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Haigis AC, Vergauwen L, LaLone CA, Villeneuve DL, O'Brien JM, Knapen D. Cross-species applicability of an adverse outcome pathway network for thyroid hormone system disruption. Toxicol Sci 2023; 195:1-27. [PMID: 37405877 DOI: 10.1093/toxsci/kfad063] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023] Open
Abstract
Thyroid hormone system disrupting compounds are considered potential threats for human and environmental health. Multiple adverse outcome pathways (AOPs) for thyroid hormone system disruption (THSD) are being developed in different taxa. Combining these AOPs results in a cross-species AOP network for THSD which may provide an evidence-based foundation for extrapolating THSD data across vertebrate species and bridging the gap between human and environmental health. This review aimed to advance the description of the taxonomic domain of applicability (tDOA) in the network to improve its utility for cross-species extrapolation. We focused on the molecular initiating events (MIEs) and adverse outcomes (AOs) and evaluated both their plausible domain of applicability (taxa they are likely applicable to) and empirical domain of applicability (where evidence for applicability to various taxa exists) in a THSD context. The evaluation showed that all MIEs in the AOP network are applicable to mammals. With some exceptions, there was evidence of structural conservation across vertebrate taxa and especially for fish and amphibians, and to a lesser extent for birds, empirical evidence was found. Current evidence supports the applicability of impaired neurodevelopment, neurosensory development (eg, vision) and reproduction across vertebrate taxa. The results of this tDOA evaluation are summarized in a conceptual AOP network that helps prioritize (parts of) AOPs for a more detailed evaluation. In conclusion, this review advances the tDOA description of an existing THSD AOP network and serves as a catalog summarizing plausible and empirical evidence on which future cross-species AOP development and tDOA assessment could build.
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Affiliation(s)
- Ann-Cathrin Haigis
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Carlie A LaLone
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Daniel L Villeneuve
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Jason M O'Brien
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Carleton University, Ottawa, Ontario K1S 5B6, Canada
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
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Ibrahim BA, Louie JJ, Shinagawa Y, Xiao G, Asilador AR, Sable HJK, Schantz SL, Llano DA. Developmental Exposure to Polychlorinated Biphenyls Prevents Recovery from Noise-Induced Hearing Loss and Disrupts the Functional Organization of the Inferior Colliculus. J Neurosci 2023; 43:4580-4597. [PMID: 37147134 PMCID: PMC10286948 DOI: 10.1523/jneurosci.0030-23.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/20/2023] [Accepted: 04/17/2023] [Indexed: 05/07/2023] Open
Abstract
Exposure to combinations of environmental toxins is growing in prevalence; and therefore, understanding their interactions is of increasing societal importance. Here, we examined the mechanisms by which two environmental toxins, polychlorinated biphenyls (PCBs) and high-amplitude acoustic noise, interact to produce dysfunction in central auditory processing. PCBs are well established to impose negative developmental impacts on hearing. However, it is not known whether developmental exposure to this ototoxin alters the sensitivity to other ototoxic exposures later in life. Here, male mice were exposed to PCBs in utero, and later as adults were exposed to 45 min of high-intensity noise. We then examined the impacts of the two exposures on hearing and the organization of the auditory midbrain using two-photon imaging and analysis of the expression of mediators of oxidative stress. We observed that developmental exposure to PCBs blocked hearing recovery from acoustic trauma. In vivo two-photon imaging of the inferior colliculus (IC) revealed that this lack of recovery was associated with disruption of the tonotopic organization and reduction of inhibition in the auditory midbrain. In addition, expression analysis in the inferior colliculus revealed that reduced GABAergic inhibition was more prominent in animals with a lower capacity to mitigate oxidative stress. These data suggest that combined PCBs and noise exposure act nonlinearly to damage hearing and that this damage is associated with synaptic reorganization, and reduced capacity to limit oxidative stress. In addition, this work provides a new paradigm by which to understand nonlinear interactions between combinations of environmental toxins.SIGNIFICANCE STATEMENT Exposure to common environmental toxins is a large and growing problem in the population. This work provides a new mechanistic understanding of how the prenatal and postnatal developmental changes induced by polychlorinated biphenyls (PCBs) could negatively impact the resilience of the brain to noise-induced hearing loss (NIHL) later in adulthood. The use of state-of-the-art tools, including in vivo multiphoton microscopy of the midbrain helped in identifying the long-term central changes in the auditory system after the peripheral hearing damage induced by such environmental toxins. In addition, the novel combination of methods employed in this study will lead to additional advances in our understanding of mechanisms of central hearing loss in other contexts.
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Affiliation(s)
- Baher A Ibrahim
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Jeremy J Louie
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Yoshitaka Shinagawa
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Gang Xiao
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Neuroscience Program, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Alexander R Asilador
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Neuroscience Program, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Helen J K Sable
- The Department of Psychology, The University of Memphis, Memphis, Tennessee 38152
| | - Susan L Schantz
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Neuroscience Program, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Department of Comparative Biosciences, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
| | - Daniel A Llano
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Neuroscience Program, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
- Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Urbana, Illinois 61801
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3
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Ibrahim BA, Louie J, Shinagawa Y, Xiao G, Asilador AR, Sable HJK, Schantz SL, Llano DA. Developmental exposure to polychlorinated biphenyls prevents recovery from noise-induced hearing loss and disrupts the functional organization of the inferior colliculus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.23.534008. [PMID: 36993666 PMCID: PMC10055398 DOI: 10.1101/2023.03.23.534008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Exposure to combinations of environmental toxins is growing in prevalence, and therefore understanding their interactions is of increasing societal importance. Here, we examined the mechanisms by which two environmental toxins - polychlorinated biphenyls (PCBs) and high-amplitude acoustic noise - interact to produce dysfunction in central auditory processing. PCBs are well-established to impose negative developmental impacts on hearing. However, it is not known if developmental exposure to this ototoxin alters the sensitivity to other ototoxic exposures later in life. Here, male mice were exposed to PCBs in utero, and later as adults were exposed to 45 minutes of high-intensity noise. We then examined the impacts of the two exposures on hearing and the organization of the auditory midbrain using two-photon imaging and analysis of the expression of mediators of oxidative stress. We observed that developmental exposure to PCBs blocked hearing recovery from acoustic trauma. In vivo two-photon imaging of the inferior colliculus revealed that this lack of recovery was associated with disruption of the tonotopic organization and reduction of inhibition in the auditory midbrain. In addition, expression analysis in the inferior colliculus revealed that reduced GABAergic inhibition was more prominent in animals with a lower capacity to mitigate oxidative stress. These data suggest that combined PCBs and noise exposure act nonlinearly to damage hearing and that this damage is associated with synaptic reorganization, and reduced capacity to limit oxidative stress. In addition, this work provides a new paradigm by which to understand nonlinear interactions between combinations of environmental toxins. Significance statement Exposure to common environmental toxins is a large and growing problem in the population. This work provides a new mechanistic understanding of how the pre-and postnatal developmental changes induced by polychlorinated biphenyls could negatively impact the resilience of the brain to noise-induced hearing loss later in adulthood. The use of state-of-the-art tools, including in vivo multiphoton microscopy of the midbrain helped in identifying the long-term central changes in the auditory system after the peripheral hearing damage induced by such environmental toxins. In addition, the novel combination of methods employed in this study will lead to additional advances in our understanding of mechanisms of central hearing loss in other contexts.
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Affiliation(s)
- Baher A. Ibrahim
- Department of Molecular & Integrative Physiology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Jeremy Louie
- Department of Molecular & Integrative Physiology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Yoshitaka Shinagawa
- Department of Molecular & Integrative Physiology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Gang Xiao
- Department of Molecular & Integrative Physiology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Neuroscience Program, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Alexander R. Asilador
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Neuroscience Program, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Helen J. K. Sable
- The Department of Psychology, The University of Memphis, Memphis, TN 38152, USA
| | - Susan L. Schantz
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Department of Comparative Biosciences, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Daniel A. Llano
- Department of Molecular & Integrative Physiology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Beckman Institute for Advanced Science & Technology, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Neuroscience Program, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
- Carle Illinois College of Medicine, the University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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Fábelová L, Loffredo CA, Klánová J, Hilscherová K, Horvat M, Tihányi J, Richterová D, Palkovičová Murínová Ľ, Wimmerová S, Sisto R, Moleti A, Trnovec T. Environmental ototoxicants, a potential new class of chemical stressors. ENVIRONMENTAL RESEARCH 2019; 171:378-394. [PMID: 30716515 DOI: 10.1016/j.envres.2019.01.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 01/24/2019] [Accepted: 01/25/2019] [Indexed: 05/28/2023]
Abstract
Hearing loss is an injury that can develop over time, and people may not even be aware of it until it becomes a severe disability. Ototoxicants are substances that may damage the inner ear by either affecting the structures in the ear itself or by affecting the nervous system. We have examined the possibility that ototoxicants may present a health hazard in association with environmental exposures, adding to existing knowledge of their proven hazards under medical therapeutic conditions or occupational activities. In addition to the already described human environmental ototoxicants, mainly organochlorines such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB), we have examined the ubiquitous chemical stressors phthalates, bisphenol A/S/F/, PFCs, flame retardants (FRs) and cadmium for potential ototoxic properties, both as single substances or as chemical mixtures. Our literature review confirmed that these chemicals may disturb thyroid hormones homeostasis, activate aryl hydrocarbon receptor (AhR), and induce oxidative stress, which in turn may initiate a chain of events resulting in impairment of cochlea and hearing loss. With regard to auditory plasticity, diagnostics of a mixture of effects of ototoxicants, potential interactions of chemical and physical agents with effects on hearing, parallel deterioration of hearing due to chemical exposures and ageing, metabolic diseases or obesity, even using specific methods as brainstem auditory evoked potentials (BAEP) or otoacoustic emissions (OAEs) registration, may be difficult, and establishment of concentration-response relationships problematic. This paper suggests the establishment of a class of environmental oxotoxicants next to the established classes of occupational and drug ototoxicants. This will help to properly manage risks associated with human exposure to chemical stressors with ototoxic properties and adequate regulatory measures.
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Affiliation(s)
- Lucia Fábelová
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia
| | - Christopher A Loffredo
- Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C. 20057, USA
| | - Jana Klánová
- Masaryk University, Research Centre for Toxic Compounds in the Environment, RECETOX, Brno, Czech Republic
| | - Klára Hilscherová
- Masaryk University, Research Centre for Toxic Compounds in the Environment, RECETOX, Brno, Czech Republic
| | - Milena Horvat
- Jožef Stefan Institute, Department of Environmental Sciences, Ljubljana, Slovenia
| | - Juraj Tihányi
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia
| | - Denisa Richterová
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia
| | - Ľubica Palkovičová Murínová
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia
| | - Soňa Wimmerová
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia
| | - Renata Sisto
- INAIL, Research Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Monte Porzio Catone, Italy
| | - Arturo Moleti
- University of Roma, Tor Vergata, Department of Physics, Roma, Italy
| | - Tomáš Trnovec
- Slovak Medical University, Faculty of Public Health, Department of Environmental Medicine, Limbova 12, 83303 Bratislava, Slovakia.
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Palkovičová Murínová Ľ, Moleti A, Sisto R, Wimmerová S, Jusko TA, Tihányi J, Jurečková D, Kováč J, Koštiaková V, Drobná B, Trnovec T. PCB exposure and cochlear function at age 6 years. ENVIRONMENTAL RESEARCH 2016; 151:428-435. [PMID: 27552711 PMCID: PMC6044450 DOI: 10.1016/j.envres.2016.08.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 08/16/2016] [Accepted: 08/16/2016] [Indexed: 06/01/2023]
Abstract
Epidemiological studies have documented adverse associations between exposure to polychlorinated biphenyls (PCBs) and otological outcomes. Previously, we documented decreased distortion product otoacoustic emission (DPOAE) levels in children exposed to PCBs, up to the age of 45 months, amongst a cohort of children in eastern Slovakia. The objective of the present study is to evaluate cochlear dysfunction at 72 months of age in 214 children from this same cohort and to compare the otoacoustic test sensitivity to that of pure tone audiometry (PTA). The association between DPOAE, PTA, and PCBs was estimated by means of multivariate ANOVA (MANOVA) and linear regression models. ROC curves were computed to estimate the DPOAE-test power in children. The DPOAE level at 72 months was related to PCB-153 serum levels. The DPOAE Input/Output function test at mid-frequency (2kHz) has shown instead nonmonotonic dependence on PCB exposure, for the left ears of children, over the whole growth curve. No significant association was found between PTA hearing levels and PCB-153 concentration. High diagnostic power of the DPOAE-test was found in children, similar to that found by the same authors in adults. In conclusions the DPOAE-PCB correlation obtained at 72 months is similar to that at 45 months suggesting a permanent and stable ototoxic effect of the PCB exposure. The lack of statistical significance of the PCB-PTA correlation suggests that DPOAEs are sensitive biomarkers of cochlear damage.
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Affiliation(s)
- Ľubica Palkovičová Murínová
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic
| | - Arturo Moleti
- University of Roma, Tor Vergata, Department of Physics, Roma, Italy
| | - Renata Sisto
- INAIL Research, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Monte Porzio Catone, Italy
| | - Soňa Wimmerová
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic
| | - Todd A Jusko
- Departments of Public Health Sciences and Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Juraj Tihányi
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic
| | - Dana Jurečková
- The Štefan Kukura Hospital and Policlinic, Michalovce, Slovak Republic
| | - Ján Kováč
- Department of Stomatology and Maxillofacial Surgery, Comenius University, Faculty of Medicine in Bratislava, Bratislava, Slovak Republic
| | - Vladimíra Koštiaková
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic
| | - Beata Drobná
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic
| | - Tomáš Trnovec
- Slovak Medical University, Faculty of Public Health, Department of Health Protection, Limbová 12, 833 03 Bratislava 37, Slovak Republic.
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Sisto R, Moleti A, Palkovičová Murínová Ľ, Wimmerová S, Lancz K, Tihányi J, Čonka K, Šovčíková E, Hertz-Picciotto I, Jusko TA, Trnovec T. Environmental exposure to organochlorine pesticides and deficits in cochlear status in children. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:14570-8. [PMID: 25989860 PMCID: PMC4592791 DOI: 10.1007/s11356-015-4690-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 05/11/2015] [Indexed: 05/24/2023]
Abstract
The aim of this study was to examine the hypothesis that organochlorine pesticides (OCPs), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT) and its metabolite 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (p,p'- DDE) are ototoxic to humans. A multivariate general linear model was designed, in which the statistical relation between blood serum concentrations of HCB, β-HCH, p,p'-DDT, or p,p'-DDE at different ages (at birth, 6, 16, and 45 months) and the distortion product otoacoustic emissions (DPOAEs) was treated as multivariate outcome variables. Polychlorinated biphenyl (PCB) congeners and OCPs were strongly correlated in serum of children from our cohort. To ascertain that the association between DPOAEs at a given frequency and concentration of a pesticide is not influenced by PCBs or other OCP also present in serum, we calculated benchmark concentrations (BMCs) relating DPOAEs to a serum pesticide alone and in presence of confounding PCB-153 or other OCPs. We found that BMCs relating DPOAEs to serum pesticides are not affected by confounders. DPOAE amplitudes were associated with serum OCPs at all investigated time intervals, however, in a positive way with prenatal exposure and in a negative way with all postnatal exposures. We observed tonotopicity in the association of pesticides with amplitude of DPOAEs as its strength was frequency dependent. We conclude that exposure to OCPs in infancy at environmental concentrations may be associated with hearing deficits.
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Affiliation(s)
- Renata Sisto
- Department of Occupational Hygiene, INAIL, Monte Porzio Catone, Italy
| | - Arturo Moleti
- Department of Physics, University of Rome Tor Vergata, Rome, Italy
| | | | - Soňa Wimmerová
- Institute of Biophysics, Informatics and Biostatistics, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia
| | - Kinga Lancz
- Department of Environmental Medicine, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia
| | - Juraj Tihányi
- Department of Environmental Medicine, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia
| | - Kamil Čonka
- Department of Toxic Organic Pollutants, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia
| | - Eva Šovčíková
- Department of Environmental Medicine, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia
| | - Irva Hertz-Picciotto
- Division of Environmental and Occupational Health, Department of Public Health Sciences, School of Medicine, University of California Davis, Davis, CA, USA
| | - Todd A Jusko
- Division of Epidemiology, Department of Public Health Sciences, University of Rochester School of Medicine and Dentistry, 265 Crittenden Blvd, CU420644, Rochester, NY, 14642, USA
| | - Tomáš Trnovec
- Department of Environmental Medicine, Slovak Medical University, Limbová 12, 83303, Bratislava, Slovakia.
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Developmental exposure to purity-controlled polychlorinated biphenyl congeners (PCB74 and PCB95) in rats: effects on brainstem auditory evoked potentials and catalepsy. Toxicology 2014; 327:22-31. [PMID: 25449634 DOI: 10.1016/j.tox.2014.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 11/11/2014] [Accepted: 11/11/2014] [Indexed: 01/12/2023]
Abstract
Whereas the effects of dioxin-like polychlorinated biphenyls (DL-PCBs) are well described, less is known about non-dioxin-like PCBs (NDL-PCBs), including influences on the nervous system and related behavioral effects after developmental exposure. Following the examination of the highly purified NDL congeners PCB52 and PCB180, we report here the results of experiments with PCB74 and PCB95. Rat dams were orally exposed to equimolar doses of either congener (40μmol/kg bw - 11.68mg PCB74/kg bw or 13.06mg PCB95/kg bw) from gestational day (GD) 10 to postnatal day (PND) 7. Control dams were given the vehicle. Adult offspring were tested for cataleptic behavior after induction with haloperidol, a classical neuroleptic drug, and brainstem auditory evoked potentials (BAEPs), using clicks and tone pips of different frequencies for stimulation. Results revealed slight effects on latencies to movement onset in female offspring exposed to PCB74, whereas PCB74 males and offspring exposed to PCB95 were not affected. Pronounced changes were observed in BAEPs at low frequencies in PCB74 offspring, with elevated thresholds in both sexes. PCB95 increased thresholds in males, but not females. Small effects were detected on latency of the late wave IV in both sexes after developmental exposure to PCB74 or PCB95. Compared with the other NDL-PCB congeners tested, PCB74 caused the most pronounced effects on BAEPs.
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8
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Jusko TA, Sisto R, Iosif AM, Moleti A, Wimmerová S, Lancz K, Tihányi J, Sovčiková E, Drobná B, Palkovičová L, Jurečková D, Thevenet-Morrison K, Verner MA, Sonneborn D, Hertz-Picciotto I, Trnovec T. Prenatal and postnatal serum PCB concentrations and cochlear function in children at 45 months of age. ENVIRONMENTAL HEALTH PERSPECTIVES 2014; 122:1246-52. [PMID: 25051575 PMCID: PMC4216161 DOI: 10.1289/ehp.1307473] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 07/21/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND Some experimental and human data suggest that exposure to polychlorinated biphenyls (PCBs) may induce ototoxicity, though results of previous epidemiologic studies are mixed and generally focus on either prenatal or postnatal PCB concentrations exclusively. OBJECTIVES Our aim was to evaluate the association between pre- and postnatal PCB concentrations in relation to cochlear status, assessed by distortion product otoacoustic emissions (DPOAEs), and to further clarify the critical periods in development where cochlear status may be most susceptible to PCBs. METHODS A total of 351 children from a birth cohort in eastern Slovakia underwent otoacoustic testing at 45 months of age. Maternal pregnancy, cord, and child 6-, 16-, and 45-month blood samples were collected and analyzed for PCB concentrations. At 45 months of age, DPOAEs were assessed at 11 frequencies in both ears. Multivariate, generalized linear models were used to estimate the associations between PCB concentrations at different ages and DPOAEs, adjusting for potential confounders. RESULTS Maternal and cord PCB-153 concentrations were not associated with DPOAEs at 45 months. Higher postnatal PCB concentrations at 6-, 16-, and 45-months of age were associated with lower (poorer) DPOAE amplitudes. When all postnatal PCB exposures were considered as an area-under-the-curve metric, an increase in PCB-153 concentration from the 25th to the 75th percentile was associated with a 1.6-dB SPL (sound pressure level) decrease in DPOAE amplitude (95% CI: -2.6, -0.5; p = 0.003). CONCLUSIONS In this study, postnatal rather than maternal or cord PCB concentrations were associated with poorer performance on otoacoustic tests at age 45 months.
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Affiliation(s)
- Todd A Jusko
- Division of Epidemiology, Department of Public Health Sciences, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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9
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Lilienthal H, Heikkinen P, Andersson PL, van der Ven LTM, Viluksela M. Auditory Effects of Developmental Exposure to Purity-Controlled Polychlorinated Biphenyls (PCB52 and PCB180) in Rats. Toxicol Sci 2011; 122:100-11. [DOI: 10.1093/toxsci/kfr077] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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10
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Haijima A, Endo T, Zhang Y, Miyazaki W, Kakeyama M, Tohyama C. In utero and lactational exposure to low doses of chlorinated and brominated dioxins induces deficits in the fear memory of male mice. Neurotoxicology 2010; 31:385-90. [PMID: 20398696 DOI: 10.1016/j.neuro.2010.04.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 03/20/2010] [Accepted: 04/06/2010] [Indexed: 01/10/2023]
Abstract
Environmental-level in utero and lactational exposures to dioxins have been considered to affect brain functions of offspring. Here, we determined whether in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD), at the dose that does not harm the dams, affects the acquisition and retention of fear memory in mouse offspring. Pregnant C57BL/6J mice were administered by gavages TCDD or TBDD at a dose of 0 or 3.0 microg/kg body weight on gestation day 12.5, and their male offspring were examined for their behavior in adulthood. In the fear conditioning, a paired presentation of tone and foot shock was repeated three times, and retention tests for contextual and auditory fear memory were carried out 1 and 24h after the fear conditioning. Groups of mice that were exposed to TCDD and TBDD in utero and via lactation showed deficits in the contextual and auditory retention tests at 1 and 24h retention intervals. The present results suggest that maternal exposure to a low dose of TCDD or TBDD disrupts the functions of memory and emotion in male mouse offspring, and that the developmental toxicities of these chemicals are similar to each other.
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Affiliation(s)
- Asahi Haijima
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan
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11
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Powers BE, Poon E, Sable HJ, Schantz SL. Developmental exposure to PCBs, MeHg, or both: long-term effects on auditory function. ENVIRONMENTAL HEALTH PERSPECTIVES 2009; 117:1101-7. [PMID: 19654920 PMCID: PMC2717137 DOI: 10.1289/ehp.0800428] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Accepted: 04/03/2009] [Indexed: 05/06/2023]
Abstract
BACKGROUND Developmental exposure to polychlorinated biphenyls (PCBs) or methylmercury (MeHg) can result in a variety of neurotoxic effects, including long-term auditory deficits. However, little is known about the effects of combined exposure to PCBs and MeHg on auditory function. OBJECTIVE We developmentally exposed rats to PCBs and/or MeHg and assessed auditory function in adulthood to determine the effects of exposure to these contaminants individually and in combination. METHODS We exposed female Long-Evans rats to 1 or 3 mg/kg PCB in corn oil, 1.5 or 4.5 ppm MeHg in drinking water, or combined exposure to 1 mg/kg PCB + 1.5 ppm MeHg or 3 mg/kg PCB + 4.5 ppm MeHg. Controls received corn oil vehicle and unadulterated water. Dosing began 28 days before breeding and continued until weaning at postnatal day (PND) 21. Auditory function of the offspring was assessed at approximately PND 200 by measuring distortion product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). RESULTS Groups exposed to PCBs alone had attenuated DPOAE amplitudes, elevated DPOAE thresholds, and elevated ABR thresholds compared with controls. Groups exposed to MeHg alone did not differ from controls. Unexpectedly, the effects of PCB exposure appeared to be attenuated by coexposure to MeHg. CONCLUSION Developmental exposure to PCBs can result in permanent hearing deficits, and the changes in DPOAE amplitudes and thresholds suggest a cochlear site of action. Coexposure to MeHg appeared to attenuate the PCB-related deficits, but the mechanism for this unexpected interaction remains to be determined.
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Affiliation(s)
- Brian E. Powers
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Emily Poon
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Helen J.K. Sable
- Psychology Department, University of Memphis, Memphis, Tennessee, USA
| | - Susan L. Schantz
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Address correspondence to S. Schantz, Department of Veterinary Biosciences, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Ave., Urbana, IL 61802 USA. Telephone: (217) 333-6230. Fax: (217) 244-1652. E-mail:
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Crofton KM, Zoeller RT. Mode of Action: Neurotoxicity Induced by Thyroid Hormone Disruption During Development—Hearing Loss Resulting From Exposure to PHAHs. Crit Rev Toxicol 2008; 35:757-69. [PMID: 16417043 DOI: 10.1080/10408440591007304] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
An increasing incorporation of mode of action (MOA) information into risk assessments has led to examination of animal MOAs to determine relevance to humans. We examined a specific MOA for developmental neurotoxicity using the MOA/Human Relevance Framework (Meek et al., 2003). The postulated MOA of ototoxicity in rats involves early postnatal exposure to polychlorinated biphenyls (PCBs) via lactation, an upregulation of hepatic uridine diphosphoglucuronyltransferases (UGTs), and subsequent hypothyroxinemia during a critical period of cochlear development, with the ultimate neurotoxic consequence of hearing loss. This review concludes with high confidence in the animal MOA and medium confidence for the interspecies concordance for the key events in the MOA. Possible interspecies differences in toxicodynamic factors moderate confidence in some key events. In addition, there is a question of whether ambient human exposures are large enough to cause human fetal hypothyroxinemia to the degree needed to cause hearing loss. Data gaps identified by this analysis include a need to characterize the induciblity of human fetal UGTs and the comparative sensitivity of UGT induction by xenobiotics in rats and humans. Research on these areas of uncertainty will increase confidence that this MOA for PCBs is not likely to not occur in humans, assuming normal conditions of limited ambient exposure.
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Affiliation(s)
- Kevin M Crofton
- US Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Axelstad M, Hansen PR, Boberg J, Bonnichsen M, Nellemann C, Lund SP, Hougaard KS, Hass U. Developmental neurotoxicity of propylthiouracil (PTU) in rats: relationship between transient hypothyroxinemia during development and long-lasting behavioural and functional changes. Toxicol Appl Pharmacol 2008; 232:1-13. [PMID: 18573268 DOI: 10.1016/j.taap.2008.05.020] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 05/14/2008] [Accepted: 05/19/2008] [Indexed: 11/18/2022]
Abstract
Markedly lowered thyroid hormone levels during development may influence a child's behaviour, intellect, and auditory function. Recent studies, indicating that even small changes in the mother's thyroid hormone status early in pregnancy may cause adverse effects on her child, have lead to increased concern for thyroid hormone disrupting chemicals in the environment. The overall aim of the study was therefore to provide a detailed knowledge on the relationship between thyroid hormone levels during development and long-lasting effects on behaviour and hearing. Groups of 16-17 pregnant rats (HanTac:WH) were dosed with PTU (0, 0.8, 1.6 or 2.4 mg/kg/day) from gestation day (GD) 7 to postnatal day (PND) 17, and the physiological and behavioural development of rat offspring was assessed. Both dams and pups in the higher dose groups had markedly decreased thyroxine (T(4)) levels during the dosing period, and the weight and histology of the thyroid glands were severely affected. PTU exposure caused motor activity levels to decrease on PND 14, and to increase on PND 23 and in adulthood. In the adult offspring, learning and memory was impaired in the two highest dose groups when tested in the radial arm maze, and auditory function was impaired in the highest dose group. Generally, the results showed that PTU-induced hypothyroxinemia influenced the developing rat brain, and that all effects on behaviour and loss of hearing in the adult offspring were significantly correlated to reductions in T(4) during development. This supports the hypothesis that decreased T(4) may be a relevant predictor for long-lasting developmental neurotoxicity.
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Affiliation(s)
- Marta Axelstad
- Department of Toxicology and Risk Assessment, National Food Institute, Technical University of Denmark, Søborg, Denmark.
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14
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Exposure to tetrabromobisphenol A (TBBPA) in Wistar rats: Neurobehavioral effects in offspring from a one-generation reproduction study. Toxicology 2008; 246:45-54. [DOI: 10.1016/j.tox.2008.01.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 01/09/2008] [Accepted: 01/10/2008] [Indexed: 11/24/2022]
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15
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Trnovec T, Sovčíková E, Hust'ák M, Wimmerová S, Kočan A, Jurečková D, Langer P, Palkovičová L, Drobná B. Exposure to polychlorinated biphenyls and hearing impairment in children. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2008; 25:183-7. [PMID: 21783857 DOI: 10.1016/j.etap.2007.10.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The objective of this cross-sectional epidemiological study was to assess if long-term exposure to polychlorinated biphenyls (PCBs) is associated with hearing impairment. Four hundred and thirty-three children aged 8-9 years residing in an area polluted by PCBs in Eastern Slovakia were examined otoscopically, tympanometrically and by pure tone audiometry. PCB levels in their serum were determined by gas chromatography. Transient otoacoustic emissions (TEOAE) were measured in a subgroup of 161 children. The mean of the sum of PCB concentrations in serum was 528.2ng/g serum lipids (median 321ng/g serum lipids). Serum PCB concentrations were associated with an increase of hearing threshold at low frequencies and a negative correlation between serum PCBs and the amplitude of TEOAE response was observed in the uppermost tertile of children grouped with regard to serum PCBs, not related to thyroid hormone levels. It was concluded that long-term environmental exposure to PCBs is associated with subclinical but diagnosable hearing deficits.
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Affiliation(s)
- Tomáš Trnovec
- Slovak Medical University, Limbová 12, 83303 Bratislava, Slovak Republic
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16
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Roegge CS, Schantz SL. Motor function following developmental exposure to PCBS and/or MEHG. Neurotoxicol Teratol 2006; 28:260-77. [PMID: 16487679 DOI: 10.1016/j.ntt.2005.12.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 12/16/2005] [Accepted: 12/20/2005] [Indexed: 11/23/2022]
Abstract
Recent studies raise concern for combined exposure to polychlorinated biphenyls (PCBs) and methylmercury (MeHg), two environmental contaminants that are found in fish and seafood. Past accidental poisonings in humans show that exposure to high levels of either contaminant is associated with motor impairments, including alterations in cerebellar functions such as balance and coordination. Epidemiological studies of lower level exposures suggest some neuromotor impairment in exposed children, but the majority of these studies have focused on cognitive endpoints rather than examining a full-range of motor function. In particular, the cerebellum could be a sensitive target for combined PCB and MeHg toxicity. MeHg exposure during development damages the cerebellum along with cortical areas, and PCBs may also cause cerebellar damage via thyroid hormone disruption during development. In addition, in vitro studies report interactive effects of PCBs and MeHg on ryanodine-sensitive calcium signaling. Ryanodine receptors are found especially within the cerebellum, and alterations in calcium signaling within the cerebellum could impair long-term depression and subsequent motor learning. This article reviews the motor impairments reported in humans and laboratory animals following exposure to PCBs and/or MeHg during development. There is need for a better understanding of the interactive effects of PCBs and MeHg, especially in regard to motor function.
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Affiliation(s)
- Cindy S Roegge
- Psychiatry Department, Duke University Medical Center, Box 3415 Bell Building, Durham, NC 27710, USA.
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17
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Opinion of the Scientific Panel on contaminants in the food chain [CONTAM] related to the presence of non dioxin-like polychlorinated biphenyls (PCB) in feed and food. EFSA J 2005. [DOI: 10.2903/j.efsa.2005.284] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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18
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Bemis JC, Nazarenko DA, Gasiewicz TA. Coplanar Polychlorinated Biphenyls Activate the Aryl Hydrocarbon Receptor in Developing Tissues of Two TCDD-Responsive lacZ Mouse Lines. Toxicol Sci 2005; 87:529-36. [PMID: 16033994 DOI: 10.1093/toxsci/kfi260] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can have an immediate impact on developmental processes that then lead to long-term deficits in function. To define the specific tissues affected by TCDD during development, we developed a lacZ-reporter gene mouse model driven by activation of the aryl hydrocarbon receptor (AhR). Exposure to TCDD on gestational day (GD) 14 results in strong activation of the lacZ transgene in numerous tissues including fore and hind paws, ear, and genital tubercle. Experiments were conducted to examine the ability of alternative AhR ligands to activate our model system. The coplanar polychlorinated biphenyl congeners 3,4,5,3',4'-pentachlorobiphenyl (PCB126) and 3,4,3',4'-tetrachlorobiphenyl (PCB77) both induced staining in fetal tissues identical to that observed following TCDD exposure. Exposure of fetuses to the PCB mixture Aroclor 1254 and the non-coplanar congener 2,3,6,2',5'-pentachlorobiphenyl (PCB95) did not result in any activation of the lacZ transgene. In addition to the testing of alternative ligands, another line of reporter mice was generated to determine the potential influence of the site of insertion of the lacZ transgene on the reported observations. Both TCDD and the coplanar PCBs induced a similar pattern of staining in the new line as compared to that observed in the original lacZ reporter mouse line. The ability of AhR ligands, other than TCDD, to activate the AhR-mediated transgene, in combination with the insertion-site independence of the response, strengthens the data previously derived from this model and increases the utility of this system for investigations examining AhR-mediated events during development.
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Affiliation(s)
- Jeffrey C Bemis
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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19
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20
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From Animals to Humans: Models and Constructs. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0074-7750(05)30010-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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21
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Crofton KM. Developmental disruption of thyroid hormone: correlations with hearing dysfunction in rats. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2004; 24:1665-1671. [PMID: 15660619 DOI: 10.1111/j.0272-4332.2004.00557.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A wide variety of environmental contaminants adversely affect thyroid hormone (TH) homeostasis. Hypothyroidism and/or hypothyroxinemia during the early postnatal period in the rat leads to permanent structural damage and loss of function in the cochlea. A major uncertainty in assessing the risks of developmental exposure to thyroid-disrupting chemicals (TDCs) is the lack of a clear characterization of the dose-response relationship, especially in the lower region, between disruption of hormones and adverse consequences. The current work correlated early postnatal hypothyroxinemia with hearing loss in the adult rat. Linear regression was performed on the log transform for total serum thyroxine (T4) concentrations on postnatal day 14 or 21 versus dB(SPL) of hearing loss in adult animals developmentally exposed to TDCs. Regression analyses revealed a highly significant correlation between T4 concentration and hearing loss. In the rat, a 50-60% decrease in circulating T4 was needed to significantly impact hearing function. This correlation suggests that T4 serum concentrations at 14 or 21 days of postnatal age may be a good predictive biomarker in rodents of the adverse consequence of developmental exposure to TDCs.
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Affiliation(s)
- K M Crofton
- Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. EPA, Research Triangle Park, NC 27711, USA.
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22
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Longnecker MP, Hoffman HJ, Klebanoff MA, Brock JW, Zhou H, Needham L, Adera T, Guo X, Gray KA. In utero exposure to polychlorinated biphenyls and sensorineural hearing loss in 8-year-old children. Neurotoxicol Teratol 2004; 26:629-37. [PMID: 15315812 DOI: 10.1016/j.ntt.2004.04.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Revised: 04/20/2004] [Accepted: 04/26/2004] [Indexed: 10/26/2022]
Abstract
Early-life exposure to polychlorinated biphenyls (PCBs), a ubiquitous environmental contaminant, increases the hearing threshold at selected frequencies in rats. Among humans from the Faroe Islands with unusually high early-life PCB exposure, exposure was directly associated with increased hearing thresholds at two frequencies, although the deficits were present in the left ear but not the right. We examined PCB levels in maternal pregnancy serum in relation with audiometrically determined hearing thresholds among offspring when they were of school age. Complete data were available for 195 children with sensorineural hearing loss (SNHL) and 615 children selected at random, all of whom were born in 1959-1966 in the Collaborative Perinatal Project (CPP) U.S. cohort. The median exposure among those selected at random, as reflected by the mother's third trimester serum total PCB concentration, was 2.8 microg/l, about twofold higher than recent background levels in the United States. Based on the average hearing threshold across the frequencies essential for speech recognition in the "worst ear," the maternal serum PCB level was unrelated to the adjusted odds of SNHL or to adjusted mean hearing threshold. Overall, an adverse effect of early-life, background-level PCB exposure on SNHL was not supported by these data.
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Affiliation(s)
- Matthew P Longnecker
- Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, P.O. Box 12233, MD A3-05, Research Triangle Park, NC 27709, USA.
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23
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Hadjab S, Maurel D, Cazals Y, Siaud P. Hexachlorobenzene, a dioxin-like compound, disrupts auditory function in rat. Hear Res 2004; 191:125-34. [PMID: 15109712 DOI: 10.1016/j.heares.2003.12.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2003] [Accepted: 12/29/2003] [Indexed: 10/26/2022]
Abstract
Hexachlorobenzene (HCB) is a dioxin-like compound widely distributed in the environment. In this study, we investigated the effects of HCB on the cochlea. Conscious free-moving rats were given HCB per os daily for 4 weeks at doses of 0.16, 4 or 16 mg/kg in olive oil, whereas the control group received olive oil only. The effects of HCB were evaluated at various time intervals, by measuring auditory nerve acoustic thresholds and plasma thyroid hormone concentration by radioimmunoassay. Histological evaluation involved surface preparation and scanning electron microscopy observations of cochlear hair cells. At a dose of 0.16 mg/kg, HCB induced no loss of acoustic sensitivity, whereas at 4 mg/kg, it induced cochlear sensitivity deficits at the mid-frequencies (2-16 kHz) with complete recovery once treatment was stopped. At a dose of 16 mg/kg, permanent threshold shifts were observed at all frequencies tested (from 1 to 32 kHz). Morphological studies showed no cochlear hair cell loss or alteration of stereocilia. HCB treatment reduced circulating thyroxine concentrations. Thyroidectomy had no effect on cochlear sensitivity in control animals. Thus, HCB is a potent oto-toxicant, and its ototoxicity may be independent of its thyroidal effects.
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Affiliation(s)
- Saida Hadjab
- Laboratoire d'Otologie Neuro-Otologie, EMI 9902 INSERM, Faculté de Médecine Secteur Nord, Université de la Méditerranée, Boulevard Pierre Dramard, 13916 Marseille Cedex 20, France
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24
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Newland MC. Neurobehavioral toxicity of methylmercury and PCBs Effects-profiles and sensitive populations. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2002; 12:119-128. [PMID: 21782631 DOI: 10.1016/s1382-6689(02)00030-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A large and growing body of literature is available on the neurotoxicity of methylmercury and PCBs as expressed in the behavior of both humans and laboratory animals. Methylmercury and PCBs will be compared with PCBs with attention directed at overlaps and distinctions in their profiles of neurotoxicity. It is possible with methylmercury and, to a lesser extent, with PCBs to characterize the sensory, motor, and cognitive consequences of exposure. Methylmercury is emerging as a life-span developmental neurotoxicant: adverse effects of exposure have been identified in development and during aging in human populations as well as in laboratory animals. Less is known about the PCBs on this count. While the mechanisms of neurotoxicity are not understood for either class of compounds, emerging clues are pointing to the possibility of overlap in some mechanisms of neurotoxicity.
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Herr DW, Graff JE, Derr-Yellin EC, Crofton KM, Kodavanti PR. Flash-, somatosensory-, and peripheral nerve-evoked potentials in rats perinatally exposed to Aroclor 1254. Neurotoxicol Teratol 2001; 23:591-601. [PMID: 11792527 DOI: 10.1016/s0892-0362(01)00180-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Pregnant Long-Evans rats were exposed to 0, 1 or 6 mg/kg/day of Aroclor 1254 (A1254; Lot no. 124-191), a commercial mixture of polychlorinated biphenyls (PCBs), from gestation day (GD) 6 through postnatal day (PND) 21. At 128-140 days of age, male and female offspring were tested for visual-, somatosensory- and peripheral nerve-evoked potentials. The evoked responses increased in amplitude with larger stimulus intensities, and gender differences were detected for some endpoints. In contrast, developmental exposure to A1254 failed to significantly affect the electrophysiological measures. A subset of the animals were tested for low-frequency hearing dysfunction using reflex modification audiometry (RMA). An elevated threshold for a 1-kHz tone was observed, replicating previous findings of A1254-induced auditory deficits [Hear. Res. 144 (2000) 196; Toxicol. Sci. 45(1) (1998) 94; Toxicol. Appl. Pharmacol. 135(1) (1995) 77.]. These findings indicate no statistically significant changes in visual-, somatosensory- or peripheral nerve-evoked potentials following developmental exposure to doses of A1254 that produce behavioral hearing deficits. However, subtle changes in the function of the visual or somatosensory systems cannot be disproved.
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Affiliation(s)
- D W Herr
- Neurotoxicology Division, MD-74B, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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26
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Abstract
The neurological effects of polychlorinated biphenyls (PCBs) have been extensively investigated in humans and in animals. The main focus in human studies has been on the effects in neonates and young children, although studies of adults have also been conducted. A great deal of concern exists that even low levels of PCBs transferred to the fetus across the placenta may induce long-lasting neurological damage. Because PCBs are lipophilic substances, there is also concem that significant amounts might be transferred to nursing infants via breast milk. Studies in humans who consumed large amounts of Great Lakes fish contaminated with environmentally persistent chemicals, including PCBs. have provided evidence that PCBs are important contributors to subtle neurobehavioral alterations observed in newborn children and that some of these alterations persist during childhood. Some consistent observations at birth have been motor immaturity and hyporeflexia and lower psychomotor scores between 6 months and 2 years old. There is preliminary evidence that highly chlorinated PCB congeners, which accumulate in certain fish, are associated with neurobehavioral alterations seen in some newbom children. Subtle neurobehavioral alterations have also been observed in children bom to mothers in the general population with the highest PCB body burdens. Because of the limitations of epidemiological studies, these effects cannot be attributed entirely to PCB exposure. In one general population study, there was strong evidence that dioxins, as well as PCBs, were contributors to the neurobehavioral effects seen in exposed children. Children born to women who accidentally consumed rice oil contaminated with relatively high amounts of PCBs and chlorinated dibenzofurans (CDFs) during pregnancy also had neurodevelopmental changes. Studies in animals support the human data. Neurobehavioral alterations have been also observed in rats and monkeys following prenatal and/or postnatal exposure to commercial Aroclor mixtures, defined experimental congener mixtures, single PCB congeners, and Great Lakes contaminated fish. In addition, monkeys exposed postnatally to PCB mixtures of congeneric composition and concentration similar to that found in human breast milk showed learning deficits long after exposure had ceased. A few other generalizations can be made from the data in animals. It appears that ortho-substituted PCB congeners are more active than coplanar PCBs in modifying cognitive processes. In addition, one effect observed in both rats and monkeys--deficits on delayed spatial alternation--has been known to be induced by exposure to ortho-substituted PCBs, defined experimental mixtures, and commercial Aroclors. Both dioxin-like and non-dioxin-like PCB congeners have been shown to induce neurobehavioral alterations in animals. Changes in levels of neurotransmitters in various brain areas have also been observed in monkeys, rats, and mice. Of all the observed changes, the most consistent has been a decrease in dopamine content in basal ganglia and prefrontal cortex, but further research is needed before specific neurobehavioral deficits can be correlated with PCB-induced changes in specific neurotransmitters in specific brain areas.
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Affiliation(s)
- O Faroon
- Agency for Toxic Substances and Disease Registry (ATSDR) US Department of Health and Human Services, Atlanta, Georgia 30333, USA.
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27
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Geller AM, Bushnell PJ, Rice DC. Behavioral and electrophysiological estimates of visual thresholds in awake rats treated with 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Neurotoxicol Teratol 2000; 22:521-31. [PMID: 10974590 DOI: 10.1016/s0892-0362(00)00067-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Visual thresholds for luminance increments were obtained behaviorally and electrophysiologically from rats exposed to a polychlorinated biphenyl (PCB) during development. Male Long-Evans rats exposed to 0, 0.25, or 1.0 microg/kg/day of 3,3',4,4', 5-pentachlorobiphenyl (PCB 126) through gestation and weaning were trained as adults to perform a signal detection task. Estimates of threshold were derived from psychometric functions for each animal relating the proportion of hits to signal intensity. Thresholds derived under three luminance conditions did not differ significantly among the PCB-treated groups. After behavioral testing was completed, flash-evoked potentials were recorded from dark-adapted awake animals. Peak amplitudes increased linearly over approximately 3 log units of intensity. Extrapolations to 0 amplitude along the linear portion of the amplitude-log intensity functions produced estimates of absolute threshold of -5.44 to -5.53 log cd/m(2)-s. Waveforms recorded from awake animals had a large late negative component that was absent in previously reported anesthetized preparations. Developmental exposure to PCB 126 had no significant effect on absolute threshold or peak amplitudes and latencies.
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Affiliation(s)
- A M Geller
- Neurotoxicology Division, US EPA, Research Triangle Park, NC 27711, USA.
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Gilbert ME, Crofton KM. Developmental exposure to a commercial PCB mixture (Aroclor 1254) produces a persistent impairment in long-term potentiation in the rat dentate gyrus in vivo. Brain Res 1999; 850:87-95. [PMID: 10629752 DOI: 10.1016/s0006-8993(99)02107-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Developmental exposure to polycholorinated biphenyls (PCBs) has been associated with cognitive deficits in humans and laboratory animals. The present study sought to examine synaptic plasticity in the hippocampus, a brain region critical for some types of memory function, in animals exposed to PCBs early in development. Pregnant Long-Evans rats were administered either corn oil (control) or 6 mg/kg/day of a commercial PCB mixture, Aroclor 1254 (A1254) by gavage from gestational day (GD) 6 until pups were weaned on postnatal day (PND) 21. In adult male offspring (3-6 months of age), field potentials evoked by perforant path stimulation were recorded in the dentate gyrus under urethane anesthesia. Input/output (I/O) functions were assessed by averaging the response evoked in the dentate gyrus to stimulus pulses delivered to the perforant path in an ascending intensity series. Long-term potentiation (LTP) was induced by delivering a series of brief high frequency (400 Hz) train bursts to the perforant path at a moderate stimulus intensity and I/O functions were reassessed 1 h later. No differences in baseline synaptic population spike (PS) and minor effects on excitatory postsynaptic potential (EPSP) slope amplitudes were discerned between the groups prior to train delivery. Post-train I/O functions, however, revealed a 50% decrement in the magnitude of LTP in PCB-exposed animals. These data are the first to demonstrate persistent decrements in hippocampal synaptic plasticity in the intact animal following developmental exposure to PCBs. Disruption of early brain ontogeny due to developmental PCB exposure may underlie perturbations in the neurological substrates that support synaptic plasticity and contribute to deficits in LTP and learning that persist into adulthood.
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Affiliation(s)
- M E Gilbert
- Neurotoxicology Division, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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