Chronic effects of mercury on Bufo gargarizans larvae: Thyroid disruption, liver damage, oxidative stress and lipid metabolism disorder

Does mercury affect morphology, developmental stability and canalization of the skull in the Common wall lizard (Podarcis muralis)?

Environmental pollution by metals and metalloids can have a detrimental effect on the fitness and development of organisms. Studies on the influence of metals and metalloids as environmental stressors on developmentally and functionally complex morphological structures of reptiles are important, as this group of vertebrates is highly threatened and is an important component of food webs. To assess the effects of chronic mercury exposure on cranium morphology and post-natal development in a model species of lizards, we analysed the concentration of this metal in liver tissues in the population of the Common wall lizard (Podarcis muralis) from the mercury mine tailings and the control population, and possible differences in skull size, shape, developmental stability and canalization between the two groups. Patterns of variation and asymmetry of the cranium shape were analysed using geometric morphometrics. The mercury concentration was significantly higher in the population from the polluted locality, but had very little to no effect on the cranial morphology. Juveniles and females from both sites had the same size and shape of the dorsal and ventral cranium, while males showed small differences in ventral cranium shape, reflected in slightly longer maxillae and wider crania at the polluted site. The pattern of sexual dimorphism remained constant at both localities. Both static and ontogenetic allometry were significant in both groups, and allometric trajectories did not differ between the two sites. The differences in fluctuating asymmetry (FA) between localities were not statistically significant for the dorsal and ventral cranium. The results do not support the idea that FA can be used as an early indicator mercury exposure at the population level.

Surface modification of cellulose by sequential metal-free photoinduced atom transfer radical polymerization and its application for aqueous Hg(II) removal

Cellulose-based polymer brush-on-brush composite adsorbent is prepared under simple and mild conditions via a four-step two sequential organophotocatalyzed atom transfer radical polymerization for the efficient removal of Hg(II) from aqueous media. The defined structure of the cellulose-based composites was supported by the characterization results. Influences of solution pH, temperature and adsorbent dosage on the adsorption behavior of the adsorbent were determined by batch experiments. The adsorption performance of the polymer brush composite intermediate was also investigated as a comparison to the final adsorbent to illustrate the significance of the topological surface structure on adsorption efficiency and capacity. Adsorption kinetics, isotherm and mechanism were studied systematically to further clarify the adsorption process. In addition, the adsorbent exhibits good applicability as it can be reused for 5 times without obvious decrease in desorption rate (>90 %), which showed potential utility for preconcentration and recovery of aqueous Hg(II).

Dual-mode SPR/SERS optical fiber sensor for ultra-trace mercury ions detection

The detection of mercury ions (Hg2+) is crucial due to its harmful effects on health and environment. In this article, what we believe to be a novel dual-mode optical fiber sensor incorporating surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) is proposed for ultra-trace Hg2+ detection. The sensing probe comprises gold (Au)/graphene oxide (GO) composite membrane structure and Au nanospheres (AuNPs), which are connected via double-stranded DNA. In the presence of Hg2+, two single-stranded DNA (ssDNA) modified on the sensing region and AuNPs asymmetrically pair to form a thymine (T) - Hg2+ - T structure, facilitating AuNPs attachment to the sensing region. This attachment induces spectral changes, thereby enabling Hg2+ detection. In the SPR mode, the limit of detection (LOD) for Hg2+ is 1.82 × 10-12 M. In the SERS mode, AuNPs generate numerous "hot spots" that amplify the Raman signal through electromagnetic enhancement mechanism (EM), the Au/GO composite membrane can undergo charge transfer with Raman molecule to further enhance the Raman signal through chemical enhancement mechanism (CM), thus achieving detection of Hg2+ with a LOD of 3.94 × 10-13 M. The synergy between SPR mode and SERS mode enhances cross-validation of results and improves accuracy and reliability of the assay. Therefore, the sensor proposed in this paper demonstrates strong potential for diverse practical applications.

Response characteristic and potential molecular mechanism of tail resorption in Bufo gargarizans after exposure to lead and copper, alone or combined

Tail resorption during amphibian metamorphosis is one of the most dramatic processes that is obligatorily dependent on thyroid hormone (TH). Heavy metals could result in thyroid gland damages and disturb TH homeostasis. Lead (Pb) and copper (Cu) often co-exist in natural aquatic ecosystems. However, there is still little information on how tail resorption responds to alone or combined exposure to Pb and Cu. Our study investigated the effects of Pb and Cu alone or combined exposure on the morphological parameters of the tail, histological changes of thyroid gland and tail, and gene expression programs involved in cell death of the tail in Bufo gargarizans tadpoles at the climax of metamorphosis. Results demonstrated that Pb, Cu and Pb-Cu mixture exposure resulted in a significantly longer tail compared with control. Damages to notochord, muscle, skin and spinal cord of the tail were found in Pb and Cu exposure groups. The colloid area, the height of follicular cells and number of phagocytic vesicles of thyroid gland in Pb-Cu mixture exposure groups were significantly reduced. In addition, the expression levels of TH, apoptosis, autophagy, degradation of cellular components and oxidative stress-related genes in the tail were significantly altered following Pb and Cu exposure. The present work revealed the relationship between environmental pollutants and tail resorption, providing scientific basis for amphibian protection.

Natural modulation of redox status throughout the ontogeny of Amazon frog Physalaemus ephippifer (Anura, Leptodactylidae)

During their development, amphibians undergo various physiological processes that may affect their susceptibility to environmental pollutants. Naturally occurring fluctuations caused by developmental events are often overlooked in ecotoxicological studies. Our aim is to investigate how biomarkers of oxidative stress are modulated at different stages of larval development in the Amazonian amphibian species, Physalaemus ephippifer. The premetamorphosis, prometamorphosis and metamorphic climax stages were used to analyze total antioxidant capacity (ACAP), glutathione S-transferase (GST) activity, lipid peroxidation (LPO) levels and the expression of genes nrf2, gst, gsr (glutathione reductase) and gclc (glycine-cysteine ligase, catalytic subunit). Although there was no difference in ACAP and the genes expression among the studied stages, individuals from the premetamorphosis and prometamorphosis showed higher GST activity than ones under the climax. LPO levels were highest in individuals from the metamorphic climax. The present study suggests that the oxidative status changes during ontogeny of P. ephippifer tadpoles, especially during the metamorphic climax, the most demanding developmental phase. Variations in the redox balance at different developmental stages may lead to a divergent response to pollution. Therefore, we recommend that studies using anuran larvae as biomonitors consider possible physiological differences during ontogeny in their respective analyses.

The impact of chemical pollution across major life transitions: a meta-analysis on oxidative stress in amphibians

Among human actions threatening biodiversity, the release of anthropogenic chemical pollutants which have become ubiquitous in the environment, is a major concern. Chemical pollution can induce damage to macromolecules by causing the overproduction of reactive oxygen species, affecting the redox balance of animals. In species undergoing metamorphosis (i.e. the vast majority of the extant animal species), antioxidant responses to chemical pollution may differ between pre- and post-metamorphic stages. Here, we meta-analysed (N = 104 studies, k = 2283 estimates) the impact of chemical pollution on redox balance across the three major amphibian life stages (embryo, tadpole, adult). Before metamorphosis, embryos did not experience any redox change while tadpoles activate their antioxidant pathways and do not show increased oxidative damage from pollutants. Tadpoles may have evolved stronger defences against pollutants to reach post-metamorphic life stages. In contrast, post-metamorphic individuals show only weak antioxidant responses and marked oxidative damage in lipids. The type of pollutant (i.e. organic versus inorganic) has contrasting effects across amphibian life stages. Our findings show a divergent evolution of the redox balance in response to pollutants across life transitions of metamorphosing amphibians, most probably a consequence of differences in the ecological and developmental processes of each life stage.

Assessing the hepatotoxicity of phosphogypsum leachate in zebrafish (Danio rerio)

The improper disposal of large amounts of phosphogypsum generated during the production process of the phosphorus chemical industry (PCI) still exists. The leachate formed by phosphogypsum stockpiles could pose a threat to the ecological environment and human health. Nevertheless, information regarding the harmful effects of phosphogypsum leachate on organisms is still limited. Herein, the physicochemical characteristics of phosphogypsum leachate were analyzed, and its toxicity effect on zebrafish (Danio rerio), particularly in terms of hepatotoxicity and potential mechanisms, were evaluated. The results indicated that P, NH3-N, TN, F-, As, Cd, Cr, Co, Ni, Zn, Mn, and Hg of phosphogypsum leachate exceeded the V class of surface water environmental quality standards (GB 3838-2002) to varying degrees. Acute toxicity test showed that the 96 h LC50 values of phosphogypsum leachate to zebrafish was 2.08 %. Under exposure to phosphogypsum leachate, zebrafish exhibited concentration-dependent liver damage, characterized by vacuolization and infiltration of inflammatory cells. The increased in Malondialdehyde (MDA) content and altered activities of antioxidant enzymes in the liver indicated the induction of oxidative stress and oxidative damage. The expression of apoptosis-related genes (P53, PUMA, Caspase3, Bcl-2, and Bax) were up-regulated at low dosage group and down-regulated at medium and high dosage groups, suggesting the occurrence of hepatocyte apoptosis or necrosis. Additionally, phosphogypsum leachate influenced the composition of the zebrafish gut microbiota by reducing the relative abundance of Bacteroidota, Aeromonas, Flavobacterium, Vibrio, and increasing that of Rhodobacter and Pirellula. Correlation analysis revealed that gut microbiota dysbiosis was associated with phosphogypsum leachate-induced hepatotoxicity. Altogether, exposure to phosphogypsum leachate caused liver damage in zebrafish, likely through oxidative stress and apoptosis, with the intestinal flora also playing a significant role. These findings contribute to understanding the ecological toxicity of phosphogypsum leachate and promote the sustainable development of PCI.

Chemical contaminants in blood and their implications in chronic diseases

Artificial chemical products are widely used and ubiquitous worldwide and pose a threat to the environment and human health. Accumulating epidemiological and toxicological evidence has elucidated the contributions of environmental chemical contaminants to the incidence and development of chronic diseases that have a negative impact on quality of life or may be life-threatening. However, the pathways of exposure to these chemicals and their involvements in chronic diseases remain unclear. We comprehensively reviewed the research progress on the exposure risks of humans to environmental contaminants, their body burden as indicated by blood monitoring, and the correlation of blood chemical contaminants with chronic diseases. After entering the human body through various routes of exposure, environmental contaminants are transported to target organs through blood circulation. The application of the modern analytical techniques based on human plasma or serum specimens is promising for determining the body burden of environmental contaminants, including legacy persistent organic pollutants, emerging pollutants, and inorganic elements. Furthermore, their body burden, as indicated by blood monitoring correlates with the incidence and development of metabolic syndromes, cancers, chronic nervous system diseases, cardiovascular diseases, and reproductive disorders. On this basis, we highlight the urgent need for further research on environmental pollution causing health problems in humans.

Poison in the nursery: Mercury contamination in the tadpole-rearing sites of an Amazonian frog

Artisanal and small-scale gold mining (ASGM) has become a major threat for Neotropical forests. This technique for obtaining gold is a substantial driver of small-scale deforestation and the largest contributor of Hg emissions to both the atmosphere and freshwater systems globally. Previous studies have demonstrated the impacts of Hg accumulation on various aquatic ecosystems and organisms. However, its consequences in other, more discrete systems such as phytotelmata (water-holding plant structures), and the organisms therein, have so far gone unnoticed. Here, we show high concentrations of Hg (mean ± SD: 1.43 ± 2.19 ppm) in phytotelmata and other small pools, the aquatic microenvironments used by the Neotropical poison frog Dendrobates tinctorius as tadpole-rearing sites. In 17 % of the cases, we detected Hg concentrations above the severe effect level (SEL = 2 ppm) for freshwater sediments. Hg concentrations varied depending on pool characteristics and tended to increase in proximity to known ASGM sites. We did not find an effect of Hg concentration on the number of D. tinctorius tadpoles in a given pool. Tadpoles were found in pools with concentrations of up to 8.68 ppm, suggesting that D. tinctorius fathers do not avoid pools with high Hg levels for tadpole deposition. While further research is needed to determine the potential effects of Hg on tadpole development, we found an intriguing tendency for tadpoles in later developmental stages to have lower body condition when occurring in pools with higher Hg concentrations. Our findings provide evidence of relevant Hg concentrations in the terrestrial water systems used by phytotelm-breeding anurans, and highlight the need of further field and experimental studies investigating the implications of Hg contamination for tadpole development and behaviour and the overall conservation of Amazonian biodiversity.

Association of Blood Total Mercury with Dyslipidemia in a sample of U.S. Adolescents: Results from the National Health and Nutrition Examination Survey Database, 2011-2018

Background

Abnormal lipid profiles in adolescents predict metabolic and cardiovascular diseases in adulthood. While seafood consumption is the primary source of mercury exposure, it also provides beneficial nutrients such as omega-3 fatty acids (O3FA). Prior studies indicate that blood total mercury (TBHg) has endocrine disrupting effects and may be associated with abnormal lipid profiles in adolescents. However, the impact of beneficial nutrients on this relationship has not been examined. Our study investigated the relationship of TBHg with dyslipidemia and lipid profiles and potential confounding and modification of these relationships by sex, body mass index (BMI), selenium and O3FA from seafood consumption.

Methods

We examined 1,390 National Health and Nutrition Examination Survey participants 12-19 years of age from the 2011-2018 cycles. Using logistic and linear regression adjusted for survey design variables and stratified by sex a priori, we estimated the associations of TBHg and methylmercury with dyslipidemia, and with total cholesterol (TC), high (HDL-C) and low-density lipoprotein cholesterol (LDL-C) and triglycerides.

Results

The geometric mean of TBHg in this adolescent population was 0.44 μg/L. After controlling for socio-demographic covariates, BMI, serum selenium, age at menarche (females only) and average daily intake of O3FA; TBHg was significantly associated with higher TC levels (β=3.34, 95% CI: 0.19, 6.50; p<0.05) in females but not males. Methyl Hg was also associated with increased TC, as well as decreased HDL-C in females but not males. We did not find significant associations of Hg exposure with dyslipidemia, LDL-C or triglycerides levels in either male or female adolescents. However, we observed evidence of effect modification by BMI and serum selenium for associations of TBHg with TC levels in male and female adolescents, respectively.

Conclusion

Our findings of elevated TC levels in females but not males necessitates further research to better understand the underlying mechanisms driving these sex-specific associations.

Highly selective and sensitive detection of Hg2+ by a novel fluorescent probe with dual recognition sites

A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg²⁺) ion was developed. The synthesized probe possessed both fluorogenic ("off-on") and chromogenic (from colorless to blackish brown) sensing performance towards Hg²⁺ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg²⁺. As expected, the probe exhibited excellent selectivity and sensitivity for Hg²⁺ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg²⁺ (0-40 μM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 μM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg²⁺ ions over a broad working pH range of 3-11. It is reliable and qualifies for the quantitative determination of Hg²⁺ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg²⁺ in living cells and plants with good biocompatibility.

Effects of Endocrine-Disrupting Heavy Metals on Human Health

Heavy metals play an important endocrine-disrupting role in the health consequences. However, the endocrine-disrupting mechanism of heavy metals is unclear. There are long-term and low-level metal/element exposure scenes for the human body in real life. Therefore, animal models exposed to high doses of heavy metals may not provide key information to elucidate the underlying pathogeny of human diseases. This review collects current knowledge regarding the endocrine-disrupting roles of heavy metals such as lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), nickel (Ni), copper (Cu), zinc (Zn), and manganese (Mn), summarizes the possible molecular mechanisms of these endocrine-disrupting chemicals (EDCs), and briefly evaluates their endocrine toxicity on animals and humans.

Mercury may reduce the protective effect of sea fish consumption on serum triglycerides levels in Chinese adults: Evidence from China National Human Biomonitoring

Sea fish contain omega-3 polyunsaturated fatty acids (omega-3 PUFAs) which have been found to reduce triglyceride (TG) levels. However, sea fish may contain pollutants such as mercury which cause oxidative stress and increase TG levels. Therefore, the relationship between sea fish and TG remains unclear. We aimed to explore whether blood mercury (BHg) can affect the effect of sea fish consumption frequency on TG level among Chinese adults. A total of 10,780 participants were included in this study. BHg levels were measured using inductively coupled plasma mass spectrometry (ICP-MS). The associations of sea fish consumption frequency with BHg and TG levels as well as the association of BHg with TG levels were evaluated using multiple linear regression. Causal mediation analysis was used to evaluate the mediation effect of BHg levels on the association of sea fish consumption frequency with TG levels. The frequency of sea fish consumption showed a negative association with TG level. Compared with the participants who never ate sea fish, the TG level decreased by 0.193 mmol/L in those who ate sea fish once a week or more [β (95%CI): -0.193 (-0.370, -0.015)]. Significant positive associations were observed of BHg with TG levels. With one unit increase of log2-transformed BHg, the change of TG level was 0.030 mmol/L [0.030 (0.009, 0.051)]. The association between sea fish consumption and TG was mediated by log2-transformed BHg [total effect = -0.037 (-0.074, -0.001); indirect effect = 0.009 (0.004, 0.015)], and the proportion mediated by log2-transformed BHg was 24.25%. BHg may reduce the beneficial effect of sea fish consumption frequency on TG levels among Chinese adults. Overall, sea fish consumption has more benefits than harms to TG.

Short-term mercury exposure disrupts muscular and hepatic lipid metabolism in a migrant songbird

Methylmercury (MeHg) is a global pollutant that can cause metabolic disruptions in animals and thereby potentially compromise the energetic capacity of birds for long-distance migration, but its effects on avian lipid metabolism pathways that support endurance flight and stopover refueling have never been studied. We tested the effects of short-term (14-d), environmentally relevant (0.5 ppm) dietary MeHg exposure on lipid metabolism markers in the pectoralis and livers of yellow-rumped warblers (Setophaga coronata) that were found in a previous study to have poorer flight endurance in a wind tunnel than untreated conspecifics. Compared to controls, MeHg-exposed birds displayed lower muscle aerobic and fatty acid oxidation capacity, but similar muscle glycolytic capacity, fatty acid transporter expression, and PPAR expression. Livers of exposed birds indicated elevated energy costs, lower fatty acid uptake capacity, and lower PPAR-γ expression. The lower muscle oxidative enzyme capacity of exposed birds likely contributed to their weaker endurance in the prior study, while the metabolic changes observed in the liver have potential to inhibit lipogenesis and stopover refueling. Our findings provide concerning evidence that fatty acid catabolism, synthesis, and storage pathways in birds can be dysregulated by only brief exposure to MeHg, with potentially significant consequences for migratory performance.

In utero exposure to methylmercury impairs cognitive function in adult offspring: Insights from proteomic modulation

Methylmercury (MeHg) is a hazardous substance that has unique neurodevelopmental toxic effects. However, its molecular alteration profile, sensitive response biomarkers, and mechanism of neuronal injury remain largely unknown. Here, the effects of intrauterine methylmercury chloride (low-, medium- and high-dose groups: 0.6 mg/kg/d, 1.2 mg/kg/d, 2.4 mg/ kg /d, respectively) exposure on learning and memory were assessed in offspring rats by behavioral tests, pathological analysis and hippocampal proteomic analysis. The results suggested that intrauterine MeHg exposure impairs spatial learning and memory and leads a significant reduction in the number and dispersion scattered arrangement in the hippocampus of offspring. Furthermore, in the tandem mass tag-based proteomics analysis, compared with the control group, a total of 74 differentially expressed proteins (DEPs) were found in the MeHg exposure groups; specifically, 32 down-regulated and 42 up-regulated proteins were identified. In addition, the pathways enrichment analysis indicated that these DEPs are implicated in several biological processes, such as synaptic plasticity and energy metabolism, as well as various molecular functional categories. Simultaneously, MeHg reduced the postsynaptic density, diminished the active zone, amplified the synaptic cleft and changed the synaptic interface of pyramidal cells. Western blot analysis further revealed that MeHg significantly reduced the levels of Forkhead box protein (FOXP2), Synaptophysin (SYP) and Postsynaptic density protein 95 (PSD-95), and down-regulated the N-methyl-D-aspartate receptor 1 (NMDAR1), N-methyl-D-aspartate receptor 2 A (NR2A) and N-methyl-D-aspartate receptor 2B (NR2B). In general, from a functional perspective, most overlapping proteins were related to NMDA receptor-mediated glutamatergic signaling, which is an excitotoxicity mechanism known to influence learning and memory. These discoveries contribute to our understanding of the relationship between MeHg and cognitive deficits and provide insight into the protein mediators of this relationship and possible prospective early biomarkers.

Exposure to mercury and thyroid function: Is there a connection?

Mercury (Hg) is one of the most important environmental pollutants with endocrinedisrupting properties. There is little data from epidemiological studies describing the doseresponse relationship between toxic metal levels and hormone levels. The aim of this study was to use the nearest neighbor matching analysis to determine the difference in Hg concentration in healthy/sick subjects with thyroid disease and to use Benchmark modeling to determine the doseresponse relationship between Hg levels in the blood and thyroid-stimulating hormone (TSH) and thyroid hormones in serum. Blood samples were collected and used for Hg measurement using the ICP-MS method, and separated serum was used for hormone analysis. The study showed the existence of a statistically significant difference in Hg levels measured in healthy and sick subjects and the existence of a dose-response relationship between Hg and all measured hormones, with a narrow interval obtained for the Hg-TSH pair. The results of this research support the use of the Benchmark dose approach for the purpose of analyzing data from human studies, and our further research will be focused on examining the impact of low doses on animal models in order to determine more precise effects of low doses on the organism.

Cadmium induced cardiac toxicology in developing Japanese quail (Coturnix japonica): Histopathological damages, oxidative stress and myocardial muscle fiber formation disorder

The anthropogenic-induced cadmium (Cd) pollution poses great threats to human health and wildlife survival. Birds also suffer from Cd contamination and Cd exerts negative impacts on multiple organs in birds. However, its toxic effects on cardiac organ of birds are still unclear. In this study, one-week old male Japanese quails were exposed to 15, 30, 60 and 75 mg/kg Cd for 5 weeks when birds in control group reached sex maturity. The results showed that Cd could cause microstructural damages including congestion and myocardial fiberolysis. Ultrastructural analysis also showed myocardial muscle fiber disarrangement and rupture as well as mitochondrial swelling, vacuolation and membrane lysis in Cd concentration groups. Moreover, Cd induced oxidative stress in the heart by decreasing antioxidant enzyme activities of catalase (CAT), glutathione peroxidase (GPX), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) while increasing oxidative biomarkers such as malondialdehyde (MDA), inducible nitric oxide synthase (iNOS), and content of nitric oxide (NO). In addition, mRNA expression levels of genes involved in muscle fiber formation signaling pathway such as Follistatin (FST), paired box 3 (PAX3), myogenic differentiation 1 (MYoD1) and SRY-box transcription factor 6 (SOX6), were down-regulated by Cd exposure. Furthermore, PI3K/Akt/mTOR signaling pathway were disrupted by Cd exposure implying energy supply deficiency in the heart. We concluded that Cd caused cardiac dysfunction by inducing heart underdevelopment, histopathological injury, oxidative stress and myocardial muscle fiber formation disruption.

Selenium alleviates mercury chloride-induced liver injury by regulating mitochondrial dynamics to inhibit the crosstalk between energy metabolism disorder and NF-κB/NLRP3 inflammasome-mediated inflammation

Mercury (Hg) is a persistent heavy metal contaminant with definite hepatotoxicity. Selenium (Se) has been shown to alleviate liver damage induced by heavy metals. Therefore, the present study aimed to explore the mechanism of the antagonistic effect of Se on mercury chloride (HgCl2)-induced hepatotoxicity in chickens. Firstly, we confirmed that Se alleviated HgCl2-induced liver injury through histopathological observation and liver function analyzation. The results also showed that Se prevented HgCl2-induced liver lipid accumulation and dyslipidemia by regulating the gene expression related to lipid as well as glucose metabolism. Moreover, Se blocked the nuclear factor kappa B (NF-κB)/NLR family pyrin domain containing 3 (NLRP3) inflammasome signaling pathway, which was the key to alleviate the inflammation caused by HgCl2. Mechanically, Se inhibited immoderate mitochondrial division, fusion, and biogenesis caused by HgCl2, and also improved mitochondrial respiration, which were essential for preventing energy metabolism disorder and inflammation. In conclusion, our results suggested that Se inhibited energy metabolism disorder and inflammation by regulating mitochondrial dynamics, thereby alleviating HgCl2-induced liver injury in chickens. These results are expected to provide potential intervention and therapeutic targets for diseases caused by inorganic mercury poisoning.

Real-time in vitro monitoring of the subcellular toxicity of inorganic Hg and methylmercury in zebrafish cells

Mercury (Hg) is a prominent environmental contaminant and can cause various subcellular effects. Elucidating the different subcellular toxicities of inorganic Hg (Hg²⁺) and methylmercury (MeHg) is critical for understanding their overall cytotoxicity. In this study, we employed aggregation-induced emission (AIE) probes to investigate the toxicity of Hg at the subcellular level using an aquatic embryonic zebrafish fibroblast cell line ZF4 as a model. The dynamic monitoring of lysosomal pH and the mapping of pH distribution during Hg²⁺ or MeHg exposure were successfully realized for the first time. We found that both Hg²⁺ and MeHg decreased the mean lysosomal pH, but with contrasting effects and mechanisms. Hg²⁺ had a greater impact on lysosomal pH than MeHg at a similar intracellular concentration. In addition, Hg²⁺ in comparison to MeHg exposure led to an increased number of lysosomes, probably because of their different effects on autophagy. We further showed that MeHg (200 nM) exposure had an inverse effect on mitochondrial respiratory function. A high dose (1000 nM) of Hg²⁺ increased the amount of intracellular lipid droplets by 13%, indicating that lipid droplets may potentially play a role in Hg²⁺detoxification. Our study suggested that, compared with other parameters, lysosome pH was most sensitive to Hg²⁺ and MeHg. Therefore, lysosomal pH can be used as a potential biomarker to assess the cellular toxicity of Hg in vitro.

Transcriptomic analysis of lead-induced hepatoxicology in female Japanese quails (Coturnix japonica): Implications of triglyceride synthesis, degradation and transport disruption

Lead (Pb) pollution poses great threats to mammals including human and it is also hazardous to bird life. In this study, RNA sequencing analysis was employed to examine the molecular responses to lead exposure in the liver of a toxicological model species Japanese quails (Coturnix japonica). Female birds were exposed to 0, 50, 500 and 1000 ppm waterborne Pb for 49 days. The results showed that hepatic microstructure was damaged under lead exposure featured by sinusoids dilation and irregularity as well as cell necrosis. Moreover, ultrastructural injury in the liver including mitochondrial swelling and vacuolization as well as nuclear deformation was induced by lead exposure. Lead exposure also caused the decrease of lipid droplets in the liver by oil red O staining. In addition, liver transcriptomic analysis revealed that molecular signaling and functional pathways were disrupted by lead exposure. Meanwhile, the expression of genes involved with hepatic glycerophospholipids metabolism of triglyceride synthesis and lipid transport of triglyceride transfer was significantly down-regulated by lead exposure. Moreover, the up-regulation of genes associated with fatty acid oxidation and the down-regulation of genes related with fatty acid synthesis were caused by lead exposure. The present study implied that lead induced liver malfunction and bird health risks through histopathological damages, molecular signaling disruption, genetic expression alteration and triglyceride metabolism disturbance.

Cadmium induced skeletal underdevelopment, liver cell apoptosis and hepatic energy metabolism disorder in Bufo gargarizans larvae by disrupting thyroid hormone signaling

Cadmium (Cd) is hazardous to human health and it is also highly detrimental to amphibian life. In this study, Bufo gargarizans larvae were exposed to environmentally relevant Cd concentrations of 5, 100 and 200 μg L^-1 from Gosner stage (Gs) 26 to Gs 42 of metamorphic climax about 6 weeks. The results showed thyroid structural injuries and thyroid signaling disruption were induced by high Cd exposure (100 and 200 μg L^-1). Moreover, tadpole skeleton including whole body, vertebrata, forelimb and hindlimb was developmentally delayed by high Cd exposure through downregulating the mRNA expressions of genes involved with skeletal ossification and growth pathway. Moreover, liver histopathological injuries were caused by high Cd exposure featured by hepatocytes malformation, nuclear degeneration and increasing melanomacrophage centers. Meanwhile, liver apoptosis rate showed on the rise in a dose-dependent way and Cd stimulated liver apoptosis by upregulating mRNA expressions of genes related to extrinsic and intrinsic apoptosis pathways. Furthermore, high Cd caused hepatic glucometabolism disorder by decreasing the genetic expressions associated with glycolysis and mitochondrial oxidative phosphorylation. In addition, liver lipid metabolism was disrupted by high Cd exposure through downregulating mRNA levels of genes related to fatty oxidation and upregulating mRNA levels of genes related to fatty acid synthesis. We suggested that Cd did great harm to tadpole health by disturbing thyroid function, skeletal growth, liver cell apoptosis signaling and hepatic energy metabolism pathway.

Associations between metabolic syndrome and four heavy metals: A systematic review and meta-analysis

Four most concerned heavy metal pollutants, arsenic, cadmium, lead, and mercury may share common mechanisms to induce metabolic syndrome (MetS). However, recent studies exploring the relationships between MetS and metal exposure presented inconsistent findings. We aimed to clarify the relationship between heavy metal exposure biomarkers and MetS using a meta-analysis and systematic review approach. Literature search was conducted in international and the Chinese national databases up to June 2020. Of selected studies, we extracted the relevant data and evaluated the quality of each study's methodology. We then calculated the pooled effect sizes (ESs), standardized mean differences (SMDs), and their 95% confidence intervals (CIs) using a random-effect meta-analysis approach followed by stratification analyses for control of potential confounders. Involving 55,536 participants, the included 22 articles covered 52 observational studies reporting ESs and/or metal concentrations on specific metal and gender. Our results show that participants with MetS had significantly higher levels of heavy metal exposure [pooled ES = 1.16, 95% CI: 1.09, 1.23; n = 42, heterogeneity I2 = 75.6%; and SMD = 0.22, 95% CI: 0.15, 0.29; n = 32, I2 = 94.2%] than those without MetS. Pooled ESs in the subgroups stratified by arsenic, cadmium, lead, and mercury were 1.04 (95% CI: 0.97, 1.10; n = 8, I2 = 61.0%), 1.10 (0.95, 1.27; 11, 45.0%), 1.21 (1.00, 1.48; 12, 82.9%), and 1.26 (1.06, 1.48; 11, 67.7%), respectively. Pooled ESs in the subgroups stratified by blood, urine, and the other specimen were 1.22 (95% CI: 1.08, 1.38; n = 26, I2 = 75.8%), 1.06 (1.00, 1.13; 14, 58.1%), and 2.41 (1.30, 4.43; 2, 0.0%), respectively. In conclusion, heavy metal exposure was positively associated with MetS. Further studies are warranted to examine the effects of individual metals and their interaction on the relationship between MetS and heavy metals.

The sex-specific effects of blood lead, mercury, and cadmium levels on hepatic steatosis and fibrosis: Korean nationwide cross-sectional study

AIM

The potential effects of heavy metals on non-alcoholic fatty liver disease (NAFLD) remain unknown. We investigated the sex-specific relationships of blood lead (BPb), mercury (BHg), and cadmium (BCd) levels with hepatic steatosis (HS) and fibrosis (HF).

METHOD

We included 4420 participants from the 2016-2017 Korea National Health and Nutrition Examination Survey. High-risk alcoholics and patients with chronic hepatitis B or C infections or liver cirrhosis were excluded. We calculated the hepatic steatosis index (HSI) and fibrosis-4 index (FIB-4) values; we defined the presence of HS and HF as an HSI ≥ 36 and FIB-4 score >2.67, respectively. We adjusted for age, smoking and alcohol consumption statuses, hypertension, obesity, diabetes, hypertriglyceridemia, and BPb, BHg, and BCd levels.

RESULT

In males (n = 1860), the HSI was correlated negatively with the BPb level and positively with the BHg level (both p < 0.01). The FIB-4 score was correlated positively with the BPb and BCd levels (both p < 0.01). In females (n = 2560), the HSI and FIB-4 score were correlated positively with the BPb, BHg, and BCd levels (all p < 0.01). After adjustments, the BHg level increased the risk of HS in both males (OR = 1.065, p = 0.003) and females (OR = 1.061, p = 0.048), and the BCd level increased the risk of HF in females (OR = 1.668, p = 0.012).

CONCLUSION

Blood heavy metal levels were generally correlated positively with the HSI and FIB4 score, more so in females than males. The BHg level was associated with HS in males and females, and the BCd level was associated with HF in females. Further studies on NAFLD progression according to heavy metal status and sex are warranted.

Low-dose methylmercury exposure impairs the locomotor activity of zebrafish: Role of intestinal inositol metabolism

Methylmercury (MeHg) is a ubiquitous environmental toxicant with neurotoxic effects. Although its neurotoxicity had been more studied, the role of gut microbiota remains unclear. In this study, adult zebrafish and larvae were exposed to MeHgCl at the dose of 0, 1 and 10 ng/mL. MeHgCl exposure impaired the locomotor activity via upregulation of apoptosis and autophagy related genes in the brain. Intestinal and cerebral metabolome indicated that phosphatidylinositol signaling system and inositol phosphate metabolism pathways were significantly impacted in adult zebrafish upon MeHgCl exposure. The levels of myo-inositol (MI) in the intestine and brain were decreased and positively correlated. 16 S rRNA sequencing data from adult zebrafish showed that MeHgCl exposure also shifted the structure of gut microbiota and reduced the relative abundance of Bacteroidetes and Proteobacteria, which were further identified at genus level as Aeromonas and Cetobacterium. Further functional analysis indicated that MeHgCl disrupted inositol phosphate metabolism of gut microbiota. Notably, MI supplementation restored the impairment of locomotor activity and inhibited the upregulation of apoptosis and autophagy related genes, such as bcl-2 and atg5. Thus, this study not only revealed the key role of gut microbiota in MeHgCl-mediated neurotoxicity but also gave new insights into antagonizing its toxicity.

Multiple-element exposure and metabolic syndrome in Chinese adults: A case-control study based on the Beijing population health cohort

BACKGROUND

Metabolic syndrome (MetS) patients have a considerably increased risk for noncommunicable diseases, which poses a serious burden on public health. The effects of different elements on MetS have received increasing attention in the field of noncommunicable diseases over the past decade. These elements can exert adverse or favourable effects on human health by synergistic or antagonistic actions. Nevertheless, few studies have explored the relationship between multiple-element exposure and MetS.

METHOD

A total of 2095 MetS patients and 2039 controls free of major cardiovascular disease at baseline and follow-up visits were frequency matched for age (±5 years) and sex. The internal exposure levels of 15 elements in serum were investigated. Logistic regression models were employed to estimate odds ratios (ORs) of MetS for element concentrations categorized according to quartiles in the controls.

RESULT

Magnesium (Mg), selenium (Se), barium (Ba) and mercury (Hg) were significantly associated with MetS in the multi-element exposure model. The ORs for the extreme quartiles of Mg, Se, Ba, and Hg were 0.29 (95% CI: 0.23-0.37, P-trend < 0.001), 0.52 (95% CI: 0.42-0.65, P-trend < 0.001), 1.86 (95% CI: 1.51-2.28, P-trend < 0.001), and 2.61 (95% CI: 2.11-3.22, P-trend < 0.001), respectively. Ba may be antagonistic to Mg and Se in the human body.

CONCLUSIONS

Our study suggested that MetS was negatively associated with Mg and Se and positively associated with Ba and Hg. There were significant dose-response relationships between Mg, Se, Ba and Hg and the prevalence of MetS, suggesting that multiple elements may be involved in MetS.

Effect of glyphosate (Roundup Active®) on liver of tadpoles of the colombian endemic frog Dendropsophus molitor (amphibia: Anura)

Glyphosate-based herbicide (GBH) using is increasing on a global scale. Few studies have investigated the sub-lethal effects of GBH in endemic amphibian species. The present work tested the GBH Roundup Active® on the tadpoles of Dendropsophus molitor. The exposure was in a range of plausible environmental concentrations (0-0.75 μg a.e./L) during a month. D. molitor is an endemic tropical frog of South America. The exposure from 325 μg a.e./L caused histological alterations in the liver. The high-resolution optical microscopy (HROM) detected sinusoidal dilatation and cytoplasmic vacuolization. The transmission electron microscopy (TEM) showed disorganization of the endoplasmic reticulum. Since the liver is essential for detoxification, these results suggest choric effects. Exposure to another GBH has caused histological alterations in liver tadpoles liver in a previous study, but, this study tested another endemic South-American frog for only 96h. The present work applied HROM to observe lipid alterations since it does not use organic solvents; and TEM for the ultrastructural observation of hepatocytes. Environmental risk of GBH can improve by including sub-lethal effects in endemic species.

An association of blood mercury levels and hypercholesterolemia among Korean adolescents

PURPOSE

A few experimental studies have suggested that mercury exposure might be associated with dyslipidemia, possibly through its interference with the activities of genes and enzymes involved in lipid metabolism. Mercury exposure has been associated with the risk of dyslipidemia and cardiovascular disease in previous adult studies. However, only a few studies have been conducted in pediatric populations. We aimed to assess the associations between total blood mercury concentrations and lipid profiles in Korean adolescents.

METHODS

The study population comprised 1890 adolescents (963 males and 927 females; age: 10-19 years) who participated in the Korea National Health and Nutrition Examination Survey 2010-2013 and 2016 and whose fasting blood samples were obtained to determine their blood mercury concentrations and lipid profiles. We analyzed the distribution of lipid profiles and the prevalence of dyslipidemia based on the total blood mercury concentrations.

RESULTS

The geometric mean of the blood mercury concentration was 1.89 μg/L and was significantly higher in males (1.96 μg/L) than in females (1.83 μg/L). The total cholesterol and low-density lipoprotein (LDL) cholesterol levels significantly increased as the blood total mercury concentration increased in males, not in females. High-density lipoprotein cholesterol and triglyceride levels did not show significant associations with total blood mercury levels. The prevalence of hyper-LDL-cholesterolemia also significantly increased in the highest blood mercury quartile group compared with that in the lowest blood mercury quartile group in males (P-for-trend <0.001). Male adolescents in the highest total blood mercury quartile group were found to be at higher risk of hypercholesterolemia than those in the lowest quartile group after adjusting for the covariates including obesity [odds ratios (95% confidential interval): 3.72 (1.03-13.4)]. Total blood mercury quartile showed a positive linear relationship with the risk of hyper-LDL-cholesterolemia after controlling for the covariates in males.

CONCLUSION

Our results suggest the potential association between mercury exposure and the risk of hyper-LDL-cholesterolemia in male adolescents.

Nanozyme-based sensing platforms for detection of toxic mercury ions: An alternative approach to conventional methods

Mercury (Hg) is known as a poisonous heavy metal which stimulates a wide range of adverse effects on the human health. Therefore, development of some feasible, practical and highly sensitive platforms would be desirable in determination of Hg²⁺ level as low as nmol L^-1 or pmol L^-1. Different approaches such as ICP-MS, AAS/AES, and nanomaterial-based nanobiosensors have been manipulated for determination of Hg²⁺ level. However, these approaches suffer from expensive instruments and complicated sample preparation. Recently, nanozymes have been assembled to address some disadvantages of conventional methods in the detection of Hg²⁺. Along with the outstanding progress in nanotechnology and computational approaches, pronounced improvement has been attained in the field of nanozymes, recently. To accentuate these progresses, this review presents an overview on the different reports of Hg²⁺-induced toxicity on the different tissues followed by various conventional approaches validated for the determination of Hg²⁺ level. Afterwards, different types of nanozymes like AuNPs, PtNPs for quantitative detection of Hg²⁺ were surveyed. Finally, the current challenges and the future directions were explored to alleviate the limitation of nanozyme-based platforms with potential engineering in detection of heavy metals, namely Hg²⁺. The current overview can provide outstanding information to develop nano-based platforms for improvement of LOD and LOQ of analytical methods in sensitive detection of Hg²⁺ and other heavy metals.

The effects of chronic lead exposure on the liver of female Japanese quail (Coturnix japonica): Histopathological damages, oxidative stress and AMP-activated protein kinase based lipid metabolism disorder

Lead (Pb) is one of the most toxic metals to human and wildlife. It also had multiple negative influences on birds with physical, neurological and hematological clinical signs. However, the impacts of lead on bird liver lipid metabolism are still unclear. In this study, female Japanese quails were used to examine the effects of chronic lead exposure on liver histology, oxidative stress and AMPK (AMP-activated protein kinase) based lipid metabolism. Quails were randomly divided into 5 groups and each group was respectively fed with 0, 50, 250, 500 and 1000 ppm lead solution for 49 days. The result showed that exposure to 250, 500 and 1000 ppm Pb induced severe histopathological damages characterized by liver lipid vacuoles and accumulation, hepatic cytoplasmic hyalinization and vacuolization, hepatocytes necrosis, hepatic sinusoid congestion, and it also caused ultrastructural alterations featured by swelling and vacuolar mitochondria, the depolymerization of polyribosome, and lipid droplets accumulation. Moreover, significant decrease of activities of GPx (glutathione peroxidase), SOD (superoxide dismutase), CAT (catalase) and level of T-AOC (total antioxidant capacity) while significant increase of MDA (malondialdehyde) content were found in livers of all Pb groups. In addition, the expressions of genes related to fatty synthesis were significantly upregulated in livers of all Pb groups while the expressions of genes related to fatty β-oxidation were significantly downregulated in livers of 250 ppm Pb group. The present study indicated lead exposure does cause bird health damages through inducing liver microstructural and ultrastructural injury, oxidative damages and lipid metabolism disorder.

"On-off" ratiometric fluorescent detection of Hg2+ based on N-doped carbon dots-rhodamine B@TAPT-DHTA-COF

Covalent-organic frameworks (COFs) are new porous crystalline materials owning outstanding stability, adsorbability and hypotoxicity. The assembly of fluorescence probes into porous COF provides a good method for ratiometric fluorescence detection avoiding the toxic effects of fluorescence probes to the samples. Herein, a two-dimensional COF (TAPT-DHTA-COF) was employed as a host to encapsulate N-doped carbon dots (NCDs) and Rhodamine B (RhB) (NCDs-RhB@COF). NCDs and RhB were uniformly assembled into the pores of TAPT-DHTA- COF based on the hydrogen bond. The as-prepared NCDs-RhB@COF nanocomposites exhibited blue emission of NCDs at 440 nm and red emission of RhB at 570 nm at excitation of 340 nm. After the addition of Hg²⁺, the blue emission became weaker while the red emission was enhanced due to the strong coordination between NCDs-RhB@COF and Hg²⁺. This "on-off" fluorescence probe was applied in detection of trace Hg²⁺ with linear range of 0.048-10 μM and detection limit of 15.9 nM together with appropriate selectivity, acceptable sensitivity and stability. The work shreds some light for COF as platform to construct ratiometric fluorescent sensor for industrial and biological application.

Evaluation of the effects of chronic occupational exposure to metallic mercury on the thyroid parenchyma and hormonal function

INTRODUCTION

Experiments in animals exposed to mercury (Hg) in different chemical states have shown thyroid parenchymal and hormone alterations. However, these experiments did not allow the establishment of dose-response curves or provide an understanding of whether these Hg effects on the thyroid parenchyma occur in humans.

OBJECTIVE

To evaluate the association between chronic occupational exposure to metallic Hg and alterations in thyroid hormones and gland parenchyma 14 years after the last exposure.

METHODS

A cross-sectional study including 55 males exposed in the past to metallic Hg and 55 non-exposed males, paired by age, was conducted in the Hospital das Clínicas (Brazil) from 2016 to 2017. Serum concentrations of total and free triiodothyronine (TT3 and FT3), free thyroxine (FT4), thyrotropin (TSH), reverse T3 (RT3), selenium and antithyroid antibody titers were obtained. The Hg and iodine concentrations were measured in urine. The thyroid parenchyma was evaluated by B-mode ultrasonography with Doppler. The nodules with aspects suspicious for malignancy were submitted to aspiration puncture with a thin needle, and the cytology assessment was classified by the Bethesda system. The t test or Mann-Whitney test, Chi-square test and Spearman correlation were used to compare the exposed and non-exposed groups and examine the relationships between the variables. Univariate and multivariate logistic regression models were used to trace determinants of the risk of thyroid hormone alteration. Statistical significance was defined by p < 0.05.

RESULTS

The urinary Hg average was significantly higher in the exposed group than in the non-exposed group (p < 0.01). The mean TSH serum concentration in the exposed group was higher, with a statistically significant difference between the groups (p = 0.03). Serum concentrations of TSH exceeded the normality limit (4.20 µIU/ml) in 13 exposed individuals (27.3%) and 4 non-exposed individuals (7.3%), with a statistically significant association between the hormonal increase and exposure to Hg (p = 0.02). In the logistic regression model, exposure to Hg (yes or no) showed an odds ratio = 4.86 associated with an increase of TSH above the normal limit (p = 0.04). The serum concentrations of RT3 showed a statistically borderline difference between the groups (p = 0.06). There was no statistically significant difference between the mean TT3, FT3 and FT4 serum concentrations in the Hg-exposed group compared to the non-exposed group. The proportions of the echogenicity alterations were higher in the exposed group compared to the non-exposed group (27.3% versus 9.1%; p = 0.03). Papillary carcinomas were documented in three exposed individuals and one non-exposed individual. A follicular carcinoma was recorded in one non-exposed individual.

CONCLUSIONS

Due to the higher serum TSH concentration and the prevalence of parenchymal alterations in the Hg-exposed group, even after cessation of exposure, it is recommended that the thyroid status of exposed workers be followed for a long period.

Chronic lead exposure induces histopathological damage, microbiota dysbiosis and immune disorder in the cecum of female Japanese quails (Coturnix japonica)

Lead (Pb) is one of the most hazardous metals to human and wildlife and it also has multiple negative impacts on birds. However, its influences on bird gut morphology and intestinal microbiota were still unclear. We used female Japanese quails (Coturnix japonica) to examine the effects of chronic lead exposure (0, 50 ppm and 1000 ppm) on cecal histology, microbial communities and immune function. The results showed 50 ppm lead exposure caused subtle damages of cecum cell structure. However, 1000 ppm lead exposure caused severe cecum histopathological changes characterized by mucosa abscission, Lieberkühn glands destruction and lymphocyte proliferation. Moreover, both lead concentrations induced ultrastructural damages featured by nucleus pyknosis, mitochondrial vacuolation and microvilli contraction. Meanwhile, microbial community structure, species diversity, taxonomic compositions and taxa abundance in the cecum were affected by lead exposure. Furthermore, the mRNA relative expression of immunity-related genes such as interleukin 2 (IL-2) and gamma interferon (IFN-γ) was significantly downregulated while that of interleukin 6 (IL-6), tumor necrosis factor α (TNF-α) and natural killer kappa B (NF-κB) was significantly upregulated in the cecum of 50 and 1000 ppm lead exposure groups. We concluded that lead exposure may cause gut health impairment of female Japanese quails by inducing cecal histopathological changes, microbiota dysbiosis and cecal immune disorder.

Contaminant and Environmental Influences on Thyroid Hormone Action in Amphibian Metamorphosis

Aquatic and terrestrial environments are increasingly contaminated by anthropogenic sources that include pharmaceuticals, personal care products, and industrial and agricultural chemicals (i. e., pesticides). Many of these substances have the potential to disrupt endocrine function, yet their effect on thyroid hormone (TH) action has garnered relatively little attention. Anuran postembryonic metamorphosis is strictly dependent on TH and perturbation of this process can serve as a sensitive barometer for the detection and mechanistic elucidation of TH disrupting activities of chemical contaminants and their complex mixtures. The ecological threats posed by these contaminants are further exacerbated by changing environmental conditions such as temperature, photoperiod, pond drying, food restriction, and ultraviolet radiation. We review the current knowledge of several chemical and environmental factors that disrupt TH-dependent metamorphosis in amphibian tadpoles as assessed by morphological, thyroid histology, behavioral, and molecular endpoints. Although the molecular mechanisms for TH disruption have yet to be determined for many chemical and environmental factors, several affect TH synthesis, transport or metabolism with subsequent downstream effects. As molecular dysfunction typically precedes phenotypic or histological pathologies, sensitive assays that detect changes in transcript, protein, or metabolite abundance are indispensable for the timely detection of TH disruption. The emergence and application of 'omics techniques-genomics, transcriptomics, proteomics, metabolomics, and epigenomics-on metamorphosing tadpoles are powerful emerging assets for the rapid, proxy assessment of toxicant or environmental damage for all vertebrates including humans. Moreover, these highly informative 'omics techniques will complement morphological, behavioral, and histological assessments, thereby providing a comprehensive understanding of how TH-dependent signal disruption is propagated by environmental contaminants and factors.

Comparative effects of mercury chloride and methylmercury exposure on early neurodevelopment in zebrafish larvae

Mercury (Hg) is a ubiquitous environmental toxicant with important public health implications. Hg causes neurotoxicity through astrocytes, Ca2+, neurotransmitters, mitochondrial damage, elevations of reactive oxygen species and post-translational modifications. However, the similarities and differences between the neurotoxic mechanisms caused by different chemical forms of Hg remain unclear. Zebrafish embryos were exposed to methylmercury (MeHgCl) or mercury chloride (HgCl2) (0, 4, 40, 400 nM) up for 96 h. HgCl2 exposure could significantly decrease survival rate, body length and eye size, delay the hatching period, induce tail bending and reduce the locomotor activity, and these effects were aggravated in the MeHgCl group. The compounds could increase the number of apoptotic cells in the brain and downregulate the expression of Shha, Ngn1 and Nrd, which contribute to early nervous development. The underlying mechanisms were investigated by metabolomics data. Galactose metabolism, tyrosine metabolism and starch and sucrose metabolism pathways were disturbed after HgCl2 or MeHgCl exposure. In addition, the levels of three neurotransmitters including tyrosine, dopamine and tryptophan were reduced after HgCl2 or MeHgCl exposure. Oxidative stress is related to metabolite changes, such as changes in the putrescine, niacinamide and uric acid contents in the HgCl2 group, and squalene in the MeHgCl group. These data indicated that downregulation of these genes and abnormal metabolic profile and pathways contribute to the neurotoxicity of HgCl2 and MeHgCl.

Lactobacillus brevis 23017 Relieves Mercury Toxicity in the Colon by Modulation of Oxidative Stress and Inflammation Through the Interplay of MAPK and NF-κB Signaling Cascades

Aims: Lactobacillus strains have protective effects against heavy metals while relieving oxidative stress and modulating the immune response. Mechanisms that ameliorate heavy metal toxicity and the relationship between probiotics and gut barrier protection in the process of heavy metal pathogenesis was poorly understood. Methods and Results: In this study, Lactobacillus brevis 23017 (LAB, L. brevis 23017), a selected probiotics strain with strong mercury binding capacities, was applied to evaluate the efficiency against mercury toxicity in a mouse model. Histopathological results along with HE stains show that L. brevis 23017 protects the integrity of the small intestinal villus, which slows weight loss in response to Hg exposure. The qRT-PCR results demonstrate that L. brevis 23017 maintains a normal mucosal barrier via modulation of tight junction proteins. Importantly, the present study demonstrates that L. brevis 23017 effectively ameliorates injury of the small intestine by reducing intestinal inflammation and alleviating oxidative stress in animal models. Moreover, L. brevis 23017 blocks oxidative stress and inflammation through MAPK and NF-κB pathways, as shown by western blot. Conclusions: Together, these results reveal that L. brevis 23017 may have applications in the prevention and treatment of oral Hg exposure with fermented functional foods by protecting gut health in daily life.