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      Nuclear Hormone Receptor Activity of Polybrominated Diphenyl Ethers and Their Hydroxylated and Methoxylated Metabolites in Transactivation Assays Using Chinese Hamster Ovary Cells

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          Abstract

          Background

          An increasing number of studies are reporting the existence of polybrominated diphenyl ethers (PBDEs) and their hydroxylated (HO) and methoxylated (MeO) metabolites in the environment and in tissues from wildlife and humans.

          Objective

          Our aim was to characterize and compare the agonistic and antagonistic activities of principle PBDE congeners and their HO and MeO metabolites against human nuclear hormone receptors.

          Methods

          We tested the hormone receptor activities of estrogen receptor α (ERα), ERβ, androgen receptor (AR), glucocorticoid receptor (GR), thyroid hormone receptor α 1 (TRα 1), and TRβ 1 against PBDE congeners BDEs 15, 28, 47, 85, 99, 100, 153, and 209, four para-HO-PBDEs, and four para-MeO-PBDEs by highly sensitive reporter gene assays using Chinese hamster ovary cells.

          Results

          Of the 16 compounds tested, 6 and 2 showed agonistic activities in the ERα and ERβ assays, respectively, and 6 and 6 showed antagonistic activities in these assays. 4′-HO-BDE-17 showed the most potent estrogenic activity via ERα/β, and 4′-HO-BDE-49 showed the most potent anti estrogenic activity via ERα/β. In the AR assay, 13 compounds showed antagonistic activity, with 4′-HO-BDE-17 in particular inhibiting AR-mediated transcriptional activity at low concentrations in the order of 10 −8 M. In the GR assay, seven compounds, including two HO-PBDEs and two MeO-PBDEs, showed weak antagonistic activity. In the TRα 1 and TRβ 1 assays, only 4-HO-BDE-90 showed weak antagonistic activity.

          Conclusions

          Taken together, these results suggest that PBDEs and their metabolites might have multiple endocrine-disrupting effects via nuclear hormone receptors, and para-HO-PBDEs, in particular, possess more potent receptor activities compared with those of the parent PBDEs and corresponding para-MeO-PBDEs.

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          Most cited references 47

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          Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta.

          The rat estrogen receptor (ER) exists as two subtypes, ER alpha and ER beta, which differ in the C-terminal ligand binding domain and in the N-terminal transactivation domain. In this study we investigated the messenger RNA expression of both ER subtypes in rat tissues by RT-PCR and compared the ligand binding specificity of the ER subtypes. Saturation ligand binding analysis of in vitro synthesized human ER alpha and rat ER beta protein revealed a single binding component for 16 alpha-iodo-17 beta-estradiol with high affinity [dissociation constant (Kd) = 0.1 nM for ER alpha protein and 0.4 nM for ER beta protein]. Most estrogenic substances or estrogenic antagonists compete with 16 alpha-[125I]iodo-17 beta-estradiol for binding to both ER subtypes in a very similar preference and degree; that is, diethylstilbestrol > hexestrol > dienestrol > 4-OH-tamoxifen > 17 beta-estradiol > coumestrol, ICI-164384 > estrone, 17 alpha-estradiol > nafoxidine, moxestrol > clomifene > estriol, 4-OH-estradiol > tamoxifen, 2-OH-estradiol, 5-androstene-3 beta, 17 beta-diol, genistein for the ER alpha protein and dienestrol > 4-OH-tamoxifen > diethylstilbestrol > hexestrol > coumestrol, ICI-164384 > 17 beta-estradiol > estrone, genistein > estriol > nafoxidine, 5-androstene-3 beta, 17 beta-diol > 17 alpha-estradiol, clomifene, 2-OH-estradiol > 4-OH-estradiol, tamoxifen, moxestrol for the ER beta protein. The rat tissue distribution and/or the relative level of ER alpha and ER beta expression seems to be quite different, i.e. moderate to high expression in uterus, testis, pituitary, ovary, kidney, epididymis, and adrenal for ER alpha and prostate, ovary, lung, bladder, brain, uterus, and testis for ER beta. The described differences between the ER subtypes in relative ligand binding affinity and tissue distribution could contribute to the selective action of ER agonists and antagonists in different tissues.
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            Persistent DDT metabolite p,p'-DDE is a potent androgen receptor antagonist.

            The increase in the number of reports of abnormalities in male sex development in wildlife and humans coincided with the introduction of 'oestrogenic' chemicals such as DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) into the environment. Although these phenotypic alterations are thought to be mediated by the oestrogen receptor, they are also consistent with inhibition of androgen receptor-mediated events. Here we report that the major and persistent DDT metabolite, p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), has little ability to bind the oestrogen receptor, but inhibits androgen binding to the androgen receptor, androgen-induced transcriptional activity, and androgen action in developing, pubertal and adult male rats. The results suggest that abnormalities in male sex development induced by p,p'-DDE and related environmental chemicals may be mediated at the level of the androgen receptor.
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              An overview of commercially used brominated flame retardants, their applications, their use patterns in different countries/regions and possible modes of release.

              Brominated flame retardants (BFRs) are used in a variety of consumer products and several of those are produced in large quantities. These compounds have been detected in environmental samples, which can be attributed to the anthropogenic uses of these compounds. Brominated flame retardants are produced via direct bromination of organic molecules or via addition of bromine to alkenes; hence, an overview of the production and usage of bromine over the past three decades is covered. Production, application, and environmental occurrence of high production brominated flame retardants including Tetrabromobisphenol A, polybrominated biphenyls, Penta-, Octa-, Deca-brominated diphenyl ether (oxide) formulation and hexabromocyclododecane are discussed.
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                Author and article information

                Journal
                Environ Health Perspect
                Environmental Health Perspectives
                National Institute of Environmental Health Sciences
                0091-6765
                1552-9924
                August 2009
                28 April 2009
                : 117
                : 8
                : 1210-1218
                Affiliations
                [1 ]Hokkaido Institute of Public Health, Sapporo, Japan
                [2 ]Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
                [3 ]Nihon Pharmaceutical University, Saitama, Japan
                [4 ]Asahikawa Medical School, Asahikawa, Japan
                Author notes
                Address correspondence to H. Kojima, Hokkaido Institute of Public Health, Kita-19, Nishi-12, Kita-ku, Sapporo 060-0819, Japan. Telephone: 81-11-747-2733. Fax: 81-11-736-9476. E-mail: kojima@ 123456iph.pref.hokkaido.jp

                The authors declare they have no competing financial interests.

                Article
                ehp-117-1210
                10.1289/ehp.0900753
                2721863
                19672399
                This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
                Categories
                Research

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