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Constantin S, Sokanovic SJ, Mochimaru Y, Smiljanic K, Sivcev S, Prévide RM, Wray S, Balla T, Stojilkovic SS. Postnatal Development and Maintenance of Functional Pituitary Gonadotrophs Is Dependent on PI4-Kinase A. Endocrinology 2023; 164:bqad168. [PMID: 37935042 PMCID: PMC10652335 DOI: 10.1210/endocr/bqad168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/27/2023] [Accepted: 11/01/2023] [Indexed: 11/09/2023]
Abstract
Postnatal development of functional pituitary gonadotrophs is necessary for maturation of the hypothalamic-pituitary-gonadal axis, puberty, and reproduction. Here we examined the role of PI4-kinase A, which catalyzes the biosynthesis of PI4P in mouse reproduction by knocking out this enzyme in cells expressing the gonadotropin-releasing hormone (GnRH) receptor. Knockout (KO) mice were infertile, reflecting underdeveloped gonads and reproductive tracts and lack of puberty. The number and distribution of hypothalamic GnRH neurons and Gnrh1 expression in postnatal KOs were not affected, whereas Kiss1/kisspeptin expression was increased. KO of PI4-kinase A also did not alter embryonic establishment and neonatal development and function of the gonadotroph population. However, during the postnatal period, there was a progressive loss of expression of gonadotroph-specific genes, including Fshb, Lhb, and Gnrhr, accompanied by low gonadotropin synthesis. The postnatal gonadotroph population also progressively declined, reaching approximately one-third of that observed in controls at 3 months of age. In these residual gonadotrophs, GnRH-dependent calcium signaling and calcium-dependent membrane potential changes were lost, but intracellular administration of inositol-14,5-trisphosphate rescued this signaling. These results indicate a key role for PI4-kinase A in the postnatal development and maintenance of a functional gonadotroph population.
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Affiliation(s)
- Stephanie Constantin
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Srdjan J Sokanovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yuta Mochimaru
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kosara Smiljanic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sonja Sivcev
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rafael M Prévide
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Susan Wray
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Stanko S Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Constantin S, Bjelobaba I, Stojilkovic SS. Pituitary gonadotroph-specific patterns of gene expression and hormone secretion. Curr Opin Pharmacol 2022; 66:102274. [PMID: 35994915 PMCID: PMC9509429 DOI: 10.1016/j.coph.2022.102274] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/30/2022] [Accepted: 07/04/2022] [Indexed: 11/28/2022]
Abstract
Pituitary gonadotrophs play a key role in reproductive functions by secreting luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The LH secretory activity of gonadotroph is controlled by hypothalamic gonadotropin-releasing hormone (GnRH) via GnRH receptors and is accompanied by only minor effects on high basal Lhb gene expression. The secretory profiles of GnRH and LH are highly synchronized, with the latter reflecting a depletion of prestored LH in secretory vesicles by regulated exocytosis. In contrast, FSH is predominantly released by constitutive exocytosis, and secretory activity reflects the kinetics of Fshb gene expression controlled by GnRH, activin, and inhibin. Here is a review of recent data to improve the understanding of multiple patterns of gonadotroph gene expression and hormone secretion.
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Affiliation(s)
- Stephanie Constantin
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ivana Bjelobaba
- Department for Neurobiology, Institute for Biological Research "Siniša Stanković" - National Institute of Republic of Serbia, University of Belgrade, Bulevar Despota Stefana 142, 11000, Belgrade, Serbia
| | - Stanko S Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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Abstract
Dexamethasone-induced Ras-related protein 1 (Rasd1) is a member of the Ras superfamily of monomeric G proteins that have a regulatory function in signal transduction. Rasd1, also known as Dexras1 or AGS1, is rapidly induced by dexamethasone (Dex). While prior data indicates that Rasd1 is highly expressed in the pituitary and that the gene may function in regulation of corticotroph activity, its exact cellular localization in this tissue has not been delineated. Nor has it been determined which endocrine pituitary cell type(s) are responsive to Dex-induced expression of Rasd1. We hypothesized that Rasd1 is primarily localized in corticotrophs and furthermore, that its expression in these cells would be upregulated in response to exogenous Dex administration. Rasd1 expression in each pituitary cell type both under basal conditions and 1-hour post Dex treatment were examined in adult male mice. While a proportion of all endocrine pituitary cell types expressed Rasd1, a majority of corticotrophs and thyrotrophs expressed Rasd1 under basal condition. In vehicle treated animals, approximately 50-60% of corticotrophs and thyrotrophs cells expressed Rasd1 while the gene was detected in only 15-30% of lactotrophs, somatotrophs, and gonadotrophs. In Dex treated animals, Rasd1 expression was significantly increased in corticotrophs, somatotrophs, lactotrophs, and gonadotrophs but not thyrotrophs. In Dex treated animals, Rasd1 was detected in 80-95% of gonadotrophs and corticotrophs. In contrast, Dex treatment increased Rasd1 expression to a lesser extent (55-60%) in somatotrophs and lactotrophs. Corticotrophs of the pars intermedia, which lack glucocorticoid receptors, failed to display increased Rasd1 expression in Dex treated animals. Rasd1 is highly expressed in corticotrophs under basal conditions and is further increased after Dex treatment, further supporting its role in glucocorticoid negative feedback. In addition, the presence and Dex-induced expression of Rasd1 in endocrine pituitary cell types, other than corticotrophs, may implicate Rasd1 in novel pituitary functions.
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Affiliation(s)
- Chad D Foradori
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Laci Mackay
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Chen-Che J Huang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Robert J Kemppainen
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
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Bjelobaba I, Janjic MM, Prévide RM, Abebe D, Kucka M, Stojilkovic SS. Distinct Expression Patterns of Osteopontin and Dentin Matrix Protein 1 Genes in Pituitary Gonadotrophs. Front Endocrinol (Lausanne) 2019; 10:248. [PMID: 31057484 PMCID: PMC6478748 DOI: 10.3389/fendo.2019.00248] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 03/29/2019] [Indexed: 01/06/2023] Open
Abstract
Cell-matrix interactions play important roles in pituitary development, physiology, and pathogenesis. In other tissues, a family of non-collagenous proteins, termed SIBLINGs, are known to contribute to cell-matrix interactions. Anterior pituitary gland expresses two SIBLING genes, Dmp1 (dentin matrix protein-1) and Spp1 (secreted phosphoprotein-1) encoding DMP1 and osteopontin proteins, respectively, but their expression pattern and roles in pituitary functions have not been clarified. Here we provide novel evidence supporting the conclusion that Spp1/osteopontin, like Dmp1/DMP1, are expressed in gonadotrophs in a sex- and age-specific manner. Other anterior pituitary cell types do not express these genes. In contrast to Dmp1, Spp1 expression is higher in males; in females, the expression reaches the peak during the diestrus phase of estrous cycle. In further contrast to Dmp1 and marker genes for gonadotrophs, the expression of Spp1 is not regulated by gonadotropin-releasing hormone in vivo and in vitro. However, Spp1 expression increases progressively after pituitary cell dispersion in both female and male cultures. We may speculate that gonadotrophs signal to other pituitary cell types about changes in the structure of pituitary cell-matrix network by osteopontin, a function consistent with the role of this secretory protein in postnatal tissue remodeling, extracellular matrix reorganization after injury, and tumorigenesis.
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Affiliation(s)
- Ivana Bjelobaba
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
- Institute for Biological Research Sinisa Stankovic, University of Belgrade, Belgrade, Serbia
| | - Marija M. Janjic
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
- Institute for Biological Research Sinisa Stankovic, University of Belgrade, Belgrade, Serbia
| | - Rafael Maso Prévide
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
| | - Daniel Abebe
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
| | - Marek Kucka
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
| | - Stanko S. Stojilkovic
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, MD, United States
- *Correspondence: Stanko S. Stojilkovic
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Abstract
Gonadotrophs are basophilic cells of the anterior pituitary gland specialized to secrete gonadotropins in response to elevation in intracellular calcium concentration. These cells fire action potentials (APs) spontaneously, coupled with voltage-gated calcium influx of insufficient amplitude to trigger gonadotropin release. The spontaneous excitability of gonadotrophs reflects the expression of voltage-gated sodium, calcium, potassium, non-selective cation-conducting, and chloride channels at their plasma membrane (PM). These cells also express the hyperpolarization-activated and cyclic nucleotide-gated cation channels at the PM, as well as GABAA, nicotinic, and purinergic P2X channels gated by γ-aminobutyric acid (GABA), acetylcholine (ACh), and ATP, respectively. Activation of these channels leads to initiation or amplification of the pacemaking activity, facilitation of calcium influx, and activation of the exocytic pathway. Gonadotrophs also express calcium-conducting channels at the endoplasmic reticulum membranes gated by inositol trisphosphate and intracellular calcium. These channels are activated potently by hypothalamic gonadotropin-releasing hormone (GnRH) and less potently by several paracrine calcium-mobilizing agonists, including pituitary adenylate cyclase-activating peptides, endothelins, ACh, vasopressin, and oxytocin. Activation of these channels causes oscillatory calcium release and a rapid gonadotropin release, accompanied with a shift from tonic firing of single APs to periodic bursting type of electrical activity, which accounts for a sustained calcium signaling and gonadotropin secretion. This review summarizes our current understanding of ion channels as signaling molecules in gonadotrophs, the role of GnRH and paracrine agonists in their gating, and the cross talk among channels.
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Affiliation(s)
- Stanko S. Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Stanko S. Stojilkovic,
| | - Ivana Bjelobaba
- Institute for Biological Research “Siniša Stanković”, University of Belgrade, Belgrade, Serbia
| | - Hana Zemkova
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czechia
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Janjic MM, Stojilkovic SS, Bjelobaba I. Intrinsic and Regulated Gonadotropin-Releasing Hormone Receptor Gene Transcription in Mammalian Pituitary Gonadotrophs. Front Endocrinol (Lausanne) 2017; 8:221. [PMID: 28928715 PMCID: PMC5591338 DOI: 10.3389/fendo.2017.00221] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 08/16/2017] [Indexed: 12/14/2022] Open
Abstract
The hypothalamic decapeptide gonadotropin-releasing hormone (GnRH), acting via its receptors (GnRHRs) expressed in pituitary gonadotrophs, represents a critical molecule in control of reproductive functions in all vertebrate species. GnRH-activated receptors regulate synthesis of gonadotropins in a frequency-dependent manner. The number of GnRHRs on the plasma membrane determines the responsiveness of gonadotrophs to GnRH and varies in relation to age, sex, and physiological status. This is achieved by a complex control that operates at transcriptional, translational, and posttranslational levels. This review aims to overview the mechanisms of GnRHR gene (Gnrhr) transcription in mammalian gonadotrophs. In general, Gnrhr exhibits basal and regulated transcription activities. Basal Gnrhr transcription appears to be an intrinsic property of native and immortalized gonadotrophs that secures the presence of a sufficient number GnRHRs to preserve their functionality independently of the status of regulated transcription. On the other hand, regulated transcription modulates GnRHR expression during development, reproductive cycle, and aging. GnRH is crucial for regulated Gnrhr transcription in native gonadotrophs but is ineffective in immortalized gonadotrophs. In rat and mouse, both basal and GnRH-induced Gnrhr transcription rely primarily on the protein kinase C signaling pathway, with subsequent activation of mitogen-activated protein kinases. Continuous GnRH application, after a transient stimulation, shuts off regulated but not basal transcription, suggesting that different branches of this signaling pathway control transcription. Pituitary adenylate cyclase-activating polypeptide, but not activins, contributes to the regulated transcription utilizing the protein kinase A signaling pathway, whereas a mechanisms by which steroid hormones modulate Gnrhr transcription has not been well characterized.
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Affiliation(s)
- Marija M. Janjic
- Department of Neurobiology, Institute for Biological Research “Sinisa Stankovic”, University of Belgrade, Belgrade, Serbia
| | - Stanko S. Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Ivana Bjelobaba
- Department of Neurobiology, Institute for Biological Research “Sinisa Stankovic”, University of Belgrade, Belgrade, Serbia
- *Correspondence: Ivana Bjelobaba,
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Anwar H, Rahman ZU. Dynamics of anterior pituitary immunoreactive gonadotrophs in moulted hens supplemented with protein, symbiotic and probiotics. J Anim Physiol Anim Nutr (Berl) 2015; 100:448-55. [PMID: 26335931 DOI: 10.1111/jpn.12382] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 06/29/2015] [Indexed: 11/28/2022]
Abstract
The present work delineates redistribution patterns of the hormone-producing cells of the anterior pituitary, after the phase of moulting. Two hundred single comb White Leghorn hens at the end of their first production cycle (Age = 70 week) were purchased from the commercial poultry farm and were induced to moult by high-dietary zinc (3 g/kg feed/day) after 1 week of acclimatization, at the experimental research station, Department of Physiology and Pharmacology, University of Agriculture, Faisalabad. The moulted birds were equally (n = 50) and randomly allocated to their respective groups as G1 (control; CP (Crude protein) 16%, no supplement), G2 (CP18%, no other supplement), G3 (CP16%, symbiotic at does rate of 85 mg/l in drinking water daily) and G4 (CP16%, probiotic at dose rate of 85 mg/l in drinking water daily). Ten birds were slaughtered in each group at 5% and at peak of post-moult production stage to collect their pituitary glands. An earlier post-moult production recovery, sustained and lengthier production span was seen in the G2 as compared to all other groups. The lowest production and an earlier production decline were seen in G1. The cell diameter and area of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) gonadotroph increased (p ≤ 0.01) in G2 and G3 as compared to G1. The FSH gonadotroph nucleus diameter and area did increase (p ≤ 0.01) in G2 and G3, while LH gonadotroph nucleus diameter and area decreased (p ≤ 0.01) in G2 and G3 as compared to G1. The increased FSH and LH gonadotroph diameter in protein and symbiotic supplemented birds is accountable for the increased egg production in these groups.
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Affiliation(s)
- H Anwar
- Department of Physiology, Government College University, Faisalabad, Pakistan
| | - Z U Rahman
- Institute of Pharmacy, Physiology and Pharmacology, University of Agriculture, Faisalabad, Pakistan
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Chaube R, Joy KP, Acharjee A. Catfish gonadotrophins: cellular origin, structural properties and physiology. J Neuroendocrinol 2015; 27:536-43. [PMID: 25879854 DOI: 10.1111/jne.12286] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 03/09/2015] [Accepted: 04/09/2015] [Indexed: 02/02/2023]
Abstract
Gonadotrophins (GTHs) play a central role in the regulation of gametogenesis and spawning. The structural duality of the GTHs [luteinising hormone (LH) and follicle-stimulating hormone (FSH)] is established in fishes with the exception of ancestral vertebrates. Most studies indicate that, in teleosts, the GTHs are secreted in separate cells. Phylogenetic analysis shows that the common α-subunit of the GTHs (and also of thyroid-stimulating hormone) and LHβ are highly conserved in fishes, as in tetrapods. However, FSHβ shows considerable divergence in teleosts. There may be 12 or 13 cysteine residues, with an additional one near the N-terminus. There may be one or two N-linked glycolsyation sites. In catfishes, there are 13 cysteine residues and one N-linked glycosylation site. In an extreme situation, a potential glycosylation site is lacking in some fishes. Both FSH and LH receptors are characterised in teleosts. The FSH receptor is promiscuous and can be cross-activated by LH. By contrast, the LH receptor is highly selective, being activated by its natural ligand or by heterologous ligands (e.g. human chorionic gonadotrophin). Consequently, teleosts show different patterns of LH and FSH secretion. In catfishes, in the absence of native FSH protein, LH controls all aspects of reproduction, from early gametogenesis to spawning.
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Affiliation(s)
- R Chaube
- Zoology Department, Mahila Mahavidhylaya, Banaras Hindu University, Varanasi, India
| | - K P Joy
- Department of Zoology, Centre of Advanced Study, Banaras Hindu University, Varanasi, India
| | - A Acharjee
- Department of Zoology, Centre of Advanced Study, Banaras Hindu University, Varanasi, India
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Abel MH, Widen A, Wang X, Huhtaniemi I, Pakarinen P, Kumar TR, Christian HC. Pituitary gonadotrophic hormone synthesis, secretion, subunit gene expression and cell structure in normal and follicle-stimulating hormone β knockout, follicle-stimulating hormone receptor knockout, luteinising hormone receptor knockout, hypogonadal and ovariectomised female mice. J Neuroendocrinol 2014; 26:785-95. [PMID: 25039914 PMCID: PMC5604239 DOI: 10.1111/jne.12178] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 07/02/2014] [Accepted: 07/13/2014] [Indexed: 11/27/2022]
Abstract
To investigate the relationship between gonadotroph function and ultrastructure, we have compared, in parallel in female mice, the effects of several different mutations that perturb the hypothalamic-pituitary-gonadal axis. Specifically, serum and pituitary gonadotrophin concentrations, gonadotrophin gene expression, gonadotroph structure and number were measured. Follicle-stimulating hormone β knockout (FSHβKO), follicle-stimulating hormone receptor knockout (FSHRKO), luteinising hormone receptor knockout (LuRKO), hypogonadal (hpg) and ovariectomised mice were compared with control wild-type or heterozygote female mice. Serum levels of LH were elevated in FSHβKO and FSHRKO compared to heterozygote females, reflecting the likely decreased oestrogen production in KO females, as demonstrated by the threadlike uteri and acyclicity. As expected, there was no detectable FSH in the serum or pituitary and an absence of expression of the FSHβ subunit gene in FSHβKO mice. However, there was a significant increase in expression of the FSHβ and LHβ subunit genes in FSHRKO female mice. The morphology of FSHβKO and FSHRKO gonadotrophs was not significantly different from the control, except that secretory granules in FSHRKO gonadotrophs were larger in diameter. In LuRKO and ovariectomised mice, stimulation of LHβ and FSHβ mRNA, as well as serum protein concentrations, were reflected in subcellular changes in gonadotroph morphology, including more dilated rough endoplasmic reticula and fewer, larger secretory granules. In the gonadotophin-releasing hormone deficient hpg mouse, gonadotrophin mRNA and protein levels were significantly lower than in control mice and gonadotrophs were correspondingly smaller with less abundant endoplasmic reticula and reduced numbers of secretory granules. In summary, major differences in pituitary content and serum concentrations of the gonadotrophins LH and FSH were found between control and mutant female mice. These changes were associated with changes in expression of the gonadotrophin subunit genes and were reflected in the cellular structure and secretory granule appearance within the gonadotroph cells.
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Affiliation(s)
- M. H. Abel
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - A. Widen
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - X. Wang
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - I. Huhtaniemi
- Department of Physiology, University of Turku, Turku, Finland
| | - P. Pakarinen
- Department of Physiology, University of Turku, Turku, Finland
| | - T. R. Kumar
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, USA
| | - H. C. Christian
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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Abel MH, Charlton HM, Huhtaniemi I, Pakarinen P, Kumar TR, Christian HC. An investigation into pituitary gonadotrophic hormone synthesis, secretion, subunit gene expression and cell structure in normal and mutant male mice. J Neuroendocrinol 2013; 25:863-75. [PMID: 23895394 PMCID: PMC5599115 DOI: 10.1111/jne.12081] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 07/16/2013] [Accepted: 07/24/2013] [Indexed: 01/30/2023]
Abstract
To investigate brain-pituitary-gonadal inter-relationships, we have compared the effects of mutations that perturb the hypothalamic-pituitary-gonadal axis in male mice. Specifically, serum and pituitary gonadotrophin concentrations, gonadotrophin gene expression, and gonadotroph structure and number were measured. Follicle-stimulating hormone (FSH)β knockout (FSHβKO), FSH receptor knockout (FSHRKO), luteinising hormone (LH) receptor knockout (LuRKO), hypogonadal (hpg), testicular feminised (tfm) and gonadectomised mice were compared with control wild-type mice or heterozygotes. Serum levels of LH were similar in FSHβKO, FSHRKO and heterozygote males despite decreased androgen production in KO males. As expected, there was no detectable FSH in the serum or pituitary and an absence of expression of the FSHβ subunit gene in FSHβKO mice. However, there was a significant increase in expression of the common α and LHβ subunit genes in FSHRKO males. The morphology of FSHβKO and FSHRKO gonadotrophs was not significantly different from controls, except that the subpopulation of granules consisting of an electron-dense core and electron-lucent 'halo' was not observed in FSHβKO gonadotrophs and the granules were smaller in diameter. In the gonadotrophin-releasing hormone deficient hpg mouse, gonadotrophin mRNA and hormone levels were significantly lower compared to control mice and gonadotrophs were correspondingly smaller, with less abundant endoplasmic reticulum and reduced secretory granules. In LuRKO, tfm and gonadectomised mice, hyperstimulation of LHβ and FSHβ mRNA and serum protein concentrations was reflected by subcellular changes in gonadotroph morphology, including more dilated rough endoplasmic reticulum and more secretory granules distributed adjacent to the plasma membrane. In summary, major differences in pituitary content and serum concentrations of the gonadotrophins LH and FSH have been found between normal and mutant male mice. These changes are associated with changes in transcriptional activity of the gonadotrophin subunit genes and are reflected by changes in the cellular structure and secretory granule architecture within the gonadotroph cells.
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Affiliation(s)
- M. H. Abel
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - H. M. Charlton
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - I. Huhtaniemi
- Department of Physiology, University of Turku, Turku, Finland
| | - P. Pakarinen
- Department of Physiology, University of Turku, Turku, Finland
| | - T. R. Kumar
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center,, Kansas City, KS, USA
| | - H. C. Christian
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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11
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Durán-Pastén ML, Fiordelisio T. GnRH-Induced Ca(2+) Signaling Patterns and Gonadotropin Secretion in Pituitary Gonadotrophs. Functional Adaptations to Both Ordinary and Extraordinary Physiological Demands. Front Endocrinol (Lausanne) 2013; 4:127. [PMID: 24137156 PMCID: PMC3786263 DOI: 10.3389/fendo.2013.00127] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Accepted: 08/31/2013] [Indexed: 11/13/2022] Open
Abstract
PITUITARY GONADOTROPHS ARE A SMALL FRACTION OF THE ANTERIOR PITUITARY POPULATION, YET THEY SYNTHESIZE GONADOTROPINS: luteinizing (LH) and follicle-stimulating (FSH), essential for gametogenesis and steroidogenesis. LH is secreted via a regulated pathway while FSH release is mostly constitutive and controlled by synthesis. Although gonadotrophs fire action potentials spontaneously, the intracellular Ca(2+) rises produced do not influence secretion, which is mainly driven by Gonadotropin-Releasing Hormone (GnRH), a decapeptide synthesized in the hypothalamus and released in a pulsatile manner into the hypophyseal portal circulation. GnRH binding to G-protein-coupled receptors triggers Ca(2+) mobilization from InsP3-sensitive intracellular pools, generating the global Ca(2+) elevations necessary for secretion. Ca(2+) signaling responses to increasing (GnRH) vary in stereotyped fashion from subthreshold to baseline spiking (oscillatory), to biphasic (spike-oscillatory or spike-plateau). This progression varies somewhat in gonadotrophs from different species and biological preparations. Both baseline spiking and biphasic GnRH-induced Ca(2+) signals control LH/FSH synthesis and exocytosis. Estradiol and testosterone regulate gonadotropin secretion through feedback mechanisms, while FSH synthesis and release are influenced by activin, inhibin, and follistatin. Adaptation to physiological events like the estrous cycle, involves changes in GnRH sensitivity and LH/FSH synthesis: in proestrus, estradiol feedback regulation abruptly changes from negative to positive, causing the pre-ovulatory LH surge. Similarly, when testosterone levels drop after orquiectomy the lack of negative feedback on pituitary and hypothalamus boosts both GnRH and LH secretion, gonadotrophs GnRH sensitivity increases, and Ca(2+) signaling patterns change. In addition, gonadotrophs proliferate and grow. These plastic changes denote a more vigorous functional adaptation in response to an extraordinary functional demand.
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Affiliation(s)
- Maria Luisa Durán-Pastén
- Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México (UNAM), México DF, México
| | - Tatiana Fiordelisio
- Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México (UNAM), México DF, México
- *Correspondence: Tatiana Fiordelisio, Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México (UNAM), Circuito exterior s/n. Ciudad Universitaria, C.P. 04510 México DF, México e-mail:
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Brannick KE, Craig ZR, Himes AD, Peretz JR, Wang W, Flaws JA, Raetzman LT. Prenatal exposure to low doses of bisphenol A increases pituitary proliferation and gonadotroph number in female mice offspring at birth. Biol Reprod 2012; 87:82. [PMID: 22875908 PMCID: PMC3507543 DOI: 10.1095/biolreprod.112.100636] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 05/09/2012] [Accepted: 08/01/2012] [Indexed: 12/15/2022] Open
Abstract
The pituitary gland is composed of hormone-producing cells essential for homeostasis and reproduction. Pituitary cells are sensitive to endocrine feedback in the adult and can have altered hormonal secretion from exposure to the endocrine disruptor bisphenol A (BPA). BPA is a prevalent plasticizer used in food and beverage containers, leading to widespread human exposure. Although prenatal exposure to BPA can impact reproductive function in the adult, the effects of BPA on the developing pituitary are unknown. We hypothesized that prenatal exposure to low doses of BPA impacts gonadotroph cell number or parameters of hormone synthesis. To test this, pregnant mice were administered 0.5 μg/kg/day of BPA, 50 μg/kg/day of BPA, or vehicle beginning on Embryonic Day 10.5. At parturition, pituitaries from female offspring exposed in utero to either dose of BPA had increased proliferation, as assessed by mKi67 mRNA levels and immunohistochemistry. Coincidently, gonadotroph number also increased in treated females. However, we observed a dichotomy between mRNA levels of Lhb and Fshb. Female mice exposed to 0.5 μg/kg/day BPA had increased mRNA levels of gonadotropins and the gonadotropin-receptor hormone (GNRH) receptor (Gnrhr), which mediates GNRH regulation of gonadotropin production and release. In contrast, mice treated with 50 μg/kg/day of BPA had decreased gonadotropin mRNA levels, Gnrhr and Nr5a1, a transcription factor required for gonadotroph differentiation. No other pituitary hormones were altered on the day of birth in response to in utero BPA exposure, and male pituitaries showed no change in the parameters tested. Collectively, these results show that prenatal exposure to BPA affects pituitary gonadotroph development in females.
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Affiliation(s)
- Katherine E. Brannick
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Zelieann R. Craig
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Ashley D. Himes
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Jackye R. Peretz
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Wei Wang
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Jodi A. Flaws
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Lori T. Raetzman
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois
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Tomić M, Kucka M, Kretschmannova K, Li S, Nesterova M, Stratakis CA, Stojilkovic SS. Role of nonselective cation channels in spontaneous and protein kinase A-stimulated calcium signaling in pituitary cells. Am J Physiol Endocrinol Metab 2011; 301:E370-9. [PMID: 21586701 PMCID: PMC3154538 DOI: 10.1152/ajpendo.00130.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Several receptors linked to the adenylyl cyclase signaling pathway stimulate electrical activity and calcium influx in endocrine pituitary cells, and a role for an unidentified sodium-conducting channel in this process has been proposed. Here we show that forskolin dose-dependently increases cAMP production and facilitates calcium influx in about 30% of rat and mouse pituitary cells at its maximal concentration. The stimulatory effect of forskolin on calcium influx was lost in cells with inhibited PKA (cAMP-dependent protein kinase) and in cells that were haploinsufficient for the main PKA regulatory subunit but was preserved in cells that were also haploinsufficient for the main PKA catalytic subunit. Spontaneous and forskolin-stimulated calcium influx was present in cells with inhibited voltage-gated sodium and hyperpolarization-activated cation channels but not in cells bathed in medium, in which sodium was replaced with organic cations. Consistent with the role of sodium-conducting nonselective cation channels in PKA-stimulated Ca(2+) influx, cAMP induced a slowly developing current with a reversal potential of about 0 mV. Two TRP (transient receptor potential) channel blockers, SKF96365 and 2-APB, as well as flufenamic acid, an inhibitor of nonselective cation channels, also inhibited spontaneous and forskolin-stimulated electrical activity and calcium influx. Quantitative RT-PCR analysis indicated the expression of mRNA transcripts for TRPC1 >> TRPC6 > TRPC4 > TRPC5 > TRPC3 in rat pituitary cells. These experiments suggest that in pituitary cells constitutively active cation channels are stimulated further by PKA and contribute to calcium signaling indirectly by controlling the pacemaking depolarization in a sodium-dependent manner and directly by conducting calcium.
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Affiliation(s)
- Melanija Tomić
- National Institute of Child Health and Human Development/NIH, 49 Convent Dr., Bethesda, MD 20892-4510, USA
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Van Goor F, Li YX, Stojilkovic SS. Paradoxical role of large-conductance calcium-activated K+ (BK) channels in controlling action potential-driven Ca2+ entry in anterior pituitary cells. J Neurosci 2001; 21:5902-15. [PMID: 11487613 PMCID: PMC6763171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
Activation of high-conductance Ca(2+)-activated K(+) (BK) channels normally limits action potential duration and the associated voltage-gated Ca(2+) entry by facilitating membrane repolarization. Here we report that BK channel activation in rat pituitary somatotrophs prolongs membrane depolarization, leading to the generation of plateau-bursting activity and facilitated Ca(2+) entry. Such a paradoxical role of BK channels is determined by their rapid activation by domain Ca(2+), which truncates the action potential amplitude and thereby limits the participation of delayed rectifying K(+) channels during membrane repolarization. Conversely, pituitary gonadotrophs express relatively few BK channels and fire single spikes with a low capacity to promote Ca(2+) entry, whereas an elevation in BK current expression in a gonadotroph model system leads to the generation of plateau-bursting activity and high-amplitude Ca(2+) transients.
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Affiliation(s)
- F Van Goor
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, USA
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