bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of nuclear factor kappa B in the regulation of rat luteal function: potential roles as survival factor and inhibitor of 20alpha-hydroxysteroid dehydrogenase
Authors: Telleria CM , Goyeneche AA , Stocco CO , Gibori G
Published: December 2004

Nuclear factor kappa B (NFkappaB) is an important intracellular conveyor of extracellular signals and modulates a number of gene responses. Due to the potential significance of NFkappaB in regulating ovarian gene expression, we examined in the rat: (i) whether NFkappaB is activated and developmentally regulated in the corpus luteum (CL) throughout pregnancy; (ii) the proteins forming the NFkappaB complex in luteal cells; and (iii) the role of this transcription factor in luteal function. Western analysis and immunohistochemistry revealed that p65 and p50 were highly expressed throughout pregnancy and were located in both the nucleus and cytoplasm of luteal cells. In addition, because NFkappaB is maintained in the cytoplasm bound to IkappaB, whose phosphorylation allows NFkappaB translocation to the nucleus, we studied the developmental expression of phosphorylated and nonphosphorylated forms of IkappaBalpha. Western analysis revealed that IkappaBalpha was present and phosphorylated throughout pregnancy in the CL whereas by protein/DNA array and electromobility shift assays we found that luteal nuclear extracts bind to an NFkappaB consensus sequence, and that the binding activity decreased along pregnancy. The specific binding was supershifted only by an anti-p65 antibody and not by antibodies against p50, p52, cRel, or RelB. Using day 4 postpartum ovaries, we found higher NFkappaB binding activity in the newly formed CL than in old CL of pregnancy. Furthermore, NFkappaB DNA binding activity was enhanced by prolactin in luteinized granulosa cells. In our first functional study, blockade of NFkappaB/p65 binding to DNA with the sesquiterpene lactone helenalin in luteinized granulosa cells correlated with induction of cell death in a dose-dependent manner. In a second functional study, overexpression of NFkappaB/p65 in luteal cells resulted in inhibition of 20alpha-hydroxysteroid dehydrogenase (20alphaHSD) promoter activity as well as endogenous 20alphaHSD mRNA expression. In summary, we have shown that: (i) NFkappaB is expressed within the CL, primary luteinized granulosa cells, and a rat luteal cell line; (ii) NFkappaB activation within the CL is developmentally regulated in pregnancy, depends on the age of the gland, and can be upregulated by prolactin; (iii) inhibition of NFkappaB/p65 binding to an NFkappaB DNA consensus sequence correlates with induction of cell death in ovarian luteinized granulosa cells; and (iv) overexpression of NFkappaB in luteal cells inhibits 20alphaHSD gene expression. The results further support a role for NFkappaB as a survival factor in the CL.
A mutant receptor with enhanced dominant-negative activity for the blockade of human prolactin signalling
Authors: Flynn A , Whittington H , Goffin V , Uney J , Norman M
Published: December 2004

An effective mechanism for interfering with prolactin signalling would provide a powerful tool for clarifying the importance of prolactin in breast cancer, as well as for investigating functions of prolactin in other tissues. Based on our previous identification of a dominant-negative mutation in the growth hormone receptor that causes familial short stature, we investigated the potential for using a similar truncated mutant of the prolactin receptor (PRLR1-242). Like the mutant growth hormone receptor, PRLR1-242 exerts an exceptionally powerful dominant-negative effect. A probable explanation for the strong dominant-negative activity of this class of mutation is that, lacking internalisation motifs, the truncated mutants accumulate at the cell surface and form non-functional heterodimers with wild-type receptors. In accordance with evidence for heterodimer formation between the two receptors, PRLR1-242 also blocks signalling by the growth hormone receptor. When expressed from an adenoviral vector, PRLR1-242 inhibits activation of STAT5 (signal transducer and activator of transcription 5) by prolactin in T47-D breast cancer cells, and blocks the ability of prolactin to induce proliferation in these cells. Thus PRLR1-242 provides an effective means of blocking the responsiveness of target tissues to human prolactin.
Estrogen regulation in human breast cancer cells of new downstream gene targets involved in estrogen metabolism, cell proliferation and cell transformation
Authors: Vendrell JA , Magnino F , Danis E , Duchesne MJ , Pinloche S , Pons M , Birnbaum D , Nguyen C , Theillet C , Cohen PA
Published: December 2004

We explored, by cDNA mini-arrays, gene expression measurements of MVLN, a human breast carcinoma cell line derived from MCF-7, after 4 days of exposure to 17beta-estradiol (E(2)) treatment, in order to extend our understanding of the mechanism of the pharmacological action of estrogens. We focused on 22 genes involved in estrogen metabolism, cell proliferation regulation and cell transformation. The specificity of the E(2) response was reinforced by comparison with 4-hydroxytamoxifen (OH-Tam), ICI 182,780 and E(2)+OH-Tam expression profiles. Real-time quantitative PCR (RTQ-PCR) confirmed the variation of expression of known (TFF1, AREG, IRS1, IGFBP4, PCNA, ERBB2, CTSD, MYC) as well as novel (DLEU2, CCNA2, UGT1A1, ABCC3, ABCC5, TACC1, EFNA1, NOV, CSTA, MMP15, ZNF217) genes. The temporal response of these gene expression regulations was then investigated after 6 and 18 h of E(2) treatment and this allowed the identification of different time-course patterns. Cycloheximide treatment studies indicated first that estrogen affected the transcript levels of ABCC3 and ABCC5 through dissimilar pathways, and secondly that protein synthesis was needed for modulation of the expression of the CCNA2 and TACC1 genes by estrogens. Western blot analysis performed on TFF1, IRS1, IGFBP4, amphiregulin, PCNA, cyclin A2, TACC1 and ABCC5 proteins confirmed the mini-array and RTQ-PCR data, even for genes harboring low variations of mRNA expression. Our findings should enhance the understanding of changes induced by E(2) on the transcriptional program of human E(2)-responsive cells and permit the identification of new potential diagnostic/prognostic tools for the monitoring of estrogen-related disease conditions such as breast cancer.
Leptin reduces glucose transport and cellular ATP levels in INS-1 beta-cells
Authors: Lam NT , Cheung AT , Riedel MJ , Light PE , Cheeseman CI , Kieffer TJ
Published: December 2004

Leptin suppresses insulin secretion by opening ATP-sensitive K(+) (K(ATP)) channels and hyperpolarizing beta-cells. We measured the intracellular concentration of ATP ([ATP](i)) in tumor-derived beta-cells, INS-1, and found that leptin reduced [ATP](i) by approximately 30%, suggesting that the opening of K(ATP) channels by leptin is mediated by decreased [ATP](i). A reduction in glucose availability for metabolism may explain the decreased [ATP](i), since leptin (30 min) reduced glucose transport into INS-1 cells by approximately 35%, compared to vehicle-treated cells. The twofold induction of GLUT2 phosphorylation by GLP-1, an insulin secretagogue, was abolished by leptin. Therefore, the acute effect of leptin could involve covalent modification of GLUT2. These findings suggest that leptin may inhibit insulin secretion by reducing [ATP](i) as a result of reduced glucose availability for the metabolic pathway. In addition, leptin reduced glucose transport by 35% in isolated rat hepatocytes that also express GLUT2, suggesting that glucose transport may also be altered by leptin in other glucose-responsive tissues such as the liver.
Transcription factor EGR3 is involved in the estrogen-signaling pathway in breast cancer cells
Authors: Inoue A , Omoto Y , Yamaguchi Y , Kiyama R , Hayashi SI
Published: December 2004

Estrogen has been closely associated with the genesis and malignant progression of breast cancer. However, the molecular mechanism underlying the effects of estrogen is far from being completely clarified. We previously developed a custom-made cDNA microarray consisting of approximately 200 estrogen-responsive genes in breast cancer cells. Using this system, we found one estrogen-induced gene in various cancer cell lines, including breast cancer MCF-7 cells, which encode a zinc-finger transcription factor, EGR3 (early growth response 3). Northern blot analysis of estradiol-treated MCF-7 cells showed rapid and robust induction of Egr3, and addition of cycloheximide or ICI 182,780 suggested that Egr3 is the bona fide target for the estrogen receptor alpha (ERalpha). Using stable transformants derived from MCF-7 cells which were transfected with expression-controllable Egr3-expression vector, we demonstrated that Nab2 is one of the target genes for EGR3. Microarray analysis of the transformants revealed other candidate EGR3-induced genes. These strategies could be useful for analyzing downstream genes of ERalpha, and may contribute to elucidating the extensive signaling network of estrogen stimuli. Furthermore, a reporter assay using the upstream region of fasL probably involving escape from the immune system revealed that fasL is another target gene for EGR3. The roles of EGR3 in the physiology of breast cancer are discussed.
A genomic view of estrogen actions in human breast cancer cells by expression profiling of the hormone-responsive transcriptome
Authors: Cicatiello L , Scafoglio C , Altucci L , Cancemi M , Natoli G , Facchiano A , Iazzetti G , Calogero R , Biglia N , De Bortoli M , Sfiligoi C , Sismondi P , Bresciani F , Weisz A
Published: December 2004

Estrogen controls key cellular functions of responsive cells including the ability to survive, replicate, communicate and adapt to the extracellular milieu. Changes in the expression of 8400 genes were monitored here by cDNA microarray analysis during the first 32 h of human breast cancer (BC) ZR-75.1 cell stimulation with a mitogenic dose of 17beta-estradiol, a timing which corresponds to completion of a full mitotic cycle in hormone-stimulated cells. Hierarchical clustering of 344 genes whose expression either increases or decreases significantly in response to estrogen reveals that the gene expression program activated by the hormone in these cells shows 8 main patterns of gene activation/inhibition. This newly identified estrogen-responsive transcriptome represents more than a simple cell cycle response, as only a few affected genes belong to the transcriptional program of the cell division cycle of eukaryotes, or showed a similar expression profile in other mitogen-stimulated human cells. Indeed, based on the functions assigned to the products of the genes they control, estrogen appears to affect several key features of BC cells, including their metabolic status, proliferation, survival, differentiation and resistance to stress and chemotherapy, as well as RNA and protein synthesis, maturation and turn-over rates. Interestingly, the estrogen-responsive transcriptome does not appear randomly interspersed in the genome. In chromosome 17, for example, a site particularly rich in genes activated by the hormone, physical association of co-regulated genes in clusters is evident in several instances, suggesting the likely existence of estrogen-responsive domains in the human genome.
Oestrogen receptor beta is required for androgen-stimulated proliferation of LNCaP prostate cancer cells
Authors: Maggiolini M , Recchia AG , Carpino A , Vivacqua A , Fasanella G , Rago V , Pezzi V , Briand PA , Picard D , Ando S
Published: December 2004

The role of oestrogens in the development of prostate cancer is poorly understood. However, a large body of evidence has suggested that oestrogenic hormones may be involved in prostatic malignancy. The localization of oestrogen receptor beta (ERbeta) in the secretory epithelium of the human prostate has raised the intriguing possibility that the action of oestrogen could be mediated, at least in part, by this receptor during the process of carcinogenesis. Hence, specific interference with oestrogen-activated and ERbeta-mediated transcriptional activity could open new issues in the endocrine manipulation of prostate tumours. In the present study, we provide new insights into the role of ERbeta in the context of an androgen-responsive prostate cancer cell line such as LNCaP, which was used as a model system together with steroid receptor negative HeLa cells. ERbeta and the mutated androgen receptor (AR) T877A did not discriminate between oestrogen- or androgen-induced transactivation, whereas ERbeta and AR transcriptional activity were inhibited only by the respective hormone antagonists ICI 182,780 and casodex. Furthermore, the nuclear localization of ERbeta evaluated by immunocytochemistry confirmed the promiscuous response to hormones in addition to the specific inhibitory action of antagonists. Interestingly, ICI 182,780 and an ERbeta antisense expression vector repressed the growth effects of both 17beta-oestradiol and 5alpha-dihydrotestosterone, suggesting that ERbeta has a key role in the proliferation induced by these steroids in LNCaP prostate cancer cells. Thus our findings implicate ERbeta as a potential target for the treatment of prostate tumours.
Gene expression profiling identifies liver X receptor alpha as an estrogen-regulated gene in mouse adipose tissue
Authors: Lundholm L , Moverare S , Steffensen KR , Nilsson M , Otsuki M , Ohlsson C , Gustafsson JA , Dahlman-Wright K
Published: December 2004

Estrogens reduce adipose tissue mass in both humans and animals. The molecular mechanisms for this effect are, however, not well characterized. We took a gene expression profiling approach to study the direct effects of estrogen on mouse white adipose tissue (WAT). Female ovariectomized mice were treated for 10, 24 and 48 h with 17beta-estradiol or vehicle. RNA was extracted from gonadal fat and hybridized to Affymetrix MG-U74Av2 arrays. 17beta-Estradiol was shown to decrease mRNA expression of liver X receptor (LXR) alpha after 10 h of treatment compared with the vehicle control. The expression of several LXRalpha target genes, such as sterol regulatory element-binding protein 1c, apolipoprotein E, phospholipid transfer protein, ATP-binding cassette A1 and ATP-binding cassette G1, was similarly decreased. We furthermore identified a 1.5 kb LXRalpha promoter fragment that is negatively regulated by estrogen. Several genes involved in lipogenesis and lipolysis were identified as novel targets that could mediate estrogenic effects on adipose tissue. Finally, we show that ERalpha is the main estrogen receptor expressed in mouse white adipose tissue (WAT) with mRNA levels several hundred times higher than those of ERbeta mRNA.
Acute neurosteroid modulation and subunit isolation of the gamma-aminobutyric acidA receptor in the bullfrog, Rana catesbeiana
Authors: Hollis DM , Goetz FW , Roberts SB , Boyd SK
Published: December 2004

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) has multiple receptors. In mammals, the GABA(A) receptor subtype is modulated by neurosteroids. However, whether steroid interaction with the GABA(A) receptor is unique to mammals or a conserved feature in vertebrates is unknown. Thus, neurosteroid modulation of the GABA(A) receptor was investigated in the brain of the bullfrog (Rana catesbeiana) using the mammalian GABA(A) receptor agonist [(3)H]muscimol. Two neurosteroids, allopregnanolone and pregnenolone sulfate, affected [(3)H]muscimol specific binding in bullfrog brain membrane preparations. Allopregnanolone significantly increased [(3)H]muscimol specific binding in a dose- and time-dependent manner. The pattern of allopregnanolone modulation supports the hypothesis that the bullfrog brain possesses both high-affinity and low-affinity [(3)H]muscimol binding sites. Unlike allopregnanolone, pregnenolone sulfate showed biphasic modulation with increased [(3)H]muscimol specific binding at low nanomolar concentrations and decreased specific binding at micromolar concentrations. Additionally, three cDNA fragments with significant homology to mammalian GABA(A) receptor subunits were isolated from the bullfrog brain. These fragments belong to the alpha1, beta1, and gamma2 subunit families. In mammals, GABA(A) receptors composed of these specific subunit isoforms are effectively modulated by neurosteroids, including allopregnanolone. Neurosteroid modulation of the amphibian brain GABA(A) receptor is therefore supported by both [(3)H]muscimol binding studies and subunit sequences. Allopregnanolone and pregnenolone sulfate modulation of this receptor may thus represent a significant mechanism for steroid influence on amphibian brain and behavior.
Expression of an estrogen receptor variant lacking exon 3 in derivatives of MCF-7 cells with acquired estrogen independence or tamoxifen resistance
Authors: Han F , Miksicek R , Clarke R , Conrad SE
Published: December 2004

The estrogen receptor (ER) plays important roles in the development and progression of breast cancer, and is a major target for tumor therapy. In this study, we investigated ER function in two derivatives of MCF-7 cells that were selected for their ability to proliferate in the absence of estrogen or in the presence of the antiestrogen, tamoxifen. Reporter gene assays indicated decreased ER activity in both cells lines, although the activity remaining retained responsiveness to both estrogen and tamoxifen. The decreased ER activity correlated with expression of a 61 kDa variant ER protein, and sequencing of RT-PCR products indicated that this variant was the product of an exon 3 deletion (ERDeltaE3). To study its effects on cell proliferation, ERDeltaE3 cDNA was stably transfected into both the MCF-7 cell line and its estrogen-independent/tamoxifen-sensitive derivative MCF-7/LCC1 (LCC1), and the phenotypes of transfectants were examined. Expression of ERDeltaE3 was not sustainable in MCF-7 cells, but was maintained for at least 17 passages in LCC1 cells. These results are in agreement with previous reports that ERDeltaE3 inhibits wild-type ER activity and negatively regulates proliferation of MCF-7 cells. They further suggest that the alteration that leads to estrogen independence in LCC1 cells allows for sustained expression of ERDeltaE3, and that additional changes are required to confer tamoxifen resistance to these cells.
Identification and tissue distribution of mRNAs encoding salmon-type calcitonins-IV and -V in the rainbow trout
Authors: Hidaka Y , Suzuki M
Published: December 2004

Four types of calcitonin are produced in salmonid fish, although their functional diversity is almost unknown. To explore the significance of these isoforms, we have characterized salmon-type calcitonin (sCT) mRNAs in the rainbow trout (Oncorhynchus mykiss), and examined their tissue distribution. In addition to the previously isolated sCT-I cDNAs, two new forms of sCT cDNA were cloned from the ultimobranchial gland, and one of them (sCT-IV cDNA) was predicted to encode an N-terminal peptide of 80 amino acid residues, a putative cleavage site Lys-Arg, sCT-IV, a cleavage and amidation sequence Gly-Lys-Lys-Arg, and a C-terminal peptide of 18 amino acids. The sCT-IV precursor was 78% identical with the rainbow trout sCT-I precursors. The other cloned cDNA encoded a precursor for a novel CT, sCT-V. The sCT-V peptide was different from sCT-IV by only one amino acid residue: Val at position 8 in the latter was replaced by Met. The sCT-V precursor had 80 and 90% identity with the sCT-I and -IV precursors respectively. No cDNA clones were obtained for sCTs-II or -III.Tissue distribution of sCT-I, -IV and -V mRNAs was examined by RT-PCR and specific cleavage with restriction enzymes. An amplified fragment from sCT-I mRNA was detected not only in the ultimobranchial gland, but also in the gills, testis and ovary. RT-PCR analysis coupled to restriction digestion further revealed that sCT-IV mRNA was expressed in both the testis and the ultimobranchial gland. The expression sites of sCT-IV mRNA were localized to the Leydig cells of the testis and to the parenchymal cells of the ultimobranchial gland, by in situ hybridization histochemistry. Although the amino acid sequence of sCT-V peptide was nearly the same as that of sCT-IV, the sCT-V gene showed a much wider pattern of expression: the band amplified by RT-PCR was detected in all the tissues examined except the kidney, gills and blood cells. The sCT-V mRNA was shown to be localized in the parenchymal cells of the ultimobranchial gland, but not in other tissues at the cellular level, suggesting very low expression of sCT-V mRNA in those tissues. Our results show different patterns of tissue expression of three types of sCT genes in the rainbow trout, suggesting that sCTs-I, -IV and -V might differ in their local actions.
Selective degradation of cyclin B1 mRNA in rat oocytes by RNA interference (RNAi)
Authors: Lazar S , Gershon E , Dekel N
Published: December 2004

Cyclic adenosine monophosphate (cAMP) keeps oocytes in meiotic arrest, thereby preventing activation of the key regulators of meiosis, p34cdc2/cyclin B1, (known as maturation-promoting factor (MPF)) and Erk 1 and 2, members of the mitogen-activated protein kinase (MAPK) family. The activity of MAPK in oocytes is upregulated by Mos. We previously demonstrated that Mos translation in rat oocytes is negatively regulated by a PKA-mediated cAMP action, which inhibits c-mos mRNA polyadenylation and is associated with the suppression of p34 cdc2 kinase. The goal of the present study was to provide definitive evidence that Mos translation is subjected to MPF regulation. In order to inhibit MPF activity, we employed the double-stranded (ds) RNA interference (RNAi) of gene expression. We demonstrated that the introduction of cyclin B1 dsRNA into rat oocytes selectively depleted the corresponding mRNA, further ablating its protein product. These oocytes, which exhibit low MPF activity, failed to elongate the c-mos mRNA poly(A) tail, did not accumulate Mos and were unable to activate MAPK. We conclude that an active MPF in rat oocytes is necessary for c-mos mRNA polyadenylation and Mos translation.
Testosterone modulates mitochondrial aconitase in the full-length human androgen receptor-transfected PC-3 prostatic carcinoma cells
Authors: Juang HH , Hsieh ML , Tsui KH
Published: December 2004

In vitro studies indicated that dihydrotestosterone (DHT) stimulates the enzymatic activity of the mitochondrial aconitase (mACON) in androgen-sensitive prostatic carcinoma cells, LNCaP. Cell proliferation assay determined that DHT doubles the optimal proliferation response of LNCaP cells. The androgen-insensitive human prostatic carcinoma cells, PC-3, were overexpressed in the human androgen receptor to assess the involvement of the native androgen receptor in the regulation by DHT of mACON gene expression. A stable-transfected clone that expresses the full-length androgen receptor was selected and termed PCAR9. The results revealed that DHT-treated PCAR9 cells paradoxically not only reduced the enzymatic activity of mACON but also blocked the biosynthesis of intracellular ATP attenuating cell proliferation. Transient gene expression assay indicated that DHT divergently regulates the promoter activity of the mACON gene in LNCaP and PCAR9 cells. This study suggested that DHT regulates mACON gene expression and the proliferation of cells in a receptor-dependent model through modulation by unidentified non-receptor factors.
Tissue-specific estrogenic and non-estrogenic effects of a xenoestrogen, nonylphenol
Authors: Watanabe H , Suzuki A , Goto M , Lubahn DB , Handa H , Iguchi T
Published: December 2004

Alkylphenols perturb the endocrine system and are considered to have weak estrogenic activities. Although it is known that nonylphenol can bind weakly to the estrogen receptor, it is unclear whether all reported effects of nonylphenol are attributable to its estrogen receptor-binding activity. In order to examine whether alkylphenols have similar effects to the natural hormone, estradiol, we used a mouse model to examine the effects of nonylphenol on gene expression and compared it with estradiol. DNA microarray analysis revealed that, in the uterus, most of the genes activated by this alkylphenol at a high dose (50 mg/kg) were also activated by estradiol. At lower doses, nonylphenol (0.5 mg/kg and 5 mg/kg) had little effect on the genes that were activated by estradiol. Thus, we concluded that the effects of nonylphenol at a high dose (50 mg/kg) were very similar to estradiol in uterine tissue. Moreover, since evaluation of estrogenic activity by gene expression levels was comparable with the uterotrophic assay, it indicated that analysis of gene expression profiles can predict the estrogenic activities of chemicals. In contrast to the similar effects of nonylphenol and estradiol observed in the uterus, in the liver, gene expression was more markedly affected by nonylphenol than by estradiol. This indicated that, in the liver, nonylphenol could activate another set of genes that are distinct from estrogen-responsive genes. These results indicated that nonylphenol has very similar effects to estradiol on gene expression in uterine but not in liver tissue, indicating that tissue-specific effects should be considered in order to elucidate the distinct effects of alkylphenols.
Estrogen response element and the promoter context of the human and mouse lactoferrin genes influence estrogen receptor α-mediated transactivation activity in mammary gland cells
Authors: Stokes Kenya , Alston-Mills Brenda , Teng Christina
Published: December 2004

A critical step in estrogen action is the recognition of estrogen responsive elements (EREs) by liganded estrogen receptor. Our current studies were designed to determine whether an extended estrogen response element half-site (ERRE) contributes to the differential estrogen responses of the human and mouse lactoferrin overlapping chicken ovalbumin upstream promoter/ERE sequences (estrogen response modules, ERMs) in the context of their natural promoters. Transient transfections of MCF-7 cells show that liganded estrogen receptor α (ERα) activates transcription of the human lactoferrin ERM fourfold higher than the mouse lactoferrin ERM in the context of their natural promoters. Since the ERRE of the human lactoferrin gene naturally occurs 18 bp upstream from the ERM and is absent in the mouse lactoferrin gene promoter, we created a chimeric mouse lactoferrin CAT reporter, which now encodes the ERRE in the identical location as in the human lactoferrin gene. The addition of the ERRE in the mouse lactoferrin gene rendered this reporter extremely responsive to estrogen stimulation. Using limited protease digestions and electrophoretic mobility shift assays, we showed that the binding and protease sensitivity of ERα bound to the mouse ERM with or without the ERRE, differed. Importantly, occupancy of additional nuclear receptors at the ERRE may contribute to ERα binding and activation. Furthermore, the presence of ERRE influences the selectivity of coactivators in liganded ERα-mediated transcriptional activity. When the receptor is bound to human and mouse plus genes, which contain the ERRE, steroid receptor coactivator (SRC)-2 was preferred, while SRC-1 and SRC-3 coactivators selectively enhanced the mouse lactoferrin gene activity. Moreover, peroxisome proliferator activated receptor-γ coactivator-1 (PGC-1α) and PGC-1-related estrogen receptor coactivator (PERC) robustly increase the transcriptional function of ERα in the presence of the ERRE. In conclusion, these data show that the context of the lactoferrin gene influences the ERα-mediated transcriptional activity.
Multiple plasma proteins control atrial natriuretic peptide (ANP) aggregation
Authors: Torricelli C , Capurro E , Santucci A , Paffetti A , D’Ambrosio C , Scaloni A , Maioli E , Pacini A
Published: December 2004

We have recently demonstrated that human α-atrial natriuretic peptide (α-hANP), an amyloidogenic peptide responsible for isolated atrial amyloidosis, binds to a dimeric form of apo A-I belonging to small high-density lipoproteins (HDL). This binding phenomenon is considered a protective mechanism since it inhibits or strongly reduces the ANP aggregation process. The observation that plasma exhibits at least four times greater amyloid inhibitory activity than HDL prompted us to determine whether small HDL are the only ANP plasma-binding factors. After incubation of whole plasma with labelled ANP, the macromolecular complexes were subjected to two-dimensional gel electrophoresis followed by autoradiography. The results presented here provide novel evidence of additional binding proteins, in addition to apo A-I dimer, able to bind ANP in vitro and to prevent its aggregation. The mass spectrometry analysis of the radioactive spots identified them as albumin, α-1 antitrypsin, orosomucoid and apo A-IV-TTR complex. The putative impact of these findings in the amyloidogenic/antiamyloidogenic peptides network is discussed.
Somatostatin does not inhibit prolactin synthesis in normal male rat pituitary cells but inhibits prolactin synthesis in estradiol-primed pituitary cells
Authors: Lee S C , Shin S H
Published: December 2004

The effects of somatostatin (SRIF) on prolactin (PRL) synthesis and release were examined in primary cultured pituitary cells derived from normal and estradiol (E2)-primed male rat pituitaries. The cells were continuously incubated in a pulse medium containing [3H]leucine with or without 10−6 mol/l SRIF for a period of 15, 30, 60, 180 or 360 min. Following incubation, the medium was recovered and the cells were fractionated into cytosolic and granular fractions. PRL was isolated by SDS-PAGE and newly synthesized PRL ([3H]PRL) was identified by coincident peaks of tritium activities and PRL contents. The specific activity (SA, c.p.m./ng), a ratio of [3H]PRL to total PRL, was determined for the granular, cytosolic and medium fractions.

In control and SRIF-treated groups of non-primed pituitary cells, SAs of all three fractions significantly increased during the 6-h incubation. Cytosolic and granular SAs showed similar profiles of increasing rate in comparison to control. Medium SAs showed a significantly higher value in the SRIF-treated group than in the control group only at 180 min. These observations indicate that, in the non-primed condition, PRL synthesis is not inhibited by SRIF. Medium SAs in the E2-primed group were significantly higher than SAs in the non-primed control cells during the initial 3 h of incubation, and cytosolic and granular SAs were significantly higher than those of the non-primed control during the 3- to 6-h incubation period. These observations demonstrate that E2 enhances PRL synthesis and secretion of newly synthesized PRL. SRIF treatment of E2-primed lactotrophs resulted in a significant decrease in SAs of all three fractions as compared with those of the E2-primed control. Our results indicate that in normal male rat pituitary cells SRIF does not inhibit PRL synthesis but effectively inhibits PRL synthesis in E-primed lactotrophs. This suggests that the inhibitory action of SRIF on PRL synthesis is estrogen dependent.

Journal of Endocrinology (1996) 148, 69–76
Inhibition of agonist-mediated calcium entry by calmodulin antagonists and by the Ca2+/calmodulin kinase II inhibitor KN-62. Studies with thyroid FRTL-5 cells
Authors: Törnquist K , Ekokoski E
Published: December 2004

Calmodulin and calmodulin-dependent mechanisms are probably important in regulating thyroid cell function. However, calmodulin antagonists may directly modify calcium fluxes in cells. In the present investigation the effects of several calmodulin inhibitors and of KN-62, a specific calcium/calmodulin kinase II inhibitor, on the ATP- and thapsigargin-evoked changes in intracellular free calcium ([Ca2+]i) were investigated in Fura-2 loaded thyroid FRTL-5 cells. All of the inhibitors tested attenuated agonist-evoked calcium entry. The inhibitor calmidazolium per se potently released sequestered calcium followed by enhanced calcium entry. Pretreatment of the cells with calmidazolium inhibited both the thapsigarginand the ATP-evoked calcium entry. Our results show that calmodulin antagonists are potent inhibitors of calcium entry in thyroid cells, possibly by directly inhibiting the calcium entry pathway. This inhibition may explain, in part, the results obtained with calmodulin inhibitors in previous studies.

Journal of Endocrinology (1996) 148, 131–138
Interleukin-1 effect on glycemia in the non-obese diabetic mouse at the pre-diabetic stage
Authors: Amrani A , Jafarian-Tehrani M , Mormède P , Durant S , Pleau J-M , Haour F , Dardenne M , Homo-Delarche F
Published: December 2004

Cytokines, particularly interleukin 1 (IL-1) and tumor necrosis factor, are known to induce hypoglycemia in normal rodents or different experimental models of type II diabetes. We investigated, at the pre-diabetic stage, the effect of short-term administration of murine recombinant interleukin-1α (mrIL-1α) on the levels of glucose, insulin and corticosterone in the non-obese diabetic (NOD) mouse, a spontaneous model of type I diabetes. Two-month-old, pre-diabetic NOD mice of both sexes were insensitive to mrIL-1α (12·5 and 50 μg/kg) 2 h after administration, the time at which the maximal decrease (around 50%) was observed in the C57BL/6 mouse strain. Kinetic studies however showed that mrIL-1α lowered glycemia in both sexes of NOD mice, but the effect was limited and delayed. In the NOD and C57BL/6 strains, mrIL-1α had no influence on insulin levels in females, but significantly increased them in males (P<0·0001). Castration of NOD males abrogated the stimulatory effect of mrIL-1α on insulin secretion. Corticosterone secretion was stimulated by mrIL-1α in both sexes of NOD and C57BL/6 mice, and this effect was faster and greater in NOD females than in C57BL/6 females. The incomplete hypoglycemic response to mrIL-1α in females may be attributed to the anti-insulin effect of glucocorticoids, an effect which can be demonstrated when mrIL-1α is administered to adrenalectomized animals or when mrIL-1α is administered together with the glucocorticoid antagonist RU38486. In NOD males, in contrast, glucocorticoids did not play a major role in the limited hypoglycemic response to mrIL-1α, since RU38486 and adrenalectomy were not able to unmask a hypoglycemic effect. Moreover, NOD mice of both sexes were less sensitive than C57BL/6 mice to the hypoglycemic effect of insulin (2·5 U/kg), which suggests some degree of insulin-resistance in NOD mice. With regard to the effect of IL-1 on NOD mouse glycemia, therefore, these results suggest that glucocorticoids and/or androgens, according to the animal's sex, may induce a state of insulin-resistance.

Journal of Endocrinology (1996) 148, 139–148
Thermic effect of food in hypothyroid rats
Authors: Iossa S , Lionetti L , Mollica M P , Barletta A , Liverini G
Published: December 2004

The regulatory and obligatory components of cephalic and gastrointestinal phases of the thermic effect of food (TEF) were measured in control and hypothyroid rats. A significant decrease (P<0·05) in regulatory and obligatory components of cephalic and gastrointestinal TEF, after either a control or energy-dense meal, was found in hypothyroid rats compared with control rats. Our findings indicate that hypothyroidism is associated with a decreased thermogenic response to food which contributes to the reduced energy expenditure of hypothyroid rats. Our results also suggest that tri-iodothyronine is involved in the regulation of postprandial thermogenesis directly as well as through its influence on β-adrenergic response and insulin release.

Journal of Endocrinology (1996) 148, 167–174
Growth hormone-releasing factor expression is discordantly regulated in the hypothalamus and testis of streptozotocin-diabetic rats
Authors: Olchovsky D , Bruno J F , Berelowitz M
Published: December 2004

Growth hormone-releasing factor (GRF) mRNA expression in male rats occurs predominantly in the hypothalamus (mainly in the arcuate nucleus), and among extraneural sites primarily in the testis. Hypothalamic GRF is the physiological tropic stimulus to growth hormone secretion. However, the role of GRF in the testis is unknown. We have shown previously that hypothalamic GRF mRNA expression is significantly reduced in streptozotocin (STZ)-diabetic rats. This reduction is confined to the arcuate nucleus and probably accounts for the suppression of growth hormone pulsatility.

The present studies were performed to evaluate GRF expression in the testis of streptozotocin (STZ)-diabetic rats. Diabetes was induced by injection of STZ (100 mg/kg i.p.). Seventeen to twenty days later diabetic rats were hyperglycemic compared with vehicle-injected controls and demonstrated growth failure. Insulin treatment reduced the glycemia and increased body weight towards normal. Total RNA was extracted from the hypothalamus and testis, and GRF mRNA levels estimated by solution hybridization/nuclease protection assay. Levels of hypothalamic somatostatin mRNA were measured to serve as control values. GRF mRNA was significantly (P<0·001) decreased in the hypothalamus of STZ-diabetic rats (0·2 ± 0·07 mean relative densitometric units, n=8) compared with controls (1·0 ± 0·19, n=8) with no change in somatostatin mRNA expression. In contrast, testicular GRF mRNA was increased 70% (P<0·05) in STZ-diabetic rats. Insulin treatment resulted in normalization of hypothalamic GRF mRNA levels (1·1 ± 0·17, n=5) with no effect on testicular GRF mRNA expression.

In conclusion GRF gene expression is discordantly regulated in tissues of male STZ-diabetic rats. While reduced GRF expression may account for the low growth hormone state in this model, increased testicular GRF mRNA (with the previously reported reduction of insulin-like growth factor-I mRNA) resembles the response seen in growth hormone-sensitive tissue (especially the hypothalamus) to this growth hormone-deficient state.

Journal of Endocrinology (1996) 148, 189–192
The effects of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on intracellular adenosine 3′,5′-monophosphate (cAMP) levels and GH secretion in ovine and rat somatotrophs
Authors: Wu D , Chen C , Zhang J , Bowers C Y , Clarke I J
Published: December 2004

The mechanism of action of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on GH release was investigated in ovine and rat pituitary cells in vitro. In partially purified sheep somatotrophs, GHRP-2 and GH-releasing factor (GRF) increased intracellular cyclic AMP (cAMP) concentrations and caused GH release in a dose-dependent manner; GHRP-6 did not increase cAMP levels. An additive effect of maximal doses of GRF and GHRP-2 was observed in both cAMP and GH levels whereas combined GHRP-6 and GHRP-2 at maximal doses produced an additive effect on GH release only. Pretreatment of the cells with MDL 12,330A, an adenylyl cyclase inhibitor, prevented cAMP accumulation and the subsequent release of GH that was caused by either GHRP-2 or GRF. The cAMP antagonist, Rp-cAMP also blocked GH release in response to GHRP-2 and GRF. The cAMP antagonist did not prevent the effect of GHRP-6 on GH secretion whereas MDL 12,330A partially reduced the effect. An antagonist for the GRF receptor, [Ac-Tyr1,d-Arg2]-GRF 1–29, significantly diminished the effect of GHRP-2 and GRF on cAMP accumulation and GH release, but did not affect GH release induced by GHRP-6. Somatostatin prevented cAMP accumulation and GH release responses to GHRP-2, GRF and GHRP-6. Ca2+ channel blockade did not affect the cAMP increase in response to GHRP-2 or GRF but totally prevented GH release in response to GHRP-2, GRF and GHRP-6. These results indicated that GHRP-2 acts on ovine pituitary somatotrophs to increase cAMP concentration in a manner similar to that of GRF; this occurs even during the blockade of Ca2+ influx. GHRP-6 caused GH release without an increase in intracellular cAMP levels. GH release in response to all three secretagogues was reduced by somatostatin and was dependent upon the influx of extracellular Ca2+. The additive effect of GHRP-2 and GRF or GHRP-6 suggested that the three peptides may act on different receptors. In rat pituitary cell cultures, GHRP-6 had no effect on cAMP levels, but potentiated the effect of GRF on cAMP accumulation. The synergistic effect of GRF and GHRP-6 on cAMP accumulation did not occur in sheep somatotrophs. Whereas GHRP-2 caused cAMP accumulation in sheep somatotrophs, it did not do so in rat pituitary cells. These data indicate species differences in the response of pituitary somatotrophs to the GHRPs and this is probably due to different subtypes of GHRP receptor in rat or sheep.

Journal of Endocrinology (1996) 148, 197–205
Possible mechanism for the first response to short captivity stress in the water frog, Rana esculenta
Authors: Gobbetti A , Zerani M
Published: December 2004

To clarify the endocrine mechanism involved in the short captivity stress in the water frog, Rana esculenta, the activity of 9-ketoreductase, the enzyme which converts prostaglandin E2 (PGE2) into prostaglandin F2α (PGF2α), and aromatase, which converts testosterone into oestradiol-17β, were studied. Adult male and female frogs were sacrificed 0, 1·5, 3, 6, 12, 24, 48, 72, 168 and 336 h after capture in the field. PGE2, PGF2α, progesterone, testosterone, oestradiol-17β and corticosterone plasma levels were detected by RIA at each time point. 9-Ketoreductase (conversion of [3H]PGE2 into [3H]PGF2α) and aromatase (conversion of [3H]testosterone into [3H]oestradiol-17β) activities in the brain, testis, ovary and interrenal were also determined at each time point. After capture, levels of plasma PGF2α increased (male: 228%; female: 288%) and PGE2 decreased (male: 68%; female: 81%) at 1·5 h, oestradiol-17β increased (male: 399%; female: 425%) and testosterone decreased (male: 87%; female: 83%) at 6 h, and corticosterone increased (male: 421%; female: 426%) at 72 h. 9-Ketoreductase activity in the brain was enhanced at 1·5 h after capture (male: 249%; female: 262%); aromatase activity increased at 6 h in the testis (261%), ovary (273%) and interrenal (male: 227%; female: 267%). These results indicate that short captivity stress could induce an increase in plasma PGF2α through activation of brain 9-ketoreductase. In turn, PGF2α might enhance the levels of circulating oestradiol-17β through activation of gonadal and interrenal aromatase.

Journal of Endocrinology (1996) 148, 233–239
Studies on the role of TRH and corticosterone in the regulation of prolactin and thyrotrophin secretion during lactation
Authors: van Haasteren G A C , van Toor H , Klootwijk W , Handler B , Linkels E , van der Schoot P , van Ophemert J , de Jong F H , Visser T J , de Greef W J
Published: December 2004

This study describes the effects of litter size and acute suckling on the synthesis and release of hypothalamic TRH, as indirectly estimated by determination of hypothalamic prothyrotrophin-releasing hormone (proTRH) mRNA and median eminence TRH content. The effects of litter size (five or ten pups) were studied throughout lactation, while suckling-induced acute changes were analyzed on day 13 of lactation in dams with ten pups. In view of the enhanced adrenal activity during lactation and recent evidence that corticosteroids have negative effects on hypothalamic TRH, we also studied adrenalectomized (ADX) dams treated with corticosterone to maintain basal plasma corticosterone levels.

In addition to an increased plasma level of prolactin (PRL), adrenal weight and plasma corticosterone increased, while plasma TSH, tri-iodothyronine (T3), thyroxine (T4) and free T4 (FT4) levels decreased during lactation. Litter size correlated positively with plasma PRL, adrenal weight and plasma corticosterone. No effect of litter size was observed on plasma T3, but rats with ten pups had lower plasma TSH, T4 and FT4 than rats with a five-pup litter. Compared with dioestrous rats, lactating rats showed an increased hypothalamic proTRH mRNA content on day 2, but not on days 8 and 15 of lactation. Median eminence TRH in lactating rats gradually increased until day 15 and decreased thereafter. Acute suckling, after a 6-h separation of mother and pups, rapidly increased plasma PRL and corticosterone in the mothers, but had no effects on plasma TSH and thyroid hormone levels. Hypothalamic proTRH mRNA increased twofold after 0·5 h of suckling, and then gradually returned to presuckling values after 6 h. Compared with sham-operated rats, corticosterone-substituted ADX rats with ten pups had increased plasma PRL and TSH, hypothalamic proTRH mRNA and pituitary TSH β mRNA on day 15 of lactation. Moreover, while acute suckling did not enhance TSH release in sham-operated rats, it provoked not only PRL but also TSH release in corticosterone-substituted ADX dams.

It is concluded that suckling exerts a rapid, positive effect on hypothalamic proTRH mRNA content. However, the concurrent enhanced adrenal activity has negative effects on hypothalamic proTRH gene expression resulting in a suppressed hypophysial-thyroid axis during lactation. While TRH appears to play a role in PRL release during the first days of lactation and during acute suckling, TRH seems not important in maintaining PRL secretion during continued suckling.

Journal of Endocrinology (1996) 148, 325–336
Glucose tolerance and insulin secretion after adrenalectomy in mice made obese with gold thioglucose
Authors: Blair S C , Caterson I D , Cooney G J
Published: December 2004

The effect of adrenalectomy (ADX) on glucose tolerance and insulin secretion was examined in conscious mice made obese by a single injection of gold thioglucose (GTG). To facilitate such a study a chronic jugular catheter was implanted into the mice at the time of performing the ADX or sham-ADX. One week after ADX, the body weight (GTG-obese+sham-ADX, 35·6 ± 0·6 g; GTG-obese+ADX, 33·1 ± 0·6 g; P<0·05) and glycogen content of the liver (GTG-obese+sham-ADX, 2·4 ± 0·2 μmol/liver; GTG-obese+ADX, 1·6 ± 0·1 μmol/liver; P<0·05) of GTG-injected mice were reduced. Plasma glucose concentrations, in both the overnight fasted state and in response to an intravenous glucose load were also reduced following ADX of GTG-obese mice, but not to the level of the sham-ADX control mice. However, ADX completely normalized plasma insulin concentrations in both the basal state and also in response to a glucose load, as indicated by the finding that the integrated insulin secretory response of the ADX GTG-obese mice was not different from that of sham-ADX control mice (control+sham-ADX, 192 ± 5 min.μU/ml; GTG-obese+ADX, 196 ± 10 min.μU/ml). The effects of ADX on carbohydrate metabolism were not restricted to GTG-injected mice, as ADX of control mice decreased fasting plasma glucose levels and reduced liver glycogen and plasma insulin concentrations. The normalization of insulin release in ADX GTG-obese mice occurred while these mice were still obese and glucose intolerant. This suggests that the decreased insulin release was not due solely to an ADX-induced improvement in insulin sensitivity and/or weight loss. Removal of central glucocorticoid effects on the parasympathetic stimulation of insulin release may play a role in the reduced insulin release observed after ADX of obese and control mice, although peripheral effects of glucocorticoid deficiency on glycogen synthesis in the liver may also influence whole animal glucose homeostasis.

Journal of Endocrinology (1996) 148, 391–398