Assessing neurodevelopmental effects of arsenolipids in pre-differentiated human neurons

Speciation of arsenic in milk from cows fed seaweed

BACKGROUND

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.

RESULTS

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.

CONCLUSION

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.

Speciation analysis and toxicity evaluation of arsenolipids-an overview focusing on sea food

Arsenic, which can be divided into inorganic and organic arsenic, is a toxic metalloid that has been identified as a human carcinogen. A common source of arsenic exposure in seafood is arsenolipid, which is a complex structure of lipid-soluble organic arsenic compounds. At present, the known arsenolipid species mainly include arsenic-containing fatty acids (AsFAs), arsenic-containing hydrocarbons (AsHCs), arsenic glycophospholipids (AsPLs), and cationic trimethyl fatty alcohols (TMAsFOHs). Furthermore, the toxicity between different species is unique. However, the mechanism underlying arsenolipid toxicity and anabolism remain unclear, as arsenolipids exhibit a complex structure, are present at low quantities, and are difficult to extract and detect. Therefore, the objective of this overview is to summarize the latest research progress on methods to evaluate the toxicity and analyze the main speciation of arsenolipids in seafood. In addition, novel insights are provided to further elucidate the speciation, toxicity, and anabolism of arsenolipids and assess the risks on human health.

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

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

Human urinary arsenic species, associated exposure determinants and potential health risks assessed in the HBM4EU Aligned Studies

The European Joint Programme HBM4EU coordinated and advanced human biomonitoring (HBM) in Europe in order to provide science-based evidence for chemical policy development and improve chemical management. Arsenic (As) was selected as a priority substance under the HBM4EU initiative for which open, policy relevant questions like the status of exposure had to be answered. Internal exposure to inorganic arsenic (iAs), measured as Toxic Relevant Arsenic (TRA) (the sum of As(III), As(V), MMA, DMA) in urine samples of teenagers differed among the sampling sites (BEA (Spain) > Riksmaten adolescents (Sweden), ESTEBAN (France) > FLEHS IV (Belgium), SLO CRP (Slovenia)) with geometric means between 3.84 and 8.47 μg/L. The ratio TRA to TRA + arsenobetaine or the ratio TRA to total arsenic varied between 0.22 and 0.49. Main exposure determinants for TRA were the consumption of rice and seafood. When all studies were combined, Pearson correlation analysis showed significant associations between all considered As species. Higher concentrations of DMA, quantitatively a major constituent of TRA, were found with increasing arsenobetaine concentrations, a marker for organic As intake, e.g. through seafood, indicating that other sources of DMA than metabolism of inorganic As exist, e.g. direct intake of DMA or via the intake of arsenosugars or -lipids. Given the lower toxicity of DMA(V) versus iAs, estimating the amount of DMA not originating from iAs, or normalizing TRA for arsenobetaine intake could be useful for estimating iAs exposure and risk. Comparing urinary TRA concentrations with formerly derived biomonitoring equivalent (BE) for non-carcinogenic effects (6.4 μg/L) clearly shows that all 95th percentile exposure values in the different studies exceeded this BE. This together with the fact that cancer risk may not be excluded even at lower iAs levels, suggests a possible health concern for the general population of Europe.

Arsenolipids reduce butyrate levels and influence human gut microbiota in a donor-dependent way

Arsenolipids are organic arsenic species with variable toxicity. Accurate assessment of the risks derived from arsenic-contaminated seafood intake requires studying the interplay between arsenolipids and the human gut microbiota. This research used the in vitro mucosal simulator of the human intestinal microbial ecosystem (M-SHIME) to assess the effect of defined chemical standards of arsenolipids (AsFA 362 and AsHC 332) on a simulated healthy human gut microbiota (n = 4). Microbial-derived metabolites were quantified by gas chromatography and microbiota structure was characterized by 16S rRNA gene sequencing. A specific reduction in butyrate production (control=5.28 ± 0.3 mM; AsFAs=4.56 ± 0.4 mM; AsHC 332=4.4 ± 0.6 mM, n = 4 donors), concomitant with a reduction in the abundance of Lachnospiraceae UCG-004 group and the Faecalibacterium genus was observed, albeit in a donor-dependent manner. Furthermore, an increase in Escherichia/Shigella, Proteobacteria and Fusobacterium abundance was observed after arsenolipid treatments, depending on individual microbiota background. These alterations in microbial functionality and microbial community structure suggest a detrimental effect of arsenolipids intake towards the commensal gut microbiome, and consequently, on human health.

Exposure to arsenolipids and inorganic arsenic from marine-sourced dietary supplements

Dietary supplements sourced from marine environments, such as fish oils and seaweed-based supplements, are widely consumed to boost nutrient intakes, including by vulnerable populations such as pregnant women. Like other marine foods, these supplements are also a potential source of exposure to arsenic, including the known toxic species, inorganic arsenic, and the cytotoxic, lipid-soluble arsenic compounds, arsenic hydrocarbons. A study of 32 marine-sourced supplements found higher total arsenic concentrations (>1000 ng g^-1) in supplements made from seaweed, krill and calanus oil, and in fish and fish liver products marketed as "unprocessed". Inorganic arsenic was only detectable in the seaweed samples, and was elevated (8900 ng g^-1) in one product. Arsenic hydrocarbons were not detected in krill oil samples but were present at concentrations from 169 to 2048 ng g^-1 in "unprocessed" fish and fish liver oil, and calanus oil. Survey data from the New Hampshire Birth Cohort Study (NHBCS) found 13.5% of pregnant women (n = 1997) reported taking fish oil supplements; and of those, most did so daily (75.6%, 6 or more times per week). Only a small percentage (9%) of those who reported consuming fish oil used products associated with higher arsenic levels. Higher urinary arsenic concentrations were found among women who consumed fish oil compared with those who did not, and specifically higher arsenobetaine and dimethyl arsenic concentrations. Dietary supplements are becoming common components of modern diets, and some marine-sourced dietary supplements are a source of inorganic arsenic and arsenic hydrocarbons.

The Need to Unravel Arsenolipid Transformations in Humans

The main source of arsenic exposure to humans worldwide is the diet, in particular, drinking water, rice, and seafood. Although arsenic is often considered toxic, it can exist in food as more than 300 chemical species with different toxicities. This diversity makes it difficult for food safety and health authorities to regulate arsenic levels in food, which are currently based on a few arsenic species. Of particular interest are arsenolipids, a type of arsenic species widely found in seafood. Emerging evidence indicates that there are risks associated with human exposure to arsenolipids (e.g., accumulation in breast milk, ability to cross the blood-brain barrier and accumulate in the brain, and potential development of neurodegenerative disorders). Still, more research is needed to fully understand the impact of arsenolipid exposure, which requires establishing interdisciplinary collaborations.

Arsenolipids in salmon are partly converted to thioxo analogs during cooking

BACKGROUND

Arsenic hydrocarbons, major arsenolipids occurring naturally in marine fish, have substantial cytotoxicity leading to human health-related studies of their distribution and abundance in foods. These studies have all investigated fresh foods; because most fish are cooked before being consumed, it is both food- and health-relevant to determine the arsenolipids present in cooked fish.

METHODS

We used HPLC/mass spectrometry to investigate the arsenolipids present in salmon (Salmo salar) before and after cooking by either baking or steaming.

RESULTS

In raw salmon (total As 2.74 mg kg^-1 dry mass, of which 6% was lipid-soluble), major arsenolipids were three arsenic hydrocarbons (oxo-AsHC 332, oxo-AsHC 360, and oxo-AsHC 404, ca 55% of total arsenolipids) and a band of unidentified less-polar arsenolipids (ca 40%), trace amounts of another four arsenic hydrocarbons and two thioxo analogs were also detected. During the cooking process, 28% of the oxo-AsHCs were converted to their thioxo analogs.

CONCLUSION

Our study shows that arsenic hydrocarbons naturally present in fresh fish are partly converted to their thioxo analogs during cooking by either baking or steaming. The greater lipophilicity of the thioxo analogs could alter the mode of toxicity of arsenic hydrocarbons, and hence future food regulations for arsenic should consider the influence of cooking on the precise type of arsenolipid in fish.

Effect of arsenic-containing hydrocarbon on the long-term potentiation at Schaffer Collateral-CA1 synapses from infantile male rat

Arsenic-containing hydrocarbons (AsHCs) are common constituents of marine organisms and have potential toxicity to human health. This work is to study the effect of AsHCs on long-term potentiation (LTP) for the first time. A multi-electrode array (MEA) system was used to record the field excitatory postsynaptic potential (fEPSP) of CA1 before and after treatment with AsHC 360 in hippocampal slices from infantile male rats. The element content of Na, K, Ca, Mg, Mn, Cu, Zn, and As in the hippocampal slices were analyzed by elemental mass spectrometry after the neurophysiological experiment. The results showed that low AsHC 360 (1.5 μg As L^-1) had no effect on the LTP, moderate AsHC 360 (3.75-15 μg As L^-1) enhanced the LTP, and high AsHC 360 (45-150 μg As L^-1) inhibited the LTP. The enhancement of the LTP by promoting Ca²⁺ influx was proved by a Ca²⁺ gradient experiment. The inhibition of the LTP was likely due to damage of synaptic cell membrane integrity. This study on the neurotoxicity of AsHCs showed that high concentrations have a strong toxic effect on the LTP in hippocampus slices of the infantile male rat, which may lead to a negative effect on the development, learning, and memory.

Cellular toxicological characterization of a thioxolated arsenic-containing hydrocarbon

Arsenolipids, especially arsenic-containing hydrocarbons (AsHC), are an emerging class of seafood originating contaminants. Here we toxicologically characterize a recently identified oxo-AsHC 332 metabolite, thioxo-AsHC 348 in cultured human liver (HepG2) cells. Compared to results of previous studies of the parent compound oxo-AsHC 332, thioxo-AsHC 348 substantially affected cell viability in the same concentration range but exerted about 10-fold lower cellular bioavailability. Similar to oxo-AsHC 332, thioxo-AsHC 348 did not substantially induce oxidative stress nor DNA damage. Moreover, in contrast to oxo-AsHC 332 mitochondria seem not to be a primary subcellular toxicity target for thioxo-AsHC 348. This study indicates that thioxo-AsHC 348 is at least as toxic as its parent compound oxo-AsHC 332 but very likely acts via a different mode of toxic action, which still needs to be identified.

Arsenic Toxicity: Molecular Targets and Therapeutic Agents

High arsenic (As) levels in food and drinking water, or under some occupational conditions, can precipitate chronic toxicity and in some cases cancer. Millions of people are exposed to unacceptable amounts of As through drinking water and food. Highly exposed individuals may develop acute, subacute, or chronic signs of poisoning, characterized by skin lesions, cardiovascular symptoms, and in some cases, multi-organ failure. Inorganic arsenite(III) and organic arsenicals with the general formula R-As²⁺ are bound tightly to thiol groups, particularly to vicinal dithiols such as dihydrolipoic acid (DHLA), which together with some seleno-enzymes constitute vulnerable targets for the toxic action of As. In addition, R-As²⁺-compounds have even higher affinity to selenol groups, e.g., in thioredoxin reductase that also possesses a thiol group vicinal to the selenol. Inhibition of this and other ROS scavenging seleno-enzymes explain the oxidative stress associated with arsenic poisoning. The development of chelating agents, such as the dithiols BAL (dimercaptopropanol), DMPS (dimercapto-propanesulfonate) and DMSA (dimercaptosuccinic acid), took advantage of the fact that As had high affinity towards vicinal dithiols. Primary prevention by reducing exposure of the millions of people exposed to unacceptable As levels should be the prioritized strategy. However, in acute and subacute and even some cases with chronic As poisonings chelation treatment with therapeutic dithiols, in particular DMPS appears promising as regards alleviation of symptoms. In acute cases, initial treatment with BAL combined with DMPS should be considered.

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

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

Toxicity of three types of arsenolipids: species-specific effects inCaenorhabditis elegans

AsHCs and AsTAG are highly bioavailable toC. elegans., AsHCs are metabolized byC. elegans., AsHCs but not AsTAG and AsFA affect survival and development inC. elegans.

An Important Need to Monitor from an Early Age the Neurotoxins in the Blood or by an Equivalent Biomarker

An overwhelming amount of evidence now suggests that some people are becoming overloaded with neurotoxins. This is mainly from changes in their living environment and style, coupled with the fact that all people are different and display a broad distribution of genetic susceptibilities. It is important for individuals to know where they lie concerning their ability to either reject or retain toxins. Everyone is contaminated with a certain baseline of toxins that are alien to the body, namely aluminum, arsenic, lead, and mercury. Major societal changes have modified their intake, such as vaccines in enhanced inoculation procedures and the addition of sushi into diets, coupled with the ever-present lead, arsenic, and traces of manganese. It is now apparent that no single toxin is responsible for the current neurological epidemics, but rather a collaborative interaction with possible synergistic components. Selenium, although also a neurotoxin if in an excessive amount, is always present and is generally more present than other toxins. It performs as the body’s natural chelator. However, it is possible that the formation rates of active selenium proteins may become overburdened by other toxins. Every person is different and it now appears imperative that the medical profession establish an individual’s neurotoxicity baseline. Moreover, young women should certainly establish their baselines long before pregnancy in order to identify possible risk factors.