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Bjerregaard P, Møller LM. Exposure to methylmercury and inorganic mercury in the food does not lead to trophic magnification in the sea star Asterias rubens. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 285:117401. [PMID: 34051567 DOI: 10.1016/j.envpol.2021.117401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 04/19/2021] [Accepted: 05/15/2021] [Indexed: 06/12/2023]
Abstract
Methylmercury accumulated at the top of aquatic food chains constitutes a toxicological risk to humans and other top predators. Biomagnification of methylmercury takes place among vertebrates at the higher trophic levels, but this process is less elucidated in benthic invertebrates at the lower trophic levels. Therefore, we investigated the accumulation from food and elimination of methylmercury and inorganic mercury in the benthic sea star Asterias rubens (L.) - a representative of trophic level ~3 - in laboratory experiments. Sea stars fed over 49 days with contaminated mussels (Mytilus edulis) accumulate methylmercury and inorganic mercury to the highest concentrations in the digestive glands, the pyloric caeca, less in stomach, gonad, tube feet, aboral body wall and not to detectable levels in the coelomic fluid. Concerning whole body contents, steady states were reached for both methylmercury and inorganic mercury during the 7-week feeding period and the sea stars reached approximately ½ and ¼ of the concentrations in the mussel food for the two mercury forms, respectively. Half-lives for the elimination of the two mercury forms varied between 45 and 173 days in a 140-d elimination period following the feeding period; inorganic mercury was eliminated faster than methylmercury. Examination of total mercury concentrations in field-collected sea stars confirmed this lack of trophic magnification in relation to the major food items, soft parts of molluscs. We suggest that mercury is not trophically magnified in sea stars 1) because they eliminate methylmercury faster than larger fish and decapod crustaceans and 2) maybe more importantly, because inorganic mercury with its faster elimination constitutes a larger fraction of the total mercury in the food at the lower trophic levels - as opposed to methylmercury which dominates at the higher trophic levels.
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Affiliation(s)
- Poul Bjerregaard
- Department of Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense, Denmark.
| | - Lise Marianne Møller
- Department of Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense, Denmark
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Gerson JR, Walters DM, Eagles-Smith CA, Bernhardt ES, Brandt JE. Do Two Wrongs Make a Right? Persistent Uncertainties Regarding Environmental Selenium-Mercury Interactions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:9228-9234. [PMID: 32633495 DOI: 10.1021/acs.est.0c01894] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Mercury (Hg) is a pervasive environmental pollutant and contaminant of concern for both people and wildlife that has been a focus of environmental remediation efforts for decades. A growing body of literature has motivated calls for revising Hg consumption advisories to co-consider selenium (Se) levels in seafood and implies that remediating aquatic ecosystems with ecosystem-scale Se additions could be a robust solution to Hg contamination. Provided that elevated Se concentrations are also known toxicological threats to aquatic animals, we performed a literature search to evaluate the strength of evidence supporting three assertions underpinning the ameliorating benefits of Se: (1) dietary Se reduces MeHg toxicity in consumers; (2) environmental Se reduces Hg bioaccumulation and biomagnification in aquatic food webs; and (3) Se inhibits Hg bioavailability to, and/or methylmercury production by, microbial communities. Limited or ambiguous support for each criterion indicates that many scientific uncertainties and gaps remain regarding Se mediation of Hg behavior and toxicity in abiotic and biotic compartments. Significantly more information is needed to provide a strong scientific basis for modifying current fish consumption advisories on the basis of Se:Hg ratios or for applying Se amendments to remediate Hg-contaminated ecosystems.
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Affiliation(s)
- Jacqueline R Gerson
- Department of Biology, Duke University, Durham, North Carolina 27708, United States
| | - David M Walters
- U.S. Geological Survey, Columbia Environmental Research Center, Columbia, Missouri 65201, United States
| | - Collin A Eagles-Smith
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, Oregon 97330, United States
| | - Emily S Bernhardt
- Department of Biology, Duke University, Durham, North Carolina 27708, United States
| | - Jessica E Brandt
- Department of Natural Resources and the Environment & Center for Environmental Sciences and Engineering, University of Connecticut, Storrs, Connecticut 06269, United States
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Kuras R, Kozlowska L, Reszka E, Wieczorek E, Jablonska E, Gromadzinska J, Stanislawska M, Janasik B, Wasowicz W. Environmental mercury exposure and selenium-associated biomarkers of antioxidant status at molecular and biochemical level. A short-term intervention study. Food Chem Toxicol 2019; 130:187-198. [PMID: 31078725 DOI: 10.1016/j.fct.2019.04.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 04/16/2019] [Accepted: 04/29/2019] [Indexed: 11/30/2022]
Abstract
Mercury (Hg) is a potent toxicant. In the field of public health a chronic-low-level environmental Hg exposure resulting from fish consumption in general population is still being discussed. The objective of the study was to assess the influence of real Hg exposure on biomarkers of selenium (Se) status and selected biomarkers of pro-oxidant/anti-oxidant effects in healthy men (n = 67) who participated in the short-term intervention study consisting in daily fish consumption for two weeks. The analysis included Se level, Se-associated antioxidants at molecular (profile of 7 genes encoding selected proteins related to antioxidant defense) and biochemical levels (Se-dependent glutathione peroxidases activities and plasma selenoprotein P concentration). A pro-oxidant/anti-oxidant balance was explored using a biomarker of plasma lipid peroxidation and total antioxidant activity. The study revealed significant correlations (p < 0.05) between the biomarkers of exposure to Hg, Se level and Se-dependent antioxidants. Even though the risk of adverse effects of Hg for volunteers was substantially low, biomarkers of Hg altered levels of circulation selenoproteins and their genes expression. Changes in genes expression during study differed between the main enzymes involved in two systems: downregulation of thioredoxin reductase1 and upregulation of glutathione peroxidases. Hg exposure caused imbalance between the biomarkers of pro-oxidant/anti-oxidant effects.
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Affiliation(s)
- Renata Kuras
- Nofer Institute of Occupational Medicine, Department of Biological and Environmental Monitoring, 8 Teresy St, 91-348, Lodz, Poland.
| | - Lucyna Kozlowska
- Department of Dietetics, Faculty of Human Nutrition and Consumer Sciences, University of Life Sciences, Nowoursynowska 159c St., Building 32, 02-776, Warsaw, Poland
| | - Edyta Reszka
- Nofer Institute of Occupational Medicine, Department of Molecular Genetics and Epigenetics, 8 Teresy St, 91-348, Lodz, Poland
| | - Edyta Wieczorek
- Nofer Institute of Occupational Medicine, Department of Molecular Genetics and Epigenetics, 8 Teresy St, 91-348, Lodz, Poland
| | - Ewa Jablonska
- Nofer Institute of Occupational Medicine, Department of Molecular Genetics and Epigenetics, 8 Teresy St, 91-348, Lodz, Poland
| | - Jolanta Gromadzinska
- Nofer Institute of Occupational Medicine, Department of Biological and Environmental Monitoring, 8 Teresy St, 91-348, Lodz, Poland
| | - Magdalena Stanislawska
- Nofer Institute of Occupational Medicine, Department of Biological and Environmental Monitoring, 8 Teresy St, 91-348, Lodz, Poland
| | - Beata Janasik
- Nofer Institute of Occupational Medicine, Department of Biological and Environmental Monitoring, 8 Teresy St, 91-348, Lodz, Poland
| | - Wojciech Wasowicz
- Nofer Institute of Occupational Medicine, Department of Biological and Environmental Monitoring, 8 Teresy St, 91-348, Lodz, Poland
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Nogara PA, Oliveira CS, Schmitz GL, Piquini PC, Farina M, Aschner M, Rocha JBT. Methylmercury's chemistry: From the environment to the mammalian brain. Biochim Biophys Acta Gen Subj 2019; 1863:129284. [PMID: 30659885 DOI: 10.1016/j.bbagen.2019.01.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 12/14/2018] [Accepted: 01/09/2019] [Indexed: 02/06/2023]
Abstract
Methylmercury is a neurotoxicant that is found in fish and rice. MeHg's toxicity is mediated by blockage of -SH and -SeH groups of proteins. However, the identification of MeHg's targets is elusive. Here we focus on the chemistry of MeHg in the abiotic and biotic environment. The toxicological chemistry of MeHg is complex in metazoans, but at the atomic level it can be explained by exchange reactions of MeHg bound to -S(e)H with another free -S(e)H group (R1S(e)-HgMe + R2-S(e)H ↔ R1S(e)H + R2-S(e)-HgMe). This reaction was first studied by professor Rabenstein and here it is referred as the "Rabenstein's Reaction". The absorption, distribution, and excretion of MeHg in the environment and in the body of animals will be dictated by Rabenstein's reactions. The affinity of MeHg by thiol and selenol groups and the exchange of MeHg by Rabenstein's Reaction (which is a diffusion controlled reaction) dictates MeHg's neurotoxicity. However, it is important to emphasize that the MeHg exchange reaction velocity with different types of thiol- and selenol-containing proteins will also depend on protein-specific structural and thermodynamical factors. New experimental approaches and detailed studies about the Rabenstein's reaction between MeHg with low molecular mass thiol (LMM-SH) molecules (cysteine, GSH, acetyl-CoA, lipoate, homocysteine) with abundant high molecular mass thiol (HMM-SH) molecules (albumin, hemoglobin) and HMM-SeH (GPxs, Selenoprotein P, TrxR1-3) are needed. The study of MeHg migration from -S(e)-Hg- bonds to free -S(e)H groups (Rabenstein's Reaction) in pure chemical systems and neural cells (with special emphasis to the LMM-SH and HMM-S(e)H molecules cited above) will be critical to developing realistic constants to be used in silico models that will predict the distribution of MeHg in humans.
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Affiliation(s)
- Pablo A Nogara
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Cláudia S Oliveira
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Gabriela L Schmitz
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Paulo C Piquini
- Departamento de Física, CCNE, Universidade Federal de Santa Maria (UFSM), Santa Maria, RS, Brazil
| | - Marcelo Farina
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.
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