ERα signaling regulates MMP3 expression to induce FasL cleavage and osteoclast apoptosis

The benefits of estrogens on bone health are well established; how estrogens signal to regulate bone formation and resorption is less well understood. We show here that 17β‐estradiol (E2)‐induced apoptosis of bone‐resorbing osteoclasts is mediated by cleavage and solubilization of osteoblast‐expressed Fas ligand (FasL). U2OS‐ERα osteoblast‐like cells expressing an EGFP‐tagged FasL at the C‐terminus showed decreased fluorescence after E2 treatment, indicative of a cleavage event. Treatment of U2OS‐ERα cultures with a specific MMP3 inhibitor in the presence of E2 blocked FasL cleavage and showed an increase in the number of EGFP‐FasL⁺ cells. siRNA experiments successfully knocked down MMP3 expression and restored full‐length FasL to basal levels. E2 treatment of both human and murine primary osteoblasts showed upregulation of MMP3 mRNA expression, and calvarial organ cultures showed increased expression of MMP3 protein and colocalization with the osteoblast‐specific RUNX2 after E2 treatment. In addition, osteoblast cell cultures derived from ERαKO mice showed decreased expression of MMP3 but not MMP7 and ADAM10, two known FasL proteases, demonstrating that ERα signaling regulates MMP3. Also, conditioned media of E2‐treated calvarial osteoblasts showed an approximate sixfold increase in the concentration of soluble FasL, indicating extensive cleavage, and soluble FasL concentrations were reduced in the presence of a specific MMP3 inhibitor. Finally, to show the role of soluble FasL in osteoclast apoptosis, human osteoclasts were cocultured with MC3T3 osteoblasts. Both a specific MMP3 inhibitor and an MMP inhibitor cocktail preserved osteoclast differentiation and survival in the presence of E2 and demonstrate the necessity of MMP3 for E2‐induced osteoclast apoptosis. These experiments further define the molecular mechanism of estrogen's bone‐protective effects by inducing osteoclast apoptosis through upregulation of MMP3 and FasL cleavage. © 2013 American Society for Bone and Mineral Research     

The effects of tibolone on the human primary glioblastoma multiforme cell culture and the rat C6 glioma model

Abstract

Objectives: In the light of recent advances in tumor biology and genetics, we hypothesized that tibolone, an estrogen receptor agonist, may have antiproliferative effects on primary human glioblastoma cells and rat C6 malignant glioma cell lines. We thought that tibolone should exert its antiproliferative effects by augmenting glial cell differentiation through the naive, nonhypermethylated estrogen receptors in the glioma cells.

Methods: Human primary glioblastoma multiforme (GBM) cells were acquired perioperatively from ten patients aged between 45 and 69 years, diagnosed clinically and radiologically with GBM. The diagnosis was confirmed using immunohistochemical assays. Human GBM and rat C6 malignant glioma cells were cultivated in vitro to obtain monolayer cell cultures. Tibolone was then applied to these cultures in wells, each containing 500,000 tumor cells.

Results: Tibolone significantly decreased the number of human GBM cells at the concentrations of 10 and 100 mg/ml. For tibolone, a strong dose-dependent correlation in tumor inhibition was found (p=0.001). This antiproliferative effect of tibolone in human GBM cells was not observed in rat C6 malignant glioma cells. Tibolone demonstrated differential effects on human GBM and rat C6 glioma cells.

Discussion: In vitro antiproliferative effects of tibolone on human GBM need to be investigated further in in vivo works.     

The Estrogen Receptor: A Logical Target for the Prevention of Breast Cancer with Antiestrogens

A strategy for the prevention of breast cancerhas been refined over the last century beginning withthe first observation that oophorectomy caused diseaseregression in some patients, to the identification of the estrogen receptor some 60 years later,and finally to the synthesis of the first nonsteroidalantiestrogen. Tamoxifen was the first clinically usefulantiestrogen and has been used for the treatment of breast cancer for the last twenty-one yearsin the United States. It is therefore a logicalprogression that antiestrogens are now recognized asuseful agents for the prevention of breast cancer. We will discuss the estrogen receptor as a targetfor the treatment and now the prevention of breastcancer. Data from the National Surgical and BowelProject (NSABP)⁴ tamoxifen prevention trial will be discussed with the preliminary resultsof two other European studies. The status of breastcancer prevention to date involves the comparison of thecurrent standard of prevention, tamoxifen, with the osteoporosis prevention drug, raloxifene inan ongoing trial called Study of Tamoxifen andRaloxifene (STAR).     

Estrogen Responsiveness and Control of Normal Human Breast Proliferation

Our understanding of the hormonal control of theproliferation of normal human breast epithelium is stillsurprisingly meager. However, the results of a number ofrecent studies have confirmed that estrogen is the major steroid mitogen for the luminalepithelial cell population (the usual targets forneoplastic transformation). Estrogen seemingly exertsits effects on cell division indirectly as there iscomplete dissociation between the population of luminalepithelial cells expressing the estrogen receptor (ER)4and those that proliferate. We suggest that theER-negative proliferating cells represent a precursor or stem cell population that differentiates toER-containing, nonproliferative cells. In turn, theseER-positive cells act as 'estrogen sensors' and transmitpositive or negative paracrine growth signals to the precursor cells depending on theprevailing hormonal environment.As yetthere is nodirectevidence supporting this hypothesis but we suggestways in which it may be obtained. The implication ofthese studies is that inhibition of luminalepithelial proliferation with tamoxifen or pureantiestrogens or by preventing ovarian steroid secretionshould be an effective strategy for the prevention ofbreast cancer. In addition, we may be able to predictthe risk of breast cancer in an individual by measuringthe intrinsic estrogen sensitivity of her breastepithelium. Finally, study of the paracrine mechanisms of growth control in the normal human breastmay provide new, more specific, therapeutic targets forbreast cancer prevention.     

Short-term changes in endogenous estrogen levels and consumption of soy isoflavones affect working and verbal memory in young adult females

Abstract

Estrogen is known to modulate certain cognitive functions, most notably improving working memory and verbal memory. Soy foods contain isoflavones, phytoestrogens structurally similar to estrogen that weakly bind to estrogen receptors. We investigated the effects of natural variations in estrogen levels and short-term dietary supplementation with soy isoflavones on cognitive function in 28 young women. Performance was examined across a range of cognitive tasks on three occasions during separate menstrual cycles: during a menses phase (low estrogen), during a luteal phase (highest estrogen), and once during a menses phase after a 3-day phytoestrogen-rich dietary intervention. Soy supplementation during menses led to an improvement in working memory and verbal memory. The menstrual cycle effects were mixed, with high estrogen improving performance on a verbal memory task but not on working memory. Our results suggest that soy phytoestrogens may improve working memory through estrogen-independent mechanisms.     

强肌健力饮对肾阳虚大鼠下丘脑-垂体-性腺轴作用的实验研究

[目的]观察强肌健力饮对肾阳虚大鼠下丘脑-垂体-性腺轴作用的影响.[方法]将SD大鼠随机分为正常对照组,肾阳虚模型组,强肌健力饮低、中、高剂量组(剂量分别为7.8、15.6、23.4 g·kg-1·d-1)、右归丸组(剂量为5.8 g·kg-1·d-1),除正常对照组外,均采用氢化可的松(剂量为25 mg·kg-1·d-1)肌肉注射复制肾阳虚大鼠模型.观察动物的一般状态,计算下丘脑、睾丸指数并对睾丸做组织形态观察,采用放射免疫分析法检测血清睾酮(T)和雌二醇(E2)含量.[结果]强肌健力饮能显著降低下丘脑指数,升高肾阳虚模型大鼠血清T含量及降低E2/T比值(均P＜0.01),而E2含量无明显变化(P＞0.05);组织形态学观察发现,强肌健力饮各剂量组睾丸曲精小管内精细胞体积明显大于肾阳虚模型组,精原细胞核染色质和初级精母细胞核染色体比较显著.[结论]强肌健力饮防治中医肾阳虚证的作用机制可能与其能调控性腺轴的水平有关.     

Role of estrogen receptors and aromatase on brain protein synthesis rates in ovariectomized female rats fed genistein

Abstract

We have reported that the dietary addition of genistein, a phytoestrogen found abundantly in soy products, stimulates brain protein synthesis rates of ovariectomized female rats. In the present study, we determine whether stimulation of brain protein synthesis rates in ovariectomized female rats by the dietary addition of genistein was conducted via estrogen receptors and aromatase-mediating actions. After ovariectomy, Wistar female rats were treated with genistein, the estrogen receptor antagonist ICI 182,780, and/or fadrozole a systemic aromatase inhibitor. In the cerebral cortex, the cerebellum and the hypothalamus, the fractional (Ks) rates of protein synthesis were increased by the dietary addition of genistein. These effects of genistein were inhibited by the administration of ICI 182,780 and fadrozole. However, the degrees to which ICI 182,780 and fadrozole inhibited the effects of genistein differed depending on the brain region. This result suggests that dietary genistein elevates the rate of protein synthesis in the brain of ovariectomized female rats. In addition, the estrogen receptors of the brain and the aromatase of the peripheral tissue and brain are, at least partly, related to the rate of brain protein synthesis caused by genistein.     

针刺对乳腺增生模型大鼠雌激素、雌激素受体及其信号传导的干预作用

[目的]观察针刺对雌激素介导的乳腺增生模型大鼠的影响.[方法]选用sD雌性未孕大鼠,随机分为4组:正常组、模型组、针刺组(电针膻中、三阴交穴)、西药组(灌胃三苯氧胺0.5 mg·kg-1·d-1);除正常组外,其他组均采用肌注己烯雌酚(剂量为0.5 mg·kg-1·d-1)及黄体酮(剂量为4mg·kg-1·d-1)方法复制乳腺增生模型;造模成功后针刺组及西药组治疗30d,采集标本,检测各组大鼠体质量,第2对乳头高度,血清雌激素(E2)水平,雌激素受体(ER)、细胞外信号调节激酶(ERK)、内皮型一氧化氮合酶(eNOS)的表达及乳腺组织形态学变化.[结果]各组大鼠治疗前后体质量、治疗前乳头高度差异无显著性意义(均P>0.05),治疗后模型组乳头高度显著增加(P相似文献   

Estrogen receptor‐α is required for the osteogenic response to mechanical loading in a ligand‐independent manner involving its activation function 1 but not 2

Estrogen receptor‐α (ERα) is crucial for the adaptive response of bone to loading but the role of endogenous estradiol (E2) for this response is unclear. To determine in vivo the ligand dependency and relative roles of different ERα domains for the osteogenic response to mechanical loading, gene‐targeted mouse models with (1) a complete ERα inactivation (ERα^?/?), (2) specific inactivation of activation function 1 (AF‐1) in ERα (ERαAF‐1⁰), or (3) specific inactivation of ERαAF‐2 (ERαAF‐2⁰) were subjected to axial loading of tibia, in the presence or absence (ovariectomy [ovx]) of endogenous E2. Loading increased the cortical bone area in the tibia mainly as a result of an increased periosteal bone formation rate (BFR) and this osteogenic response was similar in gonadal intact and ovx mice, demonstrating that E2 (ligand) is not required for this response. Female ERα^?/? mice displayed a severely reduced osteogenic response to loading with changes in cortical area (?78% ± 15%, p < 0.01) and periosteal BFR (?81% ± 9%, p < 0.01) being significantly lower than in wild‐type (WT) mice. ERαAF‐1⁰ mice also displayed a reduced response to mechanical loading compared with WT mice (cortical area ?40% ± 11%, p < 0.05 and periosteal BFR ?41% ± 8%, p < 0.01), whereas the periosteal osteogenic response to loading was unaffected in ERαAF‐2⁰ mice. Mechanical loading of transgenic estrogen response element (ERE)‐luciferase reporter mice did not increase luciferase expression in cortical bone, suggesting that the loading response does not involve classical genomic ERE‐mediated pathways. In conclusion, ERα is required for the osteogenic response to mechanical loading in a ligand‐independent manner involving AF‐1 but not AF‐2. © 2013 American Society for Bone and Mineral Research