scholarly journals High Glucose Alters Cx43 Expression and Gap Junction Intercellular Communication in Retinal Müller Cells: Promotes Müller Cell and Pericyte Apoptosis

2014 ◽  
Vol 55 (7) ◽  
pp. 4327 ◽  
Author(s):  
Tetsuya Muto ◽  
Thomas Tien ◽  
Dongjoon Kim ◽  
Vijay P. Sarthy ◽  
Sayon Roy
Keyword(s):  
Gap Junction ◽  
Intercellular Communication ◽  
High Glucose ◽  
Müller Cells ◽  
Müller Cell ◽  
Muller Cells ◽  
Cx43 Expression ◽  
Gap Junction Intercellular Communication ◽  
Muller Cell

scholarly journals High-Glucose-Induced Rab20 Upregulation Disrupts Gap Junction Intercellular Communication and Promotes Apoptosis in Retinal Endothelial and Müller Cells: Implications for Diabetic Retinopathy

2020 ◽  
Vol 9 (11) ◽  
pp. 3710
Author(s):  
Dongjoon Kim ◽  
Casey Stottrup Lewis ◽  
Vijay P. Sarthy ◽  
Sayon Roy
Keyword(s):  
Diabetic Retinopathy ◽  
Gap Junction ◽  
Intercellular Communication ◽  
High Glucose ◽  
Connexin 43 ◽  
Müller Cells ◽  
Muller Cells ◽  
Dye Transfer ◽  
Cx43 Expression ◽  
Gap Junction Intercellular Communication

To investigate whether high glucose (HG) alters Rab20 expression and compromises gap junction intercellular communication (GJIC) and cell survival, retinal cells were studied for altered intracellular trafficking of connexin 43 (Cx43). Retinal endothelial cells (RRECs) and retinal Müller cells (rMCs) were grown in normal (N; 5 mM glucose) or HG (30 mM glucose) medium for seven days. In parallel, cells grown in HG medium were transfected with either Rab20 siRNA or scrambled siRNA as a control. Rab20 and Cx43 expression and their localization and distribution were assessed using Western Blot and immunostaining, respectively. Changes in GJIC activity were assessed using scrape load dye transfer, and apoptosis was identified using differential dye staining assay. In RRECs or rMCs grown in HG medium, Rab20 expression was significantly increased concomitant with a decreased number of Cx43 plaques. Importantly, a significant increase in the number of Cx43 plaques and GJIC activity was observed in cells transfected with Rab20 siRNA. Additionally, Rab20 downregulation inhibited HG-induced apoptosis in RRECs and rMCs. Results indicate HG-mediated Rab20 upregulation decreases Cx43 localization at the cell surface, resulting in compromised GJIC activity. Reducing Rab20 expression could be a useful strategy in preventing HG-induced vascular and Müller cell death associated with diabetic retinopathy.

scholarly journals Gap junctional coupling and connexin immunoreactivity in rabbit retinal glia

2006 ◽  
Vol 23 (1) ◽  
pp. 1-10 ◽  
Author(s):  
KATHLEEN R. ZAHS ◽  
PAUL W. CEELEN
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Lucifer Yellow ◽  
Müller Cells ◽  
Müller Cell ◽  
Muller Cells ◽  
Junctional Coupling ◽  
Muller Cell ◽  
Gap Junctional ◽  
Gap Junctional Coupling

Gap junctions provide a pathway for the direct intercellular exchange of ions and small signaling molecules. Gap junctional coupling between retinal astrocytes and between astrocytes and Müller cells, the principal glia of vertebrate retinas, has been previously demonstrated by the intercellular transfer of gap-junction permeant tracers. However, functional gap junctions have yet to be demonstrated between mammalian Müller cells. In the present study, when the gap-junction permeant tracers Neurobiotin and Lucifer yellow were injected into a Müller cellviaa patch pipette, the tracers transferred to at least one additional cell in more than half of the cases examined. Simultaneous whole-cell recordings from pairs of Müller cells in the isolated rabbit retina revealed electrical coupling between closely neighboring cells, confirming the presence of functional gap junctions between rabbit Müller cells. The limited degree of this coupling suggests that Müller cell–Müller cell gap junctions may coordinate the functions of small ensembles of these glial cells. Immunohistochemistry and immunoblotting were used to identify the connexins in rabbit retinal glia. Connexin30 (Cx30) and connexin43 (Cx43) immunoreactivities were associated with astrocytes in the medullary ray region of the retinas of both pigmented and albino rabbits. Connexin43 was also found in Müller cells, but antibody recognition differed between astrocytic and Müller cell connexin43.

scholarly journals Purinergic regulation of high-glucose-induced caspase-1 activation in the rat retinal Müller cell line rMC-1

2011 ◽  
Vol 301 (5) ◽  
pp. C1213-C1223 ◽  
Author(s):  
Katherine E. Trueblood ◽  
Susanne Mohr ◽  
George R. Dubyak
Keyword(s):  
High Glucose ◽  
Müller Cells ◽  
Müller Cell ◽  
Muller Cells ◽  
Interacting Protein ◽  
Caspase 1 ◽  
Muller Cell ◽  
Stimulation Of

Chronic activation of proinflammatory caspase-1 in the retinas of diabetic animals and patients in vivo and retinal Müller cells in vitro is well documented. In this study we characterized how elevated glucose and extracellular purines contribute to the activation of caspase-1 in a cultured rat Müller cell (rMC-1) model. The ability of high glucose (25 mM, 24 h) to activate caspase-1 was attenuated by either apyrase, which metabolizes extracellular ATP to AMP, or adenosine deaminase (ADA), which metabolizes extracellular adenosine to inosine. This suggested that autocrine stimulation of ATP-sensing P2 receptors and adenosine-sensing P1 receptors may in part mediate the response to high glucose. Exogenous ATP, 5′- N-ethylcarboxamido-adenosine (NECA), a nonselective P1 receptor agonist, or forskolin (FSK) increased caspase-1 activity in rMC-1 cells cultured in control glucose (5 mM) medium. Accumulation of active caspase-1 was also increased by dipyridamole, which suppresses adenosine reuptake. High-glucose stimulation of caspase-1 was attenuated by suramin, a nonselective P2 antagonist, or A2 adenosine receptor antagonists, but not by antagonism of P2X7 ATP-gated ion channel receptors. Although high glucose increased P2X7 mRNA, neither P2X7 protein nor function was detected in rMC-1 cells. The increased caspase-1 activity stimulated by high glucose, FSK, NECA, or ATP was correlated with increased gene expression of caspase-1 and thioredoxin-interacting-protein (TXNIP). These findings support a novel role for autocrine P1 and P2 purinergic receptors coupled to cAMP signaling cascades and transcriptional induction of caspase-1 in mediating the high-glucose-induced activation of caspase-1 and secretion of IL-1β in a cell culture model of nonhematopoietic retinal Müller cells.

scholarly journals Release of taurine and glutamate contributes to cell volume regulation in human retinal Müller cells: differences in modulation by calcium

2018 ◽  
Vol 120 (3) ◽  
pp. 973-984 ◽  
Author(s):  
Vanina Netti ◽  
Alejandro Pizzoni ◽  
Martha Pérez-Domínguez ◽  
Paula Ford ◽  
Herminia Pasantes-Morales ◽  
...  
Keyword(s):  
Cell Volume ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Müller Cells ◽  
Anion Channel ◽  
Müller Cell ◽  
Regulatory Mechanisms ◽  
Muller Cells ◽  
Muller Cell ◽  
Volume Decrease

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.

scholarly journals Mediation of FoxO1 in Activated Neuroglia Deficient for Nucleoside Diphosphate Kinase B during Vascular Degeneration

Neuroglia ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 280-291 ◽  
Author(s):  
Yi Qiu ◽  
Hongpeng Huang ◽  
Anupriya Chatterjee ◽  
Loïc Teuma ◽  
Fabienne Baumann ◽  
...  
Keyword(s):  
Diabetic Retinopathy ◽  
Cell Activation ◽  
Neurovascular Unit ◽  
Nucleoside Diphosphate Kinase ◽  
Müller Cells ◽  
Müller Cell ◽  
Muller Cells ◽  
Nucleoside Diphosphate Kinase B ◽  
Muller Cell ◽  
Underlying Mechanisms

The pathogenesis of diabetic retinopathy is closely associated with the breakdown of the neurovascular unit including the glial cells. Deficiency of nucleoside diphosphate kinase B (NDPK-B) results in retinal vasoregression mimicking diabetic retinopathy. Increased retinal expression of Angiopoietin-2 (Ang-2) initiates vasoregression. In this study, Müller cell activation, glial Ang-2 expression, and the underlying mechanisms were investigated in streptozotocin-induced diabetic NDPK-B deficient (KO) retinas and Müller cells isolated from the NDPK-B KO retinas. Müller cells were activated and Ang-2 expression was predominantly increased in Müller cells in normoglycemic NDPK-B KO retinas, similar to diabetic wild type (WT) retinas. Diabetes induction in the NDPK-B KO mice did not further increase its activation. Additionally, cultured NDPK-B KO Müller cells were more activated and showed higher Ang-2 expression than WT cells. Müller cell activation and Ang-2 elevation were observed upon high glucose treatment in WT, but not in NDPK-B KO cells. Moreover, increased levels of the transcription factor forkhead box protein O1 (FoxO1) were detected in non-diabetic NDPK-B KO Müller cells. The siRNA-mediated knockdown of FoxO1 in NDPK-B deficient cells interfered with Ang-2 upregulation. These data suggest that FoxO1 mediates Ang-2 upregulation induced by NDPK-B deficiency in the Müller cells and thus contributes to the onset of retinal vascular degeneration.

Ranibizumab prevents Müller cell edema by decreasing VEGF-A in diabetic retinopathy

2020 ◽  
Author(s):  
Tianqin Wang ◽  
Chaoyang Zhang ◽  
Hai Xie ◽  
Qiuxue Yi ◽  
Dandan Liu ◽  
...  
Keyword(s):  
Diabetic Retinopathy ◽  
Potassium Level ◽  
Müller Cells ◽  
Müller Cell ◽  
Intracellular Sodium ◽  
K Channel ◽  
Diabetic Rat ◽  
Muller Cells ◽  
Intracellular Potassium ◽  
Muller Cell

Abstract Background: Diabetic macular edema (DME) is the most common cause of vision loss in patients with diabetic retinopathy. The efficacy of anti-VEGF therapy has been well demonstrated and become the standard of care in the management of DME. The present study is to explore the possible mechanism(s) of ranibizumab in protecting Müller cells from cellular edema in experimental diabetic retinopathy. Methods: Sprague-Dawley rats were rendered diabetes with intraperitoneal injection of streptozotocin. Intravitreal injection of ranibizumab was performed 8 weeks after diabetes onset. Four weeks later, the rats were killed and the retinas were harvested for examination. rMC-1 cells (rat Müller cell line) were treated with glyoxal for 24 hours, with or without ranibizumab. Cell viability was detected with CCK-8 assay. The expressions of inwardly rectifying K + channel 4.1 (Kir4.1), aquaporin 4 (AQP4), Dystrophin 71 (Dp71), vascular endothelial growth factor A (VEGF-A), glutamine synthetase (GS) and sodium-potassium-ATPase (Na + -K + -ATPase) were examined with Western blot. VEGF-A in the supernatant of cell culture was detected with ELISA. The intracellular potassium and sodium levels were detected with specific indicators. Results: Compared to the normal control, the protein expressions of Kir4.1, AQP4 and Dp71 were down-regulated significantly in diabetic rat retinas, which were prevented by ranibizumab. The above changes were recapitulated in vitro . As compared with the control, the intracellular potassium level in glyoxal-treated rMC-1 cells was increased, while the intracellular sodium level and Na + -K + -ATPase protein level remained unchanged. However, ranibizumab treatment increased Na + -K + -ATPase protein expression and decreased intracellular sodium, but not potassium level. Conclusion: Ranibizumab protected Müller cells from intracellular edema through up-regulation of Kir4.1, AQP4, and Dp71 by directly binding VEGF-A. It also increased the expression of Na + -K + -ATPase, contributing to reduction of the intracellular osmotic pressure.

Blockade of amiloride-sensitive sodium channels alters multiple components of the mammalian electroretinogram

2005 ◽  
Vol 22 (2) ◽  
pp. 143-151 ◽  
Author(s):  
LAURA M. BROCKWAY ◽  
DALE J. BENOS ◽  
KENT T. KEYSER ◽  
TIMOTHY W. KRAFT
Keyword(s):  
Physiological Role ◽  
Müller Cells ◽  
Müller Cell ◽  
Cell Physiology ◽  
Muller Cells ◽  
Retinal Neurons ◽  
Multiple Components ◽  
Cell Components ◽  
Slow Piii ◽  
Muller Cell

Retinal neurons and Müller cells express amiloride-sensitive Na+ channels (ASSCs). Although all major subunits of these channels are expressed, their physiological role is relatively unknown in this system. In the present study, we used the electroretinogram (ERG) recorded from anesthetized rabbits and isolated rat and rabbit retina preparations to investigate the physiological significance of ASSCs in the retina. Based upon our previous study showing expression of α-ENaC and functional amiloride-sensitive currents in rabbit Müller cells, we expected changes in Müller cell components of the ERG. However, we observed changes in other components of the ERG as well. The presence of amiloride elicited changes in all major components of the ERG; the a-wave, b-wave, and d-wave (off response) were enhanced, while there was a reduction in the amplitude of the Müller cell response (slow PIII). These results suggest that ASSCs play an important role in retinal function including neuronal and Müller cell physiology.

Müller cell endfeet at the inner surface of the retina: light microscopy

1988 ◽  
Vol 1 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Zofia Dreher ◽  
Mignon Wegner ◽  
Jonathan Stone
Keyword(s):  
Ganglion Cells ◽  
Müller Cells ◽  
Müller Cell ◽  
Postnatal Life ◽  
Muller Cells ◽  
Regular Array ◽  
Differential Growth ◽  
Cat Retina ◽  
Inner Surface ◽  
Muller Cell

AbstractUsing fractions of the protein spectrum of the cat retina as immunogens, we have generated antibodies with substantial specificity for the Müller cells of the retina of cat, rabbit, guinea pig, and rat. The antibodies appear to bind to the filamentous components of the Müller cells and allow demonstration of the pattern of Müller cell endfeet at the inner surface of the retina, best seen in wholemount preparations. In sections and at the edge of wholemount preparations the somas and processes of the cells can be observed. Müller cells are more evenly distributed over the retina than ganglion cells, indicating that their proliferation continues during the differential growth of retina which continues into postnatal life. The morphology and distribution of the endfeet varies with the structures present at the inner surface of the retina. Where the axon bundles are thick, the endfeet are relatively small and are confined to narrow rows between bundles. Müller cell endfeet are also separated widely by large blood vessels. In both situations, it seems likely that Müller cells and astrocytes both contribute, perhaps competitively, to form the glia limitans of the inner surface of the retina. Where the somas of neurones are densely packed in the ganglion cell layer, the endfeet are small and numerous, forming rings around the somas. Where axon bundles, vessels, and somas are sparse, the endfeet appear largest and form a regular array.

scholarly journals Gap Junction Intercellular Communication Mediated by Connexin43 in Astrocytes Is Essential for Their Resistance to Oxidative Stress

2013 ◽  
Vol 289 (3) ◽  
pp. 1345-1354 ◽  
Author(s):  
Hoa T. Le ◽  
Wun Chey Sin ◽  
Shannon Lozinsky ◽  
John Bechberger ◽  
José Luis Vega ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Protective Effect ◽  
Gap Junction ◽  
Intercellular Communication ◽  
Cx43 Expression ◽  
Knock Out ◽  
Gap Junction Intercellular Communication ◽  
Junction Protein ◽  
A Cell ◽  
Hypoxia Reoxygenation

Oxidative stress induced by reactive oxygen species (ROS) is associated with various neurological disorders including aging, neurodegenerative diseases, as well as traumatic and ischemic insults. Astrocytes have an important role in the anti-oxidative defense in the brain. The gap junction protein connexin43 (Cx43) forms intercellular channels as well as hemichannels in astrocytes. In the present study, we investigated the contribution of Cx43 to astrocytic death induced by the ROS hydrogen peroxide (H2O2) and the mechanism by which Cx43 exerts its effects. Lack of Cx43 expression or blockage of Cx43 channels resulted in increased ROS-induced astrocytic death, supporting a cell protective effect of functional Cx43 channels. H2O2 transiently increased hemichannel activity, but reduced gap junction intercellular communication (GJIC). GJIC in wild-type astrocytes recovered after 7 h, but was absent in Cx43 knock-out astrocytes. Blockage of Cx43 hemichannels incompletely inhibited H2O2-induced hemichannel activity, indicating the presence of other hemichannel proteins. Panx1, which is predicted to be a major hemichannel contributor in astrocytes, did not appear to have any cell protective effect from H2O2 insults. Our data suggest that GJIC is important for Cx43-mediated ROS resistance. In contrast to hypoxia/reoxygenation, H2O2 treatment decreased the ratio of the hypophosphorylated isoform to total Cx43 level. Cx43 has been reported to promote astrocytic death induced by hypoxia/reoxygenation. We therefore speculate the increase in Cx43 dephosphorylation may account for the facilitation of astrocytic death. Our findings suggest that the role of Cx43 in response to cellular stress is dependent on the activation of signaling pathways leading to alteration of Cx43 phosphorylation states.

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