Potential Biological Functions Emerging from the Different Estrogen Receptors

Demystifying the Functional Role of Nuclear Receptors in Esophageal Cancer

Esophageal cancer (EC), an aggressive and poorly understood disease, is one of the top causes of cancer-related fatalities. GLOBOCAN 2020 reports that there are 544,076 deaths and 604,100 new cases expected worldwide. Even though there are various advancements in treatment procedures, this cancer has been reported as one of the most difficult cancers to cure, and to increase patient survival; treatment targets still need to be established. Nuclear receptors (NRs) are a type of transcription factor, which has a key role in several biological processes such as reproduction, development, cellular differentiation, stress response, immunity, metabolism, lipids, and drugs, and are essential regulators of several diseases, including cancer. Numerous studies have demonstrated the importance of NRs in tumor immunology and proved the well-known roles of multiple NRs in modulating proliferation, differentiation, and apoptosis. There are surplus of studies conducted on NRs and their implications in EC, but only a few studies have demonstrated the diagnostic and prognostic potential of NRs. Therefore, there is still a paucity of the role of NRs and different ways to target them in EC cells to stop them from spreading malignancy. This review emphasizes the significance of NRs in EC by discussing their diverse agonists as well as antagonists and their response to tumor progression. Additionally, we emphasize NRs’ potential to serve as a novel therapeutic target and their capacity to treat and prevent EC.

Functional Significance of Selective Expression of ERα and ERβ in Mammary Gland Organ Culture

Thoracic pair of mammary glands from steroid hormone-pretreated mice respond to hormones structurally and functionally in organ culture. A short exposure of glands for 24 h to 7,12 Dimethylbenz(a)anthracene (DMBA) during a 24-day culture period induced alveolar or ductal lesions. Methods: To differentiate the functional significance of ERα and ERβ, we employed estrogen receptor (ER) knockout mice. We compared the effects of DMBA on the development of preneoplastic lesions in the glands in the absence of ERα (αERKO) and ERβ (βERKO) using an MMOC protocol. Glands were also subjected to microarray analyses. We showed that estradiol can be replaced by EGF for pretreatment of mice. The carcinogen-induced lesions developed under both steroids and EGF pretreatment protocols. The glands from αERKO did not develop any lesions, whereas in βERKO mice in which ERα is intact, mammary alveolar lesions developed. Comparison of microarrays of control, αERKO and βERKO mice showed that ERα was largely responsible for proliferation and the MAP kinase pathways, whereas ERβ regulated steroid metabolism-related genes. The results indicate that ERα is essential for the development of precancerous lesions. Both subtypes, ERα and Erβ, differentially regulated gene expression in mammary glands in organ cultures.

Endometrial changes in estrogen and progesterone receptor expression during implantation in an oocyte donation program

Implantation is the final and most important stage of embryogenesis and is of paramount importance in achieving a successful pregnancy. Progesterone and estrogen are steroid hormones responsible for the regulation of the implantation window and the current study hypothesised that their receptors may be implicated in women undergoing oocyte donation. A total of 15 women aged 25-32 years old (mean ± SD, 28.9±2.89) undergoing oocyte donation were recruited into the present study. Participants underwent ovarian stimulation with gonadotrophin-releasing hormone antagonist and recombinant follicle-stimulating hormone. Endometrial aspiration biopsy was performed on the day of oocyte retrieval and after 5 days (on days 0 and 5, respectively). Endometrial histology and evaluation of estrogen receptor (ER)α and progesterone receptor (PR)-B were performed on days 0 and 5. The ER nodal staining percentage on day 0 was age-associated, with patients aged <30 years demonstrating 100% staining and those aged >30 years exhibiting 90% staining. Pathological staining revealed statistically significant differences between days 0 and 5 following all staining procedures. Wilcoxon signed-rank test resulted in the following P-values, for ER (nodes % and stromal %) day 0/5, P=0.0001; for PR (nodes % and stromal %) day 0/5, P=0.0001 and P=0.035, respectively; for ER (grade nodes and stromal %) day 0/5, P=0.0001; and PR (grade nodes and stromal %) day 0/5 P=0.0001 and P=0.016, respectively. Synchronization between blastocyst development and the acquisition of endometrial receptivity is a prerequisite for the success of in vitro fertilisation (IVF). Aside from the recent discovery of molecules that are considered crucial for successful embryo implantation, assessing the functional characteristics of the endometrium may offer unique insights into this process, thus improving IVF results.

Maternal Testosterone Excess Contributes to Reproductive System Dysfunction of Female Offspring Mice

Hyperandrogenism is considered 1 of the most important characteristics of polycystic ovary syndrome, which affects more than 10% of females of reproductive age and is a common cause of infertility. In addition to the effects on patients themselves, maternal androgen excess has also been reported to impair the growth and development of offspring. In our current study, we found that maternal testosterone (T) treatment during different gestational stages increased the percentage of atretic follicle and decreased corpus luteum formation in female offspring. In addition, decreased serum estradiol and increased T levels were also observed in female offspring of T-treated mice during late gestational stage. Further studies revealed that Forkhead box protein L2 (FOXL2) and Cytochrome P450 family 19 subfamily a member 1 (CYP19A1) expression in granulosa cells of these female offspring mice were decreased. By using mouse primary granulosa cells and the KGN cell line, we demonstrated that decreasing FOXL2 and CYP19A1 levels in ovarian granulosa cells partially may contribute to disturbed sex hormone synthesis in female offspring of T-treated mice during the late gestational stage. Findings from our current study highlight a critical role of excess maternal T exposure, especially during the late gestational stage, which could further lead to aberrant ovary development and sex hormone synthesis in female offspring.

Edible bird's nest impact on rats' uterine histomorphology, expressions of genes of growth factors and proliferating cell nuclear antigen, and oxidative stress level

Aim:

This study aimed to evaluate the effect of edible bird’s nest (EBN) supplementation on the uteri of rats based on analyses of the morphological and histomorphometric changes, and expressions of epidermal growth factor (EGF) and its receptor (REGF) genes, vascular endothelial growth factor (VEGF), proliferating cell nuclear antigen (PCNA), and steroid receptors.

Materials and Methods:

Twenty-four: Sprague Dawley rats were equally distributed into the following four groups: G1 (control), G2, G3, and G4 represented the groups treated with EBN at graded concentrations of 0, 30, 60, and 120 mg/kg body weight (BW) per day for 8 weeks, respectively. During the experimental period, the BW of each rat was recorded weekly. At the proestrus stage of estrous cycle, blood samples were collected from the hearts of anesthetized rats that were later sacrificed. The uteri were removed for histological and immunohistochemical analyses.

Results:

The EBN-treated groups showed an increase in the weights and lengths of uteri as compared to the control. Results showed that relative to G1 and G2, G3 and G4 exhibited proliferation in their uterine luminal and glandular epithelia and uterine glands, and up-regulated expressions of EGF, REGF, VEGF, PCNA, and progesterone receptor, and estrogen receptor in their uteri. The EBN increased the antioxidant (AO) and total AO capacities and reduced the oxidative stress (OS) levels in non-pregnant rats.

Conclusion:

Findings of this study revealed that EBN promotes proliferation of the uterine structures as evidenced by the upregulation of the expressions of steroid receptors, EGF, REGF, VEGF, and PCNA in the uterus and increased in the plasma concentrations of AO and reduced levels of OS.

Dimethyl-Benz(a)anthracene: A mammary carcinogen and a neuroendocrine disruptor

Polycyclic Aromatic Hydrocarbons (PAHs) are potent carcinogens. Among these, dimethylbenz(a)anthracene (DMBA) is well known for its capacity to induce mammary carcinomas in female Sprague-Dawley (SD) rats. Ovariectomy suppresses the susceptibility of this model to DMBA, thus suggesting that the inducible action of the carcinogen depends on ovarian hormones. The promotion of DMBA-induced adenocarcinoma is accompanied by a series of neuroendocrine disruptions of both Hypothalamo-Pituitary-Gonadal (HPG) and Hypothalamo-Pituitary-Adrenal (HPA) axes and of the secretion of melatonin during the latency period of 2 months that precedes the occurrence of the first mammary tumor. The present review analyses the various neuroendocrine disruptions that occur along the HPG and the HPA axes, and the marked inhibitory effect of the carcinogen on melatonin secretion. The possible relationships between the neuroendocrine disruptions, which essentially consist in an increased pre-ovulatory secretion of 17β-estradiol and prolactin, associated with a marked reduction of melatonin secretion, and the decrease in gene expression of the receptors for aryl-hydrocarbons receptor (AhR) and 17β-estradiol (ERα; ERβ) are also discussed.

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Polycyclic Aromatic Hydrocarbons influence promotion of breast tumorigenesis.

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Dimethylbenz(a)anthracene (DMBA) alters neuroendocrine axes and melatonin secretion.

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DMBA modulates the activity of aryl hydrocarbon and 17β-estradiol receptors.

Research Resources for Nuclear Receptor Signaling Pathways

Nuclear receptor (NR) signaling pathways impact cellular function in a broad variety of tissues in both normal physiology and disease states. The complex tissue-specific biology of these pathways is an enduring impediment to the development of clinical NR small-molecule modulators that combine therapeutically desirable effects in specific target tissues with suppression of off-target effects in other tissues. Supporting the important primary research in this area is a variety of web-based resources that assist researchers in gaining an appreciation of the molecular determinants of the pharmacology of a NR pathway in a given tissue. In this study, selected representative examples of these tools are reviewed, along with discussions on how current and future generations of tools might optimally adapt to the future of NR signaling research.

A role for glucocorticoids in stress-impaired reproduction: beyond the hypothalamus and pituitary

In addition to the well-characterized role of the sex steroid receptors in regulating fertility and reproduction, reproductive events are also mediated by the hypothalamic-pituitary-adrenal axis in response to an individual's environment. Glucocorticoid secretion in response to stress contributes to the well-characterized suppression of the hypothalamic-pituitary-gonadal axis through central actions in the hypothalamus and pituitary. However, both animal and in vitro studies indicate that other components of the reproductive system are also regulated by glucocorticoids. Furthermore, in the absence of stress, it appears that homeostatic glucocorticoid signaling plays a significant role in reproduction and fertility in all tissues comprising the hypothalamic-pituitary-gonadal axis. Indeed, as central regulators of the immune response, glucocorticoids are uniquely poised to integrate an individual's infectious, inflammatory, stress, nutritional, and metabolic status through glucocorticoid receptor signaling in target tissues. Endocrine signaling between tissues regulating the immune and stress response and those determining reproductive status provides an evolutionary advantage, facilitating the trade-off between reproductive investment and offspring fitness. This review focuses on the actions of glucocorticoids in tissues important for fertility and reproduction, highlighting recent studies that show glucocorticoid signaling plays a significant role throughout the hypothalamic-pituitary-gonadal axis and characterizing these effects as permissive or inhibitory in terms of facilitating reproductive success.

Epigenetic mechanisms in the actions of endocrine-disrupting chemicals: gonadal effects and role in female reproduction

There is a heightened interest and concern among scientists, clinicians and regulatory agencies as well as the general public, regarding the effects of environmental endocrine-disrupting chemicals (EDCs). In this review, we identify the main epigenetic mechanisms and describe key ovarian processes that are vulnerable to the epigenetic actions of EDCs. We also provide an overview of the human epidemiological evidence documenting the detrimental effects of several common environmental EDCs on female reproduction. We then focus on experimental evidence demonstrating the epigenetic effects of these EDCs in the ovary and female reproductive system, with an emphasis on methoxychlor, an organochlorine pesticide. We conclude the review by describing several critical issues in studying epigenetic effects of EDCs in the ovary, including transgenerational epigenetic effects.

Study of proliferative processes and nuclear estradiol and progesterone receptors in myocytes in pregnant and postpartum mouse uterus

Numerical densities of the nuclei were morhometrically evaluated in all myocytes and myocytes expressing nuclear estrogen- and progesterone-receptor complexes, which were revealed immunohistochemically with monoclonal antibodies in C57Bl/6 mice. It was shown that the above quantitative parameters of myometrial cells after the first pregnancy were similar to those in nonpregnant mice by day 10 after delivery. In the third pregnancy, especially developed after the second interrupted pregnancy, proliferation processes in the myometrium were not completed by postpartum day 10, but dramatically progressed. It was associated with a significant decrease in the fraction of myocytes carrying nuclear hormone-receptor complexes with estradiol and progesterone and their disturbed physiological relations in the myometrium during and after pregnancy probably due to dedifferentiation of a considerable part of myocytes.

Identification and characterization of lipopolysaccharide binding protein (LBP) as an estrogen receptor α specific serum biomarker

Estrogen Receptor a (ERα) and Estrogen Receptor β (ERβ) are steroid nuclear receptors that transduce estrogen signaling to control diverse physiological processes linked to reproduction, bone remodeling, behavior, immune response and endocrine-related diseases. In order to differentiate between ERα and ERβ mediated effects in vivo, ER subtype selective biomarkers are essential. We utilized ERα knockout (AERKO) and ERβ knockout (BERKO) mouse liver RNA and genome wide profiling to identify novel ERα selective serum biomarker candidates. Results from the gene array experiments were validated using real-time RT-PCR and subsequent ELISA's to demonstrate changes in serum proteins. Here we present data that Lipopolysacharide Binding Protein (LBP) is a novel liver-derived ERα selective biomarker that can be measured in serum.

ERβ-specific agonists and genistein inhibit proliferation and induce apoptosis in the large and small intestine

Epidemiological data indicate that intake of estrogens and isoflavones may be beneficial for the prevention of colorectal cancer (CRC). Based on this data, the aim of the study was to investigate estrogen receptor (ER) subtype-specific effects on intestinal homeostasis. Ovariectomized (OVX) female Wistar rats were either treated with 17β-estradiol (4 μg/kg body wt/day) (E2), an ERα-specific agonist (ALPHA) (10 μg/kg body wt/day), an ERβ-specific agonist (BETA) (100 μg/kg body wt/day) or genistein (GEN) (10 mg/kg body wt/day) for three weeks. Vehicle-treated OVX and SHAM animals and those cotreated with BETA and the pure antiestrogen Fulvestrant (ICI 182780) (100 μg/kg body wt/day and 3 mg/kg body wt/day) served as controls. GEN and BETA treatment but not E2 and ALPHA administration reduced proliferation in ileal and colonic mucosa cells. The rate of apoptosis in the small intestine and colon was increased by treatment with BETA and GEN, but not by E2. BETA induced antiproliferative and proapoptotic activity also in SHAM animals. The effects were antagonized by the pure antiestrogen Fulvestrant. Polymerase chain reaction gene array analysis revealed that BETA resulted in the downregulation of the oncogene transformation-related protein 63 (p63). Our data indicate that activation of the ERβ by specific ERβ agonists and GEN induces antiproliferative and proapoptotic effects in the intestinal tract. This observation can be taken as an indication that intake of GEN and specific ERβ agonists may protect the ileal and colonic epithelium from tumor development via modulation of tissue homeostasis.

Challenging estrogen receptor beta with phosphorylation

From classical gland-based endocrinology to nuclear hormone receptor biology, tremendous progress has been made in our understanding of hormone responses underlying cellular communication. Estrogen elicits a myriad of biological processes in reproductive and peripheral target tissues through its interaction with the estrogen receptors ERalpha and ERbeta. However, our knowledge of estrogen-dependent and independent action has mainly focused on ERalpha, leaving the role of ERbeta obscure. This review discusses our current understanding of ERbeta function and the emerging role of intracellular signals that act upon and achieve estrogen-like effects through phosphorylation of ERbeta protein. Improving our understanding of how cellular determinants impact estrogen receptor actions will likely lead to treatment strategies for related endocrine diseases affecting women's health.

Characterization of the ovarian and reproductive abnormalities in prepubertal and adult estrogen non-responsive estrogen receptor alpha knock-in (ENERKI) mice

Estrogen non-responsive estrogen receptor alpha (ERalpha) knock-in (ENERKI) mice have a mutation (glycine 525 to leucine, G525L) in the ligand-binding domain of ERalpha. The mutant ERalpha protein has a significantly lower affinity and response to endogenous estrogens, while not altering growth factor activated ligand-independent pathways. ENERKI females demonstrated signs of early follicle development as determined by a significant increase in antral follicle formation by 20 days of age. Adult ENERKI females were infertile, had hemorrhagic ovarian follicular cysts, and failed to develop corpora lutea in response to a superovulation regimen. These results illustrate the importance of ERalpha ligand-induced signaling for ovarian development and for estrogen feedback on the hypothalamus and pituitary. Although ERalpha ligand-induced signaling by endogenous estrogens is lost in ENERKI females, the ERalpha selective agonist propyl pyrazole triol (PPT), a synthetic nonsteroidal compound, is still able to activate G525L ERalphain vivo to increase uterine weight. To test whether PPT could restore ligand-dependent receptor activation, ENERKI females were treated with PPT and evaluated for spontaneous ovulation, ovarian hemorrhagic cysts, and LH serum levels. Daily PPT treatments beginning on day 4 of life prevented formation of ovarian hemorrhagic cysts in adult ENERKI animals. In accordance with this result, preputial gland weight and LH levels were also lowered in these animals, indicating PPT treatments most likely led to restoration of ERalpha negative feedback of the hypothalamic-pituitary axis.

Drug and cell type-specific regulation of genes with different classes of estrogen receptor beta-selective agonists

Estrogens produce biological effects by interacting with two estrogen receptors, ERα and ERβ. Drugs that selectively target ERα or ERβ might be safer for conditions that have been traditionally treated with non-selective estrogens. Several synthetic and natural ERβ-selective compounds have been identified. One class of ERβ-selective agonists is represented by ERB-041 (WAY-202041) which binds to ERβ much greater than ERα. A second class of ERβ-selective agonists derived from plants include MF101, nyasol and liquiritigenin that bind similarly to both ERs, but only activate transcription with ERβ. Diarylpropionitrile represents a third class of ERβ-selective compounds because its selectivity is due to a combination of greater binding to ERβ and transcriptional activity. However, it is unclear if these three classes of ERβ-selective compounds produce similar biological activities. The goals of these studies were to determine the relative ERβ selectivity and pattern of gene expression of these three classes of ERβ-selective compounds compared to estradiol (E₂), which is a non-selective ER agonist. U2OS cells stably transfected with ERα or ERβ were treated with E₂ or the ERβ-selective compounds for 6 h. Microarray data demonstrated that ERB-041, MF101 and liquiritigenin were the most ERβ-selective agonists compared to estradiol, followed by nyasol and then diarylpropionitrile. FRET analysis showed that all compounds induced a similar conformation of ERβ, which is consistent with the finding that most genes regulated by the ERβ-selective compounds were similar to each other and E₂. However, there were some classes of genes differentially regulated by the ERβ agonists and E₂. Two ERβ-selective compounds, MF101 and liquiritigenin had cell type-specific effects as they regulated different genes in HeLa, Caco-2 and Ishikawa cell lines expressing ERβ. Our gene profiling studies demonstrate that while most of the genes were commonly regulated by ERβ-selective agonists and E₂, there were some genes regulated that were distinct from each other and E₂, suggesting that different ERβ-selective agonists might produce distinct biological and clinical effects.

Downregulation of cilia-localized Il-6Rα by 17β-estradiol in mouse and human fallopian tubes

The action of interleukin-6 (IL-6) impacts female reproduction. Although IL-6 was recently shown to inhibit cilia activity in human fallopian tubes in vitro, the molecular mechanisms underlying IL-6 signaling to tubal function remain elusive. Here, we investigate the cellular localization, regulation, and possible function of two IL-6 receptors (IL-6Rα and gp130) in mouse and human fallopian tubes in vivo. We show that IL-6Rα is restricted to the cilia of epithelial cells in both mouse and human fallopian tubes. Exogenous 17β-estradiol (E2), but not progesterone (P4), causes a time-dependent decrease in IL-6Rα expression, which is blocked by the estrogen receptor (ER) antagonist ICI-182,780. Exposure of different ER-selective agonists propyl-(1H)-pyrazole-1,3,5-triyl-trisphenol or 2,3-bis-(4-hydroxyphenyl)-propionitrile demonstrated an ER subtype-specific regulation of IL-6Rα in mouse fallopian tubes. In contrast to IL-6Rα, gp130 was detected in tubal epithelial cells in mice but not in humans. In humans, gp130 was found in the muscle cells and was decreased in the periovulatory and luteal phases during the reproductive cycles, indicating a species-specific expression and regulation of gp130 in the fallopian tube. Expression of tubal IL-6Rα and gp130 in IL-6 knockout mice was found to be normal; however, E2 treatment increased IL-6Rα, but not gp130, in IL-6 knockout mice when compared with wild-type mice. Furthermore, expression levels of IL-6Rα, but not gp130, decreased in parallel with estrogenic accelerated oocyte-cumulus complex (OCC) transport in mouse fallopian tubes. Our findings open the posibility that cilia-specific IL-6Rα may play a role in the regulation of OCC transport and suggest an estrogen-regulatory pathway of IL-6Rα in the fallopian tube.

The role of growth factors and cytokines during implantation: endocrine and paracrine interactions

Implantation, a critical step for establishing pregnancy, requires molecular and cellular events resulting in uterine growth and differentiation, blastocyst adhesion, invasion, and placental formation. Successful implantation requires a receptive endometrium, a normal and functional embryo at the blastocyst stage, and a synchronized dialogue between maternal and embryonic tissues. In addition to the well-characterized role of sex steroids, the complexity of embryo implantation and placentation is exemplified by the number of cytokines and growth factors with demonstrated roles in these processes. Disturbances in the normal expression and action of these cytokines result in an absolute or partial failure of implantation and abnormal placental formation in mice and human. Members of the gp130 cytokine family, interleukin-11 (IL-11) and leukemia inhibitory factor, the transforming growth factor beta superfamily, the colony-stimulating factors, and the IL-1 and IL-15 systems are crucial molecules for a successful implantation. Chemokines are also important, both in recruiting specific cohorts of leukocytes to the implantation site and in trophoblast trafficking and differentiation. This review provides discussion of the embryonic and uterine factors that are involved in the process of implantation in autocrine, paracrine, and/or juxtacrine manners at the hormonal, cellular, and molecular levels.

Prevention of skin flap necrosis by estradiol involves reperfusion of a protected vascular network

Although 17beta-estradiol (E2) is protective in experimental models of myocardial and brain ischemia, its effect on skin ischemia remains unknown. Here, we assessed the protective effect of E2 in a mouse model of skin ischemia, mimicking the surgery of skin flaps. Whereas necrosis appeared in the half portion of the skin flap within 1 week after surgery in ovariectomized mice, it was reduced up to 10-fold when mice were pretreated with E2, at least 3 days before the surgery. The beneficial effect of E2 appeared to be attributable to an increase in skin survival, revealed by measuring viability of ex vivo explants and enhancement of the antiapoptotic Bcl-2 protein expression in vivo. This protective effect on the skin contributed to the protection of the vascular network and facilitated reperfusion, which was found to be accelerated in ovariectomized E2-treated mice, whereas hemorrhages were observed in untreated mice. E2 also increased expression of fibroblast growth factor-2 isoforms in the skin and circulating vascular endothelial growth factor in the serum. Finally, this protective effect of E2 was abolished in estrogen receptor-deficient mice (ERalpha(-/-)) but maintained in chimeric mice reconstituted with ERalpha-deficient bone marrow, indicating dispensable action of E2 in bone marrow-derived cells. This protective effect of E2 was mimicked by treatment with tamoxifen, a selective estrogen receptor modulator. In conclusion, we have demonstrated for the first time that E2 exerts a major preventive effect of skin flap necrosis through a prevention of ischemic-induced skin lesions, including those of the vascular network, which contributes to accelerate the reperfusion of the skin flap.

Steroid receptor coactivator-1 from brain physically interacts differentially with steroid receptor subtypes

In vitro studies reveal that nuclear receptor coactivators enhance the transcriptional activity of steroid receptors, including estrogen (ER) and progestin receptors (PR), through ligand-dependent interactions. Whereas work from our laboratory and others shows that steroid receptor coactivator-1 (SRC-1) is essential for efficient ER and PR action in brain, very little is known about receptor-coactivator interactions in brain. In the present studies, pull-down assays were used to test the hypotheses that SRC-1 from hypothalamic and hippocampal tissue physically associate with recombinant PR or ER in a ligand-dependent manner. SRC-1, from hypothalamus or hippocampus, interacted with PR-A and PR-B in the presence of an agonist, but not in the absence of ligand or in the presence of a selective PR modulator, RU486. Interestingly, SRC-1 from brain associated more with PR-B, the stronger transcriptional activator, than with PR-A. In addition, SRC-1 from brain, which was confirmed by mass spectrometry, interacted with ERalpha and ERbeta in the presence of agonist but not when unliganded or in the presence of the selective ER modulator, tamoxifen. Furthermore, SRC-1 from hypothalamus, but not hippocampus, interacted more with ERalpha than ERbeta, suggesting distinct expression patterns of other cofactors in these brain regions. These findings suggest that interactions of SRC-1 from brain with PR and ER are dependent on ligand, receptor subtype, and brain region to manifest the pleiotropic functional consequences that underlie steroid-regulated behaviors. The present findings reveal distinct contrasts with previous cell culture studies and emphasize the importance of studying receptor-coactivator interactions using biologically relevant tissue.

Selective estrogen receptor modulators: an update on recent clinical findings

Recent clinical data on selective estrogen receptor modulators (SERMs) have provided the basis for reassessment of the SERM concept. The molecular basis of SERM activity involves binding of the ligand SERM to the estrogen receptor (ER), causing conformational changes which facilitate interactions with coactivator or corepressor proteins, and subsequently initiate or suppress transcription of target genes. SERM activity is intrinsic to each ER ligand, which accomplishes its unique profile by specific interactions in the target cell, leading to tissue selective actions. We discuss the estrogenic and anti-estrogenic effects of early SERMs, such as clomiphene citrate, used for treatment of ovulation induction, and the triphenylethylene, tamoxifen, which has ER antagonist activity in the breast, and is used for prevention and treatment of ER-positive breast cancer. Since the development of tamoxifen, other triphenylethylene SERMs have been studied for breast cancer prevention, including droloxifene, idoxifene, toremifene, and ospemifene. Other SERMs have entered clinical development more recently, including benzothiophenes (raloxifene and arzoxifene), benzopyrans (ormeloxifene, levormeloxifene, and EM-800), lasofoxifene, pipendoxifene, bazedoxifene, HMR-3339, and fulvestrant, an anti-estrogen which is approved for breast cancer treatment. SERMs have effects on tissues containing ER, such as the breast, bone, uterine and genitourinary tissues, and brain, and on markers of cardiovascular risk. Current evidence indicates that each SERM has a unique array of clinical activities. Differences in the patterns of action of SERMs suggest that each clinical end point must be evaluated individually, and conclusions about any particular SERM can only be established through appropriate clinical trials.

Exogenous leptin promotes the recovery of regressed ovary in fasted ducks

The present study was undertaken to examine the effect of administered recombinant mouse leptin on the recovery of regressed ovary in fasted ducks. Twenty-eight ducks were divided into five groups: fed ad libitum (control; n=5), fasted control (FC; n=5), fasted+low dose of leptin (F+L; n=5), fasted+medium dose of leptin (F+M; n=5) and fasted+high dose of leptin (F+H; n=3). All four fasted groups were fasted for 2 days and then ad libitum and the ducks were treated with leptin at doses of 0 (control and FC), 50 (F+L), 250 (F+M) and 1000 (F+H) microg/kg body weight/day on day 3-5. Results showed that a moderate dose of leptin (250 microg/kg body weight/day) injected during the re-feeding period: (i) promoted the recovery of the regressed ovary as evidenced by an increase in ovary weight and recovery of yellow hierarchical follicles; (ii) elevated the plasma 17beta-estradiol (E(2)) level; (iii) increased the mRNA levels of ovary follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR) and estrogen receptor-beta (ER-beta). Furthermore, the results also showed that a high dose of leptin (1000 microg/kg body weight/day) may have a negative effect on the recovery of the regressed ovary. In conclusion, this study indicates that, in ducks, leptin may be involved in the recovery of the regressed ovary caused by 2 days of fasting. This effect may be related to increased plasma E(2) levels and stimulation of the mRNA levels of ovarian FSHR, LHR and especially ER-beta.

Basic aspects of implantation

Implantation, a critical step for establishing pregnancy, requires molecular and cellular events resulting in healthy uterine growth and differentiation, blastocyst adhesion, invasion and placental formation. Successful implantation requires a receptive endometrium, a normal and functional embryo at the blastocyst stage and a synchronized dialogue between maternal and embryonic tissues. In addition to the main role of sex steroids, the complexity of embryo implantation and placentation is exemplified by the number of cytokines and growth factors with demonstrated roles in these processes. Disturbances of the normal expression and action of these cytokines result in absolute or partial failure of implantation and abnormal placental formation in mice and humans. Members of the gp130 cytokine family, interleukin (IL)-11 and leukaemia inhibitory factor, the transforming growth factor-beta superfamily, colony-stimulating factors, and the IL-1 and IL-15 systems are all crucial for successful implantation. In addition, chemokines are important both in recruiting specific cohorts of leukocytes to the implantation site, and in trophoblast trafficking and differentiation. This review provides discussion on embryonic and uterine factors that are involved in the process of implantation in autocrine, paracrine and/or juxtacrine manners at hormonal, cellular, and molecular levels.

Maternal nutrient supplementation counteracts bisphenol A-induced DNA hypomethylation in early development

The hypothesis of fetal origins of adult disease posits that early developmental exposures involve epigenetic modifications, such as DNA methylation, that influence adult disease susceptibility. In utero or neonatal exposure to bisphenol A (BPA), a high-production-volume chemical used in the manufacture of polycarbonate plastic, is associated with higher body weight, increased breast and prostate cancer, and altered reproductive function. This study shows that maternal exposure to this endocrine-active compound shifted the coat color distribution of viable yellow agouti (Avy) mouse offspring toward yellow by decreasing CpG (cytosine-guanine dinucleotide) methylation in an intracisternal A particle retrotransposon upstream of the Agouti gene. CpG methylation also was decreased at another metastable locus, the CDK5 activator-binding protein (CabpIAP). DNA methylation at the Avy locus was similar in tissues from the three germ layers, providing evidence that epigenetic patterning during early stem cell development is sensitive to BPA exposure. Moreover, maternal dietary supplementation, with either methyl donors like folic acid or the phytoestrogen genistein, negated the DNA hypomethylating effect of BPA. Thus, we present compelling evidence that early developmental exposure to BPA can change offspring phenotype by stably altering the epigenome, an effect that can be counteracted by maternal dietary supplements.