Relationship between the results of in vitro receptor binding assay to human estrogen receptor α and in vivo uterotrophic assay: Comparative study with 65 selected chemicals
ABSTRACT For screening chemicals possessing endocrine disrupting potencies, the uterotrophic assay has been placed in a higher level in the OECD testing framework than the ER binding assay to detect ER-mediated activities. However, there are no studies that can demonstrate a clear relationship between these assays. In order to clarify the relationship between the in vitro ER binding and in vivo uterotrophic assays and to determine meaningful binding potency from the ER binding assay, we compared the results from these assays for 65 chemicals spanning a variety of chemicals classes. Under the quantitative comparison between logRBAs (relative binding affinities) and logLEDs (lowest effective doses), the log RBA was well correlated with both logLEDs of estrogenic and anti-estrogenic compounds at r(2)=0.67 (n=28) and 0.79 (n=23), respectively. The RBA of 0.00233% was found to be the lowest ER binding potency to elicit estrogenic or anti-estrogenic activities in the uterotrophic assay, accordingly this value is considered as the detection limit of estrogenic or anti-estrogenic activities in the uterotrophic assay. The usage of this value as cutoff provided the best concordance rate (82%). These findings are useful in a tiered approach for identifying chemicals that have potential to induce ER-mediated effects in vivo.
- SourceAvailable from: Daniela M. Goldinger
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- "Additionally, BPF has been shown to exhibit in vitro androgenic and anti-androgenic effects (Cabaton et al., 2009; Kitamura et al., 2005; Stroheker et al., 2004). BPF was shown to have estrogenic and anti-estrogenic activity in some in vivo studies with female rats (Akahori et al., 2008). For D-8 there is only limited evidence of endocrine activity. "
ABSTRACT: Alternatives to bisphenol A (BPA) are more and more used in thermal paper receipts.To get an overview of the situation in Switzerland, 124 thermal paper receipts were collected and analyzed. Whereas BPA was detected in most samples (n=100), some alternatives, namely Bisphenol S (BPS) , Pergafast(®) 201 and D-8 have been found in respectively 4, 11 and 9 samples. As no or few data on their endocrine activity are available, these chemicals and bisphenol F (BPF) were tested in vitro using the H295R steroidogenesis assay. 17β-estradiol production was induced by BPA and BPF, whereas free testosterone production was inhibited by BPA and BPS. Both non-bisphenol substances did not show significant effects. The binding affinity to 16 proteins and the toxicological potential (TP) were further calculated in silico using VirtualToxLab(TM). TP values lay between 0.269 and 0.476 and the main target was the estrogen receptor β (84.4 nM to 1.33 μM). A substitution of BPA by BPF and BPS should be thus considered with caution, since they exhibit almost a similar endocrine activity as BPA. D-8 and Pergafast(®) 201 could be alternatives to replace BPA, however further analyses are needed to better characterize their effects on the hormonal system. Copyright © 2015. Published by Elsevier Inc.Regulatory Toxicology and Pharmacology 01/2015; 22(3). DOI:10.1016/j.yrtph.2015.01.002 · 2.14 Impact Factor
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- "Tetrabromo-bisphenol A (TBBPA) is used primarily as a flame retardant in epoxy resin circuit boards, electronic enclosures, paper, plastic, and textiles (NTP, 2002; Olsen et al., 2003) and bisphenol AF (BPAF) is used in fluoroelastomers, polyamides, polyesters, polycarbonate copolymers , and other specialty polymers (Akahori et al., 2008; NTP, 2008; Perez et al., 1998). BPA and BPAF have been shown to induce estrogen-dependent responses in vivo and in vitro via binding to estrogen receptor (ER) ERa and ERb (Akahori et al., 2008; Bay et al., 2004; Wetherill et al., 2007; Yamasaki et al., 2003), whereas studies on the estrogenicity of TBBPA in vitro are inconsistent. Both BPAF and TBBPA have been nominated for toxicological characterization by the NTP, National Institute of Environmental Health Sciences (NTP, 2002, 2008). "
ABSTRACT: Exposure to xenoestrogens occurs against a backdrop to physiological levels of endogenous estrogens. Endogenous estrogen levels vary from low levels in early childhood to high levels during pregnancy and in young women. However, few studies have addressed how xenoestrogens interact with endogenous estrogens. The current study was designed to characterize the individual dose-response curves of estradiol-17beta (E(2)), bisphenol A (BPA), tetrabromo-bisphenol A (TBBPA), and bisphenol AF (BPAF, 4,4'-hexafluoroisopropylidene diphenol) on estrogen-dependent luciferase expression in T47D-KBluc cells and to determine how binary (8 x 8 factorial) and ternary (4 x 4 x 4 factorial) mixtures of an endogenous estrogen (E(2)) interact with BPA and/or BPAF. Log EC(50) and hillslope values with SEs, respectively, for individual compounds were as follows: E(2), -12.10M +/- 0.06071, 0.7702 +/- 0.1739; BPA, -6.679M +/- 0.08505, 1.194 +/- 0.2137; and BPAF, -7.648M +/- 0.05527, 1.273 +/- 0.1739. TBBPA was not evaluated in mixture studies because of its minimally estrogenic response at 3 x10(-5)M and elicited cytotoxicity at higher concentrations. Both the binary mixtures of E(2) with BPA and BPAF and the ternary mixture of E(2), BPA, and BPAF behaved in an additive manner. For binary mixtures, as E(2) concentration increased, higher concentrations of BPA and BPAF were necessary to induce a significant increase in the estrogenic response. Understanding the behavior of mixture interactions of xenoestrogens, like BPA and BPAF, with endogenous estrogens will allow a better assessment of the potential risk associated with exposure to these chemicals, individually or as mixtures.Toxicological Sciences 05/2010; 116(2):477-87. DOI:10.1093/toxsci/kfq156 · 4.48 Impact Factor
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- "Although the automated approach is efficient and requires minimal manual preparation, a compound can only be identified as ER ligand with the MALDI methodology if its RBA is in the range of several percent. RBAs are determined in a competition experiment with a labelled ligand and expressed relative to the concentration of E2 required to induce a 50% drop of the signal (Kuiper et al., 1998; Blair et al., 2000; Okubo et al., 2004; Akahori et al., 2008). Therefore, a ligand with a 7% RBA requires a concentration ca. "
ABSTRACT: High-mass matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with chemical cross-linking has the ability to monitor the ligand-dependent dimerization of the human estrogen receptor alpha ligand binding domain (hERalpha LBD) in solution. Because only ER ligands enhance the homodimer abundance, we evaluated the ability of this label-free approach for identifying endocrine disrupting compounds (EDCs) in a high-throughput manner. This was achieved by combining an automated liquid handler with an automated MS acquisition procedure, which allowed a five-fold gain in operator time compared to a fully manual approach. To detect ligand binding with enough confidence, the receptor has to be incubated with at least a 10 microM concentration of the test compound. Based on the increase of the measured homodimer intensity, eight compounds with a relative binding affinity (RBA, relative to the natural hormone estradiol) >7% were identified as ER ligands among the 28 chemicals tested. Two other compounds, quercetin and 4-tert-amylphenol, were also identified as ER ligands, although their RBAs have been reported to be only 0.01% and 0.000055%, respectively. This suggests that these two ligands have a higher affinity for hERalpha LBD than reported in the literature. The high-mass MALDI approach thus allows identifying high affinity EDCs in an efficient way.Toxicology in Vitro 03/2009; 23(4):704-9. DOI:10.1016/j.tiv.2009.02.004 · 3.21 Impact Factor