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Turner MJ, Saint-Criq V, Patel W, Ibrahim SH, Verdon B, Ward C, Garnett JP, Tarran R, Cann MJ, Gray MA. Hypercapnia modulates cAMP signalling and cystic fibrosis transmembrane conductance regulator-dependent anion and fluid secretion in airway epithelia. J Physiol 2015; 594:1643-61. [PMID: 26574187 PMCID: PMC4799982 DOI: 10.1113/jp271309] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 11/05/2015] [Indexed: 12/20/2022] Open
Abstract
Hypercapnia is clinically defined as an arterial blood partial pressure of CO2 of above 40 mmHg and is a feature of chronic lung disease. In previous studies we have demonstrated that hypercapnia modulates agonist-stimulated cAMP levels through effects on transmembrane adenylyl cyclase activity. In the airways, cAMP is known to regulate cystic fibrosis transmembrane conductance regulator (CFTR)-mediated anion and fluid secretion, which contributes to airway surface liquid homeostasis. The aim of the current work was to investigate if hypercapnia could modulate cAMP-regulated ion and fluid transport in human airway epithelial cells. We found that acute exposure to hypercapnia significantly reduced forskolin-stimulated elevations in intracellular cAMP as well as both adenosine- and forskolin-stimulated increases in CFTR-dependent transepithelial short-circuit current, in polarised cultures of Calu-3 human airway cells. This CO2 -induced reduction in anion secretion was not due to a decrease in HCO3 (-) transport given that neither a change in CFTR-dependent HCO3 (-) efflux nor Na(+) /HCO3 (-) cotransporter-dependent HCO3 (-) influx were CO2 -sensitive. Hypercapnia also reduced the volume of forskolin-stimulated fluid secretion over 24 h, yet had no effect on the HCO3 (-) content of the secreted fluid. Our data reveal that hypercapnia reduces CFTR-dependent, electrogenic Cl(-) and fluid secretion, but not CFTR-dependent HCO3 (-) secretion, which highlights a differential sensitivity of Cl(-) and HCO3 (-) transporters to raised CO2 in Calu-3 cells. Hypercapnia also reduced forskolin-stimulated CFTR-dependent anion secretion in primary human airway epithelia. Based on current models of airways biology, a reduction in fluid secretion, associated with hypercapnia, would be predicted to have important consequences for airways hydration and the innate defence mechanisms of the lungs.
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Affiliation(s)
- Mark J Turner
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.,Department of Physiology, McIntyre Medical Sciences Building, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada, H3G 1Y6
| | - Vinciane Saint-Criq
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Waseema Patel
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Salam H Ibrahim
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Bernard Verdon
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Christopher Ward
- Institute for Cellular Medicine, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - James P Garnett
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert Tarran
- Marsico Lung Institute, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Martin J Cann
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Michael A Gray
- Institute for Cell & Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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Berkowitz BA, Kern TS, Bissig D, Patel P, Bhatia A, Kefalov VJ, Roberts R. Systemic Retinaldehyde Treatment Corrects Retinal Oxidative Stress, Rod Dysfunction, and Impaired Visual Performance in Diabetic Mice. Invest Ophthalmol Vis Sci 2015; 56:6294-303. [PMID: 26431483 PMCID: PMC4594469 DOI: 10.1167/iovs.15-16990] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 08/04/2015] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Diabetes appears to induce a visual cycle defect because rod dysfunction is correctable with systemic treatment of the visual cycle chromophore 11-cis-retinaldehyde. However, later studies have found no evidence for visual cycle impairment. Here, we further examined whether photoreceptor dysfunction is corrected with 11-cis-retinaldehyde. Because antioxidants correct photoreceptor dysfunction in diabetes, the hypothesis that exogenous visual chromophores have antioxidant activity in the retina of diabetic mice in vivo was tested. METHODS Rod function in 2-month-old diabetic mice was evaluated using transretinal electrophysiology in excised retinas and apparent diffusion coefficient (ADC) MRI to measure light-evoked expansion of subretinal space (SRS) in vivo. Optokinetic tracking was used to evaluate cone-based visual performance. Retinal production of superoxide free radicals, generated mostly in rod cells, was biochemically measured with lucigenin. Diabetic mice were systemically treated with a single injection of either 11-cis-retinaldehyde, 9-cis-retinaldehyde (a chromophore surrogate), or all-trans-retinaldehyde (the photoisomerization product of 11-cis-retinaldehyde). RESULTS Consistent with previous reports, diabetes significantly reduced (1) dark-adapted rod photo responses (transretinal recording) by ∼18%, (2) rod-dominated light-stimulated SRS expansion (ADC MRI) by ∼21%, and (3) cone-dominated contrast sensitivity (using optokinetic tracking [OKT]) by ∼30%. Both 11-cis-retinaldehyde and 9-cis-retinaldehyde largely corrected these metrics of photoreceptor dysfunction. Higher-than-normal retinal superoxide production in diabetes by ∼55% was also significantly corrected following treatment with 11-cis-retinaldehyde, 9-cis-retinaldehyde, or all-trans-retinaldehyde. CONCLUSIONS Collectively, data suggest that retinaldehydes improve photoreceptor dysfunction in diabetic mice, independent of the visual cycle, via an antioxidant mechanism.
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Affiliation(s)
- Bruce A. Berkowitz
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
- Department of Ophthalmology, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Timothy S. Kern
- Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States
| | - David Bissig
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Priya Patel
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Ankit Bhatia
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Vladimir J. Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Robin Roberts
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
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53
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Berkowitz BA, Bissig D, Roberts R. MRI of rod cell compartment-specific function in disease and treatment in vivo. Prog Retin Eye Res 2015; 51:90-106. [PMID: 26344734 DOI: 10.1016/j.preteyeres.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
Rod cell oxidative stress is a major pathogenic factor in retinal disease, such as diabetic retinopathy (DR) and retinitis pigmentosa (RP). Personalized, non-destructive, and targeted treatment for these diseases remains elusive since current imaging methods cannot analytically measure treatment efficacy against rod cell compartment-specific oxidative stress in vivo. Over the last decade, novel MRI-based approaches that address this technology gap have been developed. This review summarizes progress in the development of MRI since 2006 that enables earlier evaluation of the impact of disease on rod cell compartment-specific function and the efficacy of anti-oxidant treatment than is currently possible with other methods. Most of the new assays of rod cell compartment-specific function are based on endogenous contrast mechanisms, and this is expected to facilitate their translation into patients with DR and RP, and other oxidative stress-based retinal diseases.
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Affiliation(s)
- Bruce A Berkowitz
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA; Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - David Bissig
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Robin Roberts
- Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
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54
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Lima-Gómez V, Bermúdez-Zapata DA, Blanco-Hernández DMR. [Efficacy of dorzolamide in reducing retinal thickness after photocoagulation in diabetic macular oedema]. CIR CIR 2015; 83:3-8. [PMID: 25982601 DOI: 10.1016/j.circir.2014.08.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 10/23/2022]
Abstract
BACKGROUND Focal photocoagulation interrupts vascular leakage in diabetic macular edema, and allows the retinal pigment epithelium to withdraw fluid that thickens the retina; this mechanism could be enhanced by dorzolamida, a topical carbonic anhydrase inhibitor. OBJECTIVE To determine the efficacy of dorzolamida compared against placebo, in reducing retinal thickness after focal photocoagulation, in eyes with diabetic macular oedema. MATERIAL AND METHODS Experimental, comparative, prospective, longitudinal, double blind study in diabetics with focal macular oedema treated with photocoagulation. Treated eyes were randomly assigned three weeks after the procedure to receive dorzolamide (group 1) or placebo (group 2), three times daily during three weeks. Means of visual acuity, center point thickness and macular volume were compared 3 and 6 weeks after photocoagulation within groups (Wilcoxon's t) and between groups (Mann-Whitneys's U). RESULTS Sixty-nine eyes form patients aged 58.3 ± 8.3 years; 37 were assigned to group 1 and 42 to group 2. Mean center point thickness changed from 178.4 ± 34μm to 170 ± 29.1μm in group 1 (p = 0.04), and from 179.2 ± 22.4μm to 178.6 ± 20.8μm in group 2 (p = 0.7); mean macular volume changed from 7.63 ± 0.52mm(3) to 7.50 ± 0.50mm(3) in group 1 (p = 0.02) and from 7.82 ± 0.43mm(3) to 7.76 ± 0.42mm(3) in group 2 (p = 0.014). CONCLUSIONS The efficacy of dorzolamide was higher than that of placebo, to reduce retinal thickness after focal photocoagulation in diabetics with macular oedema.
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Berkowitz BA, Grady EM, Khetarpal N, Patel A, Roberts R. Oxidative stress and light-evoked responses of the posterior segment in a mouse model of diabetic retinopathy. Invest Ophthalmol Vis Sci 2015; 56:606-15. [PMID: 25574049 PMCID: PMC4309313 DOI: 10.1167/iovs.14-15687] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/12/2014] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To test the hypothesis that in a mouse model of diabetic retinopathy, oxidative stress is linked with impaired light-evoked expansion of choroidal thickness and subretinal space (SRS). METHODS We examined nondiabetic mice (wild-type, wt) with and without administration of manganese, nondiabetic mice deficient in rod phototransduction (transducin alpha knockout; GNAT1(-/-)), and diabetic mice (untreated or treated with the antioxidant α-lipoic acid [LPA]). Magnetic resonance imaging (MRI) was used to measure light-evoked increases in choroidal thickness and the apparent diffusion coefficient (ADC) at 88% to 100% depth into the retina (i.e., the SRS layer). RESULTS Choroidal thickness values were similar (P > 0.05) between all untreated nondiabetic dark-adapted groups and increased significantly (P < 0.05) with light; this expansion was subnormal (P < 0.05) in both diabetic groups. Apparent diffusion coefficient values in the SRS layer robustly increased (P < 0.05) in a light duration-dependent manner, and this effect was independent of the presence of Mn(2+). The light-stimulated increase in ADC at the location of the SRS was absent in GNAT1(-/-) and diabetic mice (P > 0.05). In diabetic mice, the light-dependent increase in SRS ADC was significantly (P < 0.05) restored with LPA. CONCLUSIONS Apparent diffusion coefficient MRI is a sensitive method for evaluating choroid thickness and its light-evoked expansion together with phototransduction-dependent changes in the SRS layer in mice in vivo. Because ADC MRI exploits an endogenous contrast mechanism, its translational potential is promising; it can also be performed in concert with manganese-enhanced MRI (MEMRI). Our data support a link between diabetes-related oxidative stress and rod, but not choroidal, pathophysiology.
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Affiliation(s)
- Bruce A. Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
- Department of Ophthalmology, Wayne State University, Detroit, Michigan, United States
| | - Edmund Michael Grady
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
| | - Nikita Khetarpal
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
| | - Akshar Patel
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
| | - Robin Roberts
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
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Lehmann GL, Benedicto I, Philp NJ, Rodriguez-Boulan E. Plasma membrane protein polarity and trafficking in RPE cells: past, present and future. Exp Eye Res 2014; 126:5-15. [PMID: 25152359 DOI: 10.1016/j.exer.2014.04.021] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 04/15/2014] [Accepted: 04/24/2014] [Indexed: 10/24/2022]
Abstract
The retinal pigment epithelium (RPE) comprises a monolayer of polarized pigmented epithelial cells that is strategically interposed between the neural retina and the fenestrated choroid capillaries. The RPE performs a variety of vectorial transport functions (water, ions, metabolites, nutrients and waste products) that regulate the composition of the subretinal space and support the functions of photoreceptors (PRs) and other cells in the neural retina. To this end, RPE cells display a polarized distribution of channels, transporters and receptors in their plasma membrane (PM) that is remarkably different from that found in conventional extra-ocular epithelia, e.g. intestine, kidney, and gall bladder. This characteristic PM protein polarity of RPE cells depends on the interplay of sorting signals in the RPE PM proteins and sorting mechanisms and biosynthetic/recycling trafficking routes in the RPE cell. Although considerable progress has been made in our understanding of the RPE trafficking machinery, most available data have been obtained from immortalized RPE cell lines that only partially maintain the RPE phenotype and by extrapolation of data obtained in the prototype Madin-Darby Canine Kidney (MDCK) cell line. The increasing availability of RPE cell cultures that more closely resemble the RPE in vivo together with the advent of advanced live imaging microscopy techniques provides a platform and an opportunity to rapidly expand our understanding of how polarized protein trafficking contributes to RPE PM polarity.
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Affiliation(s)
- Guillermo L Lehmann
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, 1300 York Ave, New York, NY 100652, USA
| | - Ignacio Benedicto
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, 1300 York Ave, New York, NY 100652, USA
| | - Nancy J Philp
- Thomas Jefferson University, Department of Pathology, Anatomy, and Cell Biology, Philadelphia, PA 19107, USA.
| | - Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Department of Ophthalmology, Weill Cornell Medical College, 1300 York Ave, New York, NY 100652, USA.
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57
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Lee YS, Marmorstein LY, Marmorstein AD. Soluble adenylyl cyclase in the eye. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2579-83. [PMID: 25108282 DOI: 10.1016/j.bbadis.2014.07.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/26/2014] [Accepted: 07/30/2014] [Indexed: 11/26/2022]
Abstract
Adenylyl cyclases (ACs) are a family of enzymes which convert ATP to cAMP, an essential intermediate in many signal transduction pathways. Of the 10 AC genes in man, 9 fall into the category of transmembrane ACs (tmACs), which associate with G-protein coupled receptors (GPCRs) and are activated by forskolin. The 10th AC, termed soluble AC (sAC) is neither activated by forskolin nor does it interact with GPCRs. Rather, sAC can be found in many compartments within the cell and is activated by bicarbonate. As such, sAC is considered a major sensor of bicarbonate in many tissues. The pathways involving sAC vary in different tissues and organ systems, and are as diverse as facilitating sperm capacitation and regulating pressure in the eye. The role of sAC in the eye has only recently begun to receive significant attention. Here we summarize what is known about the roles of sAC in the eye. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.
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Affiliation(s)
- Yong S Lee
- Department of Ophthalmology, Mayo Clinic, Rochester, MN 55902, USA
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Duncker T, Greenberg JP, Ramachandran R, Hood DC, Smith RT, Hirose T, Woods RL, Tsang SH, Delori FC, Sparrow JR. Quantitative fundus autofluorescence and optical coherence tomography in best vitelliform macular dystrophy. Invest Ophthalmol Vis Sci 2014; 55:1471-82. [PMID: 24526438 DOI: 10.1167/iovs.13-13834] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Quantitative fundus autofluorescence (qAF), spectral domain optical coherence tomography (SD-OCT) segmentation, and multimodal imaging were performed to elucidate the pathogenesis of Best vitelliform macular dystrophy (BVMD) and to identify abnormalities in lesion versus nonlesion fundus areas. METHODS Sixteen patients with a clinical diagnosis of BVMD were studied. Autofluorescence images (30°, 488-nm excitation) were acquired with a confocal scanning laser ophthalmoscope equipped with an internal fluorescent reference to account for variable laser power and detector sensitivity. The grey levels (GLs) of each image were calibrated to the reference, zero GL, magnification, and normative optical media density, to yield qAF. Horizontal SD-OCT scans were obtained and retinal layers manually segmented. Additionally, color and near-infrared reflectance (NIR-R) images were registered to AF images. All patients were screened for mutations in BEST1. In three additional BVMD patients, in vivo spectrofluorometric measurements were obtained within the vitelliform lesion. RESULTS Mean nonlesion qAF was within normal limits for age. Maximum qAF within the lesion was markedly increased compared with controls. By SD-OCT segmentation, outer segment equivalent thickness was increased and outer nuclear layer thickness decreased in the lesion. Changes were also present in a transition zone beyond the lesion border. In subclinical patients, no abnormalities in retinal layer thickness were identified. Fluorescence spectra recorded from the vitelliform lesion were consistent with those of retinal pigment epithelial cell lipofuscin. CONCLUSIONS Based on qAF, mutations in BEST1 do not cause increased lipofuscin levels in nonlesion fundus areas.
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Affiliation(s)
- Tobias Duncker
- Department of Ophthalmology, Harkness Eye Institute, Columbia University, New York, New York
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Adijanto J, Philp NJ. Cultured primary human fetal retinal pigment epithelium (hfRPE) as a model for evaluating RPE metabolism. Exp Eye Res 2014; 126:77-84. [PMID: 24485945 DOI: 10.1016/j.exer.2014.01.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 01/15/2014] [Accepted: 01/19/2014] [Indexed: 12/20/2022]
Abstract
Mitochondrial dysfunction has been shown to contribute to age-related and proliferative retinal diseases. Over the past decade, the primary human fetal RPE (hfRPE) culture model has emerged as an effective tool for studying RPE function and mechanisms of retinal diseases. This model system has been rigorously characterized and shown to closely resemble native RPE cells at the genomic and protein level, and that they are capable of accomplishing the characteristic functions of a healthy native RPE (e.g., rod phagocytosis, ion and fluid transport, and retinoid cycle). In this review, we demonstrated that the metabolic activity of the RPE is an indicator of its health and state of differentiation, and present the hfRPE culture model as a valuable in vitro system for evaluating RPE metabolism in the context of RPE differentiation and retinal disease.
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Affiliation(s)
- Jeffrey Adijanto
- Thomas Jefferson University, Dept. of Pathology, Anatomy, & Cell Biology, 1020 Locust Street, Rm315, Philadelphia, PA 19107, USA.
| | - Nancy J Philp
- Thomas Jefferson University, Dept. of Pathology, Anatomy, & Cell Biology, 1020 Locust Street, Rm315, Philadelphia, PA 19107, USA.
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Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
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Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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Panfoli I, Calzia D, Bruschi M, Oneto M, Bianchini P, Ravera S, Petretto A, Diaspro A, Candiano G. Functional expression of oxidative phosphorylation proteins in the rod outer segment disc. Cell Biochem Funct 2013; 31:532-8. [PMID: 23322616 DOI: 10.1002/cbf.2943] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/06/2012] [Accepted: 11/28/2012] [Indexed: 11/09/2022]
Abstract
The rod Outer Segment (OS) disc, an organelle devoid of mitochondria, is specialized in phototransduction, a process requiring a continual chemical energy supply. We have shown that OS discs express functional mitochondrial electron transport chains, Fo F1 -ATP synthase and the tricarboxylic acid cycle enzymes, all mitochondrial features. Here, we focus on oxygen consumption and adenosine triphosphate (ATP) synthesis by OS discs analysing electron transport chain I-III-IV and II-II-IV pathways, supported by reduced nicotinamide adenine dinucleotide and succinate, respectively. Interestingly, respiratory capacity of discs was measurable also in the presence of 3-hydroxy-butyrrate, a typical metabolic substrate for the brain. Data were supported by a two-dimensional electrophoresis analyses conducted as our previous one, but focused to those mitochondrial proteins that are involved in oxidative phosphorylation. Carbonic anhydrase was also found active in OS discs. Moreover, colocalization of Rhodopsin with respiratory complex I and ATP synthase seems a further step in the characterization of some proteins typical of the mitochondrial inner membranes that are expressed in the rod discs. The existence of oxygen utilization in the outer retina, likely supplying ATP for phototransduction, may shed light on some retinal pathologies related to oxidative stress of the outer retina.
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Affiliation(s)
- Isabella Panfoli
- DIFAR-Biochemistry Lab., University of Genoa, 16132 Genova, Italy.
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Abe S, Nakao T, Yoshimoto T, Yoshihito T, Parkkila S, Murakami G, Cho BH. Expression of carbonic anhydrase in the fetal eye and extra-ocular tissues. Okajimas Folia Anat Jpn 2013; 90:59-68. [PMID: 24670491 DOI: 10.2535/ofaj.90.59] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Carbonic anhydrases (CAs) plays a critical functional role in the ciliary body and retina for maintenance of microenvironment. With immunohistochemistry using orbital contents from 8 human fetuses (12-16 weeks of gestation), we examined expressions of CAs isozymes-1, 2, 3, 6, 7 9 and 12 and found strong reactivity of CA9 in extra-ocular fibrous tissues in the anterior and posterior eyes. CA9 is known to express in the fetal joint cartilage to maintain pH against hypoxia: actually, in the present specimens, the SO pulley and its tendon was strongly positive for CA9. The CA9-positive anterior fibrous tissues were positive for smooth muscle actin and connected the orbital aspect of the 4 rectus muscle with the palpebral conjunctiva, whereas the posterior tissue was negative for smooth muscle actin and corresponded to the lateral insertion tendon of the orbitalis muscle. The anterior CA9-positve tissues seemed to correspond to the primitive form of the sleeve and pulley system. Any of matrix substances (collagen types I and II, aggrecan, versican, fibronectin, tenascin and hyaluronan) displayed a distribution pattern specific for the CA9-positive fibrous tissues. Therefore, whether or not CA9 was positive in the fibrous tissue seemed not to depend on the tissue components such as the extracellular matrix and intermediate filaments but to suggest a stressful condition such as hypoxia, unsuitable base balance and/or under mechanical stress.
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Giansanti V, Villalpando Rodriguez GE, Savoldelli M, Gioia R, Forlino A, Mazzini G, Pennati M, Zaffaroni N, Scovassi AI, Torriglia A. Characterization of stress response in human retinal epithelial cells. J Cell Mol Med 2012. [PMID: 23205553 PMCID: PMC3823140 DOI: 10.1111/j.1582-4934.2012.01652.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The pathogenesis of age-related macular degeneration (AMD) involves demise of the retinal pigment epithelium and death of photoreceptors. In this article, we investigated the response of human adult retinal pigmented epithelial (ARPE-19) cells to 5-(N,N-hexamethylene)amiloride (HMA), an inhibitor of Na+/H+ exchangers. We observed that ARPE-19 cells treated with HMA are unable to activate ‘classical’ apoptosis but they succeed to activate autophagy. In the first 2 hrs of HMA exposure, autophagy is efficient in protecting cells from death. Thereafter, autophagy is impaired, as indicated by p62 accumulation, and this protective mechanism becomes the executioner of cell death. This switch in autophagy property as a function of time for a single stimulus is here shown for the first time. The activation of autophagy was observed, at a lesser extent, with etoposide, suggesting that this event might be a general response of ARPE cells to stress and the most important pathway involved in cell resistance to adverse conditions and toxic stimuli.
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Affiliation(s)
| | - Gloria E Villalpando Rodriguez
- U872 eq. 17, Centre de Recherches des Cordeliers, INSERMParis, France
- Centre de Recherches des Cordeliers, Université Pierre et Marie CurieParis, France
- Centre de Recherches des Cordeliers, Université Paris DescartesParis, France
| | | | - Roberta Gioia
- Dipartimento di Biochimica, Università di PaviaPavia, Italy
| | | | | | - Marzia Pennati
- Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei TumoriMilano, Italy
| | - Nadia Zaffaroni
- Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei TumoriMilano, Italy
| | | | - Alicia Torriglia
- U872 eq. 17, Centre de Recherches des Cordeliers, INSERMParis, France
- Centre de Recherches des Cordeliers, Université Pierre et Marie CurieParis, France
- Centre de Recherches des Cordeliers, Université Paris DescartesParis, France
- *Correspondence to: Alicia TORRIGLIA, U872 eq. 17, Centre de Recherches des Cordeliers, INSERM, Paris, France. Tel: +33 1 44 27 81 73 Fax: +33 1 44 27 81 83 E-mail:
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Bissig D, Berkowitz BA. Light-dependent changes in outer retinal water diffusion in rats in vivo. Mol Vis 2012; 18:2561-xxx. [PMID: 23129976 PMCID: PMC3482170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 10/18/2012] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To test the hypothesis that in rats, intraretinal light-dependent changes on diffusion-weighted magnetic resonance imaging (MRI) in vivo are consistent with known retinal layer-specific physiology. METHODS In male Sprague-Dawley rats, retinal morphology (thickness, extent, surface area, volume) and intraretinal profiles of the apparent diffusion coefficient (ADC, i.e., water mobility) parallel and perpendicular to the optic nerve were measured in vivo using quantitative MRI methods during light and dark stimulation. RESULTS The parallel ADC in the posterior half of the avascular, photoreceptor-dominated outer retina was significantly higher in light than dark, and this pattern was reversed (dark>light) in the anterior outer retina. The perpendicular ADC in the posterior outer retina was similar in light and dark, but was significantly higher in dark than light in the anterior outer retina. No light-dark changes in the inner retina were noted. CONCLUSIONS We identified light-dependent intraretinal diffusion changes that reflected established stimulation-based changes in outer retinal hydration. These findings are expected to motivate future applications of functional diffusion-based MRI in blinding disorders of the outer retina.
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Affiliation(s)
- David Bissig
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Bruce A. Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI,Department of Ophthalmology, Wayne State University, Detroit, MI
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65
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Peng S, Gan G, Rao VS, Adelman RA, Rizzolo LJ. Effects of proinflammatory cytokines on the claudin-19 rich tight junctions of human retinal pigment epithelium. Invest Ophthalmol Vis Sci 2012; 53:5016-28. [PMID: 22761260 DOI: 10.1167/iovs.11-8311] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Chronic, subclinical inflammation contributes to the pathogenesis of several ocular diseases, including age-related macular degeneration. Proinflammatory cytokines affect tight junctions in epithelia that lack claudin-19, but in the retinal pigment epithelium claudin-19 predominates. We examined the effects of cytokines on the tight junctions of human fetal RPE (hfRPE). METHODS hfRPE was incubated with interleukin 1-beta (IL-1β), interferon-gamma (IFNγ), or tumor necrosis factor-alpha (TNFα), alone or in combination. Permeability and selectivity of the tight junctions were assessed using nonionic tracers and electrophysiology. Claudins, occludin, and ZO-1 were examined using PCR, immunoblotting, and confocal immunofluorescence microscopy. RESULTS Only TNFα consistently reduced transepithelial electrical resistance (TER) >80%. A serum-free medium revealed two effects of TNFα: (1) decreased TER was observed only when TNFα was added to the apical side of the monolayer, and (2) expression of TNFα receptors and inhibitors of apoptosis were induced from either side of the monolayer. In untreated cultures, tight junctions were slightly cation selective, and this was affected minimally by TNFα. The results were unexplained by effects on claudin-2, claudin-3, claudin-19, occludin, and ZO-1, but changes in the morphology of the junctions and actin cytoskeleton may have a role. CONCLUSIONS Claudin-19-rich tight junctions have low permeability for ionic and nonionic solutes, and are slightly cation-selective. Claudin-19 is not a direct target of TNFα. TNFα may protect RPE from apoptosis, but makes the monolayer leaky when it is presented to the apical side of the monolayer. Unlike other epithelia, IFNγ failed to augment the effect of TNFα on tight junctions.
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Affiliation(s)
- Shaomin Peng
- Department of Surgery, Yale University School of Medicine, New Haven, Connecticut, USA
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66
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Adijanto J, Castorino JJ, Wang ZX, Maminishkis A, Grunwald GB, Philp NJ. Microphthalmia-associated transcription factor (MITF) promotes differentiation of human retinal pigment epithelium (RPE) by regulating microRNAs-204/211 expression. J Biol Chem 2012; 287:20491-503. [PMID: 22523078 DOI: 10.1074/jbc.m112.354761] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The retinal pigment epithelium (RPE) plays a fundamental role in maintaining visual function and dedifferentiation of RPE contributes to the pathophysiology of several ocular diseases. To identify microRNAs (miRNAs) that may be involved in RPE differentiation, we compared the miRNA expression profiles of differentiated primary human fetal RPE (hfRPE) cells to dedifferentiated hfRPE cells. We found that miR-204/211, the two most highly expressed miRNAs in the RPE, were significantly down-regulated in dedifferentiated hfRPE cells. Importantly, transfection of pre-miR-204/211 into hfRPE cells promoted differentiation whereas adding miR-204/211 inhibitors led to their dedifferentiation. Microphthalmia-associated transcription factor (MITF) is a key regulator of RPE differentiation that was also down-regulated in dedifferentiated hfRPE cells. MITF knockdown decreased miR-204/211 expression and caused hfRPE dedifferentiation. Significantly, co-transfection of MITF siRNA with pre-miR-204/211 rescued RPE phenotype. Collectively, our data show that miR-204/211 promote RPE differentiation, suggesting that miR-204/211-based therapeutics may be effective treatments for diseases that involve RPE dedifferentiation such as proliferative vitreoretinopathy.
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Affiliation(s)
- Jeffrey Adijanto
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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67
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Adijanto J, Philp NJ. The SLC16A family of monocarboxylate transporters (MCTs)--physiology and function in cellular metabolism, pH homeostasis, and fluid transport. CURRENT TOPICS IN MEMBRANES 2012. [PMID: 23177990 DOI: 10.1016/b978-0-12-394316-3.00009-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The SLC16A family of monocarboxylate transporters (MCTs) is composed of 14 members. MCT1 through MCT4 (MCTs 1-4) are H(+)-coupled monocarboxylate transporters, MCT8 and MCT10 transport thyroid hormone and aromatic amino acids, while the substrate specificity and function of other MCTs have yet to be determined. The focus of this review is on MCTs 1-4 because their role in lactate transport is intrinsically linked to cellular metabolism in various biological systems, including skeletal muscle, brain, retina, and testis. Although MCTs 1-4 all transport lactate, they differ in their transport kinetics and vary in tissue and subcellular distribution, where they facilitate "lactate-shuttling" between glycolytic and oxidative cells within tissues and across blood-tissue barriers. However, the role of MCTs 1-4 is not confined to cellular metabolism. By interacting with bicarbonate transport proteins and carbonic anhydrases, MCTs participate in the regulation of pH homeostasis and fluid transport in renal proximal tubule and corneal endothelium, respectively. Here, we provide a comprehensive review of MCTs 1-4, linking their cellular distribution to their functions in various parts of the human body, so that we can better understand the physiological roles of MCTs at the systemic level.
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Affiliation(s)
- Jeffrey Adijanto
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA.
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68
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Wen R, Tao W, Li Y, Sieving PA. CNTF and retina. Prog Retin Eye Res 2011; 31:136-51. [PMID: 22182585 DOI: 10.1016/j.preteyeres.2011.11.005] [Citation(s) in RCA: 156] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 10/29/2011] [Accepted: 11/17/2011] [Indexed: 11/15/2022]
Abstract
Ciliary neurotrophic factor (CNTF) is one of the most studied neurotrophic factors for neuroprotection of the retina. A large body of evidence demonstrates that CNTF promotes rod photoreceptor survival in almost all animal models. Recent studies indicate that CNTF also promotes cone photoreceptor survival and cone outer segment regeneration in the degenerating retina and improves cone function in dogs with congenital achromotopsia. In addition, CNTF is a neuroprotective factor and an axogenesis factor for retinal ganglion cells (RGCs). This review focuses on the effects of exogenous CNTF on photoreceptors and RGCs in the mammalian retina and the potential clinical application of CNTF for retinal degenerative diseases.
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Affiliation(s)
- Rong Wen
- Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.
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69
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Iserovich P, Qin Q, Petrukhin K. DPOFA, a Cl⁻/HCO₃⁻ exchanger antagonist, stimulates fluid absorption across basolateral surface of the retinal pigment epithelium. BMC Ophthalmol 2011; 11:33. [PMID: 22085910 PMCID: PMC3271048 DOI: 10.1186/1471-2415-11-33] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 11/15/2011] [Indexed: 11/25/2022] Open
Abstract
Background Retinal detachment is a disorder of the eye in which sensory retina separates from the retinal pigment epithelium (RPE) due to accumulation of fluid in subretinal space. Pharmacological stimulation of fluid reabsorption from subretinal space to choroid across the RPE has been suggested as a treatment strategy for retinal detachment. DPOFA, (R)-(+)-(5,6-dichloro 2,3,9,9a-tetrahydro 3-oxo-9a-propyl-1H-fluoren-7-yl)oxy]acetic acid, is an abandoned drug capable of inhibiting Cl-/HCO3- exchanger activity. We hypothesized that DPOFA may increase fluid absorption across basolateral surface of the RPE. Methods Reverse transcription polymerase chain reaction (RT-PCR) analysis of mRNA for six different transporters that may act as Cl-/HCO3- exchangers was conducted in bovine and human RPE to confirm that RPE from two species expresses the same repertoire of Cl-/HCO3- exchanger isoforms. The degree of amino acid homology between orthologous human and bovine RPE-specific isoforms was calculated after performing protein alignments. Transport of fluid across bovine RPE-choroid explants mounted in the Ussing chamber was used to assess the ability of DPOFA to modulate fluid absorption across the RPE. Results Using RT-PCR we showed that three isoforms (SLC4A2, SLC4A3, and SLC26A6) are strongly expressed in human and bovine RPE preparations. Amino acid comparisons conducted for RPE-specific isoforms support the use of bovine RPE-choroid explants as an adequate experimental system for assessing fluid absorption activity for DPOFA. Our data is consistent with the fact that DPOFA stimulates fluid absorption across the RPE in bovine RPE-choroid explants. Conclusions DPOFA seems to stimulate transport of water across the RPE in bovine RPE-choroid explants. Additional experiments are required to establish dose-dependent effect of DPOFA on fluid absorption in the bovine RPE-choroid experimental system.
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Affiliation(s)
- Pavel Iserovich
- Department of Ophthalmology, Columbia University Medical Center, New York, NY, USA
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70
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Li R, Wen R, Banzon T, Maminishkis A, Miller SS. CNTF mediates neurotrophic factor secretion and fluid absorption in human retinal pigment epithelium. PLoS One 2011; 6:e23148. [PMID: 21912637 PMCID: PMC3166283 DOI: 10.1371/journal.pone.0023148] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 07/07/2011] [Indexed: 12/14/2022] Open
Abstract
Ciliary neurotrophic factor (CNTF) protects photoreceptors and regulates their phototransduction machinery, but little is known about CNTF's effects on retinal pigment epithelial (RPE) physiology. Therefore, we determined the expression and localization of CNTF receptors and the physiological consequence of their activation in primary cultures of human fetal RPE (hfRPE). Cultured hfRPE express CNTF, CT1, and OsM and their receptors, including CNTFRα, LIFRβ, gp130, and OsMRβ, all localized mainly at the apical membrane. Exogenous CNTF, CT1, or OsM induces STAT3 phosphorylation, and OsM also induces the phosphorylation of ERK1/2 (p44/42 MAP kinase). CNTF increases RPE survivability, but not rates of phagocytosis. CNTF increases secretion of NT3 to the apical bath and decreases that of VEGF, IL8, and TGFβ2. It also significantly increases fluid absorption (JV) across intact monolayers of hfRPE by activating CFTR chloride channels at the basolateral membrane. CNTF induces profound changes in RPE cell biology, biochemistry, and physiology, including the increase in cell survival, polarized secretion of cytokines/neurotrophic factors, and the increase in steady-state fluid absorption mediated by JAK/STAT3 signaling. In vivo, these changes, taken together, could serve to regulate the microenvironment around the distal retinal/RPE/Bruch's membrane complex and provide protection against neurodegenerative disease.
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Affiliation(s)
- Rong Li
- National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rong Wen
- Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida, United States of America
| | - Tina Banzon
- National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Arvydas Maminishkis
- National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sheldon S. Miller
- National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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71
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Du H, Lim SL, Grob S, Zhang K. Induced pluripotent stem cell therapies for geographic atrophy of age-related macular degeneration. Semin Ophthalmol 2011; 26:216-24. [PMID: 21609235 DOI: 10.3109/08820538.2011.577498] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
There is currently no FDA-approved therapy for treating patients with geographic atrophy (GA), a late stage of age-related macular degeneration (AMD). Cell transplantation has the potential to restore vision in these patients. This review discusses how recent advancement in induced pluripotent stem (iPS) cells provides a promising therapy for GA treatment. Recent advances in stem cell biology have demonstrated that it is possible to derive iPS cells from human somatic cells by introducing reprogramming factors. Human retinal pigment epithelium (RPE) cells and photoreceptors can be derived from iPS cells by defined factors. Studies show that transplanting these cells can stabilize or recover vision in animal models. However, cell derivation protocols and transplantation procedures still need to be optimized. Much validation has to be done before clinical-grade, patient-derived iPS can be applied for human therapy. For now, RPE cells and photoreceptors derived from patient-specific iPS cells can serve as a valuable tool in elucidating the mechanism of pathogenesis and drug discovery for GA.
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Affiliation(s)
- Hongjun Du
- Institute for Genomic Medicine and Shiley Eye Center, University of California at San Diego, La Jolla, CA 92093, USA
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72
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Rizzolo LJ, Peng S, Luo Y, Xiao W. Integration of tight junctions and claudins with the barrier functions of the retinal pigment epithelium. Prog Retin Eye Res 2011; 30:296-323. [PMID: 21704180 DOI: 10.1016/j.preteyeres.2011.06.002] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 06/01/2011] [Accepted: 06/06/2011] [Indexed: 02/02/2023]
Abstract
The retinal pigment epithelium (RPE) forms the outer blood-retinal barrier by regulating the movement of solutes between the fenestrated capillaries of the choroid and the photoreceptor layer of the retina. Blood-tissue barriers use various mechanisms to accomplish their tasks including membrane pumps, transporters, and channels, transcytosis, metabolic alteration of solutes in transit, and passive but selective diffusion. The last category includes tight junctions, which regulate transepithelial diffusion through the spaces between neighboring cells of the monolayer. Tight junctions are extraordinarily complex structures that are dynamically regulated. Claudins are a family of tight junctional proteins that lend tissue specificity and selectivity to tight junctions. This review discusses how the claudins and tight junctions of the RPE differ from other epithelia and how its functions are modulated by the neural retina. Studies of RPE-retinal interactions during development lend insight into this modulation. Notably, the characteristics of RPE junctions, such as claudin composition, vary among species, which suggests the physiology of the outer retina may also vary. Comparative studies of barrier functions among species should deepen our understanding of how homeostasis is maintained in the outer retina. Stem cells provide a way to extend these studies of RPE-retinal interactions to human RPE.
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Affiliation(s)
- Lawrence J Rizzolo
- Department of Surgery and Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208062, New Haven, CT 06520-8062, USA.
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73
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Panfoli I, Calzia D, Ravera S, Bruschi M, Tacchetti C, Candiani S, Morelli A, Candiano G. Extramitochondrial tricarboxylic acid cycle in retinal rod outer segments. Biochimie 2011; 93:1565-75. [PMID: 21683117 DOI: 10.1016/j.biochi.2011.05.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 05/23/2011] [Indexed: 01/23/2023]
Abstract
Vertebrate retinal rod Outer Segments (OS) are the site of visual transduction, an energy demanding process for which mechanisms of ATP supply are still poorly known. Glycolysis or diffusion of either ATP or phosphocreatine from the Inner Segment (IS) does not seem to display adequate timing to supply ATP for phototransduction. We have previously reported data suggesting an aerobic metabolism in OS, which would largely account for the light-stimulated ATP need of the photoreceptor. Here, by oxymetry and biochemical analyses we show that: (i) disks isolated by Ficoll flotation consume O(2) in the presence of physiological respiring substrates either in coupled or uncoupled conditions; (ii) OS homogenates contain the whole biochemical machinery for the degradation of glucose, i.e. glycolysis and the tricarboxylic acid cycle (TCA cycle), consistently with the results of our previous proteomic study. Activities of the 8 TCA cycle enzymes in OS were comparable to those in retinal mitochondria-enriched fractions. Disk and OS preparations were subjected to TEM analysis, and while they can be considered free of inner segment contaminants, immunogold with specific antibodies demonstrate the expression therein of both the visual pigment rhodopsin and F(o)F(1)-ATP synthase. Finally, double immunofluorescence on mouse retina sections demonstrated a colocalization of some respiratory complex mitochondrial proteins with rhodopsin in rod OS. Data, suggestive of the exportability of the mitochondrial machinery for aerobic metabolism, may shed light on those retinal pathologies related to energy supply impairment in OS and to mutations in TCA enzymes.
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Affiliation(s)
- Isabella Panfoli
- Department of Biology, University of Genoa, Viale Benedetto XV, 5, 16132 Genova, Italy.
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74
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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: 412] [Impact Index Per Article: 31.7] [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.
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Affiliation(s)
- J R Sparrow
- Department of Ophthalmology, Columbia University, New York, NY 10032, USA.
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75
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Maminishkis A, Miller SS. Experimental models for study of retinal pigment epithelial physiology and pathophysiology. J Vis Exp 2010:2032. [PMID: 21085105 PMCID: PMC3144659 DOI: 10.3791/2032] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We have developed a cell culture procedure that can produce large quantities of confluent monolayers of primary human fetal retinal pigment epithelium (hfRPE) cultures with morphological, physiological and genetic characteristics of native human RPE. These hfRPE cell cultures exhibit heavy pigmentation, and electron microscopy show extensive apical membrane microvilli. The junctional complexes were identified with immunofluorescence labeling of various tight junction proteins. Epithelial polarity and function of these easily reproducible primary cultures closely resemble previously studied mammalian models of native RPE, including human. These results were extended by the development of therapeutic interventions in several animal models of human eye disease. We have focused on strategies for the removal of abnormal fluid accumulation in the retina or subretinal space. The extracellular subretinal space separates the photoreceptor outer segments and the apical membrane of the RPE and is critical for maintenance of retinal attachments and a whole host of RPE/retina interactions.
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76
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Bharti K, Miller SS, Arnheiter H. The new paradigm: retinal pigment epithelium cells generated from embryonic or induced pluripotent stem cells. Pigment Cell Melanoma Res 2010; 24:21-34. [PMID: 20846177 DOI: 10.1111/j.1755-148x.2010.00772.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Compared with neural crest-derived melanocytes, retinal pigment epithelium (RPE) cells in the back of the eye are pigment cells of a different kind. They are a part of the brain, form an epithelial monolayer, respond to distinct extracellular signals, and provide functions that far exceed those of a light-absorbing screen. For instance, they control nutrient and metabolite flow to and from the retina, replenish 11-cis-retinal by re-isomerizing all-trans-retinal generated during photoconversion, phagocytose daily a portion of the photoreceptors' outer segments, and secrete cytokines that locally control the innate and adaptive immune systems. Not surprisingly, RPE cell damage is a major cause of human blindness worldwide, with age-related macular degeneration a prevalent example. RPE replacement therapies using RPE cells generated from embryonic or induced pluripotent stem cells provide a novel approach to a rational treatment of such forms of blindness. In fact, RPE-like cells can be obtained relatively easily when stem cells are subjected to a two-step induction protocol, a first step that leads to a neuroectodermal fate and a second to RPE differentiation. Here, we discuss the characteristics of such cells, propose criteria they should fulfill in order to be considered authentic RPE cells, and point out the challenges one faces when using such cells in attempts to restore vision.
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Affiliation(s)
- Kapil Bharti
- Mammalian Development Section, National Institutes of Neurological Disorders and Stroke, Bethesda, MD, USA.
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77
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Strunnikova NV, Maminishkis A, Barb JJ, Wang F, Zhi C, Sergeev Y, Chen W, Edwards AO, Stambolian D, Abecasis G, Swaroop A, Munson PJ, Miller SS. Transcriptome analysis and molecular signature of human retinal pigment epithelium. Hum Mol Genet 2010; 19:2468-86. [PMID: 20360305 PMCID: PMC2876890 DOI: 10.1093/hmg/ddq129] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Retinal pigment epithelium (RPE) is a polarized cell layer critical for photoreceptor function and survival. The unique physiology and relationship to the photoreceptors make the RPE a critical determinant of human vision. Therefore, we performed a global expression profiling of native and cultured human fetal and adult RPE and determined a set of highly expressed ‘signature’ genes by comparing the observed RPE gene profiles to the Novartis expression database (SymAtlas: http://wombat.gnf.org/index.html) of 78 tissues. Using stringent selection criteria of at least 10-fold higher expression in three distinct preparations, we identified 154 RPE signature genes, which were validated by qRT-PCR analysis in RPE and in an independent set of 11 tissues. Several of the highly expressed signature genes encode proteins involved in visual cycle, melanogenesis and cell adhesion and Gene ontology analysis enabled the assignment of RPE signature genes to epithelial channels and transporters (ClCN4, BEST1, SLCA20) or matrix remodeling (TIMP3, COL8A2). Fifteen RPE signature genes were associated with known ophthalmic diseases, and 25 others were mapped to regions of disease loci. An evaluation of the RPE signature genes in a recently completed AMD genomewide association (GWA) data set revealed that TIMP3, GRAMD3, PITPNA and CHRNA3 signature genes may have potential roles in AMD pathogenesis and deserve further examination. We propose that RPE signature genes are excellent candidates for retinal diseases and for physiological investigations (e.g. dopachrome tautomerase in melanogenesis). The RPE signature gene set should allow the validation of RPE-like cells derived from human embryonic or induced pluripotent stem cells for cell-based therapies of degenerative retinal diseases.
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Affiliation(s)
- N V Strunnikova
- Ophthalmic Genetics & Visual Function Branch, NIH, Bethesda, MD 20892-2510, USA
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Wang FE, Zhang C, Maminishkis A, Dong L, Zhi C, Li R, Zhao J, Majerciak V, Gaur AB, Chen S, Miller SS. MicroRNA-204/211 alters epithelial physiology. FASEB J 2010; 24:1552-71. [PMID: 20056717 DOI: 10.1096/fj.08-125856] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
MicroRNA (miRNA) expression in fetal human retinal pigment epithelium (hfRPE), retina, and choroid were pairwise compared to determine those miRNAs that are enriched by 10-fold or more in each tissue compared with both of its neighbors. miRs-184, 187, 200a/200b, 204/211, and 221/222 are enriched in hfRPE by 10- to 754-fold compared with neuroretina or choroid (P<0.05). Five of these miRNAs are enriched in RPE compared with 20 tissues throughout the body and are 10- to 20,000-fold more highly expressed (P<0.005). miR-204 and 211 are the most highly expressed in the RPE. In addition, expression of miR-204/211 is significantly lower in the NCI60 tumor cell line panel compared with that in 13 normal tissues, suggesting the progressive disruption of epithelial barriers and increased proliferation. We demonstrated that TGF-beta receptor 2 (TGF-betaR2) and SNAIL2 are direct targets of miR-204 and that a reduction in miR-204 expression leads to reduced expression of claudins 10, 16, and 19 (message/protein) consistent with our observation that anti-miR-204/211 decreased transepithelial resistance by 80% and reduced cell membrane voltage and conductance. The anti-miR-204-induced decrease in Kir7.1 protein levels suggests a signaling pathway that connects TGF-betaR2 and maintenance of potassium homeostasis. Overall, these data indicate a critical role for miR-204/211 in maintaining epithelial barrier function and cell physiology.
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Affiliation(s)
- Fei E Wang
- National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-2510, USA
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79
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Li R, Maminishkis A, Banzon T, Wan Q, Jalickee S, Chen S, Miller SS. IFN{gamma} regulates retinal pigment epithelial fluid transport. Am J Physiol Cell Physiol 2009; 297:C1452-65. [PMID: 19794146 PMCID: PMC2793058 DOI: 10.1152/ajpcell.00255.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Accepted: 09/25/2009] [Indexed: 12/14/2022]
Abstract
The present experiments show that IFNgamma receptors are mainly localized to the basolateral membrane of human retinal pigment epithelium (RPE). Activation of these receptors in primary cultures of human fetal RPE inhibited cell proliferation and migration, decreased RPE mitochondrial membrane potential, altered transepithelial potential and resistance, and significantly increased transepithelial fluid absorption. These effects are mediated through JAK-STAT and p38 MAPK signaling pathways. Second messenger signaling through cAMP-PKA pathway- and interferon regulatory factor-1-dependent production of nitric oxide/cGMP stimulated the CFTR at the basolateral membrane and increased transepithelial fluid absorption. In vivo experiments using a rat model of retinal reattachment showed that IFNgamma applied to the anterior surface of the eye can remove extra fluid deposited in the extracellular or subretinal space between the retinal photoreceptors and RPE. Removal of this extra fluid was blocked by a combination of PKA and JAK-STAT pathway inhibitors injected into the subretinal space. These results demonstrate a protective role for IFNgamma in regulating retinal hydration across the outer blood-retinal barrier in inflammatory disease processes and provide the basis for possible therapeutic interventions.
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Affiliation(s)
- Rong Li
- NIH, Bethesda, MD 20892-2510, USA
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