Measuring the kinetics of the binding of xenoestrogens and estrogen receptor alpha by fluorescence polarization

Dibutyl phthalate promotes angiogenesis in EA.hy926 cells through estrogen receptor-dependent activation of ERK1/2, PI3K-Akt, and NO signaling pathways

Dibutyl phthalate (DBP) is an endocrine disruptor that has been widely used in various products of human use. DBP exposure has been associated with reproductive and cardiovascular diseases and metabolic disorders. Although dysfunction of the vascular endothelium is responsible for many cardiovascular and metabolic diseases, little is known about the effects of DBP on human endothelium. In this study, we investigated the effect of three concentrations of DBP (10^-6, 10^-5, and 10^-4 M) on angiogenesis in human endothelial cell (EC) line EA.hy926 after acute exposure. Tube formation assay was used to investigate in vitro angiogenesis, whereas qRT-PCR was employed to measure mRNA expression. The effect of DBP on extracellular signal-regulated kinase 1/2 (ERK1/2), phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt), and endothelial nitric oxide (NO) synthase (eNOS) activation was examined using Western blotting, whereas the Griess method was used to assess NO production. Results show that the 24-h-long exposure to 10^-4 M DBP increased endothelial tube formation, which was prevented by addition of U0126 (ERK1/2 inhibitor), wortmannin (PI3K-Akt inhibitor), and l-NAME (NOS inhibitor). Short exposure to 10^-4 M DBP (from 15 to 120 min) phosphorylated ERK1/2, Akt, and eNOS in different time points and increased NO production after 24 and 48 h of exposure. Application of nuclear estrogen receptor (ER) and G protein-coupled ER (GPER) inhibitors ICI 182,780 and G-15, respectively, abolished the DBP-mediated ERK1/2, Akt, and eNOS phosphorylation and increase in NO production. In this study, we report for the first time that DBP exerts a pro-angiogenic effect on human vascular ECs and describe the molecular mechanism involving ER- and GPER-dependent activation of ERK1/2, PI3K-Akt, and NO signaling pathways.

Mechanism of Vitamin D Receptor Ligand-Binding Domain Regulation Studied by gREST Simulations

The vitamin D receptor ligand-binding domain (VDR-LBD) undergoes conformational changes upon ligand binding. In this nuclear receptor family, agonistic or antagonistic activities are controlled by the conformation of the helix (H)12. However, all crystal structures of VDR-LBD reported to date correspond to the active H12 conformation, regardless of agonist/antagonist binding. To understand the mechanism of VDR-LBD regulation structurally, conformational samplings of agonist- and antagonist-bound rat VDR-LBD were performed using the generalized replica exchange with solute tempering (gREST) method. The gREST simulations demonstrated different structural responses of rat VDR-LBD to agonist or antagonist binding, whereas in conventional molecular dynamics simulations, the conformation was the same as that of the crystal structures, regardless of agonist/antagonist binding. In the gREST simulations, a spontaneous conformational change of H12 was observed only for the antagonist complex. The different responses to agonist/antagonist binding were attributed to hydrophobic core formation at the ligand-binding pocket and cooperative rearrangements of H11. The gREST method can be applied to the examination of structure-activity relationships for multiple VDR-LBD ligands.

Understanding the interaction of estrogenic ligands with estrogen receptors: a survey of the functional and binding kinetic studies

The investigation of estrogen actions and their interaction characteristics with estrogen receptors (ERs) to induce unique functional features inside cells have allowed us to understand better the regulation of many vital physiological and cellular processes in humans. The biological effects of estrogenic ligands or compounds are mediated via estrogen receptors that act as the ligand-activated transcription factors. Therefore, the study on ligand-ER interaction properties and mechanism of ligand-ER complexes binding to specific estrogen response elements located in the promoters of target genes are very critical to realize the complicated biological process regulated by the endogenous estrogens. Several reviews have provided comprehensive and updated information on the influence of estrogen receptors in health and disease. However, the mechanism of estrogen-ERs binding and affinity aspects at molecular level is relatively under-investigated. This review thus aims to shed light on the significance of the binding kinetics of ligand-ER interactions because the information provide great assistance to define how a ligand or a drug can communicate with physiology to produce a desired therapeutic response. In addition, the most frequently used methodologies for the binding kinetic study are highlighted over the last decade.

Carcinogenic risk and Bisphenol A exposure: A focus on molecular aspects in endoderm derived glands

Epidemiological and experimental evidence associates the exposure to Bisphenol A with the increase of cancer risk in several organs, including prostate. BPA targets different pathways involved in carcinogenicity including the Nuclear Receptors (i.e. estrogen and androgen receptors), stress regulated proteins and, finally, epigenetic changes. Here, we analyse BPA-dependent carcinogenesis in endoderm-derived glands, thyroid, liver, pancreas and prostate focusing on cell signalling, DNA damage repair pathways and epigenetic modifications. Mainly, we gather molecular data evidencing harmful effects at doses relevant for human risk (low-doses). Since few molecular data are available, above all for the pancreas, we analysed transcriptomic data generated in our laboratory to suggest possible mechanisms of BPA carcinogenicity in endoderm-derived glands, discussing the role of nuclear receptors and stress/NF-kB pathways. We evidence that an in vitro toxicogenomic approach might suggest mechanisms of toxicity applicable to cells having the same developmental origin. Although we cannot draw firm conclusions, published data summarized in this review suggest that exposure to BPA, primarily during the developmental stages, represents a risk for carcinogenesis of endoderm-derived glands.

Estrogenicity assessment of membrane concentrates from landfill leachate treated by the UV-Fenton process using a human breast carcinoma cell line

Membrane concentrates (MCs) are generated when membranes are used to concentrate landfill leachate. It contains high concentrations of inorganic and organic environmental pollutants, which are highly toxic and carcinogenic. In this paper, the proliferation effect (PE) from MC before and after treatment with the UV-Fenton process was assessed using the human breast carcinoma cell line MCF-7. The highest value of 116% was found at 5% (v/v) concentration after a 10 min reaction. Phthalic acid esters (PAEs) play an important role in the MC estrogenicity. Estrogen simulation solutions (ESS) of PAEs were prepared to simulate the changes in estrogenic active substances during the UV-Fenton process. The ESS degradation conformed to the first-order kinetics model. The estrogenicity decreased after an initial increase until it acted in a non-estrogenic manner. Convincingly, the intermediates were determined by GC/MS, and the estrogenicity was assessed during the degradation process. The estrogenicity was highly related to the generation of intermediates and the PAE concentration. The results provide guidance for UV-Fenton application in MC estrogenicity reduction.

Rapid and efficient pesticide detection via cyclodextrin-promoted energy transfer

Cyclodextrins facilitate non-covalent fluorescence energy transfer from a variety of pesticides to high quantum-yield fluorophores, resulting in a rapid, sensitive detection scheme for these compounds with detection limits as low as two micromolar. Such a facile detection tool has significant potential applications in agriculture and public health research.