Estrogenicity of halogenated bisphenol A: in vitro and in silico investigations
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The binding interactions of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to human estrogen receptor α ligand binding domain (hERα-LBD) was investigated using a combined in vitro and in silico approach. First, the recombinant hERα-LBD was prepared as a soluble protein in Escherichia coli BL21(DE3)pLysS. A native fluorescent phytoestrogen, coumestrol, was employed as tracer for the fluorescence polarization assay. The results of the in vitro binding assay showed that bisphenol compounds could bind to hERα-LBD as the affinity ligands. All the tested halogenated BPAs exhibited weaker receptor binding than BPA, which might be explained by the steric effect of substituents. Molecular docking studies elucidated that the halogenated BPAs adopted different conformations in the flexible hydrophobic ligand binding pocket (LBP), which is mainly dependent on their distinct halogenation patterns. The compounds with halogen substituents on the phenolic rings and on the bridging alkyl moiety acted as agonists and antagonists for hERα, respectively. Interestingly, all the compounds in the agonist conformation of hERα formed a hydrogen bond with His524, while the compounds in the antagonist conformation formed a hydrogen bond with Thr347. These docking results suggested a pivotal role of His524/Thr347 in maintaining the hERα structure in the biologically active agonist/antagonist conformation. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation, which might be applicable for the structure-based design of novel bisphenol compounds with reduced toxicities and for environmental risk assessment. In addition, based on hERα-LBD as a recognition element, the proposed fluorescence polarization assay may offer an alternative to chromatographic techniques for the multi-residue determination of bisphenol compounds.
KeywordsHalogenated bisphenol A Estrogen receptor α Fluorescence polarization Molecular modeling
This work was supported by the National Key Research and Development Program of China (2017YFD0300303 and 2017YFD0300603), the National Natural Science Foundation of China (31601534), the Project funded by China Postdoctoral Science Foundation (2017M621213), and the Agricultural Science and Technology Innovation Program of Jilin Province (CXGC2017JQ006 and CXGC2017JQ010).
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Conflict of interest
The authors declare that they have no conflict of interests.
The manuscript does not contain clinical studies or participant data.
- Delfosse V, Grimaldi M, Pons J-L et al (2012) Structural and mechanistic insights into bisphenols action provide guidelines for risk assessment and discovery of bisphenol A substitutes. Proc Natl Acad Sci USA 109(37):14930–14935. https://doi.org/10.1073/pnas.1203574109 CrossRefPubMedPubMedCentralGoogle Scholar
- Hong H, Kohli K, Trivedi A, Johnson DL, Stallcup MR (1996) GRIP1, a novel mouse protein that serves as a transcriptional coactivator in yeast for the hormone binding domains of steroid receptors. Proc Natl Acad Sci USA 93(10):4948–4952. https://doi.org/10.1073/pnas.93.10.4948 CrossRefPubMedPubMedCentralGoogle Scholar
- Lin W, Huang J, Liao X et al (2016) Neo-tanshinlactone selectively inhibits the proliferation of estrogen receptor positive breast cancer cells through transcriptional down-regulation of estrogen receptor alpha. Pharmacol Res 111:849–858. https://doi.org/10.1016/j.phrs.2016.07.044 CrossRefPubMedGoogle Scholar
- Molina-Molina J-M, Amaya E, Grimaldi M et al (2013) In vitro study on the agonistic and antagonistic activities of bisphenol-S and other bisphenol-A congeners and derivatives via nuclear receptors. Toxicol Appl Pharmacol 272(1):127–136. https://doi.org/10.1016/j.taap.2013.05.015 CrossRefPubMedGoogle Scholar
- Nadal A, Ropero AB, Laribi O, Maillet M, Fuentes E, Soria B (2000) Nongenomic actions of estrogens and xenoestrogens by binding at a plasma membrane receptor unrelated to estrogen receptor α and estrogen receptor β. Proc Natl Acad Sci USA 97(21):11603–11608. https://doi.org/10.1073/pnas.97.21.11603 CrossRefPubMedPubMedCentralGoogle Scholar
- Zoeller RT, Bansal R, Parris C (2005) Bisphenol-A, an environmental contaminant that acts as a thyroid hormone receptor antagonist in vitro, increases serum thyroxine, and alters RC3/neurogranin expression in the developing rat brain. Endocrinology 146(2):607–612. https://doi.org/10.1210/en.2004-1018 CrossRefPubMedGoogle Scholar