Hg Toxicity Research Articles

Transcriptomic and proteomic analysis of Chinese rare minnow (Gobiocypris rarus) larvae in response to acute waterborne cadmium or mercury stress.

In this study, Chinese rare minnow (Gobiocypris rarus) larvae were exposed to the control group, Cd concentrations (0.5 and 2.5mg/L), and Hg concentrations (0.1 and 0.3mg/L) for 96h. Transcriptome analysis showed that 816 and 1599 significantly differentially expressed genes (DEGs) were identified in response to 2.5mg/L Cd2+ and 0.3mg/L Hg2+, respectively. Functional enrichment analysis revealed that DEGs were mostly associated with immune responses after Cd exposure, such as antigen processing and presentation, phagosome, apoptosis, and lysosome. Similarly, functional enrichment analysis showed that many pathways were mostly involved in metabolism after Hg exposure, such as glutathione metabolism and starch and sucrose metabolism. Results of two-dimensional electrophoresis (2-DE) showed that the abundance of 10 protein spots was significantly altered in the Cd2+ treatments. The proteomic analysis demonstrated that Cd toxicity might impair cytoskeletal and cell motility-related protein activity in the liver of G. rarus. Similarly, the abundance of 24 protein spots was significantly altered in the Hg2+ treatments. Hg toxicity regulates the expression of proteins belonging to several functional categories, including cytoskeleton, oxidative stress, digestive system, and energy metabolism. This study provides valuable relevant insight into the molecular mechanisms in response to Cd or Hg toxicity in aquatic organisms and will help screen for potential biomarkers to respond to Cd and Hg pollutants.

Exploration of Aqueous Phyllanthus amarus Leaf Extract as a Protective Agent in Mercury Chloride-Exposed Wistar Rats: A Neurobehavioural Study

Mercury (Hg) exposure is known to damage vital components of the central nervous system primarily through oxidative stress. Although Phyllanthus amarus (PA) is reported to be rich in antioxidants, there is a dearth of relevant research evidence to show its protective activity against Mercuric chloride (HgCl2)-induced neurotoxicity. Accordingly, this study was designed to investigate the possible protective activity of aqueous Phyllanthus amarus leaf extract (APALE) in HgCl2-exposed rats using standard neurobehavioral assessments. Thirty adult Wistar rats were randomized into six groups of five rats each viz: A: Control, distilled water; B: HgCl2 (4 mg/kg body wt.); C: APALE (200 mg/kg body wt.) + HgCl2 (4 mg/kg); D: APALE (400 mg/kg body wt.) + HgCl2 (4 mg/kg); E: APALE (200 mg/kg body wt.); F: APALE (400 mg/kg body wt.). All administrations were through an orogastric tube for 14 days. Thereafter, neurobehavioral tests (open field, novel object and Y-maze) were done and experimental rats were sacrificed by cervical dislocation. Body, brain and cerebellar weights were examined across all groups. HgCl2 exposure significantly (p<0.0.05) decreased whole body weight across experimental groups. Similarly, a reduction in brain and cerebellar weight was observed. Significant neurobehavioral alterations to locomotion, discrimination index and cognition/memory, induced by HgCl2, were observed across experimental groups. However, protection against the deleterious effects induced by HgCl2 was observed following pretreatment with APALE. Conclusively, these findings show that APALE demonstrated potent protective activity against HgCl2-induced neurotoxicity and may be useful in the management of Hg toxicity and other related disorders.

Biogeochemical cycle of mercury and controlling technologies: Publications in critical reviews in environmental science & technology in the period of 2017–2021

The Minamata Convention on Mercury (Hg) calls for global efforts to reduce the release and risk of Hg. A better understanding of the global Hg budget, transformation and transport as well as toxicity of Hg in the environment, and the Hg emission controlling technologies, is important to minimize Hg pollution and exposure risks. Here, we summarized recent findings regarding the Hg cycle, transport, transformation, and controlling technologies, based on publications in Critical Review in Environmental Science and Technology (CREST) during 2017–2021. In terms of CREST publications we first focused on the biogeochemical cycle and impacts of Hg in the sensitive environment of the Tibet Plateau, and technologies being used to control Hg0 emission from thermal power plants. Second, we discussed the roles of forest in the global cycle of Hg. Third, we reviewed the transport of Hg at artisanal and small-scale gold mining sites, and the mobility and transformation of Hg species in the environment. This special issue covers the recent studies on the cycle, transport, and transformation of Hg, enhances our abilities to develop better strategies to minimize its risks. There are emerging concerns with climatic change and natural and human perturbations on the biogeochemical cycle of Hg in the environment and futures studies are warranted in these areas as well as the global Hg cycle, transport, and remediation.

Mercury, selenium, and fatty acids in the axial muscle of largemouth bass: evaluating the influence of seasonal and sexual changes in fish condition and reproductive status.

Largemouth bass (LMB, 265-475 mm) were collected to document whether changes in fish condition and reproductive status influenced the concentration of total mercury (Hg) and selenium (Se) in axial muscle by season and sex. The fatty acid (FA) composition of fish was also examined to describe seasonal and sexual differences and identify whether arachidonic acid (ARA) could be used as a biomarker of Hg toxicity. There was a trend for females to have lower (p < 0.062) Se concentrations than males. The concentration of Se for females during spring (mean ± SD, 686 ± 51 ng/g dw) was 15% lower than males (806 ± 67 ng/g dw). Lower Se concentrations in females than males continued through summer and fall. Concentration of Hg for females during spring (152 ± 39 ng/g ww) was also 59% lower than males (373 ± 303 ng/g ww), but the difference was not significant (p > 0.2). The percent of lipids was greatest in fall and winter (3%) and comprised primarily of omega-3 fatty acids (35 g/100 g lipid). Fish condition as measured by percent lipids and relative weight was negatively (p < 0.02) related to Hg concentration for females and males. Lipid content for both sexes was also positively (p < 0.05) related to the Se:Hg ratio. Relative weight was positively related to the Se:Hg ratio for females during all seasons (p = 0.014), but only during spring and summer for males (p < 0.007). A low Se:Hg value was associated with an elevation in ARA for both sexes and a reduced hepatosomatic index in males. Data suggested that females transferred muscle stores of Se and Hg to developing oocytes during spring. This study generates hypotheses regarding the physiological drivers of seasonal and sexual variability in Hg, Se, and FA in LMB that may be applicable to other species and have implications for fisheries health and management.

Levels of non-essential trace metals and their impact on placental health: a review.

According to recent research, even low levels of environmental chemicals, particularly heavy metals, can considerably disrupt placental homeostasis. This review aims to explore the profile of non-essential trace metals in placental tissues across the globe and to specify trace metal(s) that can be candidates for impaired placental health. Accordingly, we conducted an extensive survey on relevant databases of peer-reviewed papers published in the last two decades. Among a considerable number of non-essential trace metals, arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) were identified as the most detrimental to placental health. Comparative analysis showed remarkable differences in placental levels of these trace metals worldwide. Based on current data reported across the globe, a median (min-max) range from 0.55 to 15ng/g for placental As levels could be deemed safe. The placental Cd and Pb levels were markedly higher in smokers than in non-smokers. Occupationally exposed pregnant women had several orders of magnitude higher Cd, Pb, and Hg levels in placental tissues than non-occupationally exposed women. Also, we concluded that even low-level exposure to As, Cd, Pb, and Hg could be deleterious to proper fetal development. This review implies the need to reduce exposure to non-essential trace metals to preserve placental health and prevent numerous poor pregnancy outcomes. Overall, the information presented is expected to help plan future fundamental and applied investigations on the placental toxicity of As, Cd, Pb, and Hg.

Mercury toxicity affects oxidative metabolism and induces stress responsive mechanisms in wheat (Triticum aestivum L.).

Mercury (Hg) toxicity is an increasing problem worldwide, with a negative impact on the environment and living organisms including both animals and plants. In this study, we analyzed molecular and biochemical changes related to Hg toxicity in wheat (Triticum aestivum L.) seedlings. Seven-day-old seedlings were exposed to various concentrations (5, 10, and 20 µM) of HgCl2 for 24 and 48h. Our results showed that HgCl2 treatments led to an increase in the Hg content of wheat leaves in a time- and concentration-dependent manner. Furthermore, significant increases were observed in hydrogen peroxide, malondialdehyde, and proline contents in response to Hg toxicity. While all HgCl2 treatments decreased the level of superoxide dismutase (SOD), the level of catalase (CAT) was reduced only in seedlings exposed to 5 µM of HgCl2. Mercury stress caused a decline in the expression of Cu/Zn-SOD, Fe-SOD, TaWRKY19, and TaDREB1 genes at both exposure times. On the other hand, 10 and 20 µM HgCl2 treatments caused significant induction (1.9 to 6.1-fold) in the expression of the CAT gene in wheat leaves. The mRNA level of the Mn-SOD and TaWRKY2 genes showed different patterns depending on the concentration and exposure period of HgCl2. In conclusion, the findings of this work demonstrate that Hg toxicity causes oxidative damage in wheat seedlings and changes the expression of some genes encoding WRKY and DREB transcription factor families, which have important functions in abiotic stress response.

Heavy metals and metalloid levels in the tissues of yellow-legged gulls (Larus michahellis) from Spain: sex, age, and geographical location differences

In the present study, mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se), and arsenic (As) were measured in liver, kidney, and feathers of adult, juvenile, and chick seagulls (Larus michahellis) collected from the northwest of Spain. Age, sex, and the geographical location of samples were considered variables that can influence metal bioaccumulation, for which concentrations were determined by means of ICP-MS. The mean concentrations (dry weight) found in seagulls were 7.01 ± 0.37 mg Hg/kg, 22.82 ± 2.83 mg Cd/kg, 7.36 ± 1.36 mg Pb/kg, 18.64 ± 0.63 mg Se/kg, and 10.64 ± 0.59 mg As/kg. Regarding the different factors analyzed, Hg was the only metal showing sex-related differences, being significantly higher (p < 0.05) the concentrations found in feathers of males (1.26 ± 0.12 mg/kg) than those in females (0.99 ± 0.11 mg/kg). A highly significant (p < 0.01) increase in levels of some metals was found in liver related to the increase of age: Hg (adults (A) 3.33 ± 0.22 mg/kg vs chicks (C) 1.76 ± 0.28 mg/kg), Cd (A 4.74 ± 0.62 mg/kg vs C 1.79 ± 0.2), Pb (A 0.65 ± 0.12 mg/kg vs juveniles 0.4 ± 0.11 mg/kg), and Se (A 7.56 ± 0.43 mg/kg vs C 5.24 ± 0.53 mg/kg). Positive correlations between Cd-Hg and Se–Hg were found in liver (p < 0.001), kidney (p < 0.001), and feathers (p < 0.05 and p < 0.001, respectively). The associations found may reflect antagonistic interactions between Se and Cd on Hg toxicity. The results suggest that L. michahellis can reveal local contamination around the foraging and breeding sites and can be a very useful monitoring instrument for assessing heavy metal contamination and sentinel species of environmental health.

Mercury, selenium and arsenic concentrations in Canadian freshwater fish and a perspective on human consumption intake and risk

Mercury (Hg) and arsenic (As) contamination of fish can be toxic and limit safe human consumption, whereas selenium (Se) can potentially protect fish and consumers from the adverse effects of Hg and As. We assembled datasets of the above-mentioned elements in Canadian freshwater fish and compare them with risk assessment thresholds. We further assessed linkages between the elemental concentrations and anthropogenic activities and ecozones. Mercury concentrations exceeded the retail fish Canadian threshold (0.5 µg/g wet weight) in 31% of all Walleye; this proportion rose to 64% in reservoirs. Reservoirs and lakes impacted by logging and urbanization had higher fish [Hg] than other types of impacted systems. Se and As concentrations exceeded Canadian guidelines in 5% (aquatic life) and 0.2% of all fish, respectively. In mining areas, fish [Hg] were low and negatively correlated with [Se], and fish [Se] were positively correlated with [As]. In all areas, we observed an important overall and previously unpublished negative relationship between mean fish [As] and [Hg], suggesting an inverse consumption risk for these two elements. The ratio Se/Hg was lower than the protective value of 1 for 14% of all fish and was negatively correlated with fish length. However, the benefit-risk value (BRV) threshold, which accounts for the Se intake from other food products, did not suggest any fish consumption limitations, except for few very contaminated top predators (> 2 µg/g ww). More studies need to assess the role of Se against Hg toxicity and adjust fish consumption guidelines accordingly.

Zinc Oxide Nanoparticles Improve Pleioblastus pygmaeus Plant Tolerance to Arsenic and Mercury by Stimulating Antioxidant Defense and Reducing the Metal Accumulation and Translocation.

The utilization of nanoparticles to potentially reduce toxicity from metals/metalloids in plants has increased in recent years, which can help them to achieve tolerance under the stressful conditions. An in vitro experiment was conducted to investigate five different levels of zinc oxide nanoparticles (ZnO-NPs; 0, 50, 100, 150, and 200 μM) both alone and in combination with 150 μM arsenic (As) and 150 μM mercury (Hg) in one-year-old Pleioblastus pygmaeus (Miq.) Nakai plants through four replications. The results demonstrated that As and Hg alone had damaging effects on the plant growth and development. However, the addition of various concentrations of ZnO-NPs led to increased antioxidant activity, proline (79%) content, glycine betaine (71%) content, tyrosine ammonia-lyase (43%) activity, phenylalanine ammonia-lyase (69%) activity, chlorophyll indices, and eventually plant biomass, while the lipoxygenase activity, electrolyte leakage, soluble protein, hydrogen peroxide content, and thiobarbituric acid reactive substances were reduced. We concluded that ZnO-NPs detoxified As and Hg toxicity in the plants through increasing antioxidant activity, reducing As and Hg accumulation, As and Hg translocation from roots to shoots, and adjusting stomatal closure. This detoxification was further confirmed by the reduction of the translocation factor of As and Hg and the enhancement of the tolerance index in combination with ZnO-NPs. However, there is a need for further investigation with different metals/metalloids.

Trace elements in seabass, farmed by Turkey, and health risks to the main consumers: Turkish and Dutch populations.

Turkey ranked first in sea bass farming in Europe, and almost all extra-EU seabass come from this country. The share of Turkish sea bass in the fish consumption of Europeans has increased significantly, and assessment of potential health risks of trace metals via sea bass, cultured by Turkey, became important. The Netherlands is the main buyer of the Turkish sea bass. Therefore, potential health risks were determined for Turkish and Dutch consumers. In the study, the concentrations of lead (Pb) and mercury (Hg) were below the limits, but the level of cadmium (Cd) was above the guidelines, in spring and winter. Dietary intake and potential health risk were found higher for the Dutch consumer, but all target hazard quotients (THQs) and total THQ (TTHQ) values were well below 1, showing no significant health risk due to the consumption of sea bass, cultured and exported by Turkey. It was determined that these sea basses can be safely consumed in quite high amounts, such as at least 31 meals a month. Se/Hg molar ratios were all above 1 and selenium health benefit values (Se-HBVs) were positive, indicating that selenium (Se) had a protective effect on Hg toxicity and positive health effects. Considering the average annual intake in Turkey and Netherlands, the consumption of sea bass, cultured by Turkey, is safe. Since the risk levels of communities may differ due to their eating habits, it is important to determine the public health impacts of the international fish trade.

Efficient mercury sequestration from wastewaters using palm kernel and coconut shell derived biochars

Elevated mercury (Hg) concentrations in water bodies caused by illegal artisanal gold mining in Ghana is a serious health concern given the toxicity of Hg. As an ecofriendly cost-effective solution for removing Hg from these water bodies, we synthesized biochars using palm kernel (PB) and coconut shells (CB), which are dominant biomass wastes in Ghana. The biochars were sulfurized (SPB, SCB) and fabricated into polysulfone-based beads for Hg(II) sorption. The Hg(II) concentration, contact time, sorbent mass, and solution pH were investigated and were found to be influential on the sorption of Hg(II) from aqueous solution. The sulfurized biochars showed a faster Hg(II) removal (within 1h) compared to the pristine biochars. Sorption tests conducted using natural riverine water samples confirmed the potential use of the biochars, with SPB and SCB showing higher efficiencies than pristine PB and CB. The fabricated beads exhibited 70–90% efficiency in Hg(II) removal from 1.0 mg L−1 Hg solution and the sorption capacity was below 0.1 mg g−1, which we attribute to the mass of biochar used for the beads. The Hg(II) sorption mechanisms of PB and CB from spectroscopic analyses suggest that the biochars synthesized in this study can be used to treat Hg polluted waters and suitable for large-scale applications in natural water bodies.

Selenium-enriched Bacillus subtilis reduces the effects of mercury-induced on inflammation and intestinal microbes in carp (Cyprinus carpio var. specularis)

Mercury (Hg) is a global pollutant that affects the health of humans and ecosystems. Selenium (Se) is an essential trace element for many organisms including humans. Bacillus subtilis is one of the main probiotics used in aquaculture, and has a certain adsorption effect on heavy metals. The interaction between Hg and Se was rigorously studied, especially due to the observation of the protective effect of Se on Hg toxicity. The objective of this study was to research the effects of Hg, Se, and B. subtilis on inflammation and intestinal microbes in common carp. The common carp was exposed to Hg (0.03mg/L), and 105cfu/g Se-rich B. subtilis was added to the feed. After 30days of feeding, samples were taken to evaluate the growth performance, serological response, inflammatory response, and intestinal microbial changes. In this study, when fish were exposed to Hg, the growth performance of the Se-rich B. subtilis plus 0.03mg/L Hg fish group was lower than that of the control group and higher than 0.03mg/L Hg; The levels of serum immunoglobulin M (IgM) and lysozyme (LZM) decreased, but after supplementation with Se-rich B. subtilis, the levels of LZM and IgM increased; Hg treatment significantly upregulated the mRNA expression of interleukin-1β (IL-1β), interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), and nuclear factor-kB (NF-κB P65), but downregulated the mRNA expression of interleukin-10 (IL-10), transforming growth factor-β (TGF-β) and NF-kappa-B inhibitor alpha (IkBα). However, compared with the Hg group, the Se-rich B. subtilis plus Hg group can significantly increase the mRNA expression levels of IL-1β, IL-8, TNF-α, and NF-κB P65, but reduce the regulation of IL-10, TGF-β, and IkBα expression. Through the analysis of the microbiological, we found that the Hg group was mainly composed of Aeromonas sobria and Aeromonas hydrophila. However, in the Se-rich B. subtilis treatment group, we found that Aeromonas sobria was significantly less than the Hg group. Se-rich B. subtilis improves Hg-induced intestinal microbial changes, alleviates the abundance of Aeromonas, and alleviates the inflammation of the fish. The results of this study show that Se-rich B. subtilis dietary supplements can effectively protect common carp against Hg toxicity.

Two cetacean species reveal different long-term trends for toxic trace elements in European Atlantic French waters

Cetaceans have been naturally exposed to toxic trace elements (TEs) on an evolutionary time scale. Hence, they have developed mechanisms to control and/or mitigate their toxic effects. These long-lived species located at high trophic positions and bioaccumulating toxic elements are assumed to be good biomonitoring organisms. However, anthropogenic emissions have strongly increased environmental levels of toxic TEs in the last decades, questioning the efficiency of the detoxication mechanisms in cetaceans. In this context, temporal trends of mercury (Hg), cadmium (Cd) and lead (Pb) concentrations were studied through the analysis of 264 individuals from two cetacean species the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena) and belonging to two different Management Units (MUs) for the latter. These individuals stranded along the French Atlantic coasts from 2000s to 2017. All the trends presented were age- and sex-corrected and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were measured as proxies of their feeding ecology. Results showed that Pb concentrations clearly decreased over time in both species and MUs. This decrease agrees with the lead petrol regulation after 2000s, supporting the use of these species as valuable bioindicators of changes for TE levels in the marine environment. A significant long-term increase of total Hg concentrations was only observed in common dolphins. Cadmium concentrations also revealed different trends over the period in both species. The different Hg and Cd trends observed in the two species, probably reflected a contrasted contamination of habitat and prey species than a global increase of the contamination in the environment. These results highlight the necessity and gain of using different species to monitor changes in marine environments, each of them informing on the contamination of its own ecological niche. Lastly, the Se:Hg molar ratios of species suggested a low risk for Hg toxicity over time.

Mercury toxicity risk and corticosterone levels across the breeding range of the Yellow-breasted Chat

Mercury (Hg) is an environmental contaminant that can negatively impact human and wildlife health. For songbirds, Hg risk may be elevated near riparian habitats due to the transfer of methylmercury (MeHg) from aquatic to terrestrial food webs. We measured Hg levels in tail feathers sampled across the breeding range of the Yellow-breasted Chat (Icteria virens), a riparian songbird species of conservation concern. We assessed the risk of Hg toxicity based on published benchmarks. Simultaneously, we measured corticosterone, a hormone implicated in the stress response system, released via the hypothalamus-pituitary-adrenal axis. To better understand range-wide trends in Hg and corticosterone, we examined whether age, sex, subspecies, or range position were important predictors. Lastly, we examined whether Hg and corticosterone were correlated. Hg levels in chats were relatively low: 0.30 ± 0.02 µg/g dry weight. 148 out of 150 (98.6%) had Hg levels considered background, and 2 (1.6%) had levels considered low toxicity risk. Hg levels were similar between sexes and subspecies. Younger chats (<1 year) had higher Hg levels than older chats (>1 year). Hg levels were lowest in the northern and central portion of the eastern subspecies’ range. Corticosterone concentrations in feathers averaged 3.68 ± 0.23 pg/mm. Corticosterone levels were similar between ages and sexes. Western chats had higher levels of corticosterone than eastern chats. Hg and corticosterone were not correlated, suggesting these low Hg burdens did not affect the activity of the hypothalamus-pituitary-adrenal axis. Altogether, the chat has low Hg toxicity risk across its breeding range, despite living in riparian habitats.

Efficient treatment of mercury(Ⅱ)-containing wastewater in aerated constructed wetland microcosms packed with biochar

Effective removal of mercury (Hg) pollutants from contaminated water/wastewater to prevent severe environmental pollution is of great significance due to the extremely high toxicity of Hg. In this study, granular biochar and gravel (control) were packed into intermittently aerated constructed wetland (CW) microcosms to treat Hg(Ⅱ)-containing wastewater over 100 d. The results showed that the biochar-filled CWs exhibited notably better Hg(Ⅱ) removal than the gravel systems by facilitating chemical and microbial Hg(Ⅱ) reduction and volatilization and promoting plant growth and Hg assimilation. More than ten times more Hg was absorbed by the plants (L. salicaria) in biochar CWs than in the gravel systems, with the roots acting as the major sink. In contrast, substrate binding in a predominantly oxidizable fraction was the dominant pathway for Hg removal in the gravel CWs. Biochar substrates also exhibited higher levels of COD, N and P removal, and Hg(Ⅱ) import impacted the removal of these pollutants only slightly. Filling material played a more crucial role than Hg input in shaping the microbial communities in the CWs. The proportions of some dominant genera, including Arenimonas, Lysobacter, Micropruina and Hydrogenophaga, increased in the presence of Hg, implying their tolerance to Hg toxicity and potential roles in Hg detoxification in the CWs. Granular biochar-based CW has high potential for treating Hg(Ⅱ)-contaminated wastewater.

Patterns of maternal transfer of trace elements in the pelagic thresher shark (Alopias pelagicus) of the Eastern Pacific Ocean

Pelagic sharks are vulnerable to overfishing due to slow growth rates, late-at-maturity and low fecundity, 90% of which are Near Threatened with an elevated risk of extinction according to IUCN Red List Criteria. Trace elements can be accumulated by marine predators and may have detrimental effects on population dynamics. In this study, we analyzed the concentrations of 11 trace elements (Zn, Cu, Cr, Ni, Mn, Se, Co, Hg, Cd, Pb, and As) in muscle and liver tissues of 10 pregnant pelagic thresher sharks (Alopias pelagicus) and their 18 embryos. The results showed that four essential elements (Cu, Cr, Mn, and Se) were accumulated in both tissue types of embryos. Ni and Zn concentrations were higher in embryonic muscle than that in the liver. For nonessential elements, concentrations of As, Cd and Hg in both embryonic tissues were lower than those of their mothers. Though maternal and embryonic tissues had high levels of Hg, the Se/Hg molar ratios in both tissues of the embryo were above 1 with larger values in the embryos, indicating that Se played a protective role against Hg toxicity in embryonic tissues. Liver is the primary energy resource of embryo development. There was no correlation for element concentrations between embryonic and maternal liver tissues, indicating there is a regulatory mechanism to maintain the stability of element contents during maternal transfer in pelagic thresher shark.

Formation Mechanism and Toxicological Significance of Biogenic Mercury Selenide Nanoparticles in Human Hepatoma HepG2 Cells.

It is widely recognized that the toxicity of mercury (Hg) is attenuated by the simultaneous administration of selenium (Se) compounds in various organisms. In this study, we revealed the mechanisms underlying the antagonistic effect of sodium selenite (Na2SeO3) on inorganic Hg (Hg2+) toxicity in human hepatoma HepG2 cells. Observations by transmission electron microscopy indicated that HgSe (tiemannite) granules of up to 100 nm in diameter were accumulated in lysosomal-like structures in the cells. The HgSe granules were composed of a number of HgSe nanoparticles, each measuring less than 10 nm in diameter. No accumulation of HgSe nanoparticles in lysosomes was observed in the cells exposed to chemically synthesized HgSe nanoparticles. This suggests that intracellular HgSe nanoparticles were biologically generated from Na2SeO3 and Hg2+ ions transported into the cells and were not derived from HgSe nanoparticles formed in the extracellular fluid. Approximately 85% of biogenic HgSe remained in the cells at 72 h post culturing, indicating that biogenic HgSe was hardly excreted from the cells. Moreover, the cytotoxicity of Hg2+ was ameliorated by the simultaneous exposure to Na2SeO3 even before the formation of insoluble HgSe nanoparticles. Our data confirmed for the first time that HepG2 cells can circumvent the toxicity of Hg2+ through the direct interaction of Hg2+ with a reduced form of Se (selenide) to form HgSe nanoparticles via a Hg-Se soluble complex in the cells. Biogenic HgSe nanoparticles are considered the ultimate metabolite in the Hg detoxification process.

Alteration of acute toxicity of inorganic and methyl mercury to Daphnia magna by dietary addition

Acute toxicity of inorganic mercury [Hg(II)] and methylmercury (MeHg) to Daphnia magna was characterized using a 48-h static, non-renewal acute toxicity test, in which we compared the toxicity of Hg(II) and MeHg in the absence (water-only) and presence of diet [green alga (Raphidocelis subcapitata), yeast, Cerophyll, and trout chow (YCT), or both]. Overall, Hg(II) is more toxic to D. magna than MeHg, with 48-h median lethal concentrations (LC50s) being 4.3 µg/L (95% confidence interval: 4.1–4.5 µg/L) for Hg(II) and 14.3 µg/L (13.2–15.3 µg/L) for MeHg. For Hg(II), the addition of any diet would significantly increase its 48-h LC50, but the 48-h LC50 for MeHg decreased significantly to 7.1 µg/L (6.4–7.8 µg/L) with the algal addition. We also show that the addition of diets significantly influenced the levels and speciation (dissolved vs. particulate) of both Hg forms in the test solution. The bioaccumulation of Hg(II) and MeHg was impacted by the dietary addition, and it appears that the body residue level triggering mortality varied widely among treatments. The results suggest that standard short-term toxicity tests (water-only) should be supplemented with extra tests with dietary addition to provide a more environmentally relevant estimation of short-term toxicity of chemical compounds.

Hemodialysis Effect on the Composition of the Eye Fluid of Cataract Patients.

Numerous reports have proven that dialysis patients experience disturbances in the levels of elements in biological fluids. Disturbances in the homeostasis of essential elements or the appearance of highly toxic elements are serious problems also in clinical ophthalmology. The purpose of this study was to investigate the influence of hemodialysis (HD) on the elemental composition of anterior chamber aqueous humor (AH) in patients undergoing cataract surgery. The study involved 22 patients. The control group enrolled 16 patients (age 75.68 ± 9.67, female 54.55%, male 45.45%) with cataract and normal kidney function (control), and the second group included six patients (age 70.33 ± 12.74, female 33.33%, male 66.67%) with cataract undergoing HD treatment. The elements quantification was established using an inductively coupled plasma optical emission spectrometer (ICP-MS). In the eye fluid of dialysis patients, there were increased levels of manganese (Mn) and mercury (Hg) and decreased levels of vanadium (V) and zinc (Zn). In addition, a statistically significant increase in the Hg/Zn and Hg/selenium (Se) ratios and a lowering of the iron (Fe)/Mn ratio were observed in the studied group in comparison to the control. The obtained results indicated the need for Zn and Se supplementation in order to eliminate the hazards caused by Hg toxicity. A lower level of V in the eye fluid of dialysis patients may have a positive effect on maintaining a calcium and phosphorus homeostasis. Our study gives a deep insight into changes of elements concentrations in AH induced by HD.

Drivers of biomagnification of Hg, As and Se in aquatic food webs: A review

Biomagnification of trace elements is increasingly evident in aquatic ecosystems. In this review we investigate the drivers of biomagnification of mercury (Hg), arsenic (As) and selenium (Se) in aquatic food webs. Despite Hg, As and Se biomagnify in food webs, the biomagnification potential of Hg is much higher than that of As and Se. The slope of trophic increase of Hg is consistent between temperate (0.20), tropical (0.22) and Arctic (0.22) ecosystems. Se exerts a mitigating role against Hg toxicity but desired maximum and minimum concentrations are unknown. Environmental (e.g. latitude, temperature and physicochemical characteristics) and ecological factors (e.g. trophic structure composition and food zone) can substantially influence the biomagnification process these metal (oids). Besides the level of bioaccumulated concentration, biomagnification depends on the biology, ecology and physiology of the organisms that play a key role in this process. However, it may be necessary to determine strictly biological, physiological and environmental factors that could modulate the concentrations of As and Se in particular. The information presented here should provide clues for research that include under-researched variables. Finally, we suggest that biomagnification be incorporated into environmental management policies, mainly in risk assessment, monitoring and environmental protection methods.