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Marchese NA, Ríos MN, Guido ME. Müller glial cell photosensitivity: a novel function bringing higher complexity to vertebrate retinal physiology. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2023. [DOI: 10.1016/j.jpap.2023.100162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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Tworig JM, Feller MB. Müller Glia in Retinal Development: From Specification to Circuit Integration. Front Neural Circuits 2022; 15:815923. [PMID: 35185477 PMCID: PMC8856507 DOI: 10.3389/fncir.2021.815923] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 12/23/2021] [Indexed: 01/21/2023] Open
Abstract
Müller glia of the retina share many features with astroglia located throughout the brain including maintenance of homeostasis, modulation of neurotransmitter spillover, and robust response to injury. Here we present the molecular factors and signaling events that govern Müller glial specification, patterning, and differentiation. Next, we discuss the various roles of Müller glia in retinal development, which include maintaining retinal organization and integrity as well as promoting neuronal survival, synaptogenesis, and phagocytosis of debris. Finally, we review the mechanisms by which Müller glia integrate into retinal circuits and actively participate in neuronal signaling during development.
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Affiliation(s)
- Joshua M. Tworig
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
- *Correspondence: Joshua M. Tworig,
| | - Marla B. Feller
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
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Marchese NA, Ríos MN, Guido ME. The Intrinsic Blue Light Responses of Avian Müller Glial Cells Imply Calcium Release from Internal Stores. ASN Neuro 2022; 14:17590914221076698. [PMID: 35103506 PMCID: PMC8814826 DOI: 10.1177/17590914221076698] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The retina of vertebrates is responsible for capturing light through visual
(cones and rods) and non-visual photoreceptors (intrinsically photosensitive
retinal ganglion cells and horizontal cells) triggering a number of essential
activities associated to image- and non-image forming functions (photic
entrainment of daily rhythms, pupillary light reflexes, pineal melatonin
inhibition, among others). Although the retina contains diverse types of
neuronal based-photoreceptors cells, originally classified as ciliary- or
rhabdomeric-like types, in recent years, it has been shown that the major glial
cell type of the retina, the Müller glial cells (MC), express blue photopigments
as Opn3 (encephalopsin) and Opn5 (neuropsin) and display light responses
associated to intracellular Ca2 + mobilization. These findings strongly propose
MC as novel retinal photodetectors (Rios et al., 2019). Herein, we further
investigated the intrinsic light responses of primary cultures of MC from
embryonic chicken retinas specially focused on Ca2 + mobilization by
fluorescence imaging and the identity of the internal Ca2 + stores responsible
for blue light responses. Results clearly demonstrated that light responses were
specific to blue light of long time exposure, and that the main Ca2 + reservoir
to trigger downstream responses came from intracellular stores localized in the
endoplasmic reticulum These observations bring more complexity to the intrinsic
photosensitivity of retinal cells, particularly with regard to the detection of
light in the blue range of visible spectra, and add novel functions to glial
cells cooperating with other photoreceptors to detect and integrate ambient
light in the retinal circuit and participate in cell to cell communication.
Summary statement:
Non-neuronal cells in the vertebrate retina, Muller glial cells, express
non-canonical photopigments and sense blue light causing calcium release from
intracellular stores strongly suggesting a novel intrinsic photosensitivity and
new regulatory events mediating light-driven processes with yet unknown
physiological implications.
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Affiliation(s)
- Natalia A Marchese
- 373607CIQUIBIC-CONICET, Facultad de Ciencias Químicas, 28217Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto", Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Maximiliano N Ríos
- 373607CIQUIBIC-CONICET, Facultad de Ciencias Químicas, 28217Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto", Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Mario E Guido
- 373607CIQUIBIC-CONICET, Facultad de Ciencias Químicas, 28217Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto", Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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Non-visual Opsins and Novel Photo-Detectors in the Vertebrate Inner Retina Mediate Light Responses Within the Blue Spectrum Region. Cell Mol Neurobiol 2020; 42:59-83. [PMID: 33231827 DOI: 10.1007/s10571-020-00997-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/03/2020] [Indexed: 02/06/2023]
Abstract
In recent decades, a number of novel non-visual opsin photopigments belonging to the family of G protein- coupled receptors, likely involved in a number of non-image-forming processes, have been identified and characterized in cells of the inner retina of vertebrates. It is now known that the vertebrate retina is composed of visual photoreceptor cones and rods responsible for diurnal/color and nocturnal/black and white vision, and cells like the intrinsically photosensitive retinal ganglion cells (ipRGCs) and photosensitive horizontal cells in the inner retina, both detecting blue light and expressing the photopigment melanopsin (Opn4). Remarkably, these non-visual photopigments can continue to operate even in the absence of vision under retinal degeneration. Moreover, inner retinal neurons and Müller glial cells have been shown to express other photopigments such as the photoisomerase retinal G protein-coupled receptor (RGR), encephalopsin (Opn3), and neuropsin (Opn5), all able to detect blue/violet light and implicated in chromophore recycling, retinal clock synchronization, neuron-to-glia communication, and other activities. The discovery of these new photopigments in the inner retina of vertebrates is strong evidence of novel light-regulated activities. This review focuses on the features, localization, photocascade, and putative functions of these novel non-visual opsins in an attempt to shed light on their role in the inner retina of vertebrates and in the physiology of the whole organism.
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Rios MN, Marchese NA, Guido ME. Expression of Non-visual Opsins Opn3 and Opn5 in the Developing Inner Retinal Cells of Birds. Light-Responses in Müller Glial Cells. Front Cell Neurosci 2019; 13:376. [PMID: 31474836 PMCID: PMC6706981 DOI: 10.3389/fncel.2019.00376] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 08/02/2019] [Indexed: 11/30/2022] Open
Abstract
The avian retina is composed of different types of photoreceptors responsible for image and non-image forming tasks: the visual photoreceptor cells (cones and rods), the melanopsin-expressing intrinsically photoresponsive retinal ganglion cells (ipRGCs) and horizontal cells. Furthermore, the non-visual opsins Opn3 (encephalopsin/panaopsin) and Opn5 (neuropsin) have been shown to be expressed in the vertebrate inner retina, responding to blue (BL) and UV light, respectively. Here we investigated the expression and localization of Opn3 and Opn5 in the developing chick retina at different embryonic days (E) as well as in primary cultures of retinal Müller glial cells (MCs). Opn3 and Opn5 mRNAs and proteins appeared as early as E10 although traces of Opn3- and Opn5-like proteins were seen earlier by E7 in the forming RGC layer and in glial cells extending throughout the developing nuclear layer. Later on, at postnatal days 1–10 (PN1–10) a significant expression of Opn3 was observed in inner retinal cells and processes in plexiform layers, together with expression of the glial markers glutamine synthetase (GS) and the glial fibrillary acidic protein (GFAP). Opn3 and Opn5 were found to be expressed in primary MC cultures prepared at E8 and kept for 2 weeks. In addition, significant effects of BL exposure on Opn3 expression and subcellular localization were observed in MCs as BL significantly increased its levels and modified its nuclear location when compared with dark controls, through a mechanism dependent on protein synthesis. More importantly, a subpopulation of MCs responded to brief BL pulses by increasing intracellular Ca2+ levels; whereas light-responses were completely abolished with the retinal bleacher hydroxylamine pretreatment. Taken together, our findings show that these two opsins are expressed in inner retinal cells and MCs of the chicken retina at early developmental phases and remain expressed in the mature retina at PN days. In addition, the novel photic responses seen in MCs may suggest another important role for the glia in retinal physiology.
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Affiliation(s)
- Maximiliano N Rios
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto," Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Natalia A Marchese
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto," Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Mario E Guido
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.,Departamento de Química Biológica "Ranwel Caputto," Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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Yarishkin O, Phuong TTT, Lakk M, Križaj D. TRPV4 Does Not Regulate the Distal Retinal Light Response. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1074:553-560. [PMID: 29721987 DOI: 10.1007/978-3-319-75402-4_67] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The transient receptor potential vanilloid isoform 4 (TRPV4) functions as polymodal transducer of swelling, heat, stretch, and lipid metabolites, is widely expressed across sensory tissues, and has been implicated in pressure sensing in vertebrate retinas. Although TRPV4 knockout mice exhibit a variety of mechanosensory, nociceptive, and thermo- and osmoregulatory phenotypes, it is not known whether the transmission of light-induced signals in the eye is affected by the loss of TRPV4. We utilized field potentials, a measure of rod and cone signaling, to determine whether TRPV4 impacts on the generation and/or transmission of the photoreceptor light response and neurotransmission. Luminance intensity-response relationships were acquired in anesthetized wild-type and TRPV4-/- mice and evaluated for peak amplitude and implicit time under scotopic and photopic conditions. We found that the morphology of the outer retina is unaffected by the ablation of the Trpv4 gene. Calcium imaging of dissociated Müller glia showed that selective TRPV4 stimulation induces oscillatory calcium signals in adjacent rods. However, no differences in scotopic or photopic light-evoked signaling in the distal retina were observed in TRPV4-/- eyes, suggesting that TRPV4 signaling in healthy Müller cells does not modulate the transmission of light-evoked signals at rod and cone synapses.
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Affiliation(s)
- Oleg Yarishkin
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, Salt Lake City, UT, USA
| | - Tam T T Phuong
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, Salt Lake City, UT, USA
| | - Monika Lakk
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, Salt Lake City, UT, USA
| | - David Križaj
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, Salt Lake City, UT, USA. .,Department of Bioengineering, University of Utah, Salt Lake City, UT, USA. .,Department of Neurobiology & Anatomy, University of Utah, Salt Lake City, UT, USA.
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Abstract
Müller glia, the principal macroglia of the retina, express diverse subtypes of adenosine and metabotropic purinergic (P2Y) receptors. Müller cells of several species, including man, also express ionotropic P2X7 receptors. ATP is liberated from Müller cells after activation of metabotropic glutamate receptors and during osmotic and mechanical induction of membrane stretch; adenosine is released through equilibrative nucleoside transporters. Müller cell-derived purines modulate the neuronal activity and have autocrine effects, for example, induction of glial calcium waves and regulation of the cellular volume. Glial calcium waves induced by neuron-derived ATP mediate functional hyperemia in the retina. Purinergic signaling contributes to the induction of Müller cell gliosis, for example, of cellular proliferation and downregulation of potassium channels, which are important for the homeostatic functions of Müller cells. Purinergic glial calcium waves may also promote the long-range propagation of gliosis and neuronal degeneration across the retinal tissue. The osmotic ATP release is inhibited under pathological conditions. Inhibition of the ATP release may result in osmotic Müller cell swelling and dysregulation of the water transport through the cells; both may contribute to the development of retinal edema. Suppression of the osmotic ATP release and upregulation of the ecto-apyrase (NTPDase1), which facilitate the extracellular degradation of ATP and the formation of adenosine, may protect neurons and photoreceptors from death due to overactivation of P2X receptors. Pharmacological inhibition of P2X7 receptors and stimulation of adenosine receptors may represent clinical approaches to prevent retinal cell death and dysregulated cell proliferation, and to treat retinal edema.
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Affiliation(s)
- Andreas Reichenbach
- 1 Paul Flechsig Institute of Brain Research, University of Leipzig , Leipzig, Germany
| | - Andreas Bringmann
- 2 Department of Ophthalmology and Eye Hospital, University of Leipzig , Leipzig, Germany
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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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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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Thrivikraman G, Madras G, Basu B. Electrically driven intracellular and extracellular nanomanipulators evoke neurogenic/cardiomyogenic differentiation in human mesenchymal stem cells. Biomaterials 2016; 77:26-43. [DOI: 10.1016/j.biomaterials.2015.10.078] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 10/26/2015] [Accepted: 10/29/2015] [Indexed: 12/27/2022]
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Grosche A, Hauser A, Lepper MF, Mayo R, von Toerne C, Merl-Pham J, Hauck SM. The Proteome of Native Adult Müller Glial Cells From Murine Retina. Mol Cell Proteomics 2015; 15:462-80. [PMID: 26324419 PMCID: PMC4739667 DOI: 10.1074/mcp.m115.052183] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 12/26/2022] Open
Abstract
To date, the proteomic profiling of Müller cells, the dominant macroglia of the retina, has been hampered because of the absence of suitable enrichment methods. We established a novel protocol to isolate native, intact Müller cells from adult murine retinae at excellent purity which retain in situ morphology and are well suited for proteomic analyses. Two different strategies of sample preparation - an in StageTips (iST) and a subcellular fractionation approach including cell surface protein profiling were used for quantitative liquid chromatography-mass spectrometry (LC-MSMS) comparing Müller cell-enriched to depleted neuronal fractions. Pathway enrichment analyses on both data sets enabled us to identify Müller cell-specific functions which included focal adhesion kinase signaling, signal transduction mediated by calcium as second messenger, transmembrane neurotransmitter transport and antioxidant activity. Pathways associated with RNA processing, cellular respiration and phototransduction were enriched in the neuronal subpopulation. Proteomic results were validated for selected Müller cell genes by quantitative real time PCR, confirming the high expression levels of numerous members of the angiogenic and anti-inflammatory annexins and antioxidant enzymes (e.g. paraoxonase 2, peroxiredoxin 1, 4 and 6). Finally, the significant enrichment of antioxidant proteins in Müller cells was confirmed by measurements on vital retinal cells using the oxidative stress indicator CM-H2DCFDA. In contrast to photoreceptors or bipolar cells, Müller cells were most efficiently protected against H2O2-induced reactive oxygen species formation, which is in line with the protein repertoire identified in the proteomic profiling. Our novel approach to isolate intact glial cells from adult retina in combination with proteomic profiling enabled the identification of novel Müller glia specific proteins, which were validated as markers and for their functional impact in glial physiology. This provides the basis to allow the discovery of novel glial specializations and will enable us to elucidate the role of Müller cells in retinal pathologies — a topic still controversially discussed.
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Affiliation(s)
- Antje Grosche
- From the ‡Insitute of Human Genetics, University of Regensburg, D-93053 Regensburg, Germany;
| | - Alexandra Hauser
- From the ‡Insitute of Human Genetics, University of Regensburg, D-93053 Regensburg, Germany
| | - Marlen Franziska Lepper
- §Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany
| | - Rebecca Mayo
- From the ‡Insitute of Human Genetics, University of Regensburg, D-93053 Regensburg, Germany
| | - Christine von Toerne
- §Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany
| | - Juliane Merl-Pham
- §Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany
| | - Stefanie M Hauck
- §Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany
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Purinergic neuron-glia interactions in sensory systems. Pflugers Arch 2014; 466:1859-72. [DOI: 10.1007/s00424-014-1510-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 03/26/2014] [Accepted: 03/26/2014] [Indexed: 02/06/2023]
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Abstract
Calcium acts as a prominent second messenger in virtually every cell type and modulates a plethora of cell functions. Thus, Ca(2+) microfluorimetry became a valuable tool to assess information about mechanisms involved in the regulation of the intracellular calcium level in research on living tissues. Here we offer insight into distinct approaches to detect changes in calcium levels specifically in Müller cells, the principal macroglial cells of the retina.
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Reichenbach A, Bringmann A. New functions of Müller cells. Glia 2013; 61:651-78. [PMID: 23440929 DOI: 10.1002/glia.22477] [Citation(s) in RCA: 466] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/10/2012] [Indexed: 12/12/2022]
Abstract
Müller cells, the major type of glial cells in the retina, are responsible for the homeostatic and metabolic support of retinal neurons. By mediating transcellular ion, water, and bicarbonate transport, Müller cells control the composition of the extracellular space fluid. Müller cells provide trophic and anti-oxidative support of photoreceptors and neurons and regulate the tightness of the blood-retinal barrier. By the uptake of glutamate, Müller cells are more directly involved in the regulation of the synaptic activity in the inner retina. This review gives a survey of recently discoved new functions of Müller cells. Müller cells are living optical fibers that guide light through the inner retinal tissue. Thereby they enhance the signal/noise ratio by minimizing intraretinal light scattering and conserve the spatial distribution of light patterns in the propagating image. Müller cells act as soft, compliant embedding for neurons, protecting them in case of mechanical trauma, and also as soft substrate required for neurite growth and neuronal plasticity. Müller cells release neuroactive signaling molecules which modulate neuronal activity, are implicated in the mediation of neurovascular coupling, and mediate the homeostasis of the extracellular space volume under hypoosmotic conditions which are a characteristic of intense neuronal activity. Under pathological conditions, a subset of Müller cells may differentiate to neural progenitor/stem cells which regenerate lost photoreceptors and neurons. Increasing knowledge of Müller cell function and responses in the normal and diseased retina will have great impact for the development of new therapeutic approaches for retinal diseases.
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Affiliation(s)
- Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
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Bringmann A, Grosche A, Pannicke T, Reichenbach A. GABA and Glutamate Uptake and Metabolism in Retinal Glial (Müller) Cells. Front Endocrinol (Lausanne) 2013; 4:48. [PMID: 23616782 PMCID: PMC3627989 DOI: 10.3389/fendo.2013.00048] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 04/04/2013] [Indexed: 12/11/2022] Open
Abstract
Müller cells, the principal glial cells of the retina, support the synaptic activity by the uptake and metabolization of extracellular neurotransmitters. Müller cells express uptake and exchange systems for various neurotransmitters including glutamate and γ-aminobutyric acid (GABA). Müller cells remove the bulk of extracellular glutamate in the inner retina and contribute to the glutamate clearance around photoreceptor terminals. By the uptake of glutamate, Müller cells are involved in the shaping and termination of the synaptic activity, particularly in the inner retina. Reactive Müller cells are neuroprotective, e.g., by the clearance of excess extracellular glutamate, but may also contribute to neuronal degeneration by a malfunctioning or even reversal of glial glutamate transporters, or by a downregulation of the key enzyme, glutamine synthetase. This review summarizes the present knowledge about the role of Müller cells in the clearance and metabolization of extracellular glutamate and GABA. Some major pathways of GABA and glutamate metabolism in Müller cells are described; these pathways are involved in the glutamate-glutamine cycle of the retina, in the defense against oxidative stress via the production of glutathione, and in the production of substrates for the neuronal energy metabolism.
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Affiliation(s)
- Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, Faculty of Medicine, University of LeipzigLeipzig, Germany
| | - Antje Grosche
- Paul Flechsig Institute of Brain Research, Faculty of Medicine, University of LeipzigLeipzig, Germany
| | - Thomas Pannicke
- Paul Flechsig Institute of Brain Research, Faculty of Medicine, University of LeipzigLeipzig, Germany
| | - Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, Faculty of Medicine, University of LeipzigLeipzig, Germany
- *Correspondence: Andreas Reichenbach, Paul Flechsig Institute of Brain Research, University of Leipzig, Jahnallee 59, D-04109 Leipzig, Germany. e-mail:
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Reichenbach A, Bringmann A. Cell Biology of the Müller Cell. Retina 2013. [DOI: 10.1016/b978-1-4557-0737-9.00017-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Group I mGluR-mediated inhibition of Kir channels contributes to retinal Müller cell gliosis in a rat chronic ocular hypertension model. J Neurosci 2012; 32:12744-55. [PMID: 22972998 DOI: 10.1523/jneurosci.1291-12.2012] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Müller cell gliosis, which is characterized by upregulated expression of glial fibrillary acidic protein (GFAP), is a universal response in many retinal pathological conditions. Whether down-regulation of inward rectifying K+ (Kir) channels, which commonly accompanies the enhanced GFAP expression, could contribute to Müller cell gliosis is poorly understood. We investigated changes of Kir currents, GFAP and Kir4.1 protein expression in Müller cells in a rat chronic ocular hypertension (COH) model, and explored the mechanisms underlying Müller cell gliosis. We show that Kir currents and Kir4.1 protein expression in Müller cells were reduced significantly, while GFAP expression was increased in COH rats, and these changes were eliminated by MPEP, a group I metabotropic glutamate receptors (mGluR I) subtype mGluR5 antagonist. In normal isolated Müller cells, the mGluR I agonist (S)-3,5-dihydroxyphenylglycine (DHPG) suppressed the Kir currents and the suppression was blocked by MPEP. The DHPG effect was mediated by the intracellular Ca2+ -dependent PLC/IP3-ryanodine/PKC signaling pathway, but the cAMP-PKA pathway was not involved. Moreover, intravitreal injection of DHPG in normal rats induced changes in Müller cells, similar to those observed in COH rats. The DHPG-induced increase of GFAP expression in Müller cells was obstructed by Ba2+, suggesting the involvement of Kir channels. We conclude that overactivation of mGluR5 by excessive extracellular glutamate in COH rats could contribute to Müller cell gliosis by suppressing Kir channels.
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Abstract
Cone photoreceptors transmit signals at high temporal frequencies and mediate fine spatial vision. High-frequency transmission requires a high rate of glutamate release, which could promote spillover to neighboring cells, whereas spatial vision requires that cones within a tightly packed array signal light to postsynaptic bipolar cells with minimal crosstalk. Glutamate spread from the cone terminal is thought to be limited by presynaptic transporters and nearby glial processes. In addition, there is no ultrastructural evidence for chemical synapses between mammalian cones, although such synapses have been described in lower vertebrate retinas. We tested for cone-cone glutamate diffusion by recording from adjacent cone pairs in the ground squirrel retina, and instead found that the glutamate released by one cone during electrical stimulation activates glutamate transporter Cl(-) conductances on neighboring cones. Unlike in other systems, where crosstalk is diminished by increasing the temperature and by moving to a more intact preparation, glutamate spread persisted at physiological temperatures (37°C) and in retinal flat mounts. The glutamate-gated anion conductance in cones has a reversal potential of ∼-30 mV compared with a cone resting potential of ∼-50 mV; thus, crosstalk should have a depolarizing effect on the cone network. Cone-cone glutamate spread is regulated by the physiological stimulus, light, and under physiological conditions can produce a response of ∼2 mV, equivalent to 13-20% of a cone's light response. We conclude that in the absence of discrete chemical synapses, glutamate flows between cones during a light response and may mediate a spatially distributed positive feedback.
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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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Loiola EC, Ventura ALM. Release of ATP from avian Müller glia cells in culture. Neurochem Int 2010; 58:414-22. [PMID: 21193002 DOI: 10.1016/j.neuint.2010.12.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 12/17/2010] [Accepted: 12/20/2010] [Indexed: 01/07/2023]
Abstract
ATP can be released from neurons and act as a neuromodulator in the nervous system. Besides neurons, cortical astrocytes also are capable of releasing ATP from acidic vesicles in a Ca(2+)-dependent way. In the present work, we investigated the release of ATP from Müller glia cells of the chick embryo retina by examining quinacrine staining and by measuring the extracellular levels of ATP in purified Müller glia cultures. Our data revealed that glial cells could be labeled with quinacrine, a reaction that was prevented by incubation of the cells with 1μM bafilomycin A1 or 2μM Evans blue, potent inhibitors of vacuolar ATPases and of the vesicular nucleotide transporter, respectively. Either 50mM KCl or 1mM glutamate was able to decrease quinacrine staining of the cells, as well as to increase the levels of ATP in the extracellular medium by 77% and 89.5%, respectively, after a 5min incubation of the cells. Glutamate-induced rise in extracellular ATP could be mimicked by 100μM kainate (81.5%) but not by 100μM NMDA in medium without MgCl(2) but with 2mM glycine. However, both glutamate- and kainate-induced increase in extracellular ATP levels were blocked by 50μM of the glutamatergic antagonists DNQX and MK-801, suggesting the involvement of both NMDA and non-NMDA receptors. Extracellular ATP accumulation induced by glutamate was also blocked by incubation of the cells with 30μM BAPTA-AM or 1μM bafilomycin A1. These results suggest that glutamate, through activation of both NMDA and non-NMDA receptors, induces the release of ATP from retinal Müller cells through a calcium-dependent exocytotic mechanism.
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Affiliation(s)
- Erick Correia Loiola
- Department of Neurobiology, Neuroscience Program, Institute of Biology, Federal Fluminense University, Niterói, RJ, Brazil
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Lee H, Brecha NC. Immunocytochemical evidence for SNARE protein-dependent transmitter release from guinea pig horizontal cells. Eur J Neurosci 2010; 31:1388-401. [PMID: 20384779 DOI: 10.1111/j.1460-9568.2010.07181.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Horizontal cells are lateral interneurons that participate in visual processing in the outer retina but the cellular mechanisms underlying transmitter release from these cells are not fully understood. In non-mammalian horizontal cells, GABA release has been shown to occur by a non-vesicular mechanism. However, recent evidence in mammalian horizontal cells favors a vesicular mechanism as they lack plasmalemmal GABA transporters and some soluble NSF attachment protein receptor (SNARE) core proteins have been identified in rodent horizontal cells. Moreover, immunoreactivity for GABA and the molecular machinery to synthesize GABA have been found in guinea pig horizontal cells, suggesting that if components of the SNARE complex are expressed they could contribute to the vesicular release of GABA. In this study we investigated whether these vesicular and synaptic proteins are expressed by guinea pig horizontal cells using immunohistochemistry with well-characterized antibodies to evaluate their cellular distribution. Components of synaptic vesicles including vesicular GABA transporter, synapsin I and synaptic vesicle protein 2A were localized to horizontal cell processes and endings, along with the SNARE core complex proteins, syntaxin-1a, syntaxin-4 and synaptosomal-associated protein 25 (SNAP-25). Complexin I/II, a cytosolic protein that stabilizes the activated SNARE fusion core, strongly immunostained horizontal cell soma and processes. In addition, the vesicular Ca(2+)-sensor, synaptotagmin-2, which is essential for Ca(2+)-mediated vesicular release, was also localized to horizontal cell processes and somata. These morphological findings from guinea pig horizontal cells suggest that mammalian horizontal cells have the capacity to utilize a regulated Ca(2+)-dependent vesicular pathway to release neurotransmitter, and that this mechanism may be shared among many mammalian species.
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Affiliation(s)
- Helen Lee
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095-1763, USA.
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