Membrane estrogen receptors activate the metabotropic glutamate receptors mGluR5 and mGluR3 to bidirectionally regulate CREB phosphorylation in female rat striatal neurons

Along with its ability to directly regulate gene expression, estradiol influences cell signaling and brain functions via rapid, membrane-initiated events. In the female rat striatum, estradiol activates membrane-localized estrogen receptors to influence synaptic neurotransmission, calcium channel activity, and behaviors related to motor control. Yet, the mechanism by which estradiol acts to rapidly affect striatal physiology has remained elusive. Here we find that membrane estrogen receptors (ERs) couple to the metabotropic glutamate receptors mGluR5 and mGluR3, providing the framework to understand how membrane estrogen receptors affect striatal function. Using CREB phosphorylation as a downstream measure of ER/mGluR activation, membrane-localized estrogen receptor α (ERα) activates mGluR5 signaling to mediate mitogen-activated protein kinase (MAPK)-dependent CREB phosphorylation. Further, ERα and estrogen receptor β (ERβ) activate mGluR3 to attenuate L-type calcium channel-dependent CREB signaling. Interestingly, while this fundamental mechanism of ER/mGluR signaling was initially characterized in hippocampal neurons, estrogen receptors in striatal neurons are paired with a different set of mGluRs, resulting in the potential to functionally isolate membrane-initiated estrogen signaling across brain regions via use of specific mGluR modulators. These results provide both a mechanism for the rapid actions of estrogens within the female striatum, as well as demonstrate that estrogen receptors can interact with a more diverse set of surface membrane receptors than previously recognized.     

胞膜雌激素受体信号通路与乳腺癌的关系

雌激素通过分布于细胞膜的雌激素结合蛋白, 激活细胞内信号级联放大反应，从而改变胞内蛋白功能和调控基因表达，此为雌激素非基因组作用模式或称膜启动的雌激素应答。雌激素基因组与非基因组作用的交叉对话在调控转录中有重要意义。在人类乳腺癌的发生、发展和转化过程中，除由雌激素诱导的核内事件外，膜启动的雌激素应答同样影响细胞的增殖与凋亡机制。     

Estrogen receptor alpha is expressed on the cell-surface of embryonic hypothalamic neurons

Although the biological activity of estrogen is generally mediated through nuclear estrogen receptors, a large body of evidence indicates that estrogen may also affect target cells upon binding to putative membrane estrogen receptors (mER) coupled to intracellular signaling cascades; however, no agreement has been reached on the nature and precise location of the putative estrogen receptor (ER) responsible for these rapid effects. In the present report we show that the expression of ERalpha is associated with the plasma membrane fraction of rat hypothalamic tissue at embryonic day 16. Moreover, our experiments extend these results to rat hypothalamic neurons in vitro showing that ERalpha can be detected from the cell exterior as a biotinylated cell-surface protein. We have also shown that the mERalpha is under regulation of estradiol, and the ERalpha agonist, 4,4',4'-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol, induced extracellular-signal-regulated kinase signaling in a dose-dependent manner and in a time-course not compatible with genomic actions, supporting the notion of a membrane-initiated phenomenon.     

The rapid effects of estrogen are implicated in estrogen-mediated neuroprotection

A review of the literature reveals an impressively broad spectrum of effects of the hormone estrogen in the CNS. One of the more recently documented is the ability of estrogen to protect neurons from cell death associated with a variety of insults. While some of these actions can be attributed to nuclear effects of the hormone, mediated by the estrogen receptors alpha and/or beta, an increasing number of these effects appear to result from actions of the hormone mediated by signal transduction pathways traditionally associated with activation of membrane receptors. Here, we review current findings on actions of estrogen mediated by two pathways: those dependent on cAMP and Protein Kinase A, and those related to activation of the Mitogen Acivated Protein Kinase cascade. The evidence that estrogen can rapidly activate either pathway, and the potential involvement of the estrogen receptors alpha or beta acting in the vicinity of the cell membrane will be discussed. The possible role of MAP-Kinase activation and BCL-2 induction in the phenomenon of estrogen-neuroprotection will also be addressed.     

Effects of estrogen and raloxifene on neuroglia number and morphology in the hippocampus of aged female mice

Hormone replacement therapy with the gonadal steroid estrogen or synthetic agents such as raloxifene, a selective estrogen receptor modulator, may affect cellular function in brains of postmenopausal women. In vitro studies suggest that 17beta estradiol and raloxifene can alter the microglial and astrocyte expression of immuno-neuronal modulators, such as cytokines, complement factors, chemokines, and other molecules involved in neuroinflammation and neurodegeneration. To directly test whether exogenous 17beta estradiol and raloxifene affect the number of glial cells in brain, C57BL/6NIA female mice aged 20-24 months received bilateral ovariectomy followed by s.c. placement of a 60-day release pellet containing 17beta estradiol (1.7 mg), raloxifene (10 mg), or placebo (cholesterol). After 60 days, numbers of microglia and astrocytes were quantified in dentate gyrus and CA1 regions of the hippocampal formation using immunocytochemistry and design-based stereology. The results show that long-term 17beta estradiol treatment in aged female mice significantly lowered the numbers of astrocytes and microglial cells in dentate gyrus and CA1 regions compared with placebo. After long-term treatment with raloxifene, a similar reduction was observed in numbers of astrocytes and microglial cells in the hippocampal formation. These findings indicate that estrogen and selective estrogen receptor modulators can influence glial-mediated inflammatory pathways and possibly protect against age- and disease-related neuropathology.     

Lasofoxifene enhances vaginal mucus formation without causing hypertrophy and increases estrogen receptor beta and androgen receptor in rats

OBJECTIVE: Lasofoxifene, a new selective estrogen-receptor modulator (SERM), shows efficacy in vaginal and vulvar atrophy in postmenopausal women. Here, we sought to explore the possible mechanisms of action for this effect in comparison with other SERMs using an immature ovariectomized rat model. DESIGN: SERMs (lasofoxifene, raloxifene, and tamoxifen) and 17alpha-ethinyl estradiol were administered orally to immature ovariectomized rats daily for 1 or 4 days. Vaginal and uterine tissues were weighed and processed for histomorphometric measurements, vaginal mucopolysaccharide staining, and immunohistochemistry of 5-bromo-2'-deoxyuridine and steroid receptors. Receptor quantification was determined by a novel ultrasensitive enzyme-linked immunosorbent assay method. RESULTS: Lasofoxifene and raloxifene showed a minimal increase in vaginal and uterine weight, epithelial cell proliferation, and epithelial thickness in comparison with estradiol and tamoxifen. Lasofoxifene significantly enhanced vaginal mucus formation in a dose-dependent manner. Vaginal progesterone receptor protein was increased fivefold by estradiol and all three SERMs tested. 17alpha-Ethinyl estradiol caused a significant decrease in estrogen receptor alpha, but no change with other treatments. Only lasofoxifene significantly increased vaginal estrogen receptor beta and androgen receptor protein levels. CONCLUSIONS: These results demonstrated that lasofoxifene stimulated vaginal mucus formation without causing cell proliferation in the rat reproductive tract. These effects may be due to the increased vaginal estrogen receptor beta and androgen receptor levels. This cellular and molecular profile of lasofoxifene in the vagina may account for its efficacy in the treatment of vaginal and vulvar atrophy in postmenopausal women.     

雌激素受体在骨生长、代谢及其力学响应中的作用和机制

力学信号在骨组织的生长、重建和疾病治疗中发挥着重要的作用。近年来的研究发现雌激素受体(estrogenreceptor,ER)能介导雌激素效应调节骨组织细胞的增殖、凋亡以及功能活性,从而影响骨形成和骨吸收,在骨组织生长、骨重建中发挥重要作用;同时参与骨组织及其细胞对力学刺激的响应过程。骨组织响应力学刺激的效应要受到ER数量和(或)功能活性的影响。这些研究提示了力学刺激和雌激素可能通过一些共同的信号通路来调节骨组织细胞的功能活性。本文着重关注ER在骨组织及其力学响应中的作用和机制。     

Cytochemical study of estrogen receptor in human mammary cancer.

A 17beta-estradiol-6-carboxymethyl-oxime-bovine serum albumin--fluorescein isothiocyanate conjugate is prepared by attaching on the average 11 moles of the fluorescein dye and 24 moles of the steroid hormone to each mole of the protein carrier. This fluorescent estradiol conjugate is used as a tracer to detect estrogen receptor of human mammary cancer cells in frozen sections. The cytochemical findings indicate that mammary carcinomas are composed of heterogeneous populations of receptor-positive and receptor-negative cancer cells in varying proportions and probably should be classified according to the percentages of receptor-positive cells in the cancer cell populations for better correlation with endocrine therapies.     

Effects of estradiol,sex, and season on estrogen receptor alpha mRNA expression and forebrain morphology in adult green anole lizards

Steroid hormones, especially estradiol, facilitate reproductive behaviors in male and female rodents and birds. In green anole lizards estradiol facilitates receptivity in females but, unlike in some other species, is not the activating hormone for courtship and copulatory behavior in males. Instead, testicular androgens directly facilitate male courtship and copulation. Yet, activity of the estradiol synthesizing enzyme aromatase is higher in the brain of male than female green anoles, and it is increased during the breeding compared to the non-breeding season. The functional relevance of these differences in local estradiol production is unknown. They might prime the male forebrain to facilitate production of appropriate sexual behaviors, perhaps by modifying morphology of relevant brain regions. In addition, we recently reported increased expression of estrogen receptor alpha (ERα) in selected brain regions in females compared to males [Beck LA, Wade J (2009b) Sexually dimorphic estrogen receptor α mRNA expression in the preoptic area and ventromedial hypothalamus of green anole lizards. 55:398–403]. Thus, it is possible that the hormone serves to downregulate its receptor in males to inhibit the expression of estradiol-dependent receptive behaviors. To begin to address these ideas, the present study examines the effects of estradiol treatment, sex, and season on forebrain morphology and ERα mRNA abundance in three regions important for anole reproductive behavior—the preoptic area, ventromedial amygdala, and ventromedial hypothalamus. While a number of effects of sex and season on forebrain morphology were detected, direct effects of estradiol treatment on these measures were minimal. ERα expression was greatest in the ventromedial hypothalamus, and a large female-biased sex difference was detected in this area alone; it resulted from estradiol-treated animals. These results indicate a sex- and region-specific mechanism by which estradiol can modify ERα expression in the green anole and could impact the expression of female-typical receptivity.     

Biomarkers in urothelial carcinoma of the bladder: The potential cross-talk between transforming growth factor-β1 and estrogen receptor β/androgen receptor pathways

Urothelial carcinoma of the bladder is nearly three times more common in men than in women. Although it has been primarily attributed to differences in exposure to smoking and industrial chemicals, it is evident now that hormonal factors also play a role. One of the explanations for the differential biologic aggressiveness of urothelial carcinoma of the bladder between genders has focused on sex steroid hormones and their receptors. Recent studies indicated that both estrogen receptor β and androgen receptor have a role within urothelial carcinoma of the bladder and their expression and activity are altered in the carcinogenesis and progression. Moreover, expression of transforming growth factor-β1 is a strong predictor of recurrence and specific mortality. We conjecture about the potential cross-talk between transforming growth factor-β1 and estrogen receptor β/androgen receptor pathways. Clinical significance of expression of transforming growth factor-β1 could be improved, when they are related with the determination of estrogen receptor β/androgen receptor status. Further subgrouping of transforming growth factor-β1 level combined with estrogen receptor β/androgen receptor status, would be more accurately determine the prognosis of patients. This hypothesis could be easily verified in corresponding clinical research, and combined analysis of expression of TGF-β1 and ERβ/AR signaling proteins may provide clinicians useful information regarding tumor initiation and progression, and guide patient prognosis and management with specific therapies.     

Effects of testosterone and estrogen treatment on the distribution of sex hormone receptors in the endometrium of postmenopausal women

OBJECTIVE: Our aim was to investigate the effects of the addition of testosterone to estrogen compared with those of estrogen alone on the expression and distribution of sex hormone receptors in glands and stroma of the endometrium of postmenopausal women. DESIGN: An open, randomized clinical study with parallel group comparison was performed in the Women's Health Research Unit at a university hospital. Thirty-one postmenopausal women were given oral estradiol valerate (2 mg daily) or estradiol valerate in combination with testosterone undecanoate (40 mg every 2 days) for 3 months. Before and at the end of treatment, endometrial biopsy samples were obtained, and expressions of estrogen receptor (ER)-alpha, ER-beta, progesterone receptor isoforms A and B, and androgen receptor (AR) were evaluated by immunohistochemical analysis. RESULTS: At baseline, expressions of ER-alpha and progesterone receptors were stronger in glands than in stroma, whereas the immunostaining of AR was stronger in stroma than in glands. After treatment, expressions of ER-alpha and progesterone receptors were up-regulated in both glands and stroma by both treatments, but to a lesser extent in glands by combined treatment. The expression of ER-beta in glands was significantly higher with combined treatment than with estrogen alone. Moreover, AR immunostaining was significantly higher after combined treatment than after treatment with estrogen alone. CONCLUSIONS: Expressions of AR and ER-beta were stronger in glands of the endometrium of postmenopausal women after treatment with testosterone added to estrogen than after estrogen alone. In contrast, expressions of ER-alpha and progesterone receptors were up-regulated in the endometrium with estrogen-alone treatment, whereas these expressions were less increased in glands after combined treatment. These data indicate that testosterone is involved in the regulation of sex hormone receptor expression in the postmenopausal endometrium and may therefore influence endometrial proliferation and differentiation.     

Menopausal estrogen therapy predicts better nocturnal oxyhemoglobin saturation

OBJECTIVES: The respiratory responses in the few previous studies evaluating the effects of short-term unopposed estrogen therapy on breathing in postmenopausal women have been inconsistent. We performed a study to investigate whether long-term estrogen therapy would prevent age-related decline in nocturnal arterial oxyhemoglobin saturation and whether higher serum estradiol concentration is associated with better arterial oxyhemoglobin saturation. METHODS: Sixty-four healthy postmenopausal women were followed-up for 5 years in a 5-year prospective open follow-up study. The women were users or non-users of estrogen therapy according to their personal preference. RESULTS: Mean overnight arterial oxyhemoglobin saturation was similar at baseline (94.3 +/- 1.1%) and after follow-up (94.5 +/- 1.6%). Present estrogen users had higher mean arterial oxyhemoglobin saturation (95.2 +/- 1.4%) than present non-users (94.0 +/- 1.5%), when adjusted for age and body mass index (p = 0.042). The change in mean arterial oxyhemoglobin saturation during follow-up was not associated with serum estradiol concentration at baseline but associated with estradiol at follow-up (p = 0.042), when adjusted for age and body mass index. At follow-up, women with higher serum estradiol concentration had also higher mean nocturnal arterial oxyhemoglobin saturation (Pearson r = 0.29, p = 0.019) and lower apnea-hypopnea index (Spearman r = -0.28, p = 0.031). The pooled current estrogen users spent proportionally less time with SaO(2) below 90% than non-users (ANCOVA adjusted for age and BMI, p = 0.017). CONCLUSIONS: Estrogen use and especially high serum estradiol concentration predict higher mean overnight arterial oxyhemoglobin saturation. The present data suggest that estrogen therapy has favorable respiratory effects.     

Depression, estrogen, and the Women's Health Initiative

This clinical observation report compares hormone use and clinical presentation in a series of middle-aged depressed women before and after publication of the Women's Health Initiative. Depressed women over age 40 seen at a general hospital academic women's affective disorders practice 6 months before and after publication of the Women's Health Initiative were compared for medication changes, hormone therapy, lifetime depressive episodes, time since last episode, time to depression recurrence after hormone cessation, symptoms, and treatment response. More women stopped hormone therapy and reported onset of depression within 3 weeks of hormone discontinuation after than before publication of the Women's Health Initiative. Depression in most women responded to reinstitution of estrogen or initiation or increase in antidepressant dose. Discontinuation of hormone therapy appears to be associated with the rapid recurrence of depression in some women with a history of depression. Randomized controlled trials in middle-aged depressed women of estrogen or a selective estrogen receptor modulator as monotherapy or as an augmentation agent are urgently needed.