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Stoddart PR, Begeng JM, Tong W, Ibbotson MR, Kameneva T. Nanoparticle-based optical interfaces for retinal neuromodulation: a review. Front Cell Neurosci 2024; 18:1360870. [PMID: 38572073 PMCID: PMC10987880 DOI: 10.3389/fncel.2024.1360870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Accepted: 03/04/2024] [Indexed: 04/05/2024] Open
Abstract
Degeneration of photoreceptors in the retina is a leading cause of blindness, but commonly leaves the retinal ganglion cells (RGCs) and/or bipolar cells extant. Consequently, these cells are an attractive target for the invasive electrical implants colloquially known as "bionic eyes." However, after more than two decades of concerted effort, interfaces based on conventional electrical stimulation approaches have delivered limited efficacy, primarily due to the current spread in retinal tissue, which precludes high-acuity vision. The ideal prosthetic solution would be less invasive, provide single-cell resolution and an ability to differentiate between different cell types. Nanoparticle-mediated approaches can address some of these requirements, with particular attention being directed at light-sensitive nanoparticles that can be accessed via the intrinsic optics of the eye. Here we survey the available known nanoparticle-based optical transduction mechanisms that can be exploited for neuromodulation. We review the rapid progress in the field, together with outstanding challenges that must be addressed to translate these techniques to clinical practice. In particular, successful translation will likely require efficient delivery of nanoparticles to stable and precisely defined locations in the retinal tissues. Therefore, we also emphasize the current literature relating to the pharmacokinetics of nanoparticles in the eye. While considerable challenges remain to be overcome, progress to date shows great potential for nanoparticle-based interfaces to revolutionize the field of visual prostheses.
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Affiliation(s)
- Paul R. Stoddart
- School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, VIC, Australia
| | - James M. Begeng
- School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, VIC, Australia
- Department of Biomedical Engineering, Faculty of Engineering & Information Technology, The University of Melbourne, Melbourne, VIC, Australia
| | - Wei Tong
- Department of Biomedical Engineering, Faculty of Engineering & Information Technology, The University of Melbourne, Melbourne, VIC, Australia
- School of Physics, The University of Melbourne, Melbourne, VIC, Australia
| | - Michael R. Ibbotson
- Department of Biomedical Engineering, Faculty of Engineering & Information Technology, The University of Melbourne, Melbourne, VIC, Australia
| | - Tatiana Kameneva
- School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, VIC, Australia
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2
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Shinozaki Y, Saito K, Kashiwagi K, Koizumi S. Ocular P2 receptors and glaucoma. Neuropharmacology 2023; 222:109302. [PMID: 36341810 DOI: 10.1016/j.neuropharm.2022.109302] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 10/08/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022]
Abstract
Adenosine triphosphate (ATP), an energy source currency in cells, is released or leaked to the extracellular space under both physiological and pathological conditions. Extracellular ATP functions as an intercellular signaling molecule through activation of purinergic P2 receptors. Ocular tissue and cells release ATP in response to physiological stimuli such as intraocular pressure (IOP), and P2 receptor activation regulates IOP elevation or reduction. Dysregulated purinergic signaling may cause abnormally elevated IOP, which is one of the major risk factors for glaucoma. Glaucoma, a leading cause of blindness worldwide, is characterized by progressive degeneration of optic nerves and retinal ganglion cells (RGCs), which are essential retinal neurons that transduce visual information to the brain. An elevation in IOP may stress RGCs and increase the risk for glaucoma pathogenesis. In the aqueous humor of human patients with glaucoma, the ATP level is significantly elevated. Such excess amount of ATP may directly cause RGC death via a specific subtype of P2 receptors. Dysregulated purinergic signaling may also trigger inflammation, oxidative stress, and excitotoxicity via activating non-neuronal cell types such as glial cells. In this review, we discussed the physiological roles of extracellular nucleotides in the ocular tissue and their potential role in the pathogenesis of glaucoma. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.
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Affiliation(s)
- Youichi Shinozaki
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan; Interdisciplinary Brain-Immune Research Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kozo Saito
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kenji Kashiwagi
- Department of Ophthalmology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan; Interdisciplinary Brain-Immune Research Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.
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3
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Fletcher EL. Advances in understanding the mechanisms of retinal degenerations. Clin Exp Optom 2020; 103:723-732. [PMID: 33090561 DOI: 10.1111/cxo.13146] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 08/21/2020] [Accepted: 08/23/2020] [Indexed: 01/13/2023] Open
Abstract
Photoreceptor death is an important contributor to irreversible vision loss worldwide. In this review, I outline our work examining the role that purines, such as adenosine triphosphate (ATP), have in normal retinal function and in retinal disease. Our work shows that the actions of ATP, mediated by P2X receptors, are expressed in various retinal layers including photoreceptor terminals, and when stimulated by excessive levels of ATP is associated with rapid death of neurons. Treatment with a compound that blocks the action of P2X and some P2Y receptors reduces photoreceptor death in a mouse model of retinal degeneration. Our observations not only provide a means for developing a potential treatment for reducing photoreceptor death, but also provides a novel way of studying the neural plasticity effects that develop in the inner retina following photoreceptor death. There are a range of inner retinal changes that could influence the effectiveness of retinal prostheses. Indeed, using an ATP-induced degeneration model, we established that the amount of electrical stimulation required to elicit a response in the visual cortex was affected by the level of glial scarring. However, changes in P2X7 receptor expression by OFF ganglion cells during retinal degeneration can also be exploited by photoswitches to restore light sensitivity to degenerated retinae. Finally, our work has also considered how P2X7 expression by innate immune cells, and its role as a scavenger receptor, contributes to age-related macular degeneration (AMD). Our results show that loss of P2X7 function is associated with thickening of Bruch's membrane as well as increased risk of advanced disease in people with AMD. Overall, our work over the last 20 years highlights the importance of purinergic signalling in normal retinal function and retinal disease and suggest that developing therapies that target P2X7 function could be of benefit for these diseases.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Neuroscience, The University of Melbourne, Melbourne, Victoria, Australia
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4
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Yan W, Laboulaye MA, Tran NM, Whitney IE, Benhar I, Sanes JR. Mouse Retinal Cell Atlas: Molecular Identification of over Sixty Amacrine Cell Types. J Neurosci 2020; 40:5177-5195. [PMID: 32457074 PMCID: PMC7329304 DOI: 10.1523/jneurosci.0471-20.2020] [Citation(s) in RCA: 149] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 05/07/2020] [Accepted: 05/13/2020] [Indexed: 02/01/2023] Open
Abstract
Amacrine cells (ACs) are a diverse class of interneurons that modulate input from photoreceptors to retinal ganglion cells (RGCs), rendering each RGC type selectively sensitive to particular visual features, which are then relayed to the brain. While many AC types have been identified morphologically and physiologically, they have not been comprehensively classified or molecularly characterized. We used high-throughput single-cell RNA sequencing to profile >32,000 ACs from mice of both sexes and applied computational methods to identify 63 AC types. We identified molecular markers for each type and used them to characterize the morphology of multiple types. We show that they include nearly all previously known AC types as well as many that had not been described. Consistent with previous studies, most of the AC types expressed markers for the canonical inhibitory neurotransmitters GABA or glycine, but several expressed neither or both. In addition, many expressed one or more neuropeptides, and two expressed glutamatergic markers. We also explored transcriptomic relationships among AC types and identified transcription factors expressed by individual or multiple closely related types. Noteworthy among these were Meis2 and Tcf4, expressed by most GABAergic and most glycinergic types, respectively. Together, these results provide a foundation for developmental and functional studies of ACs, as well as means for genetically accessing them. Along with previous molecular, physiological, and morphologic analyses, they establish the existence of at least 130 neuronal types and nearly 140 cell types in the mouse retina.SIGNIFICANCE STATEMENT The mouse retina is a leading model for analyzing the development, structure, function, and pathology of neural circuits. A complete molecular atlas of retinal cell types provides an important foundation for these studies. We used high-throughput single-cell RNA sequencing to characterize the most heterogeneous class of retinal interneurons, amacrine cells, identifying 63 distinct types. The atlas includes types identified previously as well as many novel types. We provide evidence for the use of multiple neurotransmitters and neuropeptides, and identify transcription factors expressed by groups of closely related types. Combining these results with those obtained previously, we proposed that the mouse retina contains ∼130 neuronal types and is therefore comparable in complexity to other regions of the brain.
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Affiliation(s)
- Wenjun Yan
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Mallory A Laboulaye
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Nicholas M Tran
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Irene E Whitney
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Inbal Benhar
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142
| | - Joshua R Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
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5
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The Role of Purinergic Receptors in the Circadian System. Int J Mol Sci 2020; 21:ijms21103423. [PMID: 32408622 PMCID: PMC7279285 DOI: 10.3390/ijms21103423] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 12/24/2022] Open
Abstract
The circadian system is an internal time-keeping system that synchronizes the behavior and physiology of an organism to the 24 h solar day. The master circadian clock, the suprachiasmatic nucleus (SCN), resides in the hypothalamus. It receives information about the environmental light/dark conditions through the eyes and orchestrates peripheral oscillators. Purinergic signaling is mediated by extracellular purines and pyrimidines that bind to purinergic receptors and regulate multiple body functions. In this review, we highlight the interaction between the circadian system and purinergic signaling to provide a better understanding of rhythmic body functions under physiological and pathological conditions.
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6
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Yamagata M, Sanes JR. Expression and Roles of the Immunoglobulin Superfamily Recognition Molecule Sidekick1 in Mouse Retina. Front Mol Neurosci 2019; 11:485. [PMID: 30687002 PMCID: PMC6333872 DOI: 10.3389/fnmol.2018.00485] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 12/13/2018] [Indexed: 12/24/2022] Open
Abstract
Processes of >100 types of interneurons (bipolar and amacrine cells) and projection neurons (retinal ganglion cells, RGCs) form specific and stereotyped patterns of connections in the inner plexiform layer (IPL) of the mouse retina. Four closely related homophilic immunoglobulin superfamily recognition molecules (Sidekick [Sdk] 1, Sdk 2, Dscam, and DscamL1) have been shown to play roles in patterning neuronal arbors and connections in chick retina, and all but Sdk1 have been shown to play related roles in mice. Here, we compare patterns of Sdk1 and Sdk2 expression in mouse retina and use genetic methods to assess roles of Sdk1. In adult retina, 3 neuronal types express sdk1 but not sdk2 at detectable levels, 5 express sdk2 but not sdk1 and 3 express both. Patterns of gene expression and protein localization at or near synapses are established during the first postnatal week. Dendrites of amacrine cells and RGCs that express sdk1 but not sdk2 arborize in the same narrow stratum in the center of the IPL. In the absence of Sdk1, this laminar restriction is degraded. Overexpression of sdk1 in developing cells that normally express sdk2 reorients their dendrites to resemble those of endogenously Sdk1-positive cells, indicating that Sdk1 plays an instructive role in patterning the IPL. Sdk1 fails to affect arbors when introduced after they are mature, suggesting that it is required to form but not maintain laminar restrictions. The effect of ectopically expressed sdk1 requires the presence of endogenous Sdk1, suggesting that the effect requires homophilic interactions among Sdk1-positive neurites. Together with previous results on Sdk2, Dscam, DscamL1, as well as the related Contactins, our results support the idea that an elaborate immunoglobulin superfamily code plays a prominent role in establishing neural circuits in the retina by means of tightly regulated cell type-specific expression and homophilically restricted intercellular interactions.
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Affiliation(s)
- Masahito Yamagata
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, MA, United States
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, MA, United States
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7
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Ventura ALM, Dos Santos-Rodrigues A, Mitchell CH, Faillace MP. Purinergic signaling in the retina: From development to disease. Brain Res Bull 2018; 151:92-108. [PMID: 30458250 DOI: 10.1016/j.brainresbull.2018.10.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/14/2018] [Accepted: 10/23/2018] [Indexed: 02/07/2023]
Abstract
Retinal injuries and diseases are major causes of human disability involving vision impairment by the progressive and permanent loss of retinal neurons. During development, assembly of this tissue entails a successive and overlapping, signal-regulated engagement of complex events that include proliferation of progenitors, neurogenesis, cell death, neurochemical differentiation and synaptogenesis. During retinal damage, several of these events are re-activated with both protective and detrimental consequences. Purines and pyrimidines, along with their metabolites are emerging as important molecules regulating both retinal development and the tissue's responses to damage. The present review provides an overview of the purinergic signaling in the developing and injured retina. Recent findings on the presence of vesicular and channel-mediated ATP release by retinal and retinal pigment epithelial cells, adenosine synthesis and release, expression of receptors and intracellular signaling pathways activated by purinergic signaling in retinal cells are reported. The pathways by which purinergic receptors modulate retinal cell proliferation, migration and death of retinal cells during development and injury are summarized. The contribution of nucleotides to the self-repair of the injured zebrafish retina is also discussed.
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Affiliation(s)
- Ana Lucia Marques Ventura
- Department of Neurobiology, Neuroscience Program, Fluminense Federal University, Niterói, RJ, Brazil.
| | | | - Claire H Mitchell
- Department of Anatomy and Cell Biology, Ophthalmology, and Physiology, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - Maria Paula Faillace
- Instituto de Fisiología y Biofísica Prof. Bernardo Houssay (IFIBIO-Houssay), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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8
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2016 Glenn A. Fry Award Lecture: Mechanisms and Potential Treatments of Early Age-Related Macular Degeneration. Optom Vis Sci 2017; 94:939-945. [DOI: 10.1097/opx.0000000000001124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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9
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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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Ho T, Aplin FP, Jobling AI, Phipps JA, de Iongh RU, Greferath U, Vessey KA, Fletcher EL. Localization and Possible Function of P2X Receptors in Normal and Diseased Retinae. J Ocul Pharmacol Ther 2016; 32:509-517. [DOI: 10.1089/jop.2015.0158] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Tracy Ho
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Felix P. Aplin
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Andrew I. Jobling
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Joanna A. Phipps
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Robb U. de Iongh
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Ursula Greferath
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Kirstan A. Vessey
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
| | - Erica L. Fletcher
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Australia
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11
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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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12
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Carracedo G, Crooke A, Guzman-Aranguez A, Pérez de Lara MJ, Martin-Gil A, Pintor J. The role of dinucleoside polyphosphates on the ocular surface and other eye structures. Prog Retin Eye Res 2016; 55:182-205. [PMID: 27421962 DOI: 10.1016/j.preteyeres.2016.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 06/30/2016] [Accepted: 07/05/2016] [Indexed: 11/17/2022]
Abstract
Dinucleoside polyphosphates comprises a group of dinucleotides formed by two nucleosides linked by a variable number of phosphates, abbreviated NpnN (where n represents the number of phosphates). These compounds are naturally occurring substances present in tears, aqueous humour and in the retina. As the consequence of their presence, these dinucleotides contribute to many ocular physiological processes. On the ocular surface, dinucleoside polyphosphates can stimulate tear secretion, mucin release from goblet cells and they help epithelial wound healing by accelerating cell migration rate. These dinucleotides can also stimulate the presence of proteins known to protect the ocular surface against microorganisms, such as lysozyme and lactoferrin. One of the latest discoveries is the ability of some dinucleotides to facilitate the paracellular way on the cornea, therefore allowing the delivery of compounds, such as antiglaucomatous ones, more easily within the eye. The compound Ap4A has been described being abnormally elevated in patient's tears suffering of dry eye, Sjogren syndrome, congenital aniridia, or after refractive surgery, suggesting this molecule as biomarker for dry eye condition. At the intraocular level, some diadenosine polyphosphates are abnormally elevated in glaucoma patients, and this can be related to the stimulation of a P2Y2 receptor that increases the chloride efflux and water movement in the ciliary epithelium. In the retina, the dinucleotide dCp4U, has been proven to be useful to help in the recovery of retinal detachments. Altogether, dinucleoside polyphosphates are a group of compounds which present relevant physiological actions but which also can perform promising therapeutic benefits.
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Affiliation(s)
- Gonzalo Carracedo
- Department of Optics II (Optometry and Vision), Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Almudena Crooke
- Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Ana Guzman-Aranguez
- Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Maria J Pérez de Lara
- Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Alba Martin-Gil
- Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Jesús Pintor
- Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain.
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13
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Chavda S, Luthert PJ, Salt TE. P2X 7R modulation of visually evoked synaptic responses in the retina. Purinergic Signal 2016; 12:611-625. [PMID: 27393519 PMCID: PMC5123999 DOI: 10.1007/s11302-016-9522-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 06/24/2016] [Indexed: 10/29/2022] Open
Abstract
P2X7Rs are distributed throughout all layers of the retina, and thus, their localisation on various cell types puts into question their specific site(s) of action. Using a dark-adapted, ex vivo mouse retinal whole mount preparation, the present study aimed to characterise the effect of P2X7R activation on light-evoked, excitatory RGC ON-field excitatory post-synaptic potentials (fEPSPs) and on outer retinal electroretinogram (ERG) responses under comparable conditions. The pharmacologically isolated NMDA receptor-mediated RGC ON-fEPSP was reduced in the presence of BzATP, an effect which was significantly attenuated by A438079 and other selective P2X7R antagonists A804598 or AF27139. In physiological Krebs medium, BzATP induced a significant potentiation of the ERG a-wave, with a concomitant reduction in the b-wave and the power of the oscillatory potentials. Conversely, in the pharmacologically modified Mg2+-free perfusate, BzATP reduced both the a-wave and b-wave. The effects of BzATP on the ERG components were suppressed by A438079. A role for P2X7R function in visual processing in both the inner and outer retina under physiological conditions remains controversial. The ON-fEPSP was significantly reduced in the presence of A804598 but not by A438079 or AF27139. Furthermore, A438079 did not have any effect on the ERG components in physiological Krebs but potentiated and reduced the a-wave and b-wave, respectively, when applied to the pharmacologically modified medium. Therefore, activation of P2X7Rs affects the function in the retinal ON pathway. The presence of a high concentration of extracellular ATP would most likely contribute to the modulation of visual transmission in the retina in the pathophysiological microenvironment.
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Affiliation(s)
- Seetal Chavda
- Visual Neuroscience, UCL Institute of Ophthalmology, London, EC1V 9EL, UK
| | - Philip J Luthert
- Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, London, EC1V 9EL, UK.,NIHR Biomedical Research Centre in Ophthalmology, London, EC1V 9EL, UK
| | - Thomas E Salt
- Visual Neuroscience, UCL Institute of Ophthalmology, London, EC1V 9EL, UK.
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Ho T, Jobling AI, Greferath U, Chuang T, Ramesh A, Fletcher EL, Vessey KA. Vesicular expression and release of ATP from dopaminergic neurons of the mouse retina and midbrain. Front Cell Neurosci 2015; 9:389. [PMID: 26500494 PMCID: PMC4593860 DOI: 10.3389/fncel.2015.00389] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 09/17/2015] [Indexed: 12/20/2022] Open
Abstract
Vesicular nucleotide transporter (VNUT) is required for active accumulation of adenosine tri-phosphate (ATP) into vesicles for purinergic neurotransmission, however, the cell types that express VNUT in the central nervous system remain unknown. This study characterized VNUT expression within the mammalian retina and brain and assessed a possible functional role in purinergic signaling. Two native isoforms of VNUT were detected in mouse retina and brain based on RNA transcript and protein analysis. Using immunohistochemistry, VNUT was found to co-localize with tyrosine hydroxylase (TH) positive, dopaminergic (DA) neurons of the substantia nigra and ventral tegmental area, however, VNUT expression in extranigral non-DA neurons was also observed. In the retina, VNUT labeling was found to co-localize solely with TH-positive DA-cells. In the outer retina, VNUT-positive interplexiform cell processes were in close contact with horizontal cells and cone photoreceptor terminals, which are known to express P2 purinergic-receptors. In order to assess function, dissociated retinal neurons were loaded with fluorescent ATP markers (Quinacrine or Mant-ATP) and the DA marker FFN102, co-labeled with a VNUT antibody and imaged in real time. Fluorescent ATP markers and FFN102 puncta were found to co-localize in VNUT positive neurons and upon stimulation with high potassium, ATP marker fluorescence at the cell membrane was reduced. This response was blocked in the presence of cadmium. These data suggest DA neurons co-release ATP via calcium dependent exocytosis and in the retina this may modulate the visual response by activating purine receptors on closely associated neurons.
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Affiliation(s)
- Tracy Ho
- Visual Neuroscience Laboratory, Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
| | - Andrew I Jobling
- Visual Neuroscience Laboratory, Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
| | - Ursula Greferath
- Visual Neuroscience Laboratory, Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
| | - Trinette Chuang
- Polyclonal Antibody Development, R&D Antibody Development, EMD Millipore Temecula, CA, USA
| | - Archana Ramesh
- Polyclonal Antibody Development, R&D Antibody Development, EMD Millipore Temecula, CA, USA
| | - Erica L Fletcher
- Visual Neuroscience Laboratory, Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
| | - Kirstan A Vessey
- Visual Neuroscience Laboratory, Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
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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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Greferath U, Vessey KA, Jobling AI, Mills SA, Bui BV, He Z, Nag N, Ohtsu H, Fletcher EL. The role of histamine in the retina: studies on the Hdc knockout mouse. PLoS One 2014; 9:e116025. [PMID: 25545149 PMCID: PMC4278841 DOI: 10.1371/journal.pone.0116025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 12/01/2014] [Indexed: 12/18/2022] Open
Abstract
The role of histamine in the retina is not well understood, despite it regulating a number of functions within the brain, including sleep, feeding, energy balance, and anxiety. In this study we characterized the structure and function of the retina in mice that lacked expression of the rate limiting enzyme in the formation of histamine, histidine decarboxylase (Hdc−/− mouse). Using laser capture microdissection, Hdc mRNA expression was assessed in the inner and outer nuclear layers of adult C57Bl6J wildtype (WT) and Hdc−/−-retinae. In adult WT and Hdc−/−-mice, retinal fundi were imaged, retinal structure was assessed using immunocytochemistry and function was probed by electroretinography. Blood flow velocity was assessed by quantifying temporal changes in the dynamic fluorescein angiography in arterioles and venules. In WT retinae, Hdc gene expression was detected in the outer nuclear layer, but not the inner nuclear layer, while the lack of Hdc expression was confirmed in the Hdc−/− retina. Preliminary examination of the fundus and retinal structure of the widely used Hdc−/−mouse strain revealed discrete lesions across the retina that corresponded to areas of photoreceptor abnormality reminiscent of the rd8 (Crb1) mutation. This was confirmed after genotyping and the strain designated Hdcrd8/rd8. In order to determine the effect of the lack of Hdc-alone on the retina, Hdc−/− mice free of the Crb1 mutation were bred. Retinal fundi appeared normal in these animals and there was no difference in retinal structure, macrogliosis, nor any change in microglial characteristics in Hdc−/− compared to wildtype retinae. In addition, retinal function and retinal blood flow dynamics showed no alterations in the Hdc−/− retina. Overall, these results suggest that histamine plays little role in modulating retinal structure and function.
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Affiliation(s)
- Ursula Greferath
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Kirstan A. Vessey
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Andrew I. Jobling
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Samuel A. Mills
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Bang V. Bui
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Nupur Nag
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Hiroshi Ohtsu
- Department of Engineering, Medical School of Tohoku University, Sendai, Japan
| | - Erica L. Fletcher
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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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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Vessey KA, Greferath U, Aplin FP, Jobling AI, Phipps JA, Ho T, De Iongh RU, Fletcher EL. Adenosine triphosphate-induced photoreceptor death and retinal remodeling in rats. J Comp Neurol 2014; 522:2928-50. [PMID: 24639102 PMCID: PMC4265795 DOI: 10.1002/cne.23558] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 02/06/2014] [Accepted: 02/07/2014] [Indexed: 02/06/2023]
Abstract
Many common causes of blindness involve the death of retinal photoreceptors, followed by progressive inner retinal cell remodeling. For an inducible model of retinal degeneration to be useful, it must recapitulate these changes. Intravitreal administration of adenosine triphosphate (ATP) has recently been found to induce acute photoreceptor death. The aim of this study was to characterize the chronic effects of ATP on retinal integrity. Five-week-old, dark agouti rats were administered 50 mM ATP into the vitreous of one eye and saline into the other. Vision was assessed using the electroretinogram and optokinetic response and retinal morphology investigated via histology. ATP caused significant loss of visual function within 1 day and loss of 50% of the photoreceptors within 1 week. At 3 months, 80% of photoreceptor nuclei were lost, and total photoreceptor loss occurred by 6 months. The degeneration and remodeling were similar to those found in heritable retinal dystrophies and age-related macular degeneration and included inner retinal neuronal loss, migration, and formation of new synapses; Müller cell gliosis, migration, and scarring; blood vessel loss; and retinal pigment epithelium migration. In addition, extreme degeneration and remodeling events, such as neuronal and glial migration outside the neural retina and proliferative changes in glial cells, were observed. These extreme changes were also observed in the 2-year-old P23H rhodopsin transgenic rat model of retinitis pigmentosa. This ATP-induced model of retinal degeneration may provide a valuable tool for developing pharmaceutical therapies or for testing electronic implants aimed at restoring vision.
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Affiliation(s)
- Kirstan A Vessey
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Ursula Greferath
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Felix P Aplin
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital,East Melbourne, Victoria, 3002, Australia
- The Bionics Institute,East Melbourne, Victoria, 3002, Australia
| | - Andrew I Jobling
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Joanna A Phipps
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Tracy Ho
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Robbert U De Iongh
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
| | - Erica L Fletcher
- Department of Anatomy and Neuroscience, The University of Melbourne,Melbourne, Victoria, 3010, Australia
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Sanderson J, Dartt DA, Trinkaus-Randall V, Pintor J, Civan MM, Delamere NA, Fletcher EL, Salt TE, Grosche A, Mitchell CH. Purines in the eye: recent evidence for the physiological and pathological role of purines in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland. Exp Eye Res 2014; 127:270-9. [PMID: 25151301 DOI: 10.1016/j.exer.2014.08.009] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/24/2014] [Accepted: 08/12/2014] [Indexed: 12/21/2022]
Abstract
This review highlights recent findings that describ how purines modulate the physiological and pathophysiological responses of ocular tissues. For example, in lacrimal glands the cross-talk between P2X7 receptors and both M3 muscarinic receptors and α1D-adrenergic receptors can influence tear secretion. In the cornea, purines lead to post-translational modification of EGFR and structural proteins that participate in wound repair in the epithelium and influence the expression of matrix proteins in the stroma. Purines act at receptors on both the trabecular meshwork and ciliary epithelium to modulate intraocular pressure (IOP); ATP-release pathways of inflow and outflow cells differ, possibly permitting differential modulation of adenosine delivery. Modulators of trabecular meshwork cell ATP release include cell volume, stretch, extracellular Ca(2+) concentration, oxidation state, actin remodeling and possibly endogenous cardiotonic steroids. In the lens, osmotic stress leads to ATP release following TRPV4 activation upstream of hemichannel opening. In the anterior eye, diadenosine polyphosphates such as Ap4A act at P2 receptors to modulate the rate and composition of tear secretion, impact corneal wound healing and lower IOP. The Gq11-coupled P2Y1-receptor contributes to volume control in Müller cells and thus the retina. P2X receptors are expressed in neurons in the inner and outer retina and contribute to visual processing as well as the demise of retinal ganglion cells. In RPE cells, the balance between extracellular ATP and adenosine may modulate lysosomal pH and the rate of lipofuscin formation. In optic nerve head astrocytes, mechanosensitive ATP release via pannexin hemichannels, coupled with stretch-dependent upregulation of pannexins, provides a mechanism for ATP signaling in chronic glaucoma. With so many receptors linked to divergent functions throughout the eye, ensuring the transmitters remain local and stimulation is restricted to the intended target may be a key issue in understanding how physiological signaling becomes pathological in ocular disease.
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Affiliation(s)
| | - Darlene A Dartt
- Schepens Eye Research Institute/Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Vickery Trinkaus-Randall
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA, USA; Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Jesus Pintor
- Department of Biochemistry, Faculty of Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Mortimer M Civan
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Nicholas A Delamere
- Department of Physiology, University of Arizona, Tucson, AZ, USA; Department of Ophthalmology and Vision Science, University of Arizona, Tucson, AZ, USA
| | - Erica L Fletcher
- Department of Anatomy and of Neuroscience, University of Melbourne, Victoria, Australia
| | - Thomas E Salt
- Department of Visual Neuroscience, UCL Institute of Ophthalmology, London, UK
| | - Antje Grosche
- Institute of Human Genetics, Franz-Josef-Strauß-Allee, Regensburg, Germany
| | - Claire H Mitchell
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, USA.
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Vitanova LA, Kupenova PN. Ionotropic purinergic receptors P2X in frog and turtle retina: glial and neuronal localization. Acta Histochem 2014; 116:694-701. [PMID: 24461518 DOI: 10.1016/j.acthis.2013.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 12/12/2013] [Accepted: 12/16/2013] [Indexed: 12/15/2022]
Abstract
Purinergic signaling is represented in both the peripheral and central nervous system (CNS), and in particular in the retina, which may be regarded as a part of the CNS. While purigenic signaling is relatively well studied in mammalian retinas, little is known about it in retinas of lower vertebrates. The aim of present study was to investigate, using immunocytochemistry, the distribution of purinoreceptors P2X in retinas of frog and turtle, which are appropriate models of the brain neuron-to-glia interactions. The results showed widespread expression of all seven ionotropic purinoreceptors (P2X1-P2X7) in both frog and turtle retinas. They were predominantly expressed in Müller cells, the principal glial cells in the retina. All structures typical of Müller cells: the outer and the inner limiting membranes, the cells bodies in the inner nuclear layer, the radial processes in the inner plexiform layer (IPL), and the so called endfeet (frog) or the orthogonal arrays of particles (turtle) in the ganglion cells layer were immunostained. Colocalizations between P2X1-P2X7 and the glial cell marker Vimentin proved that the immunostaining was in the Müller cells. In addition to the glial staining, neuronal staining was also seen as fine puncta in the inner plexiform layer and by small dots and patches in the outer plexiform layer. Some cell bodies of horizontal, amacrine and ganglion cells were also stained. The results obtained imply that the purinergic P2X receptors may significantly contribute to the neuron-to-glia signaling in retinas of the lower vertebrates.
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22
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Guzman-Aranguez A, Santano C, Martin-Gil A, Fonseca B, Pintor J. Nucleotides in the eye: focus on functional aspects and therapeutic perspectives. J Pharmacol Exp Ther 2013; 345:331-41. [PMID: 23504005 DOI: 10.1124/jpet.112.202473] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The presence and activity of nucleotides and dinucleotides in the physiology of most, if not all, organisms, from bacteria to humans, have been recognized by the scientific community, and the eye is no exception. Nucleotides in the dynamic fluids interact with many ocular structures, such as the tears and aqueous humor. Moreover, high concentrations of nucleotides in these secretions may reflect disease states such as dry eye and glaucoma. Apart from the nucleotide concentration in these fluids, P2 purinergic receptors have been described on the ocular surface (cornea and conjunctiva), anterior pole (ciliary body, trabecular meshwork), and posterior pole (retina). P2X and P2Y purinergic receptors are essential in maintaining the homeostasis of ocular processes, such as tear secretion, aqueous humor production, or retinal modulation. When they are functioning properly, they allow the eye to do its job (to see), but in some cases, a lack or an excess of nucleotides or a malfunction in the corresponding purinergic receptors leads to disease. This Perspective is focused on the nucleotides and dinucleotides and the P2 purinergic receptors in the eye and how they contribute to normal and disease states. We also emphasize the action of nucleotides and their receptors and antagonists as potential therapeutic agents.
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Affiliation(s)
- Ana Guzman-Aranguez
- Department of Biochemistry and Molecular Biology, Faculty of Optics and Optometry, Universidad Complutense Madrid, C/Arcos de Jalón 118, 28037 Madrid, Spain
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Ford AP. P2X3 antagonists: novel therapeutics for afferent sensitization and chronic pain. Pain Manag 2012; 2:267-77. [DOI: 10.2217/pmt.12.16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
SUMMARY Despite decades of innovation and effort, the pharmaceutical needs of countless patients with chronic pain remain underserved. Effective and safe treatments must clearly come from novel approaches, yet targets and molecules selected hitherto have returned little benefit. Antagonism of P2X3 purinoceptors on pain-conveying nerves is a highly novel approach, and compounds from this class are advancing into patient studies. P2X3 channels are found in C- and Aδ-primary afferent neurons in most tissues, and are strikingly specific to pain detection. P2X3 antagonists block peripheral activation of these fibers via ATP, released from most cells by inflammation, injury, stress and distension, and clearly provide an alternative pharmacological mechanism to attenuate pain signals. P2X3 is also expressed presynaptically at central spinal terminals of afferent neurons, where ATP further sensitizes painful signals en route to the brain. The selectivity of P2X3 expression allows hope of a lower potential for adverse effects in brain, gut and cardiovascular tissues – limiting factors for most analgesics. P2X3 receptor-mediated sensitization has been implicated in rodent models in inflammatory, visceral, neuropathic and cancer pain states, as well as in airways hyper-reactivity, migraine and visceral organ irritability. Although we are often reminded that the effects of new medicines can translate poorly into clinical effectiveness, the broad efficacy seen following P2X3 inhibition in rodent models strengthens the prospect that an unprecedented mechanism to counter sensitization of afferent pathways may offer some merciful relief to millions of patients struggling daily with persistent discomfort and pain.
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Affiliation(s)
- Anthony P Ford
- Afferent Pharmaceuticals, 2755 Campus Drive, Suite 100, San Mateo, CA 94403, USA
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Vessey KA, Fletcher EL. Rod and cone pathway signalling is altered in the P2X7 receptor knock out mouse. PLoS One 2012; 7:e29990. [PMID: 22253851 PMCID: PMC3254638 DOI: 10.1371/journal.pone.0029990] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 12/11/2011] [Indexed: 01/27/2023] Open
Abstract
The P2X7 receptor (P2X7-R) is expressed in the retina and brain and has been implicated in neurodegenerative diseases. However, whether it is expressed by neurons and plays a role as a neurotransmitter receptor has been the subject of controversy. In this study, we first show that the novel vesicular transporter for ATP, VNUT, is expressed in the retina, verifying the presence of the molecular machinery for ATP to act as neurotransmitter at P2X7-Rs. Secondly we show the presence of P2X7-R mRNA and protein in the retina and cortex and absence of the full length variant 1 of the receptor in the P2X7-R knock out (P2X7-KO) mouse. The role of the P2X7-R in neuronal function of the retina was assessed by comparing the electroretinogram response of P2X7-KO with WT mice. The rod photoreceptor response was found to be similar, while both rod and cone pathway post-photoreceptor responses were significantly larger in P2X7-KO mice. This suggests that activation of P2X7-Rs modulates output of second order retinal neurons. In line with this finding, P2X7-Rs were found in the outer plexiform layer and on inner retinal cell classes, including horizontal, amacrine and ganglion cells. The receptor co-localized with conventional synapses in the IPL and was expressed on amacrine cells post-synaptic to rod bipolar ribbon synapses. In view of the changes in visual function in the P2X7-KO mouse and the immunocytochemical location of the receptor in the normal retina, it is likely the P2X7-R provides excitatory input to photoreceptor terminals or to inhibitory cells that shape both the rod and cone pathway response.
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Affiliation(s)
- Kirstan A. Vessey
- Department of Anatomy and Cell Biology, The University of Melbourne, Melbourne, Victoria, Australia
| | - Erica L. Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Melbourne, Victoria, Australia
- * E-mail:
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In pursuit of P2X3 antagonists: novel therapeutics for chronic pain and afferent sensitization. Purinergic Signal 2011; 8:3-26. [PMID: 22095157 PMCID: PMC3265711 DOI: 10.1007/s11302-011-9271-6] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 09/19/2011] [Indexed: 12/20/2022] Open
Abstract
Treating pain by inhibiting ATP activation of P2X3-containing receptors heralds an exciting new approach to pain management, and Afferent's program marks the vanguard in a new class of drugs poised to explore this approach to meet the significant unmet needs in pain management. P2X3 receptor subunits are expressed predominately and selectively in so-called C- and Aδ-fiber primary afferent neurons in most tissues and organ systems, including skin, joints, and hollow organs, suggesting a high degree of specificity to the pain sensing system in the human body. P2X3 antagonists block the activation of these fibers by ATP and stand to offer an alternative approach to the management of pain and discomfort. In addition, P2X3 is expressed pre-synaptically at central terminals of C-fiber afferent neurons, where ATP further sensitizes transmission of painful signals. As a result of the selectivity of the expression of P2X3, there is a lower likelihood of adverse effects in the brain, gastrointestinal, or cardiovascular tissues, effects which remain limiting factors for many existing pain therapeutics. In the periphery, ATP (the factor that triggers P2X3 receptor activation) can be released from various cells as a result of tissue inflammation, injury or stress, as well as visceral organ distension, and stimulate these local nociceptors. The P2X3 receptor rationale has aroused a formidable level of investigation producing many reports that clarify the potential role of ATP as a pain mediator, in chronic sensitized states in particular, and has piqued the interest of pharmaceutical companies. P2X receptor-mediated afferent activation has been implicated in inflammatory, visceral, and neuropathic pain states, as well as in airways hyperreactivity, migraine, itch, and cancer pain. It is well appreciated that oftentimes new mechanisms translate poorly from models into clinical efficacy and effectiveness; however, the breadth of activity seen from P2X3 inhibition in models offers a realistic chance that this novel mechanism to inhibit afferent nerve sensitization may find its place in the sun and bring some merciful relief to the torment of persistent discomfort and pain. The development philosophy at Afferent is to conduct proof of concept patient studies and best identify target patient groups that may benefit from this new intervention.
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The role of purinergic receptors in retinal function and disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 664:385-91. [PMID: 20238039 DOI: 10.1007/978-1-4419-1399-9_44] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Extracellular ATP acts as a neurotransmitter in the central and peripheral nervous systems. In this review, the role of purinergic receptors in neuronal signaling and bi-directional glial-neuronal communication in the retina will be considered. There is growing evidence that a range of P2X and P2Y receptors are expressed on most classes of retinal neurons and that activation of P2 receptors modulates retinal function. Furthermore, neuronal control of glial function is achieved through neuronal release of ATP and activation of P2Y receptors expressed by Müller cells. Altered purinergic signaling in Müller cells has been implicated in gliotic changes in the diseased retina and furthermore, elevations in extracellular ATP may lead to apoptosis of retinal neurons.
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27
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Wurm A, Pannicke T, Iandiev I, Francke M, Hollborn M, Wiedemann P, Reichenbach A, Osborne NN, Bringmann A. Purinergic signaling involved in Müller cell function in the mammalian retina. Prog Retin Eye Res 2011; 30:324-42. [DOI: 10.1016/j.preteyeres.2011.06.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 06/06/2011] [Accepted: 06/06/2011] [Indexed: 10/18/2022]
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Abstract
The development of treatments that slow photoreceptor death could profoundly improve patient wellbeing in those with inherited retinal degenerations. Over recent years, it has emerged that extracellular adenosine-tri-phosphate (ATP) regulates the function of photoreceptors in rodents and primates. Moreover, when the retina is exposed to high levels of ATP, rapid death of photoreceptors occurs, which can be blocked by pretreatment with antagonists to P2X receptors. Compounds that inhibit the action of extracellular ATP slow photoreceptor loss in an animal model of inherited retinal degeneration. In this article, I provide an overview of our work in relation to other research in this area and suggest a model by which ATP contributes to photoreceptor death in inherited retinal degenerations.
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Acosta ML, Shin YS, Ready S, Fletcher EL, Christie DL, Kalloniatis M. Reply to “Letter to the editor: ‘Comments on retinal metabolic state in P23H and normal retinas’”. Am J Physiol Cell Physiol 2010. [DOI: 10.1152/ajpcell.00132.2010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | | | - Sarah Ready
- Department of Optometry and Vision Science and
| | - Erica L. Fletcher
- Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria; and
| | - David L. Christie
- Molecular, Cellular, and Developmental Biology, School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Michael Kalloniatis
- Department of Optometry and Vision Science and
- Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria; and
- Centre for Eye Health and
- School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
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Fletcher EL, Phipps JA, Ward MM, Vessey KA, Wilkinson-Berka JL. The renin-angiotensin system in retinal health and disease: Its influence on neurons, glia and the vasculature. Prog Retin Eye Res 2010; 29:284-311. [PMID: 20380890 DOI: 10.1016/j.preteyeres.2010.03.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Renin-Angiotensin System is classically recognized for its role in the control of systemic blood pressure. However, the retina is recognized to have all the components necessary for angiotensin II formation, suggestive of a role for Angiotensin II in the retina that is independent of the systemic circulation. The most well described effects of Angiotensin II are on the retinal vasculature, with roles in vasoconstriction and angiogenesis. However, it is now emerging that Angiotensin II has roles in modulation of retinal function, possibly in regulating GABAergic amacrine cells. In addition, Angiotensin II is likely to have effects on glia. Angiotensin II has also been implicated in retinal vascular diseases such as Retinopathy of Prematurity and diabetic retinopathty, and more recently actions in choroidal neovascularizaiton and glaucoma have also emerged. The mechanisms by which Angiotensin II promotes angiogensis in retinal vascular diseases is indicative of the complexity of the RAS and the variety of cell types that it effects. Indeed, these diseases are not purely characterized by direct effects of Angiotensin II on the vasculature. In retinopathy of prematurity, for example, blockade of AT1 receptors prevents pathological angiogenesis, but also promotes revascularization of avascular regions of the retina. The primary site of action of Angiotensin II in this disease may be on retinal glia, rather than the vasculature. Indeed, blockade of AT1 receptors prevents glial loss and promotes the re-establishment of normal vessel growth. Blockade of RAS as a treatment for preventing the incidence and progression of diabetic retinopathy has also emerged based on a series of studies in animal models showing that blockade of the RAS prevents the development of a variety of vascular and neuronal deficits in this disease. Importantly these effects may be independent of actions on systemic blood pressure. This has culminated recently with the completion of several large multi-centre clinical trials that showed that blockade of the RAS may be of benefit in some at risk patients with diabetes. With the emergence of novel compounds targeting different aspects of the RAS even more effective ways of blocking the RAS may be possible in the future.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville 3010, Victoria, Australia.
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Downie LE, Hatzopoulos KM, Pianta MJ, Vingrys AJ, Wilkinson-Berka JL, Kalloniatis M, Fletcher EL. Angiotensin type-1 receptor inhibition is neuroprotective to amacrine cells in a rat model of retinopathy of prematurity. J Comp Neurol 2010; 518:41-63. [DOI: 10.1002/cne.22205] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
P2X and P2Y nucleotide receptors are described on sensory neurons and their peripheral and central terminals in dorsal root, nodose, trigeminal, petrosal, retinal and enteric ganglia. Peripheral terminals are activated by ATP released from local cells by mechanical deformation, hypoxia or various local agents in the carotid body, lung, gut, bladder, inner ear, eye, nasal organ, taste buds, skin, muscle and joints mediating reflex responses and nociception. Purinergic receptors on fibres in the dorsal spinal cord and brain stem are involved in reflex control of visceral and cardiovascular activity, as well as relaying nociceptive impulses to pain centres. Purinergic mechanisms are enhanced in inflammatory conditions and may be involved in migraine, pain, diseases of the special senses, bladder and gut, and the possibility that they are also implicated in arthritis, respiratory disorders and some central nervous system disorders is discussed. Finally, the development and evolution of purinergic sensory mechanisms are considered.
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Stella SL, Hu WD, Brecha NC. Adenosine suppresses exocytosis from cone terminals of the salamander retina. Neuroreport 2009; 20:923-9. [PMID: 19491713 DOI: 10.1097/wnr.0b013e32832ca4b0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the retina, adenosine is released in the dark and has been shown to inhibit Ca2+ influx through voltage-gated Ca2+ channels in cones. Therefore, we tested whether adenosine can inhibit exocytosis from isolated cone photoreceptors. Simultaneous measurements of membrane exocytosis and Ca2+ were made from cones using the activity-dependent dye, Synaptored-C2, and the Ca2+ indicator dye, Fluo-4. Adenosine suppressed exocytosis in cones, indicating that transmitter release is also reduced from cone terminals, and further supports an inhibitory mechanism for modulating transmitter release onto second-order neurons. Furthermore, this raises the possibility that adenosine might be neuroprotective for photoreceptors and second-order neurons by suppressing Ca2+ levels in cones and reducing exocytosis of L-glutamate, respectively.
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Affiliation(s)
- Salvatore L Stella
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-1763, USA.
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Puthussery T, Fletcher E. Extracellular ATP induces retinal photoreceptor apoptosis through activation of purinoceptors in rodents. J Comp Neurol 2009; 513:430-40. [PMID: 19180669 DOI: 10.1002/cne.21964] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We have previously demonstrated that photoreceptors express P2X(7) purinoceptors. These excitatory receptors are activated by extracellular adenosine 5'-triphosphate (ATP) and have been implicated in neurodegeneration in other parts of the central nervous system (CNS). In this study we examined whether extracellular ATP could contribute to photoreceptor degeneration in rodents through excessive activation of P2 purinoceptors. Intravitreal injection of high concentrations of extracellular ATP into normal rat eyes induced extensive and selective apoptosis of photoreceptors within 18 hours of injection. Five days after injection the outer nuclear layer was severely degenerated and electroretinographic responses were impaired. Preinjection of the purinergic antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) protected against ATP-mediated apoptosis. The initial phase of ATP-induced photoreceptor death did not temporally coincide with retinal pigment epithelium degeneration or microglial activation, suggesting that cell death was due to direct activation of purinergic receptors on photoreceptors. Finally, we demonstrate that intravitreal injection of PPADS results in a 30% increase in photoreceptor survival in the rd1 mouse, a model of human recessive retinitis pigmentosa (RP). These findings highlight the importance of extracellular ATP in retinal neurodegeneration and provide a potential new avenue for therapeutic intervention in RP.
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Affiliation(s)
- Theresa Puthussery
- Department of Anatomy and Cell Biology, University of Melbourne, 3010, Victoria, Australia
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Ricatti MJ, Alfie LD, Lavoie EG, Sévigny J, Schwarzbaum PJ, Faillace MP. Immunocytochemical localization of NTPDases1 and 2 in the neural retina of mouse and zebrafish. Synapse 2009; 63:291-307. [PMID: 19116950 DOI: 10.1002/syn.20605] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) are a family of membrane-bound enzymes that hydrolyze extracellular di- and triphosphate nucleosides. E-NTPDases have been proposed to control extracellular nucleotide levels that mediate intercellular communication by binding to specific membrane receptors. Here we show a detailed immunocytochemical localization of two enzymes of the E-NTPDase family in the retinal layers of two vertebrate species, namely, the mouse and the zebrafish. In the mouse retina, NTPDase2 was chiefly localized in Müller glia and ganglion cell processes. NTPDase1 was located on neurons as well, since it was expressed by horizontal and ganglion cell processes, suggesting that nucleotides such as ATP and ADP can be hydrolyzed at the surface of these cells. NTPDase1 was also detected in intraretinal blood vessels of the mouse. Regarding zebrafish, NTPDases1 and 2 seem to be differentially localized in horizontal cell processes, photoreceptor segments, and ganglion cell dendrites and axons, but absent from Müller glia. Moreover, NTPDases1 and 2 appear to be expressed within the germinal margin of the zebrafish retina that contains proliferative and differentiating cells. Retinal homogenates from both species exhibited ecto-ATPase activity which might be attributed at least to NTPDases1 and 2, whose expression is described in this report. Our results suggest a compartmentalized regulation of extracellular nucleotide/nucleoside concentration in the retinal layers, supporting a relevant role for extracellular nucleotide mediated-signaling in vertebrate retinas.
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Affiliation(s)
- María Jimena Ricatti
- Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, C1121ABG, Ciudad Autónoma de Buenos Aires, Argentina
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Downie LE, Vessey K, Miller A, Ward MM, Pianta MJ, Vingrys AJ, Wilkinson-Berka JL, Fletcher EL. Neuronal and glial cell expression of angiotensin II type 1 (AT1) and type 2 (AT2) receptors in the rat retina. Neuroscience 2009; 161:195-213. [PMID: 19298848 DOI: 10.1016/j.neuroscience.2009.02.084] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2008] [Revised: 02/27/2009] [Accepted: 02/28/2009] [Indexed: 10/21/2022]
Abstract
The bio-active peptide, angiotensin II (Ang II), has been suggested to exert a neuromodulatory effect on inner retinal neurons. In this study, we examined the distribution of angiotensin receptors (ATRs) in the developing and mature rat retina and optic nerve using immunofluorescence immunocytochemistry. Double-labeling experiments were performed with established markers to identify different retinal cell populations. In adult retinae, ATRs were observed on neurons involved in "ON" pathways of neurotransmission. Angiotensin II type 1 receptors (AT(1)Rs) were expressed by a sub-population of "ON" cone bipolar cells that also labeled for G alpha(0) and islet-1. Extra-neuronal expression of AT(1)Rs was evident on retinal astrocytes, Müller cells and blood vessels. Immunoreactivity for the angiotensin II type 2 receptor (AT(2)R) was observed on conventional and displaced GABAergic amacrine cells. Co-localization studies showed that AT(2)R-expressing amacrine cells constituted at least two separate sub-populations. Cell counts revealed that all wide-field amacrine cells expressing protein kinase C-alpha were also AT(2)R-positive; a further subset of amacrine cells expressing AT(2)Rs and stratifying in sublamina "b" of the inner plexiform layer (IPL) was identified. Developmental expression of AT(1)Rs was dynamic, involving multiple inner neuronal classes. At postnatal day 8 (P8), AT(1)R immunoreactivity was observed on putative ganglion cells. The characteristic bipolar cell labeling observed in adults was not evident until P13. In contrast, AT(2)Rs were detected as early as P2 and localized specifically to amacrine cells from this age onward. These data provide further evidence for the potential role of angiotensin II in the modulation of retinal neurons and glia. The differential pattern of expression of these receptors across these cell types is similar to that observed in the brain and suggests that a similar functional role for Ang II may also exist within the retina.
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Affiliation(s)
- L E Downie
- Department of Anatomy and Cell Biology, The University of Melbourne, Grattan Street, Parkville 3010, Victoria, Australia 3010
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Housley GD, Bringmann A, Reichenbach A. Purinergic signaling in special senses. Trends Neurosci 2009; 32:128-41. [DOI: 10.1016/j.tins.2009.01.001] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/22/2008] [Accepted: 01/05/2009] [Indexed: 02/06/2023]
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Role of retinal glial cells in neurotransmitter uptake and metabolism. Neurochem Int 2009; 54:143-60. [DOI: 10.1016/j.neuint.2008.10.014] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 10/15/2008] [Accepted: 10/20/2008] [Indexed: 11/30/2022]
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Fletcher EL, Downie LE, Ly A, Ward MM, Batcha AH, Puthussery T, Yee P, Hatzopoulos KM. A review of the role of glial cells in understanding retinal disease. Clin Exp Optom 2008; 91:67-77. [PMID: 18045252 DOI: 10.1111/j.1444-0938.2007.00204.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Retinal vascular diseases such as diabetic retinopathy and retinopathy of prematurity are major causes of visual loss. Although the focus of a great deal of research has been on the aetiology of vascular growth, it is now emerging that anomalies in other retinal cell types, especially glial cells, occur very early in the course of the disease. Glial cells have major roles in every stage of disease, from the earliest subtle variations in neural function, to the development of epi-retinal membranes and tractional detachment. Therefore, having a firm understanding of the function of retinal glia is important in our understanding of retinal disease and is crucial for the development of new treatment strategies.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Victoria, Australia.
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Iandiev I, Wurm A, Pannicke T, Wiedemann P, Reichenbach A, Robson SC, Zimmermann H, Bringmann A. Ectonucleotidases in Müller glial cells of the rodent retina: Involvement in inhibition of osmotic cell swelling. Purinergic Signal 2007; 3:423-33. [PMID: 18404455 PMCID: PMC2072913 DOI: 10.1007/s11302-007-9061-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 07/10/2007] [Indexed: 11/20/2022] Open
Abstract
Extracellular nucleotides mediate glia-to-neuron signalling in the retina and are implicated in the volume regulation of retinal glial (Müller) cells under osmotic stress conditions. We investigated the expression and functional role of ectonucleotidases in Müller cells of the rodent retina by cell-swelling experiments, calcium imaging, and immuno- and enzyme histochemistry. The swelling of Müller cells under hypoosmotic stress was inhibited by activation of an autocrine purinergic signalling cascade. This cascade is initiated by exogenous glutamate and involves the consecutive activation of P2Y1 and adenosine A1 receptors, the action of ectoadenosine 5′-triphosphate (ATP)ases, and a nucleoside-transporter-mediated release of adenosine. Inhibition of ectoapyrases increased the ATP-evoked calcium responses in Müller cell endfeet. Müller cells were immunoreactive for nucleoside triphosphate diphosphohydrolases (NTPDase)2 (but not NTPDase1), ecto-5′-nucleotidase, P2Y1, and A1 receptors. Enzyme histochemistry revealed that ATP but not adenosine 5′-diphosphate (ADP) is extracellularly metabolised in retinal slices of NTPDase1 knockout mice. NTPDase1 activity and protein is restricted to blood vessels, whereas activity of alkaline phosphatase is essentially absent at physiological pH. The data suggest that NTPDase2 is the major ATP-degrading ectonucleotidase of the retinal parenchyma. NTPDase2 expressed by Müller cells can be implicated in the regulation of purinergic calcium responses and cellular volume.
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Affiliation(s)
- Ianors Iandiev
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
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