Gonadotropin-releasing Hormone Receptor Expression Research Articles

High water temperature impairs ovarian activity and gene expression in the brain–pituitary–gonadal axis in female red seabream during the spawning season

Temperature plays a pivotal role in the control of seasonal reproduction in temperate fish species. It is well known that temperatures that exceed a certain threshold impair gonadal development, maturation, and spawning. However, the endocrine mechanisms that underlie these effects are poorly understood. We evaluated the effect of high water temperature on the brain–pituitary–gonadal (B–P–G) axis of a perciform fish, red seabream, Pagrus (Chrysophrys) major during its spawning season (April–May). Fish were reared at either high (24°C: H-group) or optimal/control (17°C: C-group) temperatures for 5 or 10d. After 5d, the transcript abundance of gonadotropin-releasing hormone-1 (GnRH1) in the brain and GnRH receptor (GnRH-R) and FSH-β in the pituitary were significantly lower in H-group than in C-group. Conversely, there was no difference in pituitary LH-β mRNA levels, serum concentrations of estradiol-17β (E2), or the gonadosomatic index (GSIs) between H- and C-groups on Day 5. After 10d, the ovaries of all H-group fish had completely regressed and were filled with only perinucleolar stage primary oocytes and atretic oocytes. The brain GnRH1 expression, pituitary GnRH-R and pituitary LH-β expression, serum E2 concentrations, and the GSI were significantly lower in the H-group on Day 10. Our results suggest that high water temperature is the proximate driver of the termination of the spawning season of female red seabream. The effect appears to be mediated by suppression of gene expression in the B–P–G axis.

Combined Subchronic Toxicity of Bisphenol A and Dibutyl Phthalate on Male Rats

ObjectiveTo evaluate the combined subchronic toxicity of bisphenol A (BPA) and dibutyl phthalate (DBP) in male Sprague Dawley (SD) rats. MethodsForty 4-week-old male rats weighing 115–125 g were randomly divided into BPA-treated, DBP-treated group, BPA+DBP-treated and control groups and fed with a soy- and alfalfa-free diet containing 285.4 ppm BPA, 285.4 ppm DBP, 285.4 ppm BPA plus 285.4 ppm DBP, and a control diet, respectively, for 90 consecutive days. At the end of the study, the animals were sacrificed by exsanguination via the carotid artery under diethyl etherane aesthesia and weighed. Organs, including liver, kidneys, spleen, thymus, heart, brain, and testis underwent pathological examination. The androgen receptor (AR), gonadotropin-releasing hormone receptor (GNRHR), and progesterone hormone receptor (PR) genes from the hypothalamus were detected by real-time PCR. The biomedical parameters were analyzed. ResultsNo significant difference was found in food intake, body weight, tissue weight, organ/brain weight ratio, and biomedical parameters among the four groups (P>0.05). However, BPA and DBP up-regulated AR, PR and GNRHR expression levels in rats and showed a synergistic or an additive effect in the BPA+DBP group. ConclusionThe combined subchronic toxicity of BPA and DBP is synergistic or additive in male SD rats.

Characterization of the Gonadotropin Releasing Hormone Receptor (GnRHR) Expression and Activity in the Female Mouse Ovary

GnRH agonists (GnRHa) are increasingly used for fertility preservation in women undergoing gonadotoxic chemotherapy. However, the protective mechanisms of action for these compounds have not yet been elucidated. In this study, we aimed to determine whether GnRHa have a direct effect on ovarian granulosa cells. GnRH receptor (GnRHR) expression was determined in mouse somatic and gonadal tissues including granulosa/cumulus cells and oocytes using quantitative RT-PCR and immunohistochemistry. Granulosa cells were isolated from mouse ovaries primed with pregnant mare serum gonadotropin. Response to GnRHa in cultured granulosa cells was assessed by determining the increase of intracellular cAMP and by assessing phosphorylation of downstream mediators of GnRH signaling: ERK and p38. To measure intracellular cAMP in our system, the cells were transfected with a cAMP-responsive luciferase reporter plasmid and stimulated with GnRHa. For all experiments, pituitary tissue and/or the αT3-1 mouse pituitary cell line were used as controls. GnRHR mRNA and protein were detected in mouse ovaries, granulosa/cumulus cells, and oocytes. After GnRHa stimulation at various time intervals, we were unable to detect a cAMP increase or activation of the ERK or p38 signaling pathway in cultured primary mouse granulosa cells, whereas activation was detected in the control αT3-1 mouse pituitary cells. In this study, we have not detected activation of the canonical GnRH signaling pathways in mouse ovarian somatic cells. Our findings suggest that the mechanism of action of GnRHa in the ovary is either below the detection level of our experimental design or is different from that in the pituitary.

Pituitary adenylate cyclase-activating polypeptide (PACAP) increases expression of the gonadotropin-releasing hormone (GnRH) receptor in GnRH-producing GT1-7 cells overexpressing PACAP type I receptor

The present study demonstrates the action of pituitary adenylate cyclase-activating polypeptide (PACAP) on gonadotropin-releasing hormone (GnRH)-producing neuronal cells, GT1-7. Because we found the expression levels of PACAP type 1 receptor (PAC1R) to be low in these cells, we transfected them with PAC1R expression vector and observed the outcome. PACAP increased the activity of the serum response element (Sre) promoter, a target of extracellular signal-regulated kinase (ERK), as well as the cAMP response element (Cre) promoter in GT1-7 cells overexpressing PAC1R. We also observed ERK phosphorylation and cAMP accumulation upon PACAP stimulation. PACAP stimulated the promoter activity of GnRH receptor (GnRHR) with increasing levels of GnRHR proteins. Notably, the increase in GnRHR promoter activity from kisspeptin was potentiated in the presence of PACAP. A similar increasing effect of PACAP on the action of kisspeptin was observed for Cre promoter activity. On the other hand, the Sre promoter activated by kisspeptin was inhibited by co-treatment with kisspeptin and PACAP. Likewise, kisspeptin-increased GnRHR promoter activity and Cre promoter activity were both potentiated in the presence of cAMP, whereas the Sre promoter activated by kisspeptin was inhibited in the presence of cAMP. Our observations show that PACAP increases GnRHR expression and stimulates kisspeptin’s effect on GnRHR expression in association with the cAMP/PKA signaling pathway in GT1-7 cells overexpressing PAC1R. In addition, PACAP was shown to have an inhibitory effect on ERK-mediated kisspeptin action.

Melatonin Inhibits GnRH-1, GnRH-3 and GnRH Receptor Expression in the Brain of the European Sea Bass, Dicentrarchus labrax

Several evidences supported the existence of melatonin effects on reproductive system in fish. In order to investigate whether melatonin is involved in the modulation of GnRH systems in the European sea bass, we have injected melatonin (0.5 μg/g body mass) in male specimens. The brain mRNA transcript levels of the three GnRH forms and the five GnRH receptors present in this species were determined by real time quantitative PCR. Our findings revealed day–night variations in the brain expression of GnRH-1, GnRH-3 and several GnRH receptors (dlGnRHR-II-1c, -2a), which exhibited higher transcript levels at mid-light compared to mid-dark phase of the photocycle. Moreover, an inhibitory effect of melatonin on the nocturnal expression of GnRH-1, GnRH-3, and GnRH receptors subtypes 1c, 2a and 2b was also demonstrated. Interestingly, the inhibitory effect of melatonin affected the expression of hypophysiotrophic GnRH forms and GnRH receptors that exhibit day–night fluctuations, suggesting that exogenous melatonin reinforce physiological mechanisms already established. These interactions between melatoninergic and GnRH systems could be mediating photoperiod effects on reproductive and other rhythmic physiological events in the European sea bass.

1025 INFLUENCE OF ENDOCRINE DISRUPTORS IN WATER ON ANDROGENITAL SYSTEMS OF RATS

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Basic Research (II)1 Apr 20131025 INFLUENCE OF ENDOCRINE DISRUPTORS IN WATER ON ANDROGENITAL SYSTEMS OF RATS Gökhan Hadi Komesli, Haldun Umudum, Okan Tarik Komesli, Celal Ferdi GÖkçay, and Ibrahim Yaþar Özgök Gökhan Hadi KomesliGökhan Hadi Komesli Erzurum , Turkey More articles by this author , Haldun UmudumHaldun Umudum Ankara, Turkey More articles by this author , Okan Tarik KomesliOkan Tarik Komesli Erzurum , Turkey More articles by this author , Celal Ferdi GÖkçayCelal Ferdi GÖkçay Ankara, Turkey More articles by this author , and Ibrahim Yaþar ÖzgökIbrahim Yaþar Özgök Ankara, Turkey More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.610AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES ED are chemicals that disrupt function of endocrine systems. ED's exist in drinking and waste water. Current study aims to investigate Bisphenol-A, progesterone, estrogen and carbamazapine compounds and their non-biodegraded metabolites on genital systems of male rats. METHODS Current study was financed by “Scientific and technological research council of Turkey-TUBITAK”. Local ethics committee approved the project. Spraque-Dowley rats were utilized in study.. Bisphenol-A, progesterone and estrogen solutions that are equal to their solutions in waste water were prepared in Middle East Technical University, Department of Environmental Engineering. Total 96 rat were assigned into 9 groups (BPA only, EP only, PROG only, combinations and control). ED's have been given in drinking water. Hormone profiles were obtained from venous blood. Rats were sacrified after anesthesia and internal genital organs were dissected. After conventional histopathological assessment, immunohistochemical expression of androgen receptor and GnRH receptor were evaluated. RESULTS Testesteron and free testesteron leves were significantly lower in combination group ( p<0.05, FA). In prog group, testesteron levels were significantly increased (P<0.05). The most prominent difference was that testicular weight were significantly reduced in rats who was fed with combination ED's There were 3 spermatositik arrest in 2 rat. Expression of AR and GnRh aee not different among groups. CONCLUSIONS Prevalence of disease that result in male fertility has been increasing over the last decade. ED's were held responsible for this increase. Current data showed that exposure of mammals to ED' even after birth might affect off*-spring's fertility. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e420 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Gökhan Hadi Komesli Erzurum , Turkey More articles by this author Haldun Umudum Ankara, Turkey More articles by this author Okan Tarik Komesli Erzurum , Turkey More articles by this author Celal Ferdi GÖkçay Ankara, Turkey More articles by this author Ibrahim Yaþar Özgök Ankara, Turkey More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Alarelin active immunization influences expression levels of GnRHR, FSHR and LHR proteins in the ovary and enhances follicular development in ewes

We investigated the effects of gonadotropin releasing hormone (GnRH) agonist on expressions of GnRH receptor (GnRHR), follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) proteins in the ovaries and follicular development in the ewes. Forty-two pre-pubertal ewes were assigned to experimental groups 1 to 5 (EG-I to EG-V) and control group (CG). Ewes in EG-I, EG-II and EG-III were subcutaneously injected with 200, 300 or 400 μg alarelin antigens twice (on days 0 and 14), respectively. Ewes in EG-IV and EG-V were subcutaneously injected with 200 μg and 300 μg alarelin antigen four times (on days 0, 7, 14 and 21). Ewes in CG were subcutaneously injected with a solvent twice (on days 0 and 14). Serum concentrations of GnRH antibody in the EGs increased and were higher than (P<0.05) that of CG from day 14 to day 60. GnRH antibody concentrations in EG-IV and EG-V were higher than that in EG-I, EG-II and EG-III from days 35 to 45. Expressions of GnRHR protein in EG-IV and EG-V were lower than that in CG (P<0. 01). Expressions of FSHR and LHR proteins in EGs increased. Levels of FSHR and LHR proteins in EG-IV and EG-V (P<0.05) were higher than CG. Ovarian weights in EGs increased. Values of follicle vertical diameter, follicle transverse diameter, follicle wall thickness, follicle externatheca thickness and follicle internatheca thickness in EG-III and EG-V were greater than other groups. Primordial follicles and primary follicles developed quickly in alarelin-immunized animals. Secondary follicles and mature follicles became more abundant. Mitochondria, mitochondrial cristaes and cortical granules increased. Serum FSH concentrations of EGs remained higher than that in CG from days 28 to 70 (P<0.05). Alarelin immunization stimulated GnRH antibody production, suppressed expression of GnRHR protein, enhanced expressions of FSHR and LHR proteins in ovaries, promoted FSH secretion and thereby accelerated the development of ovaries and follicles in ewes.

Msx1 Homeodomain Protein Represses the αGSU and GnRH Receptor Genes During Gonadotrope Development

Multiple homeodomain transcription factors are crucial for pituitary organogenesis and cellular differentiation. A homeodomain repressor, Msx1, is expressed from the ventral aspect of the developing anterior pituitary and implicated in gonadotrope differentiation. Here, we find that Msx1 represses transcription of lineage-specific pituitary genes such as the common α-glycoprotein subunit (αGSU) and GnRH receptor (GnRHR) promoters in the mouse gonadotrope-derived cell lines, αT3-1 and LβT2. Repression of the mouse GnRHR promoter by Msx1 is mediated through a consensus-binding motif in the downstream activin regulatory element (DARE). Truncation and mutation analyses of the human αGSU promoter map Msx1 repression to a site at -114, located at the junctional regulatory element (JRE). Dlx activators are closely related to the Msx repressors, acting through the same elements, and Dlx3 and Dlx2 act as transcriptional activators for GnRHR and αGSU, respectively. Small interfering RNA knockdown of Msx1 in αT3-1 cells increases endogenous αGSU and GnRHR mRNA expression. Msx1 gene expression reaches its maximal expression at the rostral edge at e13.5. The subsequent decline in Msx1 expression specifically coincides with the onset of expression of both αGSU and GnRHR. The expression levels of both αGSU and GnRHR in Msx1-null mice at e18.5 are higher compared with wild type, further confirming a role for Msx1 in the repression of αGSU and GnRHR. In summary, Msx1 functions as a negative regulator early in pituitary development by repressing the gonadotrope-specific αGSU and GnRHR genes, but a temporal decline in Msx1 expression alleviates this repression allowing induction of GnRHR and αGSU, thus serving to time the onset of gonadotrope-specific gene program.

A Novel Reproductive Peptide, Phoenixin

Normal anterior pituitary function is essential for fertility. Release from the gland of the reproductive hormones luteinising hormone and follicle-stimulating hormone is regulated primarily by hypothalamically-derived gonadotrophin-releasing hormone (GnRH), although other releasing factors (RF) have been postulated to exist. Using a bioinformatic approach, we have identified a novel peptide, phoenixin, that regulates pituitary gonadotrophin secretion by modulating the expression of the GnRH receptor, an action with physiologically relevant consequences. Compromise of phoenixin in vivo using small interfering RNA resulted in the delayed appearance of oestrus and a reduction in GnRH receptor expression in the pituitary. Phoenixin may represent a new class of hypothalamically-derived pituitary priming factors that sensitise the pituitary to the action of other RFs, rather than directly stimulating the fusion of secretary vesicles to pituitary membranes.

Overexpression of Wild-Type but Not C134W Mutant FOXL2 Enhances GnRH-Induced Cell Apoptosis by Increasing GnRH Receptor Expression in Human Granulosa Cell Tumors

The etiology of granulosa cell tumors (GCTs) is largely unknown. The primary mode of treatment is surgical, however not all women are cured by surgery alone. Thus, it is important to develop improved treatments through a greater understanding of the molecular mechanisms that contribute to this disease. Recently, it has been shown that a FOXL2 402C>G (C134W) mutation is present in 97% of human adult-type GCTs, suggesting an important role for this mutation in the development of GCTs. We have shown previously that gonadotropin-releasing hormone (GnRH)-I and -II induce apoptosis in cultured normal human granulosa cells. Moreover, it has been reported that FOXL2 can bind to the promoter of the mouse GnRH receptor gene and regulate its transcription. Thus, we hypothesized that C134W mutant FOXL2 could modulate the pro-apoptotic effects of GnRH via aberrant regulation of GnRH receptor levels. Using KGN cells, a human GCT-derived cell line which harbors the FOXL2 402C>G mutation, we show that treatment with GnRH-I and -II induces cell apoptosis, and that small interfering RNA-mediated depletion of GnRH receptor abolishes these effects. Overexpression of wild-type FOXL2 increases both mRNA and protein levels of GnRH receptor and consequently enhances GnRH-induced apoptosis. Importantly, neither the expression levels of GnRH receptor nor GnRH-induced apoptosis were affected by overexpression of the C134W mutant FOXL2. Interestingly, knockdown of endogenous FOXL2 down-regulates GnRHR expression in normal human granulosa cells with wild-type FOXL2, but not in KGN cells. These results suggest that the FOXL2 402C>G mutation may contribute to the development of human adult-type GCTs by reducing the expression of GnRH receptor, thus conferring resistance to GnRH-induced cell apoptosis.

The Extrapituitary Effects of GnRH Antagonists and Their Potential Clinical Implications: A Narrated Review

Potential roles of gonadotropin-releasing hormone (GnRH) antagonists on GnRH/GnRH receptor systems and their effects on the extrapituitary tissues are largely elusive. In this narrated review, we summarized the systemic effects of GnRH antagonists on ovary, endometrium, embryo implantation, placental development, fetal teratogenicity, reproductive tissue cancer cells, and heart while briefly reviewing the GnRH and GnRH receptor system. GnRH antagonists may have direct effects on ovarian granulosa cells. Data are conflicting regarding their effects on endometrial receptivity. The GnRH antagonists may potentially have detrimental effect on early placentation by decreasing the invasive ability of cytotrophoblasts if the exposure to them occurs during early pregnancy. The GnRH antagonists were not found to increase the rates of congenital malformations. Comparative clinical data are required to explore their systemic effects on various extrapituitary tissues such as on cardiac function in the long term as well as their potential use in other human cancers that express GnRH receptors.

Negative Effects of High Glucose Exposure in Human Gonadotropin-Releasing Hormone Neurons

Metabolic disorders are often associated with male hypogonadotropic hypogonadism, suggesting that hypothalamic defects involving GnRH neurons may impair the reproductive function. Among metabolic factors hyperglycemia has been implicated in the control of the reproductive axis at central level, both in humans and in animal models. To date, little is known about the direct effects of pathological high glucose concentrations on human GnRH neurons. In this study, we investigated the high glucose effects in the human GnRH-secreting FNC-B4 cells. Gene expression profiling by qRT-PCR, confirmed that FNC-B4 cells express GnRH and several genes relevant for GnRH neuron function (KISS1R, KISS1, sex steroid and leptin receptors, FGFR1, neuropilin 2, and semaphorins), along with glucose transporters (GLUT1, GLUT3, and GLUT4). High glucose exposure (22 mM; 40 mM) significantly reduced gene and protein expression of GnRH, KISS1R, KISS1, and leptin receptor, as compared to normal glucose (5 mM). Consistent with previous studies, leptin treatment significantly induced GnRH mRNA expression at 5 mM glucose, but not in the presence of high glucose concentrations. In conclusion, our findings demonstrate a deleterious direct contribution of high glucose on human GnRH neurons, thus providing new insights into pathogenic mechanisms linking metabolic disorders to reproductive dysfunctions.

Effect of salsolinol on GnRH receptor and LHβ subunit gene expression in the anterior pituitary of lactating sheep

Effect of salsolinol on GnRH receptor and LHβ subunit gene expression in the anterior pituitary of lactating sheep

Targeting Gonadotropin-releasing Hormone Receptor Inhibits the Early Step of Ovarian Cancer Metastasis by Modulating Tumor-mesothelial Adhesion

Ovarian cancer has a clear predilection to metastasize to the peritoneum, which represents one of the most important prognostic factors of poor clinical outcome. Gonadotropin-releasing hormone (GnRH) receptor is significantly overexpressed during the malignant progression of human ovarian cancer. Here, using lentiviral-based small interfering RNA (siRNA) technology to downregulate GnRH receptor in metastatic ovarian cancer cells, we show that GnRH receptor is an important mediator of ovarian cancer peritoneal metastasis. GnRH receptor downregulation dramatically attenuated their adhesion to the peritoneal mesothelium. By inhibiting the expression of GnRH receptor, we showed decreased expression of α2β1 and α5β1 integrin and adhesion to specific extracellular matrix (ECM) proteins. This was also associated with a reduction of P-cadherin. Furthermore, adhesion of ovarian cancer cells to different ECMs and the mesothelium were abrogated in response to β1 integrin and P-cadherin reduction, confirming that the effects were β1 integrin- and P-cadherin-specific. Using a mouse model of human ovarian cancer metastasis, we found that the inhibition of GnRH receptor, β1 integrin, and P-cadherin significantly attenuated tumor growth, ascites formation, and the number of metastatic implants. These results define a new role for GnRH receptor in early metastasis and offer the possibility of novel therapeutic targets.

Pharmacoperone IN3 enhances the apoptotic effect of leuprolide in prostate cancer cells by increasing the gonadotropin-releasing hormone receptor in the cell membrane

Gonadotropin-releasing hormone (GnRH) agonists are widely used for the treatment of advanced prostate cancer (PCa). Agonists activate the GnRH receptor (GnRH-R), triggering apoptosis in PCa cells. In gonadotropes, the amount of GnRH-R in the plasma membrane is regulated by protein folding and endoplasmic reticulum retention, mechanisms that can be overcome by the pharmacoperone IN3. Our aim was to describe the intracellular distribution of GnRH-R in PCa cells and its relation to response to GnRH analog treatments. The expressions of GnRH-R in PCa biopsies were evaluated by immunohistochemistry and the intracellular distribution was determined by immunofluorescence in primary cell cultures from human PCa samples. Cultured cells were pretreated with IN3 and then with leuprolide. Cell survival was evaluated by 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) thiazolyl blue formazan and cell cycle and apoptosis by flow cytometry. We observed that the expression of GnRH-R decreased according to malignant progression. Most GnRH-R are located inside the cell, colocalizing with endoplasmic reticulum markers. The treatment with IN3 decreased cellular GnRH-R retention, increasing plasma membrane expression in approximately 60%. Pretreatment with IN3 decreased PCa cell survival compared with leuprolide-alone treatment, primarily because of an increase in apoptosis. We conclude that the response of PCa cells to leuprolide is related to the amount of GnRH-R in the plasma membrane. Therefore, pretreatment evaluation of the amount of these receptors may be a predictor of the outcome of leuprolide treatment in PCa patients. Assessment of systemic IN3 effect would be necessary to determine its utility as an adjuvant treatment in hormone-resistant tumors.

Localization of Gonadotropin‐Releasing Hormone (GnRH), Gonadotropin‐Inhibitory Hormone (GnIH), Kisspeptin and GnRH Receptor and Their Possible Roles in Testicular Activities From Birth to Senescence in Mice

The changes in distribution and concentration of neuropeptides, gonadotropin-releasing hormone (GnRH), gonadotropin-inhibitory hormone (GnIH), kisspeptin, and gonadotropin-releasing hormone receptor (GnRH-R) were evaluated and compared with reproductive parameters, such as cytochrome P450 side-chain cleavage (P450 SCC) enzyme activity, androgen receptors (AR) in the testis and serum testosterone levels, from birth to senescence in mice. The results showed the localization of these molecules mainly in the interstitial and germ cells as well as showed significant variations in immunostatining from birth to senescence. It was found that increased staining of testicular GnRH-R coincided with increased steroidogenic activity during pubertal and adult stages, whereas decreased staining coincides with decreased steroidogenic activity during senescence. Similar changes in immunostaining were confirmed by Western/slot blot analysis. Thus, these results suggest a putative role of GnRH during testicular pubertal development and senescence. Treatment with a GnRH agonist ([DTrp(6), Pro(9)-NEt] GnRH) to mice from prepubertal to pubertal period showed a significant increase in steroidogenic activity of the mouse testis and provided further support to the role of GnRH in testicular pubertal maturation. The significant decline in GnRH-R during senescence may be due to a significant increase in GnIH synthesis during senescence causing the decrease in GnRH-R expression. It is considered that significant changes in the levels of GnRH-R may be responsible for changes in steroidogenesis that causes either pubertal activation or senescence in testis of mice. Furthermore, changes in the levels of GnRH-R may be modulated by interactions among GnRH, GnIH, and kisspeptin in the testis.

Cospeptin, a novel reproductive peptide

Using a bioinformatics screen, our group recently discovered the novel neuropeptide cospeptin. We detected highest levels of cospeptin in the hypothalamus, including the periventricular nucleus, suggesting that cospeptin may influence pituitary hormone secretion. Cospeptin treatment alone failed to alter secretion of anterior pituitary (AP) hormones from dispersed primary rat pituitary cells; however, we found that cospeptin pre‐treatment potentiated release of luteinizing hormone in response to gonadotrophin‐releasing hormone (GnRH) stimulation. To determine if cospeptin plays a role in regulation of reproductive function, we compromised production of endogenous cospeptin by administration of siRNA directed against cospeptin into the lateral cerebroventricle of adult female rats, and used vaginal cytology to track the integrity of the estrous cycle. Treatment with cospeptin siRNA caused a delay in the appearance of the next estrus, and led to a decrease in GnRH receptor message in AP, suggesting cospeptin sensitizes gonadotrophs by upregulating the transcription of the GnRH receptor. These and other results suggest that cospeptin is an important reproductive hormone that modulates the sensitivity of pituitary gonadotrophs to GnRH through regulation of the expression of GnRH receptor.

Effect of gonadotropin-releasing hormone on phagocytic leucocytes of rainbow trout

To clarify the role of gonadotropin-releasing hormone (GnRH) in the fish immune system, in vitro effect of GnRH was examined in phagocytic leucocytes of rainbow trout (Oncorhynchus mykiss). Gene expression of GnRH-receptor was detected by RT-PCR in leucocytes from head kidney. Administration of sGnRH increased proliferation and mRNA levels of a proinflammatory cytokine, tumor necrosis factor (TNF)-α, in trout leucocytes. Superoxide production in zymosan-stimulated phagocytic leucocytes was also increased by sGnRH in a dose-related manner from 0.01 to 100nM. There was no significant effect of sGnRH on mRNA levels of growth hormone (GH) expressed in trout phagocytic leucocytes. Immunoneutralization of GH by addition of anti-salmon GH serum into the medium could not block the stimulatory effect of sGnRH on superoxide production. These results indicate that GnRH stimulates phagocytosis in fish leucocytes through a GnRH-receptor-dependent pathway, and that the effect of GnRH is not mediated through paracrine GH in leucocytes.

Overexpression of Wild-type FOXL2 but Not C134W Mutant FOXL2 Enhances GnRH-induced Cell Apoptosis by Increasing GnRH Receptor Expression in Human Granulosa Tumor Cells.

Overexpression of Wild-type FOXL2 but Not C134W Mutant FOXL2 Enhances GnRH-induced Cell Apoptosis by Increasing GnRH Receptor Expression in Human Granulosa Tumor Cells.

Genetic Identification of GnRH Receptor Neurons: A New Model for Studying Neural Circuits Underlying Reproductive Physiology in the Mouse Brain

GnRH signaling regulates reproductive physiology in vertebrates via the hypothalamic-pituitary-gonadal axis. In addition, GnRH signaling has been postulated to act on the brain. However, elucidating its functional role in the central nervous system has been hampered because of the difficulty in identifying direct GnRH signaling targets in live brain tissue. Here we used a binary genetic strategy to visualize GnRH receptor (GnRHR) neurons in the mouse brain and started to characterize these cells. First, we expressed different fluorescent proteins in GnRHR neurons and mapped their precise distribution throughout the brain. Remarkably, neuronal GnRHR expression was only initiated after postnatal day 16, suggesting peri- and postpubertal functions of GnRH signaling in this organ. GnRHR neurons were found in different brain areas. Many GnRHR neurons were identified in areas influencing sexual behaviors. Furthermore, GnRHR neurons were detected in brain areas that process olfactory and pheromonal cues, revealing one efferent pathway by which the neuroendocrine hypothalamus may influence the sensitivity towards chemosensory cues. Using confocal Ca(2+) imaging in brain slices, we show that GnRHR neurons respond reproducibly to extracellular application of GnRH or its analog [D-TRP(6)]-LH-RH, indicating that these neurons express functional GnRHR. Interestingly, the duration and shape of the Ca(2+) responses were similar within and different between brain areas, suggesting that GnRH signaling may differentially influence brain functions to affect reproductive success. Our new mouse model sets the stage to analyze the next level of GnRH signaling in reproductive physiology and behavior.