Estrogen receptor binding to DNA is not required for its activity through the nonclassical AP1 pathway

Estrogen receptor β affects hypoxia response in colorectal cancer cells

The occurrence of colorectal cancer (CRC) is inversely correlated with estrogen receptor beta (ERβ) presence. Additionally, multiple studies associate low ERβ expression with poorer overall survival of CRC patients. Molecular pathways involved in ERβ - related reduced tumorigenesis include enhanced apoptosis, decreased proliferation, or repression of oncogenes. Moreover, the development of solid tumors, such as CRC, is often associated with an increased tumor mass that results in decreased oxygen partial tension, known as hypoxia, clinically associated with decreased prognosis and therapeutic resistance. Our high-throughput study suggests that ERβ also represses a hypoxic response in CRC cells. We observed a significantly altered transcriptional profile in HCT116 ERβ overexpressing cells that was further stimulated by E2 treatment under hypoxic conditions. The achieved data for downregulation of VEGFA, PDGFA and ANGPTL4 were validated in a time course experiment in DLD-1 cells. In addition, using an ERβ construct with a mutated DNA binding domain we observed that the downregulation of selected genes is dependent on the direct binding of this receptor to regulatory region genes. In addition, we observed that ERβ may affect the expression of the main hypoxia regulator, HIF1A, at the transcriptional and translational levels. In summary, ERβ alters the hypoxic outcome in CRC cells.

Alternative promoters and splicing create multiple functionally distinct isoforms of oestrogen receptor alpha in breast cancer and healthy tissues

BACKGROUND

Oestrogen receptor alpha (ER) is involved in cell growth and proliferation and functions as a transcription factor, a transcriptional coregulator, and in cytoplasmic signalling. It affects, for example, bone, endometrium, ovaries and mammary epithelium. It is a key biomarker in clinical management of breast cancer, where it is used as a prognostic and treatment-predictive factor, and a therapeutical target. Several ER isoforms have been described, but transcript annotation in public databases is incomplete and inconsistent, and functional differences are not well understood.

METHODS

We have analysed short- and long-read RNA sequencing data from breast tumours, breast cancer cell lines, and normal tissues to create a comprehensive annotation of ER transcripts and combined it with experimental studies of full-length protein and six alternative isoforms.

RESULTS

The isoforms have varying transcription factor activity, subcellular localisation, and response to the ER-targeting drugs tamoxifen and fulvestrant. Antibodies differ in ability to detect alternative isoforms, which raises concerns for the interpretation of ER-status in routine pathology.

CONCLUSIONS

Future work should investigate the effects of alternative isoforms on patient survival and therapy response. An accurate annotation of ER isoforms will aid in interpretation of clinical data and inform functional studies to improve our understanding of the ER in health and disease.

High expression of the RET receptor tyrosine kinase and its ligand GDNF identifies a high-risk subset of estrogen receptor positive breast cancer

PURPOSE

Resistance to endocrine therapy is the primary cause of treatment failure and death in patients with ER-positive (ER +)/luminal breast cancer. Expression and activation of the RET receptor tyrosine kinase may be driving poor outcomes. We aim to identify high-risk patients and druggable pathways for biomarker-based clinical trials.

METHODS

We obtained batch-normalized mRNA expression data from Breast Invasive Carcinoma-The Cancer Genome Atlas, PanCancer Atlas (BRCA-TCGA). To determine clinically significant cutoffs for RET expression, patients were grouped at different thresholds for Kaplan-Meier plotting. Differential gene expression (DGE) analysis and enrichment for gene sets was performed. transcriptomic dataset of antiestrogen-treated ER + tumors stratified by clinical response was then analyzed.

RESULTS

High RET expression was associated with worse outcomes in patients with ER + tumors, and stratification was enhanced by incorporating GDNF expression. High RET/GDNF patients had significantly lower overall survival (HR = 2.04, p = 0.012), progression-free survival (HR = 2.87, p < 0.001), disease-free survival (HR = 2.67, p < 0.001), and disease-specific survival (HR = 3.53, p < 0.001) than all other ER + patients. High RET/GDNF tumors were enriched for estrogen-independent signaling and targetable pathways including NTRK, PI3K, and KRAS. Tumors with adaptive resistance to endocrine therapy were enriched for gene expression signatures of high RET/GDNF primary tumors.

CONCLUSION

Expression and activation of the RET receptor tyrosine kinase may be driving poor outcomes in some patients with ER + breast cancer. ER + patients above the 75th percentile may benefit from clinical trials with tyrosine kinase inhibitors.

The hormonal environment and estrogen receptor signaling alters Chlamydia muridarum infection in vivo

Genital Chlamydia is the most common bacterial sexually transmitted infection in the United States and worldwide. Previous studies indicate that the progression of chlamydial infection is influenced by various factors, including the female sex hormones estrogen and progesterone. Sex hormone levels naturally fluctuate in women throughout their menstrual cycle. Varying concentrations of estrogen and progesterone may impact the progression of chlamydial infection and the host's immune response to Chlamydia. Estrogen signals through estrogen receptors (ERs), ERα and ERβ. These receptors are similar in structure and function, but are differentially expressed in tissues throughout the body, including the genital tract and on cells of the immune system. In this study, we used ovariectomized (OVT) BALB/c mice to investigate the impact of long-term administration of physiologically relevant concentrations of estrogen (E2), progesterone (P4), or a combination of E2/P4 on the progression of and immune response to C. muridarum infection. Additionally, we used ERα and ERβ knockout C57/BL6 mice to determine the how ERs affect chlamydial infection and the resulting immune response. Estrogen exposure prevented C. muridarum infection in vaginally infected OVT mice exposed to E2 alone or in combination with P4, while OVT or Sham mice exposed to hormone free, P4 or depo-medroxyprogesterone acetate shed similar amounts of chlamydiae. The hormonal environment also altered T cell recruitment and IFNϵ production the genital tracts of infected OVT and Sham mice on day 10 post infection. The absence of ERα, but not ERβ, in ER knockout mouse strains significantly changed the timing of C. muridarum infection. ERαKO mice shed significantly more chlamydiae at day 3 post infection and resolved the infection faster than WT or ERβKO animals. At day 9 post infection, flow cytometry showed that ERαKO mice had more T cells present and targeted RNA sequencing revealed increased expression of CD4 and FOXP3, suggesting that ERαKO mice had increased numbers of regulatory T cells compared to ERβKO and WT mice. Mock and chlamydia-infected ERαKO mice also expressed more IFNϵ early during infection. Overall, the data from these studies indicate that sex hormones and their receptors, particularly ERα and ERβ, differentially affect C. muridarum infection in murine models of infection.

GPNMB promotes abdominal fat deposition in chickens: genetic variation, expressional profile, biological function, and transcriptional regulation

Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a vital secreted factor that promotes the occurrence of obesity in mammals. However, the effects of GPNMB on abdominal fat deposition is still unknown in chickens. In this study, we looked into the genetic and expression association of GPNMB gene with abdominal fat traits in chicken, and found that a genetic variation rs31126482 in GPNMB promoter was significantly associated with abdominal fat weight (AFW, P < 0.05) and abdominal fat percentage (AFP, P < 0.01). Express profile analysis of the GPNMB indicated that the gene was mainly expressed in abdominal fat tissue, and its expression level was strongly positively correlated with AFW (R² = 0.6356, P = 4.10E−05) and AFP (R² = 0.6450, P = 2.90E−05). We then investigated biological function of GPNMB on adipogenesis in chicken, and found that GPNMB could inhibit abdominal preadipocyte proliferation, but promote abdominal preadipocyte differentiation and lipid deposition. Furthermore, we explored regulatory mechanism of GPNMB gene in chicken, and detected one nonclassical estrogen regulatory element (AP1) and one peroxisome proliferator-activated receptor α (PPARα) responsive element in the 2 kb promoter region of GPNMB gene, and demonstrated that estrogen could up-regulate GPNMB mRNA expression in adipose tissue and primary abdominal preadipocytes, while PPARα could down-regulate GPNMB expression in primary preadipocytes. Taken together, this study brings new insights into understanding the function and transcriptional control of GPNMB gene, and provides genetic markers for breeding selection to improve abdominal fat traits in chicken.

Estrogen Receptor α Inactivation in 2 Sisters: Different Phenotypic Severities for the Same Pathogenic Variant

CONTEXT

Estrogens play an essential role in reproduction. Their action is mediated by nuclear α and β receptors (ER) and by membrane receptors. Only 3 females and 2 males, from 3 families, with a loss of ERα function have been reported to date.

OBJECTIVE

We describe here a new family, in which 2 sisters display endocrine and ovarian defects of different severities despite carrying the same homozygous rare variant of ESR1.

METHODS

A 36-year-old woman from a consanguineous Jordanian family presented with primary amenorrhea and no breast development, with high plasma levels of 17β-estradiol (E2), follicle-stimulating hormone and luteinizing hormone, and enlarged multifollicular ovaries, strongly suggesting estrogen resistance. Her 18-year-old sister did not enter puberty and had moderately high levels of E2, high plasma gonadotropin levels, and normal ovaries.

RESULTS

Genetic analysis identified a homozygous variant of ESR1 leading to the replacement of a highly conserved glutamic acid with a valine (ERα-E385V). The transient expression of ERα-E385V in HEK293A and MDA-MB231 cells revealed highly impaired ERE-dependent transcriptional activation by E2. The analysis of the KISS1 promoter activity revealed that the E385V substitution induced a ligand independent activation of ERα. Immunofluorescence analysis showed that less ERα-E385V than ERα-WT was translocated into the nucleus in the presence of E2.

CONCLUSION

These 2 new cases are remarkable given the difference in the severity of their ovarian and hormonal phenotypes. This phenotypic discrepancy may be due to a mechanism partially compensating for the ERα loss of function.

An Optimized ChIP-Seq Protocol to Determine Chromatin Binding of Estrogen Receptor Beta

Estrogen regulates transcription through two nuclear receptors, ERα and ERβ, in a tissue and cellular-dependent manner. Both the receptors bind estrogen and activate transcription through direct or indirect interactions with DNA. Revealing their interactions with the chromatin is key to understanding their transcriptional activities and their biological functions. Chromatin-immunoprecipitation followed by sequencing (ChIP-Seq) is a powerful technique to map protein-DNA interactions at precise genomic locations. The genome-wide binding of ERα has been extensively studied. Similar studies of ERβ, however, have been more difficult, in part due to a lack of endogenous expression in cell lines and lack of specific antibodies. In this chapter, we provide an optimized stepwise ChIP protocol for a well-validated ERβ antibody, which is applicable for ChIP-Seq analysis of cell lines with exogenous expression of ERβ.

The physiological role of estrogen receptor functional domains

Estrogen receptor (ER) is a member of the nuclear receptor superfamily whose members share conserved domain structures, including a DNA-binding domain (DBD) and ligand-binding domain (LBD). Estrogenic chemicals work as ligands for activation or repression of ER-mediated transcriptional activity derived from two transactivation domains: AF-1 and AF-2. AF-2 is localized in the LBD, and helix 12 of the LBD is essential for controlling AF-2 functionality. The positioning of helix 12 defines the ER alpha (ERα) ligand properties as agonists or antagonists. In contrast, it is still less well defined as to the ligand-dependent regulation of N-terminal AF-1 activity. It has been thought that the action of selective estrogen receptor modulators (SERMs) is mediated by the regulation of a tissue specific AF-1 activity rather than AF-2 activity. However, it is still unclear how SERMs regulate AF-1 activity in a tissue-selective manner. This review presents some recent observations toward information of ERα mediated SERM actions related to the ERα domain functionality, focusing on the following topics. (1) The F-domain, which is connected to helix 12, controls 4-hydroxytamoxifen (4OHT) mediated AF-1 activation associated with the receptor dimerization activity. (2) The zinc-finger property of the DBD for genomic sequence recognition. (3) The novel estrogen responsive genomic DNA element, which contains multiple long-spaced direct-repeats without a palindromic ERE sequence, is differentially recognized by 4OHT and E2 ligand bound ERα transactivation complexes.

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, being frequently associated with obesity, unbalanced dietary regimens, and reduced physical activity. Despite their greater adiposity and reduced physical activity, women show a lower risk of developing NAFLD in comparison to men, likely a consequence of a sex-specific regulation of liver metabolism. In the liver, sex differences in the uptake, synthesis, oxidation, deposition, and mobilization of lipids, as well as in the regulation of inflammation, are associated with differences in NAFLD prevalence and progression between men and women. Given the major role of sex hormones in driving hepatic sexual dimorphism, this review will focus on the role of sex hormones and their signaling in the regulation of hepatic metabolism and in the molecular mechanisms triggering NAFLD development and progression.

Sex Differences, Estrogen Metabolism and Signaling in the Development of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex and devastating disease with a poor long-term prognosis. While women are at increased risk for developing PAH, they exhibit superior right heart function and higher survival rates than men. Susceptibility to disease risk in PAH has been attributed, in part, to estrogen signaling. In contrast to potential pathological influences of estrogen in patients, studies of animal models reveal estrogen demonstrates protective effects in PAH. Consistent with this latter observation, an ovariectomy in female rats appears to aggravate the condition. This discrepancy between observations from patients and animal models is often called the "estrogen paradox." Further, the tissue-specific interactions between estrogen, its metabolites and receptors in PAH and right heart function remain complex; nonetheless, these relationships are essential to characterize to better understand PAH pathophysiology and to potentially develop novel therapeutic and curative targets. In this review, we explore estrogen-mediated mechanisms that may further explain this paradox by summarizing published literature related to: (1) the synthesis and catabolism of estrogen; (2) activity and functions of the various estrogen receptors; (3) the multiple modalities of estrogen signaling in cells; and (4) the role of estrogen and its diverse metabolites on the susceptibility to, and progression of, PAH as well as their impact on right heart function.

Kisspeptin Neurons and Estrogen-Estrogen Receptor α Signaling: Unraveling the Mystery of Steroid Feedback System Regulating Mammalian Reproduction

Estrogen produced by ovarian follicles plays a key role in the central mechanisms controlling reproduction via regulation of gonadotropin-releasing hormone (GnRH) release by its negative and positive feedback actions in female mammals. It has been well accepted that estrogen receptor α (ERα) mediates both estrogen feedback actions, but precise targets had remained as a mystery for decades. Ever since the discovery of kisspeptin neurons as afferent ERα-expressing neurons to govern GnRH neurons, the mechanisms mediating estrogen feedback are gradually being unraveled. The present article overviews the role of kisspeptin neurons in the arcuate nucleus (ARC), which are considered to drive pulsatile GnRH/gonadotropin release and folliculogenesis, in mediating the estrogen negative feedback action, and the role of kisspeptin neurons located in the anteroventral periventricular nucleus-periventricular nucleus (AVPV-PeN), which are thought to drive GnRH/luteinizing hormone (LH) surge and consequent ovulation, in mediating the estrogen positive feedback action. This implication has been confirmed by the studies showing that estrogen-bound ERα down- and up-regulates kisspeptin gene (Kiss1) expression in the ARC and AVPV-PeN kisspeptin neurons, respectively. The article also provides the molecular and epigenetic mechanisms regulating Kiss1 expression in kisspeptin neurons by estrogen. Further, afferent ERα-expressing neurons that may regulate kisspeptin release are discussed.

Enhancer RNAs Mediate Estrogen-Induced Decommissioning of Selective Enhancers by Recruiting ERα and Its Cofactor

The function of enhancer RNAs (eRNAs) in transcriptional regulation remains obscure. By analyzing the genome-wide nascent transcript profiles in breast cancer cells, we identify a special group of eRNAs that are essential for estrogen-induced transcriptional repression. Using eRNAs of TM4SF1 and EFEMP1 as the paradigms, we find that these RNA molecules not only stabilize promoter-enhancer interactions but also recruit liganded estrogen receptor α (ERα) to particular enhancer regions, facilitate the formation of a functional transcriptional complex, and cause gene silencing. Interestingly, ERα is shown to directly bind with eRNAs by its DNA-binding domain. These eRNAs help with the formation of a specific ERα-centered transcriptional complex and promote the association of the histone demethylase KDM2A, which dismisses RNA polymerase II from designated enhancers and suppresses the transcription of target genes. Our work demonstrates a complete mechanism underlying the action of eRNAs in modulating and refining the locus-specific transcriptional program.

Yang et al. identified a group of eRNAs that are essential for estrogen-induced transcriptional repression by assisting with the chromatin recruitment of ERα through binding to its DNA-binding domain and facilitating the interaction of ERα with its cofactors, which leads to the dismissal of RNA polymerase II.

Regulatory Role of Sex Hormones in Cardiovascular Calcification

Sex differences in cardiovascular disease (CVD), including aortic stenosis, atherosclerosis and cardiovascular calcification, are well documented. High levels of testosterone, the primary male sex hormone, are associated with increased risk of cardiovascular calcification, whilst estrogen, the primary female sex hormone, is considered cardioprotective. Current understanding of sexual dimorphism in cardiovascular calcification is still very limited. This review assesses the evidence that the actions of sex hormones influence the development of cardiovascular calcification. We address the current question of whether sex hormones could play a role in the sexual dimorphism seen in cardiovascular calcification, by discussing potential mechanisms of actions of sex hormones and evidence in pre-clinical research. More advanced investigations and understanding of sex hormones in calcification could provide a better translational outcome for those suffering with cardiovascular calcification.

Genome-wide estrogen receptor β chromatin binding in human colon cancer cells reveals its tumor suppressor activity

Colorectal cancer (CRC) is the third leading cause of cancer death in the western world. In women, menopausal hormone therapy has been shown to reduce CRC incidence by 20%. Studies demonstrate that estrogen activating estrogen receptor beta (ERβ) protects against CRC. ERβ is a nuclear receptor that regulates gene expression through interactions with the chromatin. This molecular mechanism is, however, not well characterized in colon. Here, we present for the first time, the cistrome of ERβ in different colon cancer cell lines. We use cell lines engineered to express ERβ, optimize and validate an ERβ antibody for chromatin-immunoprecipitation (ChIP), and perform ChIP-Seq. We identify key binding motifs, including ERE, AP-1, and TCF sites, and we determine enrichment of binding to cis-regulatory chromatin sites of genes involved in tumor development, cell migration, cell adhesion, apoptosis, and Wnt signaling pathways. We compare the corresponding cistromes of colon and breast cancer and find that they are conserved for about a third of genes, including GREB1, but that ERβ tethering to TCF and KLF family motifs is characteristic for colon. We exemplify upregulation of putative CRC tumor suppressor gene CST5 where ERβ in colon cells binds to cis-regulatory regions nearby (-351 bp) the transcriptional start site. Our work provides a foundation for understanding the mechanism of action of ERβ in CRC prevention.

Sexual hormones and diabetes: The impact of estradiol in pancreatic β cell

Diabetes is one of the most prevalent metabolic diseases and its incidence is increasing throughout the world. Data from World Health Organization (WHO) point-out that diabetes is a major cause of blindness, kidney failure, heart attacks, stroke and lower limb amputation and estimated 1.6 million deaths were directly caused by it in 2016. Population studies show that the incidence of this disease increases in women after menopause, when the production of estrogen is decreasing in them. Knowing the impact that estrogenic signaling has on insulin-secreting β cells is key to prevention and design of new therapeutic targets. This chapter explores the role of estrogen and their receptors in the regulation of insulin secretion and biosynthesis, proliferation, regeneration and survival in pancreatic β cells. In addition, delves into the genetic animal models developed and its application for the specific study of the different estrogen signaling pathways. Finally, discusses the impact of menopause and hormone replacement therapy on pancreatic β cell function.

In-silico identification of potential inhibitors targeting the DNA binding domain of estrogen receptor α for the treatment of hormone therapy-resistant breast cancer

Estrogen receptor α (ERα) plays a critical role in breast cancer (BC) development. The standard therapeutic strategies for ERα- positive (ERα+) BC consist of impairing ERα signalling pathway by either estrogen competitors blocking its interaction with the ligand binding domain (LBD) or agents inhibiting the production of estrogen. These strategies are limited by many factors that lead to constitutive activation of ERα and consequently, resistance to treatment. Targeting the DNA binding domain (DBD) of ERα instead of its LBD with small-molecule inhibitors could be an alternative to impair ERα's signalling pathway. For this purpose, we conducted a structure based virtual screening of DrugBank against the crystal structure of ERα-DBD (PDB ID: 1HCQ) using the Glide module in standard precision (SP) and extra precision (XP) mode of docking. Molecules with XP Gscore less than -8 kcal/mol were selected and visually inspected to keep only the reasonable docking poses. Subsequently, these molecules were clustered using structural interaction fingerprints analysis and the complexes of the top ranked molecules of each cluster based on XP Gscore were subjected to 200 ns molecular dynamics simulations followed by MM-GBSA binding free energy calculation for the last 100 ns of each complex. In this study, we identified three molecules from DrugBank namely DB03450, DB02593 and DB08001 showing significant stability and strong interaction with the key amino acids during MD simulation suggesting a potential inhibition of the target. These molecules could be used as promising lead compounds to impair the ERα signalisation in hormone therapy-resistant breast cancer.Communicated by Ramaswamy H. Sarma.

R269C variant of ESR1: high prevalence and differential function in a subset of pancreatic cancers

Background

Estrogen receptor α (ESR1) plays a critical role in promoting growth of various cancers. Yet, its role in the development of pancreatic cancer is not well-defined. A less studied region of ESR1 is the hinge region, connecting the ligand binding and DNA domains. rs142712646 is a rare SNP in ESR1, which leads to a substitution of arginine to cysteine at amino acid 269 (R269C). The mutation is positioned in the hinge region of ESR1, hence may affect the receptor structure and function. We aimed to characterize the activity of R269C-ESR1 and study its role in the development of pancreatic cancer.

Methods

Transcriptional activity was evaluated by E2-response element (ERE) and AP1 –luciferase reporter assays and qRT-PCR. Proliferation and migration were assessed using MTT and wound healing assays. Gene-expression analysis was performed using RNAseq.

Results

We examined the presence of this SNP in various malignancies, using the entire database of FoundationOne and noted enrichment of it in a subset of pancreatic non-ductal adenocarcinoma (n = 2800) compared to pancreatic ductal adenocarcinoma (PDAC) as well as other tumor types (0.53% vs 0.29%, p = 0.02). Studies in breast and pancreatic cancer cells indicated cell type-dependent activity of ESR1 harboring R269C. Thus, expression of R269C-ESR1 enhanced proliferation and migration of PANC-1 and COLO-357 pancreatic cancer cells but not of MCF-7 breast cancer cells. Moreover, R269C-ESR1 enhanced E2-response elements (ERE) and AP1-dependent transcriptional activity and increased mRNA levels of ERE and AP1-regulated genes in pancreatic cancer cell lines, but had a modest effect on MCF-7 breast cancer cells. Accordingly, whole transcriptome analysis indicated alterations of genes associated with tumorigenicity in pancreatic cancer cells and upregulation of genes associated with cell metabolism and hormone biosynthesis in breast cancer cells.

Conclusions

Our study shed new light on the role of the hinge region in regulating transcriptional activity of the ER and indicates cell-type specific activity, namely increased activity in pancreatic cancer cells but reduced activity in breast cancer cells. While rare, the presence of rs142712646 may serve as a novel genetic risk factor, and a possible target for therapy in a subset of non-ductal pancreatic cancers.

Estrogen Reverses HDAC Inhibitor-Mediated Repression of Aicda and Class-Switching in Antibody and Autoantibody Responses by Downregulation of miR-26a

Estrogen contributes to females' strong antibody response to microbial vaccines and proneness to autoimmunity, particularly antibody-mediated systemic autoimmunity, in females. We have hypothesized that this is due to estrogen-mediated potentiation of class switch DNA recombination (CSR) and somatic hypermutation (SHM). As we have shown, estrogen boosts AID expression, which is critical for both CSR and SHM, through upregulation of HoxC4, which together with NF-κB critically mediates Aicda (AID gene) promoter activation. We contend here that additional regulation of Aicda expression by estrogen occurs through epigenetic mechanisms. As we have shown, histone deacetylase inhibitors (HDIs) short-chain fatty acid (SCFA) butyrate and propionate as well as the pharmacologic HDI valproic acid upregulate miRNAs that silence AID expression, thereby modulating specific antibody responses in C57BL/6 mice and autoantibody responses in lupus-prone MRL/Faslpr/lpr mice. Here, using constitutive knockout Esr1-/- mice and B cells as well as conditional knockout Aicdacre/creEsr1flox/flox mice and B cells, we showed that the HDI-mediated downregulation of Aicda expression as well as the maturation of antibody and autoantibody responses is reversed by estrogen and enhanced by deletion of ERα or E2 inhibition. Estrogen's reversion of HDI-mediated inhibition of Aicda and CSR in antibody and autoantibody responses occurred through downregulation of B cell miR-26a, which, as we showed, targets Aicda mRNA 3'UTR. miR-26a was significantly upregulated by HDIs. Accordingly, enforced expression of miR-26a reduced Aicda expression and CSR, while miR-26a-sponges (competitive inhibitors of miR-26a) increased Aicda expression and CSR. Thus, our findings show that estrogen reverses the HDI-mediated downregulation of AID expression and CSR through selective modulation of miR-26a. They also provide mechanistic insights into the immunomodulatory activity of this hormone and a proof-of-principle for using combined ER inhibitor-HDI as a potential therapeutic approach.

Estrogen-Receptor Expression and Function in Female Reproductive Disease

Estrogen receptors (ER) include ER alpha, ER beta and new membrane receptor G protein-coupled receptor 30 (GPR30). Estrogen receptors are key receptors to maintain ovarian granulosa cell differentiation, follicle and oocyte growth and development, and ovulation function. The abnormal functions of estrogen, its receptors, and estradiol synthesis-related enzymes are closely related to clinical reproductive endocrine diseases, such as polycystic ovary syndrome (PCOS) and endometriosis (EMS). At present, hormone therapy is the main treatment for ovarian-related diseases, and a stable hormone environment is established by regulating ovarian function. In recent years, some estrogen-related drugs have made great progress, such as clomiphene, which is a nonsteroidal antiestrogen drug in clinical application. This article elaborates on the regulatory role of estrogen and its nuclear receptors and membrane receptors in oocyte development, especially female reproductive diseases related to the abnormal expression of estrogen and its receptors. We also highlighted the latest advances of treatment strategy for these diseases and the application of related targeted small molecule drugs in clinical research and treatment, so as to provide reference for the treatment of female reproductive diseases.

Dynamic interactions between the extracellular matrix and estrogen activity in progression of ER+ breast cancer

Metastatic, anti-estrogen resistant estrogen receptor α positive (ER+) breast cancer is the leading cause of breast cancer deaths in U.S. women. While studies have demonstrated the importance of the stromal tumor microenvironment in cancer progression and therapeutic responses, effects on the responses of ER+ cancers to estrogen and anti-estrogens are poorly understood, particularly in the complex in vivo environment. In this study, we used an estrogen responsive syngeneic mouse model to interrogate how a COL1A1-enriched fibrotic ECM modulates integrated hormonal responses in cancer progression. We orthotopically transplanted the ER+ TC11 cell line into wild-type (WT) or collagen-dense (Col1a1^tm1Jae/+, mCol1a1) syngeneic FVB/N female mice. Once tumors were established, recipients were supplemented with 17β-estradiol (E2), tamoxifen, or left untreated. Although the dense/stiff environment in mCol1a1 recipients did not alter the rate of E2-induced proliferation of the primary tumor, it fostered the agonist activity of tamoxifen to increase proliferation and AP-1 activity. Manipulation of estrogen activity did not alter the incidence of lung lesions in either WT or mCol1a1 hosts. However, the mCol1a1 environment enabled tamoxifen-stimulated growth of pulmonary metastases and further fueled estrogen-driven growth. Moreover, E2 remodeled peritumoral ECM architecture in WT animals, modifying alignment of collagen fibers and altering synthesis of ECM components associated with increased alignment and stiffness, and increasing FN1 and POSTN expression in the pulmonary metastatic niche. These studies demonstrate dynamic interactions between ECM properties and estrogen activity in progression of ER+ breast cancer, and support the need for therapeutics that target both ER and the tumor microenvironment.

Estrogen signaling: An emanating therapeutic target for breast cancer treatment

Breast cancer, a most common malignancy in women, was known to be associated with steroid hormone estrogen. The discovery of estrogen receptor (ER) gave us not only a powerful predictive and prognostic marker, but also an efficient target for the treatment of hormone-dependent breast cancer with various estrogen ligands. ER consists of two subtypes i.e. ERα and ERβ, that are mostly G-protein-coupled receptors and activated by estrogen, specially 17β-estradiol. The activation is followed by translocation into the nucleus and binding with DNA to modulate activities of different genes. ERs can manage synthesis of RNA through genomic actions without directly binding to DNA. Receptors are tethered by protein-protein interactions to a transcription factor complex to communicate with DNA. Estrogens also exhibit nongenomic actions, a characteristic feature of steroid hormones, which are so rapid to be considered by the activation of RNA and translation. These are habitually related to stimulation of different protein kinase cascades. Majority of post-menopausal breast cancer is estrogen dependent, mostly potent biological estrogen (E2) for continuous growth and proliferation. Estrogen helps in regulating the differentiation and proliferation of normal breast epithelial cells. In this review we have investigated the important role of ER in development and progression of breast cancer, which is complicated by receptor's interaction with co-regulatory proteins, cross-talk with other signal transduction pathways and development of treatment strategies viz. selective estrogen receptor modulators (SERMs), selective estrogen receptor down regulators (SERDs), aromatase and sulphatase inhibitors.

Repression of insulin gene transcription by indirect genomic signaling via the estrogen receptor in pancreatic beta cells

The mechanism whereby 17β-estradiol (E2) mediates insulin gene transcription has not been fully elucidated. In this study, exposure of hamster insulinoma (HIT-T15) cells to 5 × 10-9 to 1 × 10-7 M E2 led to a concentration-dependent decrease of insulin mRNA levels. Transient expression of the estrogen receptor (ER) in HIT-T15 cells revealed that estrogen receptor α (ERα) repressed transcription of the rat insulin II promoter in both ligand-dependent and ligand-independent manners. The N-terminal A/B domain of ERα was not required for either activity. However, the repression was absent with mutated ER lacking the DNA-binding domain. Moreover, introducing mutations in the D-box and P-box of the zinc finger of ER (C227S, C202L) also abolished the repression. Deletion of the insulin promoter region revealed that nucleotide positions - 238 to - 144 (relative to the transcriptional start site) were needed for ER repression of the rat insulin II gene. PDX1- and BETA2-binding sites were required for the repression, but an estrogen response element-like sequence or an AP1 site in the promoter was not involved. In conclusion, we found that estrogen repressed insulin mRNA expression in a beta cell line. In addition, the ER suppressed insulin gene transcription in a ligand-independent matter. These observations suggest ER may regulate insulin transcription by indirect genomic signaling.

Mechanisms of Sex Disparities in Cardiovascular Function and Remodeling

Epidemiological studies demonstrate disparities between men and women in cardiovascular disease prevalence, clinical symptoms, treatments, and outcomes. Enrollment of women in clinical trials is lower than men, and experimental studies investigating molecular mechanisms and efficacy of certain therapeutics in cardiovascular disease have been primarily conducted in male animals. These practices bias data interpretation and limit the implication of research findings in female clinical populations. This review will focus on the biological origins of sex differences in cardiovascular physiology, health, and disease, with an emphasis on the sex hormones, estrogen and testosterone. First, we will briefly discuss epidemiological evidence of sex disparities in cardiovascular disease prevalence and clinical manifestation. Second, we will describe studies suggesting sexual dimorphism in normal cardiovascular function from fetal life to older age. Third, we will summarize and critically discuss the current literature regarding the molecular mechanisms underlying the effects of estrogens and androgens on cardiac and vascular physiology and the contribution of these hormones to sex differences in cardiovascular disease. Fourth, we will present cardiovascular disease risk factors that are positively associated with the female sex, and thus, contributing to increased cardiovascular risk in women. We conclude that inclusion of both men and women in the investigation of the role of estrogens and androgens in cardiovascular physiology will advance our understanding of the mechanisms underlying sex differences in cardiovascular disease. In addition, investigating the role of sex-specific factors in the development of cardiovascular disease will reduce sex and gender disparities in the treatment and diagnosis of cardiovascular disease. © 2019 American Physiological Society. Compr Physiol 9:375-411, 2019.

Estrogen Receptors: New Directions in the New Millennium

Nineteen years have passed since our previous review in this journal in 1999 regarding estrogen receptors. At that time, we described the current assessments of the physiological activities of estrogen and estrogen receptors. Since that time there has been an explosion of progress in our understanding of details of estrogen receptor-mediated processes from the molecular and cellular level to the whole organism. In this review we discuss the basic understanding of estrogen signaling and then elaborate on the progress and current understanding of estrogen receptor actions that have developed using new models and continuing clinical studies.

Dynamic Expression Profile, Regulatory Mechanism and Correlation with Egg-laying Performance of ACSF Gene Family in Chicken (Gallus gallus)

Acyl-CoA synthetases (ACSs) are responsible for acyl-CoA synthesis from nonpolar hydrophilic fatty acids and play a vital role in many metabolic processes. As a category of ACS isozymes, members of ACS family (ACSF1-3) participate in lipid metabolism; however, their expression patterns, regulatory mechanisms and effects on egg-laying performance in chicken are poorly understood. Our in vivo and in vitro studies showed that ACSF1-3 genes were extensively expressed, and their expression levels changed dynamically in the liver among different development stages. Moreover, ACSF1 expression was upregulated and ACSF2 expression was downregulated by estrogen, but ACSF3 showed no response to estrogen treatment. The regulatory effect of estrogen on ACSF1 expression was mediated via ERα. The ACSF2 was highly expressed in the liver in peak-laying hens compared with pre-laying and late-laying hens, and also highly expressed in the liver continued egg-laying hens compared with inactive egg-laying hens. It is suggested that hepatic ACSF2 expression level might relate to egg-laying performance in chicken. In conclusion, the expression of ACSF1 was upregulated by estrogen via ERα, and the expression of ACSF2 was downregulated by estrogen and might be related to egg-laying performance in chicken.

Experimental models for evaluating non-genomic estrogen signaling

Non-genomic effects of estrogen receptor α (ERα) signaling have been described for decades. However, the mechanisms and physiological processes resulting solely from non-genomic signaling are poorly understood. Challenges in studying these effects arise from the strongly nucleophilic tendencies of estrogen receptor, and many approaches to excluding ERα from the nucleus have been explored over the years. In this review, we discuss past strategies for studying ERα's non-genomic action and current models, specifically H2NES ERα, first described by Burns et al. (2011). In vitro and preliminary in vivo data from H2NES ERα and H2NES mice suggest a promising avenue for pinpointing specific non-genomic ERα action.

Spotlight on triptorelin in the treatment of premenopausal women with early-stage breast cancer

Endocrine treatment represents the cornerstone of endocrine-sensitive premenopausal early breast cancer. The estrogen blockade plays a leading role in the therapeutic management of hormone receptor-positive breast cancer together with surgery, radiotherapy, and selective antiestrogen treatments. For several years, selective estrogen receptor modulators, such as tamoxifen, have represented the mainstay of therapy. The role of amenorrhea has been extensively elucidated in the past year: the benefit observed with chemotherapy-induced amenorrhea has strengthened its therapeutic role. Luteinizing hormone-releasing hormone (LHRH) has been introduced in oncology practice to induce amenorrhea in order to increase the advantage obtained from endocrine treatment. Triptorelin is one of the most widely used LHRH analogs currently available in clinical practice. It was recently investigated in two major clinical trials that studied the role of complete estrogen blockade in the premenopausal setting. Both showed the clinical benefit due to ovarian suppression treatment, primarily in high-risk patients. Furthermore, triptorelin and other LHRH analogs have recently been investigated in the attempt to preserve the ovarian function in young patients. The medical treatment of early breast cancer is always evolving in the effort to search for safe and efficacious treatments. The role of LHRH analogs is actually well recognized as contributing to the improvement of the medical treatment of premenopausal women with early breast cancer.

Hormone signaling and fatty liver in females: analysis of estrogen receptor α mutant mice

BACKGROUND

Treatment with estrogen in early menopausal women protects against development of hepatic steatosis and nonalcoholic fatty liver disease but estrogen has undesirable side effects, which negate its beneficial effects in premenopausal and postmenopausal women. Targeted therapies require better understanding of the target sites and mechanisms by which estrogen signaling exerts its protective effects in women. Estrogen receptor α (ERα) is thought to be the primary mediator for estrogen signaling to protect against hepatic steatosis. ERα has several mechanisms for signal transduction: (1) inducing gene transcription by direct binding to specific DNA sequences, (2) inducing tethered transcription with other DNA-binding factors, and (3) stimulating nongenomic action through membrane-associated ERα. However, it is still unclear which mechanisms mediate ERα-dependent protection against hepatic steatosis.

METHODS

To understand the mechanisms of estrogen signaling for protection against hepatic steatosis in females, we analyzed the global ERα knockout mouse (αERKO), ERα DNA-binding domain mutant mouse (KIKO) and liver-specific ERα knockout mouse (LERKO) fed high-fat diets (HFD). The KIKO mouse disrupts the direct DNA-binding transcription activity but retains tethered transcription regulation and nongenomic action. Hepatic steatosis was evaluated by scoring the macrovesicular and microvesicular steatosis as well as serum alanine aminotransferase (ALT) levels. We analyzed serum testosterone to assess its correlation with hepatic steatosis.

RESULTS

Liver fat accumulation was far greater in HFD-fed αERKO and KIKO females than in HFD-fed wild-type (WT) controls. Conversely, HFD-fed LERKO females did not accumulate excess liver fat. HFD-fed αERKO and KIKO females showed higher microvesicular steatosis and ALT levels than WT controls that correlated with increased serum testosterone levels.

CONCLUSIONS

ERα-mediated direct transcription in non-hepatic tissues is essential for estrogen-mediated protection against hepatic steatosis in HFD-fed females. The balance between non-hepatic estrogen signaling and hepatic or non-hepatic testosterone action may control hepatic steatosis.

Estrogen Hormone Biology

The hormone estrogen is involved in both female and male reproduction, as well as numerous other biological systems including the neuroendocrine, vascular, skeletal, and immune systems. Therefore, it is also implicated in many different diseases and conditions such as infertility, obesity, osteoporosis, endometriosis, and a variety of cancers. Estrogen works through its two distinct nuclear receptors, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Various transcriptional regulation mechanisms have been identified as the mode of action for estrogen, mainly the classical mechanism with direct DNA binding but also a nongenomic mode of action and one using tethered or indirect binding. The expression profiles of ERα and ERβ are unique with the primary sites of ERα expression being the uterus and pituitary gland and the main site of ERβ expression being the granulosa cells of the ovary. Mouse models with knockout or mutation of Esr1 and Esr2 have furthered our understanding of the role of each individual receptor plays in physiology. From these studies, it is known that the primary roles for ERα are in the uterus and neuroendocrine system, as female mice lacking ERα are infertile due to impaired ovarian and uterine function, whereas female mice lacking ERβ are subfertile due to ovarian defects. The development of effective therapies for estrogen-related diseases has relied on an understanding of the physiological roles and mechanistic functionalities of ERα and ERβ in human health and disease.

A plasmonic multi-logic gate platform based on sequence-specific binding of estrogen receptors and gold nanorods

A hybrid system made of gold nanorods (AuNRs) and double-stranded DNA (dsDNA) is used to build a versatile multi-logic gate platform, capable of performing six different logic operations. The sequence-specific binding of transcription factors to the DNA drives the optical response of the design.

Molecular mechanism of estrogen-estrogen receptor signaling

17β‐Estradiol (E2), as the main circulating estrogen hormone, regulates many tissue and organ functions in physiology. The effects of E2 on cells are mediated by the transcription factors and estrogen receptor (ER)α and ERβ that are encoded by distinct genes. Localized at the peri‐membrane, mitochondria, and the nucleus of cells that are dependent on estrogen target tissues, the ERs share similar, as well as distinct, regulatory potentials. Different intracellular localizations of the ERs result in dynamically integrated and finely tuned E2 signaling cascades that orchestrate cellular growth, differentiation, and death. The deregulation of E2–ER signaling plays a critical role in the initiation and progression of target tissue malignancies. A better understanding of the complex regulatory mechanisms that underlie ER actions in response to E2 therefore holds a critical trajectory for the development of novel prognostic and therapeutic approaches with substantial impacts on the systemic management of target tissue diseases.

GR and ER Coactivation Alters the Expression of Differentiation Genes and Associates with Improved ER+ Breast Cancer Outcome

In estrogen receptor (ER)-negative breast cancer, high tumor glucocorticoid receptor (GR) expression has been associated with a relatively poor outcome. In contrast, using a meta-analysis of several genomic datasets, here we find that tumor GR mRNA expression is associated with improved ER(+) relapse-free survival (RFS; independently of progesterone receptor expression). To understand the mechanism by which GR expression is associated with a better ER(+) breast cancer outcome, the global effect of GR-mediated transcriptional activation in ER(+) breast cancer cells was studied. Analysis of GR chromatin immunoprecipitation followed by high-throughput sequencing in ER(+)/GR(+) MCF-7 cells revealed that upon coactivation of GR and ER, GR chromatin association became enriched at proximal promoter regions. Furthermore, following ER activation, increased GR chromatin association was observed at ER, FOXO, and AP1 response elements. In addition, ER associated with GR response elements, suggesting that ER and GR interact in a complex. Coactivation of GR and ER resulted in increased expression (relative to ER activation alone) of transcripts that encode proteins promoting cellular differentiation (e.g., KDM4B, VDR) and inhibiting the Wnt signaling pathway (IGFBP4). Finally, expression of these individual prodifferentiation genes was associated with significantly improved RFS in ER(+) breast cancer patients. Together, these data suggest that the coexpression and subsequent activity of tumor cell GR and ER contribute to the less aggressive natural history of early-stage breast cancer by coordinating the altered expression of genes favoring differentiation.

IMPLICATIONS

The interaction between ER and GR activity highlights the importance of context-dependent nuclear receptor function in cancer. Mol Cancer Res; 14(8); 707-19. ©2016 AACR.

Oestrogens Downregulate Tissue Factor Pathway Inhibitor through Oestrogen Response Elements in the 5'-Flanking Region

Oestrogens influence the pathology and development of hormone-sensitive breast cancers. Tissue factor pathway inhibitor (TFPI) has been shown to be associated with breast cancer pathogenesis. Recently, we found TFPI mRNA levels to be significantly reduced by oestrogens in a breast cancer cell line (MCF7), a process mediated through the oestrogen receptor alpha (ERα). The aim of the present study was to investigate the mechanism(s) by which oestrogens may regulate TFPI at the transcriptional level. The TFPI 5’-flanking region contains three oestrogen response element (ERE) half-sites at positions -845, -769 and -50. Constructs containing the wild type or mutated ERE half-sites of the TFPI 5’-flanking region were generated in a luciferase reporter gene vector and transiently co-transfected with an ERα expression vector into HEK293 cells and subsequently treated with oestrogens. We found that luciferase activity was significantly downregulated after oestrogen stimulation in cells transfected with the wild type construct, an effect that was abolished by mutating either ERE half-sites. Electrophoretic mobility shift assay suggested direct and specific interaction of ERα with the ERE half-sites in the TFPI 5’-flanking region. Chromatin immunoprecipitation showed that ERα was recruited to the region -899 to -578 of the TFPI 5’-flanking region in vivo, where the ERE half-sites -845 and -769 are located. Our results indicate that ERα can interact with all three ERE half-sites in the TFPI 5’-flanking region and thus participate in the repression of oestrogen mediated TFPI transcription in breast cancer cells.

Silent Polymorphisms: Can the tRNA Population Explain Changes in Protein Properties?

Silent mutations are being intensively studied. We previously showed that the estrogen receptor alpha Ala87’s synonymous polymorphism affects its functional properties. Whereas a link has been clearly established between the effect of silent mutations, tRNA abundance and protein folding in prokaryotes, this connection remains controversial in eukaryotic systems. Although a synonymous polymorphism can affect mRNA structure or the interaction with specific ligands, it seems that the relative frequencies of isoacceptor tRNAs could play a key role in the protein-folding process, possibly through modulation of translation kinetics. Conformational changes could be subtle but enough to cause alterations in solubility, proteolysis profiles, functional parameters or intracellular targeting. Interestingly, recent advances describe dramatic changes in the tRNA population associated with proliferation, differentiation or response to chemical, physical or biological stress. In addition, several reports reveal changes in tRNAs’ posttranscriptional modifications in different physiological or pathological conditions. In consequence, since changes in the cell state imply quantitative and/or qualitative changes in the tRNA pool, they could increase the likelihood of protein conformational variants, related to a particular codon usage during translation, with consequences of diverse significance. These observations emphasize the importance of genetic code flexibility in the co-translational protein-folding process.

ERα Mediates Estrogen-Induced Expression of the Breast Cancer Metastasis Suppressor Gene BRMS1

Recently, estrogen has been reported as putatively inhibiting cancer cell invasion and motility. This information is in direct contrast to the paradigm of estrogen as a tumor promoter. However, data suggests that the effects of estrogen are modulated by the receptor isoform with which it interacts. In order to gain a clearer understanding of the role of estrogen in potentially suppressing breast cancer metastasis, we investigated the regulation of estrogen and its receptor on the downstream target gene, breast cancer metastasis suppressor 1 (BRMS1) in MCF-7, SKBR3, TTU-1 and MDA-MB-231 breast cancer cells. Our results showed that estrogen increased the transcription and expression of BRMS1 in the ERα positive breast cancer cell line, MCF-7. Additionally, the ERα specific agonist PPT also induced the transcription and expression of BRMS1. However, the two remaining estrogen receptor (ER) subtype agonists had no effect on BRMS1 expression. In order to further examine the influence of ERα on BRMS1 expression, ERα expression was knocked down using siRNA (siERα). Western blot analysis showed that siERα reduced estrogen-induced and PPT-induced BRMS1 expression. In summary, this study demonstrates estrogen, via its α receptor, positively regulates the expression of BRMS1, providing new insight into a potential inhibitory effect of estrogen on metastasis suppression.

Estrogen receptor α in cancer associated fibroblasts suppresses prostate cancer invasion via reducing CCL5, IL6 and macrophage infiltration in the tumor microenvironment

Background

Cancer associated fibroblasts (CAF) play important roles in tumor growth that involves inflammation and epithelial cell differentiation. Early studies suggested that estrogen receptor alpha (ERα) was expressed in stromal cells in normal prostates and prostate cancer (PCa), but the detailed functions of stromal ERα in the PCa remain to be further elucidated.

Methods

Migration and invasion assays demonstrated the presence of high levels of ERα in CAF cells (CAF.ERα(+)) suppressed PCa invasion via influencing the infiltration of tumor associated macrophages. ERα decreased CAF CCL5 secretion via suppressing the CCL5 promoter activity was examined by luciferase assay. ERα decreased CCL5 and IL-6 expression in conditioned media that was collected from CAF cell only or CAF cell co-cultured with macrophages as measured by ELISA assay.

Results

Both in vitro and in vivo studies demonstrated CAF.ERα(+) led to a reduced macrophage migration toward PCa via inhibiting CAF cells secreted chemokine CCL5. This CAF.ERα(+) suppressed macrophage infiltration affected the neighboring PCa cells invasion and the reduced invasiveness of PCa cells are at least partly due to reduced IL6 expression in the macrophages and CAF.

Conclusion

Our data suggest that CAF ERα could be applied as a prognostic marker to predict cancer progression, and targeting CCL5 and IL6 may be applied as an alternative therapeutic approach to reduce M2 type macrophages and PCa invasion in PCa patients with low or little ERα expression in CAF cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0488-9) contains supplementary material, which is available to authorized users.

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Estrogen has important effects on cardiovascular function including regulation of vascular function, blood pressure, endothelial relaxation, and the development of hypertrophy and cardioprotection. However, the mechanisms by which estrogen mediates these effects are still poorly understood. As detailed in this review, estrogen can regulate transcription by binding to 2 nuclear receptors, ERα and ERβ, which differentially regulate gene transcription. ERα and ERβ regulation of gene transcription is further modulated by tissue-specific coactivators and corepressors. Estrogen can bind to ERα and ERβ localized at the plasma membrane as well as G-protein-coupled estrogen receptor to initiate membrane delimited signaling, which enhances kinase signaling pathways that can have acute and long-term effects. The kinase signaling pathways can also mediate transcriptional changes and can synergize with the ER to regulate cell function. This review will summarize the beneficial effects of estrogen in protecting the cardiovascular system through ER-dependent mechanisms with an emphasis on the role of the recently described ER membrane signaling mechanisms.

The Estrogen Receptors: An Overview from Different Perspectives

The estrogen receptors, ERα, ERβ, and GPER, mediate the effects of estrogenic compounds on their target tissues. Estrogen receptors are located in the tissues of the female reproductive tract and breast as one would expect, but also in tissues as diverse as bone, brain, liver, colon, skin, and salivary gland. The purpose of this discussion of the estrogen receptors is to provide a brief overview of the estrogen receptors and estrogen action from perspectives such as the historical, physiological, pharmacological, pathological, structural, and ligand perspectives.

Molecular and Epigenetic Mechanism Regulating Hypothalamic Kiss1 Gene Expression in Mammals

After the discovery of hypothalamic kisspeptin encoded by the Kiss1 gene, the central mechanism regulating gonadotropin-releasing hormone (GnRH) secretion, and hence gonadotropin secretion, is gradually being unraveled. This has increased our understanding of the central mechanism regulating puberty and subsequent reproductive performance in mammals. Recently, emerging evidence has indicated the molecular and epigenetic mechanism regulating hypothalamic Kiss1 gene expression. Here we compile data regarding DNA and histone modifications in the Kiss1 promoter region and provide a hypothetic scheme of the molecular and epigenetic mechanism regulating Kiss1 gene expression in two populations of hypothalamic kisspeptin neurons, which govern puberty and subsequent reproductive performance via GnRH/gonadotropin secretion.

Estrogen receptor alpha inhibits RLR-mediated immune response via ubiquitinating TRAF3

RIG-I-like receptors (RLRs) function as key sentinel receptor for invading viruses. Moderate activation of RLR signaling is critical for efficient viral clearance without harmful immunopathology. Estrogen receptor alpha (ERα) is a member of the nuclear receptor superfamily of ligand-activated transcription factors and is involved in the regulation of innate immune responses. However, the effects of ERα on RLR signaling and the molecular mechanisms are poorly understood. In this study, we identify ERα as a negative regulator of RLR-triggered antiviral immune responses. The expression level of ERα is upregulated following RLR activation in macrophages. In the absence of ligand, VSV infection phosphorylates ERα at serine 167. ERα inhibits VSV-induced IRF3 activation. We further demonstrate that ERα directly interacts with TRAF3 and promotes K48-linked proteasomal degradation of TRAF3. Consistently, ERα inhibits VSV-triggered IFN-β production in macrophages in a ligand independent mechanism. Thus, ERα functions as a negative feedback regulator of RLR-triggered antiviral immune responses. These findings also provide the insights that separate the immune effects of ERα from its ligand-induced hormonal effects.

Gonadotropin and kisspeptin gene expression, but not GnRH, are impaired in cFOS deficient mice

cFOS is a pleiotropic transcription factor, which binds to the AP1 site in the promoter of target genes. In the pituitary gonadotropes, cFOS mediates induction of FSHβ and GnRH receptor genes. Herein, we analyzed reproductive function in the cFOS-deficient mice to determine its role in vivo. In the pituitary cFOS is necessary for gonadotropin subunit expression, while TSHβ is unaffected. Additionally, cFOS null animals have the same sex-steroid levels, although gametogenesis is impeded. In the brain, cFOS is not necessary for GnRH neuronal migration, axon targeting, cell number, or mRNA levels. Conversely, cFOS nulls, particularly females, have decreased Kiss1 neuron numbers and lower Kiss1 mRNA levels. Collectively, our novel findings suggest that cFOS plays a cell-specific role at multiple levels of the hypothalamic-pituitary-gonadal axis, affecting gonadotropes but not thyrotropes in the pituitary, and kisspeptin neurons but not GnRH neurons in the hypothalamus, thereby contributing to the overall control of reproduction.

The Tumor Macroenvironment: Cancer-Promoting Networks Beyond Tumor Beds

During tumor progression, alterations within the systemic tumor environment, or macroenvironment, result in the promotion of tumor growth, tumor invasion to distal organs, and eventual metastatic disease. Distally produced hormones, commensal microbiota residing within mucosal surfaces, myeloid cells and even the bone marrow impact the systemic immune system, tumor growth, and metastatic spread. Understanding the reciprocal interactions between the cells and soluble factors within the macroenvironment and the primary tumor will enable the design of specific therapies that have the potential to prevent dissemination and metastatic spread. This chapter will summarize recent findings detailing how the primary tumor and systemic tumor macroenvironment coordinate malignant progression.

Geniposide, the component of the Chinese herbal formula Tongluojiunao, protects amyloid-β peptide (1-42-mediated death of hippocampal neurons via the non-classical estrogen signaling pathway

Tongluojiunao (TLJN) is an herbal medicine consisting of two main components, geniposide and ginsenoside Rg1. TLJN has been shown to protect primary cultured hippocampal neurons. However, its mechanism of action remains unclear. In the present study, primary cultured hippocampal neurons treated with Aβ_1–42 (10 µmol/L) significantly increased the release of lactate dehydrogenase, which was markedly reduced by TLJN (2 µL/mL), specifically by the component geniposide (26 µmol/L), but not ginsenoside Rg1 (2.5 µmol/L). The estrogen receptor inhibitor, ICI182780 (1 µmol/L), did not block TLJN- or geniposide-mediated decrease of lactate dehydrogenase under Aβ_1–42-exposed conditions. However, the phosphatidyl inositol 3-kinase or mitogen-activated protein kinase pathway inhibitor, LY294002 (50 µmol/L) or U0126 (10 µmol/L), respectively blocked the decrease of lactate dehydrogenase mediated by TLJN or geniposide. Therefore, these results suggest that the non-classical estrogen pathway (i.e., phosphatidyl inositol 3-kinase or mitogen-activated protein kinase) is involved in the neuroprotective effect of TLJN, specifically its component, geniposide, against Aβ_1–42-mediated cell death in primary cultured hippocampal neurons.

The transcriptional activities and cellular localization of the human estrogen receptor alpha are affected by the synonymous Ala87 mutation

Until recently, synonymous mutations (which do not change amino acids) have been much neglected. Some evidence suggests that this kind of mutations could affect mRNA secondary structure or stability, translation kinetics and protein structure. To explore deeper the role of synonymous mutations, we studied their consequence on the functional activity of the estrogen receptor alpha (ERα). The ERα is a ligand-inducible transcription factor that orchestrates pleiotropic cellular effects, at both genomic and non-genomic levels in response to estrogens. In this work we analyzed in transient transfection experiments, the activity of ERα carrying the synonymous mutation Ala87, a polymorphism involving about 5-10% of the population. In comparison to the wild type receptor, our results show that ERαA87 mutation reduces the transactivation efficiency of ERα on an ERE reporter gene while its expression level remains similar. This mutation enhances 4-OHT-induced transactivation of ERα on an AP1 reporter gene. Finally, the mutation affects the subcellular localization of ERα in a cell type specific manner. It enhances the cytoplasmic location of ERα without significant changes in non-genomic effects of E2. The functional alteration of the ERαA87 determined in this work highlights the relevance of synonymous mutations for biomedical and pharmacological points of view.

Mechanisms of estradiol in fear circuitry: implications for sex differences in psychopathology

Over the past two decades, substantial knowledge has been attained about the mechanisms underlying the acquisition and subsequent extinction of conditioned fear. Knowledge gained on the biological basis of Pavlovian conditioning has led to the general acceptance that fear extinction may be a useful model in understanding the underlying mechanisms in the pathophysiology of anxiety disorders and may also be a good model for current therapies treating these disorders. Lacking in the current knowledge is how men and women may or may not differ in the biology of fear and its extinction. It is also unclear how the neural correlates of fear extinction may mediate sex differences in the etiology, maintenance, and prevalence of psychiatric disorders. In this review, we begin by highlighting the epidemiological differences in incidence rate. We then discuss how estradiol (E2), a primary gonadal hormone, may modulate the mechanisms of fear extinction and mediate some of the sex differences observed in psychiatric disorders.

Research resource: comparison of gene profiles from wild-type ERα and ERα hinge region mutants

We showed previously that the hinge region of estrogen receptor (ER) α is involved in mediating its actions. The hinge 1 (H1) ERα mutant has disrupted nuclear localization and has lost interaction with c-JUN, but retains estrogen response element (ERE)-mediated functions. The hinge 2 + nuclear export sequence (H2NES) ERα mutant does not maintain nuclear translocation with hormone and no longer activates ERE target genes but does retain a nongenomic, nonnuclear, rapid-action response. Herein, we used the human endometrial cancer Ishikawa stable cell lines (Ishikawa/vector, Ishikawa/wild-type [WT] ERα, Ishikawa/H1 ERα, or Ishikawa/H2NES ERα) to characterize the biological activities of these 2 ERα hinge region mutants. We confirmed by confocal microscopy increased cytoplasmic ERα in the H1 ERα cell line and full cytoplasmic ERα localization in the H2NES ERα cell line. Luciferase assays using the 3xERE reporter showed activation of H1 ERα and H2NES ERα by estradiol (E2) treatment, but using the endogenous pS2 reporter, luciferase activity was only seen with the H1 ERα cell line. Examining cell proliferation revealed that only the WT ERα and H1 ERα cell lines increased proliferation after treatment. Using microarrays, we found that WT ERα and H1 ERα cluster together, whereas vector and H2NES ERα are most similar and cluster independently of E2 treatment. These studies revealed that the nongenomic activities of ERα are unable to mediate proliferative changes or the transcriptional profile after treatment and demonstrate the importance of genomic action for ERα/E2-mediated responses with the nongenomic actions of ERα being complementary to elicit the full biological actions of ERα.

Dissection of estrogen receptor alpha signaling pathways in osteoblasts using RNA-sequencing

The effects of 17-β-estradiol in osteoblasts are primarily mediated by the nuclear transcription factors, estrogen receptor (ER)α and ERβ. ERs function through three general modes of action: DNA-binding dependent through estrogen response elements (EREs; designated nuclear ERE signaling); nuclear signaling via protein-protein interactions to other transcription factors (nuclear non-ERE signaling); and extra-nuclear signaling (membrane-bound functions of ERs). Identification of the specific transcriptional signatures regulated by each of these modes of action should contribute to an enhanced understanding of estrogen signaling in osteoblasts. To achieve this goal, we utilized specific mutations of ERα that eliminate the ability of the receptor to signal through a specific mode of action. The non-classical ERα knock-in (NERKI) mutation is incapable of signaling through direct DNA binding to EREs and the nuclear only ERα (NOER) mutation eliminates all membrane-localized signaling. Comparison of the gene expression patterns elicited by these mutations with the wild-type ERα (WT) pattern provides mode-specific data concerning transcriptional regulation by ERα. We expressed these constructs in the ER-negative osteoblastic cell line hFOB (−/+ estrogen) and performed global RNA-sequencing. Using a series of pair-wise comparisons, we generated three lists of genes that were regulated either by the nuclear ERE-dependent, nuclear ERE-independent, or extra-nuclear actions of ERα. Pathway and gene ontology analyses revealed that genes regulated through the nuclear ERE and nuclear non-ERE pathways were largely involved in transcriptional regulation, whereas genes regulated through extra-nuclear mechanisms are involved in cytoplasmic signaling transduction pathways. We also intersected our data with genes linked to bone density and fractures from a recent genome-wide association study and found 25 of 72 genes (35%) regulated by estrogen. These data provide a comprehensive list of genes and pathways targeted by these specific modes of ERα action and suggest that “mode-specific” ligands could be developed to modulate specific ERα functionality in bone.

Estrogen regulation of protein expression and signaling pathways in the heart

Sex differences in cardiovascular disease and cardiac physiology have been reported in humans as well as in animal models. Premenopausal women have reduced cardiovascular disease compared to men, but the incidence of cardiovascular disease in women increases following menopause. Sex differences in cardiomyocytes likely contribute to the differences in male-female physiology and response to disease. Sex differences in the heart have been noted in electrophysiology, contractility, signaling, metabolism, and cardioprotection. These differences appear to be due, at least in part, to differences in gene and protein expression as well as in posttranslational protein modifications. This review will focus primarily on estrogen-mediated male-female differences in protein expression and signaling pathways in the heart and cardiac cells. It should be emphasized that these basic differences are not intrinsically beneficial or detrimental per se; the difference can be good or bad depending on the context and circumstances.