Estrogen-related receptor gamma modulates energy metabolism target genes in human trophoblast

Trophoblast Syncytialization: A Metabolic Crossroads

During placentation, villous cytotrophoblast (CTB) stem cells proliferate and fuse, giving rise to the multinucleated syncytiotrophoblast (STB), which represents the terminally differentiated villous layer as well as the maternal-fetal interface. The syncytiotrophoblast is at the forefront of nutrient, gas, and waste exchange while also harboring essential endocrine functions to support pregnancy and fetal development. Considering that mitochondrial dynamics and respiration have been implicated in stem cell fate decisions of several cell types and that the placenta is a mitochondria-rich organ, we will highlight the role of mitochondria in facilitating trophoblast differentiation and maintaining trophoblast function. We discuss both the process of syncytialization and the distinct metabolic characteristics associated with CTB and STB sub-lineages prior to and during syncytialization. As mitochondrial respiration is tightly coupled to redox homeostasis, we emphasize the adaptations of mitochondrial respiration to the hypoxic placental environment. Furthermore, we highlight the critical role of mitochondria in conferring the steroidogenic potential of the STB following differentiation. Ultimately, mitochondrial function and morphological changes centrally regulate respiration and influence trophoblast fate decisions through the production of reactive oxygen species (ROS), whose levels modulate the transcriptional activation or suppression of pluripotency or commitment genes.

Rational Design of Nanomedicine for Placental Disorders: Birthing a New Era in Women's Reproductive Health

The placenta is a transient organ that forms during pregnancy and acts as a biological barrier, mediating exchange between maternal and fetal circulation. Placental disorders, such as preeclampsia, fetal growth restriction, placenta accreta spectrum, and gestational trophoblastic disease, originate in dysfunctional placental development during pregnancy and can lead to severe complications for both the mother and fetus. Unfortunately, treatment options for these disorders are severely lacking. Challenges in designing therapeutics for use during pregnancy involve selectively delivering payloads to the placenta while protecting the fetus from potential toxic side effects. Nanomedicine holds great promise in overcoming these barriers; the versatile and modular nature of nanocarriers, including prolonged circulation times, intracellular delivery, and organ-specific targeting, can control how therapeutics interact with the placenta. In this review, nanomedicine strategies are discussed to treat and diagnose placental disorders with an emphasis on understanding the unique pathophysiology behind each of these diseases. Finally, prior study of the pathophysiologic mechanisms underlying these placental disorders has revealed novel disease targets. These targets are highlighted here to motivate the rational design of precision nanocarriers to improve therapeutic options for placental disorders.

Placental expression of Estrogen related receptor gamma (ESRRG) is reduced in FGR pregnancies and is mediated by hypoxia

Fetal growth restriction (FGR) describes a fetus which has not achieved its genetic growth potential; it is closely linked to placental dysfunction and uteroplacental hypoxia. Estrogen-related receptor gamma (ESRRG) is regulated by hypoxia and is highly expressed in the placenta. We hypothesized ESRRG is a regulator of hypoxia-mediated placental dysfunction in FGR pregnancies. Placentas were collected from women delivering appropriate for gestational age (AGA; n = 14) or FGR (n = 14) infants. Placental explants (n = 15) from uncomplicated pregnancies were cultured for up to 4 days in 21% or 1% O₂, or with 200 μM cobalt chloride (CoCl₂), or treated with the ESRRG agonists DY131 under different oxygen concentrations. RT-PCR, Western blotting, and immunochemistry were used to assess mRNA and protein levels of ESRRG and its localization in placental tissue from FGR or AGA pregnancies, and in cultured placental explants. ESRRG mRNA and protein expression were significantly reduced in FGR placentas, as was mRNA expression of the downstream targets of ESRRG, hydroxysteroid 11-beta dehydrogenase 2 (HSD11B2), and cytochrome P-450 (CYP19A1.1). Hypoxia-inducible factor 1-alpha protein localized to the nuclei of the cytotrophoblasts and stromal cells in the explants exposed to CoCl₂ or 1% O₂. Both hypoxia and CoCl₂ treatment decreased ESRRG and its downstream genes’ mRNA expression, but not ESRRG protein expression. DY131 increased the expression of ESRRG signaling pathways and prevented abnormal cell turnover induced by hypoxia. These data show that placental ESRRG is hypoxia-sensitive and altered ESRRG-mediated signaling may contribute to hypoxia-induced placental dysfunction in FGR. Furthermore, DY131 could be used as a novel therapeutic approach for the treatment of placental dysfunction.

Sex-specific effects of Bisphenol a on the signalling pathway of ESRRG in the human placenta

Bisphenol A (BPA) exposure during pregnancy is associated with low fetal weight, particularly in male fetuses. The expression of estrogen-related receptor gamma (ESRRG), a receptor for BPA in the human placenta, is reduced in fetal growth restriction. This study sought to explore whether ESRRG signaling mediates BPA-induced placental dysfunction and determine whether changes in the ESRRG signaling pathway are sex-specific. Placental villous explants from 18 normal term pregnancies were cultured with a range of BPA concentrations (1 nM–1 μM). Baseline BPA concentrations in the placental tissue used for explant culture ranged from 0.04 to 5.1 nM (average 2.3 ±1.9 nM; n = 6). Expression of ESRRG signaling pathway constituents and cell turnover were quantified. BPA (1 μM) increased ESRRG mRNA expression after 24 h in both sexes. ESRRG mRNA and protein expression was increased in female placentas treated with 1 μM BPA for 24 h but was decreased in male placentas treated with 1 nM or 1 μM for 48 h. Levels of 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) and placenta specific-1 (PLAC1), genes downstream of ESRRG, were also affected. HSD17B1 mRNA expression was increased in female placentas by 1 μM BPA; however, 1 nM BPA reduced HSD17B1 and PLAC1 expression in male placentas at 48 h. BPA treatment did not affect rates of proliferation, apoptosis, or syncytiotrophoblast differentiation in cultured villous explants. This study has demonstrated that BPA affects the ESRRG signaling pathway in a sex-specific manner in human placentas and a possible biological mechanism to explain the differential effects of BPA exposure on male and female fetuses observed in epidemiological studies.

Single nuclei RNA-seq of mouse placental labyrinth development

The placenta is the interface between mother and fetus in all eutherian species. However, our understanding of this essential organ remains incomplete. A substantial challenge has been the syncytial cells of the placenta, which have made dissociation and independent evaluation of the different cell types of this organ difficult. Here, we address questions concerning the ontogeny, specification, and function of the cell types of a representative hemochorial placenta by performing single nuclei RNA sequencing (snRNA-seq) at multiple stages of mouse embryonic development focusing on the exchange interface, the labyrinth. Timepoints extended from progenitor-driven expansion through terminal differentiation. Analysis by snRNA-seq identified transcript profiles and inferred functions, cell trajectories, signaling interactions, and transcriptional drivers of all but the most highly polyploid cell types of the placenta. These data profile placental development at an unprecedented resolution, provide insights into differentiation and function across time, and provide a resource for future study.

Prenatal urinary concentrations of environmental phenols and birth outcomes in the mother-infant pairs of Tehran Environment and Neurodevelopmental Disorders (TEND) cohort study

Daily exposure to environmental phenols can lead to potential undesirable effects on the health of pregnant women and fetuses. The present study is aimed to evaluate the relationship between maternal urinary concentrations of phenols in pregnancy and anthropometric birth outcomes. The studied population comprised of 189 pregnant women participating in the Tehran Environment and Neurodevelopmental Disorders (TEND) prospective cohort study, which had been ongoing since March 2016 in some hospitals and health care delivery centers in Tehran, Iran. Concentrations of bisphenol-A, triclosan, 4-nonylphenol, and parabens were determined in spot urine samples of pregnant mothers in the first trimester. Weight, length, and head circumference at birth were also extracted from the mothers' delivery files. Multivariable linear regression was used to examine the relationship between log-concentrations of phenols and birth outcomes. When we analyzed all samples regardless of neonates' gender, none of the urinary concentrations of phenols were associated with weight and length at birth. Indeed, in sex-stratified adjusted models, one log-unit increase of butylparaben was related to a 283.6 g (95% CI: 23, 544) increase in boys' birth weight. Prenatal urinary concentration of triclosan and propylparaben was respectively related to a decrease of 4.8 cm (95% C: -8.5, -1.1) in boys' length and 0.9 cm (95%CI: -1.8, -0.04) in girls' length. In the adjusted models for estimating the changes in head circumference, one log-unit increase of triclosan, methylparaben, and butylparaben led to a reduction of 1.6 cm (95% CI: -3.17, 0.03), increase of 0.8 cm (95% CI: -0.01, 1.6) and 0.7 cm (95% CI: 0.08, 1.4) in head circumference at birth respectively. Our results suggested that prenatal triclosan and parabens exposure might be associated with head circumference at birth. Furthermore, we observed a sexually dimorphic pattern between maternal triclosan and parabens exposure during pregnancy and fetal growth. However, these findings must be interpreted while taking into account the limitations of this study.

MicroRNAs in Uteroplacental Vascular Dysfunction

Pregnancy complications of preeclampsia and intrauterine growth restriction (IUGR) are major causes of maternal and perinatal/neonatal morbidity and mortality. Although their etiologies remain elusive, it is generally accepted that they are secondary to placental insufficiency conferred by both failure in spiral artery remodeling and uteroplacental vascular malfunction. MicroRNAs (miRNAs) are small no-coding RNA molecules that regulate gene expression at the post-transcriptional level. Increasing evidence suggests that miRNAs participate in virtually all biological processes and are involved in numerous human diseases. Differentially expressed miRNAs in the placenta are typical features of both preeclampsia and IUGR. Dysregulated miRNAs target genes of various signaling pathways in uteroplacental tissues, contributing to the development of both complications. In this review, we provide an overview of how aberrant miRNA expression in preeclampsia and IUGR impacts the expression of genes involved in trophoblast invasion and uteroplacental vascular adaptation.

Ergot alkaloid exposure during gestation alters. I. Maternal characteristics and placental development of pregnant ewes1

Tall fescue [Lolium arundinaceum (Scheyreb.) Darbysh] is the primary cool season forage grass in the Southeastern United States. Most tall fescue contains an endophytic fungus (Epichloë coenophiala) that produces ergot alkaloids and upon ingestion induces fescue toxicosis. The objective of this study was to assess how exposure to endophyte-infected (E+; 1.77 mg hd-1 d-1 ergovaline and ergovalinine) or endophyte-free (E-; 0 mg hd-1 d-1 ergovaline and ergovalinine) tall fescue seed fed during 2 stages of gestation (MID, days 35-85/LATE, days 86-133) alters placental development. Thirty-six, fescue naïve Suffolk ewes were randomly assigned to 1 of 4 fescue treatments: E-/E-, E-/E+, E+/E-, or E+/E+. Ewes were individually fed the same amount of E+ or E- seed mixed into total mixed ration during MID and LATE gestation. Terminal surgeries were conducted on day 133 of gestation. Ewes fed E+ fescue seed had elevated (P < 0.001) ergot alkaloid excretion and reduced (P < 0.001) prolactin levels during the periods when fed E+ seed. Ewes switched on day 86 from E- to E+ seed had a 4% reduction (P = 0.005) in DMI during LATE gestation, which translated to a 2% reduction (P = 0.07) in DMI overall. Average daily gain was also reduced (P = 0.049) by 64% for E-/E+ ewes during LATE gestation and tended to be reduced (P = 0.06) by 33% overall. Ewes fed E+ seed during LATE gestation exhibited a 14% and 23% reduction in uterine (P = 0.03) and placentome (P = 0.004) weights, respectively. Caruncle weights were also reduced by 28% (P = 0.003) for E-/E+ ewes compared with E-/E- and E+/E-. Ewes fed E+ seed during both MID and LATE gestation exhibited a 32% reduction in cotyledon (P = 0.01) weights, whereas ewes fed E+ seed only during MID gestation (E+/E-) had improved (P = 0.01) cotyledon weights. The percentage of type A placentomes tended to be greater (P = 0.08) for E+/E+ ewes compared with other treatments. Other placentome types (B, C, or D) did not differ (P > 0.05). Total fetal weight per ewe was reduced (P = 0.01) for ewes fed E+ seed during LATE gestation compared with E-; however, feeding E+ seed during MID gestation did not alter (P = 0.70) total fetal weight per ewe. These results suggest that exposure to ergot alkaloids during LATE (days 86-133) gestation has the greatest impact on placental development by reducing uterine and placentome weights. This, in turn, reduced total fetal weight per ewe by 15% in ewes fed E+ seed during LATE gestation (E-/E+ and E+/E+).

A genome-wide search for new imprinted genes in the human placenta identifies DSCAM as the first imprinted gene on chromosome 21

We identified, through a genome-wide search for new imprinted genes in the human placenta, DSCAM (Down Syndrome Cellular Adhesion Molecule) as a paternally expressed imprinted gene. Our work revealed the presence of a Differentially Methylated Region (DMR), located within intron 1 that might regulate the imprinting in the region. This DMR showed a maternal allele methylation, compatible with its paternal expression. We showed that DSCAM is present in endothelial cells and the syncytiotrophoblast layer of the human placenta. In mouse, Dscam expression is biallelic in foetal brain and placenta excluding any possible imprinting in these tissues. This gene encodes a cellular adhesion molecule mainly known for its role in neurone development but its function in the placenta remains unclear. We report here the first imprinted gene located on human chromosome 21 with potential clinical implications.

Integrated Systems Biology Approach Identifies Novel Maternal and Placental Pathways of Preeclampsia

Preeclampsia is a disease of the mother, fetus, and placenta, and the gaps in our understanding of the complex interactions among their respective disease pathways preclude successful treatment and prevention. The placenta has a key role in the pathogenesis of the terminal pathway characterized by exaggerated maternal systemic inflammation, generalized endothelial damage, hypertension, and proteinuria. This sine qua non of preeclampsia may be triggered by distinct underlying mechanisms that occur at early stages of pregnancy and induce different phenotypes. To gain insights into these molecular pathways, we employed a systems biology approach and integrated different "omics," clinical, placental, and functional data from patients with distinct phenotypes of preeclampsia. First trimester maternal blood proteomics uncovered an altered abundance of proteins of the renin-angiotensin and immune systems, complement, and coagulation cascades in patients with term or preterm preeclampsia. Moreover, first trimester maternal blood from preterm preeclamptic patients in vitro dysregulated trophoblastic gene expression. Placental transcriptomics of women with preterm preeclampsia identified distinct gene modules associated with maternal or fetal disease. Placental "virtual" liquid biopsy showed that the dysregulation of these disease gene modules originates during the first trimester. In vitro experiments on hub transcription factors of these gene modules demonstrated that DNA hypermethylation in the regulatory region of ZNF554 leads to gene down-regulation and impaired trophoblast invasion, while BCL6 and ARNT2 up-regulation sensitizes the trophoblast to ischemia, hallmarks of preterm preeclampsia. In summary, our data suggest that there are distinct maternal and placental disease pathways, and their interaction influences the clinical presentation of preeclampsia. The activation of maternal disease pathways can be detected in all phenotypes of preeclampsia earlier and upstream of placental dysfunction, not only downstream as described before, and distinct placental disease pathways are superimposed on these maternal pathways. This is a paradigm shift, which, in agreement with epidemiological studies, warrants for the central pathologic role of preexisting maternal diseases or perturbed maternal-fetal-placental immune interactions in preeclampsia. The description of these novel pathways in the "molecular phase" of preeclampsia and the identification of their hub molecules may enable timely molecular characterization of patients with distinct preeclampsia phenotypes.

Estrogen-related receptor γ regulates expression of 17β-hydroxysteroid dehydrogenase type 1 in fetal growth restriction

INTRODUCTION

Estrogen-related receptor γ (ERRγ) and 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) have important roles in cell invasion and in the proliferation of many types of cancer cells. However, it remains unknown whether ERRγ and HSD17B1 contribute to abnormal placental structure and dysfunction which characterize fetal growth restriction (FGR). Therefore, the aim of this study was to investigate the expression profiles of ERRγ and HSD17B1 in placenta tissues affected by FGR and to examine a possible molecular mechanism by which ERRγ is able to regulate HSD17B1 during development of FGR.

METHODS

Placenta tissues were collected from women affected by FGR (n = 28) and from women with appropriately gestational age (AGA) (n = 30). Relative mRNA and protein levels of ERRγ and HSD17B1 in both groups were assessed by quantitative real-time PCR, immunohistochemistry, and Western blot analyses. The effect of ERRγ on trophoblast function and its associated mechanistic details were studied in the trophoblast cell line, HTR-8/SVneo, which was transfected with small interfering RNA (siRNA) targeting ERRγ.

RESULTS

Both mRNA and protein levels of ERRγ and HSD17B1 were significantly lower in FGR placentae (P < 0.05). When ERRγ expression was knocked down in HTR-8/SVneo cells with siRNA, invasion and proliferation were inhibited. In addition, HSD17B1 expression was significantly decreased. In dual luciferase reporter assays, ERRγ stimulated transcription of HSD17B1 by targeting the ERRγ response element within its 5'-flanking promoter region.

DISCUSSION

Aberrant ERRγ expression may contribute to the pathogenesis of FGR by regulating the transcriptional activity of HSD17B1.

The accessible chromatin landscape during conversion of human embryonic stem cells to trophoblast by bone morphogenetic protein 4

Human embryonic stem cells (hESCs) exposed to the growth factor bone morphogenetic protein 4 (BMP4) in the absence of FGF2 have been used as a model to study the development of placental development. However, little is known about the cis-regulatory mechanisms underlying this important process. In this study, we used the public available chromatin accessibility data of hESC H1 cells and BMP4-induced trophoblast (TB) cell lines to identify DNase I hypersensitive sites (DHSs) in the two cell lines, as well as the transcription factor (TF) binding sites within the DHSs. By comparing read profiles in H1 and TB, we identified 17 472 TB-specific DHSs. The TB-specific DHSs are enriched in terms of "blood vessel" and "trophectoderm," consisting of TF motifs family: Leucine Zipper, Helix-Loop-Helix, GATA, and ETS. To validate differential expression of the TFs binding to these motifs, we analyzed public available RNA-seq and microarray data in the same context. Finally, by integrating the protein-protein interaction data, we constructed a TF network for placenta development and identified top 20 key TFs through centrality analysis in the network. Our results indicate BMP4-induced TB system provided an invaluable model for the study of TB development and highlighted novel candidate genes in placenta development in human.

Perinatal exposure to 4-nonylphenol can affect fatty acid synthesis in the livers of F1 and F2 generation rats

Objective: To explore the effects of different dosages of 4-nonylphenol (4-NP) on the fatty acid synthesis and estrogen receptor α (ERα) expression in the livers of F1 and F2 rats. Method: Pregnant rats were randomly divided into four groups: control, NP-5 (5 μg per kg per day), NP-25 (25 μg per kg per day) and NP-125 (125 μg per kg per day). 4-NP was gavaged from gestation day (GD) 6 to postnatal day (PND) 21. Some female rats from the experimental groups were mated with male rats from the control group to obtain the F2 rats. F1 generation rats (23 weeks old) and F2 generation rats (13 weeks old) were killed to detect blood biochemistry and the expression of genes and proteins. Results: Compared with the control group, 4-NP (NP-5, NP-25 and NP-125) can increase the liver organ coefficient of the F1 male offspring (P < 0.05 or P < 0.01). The concentration of high density lipoprotein (HDL) in the F1 female NP-5 group was significantly higher than that of the control group (P < 0.01); other indicators had not changed, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC) and low density lipoprotein (LDL). As the dosage of 4-NP increased, more significant changes of blood biochemistry were found, especially in the NP-125 rats (P < 0.05 or P < 0.01). The changes of histopathology by liver biopsy were consistent with biochemical indices of blood (P < 0.05 or P < 0.01). Compared with the control group, the expression of genes involved in fatty acid synthesis increased significantly (P < 0.05 or P < 0.01), and the degrees of increase were proportional to the dose of 4-NP, as measured by lipoprotein lipase (Lpl), fatty acid synthetase (Fas), sterol regulatory element-binding protein 1 (Srebp-1) and peroxisome proliferator-activated receptor (Ppar)-γ. The expression of genes and proteins of ERα were changed significantly, as well (P < 0.05 or P < 0.01). The above changes in the liver tissues of F2 generation rats were consistent with the F1 generation rats. Conclusion: Perinatal exposure to 4-NP can affect the synthesis of fatty acid in the livers of F1 and F2 generation rats. The low expression of ERα may be one of the mechanisms by which 4-NP affected fatty acid synthesis in the livers of rats.

Genomic association for sexual precocity in beef heifers using pre-selection of genes and haplotype reconstruction

Reproductive traits are of the utmost importance for any livestock farming, but are difficult to measure and to interpret since they are influenced by various factors. The objective of this study was to detect associations between known polymorphisms in candidate genes related to sexual precocity in Nellore heifers, which could be used in breeding programs. Records of 1,689 precocious and non-precocious heifers from farms participating in the Conexão Delta G breeding program were analyzed. A subset of single nucleotide polymorphisms (SNP) located in the region of the candidate genes at a distance of up to 5 kb from the boundaries of each gene, were selected from the panel of 777,000 SNPs of the High-Density Bovine SNP BeadChip. Linear mixed models were used for statistical analysis of early heifer pregnancy, relating the trait with isolated SNPs or with haplotype groups. The model included the contemporary group (year and month of birth) as fixed effect and parent of the animal (sire effect) as random effect. The fastPHASE® and GenomeStudio® were used for reconstruction of the haplotypes and for analysis of linkage disequilibrium based on r² statistics. A total of 125 candidate genes and 2,024 SNPs forming haplotypes were analyzed. Statistical analysis after Bonferroni correction showed that nine haplotypes exerted a significant effect (p<0.05) on sexual precocity. Four of these haplotypes were located in the Pregnancy-associated plasma protein-A2 gene (PAPP-A2), two in the Estrogen-related receptor gamma gene (ESRRG), and one each in the Pregnancy-associated plasma protein-A gene (PAPP-A), Kell blood group complex subunit-related family (XKR4) and mannose-binding lectin genes (MBL-1) genes. Although the present results indicate that the PAPP-A2, PAPP-A, XKR4, MBL-1 and ESRRG genes influence sexual precocity in Nellore heifers, further studies are needed to evaluate their possible use in breeding programs.

Bisphenol a induces steatosis in HepaRG cells using a model of perinatal exposure

Human exposure to bisphenol A (BPA) could favor obesity and related metabolic disorders such as hepatic steatosis. Investigations in rodents have shown that these deleterious effects are observed not only when BPA is administered during the adult life but also with different protocols of perinatal exposure. Whether perinatal BPA exposure could pose a risk in human is currently unknown, and thus appropriate in vitro models could be important to tackle this major issue. Accordingly, we determined whether long-term BPA treatment could induce steatosis in human HepaRG cells by using a protocol mimicking perinatal exposure. To this end, the kinetics of expression of seven proteins differentially expressed during liver development was determined during a 4-week period of cell culture required for proliferation and differentiation. By analogy with data reported in rodents and humans, our results indicated that the period of cell culture around day 15 and day 18 after seeding could be considered as the "natal" period. Consequently, HepaRG cells were treated for 3 weeks with BPA (from 0.2 to 2000 nM), with a treatment starting during the proliferating period. BPA was able to induce steatosis with a nonmonotonic dose response profile, with significant effects on neutral lipids and triglycerides observed for the 2 nM concentration. However, the expression of many enzymes involved in lipid and carbohydrate homeostasis was unchanged in exposed HepaRG cells. The expression of other potential BPA targets and enzymes involved in BPA biotransformation was also determined, giving answers as well as new questions regarding the mechanisms of action of BPA. Hence, HepaRG cells provide a valuable model that can prove useful for the toxicological assessment of endocrine disruptors on hepatic metabolisms, in particular in the developing liver. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1024-1036, 2017.

Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review

Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.

Maternal creatine homeostasis is altered during gestation in the spiny mouse: is this a metabolic adaptation to pregnancy?

BACKGROUND

Pregnancy induces adaptations in maternal metabolism to meet the increased need for nutrients by the placenta and fetus. Creatine is an important intracellular metabolite obtained from the diet and also synthesised endogenously. Experimental evidence suggests that the fetus relies on a maternal supply of creatine for much of gestation. However, the impact of pregnancy on maternal creatine homeostasis is unclear. We hypothesise that alteration of maternal creatine homeostasis occurs during pregnancy to ensure adequate levels of this essential substrate are available for maternal tissues, the placenta and fetus. This study aimed to describe maternal creatine homeostasis from mid to late gestation in the precocial spiny mouse.

METHODS

Plasma creatine concentration and urinary excretion were measured from mid to late gestation in pregnant (n = 8) and age-matched virgin female spiny mice (n = 6). At term, body composition and organ weights were assessed and tissue total creatine content determined. mRNA expression of the creatine synthesising enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), and the creatine transporter (CrT1) were assessed by RT-qPCR. Protein expression of AGAT and GAMT was also assessed by western blot analysis.

RESULTS

Plasma creatine and renal creatine excretion decreased significantly from mid to late gestation (P < 0.001, P < 0.05, respectively). Pregnancy resulted in increased lean tissue (P < 0.01), kidney (P < 0.01), liver (P < 0.01) and heart (P < 0.05) mass at term. CrT1 expression was increased in the heart (P < 0.05) and skeletal muscle (P < 0.05) at term compared to non-pregnant tissues, and creatine content of the heart (P < 0.05) and kidney (P < 0.001) were also increased at this time. CrT1 mRNA expression was down-regulated in the liver (<0.01) and brain (<0.01) of pregnant spiny mice at term. Renal AGAT mRNA (P < 0.01) and protein (P < 0.05) expression were both significantly up-regulated at term, with decreased expression of AGAT mRNA (<0.01) and GAMT protein (<0.05) observed in the term pregnant heart. Brain AGAT (<0.01) and GAMT (<0.001) mRNA expression were also decreased at term.

CONCLUSION

Change of maternal creatine status (increased creatine synthesis and reduced creatine excretion) may be a necessary adjustment of maternal physiology to pregnancy to meet the metabolic demands of maternal tissues, the placenta and developing fetus.

The multiple universes of estrogen-related receptor α and γ in metabolic control and related diseases

The identification of the estrogen-related receptors (ERRs) as the first orphan nuclear receptors ignited a new era in molecular endocrinology, which led to the discovery of new ligand-dependent response systems. Although ERR subfamily members have yet to be associated with a natural ligand, the characterization of these orphan receptors has demonstrated that they occupy a strategic node in the transcriptional control of cellular energy metabolism. In particular, ERRs are required for the response to various environmental challenges that require high energy levels by the organism. As central regulators of energy homeostasis, ERRs may also be implicated in the etiology of metabolic disorders, such as type 2 diabetes and metabolic syndrome. Here, we review the recent evidence that further highlights the role of ERRs in metabolic control, particularly in liver and skeletal muscle, and their likely involvement in metabolic diseases. Consequently, we also explore the promises and pitfalls of ERRs as potential therapeutic targets.

Trophoblast syncytialisation necessitates mitochondrial function through estrogen-related receptor-γ activation

Human pregnancy needs a correct placentation which depends on adequate cytotrophoblast proliferation, differentiation and invasion. In this study, using specific mitochondrial respiratory chain inhibitors, we observed a decrease of hormone production (hCG and leptin) and cell fusion of human primary villous cytotrophoblasts (CT). These results demonstrated that mitochondria are involved in the control of CT differentiation process. Moreover, we also observed a decrease of mitochondrial mass associated with an increase of mitochondrial DNA during CT differentiation. Furthermore, lactate production increased during CT differentiation suggesting that anaerobic metabolism was enhanced in differentiated CTs, and that the role of mitochondria in CT fusion is not only related to its energetic function. Otherwise, the orphan nuclear receptor, estrogen-related receptor γ (ERRγ) is known to orchestrate transcriptional control of energy metabolism genes. In this study, using RNA knockdown and transcriptional activation with DY131 (an ERRγ agonist), we clearly demonstrated that ERRγ promotes hormone production and cell fusion indicating that ERRγ is a key positive transcriptional factor involved in CT differentiation. Finally, we showed that ERRγ promotes mitochondrial biogenesis and function during CT differentiation, and that the role of ERRγ during trophoblast differentiation is mainly mediated by the control of mitochondrial functions.

Evolutionary origins of the placental expression of chromosome 19 cluster galectins and their complex dysregulation in preeclampsia

INTRODUCTION

The dysregulation of maternal-fetal immune tolerance is one of the proposed mechanisms leading to preeclampsia. Galectins are key regulator proteins of the immune response in vertebrates and maternal-fetal immune tolerance in eutherian mammals. Previously we found that three genes in a Chr19 cluster encoding for human placental galectin-13 (PP13), galectin-14 and galectin-16 emerged during primate evolution and may confer immune tolerance to the semi-allogeneic fetus.

MATERIALS AND METHODS

This study involved various methodologies for gene and protein expression profiling, genomic DNA methylation analyses, functional assays on differentiating trophoblasts including gene silencing, luciferase reporter and methylation assays. These methods were applied on placental specimens, umbilical cord blood cells, primary trophoblasts and BeWo cells. Genomic DNA sequences were analyzed for transposable elements, transcription factor binding sites and evolutionary conservation.

RESULTS AND DISCUSSION

The villous trophoblastic expression of Chr19 cluster galectin genes is developmentally regulated by DNA methylation and induced by key transcription factors of villous placental development during trophoblast fusion and differentiation. This latter mechanism arose via the co-option of binding sites for these transcription factors through promoter evolution and the insertion of an anthropoid-specific L1PREC2 transposable element into the 5' untranslated region of an ancestral gene followed by gene duplication events. Among placental Chr19 cluster galectin genes, the expression of LGALS13 and LGALS14 is down-regulated in preterm severe preeclampsia associated with SGA. We reveal that this phenomenon is partly originated from the dysregulated expression of key transcription factors controlling trophoblastic functions and galectin gene expression. In addition, the differential DNA methylation of these genes was also observed in preterm preeclampsia irrespective of SGA.

CONCLUSIONS

These findings reveal the evolutionary origins of the placental expression of Chr19 cluster galectins. The complex dysregulation of these genes in preeclampsia may alter immune tolerance mechanisms at the maternal-fetal interface.

A characteristic back support structure in the bisphenol A-binding pocket in the human nuclear receptor ERRγ

The endocrine disruptor bisphenol A (BPA) affects various genes and hormones even at merely physiological levels. We recently demonstrated that BPA binds strongly to human nuclear receptor estrogen-related receptor (ERR) γ and that the phenol-A group of BPA is in a receptacle pocket with essential amino acid residues to provide structural support at the backside. This led BPA to bind to ERRγ in an induced-fit-type binding mode, for example, with a rotated motion of Val313 to support the Tyr326-binding site. A similar binding mechanism appears to occur at the binding site of the BPA phenol-B ring. X-ray crystal analysis of the ERRγ-ligand-binding domain/BPA complex suggested that the ERRγ receptor residues Leu342, Leu345, Asn346, and Ile349 function as intrinsic binding sites of the BPA phenol-B, whereas Leu265, Leu268, Ile310, Val313, Leu324, Tyr330, Lys430, Ala431, and His434 work as structural elements to assist these binding sites. In the present study, by evaluating the mutant receptors replaced by a series of amino acids, we demonstrated that a finely assembled structural network indeed exists around the two adjacent Leu342-Asn346 and Leu345-Ile349 ridges on the same α-helix 7 (H7), constructing a part of the binding pocket structure with back support residues for the BPA phenol-B ring. The results reveal that the double-layer binding sites, namely, the ordinary ligand binding sites and their back support residues, substantiate the strong binding of BPA to ERRγ. When ERRγ-Asn346 was replaced by the corresponding Gly and Tyr in ERRα and ERRβ, respectively, the binding affinity of BPA and even 4-hydroxytamxifen (4-OHT) is much reduced. Asn346 was found to be one of the residues that make ERRγ to be exclusive to BPA.

Estrogen-related receptor γ serves a role in blood pressure homeostasis during pregnancy

Persistent hypoxia caused by shallow trophoblast invasion and poor placental perfusion may underlie the pathophysiology of preeclampsia, a leading cause of maternal and neonatal morbidity and mortality. Previously, we found that estrogen-related receptor γ (ERRγ) serves a critical and O2-dependent role in differentiation of human trophoblasts in culture and expression of tissue kallikrein and voltage-gated K(+) channels. In this study, we surprisingly observed that ERRγ expression was significantly increased in placentas from preeclamptic women compared with that in gestation-matched normotensive women. To further investigate a functional role for ERRγ during pregnancy, we analyzed ERRγ-deficient mice. Maternal systolic blood pressure was significantly reduced in pregnant ERRγ(+/-) females bred to ERRγ(+/-) males compared with that in wild-type (WT) mice and was markedly up-regulated by treatment of WT pregnant mice with the ERRγ agonist DY131. Placentas of ERRγ(+/-) mice manifested increased vascular endothelial growth factor A expression compared with that in WT mice. Notably, circulating levels of the antiangiogenic factor, soluble fms-like tyrosine kinase-1, were significantly reduced in ERRγ(+/-) pregnant mice as was serum aldosterone. These effects were associated with a decrease in maternal adrenal Cyp11b1 (steroid 11β-hydroxylase) and Cyp11b2 (aldosterone synthase) expression. In contrast, adrenal Cyp11b1 and Cyp11b2 mRNA were increased in pregnant WT mice treated with DY131. Moreover, chromatin immunoprecipitation and luciferase reporter assays identified Cyp11b2 as a transcriptional target of ERRγ. Collectively, these findings reveal a potential role of ERRγ in maternal blood pressure homeostasis during pregnancy and suggest that aberrant ERRγ expression may contribute to the pathogenesis of preeclampsia.

Placental mitochondrial content and function in intrauterine growth restriction and preeclampsia

Intrauterine growth restriction (IUGR) and pregnancy hypertensive disorders such as preeclampsia (PE) associated with IUGR share a common placental phenotype called "placental insufficiency", originating in early gestation when high availability of energy is required. Here, we assess mitochondrial content and the expression and activity of respiratory chain complexes (RCC) in placental cells of these pathologies. We measured mitochondrial (mt)DNA and nuclear respiratory factor 1 (NRF1) expression in placental tissue and cytotrophoblast cells, gene and protein expressions of RCC (real-time PCR and Western blotting) and their oxygen consumption, using the innovative technique of high-resolution respirometry. We analyzed eight IUGR, six PE, and eight uncomplicated human pregnancies delivered by elective cesarean section. We found lower mRNA levels of complex II, III, and IV in IUGR cytotrophoblast cells but no differences at the protein level, suggesting a posttranscriptional compensatory regulation. mtDNA was increased in IUGR placentas. Both mtDNA and NRF1 expression were instead significantly lower in their isolated cytotrophoblast cells. Finally, cytotrophoblast RCC activity was significantly increased in placentas of IUGR fetuses. No significant differences were found in PE placentas. This study provides genuine new data into the complex physiology of placental oxygenation in IUGR fetuses. The higher mitochondrial content in IUGR placental tissue is reversed in cytotrophoblast cells, which instead present higher mitochondrial functionality. This suggests different mitochondrial content and activity depending on the placental cell lineage. Increased placental oxygen consumption might represent a limiting step in fetal growth restriction, preventing adequate oxygen delivery to the fetus.

Associations of prenatal exposure to phenols with birth outcomes

Many phenols are known to mimic or antagonize hormonal activities and may adversely affect fetal growth. A study of 567 pregnant women was conducted to investigate the relationship between prenatal phenol exposure and birth outcomes, including birth weight, length, and gestational age. We measured the concentrations of bisphenol A, benzophenone-3, 4-n-octylphenol and 4-n-nonylphenol in maternal urine and examine their association with birth outcomes. Categories of urinary benzophenone-3 concentration were associated with decreased gestational age in all infants (p for trend = 0.03). Between middle and low exposure groups, we also found bisphenol A was negatively associated with gestational duration (βadjusted = -0.48 week; 95% confidence interval: -0.91, -0.05). After stratification by gender, we found the consistent results in infant boys with those in all infants, but we did not observe significant association for girls. In conclusion, we found prenatal phenol exposure was sex-specifically related to birth outcomes.

Transcriptional cross talk between orphan nuclear receptor ERRγ and transmembrane transcription factor ATF6α coordinates endoplasmic reticulum stress response

Orphan nuclear receptor ERRγ is a member of nuclear receptor superfamily that regulates several important cellular processes including hepatic glucose and alcohol metabolism. However, mechanistic understanding of transcriptional regulation of the ERRγ gene remains to be elucidated. Here, we report that activating transcription factor 6α (ATF6α), an endoplasmic reticulum (ER)-membrane–bound basic leucine zipper (bZip) transcription factor, directly regulates ERRγ gene expression in response to ER stress. ATF6α binds to ATF6α responsive element in the ERRγ promoter. The transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) is required for this transactivation. Chromatin immunoprecipitation (ChIP) assay confirmed the binding of both ATF6α and PGC1α on the ERRγ promoter. ChIP assay demonstrated histone H3 and H4 acetylation occurs at the ATF6α and PGC1α binding site. Of interest, ERRγ along with PGC1α induce ATF6α gene transcription upon ER stress. ERRγ binds to an ERRγ responsive element in the ATF6α promoter. ChIP assay confirmed that both ERRγ and PGC1α bind to a site in the ATF6α promoter that exhibits histone H3 and H4 acetylation. Overall, for the first time our data show a novel pathway of cross talk between nuclear receptors and ER-membrane–bound transcription factors and suggest a positive feed-forward loop regulates ERRγ and ATF6α gene transcription.

Estrogen-related receptor γ (ERRγ) regulates oxygen-dependent expression of voltage-gated potassium (K+) channels and tissue kallikrein during human trophoblast differentiation

Estrogen-related receptor γ (ERRγ) serves a critical O2-dependent regulatory role in the differentiation of human cytotrophoblasts to syncytiotrophoblast. In this study, we investigated expression of genes encoding tissue kallikrein (KLK1) and voltage-gated K(+) channels (KV7) during differentiation of human trophoblasts in culture and the roles of ERRγ and O2 tension in their regulation. Expression of KLK1 and the KV7 channel subunits, KCNQ1, KCNE1, KCNE3, and KCNE5, increased during differentiation of cultured human trophoblast cells in a 20% O2 environment. Notably, together with ERRγ, expression of KLK1, KCNQ1, KCNE1, KCNE3, and KCNE5 was markedly reduced when cells were cultured in a hypoxic environment (2% O2). Moreover, upon transduction of trophoblast cells with short hairpin RNAs for endogenous ERRγ, KLK1, KCNQ1, KCNE1, and KCNE3 expression was significantly decreased. Promoter and site-directed mutagenesis studies in transfected cells identified putative ERRγ response elements within the KLK1 and KCNE1 5'-flanking regions required for ERRγ-stimulated transcriptional activity. Binding of endogenous ERRγ to these ERRγ response elements increased during trophoblast differentiation in culture and was inhibited by hypoxia. The KV7 blocker linopirdine reduced human chorionic gonadotropin secretion and aggregation of cultured human trophoblasts, suggesting a possible role of KV7 channels in cell fusion and differentiation. Illumina gene expression arrays of cultured human trophoblast cells revealed several genes upregulated during syncytiotrophoblast differentiation and downregulated upon ERRγ knockdown involved in cell differentiation, adhesion, and synthesis of steroid and peptide hormones required for placental development and function. Collectively, these findings suggest that ERRγ mediates O2-dependent expression of genes involved in human trophoblast differentiation, function, and vascular homeostasis.

Bisphenol A affects androgen receptor function via multiple mechanisms

Bisphenol A (BPA), is a well-known endocrine disruptor compound (EDC) that affects the normal development and function of the female and male reproductive system, however the mechanisms of action remain unclear. To investigate the molecular mechanisms of how BPA may affect ten different nuclear receptors, stable cell lines containing individual nuclear receptor ligand binding domain (LBD)-linked to the β-Gal reporter were examined by a quantitative high throughput screening (qHTS) format in the Tox21 Screening Program of the NIH. The results showed that two receptors, estrogen receptor alpha (ERα) and androgen receptor (AR), are affected by BPA in opposite direction. To confirm the observed effects of BPA on ERα and AR, we performed transient transfection experiments with full-length receptors and their corresponding response elements linked to luciferase reporters. We also included in this study two BPA analogs, bisphenol AF (BPAF) and bisphenol S (BPS). As seen in African green monkey kidney CV1 cells, the present study confirmed that BPA and BPAF act as ERα agonists (half maximal effective concentration EC50 of 10-100 nM) and as AR antagonists (half maximal inhibitory concentration IC50 of 1-2 μM). Both BPA and BPAF antagonized AR function via competitive inhibition of the action of synthetic androgen R1881. BPS with lower estrogenic activity (EC50 of 2.2 μM), did not compete with R1881 for AR binding, when tested at 30 μM. Finally, the effects of BPA were also evaluated in a nuclear translocation assays using EGPF-tagged receptors. Similar to 17β-estradiol (E2) which was used as control, BPA was able to enhance ERα nuclear foci formation but at a 100-fold higher concentration. Although BPA was able to bind AR, the nuclear translocation was reduced. Furthermore, BPA was unable to induce functional foci in the nuclei and is consistent with the transient transfection study that BPA is unable to activate AR.