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Long Y, Kozhemyakin M, Wu SM, Pang JJ. TRPV4 affects visual signals in photoreceptors and rod bipolar cells. Front Cell Neurosci 2024; 18:1404929. [PMID: 38903773 PMCID: PMC11188360 DOI: 10.3389/fncel.2024.1404929] [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: 03/21/2024] [Accepted: 05/17/2024] [Indexed: 06/22/2024] Open
Abstract
Introduction Mechanical sensitive channels expressed in mammalian retinas are effectors of elevated pressure stresses, but it is unclear how their activation affects visual function in pressure-related retinal disorders. Methods This study investigated the role of the transient potential channel vanilloid TRPV4 in photoreceptors and rod bipolar cells (RBCs) with immunohistochemistry, confocal microscopy, electroretinography (ERG), and patch-clamp techniques. Results TRPV4 immunoreactivity (IR) was found in the outer segments of photoreceptors, dendrites and somas of PKCα-positive RBCs and other BCs, plexiform layers, and retinal ganglion cells (RGCs) in wild-type mice. TRPV4-IR was largely diminished in the retinas of homozygous TRPV4 transgenic mice. Genetically suppressing TRPV4 expression moderately but significantly enhanced the amplitude of ERG a- and b-waves evoked by scotopic and mesopic lights (0.55 to 200 Rh*rod-1 s-1) and photopic lights (105-106 Rh*rod-1 s-1) compared to wild-type mice in fully dark-adapted conditions. The implicit time evoked by dim lights (0.55 to 200 Rh*rod-1 s-1) was significantly decreased for b-waves and elongated for a-waves in the transgenic mice. ERG b-wave evoked by dim lights is primarily mediated by RBCs, and under voltage-clamp conditions, the latency of the light-evoked cation current in RBCs of the transgenic mice was significantly shorter compared to wild-type mice. About 10% of the transgenic mice had one eye undeveloped, and the percentage was significantly higher than in wild-type mice. Conclusions The data indicates that TRPV4 involves ocular development and is expressed and active in outer retinal neurons, and interventions of TRPV4 can variably affect visual signals in rods, cones, RBCs, and cone ON BCs.
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Affiliation(s)
| | | | | | - Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, United States
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2
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Yang P, Feng J, Zhu Y, Hao Y. A Novel Cell Volume Sensor for Real-Time Analysis of Ca 2+-Activated K + Channel. ACS Biomater Sci Eng 2023; 9:5255-5259. [PMID: 37639544 DOI: 10.1021/acsbiomaterials.3c00771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Potassium channels play a vital role in cell volume regulation. A cell volume sensor was constructed by integrating regulatory volume decrease (RVD) with quartz-crystal microbalance (QCM) for studying potassium channels and their expression. The sensor successfully monitored the K+ channel's activities during RVD by sensitive and noninvasive means. It showed that Ca2+ activated the K+ channel (KCa) and enhanced the RVD level. The inhibition of blockers on K+ channels exhibited an obvious difference in RVD level between normal and cancerous nasopharyngeal cells, suggesting that the KCa channel contributes a dominant role to the RVD function and provides an approach to identify the activation of various K+ channels.
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Affiliation(s)
- Peihui Yang
- Department of Chemistry, College of Chemistry and Materials Science, Jinan University, Guangzhou 510632, People's Republic of China
| | - Jingwei Feng
- Department of Chemistry, College of Chemistry and Materials Science, Jinan University, Guangzhou 510632, People's Republic of China
| | - Yeyan Zhu
- Department of Chemistry, College of Chemistry and Materials Science, Jinan University, Guangzhou 510632, People's Republic of China
| | - Yan Hao
- Department of Chemistry, College of Chemistry and Materials Science, Jinan University, Guangzhou 510632, People's Republic of China
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3
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Barile B, Mola MG, Formaggio F, Saracino E, Cibelli A, Gargano CD, Mogni G, Frigeri A, Caprini M, Benfenati V, Nicchia GP. AQP4-independent TRPV4 modulation of plasma membrane water permeability. Front Cell Neurosci 2023; 17:1247761. [PMID: 37720545 PMCID: PMC10500071 DOI: 10.3389/fncel.2023.1247761] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/14/2023] [Indexed: 09/19/2023] Open
Abstract
Despite of the major role of aquaporin (AQP) water channels in controlling transmembrane water fluxes, alternative ways for modulating water permeation have been proposed. In the Central Nervous System (CNS), Aquaporin-4 (AQP4) is reported to be functionally coupled with the calcium-channel Transient-Receptor Potential Vanilloid member-4 (TRPV4), which is controversially involved in cell volume regulation mechanisms and water transport dynamics. The present work aims to investigate the selective role of TRPV4 in regulating plasma membrane water permeability in an AQP4-independent way. Fluorescence-quenching water transport experiments in Aqp4-/- astrocytes revealed that cell swelling rate is significantly increased upon TRPV4 activation and in the absence of AQP4. The biophysical properties of TRPV4-dependent water transport were therefore assessed using the HEK-293 cell model. Calcein quenching experiments showed that chemical and thermal activation of TRPV4 overexpressed in HEK-293 cells leads to faster swelling kinetics. Stopped-flow light scattering water transport assay was used to measure the osmotic permeability coefficient (Pf, cm/s) and activation energy (Ea, kcal/mol) conferred by TRPV4. Results provided evidence that although the Pf measured upon TRPV4 activation is lower than the one obtained in AQP4-overexpressing cells (Pf of AQP4 = 0.01667 ± 0.0007; Pf of TRPV4 = 0.002261 ± 0.0004; Pf of TRPV4 + 4αPDD = 0.007985 ± 0.0006; Pf of WT = 0.002249 ± 0.0002), along with activation energy values (Ea of AQP4 = 0.86 ± 0.0006; Ea of TRPV4 + 4αPDD = 2.73 ± 1.9; Ea of WT = 8.532 ± 0.4), these parameters were compatible with a facilitated pathway for water movement rather than simple diffusion. The possibility to tune plasma membrane water permeability more finely through TRPV4 might represent a protective mechanism in cells constantly facing severe osmotic challenges to avoid the potential deleterious effects of the rapid cell swelling occurring via AQP channels.
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Affiliation(s)
- Barbara Barile
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Francesco Formaggio
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Antonio Cibelli
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Domenica Gargano
- Department of Translational Biomedicine and Neuroscience (DiBraiN), School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Guido Mogni
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- Department of Translational Biomedicine and Neuroscience (DiBraiN), School of Medicine, University of Bari Aldo Moro, Bari, Italy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY, United States
| | - Marco Caprini
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY, United States
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4
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Ek-Vitorin JF, Shahidullah M, Lopez Rosales JE, Delamere NA. Patch clamp studies on TRPV4-dependent hemichannel activation in lens epithelium. Front Pharmacol 2023; 14:1101498. [PMID: 36909173 PMCID: PMC9998544 DOI: 10.3389/fphar.2023.1101498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 02/06/2023] [Indexed: 02/26/2023] Open
Abstract
ATP release from the lens via hemichannels has been explained as a response to TRPV4 activation when the lens is subjected to osmotic swelling. To explore the apparent linkage between TRPV4 activation and connexin hemichannel opening we performed patch-clamp recordings on cultured mouse lens epithelial cells exposed to the TRPV4 agonist GSK1016790A (GSK) in the presence or absence of the TRPV4 antagonist HC067047 (HC). GSK was found to cause a fast, variable and generally large non-selective increase of whole cell membrane conductance evident as a larger membrane current (Im) over a wide voltage range. The response was prevented by HC. The GSK-induced Im increase was proportionally larger at negative voltages and coincided with fast depolarization and the simultaneous disappearance of an outward current, likely a K+ current. The presence of this outward current in control conditions appeared to be a reliable predictor of a cell's response to GSK treatment. In some studies, recordings were obtained from single cells by combining cell-attached and whole-cell patch clamp configurations. This approach revealed events with a channel conductance 180-270 pS following GSK application through the patch pipette on the cell-attached side. The findings are consistent with TRPV4-dependent opening of Cx43 hemichannels.
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Affiliation(s)
- Jose F Ek-Vitorin
- Department of Physiology, University of Arizona, Tucson, AZ, United States
| | - Mohammad Shahidullah
- Department of Physiology, University of Arizona, Tucson, AZ, United States.,Department of Ophthalmology and Vision Science, University of Arizona, Tucson, AZ, United States
| | | | - Nicholas A Delamere
- Department of Physiology, University of Arizona, Tucson, AZ, United States.,Department of Ophthalmology and Vision Science, University of Arizona, Tucson, AZ, United States
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Križaj D, Cordeiro S, Strauß O. Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration. Prog Retin Eye Res 2023; 92:101114. [PMID: 36163161 PMCID: PMC9897210 DOI: 10.1016/j.preteyeres.2022.101114] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 08/03/2022] [Accepted: 08/08/2022] [Indexed: 02/05/2023]
Abstract
Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.
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Affiliation(s)
- David Križaj
- Departments of Ophthalmology, Neurobiology, and Bioengineering, University of Utah, Salt Lake City, USA
| | - Soenke Cordeiro
- Institute of Physiology, Faculty of Medicine, Christian-Albrechts-University Kiel, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a Corporate Member of Freie Universität, Humboldt-University, The Berlin Institute of Health, Berlin, Germany.
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6
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Marshall AT, Crewther SG. Osmotic gradients and transretinal water flow-a quantitative elemental microanalytical study of frozen hydrated chick eyes. Front Cell Neurosci 2022; 16:975313. [PMID: 36353149 PMCID: PMC9639504 DOI: 10.3389/fncel.2022.975313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 10/03/2022] [Indexed: 08/30/2023] Open
Abstract
Optical clarity and efficient phototransduction are necessary for optimal vision, however, how the associated processes of osmoregulation and continuous fluid drainage across the whole eye are achieved remains relatively unexplored. Hence, we have employed elemental microanalysis of planed surfaces of light-adapted bulk frozen-hydrated chick eyes to determine the unique intracellular elemental localization, compositions, and hydration states that contribute to maintaining osmotic gradients and water flow from the vitreous, across the retina, retinal pigment epithelium (RPE), to choroid and sclera. As expected, the greatest difference in resultant osmotic concentration gradients, [calculated using the combined concentrations of sodium (Na) and potassium (K)] and tissue hydration [oxygen-defined water concentration], occurs in the outer retina and, in particular, in the RPE where the apical and basal membranes are characterized by numerous bioenergetically active, osmoregulating ion transport mechanisms, aquaporins, and chloride (Cl) channels. Our results also demonstrate that the high intracellular Na+ and K+ concentrations in the apical region of the RPE are partially derived from the melanosomes. The inclusion of the ubiquitous osmolyte taurine to the calculation of the osmotic gradients suggests a more gradual increase in the osmotic transport of water from the vitreous into the ganglion cell layer across the inner retina to the outer segments of the photoreceptor/apical RPE region where the water gradient increases rapidly towards the basal membrane. Thus transretinal water is likely to cross the apical membrane from the retina into the RPE cells down the Na+ and K+ derived osmotic concentration gradient and leave the RPE for the choroid across the basal membrane down the Cl- derived osmotic concentration gradient that is sustained by the well-described bioenergetically active RPE ion transporters and channels.
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Affiliation(s)
- Alan T. Marshall
- Analytical Electron Microscopy Laboratory, Department of Genetics and Environment, La Trobe University, Melbourne, VIC, Australia
| | - Sheila G. Crewther
- Department of Psychology and Counselling, La Trobe University, Melbourne, VIC, Australia
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Lapajne L, Rudzitis CN, Cullimore B, Ryskamp D, Lakk M, Redmon SN, Yarishkin O, Krizaj D. TRPV4: Cell type-specific activation, regulation and function in the vertebrate eye. CURRENT TOPICS IN MEMBRANES 2022; 89:189-219. [PMID: 36210149 PMCID: PMC9879314 DOI: 10.1016/bs.ctm.2022.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The architecture of the vertebrate eye is optimized for efficient delivery and transduction of photons and processing of signaling cascades downstream from phototransduction. The cornea, lens, retina, vasculature, ciliary body, ciliary muscle, iris and sclera have specialized functions in ocular protection, transparency, accommodation, fluid regulation, metabolism and inflammatory signaling, which are required to enable function of the retina-light sensitive tissue in the posterior eye that transmits visual signals to relay centers in the midbrain. This process can be profoundly impacted by non-visual stimuli such as mechanical (tension, compression, shear), thermal, nociceptive, immune and chemical stimuli, which target these eye regions to induce pain and precipitate vision loss in glaucoma, diabetic retinopathy, retinal dystrophies, retinal detachment, cataract, corneal dysfunction, ocular trauma and dry eye disease. TRPV4, a polymodal nonselective cation channel, integrate non-visual inputs with homeostatic and signaling functions of the eye. The TRPV4 gene is expressed in most if not all ocular tissues, which vary widely with respect to the mechanisms of TRPV4 channel activation, modulation, oligomerization, and participation in protein- and lipid interactions. Under- and overactivation of TRPV4 may affect intraocular pressure, maintenance of blood-retina barriers, lens accommodation, neuronal function and neuroinflammation. Because TRPV4 dysregulation precipitates many pathologies across the anterior and posterior eye, the channel could be targeted to mitigate vision loss.
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Affiliation(s)
- Luka Lapajne
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States; Department of Ophthalmology, University Medical Centre, University of Ljubljana, Ljubljana, Slovenia
| | - Christopher N Rudzitis
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Brenan Cullimore
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Daniel Ryskamp
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Monika Lakk
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Sarah N Redmon
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Oleg Yarishkin
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - David Krizaj
- Department of Ophthalmology & Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, United States; Department of Neurobiology, University of Utah, Salt Lake City, UT, United States; Department of Bioengineering, University of Utah, Salt Lake City, UT, United States.
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8
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Ochoa-de la Paz LD, Gulias-Cañizo R. Glia as a key factor in cell volume regulation processes of the central nervous system. Front Cell Neurosci 2022; 16:967496. [PMID: 36090789 PMCID: PMC9453262 DOI: 10.3389/fncel.2022.967496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/03/2022] [Indexed: 11/23/2022] Open
Abstract
Brain edema is a pathological condition with potentially fatal consequences, related to cerebral injuries such as ischemia, chronic renal failure, uremia, and diabetes, among others. Under these pathological states, the cell volume control processes are fully compromised, because brain cells are unable to regulate the movement of water, mainly regulated by osmotic gradients. The processes involved in cell volume regulation are homeostatic mechanisms that depend on the mobilization of osmolytes (ions, organic molecules, and polyols) in the necessary direction to counteract changes in osmolyte concentration in response to water movement. The expression and coordinated function of proteins related to the cell volume regulation process, such as water channels, ion channels, and other cotransport systems in the glial cells, and considering the glial cell proportion compared to neuronal cells, leads to consider the astroglial network the main regulatory unit for water homeostasis in the central nervous system (CNS). In the last decade, several studies highlighted the pivotal role of glia in the cell volume regulation process and water homeostasis in the brain, including the retina; any malfunction of this astroglial network generates a lack of the ability to regulate the osmotic changes and water movements and consequently exacerbates the pathological condition.
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Affiliation(s)
- Lenin David Ochoa-de la Paz
- Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico
- Asociación para Evitar la Ceguera en México (APEC), Unidad de Investigación APEC-UNAM, Mexico
- *Correspondence: Lenin David Ochoa-de la Paz
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9
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Sanhueza Salas LF, García-Venzor A, Beltramone N, Capurro C, Toiber D, Silberman DM. Metabolic Imbalance Effect on Retinal Müller Glial Cells Reprogramming Capacity: Involvement of Histone Deacetylase SIRT6. Front Genet 2021; 12:769723. [PMID: 34804128 PMCID: PMC8599966 DOI: 10.3389/fgene.2021.769723] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 10/15/2021] [Indexed: 12/13/2022] Open
Abstract
Retinal Müller glial cells (MGs) are among the first to demonstrate metabolic changes during retinal disease and are a potential source of regenerative cells. In response to a harmful stimulus, they can dedifferentiate acquiring neural stem cells properties, proliferate and migrate to the damaged retinal layer and differentiate into lost neurons. However, it is not yet known how this reprogramming process is regulated in mammals. Since glucose and oxygen are important regulatory elements that may help directing stem cell fate, we aimed to study the effect of glucose variations and oxidative stress in Müller cells reprogramming capacity and analyze the participation the histone deacetylase SIRT6, as an epigenetic modulator of this process. We found that the combination of high glucose and oxidative stress induced a decrease in the levels of the marker glutamine synthetase, and an increase in the migration capacity of the cells suggesting that these experimental conditions could induce some degree of dedifferentiation and favor the migration ability. High glucose induced an increase in the levels of the pluripotent factor SOX9 and a decrease in SIRT6 levels accompanied by the increase in the acetylation levels of H3K9. Inhibiting SIRT6 expression by siRNA rendered an increase in SOX9 levels. We also determined SOX9 levels in retinas from mice with a conditional deletion of SIRT6 in the CNS. To further understand the mechanisms that regulate MGs response under metabolic impaired conditions, we evaluated the gene expression profile and performed Gene Ontology enrichment analysis of Müller cells from a murine model of Diabetes. We found several differentially expressed genes and observed that the transcriptomic change involved the enrichment of genes associated with glucose metabolism, cell migration, development and pluripotency. We found that many functional categories affected in cells of diabetic animals were directly related to SIRT6 function. Transcription factors enrichment analysis allowed us to predict several factors, including SOX9, that may be involved in the modulation of the differential expression program observed in diabetic MGs. Our results underline the heterogeneity of Müller cells response and the challenge that the study of metabolic impairment in vivo represents.
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Affiliation(s)
- L Francisco Sanhueza Salas
- Centro de Estudios Farmacológicos y Botánicos (CEFYBO-UBA-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Alfredo García-Venzor
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,The Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Natalia Beltramone
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Claudia Capurro
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Debra Toiber
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,The Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Dafne Magalí Silberman
- Centro de Estudios Farmacológicos y Botánicos (CEFYBO-UBA-CONICET), Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
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Netti V, Fernández J, Melamud L, Garcia-Miranda P, Di Giusto G, Ford P, Echevarría M, Capurro C. Aquaporin-4 Removal from the Plasma Membrane of Human Müller Cells by AQP4-IgG from Patients with Neuromyelitis Optica Induces Changes in Cell Volume Homeostasis: the First Step of Retinal Injury? Mol Neurobiol 2021; 58:5178-5193. [PMID: 34263427 DOI: 10.1007/s12035-021-02491-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 07/11/2021] [Indexed: 11/27/2022]
Abstract
Aquaporin-4 (AQP4) is the target of the specific immunoglobulin G autoantibody (AQP4-IgG) produced in patients with neuromyelitis optica spectrum disorders (NMOSD). Previous studies demonstrated that AQP4-IgG binding to astrocytic AQP4 leads to cell-destructive lesions. However, the early physiopathological events in Müller cells in the retina are poorly understood. Here, we investigated the consequences of AQP4-IgG binding to AQP4 of Müller cells, previous to the inflammatory response, on two of AQP4's key functions, cell volume regulation response (RVD) and cell proliferation, a process closely associated with changes in cell volume. Experiments were performed in a human retinal Müller cell line (MIO-M1) exposed to complement-inactivated sera from healthy volunteers or AQP4-IgG positive NMOSD patients. We evaluated AQP4 expression (immunofluorescence and western blot), water permeability coefficient, RVD, intracellular calcium levels and membrane potential changes during hypotonic shock (fluorescence videomicroscopy) and cell proliferation (cell count and BrdU incorporation). Our results showed that AQP4-IgG binding to AQP4 induces its partial internalization, leading to the decrease of the plasma membrane water permeability, a reduction of swelling-induced increase of intracellular calcium levels and the impairment of RVD in Müller cells. The loss of AQP4 from the plasma membrane induced by AQP4-IgG positive sera delayed Müller cells' proliferation rate. We propose that Müller cell dysfunction after AQP4 removal from the plasma membrane by AQP4-IgG binding could be a non-inflammatory mechanism of retinal injury in vivo, altering cell volume homeostasis and cell proliferation and consequently, contributing to the physiopathology of NMOSD.
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Affiliation(s)
- Vanina Netti
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Facultad de Medicina, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas Y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Juan Fernández
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Facultad de Medicina, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas Y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Luciana Melamud
- Servicio de Neurología, Centro Universitario de Neurología Dr. J.M. Ramos Mejía, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Pablo Garcia-Miranda
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC, Universidad de Sevilla, Seville, Spain
| | - Gisela Di Giusto
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Facultad de Medicina, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas Y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Paula Ford
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Facultad de Medicina, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas Y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Miriam Echevarría
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC, Universidad de Sevilla, Seville, Spain
| | - Claudia Capurro
- Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Facultad de Medicina, Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-HOUSSAY), Consejo Nacional de Investigaciones Científicas Y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina.
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11
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Llorián-Salvador M, Barabas P, Byrne EM, Lechner J, Augustine J, Curtis TM, Chen M, Xu H. VEGF-B Is an Autocrine Gliotrophic Factor for Müller Cells under Pathologic Conditions. Invest Ophthalmol Vis Sci 2021; 61:35. [PMID: 32945843 PMCID: PMC7509798 DOI: 10.1167/iovs.61.11.35] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Purpose Müller glia are important in retinal health and disease and are a major source of retinal VEGF-A. Of the different VEGF family members, the role of VEGF-A in retinal health and disease has been studied extensively. The potential contribution of other VEGF family members to retinal pathophysiology, however, remains poorly defined. This study aimed to understand the role of VEGF-B in Müller cell pathophysiology. Methods The expression of different VEGFs and their receptors in human MIO-M1 and mouse QMMuC-1 Müller cell lines and primary murine Müller cells was examined by RT-PCR, ELISA, and Western blot. The effect of recombinant VEGF-B or VEGF-B neutralization on Müller cell viability and survival under normal, hypoxic, and oxidative (4-hydroxynonenal [4-HNE]) conditions was evaluated by Alamar Blue, Yo-Pro uptake, and immunocytochemistry. The expression of glial fibrillary acidic protein, aquaporin-4, inward rectifying K+ channel subtype 4.1, glutamine synthetase, and transient receptor potential vanilloid 4 under different treatment conditions was examined by RT-PCR, immunocytochemistry, and Western blot. Transient receptor potential vanilloid 4 channel activity was assessed using a Fura-2–based calcium assay. Results VEGF-B was expressed in Müller cells at the highest levels compared with other members of the VEGF family. VEGF-B neutralization did not affect Müller cell viability or functionality under normal conditions, but enhanced hypoxia– or 4-HNE–induced Müller cell death and decreased inward rectifying K+ channel subtype 4.1 and aquaporin-4 expression. Recombinant VEGF-B restored Müller cell glutamine synthetase expression under hypoxic conditions and protected Müller cells from 4-HNE–induced damage by normalizing transient receptor potential vanilloid 4 channel expression and activity. Conclusions Autocrine production of VEGF-B protects Müller cells under pathologic conditions.
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Affiliation(s)
- María Llorián-Salvador
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Peter Barabas
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Eimear M Byrne
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Judith Lechner
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Josy Augustine
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Timothy M Curtis
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Mei Chen
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
| | - Heping Xu
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, BT9 7BL. Belfast, United Kingdom
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12
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Pang JJ. Roles of the ocular pressure, pressure-sensitive ion channel, and elasticity in pressure-induced retinal diseases. Neural Regen Res 2021; 16:68-72. [PMID: 32788449 PMCID: PMC7818868 DOI: 10.4103/1673-5374.286953] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The intraocular pressure inside the human eye maintains 10–21 mmHg above the atmospheric pressure. Elevation of intraocular pressure is highly correlated with the retinopathy in glaucoma, and changes in the exterior pressure during mountain hiking, air traveling, and diving may also induce vision decline and retinopathy. The pathophysiological mechanism of these pressure-induced retinal disorders has not been completely clear. Retinal neurons express pressure-sensitive channels intrinsically sensitive to pressure and membrane stretch, such as the transient receptor potential channel (TRP) family permeable to Ca2+ and Na+ and the two-pore domain K channel family. Recent data have shown that pressure excites the primate retinal bipolar cell by opening TRP vanilloid 4 to mediate transient depolarizing currents, and TRP vanilloid 4 agonists enhance the membrane excitability of primate retinal ganglion cells. The eyeball wall is constructed primarily by the sclera and cornea of low elasticity, and the flow rate of the aqueous humor and intraocular pressure both fluctuate, but the mathematical relationship between the ocular elasticity, aqueous humor volume, and intraocular pressure has not been established. This review will briefly review recent literature on the pressure-related retinal pathophysiology in glaucoma and other pressure-induced retinal disorders, the elasticity of ocular tissues, and pressure-sensitive cation channels in retinal neurons. Emerging data support the global volume and the elasticity and thickness of the sclera and cornea as variables to affect the intraocular pressure level like the volume of the aqueous humor. Recent results also suggest some potential routes for TRPs to mediate retinal ganglion cell dysfunction: TRP opening upon intraocular pressure elevation and membrane stretch, enhancing glutamate release from bipolar cells, increasing intracellular Na+, Ca2+ concentration in retinal ganglion cells and extracellular glutamate concentration, inactivating voltage-gated Na+ channels, and causing excitotoxicity and dysfunction of retinal ganglion cells. Further studies on these routes likely identify novel targets and therapeutic strategies for the treatment of pressure-induced retinal disorders.
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Affiliation(s)
- Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
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13
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Li W, Liu X, Tu Y, Ding D, Yi Q, Sun X, Wang Y, Wang K, Zhu M, Mao J. Dysfunctional Nurr1 promotes high glucose-induced Müller cell activation by up-regulating the NF-κB/NLRP3 inflammasome axis. Neuropeptides 2020; 82:102057. [PMID: 32461025 DOI: 10.1016/j.npep.2020.102057] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 04/25/2020] [Accepted: 05/17/2020] [Indexed: 12/27/2022]
Abstract
Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM). During DR, high glucose levels induce Müller cell gliosis, and the dysfunction of Müller cells further promotes the pathogenesis of DR. Transcription factor nuclear receptor subfamily 4 group A member 2 (Nurr1) inhibits the inflammatory response by suppressing nuclear factor-kappa B (NF-κB) and downregulating the downstream NACHT, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome. This study aimed to investigate whether Nurr1 dysfunction in Müller cells promoted the NF-κB/NLRP3 inflammasome axis during DR. In vitro, Nurr1 expression and nuclear translocation decreased in Müller cells exposed to high glucose levels; therefore, p65 was activated, and the downstream NLRP3 inflammasome was up-regulated via the interaction of p65 with its promoter. These phenomena promoted Müller cell activation and proliferation. Moreover, in vivo, gavage of the Nurr1 agonist C-DIM12 reduced retinal ganglion cell (RGC) loss in a mouse model of streptozotocin (STZ)-induced diabetes. Together, these results showed that Nurr1 played important anti-inflammatory and neuroprotective roles in Müller cells during DR, suggesting that Nurr1 may be a potential molecular target for the treatment of DR.
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Affiliation(s)
- Wendie Li
- Department of Ophthalmology, Ningbo Eye Hospital, Ningbo, China
| | - Xiaojuan Liu
- Department of Pathogen Biology, Medical College, Nantong University, Nantong, China
| | - Yuanyuan Tu
- Department of Ophthalmology, Lixiang Eye Hospital of Soochow University, Suzhou, China
| | - Dongmei Ding
- Department of Ophthalmology, Laizhou City People's Hospital, Yantai, China
| | - Quanyong Yi
- Department of Ophthalmology, Ningbo Eye Hospital, Ningbo, China
| | - Xiaolei Sun
- Department of Pathogen Biology, Medical College, Nantong University, Nantong, China
| | - Yanyan Wang
- Department of Ophthalmology, Ningbo Eye Hospital, Ningbo, China
| | - Kun Wang
- Department of Ophthalmology, Lixiang Eye Hospital of Soochow University, Suzhou, China
| | - Manhui Zhu
- Department of Ophthalmology, Lixiang Eye Hospital of Soochow University, Suzhou, China.
| | - Jinghai Mao
- Department of Ophthalmology, Ningbo Eye Hospital, Ningbo, China..
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14
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Politi MT, Ochoa F, Netti V, Ferreyra R, Bortman G, Sanjuan N, Morales C, Piazza A, Capurro C. Changes in cardiac Aquaporin expression during aortic valve replacement surgery with cardiopulmonary bypass. Eur J Cardiothorac Surg 2020; 57:556-564. [PMID: 31535145 DOI: 10.1093/ejcts/ezz249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/21/2019] [Accepted: 08/13/2019] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVES Cardiopulmonary bypass (CPB) use is an essential strategy for many cardiovascular surgeries. However, its use and duration have been associated with a higher rate of postoperative complications, such as low cardiac output syndrome due to myocardial oedema and dysfunction. Though Aquaporin water channels have been implicated in myocardial water balance, their specific role in this clinical scenario has not been established. METHODS In a consecutive study of 17 patients with severe aortic stenosis undergoing aortic valve replacement surgery, 2 myocardial biopsies of the left ventricle were taken: 1 before and 1 after CPB use. Sociodemographic, clinical and laboratory data were collected. Western blot and immunohistochemistry studies were performed. RESULTS After CPB use, there was a mean increase of ∼62% in Aquaporin 1 protein levels (P = 0.001) and a mean reduction of ∼38% in Aquaporin 4 protein levels (P = 0.030). In immunohistochemistry assays, Aquaporin 1 was found lining small blood vessels, while Aquaporin 4 formed a circular label in cardiomyocytes. There were no changes in the localization of either protein following CPB use. During the observed on-pump time interval, there was a 1.7%/min mean increase in Aquaporin 1 (P = 0.021) and a 2.5%/min mean decrease in Aquaporin 4 (P = 0.018). Myocardial interstitial oedema increased by 42% (95% confidence interval 31-54%) after CPB use. Patients who developed low cardiac output syndrome were in the upper half of the median percentage change of Aquaporin expression. CONCLUSION Time-dependent changes in cardiac Aquaporin expression may be associated with myocardial oedema and dysfunction related to CPB use.
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Affiliation(s)
- María Teresa Politi
- School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Institute of Physiology and Biophysics "Bernardo Houssay" (IFIBIO-HOUSSAY), Buenos Aires, Argentina
| | - Federico Ochoa
- School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Institute of Physiology and Biophysics "Bernardo Houssay" (IFIBIO-HOUSSAY), Buenos Aires, Argentina
| | - Vanina Netti
- School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Institute of Physiology and Biophysics "Bernardo Houssay" (IFIBIO-HOUSSAY), Buenos Aires, Argentina
| | - Raúl Ferreyra
- Department of Cardiology, Sanatorio de la Trinidad-Mitre, Buenos Aires, Argentina
| | - Guillermo Bortman
- Department of Cardiology, Sanatorio de la Trinidad-Mitre, Buenos Aires, Argentina
| | - Norberto Sanjuan
- Laboratory of Experimental Pathology, Department of Microbiology (IMPaM-CONICET), School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Buenos Aires, Argentina
| | - Celina Morales
- School of Medicine, Facultad de Medicina, University of Buenos Aires, Institute of Cardiovascular Pathophysiology (INFICA), Buenos Aires, Argentina
| | - Antonio Piazza
- Department of Cardiovascular Surgery, Sanatorio de la Trinidad-Mitre, Buenos Aires, Argentina
| | - Claudia Capurro
- School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Institute of Physiology and Biophysics "Bernardo Houssay" (IFIBIO-HOUSSAY), Buenos Aires, Argentina
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15
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Gao F, Yang Z, Jacoby RA, Wu SM, Pang JJ. The expression and function of TRPV4 channels in primate retinal ganglion cells and bipolar cells. Cell Death Dis 2019; 10:364. [PMID: 31064977 PMCID: PMC6504919 DOI: 10.1038/s41419-019-1576-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/25/2019] [Indexed: 12/26/2022]
Abstract
The transient receptor potential vanilloid 4 (TRPV4) channel may be opened by mechanical stimuli to mediate Ca2+ and Na+ influxes, and it has been suggested to mediate glaucoma retinopathy. However, it has been mostly unclear how TRPV4 activities affect the function of primate retinal ganglion cells (RGCs). We studied RGCs and bipolar cells (BCs) in the peripheral retina of the old-world primate using whole-cell current-clamp and voltage-clamp recordings, immunomarkers and confocal microscopy. RGCs were distinguished from displaced amacrine cells (ACs) by the absence of GABA and glycine immunoreactivity and possession of an axon and a large soma in the RGC layer. Strong TRPV4 signal was concentrated in medium to large somas of RGCs, and some TRPV4 signal was found in BCs (including PKCα-positive rod BCs), as well as the end feet, soma and outer processes of Mȕller cells. TRPV4 immunoreactivity quantified by the pixel intensity histogram revealed a high-intensity component for the plexiform layers, a low-intensity component for the soma layers of ACs and Mȕller cells, and both components in the soma layers of RGCs and BCs. In large RGCs, TRPV4 agonists 4α-phorbol 12,13 didecanoate (4αPDD) and GSK1016790A reversibly enhanced the spontaneous firing and shortened the delay of voltage-gated Na+ (Nav) currents under current-clamp conditions, and under voltage-clamp conditions, 4αPDD largely reversibly increased the amplitude and frequency of spontaneous excitatory postsynaptic currents. In BCs, changes in the membrane tension induced by either applying pressure or releasing the pressure both activated a transient cation current, which reversed at ~ -10 mV and was enhanced by heating from 24 °C to 30 °C. The pressure for the half-maximal effect was ~18 mmHg. These data indicate that functional TRPV4 channels are variably expressed in primate RGCs and BCs, possibly contributing to pressure-related changes in RGCs in glaucoma.
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Affiliation(s)
- Fan Gao
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Zhuo Yang
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Roy A Jacoby
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Samuel M Wu
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA.
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16
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Gambogenic acid triggers apoptosis in human nasopharyngeal carcinoma CNE-2Z cells by activating volume-sensitive outwardly rectifying chloride channel. Fitoterapia 2019; 133:150-158. [DOI: 10.1016/j.fitote.2019.01.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 01/06/2019] [Accepted: 01/11/2019] [Indexed: 02/08/2023]
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17
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Abdul Kadir L, Stacey M, Barrett-Jolley R. Emerging Roles of the Membrane Potential: Action Beyond the Action Potential. Front Physiol 2018; 9:1661. [PMID: 30519193 PMCID: PMC6258788 DOI: 10.3389/fphys.2018.01661] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 11/02/2018] [Indexed: 01/03/2023] Open
Abstract
Whilst the phenomenon of an electrical resting membrane potential (RMP) is a central tenet of biology, it is nearly always discussed as a phenomenon that facilitates the propagation of action potentials in excitable tissue, muscle, and nerve. However, as ion channel research shifts beyond these tissues, it became clear that the RMP is a feature of virtually all cells studied. The RMP is maintained by the cell’s compliment of ion channels. Transcriptome sequencing is increasingly revealing that equally rich compliments of ion channels exist in both excitable and non-excitable tissue. In this review, we discuss a range of critical roles that the RMP has in a variety of cell types beyond the action potential. Whereas most biologists would perceive that the RMP is primarily about excitability, the data show that in fact excitability is only a small part of it. Emerging evidence show that a dynamic membrane potential is critical for many other processes including cell cycle, cell-volume control, proliferation, muscle contraction (even in the absence of an action potential), and wound healing. Modulation of the RMP is therefore a potential target for many new drugs targeting a range of diseases and biological functions from cancer through to wound healing and is likely to be key to the development of successful stem cell therapies.
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Affiliation(s)
- Lina Abdul Kadir
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Michael Stacey
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, United States
| | - Richard Barrett-Jolley
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
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18
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Netti V, Pizzoni A, Pérez-Domínguez M, Ford P, Pasantes-Morales H, Ramos-Mandujano G, Capurro C. Release of taurine and glutamate contributes to cell volume regulation in human retinal Müller cells: differences in modulation by calcium. J Neurophysiol 2018; 120:973-984. [PMID: 29790838 DOI: 10.1152/jn.00725.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuronal activity in the retina generates osmotic gradients that lead to Müller cell swelling, followed by a regulatory volume decrease (RVD) response, partially due to the isoosmotic efflux of KCl and water. However, our previous studies in a human Müller cell line (MIO-M1) demonstrated that an important fraction of RVD may also involve the efflux of organic solutes. We also showed that RVD depends on the swelling-induced Ca2+ release from intracellular stores. Here we investigate the contribution of taurine (Tau) and glutamate (Glu), the most relevant amino acids in Müller cells, to RVD through the volume-regulated anion channel (VRAC), as well as their Ca2+ dependency in MIO-M1 cells. Swelling-induced [3H]Tau/[3H]Glu release was assessed by radiotracer assays and cell volume by fluorescence videomicroscopy. Results showed that cells exhibited an osmosensitive efflux of [3H]Tau and [3H]Glu (Tau > Glu) blunted by VRAC inhibitors 4-(2-butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)-oxybutyric acid and carbenoxolone reducing RVD. Only [3H]Tau efflux was mainly dependent on Ca2+ release from intracellular stores. RVD was unaffected in a Ca2+-free medium, probably due to Ca2+-independent Tau and Glu release, but was reduced by chelating intracellular Ca2+. The inhibition of phosphatidylinositol-3-kinase reduced [3H]Glu efflux but also the Ca2+-insensitive [3H]Tau fraction and decreased RVD, providing evidence of the relevance of this Ca2+-independent pathway. We propose that VRAC-mediated Tau and Glu release has a relevant role in RVD in Müller cells. The observed disparities in Ca2+ influence on amino acid release suggest the presence of VRAC isoforms that may differ in substrate selectivity and regulatory mechanisms, with important implications for retinal physiology. NEW & NOTEWORTHY The mechanisms for cell volume regulation in retinal Müller cells are still unknown. We show that swelling-induced taurine and glutamate release mediated by the volume-regulated anion channel (VRAC) largely contributes the to the regulatory volume decrease response in a human Müller cell line. Interestingly, the hypotonic-induced efflux of these amino acids exhibits disparities in Ca2+-dependent and -independent regulatory mechanisms, which strongly suggests that Müller cells may express different VRAC heteromers formed by the recently discovered leucine-rich repeat containing 8 (LRRC8) proteins.
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Affiliation(s)
- Vanina Netti
- Universidad de Buenos Aires, Facultad de Medicina. Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas , Buenos Aires , Argentina.,CONICET-Universidad de Buenos Aires. Instituto de Fisiología y Biofísica "Bernardo Houssay," Buenos Aires, Argentina
| | - Alejandro Pizzoni
- Universidad de Buenos Aires, Facultad de Medicina. Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas , Buenos Aires , Argentina.,CONICET-Universidad de Buenos Aires. Instituto de Fisiología y Biofísica "Bernardo Houssay," Buenos Aires, Argentina
| | - Martha Pérez-Domínguez
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Paula Ford
- Universidad de Buenos Aires, Facultad de Medicina. Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas , Buenos Aires , Argentina.,CONICET-Universidad de Buenos Aires. Instituto de Fisiología y Biofísica "Bernardo Houssay," Buenos Aires, Argentina
| | - Herminia Pasantes-Morales
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Gerardo Ramos-Mandujano
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Claudia Capurro
- Universidad de Buenos Aires, Facultad de Medicina. Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas , Buenos Aires , Argentina.,CONICET-Universidad de Buenos Aires. Instituto de Fisiología y Biofísica "Bernardo Houssay," Buenos Aires, Argentina
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