Tamoxifen increases nuclear respiratory factor 1 transcription by activating estrogen receptor beta and AP-1 recruitment to adjacent promoter binding sites

Tamoxifen protects photoreceptors in the sodium iodate model

Because the selective estrogen receptor modulator tamoxifen was shown to be retina-protective in the light damage and rd10 models of retinal degeneration, the purpose of this study was to test whether tamoxifen is retina-protective in a model where retinal pigment epithelium (RPE) toxicity appears to be the primary insult: the sodium iodate (NaIO3) model. C57Bl/6J mice were given oral tamoxifen (in the diet) or the same diet lacking tamoxifen, then given an intraperitoneal injection of NaIO3 at 25 mg/kg. The mice were imaged a week later using optical coherence tomography (OCT). ImageJ with a custom macro was utilized to measure retinal thicknesses in OCT images. Electroretinography (ERG) was used to measure retinal function one week post-injection. After euthanasia, quantitative real-time PCR (qRT-PCR) was performed. Tamoxifen administration partially protected photoreceptors. There was less photoreceptor layer thinning in OCT images of tamoxifen-treated mice. qRT-PCR revealed, in the tamoxifen-treated group, less upregulation of antioxidant and complement factor 3 mRNAs, and less reduction in the rhodopsin and short-wave cone opsin mRNAs. Furthermore, ERG results demonstrated preservation of photoreceptor function for the tamoxifen-treated group. Cone function was better protected than rods. These results indicate that tamoxifen provided structural and functional protection to photoreceptors against NaIO3. RPE cells were not protected. These neuroprotective effects suggest that estrogen-receptor modulation may be retina-protective. The fact that cones are particularly protected is intriguing given their importance for human visual function and their survival until the late stages of retinitis pigmentosa. Further investigation of this protective pathway could lead to new photoreceptor-protective therapeutics.

Nuclear respiratory factor 1 protects H9C2 cells against hypoxia-induced apoptosis via the death receptor pathway and mitochondrial pathway

Hypoxia-induced cardiomyocyte apoptosis is one of the leading causes of heart failure. Nuclear respiratory factor 1 (NRF-1) was suggested as a protector against cell apoptosis; However, the mechanism is not clear. Therefore, the aim of this study was to elucidate the role of NRF-1 in hypoxia-induced H9C2 cardiomyocyte apoptosis and to explore its effect on regulating the death receptor pathway and mitochondrial pathway. NRF-1 was overexpressed or knocked down in H9C2 cells, which were then exposed to a hypoxia condition for 0, 3, 6, 12, and 24 h. Changes in cell proliferation, cell viability, reactive oxygen species (ROS) generation, and mitochondrial membrane potential (MMP) were investigated. The activities of caspase-3, -8, and -9, apoptosis rate, and the gene and protein expression levels of the death receptor pathway and mitochondrial pathway were analyzed. Under hypoxia exposure, NRF-1 overexpression improved the proliferation and viability of H9C2 cells and decreased ROS generation, MMP loss, caspase activities, and the apoptosis rate. However, the NRF-1 knockdown group showed the opposite results. Additionally, NRF-1 upregulated the expression of antiapoptotic molecules involved in the death receptor and mitochondrial pathways, such as CASP8 and FADD-like apoptosis regulator, B-cell lymphoma 2, B-cell lymphoma-extra-large, and cytochrome C. Conversely, the expression of proapoptotic molecules, such as caspase-8, BH3-interacting domain death agonist, Bcl-2-associated X protein, caspase-9, and caspase-3 was downregulated by NRF-1 overexpression in hypoxia-induced H9C2 cells. These results suggest that NRF-1 functions as an antiapoptotic factor in the death receptor and mitochondrial pathways to mitigate hypoxia-induced apoptosis in H9C2 cardiomyocytes.

Screening of potential oestrogen receptor α agonists in pesticides via in silico, in vitro and in vivo methods

In modern agricultural management, the use of pesticides is indispensable. Due to their massive use worldwide, pesticides represent a latent risk to both humans and the environment. In the present study, 1056 frequently used pesticides were screened for oestrogen receptor (ER) agonistic activity by using in silico methods. We found that 72 and 47 pesticides potentially have ER agonistic activity by the machine learning methods random forest (RF) and deep neural network (DNN), respectively. Among endocrine-disrupting chemicals (EDCs), 14 have been reported as EDCs or ER agonists by previous studies. We selected 3 reported and 7 previously unreported pesticides from 76 potential ER agonists to further assess ERα agonistic activity. All 10 selected pesticides exhibited ERα agonistic activity in human cells or zebrafish. In the dual-luciferase reporter gene assays, six pesticides exhibited ERα agonistic activity. Additionally, nine pesticides could induce mRNA expression of the pS2 and NRF1 genes in MCF-7 cells, and seven pesticides could induce mRNA expression of the vtg1 and vtg2 genes in zebrafish. Importantly, the remaining 48 out of 76 potential ER agonists, none of which have previously been reported to have endocrine-disrupting effects or oestrogenic activity, should be of great concern. Our screening results can inform environmental protection goals and play an important role in environmental protection and early warnings to human health.

The role of estrogen receptor beta in breast cancer

Breast cancer, a malignant tumor originating from mammary epithelial tissue, is the most common cancer among women worldwide. Challenges facing the diagnosis and treatment of breast cancer necessitate the search for new mechanisms and drugs to improve outcomes. Estrogen receptor (ER) is considered to be important for determining the diagnosis and treatment strategy. The discovery of the second estrogen receptor, ERβ, provides an opportunity to understand estrogen action. The emergence of ERβ can be traced back to 1996. Over the past 20 years, an increasing body of evidence has implicated the vital effect of ERβ in breast cancer. Although there is controversy among scholars, ERβ is generally thought to have antiproliferative effects in disease progression. This review summarizes available evidence regarding the involvement of ERβ in the clinical treatment and prognosis of breast cancer and describes signaling pathways associated with ERβ. We hope to highlight the potential of ERβ as a therapeutic target.

Impaired autophagic and mitochondrial functions are partially restored by ERT in Gaucher and Fabry diseases

The major cellular clearance pathway for organelle and unwanted proteins is the autophagy-lysosome pathway (ALP). Lysosomes not only house proteolytic enzymes, but also traffic organelles, sense nutrients, and repair mitochondria. Mitophagy is initiated by damaged mitochondria, which is ultimately degraded by the ALP to compensate for ATP loss. While both systems are dynamic and respond to continuous cellular stressors, most studies are derived from animal models or cell based systems, which do not provide complete real time data about cellular processes involved in the progression of lysosomal storage diseases in patients. Gaucher and Fabry diseases are rare sphingolipid disorders due to the deficiency of the lysosomal enzymes; glucocerebrosidase and α-galactosidase A with resultant lysosomal dysfunction. Little is known about ALP pathology and mitochondrial function in patients with Gaucher and Fabry diseases, and the effects of enzyme replacement therapy (ERT). Studying blood mononuclear cells (PBMCs) from patients, we provide in vivo evidence, that regulation of ALP is defective. In PBMCs derived from Gaucher patients, we report a decreased number of autophagic vacuoles with increased cytoplasmic localization of LC3A/B, accompanied by lysosome accumulation. For both Gaucher and Fabry diseases, the level of the autophagy marker, Beclin1, was elevated and ubiquitin binding protein, SQSTM1/p62, was decreased. mTOR inhibition did not activate autophagy and led to ATP inhibition in PBMCs. Lysosomal abnormalities, independent of the type of the accumulated substrate suppress not only autophagy, but also mitochondrial function and mTOR signaling pathways. ERT partially restored ALP function, LC3-II accumulation and decreased LC3-I/LC3-II ratios. Levels of lysosomal (LAMP1), autophagy (LC3), and mitochondrial markers, (Tfam), normalized after ERT infusion. In conclusion, there is mTOR pathway dysfunction in sphingolipidoses, as observed in both PBMCs derived from patients with Gaucher and Fabry diseases, which leads to impaired autophagy and mitochondrial stress. ERT partially improves ALP function.

Estrogens regulate life and death in mitochondria

Estrogens coordinate and integrate cellular metabolism and mitochondrial activities by direct and indirect mechanisms mediated by differential expression and localization of estrogen receptors (ER) in a cell-specific manner. Estrogens regulate transcription and cell signaling pathways that converge to stimulate mitochondrial function- including mitochondrial bioenergetics, mitochondrial fusion and fission, calcium homeostasis, and antioxidant defense against free radicals. Estrogens regulate nuclear gene transcription by binding and activating the classical genomic estrogen receptors α and β (ERα and ERβ) and by activating plasma membrane-associated mERα, mERβ, and G-protein coupled ER (GPER, GPER1). Localization of ERα and ERβ within mitochondria and in the mitochondrial membrane provides additional mechanisms of regulation. Here we review the mechanisms of rapid and longer-term effects of estrogens and selective ER modulators (SERMs, e.g., tamoxifen (TAM)) on mitochondrial biogenesis, morphology, and function including regulation of Nuclear Respiratory Factor-1 (NRF-1, NRF1) transcription. NRF-1 is a nuclear transcription factor that promotes transcription of mitochondrial transcription factor TFAM (mtDNA maintenance factorFA) which then regulates mtDNA-encoded genes. The nuclear effects of estrogens on gene expression directly controlling mitochondrial biogenesis, oxygen consumption, mtDNA transcription, and apoptosis are reviewed.

Nuclear respiratory factor 1 promotes spheroid survival and mesenchymal transition in mammary epithelial cells

Epithelial cells aggregate into spheroids when deprived of matrix, and the proclivity for spheroid formation and survival is a hallmark of normal and tumorigenic mammary stem cells. We show here that Nuclear Respiratory Factor 1 (NRF1) is a spheroid promoter by in silico identification of this transcription factor as highly connected to top shRNA-hits deduced from re-iterative selections for shRNAs enriched in MCF10A spheroids. NRF1-promoted spheroid survival is linked to its stimulation of mitochondrial OXPHOS, cell migration, invasion, and mesenchymal transition. Conversely, NRF1 knockdown in breast cancer MDA-MB-231 cells reduced spheroids, migration, invasion, and mesenchymal marker expression. NRF1 knockdown also reduced tumor burden in mammary fat pads and lungs of orthotopic- or tail vein-transplanted mice. With the Luminal A subtype of breast cancer, higher NRF1 expression is associated with lower survival. These results show that NRF1, an activator of mitochondrial metabolism, supports mammary spheroid survival and tumor development.

Tributyltin induces epigenetic changes and decreases the expression of nuclear respiratory factor-1

Tributyltin (TBT), a common organotin environmental pollutant, has been widely used as a component of marine antifouling paints. We previously reported that exposure to TBT inhibits the expression and DNA binding of nuclear respiratory factor-1 (NRF-1) and causes neurotoxicity. In the present study, we focused on the epigenetic effects of TBT and investigated whether TBT decreases NRF-1 expression via epigenetic modifications in SH-SY5Y human neuroblastoma cells. First, we found that exposure to 300 nM TBT decreases NRF-1 expression. We examined epigenetic changes induced by TBT, and showed that TBT causes hypermethylation of the NRF-1 promoter region, increases the amount of methyl-CpG-binding protein 2 (MeCP2) bound to the NRF-1 promoter, and alters the expression of DNA methyltransferases and ten-eleven translocation (TET) demethylation enzymes. These results suggest that epigenetic changes play an important role in regulation of NRF-1 expression. Next, we investigated effect of NRF-1 expression decrease on cells, and TBT reduces mitochondrial membrane potential and overexpression of NRF-1 rescued this reduction in membrane potential. Thus, we suggested that NRF-1 is important for maintaining mitochondrial membrane potential. Our study indicates that TBT causes epigenetic changes such as hypermethylation, which increases recruitment of MeCP2 to the NRF-1 promoter and probably lead to decreased of NRF-1 expression and mitochondrial membrane potential. Therefore, this research provides new evidence of the epigenetic action caused by organotin.

Membrane estrogen receptor 1 is required for normal reproduction in male and female mice

Steroid hormones, acting through their cognate nuclear receptors, are critical for many reproductive and non-reproductive functions. Over the past two decades, it has become increasingly clear that in addition to cytoplasmic/nuclear steroid receptors that alter gene transcription when liganded, a small fraction of cellular steroid receptors are localized to the cell membranes, where they mediate rapid steroid hormone effects. 17β-Estradiol (E2), a key steroid hormone for both male and female reproduction, acts predominately through its main receptor, estrogen receptor 1 (ESR1). Most ESR1 is nuclear; however, 5-10% of ESR1 is localized to the cell membrane after being palmitoylated at cysteine 451 in mice. This review discusses reproductive phenotypes of a newly-developed mouse model with a C451A point mutation that precludes membrane targeting of ESR1. This transgenic mouse, termed the nuclear-only ESR1 (NOER) mouse, shows extensive male and female reproductive abnormalities and infertility despite normally functional nuclear ESR1 (nESR1). These results provide the first in vivo evidence that membrane-initiated E2/ESR1 signaling is required for normal male and female reproductive functions and fertility. Signaling mechanisms for membrane ESR1 (mESR1), as well as how mESR1 works with nESR1 to mediate estrogen effects, are still being established. We discuss some possible mechanisms by which mESR1 might facilitate nESR1 signaling, as well as the emerging evidence that mESR1 might be a major mediator of epigenetic effects of estrogens, which are potentially linked to various adult-onset pathologies.

Cytochrome c1 in ductal carcinoma in situ of breast associated with proliferation and comedo necrosis

It is well known that comedo necrosis is closely associated with an aggressive phenotype of ductal carcinoma in situ (DCIS) of human breast, but its molecular mechanisms remain largely unclear. Therefore, in this study, we first examined the gene expression profile of comedo DCIS based on microarray data and identified CYC1 as a gene associated with comedo necrosis. Cytochrome c1 (CYC1) is a subunit of complex III in the mitochondrial oxidative phosphorylation that is involved in energy production. However, the significance of CYC1 has not yet been examined in DCIS. We therefore immunolocalized CYC1 in 47 DCIS cases. CYC1 immunoreactivity was detected in 40% of DCIS cases, and the immunohistochemical CYC1 status was significantly associated with tumor size, nuclear grade, comedo necrosis, van Nuys classification, and Ki‐67 labeling index. Subsequent in vitro studies indicated that CYC1 was significantly associated with mitochondrial membrane potential in MCF10DCIS.com DCIS cells. Moreover, CYC1 significantly promoted proliferation activity of MCF10DCIS.com cells and the cells transfected with CYC1 siRNA decreased pro‐apoptotic caspase 3 activity under hypoxic or anoxic conditions. Considering that the center of DCIS is poorly oxygenated, these results indicate that CYC1 plays important roles in cell proliferation and comedo necrosis through the elevated oxidative phosphorylation activity in human DCIS.

Redox signalling to nuclear regulatory proteins by reactive oxygen species contributes to oestrogen-induced growth of breast cancer cells

Background:

17β-Oestradiol (E2)-induced reactive oxygen species (ROS) have been implicated in regulating the growth of breast cancer cells. However, the underlying mechanism of this is not clear. Here we show how ROS through a novel redox signalling pathway involving nuclear respiratory factor-1 (NRF-1) and p27 contribute to E2-induced growth of MCF-7 breast cancer cells.

Methods:

Chromatin immunoprecipitation, qPCR, mass spectrometry, redox western blot, colony formation, cell proliferation, ROS assay, and immunofluorescence microscopy were used to study the role of NRF-1.

Results:

The major novel finding of this study is the demonstration of oxidative modification of phosphatases PTEN and CDC25A by E2-generated ROS along with the subsequent activation of AKT and ERK pathways that culminated in the activation of NRF-1 leading to the upregulation of cell cycle genes. 17β-Oestradiol-induced ROS by influencing nuclear proteins p27 and Jab1 also contributed to the growth of MCF-7 cells.

Conclusions:

Taken together, our results present evidence in the support of E2-induced ROS-mediated AKT signalling leading to the activation of NRF-1-regulated cell cycle genes as well as the impairment of p27 activity, which is presumably necessary for the growth of MCF-7 cells. These observations are important because they provide a new paradigm by which oestrogen may contribute to the growth of breast cancer.

Bioenergetic differences between MCF-7 and T47D breast cancer cells and their regulation by oestradiol and tamoxifen

Oestrogen receptor α (ERα+) breast tumours rely on mitochondria (mt) to generate ATP. The goal of the present study was to determine how oestradiol (E2) and 4-hydroxytamoxifen (4-OHT) affect cellular bioenergetic function in MCF-7 and T47D ERα+ breast cancer cells in serum-replete compared with dextran-coated charcoal (DCC)-stripped foetal bovine serum (FBS)-containing medium ('serum-starved'). Serum-starvation reduced oxygen consumption rate (OCR), extracellular acidification rate (ECAR), ATP-linked OCR and maximum mt capacity, reflecting lower ATP demand and mt respiration. Cellular respiratory stateapparent was unchanged by serum deprivation. 4-OHT reduced OCR independent of serum status. Despite having a higher mt DNA/nuclear DNA ratio than MCF-7 cells, T47D cells have a lower OCR and ATP levels and higher proton leak. T47D express higher nuclear respiratory factor-1 (NRF-1) and NRF-1-regulated, nuclear-encoded mitochondrial transcription factor TFAM and cytochrome c, but lower levels of cytochrome c oxidase, subunit IV, isoform 1 (COX4, COX4I1). Mitochondrial reserve capacity, reflecting tolerance to cellular stress, was higher in serum-starved T47D cells and was increased by 4-OHT, but was decreased by 4-OHT in MCF-7 cells. These data demonstrate critical differences in cellular energetics and responses to 4-OHT in these two ERα+ cell lines, likely reflecting cancer cell avoidance of apoptosis.

Effect of nonpersistent pesticides on estrogen receptor, androgen receptor, and aryl hydrocarbon receptor

Nonpersistent pesticides are considered less harmful for the environment, but their impact as endocrine disruptors has not been fully explored. The pesticide Switch was applied to grape vines, and the maximum residue concentration of its active ingredients was quantified. The transactivation potential of the pesticides Acorit, Frupica, Steward, Reldan, Switch, Cantus, Teldor, and Scala and their active compounds (hexythiazox, mepanipyrim, indoxacarb, chlorpyrifos-methyl, cyprodinil, fludioxonil, boscalid, fenhexamid, and pyrimethanil) were tested on human estrogen receptor α (ERα), androgen receptor (AR) and arylhydrocarbon receptor (AhR) in vitro. Relative binding affinities of the pure pesticide constituents for AR and their effect on human breast cancer and prostate cancer cell lines were evaluated. Residue concentrations of Switch's ingredients were below maximum residue limits. Fludioxonil and fenhexamid were ERα agonists (EC50 -values of 3.7 and 9.0 μM, respectively) and had time-dependent effects on endogenous ERα-target gene expression (cyclin D1, progesterone receptor, and nuclear respiratory factor 1) in MCF-7 human breast cancer cells. Fludioxonil, mepanipyrim, cyprodinil, pyrimethanil, and chlorpyrifos-methyl were AhR-agonists (EC50 s of 0.42, 0.77, 1.4, 4.6, and 5.1 μM, respectively). Weak AR binding was shown for chlorpyrifos-methyl, cyprodinil, fenhexamid, and fludioxonil. Assuming a total uptake which does not take metabolism and clearance rates into account, our in vitro evidence suggests that pesticides could activate pathways affecting hormonal balance, even within permitted limits, thus potentially acting as endocrine disruptors.

Assessment of cytochrome C oxidase dysfunction in the substantia nigra/ventral tegmental area in schizophrenia

Perturbations in metabolism are a well-documented but complex facet of schizophrenia pathology. Optimal cellular performance requires the proper functioning of the electron transport chain, which is constituted by four enzymes located within the inner membrane of mitochondria. These enzymes create a proton gradient that is used to power the enzyme ATP synthase, producing ATP, which is crucial for the maintenance of cellular functioning. Anomalies in a single enzyme of the electron transport chain are sufficient to cause disruption of cellular metabolism. The last of these complexes is the cytochrome c oxidase (COX) enzyme, which is composed of thirteen different subunits. COX is a major site for oxidative phosphorylation, and anomalies in this enzyme are one of the most frequent causes of mitochondrial pathology. The objective of the present report was to assess if metabolic anomalies linked to COX dysfunction may contribute to substantia nigra/ventral tegmental area (SN/VTA) pathology in schizophrenia. We tested COX activity in postmortem SN/VTA from schizophrenia and non-psychiatric controls. We also tested the protein expression of key subunits for the assembly and activity of the enzyme, and the effect of antipsychotic medication on subunit expression. COX activity was not significantly different between schizophrenia and non-psychiatric controls. However, we found significant decreases in the expression of subunits II and IV-I of COX in schizophrenia. Interestingly, these decreases were observed in samples containing the entire rostro-caudal extent of the SN/VTA, while no significant differences were observed for samples containing only mid-caudal regions of the SN/VTA. Finally, rats chronically treated with antipsychotic drugs did not show significant changes in COX subunit expression. These findings suggest that COX subunit expression may be compromised in specific sub-regions of the SN/VTA (i.e. rostral regions), which may lead to a faulty assembly of the enzyme and a greater vulnerability to metabolic insult.

β-D-glucan inhibits endocrine-resistant breast cancer cell proliferation and alters gene expression

Endocrine therapies have been successfully used for breast cancer patients with estrogen receptor α (ERα) positive tumors, but ∼40% of patients relapse due to endocrine resistance. β-glucans are components of plant cell walls that have immunomodulatory and anticancer activity. The objective of this study was to examine the activity of β-D-glucan, purified from barley, in endocrine-sensitive MCF-7 versus endocrine-resistant LCC9 and LY2 breast cancer cells. β-D-glucan dissolved in DMSO but not water inhibited MCF-7 cell proliferation in a concentration-dependent manner as measured by BrdU incorporation with an IC₅₀ of ∼164±12 μg/ml. β-D-glucan dissolved in DMSO inhibited tamoxifen/endocrine-resistant LCC9 and LY2 cell proliferation with IC₅₀ values of 4.6±0.3 and 24.2±1.4 μg/ml, respectively. MCF-10A normal breast epithelial cells showed a higher IC₅₀ ∼464 μg/ml and the proliferation of MDA-MB-231 triple negative breast cancer cells was not inhibited by β-D-glucan. Concentration-dependent increases in the BAX/BCL2 ratio and cell death with β-D-glucan were observed in MCF-7 and LCC9 cells. PCR array analysis revealed changes in gene expression in response to 24-h treatment with 10 or 50 μg/ml β-D-glucan that were different between MCF-7 and LCC9 cells as well as differences in basal gene expression between the two cell lines. Select results were confirmed by quantitative real-time PCR demonstrating that β-D-glucan increased RASSF1 expression in MCF-7 cells and IGFBP3, CTNNB1 and ERβ transcript expression in LCC9 cells. Our data indicate that β-D-glucan regulates breast cancer-relevant gene expression and may be useful for inhibiting endocrine-resistant breast cancer cell proliferation.

Mitochondrial and sex steroid hormone crosstalk during aging

Decline in circulating sex steroid hormones accompanies several age-associated pathologies which may influence human healthspan. Mitochondria play important roles in biosynthesis of sex steroid hormones, and these hormones can also regulate mitochondrial function. Understanding the cross talk between mitochondria and sex steroid hormones may provide insights into the pathologies associated with aging. The aim of this review is to summarize the current knowledge regarding the interplay between mitochondria and sex steroid hormones during the aging process. The review describes the effect of mitochondria on sex steroid hormone production in the gonads, and then enumerates the contribution of sex steroid hormones on mitochondrial function in hormone responsive cells. Decline in sex steroid hormones and accumulation of mitochondrial damage may create a positive feedback loop that contributes to the progressive degeneration in tissue function during aging. The review further speculates whether regulation between mitochondrial function and sex steroid hormone action can potentially influence healthspan.

Estradiol and tamoxifen regulate NRF-1 and mitochondrial function in mouse mammary gland and uterus

Nuclear respiratory factor-1 (NRF-1) stimulates the transcription of nuclear-encoded genes that regulate mitochondrial (mt) genome transcription and biogenesis. We reported that estradiol (E2) and 4-hydroxytamoxifen (4-OHT) stimulate NRF-1 transcription in an estrogen receptor α (ERα)- and ERβ-dependent manner in human breast cancer cells. The aim of this study was to determine whether E2 and 4-OHT increase NRF-1 in vivo. Here, we report that E2 and 4-OHT increase NRF-1 expression in mammary gland (MG) and uterus of ovariectomized C57BL/6 mice in a time-dependent manner. E2 increased NRF-1 protein in the uterus and MG; however, in MG, 4-OHT increased Nrf1 mRNA but not protein. Chromatin immunoprecipitation assays revealed increased in vivo recruitment of ERα to the Nrf1 promoter and intron 3 in MG and uterus 6 h after E2 and 4-OHT treatment, commensurate with increased NRF-1 expression. E2- and 4-OHT-induced increases in NRF-1 and its target genes Tfam, Tfb1m, and Tfb2m were coordinated in MG but not in uterus due to uterine-selective inhibition of the expression of the NRF-1 coactivators Ppargc1a and Ppargc1b by E2 and 4-OHT. E2 transiently increased NRF-1 and PGC-1α nuclear staining while reducing PGC-1α in uterus. E2, not 4-OHT, activates mt biogenesis in MG and uterus in a time-dependent manner. E2 increased mt outer membrane Tomm40 protein levels in MG and uterus whereas 4-OHT increased Tomm40 only in uterus. These data support the hypothesis of tissue-selective regulation of NRF-1 and its downstream targets by E2 and 4-OHT in vivo.

Estrogen receptor α mediates proliferation of osteoblastic cells stimulated by estrogen and mechanical strain, but their acute down-regulation of the Wnt antagonist Sost is mediated by estrogen receptor β

Mechanical strain and estrogens both stimulate osteoblast proliferation through estrogen receptor (ER)-mediated effects, and both down-regulate the Wnt antagonist Sost/sclerostin. Here, we investigate the differential effects of ERα and -β in these processes in mouse long bone-derived osteoblastic cells and human Saos-2 cells. Recruitment to the cell cycle following strain or 17β-estradiol occurs within 30 min, as determined by Ki-67 staining, and is prevented by the ERα antagonist 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride. ERβ inhibition with 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-β]pyrimidin-3-yl] phenol (PTHPP) increases basal proliferation similarly to strain or estradiol. Both strain and estradiol down-regulate Sost expression, as does in vitro inhibition or in vivo deletion of ERα. The ERβ agonists 2,3-bis(4-hydroxyphenyl)-propionitrile and ERB041 also down-regulated Sost expression in vitro, whereas the ERα agonist 4,4′,4″-[4-propyl-(1H)-pyrazol-1,3,5-triyl]tris-phenol or the ERβ antagonist PTHPP has no effect. Tamoxifen, a nongenomic ERβ agonist, down-regulates Sost expression in vitro and in bones in vivo. Inhibition of both ERs with fulvestrant or selective antagonism of ERβ, but not ERα, prevents Sost down-regulation by strain or estradiol. Sost down-regulation by strain or ERβ activation is prevented by MEK/ERK blockade. Exogenous sclerostin has no effect on estradiol-induced proliferation but prevents that following strain. Thus, in osteoblastic cells the acute proliferative effects of both estradiol and strain are ERα-mediated. Basal Sost down-regulation follows decreased activity of ERα and increased activity of ERβ. Sost down-regulation by strain or increased estrogens is mediated by ERβ, not ERα. ER-targeting therapy may facilitate structurally appropriate bone formation by enhancing the distinct ligand-independent, strain-related contributions to proliferation of both ERα and ERβ.

DHEA metabolites activate estrogen receptors alpha and beta

Dehydroepiandrosterone (DHEA) levels were reported to associate with increased breast cancer risk in postmenopausal women, but some carcinogen-induced rat mammary tumor studies question this claim. The purpose of this study was to determine how DHEA and its metabolites affect estrogen receptors α or β (ERα or ERβ)-regulated gene transcription and cell proliferation. In transiently transfected HEK-293 cells, androstenediol, DHEA, and DHEA-S activated ERα. In ERβ transfected HepG2 cells, androstenedione, DHEA, androstenediol, and 7-oxo DHEA stimulated reporter activity. ER antagonists ICI 182,780 (fulvestrant) and 4-hydroxytamoxifen, general P450 inhibitor miconazole, and aromatase inhibitor exemestane inhibited activation by DHEA or metabolites in transfected cells. ERβ-selective antagonist R,R-THC (R,R-cis-diethyl tetrahydrochrysene) inhibited DHEA and DHEA metabolite transcriptional activity in ERβ-transfected cells. Expression of endogenous estrogen-regulated genes: pS2, progesterone receptor, cathepsin D1, and nuclear respiratory factor-1 was increased by DHEA and its metabolites in an ER-subtype, gene, and cell-specific manner. DHEA metabolites, but not DHEA, competed with 17β-estradiol for ERα and ERβ binding and stimulated MCF-7 cell proliferation, demonstrating that DHEA metabolites interact directly with ERα and ERβin vitro, modulating estrogen target genes in vivo.

Estrogen receptor-beta and breast cancer: translating biology into clinical practice

Estrogen receptor (ER) β was discovered over a decade ago. The design of most studies on this receptor was based on knowledge of its predecessor, ERα. Although breast cancer (BCa) has been a main focus of ERβ research, its precise roles in breast carcinogenesis remain elusive. Data from in vitro models have not always matched those from observational or clinical studies. Several inherent factors may contribute to these discrepancies: (a) several ERβ spliced variants are expressed at the protein level, and isoform-specific antibodies are unavailable for some variants; (b) post-translational modifications of the receptor regulate receptor functions; (c) the role of the receptor differs significantly depending on the type of ligands, cis-elements, and co-regulators that interact with the receptor; and (d) the diversity of distribution of the receptor among intracellular organelles of BCa cells. This review addresses the gaps in knowledge in ERβ research as it pertains to BCa regarding the following questions: (1) is ERβ a tumor suppressor in BCa?; (2) do ERβ isoforms play differential roles in breast carcinogenesis?; (3) do nuclear signaling and extranuclear ERβ signaling differ in BCa?; (4) what are the consequences of post-translational modifications of ERβ in BCa?; (5) how do co-regulators and interacting proteins increase functional diversity of ERβ?; and (6) how do the types of ligand and regulatory cis-elements affect the action of ERβ in BCa?. Insights gained from these key questions in ERβ research should help in prevention, diagnosis/prognosis, and treatment of BCa.

Diesel exhaust particulate extracts inhibit transcription of nuclear respiratory factor-1 and cell viability in human umbilical vein endothelial cells

Endothelial dysfunction precedes cardiovascular disease and is accompanied by mitochondrial dysfunction. Here we tested the hypothesis that diesel exhaust particulate extracts (DEPEs), prepared from a truck run at different speeds and engine loads, would inhibit genomic estrogen receptor activation of nuclear respiratory factor-1 (NRF-1) transcription in human umbilical vein endothelial cells (HUVECs). Additionally, we examined how DEPEs affect NRF-1-regulated TFAM expression and, in turn, Tfam-regulated mtDNA-encoded cytochrome c oxidase subunit I (COI, MTCO1) and NADH dehydrogenase subunit I (NDI) expression as well as cell proliferation and viability. We report that 17β-estradiol (E(2)), 4-hydroxytamoxifen (4-OHT), and raloxifene increased NRF-1 transcription in HUVECs in an ER-dependent manner. DEPEs inhibited NRF-1 transcription, and this suppression was not ablated by concomitant treatment with E(2), 4-OHT, or raloxifene, indicating that the effect was not due to inhibition of ER activity. While E(2) increased HUVEC proliferation and viability, DEPEs inhibited viability but not proliferation. Resveratrol increased NRF-1 transcription in an ER-dependent manner in HUVECs, and ablated DEPE inhibition of basal NRF-1 expression. Given that NRF-1 is a key nuclear transcription factor regulating genes involved in mitochondrial activity and biogenesis, these data suggest that DEPEs may adversely affect mitochondrial function leading to endothelial dysfunction and resveratrol may block these effects.

Early life exposure to endocrine-disrupting chemicals causes lifelong molecular reprogramming of the hypothalamus and premature reproductive aging

Gestational exposure to the estrogenic endocrine disruptor methoxychlor (MXC) disrupts the female reproductive system at the molecular, physiological, and behavioral levels in adulthood. The current study addressed whether perinatal exposure to endocrine disruptors re-programs expression of a suite of genes expressed in the hypothalamus that control reproductive function and related these molecular changes to premature reproductive aging. Fischer rats were exposed daily for 12 consecutive days to vehicle (dimethylsulfoxide), estradiol benzoate (EB) (1 mg/kg), and MXC (low dose, 20 μg/kg or high dose, 100 mg/kg), beginning on embryonic d 19 through postnatal d 7. The perinatally exposed females were aged to 16-17 months and monitored for reproductive senescence. After euthanasia, hypothalamic regions [preoptic area (POA) and medial basal hypothalamus] were dissected for real-time PCR of gene expression or pyrosequencing to assess DNA methylation of the Esr1 gene. Using a 48-gene PCR platform, two genes (Kiss1 and Esr1) were significantly different in the POA of endocrine-disrupting chemical-exposed rats compared with vehicle-exposed rats after Bonferroni correction. Fifteen POA genes were up-regulated by at least 50% in EB or high-dose MXC compared with vehicle. To understand the epigenetic basis of the increased Esr1 gene expression, we performed bisulfite conversion and pyrosequencing of the Esr1 promoter. EB-treated rats had significantly higher percentage of methylation at three CpG sites in the Esr1 promoter compared with control rats. Together with these molecular effects, perinatal MXC and EB altered estrous cyclicity and advanced reproductive senescence. Thus, early life exposure to endocrine disruptors has lifelong effects on neuroendocrine gene expression and DNA methylation, together with causing the advancement of reproductive senescence.