child neurodevelopment, particularly at low levels. Further, little is known about the critical window of exposure. ObjectiveTo estimate the associations of arsenic exposure and arsenic metabolism in different pregnancy periods with neurodevelopment of two-year-old children. MethodsConcentrations of arsenobetaine (AsB), arsenite, arsenate, monomethyl arsenic acid (MMA), and dimethyl arsenic acid (DMA) in urine samples collected in three trimesters from 1006 mothers were measured using HPLC − ICPMS. Inorganic arsenic (iAs) was calculated as the sum of arsenite and arsenate. Total arsenic (tAs) was calculated as the sum of iAs, MMA and DMA. Child neurodevelopment was assessed with the Bayley Scales of Infant Development. ResultsThe geometric mean (GM) of SG-adjusted tAs in the first, second, third trimester was 16.37, 12.94, 13.04 μg/L, respectively. The mental development index (MDI) score was inversely associated with iAs and tAs. Compared to the 1st quartile, the MDI score decreased 0.43 (95%CI: −4.22, 3.36) for the 2nd, 6.50 (95%CI: −11.73, −1.27) for the 3rd, 5.42 (95%CI: −10.74, −0.10) for the 4th quartiles of iAs, and decreased 4.03 (95%CI: −7.90, −0.15) in the 4th quartile of tAs. In trimester-specific models, negative associations of DMA [−1.94 (95%CI: −3.18, −0.71)] and tAs [−1.61 (95%CI: −3.02, −0.20)] with the psychomotor development index (PDI) were only observed in 1st trimester. ConclusionsOur study found inverse associations between prenatal arsenic exposure, especially in early pregnancy, and neurodevelopment of children at two years old, even at low exposure levels.

Speciated and Total Urinary Arsenic Levels in Belo Horizonte, the Largest Brazilian City within the Mineral-Rich Region “Iron Quadrangle”

The “Quadrilátero Ferrífero” (Iron Quadrangle) is a mineral-rich province in Brazil, where arsenic anomalies are associated with gold mining and tailings dam failures. Urine samples were randomly collected from residents of Belo Horizonte (BH) city (N = 506 total/138 speciation) and the metropolitan area (N = 35 total/10 speciation), with stratifications in age, female-male and geopolitical regions. Creatinine, acid-digested total arsenic (TAs), and five inorganic and organic arsenic species were measured: arsenobetaine (AsB); arsenous (AsIII) and arsenic (AsV) acids and their dissociation products; monomethylarsonic acid (MMA); and dimethylarsinic acid DMA). Overall, the TAs GM (μg/g creat) of all stratification groups indicated no statistical difference. The TAs geometric mean (GM) of BH was 9.68 [9.17–10.2] μg/g creat, being AsB (43.8%) and DMA (20.7%) the major components. The toxic arsenic (ToxAs) fraction (i.e., AsIII + AsV + MMA + DMA) was 5.23 [4.45–6.15] μg/L. These TAs and ToxAs values are lower than international benchmarks and the Brazilian legislated standard of 35 μg/L for ToxAs. The TAs GM (μg/L) and creatinine were 36% higher for males than for females (p < 0.0001), making TAs GMs comparable, after creatinine correction. Similarly, though the 10–19 age group showed significantly higher ToxAs GM (12.7 [6.49–24.8] μg/L) (p = 0.048) and creatinine (p < 0.001), the ToxAs GM (7.22 [2.92–17.9] μg/g creat), was not statistically different than those from the other age groups. The study, the first one in Brazil, identifies the relative contribution of inorganic and organic arsenic and provides a baseline level for clinical reference and bio-monitoring studies, particularly applicable to both occupational and non-occupational populations in a mineral-rich region.Graphical abstract

Role of microbial microbes in arsenic bioaccumulation and biotransformation in mice

Although gut microbes can affect the accumulation and metabolism of arsenic (As), the microbes contributing to these processes remain largely unknown. Therefore, this study aimed to investigate the bioaccumulation and biotransformation of arsenate [As(V)] and arsenobetaine (AsB) in mice with a disordered gut microbiome. We used cefoperazone (Cef) to construct a mouse model of gut microbiome disruption along with 16S rRNA sequencing to elucidate the effect of gut microbiome destruction on the biotransformation and bioaccumulation of As(V) and AsB. This revealed the role of specific bacteria in As metabolism. Gut microbiome destruction increased the bioaccumulation of As(V) and AsB in various organs and reduced the excretion of As(V) and AsB in the feces. Further, gut microbiome destruction was found to be important for the biotransformation of As(V). Interference with Cef can significantly decrease Blautia and Lactobacillus while increasing Enterococcus, leading to increase As accumulation in mice and enhanced methylation. We also identified Lachnoclostridium, Erysipelatoclostridium, Blautia, Lactobacillus, and Enterococcus as biomarkers involved in As bioaccumulation and biotransformation. In conclusion, specific microbes can increase As accumulation in the host, exacerbating its potential health risks.

Evaluation of the long-term stability of arsenic species in certified reference materials: certification of arsenobetaine, As(V), and dimethylarsinic acid in NMIJ CRMs 7901-a, 7912-a, and 7913-a.

The long-term stabilities of arsenobetaine (AsB), arsenate (As(V)), and dimethylarsinic acid (DMA), which are arsenic (As) compounds in certified reference materials (CRMs), namely, NMIJ CRMs 7901-a, 7912-a, and 7913-a, were monitored. The CRMs were developed and certified by the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) in 2009 to prepare a calibrant for the speciation analysis of As species. The CRMs were prepared from high-purity reagent powders as raw materials, and each reagent was dissolved in water or diluted acid. The certification of the CRMs for AsB, As(V), and DMA was conducted by NMIJ. The concentration of total As was determined by more than three independent analytical techniques. Then, the obtained As concentrations were converted into the concentration of each chemical species, and the mass fractions of each certified value were certificated. The long-term stability of As species in the CRMs under storage was performed by liquid chromatography-inductively coupled plasma-mass spectrometry, and this report presents data on long-term stability that occurred approximately 13years. The obtained monitoring results were evaluated using both measurement results with uncertainty and a statistical parameter method, complying with ISO Guide 35. According to the results, the long-term stability of all mass fractions was confirmed.

Significant Biotransformation of Arsenobetaine into Inorganic Arsenic in Mice

Arsenic (As) is extremely toxic to living organisms at high concentrations. Arsenobetaine (AsB), confirmed to be a non-toxic form, is the main contributor to As in the muscle tissue of marine fish. However, few studies have investigated the biotransformation and biodegradation of AsB in mammals. In the current study, C57BL/6J mice were fed four different diets, namely, Yangjiang and Zhanjiang fish diets spiked with marine fish muscle containing AsB, and arsenite (As(III)) and arsenate (As(V)) diets spiked with As(III) and As(V), respectively, to investigate the biotransformation and bioaccumulation of AsB in mouse tissues for 42 d. Different diets exhibited different As species distributions, which contributed to varying levels of As bioaccumulation in different tissues. The intestines accumulated the highest level of As, regardless of form, which played a major part in As absorption and distribution in mice. We observed a significant biotransformation of AsB to As(V) following its diet exposure, and the liver, lungs, and spleen of AsB-treated mice showed higher As accumulation levels than those of As(III)- or As(V)-treated mice. Inorganic As showed relatively high accumulation levels in the lungs and spleen after long-term exposure to AsB. Overall, these findings provided strong evidence that AsB undergoes biotransformation to As(V) in mammals, indicating the potential health risk associated with long-term AsB intake in mammals.

Biotransformation and detoxification mechanism of inorganic arsenic in a freshwater benthic fish Tachysurus fulvidraco with dietborne exposure

Inorganic arsenic (iAs) is a pervasive environmental toxin, its metabolism and detoxification mechanism in freshwater benthic fish under dietary exposure remain unknown. In this study, dietborne exposure of two iAs (arsenate (AsV) and arsenite (AsIII)) was conducted for yellow catfish (Tachysurus fulvidraco) to investigate the bioaccumulation, biotransformation, and detoxification of iAs in the fish liver. The results showed that As significantly accumulated in both the AsIII and AsV treatments compared to the control, and the final As concentration was comparable for both treatments. The detoxification of iAs in freshwater fish depends on the degree of arsenic methylation and the level of antioxidants. Both reduction processes of AsV to AsIII and oxidation processes of AsIII to AsV were found in AsV and AsIII treatments. The major-low toxicity intermediates, which also are detoxification products in the AsIII treatment, were pentavalent dimethylarsinic acid and arsenobetaine (AsB), and AsB was major-low toxicity intermediate in the AsV treatment. Both antioxidants glutathione and glutathione S-transferase contribute to the detoxification of iAs by scavenging excessive reactive oxygen species and promoting iAs methylation in yellow catfish under iAs exposure.

Arsenic speciation in canned tuna fish samples (Thunnus) using ionic chromatography inductively coupled plasma mass spectrometry

Arsenic speciation analysis was conducted on in oil and in brine canned solid tuna samples using ionic chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS). First, the method was optimized and validated. The extraction of water-soluble arsenic species (arsenobetaine (AsB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), As (III), and As (V)) was performed with (NH4)2CO3 at pH 10.5. The presence of the sample matrix showed no effect on the selectivity of the method by a t-test (p < 0.05) and an external calibration method was applied. The limits of quantification for the five arsenic species were 0.59 mg kg−1 (AsB), 0.10 mg kg−1 (DMA), 0.12 mg kg−1 (As (III)), 0.07 mg kg−1 (MMA) and 0.10 mg kg−1 (As (V)). Method accuracy was tested through the analysis of the reference material BCR-627 (tuna fish muscle tissue) and a good agreement was obtained. Total arsenic in the solid canned tuna ranged from 2.65 to 5.81 mg kg−1 in-oil samples and from 2.74 to 5.70 mg kg−1 in the in-brine samples, levels higher than the limits established by the Brazilian sanitary standards. However, the speciation showed that the major species is the non-toxic arsenobetaine.