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Martín-Estebané M, Navascués J, Sierra-Martín A, Martín-Guerrero SM, Cuadros MA, Carrasco MC, Marín-Teva JL. Onset of microglial entry into developing quail retina coincides with increased expression of active caspase-3 and is mediated by extracellular ATP and UDP. PLoS One 2017; 12:e0182450. [PMID: 28763502 PMCID: PMC5538646 DOI: 10.1371/journal.pone.0182450] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/18/2017] [Indexed: 12/31/2022] Open
Abstract
Microglial cell precursors located in the area of the base of the pecten and the optic nerve head (BP/ONH) start to enter the retina of quail embryos at the 7th day of incubation (E7), subsequently colonizing the entire retina by central-to-peripheral tangential migration, as previously shown by our group. The present study demonstrates a precise chronological coincidence of the onset of microglial cell entry into the retina with a striking increase in death of retinal cells, as revealed by their active caspase-3 expression and TUNEL staining, in regions dorsal to the BP/ONH area, suggesting that dying retinal cells would contribute to the microglial cell inflow into the retina. However, the molecular mechanisms involved in this inflow are currently unclear. Extracellular nucleotides, such as ATP and UDP, have previously been shown to favor migration of microglia towards brain injuries because they are released by apoptotic cells and stimulate both chemotaxis and chemokinesis in microglial cells via signaling through purinergic receptors. Hence, we tested here the hypothesis that ATP and UDP play a role in the entry and migration of microglial precursors into the developing retina. For this purpose, we used an experimental model system based on organotypic cultures of E6.5 quail embryo retina explants, which mimics the entry and migration of microglial precursors in the in situ developing retina. Inhibition of purinergic signaling by treating retina explants with either apyrase, a nucleotide-hydrolyzing enzyme, or suramin, a broad spectrum antagonist of purinergic receptors, significantly prevents the entry of microglial cells into the retina. In addition, treatment of retina explants with either exogenous ATP or UDP results in significantly increased numbers of microglial cells entering the retina. In light of these findings, we conclude that purinergic signaling by extracellular ATP and UDP is necessary for the entry and migration of microglial cells into the embryonic retina by inducing chemokinesis in these cells.
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Affiliation(s)
- María Martín-Estebané
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Julio Navascués
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Ana Sierra-Martín
- Departamento de Biología Celular, Fisiología e Inmunología, Facultad de Biociencias, Universidad Autónoma de Barcelona, Bellaterra, Barcelona, Spain
| | | | - Miguel A. Cuadros
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - María-Carmen Carrasco
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - José L. Marín-Teva
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Granada, Spain
- * E-mail:
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Whyte-Fagundes P, Zoidl G. Mechanisms of pannexin1 channel gating and regulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:65-71. [PMID: 28735901 DOI: 10.1016/j.bbamem.2017.07.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/17/2017] [Accepted: 07/18/2017] [Indexed: 01/07/2023]
Abstract
Pannexins are a family of integral membrane proteins with distinct post-translational modifications, sub-cellular localization and tissue distribution. Panx1 is the most studied and best-characterized isoform of this gene family. The ubiquitous expression, as well as its function as a major ATP release and nucleotide permeation channel, makes Panx1 a primary candidate for participating in the pathophysiology of CNS disorders. While many investigations revolve around Panx1 functions in health and disease, more recently, details started emerging about mechanisms that control Panx1 channel activity. These advancements in Panx1 biology have revealed that beyond its classical role as an unopposed plasma membrane channel, it participates in alternative pathways involving multiple intracellular compartments, protein complexes and a myriad of extracellular participants. Here, we review recent progress in our understanding of Panx1 at the center of these pathways, highlighting its modulation in a context specific manner. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
| | - Georg Zoidl
- Biology, York University, Toronto, Canada; Psychology, York University, Toronto, Canada.
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Platania CBM, Giurdanella G, Di Paola L, Leggio GM, Drago F, Salomone S, Bucolo C. P2X7 receptor antagonism: Implications in diabetic retinopathy. Biochem Pharmacol 2017; 138:130-139. [PMID: 28479300 DOI: 10.1016/j.bcp.2017.05.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/02/2017] [Indexed: 12/13/2022]
Abstract
Diabetic retinopathy (DR) is the most frequent complication of diabetes and one of leading causes of blindness worldwide. Early phases of DR are characterized by retinal pericyte loss mainly related to concurrent inflammatory process. Recently, an important link between P2X7 receptor (P2X7R) and inflammation has been demonstrated indicating this receptor as potential pharmacological target in DR. Here we first carried out an in silico molecular modeling study in order to characterize the allosteric pocket in P2X7R, and identify a suitable P2X7R antagonist through molecular docking. JNJ47965567 was identified as the hit compound in docking calculations, as well as for its absorption, distribution, metabolism and excretion (ADME) profile. As an in vitro model of early diabetic retinopathy, human retinal pericytes were exposed to high glucose (25mM, 48h) that caused a significant (p<0.05) release of IL-1β and LDH. The block of P2X7R by JNJ47965567 significantly (p<0.05) reverted the damage elicited by high glucose, detected as IL-1β and LDH release. Overall, our findings suggest that the P2X7R represents an attractive pharmacological target to manage the early phase of diabetic retinopathy, and the compound JNJ47965567 is a good template to discover other P2X7R selective antagonists.
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Affiliation(s)
- Chiara Bianca Maria Platania
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy
| | - Giovanni Giurdanella
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy
| | - Luisa Di Paola
- School of Engineering, University Campus BioMedico, Roma, Italy
| | - Gian Marco Leggio
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy; Center for Research in Ocular Pharmacology - CERFO, University of Catania, Catania, Italy
| | - Filippo Drago
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy; Center for Research in Ocular Pharmacology - CERFO, University of Catania, Catania, Italy
| | - Salvatore Salomone
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy; Center for Research in Ocular Pharmacology - CERFO, University of Catania, Catania, Italy
| | - Claudio Bucolo
- Section of Pharmacology, Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Catania, Italy; Center for Research in Ocular Pharmacology - CERFO, University of Catania, Catania, Italy.
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54
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Expression of peptidylarginine deiminase 4 in an alkali injury model of retinal gliosis. Biochem Biophys Res Commun 2017; 487:134-139. [PMID: 28400047 DOI: 10.1016/j.bbrc.2017.04.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 04/07/2017] [Indexed: 11/20/2022]
Abstract
Citrullination is an important posttranslational modification that occurs during retinal gliosis. We examined the expression of peptidyl arginine deiminases (PADs) to identify the PADs that mediate citrullination in a model of alkali-induced retinal gliosis. Mouse corneas were exposed to 1.0 N NaOH and posterior eye tissue from injured and control uninjured eyes was evaluated for transcript levels of various PADs by reverse-transcription polymerase chain reaction (RT-PCR), and quantitative RT-PCR (qPCR). Retinas were also subjected to immunohistochemistry (IHC) for glial fibrillary acidic protein (GFAP), citrullinated species, PAD2, and PAD4 and tissue levels of GFAP, citrullinated species, and PAD4 were measured by western blots. In other experiments, the PAD4 inhibitor streptonigrin was injected intravitreally into injured eyes ex vivo to test inhibitory activity in an organ culture system. We found that uninjured retina and choroid expressed Pad2 and Pad4 transcripts. Pad4 transcript levels increased by day 7 post-injury (p < 0.05), whereas Pad2 levels did not change significantly (p > 0.05) by qPCR. By IHC, PAD2 was expressed in uninjured eyes along ganglion cell astrocytes, but in injured retina PAD2 was downregulated at 7 days. On the other hand, PAD4 showed increased staining in the retina upon injury revealing a pattern that overlapped with filamentous GFAP staining in Müller glial processes by 7 days. Injury-induced citrullination and soluble GFAP protein levels were reduced by PAD4 inhibition in western blot experiments of organ cultures. Together, our findings for the first time identify PAD4 as a novel injury-inducible druggable target for retinal gliosis.
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Sakuragi S, Niwa F, Oda Y, Mikoshiba K, Bannai H. Astroglial Ca 2+ signaling is generated by the coordination of IP 3R and store-operated Ca 2+ channels. Biochem Biophys Res Commun 2017; 486:879-885. [PMID: 28336440 DOI: 10.1016/j.bbrc.2017.03.096] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 03/19/2017] [Indexed: 12/21/2022]
Abstract
Astrocytes play key roles in the central nervous system and regulate local blood flow and synaptic transmission via intracellular calcium (Ca2+) signaling. Astrocytic Ca2+ signals are generated by multiple pathways: Ca2+ release from the endoplasmic reticulum (ER) via the inositol 1, 4, 5-trisphosphate receptor (IP3R) and Ca2+ influx through various Ca2+ channels on the plasma membrane. However, the Ca2+ channels involved in astrocytic Ca2+ homeostasis or signaling have not been fully characterized. Here, we demonstrate that spontaneous astrocytic Ca2+ transients in cultured hippocampal astrocytes were induced by cooperation between the Ca2+ release from the ER and the Ca2+ influx through store-operated calcium channels (SOCCs) on the plasma membrane. Ca2+ imaging with plasma membrane targeted GCaMP6f revealed that spontaneous astroglial Ca2+ transients were impaired by pharmacological blockade of not only Ca2+ release through IP3Rs, but also Ca2+ influx through SOCCs. Loss of SOCC activity resulted in the depletion of ER Ca2+, suggesting that SOCCs are activated without store depletion in hippocampal astrocytes. Our findings indicate that sustained SOCC activity, together with that of the sarco-endoplasmic reticulum Ca2+-ATPase, contribute to the maintenance of astrocytic Ca2+ store levels, ultimately enabling astrocytic Ca2+ signaling.
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Affiliation(s)
- Shigeo Sakuragi
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
| | - Fumihiro Niwa
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Yoichi Oda
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Hiroko Bannai
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan; Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; Nagoya Research Center for Brain & Neural Circuits, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan; Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
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56
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Hollborn M, Fischer S, Kuhrt H, Wiedemann P, Bringmann A, Kohen L. Osmotic regulation of NFAT5 expression in RPE cells: The involvement of purinergic receptor signaling. Mol Vis 2017; 23:116-130. [PMID: 28356704 PMCID: PMC5360457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 03/16/2017] [Indexed: 11/22/2022] Open
Abstract
PURPOSE Systemic hypertension is a risk factor for age-related neovascular retinal diseases. The major condition that induces hypertension is the intake of dietary salt (NaCl) resulting in increased extracellular osmolarity. High extracellular NaCl was has been shown to induce angiogenic factor production in RPE cells, in part via the transcriptional activity of nuclear factor of activated T cell 5 (NFAT5). Here, we determined the signaling pathways that mediate the osmotic expression of the NFAT5 gene in RPE cells. METHODS Cultured human RPE cells were stimulated with high (+100 mM) NaCl. Alterations in gene and protein expression were determined with real-time reverse transcriptase (RT)-PCR and western blot analysis, respectively. RESULTS NaCl-induced NFAT5 gene expression was fully inhibited by calcium chelation and blockers of inositol triphosphate (IP3) receptors and phospholipases C and A2. Blockers of phospholipases C and A2 also prevented the NaCl-induced increase of the cellular NFAT5 protein level. Inhibitors of multiple intracellular signaling transduction pathways and kinases, including p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), phosphatidylinositol-3 kinase (PI3K), protein kinases A and C, Src tyrosine kinases, and calpains, as well as cyclooxygenase inhibitors, decreased the NaCl-induced expression of the NFAT5 gene. In addition, autocrine purinergic signaling mediated by a release of ATP and a nucleoside transporter-mediated release of adenosine, activation of P2X7, P2Y1, P2Y2, and adenosine A1 receptors, but not adenosine A2A receptors, is required for the full expression of the NFAT5 gene under hyperosmotic conditions. NaCl-induced NFAT5 gene expression is in part dependent on the activity of nuclear factor κB (NF-κB). The NaCl-induced expression of NFAT5 protein was prevented by inhibitors of phospholipases C and A2 and an inhibitor of NF-κB, but it was not prevented by a P2Y1 inhibitor. CONCLUSIONS The data suggest that in addition to calcium signaling and activation of inflammatory enzymes, autocrine/paracrine purinergic signaling contributes to the stimulatory effect of hyperosmotic stress on the expression of the NFAT5 gene in RPE cells. It is suggested that high intake of dietary salt induces RPE cell responses, which may contribute to age-related retinal diseases.
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Affiliation(s)
- Margrit Hollborn
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
| | - Sarah Fischer
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
| | - Heidrun Kuhrt
- Paul Flechsig Institute of Brain Research, University of Leipzig Medical Faculty, Leipzig, Germany
| | - Peter Wiedemann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
| | - Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
| | - Leon Kohen
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany,Helios Klinikum Aue, Aue, Germany
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57
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Pannicke T, Ivo Chao T, Reisenhofer M, Francke M, Reichenbach A. Comparative electrophysiology of retinal Müller glial cells-A survey on vertebrate species. Glia 2016; 65:533-568. [PMID: 27767232 DOI: 10.1002/glia.23082] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/15/2016] [Accepted: 09/28/2016] [Indexed: 12/13/2022]
Abstract
Müller cells are the dominant macroglial cells in the retina of all vertebrates. They fulfill a variety of functions important for retinal physiology, among them spatial buffering of K+ ions and uptake of glutamate and other neurotransmitters. To this end, Müller cells express inwardly rectifying K+ channels and electrogenic glutamate transporters. Moreover, a lot of voltage- and ligand-gated ion channels, aquaporin water channels, and electrogenic transporters are expressed in Müller cells, some of them in a species-specific manner. For example, voltage-dependent Na+ channels are found exclusively in some but not all mammalian species. Whereas a lot of data exist from amphibians and mammals, the results from other vertebrates are sparse. It is the aim of this review to present a survey on Müller cell electrophysiology covering all classes of vertebrates. The focus is on functional studies, mainly performed using the whole-cell patch-clamp technique. However, data about the expression of membrane channels and transporters from immunohistochemistry are also included. Possible functional roles of membrane channels and transporters are discussed. Obviously, electrophysiological properties involved in the main functions of Müller cells developed early in vertebrate evolution. GLIA 2017;65:533-568.
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Affiliation(s)
- Thomas Pannicke
- Paul-Flechsig-Institut für Hirnforschung, Abteilung Pathophysiologie der Neuroglia, Universität Leipzig, Germany
| | - T Ivo Chao
- Institute of Anatomy and Cell Biology, Medical School Göttingen, Germany
| | - Miriam Reisenhofer
- Department of Chemistry, University of Zürich, Switzerland
- Department of Ophthalmology, Inselspital, Bern University Hospital, University of Bern, Switzerland
| | - Mike Francke
- Paul-Flechsig-Institut für Hirnforschung, Abteilung Pathophysiologie der Neuroglia, Universität Leipzig, Germany
- Sächsischer Inkubator für klinische Translation (SIKT), Universität Leipzig, Germany
| | - Andreas Reichenbach
- Paul-Flechsig-Institut für Hirnforschung, Abteilung Pathophysiologie der Neuroglia, Universität Leipzig, Germany
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Mishra A. Binaural blood flow control by astrocytes: listening to synapses and the vasculature. J Physiol 2016; 595:1885-1902. [PMID: 27619153 DOI: 10.1113/jp270979] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 07/15/2016] [Indexed: 12/28/2022] Open
Abstract
Astrocytes are the most common glial cells in the brain with fine processes and endfeet that intimately contact both neuronal synapses and the cerebral vasculature. They play an important role in mediating neurovascular coupling (NVC) via several astrocytic Ca2+ -dependent signalling pathways such as K+ release through BK channels, and the production and release of arachidonic acid metabolites. They are also involved in maintaining the resting tone of the cerebral vessels by releasing ATP and COX-1 derivatives. Evidence also supports a role for astrocytes in maintaining blood pressure-dependent change in cerebrovascular tone, and perhaps also in blood vessel-to-neuron signalling as posited by the 'hemo-neural hypothesis'. Thus, astrocytes are emerging as new stars in preserving the intricate balance between the high energy demand of active neurons and the supply of oxygen and nutrients from the blood by maintaining both resting blood flow and activity-evoked changes therein. Following neuropathology, astrocytes become reactive and many of their key signalling mechanisms are altered, including those involved in NVC. Furthermore, as they can respond to changes in vascular pressure, cardiovascular diseases might exert previously unknown effects on the central nervous system by altering astrocyte function. This review discusses the role of astrocytes in neurovascular signalling in both physiology and pathology, and the impact of these findings on understanding BOLD-fMRI signals.
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Affiliation(s)
- Anusha Mishra
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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59
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Involvement of P2X 7 receptors in retinal ganglion cell apoptosis induced by activated Müller cells. Exp Eye Res 2016; 153:42-50. [PMID: 27720859 DOI: 10.1016/j.exer.2016.10.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 08/25/2016] [Accepted: 10/05/2016] [Indexed: 12/22/2022]
Abstract
Müller cell reactivation (gliosis) is an early response in glaucomatous retina. Previous studies have demonstrated that activation of P2X7 receptors results in retinal ganglion cell (RGC) apoptosis. Here, the issues of whether and how activated Müller cells may contribute to RGC apoptosis through P2X7 receptors were investigated. Either intravitreal injection of (S)-3,5-dihydroxyphenylglycine (DHPG), a group I metabotropic glutamate receptor (mGluR I) agonist, in normal rat retinas, or DHPG treatment of purified cultured rat retinal Müller cells induced an increase in glial fibrillary acidic protein (GFAP) expression, indicative of Müller cell gliosis. In addition, an increase in adenosine triphosphate (ATP) release from purified cultured Müller cells was detected during DHPG treatment (for 10 min to 48 h), which was mediated by the intracellular mGluR5/Gq/PI-PLC/PKC signaling pathway. Intravitreal injection of DHPG mimicked the reduction in the number of fluorogold retrogradely labeled RGCs in chronic ocular hypertension (COH) rats. Treatment with the conditioned culture medium (CM) obtained from the DHPG-activated Müller cell medium induced an increase in the number of TUNEL-positive cells in cultured RGCs, which was mimicked by benzoylbenzoyl adenosine triphosphate (BzATP), a P2X7 receptor agonist, but was partially blocked by brilliant blue G (BBG), a P2X7 receptor antagonist. Moreover, the CM treatment of cultured RGCs significantly increased Bax protein level and decreased Bcl-2 protein level, which was also mimicked by BzATP and partially blocked by BBG, respectively. These results suggest that reactivated Müller cells may release excessive ATP, in turn leading to RGC apoptosis through activating P2X7 receptors in these cells.
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Ichinohe S, Ishii T, Takahashi H, Kaneda M. Physiological contribution of P2X receptors in postreceptoral signal processing in the mouse retina. Neurosci Res 2016; 115:5-12. [PMID: 27720754 DOI: 10.1016/j.neures.2016.09.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 09/26/2016] [Accepted: 09/28/2016] [Indexed: 10/20/2022]
Abstract
ATP activates P2X receptors and acts as a neurotransmitter in the nervous system. We have previously reported that P2X receptors modulate the firing rate of retinal ganglion cells. Since many subtypes of P2X receptors are distributed in the mouse retina, it is likely that the modulatory effects of P2X receptor-mediated signaling can occur at multiple synaptic levels in the retina. In this study, we investigated whether P2X receptors expressed between the photoreceptor layer and the inner nuclear layer in the mouse retina were physiologically functional, by electroretinography (ERG). In the combined rod-cone ERG and the scotopic ERG, intravitreal injection of PPADS, an antagonist of P2X receptors, had no effects on the amplitude of the a-wave, but decreased the amplitude of the b-wave. In the photopic ERG, intravitreal injection of PPADS significantly decreased the amplitude of both the a-wave and the b-wave. In ex vivo recordings, a decrease in the b-wave amplitude was observed at 20μM PPADS, confirming that the inhibition of the b-wave by intravitreal injection of PPADS is due to the inhibition of P2X receptors. Our findings suggest that P2X receptor-mediated signaling has a physiological effect in both the rod and the cone pathways in postreceptoral processing.
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Affiliation(s)
- Sho Ichinohe
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
| | - Toshiyuki Ishii
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
| | - Hiroshi Takahashi
- Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
| | - Makoto Kaneda
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
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Agte S, Pannicke T, Ulbricht E, Reichenbach A, Bringmann A. Two different mechanosensitive calcium responses in Müller glial cells of the guinea pig retina: Differential dependence on purinergic receptor signaling. Glia 2016; 65:62-74. [PMID: 27706854 DOI: 10.1002/glia.23054] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 08/16/2016] [Accepted: 08/22/2016] [Indexed: 11/12/2022]
Abstract
Tractional forces or mechanical stimulation are known to induce calcium responses in retinal glial cells. The aim of the study was to determine the characteristics of calcium responses in Müller glial cells of the avascular guinea pig retina induced by focal mechanical stimulation. Freshly isolated retinal wholemounts were loaded with Mitotracker Deep Red (to fill Müller cells) and the calcium-sensitive dye Fluo-4/AM. The inner retinal surface was mechanically stimulated with a micropipette tip for 10 ms. Stimulation induced two different cytosolic calcium responses in Müller cells with different kinetics in dependence on the distance from the stimulation site. Müller cells near the stimulation site displayed an immediate and long-lasting calcium response with high amplitude. This response was mediated by calcium influx from the extracellular space likely triggered by activation of ATP-insensitive P2 receptors. More distant Müller cells displayed, with a delay of 2.4 s, transient calcium responses which propagated laterally in a wave-like fashion. Propagating calcium waves were induced by a calcium-independent release of ATP from Müller cells near the stimulation site, and were mediated by a release of calcium from internal stores triggered by ATP, acting in part at P2Y1 receptors. The data suggest that mechanically stimulated Müller cells of the guinea pig retina release ATP which induces a propagating calcium wave in surrounding Müller cells. Propagating calcium waves may be implicated in the spatial regulation of the neuronal activity and homeostatic glial functions, and may transmit gliosis-inducing signals across the retina. Mechanical stimulation of guinea pig Müller cells induces two calcium responses: an immediate response around the stimulation site and propagating calcium waves. Both responses are differentially mediated by activation of purinergic receptors. GLIA 2016 GLIA 2017;65:62-74.
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Affiliation(s)
- Silke Agte
- Department of Pathophysiology of Neuroglia, Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Thomas Pannicke
- Department of Pathophysiology of Neuroglia, Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Elke Ulbricht
- Department of Cellular Machines, Biotechnology Center, Technische Universität Dresden, Dresden, Germany
| | - Andreas Reichenbach
- Department of Pathophysiology of Neuroglia, Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
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Activated Müller Cells Involved in ATP-Induced Upregulation of P2X 7 Receptor Expression and Retinal Ganglion Cell Death. BIOMED RESEARCH INTERNATIONAL 2016; 2016:9020715. [PMID: 27738636 PMCID: PMC5050355 DOI: 10.1155/2016/9020715] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 08/10/2016] [Accepted: 08/28/2016] [Indexed: 11/17/2022]
Abstract
P2X7 receptor (P2X7R), an ATP-gated ion channel, plays an important role in glaucomatous retinal ganglion cell (RGC) apoptotic death, in which activated retinal Müller glial cells may be involved by releasing ATP. In the present study, we investigated whether and how activated Müller cells may induce changes in P2X7R expression in RGCs by using immunohistochemistry and Western blot techniques. Intravitreal injection of DHPG, a group I metabotropic glutamate receptor (mGluR I) agonist, induced upregulation of GFAP expression, suggestive of Müller cell activation (gliosis), as we previously reported. Accompanying Müller cell activation, P2X7R protein expression was upregulated, especially in the cells of ganglion cell layer (GCL), which was reversed by coinjection of brilliant blue G (BBG), a P2X7R blocker. In addition, intravitreal injection of ATP also induced upregulation of P2X7R protein expression. Similar results were observed in cultured retinal neurons by ATP treatment. Moreover, both DHPG and ATP intravitreal injection induced a reduction in the number of fluorogold retrogradely labeled RGCs, and the DHPG effect was partially rescued by coinjection of BBG. All these results suggest that activated Müller cells may release ATP and, in turn, induce upregulation of P2X7R expression in the cells of GCL, thus contributing to RGC death.
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de Almeida-Pereira L, Magalhães CF, Repossi MG, Thorstenberg MLP, Sholl-Franco A, Coutinho-Silva R, Ventura ALM, Fragel-Madeira L. Adenine Nucleotides Control Proliferation In Vivo of Rat Retinal Progenitors by P2Y 1 Receptor. Mol Neurobiol 2016; 54:5142-5155. [PMID: 27558237 DOI: 10.1007/s12035-016-0059-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/15/2016] [Indexed: 11/30/2022]
Abstract
Previous studies demonstrated that exogenous ATP is able to regulate proliferation of retinal progenitor cells (RPCs) in vitro possibly via P2Y1 receptor, a G protein-coupled receptor. Here, we evaluated the function of adenine nucleotides in vivo during retinal development of newborn rats. Intravitreal injection of apyrase, an enzyme that hydrolyzes nucleotides, reduced cell proliferation in retinas at postnatal day 2 (P2). This decrease was reversed when retinas were treated together with ATPγ-S or ADPβ-S, two hydrolysis-resistant analogs of ATP and ADP, respectively. During early postnatal days (P0 to P5), an increase in ectonucleotidase (E-NTPDase) activity was observed in the retina, suggesting a decrease in the availability of adenine nucleotides, coinciding with the end of proliferation. Interestingly, intravitreal injection of the E-NTPDase inhibitor ARL67156 increased proliferation by around 60 % at P5 rats. Furthermore, immunolabeling against P2Y1 receptor was observed overall in retina layers from P2 rats, including proliferating Ki-67-positive cells in the neuroblastic layer (NBL), suggesting that this receptor could be responsible for the action of adenine nucleotides upon proliferation of RPCs. Accordingly, intravitreal injection of MRS2179, a selective antagonist of P2Y1 receptors, reduced cell proliferation by approximately 20 % in P2 rats. Moreover, treatment with MRS 2179 caused an increase in p57KIP2 and cyclin D1 expression, a reduction in cyclin E and Rb phosphorylated expression and in BrdU-positive cell number. These data suggest that the adenine nucleotides modulate the proliferation of rat RPCs via activation of P2Y1 receptors regulating transition from G1 to S phase of the cell cycle.
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Affiliation(s)
- Luana de Almeida-Pereira
- Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - Camila Feitosa Magalhães
- Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - Marinna Garcia Repossi
- Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | | | - Alfred Sholl-Franco
- Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Robson Coutinho-Silva
- Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Lucianne Fragel-Madeira
- Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, Brazil.
- Laboratório de Desenvolvimento e Regeneração Neural, Departmento de Neurobiologia, Universidade Federal Fluminense, Cx. Postal 100180, Niterói, RJ, 24020-141, Brazil.
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Abstract
Aquaporins (AQPs) represent a diverse family of membrane proteins found in prokaryotes and eukaryotes. The primary aquaporins expressed in the mammalian brain are AQP1, which is densely packed in choroid plexus cells lining the ventricles, and AQP4, which is abundant in astrocytes and concentrated especially in the end-feet structures that surround capillaries throughout the brain and are present in glia limitans structures, notably in osmosensory areas such the supraoptic nucleus. Water movement in brain tissues is carefully regulated from the micro- to macroscopic levels, with aquaporins serving key roles as multifunctional elements of complex signaling assemblies. Intriguing possibilities suggest links for AQP1 in Alzheimer's disease, AQP4 as a target for therapy in brain edema, and a possible contribution of AQP9 in Parkinson's disease. For all the aquaporins, new contributions to physiological functions are likely to continue to be discovered with ongoing work in this rapidly expanding field of research. NEUROSCIENTIST 13(5):470—485, 2007.
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Affiliation(s)
- Andrea J Yool
- Department of Physiology, The BIO5 Institute, and the Arizona Research Laboratories Division of Neurobiology, University of Arizona, Tucson, AZ 84724, USA.
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65
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Bazargani N, Attwell D. Astrocyte calcium signaling: the third wave. Nat Neurosci 2016; 19:182-9. [PMID: 26814587 DOI: 10.1038/nn.4201] [Citation(s) in RCA: 567] [Impact Index Per Article: 70.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023]
Abstract
The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.
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Affiliation(s)
- Narges Bazargani
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
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66
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Phuong TTT, Yarishkin O, Križaj D. Subcellular propagation of calcium waves in Müller glia does not require autocrine/paracrine purinergic signaling. Channels (Austin) 2016; 10:421-427. [PMID: 27221769 DOI: 10.1080/19336950.2016.1193276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The polarized morphology of radial glia allows them to functionally interconnect different layers of CNS tissues including the retina, cerebellum, and cortex. A likely mechanism involves propagation of transcellular Ca2+ waves which were proposed to involve purinergic signaling. Because it is not known whether ATP release is required for astroglial Ca2+ wave propagation we investigated this in mouse Müller cells, radial astroglia-like retinal cells in which in which waves can be induced and supported by Orai/TRPC1 (transient receptor potential isoform 1) channels. We found that depletion of endoplasmic reticulum (ER) stores triggers regenerative propagation of transcellular Ca2+ waves that is independent of ATP release and activation of P2X and P2Y receptors. Both the amplitude and kinetics of transcellular, depletion-induced waves were resistant to non-selective purinergic P2 antagonists such as pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). Thus, store-operated calcium entry (SOCE) is itself sufficient for the initiation and subcellular propagation of calcium waves in radial glia.
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Affiliation(s)
- Tam T T Phuong
- a Department of Ophthalmology & Visual Sciences , University of Utah School of Medicine , Salt Lake City , UT , USA
| | - Oleg Yarishkin
- a Department of Ophthalmology & Visual Sciences , University of Utah School of Medicine , Salt Lake City , UT , USA
| | - David Križaj
- a Department of Ophthalmology & Visual Sciences , University of Utah School of Medicine , Salt Lake City , UT , USA.,b Department of Neurobiology & Anatomy , University of Utah School of Medicine , Salt Lake City , UT , USA.,c Department of Bioengineering , University of Utah , Salt Lake City , UT USA
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67
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Nicchia GP, Pisani F, Simone L, Cibelli A, Mola MG, Dal Monte M, Frigeri A, Bagnoli P, Svelto M. Glio-vascular modifications caused by Aquaporin-4 deletion in the mouse retina. Exp Eye Res 2016; 146:259-268. [DOI: 10.1016/j.exer.2016.03.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/08/2016] [Accepted: 03/22/2016] [Indexed: 10/22/2022]
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68
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Vogler S, Pannicke T, Hollborn M, Kolibabka M, Wiedemann P, Reichenbach A, Hammes HP, Bringmann A. Impaired Purinergic Regulation of the Glial (Müller) Cell Volume in the Retina of Transgenic Rats Expressing Defective Polycystin-2. Neurochem Res 2016; 41:1784-96. [PMID: 27038933 DOI: 10.1007/s11064-016-1894-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 12/19/2022]
Abstract
Retinal glial (Müller) cells possess an endogenous purinergic signal transduction cascade which normally prevents cellular swelling in osmotic stress. The cascade can be activated by osmotic or glutamate receptor-dependent ATP release. We determined whether activation of this cascade is altered in Müller cells of transgenic rats that suffer from a slow photoreceptor degeneration due to the expression of a truncated human cilia gene polycystin-2 (CMV-PKD21/703 HA). Age-matched Sprague-Dawley rats served as control. Retinal slices were superfused with a hypoosmotic solution (60 % osmolarity). Müller cells in retinas of PKD21/703 rats swelled immediately in hypoosmotic stress; this was not observed in control retinas. Pharmacological blockade of P2Y1 or adenosine A1 receptors induced osmotic swelling of Müller cells from control rats. The swelling induced by the P2Y1 receptor antagonist was mediated by induction of oxidative-nitrosative stress, mitochondrial dysfunction, production of inflammatory lipid mediators, and a sodium influx from the extracellular space. Exogenous VEGF or glutamate prevented the hypoosmotic swelling of Müller cells from PKD21/703 rats; this effect was mediated by activation of the purinergic signaling cascade. In neuroretinas of PKD21/703 rats, the gene expression levels of P2Y1 and A1 receptors, pannexin-1, connexin 45, NTPDases 1 and 2, and various subtypes of nucleoside transporters are elevated compared to control. The data may suggest that the osmotic swelling of Müller cells from PKD21/703 rats is caused by an abrogation of the osmotic ATP release while the glutamate-induced ATP release is functional. In the normal retina, ATP release and autocrine P2Y1 receptor activation serve to inhibit the induction of oxidative-nitrosative stress, mitochondrial dysfunction, and production of inflammatory lipid mediators, which otherwise will induce a sodium influx and cytotoxic Müller cell swelling under anisoosmotic conditions. Purinergic receptors may represent a target for the protection of retinal glial cells from mitochondrial oxidative stress.
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Affiliation(s)
- Stefanie Vogler
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Thomas Pannicke
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Margrit Hollborn
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Matthias Kolibabka
- 5th Medical Department, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Peter Wiedemann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
| | - Hans-Peter Hammes
- 5th Medical Department, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany.
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69
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McCleney ZT, Kilpatrick ZP. Entrainment in up and down states of neural populations: non-smooth and stochastic models. J Math Biol 2016; 73:1131-1160. [DOI: 10.1007/s00285-016-0984-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 12/21/2015] [Indexed: 02/02/2023]
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70
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Connexin43 in retinal injury and disease. Prog Retin Eye Res 2016; 51:41-68. [DOI: 10.1016/j.preteyeres.2015.09.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 09/25/2015] [Accepted: 09/27/2015] [Indexed: 12/26/2022]
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71
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Suarez Castellanos IM, Balteanu B, Singh T, Zderic V. Therapeutic Modulation of Calcium Dynamics Using Ultrasound and Other Energy-Based Techniques. IEEE Rev Biomed Eng 2016; 9:177-191. [DOI: 10.1109/rbme.2016.2555760] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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72
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Taguchi M, Shinozaki Y, Kashiwagi K, Shigetomi E, Robaye B, Koizumi S. Müller cell-mediated neurite outgrowth of the retinal ganglion cells via P2Y 6 receptor signals. J Neurochem 2015; 136:741-751. [PMID: 26560804 DOI: 10.1111/jnc.13427] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 10/22/2015] [Accepted: 10/30/2015] [Indexed: 12/27/2022]
Abstract
Müller cells, the primary macroglia of the retina, support various functions of retinal ganglion cells (RGCs). Here, we demonstrate a nucleotide-mediated communication between these two types of cells, by which Müller cells control neurite outgrowth of RGCs by activation of P2 receptors such as P2Y6 . Cultured mouse RGCs had significantly enhanced neurite outgrowth when cultured with either cultured mouse Müller cells or conditioned medium derived from Müller cells, and this was completely inhibited by the nucleotide-degrading enzyme, apyrase. This increase in outgrowth was mimicked by exogenously applied nucleotides such as ATP, uridine triphosphate, and uridine diphosphate. Pharmacological and genetic analysis revealed that P2Y6 receptor in RGCs was responsible for the increased neurite outgrowth. P2Y6 receptor was expressed in the ganglion cell layer of the retina and in RGC primary cultures. High performance liquid chromatography has revealed that Müller cells constitutively release uridine triphosphate, which is immediately metabolized into uridine diphosphate, an endogenous agonist for P2Y6 receptor. In the in vitro ocular hypertension model (i.e., glaucoma model), neurite outgrowth in RGCs was significantly reduced, which was associated with a decrease in P2Y6 receptors. Taken together, Müller cells control neurite outgrowth of RGCs by activating P2 receptors such as P2Y6 receptor, and the receptor expression level might be down-regulated in glaucoma. Müller cells support various functions of retina including those of retinal ganglion cells (RGCs). Here, we report an importance of nucleotide-mediated communication between these two types of cells. Müller cells were found to release uridine diphosphate (UTD), uridine triphosphate (UTP), and activate P2Y6 receptors in RGCs, which was essential for neurite outgrowth of RGCs. In addition, P2Y6 receptors in RGCs were reduced in a glaucoma model in vitro, suggesting an involvement of their dysfunction in the pathogenesis of glaucoma.
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Affiliation(s)
- Masanori Taguchi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Youichi Shinozaki
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Kenji Kashiwagi
- Department of Ophthalmology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Eiji Shigetomi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan
| | - Bernard Robaye
- Institute of Interdisciplinary Research, Institute of Biology and Molecular Medicine, Université Libre de Bruxelles, Gosselies, Belgium
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan
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73
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Zimmermann H. Extracellular ATP and other nucleotides-ubiquitous triggers of intercellular messenger release. Purinergic Signal 2015; 12:25-57. [PMID: 26545760 DOI: 10.1007/s11302-015-9483-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 10/29/2015] [Indexed: 12/21/2022] Open
Abstract
Extracellular nucleotides, and ATP in particular, are cellular signal substances involved in the control of numerous (patho)physiological mechanisms. They provoke nucleotide receptor-mediated mechanisms in select target cells. But nucleotides can considerably expand their range of action. They function as primary messengers in intercellular communication by stimulating the release of other extracellular messenger substances. These in turn activate additional cellular mechanisms through their own receptors. While this applies also to other extracellular messengers, its omnipresence in the vertebrate organism is an outstanding feature of nucleotide signaling. Intercellular messenger substances released by nucleotides include neurotransmitters, hormones, growth factors, a considerable variety of other proteins including enzymes, numerous cytokines, lipid mediators, nitric oxide, and reactive oxygen species. Moreover, nucleotides activate or co-activate growth factor receptors. In the case of hormone release, the initially paracrine or autocrine nucleotide-mediated signal spreads through to the entire organism. The examples highlighted in this commentary suggest that acting as ubiquitous triggers of intercellular messenger release is one of the major functional roles of extracellular nucleotides. While initiation of messenger release by nucleotides has been unraveled in many contexts, it may have been overlooked in others. It can be anticipated that additional nucleotide-driven messenger functions will be uncovered with relevance for both understanding physiology and development of therapy.
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Affiliation(s)
- Herbert Zimmermann
- Institute of Cell Biology and Neuroscience, Molecular and Cellular Neurobiology, Goethe University, Max-von-Laue-Str. 13, Frankfurt am Main, Germany.
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74
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Hirase H, Iwai Y, Takata N, Shinohara Y, Mishima T. Volume transmission signalling via astrocytes. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130604. [PMID: 25225097 PMCID: PMC4173289 DOI: 10.1098/rstb.2013.0604] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The influence of astrocytes on synaptic function has been increasingly studied, owing to the discovery of both gliotransmission and morphological ensheathment of synapses. While astrocytes exhibit at best modest membrane potential fluctuations, activation of G-protein coupled receptors (GPCRs) leads to a prominent elevation of intracellular calcium which has been reported to correlate with gliotransmission. In this review, the possible role of astrocytic GPCR activation is discussed as a trigger to promote synaptic plasticity, by affecting synaptic receptors through gliotransmitters. Moreover, we suggest that volume transmission of neuromodulators could be a biological mechanism to activate astrocytic GPCRs and thereby to switch synaptic networks to the plastic mode during states of attention in cerebral cortical structures.
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Affiliation(s)
- Hajime Hirase
- Laboratory for Neuron-Glia Circuitry, RIKEN Brain Science Institute, Wako, Saitama, Japan Saitama University Brain Science Institute, Saitama, Saitama, Japan
| | - Youichi Iwai
- Laboratory for Neuron-Glia Circuitry, RIKEN Brain Science Institute, Wako, Saitama, Japan
| | - Norio Takata
- Laboratory for Neuron-Glia Circuitry, RIKEN Brain Science Institute, Wako, Saitama, Japan Department of Neuropsychiatry, School of Medicine, Keio University, Shinjuku, Tokyo, Japan
| | - Yoshiaki Shinohara
- Laboratory for Neuron-Glia Circuitry, RIKEN Brain Science Institute, Wako, Saitama, Japan
| | - Tsuneko Mishima
- Laboratory for Neuron-Glia Circuitry, RIKEN Brain Science Institute, Wako, Saitama, Japan
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75
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Savtchenko LP, Rusakov DA. Regulation of rhythm genesis by volume-limited, astroglia-like signals in neural networks. Philos Trans R Soc Lond B Biol Sci 2015; 369:20130614. [PMID: 25225103 PMCID: PMC4173295 DOI: 10.1098/rstb.2013.0614] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Rhythmic activity of the brain often depends on synchronized spiking of interneuronal networks interacting with principal neurons. The quest for physiological mechanisms regulating network synchronization has therefore been firmly focused on synaptic circuits. However, it has recently emerged that synaptic efficacy could be influenced by astrocytes that release signalling molecules into their macroscopic vicinity. To understand how this volume-limited synaptic regulation can affect oscillations in neural populations, here we explore an established artificial neural network mimicking hippocampal basket cells receiving inputs from pyramidal cells. We find that network oscillation frequencies and average cell firing rates are resilient to changes in excitatory input even when such changes occur in a significant proportion of participating interneurons, be they randomly distributed or clustered in space. The astroglia-like, volume-limited regulation of excitatory synaptic input appears to better preserve network synchronization (compared with a similar action evenly spread across the network) while leading to a structural segmentation of the network into cell subgroups with distinct firing patterns. These observations provide us with some previously unknown insights into the basic principles of neural network control by astroglia.
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Affiliation(s)
- Leonid P Savtchenko
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
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76
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Ma B, Buckalew R, Du Y, Kiyoshi CM, Alford CC, Wang W, McTigue DM, Enyeart JJ, Terman D, Zhou M. Gap junction coupling confers isopotentiality on astrocyte syncytium. Glia 2015; 64:214-26. [PMID: 26435164 DOI: 10.1002/glia.22924] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 08/31/2015] [Accepted: 09/11/2015] [Indexed: 02/04/2023]
Abstract
Astrocytes are extensively coupled through gap junctions into a syncytium. However, the basic role of this major brain network remains largely unknown. Using electrophysiological and computational modeling methods, we demonstrate that the membrane potential (VM) of an individual astrocyte in a hippocampal syncytium, but not in a single, freshly isolated cell preparation, can be well-maintained at quasi-physiological levels when recorded with reduced or K(+) free pipette solutions that alter the K(+) equilibrium potential to non-physiological voltages. We show that an astrocyte's associated syncytium provides powerful electrical coupling, together with ionic coupling at a lesser extent, that equalizes the astrocyte's VM to levels comparable to its neighbors. Functionally, this minimizes VM depolarization attributable to elevated levels of local extracellular K(+) and thereby maintains a sustained driving force for highly efficient K(+) uptake. Thus, gap junction coupling functions to achieve isopotentiality in astrocytic networks, whereby a constant extracellular environment can be powerfully maintained for crucial functions of neural circuits.
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Affiliation(s)
- Baofeng Ma
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - Richard Buckalew
- Mathematical Biosciences Institute, the Ohio State University, Columbus, Ohio, 43210
| | - Yixing Du
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - Conrad M Kiyoshi
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - Catherine C Alford
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - Wei Wang
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - Dana M McTigue
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - John J Enyeart
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
| | - David Terman
- Department of Mathematics, the Ohio State University, Columbus, Ohio, 43210
| | - Min Zhou
- Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210
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77
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Decrock E, De Bock M, Wang N, Bultynck G, Giaume C, Naus CC, Green CR, Leybaert L. Connexin and pannexin signaling pathways, an architectural blueprint for CNS physiology and pathology? Cell Mol Life Sci 2015; 72:2823-51. [PMID: 26118660 PMCID: PMC11113968 DOI: 10.1007/s00018-015-1962-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 02/06/2023]
Abstract
The central nervous system (CNS) is composed of a highly heterogeneous population of cells. Dynamic interactions between different compartments (neuronal, glial, and vascular systems) drive CNS function and allow to integrate and process information as well as to respond accordingly. Communication within this functional unit, coined the neuro-glio-vascular unit (NGVU), typically relies on two main mechanisms: direct cell-cell coupling via gap junction channels (GJCs) and paracrine communication via the extracellular compartment, two routes to which channels composed of transmembrane connexin (Cx) or pannexin (Panx) proteins can contribute. Multiple isoforms of both protein families are present in the CNS and each CNS cell type is characterized by a unique Cx/Panx portfolio. Over the last two decades, research has uncovered a multilevel platform via which Cxs and Panxs can influence different cellular functions within a tissue: (1) Cx GJCs enable a direct cell-cell communication of small molecules, (2) Cx hemichannels and Panx channels can contribute to autocrine/paracrine signaling pathways, and (3) different structural domains of these proteins allow for channel-independent functions, such as cell-cell adhesion, interactions with the cytoskeleton, and the activation of intracellular signaling pathways. In this paper, we discuss current knowledge on their multifaceted contribution to brain development and to specific processes in the NGVU, including synaptic transmission and plasticity, glial signaling, vasomotor control, and blood-brain barrier integrity in the mature CNS. By highlighting both physiological and pathological conditions, it becomes evident that Cxs and Panxs can play a dual role in the CNS and that an accurate fine-tuning of each signaling mechanism is crucial for normal CNS physiology.
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Affiliation(s)
- Elke Decrock
- Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B, 3rd floor), 9000 Ghent, Belgium
| | - Marijke De Bock
- Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B, 3rd floor), 9000 Ghent, Belgium
| | - Nan Wang
- Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B, 3rd floor), 9000 Ghent, Belgium
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signalling, Department of Cellular and Molecular Medicine, KU Leuven, Louvain, Belgium
| | - Christian Giaume
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, 75231 Paris Cedex 05, France
- University Pierre et Marie
Curie, ED, N°158, 75005 Paris, France
- MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, 75005 Paris, France
| | - Christian C. Naus
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC V6T 1Z3 Canada
| | - Colin R. Green
- Department of Ophthalmology, The University of Auckland, Auckland, New Zealand
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 (Block B, 3rd floor), 9000 Ghent, Belgium
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Reichenbach A, Bringmann A. Purinergic signaling in retinal degeneration and regeneration. Neuropharmacology 2015; 104:194-211. [PMID: 25998275 DOI: 10.1016/j.neuropharm.2015.05.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/07/2015] [Accepted: 05/07/2015] [Indexed: 02/01/2023]
Abstract
Purinergic signaling is centrally involved in mediating the degeneration of the injured and diseased retina, the induction of retinal gliosis, and the protection of the retinal tissue from degeneration. Dysregulated calcium signaling triggered by overactivation of P2X7 receptors is a crucial step in the induction of neuronal and microvascular cell death under pathogenic conditions like ischemia-hypoxia, elevated intraocular pressure, and diabetes, respectively. Overactivation of P2X7 plays also a pathogenic role in inherited and age-related photoreceptor cell death and in the age-related dysfunction and degeneration of the retinal pigment epithelium. Gliosis of micro- and macroglial cells, which is induced and/or modulated by purinergic signaling and associated with an impaired homeostatic support to neurons, and the ATP-mediated propagation of retinal gliosis from a focal injury into the surrounding noninjured tissue are involved in inducing secondary cell death in the retina. On the other hand, alterations in the glial metabolism of extracellular nucleotides, resulting in a decreased level of ATP and an increased level of adenosine, may be neuroprotective in the diseased retina. Purinergic signals stimulate the proliferation of retinal glial cells which contributes to glial scarring which has protective effects on retinal degeneration and adverse effects on retinal regeneration. Pharmacological modulation of purinergic receptors, e.g., inhibition of P2X and activation of adenosine receptors, may have clinical importance for the prevention of photoreceptor, neuronal, and microvascular cell death in diabetic retinopathy, retinitis pigmentosa, age-related macular degeneration, and glaucoma, respectively, for the clearance of retinal edema, and the inhibition of dysregulated cell proliferation in proliferative retinopathies. This article is part of a Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
| | - Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
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79
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Astrocyte physiopathology: At the crossroads of intercellular networking, inflammation and cell death. Prog Neurobiol 2015; 130:86-120. [PMID: 25930681 DOI: 10.1016/j.pneurobio.2015.04.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022]
Abstract
Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.
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80
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Chara O, Brusch L. Mathematical modelling of fluid transport and its regulation at multiple scales. Biosystems 2015; 130:1-10. [DOI: 10.1016/j.biosystems.2015.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 02/04/2015] [Accepted: 02/04/2015] [Indexed: 12/20/2022]
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Lee J, Chun YE, Han KS, Lee J, Woo DH, Lee CJ. Ca(2+) Entry is Required for Mechanical Stimulation-induced ATP Release from Astrocyte. Exp Neurobiol 2015; 24:17-23. [PMID: 25792866 PMCID: PMC4363330 DOI: 10.5607/en.2015.24.1.17] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 02/28/2015] [Accepted: 03/02/2015] [Indexed: 11/19/2022] Open
Abstract
Astrocytes and neurons are inseparable partners in the brain. Neurotransmitters released from neurons activate corresponding G protein-coupled receptors (GPCR) expressed in astrocytes, resulting in release of gliotransmitters such as glutamate, D-serine, and ATP. These gliotransmitters in turn influence neuronal excitability and synaptic activities. Among these gliotransmitters, ATP regulates the level of network excitability and is critically involved in sleep homeostasis and astrocytic Ca2+ oscillations. ATP is known to be released from astrocytes by Ca2+-dependent manner. However, the precise source of Ca2+, whether it is Ca2+ entry from outside of cell or from the intracellular store, is still not clear yet. Here, we performed sniffer patch to detect ATP release from astrocyte by using various stimulation. We found that ATP was not released from astrocyte when Ca2+ was released from intracellular stores by activation of Gαq-coupled GPCR including PAR1, P2YR, and B2R. More importantly, mechanical stimulation (MS)-induced ATP release from astrocyte was eliminated when external Ca2+ was omitted. Our results suggest that Ca2+ entry, but not release from intracellular Ca2+ store, is critical for MS-induced ATP release from astrocyte.
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Affiliation(s)
- Jaekwang Lee
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - Ye-Eun Chun
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea. ; Neuroscience Program, University of Science and Technology (UST), Daejeon 305-350, Korea
| | - Kyung-Seok Han
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - Jungmoo Lee
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea. ; KU-KIST Graduate School of Converging Science and Technology, Seoul 136-701, Korea
| | - Dong Ho Woo
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - C Justin Lee
- Center for Functional Connectomics, and Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea. ; Neuroscience Program, University of Science and Technology (UST), Daejeon 305-350, Korea. ; KU-KIST Graduate School of Converging Science and Technology, Seoul 136-701, Korea
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Nimmerjahn A, Bergles DE. Large-scale recording of astrocyte activity. Curr Opin Neurobiol 2015; 32:95-106. [PMID: 25665733 DOI: 10.1016/j.conb.2015.01.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 01/21/2015] [Accepted: 01/22/2015] [Indexed: 12/17/2022]
Abstract
Astrocytes are highly ramified glial cells found throughout the central nervous system (CNS). They express a variety of neurotransmitter receptors that can induce widespread chemical excitation, placing these cells in an optimal position to exert global effects on brain physiology. However, the activity patterns of only a small fraction of astrocytes have been examined and techniques to manipulate their behavior are limited. As a result, little is known about how astrocytes modulate CNS function on synaptic, microcircuit, or systems levels. Here, we review current and emerging approaches for visualizing and manipulating astrocyte activity in vivo. Deciphering how astrocyte network activity is controlled in different physiological and pathological contexts is crucial for defining their roles in the healthy and diseased CNS.
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Affiliation(s)
- Axel Nimmerjahn
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Dwight E Bergles
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, WBSB 1001, Baltimore, MD 21205, USA.
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84
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Voigt J, Grosche A, Vogler S, Pannicke T, Hollborn M, Kohen L, Wiedemann P, Reichenbach A, Bringmann A. Nonvesicular release of ATP from rat retinal glial (Müller) cells is differentially mediated in response to osmotic stress and glutamate. Neurochem Res 2015; 40:651-60. [PMID: 25567481 DOI: 10.1007/s11064-014-1511-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 12/29/2014] [Indexed: 01/01/2023]
Abstract
Retinal glial (Müller) cells release ATP upon osmotic stress or activation of metabotropic glutamate receptors. ATP inhibits the osmotic Müller cell swelling by activation of P2Y1 receptors. In the present study, we determined the molecular pathways of the ATP release from Müller cells in slices of the rat retina. Administration of the ATP/ADPase apyrase induced a swelling of Müller cells under hypoosmotic conditions, and prevented the swelling-inhibitory effect of glutamate, suggesting that swelling inhibition is mediated by extracellular ATP. A hypoosmotic swelling of Müller cells was also observed in the presence of a blocker of multidrug resistance channels (MK-571), a CFTR inhibitor (glibenclamide), and connexin hemichannel blockers (18-α-glycyrrhetinic acid, 100 µM carbenoxolone). The swelling-inhibitory effect of glutamate was prevented by MK-571, the connexin hemichannel blockers, and a pannexin-1 hemichannel blocker (5 µM carbenoxolone). The p-glycoprotein blocker verapamil had no effect. As revealed by single-cell RT-PCR, subpopulations of Müller cells expressed mRNAs for pannexin-1 and -2, and connexins 30, 30.3, 32, 43, 45, and 46. The data may suggest that rat Müller cells release ATP by multidrug resistance channels, CFTR, and connexin hemichannels in response to osmotic stress, while glutamate induces a release of ATP via multidrug resistance channels, connexin hemichannels, and pannexin-1.
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Affiliation(s)
- Juliane Voigt
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
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85
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Andjelić S, Lumi X, Yan X, Graw J, Moe MC, Facskó A, Hawlina M, Petrovski G. Characterization of ex vivo cultured neuronal- and glial- like cells from human idiopathic epiretinal membranes. BMC Ophthalmol 2014; 14:165. [PMID: 25540050 PMCID: PMC4324881 DOI: 10.1186/1471-2415-14-165] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Accepted: 12/11/2014] [Indexed: 01/29/2023] Open
Abstract
Background Characterization of the neuro-glial profile of cells growing out of human idiopathic epiretinal membranes (iERMs) and testing their proliferative and pluripotent properties ex vivo is needed to better understand the pathogenesis of their formation. Methods iERMs obtained during uneventful vitrectomies were cultivated ex vivo under adherent conditions and assessed by standard morphological and immunocytochemical methods. The intracellular calcium dynamics of the outgrowing cells was assessed by fluorescent dye Fura-2 in response to acetylcholine (ACh)- or mechano- stimulation. Results The cells from the iERMs formed sphere-like structures when cultured ex vivo. The diameter of the spheres increased by 5% at day 6 and kept an increasing tendency over a month time. The outgrowing cells from the iERM spheres had mainly glial- and some neuronal- like morphology. ACh- or mechano- stimulation of these cells induced intracellular calcium propagation in both cell types; in the neuronal-like cells resembling action potential from the soma to the dendrites. Immunocytochemistry confirmed presence of glial- and neuronal cell phenotype (GFAP and Nestin-1 positivity, respectively) in the iERMs, as well as presence of pluripotency marker (Sox2). Conclusion iERMs contain cells of neuronal- and glial- like origin which have proliferative and pluripotent potential, show functionality reflected through calcium dynamics upon ACh and mechano- stimulation, and a corresponding molecular phenotype.
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Affiliation(s)
| | | | | | | | | | | | | | - Goran Petrovski
- Eye Hospital, University Medical Centre, Grablovičeva ulica 46, 1000 Ljubljana, Slovenia.
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86
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Streifel KM, Gonzales AL, De Miranda B, Mouneimne R, Earley S, Tjalkens R. Dopaminergic neurotoxicants cause biphasic inhibition of purinergic calcium signaling in astrocytes. PLoS One 2014; 9:e110996. [PMID: 25365260 PMCID: PMC4217743 DOI: 10.1371/journal.pone.0110996] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 09/27/2014] [Indexed: 11/18/2022] Open
Abstract
Dopaminergic nuclei in the basal ganglia are highly sensitive to damage from oxidative stress, inflammation, and environmental neurotoxins. Disruption of adenosine triphosphate (ATP)-dependent calcium (Ca2+) transients in astrocytes may represent an important target of such stressors that contributes to neuronal injury by disrupting critical Ca2+-dependent trophic functions. We therefore postulated that plasma membrane cation channels might be a common site of inhibition by structurally distinct cationic neurotoxicants that could modulate ATP-induced Ca2+ signals in astrocytes. To test this, we examined the capacity of two dopaminergic neurotoxicants to alter ATP-dependent Ca2+ waves and transients in primary murine striatal astrocytes: MPP+, the active metabolite of 1-methyl 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and 6-hydroxydopamine (6-OHDA). Both compounds acutely decreased ATP-induced Ca2+ transients and waves in astrocytes and blocked OAG-induced Ca2+ influx at micromolar concentrations, suggesting the transient receptor potential channel, TRPC3, as an acute target. MPP+ inhibited 1-oleoyl-2-acetyl-sn-glycerol (OAG)-induced Ca2+ transients similarly to the TRPC3 antagonist, pyrazole-3, whereas 6-OHDA only partly suppressed OAG-induced transients. RNAi directed against TRPC3 inhibited the ATP-induced transient as well as entry of extracellular Ca2+, which was augmented by MPP+. Whole-cell patch clamp experiments in primary astrocytes and TRPC3-overexpressing cells demonstrated that acute application of MPP+ completely blocked OAG-induced TRPC3 currents, whereas 6-OHDA only partially inhibited OAG currents. These findings indicate that MPP+ and 6-OHDA inhibit ATP-induced Ca2+ signals in astrocytes in part by interfering with purinergic receptor mediated activation of TRPC3, suggesting a novel pathway in glia that could contribute to neurotoxic injury.
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Affiliation(s)
- Karin M. Streifel
- Center for Environmental Medicine, Colorado State University, Fort Collins, Colorado, United States of America
| | - Albert L. Gonzales
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Briana De Miranda
- Center for Environmental Medicine, Colorado State University, Fort Collins, Colorado, United States of America
| | - Rola Mouneimne
- Department of Veterinary Integrative Biosciences, Texas A & M University, College Station, Texas, United States of America
| | - Scott Earley
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Ronald Tjalkens
- Center for Environmental Medicine, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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Abstract
Astrocytes have been found to play important roles in physiology being fundamental for ionic homeostasis and glutamate clearance from the synaptic cleft by their plasma membrane glutamate transporters. Astrocytes are electrically non-excitable, but they exhibit Ca(2+) signaling, which now has been demonstrated to serve as an indirect mediator of neuron-glia bidirectional interactions through gliotransmission via tripartite synapses and to modulate synaptic function and plasticity. Spontaneous astrocytic Ca(2+) signaling was observed in vivo. Intercellular Ca(2+) waves in astrocytes can be evoked by a variety of stimulations. Astrocytes are critically involved in many pathological conditions including ischemic stroke. For example, it is well known that astrocytes become reactive and form glial scar after stroke. In animal models of some brain disorders, astrocytes have been shown to exhibit enhanced Ca(2+) excitability featured as regenerative intercellular Ca(2+) waves. This chapter briefly summarizes astrocytic Ca(2+) signaling pathways under normal conditions and in experimental in vitro and in vivo ischemic models. It discusses the possible mechanisms and therapeutic implication underlying the enhanced astrocytic Ca(2+) excitability in stroke.
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Affiliation(s)
- Shinghua Ding
- Dalton Cardiovascular Research Center, Department of Bioengineering, University of Missouri-Columbia, 134 Research Park Drive, Columbia, MO, 65211, USA,
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88
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Immunolocalization of the P2X4 receptor on neurons and glia in the mammalian retina. Neuroscience 2014; 277:55-71. [DOI: 10.1016/j.neuroscience.2014.06.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 06/23/2014] [Accepted: 06/24/2014] [Indexed: 02/07/2023]
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89
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Sodhi P, Hartwick ATE. Adenosine modulates light responses of rat retinal ganglion cell photoreceptors througha cAMP-mediated pathway. J Physiol 2014; 592:4201-20. [PMID: 25038240 DOI: 10.1113/jphysiol.2014.276220] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adenosine is an established neuromodulator in the mammalian retina, with A1 adenosine receptors being especially prevalent in the innermost ganglion cell layer. Activation of A1 receptors causes inhibition of adenylate cyclase, decreases in intracellular cyclic AMP (cAMP) levels and inhibition of protein kinase A (PKA). In this work, our aim was to characterize the effects of adenosine on the light responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) and to determine whether these photoreceptors are subject to neuromodulation through intracellular cAMP-related signalling pathways. Using multielectrode array recordings from postnatal and adult rat retinas, we demonstrated that adenosine significantly shortened the duration of ipRGC photoresponses and reduced the number of light-evoked spikes fired by these neurons. The effects were A1 adenosine receptor-mediated, and the expression of this receptor on melanopsin-containing ipRGCs was confirmed by calcium imaging experiments on isolated cells in purified cultures. While inhibition of the cAMP/PKA pathway by adenosine shortened ipRGC light responses, stimulation of this pathway with compounds such as forskolin had the opposite effect and lengthened the duration of ipRGC spiking. Our findings reveal that the modification of ipRGC photoresponses through a cAMP/PKA pathway is a general feature of rat ganglion cell photoreceptors, and this pathway can be inhibited through activation of A1 receptors by adenosine. As adenosine levels in the retina rise at night, adenosinergic modulation of ipRGCs may serve as an internal regulatory mechanism to limit transmission of nocturnal photic signals by ipRGCs to the brain. Targeting retinal A1 adenosine receptors for ipRGC inhibition represents a potential therapeutic target for sleep disorders and migraine-associated photophobia.
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Affiliation(s)
- Puneet Sodhi
- Department of Neuroscience, Ohio State University, Columbus, OH, 43210, USA
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90
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Cuenca N, Fernández-Sánchez L, Campello L, Maneu V, De la Villa P, Lax P, Pinilla I. Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases. Prog Retin Eye Res 2014; 43:17-75. [PMID: 25038518 DOI: 10.1016/j.preteyeres.2014.07.001] [Citation(s) in RCA: 296] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 07/03/2014] [Accepted: 07/07/2014] [Indexed: 01/17/2023]
Abstract
Retinal neurodegenerative diseases like age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa each have a different etiology and pathogenesis. However, at the cellular and molecular level, the response to retinal injury is similar in all of them, and results in morphological and functional impairment of retinal cells. This retinal degeneration may be triggered by gene defects, increased intraocular pressure, high levels of blood glucose, other types of stress or aging, but they all frequently induce a set of cell signals that lead to well-established and similar morphological and functional changes, including controlled cell death and retinal remodeling. Interestingly, an inflammatory response, oxidative stress and activation of apoptotic pathways are common features in all these diseases. Furthermore, it is important to note the relevant role of glial cells, including astrocytes, Müller cells and microglia, because their response to injury is decisive for maintaining the health of the retina or its degeneration. Several therapeutic approaches have been developed to preserve retinal function or restore eyesight in pathological conditions. In this context, neuroprotective compounds, gene therapy, cell transplantation or artificial devices should be applied at the appropriate stage of retinal degeneration to obtain successful results. This review provides an overview of the common and distinctive features of retinal neurodegenerative diseases, including the molecular, anatomical and functional changes caused by the cellular response to damage, in order to establish appropriate treatments for these pathologies.
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Affiliation(s)
- Nicolás Cuenca
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain; Multidisciplinary Institute for Environmental Studies "Ramon Margalef", University of Alicante, Alicante, Spain.
| | - Laura Fernández-Sánchez
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Laura Campello
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Victoria Maneu
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Pedro De la Villa
- Department of Systems Biology, University of Alcalá, Alcalá de Henares, Spain
| | - Pedro Lax
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Isabel Pinilla
- Department of Ophthalmology, Lozano Blesa University Hospital, Aragon Institute of Health Sciences, Zaragoza, Spain
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Ding S, Huang W, Ye Y, Yang J, Hu J, Wang X, Liu L, Lu Q, Lin Y. Elevated intracranial dopamine impairs the glutamate‑nitric oxide‑cyclic guanosine monophosphate pathway in cortical astrocytes in rats with minimal hepatic encephalopathy. Mol Med Rep 2014; 10:1215-24. [PMID: 25059564 PMCID: PMC4121426 DOI: 10.3892/mmr.2014.2386] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 04/16/2014] [Indexed: 01/28/2023] Open
Abstract
In a previous study by our group memory impairment in rats with minimal hepatic encephalopathy (MHE) was associated with the inhibition of the glutamate-nitric oxide-cyclic guanosine monophosphate (Glu-NO-cGMP) pathway due to elevated dopamine (DA). However, the effects of DA on the Glu-NO-cGMP pathway localized in primary cortical astrocytes (PCAs) had not been elucidated in rats with MHE. In the present study, it was identified that when the levels of DA in the cerebral cortex of rats with MHE and high-dose DA (3 mg/kg)-treated rats were increased, the co-localization of N-methyl-d-aspartate receptors subunit 1 (NMDAR1), calmodulin (CaM), nitric oxide synthase (nNOS), soluble guanylyl cyclase (sGC) and cyclic guanine monophosphate (cGMP) with the glial fibrillary acidic protein (GFAP), a marker protein of astrocytes, all significantly decreased, in both the MHE and high-dose DA-treated rats (P<0.01). Furthermore, NMDA-induced augmentation of the expression of NMDAR1, CaM, nNOS, sGC and cGMP localized in PCAs was decreased in MHE and DA-treated rats, as compared with the controls. Chronic exposure of cultured cerebral cortex PCAs to DA treatment induced a dose-dependent decrease in the concentration of intracellular calcium, nitrites and nitrates, the formation of cGMP and the expression of NMDAR1, CaM, nNOS and sGC/cGMP. High doses of DA (50 μM) significantly reduced NMDA-induced augmentation of the formation of cGMP and the contents of NMDAR1, CaM, nNOS, sGC and cGMP (P<0.01). These results suggest that the suppression of DA on the Glu-NO-cGMP pathway localized in PCAs contributes to memory impairment in rats with MHE.
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Affiliation(s)
- Saidan Ding
- Zhejiang Provincial Key Laboratory of Aging and Neurological Disease Research, Department of Surgery Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Weilong Huang
- Neurosurgery Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Yiru Ye
- Department of Computer, Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Jianjing Yang
- Neurosurgery Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Jiangnan Hu
- Neurosurgery Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Xiaobin Wang
- Neurosurgery Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Leping Liu
- Zhejiang Provincial Key Laboratory of Aging and Neurological Disease Research, Department of Surgery Laboratory, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Qin Lu
- Neurosurgery Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Yuanshao Lin
- First Department of Neurology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
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92
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Ross AE, Nguyen MD, Privman E, Venton BJ. Mechanical stimulation evokes rapid increases in extracellular adenosine concentration in the prefrontal cortex. J Neurochem 2014; 130:50-60. [PMID: 24606335 PMCID: PMC4065624 DOI: 10.1111/jnc.12711] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 02/28/2014] [Accepted: 03/05/2014] [Indexed: 12/22/2022]
Abstract
Mechanical perturbations can release ATP, which is broken down to adenosine. In this work, we used carbon-fiber microelectrodes and fast-scan cyclic voltammetry to measure mechanically stimulated adenosine in the brain by lowering the electrode 50 μm. Mechanical stimulation evoked adenosine in vivo (average: 3.3 ± 0.6 μM) and in brain slices (average: 0.8 ± 0.1 μM) in the prefrontal cortex. The release was transient, lasting 18 ± 2 s. Lowering a 15-μm-diameter glass pipette near the carbon-fiber microelectrode produced similar results as lowering the actual microelectrode. However, applying a small puff of artificial cerebral spinal fluid was not sufficient to evoke adenosine. Multiple stimulations within a 50-μm region of a slice did not significantly change over time or damage cells. Chelating calcium with EDTA or blocking sodium channels with tetrodotoxin significantly decreased mechanically evoked adenosine, signifying that the release is activity dependent. An alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, did not affect mechanically stimulated adenosine; however, the nucleoside triphosphate diphosphohydrolase 1,2 and 3 (NTDPase) inhibitor POM-1 significantly reduced adenosine so a portion of adenosine is dependent on extracellular ATP metabolism. Thus, mechanical perturbations from inserting a probe in the brain cause rapid, transient adenosine signaling which might be neuroprotective. We have discovered immediate changes in adenosine concentration in the prefrontal cortex following mechanical stimulation. The adenosine increase lasts only about 20 s. Mechanically stimulated adenosine was activity dependent and mostly because of extracellular ATP metabolism. This rapid, transient increase in adenosine may help protect tissue and would occur during implantation of any electrode, such as during deep brain stimulation.
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Affiliation(s)
| | | | | | - B. Jill Venton
- corresponding author Dept. of Chemistry University of Virginia Charlottesville, VA 22904 (434) 243-2132
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93
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Beckel JM, Argall AJ, Lim JC, Xia J, Lu W, Coffey EE, Macarak EJ, Shahidullah M, Delamere NA, Zode GS, Sheffield VC, Shestopalov VI, Laties AM, Mitchell CH. Mechanosensitive release of adenosine 5'-triphosphate through pannexin channels and mechanosensitive upregulation of pannexin channels in optic nerve head astrocytes: a mechanism for purinergic involvement in chronic strain. Glia 2014; 62:1486-501. [PMID: 24839011 DOI: 10.1002/glia.22695] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 12/21/2022]
Abstract
As adenosine 5'-triphosphate (ATP) released from astrocytes can modulate many neural signaling systems, the triggers and pathways for this ATP release are important. Here, the ability of mechanical strain to trigger ATP release through pannexin channels and the effects of sustained strain on pannexin expression were examined in rat optic nerve head astrocytes. Astrocytes released ATP when subjected to 5% of equibiaxial strain or to hypotonic swelling. Although astrocytes expressed mRNA for pannexins 1-3, connexin 43, and VNUT, pharmacological analysis suggested a predominant role for pannexins in mechanosensitive ATP release, with Rho kinase contribution. Astrocytes from panx1(-/-) mice had reduced baseline and stimulated levels of extracellular ATP, confirming the role for pannexins. Swelling astrocytes triggered a regulatory volume decrease that was inhibited by apyrase or probenecid. The swelling-induced rise in calcium was inhibited by P2X7 receptor antagonists A438079 and AZ10606120, in addition to apyrase and carbenoxolone. Extended stretch of astrocytes in vitro upregulated expression of panx1 and panx2 mRNA. A similar upregulation was observed in vivo in optic nerve head tissue from the Tg-MYOC(Y437H) mouse model of chronic glaucoma; genes for panx1, panx2, and panx3 were increased, whereas immunohistochemistry confirmed increased expression of pannexin 1 protein. In summary, astrocytes released ATP in response to mechanical strain, with pannexin 1 the predominant efflux pathway. Sustained strain upregulated pannexins in vitro and in vivo. Together, these findings provide a mechanism by which extracellular ATP remains elevated under chronic mechanical strain, as found in the optic nerve head of patients with glaucoma.
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Affiliation(s)
- Jonathan M Beckel
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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94
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Pires M, Raischel F, Vaz SH, Cruz-Silva A, Sebastião AM, Lind PG. Modeling the functional network of primary intercellular Ca2+ wave propagation in astrocytes and its application to study drug effects. J Theor Biol 2014; 356:201-12. [PMID: 24813072 DOI: 10.1016/j.jtbi.2014.04.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/17/2014] [Accepted: 04/17/2014] [Indexed: 11/15/2022]
Abstract
We introduce a simple procedure of multivariate signal analysis to uncover the functional connectivity among cells composing a living tissue and describe how to apply it for extracting insight on the effect of drugs in the tissue. The procedure is based on the covariance matrix of time resolved activity signals. By determining the time-lag that maximizes covariance, one derives the weight of the corresponding connection between cells. Introducing simple constraints, it is possible to conclude whether pairs of cells are functionally connected and in which direction. After testing the method against synthetic data we apply it to study intercellular propagation of Ca(2+) waves in astrocytes following an external stimulus, with the aim of uncovering the functional cellular connectivity network. Our method proves to be particularly suited for this type of networking signal propagation where signals are pulse-like and have short time-delays, and is shown to be superior to standard methods, namely a multivariate Granger algorithm. Finally, based on the statistical analysis of the connection weight distribution, we propose simple measures for assessing the impact of drugs on the functional connectivity between cells.
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Affiliation(s)
- Marcelo Pires
- Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Campo Grande 1649-003 Lisboa, Portugal; Departamento de Física, Universidade Federal do Amapá, Jardim Marco Zero, 68903-419 Macapá/AP, Brazil
| | - Frank Raischel
- Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Campo Grande 1649-003 Lisboa, Portugal; Centro de Geofísica, Instituto Dom Luiz, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Sandra H Vaz
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Andreia Cruz-Silva
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Ana M Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Pedro G Lind
- Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Campo Grande 1649-003 Lisboa, Portugal; Institute für Physik and ForWind, Carl-von-Ossietzky Universität Oldenburg, DE-26111 Oldenburg, Germany.
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95
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De Bock M, Decrock E, Wang N, Bol M, Vinken M, Bultynck G, Leybaert L. The dual face of connexin-based astroglial Ca(2+) communication: a key player in brain physiology and a prime target in pathology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2211-32. [PMID: 24768716 DOI: 10.1016/j.bbamcr.2014.04.016] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/21/2022]
Abstract
For decades, studies have been focusing on the neuronal abnormalities that accompany neurodegenerative disorders. Yet, glial cells are emerging as important players in numerous neurological diseases. Astrocytes, the main type of glia in the central nervous system , form extensive networks that physically and functionally connect neuronal synapses with cerebral blood vessels. Normal brain functioning strictly depends on highly specialized cellular cross-talk between these different partners to which Ca(2+), as a signaling ion, largely contributes. Altered intracellular Ca(2+) levels are associated with neurodegenerative disorders and play a crucial role in the glial responses to injury. Intracellular Ca(2+) increases in single astrocytes can be propagated toward neighboring cells as intercellular Ca(2+) waves, thereby recruiting a larger group of cells. Intercellular Ca(2+) wave propagation depends on two, parallel, connexin (Cx) channel-based mechanisms: i) the diffusion of inositol 1,4,5-trisphosphate through gap junction channels that directly connect the cytoplasm of neighboring cells, and ii) the release of paracrine messengers such as glutamate and ATP through hemichannels ('half of a gap junction channel'). This review gives an overview of the current knowledge on Cx-mediated Ca(2+) communication among astrocytes as well as between astrocytes and other brain cell types in physiology and pathology, with a focus on the processes of neurodegeneration and reactive gliosis. Research on Cx-mediated astroglial Ca(2+) communication may ultimately shed light on the development of targeted therapies for neurodegenerative disorders in which astrocytes participate. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium.
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, B-1090 Brussels, Belgium
| | - Geert Bultynck
- Department of Cellular and Molecular Medicine, Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N-I bus 802, B-3000 Leuven, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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96
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Lallouette J, De Pittà M, Ben-Jacob E, Berry H. Sparse short-distance connections enhance calcium wave propagation in a 3D model of astrocyte networks. Front Comput Neurosci 2014; 8:45. [PMID: 24795613 PMCID: PMC3997029 DOI: 10.3389/fncom.2014.00045] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/27/2013] [Indexed: 11/13/2022] Open
Abstract
Traditionally, astrocytes have been considered to couple via gap-junctions into a syncytium with only rudimentary spatial organization. However, this view is challenged by growing experimental evidence that astrocytes organize as a proper gap-junction mediated network with more complex region-dependent properties. On the other hand, the propagation range of intercellular calcium waves (ICW) within astrocyte populations is as well highly variable, depending on the brain region considered. This suggests that the variability of the topology of gap-junction couplings could play a role in the variability of the ICW propagation range. Since this hypothesis is very difficult to investigate with current experimental approaches, we explore it here using a biophysically realistic model of three-dimensional astrocyte networks in which we varied the topology of the astrocyte network, while keeping intracellular properties and spatial cell distribution and density constant. Computer simulations of the model suggest that changing the topology of the network is indeed sufficient to reproduce the distinct ranges of ICW propagation reported experimentally. Unexpectedly, our simulations also predict that sparse connectivity and restriction of gap-junction couplings to short distances should favor propagation while long–distance or dense connectivity should impair it. Altogether, our results provide support to recent experimental findings that point toward a significant functional role of the organization of gap-junction couplings into proper astroglial networks. Dynamic control of this topology by neurons and signaling molecules could thus constitute a new type of regulation of neuron-glia and glia-glia interactions.
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Affiliation(s)
- Jules Lallouette
- EPI Beagle, INRIA Rhône-Alpes Villeurbanne, France ; LIRIS, UMR 5205 CNRS-INSA, Université de Lyon Villeurbanne, France
| | - Maurizio De Pittà
- EPI Beagle, INRIA Rhône-Alpes Villeurbanne, France ; LIRIS, UMR 5205 CNRS-INSA, Université de Lyon Villeurbanne, France ; School of Physics and Astronomy, Tel Aviv University Ramat Aviv, Israel
| | - Eshel Ben-Jacob
- School of Physics and Astronomy, Tel Aviv University Ramat Aviv, Israel ; Center for Theoretical Biological Physics, Rice University Houston, TX, USA
| | - Hugues Berry
- EPI Beagle, INRIA Rhône-Alpes Villeurbanne, France ; LIRIS, UMR 5205 CNRS-INSA, Université de Lyon Villeurbanne, France
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97
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Abstract
In the developing nervous system, ordered neuronal activity patterns can occur even in the absence of sensory input and to investigate how these arise, we have used the model system of the embryonic chicken spinal motor circuit, focusing on motor neurons of the lateral motor column (LMC). At the earliest stages of their molecular differentiation, we can detect differences between medial and lateral LMC neurons in terms of expression of neurotransmitter receptor subunits, including CHRNA5, CHRNA7, GRIN2A, GRIK1, HTR1A and HTR1B, as well as the KCC2 transporter. Using patch-clamp recordings we also demonstrate that medial and lateral LMC motor neurons have subtly different activity patterns that reflect the differential expression of neurotransmitter receptor subunits. Using a combination of patch-clamp recordings in single neurons and calcium-imaging of motor neuron populations, we demonstrate that inhibition of nicotinic, muscarinic or GABA-ergic activity, has profound effects of motor circuit activity during the initial stages of neuromuscular junction formation. Finally, by analysing the activity of large populations of motor neurons at different developmental stages, we show that the asynchronous, disordered neuronal activity that occurs at early stages of circuit formation develops into organised, synchronous activity evident at the stage of LMC neuron muscle innervation. In light of the considerable diversity of neurotransmitter receptor expression, activity patterns in the LMC are surprisingly similar between neuronal types, however the emergence of patterned activity, in conjunction with the differential expression of transmitter systems likely leads to the development of near-mature patterns of locomotor activity by perinatal ages.
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Affiliation(s)
- Chris Law
- Institut de recherches cliniques de Montréal (IRCM), Montréal, Canada
| | - Michel Paquet
- Institut de recherches cliniques de Montréal (IRCM), Montréal, Canada
| | - Artur Kania
- Institut de recherches cliniques de Montréal (IRCM), Montréal, Canada
- Departments of Anatomy and Cell Biology, and Biology, Division of Experimental Medicine, McGill University Montréal, Montréal, Canada, and Faculté de Médecine, Université de Montréal, Montréal, Canada
- * E-mail:
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98
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Innexin and pannexin channels and their signaling. FEBS Lett 2014; 588:1396-402. [PMID: 24632288 DOI: 10.1016/j.febslet.2014.03.007] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 03/06/2014] [Indexed: 01/24/2023]
Abstract
Innexins are bifunctional membrane proteins in invertebrates, forming gap junctions as well as non-junctional membrane channels (innexons). Their vertebrate analogues, the pannexins, have not only lost the ability to form gap junctions but are also prevented from it by glycosylation. Pannexins appear to form only non-junctional membrane channels (pannexons). The membrane channels formed by pannexins and innexins are similar in their biophysical and pharmacological properties. Innexons and pannexons are permeable to ATP, are present in glial cells, and are involved in activation of microglia by calcium waves in glia. Directional movement and accumulation of microglia following nerve injury, which has been studied in the leech which has unusually large glial cells, involves at least 3 signals: ATP is the "go" signal, NO is the "where" signal and arachidonic acid is a "stop" signal.
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99
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Kur J, Newman EA. Purinergic control of vascular tone in the retina. J Physiol 2014; 592:491-504. [PMID: 24277867 PMCID: PMC3930435 DOI: 10.1113/jphysiol.2013.267294] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 11/18/2013] [Indexed: 12/19/2022] Open
Abstract
Purinergic control of vascular tone in the CNS has been largely unexplored. This study examines the contribution of endogenous extracellular ATP, acting on vascular smooth muscle cells, in controlling vascular tone in the in vivo rat retina. Retinal vessels were labelled by i.v. injection of a fluorescent dye and imaged with scanning laser confocal microscopy. The diameters of primary arterioles were monitored under control conditions and following intravitreal injection of pharmacological agents. Apyrase (500 units ml(-1)), an ATP hydrolysing enzyme, dilated retinal arterioles by 40.4 ± 2.8%, while AOPCP (12.5 mm), an ecto-5'-nucleotidase inhibitor that increases extracellular ATP levels, constricted arterioles by 58.0 ± 3.8% (P < 0.001 for both), demonstrating the importance of ATP in the control of basal vascular tone. Suramin (500 μm), a broad-spectrum P2 receptor antagonist, dilated retinal arterioles by 50.9 ± 3.7% (P < 0.001). IsoPPADS (300 μm) and TNP-ATP (50 μm), more selective P2X antagonists, dilated arterioles by 41.0 ± 5.3% and 55.2 ± 6.1% respectively (P < 0.001 for both). NF023 (50 μm), a potent antagonist of P2X1 receptors, dilated retinal arterioles by 32.1 ± 2.6% (P < 0.001). A438079 (500 μm) and AZ10606120 (50 μm), P2X7 antagonists, had no effect on basal vascular tone (P = 0.99 and P = 1.00 respectively). In the ex vivo retina, the P2X1 receptor agonist α,β-methylene ATP (300 nm) evoked sustained vasoconstrictions of 18.7 ± 3.2% (P < 0.05). In vivo vitreal injection of the gliotoxin fluorocitrate (150 μm) dilated retinal vessels by 52.3 ± 1.1% (P < 0.001) and inhibited the vasodilatory response to NF023 (50 μm, 7.9 ± 2.0%; P < 0.01). These findings suggest that vascular tone in rat retinal arterioles is maintained by tonic release of ATP from the retina. ATP acts on P2X1 receptors, although contributions from other P2X and P2Y receptors cannot be ruled out. Retinal glial cells are a possible source of the vasoconstricting ATP.
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Affiliation(s)
- Joanna Kur
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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100
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Dye coupling and immunostaining of astrocyte-like glia following intracellular injection of fluorochromes in brain slices of the grasshopper, Schistocerca gregaria. Methods Mol Biol 2014; 1082:99-113. [PMID: 24048929 DOI: 10.1007/978-1-62703-655-9_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Injection of fluorochromes such as Alexa Fluor(®) 568 into single cells in brain slices reveals a network of dye-coupled cells to be associated with the central complex. Subsequent immunolabeling shows these cells to be repo positive/glutamine synthetase positive/horseradish peroxidase negative, thus identifying them as astrocyte-like glia. Dye coupling fails in the presence of n-heptanol indicating that dye spreads from cell to cell via gap junctions. A cellular network of dye-coupled, astrocyte-like, glia surrounds and infiltrates developing central complex neuropils. Intracellular dye injection techniques complement current molecular approaches in analyzing the functional properties of such networks.
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