Estrogen targets genes involved in protein processing, calcium homeostasis, and Wnt signaling in the mouse uterus independent of estrogen receptor-alpha and -beta

Identification and Analysis of ZIC-Related Genes in Cerebellum of Autism Spectrum Disorders

Objective

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with significant genetic heterogeneity. The ZIC gene family can regulate neurodevelopment, especially in the cerebellum, and has been implicated in ASD-like behaviors in mice. We performed bioinformatic analysis to identify the ZIC gene family in the ASD cerebellum.

Methods

We explored the roles of ZIC family genes in ASD by investigating (i) the association of ZIC genes with ASD risk genes from the Simons Foundation Autism Research Initiative (SFARI) database and ZIC genes in the brain regions of the Human Protein Atlas (HPA) database; (ii) co-expressed gene networks of genes positively and negatively correlated with ZIC1, ZIC2, and ZIC3, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and receiver operating characteristic (ROC) curve analysis of genes in these networks; and (iii) the relationship between ZIC1, ZIC2, ZIC3, and their related genes with cerebellar immune cells and stromal cells in ASD patients.

Results

(i) ZIC1, ZIC2, and ZIC3 were associated with neurodevelopmental disorders and risk genes related to ASD in the human cerebellum and (ii) ZIC1, ZIC2, and ZIC3 were highly expressed in the cerebellum, which may play a pathogenic role by affecting neuronal development and the cerebellar internal environment in patients with ASD, including immune cells, astrocytes, and endothelial cells. (iii) OLFM3, SLC27A4, GRB2, TMED1, NR2F1, and STRBP are closely related to ZIC1, ZIC2, and ZIC3 in ASD cerebellum and have good diagnostic accuracy. (iv) ASD mice in the maternal immune activation model demonstrated that Zic3 and Nr2f1 levels were decreased in the immune-activated cerebellum.

Conclusion

Our study supports the role of ZIC1, ZIC2, and ZIC3 in ASD pathogenesis and provides potential targets for early and accurate prediction of ASD.

Estrogen depletion on In vivo osteocyte calcium signaling responses to mechanical loading

Microstructural adaptation of bone in response to mechanical stimuli is diminished with estrogen deprivation. Here we tested in vivo whether ovariectomy (OVX) alters the acute response of osteocytes, the principal mechanosensory cells of bone, to mechanical loading in mice. We also used super resolution microscopy (Structured Illumination microscopy or SIM) in conjunction with immunohistochemistry to assess changes in the number and organization of "osteocyte mechanosomes" - complexes of Panx1 channels, P2X7 receptors and CaV3 voltage-gated Ca²⁺ channels clustered around α_vβ₃ integrin foci on osteocyte processes. Third metatarsals bones of mice expressing an osteocyte-targeted genetically encoded Ca²⁺ indicator (DMP1-GCaMP3) were cyclically loaded in vivo to strains from 250 to 3000 με and osteocyte intracellular Ca²⁺ signaling responses were assessed in mid-diaphyses using multiphoton microscopy. The number of Ca²⁺ signaling osteocytes in control mice increase monotonically with applied strain magnitude for the physiological range of strains. The relationship between the number of Ca²⁺ signaling osteocytes and loading was unchanged at 2 days post-OVX. However, it was altered markedly at 28 days post-OVX. At loads up to 1000 με, there was a dramatic reduction in number of responding (i.e. Ca²⁺ signaling) osteocytes; however, at higher strains the numbers of Ca²⁺ signaling osteocytes were similar to control mice. OVX significantly altered the abundance, make-up and organization of osteocyte mechanosome complexes on dendritic processes. Numbers of α_vβ₃ foci also staining with either Panx 1, P2X7R or CaV3 declined by nearly half after OVX, pointing to a loss of osteocyte mechanosomes on the dendritic processes with estrogen depletion. At the same time, the areas of the remaining foci that stained for α_vβ₃ and channel proteins increased significantly, a redistribution of mechanosome components suggesting a potential compensatory response. These results demonstrate that the deleterious effects of estrogen depletion on skeletal mechanical adaptation appear at the level of mechanosensation; osteocytes lose the ability to sense small (physiological) mechanical stimuli. This decline may result at least partly from changes in the structure and organization of osteocyte mechanosomes, which contribute to the distinctive sensitivity of osteocytes (particularly their dendritic processes) to mechanical stimulation.

Heat Shock Proteins and Their Role in Pregnancy: Redefining the Function of "Old Rum in a New Bottle"

Pregnancy in humans is a multi-step complex physiological process comprising three discrete events, decidualization, implantation and placentation. Its overall success depends on the incremental advantage that each of the preceding stages passes on to the next. The success of these synchronized sequels of events is an outcome of timely coordination between them. The pregnancy events are coordinated and governed primarily by the ovarian steroid hormones, estrogen and progesterone, which are essentially ligand-activated transcription factors. It's well known that intercellular signaling of steroid hormones engages a plethora of adapter proteins that participate in executing the biological functions. This involves binding of the hormone receptor complex to the DNA response elements in a sequence specific manner. Working with Drosophila melanogaster, the heat shock proteins (HSPs) were originally described by Ferruccio Ritossa back in the early 1960s. Over the years, there has been considerable advancement of our understanding of these conserved families of proteins, particularly in pregnancy. Accumulating evidence suggests that endometrial and uterine cells have an abundance of HSP27, HSP60, HSP70 and HSP90, implying their possible involvement during the pregnancy process. HSPs have been found to be associated with decidualization, implantation and placentation, with their dysregulation associated with implantation failure, pregnancy loss and other feto-maternal complications. Furthermore, HSP is also associated with stress response, specifically in modulating the ER stress, a critical determinant for reproductive success. Recent advances suggest a therapeutic role of HSPs proteins in improving the pregnancy outcome. In this review, we summarized our latest understanding of the role of different members of the HSP families during pregnancy and associated complications based on experimental and clinical evidences, thereby redefining and exploring their novel function with new perspective, beyond their prototype role as molecular chaperones.

Scl-Ab reverts pro-osteoclastogenic signalling and resorption in estrogen deficient osteocytes

Background

Neutralising antibodies to sclerostin (Scl-Ab) have shown significant potential to induce bone formation and decrease bone resorption, increase strength and substantially reduce fracture risk in animal studies and clinical trials. Mechanical loading negatively regulates sclerostin expression, and sclerostin has been shown to induce RANKL synthesis in osteocytes. However, how Scl-Ab governs osteocyte regulation of osteoclast differentiation and function is not fully understood. We have recently discovered that osteoblasts and osteocytes alter osteoclastogenic signalling (RANKL/OPG) during estrogen-deficiency, and that osteoblast-induced osteoclastogenesis and resorption are exacerbated. However, it is not known whether estrogen deficient osteocytes exacerbate osteoclastogenesis. The aims of this study were to (1) establish whether osteocytes induce osteoclastogenesis and bone resorption during estrogen deficiency in vitro (2) investigate whether the sclerostin antibody can revert osteocyte-mediated osteoclastogenesis and resorption by attenuating RANKL/OPG expression.

Results

Using conditioned media and co-culture experiments we found increased osteocyte-induced osteoclastogenesis and bone resorption in estrogen deficient conditions. This is the first study to report that administration of Scl-Ab has the ability to revert osteocyte-mediated osteoclastogenesis and resorption by decreasing RANKL/OPG ratio expression and increasing WISP1 expression in estrogen deficient osteocytes.

Conclusions

This study provides an enhanced understanding of the biological changes underpinning decreases in bone resorption following Scl-Ab treatment observed in vivo by revealing that Scl-Ab can reduce pro-osteoclastogenic cell signalling between osteocytes and osteoclasts.

Inside the Endometrial Cell Signaling Subway: Mind the Gap(s)

Endometrial cells perceive and respond to their microenvironment forming the basis of endometrial homeostasis. Errors in endometrial cell signaling are responsible for a wide spectrum of endometrial pathologies ranging from infertility to cancer. Intensive research over the years has been decoding the sophisticated molecular means by which endometrial cells communicate to each other and with the embryo. The objective of this review is to provide the scientific community with the first overview of key endometrial cell signaling pathways operating throughout the menstrual cycle. On this basis, a comprehensive and critical assessment of the literature was performed to provide the tools for the authorship of this narrative review summarizing the pivotal components and signaling cascades operating during seven endometrial cell fate “routes”: proliferation, decidualization, implantation, migration, breakdown, regeneration, and angiogenesis. Albeit schematically presented as separate transit routes in a subway network and narrated in a distinct fashion, the majority of the time these routes overlap or occur simultaneously within endometrial cells. This review facilitates identification of novel trajectories of research in endometrial cellular communication and signaling. The meticulous study of endometrial signaling pathways potentiates both the discovery of novel therapeutic targets to tackle disease and vanguard fertility approaches.

Crosstalk between nuclear and G protein-coupled estrogen receptors

In 2005, two groups independently discovered that the G protein-coupled receptor GPR30 binds estradiol in cultured cells and, in response, initiates intracellular signaling cascades Revankar et al. (2005), Thomas et al. (2005). GPR30 is now referred to as GPER, the G-protein coupled estrogen receptor Prossnitz and Arterburn (2015). While studies in animal models are illuminating GPER function, there is controversy as to whether GPER acts as an autonomous estrogen receptor in vivo, or whether GPER interacts with nuclear estrogen receptor signaling pathways in response to estrogens. Here, we review the evidence that GPER acts as an autonomous estrogen receptor in vivo and discuss experimental approaches to test this hypothesis directly. We propose that the degree to which GPER influences nuclear estrogen receptor signaling likely depends on cell type, developmental stage and pathology.

Inhibition of Wnt Signaling Pathways Impairs Chlamydia trachomatis Infection in Endometrial Epithelial Cells

Chlamydia trachomatis infections represent the predominant cause of bacterial sexually transmitted infections. As an obligate intracellular bacterium, C. trachomatis is dependent on the host cell for survival, propagation, and transmission. Thus, factors that affect the host cell, including nutrition, cell cycle, and environmental signals, have the potential to impact chlamydial development. Previous studies have demonstrated that activation of Wnt/β-catenin signaling benefits C. trachomatis infections in fallopian tube epithelia. In cervical epithelial cells chlamydiae sequester β-catenin within the inclusion. These data indicate that chlamydiae interact with the Wnt signaling pathway in both the upper and lower female genital tract (FGT). However, hormonal activation of canonical and non-canonical Wnt signaling pathways is an essential component of cyclic remodeling in another prominent area of the FGT, the endometrium. Given this information, we hypothesized that Wnt signaling would impact chlamydial infection in endometrial epithelial cells. To investigate this hypothesis, we analyzed the effect of Wnt inhibition on chlamydial inclusion development and elementary body (EB) production in two endometrial cell lines, Ishikawa (IK) and Hec-1B, in nonpolarized cell culture and in a polarized endometrial epithelial (IK)/stromal (SHT-290) cell co-culture model. Inhibition of Wnt by the small molecule inhibitor (IWP2) significantly decreased inclusion size in IK and IK/SHT-290 cultures (p < 0.005) and chlamydial infectivity (p ≤ 0.01) in both IK and Hec-1B cells. Confocal and electron microscopy analysis of chlamydial inclusions revealed that Wnt inhibition caused chlamydiae to become aberrant in morphology. EB formation was also impaired in IK, Hec-1B and IK/SHT-290 cultures regardless of whether Wnt inhibition occurred throughout, in the middle (24 hpi) or late (36 hpi) during the development cycle. Overall, these data lead us to conclude that Wnt signaling in the endometrium is a key host pathway for the proper development of C. trachomatis.

Endoplasmic Reticulum Stress and Homeostasis in Reproductive Physiology and Pathology

The endoplasmic reticulum (ER), comprises 60% of the total cell membrane and interacts directly or indirectly with several cell organelles i.e., Golgi bodies, mitochondria and proteasomes. The ER is usually associated with large numbers of attached ribosomes. During evolution, ER developed as the specific cellular site of synthesis, folding, modification and trafficking of secretory and cell-surface proteins. The ER is also the major intracellular calcium storage compartment that maintains cellular calcium homeostasis. During the production of functionally effective proteins, several ER-specific molecular steps sense quantity and quality of synthesized proteins as well as proper folding into their native structures. During this process, excess accumulation of unfolded/misfolded proteins in the ER lumen results in ER stress, the homeostatic coping mechanism that activates an ER-specific adaptation program, (the unfolded protein response; UPR) to increase ER-associated degradation of structurally and/or functionally defective proteins, thus sustaining ER homeostasis. Impaired ER homeostasis results in aberrant cellular responses, contributing to the pathogenesis of various diseases. Both female and male reproductive tissues undergo highly dynamic cellular, molecular and genetic changes such as oogenesis and spermatogenesis starting in prenatal life, mainly controlled by sex-steroids but also cytokines and growth factors throughout reproductive life. These reproductive changes require ER to provide extensive protein synthesis, folding, maturation and then their trafficking to appropriate cellular location as well as destroying unfolded/misfolded proteins via activating ER-associated degradation mediated proteasomes. Many studies have now shown roles for ER stress/UPR signaling cascades in the endometrial menstrual cycle, ovarian folliculogenesis and oocyte maturation, spermatogenesis, fertilization, pre-implantation embryo development and pregnancy and parturition. Conversely, the contribution of impaired ER homeostasis by severe/prolong ER stress-mediated UPR signaling pathways to several reproductive tissue pathologies including endometriosis, cancers, recurrent pregnancy loss and pregnancy complications associated with pre-term birth have been reported. This review focuses on ER stress and UPR signaling mechanisms, and their potential roles in female and male reproductive physiopathology involving in menstrual cycle changes, gametogenesis, preimplantation embryo development, implantation and placentation, labor, endometriosis, pregnancy complications and preterm birth as well as reproductive system tumorigenesis.

Mechanisms of uterine estrogen signaling during early pregnancy in mice: an update

Adherence of an embryo to the uterus represents the most critical step of the reproductive process. Implantation is a synchronized event between the blastocyst and the uterine luminal epithelium, leading to structural and functional changes for further embryonic growth and development. The milieu comprising the complex process of implantation is mediated by estrogen through diverse but interdependent signaling pathways. Mouse models have demonstrated the relevance of the expression of estrogen-modulated paracrine factors to uterine receptivity and implantation window. More importantly, some factors seem to serve as molecular links between different estrogen pathways, promoting cell growth, acting as molecular chaperones, or amplifying estrogenic effects. Abnormal expression of these factors can lead to implantation failure and infertility. This review provides an overview of several well-characterized signaling pathways that elucidates the molecular cross talk involved in the uterus during early pregnancy.

Estrogen Enhances Linkage in the Vascular Endothelial Calmodulin Network via a Feedforward Mechanism at the G Protein-coupled Estrogen Receptor 1

Estrogen exerts many effects on the vascular endothelium. Calmodulin (CaM) is the transducer of Ca(2+) signals and is a limiting factor in cardiovascular tissues. It is unknown whether and how estrogen modifies endothelial functions via the network of CaM-dependent proteins. Here we show that 17β-estradiol (E2) up-regulates total CaM level in endothelial cells. Concurrent measurement of Ca(2+) and Ca(2+)-CaM indicated that E2 also increases free Ca(2+)-CaM. Pharmacological studies, gene silencing, and receptor expression-specific cell studies indicated that the G protein-coupled estrogen receptor 1 (GPER/GPR30) mediates these effects via transactivation of EGFR and subsequent MAPK activation. The outcomes were then examined on four distinct members of the intracellular CaM target network, including GPER/GPR30 itself and estrogen receptor α, the plasma membrane Ca(2+)-ATPase (PMCA), and endothelial nitric-oxide synthase (eNOS). E2 substantially increases CaM binding to estrogen receptor α and GPER/GPR30. Mutations that reduced CaM binding to GPER/GPR30 in separate binding domains do not affect GPER/GPR30-Gβγ preassociation but decrease GPER/GPR30-mediated ERK1/2 phosphorylation. E2 increases CaM-PMCA association, but the expected stimulation of Ca(2+) efflux is reversed by E2-stimulated tyrosine phosphorylation of PMCA. These effects sustain Ca(2+) signals and promote Ca(2+)-dependent CaM interactions with other CaM targets. Consequently, E2 doubles CaM-eNOS interaction and also promotes dual phosphorylation of eNOS at Ser-617 and Ser-1179. Calculations using in-cell and in vitro data revealed substantial individual and combined contribution of these effects to total eNOS activity. Taken together, E2 generates a feedforward loop via GPER/GPR30, which enhances Ca(2+)/CaM signals and functional linkage in the endothelial CaM target network.

Uterine endoplasmic reticulum stress-unfolded protein response regulation of gestational length is caspase-3 and -7-dependent

We previously identified myometrial caspase-3 (CASP3) as a potential regulator of uterine quiescence. We also determined that during pregnancy, the functional activation of uterine CASP3 is likely governed by an integrated endoplasmic reticulum stress response (ERSR) and is consequently limited by an increased unfolded protein response (UPR). The present study examined the functional relevance of uterine UPR-ERSR in maintaining myometrial quiescence and regulating the timing of parturition. In vitro analysis of the human uterine myocyte hTERT-HM cell line revealed that tunicamycin (TM)-induced ERSR modified uterine myocyte contractile responsiveness. Accordingly, alteration of in vivo uterine UPR-ERSR using a pregnant mouse model significantly modified gestational length. We determined that "normal" gestational activation of the ERSR-induced CASP3 and caspase 7 (CASP7) maintains uterine quiescence through previously unidentified proteolytic targeting of the gap junction protein, alpha 1(GJA1); however, surprisingly, TM-induced uterine ERSR triggered an exaggerated UPR that eliminated uterine CASP3 and 7 tocolytic action precociously. These events allowed for a premature increase in myometrial GJA1 levels, elevated contractile responsiveness, and the onset of preterm labor. Importantly, a successful reversal of the magnified ERSR-induced preterm birth phenotype could be achieved by pretreatment with 4-phenylbutrate, a chaperone protein mimic.

What have we learned about GPER function in physiology and disease from knockout mice?

Estrogens, predominantly 17β-estradiol, exert diverse effects throughout the body in both normal and pathophysiology, during development and in reproductive, metabolic, endocrine, cardiovascular, nervous, musculoskeletal and immune systems. Estrogen and its receptors also play important roles in carcinogenesis and therapy, particularly for breast cancer. In addition to the classical nuclear estrogen receptors (ERα and ERβ) that traditionally mediate predominantly genomic signaling, the G protein-coupled estrogen receptor GPER has become recognized as a critical mediator of rapid signaling in response to estrogen. Mouse models, and in particular knockout (KO) mice, represent an important approach to understand the functions of receptors in normal physiology and disease. Whereas ERα KO mice display multiple significant defects in reproduction and mammary gland development, ERβ KO phenotypes are more limited, and GPER KO exhibit no reproductive deficits. However, the study of GPER KO mice over the last six years has revealed that GPER deficiency results in multiple physiological alterations including obesity, cardiovascular dysfunction, insulin resistance and glucose intolerance. In addition, the lack of estrogen-mediated effects in numerous tissues of GPER KO mice, studied in vivo or ex vivo, including those of the cardiovascular, endocrine, nervous and immune systems, reveals GPER as a genuine mediator of estrogen action. Importantly, GPER KO mice have also demonstrated roles for GPER in breast carcinogenesis and metastasis. In combination with the supporting effects of GPER-selective ligands and GPER knockdown approaches, GPER KO mice demonstrate the therapeutic potential of targeting GPER activity in diseases as diverse as obesity, diabetes, multiple sclerosis, hypertension, atherosclerosis, myocardial infarction, stroke and cancer.

Muscle Segment Homeobox Genes Direct Embryonic Diapause by Limiting Inflammation in the Uterus

Embryonic diapause is a reproductive strategy widespread in the animal kingdom. This phenomenon is defined by a temporary arrest in blastocyst growth and metabolic activity within a quiescent uterus without implantation until the environmental and maternal milieu become favorable for pregnancy to progress. We found that uterine Msx expression persists during diapause across species; their inactivation in the mouse uterus results in termination of diapause with the development of implantation-like responses ("pseudoimplantation") that ultimately succumbed to resorption. To understand the cause of this failure, we compared proteome profiles between floxed and Msx-deleted uteri. In deleted uteri, several functional networks, including transcription/translation, ubiquitin-proteasome, inflammation, and endoplasmic reticulum stress, were dysregulated. Computational modeling predicted intersection of these pathways on an enhanced inflammatory signature. Further studies showed that this signature was reflected in increased phosphorylated IκB levels and nuclear NFκB in deleted uteri. This was associated with enhanced proteasome activity and endoplasmic reticulum stress. Interestingly, treatment with anti-inflammatory glucocorticoid (dexamethasone) reduced the inflammatory signature with improvement of the diapause phenotype. These findings highlight an unexpected role of uterine Msx in limiting aberrant inflammatory responses to maintain embryonic diapause.

Reactive oxygen species via redox signaling to PI3K/AKT pathway contribute to the malignant growth of 4-hydroxy estradiol-transformed mammary epithelial cells

The purpose of this study was to investigate the effects of 17-β-estradiol (E2)-induced reactive oxygen species (ROS) on the induction of mammary tumorigenesis. We found that ROS-induced by repeated exposures to 4-hydroxy-estradiol (4-OH-E2), a predominant catechol metabolite of E2, caused transformation of normal human mammary epithelial MCF-10A cells with malignant growth in nude mice. This was evident from inhibition of estrogen-induced breast tumor formation in the xenograft model by both overexpression of catalase as well as by co-treatment with Ebselen. To understand how 4-OH-E2 induces this malignant phenotype through ROS, we investigated the effects of 4-OH-E2 on redox-sensitive signal transduction pathways. During the malignant transformation process we observed that 4-OH-E2 treatment increased AKT phosphorylation through PI3K activation. The PI3K-mediated phosphorylation of AKT in 4-OH-E2-treated cells was inhibited by ROS modifiers as well as by silencing of AKT expression. RNA interference of AKT markedly inhibited 4-OH-E2-induced in vitro tumor formation. The expression of cell cycle genes, cdc2, PRC1 and PCNA and one of transcription factors that control the expression of these genes - nuclear respiratory factor-1 (NRF-1) was significantly up-regulated during the 4-OH-E2-mediated malignant transformation process. The increased expression of these genes was inhibited by ROS modifiers as well as by silencing of AKT expression. These results indicate that 4-OH-E2-induced cell transformation may be mediated, in part, through redox-sensitive AKT signal transduction pathways by up-regulating the expression of cell cycle genes cdc2, PRC1 and PCNA, and the transcription factor - NRF-1. In summary, our study has demonstrated that: (i) 4-OH-E2 is one of the main estrogen metabolites that induce mammary tumorigenesis and (ii) ROS-mediated signaling leading to the activation of PI3K/AKT pathway plays an important role in the generation of 4-OH-E2-induced malignant phenotype of breast epithelial cells. In conclusion, ROS are important signaling molecules in the development of estrogen-induced malignant breast lesions.

Derailed estrogen signaling and breast cancer: an authentic couple

Estrogen or 17β-estradiol, a steroid hormone, plays a critical role in the development of mammary gland via acting through specific receptors. In particular, estrogen receptor-α (ERα) acts as a transcription factor and/or a signal transducer while participating in the development of mammary gland and breast cancer. Accumulating evidence suggests that the transcriptional activity of ERα is altered by the action of nuclear receptor coregulators and might be responsible, at least in part, for the development of breast cancer. In addition, this process is driven by various posttranslational modifications of ERα, implicating active participation of the upstream receptor modifying enzymes in breast cancer progression. Emerging studies suggest that the biological outcome of breast cancer cells is also influenced by the cross talk between microRNA and ERα signaling, as well as by breast cancer stem cells. Thus, multiple regulatory controls of ERα render mammary epithelium at risk for transformation upon deregulation of normal homeostasis. Given the importance that ERα signaling has in breast cancer development, here we will highlight how the activity of ERα is controlled by various regulators in a spatial and temporal manner, impacting the progression of the disease. We will also discuss the possible therapeutic value of ERα modulators as alternative drug targets to retard the progression of breast cancer.

Epigenetic changes through DNA methylation contribute to uterine stromal cell decidualization

Embryo-uterine interaction during early pregnancy critically depends on the coordinated expression of numerous genes at the site of implantation. The epigenetic mechanism through DNA methylation (DNM) plays a major role in the control of gene expression, although this regulatory event remains unknown in uterine implantation sites. Our analysis revealed the presence of DNA methyltransferase 1 (Dnmt1) in mouse endometrial cells on the receptive d 4 of pregnancy and early postattachment (d 5) phase, whereas Dnmt3a had lower abundant expression. Both Dnmt1 and Dnmt3a were coordinately expressed in decidual cells on d 6-8. 5-Methycytosine showed a similar expression pattern to that of Dnmt1. The preimplantation inhibition of DNM by 5-aza-2'-deoxycytodine was not antagonistic for embryonic attachment, although endometrial stromal cell proliferation at the site of implantation was down-regulated, indicating a disturbance with the postattachment decidualization event. Indeed, the peri- or postimplantation inhibition of DNM caused significant abrogation of decidualization, with concomitant loss of embryos. We next identified decidual genes undergoing alteration of DNM using methylation-sensitive restriction fingerprinting. One such gene, Chromobox homolog 4, an epigenetic regulator in the polycomb group protein family, exhibited hypomethylation in promoter DNA and increased expression with the onset of decidualization. Furthermore, inhibition of DNM resulted in enhanced expression of hypermethylated genes (Bcl3 and Slc16a3) in the decidual bed as compared with control, indicating aberration of gene expression may be associated with DNM-inhibition-induced decidual perturbation. Overall, these results suggest that uterine DNM plays a major role for successful decidualization and embryo development during early pregnancy.

Galectin-1 markedly reduces the incidence of resorptions in mice missing immunophilin FKBP52

Progesterone (P(4)) signaling is critical for pregnancy. We previously showed that immunopilin FK506 binding protein (FKBP)52 serves as a cochaperone to optimize progesterone receptor (PR) function in the uterus, and its deficiency leads to P(4) resistance in a pregnancy stage-specific and genetic background-dependent manner in mice. In particular, sc placement of SILASTIC implants carrying P(4) rescued implantation failure in CD1 Fkbp52(-/-) mice, but the resorption rate was substantially high at midgestation due to reduced P(4) responsiveness. Because downstream targets of P(4)-FKBP52-PR signaling in the uterus to support pregnancy are not clearly understood, we performed proteomic analysis using Fkbp52(-/-), PR-deficient (Pgr(-/-)), and wild-type (WT) uteri. We found that the expression of galectin-1 (Gal1), an evolutionarily conserved glycan-binding protein, was significantly down-regulated in both Fkbp52(-/-) and Pgr(-/-) uteri compared with WT uteri. During early gestation, Lgals1, which encodes Gal1, was distinctly expressed in stromal and decidual cells. Lgals1 expression was much lower in d 4 Fkbp52(-/-) uteri compared with WT uteri, and this reduction was reversed by P(4) supplementation. More interestingly, concomitant supplementation of recombinant Gal1 significantly suppressed the high resorption rate and leukocyte infiltration at implantation sites in CD1 Fkbp52(-/-) females carrying P(4) SILASTIC implants. These findings suggest that uterine Gal1 is an important downstream target of P(4)-FKBP52-PR signaling in the uterus to support P(4) responsiveness during pregnancy.

Nucleolar Sik-similar protein (Sik-SP) is required for the maintenance of uterine estrogen signaling mechanism via ERα

Sik-similar protein (Sik-SP), a small nucleolar ribonucleoprotein, has been shown to be primarily involved in ribosome biogenesis. However, its role in the hormone-directed nuclear receptor signaling is largely unknown. Here, we provide novel evidence that Sik-SP is required for appropriate regulation of estrogen receptor (ER)α-mediated estradiol-17β (E2)-dependent uterine physiologic responses in mice. Studies by Western blotting using the newly developed antibodies for Sik-SP showed that this protein is up-regulated in both the ovariectomized wild-type and ERα null uteri by E2. Immunohistochemical analyses in uterine sections showed that this protein is induced in the epithelial and stromal cells. Coimmunoprecipitation studies revealed that E2 directs molecular interaction between Sik-SP and ERα. Furthermore, gel-mobility shift and chromatin immunoprecipitation analyses provided evidence that Sik-SP is recruited with ERα to estrogen-responsive uterine gene promoters. Overexpression of Sik-SP in vitro demonstrated a role for Sik-SP in cellular growth and viability. In a primary uterine epithelial-stromal coculture system, E2 exhibited early induction of Sik-SP in both the epithelial and stromal cells. Interestingly, suppression of Sik-SP in this coculture model, for the stromal but not epithelial cells, caused perturbation of E2-dependent proliferation in the epithelial cell layer. Similarly, in vivo uterine suppression of Sik-SP also caused inhibition of epithelial cell proliferation and aberrant prolongation of water imbibition in the late phase by E2. Finally, studies showed that Sik-SP is physiologically important during the onset of implantation by E2. In conclusion, Sik-SP, an early E2-responsive nucleolar protein, is necessary to induce E2-dependent ERα-mediated appropriate physiologic responses in the uterus.

GPR30 activation opposes estrogen-dependent uterine growth via inhibition of stromal ERK1/2 and estrogen receptor alpha (ERα) phosphorylation signals

Although estradiol-17β (E2)-regulated early and late phase uterine responses have been well defined, the molecular mechanisms linking the phases remain poorly understood. We have previously shown that E2-regulated early signals mediate cross talk with estrogen receptor (ER)-α to elicit uterine late growth responses. G protein-coupled receptor (GPR30) has been implicated in early nongenomic signaling mediated by E2, although its role in E2-dependent uterine biology is unclear. Using selective activation of GPR30 by G-1, we show here a new function of GPR30 in regulating early signaling events, including the inhibition of ERK1/2 and ERα (Ser118) phosphorylation signals and perturbation of growth regulation under the direction of E2 in the mouse uterus. We observed that GPR30 primarily localizes in the uterine epithelial cells, and its activation alters gene expression and mediates inhibition of ERK1/2 and ERα (Ser118) phosphorylation signals in the stromal compartment, suggesting a paracrine signaling is involved. Importantly, viral-driven manipulation of GPR30 or pharmacological inhibition of ERK1/2 activation effectively alters E2-dependent uterine growth responses. Overall, GPR30 is a negative regulator of ERα-dependent uterine growth in response to E2. Our work has uncovered a novel GPR30-regulated inhibitory event, which may be physiologically relevant in both normal and pathological situations to negatively balance ERα-dependent uterine growth regulatory functions induced by E2.

Bidirectional interaction between unfolded-protein-response key protein HSPA5 and estrogen signaling in human endometrium

The human endometrium is a dynamic tissue that undergoes cyclic changes under the influence of steroid hormones as well as numerous local paracrine and autocrine factors. Heat shock 70 kDa protein (HSPA5; also known as GRP78/BiP), a molecular chaperone within the endoplasmic reticulum, plays crucial roles in normal cellular processes as well as in stress conditions, in which it is a central regulator for the unfolded protein response (UPR). We hypothesized that HSPA5 expression level is variable throughout the menstrual cycle in human endometrium and that estrogen signaling cross-talks with UPR signaling by interacting with HSPA5. HSPA5 expression throughout the menstrual cycle was evaluated in vivo in normal human endometrium. Using in vitro techniques, we then assessed the bidirectional regulation of HSPA5 and estrogen signaling in human endometrial glandular (Ishikawa) and stromal cells (ESC). HSPA5 immunoreactivity in endometrial glandular and stromal cells was cycle-dependent, and was significantly higher in phases of the menstrual cycle when estradiol (E(2)) levels are known to be the lowest compared with the rest of the cycle (P < 0.001). E(2) did not affect HSPA5 expression after 8-24 h incubation in Ishikawa cells and ESC in vitro. However, tunicamycin-induced HSPA5 expression was significantly lowered in these cells when pretreated with E(2) (P < 0.01 and P < 0.05, respectively). On the other hand, tunicamycin decreased E(2) up-regulated alkaline phosphatase activity (P < 0.001). In conclusion, there is cycle-dependent HSPA5 expression with a possible inverse correlation between HSPA5 expression and E(2) levels in human endometrium. We suggest that estrogen signaling cross-talks with the UPR cascade by interacting with HSPA5, as supported by our in vitro findings.

Steroid hormone receptors in cancer development: a target for cancer therapeutics

The steroid hormone receptors (SHRs) are ligand-dependent intracellular transcription factors that are known to influence the development and growth of many human cancers. SHRs pass signals from a steroid/hormone to the target genes by interacting with specific response element DNA sequences and various coregulatory proteins that consists of activators and/or corepressors. Disruptions in physiological functions of SHRs leads to several types of malignancies such as breast cancer, leukemia and lymphoma, prostate cancer, ovarian cancer, and lung cancer among others. Steroids/hormones/SHRs and their coregulators have opened up a unique window for novel steroid-based targeted therapies for cancer. Thus, dysregulation of SHR signaling in cancers compared with normal tissues can be exploited to target drugs that prevent and treat human cancers. In recent years, hormonal therapy has made a major contribution to the treatment of several cancers including reduced recurrence rates and longer survival rates. Development of various steroid receptor modulators and their potential therapeutic efficacies has provided us a great opportunity to effectively manage diseases like cancer in future. In this review article, we have summarized up-to-date knowledge of the role of SHRs in the development and progression of cancers, and potential endocrine-based therapeutic approaches to tackle these diseases.

Estrogen induces distinct patterns of microRNA expression within the mouse uterus

Control of estrogenic activity within the uterus is evident as unopposed estrogen action is associated with endometrial pathologies such as endometriosis and endometrial carcinoma. MicroRNAs (miRNAs) have emerged as important posttranscriptional regulators, which are postulated to fine-tune the actions of steroids in many systems including the uterus. The objective of the current study was to examine uterine expression of miRNAs in response to estrogen treatment within the mouse uterus using an ovariectomized, steroid-reconstituted mouse model. MicroRNA microarray analysis and subsequent quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) verification revealed that expression of mirn155, mirn429, and mirn451 was significantly increased by estrogen administration whereas mirn181b and mirn204 expression was significantly reduced. Pretreatment with the estrogen receptor (ER) antagonist ICI 182,780 confirmed that estrogen regulation was mediated via the classical ER pathway. This study demonstrates that estrogen regulates specific miRNAs within the murine uterus, which may participate in posttranscriptional regulation of estrogen-regulated genes.

Progesterone receptor-mediated up-regulation of transthyretin in preimplantation mouse uterus

Transthyretin (TTR), a carrier for thyroxine and retinol, has its messenger RNA (mRNA) expressed in the glandular endometrial epithelium and its protein detected in the glandular endometrial epithelium and the uterine lumen. TTR mRNA is dramatically up-regulated in the preimplantation mouse uterus as well as the P-treated ovariectomized mouse uterus, and in both situations the up-regulation of TTR is blocked by treatment with the P receptor antagonist RU486.

In pursuit of leucine-rich repeat-containing G protein-coupled receptor-5 regulation and function in the uterus

Leucine-rich repeat-containing G protein-coupled receptor (LGR)-5 is a recently identified marker of stem cells in adult intestinal epithelium and hair follicles. Because of this characteristic, we studied the status of Lgr5 expression in the mouse uterus under various conditions. Lgr5 is highly expressed in the uterine epithelium of immature mice and is dramatically down-regulated after the mice resume estrous cycles. Surprisingly, whereas its expression is up-regulated in uteri of ovariectomized mice, the expression is down-regulated by estrogen and progesterone via their cognate nuclear receptors, estrogen receptor-alpha and progesterone receptor, respectively. Using a mouse endometrial cancer model, we also found that Lgr5 is highly expressed in the epithelium during the initial stages of tumorigenesis but is remarkably down-regulated in fully developed tumors. Lgr5 is a downstream target of Wnt signaling in the intestine. Genetic evidence shows that either excessive or absence of Wnt signaling dampens Lgr5 expression in the uterus. Collectively, our results show that Lgr5 expression in the mouse uterine epithelium is unique and dynamically regulated under various physiological and pathological states of the uterus, suggesting that this orphan receptor has important functions in uterine biology. However, identifying definitive uterine function of LGR5 will require further investigation using conditional deletion of uterine Lgr5 because systemic deletion of this gene is neonatally lethal.

Mechanisms of estrogen signaling and gene expression via GPR30

The effects of estrogen are widespread throughout the body. Although the classical nuclear estrogen receptors have been known for many years to decades and their primary modes of action as transcriptional regulators is well understood, certain aspects of estrogen biology remain inconsistent with the mechanisms of action of these receptor. More recently, the G protein-coupled receptor, GPR30/GPER, has been suggested to contribute to some of the cellular and physiological effects of estrogen. Not only does GPR30 mediate some of the rapid signal transduction events following cell stimulation, such as calcium mobilization and kinase activation, it also appears to regulate rapid transcriptional activation of genes such as c-fos. Since many cells and tissues co-express classical estrogen receptors and GPR30, there exists great diversity in the possible avenues of synergism and antagonism. In this review, we will provide an overview of GPR30 function, focusing on the rapid signaling events that culminate in the transcriptional activation of certain genes.

Role of osteoblast suppression in multiple myeloma

Multiple myeloma is the most common form of plasma cell dyscrasia and virtually all cases of myeloma exhibit osteolytic lesions, which result in bone pain, pathological fractures, spinal cord compression, and hypercalcaemia. Malignant plasma cells disrupt the delicate balance between bone formation and bone resorption, which ultimately leads to the debilitating osteolytic lesions. This review focuses principally on mechanisms of osteoblast inhibition by malignant plasma cells with emphasis placed on our experimental findings, which support a model for abnormal Wnt signaling in osteoblast suppression. We describe how excessive amounts of soluble Wnt inhibitors secreted by malignant plasma cells in multiple myeloma could promote osteolytic lesions, tumor growth, suppress hematopoiesis, prevent proper engraftment, and expansion of transplanted stem cells. Finally, we detail current therapies shown to disrupt the interaction between the myeloma cell and the microenvironment, leading to activation of osteoblasts.

Glucose-regulated protein 78 (Grp78/BiP) is secreted by human oviduct epithelial cells and the recombinant protein modulates sperm-zona pellucida binding

OBJECTIVE

To determine the secretion of Grp78 by human oviduct epithelial cells, its association to spermatozoa, and its involvement in gamete interaction.

DESIGN

Prospective study.

SETTING

Basic research laboratory.

SUBJECT(S)

Semen samples obtained from normozoospermic volunteers. Tubal tissue provided by patients undergoing hysterectomies. Oocytes collected from women undergoing IVF-ET.

INTERVENTION(S)

Analysis of Grp78 expression and secretion by oviductal tissue. Gamete incubation with recombinant Grp78 (rec-Grp78).

MAIN OUTCOME MEASURE(S)

Assessment of protein expression and secretion by immunohistochemistry and Western immunoblotting, respectively. Evaluation of rec-Grp78 binding to human spermatozoa by immunocytochemistry, and analysis of its effect upon gamete interaction using the hemizona assay.

RESULT(S)

Grp78 was found in the surface of oviduct epithelial cells. Soluble Grp78 was detected in oviductal fluids from women in the periovulatory period and in oviductal tissue conditioned medium. Rec-Grp78 was able to bind to the sperm acrosomal cap, and its presence during gamete interaction led to a decrease in the number of spermatozoa bound to the zona pellucida (ZP). When calcium ions from the incubation medium were replaced by strontium, rec-Grp78 enhanced sperm-ZP interaction.

CONCLUSION(S)

Grp78 is expressed and secreted by oviduct epithelial cells. The protein would bind to the gametes and may modulate their interaction in a calcium-dependent manner.

GPR30 does not mediate estrogenic responses in reproductive organs in mice

The G protein-coupled receptor Gpr30 (Gper) was recently claimed to bind to estradiol and to activate cytoplasmic signal transduction pathways in response to estradiol. However, there are conflicting data regarding the role of Gpr30 as an estrogen receptor (ER): several laboratories were unable to demonstrate estradiol binding to GPR30 or estradiol-activated signal transduction in Gpr30-expressing cells. To clarify the potential role of Gpr30 as an ER, we generated Gpr30-deficient mice. Although Gpr30 was expressed in all reproductive organs, histopathological analysis did not reveal any abnormalities in these organs in Gpr30-deficient mice. Mutant male and female mice were as fertile as their wild-type littermates, indicating normal function of the hypothalamic-pituitary-gonadal axis. Moreover, we analyzed estrogenic responses in two major estradiol target organs, the uterus and the mammary gland. For that purpose, we examined different readout paradigms such as morphological measures, cellular proliferation, and target gene expression. Our data demonstrate that in vivo Gpr30 is dispensable for the mediation of estradiol effects in reproductive organs. These results are in clear contrast to the phenotype of mice lacking the classic ER alpha (Esr1) or aromatase (Cyp19a1). We conclude that the perception of Gpr30 (based on homology related to peptide receptors) as an ER might be premature and has to be reconsidered.

Epigenetic and phenotypic changes result from a continuous pre and post natal dietary exposure to phytoestrogens in an experimental population of mice

BACKGROUND

Developmental effects of exposure to endocrine disruptors can influence adult characters in mammals, but could also have evolutionary consequences. The aim of this study was to simulate an environmental exposure of an experimental population of mice to high amounts of nutritional phytoestrogens and to evaluate parameters of relevance for evolutionary change in the offspring. The effect of a continuous pre- and post-natal exposure to high levels of dietary isoflavones was evaluated on sexual maturity, morphometric parameters and DNA methylation status in mice. Adult mice male/female couples were fed ad libitum either with control diet (standard laboratory chow) or ISF diet (control diet plus a soy isoflavone extract at 2% (w/w) that contained the phytoestrogens genistein and daidzein). In the offspring we measured: i) the onset of vaginal opening (sexual maturation) in females, ii) weight and size in all pups at 7, 14, 21 and 42 days post-natal (dpn) and iii) DNA methylation patterns in skeletal alpha-actin (Acta1), estrogen receptor-alpha and c-fos in adults (42 dpn).

RESULTS

Vaginal opening was advanced in female pups in the ISF group, from 31.6 +/- 0.75 dpn to 25.7 +/- 0.48. No differences in size or weight at ages 7, 14 or 21 dpn were detected between experimental groups. Nevertheless, at age 42 dpn reduced size and weight were observed in ISF pups, in addition to suppression of normal gender differences in weight seen in the control group (males heavier that females). Also, natural differences seen in DNA methylation at Acta1 promoter in the offspring originated in the control group were suppressed in the ISF group. Acta1 is known to be developmentally regulated and related to morphomotric features.

CONCLUSION

This study demonstrates in mammals that individuals from a population subjected to a high consumption of isoflavones can show alterations in characters that may be of importance from an evolutionary perspective, such as epigenetic and morphometric characters or sexual maturation, a life history character.

Estrogen signaling through the transmembrane G protein-coupled receptor GPR30

Steroids play an important role in the regulation of normal physiology and the treatment of disease. Steroid receptors have classically been described as ligand-activated transcription factors mediating long-term genomic effects in hormonally regulated tissues. It is now clear that steroids also mediate rapid signaling events traditionally associated with growth factor receptors and G protein-coupled receptors. Although evidence suggests that the classical steroid receptors are capable of mediating many of these events, more recent discoveries reveal the existence of transmembrane receptors capable of responding to steroids with cellular activation. One such receptor, GPR30, is a member of the G protein-coupled receptor superfamily and mediates estrogen-dependent kinase activation as well as transcriptional responses. In this review, we provide an overview of the evidence for the cellular and physiological actions of GPR30 in estrogen-dependent processes and discuss the relationship of GPR30 with classical estrogen receptors.

Cooperative control via lymphoid enhancer factor 1/T cell factor 3 and estrogen receptor-alpha for uterine gene regulation by estrogen

Accumulating evidence indicates that estrogen regulates diverse but interdependent signaling pathways via estrogen receptor (ER)-dependent and -independent mechanisms. However, molecular relationship between these pathways for gene regulation under the direction of estrogen remains unknown. To address this possibility, our uterine analysis of Wnt/beta-catenin downstream effectors revealed that lymphoid enhancer factor 1 (Lef-1) and T cell factor 3 (Tcf-3) are up-regulated temporally by 17beta-estradiol (E2) in an ER-independent manner. Lef-1 is abundantly up-regulated early (within 2 h), whereas Tcf-3 is predominantly induced after 6 h, and both are sustained through 24 h. Interestingly, activated Lef-1/Tcf-3 molecularly interacted with ERalpha in a time-dependent manner, suggesting they possess a cross talk in the uterus by E2. Moreover, dual immunofluorescence studies confirm their colocalization in uterine epithelial cells after E2. Most importantly, using chromatin immunoprecipitation followed by PCR analyses, we provide evidence for an interesting possibility that ERalpha and Tcf-3/Lef-1 complex occupies at certain DNA regions of estrogen-responsive endogenous gene promoters in the mouse uterus. By selective perturbation of activated Lef-1/Tcf-3 or ERalpha signaling events, we provide in this study novel evidence that cooperative interactions, by these two different classes of transcription factors at the level of chromatin, direct uterine regulation of estrogen-responsive genes. Collectively, these studies support a mechanism that integration of a nonclassically induced beta-catenin/Lef-1/Tcf-3 signaling with ERalpha is necessary for estrogen-dependent endogenous gene regulation in uterine biology.

Trans-synaptic regulation of calmodulin gene expression after experimentally induced orofacial inflammation and subsequent corticosteroid treatment in the principal sensory and motor trigeminal nuclei of the rat

The cutaneous and mucosal surfaces in the infraorbital region around the whisker pad are innervated by the maxillary division of the afferent fibers of the trigeminal nerve, while certain ganglion cells project to the principal sensory trigeminal nucleus (Pr5). In turn, some of the neurons in the Pr5 project to the motor trigeminal nucleus (Mo5), whose neurons do not innervate the infraorbital skin. We analyzed the calmodulin (CaM) gene expression in these nuclei after dithranol-induced inflammation and subsequent treatment with corticosteroid in the infraorbital skin. CaM gene-specific mRNA populations were detected through quantitative image analysis of the distribution of CaM gene-specific riboprobes in brain stem cryostat sections of control rats and rats chronically treated with dithranol, corticosteroid or both. These nuclei displayed a differentially altered CaM gene expression in response to the treatments. While the CaM I and II mRNA contents were increased, the CaM III transcripts remained unaltered after chronic dithranol treatment in the Mo5. In the Pr5, however, the CaM mRNA contents were either unchanged (CaM I and III) or increased (CaM II). Subsequent corticosteroid treatment reversed the stimulatory effects of dithranol on the expression of all the CaM genes in the Mo5, but was without significant effects on the CaM I and II genes, or even increased the CaM III mRNA contents in the Pr5. Corticosteroid treatment alone was either ineffective or decreased the levels of CaM mRNAs in these nuclei. These data suggest that peripheral noxae of dermal origin may result in a trans-synaptically acting differential regulation of the multiple CaM genes in the brain.

Estrogen regulation of genes important for K+ channel signaling in the arcuate nucleus

Estrogen affects the electrophysiological properties of a number of hypothalamic neurons by modulating K(+) channels via rapid membrane actions and/or changes in gene expression. The interaction between these pathways (membrane vs. transcription) ultimately determines the effects of estrogen on hypothalamic functions. Using suppression subtractive hybridization, we produced a cDNA library of estrogen-regulated, brain-specific guinea pig genes, which included subunits from three prominent K+ channels (KCNQ5, Kir2.4, Kv4.1, and Kvbeta(1)) and signaling molecules that impact channel function including phosphatidylinositol 3-kinase (PI3K), protein kinase Cepsilon (PKCepsilon), cAMP-dependent protein kinase (PKA), A-kinase anchor protein (AKAP), phospholipase C (PLC), and calmodulin. Based on these findings, we dissected the arcuate nucleus from ovariectomized guinea pigs treated with estradiol benzoate (EB) or vehicle and analyzed mRNA expression using quantitative real-time PCR. We found that EB significantly increased the expression of KCNQ5 and Kv4.1 and decreased expression of KCNQ3 and AKAP in the rostral arcuate. In the caudal arcuate, EB increased KCNQ5, Kir2.4, Kv4.1, calmodulin, PKCepsilon, PLCbeta(4), and PI3Kp55gamma expression and decreased Kvbeta(1). The effects of estrogen could be mediated by estrogen receptor-alpha, which we found to be highly expressed in the guinea pig arcuate nucleus and, in particular, proopiomelanocortin neurons. In addition, single-cell RT-PCR analysis revealed that about 50% of proopiomelanocortin and neuropeptide Y neurons expressed KCNQ5, about 40% expressed Kir2.4, and about 60% expressed Kv4.1. Therefore, it is evident that the diverse effects of estrogen on arcuate neurons are mediated in part by regulation of K(+) channel expression, which has the potential to affect profoundly neuronal excitability and homeostatic functions, especially when coupled with the rapid effects of estrogen on K(+) channel function.

Increased level of cellular Bip critically determines estrogenic potency for a xenoestrogen kepone in the mouse uterus

Xenoestrogen mimics estrogen-like activities primarily based on alterations of gene expression and interactions with estrogen receptor (ER)-alpha and -beta. However, the requirement for large concentrations to induce estrogenic phenotypes and low affinity for ERs has challenged the notion that prevailing xenoestrogens are significant health hazards. Here in this study, we show that under certain conditions, exposure of xenoestrogen could be potentially harmful in respect to enhanced uterine estrogenicity. Previously, we have demonstrated that estradiol-17beta up-regulates uterine Bip, a stress-related endoplasmic reticulum protein, via an ER-independent mechanism in mice. Moreover, this protein essentially involves in estradiol-17beta-mediated uterine growth response and ERalpha-dependent gene transcription. Here, we demonstrate that among three tested xenoestrogens, only kepone (>15-30 mg/kg) exerts sustained inductive response for uterine Bip expression. Interestingly, this kepone-induced Bip strongly correlates with ERalpha-dependent growth and gene expressional responses in the mouse uterus. Furthermore, these effects were strongly suppressed after knockdown of uterine Bip, via the adenovirus approach. Although kepone at 7.5 mg/kg was not effective, it was strongly stimulatory by the adenovirus-driven forced expression of uterine Bip. In contrast, the control green fluorescence protein virus was not effective in the aforementioned responses. Furthermore, the induction of uterine Bip by stress-related signals also revealed the onset of uterine growth in mice when exposed to a sublethal dose of kepone. Collectively, studies provide novel molecular evidence that Bip acts as a critical regulator to amplify estrogenic potency for a weak xenoestrogen kepone.

Functional interactions between calmodulin and estrogen receptor-α

The effects of estrogen in breast epithelial cells are mediated primarily via estrogen receptor alpha and estrogen receptor beta (ERalpha and ERbeta). Accumulating evidence implicates a role for Ca2+ and calmodulin in breast carcinoma, as well as in the function of ERalpha. Calmodulin contributes to the regulation of both ERalpha degradation and ERalpha-mediated transcriptional activation. Recent data will be summarized in this review. Models to explain the molecular mechanisms by which calmodulin modulates ERalpha function are proposed.

The expression of CD9 in the peri-implantation mouse uterus is upregulated in an ovarian steroid hormone-dependent manner

OBJECTIVE

To examine the spatiotemporal expression of CD9 protein in the peri-implantation mouse uterus as well as the effects of ovarian steroid hormones on CD9.

DESIGN

Experimental animal study.

SETTING

Reproductive biological center of Chinese Academy of Sciences.

ANIMAL(S)

Female Kunming white strain mice (6-8 weeks old).

INTERVENTION(S)

Subcutaneous injection of P(4)/E(2); uterine tissues were collected at different times after injection.

MAIN OUTCOME MEASURE(S)

The levels of protein and mRNA were detected in mouse uterus during peri-implantation and after steroid hormones treatment.

RESULT(S)

CD9 protein was expressed intensely in the stromal cells on days 1 and 2 of pregnancy. On days 3 and 4, the glandular and luminal epithelial cells exhibited accumulation of CD9 protein. After the initial attachment reaction on day 5, luminal epithelial and stromal cells immediately surrounding the blastocysts exhibited distinct accumulation of CD9. On days 6-8, the accumulation of CD9 occurred in decidual cells. Using ovariectomized mice, we also observed that both progesterone and estrogen upregulated uterine CD9 expression.

CONCLUSION(S)

The results of the current investigation showed that CD9 was differentially expressed in the uterus depending on the stage of implantation and was upregulated in ovarian steroid hormone-dependent manner, implicating multiple roles of CD9 in the regulation of embryo implantation during the peri-implantation period.

Chromatin immunoprecipitation assay detects ERalpha recruitment to gene specific promoters in uterus

Chromatin immunoprecipitation (ChIP) technique allows detection of proteins that bind to chromatin. While this technique has been applied extensively in cell-based studies, its tissue-based application remains poorly explored. We are specifically interested in examining estrogen-dependent transcriptional mechanism in respect of recruitment of estrogen receptor-alpha (ERα), a ligand-activated transcription factor, to uterine gene promoters in mice. Recent gene-array studies, utilizing ERα knock-out vs. wild-type mice, have revealed that estrogen regulates numerous uterine genes temporally and most importantly via ERα during the phase-II response, including three well characterized genes viz., lactoferrin (Ltf), progesterone receptor (Pgr) and cyclinD1 (Ccnd1). Here, utilizing systematic ChIP studies, we demonstrate endogenous recruitment of ERα to above uterine gene promoters following estradiol-17β (E₂) injection in mice.

Estradiol-17β stimulates proliferation of mouse embryonic stem cells: involvement of MAPKs and CDKs as well as protooncogenes

Although the importance of estradiol-17β (E2) in many physiological processes has been reported, to date no researchers have investigated the effects of E2 on embryonic stem (ES) cell proliferation. Therefore, in the present study, we have examined the effect of E2 on the DNA synthesis of murine ES (ES-E14TG2a) cells and its related signaling pathways. The results of this study show that E2 (10−9 M) significantly increased [3H]thymidine incorporation at >4 h and that E2 (>10−12 M) induced an increase of [3H]thymidine incorporation after 8-h incubation. Moreover, E2 (>10−12 M) also increased 5′-bromo-2′-deoxyuridine (BrdU) incorporation and cell number. Indeed, E2 stimulated estrogen receptor (ER)-α and -β protein levels and increased mRNA expression levels of protooncogenes (c- fos, c- jun, and c- myc). Tamoxifen (antiestrogen) completely inhibited E2-induced increases in [3H]thymidine incorporation. In addition, estradiol-6- O-carboxymethyl oxime-BSA (E2-BSA; 10−9 M) increased [3H]thymidine incorporation at >1 h, and E2-BSA (>10−12 M) increased [3H]thymidine incorporation after 1-h incubation. E2-BSA-induced increase in BrdU incorporation also occurred in a dose-dependent manner. Tamoxifen had no effect on E2-BSA-induced increase of [3H]thymidine incorporation. Also, E2 and E2-BSA displayed maximal phosphorylation of p44/42 MAPKs at 10 and 5 min, respectively. E2 increased cyclins D1 and E as well as cyclin-dependent kinase (CDK)2 and CDK4. In contrast, E2 decreased the levels of p21cip1 and p27kip1 (CDK-inhibitory proteins). Increases of these cell cycle regulators were blocked by 10−5 M PD-98059 (MEK inhibitor). Moreover, E2-induced increase of [3H]thymidine incorporation was inhibited by PD-98059 or butyrolactone I (CDK2 inhibitor). In conclusion, estradiol-17β stimulates the proliferation of murine ES cells, and this action is mediated by MAPKs, CDKs, or protooncogenes.

Bip is a molecular link between the phase I and phase II estrogenic responses in uterus

Uterine estrogenic actions are biphasic, early (phase I) and late (phase II) responses. However, the molecular linkage between these phases is not known. Although certain phase I responses are considered estrogen receptor (ER)alpha and ERbeta independent, the phase II responses are ERalpha dependent. We previously observed that among several genes Bip is induced by estrogen in the mouse uterus in an ER-independent manner as a phase I response. Bip is a member of the chaperone family and plays roles in protein processing and confers cellular protection. However, its role in estrogen-dependent uterine biology is unknown. We show here a new function of Bip in regulating estrogen signaling in the uterus. Bip, induced during the phase I responses, molecularly interacts with ERalpha required for estrogen-mediated phase II growth responses. Utilizing in vivo and in vitro model systems, we found that adenovirus-driven suppression of Bip antagonizes ERalpha-mediated uterine gene transcription. Importantly, down-regulation of Bip compromises estrogen-dependent phase II growth responses with sustained phase I responses. In conclusion, Bip is critical for coordinating estrogen-elicited biphasic responses and serves as a molecular link between ERalpha-independent and -dependent estrogenic responses in the uterus.

E6AP and calmodulin reciprocally regulate estrogen receptor stability

Estrogen promotes the proliferation of human breast epithelial cells by interacting with the estrogen receptor (ER). Physiological responses of cells to estrogen are regulated in part by degradation of the ER. Previous studies revealed that calmodulin binds directly to the ER, thereby enhancing its stability. Consistent with these findings, cell-permeable calmodulin antagonists dramatically reduced the number of ER in MCF-7 human breast epithelial cells. Here we investigated the molecular mechanism by which calmodulin attenuates ER degradation. MG132 and lactacystin, inhibitors of the ubiquitin-proteasome pathway, prevented the calmodulin antagonist CGS9343B from reducing the amount of ER in MCF-7 cells. In contrast, protease inhibitors afforded no protection. Moreover, CGS9343B enhanced ER ubiquitination. A point mutant ER construct that is unable to bind calmodulin, termed ERDeltaCaM, is ubiquitinated to a greater extent than wild type ER. The ubiquitin-protein isopeptide ligase E6-associated protein (E6AP) associated with and promoted the degradation of ER. The possible convergence of calmodulin and E6AP on ER degradation was examined. ERDeltaCaM bound E6AP with higher affinity than that of wild type ER. Moreover, calmodulin attenuated the in vitro interaction between ER and E6AP in a Ca(2+)-dependent manner. Collectively, our data reveal that E6AP is a component of ER degradation via the ubiquitin-proteasome pathway and that Ca(2+)/calmodulin modulates this degradation mechanism. These results have potential implications for the development of selectively targeted therapeutic agents for breast cancer.

Environmental signaling and evolutionary change: can exposure of pregnant mammals to environmental estrogens lead to epigenetically induced evolutionary changes in embryos?

DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic expression in mammalian cells. In this review, we propose how certain natural agents, through their dietary consumption, could induce changes in physiological aspects in mammalian mothers, leading to alterations in DNA methylation patterns of the developing fetus and to the emergence of new phenotypes and evolutionary change. Nevertheless, we hypothesize that this process would require (i) certain key periods in the ontogeny of the organism where the environmental stimuli could produce effects, (ii) particular environmental agents as such stimuli, and (iii) that a genomic persistent change be consequently produced in a population. Depending on the persistence of the environmental stimuli and on whether the affected genes are imprinted genes, induced changes in DNA methylation patterns could become persistent. Moreover, some fragments could be more frequently methylated than others over several generations, leading to biased base change and evolutionary consequences.

Estrogen regulation of testicular function

Evidence supporting a role for estrogen in male reproductive tract development and function has been collected from rodents and humans. These studies fall into three categories: i) localization of aromatase and the target protein for estrogen (ER-alpha and ER-beta) in tissues of the reproductive tract; ii) analysis of testicular phenotypes in transgenic mice deficient in aromatase, ER-alpha and/or ER-beta gene; and, iii) investigation of the effects of environmental chemicals on male reproduction. Estrogen is thought to have a regulatory role in the testis because estrogen biosynthesis occurs in testicular cells and the absence of ERs caused adverse effects on spermatogenesis and steroidogenesis. Moreover, several chemicals that are present in the environment, designated xenoestrogens because they have the ability to bind and activate ERs, are known to affect testicular gene expression. However, studies of estrogen action are confounded by a number of factors, including the inability to dissociate estrogen-induced activity in the hypothalamus and pituitary from action occurring directly in the testis and expression of more than one ER subtype in estrogen-sensitive tissues. Use of tissue-specific knockout animals and administration of antiestrogens and/or aromatase inhibitors in vivo may generate additional data to advance our understanding of estrogen and estrogen receptor biology in the developing and mature testis.

Variation in commercial rodent diets induces disparate molecular and physiological changes in the mouse uterus

Although ovarian estrogen, estradiol-17beta, is a key modulator of normal reproductive functions, natural and synthetic compounds with estrogen-like activities can further influence reproductive functions. Plant-derived phytoestrogens specifically have received much attention because of associated health benefits. However, a comprehensive understanding of the beneficial and/or detrimental impacts of phytoestrogen consumption through commercial rodent diets on uterine biology and early pregnancy at the molecular level remains largely unexplored. Using multiple approaches, we demonstrate here that exposure of adult female mice to a commercial rodent diet with higher phytoestrogen levels facilitates uterine growth in the presence or absence of ovarian estrogen, alters uterine expression of estrogen-responsive genes, and advances the timing of implantation compared with a diet with lower phytoestrogen levels. The finding that variability in phytoestrogen content in commercial rodent diets, both within and between brands, influences experimental results stresses the importance of this investigation and raises caution for investigators using rodents as animal models.

Canonical Wnt signaling is critical to estrogen-mediated uterine growth

Major biological effects of estrogen in the uterus are thought to be primarily mediated by nuclear estrogen receptors, ERalpha and ERbeta. We show here that estrogen in an ER-independent manner rapidly up-regulates the expression of Wnt4 and Wnt5a of the Wnt family and frizzled-2 of the Wnt receptor family in the mouse uterus. One of the mechanisms by which Wnts mediate canonical signaling involves stabilization of intracellular beta-catenin. We observed that estrogen treatment prompts nuclear localization of active beta-catenin in the uterine epithelium. We also found that adenovirus mediated in vivo delivery of SFRP-2, a Wnt antagonist, down-regulates estrogen-dependent beta-catenin activity without affecting some of the early effects (water imbibition and angiogenic markers) and inhibits uterine epithelial cell growth, suggesting that canonical Wnt signaling is critical to estrogen-induced uterine growth. Our present results provide evidence for a novel role of estrogen that targets early Wnt/beta-catenin signaling in an ER-independent manner to regulate the late uterine growth response that is ER dependent.

Molecular cues to implantation

Successful implantation is the result of reciprocal interactions between the implantation-competent blastocyst and receptive uterus. Although various cellular aspects and molecular pathways of this dialogue have been identified, a comprehensive understanding of the implantation process is still missing. The receptive state of the uterus, which lasts for a limited period, is defined as the time when the uterine environment is conducive to blastocyst acceptance and implantation. A better understanding of the molecular signals that regulate uterine receptivity and implantation competency of the blastocyst is of clinical relevance because unraveling the nature of these signals may lead to strategies to correct implantation failure and improve pregnancy rates. Gene expression studies and genetically engineered mouse models have provided valuable clues to the implantation process with respect to specific growth factors, cytokines, lipid mediators, adhesion molecules, and transcription factors. However, a staggering amount of information from microarray experiments is also being generated at a rapid pace. If properly annotated and explored, this information will expand our knowledge regarding yet-to-be-identified unique, complementary, and/or redundant molecular pathways in implantation. It is hoped that the forthcoming information will generate new ideas and concepts for a process that is essential for maintaining procreation and solving major reproductive health issues in women.

A molecular basis for embryo apposition at the luminal epithelium

To obtain a gene expression profile during embryo apposition to the luminal epithelium, we isolated mouse luminal epithelium from implantation (IM) and interimplantation (INTER) sites using laser capture microdissection (LCM), and analyzed their gene expression by microarray analysis. IM and INTER sites were sampled on day 4.5 after mating of female mice with fertile males (day 0.5 = vaginal plug). RNA was extracted, amplified, labeled, and hybridized to microarrays and results were analyzed using the significance analysis of microarrays (SAM) method. Comparison of IM and INTER sites by SAM identified 73 genes most highly ranked at IM, while 13 genes most highly expressed at the INTER sites, within the estimated false discovery rate (FDR) of 0.163. Among 73 genes at IM, 20 were ESTs or were of unknown function, and the remain 53 genes had known functions mainly relating to cellular structuring and others such as cell cycling, gene/protein expression, immune responses, invasion, metabolism, oxidative stress, or signal transduction. Specifically, of the 24 structural genes, 14 were implicated in extracellular matrix and tissue remodeling. Meanwhile, of the 13 genes that were highly expressed at INTER, eight were ESTs or of unknown function, and the remaining five were implicated in metabolism, signal transduction, and gene/protein expression. Among these 58 (53 + 5) genes with known functions, 13 genes (22.4%) were associated with Ca2+ for their function. Results of the present study suggest that (1) at IM sites, active tissue remodeling is occurring for embryo invasion while the INTER sites are relatively quiescent and (2) Ca2+ may be a vital regulatory factor in the apposition process. Investigations of human homologues of those genes expressed in the mouse luminal epithelium during apposition may help to understand the implantation process and/or implantation failure in humans.