1
|
Bramatti I, Aschner M, Branco V, Carvalho C. Exposure of human glioblastoma cells to thimerosal inhibits the thioredoxin system and decreases tumor growth-related factors. Toxicol Appl Pharmacol 2024; 484:116844. [PMID: 38325586 DOI: 10.1016/j.taap.2024.116844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/25/2024] [Accepted: 02/04/2024] [Indexed: 02/09/2024]
Abstract
Glioblastoma multiforme (GBM) is the most common, aggressive, and fatal primary malignant brain tumor in adults. The therapeutic efficacy of temozolomide (TMZ) is limited owing to frequent treatment resistance. The latter is in part related to the overexpression of redox systems such as the thioredoxin system. This system is fundamental for cell survival and proliferation, regulating hypoxia inducible factor-1alpha (HIF-1α) activity, in turn controlling vascular endothelial growth factor (VEGF), which is indispensable for tumor invasiveness, angiogenesis and microenvironment maintenance. HIF-1α can also be regulated by the signal transducer and activator of transcription 3 (STAT3), an oncogene stimulated by pro-inflammatory cytokines and growth factors. The thioredoxin system has several known inhibitors including mercury compounds such as Thimerosal (TmHg) which readily crosses the blood-brain barrier (BBB) and accumulates in the brain. Though previously used in various applications epidemiological evidence on TmHg's neurotoxicity is lacking. The objective of this study was to verify whether thimerosal is a suitable candidate for hard repurposing to control glioblastoma; therefore, the effects of this molecule were evaluated in human GBM (U87) cells. Our novel results show that TmHg decreased cellular viability (>50%) and migration (up to 90% decrease in wound closure), reduced thioredoxin reductase (TrxR/TXNRD1) and thioredoxin (Trx) activity, and increased reactive oxygen species (ROS) generation. Moreover, TmHg reduced HIF-1α expression (35%) as observed by immunofluorescence. Co-exposure of U87 cells to TmHg and TMZ reduced HIF-1α, VEGF, and phosphorylated STAT3. Consequently, TmHg alone or combined with chemotherapeutic drugs can reduce neoangiogenesis and ameliorate glioblastoma progression and treatment.
Collapse
Affiliation(s)
- Isabella Bramatti
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisboa 1649-003, Portugal
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Vasco Branco
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisboa 1649-003, Portugal; Department of Pharmaceutical Sciences and Medicines, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Cristina Carvalho
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, Lisboa 1649-003, Portugal; Department of Pharmaceutical Sciences and Medicines, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal.
| |
Collapse
|
2
|
da Rocha Junior ER, Porto VA, Crispim AC, Ursulino JS, de Jesus LWO, de Souza Bento E, Santos JCC, de Aquino TM. Assessment of thimerosal effects in sublethal concentrations on zebrafish (Danio rerio) embryos exploring NMR-based metabolomics profile. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2024; 106:104361. [PMID: 38211665 DOI: 10.1016/j.etap.2024.104361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 12/22/2023] [Accepted: 01/05/2024] [Indexed: 01/13/2024]
Abstract
Thimerosal, a preservative commonly used in the pharmaceutical and cosmetic industry, has raised concerns regarding its potentially toxic effects as an organic mercury compound. Within this context, using an NMR-based metabolomics profile and chemometric analysis, zebrafish embryos were used as an in vivo model to study the effects of thimerosal in metabolic profiles after exposure to sublethal concentrations of the mercury compound. The thimerosal concentrations of 40 and 80 nM were employed, corresponding to 40% and 80% of the LC50, respectively, for zebrafish embryos. The most significant alterations in the metabolic profile included changes in carbohydrates, amino acids, nucleotides, trimethylamine-N-oxide, ethanolamine, betaine, and ethanol. Furthermore, thimerosal exposure affects various metabolic pathways, impairing the nervous system, disrupting protein metabolism, and potentially causing oxidative damage. Therefore, adopting a metabolomics approach in this investigation provided insights into the potentially implicated metabolic pathways contributing to the deleterious effects of thimerosal in biological systems.
Collapse
Affiliation(s)
- Edmilson Rodrigues da Rocha Junior
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil
| | - Viviane Amaral Porto
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil
| | - Alessandre Carmo Crispim
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil
| | - Jeferson Santana Ursulino
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil
| | | | - Edson de Souza Bento
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil
| | | | - Thiago Mendonça de Aquino
- Nucleus of Analysis and Research in Nuclear Magnetic Resonance - NAPRMN, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, Brazil.
| |
Collapse
|
3
|
Galiciolli MEA, Silva JF, Prodocimo MM, Laureano HA, Calado SLDM, Oliveira CS, Guiloski IC. Toxicological Effects of Thimerosal and Aluminum in the Liver, Kidney, and Brain of Zebrafish ( Danio rerio). Metabolites 2023; 13:975. [PMID: 37755255 PMCID: PMC10537066 DOI: 10.3390/metabo13090975] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/18/2023] [Accepted: 08/23/2023] [Indexed: 09/28/2023] Open
Abstract
Vaccination programs in the first years of a child's life are effective and extremely important strategies for the successful eradication of diseases. However, as no intervention is without risks, the metal-based components of some vaccines, such as thimerosal (TMS), a preservative composed of ethylmercury, and aluminum (Al), have begun to generate distrust on the part of the population. Therefore, this study evaluated the effects of exposure to thimerosal and aluminum hydroxide (alone or in mixture) on Danio rerio (zebrafish) specimens. The fish were exposed to thimerosal and/or aluminum hydroxide intraperitoneally. The liver, kidney, and brain were removed for a biochemical biomarker analysis, histopathological analysis, and metal quantification. As a result, we observed changes in the activity of the analyzed enzymes (SOD, GST, GPx) in the kidney and brain of the zebrafish, a reduction in GSH levels in all analyzed tissues, and a reduction in MT levels in the kidney and liver as well as in the brain. Changes in AChE enzyme activity were observed. The biochemical results corroborate the changes observed in the lesion index and histomorphology sections. We emphasize the importance of joint research on these compounds to increase the population's safety against their possible toxic effects.
Collapse
Affiliation(s)
- Maria Eduarda Andrade Galiciolli
- Instituto de Pesquisa Pelé Pequeno Príncipe, Avenida Silva Jardim, 1632, Água Verde, Curitiba 80250-200, PR, Brazil; (M.E.A.G.); (J.F.S.)
- Faculdades Pequeno Príncipe, Curitiba 80230-020, PR, Brazil
| | - Juliana Ferreira Silva
- Instituto de Pesquisa Pelé Pequeno Príncipe, Avenida Silva Jardim, 1632, Água Verde, Curitiba 80250-200, PR, Brazil; (M.E.A.G.); (J.F.S.)
- Faculdades Pequeno Príncipe, Curitiba 80230-020, PR, Brazil
| | - Maritana Mela Prodocimo
- Departamento de Biologia Celular e Molecular, Universidade Federal do Paraná, Centro Politécnico, Avenida Cel. Francisco H. dos Santos, 100—Jardim das Américas, Curitiba—PR, Curitiba 81531-980, PR, Brazil;
| | - Henrique Aparecido Laureano
- Instituto de Pesquisa Pelé Pequeno Príncipe, Avenida Silva Jardim, 1632, Água Verde, Curitiba 80250-200, PR, Brazil; (M.E.A.G.); (J.F.S.)
- Faculdades Pequeno Príncipe, Curitiba 80230-020, PR, Brazil
| | | | - Claudia Sirlene Oliveira
- Instituto de Pesquisa Pelé Pequeno Príncipe, Avenida Silva Jardim, 1632, Água Verde, Curitiba 80250-200, PR, Brazil; (M.E.A.G.); (J.F.S.)
- Faculdades Pequeno Príncipe, Curitiba 80230-020, PR, Brazil
| | - Izonete Cristina Guiloski
- Instituto de Pesquisa Pelé Pequeno Príncipe, Avenida Silva Jardim, 1632, Água Verde, Curitiba 80250-200, PR, Brazil; (M.E.A.G.); (J.F.S.)
- Faculdades Pequeno Príncipe, Curitiba 80230-020, PR, Brazil
| |
Collapse
|
4
|
Rahimian A, Lakzaei M, Askari H, Dostdari S, Khafri A, Aminian M. In vitro assessment of Thimerosal cytotoxicity and antimicrobial activity. J Trace Elem Med Biol 2023; 77:127129. [PMID: 36630761 DOI: 10.1016/j.jtemb.2023.127129] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 12/04/2022] [Accepted: 01/03/2023] [Indexed: 01/06/2023]
Abstract
BACKGROUND Thimerosal (Merthiolate) is a well-known preservative used in pharmaceutical products, the safety of which was a matter of controversy for decades. Thimerosal is a mercury compound, and there is a debate as to whether Thimerosal exposure from vaccination can contribute to the incidence of mercury-driven disorders. To date, there is no consensus on Thimerosal safety in Vaccines. In 1977, a maximum safe dose of 200 μg/ml (0.5 mM) was recommended for Thimerosal by the WHO experts committee on biological standardization. Up-to-date guidelines, however, urge national control authorities to establish their own standards for the concentration of vaccine preservatives. We believe such safety limits must be studied at the cellular level first. The present study seeks a safe yet efficient dose of Thimerosal exposure for human and animal cells and control microorganism strains. METHODS The safety of Thimerosal exposure on cells was analyzed through an MTT cell toxicity assay. The viability of four cell types, including HepG2, C2C12, Vero Cells, and Peripheral blood mononuclear cells (PBMCs), was examined in the presence of different Thimerosal concentrations and the maximum tolerable dose (MTD) and the half maximal inhibitory concentration (IC50) values for each cell line were determined. The antimicrobial effectiveness of Thimerosal was evaluated on four control strains, including Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus brasiliensis, to obtain the minimum inhibitory concentration (MIC) of Thimerosal. The MIC test was performed in culture media and under optimal growth conditions of microorganisms in the presence of different Thimerosal concentrations. RESULTS The viability of all examined cell lines was suppressed entirely in the presence of 4.6 μg/ml (12.5 μM) of Thimerosal. The MTD for HepG2, C2C12, PBMC, and Vero cells was 2, 1.6, 1, and 0.29 μg/ml (5.5, 4.3, 2.7 and 0.8 μM), respectively. The IC50 of Thimerosal exposure for HepG2, C2C12, PBMC, and Vero cells was 2.62, 3.17, 1.27, and 0.86 μg/ml (7.1, 8.5, 3.5 and 2.4 μM), respectively. As for antimicrobial effectiveness, the growth capability of Candida albicans and Staphylococcus aureus was suppressed entirely in the presence of 6.25 µg/ml (17 μM) Thimerosal. The complete growth inhibition of Pseudomonas aeruginosa in culture media was achieved in 100 µg/ml (250 µM) Thimerosal concentration. This value was 12.5 µg/ml (30 μM) for Aspergillus brasiliensis. CONCLUSION According to our results Thimerosal should be present in culture media at 100 μg/ml (250 µM) concentration to achieve an effective antimicrobial activity. We showed that this amount of Thimerosal is toxic for human and animal cells in vitro since the viability of all examined cell lines was suppressed in the presence of less than 5 μg/ml (12.5 μM) of Thimerosal. Overall, our study revealed Thimerosal was 333-fold more cytotoxic to human and animal cells as compared to bacterial and fungal cells. Our results promote more study on Thimerosal toxicity and its antimicrobial effectiveness to obtain more safe concentrations in biopharmaceuticals.
Collapse
Affiliation(s)
- Aliasghar Rahimian
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mostafa Lakzaei
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Hooman Askari
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Sajad Dostdari
- Department of Bacterial Vaccines Quality Control, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
| | - Abolfazl Khafri
- Department of Bacterial Vaccines Quality Control, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran.
| | - Mahdi Aminian
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
5
|
Abu Lila AS, Alharby TN, Alanazi J, Alanazi M, Abdallah MH, Rizvi SMD, Moin A, Khafagy ES, Tabrez S, Al Balushi AA, Hegazy WAH. Clinical Resistant Strains of Enterococci and Their Correlation to Reduced Susceptibility to Biocides: Phenotypic and Genotypic Analysis of Macrolides, Lincosamides, and Streptogramins. Antibiotics (Basel) 2023; 12:antibiotics12030461. [PMID: 36978327 PMCID: PMC10044631 DOI: 10.3390/antibiotics12030461] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 03/03/2023] Open
Abstract
Enterococci are troublesome nosocomial, opportunistic Gram-positive cocci bacteria showing enhanced resistance to many commonly used antibiotics. This study aims to investigate the prevalence and genetic basis of antibiotic resistance to macrolides, lincosamides, and streptogramins (MLS) in Enterococci, as well as the correlation between MLS resistance and biocide resistance. From 913 clinical isolates collected from King Khalid Hospital, Hail, Saudi Arabia, 131 isolates were identified as Enterococci spp. The susceptibility of the clinical enterococcal isolates to several MLS antibiotics was determined, and the resistance phenotype was detected by the triple disk method. The MLS-involved resistance genes were screened in the resistant isolates. The current results showed high resistance rates to MLS antibiotics, and the constitutive resistance to all MLS (cMLS) was the most prevalent phenotype, observed in 76.8% of resistant isolates. By screening the MLS resistance-encoding genes in the resistant isolates, the erythromycin ribosome methylase (erm) genes that are responsible for methylation of bacterial 23S rRNA were the most detected genes, in particular, ermB. The ereA esterase-encoding gene was the most detected MLS modifying-encoding genes, more than lnuA (adenylation) and mphC (phosphorylation). The minimum inhibitory concentrations (MICs) of commonly used biocides were detected in resistant isolates and correlated with the MICs of MLS antibiotics. The present findings showed a significant correlation between MLS resistance and reduced susceptibility to biocides. In compliance with the high incidence of the efflux-encoding genes, especially mefA and mefE genes in the tolerant isolates with higher MICs to both MLS antibiotics and biocides, the efflux of resistant isolates was quantified, and there was a significant increase in the efflux of resistant isolates with higher MICs as compared to those with lower MICs. This could explain the crucial role of efflux in developing cross-resistance to both MLS antibiotics and biocides.
Collapse
Affiliation(s)
- Amr Selim Abu Lila
- Department of Pharmaceutics, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
- Molecular Diagnostics and Personalized Therapeutics Unit, University of Ha’il, Ha’il 81442, Saudi Arabia
- Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
- Correspondence: (A.S.A.L.); (W.A.H.H.)
| | - Tareq Nafea Alharby
- Department of Clinical Pharmacy, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
| | - Jowaher Alanazi
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
| | - Muteb Alanazi
- Department of Clinical Pharmacy, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
| | - Marwa H. Abdallah
- Department of Pharmaceutics, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
- Molecular Diagnostics and Personalized Therapeutics Unit, University of Ha’il, Ha’il 81442, Saudi Arabia
- Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
| | - Syed Mohd Danish Rizvi
- Department of Pharmaceutics, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
- Molecular Diagnostics and Personalized Therapeutics Unit, University of Ha’il, Ha’il 81442, Saudi Arabia
| | - Afrasim Moin
- Department of Pharmaceutics, College of Pharmacy, University of Ha’il, Ha’il 81442, Saudi Arabia
- Molecular Diagnostics and Personalized Therapeutics Unit, University of Ha’il, Ha’il 81442, Saudi Arabia
| | - El-Sayed Khafagy
- Department of Pharmaceutics, College of Pharmacy, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
- Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Suez Canal University, Ismailia 41522, Egypt
| | - Shams Tabrez
- King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589, Saudi Arabia
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Abdullah Ali Al Balushi
- Pharmacy Program, Department of Pharmaceutics, Oman College of Health Sciences, Muscat 113, Oman
| | - Wael A. H. Hegazy
- Department of Microbiology and Immunology, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
- Pharmacy Program, Department of Pharmaceutical Sciences, Oman College of Health Sciences, Muscat 113, Oman
- Correspondence: (A.S.A.L.); (W.A.H.H.)
| |
Collapse
|
6
|
Azevedo LF, Karpova N, Rocha BA, Barbosa Junior F, Gobe GC, Hornos Carneiro MF. Evidence on Neurotoxicity after Intrauterine and Childhood Exposure to Organomercurials. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1070. [PMID: 36673825 PMCID: PMC9858833 DOI: 10.3390/ijerph20021070] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 06/17/2023]
Abstract
Although the molecular mechanisms underlying methylmercury toxicity are not entirely understood, the observed neurotoxicity in early-life is attributed to the covalent binding of methylmercury to sulfhydryl (thiol) groups of proteins and other molecules being able to affect protein post-translational modifications from numerous molecular pathways, such as glutamate signaling, heat-shock chaperones and the antioxidant glutaredoxin/glutathione system. However, for other organomercurials such as ethylmercury or thimerosal, there is not much information available. Therefore, this review critically discusses current knowledge about organomercurials neurotoxicity-both methylmercury and ethylmercury-following intrauterine and childhood exposure, as well as the prospects and future needs for research in this area. Contrasting with the amount of epidemiological evidence available for methylmercury, there are only a few in vivo studies reporting neurotoxic outcomes and mechanisms of toxicity for ethylmercury or thimerosal. There is also a lack of studies on mechanistic approaches to better investigate the pathways involved in the potential neurotoxicity caused by both organomercurials. More impactful follow-up studies, especially following intrauterine and childhood exposure to ethylmercury, are necessary. Childhood vaccination is critically important for controlling infectious diseases; however, the safety of mercury-containing thimerosal and, notably, its effectiveness as preservative in vaccines are still under debate regarding its potential dose-response effects to the central nervous system.
Collapse
Affiliation(s)
- Lara Ferreira Azevedo
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Nina Karpova
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Bruno Alves Rocha
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Fernando Barbosa Junior
- Department of Clinical Analyses, Toxicology and Food Sciences, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14040-903, SP, Brazil
| | - Glenda Carolyn Gobe
- Kidney Disease Research Group, School of Medicine, Translational Research Institute, University of Queensland, 37 Kent Street, Woolloongabba, QLD 4102, Australia
| | - Maria Fernanda Hornos Carneiro
- Department of Pharmacy, Faculty of Chemistry and Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
| |
Collapse
|
7
|
Wildner G, Loreto JS, de Almeida P, Claro MT, Ferreira SA, Barbosa NV. Short exposure to ethyl and methylmercury prompts similar toxic responses in Drosophila melanogaster. Comp Biochem Physiol C Toxicol Pharmacol 2022; 252:109216. [PMID: 34710619 DOI: 10.1016/j.cbpc.2021.109216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/07/2021] [Accepted: 10/14/2021] [Indexed: 12/30/2022]
Abstract
Methylmercury (MeHg) and ethylmercury (EtHg) are important mercury organic forms in terms of human poisoning. Since the comparative effects of compounds are mainly in vitro, this study was designed to investigate the toxicities induced by MeHg and EtHg in an in vivo study using adult Drosophila melanogaster (D. melanogaster). Firstly, we performed a survival curve, where the flies were fed on a medium containing MeHg and EtHg at concentrations ranging from 2.5 to 200 μM, until the end of their lifespan. After that, the concentrations 25 and 200 μM of MeHg and EtHg were chosen to be tested in a short exposure for 5 days. The analysis of survival by Kaplan-Meier plot revealed that all concentrations of MeHg and EtHg reduced significantly the lifespan of the flies. Short exposure to both concentrations of MeHg and EtHg impaired the ability of flies in the climbing assay and induced lipid peroxidation. Only the flies exposed to the highest concentration had viability loss, thiol depletion, and increased reactive species (RS) and Hg levels in the whole body. Our findings indicate that MeHg and EtHg exhibit similar toxic effects in vivo, and that oxidative stress is a phenomenon behind the toxicity of both mercurials. The data obtained also reinforce the use of D. melanogaster as a useful organism for basic toxicological research.
Collapse
Affiliation(s)
- Guilherme Wildner
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
| | - Julia Sepel Loreto
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
| | - Pamela de Almeida
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
| | - Mariana Torri Claro
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
| | - Sabrina Antunes Ferreira
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
| | - Nilda Vargas Barbosa
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Santa Maria, Avenida Roraima, 1000, 97105-900 Santa Maria, RS, Brazil.
| |
Collapse
|
8
|
Dórea JG. Neurodevelopment and exposure to neurotoxic metal(loid)s in environments polluted by mining, metal scrapping and smelters, and e-waste recycling in low and middle-income countries. ENVIRONMENTAL RESEARCH 2021; 197:111124. [PMID: 33861977 DOI: 10.1016/j.envres.2021.111124] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/01/2021] [Accepted: 04/01/2021] [Indexed: 06/12/2023]
Abstract
This review covers a wide body of literature to gain an understanding of the impacts of informal activities related to metal extraction (primary mining and recycling) on early life exposure to neurotoxicants and on neurodevelopment. In primary mining, gold extraction with Hg amalgamation is the main environmental cause of Hg pollution in most artisanal small-scale gold mining (ASGM) activities around the world. Nevertheless, in Sub-Saharan Africa (SSA), Pb disrupted from gold-related ores, mining, and artisanal cookware production are an important neurotoxicant that seriously contaminates the affected population, with devastating effects on children. In e-waste recycling settings, the range of neurotoxic substances that contaminate mothers and children is wider than in primary mining environments. Thus, Hg and Pb are major pre- and postnatal neurotoxicants affecting children in the informal metal extraction activities and SSA countries show the highest record of human contamination and of neurotoxic effects on children. There are additional sources of neurotoxic contamination from mining and metal processing activities (cyanide tailing in South America and SSA) and/or co-exposure to Hg-containing products such as cosmetics (soaps and Hg-based skin lightning creams in Africa) and pediatric Thimerosal-containing vaccines (TCVs, that breaks down to ethyl-mercury) in current use in middle and low income countries. However, the action of these neurotoxicants (per se or in combination) on children needs more attention and research. Studies show a negative association between biomarkers of all environmental metal(loid)s (As, Cd, Hg, Mn, and Pb) studied and neurodevelopment in young children. Sadly, in many unregulated activities, child labor is widely employed, thus presenting an additional occupational exposure. Children living in polluted environments related to metal processing are disproportionately exposed to a wide range of co-occurring neurotoxic substances. The review showed compelling evidence from highly representative parts of the world (Africa, Asia, and Latin America) that the studied neurotoxic substances negatively affected areas of the brain associated with language, memory and executive function, as well as psychosocial behavior. Protecting the environment and children from unregulated and highly polluting metal extraction and processing are inextricably intertwined and deserve urgent attention.
Collapse
Affiliation(s)
- José G Dórea
- Universidade de Brasília, Brasília, 70919-970, DF, Brazil.
| |
Collapse
|
9
|
Zwolak I. Epigallocatechin Gallate for Management of Heavy Metal-Induced Oxidative Stress: Mechanisms of Action, Efficacy, and Concerns. Int J Mol Sci 2021; 22:4027. [PMID: 33919748 PMCID: PMC8070748 DOI: 10.3390/ijms22084027] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/10/2021] [Accepted: 04/12/2021] [Indexed: 02/07/2023] Open
Abstract
In this review, we highlight the effects of epigallocatechin gallate (EGCG) against toxicities induced by heavy metals (HMs). This most active green tea polyphenol was demonstrated to reduce HM toxicity in such cells and tissues as testis, liver, kidney, and neural cells. Several protective mechanisms that seem to play a pivotal role in EGCG-induced effects, including reactive oxygen species scavenging, HM chelation, activation of nuclear factor erythroid 2-related factor 2 (Nrf2), anti-inflammatory effects, and protection of mitochondria, are described. However, some studies, especially in vitro experiments, reported potentiation of harmful HM actions in the presence of EGCG. The adverse impact of EGCG on HM toxicity may be explained by such events as autooxidation of EGCG, EGCG-mediated iron (Fe3+) reduction, depletion of intracellular glutathione (GSH) levels, and disruption of mitochondrial functions. Furthermore, challenges hampering the potential EGCG application related to its low bioavailability and proper dosing are also discussed. Overall, in this review, we point out insights into mechanisms that might account for both the beneficial and adverse effects of EGCG in HM poisoning, which may have a bearing on the design of new therapeutics for HM intoxication therapy.
Collapse
Affiliation(s)
- Iwona Zwolak
- Centre for Interdisciplinary Research, Laboratory of Oxidative Stress, The John Paul II Catholic University of Lublin, Konstantynów Ave. 1J, 20-708 Lublin, Poland
| |
Collapse
|
10
|
Tall A, da Costa KR, de Oliveira MJ, Tapsoba I, Rocha U, Sales TO, Goulart MOF, Santos JCC. Photoluminescent nanoprobes based on thiols capped CdTe quantum dots for direct determination of thimerosal in vaccines. Talanta 2021; 221:121545. [DOI: 10.1016/j.talanta.2020.121545] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 07/06/2020] [Accepted: 08/12/2020] [Indexed: 12/17/2022]
|
11
|
Dórea JG. Neurotoxic effects of combined exposures to aluminum and mercury in early life (infancy). ENVIRONMENTAL RESEARCH 2020; 188:109734. [PMID: 32544722 DOI: 10.1016/j.envres.2020.109734] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/22/2020] [Accepted: 05/23/2020] [Indexed: 06/11/2023]
Abstract
Aluminum and mercury are environmentally ubiquitous. Individually they are both neurotoxic elements with shared neuro-pathogenic pathways: oxidative stress, altered neurotransmission, and disruption of the neuroendocrine and immune systems. In the infant, Al and Hg differ in type of exposure, absorption, distribution (brain access), and metabolism. In environmentally associated exposure (breast milk and infant formulas) their co-occurrences fluctuate randomly, but in Thimerosal-containing vaccines (TCVs) they occur combined in a proprietary ratio; in these cases, low-doses of Thimerosal-ethylmercury (EtHg) and adjuvant-Al present the most widespread binary mixture in less developed countries. Although experimental studies at low doses of the binary Hg and Al mixture are rare, when studied individually they have been shown to affect neurological outcomes negatively. In invitro systems, comparative neurotoxicity between Al and Hg varies in relation to the measured parameters but seems less for Al than for Hg. While neurotoxicity of environmental Hg (mainly fish methyl-Hg, MeHg) is associated with neurobehavioral outcomes in children, environmental Al is not associated, except in certain clinical conditions. Therefore, the issues of their neurotoxic effects (singly or combined) are discussed. In the infant (up to six months) the organic-Hg and Al body burdens from a full TCV schedule are estimated to reach levels higher than that originating from breastfeeding or from high aluminum soy-based formulas. Despite worldwide exposure to both Al and Hg (inorganic Hg, MeHg, and Thimerosal/EtHg), our knowledge on this combined exposure is insufficient to predict their combined neurotoxic effects (and with other co-occurring neurotoxicants).
Collapse
Affiliation(s)
- José G Dórea
- Universidade de Brasília, Brasília, 70919-970, DF, Brazil.
| |
Collapse
|
12
|
Attiya N, Fattahi R, El-Haidani A, Lahrach N, Amarouch MY, Filali-Zegzouti Y. [Mercury exposure and dentists' health status in two regions of centrall Morocco: descriptive cross-sectional survey]. Pan Afr Med J 2020; 36:110. [PMID: 32821321 PMCID: PMC7406463 DOI: 10.11604/pamj.2020.36.110.19623] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 05/11/2020] [Indexed: 12/14/2022] Open
Abstract
INTRODUCTION mercury exposure is recognized as a worldwide public health concern. However, the effect of long-term exposure to low-doses of this heavy metal is still subject to debate. Due to the use of mercury in dental amalgam, dental health care professionals are chronically exposed to low-doses of this metal. In this context, we have conducted a descriptive cross-sectional survey among liberal dentists in two regions of the center of Morocco. In parallel, the global health status of participants was investigated to assess the relevance of a subsequent etiological survey. METHODS data were collected through a self-reported questionnaire. Occupational exposure of dentists to mercury was evaluated based on their use of dental amalgam. Moreover, the other common factors increasing the background pollution or inducing exposure peaks were also investigated. On the other hand, smoking, vaccination, fish consumption, and the number of dental amalgam in mouth were considered as non-occupational exposure sources. Finally, the self-reported global health problems of participants were collected. RESULTS 192 dentists were included in the present study. Seventy-six percent (76.04%) of them declared using dental amalgam in their practice. Moreover, the presence of dental amalgam in mouth was identified as the main non-occupational source of exposure to mercury (63.45% of participants). Finally, most of participants (46.35%) have expressed neuropsychological complaints. CONCLUSION altogether, our results revealed a real mercury exposure in the studied population. Thus, effective preventive measures should be promoted to minimize the mercury exposure in dental offices. Moreover, an etiological study will be of great interest to reveal the impact of mercury exposure in this population.
Collapse
Affiliation(s)
- Nourdine Attiya
- Laboratoire Bioactifs, Santé et Environnement, Université Moulay Ismaïl, Meknès, Maroc
| | - Rkia Fattahi
- Laboratoire Bioactifs, Santé et Environnement, Université Moulay Ismaïl, Meknès, Maroc
- Institut Supérieur des Professions Infirmières et Techniques de Santé, Errachidia, Maroc
| | - Ahmed El-Haidani
- Equipe Ethnopharmacologie et Pharmacognosie, Faculté des Sciences et Technique Errachidia, Université Moulay Ismaïl, Maroc
| | - Nadia Lahrach
- Equipe Ethnopharmacologie et Pharmacognosie, Faculté des Sciences et Technique Errachidia, Université Moulay Ismaïl, Maroc
| | - Mohamed-Yassine Amarouch
- Laboratoire Ressources Naturelles et Environnement, Faculté Polydisciplinaire de Taza, Université Sidi Mohamed Ben Abdellah de Fès, Fès, Maroc
| | | |
Collapse
|
13
|
de Magalhães Silva M, de Araújo Dantas MD, da Silva Filho RC, Dos Santos Sales MV, de Almeida Xavier J, Leite ACR, Goulart MOF, Grillo LAM, de Barros WA, de Fátima Â, Figueiredo IM, Santos JCC. Toxicity of thimerosal in biological systems: Conformational changes in human hemoglobin, decrease of oxygen binding capacity, increase of protein glycation and amyloid's formation. Int J Biol Macromol 2020; 154:661-671. [PMID: 32198046 DOI: 10.1016/j.ijbiomac.2020.03.156] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/11/2020] [Accepted: 03/16/2020] [Indexed: 02/06/2023]
Abstract
Thimerosal (TH), an organomercurial compound, is used as a preservative in vaccines and cosmetics. Its interaction with human hemoglobin (Hb) was investigated under physiological conditions using biophysical and biological assays, aiming to evaluate hazardous effects. TH interacts spontaneously with Hb (stoichiometry 2:1, ligand-protein), preferably by electrostatic forces, with a binding constant of 1.41 × 106 M-1. Spectroscopic data allows to proposing that TH induces structural changes in Hg, through ethylmercury transfer to human Hb-Cys93 residues, forming thiosalicylic acid, which, in turn, interacts with the positive side of the amino acid in the Hb-HgEt adduct chain. As a consequence, inhibition of Hb-O2 binding capacity up to 72% (human Hb), and 50% (human erythrocytes), was verified. Dose-dependent induction of TH forming advanced glycation end products (AGE) and protein aggregates (amyloids) was additionally observed. Finally, these results highlight the toxic potential of the use of TH in biological systems, with a consequent risk to human health.
Collapse
Affiliation(s)
- Marina de Magalhães Silva
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Maria Dayanne de Araújo Dantas
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Reginaldo Correia da Silva Filho
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Marcos Vinicius Dos Santos Sales
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Jadriane de Almeida Xavier
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Ana Catarina Rezende Leite
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Marília Oliveira Fonseca Goulart
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | | | - Wellington Alves de Barros
- Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, Minas Gerais, Brazil
| | - Ângelo de Fátima
- Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, Minas Gerais, Brazil
| | - Isis Martins Figueiredo
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil
| | - Josué Carinhanha Caldas Santos
- Institute of Chemistry and Biotechnology, Federal University of Alagoas (UFAL), Campus A.C. Simões, 57072-900 Maceió, Alagoas, Brazil.
| |
Collapse
|
14
|
Kern JK, Geier DA, Homme KG, Geier MR. Examining the evidence that ethylmercury crosses the blood-brain barrier. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2020; 74:103312. [PMID: 31841767 DOI: 10.1016/j.etap.2019.103312] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Abstract
Scientific research can provide us with factual, repeatable, measurable, and determinable results. As such, scientific research can provide information that can be used in the decision-making process in the care of patients and in public policy. Although it has been suggested that ethylmercury (C2H5Hg+)-containing compounds do not cross the blood-brain barrier (BBB), this review examines the literature that addresses the question as to whether ethylmercury-containing compounds cross the BBB. The review will begin with cellular studies that provide evidence for the passive and active transport of mercury species across the BBB. Then, animal and clinical studies will be presented that specifically examine whether mercury accumulates in the brain after exposure to ethylmercury-containing compounds or Thimerosal (an ethylmercury-containing compound used as a preservative in vaccines and other drugs that metabolizes or degrades to ethylmercury-containing compounds and thiosalicylate). The results indicate that ethylmercury-containing compounds are actively transported across membranes by the L (leucine-preferring)-amino acid transport (LAT) system, the same as methylmercury-containing compounds. Further, 22 studies from 1971 to 2019 show that exposure to ethylmercury-containing compounds (intravenously, intraperitoneally, topically, subcutaneously, intramuscularly, or intranasally administered) results in accumulation of mercury in the brain. In total, these studies indicate that ethylmercury-containing compounds and Thimerosal readily cross the BBB, convert, for the most part, to highly toxic inorganic mercury-containing compounds, which significantly and persistently bind to tissues in the brain, even in the absence of concurrent detectable blood mercury levels.
Collapse
Affiliation(s)
- Janet K Kern
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA; CONEM US Autism Research Group, Allen, TX, USA.
| | - David A Geier
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA
| | - Kristin G Homme
- International Academy of Oral Medicine and Toxicology, ChampionsGate, FL, USA
| | - Mark R Geier
- Institute of Chronic Illnesses, Inc, Silver Spring, MD, USA; CoMeD, Inc, Silver Spring, MD, USA
| |
Collapse
|
15
|
Dórea JG. Environmental exposure to low-level lead (Pb) co-occurring with other neurotoxicants in early life and neurodevelopment of children. ENVIRONMENTAL RESEARCH 2019; 177:108641. [PMID: 31421445 DOI: 10.1016/j.envres.2019.108641] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 08/08/2019] [Accepted: 08/08/2019] [Indexed: 06/10/2023]
Abstract
Lead (Pb) is a worldwide environmental contaminant that even at low levels influences brain development and affects neurobehavior later in life; nevertheless it is only a small fraction of the neurotoxicant (NT) exposome. Exposure to environmental Pb concurrent with other NT substances is often the norm, but their joint effects are challenging to study during early life. The aim of this review is to integrate studies of Pb-containing NT mixtures during the early life and neurodevelopment outcomes of children. The Pb-containing NT mixtures that have been most studied involve other metals (Mn, Al, Hg, Cd), metalloids (As), halogen (F), and organo-halogen pollutants. Co-occurring Pb-associated exposures during pregnancy and lactation depend on the environmental sources and the metabolism and half-life of the specific NT contaminant; but offspring neurobehavioral outcomes are also influenced by social stressors. Nevertheless, Pb-associated effects from prenatal exposure portend a continued burden on measurable neurodevelopment; they thus favor increased neurological health issues, decrements in neurobehavioral tests and reductions in the quality of life. Neurobehavioral test outcomes measured in the first 1000 days showed Pb-associated negative outcomes were frequently noticed in infants (<6 months). In older (preschool and school) children studies showed more variations in NT mixtures, children's age, and sensitivity and/or specificity of neurobehavioral tests; these variations and choice of statistical model (individual NT stressor or collective effect of mixture) may explain inconsistencies. Multiple exposures to NT mixtures in children diagnosed with 'autism spectrum disorders' (ASD) and 'attention deficit and hyperactivity disorders' (ADHD), strongly suggest a Pb-associated effect. Mixture potency (number or associated NT components and respective concentrations) and time (duration and developmental stage) of exposure often showed a measurable impact on neurodevelopment; however, net effects, reversibility and/or predictability of delays are insufficiently studied and need urgent attention. Nevertheless, neurodevelopment delays can be prevented and/or attenuated if public health policies are implemented to protect the unborn and the young child.
Collapse
Affiliation(s)
- José G Dórea
- Universidade de Brasília, Brasília, 70919-970, DF, Brazil.
| |
Collapse
|
16
|
Dórea JG. Multiple low-level exposures: Hg interactions with co-occurring neurotoxic substances in early life. Biochim Biophys Acta Gen Subj 2018; 1863:129243. [PMID: 30385391 DOI: 10.1016/j.bbagen.2018.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/01/2018] [Accepted: 10/19/2018] [Indexed: 12/11/2022]
Abstract
All chemical forms of Hg can affect neurodevelopment; however, low levels of organic Hg (methylmercury-MeHg and ethylmercury-EtHg in Thimerosal-containing vaccines, hereafter 'TCV') exposures during early life (pregnancy and lactation) co-occur with other environmental neurotoxic substances. These neurotoxicants may act in parallel, synergistically, or antagonistically to Hg. Nevertheless, the risks of neurotoxicity associated with multiple neuro-toxicants depend on type, time, combinations of exposure, and environmental and/or genetic-associated factors. Neurological developmental disorders, delays in cognition and behavioral outcomes associated with multiple exposures (which include Hg) may show transient or lasting outcomes depending on constitutional and/or environmental factors that can interact to neutralize, aggravate or attenuate these effects; often these studies are challenging to interpret. During pregnancy and lactation, fish-MeHg exposure is frequently confounded with the opposing effects of neuroactive nutrients (in fish) that lead to positive, negative, or no effects on neurobehavioral tests. In infancy, exposures to acute binary mixtures (TCV- EtHg and Al-adjuvants in infant immunizations) are associated with increased risks of tics and other developmental disorders. Despite the certitude that promulgates single environmental neurotoxicants, empirical comparisons of combined exposures indicate that Hg-related outcome is uneven. Hg in combination with other neurotoxic mixtures may elevate risks of neurotoxicity, but these risks arise in circumstances that are not yet predictable. Therefore, to achieve the goals of the Minamata treaty and to safeguard the health of children, low levels of mercury exposure (in any chemical form) needs to be further reduced whether the source is environmental (air- and food-borne) or iatrogenic (pediatric TCVs).
Collapse
Affiliation(s)
- José G Dórea
- Universidade de Brasília, Brasília 70919-970, DF, Brazil..
| |
Collapse
|