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Muñoz EM. Microglia in Circumventricular Organs: The Pineal Gland Example. ASN Neuro 2022; 14:17590914221135697. [PMID: 36317305 PMCID: PMC9629557 DOI: 10.1177/17590914221135697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The circumventricular organs (CVOs) are unique areas within the central nervous system. They serve as a portal for the rest of the body and, as such, lack a blood-brain barrier. Microglia are the primary resident immune cells of the brain parenchyma. Within the CVOs, microglial cells find themselves continuously challenged and stimulated by local and systemic stimuli, even under steady-state conditions. Therefore, CVO microglia in their typical state often resemble the activated microglial forms found elsewhere in the brain as they are responding to pathological conditions or other stressors. In this review, I focus on the dynamics of CVO microglia, using the pineal gland as a specific CVO example. Data related to microglia heterogeneity in both homeostatic and unhealthy environments are presented and discussed, including those recently generated by using advanced single-cell and single-nucleus technology. Finally, perspectives in the CVO microglia field are also included.Summary StatementMicroglia in circumventricular organs (CVOs) continuously adapt to react differentially to the diverse challenges they face. Herein, I discuss microglia heterogeneity in CVOs, including pineal gland. Further studies are needed to better understand microglia dynamics in these unique brain areas. .
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Affiliation(s)
- Estela M. Muñoz
- Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos (IHEM), Universidad Nacional de Cuyo (UNCuyo), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mendoza, Argentina,Estela M. Muñoz, IHEM-UNCuyo-CONICET, Parque General San Martin, Ciudad de Mendoza, M5502JMA, Mendoza, Argentina.
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2
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Madhani SI, Klein DC, Muñoz EM, Savastano LE. Surgical Techniques and Nuances for Superior Cervical Ganglionectomy and Decentralization in Rats. Methods Mol Biol 2022; 2550:53-62. [PMID: 36180677 DOI: 10.1007/978-1-0716-2593-4_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The sympathetic nervous system has been implicated in various physiological and pathological processes, including regulation of homeostatic functions, maintenance of the circadian rhythms, and neuronal disruption and recovery after injury. Of special interest is focus on the role of the superior cervical ganglion (SCG) in regulating the daily changes in pineal function. Removal of the superior cervical ganglion (SCGx) and decentralization have served as valuable microsurgical models to investigate the effects of surgical denervation on this gland or organ. In this chapter, we offer information about methodologies for performing SCGx along with decentralization and denervation procedures, including details about recommended equipment as well as tips that can improve these techniques.
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Affiliation(s)
- Sarosh Irfan Madhani
- Department of Neurosurgery, University of California, San Francisco, San Francisco, CA, USA
| | - David C Klein
- Section on Neuroendocrinology, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Estela M Muñoz
- Laboratory of Neurobiology: Section of Chronobiology, Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - Luis E Savastano
- Department of Neurosurgery, University of California, San Francisco, San Francisco, CA, USA.
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Reperfusion Arrhythmias Increase after Superior Cervical Ganglionectomy Due to Conduction Disorders and Changes in Repolarization. Int J Mol Sci 2020; 21:ijms21051804. [PMID: 32155697 PMCID: PMC7084297 DOI: 10.3390/ijms21051804] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 02/20/2020] [Accepted: 03/04/2020] [Indexed: 01/15/2023] Open
Abstract
Pharmacological concentrations of melatonin reduce reperfusion arrhythmias, but less is known about the antiarrhythmic protection of the physiological circadian rhythm of melatonin. Bilateral surgical removal of the superior cervical ganglia irreversibly suppresses melatonin rhythmicity. This study aimed to analyze the cardiac electrophysiological effects of the loss of melatonin circadian oscillation and the role played by myocardial melatonin membrane receptors, SERCA2A, TNFα, nitrotyrosine, TGFβ, KATP channels, and connexin 43. Three weeks after bilateral removal of the superior cervical ganglia or sham surgery, the hearts were isolated and submitted to ten minutes of regional ischemia followed by ten minutes of reperfusion. Arrhythmias, mainly ventricular tachycardia, increased during reperfusion in the ganglionectomy group. These hearts also suffered an epicardial electrical activation delay that increased during ischemia, action potential alternants, triggered activity, and dispersion of action potential duration. Hearts from ganglionectomized rats showed a reduction of the cardioprotective MT2 receptors, the MT1 receptors, and SERCA2A. Markers of nitroxidative stress (nitrotyrosine), inflammation (TNFα), and fibrosis (TGFβ and vimentin) did not change between groups. Connexin 43 lateralization and the pore-forming subunit (Kir6.1) of KATP channels increased in the experimental group. We conclude that the loss of the circadian rhythm of melatonin predisposes the heart to suffer cardiac arrhythmias, mainly ventricular tachycardia, due to conduction disorders and changes in repolarization.
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Signaling within the pineal gland: A parallelism with the central nervous system. Semin Cell Dev Biol 2018; 95:151-159. [PMID: 30502386 DOI: 10.1016/j.semcdb.2018.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 11/15/2018] [Accepted: 11/27/2018] [Indexed: 12/22/2022]
Abstract
The pineal gland (PG) derives from the neural tube, like the rest of the central nervous system (CNS). The PG is specialized in synthesizing and secreting melatonin in a circadian fashion. The nocturnal elevation of melatonin is a highly conserved feature among species which proves its importance in nature. Here, we review a limited set of intrinsic and extrinsic regulatory elements that have been shown or proposed to influence the PG's melatonin production, as well as pineal ontogeny and homeostasis. Intrinsic regulators include the transcription factors CREB, Pax6 and NeuroD1. In addition, microglia within the PG participate as extrinsic regulators of these functions. We further discuss how these same elements work in other parts of the CNS, and note similarities and differences to their roles in the PG. Since the PG is a relatively well-defined and highly specialized organ within the CNS, we suggest that applying this comparative approach to additional PG regulators may be a useful tool for understanding complex areas of the brain, as well as the influence of the PG in both health and disease, including circadian functions and disorders.
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Ibañez Rodriguez MP, Galiana MD, Rásmussen JA, Freites CL, Noctor SC, Muñoz EM. Differential response of pineal microglia to surgical versus pharmacological stimuli. J Comp Neurol 2018; 526:2462-2481. [PMID: 30246867 DOI: 10.1002/cne.24505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 07/18/2018] [Accepted: 07/19/2018] [Indexed: 12/17/2022]
Abstract
Microglial cells are one of the interstitial elements of the pineal gland (PG). We recently reported the pattern of microglia colonization and activation, and microglia-Pax6+ cell interactions during normal pineal ontogeny. Here, we describe the dynamics of microglia-Pax6+ cell associations and interactions after surgical or pharmacological manipulation. In adult rats, the superior cervical ganglia (SCG) were exposed, and either bilaterally excised (SCGx) or decentralized (SCGd). In the SCGx PGs, the density of Iba1+ microglia increased after surgery and returned to sham baseline levels 13 days later. Pineal microglia also responded to SCGd, a more subtle denervation. The number of clustered Iba1+ /PCNA+ /ED1+ microglia was higher 4 days after both surgeries compared to the sham-operated group. However, the number of Pax6+ /PCNA- cells and the percentage of Pax6+ cells contacted by and/or phagocytosed by microglia increased significantly only after SCGx. Separate groups of rats were treated with either bacterial lipopolysaccharides (LPS) or doxycycline (DOX) to activate or inhibit pineal microglia, respectively. Peripheral LPS administration caused an increase in the number of clustered Iba1+ /PCNA+ /ED1+ microglial cells, and in the percentage of Pax6+ cells associated with and/or engulfed by microglia. In the LPS-treated PGs, we also noted an increase in the number of PCNA+ cells that were Iba1- within the microglial cell clusters. The density of Pax6+ cells did not change after LPS treatment. DOX administration did not influence the parameters analyzed. These data suggest that pineal microglia are highly receptive cells capable of rapidly responding in a differential manner to surgical and pharmacological stimuli.
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Affiliation(s)
- María P Ibañez Rodriguez
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - María D Galiana
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - Jorge A Rásmussen
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - Carlos L Freites
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - Stephen C Noctor
- Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California, Davis, School of Medicine Sacramento, California
| | - Estela M Muñoz
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
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Lawson R, Maret W, Hogstrand C. Prolonged stimulation of insulin release from MIN6 cells causes zinc depletion and loss of β-cell markers. J Trace Elem Med Biol 2018; 49:51-59. [PMID: 29895372 DOI: 10.1016/j.jtemb.2018.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/19/2018] [Accepted: 04/18/2018] [Indexed: 11/17/2022]
Abstract
Zinc is integral for the normal function of pancreatic β-cells in glycaemic control. Large amounts of zinc are secreted from β-cells following insulin exocytosis and regulated replenishment is required, which is thought to be mediated by the ZIP family of zinc importer proteins. Within Type 2 Diabetic patients, β-cells are stressed through prolonged stimulation by hyperglycaemia and this is thought to be a major factor contributing to loss of β-cell identity and mass. However, the consequences for the β-cell zinc status remain largely unexplored. We used inductively coupled plasma mass spectrometry (ICP-MS) to show that 24 h treatment of MIN6 cells with potassium chloride, mimicking hyperglycaemic stimulation, reduces the total cellular zinc content 2.8-fold, and qPCR to show an increase in mRNA expression for metallothioneins (Mt1 and Mt2) following 4 and 24 h of stimulation, suggestive of an early rise in cytosolic zinc. To determine which ZIP paralogues may be responsible for zinc replenishment, we used immunocytochemistry, Western blot and qPCR to demonstrate initial ZIP1 protein upregulation proceeded by downregulation of mRNA coding for ZIP1, ZIP6, ZIP7 and ZIP14. To assign a biological significance to the decreased total cellular zinc content, we assessed expression of key β-cell markers to show downregulation of mRNA for MafA, Mnx-1, Nkx2.2 and Pax6. Our data suggest hyperglycaemia-induced zinc depletion may contribute to loss of β-cell markers and promote β-cell dedifferentiation through disrupting expression of key transcription factors.
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Affiliation(s)
- Rebecca Lawson
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
| | - Wolfgang Maret
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
| | - Christer Hogstrand
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
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Zhang J, Qiu J, Zhou Y, Wang Y, Li H, Zhang T, Jiang Y, Gou K, Cui S. LIM homeobox transcription factor Isl1 is required for melatonin synthesis in the pig pineal gland. J Pineal Res 2018; 65:e12481. [PMID: 29480946 DOI: 10.1111/jpi.12481] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/13/2018] [Indexed: 01/10/2023]
Abstract
Melatonin is a key hormone that regulates circadian rhythms, metabolism, and reproduction. However, the mechanisms of melatonin synthesis and secretion have not been fully defined. The purpose of this study was to investigate the functions of the LIM homeobox transcription factor Isl1 in regulating melatonin synthesis and secretion in porcine pineal gland. We found that Isl1 is highly expressed in the melatonin-producing cells in the porcine pineal gland. Further functional studies demonstrate that Isl1 knockdown in cultured primary porcine pinealocytes results in the decline of melatonin and arylalkylamine N-acetyltransferase (AANAT) mRNA levels by 29.2% and 72.2%, respectively, whereas Isl1 overexpression raised by 1.3-fold and 2.7-fold. In addition, the enhancing effect of norepinephrine (NE) on melatonin synthesis was abolished by Isl1 knockdown. The in vivo intracerebroventricular NE injections upregulate Isl1 mRNA and protein levels by about threefold and 4.5-fold in the porcine pineal gland. We then examined the changes in Isl1 expression in the pineal gland and global melatonin levels throughout the day. The results show that Isl1 protein level at 24:00 is 2.5-fold higher than that at 12:00, which is parallel to melatonin levels. We further found that Isl1 increases the activity of AANAT promoter, and the effect of NE on Isl1 expression was blocked by an ERK inhibitor. Collectively, the results presented here demonstrate that Isl1 positively modulates melatonin synthesis by targeting AANAT, via the ERK signaling pathway of NE. These suggest that Isl1 plays important roles in maintaining the daily circadian rhythm.
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Affiliation(s)
- Jinglin Zhang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jingtao Qiu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yewen Zhou
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yue Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Hongjiao Li
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Taojie Zhang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Ying Jiang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Kemian Gou
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Sheng Cui
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China
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Chen W, Zhang B, Xu S, Lin R, Wang W. Lentivirus carrying the NeuroD1 gene promotes the conversion from glial cells into neurons in a spinal cord injury model. Brain Res Bull 2017; 135:143-148. [DOI: 10.1016/j.brainresbull.2017.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/27/2017] [Accepted: 10/03/2017] [Indexed: 12/17/2022]
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Ibañez Rodriguez MP, Noctor SC, Muñoz EM. Cellular Basis of Pineal Gland Development: Emerging Role of Microglia as Phenotype Regulator. PLoS One 2016; 11:e0167063. [PMID: 27861587 PMCID: PMC5115862 DOI: 10.1371/journal.pone.0167063] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 11/08/2016] [Indexed: 12/04/2022] Open
Abstract
The adult pineal gland is composed of pinealocytes, astrocytes, microglia, and other interstitial cells that have been described in detail. However, factors that contribute to pineal development have not been fully elucidated, nor have pineal cell lineages been well characterized. We applied systematic double, triple and quadruple labeling of cell-specific markers on prenatal, postnatal and mature rat pineal gland tissue combined with confocal microscopy to provide a comprehensive view of the cellular dynamics and cell lineages that contribute to pineal gland development. The pineal gland begins as an evagination of neuroepithelium in the roof of the third ventricle. The pineal primordium initially consists of radially aligned Pax6+ precursor cells that express vimentin and divide at the ventricular lumen. After the tubular neuroepithelium fuses, the distribution of Pax6+ cells transitions to include rosette-like structures and later, dispersed cells. In the developing gland all dividing cells express Pax6, indicating that Pax6+ precursor cells generate pinealocytes and some interstitial cells. The density of Pax6+ cells decreases across pineal development as a result of cellular differentiation and microglial phagocytosis, but Pax6+ cells remain in the adult gland as a distinct population. Microglial colonization begins after pineal recess formation. Microglial phagocytosis of Pax6+ cells is not common at early stages but increases as microglia colonize the gland. In the postnatal gland microglia affiliate with Tuj1+ nerve fibers, IB4+ blood vessels, and Pax6+ cells. We demonstrate that microglia engulf Pax6+ cells, nerve fibers, and blood vessel-related elements, but not pinealocytes. We conclude that microglia play a role in pineal gland formation and homeostasis by regulating the precursor cell population, remodeling blood vessels and pruning sympathetic nerve fibers.
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Affiliation(s)
- María P. Ibañez Rodriguez
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
| | - Stephen C. Noctor
- Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California, Davis, School of Medicine, Sacramento, CA, United States of America
- * E-mail: (EMM); (SCN)
| | - Estela M. Muñoz
- Institute of Histology and Embryology of Mendoza (IHEM), National University of Cuyo, National Scientific and Technical Research Council (CONICET), Mendoza, Argentina
- * E-mail: (EMM); (SCN)
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Yu H, Benitez SG, Jung SR, Farias Altamirano LE, Kruse M, Seo JB, Koh DS, Muñoz EM, Hille B. GABAergic signaling in the rat pineal gland. J Pineal Res 2016; 61:69-81. [PMID: 27019076 PMCID: PMC5489258 DOI: 10.1111/jpi.12328] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 03/25/2016] [Indexed: 11/29/2022]
Abstract
Pinealocytes secrete melatonin at night in response to norepinephrine released from sympathetic nerve terminals in the pineal gland. The gland also contains many other neurotransmitters whose cellular disposition, activity, and relevance to pineal function are not understood. Here, we clarify sources and demonstrate cellular actions of the neurotransmitter γ-aminobutyric acid (GABA) using Western blotting and immunohistochemistry of the gland and electrical recording from pinealocytes. GABAergic cells and nerve fibers, defined as containing GABA and the synthetic GAD67, were identified. The cells represent a subset of interstitial cells while the nerve fibers were distinct from the sympathetic innervation. The GABAA receptor subunit α1 was visualized in close proximity of both GABAergic and sympathetic nerve fibers as well as fine extensions among pinealocytes and blood vessels. The GABAB 1 receptor subunit was localized in the interstitial compartment but not in pinealocytes. Electrophysiology of isolated pinealocytes revealed that GABA and muscimol elicit strong inward chloride currents sensitive to bicuculline and picrotoxin, clear evidence for functional GABAA receptors on the surface membrane. Applications of elevated potassium solution or the neurotransmitter acetylcholine depolarized the pinealocyte membrane potential enough to open voltage-gated Ca(2+) channels leading to intracellular calcium elevations. GABA repolarized the membrane and shut off such calcium rises. In 48-72-h cultured intact glands, GABA application neither triggered melatonin secretion by itself nor affected norepinephrine-induced secretion. Thus, strong elements of GABA signaling are present in pineal glands that make large electrical responses in pinealocytes, but physiological roles need to be found.
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Affiliation(s)
- Haijie Yu
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
| | - Sergio G. Benitez
- Laboratory of Neurobiology: Chronobiology Section, Institute of Histology and Embryology of Mendoza (IHEM-CONICET), School of Medicine, National University of Cuyo, Mendoza, Argentina
| | - Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
| | - Luz E. Farias Altamirano
- Laboratory of Neurobiology: Chronobiology Section, Institute of Histology and Embryology of Mendoza (IHEM-CONICET), School of Medicine, National University of Cuyo, Mendoza, Argentina
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
| | - Jong-Bae Seo
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
| | - Duk-Su Koh
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
| | - Estela M. Muñoz
- Laboratory of Neurobiology: Chronobiology Section, Institute of Histology and Embryology of Mendoza (IHEM-CONICET), School of Medicine, National University of Cuyo, Mendoza, Argentina
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA
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Rath MF, Coon SL, Amaral FG, Weller JL, Møller M, Klein DC. Melatonin Synthesis: Acetylserotonin O-Methyltransferase (ASMT) Is Strongly Expressed in a Subpopulation of Pinealocytes in the Male Rat Pineal Gland. Endocrinology 2016; 157:2028-40. [PMID: 26950199 PMCID: PMC4870883 DOI: 10.1210/en.2015-1888] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The rat pineal gland has been extensively used in studies of melatonin synthesis. However, the cellular localization of melatonin synthesis in this species has not been investigated. Here we focus on the localization of melatonin synthesis using immunohistochemical methods to detect the last enzyme in melatonin synthesis, acetylserotonin O-methyltransferase (ASMT), and in situ hybridization techniques to study transcripts encoding ASMT and two other enzymes in melatonin synthesis, tryptophan hydroxylase (TPH)-1 and aralkylamine N-acetyltransferase. In sections of the rat pineal gland, marked cell-to-cell differences were found in ASMT immunostaining intensity and in the abundance of Tph1, Aanat, and Asmt transcripts. ASMT immunoreactivity was localized to the cytoplasm in pinealocytes in the parenchyma of the superficial pineal gland, and immunopositive pinealocytes were also detected in the pineal stalk and in the deep pineal gland. ASMT was found to inconsistently colocalize with S-antigen, a widely used pinealocyte marker; this colocalization was seen in cells throughout the pineal complex and also in displaced pinealocyte-like cells of the medial habenular nucleus. Inconsistent colocalization between ASMT and TPH protein was also detected in the pineal gland. ASMT protein was not detected in extraepithalamic parts of the central nervous system or in peripheral tissues. The findings in this report are of special interest because they provide reason to suspect that melatonin synthesis varies significantly among individual pinealocytes.
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Affiliation(s)
- Martin F Rath
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Steven L Coon
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Fernanda G Amaral
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Joan L Weller
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Morten Møller
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - David C Klein
- Department of Neuroscience and Pharmacology (M.F.R., M.M.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark; and Section on Neuroendocrinology (M.F.R., S.L.C., F.G.A., J.L.W., D.C.K.), Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
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