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 (ERβ), 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 ERβ dimerization and ER transactivation assays to differentiate the specific binding and function of ERα and ERβ from 12 representative natural and synthetic estrogenic substances. Results revealed that 11 chemicals mediated receptor ERα and ERβ 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.

Effects of treadmill exercise on anxiety-like behavior in association with changes in estrogen receptors ERα, ERβ and oxytocin of C57BL/6J female mice

Exercise can reduce the incidence of stress-related mental diseases, such as depression and anxiety. Control group was neither exposed to CVMS nor TRE (noCVMS/noTRE). Females were tested and levels of serum17-beta-oestradiol (E₂), estrogen receptors α immunoreactive neurons (ERα-IRs), estrogen receptors β immunoreactive neurons (ERβ-IRs) and oxytocin immunoreactive neurons (OT-IRs) were measured. The results showed there's increased anxiety-like behaviors for mice from CVMS/noTRE, CVMS/higher speed TRE (CVMS/HTRE) and noCVMS/HTRE groups when they were put in open field and elevated maze tests. They had lower serum E₂ levels than mice from CVMS/low-moderate speed TRE (CVMS/LMTRE), noCVMS/LMTRE and noCVMS/noTRE groups. The three groups of CVMS/noTRE, CVMS/HTRE and noCVMS/HTRE mice had more ERα-IRs and less ERβ-IRs in the medial preoptic area (mPOA), bed nucleus of the stria terminalis (BNST) and medial amygdala (MeA), hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON). The number of OT-IRs in PVN and SON of CVMS/noTRE, CVMS/HTRE and noCVMS/HTRE mice was also lower than that of mice from CVMS/LMTRE, noCVMS/LMTRE and noCVMS/noTRE groups. Interestingly, CVMS/LMTRE and noCVMS/LMTRE mice were similar to noCVMS/noTRE mice in that they did not show anxiety, while CVMS/HTRE and noCVMS/HTRE mice did not, which were similar to the mice in CVMS/noTRE. We propose that LMTRE instead of HTRE changes the serum concentration of E₂. ERβ/ERα ratio and OT level in the brain may be responsible for the decrease in anxiety-like behavior in female mice exposed to anxiety-inducing stress conditions.

PM2.5 organic extract mediates inflammation through the ERβ pathway to contribute to lung carcinogenesis in vitro and vivo

An increasing number of researches have shown that fine particulate matter (PM2.5) is closely related to increased respiratory inflammation and can even lead to lung cancer. Estrogen receptor β (ERβ) has been demonstrated to be involved in several cancers. However, the exact role of ERβ in PM2.5 organic extract (Po)-promoted inflammation and lung cancer remains unknown. The purpose of this study was to investigate whether ERβ is involved in Po induced inflammation and lung cancer. In vitro, our results showed that interleukin-6 (IL-6) and ERβ were simultaneously increased in lung bronchial epithelial cells exposed to Po; additionally, inhibition of ERβ decreased IL-6 expression and secretion through inactivating ERK and AKT and further promoted cells malignant transformation. Moreover, we performed an animal model of inhalation exposure to Po using female C57BL/6 mice. Although we were unable to find tumor tissue in mice exposed to Po, we detected evidence of lung inflammation, epithelial-to-mesenchymal transition (EMT) phenotype and severe pulmonary injury; in addition, intraperitoneal injection of PHTPP (an ERβ inhibitor) showed that the above phenomena have been improved, which demonstrate that Po stimulates IL-6 expression to promote inflammation, EMT phenotype and lung injury through the ERβ pathway. In conclusion, our results confirmed the potential toxic effect of PM2.5, and increased our understanding of PM2.5 carcinogenic potential by exploring the mechanism of ERβ regulating inflammation.

Estradiol Treatment during Perinatal Development Alters Adult Partner Preference, Mating Behavior and Estrogen Receptors α and β in the Female Mandarin Vole (Microtus mandarinus)

During development, many aspects of behavior, including partner preferences and sexual conduct, are "organized" by estradiol. This study aimed at analyze these processes in the mandarin vole (Microtus mandarinus), a novel experimental mammal with strong monogamous pair bonds. Female pups were treated daily with an oil vehicle (FC) or β-Estradiol (E2, FT) from prenatal day 14 to postnatal day 10. Male pups were treated daily with the oil vehicle only (MC). Partner preferences, sexual conduct and the expression of estrogen receptors α (ERα) and β (ERβ) were examined when animals were 3 months old. FT and MC groups showed female-directed partner preferences and masculinized behavior. ERα- immunoreactive neurons (ERα-IRs) in the bed nucleus of stria terminalis (BNST) and medial amygdaloid nucleus (MeA) was greater in FT females than MC males, and there was no significant difference in the number of ERα-IRs between FT and FC females. No difference was found for ERα-IRs in the preoptic area (mPOA) or ventromedial nucleus of the hypothalamus (VMH) of FT females or MC males, and they were significantly fewer than in FC females. ERβ-immunoreactive neurons (ERβ-IRs) in these four brain regions did not alter the ERβ/ERα ratio in different brain regions during perintal developments. However, the number of ERβ-IRs in FT females and MC males were greater than in FC females. We propose that estradiol treatment during perinatal development is responsible for adult partner preferences and mating behavior.

Estrogen receptor beta increases sensitivity to enzalutamide in androgen receptor-positive triple-negative breast cancer

PURPOSE

Androgen receptor (AR) is playing an important role in the progression of a subset of TNBC. We evaluated the impact of ERβ expression along with anti-AR drugs in AR-positive TNBC.

METHODS

ERβ expression was examined in AR-positive TNBC cell line using MTT assay, scratch and Annexin V-FITC assay in the presence or absence of anti-androgens. Protein levels of involved molecules were assessed using Western blot. Receptors' localization was detected by immunofluorescence and their physical association was examined using proximity ligation assay (PLA), which enables the visualization of interacting proteins in fixed cells and tissues.

RESULTS

Transient transfection of ERβ in MDA-MB 453 AR-positive TNBC cell line significantly inhibited cell proliferation, metastatic potential and induced apoptosis. ERβ expression reversed the aggravating role of AR in both indirect and direct ways. Indirectly, ERβ decreased AR activation through the inhibition of PI3K/AKT signaling pathway. Directly, ERβ formed heterodimers with AR in MDA-MB 453 cells and in human tissue samples impeding AR from forming homodimers. Enzalutamide is a more potent anti-androgen in AR + TNBC compared to bicalutamide. ERβ expression increased the sensitivity of MDA-MB 453 cells to anti-androgens and especially to enzalutamide. The administration of enzalutamide enhanced AR:ERβ heterodimers formation increasing the anti-tumor capacity of ERβ.

CONCLUSIONS

Collectively, our results provide evidence for a novel mechanism by which ERβ exerts oncosuppressive effect in AR-positive TBNC through direct and indirect interactions with AR. Moreover, ERβ expression may identify a new subset of TNBC that would respond more favorable to anti-androgens.

ERβ and ApoE isoforms interact to regulate BDNF-5-HT2A signaling and synaptic function in the female brain

Background

Depression has been reported to be commonly manifested in patients with Alzheimer’s disease (AD) and is considered a risk factor for AD. The human apolipoprotein E (ApoE) gene exists in three major isoforms (coded by ε2, ε3, and ε4), and the ε4 allele has been associated with a greater incidence of both depression and AD. Although mounting evidence points to the potentially complex interaction between these two brain disorders in which ApoE might play a role, the underlying mechanisms are largely unknown.

Methods

Using human ApoE2, ApoE3, and ApoE4 gene-targeted replacement (hApoE-TR) mouse models, we investigated the role of ApoE isoforms and their potential interactions with estrogen receptor β (ERβ) signaling in modulating the brain mechanisms involved in depression.

Results

Our initial analyses in 6-month-old female hApoE-TR mice demonstrated that ApoE influenced the expression of brain-derived neurotrophic factor (BDNF) and the 5-hydroxytryptamine 2A (5-HT_2A) serotonin receptor in an isoform-dependent manner, with the ApoE4 brain exhibiting the lowest level of BDNF and the highest level of 5-HT_2A. In addition, both presynaptic and postsynaptic proteins were downregulated, indicating a synaptic deficit in ApoE4 brains. Our subsequent analyses revealed that a 3-month chronic treatment with an ERβ-targeted (83-fold selectivity over ERα) phytoestrogenic diet induced several changes in ApoE2 and ApoE3 brains, including a significant decrease in the expression of 5-HT_2A receptors and an increase in BDNF/tropomyosin receptor kinase B and synaptic proteins. In contrast, ApoE4 brains were largely unresponsive to the treatment, with an increase only in select synaptic proteins in the treated group.

Conclusions

Taken together, these results indicate that ApoE4 negatively impacts BDNF–5-HT_2A signaling in the female brain, which could in part underlie the ApoE4-mediated increased risk for depression. In a larger context, this mechanism could serve as a molecular link between depression and AD associated with ApoE4. Enhancing ERβ activity could provide a greater therapeutic benefit to non-ApoE4 carriers than to ApoE4 carriers in interventions for these brain disorders.

Estrogen receptor β deficiency impairs BDNF-5-HT2A signaling in the hippocampus of female brain: A possible mechanism for menopausal depression

Depression currently affects 350 million people worldwide and 19 million Americans each year. Women are 2.5 times more likely to experience major depression than men, with some women appearing to be at a heightened risk during the menopausal transition. Estrogen signaling has been implicated in the pathophysiology of mood disorders including depression; however, the underlying mechanisms are poorly understood. In this study, the role of estrogen receptor (ER) subtypes, ERα and ERβ, in the regulation of brain-derived neurotrophic factor (BDNF) and serotonin (5-HT) signaling was investigated; two pathways that have been hypothesized to be interrelated in the etiology of depression. The analyses in ERα^-/- and ERβ^-/- mouse models demonstrated that BDNF was significantly downregulated in ERβ^-/- but not ERα^-/- mice, and the ERβ^-/--mediated effect was brain-region specific. A 40% reduction in BDNF protein expression was found in the hippocampus of ERβ^-/- mice; in contrast, the changes in BDNF were at a much smaller magnitude and insignificant in the cortex and hypothalamus. Further analyses in primary hippocampal neurons indicated that ERβ agonism significantly enhanced BDNF/TrkB signaling and the downtream cascades involved in synaptic plasticity. Subsequent study in ERβ mutant rat models demonstrated that disruption of ERβ was associated with a significantly elevated level of 5-HT_2A but not 5-HT_1A in rat hippocampus, indicating ERβ negatively regulates 5-HT_2A. Additional analyses in primary neuronal cultures revealed a significant association between BDNF and 5-HT_2A pathways, and the data showed that TrkB activation downregulated 5-HT_2A whereas activation of 5-HT_2A had no effect on BDNF, suggesting that BDNF/TrkB is an upstream regulator of the 5-HT_2A pathway. Collectively, these findings implicate that the disruption in estrogen homeostasis during menopause leads to dysregulation of BDNF-5-HT_2A signaling and weakened synaptic plasticity, which together predispose the brain to a vulnerable state for depression. Timely intervention with an ERβ-targeted modulator could potentially attenuate this susceptibility and reduce the risk or ameliorate the clinical manifestation of this brain disorder.

Prognostic value of the expression of estrogen receptor β in patients with non-small cell lung cancer: a meta-analysis

BACKGROUND

Lung cancer remains the leading cause of cancer-related deaths in men and the second leading cause in women worldwide. It is becoming increasingly clear that estrogen and estrogen receptors are involved in the pathogenesis and development of lung cancer. However, observational studies on the prognostic role of estrogen receptor β (ERβ) in non-small cell lung cancer (NSCLC) are controversial.

METHODS

To clarify the impact of ERβ in NSCLC survival, we performed this meta-analysis that included eligible studies. The combined hazard ratios (HR) and their corresponding 95% confidence intervals (CIs) were calculated in terms of overall survival.

RESULTS

A total of eleven studies with 3,300 patients were evaluable for this meta-analysis. Our results suggested that ERβ overexpression had no relationship on survival of patients with NSCLC, the HR (95% CI) was 1.000 (0.954-1.047) overall. Moreover, there was no heterogeneity between the studies.

CONCLUSIONS

ERβ overexpression indicates no relationship of prognosis for patients with NSCLC.