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Schrenk D, Bignami M, Bodin L, Chipman JK, del Mazo J, Grasl‐Kraupp B, Hogstrand C, (Ron) Hoogenboom L, Leblanc J, Nebbia CS, Nielsen E, Ntzani E, Petersen A, Sand S, Schwerdtle T, Wallace H, Benford D, Fürst P, Hart A, Rose M, Schroeder H, Vrijheid M, Ioannidou S, Nikolič M, Bordajandi LR, Vleminckx C. Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food. EFSA J 2024; 22:e8497. [PMID: 38269035 PMCID: PMC10807361 DOI: 10.2903/j.efsa.2024.8497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024] Open
Abstract
The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.
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Subbamanda YD, Bhargava A. Intercommunication between Voltage-Gated Calcium Channels and Estrogen Receptor/Estrogen Signaling: Insights into Physiological and Pathological Conditions. Cells 2022; 11:cells11233850. [PMID: 36497108 PMCID: PMC9739980 DOI: 10.3390/cells11233850] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/25/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022] Open
Abstract
Voltage-gated calcium channels (VGCCs) and estrogen receptors are important cellular proteins that have been shown to interact with each other across varied cells and tissues. Estrogen hormone, the ligand for estrogen receptors, can also exert its effects independent of estrogen receptors that collectively constitute non-genomic mechanisms. Here, we provide insights into the VGCC regulation by estrogen and the possible mechanisms involved therein across several cell types. Notably, most of the interaction is described in neuronal and cardiovascular tissues given the importance of VGCCs in these electrically excitable tissues. We describe the modulation of various VGCCs by estrogen known so far in physiological conditions and pathological conditions. We observed that in most in vitro studies higher concentrations of estrogen were used while a handful of in vivo studies used meager concentrations resulting in inhibition or upregulation of VGCCs, respectively. There is a need for more relevant physiological assays to study the regulation of VGCCs by estrogen. Additionally, other interacting receptors and partners need to be identified that may be involved in exerting estrogen receptor-independent effects of estrogen.
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Dungar BM, Schupbach CD, Jacobson JR, Kopf PG. Adrenal Corticosteroid Perturbation by the Endocrine Disruptor BDE-47 in a Human Adrenocortical Cell Line and Male Rats. Endocrinology 2021; 162:6346795. [PMID: 34370853 PMCID: PMC8402933 DOI: 10.1210/endocr/bqab160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Indexed: 01/04/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) have been previously shown to alter various endocrine biosynthetic pathways. Growing epidemiological evidence suggests that PBDEs alter cardiovascular function. The goal of this study was to examine the effects of BDE-47 on adrenal corticosteroid pathways that play vital roles in cardiovascular homeostasis and pathophysiology. The effect of BDE-47 on aldosterone and cortisol secretion was characterized in a human adrenocortical cell line. HAC15 cells were exposed to various concentrations of BDE-47 (1 nM to 100 μM). Cell viability, corticosteroid secretion, gene expression of enzymes involved in corticosteroid synthesis, and metabolic activity was examined. Additionally, Sprague Dawley male rats were orally exposed to BDE-47 (10 or 100 µg/kg), 5 days per week for 16 weeks. Organ weights and plasma corticosteroid levels were measured. In HAC15 cells, basal and stimulated aldosterone and cortisol secretion was significantly increased by BDE-47. Gene expression of several enzymes involved in corticosteroid synthesis and mitochondrial metabolism also increased. In Sprague Dawley rats, adrenal but not heart, kidney, or liver weights, were significantly increased in BDE-47 treatment groups. Plasma corticosterone levels were significantly increased in the 100 µg BDE-47/kg treatment group. No change in plasma aldosterone levels were observed with BDE-47 exposure. These data indicate that BDE-47 disrupts the regulation of corticosteroid secretion and provides further evidence that PBDEs are potential endocrine disruptors. Future studies will determine the underlying molecular mechanism of altered corticosteroid production and examine whether these alterations result in underlying cardiovascular disease in our rodent model of 16-week BDE-47 exposure.
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Affiliation(s)
- Benjamin M Dungar
- Department of Pharmacology, College of Graduate Studies, Midwestern University, Downers Grove, IL 60515, USA
| | - Chad D Schupbach
- Department of Pharmacology, College of Graduate Studies, Midwestern University, Downers Grove, IL 60515, USA
| | - Jessie R Jacobson
- Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60515, USA
| | - Phillip G Kopf
- Department of Pharmacology, College of Graduate Studies, Midwestern University, Downers Grove, IL 60515, USA
- Correspondence: Phillip G. Kopf, PhD, Department of Pharmacology, Midwestern University, 555 31st Street, Downers Grove, IL 60515, USA.
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Xu L, Wang Y, Song E, Song Y. Nucleophilic and redox properties of polybrominated diphenyl ether derived-quinone/hydroquinone metabolites are responsible for their neurotoxicity. JOURNAL OF HAZARDOUS MATERIALS 2021; 420:126697. [PMID: 34329100 DOI: 10.1016/j.jhazmat.2021.126697] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 07/06/2021] [Accepted: 07/18/2021] [Indexed: 06/13/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are a category of brominated flame retardants, which were widely used in industrial products since the 1970 s. Our previous studies indicated quinone-type metabolites of PBDEs (PBDE-Qs) cause neurotoxicity, however, their inherent toxicological mechanism remains unclear. Here, we first synthesized PBDE-Qs and corresponding reduced hydroquinone homologous (PBDE-HQs) with different pattern of bromine substitution. Their nucleophilic and redox properties were investigated. PBDE-Qs react with reduced glutathione (GSH) via Michael addition and bromine displacement reaction, whilst PBDE-HQs lack the ability of reacting with GSH. Of note, the displacement reaction only occurs with bromine on the quinone ring of PBDE-Qs but not phenyl ring. Next, electron paramagnetic resonance (EPR) analysis revealed the generation of SQ•-, along with their downstream hydroxyl radical (HO•) and methyl radical (•CH3) through a PBDE quinone/semiquinone/hydroquinone (Q/SQ•-/HQ) futile cycle. In addition, a structure-dependent cytotoxicity pattern was found, the exposure of PBDE-Q/HQ with bromine substitution on the quinone ring resulted in higher level of apoptosis and autophagy in BV2 cells. In conclusion, this work clearly demonstrated that the nucleophilic and redox properties of PBDE-Qs/HQs are responsible for their neurotoxicity, and this finding provide better understanding of neurotoxicity of PBDEs.
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Affiliation(s)
- Lei Xu
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, 2 Tiansheng Rd, Beibei District, Chongqing 400715, China
| | - Yuting Wang
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, 2 Tiansheng Rd, Beibei District, Chongqing 400715, China
| | - Erqun Song
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, 2 Tiansheng Rd, Beibei District, Chongqing 400715, China
| | - Yang Song
- Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, 2 Tiansheng Rd, Beibei District, Chongqing 400715, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Rd, Haidian District, Beijing 100085, China.
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Ingle ME, Mínguez-Alarcón L, Carignan CC, Stapleton HM, Williams PL, Ford JB, Moravek MB, Hauser R, Meeker JD. Exploring reproductive associations of serum polybrominated diphenyl ether and hydroxylated brominated diphenyl ether concentrations among women undergoing in vitro fertilization. Hum Reprod 2021; 35:1199-1210. [PMID: 32424407 DOI: 10.1093/humrep/deaa063] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 02/21/2020] [Indexed: 12/15/2022] Open
Abstract
STUDY QUESTION Are serum concentrations of polybrominated diphenyl ethers (PBDEs) and hydroxylated brominated diphenyl ethers (OH-BDEs) associated with IVF endpoints? SUMMARY ANSWER Positive associations were observed for BDE153 and several OH-BDEs with IVF endpoints. WHAT IS KNOWN ALREADY PBDEs have been voluntarily phased out of production in the USA and EU due to their persistence and toxicity to humans and ecosystems. PBDEs have been associated with implantation failure among women undergoing IVF, yet some animal studies suggest greater toxicity from their metabolites, OH-BDEs. STUDY DESIGN, SIZE, DURATION We evaluated a subset of 215 women (contributing 330 IVF cycles) enrolled between 2005 and 2016 in a longitudinal cohort based at Massachusetts General Hospital Fertility Center. PARTICIPANTS/MATERIALS, SETTING, METHODS The following PBDEs were quantified: 47, 99, 100, 153 and 154 and the following OH-BDEs: 3-OH-BDE47, 5-OH-BDE47, 6-OH-BDE47 and 4-OH-BDE49. Clinical endpoints of IVF treatments were abstracted from electronic medical records. Associations of log-transformed PBDEs and OH-BDEs with IVF outcomes were assessed using multivariable generalized mixed models and cluster weighted generalized estimating equation models adjusted for lipids, age, BMI, race, year of sample collection, IVF protocol and FSH levels. Outcomes were adjusted to represent a percent change in outcome with an increase equal to the magnitude of the difference between the 75th and 25th percentiles for each specific compound (interquartile range (IQR) increase). MAIN RESULTS AND THE ROLE OF CHANCE Detection frequencies were highest for congeners 47 and 153 (82% ≥ method detection limit (MDL)) and metabolites 3 and 5-OH-BDE47 and 4-OH-BDE49 (92% > MDL). PBDE and OH-BDE geometric mean concentrations declined by up to 80% between participants recruited in 2005 and those recruited in 2016. An IQR increase of BDE153 was associated with an increase in the probability of implantation (relative risk (RR) = 1.26, 95% CI: 1.16, 1.36), clinical pregnancy (RR = 1.32, 95% CI: 1.19, 1.46) and live birth (RR = 1.34; 95% CI: 1.15, 1.54). An IQR increase in 3 and 5-OH-BDE47 was associated with increased probabilities of implantation (RR = 1.52; 95% CI: 1.11, 2.09), clinical pregnancy (RR = 1.66; 95% CI: 1.17, 2.36), and live birth (RR = 1.61; 95% CI: 1.07, 2.40). When models were stratified by race (White (86%)/Other race (14%)), associations remained positive for White women, yet inverse associations were observed for Other race women. An IQR increase in BDE47 was associated with a 46% decreased probability of clinical pregnancy (95% CI: 0.31, 0.95) for Other race women. LIMITATIONS, REASONS FOR CAUTION Despite the long half-lives of PBDEs and OH-BDEs, exposure misclassification is possible for women who underwent multiple treatment cycles over several months or years. It is also possible another medium, such as follicular fluid would be optimal to characterize exposure. We also tested associations for multiple congeners and metabolites with multiple outcomes. WIDER IMPLICATIONS OF THE FINDINGS Detections of serum concentrations of PBDEs and OH-BDEs were highest in the early years of the study and suggests that the phase-out of these compounds has contributed to a decrease in exposure. The negative associations found for PBDEs and IVF outcomes among other race women suggests the potential for racial disparity. Potential racial disparities in PBDE exposure and exploration of alternative flame retardants with reproductive health outcomes should be the focus of future investigations. STUDY FUNDING/COMPETING INTEREST(S) Funding for this research was supported by the National Institutes of Environmental Health Sciences (NIEHS) [R01 ES009718, ES022955, ES000002 and 009718T32ES007069]. The authors have no conflicts of interest.
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Affiliation(s)
- Mary E Ingle
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, USA
| | - Lidia Mínguez-Alarcón
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Courtney C Carignan
- Department of Food Science and Nutrition, Michigan State University, East Lansing, MI, USA.,Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
| | | | - Paige L Williams
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Jennifer B Ford
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Molly B Moravek
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Russ Hauser
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, University of Michigan, Ann Arbor, MI, USA.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Obstetrics and Gynecology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - John D Meeker
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, USA
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40 Years of Research on Polybrominated Diphenyl Ethers (PBDEs)-A Historical Overview and Newest Data of a Promising Anticancer Drug. Molecules 2021; 26:molecules26040995. [PMID: 33668501 PMCID: PMC7918430 DOI: 10.3390/molecules26040995] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/10/2021] [Indexed: 12/11/2022] Open
Abstract
Polybrominated diphenyl ethers (PBDEs) are a group of molecules with an ambiguous background in literature. PBDEs were first isolated from marine sponges of Dysidea species in 1981 and have been under continuous research to the present day. This article summarizes the two research aspects, (i) the marine compound chemistry research dealing with naturally produced PBDEs and (ii) the environmental toxicology research dealing with synthetically-produced brominated flame-retardant PBDEs. The different bioactivity patterns are set in relation to the structural similarities and dissimilarities between both groups. In addition, this article gives a first structure-activity relationship analysis comparing both groups of PBDEs. Moreover, we provide novel data of a promising anticancer therapeutic PBDE (i.e., 4,5,6-tribromo-2-(2',4'-dibromophenoxy)phenol; termed P01F08). It has been known since 1995 that P01F08 exhibits anticancer activity, but the detailed mechanism remains poorly understood. Only recently, Mayer and colleagues identified a therapeutic window for P01F08, specifically targeting primary malignant cells in a low µM range. To elucidate the mechanistic pathway of cell death induction, we verified and compared its cytotoxicity and apoptosis induction capacity in Ramos and Jurkat lymphoma cells. Moreover, using Jurkat cells overexpressing antiapoptotic Bcl-2, we were able to show that P01F08 induces apoptosis mainly through the intrinsic mitochondrial pathway.
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Bustamante J, Acosta L, Karadayian AG, Lores-Arnaiz S. Ketamine induced cell death can be mediated by voltage dependent calcium channels in PC12 cells. Exp Mol Pathol 2019; 111:104318. [DOI: 10.1016/j.yexmp.2019.104318] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 09/27/2019] [Accepted: 10/11/2019] [Indexed: 02/06/2023]
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Zhang W, Hou X, Huang M, Zeng X, He X, Liao Y. TDCPP protects cardiomyocytes from H2O2-induced injuries via activating PI3K/Akt/GSK3β signaling pathway. Mol Cell Biochem 2018; 453:53-64. [DOI: 10.1007/s11010-018-3431-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/16/2018] [Indexed: 10/28/2022]
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Dingemans MML, Kock M, van den Berg M. Mechanisms of Action Point Towards Combined PBDE/NDL-PCB Risk Assessment. Toxicol Sci 2018; 153:215-24. [PMID: 27672163 DOI: 10.1093/toxsci/kfw129] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
At present, human risk assessment of the structurally similar non-dioxin-like (NDL) PCBs and polybrominated diphenylethers (PBDEs) is done independently for both groups of compounds. There are however obvious similarities between NDL-PCBs and PBDEs with regard to modulation of the intracellular calcium homeostasis (basal calcium levels, voltage-gated calcium channels, calcium uptake, ryanodine receptor) and thyroid hormone (TH) homeostasis (TH levels and transport). which are mechanisms of action related to neurobehavioral effects (spontaneous activity, habituation and learning ability). There also similarities in agonistic interactions with the hepatic nuclear receptors PXR and CAR. Several effects on developmental (reproductive) processes have also been observed, but results were more dispersed and insufficient to compare both groups of compounds. The available mechanistic information is sufficient to warrant a dose addition model for NDL-PCBs and PBDEs, including their hydroxylated metabolites.Although many of the observed effects are similar from a qualitative point of view for both groups, congener or tissue specific differences have also been found. As this is a source of uncertainty in the combined hazard and risk assessment of these compounds, molecular entities involved in the observed mechanisms and adverse outcomes associated with these compounds need to be identified. The systematical generation of (quantitative) structure-activity information for NDL-PCBs and PBDEs on these targets (including potential non-additive effects) will allow a more realistic risk estimation associated with combined exposure to both groups of compounds during early life. Additional validation studies are needed to quantify these uncertainties for risk assessment of NDL-PCBs and PBDEs.
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Affiliation(s)
- Milou M L Dingemans
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Marjolijn Kock
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Martin van den Berg
- Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Chen H, Streifel KM, Singh V, Yang D, Mangini L, Wulff H, Lein PJ. From the Cover: BDE-47 and BDE-49 Inhibit Axonal Growth in Primary Rat Hippocampal Neuron-Glia Co-Cultures via Ryanodine Receptor-Dependent Mechanisms. Toxicol Sci 2018; 156:375-386. [PMID: 28003438 DOI: 10.1093/toxsci/kfw259] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Polybrominated diphenyl ethers (PBDEs) are widespread environmental contaminants associated with adverse neurodevelopmental outcomes in children and preclinical models; however, the mechanisms by which PBDEs cause developmental neurotoxicity remain speculative. The structural similarity between PBDEs and nondioxin-like (NDL) polychlorinated biphenyls (PCBs) suggests shared toxicological properties. Consistent with this, both NDL PCBs and PBDEs have been shown to stabilize ryanodine receptors (RyRs) in the open configuration. NDL PCB effects on RyR activity are causally linked to increased dendritic arborization, but whether PBDEs similarly enhance dendritic growth is not known. In this study, we quantified the effects of individual PBDE congeners on not only dendritic but also axonal growth since both are regulated by RyR-dependent mechanisms, and both are critical determinants of neuronal connectivity. Neuronal-glial co-cultures dissociated from the neonatal rat hippocampus were exposed to BDE-47 or BDE-49 in the culture medium. At concentrations ranging from 20 pM to 2 µM, neither PBDE congener altered dendritic arborization. In contrast, at concentrations ≥ 200 pM, both congeners delayed neuronal polarization resulting in significant inhibition of axonal outgrowth during the first few days in vitro. The axon inhibitory effects of these PBDE congeners occurred independent of cytotoxicity, and were blocked by pharmacological antagonism of RyR or siRNA knockdown of RyR2. These results demonstrate that the molecular and cellular mechanisms by which PBDEs interfere with neurodevelopment overlap with but are distinct from those of NDL PCBs, and suggest that altered patterns of neuronal connectivity may contribute to the developmental neurotoxicity of PBDEs.
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Affiliation(s)
- Hao Chen
- Department of Molecular Biosciences, School of Veterinary Medicine
| | - Karin M Streifel
- Department of Molecular Biosciences, School of Veterinary Medicine
| | - Vikrant Singh
- Department of Pharmacology, School of Medicine, University of California-Davis, Davis, California 95616
| | - Dongren Yang
- Department of Molecular Biosciences, School of Veterinary Medicine
| | - Linley Mangini
- Department of Molecular Biosciences, School of Veterinary Medicine
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California-Davis, Davis, California 95616
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine
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He X, Li S, Fang X, Liao Y. TDCPP protects cardiomyocytes from hypoxia-reoxygenation injury induced apoptosis through mitigating calcium overload and promotion GSK-3β phosphorylation. Regul Toxicol Pharmacol 2017; 92:39-45. [PMID: 29129621 DOI: 10.1016/j.yrtph.2017.11.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 11/06/2017] [Accepted: 11/08/2017] [Indexed: 10/18/2022]
Abstract
TDCPP, Tris (1, 3-dichloro-2-propyl) phosphate belongs to a group of chemicals known as triester organophosphate flame retardants, It can alter calcium homeostasis at much lower concentrations in normal conditions, but the mechanism is unclear till now. Calcium overload is a leading cause of apoptosis in myocardial ischemia/reperfusion (I/R) injury, thus how to mitigate Ca2+-overload is deserved to be investigated. We therefore hypothesized that TDCPP could attenuate cardiomyocytes apoptosis in I/R injury. H/R (hypoxia/reoxygenation) experiments in vitro were used to simulate in vivo I/R injury. The present study aimed to explore the potential effect of TDCPP in cardiomyocytes after H/R injury, Ca2+ imaging technique was used to explore SOCE(store-operated calcium entry) and Ca2+-overload levels, western blot technique was used to explore the potential target, the cell morphology, cell viability and mitochondrial membrane potential were also detected. The results have shown that: TDCPP could decrease SOCE, restore H9c2 cell viability, mitigate Ca2+-overload in H/R injury and reduce the mitochondrial membrane potential. Furthermore, TDCPP decreased STIM1 expression and promoted GSK3β phosphorylation. Collectively, for the first time, this study suggest the antiapoptosis roles of TDCPP in H/R injury are via mitigation Ca2+-overload and promoting GSK-3β phosphorylation.
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Affiliation(s)
- Xiju He
- Department of Anatomy, Hubei University of Medicine, Shiyan, Hubei 442000, China; Department of Anatomy, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
| | - Shoutian Li
- Department of Anatomy, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
| | - Xiaoxia Fang
- Department of Neurology, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, 42000, China.
| | - Yanhong Liao
- Department of Anatomy, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
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Wong S, Giulivi C. Autism, Mitochondria and Polybrominated Diphenyl Ether Exposure. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2017; 15:614-23. [PMID: 27071785 DOI: 10.2174/1871527315666160413122624] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/29/2015] [Accepted: 01/09/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND Autism spectrum disorders (ASD) are a growing concern with more than 1 in every 68 children affected in the United States by age 8. Limited scientific advances have been made regarding the etiology of autism, with general agreement that both genetic and environmental factors contribute to this disorder. OBJECTIVE To explore the link between exposure to PBDE, mitochondrial dysfunction and autism risk. RESULTS Perinatal exposures to PBDEs may contribute to the etiology or morbidity of ASD including mitochondrial dysfunction based on (i) their increased environmental abundance and human exposures, (ii) their activity towards implicated in neuronal development and synaptic plasticity including mitochondria, and (iii) their bioaccumulation in mitochondria. CONCLUSION In this review, we propose that PBDE, and possibly other environmental exposures, during child development can induce or compound mitochondrial dysfunction, which in conjunction with a dysregulated antioxidant response, increase a child's susceptibility of autism.
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Affiliation(s)
| | - Cecilia Giulivi
- University of California, Department of Molecular Biosciences, 1089 Veterinary Medicine Dr., 3009 VetMed3B, Davis, CA 95616, USA.
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Human Excretion of Polybrominated Diphenyl Ether Flame Retardants: Blood, Urine, and Sweat Study. BIOMED RESEARCH INTERNATIONAL 2017; 2017:3676089. [PMID: 28373979 PMCID: PMC5360950 DOI: 10.1155/2017/3676089] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 02/26/2017] [Indexed: 01/17/2023]
Abstract
Commonly used as flame retardants, polybrominated diphenyl ethers (PBDEs) are routinely detected in the environment, animals, and humans. Although these persistent organic pollutants are increasingly recognized as having serious health implications, particularly for children, this is the first study, to our knowledge, to investigate an intervention for human elimination of bioaccumulated PBDEs. Objectives. To determine the efficacy of blood, urine, and perspiration as PBDE biomonitoring mediums; assess excretion of five common PBDE congeners (28, 47, 99, 100, and 153) in urine and perspiration; and explore the potential of induced sweating for decreasing bioaccumulated PBDEs. Results. PBDE congeners were not found in urine samples; findings focus on blood and perspiration. 80% of participants tested positive in one or more body fluids for PBDE 28, 100% for PBDE 47, 95% for PBDE 99, and 90% for PBDE 100 and PBDE 153. Induced perspiration facilitated excretion of the five congeners, with different rates of excretion for different congeners. Conclusion. Blood testing provides only a partial understanding of human PBDE bioaccumulation; testing of both blood and perspiration provides a better understanding. This study provides important baseline evidence for regular induced perspiration as a potential means for therapeutic PBDE elimination. Fetotoxic and reproductive effects of PBDE exposure highlight the importance of further detoxification research.
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Validation of a novel and rapid method for the simultaneous determination of some phenolic organohalogens in human serum by GC–MS. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1036-1037:66-75. [DOI: 10.1016/j.jchromb.2016.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/23/2016] [Accepted: 10/02/2016] [Indexed: 11/15/2022]
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Marchitti SA, Mazur CS, Dillingham CM, Rawat S, Sharma A, Zastre J, Kenneke JF. Inhibition of the Human ABC Efflux Transporters P-gp and BCRP by the BDE-47 Hydroxylated Metabolite 6-OH-BDE-47: Considerations for Human Exposure. Toxicol Sci 2016; 155:270-282. [PMID: 28031414 DOI: 10.1093/toxsci/kfw209] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
High body burdens of polybrominated diphenyl ethers (PBDEs) in infants and young children have led to increased concern over their potential impact on human development. PBDE exposure can alter the expression of genes involved in thyroid homeostasis, including those of ATP-binding cassette (ABC) transporters, which mediate cellular xenobiotic efflux. However, little information exists on how PBDEs interact with ABC transporters such as P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). The purpose of this study was to evaluate the interactions of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and its hydroxylated metabolite 6-OH-BDE-47 with P-gp and BCRP, using human MDR1- and BCRP-expressing membrane vesicles and stably transfected NIH-3T3-MDR1 and MDCK-BCRP cells. In P-gp membranes, BDE-47 did not affect P-gp activity; however, 6-OH-BDE-47 inhibited P-gp activity at low µM concentrations (IC50 = 11.7 µM). In BCRP membranes, BDE-47 inhibited BCRP activity; however, 6-OH-BDE-47 was a stronger inhibitor [IC50 = 45.9 µM (BDE-47) vs. IC50 = 9.4 µM (6-OH-BDE-47)]. Intracellular concentrations of known P-gp and BCRP substrates [(3H)-paclitaxel and (3H)-prazosin, respectively] were significantly higher (indicating less efflux) in NIH-3T3-MDR1 and MDCK-BCRP cells in the presence of 6-OH-BDE-47, but not BDE-47. Collectively, our results indicate that the BDE-47 metabolite 6-OH-BDE-47 is an inhibitor of both P-gp and BCRP efflux activity. These findings suggest that some effects previously attributed to BDE-47 in biological systems may actually be due to 6-OH-BDE-47. Considerations for human exposure are discussed.
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Affiliation(s)
- Satori A Marchitti
- U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, Georgia 30605
| | - Christopher S Mazur
- U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, Georgia 30605
| | - Caleb M Dillingham
- U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, Georgia 30605
| | - Swati Rawat
- U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, Georgia 30605
| | - Anshika Sharma
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia 30602
| | - Jason Zastre
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia 30602
| | - John F Kenneke
- U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, Georgia 30605;
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16
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The Pivotal Role of Ca 2+ Homeostasis in PBDE-47-Induced Neuronal Apoptosis. Mol Neurobiol 2015; 53:7078-7088. [PMID: 26676572 DOI: 10.1007/s12035-015-9573-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 11/29/2015] [Indexed: 10/22/2022]
Abstract
Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants and are ubiquitous in the environment and human tissues. Recent evidence has demonstrated that PBDE-induced neurotoxicity is associated with neuronal apoptosis via interfering with the calcium ion (Ca2+) homeostasis; however, the underlying mechanisms remain elusive. Thus, we sought to investigate the role of Ca2+ homeostasis in PBDE-47-induced neuronal apoptosis. Here, we showed that PBDE-47 significantly decreased neuronal number while increased neuronal apoptosis in vitro and in vivo, as manifested by an increased percentage of Annexin V-positive staining cells and caspase-3 activation in human neuroblastoma SH-SY5Y cells and hippocampal neurons of rats. Further study identified that PBDE-47 elicited ΔΨm collapse following an early and sustained [Ca2+] i, overload, as well as stimulated cytochrome c release from mitochondria into the cytosol in SH-SY5Y cells and rat hippocampal tissue. Interestingly, the extracellular Ca2+ chelator ethylene glycol-bis (2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) blocked PBDE-47-induced [Ca2+] i elevation, ΔΨm collapse, cytochrome c release, and caspase-3 activation in SH-SY5Y cells, whereas the intracellular Ca2+ chelator 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM) had no influences on them, indicating that the [Ca2+] i overload originates primarily from extracellular Ca2+ component rather than from intracellular calcium storage and that the increase in [Ca2+] i is a major contributor to ΔΨm collapse and subsequent neuronal apoptosis. Overall, these findings suggest that PBDE-47 affects Ca2+ homeostasis as a crucial event in activation of neuronal death associated with mitochondria and provide novel insight into the mechanism of action underlying PBDE neurotoxicity.
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17
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Macaulay LJ, Chen A, Rock KD, Dishaw LV, Dong W, Hinton DE, Stapleton HM. Developmental toxicity of the PBDE metabolite 6-OH-BDE-47 in zebrafish and the potential role of thyroid receptor β. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2015; 168:38-47. [PMID: 26433919 PMCID: PMC4618599 DOI: 10.1016/j.aquatox.2015.09.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 09/14/2015] [Accepted: 09/15/2015] [Indexed: 05/13/2023]
Abstract
6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (6-OH-BDE-47) is both a polybrominated diphenyl ether (PBDE) flame retardant metabolite and a marine natural product. It has been identified both as a neurotoxicant in cell-based studies and as a developmental toxicant in zebrafish. However, hydroxylated PBDE metabolites are also considered thyroid hormone disruptors due to their structural similarity to endogenous thyroid hormones. The purpose of this study was to evaluate the effects of 6-OH-BDE-47 on a developmental pathway regulated by thyroid hormones in zebrafish. Morphological measurements of development (head trunk angle, otic vesicle length, and eye pigmentation) were recorded in embryos at 30h post fertilization (hpf) and detailed craniofacial morphology was examined in 4 day old larvae using cartilage staining. Exposure to 6-OH-BDE-47 resulted in severe developmental delays. A 100nM concentration resulted in a 26% decrease in head trunk angle, a 54% increase in otic vesicle length, and a 42% decrease in eye pigmentation. Similarly, altered developmental morphology was observed following thyroid receptor β morpholino knockdown, exposure to the thyroid hormone triiodothyronine (T3) or to thyroid disrupting chemicals (TDC; iopanoic acid and propylthiouracil). The threshold for lower jaw deformities and craniofacial cartilage malformations was at doses greater than 50nM. Of interest, these developmental delays and effects were rescued by microinjection of TRβ mRNA during the 1-2 cell stage. These data indicate that OH-BDEs can adversely affect early life development of zebrafish and suggest they may be impacting thyroid hormone regulation in vivo through downregulation of the thyroid hormone receptor.
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Affiliation(s)
- Laura J Macaulay
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Albert Chen
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Kylie D Rock
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Laura V Dishaw
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Wu Dong
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - David E Hinton
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
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18
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Butryn DM, Gross MS, Chi LH, Schecter A, Olson JR, Aga DS. "One-shot" analysis of polybrominated diphenyl ethers and their hydroxylated and methoxylated analogs in human breast milk and serum using gas chromatography-tandem mass spectrometry. Anal Chim Acta 2015; 892:140-7. [PMID: 26388484 PMCID: PMC4589300 DOI: 10.1016/j.aca.2015.08.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/21/2015] [Accepted: 08/08/2015] [Indexed: 11/19/2022]
Abstract
The presence of polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH-BDE) and methoxylated (MeO-BDE) analogs in humans is an area of high interest to scientists and the public due to their neurotoxic and endocrine disrupting effects. Consequently, there is a rise in the investigation of the occurrence of these three classes of compounds together in environmental matrices and in humans in order to understand their bioaccumulation patterns. Analysis of PBDEs, OH-BDEs, and MeO-BDEs using liquid chromatography-mass spectrometry (LC-MS) can be accomplished simultaneously, but detection limits for PBDEs and MeO-BDEs in LC-MS is insufficient for trace level quantification. Therefore, fractionation steps of the phenolic (OH-BDEs) and neutral (PBDEs and MeO-BDEs) compounds during sample preparation are typically performed so that different analytical techniques can be used to achieve the needed sensitivities. However, this approach involves multiple injections, ultimately increasing analysis time. In this study, an analytical method was developed for a "one-shot" analysis of 12 PBDEs, 12 OH-BDEs, and 13 MeO-BDEs using gas chromatography with tandem mass spectrometry (GC-MS/MS). This overall method includes simultaneous extraction of all analytes via pressurized liquid extraction followed by lipid removal steps to reduce matrix interferences. The OH-BDEs were derivatized using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (TBDMS-MTFA), producing OH-TBDMS derivatives that can be analyzed together with PBDEs and MeO-BDEs by GC-MS/MS in "one shot" within a 25-min run time. The overall recoveries were generally higher than 65%, and the limits of detection ranged from 2 to 14 pg in both breast milk and serum matrices. The applicability of the method was successfully validated on four paired human breast milk and serum samples. The mean concentrations of total PBDEs, OH-BDEs, and MeO-BDEs in breast milk were 59, 2.2, and 0.57 ng g(-1) lipid, respectively. In serum, the mean total concentrations were 79, 38, and 0.96 ng g(-1) lipid, respectively, exhibiting different distribution profiles from the levels detected in breast milk. This "one-shot" GC-MS/MS method will prove useful and cost-effective in large-scale studies needed to further understand the partitioning behavior, and ultimately the adverse health effects, of these important classes of brominated flame retardants in humans.
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Affiliation(s)
- Deena M Butryn
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Michael S Gross
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Lai-Har Chi
- Department of Pharmacology and Toxicology, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA; Department of Epidemiology and Environmental Health, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA
| | - Arnold Schecter
- Department of Pharmacology and Toxicology, University of Louisville College of Medicine, Louisville, KY 40202, USA
| | - James R Olson
- Department of Pharmacology and Toxicology, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA; Department of Epidemiology and Environmental Health, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA
| | - Diana S Aga
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
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19
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Meijer M, Brandsema JAR, Nieuwenhuis D, Wijnolts FMJ, Dingemans MML, Westerink RHS. Inhibition of Voltage-Gated Calcium Channels After Subchronic and Repeated Exposure of PC12 Cells to Different Classes of Insecticides. Toxicol Sci 2015; 147:607-17. [PMID: 26187449 DOI: 10.1093/toxsci/kfv154] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We previously demonstrated that acute inhibition of voltage-gated calcium channels (VGCCs) is a common mode of action for (sub)micromolar concentrations of chemicals, including insecticides. However, because human exposure to chemicals is usually chronic and repeated, we investigated if selected insecticides from different chemical classes (organochlorines, organophosphates, pyrethroids, carbamates, and neonicotinoids) also disturb calcium homeostasis after subchronic (24 h) exposure and after a subsequent (repeated) acute exposure. Effects on calcium homeostasis were investigated with single-cell fluorescence (Fura-2) imaging of PC12 cells. Cells were depolarized with high-K(+) saline to study effects of subchronic or repeated exposure on VGCC-mediated Ca(2+) influx. The results demonstrate that except for carbaryl and imidacloprid, all selected insecticides inhibited depolarization (K(+))-evoked Ca(2+) influx after subchronic exposure (IC50's: approximately 1-10 µM) in PC12 cells. These inhibitory effects were not or only slowly reversible. Moreover, repeated exposure augmented the inhibition of the K(+)-evoked increase in intracellular calcium concentration induced by subchronic exposure to cypermethrin, chlorpyrifos, chlorpyrifos-oxon, and endosulfan (IC50's: approximately 0.1-4 µM). In rat primary cortical cultures, acute and repeated chlorpyrifos exposure also augmented inhibition of VGCCs compared with subchronic exposure. In conclusion, compared with subchronic exposure, repeated exposure increases the potency of insecticides to inhibit VGCCs. However, the potency of insecticides to inhibit VGCCs upon repeated exposure was comparable with the inhibition previously observed following acute exposure, with the exception of chlorpyrifos. The data suggest that an acute exposure paradigm is sufficient for screening chemicals for effects on VGCCs and that PC12 cells are a sensitive model for detection of effects on VGCCs.
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Affiliation(s)
- Marieke Meijer
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Joske A R Brandsema
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Desirée Nieuwenhuis
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Fiona M J Wijnolts
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Milou M L Dingemans
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Remco H S Westerink
- Neurotoxicology Research Group, Toxicology Division, Faculty of Veterinary Medicine, Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, The Netherlands
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20
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Human hydroxylated metabolites of BDE-47 and BDE-99 are glucuronidated and sulfated in vitro. Toxicol Lett 2015; 236:98-109. [DOI: 10.1016/j.toxlet.2015.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 04/29/2015] [Accepted: 05/04/2015] [Indexed: 11/24/2022]
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21
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Macaulay LJ, Bailey JM, Levin ED, Stapleton HM. Persisting effects of a PBDE metabolite, 6-OH-BDE-47, on larval and juvenile zebrafish swimming behavior. Neurotoxicol Teratol 2015; 52:119-26. [PMID: 25979796 DOI: 10.1016/j.ntt.2015.05.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 04/30/2015] [Accepted: 05/04/2015] [Indexed: 12/09/2022]
Abstract
Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that are widely detected in the environment, biota, and humans. In mammals, PBDEs can be oxidatively metabolized to form hydroxylated polybrominated diphenyl ethers (OH-BDEs). While studies have examined behavioral deficits or alterations induced by exposure to PBDEs in both rodents and fish, no study to date has explored behavioral effects from exposure to OH-BDEs, which have been shown to have greater endocrine disrupting potential compared to PBDEs. In the present study, zebrafish (Danio rerio) were exposed during embryonic and larval development (0-6 days post fertilization, dpf) to a PBDE metabolite, 6-hydroxy, 2,2',4,4' tetrabromodiphenyl ether (10-50 nM) and then examined for short and long-term behavioral effects. Exposed zebrafish tested as larvae (6 dpf) showed an altered swimming response to light-dark transitions, exhibiting hypoactivity in light periods compared to control fish. When fish exposed from 0-6 dpf were tested as juveniles (45 dpf), they showed an increased fear response and hyperactivity in response to tests of novel environment exploration and habituation learning. These results demonstrate that early life exposure to a PBDE metabolite can have immediate or later life (more than a month after exposure) effects on activity levels, habituation, and fear/anxiety.
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Affiliation(s)
- Laura J Macaulay
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Jordan M Bailey
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA
| | - Edward D Levin
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA; Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA
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22
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The brominated flame retardant BDE-47 causes oxidative stress and apoptotic cell death in vitro and in vivo in mice. Neurotoxicology 2015; 48:68-76. [PMID: 25797475 DOI: 10.1016/j.neuro.2015.03.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/11/2015] [Accepted: 03/11/2015] [Indexed: 12/14/2022]
Abstract
Polybrominated diphenyl ethers (PBDEs), used for decades as flame retardants, have become widespread environmental contaminants. Exposure is believed to occur primarily through diet and dust, and infants and toddlers have the highest body burden, raising concern for potential developmental neurotoxicity. The exact mechanisms of PBDE neurotoxicity have not been elucidated, but two relevant modes of action relate to impairment of thyroid hormone homeostasis and to direct effects on brain cells causing alterations in signal transduction, oxidative stress and apoptotic cell death. The present study shows that BDE-47 (2,2',4,4'-tetrabromodiphenyl ether) induces oxidative stress and ensuing apoptotic cell death in mouse cerebellar granule neurons in vitro. Similarly, in vivo administration of BDE-47, according to an exposure protocol shown to induce behavioral and biochemical alterations (10mg/kg, per os on post-natal day 10), induces oxidative stress and apoptosis, without altering serum levels of thyroid hormones. The effects of BDE-47 both in vitro and in vivo were more pronounced in a mouse model lacking the modifier subunit of glutamate cysteine ligase (GCLM) which results in reduced anti-oxidant capability due to low levels of GSH. Concentrations of BDE-47 in brain were in the mid-nanomolar range. These findings indicate that effects observed with BDE-47 in vitro are also present after in vivo administration, suggesting that in addition to potential endocrine effects, which were not seen here, direct interactions with brain cells should be considered as a potential mechanism of BDE-47 neurotoxicity.
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23
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Gross MS, Butryn DM, McGarrigle BP, Aga DS, Olson JR. Primary role of cytochrome P450 2B6 in the oxidative metabolism of 2,2',4,4',6-pentabromodiphenyl ether (BDE-100) to hydroxylated BDEs. Chem Res Toxicol 2015; 28:672-81. [PMID: 25629761 DOI: 10.1021/tx500446c] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human exposure to polybrominated diphenyl ethers (PBDEs) through various routes poses deleterious health effects. PBDEs are biotransformed into hydroxylated metabolites (OH-BDEs) via cytochrome P450s (P450s), which may add to their neurotoxic effects. This study characterizes the in vitro metabolism of 2,2',4,4',6-pentabromodiphenyl ether (BDE-100), one of the most abundant PBDE congeners found in humans, by recombinant human P450s and pooled human liver microsomes (HLMs). Ten recombinant P450s were individually incubated with BDE-100 to monitor P450-specific metabolism. P450 2B6 was found to be the predominant enzyme responsible for nearly all formation of six mono-OH-pentaBDE and two di-OH-pentaBDE metabolites. Four metabolites were identified as 3-hydroxy-2,2',4,4',6-pentabromodiphenyl ether (3-OH-BDE-100), 5'-hydroxy-2,2',4,4',6-pentabromodiphenyl ether (5'-OH-BDE-100), 6'-hydroxy-2,2',4,4',6-pentabromodiphenyl ether (6'-OH-BDE-100), and 4'-hydroxy-2,2',4,5',6-pentabromodiphenyl ether (4'-OH-BDE-103) through use of reference standards. The two remaining mono-OH-pentaBDE metabolites were hypothesized using mass spectral fragmentation characteristics of derivatized OH-BDEs, which allowed prediction of an ortho-OH-pentaBDE and a para-OH-pentaBDE positional isomer. Additional information based on theoretical boiling point calculations using COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) and experimental chromatographic retention times were used to identify the hypothesized metabolites as 2'-hydroxy-2,3',4,4',6-pentabromodiphenyl ether (2'-OH-BDE-119) and 4-hydroxy-2,2',4',5,6-pentabromodiphenyl ether (4-OH-BDE-91), respectively. Kinetic studies of BDE-100 metabolism using P450 2B6 and HLMs revealed Km values ranging from 4.9 to 7.0 μM and 6-10 μM, respectively, suggesting a high affinity toward the formation of OH-BDEs. Compared to the metabolism of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) reported in previous studies, BDE-100 appears to be more slowly metabolized by P450s due to the presence of a third ortho-substituted bromine atom.
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Affiliation(s)
- Michael S Gross
- †Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Deena M Butryn
- †Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Barbara P McGarrigle
- ‡Department of Pharmacology and Toxicology and Department of Epidemiology and Environmental Health, University at Buffalo, The State University of New York, Buffalo, New York 14214, United States
| | - Diana S Aga
- †Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - James R Olson
- ‡Department of Pharmacology and Toxicology and Department of Epidemiology and Environmental Health, University at Buffalo, The State University of New York, Buffalo, New York 14214, United States
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24
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Costa LG, de Laat R, Tagliaferri S, Pellacani C. A mechanistic view of polybrominated diphenyl ether (PBDE) developmental neurotoxicity. Toxicol Lett 2014; 230:282-94. [PMID: 24270005 PMCID: PMC4028440 DOI: 10.1016/j.toxlet.2013.11.011] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/12/2013] [Indexed: 01/01/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs), extensively used in the past few decades as flame retardants in a variety of consumer products, have become world-wide persistent environmental pollutants. Levels in North America are usually higher than those in Europe and Asia, and body burden is 3-to-9-fold higher in infants and toddlers than in adults. The latter has raised concern for potential developmental toxicity and neurotoxicity of PBDEs. Experimental studies in animals and epidemiological observations in humans suggest that PBDEs may be developmental neurotoxicants. Pre- and/or post-natal exposure to PBDEs may cause long-lasting behavioral abnormalities, particularly in the domains of motor activity and cognition. The mechanisms underlying the developmental neurotoxic effects of PBDEs are not known, though several hypotheses have been put forward. One general mode of action relates to the ability of PBDEs to impair thyroid hormone homeostasis, thus indirectly affecting the developing brain. An alternative or additional mode of action involves a direct effect of PBDEs on nervous system cells; PBDEs can cause oxidative stress-related damage (DNA damage, mitochondrial dysfunction, apoptosis), and interfere with signal transduction (particularly calcium signaling), and with neurotransmitter systems. Important issues such as bioavailability and metabolism of PBDEs, extrapolation of results to low level of exposures, and the potential effects of interactions among PBDE congeners and between PBDEs and other contaminants also need to be taken into account.
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Affiliation(s)
- Lucio G Costa
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, USA; Department of Neuroscience, University of Parma, Parma, Italy.
| | - Rian de Laat
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, USA
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25
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Meijer M, Hamers T, Westerink RH. Acute disturbance of calcium homeostasis in PC12 cells as a novel mechanism of action for (sub)micromolar concentrations of organophosphate insecticides. Neurotoxicology 2014; 43:110-116. [DOI: 10.1016/j.neuro.2014.01.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 01/02/2014] [Accepted: 01/18/2014] [Indexed: 12/26/2022]
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26
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Meijer M, Dingemans MML, van den Berg M, Westerink RHS. Inhibition of voltage-gated calcium channels as common mode of action for (mixtures of) distinct classes of insecticides. Toxicol Sci 2014; 141:103-11. [PMID: 24913802 DOI: 10.1093/toxsci/kfu110] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Humans are exposed to distinct structural classes of insecticides with different neurotoxic modes of action. Because calcium homeostasis is essential for proper neuronal function and development, we investigated the effects of insecticides from different classes (pyrethroid: (α-)cypermethrin; organophosphate: chlorpyrifos; organochlorine: endosulfan; neonicotinoid: imidacloprid) and mixtures thereof on the intracellular calcium concentration ([Ca(2+)]i). Effects of acute (20 min) exposure to (mixtures of) insecticides on basal and depolarization-evoked [Ca(2+)]i were studied in vitro with Fura-2-loaded PC12 cells and high resolution single-cell fluorescence microscopy. The data demonstrate that cypermethrin, α-cypermethrin, endosulfan, and chlorpyrifos concentration-dependently decreased depolarization-evoked [Ca(2+)]i, with 50% (IC50) at 78nM, 239nM, 250nM, and 899nM, respectively. Additionally, acute exposure to chlorpyrifos or endosulfan (10μM) induced a modest increase in basal [Ca(2+)]i, amounting to 68 ± 8nM and 53 ± 8nM, respectively. Imidacloprid did not disturb basal or depolarization-evoked [Ca(2+)]i at 10μM. Following exposure to binary mixtures, effects on depolarization-evoked [Ca(2+)]i were within the expected effect additivity range, whereas the effect of the tertiary mixture was less than this expected additivity effect range. These results demonstrate that different types of insecticides inhibit depolarization-evoked [Ca(2+)]i in PC12 cells by inhibiting voltage-gated calcium channels (VGCCs) in vitro at concentrations comparable with human occupational exposure levels. Moreover, the effective concentrations in this study are below those for earlier described modes of action. Because inhibition of VGCCs appears to be a common and potentially additive mode of action of several classes of insecticides, this target should be considered in neurotoxicity risk assessment studies.
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Affiliation(s)
- Marieke Meijer
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Milou M L Dingemans
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Martin van den Berg
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, NL-3508 TD Utrecht, The Netherlands
| | - Remco H S Westerink
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, NL-3508 TD Utrecht, The Netherlands
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Westerink RHS. Modulation of cell viability, oxidative stress, calcium homeostasis, and voltage- and ligand-gated ion channels as common mechanisms of action of (mixtures of) non-dioxin-like polychlorinated biphenyls and polybrominated diphenyl ethers. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:6373-6383. [PMID: 23686757 DOI: 10.1007/s11356-013-1759-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 04/22/2013] [Indexed: 06/02/2023]
Abstract
Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that exert neurodevelopmental and neurobehavioral effects in vivo in humans and animals. Acute in vitro neurotoxic effects include changes in cell viability, oxidative stress, and basal intracellular calcium levels. Though these acute cellular effects could partly explain the observed in vivo effects, other mechanisms, such as effects on calcium influx and neurotransmitter receptor function, likely contribute to the disturbance in neurotransmission. This concise review combines in vitro data on cell viability, oxidative stress and basal calcium levels with recent data that clearly demonstrate that (hydroxylated) PCBs and (hydroxylated) PBDEs can exert acute effects on voltage-gated Ca(2+) channels as well as on excitatory and inhibitory neurotransmitter receptors in vitro. These novel mechanisms of action are shared by NDL-PCBs, OH-PBDEs, and some other persistent organic pollutants, such as tetrabromobisphenol-A, and could have profound effects on neurodevelopment, neurotransmission, and neurobehavior in vivo.
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Affiliation(s)
- Remco H S Westerink
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.177, 3508 TD, Utrecht, The Netherlands,
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Feo ML, Gross MS, McGarrigle BP, Eljarrat E, Barceló D, Aga DS, Olson JR. Biotransformation of BDE-47 to potentially toxic metabolites is predominantly mediated by human CYP2B6. ENVIRONMENTAL HEALTH PERSPECTIVES 2013; 121:440-6. [PMID: 23249762 PMCID: PMC3620761 DOI: 10.1289/ehp.1205446] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 12/17/2012] [Indexed: 05/03/2023]
Abstract
BACKGROUND Previous studies have indicated that cytochrome P450s (CYPs) are involved in the metabolism of polybrominated diphenyl ether (PBDE) flame retardants in humans, resulting in the formation of hydroxylated PBDEs (OH-PBDEs) that are potentially more toxic than the parent PBDEs. However, the specific enzymes responsible for the formation of OH-PBDEs are unknown. OBJECTIVES The purposes of this study were to characterize the in vitro metabolism of 2,2´,4,4´-tetrabromodiphenyl ether (BDE-47) by human liver microsomes (HLM) and recombinant human CYPs, and to identify the CYP(s) that are active in the oxidative metabolism of BDE-47. METHODS Recombinant human CYPs (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4) were incubated with BDE-47 (20 µM), and the metabolites were measured and characterized using gas chromatography with tandem mass spectrometry (GC-MS/MS). For kinetic studies, CYP2B6 and pooled human liver microsomes (HLMs) were incubated with BDE-47 (0-60 µM). RESULTS CYP2B6 was the predominant CYP capable of forming six OH-BDEs, including 3-OH-BDE-47, 5-OH-BDE-47, 6-OH-BDE-47, 4-OH-BDE-42, 4´-OH-BDE-49, and a metabolite tentatively identified as 2´-OH-BDE-66. On the basis of full-scan GC-MS analysis, we hypothesized the formation of two other metabolites: di-OH-tetra-BDE and di-OH-tetrabrominated dioxin. In kinetic studies of BDE-47 metabolism by CYP2B6 and pooled HLMs, we found Km values ranging from 3.8 to 6.4 µM and 7.0 to 11.4 µM, respectively, indicating the high affinity toward the formation of OH-BDEs. CONCLUSION Our findings support a predominant role of CYP2B6 in the metabolism of BDE-47 to potentially toxic metabolites, including a hypothesized di-OH-tetrabrominated dioxin metabolite. These results will assist future epidemiological studies investigating the potential of PBDEs and their metabolites to produce neurobehavioral/neurodevelopmental disorders.
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Affiliation(s)
- Maria Luisa Feo
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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Slotkin TA, Card J, Infante A, Seidler FJ. BDE99 (2,2',4,4',5-pentabromodiphenyl ether) suppresses differentiation into neurotransmitter phenotypes in PC12 cells. Neurotoxicol Teratol 2013; 37:13-7. [PMID: 23422510 DOI: 10.1016/j.ntt.2013.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 01/23/2013] [Accepted: 02/02/2013] [Indexed: 11/29/2022]
Abstract
Early-life exposures to brominated diphenyl ethers (BDEs) lead to neurobehavioral abnormalities later in life. Although these agents are thyroid disruptors, it is not clear whether this mechanism alone accounts for the adverse effects. We evaluated the impact of 2,2',4,4',5-pentabromodiphenyl ether (BDE99) on PC12 cells undergoing neurodifferentiation, contrasting the effects with chlorpyrifos, a known developmental neurotoxicant. BDE99 elicited decrements in the number of cells, evidenced by a reduction in DNA levels, to a lesser extent than did chlorpyrifos. This did not reflect cytotoxicity from oxidative stress, since cell enlargement, monitored by the total protein/DNA ratio, was not only unimpaired by BDE99, but was actually enhanced. Importantly, BDE99 impaired neurodifferentiation into both the dopamine and acetylcholine neurotransmitter phenotypes. The cholinergic phenotype was affected to a greater extent, so that neurotransmitter fate was diverted away from acetylcholine and toward dopamine. Chlorpyrifos produced the same imbalance, but through a different underlying mechanism, promoting dopaminergic development at the expense of cholinergic development. In our earlier work, we did not find these effects with BDE47, a BDE that has greater endocrine disrupting and cytotoxic effects than BDE99. Thus, our results point to interference with neurodifferentiation by specific BDE congeners, distinct from cytotoxic or endocrine mechanisms.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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Napoli E, Hung C, Wong S, Giulivi C. Toxicity of the flame-retardant BDE-49 on brain mitochondria and neuronal progenitor striatal cells enhanced by a PTEN-deficient background. Toxicol Sci 2013; 132:196-210. [PMID: 23288049 DOI: 10.1093/toxsci/kfs339] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Polybrominated diphenyl ethers (PBDEs) represent an important group of flame retardants extensively used, tonnage of which in the environment has been steadily increasing over the past 25 years. PBDEs or metabolites can induce neurotoxicity and mitochondrial dysfunction (MD) through a variety of mechanisms. Recently, PBDEs with < 5 Br substitutions (i.e., 2,2',4,4'-tetrabromodiphenyl ether [BDE-47] and 2,2',4,5'-tetrabromodiphenyl ether [BDE-49]) have gained interest because of their high bioaccumulation. In particular, congeners such as BDE-49 arise as one of the most biologically active, with concentrations typically lower than those observed for BDE-47 in biological tissues; however, its potential to cause MD at biologically relevant concentrations is unknown. To this end, the effect of BDE-49 was studied in brain mitochondria and neuronal progenitor striatal cells (NPC). BDE-49 uncoupled mitochondria at concentrations < 0.1 nM, whereas at > 1 nM, it inhibited the electron transport at Complex V (mixed type inhibition; IC(50) = 6 nM) and Complex IV (noncompetitive inhibition; IC(50) = 40 nM). These concentrations are easily achieved in plasma concentrations considering that BDE-49 (this study, 400-fold) and other PBDEs accumulate 1-3 orders of magnitude in the cells, particularly in mitochondria and microsomes. Similar effects were observed in NPC and exacerbated with PTEN (negative modulator of the PI3K/Akt pathway) deficiency, background associated with autism-like behavior, schizophrenia, and epilepsy. PBDE-mediated MD per se or enhanced by a background that confers susceptibility to this exposure may have profound implications in the energy balance of brain.
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Affiliation(s)
- Eleonora Napoli
- Department of Molecular Biosciences, University of California, Davis, CA, USA
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Stapleton HM, Eagle S, Sjödin A, Webster TF. Serum PBDEs in a North Carolina toddler cohort: associations with handwipes, house dust, and socioeconomic variables. ENVIRONMENTAL HEALTH PERSPECTIVES 2012; 120:1049-54. [PMID: 22763040 PMCID: PMC3404669 DOI: 10.1289/ehp.1104802] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 05/14/2012] [Indexed: 05/17/2023]
Abstract
BACKGROUND Polybrominated diphenyl ethers (PBDEs) are persistent, bioaccumulative, and endocrine-disrupting chemicals. OBJECTIVES We used handwipes to estimate exposure to PBDEs in house dust among toddlers and examined sex, age, breast-feeding, race, and parents' education as predictors of serum PBDEs. METHODS Eighty-three children from 12 to 36 months of age were enrolled in North Carolina between May 2009 and November 2010. Blood, handwipe, and house dust samples were collected and analyzed for PBDEs. A questionnaire was administered to collect demographic data. RESULTS PBDEs were detected in all serum samples (geometric mean for ΣpentaBDE in serum was 43.3 ng/g lipid), 98% of the handwipe samples, and 100% of the dust samples. Serum ΣpentaBDEs were significantly correlated with both handwipe and house dust ΣpentaBDE levels, but were more strongly associated with handwipe levels (r = 0.57; p < 0.001 vs. r = 0.35; p < 0.01). Multivariate model estimates revealed that handwipe levels, child's sex, child's age, and father's education accounted for 39% of the variation in serum ΣBDE3 levels (sum of BDEs 47, 99, and 100). In contrast, age, handwipe levels, and breast-feeding duration explained 39% of the variation in serum BDE 153. CONCLUSIONS Our study suggests that hand-to-mouth activity may be a significant source of exposure to PBDEs. Furthermore, age, socioeconomic status, and breast-feeding were significant predictors of exposure, but associations varied by congener. Specifically, serum ΣBDE3 was inversely associated with socioeconomic status, whereas serum BDE-153 was positively associated with duration of breast-feeding and mother's education.
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Affiliation(s)
- Heather M Stapleton
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, USA.
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Driscoll LL, Kaplan J, Bucuvalas E, Allen H, Kraut J, Fitzpatrick J. Acute postnatal exposure to the pentaBDE commercial mixture DE-71 at 5 or 15mg/kg/day does not produce learning or attention deficits in rats. Neurotoxicol Teratol 2012; 34:20-6. [DOI: 10.1016/j.ntt.2011.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 09/30/2011] [Accepted: 10/03/2011] [Indexed: 10/16/2022]
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Altered cardiovascular reactivity and osmoregulation during hyperosmotic stress in adult rats developmentally exposed to polybrominated diphenyl ethers (PBDEs). Toxicol Appl Pharmacol 2011; 256:103-13. [DOI: 10.1016/j.taap.2011.07.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 07/19/2011] [Accepted: 07/21/2011] [Indexed: 11/23/2022]
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Dingemans MML, van den Berg M, Westerink RHS. Neurotoxicity of brominated flame retardants: (in)direct effects of parent and hydroxylated polybrominated diphenyl ethers on the (developing) nervous system. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:900-7. [PMID: 21245014 PMCID: PMC3223008 DOI: 10.1289/ehp.1003035] [Citation(s) in RCA: 243] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 01/18/2011] [Indexed: 05/17/2023]
Abstract
BACKGROUND/OBJECTIVE Polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH-) or methoxylated forms have been detected in humans. Because this raises concern about adverse effects on the developing brain, we reviewed the scientific literature on these mechanisms. DATA SYNTHESIS Many rodent studies reported behavioral changes after developmental, neonatal, or adult exposure to PBDEs, and other studies documented subtle structural and functional alterations in brains of PBDE-exposed animals. Functional effects have been observed on synaptic plasticity and the glutamate-nitric oxide-cyclic guanosine monophosphate pathway. In the brain, changes have been observed in the expression of genes and proteins involved in synapse and axon formation, neuronal morphology, cell migration, synaptic plasticity, ion channels, and vesicular neurotransmitter release. Cellular and molecular mechanisms include effects on neuronal viability
(via apoptosis and oxidative stress), neuronal differentiation and migration, neurotransmitter release/uptake, neurotransmitter receptors and ion channels, calcium (Ca²⁺) homeostasis, and intracellular signaling pathways. DISCUSSION Bioactivation of PBDEs by hydroxylation has been observed for several endocrine end points. This has also been observed for mechanisms related to neurodevelopment, including binding to thyroid hormone receptors and transport proteins, disruption of Ca²⁺ homeostasis, and modulation of GABA and nicotinic acetylcholine receptor function. CONCLUSIONS The increased hazard for developmental neurotoxicity by hydroxylated (OH-)PBDEs compared with their parent congeners via direct neurotoxicity and thyroid disruption clearly warrants further investigation into a) the role of oxidative metabolism in producing active metabolites of PBDEs and their impact on brain development; b) concentrations of parent and OH-PBDEs in the brain; and c) interactions between different environmental contaminants during exposure to mixtures, which may increase neurotoxicity.
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Affiliation(s)
- Milou M L Dingemans
- Neurotoxicology Research Group, Toxicology Division, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
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Kim KH, Bose DD, Ghogha A, Riehl J, Zhang R, Barnhart CD, Lein PJ, Pessah IN. Para- and ortho-substitutions are key determinants of polybrominated diphenyl ether activity toward ryanodine receptors and neurotoxicity. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:519-26. [PMID: 21106467 PMCID: PMC3080935 DOI: 10.1289/ehp.1002728] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 11/24/2010] [Indexed: 05/17/2023]
Abstract
BACKGROUND Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants that bioaccumulate in human tissues. Their neurotoxicity involves dysregulation of calcium ion (Ca(2+))signaling; however, specific mechanisms have yet to be defined. OBJECTIVE We aimed to define the structure-activity relationship (SAR) for PBDEs and their metabolites toward ryanodine receptors type 1 (RyR1) and type 2 (RyR2) and to determine whether it predicts neurotoxicity. METHODS We analyzed [3H]ryanodine binding, microsomal Ca(2+) fluxes, cellular measurements of Ca(2+) homeostasis, and neurotoxicity to define mechanisms and specificity of PBDE-mediated Ca(2+) dysregulation. RESULTS PBDEs possessing two ortho-bromine substituents and lacking at least one para-bromine substituent (e.g., BDE-49) activate RyR1 and RyR2 with greater efficacy than corresponding congeners with two para-bromine substitutions (e.g., BDE-47). Addition of a methoxy group in the free para position reduces the activity of parent PBDEs. The hydroxylated BDEs 6-OH-BDE-47 and 4´-OH-BDE-49 are biphasic RyR modulators. Pretreatment of HEK293 cells (derived from human embryonic kidney cells) expressing either RyR1 or RyR2 with BDE-49 (250 nM) sensitized Ca2+ flux triggered by RyR agonists, whereas BDE-47 (250 nM) had negligible activity. The divergent activity of BDE-49, BDE-47, and 6-OH-BDE-47 toward RyRs predicted neurotoxicity in cultures of cortical neurons. CONCLUSIONS We found that PBDEs are potent modulators of RyR1 and RyR2. A stringent SAR at the ortho and para position determined whether a congener enhanced, inhibited, or exerted nonmonotonic actions toward RyRs. These results identify a convergent molecular target of PBDEs previously identified for noncoplanar polychlorinated biphenyls (PCBs) that predicts their cellular neurotoxicity and therefore could be a useful tool in risk assessment of PBDEs and related compounds.
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Affiliation(s)
- Kyung Ho Kim
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, Davis, California 95616, USA.
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Gascon M, Vrijheid M, Martínez D, Forns J, Grimalt JO, Torrent M, Sunyer J. Effects of pre and postnatal exposure to low levels of polybromodiphenyl ethers on neurodevelopment and thyroid hormone levels at 4 years of age. ENVIRONMENT INTERNATIONAL 2011; 37:605-611. [PMID: 21237513 DOI: 10.1016/j.envint.2010.12.005] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 11/22/2010] [Accepted: 12/13/2010] [Indexed: 05/29/2023]
Abstract
There are at present very few studies of the effects of polybromodiphenyl ethers (PBDEs), used as flame retardants in consumer products, on neurodevelopment or thyroid hormone levels in humans. The present study aims to examine the association between pre and postnatal PBDE concentrations and neurodevelopment and thyroid hormone levels in children at age 4years and isolate the effects of PBDEs from those of PCBs, DDT, DDE and HCB. A prospective birth cohort in Menorca (Spain) enrolled 482 pregnant mothers between 1997 and 1998. At 4years, children were assessed for motor and cognitive function (McCarthy Scales of Children's Abilities), attention-deficit, hyperactivity and impulsivity (ADHD-DSM-IV) and social competence (California Preschool Social Competence Scale). PBDE concentrations were measured in cord blood (N=88) and in serum of 4years olds (N=244). Among all congeners analyzed only PBDE 47 was quantified in a reasonable number of samples (LOQ=0.002ng/ml). Exposure to PBDE 47 was analyzed as a dichotomous variable: concentrations above the LOQ (exposed) and concentrations below (referents). Scores for cognitive and motor functions were always lower in children pre and postnatally exposed to PBDE47 than in referents, but none of these associations was statistically significant (β coefficient (95%CI) of the total cognition score: -2.7 (-7.0, 1.6) for postnatal exposure, and -1.4 (-9.2, 6.5) for prenatal exposure). Postnatal exposure to PBDE 47 was statistically significantly related to an increased risk of symptoms on the attention deficit subscale of ADHD symptoms (RR (95%CI)=1.8 (1.0, 3.2)) but not to hyperactivity symptoms. A statistically significant higher risk of poor social competence symptoms was observed as a consequence of postnatal PBDE 47 exposure (RR (95%CI)=2.6 (1.2, 5.9)). Adjustment for other organochlorine compounds did not influence the results. Levels of thyroid hormones were not associated to PBDE exposure. This study highlights the importance of assessing the effects of PBDE exposure not just prenatally but also during the early years of life. In the light of current evidence a precautionary approach towards PBDE exposure of both mothers and children seems warranted.
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Affiliation(s)
- Mireia Gascon
- Center for Research in Environmental Epidemiology (CREAL), Dr. Aiguader 88, 08003 Barcelona, Spain.
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Inman WD, Crews P. Unraveling the bastarane and isobastarane oximo amide configurations and associated macrocycle conformations: implications of their influence on bioactivities. JOURNAL OF NATURAL PRODUCTS 2011; 74:402-410. [PMID: 21214221 PMCID: PMC3064723 DOI: 10.1021/np100798q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Our rigorous re-examination of the conformational properties of bastadins that comprise the isobastarane and bastarane-type macrocycle has generated some interesting new insights. We determined that these macrocycles are flexible and possess a surprising degree of reflection symmetry that generates enantiomeric conformations. The macrocycle symmetry arises from its ability to twist in a disrotatory fashion, providing one set of conformers, and then twists with the opposite disrotation to generate a corresponding set of enantiomers. Overall, the isobastarane conformations for (E,E)-bastadin 19 (1a) are complex and can access several distinct ring conformations. In contrast, the bastarane macrocycle in bastadin 5 (2) and bastadin 6 (3) maintains a similar overall shape. We postulate that the short-term stability of the (Z)-oximo amide, an uncommon configuration found in bastadins and psammaplins, is due to the existence of conformers with intramolecular hydrogen bonds involving the (Z)-oxime, and hydrogen bonding impedes oxime isomerization to the more stable (E)-oximo amide in solution. Finally, the modeling results provided insights toward understanding the different antiproliferative activity against endothelial cells as well as Ca(2+) channel modulation activities attributed to bastaranes 2 and 3 versus isobastarane 1a.
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Affiliation(s)
- Wayne D. Inman
- To whom correspondence should be addressed. Tel.: 831-459-2603. Fax: 831-459-2935. ;
| | - Phillip Crews
- To whom correspondence should be addressed. Tel.: 831-459-2603. Fax: 831-459-2935. ;
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Ta TA, Koenig CM, Golub MS, Pessah IN, Qi L, Aronov PA, Berman RF. Bioaccumulation and behavioral effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in perinatally exposed mice. Neurotoxicol Teratol 2011; 33:393-404. [PMID: 21334437 DOI: 10.1016/j.ntt.2011.02.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 02/10/2011] [Accepted: 02/14/2011] [Indexed: 01/09/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants that have become pervasive environmental contaminants and may contribute to adverse health outcomes. We evaluated in mice the developmental neurotoxicity of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), one of the most abundant PBDE congeners detected in animal and human tissues. Female C57BL/6J mice were exposed to daily doses of 0, 0.03, 0.1 or 1mg/kg beginning 4 weeks prior to conception, continuing through gestation and lactation, and ending at weaning on postnatal day (PND) 21. Levels of BDE-47 in blood, brain, liver and adipose tissues of dams were markedly increased after 4 weeks of exposure, around the time of mating, and continued to increase through the time of parturition. Blood levels of BDE-47 in the dosed dams were within the range reported in humans. BDE-47 tissue levels in the dams decreased between parturition and weaning, possibly reflecting mobilization during lactation. Brain BDE-47 levels in the offspring at PND 1 approached those of the dams at parturition. Perinatal exposure to BDE-47 resulted in significant dose dependent growth retardation, slower motor performance in several behavioral tests, and mice exposed to 1mg/kg/day BDE-47 showed altered performance in the Morris water maze. There were no differences between groups in the numbers of pyramidal neurons in hippocampus CA1. These results document accumulation of BDE-47 in several organ systems following exposure to low-levels of BDE-47, and provide evidence that such exposure is associated with early behavioral deficits in exposed neonates.
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Affiliation(s)
- Tram Anh Ta
- Center for Children's Environmental Health, University of California-Davis, One Shields Avenue, Davis, CA 95616, United States
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Ibhazehiebo K, Iwasaki T, Kimura-Kuroda J, Miyazaki W, Shimokawa N, Koibuchi N. Disruption of thyroid hormone receptor-mediated transcription and thyroid hormone-induced Purkinje cell dendrite arborization by polybrominated diphenyl ethers. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:168-75. [PMID: 20870570 PMCID: PMC3040602 DOI: 10.1289/ehp.1002065] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 09/22/2010] [Indexed: 05/03/2023]
Abstract
BACKGROUND Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants and are becoming a ubiquitous environmental contaminant. Adverse effects in the developing brain are of great health concern. OBJECTIVE We investigated the effect of PBDEs/hydroxylated PBDEs (OH-PBDEs) on thyroid hormone (TH) receptor (TR)-mediated transcription and on TH-induced dendrite arborization of cerebellar Purkinje cells. METHODS We examined the effect of PBDEs/OH-PBDEs on TR action using a transient transfection-based reporter gene assay. TR-cofactor binding was studied by the mammalian two-hybrid assay, and TR-DNA [TH response element (TRE)] binding was examined by the liquid chemiluminescent DNA pull-down assay. Chimeric receptors generated from TR and glucocorticoid receptor (GR) were used to identify the functional domain of TR responsible for PBDE action. The change in dendrite arborization of the Purkinje cell in primary culture of newborn rat cerebellum was also examined. RESULTS Several PBDE congeners suppressed TR-mediated transcription. The magnitude of suppression correlated with that of TR-TRE dissociation. PBDEs suppressed transcription of chimeric receptors containing the TR DNA binding domain (TR-DBD). We observed no such suppression with chimeras containing GR-DBD. In the cerebellar culture, PBDE significantly suppressed TH-induced Purkinje cell dendrite arborization. CONCLUSIONS Several PBDE congeners may disrupt the TH system by partial dissociation of TR from TRE acting through TR-DBD and, consequently, may disrupt normal brain development.
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Affiliation(s)
- Kingsley Ibhazehiebo
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Toshiharu Iwasaki
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
- Address correspondence to T. Iwasaki, Department of Integrative Physiology, Division of Biological Regulations, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. Telephone: 81-27-220-7923. Fax: 81-27-220-7926. E-mail:
| | - Junko Kimura-Kuroda
- Department of Developmental Morphology, Tokyo Metropolitan Institute for Neuroscience, Tokyo, Japan
| | - Wataru Miyazaki
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Noriaki Shimokawa
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Noriyuki Koibuchi
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
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Ibhazehiebo K, Iwasaki T, Xu M, Shimokawa N, Koibuchi N. Brain-derived neurotrophic factor (BDNF) ameliorates the suppression of thyroid hormone-induced granule cell neurite extension by hexabromocyclododecane (HBCD). Neurosci Lett 2011; 493:1-7. [PMID: 21281695 DOI: 10.1016/j.neulet.2011.01.062] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 01/10/2011] [Accepted: 01/23/2011] [Indexed: 11/16/2022]
Abstract
Thyroid hormone (TH) plays an essential role in growth and differentiation of the central nervous system. Deficiency of TH during perinatal period results in abnormal brain development known as cretinism in human. We recently reported that an environmental chemical 1,2,5,6,9,10-α-hexabromocyclododecane (HBCD) suppressed TH receptor (TR)-mediated transcription. To examine the effect of HBCD on cerebellar granule cells, we used purified rat cerebellar granule cells in reaggregate culture. Low dose HBCD (10(-10)M) significantly suppressed TH-induced neurite extension of granule cell aggregate. To clarify further the mechanisms of such suppression, we added brain-derived neurotrophic factor (BDNF) into culture medium, since BDNF plays a critical role in promoting granule cell development and is regulated by TH. BDNF completely rescued HBCD-induced suppression of granule cell neurite extension in the presence of T3. These results indicate that HBCD may disrupt TH-mediated brain development at least in part due to a disruption of the T3 stimulated increase in BDNF and BDNF may possess ability to ameliorate the effect of HBCD in granule cells.
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Affiliation(s)
- Kingsley Ibhazehiebo
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan
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Is the PentaBDE replacement, tris (1,3-dichloro-2-propyl) phosphate (TDCPP), a developmental neurotoxicant? Studies in PC12 cells. Toxicol Appl Pharmacol 2011; 256:281-9. [PMID: 21255595 DOI: 10.1016/j.taap.2011.01.005] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 01/06/2011] [Accepted: 01/08/2011] [Indexed: 11/20/2022]
Abstract
Organophosphate flame retardants (OPFRs) are used as replacements for the commercial PentaBDE mixture that was phased out in 2004. OPFRs are ubiquitous in the environment and detected at high concentrations in residential dust, suggesting widespread human exposure. OPFRs are structurally similar to neurotoxic organophosphate pesticides, raising concerns about exposure and toxicity to humans. This study evaluated the neurotoxicity of tris (1,3-dichloro-2-propyl) phosphate (TDCPP) compared to the organophosphate pesticide, chlorpyrifos (CPF), a known developmental neurotoxicant. We also tested the neurotoxicity of three structurally similar OPFRs, tris (2-chloroethyl) phosphate (TCEP), tris (1-chloropropyl) phosphate (TCPP), and tris (2,3-dibromopropyl) phosphate (TDBPP), and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), a major component of PentaBDE. Using undifferentiated and differentiating PC12 cells, changes in DNA synthesis, oxidative stress, differentiation into dopaminergic or cholinergic neurophenotypes, cell number, cell growth and neurite growth were assessed. TDCPP displayed concentration-dependent neurotoxicity, often with effects equivalent to or greater than equimolar concentrations of CPF. TDCPP inhibited DNA synthesis, and all OPFRs decreased cell number and altered neurodifferentiation. Although TDCPP elevated oxidative stress, there was no adverse effect on cell viability or growth. TDCPP and TDBPP promoted differentiation into both neuronal phenotypes, while TCEP and TCPP promoted only the cholinergic phenotype. BDE-47 had no effect on cell number, cell growth or neurite growth. Our results demonstrate that different OPFRs show divergent effects on neurodifferentiation, suggesting the participation of multiple mechanisms of toxicity. Additionally, these data suggest that OPFRs may affect neurodevelopment with similar or greater potency compared to known and suspected neurotoxicants.
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Free Ca2+ as an early intracellular biomarker of exposure of cyanobacteria to environmental pollution. Anal Bioanal Chem 2010; 400:1015-29. [DOI: 10.1007/s00216-010-4209-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 09/08/2010] [Accepted: 09/08/2010] [Indexed: 10/19/2022]
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