Role of steroid hormone coregulators in health and disease

Modulation of neural gene networks by estradiol in old rhesus macaque females

The postmenopausal decrease in circulating estradiol (E2) levels has been shown to contribute to several adverse physiological and psychiatric effects. To elucidate the molecular effects of E2 on the brain, we examined differential gene expression and DNA methylation (DNAm) patterns in the nonhuman primate brain following ovariectomy (Ov) and subsequent E2 treatment. We identified several dysregulated molecular networks, including MAPK signaling and dopaminergic synapse response, that are associated with ovariectomy and shared across two different brain areas, the occipital cortex (OC) and prefrontal cortex (PFC). The finding that hypomethylation (p=1.6×10-51) and upregulation (p=3.8×10-3) of UBE2M across both brain regions, provide strong evidence for molecular differences in the brain induced by E2 depletion. Additionally, differential expression (p=1.9×10-4; interaction p=3.5×10-2) of LTBR in the PFC, provides further support for the role E2 plays in the brain, by demonstrating that the regulation of some genes that are altered by ovariectomy may also be modulated by Ov followed by hormone replacement therapy (HRT). These results present real opportunities to understand the specific biological mechanisms that are altered with depleted E2. Given E2's potential role in cognitive decline and neuroinflammation, our findings could lead to the discovery of novel therapeutics to slow cognitive decline. Together, this work represents a major step towards understanding molecular changes in the brain that are caused by ovariectomy and how E2 treatment may revert or protect against the negative neuro-related consequences caused by a depletion in estrogen as women approach menopause.

Modular Coculture to Reduce Substrate Competition and Off-Target Intermediates in Androstenedione Biosynthesis

Substrate competition within a metabolic network constitutes a common challenge in microbial biosynthesis system engineering, especially if indispensable enzymes can produce multiple intermediates from a single substrate. Androstenedione (4AD) is a central intermediate in the production of a series of steroidal pharmaceuticals; however, its yield via the coexpression of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17α-hydroxylase/17,20-lyase (CYP17A1) in a microbial chassis affords a nonlinear pathway in which these enzymes compete for substrates and produce structurally similar unwanted intermediates, thereby reducing 4AD yields. To avoid substrate competition, we split the competing 3β-HSD and CYP17A1 pathway components into two separate Yarrowia lipolytica strains to linearize the pathway. This spatial segregation increased substrate availability for 3β-HSD in the upstream strain, consequently decreasing the accumulation of the unwanted intermediate 17-hydroxypregnenolone (17OHP5) from 94.8 ± 4.4% in single-chassis monocultures to 24.8 ± 12.6% in cocultures of strains expressing 3β-HSD and CYP17A1 separately. Orthologue screening to increase CYP17A1 catalytic efficiency and the preferential production of desired intermediates increased the biotransformation capacity in the downstream pathway, further decreasing 17OHP5 accumulation to 3.9%. Furthermore, nitrogen limitation induced early 4AD accumulation (final titer, 7.71 mg/L). This study provides a framework for reducing intrapathway competition between essential enzymes during natural product biosynthesis as well as a proof-of-concept platform for linear steroid production.

Regulation of mineralocorticoid receptor activation by circadian protein TIMELESS

The mineralocorticoid receptor (MR) is a ligand-activated transcription factor that regulates cardiorenal physiology and disease. Ligand-dependent MR transactivation involves a conformational change in the MR and recruitment of coregulatory proteins to form a unique DNA-binding complex at the hormone response element in target gene promoters. Differences in the recruitment of coregulatory proteins can promote tissue-, ligand- or gene-specific transcriptional outputs. The goal of this study was to evaluate the circadian protein TIMELESS as a selective regulator of MR transactivation. TIMELESS has an established role in cell cycle regulation and DNA repair. TIMELESS may not be central to mammalian clock function and does not bind DNA; however, RNA and protein levels oscillate over 24 h. Co-expression of TIMELESS down-regulated MR transactivation of an MR-responsive reporter in HEK293 cells, yet enhanced transactivation mediated by other steroid receptors. TIMELESS markedly inhibited MR transactivation of synthetic and native gene promoters and expression of MR target genes in H9c2 cardiac myoblasts. Immunofluorescence showed aldosterone induces colocalisation of TIMELESS and MR, although a direct interaction was not confirmed by coimmunoprecipitation. Potential regulation of circadian clock targets cryptochrome 1 and 2 by TIMELESS was not detected. However, our data suggest that these effects may involve TIMELESS coactivation of oestrogen receptor alpha (ERα). Taken together, these data suggest that TIMELESS may contribute to MR transcriptional outputs via enhancing ERα inhibitory actions on MR transactivation. Given the variable expression of TIMELESS in different cell types, these data offer new opportunities for the development of MR modulators with selective actions.

Bioengineered polyester nanoparticles for the synergistic treatment of androgenic alopecia via the suppression of 5α-reductase and knockdown of androgen receptor

Androgenic alopecia (AGA) is a common disease that negatively affects patients’ physical and mental health. AGA can be treated with drugs that improve the perifollicular microenvironment, such as 5α-reductase inhibitors (e.g., dutasteride [DUT]), androgen receptor blockers, and minoxidil. However, the efficacy of these treatments is limited. Therefore, this study aimed to show that nanoparticles are effective as stable carriers with high curative benefits and little adverse effects. The in vitro study showed that PLGA-DUT/siAR@DPCM NPs could deliver both DUT and siAR to dermal papilla cells. They could successfully suppress 5α-reductase and knock down androgen receptor, respectively, and thereby promote cell proliferation. In the in vivo study, PLGA-DUT/siAR@DPCM NPs showed a significant therapeutic effect in an AGA mouse model. They successfully penetrated the stratum corneum and showed a clear targeting effect on hair follicles and surrounding tissues. PLGA-DUT/siAR@DPCM NPs could enable the targeted delivery of DUT and siAR through percutaneous penetration, enhancing phagocytosis and decreasing adverse effects. Thus, they have great potential in the clinical treatment of AGA.

Neuromodulating roles of estrogen and phytoestrogens in cognitive therapeutics through epigenetic modifications during aging

Estrogen (E2) plays important role in regulating hippocampal learning and memory. The decline of E2 after menopause affects learning and memory and increases the risk of neurodegenerative diseases like Alzheimer's disease (AD). Additionally, from the estrogen receptor (ER) mediated gene regulation; E2 also regulates gene expression at the transcriptional and posttranscriptional levels through epigenetic modifications. E2 recruits a number of proteins called co-regulators at the promoter region of genes. These co-regulators act as chromatin modifiers, alter DNA and histone modifications and regulate gene expression. Several studies show that E2 regulates learning and memory by altering chromatin at the promoters of memory-linked genes. Due to structural similarities with E2 and low side effects, phytoestrogens are now used as neuroprotective agents to recover learning and memory in animal models as well as human subjects during aging and different neurological disorders. Growing evidence suggests that apart from anti-oxidative and anti-inflammatory properties, phytoestrogens also act as epigenetic modifiers and regulate gene expression through epigenetic modifications. The epigenetic modifying properties of phytoestrogens are mostly studied in cancer cells but very little is known regarding the regulation of synaptic plasticity genes, learning and memory, and neurological disorders. In this article, we discuss the epigenetic modifying properties of E2 and the roles of phytoestrogens as epigenetic modifiers in the brain to recover and maintain cognitive functions.

Effect of dihydrotestosterone on melatonin secretion and the expression of melatonin receptors and apoptosis-related factors in sheep epididymides

Melatonin (MEL) is involved in homeostasis of the epididymis lumen environment. Dihydrotestosterone (DHT) partakes in the development of gonads and organs in male animals. However, whether MEL secretion, the expression of its receptors, MT1 and MT2, and sheep epididymal epithelial cell apoptosis is regulated by DHT remains unclear. In this study, we used immunohistochemical staining to detect the distribution patterns of DHT synthetases [5α-reductase (5α-red)] and its androgen receptor (AR) in sheep epididymides. 5α-red1, 5α-red2, and AR were positively expressed in sperm, epididymal epithelial cells, and the smooth muscle cells of the caput, corpus, and cauda regions of the epididymis. DHT concentration and the expression levels of 5α-red and AR in the caput, corpus, and cauda regions were measured by enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry, real-time quantitative polymerase chain reaction, and western blot analysis. DHT concentration in the caput was significantly higher than those in corpus and cauda, probably because of the high expression of 5α-red2 in the caput and secretion and transport of DHT by the testicles. DHT inhibited MEL secretion, the expression of its membrane receptors, and MEL synthetases in cultured sheep epididymal epithelial cells in vitro. In addition, the Bax/Bcl-2 ratio, ACT CASP3, and caspase-3 mRNA expression were also decreased. The decreasing effect was partially reversed after flutamide treatment. Therefore, DHT regulates sheep epididymal function by influencing MEL expression and apoptosis-related factors. This study provides basic data for further research on the reproductive physiology of male animals.

Androgen-induced epigenetic modulations in the ovary

In recent years, androgens have emerged as critical regulators of female reproduction and women's health in general. While high levels of androgens in women are associated with polycystic ovary syndrome (PCOS), recent evidence suggests that a certain amount of direct androgen action through androgen receptor is also essential for normal ovarian function. Moreover, prenatal androgen exposure has been reported to cause developmental reprogramming of the fetus that manifests into adult pathologies, supporting the Developmental Origins of Health and Disease (DOHaD) hypothesis. Therefore, it has become imperative to understand the underlying mechanism of androgen actions and its downstream effects under normal and pathophysiological conditions. Over the years, there has been a lot of studies on androgen receptor function as a transcriptional regulator in the nucleus as well as androgen-induced rapid extra-nuclear signaling. Conversely, new evidence suggests that androgen actions may also be mediated through epigenetic modulation involving both the nuclear and extra-nuclear androgen signaling. This review focuses on androgen-induced epigenetic modifications in female reproduction, specifically in the ovary, and discusses emerging concepts, latest perceptions, and highlight the areas that need further investigation.

Role of Steroid Hormones in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and may progress to cirrhosis or even hepatocellular carcinoma. A number of steroid hormones are important regulators of lipid homeostasis through fine tuning the expression of genes related to lipid synthesis, export, and metabolism. Dysregulation of such pathways has been implicated in the pathogenesis of NAFLD. The aim of this review is to clarify the potential impact of steroid hormones on NAFLD. We also highlight potential interventions through modulating steroid hormone levels or the activities of their cognate receptors as therapeutic strategies for preventing NAFLD.

Light-Driven Intermolecular Charge Transfer Induced Reactivity of Ethynylbenziodoxol(on)e and Phenols

Ethynylbenziodoxol(on)es (EBXs) have been widely used in organic synthesis as electrophilic alkyne-transfer reagents involving carbon- and heteroatom-based nucleophiles. However, potential reactions of EBXs with phenols remain uninvestigated. Here, we present the formation of ( Z)-2-iodovinyl phenyl ethers with excellent regio- and stereoselectivity through the reactivity between EBXs and phenols driven by visible light. We propose that this light-activated transformation proceeds through electron donor-acceptor complexes to enable new reactivity beyond existing mechanisms for alkynylation of carbon- and heteroatom-based nucleophiles. This operationally robust process was employed for the synthesis of diverse ( Z)-2-iodovinyl phenyl ethers through irradiating a solution containing a phenyl-EBX, a phenol, and the base Cs₂CO₃ with a commercially available blue LED at room temperature. The ( Z)-2-iodovinyl phenyl ether products can be further stereospecifically functionalized to form trisubstituted alkenes, demonstrating the potential of these products en route to chemical complexity.

Estrogen Receptor α- and β-Interacting Proteins Contain Consensus Secondary Structures: An Insilico Study

Background

Estrogen receptor (ER)α and ERβ are ligand-activated transcription factors that regulate gene expression by binding to estrogen-responsive elements and interacting with several coregulators through protein-protein interactions. Usually, these coregulators bind to the various conserved and functional domains of the receptor through a consensus LXXLL sequence, although variations can be found. The interaction of receptor domains and the consensus motif can be a possible target for nuclear receptor (NR) pharmacology, since modifications in these are responsible for possible pathogenesis of various diseases.

Purpose

The present study focuses on the secondary structure and conserved domains of the ERα and ERβ interacting proteins, using bioinformatics tools and their relation to the function of the coregulators.

Methods

Bioinformatics-based prediction tools like STRING, PSIPRED, PROTPARAM and Conserved Domain Database (CDD) were used. The prediction tools utilized in this study basically determines the characteristics of a possible coregulator by using an already existing protein as a template and determines the presence of any conserved consensus sequence. Coregulators have been enlisted with the help of NCBI, STRING and iHOP. The secondary structures were analyzed using PSIPRED and conserved domains were determined using CDD.

Results

The analysis of the structure has shown the presence of conserved domains and homology between the various coregulators. Each interacting protein contains conserved domains like the nuclear coactivators' domain, the helix-loop-helix domain and the SRC domain.

Conclusion

Such studies give the characteristic features of ERα and ERβ interacting proteins and maybe useful to determine their family and uses in NR pharmacology in health and diseases.

Amphiphilic derivatives of (3β,17β)-3-hydroxyandrost-5-ene-17-carboxylic acid

A series of amphiphilic derivatives of (3β,17β)-3-hydroxyandrost-5-ene-17-carboxylic acid (1) with the polyamine spermine and three other diamines, 1,2-diaminoethane, piperazine and cadaverine, were synthesized and their antimicrobial activity and cytotoxicity were investigated. Among the target compounds, several ones showed antimicrobial activity on Gram positive and Gram negative microorganisms. The most active compounds were 20 (Streptococcus mutans CCM 7409, 3.125 µM), 16 (Streptococcus mutans CCM 7409, 12.5 µM) and 10d (Escherichia coli CCM 3954, 12.5 µM). In addition, compounds 5d, 10d, 13 and 20 displayed cytotoxicity on CEM (12.1 ± 2.1 µM, 7.6 ± 1.0 µM, 19.0 ± 0.4 µM and 5.9 ± 0.7 µM, respectively). Two additional compounds displayed medium cytotoxicity on CEM, 5a (34.6 ± 5.2 µM) and 5c (37.7 ± 5.9 µM). The compound 13 and 20 displayed high toxicity also on normal fibroblasts.

Sex hormones and macronutrient metabolism

The biological differences between males and females are determined by a different set of genes and by a different reactivity to environmental stimuli, including the diet, in general. These differences are further emphasized and driven by the exposure to a different hormone flux throughout the life.

These differences have not been taken into appropriate consideration by the scientific community. Nutritional sciences are not immune from this “bias” and when nutritional needs are concerned, females are considered only when pregnant, lactating or when their hormonal profile is returning back to “normal,” i.e., to the male-like profile.

The authors highlight some of the most evident differences in aspects of biology that are associated with nutrition.

This review presents and describes available data addressing differences and similarities of the “reference man” vs. the “reference woman” in term of metabolic activity and nutritional needs. According to this assumption, available evidences of sex-associated differences of specific biochemical pathways involved in substrate metabolism are reported and discussed. The modulation by sexual hormones affecting glucose, amino acid and protein metabolism and the metabolization of nutritional fats and the distribution of fat depots, is considered targeting a tentative starting up background for a gender concerned nutritional science.

Progesterone and allopregnanolone in the central nervous system: response to injury and implication for neuroprotection

Progesterone is a well-known steroid hormone, synthesized by ovaries and placenta in females, and by adrenal glands in both males and females. Several tissues are targets of progesterone and the nervous system is a major one. Progesterone is also locally synthesized by the nervous system and qualifies, therefore, as a neurosteroid. In addition, the nervous system has the capacity to bio-convert progesterone into its active metabolite allopregnanolone. The enzymes required for progesterone and allopregnanolone synthesis are widely distributed in brain and spinal cord. Increased local biosynthesis of pregnenolone, progesterone and 5α-dihydroprogesterone may be a part of an endogenous neuroprotective mechanism in response to nervous system injuries. Progesterone and allopregnanolone neuroprotective effects have been widely recognized. Multiple receptors or associated proteins may contribute to the progesterone effects: classical nuclear receptors (PR), membrane progesterone receptor component 1 (PGRMC1), membrane progesterone receptors (mPR), and γ-aminobutyric acid type A (GABAA) receptors after conversion to allopregnanolone. In this review, we will succinctly describe progesterone and allopregnanolone biosynthetic pathways and enzyme distribution in brain and spinal cord. Then, we will summarize our work on progesterone receptor distribution and cellular expression in brain and spinal cord; neurosteroid stimulation after nervous system injuries (spinal cord injury, traumatic brain injury, and stroke); and on progesterone and allopregnanolone neuroprotective effects in different experimental models including stroke and spinal cord injury. We will discuss in detail the neuroprotective effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABAA receptors.

Revisiting the roles of progesterone and allopregnanolone in the nervous system: resurgence of the progesterone receptors

Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain.

A naturally occurring insertion of a single amino acid rewires transcriptional regulation by glucocorticoid receptor isoforms

In addition to guiding proteins to defined genomic loci, DNA can act as an allosteric ligand that influences protein structure and activity. Here we compared genome-wide binding, transcriptional regulation, and, using NMR, the conformation of two glucocorticoid receptor (GR) isoforms that differ by a single amino acid insertion in the lever arm, a domain that adopts DNA sequence-specific conformations. We show that these isoforms differentially regulate gene expression levels through two mechanisms: differential DNA binding and altered communication between GR domains. Our studies suggest a versatile role for DNA in both modulating GR activity and also in directing the use of GR isoforms. We propose that the lever arm is a "fulcrum" for bidirectional allosteric signaling, conferring conformational changes in the DNA reading head that influence DNA sequence selectivity, as well as conferring changes in the dimerization domain that connect functionally with remote regulatory surfaces, thereby influencing which genes are regulated and the magnitude of their regulation.

Synthesis of sex hormone-derived modified steroids possessing antiproliferative activity

During recent years intensive research has been focused on the synthesis of structurally modified steroid hormones in order to obtain compounds with beneficial biological activity such as cell-growth inhibition. Experimental results have revealed that some steroidal derivatives possess direct cytostatic effect on cancer cells in a hormone receptor-independent manner. After a brief account on the most important biological function and characteristics of the naturally occurring sex hormones in physiological and pathological conditions, structural modifications of estrane and androstane scaffolds are discussed in detail. The review covers literature publications (from 2002 to 2012) relating to the synthesis and antiproliferative activity of semisynthetic sex hormone-derived molecules containing simple or heterocyclic substituents. The compounds reviewed are divided into three main categories according to their sterane framework and the nature of substitution. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Mechanisms of endometrial progesterone resistance

Throughout the reproductive years, the rise and fall in ovarian hormones elicit in the endometrium waves of cell proliferation, differentiation, recruitment of inflammatory cells, apoptosis, tissue breakdown and regeneration. The activated progesterone receptor, a member of the superfamily of ligand-dependent transcription factors, is the master regulator of this intense tissue remodelling process in the uterus. Its activity is tightly regulated by interaction with cell-specific transcription factors and coregulators as well as by specific posttranslational modifications that respond dynamically to a variety of environmental and inflammatory signals. Endometriosis, a chronic inflammatory disorder, disrupts coordinated progesterone responses throughout the reproductive tract, including in the endometrium. This phenomenon is increasingly referred to as 'progesterone resistance'. Emerging evidence suggests that progesterone resistance in endometriosis is not just a consequence of perturbed progesterone signal transduction caused by chronic inflammation but associated with epigenetic chromatin changes that determine the intrinsic responsiveness of endometrial cells to differentiation cues.

Estrogen receptor β and its domains interact with casein kinase 2, phosphokinase C, and N-myristoylation sites of mitochondrial and nuclear proteins in mouse brain

The localization of estrogen receptor (ER)β in mitochondria suggests ERβ-dependent regulation of genes, which is poorly understood. Here, we analyzed the ERβ interacting mitochondrial as well as nuclear proteins in mouse brain using pull-down assay and matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS). In the case of mitochondria, ERβ interacted with six proteins of 35-152 kDa, its transactivation domain (TAD) interacted with four proteins of 37-172 kDa, and ligand binding domain (LBD) interacted with six proteins of 37-161 kDa. On the other hand, in nuclei, ERβ interacted with seven proteins of 30-203 kDa, TAD with ten proteins of 31-160 kDa, and LBD with fourteen proteins of 42-179 kDa. For further identification, these proteins were cleaved by trypsin into peptides and analyzed by MALDI-MS using mascot search engine, immunoprecipitation, immunoblotting, and far-Western blotting. To find the consensus binding motifs in interacting proteins, their unique tryptic peptides were analyzed by the motif scan software. All the interacting proteins were found to contain casein kinase (CK) 2, phosphokinase (PK)C phosphorylation, and N-myristoylation sites. These were further confirmed by peptide pull-down assays using specific mutations in the interacting sites. Thus, the present findings provide evidence for the interaction of ERβ with specific mitochondrial and nuclear proteins through consensus CK2, PKC phosphorylation, and N-myristoylation sites, and may represent an essential step toward designing selective ER modulators for regulating estrogen-mediated signaling.

Structural dynamics, intrinsic disorder, and allostery in nuclear receptors as transcription factors

Steroid hormone receptors (SHRs) and nuclear receptors (NRs) in general are flexible, allosterically regulated transcription factors. The classic model is inadequate to explain all their behavior. Keys to function are their regions of intrinsic disorder (ID). Data show the dynamic structure and allosteric interactions of the three classic SHR domains: ligand-binding (LBD), DNA-binding (DBD), and N-terminal (NTD). Each responds to its ligands by stabilizing its structure. The LBD responds to classic steroidal and nonsteroidal small ligands; both may selectively modify SHR activity. The DBD responds differentially to the DNA sequences of its response elements. The NTD, with its high ID content and AF1, interacts allosterically with the LBD and DBD. Each domain binds heterologous proteins, potential allosteric ligands. An ensemble framework improves the classic model, shows how ID regions poise the SHR/NR family for optimal allosteric response, and provides a basis for quantitative evaluation of SHR/NR actions.

Expression of Trk A and Src and their interaction with ERβ ligand binding domain show age and sex dependent alteration in mouse brain

Following the binding of estrogen to estrogen receptor (ER)β ligand binding domain (LBD) and its interaction with the target genes, a host of nuclear proteins is recruited to regulate the expression of specific genes(s). It is not known which proteins interact with ERβLBD and whether they vary with age and sex in the brain. Therefore, using pull down assay, immunoprecipitation and immunoblotting, we report that cell signaling molecules Trk A and Src interacted with ERβLBD, and showed alteration in the level of interaction and expression in the brain of AKR strain young (6 weeks), adult (25 weeks) and old (70 weeks) mice of both sexes. Trk A showed decreasing interaction with age, and lower expression in adult as compared to young and old males, whereas female mice exhibited decline in both interaction and expression as a function of age. On the other hand, Src interaction with ERβLBD decreased, but its expression increased with age in males, whereas the interaction and expression was lower in adult but higher in old as compared to young females. These findings suggest the implication of Trk A and Src in ERβ mediated brain functions and related disorders during aging.

Down-regulation of the histone methyltransferase EZH2 contributes to the epigenetic programming of decidualizing human endometrial stromal cells

Differentiation of human endometrial stromal cells (HESC) into decidual cells represents a highly coordinated process essential for embryo implantation. We show that decidualizing HESC down-regulate the histone methyltransferase enhancer of Zeste homolog 2 (EZH2), resulting in declining levels of trimethylation of histone 3 on lysine 27 (H3K27me3) at the proximal promoters of key decidual marker genes PRL and IGFBP1. Loss of H3K27me3 was associated with a reciprocal enrichment in acetylation of the same lysine residue, indicating active remodeling from repressive to transcriptionally permissive chromatin. Chromatin immunoprecipitation coupled with DNA microarray analysis demonstrated that decidualization triggers genome-wide changes in H3K27me3 distribution that only partly overlap those observed upon EZH2 knockdown in undifferentiated HESC. Gene ontology revealed that gain of the repressive H3K27me3 mark in response to decidualization and upon EZH2 knockdown in undifferentiated cells was enriched at the promoter regions of genes involved in transcriptional regulation and growth/cell proliferation, respectively. However, loss of the H3K27me3 mark (indicating increased chromatin accessibility) in decidualizing cells and upon EZH2 knockdown occurred at selective loci enriched for genes functionally implicated in responses to stimulus. In agreement, EZH2 knockdown in undifferentiated HESC was sufficient to augment the induction of decidual marker genes in response to cyclic AMP and progesterone signaling. Thus, loss of EZH2-dependent methyltransferase activity in the endometrium is integral to the process of chromatin remodeling that enables the transition from a proliferative to a decidual phenotype in response to differentiation cues.

AIB1 shows variation in interaction with ERβTAD and expression as a function of age in mouse brain

Estrogen mediates its multiple functions in the brain through the recruitment of a number of interacting proteins. In this paper, we report the identification of 160 kD interacting nuclear protein of estrogen receptor (ER)β-transactivation domain (TAD) as amplified in breast cancer 1(AIB1) by pull down assay, immunoblotting, far-western analysis and immunoprecipitation. Further we show the age dependent interaction and expression of AIB1 in the brain of young (6 weeks), adult (25 weeks) and old (70 weeks) AKR strain mice of both sexes. The immunoprecipitation data revealed higher interaction of AIB1 in young than adult and old male mice. In contrast, the interaction was low in young, increased in adult but decreased in old female. However, immunoblotting showed age related increase in the expression of AIB1 in both male and female mice. Further, the level of interaction of AIB1 with ERβTAD in young and old male was significantly higher than female of same age, whereas the expression of AIB1 in adult and old female was significantly higher than male of same age. These data suggest that such age dependent variation in the interaction of AIB1 with ERβTAD and its expression may be helpful to regulate estrogen-mediated gene functions during aging and neurodegenerative diseases.

Hormone response element binding proteins: novel regulators of vitamin D and estrogen signaling

Insights from vitamin D-resistant New World primates and their human homologues as models of natural and pathological insensitivity to sterol/steroid action have uncovered a family of novel intracellular vitamin D and estrogen regulatory proteins involved in hormone action. The proteins, known as "vitamin D or estrogen response element-binding proteins", behave as potent cis-acting, transdominant regulators to inhibit steroid receptor binding to DNA response elements and is responsible for vitamin D and estrogen resistances. This set of interactors belongs to the heterogeneous nuclear ribonucleoprotein (hnRNP) family of previously known pre-mRNA-interacting proteins. This review provides new insights into the mechanism by which these novel regulators of signaling and metabolism can act to regulate responses to vitamin D and estrogen. In addition the review also describes other molecules that are known to influence nuclear receptor signaling through interaction with hormone response elements.

Use of 1,25α dihydroxyvitamin D3 as a cryosensitizing agent in a murine prostate cancer model

Cryotherapy has emerged as a primary treatment option for prostate cancer (CaP); however, incomplete ablation in the periphery of the cryogenic lesion can lead to recurrence. Accordingly, we investigated the use of a non-toxic adjunctive agent, vitamin D3 (VD3), with cryotherapy to sensitize CaP to low temperature-induced, non-ice rupture-related cell death. VD3 (calcitriol) has been identified as a possible adjunct in the treatment of cancer because of its antiproliferative and antitumorigenic properties. This study aimed to identify the cellular responses and molecular pathways activated when VD3 (calcitriol) is combined with cryotherapy in a murine CaP model. Single freeze-thaw events above -15 °C had little effect on cancer cell viability; however, pretreatment with calcitriol in conjunction with cryo significantly increased cell death. The -15 °C calcitriol combination increased cell death to 55% following a single freeze compared with negligible cell loss by freezing or calcitriol alone. Repeated cryo combination yielded 90% cell death compared with 65% in dual freeze-only cycles. Western blot analysis following calcitriol cryosensitization regimes confirmed the activation of apoptosis. Specifically, proapoptotic Bid and procaspase-3 were found to decrease at 1 h following combination treatment, indicating cleavage to the active forms. A parallel in vivo study confirmed the increased cell death when combining cryotherapy with calcitriol pretreatment. The development of an adjunctive therapy combining calcitriol and cryotherapy represents a potentially highly effective, less toxic, minimally invasive treatment option. These results suggest a role for calcitriol and cryo as a combinatorial treatment for CaP, with the potential for clinical translation.

Gene targeting by the vitamin D response element binding protein reveals a role for vitamin D in osteoblast mTOR signaling

Transcriptional regulation by hormonal 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] involves occupancy of vitamin D response elements (VDREs) by the VDRE binding protein (VDRE-BP) or 1,25(OH)(2)D(3)-bound vitamin D receptor (VDR). This relationship is disrupted by elevated VDRE-BP, causing a form of hereditary vitamin D-resistant rickets (HVDRR). DNA array analysis showed that of 114 genes regulated by 1,25(OH)(2)D(3) in control cells, almost all (113) were rendered insensitive to the hormone in VDRE-BP-overexpressing HVDRR cells. Among these was the gene for DNA-damage-inducible transcript 4 (DDIT4), an inhibitor of mammalian target of rapamycin (mTOR) signaling. Chromatin immunoprecipitation PCR using 1,25(OH)(2)D(3)-treated osteoblasts confirmed that VDR and VDRE-BP compete for binding to the DDIT4 gene promoter. Expression of DDIT4 mRNA in these cells was induced (1.6-6 fold) by 1,25(OH)(2)D(3) (10-100 nM), and Western blot and flow cytometry analysis showed that this response involved suppression of phosphorylated S6K1(T389) (a downstream target of mTOR) similar to rapamycin treatment. siRNA knockdown of DDIT4 completely abrogated antiproliferative responses to 1,25(OH)(2)D(3), whereas overexpression of VDRE-BP exerted a dominant-negative effect on transcription of 1,25(OH)(2)D(3)-target genes. DDIT4, an inhibitor of mTOR signaling, is a direct target for 1,25(OH)(2)D(3) and VDRE-BP, and functions to suppress cell proliferation in response to vitamin D.

Nuclear receptor coregulators as a new paradigm for therapeutic targeting

The complex function and regulation of nuclear receptors cannot be fully understood without a thorough knowledge of the receptor-associated coregulators that either enhance (coactivators) or inhibit (corepressors) transcription. While nuclear receptors themselves have garnered much attention as therapeutic targets, the clinical and etiological relevance of the coregulators to human diseases is increasingly recognized. Aberrant expression or function of coactivators and corepressors has been associated with malignant and metabolic disease development. Many of them are key epigenetic regulators and utilize enzymatic activities to modify chromatin through histone acetylation/deacetylation, histone methylation/demethylation or chromatin remodeling. In this review, we showcase and evaluate coregulators--such as SRCs and ANCCA--with the most promising therapeutic potential based on their physiological roles and involvement in various diseases that are revealed thus far. We also describe the structural features of the coactivator and corepressor functional domains and highlight areas that can be further explored for molecular targeting.

Interaction of Estrogen Receptor Associated Protein (ERAP) 140 with ER beta decreases but its expression increases in aging mouse cerebral cortex

Following binding to cognate ligand, estrogen receptor (ER) beta interacts with specific responsive elements of the target genes and recruits a host of nuclear proteins for hormone dependent gene regulation. However, it is poorly known which proteins interact with ER beta in mouse brain and whether their interaction and expression change with age. In this report, we have used his-tag mouse ER beta for interaction with nuclear proteins of cerebral cortex of young (6 +/- 1 weeks), adult (25 +/- 2 weeks), and old (70 +/- 5 weeks) female mice. We have identified estrogen receptor-associated protein (ERAP) 140 as one of the interacting proteins and studied its interaction by pull down immunoblotting, far-Western blotting and immunoprecipitation, and expression by western blotting. The data show that ERAP 140 interacts with ER beta and its interaction decreases but its expression increases with age in mouse cerebral cortex, suggesting its role in estrogen-mediated brain functions during aging.