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Spiller HA, Hays HL, Casavant MJ. Rethinking treatment of mercury poisoning: the roles of selenium, acetylcysteine, and thiol chelators in the treatment of mercury poisoning: a narrative review. Toxicology Communications 2021. [DOI: 10.1080/24734306.2020.1870077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Henry A. Spiller
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Hannah L. Hays
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Departments of Emergency Medicine and Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Marcel J. Casavant
- Central Ohio Poison Center, Nationwide Children’s Hospital, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
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Correia MM, Chammas MC, Zavariz JD, Arata A, Martins LC, Marui S, Pereira LAA. Evaluation of the effects of chronic occupational exposure to metallic mercury on the thyroid parenchyma and hormonal function. Int Arch Occup Environ Health 2020; 93:491-502. [PMID: 31832764 DOI: 10.1007/s00420-019-01499-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 11/28/2019] [Indexed: 10/24/2022]
Abstract
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.
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THONGSAW A, SANANMUANG R, UDNAN Y, AMPIAH-BONNEY RJ, CHAIYASITH WC. Immobilized Activated Carbon as Sorbent in Solid Phase Extraction with Cold Vapor Atomic Absorption Spectrometry for the Preconcentration and Determination of Mercury Species in Water and Freshwater Fish Samples. ANAL SCI 2019; 35:1195-1202. [DOI: 10.2116/analsci.19p164] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Arnon THONGSAW
- Department of Chemistry, Research Center for Academic Excellence in Petroleum, Petrochemical and Advanced Materials, Faculty of Science, Naresuan University
| | - Ratana SANANMUANG
- Department of Chemistry, Research Center for Academic Excellence in Petroleum, Petrochemical and Advanced Materials, Faculty of Science, Naresuan University
| | - Yuthapong UDNAN
- Department of Chemistry, Research Center for Academic Excellence in Petroleum, Petrochemical and Advanced Materials, Faculty of Science, Naresuan University
| | | | - Wipharat Chuachuad CHAIYASITH
- Department of Chemistry, Research Center for Academic Excellence in Petroleum, Petrochemical and Advanced Materials, Faculty of Science, Naresuan University
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Abstract
This review examines the effects of neurotoxic electrophiles on selenium (Se) metabolism. Selenium-dependent enzymes depend on the unique and elite functions of selenocysteine (Sec), the 21st proteinogenic amino acid, to perform their biochemical roles. Humans possess 25 selenoprotein genes, ~ half of which are enzymes (selenoenzymes) required for preventing, controlling, or reversing oxidative damage, while others participate in regulating calcium metabolism, thyroid hormone status, protein folding, cytoskeletal structure, Sec synthesis and Se transport. While selenoproteins are expressed in tissue dependent distributions and levels in all cells of all vertebrates, they are particularly important in brain development, health, and functions. As the most potent intracellular nucleophile, Sec is subject to binding by mercury (Hg) and other electron poor soft neurotoxic electrophiles. Epidemiological and environmental studies of the effects of exposures to methyl-Hg (CH3Hg+), elemental Hg (Hg°), and/or other metallic/organic neurotoxic soft electrophiles need to consider the concomitant effects of all members of this class of toxicants in relation to the Se status of their study populations. The contributions of individual electrophiles' discrete and cooperative rates of Se sequestration need to be evaluated in relation to tissue Se reserves of the exposed populations to identify sensitive subgroups which may be at accentuated risk due to poor Se status. Additional study is required to examine possibilities of inherited, acquired, or degenerative neurological disorders of Se homeostasis that may influence vulnerability to soft electrophile exposures. Investigations of soft electrophile toxicity will be enhanced by considering the concomitant effects of combined exposures on tissue Se-availability in relation to pathological consequences during fetal development or in relation to etiologies of neurological disorders and neurodegenerative diseases. Since selenoenzymes are molecular "targets" of soft electrophiles, concomitant evaluation of aggregate exposures to these toxicants in relation to dietary Se intakes will assist regulatory agencies in their goals of improving and protecting public health.
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Affiliation(s)
- Nicholas Vc Ralston
- Earth System Science and Policy, University of North Dakota, Grand Forks, ND, USA.
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Affiliation(s)
- Henry A. Spiller
- Central Ohio Poison Center, Columbus, OH, USA
- Department of Pediatrics, College of Medicine, Ohio State University, Columbus, OH, USA
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Ren X, Zou L, Zhang X, Branco V, Wang J, Carvalho C, Holmgren A, Lu J. Redox Signaling Mediated by Thioredoxin and Glutathione Systems in the Central Nervous System. Antioxid Redox Signal 2017; 27:989-1010. [PMID: 28443683 PMCID: PMC5649126 DOI: 10.1089/ars.2016.6925] [Citation(s) in RCA: 200] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SIGNIFICANCE The thioredoxin (Trx) and glutathione (GSH) systems play important roles in maintaining the redox balance in the brain, a tissue that is prone to oxidative stress due to its high-energy demand. These two disulfide reductase systems are active in various areas of the brain and are considered to be critical antioxidant systems in the central nervous system (CNS). Various neuronal disorders have been characterized to have imbalanced redox homeostasis. Recent Advances: In addition to their detrimental effects, recent studies have highlighted that reactive oxygen species/reactive nitrogen species (ROS/RNS) act as critical signaling molecules by modifying thiols in proteins. The Trx and GSH systems, which reversibly regulate thiol modifications, regulate redox signaling involved in various biological events in the CNS. CRITICAL ISSUES In this review, we focus on the following: (i) how ROS/RNS are produced and mediate signaling in CNS; (ii) how Trx and GSH systems regulate redox signaling by catalyzing reversible thiol modifications; (iii) how dysfunction of the Trx and GSH systems causes alterations of cellular redox signaling in human neuronal diseases; and (iv) the effects of certain small molecules that target thiol-based signaling pathways in the CNS. FUTURE DIRECTIONS Further study on the roles of thiol-dependent redox systems in the CNS will improve our understanding of the pathogenesis of many human neuronal disorders and also help to develop novel protective and therapeutic strategies against neuronal diseases. Antioxid. Redox Signal. 27, 989-1010.
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Affiliation(s)
- Xiaoyuan Ren
- 1 Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Stockholm, Sweden
| | - Lili Zou
- 1 Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Stockholm, Sweden .,2 Translational Neuroscience and Neural Regeneration and Repair Institute/Institute of Cell Therapy, The First Hospital of Yichang, Three Gorges University , Yichang, China
| | - Xu Zhang
- 1 Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Stockholm, Sweden
| | - Vasco Branco
- 3 Research Institute for Medicines (iMed.ULisboa) , Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - Jun Wang
- 2 Translational Neuroscience and Neural Regeneration and Repair Institute/Institute of Cell Therapy, The First Hospital of Yichang, Three Gorges University , Yichang, China
| | - Cristina Carvalho
- 3 Research Institute for Medicines (iMed.ULisboa) , Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal
| | - Arne Holmgren
- 1 Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Stockholm, Sweden
| | - Jun Lu
- 4 School of Pharmaceutical Sciences, Southwest University , Chongqing, China
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Abstract
Methyl mercury (MeHg) is a highly toxic substance and the effect of selenium against MeHg toxicity is a hot topic. Until now, no related works have been reported from the view of the point of elemental speciation which is promising to study the mechanism at the molecular level. In this work, to reveal the effect of selenocystine (SeCys2) against MeHg cytotoxicity in HepG2 cells, a comprehensive analytical platform for speciation study of mercury and selenium in MeHg incubated or MeHg and SeCys2 co-incubated HepG2 cells was developed by integrating liquid chromatography (LC) - inductively coupled plasma mass spectrometry (ICP-MS) hyphenated techniques and chip-based pretreatment method. Interesting phenomenon was found that the co-incubation of MeHg with SeCys2 promoted the uptake of MeHg in HepG2 cells, but reduced the cytotoxicity of MeHg. Results obtained by ICP-MS based hyphenated techniques revealed a possible pathway for the incorporation and excretion of mercury species with the coexistence of SeCys2. The formation of MeHg and SeCys2 aggregation promotes the uptake of MeHg; majority of MeHg transforms into small molecular complexes (MeHg-glutathione (GSH) and MeHg-cysteine (Cys)) in HepG2 cells; and MeHg-GSH is the elimination species which results in reducing the cytotoxicity of MeHg.
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Wang H, Chen B, Zhu S, Yu X, He M, Hu B. Chip-Based Magnetic Solid-Phase Microextraction Online Coupled with MicroHPLC–ICPMS for the Determination of Mercury Species in Cells. Anal Chem 2015; 88:796-802. [DOI: 10.1021/acs.analchem.5b03130] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Han Wang
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
| | - Beibei Chen
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
| | - Siqi Zhu
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
| | - Xiaoxiao Yu
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
| | - Man He
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
| | - Bin Hu
- Key Laboratory of Analytical Chemistry
for Biology and Medicine, Ministry of Education, Department
of Chemistry, Wuhan University, Wuhan 430072, China
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Luque-garcia JL, Cabezas-sanchez P, Anunciação DS, Camara C. Analytical and bioanalytical approaches to unravel the selenium–mercury antagonism: A review. Anal Chim Acta 2013; 801:1-13. [DOI: 10.1016/j.aca.2013.08.043] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/24/2013] [Accepted: 08/27/2013] [Indexed: 01/24/2023]
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Branco V, Ramos P, Canário J, Lu J, Holmgren A, Carvalho C. Biomarkers of adverse response to mercury: histopathology versus thioredoxin reductase activity. J Biomed Biotechnol 2012; 2012:359879. [PMID: 22888199 DOI: 10.1155/2012/359879] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 05/25/2012] [Indexed: 11/24/2022] Open
Abstract
Exposure to mercury is normally assessed by measuring its accumulation in hair, blood or urine. Currently, the biomarkers of effect that have been proposed for mercurials, such as coproporphyrines or oxidative stress markers, are not sensitive enough and lack specificity. Selenium and selenoproteins are important targets for mercury and thioredoxin reductase (TrxR) in particular was shown to be very sensitive to mercury compounds both in vitro and in vivo. In this study we looked into the relation between the inhibition of thioredoxin reductase (TrxR) activity and histopathological changes caused by exposure to mercurials. Juvenile zeabra-seabreams were exposed to Hg2+ or MeHg for 28 days and histopathological changes were analyzed in the liver and kidney as well as TrxR activity. Both mercurials caused histopathological changes in liver and kidney, albeit Hg2+ caused more extensive and severe lesions. Likewise, both mercurials decreased TrxR activity, being Hg2+ a stronger inhibitor. Co-exposure to Hg2+ and Se fully prevented TrxR inhibition in the liver and reduced the severity of lesions in the organ. These results show that upon exposure to mercurials, histopathological alterations correlate with the level of TrxR activity and point to the potential use of this enzyme as a biomarker of mercury toxicity.
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Branco V, Canário J, Lu J, Holmgren A, Carvalho C. Mercury and selenium interaction in vivo: effects on thioredoxin reductase and glutathione peroxidase. Free Radic Biol Med 2012; 52:781-93. [PMID: 22198265 DOI: 10.1016/j.freeradbiomed.2011.12.002] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 11/29/2011] [Accepted: 12/05/2011] [Indexed: 12/14/2022]
Abstract
Mercury compounds exert toxic effects via interaction with many vital enzymes involved in antioxidant regulation, such as selenoenzymes thioredoxin reductase (TrxR) and glutathione peroxidase (GPx). Selenium supplementation can reactivate the mercury-inhibited TrxR and recover the cell viability in vitro. To gain an insight on how selenium supplementation affects mercury toxicity in vertebrates, we investigated the effects of selenium on the mercury accumulation and TrxR and GPx activities in a fish model. Juvenile zebra-seabreams were exposed either to methylmercury (MeHg) or inorganic mercury (Hg(2+)) in the presence or absence of sodium selenite (Se) for 28 days followed by 14 days of depuration. Mercury accumulation was found to be 10-fold higher under MeHg exposure than under Hg(2+) exposure. Selenium supplementation caused a half decrease of the accumulation of MeHg but did not influence Hg(2+) accumulation. Exposure to both mercurials led to a decrease of the activity of TrxR (<50% of control) in all organs. Se supplementation coincident with Hg(2+) exposure protected the thioredoxin system in fish liver. However, supplementation of Se during the depuration phase had no effects. The activity of GPx was only affected in the brain of fishes upon the exposure to MeHg and coexposure to MeHg and Se. Selenium supplementation has a limited capacity to prevent mercury effects in brain and kidney. These results demonstrate that Se supplementation plays a protective role in a tissue-specific manner and also highlight the importance of TrxR as a main target for mercurials in vivo.
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Affiliation(s)
- Vasco Branco
- Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto 1649-003 Lisbon, Portugal.
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Kaur P, Evje L, Aschner M, Syversen T. The in vitro effects of selenomethionine on methylmercury-induced neurotoxicity. Toxicol In Vitro 2009; 23:378-85. [DOI: 10.1016/j.tiv.2008.12.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 11/14/2008] [Accepted: 12/19/2008] [Indexed: 11/23/2022]
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Abstract
Mercury is a well-known environmental toxicant, particularly in its most common organic form, methylmercury. Consumption of fish and shellfish that contain methylmercury is a dominant source of mercury exposure in humans and piscivorous wildlife. Considerable efforts have focused on assessment of mercury and its attendant risks in the environment and food sources, including the studies reported in this issue. However, studies of mercury intoxication have frequently failed to consider the protective effects of the essential trace element, selenium. Mercury binds to selenium with extraordinarily high affinity, and high maternal exposures inhibit selenium-dependent enzyme activities in fetal brains. However, increased maternal dietary selenium intakes preserve these enzyme activities, thereby preventing the pathological effects that would otherwise arise in their absence. Recent evidence indicates that assessments of mercury exposure and tissue levels need to consider selenium intakes and tissue distributions in order to provide meaningful risk evaluations.
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Affiliation(s)
- Marla J Berry
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Biomedical Sciences Building, Suite 222, 651 Ilalo Street, Honolulu, 96813 HI, USA.
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Roveri A, Vitale MP, Serain E, Zaccarin M, Mauri P, Di Silvestre D, De Palma A, Gion M, Toppo S, Maiorino M, Ursini F. Differential liquid phase proteomic analysis of the effect of selenium supplementation in LNCaP cells. J Chromatogr B Analyt Technol Biomed Life Sci 2008; 865:63-73. [PMID: 18329347 DOI: 10.1016/j.jchromb.2008.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 02/05/2008] [Accepted: 02/17/2008] [Indexed: 11/28/2022]
Abstract
The effect of 100 nM sodium selenite supplementation was studied on LNCaP cells by a proteomic approach, on ProteomeLab PF 2D platform. Proteins were separated by liquid phase bi-dimensional chromatography and analyzed by pair-wise alignment of peaks to detect those differentially expressed. Differential expression threshold was set at a twice difference level and proteins matching this criterion were identified by MALDI-TOF and confirmed by ESI-ion trap MS/MS. Not all differentially expressed proteins found by PF 2D could be identified by MS analysis, the sensitivity of which emerging as the limiting factor. Thus, only the most abundant proteins, differently expressed following selenium supplementation, were identified. We positively showed an increase of expression of thioredoxin reductase 1, enolase 1, phosphoglycerate mutase 1, glyceraldehyde-3-phosphate dehydrogenase, heterogeneous nuclear ribonucleoprotein A2/B1, isoform A2, Ras-GTPase-activating protein SH3-domain-binding protein and Keratin 18 and a decrease of expression of peroxiredoxin 1 and heat shock protein 70, protein 8, isoform 1. Results are consistent, at least in part, with the less oxidant environment brought about by the synthesis of Se-dependent peroxidases, keeping low the steady-state concentration of hydrogen peroxide.
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Affiliation(s)
- Antonella Roveri
- Department of Biological Chemistry, University of Padova, I-35131 Padova, Italy
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Klapec T, Cavar S, Kasac Z, Rucević S, Popinjac A. Selenium in placenta predicts birth weight in normal but not intrauterine growth restriction pregnancy. J Trace Elem Med Biol 2008; 22:54-8. [PMID: 18319141 DOI: 10.1016/j.jtemb.2007.10.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 09/03/2007] [Accepted: 10/02/2007] [Indexed: 11/18/2022]
Abstract
Placental selenium, lead and cadmium concentrations were determined in a group of pregnancies with birth weight appropriate for gestational age and in a group of intrauterine growth restriction cases. Following adjustment for a number of confounding variables, selenium was found to be a significant predictor of newborn weight only in the group of pregnancies with birth weights appropriate for gestational age. Placental lead and cadmium levels were not associated with birth weight in either group.
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Affiliation(s)
- Tomislav Klapec
- Faculty of Food Technology, F. Kuhaca 18, HR-31107 Osijek, Croatia.
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Abstract
Selenium-mercury interactions were most extensively studied in relation to alleviation of Hg toxicity by added selenium. This presentation considers the influence of mercury on endogenous selenium, on its tissue and cellular "status" after lifelong or acute exposure to mercury vapor (Hg o). Discussed are data obtained from (1) humans living near or working in a mercury mine, and (2) rats experimentally exposed in the mine. Mercury vapor is unique--or similar to methylmercury--because of its ability to penetrate cell membranes and so invade all cells, where it is oxidized in the biologically active form (Hg++) by catalase. Such in situ-generated ions can react with endogenously generated highly reactive Se metabolites, like HSe-, and render a part of the selenium unavailable for selenoprotein synthesis. Data on human populations indicate that in moderate Hg exposure combined with an adequate selenium supply through diet, Se bioavailability can be preserved. On the other hand, the results of an acute exposure study emphasize the dual role of selenium in mercury detoxification. Besides the well-known Se coaccumulation through formation of nontoxic Hg-Se complexes, we observed noticeable Se (co)excretion, at least at the beginning of exposure. The higher Hg accumulation rate in the group of animals with lower basal selenium levels can also point to selenium involvement in mercury excretion. In such conditions there is a higher probability for decreased selenoprotein levels (synthesis) in some tissues or organs, depending on the synthesis hierarchy.
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Affiliation(s)
- Ingrid Falnoga
- Department of Environmental Sciences, Jozef Stefan Institute, Ljubljana, Slovenia.
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