201
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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: 269] [Impact Index Per Article: 24.5] [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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202
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Murakami Y, Notomi S, Hisatomi T, Nakazawa T, Ishibashi T, Miller JW, Vavvas DG. Photoreceptor cell death and rescue in retinal detachment and degenerations. Prog Retin Eye Res 2013; 37:114-40. [PMID: 23994436 DOI: 10.1016/j.preteyeres.2013.08.001] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Revised: 08/08/2013] [Accepted: 08/10/2013] [Indexed: 02/08/2023]
Abstract
Photoreceptor cell death is the ultimate cause of vision loss in various retinal disorders, including retinal detachment (RD). Photoreceptor cell death has been thought to occur mainly through apoptosis, which is the most characterized form of programmed cell death. The caspase family of cysteine proteases plays a central role for inducing apoptosis, and in experimental models of RD, dying photoreceptor cells exhibit caspase activation; however, there is a paradox that caspase inhibition alone does not provide a sufficient protection against photoreceptor cell loss, suggesting that other mechanisms of cell death are involved. Recent accumulating evidence demonstrates that non-apoptotic forms of cell death, such as autophagy and necrosis, are also regulated by specific molecular machinery, such as those mediated by autophagy-related proteins and receptor-interacting protein kinases, respectively. Here we summarize the current knowledge of cell death signaling and its roles in photoreceptor cell death after RD and other retinal degenerative diseases. A body of studies indicate that not only apoptotic but also autophagic and necrotic signaling are involved in photoreceptor cell death, and that combined targeting of these pathways may be an effective neuroprotective strategy for retinal diseases associated with photoreceptor cell loss.
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Affiliation(s)
- Yusuke Murakami
- Retina Service, Angiogenesis Laboratory, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA; Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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203
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Abstract
Age-related macular degeneration (AMD) is a leading cause of blindness in aged individuals. Recent advances have highlighted the essential role of immune processes in the development, progression and treatment of AMD. In this Review we discuss recent discoveries related to the immunological aspects of AMD pathogenesis. We outline the diverse immune cell types, inflammatory activators and pathways that are involved. Finally, we discuss the future of inflammation-directed therapeutics to treat AMD in the growing aged population.
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204
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Said T, Tremblay-Mercier J, Berrougui H, Rat P, Khalil A. Effects of vegetable oils on biochemical and biophysical properties of membrane retinal pigment epithelium cells. Can J Physiol Pharmacol 2013; 91:812-7. [PMID: 24144052 DOI: 10.1139/cjpp-2013-0036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate the effect of vegetable oil enrichment of retinal pigment epithelial (RPE) cells on their biochemical and biophysical properties. For this, RPE cells were incubated with 4 different vegetables oils (olive oil, corn oil, argan oil, and camelina oil). The cytotoxicity of these vegetable oils was assessed in vivo on 8-week-old mice and in vitro by using the neutral red and YO-PRO-1 tests. Membrane fluidity was evaluated by fluorescence anisotropy using the fluorescent probe diphenylhexatriene, and membrane fatty acid composition was assessed by gas chromatography. None of the oils tested displayed cytotoxic effects. In vitro, omega-3 rich oils improved membrane fluidity by 47% compared with the control cells. The omega-3 PUFA content within membranes decreased by 38% to 55% when cells were incubated separately with olive oil, corn oil, or argan oil, and increased when cells were incubated with a mixture of those oils, or with camelina oil alone (50% and 103% increase, respectively). Our results show that the fatty acids in vegetable oil incorporate into retinal cells and increase the plasma membrane fluidity.
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Affiliation(s)
- Toihiri Said
- a Research Center on Aging, Fleurimont Site, 3001, 12ème Avenue Nord, Sherbrooke, QC J1H 4N4, Canada
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205
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Li CP, Yao J, Tao ZF, Li XM, Jiang Q, Yan B. Epigallocatechin-gallate (EGCG) regulates autophagy in human retinal pigment epithelial cells: a potential role for reducing UVB light-induced retinal damage. Biochem Biophys Res Commun 2013; 438:739-45. [PMID: 23916613 DOI: 10.1016/j.bbrc.2013.07.097] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Accepted: 07/24/2013] [Indexed: 12/19/2022]
Abstract
Autophagy is an intracellular catabolic process involved in protein and organelle degradation via the lysosomal pathway that has been linked in the pathogenesis of age-related macular degeneration (AMD). UVB irradiation-mediated degeneration of the macular retinal pigment epithelial (RPE) cells is an important hallmark of AMD, which is along with the change in RPE autophagy. Thus, pharmacological manipulation of RPE autophagy may offer an alternative therapeutic target in AMD. Here, we found that epigallocatechin-3-gallate (EGCG), a polyphenolic compound from green tea, plays a regulatory role in UVB irradiation-induced autophagy in RPE cells. UVB irradiation results in a marked increase in the amount of LC3-II protein in a dose-dependent manner. EGCG administration leads to a significant reduction in the formation of LC3-II and autophagosomes. mTOR signaling activation is required for EGCG-induced LC3-II formation, as evidenced by the fact that EGCG-induced LC3-II formation is significantly impaired by rapamycin administration. Moreover, EGCG significantly alleviates the toxic effects of UVB irradiation on RPE cells in an autophagy-dependent manner. Collectively, our study reveals a novel role of EGCG in RPE autophagy. EGCG may be exploited as a potential therapeutic reagent for the treatment of pathological conditions associated with abnormal autophagy.
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Affiliation(s)
- Chao-Peng Li
- Eye hospital, Nanjing Medical University, Nanjing 210029, China
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206
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Diminishing risk for age-related macular degeneration with nutrition: a current view. Nutrients 2013; 5:2405-56. [PMID: 23820727 PMCID: PMC3738980 DOI: 10.3390/nu5072405] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 06/24/2013] [Accepted: 06/24/2013] [Indexed: 02/02/2023] Open
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Clinical hallmarks of AMD are observed in one third of the elderly in industrialized countries. Preventative interventions through dietary modification are attractive strategies, because they are more affordable than clinical therapies, do not require specialists for administration and many studies suggest a benefit of micro- and macro-nutrients with respect to AMD with few, if any, adverse effects. The goal of this review is to provide information from recent literature on the value of various nutrients, particularly omega-3 fatty acids, lower glycemic index diets and, perhaps, some carotenoids, with regard to diminishing risk for onset or progression of AMD. Results from the upcoming Age-Related Eye Disease Study (AREDS) II intervention trial should be particularly informative.
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207
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Athanasiou D, Aguilà M, Bevilacqua D, Novoselov SS, Parfitt DA, Cheetham ME. The cell stress machinery and retinal degeneration. FEBS Lett 2013; 587:2008-17. [PMID: 23684651 PMCID: PMC4471140 DOI: 10.1016/j.febslet.2013.05.020] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 05/01/2013] [Accepted: 05/02/2013] [Indexed: 12/12/2022]
Abstract
Retinal degenerations are a group of clinically and genetically heterogeneous disorders characterised by progressive loss of vision due to neurodegeneration. The retina is a highly specialised tissue with a unique architecture and maintaining homeostasis in all the different retinal cell types is crucial for healthy vision. The retina can be exposed to a variety of environmental insults and stress, including light-induced damage, oxidative stress and inherited mutations that can lead to protein misfolding. Within retinal cells there are different mechanisms to cope with disturbances in proteostasis, such as the heat shock response, the unfolded protein response and autophagy. In this review, we discuss the multiple responses of the retina to different types of stress involved in retinal degenerations, such as retinitis pigmentosa, age-related macular degeneration and glaucoma. Understanding the mechanisms that maintain and re-establish proteostasis in the retina is important for developing new therapeutic approaches to fight blindness.
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Affiliation(s)
| | - Monica Aguilà
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
| | - Dalila Bevilacqua
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
| | | | - David A. Parfitt
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
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208
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Hoh Kam J, Lenassi E, Malik TH, Pickering MC, Jeffery G. Complement component C3 plays a critical role in protecting the aging retina in a murine model of age-related macular degeneration. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 183:480-92. [PMID: 23747511 DOI: 10.1016/j.ajpath.2013.04.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 03/04/2013] [Accepted: 04/05/2013] [Indexed: 01/17/2023]
Abstract
Complement component C3 is the central complement component and a key inflammatory protein activated in age-related macular degeneration (AMD). AMD is associated with genetic variation in complement proteins that results in enhanced activation of C3 through the complement alternative pathway. These include complement factor H (CFH), a negative regulator of C3 activation. Both C3 inhibition and/or CFH augmentation are potential therapeutic strategies in AMD. Herein, we examined retinal integrity in aged (12 months) mice deficient in both factors H and C3 (CFH(-/-).C3(-/-)), CFH alone (CFH(-/-)), or C3 alone (C3(-/-)), and wild-type mice (C57BL/6). Retinal function was assessed by electroretinography, and retinal morphological features were analyzed at light and electron microscope levels. Retinas were also stained for amyloid β (Aβ) deposition, inflammation, and macrophage accumulation. Contrary to expectation, electroretinograms of CFH(-/-).C3(-/-) mice displayed more severely reduced responses than those of other mice. All mutant strains showed significant photoreceptor loss and thickening of Bruch's membrane compared with wild-type C57BL/6, but these changes were greater in CFH(-/-).C3(-/-) mice. CFH(-/-).C3(-/-) mice had significantly more Aβ on Bruch's membrane, fewer macrophages, and high levels of retinal inflammation than the other groups. Our data show that both uncontrolled C3 activation (CFH(-/-)) and complete absence of C3 (CFH(-/-).C3(-/-) and C3(-/-)) negatively affect aged retinas. These findings suggest that strategies that inhibit C3 in AMD may be deleterious.
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Affiliation(s)
- Jaimie Hoh Kam
- Institute of Ophthalmology, University College London, London, United Kingdom
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209
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Rodríguez‐Muela N, Koga H, García‐Ledo L, Villa P, Rosa EJ, Cuervo AM, Boya P. Balance between autophagic pathways preserves retinal homeostasis. Aging Cell 2013; 12:478-88. [PMID: 23521856 DOI: 10.1111/acel.12072] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2013] [Indexed: 01/20/2023] Open
Abstract
Aging contributes to the appearance of several retinopathies and is the largest risk factor for aged-related macular degeneration, major cause of blindness in the elderly population. Accumulation of undegraded material as lipofuscin represents a hallmark in many pathologies of the aged eye. Autophagy is a highly conserved intracellular degradative pathway that plays a critical role in the removal of damaged cell components to maintain the cellular homeostasis. A decrease in autophagic activity with age observed in many tissues has been proposed to contribute to the aggravation of age-related diseases. However, the participation of different autophagic pathways to the retina physiopathology remains unknown. Here, we describe a marked reduction in macroautophagic activity in the retina with age, which coincides with an increase in chaperone-mediated autophagy (CMA). This increase in CMA is also observed during retinal neurodegeneration in the Atg5(flox/flox) ; nestin-Cre mice, a mouse model with downregulation of macroautophagy in neuronal precursors. In contrast to other cell types, this autophagic cross talk in retinal cells is not bi-directional and CMA inhibition renders cone photoreceptor very sensitive to stress. Temporal and cell-type-specific differences in the balance between autophagic pathways may be responsible for the specific pattern of visual loss that occurs with aging. Our results show for the first time a cross talk of different lysosomal proteolytic systems in the retina during normal aging and may help the development of new therapeutic intervention for age-dependent retinal diseases.
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Affiliation(s)
- Natalia Rodríguez‐Muela
- Department of Cellular and Molecular Biology CIB CSIC Ramiro de Maeztu 9 E‐28040Madrid Spain
| | - Hiroshi Koga
- Department of Developmental and Molecular Biology and Institute for Aging Studies Albert Einstein College of Medicine Bronx NY 10461USA
| | - Lucía García‐Ledo
- Department of Cellular and Molecular Biology CIB CSIC Ramiro de Maeztu 9 E‐28040Madrid Spain
| | - Pedro Villa
- Department of Physiology Universidad de Alcalá E‐28871Alcalá de Henares Spain
| | - Enrique J. Rosa
- 3D Lab Department of Cellular and Molecular Medicine CIB CSIC Ramiro de Maeztu 9E‐28040Madrid Spain
| | - Ana María Cuervo
- Department of Developmental and Molecular Biology and Institute for Aging Studies Albert Einstein College of Medicine Bronx NY 10461USA
| | - Patricia Boya
- Department of Cellular and Molecular Biology CIB CSIC Ramiro de Maeztu 9 E‐28040Madrid Spain
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210
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Juel HB, Faber C, Svendsen SG, Vallejo AN, Nissen MH. Inflammatory cytokines protect retinal pigment epithelial cells from oxidative stress-induced death. PLoS One 2013; 8:e64619. [PMID: 23705001 PMCID: PMC3660526 DOI: 10.1371/journal.pone.0064619] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 04/15/2013] [Indexed: 11/29/2022] Open
Abstract
Purpose To investigate the effects of inflammatory factors and oxidative stress on cell survival of the human retinal pigment epithelial (RPE) cell line, ARPE-19. Methods Confluent RPE cells were treated with peripheral blood mononuclear cells-conditioned medium (PCM), H2O2, NaIO3, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, or combinations of these. Cell viability was determined by viability assays and by light microscopy. Effector molecules of cell death were investigated by immunofluorescence microscopy and flow cytometry. Microarrays were performed to screen for differential expression of anti-oxidative enzymes, and protein expression was validated by immunoblotting. Results Viability of RPE cells was reduced by exposure to inflammatory agents (PCM, IFNγ+/-TNFα) or to oxidative agents (H2O2 or NaIO3). Unexpectedly, cells treated with either H2O2 or NaIO3 were partially protected from cell death by the addition of PCM. This protection was conferred, at least in part, by IFNγ and TNFα. Cell death induced by H2O2 or NaIO3 was preceded by mitochondrial dysfunction and by p62 upregulation, both of which were attenuated by PCM and/or by IFNγ+TNFα. RPE cells co-cultured with activated T cells, or treated with cytokines showed increased expression of anti-oxidative genes, with upregulation of superoxide dismutase 2 protein following PCM treatment. Conclusion Oxidative stress-induced cell death was reduced by concomitant inflammatory stress. This is likely due to the cytokine-mediated induction of the anti-oxidative stress response, upregulating protective anti-oxidant pathway(s). These findings suggest caution for the clinical use of anti-inflammatory agents in the management of immune-associated eye diseases such as age-related macular degeneration.
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Affiliation(s)
- Helene B Juel
- Eye Research Unit, Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
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211
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Roccaro AM, Sacco A, Maiso P, Azab AK, Tai YT, Reagan M, Azab F, Flores LM, Campigotto F, Weller E, Anderson KC, Scadden DT, Ghobrial IM. BM mesenchymal stromal cell-derived exosomes facilitate multiple myeloma progression. J Clin Invest 2013; 123:1542-55. [PMID: 23454749 DOI: 10.1172/jci66517] [Citation(s) in RCA: 594] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 01/03/2013] [Indexed: 12/13/2022] Open
Abstract
BM mesenchymal stromal cells (BM-MSCs) support multiple myeloma (MM) cell growth, but little is known about the putative mechanisms by which the BM microenvironment plays an oncogenic role in this disease. Cell-cell communication is mediated by exosomes. In this study, we showed that MM BM-MSCs release exosomes that are transferred to MM cells, thereby resulting in modulation of tumor growth in vivo. Exosomal microRNA (miR) content differed between MM and normal BM-MSCs, with a lower content of the tumor suppressor miR-15a. In addition, MM BM-MSC-derived exosomes had higher levels of oncogenic proteins, cytokines, and adhesion molecules compared with exosomes from the cells of origin. Importantly, whereas MM BM-MSC-derived exosomes promoted MM tumor growth, normal BM-MSC exosomes inhibited the growth of MM cells. In summary, these in vitro and in vivo studies demonstrated that exosome transfer from BM-MSCs to clonal plasma cells represents a previously undescribed and unique mechanism that highlights the contribution of BM-MSCs to MM disease progression.
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Affiliation(s)
- Aldo M Roccaro
- Dana-Farber Cancer Institute, Department of Medical Oncology, Harvard Medical School, Boston, Massachusetts 02215, USA
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212
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Biasutto L, Chiechi A, Couch R, Liotta LA, Espina V. Retinal pigment epithelium (RPE) exosomes contain signaling phosphoproteins affected by oxidative stress. Exp Cell Res 2013; 319:2113-2123. [PMID: 23669273 DOI: 10.1016/j.yexcr.2013.05.005] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/03/2013] [Accepted: 05/04/2013] [Indexed: 12/23/2022]
Abstract
Age-related macular degeneration (AMD) is a leading cause of vision loss and blindness among the elderly population in the industrialized world. One of the typical features of this pathology is the gradual death of retinal pigment epithelial (RPE) cells, which are essential for maintaining photoreceptor functions and survival. The etiology is multifactorial, and oxidative stress is clearly one of the key factors involved in disease pathogenesis (Plafker, Adv. Exp. Med. Biol. 664 (2010) 447-56; Qin, Drug Dev. Res. 68 (2007) 213-225). Recent work has revealed the presence of phosphorylated signaling proteins in the vitreous humour of patients affected by AMD or other retinal diseases. While the location of these signaling proteins is typically the cell membrane or intracellular compartments, vitreous samples were proven to be cell-free (Davuluri et al., Arch. Ophthalmol. 127 (2009) 613-21). To gain a better understanding of how these proteins can be shed into the vitreous, we used reverse phase protein arrays (RPMA) to analyze the protein and phosphoprotein content of exosomes shed by cultured ARPE-19 cells under oxidative stress conditions. Seventy two proteins were shown to be released by ARPE-19 cells and compartmentalized within exosomes. Forty one of them were selectively detected in their post-translationally modified form (i.e., phosphorylated or cleaved) for the first time in exosomes. Sets of these proteins were linked together reflecting activation of pathway units within exosomes. A subset of (phospho)proteins were altered in exosomes secreted by ARPE-19 cells subjected to oxidative stress, compared to that secreted by control/non stressed cells. Stress-altered exosome proteins were found to be involved in pathways regulating apoptosis/survival (i.e, Bak, Smac/Diablo, PDK1 (S241), Akt (T308), Src (Y416), Elk1 (S383), ERK 1/2 (T202/Y204)) and cell metabolism (i.e., AMPKα1 (S485), acetyl-CoA carboxylase (S79), LDHA). Exosomes may thus represent the conduit through which membrane and intracellular signaling proteins are released into the vitreous. Changes in their (phospho)protein content upon stress conditions suggest their possible role in mediating cell-cell signaling during physio-pathological events; furthermore, exosomes may represent a potential source of biomarkers.
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Affiliation(s)
- Lucia Biasutto
- CNR Institute of Neuroscience, Viale G. Colombo 3, 35121 Padova, Italy; Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy.
| | - Antonella Chiechi
- Center for Applied Proteomics and Molecular Medicine, George Mason University, 10900 University Blvd, Manassas, VA 20110, USA
| | - Robin Couch
- Department of Chemistry and Biochemistry, George Mason University, 10900 University Blvd, Manassas, VA 20110, USA
| | - Lance A Liotta
- Center for Applied Proteomics and Molecular Medicine, George Mason University, 10900 University Blvd, Manassas, VA 20110, USA
| | - Virginia Espina
- Center for Applied Proteomics and Molecular Medicine, George Mason University, 10900 University Blvd, Manassas, VA 20110, USA.
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213
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Autophagy regulating kinases as potential therapeutic targets for age-related macular degeneration. Future Med Chem 2013. [PMID: 23190104 DOI: 10.4155/fmc.12.169] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Age-related macular degeneration (AMD) is the leading cause of central vision loss in the elderly in the developed countries. The number of AMD patients will double during the next decades due to increasing number of aged people. Chronic oxidative stress, inflammation and accumulation of protein-rich deposits both in the retinal pigment epithelium lysosomes and under the retinal pigment epithelium herald the onset of AMD. The disease can be divided into dry and wet AMD forms. The dry form of the disease is more prevalent accounting for up to 90% of all cases. Continued intraocular injections are the current treatment strategy to prevent progression of wet AMD. It is a major challenge to develop new drugs that could prevent or at least ease the symptoms of the increasing population of AMD patients. Since AMD pathology is clearly associated with accumulated protein deposits, the autophagy clearance system might represent a potential future therapeutic target for AMD as is thoroughly discussed here.
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214
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Klettner A, Kauppinen A, Blasiak J, Roider J, Salminen A, Kaarniranta K. Cellular and molecular mechanisms of age-related macular degeneration: from impaired autophagy to neovascularization. Int J Biochem Cell Biol 2013; 45:1457-67. [PMID: 23603148 DOI: 10.1016/j.biocel.2013.04.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 04/08/2013] [Accepted: 04/09/2013] [Indexed: 01/18/2023]
Abstract
Age-related macular degeneration (AMD) is a complex, degenerative and progressive disease involving multiple genetic and environmental factors. It can result in severe visual loss e.g. AMD is the leading cause of blindness in the elderly in the western countries. Although age, genetics, diet, smoking, and many cardiovascular factors are known to be linked with this disease there is increasing evidence that long-term oxidative stress, impaired autophagy clearance and inflammasome mediated inflammation are involved in the pathogenesis. Under certain conditions these may trigger detrimental processes e.g. release of vascular endothelial growth factor (VEGF), causing choroidal neovascularization e.g. in wet AMD. This review ties together these crucial pathological threads in AMD.
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Affiliation(s)
- Alexa Klettner
- Department of Ophthalmology, University Medical Center Schleswig-Holstein, Kiel, Germany
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215
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Kaarniranta K, Sinha D, Blasiak J, Kauppinen A, Veréb Z, Salminen A, Boulton ME, Petrovski G. Autophagy and heterophagy dysregulation leads to retinal pigment epithelium dysfunction and development of age-related macular degeneration. Autophagy 2013; 9:973-84. [PMID: 23590900 PMCID: PMC3722332 DOI: 10.4161/auto.24546] [Citation(s) in RCA: 239] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Age-related macular degeneration (AMD) is a complex, degenerative and progressive eye disease that usually does not lead to complete blindness, but can result in severe loss of central vision. Risk factors for AMD include age, genetics, diet, smoking, oxidative stress and many cardiovascular-associated risk factors. Autophagy is a cellular housekeeping process that removes damaged organelles and protein aggregates, whereas heterophagy, in the case of the retinal pigment epithelium (RPE), is the phagocytosis of exogenous photoreceptor outer segments. Numerous studies have demonstrated that both autophagy and heterophagy are highly active in the RPE. To date, there is increasing evidence that constant oxidative stress impairs autophagy and heterophagy, as well as increases protein aggregation and causes inflammasome activation leading to the pathological phenotype of AMD. This review ties together these crucial pathological topics and reflects upon autophagy as a potential therapeutic target in AMD.
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Affiliation(s)
- Kai Kaarniranta
- Department of Ophthalmology; Institute of Clinical Medicine; University of Eastern Finland; Kuopio, Finland; Department of Ophthalmology; Kuopio University Hospital; Kuopio, Finland
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216
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Romao S, Gannage M, Münz C. Checking the garbage bin for problems in the house, or how autophagy assists in antigen presentation to the immune system. Semin Cancer Biol 2013; 23:391-6. [PMID: 23541679 DOI: 10.1016/j.semcancer.2013.03.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Macroautophagy was originally discovered as a nutrient salvage pathway during starvation. By now it has not only become clear that degradation of cytoplasmic constituents via transport by autophagosomes to lysosomes can be used for innate and adaptive immunity, but that the core machinery assists antigen presentation to the immune system by a variety of vesicular transport pathways. All of these rely on the presentation of small protein waste fragments, which are generated by a variety of catabolic pathways, including macroautophagy, on major histocompatibility complex (MHC) molecules. In this review, we will point out how classical macroautophagy, as well as phagocytosis and exocytosis, which both benefit from the core autophagic machinery, assist in antigen presentation on MHC class I and II molecules to CD8+ and CD4+ T cells, respectively. Finally to high-light that macroautophagy is always intimately interconnected with cell death in addition to the various supported vesicular transport function, its role in lymphocyte, especially T cell, development and function will be discussed. From this body of work a picture is emerging that the core machinery of macroautophagy can be used for a variety of vesicular transport pathways and to modulate cell survival, besides its classical role in delivering intracellular material for lysosomal degradation.
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Affiliation(s)
- Susana Romao
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Switzerland
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217
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Xu D, Tahara H. The role of exosomes and microRNAs in senescence and aging. Adv Drug Deliv Rev 2013; 65:368-75. [PMID: 22820533 DOI: 10.1016/j.addr.2012.07.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 07/03/2012] [Accepted: 07/08/2012] [Indexed: 12/31/2022]
Abstract
Senescence is viewed as a cellular counterpart to aging of tissues and organisms, characterized by an irreversible growth arrest and a combination of changes in cell morphology, function and behavior. microRNAs (miRNAs), the most studied small non-coding RNAs, play an important role in many biological processes by the regulation of gene expression. Recent evidence has shown that miRNAs are contained in exosomes that are tiny vesicles of endocytic origin and released by a variety of different cells as a means for cell-to-cell contact and information transfer. Exosomes and miRNAs have been found to participate in the complex networks of cellular senescence and contribute to aging. Here, we will give an overview on the involvement of secretory factors including exosomes and miRNA in the regulation of cellular senescence, demonstrating the potential role of exosomes and miRNAs in biological processes and signaling pathways of senescence and aging.
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218
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Oczypok EA, Oury TD, Chu CT. It's a cell-eat-cell world: autophagy and phagocytosis. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 182:612-22. [PMID: 23369575 PMCID: PMC3589073 DOI: 10.1016/j.ajpath.2012.12.017] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 12/06/2012] [Indexed: 11/26/2022]
Abstract
The process of cellular eating, or the phagocytic swallowing of one cell by another, is an ancient manifestation of the struggle for life itself. Following the endosymbiotic origin of eukaryotic cells, increased cellular and then multicellular complexity was accompanied by the emergence of autophagic mechanisms for self-digestion. Heterophagy and autophagy function not only to protect the nutritive status of cells, but also as defensive responses against microbial pathogens externally or the ill effects of damaged proteins and organelles within. Because of the key roles played by phagocytosis and autophagy in a wide range of acute and chronic human diseases, pathologists have played similarly key roles in elucidating basic regulatory phases for both processes. Studies in diverse organ systems (including the brain, liver, kidney, lung, and muscle) have defined key roles for these lysosomal pathways in infection control, cell death, inflammation, cancer, neurodegeneration, and mitochondrial homeostasis. The literature reviewed here exemplifies the role of pathology in defining leading-edge questions for continued molecular and pathophysiological investigations into all forms of cellular digestion.
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Affiliation(s)
- Elizabeth A. Oczypok
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Tim D. Oury
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Charleen T. Chu
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Center for Neuroscience, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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219
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Wavre-Shapton ST, Tolmachova T, da Silva ML, Futter CE, Seabra MC. Conditional ablation of the choroideremia gene causes age-related changes in mouse retinal pigment epithelium. PLoS One 2013; 8:e57769. [PMID: 23460904 PMCID: PMC3584022 DOI: 10.1371/journal.pone.0057769] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/25/2013] [Indexed: 01/25/2023] Open
Abstract
The retinal pigment epithelium (RPE) is a pigmented monolayer of cells lying between the photoreceptors and a layer of fenestrated capillaries, the choriocapillaris. Choroideremia (CHM) is an X-linked progressive degeneration of these three layers caused by the loss of function of Rab Escort protein-1 (REP1). REP1 is involved in the prenylation of Rab proteins, key regulators of membrane trafficking. To study the pathological consequences of chronic disruption of membrane traffic in the RPE we used a cell type-specific knock-out mouse model of the disease, where the Chm/Rep1 gene is deleted only in pigmented cells (ChmFlox, Tyr-Cre+). Transmission electron microscopy (TEM) was used to quantitate the melanosome distribution in the RPE and immunofluorescent staining of rhodopsin was used to quantitate phagocytosed rod outer segments in retinal sections. The ultrastructure of the RPE and Bruch’s membrane at different ages was characterised by TEM to analyse age-related changes occurring as a result of defects in membrane traffic pathways. Chm/Rep1 gene knockout in RPE cells resulted in reduced numbers of melanosomes in the apical processes and delayed phagosome degradation. In addition, the RPE accumulated pathological changes at 5–6 months of age similar to those observed in 2-year old controls. These included the intracellular accumulation of lipofuscin-containing deposits, disorganised basal infoldings and the extracellular accumulation of basal laminar and basal linear deposits. The phenotype of the ChmFlox, Tyr-Cre+ mice suggests that loss of the Chm/Rep1 gene causes premature accumulation of features of aging in the RPE. Furthermore, the striking similarities between the present observations and some of the phenotypes reported in age-related macular degeneration (AMD) suggest that membrane traffic defects may contribute to the pathogenesis of AMD.
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Affiliation(s)
- Silène T. Wavre-Shapton
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Tanya Tolmachova
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Mafalda Lopes da Silva
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Clare E. Futter
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
- * E-mail: (CEF); (MCS)
| | - Miguel C. Seabra
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- * E-mail: (CEF); (MCS)
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220
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Forrester JV. Bowman lecture on the role of inflammation in degenerative disease of the eye. Eye (Lond) 2013; 27:340-52. [PMID: 23288138 DOI: 10.1038/eye.2012.265] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Inflammation, in the pathogenesis of many diseases previously thought to be strictly genetic, degenerative, metabolic, or endocrinologic in aetiology, has gradually entered the framework of a general mechanism of disease. This is exemplified by conditions such as Parkinson's disease, Alzheimer's disease, atherosclerosis, diabetes, and the more recently described Metabolic Syndrome. Chronic inflammatory processes have a significant, if not primary role, in ophthalmic diseases, particularly in retinal degenerative diseases. However, inflammation itself is not easy to define, and some aspects of inflammation may be beneficial, in a process described as 'para-inflammation' by Medhzitov. In contrast, the damaging effects of inflammation, mediated by pro-inflammatory macrophages through activation of the intracellular protein-signalling complexes, termed inflammasomes, are well recognised and are important therapeutic targets. In this review, the range of inflammatory processes in the eye is evaluated in the context of how these processes impact upon retinal degenerative disease, particularly diabetic retinopathy and age-related macular degeneration.
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Affiliation(s)
- J V Forrester
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, UK.
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221
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Mader BJ, Pivtoraiko VN, Flippo HM, Klocke BJ, Roth KA, Mangieri LR, Shacka JJ. Rotenone inhibits autophagic flux prior to inducing cell death. ACS Chem Neurosci 2012; 3:1063-72. [PMID: 23259041 DOI: 10.1021/cn300145z] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 09/13/2012] [Indexed: 12/21/2022] Open
Abstract
Rotenone, which selectively inhibits mitochondrial complex I, induces oxidative stress, α-synuclein accumulation, and dopaminergic neuron death, principal pathological features of Parkinson's disease. The autophagy-lysosome pathway degrades damaged proteins and organelles for the intracellular maintenance of nutrient and energy balance. While it is known that rotenone causes autophagic vacuole accumulation, the mechanism by which this effect occurs has not been thoroughly investigated. Treatment of differentiated SH-SY5Y cells with rotenone (10 μM) induced the accumulation of autophagic vacuoles at 6 h and 24 h as indicated by Western blot analysis for microtubule associated protein-light chain 3-II (MAP-LC3-II). Assessment of autophagic flux at these time points indicated that autophagic vacuole accumulation resulted from a decrease in their effective lysosomal degradation, which was substantiated by increased levels of autophagy substrates p62 and α-synuclein. Inhibition of lysosomal degradation may be explained by the observed decrease in cellular ATP levels, which in turn may have caused the observed concomitant increase in acidic vesicle pH. The early (6 h) effects of rotenone on cellular energetics and autophagy-lysosome pathway function preceded the induction of cell death and apoptosis. These findings indicate that the classical mitochondrial toxin rotenone has a pronounced effect on macroautophagy completion that may contribute to its neurotoxic potential.
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Affiliation(s)
- Burton J. Mader
- Department
of Pathology, Neuropathology
Division, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Birmingham VA Medical Center, Birmingham, Alabama, United States
| | - Violetta N. Pivtoraiko
- Department
of Pathology, Neuropathology
Division, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Hilary M. Flippo
- Department
of Pathology, Neuropathology
Division, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | | | | | - Leandra R. Mangieri
- Department
of Pathology, Neuropathology
Division, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - John J. Shacka
- Department
of Pathology, Neuropathology
Division, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Birmingham VA Medical Center, Birmingham, Alabama, United States
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223
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Baltazar GC, Guha S, Lu W, Lim J, Boesze-Battaglia K, Laties AM, Tyagi P, Kompella UB, Mitchell CH. Acidic nanoparticles are trafficked to lysosomes and restore an acidic lysosomal pH and degradative function to compromised ARPE-19 cells. PLoS One 2012; 7:e49635. [PMID: 23272048 PMCID: PMC3525582 DOI: 10.1371/journal.pone.0049635] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 10/16/2012] [Indexed: 11/18/2022] Open
Abstract
Lysosomal enzymes function optimally in acidic environments, and elevation of lysosomal pH can impede their ability to degrade material delivered to lysosomes through autophagy or phagocytosis. We hypothesize that abnormal lysosomal pH is a key aspect in diseases of accumulation and that restoring lysosomal pH will improve cell function. The propensity of nanoparticles to end up in the lysosome makes them an ideal method of delivering drugs to lysosomes. This study asked whether acidic nanoparticles could traffic to lysosomes, lower lysosomal pH and enhance lysosomal degradation by the cultured human retinal pigmented epithelial cell line ARPE-19. Acidic nanoparticles composed of poly (DL-lactide-co-glycolide) (PLGA) 502 H, PLGA 503 H and poly (DL-lactide) (PLA) colocalized to lysosomes of ARPE-19 cells within 60 min. PLGA 503 H and PLA lowered lysosomal pH in cells compromised by the alkalinizing agent chloroquine when measured 1 hr. after treatment, with acidification still observed 12 days later. PLA enhanced binding of Bodipy-pepstatin-A to the active site of cathepsin D in compromised cells. PLA also reduced the cellular levels of opsin and the lipofuscin-like autofluorescence associated with photoreceptor outer segments. These observations suggest the acidification produced by the nanoparticles was functionally effective. In summary, acid nanoparticles lead to a rapid and sustained lowering of lysosomal pH and improved degradative activity.
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Affiliation(s)
- Gabriel C. Baltazar
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Sonia Guha
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Wennan Lu
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jason Lim
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alan M. Laties
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Puneet Tyagi
- Pharmaceutical Sciences and Ophthalmology, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Uday B. Kompella
- Pharmaceutical Sciences and Ophthalmology, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Claire H. Mitchell
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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224
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Shang F, Taylor A. Roles for the ubiquitin-proteasome pathway in protein quality control and signaling in the retina: implications in the pathogenesis of age-related macular degeneration. Mol Aspects Med 2012; 33:446-66. [PMID: 22521794 PMCID: PMC3417153 DOI: 10.1016/j.mam.2012.04.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 04/05/2012] [Indexed: 10/28/2022]
Abstract
The accumulation of damaged or postsynthetically modified proteins and dysregulation of inflammatory responses and angiogenesis in the retina/RPE are thought be etiologically related to formation of drusen and choroidal neovascularization (CNV), hallmarks of age-related macular degeneration (AMD). The ubiquitin-proteasome pathway (UPP) plays crucial roles in protein quality control, cell cycle control and signal transduction. Selective degradation of aberrant proteins by the UPP is essential for timely removal of potentially cytotoxic damaged or otherwise abnormal proteins. Proper function of the UPP is thought to be required for cellular function. In contrast, age--or stress induced--impairment the UPP or insufficient UPP capacity may contribute to the accumulation of abnormal proteins, cytotoxicity in the retina, and AMD. Crucial roles for the UPP in eye development, regulation of signal transduction, and antioxidant responses are also established. Insufficient UPP capacity in retina and RPE can result in dysregulation of signal transduction, abnormal inflammatory responses and CNV. There are also interactions between the UPP and lysosomal proteolytic pathways (LPPs). Means that modulate the proteolytic capacity are making their way into new generation of pharmacotherapies for delaying age-related diseases and may augment the benefits of adequate nutrition, with regard to diminishing the burden of AMD.
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Affiliation(s)
- Fu Shang
- Laboratory for Nutrition and Vision Research, USDA Human Nutrition Research Center on Aging, Boston, MA 02111, USA.
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225
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Kannan R, Sreekumar PG, Hinton DR. Novel roles for α-crystallins in retinal function and disease. Prog Retin Eye Res 2012; 31:576-604. [PMID: 22721717 DOI: 10.1016/j.preteyeres.2012.06.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 05/31/2012] [Accepted: 06/04/2012] [Indexed: 01/18/2023]
Abstract
α-Crystallins are key members of the superfamily of small heat shock proteins that have been studied in detail in the ocular lens. Recently, novel functions for α-crystallins have been identified in the retina and in the retinal pigmented epithelium (RPE). αB-Crystallin has been localized to multiple compartments and organelles including mitochondria, golgi apparatus, endoplasmic reticulum and nucleus. α-Crystallins are regulated by oxidative and endoplasmic reticulum stress, and inhibit apoptosis-induced cell death. α-Crystallins interact with a large number of proteins that include other crystallins, and apoptotic, cytoskeletal, inflammatory, signaling, angiogenic, and growth factor molecules. Studies with RPE from αB-crystallin deficient mice have shown that αB-crystallin supports retinal and choroidal angiogenesis through its interaction with vascular endothelial growth factor. αB-Crystallin has also been shown to have novel functions in the extracellular space. In RPE, αB-crystallin is released from the apical surface in exosomes where it accumulates in the interphotoreceptor matrix and may function to protect neighboring cells. In other systems administration of exogenous recombinant αB-crystallin has been shown to be anti-inflammatory. Another newly described function of αB-crystallin is its ability to inhibit β-amyloid fibril formation. α-Crystallin minichaperone peptides have been identified that elicit anti-apoptotic function in addition to being efficient chaperones. Generation of liposomal particles and other modes of nanoencapsulation of these minipeptides could offer great therapeutic advantage in ocular delivery for a wide variety of retinal degenerative, inflammatory and vascular diseases including age-related macular degeneration and diabetic retinopathy.
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Affiliation(s)
- Ram Kannan
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, CA 90033, United States
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226
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Mettu PS, Wielgus AR, Ong SS, Cousins SW. Retinal pigment epithelium response to oxidant injury in the pathogenesis of early age-related macular degeneration. Mol Aspects Med 2012; 33:376-98. [PMID: 22575354 DOI: 10.1016/j.mam.2012.04.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 04/14/2012] [Indexed: 01/06/2023]
Abstract
Age-related macular degeneration (AMD) represents the leading cause of vision loss in the elderly. Accumulation of lipid- and protein-rich deposits under the retinal pigment epithelium (RPE) heralds the onset of early AMD, but the pathogenesis of subretinal deposit formation is poorly understood. Numerous hypothetical models of deposit formation have been proposed, including hypotheses for a genetic basis, choroidal hypoperfusion, abnormal barrier formation, and lysosomal failure. This review explore the RPE injury hypothesis, characterized by three distinct stages (1) Initial RPE oxidant injury, caused by any number of endogenous or exogenous oxidants, results in extrusion of cell membrane "blebs," together with decreased activity of matrix metalloproteinases (MMPs), promoting bleb accumulation under the RPE as basal laminar deposits (BLD). (2) RPE cells are subsequently stimulated to increase synthesis of MMPs and other molecules responsible for extracellular matrix turnover (i.e., producing decreased collagen), affecting both RPE basement membrane and Bruchs membrane (BrM). This process leads to progression of BLD into basal linear deposits (BLinD) and drusen by admixture of blebs into BrM, followed by the formation of new basement membrane under the RPE to trap these deposits within BrM. We postulate that various hormones and other plasma-derived molecules related to systemic health cofactors are implicated in this second stage. (3) Finally, macrophages are recruited to sites of RPE injury and deposit formation. The recruitment of nonactivated or scavenging macrophages may remove deposits without further injury, while the recruitment of activated or reparative macrophages, through the release of inflammatory mediators, growth factors, or other substances, may promote complications and progression to the late forms of the disease.
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Affiliation(s)
- Priyatham S Mettu
- Duke Center for Macular Diseases, Duke Eye Center, Durham, NC 27710, USA
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227
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Autophagy in the retina: a potential role in age-related macular degeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:83-90. [PMID: 22183319 DOI: 10.1007/978-1-4614-0631-0_12] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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228
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Weikel KA, Chiu CJ, Taylor A. Nutritional modulation of age-related macular degeneration. Mol Aspects Med 2012; 33:318-75. [PMID: 22503690 DOI: 10.1016/j.mam.2012.03.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 03/30/2012] [Indexed: 11/24/2022]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. It affects 30-50 million individuals and clinical hallmarks of AMD are observed in at least one third of persons over the age of 75 in industrialized countries (Gehrs et al., 2006). Costs associated with AMD are in excess of $340 billion US (American-Health-Assistance-Foundation, 2012). The majority of AMD patients in the United States are not eligible for clinical treatments (Biarnes et al., 2011; Klein et al., 2011). Preventive interventions through dietary modulation are attractive strategies because many studies suggest a benefit of micro- and macronutrients with respect to AMD, as well as other age-related debilities, and with few, if any, adverse effects (Chiu, 2011). Preservation of vision would enhance quality of life for millions of elderly people, and alleviate the personal and public health financial burden of AMD (Frick et al., 2007; Wood et al., 2011). Observational studies indicate that maintaining adequate levels of omega-3 fatty acids (i.e. with 2 servings/week of fish) or a low glycemic index diet may be particularly beneficial for early AMD and that higher levels of carotenoids may be protective, most probably, against neovascular AMD. Intervention trials are needed to better understand the full effect of these nutrients and/or combinations of nutrients on retinal health. Analyses that describe effects of a nutrient on onset and/or progress of AMD are valuable because they indicate the value of a nutrient to arrest AMD at the early stages. This comprehensive summary provides essential information about the value of nutrients with regard to diminishing risk for onset or progress of AMD and can serve as a guide until data from ongoing intervention trials are available.
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Affiliation(s)
- Karen A Weikel
- Laboratory for Nutrition and Vision Research, JM-USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA
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229
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Adiponectin receptor 1 gene (ADIPOR1) variant is associated with advanced age-related macular degeneration in Finnish population. Neurosci Lett 2012; 513:233-7. [DOI: 10.1016/j.neulet.2012.02.050] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/01/2012] [Accepted: 02/14/2012] [Indexed: 12/20/2022]
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230
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Plafker SM, O'Mealey GB, Szweda LI. Mechanisms for countering oxidative stress and damage in retinal pigment epithelium. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 298:135-77. [PMID: 22878106 DOI: 10.1016/b978-0-12-394309-5.00004-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Clinical and experimental evidence supports that chronic oxidative stress is a primary contributing factor to numerous retinal degenerative diseases, such as age-related macular degeneration (AMD). Eyes obtained postmortem from AMD patients have extensive free radical damage to the proteins, lipids, DNA, and mitochondria of their retinal pigment epithelial (RPE) cells. In addition, several mouse models of chronic oxidative stress develop many of the pathological hallmarks of AMD. However, the extent to which oxidative stress is an etiologic component versus its involvement in disease progression remains a major unanswered question. Further, whether the primary target of oxidative stress and damage is photoreceptors or RPE cells, or both, is still unclear. In this review, we discuss the major functions of RPE cells with an emphasis on the oxidative challenges these cells encounter and the endogenous antioxidant mechanisms employed to neutralize the deleterious effects that such stresses can elicit if left unchecked.
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Affiliation(s)
- Scott M Plafker
- Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
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231
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Furda AM, Bess AS, Meyer JN, Van Houten B. Analysis of DNA damage and repair in nuclear and mitochondrial DNA of animal cells using quantitative PCR. Methods Mol Biol 2012; 920:111-32. [PMID: 22941600 DOI: 10.1007/978-1-61779-998-3_9] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This chapter was written as a guide to using the long-amplicon quantitative PCR (QPCR) assay for the measurement of DNA damage in mammalian as well as nonmammalian species such as Caenorhabditis elegans (nematodes), Drosophila melanogaster (fruit flies), and two species of fish (Fundulus heteroclitus and Danio rerio). Since its development in the early 1990s (Kalinowski et al., Nucleic Acids Res 20:3485-3494, 1992; Salazar and Van Houten, Mutat Res 385:139-149, 1997; Yakes and Van Houten, Proc Natl Acad Sci USA 94:514-519, 1997), the QPCR assay has been widely used to measure DNA damage and repair kinetics in nuclear and mitochondrial genomes after genotoxin exposure (Yakes and Van Houten, Proc Natl Acad Sci USA 94:514-519, 1997; Santos et al., J Biol Chem 278:1728-1734, 2003; Mandavilli et al., Mol Brain Res 133:215-223, 2005). One of the main strengths of the assay is that the labor-intensive and artifact-generating step of mitochondrial isolation is not needed for the accurate measurement of mitochondrial DNA copy number and damage. Below we present the advantages and limitations of using QPCR to assay DNA damage in animal cells and provide a detailed protocol of the QPCR assay that integrates its usage in newly developed animal systems.
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Affiliation(s)
- Amy M Furda
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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232
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Shang F, Taylor A. Role of the ubiquitin-proteasome in protein quality control and signaling: implication in the pathogenesis of eye diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 109:347-96. [PMID: 22727427 DOI: 10.1016/b978-0-12-397863-9.00010-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ubiquitin-proteasome pathway (UPP) plays important roles in many cellular functions, such as protein quality control, cell cycle control, and signal transduction. The selective degradation of aberrant proteins by the UPP is essential for the timely removal of potential cytotoxic damaged or otherwise abnormal proteins. Conversely, accumulation of the cytotoxic abnormal proteins in eye tissues is etiologically associated with many age-related eye diseases such as retina degeneration, cataract, and certain types of glaucoma. Age- or stress-induced impairment or overburdening of the UPP appears to contribute to the accumulation of abnormal proteins in eye tissues. Cell cycle and signal transduction are regulated by the conditional UPP-dependent degradation of the regulators of these processes. Impairment or overburdening of the UPP could also result in dysregulation of cell cycle control and signal transduction. The consequences of the improper cell cycle and signal transduction include defects in ocular development, wound healing, angiogenesis, or inflammatory responses. Methods that enhance or preserve UPP function or reduce its burden may be useful strategies for preventing age-related eye diseases.
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Affiliation(s)
- Fu Shang
- Laboratory for Nutrition and Vision Research, USDA Human Nutrition Research Center on Aging, Boston, Massachusetts, USA
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233
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Hyttinen JMT, Petrovski G, Salminen A, Kaarniranta K. 5'-Adenosine monophosphate-activated protein kinase--mammalian target of rapamycin axis as therapeutic target for age-related macular degeneration. Rejuvenation Res 2011; 14:651-60. [PMID: 22007913 DOI: 10.1089/rej.2011.1220] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Age-related macular degeneration (AMD) is the most common reason for blindness in developed countries. AMD essentially involves chronic oxidative stress, increased accumulation of lipofuscin in retinal pigment epithelial (RPE) cells, and extracellular drusen formation, as well as presence of chronic inflammation in the retina. The capacity to prevent the accumulation of cellular cytotoxic protein aggregates is decreased in senescent cells, which may evoke lipofuscin accumulation into lysosomes in postmitotic RPE cells. The formation of lipofuscin, in turn, decreases the lysosomal enzyme activity and impairs the autophagic clearance of damaged proteins destined for cellular removal. 5'-Adenosine monophosphate-activated protein kinase (AMPK) is a well-known inhibitor of mammalian target of rapamycin (mTOR) that subsequently evokes induction of autophagy. This review examines the novel potential therapeutic targets on the AMPK-mTOR axis and the ways in which autophagy clearance can suppress or prevent RPE degeneration and development of AMD.
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Affiliation(s)
- Juha M T Hyttinen
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, P.O.Box 1627, FI-70211 Kuopio, Finland.
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234
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Münz C. Antigen processing by macroautophagy for MHC presentation. Front Immunol 2011; 2:42. [PMID: 22566832 PMCID: PMC3342048 DOI: 10.3389/fimmu.2011.00042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 08/22/2011] [Indexed: 12/16/2022] Open
Abstract
T cells recognize antigen fragments, presented to them by MHC molecules. It lies in the interest of the immune system to display a maximal diversity of these peptides and utilize all catabolic processes to generate them. Macroautophagy, a pathway that delivers cytoplasmic constituents for lysosomal degradation is no exception. In recent years, it has become apparent that macroautophagy assists in intra- and extracellular antigen processing for MHC class II presentation to CD4+ helper T cells. Surprisingly, however, macroautophagy also assists in antigen packaging for better cross-presentation on MHC molecules of bystander cells, which could be consistent with its role in unconventional protein secretion. These three pathways of antigen processing for MHC presentation via macroautophagy will be discussed in this review and cell biological aspects will be high-lighted that might explain, how the molecular machinery of macroautophagy might assist these diverse antigen processing pathways.
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Affiliation(s)
- Christian Münz
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich Zürich, Switzerland.
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Kang HT, Lee KB, Kim SY, Choi HR, Park SC. Autophagy impairment induces premature senescence in primary human fibroblasts. PLoS One 2011; 6:e23367. [PMID: 21858089 PMCID: PMC3152578 DOI: 10.1371/journal.pone.0023367] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Accepted: 07/15/2011] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Recent studies have demonstrated that activation of autophagy increases the lifespan of organisms from yeast to flies. In contrast to the lifespan extension effect in lower organisms, it has been reported that overexpression of unc-51-like kinase 3 (ULK3), the mammalian homolog of autophagy-specific gene 1 (ATG1), induces premature senescence in human fibroblasts. Therefore, we assessed whether the activation of autophagy would genuinely induce premature senescence in human cells. METHODOLOGY/PRINCIPAL FINDINGS Depletion of ATG7, ATG12, or lysosomal-associated membrane protein 2 (Lamp2) by transfecting siRNA or infecting cells with a virus containing gene-specific shRNA resulted in a senescence-like state in two strains of primary human fibroblasts. Prematurely senescent cells induced by autophagy impairment exhibited the senescent phenotypes, similar to the replicatively senescent cells, such as increased senescence associated β-galactosidase (SA-β-gal) activity, reactive oxygen species (ROS) generation, and accumulation of lipofuscin. In addition, expression levels of ribosomal protein S6 kinase1 (S6K1), p-S6K1, p-S6, and eukaryotic translation initiation factor 4E (eIF4E) binding protein 1 (4E-BP1) in the mammalian target of rapamycin (mTOR) pathway and beclin-1, ATG7, ATG12-ATG5 conjugate, and the sequestosome 1 (SQSTM1/p62) monomer in the autophagy pathway were decreased in both the replicatively and the autophagy impairment-induced prematurely senescent cells. Furthermore, it was found that ROS scavenging by N-acetylcysteine (NAC) and inhibition of p53 activation by pifithrin-α or knockdown of p53 using siRNA, respectively, delayed autophagy impairment-induced premature senescence and restored the expression levels of components in the mTOR and autophagy pathways. CONCLUSION Taken together, we concluded that autophagy impairment induces premature senescence through a ROS- and p53-dependent manner in primary human fibroblasts.
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Affiliation(s)
- Hyun Tae Kang
- Institute on Aging, Seoul National University College of Medicine, Seoul, Korea
| | - Ki Baek Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, Korea
| | - Sung Young Kim
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, Korea
| | - Hae Ri Choi
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, Korea
| | - Sang Chul Park
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, Korea
- Institute on Aging, Seoul National University College of Medicine, Seoul, Korea
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
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236
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Buschini E, Piras A, Nuzzi R, Vercelli A. Age related macular degeneration and drusen: neuroinflammation in the retina. Prog Neurobiol 2011; 95:14-25. [PMID: 21740956 DOI: 10.1016/j.pneurobio.2011.05.011] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/03/2011] [Accepted: 05/09/2011] [Indexed: 12/19/2022]
Abstract
Inflammation protects from dangerous stimuli, restoring normal tissue homeostasis. Inflammatory response in the nervous system ("neuroinflammation") has distinct features, which are shared in several diseases. The retina is an immune-privileged site, and the tight balance of immune reaction can be disrupted and lead to age-related macular disease (AMD) and to its peculiar sign, the druse. Excessive activation of inflammatory and immunological cascade with subsequent induction of damage, persistent activation of resident immune cells, accumulation of byproducts that exceeds the normal capacity of clearance giving origin to a chronic local inflammation, alterations in the activation of the complement system, infiltration of macrophages, T-lymphocytes and mast-cells from the bloodstream, participate in the mechanisms which originate the drusen. In addition, aging of the retina and AMD involve also para-inflammation, by which immune cells react to persistent stressful stimuli generating low-grade inflammation, aimed at restoring function and maintaining tissue homeostasis by varying the set point in relation to the new altered conditions. This mechanism is also seen in the normal aging retina, but, in the presence of noxious stimuli as in AMD, it can become chronic and have an adverse outcome. Finally, autophagy may provide new insights to understand AMD pathology, due to its contribution in the removal of defective proteins. Therefore, the AMD retina can represent a valuable model to study neuroinflammation, its mechanisms and therapy in a restricted and controllable environment. Targeting these pathways could represent a new way to treat and prevent both exudative and dry forms of AMD.
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Affiliation(s)
- Elisa Buschini
- NICO, Neuroscience Institute of the Cavalieri Ottolenghi Foundation, University of Torino, Regione Gonzole 10, Orbassano (TO), Italy.
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Abstract
Background Cumulative oxidative damage is implicated in the pathogenesis of age-related macular degeneration (AMD). Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that plays key roles in retinal antioxidant and detoxification responses. The purposes of this study were to determine whether NRF2-deficient mice would develop AMD-like retinal pathology with aging and to explore the underlying mechanisms. Methods and Findings Eyes of both wild type and Nrf2−/− mice were examined in vivo by fundus photography and electroretinography (ERG). Structural changes of the outer retina in aged animals were examined by light and electron microscopy, and immunofluorescence labeling. Our results showed that Nrf2−/− mice developed age-dependent degenerative pathology in the retinal pigment epithelium (RPE). Drusen-like deposits, accumulation of lipofuscin, spontaneous choroidal neovascularization (CNV) and sub-RPE deposition of inflammatory proteins were present in Nrf2−/− mice after 12 months. Accumulation of autophagy-related vacuoles and multivesicular bodies was identified by electron microcopy both within the RPE and in Bruch's membrane of aged Nrf2−/− mice. Conclusions Our data suggest that disruption of Nfe2l2 gene increased the vulnerability of outer retina to age-related degeneration. NRF2-deficient mice developed ocular pathology similar to cardinal features of human AMD and deregulated autophagy is likely a mechanistic link between oxidative injury and inflammation. The Nrf2−/− mice can provide a novel model for mechanistic and translational research on AMD.
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238
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Gangalum RK, Atanasov IC, Zhou ZH, Bhat SP. AlphaB-crystallin is found in detergent-resistant membrane microdomains and is secreted via exosomes from human retinal pigment epithelial cells. J Biol Chem 2011; 286:3261-9. [PMID: 21097504 PMCID: PMC3030331 DOI: 10.1074/jbc.m110.160135] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 11/15/2010] [Indexed: 12/22/2022] Open
Abstract
αB-crystallin (αB) is known as an intracellular Golgi membrane-associated small heat shock protein. Elevated levels of this protein have been linked with a myriad of neurodegenerative pathologies including Alzheimer disease, multiple sclerosis, and age-related macular degeneration. The membrane association of αB has been known for more than 3 decades, yet its physiological import has remained unexplained. In this investigation we show that αB is secreted from human adult retinal pigment epithelial cells via microvesicles (exosomes), independent of the endoplasmic reticulum-Golgi protein export pathway. The presence of αB in these lipoprotein structures was confirmed by its susceptibility to digestion by proteinase K only when exosomes were exposed to Triton X-100. Transmission electron microscopy was used to localize αB in immunogold-labeled intact and permeabilized microvesicles. The saucer-shaped exosomes, with a median diameter of 100-200 nm, were characterized by the presence of flotillin-1, α-enolase, and Hsp70, the same proteins that associate with detergent-resistant membrane microdomains (DRMs), which are known to be involved in their biogenesis. Notably, using polarized adult retinal pigment epithelial cells, we show that the secretion of αB is predominantly apical. Using OptiPrep gradients we demonstrate that αB resides in the DRM fraction. The secretion of αB is inhibited by the cholesterol-depleting drug, methyl β-cyclodextrin, suggesting that the physiological function of this protein and the regulation of its export through exosomes may reside in its association with DRMs/lipid rafts.
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Affiliation(s)
| | | | - Z. Hong Zhou
- the California NanoSystems Institute, and
- the Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, California 90095
| | - Suraj P. Bhat
- From the Jules Stein Eye Institute
- the Geffen School of Medicine, Brain Research Institute and Molecular Biology Institute
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239
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Cho YS, Kwon HJ. Control of autophagy with small molecules. Arch Pharm Res 2010; 33:1881-9. [PMID: 21191751 DOI: 10.1007/s12272-010-1201-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 08/17/2010] [Accepted: 08/18/2010] [Indexed: 12/25/2022]
Abstract
Autophagy is the mass degradation system that removes long-lived proteins and malfunctioning organelles within the cell. Dysfunctional autophagic processes can cause various diseases such as cancer and neurodegenerative disorders, but the underlying mechanisms responsible for such events remain undefined. Small molecules that control autophagy could be powerful tools to reveal autophagy mechanisms, and to develop treatments for autophagy-related diseases including Alzheimer's disease, Parkinson's disease and various cancer types. This review discusses the small molecules that have been identified to control autophagy and how they can be used to understand signaling pathways important for autophagy in the context of chemical genomics.
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Affiliation(s)
- Yoon Sun Cho
- Chemical Genomics National Research Laboratory, Department of Biotechnology, Translational Research Center for Protein Function Control, College of Life Science & Biotechnology, Yonsei University, Seoul 120-749, Korea
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Truong A, Wong TY, Khachigian LM. Emerging therapeutic approaches in the management of retinal angiogenesis and edema. J Mol Med (Berl) 2010; 89:343-61. [DOI: 10.1007/s00109-010-0709-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2010] [Revised: 10/22/2010] [Accepted: 11/10/2010] [Indexed: 12/16/2022]
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241
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Sheline CT, Zhou Y, Bai S. Light-induced photoreceptor and RPE degeneration involve zinc toxicity and are attenuated by pyruvate, nicotinamide, or cyclic light. Mol Vis 2010; 16:2639-52. [PMID: 21179242 PMCID: PMC3002969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 12/04/2010] [Indexed: 11/18/2022] Open
Abstract
PURPOSE Light-induced damage can be a problem after surgery or sun exposure. Short-duration, intense light causes preferential photoreceptor death in the superior central retina of albino mice and rats and serves as a model of oxidation-induced neurodegeneration. Previous work on retinal ischemia-induced neuronal death suggests the involvement of zinc (Zn(2+)) toxicity in the death and collapse of many retinal cell layers and demonstrates the protective efficacy of pyruvate. Retinal pigment epithelial (RPE) cells were shown to be sensitive to oxidative stress, and zinc, causing loss of nicotinamide adenine dinucleotide (NAD+) and adenine triphosphate (ATP), which was prevented by pyruvate and nicotinamide. We previously showed similar results in cortical neurons exposed to oxidative stress or Zn(2+). In vivo, Zn(2+) is normally present in the inner and outer segments (associated with rhodopsin), Bruch's membrane and sclera (elastin), RPE, and the outer plexiform layer of the eye (synaptic). In this study, we examine the role of Zn(2+) in oxidative stress and light-induced damage in vitro and in vivo. METHODS We modeled retinal toxicity in cell-culture lines derived from retinal tissue: Müller and human retinal pigment epithelial (ARPE-19) cells and a cone photoreceptor-derived line (661W). These cultures were exposed to Zn(2+) and OS, and the therapeutic efficacy of pyruvate, nicotinamide, and NAD(+) was determined. Sprague Dawley albino rats were exposed to 18 kLux of white fluorescent light for 1-4 h in the presence and absence of pyruvate, nicotinamide, lactate, and cyclic light. The intracellular free zinc concentration ([Zn(2+)](i)) and cell damage were assessed 0.5 and 7 days later, respectively. RESULTS We show that Zn(2+) and oxidative stress results in increased [Zn(2+)](i) and that Zn(2+) therapeutic compounds (pyruvate, nicotinamide, and NAD(+)) and inhibitors of previously implicated pathways (sirtuin) are efficacious in vitro. Exposure to 18 kLux of cool white fluorescent light for 1 h induced a large increase in Zn(2+) staining 4-14 h later, particularly in the superior outer nuclear layer and RPE of dark-maintained Sprague Dawley albino rats; 4 h of light was required to induce similar damage in cyclic light-maintained rats. Photoreceptors and RPE cells died in untreated animals at 3-7 days. However, nicotinamide and pyruvate (intraperitoneal), but not lactate, attenuated this death in treated animals, as measured using optical coherence tomography and confirmed by counting photoreceptor nuclei. CONCLUSIONS Zn(2+) plays a role in this injury, as suggested by the increased Zn(2+) staining and the efficacy of Zn(2+) therapeutics. These results suggest that cyclic light maintenance, Zn(2+) chelation, pyruvate, and nicotinamide promote RPE and photoreceptor survival after injury and could be effective for various forms of retinal neurodegeneration. These results could have immediate clinical applications in surgery- or sun exposure- induced light damage to the retina.
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Affiliation(s)
- Christian T Sheline
- Department of Ophthalmology and the Neuroscience Center of Excellence LSU Health Sciences Center, New Orleans, LA 70112, USA.
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242
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Kopplin LJ, Igo RP, Wang Y, Sivakumaran TA, Hagstrom SA, Peachey NS, Francis PJ, Klein ML, SanGiovanni JP, Chew EY, Pauer GJT, Sturgill GM, Joshi T, Tian L, Xi Q, Henning AK, Lee KE, Klein R, Klein BEK, Iyengar SK. Genome-wide association identifies SKIV2L and MYRIP as protective factors for age-related macular degeneration. Genes Immun 2010; 11:609-21. [PMID: 20861866 PMCID: PMC3375062 DOI: 10.1038/gene.2010.39] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 05/17/2010] [Accepted: 05/17/2010] [Indexed: 01/11/2023]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly in the developed world. We conducted a genome-wide association study in a series of families enriched for AMD and completed a meta-analysis of this new data with results from reanalysis of an existing study of a late-stage case-control cohort. We tested the top findings for replication in 1896 cases and 1866 controls and identified two novel genetic protective factors for AMD. In addition to the complement factor H (CFH) (P=2.3 × 10⁻⁶⁴) and age-related maculopathy susceptibility 2 (ARMS2) (P=1.2 × 10⁻⁶⁰) loci, we observed a protective effect at rs429608, an intronic SNP in SKIV2L (P=5.3 × 10⁻¹⁵), a gene near the complement component 2 (C2)/complement factor B (BF) locus, that indicates the protective effect may be mediated by variants other than the C2/BF variants previously studied. Haplotype analysis at this locus identified three protective haplotypes defined by the rs429608 protective allele. We also identified a new potentially protective effect at rs2679798 in MYRIP (P=2.9 × 10⁻⁴), a gene involved in retinal pigment epithelium melanosome trafficking. Interestingly, MYRIP was initially identified in the family-based scan and was confirmed in the case-control set. From these efforts, we report the identification of two novel protective factors for AMD and confirm the previously known associations at CFH, ARMS2 and C3.
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Affiliation(s)
- L J Kopplin
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA
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Abstract
Cellular senescence is a specialized form of growth arrest, confined to mitotic cells, induced by various stressful stimuli and characterized by a permanent growth arrest, resistance to apoptosis, an altered pattern of gene expression and the expression of some markers that are characteristic, although not exclusive, to the senescent state. Senescent cells profoundly modify neighboring and remote cells through the production of an altered secretome, eventually leading to inflammation, fibrosis and possibly growth of neoplastic cells. Mammalian aging has been defined as a reduction in the capacity to adequately maintain tissue homeostasis or to repair tissues after injury. Tissue homeostasis and regenerative capacity are nowadays considered to be related to the stem cell pool present in every tissue. For this reason, pathological and patho-physiological conditions characterized by altered tissue homeostasis and impaired regenerative capacity can be viewed as a consequence of the reduction in stem cell number and/or function. Last, cellular senescence is a double-edged sword, since it may inhibit the growth of transformed cells, preventing the occurrence of cancer, while it may facilitate growth of preneoplastic lesions in a paracrine fashion; therefore, interventions targeting this cell response to stress may have a profound impact on many age-related pathologies, ranging from cardiovascular disease to oncology. Aim of this review is to discuss both molecular mechanisms associated with stem cell senescence and interventions that may attenuate or reverse this process.
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244
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αB crystallin is apically secreted within exosomes by polarized human retinal pigment epithelium and provides neuroprotection to adjacent cells. PLoS One 2010; 5:e12578. [PMID: 20949024 PMCID: PMC2951891 DOI: 10.1371/journal.pone.0012578] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/08/2010] [Indexed: 12/20/2022] Open
Abstract
αB Crystallin is a chaperone protein with anti-apoptotic and anti-inflammatory functions and has been identified as a biomarker in age-related macular degeneration. The purpose of this study was to determine whether αB crystallin is secreted from retinal pigment epithelial (RPE) cells, the mechanism of this secretory pathway and to determine whether extracellular αB crystallin can be taken up by adjacent retinal cells and provide protection from oxidant stress. We used human RPE cells to establish that αB crystallin is secreted by a non-classical pathway that involves exosomes. Evidence for the release of exosomes by RPE and localization of αB crystallin within the exosomes was achieved by immunoblot, immunofluorescence, and electron microscopic analyses. Inhibition of lipid rafts or exosomes significantly reduced αB crystallin secretion, while inhibitors of classic secretory pathways had no effect. In highly polarized RPE monolayers, αB crystallin was selectively secreted towards the apical, photoreceptor-facing side. In support, confocal microscopy established that αB crystallin was localized predominantly in the apical compartment of RPE monolayers, where it co-localized in part with exosomal marker CD63. Severe oxidative stress resulted in barrier breakdown and release of αB crystallin to the basolateral side. In normal mouse retinal sections, αB crystallin was identified in the interphotoreceptor matrix. An increased uptake of exogenous αB crystallin and protection from apoptosis by inhibition of caspase 3 and PARP activation were observed in stressed RPE cultures. αB Crystallin was taken up by photoreceptors in mouse retinal explants exposed to oxidative stress. These results demonstrate an important role for αB crystallin in maintaining and facilitating a neuroprotective outer retinal environment and may also explain the accumulation of αB crystallin in extracellular sub-RPE deposits in the stressed microenvironment in age-related macular degeneration. Thus evidence from our studies supports a neuroprotective role for αB crystallin in ocular diseases.
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245
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Abstract
The glycemic index (GI) indicates how fast blood glucose is raised after consuming a carbohydrate-containing food. Human metabolic studies indicate that GI is related to patho-physiological responses after meals. Compared with a low-GI meal, a high-GI meal is characterized with hyperglycemia during the early postprandial stage (0-2h) and a compensatory hyperlipidemia associated with counter-regulatory hormone responses during late postprandial stage (4-6h). Over the past three decades, several human health disorders have been related to GI. The strongest relationship suggests that consuming low-GI foods prevents diabetic complications. Diabetic retinopathy (DR) is a complication of diabetes. In this aspect, GI appears to be useful as a practical guideline to help diabetic people choose foods. Abundant epidemiological evidence also indicates positive associations between GI and risk for type 2 diabetes, cardiovascular disease, and more recently, age-related macular degeneration (AMD) in people without diabetes. Although data from randomized controlled intervention trials are scanty, these observations are strongly supported by evolving molecular mechanisms which explain the pathogenesis of hyperglycemia. This wide range of evidence implies that dietary hyperglycemia is etiologically related to human aging and diseases, including DR and AMD. In this context, these diseases can be considered as metabolic retinal diseases. Molecular theories that explain hyperglycemic pathogenesis involve a mitochondria-associated pathway and four glycolysis-associated pathways, including advanced glycation end products formation, protein kinase C activation, polyol pathway, and hexosamine pathway. While the four glycolysis-associated pathways appear to be universal for both normoxic and hypoxic conditions, the mitochondria-associated mechanism appears to be most relevant to the hyperglycemic, normoxic pathogenesis. For diseases that affect tissues with highly active metabolism and that frequently face challenge from low oxygen tension, such as retina in which metabolism is determined by both glucose and oxygen homeostases, these theories appear to be insufficient. Several lines of evidence indicate that the retina is particularly vulnerable when hypoxia coincides with hyperglycemia. We propose a novel hyperglycemic, hypoxia-inducible factor (HIF) pathway, to complement the current theories regarding hyperglycemic pathogenesis. HIF is a transcription complex that responds to decrease oxygen in the cellular environment. In addition to playing a significant role in the regulation of glucose metabolism, under hyperglycemia HIF has been shown to increase the expression of HIF-inducible genes, such as vascular endothelial growth factor (VEGF) leading to angiogenesis. To this extent, we suggest that HIF can also be described as a hyperglycemia-inducible factor. In summary, while management of dietary GI appears to be an effective intervention for the prevention of metabolic diseases, specifically AMD and DR, more interventional data is needed to evaluate the efficacy of GI management. There is an urgent need to develop reliable biomarkers of exposure, surrogate endpoints, as well as susceptibility for GI. These insights would also be helpful in deciphering the detailed hyperglycemia-related biochemical mechanisms for the development of new therapeutic agents.
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246
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Hunter SE, Jung D, Di Giulio RT, Meyer JN. The QPCR assay for analysis of mitochondrial DNA damage, repair, and relative copy number. Methods 2010; 51:444-51. [PMID: 20123023 PMCID: PMC2912960 DOI: 10.1016/j.ymeth.2010.01.033] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 01/26/2010] [Indexed: 11/25/2022] Open
Abstract
The quantitative polymerase chain reaction (QPCR) assay allows measurement of DNA damage in the mitochondrial and nuclear genomes without isolation of mitochondria. It also permits measurement of relative mitochondrial genome copy number. Finally, it can be used for measurement of DNA repair in vivo when employed appropriately. In this manuscript we briefly review the methodology of the QPCR assay, discuss its strengths and limitations, address considerations for measurement of mitochondrial DNA repair, and describe methodological changes implemented in recent years. We present QPCR assay primers and reaction conditions for five species not previously described in a methods article: Caenorhabditis elegans, Fundulus heteroclitus, Danio rerio, Drosophila melanogaster, and adenovirus. Finally, we illustrate the use of the assay by measuring repair of ultraviolet C radiation-induced DNA damage in the nuclear but not mitochondrial genomes of a zebrafish cell culture.
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Affiliation(s)
- Senyene E Hunter
- Nicholas School of the Environment, Duke University, Durham, NC 27708-0328, USA
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247
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Viiri J, Hyttinen JMT, Ryhänen T, Rilla K, Paimela T, Kuusisto E, Siitonen A, Urtti A, Salminen A, Kaarniranta K. p62/sequestosome 1 as a regulator of proteasome inhibitor-induced autophagy in human retinal pigment epithelial cells. Mol Vis 2010; 16:1399-414. [PMID: 20680098 PMCID: PMC2913138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 07/22/2010] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The pathogenesis of age-related macular degeneration involves impaired protein degradation in retinal pigment epithelial (RPE) cells. The ubiquitin-proteasome pathway and the lysosomal pathway including autophagy are the major proteolytic systems in eukaryotic cells. Prior to proteolysis, heat shock proteins (HSPs) attempt to refold stress-induced misfolded proteins and thus prevent the accumulation of cytoplasmic protein aggregates. Recently, p62/sequestosome 1 (p62) has been shown to be a key player linking the proteasomal and lysosomal clearance systems. In the present study, the functional roles of p62 and HSP70 were evaluated in conjunction with proteasome inhibitor-induced autophagy in human RPE cells (ARPE-19). METHODS The p62, HSP70, and ubiquitin protein levels and localization were analyzed by western blotting and immunofluorescense. Confocal and transmission electron microscopy were used to detect cellular organelles and to evaluate the morphological changes. The p62 and HSP70 levels were modulated using RNA interference and overexpression techniques. Cell viability was measured by colorimetric assay. RESULTS Proteasome inhibition evoked the accumulation of perinuclear aggregates that strongly colocalized with p62 and HSP70. The p62 perinuclear accumulation was time- and concentration-dependent after MG-132 proteasome inhibitor loading. The silencing of p62, rather than Hsp70, evoked suppression of autophagy, when related to decreased LC3-II levels after bafilomycin treatment. In addition, the p62 silencing decreased the ubiquitination level of the perinuclear aggregates. Recently, we showed that hsp70 mRNA depletion increased cell death in ARPE-19 cells. Here, we demonstrate that p62 mRNA silencing has similar effects on cellular viability. CONCLUSIONS Our findings open new avenues for understanding the mechanisms of proteolytic processes in retinal cells, and could be useful in the development of novel therapies targeting p62 and HSP70.
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Affiliation(s)
- Johanna Viiri
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Juha M. T. Hyttinen
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Tuomas Ryhänen
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Kirsi Rilla
- Department of Anatomy, Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland
| | - Tuomas Paimela
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Erkki Kuusisto
- Department of Neurology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Ari Siitonen
- Department of Neurology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Arto Urtti
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Antero Salminen
- Department of Neurology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Kai Kaarniranta
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland,Department of Ophthalmology, Kuopio University Hospital, Kuopio, Finland
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Yuan X, Gu X, Crabb JS, Yue X, Shadrach K, Hollyfield JG, Crabb JW. Quantitative proteomics: comparison of the macular Bruch membrane/choroid complex from age-related macular degeneration and normal eyes. Mol Cell Proteomics 2010; 9:1031-46. [PMID: 20177130 PMCID: PMC2877969 DOI: 10.1074/mcp.m900523-mcp200] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 01/19/2010] [Indexed: 11/29/2022] Open
Abstract
A quantitative proteomics analysis of the macular Bruch membrane/choroid complex was pursued for insights into the molecular mechanisms of age-related macular degeneration (AMD). Protein in trephine samples from the macular region of 10 early/mid-stage dry AMD, six advanced dry AMD, eight wet AMD, and 25 normal control post-mortem eyes was analyzed by LC MS/MS iTRAQ (isobaric tags for relative and absolute quantitation) technology. A total of 901 proteins was quantified, including 556 proteins from > or =3 AMD samples. Most proteins differed little in amount between AMD and control samples and therefore reflect the proteome of normal macular tissues of average age 81. A total of 56 proteins were found to be elevated and 43 were found to be reduced in AMD tissues relative to controls. Analysis by category of disease progression revealed up to 16 proteins elevated or decreased in each category. About 60% of the elevated proteins are involved in immune response and host defense, including many complement proteins and damage-associated molecular pattern proteins such as alpha-defensins 1-3, protein S100s, crystallins, histones, and galectin-3. Four retinoid processing proteins were elevated only in early/mid-stage AMD, supporting a role for retinoids in AMD initiation. Proteins uniquely decreased in early/mid-stage AMD implicate hematologic malfunctions and weakened extracellular matrix integrity and cellular interactions. Galectin-3, a receptor for advanced glycation end products, was the most significantly elevated protein in advanced dry AMD, supporting a role for advanced glycation end products in dry AMD progression. The results endorse inflammatory processes in both early and advanced AMD pathology, implicate different pathways of progression to advanced dry and wet AMD, and provide a new database for hypothesis-driven and discovery-based studies of AMD.
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Affiliation(s)
- Xianglin Yuan
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Xiaorong Gu
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - John S. Crabb
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Xiuzhen Yue
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Karen Shadrach
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Joe G. Hollyfield
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
- ¶Departments of Ophthalmology and Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio 44106
| | - John W. Crabb
- From the ‡Cole Eye Institute and
- §Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195
- ‖Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, and
- ¶Departments of Ophthalmology and Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio 44106
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249
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Wang L, Clark ME, Crossman DK, Kojima K, Messinger JD, Mobley JA, Curcio CA. Abundant lipid and protein components of drusen. PLoS One 2010; 5:e10329. [PMID: 20428236 PMCID: PMC2859054 DOI: 10.1371/journal.pone.0010329] [Citation(s) in RCA: 258] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2010] [Accepted: 03/30/2010] [Indexed: 01/24/2023] Open
Abstract
Background Drusen are extracellular lesions characteristic of aging and age-related maculopathy, a major retinal disease of the elderly. We determined the relative proportions of lipids and proteins in drusen capped with retinal pigment epithelium (RPE) and in RPE isolated from non-macular regions of 36 human retinas with grossly normal maculas obtained <6 hr after death. Methodology/Principal Findings Druse pellets were examined by light and electron microscopy. Component proteins were extracted using novel methods for preserved tissues, separated, subjected to tryptic digestion and LC-MS(MS)2 analysis using an ion trap mass spectrometer, and identified with reference to databases. Lipid classes were separated using thin layer chromatography and quantified by densitometry. Major druse components were esterified cholesterol (EC), phosphatidylcholine (PC), and protein (37.5±13.7, 36.9±12.9, and 43.0±11.5 ng/druse, respectively). Lipid-containing particles (median diameter, 77 nm) occupied 37–44% of druse volume. Major proteins include vitronectin, complement component 9, apoE, and clusterin, previously seen in drusen, and ATP synthase subunit β, scavenger receptor B2, and retinol dehydrogenase 5, previously seen in RPE. Drusen and RPE had similar protein profiles, with higher intensities and greater variability in drusen. C8, part of the complement membrane attack complex, was localized in drusen by immunofluorescence. Conclusions/Significance At least 40% of druse content is comprised by lipids dominated by EC and PC, 2 components that are potentially accounted for by just one pathway, the secretion of lipoproteins by RPE. Manipulating genes encoding apolipoprotein pathways would be a fruitful approach to producing drusen with high EC content in laboratory animals. Therapies that directly mitigate drusen should prepare for the substantial volume of neutral lipids. The catalog of major druse proteins is nearing completion.
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Affiliation(s)
- Lan Wang
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Mark E. Clark
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - David K. Crossman
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Kyoko Kojima
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Jeffrey D. Messinger
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - James A. Mobley
- Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Christine A. Curcio
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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250
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Zeiss CJ. Animals as models of age-related macular degeneration: an imperfect measure of the truth. Vet Pathol 2010; 47:396-413. [PMID: 20382825 DOI: 10.1177/0300985809359598] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Age-related macular degeneration (AMD) is a degenerative condition that begins in Bruch's membrane and progresses to involve the retinal pigment epithelium and ultimately the overlying photoreceptors. The only required etiologic factor is age, and AMD is regarded as the leading cause of blindness in individuals older than 65 years. AMD results from variable contributions of age, environment, and genetic predisposition. Many loci are linked to AMD; in the majority of cases, the disease is associated with polymorphisms within these genes, rather than mutations that ablate gene function. The etiologic complexity of AMD is reflected by the paucity of animal models that entirely replicate the human disease. This review compares the salient anatomy of the primate and rodent retina, particularly in the light of AMD pathology. It next discusses prevailing hypotheses explaining how AMD may develop. These include the role of complement activation and macrophage chemotaxis in AMD, molecular mechanisms of choroidal neovascularization, and the roles of oxidative damage and lipid metabolism. Finally, the article gives an overview of spontaneous and induced nonhuman primate models and describes relevant mouse models in the context of each pathogenetic mechanism.
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Affiliation(s)
- C J Zeiss
- Yale University School of Medicine, Section of Comparative Medicine, 375 Congress Avenue, New Haven, CT 06520, USA.
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