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Khalifa A, Guijarro A, Ravera S, Bertola N, Adorni MP, Papotti B, Raffaghello L, Benelli R, Becherini P, Namatalla A, Verzola D, Reverberi D, Monacelli F, Cea M, Pisciotta L, Bernini F, Caffa I, Nencioni A. Cyclic fasting bolsters cholesterol biosynthesis inhibitors' anticancer activity. Nat Commun 2023; 14:6951. [PMID: 37907500 PMCID: PMC10618279 DOI: 10.1038/s41467-023-42652-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 10/17/2023] [Indexed: 11/02/2023] Open
Abstract
Identifying oncological applications for drugs that are already approved for other medical indications is considered a possible solution for the increasing costs of cancer treatment. Under the hypothesis that nutritional stress through fasting might enhance the antitumour properties of at least some non-oncological agents, by screening drug libraries, we find that cholesterol biosynthesis inhibitors (CBIs), including simvastatin, have increased activity against cancers of different histology under fasting conditions. We show fasting's ability to increase CBIs' antitumour effects to depend on the reduction in circulating insulin, insulin-like growth factor-1 and leptin, which blunts the expression of enzymes from the cholesterol biosynthesis pathway and enhances cholesterol efflux from cancer cells. Ultimately, low cholesterol levels through combined fasting and CBIs reduce AKT and STAT3 activity, oxidative phosphorylation and energy stores in the tumour. Our results support further studies of CBIs in combination with fasting-based dietary regimens in cancer treatment and highlight the value of fasting for drug repurposing in oncology.
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Affiliation(s)
- Amr Khalifa
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Ana Guijarro
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Silvia Ravera
- Department of Experimental Medicine, University of Genoa, Via Leon Battista Alberti 2, 16132, Genoa, Italy
| | - Nadia Bertola
- Department of Experimental Medicine, University of Genoa, Via Leon Battista Alberti 2, 16132, Genoa, Italy
| | - Maria Pia Adorni
- Department of Medicine and Surgery, University of Parma, 43125, Parma, Italy
| | - Bianca Papotti
- Department of Food and Drug, University of Parma, 43124, Parma, Italy
| | - Lizzia Raffaghello
- Center of Translational and Experimental Myology, IRCCS Istituto Giannina Gaslini, 16147, Genoa, Italy
| | - Roberto Benelli
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Pamela Becherini
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
| | - Asmaa Namatalla
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
| | - Daniela Verzola
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
| | - Daniele Reverberi
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Fiammetta Monacelli
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Michele Cea
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Livia Pisciotta
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Franco Bernini
- Department of Food and Drug, University of Parma, 43124, Parma, Italy
| | - Irene Caffa
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy.
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy.
| | - Alessio Nencioni
- Department of Internal Medicine and Medical Specialties, University of Genoa, Viale Benedetto XV 6, 16132, Genoa, Italy.
- Ospedale Policlinico San Martino IRCCS, Largo Rosanna Benzi 10, 16132, Genoa, Italy.
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Abstract
Cholesterol is a quantitatively and biologically significant constituent of all mammalian cell membrane, including those that comprise the retina. Retinal cholesterol homeostasis entails the interplay between de novo synthesis, uptake, intraretinal sterol transport, metabolism, and efflux. Defects in these complex processes are associated with several congenital and age-related disorders of the visual system. Herein, we provide an overview of the following topics: (a) cholesterol synthesis in the neural retina; (b) lipoprotein uptake and intraretinal sterol transport in the neural retina and the retinal pigment epithelium (RPE); (c) cholesterol efflux from the neural retina and the RPE; and (d) biology and pathobiology of defects in sterol synthesis and sterol oxidation in the neural retina and the RPE. We focus, in particular, on studies involving animal models of monogenic disorders pertinent to the above topics, as well as in vitro models using biochemical, metabolic, and omic approaches. We also identify current knowledge gaps and opportunities in the field that beg further research in this topic area.
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Affiliation(s)
- Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA.
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Cytoprotective Potential of Fucoxanthin in Oxidative Stress-Induced Age-Related Macular Degeneration and Retinal Pigment Epithelial Cell Senescence In Vivo and In Vitro. Mar Drugs 2021; 19:md19020114. [PMID: 33670685 PMCID: PMC7923087 DOI: 10.3390/md19020114] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 02/07/2023] Open
Abstract
Oxidative stress is identified as a major inducer of retinal pigment epithelium (RPE) cell dysregulation and is associated with age-related macular degeneration (AMD). The protection of RPE disorders plays an essential role in the pathological progress of retinal degeneration diseases. The pharmacological functions of fucoxanthin, a characteristic carotenoid, including anti-inflammatory and antioxidant properties, may ameliorate an outstanding bioactivity against premature senescence and cellular dysfunction. This study demonstrates that fucoxanthin protects RPE cells from oxidative stress-induced premature senescence and decreased photoreceptor cell loss in a sodium iodate-induced AMD animal model. Similarly, oxidative stress induced by hydrogen peroxide, nuclear phosphorylated histone (γH2AX) deposition and premature senescence-associated β-galactosidase staining were inhibited by fucoxanthin pretreatment in a human RPE cell line, ARPE-19 cells. Results reveal that fucoxanthin treatment significantly inhibited reactive oxygen species (ROS) generation, reduced malondialdehyde (MDA) concentrations and increased the mitochondrial metabolic rate in oxidative stress-induced RPE cell damage. Moreover, atrophy of apical microvilli was inhibited in cells treated with fucoxanthin after oxidative stress. During aging, the RPE undergoes well-characterized pathological changes, including amyloid beta (Aβ) deposition, beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) expression and tight junction disruption, which were also reduced in fucoxanthin-treated groups by immunofluorescence. Altogether, pretreatment with fucoxanthin may protect against premature senescence and cellular dysfunction in retinal cells by oxidative stress in experimental AMD animal and human RPE cell models.
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Fu D, Yu JY, Connell AR, Hookham MB, McLeese RH, Lyons TJ. Effects of Modified Low-Density Lipoproteins and Fenofibrate on an Outer Blood-Retina Barrier Model: Implications for Diabetic Retinopathy. J Ocul Pharmacol Ther 2020; 36:754-764. [PMID: 33107777 PMCID: PMC7757531 DOI: 10.1089/jop.2020.0068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Purpose: There is a lack of treatment for early diabetic retinopathy (DR), including blood-retina barrier (BRB) breakdown. The robust clinical benefit of fenofibrate in DR provides an opportunity to explore disease mechanisms and therapeutic targets. We have previously found that modified lipoproteins contribute to DR and that fenofibrate protects the inner BRB. We now investigate (1) whether modified lipoproteins elicit outer BRB injury and (2) whether fenofibrate may alleviate such damage. Methods: Human retinal pigment epithelium ARPE-19 cells were cultured in semipermeable transwells to establish a monolayer barrier and then exposed to heavily oxidized, glycated low-density lipoprotein (HOG-LDL, 25–300 mg/L, up to 24 h) versus native (N)-LDL. Transepithelial electric resistance (TEER) and FITC-dextran permeability were measured. The effects of fenofibrate, its active metabolite fenofibric acid, and other peroxisome proliferator-activated receptor (PPARα) agonists (gemfibrozil, bezafibrate, and WY14643) were evaluated, with and without the PPARα antagonist GW6471 or the adenosine monophosphate-activated protein kinase (AMPK) inhibitor Compound C. Results: HOG-LDL induced concentration- and time-dependent barrier impairment, decreasing TEER and increasing dextran leakage, effects that were amplified by high glucose. Fenofibric acid, but not fenofibrate, gemfibrozil, bezafibrate, or WY14643, attenuated barrier impairment. This effect was reversed significantly by Compound C, but not by GW6471. Conclusions: Modified lipoproteins elicited outer BRB injury in an experimental model, which was reduced by fenofibric acid through a PPARα-independent, AMPK-mediated mechanism. These findings suggest a protective role of fenofibric acid on the outer BRB in diabetic retina.
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Affiliation(s)
- Dongxu Fu
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom
| | - Jeremy Y Yu
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom.,Division of Endocrinology, Diabetes and Metabolic Diseases, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Anna R Connell
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom
| | - Michelle B Hookham
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom
| | - Rebecca H McLeese
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom.,Division of Endocrinology, Diabetes and Metabolic Diseases, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Timothy J Lyons
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Northern Ireland, United Kingdom.,Division of Endocrinology, Diabetes and Metabolic Diseases, Medical University of South Carolina, Charleston, South Carolina, USA.,Diabetes Free SC, BlueCross BlueShield of South Carolina, Columbia, South Carolina, USA
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Abokyi S, To CH, Lam TT, Tse DY. Central Role of Oxidative Stress in Age-Related Macular Degeneration: Evidence from a Review of the Molecular Mechanisms and Animal Models. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:7901270. [PMID: 32104539 PMCID: PMC7035553 DOI: 10.1155/2020/7901270] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Accepted: 01/18/2020] [Indexed: 11/17/2022]
Abstract
Age-related macular degeneration (AMD) is a common cause of visual impairment in the elderly. There are very limited therapeutic options for AMD with the predominant therapies targeting vascular endothelial growth factor (VEGF) in the retina of patients afflicted with wet AMD. Hence, it is important to remind readers, especially those interested in AMD, about current studies that may help to develop novel therapies for other stages of AMD. This study, therefore, provides a comprehensive review of studies on human specimens as well as rodent models of the disease, to identify and analyze the molecular mechanisms behind AMD development and progression. The evaluation of this information highlights the central role that oxidative damage in the retina plays in contributing to major pathways, including inflammation and angiogenesis, found in the AMD phenotype. Following on the debate of oxidative stress as the earliest injury in the AMD pathogenesis, we demonstrated how the targeting of oxidative stress-associated pathways, such as autophagy and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling, might be the futuristic direction to explore in the search of an effective treatment for AMD, as the dysregulation of these mechanisms is crucial to oxidative injury in the retina. In addition, animal models of AMD have been discussed in great detail, with their strengths and pitfalls included, to assist inform in the selection of suitable models for investigating any of the molecular mechanisms.
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Affiliation(s)
- Samuel Abokyi
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong
- Department of Optometry, University of Cape Coast, Ghana
| | - Chi-Ho To
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong
| | - Tim T. Lam
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong
| | - Dennis Y. Tse
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong
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Yang C, Xie L, Gu Q, Qiu Q, Wu X, Yin L. 7-Ketocholesterol disturbs RPE cells phagocytosis of the outer segment of photoreceptor and induces inflammation through ERK signaling pathway. Exp Eye Res 2019; 189:107849. [DOI: 10.1016/j.exer.2019.107849] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 10/13/2019] [Accepted: 10/18/2019] [Indexed: 10/25/2022]
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Salvianolic Acid A Inhibits OX-LDL Effects on Exacerbating Choroidal Neovascularization via Downregulating CYLD. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:6210694. [PMID: 29081889 PMCID: PMC5610829 DOI: 10.1155/2017/6210694] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 02/28/2017] [Accepted: 03/08/2017] [Indexed: 11/17/2022]
Abstract
Backgrounds Age-related macular degeneration is closely related to lipid oxidation, while relationship between OX-LDL and choroidal neovascularization is unclear. Recently, cylindromatosis is proved to regulate angiogenesis. However, its role in CNV progression remained unclear. Salvianolic acid A is widely used in vascular diseases. We investigated the relationship between OX-LDL and CNV and explore antineovascularization mechanism of Sal A. Methods C57BL6/J mice were randomized into four groups and injected with PBS or OX-LDL, together with Sal A for one week. CNV was induced by laser; CNV severity was analyzed by fundus fluorescein angiography, H&E staining, and choroid flat mount after 1 week. In in vitro experiments, ARPE-19 and HUVECs were cultured with OX-LDL (with or without Sal A) for 48 hours. Angiogenic proteins, cell junction integrity, and tube formation were measured. CYLD siRNA and specific inhibitors were used to explore mechanisms of CYLD in promoting OX-LDL-induced CNV progression. Results OX-LDL promoted laser-induced CNV volume by increasing VEGF, PDGF, and CYLD levels. Sal A antagonized OX-LDL effects and restrained CNV progression by decreasing VEGF/PDGF/CYLD, increasing antiangiostatin levels, and promoting P62-CYLD-TRAF6 interaction. Conclusions We demonstrated oxidation damage exacerbates CNV progression, and Sal A could be a clinical therapeutic reagent to exudative AMD.
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The Association between the Lipids Levels in Blood and Risk of Age-Related Macular Degeneration. Nutrients 2016; 8:nu8100663. [PMID: 27782072 PMCID: PMC5084049 DOI: 10.3390/nu8100663] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 10/03/2016] [Accepted: 10/17/2016] [Indexed: 12/16/2022] Open
Abstract
Lipid metabolism may be involved in the pathogenic mechanism of age-related macular degeneration (AMD). However, conflicting results have been reported in the associations of AMD with blood lipids. We performed a meta-analysis including a total of 19 studies to evaluate associations between blood lipids and this disease. The result reported that the high level of high-density lipoprotein cholesterol (HDL-C) obtained with an increment of 1 mmol/L could result in a significantly increase in the AMD risk of approximately 18% (relative risk (RR), 1.18; 95% confidence interval (CI), 1.01 to 1.35; I2 = 53.8%; p = 0.007). High levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) were significantly associated with a decreased risk of AMD (RRs ranging from 0.92 to 0.95; all p < 0.05). The stratified analysis based on AMD subtypes showed that these blood lipids were only significantly associated with the risk of early AMD (all p < 0.05). The association between the blood lipids and AMD risk did not differ substantially based on the other characteristics of the participants. A high HDL-C level was associated with an increased AMD risk, whereas participants with high TC, LDL-C, and TG concentrations may show a decreased risk for this disease. Further well-designed large studies are warranted to confirm the conclusions.
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Yu JY, Du M, Elliott MH, Wu M, Fu D, Yang S, Basu A, Gu X, Ma JX, Aston CE, Lyons TJ. Extravascular modified lipoproteins: a role in the propagation of diabetic retinopathy in a mouse model of type 1 diabetes. Diabetologia 2016; 59:2026-35. [PMID: 27306616 PMCID: PMC4969344 DOI: 10.1007/s00125-016-4012-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/13/2016] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS We aimed to determine whether plasma lipoproteins, after leakage into the retina and modification by glycation and oxidation, contribute to the development of diabetic retinopathy in a mouse model of type 1 diabetes. METHODS To simulate permeation of plasma lipoproteins into retinal tissues, streptozotocin-induced mouse models of diabetes and non-diabetic mice were challenged with intravitreal injection of human 'highly-oxidised glycated' low-density lipoprotein (HOG-LDL), native- (N-) LDL, or the vehicle PBS. Retinal histology, electroretinography (ERG) and biochemical markers were assessed over the subsequent 14 days. RESULTS Intravitreal administration of N-LDL and PBS had no effect on retinal structure or function in either diabetic or non-diabetic animals. In non-diabetic mice, HOG-LDL elicited a transient inflammatory response without altering retinal function, but in diabetic mice it caused severe, progressive retinal injury, with abnormal morphology, ERG changes, vascular leakage, vascular endothelial growth factor overexpression, gliosis, endoplasmic reticulum stress, and propensity to apoptosis. CONCLUSIONS/INTERPRETATION Diabetes confers susceptibility to retinal injury imposed by intravitreal injection of modified LDL. The data add to the existing evidence that extravasated, modified plasma lipoproteins contribute to the propagation of diabetic retinopathy. Intravitreal delivery of HOG-LDL simulates a stress known to be present, in addition to hyperglycaemia, in human diabetic retinopathy once blood-retinal barriers are compromised.
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Affiliation(s)
- Jeremy Y Yu
- Centre for Experimental Medicine, School of Medicine, Dentistry, and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, UK.
| | - Mei Du
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael H Elliott
- Department of Ophthalmology, Dean A. McGee Eye Institute, Oklahoma City, OK, USA
| | - Mingyuan Wu
- Section of Diabetes and Endocrinology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Dongxu Fu
- Centre for Experimental Medicine, School of Medicine, Dentistry, and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, UK
| | - Shihe Yang
- Section of Diabetes and Endocrinology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Arpita Basu
- Department of Nutritional Sciences, Oklahoma State University, Stillwater, OK, USA
| | - Xiaowu Gu
- Department of Ophthalmology, Dean A. McGee Eye Institute, Oklahoma City, OK, USA
| | - Jian-Xing Ma
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Christopher E Aston
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Timothy J Lyons
- Centre for Experimental Medicine, School of Medicine, Dentistry, and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, UK.
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Yating Q, Yuan Y, wei Z, Qing G, xingwei W, Qiu Q, Lili Y. Oxidized LDL Induces Apoptosis of Human Retinal Pigment Epithelium Through Activation of ERK-Bax/Bcl-2 Signaling Pathways. Curr Eye Res 2014; 40:415-22. [DOI: 10.3109/02713683.2014.927507] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Ardeljan D, Chan CC. Aging is not a disease: distinguishing age-related macular degeneration from aging. Prog Retin Eye Res 2013; 37:68-89. [PMID: 23933169 PMCID: PMC3830684 DOI: 10.1016/j.preteyeres.2013.07.003] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 07/29/2013] [Accepted: 07/30/2013] [Indexed: 12/18/2022]
Abstract
Age-related macular degeneration (AMD) is a disease of the outer retina, characterized most significantly by atrophy of photoreceptors and retinal pigment epithelium accompanied with or without choroidal neovascularization. Development of AMD has been recognized as contingent on environmental and genetic risk factors, the strongest being advanced age. In this review, we highlight pathogenic changes that destabilize ocular homeostasis and promote AMD development. With normal aging, photoreceptors are steadily lost, Bruch's membrane thickens, the choroid thins, and hard drusen may form in the periphery. In AMD, many of these changes are exacerbated in addition to the development of disease-specific factors such as soft macular drusen. Para-inflammation, which can be thought of as an intermediate between basal and robust levels of inflammation, develops within the retina in an attempt to maintain ocular homeostasis, reflected by increased expression of the anti-inflammatory cytokine IL-10 coupled with shifts in macrophage plasticity from the pro-inflammatory M1 to the anti-inflammatory M2 polarization. In AMD, imbalances in the M1 and M2 populations together with activation of retinal microglia are observed and potentially contribute to tissue degeneration. Nonetheless, the retina persists in a state of chronic inflammation and increased expression of certain cytokines and inflammasomes is observed. Since not everyone develops AMD, the vital question to ask is how the body establishes a balance between normal age-related changes and the pathological phenotypes in AMD.
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Affiliation(s)
- Daniel Ardeljan
- Immunopathology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Abstract
Clinical epidemiological studies have revealed relatively weak, yet statistically significant, associations between dyslipidemia/dyslipoproteinemia and diabetic retinopathy (DR). Recent large interventional studies, however, demonstrated an unexpectedly robust efficacy of fenofibrate on the development of DR, possibly independent of plasma lipids. To unify the apparent discrepancies, we hypothesize that plasma lipoproteins play an indirect but important role in DR, contingent on the integrity of the blood-retina-barrier (BRB). In retinas with an intact BRB, plasma lipoproteins may be largely irrelevant; however, important effects become operative after the BRB is impaired in diabetes, leading to lipoprotein extravasation and subsequent modification, hence toxicity to the neighbouring retinal cells. In this hypothesis, BRB leakage is the key, plasma lipoprotein concentrations mainly modulate its consequences, and fenofibrate has intra-retinal actions. This review summarizes our current knowledge of the direct effects and mechanisms of modified lipoproteins on retinal cells and their potential contribution to the pathogenesis of DR.
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Affiliation(s)
- Jeremy Y Yu
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Northern Ireland, UK
| | - Timothy J Lyons
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Northern Ireland, UK ; Harold Hamm Diabetes Center and Section of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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