1
|
Puddu A, Maggi DC. Klotho: A new therapeutic target in diabetic retinopathy? World J Diabetes 2023; 14:1027-1036. [PMID: 37547589 PMCID: PMC10401458 DOI: 10.4239/wjd.v14.i7.1027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/12/2023] [Accepted: 05/22/2023] [Indexed: 07/12/2023] Open
Abstract
Klotho (Kl) is considered an antiaging gene, mainly for the inhibition of the insulin-like growth factor-1 signaling. Kl exists as full-length transmembrane, which acts as co-receptor for fibroblast growth factor receptor, and in soluble forms (sKl). The sKl may exert pleiotropic effects on organs and tissues by regulating several pathways involved in the pathogenesis of diseases associated with oxidative and inflammatory state. In diabetic Patients, serum levels of Kl are significantly decreased compared to healthy subjects, and are related to duration of diabetes. In diabetic retinopathy (DR), one of the most common microvascular complications of type 2 diabetes, serum Kl levels are negatively correlated with progression of the disease. A lot of evidences showed that Kl regulates several mechanisms involved in maintaining homeostasis and functions of retinal cells, including phagocytosis, calcium signaling, secretion of vascular endothelial growth factor A (VEGF-A), maintenance of redox status, and melanin biosynthesis. Experimental data have been shown that Kl exerts positive effects on several mechanisms involved in onset and progression of DR. In particular, treatment with Kl: (1) Prevents apoptosis induced by oxidative stress in human retinal endothelial cells and in retinal pigment epithelium (RPE) cells; (2) reduces secretion of VEGF-A by RPE cells; and (3) decreases subretinal fibrosis and preserves autophagic activity. Therefore, Kl may become a novel biomarker and a good candidate for the treatment of DR.
Collapse
Affiliation(s)
- Alessandra Puddu
- Department of Internal Medicine and Medical Specialties, University of Genova, Genova 16132, Italy
| | - Davide Carlo Maggi
- Department of Internal Medicine and Medical Specialties, University of Genova, Genova 16132, Italy
| |
Collapse
|
2
|
Nita M, Grzybowski A. Antioxidative Role of Heterophagy, Autophagy, and Mitophagy in the Retina and Their Association with the Age-Related Macular Degeneration (AMD) Etiopathogenesis. Antioxidants (Basel) 2023; 12:1368. [PMID: 37507908 PMCID: PMC10376332 DOI: 10.3390/antiox12071368] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/09/2023] [Accepted: 06/26/2023] [Indexed: 07/30/2023] Open
Abstract
Age-related macular degeneration (AMD), an oxidative stress-linked neurodegenerative disease, leads to irreversible damage of the central retina and severe visual impairment. Advanced age and the long-standing influence of oxidative stress and oxidative cellular damage play crucial roles in AMD etiopathogenesis. Many authors emphasize the role of heterophagy, autophagy, and mitophagy in maintaining homeostasis in the retina. Relevantly modifying the activity of both macroautophagy and mitophagy pathways represents one of the new therapeutic strategies in AMD. Our review provides an overview of the antioxidative roles of heterophagy, autophagy, and mitophagy and presents associations between dysregulations of these molecular mechanisms and AMD etiopathogenesis. The authors performed an extensive analysis of the literature, employing PubMed and Google Scholar, complying with the 2013-2023 period, and using the following keywords: age-related macular degeneration, RPE cells, reactive oxygen species, oxidative stress, heterophagy, autophagy, and mitophagy. Heterophagy, autophagy, and mitophagy play antioxidative roles in the retina; however, they become sluggish and dysregulated with age and contribute to AMD development and progression. In the retina, antioxidative roles also play in RPE cells, NFE2L2 and PGC-1α proteins, NFE2L2/PGC-1α/ARE signaling cascade, Nrf2 factor, p62/SQSTM1/Keap1-Nrf2/ARE pathway, circulating miRNAs, and Yttrium oxide nanoparticles performed experimentally in animal studies.
Collapse
Affiliation(s)
- Małgorzata Nita
- Domestic and Specialized Medicine Centre "Dilmed", 40-231 Katowice, Poland
| | - Andrzej Grzybowski
- Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, Gorczyczewskiego 2/3, 61-553 Poznań, Poland
| |
Collapse
|
3
|
Ignatova I, Frolov R, Nymark S. The retinal pigment epithelium displays electrical excitability and lateral signal spreading. BMC Biol 2023; 21:84. [PMID: 37069561 PMCID: PMC10111697 DOI: 10.1186/s12915-023-01559-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 03/10/2023] [Indexed: 04/19/2023] Open
Abstract
BACKGROUND The non-neuronal retinal pigment epithelium (RPE) functions in intimate association with retinal photoreceptors, performing a multitude of tasks critical for maintaining retinal homeostasis and collaborating with retinal glial cells to provide metabolic support and ionic buffering. Accordingly, the RPE has recently been shown to display dynamic properties mediated by an array of ion channels usually more characteristic of astrocytes and excitable cells. The recent discovery of canonical voltage-activated Na+ channels in the RPE and their importance for phagocytosis of photoreceptor outer segments raises a question about their electrogenic function. Here, we performed a detailed electrophysiological analysis related to the functioning of these channels in human embryonic stem cell (hESC)-derived RPE. RESULTS Our studies examining the electrical properties of the hESC-RPE revealed that its membrane mainly displays passive properties in a broad voltage range, with the exception of depolarization-induced spikes caused by voltage-activated Na+ current (INa). Spike amplitude depended on the availability of INa and spike kinetics on the membrane time constant, and the spikes could be largely suppressed by TTX. Membrane resistance fluctuated rapidly and strongly, repeatedly changing over the course of recordings and causing closely correlated fluctuations in resting membrane potential. In a minority of cells, we found delayed secondary INa-like inward currents characterized by comparatively small amplitudes and slow kinetics, which produced secondary depolarizing spikes. Up to three consecutive delayed inward current waves were detected. These currents could be rapidly and reversibly augmented by applying L-type Ca2+ channel blocker nifedipine to diminish influx of calcium and thus increase gap junctional conductance. CONCLUSIONS This work shows, for the first time, that INa and INa-mediated voltage spikes can spread laterally through gap junctions in the monolayer of cells that are traditionally considered non-excitable. Our findings support a potential role of the RPE that goes beyond giving homeostatic support to the retina.
Collapse
Affiliation(s)
- Irina Ignatova
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | | | - Soile Nymark
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.
| |
Collapse
|
4
|
Vollmar BS, Fei M, Liang WC, Bravo DD, Wang J, Yu L, Corr N, Zhang G, McNamara E, Masih S, Chee E, Shin G, Ohri R, Leipold DD, Wu C, Dere E, Wang J, Huang H, Wu Y, Yan M. PEGylation of anti-MerTK Antibody Modulates Ocular Biodistribution. Bioconjug Chem 2022; 33:1837-1851. [DOI: 10.1021/acs.bioconjchem.2c00276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Breanna S. Vollmar
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Mingjian Fei
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Wei-Ching Liang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Daniel D. Bravo
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Joy Wang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Lanlan Yu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Nick Corr
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Gu Zhang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Erin McNamara
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Shabkhaiz Masih
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Elin Chee
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Gawon Shin
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Rachana Ohri
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Douglas D. Leipold
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Cong Wu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Edward Dere
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jianyong Wang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Haochu Huang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Yan Wu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Minhong Yan
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| |
Collapse
|
5
|
Banderali U, Jain M, Thakur S, Jayanthan A, Belke DD, Giles WR, Narendran A. The T-type Calcium Channel Cav3.1 in Y79 Retinoblastoma Cells is Regulated by the Epidermal Growth Factor Receptor via the MAPK Signaling Pathway. Curr Eye Res 2021; 47:426-435. [PMID: 34674590 DOI: 10.1080/02713683.2021.1988982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE Retinoblastoma is the most frequent intraocular cancer in children. It is also one of the most common causes for enucleation and carries a significant morbidity rate in affected individuals. Hence, studies on its pathophysiological and growth regulatory mechanisms are urgently needed to identify more effective novel therapeutics. METHODS Using the Y79 retinoblastoma cell line, we investigated the electrophysiological and functional activities of the T-type voltage-gated calcium channel Cav3.1, that is constitutively expressed in these cells. We also analyzed the Akt and MAPK signaling pathways downstream of the epidermal growth factor receptor (EGFR) to understand the mechanism responsible for the inhibition of Cav3.1. RESULTS We demonstrate that the EGFR inhibitor Afatinib significantly reduced cell viability and Cav3.1 mRNA expression and electrophysiological activity. At low concentrations (1 µM), Afatinib reduced the amplitude of Cav3.1 current density, whereas at a high concentration (10 µM), it completely abolished the voltage-gated calcium current. Our results show that inhibition of the MAPK pathway by a specific inhibitor VX-11e affected the Cav3.1 current in a dose-dependent manner. VX-11e (50 nM-1 µM) treatment reduced Cav3.1 current densities in Y79 cells, with complete abolishment of Cav3.1 current at higher concentrations (5 µM). We also demonstrate that the specific inhibition of the Akt kinase (using MK-2206) had no effect on the Cav3.1 currents. CONCLUSION Our study provides a functional relationship between the MAPK pathway and EGFR signaling and indicates that the MAPK signaling pathway mediates the control of Cav3.1 by EGFR in retinoblastoma.
Collapse
Affiliation(s)
- Umberto Banderali
- Human Health Therapeutics Research Centre, National Research Council of Canada, Ottawa, Canada
| | - Mohit Jain
- POETIC Laboratory for Pre-Clinical Studies and the Division of Pediatric Oncology, Alberta Children's Hospital, Faculty of Medicine, University of Calgary, Calgary, AB, Canada
| | - Satbir Thakur
- POETIC Laboratory for Pre-Clinical Studies and the Division of Pediatric Oncology, Alberta Children's Hospital, Faculty of Medicine, University of Calgary, Calgary, AB, Canada
| | - Aarthi Jayanthan
- POETIC Laboratory for Pre-Clinical Studies and the Division of Pediatric Oncology, Alberta Children's Hospital, Faculty of Medicine, University of Calgary, Calgary, AB, Canada
| | - Darrell D Belke
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Wayne R Giles
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Aru Narendran
- POETIC Laboratory for Pre-Clinical Studies and the Division of Pediatric Oncology, Alberta Children's Hospital, Faculty of Medicine, University of Calgary, Calgary, AB, Canada
| |
Collapse
|
6
|
Acute RhoA/Rho Kinase Inhibition Is Sufficient to Restore Phagocytic Capacity to Retinal Pigment Epithelium Lacking the Engulfment Receptor MerTK. Cells 2021; 10:cells10081927. [PMID: 34440696 PMCID: PMC8394172 DOI: 10.3390/cells10081927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/26/2021] [Accepted: 07/26/2021] [Indexed: 12/27/2022] Open
Abstract
The diurnal phagocytosis of spent photoreceptor outer segment fragments (POS) by retinal pigment epithelial (RPE) cells is essential for visual function. POS internalization by RPE cells requires the assembly of F-actin phagocytic cups beneath surface-tethered POS and Mer tyrosine kinase (MerTK) signaling. The activation of the Rho family GTPase Rac1 is necessary for phagocytic cup formation, and Rac1 is activated normally in MerTK-deficient RPE. We show here that mutant RPE lacking MerTK and wild-type RPE deprived of MerTK ligand both fail to form phagocytic cups regardless of Rac1 activation. However, in wild-type RPE in vivo, a decrease in RhoA activity coincides with the daily phagocytosis burst, while RhoA activity in MerTK-deficient RPE is constant. Elevating RhoA activity blocks phagocytic cup formation and phagocytosis by wild-type RPE. Conversely, inhibiting RhoA effector Rho kinases (ROCKs) rescues both F-actin assembly and POS internalization of primary RPE if MerTK or its ligand are lacking. Most strikingly, acute ROCK inhibition is sufficient to induce the formation and acidification of endogenous POS phagosomes by MerTK-deficient RPE ex vivo. Altogether, RhoA pathway inactivation is a necessary and sufficient downstream effect of MerTK phagocytic signaling such that the acute manipulation of cytosolic ROCK activity suffices to restore phagocytic capacity to MerTK-deficient RPE.
Collapse
|
7
|
Mamaeva D, Jazouli Z, DiFrancesco ML, Erkilic N, Dubois G, Hilaire C, Meunier I, Boukhaddaoui H, Kalatzis V. Novel roles for voltage-gated T-type Ca 2+ and ClC-2 channels in phagocytosis and angiogenic factor balance identified in human iPSC-derived RPE. FASEB J 2021; 35:e21406. [PMID: 33724552 DOI: 10.1096/fj.202002754r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/13/2021] [Accepted: 01/19/2021] [Indexed: 01/26/2023]
Abstract
Human-induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) is a powerful tool for pathophysiological studies and preclinical therapeutic screening, as well as a source for clinical cell transplantation. Thus, it must be validated for maturity and functionality to ensure correct data readouts and clinical safety. Previous studies have validated hiPSC-derived RPE as morphologically characteristic of the tissue in the human eye. However, information concerning the expression and functionality of ion channels is still limited. We screened hiPSC-derived RPE for the polarized expression of a panel of L-type (CaV 1.1, CaV 1.3) and T-type (CaV 3.1, CaV 3.3) Ca2+ channels, K+ channels (Maxi-K, Kir4.1, Kir7.1), and the Cl- channel ClC-2 known to be expressed in native RPE. We also tested the roles of these channels in key RPE functions using specific inhibitors. In addition to confirming the native expression profiles and function of certain channels, such as L-type Ca2+ channels, we show for the first time that T-type Ca2+ channels play a role in both phagocytosis and vascular endothelial growth factor (VEGF) secretion. Moreover, we demonstrate that Maxi-K and Kir7.1 channels are involved in the polarized secretion of VEGF and pigment epithelium-derived factor (PEDF). Furthermore, we show a novel localization for ClC-2 channel on the apical side of hiPSC-derived RPE, with an overexpression at the level of fluid-filled domes, and demonstrate that it plays an important role in phagocytosis, as well as VEGF and PEDF secretion. Taken together, hiPSC-derived RPE is a powerful model for advancing fundamental knowledge of RPE functions.
Collapse
Affiliation(s)
- Daria Mamaeva
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Zhour Jazouli
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Mattia L DiFrancesco
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Nejla Erkilic
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France.,National Reference Centre for Inherited Sensory Diseases, Montpellier University, CHU, Montpellier, France
| | - Gregor Dubois
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Cecile Hilaire
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Isabelle Meunier
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France.,National Reference Centre for Inherited Sensory Diseases, Montpellier University, CHU, Montpellier, France
| | - Hassan Boukhaddaoui
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| | - Vasiliki Kalatzis
- Institute for Neurosciences of Montpellier, Inserm, Montpellier University, Montpellier, France
| |
Collapse
|
8
|
MERTK-Dependent Ensheathment of Photoreceptor Outer Segments by Human Pluripotent Stem Cell-Derived Retinal Pigment Epithelium. Stem Cell Reports 2021; 14:374-389. [PMID: 32160519 PMCID: PMC7066375 DOI: 10.1016/j.stemcr.2020.02.004] [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: 04/23/2019] [Revised: 02/06/2020] [Accepted: 02/10/2020] [Indexed: 11/22/2022] Open
Abstract
Maintenance of a healthy photoreceptor-retinal pigment epithelium (RPE) interface is essential for vision. At the center of this interface, apical membrane protrusions stemming from the RPE ensheath photoreceptor outer segments (POS), and are possibly involved in the recycling of POS through phagocytosis. The molecules that regulate POS ensheathment and its relationship to phagocytosis remain to be deciphered. By means of ultrastructural analysis, we revealed that Mer receptor tyrosine kinase (MERTK) ligands, GAS6 and PROS1, rather than αVβ5 integrin receptor ligands, triggered POS ensheathment by human embryonic stem cell (hESC)-derived RPE. Furthermore, we found that ensheathment is required for POS fragmentation before internalization. Consistently, POS ensheathment, fragmentation, and internalization were abolished in MERTK mutant RPE, and rescue of MERTK expression in retinitis pigmentosa (RP38) patient RPE counteracted these defects. Our results suggest that loss of ensheathment due to MERTK dysfunction might contribute to vision impairment in RP38 patients. POS are ensheathed in vitro by human embryonic stem cell-derived RPE POS ensheathment is upregulated by MERTK ligands: GAS6 and PROS1 αVβ5 integrin receptor ligands do not stimulate POS ensheathment MERTK is essential for POS ensheathment and fragmentation before internalization
Collapse
|
9
|
Kwon W, Freeman SA. Phagocytosis by the Retinal Pigment Epithelium: Recognition, Resolution, Recycling. Front Immunol 2020; 11:604205. [PMID: 33281830 PMCID: PMC7691529 DOI: 10.3389/fimmu.2020.604205] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Tissue-resident phagocytes are responsible for the routine binding, engulfment, and resolution of their meals. Such populations of cells express appropriate surface receptors that are tailored to recognize the phagocytic targets of their niche and initiate the actin polymerization that drives internalization. Tissue-resident phagocytes also harbor enzymes and transporters along the endocytic pathway that orchestrate the resolution of ingested macromolecules from the phagolysosome. Solutes fluxed from the endocytic pathway and into the cytosol can then be reutilized by the phagocyte or exported for their use by neighboring cells. Such a fundamental metabolic coupling between resident phagocytes and the tissue in which they reside is well-emphasized in the case of retinal pigment epithelial (RPE) cells; specialized phagocytes that are responsible for the turnover of photoreceptor outer segments (POS). Photoreceptors are prone to photo-oxidative damage and their long-term health depends enormously on the disposal of aged portions of the outer segment. The phagocytosis of the POS by the RPE is the sole means of this turnover and clearance. RPE are themselves mitotically quiescent and therefore must resolve the ingested material to prevent their toxic accumulation in the lysosome that otherwise leads to retinal disorders. Here we describe the sequence of events underlying the healthy turnover of photoreceptors by the RPE with an emphasis on the signaling that ensures the phagocytosis of the distal POS and on the transport of solutes from the phagosome that supersedes its resolution. While other systems may utilize different receptors and transporters, the biophysical and metabolic manifestations of such events are expected to apply to all tissue-resident phagocytes that perform regular phagocytic programs.
Collapse
Affiliation(s)
- Whijin Kwon
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| |
Collapse
|
10
|
Cordes M, Bucichowski P, Alfaar AS, Tsang SH, Almedawar S, Reichhart N, Strauß O. Inhibition of Ca 2+ channel surface expression by mutant bestrophin-1 in RPE cells. FASEB J 2020; 34:4055-4071. [PMID: 31930599 DOI: 10.1096/fj.201901202rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 12/09/2019] [Accepted: 12/31/2019] [Indexed: 01/11/2023]
Abstract
The BEST1 gene product bestrophin-1, a Ca2+ -dependent anion channel, interacts with CaV 1.3 Ca2+ channels in the retinal pigment epithelium (RPE). BEST1 mutations lead to Best vitelliform macular dystrophy. A common functional defect of these mutations is reduced trafficking of bestrophin-1 into the plasma membrane. We hypothesized that this defect affects the interaction partner CaV 1.3 channel affecting Ca2+ signaling and altered RPE function. Thus, we investigated the protein interaction between CaV 1.3 channels and bestrophin-1 by immunoprecipitation, CaV 1.3 activity in the presence of mutant bestrophin-1 and intracellular trafficking of the interaction partners in confluent RPE monolayers. We selected four BEST1 mutations, each representing one mutational hotspot of the disease: T6P, F80L, R218C, and F305S. Heterologously expressed L-type channels and mutant bestrophin-1 showed reduced interaction, reduced CaV 1.3 channel activity, and changes in surface expression. Transfection of polarized RPE (porcine primary cells, iPSC-RPE) that endogenously express CaV 1.3 and wild-type bestrophin-1, with mutant bestrophin-1 confirmed reduction of CaV 1.3 surface expression. For the four selected BEST1 mutations, presence of mutant bestrophin-1 led to reduced CaV 1.3 activity by modulating pore-function or decreasing surface expression. Reduced CaV 1.3 activity might open new ways to understand symptoms of Best vitelliform macular dystrophy such as reduced electro-oculogram, lipofuscin accumulation, and vision impairment.
Collapse
Affiliation(s)
- Magdalena Cordes
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a corporate member of Freie Universität, Humboldt-University, the Berlin Institute of Health, Berlin, Germany
| | - Piotr Bucichowski
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a corporate member of Freie Universität, Humboldt-University, the Berlin Institute of Health, Berlin, Germany
| | - Ahmad S Alfaar
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a corporate member of Freie Universität, Humboldt-University, the Berlin Institute of Health, Berlin, Germany
| | - Stephen H Tsang
- Jonas Children's Vision Care, and Bernard & Shirlee Brown Glaucoma Laboratory, Department of Ophthalmology, Columbia Stem Cell Initiative, Departments of Ophthalmology Pathology & Cell Biology, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY, USA.,Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
| | - Seba Almedawar
- Center for Molecular and Cellular Bioengineering (CMCB), Center for Regenerative Therapies, Dresden (CRTD), Technische Universität Dresden, Dresden, Germany
| | - Nadine Reichhart
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a corporate member of Freie Universität, Humboldt-University, the Berlin Institute of Health, Berlin, 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
| |
Collapse
|
11
|
Johansson JK, Karema-Jokinen VI, Hakanen S, Jylhä A, Uusitalo H, Vihinen-Ranta M, Skottman H, Ihalainen TO, Nymark S. Sodium channels enable fast electrical signaling and regulate phagocytosis in the retinal pigment epithelium. BMC Biol 2019; 17:63. [PMID: 31412898 PMCID: PMC6694495 DOI: 10.1186/s12915-019-0681-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 07/11/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Voltage-gated sodium (Nav) channels have traditionally been considered a trademark of excitable cells. However, recent studies have shown the presence of Nav channels in several non-excitable cells, such as astrocytes and macrophages, demonstrating that the roles of these channels are more diverse than was previously thought. Despite the earlier discoveries, the presence of Nav channel-mediated currents in the cells of retinal pigment epithelium (RPE) has been dismissed as a cell culture artifact. We challenge this notion by investigating the presence and possible role of Nav channels in RPE both ex vivo and in vitro. RESULTS Our work demonstrates that several subtypes of Nav channels are found in human embryonic stem cell (hESC)-derived and mouse RPE, most prominently subtypes Nav1.4, Nav1.6, and Nav1.8. Whole cell patch clamp recordings from the hESC-derived RPE monolayers showed that the current was inhibited by TTX and QX-314 and was sensitive to the selective blockers of the main Nav subtypes. Importantly, we show that the Nav channels are involved in photoreceptor outer segment phagocytosis since blocking their activity significantly reduces the efficiency of particle internalization. Consistent with this role, our electron microscopy results and immunocytochemical analysis show that Nav1.4 and Nav1.8 accumulate on phagosomes and that pharmacological inhibition of Nav channels as well as silencing the expression of Nav1.4 with shRNA impairs the phagocytosis process. CONCLUSIONS Taken together, our study shows that Nav channels are present in RPE, giving this tissue the capacity of fast electrical signaling. The channels are critical for the physiology of RPE with an important role in photoreceptor outer segment phagocytosis.
Collapse
Affiliation(s)
- Julia K Johansson
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Viivi I Karema-Jokinen
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Satu Hakanen
- Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Antti Jylhä
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Hannu Uusitalo
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
- Tays Eye Centre, Tampere University Hospital, Tampere, Finland
| | - Maija Vihinen-Ranta
- Department of Biological and Environmental Science and Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Heli Skottman
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Teemu O Ihalainen
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Soile Nymark
- BioMediTech, Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.
| |
Collapse
|
12
|
Korkka I, Viheriälä T, Juuti-Uusitalo K, Uusitalo-Järvinen H, Skottman H, Hyttinen J, Nymark S. Functional Voltage-Gated Calcium Channels Are Present in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium. Stem Cells Transl Med 2018; 8:179-193. [PMID: 30394009 PMCID: PMC6344904 DOI: 10.1002/sctm.18-0026] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 08/24/2018] [Accepted: 09/07/2018] [Indexed: 11/25/2022] Open
Abstract
Retinal pigment epithelium (RPE) performs important functions for the maintenance of photoreceptors and vision. Malfunctions within the RPE are implicated in several retinal diseases for which transplantations of stem cell‐derived RPE are promising treatment options. Their success, however, is largely dependent on the functionality of the transplanted cells. This requires correct cellular physiology, which is highly influenced by the various ion channels of RPE, including voltage‐gated Ca2+ (CaV) channels. This study investigated the localization and functionality of CaV channels in human embryonic stem cell (hESC)‐derived RPE. Whole‐cell patch‐clamp recordings from these cells revealed slowly inactivating L‐type currents comparable to freshly isolated mouse RPE. Some hESC‐RPE cells also carried fast transient T‐type resembling currents. These findings were confirmed by immunostainings from both hESC‐ and mouse RPE that showed the presence of the L‐type Ca2+ channels CaV1.2 and CaV1.3 as well as the T‐type Ca2+ channels CaV3.1 and CaV3.2. The localization of the major subtype, CaV1.3, changed during hESC‐RPE maturation co‐localizing with pericentrin to the base of the primary cilium before reaching more homogeneous membrane localization comparable to mouse RPE. Based on functional assessment, the L‐type Ca2+ channels participated in the regulation of vascular endothelial growth factor secretion as well as in the phagocytosis of photoreceptor outer segments in hESC‐RPE. Overall, this study demonstrates that a functional machinery of voltage‐gated Ca2+ channels is present in mature hESC‐RPE, which is promising for the success of transplantation therapies. stem cells translational medicine2019;8:179&15
Collapse
Affiliation(s)
- Iina Korkka
- Faculty of Biomedical Sciences and Engineering, BioMediTech, Tampere University of Technology, Tampere, Finland
| | - Taina Viheriälä
- Faculty of Biomedical Sciences and Engineering, BioMediTech, Tampere University of Technology, Tampere, Finland.,Faculty of Medicine and Life Sciences, BioMediTech, University of Tampere, Tampere, Finland
| | - Kati Juuti-Uusitalo
- Faculty of Medicine and Life Sciences, BioMediTech, University of Tampere, Tampere, Finland
| | - Hannele Uusitalo-Järvinen
- Eye Centre, Tampere University Hospital, Tampere, Finland.,Faculty of Medicine and Life Sciences, Department of Ophthalmology, University of Tampere, Tampere, Finland
| | - Heli Skottman
- Faculty of Medicine and Life Sciences, BioMediTech, University of Tampere, Tampere, Finland
| | - Jari Hyttinen
- Faculty of Biomedical Sciences and Engineering, BioMediTech, Tampere University of Technology, Tampere, Finland
| | - Soile Nymark
- Faculty of Biomedical Sciences and Engineering, BioMediTech, Tampere University of Technology, Tampere, Finland
| |
Collapse
|
13
|
Ao J, Wood JP, Chidlow G, Gillies MC, Casson RJ. Retinal pigment epithelium in the pathogenesis of age-related macular degeneration and photobiomodulation as a potential therapy? Clin Exp Ophthalmol 2018; 46:670-686. [PMID: 29205705 DOI: 10.1111/ceo.13121] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/27/2017] [Accepted: 11/28/2017] [Indexed: 12/11/2022]
Abstract
The retinal pigment epithelium (RPE) comprises a monolayer of cells located between the neuroretina and the choriocapillaries. The RPE serves several important functions in the eye: formation of the blood-retinal barrier, protection of the retina from oxidative stress, nutrient delivery and waste disposal, ionic homeostasis, phagocytosis of photoreceptor outer segments, synthesis and release of growth factors, reisomerization of all-trans-retinal during the visual cycle, and establishment of ocular immune privilege. Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. Dysfunction of the RPE has been associated with the pathogenesis of AMD in relation to increased oxidative stress, mitochondrial destabilization and complement dysregulation. Photobiomodulation or near infrared light therapy which refers to non-invasive irradiation of tissue with light in the far-red to near-infrared light spectrum (630-1000 nm), is an intervention that specifically targets key mechanisms of RPE dysfunction that are implicated in AMD pathogenesis. The current evidence for the efficacy of photobiomodulation in AMD is poor but its safety profile and proposed mechanisms of action motivate further research as a novel therapy for AMD.
Collapse
Affiliation(s)
- Jack Ao
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia
| | - John Pm Wood
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia
| | - Glyn Chidlow
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia
| | - Mark C Gillies
- The Save Sight Institute, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Robert J Casson
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia
| |
Collapse
|
14
|
Pharmacology of the retinal pigment epithelium, the interface between retina and body system. Eur J Pharmacol 2016; 787:84-93. [PMID: 27044435 DOI: 10.1016/j.ejphar.2016.03.066] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/14/2016] [Accepted: 03/31/2016] [Indexed: 12/12/2022]
Abstract
The retinal pigment epithelium (RPE) is a close, interactive partner to the photoreceptors as well as an interface with the endothelium of the choroid and thus with the body's circulatory system. To fulfill these roles, the RPE communicates with neighboring tissue by secretion of a large variety of factors and is able to react to secreted factors via a plethora of transmembrane receptors. Clinically relevant local pharmacological effects are caused by anti-VEGF-A treatment in choroidal neovascularization or by carboanhydrase inhibitors reducing fluid accumulation in the macula. Being exposed to the bloodstream, the RPE reacts to systemic disease, such as diabetes or hypertension, but also to systemic pharmacological intervention, for example to hypotensive drugs acting on the renin-angiotensin-system. Sustained pharmacological treatments, in particular, cause side effects at the RPE with consequences for both RPE function and photoreceptor survival. Among these are systemic inhibition of angiotensin-converting enzyme, insulin treatment in diabetes and anti-VEGF-A therapy. Given the special anatomical and functional relationships of the RPE, pharmacological intervention targeting either the eye or the body systemically should take potential alteration of RPE and subsequently photoreceptor function into account.
Collapse
|
15
|
Strauß O, Reichhart N, Gomez NM, Müller C. Contribution of Ion Channels in Calcium Signaling Regulating Phagocytosis: MaxiK, Cav1.3 and Bestrophin-1. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:739-44. [PMID: 26427483 DOI: 10.1007/978-3-319-17121-0_98] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mutations in the BEST1 gene lead to a variety of retinal degenerations including Best's vitelliforme macular degeneration. The BEST1 gene product, bestrophin-1, is expressed in the retinal pigment epithelium (RPE). It is likely that mutant bestrophin-1 impairs functions of the RPE which support photoreceptor function and will thus lead to retinal degeneration. However, the RPE function which is influenced by bestrophin-1 is so far not identified. Previously we showed that bestrophin-1 interacts with L-type Ca²⁺ channels of the CaV1.3 subtype and that the endogenously expressed bestrophin-1 is required for intracellular Ca²⁺ regulation. A hallmark of Best's disease is the fast lipofuscin accumulation occurring already at young ages. Therefore, we addressed the hypothesis that bestrophin-1 might influence phagocytosis of photoreceptor outer segments (POS) by the RPE. Here, siRNA knock-down of bestrophin-1 expression as well as inhibition of L-type Ca²⁺ channel activity modulated the POS phagocytosis in vitro. In vivo CaV1.3 expression appeared to be diurnal regulated with a higher expression rate in the afternoon. Compared to wild-type littermates, Ca V 1.3 (-/-) mice showed a shift in the circadian POS phagocytosis with an increased activity in the afternoon. Thus we suggest that mutant bestrophin-1 leads to an impaired regulation of the POS phagocytosis by the RPE which would explain the fast lipofuscin accumulation in Best patients.
Collapse
Affiliation(s)
- Olaf Strauß
- Experimental Ophthalmology, Department of Ophthalmology, Charite University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Nadine Reichhart
- Experimental Ophthalmology, Department of Ophthalmology, Charite University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Nestor Mas Gomez
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Augustenburger Platz 1, 240 South 40th Street, 19104-6030, Philadelphia, PA, USA.
| | - Claudia Müller
- Department of Biological Sciences, Center for Cancer, Genetic Diseases and Gene Regulation, Fordham University Bronx, 10458, Bronx, NY, USA.
| |
Collapse
|
16
|
Giblin JP, Comes N, Strauss O, Gasull X. Ion Channels in the Eye: Involvement in Ocular Pathologies. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2015; 104:157-231. [PMID: 27038375 DOI: 10.1016/bs.apcsb.2015.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The eye is the sensory organ of vision. There, the retina transforms photons into electrical signals that are sent to higher brain areas to produce visual sensations. In the light path to the retina, different types of cells and tissues are involved in maintaining the transparency of avascular structures like the cornea or lens, while others, like the retinal pigment epithelium, have a critical role in the maintenance of photoreceptor function by regenerating the visual pigment. Here, we have reviewed the roles of different ion channels expressed in ocular tissues (cornea, conjunctiva and neurons innervating the ocular surface, lens, retina, retinal pigment epithelium, and the inflow and outflow systems of the aqueous humor) that are involved in ocular disease pathophysiologies and those whose deletion or pharmacological modulation leads to specific diseases of the eye. These include pathologies such as retinitis pigmentosa, macular degeneration, achromatopsia, glaucoma, cataracts, dry eye, or keratoconjunctivitis among others. Several disease-associated ion channels are potential targets for pharmacological intervention or other therapeutic approaches, thus highlighting the importance of these channels in ocular physiology and pathophysiology.
Collapse
Affiliation(s)
- Jonathan P Giblin
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Nuria Comes
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | | | - Xavier Gasull
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
| |
Collapse
|
17
|
Singh R, Kuai D, Guziewicz KE, Meyer J, Wilson M, Lu J, Smith M, Clark E, Verhoeven A, Aguirre GD, Gamm DM. Pharmacological Modulation of Photoreceptor Outer Segment Degradation in a Human iPS Cell Model of Inherited Macular Degeneration. Mol Ther 2015; 23:1700-1711. [PMID: 26300224 DOI: 10.1038/mt.2015.141] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/23/2015] [Indexed: 12/16/2022] Open
Abstract
Degradation of photoreceptor outer segments (POS) by retinal pigment epithelium (RPE) is essential for vision, and studies have implicated altered POS processing in the pathogenesis of some retinal degenerative diseases. Consistent with this concept, a recently established hiPSC-RPE model of inherited macular degeneration, Best disease (BD), displayed reduced rates of POS breakdown. Herein we utilized this model to determine (i) if disturbances in protein degradation pathways are associated with delayed POS digestion and (ii) whether such defect(s) can be pharmacologically targeted. We found that BD hiPSC-RPE cultures possessed increased protein oxidation, decreased free-ubiquitin levels, and altered rates of exosome secretion, consistent with altered POS processing. Application of valproic acid (VPA) with or without rapamycin increased rates of POS degradation in our model, whereas application of bafilomycin-A1 decreased such rates. Importantly, the negative effect of bafilomycin-A1 could be fully reversed by VPA. The utility of hiPSC-RPE for VPA testing was further evident following examination of its efficacy and metabolism in a complementary canine disease model. Our findings suggest that disturbances in protein degradation pathways contribute to the POS processing defect observed in BD hiPSC-RPE, which can be manipulated pharmacologically. These results have therapeutic implications for BD and perhaps other maculopathies.
Collapse
Affiliation(s)
- Ruchira Singh
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA; McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, USA
| | - David Kuai
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Karina E Guziewicz
- Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jackelyn Meyer
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Molly Wilson
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jianfeng Lu
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Molly Smith
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Eric Clark
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Amelia Verhoeven
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Gustavo D Aguirre
- Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - David M Gamm
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA; McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, USA.
| |
Collapse
|
18
|
Jun JI, Kim KH, Lau LF. The matricellular protein CCN1 mediates neutrophil efferocytosis in cutaneous wound healing. Nat Commun 2015; 6:7386. [PMID: 26077348 PMCID: PMC4480344 DOI: 10.1038/ncomms8386] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 05/04/2015] [Indexed: 02/06/2023] Open
Abstract
Neutrophil infiltration constitutes the first step in wound healing, although their timely clearance by macrophage engulfment, or efferocytosis, is critical for efficient tissue repair. However, the specific mechanism for neutrophil clearance in wound healing remains undefined. Here we uncover a key role for CCN1 in neutrophil efferocytosis by acting as a bridging molecule that binds phosphatidylserine, the “eat-me” signal on apoptotic cells, and integrins αvβ3/αvβ5 in macrophages to trigger efferocytosis. Both knockin mice expressing a mutant CCN1 that is unable to bind αvβ3/αvβ5 and mice with Ccn1 knockdown are defective in neutrophil efferocytosis, resulting in exuberant neutrophil accumulation and delayed healing. Treatment of wounds with CCN1 accelerates neutrophil clearance in both Ccn1 knockin mice and diabetic Leprdb/db mice, which suffer from neutrophil persistence and impaired healing. These findings establish CCN1 as a critical opsonin in skin injury and suggest a therapeutic potential for CCN1 in certain types of non-healing wounds.
Collapse
Affiliation(s)
- Joon-Il Jun
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, USA
| | - Ki-Hyun Kim
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, USA
| | - Lester F Lau
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, Illinois 60607, USA
| |
Collapse
|
19
|
Ion channels and transporters of the retinal pigment epithelium. Exp Eye Res 2014; 126:27-37. [DOI: 10.1016/j.exer.2014.05.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 05/02/2014] [Accepted: 05/12/2014] [Indexed: 12/19/2022]
|
20
|
CaV1.3 L-type channels, maxiK Ca2+-dependent K+ channels and bestrophin-1 regulate rhythmic photoreceptor outer segment phagocytosis by retinal pigment epithelial cells. Cell Signal 2014; 26:968-78. [DOI: 10.1016/j.cellsig.2013.12.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 12/31/2013] [Indexed: 11/20/2022]
|
21
|
Yao J, Jia L, Shelby SJ, Ganios AM, Feathers K, Thompson DA, Zacks DN. Circadian and noncircadian modulation of autophagy in photoreceptors and retinal pigment epithelium. Invest Ophthalmol Vis Sci 2014; 55:3237-46. [PMID: 24781939 DOI: 10.1167/iovs.13-13336] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
PURPOSE Autophagy in photoreceptors and the RPE promotes homeostasis and survival. The purpose of this study is to determine the daily pattern of changes in autophagy and factors contributing to its regulation in the outer retina. METHODS Levels of autophagy markers in the retina and RPE were evaluated over a 24-hour period. To assess the role of phagocytosis in stimulating autophagy in the RPE, cultured RPE-J cells were incubated with isolated photoreceptor outer segments and levels of autophagy markers were measured. Electron microscopy was performed on retina sections and RPE-J cells to assess formation of double-membraned vesicles consistent with autophagosomes. RESULTS In wild-type C57BL/6 mice maintained under normal cycling light conditions, autophagy in photoreceptor cells and the RPE exhibited a bimodal pattern of activation. In photoreceptors, shifts between light and dark evoked a sharp decrease in autophagy that was followed by a time-dependent increase. In photoreceptors, translocation of transducin and arrestin from the outer to inner segment appeared to contribute to the light-dependent upregulation of autophagy. In contrast, the cyclic variations in RPE autophagy were independent of lighting conditions, and are triggered, at least in part, by ingestion of outer segments. CONCLUSIONS Activation of autophagy in the outer retina exhibits a bimodal pattern that correlates with shifts in transduction proteins within the photoreceptor and by circadian ingestion of outer segments in the RPE. These dynamic shifts suggest a critical role for this pathway in maintaining homeostasis, with further study needed to define the mechanisms underlying the regulation of this phenomenon.
Collapse
Affiliation(s)
- Jingyu Yao
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Lin Jia
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Shameka J Shelby
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Anna M Ganios
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Kecia Feathers
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Debra A Thompson
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - David N Zacks
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| |
Collapse
|
22
|
Singh R, Phillips MJ, Kuai D, Meyer J, Martin JM, Smith MA, Perez ET, Shen W, Wallace KA, Capowski EE, Wright LS, Gamm DM. Functional analysis of serially expanded human iPS cell-derived RPE cultures. Invest Ophthalmol Vis Sci 2013; 54:6767-78. [PMID: 24030465 DOI: 10.1167/iovs.13-11943] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
PURPOSE To determine the effects of serial expansion on the cellular, molecular, and functional properties of human iPS cell (hiPSC)-derived RPE cultures. METHODS Fibroblasts obtained from four individuals were reprogrammed into hiPSCs and differentiated to RPE cells using previously described methods. Patches of deeply pigmented hiPSC-RPE were dissected, dissociated, and grown in culture until they re-formed pigmented monolayers. Subsequent passages were obtained by repeated dissociation, expansion, and maturation of RPE into pigmented monolayers. Gene and protein expression profiles and morphological and functional characteristics of hiPSC-RPE at different passages were compared with each other and to human fetal RPE (hfRPE). RESULTS RPE from all four hiPSC lines could be expanded more than 1000-fold when serially passaged as pigmented monolayer cultures. Importantly, expansion of hiPSC-RPE monolayers over the first three passages (P1-P3) resulted in decreased expression of pluripotency and neuroretinal markers and maintenance of characteristic morphological features and gene and protein expression profiles. Furthermore, P1 to P3 hiPSC-RPE monolayers reliably demonstrated functional tight junctions, G-protein-coupled receptor-mediated calcium transients, phagocytosis and degradation of photoreceptor outer segments, and polarized secretion of biomolecules. In contrast, P4 hiPSC-RPE cells failed to form monolayers and possessed altered morphological and functional characteristics and gene expression levels. CONCLUSIONS Highly differentiated, pigmented hiPSC-RPE monolayers can undergo limited serial expansion while retaining key cytological and functional attributes. However, passaging hiPSC-RPE cultures beyond senescence leads to loss of such features. Our findings support limited, controlled passaging of patient-specific hiPSC-RPE to procure cells needed for in vitro disease modeling, drug screening, and cellular transplantation.
Collapse
Affiliation(s)
- Ruchira Singh
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Lacritin and the tear proteome as natural replacement therapy for dry eye. Exp Eye Res 2013; 117:39-52. [PMID: 23769845 DOI: 10.1016/j.exer.2013.05.020] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/23/2013] [Accepted: 05/31/2013] [Indexed: 12/21/2022]
Abstract
Tear proteins are potential biomarkers, drug targets, and even biotherapeutics. As a biotherapeutic, a recombinant tear protein might physiologically rescue the ocular surface when a deficiency is detected. Such a strategy pays more attention to the natural prosecretory and protective properties of the tear film and seeks to alleviate symptoms by addressing cause, rather than the current palliative, non-specific and temporary approaches. Only a handful of tear proteins appear to be selectively downregulated in dry eye, the most common eye disease. Lacritin and lipocalin-1 are two tear proteins selectively deficient in dry eye. Both proteins influence ocular surface health. Lacritin is a prosecretory mitogen that promotes basal tearing when applied topically. Levels of active monomeric lacritin are negatively regulated by tear tissue transglutaminase, whose expression is elevated in dry eye with ocular surface inflammation. Lipocalin-1 is the master lipid sponge of the ocular surface, without which residual lipids could interfere with epithelial wetting. It also is a carrier for vitamins and steroid hormones, and is a key endonuclease. Accumulation of DNA in tears is thought to be proinflammatory. Functions of these and other tear proteins may be influenced by protein-protein interactions. Here we discuss new advances in lacritin biology and provide an overview on lipocalin-1, and newly identified members of the tear proteome.
Collapse
|
24
|
Cheng ZY, Wang XP, Schmid KL, Liu L. Identification of GABA receptors in chick retinal pigment epithelium. Neurosci Lett 2013; 539:43-7. [DOI: 10.1016/j.neulet.2013.01.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 01/18/2013] [Indexed: 01/09/2023]
|
25
|
Milenkovic VM, Krejcova S, Reichhart N, Wagner A, Strauß O. Interaction of bestrophin-1 and Ca2+ channel β-subunits: identification of new binding domains on the bestrophin-1 C-terminus. PLoS One 2011; 6:e19364. [PMID: 21559412 PMCID: PMC3084833 DOI: 10.1371/journal.pone.0019364] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 04/01/2011] [Indexed: 12/21/2022] Open
Abstract
Bestrophin-1 modulates currents through voltage-dependent L-type Ca2+ channels by physically interacting with the β-subunits of Ca2+ channels. The main function of β-subunits is to regulate the number of pore-forming CaV-subunits in the cell membrane and modulate Ca2+ channel currents. To understand the influence of full-length bestrophin-1 on β-subunit function, we studied binding and localization of bestrophin-1 and Ca2+ channel subunits, together with modulation of CaV1.3 Ca2+ channels currents. In heterologeous expression, bestrophin-1 showed co-immunoprecipitation with either, β3-, or β4-subunits. We identified a new highly conserved cluster of proline-rich motifs on the bestrophin-1 C-terminus between amino acid position 468 and 486, which enables possible binding to SH3-domains of β-subunits. A bestrophin-1 that lacks these proline-rich motifs (ΔCT-PxxP bestrophin-1) showed reduced efficiency to co-immunoprecipitate with β3 and β4-subunits. In the presence of ΔCT-PxxP bestrophin-1, β4-subunits and CaV1.3 subunits partly lost membrane localization. Currents from CaV1.3 subunits were modified in the presence of β4-subunit and wild-type bestrophin-1: accelerated time-dependent activation and reduced current density. With ΔCTPxxP bestrophin-1, currents showed the same time-dependent activation as with wild-type bestrophin-1, but the current density was further reduced due to decreased number of Ca2+ channels proteins in the cell membrane. In summary, we described new proline-rich motifs on bestrophin-1 C-terminus, which help to maintain the ability of β-subunits to regulate surface expression of pore-forming CaV Ca2+-channel subunits.
Collapse
Affiliation(s)
- Vladimir M. Milenkovic
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Sarka Krejcova
- Experimentelle Ophthalmologie, Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Nadine Reichhart
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Andrea Wagner
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
- * E-mail:
| |
Collapse
|
26
|
Sparrow JR, Hicks D, Hamel CP. The retinal pigment epithelium in health and disease. Curr Mol Med 2011; 10:802-23. [PMID: 21091424 DOI: 10.2174/156652410793937813] [Citation(s) in RCA: 417] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 09/13/2010] [Indexed: 12/15/2022]
Abstract
Retinal pigment epithelial cells (RPE) constitute a simple layer of cuboidal cells that are strategically situated behind the photoreceptor (PR) cells. The inconspicuousness of this monolayer contrasts sharply with its importance [1]. The relationship between the RPE and PR cells is crucial to sight; this is evident from basic and clinical studies demonstrating that primary dysfunctioning of the RPE can result in visual cell death and blindness. RPE cells carry out many functions including the conversion and storage of retinoid, the phagocytosis of shed PR outer segment membrane, the absorption of scattered light, ion and fluid transport and RPE-PR apposition. The magnitude of the demands imposed on this single layer of cells in order to execute these tasks, will become apparent to the reader of this review as will the number of clinical disorders that take origin from these cells.
Collapse
Affiliation(s)
- J R Sparrow
- Department of Ophthalmology, Columbia University, New York, NY 10032, USA.
| | | | | |
Collapse
|
27
|
Nifedipine alters the light-rise of the electro-oculogram in man. Graefes Arch Clin Exp Ophthalmol 2011; 249:677-84. [DOI: 10.1007/s00417-010-1604-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 11/30/2010] [Accepted: 12/10/2010] [Indexed: 10/18/2022] Open
|
28
|
Effect of bestrophin-1 on L-type Ca2+ channel activity depends on the Ca2+ channel beta-subunit. Exp Eye Res 2010; 91:630-9. [DOI: 10.1016/j.exer.2010.08.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Revised: 07/02/2010] [Accepted: 08/02/2010] [Indexed: 11/17/2022]
|
29
|
Ferrara DC, Costa RA, Tsang S, Calucci D, Jorge R, Freund KB. Multimodal fundus imaging in Best vitelliform macular dystrophy. Graefes Arch Clin Exp Ophthalmol 2010; 248:1377-86. [PMID: 20414784 DOI: 10.1007/s00417-010-1381-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 03/19/2010] [Accepted: 04/02/2010] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Best vitelliform macular dystrophy (BVMD) is a rare autosomal dominant retinal disease of highly variable phenotypic expression. Interpretations of disease mechanisms based on histopathology, electrophysiology, genetic analysis, and retinal imaging are somewhat discordant in fundamental issues such as the location and extension of primary retinal changes. Herein we describe the morphological macular features in patients with BVMD undergoing simultaneous multimodal fundus imaging and compare to those of normal age-matched subjects. METHODS Comparative study including seven patients with BVMD (14 eyes) and seven age-matched healthy subjects (14 eyes). All participants were submitted to complete ophthalmological examination, fundus photography, and standardized multimodal fundus imaging protocol including Fourier-domain optical coherence tomography (Fd-OCT) combined with near-infrared reflectance and blue-light fundus autofluorescence (FAF). RESULTS In two eyes in the "subclinical" stage, Fd-OCT revealed thickening of the middle highly reflective layer (HRL) localized between the photoreceptors' inner/outer segments junction (inner-HRL) and RPE/Bruch's membrane reflective complex (outer-HRL) throughout the macula. In one eye in the "vitelliform" stage, a homogeneous hyper-reflective material on Fd-OCT was observed between the middle-HRL and outer-HRL; this material presented increased fluorescence on FAF. The outer nuclear layer (ONL) was thinned in the central macula and subretinal fluid was not identified in these earlier disease stages. In patients of "pseudohypopyon" (two eyes), "vitelliruptive" (eight eyes) and "atrophic" (one eye) stages, Fd-OCT revealed a variety of changes in the middle- and inner-HRLs and thinning of ONL. These changes were found to be associated with the level of visual acuity observed. Thickening of the middle-HRL was observed beyond the limits of the clinically evident macular lesion in all eyes. CONCLUSIONS Multimodal fundus imaging demonstrated thickening of the reflective layer corresponding to the photoreceptors' outer segments throughout the macula with no subretinal fluid accumulation as the earliest detectable feature in BVMD. Changes detected in the photoreceptors' reflective layers (middle- and inner- HRLs) and ONL thinning seemed to be progressive with direct implications for the level of visual acuity impairment observed among the different stages of the disease.
Collapse
Affiliation(s)
- Daniela C Ferrara
- Department of Ophthalmology, Otolaryngology and Head and Neck Surgery, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | | | | | | | | | | |
Collapse
|
30
|
Marmorstein AD, Cross HE, Peachey NS. Functional roles of bestrophins in ocular epithelia. Prog Retin Eye Res 2009; 28:206-26. [PMID: 19398034 DOI: 10.1016/j.preteyeres.2009.04.004] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
There are four members of the bestrophin family of proteins in the human genome, of which two are known to be expressed in the eye. The gene BEST1 (formerly VMD2) which encodes the protein bestrophin-1 (Best1) was first identified in 1998. Mutations in this gene have now been associated with four clinically distinguishable human eye diseases, collectively referred to as "bestrophinopathies". Over the last decade, laboratories have sought to understand how Best1 mutations could result in eye diseases that range in presentation from macular degeneration to nanophthalmos. The majority of our knowledge comes from studies that have sought to understand how Best1 mutations or dysfunction could induce the classical symptoms of the most common of these diseases: Best vitelliform macular dystrophy (BVMD). BVMD is a dominant trait that is characterized electrophysiologically by a diminished electrooculogram light peak with a normal clinical electroretinogram. This together with the localization of Best1 to the retinal pigment epithelium (RPE) basolateral plasma membrane and data from heterologous expression studies, have led to the proposal that Best1 generates the light peak, and that bestrophins are a family of Ca(2+) activated Cl(-) channels (CaCCs). However, data from Best1 knock-out and knock-in mice, coupled with the recent discovery of a recessive bestrophinopathy suggest that Best1 does not generate the light peak. Recently Best2 was found to be expressed in non-pigmented epithelia in the ciliary body. However, aqueous dynamics in Best2 knock-out mice do not support a role for Best2 as a Cl(-) channel. Thus, the purported CaCC function of the bestrophins and how loss of this function relates to clinical disease needs to be reassessed. In this article, we examine data obtained from tissue-type and animal models and discuss the current state of bestrophin research, what roles Best1 and Best2 may play in ocular epithelia and ocular electrophysiology, and how perturbation of these functions may result in disease.
Collapse
Affiliation(s)
- Alan D Marmorstein
- Department of Ophthalmology and Vision Science, University of Arizona, Tucson, AZ 85711, USA.
| | | | | |
Collapse
|
31
|
Boon CJ, Klevering BJ, Leroy BP, Hoyng CB, Keunen JE, den Hollander AI. The spectrum of ocular phenotypes caused by mutations in the BEST1 gene. Prog Retin Eye Res 2009; 28:187-205. [DOI: 10.1016/j.preteyeres.2009.04.002] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|