Comprehensive assessment of the estrogenic activity of resin composites.

Resin-based dental composites have been developed to restore decayed teeth or modify tooth color due to their excellent physical and chemical properties. Such composites may have intrinsic toxicity due to components released into the mouth during the early stage of polymerization, and afterward as a result of erosion or material decomposition. In addition, resin-based dental composites have potential environmental pollutant by elution of monomers and degradation. Since certain monomers of resin matrices are synthesized from bisphenol A (BPA), which acts as an estrogenic endocrine disruptor, these resin matrices may have estrogenic activity. Therefore, the estrogenic endocrine-disrupting activity of various dental composites should be evaluated. In this study, we evaluated the estrogenic endocrine-disrupting activity of 10 resin composites by using a BRET-based estrogen receptor (ER)α and ERß dimerization assays and ER transactivation assay. BPA, BisDMA, BisGMA, BisEMA, TEGDMA, HMBP, and DMPA mediated ERα dimerization, and BPA, BisDMA, and DMPA also mediated ERß dimerization. Except for UDMA and CQ, all the compounds were identified as estrogen agonists or antagonists. In-depth information for the safe use of dental composites was acquired, and it was confirmed how the component of dental composites acts in the ER signaling pathway. Further studies on the low-dose and long-term release of these compounds are needed to ensure the safe use of these resin-based dental composites.

Comprehensive analysis of cellular estrogen signaling in representative estrogen receptor ligands.

The estrogen receptor (ER)-mediated signaling pathway in physiological and biochemical aspects is very important in the environment, including food. The physiological action of estrogen is mediated by ER alpha (ERα) and beta (ERß), whose physiological action on estrogenic substances is complex because of the relatively low ligand-binding domain (LBD) similarity of the two ERs. In this study, the comprehensive activity of representative ER ligands was evaluated by using BRET-based ERα and ERß dimerization and ER transactivation assays to differentiate the specific binding and function of ERα and ERß from 12 representative natural and synthetic estrogenic substances. Results revealed that 11 chemicals mediated receptor ERα and ERß dimerization, 7 out of 12 chemicals were confirmed to be estrogen agonists, and 5 chemicals were antagonistic. Overall, this study demonstrated consistency between BRET dimerization and transactivation responses, supporting potential supplementary application of mechanism-based BRET assays as high-throughput screening methods for evaluation of potential endocrine-disrupting activity of environmental agents. This study also provided information about receptor specificity of ligand-mediated estrogenic activity via dimerization assays and elucidated cellular estrogen signaling pathways.

Human cell-based estrogen receptor beta dimerization assay.

Estrogen is not only responsible for important functions in the human body, such as cell growth, reproduction, differentiation, and development, but it is also deeply related to pathological processes, such as cancer, metabolic and cardiovascular diseases, and neurodegeneration. Estrogens and other estrogenic compounds have transcriptional activities through binding with the estrogen receptor (ER) to induce ER dimerization. The two estrogen receptor subtypes, estrogen receptor alpha (ERα) and estrogen receptor beta (ERß), show structural differences and have different expression ratios in specific cells and tissues. Currently, the methods for confirming the estrogenic properties of compounds are the binding (Test guideline no. 493) and transactivation (Test guideline no. 455) assays provided by the Organization for Economic Co-operation and Development (OECD). In a previous study, we developed an ERα dimerization assay based on the bioluminescence resonance energy transfer (BRET) system, but there are currently no available tests that can confirm the effect of estrogenic compounds on ERß. Therefore, in this study, we developed a BRET-based ERß dimerization assay to confirm the estrogenic prosperities of compounds. The BRET-based ERß dimerization assay was verified using nine representative ER ligands and the results were compared with the dimerization activity of ERα. In conclusion, our BRET-based ERß dimerization assay can provide information on the ERß dimerization potential of estrogenic compounds.

An In vitro dimerization assay for the adverse outcome pathway approach in risk assessment of human estrogen receptor α-mediated endocrine-disrupting chemicals.

The adverse outcome pathway (AOP) has been recently proposed as an effective framework for chemical risk assessment. The AOP framework offers the advantage of effectively integrating individual in vitro studies and in silico prediction models. Thus, the development of an effective testing method to measure key events caused by chemicals is essential for chemical risk assessment through a fully developed AOP framework. We developed a human cell-based estrogen receptor α (ERα) dimerization assay using the bioluminescence resonance energy transfer (BRET) technique and evaluated the ERα dimerization activities of 72 chemicals. Fifty-one chemicals were identified to mediate dimerization of ERα, and the BRET-based ERα dimerization assay could effectively measure the events that mediated dimerization of ERα by the estrogenic chemicals. These results were compared with the results of pre-existing assay to determine whether the BRET-based ERα dimerization assay could be employed as an in vitro test method to provide scientific information for explaining key events as a part of the AOP framework. Consequently, we propose that the BRET-based ERα dimerization assay is suitable for measuring the chemical-mediated dimerization of ERα, a key event in the AOP framework for cellular-level risk assessment of estrogenic chemicals.

Comparative study of estrogenic activities of phytoestrogens using OECD in vitro and in vivo testing methods.

With growing scientific interest in phytoestrogens, a number of studies have investigated the estrogenic potential of phytoestrogens in a wide variety of assay systems. However, evaluations of individual phytoestrogens with different assay systems make it difficult for predicting their relative estrogenic potency. The objective of this study was to compare estrogenic properties of fifteen known phytoestrogens using an estrogen receptor-α (ER-α) dimerization assay and Organization for Economic Cooperation and Development (OECD) standardized methods including in vitro estrogen receptor (ER) transactivation assay using VM7Luc4E2 cells and in vivo uterotrophic assay using an immature rat model. Human ER-α dimerization assay showed positive responses of eight test compounds and negative responses of seven compounds. These results were consistently found in luciferase reporter assay results for evaluating ER transactivation ability. Seven test compounds exhibiting relatively higher in vitro estrogenic activities were subjected to uterotrophic bioassays. Significant increases in uterine weights were only found after treatments with biochanin A, 8-prenylnaringenin, and coumestrol. Importantly, their uterotrophic effects were lost when animals were co-treated with antagonist of ER, indicating their ER-dependent effects in the uterus. In addition, analysis of estrogen responsive genes revealed that these phytoestrogens regulated uterine gene expressions differently compared to estrogens. Test methods used in this study provided a high consistency between in vitro and in vivo results. Thus, they could be used as effective screening tools for phytoestrogens, particularly focusing on their interactions with ER-α.

Effects of the frequency of ostomy management reinforcement education on self-care knowledge, self-efficacy, and ability of stoma appliance change among Korean hospitalised ostomates.

Patients who undergo stoma surgery experience difficulties in adapting physically and psychologically. The priority is to support them in learning self-care for successful rehabilitation and psychosocial adaption to a new life. In order to do this, it is important to provide ostomates with repetitive reinforcement education on self-care in a continuous and individual manner, not just to increase knowledge or perform related skills. This study aims to evaluate the effects of ostomy management reinforcement education (OMRE) in ostomates and to identify the optimal frequency of reinforcement education using an equivalent control group post-test design. Participants were 60 ostomates admitted to a university hospital after ostomy formation surgery, and they were randomly assigned to a control and two experimental groups of this study. The OMRE was given to the control group (n = 20), experimental group 1 (n = 20), and experimental group 2 (n = 20) once, twice, and three times, respectively. Participants' self-care knowledge, self-efficacy, and ability of stoma appliance change were evaluated before and after the OMRE. Major results of this study were as follows: the self-care knowledge score of post-test was higher than the pretest in the control, experimental 1, and experimental two groups (P < 0.001). The self-efficacy score of post-test was higher than the pretest in the control, experimental 1, and experimental 2 groups (P < 0.001). The self-care knowledge score according to the frequency of OMRE did not differ among the control, experimental 1, and experimental 2 groups (F = 1.921, P = 0.156). The self-efficacy score according to the frequency of OMRE was significantly different between the control and experimental groups (F = 8.616, P = 0.001), but there was no difference between the experimental 1 and experimental 2 groups (Scheffe's post-hoc analysis: a < b, c). The ability of stoma appliance change score according to the frequency of OMRE was significantly different between the control and experimental groups (F = 49.546, P < 0.001), but there was no difference between the experimental 1 and experimental 2 groups (Scheffe's post-hoc analysis: a < b, c). Results of this study suggested that the OMRE was effective for promoting hospitalised ostomates' self-care knowledge, self-efficacy, and ability of stoma appliance change, and two sessions of the OMRE was the most effective. Findings of this study may be useful in planning education programmes designed to improve self-care ability for hospitalised ostomates.