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Masmoudi-Kouki O, Namsi A, Hamdi Y, Bahdoudi S, Ghouili I, Chuquet J, Leprince J, Lefranc B, Ghrairi T, Tonon MC, Lizard G, Vaudry D. Cytoprotective and Neurotrophic Effects of Octadecaneuropeptide (ODN) in in vitro and in vivo Models of Neurodegenerative Diseases. Front Endocrinol (Lausanne) 2020; 11:566026. [PMID: 33250858 PMCID: PMC7672186 DOI: 10.3389/fendo.2020.566026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/28/2020] [Indexed: 11/13/2022] Open
Abstract
Octadecaneuropeptide (ODN) and its precursor diazepam-binding inhibitor (DBI) are peptides belonging to the family of endozepines. Endozepines are exclusively produced by astroglial cells in the central nervous system of mammals, and their release is regulated by stress signals and neuroactive compounds. There is now compelling evidence that the gliopeptide ODN protects cultured neurons and astrocytes from apoptotic cell death induced by various neurotoxic agents. In vivo, ODN causes a very strong neuroprotective action against neuronal degeneration in a mouse model of Parkinson's disease. The neuroprotective activity of ODN is based on its capacity to reduce inflammation, apoptosis, and oxidative stress. The protective effects of ODN are mediated through its metabotropic receptor. This receptor activates a transduction cascade of second messengers to stimulate protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) signaling pathways, which in turn inhibits the expression of proapoptotic factor Bax and the mitochondrial apoptotic pathway. In N2a cells, ODN also promotes survival and stimulates neurite outgrowth. During the ODN-induced neuronal differentiation process, numerous mitochondria and peroxisomes are identified in the neurites and an increase in the amount of cholesterol and fatty acids is observed. The antiapoptotic and neurotrophic properties of ODN, including its antioxidant, antiapoptotic, and pro-differentiating effects, suggest that this gliopeptide and some of its selective and stable derivatives may have therapeutic value for the treatment of some neurodegenerative diseases.
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Affiliation(s)
- Olfa Masmoudi-Kouki
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
| | - Amira Namsi
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
- Team Bio-PeroxIL, Biochemistry of the Peroxisome, Inflammation and Lipid Metabolism/University Bourgogne Franche-Comté (UBFC)/Inserm, Dijon, France
| | - Yosra Hamdi
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
| | - Seyma Bahdoudi
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
| | - Ikram Ghouili
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
| | - Julien Chuquet
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
| | - Jérôme Leprince
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
- Normandy University, Regional Platform for Cell Imaging of Normandy (PRIMACEN), Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Benjamin Lefranc
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
- Normandy University, Regional Platform for Cell Imaging of Normandy (PRIMACEN), Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Taoufik Ghrairi
- Laboratory of Neurophysiology Cellular Physiopathology and Biomolecule Valorisation, LR18ES03, Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, Tunisia
| | - Marie-Christine Tonon
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
| | - Gérard Lizard
- Team Bio-PeroxIL, Biochemistry of the Peroxisome, Inflammation and Lipid Metabolism/University Bourgogne Franche-Comté (UBFC)/Inserm, Dijon, France
| | - David Vaudry
- Normandy University, Neuronal and Neuroendocrine Differentiation and Communication, Inserm U1239, Rouen, France
- Normandy University, Regional Platform for Cell Imaging of Normandy (PRIMACEN), Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
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Tonon MC, Vaudry H, Chuquet J, Guillebaud F, Fan J, Masmoudi-Kouki O, Vaudry D, Lanfray D, Morin F, Prevot V, Papadopoulos V, Troadec JD, Leprince J. Endozepines and their receptors: Structure, functions and pathophysiological significance. Pharmacol Ther 2020; 208:107386. [DOI: 10.1016/j.pharmthera.2019.06.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/20/2019] [Indexed: 02/06/2023]
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Sullivan B, Robison G, Pushkar Y, Young JK, Manaye KF. Copper accumulation in rodent brain astrocytes: A species difference. J Trace Elem Med Biol 2017; 39:6-13. [PMID: 27908425 PMCID: PMC5141684 DOI: 10.1016/j.jtemb.2016.06.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 05/23/2016] [Accepted: 06/30/2016] [Indexed: 12/15/2022]
Abstract
Changes in Cu homeostasis have been implicated in multiple neurodegenerative diseases. Factors controlling and regulating the distribution of Cu in the brain remain largely unknown. We have previously reported that a sub-set of astrocytes in the subventricular zone (SVZ) contain Cu-rich aggregates. Here we expand previous studies with detailed X-ray fluorescent imaging (XRF) analysis of the additional brain areas of hippocampus (HP) and rostral migratory stream (RMS). We also use conventional DAB (3,3'-diaminobenzidine) staining which accesses both peroxidase and pseudo-peroxidase activities. Both the HP and RMS support neurogenesis while the latter also serves as a migratory pathway for neuronal precursors. Some variations in neurogenic activities have been noticed between species (such as mice and rats). We report here that in rats, the HP, rostral migratory stream (RMS) and third ventricle contain glia which stain positively for DAB and contain copper-rich aggregates as measured by XRF. In contrast, mice hippocampi and RMS display neither DAB+ aggregates nor Cu-rich accumulations via XRF. DAB+ aggregates were not induced in the HP of mice transgenic for human amyloid precursor protein (APP) and presenilin, suggesting that accumulations positively stained for DAB are not directly caused by APP. These observed critical differences suggest different properties of the astrocytes in two species. Results suggest that the rat model may have important advantages over the mouse model for the study of hippocampal aging and neurodegeneration.
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Affiliation(s)
- Brendan Sullivan
- Department of Physics and Astronomy, Purdue University, 525 Northwestern Ave., West Lafayette, IN 47907, United States
| | - Gregory Robison
- Department of Physics and Astronomy, Purdue University, 525 Northwestern Ave., West Lafayette, IN 47907, United States; Department of Physics, Hanover College, Hanover, IN, United States
| | - Yulia Pushkar
- Department of Physics and Astronomy, Purdue University, 525 Northwestern Ave., West Lafayette, IN 47907, United States.
| | - John K Young
- Department of Anatomy, Howard University College of Medicine 520 W St., NW, Washington DC 20059, United States
| | - Kebreten F Manaye
- Department of Physiology, Howard University College of Medicine 520 W St., NW, Washington DC 20059, United States
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Kuo J, Hariri OR, Bondar G, Ogi J, Micevych P. Membrane estrogen receptor-alpha interacts with metabotropic glutamate receptor type 1a to mobilize intracellular calcium in hypothalamic astrocytes. Endocrinology 2009; 150:1369-76. [PMID: 18948402 PMCID: PMC2654734 DOI: 10.1210/en.2008-0994] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Estradiol, acting on a membrane-associated estrogen receptor-alpha (mERalpha), induces an increase in free cytoplasmic calcium concentration ([Ca(2+)](i)) needed for progesterone synthesis in hypothalamic astrocytes. To determine whether rapid estradiol signaling involves an interaction of mERalpha with metabotropic glutamate receptor type 1a (mGluR1a), changes in [Ca(2+)](i) were monitored with the calcium indicator, Fluo-4 AM, in primary cultures of female postpubertal hypothalamic astrocytes. 17beta-Estradiol over a range of 1 nm to 100 nm induced a maximal increase in [Ca(2+)](i) flux measured as a change in relative fluorescence [DeltaF Ca(2+) = 615 +/- 36 to 641 +/- 47 relative fluorescent units (RFU)], whereas 0.1 nm of estradiol stimulated a moderate [Ca(2+)](i) increase (275 +/- 16 RFU). The rapid estradiol-induced [Ca(2+)](i) flux was blocked with 1 microm of the estrogen receptor antagonist ICI 182,780 (635 +/- 24 vs. 102 +/- 11 RFU, P < 0.001) and 20 nmof the mGluR1a antagonist LY 367385 (617 +/- 35 vs. 133 +/- 20 RFU, P < 0.001). Whereas the mGluR1a receptor agonist (RS)-3,5-dihydroxyphenyl-glycine (50 microm) also stimulated a robust [Ca(2+)](i) flux (626 +/- 23 RFU), combined treatment of estradiol (1 nm) plus (RS)-3,5-dihydroxyphenyl-glycine (50 microm) augmented the [Ca(2+)](i) response (762 +/- 17 RFU) compared with either compound alone (P < 0.001). Coimmunoprecipitation demonstrated a direct physical interaction between mERalpha and mGluR1a in the plasma membrane of hypothalamic astrocytes. These results indicate that mERalpha acts through mGluR1a, and mGluR1a activation facilitates the estradiol response, suggesting that neural activity can modify estradiol-induced membrane signaling in astrocytes.
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Affiliation(s)
- John Kuo
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, 10833 LeConte Avenue, 73-078 CHS, Los Angeles, California 90095-1763.
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Micevych P, Sinchak K. Estradiol regulation of progesterone synthesis in the brain. Mol Cell Endocrinol 2008; 290:44-50. [PMID: 18572304 PMCID: PMC2603025 DOI: 10.1016/j.mce.2008.04.016] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 04/26/2008] [Accepted: 04/26/2008] [Indexed: 12/22/2022]
Abstract
Steroidogenesis is now recognized as a global phenomenon in the brain, but how it is regulated and its relationship to circulating steroids of peripheral origin have remained more elusive issues. Neurosteroids, steroids synthesized de novo in nervous tissue, have a large range of actions in the brain, but it is only recently that the role of neuroprogesterone in the regulation of arguably the quintessential steroid-dependent neural activity, regulation of the reproduction has been appreciated. Circuits involved in controlling the LH surge and sexual behaviors were thought to be influenced by estradiol and progesterone synthesized in the ovary and perhaps the adrenal. It is now apparent that estradiol of ovarian origin regulates the synthesis of neuroprogesterone, and it is the locally produced neuroprogesterone that is involved in the initiation of the LH surge and subsequent ovulation. In this model, estradiol induces the transcription of progesterone receptors while stimulating synthesis of neuroprogesterone. Although the complete signaling cascade has not been elucidated, many of the features have been characterized. The synthesis of neuroprogesterone occurs primarily in astrocytes and requires the interaction of membrane-associated estrogen receptor-alpha with metabotropic glutamate receptor-1a. This G protein-coupled receptor activates a phospholipase C that in turn increases inositol trisphosphate (IP3) levels mediating the release of intracellular stores of Ca2+ via an IP3 receptor gated Ca2+ channel. The large increase in free cytoplasmic Ca2+ ([Ca2+]i) stimulates the synthesis of progesterone, which can then diffuse out of the astrocyte and activate estradiol-induced progesterone receptors in local neurons to trigger the neural cascade to produce the LH surge. Thus, it is a cooperative action of astrocytes and neurons that is needed for estrogen positive feedback and stimulation of the LH surge.
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Affiliation(s)
- Paul Micevych
- Department of Neurobiology, David Geffen School of Medicine at ULCA, Los Angeles, CA 90095, USA.
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Abstract
The physiology and regulation of steroid synthesis in the brain have emerged as important for understanding brain function. Neurosteroids, those steroids synthesized de novo in nervous tissue, have been associated with numerous central nervous system functions, including myelination, mental retardation, and epilepsy. Central regulation of reproduction was thought to depend on steroids of peripheral origin. Only recently has the role of neurosteroids in reproduction been appreciated. This minireview describes our work trying to understand how circulating estradiol modulates the synthesis of neuroprogesterone. The synthesis of neuroprogesterone occurs primarily in astrocytes, and requires the interaction of membrane-associated estrogen receptor with metabotropic glutamate receptor and the release of intracellular calcium stores. The newly synthesized neuroprogesterone acts on estradiol-induced progesterone receptors in nearby neurons to initiate the LH surge.
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Affiliation(s)
- Paul Micevych
- Department of Neurobiology, David Geffen School of Medicine, Brain Research Institute at University of California Los Angeles, Los Angeles, California 90095-1763, USA.
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Cheunsuang O, Morris R. Astrocytes in the arcuate nucleus and median eminence that take up a fluorescent dye from the circulation express leptin receptors and neuropeptide Y Y1 receptors. Glia 2006; 52:228-33. [PMID: 15968634 DOI: 10.1002/glia.20239] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Following systemic injection, several different dyes and markers are found to accumulate rapidly in cells in the arcuate nucleus and median eminence, and the capillaries in this region appear specialised for exchange of molecules. The present study used hydroxystilbamidine (FluoroGold equivalent) to identify cells that take up molecules from the circulation in these regions; 2-6 h following injection, uptake was seen in the external and intermediate zones of the median eminence and the adjacent ventral part of the arcuate nucleus, but not in other regions of the hypothalamus. The labelled cells were small; double-labelling experiments revealed that they expressed glial fibrillary acid protein (GFAP), but not NeuN, Agouti-related protein (AgRP) or beta-endorphin. They had the morphology of astrocytes and were readily distinguished from tanycytes by staining for vimentin. Many of these labelled astrocytes also expressed leptin receptors and neuropeptide Y Y1 receptors. The surrounding neurons that expressed these receptors did not take up this dye. This demonstrates that astrocytes take up molecules from the circulation in the median eminence and adjacent arcuate nucleus, and may have a significant signalling role in regulation of food intake.
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Affiliation(s)
- Ornsiri Cheunsuang
- Department of Veterinary Anatomy, Chulalongkorn University, Bangkok, Thailand
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Katsura M, Shuto K, Mohri Y, Tsujimura A, Shibata D, Tachi M, Ohkuma S. Continuous exposure to nitric oxide enhances diazepam binding inhibitor mRNA expression in mouse cerebral cortical neurons. ACTA ACUST UNITED AC 2004; 124:29-39. [PMID: 15093683 DOI: 10.1016/j.molbrainres.2004.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/11/2004] [Indexed: 10/26/2022]
Abstract
Effects of sustained exposure to nitric oxide (NO) formed by long-term activation of N-methyl-D-aspartate (NMDA) receptors and liberated from a long-lasting NO generator, DETA NONOate, on diazepam binding inhibitor (DBI) and its mRNA expressions were examined using mouse cerebral cortical neurons. Long-term exposure to NMDA increased DBI mRNA expression, and NO synthase inhibitors dose-dependently inhibited this increase. DETA NONOate dose-dependently increased DBI mRNA expression when exposing the neurons to this agent for 3 days and a maximal enhancement of the expression was found at 100 microM of the NO generator. In addition, a significant increase in DBI mRNA expression was observed 1 day after the exposure to 100 microM DETA NONOate, and the maximal expression was observed 2 days after the exposure, whereas transient exposure for less than 3 h to 100 microM DETA NONOate produced no changes in the expression. DETA NONOate (100 microM)-induced increase in DBI mRNA expression was completely abolished by concomitant exposure to hemoglobin. DBI content was also dose-dependently increased by DETA NONOate after the exposure for 3 days. The inhibition of cGMP formation by 1H-[1,2,4] oxadiazolo [4,3-alpha]quinoxalin-1-one (ODQ) showed no affects on the DETA NONOate-induced expression, suggesting that the increased expression of DBI mRNA is mediated via processes independent of cGMP. These results indicate that continuous exposure of the neurons to NO is an essential factor for increasing DBI mRNA expression in the neurons.
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Affiliation(s)
- Masashi Katsura
- Department of Pharmacology, Kawasaki Medical School, Matsushima, Kurashiki 701-0192, Japan
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Mohri Y, Katsura M, Shuto K, Tsujimura A, Ishii R, Ohkuma S. L-type high voltage-gated calcium channels cause an increase in diazepam binding inhibitor mRNA expression after sustained exposure to ethanol in mouse cerebral cortical neurons. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 113:52-6. [PMID: 12750006 DOI: 10.1016/s0169-328x(03)00089-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mechanisms for increase in diazepam binding inhibitor (DBI) mRNA expression after sustained exposure to ethanol (EtOH) were investigated. Increases in 30 mM KCl-induced [45Ca(2+)] influx and DBI mRNA expression after EtOH (50 mM) exposure for 3 days were completely abolished by nifedipine, but not by omega-agatoxin VIA and omega-conotoxin GIVA. These results indicate that EtOH-induced increase in DBI mRNA expression is mediated via increased Ca(2+) entry through up-regulated L-type high voltage-gated calcium channels.
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Affiliation(s)
- Yutaka Mohri
- Department of Pharmacology, Kawasaki Medical School, Matsushima, Kurashiki 701-0192, Japan
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Compère V, Li S, Leprince J, Tonon MC, Vaudry H, Pelletier G. Effect of intracerebroventricular administration of the octadecaneuropeptide on the expression of pro-opiomelanocortin, neuropeptide Y and corticotropin-releasing hormone mRNAs in rat hypothalamus. J Neuroendocrinol 2003; 15:197-203. [PMID: 12535162 DOI: 10.1046/j.1365-2826.2003.00970.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intracerebroventricular (i.c.v.) administration of the octadecaneuropeptide (diazepam-binding inhibitor [33-50]; ODN) exerts a potent anorexigenic effect in the rat. We studied the effect of ODN on three neuropeptides involved in feeding behaviour: the orexigenic peptide neuropeptide Y (NPY) and two anorexigenic peptides, corticotropin-releasing hormone (CRH) and the pro-opiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone. The effect of i.c.v. administration of ODN (0.1 microg/kg and 1 microg/kg) on mRNA expression of the peptides in male rat hypothalamus was evaluated by semiquantitative in situ hybridization. In the arcuate nucleus, NPY-expressing neurones were mostly found in the inner zone in close proximity of the third ventricle. ODN at the dose of 0.1 microg/kg induced a significant decrease of 17.4% in NPY mRNA expression, while the depressing effect was more marked (31.4%) with the highest dose of ODN (1 microg/kg). POMC-expressing neurones were more laterally located in the arcuate nucleus. Administration of ODN at 0.1 microg/kg and 1 microg/kg doses induced increases of 33.5% and 27.4% in POMC mRNA expression, respectively. Labelling obtained with the CRH cRNA probe was essentially distributed throughout the medial parvocellular area of the hypothalamic paraventricular nucleus. ODN, at doses of 0.1 and 1 microg/kg, resulted in 17.8% and 32.8% decreases in CRH mRNA expression, respectively. The present data suggest that ODN might exert its anorexigenic effect by increasing mRNA expression of POMC and decreasing mRNA expression of NPY in the arcuate nucleus.
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Affiliation(s)
- V Compère
- European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, Mont-Saint-Aignan, France
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Abstract
We have previously reported that a specialized subpopulation of astrocytes in the arcuate nucleus of the hypothalamus show an unusually intense immunoreactivity for brain fatty acid binding protein (bFABP). Since bFABP has been shown to regulate the activity of an enzyme, fatty acid synthase, that has a potent influence upon the regulation of feeding by the hypothalamus, it was of interest to determine if bFABP + astrocytes are positioned to potentially influence the activity of feeding-regulating neurones. In this study, we examined the anatomical relationship between specialized arcuate astrocytes immunoreactive for bFABP and feeding-regulating neurones that are responsive to leptin and which are immunoreactive for the transcription factor STAT3. The results show that both cell types are abundant in the arcuate nucleus of the hypothalamus and are frequently closely adjacent to each other. This study provides an anatomical basis for the possibility that specialized arcuate astrocytes regulate the function of leptin-sensitive, feeding-regulating neurones of the arcuate nucleus.
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Affiliation(s)
- John K Young
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA.
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Wayte J, Buckingham JC, Cowell AM. [3H]L-arginine transport and nitric oxide synthase activity in foetal hypothalamic cultures. Neuroreport 1996; 8:267-71. [PMID: 9051793 DOI: 10.1097/00001756-199612200-00053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
[3H]L-arginine uptake and the conversion of [3H]L-arginine to [3H]citrulline were characterized in foetal hypothalamic cultures. [3H]L-arginine uptake was reduced by L-ornithine (10 microM-1 mM), high extracellular K+ (56 mM), L-glutamate (100 microM) and removal of extracellular Ca2+, but was increased by the nitric oxide synthase inhibitor, Nw-nitro-L-arginine benzyl ester (L-NABE; 1 mM). [3H]citrulline formation was inhibited by L-NABE (1 mM), increased by high extracellular K+ (56 mM) and unaffected by L-glutamate (100 microM). Removal of extracellular Ca2+ reduced [3H]citrulline formation by mixed (neurones and glia) and neurone-enriched cultures but not by glial-enriched cells. The results suggest that [3H]L-arginine uptake into hypothalamic cultures is mediated by the system y+ transporter and is dependent on extracellular Ca2+. [3H]citrulline production in hypothalamic neuronal, but not glial, cells is also dependent on extracellular Ca2+.
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Affiliation(s)
- J Wayte
- Department of Pharmacology, Charing Cross & Westminster Medical School, London, UK
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Abstract
Gomori-positive (GP) astrocytes are a subset of brain astrocytes with highly stained cytoplasmic granules that arise from the degradation of mitochondria. The GP granules of these astrocytes are most prominent in the arcuate nucleus of the hypothalamus, but can also be detected in the olfactory bulbs, hippocampus, habenula, and other selected brain regions. The cause and functional effects of this mitochondrial pathology in these glia are not yet known with certainty. In other tissues, mitochondrial dysfunction is associated with elevations in cytoplasmic lipids and lipid-binding proteins, due to impaired mitochondrial oxidation of lipids. To see if GP astrocytic mitochondrial pathology is also associated with an elevation in lipid binding proteins, rat brain sections were stained for brain fatty acid binding protein (B-FABP), using immunocytochemistry. Astrocytes immunoreactive for B-FABP were much more abundant in brain regions enriched in GP astrocytes than in other brain regions. Semi-thin sections revealed that astrocytic B-FABP immunoreactivity was often, but not always, associated with GP cytoplasmic granules. These data suggest that GP astrocytes have an unusual lipid metabolism, which may relate to degenerative processes occurring in the selected brain regions that contain GP astrocytes.
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Affiliation(s)
- J K Young
- Department of Anatomy, Howard University, Washington DC 20059, USA
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