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Barbotin AL, Mimouni NEH, Kuchcinski G, Lopes R, Viard R, Rasika S, Mazur D, Silva MSB, Simon V, Boursier A, Pruvo JP, Yu Q, Candlish M, Boehm U, Bello FD, Medana C, Pigny P, Dewailly D, Prevot V, Catteau-Jonard S, Giacobini P. Hypothalamic neuroglial plasticity is regulated by anti-Müllerian hormone and disrupted in polycystic ovary syndrome. EBioMedicine 2023; 90:104535. [PMID: 37001236 PMCID: PMC10070524 DOI: 10.1016/j.ebiom.2023.104535] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 03/03/2023] [Accepted: 03/08/2023] [Indexed: 03/31/2023] Open
Abstract
BACKGROUND Polycystic ovary syndrome (PCOS) is the most common reproductive-endocrine disorder affecting between 5 and 18% of women worldwide. An elevated frequency of pulsatile luteinizing hormone (LH) secretion and higher serum levels of anti-Müllerian hormone (AMH) are frequently observed in women with PCOS. The origin of these abnormalities is, however, not well understood. METHODS We studied brain structure and function in women with and without PCOS using proton magnetic resonance spectroscopy (MRS) and diffusion tensor imaging combined with fiber tractography. Then, using a mouse model of PCOS, we investigated by electron microscopy whether AMH played a role on the regulation of hypothalamic structural plasticity. FINDINGS Increased AMH serum levels are associated with increased hypothalamic activity/axonal-glial signalling in PCOS patients. Furthermore, we demonstrate that AMH promotes profound micro-structural changes in the murine hypothalamic median eminence (ME), creating a permissive environment for GnRH secretion. These include the retraction of the processes of specialized AMH-sensitive ependymo-glial cells called tanycytes, allowing more GnRH neuron terminals to approach ME blood capillaries both during the run-up to ovulation and in a mouse model of PCOS. INTERPRETATION We uncovered a central function for AMH in the regulation of fertility by remodeling GnRH terminals and their tanycytic sheaths, and provided insights into the pivotal role of the brain in the establishment and maintenance of neuroendocrine dysfunction in PCOS. FUNDING INSERM (U1172), European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement n° 725149), CHU de Lille, France (Bonus H).
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Affiliation(s)
- Anne-Laure Barbotin
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France; CHU Lille, Institut de Biologie de la Reproduction-Spermiologie-CECOS, Lille F-59000, France
| | - Nour El Houda Mimouni
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Grégory Kuchcinski
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France; CHU Lille, Department of Neuroradiology, Lille F-59000, France
| | - Renaud Lopes
- CHU Lille, Department of Neuroradiology, Lille F-59000, France
| | - Romain Viard
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, US 41 - UAR 2014 - PLBS, Lille F-59000, France
| | - Sowmyalakshmi Rasika
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Daniele Mazur
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Mauro S B Silva
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Virginie Simon
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Angèle Boursier
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France; CHU Lille, Institut de Biologie de la Reproduction-Spermiologie-CECOS, Lille F-59000, France
| | | | - Qiang Yu
- Experimental Pharmacology, Center for Molecular Signalling (PZMS), Saarland University School of Medicine, Homburg 66123, Germany
| | - Michael Candlish
- Experimental Pharmacology, Center for Molecular Signalling (PZMS), Saarland University School of Medicine, Homburg 66123, Germany
| | - Ulrich Boehm
- Experimental Pharmacology, Center for Molecular Signalling (PZMS), Saarland University School of Medicine, Homburg 66123, Germany
| | - Federica Dal Bello
- Department of Molecular Biotechnology and Health Science, University of Turin, Turin 10125, Italy
| | - Claudio Medana
- Department of Molecular Biotechnology and Health Science, University of Turin, Turin 10125, Italy
| | - Pascal Pigny
- CHU Lille, Service de Biochimie et Hormonologie, Centre de Biologie Pathologie, Lille F-59000, France
| | - Didier Dewailly
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Vincent Prevot
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France
| | - Sophie Catteau-Jonard
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France; CHU Lille, Service de Gynécologie Médicale, Hôpital Jeanne de Flandre, Lille F-59000, France
| | - Paolo Giacobini
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, Lille F-59000, France.
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Prevot V, Sharif A. The polygamous GnRH neuron: Astrocytic and tanycytic communication with a neuroendocrine neuronal population. J Neuroendocrinol 2022; 34:e13104. [PMID: 35233849 DOI: 10.1111/jne.13104] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/12/2022] [Accepted: 01/30/2022] [Indexed: 11/28/2022]
Abstract
To ensure the survival of the species, hypothalamic neuroendocrine circuits controlling fertility, which converge onto neurons producing gonadotropin-releasing hormone (GnRH), must respond to fluctuating physiological conditions by undergoing rapid and reversible structural and functional changes. However, GnRH neurons do not act alone, but through reciprocal interactions with multiple hypothalamic cell populations, including several glial and endothelial cell types. For instance, it has long been known that in the hypothalamic median eminence, where GnRH axons terminate and release their neurohormone into the pituitary portal blood circulation, morphological plasticity displayed by distal processes of tanycytes modifies their relationship with adjacent neurons as well as the spatial properties of the neurohemal junction. These alterations not only regulate the capacity of GnRH neurons to release their neurohormone, but also the activation of discrete non-neuronal pathways that mediate feedback by peripheral hormones onto the hypothalamus. Additionally, a recent breakthrough has demonstrated that GnRH neurons themselves orchestrate the establishment of their neuroendocrine circuitry during postnatal development by recruiting an entourage of newborn astrocytes that escort them into adulthood and, via signalling through gliotransmitters such as prostaglandin E2, modulate their activity and GnRH release. Intriguingly, several environmental and behavioural toxins perturb these neuron-glia interactions and consequently, reproductive maturation and fertility. Deciphering the communication between GnRH neurons and other neural cell types constituting hypothalamic neuroendocrine circuits is thus critical both to understanding physiological processes such as puberty, oestrous cyclicity and aging, and to developing novel therapeutic strategies for dysfunctions of these processes, including the effects of endocrine disruptors.
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Affiliation(s)
- Vincent Prevot
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S1172, FHU 1000 Days for Health, Lille, France
| | - Ariane Sharif
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S1172, FHU 1000 Days for Health, Lille, France
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3
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Vanacker C, Defazio RA, Sykes CM, Moenter SM. A role for glial fibrillary acidic protein (GFAP)-expressing cells in the regulation of gonadotropin-releasing hormone (GnRH) but not arcuate kisspeptin neuron output in male mice. eLife 2021; 10:68205. [PMID: 34292152 PMCID: PMC8337074 DOI: 10.7554/elife.68205] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 07/21/2021] [Indexed: 01/05/2023] Open
Abstract
GnRH neurons are the final central neural output regulating fertility. Kisspeptin neurons in the hypothalamic arcuate nucleus (KNDy neurons) are considered the main regulator of GnRH output. GnRH and KNDy neurons are surrounded by astrocytes, which can modulate neuronal activity and communicate over distances. Prostaglandin E2 (PGE2), synthesized primarily by astrocytes, increases GnRH neuron activity and downstream pituitary release of luteinizing hormone (LH). We hypothesized that glial fibrillary acidic protein (GFAP)-expressing astrocytes play a role in regulating GnRH and/or KNDy neuron activity and LH release. We used adeno-associated viruses to target designer receptors exclusively activated by designer drugs (DREADDs) to GFAP-expressing cells to activate Gq- or Gi-mediated signaling. Activating Gq signaling in the preoptic area, near GnRH neurons, but not in the arcuate, increases LH release in vivo and GnRH firing in vitro via a mechanism in part dependent upon PGE2. These data suggest that astrocytes can activate GnRH/LH release in a manner independent of KNDy neurons.
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Affiliation(s)
- Charlotte Vanacker
- Departments of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, United States
| | - R Anthony Defazio
- Departments of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, United States
| | - Charlene M Sykes
- Departments of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, United States
| | - Suzanne M Moenter
- Departments of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, United States.,Internal Medicine, University of Michigan, Ann Arbor, United States.,Obstetrics & Gynecology, University of Michigan, Ann Arbor, United States.,Reproductive Sciences Program, University of Michigan, Ann Arbor, United States
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Smedlund KB, Hill JW. The role of non-neuronal cells in hypogonadotropic hypogonadism. Mol Cell Endocrinol 2020; 518:110996. [PMID: 32860862 DOI: 10.1016/j.mce.2020.110996] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/01/2020] [Accepted: 08/16/2020] [Indexed: 12/18/2022]
Abstract
The hypothalamic-pituitary-gonadal axis is controlled by gonadotropin-releasing hormone (GnRH) released by the hypothalamus. Disruption of this system leads to impaired reproductive maturation and function, a condition known as hypogonadotropic hypogonadism (HH). Most studies to date have focused on genetic causes of HH that impact neuronal development and function. However, variants may also impact the functioning of non-neuronal cells known as glia. Glial cells make up 50% of brain cells of humans, primates, and rodents. They include radial glial cells, microglia, astrocytes, tanycytes, oligodendrocytes, and oligodendrocyte precursor cells. Many of these cells influence the hypothalamic neuroendocrine system controlling fertility. Indeed, glia regulate GnRH neuronal activity and secretion, acting both at their cell bodies and their nerve endings. Recent work has also made clear that these interactions are an essential aspect of how the HPG axis integrates endocrine, metabolic, and environmental signals to control fertility. Recognition of the clinical importance of interactions between glia and the GnRH network may pave the way for the development of new treatment strategies for dysfunctions of puberty and adult fertility.
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Affiliation(s)
- Kathryn B Smedlund
- Department of Physiology and Pharmacology, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH, 43614, USA; Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH, 43614, USA
| | - Jennifer W Hill
- Department of Physiology and Pharmacology, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH, 43614, USA; Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, The University of Toledo, Toledo, OH, 43614, USA.
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Prevot V, Dehouck B, Sharif A, Ciofi P, Giacobini P, Clasadonte J. The Versatile Tanycyte: A Hypothalamic Integrator of Reproduction and Energy Metabolism. Endocr Rev 2018; 39:333-368. [PMID: 29351662 DOI: 10.1210/er.2017-00235] [Citation(s) in RCA: 147] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/12/2018] [Indexed: 12/16/2022]
Abstract
The fertility and survival of an individual rely on the ability of the periphery to promptly, effectively, and reproducibly communicate with brain neural networks that control reproduction, food intake, and energy homeostasis. Tanycytes, a specialized glial cell type lining the wall of the third ventricle in the median eminence of the hypothalamus, appear to act as the linchpin of these processes by dynamically controlling the secretion of neuropeptides into the portal vasculature by hypothalamic neurons and regulating blood-brain and blood-cerebrospinal fluid exchanges, both processes that depend on the ability of these cells to adapt their morphology to the physiological state of the individual. In addition to their barrier properties, tanycytes possess the ability to sense blood glucose levels, and play a fundamental and active role in shuttling circulating metabolic signals to hypothalamic neurons that control food intake. Moreover, accumulating data suggest that, in keeping with their putative descent from radial glial cells, tanycytes are endowed with neural stem cell properties and may respond to dietary or reproductive cues by modulating hypothalamic neurogenesis. Tanycytes could thus constitute the missing link in the loop connecting behavior, hormonal changes, signal transduction, central neuronal activation and, finally, behavior again. In this article, we will examine these recent advances in the understanding of tanycytic plasticity and function in the hypothalamus and the underlying molecular mechanisms. We will also discuss the putative involvement and therapeutic potential of hypothalamic tanycytes in metabolic and fertility disorders.
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Affiliation(s)
- Vincent Prevot
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Bénédicte Dehouck
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Ariane Sharif
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Philippe Ciofi
- Inserm, Neurocentre Magendie, Bordeaux, France.,Université de Bordeaux, Bordeaux, France
| | - Paolo Giacobini
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Jerome Clasadonte
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
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6
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Clasadonte J, Prevot V. The special relationship: glia-neuron interactions in the neuroendocrine hypothalamus. Nat Rev Endocrinol 2018; 14:25-44. [PMID: 29076504 DOI: 10.1038/nrendo.2017.124] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Natural fluctuations in physiological conditions require adaptive responses involving rapid and reversible structural and functional changes in the hypothalamic neuroendocrine circuits that control homeostasis. Here, we discuss the data that implicate hypothalamic glia in the control of hypothalamic neuroendocrine circuits, specifically neuron-glia interactions in the regulation of neurosecretion as well as neuronal excitability. Mechanistically, the morphological plasticity displayed by distal processes of astrocytes, pituicytes and tanycytes modifies the geometry and diffusion properties of the extracellular space. These changes alter the relationship between glial cells of the hypothalamus and adjacent neuronal elements, especially at specialized intersections such as synapses and neurohaemal junctions. The structural alterations in turn lead to functional plasticity that alters the release and spread of neurotransmitters, neuromodulators and gliotransmitters, as well as the activity of discrete glial signalling pathways that mediate feedback by peripheral signals to the hypothalamus. An understanding of the contributions of these and other non-neuronal cell types to hypothalamic neuroendocrine function is thus critical both to understand physiological processes such as puberty, the maintenance of bodily homeostasis and ageing and to develop novel therapeutic strategies for dysfunctions of these processes, such as infertility and metabolic disorders.
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Affiliation(s)
- Jerome Clasadonte
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, Bâtiment Biserte, 1 Place de Verdun, 59045, Lille, Cedex, France
- University of Lille, FHU 1000 days for Health, School of Medicine, Lille 59000, France
| | - Vincent Prevot
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, Bâtiment Biserte, 1 Place de Verdun, 59045, Lille, Cedex, France
- University of Lille, FHU 1000 days for Health, School of Medicine, Lille 59000, France
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7
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Le Tissier P, Campos P, Lafont C, Romanò N, Hodson DJ, Mollard P. An updated view of hypothalamic-vascular-pituitary unit function and plasticity. Nat Rev Endocrinol 2017; 13:257-267. [PMID: 27934864 DOI: 10.1038/nrendo.2016.193] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The discoveries of novel functional adaptations of the hypothalamus and anterior pituitary gland for physiological regulation have transformed our understanding of their interaction. The activity of a small proportion of hypothalamic neurons can control complex hormonal signalling, which is disconnected from a simple stimulus and the subsequent hormone secretion relationship and is dependent on physiological status. The interrelationship of the terminals of hypothalamic neurons and pituitary cells with the vasculature has an important role in determining the pattern of neurohormone exposure. Cells in the pituitary gland form networks with distinct organizational motifs that are related to the duration and pattern of output, and modifications of these networks occur in different physiological states, can persist after cessation of demand and result in enhanced function. Consequently, the hypothalamus and pituitary can no longer be considered as having a simple stratified relationship: with the vasculature they form a tripartite system, which must function in concert for appropriate hypothalamic regulation of physiological processes, such as reproduction. An improved understanding of the mechanisms underlying these regulatory features has implications for current and future therapies that correct defects in hypothalamic-pituitary axes. In addition, recapitulating proper network organization will be an important challenge for regenerative stem cell treatment.
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Affiliation(s)
- Paul Le Tissier
- Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh, EH8 9XD, UK
| | - Pauline Campos
- Centre National de la Recherche Scientifique (CNRS), UMR-5203, Institut de Génomique Fonctionnelle, rue de la Cardonille, F-34000 Montpellier, France
- INSERM, U661, rue de la Cardonille, F-34000 Montpellier, France
- Université de Montpellier, rue de la Cardonille, UMR-5203, F-34000 Montpellier, France
| | - Chrystel Lafont
- Centre National de la Recherche Scientifique (CNRS), UMR-5203, Institut de Génomique Fonctionnelle, rue de la Cardonille, F-34000 Montpellier, France
- INSERM, U661, rue de la Cardonille, F-34000 Montpellier, France
- Université de Montpellier, rue de la Cardonille, UMR-5203, F-34000 Montpellier, France
| | - Nicola Romanò
- Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh, EH8 9XD, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Edgbaston, B15 2TT, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, B15 2TH, UK
| | - Patrice Mollard
- Centre National de la Recherche Scientifique (CNRS), UMR-5203, Institut de Génomique Fonctionnelle, rue de la Cardonille, F-34000 Montpellier, France
- INSERM, U661, rue de la Cardonille, F-34000 Montpellier, France
- Université de Montpellier, rue de la Cardonille, UMR-5203, F-34000 Montpellier, France
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Koopman ACM, Taziaux M, Bakker J. Age-related changes in the morphology of tanycytes in the human female infundibular nucleus/median eminence. J Neuroendocrinol 2017; 29. [PMID: 28295754 DOI: 10.1111/jne.12467] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 01/21/2023]
Abstract
Tanycytes are emerging as key players in the neuroendocrine control of gonadotrophin-releasing hormone (GnRH) release. Rodent studies have demonstrated that the structural relationship between tanycytes and GnRH terminals in the median eminence is highly dynamic, regulated by gonadal steroids and undergoes age-related changes. The present study aimed to determine whether the number and organisation of tanycytes changes throughout life in the female infundibular nucleus/median eminence (INF/ME) region. Post-mortem hypothalamic tissues were collected at the Netherlands Brain Bank and were stained for vimentin by immunohistochemistry. Hypothalami of 22 control female subjects were categorised into three periods: infant/prepubertal, adult and elderly. We measured the fractional area covered by vimentin immunoreactivity in the INF. Qualitative analysis demonstrated a remarkable parallel organisation of vimentin-immunoreactive processes during the infant/prepubertal and adult periods. During the elderly period, this organisation was largely lost. Semi-quantitatively, the fractional area covered in vimentin immunoreactivity was significantly higher at the infant/prepubertal compared to the adult period and almost reached statistical significance compared to the elderly period. By contrast, the number of tanycyte cell bodies did not appear to change throughout life. The results of the present study thus demonstrate that the number and structure of tanycytic processes are altered during ageing, suggesting that tanycytes might be involved in the age-related changes observed in GnRH release.
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Affiliation(s)
- A C M Koopman
- GIGA Neurosciences, University of Liège, Liège, Belgium
| | - M Taziaux
- GIGA Neurosciences, University of Liège, Liège, Belgium
| | - J Bakker
- GIGA Neurosciences, University of Liège, Liège, Belgium
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Manganese protects against the effects of alcohol on hypothalamic puberty-related hormones. Life Sci 2016; 148:106-11. [PMID: 26876914 DOI: 10.1016/j.lfs.2016.02.047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 11/20/2022]
Abstract
AIMS Since manganese (Mn) is capable of stimulating the hypothalamic-pituitary unit and advancing female puberty, we assessed the possibility that this element might overcome some of the detrimental effects of prepubertal alcohol (ALC) exposure on the hypothalamic control of pituitary function. MAIN METHODS Rats received either saline or Mn (10mg/kg) daily by gastric gavage from day 12 to day 31. After weaning, all rats were provided Lab Chow diet ad libitum until day 27 when they began receiving either the Bio Serv control or ALC diet regime. On day 31, the medial basal hypothalamus (MBH) was collected to assess luteinizing hormone-releasing hormone (LHRH) and cyclooxygenase 2 (COX2) protein levels. Release of prostaglandin-E2 (PGE2), LHRH and serum luteinizing hormone (LH) were also assessed. Other animals were not terminated on day 31, but remained in study to assess timing of puberty. KEY FINDINGS Short-term ALC exposure caused elevated hypothalamic LHRH content, suggesting an inhibition in peptide release, resulting in a decrease in LH. Both actions of ALC were reversed by Mn supplementation. COX2 synthesis, as well as PGE2 and LHRH release were suppressed by ALC exposure, but Mn supplementation caused an increase in COX2 synthesis and subsequent PGE2 and LHRH release in the presence of ALC. Mn supplementation also ameliorated the action of ALC to delay puberty. SIGNIFICANCE These results suggest that low level Mn supplementation acts to protect the hypothalamus from some of the detrimental effects of ALC on puberty-related hormones.
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Semaphorin7A regulates neuroglial plasticity in the adult hypothalamic median eminence. Nat Commun 2015; 6:6385. [PMID: 25721933 PMCID: PMC4351556 DOI: 10.1038/ncomms7385] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 01/26/2015] [Indexed: 11/08/2022] Open
Abstract
Reproductive competence in mammals depends on the projection of gonadotropin-releasing hormone (GnRH) neurons to the hypothalamic median eminence (ME) and the timely release of GnRH into the hypothalamic-pituitary-gonadal axis. In adult rodents, GnRH neurons and the specialized glial cells named tanycytes periodically undergo cytoskeletal plasticity. However, the mechanisms that regulate this plasticity are still largely unknown. We demonstrate that Semaphorin7A, expressed by tanycytes, plays a dual role, inducing the retraction of GnRH terminals and promoting their ensheathment by tanycytic end feet via the receptors PlexinC1 and Itgb1, respectively. Moreover, Semaphorin7A expression is regulated during the oestrous cycle by the fluctuating levels of gonadal steroids. Genetic invalidation of Semaphorin7A receptors in mice induces neuronal and glial rearrangements in the ME and abolishes normal oestrous cyclicity and fertility. These results show a role for Semaphorin7A signalling in mediating periodic neuroglial remodelling in the adult ME during the ovarian cycle.
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Giacobini P, Parkash J, Campagne C, Messina A, Casoni F, Vanacker C, Langlet F, Hobo B, Cagnoni G, Gallet S, Hanchate NK, Mazur D, Taniguchi M, Mazzone M, Verhaagen J, Ciofi P, Bouret SG, Tamagnone L, Prevot V. Brain endothelial cells control fertility through ovarian-steroid-dependent release of semaphorin 3A. PLoS Biol 2014; 12:e1001808. [PMID: 24618750 PMCID: PMC3949669 DOI: 10.1371/journal.pbio.1001808] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/30/2014] [Indexed: 11/25/2022] Open
Abstract
Endothelial-cell–derived Sema3A promotes axonal outgrowth and plasticity and thereby regulates neurohormone release in the adult rodent brain in response to the ovarian cycle. Neuropilin-1 (Nrp1) guides the development of the nervous and vascular systems, but its role in the mature brain remains to be explored. Here we report that the expression of the 65 kDa isoform of Sema3A, the ligand of Nrp1, by adult vascular endothelial cells, is regulated during the ovarian cycle and promotes axonal sprouting in hypothalamic neurons secreting gonadotropin-releasing hormone (GnRH), the neuropeptide controlling reproduction. Both the inhibition of Sema3A/Nrp1 signaling and the conditional deletion of Nrp1 in GnRH neurons counteract Sema3A-induced axonal sprouting. Furthermore, the localized intracerebral infusion of Nrp1- or Sema3A-neutralizing antibodies in vivo disrupts the ovarian cycle. Finally, the selective neutralization of endothelial-cell Sema3A signaling in adult Sema3aloxP/loxP mice by the intravenous injection of the recombinant TAT-Cre protein alters the amplitude of the preovulatory luteinizing hormone surge, likely by perturbing GnRH release into the hypothalamo-hypophyseal portal system. Our results identify a previously unknown function for 65 kDa Sema3A-Nrp1 signaling in the induction of axonal growth, and raise the possibility that endothelial cells actively participate in synaptic plasticity in specific functional domains of the adult central nervous system, thus controlling key physiological functions such as reproduction. In the developing embryo, endothelial cells release chemotropic signals such as Semaphorin 3A (Sema3A) that, upon activation of its receptor Neuropilin-1 (Nrp1), regulate neuronal migration and axon guidance. However, whether endothelial cells in the adult brain retain the ability to secrete molecules that influence neuronal function is unknown. Here we show in the adult brain of rodents that vascular endothelial cells release Sema3A and that the amount released is regulated by the ovulatory cycle. Sema3A, in turn, promotes the outgrowth of axons of hypothalamic neurons that express Neuropilin-1 towards the endothelial wall of portal blood vessels. These neurons release there the neuropeptide that controls reproduction: gonadotropin-releasing hormone (GnRH). Notably, this endothelial-cell-mediated sprouting of GnRH axons regulates neuropeptide release at a key stage of the estrous cycle, the proestrus, when the surge of GnRH triggers ovulation. Thus, by promoting GnRH axonal growth in the adult brain, Sema3A/Neuropilin-1 plays a pivotal role in orchestrating the central control of reproduction. Our results suggest a model in which vascular endothelial cells are dynamic signaling components that relay peripheral information to the brain to control key physiological functions, including species survival.
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Affiliation(s)
- Paolo Giacobini
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Jyoti Parkash
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Céline Campagne
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Andrea Messina
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Filippo Casoni
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Charlotte Vanacker
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Fanny Langlet
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Barbara Hobo
- Netherlands institute for Neuroscience, Amsterdam, The Netherlands
- Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Gabriella Cagnoni
- Candiolo Cancer Institute - FPO (IRCCS) and University of Torino, Department of Oncology, Candiolo, Italy
| | - Sarah Gallet
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Naresh Kumar Hanchate
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Danièle Mazur
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
| | - Masahiko Taniguchi
- Research Institute for Frontier Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Massimiliano Mazzone
- Versalius Research Center, VIB, Laboratory of Molecular Oncology and Angiogenesis, Leuven, Belgium
- KU Keuven, Versalius Research Center, Leuven, Belgium
| | - Joost Verhaagen
- Netherlands institute for Neuroscience, Amsterdam, The Netherlands
- Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Philippe Ciofi
- INSERM, Neurocentre Magendie, U862, Université de Bordeaux, Bordeaux, France
| | - Sébastien G. Bouret
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
- The Saban Research Institute, Childrens Hospital Los Angeles, University of Southern California, Los Angeles, California, United States of America
| | - Luca Tamagnone
- Candiolo Cancer Institute - FPO (IRCCS) and University of Torino, Department of Oncology, Candiolo, Italy
| | - Vincent Prevot
- INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France
- UDSL, School of Medicine, Place de Verdun, Lille, France
- Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France
- * E-mail:
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Srivastava VK, Hiney JK, Dees WL. Actions and interactions of alcohol and transforming growth factor β1 on prepubertal hypothalamic gonadotropin-releasing hormone. Alcohol Clin Exp Res 2014; 38:1321-9. [PMID: 24588206 DOI: 10.1111/acer.12374] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 01/06/2014] [Indexed: 01/06/2023]
Abstract
BACKGROUND Alcohol (ALC) diminishes gonadotropin-releasing hormone (GnRH) secretion and delays puberty. Glial transforming growth factor β1 (TGFβ1) plays a role in glial-neuronal communications facilitating prepubertal GnRH secretion. We assessed the effects of acute ALC administration on TGFβ1-induced GnRH gene expression in the brain preoptic area (POA) and release of the peptide from the medial basal hypothalamus (MBH). Furthermore, we assessed actions and interactions of TGFβ1 and ALC on an adhesion/signaling gene family involved in glial-neuronal communications. METHODS Prepubertal female rats were administered ALC or water via gastric gavage at 7:30 am. At 9:00 am, saline or TGFβ1 (100 ng/3 μl) was administered into the third ventricle. At 3:00 pm, the POA was removed and frozen for gene expression analysis and repeated for protein assessments. In another experiment, the MBH was removed from ALC-free rats. After equilibration, tissues were incubated in Locke's medium only or medium containing TGFβ1 with or without 50 mM ALC for measurement of GnRH peptide released in vitro. RESULTS TGFβ1 induced GnRH gene expression in the POA, and this effect was blocked by ALC. We also described the presence and responsiveness of the TGFβ1 receptor in the POA and showed that acute ALC exposure not only altered the TGFβ1-induced increase in TGFβ-R1 protein expression but also the activation of receptor-associated proteins, Smad2 and Smad3, key downstream components of the TGFβ1 signaling pathway. Assessment of an adhesion/signaling family consisting of glial receptor protein tyrosine phosphatase beta and neuronal contactin-associated protein-1 (Caspr1) and contactin showed that the neuronal components were induced by TGFβ1 and that ALC blocked these effects. Finally, TGFβ1 was shown to induce release of the GnRH peptide in vitro, an action that was blocked by ALC. CONCLUSIONS We have demonstrated glial-derived TGFβ1 induces GnRH gene expression in the POA and stimulates release of the peptide from the MBH, actions necessary for driving the pubertal process. Importantly, ALC acted at both brain regions to block stimulatory effects of TGFβ1. Furthermore, ALC altered neuronal components of an adhesion/signaling family previously shown to be expressed on GnRH neurons and implicated in glial-GnRH neuronal communications. These results further demonstrate detrimental effects of ALC at puberty.
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Affiliation(s)
- Vinod K Srivastava
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, Texas
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Naugle MM, Gore AC. GnRH neurons of young and aged female rhesus monkeys co-express GPER but are unaffected by long-term hormone replacement. Neuroendocrinology 2014; 100:334-46. [PMID: 25428637 PMCID: PMC4329056 DOI: 10.1159/000369820] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 11/05/2014] [Indexed: 12/18/2022]
Abstract
Menopause is caused by changes in the function of the hypothalamic-pituitary-gonadal axis that controls reproduction. Hypophysiotropic gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus orchestrate the activity of this axis and are regulated by hormonal feedback loops. The mechanisms by which GnRH responds to the primary regulatory sex steroid hormone, estradiol (E2), are still poorly understood in the context of menopause. Our goal was to determine whether the G protein-coupled estrogen receptor (GPER) is co-expressed in adult primate GnRH neurons and whether this changes with aging and/or E2 treatment. We used immunofluorescence double-labeling to characterize the co-expression of GPER in GnRH perikarya and terminals in the hypothalamus. Young and aged rhesus macaques were ovariectomized and given long-term (~2-year) hormone treatments (E2, E2 + progesterone, or vehicle) selected to mimic currently prescribed hormone replacement therapies used for the alleviation of menopausal symptoms in women. We found that about half of GnRH perikarya co-expressed GPER, while only about 12% of GnRH processes and terminals in the median eminence (ME) were double-labeled. Additionally, many GPER-labeled processes were in direct contact with GnRH neurons, often wrapped around the perikarya and processes and in close proximity in the ME. These results extend prior work by showing robust co-localization of GPER in GnRH in a clinically relevant model, and they support the possibility that GPER-mediated E2 regulation of GnRH occurs both in the soma and terminals in nonhuman primates.
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Affiliation(s)
- Michelle M. Naugle
- Institute for Neuroscience, University of Texas at Austin, Austin, TX, 78712
| | - Andrea C. Gore
- Institute for Neuroscience, University of Texas at Austin, Austin, TX, 78712
- Pharmacology & Toxicology, College of Pharmacy, University of Texas at Austin, Austin, TX, 78712
- Institute for Cellular & Molecular Biology, University of Texas at Austin, Austin, TX, 78712
- Correspondence: Andrea C Gore, PhD, The University of Texas at Austin, 107 West Dean Keeton, C0875, Austin, TX, 78712, USA, ; Tel: +1-512-471-3669; Fax: +1-512-471-5002
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Glanowska KM, Moenter SM. Endocannabinoids and prostaglandins both contribute to GnRH neuron-GABAergic afferent local feedback circuits. J Neurophysiol 2011; 106:3073-81. [PMID: 21917995 DOI: 10.1152/jn.00046.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for central control of fertility. Regulation of GnRH neurons by long-loop gonadal steroid feedback through steroid receptor-expressing afferents such as GABAergic neurons is well studied. Recently, local central feedback circuits regulating GnRH neurons were identified. GnRH neuronal depolarization induces short-term inhibition of their GABAergic afferents via a mechanism dependent on metabotropic glutamate receptor (mGluR) activation. GnRH neurons are enveloped in astrocytes, which express mGluRs. GnRH neurons also produce endocannabinoids, which can be induced by mGluR activation. We hypothesized the local GnRH-GABA circuit utilizes glia-derived and/or cannabinoid mechanisms and is altered by steroid milieu. Whole cell voltage-clamp was used to record GABAergic postsynaptic currents (PSCs) from GnRH neurons before and after action potential-like depolarizations were mimicked. In GnRH neurons from ovariectomized (OVX) mice, this depolarization reduced PSC frequency. This suppression was blocked by inhibition of prostaglandin synthesis with indomethacin, by a prostaglandin receptor antagonist, or by a specific glial metabolic poison, together suggesting the postulate that prostaglandins, potentially glia-derived, play a role in this circuit. This circuit was also inhibited by a CB1 receptor antagonist or by blockade of endocannabinoid synthesis in GnRH neurons, suggesting an endocannabinoid element, as well. In females, local circuit inhibition persisted in androgen-treated mice but not in estradiol-treated mice or young ovary-intact mice. In contrast, local circuit inhibition was present in gonad-intact males. These data suggest GnRH neurons interact with their afferent neurons using multiple mechanisms and that these local circuits can be modified by both sex and steroid feedback.
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Affiliation(s)
- Katarzyna M Glanowska
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, USA
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Abstract
Radial glia (RG) are a glial cell type that can be found from the earliest stages of CNS development. They are clearly identifiable by their unique morphology, having a periventricular cell soma and a long process extending all the way to the opposite pial surface. Due to this striking morphology, RG have long been thought of as a transient substrate for neuron migration in the developing brain. In fact, RG cells, far from exclusively serving as a passive scaffold for cell migration, have a remarkably diverse range of critical functions in CNS development and function. These include serving as progenitors of neurons and glia both during development as well as in response to injury, helping to direct axonal and dendritic process outgrowth, and regulating synaptic development and function. RG also engage in extensive bidirectional signaling both with neurons and one another. This review describes the diversity of RG cell types in the CNS and discusses their many important activities.
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Affiliation(s)
- Mari Sild
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Hypothalamic glial-to-neuronal signaling during puberty: influence of alcohol. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2011; 8:2876-94. [PMID: 21845163 PMCID: PMC3155334 DOI: 10.3390/ijerph8072894] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 06/27/2011] [Accepted: 07/12/2011] [Indexed: 01/06/2023]
Abstract
Mammalian puberty requires complex interactions between glial and neuronal regulatory systems within the hypothalamus that results in the timely increase in the secretion of luteinizing hormone releasing hormone (LHRH). Assessing the molecules required for the development of coordinated communication networks between glia and LHRH neuron terminals in the basal hypothalamus, as well as identifying substances capable of affecting cell-cell communication are important. One such pathway involves growth factors of the epidermal growth factor (EGF) family that bind to specific erbB receptors. Activation of this receptor results in the release of prostaglandin-E2 (PGE2) from adjacent glial cells, which then acts on the nearby LHRH nerve terminals to elicit release of the peptide. Another pathway involves novel genes which synthesize adhesion/signaling proteins responsible for the structural integrity of bi-directional glial-neuronal communication. In this review, we will discuss the influence of these glial-neuronal communication pathways on the prepubertal LHRH secretory system, and furthermore, discuss the actions and interactions of alcohol on these two signaling processes.
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Srivastava VK, Hiney JK, Dees WL. Hypothalamic actions and interactions of alcohol and IGF-1 on the expression of glial receptor protein tyrosine phosphatase-β during female pubertal development. Alcohol Clin Exp Res 2011; 35:1812-21. [PMID: 21595703 DOI: 10.1111/j.1530-0277.2011.01525.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND Hypothalamic glial-neuronal communications are important for the activation of luteinizing hormone releasing hormone (LHRH) secretion at the time of puberty. As we have shown that alcohol (ALC) diminishes prepubertal LHRH secretion and delays puberty, we first assessed the effects of short-term ALC administration on the basal expression of a specific gene family involved in glial-neuronal communications. Second, as insulin-like growth factor-1 (IGF-1) is a critical regulator of LHRH secretion and the pubertal process, we then assessed whether IGF-1 could induce the expression of these signaling genes and determine whether ALC can block this affect. METHODS Immature female rats were fed a liquid diet containing ALC for 6 days beginning when 27 days old. Control animals received either the companion isocaloric liquid diet or rat chow and water. Animals were decapitated on day 33, in the late juvenile stage of development. Medial basal hypothalamic (MBH) tissues were obtained for gene and protein analyses of glial receptor protein tyrosine phosphatase-β (RPTPβ) and the 2 neuronal components, contactin and contactin-associated protein 1 (Caspr1). In the second experiment, IGF-1 was administered into the third ventricle (3V) and the MBH removed 6 hours after peptide delivery, and the above-mentioned 3 genes were analyzed by real-time PCR. To determine whether this action was affected by ALC, immature female rats were administered either ALC (3 g/kg) or water via gastric gavage at 0900 hours. At 1030 hours, the ALC and control groups were subdivided such that half of the animals were injected into the 3V with IGF-1 and the other half with an equal volume of saline. Rats were killed 6 hours after the IGF-1 injection and MBHs collected. RESULTS Real-time PCR showed that when compared with control animals, ALC caused a marked decrease (p < 0.001) in the basal expression of the RPTPβ gene, but did not affect the expression of either contactin or Caspr1. Likewise, analysis by Western blotting demonstrated that ALC caused suppressed (p < 0.001) levels of the RPTPβ protein, with the expressions of both contactin and Caspr1 proteins being unaltered. In the second experiment, results showed that only the RPTPβ gene was stimulated (p < 0.05) by IGF-1 in the MBH 6 hours after peptide delivery. Assessments revealed that the IGF-1 induced increase (p < 0.01) in the expression of the RPTPβ gene was blocked by the presence of ALC. CONCLUSIONS Prepubertal ALC exposure is capable of interfering with hypothalamic glial-neuronal communications by suppressing the synthesis of the glial product, RPTPβ, which is required for binding to the contactin-Caspr1 complex on LHRH neuronal terminals, thus suggesting that this action of ALC contributes to its detrimental effects on the pubertal process.
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Affiliation(s)
- Vinod K Srivastava
- Department of Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, Texas 77843-4458, USA
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Ojeda SR, Lomniczi A, Sandau U. Contribution of glial-neuronal interactions to the neuroendocrine control of female puberty. Eur J Neurosci 2011; 32:2003-10. [PMID: 21143655 DOI: 10.1111/j.1460-9568.2010.07515.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mammalian puberty is initiated by an increased pulsatile release of the neuropeptide gonadotropin-releasing hormone (GnRH) from hypothalamic neuroendocrine neurons. Although this increase is primarily set in motion by neuronal networks synaptically connected to GnRH neurons, glial cells contribute to the process via at least two mechanisms. One involves production of growth factors acting via receptors endowed with either serine-threonine kinase or tyrosine kinase activity. The other involves plastic rearrangements of glia-GnRH neuron adhesiveness. Growth factors of the epidermal growth factor family acting via erbB receptors play a major role in glia-to-GnRH neuron communication. In turn, neurons facilitate astrocytic erbB signaling via glutamate-dependent cleavage of erbB ligand precursors. The genetic disruption of erbB receptors delays female sexual development due to impaired erbB ligand-induced glial prostaglandin E(2) release. The adhesiveness of glial cells to GnRH neurons involves at least two different cell-cell communication systems endowed with both adhesive and intracellular signaling capabilities. One is provided by synaptic cell adhesion molecule (SynCAM1), which establishes astrocyte-GnRH neuron adhesiveness via homophilic interactions and the other involves the heterophilic interaction of neuronal contactin with glial receptor-like protein tyrosine phosphatase-β. These findings indicate that the interaction of glial cells with GnRH neurons involves not only secreted bioactive molecules, but also cell-surface adhesive proteins able to set in motion intracellular signaling cascades.
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Affiliation(s)
- Sergio R Ojeda
- Division of Neuroscience, Oregon National Primate Research Center/Oregon Health Sciences University, 505 N.W., 185th Avenue, Beaverton, OR 97006, USA.
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Hiney JK, Srivastava VK, Dees WL. Manganese induces IGF-1 and cyclooxygenase-2 gene expressions in the basal hypothalamus during prepubertal female development. Toxicol Sci 2011; 121:389-96. [PMID: 21402727 DOI: 10.1093/toxsci/kfr057] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Precocious puberty is a significant child health problem, especially in girls, because 95% of cases are idiopathic. Our earlier studies demonstrated that low-dose levels of manganese (Mn) caused precocious puberty via stimulating the secretion of luteinizing hormone-releasing hormone (LHRH). Because glial-neuronal communications are important for the activation of LHRH secretion at puberty, we investigated the effects of prepubertal Mn exposure on specific glial-derived puberty-related genes known to affect neuronal LHRH release. Animals were supplemented with MnCl(2) (10 mg/kg) or saline by gastric gavage from day 12 until day 22 or day 29, then decapitated, and brains removed. The site of LHRH release is the medial basal hypothalamus (MBH), and tissues from this area were analyzed by real-time PCR for transforming growth factor α (TGFα), insulin-like growth factor-1 (IGF-1), and cyclooxygenase-2 (COX-2) messenger RNA levels. Protein levels for IGF-1 receptor (IGF-1R) were measured by Western blot analysis. LHRH gene expression was measured in the preoptic area/anteroventral periventricular (POA/AVPV) region. In the MBH, at 22 days, IGF-1 gene expression was increased (p < 0.05) with a concomitant increase (p < 0.05) in IGF-1R protein expression. Mn also increased (p < 0.01) COX-2 gene expression. At 29 days, the upregulation of IGF-1 (p < 0.05) and COX-2 (p < 0.05) continued in the MBH. At this time, we observed increased (p < 0.05) LHRH gene expression in the POA/AVPV. Additionally, Mn stimulated prostaglandin E(2) and LHRH release from 29-day-old median eminences incubated in vitro. These results demonstrate that Mn, through the upregulation of IGF-1 and COX-2, may promote maturational events and glial-neuronal communications facilitating the increased neurosecretory activity, including that of LHRH, resulting in precocious pubertal development.
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Affiliation(s)
- Jill K Hiney
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, Texas 77843-4458, USA
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Clasadonte J, Sharif A, Baroncini M, Prevot V. Gliotransmission by prostaglandin e(2): a prerequisite for GnRH neuronal function? Front Endocrinol (Lausanne) 2011; 2:91. [PMID: 22649391 PMCID: PMC3355930 DOI: 10.3389/fendo.2011.00091] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 11/17/2011] [Indexed: 02/06/2023] Open
Abstract
Over the past four decades it has become clear that prostaglandin E(2) (PGE(2)), a phospholipid-derived signaling molecule, plays a fundamental role in modulating the gonadotropin-releasing hormone (GnRH) neuroendocrine system and in shaping the hypothalamus. In this review, after a brief historical overview, we highlight studies revealing that PGE(2) released by glial cells such as astrocytes and tanycytes is intimately involved in the active control of GnRH neuronal activity and neurosecretion. Recent evidence suggests that hypothalamic astrocytes surrounding GnRH neuronal cell bodies may respond to neuronal activity with an activation of the erbB receptor tyrosine kinase signaling, triggering the release of PGE(2) as a chemical transmitter from the glia themselves, and, in turn, leading to the feedback regulation of GnRH neuronal activity. At the GnRH neurohemal junction, in the median eminence of the hypothalamus, PGE(2) is released by tanycytes in response to cell-cell signaling initiated by glial cells and vascular endothelial cells. Upon its release, PGE(2) causes the retraction of the tanycyte end-feet enwrapping the GnRH nerve terminals, enabling them to approach the adjacent pericapillary space and thus likely facilitating neurohormone diffusion from these nerve terminals into the pituitary portal blood. In view of these new insights, we suggest that synaptically associated astrocytes and perijunctional tanycytes are integral modulatory elements of GnRH neuronal function at the cell soma/dendrite and nerve terminal levels, respectively.
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Affiliation(s)
- Jerome Clasadonte
- Jean-Pierre Aubert Research Center, Inserm, U837, F-59000Lille, France
- Laboratory of Anatomy, Université Lille Nord de FranceLille, France
- School of Medicine, UDSLLille, France
| | - Ariane Sharif
- Jean-Pierre Aubert Research Center, Inserm, U837, F-59000Lille, France
- Laboratory of Anatomy, Université Lille Nord de FranceLille, France
- School of Medicine, UDSLLille, France
| | - Marc Baroncini
- Jean-Pierre Aubert Research Center, Inserm, U837, F-59000Lille, France
- Laboratory of Anatomy, Université Lille Nord de FranceLille, France
- School of Medicine, UDSLLille, France
- Department of Neurosurgery, CHULilleLille, France
| | - Vincent Prevot
- Jean-Pierre Aubert Research Center, Inserm, U837, F-59000Lille, France
- Laboratory of Anatomy, Université Lille Nord de FranceLille, France
- School of Medicine, UDSLLille, France
- *Correspondence: Vincent Prevot, INSERM U837, Bâtiment Biserte, Place de Verdun, 59045 Lille Cedex, France. e-mail:
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Prevot V, Bellefontaine N, Baroncini M, Sharif A, Hanchate NK, Parkash J, Campagne C, de Seranno S. Gonadotrophin-releasing hormone nerve terminals, tanycytes and neurohaemal junction remodelling in the adult median eminence: functional consequences for reproduction and dynamic role of vascular endothelial cells. J Neuroendocrinol 2010; 22:639-49. [PMID: 20492366 PMCID: PMC3168864 DOI: 10.1111/j.1365-2826.2010.02033.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Although coordinated actions of several areas within the hypothalamus are involved in the secretion of gonadotrophin-releasing hormone (GnRH), the median eminence of the hypothalamus, where the nerve terminals are located, plays a particularly critical role in the release of GnRH. In adult females, prior to the preovulatory surge of GnRH, the retraction of specialised ependymoglial cells lining the floor of the third ventricle named tanycytes allows for the juxtaposition of GnRH nerve terminals with the adjacent pericapillary space of the pituitary portal vasculature, thus forming direct neurohaemal junctions. These morphological changes occur within a few hours and are reversible. Such remodelling may promote physiological conditions to enhance the central release of GnRH and potentiate oestrogen-activated GnRH release. This plasticity involves dynamic cell interactions that bring into play tanycytes, astrocytes, vascular endothelial cells and GnRH neurones themselves. The underlying signalling pathways responsible for these structural changes are comprised of highly diffusible gaseous molecules, such as endothelial nitric oxide, and paracrine communication processes involving receptors of the erbB tyrosine kinase family, transforming growth factor beta 1 and eicosanoids, such as prostaglandin E(2). Some of these molecules, as a result of their ability to diffuse within the median eminence, may also serve as synchronizing cues allowing for the occurrence of functionally meaningful episodes of GnRH secretion by coordinating GnRH release from the GnRH neuroendocrine terminals.
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Affiliation(s)
- V Prevot
- Inserm, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France.
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Prevot V, Hanchate NK, Bellefontaine N, Sharif A, Parkash J, Estrella C, Allet C, de Seranno S, Campagne C, de Tassigny XD, Baroncini M. Function-related structural plasticity of the GnRH system: a role for neuronal-glial-endothelial interactions. Front Neuroendocrinol 2010; 31:241-58. [PMID: 20546773 DOI: 10.1016/j.yfrne.2010.05.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 05/17/2010] [Accepted: 05/18/2010] [Indexed: 12/18/2022]
Abstract
As the final common pathway for the central control of gonadotropin secretion, GnRH neurons are subjected to numerous regulatory homeostatic and external factors to achieve levels of fertility appropriate to the organism. The GnRH system thus provides an excellent model in which to investigate the complex relationships between neurosecretion, morphological plasticity and the expression of a physiological function. Throughout the reproductive cycle beginning from postnatal sexual development and the onset of puberty to reproductive senescence, and even within the ovarian cycle itself, all levels of the GnRH system undergo morphological plasticity. This structural plasticity within the GnRH system appears crucial to the timely control of reproductive competence within the individual, and as such must have coordinated actions of multiple signals secreted from glial cells, endothelial cells, and GnRH neurons. Thus, the GnRH system must be viewed as a complete neuro-glial-vascular unit that works in concert to maintain the reproductive axis.
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Affiliation(s)
- Vincent Prevot
- Inserm, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, F-59000 Lille, France.
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Sidibe A, Mullier A, Chen P, Baroncini M, Boutin JA, Delagrange P, Prevot V, Jockers R. Expression of the orphan GPR50 protein in rodent and human dorsomedial hypothalamus, tanycytes and median eminence. J Pineal Res 2010; 48:263-269. [PMID: 20210849 DOI: 10.1111/j.1600-079x.2010.00750.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The melatonin receptor family is composed of three members, MT(1) and MT(2) receptors that bind melatonin with high affinity and the orphan GPR50 that does not bind melatonin but shares significant sequence homology with the two other subtypes. In the absence of any known ligand for this orphan receptor, little is still known about its function. We recently reported the development of the first anti-GPR50 antibodies that reliably recognized the recombinant human GPR50. We here used these antibodies to study the expression of GPR50 in mouse, rat and human hypothalamus, a region reported to express GPR50 mRNA. GPR50 immunoreactivity (ir) was observed in dorsomedial hypothalamic (DMH) cells co-stained with the neuronal marker HuC/D. GPR50-ir was also observed in cells of the ependymal layer of the third ventricle that co-stained with vimentin. More specifically, its localization in the lower region of the third ventricle and along the long basal processes contacting portal blood vessels in the median eminence (ME) suggested expression of GPR50 in tanycytes. Consistent staining patterns were observed in all three species with two different antibodies. Taken together, our study validates two GPR50-specific antibodies for the use in rodent and human tissue. Evolutionary conserved expression of GPR50 in DMH neurons and tanycytes, together with previously reported expression of the receptor in the pituitary, support the potentially important role of GPR50 in key hypothalamic functions, including regulation of the hypothalamo-pituitary axes.
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Affiliation(s)
- Anissa Sidibe
- Institut Cochin, Université Paris Descartes, CNRS, Paris, France
- Inserm, U1016, Paris, France
| | | | - Patty Chen
- Institut Cochin, Université Paris Descartes, CNRS, Paris, France
- Inserm, U1016, Paris, France
| | - Marc Baroncini
- Inserm, Jean-Pierre Aubert Research Center, Lille, France
- Laboratoire d'Anatomie, Faculté de médecine, Université Lille 2, Lille, France
| | | | | | - Vincent Prevot
- Inserm, Jean-Pierre Aubert Research Center, Lille, France
| | - Ralf Jockers
- Institut Cochin, Université Paris Descartes, CNRS, Paris, France
- Inserm, U1016, Paris, France
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Baroncini M, Jissendi P, Catteau-Jonard S, Dewailly D, Pruvo JP, Francke JP, Prevot V. Sex steroid hormones-related structural plasticity in the human hypothalamus. Neuroimage 2010; 50:428-33. [DOI: 10.1016/j.neuroimage.2009.11.074] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 11/24/2009] [Accepted: 11/25/2009] [Indexed: 10/20/2022] Open
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Yin W, Mendenhall JM, Monita M, Gore AC. Three-dimensional properties of GnRH neuroterminals in the median eminence of young and old rats. J Comp Neurol 2010; 517:284-95. [PMID: 19757493 DOI: 10.1002/cne.22156] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The decapeptide gonadotropin-releasing hormone (GnRH), which regulates reproduction in all vertebrates, is stored in, and secreted from, large dense-core secretory vesicles in nerve terminals in the median eminence. GnRH is released from these terminals with biological rhythms that are critical for the maintenance of normal reproduction. During reproductive aging in female rats, there is a loss of GnRH pulses and a diminution of the GnRH surge. However, information about the specific role of GnRH nerve terminals is lacking, particularly in the context of aging. We sought to gain novel ultrastructural information about GnRH neuroterminals by performing three-dimensional (3D) reconstructions of GnRH neuroterminals and their surrounding microenvironment in the median eminence of young (4-5 months) and old (22-24 months) ovariectomized Sprague-Dawley female rats. Median eminence tissues were freeze-plunge embedded and serial ultrathin sections were collected on slot grids for immunogold labeling of GnRH immunoreactivity. Sequential images were used to create 3D models of GnRH terminals. These reconstructions provided novel perspectives into the morphological properties of GnRH terminals and their neural and glial environment. We also noted that the cytoarchitectural features of the median eminence became disorganized with aging. Quantitative measures showed a significant decrease in the apposition between GnRH terminal membranes and glial cells. Our data suggest reproductive aging in rats is characterized by structural organizational changes to the GnRH terminal microenvironment in the median eminence.
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Affiliation(s)
- Weiling Yin
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, TX 78712, USA
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Micevych P, Bondar G, Kuo J. Estrogen actions on neuroendocrine glia. Neuroendocrinology 2010; 91:211-22. [PMID: 20332598 PMCID: PMC2889254 DOI: 10.1159/000289568] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 02/18/2010] [Indexed: 12/25/2022]
Abstract
Astrocytes are the most abundant cells in the central nervous system (CNS). It appears that astrocytes are as diverse as neurons, having different phenotypes in various regions throughout the brain and participating in intercellular communication that involves signaling to neurons. It is not surprising then that astrocytes in the hypothalamus have an active role in the CNS regulation of reproduction. In addition to the traditional mechanism involving ensheathment of neurons and processes, astrocytes may have a critical role in regulating estrogen-positive feedback. Work in our laboratory has focused on the relationship between circulating estradiol and progesterone synthesized de novo in the brain. We have demonstrated that circulating estradiol stimulates the synthesis of progesterone in adult hypothalamic astrocytes, and this neuroprogesterone is critical for initiating the LH surge. Estradiol cell signaling is initiated at the cell membrane and involves the transactivation of metabotropic glutamate receptor type 1a (mGluR1a) leading to the release of intracellular stores of calcium. We used surface biotinylation to demonstrate that estrogen receptor-alpha (ERalpha) is present in the cell membrane and has an extracellular portion. Like other membrane receptors, ERalpha is inserted into the membrane and removed via internalization after agonist stimulation. This trafficking is directly regulated by estradiol, which rapidly and transiently increases the levels of membrane ERalpha, and upon activation, increases internalization that finally leads to ERalpha degradation. This autoregulation temporally limits membrane-initiated estradiol cell signaling. Thus, neuroprogesterone, the necessary signal for the LH surge, is released when circulating levels of estradiol peak on proestrus and activate progesterone receptors whose expression has been induced by the gradual rise of estradiol during follicular development.
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Affiliation(s)
- Paul Micevych
- Department of Neurobiology, Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, Calif., USA
- *Paul Micevych, Department of Neurobiology, David Geffen School of Medicine at UCLA, 10833 LeConte Avenue, 73-078 CHS, Los Angeles, CA 90095-1763 (USA), Tel. +1 310 206 8265, Fax +1 310 825 2224, E-Mail
| | - Galyna Bondar
- Department of Neurobiology, Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, Calif., USA
| | - John Kuo
- Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Los Angeles, Calif., USA
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Yin W, Wu D, Noel ML, Gore AC. Gonadotropin-releasing hormone neuroterminals and their microenvironment in the median eminence: effects of aging and estradiol treatment. Endocrinology 2009; 150:5498-508. [PMID: 19819960 PMCID: PMC2795719 DOI: 10.1210/en.2009-0679] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The GnRH decapeptide controls reproductive function through its release from neuroendocrine terminals in the median eminence, a site where there is a convergence of numerous nerve terminals and glial cells. Previous work showed dynamic changes in the GnRH-glial-capillary network in the median eminence under different physiological conditions. Because aging in rats is associated with a diminution of GnRH release and responsiveness to estradiol feedback, we examined effects of age and estradiol treatment on these anatomical interactions. Rats were ovariectomized at young (4 months), middle-aged (11 months), or old (22-23 months) ages, allowed 4 wk to recover, and then treated with vehicle or estradiol for 72 h followed by perfusion. Immunofluorescence of GnRH was measured, and immunogold electron microscopic analyses were performed to study the ultrastructural properties of GnRH neuroterminals and their microenvironment. Although the GnRH immunofluorescent signal showed no significant changes with age and estradiol treatment, we found that the median eminence underwent both qualitative and quantitative structural changes with age, including a disorganization of cytoarchitecture with aging and a decrease in the apposition of GnRH neuroterminals to glia with age and estradiol treatment. Thus, although GnRH neurons can continue to synthesize and transport peptide, changes in the GnRH neuroterminal-glial-capillary machinery occur during reproductive senescence in a manner consistent with a disconnection of these elements and a potential dysregulation of GnRH neurosecretion.
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Affiliation(s)
- Weiling Yin
- Division of Pharmacology and Toxicology, The University of Texas at Austin, Austin, Texas 78712, USA
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28
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Ojeda SR, Lomniczi A, Sandau US. Glial-gonadotrophin hormone (GnRH) neurone interactions in the median eminence and the control of GnRH secretion. J Neuroendocrinol 2008; 20:732-42. [PMID: 18601696 DOI: 10.1111/j.1365-2826.2008.01712.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A wealth of information now exists showing that glial cells are actively involved in the cell-cell communication process generating and disseminating information within the central nervous system. In the hypothalamus, two types of glial cells, astrocytes and ependymal cells lining the latero-ventral portion of the third ventricle (known as tanycytes), regulate the secretory activity of neuroendocrine neurones. This function, initially described for astrocytes apposing magnocellular neurones, has been more recently characterised for neurones secreting gonadotrophin hormone-releasing hormone (GnRH). The available evidence suggests that glial cells of the median eminence regulate GnRH secretion via two related mechanisms. One involves the production of growth factors acting via receptors with tyrosine kinase activity. The other involves plastic rearrangements of glia-GnRH neurone adhesiveness. GnRH axons reach the median eminence, at least in part, directed by basic fibroblast growth factor. Their secretory activity is facilitated by insulin-like growth factor 1 and members of the epidermal growth factor family. A structural complement to these soluble molecules is provided by at least three cell-cell adhesion systems endowed with signalling capabilities. One of them uses the neuronal cell adhesion molecule (NCAM), another employs the synaptic cell adhesion molecule (SynCAM), and the third one consists of neuronal contactin interacting with glial receptor-like protein tyrosine phosphatase-beta. It is envisioned that, within the median eminence, soluble factors and adhesion molecules work coordinately to control delivery of GnRH to the portal vasculature.
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Affiliation(s)
- S R Ojeda
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006, USA
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Gill JC, Tsai PS. Expression of a Dominant Negative FGF Receptor in Developing GNRH1 Neurons Disrupts Axon Outgrowth and Targeting to the Median Eminence1. Biol Reprod 2006; 74:463-72. [PMID: 16280414 DOI: 10.1095/biolreprod.105.046904] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
During development, neurons that synthesize and release gonadotropin-releasing hormone (GNRH1) extend their axons to the median eminence (ME) to establish neurosecretory contacts necessary for hormone secretion. Signals that coordinate this process are not known, but could involve the activation of fibroblast growth factor receptors (FGFRs) expressed on developing GNRH1 neurons. Using both whole-animal and cell culture approaches, this study examines the direct role of FGFR signaling in the extension and guidance of GNRH1 axons to the ME. In vivo retrograde labeling with fluorogold (FG) first showed a significant reduction in the projections of GNRH1 axons to the circumventricular organs (including the ME) in transgenic mice expressing a dominant negative FGF receptor (dnFGFR) in GNRH1 neurons. Using a primary GNRH1 neuronal culture system, we examined if compromised axon extension and directional growth led to the reduced axon targeting efficiency seen in vivo. Primary cultures of GNRH1 neurons were established from Embryonic Day 15.5 embryos, an age when GNRH1 neurons are actively targeting the ME. Cultured GNRH1 neurons expressing dnFGFR (dnFGFR neurons) exhibited attenuated activation of signaling pathways and reduced neurite outgrowth in response to FGF2. Further, dnFGFR neurons failed to preferentially target neurites toward cocultured ME explant and FGF2-coated beads, suggesting a defect in axon pathfinding. Together, these findings describe a direct role of FGFR signaling in the elongation and guidance of GNRH1 axons to the ME.
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Affiliation(s)
- John C Gill
- Department of Integrative Physiology and the Center for Neuroscience, University of Colorado, Boulder, Colorado 80309-0354, USA.
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Ojeda SR, Lomniczi A, Mastronardi C, Heger S, Roth C, Parent AS, Matagne V, Mungenast AE. Minireview: the neuroendocrine regulation of puberty: is the time ripe for a systems biology approach? Endocrinology 2006; 147:1166-74. [PMID: 16373420 DOI: 10.1210/en.2005-1136] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The initiation of mammalian puberty requires an increase in pulsatile release of GnRH from the hypothalamus. This increase is brought about by coordinated changes in transsynaptic and glial-neuronal communication. As the neuronal and glial excitatory inputs to the GnRH neuronal network increase, the transsynaptic inhibitory tone decreases, leading to the pubertal activation of GnRH secretion. The excitatory neuronal systems most prevalently involved in this process use glutamate and the peptide kisspeptin for neurotransmission/neuromodulation, whereas the most important inhibitory inputs are provided by gamma-aminobutyric acid (GABA)ergic and opiatergic neurons. Glial cells, on the other hand, facilitate GnRH secretion via growth factor-dependent cell-cell signaling. Coordination of this regulatory neuronal-glial network may require a hierarchical arrangement. One level of coordination appears to be provided by a host of unrelated genes encoding proteins required for cell-cell communication. A second, but overlapping, level might be provided by a second tier of genes engaged in specific cell functions required for productive cell-cell interaction. A third and higher level of control involves the transcriptional regulation of these subordinate genes by a handful of upper echelon genes that, operating within the different neuronal and glial subsets required for the initiation of the pubertal process, sustain the functional integration of the network. The existence of functionally connected genes controlling the pubertal process is consistent with the concept that puberty is under genetic control and that the genetic underpinnings of both normal and deranged puberty are polygenic rather than specified by a single gene. The availability of improved high-throughput techniques and computational methods for global analysis of mRNAs and proteins will allow us to not only initiate the systematic identification of the different components of this neuroendocrine network but also to define their functional interactions.
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Affiliation(s)
- Sergio R Ojeda
- Division of Neuroscience, Oregon National Primate Research Center/Oregon Health and Science University, 505 Northwest 185th Avenue, Beaverton, Oregon 97006, USA.
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Yamamura T, Yasuo S, Hirunagi K, Ebihara S, Yoshimura T. T3 implantation mimics photoperiodically reduced encasement of nerve terminals by glial processes in the median eminence of Japanese quail. Cell Tissue Res 2006; 324:175-9. [PMID: 16432711 DOI: 10.1007/s00441-005-0126-8] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 11/09/2005] [Indexed: 10/25/2022]
Abstract
Photoperiodically generated triiodothyronin (T(3)) in the mediobasal hypothalamus (MBH) has critical roles in the photoperiodic response of the gonads in Japanese quail. In a previous study, we demonstrated seasonal morphological changes in the neuro-glial interaction between gonadotrophin-releasing hormone (GnRH) nerve terminals and glial endfeet in the median eminence (ME). However, a direct relationship between photoperiodically generated T(3) and seasonal neuro-glial plasticity in the ME remained unclear. In the present study, we examined the effect of T(3) implantation into the MBH on the neuro-glial interaction in the ME. T(3) implantation caused testicular growth and reduced encasement of nerve terminals in the external zone of the ME. In contrast, no morphological changes were observed in birds given an excessive dose of T(3), which did not cause testicular growth. These results support the hypothesis that thyroid hormone regulates photoperiodic GnRH secretion via neuro-glial plasticity in the ME.
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Affiliation(s)
- Takashi Yamamura
- Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, 464-8601, Nagoya, Japan
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De Seranno S, Estrella C, Loyens A, Cornea A, Ojeda SR, Beauvillain JC, Prevot V. Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain. J Neurosci 2005; 24:10353-63. [PMID: 15548649 PMCID: PMC6730291 DOI: 10.1523/jneurosci.3228-04.2004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Glial and endothelial cells interact throughout the brain to define specific functional domains. Whether endothelial cells convey signals to glia in the mature brain is unknown but is amenable to examination in circumventricular organs. Here we report that purified endothelial cells of one of these organs, the median eminence of the hypothalamus, induce acute actin cytoskeleton remodeling in isolated ependymoglial cells and show that this plasticity is mediated by nitric oxide (NO), a diffusible factor. We found that both soluble guanylyl cyclase and cyclooxygenase products are involved in this endothelial-mediated control of ependymoglia cytoarchitecture. We also demonstrate by electron microscopy that activation of endogenous NO release in the median eminence induces rapid structural changes, allowing a direct access of neurosecretory axons containing gonadotropin-releasing hormone (GnRH) (the neuropeptide controlling reproductive function) to the portal vasculature. Local in vivo inhibition of NO synthesis disrupts reproductive cyclicity, a process that requires a pulsatile, coordinated delivery of GnRH into the hypothalamic-adenohypophyseal portal system. Our results identify a previously unknown function for endothelial cells in inducing neuroglial plasticity and raise the intriguing possibility that endothelial cells throughout the brain may use a similar signaling mechanism to regulate glial-neuronal interactions.
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Affiliation(s)
- Sandrine De Seranno
- Institut National de la Santé et de la Recherche Médicale, Unité 422, 59045 Lille Cedex, France
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Givalois L, Arancibia S, Alonso G, Tapia-Arancibia L. Expression of brain-derived neurotrophic factor and its receptors in the median eminence cells with sensitivity to stress. Endocrinology 2004; 145:4737-47. [PMID: 15231696 DOI: 10.1210/en.2004-0616] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The median eminence (ME) is considered as the final common pathway connecting the nervous and endocrine systems. In this neurohemal structure, dynamic interactions among nerve terminals, tanycytes, and astrocytes determine through plastic processes the neurohormones access to the portal blood. Because brain-derived neurotrophic factor (BDNF) is involved in plastic changes, we investigated its presence and that of its receptors (TrkB) in the different cellular types described in the ME. Using in situ hybridization and immunohistochemical techniques, we demonstrated that BDNF immunoreactivity was essentially located in the astrocytes and to a lesser extent in tanycytes. By contrast, BDNF was not detected in nerve terminals reaching the external layer of the ME. TrkB antibodies recognizing the extracellular receptor domain labeled all of these different cell types, suggesting an autocrine or paracrine action of BDNF at this level. More selective antibodies showed that TrkB.FL immunostaining was found in tanycytes and nerve endings, whereas TrkB.T1 immunostaining was localized in all cellular types. Immobilization stress increased BDNF mRNA and BDNF immunoreactivity patterns and induced biphasic BDNF release from the ME, as analyzed by push-pull perfusion. In addition, we observed that 60-min stress intensified BDNF immunoreactivity in the internal layer and also its colocalization with glial fibrillary acidic protein. Stress also accentuated BDNF immunostaining in the perivascular space in elements that were not labeled with antibodies recognizing fibroblast or endothelial cells. These data disclosed a novel location of BDNF and its receptors in the ME, which are presumably involved in dynamic processes such as hormone release.
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Affiliation(s)
- Laurent Givalois
- Cerebral Plasticity Laboratory, Formation de Recherche en Evolution-2693 Centre National de la Recherche Scientifique, University of Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France
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Yamamura T, Hirunagi K, Ebihara S, Yoshimura T. Seasonal morphological changes in the neuro-glial interaction between gonadotropin-releasing hormone nerve terminals and glial endfeet in Japanese quail. Endocrinology 2004; 145:4264-7. [PMID: 15178649 DOI: 10.1210/en.2004-0366] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In a previous study we showed that photoperiodically generated T3 in the hypothalamus is critical for the photoperiodic response of gonads in Japanese quail. The expression of thyroid hormone receptors in the median eminence (ME) suggested that photoperiodically generated T3 acts on the ME. Because thyroid hormone is known to play a critical role in the development and plasticity of the central nervous system, in the present study we have examined ultrastructure of the ME in Japanese quail kept in short-day and long-day environments. Immunoelectron microscopy revealed that GnRH nerve terminals are in close proximity to the basal lamina under long-day conditions, and conventional transmission electron microscopy demonstrated the encasement of the terminals by the endfeet of glia under short-day conditions. These morphological changes may regulate photoperiodic GnRH secretion.
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Affiliation(s)
- Takashi Yamamura
- Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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Activation of erbB-1 signaling in tanycytes of the median eminence stimulates transforming growth factor beta1 release via prostaglandin E2 production and induces cell plasticity. J Neurosci 2003. [PMID: 14627647 DOI: 10.1523/jneurosci.23-33-10622.2003] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The activation of transforming growth factor alpha (TGFalpha)-erbB-1 and neuregulin-erbB-4 signaling pathways in hypothalamic astrocytes has been shown to play a key role in the process by which the neuroendocrine brain controls luteinizing hormone-releasing hormone (LHRH) secretion. Earlier studies suggested that tanycytes, an ependymoglial cell type of the median eminence, regulate LHRH release during the estrous cycle by undergoing plastic changes that alternatively allow or prevent direct access of the LHRH nerve terminals to the portal vasculature. Neither the molecules responsible for these plastic changes nor the underlying controlling mechanisms have been identified. Here we show that cultured tanycytes express erbB-1 and erbB-2, two of the four members of the erbB receptor family, and respond to TGFalpha with receptor phosphorylation, release of prostaglandin E2 (PGE2), and a PGE2-dependent increase in the release of TGFbeta1, a growth factor previously implicated in the glial control of LHRH secretion. Blockade of either erbB-1 receptor signal transduction or prostaglandin synthesis prevented the stimulatory effect of TGFalpha on both PGE2 and TGFbeta1 release. Time-lapse studies revealed that TGFalpha and TGFbeta1 have dramatically opposite effects on tanycyte plasticity. Whereas TGFalpha promotes tanycytic outgrowth, TGFbeta1 elicits retraction of tanycytic processes. Blockade of metalloproteinase activity abolished the effect of TGFbeta1, suggesting that TGFbeta1 induces tanycytic retraction by facilitating dissolution of the extracellular matrix. Prolonged (>12 hr) exposure of tanycytes to TGFalpha resulted in focal tanycytic retraction, an effect that was abolished by immunoneutralization of TGFbeta1 action, indicating that the retraction was attributable to TGFalpha-induced TGFbeta1 formation. These in vitro results identify tanycytes as targets of TGFalpha action and demonstrate that activation of erbB-1-mediated signaling in these cells results in plastic changes that, involving PGE2 and TGFbeta1 as downstream effectors, mimic the morphological plasticity displayed by tanycytes during the hours encompassing the preovulatory surge of LHRH.
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Abstract
In recent years compelling evidence has been provided that cell-cell interactions involving non-neuronal cells, such as glial and endothelial cells, are important in regulating the secretion of GnRH, the neuropeptide that controls both sexual development and adult reproductive function. Modification of the anatomical relationship that exist between GnRH nerve endings and glial cell processes in the external zone of the median eminence modulates the access of GnRH nerve terminals to the portal vasculature during the oestrous cycle. The establishment of direct neuro-haemal junctions between GnRH neuroendocrine terminals and the portal vasculature on the day of pro-oestrus may be critical for the transfer of GnRH upon its release into the fenestrated capillaries of the median eminence. Notwithstanding the importance of these plastic rearrangements, glial and endothelial cells also regulate GnRH neuronal function via specific cell-cell signalling molecules. While endothelial cells of the median eminence use nitric oxide to effect this regulatory control, astrocytes employ several growth factors, and in particular those of the EGF family and their erbB receptors to facilitate GnRH release during sexual development. Loss of function of each of these erbB receptors involved in the astroglial control of GnRH secretion leads to delayed sexual development. It is clear that regulation of GnRH secretion by cell-cell communication mechanisms other than transsynaptic inputs is an important component of the central neuroendocrine process controlling mammalian reproduction.
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Affiliation(s)
- Vincent Prevot
- Division of Neuroscience, Oregon Regional Primate Research Center/Oregon Health Science University, Beaverton, 97006 USA.
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Marchetti B, Gallo F, Farinella Z, Tirolo C, Testa N, Caniglia S, Morale MC. Gender, neuroendocrine-immune interactions and neuron-glial plasticity. Role of luteinizing hormone-releasing hormone (LHRH). Ann N Y Acad Sci 2001; 917:678-709. [PMID: 11268397 DOI: 10.1111/j.1749-6632.2000.tb05434.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Signals generated by the hypothalamic-pitutary-gonadal (HPG) axis powerfully modulate immune system function. This article summarizes some aspects of the impact of gender in neuroendocrine immunomodulation. Emphasis is given to the astroglial cell compartment, defined as a key actor in neuroendocrine immune communications. In the brain, the principal hormones of the HPG axis directly interact with astroglial cells. Thus, luteinizing hormone releasing hormone, LHRH, influences hypothalamic astrocyte development and growth, and hypothalamic astrocytes direct LHRH neuron differentiation. Hormonally induced changes in neuron-glial plasticity may dictate major changes in CNS output, and thus actively participate in sex dimorphic immune responses. The impact of gender in neuroimmunomodulation is further underlined by the sex dimorphism in the expression of genes encoding for neuroendocrine hormones and their receptors within the thymus, and by the potent modulation exerted by circulating sex steroids during development and immunization. The central role of glucocorticoids in the interactive communication between neuroendocrine and immune systems, and the impact of gender on hypothalamic-pituitary-adrenocortical (HPA) axis modulation is underscored in transgenic mice expressing a glucocorticoid receptor antisense RNA.
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Affiliation(s)
- B Marchetti
- Department of Pharmacology and Gynecology, Medical School, University of Sassari, Viale S. Pietro 43/B, 07100 Sassari, Italy.
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Saldanha CJ, Silverman AJ, Silver R. Direct innervation of GnRH neurons by encephalic photoreceptors in birds. J Biol Rhythms 2001; 16:39-49. [PMID: 11220777 PMCID: PMC3281767 DOI: 10.1177/074873040101600105] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In nonmammalian vertebrates, photic cues that regulate the timing of seasonal reproductive cyclicity are detected by nonretinal, nonpineal deep brain photoreceptors. It has long been assumed that the underlying mechanism involves the transmission of photic information from the photoreceptor to a circadian system, and thence to the reproductive axis. An alternative hypothesis is that there is direct communication between the brain photoreceptor and the reproductive axis. In the present study, light and confocal microscopy reveal that gonadotropin releasing hormone (GnRH) neurons and processes are scattered among photoreceptor cells (identified by their opsin-immunoreactivity) in the lateral septum (SL). In the median eminence (ME), opsin and GnRH immunoreactive fibers overlap extensively. Single and double label ultrastructural immunocytochemistry indicate that in the SL and preoptic area (POA), opsin positive terminals form axo-dendritic synapses onto GnRH dendrites. In the ME, opsin and GnRH terminals lie adjacent to each other, make contact with tanycytes, or terminate on the hypophyseal portal capillaries. These results reveal thatbrain photoreceptors communicate directly with GnRH-neurons; this represents a means by which photoperiodic information reaches the reproductive axis.
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Affiliation(s)
- Colin J. Saldanha
- The Graduate School of Arts and Sciences, Columbia University, New York, NY 10027, USA
| | - Ann-Judith Silverman
- Department of Anatomy and Cell Biology, Columbia University, New York, NY 10027, USA
| | - Rae Silver
- The Graduate School of Arts and Sciences, Columbia University, New York, NY 10027, USA
- Department of Anatomy and Cell Biology, Columbia University, New York, NY 10027, USA
- Psychology Departments, Barnard College and Columbia University, New York, NY 10027, USA
- To whom all correspondence should be addressed: Department of Psychology, Columbia University MAILCODE5501, 1190 Amsterdam Avenue, New York, NY 10027, USA;
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Neuregulins signaling via a glial erbB-2-erbB-4 receptor complex contribute to the neuroendocrine control of mammalian sexual development. J Neurosci 1999. [PMID: 10559400 DOI: 10.1523/jneurosci.19-22-09913.1999] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of erbB-1 receptors by glial TGFalpha has been shown to be a component of the developmental program by which the neuroendocrine brain controls mammalian sexual development. The participation of other members of the erbB family may be required, however, for full signaling capacity. Here, we show that activation of astrocytic erbB-2/erbB-4 receptors plays a significant role in the process by which the hypothalamus controls the advent of mammalian sexual maturation. Hypothalamic astrocytes express both the erbB-2 and erbB-4 genes, but no erbB-3, and respond to neuregulins (NRGs) by releasing prostaglandin E(2) (PGE(2)), which acts on neurosecretory neurons to stimulate secretion of luteinizing hormone-releasing hormone (LHRH), the neuropeptide controlling sexual development. The actions of TGFalpha and NRGs in glia are synergistic and involve recruitment of erbB-2 as a coreceptor, via erbB-1 and erbB-4, respectively. Hypothalamic expression of both erbB-2 and erbB-4 increases first in a gonad-independent manner before the onset of puberty, and then, at the time of puberty, in a sex steroid-dependent manner. Disruption of erbB-2 synthesis in hypothalamic astrocytes by treatment with an antisense oligodeoxynucleotide inhibited the astrocytic response to NRGs and, to a lesser extent, that to TGFalpha and blocked the erbB-dependent, glia-mediated, stimulation of LHRH release. Intracerebral administration of the oligodeoxynucleotide to developing animals delayed the initiation of puberty. Thus, activation of the erbB-2-erbB-4 receptor complex appears to be a critical component of the signaling process by which astrocytes facilitate the acquisition of female reproductive capacity in mammals.
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Ojeda SR, Ma YJ. Glial-neuronal interactions in the neuroendocrine control of mammalian puberty: facilitatory effects of gonadal steroids. JOURNAL OF NEUROBIOLOGY 1999; 40:528-40. [PMID: 10453054 DOI: 10.1002/(sici)1097-4695(19990915)40:4<528::aid-neu9>3.0.co;2-v] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It is now clear that astroglial cells actively contribute to both the generation and flow of information within the central nervous system. In the hypothalamus, astrocytes regulate the secretory activity of neuroendocrine neurons. A small subset of these neurons secrete luteinizing hormone-releasing hormone (LHRH), a neuropeptide essential for sexual development and adult reproductive function. Astrocytes stimulate LHRH secretion via cell-cell signaling mechanisms involving growth factors recognized by receptors with either serine/threonine or tyrosine kinase activity. Two members of the epidermal growth factor (EGF) family and their respective tyrosine kinase receptors appear to play key roles in this regulatory process. Transforming growth factor-alpha (TGFalpha) and its distant congeners, the neuregulins (NRGs), are produced in hypothalamic astrocytes. They stimulate LHRH secretion indirectly, via activation of erbB-1/erbB-2 and erbB-4/erbB-2 receptor complexes also located on astrocytes. Activation of these receptors leads to release of prostaglandin E(2) (PGE(2)), which then binds to specific receptors on LHRH neurons to elicit LHRH secretion. Gonadal steroids facilitate this glia-to-neuron communication process by acting at three different steps along the signaling pathway. They (a) increase astrocytic gene expression of at least one of the EGF-related ligands (TGFalpha), (b) increase expression of at least two of the receptors (erbB-4 and erbB-2), and (c) enhance the LHRH response to PGE(2) by up-regulating in LHRH neurons the expression of specific PGE(2) receptor isoforms. Focal overexpression of TGFalpha in either the median eminence or preoptic area of the hypothalamus accelerates puberty. Conversely, blockade of either TGFalpha or NRG hypothalamic actions delays the process. Thus, both TGFalpha and NRGs appear to be physiological components of the central neuroendocrine mechanism controlling the initiation of female puberty. By facilitating growth factor signaling pathways in the hypothalamus, ovarian steroids accelerate the pace and progression of the pubertal process.
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Affiliation(s)
- S R Ojeda
- Division of Neuroscience, Oregon Regional Primate Research Center/Oregon Health Sciences University, 505 N.W. 185th Avenue, Beaverton, Oregon 97006, USA
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41
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Ojeda SR, Hill J, Hill DF, Costa ME, Tapia V, Cornea A, Ma YJ. The Oct-2 POU domain gene in the neuroendocrine brain: a transcriptional regulator of mammalian puberty. Endocrinology 1999; 140:3774-89. [PMID: 10433239 DOI: 10.1210/endo.140.8.6941] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
POU homeodomain genes are transcriptional regulators that control development of the mammalian forebrain. Although they are mostly active during embryonic life, some of them remain expressed in the postnatal hypothalamus, suggesting their involvement in regulating differentiated functions of the neuroendocrine brain. We show here that Oct-2, a POU domain gene originally described in cells of the immune system, is one of the controlling components of the cell-cell signaling process underlying the hypothalamic regulation of female puberty. Lesions of the anterior hypothalamus cause sexual precocity and recapitulate some of the events leading to the normal initiation of puberty. Prominent among these events is an increased astrocytic expression of the gene encoding transforming growth factor-alpha (TGF alpha), a tropic polypeptide involved in the stimulatory control of LHRH secretion. The present study shows that such lesions result in the rapid and selective increase in Oct-2 transcripts in TGF alpha-containing astrocytes surrounding the lesion site. In both lesion-induced and normal puberty, there is a preferential increase in hypothalamic expression of the Oct-2a and Oct-2c alternatively spliced messenger RNA forms of the Oct-2 gene, with an increase in 2a messenger RNA levels preceding that in 2c and antedating the peripubertal activation of gonadal steroid secretion. Both Oct-2a and 2c trans-activate the TGF alpha gene via recognition motifs contained in the TGF alpha gene promoter. Inhibition of Oct-2 synthesis reduces TGF alpha expression in astroglial cells and delays the initiation of puberty. These results suggest that the Oct-2 gene is one of the upstream components of the glia to neuron signaling process that controls the onset of female puberty in mammals.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- DNA-Binding Proteins/genetics
- Female
- Gene Expression Regulation, Developmental
- Hypothalamus, Anterior/physiology
- Hypothalamus, Anterior/radiation effects
- Kinetics
- Mammals
- Molecular Sequence Data
- Octamer Transcription Factor-2
- Preoptic Area/physiology
- Preoptic Area/radiation effects
- Promoter Regions, Genetic
- Prosencephalon/growth & development
- Prosencephalon/physiology
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Rats
- Rats, Sprague-Dawley
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Alignment
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Sexual Maturation/genetics
- Transcription Factors/genetics
- Transcription, Genetic
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Affiliation(s)
- S R Ojeda
- Division of Neuroscience, Oregon Regional Primate Research Center/Oregon Health Sciences University, Beaverton 97006, USA.
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42
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Hebb MO, Denovan-Wright EM, Robertson HA. Expression of the Huntington's disease gene is regulated in astrocytes in the arcuate nucleus of the hypothalamus of postpartum rats. FASEB J 1999; 13:1099-106. [PMID: 10336893 DOI: 10.1096/fasebj.13.9.1099] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Huntington's disease (HD) is one of a number of neurodegenerative disorders caused by expansion of polyglutamine-encoding CAG repeats within specific genes. Huntingtin, the protein product of the HD gene, is widely expressed in neural and nonneural human and rodent tissue. The function of the wild-type or mutated form of huntingtin is currently unknown. We have observed that relative to naive and male animals, huntingtin protein was significantly increased in the arcuate nucleus of postpartum rats. Using an oligonucleotide probe, in situ and Northern blot hybridization confirmed the expression of huntingtin mRNA. Quantification of the in situ hybridization signal in the arcuate nucleus revealed an approximate sevenfold increase in the expression of huntingtin mRNA in postpartum, lactating animals compared with naive female or male animals. Emulsion autoradiography and immunohistochemistry revealed that the cells with elevated huntingtin expression had a stellate conformation that morphologically resembled astrocytes. Dual label immunofluorescence immunohistochemistry demonstrated the colocalization of huntingtin and glial fibrillary acidic protein in these cells, confirming that they were astrocytes. Astrocytes expressing huntingtin were consistently found in close apposition to neuronal soma, suggesting interactions between these cell types. During the perinatal and postnatal period, the hypothalamus undergoes alterations in metabolic function. Our results support the idea of glia-induced metabolic changes in the hypothalamus. These results provide the first demonstration of naturally occurring changes in the expression of the Huntington's disease gene in the brain and suggest that huntingtin may play an important role in the processes that regulate neuroendocrine function.
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Affiliation(s)
- M O Hebb
- Laboratory of Molecular Neurobiology, Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
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43
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Viguié C, Battaglia DF, Krasa HB, Thrun LA, Karsch FJ. Thyroid hormones act primarily within the brain to promote the seasonal inhibition of luteinizing hormone secretion in the ewe. Endocrinology 1999; 140:1111-7. [PMID: 10067833 DOI: 10.1210/endo.140.3.6543] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In the ewe, thyroid hormones are required for the seasonal suppression of GnRH and LH secretion, thereby maintaining an annual rhythm in reproductive activity. The primary site of action of thyroid hormones is unknown; in particular, there is no evidence to distinguish a central from a peripheral action. In this study, we test the hypothesis that thyroid hormones can act directly within the brain to promote GnRH/LH seasonal inhibition. Ovariectomized estradiol-treated ewes were thyroidectomized late in the breeding season to prevent seasonal LH inhibition. T4 was then infused for 3 months, either peripherally or centrally. Neuroendocrine reproductive state was monitored by assaying the LH concentration in biweekly blood samples. Central infusion of low dose T4, which restored a physiological concentration of the hormone in cerebrospinal fluid of these thyroidectomized ewes, promoted the neuroendocrine changes that lead to anestrus. The serum LH concentration in these animals fell at the same time as the seasonal LH decline in euthyroid controls. Neither this same T4 dose infused peripherally nor vehicle infused centrally was effective; LH remained elevated, signifying blockade of the mechanism for anestrus. Our results provide strong evidence that thyroid hormones can act directly within the brain to promote seasonal inhibition of neuroendocrine reproductive function in the ewe.
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Affiliation(s)
- C Viguié
- Reproductive Sciences Program, University of Michigan, Ann Arbor 48109-0404, USA
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44
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Affiliation(s)
- A E Herbison
- Laboratory of Neuroendocrinology, Babraham Institute, Cambridge, United Kingdom.
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45
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Kawakami S, Ichikawa M, Yokosuka M, Tsukamura H, Maeda K. Glial and neuronal localization of neuronal nitric oxide synthase immunoreactivity in the median eminence of female rats. Brain Res 1998; 789:322-6. [PMID: 9573392 DOI: 10.1016/s0006-8993(97)01561-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Localization of neuronal nitric oxide synthase-immunoreactivity (nNOS-IR) in the median eminence of female rats (n=4) was examined by electron microscopy to explore the possibility that nitric oxide is involved in the terminal regulation of neurosecretory peptides such as GnRH. Under light microscopy, a dense distribution of nNOS-IR was observed in this region. Electronmicroscopically, nNOS-IR was found in glial elements and nerve terminals containing dense-core vesicles. We also found a few nNOS-immunopositive synapses, in which intense immunoreactivity was found on the postsynaptic density and mitochondrial membrane. The localization of nNOS-IR in nerve terminals and glial elements in the median eminence might indicate that nNOS plays a role in regulating the release of neurosecretory peptide.
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Affiliation(s)
- S Kawakami
- School of Agricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-01, Japan
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46
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47
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Estradiol enhances prostaglandin E2 receptor gene expression in luteinizing hormone-releasing hormone (LHRH) neurons and facilitates the LHRH response to PGE2 by activating a glia-to-neuron signaling pathway. J Neurosci 1997. [PMID: 9364061 DOI: 10.1523/jneurosci.17-23-09145.1997] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Prostaglandin E2 (PGE2) mediates the stimulatory effect of norepinephrine (NE) on the secretion of luteinizing hormone-releasing hormone (LHRH), the neuropeptide controlling reproductive function. In rodents, this facilitatory effect requires previous exposure to estradiol, suggesting that the steroid affects downstream components in the cascade that leads to PGE2-induced LHRH release. Because astroglia are the predominant cell type contacting LHRH-secreting nerve terminals, we investigated the involvement of hypothalamic astrocytes in the estradiol facilitation of PGE2-induced LHRH release. A subpopulation of LHRH neurons was found to express the mRNA encoding the PGE2 receptor subtype EP1-R, which is coupled to calcium mobilization. The LHRH-producing cell line GT1-1 also contains EP1-R mRNA and, to a lesser extent, the three alternatively spliced forms of EP3-R mRNA (alpha, beta, and gamma) that encode receptors linked to inhibition and stimulation of cAMP formation. Hypothalamic astrocytes treated with estradiol produced a conditioned medium that when applied to GT1-1 cells resulted in a selective upregulation of EP1-R and EP3gamma-R mRNAs. The conditioned medium also enhanced the LHRH response to EP1-R and EP3-R agonists and the cAMP response to EP3-R activation. Thus, one mechanism by which estradiol facilitates the effect of neurotransmitters acting via PGE2 to stimulate LHRH release is by enhancing the glial production of substances that upregulate PGE2 receptors on LHRH neurons. The existence of such a mechanism underscores the emerging importance of glial-neuronal communication in the control of brain neurosecretory activity.
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48
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Photoperiodically driven changes in Fos expression within the basal tuberal hypothalamus and median eminence of Japanese quail. J Neurosci 1997. [PMID: 9348357 DOI: 10.1523/jneurosci.17-22-08909.1997] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The rapid photoperiodic response in Japanese quail is so precise that it allows neural analyses of how photoperiodic information is transduced into an endocrine response. After transfer from short [SD; 6L:18D (6:18 hr light/dark cycle)] to long (LD; 20L:4D) days, luteinizing hormone (LH) first rises 20 hr after dawn. Using Fos immunocytochemistry, we examined the basal tuberal hypothalamus (BtH) to determine the relationship between brain cell activation and the first endocrine changes. Two separate cell populations within the BtH expressed Fos-like immunoreactivity (FLI) by hour 18 of the first LD. Importantly, this activation occurred before the LH rise. Median eminence activation appeared within glial cells, whereas activated infundibular nucleus cells were neuronal, providing support to the view that gonadotropin-releasing hormone (GnRH) release can be controlled at the terminals by glia. The FLI induction parallels LH changes, suggesting that gene expression may be involved in events preceding photostimulation and is the earliest photoperiodically stimulated physiological change yet reported. Additional experiments provided further support for this hypothesis. First, photoperiodically induced activation is not a result peculiar to castrates because intact birds displayed similar results. Second, the critical length of 14 hr of light had to be exceeded to cause both BtH activation and a LH rise 30 hr from dawn. Finally, valuable evidence of the response specificity was provided by using a unique property of the quail photoperiodic clock in which exposure to 10L:26D, but not 10L:14D, causes photoinduction. The 36 hr paradigm increased both plasma LH and BtH activation.
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49
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Fernandez-Galaz MC, Morschl E, Chowen JA, Torres-Aleman I, Naftolin F, Garcia-Segura LM. Role of astroglia and insulin-like growth factor-I in gonadal hormone-dependent synaptic plasticity. Brain Res Bull 1997; 44:525-31. [PMID: 9370220 DOI: 10.1016/s0361-9230(97)00238-4] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Gonadal hormones exert a critical influence over the architecture of specific brain areas affecting the formation of neuronal contacts. Cellular mechanisms mediating gonadal hormone actions on synapses have been studied extensively in the rat arcuate nucleus, a hypothalamic center involved in the feed-back regulation of gonadotropins. Gonadal steroids exert organizational and activational effects on arcuate nucleus synaptic connectivity. Perinatal testosterone induces a sexual dimorphic pattern of synaptic contacts. Furthermore, during the preovulatory and ovulatory phases of the estrous cycle there is a transient disconnection of inhibitory synaptic inputs to the somas of arcuate neurons. This synaptic remodeling is induced by estradiol, blocked by progesterone, and begins with the onset of puberty in females. Astroglia appear to play a significant role in the organizational and the activational hormone effects on neuronal connectivity by regulating the amount of neuronal membrane available for the formation of synaptic contacts and by releasing soluble factors, such as insulin-like growth factor I (IGF-I), which promote the differentiation of neural processes. Recent evidence indicates that gonadal steroids and IGF-I may interact in their trophic effects on the neuroendocrine hypothalamus. Estradiol and IGF-I promote the survival and morphological differentiation of rat hypothalamic neurons in primary cultures. The effect of estradiol depends on IGF-I, while the effects of both estradiol and IGF-I depend on estrogen receptors. Furthermore, estrogen activation of astroglia in hypothalamic tissue fragments depends on IGF-I receptors. These findings indicate that IGF-I may mediate some of the developmental and activational effects of gonadal steroids on the brain and suggest that IGF-I may activate the estrogen receptor to induce its neurotrophic effects on hypothalamic cells. In addition, IGF-I levels in the neuroendocrine hypothalamus are regulated by gonadal steroids. IGF-I levels in tanycytes, a specific astroglia cell type present in the arcuate nucleus and median eminence, increase at puberty, are affected by neonatal androgen levels, show sex differences, and fluctuate in accordance to the natural variations in plasma levels of ovarian steroids that are associated with the estrous cycle. These changes appear to be mediated by hormonal regulation of IGF-I uptake from blood or cerebrospinal fluid by tanycytes. These results suggest that tanycytes may be involved in the regulation of neuroendocrine events in adult rats by regulating the availability of IGF-I to hypothalamic neurons. In summary, IGF-I and different forms of neuron-astroglia communication are involved in the effects of estradiol on synaptic plasticity in the hypothalamic arcuate nucleus.
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50
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Tu HM, Kim SW, Salvatore D, Bartha T, Legradi G, Larsen PR, Lechan RM. Regional distribution of type 2 thyroxine deiodinase messenger ribonucleic acid in rat hypothalamus and pituitary and its regulation by thyroid hormone. Endocrinology 1997; 138:3359-68. [PMID: 9231788 DOI: 10.1210/endo.138.8.5318] [Citation(s) in RCA: 168] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To identify the specific locations of type 2 deiodinase (D2) messenger RNA (mRNA) in the hypothalamus and pituitary gland and determine its regulation by thyroid hormone, we performed in situ hybridization histochemistry, Northern analysis, and quantitative RT-PCR in euthyroid, hypothyroid, and hyperthyroid rats. By in situ hybridization histochemistry, silver grains were concentrated over ependymal cells lining the floor and infralateral walls of the third ventricle extending from the rostral tip of the median eminence (ME) to the infundibular recess, surrounding blood vessels in the arcuate nucleus (ARC), and in the ME adjacent to the portal vessels and overlying the tuberoinfundibular sulci. Silver grains also accumulated over distinct cells in the midportion of the anterior pituitary. In hypothyroid animals, an increase in signal intensity was observed in the caudal hypothalamus, and a marked increase in the number of positive cells occurred in the anterior pituitary. Microdissection of the hypothalamus for Northern and PCR analysis established the authenticity of D2 mRNA in the caudal hypothalamus, and confirmed that the majority of D2 mRNA is concentrated in this region. The distribution of D2 mRNA suggests its expression in specialized ependymal cells, termed tanycytes, originating from the third ventricle. Thus, the tanycyte is the source of the high D2 activity previously found in the ARC-ME region of the hypothalamus. The results indicate that tanycytes may have a previously unrecognized integral role in feedback regulation of TSH secretion by T4.
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Affiliation(s)
- H M Tu
- Tupper Research Institute and Department of Medicine, New England Medical Center, Boston, Massachusetts 02111, USA
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