bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of Gonadotropin-Releasing Hormone Surges by Estrogen. I. Role of Hypothalamic Progesterone Receptors
Authors: Chappell Patrick E. , Levine Jon E. 
Published: January 2014

Abstract
Estrogen (E2) stimulates GnRH surges by coupling a daily neural signal to neuronal circuitries governing GnRH release. We have hypothesized that E2 promotes this coupling process by inducing expression of neuronal transcription factors, which are subsequently activated by neurotransmitter-mediated mechanisms representing the daily neural signal. These experiments tested the specific hypothesis that the progesterone receptor (PR) functions in this manner, viz. as an E2-induced factor whose activation is necessary for the stimulation of GnRH surges. Two complimentary experiments were performed to determine whether activation of hypothalamic PRs is obligatory for the stimulation of GnRH surges by E2. In the first, the effects of a PR antagonist on GnRH and LH surges were assessed in ovariectomized (OVX), E2-primed rats. Rats were OVX on diestrous day 2, treated with 30 μg estradiol benzoate or oil vehicle, sc, and then administered either oil vehicle or the type I antiprogestin, ZK98299 at 0900 h on proestrus. GnRH release rates and plasma LH levels were determined in each animal by microdialysis of median eminence and atrial blood sampling, respectively. Estrogen, but not oil vehicle, treatment evoked robust and contemporaneous GnRH and LH surges in animals that received no PR antagonist on proestrus. Additional treatment with ZK98299, however, completely blocked both GnRH and LH surges. In a second experiment, specific involvement of anteroventral periventricular (AVPV) PRs in E2-induced GnRH surges was assessed. Additional groups of OVX, E2-primed rats were fitted with intracerebroventricular cannulas, and PR antisense oligonucleotides were infused into the third ventricle adjacent to the AVPV to prevent expression of PR in this periventricular region. Animals infused with PR antisense oligos did not exhibit any LH surges, whereas surges were observed in saline-, missense-, and sense oligo-treated controls. Immunohistochemistry confirmed the effectiveness of PR antisense oligonucleotides in blocking PR expression. These findings provide direct support for the hypothesis that activation of PRs, specifically those in hypothalamic regions including the AVPV, is an obligatory event in the stimulation of GnRH surges by E2.
Regulation by Adrenocorticotropin (ACTH), Angiotensin II, Transforming Growth Factor-β, and Insulin-Like Growth Factor I of Bovine Adrenal Cell Steroidogenic Capacity and Expression of ACTH Receptor, Steroidogenic Acute Regulatory Protein, Cytochrome P450c17, and 3β-Hydroxysteroid Dehydrogenase*
Authors: Le Roy Christine , Li J. Yuan , Stocco Douglas M. , Langlois Dominique , Saez José M. 
Published: January 2014

AbstractThe purpose of this study was to evaluate the time-course effect of a 36-h treatment with ACTH (10−8m), transforming growth factor-β1 (TGFβ1; 10−10m), angiotensin II (AngII; 10−7m), and insulin-like growth factor I (IGF-I; 10−8m) on the steroidogenic capacity of bovine adrenocortical cells (BAC) and on messenger RNA (mRNA) levels of ACTH receptor, cytochrome P450c17, 3β-hydroxysteroid dehydrogenase (3βHSD), steroidogenic acute regulatory protein (StAR), and StAR protein. ACTH and IGF-I enhanced, in a time-dependent manner, the acute 2-h ACTH-induced cortisol production, whereas TGFβ1 and AngII markedly reduced it. ACTH, IGF-I, and AngII increased ACTH receptor mRNA, but the opposite was observed after TGFβ1 treatment. ACTH and IGF-I increased P450c17 and 3βHSD mRNAs, whereas AngII and TGFβ1 had the opposite effects. However, the effects of the four peptides on ACTH-induced cortisol production appeared before any significant alterations of the mRNA levels occurred. The most marked and rapid effect of the four peptides was on StAR mRNA. The stimulatory effect of ACTH was seen within 1.5 h, peaked at 4–6 h, and declined thereafter, but at the end of the 36-h pretreatment, the levels of StAR mRNA and protein were higher than those in control cells. IGF-I also enhanced StAR mRNA levels within 1.5 h, and these levels remained fairly constant. The effects of AngII on StAR mRNA expression were biphasic, with a peak within 1.5–3 h, followed by a rapid decline to almost undetectable levels of both mRNA and protein. TGFβ1 had no significant effect during the first 3 h, but thereafter StAR mRNA declined, and at the end of the experiment the StAR mRNA and protein were almost undetectable. Similar results were observed when cells were treated with ACTH plus TGFβ1. A 2-h acute ACTH stimulation at the end of the 36-h pretreatment caused a higher increase in StAR mRNA and protein in ACTH- or IGF-I-pretreated cells than in control cells, which, in turn, had higher levels than cells pretreated with TGFβ1, ACTH plus TGFβ1, or AngII.These results and the fact that the stimulatory (IGF-I) or inhibitory (AngII and TGFβ1) effects on ACTH-induced cortisol production were more pronounced than those on the ability of cells to transform pregnenolone into cortisol strongly suggest that regulation of StAR expression is one of the main factors, but not the only one, involved in the positive (IGF-I) or negative (TGFβ1 and AngII) regulation of BAC for ACTH steroidogenic responsiveness. A high correlation between steady state mRNA level and acute ACTH-induced cortisol production favors this conclusion.
CCAAT/Enhancer-Binding Protein-α Is a Component of the Growth Hormone-Regulated Network of Liver Transcription Factors*
Authors: Rastegar Mojgan , Rousseau Guy G. , Lemaigre Frédéric P. 
Published: January 2014

AbstractGH regulates gene expression by modulating the concentration or activity of transcription factors. To identify transcription factors that mediate the effects of GH in liver we analyzed the promoter of the gene coding for hepatocyte nuclear factor-6 (HNF-6), whose expression in liver is stimulated by GH. In protein-DNA interaction studies and in transfection experiments, we found that the liver-enriched transcription factor CCAAT/enhancer-binding protein-α (C/EBPα) binds to the hnf6 gene and inhibits its expression. This inhibitory effect involved an N-terminal subdomain of C/EBPα and two sites in the hnf6 gene promoter. Using liver nuclear extracts from GH-treated hypophysectomized rats, we found that GH induces a rapid, transient decrease in the amount of C/EBPα protein. This GH-induced change is concomitant with the transient stimulatory effect of GH on the hnf6 gene. Stimulation of the hnf6 gene by GH therefore involves lifting of the repression exerted by C/EBPα in addition to the known GH-induced stimulatory effects of STAT5 (signal transducer and activator of transcription-5) and HNF-4 on that gene. Our data provide further evidence that GH controls a network of liver transcription factors and show that C/EBPα participates in this process.
Transcellular Transport of Leptin by the Short Leptin Receptor Isoform ObRa in Madin-Darby Canine Kidney Cells*
Authors: Hileman Stanley M. , Tornøe Jens , Flier Jeffrey S. , Bjørbæk Christian 
Published: January 2014

AbstractLeptin is an adipocyte-derived hormone that acts in specific regions of the brain to regulate body weight and neuroendocrine function. The mechanism by which leptin enters the brain is unknown. We previously reported that rat brain microvessels, which constitute the blood-brain barrier, contain large amounts of messenger RNA encoding a short form of the leptin receptor (ObRa), suggesting that this site may be important for receptor-mediated transport of leptin into the brain. The purpose of this study was to determine whether ObRa is capable of transcellular transport of intact leptin. A transwell system in which Madin-Darby Canine Kidney (MDCK) cells stably expressing ObRa are grown in a monolayer was used to determine receptor distribution on apical or basolateral cell surfaces and the capacity for directional transport of 125I-leptin. Binding of 125I-leptin was greater on the apical vs. the basolateral cell surface and transport of 125I-leptin occurred only in the apical to basolateral direction. 11% of transported radioactivity appearing in the basolateral chamber represented intact leptin as assessed by TCA precipitation analysis and by SDS-PAGE. Parental MDCK cells did not express leptin receptors and did not bind or transport 125I-leptin. Epidermal growth factor (EGF) binding and transport via endogenous EGF receptors in MDCK cells also was assessed. In contrast to leptin, specific binding of 125I-EGF occurred primarily on the basolateral cell surface and transport of 125I-EGF occurred predominantly in the basolateral to apical direction. These data show that ObRa is preferentially targeted to the apical cell membrane in MDCK cells and that leptin transport occurs, albeit at a low rate, in a unidirectional manner in the apical to basolateral direction. These findings may be relevant to the putative role of ObRa in receptor-mediated transport of leptin from the circulation into the brain.
Identification of an Estrogen-Mediated Deoxyribonucleic Acid-Binding Independent Transactivation Pathway on the Epidermal Growth Factor Receptor Gene Promoter*
Authors: Salvatori Luisa , Ravenna Linda , Felli Maria Pia , Cardillo Maria Rosaria , Russo Matteo Antonio , Frati Luigi , Gulino Alberto , Petrangeli Elisa 
Published: January 2014

AbstractTo investigate the estrogenic effects on the transcriptional regulation of the epidermal growth factor (EGF) receptor (EGFR) gene, we assayed its promoter ability to direct transcription of the luciferase reporter gene after transfection into HeLa cells. Our studies demonstrated a dose-dependent activation of the EGFR gene transcription by ligand-bound estrogen receptor α (ERα). This action was retained by the 36-bp core promoter fragment and did not require the receptor DNA binding domain, as demonstrated by analyzing the role of ERα deletion mutants on EGFR gene promoter-derived constructs. The 36-bp promoter fragment does not contain an estrogen response element but an imperfect thyroid hormone response element half-site that overlaps the Sp1 binding site. ERα does not bind this imperfect thyroid hormone response element half-site but is able to enhance binding of Sp1 to its site, in gel mobility shift assays, suggesting that the mechanism by which the receptor stimulated the transcription involved protein-protein interactions that replaced DNA binding. To explain this action, we propose a model in which induction of the EGFR gene expression by estrogens in HeLa cells is dependent upon the formation of a transcriptionally active ERα-Sp1 complex that binds to the GC-rich (Sp1) region of the minimal promoter.
Induction of PG G/H Synthase-2 in Bovine Myometrial Cells by Interferon-τ Requires the Activation of the p38 MAPK Pathway
Authors: Doualla-Bell Florence , Koromilas Antonis E. 
Published: January 2014

AbstractPGs are regulators of a plethora of uterine functions during reproductive processes, including uterine contractility. In bovine uterus, the rate-limiting step in PG synthesis is catalyzed by the PG endoperoxide G/H synthase (PGHS) enzymes. It has previously been established that PGHS-2 isoform expression is affected by the ruminant-specific interferon (IFN)-τ in bovine endometrial cells. Here, we show that PGHS-2 mRNA and protein levels are induced by IFN-τ in primary cell cultures from bovine myometrium. Treatment with recombinant bovine IFN-τ induces the activation of the JAK-STAT and p38 MAPK pathways in bovine myometrial cells. Inhibition of the p38 pathway by the specific inhibitor SB203580 strongly decreases PGHS-2 mRNA and protein expression without affecting the phosphorylation and DNA-binding of transcription factors STAT-1 and STAT-2. The p38 pathway regulates PGHS-2 expression at the posttranscriptional level, because the presence of SB203580 results in the destabilization of IFN-τ-induced PGHS-2 mRNA. Taken together, these data demonstrate the ability of IFN-τ to induce the activation of the JAK-STAT pathway in a manner similar to other types of IFN (i.e. α, β, and γ) and to regulate PGHS-2 mRNA stability through the activation of the p38 pathway. These findings provide new insights into the physiological function of IFN-τ, in regard to regulation of specific genes associated with myometrial contractility.
Aberrant Growth Plate Development in VDR/RXRγ Double Null Mutant Mice
Authors: Yagishita Naoko , Yamamoto Yoko , Yoshizawa Tatsuya , Sekine Keisuke , Uematsu Yoshikatsu , Murayama Hisashi , Nagai Yumiko , Krezel Wojciech , Chambon Pierre , Matsumoto Toshio , Kato Shigeaki 
Published: January 2014

Abstract
VDR forms heterodimers with one of three RXRs, RXRα, RXRβ, and RXRγ, and it is thought that RXR ligands can also modulate the trans-activation function of VDR/RXR heterodimers. In the present study we generated VDR/RXRγ double null mutant mice to examine the convergent actions of vitamin D and vitamin A signaling and to explore the possibility of a functionally redundant VDR. Although RXRγ−/− mice exhibited no overt abnormalities, VDR−/−/RXRγ−/− mice appeared similar to VDR−/− mice, showing features typical of vitamin D-dependent rickets type II, including growth retardation, impaired bone formation, hypocalcemia, and alopecia. However, compared to VDR−/− mice, growth plate development in VDR−/−/RXRγ−/− mutant mice was more severely impaired. Normalizing mineral ion homeostasis through dietary supplementation with high calcium and phosphorous effectively prevented rachitic abnormalities, except for disarranged growth plates in VDR−/−/RXRγ−/− mutant mice, and alopecia in both VDR−/− and VDR−/−/RXRγ−/− mutant mice. Histological analysis of VDR−/−/RXRγ−/− growth plates revealed that development of the hypertrophic chondrocytes was selectively impaired. Thus, our findings indicated that the combined actions of VDR- and RXRγ-mediated signals are essential for the normal development of growth plate chondrocytes, and raised the possibility that a functionally redundant VDR is present on chondrocytes as a heterodimer with RXRγ.
Nuclear Factor-κB-Mediated X-Linked Inhibitor of Apoptosis Protein Expression Prevents Rat Granulosa Cells from Tumor Necrosis Factor α-Induced Apoptosis
Authors: Xiao Chao Wu , Ash Kristian , Tsang Benjamin K. 
Published: January 2014

AbstractAlthough X-linked inhibitor of apoptosis protein (Xiap) is an important intracellular suppressor of apoptosis in a variety of cell types and is present in ovary, its physiological role in follicular development remains unclear. The purpose of the present studies was to examine the modulatory role of Xiap in the proapoptotic action of tumor necrosis factor-α (TNFα) in rat granulosa cells. Granulosa cells from equine CG-primed immature rats were plated in RPMI 1640 medium containing 10% FCS and subsequently cultured in serum-free RPMI in the absence or presence of TNFα (20 ng/ml), the protein synthesis inhibitor cycloheximide (10 μm), and/or adenoviral Xiap sense or antisense complementary DNA. TNFα alone failed to induce granulosa cell death, but in the presence of cycloheximide, it markedly increased the number of apoptotic granulosa cells (as assessed by in situ terminal deoxynucleotidyl transferase-mediated deox-UTPbiotin end labeling and DNA fragmentation analysis). Western analysis indicated that TNFα alone increased the Xiap protein level, a response significantly reduced by adenoviral Xiap antisense expression. Down-regulation of Xiap expression by antisense complementary DNA induced granulosa cell apoptosis, which was potentiated by the cytokine. Inhibition of nuclear factor-κB activation by N-acetyl-cysteine and SN50 suppressed Xiap protein expression and enhanced apoptosis induced by TNFα. The latter phenomenon was readily attenuated by adenoviral Xiap sense expression. In conclusion, these findings suggest that Xiap is an important intracellular modulator of the TNFα death signaling pathway in granulosa cells. Its expression is regulated by the TNFα via a nuclear factor-κB-mediated mechanism.
Hydroxylases Involved in Vitamin D Metabolism Are Differentially Expressed in Murine Embryonic Kidney: Application of Whole Mount in Situ Hybridization*
Authors: Yamagata Masayo , Kimoto Akihito , Michigami Toshimi , Nakayama Masahiro , Ozono Keiichi 
Published: January 2014

AbstractIn this study we examined the expression of 25-hydroxyvitamin D-1α-hydroxylase (1α-hydroxylase) and 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase) by RT-PCR and whole mount in situ hybridization using organ culture of kidney taken from mouse embryo. First, the kidneys of mouse embryo at 11.5–17.5 days gestation were cultured in the presence or absence of forskolin and 1,25-dihydroxyvitamin D3[ 1α,25-(OH)2D3]. Forskolin and 1α,25-(OH)2D3 induced the expression of 1α-hydroxylase and 24-hydroxylase, respectively, in a dose- and time-dependent manner. In the absence of stimulants, the expression of 1α-hydroxylase and 24-hydroxylase was detected from days 13.5–17.5 gestation. The expression of vitamin D receptor and megalin was detected from days 13.5 and 11.5, respectively. Next, signals for the expression of either 1α-hydroxylase or 24-hydroxylase were detected by whole mount in situ hybridization in kidney explants taken from embryo at 15.5 days gestation after the appropriate stimulation. However, the localization of signals differed between the two enzymes; 1α-hydroxylase messenger RNA was expressed in the inner area of the kidney explants, whereas 24-hydroxylase messenger RNA was expressed in the surface area. The expression of both hydroxylases was restricted to the epithelium of developing renal tubules. The pattern of megalin expression was similar to that of 1α-hydroxylase expression. To confirm the difference in distribution of 1α-hydroxylase and 24-hydroxylase transcripts, the explants were hybridized with probes for both 1α-hydroxylase and 24-hydroxylase using double labeling techniques after simultaneous stimulation with forskolin and 1α,25-(OH)2D3, resulting in the detection at different locations of positive signals for the two enzymes. These results suggest that the expression of 1α-hydroxylase is induced in a distinct epithelium of renal tubules from that of 24-hydroxylase even at the early stage of kidney development before glomerulogenesis.
Differential Regulation of the Two Principal Runx2/Cbfa1 N-Terminal Isoforms in Response to Bone Morphogenetic Protein-2 during Development of the Osteoblast Phenotype
Authors: Banerjee Chaitali , Javed Amjad , Choi Je-Yong , Green Jack , Rosen Vicki , van Wijnen André J. , Stein Janet L. , Lian Jane B. , Stein Gary S. 
Published: January 2014

AbstractCbfa1/Runx2 is a transcription factor essential for bone formation and osteoblast differentiation. Two major N-terminal isoforms of Cbfa1, designated type I/p56 (PEBP2aA1, starting with the sequence MRIPV) and type II/p57 (til-1, starting with the sequence MASNS), each regulated by distinct promoters, are known. Here, we show that the type I transcript is constitutively expressed in nonosseous mesenchymal tissues and in osteoblast progenitor cells. Cbfa1 type I isoform expression does not change with the differentiation status of the cells. In contrast, the type II transcript is increased during differentiation of primary osteoblasts and is induced in osteoprogenitors and in premyoblast C2C12 cells in response to bone morphogenetic protein-2. The functional equivalence of the two isoforms in activation and repression of bone-specific genes indicates overlapping functional roles. The presence of the ubiquitous type I isoform in nonosseous cells and before bone morphogenetic protein-2 induced expression of the type II isoform suggests a regulatory role for Cbfa1 type I in early stages of mesenchymal cell development, whereas type II is necessary for osteogenesis and maintenance of the osteoblast phenotype. Our data indicate that Cbfa1 function is regulated by transcription, cellular protein levels, and DNA binding activity during osteoblast differentiation. Taken together, our studies suggest that developmental timing and cell type- specific expression of type I and type II Cbfa isoforms, and not necessarily molecular properties or sequences that reside in the N-terminus of Cbfa1, are the principal determinants of the osteogenic activity of Cbfa1.
STAT5b Is Required for GH-Induced Liver Igf-I Gene Expression
Authors: Davey Helen W. , Xie Tao , McLachlan Michael J. , Wilkins Richard J. , Waxman David J. , Grattan David R. 
Published: January 2014

AbstractAlthough the increased expression of Igf-I in liver in response to GH is well characterized, the intracellular signaling pathways that mediate this effect have not been identified. Intracellular signaling molecules belonging to the Janus kinase-signal transducer and activator of transcription 5b (JAK2-STAT5b) pathway are activated by GH and have previously been shown to be required for sexually dimorphic body growth and the expression of liver cytochrome P450 proteins known to be regulated by the gender-specific temporal patterns of pituitary GH secretion. Here, we evaluate the role of STAT5b in GH activation of Igf-I by monitoring the induction of Igf-I mRNA in livers of wild-type and Stat5b−/−mice stimulated with exogenous pulses of GH. GH induced the expression of liver Igf-I mRNA in hypophysectomized male wild-type, but not in hypophysectomized male Stat5b−/− mice, although theStat5b−/− mice exhibit both normal liver GH receptor expression and strong GH induction of Cytokine-inducible SH2 protein (Cis), which is believed to contribute to the down-regulation of GH-induced liver STAT5b signaling. Thus, STAT5b plays an important and specific role in liver Igf-I gene expression.
Novel Expression and Functional Role of Ghrelin in Rat Testis
Authors: Tena-Sempere M. , Barreiro M. L. , González L. C. , Gaytán F. , Zhang F.-P. , Caminos J. E. , Pinilla L. , Casanueva F. F. , Diéguez C. , Aguilar E. 
Published: January 2014

AbstractGhrelin, the endogenous ligand for the GH-secretagogue receptor (GHS-R), is a recently cloned peptide, primarily expressed in the stomach and hypothalamus, that acts at central levels to elicit GH release and, notably, to regulate food intake. However, the possibility of additional, as yet unknown, peripheral effects of ghrelin cannot be ruled out. In the present communication, we provide evidence for the novel expression of ghrelin and its functional receptor in rat testis. Testicular ghrelin gene expression was demonstrated throughout postnatal development, and ghrelin protein was detected in Leydig cells from adult testis specimens. Accordingly, ghrelin mRNA signal became undetectable in rat testis following selective Leydig cell elimination. In addition, testicular expression of the gene encoding the cognate ghrelin receptor was observed from the infantile period to adulthood, with the GHS-R mRNA being persistently expressed after selective withdrawal of mature Leydig cells. From a functional standpoint, ghrelin, in a dose-dependent manner, induced an average 30% inhibition of human CG- and cAMP-stimulated T secretion in vitro. This inhibitory effect was associated with significant decreases in human CG-stimulated expression levels of the mRNAs encoding steroid acute regulatory protein, and P450 cholesterol side-chain cleavage, 3β-hydroxy steroid dehydrogenase, and 17β-hydroxy steroid dehydrogenase type III enzymes. Overall, our data are the first to provide evidence for a possible direct action of ghrelin in the control of testicular function. Furthermore, the present results underscore an unexpected role of ghrelin as signal with ability to potentially modulate not only growth and body weight homeostasis but also reproductive function, a phenomenon also demonstrated recently for the adipocyte-derived hormone, leptin.