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Sreekumar PG, Su F, Spee C, Hong E, Komirisetty R, Araujo E, Nusinowitz S, Reddy ST, Kannan R. Paraoxonase 2 Deficiency Causes Mitochondrial Dysfunction in Retinal Pigment Epithelial Cells and Retinal Degeneration in Mice. Antioxidants (Basel) 2023; 12:1820. [PMID: 37891899 PMCID: PMC10604559 DOI: 10.3390/antiox12101820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 09/20/2023] [Accepted: 09/27/2023] [Indexed: 10/29/2023] Open
Abstract
Although AMD is a complex disease, oxidative stress is a crucial contributor to its development, especially in view of the higher oxygen demand of the retina. Paraoxonase 2 (PON2) is a ubiquitously and constitutively expressed antioxidant protein that is found intracellularly associated with mitochondrial membranes and modulates mitochondrial ROS production and function. The contribution of PON2 to AMD has not been studied to date. In this study, we examined the role of PON2 in AMD utilizing both in vitro and in vivo models of AMD with emphasis on mitochondrial function. Mitochondrial localization and regulation of PON2 following oxidative stress were determined in human primary cultured retinal pigment epithelium (hRPE) cells. PON2 was knocked down in RPE cells using siRNA and mitochondrial bioenergetics were measured. To investigate the function of PON2 in the retina, WT and PON2-deficient mice were administered NaIO3 (20 mg/kg) intravenously; fundus imaging, optical coherence tomography (OCT), electroretinography (ERG) were conducted; and retinal thickness and cell death were measured and quantified. In hRPE, mitochondrial localization of PON2 increased markedly with stress. Moreover, a time-dependent regulation of PON2 was observed following oxidative stress, with an initial significant increase in expression followed by a significant decrease. Mitochondrial bioenergetic parameters (basal respiration, ATP production, spare respiratory capacity, and maximal respiration) showed a significant decrease with oxidative stress, which was further exacerbated in the absence of PON2. NaIO3 treatment caused significant retinal degeneration, retinal thinning, and reduced rod and cone function in PON2-deficient mice when compared to WT mice. The apoptotic cells and active caspase 3 significantly increased in PON2-deficient mice treated with NaIO3, when compared to WT mice. Our investigation demonstrates that deficiency of PON2 results in RPE mitochondrial dysfunction and a decline in retinal function. These findings imply that PON2 may have a beneficial role in retinal pathophysiology and is worthy of further investigation.
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Affiliation(s)
| | - Feng Su
- Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA;
| | - Christine Spee
- Doheny Eye Institute, Pasadena, CA 91103, USA; (P.G.S.); (C.S.); (E.H.)
| | - Elise Hong
- Doheny Eye Institute, Pasadena, CA 91103, USA; (P.G.S.); (C.S.); (E.H.)
| | - Ravikiran Komirisetty
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA;
| | - Eduardo Araujo
- Jules Stein Eye Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA; (E.A.); (S.N.)
| | - Steven Nusinowitz
- Jules Stein Eye Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA; (E.A.); (S.N.)
| | - Srinivasa T. Reddy
- Department of Medicine, Division of Cardiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA;
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Ram Kannan
- Doheny Eye Institute, Pasadena, CA 91103, USA; (P.G.S.); (C.S.); (E.H.)
- Jules Stein Eye Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA; (E.A.); (S.N.)
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2
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Wang K, Chen YS, Chien HW, Chiou HL, Yang SF, Hsieh YH. Melatonin inhibits NaIO3-induced ARPE-19 cell apoptosis via suppression of HIF-1α/BNIP3-LC3B/mitophagy signaling. Cell Biosci 2022; 12:133. [PMID: 35986432 PMCID: PMC9389659 DOI: 10.1186/s13578-022-00879-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 08/10/2022] [Indexed: 11/25/2022] Open
Abstract
Background Age-related macular degeneration (AMD) leads to gradual central vision loss and eventual irreversible blindness. Melatonin, an endogenous hormone, exhibits anti-inflammatory and antitumor effects; however, the role it plays in AMD remains unclear. Herein, we investigated the anti-AMD molecular mechanism of melatonin after sodium iodate (NaIO3) treatment of ARPE-19 cells in vitro and in animal models with the goal of improving the therapeutic effect. Results The in vitro results showed that melatonin protected against NaIO3-induced cell viability decline, mitochondrial dysfunction and apoptosis in ARPE-19 cells, and melatonin also alleviated NaIO3-induced reactive oxygen species (ROS) production, mitochondrial dysfunction and mitophagy activation. Melatonin reduced NaIO3-induced mitophagy activation through HIF-1α-targeted BNIP3/LC3B transcription, whereas ROS inhibition realized with N-acetylcysteine (NAC, a ROS inhibitor) combined with melatonin reduced the effect of NaIO3 on mitophagy. An animal model of AMD was established to confirm the in vitro data. Mouse tail vein injection of NaIO3 and melatonin was associated with enhanced repair of retinal layers within 7 days, as observed by optical coherence tomography (OCT) and hematoxylin and eosin (H&E) staining. A reduction in BNIP3 and HIF-1α levels, as determined by immunohistochemistry (IHC) assay, was also observed. Conclusions These results indicate that melatonin attenuated NaIO3-induced mitophagy of ARPE-19 cells via reduction in ROS-mediated HIF-1α targeted BNIP3/LC3B signaling in vitro and in vivo. Melatonin may be a potential therapeutic drug in the treatment of AMD. Supplementary Information The online version contains supplementary material available at 10.1186/s13578-022-00879-3.
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Yang M, Tsui MG, Tsang JKW, Goit RK, Yao KM, So KF, Lam WC, Lo ACY. Involvement of FSP1-CoQ 10-NADH and GSH-GPx-4 pathways in retinal pigment epithelium ferroptosis. Cell Death Dis 2022; 13:468. [PMID: 35585057 PMCID: PMC9117320 DOI: 10.1038/s41419-022-04924-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 05/03/2022] [Accepted: 05/06/2022] [Indexed: 12/14/2022]
Abstract
Retinal pigment epithelium (RPE) degeneration plays an important role in a group of retinal disorders such as retinal degeneration (RD) and age-related macular degeneration (AMD). The mechanism of RPE cell death is not yet fully elucidated. Ferroptosis, a novel regulated cell death pathway, participates in cancer and several neurodegenerative diseases. Glutathione peroxidase 4 (GPx-4) and ferroptosis suppressor protein 1 (FSP1) have been proposed to be two main regulators of ferroptosis in these diseases; yet, their roles in RPE degeneration remain elusive. Here, we report that both FSP1-CoQ10-NADH and GSH-GPx-4 pathways inhibit retinal ferroptosis in sodium iodate (SIO)-induced retinal degeneration pathologies in human primary RPE cells (HRPEpiC), ARPE-19 cell line, and mice. GSH-GPx-4 signaling was compromised after a toxic injury caused by SIO, which was aggravated by silencing GPx-4, and ferroptosis inhibitors robustly protected RPE cells from the challenge. Interestingly, while inhibition of FSP1 caused RPE cell death, which was aggravated by SIO exposure, overexpression of FSP1 effectively protected RPE cells from SIO-induced injury, accompanied by a significant down-regulation of CoQ10/NADH and lipid peroxidation. Most importantly, in vivo results showed that Ferrostatin-1 not only remarkably alleviated SIO-induced RPE cell loss, photoreceptor death, and retinal dysfunction but also significantly ameliorated the compromised GSH-GPx-4 and FSP1-CoQ10-NADH signaling in RPE cells isolated from SIO-induced RPE degeneration. These data describe a distinct role for ferroptosis in controlling RPE cell death in vitro and in vivo and may provide a new avenue for identifying treatment targets for RPE degeneration.
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Affiliation(s)
- Ming Yang
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Michelle Grace Tsui
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Jessica Kwan Wun Tsang
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Rajesh Kumar Goit
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kwok-Ming Yao
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kwok-Fai So
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
- State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, China.
- GHM Institute of CNS Regeneration, Jinan University, Guangzhou, China.
| | - Wai-Ching Lam
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
| | - Amy Cheuk Yin Lo
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
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4
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Liu B, Wang W, Shah A, Yu M, Liu Y, He L, Dang J, Yang L, Yan M, Ying Y, Tang Z, Liu K. Sodium iodate induces ferroptosis in human retinal pigment epithelium ARPE-19 cells. Cell Death Dis 2021; 12:230. [PMID: 33658488 PMCID: PMC7930128 DOI: 10.1038/s41419-021-03520-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 12/15/2022]
Abstract
Sodium iodate (SI) is a widely used oxidant for generating retinal degeneration models by inducing the death of retinal pigment epithelium (RPE) cells. However, the mechanism of RPE cell death induced by SI remains unclear. In this study, we investigated the necrotic features of cultured human retinal pigment epithelium (ARPE-19) cells treated with SI and found that apoptosis or necroptosis was not the major death pathway. Instead, the death process was accompanied by significant elevation of intracellular labile iron level, ROS, and lipid peroxides which recapitulated the key features of ferroptosis. Ferroptosis inhibitors deferoxamine mesylate (DFO) and ferrostatin-1(Fer-1) partially prevented SI-induced cell death. Further studies revealed that SI treatment did not alter GPX4 (glutathione peroxidase 4) expression, but led to the depletion of reduced thiol groups, mainly intracellular GSH (reduced glutathione) and cysteine. The study on iron trafficking demonstrated that iron influx was not altered by SI treatment but iron efflux increased, indicating that the increase in labile iron was likely due to the release of sequestered iron. This hypothesis was verified by showing that SI directly promoted the release of labile iron from a cell-free lysate. We propose that SI depletes GSH, increases ROS, releases labile iron, and boosts lipid damage, which in turn results in ferroptosis in ARPE-19 cells.
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Affiliation(s)
- Binghua Liu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China.,Laboratory of Molecular Biology, College of Medicine, Chengdu University, Chengdu, 610106, Sichuan, PR China
| | - Weiyan Wang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Arman Shah
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Meng Yu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Yang Liu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Libo He
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Jinye Dang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Li Yang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Mengli Yan
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Yuling Ying
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Zihuai Tang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China
| | - Ke Liu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, PR China.
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5
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Ho J, Jang KH, Koo TS, Park C, Kim YH, Lee J, Kim E. Protective effects of PARP1-inhibitory compound in dry age-related macular degeneration. Biomed Pharmacother 2021; 133:111041. [PMID: 33378949 DOI: 10.1016/j.biopha.2020.111041] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/16/2020] [Accepted: 11/18/2020] [Indexed: 11/23/2022] Open
Abstract
Poly (ADP-ribose) polymerase 1 (PARP1)-dependent cell death in the retinal pigment epithelium (RPE) is implicated in dry age-related macular degeneration (AMD). Although PARP1 inhibitors are available for treating dry AMD, their delivery route is not ideal for patients. The aim of this study was to test the efficacy of a novel PARP1-inhibitory compound (PIC) in vitro and in vivo. This study presents PIC, a novel small molecule, with superior efficacy to PARP1 inhibitors in the market. PIC demonstrated a distinctive inhibitory profile against PARP isotypes than the FDA-approved PARP1 inhibitors. PIC inhibited PARP1 activation at an IC50 of 0.41 ± 0.15 nM in an enzyme-based assay in vitro and at IC50 and EC50 in ARPE-19 cells of 0.11 ± 0.02 nM and 0.22 ± 0.02 nM, respectively, upon H2O2 insult. PIC also moderated mitochondrial fission and depolarization and maintained cellular energy levels under oxidative stress in ARPE-19 cells. Furthermore, PIC demonstrated good corneal penetration in a rat model, presenting PIC as a promising candidate for eye drop therapeutics for dry AMD. When PIC was administered as an eye drop formulation, RPE morphology was preserved, maintaining the thickness of the outer nuclear layers under sodium iodate (SI) treatment in rats. In SI-treated rabbits, eye drop administration of PIC also retained the structural and functional integrity when analyzed using funduscopy and electroretinogram. Collectively, our data portray PIC as an attractive treatment measure for dry AMD.
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Affiliation(s)
- Jeongmin Ho
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea
| | - Ki-Hong Jang
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea
| | - Tae-Sung Koo
- Graduate School of New Drug Discovery and Development, Chungnam National University, Daejeon, South Korea
| | - Changmin Park
- Kukjepharma R&D Center, Sanseong-ro 47, Ansan, Gyeonggi-do, South Korea
| | - Young-Hoon Kim
- Kukjepharma R&D Center, Sanseong-ro 47, Ansan, Gyeonggi-do, South Korea
| | - Juhee Lee
- Kukjepharma R&D Center, Sanseong-ro 47, Ansan, Gyeonggi-do, South Korea
| | - Eunhee Kim
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea.
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6
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Oxidative stress in the retina and retinal pigment epithelium (RPE): Role of aging, and DJ-1. Redox Biol 2020; 37:101623. [PMID: 32826201 PMCID: PMC7767746 DOI: 10.1016/j.redox.2020.101623] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 06/22/2020] [Accepted: 06/24/2020] [Indexed: 12/15/2022] Open
Abstract
High levels of oxidative radicals generated by daily light exposure and high metabolic rate suggest that the antioxidant machinery of the retina and retinal pigment epithelium (RPE) is crucial for their survival. DJ-1 is a redox-sensitive protein that has been shown to have neuroprotective function in the brain in Parkinson's disease and other neurodegenerative diseases. Here, we analyzed the role of DJ-1 in the retina during oxidative stress and aging. We induced low-level oxidative stress in young (3-month-old) and old (15-month-old) C57BL/6J (WT) and DJ-1 knockout (KO) mice and evaluated effects in the RPE and retina. Absence of DJ-1 resulted in increased retinal dysfunction in response to low levels of oxidative stress. Our findings suggest that loss of DJ-1 affects the RPE antioxidant machinery, rendering it unable to combat and neutralize low-level oxidative stress, irrespective of age. Moreover, they draw a parallel to the retinal degeneration observed in AMD, where the occurrence of genetic variants may leave the retina and RPE unable to fight sustained, low-levels of oxidative stress. Antioxidants are upregulated in young DJ-1 KO RPE but downregulated in the retina. DJ-1 KO retinas are degenerated under low-level oxidative stress, regardless of age. Retinas of both young C57BL and DJ-1 KO were able to regulate antioxidant genes upon low-level oxidative stress. Retinas of both aged C57BL and DJ-1 KO were unable to regulate antioxidant genes upon low-level oxidative stress. RPE of aged C57BLl mice upregulated some antioxidant genes.
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Oral administration of ferulic acid or ethyl ferulate attenuates retinal damage in sodium iodate-induced retinal degeneration mice. Sci Rep 2020; 10:8688. [PMID: 32457394 PMCID: PMC7250827 DOI: 10.1038/s41598-020-65673-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 05/07/2020] [Indexed: 12/31/2022] Open
Abstract
Epidemiological studies indicate that the daily intake of antioxidants from a traditional Asian diet reduces the risk of developing age-related macular degeneration. Many of the phytochemicals that are abundant in whole grains exhibit a wide variety of biological activity such as antioxidant, anti-inflammatory, and neuroprotective effects. Ferulic acid (FA) is a phenolic acid found in vegetables and grains that has therapeutic potential for diabetes mellitus, Alzheimer's disease, and other diseases. We investigated the retinal protective effect of FA in a sodium iodate (NaIO3)-induced model of retinal degeneration. In a human retinal pigment epithelial cell line, FA attenuated H2O2-induced injury and lipopolysaccharide- or 7-ketocholesterol-induced inflammation. In mice, the oral administration of FA or its analog, ethyl ferulate, attenuated the morphological and functional features of NaIO3-induced retinal degeneration according to optical coherence tomography and electroretinography. Our results demonstrate that the oral administration of FA provides protective effects to the retina, suggesting that the intake of FA as a daily supplement or daily healthy diet containing rich vegetables and whole grains may prevent age-related macular degeneration.
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Ma H, Yang F, Ding XQ. Inhibition of thyroid hormone signaling protects retinal pigment epithelium and photoreceptors from cell death in a mouse model of age-related macular degeneration. Cell Death Dis 2020; 11:24. [PMID: 31932580 PMCID: PMC6957507 DOI: 10.1038/s41419-019-2216-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 12/11/2019] [Accepted: 12/12/2019] [Indexed: 02/01/2023]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Dry AMD is characterized by a progressive macular degeneration of the retinal pigment epithelium (RPE) and photoreceptors, and the RPE oxidative damage/dystrophy is at the core of the disease. Recent population/patients-based studies have shown an association of high free serum thyroid hormone (TH) levels with increased risk of AMD. This work investigated the effects of TH signaling inhibition on RPE and photoreceptor damage/cell death in an oxidative stress-induced mouse model of AMD. TH signaling inhibition was achieved by anti-thyroid drug treatment and oxidative stress was induced by sodium iodate (NaIO3) administration. Mice treated with NaIO3 showed severe RPE and photoreceptor cell death/necroptosis, destruction, oxidative damage, retinal stress, and reduced retinal function. Treatment with anti-thyroid drug protected RPE and photoreceptors from damage/cell death induced by NaIO3, reduced oxidative damage of RPE and photoreceptors, and preserved retinal function. Gene expression analysis showed that the NaIO3-induced RPE/photoreceptor damage/cell death involves multiple mechanisms, including cellular oxidative stress responses, activation of necroptosis/apoptosis signaling, and inflammatory responses. Treatment with anti-thyroid drug abolished these cellular stress/death responses. The findings of this study demonstrate a role of TH signaling in RPE and photoreceptor cell death after oxidative stress challenge, and support a role of TH signaling in the pathogenesis of AMD.
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Affiliation(s)
- Hongwei Ma
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Fan Yang
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xi-Qin Ding
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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Jang KH, Do YJ, Koo TS, Choi JS, Song EJ, Hwang Y, Bae HJ, Lee JH, Kim E. Protective effect of RIPK1-inhibitory compound in in vivo models for retinal degenerative disease. Exp Eye Res 2018; 180:8-17. [PMID: 30500363 DOI: 10.1016/j.exer.2018.11.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 11/04/2018] [Accepted: 11/26/2018] [Indexed: 12/16/2022]
Abstract
Receptor interacting protein kinase 1 (RIPK1) plays a key role in necroptosis, which is a type of programmed necrosis that is involved in ocular diseases, including glaucoma and dry age-related macular degeneration (AMD). We previously introduced RIPK1-inhibitory compound (RIC), which has biochemical characteristics and a mode of action that are distinct from those of the prototype RIPK1 inhibitor necrostatin-1. The intraperitoneal administration of RIC exerts a protective effect on retinal ganglion cells against a glaucomatous insult. In this study, we examined the protective effect of RIC on retinal pigment epithelium (RPE) against sodium iodate (SI) insult, which is associated with dry AMD pathogenesis. The eye drop administration of RIC that reached on the retina prevented RPE loss in SI-induced retinal degeneration. RIC consistently demonstrated retinal protection in the funduscopy and electroretinogram analyses in SI-injected rabbits and iodoacetic acid-treated mini-pigs. Moreover, the in vivo protective effects of RIC were superior to those of ACU-4429 and doxycycline, which are other medications investigated in clinical trials for the treatment of dry AMD, and RIC did not induce retinal toxicity following topical administration in rats. Collectively, RIC displayed excellent retinal penetration and prevented retinal degeneration in the pathogenesis of dry AMD with a high in vivo efficacy.
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Affiliation(s)
- Ki-Hong Jang
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea
| | - Yun-Ju Do
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea
| | - Tae-Sung Koo
- Graduate School of New Drug Discovery and Development, Chungnam National University, Daejeon, South Korea
| | - Jun-Sub Choi
- Catholic Institute for Visual Science, The Catholic University of Korea, #505 Banpo-dong, Seocho-gu, Seoul, South Korea
| | - Eun Ju Song
- Department of Drug Development, Technology Research Institute, Ensol Biosciences Inc., Daejeon, South Korea
| | - Yeseong Hwang
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea
| | - Hyun Ju Bae
- Kukjepharma R&D Center, Sanseong-ro 47, Ansan, Gyeonggi-do, South Korea
| | - Ju-Hee Lee
- Kukjepharma R&D Center, Sanseong-ro 47, Ansan, Gyeonggi-do, South Korea
| | - Eunhee Kim
- Department of Biological Sciences, Chungnam National University, Daejeon, South Korea.
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10
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Heo JH, Yoon JA, Ahn EK, Kim H, Urm SH, Oak CO, Yu BC, Lee SJ. Intraperitoneal administration of adipose tissue-derived stem cells for the rescue of retinal degeneration in a mouse model via indigenous CNTF up-regulation by IL-6. J Tissue Eng Regen Med 2017; 12:e1370-e1382. [PMID: 28715614 DOI: 10.1002/term.2522] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 04/05/2017] [Accepted: 06/20/2017] [Indexed: 12/21/2022]
Abstract
As the world's population begins to age, retinal degeneration is an increasing problem, and various treatment modalities are being developed. However, there have been no therapies for degenerative retinal conditions that are not characterized by neovascularization. We investigated whether transplantation of mouse adipose tissue-derived stem cells (mADSC) into the intraperitoneal space has a rescue effect on NaIO3 -induced retinal degeneration in mice. In this study, mADSC transplantation recovered visual function and preserved the retinal outer layer structure compared to the control group without any integration of mADSC into the retina. Moreover, endogenous ciliary neurotrophic factor (CNTF) was elevated in the retinas of mADSC-treated mice. We found that lipopolysaccharide (LPS) or LPS-stimulated monocyte supernatant induced the secretion of granulocyte colony stimulating factor (GCSF), CD54, CXCL10, interleukin-6 (IL-6), and CCL5 from the mADSC by cytokine array. Network inference was conducted to investigate signaling networks related to CNTF regulation. Based on bioinformatics data, the expression of IL-6 was related to the expression of CNTF. Additionally, intravitreal injection of IL-6 in rats produced up-regulation of endogenous CNTF in the retina. mADSC had a rescue effect on retinal degeneration through the up-regulation of endogenous CNTF by IL-6. Thus, transplantation of mADSC could be a potential treatment option for retinal degeneration.
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Affiliation(s)
- Jeong Hoon Heo
- Department of Molecular Biology and Immunology, College of Medicine, Kosin University, Pusan, Korea.,Institute for Medicine, College of Medicine, Kosin University, Pusan, Korea
| | - Jung Ae Yoon
- Department of Dental Hygiene, Dong Ju College, Pusan, Korea
| | - Eun Kyung Ahn
- Department of Biological Science, College of Natural Science, Dong-A University, Pusan, Korea
| | - Hyun Kim
- Department of Anatomy, College of Medicine, Kosin University, Pusan, Korea
| | - Sang Hwa Urm
- Department of Preventive Medicine, Inje University College of Medicine, Pusan, Korea
| | - Chul Oh Oak
- Department of Internal Medicine, College of Medicine, Kosin University, Pusan, Korea
| | - Byeng Chul Yu
- Department of Preventive Medicine, College of Medicine, Kosin University, Pusan, Korea
| | - Sang Joon Lee
- Institute for Medicine, College of Medicine, Kosin University, Pusan, Korea.,Department of Ophthalmology, College of Medicine, Kosin University, Pusan, Korea
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11
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AIF-independent parthanatos in the pathogenesis of dry age-related macular degeneration. Cell Death Dis 2017; 8:e2526. [PMID: 28055012 PMCID: PMC5386356 DOI: 10.1038/cddis.2016.437] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/24/2016] [Accepted: 11/17/2016] [Indexed: 12/26/2022]
Abstract
Cell death of retinal pigment epithelium (RPE) is characterized as an essential late-stage phenomenon of dry age-related macular degeneration (AMD). The aim of this study was to elucidate the molecular mechanism underlying RPE cell death after exposure to oxidative stress, which occurs often because of the anatomical location of RPE cells. ARPE-19, an established RPE cell line, exhibited necrotic features involving poly (ADP-ribose) polymerase-1 (PARP-1) activation in response to hydrogen peroxide (H2O2). ARPE-19 cells were resistant to H2O2 when PARP-1 was depleted using siRNA or inhibited by a pharmacological inhibitor of PARP-1, olaparib. Our data suggest a causal relationship between PARP-1 activation and ARPE-19 cell death in response to H2O2. Next, we investigated downstream molecular events in PARP-1 activation. Increased mitochondrial depolarization, mitochondrial fission and alterations of the cellular energy dynamics with reduced NAD+ and ATP were observed in H2O2-treated ARPE-19 cells. H2O2-triggered mitochondrial dysfunction was inhibited by olaparib. Nevertheless, translocation of apoptosis-inducing factor (AIF), a biochemical signature for PARP-1-dependent cell death (parthanatos), was not observed in our study. Moreover, the depletion of AIF did not affect the amplitude of cell death, demonstrating the lack of a role for AIF in the death of ARPE-19 cells in response to H2O2. This feature distinguishes the type of death observed in this study from canonical parthanatos. Next, we examined the in vivo role of PARP-1 in a dry AMD animal model system. Histological analysis of the outer nuclear layer in the mouse retina revealed protection against sodium iodate (SI) following treatment with olaparib. Moreover, retina fundus and electroretinograms also confirmed such a protective effect in the SI-treated rabbit. Collectively, we report that AIF-independent PARP-1-dependent necrosis constitutes a major mechanism of RPE cell death leading to retinal degeneration in dry AMD.
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Abstract
Sodium Iodate is an inorganic salt that is intended for use as an oxidizing agent in cosmetics, but no current uses have been reported. It is approved by the European Union for use as a preservative in rinse-off cosmetic products at concentrations no greater than 0.1%. Pure Sodium Iodate is a sufficiently strong oxidizing agent that it presents a fire risk near organic material, and it can react violently with aluminum, arsenic, carbon, copper, hydrogen peroxide, phosphorous, potassium, sulfur, and metal sulfides. Sodium Iodate is toxic to the retina; injection of 10-4 M Sodium Iodate into the vitreous of rabbit eyes inactivated the electroretinogram in 1 day. Acute toxicity studies in mice show that concentrations of 505 mg/kg delivered orally is expected to cause convulsions and death in half the animals. No mutagenic activity was seen in Ames tests. Exposure of repair proficient strains of Escherichia coli to ionizing radiation and Sodium Iodate increased the number of DNA single-strand breaks over those seen with exposure to ionizing radiation alone. Sodium Iodate combined with aflatoxin B1 showed fewer mutations in the Ames test than did aflatoxin alone. These available data were not sufficient to support the safety of Sodium Iodate for use in cosmetic formulations. Additional data were considered necessary to evaluate the safety of this ingredient, including the purpose of use and likely concentration of use in cosmetics; 28-day dermal toxicity data; and animal irritation data as a function of dose. It cannot be concluded that this ingredient is safe for use in cosmetic products until the listed safety data have been obtained and evaluated.
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Bonilha VL, Bell BA, Rayborn ME, Yang X, Kaul C, Grossman GH, Samuels IS, Hollyfield JG, Xie C, Cai H, Shadrach KG. Loss of DJ-1 elicits retinal abnormalities, visual dysfunction, and increased oxidative stress in mice. Exp Eye Res 2015. [PMID: 26215528 DOI: 10.1016/j.exer.2015.07.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
DJ-1/PARK7 mutations or deletions cause autosomal recessive early onset Parkinson's disease (PD). Thus, DJ-1 protein has been extensively studied in brain and neurons. PD patients display visual symptoms; however, the visual symptoms specifically attributed to PD patients carrying DJ-1/PARK7 mutations are not known. In this study, we analyzed the structure and physiology of retinas of 3- and 6-month-old DJ-1 knockout (KO) mice to determine how loss of function of DJ-1 specifically contributes to the phenotypes observed in PD patients. As compared to controls, the DJ-1 KO mice displayed an increase in the amplitude of the scotopic ERG b-wave and cone ERG, while the amplitude of a subset of the dc-ERG components was decreased. The main structural changes in the DJ-1 KO retinas were found in the outer plexiform layer (OPL), photoreceptors and retinal pigment epithelium (RPE), which were observed at 3 months and progressively increased at 6 months. RPE thinning and structural changes within the OPL were observed in the retinas in DJ-1 KO mice. DJ-1 KO retinas also exhibited disorganized outer segments, central decrease in red/green cone opsin staining, decreased labeling of ezrin, broader distribution of ribeye labeling, decreased tyrosine hydroxylase in dopaminergic neurons, and increased 7,8-dihydro-8-oxoguanine-labeled DNA oxidation. Accelerated outer retinal atrophy was observed in DJ-1 KO mice after selective oxidative damage induced by a single tail vein injection of NaIO3, exposing increased susceptibility to oxidative stress. Our data indicate that DJ-1-deficient retinas exhibit signs of morphological abnormalities and physiological dysfunction in association with increased oxidative stress. Degeneration of RPE cells in association with oxidative stress is a key hallmark of age-related macular degeneration (AMD). Therefore, in addition to detailing the visual defects that occur as a result of the absence of DJ-1, our data is also relevant to AMD pathogenesis.
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Affiliation(s)
- Vera L Bonilha
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.
| | - Brent A Bell
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Mary E Rayborn
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Xiaoping Yang
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Charlie Kaul
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Gregory H Grossman
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ivy S Samuels
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA; Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, USA
| | - Joe G Hollyfield
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Chengsong Xie
- Laboratory of Neurogenetics, National Institute on Aging, Bethesda, MD, USA
| | - Huaibin Cai
- Laboratory of Neurogenetics, National Institute on Aging, Bethesda, MD, USA
| | - Karen G Shadrach
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
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Wang J, Iacovelli J, Spencer C, Saint-Geniez M. Direct effect of sodium iodate on neurosensory retina. Invest Ophthalmol Vis Sci 2014; 55:1941-53. [PMID: 24481259 DOI: 10.1167/iovs.13-13075] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
PURPOSE To systematically characterize the effects of NaIO3 on retinal morphology and function. METHODS NaIO3 at 10, 20, or 30 mg/kg was administered by retro-orbital injection into adult C57BL/6J mice. Phenotypic and functional changes of the retina were assessed at 1, 3, 5, and 8 days postinjection by fundus imaging, optical coherence tomography (OCT), ERG, and histology. Direct NaIO3 cytotoxicity on ARPE-19 and 661W cells was quantified using lactate dehydrogenase (LDH) apoptosis assay. Effect of NaIO3 on RPE and photoreceptor gene expression was assessed in vitro and in vivo by quantitative PCR. RESULTS While little to no change was observed in the 10 mg/kg NaIO3-injected group, significant retinal anomalies, such as RPE atrophy and retinal thinning, were observed in both 20 and 30 mg/kg NaIO3-injected groups. Gene expression analysis showed rapid downregulation of RPE-specific genes, increase in heme oxygenase 1 expression, and induction of the ratio of Bax to Bcl-2. Electroretinographic response loss and photoreceptor gene repression preceded gross morphological changes. High NaIO3 toxicity on 661W cells was observed in vitro along with reactive oxygen species (ROS) induction. NaIO3 treatment also disrupted oxidative stress, phototransduction, and apoptosis gene expression in 661W cells. Exposure of ARPE-19 cells to NaIO3 increased expression of neurotrophins and protected photoreceptors from direct NaIO3 cytotoxicity. CONCLUSIONS Systematic characterization of changes associated with NaIO3 injection revealed a large variability in the severity of toxicity induced. Treatment with >20 mg/kg NaIO3 induced visual dysfunction associated with rapid suppression of phototransduction genes and induced oxidative stress in photoreceptors. These results suggest that NaIO3 can directly alter photoreceptor function and survival.
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Affiliation(s)
- Jinmei Wang
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
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The Influence of NaIO3-Induced Retinal Degeneration on Intra-retinal Layer and the Changes of Expression Profile/Morphology of DA-ACs and mRGCS. Mol Neurobiol 2012; 47:241-60. [DOI: 10.1007/s12035-012-8366-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 10/22/2012] [Indexed: 10/27/2022]
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Maeda A, Maeda T, Golczak M, Palczewski K. Retinopathy in mice induced by disrupted all-trans-retinal clearance. J Biol Chem 2008; 283:26684-93. [PMID: 18658157 DOI: 10.1074/jbc.m804505200] [Citation(s) in RCA: 227] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The visual (retinoid) cycle is a fundamental metabolic process in vertebrate retina responsible for production of 11-cis-retinal, the chromophore of rhodopsin and cone pigments. 11-cis-Retinal is bound to opsins, forming visual pigments, and when the resulting visual chromophore 11-cis-retinylidene is photoisomerized to all-trans-retinylidene, all-trans-retinal is released from these receptors. Toxic byproducts of the visual cycle formed from all-trans-retinal often are associated with lipofuscin deposits in the retinal pigmented epithelium (RPE), but it is not clear whether aberrant reactions of the visual cycle participate in RPE atrophy, leading to a rapid onset of retinopathy. Here we report that mice lacking both the ATP-binding cassette transporter 4 (Abca4) and enzyme retinol dehydrogenase 8 (Rdh8), proteins critical for all-trans-retinal clearance from photoreceptors, developed severe RPE/photoreceptor dystrophy at an early age. This phenotype includes lipofuscin, drusen, and basal laminar deposits, Bruch's membrane thickening, and choroidal neovascularization. Importantly, the severity of visual dysfunction and retinopathy was exacerbated by light but attenuated by treatment with retinylamine, a visual cycle inhibitor that slows the flow of all-trans-retinal through the visual cycle. These findings provide direct evidence that aberrant production of toxic condensation byproducts of the visual cycle in mice can lead to rapid, progressive retinal degeneration.
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Affiliation(s)
- Akiko Maeda
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Wang K, Li XX, Jiang YR, Dong JQ. Influential factors of thresholds for electrically evoked potentials elicited by intraorbital electrical stimulation of the optic nerve in rabbit eyes. Vision Res 2007; 47:3012-24. [PMID: 17889923 DOI: 10.1016/j.visres.2007.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 06/29/2007] [Accepted: 08/09/2007] [Indexed: 10/22/2022]
Abstract
Influential factors of electrical thresholds for electrically evoked potentials elicited by intraorbital stimulation of the optic nerve, including stimulation positions of the optic nerve, stimulating electrodes, frequency and duration of electrical pulses and pathological status of the optic nerve, were evaluated in 48 pigmented rabbit eyes. Intravenous injection of sodium iodate was used to induce transneuronal degeneration of the retinal ganglion layer subsequent to photoreceptor death. Two equations were derived to predict electrical thresholds needed to elicit cortical responses.
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Affiliation(s)
- Kai Wang
- People Eye Centre of People's Hospital, Peking University, Xicheng District, Beijing, China
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Baich A, Ziegler M. The effect of sodium iodate and melanin on the formation of glyoxylate. PIGMENT CELL RESEARCH 1992; 5:394-5. [PMID: 1492073 DOI: 10.1111/j.1600-0749.1992.tb00568.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Sodium iodate damages retinal pigment epithelium specifically, but the reason for this specificity is not well understood. The work reported here describes an effect of sodium iodate on melanin, a major component of the retinal pigment epithelium. Sodium iodate increases the ability of melanin to convert glycine to glyoxylate. Almost ten times as much glyoxylate is formed when sodium iodate is present compared to the amount formed with melanin alone, although iodate alone does not convert glycine to glyoxylate. A chemical reaction between sodium iodate and melanin is suggested as a partial explanation of the specificity of iodate toxicity towards retinal pigment epithelium.
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Affiliation(s)
- A Baich
- Biology Department, Southern Illinois University, Edwardsville 62026
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Braekevelt CR. Fine structure of the choriocapillaris, Bruch's membrane and retinal epithelium of the cow. Anat Histol Embryol 1986; 15:205-14. [PMID: 2947517 DOI: 10.1111/j.1439-0264.1986.tb00712.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Braekevelt CR. Fine structure of the choriocapillaris, Bruch's membrane and retinal epithelium in the sheep. ANATOMY AND EMBRYOLOGY 1983; 166:415-25. [PMID: 6869854 DOI: 10.1007/bf00305927] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The fine structure of the choriocapillaris, Bruch's membrane and retinal epithelium was investigated by light and electron microscopy in both the tapetal and non-tapetal fundus of the domestic sheep. The choriocapillaris are heavily fenestrated on the side facing the retina. Overlying the tapetum, the choriocapillaris also displays fenestrae on the choroidal border. Bruch's membrane is pentalaminate throughout the retina and slightly thicker over the tapetal region. In all locations the retinal epithelium consists of a single layer of cells, which vary in height depending upon their location. The epithelial cells are joined laterally by apically located tight junctions and throughout the retina display numerous basal infoldings and apical processes which enclose rod outer segments. The epithelial cell nucleus is large and vesicular. All retinal epithelial cells are rich in smooth endoplasmic reticulum and phagosomes. Although not as abundant, mitochondria, Golgi zones, profiles of rough endoplasmic reticulum and polysomes are also noted in all locations. In non-tapetal areas, melanosomes are numerous whereas over the central tapetum fibrosum they are absent. While lysosomes are present throughout the epithelial layer, over the tapetal area they appear to be more numerous. The absence of melanosomes over a functional tapetum fibrosum is to be expected. The apparent increase in lysosomal numbers in this location may indicate an enhanced shedding of outer segment material over the tapetal region. Although some retinal epithelial cells are modified to accommodate a tapetum lucidum their morphology is basically similar throughout the retina and probably indicates that all regions of the retinal epithelium are capable of the normal functions of this indispensible retinal layer.
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Nilsson SE, Knave B, Persson HE. Changes in ultrastructure and function of the sheep pigment epithelium and retina induced by sodium iodate. III. Delayed effects. Acta Ophthalmol 1977; 55:1027-43. [PMID: 579542 DOI: 10.1111/j.1755-3768.1977.tb05683.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Nilsson SE, Knave B, Persson HE. Changes in ultrastructure and function of the sheep pigment epithelium and retina induced by sodium iodate. II. Early effects. Acta Ophthalmol 1977; 55:1007-26. [PMID: 579541 DOI: 10.1111/j.1755-3768.1977.tb05682.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The present investigation shows that the membrane properties of the sheep pigment epithelial cells were very rapidly and severely affected by sodium iodate, whereas the effects concerning the neuroretina were delayed. The c-wave of the ERG was immediately abolished and replaced by a cornea-negative potential, but the a- and b-waves were preserved for about 80-100 min. Ultrastructurally the plasma membranes (particularly the basal plasma membrane) of the pigment epithelial cells were destroyed or less distinct than normally. The cell organelles were swollen and ruptured. There were indications that the pigment epithelium could no longer participate in the receptor outer segment turnover. The photoreceptor cells were morphologically undamaged, and few or no signs of injury were observed in the inner layers of the retina. The effects upon the neuroretinal functions seen after 80-100 min, consisting of a reduction of alpha- and beta-wave amplitudes, were most likely caused by an inability of the pigment epithelium to maintain in the long run its metabolic and barrier properties. It appears that at an early stage after sodium iodate injection, the present preparation may be useful for the study of the effects on the neuroretina proper of drugs and other agents.
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