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Kremers J, Huchzermeyer C. Electroretinographic responses to periodic stimuli in primates and the relevance for visual perception and for clinical studies. Vis Neurosci 2024; 41:E004. [PMID: 39523890 PMCID: PMC11579838 DOI: 10.1017/s0952523824000038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 08/01/2024] [Accepted: 08/01/2024] [Indexed: 11/16/2024]
Abstract
Currently, electroretinograms (ERGs) are mainly recorded while using flashes as stimuli. In this review, we will argue that strong flashes are not ideal for studying visual information processing. ERG responses to periodic stimuli may be more strongly associated with the activity of post-receptoral neurons (belonging to different retino-geniculate pathways) and, therefore, be more relevant for visual perception. We will also argue that the use of periodic stimuli may be an attractive addition to clinically available retinal electrophysiological methods.
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Affiliation(s)
- Jan Kremers
- Section for Retinal Physiology, University Hospital Erlangen, Erlangen, Germany
| | - Cord Huchzermeyer
- Section for Retinal Physiology, University Hospital Erlangen, Erlangen, Germany
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Chen Y, Zizmare L, Calbiague V, Wang L, Yu S, Herberg FW, Schmachtenberg O, Paquet-Durand F, Trautwein C. Retinal metabolism displays evidence for uncoupling of glycolysis and oxidative phosphorylation via Cori-, Cahill-, and mini-Krebs-cycle. eLife 2024; 12:RP91141. [PMID: 38739438 PMCID: PMC11090511 DOI: 10.7554/elife.91141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024] Open
Abstract
The retina consumes massive amounts of energy, yet its metabolism and substrate exploitation remain poorly understood. Here, we used a murine explant model to manipulate retinal energy metabolism under entirely controlled conditions and utilised 1H-NMR spectroscopy-based metabolomics, in situ enzyme detection, and cell viability readouts to uncover the pathways of retinal energy production. Our experimental manipulations resulted in varying degrees of photoreceptor degeneration, while the inner retina and retinal pigment epithelium were essentially unaffected. This selective vulnerability of photoreceptors suggested very specific adaptations in their energy metabolism. Rod photoreceptors were found to rely strongly on oxidative phosphorylation, but only mildly on glycolysis. Conversely, cone photoreceptors were dependent on glycolysis but insensitive to electron transport chain decoupling. Importantly, photoreceptors appeared to uncouple glycolytic and Krebs-cycle metabolism via three different pathways: (1) the mini-Krebs-cycle, fuelled by glutamine and branched chain amino acids, generating N-acetylaspartate; (2) the alanine-generating Cahill-cycle; (3) the lactate-releasing Cori-cycle. Moreover, the metabolomics data indicated a shuttling of taurine and hypotaurine between the retinal pigment epithelium and photoreceptors, likely resulting in an additional net transfer of reducing power to photoreceptors. These findings expand our understanding of retinal physiology and pathology and shed new light on neuronal energy homeostasis and the pathogenesis of neurodegenerative diseases.
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Affiliation(s)
- Yiyi Chen
- Institute for Ophthalmic Research, University of TübingenTuebingenGermany
| | - Laimdota Zizmare
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, University of TübingenTuebingenGermany
- Core Facility Metabolomics, Faculty of Medicine, University of TübingenTuebingenGermany
| | - Victor Calbiague
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de ValparaísoValparaísoChile
| | - Lan Wang
- Institute for Ophthalmic Research, University of TübingenTuebingenGermany
| | - Shirley Yu
- Institute for Ophthalmic Research, University of TübingenTuebingenGermany
| | - Fritz W Herberg
- Biochemistry Department, University of KasselTuebingenGermany
| | - Oliver Schmachtenberg
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de ValparaísoValparaísoChile
| | | | - Christoph Trautwein
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, University of TübingenTuebingenGermany
- Core Facility Metabolomics, Faculty of Medicine, University of TübingenTuebingenGermany
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Stürmer S, Bolz S, Zrenner E, Ueffing M, Haq W. Sustained Extracellular Electrical Stimulation Modulates the Permeability of Gap Junctions in rd1 Mouse Retina with Photoreceptor Degeneration. Int J Mol Sci 2024; 25:1616. [PMID: 38338908 PMCID: PMC10855676 DOI: 10.3390/ijms25031616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Neurons build vast gap junction-coupled networks (GJ-nets) that are permeable to ions or small molecules, enabling lateral signaling. Herein, we investigate (1) the effect of blinding diseases on GJ-nets in mouse retinas and (2) the impact of electrical stimulation on GJ permeability. GJ permeability was traced in the acute retinal explants of blind retinal degeneration 1 (rd1) mice using the GJ tracer neurobiotin. The tracer was introduced via the edge cut method into the GJ-net, and its spread was visualized in histological preparations (fluorescent tagged) using microscopy. Sustained stimulation was applied to modulate GJ permeability using a single large electrode. Our findings are: (1) The blind rd1 retinas displayed extensive intercellular coupling via open GJs. Three GJ-nets were identified: horizontal, amacrine, and ganglion cell networks. (2) Sustained stimulation significantly diminished the tracer spread through the GJs in all the cell layers, as occurs with pharmaceutical inhibition with carbenoxolone. We concluded that the GJ-nets of rd1 retinas remain coupled and functional after blinding disease and that their permeability is regulatable by sustained stimulation. These findings are essential for understanding molecular signaling in diseases over coupled networks and therapeutic approaches using electrical implants, such as eliciting visual sensations or suppressing cortical seizures.
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Affiliation(s)
| | | | | | | | - Wadood Haq
- Institute for Ophthalmic Research, University of Tuebingen, 72076 Tuebingen, Germany
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Tolone A, Haq W, Fachinger A, Roy A, Kesh S, Rentsch A, Wucherpfennig S, Zhu Y, Groten J, Schwede F, Tomar T, Herberg FW, Nache V, Paquet-Durand F. The PKG Inhibitor CN238 Affords Functional Protection of Photoreceptors and Ganglion Cells against Retinal Degeneration. Int J Mol Sci 2023; 24:15277. [PMID: 37894958 PMCID: PMC10607377 DOI: 10.3390/ijms242015277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/27/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Hereditary retinal degeneration (RD) is often associated with excessive cGMP signalling in photoreceptors. Previous research has shown that inhibition of cGMP-dependent protein kinase G (PKG) can reduce photoreceptor loss in two different RD animal models. In this study, we identified a PKG inhibitor, the cGMP analogue CN238, which preserved photoreceptor viability and functionality in rd1 and rd10 mutant mice. Surprisingly, in explanted retinae, CN238 also protected retinal ganglion cells from axotomy-induced retrograde degeneration and preserved their functionality. Furthermore, kinase activity-dependent protein phosphorylation of the PKG target Kv1.6 was reduced in CN238-treated rd10 retinal explants. Ca2+-imaging on rd10 acute retinal explants revealed delayed retinal ganglion cell repolarization with CN238 treatment, suggesting a PKG-dependent modulation of Kv1-channels. Together, these results highlight the strong neuroprotective capacity of PKG inhibitors for both photoreceptors and retinal ganglion cells, illustrating their broad potential for the treatment of retinal diseases and possibly neurodegenerative diseases in general.
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Affiliation(s)
- Arianna Tolone
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
| | - Wadood Haq
- Neuroretinal Electrophysiology and Imaging, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany;
| | - Alexandra Fachinger
- Biochemistry Department, University of Kassel, 34132 Kassel, Germany; (A.F.); (F.W.H.)
| | - Akanksha Roy
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Sandeep Kesh
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - Andreas Rentsch
- Biolog Life Science Institute GmbH & Co. KG, 28199 Bremen, Germany; (A.R.); (F.S.)
| | - Sophie Wucherpfennig
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - Yu Zhu
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
| | - John Groten
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Frank Schwede
- Biolog Life Science Institute GmbH & Co. KG, 28199 Bremen, Germany; (A.R.); (F.S.)
| | - Tushar Tomar
- PamGene International B.V., 5211 ‘s-Hertogenbosch, The Netherlands; (A.R.); (J.G.); (T.T.)
| | - Friedrich W. Herberg
- Biochemistry Department, University of Kassel, 34132 Kassel, Germany; (A.F.); (F.W.H.)
| | - Vasilica Nache
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University Jena, 07743 Jena, Germany; (S.K.); (S.W.); (V.N.)
| | - François Paquet-Durand
- Cell Death Mechanism Group, Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, 72076 Tübingen, Germany; (A.T.); (Y.Z.)
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