Oxidative Damage and Protection of the RPE (original) (raw)
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The Role of Oxidative Stress in the Onset and Development of Age-Related Macular Degeneration
Importance of Oxidative Stress and Antioxidant System in Health and Disease [Working Title]
Age-related macular degeneration (AMD) is a complex, degenerative and progressive chronic disease that leads to severe visual loss. The prevalence of early AMD accounts for 18% in the population between 65 and 74 years of age and even 30% in subjects older than 74 years. The articles published in the last decade point out to a significant role of oxidative stress in the onset and development of age-related macular degeneration. Generally, reactive oxygen species (ROS) are produced in the eye during light absorption and physiological metabolic processes. The level of oxidative stress is kept under control by the action of antioxidants and reparative enzymes. Excessive synthesis of ROS leads to increased oxidative modification of lipids, proteins and DNA, causing oxidative damage of cytoplasmic and nuclear cell elements and changes of the extracellular matrix. The accumulation of oxidatively modified compounds in drusen deposits will initiate the onset and development of AMD. The obje...
Free Radical Biology and Medicine, 2018
Non-exudative age-related macular degeneration (NE-AMD) represents the leading cause of blindness in the elderly. The macular retinal pigment epithelium (RPE) lies in a high oxidative environment because its high metabolic demand, mitochondria concentration, reactive oxygen species levels, and macular blood flow. It has been suggested that oxidative stress-induced damage to the RPE plays a key role in NE-AMD pathogenesis. The fact that the disease limits to the macular region raises the question as to why this area is particularly susceptible. We have developed a NE-AMD model induced by superior cervical ganglionectomy (SCGx) in C57BL/6J mice, which reproduces the disease hallmarks exclusively circumscribed to the temporal region of the RPE/outer retina. The aim of this work was analyzing RPE regional differences that could explain AMD localized susceptibility. Lower melanin content, thicker basal infoldings, higher mitochondrial mass, and higher levels of antioxidant enzymes, were found in the temporal RPE compared with the nasal region. Moreover, SCGx induced a decrease in the antioxidant system, and in mitochondria mass, as well as an increase in mitochondria superoxide, lipid peroxidation products, nuclear Nrf2 and heme oxygenase-1 levels, and in the occurrence of damaged mitochondria exclusively at the temporal RPE. These findings suggest that despite the wellknown differences between the human and mouse retina, it might not be NE-AMD pathophysiology which conditions the localization of the disease, but the macular RPE histologic and metabolic specific attributes that make it more susceptible to choroid alterations leading initially to a localized RPE dysfunction/damage, and secondarily to macular degeneration.
Clinics, 2011
OBJECTIVE: To investigate the role of oxidant/antioxidant status and protein oxidation in the development of agerelated macular degeneration. METHOD: The activities of serum superoxide dismutase and glutathione peroxidase and the levels of serum malondialdehyde, advanced oxidation protein products, glutathione and vitamin C were measured in 25 patients with age-related macular degeneration and 25 control subjects without age-related macular degeneration. RESULT: The malondialdehyde and advanced oxidation protein product levels in the serum were significantly higher in the age-related macular degeneration patient group than in the control group (p,0.05). The superoxide dismutase activity in the serum was significantly lower in the age-related macular degeneration patient group than in the control group (p,0.05). The levels of vitamin C and glutathione and the activity of glutathione peroxidase in the serum were unchanged between groups (p.0.05). CONCLUSION: The results of the present study suggest that decreased effectiveness of the antioxidant defense system and increased oxidative stress may play a role in the pathogenesis of age-related macular degeneration.
Antioxidants
Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered e...
Oxidative Stress Implication in Retinal Diseases—A Review
Antioxidants
Oxidative stress (OS) refers to an imbalance between free radicals (FRs), namely highly reactive molecules normally generated in our body by several pathways, and intrinsic antioxidant capacity. When FR levels overwhelm intrinsic antioxidant defenses, OS occurs, inducing a series of downstream chemical reactions. Both reactive oxygen species (ROS) and reactive nitrogen species (RNS) are produced by numerous chemical reactions that take place in tissues and organs and are then eliminated by antioxidant molecules. In particular, the scientific literature focuses more on ROS participation in the pathogenesis of diseases than on the role played by RNS. By its very nature, the eye is highly exposed to ultraviolet radiation (UVR), which is directly responsible for increased OS. In this review, we aimed to focus on the retinal damage caused by ROS/RNS and the related retinal pathologies. A deeper understanding of the role of oxidative and nitrosative stress in retinal damage is needed in o...
Oxidative stress: The achilles' heel of neurodegenerative diseases of the retina
Frontiers in Bioscience, 2012
Introduction 3. Characteristics of macular degeneration 4. Mechanisms of AMD 4.1. Hereditary effect (genetic variations) 4.1.1.Complement system 4.1.2. Other genes and DNA variations 4.2. Oxidative stress, inflammation and ER stress 4.3. Cigarette smoking 4.4. Other factors for AMD 5. Animal models of AMD 5.1. Dry AMD models 5.2. Wet AMD models 5.3. Both dry and wet AMD models 6. Therapies for AMD 6.1. Pharmacological treatment 6.1.1. Antioxidant treatment 6.1.2. Antiangiogenic treatment 6.2. Gene therapy 6.3. Regenerative medicine 6.4. Nanomedicine 7. Conclusions and perspectives 8. Acknowledgements 9. References
The impact of oxidative stress and inflammation on RPE degeneration in non-neovascular AMD
Progress in retinal and eye research, 2017
The retinal pigment epithelium (RPE) is a highly specialized, unique epithelial cell that interacts with photoreceptors on its apical side and with Bruch's membrane and the choriocapillaris on its basal side. Due to vital functions that keep photoreceptors healthy, the RPE is essential for maintaining vision. With aging and the accumulated effects of environmental stresses, the RPE can become dysfunctional and die. This degeneration plays a central role in age-related macular degeneration (AMD) pathobiology, the leading cause of blindness among the elderly in western societies. Oxidative stress and inflammation have both physiological and potentially pathological roles in RPE degeneration. Given the central role of the RPE, this review will focus on the impact of oxidative stress and inflammation on the RPE with AMD pathobiology. Physiological sources of oxidative stress as well as unique sources from photo-oxidative stress, the phagocytosis of photoreceptor outer segments, and ...
Is There Excess Oxidative Stress and Damage in Eyes of Patients with Retinitis Pigmentosa?
Antioxidants & Redox Signaling, 2015
Retinitis pigmentosa (RP) is a group of diseases in which a mutation in one of the large variety of genes causes death of rod photoreceptors. After rods die, cone photoreceptors gradually die resulting in constriction of visual fields and eventual blindness in many patients. Studies in animal models of RP have demonstrated that oxidative damage is a major contributor to cone cell death. In this study, we extended those findings to patients with RP, because compared to control patients, those with RP showed significant reduction in the reduced to oxidized glutathione (GSH/GSSG) ratio in aqueous humor and a significant increase in aqueous protein carbonyl content. In contrast, there was no significant decrease in the serum GSH/GSSG ratio or increase in carbonyl content of serum proteins. These data indicate that patients with RP have ocular oxidative stress and damage in the absence of manifestations of systemic oxidative stress and/or damage indicating that demonstrations of oxidative damage-induced cone cell death in animal models of RP may translate to human RP. These observations lead to the hypothesis that potent antioxidants will promote cone survival and function in patients with RP and that the aqueous GSH/GSSG ratio and carbonyl content on proteins may provide useful biomarkers. Antioxid. Redox Signal. 23, 643-648.
Retinitis Pigmentosa (RP): The Role of Oxidative Stress in the Degenerative Process Progression
Biomedicines, 2022
Purpose: Retinitis Pigmentosa is a term that includes a group of inherited bilateral and progressive retinal degenerations, with the involvement of rod photoreceptors, which frequently leads to blindness; oxidative stress may be involved in the degeneration progression as proposed by several recent studies. The goal of this study is to evaluate whether circulating free radicals taken from capillary blood are related to one of the most important features of Retinitis pigmentosa that can affect frequently patients: cystoid macular oedema (CME). Materials: A total of 186 patients with Retinitis Pigmentosa (range: 25–69 years) were enrolled; all patients completed an ophthalmologic examination and SD-OCT at baseline and were divided into three subgroups according to the SD-OCT features. ROS blood levels were determined using FORT with monitoring of free oxygen radicals. Results: Test levels of free oxygen radicals were significantly increased, almost twice, in RP patients showing cystoi...