1
|
Sinclair AJ, Wang Y, Li D. What Is the Evidence for Dietary-Induced DHA Deficiency in Human Brains? Nutrients 2022; 15:nu15010161. [PMID: 36615819 PMCID: PMC9824463 DOI: 10.3390/nu15010161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/20/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022] Open
Abstract
Docosahexaenoic acid (DHA) is a major constituent of neural and visual membranes and is required for optimal neural and visual function. DHA is derived from food or by endogenous synthesis from α-linolenic acid (ALA), an essential fatty acid. Low blood levels of DHA in some westernised populations have led to speculations that child development disorders and various neurological conditions are associated with sub-optimal neural DHA levels, a proposition which has been supported by the supplement industry. This review searched for evidence of deficiency of DHA in human populations, based on elevated levels of the biochemical marker of n-3 deficiency, docosapentaenoic acid (22:5n-6). Three scenarios/situations were identified for the insufficient supply of DHA, namely in the brain of new-born infants fed with high-linoleic acid (LA), low-ALA formulas, in cord blood of women at birth who were vegetarians and in the milk of women from North Sudan. Twenty post-mortem brain studies from the developed world from adults with various neurological disorders revealed no evidence of raised levels of 22:5n-6, even in the samples with reduced DHA levels compared with control subjects. Human populations most likely at risk of n-3 deficiency are new-born and weanling infants, children and adolescents in areas of dryland agriculture, in famines, or are refugees, however, these populations have rarely been studied. This is an important topic for future research.
Collapse
Affiliation(s)
- Andrew J. Sinclair
- Department of Nutrition, Dietetics and Food, School of Clinical Sciences, Monash University, Notting Hill, VIC 3168, Australia
- Faculty of Health, Deakin University, Burwood, VIC 3152, Australia
- Correspondence: ; Tel.: +61-(0)414-906-341
| | - Yonghua Wang
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China
| | - Duo Li
- Institute of Nutrition & Health, College of Public Health, Qingdao University, Qingdao 266071, China
| |
Collapse
|
2
|
Lewandowski D, Sander CL, Tworak A, Gao F, Xu Q, Skowronska-Krawczyk D. Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life. Prog Retin Eye Res 2021; 89:101037. [PMID: 34971765 PMCID: PMC10361839 DOI: 10.1016/j.preteyeres.2021.101037] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 12/13/2022]
Abstract
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
Collapse
Affiliation(s)
- Dominik Lewandowski
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Christopher L Sander
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Aleksander Tworak
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Fangyuan Gao
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Qianlan Xu
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Dorota Skowronska-Krawczyk
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA.
| |
Collapse
|
3
|
Sander CL, Sears AE, Pinto AF, Choi EH, Kahremany S, Gao F, Salom D, Jin H, Pardon E, Suh S, Dong Z, Steyaert J, Saghatelian A, Skowronska-Krawczyk D, Kiser PD, Palczewski K. Nano-scale resolution of native retinal rod disk membranes reveals differences in lipid composition. J Cell Biol 2021; 220:e202101063. [PMID: 34132745 PMCID: PMC8240855 DOI: 10.1083/jcb.202101063] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/26/2021] [Accepted: 05/18/2021] [Indexed: 02/07/2023] Open
Abstract
Photoreceptors rely on distinct membrane compartments to support their specialized function. Unlike protein localization, identification of critical differences in membrane content has not yet been expanded to lipids, due to the difficulty of isolating domain-specific samples. We have overcome this by using SMA to coimmunopurify membrane proteins and their native lipids from two regions of photoreceptor ROS disks. Each sample's copurified lipids were subjected to untargeted lipidomic and fatty acid analysis. Extensive differences between center (rhodopsin) and rim (ABCA4 and PRPH2/ROM1) samples included a lower PC to PE ratio and increased LC- and VLC-PUFAs in the center relative to the rim region, which was enriched in shorter, saturated FAs. The comparatively few differences between the two rim samples likely reflect specific protein-lipid interactions. High-resolution profiling of the ROS disk lipid composition gives new insights into how intricate membrane structure and protein activity are balanced within the ROS, and provides a model for future studies of other complex cellular structures.
Collapse
Affiliation(s)
- Christopher L. Sander
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Avery E. Sears
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Antonio F.M. Pinto
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA
| | - Elliot H. Choi
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Shirin Kahremany
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Fangyuan Gao
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - David Salom
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Hui Jin
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
| | - Els Pardon
- Vlaams Instituut voor Biotechnologie–Vrije Universiteit Brussel Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Susie Suh
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Zhiqian Dong
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
| | - Jan Steyaert
- Vlaams Instituut voor Biotechnologie–Vrije Universiteit Brussel Center for Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
| | - Alan Saghatelian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA
| | - Dorota Skowronska-Krawczyk
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
| | - Philip D. Kiser
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
- Research Service, VA Long Beach Healthcare System, Long Beach, CA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
- Department of Chemistry, University of California, Irvine, Irvine, CA
| |
Collapse
|
4
|
Yan H, Liu Q, Shen X, Liu W, Cui X, Hu P, Yuan Z, Zhang L, Song C, Liu L, Liu Y. Effects of different light conditions on the retinal microstructure and ultrastructure of Dicentrarchus labrax larvae. FISH PHYSIOLOGY AND BIOCHEMISTRY 2020; 46:613-628. [PMID: 31797174 DOI: 10.1007/s10695-019-00735-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 11/12/2019] [Indexed: 06/10/2023]
Abstract
Light is a key environmental parameter known to influence fish throughout various stages of their life, from embryonic development to sexually mature adults. In a recent study, the effects of different light conditions on the growth of Dicentrarchus labrax larvae were investigated using light-emitting diodes (LEDs) as a light source. Here, pathological examinations were carried out to assess whether variations in light affected the visual system of the larvae, including any negative impacts on the retina or the growth rate. Although light did not affect the total thickness (TT) of the retina, the thickness of the retinal pigment epithelium layer (PRE), photoreceptor layer (PRos/is), outer nuclear layer (ONL), and inner nuclear layer (INL), and the PRE/TT and ONL/TT ratios were all significantly higher in larvae exposed to blue light than in larvae exposed to white light. Additionally, the thickness of PRE and the outer nuclear layer and the RPE/TT and ONL/TT ratios of larvae exposed to 2.0 W m-2 were significantly lower than in larvae exposed to 0.3 W m-2. By contrast, the INL/TT ratio in larvae exposed to 2.0 W m-2 was significantly higher than in larvae exposed to 0.3 W m-2. Additionally, the INL and ganglion cell layer nuclei density of larvae exposed to 2.0 W m-2 were significantly higher than in those exposed to 0.3 W m-2 (p < 0.05). Transmission electron microscopy revealed different levels of abnormalities in the photoreceptor layers in all treatment groups. Considering the growth of the larvae, the results of the study suggest that continuous LED exposure induced damage to photoreceptor cells but was not relevant to the growth performance of D. labrax larvae. Moreover, the results obtained here also support the high plasticity of retinal development in response to altered environmental light conditions.
Collapse
Affiliation(s)
- Hongwei Yan
- College of Fisheries and life Science, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Qi Liu
- College of Marine Science and Environment Engineering, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Xufang Shen
- College of Fisheries and life Science, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Wenlei Liu
- College of Marine Science and Environment Engineering, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Xin Cui
- College of Fisheries and life Science, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Pengfei Hu
- College of Marine Science and Environment Engineering, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Zhen Yuan
- College of Fisheries and life Science, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Lei Zhang
- College of Marine Science and Environment Engineering, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China
| | - Changbin Song
- Institute of Semiconductors, Chinese Academy of Sciences, No.35, Qinghua East Road, Haidian District, Beijing, 10083, China
| | - Lili Liu
- Institute of Semiconductors, Chinese Academy of Sciences, No.35, Qinghua East Road, Haidian District, Beijing, 10083, China
| | - Ying Liu
- College of Marine Science and Environment Engineering, Dalian Ocean University, No. 52 Heishijiao Street, Shahekou District, Dalian, 116023, China.
| |
Collapse
|
5
|
Skowronska-Krawczyk D, Budin I. Aging membranes: Unexplored functions for lipids in the lifespan of the central nervous system. Exp Gerontol 2019; 131:110817. [PMID: 31862420 DOI: 10.1016/j.exger.2019.110817] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/11/2019] [Accepted: 12/16/2019] [Indexed: 10/25/2022]
Abstract
Lipids constitute a significant group of biological metabolites and the building blocks of all cell membranes. The abundance and stoichiometries of different lipid species are known to vary across the lifespan and metabolic state, yet the functional effects of these changes have been challenging to understand. Here we review the potentially powerful intersection of lipid metabolism, which determines membrane composition, and aging. We first introduce several key lipid classes that are associated with aging and aging-related disease, where they are found in organisms, and how they act on membrane structure and function. Instead of neutral lipids, which have primary roles in energy storage and homeostasis, we review known functions for polar lipids that control the physicochemical properties of cell membranes. We then focus on aging processes in the central nervous system (CNS), which is enriched in lipids and is highly dependent on membrane structure for function. Recent studies show how lipids act not just as biomarkers of aging and associated changes in the CNS, but as direct mediators of these processes. As a model system, we explore how fatty acid composition in the retina impact aging and aging-related disease. We propose that the biophysical effects of membrane structure on fundamental eukaryotic processes - mitochondrial respiration and autophagy - provide avenues by which lipid dysregulation can accelerate aging processes. Finally, we lay out ways in which an increased understanding of lipid membrane biology can be applied to studies of aging and lifespan.
Collapse
Affiliation(s)
- Dorota Skowronska-Krawczyk
- Viterbi Family Department of Ophthalmology, School do Medicine, University of California San Diego, La Jolla, CA 92093, USA.
| | - Itay Budin
- Department of Chemistry & Biochemistry, University of California San Diego, La Jolla, CA 92093, USA.
| |
Collapse
|
6
|
Baksheeva VE, Gancharova OS, Tiulina VV, Iomdina EN, Zamyatnin AA, Philippov PP, Zernii EY, Senin II. Iatrogenic Damage of Eye Tissues: Current Problems and Possible Solutions. BIOCHEMISTRY (MOSCOW) 2019; 83:1563-1574. [PMID: 30878031 DOI: 10.1134/s0006297918120143] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Visual system is at high risk of iatrogenic damage. Laser ocular surgery, the use of powerful illumination devices in diagnostics and surgical treatment of eye diseases, as well as long surgeries under general anesthesia provoke the development of chronic degenerative changes in eye tissues, primarily in the cornea and the retina. Despite the existence of approaches for prevention and treatment of these complications, the efficacy of these approaches is often limited. Here, we review the mechanisms of iatrogenic damage to eye tissues at the cellular and biochemical levels. It is well recognized that oxidative stress is one of the main factors hindering regeneration of eye tissues after injuries and, thereby, aggravating iatrogenic eye disorders. It is accompanied by the downregulation of low-molecular-weight antioxidants and antioxidant enzymes, as well as changes in the expression and redox status of proteins in the damaged tissue. In this regard, antioxidant therapy, in particular, the use of highly effective mitochondria-targeted antioxidants such as SkQ1, is considered as a promising approach to the prevention of iatrogenesis. Recent findings indicate that the most efficient protection of eye tissues from the iatrogenic injury is achieved by preventive use of these antioxidants. In addition to preventing corneal and retinal cell death induced by oxidative stress, SkQ1 contributes to the restoration of innate antioxidant defense of these tissues and suppresses local inflammatory response. Since the timing of routine medical manipulations is usually known in advance, iatrogenic damage to the ocular tissues can be successfully prevented using mitochondria-targeted therapy.
Collapse
Affiliation(s)
- V E Baksheeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - O S Gancharova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - V V Tiulina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - E N Iomdina
- Moscow Helmholtz Research Institute of Eye Diseases, Moscow, 105062, Russia
| | - A A Zamyatnin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.,Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow, 119991, Russia
| | - P P Philippov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - E Yu Zernii
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia. .,Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow, 119991, Russia
| | - I I Senin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.
| |
Collapse
|
7
|
van Leeuwen EM, Emri E, Merle BMJ, Colijn JM, Kersten E, Cougnard-Gregoire A, Dammeier S, Meester-Smoor M, Pool FM, de Jong EK, Delcourt C, Rodrigez-Bocanegra E, Biarnés M, Luthert PJ, Ueffing M, Klaver CCW, Nogoceke E, den Hollander AI, Lengyel I. A new perspective on lipid research in age-related macular degeneration. Prog Retin Eye Res 2018; 67:56-86. [PMID: 29729972 DOI: 10.1016/j.preteyeres.2018.04.006] [Citation(s) in RCA: 148] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 04/25/2018] [Accepted: 04/30/2018] [Indexed: 12/15/2022]
Abstract
There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.
Collapse
Affiliation(s)
- Elisabeth M van Leeuwen
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Eszter Emri
- Centre for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom
| | - Benedicte M J Merle
- Univ. Bordeaux, Inserm, Bordeaux Population Health Research Center, Team LEHA, UMR 1219, F-33000, Bordeaux, France
| | - Johanna M Colijn
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Eveline Kersten
- Department of Ophthalmology, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands
| | - Audrey Cougnard-Gregoire
- Univ. Bordeaux, Inserm, Bordeaux Population Health Research Center, Team LEHA, UMR 1219, F-33000, Bordeaux, France
| | - Sascha Dammeier
- Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Germany
| | - Magda Meester-Smoor
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Eiko K de Jong
- Department of Ophthalmology, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands
| | - Cécile Delcourt
- Univ. Bordeaux, Inserm, Bordeaux Population Health Research Center, Team LEHA, UMR 1219, F-33000, Bordeaux, France
| | | | | | | | - Marius Ueffing
- Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Germany
| | - Caroline C W Klaver
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands
| | - Everson Nogoceke
- Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Anneke I den Hollander
- Department of Ophthalmology, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands; Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Imre Lengyel
- Centre for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom.
| |
Collapse
|
8
|
Káldi I, Berta A. Progesterone Administration Fails to Protect Albino Male Rats against Photostress-Induced Retinal Degeneration. Eur J Ophthalmol 2018; 14:306-14. [PMID: 15309975 DOI: 10.1177/112067210401400405] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Female patients show better recovery after brain injury and lower incidence of vascular diseases before menopause. The aim of this study was to test the protective effect of female sexual hormones against photostress-induced photoreceptor apoptosis. METHODS Five week old male albino Sprague-Dawley rats were injected intraperitoneally with progesterone (60 mg/kg body weight) for 4 days. The control group was injected with the vehicle only (benzyl alcohol). Both groups were halved and one was stressed with light (2700 lux for 24 hours) and the other remained under the original dim cyclic light condition. For functional evaluation, baseline electroretinograms (ERGs) were recorded 7 days before light stress, with follow-up ERGs 5 days after the cessation of light exposure. Animals were sacrificed and their eyes enucleated for histology. RESULTS Light exposure caused pronounced decrease in the ERG a- and b-wave amplitudes compared to controls. However, in the light-stressed group, the difference in retinal function between progesterone-treated and nontreated animals was not statistically significant. The thickness of the outer nuclear layer and the length of rod outer and inner segments were significantly reduced in the light-stressed group, indicating loss of rod photoreceptor cells. Progesterone had no neuroprotective effect on rod cell structure. CONCLUSIONS The administration of progesterone did not prove to be protective against excessive light-caused retinal degeneration on male albino rats. The role of other sexual steroids and their interaction need to be clarified.
Collapse
Affiliation(s)
- I Káldi
- Department of Ophthalmology, Kenézy Hospital, Debrecen, Hungary.
| | | |
Collapse
|
9
|
Song H, Vijayasarathy C, Zeng Y, Marangoni D, Bush RA, Wu Z, Sieving PA. NADPH Oxidase Contributes to Photoreceptor Degeneration in Constitutively Active RAC1 Mice. Invest Ophthalmol Vis Sci 2017; 57:2864-75. [PMID: 27233035 PMCID: PMC5113981 DOI: 10.1167/iovs.15-18974] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Purpose The active form of small GTPase RAC1 is required for activation of NADPH oxidase (NOX), which in turn generates reactive oxygen species (ROS) in nonphagocytic cells. We explored whether NOX-induced oxidative stress contributes to rod degeneration in retinas expressing constitutively active (CA) RAC1. Methods Transgenic (Tg)–CA-RAC1 mice were given apocynin (10 mg/kg, intraperitoneal), a NOX inhibitor, or vehicle daily for up to 13 weeks. Superoxide production and oxidative damage were assessed by dihydroethidium staining and by protein carbonyls and malondialdehyde levels, respectively. Outer nuclear layer (ONL) cells were counted and electroretinogram (ERG) amplitudes measured in Tg-CA-RAC1 mice. Outer nuclear layer cells were counted in wild-type (WT) mice after transfer of CA-Rac1 gene by subretinal injection of AAV8-pOpsin-CA Rac1-GFP. Results Transgenic-CA-RAC1 retinas had significantly fewer photoreceptor cells and more apoptotic ONL cells than WT controls from postnatal week (Pw) 3 to Pw13. Superoxide accumulation and protein and lipid oxidation were increased in Tg-CA-RAC1 retinas and were reduced in mice treated with apocynin. Apocynin reduced the loss of photoreceptors and increased the rod ERG a- and b-wave amplitudes when compared with vehicle-injected transgenic controls. Photoreceptor loss was also observed in regions of adult WT retina transduced with AAV8-pOpsin-CA Rac1-GFP but not in neighboring regions that were not transduced or in AAV8-pOpsin-GFP–transduced retinas. Conclusions Constitutively active RAC1 promotes photoreceptor cell death by oxidative damage that occurs, at least partially, through NOX-induced ROS. Reactive oxygen species are likely involved in multiple forms of retinal degenerations, and our results support investigating RAC1 inhibition as a therapeutic approach that targets this disease pathway.
Collapse
Affiliation(s)
- Hongman Song
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States
| | - Camasamudram Vijayasarathy
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States
| | - Yong Zeng
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States
| | - Dario Marangoni
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States
| | - Ronald A Bush
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States
| | - Zhijian Wu
- Ocular Gene Therapy Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Paul A Sieving
- Section for Translational Research on Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, United States 3National Eye Institute, National Institutes of Heal
| |
Collapse
|
10
|
Marquioni-Ramella MD, Suburo AM. Photo-damage, photo-protection and age-related macular degeneration. Photochem Photobiol Sci 2015. [DOI: 10.1039/c5pp00188a] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The course of Age-related Macular Degeneration (AMD) is described as the effect of light (400–580 nm) on various molecular targets in photoreceptors and the retinal pigment epithelium (RPE). Photo-damage is followed by inflammation, increasing oxidative stress and, probably, unveiling new photosensitive molecules.
Collapse
Affiliation(s)
| | - Angela M. Suburo
- Medicina Celular y Molecular
- Facultad de Ciencias Biomédicas
- Universidad Austral
- Pilar B1629AHJ
- Argentina
| |
Collapse
|
11
|
Wu L, Ueda K, Nagasaki T, Sparrow JR. Light damage in Abca4 and Rpe65rd12 mice. Invest Ophthalmol Vis Sci 2014; 55:1910-8. [PMID: 24576873 DOI: 10.1167/iovs.14-13867] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PURPOSE Bisretinoids form in photoreceptor cells and accumulate in retinal pigment epithelium (RPE) as lipofuscin. To examine the role of these fluorophores as mediators of retinal light damage, we studied the propensity for light damage in mutant mice having elevated lipofuscin due to deficiency in the ATP-binding cassette (ABC) transporter Abca4 (Abca4(-/-) mice) and in mice devoid of lipofuscin owing to absence of Rpe65 (Rpe65(rd12)). METHODS Abca4(-/-), Rpe65(rd12), and wild-type mice were exposed to 430-nm light to produce a localized lesion in the superior hemisphere of retina. Bisretinoids of RPE lipofuscin were measured by HPLC. In histologic sections, outer nuclear layer (ONL) thickness was measured as an indicator of photoreceptor cell degeneration, and RPE nuclei were counted. RESULTS As shown previously, A2E levels were increased in Abca4(-/-) mice. These mice also sustained light damage-associated ONL thinning that was more pronounced than in age-matched wild-type mice; the ONL thinning was also greater in 5-month versus 2-month-old mice. Numbers of RPE nuclei were reduced in light-stressed mice, with the reduction being greater in the Abca4(-/-) than wild-type mice. In Rpe65(rd12) mice bisretinoid compounds of RPE lipofuscin were not detected chromatographically and light damage-associated ONL thinning was not observed. CONCLUSIONS Abca4(-/-) mice that accumulate RPE lipofuscin at increased levels were more susceptible to retinal light damage than wild-type mice. This finding, together with results showing that Rpe65(rd12) mice did not accumulate lipofuscin and did not sustain retinal light damage, indicates that the bisretinoids of retinal lipofuscin are contributors to retinal light damage.
Collapse
Affiliation(s)
- Li Wu
- Department of Ophthalmology, Columbia University, New York, New York
| | | | | | | |
Collapse
|
12
|
Tokarz P, Kaarniranta K, Blasiak J. Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD). Biogerontology 2013; 14:461-82. [PMID: 24057278 PMCID: PMC3824279 DOI: 10.1007/s10522-013-9463-2] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 09/03/2013] [Indexed: 12/20/2022]
Abstract
Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.
Collapse
Affiliation(s)
- Paulina Tokarz
- Department of Molecular Genetics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236, Lodz, Poland,
| | | | | |
Collapse
|
13
|
Cachafeiro M, Bemelmans AP, Samardzija M, Afanasieva T, Pournaras JA, Grimm C, Kostic C, Philippe S, Wenzel A, Arsenijevic Y. Hyperactivation of retina by light in mice leads to photoreceptor cell death mediated by VEGF and retinal pigment epithelium permeability. Cell Death Dis 2013; 4:e781. [PMID: 23990021 PMCID: PMC3763463 DOI: 10.1038/cddis.2013.303] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/22/2013] [Accepted: 06/17/2013] [Indexed: 11/29/2022]
Abstract
Light toxicity is suspected to enhance certain retinal degenerative processes such as age-related macular degeneration. Death of photoreceptors can be induced by their exposure to the visible light, and although cellular processes within photoreceptors have been characterized extensively, the role of the retinal pigment epithelium (RPE) in this model is less well understood. We demonstrate that exposition to intense light causes the immediate breakdown of the outer blood–retinal barrier (BRB). In a molecular level, we observed the slackening of adherens junctions tying up the RPE and massive leakage of albumin into the neural retina. Retinal pigment epithelial cells normally secrete vascular endothelial growth factor (VEGF) at their basolateral side; light damage in contrast leads to VEGF increase on the apical side – that is, in the neuroretina. Blocking VEGF, by means of lentiviral gene transfer to express an anti-VEGF antibody in RPE cells, inhibits outer BRB breakdown and retinal degeneration, as illustrated by functional, behavioral and morphometric analysis. Our data show that exposure to high levels of visible light induces hyperpermeability of the RPE, likely involving VEGF signaling. The resulting retinal edema contributes to irreversible damage to photoreceptors. These data suggest that anti-VEGF compounds are of therapeutic interest when the outer BRB is altered by retinal stresses.
Collapse
Affiliation(s)
- M Cachafeiro
- Unit of Gene Therapy & Stem Cell Biology, Jules-Gonin Eye Hospital, University of Lausanne, Lausanne, Switzerland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Falsini B, Bush RA, Sieving PA. Neuroprotection. Retina 2013. [DOI: 10.1016/b978-1-4557-0737-9.00037-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
15
|
Cellini M, Gattegna R, Toschi PG, Strobbe E, Campos EC. Multifocal electroretinogram and Optical Coherence tomography spectral-domain in arc welding macular injury: a case report. BMC Ophthalmol 2011; 11:40. [PMID: 22208163 PMCID: PMC3274443 DOI: 10.1186/1471-2415-11-40] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 12/30/2011] [Indexed: 11/14/2022] Open
Abstract
Background the purpose of this study was to report a binocular photic retinal injury induced by plasma arc welding and the follow-up after treatment with vitamin supplements for a month. In our study, we used different diagnostic tools such as fluorescein angiography (FA), optical coherence tomography (OCT) and multifocal electroretinogram (mfERG). Case presentation in the first visit after five days from arc welding injury in the left eye (LE) the visual acuity was 0.9 and 1.0 in the right eye (RE). FA was normal in both eyes. OCT in the left eye showed normal profile and normal reflectivity and one month later, a hyperreflectivity appeared in the external limiting membrane (ELM). The mfERG signal in the LE was 102.30 nV/deg2 five days after the injury and 112.62 nV/deg2 after one month and in the RE respectively 142.70 nV/deg2 and 159.46 nV/deg2. Conclusions in cases of retinal photo injury it is important for the ophthalmologist to evaluate tests such as OCT and the mfERG in the diagnosis and follow-up of the patient because the recovery of visual acuity cannot exclude the persistence of phototoxic damage charged to the complex inner-outer segment of photoreceptors.
Collapse
Affiliation(s)
- Mauro Cellini
- Department of Specialistic Surgery and Anesthesiology Science, University Ophthalmology Unit, S Orsola Malpighi-Hospital, Pelagio Palagi 9, Bologna 40138, Italy.
| | | | | | | | | |
Collapse
|
16
|
Abstract
Over the last decade, several epidemiological studies based on food frequency questionnaires suggest that omega-3 polyunsaturated fatty acids could have a protective role in reducing the onset and progression of retinal diseases. The retina has a high concentration of omega-3, particularly DHA, which optimizes fluidity of photoreceptor membranes, retinal integrity, and visual function. Furthermore, many studies demonstrated that DHA has a protective, for example antiapoptotic, role in the retina. From a nutritional point of view, it is known that western populations, particularly aged individuals, have a higher than optimal omega-6/omega-3 ratio and should enrich their diet with more fish consumption or have DHA supplementation. This paper underscores the potential beneficial effect of omega-3 fatty acids on retinal diseases.
Collapse
|
17
|
Tanito M, Brush RS, Elliott MH, Wicker LD, Henry KR, Anderson RE. Correlation between tissue docosahexaenoic acid levels and susceptibility to light-induced retinal degeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 664:567-73. [PMID: 20238060 DOI: 10.1007/978-1-4419-1399-9_65] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
In a mouse model of acute light-induced retinal degeneration, positive correlations between the levels of DHA, the levels of n3 PUFA lipid peroxidation, and the vulnerability to photooxidative stress were observed. On the other hand, higher sensitivity of the electroretinogram a-wave response, a measure of the amplification of the phototransduction cascade, was correlated with higher retinal DHA levels. These results highlight the dual roles of DHA in cellular physiology and pathology.
Collapse
Affiliation(s)
- Masaki Tanito
- Department of Ophthalmology, Shimane University Faculty of Medicine, Shimane, Japan.
| | | | | | | | | | | |
Collapse
|
18
|
Simon E, Bardet B, Grégoire S, Acar N, Bron AM, Creuzot-Garcher CP, Bretillon L. Decreasing dietary linoleic acid promotes long chain omega-3 fatty acid incorporation into rat retina and modifies gene expression. Exp Eye Res 2011; 93:628-35. [PMID: 21821023 DOI: 10.1016/j.exer.2011.07.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 07/16/2011] [Accepted: 07/26/2011] [Indexed: 10/17/2022]
Abstract
Age-related macular degeneration (AMD) may be partially prevented by dietary habits privileging the consumption of ω3 long chain polyunsaturated fatty acids (ω3s) while lowering linoleic acid (LA) intake. The present study aimed to document whether following these epidemiological guidelines would enrich the neurosensory retina and RPE with ω3s and modulate gene expression in the neurosensory retina. Rat progenitors and pups were fed with diets containing low or high LA, and low or high ω3s. After scotopic single flash and 8-Hz-Flicker electroretinography, rat pups were euthanized at adulthood. The fatty acid profile of the neurosensory retina, RPE, liver, adipose tissue and plasma was analyzed using gas chromatography. Gene expression was analyzed with real-time PCR in the neurosensory retina. Diets rich in ω3s efficiently improved the incorporation of ω3s into the organs and tissues. This raising effect was magnified by lowering LA intake. Compared to a diet with high LA and low ω3s, low LA diets significantly upregulated LDL-receptor gene expression. Similar but not significant upregulation of CD36, ABCA1, ALOX5 and ALOX12 gene expression was observed in rats fed with low LA. No effect was observed on retinal function. Increasing the intake in ω3s and lowering LA improved the enrichment with ω3s of the tissues, including the neurosensory retina and RPE, and upregulated genes involved in lipid trafficking in the neurosensory retina. Those results consistently reinforced the beneficial role of ω3s in the prevention of AMD, especially when the diet contained low levels of LA, as suggested from epidemiological data.
Collapse
Affiliation(s)
- Emilie Simon
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, UMR 1324 INRA, 6265 CNRS, University of Burgundy, Dijon, France
| | | | | | | | | | | | | |
Collapse
|
19
|
Barker FM, Snodderly DM, Johnson EJ, Schalch W, Koepcke W, Gerss J, Neuringer M. Nutritional manipulation of primate retinas, V: effects of lutein, zeaxanthin, and n-3 fatty acids on retinal sensitivity to blue-light-induced damage. Invest Ophthalmol Vis Sci 2011; 52:3934-42. [PMID: 21245404 DOI: 10.1167/iovs.10-5898] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
PURPOSE Blue-light photooxidative damage has been implicated in the etiology of age-related macular degeneration (AMD). The macular pigment xanthophylls lutein (L) and zeaxanthin (Z) and n-3 fatty acids may reduce this damage and lower the risk of AMD. This study investigated the effects of the lifelong absence of xanthophylls followed by L or Z supplementation, combined with the effects of n-3 fatty acid deficiency, on acute blue-light photochemical damage. METHODS Subjects included eight rhesus monkeys with no lifelong intake of xanthophylls and no detectable macular pigment. Of these, four had low n-3 fatty acid intake and four had adequate intakes. Control subjects had typical L, Z, and n-3 fatty acid intake. Retinas received 150-μm-diameter exposures of low-power 476-nm laser light at 0.5 mm (∼2°) eccentricity, which is adjacent to the macular pigment peak, and parafoveally at 1.5 mm (∼6°). Exposures of xanthophyll-free animals were repeated after supplementation with pure L or Z for 22 to 28 weeks. Ophthalmoscopically visible lesion areas were plotted as a function of exposure energy, with greater slopes of the regression lines indicating greater sensitivity to damage. RESULTS In control animals, the fovea was less sensitive to blue-light-induced damage than the parafovea. Foveal protection was absent in xanthophyll-free animals but was evident after supplementation. In the parafovea, animals low in n-3 fatty acids showed greater sensitivity to damage than animals with adequate levels. CONCLUSIONS After long-term xanthophyll deficiency, L or Z supplementation protected the fovea from blue light-induced damage, whereas adequate n-3 fatty acid levels reduced the damage in the parafovea.
Collapse
Affiliation(s)
- Felix M Barker
- Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Brenna JT. Animal studies of the functional consequences of suboptimal polyunsaturated fatty acid status during pregnancy, lactation and early post-natal life. MATERNAL AND CHILD NUTRITION 2011; 7 Suppl 2:59-79. [PMID: 21366867 DOI: 10.1111/j.1740-8709.2011.00301.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Scores of animal studies demonstrate that seed oils replete with linoleic acid and very low in linolenic acid fed as the exclusive source of fat through pregnancy and lactation result in visual, cognitive, and behavioural deficits in the offspring. Commodity peanut, sunflower, and safflower oils fed to mother rats, guinea pigs, rhesus monkeys, and baboons induce predictable changes in tissue polyunsaturated fatty acid composition that are abnormal in free-living land mammals as well as changes in neurotransmitter levels, catecholamines, and signalling compounds compared with animals with a supply of ω3 polyunsaturated fatty acid. These diets consistently induce functional deficits in electroretinograms, reflex responses, reward or avoidance induced learning, maze learning, behaviour, and motor development compared with ω3 replete groups. Boosting neural tissue docosahexaenoic acid (DHA) by feeding preformed DHA enhances visual and cognitive function. Though no human randomized controlled trials on minimal ω3 requirements in pregnancy and lactation have been conducted, the weight of animal evidence compellingly shows that randomizing pregnant or lactating humans to diets that include high linoleate oils as the sole source of fat would be frankly unethical because they would result in suboptimal child development. Increasing use of commodity ω3-deficient oils in developing countries, many in the name of heart health, will limit brain development of the next generation and can be easily corrected at minimal expense by substituting high oleic acid versions of these same oils, in many cases blended with small amounts of α-linolenic acid oils like flax or perilla oil. Inclusion of DHA in these diets is likely to further enhance visual and neural development.
Collapse
Affiliation(s)
- J Thomas Brenna
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
| |
Collapse
|
21
|
Abstract
The ability of light to enact damage on the neurosensory retina and underlying structures has been well understood for hundreds of years. While the eye has adapted several mechanisms to protect itself from such damage, certain exposures to light can still result in temporal or permanent damage. Both clinical observations and laboratory studies have enabled us to understand the various ways by which the eye can protect itself from such damage. Light or electromagnetic radiation can result in damage through photothermal, photomechanical, and photochemical mechanisms. The following review seeks to describe these various processes of injury and many of the variables, which can mitigate these modes of injury.
Collapse
Affiliation(s)
- P N Youssef
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Science, Madison, WI 53792, USA.
| | | | | |
Collapse
|
22
|
Abstract
By its action on rhodopsin, light triggers the well-known visual transduction cascade, but can also induce cell damage and death through phototoxic mechanisms - a comprehensive understanding of which is still elusive despite more than 40 years of research. Herein, we integrate recent experimental findings to address several hypotheses of retinal light damage, premised in part on the close anatomical and metabolic relationships between the photoreceptors and the retinal pigment epithelium. We begin by reviewing the salient features of light damage, recently joined by evidence for retinal remodeling which has implications for the prognosis of recovery of function in retinal degenerations. We then consider select factors that influence the progression of the damage process and the extent of visual cell loss. Traditional, genetically modified, and emerging animal models are discussed, with particular emphasis on cone visual cells. Exogenous and endogenous retinal protective factors are explored, with implications for light damage mechanisms and some suggested avenues for future research. Synergies are known to exist between our long term light environment and photoreceptor cell death in retinal disease. Understanding the molecular mechanisms of light damage in a variety of animal models can provide valuable insights into the effects of light in clinical disorders and may form the basis of future therapies to prevent or delay visual cell loss.
Collapse
|
23
|
Giusto NM, Pasquaré SJ, Salvador GA, Ilincheta de Boschero MG. Lipid second messengers and related enzymes in vertebrate rod outer segments. J Lipid Res 2009; 51:685-700. [PMID: 19828910 DOI: 10.1194/jlr.r001891] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Rod outer segments (ROSs) are specialized light-sensitive organelles in vertebrate photoreceptor cells. Lipids in ROS are of considerable importance, not only in providing an adequate environment for efficient phototransduction, but also in originating the second messengers involved in signal transduction. ROSs have the ability to adapt the sensitivity and speed of their responses to ever-changing conditions of ambient illumination. A major contributor to this adaptation is the light-driven translocation of key signaling proteins into and out of ROS. The present review shows how generation of the second lipid messengers from phosphatidylcholine, phosphatidic acid, and diacylglycerol is modulated by the different illumination states in the vertebrate retina. Findings suggest that the light-induced translocation of phototransduction proteins influences the enzymatic activities of phospholipase D, lipid phosphate phosphatase, diacylglyceride lipase, and diacylglyceride kinase, all of which are responsible for the generation of the second messenger molecules.
Collapse
Affiliation(s)
- Norma M Giusto
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina.
| | | | | | | |
Collapse
|
24
|
Schmitz-Valckenberg S, Guo L, Cheung W, Moss S, Fitzke F, Cordeiro M. In-vivo-Imaging retinaler Zellapoptose nach akuter Lichtexposition. Ophthalmologe 2009; 107:22-9. [DOI: 10.1007/s00347-009-1952-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
25
|
Depleting Rac1 in mouse rod photoreceptors protects them from photo-oxidative stress without affecting their structure or function. Proc Natl Acad Sci U S A 2009; 106:9397-402. [PMID: 19470639 DOI: 10.1073/pnas.0808940106] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In nonphagocytic cells, Rac1 is a component of NADPH oxidase that produces reactive oxygen species [Ushio-Fukai M (2006) Sci STKE 2006:re8]. Rac1 is expressed abundantly in mammalian retinal photoreceptors, where it is activated in response to light stimuli [Balasubramanian N, Slepak VZ (2003) Curr Biol 13:1306-1310]. We used Cre-LoxP conditional gene targeting to knock down Rac1 expression in mouse rod photoreceptors and found protection against light-induced photoreceptor death compared with WT litter-mates. We also found a similar protective effect on rods using apocynin, which inhibits NADPH oxidase activity. These results implicate both neuronal Rac1 and NADPH oxidase in cell death in this model of CNS degeneration. Studies in which dominant-mutants of Rac1 were expressed in transgenic Drosophila species demonstrated that Rac1 is a key regulator of photoreceptor morphogenesis and polarity [Chang HY, Ready DF (2000) Science 290:1978-1980]. However, we found that diminished Rac1 expression in mouse rods had no effect on retinal structure or function examined by light microscopy, electron microscopy, rhodopsin measurement, electroretinogram activity, and visual acuity, indicating rod outer segment morphogenesis proceeded normally in Rac1 conditional knockout mice. The lack of structural or functional effect of Rac1 depletion on photoreceptors, but protection under conditions of stress, indicate that the Rac1 pathway warrants exploration as a target for therapy in retinal neurodegenerative diseases.
Collapse
|
26
|
Tanito M, Brush RS, Elliott MH, Wicker LD, Henry KR, Anderson RE. High levels of retinal membrane docosahexaenoic acid increase susceptibility to stress-induced degeneration. J Lipid Res 2008; 50:807-19. [PMID: 19023138 DOI: 10.1194/jlr.m800170-jlr200] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fat-1 gene cloned from C. elegans encodes an n-3 fatty acid desaturase that converts n-6 to n-3 PUFA. Mice carrying the fat-1 transgene and wild-type controls were fed an n-3-deficient/n-6-enriched diet [fat-1- safflower oil (SFO) and wt-SFO, respectively]. Fatty acid profiles of rod outer segments (ROS), cerebellum, plasma, and liver demonstrated significantly lower n-6/n-3 ratios and higher docosahexaenoic acid (DHA) levels in fat-1-SFO compared with wt-SFO. When mice were exposed to light stress: 1) the outer nuclear layer (ONL) thickness was reduced; 2) amplitudes of the electroretinogram (ERG) were lower; 3) the number of apoptotic photoreceptor cells was greater; and 4) modification of retinal proteins by 4-hydroxyhexenal (4-HHE), an end-product of n-3 PUFA oxidation was increased in both fat-1-SFO and wt mice fed a regular lab chow diet compared with wt-SFO. The results indicate a positive correlation between the level of DHA, the degree of n-3 PUFA lipid peroxidation, and the vulnerability of the retina to photooxidative stress. In mice not exposed to intense light, the reduction in DHA resulted in reduced efficacy in phototransduction gain steps, while no differences in the retinal morphology or retinal biochemistry. These results highlight the dual roles of DHA in cellular physiology and pathology.
Collapse
Affiliation(s)
- Masaki Tanito
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | | | | | | | | | | |
Collapse
|
27
|
Abstract
Visual perception occurs when radiation with a wavelength between 400 and 760 nm reaches the retina. The retina has evolved to capture photons efficiently and initiate visual transduction. The retina, however, is vulnerable to damage by light, a vulnerability that has long been recognized. Photochemical damage has been widely studied, because it can cause retinal damage within the intensity range of natural light. Photochemical lesions are primarily located in the outer layers at the central region of the retina. Two classes of photochemical damage have been recognized: Class I damage, which is characterized by the rhodopsin action spectrum, is believed to be mediated by visual pigments, with the primary lesions located in the photoreceptors; whereas Class II damage is generally confined to the retinal pigment epithelium. The action spectrum peaks in the short wavelength region, providing the basis for the concept of blue light hazard. Several factors can modify the susceptibility of the retina to photochemical damage. Photochemical mechanisms, in particular mechanisms that arise from illumination with blue light, are responsible for solar retinitis and for iatrogenic retinal insult from ophthalmological instruments. Further, blue light may play a role in the pathogenesis of age-related macular degeneration. Laboratory studies have suggested that photochemical damage includes oxidative events. Retinal cells die by apoptosis in response to photic injury, and the process of cell death is operated by diverse damaging mechanisms. Modern molecular biology techniques help to study in-depth the basic mechanism of photochemical damage of the retina and to develop strategies of neuroprotection.
Collapse
Affiliation(s)
- Jiangmei Wu
- Department of Vitreoretinal Diseases, Saint Erik's Eye Hospital and Karolinska Institutet, Stockholm, Sweden
| | | | | |
Collapse
|
28
|
Joly S, Dorfman AL, Chemtob S, Moukhles H, Lachapelle P. Structural and functional consequences of bright light exposure on the retina of neonatal rats. Doc Ophthalmol 2006; 113:93-103. [PMID: 17047908 DOI: 10.1007/s10633-006-9018-9] [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: 06/29/2006] [Accepted: 07/26/2006] [Indexed: 10/24/2022]
Abstract
In a previous study we showed that juvenile rats exposed, for various durations of time, to a bright luminous environment between P14 (eye opening) and P34 developed a light-induced retinopathy (LIR), the severity of which depending on the duration of exposure as well as the age of the rat at the onset of exposure. Our study also revealed that the severity of the LIR increased as the time elapsed between the cessation of exposure and the structural/functional evaluation increased, suggesting that the LIR degenerative process proceeded in two distinct steps namely, an initial (rapid) acute phase that was followed by a (slower) chronic phase. In view of the above, the purpose of the present study was to reinvestigate previous claims suggesting that exposure to bright light prior to eyelid opening had no measurable consequences on the retinal structure and function; the claim being that despite a non-detectable acute phase, bright light exposure prior to eyelid opening could nonetheless yield a significant retinopathy during the chronic phase of development of LIR. In order to test our hypothesis, neonatal rats were raised in a bright luminous environment from birth to P14. At P30, analysis of the results obtained from rats exposed between P0-P14 did not reveal, as previously acknowledged by others, significant LIR damages. However, results obtained at P60 disclosed significant functional anomalies with relative sparing of the retinal ultrastructure. Our results confirm that, in spite of closed eyelids, postnatal exposure to bright environment did trigger a slow degenerative process.
Collapse
Affiliation(s)
- Sandrine Joly
- Department of Biological Sciences, University of Montreal, Montreal, QC, Canada
| | | | | | | | | |
Collapse
|
29
|
Rózanowska M, Sarna T. Light-induced damage to the retina: role of rhodopsin chromophore revisited. Photochem Photobiol 2006; 81:1305-30. [PMID: 16120006 DOI: 10.1562/2004-11-13-ir-371] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The presence of the regenerable visual pigment rhodopsin has been shown to be primarily responsible for the acute photodamage to the retina. The photoexcitation of rhodopsin leads to isomerization of its chromophore 11-cis-retinal to all-trans-retinal (ATR). ATR is a potent photosensitizer and its role in mediating photodamage has been suspected for over two decades. However, there was lack of experimental evidence that free ATR exists in the retina in sufficient concentrations to impose a risk of photosensitized damage. Identification in the retina of a retinal dimer and a pyridinium bisretinoid, so called A2E, and determination of its biosynthetic pathway indicate that substantial amounts of ATR do accumulate in the retina. Both light damage and A2E accumulation are facilitated under conditions where efficient retinoid cycle operates. Efficient retinoid cycle leads to rapid regeneration of rhodopsin, which may result in ATR release from the opsin "exit site" before its enzymatic reduction to all-trans-retinol. Here we discuss photodamage to the retina where ATR could play a role as the main toxic and/or phototoxic agent. Moreover, we discuss secondary products of (photo)toxic properties accumulating within retinal lipofuscin as a result of ATR accumulation.
Collapse
|
30
|
Ren H, Magulike N, Ghebremeskel K, Crawford M. Primary open-angle glaucoma patients have reduced levels of blood docosahexaenoic and eicosapentaenoic acids. Prostaglandins Leukot Essent Fatty Acids 2006; 74:157-63. [PMID: 16410047 DOI: 10.1016/j.plefa.2005.11.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 11/04/2005] [Accepted: 11/24/2005] [Indexed: 10/25/2022]
Abstract
The aetiology of primary open-angle glaucoma (POAG), which is the commonest cause of non-remediable blindness and visual impairment, is not well understood. Nevertheless, increased intraocular pressure, and vascular factors such as ocular blood flow deficits are thought to be risk factors. There is evidence of decreased optic nerve blood velocity and increased red blood cell aggregability in POAG. These factors are influenced by fatty acids. We have investigated if glaucoma patients have abnormal blood fatty acid composition. Patients with POAG (n=10) and their healthy siblings (n=8) were enrolled. Compared with their healthy siblings, the glaucoma patients had reduced eicosapentaenoic (EPA, P<0.01), and docosahexaenoic (DHA, P<0.05) fatty acids and total omega3 long-chain polyunsaturated fatty acids (LCPUFA) (P<0.05) in red cell choline phosphoglycerides (CPG); decreased EPA (P<0.05) in ethanolamine phosphoglycerides (EPG); lower EPA (P<0.05) and total omega3 LCPUFA (P<0.05) in serine phosphoglycerides (SPG). Similarly, they had reduced EPA, DHA and total omega3 LCPUFA in plasma CPG (P<0.005) and triglycerides (P<0.05). These findings may be significant, since EPA and DHA could modulate impaired systemic microcirculation and ocular blood flow and optic neuropathy, which are the main physiological changes associated with glaucoma.
Collapse
Affiliation(s)
- Hongmei Ren
- Institute of Brain Chemistry and Human Nutrition, London Metropolitan University, North Campus, 166-220 Holloway Road, London N7 8DB, UK, and Department of Ophthalmology, University of Nigeria Teaching Hospital, Enugu, Nigeria.
| | | | | | | |
Collapse
|
31
|
Leung IYF, Sandstrom MM, Zucker CL, Neuringer M, Max Snodderly D. Nutritional manipulation of primate retinas. IV. Effects of n--3 fatty acids, lutein, and zeaxanthin on S-cones and rods in the foveal region. Exp Eye Res 2006; 81:513-29. [PMID: 15916761 DOI: 10.1016/j.exer.2005.03.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 02/28/2005] [Accepted: 03/21/2005] [Indexed: 11/25/2022]
Abstract
Lutein and zeaxanthin are xanthophylls selectively accumulated by primate retinas that may protect the macula from age-related macular degeneration. In this project, we manipulated n-3 fatty acids, lutein and/or zeaxanthin levels in the diet and studied their possible outcome on S-cone and rod cell density in the foveal region. Rhesus monkeys (7-16 year, n=17) were fed from birth xanthophyll-free semipurified diets with either adequate or low n-3 fatty acids. Five monkeys were supplemented with lutein and six with zeaxanthin for 6-24 months, while six remained xanthophyll-free until sacrifice. Retinas were embedded in methacrylate and serial 2 microm sections were cut along the vertical meridian. Rod nuclei, and immuno-labelled outer segments of S-cones and rods, were reconstructed and counted in an 8 microm strip. The density profiles were compared with data from control monkeys (n=7) fed a standard laboratory diet. S-cone density profiles were symmetrical along the vertical meridian and the densities decreased rapidly with retinal eccentricity. Rod densities were higher in the superior region than the inferior region in most of the control and experimental animals. Unlike the significant effects observed for retinal pigment epithelial cells of these same monkeys (Leung, I.Y-F., Sandstrom, M.M., Zucker, C.L., Neuringer, M., Snodderly, D.M., 2004. Nutritional manipulation of primate retinas. II. Effects of age, n-3 fatty acids, lutein, and zeaxanthin on retinal pigment epithelium. Invest. Ophthalmol. Vis. Sci. 45, 3244-3256), neither xanthophyll supplementation nor low dietary n-3 fatty acids produced consistent effects on S-cone or rod density profiles of the experimental animals. However, monkeys low in n-3 fatty acids had increased variability of S-cone density in the fovea and low density of foveal rod outer segments. The high variability suggests that the photoreceptors of some animals were resistant to the nutritional manipulations, while others may have been affected. Thus, the photoreceptors appear less sensitive than the retinal pigment epithelium to these nutritional manipulations. However, it is possible that more consistent effects would emerge at a later age or after exposure to stressors such as high light levels.
Collapse
Affiliation(s)
- Ivan Y-F Leung
- The Schepens Eye Research Institute, 20 Staniford Street, Boston, MA 02114, USA.
| | | | | | | | | |
Collapse
|
32
|
Vaughan DK, Peachey NS, Richards MJ, Buchan B, Fliesler SJ. Light-induced exacerbation of retinal degeneration in a rat model of Smith-Lemli-Opitz syndrome. Exp Eye Res 2005; 82:496-504. [PMID: 16360150 PMCID: PMC2844790 DOI: 10.1016/j.exer.2005.08.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2005] [Revised: 08/04/2005] [Accepted: 08/10/2005] [Indexed: 11/18/2022]
Abstract
Potentiation of retinal degeneration by intense light exposure, and its amelioration by an antioxidant, were studied in a rat model of Smith-Lemli-Opitz syndrome (SLOS), in comparison with normal (control) Sprague-Dawley rats. The SLOS model is created by treating rats with AY9944, a selective inhibitor of cholesterol synthesis at the level of 3beta-hydroxysterol-Delta7-reductase. A subset of rats was treated with dimethylthiourea (DMTU), a synthetic antioxidant, 24 and 1 hr prior to light exposure. Half of the animals (+/-DMTU) were exposed to intense, constant, green light (24hr, 1700lx, 490-580 nm), while the others were maintained in darkness. Subsequently all animals were returned to dim cyclic light (20-40 lx, 12 hr light-12 hr dark) for 2 weeks, after which electroretinograms were recorded. One eye from each rat was taken for histological and quantitative morphometric analyses; sterol analysis was performed on retinas from contralateral eyes. HPLC analysis confirmed the accumulation of 7-dehydrocholesterol (7DHC) in retinas of AY9944-treated rats; cholesterol represented >99% of the sterol in control retinas. Histology of retinas from unexposed, AY9944-treated rats (6-week-old) was normal. In contrast, age-matched, light-exposed rats exhibited massive photoreceptor cell loss in both the superior and inferior hemispheres, and concomitant rod and cone dysfunction. The severity and geographic extent of the damage was far greater than that observed in normal albino rats exposed to the same conditions. DMTU pre-treatment largely prevented these degenerative changes. These findings indicate that the AY9944-induced rat SLOS model is hypersensitive to intense light-induced retinal damage, relative to normal rats. DMTU protection against light-induced damage implicates free radical-based oxidation in the retinal degeneration process. Furthermore, the use of green light (corresponding to the absorption maxima of rhodopsin) implicates rhodopsin in the initiation of the pathobiological mechanism. We propose that generation of cytotoxic oxysterols (by-products of 7DHC oxidation) is an integral part of retinal cell death in the SLOS rat model, which is exacerbated by intense light. Furthermore, the results predict light-dependent potentiation of retinal degeneration in SLOS patients, and the possible ameliorative effects of antioxidant therapy.
Collapse
Affiliation(s)
- Dana K. Vaughan
- Department of Biology, University of Wisconsin Oshkosh, Oshkosh, WI, USA
| | - Neal S. Peachey
- Cleveland VA Medical Center, and Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Michael J. Richards
- Departments of Ophthalmology and Pharmacological & Physiological Science, Saint Louis University School of Medicine, St Louis, MO, USA
| | - Blake Buchan
- Department of Biology, University of Wisconsin Oshkosh, Oshkosh, WI, USA
| | - Steven J. Fliesler
- Departments of Ophthalmology and Pharmacological & Physiological Science, Saint Louis University School of Medicine, St Louis, MO, USA
- Corresponding author. Dr Steven J. Fliesler, Saint Louis University Eye Institute, 1755 S. Grand Blvd, St Louis, MO 63104-1540. (S.J. Fliesler)
| |
Collapse
|
33
|
SanGiovanni JP, Chew EY. The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog Retin Eye Res 2005; 24:87-138. [PMID: 15555528 DOI: 10.1016/j.preteyeres.2004.06.002] [Citation(s) in RCA: 498] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this work we advance the hypothesis that omega-3 (omega-3) long-chain polyunsaturated fatty acids (LCPUFAs) exhibit cytoprotective and cytotherapeutic actions contributing to a number of anti-angiogenic and neuroprotective mechanisms within the retina. omega-3 LCPUFAs may modulate metabolic processes and attenuate effects of environmental exposures that activate molecules implicated in pathogenesis of vasoproliferative and neurodegenerative retinal diseases. These processes and exposures include ischemia, chronic light exposure, oxidative stress, inflammation, cellular signaling mechanisms, and aging. A number of bioactive molecules within the retina affect, and are effected by such conditions. These molecules operate within complex systems and include compounds classified as eicosanoids, angiogenic factors, matrix metalloproteinases, reactive oxygen species, cyclic nucleotides, neurotransmitters and neuromodulators, pro-inflammatory and immunoregulatory cytokines, and inflammatory phospholipids. We discuss the relationship of LCPUFAs with these bioactivators and bioactive compounds in the context of three blinding retinal diseases of public health significance that exhibit both vascular and neural pathology. How is omega-3 LCPUFA status related to retinal structure and function? Docosahexaenoic acid (DHA), a major dietary omega-3 LCPUFA, is also a major structural lipid of retinal photoreceptor outer segment membranes. Biophysical and biochemical properties of DHA may affect photoreceptor membrane function by altering permeability, fluidity, thickness, and lipid phase properties. Tissue DHA status affects retinal cell signaling mechanisms involved in phototransduction. DHA may operate in signaling cascades to enhance activation of membrane-bound retinal proteins and may also be involved in rhodopsin regeneration. Tissue DHA insufficiency is associated with alterations in retinal function. Visual processing deficits have been ameliorated with DHA supplementation in some cases. What evidence exists to suggest that LCPUFAs modulate factors and processes implicated in diseases of the vascular and neural retina? Tissue status of LCPUFAs is modifiable by and dependent upon dietary intake. Certain LCPUFAs are selectively accreted and efficiently conserved within the neural retina. On the most basic level, omega-3 LCPUFAs influence retinal cell gene expression, cellular differentiation, and cellular survival. DHA activates a number of nuclear hormone receptors that operate as transcription factors for molecules that modulate reduction-oxidation-sensitive and proinflammatory genes; these include the peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and the retinoid X receptor. In the case of PPAR-alpha, this action is thought to prevent endothelial cell dysfunction and vascular remodeling through inhibition of: vascular smooth muscle cell proliferation, inducible nitric oxide synthase production, interleukin-1 induced cyclooxygenase (COX)-2 production, and thrombin-induced endothelin 1 production. Research on model systems demonstrates that omega-3 LCPUFAs also have the capacity to affect production and activation of angiogenic growth factors, arachidonic acid (AA)-based vasoregulatory eicosanoids, and MMPs. Eicosapentaenoic acid (EPA), a substrate for DHA, is the parent fatty acid for a family of eicosanoids that have the potential to affect AA-derived eicosanoids implicated in abnormal retinal neovascularization, vascular permeability, and inflammation. EPA depresses vascular endothelial growth factor (VEGF)-specific tyrosine kinase receptor activation and expression. VEGF plays an essential role in induction of: endothelial cell migration and proliferation, microvascular permeability, endothelial cell release of metalloproteinases and interstitial collagenases, and endothelial cell tube formation. The mechanism of VEGF receptor down-regulation is believed to occur at the tyrosine kinase nuclear factor-kappa B (NFkappaB). NFkappaB is a nuclear transcription factor that up-regulates COX-2 expression, intracellular adhesion molecule, thrombin, and nitric oxide synthase. All four factors are associated with vascular instability. COX-2 drives conversion of AA to a number angiogenic and proinflammatory eicosanoids. Our general conclusion is that there is consistent evidence to suggest that omega-3 LCPUFAs may act in a protective role against ischemia-, light-, oxygen-, inflammatory-, and age-associated pathology of the vascular and neural retina.
Collapse
Affiliation(s)
- John Paul SanGiovanni
- Division of Epidemiology and Clinical Research, National Eye Insitute, National Institutes of Health, 31 Center Drive, Building 31, Room 6A52, MSC 2510, Bethesda, MD 20892-2510, USA.
| | | |
Collapse
|
34
|
Wenzel A, Grimm C, Samardzija M, Remé CE. Molecular mechanisms of light-induced photoreceptor apoptosis and neuroprotection for retinal degeneration. Prog Retin Eye Res 2004; 24:275-306. [PMID: 15610977 DOI: 10.1016/j.preteyeres.2004.08.002] [Citation(s) in RCA: 445] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Human retinal dystrophies and degenerations and light-induced retinal degenerations in animal models are sharing an important feature: visual cell death by apoptosis. Studying apoptosis may thus provide an important handle to understand mechanisms of cell death and to develop potential rescue strategies for blinding retinal diseases. Apoptosis is the regulated elimination of individual cells and constitutes an almost universal principle in developmental histogenesis and organogenesis and in the maintenance of tissue homeostasis in mature organs. Here we present an overview on molecular and cellular mechanisms of apoptosis and summarize recent developments. The classical concept of apoptosis being initiated and executed by endopeptidases that cleave proteins at aspartate residues (Caspases) can no longer be held in its strict sense. There is an increasing number of caspase-independent pathways, involving apoptosis inducing factor, endonuclease G, poly-(ADP-ribose) polymerase-1, proteasomes, lysosomes and others. Similarly, a considerable number and diversity of pro-apoptotic stimuli is being explored. We focus on apoptosis pathways in our model: light-damage induced by short exposures to bright white light and highlight those essential conditions known so far in the apoptotic death cascade. In our model, the visual pigment rhodopsin is the essential mediator of the initial death signal. The rate of rhodopsin regeneration defines damage threshold in different strains of mice. This rate depends on the level of the pigment epithelial protein RPE65, which in turn depends on the amino acid (leucine or methionine) encoded at position 450. Activation of the pro-apoptotic transcription factor AP-1 constitutes an essential death signal. Inhibition of rhodopsin regeneration as well as suppression of AP-1 confers complete protection in our system. Furthermore, we describe observations in other light-damage systems as well as characteristics of animal models for RP with particular emphasis on rescue strategies. There is a vast array of different neuroprotective cytokines that are applied in light-damage and RP animal models and show diverging efficacy. Some cytokines protect against light damage as well as against RP in animal models. At present, the mechanisms of neuroprotective/anti-apoptotic action represent a "black box" which needs to be explored. Even though acute light damage and RP animal models show different characteristics in many respects, we hope to gain insights into apoptotic mechanisms for both conditions by studying light damage and comparing results with those obtained in animal models. In our view, future directions may include the investigation of different apoptotic pathways in light damage (and inherited animal models). Emphasis should also be placed on mechanisms of removal of dead cells in apoptosis, which appears to be more important than initially recognized. In this context, a stimulating concept concerns age-related macular degeneration, where an insufficiency of macrophages removing debris that results from cell death and photoreceptor turnover might be an important pathogenetic event. In acute light damage, the appearance of macrophages as well as phagocytosis by the retinal pigment epithelium are a consistent and conspicuous feature, which lends itself to the study of removal of cellular debris in apoptosis. We are aware of the many excellent reviews and the earlier work paving the way to our current knowledge and understanding of retinal degeneration, photoreceptor apoptosis and neuroprotection. However, we limited this review mainly to work published in the last 7-8 years and we apologize to all the researchers which have contributed to the field but are not cited here.
Collapse
Affiliation(s)
- Andreas Wenzel
- Laboratory for Retinal Cell Biology, Department Ophthalmology, University Eye Clinic, University of Zurich, Frauenklinkstrasse 24, CH-8091 Zurich, Switzerland
| | | | | | | |
Collapse
|
35
|
Ambati J, Ambati BK, Yoo SH, Ianchulev S, Adamis AP. Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies. Surv Ophthalmol 2003; 48:257-93. [PMID: 12745003 DOI: 10.1016/s0039-6257(03)00030-4] [Citation(s) in RCA: 609] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Age-related macular degeneration is the principal cause of registered legal blindness among those aged over 65 in the United States, western Europe, Australia, and Japan. Despite intensive research, the precise etiology of molecular events that underlie age-related macular degeneration is poorly understood. However, investigations on parallel fronts are addressing this prevalent public health problem. Sophisticated biochemical and biophysical techniques have refined our understanding of the pathobiology of drusen, geographic atrophy, and retinal pigment epithelial detachments. Epidemiological identification of risk factors has facilitated an intelligent search for underlying mechanisms and fueled clinical investigation of behavior modification. Gene searches have not only brought us to the cusp of identifying the culpable gene loci in age-related macular degeneration, but also localized genes responsible for other macular dystrophies. Recent and ongoing investigations, often cued by tumor biology, have revealed an important role for various growth factors, particularly in the neovascular form of the condition. Transgenic and knockout studies have provided important mechanistic insights into the development of choroidal neovascularization, the principal cause of vision loss in age-related macular degeneration. This in turn has culminated in preclinical and clinical trials of directed molecular interventions.
Collapse
Affiliation(s)
- Jayakrishna Ambati
- Ocular Angiogenesis Laboratory, Department of Ophthalmology, University of Kentucky, Lexington, USA
| | | | | | | | | |
Collapse
|
36
|
|
37
|
Boulton M, Rózanowska M, Rózanowski B. Retinal photodamage. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 64:144-61. [PMID: 11744401 DOI: 10.1016/s1011-1344(01)00227-5] [Citation(s) in RCA: 234] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The retina represents a paradox, in that, while light and oxygen are essential for vision, these conditions also favour the formation of reactive oxygen species leading to photochemical damage to the retina. Such light damage seems to be multi-factorial and is dependent on the photoreactivity of a variety of chromophores (e.g., vitamin A metabolites, lipofuscin, melanin, flavins, porphyrins, carotenoids) endogenous to the retina. The aim of this article is to provide a detailed review of our current understanding of the photochemistry and photobiology of these chromophores and to consider how they may contribute to retinal ageing and pathology.
Collapse
Affiliation(s)
- M Boulton
- Department of Optometry and Vision Sciences, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff CF10 3NB, UK.
| | | | | |
Collapse
|
38
|
Wang JY, Saito M. Dietary supplementation of N-3 fatty acids and hydroperoxide levels in rat retinas. Free Radic Res 2001; 35:367-75. [PMID: 11697133 DOI: 10.1080/10715760100300881] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Docosahexaenoic acid (DHA) plays an important role in visual and neural development in mammals. In the present study, effect of dietary supplementation with n-3 fatty acids, primarily docosahexaenoic acid (DHA) with high purity, on the fatty acid composition of photoreceptor cells of young rats (fed from 4 weeks) was investigated. DHA in rod outer segment (ROS) membranes was significantly increased in the group of high DHA feeding (9.69% total energy). Other n-3 fatty acids (alpha-linolenic acid (ALA) and eicosapentaenoic acid (EPA)) included in the diets with DHA (0.95%-5.63% total energy) also significantly increased the proportion of DHA compared with the linoleic acid diet groups. However, the proportions of arachidonic acid (ARA) and other long chain n-6 fatty acids (22:4n6 and 22:5n6) were suppressed in these n-3 fatty acids-fed groups. Phospholipid hydroperoxides in ROS membranes were determined using a highly sensitive analytical technique, chemiluminescence-high performance liquid chromatography (CL-HPLC). There was no increasing tendency in the hydroperoxide levels of ROS membranes containing high content of DHA, and phosphatidylethanolamine hydroperoxide (PEOOH) was much lower than phosphatidylcholine hydroperoxide (PCOOH) under normal light conditions, which implies that DHA supplementation does not much affect the peroxidizability of ROS membranes in vivo. But UV irradiation on separated ROS membranes accelerated the formation of phospholipid hydroperoxides in high DHA feeding rats, and PEOOH was produced more efficiently than PCOOH in vitro.
Collapse
Affiliation(s)
- J Y Wang
- Division of Food Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan.
| | | |
Collapse
|
39
|
Abstract
An important role for docosahexaenoic acid (DHA) within the retina is suggested by its high levels and active conservation in this tissue. Animals raised on n-3-deficient diets have large reductions in retinal DHA levels that are associated with altered retinal function as assessed by the electroretinogram (ERG). Despite two decades of research in this field, little is known about the mechanisms underlying altered retinal function in n-3-deficient animals. The focus of this review is on recent research that has sought to elucidate the role of DHA in retinal function, particularly within the rod photoreceptor outer segments where DHA is found at its highest concentration. An overview is also given of human infant studies that have examined whether a neonatal dietary supply of DHA is required for the normal development of retinal function.
Collapse
Affiliation(s)
- B G Jeffrey
- Department of Paediatrics and Child Health, Flinders Medical Centre, The Flinders University of South Australia, Bedford Park, Adelaide, South Australia 5042, Australia
| | | | | | | |
Collapse
|
40
|
Beatty S, Koh H, Phil M, Henson D, Boulton M. The role of oxidative stress in the pathogenesis of age-related macular degeneration. Surv Ophthalmol 2000; 45:115-34. [PMID: 11033038 DOI: 10.1016/s0039-6257(00)00140-5] [Citation(s) in RCA: 1290] [Impact Index Per Article: 53.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blind registration in the developed world, and yet its pathogenesis remains poorly understood. Oxidative stress, which refers to cellular damage caused by reactive oxygen intermediates (ROI), has been implicated in many disease processes, especially age-related disorders. ROIs include free radicals, hydrogen peroxide, and singlet oxygen, and they are often the byproducts of oxygen metabolism. The retina is particularly susceptible to oxidative stress because of its high consumption of oxygen, its high proportion of polyunsaturated fatty acids, and its exposure to visible light. In vitro studies have consistently shown that photochemical retinal injury is attributable to oxidative stress and that the antioxidant vitamins A, C, and E protect against this type of injury. Furthermore, there is strong evidence suggesting that lipofuscin is derived, at least in part, from oxidatively damaged photoreceptor outer segments and that it is itself a photoreactive substance. However, the relationships between dietary and serum levels of the antioxidant vitamins and age-related macular disease are less clear, although a protective effect of high plasma concentrations of alpha-tocopherol has been convincingly demonstrated. Macular pigment is also believed to limit retinal oxidative damage by absorbing incoming blue light and/or quenching ROIs. Many putative risk-factors for AMD have been linked to a lack of macular pigment, including female gender, lens density, tobacco use, light iris color, and reduced visual sensitivity. Moreover, the Eye Disease Case-Control Study found that high plasma levels of lutein and zeaxanthin were associated with reduced risk of neovascular AMD. The concept that AMD can be attributed to cumulative oxidative stress is enticing, but remains unproven. With a view to reducing oxidative damage, the effect of nutritional antioxidant supplements on the onset and natural course of age-related macular disease is currently being evaluated.
Collapse
Affiliation(s)
- S Beatty
- Academic Department of Ophthalmology, Manchester Royal Eye Hospital, Manchester, United Kingdom
| | | | | | | | | |
Collapse
|
41
|
Abstract
Apoptosis is a regulated mode of single cell death that involves gene expression in many instances and occurs under physiological and pathological conditions in a large variety of systems. We briefly summarize major features of apoptosis in general and describe the occurrence of apoptosis in the retina in different situations that comprise animal models of retinitis pigmentosa, light-induced lesions, histogenesis during development, and others. Apoptosis can be separated into several phases: the induction by a multitude of stimuli, the effector phase in which the apoptotic signal is transmitted to the cellular death machinery, the excecution period when proteolytic cascades are activated, and the phagocytic removal of cellular remnants. Control mechanisms for retinal apoptosis are only beginning to be clarified. Potential apoptotic signal transducers were investigated in our laboratory, including metabolites of arachidonic acid and downstream mediators of signaling molecules such as transcription factors. Work in our laboratory revealed an essential role of the immediate-early gene product c-Fos in light-induced apoptosis. c-Fos is a member of the AP-1 family of transcription factors and, together with other members of this family, it may regulate apoptosis in the central nervous system. Expression of the c-fos gene in the retina can be evoked by light exposure and follows a diurnal rhythm. Future studies will have to clarify how light can control the expression of specific genes, and specifically, the role of c-fos and other genes of retinal apoptosis including potential target genes and signaling pathways.
Collapse
Affiliation(s)
- C E Remé
- Department of Ophthalmology, University Hospital, Zuerich, Switzerland.
| | | | | | | | | |
Collapse
|
42
|
Zhang H, Hamilton JH, Salem N, Kim HY. N–3 fatty acid deficiency in the rat pineal gland: effects on phospholipid molecular species composition and endogenous levels of melatonin and lipoxygenase products. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32520-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
43
|
Boesze-Battaglia K, Allen C. Differential rhodopsin regeneration in photoreceptor membranes is correlated with variations in membrane properties. Biosci Rep 1998; 18:29-38. [PMID: 9653516 PMCID: PMC4732725 DOI: 10.1023/a:1022240717186] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Rhodopsin, the major transmembrane protein in both the plasma membrane and the disk membranes of photoreceptor rod outer segments (ROS) forms the apo-protein opsin upon the absorption of light. In vivo the regeneration of rhodopsin is necessary for subsequent receptor activation and for adaptation, in vitro this regeneration can be followed after the addition of 11-cis retinal. In this study we investigated the ability of bleached rhodopsin to regenerate in the compositionally different membrane environments found in photoreceptor rod cells. When 11-cis retinal was added to bleached ROS plasma membrane preparations, rhodopsin did not regenerate within the same time course or to the same extent as bleached rhodopsin in disk membranes. Over 80% of the rhodopsin in newly formed disks regenerated within 90 minutes while only 40% regenerated in older disks. Since disk membrane cholesterol content increases as disks are displaced from the base to the apical tip of the outer segment, we looked at the affect of membrane cholesterol content on the regeneration process. Enrichment or depletion of disk membrane cholesterol did not alter the % rhodopsin that regenerated. Bulk membrane properties measured with a sterol analog, cholestatrienol and a fatty acid analog, cis parinaric acid, showed a more ordered, less "fluid", lipid environment within plasma membrane relative to the disks. Collectively these results show that the same membrane receptor, rhodopsin, functions differently as monitored by regeneration in the different lipid environments within photoreceptor rod cells. These differences may be due to the bulk properties of the various membranes.
Collapse
Affiliation(s)
- K Boesze-Battaglia
- Department of Molecular Biology, University of Medicine and Dentistry of New Jersey-SOM, Stratford 08084, USA
| | | |
Collapse
|
44
|
Hafezi F, Marti A, Munz K, Remé CE. Light-induced apoptosis: differential timing in the retina and pigment epithelium. Exp Eye Res 1997; 64:963-70. [PMID: 9301477 DOI: 10.1006/exer.1997.0288] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Apoptosis is a genetically regulated form of cell death. Individual cells show condensed nuclear chromatin and cytoplasm, and biochemical analysis reveals fragmentation of the DNA. Ensuing cellular components, apoptotic bodies, are removed by macrophages or neighboring cells. Genes involved in the regulation of apoptosis as well as stimuli and signal transduction systems, are only beginning to be understood in the retina. Therefore, we developed a new in vivo model system for the investigation of events leading to apoptosis in the retina and the pigment epithelium. We induced apoptosis in retinal photoreceptors and the pigment epithelium of albino rats by exposure to 3000 lux of diffuse, cool white fluorescent light for short time periods of up to 120 minutes. Animals were killed at different time intervals during and after light exposure. The eyes were enucleated and the lower central retina was processed for light- and electron microscopy. DNA fragmentation was analysed in situ by TdT-mediated dUTP nick-end labeling (TUNEL) or by gel electrophoresis of total retinal DNA. We observed that the timing of apoptosis in the photoreceptors and pigment epithelium was remarkably different, the pigment epithelium showing a distinct delay of several hours before the onset of apoptosis. In photoreceptors, apoptosis was induced within 90 minutes of light exposure, with the morphological appearance of apoptosis preceding the fragmentation of DNA. In the pigment epithelium, the morphological appearance of apoptosis and DNA fragmentation were coincident. Different regulative mechanisms may lead to apoptotic cell death in the retinal photoreceptors and pigment epithelium. This in vivo model system will allow measurement of dose-responses, a potential spectral dependence and the molecular background of apoptotic mechanisms in the retina.
Collapse
Affiliation(s)
- F Hafezi
- Department of Ophthalmology, University Hospital, Zurich, Switzerland
| | | | | | | |
Collapse
|
45
|
Abstract
Morphology of the central retina and scotopic visual sensitivity were compared in juvenile albino and normally pigmented rainbow trout living under natural and reduced daylight. Outdoor albinos avoided exposing their eyes to direct sunlight, whereas normals were indifferent to it. After 4 months outdoors (approximately 10,000 lux in albinos, approximately 100,000 lux in normals), albinos had severely truncated or missing rod outer segments (ROS) and some missing rod ellipsoids, but normal numbers of photoreceptor nuclei and fully intact cones. Albino estimated ROS volume was only 7.1% of normal in July, but increased to 20% by the following February, mainly via an increase in numbers of ROS. However, in albinos moved indoors October 7 and exposed to 10-30 lux ambient daylight, both the number and length of ROS increased significantly, with estimated ROS volume reaching 95% of normal by 34 days. Albinos generally had more phagosomes (approximately 3 x normal) and more macrophages (approximately 2 x normal) in their outer retina. An optomotor reflex was used to define the effect of ROS volume on the ability to respond visually during dark adaptation. In July, albinos and normals from outdoor raceways (3 months) or indoor raceways (35 days) showed equal sensitivity after first being placed in darkness, but after 1 h in darkness, outdoor albinos with 6% of normal ROS volume were 2.0 log units less sensitive than indoor or outdoor normals, whereas indoor albinos with 53% of normal ROS volume were only 0.7 log units less sensitive. This verifies that most rod cell bodies of albino trout can persist without functional ROS in indirect sunlight, and can regrow functional outer segments in dim daylight. This finding is distinct from the extensive retinal light damage observed in albino rats exposed to more moderate cyclic light, in which entire rod cells degenerate early on.
Collapse
Affiliation(s)
- D M Allen
- Department of Science and Mathematics, University of Texas of the Permian Basin, Odessa 79762, USA
| | | |
Collapse
|
46
|
|
47
|
Affiliation(s)
- R Uauy-Dagach
- Instituto de Nutrición y Tecnología de los Alimentos (INTA), University of Chile, Santiago, Chile
| | | |
Collapse
|
48
|
Szczesny PJ, Walther P, Müller M. Light damage in rod outer segments: the effects of fixation on ultrastructural alterations. Curr Eye Res 1996; 15:807-14. [PMID: 8921223 DOI: 10.3109/02713689609017621] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE In this electron microscopical study, we compared effects of chemical fixation versus cryofixation on the ultrastructure of acute rod outer segment alterations in the rat retina. METHODS The alterations were induced by toxic levels of diffuse white light. Albino rats were exposed to 2000 lux for 30 min. Samples from one eye of each animal were fixed by high pressure freezing and samples from the other eye were fixed by standard glutaraldehyde procedures. RESULTS Light exposed retina showed major differences in their rod outer segments, inner segments and photoreceptor synaptic regions in chemical fixation. In particular gross vesiculations of outer segment membranes were produced in light exposed experiments. In contrast, in cryo-fixed samples such prominent changes were not observed in outer segment membranes. There was, however, occasional formation of small vesicles and a reduction of the cilium diameter in response to light damage. In the dark adapted control group the morphology of chemically fixed and cryo-fixed photoreceptors was similar. CONCLUSIONS We conclude, that cryo-fixed samples better represent the living state of the retina, because high pressure freezing is a purely physical method and acts much faster than chemical fixation.
Collapse
Affiliation(s)
- P J Szczesny
- Laboratory for Electron Microscopy 1, Swiss Federal Institute of Technology, Zurich, Switzerland
| | | | | |
Collapse
|
49
|
Reinboth JJ, Gautschi K, Clausen M, Remé CE. Lipid mediators in the rat retina: light exposure and trauma elicit leukotriene B4 release in vitro. Curr Eye Res 1995; 14:1001-8. [PMID: 8585927 DOI: 10.3109/02713689508998521] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Light exposure not only elicits a visual response but may also alter functional and structural characteristics of the retina. Furthermore, light exposure can lead to reversible or irreversible lesions of photoreceptors and pigment epithelium. Previous studies in our laboratory have shown that light liberates arachidonic acid from retinal membrane phospholipids mainly by activating the phospholipase A2. In this study we show that light and trauma elicit the synthesis of leukotriene B4 in the isolated rat retina in vitro. Male albino rats were dark adapted for 36 h, isolated retinae were taken, incubated and exposed a) either to darkness or to 5,000 lux of cool white fluorescent light for 5, 10 or 15 min at 37 degrees C, b) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 0 degrees C or c) either to darkness or to 5,000 lux of cool white fluorescent light for 15 min at 37 degrees C with a 5-lipoxygenase inhibitor (zileuton). Eicosanoids were extracted and leukotriene B4 levels were determined by radioimmunoassay. Removal of retinae and incubation in darkness caused a significant rise in leukotriene B4 levels with increasing incubation time. This rise was further augmented significantly after light exposure. The leukotriene B4 levels obtained when incubating the retinae either at 0 degree C or with the lipoxygenase inhibitor zileuton as well as the high specificity of the radioimmunoassay indicate that the light- and trauma-elicited synthesis of leukotriene B4 is mediated by activating the 5-lipoxygenase. Leukotriene B4 may be involved, at least in part, in the pathogenesis of retinal diseases including light damage. Curr. Eye Res. 14: 1001-1008, 1995.
Collapse
Affiliation(s)
- J J Reinboth
- Department of Ophthalmology, University Hospital Zürich, Switzerland
| | | | | | | |
Collapse
|
50
|
Wiegand RD, Koutz CA, Chen H, Anderson RE. Effect of dietary fat and environmental lighting on the phospholipid molecular species of rat photoreceptor membranes. Exp Eye Res 1995; 60:291-306. [PMID: 7789409 DOI: 10.1016/s0014-4835(05)80111-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have previously shown that retinas of albino rats adapt to bright cyclic light (500-800 lx) by lowering the levels of docosahexaenoic acid (22:6n-3) in their rod outer segment (ROS) phospholipids. In the present study, we addressed the role of dietary fat in this process. Pregnant rats were kept in 1 lx or 250 lx cyclic illuminance (12L:12D) and fed diets containing 10% (by weight) of either hydrogenated coconut oil (COC, no n-3 or n-6 fatty acids), linseed oil (LIN, n-3 and n-6 fatty acids), or safflower oil (SAF, only n-6 fatty acids), starting 4 days before delivery. Pups were weaned at 3 weeks of age and continued on the same diet and light regime. At 12 weeks of age, 3 or 4 animals in each diet-light group were killed and the remaining animals were stressed continuously with 2000 lx light for 24 hr and then kept in 1 lx cyclic light for 10 days. Fatty acids and phospholipid molecular species (PLMS) of ROS membranes were determined. For prestressed groups, those animals fed the LIN diet had high levels of 22:6n-3 and PLMS containing 22:6n-3, with little 22:5n-6. Compared to the LIN group, the COC and SAF groups had lower levels of 22:6n-3- and 22:6n-3)-containing PLMS and higher levels of 22:5n-6 and molecular species containing 22:5n-6, such as 22:5n-6/22:6n-3, 16:0/22:5n-6 and 18:0/22:5n-6. Within each dietary group, animals raised in 250 lx cyclic illuminance had lower levels of 22:6n-3 and 22:5n-6 compared to those raised at 1 lx. This light effect was greater for 22:6n-3 in the LIN group than for 22:5n-6 in the SAF group. After the acute light stress, those animals raised in 1 lx showed dramatic reduction in PLMS containing 22:6n-3 and 22:5n-6, especially polyenoic species such as 22:6n-3/22:6n-3 in the LIN group and 22:5n-6/22:6n-3 in the COC and SAF groups. In contrast, animals raised in 250 lx showed much smaller changes.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- R D Wiegand
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | |
Collapse
|