Transcription factor cross-talk: the estrogen receptor and NF-kappaB

Testosterone: a vascular hormone in health and disease

Coronary heart disease is a leading cause of premature death in men. Epidemiological studies have shown a high prevalence of low serum testosterone levels in men with cardiovascular disease (CVD). Furthermore, a low testosterone level is associated in some but not in all observational studies with an increase in cardiovascular events and mortality. Testosterone has beneficial effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation: key mediators of atherosclerosis. A bidirectional relationship between low endogenous testosterone levels and concurrent illness complicates attempts to validate causality in this association and potential mechanistic actions are complex. Testosterone is a vasoactive hormone that predominantly has vasodilatory actions on several vascular beds, although some studies have reported conflicting effects. In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart failure. Although the mechanism of the action of testosterone on vascular tone in vivo is not understood, laboratory research has found that testosterone is an L-calcium channel blocker and induces potassium channel activation in vascular smooth muscle cells. Animal studies have consistently demonstrated that testosterone is atheroprotective, whereas testosterone deficiency promotes the early stages of atherogenesis. The translational effects of testosterone between in vitro animal and human studies, some of which have conflicting effects, will be discussed in this review. We review the evidence for a role of testosterone in vascular health, its therapeutic potential and safety in hypogonadal men with CVD, and some of the possible underlying mechanisms.

Estradiol represses the G(D3) synthase gene ST8SIA1 expression in human breast cancer cells by preventing NFκB binding to ST8SIA1 promoter

Recent data have underlined a possible role of G(D3) synthase (GD3S) and complex gangliosides in Estrogen Receptor (ER) negative breast cancer progression. Here, we describe the main transcript of the GD3S coding gene ST8SIA1 expressed in breast tumors. We characterized the corresponding core promoter in Hs578T breast cancer cells and showed that estradiol decreases ST8SIA1 mRNA expression in ER-positive MCF-7 cells and ERα-transfected ER-negative Hs578T cells. The activity of the core promoter sequence of ST8SIA1 is also repressed by estradiol. The core promoter of ST8SIA1 contains two putative Estrogen Response Elements (ERE) that were not found to be involved in the promoter activity pathway. However, NFκB was shown to be involved in ST8SIA1 transcriptional activation and we demonstrated that estradiol prevents NFκB to bind to ST8SIA1 core promoter in ERα expressing breast cancer cells by inhibiting p65 and p50 nucleus localization. The activation of NFκB pathway in ER-negative tumors, due to the absence of estradiol signaling, might explain the overexpression of G(D3) synthase in this tumor subtype.

Role of nuclear factor-ĸB in breast and colorectal cancer

The purpose of this review article is to highlight articles and new research regarding the link between NF-ĸB and several cancers. This review presents the most up-to-date NF-ĸB research and how it links this important transcription factor with hematology and oncology. It was written by conducting a thorough search of Pubmed as well as several journals such as Cancer, Nature, Science, Cell and those of one of the authors. The articles relating to the link between NF-ĸB and cancer were used to write this review. The results of this study clarified that there is a critical link between NF-ĸB and cancer. NF-ĸB has often been implicated in a variety of different diseases and it plays a variety of roles in cell survival, differentiation, and proliferation of cells. In cancer, NF-ĸB plays a pivotal role by facilitating oncogenesis as well as metastasis. A thorough understanding of NF-ĸB and its role in cancer can lead to future studies and drug development which could provide a novel option in the treatment of this disease.

Sex, stroke, and inflammation: the potential for estrogen-mediated immunoprotection in stroke

Stroke is the third leading cause of death and the primary cause of disability in the developed world. Experimental and clinical data indicate that stroke is a sexually dimorphic disease, with males demonstrating an enhanced intrinsic sensitivity to ischemic damage throughout most of their lifespan. The neuroprotective role of estrogen in the female brain is well established, however, estrogen exposure can also be deleterious, especially in older women. The mechanisms for this remain unclear. Our current understanding is based on studies examining estrogen as it relates to neuronal injury, yet cerebral ischemia also induces a robust sterile inflammatory response involving local and systemic immune cells. Despite the potent anti-inflammatory effects of estrogen, few studies have investigated the contribution of estrogen to sex differences in the inflammatory response to stroke. This review examines the potential role for estrogen-mediated immunoprotection in ischemic injury.

Estrogen represses CXCR7 gene expression by inhibiting the recruitment of NFκB transcription factor at the CXCR7 promoter in breast cancer cells

Although many studies reported mechanisms involved in the positive regulation of estrogens (E2) target genes, very little is known concerning the repressive effect of E2. In this study, we explored the molecular mechanisms by which E2 regulates CXCR7 expression in breast cancer cells. Our results show that E2-mediated down-regulation of CXCR7 occurs at the transcriptional level as demonstrated using actinomycin D and requires estrogen receptor alpha (ERα). In addition, CXCR7 is a primary ERα-target gene because the effect of E2 does not require the synthesis of an intermediary protein as revealed by the translational inhibitor cycloheximide treatment. Using an inhibitor of the NFκB pathway and chromatin immunoprecipitation assays, we demonstrated that NFκB is necessary for the high expression of CXCR7 gene and is recruited to the proximal promoter of the CXCR7 gene. Interestingly, the chromatin immunoprecipitation analyses also showed that E2-treatment significantly prevented the recruitment of NFκB to the promoter. Altogether, our results demonstrate that E2, through ERα, directly down-regulates CXCR7 expression by interfering with NFκB transcription factor at the promoter level.

Dietary phytochemicals as potent chemotherapeutic agents against breast cancer: Inhibition of NF-κB pathway via molecular interactions in rel homology domain of its precursor protein p105

BACKGROUND

Dietary phytochemicals consist of a wide variety of biologically active compounds that are ubiquitous in plants, many of which have been reported to have anti-tumor as well as anti-inflammatory properties.

OBJECTIVE

In the present study, we aimed to validate these findings by using docking protocols and explicate the possible mechanism of action for a dataset of nine phytochemicals namely boswellic acid, 1-caffeoylquinic acid, ellagic acid, emodin, genistein, guggulsterone, quercetin, resveratrol, and sylibinin from different plants against the nuclear factor- kappaB (NF-κB) precursor protein p105, an important transcription factor reported to be overexpressed in breast cancer.

MATERIALS AND METHODS

2-D structures of all phytochemicals were retrieved from PubChem Compound database and their subsequent conversion into 3-D structures was performed by using online software system CORINA. The X-ray crystallographic structure of the NF-κB precursor p105 was extracted from Brookhaven Protein Data Bank. Molecular docking simulation study was carried out by using AutoDock Tools 4.0.

RESULTS

Our results showed significant binding affinity of different phytochemicals with the Rel homology domain of the NF-κB precursor protein p105. Quercetin and 1-caffeoylquinic acid were found to be very effective inhibitors against target molecule as they showed binding energy of -12.11 and -11.50 Kcal/mol, respectively. The order of affinity of other ligands with p105 was found as follows: guggulsterone > sylibinin > emodin > resveratrol > genistein > boswellic acid > ellagic acid.

CONCLUSION

Our in silico study has explored the possible chemopreventive mechanism of these phytochemicals against the NF-κB precursor protein p105 and deciphered that quercetin, 1-caffeoylquinic acid and guggulsterone were the potent inhibitors against target molecule. In addition, large scale preclinical and clinical trials are needed to explore the role of these chemotherapeutic molecules against the NF-κB precursor protein p105 in cure and prevention of breast cancer.

Gender differences in cancer susceptibility: an inadequately addressed issue

The gender difference in cancer susceptibility is one of the most consistent findings in cancer epidemiology. Hematologic malignancies are generally more common in males and this can be generalized to most other cancers. Similar gender differences in non-malignant diseases including autoimmunity, are attributed to hormonal or behavioral differences. Even in early childhood, however, where these differences would not apply, there are differences in cancer incidence between males and females. In childhood, few cancers are more common in females, but overall, males have higher susceptibility. In Hodgkin lymphoma, the gender ratio reverses toward adolescence. The pattern that autoimmune disorders are more common in females, but cancer and infections in males suggests that the known differences in immunity may be responsible for this dichotomy. Besides immune surveillance, genome surveillance mechanisms also differ in efficiency between males and females. Other obvious differences include hormonal ones and the number of X chromosomes. Some of the differences may even originate from exposures during prenatal development. This review will summarize well-documented examples of gender effect in cancer susceptibility, discuss methodological issues in exploration of gender differences, and present documented or speculated mechanisms. The gender differential in susceptibility can give important clues for the etiology of cancers and should be examined in all genetic and non-genetic association studies.

The c-Rel Transcription Factor in Development and Disease

c-Rel is a member of the nuclear factor κB (NF-κB) transcription factor family. Unlike other NF-κB proteins that are expressed in a variety of cell types, high levels of c-Rel expression are found primarily in B and T cells, with many c-Rel target genes involved in lymphoid cell growth and survival. In addition to c-Rel playing a major role in mammalian B and T cell function, the human c-rel gene (REL) is a susceptibility locus for certain autoimmune diseases such as arthritis, psoriasis, and celiac disease. The REL locus is also frequently altered (amplified, mutated, rearranged), and expression of REL is increased in a variety of B and T cell malignancies and, to a lesser extent, in other cancer types. Thus, agents that modulate REL activity may have therapeutic benefits for certain human cancers and chronic inflammatory diseases.

Activin and inhibin, estrogens and NFκB, play roles in ovarian tumourigenesis is there crosstalk?

Ovarian cancer may be the most frequently lethal gynaecological malignancy but the heterogeneous nature of the disease and the advanced stage at which it is usually diagnosed, have contributed to the paucity of information relating to its aetiology and pathogenesis. Members of the TGF-β superfamily, estrogen and NFκB have all been implicated in the development and progression of cancers from a wide range of tissues. In the ovary, TGF-β superfamily members and estrogen play key roles in maintaining normal function. To date, little is known about the capacity of NFκB to influence normal ovarian function except that it is ubiquitously expressed. In this review we will highlight the roles that inhibin/activin, estrogen and NFκB, have been attributed within carcinogenesis and examine the potential for crosstalk between these pathways in ovarian cancer pathogenesis.

Estrogen receptors regulate an inflammatory pathway of dendritic cell differentiation: mechanisms and implications for immunity

Immune cells and hematopoietic progenitors express estrogen receptors (ER). As ligand-activated transcription factors that modulate chromatin structure, ER regulate transcriptional programs that direct the development or functional responses of immune cells. ER-regulated immune responses likely contribute to significant sex biases in infection, autoimmunity and other inflammatory diseases, and changes in immune function during the female hormonal cycle and pregnancy. Here we summarize our own and others' studies showing that ERα signaling regulates the development of dendritic cells (DCs), antigen-presenting cells crucial for initiation of innate and adaptive immunity. During inflammation, elevated GM-CSF directs the development of new DCs from monocytes or other precursors that infiltrate tissues and lymphoid organs, and these de novo populations of inflammatory DCs have critical roles in programming T cell-mediated responses during infection and autoimmunity. Estradiol acting via ERα, but not ERβ, promotes the GM-CSF-mediated inflammatory pathway of DC differentiation, leading to the development of DCs with increased functional capacity. Estradiol/ERα signaling acts directly in GM-CSF-stimulated myeloid progenitors to induce elevated levels of IRF4, a transcription factor that directs a developmental program underlying CD11b⁺ DC differentiation. In contrast, during homeostatic Flt3 Ligand-driven DC development, ERα signaling decreases numbers of myeloid progenitors and differentiated DCs, yet promotes more functionally competent DCs. Thus ERα signaling regulates the response of DC progenitors to the external cytokine environment, thereby altering the strength or integrity of DC developmental pathways. The development of increased numbers of DCs during inflammation will likely increase the magnitude of DC-mediated functional responses including cytokine production, processing and MHC-mediated presentation of antigens, and activation and polarization of T and B lymphocytes; these functions also may be regulated directly by ERα signaling. In sum, via profound effects on DC development and ensuing functional responses, ERα signaling can regulate the quality of the adaptive immune responses and influence the resolution of infection or chronic inflammatory diseases.

Nuclear factor-kappaB: a main regulator of inflammation and cell survival in endometriosis pathophysiology

OBJECTIVE

To update, analyze, and summarize the literature concerning nuclear factor-kappaB (NF-κB) participation in endometriosis pathophysiology.

DESIGN

Review.

RESULT(S)

Nuclear factor-kappaB is physiologically activated in the human endometrium, showing variable activity. A cyclic p65-DNA binding pattern was shown in the endometrium of healthy women. This cyclic pattern was altered in the endometrium of patients with endometriosis. Nuclear factor-kappaB is basally activated in peritoneal endometriotic lesions, showing higher p65 activity in red endometriotic lesions than in black lesions. In vivo and in vitro studies show up-regulation of inflammation and cell proliferation and down-regulation of apoptosis by NF-κB activity. Iron overload has been shown in the pelvic cavity of endometriosis patients, and iron overload and oxidative stress activate NF-κB in macrophages, which have been shown to participate in the endometriosis-associated inflammatory reaction.

CONCLUSION(S)

Nuclear factor-kappaB activation dysregulation in the endometrium of endometriosis patients may explain some endometrial biological alterations associated with endometriosis. The scientific evidence strongly suggests that NF-κB activity in endometriotic cells stimulates inflammation and cell proliferation and inhibits apoptosis, favoring the development and maintenance of endometriosis. Iron overload in the pelvic cavity of endometriosis patients could be a main factor enhancing oxidative stress and activating NF-κB in a chronic manner, contributing to endometriosis establishment and growth.

The importance of ERα and ERβ gene polymorphisms in PCOS

Estrogens act through binding to estrogen receptor α (ERα) and β (ERβ). Studies in knockout mice have shown that the absence of ERα leads to the polycystic ovary syndrome (PCOS) phenotype. Furthermore, the expression of ERβ gene is lower in follicles derived from women with PCOS compared with healthy women. The aim of this study was to investigate the importance of ERα and ERβ gene polymorphisms in PCOS. A cohort of 180 women with PCOS and 140 healthy controls were recruited, and the PvuII and XbaI polymorphisms of ERα, as well as, the AluI and RsaI polymorphisms of ERβ were genotyped. No difference was found in the distribution of these polymorphisms between patients and healthy controls. However, in PCOS women, carriers of TC and TT genotypes of PvuII polymorphism had lower fasting glucose to insulin ratio compared with carriers of CC genotype (p = 0.029). In addition, the presence of AA genotype of XbaI polymorphism was associated with lower levels of follicle-stimulating hormone (FSH) compared with the presence of AG and GG genotypes (p = 0.03). The association of ERα polymorphisms with insulin resistance indices and FSH levels emphasizes the importance of ERα as a genetic modifier of the PCOS phenotype.

Estrogen modulates NFκB signaling by enhancing IκBα levels and blocking p65 binding at the promoters of inflammatory genes via estrogen receptor-β

Background

NFκB signaling is critical for expression of genes involved in the vascular injury response. We have shown that estrogen (17β-estradiol, E2) inhibits expression of these genes in an estrogen receptor (ER)-dependent manner in injured rat carotid arteries and in tumor necrosis factor (TNF)-α treated rat aortic smooth muscle cells (RASMCs). This study tested whether E2 inhibits NFκB signaling in RASMCs and defined the mechanisms.

Methodology/Principal Findings

TNF-α treated RASMCs demonstrated rapid degradation of IκBα (10–30 min), followed by dramatic increases in IκBα mRNA and protein synthesis (40–60 min). E2 enhanced TNF-α induced IκBα synthesis without affecting IκBα degradation. Chromatin immunoprecipitation (ChIP) assays revealed that E2 pretreatment both enhanced TNF-α induced binding of NFκB p65 to the IκBα promoter and suppressed TNF-α induced binding of NFκB p65 to and reduced the levels of acetylated histone 3 at promoters of monocyte chemotactic protein (MCP)-1 and cytokine-induced neutrophil chemoattractant (CINC)-2β genes. ChIP analyses also demonstrated that ERβ can be recruited to the promoters of MCP-1 and CINC-2β during co-treatment with TNF-α and E2.

Conclusions

These data demonstrate that E2 inhibits inflammation in RASMCs by two distinct mechanisms: promoting new synthesis of IκBα, thus accelerating a negative feedback loop in NFκB signaling, and directly inhibiting binding of NFκB to the promoters of inflammatory genes. This first demonstration of multifaceted modulation of NFκB signaling by E2 may represent a novel mechanism by which E2 protects the vasculature against inflammatory injury.

Oestrogen attenuates tumour progression in hepatocellular carcinoma

The precise mechanisms underlying gender disparity in hepatocellular carcinoma (HCC) progression and prognosis are not understood. We demonstrate that oestrogen attenuates HCC progression in vitro and in vivo, and this may contribute to the gender differences in HCC behaviour. To investigate the role of oestrogen in HCC progression, we developed an orthotopic homograft tumour model by liver implantation of H22 cells. In combination with male castration, female ovariectomy, and oestrogen treatment, we tested the hypothesis that oestrogen contributes to gender disparity in this model. Pathological analyses were performed to examine the changes in biological behaviour of liver cancer cells, and two cell lines were used to investigate possible molecular mechanisms of the suppressive effect of oestrogen. Our data showed that oestrogen modulates HCC malignancy in vivo by reducing tumour cell invasion, arresting cell cycle progression, and promoting apoptosis, characterized by decreased expression of MMP-2, MMP-9, PCNA, cyclin A, cyclin D1, and Bcl-2, and increased expression in cleaved caspase 3. Through in vitro assays, we further confirmed the changes in expression levels of these related proteins, gained insights into the molecular cascades of oestrogen-induced HCC suppression, and indicated the oestrogen receptor α-mediated inhibition of NF-κB binding activity as a pivotal event in this process. This study represents a novel description of the mechanisms regarding the suppressive effects of oestrogen on HCC, adding a new understanding to the gender disparity in HCC progression. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Ginsenoside Rg1 protection against β-amyloid peptide-induced neuronal apoptosis via estrogen receptor α and glucocorticoid receptor-dependent anti-protein nitration pathway

Ginsenoside Rg1 (Rg1) acts as a neuroprotective agent against various insults, however, the underlying mechanism has not been fully elucidated yet. Here, we report that Rg1 protects primary rat cerebrocortical neurons against β-amyloid peptide₂₅₋₃₅ (Aβ₂₅₋₃₅) injury via estrogen receptor α (ERα) and glucocorticoid receptor (GR)-dependent anti-protein nitration pathway. In primary rat cerebrocortical neuron cultures under basal conditions, Rg1 leads to nuclear translocation of ERα and GR, induces related responsive gene PR, pS₂ and MKP-1, SGK transcription. Meantime, Rg1 also increases the basal level of ERK1/2 phosphorylation. In the presence of toxic level of Aβ₂₅₋₃₅, Rg1 maintains ERK1/2 phosphorylation, attenuates iNOS expression, NO production, and inhibits NF-κB nuclear translocation, protein nitration and cell death. The antiapoptotic effects of Rg1 via both ERα and GR were abolished by small interfering RNAs (siRNA). ERK1/2 phosphorylation inhibitor U0126 can block downstream iNOS expression and NO generation. Interestingly, the anti-protein nitration effect of Rg1 is well matched with ERα and GR activation, although its anti-ROS production effect is in an ERα- and GR-independent manner. These results suggest that Rg1 ameliorates Aβ₂₅₋₃₅-induced neuronal apoptosis at least in part by two complementary ERα- and GR-dependent downstream pathways: (1) upregulation of ERK1/2 phosphorylation followed by inhibiting iNOS expression, NO generation and protein tyrosine nitration. (2) reduction NF-κB nuclear translocation. These data provide new understanding into the mechanisms of Rg1 anti-apoptotic functions after Aβ₂₅₋₃₅ exposure, suggesting that ERα and GR-dependent anti-protein tyrosine nitration pathway might take an important role in the neuroprotective effect of Rg1.

Neuroprotective effects of 17β-estradiol rely on estrogen receptor membrane initiated signals

Besides its crucial role in many physiological events, 17β-estradiol (E2) exerts protective effects in the central nervous system. The E2 effects are not restricted to the brain areas related with the control of reproductive function, but rather are widespread throughout the developing and the adult brain. E2 actions are mediated through estrogen receptors (i.e., ERα and ERβ) belonging to the nuclear receptor super-family. As members of the ligand-regulated transcription factor family, classically, the actions of ERs in the brain were thought to mediate only the E2 long-term transcriptional effects. However, a growing body of evidence highlighted rapid, membrane initiated E2 effects in the brain that are independent of ER transcriptional activities and are involved in E2-induced neuroprotection. The aim of this review is to focus on the rapid effects of E2 in the brain highlighting the specific role of the signaling pathway(s) of the ERβ subtype in the neuroprotective actions of E2.

The effects of an in vitro exposure to 17β-estradiol and nonylphenol on rainbow trout (Oncorhynchus mykiss) peripheral blood leukocytes

While xenoestrogens are routinely detected in the aquatic environment, there is little understanding of the immunotoxicological consequences of exposure to these chemicals in fish, or of the mechanisms through which these effects are mediated. This study was conducted to determine if estrogen receptors (ERs) are present in fish leukocytes and to characterize the effects of 17β-estradiol (E2) and the xenoestrogen nonylphenol (NP) on immune system endpoints in rainbow trout (Oncorhynchus mykiss). Q-PCR was used to confirm that freshly isolated peripheral blood leukocytes (PBLs) express ERs. Following 96-h incubations with E2 or NP (1 nM to 10 μM), PBL ER transcription was again examined using Q-PCR and lipopolysaccharide (LPS)-stimulated proliferation was assessed using flow cytometry. While the transcription of all four forms of rainbow trout ER was unaffected by treatment with E2 or NP, transcription of ERα1 and ERα2 was down-regulated following LPS stimulation. Both E2 and NP, at concentrations of ≥100 nM and 10nM respectively, suppressed leukocyte proliferation. This first report of ERs in rainbow trout PBLs suggests a mechanism through with E2 and other xenoestrogens can modulate immune function. These results highlight the potential for xenoestrogens to impact host resistance to pathogens in wild fish populations.

Aromatase inhibitors, estrogens and musculoskeletal pain: estrogen-dependent T-cell leukemia 1A (TCL1A) gene-mediated regulation of cytokine expression

Introduction

Arthralgias and myalgias are major side effects associated with aromatase inhibitor (AI) therapy of breast cancer. In a recent genome-wide association study, we identified SNPs - including one that created an estrogen response element near the 3' end of the T-cell leukemia 1A (TCL1A) gene - that were associated with musculoskeletal pain in women on adjuvant AI therapy for breast cancer. We also showed estrogen-dependent, SNP-modulated variation in TCL1A expression and, in preliminary experiments, showed that TCL1A could induce IL-17RA expression. In the present study, we set out to determine whether these SNPs might influence cytokine expression and effect more widely, and, if so, to explore the mechanism of TCL1A-related AI-induced side effects.

Methods

The functional genomic experiments performed included determinations of TCL1A, cytokine and cytokine receptor expression in response to estrogen treatment of U2OS cells and lymphoblastoid cell lines that had been stably transfected with estrogen receptor alpha. Changes in mRNA and protein expression after gene knockdown and overexpression were also determined, as was NF-κB transcriptional activity.

Results

Estradiol (E2) increased TCL1A expression and, in a TCL1A SNP-dependent fashion, also altered the expression of IL-17, IL-17RA, IL-12, IL-12RB2 and IL-1R2. TCL1A expression was higher in E2-treated lymphoblastoid cell lines with variant SNP genotypes, and induction of the expression of cytokine and cytokine receptor genes was mediated by TCL1A. Finally, estrogen receptor alpha blockade with ICI-182,780 in the presence of E2 resulted in greatly increased NF-κB transcriptional activity, but only in cells that carried variant SNP genotypes. These results linked variant TCL1A SNP sequences that are associated with AI-dependent musculoskeletal pain with increased E2-dependent TCL1A expression and with downstream alterations in cytokine and cytokine receptor expression as well as NF-κB transcriptional activity.

Conclusions

SNPs near the 3' terminus of TCL1A were associated with AI-dependent musculoskeletal pain. E2 induced SNP-dependent TCL1A expression, which in turn altered IL-17, IL-17RA, IL-12, IL-12RB2, and IL-1R2 expression as well as NF-κB transcriptional activity. These results provide a pharmacogenomic explanation for a clinically important adverse drug reaction as well as insights into a novel estrogen-dependent mechanism for the modulation of cytokine and cytokine receptor expression.

Minireview: Inflammation: an instigator of more aggressive estrogen receptor (ER) positive breast cancers

Approximately 75% of breast tumors express the estrogen receptor (ER), and women with these tumors will receive endocrine therapy. Unfortunately, up to 50% of these patients will fail ER-targeted therapies due to either de novo or acquired resistance. ER-positive tumors can be classified based on gene expression profiles into Luminal A- and Luminal B-intrinsic subtypes, with distinctly different responses to endocrine therapy and overall patient outcome. However, the underlying biology causing this tumor heterogeneity has yet to become clear. This review will explore the role of inflammation as a risk factor in breast cancer as well as a player in the development of more aggressive, therapy-resistant ER-positive breast cancers. First, breast cancer risk factors, such as obesity and mammary gland involution after pregnancy, which can foster an inflammatory microenvironment within the breast, will be described. Second, inflammatory components of the tumor microenvironment, including tumor-associated macrophages and proinflammatory cytokines, which can act on nearby breast cancer cells and modulate tumor phenotype, will be explored. Finally, activation of the nuclear factor κB (NF-κB) pathway and its cross talk with ER in the regulation of key genes in the promotion of more aggressive breast cancers will be reviewed. From these multiple lines of evidence, we propose that inflammation may promote more aggressive ER-positive tumors and that combination therapy targeting both inflammation and estrogen production or actions could benefit a significant portion of women whose ER-positive breast tumors fail to respond to endocrine therapy.

Effects of chronic and acute oestrogen replacement therapy in aged animals after experimental stroke

The effect of oestrogen replacement therapy (ERT) on stroke incidence and severity has been extensively debated. Clinical trials of ERT have demonstrated an increased risk of stroke in treated women, although the study participants were well past menopause when therapy was initiated. It has been suggested that detrimental effects of ERT may be unmasked after prolonged periods of hypoestrogenicity. To date, very few studies have examined the effect of ERT in aged animals, although the timing of replacement may be critical to the neuroprotective effects of ERT. We hypothesised that chronic ERT initiated in late middle age would decrease infarct size in the brain after an induced stroke, whereas acute ERT would have no beneficial effects in aged females. To test this hypothesis, two paradigms of ERT were administered to aged mice of both sexes aiming to determine the effects on stroke outcome and to explore the possible mechanisms by which ERT interacts with age. Female mice that received chronic ERT from 17-20 months of age showed improved stroke outcomes after experimental stroke, whereas females that had acute ERT initiated at 20 months of age did not. Chronic ERT females exhibited diminished levels of nuclear factor kappa B (NF-κB) translocation compared to acute ERT females after stroke. Acute ERT females demonstrated both an increase in nuclear NF-κB and enhanced expression of pro-inflammatory cytokines. In addition, a sexual dimorphic effect of ERT was seen because males benefited from ERT, regardless of the timing of initiation. Aged males had significantly reduced expression of pro-inflammatory markers after stroke compared to age-matched females, suggesting a pro-inflammatory milieu emerges with age in females. These results are consistent with the emerging clinical literature suggesting that ERT should be initiated at the time of menopause to achieve beneficial effects. The present study demonstrates the importance of using appropriate animal models in preclinical studies.

Sexual differentiation of the gonadotropin surge release mechanism: a new role for the canonical NfκB signaling pathway

Sex differences in luteinizing hormone (LH) release patterns are controlled by the hypothalamus, established during the perinatal period and required for fertility. Female mammals exhibit a cyclic surge pattern of LH release, while males show a tonic release pattern. In rodents, the LH surge pattern is dictated by the anteroventral periventricular nucleus (AVPV), an estrogen receptor-rich structure that is larger and more cell-dense in females. Sex differences result from mitochondrial cell death triggered in perinatal males by estradiol derived from aromatization of testosterone. Herein we provide an historical perspective and an update describing evidence that molecules important for cell survival and cell death in the immune system also control these processes in the developing AVPV. We conclude with a new model proposing that development of the female AVPV requires constitutive activation of the Tnfα, Tnf receptor 2, NfκB and Bcl2 pathway that is blocked by induction of Tnf receptor-associated factor 2-inhibiting protein (Traip) in the male.

Oestrogen receptors and signalling pathways: implications for neuroprotective effects of sex steroids in Parkinson's disease

Parkinson's disease (PD) is an age-related neurodegenerative disorder with a higher incidence in the male population. In the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD, 17β-oestradiol but not androgens were shown to protect dopamine (DA) neurones. We report that oestrogen receptors (ER)α and β distinctly contribute to neuroprotection against MPTP toxicity, as revealed by examining the membrane DA transporter (DAT), the vesicular monoamine transporter 2 (VMAT2) and tyrosine hyroxylase in ER wild-type (WT) and knockout (ERKO) C57Bl/6 male mice. Intact ERKOβ mice had lower levels of striatal DAT and VMAT2, whereas ERKOα mice were the most sensitive to MPTP toxicity compared to WT and ERKOβ mice and had the highest levels of plasma androgens. In both ERKO mice groups, treatment with 17β-oestradiol did not provide neuroprotection against MPTP, despite elevated plasma 17β-oestradiol levels. Next, the recently described membrane G protein-coupled oestrogen receptor (GPER1) was examined in female Macaca fascicularis monkeys and mice. GPER1 levels were increased in the caudate nucleus and the putamen of MPTP-monkeys and in the male mouse striatum lesioned with methamphetamine or MPTP. Moreover, neuroprotective mechanisms in response to oestrogens transmit via Akt/glycogen synthase kinase-3 (GSK3) signalling. The intact and lesioned striata of 17β-oestradiol treated monkeys, similar to that of mice, had increased levels of pAkt (Ser 473)/βIII-tubulin, pGSK3 (Ser 9)/βIII-tubulin and Akt/βIII-tubulin. Hence, ERα, ERβ and GPER1 activation by oestrogens is imperative in the modulation of ER signalling and serves as a basis for evaluating nigrostriatal neuroprotection.

Context-specific regulation of NF-κB target gene expression by EZH2 in breast cancers

Both EZH2 and NF-κB contribute to aggressive breast cancer, yet whether the two oncogenic factors have functional crosstalk in breast cancer is unknown. Here, we uncover an unexpected role of EZH2 in conferring the constitutive activation of NF-κB target gene expression in ER-negative basal-like breast cancer cells. This function of EZH2 is independent of its histone methyltransferase activity but requires the physical interaction with RelA/RelB to promote the expression of NF-κB targets. Intriguingly, EZH2 acts oppositely in ER-positive luminal-like breast cancer cells and represses NF-κB target gene expression by interacting with ER and directing repressive histone methylation on their promoters. Thus, EZH2 functions as a double-facet molecule in breast cancers, either as a transcriptional activator or repressor of NF-κB targets, depending on the cellular context. These findings reveal an additional mechanism by which EZH2 promotes breast cancer progression and underscore the need for developing context-specific strategy for therapeutic targeting of EZH2 in breast cancers.

17β-estradiol protects the lung against acute injury: possible mediation by vasoactive intestinal polypeptide

Beyond their classical role as a class of female sex hormones, estrogens (e.g. 17β-estradiol) exert important biological actions, both protective and undesirable. We have investigated the ability of estradiol to protect the lung in three models of acute injury induced by 1) oxidant stress due to the herbicide paraquat; 2) excitotoxicity, caused by glutamate agonist N-methyl-d-aspartate; and 3) acute alveolar anoxia. We also assessed the role of estrogen receptors (ER) ERα and ERβ and the neuropeptide vasoactive intestinal peptide (VIP) in mediating this protection. Isolated guinea pig or rat lungs were perfused in situ at constant flow and mechanically ventilated. The onset and severity of lung injury were monitored by increases in pulmonary arterial and airway pressures, wet/dry lung weight ratio, and bronchoalveolar lavage fluid protein content. Estradiol was infused into the pulmonary circulation, beginning 10 min before induction of injury and continued for 60-90 min. Lung injury was marked by significant increases in the above measurements, with paraquat producing the most severe, and excitotoxicity the least severe, injury. Estradiol significantly attenuated the injury in each model. Both ER were constitutively expressed and immunohistochemically demonstrable in normal lung, and their selective agonists reduced anoxic injury, the only model in which they were tested. As it protected against injury, estradiol rapidly and significantly stimulated VIP mRNA expression in rat lung. Estradiol attenuated acute lung injury in three experimental models while stimulating VIP gene expression, a known mechanism of lung protection. The up-regulated VIP expression could have partially mediated the protection by estrogen.

CBP mediates NF-κB-dependent histone acetylation and estrogen receptor recruitment to an estrogen response element in the BIRC3 promoter

Estrogen receptor (ER) and NF-κB are transcription factors with profound effects on breast cancer cell proliferation and survival. While many studies demonstrate that ER and NF-κB can repress each other, we previously identified a gene signature that is synergistically upregulated by these two factors in more aggressive luminal B breast tumors. Herein, we examine a novel mechanism of cross talk between ER and NF-κB that results in the upregulation of the antiapoptotic gene BIRC3 (also known as cIAP2). We demonstrate that NF-κB, acting through two response elements, is required for ER recruitment to an adjacent estrogen response element (ERE) in the BIRC3 promoter. This effect is accompanied by a major increase in NF-κB-dependent histone acetylation around the ERE. Interestingly, CBP, a histone acetyltransferase previously implicated in repressive interactions between ER and NF-κB, plays a permissive role by promoting histone acetylation and ER recruitment, as well as enhanced expression of BIRC3. These findings suggest a new gene regulatory mechanism by which inflammation and NF-κB activation can influence ER recruitment to inherently inactive ER binding sites. This fine-tuning mechanism may explain how two factors that generally repress each other's activity may work together on certain genes to promote breast cancer cell survival and tumor progression.

Inhibition of Bcl3 gene expression mediates the anti-proliferative action of estrogen in pituitary lactotrophs in primary culture

In addition to their well-known stimulatory action, estrogens have an anti-proliferative effect. The present study was undertaken to investigate the mechanism by which 17β-estradiol (E2) inhibits insulin-like growth factor-1 (IGF-1)-induced proliferation in vitro in the rat pituitary lactotroph, a typical estrogen-responsive cell. E2 treatment of pituitary cells did not change levels of IGF-1-induced phosphorylation of proliferation-related protein kinases such as Erk1/2 and Akt. We performed global gene expression profiling by DNA microarray analysis and identified 177 genes regulated by E2 in the presence of IGF-1. These results were verified by quantitative real time PCR. The estrogen-regulated genes included several NFκB family related genes. As pharmacological inhibition of the NFκB pathway blocked IGF-1-induced lactotroph proliferation, we chose to investigate whether one NFκB pathway gene, Bcl3, was involved in the anti-proliferative action of E2. RNA interference-mediated knockdown of Bcl3 expression attenuated IGF-1-induced lactotroph proliferation. Even minimal induced overexpression of Bcl3 blocked the anti-proliferative action of E2. In contrast, Nfkb2, another E2-downregulated protein, required maximal overexpression to block the anti-proliferative action of E2. These results suggest that inhibition of Bcl3 expression is involved in the anti-proliferative action of estrogens in pituitary lactotrophs in culture.

Chronic kidney disease in postmenopausal women

Menopause is derived from the Greek words men (month) and pauses (cessation) and means permanent cessation of menstruation after the loss of ovarian activity. Chronic kidney disease (CKD) has recently been associated with cardiovascular events in several studies. CKD patients have a heavy burden of traditional cardiovascular risk factors in addition to a range of nontraditional risk factors such as inflammation and abnormal metabolism of calcium and phosphate. In this review, the association of CKD and cardiovascular disease (CVD), as well as of osteoporosis in postmenopausal women is discussed. CKD mineral and bone disorder, characterized by disturbances of calcium/phosphate/parathyroid hormone, bone abnormalities and vascular and soft tissue calcification, is highly prevalent in CKD and is a strong, independent predictor of bone fracture, CVD and death. Estrogen has been shown to: (a) decrease the expression of angiotensin type 1 receptors in vasculature and kidneys; (b) reduce the expression and activity of angiotensin-converting enzyme, and (c) cause the release of angiotensinogen substrate from the liver. However, the degree of activation or suppression of the renin-angiotensin-aldosterone system by estrogen has not been clearly established. Clinical data on the effects of estrogen therapy on bone mineral densities are extremely limited in the ESRD population. CVD is the most common cause of death in postmenopausal women with CKD and many contributing factors have been explored. Future research for prevention of CVD in postmenopausal women with CKD would focus on the biology of vascular calcification as well as bone loss.

Meta-analysis of estrogen response in MCF-7 distinguishes early target genes involved in signaling and cell proliferation from later target genes involved in cell cycle and DNA repair

Background

Many studies have been published outlining the global effects of 17β-estradiol (E2) on gene expression in human epithelial breast cancer derived MCF-7 cells. These studies show large variation in results, reporting between ~100 and ~1500 genes regulated by E2, with poor overlap.

Results

We performed a meta-analysis of these expression studies, using the Rank product method to obtain a more accurate and stable list of the differentially expressed genes, and of pathways regulated by E2. We analyzed 9 time-series data sets, concentrating on response at 3-4 hrs (early) and at 24 hrs (late). We found >1000 statistically significant probe sets after correction for multiple testing at 3-4 hrs, and >2000 significant probe sets at 24 hrs. Differentially expressed genes were examined by pathway analysis. This revealed 15 early response pathways, mostly related to cell signaling and proliferation, and 20 late response pathways, mostly related to breast cancer, cell division, DNA repair and recombination.

Conclusions

Our results confirm that meta-analysis identified more differentially expressed genes than the individual studies, and that these genes act together in networks. These results provide new insight into E2 regulated mechanisms, especially in the context of breast cancer.

Estrogen induces c-myc gene expression via an upstream enhancer activated by the estrogen receptor and the AP-1 transcription factor

c-myc oncogene is implicated in tumorigenesis of many cancers, including breast cancer. Although c-myc is a well-known estrogen-induced gene, its promoter has no estrogen-response element, and the underlying mechanism by which estrogen induces its expression remains obscure. Recent genome-wide studies by us and others suggested that distant elements may mediate estrogen induction of gene expression. In this study, we investigated the molecular mechanism by which estrogen induces c-myc expression with a focus on these distal elements. Estrogen rapidly induced c-myc expression in estrogen receptor (ER)-positive breast cancer cells. Although estrogen had little effect on c-myc proximal promoter activity, it did stimulate the activity of a luciferase reporter containing a distal 67-kb enhancer. Estrogen induction of this luciferase reporter was dependent upon both a half-estrogen response element and an activator protein 1 (AP-1) site within this enhancer, which are conserved across 11 different mammalian species. Small interfering RNA experiments and chromatin immunoprecipitation assays demonstrated the necessity of ER and AP-1 cross talk for estrogen to induce c-myc expression. TAM67, the AP-1 dominant negative, partially inhibited estrogen induction of c-myc expression and suppressed estrogen-induced cell cycle progression. Together, these results demonstrate a novel pathway of estrogen regulation of gene expression by cooperation between ER and AP-1 at the distal enhancer element and that AP-1 is involved in estrogen induction of the c-myc oncogene. These results solve the long-standing question in the field of endocrinology of how estrogen induces c-myc expression.

Inhibition of nuclear factor-kappa B sensitises anterior pituitary cells to tumour necrosis factor-α- and lipopolysaccharide-induced apoptosis

Nuclear factor-kappa B (NF-κB), an important pro-inflammatory factor, is a crucial regulator of cell survival. Both lipopolysaccharide (LPS) and tumour necrosis factor (TNF)-α activate NF-κB signalling. Oestrogens were shown to suppress NF-κB activation. Oestrogens exert a sensitising action to pro-apoptotic stimuli such as LPS and TNF-α in anterior pituitary cells. In the present study, we show by western blotting that 17β-oestradiol (E(2)) decreases TNF-α-induced NF-κB/p65 and p50 nuclear translocation in primary cultures of anterior pituitary cells from ovariectomised (OVX) rats. Also, the in vivo administration of E(2) decreases LPS-induced NF-κB/p65 and p50 nuclear translocation. To investigate whether the inhibition of NF-κB pathway sensitises anterior pituitary cells to pro-apoptotic stimuli, we used an inhibitor of NF-κB activity, BAY 11-7082 (BAY). BAY, at a concentration that fails to induce apoptosis, has permissive action on TNF-α-induced apoptosis of lactotrophs and somatotrophs from OVX rats, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Pharmacological inhibition of NF-κB signalling enhances E(2)-sensitising effect to TNF-α-induced apoptosis in lactotrophs but not in somatotrophs. In vivo administration of BAY allowed LPS-induced apoptosis in anterior pituitary cells from OVX rats (determined by fluorescence activated cell sorting). Furthermore, LPS-induced expression of Bcl-xL in pituitaries of OVX rats is decreased by E(2) administration. Our results show that inhibition of the NF-κB signalling pathway sensitises anterior pituitary cells to the pro-apoptotic action of LPS and TNF-α. Because E(2) inhibits LPS- and TNF-α-activated NF-κB nuclear translocation, the present study suggests that E(2) sensitises anterior pituitary cells to TNF-α- and LPS-induced apoptosis by inhibiting NF-κB activity.

Distinct transcriptional regulation of human large conductance voltage- and calcium-activated K+ channel gene (hSlo1) by activated estrogen receptor alpha and c-Src tyrosine kinase

Estrogen receptor α (ERα) regulates gene transcription via "genomic" (binding directly or indirectly, typically via Sp1 or AP-1 sites, to target genes) and/or "nongenomic" (signaling) mechanisms. ERα activation by estrogen up-regulates the murine Ca(2+)-activated K(+) channel α subunit gene (mSlo1) via genomic mechanisms. Here, we investigated whether ERα also drives transcription of the human (hSlo1) gene. Consistent with this view, estrogen increased hSlo1 transcript levels in primary human smooth muscle cells. Promoter studies revealed that estrogen/hERα-mediated hSlo1 transcription was nearly 6-fold more efficient than for mSlo1 (EC(50), 0.07 versus 0.4 nM). Unlike the genomic transcriptional mechanism employed by mSlo1, hSlo1 exhibits a nongenomic hERα-mediated regulatory mechanism. This is supported by the following: 1) efficient hSlo1 transcription after disruption of the DNA-binding domain of hERα or knockdown of Sp1, and 2) lack of AP-1 sites in the hSlo1 promoter. Three nongenomic signaling pathways were explored: Src, Rho, and PI3K. Inhibition of Src with 10 μM PP2, and reported downstream ERK with 25 μM PD98059 did not prevent estrogen action but caused an increase in hSlo1 basal transcription; conversely, constitutively active c-Src (Y527F) decreased hSlo1 basal transcription even preventing its estrogen/hERα-mediated transcriptional activation. Rho inhibition by coexpressed Clostridium botulinum C3 transferase did not alter estrogen action. In contrast, inhibition of PI3K activity with 10 μM LY294002 decreased estrogen-stimulated hSlo1 transcription by ∼40%. These results indicate that the nongenomic PI3K signaling pathway plays a role in estrogen/hERα-stimulated hSlo1 gene expression; whereas c-Src activity leads to hSlo1 gene tonic repression independently of estrogen, likely through ERK activation.

Activation of the immune response is a key feature of aging in mice

The process of aging is complex involving numerous factors centered on transcriptional changes with advanced age. This study was aimed at elucidating mechanisms involved in mouse aging by conducting both gene expression and biochemical analyses on isolated mouse brain, heart and kidney. The gene expression analysis was not aimed at solely highlighting age-related transcriptional changes but also revealing regulated biological processes, cellular compartments, signaling and metabolic pathways. We have uncovered a conserved increase in the expression of genes mediating immune responses in all the tissues analyzed. In addition, elevated levels of lipid hydroperoxides (LPO)—an indicator of increased levels of radical oxygen species, implicate an oxidative stress-mediated activity of NF-kB signaling. In summary, these results suggest that transcriptional changes are most probably the downstream effect of environmental and endogenous factors constantly affecting the organism during its lifetime. In addition, we propose LPO as a potential biomarker of aging.

Clinical significance of nuclear factor κB expression in primary gastrointestinal diffuse large B-cell lymphoma

AIM: To investigate the clinical significance of nuclear factor κB (NF-κB) expression in primary gastrointestinal diffuse large B-cell lymphoma (PGI-DLBCL).

METHODS: Immunohistochemical staining was used to detect the expression of CD10, Bcl-6, Mum-1 and NF-κB p65 in PGI-DLBCL. The relationship of NF-κB p65 expression with tumor subtype, biological behavior and prognosis was analyzed.

RESULTS: Of 54 cases of PGI-DLBCL detected, 28% were positive for CD10, 69% positive for Bcl-6, and 81% positive for Mum-1; 19 were classified as germinal center B-cell-like (GCB) subtype, and 35 as activated B-cell like (ABC) subtype. The positive rate of NF-κB p65 expression in PGI-DLBCL was 72% (39/54). The positive rate of NF-κB p65 expression was significantly higher in ABC-DLBCL than in GCB-DLBCL (74.4% vs 25.6%, P < 0.05). NF-κB p65 expression was correlated with extranodal invasion site in PGI-DLBCL (P < 0.05). The overall survival time of NF-κB p65-negative PGI-DLBCL patients was longer than that of NF-κB p65-positive ones (45.8 mo ± 35.9 mo vs 20.3 mo ± 29.3 mo, P < 0.05).

CONCLUSION: NF-κB p65 expression was positively correlated with the subtype, development, and invasion of PGI-DLBCL. NF-κB p65 can be used as a prognostic factor for PGI-DLBCL and may represent a new molecular target for the therapy of GI-DLBCL.

Effect of ligand-activated estrogen receptor β on lymphoma growth in vitro and in vivo

Estrogen receptor β (ERβ) is expressed in immune cells and studies have suggested an antiproliferative function of ERβ. We detected ERβ expression in murine T- and human B-cell lymphoma cell lines and analyzed the effects of estradiol and selective ERβ agonists on lymphoma growth in culture and in vivo. Treating the cells with estradiol had minor effects on cell growth, whereas the selective ERβ agonists diarylpropionitrile (DPN) and KB9520 showed a strong antiproliferative effect. When grafting mice with murine T-cell lymphoma cells, male mice developed larger tumors compared with female mice, a difference that was abolished following ovariectomy, showing estrogen-dependent growth in vivo. To investigate whether lymphoma growth may be inhibited in vivo by ERβ agonist treatment, mice grafted with murine lymphoma cells were treated with DPN or KB9520. Both ERβ-selective agonists strongly inhibited lymphoma growth. The reduced tumor size seen following either DPN or KB9520 treatment was due to reduced proliferation and increased apoptosis. Our results show an ERβ ligand-dependent antiproliferative effect of lymphoma cells expressing endogenous ERβ and that lymphoma cell growth in vivo can efficiently be inhibited by ERβ agonists. This suggests that ERβ agonists may be useful in the treatment of lymphomas.

Role of NF-κB in the skeleton

Since the discovery that deletion of the NF-κB subunits p50 and p52 causes osteopetrosis in mice, there has been considerable interest in the role of NF-κB signaling in bone. NF-κB controls the differentiation or activity of the major skeletal cell types - osteoclasts, osteoblasts, osteocytes and chondrocytes. However, with five NF-κB subunits and two distinct activation pathways, not all NF-κB signals lead to the same physiologic responses. In this review, we will describe the roles of various NF-κB proteins in basal bone homeostasis and disease states, and explore how NF-κB inhibition might be utilized therapeutically.

Endocrine disrupting chemicals targeting estrogen receptor signaling: identification and mechanisms of action

Many endocrine disrupting chemicals (EDCs) adversely impact estrogen signaling by interacting with two estrogen receptors (ERs): ERα and ERβ. Though the receptors have similar ligand binding and DNA binding domains, ERα and ERβ have some unique properties in terms of ligand selectivity and target gene regulation. EDCs that target ER signaling can modify genomic and nongenomic ER activity through direct interactions with ERs, indirectly through transcription factors such as the aryl hydrocarbon receptor (AhR), or through modulation of metabolic enzymes that are critical for normal estrogen synthesis and metabolism. Many EDCs act through multiple mechanisms as exemplified by chemicals that bind both AhR and ER, such as 3-methylcholanthrene. Other EDCs that target ER signaling include phytoestrogens, bisphenolics, and organochlorine pesticides, and many alter normal ER signaling through multiple mechanisms. EDCs can also display tissue-selective ER agonist and antagonist activities similar to selective estrogen receptor modulators (SERMs) designed for pharmaceutical use. Thus, biological effects of EDCs need to be carefully interpreted because EDCs can act through complex tissue-selective modulation of ERs and other signaling pathways in vivo. Current requirements by the U.S. Environmental Protection Agency require some in vitro and cell-based assays to identify EDCs that target ER signaling through direct and metabolic mechanisms. Additional assays may be useful screens for identifying EDCs that act through alternative mechanisms prior to further in vivo study.

Central effects of estradiol in the regulation of food intake, body weight, and adiposity

In recent years, obesity and its associated health disorders and costs have increased. Accumulation of adipose tissue, or fat, in the intra-abdominal adipose depot is associated with an increased risk of developing cardiovascular problems, type-2 diabetes mellitus, certain cancers, and other disorders like the metabolic syndrome. Males and females differ in terms of how and where their body fat is stored, in their hormonal secretions, and in their neural responses to signals regulating weight and body fat distribution. Men and post-menopausal women accumulate more fat in their intra-abdominal depots than pre-menopausal women, resulting in a greater risk of developing complications associated with obesity. The goal of this review is to discuss the current literature on sexual dimorphisms in body weight regulation, adipose tissue accrual and deposition.

Proinflammatory cytokines enhance estrogen-dependent expression of the multidrug transporter gene ABCG2 through estrogen receptor and NF{kappa}B cooperativity at adjacent response elements

Constitutive activation of NFκB in estrogen receptor (ER)-positive breast cancer is associated with tumor recurrence and development of anti-estrogen resistance. Furthermore, a gene expression signature containing common targets for ER and NFκB has been identified and found to be associated with the more aggressive luminal B intrinsic subtype of ER-positive breast tumors. Here, we describe a novel mechanism by which ER and NFκB cooperate to up-regulate expression of one important gene from this signature, ABCG2, which encodes a transporter protein associated with the development of drug-resistant breast cancer. We and others have confirmed that this gene is regulated primarily by estrogen in an ER- and estrogen response element (ERE)-dependent manner. We found that whereas proinflammatory cytokines have little effect on this gene in the absence of 17β-estradiol, they can potentiate ER activity in an NFκB-dependent manner. ER allows the NFκB family member p65 to access a latent NFκB response element located near the ERE in the gene promoter. NFκB recruitment to the gene is, in turn, required to stabilize ER occupancy at the functional ERE. The result of this cooperative binding of ER and p65 at adjacent response elements leads to a major increase in both ABCG2 mRNA and protein expression. These findings indicate that estrogen and inflammatory factors can modify each other's activity through modulation of transcription factor accessibility and/or occupancy at adjacent response elements. This novel transcriptional mechanism could have important implications in breast cancer, where both inflammation and estrogen can promote cancer progression.

Novel functions for NFκB: inhibition of bone formation

NFκB is a family of transcription factors involved in immunity and the normal functioning of many tissues. It has been well studied in osteoclasts, and new data indicate an important role for NFκB in the negative regulation of bone formation. In this article, we discuss how NFκB activation affects osteoblast function and bone formation. In particular, we describe how reduced NFκB activity in osteoblasts results in an increase in bone formation via enhanced c-Jun N-terminal kinase (JNK) activity, which regulates FOSL1 (also known as Fra1) expression. Furthermore, we discuss how estrogen and NFκB crosstalk in osteoblasts acts to oppositely regulate bone formation. Future NFκB-targeting treatments for osteoporosis, rheumatoid arthritis and other inflammatory bone diseases could lead to increased bone formation concurrent with decreased bone resorption.

Oxidative stress stimulates apoptosis and activates NF-kappaB in osteoblastic cells via a PKCbeta/p66shc signaling cascade: counter regulation by estrogens or androgens

Aging or acute loss of estrogens or androgens increases the levels of reactive oxygen species, activates nuclear factor-κB (NF-κB), and promotes the phosphorylation of p66(shc), a redox enzyme that amplifies mitochondrial reactive oxygen species generation and stimulates apoptosis. We report that in mesenchymal progenitor and osteoblastic cell models, H(2)O(2) activated a protein kinase C (PKC)β/p66(shc)/NF-κB signaling cascade and that p66(shc) was an essential mediator of the stimulating effects of H(2)O(2) on the apoptosis of osteoblastic cells as well as their ability to activate NF-κB. 17β-Estradiol (E(2)) or the nonaromatizable androgen dihydrotestosterone abrogated the effects of H(2)O(2) on p66(shc) and NF-κB activation by attenuating the phosphorylation of the redox-sensitive cytoplasmic kinase PKCβ. Additionally, both E(2) and dihydrotestosterone prevented H(2)O(2)-induced apoptosis by a mechanism that involved attenuation of p66(shc) resulting from decreased phosphorylation of PKCβ. Consistent with a kinase-mediated mechanism of sex steroid action, the effects of E(2) were reproduced by a polymeric form of estradiol that is not capable of stimulating the nuclear-initiated actions of ERα. These results demonstrate that p66(shc) is an essential mediator of the effects of oxidative stress on osteoblastic cell apoptosis, NF-κB activation, and cytokine production. The ability of either estrogen or androgen to attenuate the effects of oxidative stress on osteoblastic cell apoptosis, NF-κB activation, and cytokine production results from their common property to suppress PKCβ-induced p66(shc) phosphorylation via a mechanism that does not require stimulation of the nuclear-initiated actions of sex steroids.

Metabolic impact of sex hormones on obesity

Obesity and its associated health disorders and costs are increasing. Men and post-menopausal women have greater risk of developing complications of obesity than younger women. Within the brain, the hypothalamus is an important regulator of energy homeostasis. Two of its sub-areas, the ventrolateral portion of the ventral medial nucleus (VL VMN) and the arcuate (ARC) respond to hormones and other signals to control energy intake and expenditure. When large lesions are made in the hypothalamus which includes both the VL VMN and the ARC, animals eat more, have reduced energy expenditure, and become obese. The ARC and the VL VMN, in addition to other regions in the hypothalamus, have been demonstrated to contain estrogen receptors. There are two estrogen receptors, estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta). We and others have previously demonstrated that activation of ERalpha by estrogens reduces food intake and increases body weight. This review focuses on the relative contribution of activation of ERalpha by estrogens in the ARC and the VL VMN in the regulation of food intake and body weight. Additionally, estrogen receptors have been found in many peripheral tissues including adipose tissue. Estrogens are thought to have direct effects on adipose tissue and estrogens may provide anti-inflammatory properties both in the periphery and the in the central nervous system (CNS) which may protect women from diseases associated with inflammation. Understanding the mechanisms by which estrogens regulate body weight and inflammation will assist in determining potential therapeutic agents for menopausal women to decrease the propensity of diseases associated with obesity.

Inhibiting NF-κB activation by small molecules as a therapeutic strategy

Because nuclear factor-κB (NF-κB) is a ubiquitously expressed proinflammatory transcription factor that regulates the expression of over 500 genes involved in cellular transformation, survival, proliferation, invasion, angiogenesis, metastasis, and inflammation, the NF-κB signaling pathway has become a potential target for pharmacological intervention. A wide variety of agents can activate NF-κB through canonical and noncanonical pathways. Canonical pathway involves various steps including the phosphorylation, ubiquitination, and degradation of the inhibitor of NF-κB (IκBα), which leads to the nuclear translocation of the p50-p65 subunits of NF-κB followed by p65 phosphorylation, acetylation and methylation, DNA binding, and gene transcription. Thus, agents that can inhibit protein kinases, protein phosphatases, proteasomes, ubiquitination, acetylation, methylation, and DNA binding steps have been identified as NF-κB inhibitors. Because of the critical role of NF-κB in cancer and various chronic diseases, numerous inhibitors of NF-κB have been identified. In this review, however, we describe only small molecules that suppress NF-κB activation, and the mechanism by which they block this pathway.

Influence of selective estrogen receptor modulators on interleukin-6 expression in human retinal pigment epithelial cells (ARPE-19)

Since estrogen and selective estrogen receptor modulators can inhibit inflammatory responses, we studied the regulatory role of several selective estrogen receptor modulators on interleukin-6 (IL-6) expression in human retinal pigment epithelial cells (ARPE-19). ARPE-19 cells were exposed to lipopolysaccharide with simultaneous exposure to different selective estrogen receptor modulators with the secretion of IL-6 cytokine being analyzed by enzyme-linked immunosorbent assay (ELISA). We demonstrate that 17beta-estradiol and HM-D, a novel selective estrogen receptor modulator compound, clearly reduced the IL-6 expression levels after lipopolysaccharide exposure in ARPE-19 cells. Molecular effects of selective estrogen receptor modulators and estrogen on the estrogen response element-mediated transcription were studied using MCF-7 and ARPE-19 cell lines carrying the estrogen response element-luciferase reporter gene. Estrogen and HM-D stimulated the activity of estrogen response element-reporter gene in MCF-7 cells but did not affect the activity in ARPE-19 cells. In addition, HM-D did not activate estrogen receptor alpha when studied by nuclear receptor peptide estrogen receptor alpha ELISA in ARPE-19 cells. These results indicate that estrogen and HM-D can suppress the lipopolysaccharide-induced inflammatory response but signalling is not mediated through estrogen response element transcription in human retinal pigment epithelial cells.

17Beta-estradiol inhibits IL-8 in cystic fibrosis by up-regulating secretory leucoprotease inhibitor

RATIONALE

An unexplained gender gap is observed in cystic fibrosis (CF). Females have poorer lung function, decreased survival, and earlier Pseudomonas colonization.

OBJECTIVES

To evaluate the effect of 17beta-estradiol (E(2)) on CF bronchial epithelial cells in vitro and in vivo.

METHODS

On exposure of CFBE41o- cultures to physiological concentrations of E(2), there was a significant dose-dependent inhibition of IL-8 release induced by toll-like receptor agonists, CF bronchoalveolar lavage fluid, or Pseudomonas-conditioned media. Estrogen receptor (ER)-alpha and -beta expression was quantified in cell lines and bronchial brushings from CF and non-CF patients.

MEASUREMENTS AND MAIN RESULTS

Both receptors were expressed in vitro and in vivo, although ERbeta expression was significantly higher in CF. Using ER isoform-specific agonists and antagonists, we established that ERbeta mediates the inhibition of CF bronchoalveolar lavage fluid-induced IL-8 release. We also showed that secretory leucoprotease inhibitor gene expression and protein localization to the nucleus increased in response to E(2). Secretory leucoprotease inhibitor knockdown abrogated the inhibitory effects of E(2).

CONCLUSIONS

E(2) inhibits IL-8 release by ERbeta in CF bronchial epithelial cells through up-regulation of secretory leucoprotease inhibitor, inhibition of nuclear factor (NF)-kappaB, and IL-8 gene expression. These data implicate a novel anti-inflammatory mechanism for E(2) in females with CF, which predisposes to infection and colonization. This could, in part, account for the observed gender dichotomy in CF.