Modulation of breast cancer cell survival by aromatase inhibiting hop (Humulus lupulus L.) flavonoids

Hop flavonoids are being regarded as attractive molecules to prevent or treat certain forms of cancer. Studies have focused mainly on xanthohumol, the most abundant prenylated chalcone existing in hops extract. However, during the production of beer, or after its ingestion, xanthohumol originates different metabolites, among which isoxanthohumol and 8-prenylnaringenin. The aim of this work was to study the effect of the prenylflavonoids xanthohumol, isoxanthohumol and 8-prenylnaringenin on the breast cancer Sk-Br-3 cell line proliferation, apoptosis and activity of the enzyme aromatase (estrogen synthase). Aromatase activity was determined by a tritiated water assay, cell proliferation was assessed by [³H]thymidine incorporation, sulforhodamine B protein measurement and Ki-67 immunostaining and apoptosis was determined by TUNEL. Our results show that all tested prenylflavonoids were able to inhibit aromatase activity and thus, estrogen formation. Additionally, breast cancer cell line proliferation was decreased and apoptosis induced by all three compounds. The presence of 17β-estradiol in treatment medium was able to revert the effect of the prenylflavonoids on cellular proliferation. These observations strengthen the idea that hop flavonoids may have anti-breast cancer effects and shed new light on a possible mechanism of action by which these effects occur, namely through their ability to decrease estrogen synthesis.     

Intra-striatal estradiol in female rats impairs response learning within two hours of treatment

Estradiol treatment administered systemically or directly to the dorsolateral striatum across two days impairs performance on a response task in which rats learn to make a specific body turn to locate food on a maze. Estradiol can act through both slow and rapid signaling pathways to regulate learning impairments, however it is impossible to dissociate the slow from the rapid contributions of estradiol following long exposures. To assess the rapid effects of estradiol on striatum-sensitive learning, we trained rats on a response learning task after either relatively short or long treatments of estradiol infused directly into the striatum. Three-month-old female rats were ovariectomized 21 days before training and received guide cannulae implanted bilaterally into the dorsolateral striatum. For short duration treatments, rats were given bilateral infusions (0.5 μl) of 17β-estradiol-sulfate (0, 5, 50, or 500 nM in aCSF-vehicle) either 2 h or 15 min prior to training. For long duration treatments, rats received a series of estradiol infusions (500 nM) at 48, 24, and 2 h prior to training. Replicating previous findings (Zurkovsky et al., 2007), intra-striatal estradiol treatments given for two days prior to training impaired response learning. Estradiol-induced impairments in performance were also demonstrated 2 h, but not 15 min, after single infusions. Thus, estradiol acts within hours of exposure in the striatum, a structure lacking classical estrogen receptors, to impair response learning.     

Estradiol acts in the medial preoptic area, arcuate nucleus, and dorsal raphe nucleus to reduce food intake in ovariectomized rats

Estradiol (E2) exerts an inhibitory effect on food intake in a variety of species. While compelling evidence indicates that central, rather than peripheral, estrogen receptors (ERs) mediate this effect, the exact brain regions involved have yet to be conclusively identified. In order to identify brain regions that are sufficient for E2's anorectic effect, food intake was monitored for 48 h following acute, unilateral, microinfusions of vehicle and two doses (0.25 and 2.5 μg) of a water-soluble form of E2 in multiple brain regions within the hypothalamus and midbrain of ovariectomized rats. Dose-related decreases in 24-h food intake were observed following E2 administration in the medial preoptic area (MPOA), arcuate nucleus (ARC), and dorsal raphe nucleus (DRN). Within the former two brain areas, the larger dose of E2 also decreased 4-h food intake. Food intake was not influenced, however, by similar E2 administration in the paraventricular nucleus, lateral hypothalamus, or ventromedial nucleus. These data suggest that E2-responsive neurons within the MPOA, ARC, and DRN participate in the estrogenic control of food intake and provide specific brain areas for future investigations of the cellular mechanism underlying estradiol's anorexigenic effect.     

Profiling lipid metabolites yields unique information on sex- and time-dependent responses of fathead minnows (Pimephales promelas) exposed to 17α-ethynylestradiol

Alterations in hepatic lipid profiles of fathead minnows (FHM) exposed to the synthetic estrogen 17α-ethynylestradiol (EE2) were determined using ¹H-NMR spectroscopy-based metabolite profiling. The exposures were conducted using either 10 ng/l or 100 ng/l EE2 via a continuous flow water delivery system. Livers were collected at 1, 4, and 8 days of the exposure and 8 days after the chemical was removed from the water (i.e. an 8 day depuration). The exposure resulted in a number of sex-specific changes in lipid profiles that were also highly time dependent. Those metabolites most affected by exposure included phosphatidylcholine, diglycerides, triglycerides and cholesterol. In addition, changes in the length and degree of unsaturation of hepatic fatty acids were observed. Lipid profiles in plasma for fish collected on the 4th day of exposure were also analyzed in order to provide further insights into changes observed in hepatic metabolite changes. Using validated partial least-squares discriminant analysis (PLS-DA), the response trajectories of the male liver lipid profiles at both exposure concentrations were compared. This analysis indicated that the males exposed to the low concentration of EE2 (10 ng/l) were largely able to recover from the exposure once the chemical was removed from the water. Conversely, the males exposed to the high concentration (100 ng/l) did not appear to recover from the exposure despite the 8 day depuration.     

Endothelial cells are a potential site of interaction between estrogens and glucocorticoids

Estrogens and glucocorticoids have synergistic effects in the micro and macrovasculature of endothelial cells. Whereas in the former they both have pro-inflammatory effects, in the latter they both inhibit the expression of adhesion molecules. Since the molecular basis of this synergy has not been defined, we propose possible mechanisms of interaction. An understanding of the functional interaction between estrogens and glucocorticoids in the endothelial cells of the micro and macrovasculature may contribute to clarifying the role of the endothelial cells of different vascular beds during the inflammatory response and in chronic inflammation. These advances could contribute to the design of more effective therapeutic strategies for the prevention of diseases, such as atherosclerosis, systemic lupus erythematosus and rheumatoid arthritis, in which the inflammatory process plays an important pathogenic role.     

Paradoxical interactions among estrogen receptors, estrogens and SERMS: mutual annihilation and synergy

The phenomenon of mutual annihilation of action between 17β estradiol (E₂) and a selective estrogen receptor modulator (SERM), previously described in prepubertal rat diaphysis, epiphysis and uterus, has been investigated in ROS 17/2.8 rat osteoblastic cells and in transiently co-transfected cells in culture. In ROS 17/2.8 cells, the estrogen-induced marker enzyme creatine kinase B (CKB) was stimulated by raloxifene, tamoxifen and tamoxifen methiodide to a specific activity equal to or greater than that induced by 10 nM E₂. However, when a fully inhibitory dose of any of these SERMS was given simultaneously with E₂, no stimulation of CK activity resulted. Therefore, SERMS can be full agonists when acting alone, but complete antagonists to a super-physiological dose of estrogen. It is expected that excess tamoxifen would prevent the action of a SERM, but that the agonist activity of a SERM is abolished by 1000-fold less estrogen is a phenomenon without obvious explanation by classical pharmacology of competitive inhibition. To probe the mechanism of this interaction further, a ckb-CAT reporter plasmid, plus the human receptor expression plasmid, HEO, was transfected transiently into several cell types. In MCF-7 cells, a 1:10 ratio of E₂ to tamoxifen produced mutual annihilation, but the same ratio in ROS 17/2.8 or HeLa cells led to synergistic stimulation. In HeLa cells, co-transfected with the more efficient wild-type estrogen receptor plasmid, HEGO, synergy was demonstrated only at sub-saturation levels of HEGO. We speculate that, in the presence of estradiol and a SERM, not only active homodimers would be formed, but also hetero-dimers of estrogen-liganded and tamoxifen-liganded receptor monomers, depending on the molar ratio of their ligands and their relative affinities. The resulting hetero-dimer conformation would change the specific receptor surface for interactions with the growing number of co-activators and co-repressors, structural changes which could help to explain the mutual annihilation and synergy phenomena and their cell selectivity.     

雌激素受体β与相关肿瘤研究进展

雌激素通过与特定的雌激素受体相互作用发挥重要的细胞生长和分化作用。雌激素受体是属于细胞核受体超家族的配体依赖性的反式作用子。尽管最初认为雌激素由单一的受体,即传统的雌激素受体,现称为ERα介导其作用,第二个ER新亚型,现称为ERβ,1996年被发现,并由此引发了一场对于雌激素在正常生理学和疾病过程的作用重新评价。自从发现ERβ以来,其作为相关肿瘤的预警因子以及其潜在的作为药物介入的新靶点的价值成为研究热点。在过去的10年中,我们对雌激素信号的理解有很大改变。现在,已知ERα和ERβ组织细胞分布和功能不同。ERβ存在于许多正常和疾病组织中,包括生殖系统和其他组织器官的恶性肿瘤,如乳腺、子宫内膜、卵巢、前列腺和结肠直肠癌以及其他肿瘤。因此,ERβ在这些肿瘤的发生发展和治疗方面的作用引起了人们越来越多的关注。现就ERβ在雌激素相关肿瘤的发生、发展、预后评估以及治疗意义进行综述。     

A biosensor for estrogenic substances using the quartz crystal microbalance

This article describes a biosensor that detects estrogenic substances using a quartz crystal microbalance with a genetically engineered construct of the hormone-binding domain of the alpha-estrogen receptor. The receptor was immobilized to a piezoelectric quartz crystal via a single exposed cysteine, forming a uniform orientation on the crystal surface. Our results illustrate that this sensor responds to a variety of ligands that are known to bind to the estrogen receptor. No response was observed for nonbinding substances such as testosterone and progesterone. The sensitive response of this biosensor to estrogenic substances results from changes in the structural rigidity of the immobilized receptor that occurs with ligand binding. Agonist and antagonist show different responses.