Estrogen receptor beta in health and disease

Cellular targets of estrogen signaling in regeneration of inner ear sensory epithelia

Estrogen signaling in auditory and vestibular sensory epithelia is a newly emerging focus propelled by the role of estrogen signaling in many other proliferative systems. Understanding the pathways with which estrogen interacts can provide a means to identify how estrogen may modulate proliferative signaling in inner ear sensory epithelia. Reviewed herein are two signaling families, EGF and TGFbeta. Both pathways are involved in regulating proliferation of supporting cells in mature vestibular sensory epithelia and have well characterized interactions with estrogen signaling in other systems. It is becoming increasingly clear that elucidating the complexity of signaling in regeneration will be necessary for development of therapeutics that can initiate regeneration and prevent progression to a pathogenic state.

Endothelial NOS, estrogen receptor beta, and HIFs cooperate in the activation of a prognostic transcriptional pattern in aggressive human prostate cancer

The identification of biomarkers that distinguish between aggressive and indolent forms of prostate cancer (PCa) is crucial for diagnosis and treatment. In this study, we used cultured cells derived from prostate tissue from patients with PCa to define a molecular mechanism underlying the most aggressive form of PCa that involves the functional activation of eNOS and HIFs in association with estrogen receptor beta (ERbeta). Cells from patients with poor prognosis exhibited a constitutively hypoxic phenotype and increased NO production. Upon estrogen treatment, formation of ERbeta/eNOS, ERbeta/HIF-1alpha, or ERbeta/HIF-2alpha combinatorial complexes led to chromatin remodeling and transcriptional induction of prognostic genes. Tissue microarray analysis, using an independent cohort of patients, established a hierarchical predictive power for these proteins, with expression of eNOS plus ERbeta and nuclear eNOS plus HIF-2alpha being the most relevant indicators of adverse clinical outcome. Genetic or pharmacologic modulation of eNOS expression and activity resulted in reciprocal conversion of the transcriptional signature in cells from patients with bad or good outcome, respectively, highlighting the relevance of eNOS in PCa progression. Our work has considerable clinical relevance, since it may enable the earlier diagnosis of aggressive PCa through routine biopsy assessment of eNOS, ERbeta, and HIF-2alpha expression. Furthermore, proposing eNOS as a therapeutic target fosters innovative therapies for PCa with NO inhibitors, which are employed in preclinical trials in non-oncological diseases.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

Development of alopecia areata is associated with higher central and peripheral hypothalamic-pituitary-adrenal tone in the skin graft induced C3H/HeJ mouse model

The relationship of the stress response to the pathogenesis of alopecia areata (AA) was investigated by subjecting normal and skin graft-induced, AA-affected C3H/HeJ mice to light ether anesthesia or restraint stress. Plasma corticosterone (CORT), adrenocorticotropic hormone (ACTH), and estradiol (E2) levels were determined by RIA, whereas gene expression in brains, lymphoid organs, and skin was measured by quantitative RT-PCR for corticotropin-releasing hormone (Crh), arginine vasopressin (Avp), proopiomelanocortin (Pomc), glucocorticoid receptor (Nr3c1), mineralocorticoid receptor (Nr3c2), corticotropin-releasing hormone receptor types 1 and 2 (Crhr1, Crhr2), interleukin-12 (Il12), tumor necrosis factor-alpha (Tnf alpha), and estrogen receptors type-1 (Esr1) and type-2 (Esr2). AA mice had a marked increase in hypothalamic-pituitary-adrenal (HPA) tone and activity centrally, and peripherally in the skin and lymph nodes. There was also altered interaction between the adrenal and gonadal axes compared with that in normal mice. Stress further exacerbated changes in AA mouse HPA activity both centrally and peripherally. AA mice had significantly blunted CORT and ACTH responses to acute ether stress (physiological stressor) and a deficit in habituation to repeated restraint stress (psychological stressor). The positive correlation of HPA hormone levels with skin Th1 cytokines suggests that altered HPA activity may occur as a consequence of the immune response associated with AA.

Soy isoflavones supplementation alleviates disease severity in autoimmune-prone MRL-lpr/lpr mice

Soy isoflavones supplements, which are phyto-oestrogens widely used as alternatives to alleviate menopausal syndromes or prevent chronic diseases, may exert oestrogenic and anti-oestrogenic activities. This study aimed to investigate the effects of soy isoflavones supplement on oestrogen-related autoimmune disease, such as systemic lupus erythematosus, using autoimmune-prone female MRL- lpr/lpr mice. Eighty mice of 8 weeks were divided into five groups: 0 (Control), 2 (Isf 2), 10 (Isf 10) and 20 (Isf 20) mg/kg BW/day Phyto SoyaTM isoflavones or 0.375 mg/kg BW/day tamoxifen (TAM) as the positive control, by tube-feeding. Some mice were killed at age 15 weeks for cellular cytokine secretion. The data suggested that the Isf 20 and TAM groups had higher weight gain and survival compared with the control group. At age 22 weeks, the Isf 20 group still had 75% survival comparable to mice treated with TAM. At age 14 weeks, the TAM group showed significantly lower serum anti-double-stranded (ds) DNA IgG and anti-cardiolipin IgG. The mice in the Isf 10 and Isf 20 groups also had lower anti-dsDNA IgG and anti-cardiolipin IgG. The interferon (IFN)-γ secretion from mitogen-stimulated T cells in the Isf 20 and TAM groups were significantly lower than those of control mice. Furthermore, the oestrogenic activity of the methanol extracts of soy isoflavones for oestrogen receptor (ER)β, but not ERα, significantly increased, suggesting that soy isoflavones have a selective modulation of ER activation. Thus, soy isoflavone supplementation did not aggravate murine lupus, but apparently ameliorated the disease.

Induction of mitochondria-involved apoptosis in estrogen receptor-negative cells by a novel tamoxifen derivative, ridaifen-B

Tamoxifen is an antagonist of estrogen receptor, which is used widely as an estrogen receptor-positive breast cancer drug that blocks growth signals and provokes apoptosis. However, recent studies have revealed that tamoxifen induces apoptosis even in estrogen receptor-negative cells. In the present study, we synthesized several tamoxifen derivatives to augment the apoptosis-inducing effect of tamoxifen and evaluated the apoptosis-inducing pathway. The estrogen receptor-positive human leukemia cell line HL-60 and estrogen receptor-negative human leukemia cell line Jurkat were treated with tamoxifen and synthesized tamoxifen derivatives, and thereafter subjected to cell viability-detection assays. Tamoxifen derivatives, as well as the lead compound tamoxifen, decreased the cell viability despite the expression of estrogen receptor. Among all of the synthesized tamoxifen derivatives, ridaifen-B had more potent cancer cell-damaging activity than tamoxifen. Ridaifen-B fragmented Jurkat cell DNA and activated caspases, suggesting that the ridaifen-B-induced apoptosis pathway is estrogen receptor independent. Moreover, mitochondrial involvement during ridaifen-B-induced apoptosis was estimated. Ridaifen-B significantly reduced mitochondrial membrane potential, and overexpression of Bcl-2 inhibited ridaifen-B-induced apoptosis. These results suggest that the induction of apoptosis by ridaifen-B, a novel tamoxifen derivative, is dependent on mitochondrial perturbation without estrogen receptor involvement.

Sterility and absence of histopathological defects in nonreproductive organs of a mouse ERbeta-null mutant

Estrogen signaling is mediated by estrogen receptors alpha (ERalpha) and beta (ERbeta). Although a consensus has now been reached concerning many physiological functions of ERalpha, those of ERbeta are still controversial: When housed and examined in two distant laboratories, mice originating from the same initial ERbeta mutant exhibited widely different phenotypes, which were themselves different from the phenotype of another ERbeta mutant previously generated in our laboratory. Because, in addition to a knockout insertion in exon 3, all these mouse mutants displayed alternative splicing transcripts, we have now constructed a ERbeta mouse mutant (ERbeta(ST)(L-/L-)) in which exon 3 was cleanly deleted by Cre/LoxP-mediated excision and was devoid of any transcript downstream of exon 3. Both females and males were sterile. The histology of the ovary was mildly affected, and no histological defects were detected in other organs, neither in females nor in males. Our present results, which are in contrast with previously published data, suggest that, with the notable exception of male and female reproduction, ERbeta is not required in the mouse for the development and homeostasis of the major body systems.

Isoflavones--safe food additives or dangerous drugs?

The sales volume of products containing isoflavone has increased since the publication of the Women's Health Initiative. The many apparently contradictory results published on the effects of isoflavones on a variety of estrogen-regulated organs point to both beneficial as well as adverse effects on human health. It is of particular importance that psychovegetative climacteric complaints such as hot flushes are, if at all, only slightly influenced by isoflavones. The substances appear to have weak anti-osteoporotic effect. Their anti-atherosclerotic action is debatable, as not all authors find any beneficial effect on lipids. Most importantly, there is dispute as to whether isoflavones derived from soy or red clover have negative, positive or any effect at all on the mammary gland or endometrium. It is beyond any doubt that soy products may have cancer preventing properties in a variety of organs including the mammary gland. However, these properties may only be exerted if the developing organ was under the influence of isoflavones during childhood and puberty. This may also explain the often quoted "Japanese Phenomenon", the fact that breast cancer occurs to a lesser extent in Japanese women. When administered to isoflavone "inexperienced" women at the time of menopause, the phytoestrogens appear to share the same effects as estrogen used in classical preparations for hormone replacement therapy, i.e. they may stimulate the proliferation of endometrial and mammary gland tissue with at present unknown and unpredictable risk to these organs. Therefore, the following question arises for the clinician: Why should soy or red clover products containing isoflavone be recommended, if the positive effects are only negligible but the adverse effects serious?

ERRgamma suppresses cell proliferation and tumor growth of androgen-sensitive and androgen-insensitive prostate cancer cells and its implication as a therapeutic target for prostate cancer

Estrogen receptor-related receptors (ERR) are orphan nuclear receptors, which are constitutively activated without estrogen binding. Recent evidence indicates that the ligand-independent ERRs may be involved in similar ER-mediated regulatory pathways and modulate estrogen responsiveness in certain target cells. We recently showed that an ERR subtype, ERRgamma, is coexpressed with ERbeta in normal human prostatic epithelial cells and exhibits reduced expression in many prostate cancer cell lines and clinical neoplastic prostate tissues. Based on this, we hypothesize that ERRgamma may have growth regulatory roles in prostate and prostate cancer. We showed in this study that ERRgamma was expressed in epithelial cell nuclei in fetal and pubertal human prostates, whereas its nuclear expression became reduced in advanced prostate cancer lesions. Stable ERRgamma expression by retroviral transduction suppressed significantly both in vitro cell growth and in vivo tumorigenicity of two prostate cancer cell lines, LNCaP and DU145, as evidenced by a cell-cycle arrest at G(1)-S transition and also induction of two cyclin-dependent kinase inhibitors p21(WAF1/CIP1) and p27(KIP1). We further showed by reporter assay that induction of p21 and p27 by ERRgamma was mediated through direct transactivation of their gene promoters. Moreover, we also showed that a selective ERRgamma-agonist, DY131, could potentiate the ERRgamma-induced growth inhibition in LNCaP-ERRgamma and DU145-ERRgamma cells in a dose-dependent manner compared with respective parental cells. Taken together, our results show that ERRgamma may perform an antiproliferative or tumor-suppressing function in prostate cancer cells. More importantly, our results suggest that ERRgamma could be a novel therapeutic target for prostate cancer treatment.

AP-2 regulates the transcription of estrogen receptor (ER)-beta by acting through a methylation hotspot of the 0N promoter in prostate cancer cells

We reported previously that the loss of expression of estrogen receptor (ER)-beta during the development of prostate cancer (PCa) is associated with methylation of a CpG island located in the 5'-flanking sequence of the 0N promoter. Three methylation hotspots, referred to as centers 1, 2 and 3, were identified in the CpG island. In this study, we demonstrated that a 581-bp region with these three centers within it is sufficient for the promoter activity in PCa cells. Deletion analyses indicated that center 1 (16 bp), with a putative activator protein-2 (AP-2) binding site, is essential for gene transactivation. Chromatin immunoprecipitation assays showed that AP-2alpha occupies a short sequence containing center 1. Forced expression of AP-2alpha or -2gamma, but not -2beta, increased activity of the ERbeta 0N promoter and the accumulation of mRNA. Conversely, siRNA-mediated AP-2alpha and -2gamma knockdown reduced levels of ERbeta transcript and promoter activity. Quantitative reverse transcription-PCR showed that AP-2alpha and -2gamma are the predominant transcripts expressed in PCa cells, and levels of ERbeta transcript correlate with levels of these AP-2 transcripts among different PCa cell lines. These results provide the first evidence that ERbeta is an AP-2-regulated gene. They also support the hypothesis that certain cis-acting elements are methylation hotspots susceptible to epigenetic modifications during cancer progression.

Effects of estrogen receptor subtype-selective agonists on autoimmune disease in lupus-prone NZB/NZW F1 mouse model

The specific roles of estrogen receptor (ER) subtypes alpha and beta in mediating estrogen's influences on lupus autoimmunity are unknown. Herein we found that ovariectomized NZB/NZW F1 mice treated with propyl pyrazole triol (ERalpha-selective agonist) had significantly shorter survival, earlier development of albuminuria, higher serum concentrations of total IgG and prolactin, increased serum levels of anti-DNA IgG3, IgG2a and IgG2b and decreased anti-DNA IgG1 level compared to vehicle controls. In contrast, diarylpropionitrile (ERbeta-selective agonist) administration significantly decreased serum anti-DNA IgG2b level but did not significantly affect serum levels of other anti-DNA IgG subclasses, serum total IgG or prolactin concentration, mortality or the occurrence of albuminuria. These findings suggest that ERalpha activation plays the predominant and immunostimulatory role in estrogen-mediated modulation of lupus while ERbeta activation appears to have a slightly immunosuppressive effect on this disease. ERalpha activation coincidentally increased serum prolactin concentrations and may accelerate lupus disease activity also through this mechanism.

Apigenin suppresses cancer cell growth through ERbeta

Two flavonoids, genistein and apigenin, have been implicated as chemopreventive agents against prostate and breast cancers. However, the mechanisms behind their respective cancer-protective effects may vary significantly. The goal of this study was to determine whether the antiproliferative action of these flavonoids on prostate (DU-145) and breast (MDA-MB-231) cancer cells expressing only estrogen receptor (ER) beta is mediated by this ER subtype. It was found that both genistein and apigenin, although not 17beta-estradiol, exhibited antiproliferative effects and proapoptotic activities through caspase-3 activation in these two cell lines. In yeast transcription assays, both flavonoids displayed high specificity toward ERbeta transactivation, particularly at lower concentrations. However, in mammalian assay, apigenin was found to be more ERbeta-selective than genistein, which has equal potency in inducing transactivation through ERalpha and ERbeta. Small interfering RNA-mediated downregulation of ERbeta abrogated the antiproliferative effect of apigenin in both cancer cells but did not reverse that of genistein. Our data unveil, for the first time, that the anticancer action of apigenin is mediated, in part, by ERbeta. The differential use of ERalpha and ERbeta signaling for transaction between genistein and apigenin demonstrates the complexity of phytoestrogen action in the context of their anticancer properties.

Estrogen receptor (ER)-beta, but not ER-alpha, is present in thyroid vessels: immunohistochemical evaluations in multinodular goiter and papillary thyroid carcinoma

OBJECTIVE

Estrogen receptors (ERs) have been demostrated in the vessel structures of several systems. Little is known on the presence of ERs in the thyroid vessels.

DESIGN

We immunohistochemically evaluated both ER-alpha and ER-beta immunoreactivity (IR) in both vascular and follicular thyroid cells in tissue samples from 17 cases of multinodular goiter (MNG) and 17 cases of papillary thyroid carcinoma (PTC).

MAIN OUTCOME

ER-alpha IR was undetectable in either tissue examined. In 100% of MNG samples, nuclear ER-beta IR was detected in both endothelial and follicular cells. In PTC samples, endothelial nuclear ER-beta IR was found in 100% of cases, whereas the nuclear staining of follicular cells was found in 83% of cases. The intensity of staining of the endothelial ER-beta IR was comparable between MNG and PTC. However, when follicular cells were considered, a tendency toward a decrease in nuclear staining and a significant increase in cytoplasmic staining were found in PTC lesions as compared to MNG.

CONCLUSIONS

This study demonstrated that ER-beta, but not ER-alpha, IR is present in the endothelium of thyroid vessels. Furthermore, although data need to be confirmed in larger observations, these results suggest the lack of differences in the pattern of vascular ER-beta IR between MNG and PTC.

Estrogen receptors: new players in diabetes mellitus

Diabetes mellitus type 2 is a systemic disease characterized by imbalance of energy metabolism, which is mainly caused by inadequate insulin action. Recent data have revealed a surprising role for estradiol in regulating energy metabolism and opened new insights into the role of the two estrogen receptors, ERalpha and ERbeta, in this context. New findings on gene modulation by ERalpha and ERbeta of insulin-sensitive tissues indicate that estradiol participates in glucose homeostasis by modulating the expression of genes that are involved in insulin sensitivity and glucose uptake. Drugs that can selectively modulate the activity of either ERalpha or ERbeta in their interactions with target genes represent a promising frontier in diabetes mellitus coadjuvant therapy.

Structure-function relationship of estrogen receptor alpha and beta: impact on human health

17Beta-estradiol (E2) controls many aspects of human physiology, including development, reproduction and homeostasis, through regulation of the transcriptional activity of its cognate receptors (ERs). The crystal structures of ERs with agonists and antagonists and the use of transgenic animals have revealed much about how hormone binding influences ER conformation(s) and how this conformation(s), in turn, influences the interaction of ERs with co-activators or co-repressors and hence determines ER binding to DNA and cellular outcomes. This information has helped to shed light on the connection between E2 and the development or progression of numerous diseases. Current therapeutic strategy in the treatment of E2-related pathologies relies on the modulation of ER trancriptional activity by anti-estrogens; however, data accumulated during the last five years reveal that ER activities are not only restricted to the nucleus. ERs are very mobile proteins continuously shuttling between protein targets located within various cellular compartments (e.g., membrane, nucleus). This allows E2 to generate different and synergic signal transduction pathways (i.e., non-genomic and genomic) which provide plasticity for cell response to E2. Understanding the structural basis and the molecular mechanisms by which ER transduce E2 signals in target cells will allow to create new pharmacologic therapies aimed at the treatment of a variety of human diseases affecting the cardiovascular system, the reproductive system, the skeletal system, the nervous system, the mammary gland, and many others.

Advancing the study of stroke in women: summary and recommendations for future research from an NINDS-Sponsored Multidisciplinary Working Group

BACKGROUND AND PURPOSE

Women have poorer outcomes from stroke than men. Women also have risk factors that are unique, including pregnancy and hormone therapy. Hormone therapy for postmenopausal replacement increased the risk of ischemic stroke according to results of the Women's Health Initiative clinical trials. Based on the current understanding of the mechanisms of action of estrogen, the reasons for this increased risk are uncertain. One method to better understand the reasons for this increased risk is to re-evaluate estrogen's role in the neurovascular unit, simplistically comprised of the neurons, glia, and endothelial cells, as well as the processes of inflammation, and hemostasis/thrombosis. Besides the role of estrogen there are many gaps of knowledge about issues specific to women and stroke.

SUMMARY OF REVIEW

A multidisciplinary workshop was held in August 2005 to summarize the current evidence for estrogen and, more generally, stroke in women, and to provide recommendations for future basic, preclinical, and clinical research studies.

CONCLUSIONS

These studies may ultimately change the approach to stroke prevention and treatment in women.

Expression of metastasis-associated protein 1 (MTA1) in benign endometrium and endometrial adenocarcinomas

Endometrial carcinoma is one of the most common malignancies of the female genital tract. Metastasis-associated protein 1 (MTA1) is a component of the Mi-2/nucleosome remodeling and deacetylating complex and acts as a potent corepressor of estrogen receptor in breast cancer cells. MTA1 expression has been demonstrated in various cancers but has never been explored in endometrial carcinoma. We investigated the expression profile of MTA1 in different stages of benign endometrium as well as in endometrial endometrioid adenocarcinoma using immunohistochemistry and Western blotting. In the proliferative and secretory phases, MTA1 was expressed in both the glandular and the stromal compartments and was localized in nucleus and cytoplasm of these cells. MTA1 expression in secretory phase was less prominent when compared with the proliferative phase. In postmenopausal sections, MTA1 staining was observed in both glandular and stromal compartments and was localized in both nucleus and cytoplasm. Western blot analysis of 6 tumor specimens showed increased expression of MTA1 in all the tumors analyzed. Immunohistochemical staining performed on tumor microarray containing 70 endometrial endometrioid adenocarcinomas of various grades showed increased expression of MTA1 in 53 (75.7%) tumors. In grade 1 and grade 2 tumors, MTA1 was present in both nucleus and cytoplasm. Interestingly, in grade 3 tumors, MTA1 was localized in the cytoplasm only. Our results suggest a potential role of MTA1 in endometrial carcinomas.