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Wang C, An L, Wu S, Jia A, Sun J, Huang C, Mu D, Hu J. Potential Link between Equol Pollution and Field-Observed Intersex in Wild So-iuy Mullets ( Mugil soiuy). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:12393-12401. [PMID: 32876436 DOI: 10.1021/acs.est.0c04083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Gonadal intersex has been observed in wild fishes and is attributed to endocrine-disrupting chemicals but the specific causes remain controversial. Here, a forensic analysis utilizing field and laboratory studies was conducted to explore the causal agent(s). In a 2008-2009 survey of Liaodong Bay, China, 20.7-33.3% incidences of gonadal intersex were observed in male so-iuy mullets (Mugil soiuy), a wild sentinel fish species. Steroidal estrogen (estrone, 17β-estradiol, estriol, and ethinylestradiol) and phytoestrogen (equol) were detected in seawater where the fishes were collected with median concentrations of 0.42 ng/L (0.02-1.42 ng/L) E2 equivalent (EEQ-E2) and 22.81 ng/L (0.10-155.99 ng/L) equol. A probabilistic model was used to evaluate the ecological risk of these estrogenic chemicals based on their distribution in the field and dose-response relationship from the laboratory surrogate Japanese medaka (Oryzias latipes) fish. The probability of the incidences of gonadal intersex due to equol exposure was estimated to be 13.5 ± 12.1%, which is considerably higher than that for EEQ-E2, (7.2 ± 68.8) × 10-4. The agonistic activity of equol to the estrogen receptor α of so-iuy mullets was 3.5-fold higher than that to the estrogen receptor α of Japanese medaka, indicating that equol shows a stronger potential for inducing intersex in so-iuy mullets than in medaka. These results demonstrate that equol, rather than steroid estrogens, is a more likely causal agent for the field-observed intersex in male wild so-iuy mullets.
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Affiliation(s)
- Chen Wang
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Lihui An
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Shimin Wu
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Ai Jia
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Jianxian Sun
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Chong Huang
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Di Mu
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Jianying Hu
- College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
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McArdle ME, Freeman EL, Staveley JP, Ortego LS, Coady KK, Weltje L, Weyers A, Wheeler JR, Bone AJ. Critical Review of Read-Across Potential in Testing for Endocrine-Related Effects in Vertebrate Ecological Receptors. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2020; 39:739-753. [PMID: 32030793 PMCID: PMC7154679 DOI: 10.1002/etc.4682] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 12/01/2019] [Accepted: 02/03/2020] [Indexed: 05/21/2023]
Abstract
Recent regulatory testing programs have been designed to evaluate whether a chemical has the potential to interact with the endocrine system and could cause adverse effects. Some endocrine pathways are highly conserved among vertebrates, providing a potential to extrapolate data generated for one vertebrate taxonomic group to others (i.e., biological read-across). To assess the potential for biological read-across, we reviewed tools and approaches that support species extrapolation for fish, amphibians, birds, and reptiles. For each of the estrogen, androgen, thyroid, and steroidogenesis (EATS) pathways, we considered the pathway conservation across species and the responses of endocrine-sensitive endpoints. The available data show a high degree of confidence in the conservation of the hypothalamus-pituitary-gonadal axis between fish and mammals and the hypothalamus-pituitary-thyroid axis between amphibians and mammals. Comparatively, there is less empirical evidence for the conservation of other EATS pathways between other taxonomic groups, but this may be due to limited data. Although more information on sensitive pathways and endpoints would be useful, current developments in the use of molecular target sequencing similarity tools and thoughtful application of the adverse outcome pathway concept show promise for further advancement of read-across approaches for testing EATS pathways in vertebrate ecological receptors. Environ Toxicol Chem 2020;39:739-753. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.
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Affiliation(s)
| | | | | | - Lisa S. Ortego
- Environmental Safety, Bayer CropScienceChesterfieldMissouriUSA
| | - Katherine K. Coady
- Toxicology and Environmental Research and Consulting, Dow ChemicalMidlandMichiganUSA
| | - Lennart Weltje
- BASF SE, Agricultural Solutions‐EcotoxicologyLimburgerhofGermany
| | - Arnd Weyers
- Crop Science DivisionBayerMonheim am RheinGermany
| | | | - Audrey J. Bone
- Environmental Safety, Bayer CropScienceChesterfieldMissouriUSA
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3
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Ankley GT, LaLone CA, Gray LE, Villeneuve DL, Hornung MW. Evaluation of the scientific underpinnings for identifying estrogenic chemicals in nonmammalian taxa using mammalian test systems. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2016; 35:2806-2816. [PMID: 27074246 DOI: 10.1002/etc.3456] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 04/03/2016] [Accepted: 04/08/2016] [Indexed: 05/02/2023]
Abstract
The US Environmental Protection Agency has responsibility for assessing endocrine activity of more than 10 000 chemicals, a task that cannot reasonably be achieved solely through use of available mammalian and nonmammalian in vivo screening assays. Hence, it has been proposed that chemicals be prioritized for in vivo testing using data from in vitro high-throughput assays for specific endocrine system targets. Recent efforts focused on potential estrogenic chemicals-specifically those that activate estrogen receptor-alpha (ERα)-have broadly demonstrated feasibility of the approach. However, a major uncertainty is whether prioritization based on mammalian (primarily human) high-throughput assays accurately reflects potential chemical-ERα interactions in nonmammalian species. The authors conducted a comprehensive analysis of cross-species comparability of chemical-ERα interactions based on information concerning structural attributes of estrogen receptors, in vitro binding and transactivation data for ERα, and the effects of a range of chemicals on estrogen-signaling pathways in vivo. Overall, this integrated analysis suggests that chemicals with moderate to high estrogenic potency in mammalian systems also should be priority chemicals in nonmammalian vertebrates. However, the degree to which the prioritization approach might be applicable to invertebrates is uncertain because of a lack of knowledge of the biological role(s) of possible ERα orthologs found in phyla such as annelids. Further, comparative analysis of in vitro data for fish and reptiles suggests that mammalian-based assays may not effectively capture ERα interactions for low-affinity chemicals in all vertebrate classes. Environ Toxicol Chem 2016;35:2806-2816. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.
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Affiliation(s)
- Gerald T Ankley
- Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota.
| | - Carlie A LaLone
- Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
| | - L Earl Gray
- Toxicity Assessment Division, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Daniel L Villeneuve
- Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
| | - Michael W Hornung
- Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
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4
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Tubbs C, McDonough CE, Felton R, Milnes MR. Advances in conservation endocrinology: the application of molecular approaches to the conservation of endangered species. Gen Comp Endocrinol 2014; 203:29-34. [PMID: 24613137 DOI: 10.1016/j.ygcen.2014.02.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 02/07/2014] [Accepted: 02/09/2014] [Indexed: 01/31/2023]
Abstract
Among the numerous societal benefits of comparative endocrinology is the application of our collective knowledge of hormone signaling towards the conservation of threatened and endangered species - conservation endocrinology. For several decades endocrinologists have used longitudinal hormone profiles to monitor reproductive status in a multitude of species. Knowledge of reproductive status among individuals has been used to assist in the management of captive and free-ranging populations. More recently, researchers have begun utilizing molecular and cell-based techniques to gain a more complete understanding of hormone signaling in wildlife species, and to identify potential causes of disrupted hormone signaling. In this review we examine various in vitro approaches we have used to compare estrogen receptor binding and activation by endogenous hormones and phytoestrogens in two species of rhinoceros; southern white and greater one-horned. We have found many of these techniques valuable and practical in species where access to research subjects and/or tissues is limited due to their conservation status. From cell-free, competitive binding assays to full-length receptor activation assays; each technique has strengths and weaknesses related to cost, sensitivity, complexity of the protocols, and relevance to in vivo signaling. We then present a novel approach, in which receptor activation assays are performed in primary cell lines derived from the species of interest, to minimize the artifacts of traditional heterologous expression systems. Finally, we speculate on the promise of next generation sequencing and transcriptome profiling as tools for characterizing hormone signaling in threatened and endangered species.
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Affiliation(s)
- Christopher Tubbs
- San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States.
| | - Caitlin E McDonough
- San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States
| | - Rachel Felton
- San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States
| | - Matthew R Milnes
- Mars Hill University, PO Box 6671, 100 Athletic Street, Mars Hill, NC 28754, United States.
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5
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Yost EE, Lee Pow C, Hawkins MB, Kullman SW. Bridging the gap from screening assays to estrogenic effects in fish: potential roles of multiple estrogen receptor subtypes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:5211-9. [PMID: 24422420 PMCID: PMC4014147 DOI: 10.1021/es404093n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 01/10/2014] [Accepted: 01/14/2014] [Indexed: 05/03/2023]
Abstract
This study seeks to delineate the ligand interactions that drive biomarker induction in fish exposed to estrogenic pollutants and provide a case study on the capacity of human (h) estrogen receptor (ER)-based in vitro screening assays to predict estrogenic effects in aquatic species. Adult male Japanese medaka (Oryzias latipes) were exposed to solutions of singular steroidal estrogens or to the estrogenic extract of an anaerobic swine waste lagoon. All exposure concentrations were calibrated to be equipotent based on the yeast estrogen screen (YES), which reports activation of hERα. These exposures elicited significantly different magnitudes of hepatic vitellogenin and choriogenin gene induction in the male medaka. Effects of the same YES-calibrated solutions in the T47D-KBluc assay, which reports activation of hERα and hERβ, generally recapitulated observations in medaka. Using competitive ligand binding assays, it was found that the magnitude of vitellogenin/choriogenin induction by different estrogenic ligands correlated positively with preferential binding affinity for medaka ERβ subtypes, which are highly expressed in male medaka liver prior to estrogen exposure. Results support emerging evidence that ERβ subtypes are critically involved in the teleost estrogenic response, with the ERα:ERβ ratio being of particular importance. Accordingly, incorporation of multiple ER subtypes into estrogen screening protocols may increase predictive value for the risk assessment of aquatic systems, including complex estrogenic mixtures.
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Affiliation(s)
- Erin E. Yost
- Department
of Biological Sciences, Program in Environmental and Molecular Toxicology, North Carolina State University, 850 Main Campus Drive, Raleigh, North Carolina 27606, United States
| | - Crystal Lee Pow
- Department
of Biological Sciences, Program in Environmental and Molecular Toxicology, North Carolina State University, 850 Main Campus Drive, Raleigh, North Carolina 27606, United States
| | - Mary Beth Hawkins
- Department
of Biological Sciences, North Carolina State
University, Campus Box 7617, Raleigh, North Carolina 27695, United States
| | - Seth W. Kullman
- Department
of Biological Sciences, Program in Environmental and Molecular Toxicology, North Carolina State University, 850 Main Campus Drive, Raleigh, North Carolina 27606, United States
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6
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Hornung MW, Tapper MA, Denny JS, Kolanczyk RC, Sheedy BR, Hartig PC, Aladjov H, Henry TR, Schmieder PK. Effects-based chemical category approach for prioritization of low affinity estrogenic chemicals. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2014; 25:289-323. [PMID: 24779616 DOI: 10.1080/1062936x.2014.898692] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Regulatory agencies are charged with addressing the endocrine disrupting potential of large numbers of chemicals for which there is often little or no data on which to make decisions. Prioritizing the chemicals of greatest concern for further screening for potential hazard to humans and wildlife is an initial step in the process. This paper presents the collection of in vitro data using assays optimized to detect low affinity estrogen receptor (ER) binding chemicals and the use of that data to build effects-based chemical categories following QSAR approaches and principles pioneered by Gilman Veith and colleagues for application to environmental regulatory challenges. Effects-based chemical categories were built using these QSAR principles focused on the types of chemicals in the specific regulatory domain of concern, i.e. non-steroidal industrial chemicals, and based upon a mechanistic hypothesis of how these non-steroidal chemicals of seemingly dissimilar structure to 17ß-estradiol (E2) could interact with the ER via two distinct binding types. Chemicals were also tested to solubility thereby minimizing false negatives and providing confidence in determination of chemicals as inactive. The high-quality data collected in this manner were used to build an ER expert system for chemical prioritization described in a companion article in this journal.
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Affiliation(s)
- M W Hornung
- a US Environmental Protection Agency, Office of Research and Development , National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division , Duluth , MN , USA
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7
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Scholz S, Renner P, Belanger SE, Busquet F, Davi R, Demeneix BA, Denny JS, Léonard M, McMaster ME, Villeneuve DL, Embry MR. Alternatives to in vivo tests to detect endocrine disrupting chemicals (EDCs) in fish and amphibians--screening for estrogen, androgen and thyroid hormone disruption. Crit Rev Toxicol 2012. [PMID: 23190036 DOI: 10.3109/10408444.2012.737762] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Endocrine disruption is considered a highly relevant hazard for environmental risk assessment of chemicals, plant protection products, biocides and pharmaceuticals. Therefore, screening tests with a focus on interference with estrogen, androgen, and thyroid hormone pathways in fish and amphibians have been developed. However, they use a large number of animals and short-term alternatives to animal tests would be advantageous. Therefore, the status of alternative assays for endocrine disruption in fish and frogs was assessed by a detailed literature analysis. The aim was to (i) determine the strengths and limitations of alternative assays and (ii) present conclusions regarding chemical specificity, sensitivity, and correlation with in vivo data. Data from 1995 to present were collected related to the detection/testing of estrogen-, androgen-, and thyroid-active chemicals in the following test systems: cell lines, primary cells, fish/frog embryos, yeast and cell-free systems. The review shows that the majority of alternative assays measure effects directly mediated by receptor binding or resulting from interference with hormone synthesis. Other mechanisms were rarely analysed. A database was established and used for a quantitative and comparative analysis. For example, a high correlation was observed between cell-free ligand binding and cell-based reporter cell assays, between fish and frog estrogenic data and between fish embryo tests and in vivo reproductive effects. It was concluded that there is a need for a more systematic study of the predictive capacity of alternative tests and ways to reduce inter- and intra-assay variability.
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Affiliation(s)
- S Scholz
- Department of Bioanalytical Ecotoxicology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany.
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8
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Tubbs C, Hartig P, Cardon M, Varga N, Milnes M. Activation of southern white rhinoceros (Ceratotherium simum simum) estrogen receptors by phytoestrogens: potential role in the reproductive failure of captive-born females? Endocrinology 2012; 153:1444-52. [PMID: 22253418 PMCID: PMC3281539 DOI: 10.1210/en.2011-1962] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The captive southern white rhinoceros (SWR; Ceratotherium simum simum) population serves as an important genetic reservoir critical to the conservation of this vulnerable species. Unfortunately, captive populations are declining due to the poor reproductive success of captive-born females. Captive female SWR exhibit reproductive problems suggested to result from continual ovarian follicular activity and prolonged exposure to endogenous estrogen. However, we investigated the potential role of exogenous dietary phytoestrogens in the reproductive failure of SWR by cloning and characterizing in vitro phytoestrogen binding and activation of recombinant SWR estrogen receptors (ESR). We compared those characteristics with recombinant greater one-horned rhinoceros (GOHR; Rhinoceros unicornis) ESR, a species that receives similar captive diets yet reproduces relatively well. Our results indicate that phytoestrogens bind rhino ESR in a manner similar to other vertebrate species, but there are no differences found in phytoestrogen binding affinity of SWR ESR compared with GOHR ESR. However, species-specific differences in ESR activation by phytoestrogens were detected. The phytoestrogen coumestrol stimulated greater maximal activation of SWR ESR1 than GOHR ESR1. SWR ESR2 were also more sensitive to phytoestrogens and were activated to a greater extent by both coumestrol and daidzein. The concentrations in which significant differences in ESR activation occurred (10(-7) to 10(-5) m) are consistent with circulating concentrations measured in other vertebrate species. Taken together, these findings suggest that phytoestrogens potentially pose a risk to the reproductive health of captive SWR. However, additional studies are needed to further clarify the physiological role of dietary phytoestrogens in the reduced fertility of this species.
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Affiliation(s)
- Christopher Tubbs
- San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, California 92027, USA.
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9
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Simpkins JW, Swenberg JA, Weiss N, Brusick D, Eldridge JC, Stevens JT, Handa RJ, Hovey RC, Plant TM, Pastoor TP, Breckenridge CB. Atrazine and breast cancer: a framework assessment of the toxicological and epidemiological evidence. Toxicol Sci 2011; 123:441-59. [PMID: 21768606 PMCID: PMC3179673 DOI: 10.1093/toxsci/kfr176] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The causal relationship between atrazine exposure and the occurrence of breast cancer in women was evaluated using the framework developed by Adami et al. (2011) wherein biological plausibility and epidemiological evidence were combined to conclude that a causal relationship between atrazine exposure and breast cancer is “unlikely”. Carcinogenicity studies in female Sprague-Dawley (SD) but not Fischer-344 rats indicate that high doses of atrazine caused a decreased latency and an increased incidence of combined adenocarcinoma and fibroadenoma mammary tumors. There were no effects of atrazine on any other tumor type in male or female SD or Fischer-344 rats or in three strains of mice. Seven key events that precede tumor expression in female SD rats were identified. Atrazine induces mammary tumors in aging female SD rats by suppressing the luteinizing hormone surge, thereby supporting a state of persistent estrus and prolonged exposure to endogenous estrogen and prolactin. This endocrine mode of action has low biological plausibility for women because women who undergo reproductive senescence have low rather than elevated levels of estrogen and prolactin. Four alternative modes of action (genotoxicity, estrogenicity, upregulation of aromatase gene expression or delayed mammary gland development) were considered and none could account for the tumor response in SD rats. Epidemiological studies provide no support for a causal relationship between atrazine exposure and breast cancer. This conclusion is consistent with International Agency for Research on Cancer’s classification of atrazine as “unclassifiable as to carcinogenicity” and the United States Environmental Protection Agency's classification of atrazine as “not likely to be carcinogenic.”
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Affiliation(s)
- James W Simpkins
- Department of Pharmacology and Neurosciences, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA
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10
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Rider CV, Hartig PC, Cardon MC, Lambright CR, Bobseine KL, Guillette LJ, Gray LE, Wilson VS. Differences in sensitivity but not selectivity of xenoestrogen binding to alligator versus human estrogen receptor alpha. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2010; 29:2064-71. [PMID: 20821664 PMCID: PMC2944037 DOI: 10.1002/etc.233] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Reproductive abnormalities in alligators exposed to contaminants in Lake Apopka, Florida, USA represent a clear example of endocrine disruption in wildlife. Several of these contaminants that are not able to bind to mammalian estrogen receptors (such as atrazine and cyanazine) have previously been reported to bind to the alligator estrogen receptor from oviductal tissue. Binding of known Lake Apopka contaminants to full length estrogen receptors alpha from human (hERalpha) and alligator (aERalpha) was assessed in a side-by-side comparison within the same assay system. Baculovirus-expressed recombinant hERalpha and aERalpha were used in a competitive binding assay. Atrazine and cyanazine were not able to bind to either receptor. p,p'-Dicofol was able to bind to aERalpha with a concentration inhibiting 50% of binding (IC50) of 4 microM, while only partially displacing 17beta-estradiol (E2) from hERalpha and yielding a projected IC50 of 45 microM. Chemicals that only partially displaced E2 from either receptor, including some dichlorodiphenyltrichloroethane (DDT) metabolites and trans-nonachlor, appeared to have higher affinity for aERalpha than hERalpha. p,p'-Dicofol-mediated transcriptional activation through aERalpha and hERalpha was assessed to further explore the preferential binding of p,p'-dicofol to aERalpha over hERalpha. p,p'-Dicofol was able to stimulate transcriptional activation in a similar manner with both receptors. However, the in vitro results obtained with p,p'-dicofol were not reflected in an in vivo mammalian model, where Kelthane (mixed o,p'- and p,p'-dicofol isomers) did not elicit estrogenic effects. In conclusion, although there was no evidence of exclusively species-specific estrogen receptor binders, some xenoestrogens, especially p,p'-dicofol, had a higher affinity for aERalpha than for hERalpha.
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Affiliation(s)
- Cynthia V. Rider
- Department of Molecular Biomedical Sciences, North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27606, USA
| | - Phillip C. Hartig
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
| | - Mary C. Cardon
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
| | - Christy R. Lambright
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
| | - Kathy L. Bobseine
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
| | - Louis J. Guillette
- Department of Biology, University of Florida, 220 Bartram Hall, PO Box 118525, Gainesville, Florida 32611-8525, USA
| | - L. Earl Gray
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
| | - Vickie S. Wilson
- Reproductive Toxicology Branch, Toxicity Assessment Division, U.S. Environmental Protection Agency, MD-72, Research Triangle Park, North Carolina 27711
- To whom correspondence may be addressed ()
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11
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Blake LS, Martinović D, Gray LE, Wilson VS, Regal RR, Villeneuve DL, Ankley GT. Characterization of the androgen-sensitive MDA-kb2 cell line for assessing complex environmental mixtures. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2010; 29:1367-76. [PMID: 20821581 DOI: 10.1002/etc.166] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Synthetic and natural steroidal androgens and estrogens and many other non-steroidal endocrine-active compounds commonly occur as complex mixtures in aquatic environments. It is important to understand the potential interactive effects of these mixtures to properly assess their risk. Estrogen receptor agonists exhibit additivity in mixtures when tested in vivo and in vitro. Little is known, however, concerning possible mixture interactions of androgen receptor agonists. In these studies we used the MDA-kb2 cell line, a human breast cancer cell line with endogenous androgen receptors and a stably transfected luciferase reporter gene construct to quantify the androgenic activity of seven natural and synthetic androgens: 17beta-trenbolone, dihydrotestosterone, methyltestosterone, testosterone, trendione, 17alpha-trenbolone, and androstenedione. We tested combinations of these androgens and compared the observed activity to expected androgenic activity based on a concentration addition model. Our analyses support the hypothesis that androgen receptor agonists cause additive responses in a mixture. Binary mixtures of 17beta-trenbolone with 17beta-estradiol or triclocarban (an anti-microbial found in the environment) were also tested. 17beta-Estradiol induced androgenic activity, but only at concentrations 600-fold greater than those found in the environment. Triclocarban enhanced the activity of 17beta-trenbolone. Additionally, three anti-androgens were each paired with three androgens of varying potencies. The relative potencies of the antagonists were a vinclozolin metabolite (M2) > procymidone > prochloraz regardless of the androgen used. The results of our studies demonstrate the potential utility of the androgen-responsive MDA-kb2 cell line for quantifying the activity of mixtures of endocrine-active chemicals in complex wastes such as municipal effluents and feedlot discharges.
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Affiliation(s)
- Lindsey S Blake
- Integrated Biosciences, University of Minnesota, Duluth, 1035 University Dr., Duluth, Minnesota 55812, USA.
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12
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Dang Z. Comparison of relative binding affinities to fish and mammalian estrogen receptors: the regulatory implications. Toxicol Lett 2009; 192:298-315. [PMID: 19913605 DOI: 10.1016/j.toxlet.2009.11.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 10/30/2009] [Accepted: 11/02/2009] [Indexed: 11/20/2022]
Abstract
Screening and testing of chemicals binding to estrogen receptors (ERs) emerge as an important issue in several regulatory programs or frameworks. Discrepancies exist, however, whether fish ERs should be included in the regulatory programs. In view of the differences in binding affinities to ERalpha and ERbeta and the significant contribution of ERbeta to biological effects of chemicals, it remains unknown whether both types of ERs are needed for the regulatory purposes. This study collected publications on binding affinities to both mammalian and fish ERs for 65 chemicals, covering a wide range of strong, moderate, weak and non-ER binders. Systematic evaluation of the data was performed in order to compare the difference in binding affinity of chemicals to fish and mammalian ERs and to subtypes of ERs. Except the reference estrogen 17beta-estradiol, all 64 chemicals have differential values of relative binding affinity (RBA), which result mostly from the inter-laboratory tests other than interspecies differences. It is concluded that ER binding in one vertebrate species or one subtype of ERs could be extrapolated to other species or subtypes of ERs for most of chemicals for the regulatory purpose. Fish ERs are likely more sensitive to some chemicals of weak binders than mammalian ERs, suggesting the importance of including fish ERs in the regulatory programs. Issues on data interpretation and testing strategy for the regulatory purpose have been discussed.
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Affiliation(s)
- ZhiChao Dang
- National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
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