1
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Tan LX, Germer CJ, Thamban T, La Cunza N, Lakkaraju A. Optineurin tunes outside-in signaling to regulate lysosome biogenesis and phagocytic clearance in the retina. Curr Biol 2023; 33:3805-3820.e7. [PMID: 37586372 PMCID: PMC10529777 DOI: 10.1016/j.cub.2023.07.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/16/2023] [Accepted: 07/19/2023] [Indexed: 08/18/2023]
Abstract
Balancing the competing demands of phagolysosomal degradation and autophagy is a significant challenge for phagocytic tissues. Yet how this plasticity is accomplished in health and disease is poorly understood. In the retina, circadian phagocytosis and degradation of photoreceptor outer segments by the postmitotic retinal pigment epithelium (RPE) are essential for healthy vision. Disrupted autophagy due to mechanistic target of rapamycin (mTOR) overactivation in the RPE is associated with blinding macular degenerations; however, outer segment degradation is unaffected in these diseases, indicating that distinct mechanisms regulate these clearance mechanisms. Here, using advanced imaging and mouse models, we identify optineurin as a key regulator that tunes phagocytosis and lysosomal capacity to meet circadian demands and helps prioritize outer segment clearance by the RPE in macular degenerations. High-resolution live-cell imaging implicates optineurin in scissioning outer segment tips prior to engulfment, analogous to microglial trogocytosis of neuronal processes. Optineurin is essential for recruiting light chain 3 (LC3), which anchors outer segment phagosomes to microtubules and facilitates phagosome maturation and fusion with lysosomes. This dynamically activates transcription factor EB (TFEB) to induce lysosome biogenesis in an mTOR-independent, transient receptor potential-mucolipin 1 (TRPML1)-dependent manner. RNA-seq analyses show that expression of TFEB target genes temporally tracks with optineurin recruitment and that lysosomal and autophagy genes are controlled by distinct transcriptional programs in the RPE. The unconventional plasma membrane-to-nucleus signaling mediated by optineurin ensures outer segment degradation under conditions of impaired autophagy in macular degeneration models. Independent regulation of these critical clearance mechanisms would help safeguard the metabolic fitness of the RPE throughout the organismal lifespan.
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Affiliation(s)
- Li Xuan Tan
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Colin J Germer
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Thushara Thamban
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Nilsa La Cunza
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aparna Lakkaraju
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Anatomy, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
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2
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Helfenberger KE, Argentino GF, Benzo Y, Herrera LM, Finocchietto P, Poderoso C. Angiotensin II Regulates Mitochondrial mTOR Pathway Activity Dependent on Acyl-CoA Synthetase 4 in Adrenocortical Cells. Endocrinology 2022; 163:6763139. [PMID: 36256598 DOI: 10.1210/endocr/bqac170] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Indexed: 11/19/2022]
Abstract
Two well-known protein complexes in mammalian cells, mTOR type 1 and type 2 (mTORC1/2) are involved in several cellular processes such as protein synthesis, cell proliferation, and commonly dysregulated in cancer. An acyl-CoA synthetase type 4 (ACSL4) is one of the most recently mTORC1/2 regulators described, in breast cancer cells. The expression of ACSL4 is hormone-regulated in adrenocortical cells and required for steroid biosynthesis. mTORC1/2 have been reported to be crucial in the proliferation of human adrenocortical tumor cells H295R and interestingly reported at several subcellular locations, which has brought cell biology to the vanguard of the mTOR signaling field. In the present work, we study the regulation of mTORC1/2 activation by angiotensin II (Ang II)-the trophic hormone for adrenocortical cells-the subcellular localization of mTORC1/2 signaling proteins and the role of ACSL4 in the regulation of this pathway, in H295R cells. Ang II promotes activation by phosphorylation of mTORC1/2 pathway proteins in a time-dependent manner. Mitochondrial pools of ribosomal protein S6, protein kinase B (Akt) in threonine 308, and serine 473 and Rictor are phosphorylated and activated. Glycogen synthase kinase type 3 (GSK3) is phosphorylated and inactivated in mitochondria, favoring mTORC1 activation. Epidermal growth factor, a classic mTORC1/2 activator, promoted unique activation kinetics of mTORC1/2 pathway, except for Akt phosphorylation. Here, we demonstrate that ACSL4 is necessary for mTORC1/2 effectors phosphorylation and H295R proliferation, triggered by Ang II. Ang II promotes activation of mitochondrial mTORC1/2 signaling proteins, through ACSL4, with a direct effect on adrenocortical cellular proliferation.
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Affiliation(s)
- Katia E Helfenberger
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
| | - Giuliana F Argentino
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
| | - Yanina Benzo
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
| | - Lucía M Herrera
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
| | - Paola Finocchietto
- Laboratorio del Metabolismo del Oxígeno. Hospital de Clínicas "José de San Martín," Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Inmunología, Genética y Metabolismo (INIGEM), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
| | - Cecilia Poderoso
- Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1121ABG, Argentina
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires-CONICET, Buenos Aires C1121ABG, Argentina
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3
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Lee SJ, Kim SJ, Jo DH, Park KS, Kim JH. Blockade of mTORC1-NOX signaling pathway inhibits TGF-β1-mediated senescence-like structural alterations of the retinal pigment epithelium. FASEB J 2021; 35:e21403. [PMID: 33559185 DOI: 10.1096/fj.202001939rr] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 01/04/2021] [Accepted: 01/15/2021] [Indexed: 11/11/2022]
Abstract
The retinal pigment epithelium (RPE) undergoes characteristic structural changes and epithelial-mesenchymal transition (EMT) during normal aging, which are exacerbated in age-related macular degeneration (AMD). Although the pathogenic mechanisms of aging and AMD remain unclear, transforming growth factor-β1 (TGF-β1) is known to induce oxidative stress, morphometric changes, and EMT as a senescence-promoting factor. In this study, we examined whether intravitreal injection of TGF-β1 into the mouse eye elicits senescence-like morphological alterations in the RPE and if this can be prevented by suppressing mammalian target of rapamycin complex 1 (mTORC1) or NADPH oxidase (NOX) signaling. We verified that intravitreal TGF-β1-induced stress fiber formation and EMT in RPE cells, along with age-associated morphometric changes, including increased variation in cell size and reduced cell density. In RPE cells, exogenous TGF-β1 increased endogenous expression of TGF-β1 and upregulated Smad3-ERK1/2-mTORC1 signaling, increasing reactive oxygen species (ROS) production and EMT. We demonstrated that inhibition of the mTORC1-NOX4 pathway by pretreatment with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMP-dependent protein kinase, or GKT137831, a NOX1/4 inhibitor, decreased ROS generation, prevented stress fiber formation, attenuated EMT, and improved the regularity of the RPE structure in vitro and in vivo. These results suggest that intravitreal TGF-β1 injection could be used as a screening model to investigate the aging-related structural and functional changes to the RPE. Furthermore, the regulation of TGF-β-mTORC1-NOX signaling could be a potential therapeutic target for reducing pathogenic alterations in aged RPE and AMD.
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Affiliation(s)
- Seok Jae Lee
- Fight against Angiogenesis-Related Blindness (FARB) Laboratory, Clinical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.,Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Soo-Jin Kim
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Dong Hyun Jo
- Department of Anatomy & Cell Biology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Kyu-Sang Park
- Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Jeong Hun Kim
- Fight against Angiogenesis-Related Blindness (FARB) Laboratory, Clinical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.,Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea.,Department of Ophthalmology, College of Medicine, Seoul National University, Seoul, Republic of Korea.,Advanced Biomedical Research Center, Korea Research Institute of Bioscience & Biotechnology, Daejeon, Republic of Korea
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4
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Campello L, Singh N, Advani J, Mondal AK, Corso-Diaz X, Swaroop A. Aging of the Retina: Molecular and Metabolic Turbulences and Potential Interventions. Annu Rev Vis Sci 2021; 7:633-664. [PMID: 34061570 DOI: 10.1146/annurev-vision-100419-114940] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Multifaceted and divergent manifestations across tissues and cell types have curtailed advances in deciphering the cellular events that accompany advanced age and contribute to morbidities and mortalities. Increase in human lifespan during the past century has heightened awareness of the need to prevent age-associated frailty of neuronal and sensory systems to allow a healthy and productive life. In this review, we discuss molecular and physiological attributes of aging of the retina, with a goal of understanding age-related impairment of visual function. We highlight the epigenome-metabolism nexus and proteostasis as key contributors to retinal aging and discuss lifestyle changes as potential modulators of retinal function. Finally, we deliberate promising intervention strategies for promoting healthy aging of the retina for improved vision. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Laura Campello
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Nivedita Singh
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Jayshree Advani
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Anupam K Mondal
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Ximena Corso-Diaz
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Anand Swaroop
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
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5
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Zhang Q, Presswalla F, Ali RR, Zacks DN, Thompson DA, Miller JML. Pharmacologic activation of autophagy without direct mTOR inhibition as a therapeutic strategy for treating dry macular degeneration. Aging (Albany NY) 2021; 13:10866-10890. [PMID: 33872219 PMCID: PMC8109132 DOI: 10.18632/aging.202974] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 03/13/2021] [Indexed: 12/15/2022]
Abstract
Dry age-related macular degeneration (AMD) is marked by the accumulation of extracellular and intracellular lipid-rich deposits within and around the retinal pigment epithelium (RPE). Inducing autophagy, a conserved, intracellular degradative pathway, is a potential treatment strategy to prevent disease by clearing these deposits. However, mTOR inhibition, the major mechanism for inducing autophagy, disrupts core RPE functions. Here, we screened autophagy inducers that do not directly inhibit mTOR for their potential as an AMD therapeutic in primary human RPE culture. Only two out of more than thirty autophagy inducers tested reliably increased autophagy flux in RPE, emphasizing that autophagy induction mechanistically differs across distinct tissues. In contrast to mTOR inhibitors, these compounds preserved RPE health, and one inducer, the FDA-approved compound flubendazole (FLBZ), reduced the secretion of apolipoprotein that contributes to extracellular deposits termed drusen. Simultaneously, FLBZ increased production of the lipid-degradation product β-hydroxybutyrate, which is used by photoreceptor cells as an energy source. FLBZ also reduced the accumulation of intracellular deposits, termed lipofuscin, and alleviated lipofuscin-induced cellular senescence and tight-junction disruption. FLBZ triggered compaction of lipofuscin-like granules into a potentially less toxic form. Thus, induction of RPE autophagy without direct mTOR inhibition is a promising therapeutic approach for dry AMD.
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Affiliation(s)
- Qitao Zhang
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Feriel Presswalla
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Robin R. Ali
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- KCL Centre for Cell and Gene Therapy, London, England WC2R 2LS, United Kingdom
| | - David N. Zacks
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Debra A. Thompson
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jason ML. Miller
- Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
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6
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Yao A, Wijngaarden P. Metabolic pathways in context:
mTOR
signalling in the retina and optic nerve ‐ A review. Clin Exp Ophthalmol 2020; 48:1072-1084. [DOI: 10.1111/ceo.13819] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/21/2020] [Accepted: 07/05/2020] [Indexed: 02/06/2023]
Affiliation(s)
- Anthony Yao
- Centre for Eye Research Australia Royal Victorian Eye and Ear Hospital East Melbourne, Victoria Australia
| | - Peter Wijngaarden
- Centre for Eye Research Australia Royal Victorian Eye and Ear Hospital East Melbourne, Victoria Australia
- Ophthalmology, Department of Surgery University of Melbourne Melbourne, Victoria Australia
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7
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Go YM, Zhang J, Fernandes J, Litwin C, Chen R, Wensel TG, Jones DP, Cai J, Chen Y. MTOR-initiated metabolic switch and degeneration in the retinal pigment epithelium. FASEB J 2020; 34:12502-12520. [PMID: 32721041 DOI: 10.1096/fj.202000612r] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/23/2020] [Accepted: 07/07/2020] [Indexed: 02/06/2023]
Abstract
The retinal pigment epithelium (RPE) is a particularly vulnerable tissue to age-dependent degeneration. Over the life span, the RPE develops an expanded endo-lysosomal compartment to maintain the high efficiency of phagocytosis and degradation of photoreceptor outer segments (POS) necessary for photoreceptor survival. As the assembly and activation of the mechanistic target of rapamycin complex 1 (mTORC1) occur on the lysosome surface, increased lysosome mass with aging leads to higher mTORC1 activity. The functional consequences of hyperactive mTORC1 in the RPE are unclear. In the current study, we used integrated high-resolution metabolomic and genomic approaches to examine mice with RPE-specific deletion of the tuberous sclerosis 1 (Tsc1) gene which encodes an upstream suppressor of mTORC1. Our data show that RPE cells with constitutively high mTORC1 activity were reprogramed to be hyperactive in glucose and lipid metabolism. Lipolysis was suppressed, mitochondrial carnitine shuttle was inhibited, while genes involved in fatty acid (FA) biosynthesis were upregulated. The metabolic changes occurred prior to structural changes of RPE and retinal degeneration. These findings have revealed cellular events and intrinsic mechanisms that contribute to lipid accumulation in the RPE cells during aging and age-related degeneration.
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Affiliation(s)
- Young-Mi Go
- Department of Medicine, Emory University, Atlanta, GA, USA
| | - Jing Zhang
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA
| | - Jolyn Fernandes
- Department of Medicine, Emory University, Atlanta, GA, USA.,Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Christopher Litwin
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Rui Chen
- Department of Genetics, Baylor College of Medicine, Houston, TX, USA.,Department of Biochemistry, Baylor College of Medicine, Houston, TX, USA
| | - Theodore G Wensel
- Department of Biochemistry, Baylor College of Medicine, Houston, TX, USA
| | - Dean P Jones
- Department of Medicine, Emory University, Atlanta, GA, USA
| | - Jiyang Cai
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Yan Chen
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA.,Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Department of Biochemistry, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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8
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Mitochondrial phosphatase PGAM5 modulates cellular senescence by regulating mitochondrial dynamics. Nat Commun 2020; 11:2549. [PMID: 32439975 PMCID: PMC7242393 DOI: 10.1038/s41467-020-16312-7] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 04/27/2020] [Indexed: 12/15/2022] Open
Abstract
Mitochondria undergo dynamic fusion/fission, biogenesis and mitophagy in response to stimuli or stresses. Disruption of mitochondrial homeostasis could lead to cell senescence, although the underlying mechanism remains unclear. We show that deletion of mitochondrial phosphatase PGAM5 leads to accelerated retinal pigment epithelial (RPE) senescence in vitro and in vivo. Mechanistically, PGAM5 is required for mitochondrial fission through dephosphorylating DRP1. PGAM5 deletion leads to increased mitochondrial fusion and decreased mitochondrial turnover. As results, cellular ATP and reactive oxygen species (ROS) levels are elevated, mTOR and IRF/IFN-β signaling pathways are enhanced, leading to cellular senescence. Overexpression of Drp1 K38A or S637A mutant phenocopies or rescues mTOR activation and senescence in PGAM5-/- cells, respectively. Young but not aging Pgam5-/- mice are resistant to sodium iodate-induced RPE cell death. Our studies establish a link between defective mitochondrial fission, cellular senescence and age-dependent oxidative stress response, which have implications in age-related diseases.
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9
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Altered photoreceptor metabolism in mouse causes late stage age-related macular degeneration-like pathologies. Proc Natl Acad Sci U S A 2020; 117:13094-13104. [PMID: 32434914 PMCID: PMC7293639 DOI: 10.1073/pnas.2000339117] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The main cause for blindness in the elderly worldwide is age-related macular degeneration (AMD). What causes AMD remains unknown. The high metabolic demands of photoreceptors are thought to contribute to disease pathogenesis, yet whether photoreceptor metabolism differs in individuals with AMD has not been determined. Here, we show that photoreceptor metabolism does differ between diseased and nondiseased individuals. Mimicking the metabolic profile of diseased individuals in mouse resulted in the similar advanced pathologies as those that cause blindness in humans. A disease model with photoreceptors as a contributing factor explains also why AMD affects preferentially the macula; it is the region of highest photoreceptor density. The data might open new avenues to study the role of PRs in disease pathogenesis. Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. While the histopathology of the different disease stages is well characterized, the cause underlying the progression, from the early drusen stage to the advanced macular degeneration stage that leads to blindness, remains unknown. Here, we show that photoreceptors (PRs) of diseased individuals display increased expression of two key glycolytic genes, suggestive of a glucose shortage during disease. Mimicking aspects of this metabolic profile in PRs of wild-type mice by activation of the mammalian target of rapamycin complex 1 (mTORC1) caused early drusen-like pathologies, as well as advanced AMD-like pathologies. Mice with activated mTORC1 in PRs also displayed other early disease features, such as a delay in photoreceptor outer segment (POS) clearance and accumulation of lipofuscin in the retinal-pigmented epithelium (RPE) and of lipoproteins at the Bruch’s membrane (BrM), as well as changes in complement accumulation. Interestingly, formation of drusen-like deposits was dependent on activation of mTORC1 in cones. Both major types of advanced AMD pathologies, including geographic atrophy (GA) and neovascular pathologies, were also seen. Finally, activated mTORC1 in PRs resulted in a threefold reduction in di-docosahexaenoic acid (DHA)–containing phospholipid species. Feeding mice a DHA-enriched diet alleviated most pathologies. The data recapitulate many aspects of the human disease, suggesting that metabolic adaptations in photoreceptors could contribute to disease progression in AMD. Identifying the changes downstream of mTORC1 that lead to advanced pathologies in mouse might present new opportunities to study the role of PRs in AMD pathogenesis.
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10
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Morris DR, Bounds SE, Liu H, Ding WQ, Chen Y, Liu Y, Cai J. Exosomal MiRNA Transfer between Retinal Microglia and RPE. Int J Mol Sci 2020; 21:ijms21103541. [PMID: 32429541 PMCID: PMC7279010 DOI: 10.3390/ijms21103541] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/10/2020] [Accepted: 05/14/2020] [Indexed: 12/16/2022] Open
Abstract
The retinal pigment epithelium (RPE), the outermost layer of the retina, provides essential support to both the neural retina and choroid. Additionally, the RPE is highly active in modulating functions of immune cells such as microglia, which migrate to the subretinal compartment during aging and age-related degeneration. Recently, studies have highlighted the important roles of microRNA (miRNA) in the coordination of general tissue maintenance as well as in chronic inflammatory conditions. In this study, we analyzed the miRNA profiles in extracellular vesicles (EVs) released by the RPE, and identified and validated miRNA species whose expression levels showed age-dependent changes in the EVs. Using co-culture of RPE and retinal microglia, we further demonstrated that miR-21 was transferred between the two types of cells, and the increased miR-21 in microglia influenced the expression of genes downstream of the p53 pathway. These findings suggest that exosome-mediated miRNA transfer is a signaling mechanism that contributes to the regulation of microglia function in the aging retina.
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Affiliation(s)
- Dorothea R. Morris
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA; (D.R.M.); (Y.C.)
| | - Sarah E. Bounds
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (S.E.B.); (H.L.)
| | - Huanhuan Liu
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (S.E.B.); (H.L.)
| | - Wei-Qun Ding
- Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
| | - Yan Chen
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA; (D.R.M.); (Y.C.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Yin Liu
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Correspondence: (Y.L.); (J.C.); Tel.: +1-713-500-5632 (Y.L.); +1-405-271-2226 (J.C.)
| | - Jiyang Cai
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA; (D.R.M.); (Y.C.)
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (S.E.B.); (H.L.)
- Correspondence: (Y.L.); (J.C.); Tel.: +1-713-500-5632 (Y.L.); +1-405-271-2226 (J.C.)
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11
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Su Y, Wang F, Hu Q, Qu Y, Han Y. Arsenic trioxide inhibits proliferation of retinal pigment epithelium by downregulating expression of extracellular matrix and p27. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2020; 13:172-178. [PMID: 32211097 PMCID: PMC7061785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
The present study aimed to investigate the effect of arsenic trioxide (ATO) on the proliferation of retinal pigment epithelium (RPE) and its mechanism. RPE cells were cultivated with 0.5-11 μmol/L ATO for 24, 48, and 72 h and their survival and growth were measured by MTT assay. The expression of p27 and proliferating cell nuclear antigen (PCNA) in RPE cells was detected using cell immunofluorescence and western blotting. Dose-dependency was evident in both the experimental and control groups. The 50% inhibitory concentration was obtained at a concentration of 6 mol/L with cells treated for 3 days. The optimum concentration of ATO was 6 μmol/L based on the result of MTT. After the third day of ATO treatment, the number of cells was significantly lower in the experimental group compared with the control group. The expression of extracellular matrix (ECM) components decreased relative to the control group. The expression of p27 and PCNA declined gradually in cells treated for 72 h at 6 μmol/L ATO compared with the control group. The difference between the experimental and control groups was significant (P=0.005). ATO has the ability to inhibit the growth and proliferation of RPE cells by regulating the expression of the ECM components' p27 and PCNA, in a time- and dose-dependent manner. Thus, ATO may lead to an innovative method for the treatment of proliferative retinopathy.
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Affiliation(s)
- Ying Su
- Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical UniversityHarbin, China
| | - Feng Wang
- Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical UniversityHarbin, China
| | - Qi Hu
- Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical UniversityHarbin, China
| | - Yixin Qu
- Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical UniversityHarbin, China
| | - Ying Han
- Department of Geriatrics, The First Affiliated Hospital of Harbin Medical UniversityHarbin, China
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12
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Huang J, Gu S, Chen M, Zhang SJ, Jiang Z, Chen X, Jiang C, Liu G, Radu RA, Sun X, Vollrath D, Du J, Yan B, Zhao C. Abnormal mTORC1 signaling leads to retinal pigment epithelium degeneration. Am J Cancer Res 2019; 9:1170-1180. [PMID: 30867823 PMCID: PMC6401408 DOI: 10.7150/thno.26281] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 12/24/2018] [Indexed: 12/13/2022] Open
Abstract
Retinal pigment epithelial (RPE) degeneration is potentially involved in the pathogenesis of several retinal degenerative diseases. mTORC1 signaling is shown as a crucial regulator of many biological processes and disease progression. In this study, we aimed at investigating the role of mTORC1 signaling in RPE degeneration. Methods: Western blots were conducted to detect mTORC1 expression pattern during RPE degeneration. Cre-loxP system was used to generate RPE-specific mTORC1 activation mice. Fundus, immunofluorescence staining, transmission electron microscopy, and targeted metabolomic analysis were conducted to determine the effects of mTORC1 activation on RPE degeneration in vivo. Electroretinography, spectral-domain optical coherence tomography, and histological experiments were conducted to determine the effects of mTORC1 activation on choroidal and retinal function in vivo. Results: RPE-specific activation of mTORC1 led to RPE degeneration as shown by the loss of RPE-specific marker, compromised cell junction integrity, and intracellular accumulation of lipid droplets. RPE degeneration further led to abnormal choroidal and retinal function. The inhibition of mTORC1 signaling with rapamycin could partially reverse RPE degeneration. Targeted metabolomics analysis further revealed that mTORC1 activation affected the metabolism of purine, carboxylic acid, and niacin in RPE. Conclusion: This study revealed that abnormal activation of mTORC1 signaling leads to RPE degeneration, which could provide a promising target for the treatment of RPE dysfunction-related diseases.
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13
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Enhancing TFEB-Mediated Cellular Degradation Pathways by the mTORC1 Inhibitor Quercetin. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:5073420. [PMID: 30510622 PMCID: PMC6230393 DOI: 10.1155/2018/5073420] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 07/16/2018] [Accepted: 08/09/2018] [Indexed: 12/17/2022]
Abstract
Signaling pathways mediated by the mechanistic target of rapamycin (mTOR) play key roles in aging and age-related diseases. As a downstream protein of mTOR, transcription factor EB (TFEB) controls lysosome biogenesis and cellular trafficking, processes that are essential for the functions of phagocytic cells like the retinal pigment epithelium (RPE). In the current study, we show that a naturally occurring polyphenolic compound, quercetin, promoted TFEB nuclear translocation and enhanced its transcriptional activity in cultured RPE cells. Activated TFEB facilitated degradation of phagocytosed photoreceptor outer segments. Quercetin is a direct inhibitor of mTOR but did not influence the activity of Akt at the tested concentration range. Our data suggest that the dietary compound quercetin can have beneficial roles in neuronal tissues by improving the functions of the TFEB-lysosome axis and enhancing the capacities of cellular degradation and self-renewal.
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14
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Schottler J, Randoll N, Lucius R, Caliebe A, Roider J, Klettner A. Long-term treatment with anti-VEGF does not induce cell aging in primary retinal pigment epithelium. Exp Eye Res 2018. [DOI: 10.1016/j.exer.2018.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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Yu B, Egbejimi A, Dharmat R, Xu P, Zhao Z, Long B, Miao H, Chen R, Wensel TG, Cai J, Chen Y. Phagocytosed photoreceptor outer segments activate mTORC1 in the retinal pigment epithelium. Sci Signal 2018; 11:11/532/eaag3315. [PMID: 29844054 DOI: 10.1126/scisignal.aag3315] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The retinal pigment epithelium (RPE) transports nutrients and metabolites between the microvascular bed that maintains the outer retina and photoreceptor neurons. The RPE removes photoreceptor outer segments (POS) by receptor-mediated phagocytosis, a process that peaks in the morning. Uptake and degradation of POS initiates signaling cascades in the RPE. Upstream stimuli from various metabolic activities converge on mechanistic target of rapamycin complex 1 (mTORC1), and aberrant mTORC1 signaling is implicated in aging and age-related degeneration of the RPE. We measured mTORC1-mediated responses to RPE phagocytosis in vivo and in vitro. During the morning burst of POS shedding, there was transient activation of mTORC1-mediated signaling in the RPE. POS activated mTORC1 through lysosome-independent mechanisms, and engulfed POS served as a docking platform for mTORC1 assembly. The identification of POS as endogenous stimuli of mTORC1 in the RPE provides a mechanistic link underlying the photoreceptor-RPE interaction in the outer retina.
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Affiliation(s)
- Bo Yu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Anuoluwapo Egbejimi
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Rachayata Dharmat
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Pei Xu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Zhenyang Zhao
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Bo Long
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Hongyu Miao
- Department of Biostatistics and Data Science, School of Public Health, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Rui Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.,Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Theodore G Wensel
- Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jiyang Cai
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA.,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yan Chen
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA. .,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
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16
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Cellular Senescence in Age-Related Macular Degeneration: Can Autophagy and DNA Damage Response Play a Role? OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:5293258. [PMID: 29225722 PMCID: PMC5687149 DOI: 10.1155/2017/5293258] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/29/2017] [Accepted: 06/28/2017] [Indexed: 12/14/2022]
Abstract
Age-related macular degeneration (AMD) is the main reason of blindness in developed countries. Aging is the main AMD risk factor. Oxidative stress, inflammation and some genetic factors play a role in AMD pathogenesis. AMD is associated with the degradation of retinal pigment epithelium (RPE) cells, photoreceptors, and choriocapillaris. Lost RPE cells in the central retina can be replaced by their peripheral counterparts. However, if they are senescent, degenerated regions in the macula cannot be regenerated. Oxidative stress, a main factor of AMD pathogenesis, can induce DNA damage response (DDR), autophagy, and cell senescence. Moreover, cell senescence is involved in the pathogenesis of many age-related diseases. Cell senescence is the state of permanent cellular division arrest and concerns only mitotic cells. RPE cells, although quiescent in the retina, can proliferate in vitro. They can also undergo oxidative stress-induced senescence. Therefore, cellular senescence can be considered as an important molecular pathway of AMD pathology, resulting in an inability of the macula to regenerate after degeneration of RPE cells caused by a factor inducing DDR and autophagy. It is too early to speculate about the role of the mutual interplay between cell senescence, autophagy, and DDR, but this subject is worth further studies.
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17
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Chiang CK, Tworak A, Kevany BM, Xu B, Mayne J, Ning Z, Figeys D, Palczewski K. Quantitative phosphoproteomics reveals involvement of multiple signaling pathways in early phagocytosis by the retinal pigmented epithelium. J Biol Chem 2017; 292:19826-19839. [PMID: 28978645 DOI: 10.1074/jbc.m117.812677] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/22/2017] [Indexed: 12/12/2022] Open
Abstract
One of the major biological functions of the retinal pigmented epithelium (RPE) is the clearance of shed photoreceptor outer segments (POS) through a multistep process resembling phagocytosis. RPE phagocytosis helps maintain the viability of photoreceptors that otherwise could succumb to the high metabolic flux and photo-oxidative stress associated with visual processing. The regulatory mechanisms underlying phagocytosis in the RPE are not fully understood, although dysfunction of this process contributes to the pathogenesis of multiple human retinal degenerative disorders, including age-related macular degeneration. Here, we present an integrated transcriptomic, proteomic, and phosphoproteomic analysis of phagocytosing RPE cells, utilizing three different experimental models: the human-derived RPE-like cell line ARPE-19, cultured murine primary RPE cells, and RPE samples from live mice. Our combined results indicated that early stages of phagocytosis in the RPE are mainly characterized by pronounced changes in the protein phosphorylation level. Global phosphoprotein enrichment analysis revealed involvement of PI3K/Akt, mechanistic target of rapamycin (mTOR), and MEK/ERK pathways in the regulation of RPE phagocytosis, confirmed by immunoblot analyses and in vitro phagocytosis assays. Most strikingly, phagocytosis of POS by cultured RPE cells was almost completely blocked by pharmacological inhibition of phosphorylation of Akt. Our findings, along with those of previous studies, indicate that these phosphorylation events allow the RPE to integrate multiple signals instigated by shed POS at different stages of the phagocytic process.
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Affiliation(s)
- Cheng-Kang Chiang
- From the Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.,the Department of Chemistry, National Dong Hwa University, No. 1 Sec. 2 Da Hsueh Road, Shoufeng, Hualien 97401, Taiwan
| | | | | | - Bo Xu
- From the Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Janice Mayne
- From the Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Zhibin Ning
- From the Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Daniel Figeys
- From the Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada, .,the Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
| | - Krzysztof Palczewski
- the Department of Pharmacology and .,the Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, and
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18
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KLF9 and JNK3 Interact to Suppress Axon Regeneration in the Adult CNS. J Neurosci 2017; 37:9632-9644. [PMID: 28871032 DOI: 10.1523/jneurosci.0643-16.2017] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 01/22/2023] Open
Abstract
Neurons in the adult mammalian CNS decrease in intrinsic axon growth capacity during development in concert with changes in Krüppel-like transcription factors (KLFs). KLFs regulate axon growth in CNS neurons including retinal ganglion cells (RGCs). Here, we found that knock-down of KLF9, an axon growth suppressor that is normally upregulated 250-fold in RGC development, promotes long-distance optic nerve regeneration in adult rats of both sexes. We identified a novel binding partner, MAPK10/JNK3 kinase, and found that JNK3 (c-Jun N-terminal kinase 3) is critical for KLF9's axon-growth-suppressive activity. Interfering with a JNK3-binding domain or mutating two newly discovered serine phosphorylation acceptor sites, Ser106 and Ser110, effectively abolished KLF9's neurite growth suppression in vitro and promoted axon regeneration in vivo These findings demonstrate a novel, physiologic role for the interaction of KLF9 and JNK3 in regenerative failure in the optic nerve and suggest new therapeutic strategies to promote axon regeneration in the adult CNS.SIGNIFICANCE STATEMENT Injured CNS nerves fail to regenerate spontaneously. Promoting intrinsic axon growth capacity has been a major challenge in the field. Here, we demonstrate that knocking down Krüppel-like transcription factor 9 (KLF9) via shRNA promotes long-distance axon regeneration after optic nerve injury and uncover a novel and important KLF9-JNK3 interaction that contributes to axon growth suppression in vitro and regenerative failure in vivo These studies suggest potential therapeutic approaches to promote axon regeneration in injury and other degenerative diseases in the adult CNS.
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19
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Zhao Z, Yang M, Azar SR, Soong L, Weaver SC, Sun J, Chen Y, Rossi SL, Cai J. Viral Retinopathy in Experimental Models of Zika Infection. Invest Ophthalmol Vis Sci 2017; 58:4355–4365. [PMID: 28810265 PMCID: PMC5558627 DOI: 10.1167/iovs.17-22016] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Purpose Emerging evidence has shown that both congenital and adult Zika virus (ZIKV) infection can cause eye diseases. The goals of the current study were to explore mechanisms and pathophysiology of ZIKV-induced eye defects. Methods Wild-type or A129 interferon type I receptor–deficient mice were infected by either FSS13025 or Mex1-7 strain of ZIKV. Retinal histopathology was measured at different time points after infection. The presence of viral RNA and protein in the retina was determined by in situ hybridization and immunofluorescence staining, respectively. Growth curves of ZIKV in permissive retinal cells were assessed in cultured retinal pigment epithelial (RPE) and Müller glial cells. Results ZIKV-infected mice developed a spectrum of ocular pathologies that affected multiple layers of the retina. A primary target of ZIKV in the eye was Müller glial cells, which displayed decreased neurotrophic function and increased expression of proinflammatory cytokines after infection. ZIKV also infected RPE; and both the RPE and Müller cells expressed viral entry receptors TYRO3 and AXL. Retinitis, focal retinal degeneration, and ganglion cell loss were observed after the clearance of viral particles. Conclusions Our data suggest that ZIKV can infect infant eyes with immature blood–retinal barrier and cause structural damages to the retina. The ocular findings in microcephalic infants may not be solely caused by ZIKV-induced impairment of neurodevelopment.
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Affiliation(s)
- Zhenyang Zhao
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Matthew Yang
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Sasha R Azar
- Institute for Translational Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Lynn Soong
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, United States
| | - Scott C Weaver
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, United States.,Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States.,Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States
| | - Jiaren Sun
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, United States
| | - Yan Chen
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Shannan L Rossi
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, United States.,Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States.,Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States
| | - Jiyang Cai
- Department of Ophthalmology & Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
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20
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Zhao Z, Liang Y, Liu Y, Xu P, Flamme-Wiese MJ, Sun D, Sun J, Mullins RF, Chen Y, Cai J. Choroidal γδ T cells in protection against retinal pigment epithelium and retinal injury. FASEB J 2017; 31:4903-4916. [PMID: 28729290 DOI: 10.1096/fj.201700533r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Accepted: 07/05/2017] [Indexed: 12/17/2022]
Abstract
γδ T cells located near the epithelial barrier are integral components of local inflammatory and innate immune responses. We have previously reported the presence of choroidal γδ T cells in a model of chronic degeneration of the retinal pigment epithelium (RPE). The goals of the current study were to further define the functions of choroidal γδ T cells and to explore the underlying mechanisms of their action. Our data demonstrate that choroidal γδ T cells are activated by RPE injury in response to NaIO3 treatment, and that they express genes that encode immunosuppressive cytokines, such as IL-4 and IL-10. γδ-T-cell-deficient mice developed profound RPE and retinal damage at doses that caused minimal effects in wild-type mice, and adoptive transfer of γδ T cells prevented sensitization. Intravitreal injection of IL-4 and IL-10 ameliorated RPE toxicity that was induced by NaIO3Ex vivo coculture of γδ T cells with RPE explants activated the production of anti-inflammatory cytokines via an aryl hydrocarbon receptor (AhR)-dependent mechanism. AhR deficiency abolished the protective effects of γδ T cells after adoptive transfer. Collectively, these findings define important roles for choroid γδ T cells in maintaining tissue homeostasis in the outer retina.-Zhao, Z., Liang, Y., Liu, Y., Xu, P., Flamme-Wiese, M. J., Sun, D., Sun, J., Mullins, R. F., Chen, Y., Cai, J. Choroidal γδ T cells in protection against retinal pigment epithelium and retinal injury.
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Affiliation(s)
- Zhenyang Zhao
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA
| | - Yuejin Liang
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Yin Liu
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Pei Xu
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA
| | - Miles J Flamme-Wiese
- Stephen A. Wynn Institute for Vision Research, University of Iowa, Iowa City, Iowa, USA
| | - Deming Sun
- Doheny Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - Jiaren Sun
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Robert F Mullins
- Stephen A. Wynn Institute for Vision Research, University of Iowa, Iowa City, Iowa, USA
| | - Yan Chen
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA
| | - Jiyang Cai
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA;
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21
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Li A, Li J, Bao Y, Yuan D, Huang Z. Xuebijing injection alleviates cytokine-induced inflammatory liver injury in CLP-induced septic rats through induction of suppressor of cytokine signaling 1. Exp Ther Med 2016; 12:1531-1536. [PMID: 27602076 DOI: 10.3892/etm.2016.3476] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 06/08/2016] [Indexed: 12/17/2022] Open
Abstract
Dysregulation of inflammatory cytokines and liver injury are associated with the pathogenesis of sepsis. Xuebijing injection, a Chinese herbal medicine, has been used in the treatment of sepsis and can contribute to the improvement of patients' health. However, the underlying molecular mechanisms are not yet clearly illuminated. In the present study, a septic rat model with liver injury was established by the cecal ligation and puncture (CLP) method. Histological alterations to the liver, activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), levels of inflammatory cytokine secretion and the expression of suppressors of cytokine signaling 1 (SOCS-1) in the CLP model rats with and without Xuebijing treatment were determined. The results showed that Xuebijing injection ameliorated the pathological changes in liver tissues caused by sepsis, and reduced the sepsis-induced elevation in serum ALT and AST levels. Furthermore, Xuebijing injection markedly downregulated the expression of tumor necrosis factor α and interleukin (IL)-6, and upregulated the expression of IL-10. More importantly, SOCS1 expression levels at the protein and mRNA levels were further increased by Xuebijing. These findings demonstrate that Xuebijing injection can significantly alleviate liver injury in CLP-induced septic rats via the regulation of inflammatory cytokine secretion and the promotion of SOCS1 expression. The protective effects of Xuebijing injection suggest its therapeutic potential in the treatment of CLP-induced liver injury.
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Affiliation(s)
- Ailin Li
- Department of Emergency Medicine, The Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Jing Li
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA
| | - Yuhua Bao
- Department of Emergency Medicine, The Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Dingshan Yuan
- Department of Emergency Medicine, The Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Zhongwei Huang
- Department of Emergency Medicine, The Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
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22
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Garza-Lombó C, Gonsebatt ME. Mammalian Target of Rapamycin: Its Role in Early Neural Development and in Adult and Aged Brain Function. Front Cell Neurosci 2016; 10:157. [PMID: 27378854 PMCID: PMC4910040 DOI: 10.3389/fncel.2016.00157] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 05/30/2016] [Indexed: 01/14/2023] Open
Abstract
The kinase mammalian target of rapamycin (mTOR) integrates signals triggered by energy, stress, oxygen levels, and growth factors. It regulates ribosome biogenesis, mRNA translation, nutrient metabolism, and autophagy. mTOR participates in various functions of the brain, such as synaptic plasticity, adult neurogenesis, memory, and learning. mTOR is present during early neural development and participates in axon and dendrite development, neuron differentiation, and gliogenesis, among other processes. Furthermore, mTOR has been shown to modulate lifespan in multiple organisms. This protein is an important energy sensor that is present throughout our lifetime its role must be precisely described in order to develop therapeutic strategies and prevent diseases of the central nervous system. The aim of this review is to present our current understanding of the functions of mTOR in neural development, the adult brain and aging.
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Affiliation(s)
- Carla Garza-Lombó
- Departamento de Medicina Genómica, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México México
| | - María E Gonsebatt
- Departamento de Medicina Genómica, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México México
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23
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Sowers JL, Mirfattah B, Xu P, Tang H, Park IY, Walker C, Wu P, Laezza F, Sowers LC, Zhang K. Quantification of histone modifications by parallel-reaction monitoring: a method validation. Anal Chem 2016; 87:10006-14. [PMID: 26356480 DOI: 10.1021/acs.analchem.5b02615] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abnormal epigenetic reprogramming is one of the major causes leading to irregular gene expression and regulatory pathway perturbations, in the cells, resulting in unhealthy cell development or diseases. Accurate measurements of these changes of epigenetic modifications, especially the complex histone modifications, are very important, and the methods for these measurements are not trivial. By following our previous introduction of PRM to targeting histone modifications (Tang, H.; Fang, H.; Yin, E.; Brasier, A. R.; Sowers, L. C.; Zhang, K. Multiplexed parallel reaction monitoring targeting histone modifications on the QExactive mass spectrometer. Anal. Chem. 2014, 86 (11), 5526-34), herein we validated this method by varying the protein/trypsin ratios via serial dilutions. Our data demonstrated that PRM with SILAC histones as the internal standards allowed reproducible measurements of histone H3/H4 acetylation and methylation in the samples whose histone contents differ at least one-order of magnitude. The method was further validated by histones isolated from histone H3 K36 trimethyltransferase SETD2 knockout mouse embryonic fibroblasts (MEF) cells. Furthermore, histone acetylation and methylation in human neural stem cells (hNSC) treated with ascorbic acid phosphate (AAP) were measured by this method, revealing that H3 K36 trimethylation was significantly down-regulated by 6 days of treatment with vitamin C.
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Affiliation(s)
| | | | | | | | - In Young Park
- Institute of Biosciences and Technology, Texas A&M Health Sciences Center , Houston, Texas 77030, United States
| | - Cheryl Walker
- Institute of Biosciences and Technology, Texas A&M Health Sciences Center , Houston, Texas 77030, United States
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24
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Wang Y, Cameron EG, Li J, Stiles TL, Kritzer MD, Lodhavia R, Hertz J, Nguyen T, Kapiloff MS, Goldberg JL. Muscle A-Kinase Anchoring Protein-α is an Injury-Specific Signaling Scaffold Required for Neurotrophic- and Cyclic Adenosine Monophosphate-Mediated Survival. EBioMedicine 2015; 2:1880-7. [PMID: 26844267 PMCID: PMC4703706 DOI: 10.1016/j.ebiom.2015.10.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 10/17/2015] [Accepted: 10/22/2015] [Indexed: 12/11/2022] Open
Abstract
Neurotrophic factor and cAMP-dependent signaling promote the survival and neurite outgrowth of retinal ganglion cells (RGCs) after injury. However, the mechanisms conferring neuroprotection and neuroregeneration downstream to these signals are unclear. We now reveal that the scaffold protein muscle A-kinase anchoring protein-α (mAKAPα) is required for the survival and axon growth of cultured primary RGCs. Although genetic deletion of mAKAPα early in prenatal RGC development did not affect RGC survival into adulthood, nor promoted the death of RGCs in the uninjured adult retina, loss of mAKAPα in the adult increased RGC death after optic nerve crush. Importantly, mAKAPα was required for the neuroprotective effects of brain-derived neurotrophic factor and cyclic adenosine-monophosphate (cAMP) after injury. These results identify mAKAPα as a scaffold for signaling in the stressed neuron that is required for RGC neuroprotection after optic nerve injury. mAKAPα is a stress-specific mediator of RGC survival. mAKAP deletion does not affect RGC survival in development or in the uninjured adult retina. mAKAP is downregulated after optic nerve injury, and its further deletion exacerbates RGC death. mAKAP deletion suppresses the neuroprotective effects of cAMP and BDNF after injury.
After injury or in degenerative diseases, neurons of the central nervous system (CNS) fail to regenerate and often die partly due to a lack of pro-survival, trophic signaling. Better understanding of such signaling is important for the development of therapies that enhance survival and regeneration of neurons after injury. Here we identify a critical regulator of such signaling, mAKAPα, a scaffold protein that coordinates pro-survival signaling to enhance survival and regeneration in CNS neurons after injury. The neuroprotective role of mAKAPα will likely lead to further future insights into the detailed nature of survival signaling in adult neurons.
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Affiliation(s)
- Yan Wang
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, United States; Department of Ophthalmology, University of California, San Diego, CA 92093, United States
| | - Evan G Cameron
- Department of Ophthalmology, University of California, San Diego, CA 92093, United States; Byers Eye Institute, Stanford University, Palo Alto, CA 94303, United States
| | - Jinliang Li
- Department of Pediatrics, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Department of Medicine, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States
| | - Travis L Stiles
- Department of Ophthalmology, University of California, San Diego, CA 92093, United States
| | - Michael D Kritzer
- Department of Pediatrics, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Department of Medicine, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States
| | - Rahul Lodhavia
- Department of Ophthalmology, University of California, San Diego, CA 92093, United States
| | - Jonathan Hertz
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, United States
| | - Tu Nguyen
- Department of Ophthalmology, University of California, San Diego, CA 92093, United States
| | - Michael S Kapiloff
- Department of Pediatrics, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Department of Medicine, Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, 33136, United States
| | - Jeffrey L Goldberg
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, United States; Department of Ophthalmology, University of California, San Diego, CA 92093, United States; Byers Eye Institute, Stanford University, Palo Alto, CA 94303, United States
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Sinha D, Valapala M, Shang P, Hose S, Grebe R, Lutty GA, Zigler JS, Kaarniranta K, Handa JT. Lysosomes: Regulators of autophagy in the retinal pigmented epithelium. Exp Eye Res 2015; 144:46-53. [PMID: 26321509 DOI: 10.1016/j.exer.2015.08.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 07/09/2015] [Accepted: 08/18/2015] [Indexed: 12/19/2022]
Abstract
The retinal pigmented epithelium (RPE) is critically important to retinal homeostasis, in part due to its very active processes of phagocytosis and autophagy. Both of these processes depend upon the normal functioning of lysosomes, organelles which must fuse with (auto)phagosomes to deliver the hydrolases that effect degradation of cargo. It has become clear that signaling through mTOR complex 1 (mTORC1), is very important in the regulation of lysosomal function. This signaling pathway is becoming a target for therapeutic intervention in diseases, including age-related macular degeneration (AMD), where lysosomal function is defective. In addition, our laboratory has been studying animal models in which the gene (Cryba1) for βA3/A1-crystallin is deficient. These animals exhibit impaired lysosomal clearance in the RPE and pathological signs that are similar to some of those seen in AMD patients. The data demonstrate that βA3/A1-crystallin localizes to lysosomes in the RPE and that it is a binding partner of V-ATPase, the proton pump that acidifies the lysosomal lumen. This suggests that βA3/A1-crystallin may also be a potential target for therapeutic intervention in AMD. In this review, we focus on effector molecules that impact the lysosomal-autophagic pathway in RPE cells.
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Affiliation(s)
- Debasish Sinha
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Mallika Valapala
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peng Shang
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Ophthalmology of Shanghai Tenth Hospital and Tongji Eye Institute, Tongji University School of Medicine, Shanghai, China
| | - Stacey Hose
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rhonda Grebe
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Gerard A Lutty
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - J Samuel Zigler
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kai Kaarniranta
- Department of Ophthalmology, Institute of Clinical Medicine and Kuopio University Hospital, University of Eastern Finland, Kuopio, Finland
| | - James T Handa
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
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