Integration of the extranuclear and nuclear actions of estrogen

Mediator of ERBB2-driven cell motility (MEMO) promotes extranuclear estrogen receptor signaling involving the growth factor receptors IGF1R and ERBB2

In addition to nuclear estrogen receptor (ER) acting as a transcription factor, extranuclear ER also plays an important role in cancer cell growth regulation through activation of kinase cascades. However, the molecular mechanisms by which extranuclear ER exerts its function are still poorly understood. Here, we report that mediator of ERBB2-driven cell motility (MEMO) regulates extranuclear functions of ER. MEMO physically and functionally interacted with ER. Through its interaction with the growth factor receptors IGF1R and ERBB2, MEMO mediated extranuclear functions of ER, including activation of mitogen-activated protein kinase (MAPK) and protein kinase B/AKT, two important growth regulatory protein kinases, and integration of function with nuclear ER. Activation of MAPK and AKT was responsible for MEMO modulation of ER phosphorylation and estrogen-responsive gene expression. Moreover, MEMO increased anchorage-dependent and -independent growth of ER-positive breast cancer cells in vitro and was required for estrogen-induced breast tumor growth in nude mice. Together, our studies identified MEMO as a new component of extranuclear ER signalosome and suggest an essential role for MEMO in the regulation of ER-positive breast cancer cell growth.

Unliganded estrogen receptor alpha promotes PC12 survival during serum starvation

Many studies have reported proliferative, differentiating or protective effects of estradiol, notably through estrogen receptor alpha (ERα). On the contrary, the ligand-independent action of ERα is currently poorly documented notably in cell protection. The stable transfection of wild type, substituted or truncated form of ERα in PC12 cells (ERα negative cell line) lead the specific study of its ligand-independent action. Hence, we demonstrate here that, in the absence of E2, the expression of ERα prevents cells from apoptosis induced by serum deprivation. This protection is not due to an ERE-mediated transcription and does not require either AF-1 or AF-2 transactivation functions. It is afforded to the Y537 residue of ERα and activation of c-Src/Stat3 signaling pathway.

The AF-1 activation function of estrogen receptor α is necessary and sufficient for uterine epithelial cell proliferation in vivo

Estrogen receptor-α (ERα) regulates gene transcription through the 2 activation functions (AFs) AF-1 and AF-2. The crucial role of ERαAF-2 was previously demonstrated for endometrial proliferative action of 17β-estradiol (E2). Here, we investigated the role of ERαAF-1 in the regulation of gene transcription and cell proliferation in the uterus. We show that acute treatment with E2 or tamoxifen, which selectively activates ERαAF-1, similarly regulate the expression of a uterine set of estrogen-dependent genes as well as epithelial cell proliferation in the uterus of wild-type mice. These effects were abrogated in mice lacking ERαAF-1 (ERαAF-1(0)). Four weeks of E2 treatment led to uterine hypertrophy and sustained luminal epithelial and stromal cell proliferation in wild-type mice, but not in ERαAF-1(0) mice. However, ERαAF-1(0) mice still presented a moderate uterine hypertrophy essentially due to a stromal edema, potentially due to the persistence of Vegf-a induction. Epithelial apoptosis is largely decreased in these ERαAF-1(0) uteri, and response to progesterone is also altered. Finally, E2-induced proliferation of an ERα-positive epithelial cancer cell line was also inhibited by overexpression of an inducible ERα isoform lacking AF-1. Altogether, these data highlight the crucial role of ERαAF-1 in the E2-induced proliferative response in vitro and in vivo. Because ERαAF-1 was previously reported to be dispensable for several E2 extrareproductive protective effects, an optimal ERα modulation could be obtained using molecules activating ERα with a minimal ERαAF-1 action.

Lessons from the dissection of the activation functions (AF-1 and AF-2) of the estrogen receptor alpha in vivo

Estrogens influence most of the physiological processes in mammals, including but not limited to reproduction, cognition, behavior, vascular system, metabolism and bone integrity. Given this widespread role for estrogen in human physiology, it is not surprising that estrogen influence the pathophysiology of numerous diseases, including cancer (of the reproductive tract as breast, endometrial but also colorectal, prostate,…), as well as neurodegenerative, inflammatory-immune, cardiovascular and metabolic diseases, and osteoporosis. These actions are mediated by the activation of estrogen receptors (ER) alpha (ERα) and beta (ERβ), which regulate target gene transcription (genomic action) through two independent activation functions (AF)-1 and AF-2, but can also elicit rapid membrane initiated steroid signals (MISS). Targeted ER gene inactivation has shown that although ERβ plays an important role in the central nervous system and in the heart, ERα appears to play a prominent role in most of the other tissues. Pharmacological activation or inhibition of ERα and/or ERβ provides already the basis for many therapeutic interventions, from hormone replacement at menopause to prevention of the recurrence of breast cancer. However, the use of these estrogens or selective estrogen receptors modulators (SERMs) have also induced undesired effects. Thus, an important challenge consists now to uncouple the beneficial actions from other deleterious ones. The in vivo molecular "dissection" of ERα represents both a molecular and integrated approach that already allowed to delineate in mouse the role of the main "subfunctions" of the receptor and that could pave the way to an optimization of the ER modulation.

Emerging evidence of the importance of rapid, non-nuclear estrogen receptor signaling in the cardiovascular system

Estrogen receptors are classically known as ligand-activated transcription factors that regulate gene transcription in cells in response to hormone binding. In addition to this "genomic" signaling pathway, a "rapid, non-nuclear" signaling pathway mediated by cell membrane-associated estrogen receptors also has been recognized. Although for many years there was little evidence to support any physiological relevance of rapid-signaling, very recently evidence has been accumulating supporting the importance of the rapid, non-nuclear signaling as potentially critical for the protective effects of estrogen in the cardiovascular system. Better understanding of the rapid, non-nuclear signaling potentially provides an opportunity to design "pathway-specific" selective estrogen receptor modulators capable of differentially regulating non-nuclear vs. genomic effects that may prove useful ultimately as specific therapies for cardiovascular diseases.

Cloning, characterization and expression of estrogen receptor beta in the male half-smooth tongue sole, Cynoglossus semilaevis

A full-length sequence encoding the estrogen receptor beta was isolated from half-smooth tongue sole, Cynoglossus semilaevis (hstsERβ) using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends procedures. The hstsERβ cDNA clone was found to contain 1,791 nucleotides including an open reading frame that encodes 578 amino acids. The deduced hstsERβ protein consisted of six nuclear receptor-characteristic domains. Based on a phylogenetic analysis, the hstsERβ C and E domains are highly conserved compared to other fishes. The potential phosphorylation sites for PKC, CK-2 and PTK are also found in this protein. Highest amino acid identities were found for hstsERβ with common carp (Cyprinus carpio) ERβ (76 %) and Japanese flounder (Paralichthys olivaceus) ERβ (76 %). Tissue expression analysis confirmed that the hstsERβ was widely distributed and predominantly expressed in testis, brain and liver. Seasonal changes in the testis, brain and liver expression profiles of hstsERβ were examined by RT-PCR; the present results suggest that level of hstsERβ in brain increased to the highest then decreases with gonadal growth; whereas in the testis and liver, the hstsERβ mRNA level dropped to lowest then slightly increased.

Is interaction between age-dependent decline in mechanical stimulation and osteocyte-estrogen receptor levels the culprit for postmenopausal-impaired bone formation?

Declining estrogen levels during menopause are widely considered to be a major cause of age-dependent bone loss, which is primarily manifested by increased bone resorption by osteoclasts. We present accumulating evidence supporting another aspect of metabolic bone loss, suggesting that the combined interaction between age-dependent factors, namely, estrogen deficiency and reduced day-by-day activity/mechanical stimulation, directly leads to a reduction in anabolic processes. Such decreased bone formation results in diminished bone strength and failure to maintain the load-bearing competence of a healthy skeleton and to postmenopausal osteoporosis disorder. Estrogen receptors (ERs), as mediators of estrogenic actions, are essential components of bone osteocyte and osteoblast mechano-adaptive responses. ER expression appears to be upregulated by adequate circulating estrogen levels. ERα signaling pathways participate in the mechanotransduction response through obligatory "non-genomic" actions that occur independently of estrogen binding to ER and by a potentially "genomic", estrogen-dependent mode. The experimental data indicate that cross talk between the ERα-"non-genomic" and Wnt/β-catenin signaling pathways constitutes the major regulatory mechanism. This interaction uses mechanically and ER-induced prostaglandin E2 as a mediator for the downregulation of osteocyte production of sclerostin. Sclerostin suppression, in turn, is a central prerequisite for load-induced formation and mineralization of the bone matrix. It is therefore plausible that future strategies for preventing and treating postmenopausal osteoporosis may use estrogenic compounds (such as selective estrogen receptor modulators or phytoestrogens) with physical activity, to complement antiresorptive therapy, aimed at stopping further bone loss and possibly even reversing it by stimulation of bone gain.

Structure-function relationship of estrogen receptors in cardiovascular pathophysiological models

The ancestral status of estrogen receptor (ER) in the family of the steroid receptors has probably contributed to the pleiotropic actions of estrogens, and in particular of 17β-estradiol (E2). Indeed, in addition to their well described role in sexual development and reproduction, they influence most of the physiological processes. The pathophysiological counterpart of these actions includes several highly beneficial effects such as prevention of osteoporosis, atheroma and type 2 diabetes,… However, estrogens also promotes two deleterious actions : the stimulation of the proliferation of the epithelium of two sex targets : uterus and breast, favoring an increase in risk of epithelial cancer in these two tissues. These actions are mediated by the activation of ER alpha (ERα) and beta (ERβ), which regulate target gene transcription (genomic action) through two independent activation functions AF-1 and AF-2, but can also elicit rapid membrane initiated steroid signals. Although ERβ plays an important role in the central nervous system and in the heart, ERα appears to play a prominent role in most of the other tissues. One major challenge consists in uncoupling some beneficial actions from other deleterious ones, i.e. selective ER modulation. Tamoxifen and raloxifen are beneficial to prevent the recurrence of breast cancer, and mimic estrogen action mainly on bone, but their effets on atheroma and on type 2 diabetes are if any marginal. These last years, several labs, and in particular our lab, have attempted: 1) To perform an in vivo molecular "dissection" of ER alpha, allowing the uncoupling of some of its actions, and potentially paving the way to optimized selective ER modulators. (reviewed in Arnal JF, et al. Br J Pharmacol. 2012;165:57-66). 2) To describe an unexpected action of E2 treatment at the level of platelet responses in mice, that protects the animals from thromboembolism through the haematopoietic ER alpha. (Valéra MC et al. Blood. 2012, in press).

Estradiol promotes functional responses in inflammatory and steady-state dendritic cells through differential requirement for activation function-1 of estrogen receptor α

17β-Estradiol (E2) has been shown to regulate GM-CSF- or Flt3 ligand-driven dendritic cell (DC) development through estrogen receptor (ER) α signaling in myeloid progenitors. ERα regulates transcription of target genes through two distinct activation functions (AFs), AF-1 and AF-2, whose respective involvement varies in a cell type- or tissue-specific manner. In this study, we investigated the role of ERα AFs in the development and effector functions of inflammatory DCs, steady-state conventional DCs, and plasmacytoid DCs (pDC), using mouse lacking either AF-1 or AF-2. In agreement with previous works, we showed that E2 fostered the differentiation and effector functions of inflammatory DCs through ERα-dependent upregulation of IFN regulatory factor (IRF)-4 in GM-CSF-stimulated myeloid progenitors. Interestingly, whereas AF-1 was required for early IRF-4 upregulation in DC precursors, it was dispensable to enhance IRF-4 expression in differentiated DCs to a level compatible with the development of the more functional Ly6C(-) CD11b(+) DC subset. Presence of E2 had no effect on progenitors from either knock-in mice with 7-aa deletion in helix 12 of ERα, lacking AF-2, or ERα(-/-) mice. By contrast, in Flt3 ligand-driven DC differentiation, activation of AF-1 domain was required to promote the development of more functionally competent conventional DCs and pDCs. Moreover, lack of ERα AF-1 blunted the TLR7-mediated IFN-α response of female pDCs in vivo. Thus, our study demonstrates that ERα uses AF-1 differently in steady-state and inflammatory DC lineages to regulate their innate functions, suggesting that selective ER modulators could be used to target specific DC subsets.

The impact of gender and serum estradiol levels on HDL-mediated reverse cholesterol transport

OBJECTIVE

Premenopausal women have a lower incidence of cardiovascular disease compared to men of the same age. Endogenous oestrogens, especially estradiol, presumably protect against atherosclerosis by a variety of mechanisms. Reverse cholesterol transport (RCT) mechanisms also provide protection against this disease. RCT is defined as the removal of cholesterol from peripheral macrophage foam cells, via high-density lipoproteins (HDL), and cholesterol transportation to the liver for excretion. We have previously shown in a preliminary study that HDL, isolated from premenopausal women, enhanced macrophage cholesterol efflux compared to HDL derived from age-matched male subjects.

MATERIALS AND METHODS

Here, we expanded this study by analysing a larger population of healthy volunteers and evaluated the capacity of HDL derived from women with high or low serum E2 concentrations, mainly representing premenopausal and postmenopausal women, respectively, or men (each group consisting of 30 subjects) to facilitate cholesterol removal from human THP-1 macrophages. HDL isolated from serum samples was incubated with [(3)H] cholesterol oleate-loaded macrophages for 16 h, after which cholesterol efflux to HDL was determined.

RESULTS

No significant differences in the efflux-promoting ability of HDL existed among the three groups. Relevant plasma factors involved in further steps of RCT, such as cholesterol ester transfer protein (CETP), phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) activities were also analysed, but no differences were observed among the study groups.

CONCLUSION

The results do not support a role for estradiol status or gender in modifying the initial step of RCT as a protective mechanism against cardiovascular disease.

17β estradiol regulation of connexin 43-based gap junction and mechanosensitivity through classical estrogen receptor pathway in osteocyte-like MLO-Y4 cells

Connexin 43 (Cx43) plays an essential role in osteocyte mechanotransduction. Although estrogen involves in the adaptive responses of bone cells to mechanical loadings, its effects on osteocytic Cx43-based gap junction intercellular communication (GJIC) remain obscure. We found that 17β estradiol (E2) up-regulated Cx43, and enhanced GJIC in osteocyte-like MLO-Y4 cells in fluorescence recovery after photobleaching (FRAP) assay. Combination of E2 pre-treatment and oscillating fluid flow (OFF) further enhanced Cx43 expression and mitogen-activated protein kinase (MAPK) phosphorylation, comparing to E2 or OFF treatment alone. Both blocking of classical estrogen receptors (ERα/β) by fulvestrant and ERα knockdown by small interfering RNA inhibited E2-mediated Cx43 increase, while a GPR30-specific agonist G-1 failed to promote Cx43 expression. Our results suggest that the presence of E2 enhanced Cx43-based GJIC mainly via ERα/β pathway, and sensitized osteocytes to mechanical loading.

Linking proteomic and transcriptional data through the interactome and epigenome reveals a map of oncogene-induced signaling

Cellular signal transduction generally involves cascades of post-translational protein modifications that rapidly catalyze changes in protein-DNA interactions and gene expression. High-throughput measurements are improving our ability to study each of these stages individually, but do not capture the connections between them. Here we present an approach for building a network of physical links among these data that can be used to prioritize targets for pharmacological intervention. Our method recovers the critical missing links between proteomic and transcriptional data by relating changes in chromatin accessibility to changes in expression and then uses these links to connect proteomic and transcriptome data. We applied our approach to integrate epigenomic, phosphoproteomic and transcriptome changes induced by the variant III mutation of the epidermal growth factor receptor (EGFRvIII) in a cell line model of glioblastoma multiforme (GBM). To test the relevance of the network, we used small molecules to target highly connected nodes implicated by the network model that were not detected by the experimental data in isolation and we found that a large fraction of these agents alter cell viability. Among these are two compounds, ICG-001, targeting CREB binding protein (CREBBP), and PKF118–310, targeting β-catenin (CTNNB1), which have not been tested previously for effectiveness against GBM. At the level of transcriptional regulation, we used chromatin immunoprecipitation sequencing (ChIP-Seq) to experimentally determine the genome-wide binding locations of p300, a transcriptional co-regulator highly connected in the network. Analysis of p300 target genes suggested its role in tumorigenesis. We propose that this general method, in which experimental measurements are used as constraints for building regulatory networks from the interactome while taking into account noise and missing data, should be applicable to a wide range of high-throughput datasets.

The ways in which cells respond to changes in their environment are controlled by networks of physical links among the proteins and genes. The initial signal of a change in conditions rapidly passes through these networks from the cytoplasm to the nucleus, where it can lead to long-term alterations in cellular behavior by controlling the expression of genes. These cascades of signaling events underlie many normal biological processes. As a result, being able to map out how these networks change in disease can provide critical insights for new approaches to treatment. We present a computational method for reconstructing these networks by finding links between the rapid short-term changes in proteins and the longer-term changes in gene regulation. This method brings together systematic measurements of protein signaling, genome organization and transcription in the context of protein-protein and protein-DNA interactions. When used to analyze datasets from an oncogene expressing cell line model of human glioblastoma, our approach identifies key nodes that affect cell survival and functional transcriptional regulators.

Estrogen-sensitive PTPRO expression represses hepatocellular carcinoma progression by control of STAT3

Protein tyrosine phosphatase receptor type O (PTPRO), one of the receptor types of phosphotyrosine phosphatases (PTP), was recently described as a tumor suppressor in various kinds of cancers. We aimed to clarify the role of PTPRO in hepatocellular carcinoma (HCC). It was demonstrated in 180 pairs (120 male and 60 female) of clinical HCC specimens that the PTPRO level was significantly reduced, as compared with adjacent tissue, and the PTPRO level in male adjacent tissue was lower than in female. We further found that estrogen receptor alpha (ERα) could up-regulate PTPRO expression as a transcription factor. Moreover, an in vitro study showed that cell proliferation was inhibited and apoptosis was promoted in PTPRO-transduced HCC cell lines, whereas an in vivo study represented that tumor number and size was increased in ptpro(-/-) mice. As a result of its tumor-suppressive position, PTPRO was proved to down-regulate signal transducers and activators of transcription (STAT3) activity dependent on Janus kinase 2 (JAK2) and phosphoinositide 3-kinase (PI3K) dephosphorylation.

CONCLUSIONS

PTPRO expression results in pathological deficiency and gender bias in HCC, which could be attributed to ERα regulation. The suppressive role of PTPRO in HCC could be ascribed to STAT3 inactivation.

Brefeldin A is an estrogenic, Erk1/2-activating component in the extract of Agaricus blazei mycelia

We purified an Erk1/2-activating component in Agaricus blazei and identified it as brefeldin A (BFA). The extract of A. blazei mycelia (ABE) previously showed an estrogenic gene-expression profile and positive effects in patients with cardiovascular symptoms. Here, we demonstrate that BFA has estrogenic activity in reporter gene assays and stimulates an estrogen-receptor pathway revealed by activation of Erk1/2, although BFA had no growth-stimulating activity in breast cancer MCF-7 cells. The presence of estrogenic activity without any explicit growth-stimulating effect is unique to BFA, and such components are termed here "silent estrogens". To test this hypothesis, we examined the target-gene transcription and signaling pathways induced by BFA. Furthermore, BFA was found in the mycelium but not fruiting body of A. blazei, suggesting the potential use of ABE for therapeutics and its supplementary use in traditional medicines and functional foods.

Correlation between erythropoietin receptor(s) and estrogen and progesterone receptor expression in different breast cancer cell lines

Erythropoietin (EPO) receptor (EPOR) expression in breast cancer has been shown to correlate with the expression of estrogen receptor (ESR) and progesterone receptor (PGR) and to be associated with the response to tamoxifen in ESR+/PGR+ tumors but not in ESR- tumors. In addition, the correlation between EPOR and G protein-coupled estrogen receptor 1 [GPER; also known as G protein-coupled receptor 30 (GPR30)] has been reported, suggesting the prognostic potential of EPOR expression. Moreover, the involvement of colony stimulating factor 2 receptor, β, low‑affinity (CSF2RB) and ephrin type-B receptor 4 (EPHB4) as EPOR potential receptor partners in cancer has been indicated. This study analyzed the correlation between the expression of genes for EPO, EPOR, CSF2RB, EPHB4, ESR, PGR and GPER in the MCF-7, MDA-MB-361, T-47D, MDA-MB-231, Hs578Bst, SKBR3, MCF-10A and Hs578T cell lines. The cell lines were also treated with recombinant human EPO (rHuEPO) in order to determine its ability to activate the Jak/STAT5, MAPK and PI3K signaling pathways and modify cell growth characteristics. Expression analysis stratified the cell lines in 2 main clusters, hormone-dependent cell lines expressing ESR and PGR and a hormone-independent cluster. A significant correlation was observed between the expression levels of ESR and PGR and their expression was also associated with that of GPER. Furthermore, the expression of GPER was associated with that of EPOR, suggesting the connection between this orphan G protein and EPO signaling. A negative correlation between EPOR and CSF2RB expression was observed, questioning the involvement of these two receptors in the hetero-receptor formation. rHuEPO treatment only influenced the hormone-independent cell lines, since only the MDA-MB-231, SKBR3 and Hs578T cells responded to the treatment. The correlation between the expression of the analyzed receptors suggests that the receptors may interact in order to activate signaling pathways or to evade their inhibition. Therefore, breast cancer classification upon ESR, PGR and human epidermal growth factor receptor 2 (HER2) may not be sufficient for the selection of suitable treatment protocol. The expression of EPOR, GPER and EPHB4 may be considered as additional classification factors.

The G Protein–Coupled Receptor GPR30 Mediates the Nontranscriptional Effect of Estrogen on the Activation of PI3K/Akt Pathway in Endometrial Cancer Cells

Objective

The goal of this study was to investigate the effect of G protein–coupled receptor 30 (GPR30) on the activation of PI3K/Akt pathway induced by E2 in endometrial cancer cells.

Methods and materials

Immunohistochemistry was performed to determine the location and expression of GPR30, estrogen receptors (ERs), Akt, and phosphorylated Akt. We also investigated the expression of GPR30, ERs, and the level of phosphorylation of Akt induced by E2 in endometrial cancer cells, Ishikawa cells, and HEC-1A cells. We down-regulated the expression of GPR30 in endometrial cancer cell lines by transfection with shGPR30-pGFP-V-RS, a GPR30 antisense expression vector. The cells were then subjected to a proliferation assay. Immunoprecipitation assay was performed to determine whether GPR30 directly bind to PI3K. The stable transfected cells resuspension of 100 μL (5 × 106 cells) was injected subcutaneously into the right flank of athymic mice to perform xenograft tumor formation assays.

Results

E2 stimulated cell proliferation and induced GPR30 expression and PI3K/Akt pathway activation in endometrial cancer cells, Ishikawa cells, and HEC-1A cells, whereas the expression of ERs remained unchangeable. Down-regulation of GPR30 decreased the phosphorylation of Akt and reduced cell proliferation, and GPR30 did not bind to PI3K. Down-regulation of GPR30 significantly inhibited the tumor growth of HEC-1A cells in athymic nude mice.

Conclusions

These findings suggest that GPR30 mediates the nontranscriptional effect of estrogen on the activation of PI3K/Akt pathway in endometrial cancer cells.

G protein-coupled estrogen receptor in energy homeostasis and obesity pathogenesis

Obesity and its related metabolic diseases have reached a pandemic level worldwide. There are sex differences in the prevalence of obesity and its related metabolic diseases, with men being more vulnerable than women; however, the prevalence of these disorders increases dramatically in women after menopause, suggesting that sex steroid hormone estrogens play key protective roles against development of obesity and metabolic diseases. Estrogens are important regulators of several aspects of metabolism, including body weight and body fat, caloric intake and energy expenditure, and glucose and lipid metabolism in both males and females. Estrogens act in complex ways on their nuclear estrogen receptors (ERs) ERα and ERβ and transmembrane ERs such as G protein-coupled estrogen receptor. Genetic tools, such as different lines of knockout mouse models, and pharmacological agents, such as selective agonists and antagonists, are available to study function and signaling mechanisms of ERs. We provide an overview of the evidence for the physiological and cellular actions of ERs in estrogen-dependent processes in the context of energy homeostasis and body fat regulation and discuss its pathology that leads to obesity and related metabolic states.

Estrogen mediated protection of cytoskeleton against oxidative stress

BACKGROUND & OBJECTIVES

Cytoskeletal proteins are deregulated during oxidative stress and cataract formation. However, estrogen which protects against cataract formation and harmful effects of oxidative stress has not been tested on the cytoskeleton of lens epithelial cells (LECs). The current study was undertaken to assess if the protection rendered to LECs by estrogen was mediated by preserving the cytoskeletal proteins.

METHODS

Oxidative stress was induced by 50 μM of H 2 O 2 in cultured goat LECs (gLECs) and effect of 1 μM 17β-estradiol (E 2 ) was tested. After treatment, morphological analysis of cells was carried out using haematoxylin-eosin staining and cell density was also quantified. Cell viability was determined using Hoechst (Ho), YO-Pro (YP) and propidium iodide (PI). F-actin and vimentin were localized using phalloidin and anti-vimentin antibody, respectively, and viewed under fluorescence microscopy. Vimentin was further analysed at protein level by Western blotting.

RESULTS

H 2 O 2 led to increased condensation of nucleus, cell death and apoptosis but these were prevented with pre- and co-treatment of E 2 with increase in cell viability (P<0.001). E 2 also prevented H 2 O 2 mediated depolymerization of cytoskeleton but was not able to reverse the changes when given after induction of oxidative stress.

INTERPRETATION & CONCLUSIONS

Our findings showed that E 2 helped in preventing deteriorating effect of H 2 O 2 , inhibited cell death, apoptosis and depolymerisation of cytoskeletal proteins in LECs. However, the exact mechanism by which estrogen renders this protection to cytoskeleton of lens epithelial cells remains to be determined.

Differential inhibitory potencies and mechanisms of the type I ribosome inactivating protein marmorin on estrogen receptor (ER)-positive and ER-negative breast cancer cells

Breast cancer is the second most common cancer with a high incidence rate worldwide. One of the promising therapeutic approaches on breast cancer is to use the drugs that target the estrogen receptor (ER). In the present investigation, marmorin, a type I ribosome inactivating protein from the mushroom Hypsizigus marmoreus, inhibited the survival of breast cancer in vitro and in vivo. It evinced more potent cytotoxicity toward estrogen receptor (ER)-positive MCF7 breast cancer cells than ER-negative MDA-MB-231 cells. Further study disclosed that marmorin undermined the expression level of estrogen receptor α (ERα) and significantly inhibited the proliferation of MCF7 cells induced by 17β-estradiol. Knockdown of ERα in MCF7 cells significantly attenuated the inhibitory effect of marmorin on proliferation, suggesting that the ERα-mediated pathway was implicated in the suppressive action of marmorin on ER-positive breast cancer cells. Moreover, marmorin induced time-dependent apoptosis in both MCF7 and MDA-MB-231 cells. It brought about G2/M-phase arrest, mitochondrial membrane potential depolarization and caspase-9 activation in MCF7 cells, and to a lesser extent in MDA-MB-231 cells. Marmorin triggered the death receptor apoptotic pathway (e.g. caspase-8 activation) and endoplasmic reticulum stress (ERS, as evidenced by phosphorylation of PERK and IRE1α, cleavage of caspase-12, and up-regulation of CHOP expression) in both MCF7 and MDA-MB-231 cells. In summary, marmorin exhibited inhibitory effect on breast cancer partially via diminution of ERα and apoptotic pathways mediated by mitochondrial, death receptor and ERS. The results advocate that marmorin is a potential candidate for breast cancer therapy.

Role of DHEA in cardiovascular diseases

Dehydroepiandrosterone (DHEA) is a steroid hormone derived from cholesterol synthesized by the adrenal glands. DHEA and its 3β-sulphate ester (DHEA-S) are the most abundant circulating steroid hormones. In human, there is a clear age-related decline in serum DHEA and DHEA-S and this has suggested that a relative deficiency in these steroids may be causally related to the development of a series of diseases associated with aging including cardiovascular diseases (CVD). This commentary aims to highlight the action of DHEA in CVD and its beneficial effect in therapy. We thus discuss the possible impact of serum DHEA decline and DHEA supplementation in diseases such as hypertension, coronary artery disease and atherosclerosis. More specifically, we provide evidence for a beneficial action of DHEA in the main disease of the pulmonary circulation: pulmonary hypertension. We also examine the potential cellular mechanism of action of DHEA in terms of receptors (membrane/nuclear) and associated signaling pathways (ion channels, calcium signaling, PI3K/AKT/eNos pathway, cGMP, RhoA/RhoK pathway). We show that DHEA acts as an anti-remodeling and vasorelaxant drug. Since it is a well-tolerated and inexpensive drug, DHEA may prove to be a valuable molecule in CVD but it deserves further studies both at the molecular level and in large clinical trials.

Molecular mechanism(s) of endocrine-disrupting chemicals and their potent oestrogenicity in diverse cells and tissues that express oestrogen receptors

Endocrine-disrupting chemicals (EDCs) are natural or synthetic compounds present in the environment which can interfere with hormone synthesis and normal physiological functions of male and female reproductive organs. Most EDCs tend to bind to steroid hormone receptors including the oestrogen receptor (ER), progesterone receptor (PR) and androgen receptor (AR). As EDCs disrupt the actions of endogenous hormones, they may induce abnormal reproduction, stimulation of cancer growth, dysfunction of neuronal and immune system. Although EDCs represent a significant public health concern, there are no standard methods to determine effect of EDCs on human beings. The mechanisms underlying adverse actions of EDC exposure are not clearly understood. In this review, we highlighted the toxicology of EDCs and its effect on human health, including reproductive development in males and females as shown in in vitro and in vivo models. In addition, this review brings attention to the toxicity of EDCs via interaction of genomic and non-genomic signalling pathways through hormone receptors.

Point mutations in the ERα Gαi binding domain segregate nonnuclear from nuclear receptor function

A subpopulation of plasma membrane-associated estrogen receptor (ER)α interact directly with G proteins and mediate nonnuclear receptor signaling. This mechanism underlies numerous processes, including important cardiovascular protective actions of estradiol (E(2)), such as the activation of endothelial NO synthase (eNOS) and endothelial cell growth and migration. In the present work we sought a genetic approach to differentiate nonnuclear from nuclear ERα actions. We generated single alanine substitutions within the Gαi-binding domain of ERα (amino acids 251-260) and tested signaling to eNOS or ERK1,2 and activation of luciferase (Luc) reporters signifying transactivation via direct or indirect ERα-DNA binding in HeLa cells. The point mutants ERα-R256A, ERα-K257A, ERα-D258A, and ERα-R260A were all incapable of activating eNOS in response to E(2), and ERα-R256A and ERα-D258A also showed loss of ERK1,2 activation. In contrast, ERα-R256A, ERα-K257A, ERα-D258A, and ERα-R260A all displayed normal capacity to invoke E(2)-induced transactivation of estrogen response element (ERE)-Luc or Sp1-Luc. However, whereas activator protein 1-Luc activation by ERα-R256A and ERα-D258A was intact, ERα-K257A and ERα-R260A were incapable of activator protein 1-Luc activation. In in vitro pull-down assays with the two mutants that lack all nonnuclear functions tested and retain all nuclear functions tested, ERα-R256A and ERα-D258A, there was normal direct interaction between Gαi and ERα-R256A and an absence of interaction between Gαi and ERα-D258A. When expressed in endothelial cells, these two mutants prevented E(2)-induced migration and eNOS activation mediated by endogenous receptor, indicative of dominant-negative action. Thus, the point mutants ERα-R256A and ERα-D258A in the receptor GαI-binding domain provide genetic segregation of nonnuclear from nuclear ERα function.

Targeting estrogen receptor-α reduces adrenocortical cancer (ACC) cell growth in vitro and in vivo: potential therapeutic role of selective estrogen receptor modulators (SERMs) for ACC treatment

CONTEXT

Adrenocortical carcinoma (ACC) is a rare tumor with a very poor prognosis and no effective treatment. ACC is characterized by an increased production of IGF-II and by estrogen receptor (ER)-α up-regulation.

OBJECTIVE

The objective of this study was to define the role played by ERα in 17β-estradiol (E2)- and IGF-II-dependent ACC growth and evaluate whether selective estrogen receptor modulators are effective in controlling ACC growth in vivo.

EXPERIMENTAL DESIGN

The human adrenocortical cell line H295R was used as an in vitro model and to generate xenograft tumors in athymic nude mice.

RESULTS

In H295R cells IGF-II controlled expression of steroidogenic factor-1 that, in turn, increased aromatase transcription and, consequently, estrogen production, inducing cell proliferation. ERα silencing significantly blocked E2- and IGF-II-dependent cell proliferation. This effect was dependent on the regulation of cyclin D1 expression by ERα, activated in response to both E2 and IGF-II. In fact, IGF-II induced ERα activation by phosphorylating serine 118 and 167. Furthermore, we demonstrated that ERα mediated E2-induced nongenomic signaling that stimulated IGF-I receptor (IGF1R), ERK1/2, and AKT phosphorylation, resulting in a ligand-independent activation of the IGF1R-induced pathway. In addition, E2 potentiated this pathway by up-regulating IGF1R expression as a consequence of increased cAMP-responsive element binding protein activation and binding to IGF1R promoter. The estrogen antagonist, hydroxytamoxifen, the active metabolite of tamoxifen, reduced IGF1R protein levels and both E2- and IGF-II-induced cell proliferation. Moreover, H295R xenograft growth was strongly reduced by tamoxifen.

CONCLUSION

These findings establish a critical role for ERα in E2- and IGF-II-dependent ACC proliferation and provide a rationale for targeting ERα to control the proliferation of ACC.

Stimulation of GPR30 increases release of EMMPRIN-containing microvesicles in human uterine epithelial cells

CONTEXT

Uterine remodeling is highly dependent on the glycosylated transmembrane protein extracellular matrix metalloproteinase (MMP) inducer (EMMPRIN). Previous studies indicate estradiol can increase EMMPRIN expression in uterine cells and promote subsequent induction of MMP production.

OBJECTIVE

The aim of this study was to investigate the role of G protein-coupled receptor 30 (GPR30) stimulation on EMMPRIN microvesicle release in the human uterine epithelial cell line hTERT-EEC (EECs).

DESIGN

We examined EMMPRIN release by human EECs in response to GPR30 stimulation by microvesicle isolation, Western blot, and immunocytochemistry. We employed a pharmacological approach using the GPR30-selective agonist G1 and the antagonist G15 to determine the receptor specificity of this response.

RESULTS

We demonstrated GPR30 expression in EECs and release of EMMPRIN in microvesicles in response to stimulation of GPR30. G1, estradiol, and cholera toxin stimulated EMMPRIN release in microvesicles as detected by Western blot and immunocytochemistry, indicating that stimulation of GPR30 can induce EMMPRIN microvesicle release.

CONCLUSIONS

These data indicate that EMMPRIN release in microvesicles can be mediated by stimulation of GPR30 in human EECs, suggesting that inappropriate stimulation or expression of this receptor may be significant in uterine pathology.

Estrogen Regulates MAPK-Related Genes through Genomic and Nongenomic Interactions between IGF-I Receptor Tyrosine Kinase and Estrogen Receptor-Alpha Signaling Pathways in Human Uterine Leiomyoma Cells

Estrogen and growth factors play a major role in uterine leiomyoma (UtLM) growth possibly through interactions of receptor tyrosine kinases (RTKs) and estrogen receptor-alpha (ERα) signaling. We determined the genomic and nongenomic effects of 17β-estradiol (E₂) on IGF-IR/MAPKp44/42 signaling and gene expression in human UtLM cells with intact or silenced IGF-IR. Analysis by RT² Profiler PCR-array showed genes involved in IGF-IR/MAPK signaling were upregulated in UtLM cells by E₂ including cyclin D kinases, MAPKs, and MAPK kinases; RTK signaling mediator, GRB2; transcriptional factors ELK1 and E2F1; CCNB2 involved in cell cycle progression, proliferation, and survival; and COL1A1 associated with collagen synthesis. Silencing (si)IGF-IR attenuated the above effects and resulted in upregulation of different genes, such as transcriptional factor ETS2; the tyrosine kinase receptor, EGFR; and DLK1 involved in fibrosis. E₂ rapidly activated IGF-IR/MAPKp44/42 signaling nongenomically and induced phosphorylation of ERα at ser118 in cells with a functional IGF-IR versus those without. E₂ also upregulated IGF-I gene and protein expression through a prolonged genomic event. These results suggest a pivotal role of IGF-IR and possibly other RTKs in mediating genomic and nongenomic hormone receptor interactions and signaling in fibroids and provide novel genes and targets for future intervention and prevention strategies.

Estrogen-induced retinal endothelial cell proliferation: possible involvement of pigment epithelium-derived factor and phosphoinositide 3-kinase/mitogen-activated protein kinase pathways

PURPOSE

Diabetic retinopathy is a leading cause of blindness due to a progressive damage of the retina by neovascularization and other related ocular complications. However, the molecular mechanism underlying the development of diabetic retinopathy is not well understood. An increase in estrogen levels during puberty is associated with an accelerated development of diabetic retinopathy. Previously, we have introduced 17β-estradiol (E2) to rhesus retinal capillary endothelial cells (RhRECs) in culture and observed a dose- and time-dependent increase in the number of viable cells. The purpose of this present study was to investigate the molecular signaling pathway associated with this estrogen-induced proliferation of RhRECs.

METHODS

Estrogen receptor (ER) ER(α) and ER(β) mRNA expression, and protein synthesis were measured at 0, 3, 6, and 12 h using nested polymerase chain reaction and Western blots. Phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathway inhibitors were introduced into culture media to study their effects on E2-induced cell proliferation and pigment epithelium-derived factor (PEDF) synthesis. The levels of PEDF in the conditioned media were measured by enzyme-linked immunosorbent assay.

RESULTS

Exogenous E2 induced a significant increase in the expression of ER(β) along with an increase in the number of viable RhRECs. Cotreatment of E2 with PI3K and MAPK inhibitors significantly reduced the E2-induced effect on cell proliferation and PEDF production in a dose-dependent manner.

CONCLUSION

Results from the present study suggest that an E2-induced increase in the proliferation of RhRECs may be mediated by the action of ER(β.) Both PI3K and MAPK signaling pathways are involved in this E2-induced cell proliferation, which may follow changes in PEDF levels controlled by these pathways. Further studies will provide additional details on the interaction between these pathways to control changes in PEDF levels and cell proliferation.

Nutritional flavonoids impact on nuclear and extranuclear estrogen receptor activities

Flavonoids are a large group of nonnutrient compounds naturally produced from plants as part of their defence mechanisms against stresses of different origins. They emerged from being considered an agricultural oddity only after it was observed that these compounds possess a potential protective function against several human degenerative diseases. This has led to recommending the consumption of food containing high concentrations of flavonoids, which at present, especially as soy isoflavones, are even available as overthecounter nutraceuticals. The increased use of flavonoids has occurred even though their mechanisms are not completely understood, in particular those involving the flavonoid impact on estrogen signals. In fact, most of the human health protective effects of flavonoids are described either as estrogenmimetic, or as antiestrogenic, while others do not involve estrogen signaling at all. Thus, the same molecule is reported as an endocrine disruptor, an estrogen mimetic or as an antioxidant without estrogenic effects. This is due in part to the complexity of the estrogen mechanism, which is conducted by different pathways and involves two different receptor isoforms. These pathways can be modulated by flavonoids and should be considered for a reliable evaluation of flavonoid, both estrogenicity and antiestrogenicity, and for a correct prediction of their effects on human health.

The synergistic effect of EGFR tyrosine kinase inhibitor gefitinib in combination with aromatase inhibitor anastrozole in non-small cell lung cancer cell lines

BACKGROUND

Several studies implicated that lung cancer progression was governed by the interaction between estrogen receptor (ER) and epidermal growth factor receptor (EGFR) signaling pathways. Combined targeting of EGFR and ER may have the synergistic effect in lung cancer treatment. The aim of this study was to explore the potential utility of inhibiting these two pathways with combination of anastrozole and gefitinib in non-small cell lung cancer (NSCLC) cell lines.

MATERIALS AND METHODS

The expression levels of ER (ER-α and ER-β) in lung cancer cell lines (A549, H460, SPC-A-1, H1299) and normal bronchus epithelial cell BEAS-2B were detected using real-time PCR and Western blot. Immunocytochemistry was used to locate ER-α and ER-β in cell line with highest ER expression levels. The cells were treated with anastrozole or gefitinib alone or in combination. The cell proliferation inhibition was detected by the CCK8 assay, cell cycle and apoptosis effects were detected by flow cytometry; the expression levels of phosphorylated-EGFR (p-EGFR), ERK, phosphorylated-ERK (p-ERK), AKT and phosphorylated-AKT (p-AKT) were detected by Western blot.

RESULTS

Among these cell lines the expression levels of ER in A549 cells were highest. In A549 cell line, ER-α was mainly localized in the cytoplasm, whereas ER-β was mainly localized in the cytoplasm and to a lesser degree in the nucleus. The combination of two drugs increased the proliferation inhibition rates for 24h, 48 h, 72 h to 37.66 ± 1.02%, 63.41 ± 2.02%, 70.50 ± 0.86%, respectively, which was closely associated with elevation of the G0/G1 phase fraction (P<0.05). Apoptosis rates of A549 cells treated with anastrozole, gefitinib alone or in combination were 10.72 ± 1.12%, 17.40±1.28%, 23.02 ± 2.32%, respectively (P<0.05). The synergistic effects of the combination therapy were accompanied by reduction of p-EGFR, p-ERK and p-AKT expression compared with individual treatment.

CONCLUSIONS

The results of this study suggest that the combination of anastrozole and gefitinib compared with either drug alone can maximally inhibit cell proliferation, induce apoptosis, and affect downstream signaling pathways. Our study supports functional interaction between the ER and the EGFR pathways in lung cancer and provides a clinically exploitable strategy for non-small cell lung cancer patients.

Endocrine-disrupting chemicals: associated disorders and mechanisms of action

The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.

ERα36, a new variant of the ERα is expressed in triple negative breast carcinomas and has a specific transcriptomic signature in breast cancer cell lines

Triple negative breast cancer is deprived of estrogen receptor alpha (ERα), progesterone receptor (PR) and HER-2 protein. It constitutes the most heterogeneous and aggressive group of breast carcinomas, for which identification of novel characteristics and characterization of putative targets becomes very demanding. In the present work we have assayed the expression of ERα36, a recently identified ERα variant of 36kDa, in a series of triple negative breast cancers, in relation to the clinical behavior and other clinico-pathological features of the tumors. While widely expressed within the cytoplasm in almost all tumors, we found that exclusively the membrane/submembrane expression of the receptor exhibits a correlation with patient's survival. Moreover, membrane ERα36 correlates in an inverse manner with the expression of miRNA210, a pro-angiogenic miR, with high prognostic relevance in triple negative carcinomas. A thorough transcriptomic, pharmacological-based approach in breast cancer cell lines, revealed an early (direct) transcriptional signature of the receptor activation, related to immune system processes and T-cell differentiation, RNA biosynthesis, regulation of metabolism, VEGF signaling and regulation of the cell cycle, with a down-regulation of CREB, NFκB and STATs transcription factors. Finally, ERα36 expression is not limited within breast cancer epithelial linen, but is equally identified in tumor vasculature, peritumoral fat tissue, lymphocytic infiltrate and stromal fibroblasts. In light of the above, ERα36 could represent a major counterpart in triple negative breast cancer.

Susceptibility of estrogen receptor rapid responses to xenoestrogens: Physiological outcomes

17β-Estradiol (E2) binding induces rapid modification in the conformation of its cognate receptors (i.e., ERα and ERβ). These allosteric changes allow the association of ERs with cell specific transcriptional cofactors, thus determining cellular contexts specific variations in gene expression. In addition, E2-ER complexes could also interact with membrane and cytosolic signal molecules triggering extra-nuclear signalling pathways. The synergy between these mechanisms is necessary for E2-induced pleiotropic actions in target tissues. Besides E2, the ER ligand binding domains can accommodate many other natural and synthetic ligands. Several of these compounds act as agonist or antagonist of ER transcriptional activity due to their ability to modify the interactions between ERs and transcriptional co-regulators. However, the ability of natural or manmade ER ligands to affect the extra-nuclear interactions of the ERs has been rarely evaluated. Here, the ability of two diet-derived flavonoids (i.e., naringenin and quercetin) and of the synthetic food-contaminant bisphenol A to modulate specifically ER extra-nuclear signalling pathways will be reported. All the tested compounds bind to both ER subtypes even if lesser than E2 activating divergent signal transduction pathways. In fact, in the presence of ERα, both naringenin and quercetin decouple ERα activities by specifically interfering with ERα membrane initiating signals. On the other hand, bisphenol A, but not flavonoids, maintains ERβ at the membrane thus impairing the activation of the downstream kinases. As a whole, extra-nuclear ER signals are highly susceptible to different ligands that, by unbalancing E2-induced cell functions drive cells to different functional endpoints.

Cardiac-specific inducible and conditional gene targeting in mice

Mouse genetic engineering has revolutionized our understanding of the molecular and genetic basis of heart development and disease. This technology involves conditional tissue-specific and temporal transgenic and gene targeting approaches, as well as introduction of polymorphisms into the mouse genome. These approaches are increasingly used to elucidate the genetic pathways underlying tissue homeostasis, physiology, and pathophysiology of adult heart. They have also led to the development of clinically relevant models of human cardiac diseases. Here, we review the technologies and their limitations in general and the cardiovascular research community in particular.

Chronic estradiol treatment reduces platelet responses and protects mice from thromboembolism through the hematopoietic estrogen receptor α

Although estrogens are known to have a deleterious effect on the venous thrombosis risk and a preventive action on the development of arterial atheroma, their effect on platelet function in vivo remains unclear. Here, we demonstrate that a chronic high physiologic level of estradiol (E2) in mice leads to a marked decrease in platelet responsiveness ex vivo and in vivo compared with ovariectomized controls. E2 treatment led to increased bleeding time and a resistance to thromboembolism. Hematopoietic chimera mice harboring a selective deletion of estrogen receptors (ERs) α or β were used to demonstrate that the effects of E2 were exclusively because of hematopoietic ERα. Within ERα the activation function-1 domain was not required for resistance to thromboembolism, as was previously shown for atheroprotection. This domain is mandatory for E2-mediated reproductive function and suggests that this role is controlled independently. Differential proteomics indicated that E2 treatment modulated the expression of platelet proteins including β1 tubulin and a few other proteins that may impact platelet production and activation. Overall, these data demonstrate a previously unrecognized role for E2 in regulating the platelet proteome and platelet function, and point to new potential antithrombotic and vasculoprotective therapeutic strategies.

Testosterone rapidly increases ejaculate volume and sperm density in competitively breeding goldfish through an estrogenic membrane receptor mechanism

The social environment can have dramatic influences on reproductive behavior and physiology in many vertebrate species. In males, interactions with conspecifics affect physiological processes that increase an individual's ability to compete for mates. For example, in some species, males rapidly adjust the number of sperm they ejaculate in response to sociosexual cues from male and female conspecifics, however, little is known about the physiological mechanisms mediating this behavior. In goldfish, as in many vertebrates, social cues also drive transient surges of the gonadal hormone testosterone (T), which induces rapid effects on cellular processes via its conversion to estradiol (E2). We asked whether such surges rapidly influence ejaculate quantity and quality by experimentally manipulating peripheral levels of T and E2. We show that male goldfish injected with T increased ejaculate (milt) volume and sperm density within just 1 hr. Furthermore, increases in expressible milt were dependent on the conversion of T to E2 by the enzyme aromatase, required activation of estrogen receptors α and β, and were also elicited by BSA-conjugated E2, which acts on cell membrane-bound estrogen receptors. Together, these findings represent a novel steroid mechanism for the social modulation of sperm output over the short time scales that characterize reproductive encounters, and thus demonstrate a previously undescribed functional consequence of rapid estrogen signaling mechanisms. We suggest that such mechanisms may play a critical role in the enhancement of physiological and behavioral processes that increase reproductive success in competitive mating contexts.

Gαo potentiates estrogen receptor α activity via the ERK signaling pathway

The estrogen receptor α (ERα) is a transcription factor that mediates the biological effects of 17β-estradiol (E(2)). ERα transcriptional activity is also regulated by cytoplasmic signaling cascades. Here, several Gα protein subunits were tested for their ability to regulate ERα activity. Reporter assays revealed that overexpression of a constitutively active Gα(o) protein subunit potentiated ERα activity in the absence and presence of E(2). Transient transfection of the human breast cancer cell line MCF-7 showed that Gα(o) augments the transcription of several ERα-regulated genes. Western blots of HEK293T cells transfected with ER±Gα(o) revealed that Gα(o) stimulated phosphorylation of ERK 1/2 and subsequently increased the phosphorylation of ERα on serine 118. In summary, our results show that Gα(o), through activation of the MAPK pathway, plays a role in the regulation of ERα activity.

ERβ-mediated estradiol enhances epithelial mesenchymal transition of lung adenocarcinoma through increasing transcription of midkine

Epithelial-mesenchymal transition (EMT) plays a specific role in the migration of tumor cells. Both estrogen and midkine (MK) have been thought to be important factors in promoting the progression of non-small-cell lung cancer (NSCLC) and can enhance EMT. Some evidence indicated the correlation between estradiol (E2) and MK, but the precise mechanism on their interreaction is unknown. Here, we try to clarify whether and how E2 regulates MK expression to promote EMT. We found that E2 increased MK mRNA expression in lung adenocarcinoma cells LTEP-a2 and A549 in a time-dependent manner. E2-induced MK expression was inhibited by the estrogen receptor (ER) antagonist ICI 182,780 and tamoxifen but not by phosphoinositide-3 kinase and MAPK inhibitors, suggesting a genomic mechanism of E2 on the regulation of MK transcription. Moreover, luciferase reporter and chromatin immunoprecipitation assays exhibited that E2 induced ERβ recruitment to the estrogen response element in the MK promoter. Small interfering RNA to ERα and ERβ revealed that ERβ mainly mediated E2-induced MK transcription. Interestingly, E2 enhanced MK expression in accordance with increase of EMT, whereas knockdown of MK could block EMT under E2 stimulation. Importantly, through analyzing lung adenocarcinoma tissues, there was indeed a correlation among levels of E2, MK, and EMT-related protein expression. Taken together, we reported a previously unrecognized mechanism on E2 in the regulation of MK expression and proved that MK plays a pivotal role in progression of E2-regulated EMT.

From in vivo gene targeting of oestrogen receptors to optimization of their modulation in menopause

The ancestral status of oestrogen receptor (ER) in the family of the steroid receptors has probably contributed to the pleiotropic actions of oestrogens, and in particular, that of 17β-oestradiol (E2). Indeed, in addition to their well-described role in sexual development and reproduction, they influence most of the physiological processes. The pathophysiological counterpart of these actions includes prevention of osteoporosis, atheroma and type 2 diabetes, and also the promotion of uterus and breast cancer growth. Thus, the major challenge consists in uncoupling some beneficial actions from other deleterious ones, that is, selective ER modulation. Tamoxifen and raloxifene are already used, as they prevent the recurrence of breast cancer and mimic oestrogen action mainly on bone. Both E2 and tamoxifen exhibit a proliferative and, thus, a protumoural action on the endometrium. Activation of ERα and ERβ regulates target gene transcription (genomic action) through two independent activation functions, AF-1 and AF-2, but can also elicit rapid membrane-initiated steroid signals. In the present review, we attempted to summarize recent advances provided by the in vivo molecular 'dissection' of ERα, allowing the uncoupling of some of its actions and potentially paving the way to optimized selective ER modulators.

Estrogen receptor β and its domains interact with casein kinase 2, phosphokinase C, and N-myristoylation sites of mitochondrial and nuclear proteins in mouse brain

The localization of estrogen receptor (ER)β in mitochondria suggests ERβ-dependent regulation of genes, which is poorly understood. Here, we analyzed the ERβ interacting mitochondrial as well as nuclear proteins in mouse brain using pull-down assay and matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS). In the case of mitochondria, ERβ interacted with six proteins of 35-152 kDa, its transactivation domain (TAD) interacted with four proteins of 37-172 kDa, and ligand binding domain (LBD) interacted with six proteins of 37-161 kDa. On the other hand, in nuclei, ERβ interacted with seven proteins of 30-203 kDa, TAD with ten proteins of 31-160 kDa, and LBD with fourteen proteins of 42-179 kDa. For further identification, these proteins were cleaved by trypsin into peptides and analyzed by MALDI-MS using mascot search engine, immunoprecipitation, immunoblotting, and far-Western blotting. To find the consensus binding motifs in interacting proteins, their unique tryptic peptides were analyzed by the motif scan software. All the interacting proteins were found to contain casein kinase (CK) 2, phosphokinase (PK)C phosphorylation, and N-myristoylation sites. These were further confirmed by peptide pull-down assays using specific mutations in the interacting sites. Thus, the present findings provide evidence for the interaction of ERβ with specific mitochondrial and nuclear proteins through consensus CK2, PKC phosphorylation, and N-myristoylation sites, and may represent an essential step toward designing selective ER modulators for regulating estrogen-mediated signaling.

17β-Estradiol modulates the prolactin secretion induced by TRH through membrane estrogen receptors via PI3K/Akt in female rat anterior pituitary cell culture

Considering that estradiol is a major modulator of prolactin (PRL) secretion, the aim of the present study was to analyze the role of membrane estradiol receptor-α (mERα) in the regulatory effect of this hormone on the PRL secretion induced by thyrotropin-releasing hormone (TRH) by focusing on the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway activation. Anterior pituitary cell cultures from female rats were treated with 17β-estradiol (E(2), 10 nM) and its membrane-impermeable conjugated estradiol (E(2)-BSA, 10 nM) alone or coincubated with TRH (10 nM) for 30 min, with PRL levels being determined by RIA. Although E(2), E(2)-BSA, TRH, and E(2)/TRH differentially increased the PRL secretion, the highest levels were achieved with E(2)-BSA/TRH. ICI-182,780 did not modify the TRH-induced PRL release but significantly inhibited the PRL secretion promoted by E(2) or E(2)-BSA alone or in coincubation with TRH. The PI3K inhibitors LY-294002 and wortmannin partially inhibited the PRL release induced by E(2)-BSA, TRH, and E(2)/TRH and totally inhibited the PRL levels stimulated by E(2)-BSA/TRH, suggesting that the mER mediated the cooperative effect of E(2) on TRH-induced PRL release through the PI3K pathway. Also, the involvement of this kinase was supported by the translocation of its regulatory subunit p85α from the cytoplasm to the plasma membrane in the lactotroph cells treated with E(2)-BSA and TRH alone or in coincubation. A significant increase of phosphorylated Akt was induced by E(2)-BSA/TRH. Finally, the changes of ERα expression in the plasmalemma of pituitary cells were examined by confocal microscopy and flow cytometry, which revealed that the mobilization of intracellular ERα to the plasma membrane of lactotroph cells was only induced by E(2). These finding showed that E(2) may act as a modulator of the secretory response of lactotrophs induced by TRH through mER, with the contribution by PI3K/Akt pathway activation providing a new insight into the mechanisms underlying the nongenomic action of E(2) in the pituitary.

A differentially methylated single CpG-site is correlated with estrogen receptor alpha transcription

DNA methylation of the promoter region of estrogen receptor alpha (ESR1) is recognized as an epigenetic mechanism that regulates its mRNA abundance. We questioned whether tissues in male growing piglets were influenced in terms of DNA methylation by the developmentally occurring distinct plasma estradiol-17β (E2) concentrations. Additionally, we aimed at broadening the currently limited understanding of the epigenetic regulation of ESR1 in physiological settings. Three distinct genetic regions of ESR1 were analyzed using a combination of methylation-sensitive high resolution melting (MS-HRM) and pyrosequencing. Unexpectedly, major E2 concentration differences were only marginally associated with minor variations in DNA methylation and mRNA abundance. However, by analyzing two tissues showing the greatest differences in transcript abundance, we were able to find one single CpG site in the +1kb intragenic region of ESR1 strikingly differently methylated between heart vs. epididymis. Interestingly, this single CpG-site was identified as a putative binding site for the transcriptional repressor TG-interacting factor 1 (TGIF) which can recruit histone deacetylase 1 (HDAC1) leading to chromatin condensation. Indeed, chromatin immunoprecipitation confirmed a reduced histone H3 presence at the specific ESR1 location in case of higher DNA methylation. We therefore hypothesize that ESR1 expression may be manifested by a single-CpG-site based methylation difference impairing transcription factor binding.

Neuroprotective effects of 17β-estradiol rely on estrogen receptor membrane initiated signals

Besides its crucial role in many physiological events, 17β-estradiol (E2) exerts protective effects in the central nervous system. The E2 effects are not restricted to the brain areas related with the control of reproductive function, but rather are widespread throughout the developing and the adult brain. E2 actions are mediated through estrogen receptors (i.e., ERα and ERβ) belonging to the nuclear receptor super-family. As members of the ligand-regulated transcription factor family, classically, the actions of ERs in the brain were thought to mediate only the E2 long-term transcriptional effects. However, a growing body of evidence highlighted rapid, membrane initiated E2 effects in the brain that are independent of ER transcriptional activities and are involved in E2-induced neuroprotection. The aim of this review is to focus on the rapid effects of E2 in the brain highlighting the specific role of the signaling pathway(s) of the ERβ subtype in the neuroprotective actions of E2.

Comparison of the effects of estradiol and progesterone on serotonergic function

BACKGROUND

Ovarian hormones may contribute to the vulnerability to depression, as well as to the response to antidepressants (ADs). Previously, we reported that acute systemic treatment with estradiol or progesterone blocked the ability of the selective serotonin reuptake inhibitor, fluvoxamine, to inhibit serotonin transporter function in ovariectomized rats. In this study, behavioral consequences, as well as receptor mechanisms underlying these hormonal effects, were investigated.

METHODS

Using the forced swimming test, the acute effect of estradiol and/or progesterone on fluvoxamine's AD-like effects was investigated. Using in vivo chronoamperometry, the effect of local application of estradiol or progesterone into the hippocampus of ovariectomized rats on serotonin (5-HT) clearance, as well as on the ability of fluvoxamine to slow 5-HT clearance, were investigated.

RESULTS

The decreased immobility and increased swimming caused by fluvoxamine in the forced swimming test was blocked in rats treated with estradiol and/or progesterone. Local application of estradiol, but not progesterone, slowed 5-HT clearance and both hormones blocked the ability of fluvoxamine to slow 5-HT clearance. Use of hormone receptor agonists and antagonists, revealed that the effects of estradiol are mediated by activation of membrane, as well as nuclear estrogen receptors (ER). The AD-like effect of estradiol involved ER beta and G-protein coupled receptor 30, whereas its blockade of fluvoxamine's effects was ER alpha-mediated. The effects of progesterone occurred solely by activation of intracellular progesterone receptors.

CONCLUSIONS

Targeting of ER beta or G-protein coupled receptor 30 might reveal a strategy to permit beneficial effects of estrogen without its deleterious effect on selective serotonin reuptake inhibitor efficacy.