1
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Escrevente C, Falcão AS, Hall MJ, Lopes-da-Silva M, Antas P, Mesquita MM, Ferreira IS, Cardoso MH, Oliveira D, Fradinho AC, Ciossek T, Nicklin P, Futter CE, Tenreiro S, Seabra MC. Formation of Lipofuscin-Like Autofluorescent Granules in the Retinal Pigment Epithelium Requires Lysosome Dysfunction. Invest Ophthalmol Vis Sci 2021; 62:39. [PMID: 34313720 PMCID: PMC8322709 DOI: 10.1167/iovs.62.9.39] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose We aim to characterize the pathways required for autofluorescent granule (AFG) formation by RPE cells using cultured monolayers. Methods We fed RPE monolayers in culture with a single pulse of photoreceptor outer segments (POS). After 24 hours the cells started accumulating AFGs that were comparable to lipofuscin in vivo. Using this model, we used a variety of light and electron microscopical techniques, flow cytometry and Western blot to analyze the formation of AFGs. We also generated a mutant RPE line lacking cathepsin D by gene editing. Results AFGs seem to derive from incompletely digested POS-containing phagosomes and after 3 days are surrounded by a single membrane positive for lysosome markers. We show by various methods that lysosome-phagosome fusion is required for AFG formation, and that impairment of lysosomal pH or catalytic activity, particularly cathepsin D activity, enhances AF accumulation. Conclusions We conclude that lysosomal dysfunction results in incomplete POS degradation and enhanced AFG accumulation.
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Affiliation(s)
- Cristina Escrevente
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Ana S Falcão
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | | | - Mafalda Lopes-da-Silva
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Pedro Antas
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Miguel M Mesquita
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Inês S Ferreira
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - M Helena Cardoso
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Daniela Oliveira
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Ana C Fradinho
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Thomas Ciossek
- Research Beyond Borders, Boehringer Ingelheim, Biberach, Germany
| | - Paul Nicklin
- Research Beyond Borders, Boehringer Ingelheim, Biberach, Germany
| | | | - Sandra Tenreiro
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Miguel C Seabra
- iNOVA4Health, CEDOC - Chronic Diseases Research Center, NOVA Medical School, Universidade Nova de Lisboa, Lisboa, Portugal.,UCL Institute of Ophthalmology, London, United Kingdom
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2
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Paraoan L, Sharif U, Carlsson E, Supharattanasitthi W, Mahmud NM, Kamalden TA, Hiscott P, Jackson M, Grierson I. Secretory proteostasis of the retinal pigmented epithelium: Impairment links to age-related macular degeneration. Prog Retin Eye Res 2020; 79:100859. [PMID: 32278708 DOI: 10.1016/j.preteyeres.2020.100859] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/24/2020] [Accepted: 03/26/2020] [Indexed: 12/19/2022]
Abstract
Secretory proteostasis integrates protein synthesis, processing, folding and trafficking pathways that are essential for efficient cellular secretion. For the retinal pigment epithelium (RPE), secretory proteostasis is of vital importance for the maintenance of the structural and functional integrity of apical (photoreceptors) and basal (Bruch's membrane/choroidal blood supply) sides of the environment it resides in. This integrity is achieved through functions governed by RPE secreted proteins, which include extracellular matrix modelling/remodelling, angiogenesis and immune response modulation. Impaired RPE secretory proteostasis affects not only the extracellular environment, but leads to intracellular protein aggregation and ER-stress with subsequent cell death. Ample recent evidence implicates dysregulated proteostasis as a key factor in the development of age-related macular degeneration (AMD), the leading cause of blindness in the developed world, and research aiming to characterise the roles of various proteins implicated in AMD-associated dysregulated proteostasis unveiled unexpected facets of the mechanisms involved in degenerative pathogenesis. This review analyses cellular processes unveiled by the study of the top 200 transcripts most abundantly expressed by the RPE/choroid in the light of the specialised secretory nature of the RPE. Functional roles of these proteins and the mechanisms of their impaired secretion, due to age and genetic-related causes, are analysed in relation to AMD development. Understanding the importance of RPE secretory proteostasis in relation to maintaining retinal health and how it becomes impaired in disease is of paramount importance for the development and assessment of future therapeutic advancements involving gene and cell therapies.
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Affiliation(s)
- Luminita Paraoan
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom.
| | - Umar Sharif
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Emil Carlsson
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Wasu Supharattanasitthi
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom; Department of Physiology, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand
| | - Nur Musfirah Mahmud
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Tengku Ain Kamalden
- Eye Research Centre, Department of Ophthalmology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Paul Hiscott
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Malcolm Jackson
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Ian Grierson
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
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3
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Lakkaraju A, Umapathy A, Tan LX, Daniele L, Philp NJ, Boesze-Battaglia K, Williams DS. The cell biology of the retinal pigment epithelium. Prog Retin Eye Res 2020; 78:100846. [PMID: 32105772 PMCID: PMC8941496 DOI: 10.1016/j.preteyeres.2020.100846] [Citation(s) in RCA: 170] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/19/2020] [Accepted: 02/23/2020] [Indexed: 02/07/2023]
Abstract
The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.
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Affiliation(s)
- Aparna Lakkaraju
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Li Xuan Tan
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Lauren Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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4
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de Mera-Rodríguez JA, Álvarez-Hernán G, Gañán Y, Martín-Partido G, Rodríguez-León J, Francisco-Morcillo J. Senescence-associated β-galactosidase activity in the developing avian retina. Dev Dyn 2019; 248:850-865. [PMID: 31226225 DOI: 10.1002/dvdy.74] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 05/22/2019] [Accepted: 06/15/2019] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Senescence-associated β-galactosidase (SA-β-GAL) histochemistry is the most commonly used biomarker of cellular senescence. These SA-β-GAL-positive cells are senescent embryonic cells that are usually removed by apoptosis from the embryo, followed by macrophage-mediated clearance. RESULTS Some authors have proposed that SA-β-GAL activity in differentiated neurons from young and adult mammals cannot be uniquely attributed to cell senescence, whether in vivo or in vitro. Using the developing visual system of the chicken as a model, the present study found that SA-β-GAL detected in the developing retina corresponded to lysosomal β-galactosidase activity, and that SA-β-GAL activity did not correlate with the chronotopographical distribution of apoptotic cells. However, SA-β-GAL staining in the undifferentiated retina coincided with the appearance of early differentiating neurons. In the laminated retina, SA-β-GAL staining was concentrated in the ganglion, amacrine, and horizontal cell layers. The photoreceptors and pigment epithelial cells also exhibited SA-β-GAL activity throughout retinal development. We have also found that SA-β-GAL staining strongly correlated p21 immunoreactivity. CONCLUSION In conclusion, the results clearly show that SA-β-GAL activity cannot be regarded as a specific marker of senescence during retinal development, and that it is mainly expressed in subpopulations of postmitotic neurons, which are nonproliferative cells, even at early stages of cell differentiation.
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Affiliation(s)
- José Antonio de Mera-Rodríguez
- Área de Anatomía Humana, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - Guadalupe Álvarez-Hernán
- Área de Biología Celular, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - Yolanda Gañán
- Área de Anatomía Humana, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - Gervasio Martín-Partido
- Área de Biología Celular, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - Joaquín Rodríguez-León
- Área de Anatomía Humana, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain
| | - Javier Francisco-Morcillo
- Área de Biología Celular, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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5
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Dalvi S, Galloway CA, Winschel L, Hashim A, Soto C, Tang C, MacDonald LA, Singh R. Environmental stress impairs photoreceptor outer segment (POS) phagocytosis and degradation and induces autofluorescent material accumulation in hiPSC-RPE cells. Cell Death Discov 2019; 5:96. [PMID: 31123602 PMCID: PMC6522536 DOI: 10.1038/s41420-019-0171-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 03/19/2019] [Accepted: 03/21/2019] [Indexed: 11/09/2022] Open
Abstract
Retinal pigment epithelium (RPE) cell dysfunction is central to the pathogenesis of age-related macular degeneration (AMD), a leading cause of adult blindness. Aging, the single biggest risk factor for AMD development, favors increase in RPE autofluorescent material due to accumulation of POS-digestion by-products through lysosomal dysfunction and impaired POS degradation. Apart from aging, environmental agents affect lysosomal function in multiple model systems and are implicated in AMD. Iron (Fe) overload and cigarette smoke exposure are the two environmental factors that are known to affect the lysosomal pathway and impact RPE cell health. However, the impact of Fe and cigarette smoke, on POS processing and its consequence for autofluorescent material accumulation in human RPE cells are yet to be established. Human induced pluripotent stem cell (hiPSC)-derived RPE, which phagocytoses and degrades POS in culture and can be derived from control individuals (no history/susceptibility for retinal disease), provides a model system to investigate the singular effect of excess Fe and/or cigarette smoke on POS processing by RPE cells. Using at least three distinct control hiPSC lines, we show that, compared to untreated hiPSC-RPE cells, POS uptake is reduced in both Fe (ferric ammonium citrate or FAC) and FAC + CSE (cigarette smoke extract)-treated hiPSC-RPE cells. Furthermore, exposure of hiPSC-RPE cultures to FAC + CSE leads to reduced levels of active cathepsin-D (CTSD), a lysosomal enzyme involved in POS processing, and causes delayed degradation of POS. Notably, delayed degradation of POS over time (2 weeks) in hiPSC-RPE cells exposed to Fe and CSE was sufficient to increase autofluorescent material build-up in these cells. Given that inefficient POS processing-mediated autofluorescent material accumulation in RPE cells has already been linked to AMD development, our results implicate a causative role of environmental agents, like Fe and cigarette smoke, in AMD.
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Affiliation(s)
- Sonal Dalvi
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Chad A Galloway
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA.,5Present Address: Department of Pathology and Lab Medicine, University of Rochester, Rochester, NY USA
| | - Lauren Winschel
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Ali Hashim
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Celia Soto
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Cynthia Tang
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Leslie A MacDonald
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA
| | - Ruchira Singh
- 1Department of Ophthalmology (Flaum Eye Institute), University of Rochester, Rochester, NY USA.,2Department of Biomedical Genetics, University of Rochester, Rochester, NY USA.,3UR Stem Cell and Regenerative Medicine Institute, Rochester, NY USA.,4Center for Visual Science, University of Rochester, Rochester, NY USA
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6
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Heikkinen EM, del Amo EM, Ranta VP, Urtti A, Vellonen KS, Ruponen M. Esterase activity in porcine and albino rabbit ocular tissues. Eur J Pharm Sci 2018; 123:106-110. [DOI: 10.1016/j.ejps.2018.07.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 06/29/2018] [Accepted: 07/16/2018] [Indexed: 02/06/2023]
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7
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Shang P, Valapala M, Grebe R, Hose S, Ghosh S, Bhutto IA, Handa JT, Lutty GA, Lu L, Wan J, Qian J, Sergeev Y, Puertollano R, Zigler JS, Xu GT, Sinha D. The amino acid transporter SLC36A4 regulates the amino acid pool in retinal pigmented epithelial cells and mediates the mechanistic target of rapamycin, complex 1 signaling. Aging Cell 2017; 16:349-359. [PMID: 28083894 PMCID: PMC5334531 DOI: 10.1111/acel.12561] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2016] [Indexed: 12/14/2022] Open
Abstract
The dry (nonneovascular) form of age‐related macular degeneration (AMD), a leading cause of blindness in the elderly, has few, if any, treatment options at present. It is characterized by early accumulation of cellular waste products in the retinal pigmented epithelium (RPE); rejuvenating impaired lysosome function in RPE is a well‐justified target for treatment. It is now clear that amino acids and vacuolar‐type H+‐ATPase (V‐ATPase) regulate the mechanistic target of rapamycin, complex 1 (mTORC1) signaling in lysosomes. Here, we provide evidence for the first time that the amino acid transporter SLC36A4/proton‐dependent amino acid transporter (PAT4) regulates the amino acid pool in the lysosomes of RPE. In Cryba1 (gene encoding βA3/A1‐crystallin) KO (knockout) mice, where PAT4 and amino acid levels are increased in the RPE, the transcription factors EB (TFEB) and E3 (TFE3) are retained in the cytoplasm, even after 24 h of fasting. Consequently, genes in the coordinated lysosomal expression and regulation (CLEAR) network are not activated, and lysosomal function remains low. As these mice age, expression of RPE65 and lecithin retinol acyltransferase (LRAT), two vital visual cycle proteins, decreases in the RPE. A defective visual cycle would possibly slow down the regeneration of new photoreceptor outer segments (POS). Further, photoreceptor degeneration also becomes obvious during aging, reminiscent of human dry AMD disease. Electron microscopy shows basal laminar deposits in Bruch's membrane, a hallmark of development of AMD. For dry AMD patients, targeting PAT4/V‐ATPase in the lysosomes of RPE cells may be an effective means of preventing or delaying disease progression.
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Affiliation(s)
- Peng Shang
- Department of Ophthalmology of Shanghai Tenth People's Hospital and Laboratory of Clinical Visual Science of Tongji Eye Institute; Tongji University School of Medicine; Shanghai China
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Mallika Valapala
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Rhonda Grebe
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Stacey Hose
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Sayan Ghosh
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Imran A. Bhutto
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - James T. Handa
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Gerard A. Lutty
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Lixia Lu
- Department of Ophthalmology of Shanghai Tenth People's Hospital and Laboratory of Clinical Visual Science of Tongji Eye Institute; Tongji University School of Medicine; Shanghai China
| | - Jun Wan
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Jiang Qian
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Yuri Sergeev
- National Eye Institute; National Institutes of Health; Bethesda MD USA
| | - Rosa Puertollano
- Cell Biology and Physiology Center; National Heart, Lung and Blood Institute; National Institutes of Health; Bethesda MD USA
| | - J. Samuel Zigler
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
| | - Guo-Tong Xu
- Department of Ophthalmology of Shanghai Tenth People's Hospital and Laboratory of Clinical Visual Science of Tongji Eye Institute; Tongji University School of Medicine; Shanghai China
- Translational Medical Center for Stem Cell Therapy; Shanghai East Hospital; Tongji University School of Medicine; Shanghai China
- The Collaborative Innovation Center for Brain Science; Tongji University; Shanghai China
| | - Debasish Sinha
- The Wilmer Eye Institute; The Johns Hopkins University School of Medicine; Baltimore MD USA
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8
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Bhattacharya M, Sarkhel S, Peltoniemi J, Broadbridge R, Tuomainen M, Auriola S, Urtti A. Differentially cleaving peptides as a strategy for controlled drug release in human retinal pigment epithelial cells. J Control Release 2017; 251:37-48. [DOI: 10.1016/j.jconrel.2017.02.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/21/2022]
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9
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Zuhl AM, Nolan CE, Brodney MA, Niessen S, Atchison K, Houle C, Karanian DA, Ambroise C, Brulet JW, Beck EM, Doran SD, O'Neill BT, Am Ende CW, Chang C, Geoghegan KF, West GM, Judkins JC, Hou X, Riddell DR, Johnson DS. Chemoproteomic profiling reveals that cathepsin D off-target activity drives ocular toxicity of β-secretase inhibitors. Nat Commun 2016; 7:13042. [PMID: 27727204 PMCID: PMC5062570 DOI: 10.1038/ncomms13042] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/26/2016] [Indexed: 01/18/2023] Open
Abstract
Inhibition of β-secretase BACE1 is considered one of the most promising approaches for treating Alzheimer's disease. Several structurally distinct BACE1 inhibitors have been withdrawn from development after inducing ocular toxicity in animal models, but the target mediating this toxicity has not been identified. Here we use a clickable photoaffinity probe to identify cathepsin D (CatD) as a principal off-target of BACE1 inhibitors in human cells. We find that several BACE1 inhibitors blocked CatD activity in cells with much greater potency than that displayed in cell-free assays with purified protein. Through a series of exploratory toxicology studies, we show that quantifying CatD target engagement in cells with the probe is predictive of ocular toxicity in vivo. Taken together, our findings designate off-target inhibition of CatD as a principal driver of ocular toxicity for BACE1 inhibitors and more generally underscore the power of chemical proteomics for discerning mechanisms of drug action. Several β-secretase (BACE) inhibitors exhibit unexplained ocular toxicity in preclinical studies. Here the authors generate a clickable photoaffinity probe to interrogate off-targets in cells and animals, and identify inhibition of cathepsin D as a driver of ocular toxicity.
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Affiliation(s)
- Andrea M Zuhl
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - Charles E Nolan
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Neuroscience Research Unit
| | - Michael A Brodney
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - Sherry Niessen
- Worldwide Medicinal Chemistry.,Pfizer Worldwide Research and Development, San Diego, California 92121, USA
| | - Kevin Atchison
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Neuroscience Research Unit
| | - Christopher Houle
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Drug Safety Research and Development
| | - David A Karanian
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Drug Safety Research and Development
| | - Claude Ambroise
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Neuroscience Research Unit
| | - Jeffrey W Brulet
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - Elizabeth M Beck
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - Shawn D Doran
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Pharmacokinetics, Dynamics and Metabolism
| | - Brian T O'Neill
- Worldwide Medicinal Chemistry.,Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA
| | - Christopher W Am Ende
- Worldwide Medicinal Chemistry.,Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA
| | - Cheng Chang
- Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Pharmacokinetics, Dynamics and Metabolism
| | - Kieran F Geoghegan
- Worldwide Medicinal Chemistry.,Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Structural Biology and Biophysics Group
| | - Graham M West
- Worldwide Medicinal Chemistry.,Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.,Structural Biology and Biophysics Group
| | - Joshua C Judkins
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - Xinjun Hou
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
| | - David R Riddell
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Neuroscience Research Unit
| | - Douglas S Johnson
- Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.,Worldwide Medicinal Chemistry
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10
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Sethna S, Chamakkala T, Gu X, Thompson TC, Cao G, Elliott MH, Finnemann SC. Regulation of Phagolysosomal Digestion by Caveolin-1 of the Retinal Pigment Epithelium Is Essential for Vision. J Biol Chem 2016; 291:6494-506. [PMID: 26814131 DOI: 10.1074/jbc.m115.687004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Indexed: 01/09/2023] Open
Abstract
Caveolin-1 associates with the endo/lysosomal machinery of cells in culture, suggesting that it functions at these organelles independently of its contribution to cell surface caveolae. Here we explored mice lacking caveolin-1 specifically in the retinal pigment epithelium (RPE). The RPE supports neighboring photoreceptors via diurnal phagocytosis of spent photoreceptor outer segment fragments. Like mice lacking caveolin-1 globally, (RPE)CAV1(-/-) mice developed a normal RPE and neural retina but showed reduced rod photoreceptor light responses, indicating that lack of caveolin-1 affects photoreceptor function in a non-cell-autonomous manner. (RPE)CAV1(-/-) RPE in situ showed normal particle engulfment but delayed phagosome clearance and reversed diurnal profiles of levels and activities of lysosomal enzymes. Therefore, eliminating caveolin-1 specifically impairs phagolysosomal degradation by the RPE in vivo. Endogenous caveolin-1 was recruited to maturing phagolysosomes in RPE cells in culture. Consistent with these in vivo data, a moderate increase (to ∼ 2.5-fold) or decrease (by half) of caveolin-1 protein levels in RPE cells in culture was sufficient to accelerate or impair phagolysosomal digestion, respectively. A mutant form of caveolin-1 that fails to reach the cell surface augmented degradation like wild-type caveolin-1. Acidic lysosomal pH and increased protease activity are essential for digestion. We show that halving caveolin-1 protein levels significantly alkalinized lysosomal pH and decreased lysosomal enzyme activities. Taken together, our results reveal a novel role for intracellular caveolin-1 in modulating phagolysosomal function. Moreover, they show, for the first time, that organellar caveolin-1 significantly affects tissue functionality in vivo.
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Affiliation(s)
- Saumil Sethna
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458
| | - Tess Chamakkala
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458
| | - Xiaowu Gu
- the Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | - Timothy C Thompson
- the Department of Genitourinary Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Guangwen Cao
- the Department of Genitourinary Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Michael H Elliott
- the Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | - Silvia C Finnemann
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458,
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11
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Hanus J, Anderson C, Wang S. RPE necroptosis in response to oxidative stress and in AMD. Ageing Res Rev 2015; 24:286-98. [PMID: 26369358 PMCID: PMC4661094 DOI: 10.1016/j.arr.2015.09.002] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 08/19/2015] [Accepted: 09/09/2015] [Indexed: 12/19/2022]
Abstract
Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly. The underlying mechanism of non-neovascular AMD (dry AMD), also named geographic atrophy (GA) remains unclear and the mechanism of retinal pigment epithelial (RPE) cell death in AMD is controversial. We review the history and recent progress in understanding the mechanism of RPE cell death induced by oxidative stress, in AMD mouse models, and in AMD patients. Due to the limitation of toolsets to distinguish between apoptosis and necroptosis (or necrosis), most previous research concludes that apoptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD. Recent studies suggest necroptosis as a major mechanism of RPE cell death in response to oxidative stress. Moreover, ultrastructural and histopathological studies support necrosis as major mechanism of RPE cells death in AMD. In this review, we discuss the mechanism of RPE cell death in response to oxidative stress, in AMD mouse models, and in human AMD patients. Based on the literature, we hypothesize that necroptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD.
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Affiliation(s)
- Jakub Hanus
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
| | - Chastain Anderson
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
| | - Shusheng Wang
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA; Department of Ophthalmology, Tulane University, New Orleans, LA 70118, USA.
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12
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Ferrington DA, Sinha D, Kaarniranta K. Defects in retinal pigment epithelial cell proteolysis and the pathology associated with age-related macular degeneration. Prog Retin Eye Res 2015; 51:69-89. [PMID: 26344735 DOI: 10.1016/j.preteyeres.2015.09.002] [Citation(s) in RCA: 165] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 08/29/2015] [Accepted: 09/01/2015] [Indexed: 12/12/2022]
Abstract
Maintenance of protein homeostasis, also referred to as "Proteostasis", integrates multiple pathways that regulate protein synthesis, folding, translocation, and degradation. Failure in proteostasis may be one of the underlying mechanisms responsible for the cascade of events leading to age-related macular degeneration (AMD). This review covers the major degradative pathways (ubiquitin-proteasome and lysosomal involvement in phagocytosis and autophagy) in the retinal pigment epithelium (RPE) and summarizes evidence of their involvement in AMD. Degradation of damaged and misfolded proteins via the proteasome occurs in coordination with heat shock proteins. Evidence of increased content of proteasome and heat shock proteins in retinas from human donors with AMD is consistent with increased oxidative stress and extensive protein damage with AMD. Phagocytosis and autophagy share key molecules in phagosome maturation as well as degradation of their cargo following fusion with lysosomes. Phagocytosis and degradation of photoreceptor outer segments ensures functional integrity of the neural retina. Autophagy rids the cell of toxic protein aggregates and defective mitochondria. Evidence suggesting a decline in autophagic flux includes the accumulation of autophagic substrates and damaged mitochondria in RPE from AMD donors. An age-related decrease in lysosomal enzymatic activity inhibits autophagic clearance of outer segments, mitochondria, and protein aggregates, thereby accelerating the accumulation of lipofuscin. This cumulative damage over a person's lifetime tips the balance in RPE from a state of para-inflammation, which strives to restore cell homeostasis, to the chronic inflammation associated with AMD.
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Affiliation(s)
- Deborah A Ferrington
- Department of Ophthalmology and Visual Neurosciences, 2001 6th St SE, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Debasish Sinha
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Room M035 Robert and Clarice Smith Bldg, 400 N Broadway, Baltimore, MD, 21287, USA.
| | - Kai Kaarniranta
- Department of Ophthalmology, University of Eastern Finland and Kuopio University Hospital, P.O. Box 100, 70029 KYS, Finland.
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13
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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.
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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.
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14
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Roggia MF, Ueta T. αvβ5 Integrin/FAK/PGC-1α Pathway Confers Protective Effects on Retinal Pigment Epithelium. PLoS One 2015; 10:e0134870. [PMID: 26244551 PMCID: PMC4526642 DOI: 10.1371/journal.pone.0134870] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Accepted: 07/14/2015] [Indexed: 12/21/2022] Open
Abstract
Purpose To elucidate the mechanism of the induction of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) by photoreceptor outer segments (POS) and its effects on retinal pigment epithelium (RPE). Methods PGC-1α upregulation by POS was confirmed in ARPE-19 cells and in RPE ex vivo. To elucidate the mechanism, siRNAs against β5 integrin, CD36, Mer tyrosine kinase (MerTK), and Atg5, blocking antibodies against CD36 and MerTK, and a specific inhibitor for focal adhesion kinase (FAK) were used. We examined the effect of POS-induced PGC-1α upregulation on the levels of reactive oxygen species (ROS), mitochondrial biogenesis, senescence-associated β-galactosidase (SA-β-gal) after H2O2 treatment, and lysosomal activity. Lysosomal activity was evaluated through transcriptional factor EB and its target genes, and the activity of cathepsin D. Lipid metabolism after POS treatment was assessed using Oil Red O and BODIPY C11. RPE phenotypes of PGC-1α-deficient mice were examined. Results POS-induced PGC-1α upregulation was suppressed by siRNA against β5 integrin and a FAK inhibitor. siRNAs and blocking antibodies against CD36 and MerTK enhanced the effect of POS on PGC-1α. The upregulation of PGC-1α increased the levels of mRNA for antioxidant enzymes and stimulated mitochondrial biogenesis, decreased ROS levels, and reduced SA-β-gal staining in H2O2-treated ARPE-19 cells. PGC-1α was critical for lysosomal activity and lipid metabolism after POS treatment. PGC-1α-deficient mice demonstrated an accumulation of type 2 lysosomes in RPE, thickening of Bruch’s membrane, and poor choriocapillaris vasculature. Conclusions The binding, but not the internalization of POS confers protective effects on RPE cells through the αvβ5 integrin/FAK/PGC-1α pathway.
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Affiliation(s)
- Murilo F. Roggia
- Department of Ophthalmology, Graduate School of Medicine and Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Takashi Ueta
- Department of Ophthalmology, Graduate School of Medicine and Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- * E-mail:
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15
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Monteiro JP, Santos FM, Rocha AS, Castro-de-Sousa JP, Queiroz JA, Passarinha LA, Tomaz CT. Vitreous humor in the pathologic scope: insights from proteomic approaches. Proteomics Clin Appl 2015; 9:187-202. [PMID: 25523418 DOI: 10.1002/prca.201400133] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 12/11/2014] [Accepted: 12/15/2014] [Indexed: 12/22/2022]
Abstract
The vitreous humor (VH) is the largest component of the eye. It is a colorless, gelatinous, highly hydrated matrix that fills the posterior segment of the eye between the lens and retina in vertebrates. In VH, a diversity of proteins that can influence retinal physiology is present, including growth factors, hormones, proteins with transporter activity, and enzymes. More importantly, the protein composition of VH has been described as being altered in a number of disease states. Therefore, attempts aiming at establishing a map of VH proteins and detecting putative biomarkers for ocular illness or protein fluctuations with putative physiologic significance were conducted over the last two decades, using proteomic approaches. Proteomic strategies often involve gel-based or LC techniques as sample fractioning approaches, subsequently coupled with MS procedures. This set of studies resulted in the proteomic characterization of a range of ocular disease samples, with particular incidence on diabetic retinopathy. However, practical therapeutic applications arising from these studies are scarce at the moment. A pertinent example of therapeutic targets arising from VH proteomics has emerged concerning vasoproliferative factors present in the vitreous, which should be involved in neovascularization and subsequent fibrovascular proliferation of the retina, in ocular disease context. Therefore, this review attempts to sum up the information acquired from the proteomic approaches to ocular disease conducted in VH samples, highlighting its clinical potential for disclosing ocular disease mechanisms and engendering pharmacological therapeutic treatments.
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Affiliation(s)
- João P Monteiro
- CICS-UBI Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
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16
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Bertolotti E, Neri A, Camparini M, Macaluso C, Marigo V. Stem cells as source for retinal pigment epithelium transplantation. Prog Retin Eye Res 2014; 42:130-44. [PMID: 24933042 DOI: 10.1016/j.preteyeres.2014.06.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 05/30/2014] [Accepted: 06/05/2014] [Indexed: 12/27/2022]
Abstract
Inherited maculopathies, age related macular degeneration and some forms of retinitis pigmentosa are associated with impaired function or loss of the retinal pigment epithelium (RPE). Among potential treatments, transplantation approaches are particularly promising. The arrangement of RPE cells in a well-defined tissue layer makes the RPE amenable to cell or tissue sheet transplantation. Different cell sources have been suggested for RPE transplantation but the development of a clinical protocol faces several obstacles. The source should provide a sufficient number of cells to at least recover the macula area. Secondly, cells should be plastic enough to be able to integrate in the host tissue. Tissue sheets should be considered as well, but the substrate on which RPE cells are cultured needs to be carefully evaluated. Immunogenicity can also be an obstacle for effective transplantation as well as tumorigenicity of not fully differentiated cells. Finally, ethical concerns may represent drawbacks when embryo-derived cells are proposed for RPE transplantation. Here we discuss different cell sources that became available in recent years and their different properties. We also present data on a new source of human RPE. We provide a protocol for RPE differentiation of retinal stem cells derived from adult ciliary bodies of post-mortem donors. We show molecular characterization of the in vitro differentiated RPE tissue and demonstrate its functionality based on a phagocytosis assay. This new source may provide tissue for allogenic transplantation based on best matches through histocompatibility testing.
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Affiliation(s)
- Evelina Bertolotti
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Alberto Neri
- Ophthalmology, S.Bi.Bi.T. Department, University of Parma, Parma, Italy
| | - Monica Camparini
- Ophthalmology, S.Bi.Bi.T. Department, University of Parma, Parma, Italy
| | - Claudio Macaluso
- Ophthalmology, S.Bi.Bi.T. Department, University of Parma, Parma, Italy
| | - Valeria Marigo
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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17
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Mazzoni F, Safa H, Finnemann SC. Understanding photoreceptor outer segment phagocytosis: use and utility of RPE cells in culture. Exp Eye Res 2014; 126:51-60. [PMID: 24780752 DOI: 10.1016/j.exer.2014.01.010] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 01/10/2014] [Accepted: 01/13/2014] [Indexed: 12/21/2022]
Abstract
RPE cells are the most actively phagocytic cells in the human body. In the eye, RPE cells face rod and cone photoreceptor outer segments at all times but contribute to shedding and clearance phagocytosis of distal outer segment tips only once a day. Analysis of RPE phagocytosis in situ has succeeded in identifying key players of the RPE phagocytic mechanism. Phagocytic processes comprise three distinct phases, recognition/binding, internalization, and digestion, each of which is regulated separately by phagocytes. Studies of phagocytosis by RPE cells in culture allow specifically analyzing and manipulating these distinct phases to identify their molecular mechanisms. Here, we compare similarities and differences of primary, immortalized, and stem cell-derived RPE cells in culture to RPE cells in situ with respect to phagocytic function. We discuss in particular potential pitfalls of RPE cell culture phagocytosis assays. Finally, we point out considerations for phagocytosis assay development for future studies.
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Affiliation(s)
- Francesca Mazzoni
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
| | - Hussein Safa
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
| | - Silvia C Finnemann
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA.
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18
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Valapala M, Wilson C, Hose S, Bhutto IA, Grebe R, Dong A, Greenbaum S, Gu L, Sengupta S, Cano M, Hackett S, Xu G, Lutty GA, Dong L, Sergeev Y, Handa JT, Campochiaro P, Wawrousek E, Zigler JS, Sinha D. Lysosomal-mediated waste clearance in retinal pigment epithelial cells is regulated by CRYBA1/βA3/A1-crystallin via V-ATPase-MTORC1 signaling. Autophagy 2014; 10:480-96. [PMID: 24468901 PMCID: PMC4077886 DOI: 10.4161/auto.27292] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In phagocytic cells, including the retinal pigment epithelium (RPE), acidic compartments of the endolysosomal system are regulators of both phagocytosis and autophagy, thereby helping to maintain cellular homeostasis. The acidification of the endolysosomal system is modulated by a proton pump, the V-ATPase, but the mechanisms that direct the activity of the V-ATPase remain elusive. We found that in RPE cells, CRYBA1/βA3/A1-crystallin, a lens protein also expressed in RPE, is localized to lysosomes, where it regulates endolysosomal acidification by modulating the V-ATPase, thereby controlling both phagocytosis and autophagy. We demonstrated that CRYBA1 coimmunoprecipitates with the ATP6V0A1/V0-ATPase a1 subunit. Interestingly, in mice when Cryba1 (the gene encoding both the βA3- and βA1-crystallin forms) is knocked out specifically in RPE, V-ATPase activity is decreased and lysosomal pH is elevated, while cathepsin D (CTSD) activity is decreased. Fundus photographs of these Cryba1 conditional knockout (cKO) mice showed scattered lesions by 4 months of age that increased in older mice, with accumulation of lipid-droplets as determined by immunohistochemistry. Transmission electron microscopy (TEM) of cryba1 cKO mice revealed vacuole-like structures with partially degraded cellular organelles, undigested photoreceptor outer segments and accumulation of autophagosomes. Further, following autophagy induction both in vivo and in vitro, phospho-AKT and phospho-RPTOR/Raptor decrease, while pMTOR increases in RPE cells, inhibiting autophagy and AKT-MTORC1 signaling. Impaired lysosomal clearance in the RPE of the cryba1 cKO mice also resulted in abnormalities in retinal function that increased with age, as demonstrated by electroretinography. Our findings suggest that loss of CRYBA1 causes lysosomal dysregulation leading to the impairment of both autophagy and phagocytosis.
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Affiliation(s)
- Mallika Valapala
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Christine Wilson
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Stacey Hose
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Imran A Bhutto
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Rhonda Grebe
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Aling Dong
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Seth Greenbaum
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Limin Gu
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA; Department of Ophthalmology of Shanghai Tenth People's Hospital and Tongji Eye Institute; Tongji University School of Medicine; Shanghai, China
| | - Samhita Sengupta
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Marisol Cano
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Sean Hackett
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Guotong Xu
- Department of Ophthalmology of Shanghai Tenth People's Hospital and Tongji Eye Institute; Tongji University School of Medicine; Shanghai, China
| | - Gerard A Lutty
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Lijin Dong
- National Eye Institute; National Institutes of Health; Bethesda, MD USA
| | - Yuri Sergeev
- National Eye Institute; National Institutes of Health; Bethesda, MD USA
| | - James T Handa
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Peter Campochiaro
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Eric Wawrousek
- National Eye Institute; National Institutes of Health; Bethesda, MD USA
| | - J Samuel Zigler
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
| | - Debasish Sinha
- Wilmer Eye Institute; Johns Hopkins University School of Medicine; Baltimore, MD USA
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19
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Kim JY, Zhao H, Martinez J, Doggett TA, Kolesnikov AV, Tang PH, Ablonczy Z, Chan CC, Zhou Z, Green DR, Ferguson TA. Noncanonical autophagy promotes the visual cycle. Cell 2013; 154:365-76. [PMID: 23870125 DOI: 10.1016/j.cell.2013.06.012] [Citation(s) in RCA: 257] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/06/2013] [Accepted: 06/06/2013] [Indexed: 01/08/2023]
Abstract
Phagocytosis and degradation of photoreceptor outer segments (POS) by retinal pigment epithelium (RPE) is fundamental to vision. Autophagy is also responsible for bulk degradation of cellular components, but its role in POS degradation is not well understood. We report that the morning burst of RPE phagocytosis coincided with the enzymatic conversion of autophagy protein LC3 to its lipidated form. LC3 associated with single-membrane phagosomes containing engulfed POS in an Atg5-dependent manner that required Beclin1, but not the autophagy preinitiation complex. The importance of this process was verified in mice with Atg5-deficient RPE cells that showed evidence of disrupted lysosomal processing. These mice also exhibited decreased photoreceptor responses to light stimuli and decreased chromophore levels that were restored with exogenous retinoid supplementation. These results establish that the interplay of phagocytosis and autophagy within the RPE is required for both POS degradation and the maintenance of retinoid levels to support vision.
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Affiliation(s)
- Ji-Young Kim
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis School of Medicine, St. Louis, MO 63110, USA
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20
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Loss of melanoregulin (MREG) enhances cathepsin-D secretion by the retinal pigment epithelium. Vis Neurosci 2013; 30:55-64. [PMID: 23611523 DOI: 10.1017/s0952523813000096] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cathepsin-D (Cat-D) is a major proteolytic enzyme in phagocytic cells. In the retinal pigment epithelium (RPE), it is responsible for the daily degradation of photoreceptor outer segments (POSs) to maintain retinal homeostasis. Melanoregulin (MREG)-mediated loss of phagocytic capacity has been linked to diminished intracellular Cat-D activity. Here, we demonstrate that loss of MREG enhances the secretion of intermediate Cat-D (48 kDa), resulting in a net enhancement of extracellular Cat-D activity. These results suggest that MREG is required to maintain Cat-D homeostasis in the RPE and likely plays a protective role in retinal health. In this regard, in the Mreg dsu/dsu mouse, we observe increased basal laminin. Loss of the Mreg dsu allele is not lethal and therefore leads to slow age-dependent changes in the RPE. Thus, we propose that this model will allow us to study potential dysregulatory functions of Cat-D in retinal disease.
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21
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Bejarano-Escobar R, Holguín-Arévalo MS, Montero JA, Francisco-Morcillo J, Martín-Partido G. Macrophage and microglia ontogeny in the mouse visual system can be traced by the expression of Cathepsins B and D. Dev Dyn 2011; 240:1841-55. [PMID: 21648018 DOI: 10.1002/dvdy.22673] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2011] [Indexed: 01/11/2023] Open
Abstract
Here, we show a detailed chronotopographical analysis of cathepsin B and D expression during development of the mouse visual system. Both proteases were detected in large rounded/ameboid cells usually located in close relationship with prominent sites of extensive physiological cell death. In concordance with their morphological features and topographical distribution, we demonstrate that expressing cells corresponded with macrophages and microglial precursors. We found that as microglial precursors differentiated the expression of both cathepsins was down-regulated. Of interest, cathepsin B and D transcripts were never observed in degenerating cells. Our findings point to a role for cathepsin D and B in cell debris degradation after apoptotic processes rather than promoting cell death, as proposed for other developmental models. Additionally their pattern of expression suggests a role in the maturation of the microglial precursors.
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Affiliation(s)
- Ruth Bejarano-Escobar
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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22
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Zigler JS, Zhang C, Grebe R, Sehrawat G, Hackler L, Adhya S, Hose S, McLeod DS, Bhutto I, Barbour W, Parthasarathy G, Zack DJ, Sergeev Y, Lutty GA, Handa JT, Sinha D. Mutation in the βA3/A1-crystallin gene impairs phagosome degradation in the retinal pigmented epithelium of the rat. J Cell Sci 2011; 124:523-31. [PMID: 21266465 DOI: 10.1242/jcs.078790] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Phagocytosis of the shed outer segment discs of photoreceptors is a major function of the retinal pigmented epithelium (RPE). We demonstrate for the first time that βA3/A1-crystallin, a major structural protein of the ocular lens, is expressed in RPE cells. Further, by utilizing the Nuc1 rat, in which the βA3/A1-crystallin gene is mutated, we show that this protein is required by RPE cells for proper degradation of outer segment discs that have been internalized in phagosomes. We also demonstrate that in wild-type RPE, βA3/A1-crystallin is localized to the lysosomes. However, in the Nuc1 RPE, βA3/A1-crystallin fails to translocate to the lysosomes, perhaps because misfolding of the mutant protein masks sorting signals required for proper trafficking. The digestion of phagocytized outer segments requires a high level of lysosomal enzyme activity, and cathepsin D, the major enzyme responsible for proteolysis of the outer segments, is decreased in mutant RPE cells. Interestingly, our results also indicate a defect in the autophagy process in the Nuc1 RPE, which is probably also linked to impaired lysosomal function, because phagocytosis and autophagy might share common mechanisms in degradation of their targets. βA3/A1-crystallin is a novel lysosomal protein in RPE, essential for degradation of phagocytosed material.
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Affiliation(s)
- J Samuel Zigler
- The Wilmer Eye Institute, The Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Baltimore, MD 21287, USA
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23
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Quantitative determination and localization of cathepsin D and its inhibitors. Folia Histochem Cytobiol 2010; 47:153-77. [PMID: 19995700 DOI: 10.2478/v10042-009-0073-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A literature survey was performed of the methods of quantitative assessment of the activity and concentration of cathepsin D and its inhibitors. Usefulness of non-modified and modified proteins and synthetic peptides as measurement substrates was evaluated. The survey includes also chemical and immunochemical methods used to determine the distribution of cathepsin D and its inhibitors in cells and tissues.
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24
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Ramkumar HL, Zhang J, Chan CC. Retinal ultrastructure of murine models of dry age-related macular degeneration (AMD). Prog Retin Eye Res 2010; 29:169-90. [PMID: 20206286 DOI: 10.1016/j.preteyeres.2010.02.002] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Age-related macular degeneration (AMD) is the most prevalent form of irreversible blindness worldwide in the elderly population. The pathology of dry AMD consists of macular degeneration of photoreceptors and the RPE, lipofuscin (A2E) accumulation, and drusen formation. Mice have been widely used for generating models that simulate human AMD features for investigating the pathogenesis, treatment and prevention of the disease. Although the mouse has no macula, focal atrophy of photoreceptors and RPE, lipofuscin accumulation, and increased A2E can develop in aged mouse eyes. However, drusen are rarely seen in mice because of their simpler Bruch's membrane and different process of lipofuscin extrusion compared with humans. Thus, analyzing basal deposits at the ultrastructural level and understanding the ultrastructural pathologic differences between various mouse AMD models are critical to comprehending the significance of research findings and response to possible therapeutic options for dry AMD. Based on the multifactorial pathogenesis of AMD, murine dry AMD models can be classified into three groups. First, genetically engineered mice that target genes related to juvenile macular dystrophies are the most common models, and they include abcr(-/-) (Stargardt disease), transgenic ELOVL4 (Stargardt-3 dominant inheritary disease), Efemp1(R345W/R345W) (Doyne honeycomb retinal dystrophy), and Timp3(S156C/S156C) (Sorsby fundus dystrophy) mice. Other murine models target genes relevant to AMD, including inflammatory genes such as Cfh(-/-), Ccl2(-/-), Ccr2(-/-), Cx3cr1(-/-), and Ccl2(-/-)/cx3cr1(-/-), oxidative stress associated genes such as Sod1(-/-) and Sod2 knockdown, metabolic pathway genes such as neprilysin(-/-) (amyloid beta), transgenic mcd/mcd (cathepsin D), Cp(-/-)/Heph(-/Y) (ferroxidase ceruloplasmin/hepaestin, iron metabolism), and transgenic ApoE4 on high fat and high cholesterol diet (lipid metabolism). Second, mice have also been immunologically manipulated by immunization with carboxyethylpyrrole (CEP), an oxidative fragment of DHA found in drusen, and found to present with dry AMD features. Third, natural mouse strains such as arrd2/arrd2 (Mdm gene mutation) and the senescence accelerated mice (SAM) spontaneously develop features of dry AMD like photoreceptor atrophy and thickening of Bruch's membrane. All the aforementioned models develop retinal lesions with various features that simulate dry AMD lesions: focal photoreceptor degeneration, abnormal RPE with increased lipofuscin, basal infolding, decreased melanosomes and degeneration. However, Bruch's membrane changes are less common. Most mice develop retinal lesions at an older age (6-24 months, depending on the models), while the Ccl2(-/-)/cx3cr1(-/-) mice develop lesions by 4-6 weeks. Although murine models present various degrees of retinal and/or RPE degeneration, classical drusen is extremely rare. Using electron microscopy, small drusenoid deposits are found between RPE and Bruch's membrane in a few models including Efemp1(R345W/R345W), Ccl2(-/-)/cx3cr1(-/-), neprilysin(-/-), transgenic mcd/mcd, and ApoE4 transgenic mice on a high fat diet. High A2E levels are measured in the retinas of abcr(-/-), transgenic ELOVL4, and Ccl2(-/-)/cx3cr1(-/-) mice. In summary, murine models provide useful tools for studying AMD pathogenesis and evaluating novel therapies for this disease. This review compares the major dry AMD murine models and discusses retinal pathology at the ultrastructural level.
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Affiliation(s)
- Hema L Ramkumar
- Immunopathology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-1857, USA
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Lipid peroxidation products reduce lysosomal protease activities in human retinal pigment epithelial cells via two different mechanisms of action. Exp Eye Res 2009; 90:261-6. [PMID: 19895809 DOI: 10.1016/j.exer.2009.10.014] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 10/27/2009] [Accepted: 10/28/2009] [Indexed: 11/22/2022]
Abstract
In age-related macular degeneration (AMD), reduced lysosomal capacity may contribute to lipofuscinogenesis and progressive dysfunction of the retinal pigment epithelium (RPE). We previously demonstrated that lipid peroxidation-related protein modifications inhibit lysosomal degradation of photoreceptor outer segment (POS) proteins in RPE cells. Herein, we investigate the effects of lipid peroxidation products on activities of key RPE lysosomal proteases. In lysosomes isolated from primary human RPE cells, lipid peroxidation products 4-hydroxynonenal (HNE) and malondialdehyde (MDA) exerted a dose-dependent inhibitory effect on cysteine proteases cathepsin B and L, with biologically relevant concentrations of 1 muM resulting in a reduction of enzyme activities by 88-94%. This effect was confirmed in cultured RPE cells. Using mass spectrometry, covalent HNE and MDA adducts were detected in the active center region of inactivated cathepsins. POS previously modified with HNE and MDA likewise caused a dose-dependent reduction of cathepsin B and L activities in isolated lysosomes and, in addition, inhibited the aspartic protease cathepsin D. Our results indicate that lipid peroxidation products in vitro interfere with RPE lysosomal protease activities by two different mechanisms of action: (i) HNE and MDA directly inactivate lysosomal cysteine proteases by covalent binding to the active center; (ii) HNE- and MDA-mediated protein modifications convert proteolytic substrates into competitive inhibitors of lysosomal proteases. Via these mechanisms, lipid peroxidation products may induce lysosomal dysfunction and lipofuscinogenesis in the aging RPE and thus contribute to the pathogenesis of AMD.
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Damek-Poprawa M, Diemer T, Lopes VS, Lillo C, Harper DC, Marks MS, Wu Y, Sparrow JR, Rachel RA, Williams DS, Boesze-Battaglia K. Melanoregulin (MREG) modulates lysosome function in pigment epithelial cells. J Biol Chem 2009; 284:10877-89. [PMID: 19240024 DOI: 10.1074/jbc.m808857200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Melanoregulin (MREG), the product of the Mreg(dsu) gene, is a small highly charged protein, hypothesized to play a role in organelle biogenesis due to its effect on pigmentation in dilute, ashen, and leaden mutant mice. Here we provide evidence that MREG is required in lysosome-dependent phagosome degradation. In the Mreg(-/-) mouse, we show that loss of MREG function results in phagosome accumulation due to delayed degradation of engulfed material. Over time, the Mreg(-/-) mouse retinal pigment epithelial cells accumulate the lipofuscin component, A2E. MREG-deficient human and mouse retinal pigment epithelial cells exhibit diminished activity of the lysosomal hydrolase, cathepsin D, due to defective processing. Moreover, MREG localizes to small intracellular vesicles and associates with the endosomal phosphoinositide, phosphatidylinositol 3,5-biphosphate. Collectively, these studies suggest that MREG is required for lysosome maturation and support a role for MREG in intracellular trafficking.
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Affiliation(s)
- Monika Damek-Poprawa
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Carr AJ, Vugler A, Lawrence J, Li Chen L, Ahmado A, Chen FK, Semo M, Gias C, da Cruz L, Moore HD, Walsh J, Coffey PJ. Molecular characterization and functional analysis of phagocytosis by human embryonic stem cell-derived RPE cells using a novel human retinal assay. Mol Vis 2009; 15:283-95. [PMID: 19204785 PMCID: PMC2635847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 01/21/2009] [Indexed: 11/16/2022] Open
Abstract
PURPOSE To examine the ability of retinal pigment epithelial (RPE) cells derived from human embryonic stem cells (HESC) to phagocytose photoreceptor outer segments, and to determine whether exposure to human retina induces any morphological changes in these cells. METHODS HESC-RPE cells were derived from a super-confluent preparation of the Shef1 HESC line. Pigmented colonies were isolated and expanded into pigmented monolayers on Matrigel matrix-coated dishes or filters. Cells were exposed to fluorescently labeled outer segments isolated from the porcine eye and assessed for phagocytic activity at regular intervals. Expression of molecules associated with RPE phagocytosis was analyzed by RT-PCR, immunocytochemistry, and western blot. The role of Mer Tyrosine Kinase (MERTK) in the phagocytosis of outer segments was investigated using antibodies directed against MERTK to block function. In a novel approach, cells were also exposed to fresh human neural retina tissue then examined by electron microscopy for evidence of phagocytosis and changes in cell morphology. RESULTS HESC-derived RPE cells are capable of phagocytosing isolated porcine outer segments and express molecules associated with RPE-specific phagocytosis, including MERTK. Pre-incubation with antibodies against MERTK blocked phagocytosis of photoreceptor outer segments, but not polystyrene beads. HESC-RPE cells also phagocytosed outer segments in a novel human retinal explant system. Furthermore co-culture adjacent to human retina tissue in this preparation resulted in the appearance of features in HESC-derived RPE cells normally observed only as the RPE matures. CONCLUSIONS The ingestion of photoreceptor outer segments from an isolated population and an artificial ex vivo human retina system demonstrates HESC-derived RPE cells are functional. HESC-derived RPE possess the relevant molecules required for phagocytosis, including MERTK, which is essential for the phagocytosis of outer segments but not latex beads. Furthermore, some changes observed in cell morphology after co-culture with human retina may have implications for understanding the full development and differentiation of RPE cells.
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Affiliation(s)
| | - Anthony Vugler
- Institute of Ophthalmology, University College London, London, UK
| | - Jean Lawrence
- Institute of Ophthalmology, University College London, London, UK
| | - Li Li Chen
- Institute of Ophthalmology, University College London, London, UK
| | - Ahmed Ahmado
- Institute of Ophthalmology, University College London, London, UK
| | | | - Ma’ayan Semo
- Institute of Ophthalmology, University College London, London, UK
| | - Carlos Gias
- Institute of Ophthalmology, University College London, London, UK
| | | | - Harry D. Moore
- Department of Biomedical Science, Centre for Stem Cell Biology, University of Sheffield, UK
| | | | - Peter J. Coffey
- Institute of Ophthalmology, University College London, London, UK
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Shitama T, Hayashi H, Noge S, Uchio E, Oshima K, Haniu H, Takemori N, Komori N, Matsumoto H. Proteome Profiling of Vitreoretinal Diseases by Cluster Analysis. Proteomics Clin Appl 2008; 2:1265-1280. [PMID: 19081814 DOI: 10.1002/prca.200800017] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Vitreous samples collected in retinopathic surgeries have diverse properties, making proteomics analysis difficult. We report a cluster analysis to evade this difficulty. Vitreous and subretinal fluid samples were collected from 60 patients during surgical operation of non-proliferative diabetic retinopathy, proliferative diabetic retinopathy, proliferative vitreoretinopathy, and rhegmatogenous retinal detachment. For controls we collected vitreous fluid from patients of idiopathic macular hole, epiretinal, and from a healthy postmortem donor. Proteins from these samples were subjected to quantitative proteomics using two-dimensional gel electrophoresis. We selected 105 proteins robustly expressed among ca 400 protein spots and subjected them to permutation test. By using permutation test analysis we observed unique variations in the expression of some of these proteins in vitreoretinal diseases when compared to the control and to each other: 1) the levels of inflammation-associate proteins such as AAT, APOA4, ALB, and TF were significantly higher in all four types of vitreoretinal diseases, and 2) each vitreoretinal disease elevates a unique set of proteins which can be interpreted based on the pathology of retinopathy. Our protocol will be effective for the study of protein expression in other types of clinical samples of diverse property.
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Affiliation(s)
- Tomomi Shitama
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, P.O. Box 26901, Oklahoma City, OK73190, USA
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Azarian SM, McLeod I, Lillo C, Gibbs D, Yates JR, Williams DS. Proteomic analysis of mature melanosomes from the retinal pigmented epithelium. J Proteome Res 2007; 5:521-9. [PMID: 16512666 DOI: 10.1021/pr0502323] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The protein content of melanosomes in the retinal pigment epithelium (RPE) was analyzed by mass spectrometry. More than 100 proteins were found to be common to two out of three variations of sample preparation. Some proteins normally associated with other organelles were detected. Several lysosomal enzymes were detected, with the presence of cathepsin D confirmed by immunoelectron microscopy, thus supporting the previously suggested notion that melanosomes may contribute to the degradation of ingested photoreceptor outer segment disks.
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Affiliation(s)
- Sassan M Azarian
- Department of Pharmacology, UCSD School of Medicine, La Jolla, California 92093-0912, USA
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Kociok N, Joussen AM. Varied expression of functionally important genes of RPE and choroid in the macula and in the periphery of normal human eyes. Graefes Arch Clin Exp Ophthalmol 2006; 245:101-13. [PMID: 16598467 DOI: 10.1007/s00417-006-0266-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 01/06/2006] [Accepted: 01/06/2006] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Topographic differences in RPE and choroid between macular and peripheral areas of the eye may predispose to morphologic and cell survival changes with aging. An understanding of the molecular events that distinguish RPE and choroid by their spatial location could give hints for the identification of survival factors and the development of new therapeutic approaches. To determine the mRNA expression of functionally important genes in RPE and choroid of morphologically normal human eyes, tissue patches were dissected from the macula and peripheral locations. METHODS The mRNA levels of 29 genes with known functions or expression in the RPE/choroid were quantified in these sections by real time RT-PCR. Variations in the mRNA expression were determined due to differences in the mean normalized expression (MNE) between different peripheral locations, left and right eye of the same donor, and eyes of different donors. RESULTS In the macula, the lysosomal enzyme cathepsin D (1.27E+00+/-1.54E-01) and the MERTK ligand Gas6 (1.08E+00+/-1.60E-01) had the highest MNE, whereas the apoptosis inducer Fas-Ligand (1.41E-04+/-6.46E-05) and the ROS internalization receptor CD36 (2.15E-04+/-1.11E-05) demonstrated the lowest expression. Interestingly, the PEDF expression (1.80E-01+/-4.56E-02) was 10 times higher than the VEGF expression (1.84E-02+/-2.46E-03) in the macular area. For most of the analyzed genes (52%, e.g. MERTK, integrin alphaV and beta5, RPE65, tyrosinase, VEGF) there was equal gene expression in the macula and in the periphery. For 31% of the genes (e.g. CD36, MAP1B) there was higher expression in the macula and for 17% of the genes (e.g. 11-cis RDH, VEGF-R2, PEDF) there was higher expression in the periphery. CONCLUSIONS Whereas most of the analyzed genes expressed in RPE and choroid had equal mRNA expression levels in the macula and the periphery with donor dependent variations, there are important exceptions in genes that are involved in the maintenance of a specific vascular status in the macula (PEDF, VEGF and VEGR-R2) and in the recycling of rod outer segments (11-cis RDH). Applying this technique to the gene expression analysis of patients with AMD could identify those genes that are involved in molding of the disease.
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Affiliation(s)
- Norbert Kociok
- Department of Vitreoretinal Surgery, Center for Ophthalmology, University of Cologne, Cologne, Germany.
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Yucel I, Akar ME, Dora B, Akar Y, Taskin O, Ozer HO. Effect of the menstrual cycle on standard achromatic and blue-on-yellow visual field analysis of women with migraine. Can J Ophthalmol 2005; 40:51-7. [PMID: 15825530 DOI: 10.1016/s0008-4182(05)80117-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND It has been postulated that migraine and glaucoma may have common vascular causative factors. Significant sex-based differences in the incidence of many important ocular conditions raise the possibility that estrogens may have direct effects on the eye. We performed a study to determine the effect of the menstrual cycle on standard achromatic automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) (blue-on-yellow perimetry) of women with migraine. METHODS Both eyes of 73 normally menstruating women (31 subjects with migraine and 42 healthy control subjects) were included in the study. Subjects underwent a complete ocular examination including SAP and SWAP in both the follicular phase (12th to 13th day of the cycle) and the luteal phase (1 to 2 days before the onset of bleeding) of two consecutive menstrual cycles.We performed visual field analysis using the Humphrey Field Analyzer II with the full-threshold central 30-2 program. Mean sensitivity was calculated for the superior temporal, inferior temporal, superior nasal and inferior nasal regions separately. RESULTS Thirteen subjects were lost to follow-up (5 in the migraine group and 8 in the control group), leaving 26 subjects and 34 subjects respectively. There was no significant difference in mean age between the two groups (33.9 years [standard deviation (SD) 3.4 years] vs. 35.1 years [SD 3.3 years]). The mean duration of migraine was 7.6 (SD 3.1) years (range 3-14 years). In both groups, serum estradiol levels were significantly lower (p = 0.001) and serum progesterone levels were significantly higher (p < 0.001) in the luteal phase than in the follicular phase. In the control group, the mean sensitivity values with SWAP were significantly lower in the luteal phase than in the follicular phase (p = 0.04). A similar decrease was observed for the subjects with migraine with both SAP and SWAP (p = 0.01). There was no difference in regional mean sensitivity between the two phases with either perimetric test in the control group. For the subjects with migraine, there was no difference in regional mean sensitivity between the two phases with SAP. However, with SWAP, the mean sensitivity for the nasal visual field locations was significantly lower in the luteal phase than in the follicular phase (p = 0.01). INTERPRETATION Our study provides further evidence of an effect of sex hormones on the visual field of women with migraine. In addition to assessment of intraocular pressure, menstrual cycle phases should be considered in women with migraine at risk for glaucomatous optic neuropathy.
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Affiliation(s)
- Iclal Yucel
- Department of Ophthalmology, Akdeniz University School of Medicine, Antalya, Turkey
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Hoppe G, O'Neil J, Hoff HF, Sears J. Products of lipid peroxidation induce missorting of the principal lysosomal protease in retinal pigment epithelium. BIOCHIMICA ET BIOPHYSICA ACTA 2004; 1689:33-41. [PMID: 15158911 DOI: 10.1016/j.bbadis.2004.01.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Revised: 01/07/2004] [Accepted: 01/09/2004] [Indexed: 10/26/2022]
Abstract
Phagocytosis of photoreceptor outer segments (OS) by retinal pigment epithelium (RPE) is essential for OS renewal and survival of photoreceptors. Internalized, oxidatively modified macromolecules perturb the lysosomal function of the RPE and can lead to impaired processing of photoreceptor outer segments. In this study, we sought to investigate the impact of intracellular accumulation of oxidatively damaged lipid-protein complexes on maturation and distribution of cathepsin D, the major lysosomal protease in the RPE. Primary cultures of human RPE cells were treated with copper-oxidized low density lipoprotein (LDL) and then challenged with serum-coated latex beads to stimulate phagocytosis. Three observations were noted to occur in this experimental system. First, immature forms of cathepsin D (52 and 46 kDa) were exclusively associated with latex-containing phagosomes. Second, maturation of cathepsin D was severely impaired in RPE cells loaded with oxidized LDL (oxLDL) prior to the phagocytic challenge. Third, pre-treatment with oxLDL caused sustained secretion of pro-cathepsin D and the latent form of gelatinase A into the extracellular space in a dose-dependent manner. These data stimulate the hypothesis that intracellular accumulation of poorly degradable, oxidized lipid-protein cross-links, may alter the turnover of cathepsin D, causing its mistargeting into the extracellular space together with the enhanced secretion of a gelatinase.
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Affiliation(s)
- George Hoppe
- Department of Cell Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
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Ambati J, Ambati BK, Yoo SH, Ianchulev S, Adamis AP. Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies. Surv Ophthalmol 2003; 48:257-93. [PMID: 12745003 DOI: 10.1016/s0039-6257(03)00030-4] [Citation(s) in RCA: 609] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Age-related macular degeneration is the principal cause of registered legal blindness among those aged over 65 in the United States, western Europe, Australia, and Japan. Despite intensive research, the precise etiology of molecular events that underlie age-related macular degeneration is poorly understood. However, investigations on parallel fronts are addressing this prevalent public health problem. Sophisticated biochemical and biophysical techniques have refined our understanding of the pathobiology of drusen, geographic atrophy, and retinal pigment epithelial detachments. Epidemiological identification of risk factors has facilitated an intelligent search for underlying mechanisms and fueled clinical investigation of behavior modification. Gene searches have not only brought us to the cusp of identifying the culpable gene loci in age-related macular degeneration, but also localized genes responsible for other macular dystrophies. Recent and ongoing investigations, often cued by tumor biology, have revealed an important role for various growth factors, particularly in the neovascular form of the condition. Transgenic and knockout studies have provided important mechanistic insights into the development of choroidal neovascularization, the principal cause of vision loss in age-related macular degeneration. This in turn has culminated in preclinical and clinical trials of directed molecular interventions.
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Affiliation(s)
- Jayakrishna Ambati
- Ocular Angiogenesis Laboratory, Department of Ophthalmology, University of Kentucky, Lexington, USA
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Elner VM. Retinal pigment epithelial acid lipase activity and lipoprotein receptors: effects of dietary omega-3 fatty acids. TRANSACTIONS OF THE AMERICAN OPHTHALMOLOGICAL SOCIETY 2002; 100:301-38. [PMID: 12545699 PMCID: PMC1358968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
PURPOSE To show that fish oil-derived omega-3 polyunsaturated fatty acids, delivered to the retinal pigment epithelium (RPE) by circulating low-density lipoproteins (LDL), enhance already considerable RPE lysosomal acid lipase activity, providing for more efficient hydrolysis of intralysosomal RPE lipids, an effect that may help prevent development of age-related macular degeneration (ARMD). METHODS Colorimetric biochemical and histochemical techniques were used to demonstrate RPE acid lipase in situ, in vitro, and after challenge with phagocytic stimuli. Receptor-mediated RPE uptake of fluorescently labeled native, aceto-acetylated, and oxidized LDL was studied in vitro and in vivo. LDL effects on RPE lysosomal enzymes were assessed. Lysosomal enzyme activity was compared in RPE cells from monkeys fed diets rich in fish oil to those from control animals and in cultured RPE cells exposed to sera from these monkeys. RESULTS RPE acid lipase activity was substantial and comparable to that of mononuclear phagocytes. Acid lipase activity increased significantly following phagocytic challenge with photoreceptor outer segment (POS) membranes. Receptor-mediated RPE uptake of labeled lipoproteins was determined in vitro. Distinctive uptake of labeled lipoproteins occurred in RPE cells and mononuclear phagocytes in vivo. Native LDL enhanced RPE lysosomal enzyme activity. RPE lysosomal enzymes increased significantly in RPE cells from monkeys fed fish oil-rich diets and in cultured RPE cells exposed to their sera. CONCLUSIONS RPE cells contain substantial acid lipase for efficient metabolism of lipids imbibed by POS phagocytosis and LDL uptake. Diets rich in fish oil-derived omega-3 fatty acids, by enhancing acid lipase, may reduce RPE lipofuscin accumulation, RPE oxidative damage, and the development of ARMD.
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Affiliation(s)
- Victor M Elner
- Department of Ophthalmology, University of Michigan, Ann Arbor, USA
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Lai CM, Robertson T, Papadimitriou J, Shen WY, Daw N, Constable IJ, Rakoczy PE. Controlled production of active cathepsin D in retinal pigment epithelial cells following adenovirus-mediated gene delivery. Mol Ther 2000; 2:476-84. [PMID: 11082321 DOI: 10.1006/mthe.2000.0195] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The transduction of a low cathepsin D-producing retinal pigment epithelial cell line with a recombinant adenovirus, Ad.proCatD, carrying a viral promoter and the precursor form of the lysosomal enzyme cathepsin D, procathepsin D, led to the upregulation of proCatD expression. However, the resultant aspartic protease activity did not exceed that observed in normal primary human retinal pigment epithelial cells. Following the injection of Ad. proCatD into rat eyes, immunohistochemistry and Western blot analysis localized the expression of procathepsin D to the retinal pigment epithelial cell layer and to the sclera/choroid/retinal epithelial cell layers, respectively. This upregulation of procathepsin D expression was accompanied by a limited increase in aspartic protease activity. The injected eyes did not demonstrate any of the retinal changes that have been associated with the overproduction and secretion of active cathepsin D. Immunoelectronmicroscopy of Ad.proCatD-transduced retinal pigment epithelial cells demonstrated the presence of cathepsin D not only in cytoplasmic vesicles and lysosomes but also in the nucleoli and, less strongly, elsewhere in euchromatic regions of some 10% of cells. In spite of the upregulated expression of procathepsin D, the production of active cathepsin D in Ad.proCatD-transduced retinal pigment epithelial cells was strictly controlled. It is proposed that active cathepsin D production is controlled at the point of posttranslational modification by an intranuclear feedback mechanism initiated by the relative excess of procathepsin D in Ad. proCatD-transduced retinal pigment epithelial cells.
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Affiliation(s)
- C M Lai
- Center for Ophthalmology and Visual Science, Lions Eye Institute, Nedlands, 6009, Australia
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Zhang D, Lai MC, Constable IJ, Rakoczy PE. A novel immunoassay for the evaluation of rod outer segment digestion in cultured retinal pigment epithelial cells. Clin Exp Ophthalmol 2000; 28:216-9. [PMID: 10981803 DOI: 10.1046/j.1442-9071.2000.00297.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this work a novel enzyme-linked immunoabsorbent assay quantifying residual rod outer segments in the medium of rod outer segment-challenged retinal pigment epithelial cells is described. A retinal pigment epithelial cell line (D407) that produces low level of cathepsin D, and a primary human retinal pigment epithelial cell culture (HRPE51) that has normal cathepsin D levels, were challenged with bovine rod outer segments. At 3 days post-challenge, the amount of undigested or residual bovine rod outer segments left in the culture medium was quantified by an enzyme-linked immunoabsorbent assay. An antibody raised against bovine rod outer segments, which had been purified and labelled with nitroiodophenyl haptens, was used in the assay. The sensitivity of the immunoassay was less than 10(2) bovine rod outer segments per mL and the signal followed a linear curve, saturating around 10(6) bovine rod outer segments per mL. HRPE51 cells had no residual bovine rod outer segments present in the medium following a challenge with 10(4) bovine rod outer segments per mL. In the medium of D407 cells, residual bovine rod outer segment levels were higher at all bovine rod outer segment concentrations when compared to the residual bovine rod outer segment levels in HRPE51 cells, suggesting that D407 cells have a lower digestive capacity. These results demonstrated that the immunoassay for detecting bovine rod outer segments is a sensitive and reliable technique that can be used to quantify the amount of residual bovine rod outer segments, following bovine rod outer segment challenge of retinal pigment epithelial cells.
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Affiliation(s)
- D Zhang
- Centre for Ophthalmology and Visual Science, University of Western Australia, Australia
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Rakoczy PE, Sarks SH, Daw N, Constable IJ. Distribution of cathepsin D in human eyes with or without age-related maculopathy. Exp Eye Res 1999; 69:367-74. [PMID: 10504270 DOI: 10.1006/exer.1999.0700] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cathepsin D is a ubiquitous enzyme which plays an important role in the catabolism of proteins. Enzymatic studies showed that cathepsin D is the most important lysosomal enzyme in the proteolysis of opsin. The importance of cathepsin D in the lysosomal digestion of phagocytosed photoreceptor outer segments by the retinal pigment epithelium suggests that a decrease in cathepsin D activity might contribute to the development of hyalinized drusen and to the development of age-related maculopathy. The aim of this project was to study the immunohistochemical localization of cathepsin D in human eyes and particularly to compare the immunoreactivity of cathepsin D normal retinal pigment epithelial cells and in cells surrounding hyalinized drusen or lesions of age-related maculopathy. Following clinicopathological examinations the eyes were fixed, paraffin embedded and individual sections were subjected to Picro-Mallory staining for histopathological examination. Bleaching was performed then immunohistochemistry was carried out using a monoclonal mouse anti-human cathepsin D antibody. On the basis of the appearance of basal laminar deposit the eyes were divided into five groups corresponding to levels of progression in age-related maculopathy development. Following optimization of bleaching cathepsin D immunostaining was clearly visible in the iris epithelium, ciliary body and the retinal pigment epithelial layer of all eyes with the highest immunoreactivity present in the RPE cells. Within the neural retina the ganglion cells demonstrated a weak signal. Retinal pigment epithelial cathepsin D immunoreactivity was not impaired by age, geographical location or by age-related maculopathy status. There was a small increase in cathepsin D immunoreactivity around hyalinized drusen. The maintenance of cathepsin D immunoreactivity in eyes with hyalinized drusen or in samples with age-related maculopathy suggest that down-regulation of cathepsin D expression in the affected locations does not precede the development of these conditions. However, further studies are required to establish if the immunoreactive cathepsin D represents the fully processed biologically active enzyme.
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Affiliation(s)
- P E Rakoczy
- Molecular Ophthalmology, Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands, Perth, Australia
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Shen WY, Garrett KL, da Cruz L, Constable IJ, Rakoczy PE. Dynamics of phosphorothioate oligonucleotides in normal and laser photocoagulated retina. Br J Ophthalmol 1999; 83:852-61. [PMID: 10381674 PMCID: PMC1723113 DOI: 10.1136/bjo.83.7.852] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIMS To investigate the distribution, persistence, and stability of fluorescently labelled phosphorothioate oligonucleotides (PS-ODNs) in normal and laser photocoagulated retina following intravitreal injection in the rat. METHODS Fluorescently labelled PS-ODNs were injected intravitreally into pigmented eyes at doses of 0.5-10.0 nmol in 2.0 microl solution. The dynamics of PS-ODNs was evaluated by fluorescent microscopy of cryosections and flat mounted retinal pigment epithelium (RPE)-choroid-sclera. Genescan analysis was used to assess the integrity of PS-ODNs in the retina after injection. The dynamics of PS-ODNs was also evaluated in the retina following krypton laser photocoagulation with a protocol producing choroidal neovascularisation (CNV). RESULTS Following intravitreal injection the PS-ODNs demonstrated dose and time dependent distribution and persistence in the retina, where they accessed all neural layers. However, they preferentially accumulated in the RPE layer, demonstrated as bright granules in the cytoplasm of the cells. Injections of 5.0 and 7.5 nmol of PS-ODNs exhibited strong fluorescence in the retina for 6 weeks after injection. Genescan analysis demonstrated that the PS-ODNs remained almost completely intact for at least 12 weeks. Following laser treatment, the PS-ODNs were concentrated in the regions of laser photocoagulation and retained high intensity for at least 8 weeks after injection, particularly localised to macrophages, RPE, and the local choroidal tissue. CONCLUSIONS These results indicate that PS-ODNs are stable and accessible to most neural layers of the retina, and they preferentially accumulate in the RPE layer following intravitreal injection. The successful delivery of PS-ODNs into normal and laser photocoagulated retina suggests that PS-ODNs may have potential in the development of therapy for attenuating retinal degenerations and CNV.
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Affiliation(s)
- W Y Shen
- Department of Molecular Ophthalmology Biology, Lions Eye Institute, Western Australia
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