Estrogen receptor (ER) is a member of the nuclear receptor superfamily whose members share conserved domain structures, including a DNA-binding domain (DBD) and ligand-binding domain (LBD). ...Estrogenic chemicals work as ligands for activation or repression of ER-mediated transcriptional activity derived from two transactivation domains: AF-1 and AF-2. AF-2 is localized in the LBD, and helix 12 of the LBD is essential for controlling AF-2 functionality. The positioning of helix 12 defines the ER alpha (ERα) ligand properties as agonists or antagonists. In contrast, it is still less well defined as to the ligand-dependent regulation of N-terminal AF-1 activity. It has been thought that the action of selective estrogen receptor modulators (SERMs) is mediated by the regulation of a tissue specific AF-1 activity rather than AF-2 activity. However, it is still unclear how SERMs regulate AF-1 activity in a tissue-selective manner. This review presents some recent observations toward information of ERα mediated SERM actions related to the ERα domain functionality, focusing on the following topics. (1) The F-domain, which is connected to helix 12, controls 4-hydroxytamoxifen (4OHT) mediated AF-1 activation associated with the receptor dimerization activity. (2) The zinc-finger property of the DBD for genomic sequence recognition. (3) The novel estrogen responsive genomic DNA element, which contains multiple long-spaced direct-repeats without a palindromic ERE sequence, is differentially recognized by 4OHT and E2 ligand bound ERα transactivation complexes.
Abstract
Context
Previous case reports associated prepubertal gynecomastia with lavender-containing fragrances, but there appear to be no reports of premature thelarche.
Objective
To add to a case ...series about lavender-fragranced product use and breast growth in children and to measure endocrine-disrupting chemical activity of essential oil components.
Design, Setting, and Patients
Patients experiencing premature thelarche or prepubertal gynecomastia with continuous exposure to lavender-fragranced products were evaluated in the pediatric endocrinology departments of two institutions. Mechanistic in vitro experiments using eight components of lavender and other essential oils were performed at National Institute of Environmental Health Sciences.
Main Outcome Measures
Case reports and in vitro estrogen and androgen receptor gene expression activities in human cell lines with essential oils.
Results
Three prepubertal girls and one boy with clinical evidence of estrogenic action and a history of continuous exposure to lavender-containing fragrances were studied. Breast growth dissipated in all patients with discontinuation of the fragranced products. Some of the components tested elicited estrogenic and antiandrogenic properties of varying degrees.
Conclusion
We report cases of premature thelarche that resolved upon cessation of lavender-containing fragrance exposure commonly used in Hispanic communities. The precise developmental basis for such conditions could be multifactorial. In vitro demonstration of estrogenic and antiandrogenic properties of essential oil components suggests essential oils in these cases could be considered a possible source and supports a possible link with idiopathic prepubertal breast development. Whether the level of lavender oil estrogenic potency is sufficient to cause these effects is unknown.
Lavender-containing fragrances may cause premature thelarche and prepubertal gynecomastia.
The isolation of estrogen receptor alpha (ERα) cDNA was successful around 30 years ago. The characteristics of ERα protein have been examined from various aspects, primarily through in vitro cell ...culture studies, but more recently using in vivo experimental models. There remains, however, some uncharacterized ERα functionalities. In particular, the mechanism of partial agonist activity of selective estrogen receptor modulators (SERMs) that involves control of the N-terminal transcription function of ERα, termed AF-1, is still an unsolved ERα functionality. We review the possible mechanism of SERM-dependent regulation of ERα AF-1-mediated transcriptional activity, which includes the role of helix 12 of ERα ligand binding domain (LBD) for SERM-dependent AF-1 regulation. In addition, we describe a specific portion of the LBD that associates with blocking AF-1 activity with an additional role of the F-domain in mediating SERM activity.
Endocrine-disrupting chemicals (EDCs) influence the activity of estrogen receptors (ERs) and alter the function of the endocrine system. However, the diversity of EDC effects and mechanisms of action ...are poorly understood.
We examined the agonistic activity of EDCs through ERα and ERβ. We also investigated the effects of EDCs on ER-mediated target genes.
HepG2 and HeLa cells were used to determine the agonistic activity of EDCs on ERα and ERβ via the luciferase reporter assay. Ishikawa cells stably expressing ERα were used to determine changes in endogenous ER target gene expression by EDCs.
Twelve EDCs were categorized into three groups on the basis of product class and similarity of chemical structure. As shown by luciferase reporter analysis, the EDCs act as ER agonists in a cell type- and promoter-specific manner. Bisphenol A, bisphenol AF, and 2-2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (group 1) strongly activated ERα estrogen responsive element (ERE)-mediated responses. Daidzein, genistein, kaempferol, and coumestrol (group 2) activated both ERα and ERβ ERE-mediated activities. Endosulfan and kepone (group 3) weakly activated ERα. Only a few EDCs significantly activated the "tethered" mechanism via ERα or ERβ. Results of real-time polymerase chain reaction indicated that bisphenol A and bisphenol AF consistently activated endogenous ER target genes, but the activities of other EDCs on changes of ER target gene expression were compound specific.
Although EDCs with similar chemical structures (in the same group) tended to have comparable ERα and ERβ ERE-mediated activities, similar chemical structure did not correlate with previously reported ligand binding affinities of the EDCs. Using ERα-stable cells, we observed that EDCs differentially induced activity of endogenous ER target genes.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
The estrogen receptor (ER) is a ligand-dependent transcription factor containing two transcriptional activation domains. AF-1 is in the N terminus of the receptor protein and AF-2 activity is ...dependent on helix 12 of the C-terminal ligand-binding domain. Two point mutations of leucines 543 and 544 to alanines (L543A, L544A) in helix 12 minimized estrogen-dependent transcriptional activation and reversed the activity of the estrogen antagonists ICI182780 (ICI) and tamoxifen (TAM) into agonists in a similar manner that TAM activated WT ERα through AF-1 activation. To evaluate the physiological role of AF-1 and AF-2 for the tissue-selective function of TAM, we generated an AF-2–mutated ERα knock-in (AF2ERKI) mouse model. AF2ERKI homozygote female mice have hypoplastic uterine tissue and rudimentary mammary glands similar to ERα-KO mice. Female mice were infertile as a result of anovulation from hemorrhagic cystic ovaries and elevated serum LH and E2 levels, although the mutant ERα protein is expressed in the AF2ERKI model. The AF2ERKI phenotype suggests that AF-1 is not activated independently, even with high serum E2 levels. ICI and TAM induced uterotropic and ER-mediated gene responses in ovariectomized AF2ERKI female mice in the same manner as in TAM- and E2-treated WT mice. In contrast, ICI and TAM did not act as agonists to regulate negative feedback of serum LH or stimulate pituitary prolactin gene expression in a different manner than TAM- or E2-treated WT mice. The functionality of the mutant ERα in the pituitary appears to be different from that in the uterus, indicating that ERα uses AF-1 differently in the uterus and the pituitary for TAM action.
Endocrine-disrupting chemicals (EDCs) are suspected of altering estrogenic signaling through estrogen receptor (ER) α or β (mERβ1 in mice). Several EDC effects have been reported in animal studies ...and extrapolated to human studies. Unlike humans, rodents express a novel isoform of ERβ (mERβ2) with a modified ligand-binding domain sequence. EDC activity through this isoform remains uncharacterized.
We identified the expression pattern of mERβ2 in mouse tissues and assessed the estrogenic activity of EDCs through mERβ2.
mERβ2 mRNA expression was measured in mouse tissues. HepG2 cells were used to assess the transactivation activity of mERβ isoforms with EDCs and ER co-activators. 293A cells transiently transfected with mER isoforms were used to detect EDC-mediated changes in endogenous ER target gene expression.
Expression of mERβ2 mRNA was detected in mouse reproductive tissues (ovary, testis, and prostate) and lung and colon tissues from both female and male mice. Five (E2, DES, DPN, BPAF, Coum, 1-BP) of 16 compounds tested by reporter assay had estrogenic activity through mERβ2. mERβ2 had a compound-specific negative effect on ERβ/ligand-mediated activity and ER target genes when co-expressed with mERβ1. mERβ2 recruited coactivators SRC2 or SRC3 in the presence of EDCs, but showed less recruitment than mERβ1.
mERβ2 showed weaker estrogenic activity than mERβ1 in our
system, and can dampen mERβ1 activity.
models of EDC activity and ER-mediated toxicity should consider the role of mERβ2, as rodent tissue responses involving mERβ2 may not be reproduced in human biology.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Aging results in enhanced myelopoiesis, which is associated with an increased prevalence of myeloid leukemias and the production of myeloid-derived suppressor cells (MDSCs). Tristetraprolin (TTP) is ...an RNA binding protein that regulates immune-related cytokines and chemokines by destabilizing target mRNAs. As TTP expression is known to decrease with age in myeloid cells, we used TTP-deficient (TTPKO) mice to model aged mice to study TTP regulation in age-related myelopoiesis. Both TTPKO and myeloid-specific TTPKO (cTTPKO) mice had significant increases in both MDSC subpopulations M-MDSCs (CD11b
Ly6C
Ly6G
) and PMN-MDSCs (CD11b
Ly6C
Ly6G
), as well as macrophages (CD11b
F4/80
) in the spleen and mesenteric lymph nodes; however, no quantitative changes in MDSCs were observed in the bone marrow. In contrast, gain-of-function TTP knock-in (TTPKI) mice had no change in MDSCs compared with control mice. Within the bone marrow, total granulocyte-monocyte progenitors (GMPs) and monocyte progenitors (MPs), direct antecedents of M-MDSCs, were significantly increased in both cTTPKO and TTPKO mice, but granulocyte progenitors (GPs) were significantly increased only in TTPKO mice. Transcriptomic analysis of the bone marrow myeloid cell populations revealed that the expression of CC chemokine receptor 2 (CCR2), which plays a key role in monocyte mobilization to inflammatory sites, was dramatically increased in both cTTPKO and TTPKO mice. Concurrently, the concentration of CC chemokine ligand 2 (CCL2), a major ligand of CCR2, was high in the serum of cTTPKO and TTPKO mice, suggesting that TTP impacts the mobilization of M-MDSCs from the bone marrow to inflammatory sites during aging
regulation of the CCR2-CCL2 axis. Collectively, these studies demonstrate a previously unrecognized role for TTP in regulating age-associated myelopoiesis through the expansion of specific myeloid progenitors and M-MDSCs and their recruitment to sites of injury, inflammation, or other pathologic perturbations.
Studies using the estrogen receptor alpha (ERα) knock-out (αERKO) mice have demonstrated that ERα plays a crucial role in various estrogen-mediated metabolic regulations. ERα is a ligand dependent ...transcription regulator and its activity is regulated by estrogenic compounds. ERα consists of two transcriptional activation domains, AF-1 and AF-2. The activities of these domains are regulated through different mechanisms; however, the specific physiological role in metabolic regulation by these domains is still unclear.
We utilized an ERα AF-2 mutant knock-in mouse (AF2ERKI) to evaluate the physiological functionality of ERα transactivation domains. Due to the estrogen insensitive AF-2 mutation, the phenotypes of AF2ERKI mice are seemingly identical to the global αERKO including obesity in the females. Distinct from the αERKO, the AF-1 function of AF2ERKI mice can be activated by tamoxifen (Tam). Ovariectomized (OVX) AF2ERKI and WT females were treated with Tam and fed a high-fat diet (HFD) for 10 weeks. Additionally, indirect calorimetric analysis was performed using metabolic chambers with food intake and locomotor activity recorded for Tam-treated AF2ERKI and αERKO females.
Obesity in HFD-fed AF2ERKI females was prevented by Tam treatment; particularly, inguinal fat accumulation was strongly blocked by Tam treatment. Alterations in fat metabolism genes, however, were not found in either inguinal fat nor visceral fat to be Tam-regulated, even though fat accumulation was strongly reduced by Tam treatment. Indirect calorimetric analysis revealed that without alteration of food intake and locomotor activity Tam treatment increased energy expenditure in AF2ERKI but not αERKO females.
These results suggest that the activation of ERα AF-1 prevents fat accumulation. The prevention of obesity through AF-1 is mediated by induction of energy expenditure rather than ERα AF-1 functionality of lipid metabolism gene regulation in fat tissues.
•AF-2 disrupted ERα mutant (AF2ERKI) females are obese with a pre-diabetic condition.•Activation of ERα AF-1 prevented AF2ERKI obesity.•Inguinal fat accumulation altered more than visceral fat in AF2ERKI females.•AF-1 activation improved energy expenditure without changing activity and feeding.
Estrogen receptor alpha (ERα) is a ligand-dependent transcription factor containing two transcriptional activation function (AF) domains. AF-1 is in the N terminus of the receptor protein, and AF-2 ...activity is dependent on helix 12 of the C-terminal ligand-binding domain. We recently showed that two point mutations converting leucines 543 and 544 to alanines in helix 12 (AF2ER) minimized estrogen-dependent AF-2 transcriptional activation. A characteristic feature of AF2ER is that the estrogen antagonists ICI182780 and tamoxifen (TAM) act as agonists through intact AF-1, but not through mutated AF-2. Here we report the reproductive phenotype of male AF2ER knock-in (AF2ERKI) mice and demonstrate the involvement of ERα in male fertility. The AF2ERKI male homozygotes are infertile because of seminiferous tubular dysmorphogenesis in the testis, similar to ERα KO males. Sperm counts and motility did not differ at age 6 wk in AF2ERKI and WT mice, but a significant testis defect was observed in adult AF2ERKI male mice. The expression of efferent ductal genes involved in fluid reabsorption was significantly lower in AF2ERKI males. TAM treatment for 3 wk beginning at age 21 d activated AF-2–mutated ERα (AF2ER) and restored expression of efferent ductule genes. At the same time, the TAM treatment reversed AF2ERKI male infertility compared with the vehicle-treated group. These results indicate that the ERα AF-2 mutation results in male infertility, suggesting that the AF-1 is regulated in an AF-2–dependent manner in the male reproductive tract. Activation of ERα AF-1 is capable of rescuing AF2ERKI male infertility.
Human ovarian cancer BG-1 cells are a valuable in vitro model that has enabled several laboratories to study the estrogenic responses of ovarian cancers. We recently discovered that there are two ...different BG-1 cell lines being used for experiments, denoted here as BG-1 FR and BG-1 NIEHS, which exhibit striking morphological differences. The objective of this study was to methodically analyze these two BG-1 variants and compare their characteristics. Short tandem repeat analysis revealed that the DNA profile of BG-1 FR cells was unique, yet the Short tandem repeat pattern of BG-1 NIEHS was identical with that of MCF-7 cells. From a cytogenetic analysis, it became apparent that the BG-1 FR line had the same profile as previously reported, whereas the BG-1 NIEHS and MCF-7 cells share a similar genetic display. A significant number of unique chromosomal translocations were observed between the BG-1 NIEHS and MCF-7 cells, suggesting that acquired genotypic differences resulted in the formation of two lines from a common origin. Although all cell types demonstrated a similar estrogen responsiveness in reporter gene assays, a microarray analysis revealed distinct estrogen-responsive gene expression patterns with surprisingly moderate to low overlap. We conclude that BG-1 FR is the original ovarian cancer cell line, whereas the BG-1 NIEHS is a variant from the MCF-7 cells. These findings provide much needed clarification of the identities and characteristics of key cell line models that are widely used to study estrogen action in female reproductive cancers.
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