Neuroprotective effect of bilberry extract in a murine model of photo-stressed retina

Antiaging, Brightening, and Antioxidant Efficacy of Fermented Bilberry Extract (Vaccinium myrtillus): A Randomized, Double-Blind, Placebo-Controlled Trial

Strategies for successful aging, including the use of food supplements, are part of the approach to support skin youthfulness. To demonstrate the efficacy of fermented bilberry extract (FBE) against skin aging and uneven complexion, a clinical trial was carried out on 66 subjects with visible "crow's feet" wrinkles, mild-to-moderate skin slackness, and uneven skin tone. The wrinkle depth, skin smoothness (Ra) and roughness (Rz), skin firmness (R0) and elasticity (R2), skin coloration (ITA°), and skin antioxidant capacity were measured before and after 28 (D28), 56 (D56), and 84 (D84) days of product use (either FBE or a placebo). These parameters were also integrated with a clinical evaluation, carried out by a dermatologist, and a self-assessment questionnaire to align the measured efficacy with the visual or perceived efficacy. At D84, the wrinkle depth had decreased by 10.6%, Ra had improved by 7.9%, Rz had decreased by 7.3%, R0 had improved by 13.3%, R2 had improved by 12.4%, and skin antioxidant capacity had increased by 20.8%. ITA° increased by 20.8% and was accompanied by a decrease in the skin's redness component by 16.8% and an increase in the lightness component by 2.2%. The variation of all the above-mentioned parameters was statistically significant between the FBE and PL groups. Our findings demonstrate the efficacy of FBE in improving skin aging and complexion evenness.

A narrative review on dietary components and patterns and age-related macular degeneration

Age-related macular degeneration (AMD) is one of the most prevalent eye diseases among the ageing population worldwide. It is a leading cause of blindness in individuals over 55, particularly in industrialised Western countries. The prevalence of AMD increases with age, and genetic factors and environmental influences are believed to contribute to its development. Among the environmental factors, diet plays a significant role in AMD. This review explores the association between dietary components, dietary patterns and AMD. Various nutrients, non-nutrient substances and dietary models that have the potential to counteract oxidative stress and inflammation, which are underlying mechanisms of AMD, are discussed. Consuming fruits, vegetables, fish and seafood, whole grains, olive oil, nuts and low-glycaemic-index foods has been highlighted as beneficial for reducing the risk of AMD. Adhering to the Mediterranean diet, which encompasses these elements, can be recommended as a dietary pattern for AMD. Furthermore, the modulation of the gut microbiota through dietary interventions and probiotics has shown promise in managing AMD.

Visual fatigue a comprehensive review of mechanisms of occurrence, animal model design and nutritional intervention strategies

When the eyes work intensively, it is easy to have eye discomfort such as blurred vision, soreness, dryness, and tearing, that is, visual fatigue. Visual fatigue not only affects work and study efficiency, but long-term visual fatigue can also easily affect physical and mental health. In recent years, with the popularization of electronic products, although it has brought convenience to the office and study, it has also caused more frequent visual fatigue among people who use electronic devices. Moreover, studies have reported that the number of people with visual fatigue is showing a trend of increasing year by year. The range of people involved is also extensive, especially students, people who have been engaged in computer work and fine instruments (such as microscopes) for a long time, and older adults with aging eye function. More and more studies have proposed that supplementation with the proper nutrients can effectively relieve visual fatigue and promote eye health. This review discusses the physiological mechanisms of visual fatigue and the design ideas of animal experiments from the perspective of modern nutritional science. Functional food ingredients with the ability to alleviate visual fatigue are discussed in detail.

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

Autophagy Activation Promoted by Pulses of Light and Phytochemicals Counteracting Oxidative Stress during Age-Related Macular Degeneration

The seminal role of autophagy during age-related macular degeneration (AMD) lies in the clearance of a number of reactive oxidative species that generate dysfunctional mitochondria. In fact, reactive oxygen species (ROS) in the retina generate misfolded proteins, alter lipids and sugars composition, disrupt DNA integrity, damage cell organelles and produce retinal inclusions while causing AMD. This explains why autophagy in the retinal pigment epithelium (RPE), mostly at the macular level, is essential in AMD and even in baseline conditions to provide a powerful and fast replacement of oxidized molecules and ROS-damaged mitochondria. When autophagy is impaired within RPE, the deleterious effects of ROS, which are produced in excess also during baseline conditions, are no longer counteracted, and retinal degeneration may occur. Within RPE, autophagy can be induced by various stimuli, such as light and naturally occurring phytochemicals. Light and phytochemicals, in turn, may synergize to enhance autophagy. This may explain the beneficial effects of light pulses combined with phytochemicals both in improving retinal structure and visual acuity. The ability of light to activate some phytochemicals may further extend such a synergism during retinal degeneration. In this way, photosensitive natural compounds may produce light-dependent beneficial antioxidant effects in AMD.

Vaccinium as Potential Therapy for Diabetes and Microvascular Complications

Diabetes mellitus is one of the most critical global health concerns, with a fast-growing prevalence. The incidence of diabetic vascular complications is also rapidly increasing, exacerbating the burden on individuals with diabetes and the consumption of public medical resources. Despite the overall improvements in the prevention, diagnosis, and treatment of diabetic microvascular complications in recent years, safe and effective alternative or adjunctive therapies are urgently needed. The mechanisms underlying diabetic vascular complications are complex, with hyperglycemia-induced oxidative stress and inflammation being the leading causes. Therefore, glycemic control, antioxidation, and anti-inflammation are considered the main targets for the treatment of diabetes and its vascular comorbidities. Vaccinium L. (Ericaceae) is a genus of plants enriched with polyphenolic compounds in their leaves and fruits. Vaccinium and its extracts have demonstrated good bioactivity in reducing blood glucose, oxidative stress, and inflammation, making them excellent candidates for the management of diabetes and diabetic vascular complications. Here, we review recent preclinical and clinical studies on the potential effect of Vaccinium on ameliorating diabetes and diabetic complications, particularly diabetic kidney disease and diabetic retinopathy.

Therapeutic effects of herbal medicines in different types of retinopathies: A systematic review

Objective

Retinopathy is an ocular manifestation of systemic diseases such as diabetes and vascular diseases. Herbal drugs have been considered as an effective therapeutic option with minimal side effects for the treatment of retinopathy by reducing the symptoms and improving visual acuity. The purpose of this systematic review was to collect studies on the effectiveness of medicinal plants in the treatment or prevention of retinopathy.

Materials and Methods

A systematic literature search was performed in PubMed, Scopus, Google Scholar, and other databases in April 2021 using "herbal products" and "Retinopathy" with all their equivalent and similar terms. For this purpose, human clinical trials with the English language were included and articles with subject irrelevancy were excluded from further evaluation.

Results

Overall, 30 articles with 2324 patients were studied for possible effects of herbal therapy on retinopathy. From 30 included articles, different herbal products had been evaluated. Out of 30 selected articles, 11 articles were for the treatment of age-related macular degeneration (AMD), 14 articles covered patients with diabetic retinopathy, and the other five studies were for other retinal disorders. The outcomes in majority of the studies include changes in visual acuity (VA), fundus performance, best-corrected visual acuity (BCVA), central macular thickness (CMT), focal electroretinogram (fERG), supplements and adjuvant medications appeared to be more beneficial in patients with AMD and diabetic maculopathy.

Conclusion

Herbal therapy can be considered as a potential candidate in the adjuvant and complementary therapies of retinopathy. However, further studies are required to verify such efficiency.

Protective Effects of Dipterocarpus tuberculatus in Blue Light-Induced Macular Degeneration in A2E-Laden ARPE19 Cells and Retina of Balb/c Mice

Natural products with significant antioxidant activity have been receiving attention as one of the treatment strategies to prevent age-related macular degeneration (AMD). Reactive oxygen intermediates (ROI) including oxo-N-retinylidene-N-retinylethanolamine (oxo-A2E) and singlet oxygen-induced damage, are believed to be one of the major causes of the development of AMD. To investigate the therapeutic effects of methanol extracts of Dipterocarpus tuberculatus Roxb. (MED) against blue light (BL)-caused macular degeneration, alterations in the antioxidant activity, apoptosis pathway, neovascularization, inflammatory response, and retinal degeneration were analyzed in A2E-laden ARPE19 cells and Balb/c mice after exposure of BL. Seven bioactive components, including 2α-hydroxyursolic acid, ε-viniferin, asiatic acid, bergenin, ellagic acid, gallic acid and oleanolic acid, were detected in MED. MED exhibited high DPPH and ABTS free radical scavenging activity. BL-induced increases in intracellular reactive oxygen species (ROS) production and nitric oxide (NO) concentration were suppressed by MED treatment. A significant recovery of antioxidant capacity by an increase in superoxide dismutase enzyme (SOD) activity, SOD expression levels, and nuclear factor erythroid 2-related factor 2 (NRF2) expression were detected as results of MED treatment effects. The activation of the apoptosis pathway, the expression of neovascular proteins, cyclooxygenase-2 (COX-2)-induced inducible nitric oxide synthase (iNOS) mediated pathway, inflammasome activation, and expression of inflammatory cytokines was remarkably inhibited in the MED treated group compared to the Vehicle-treated group in the AMD cell model. Furthermore, MED displayed protective effects in BL-induced retinal degeneration through improvement in the thickness of the whole retina, outer nuclear layer (ONL), inner nuclear layer (INL), and photoreceptor layer (PL) in Balb/c mice. Taken together, these results indicate that MED exhibits protective effects in BL-induced retinal degeneration and has the potential in the future to be developed as a treatment option for dry AMD with atrophy of retinal pigment epithelial (RPE) cells.

Review of Evidence for the Usage of Antioxidants for Eye Aging

Oxidative stress is one of the common factors leading to age-related eye diseases in older adults. Factors such as high oxygen consumption, high concentration of polyunsaturated fatty acids, and cumulative exposure to high-energy visible light in the eyes, lead to excessive generation of reactive oxygen species, hence triggering apoptosis of ocular cells and giving rise to ophthalmic diseases. Dietary supplements such as carotenoids, anthocyanins, and vitamins have antioxidant properties which may be of benefit in retaining better vision or reversing vision impairment; thus, studies have been conducted to understand the role of dietary supplements in the treatment or prevention of ophthalmic diseases. While high concentration of carotenoids such as lutein and zeaxanthin decrease the risk of developing age-related macular disease, anthocyanins and vitamins play a role in the treatment and prevention of other ophthalmic diseases: saffron extract reduced intraocular pressure in glaucoma patients; bilberry extract prevented impairments in lenses and retina, as well as alleviate symptoms of dry eye disease; high concentration of beta-carotene may reduce the risk of developing cataract. Further studies with clinical measurements are required to investigate the effectiveness of antioxidants on visual function and ophthalmic diseases.

Anti-Inflammatory Activity of Bilberry (Vaccinium myrtillus L.)

Inflammation is important in the pathogenesis of several chronic diseases. The anti-inflammatory properties of berries have been investigated but the anti-inflammatory activity of bilberry has received little attention and a detailed review is yet to be published. Therefore, we compiled information on the phytochemicals of bilberry and preclinical and clinical studies of its anti-inflammatory properties. The review was based on studies from 2007 to date. Phytoconstituents of bilberries were phenolic acids, organic acids, anthocyanins, coumarins, flavonols, flavanols, tannins, terpenoids, and volatile chemicals. Data from cell and animal model studies show that bilberry has an anti-inflammatory effect by lowering tumor necrosis factor-α, interleukin (IL)-6, and IL-1β expression, inducing nitric oxide synthases and cyclooxygenases, and altering the nuclear factor kappa B and Janus kinase-signal transducer and activator of transcription signaling pathways. Bilberry supplementation as fruits (frozen, processed, and whole), juices, and anthocyanins reduced levels of inflammatory markers in most clinical studies of metabolic disorders. Therefore, bilberry may be useful for the prevention and treatment of chronic inflammatory disorders.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Effects of Epigenetic Modification of PGC-1α by a Chemical Chaperon on Mitochondria Biogenesis and Visual Function in Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a hereditary blinding disease characterized by gradual photoreceptor death, which lacks a definitive treatment. Here, we demonstrated the effect of 4-phenylbutyric acid (PBA), a chemical chaperon that can suppress endoplasmic reticulum (ER) stress, in P23H mutant rhodopsin knock-in RP models. In the RP models, constant PBA treatment led to the retention of a greater number of photoreceptors, preserving the inner segment (IS), a mitochondrial- and ER-rich part of the photoreceptors. Electroretinography showed that PBA treatment preserved photoreceptor function. At the early point, ER-associated degradation markers, xbp1s, vcp, and derl1, mitochondrial kinetic-related markers, fis1, lc3, and mfn1 and mfn2, as well as key mitochondrial regulators, pgc-1α and tfam, were upregulated in the retina of the models treated with PBA. In vitro analyses showed that PBA upregulated pgc-1α and tfam transcription, leading to an increase in the mitochondrial membrane potential, cytochrome c oxidase activity, and ATP levels. Histone acetylation of the PGC-1α promoter was increased by PBA, indicating that PBA affected the mitochondrial condition through epigenetic changes. Our findings constituted proof of concept for the treatment of ER stress-related RP using PBA and revealed PBA’s neuroprotective effects, paving the way for its future clinical application.

Discovering the Potential of Natural Antioxidants in Age-Related Macular Degeneration: A Review

Age-related macular degeneration (AMD) is a multifactorial disease associated with anatomical changes in the inner retina. Despite tremendous advances in clinical care, there is currently no cure for AMD. This review aims to evaluate the published literature on the therapeutic roles of natural antioxidants in AMD. A literature search of PubMed, Web of Science and Google Scholar for peer-reviewed articles published between 1 January 2011 and 31 October 2021 was undertaken. A total of 82 preclinical and 18 clinical studies were eligible for inclusion in this review. We identified active compounds, carotenoids, extracts and polysaccharides, flavonoids, formulations, vitamins and whole foods with potential therapeutic roles in AMD. We evaluated the integral cellular signaling pathways including the activation of antioxidant pathways and angiogenesis pathways orchestrating their mode of action. In conclusion, we examined the therapeutic roles of natural antioxidants in AMD which warrant further study for application in clinical practice. Our current understanding is that natural antioxidants have the potential to improve or halt the progression of AMD, and tailoring therapeutics to the specific disease stages may be the key to preventing irreversible vision loss.

Flavonoid and cannabinoid impact on the ocular surface

PURPOSE OF REVIEW

To evaluate the impact of flavonoids and cannabinoids as anti-inflammatory and antiallergic treatments on the anterior surface of the eye.

RECENT FINDINGS

Allergic conjunctivitis and dry eye syndrome are common ocular surface diseases that have been treated with traditional pharmacological measures, e.g. corticosteroids, antihistamines. Given the side-effect profiles of these medications and the growing interest in complementary treatment modalities as part of integrative medical interventions, well known flavonoids, such as quercetin and catechin, are under investigation for topical and systemic application methods for relief. As flavonoid derivatives, pycnogenol and epigallocatechin gallate have alleviated dry eye symptoms, including lacrimal gland inflammation, tear secretion, and the stability of the tear film. Research on ocular cannabinoid receptors and response to synthetic cannabinoids are also being considered for therapy of anterior ocular disorders. The expansion of herbal formulations provides a framework for future treatment regimens for ocular surface disorders.

SUMMARY

Flavonoids and cannabinoids show promise as potential complementary treatment for allergic diseases because of their anti-inflammatory and antiallergic properties. Several studies implementing ocular and systemic application of these compounds show potential in becoming adjuvant treatment strategies for improving quality of life while also managing ocular surface disease processes.

Neuroprotective Effect of 4-Phenylbutyric Acid against Photo-Stress in the Retina

Exposure to excessive visible light causes retinal degeneration and may influence the progression of retinal blinding diseases. However, there are currently no applied treatments. Here, we focused on endoplasmic reticulum (ER) stress, which can cause cellular degeneration and apoptosis in response to stress. We analyzed functional, histological, and molecular changes in the light-exposed retina and the effects of administering an ER-stress inhibitor, 4-phenylbutyric acid (4-PBA), in mice. We found that light-induced visual function impairment related to photoreceptor cell loss and outer segment degeneration were substantially suppressed by 4-PBA administration, following attenuated photoreceptor apoptosis. Induction of retinal ER stress soon after light exposure, represented by upregulation of the immunoglobulin heavy chain binding protein (BiP) and C/EBP-Homologous Protein (CHOP), were suppressed by 4-PBA. Concurrently, light-induced oxidative stress markers, Nuclear factor erythroid 2-related factor 2 (Nrf2) and Heme Oxygenase 1 (HO-1), and mitochondrial apoptotic markers, B-cell lymphoma 2 apoptosis regulator (Bcl-2)-associated death promoter (Bad), and Bcl-2-associated X protein (Bax), were suppressed by 4-PBA administration. Increased expression of glial fibrillary acidic protein denoted retinal neuroinflammation, and inflammatory cytokines were induced after light exposure; however, 4-PBA acted as an anti-inflammatory. Suppression of ER stress by 4-PBA may be a new therapeutic approach to suppress the progression of retinal neurodegeneration and protect visual function against photo-stress.

Emerging biological therapies for the treatment of age-related macular degeneration

INTRODUCTION

Age-related macular degeneration (AMD) is the leading cause of blindness in individuals over age 50 in developed countries. Current therapy for nonexudative AMD (neAMD) is aimed at modifying risk factors and vitamin supplementation to slow progression, while intravitreal anti-vascular endothelial factor (VEGF) injections are the mainstay for treatment of choroidal neovascularization in exudative AMD (eAMD).

AREAS COVERED

Over the past decade, promising therapies have emerged that aim to improve the current standard of care for both diseases. Clinical trials for neAMD are investigating targets in the complement cascade, vitamin A metabolism, metformin, and tetracycline, whereas clinical trials for eAMD are aiming to decrease treatment burden through novel port delivery systems, increasing drug half-life, and targeting new sites of the VEGF cascade. Stem cell and gene therapy are also being evaluated for treatment of neAMD and eAMD.

EXPERT OPINION

With an aging population, the need for effective, long term, low burden treatment options for AMD will be in increasingly high demand. Current investigations aim to address the shortcomings of current treatment options with breakthrough treatment approaches. Therapeutics in the pipeline hold promise for improving the treatment of AMD, and are on track for widespread use within the next decade.

ADIPOR1 deficiency-induced suppression of retinal ELOVL2 and docosahexaenoic acid levels during photoreceptor degeneration and visual loss

Lipid metabolism-related gene mutations can cause retinitis pigmentosa, a currently untreatable blinding disease resulting from progressive neurodegeneration of the retina. Here, we demonstrated the influence of adiponectin receptor 1 (ADIPOR1) deficiency in retinal neurodegeneration using Adipor1 knockout (KO) mice. Adipor1 mRNA was observed to be expressed in photoreceptors, predominately within the photoreceptor inner segment (PIS), and increased after birth during the development of the photoreceptor outer segments (POSs) where photons are received by the visual pigment, rhodopsin. At 3 weeks of age, visual function impairment, specifically photoreceptor dysfunction, as recorded by electroretinography (ERG), was evident in homozygous, but not heterozygous, Adipor1 KO mice. However, although photoreceptor loss was evident at 3 weeks of age and progressed until 10 weeks, the level of visual dysfunction was already substantial by 3 weeks, after which it was retained until 10 weeks of age. The rhodopsin mRNA levels had already decreased at 3 weeks, suggesting that reduced rhodopsin may have contributed to early visual loss. Moreover, inflammation and oxidative stress were induced in homozygous KO retinas. Prior to observation of photoreceptor loss via optical microscopy, electron microscopy revealed that POSs were present; however, they were misaligned and their lipid composition, including docosahexaenoic acid (DHA), which is critical in forming POSs, was impaired in the retina. Importantly, the expression of Elovl2, an elongase of very long chain fatty acids expressed in the PIS, was significantly reduced, and lipogenic genes, which are induced under conditions of reduced endogenous DHA synthesis, were increased in homozygous KO mice. The causal relationship between ADIPOR1 deficiency and Elovl2 repression, together with upregulation of lipogenic genes, was confirmed in vitro. Therefore, ADIPOR1 in the retina appears to be indispensable for ELOVL2 induction, which is likely required to supply sufficient DHA for appropriate photoreceptor function and survival.

The Functional Vision Protection Effect of Danshensu via Dopamine D1 Receptors: In Vivo Study

Danshensu, a traditional herb-based active component (Salvia miltiorrhiza Bunge), has garnered attention, due to its safety, nutritional value, and antioxidant effects, along with cardiovascular-protective and neuroprotective abilities; however, its effect on the retinal tissues and functional vision has not been fully studied. The objective of this study was to analyze the protective effect of danshensu on retinal tissues and functional vision in vivo in a mouse model of light-induced retinal degeneration. High energy light-evoked visual damage was confirmed by the loss in structural tissue integrity in the retina accompanied by a decline in visual acuity and visual contrast sensitivity function (VCSF), whereas the retina tissue exhibited severe Müller cell gliosis. Although danshensu treatment did not particularly reduce light-evoked damage to the photoreceptors, it significantly prevented Müller cell gliosis. Danshensu exerted protective effects against light-evoked deterioration on low spatial frequency-based VCSF as determined by the behavioral optomotor reflex method. Additionally, the protective effect of danshensu on VCSF can be reversed and blocked by the injection of a dopamine D1 receptor antagonist (SCH 23390). This study demonstrated that the major functional vision promotional effect of danshensu in vivo was through the dopamine D1 receptors enhancement pathway, rather than the structural protection of the retinas.

Medicinal plants and natural products as neuroprotective agents in age-related macular degeneration

The retina may suffer neurodegenerative damages, as other tissues of the central nervous system do, and serious eye diseases may develop. One of them is age-related macular degeneration, which causes progressive loss of vision due to retina degeneration. Treatment of age-related macular degeneration focuses on antioxidant agents and anti-vascular endothelial growth factor compounds, among others, that prevent/diminish oxidative stress and reduce neovascularisation respectively. The phytochemicals, medicinal plants and/or plant-diet supplements might be a useful adjunct in prevention or treatment of age-related macular degeneration owing to their antioxidant and anti-vascular endothelial growth factor properties. This review article presents the most investigated plants and natural products in relation to age-related macular degeneration, such as saffron, ginkgo, bilberry and blueberry, curcuma or turmeric, carotenoids, polyphenols, and vitamins C and E. This study provides up-to-date information on the effects, treatments, safety and efficiency of these phytotherapy products.

Oxidative stress in the light-exposed retina and its implication in age-related macular degeneration

The retina continuously receives light to enable vision, and the related processes require a marked amount of energy. During active metabolism, reactive oxygen species (ROS) are generated in exchange. Although physiologically generated ROS may be removed by endogenous antioxidant systems, and the effects of oxidative stress may be recovered by repair systems to retain homeostasis and health, when ROS and oxidative stress exceed the capacity of the antioxidant and repair systems, the condition becomes pathological. Multiple mechanisms of oxidative stress and the effects of antioxidant and repair systems in the retina have long been analyzed using light-induced retinal degeneration models. Among the mechanisms, a positive feedback loop of oxidative stress and related inflammation may be involved in the pathogenesis of a blinding aging disease, age-related macular degeneration. Treatments for suppressing ROS and oxidative stress by administrating antioxidant products may support the tissue-protective function of antioxidant systems. Moreover, recent studies have proposed a new concept for maintaining homeostasis by supplying sufficient energy to activate the repair systems. The current review will help elucidate the influence of oxidative stress and guide future analyses to explore new therapeutic approaches for oxidative stress-mediated diseases.

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Vision formation requires marked amounts of energy and produces ROS.

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Balanced oxidative stress and antioxidant/repair systems determine cellular health.

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ROS-modified molecules affect multiple pathways to cause cell death and disorders.

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A positive feedback loop of oxidative stress/related inflammation may lead to AMD.

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Homeostasis can be retained by supplying enough energy to activate repair systems.

An Open-Label Pilot Study on Macumax Supplementation for Dry-Type Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is one of the most widespread degenerative disorders in elderly people. A 90-day, open-label clinical study was conducted in 40 patients, aged 50 years or older, with early-stage dry-type AMD to evaluate the safety and efficacy of Macumax^®, a novel mixture of a phyto-mineral nutritional supplement containing ZeaLutein^® (consisting of lutein, zeaxanthin, and piperine), extracts of bilberry, saffron, and zinc monomethionine. Subjects received one capsule of the supplement twice daily for 90 days. The treatment measures included physical examination, vital signs, and assessment of subjective and objective symptoms at baseline and after treatment. For efficacy assessment, baseline values were compared with the values after treatment at 30-day intervals, on days 30, 60, and 90. The safety of the treatment was assessed during all the visits. Overall, the patients showed improvement in the subjective symptoms, such as vision scores after treatment compared with baseline. The changes in diminished and distorted vision scores were found to be significant from day 60 (P < .05). In the case of objective symptoms, only 40% of the subjects (P < .05) had abnormal Amsler's grid aberration scores on day 90 compared with 77.5% of subjects at the beginning of the study. No adverse events were observed during the study. This pilot study provides evidence that Macumax^® supplementation is safe and maintained eye health without further progression of the disease in patients with early-stage dry-type AMD. Clinical Trial Registration number: CTRI/2016/02/006676

A Re-Appraisal of Pathogenic Mechanisms Bridging Wet and Dry Age-Related Macular Degeneration Leads to Reconsider a Role for Phytochemicals

Which pathogenic mechanisms underlie age-related macular degeneration (AMD)? Are they different for dry and wet variants, or do they stem from common metabolic alterations? Where shall we look for altered metabolism? Is it the inner choroid, or is it rather the choroid–retinal border? Again, since cell-clearing pathways are crucial to degrade altered proteins, which metabolic system is likely to be the most implicated, and in which cell type? Here we describe the unique clearing activity of the retinal pigment epithelium (RPE) and the relevant role of its autophagy machinery in removing altered debris, thus centering the RPE in the pathogenesis of AMD. The cell-clearing systems within the RPE may act as a kernel to regulate the redox homeostasis and the traffic of multiple proteins and organelles toward either the choroid border or the outer segments of photoreceptors. This is expected to cope with the polarity of various domains within RPE cells, with each one owning a specific metabolic activity. A defective clearance machinery may trigger unconventional solutions to avoid intracellular substrates’ accumulation through unconventional secretions. These components may be deposited between the RPE and Bruch’s membrane, thus generating the drusen, which remains the classic hallmark of AMD. These deposits may rather represent a witness of an abnormal RPE metabolism than a real pathogenic component. The empowerment of cell clearance, antioxidant, anti-inflammatory, and anti-angiogenic activity of the RPE by specific phytochemicals is here discussed.

Ocular and Systemic Effects of Antioxidative Supplement Use in Young and Healthy Adults: Real-World Cross-Sectional Data

Randomized controlled studies have shown that antioxidative supplements are effective in suppressing the progression of age-related macular degeneration and visual display terminal syndrome. However, effects of their general use in the real-world and by young and healthy individuals have not been well documented. We analyzed 27 participants who were under 35 years of age and had no diagnosed diseases. Mean functional visual acuity (FVA) score and visual maintenance ratio, which represent quick recognition of a target, both measured using FVA system, were better (both p < 0.01) in subjects who had had regular antioxidative supplement intake for more than 2 months (11 participants) compared with those who had not. Systemic data, i.e., total cholesterol, hemoglobin A1c (HbA1c), and high-sensitivity C-reactive protein (hs-CRP) levels, which correspond to chronic low-grade inflammation, were lower (all p < 0.05) in the former. Overall, hs-CRP levels had a correlation with total cholesterol (p < 0.05) and a trend of correlation with HbA1c (p = 0.054) levels. Thus, current real-world data showed that young, healthy participants who had a regular intake of antioxidative supplements had better visual acuity and systemic levels of metabolic and low-grade inflammation markers. This study will help promote future research into the effects of general antioxidative supplement use.

Macular Pigment Optical Density and Photoreceptor Outer Segment Length as Predisease Biomarkers for Age-Related Macular Degeneration

To explore predisease biomarkers, which may help screen for the risk of age-related macular degeneration (AMD) at very early stages, macular pigment optical density (MPOD) and photoreceptor outer segment (PROS) length were analyzed. Thirty late AMD fellow eyes, which are at high risk and represent the predisease condition of AMD, were evaluated and compared with 30 age-matched control eyes without retinal diseases; there was no early AMD involvement in the AMD fellow eyes. MPOD was measured using MPS2^® (M.E. Technica Co. Ltd., Tokyo, Japan), and PROS length was measured based on optical coherence tomography images. MPOD levels and PROS length in the AMD fellow eyes were significantly lower and shorter, respectively, than in control eyes. MPOD and PROS length were positively correlated in control eyes (R = 0.386; p = 0.035) but not in AMD fellow eyes. Twenty (67%) AMD fellow eyes met the criteria of MPOD < 0.65 and/or PROS length < 35 μm, while only five (17%) control eyes did. After adjusting for age and sex, AMD fellow eyes more frequently satisfied the definition (p < 0.001; 95% confidence interval, 3.50–60.4; odds ratio, 14.6). The combination of MPOD and PROS length may be a useful biomarker for screening predisease AMD patients, although further studies are required in this regard.

Recent Research on the Health Benefits of Blueberries and Their Anthocyanins

Awareness of the human health benefits of blueberries is underpinned by a growing body of positive scientific evidence from human observational and clinical research, plus mechanistic research using animal and in vitro models. Blueberries contain a large number of phytochemicals, including abundant anthocyanin pigments. Of their various phytochemicals, anthocyanins probably make the greatest impact on blueberry health functionality. Epidemiological studies associate regular, moderate intake of blueberries and/or anthocyanins with reduced risk of cardiovascular disease, death, and type 2 diabetes, and with improved weight maintenance and neuroprotection. These findings are supported by biomarker-based evidence from human clinical studies. Among the more important healthful aspects of blueberries are their anti-inflammatory and antioxidant actions and their beneficial effects on vascular and glucoregulatory function. Blueberry phytochemicals may affect gastrointestinal microflora and contribute to host health. These aspects have implications in degenerative diseases and conditions as well as the aging process. More evidence, and particularly human clinical evidence, is needed to better understand the potential for anthocyanin-rich blueberries to benefit public health. However, it is widely agreed that the regular consumption of tasty, ripe blueberries can be unconditionally recommended.

Neuroprotective and vision-protective effect of preserving ATP levels by AMPK activator

Progression of blinding diseases, such as age-related macular degeneration, is accelerated by light exposure. However, no particular intervention is applied to the photostress. Here, we report neuroprotective effects of the adenosine monophosphate (AMP)-activated protein kinase (AMPK) activator, 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR), on light-induced visual function impairment, photoreceptor disorders and death in mice. Increase in retinal ATP levels in response to photostress was transient, because oxygen consumption rate (OCR) and cytochrome c oxidase (CcO) activity were reduced under photostress. However, AICAR treatment preserved OCR, CcO activity, and high levels of retinal ATP after light exposure. AMPK knockdown in the photoreceptor-derived cell line revealed that AMPK targeted CcO activity. Further, our data indicated that photostress reduced mitochondrial respiratory function and ATP levels, while AICAR treatment promoted neuronal survival and retained visual function, stabilizing ATP levels through preserved CcO activity. The current study has provided proof of concept for providing cells with sufficient energy to promote cell survival in the presence of cellular stress. This is in contrast to the previous reports which primarily investigated therapeutic approaches to suppress stress signals. Hence, stabilization of the ATP supply may serve as a novel therapeutic approach to support tissue survival under stress and prevent neurodegeneration.

Dietary Spirulina Supplementation Protects Visual Function From Photostress by Suppressing Retinal Neurodegeneration in Mice

PURPOSE

We investigated whether daily consumption of Spirulina, an antioxidant generating cyanobacterial nutritional supplement, would suppress photostress-induced retinal damage and prevent vision loss in mice.

METHODS

Six-week-old male BALB/cAJcl mice were allowed constant access to either a standard or Spirulina-supplemented diet (20% Spirulina) that included the antioxidants, β-carotene and zeaxanthin, and proteins for 4 weeks. Following dark adaptation, mice were exposed to 3000-lux white light for 1 hour and returned to their cages. Visual function was analyzed by electroretinogram, and retinal histology by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated, deoxyuridine triphosphate nick-end labeling (TUNEL) assay, and immunohistochemistry. Retinal expression of proteins, reactive oxygen species (ROS), and mRNAs were measured using immunoblot analysis, enzyme-linked immunosorbent assay (ELISA), 2',7'-dichlorofluorescein-diacetate, or ROS Brite 700 Dyes, and real-time reverse-transcription polymerase chain reaction, respectively.

RESULTS

Light-induced visual function impairment was suppressed by constant Spirulina intake. Thinning of the photoreceptor layer and outer segments, photoreceptor cell death, decreased rhodopsin protein, and induction of glial fibrillary acidic protein were ameliorated in the Spirulina-intake group. Increased retinal ROS levels after light exposure were reduced by Spirulina supplementation. Light-induced superoxide dismutase 2 and heme oxygenase-1 mRNAs in the retina, and Nrf2 activation in the photoreceptor cells, were preserved with Spirulina supplementation, despite reduced ROS levels, suggesting two pathways for suppressing ROS, scavenging and induction of endogenous antioxidative enzymes. Light-induced MCP-1 retinal mRNA and proteins were also suppressed by Spirulina.

CONCLUSIONS

Spirulina ingestion protected retinal photoreceptors from photostress in the retina.

TRANSLATIONAL RELEVANCE

Spirulina has potential as a nutrient supplement to prevent vision loss related to oxidative damage in the future.

N-Acetyl-L-cysteine Protects Human Retinal Pigment Epithelial Cells from Oxidative Damage: Implications for Age-Related Macular Degeneration

Age-related macular degeneration (AMD) involves the loss of retinal pigment epithelium (RPE) and photoreceptors and is one of the leading causes of blindness in the elderly. Oxidative damage to proteins, lipids, and DNA has been associated with RPE dysfunction and AMD. In this study, we evaluated oxidative stress in AMD and the efficacy of antioxidant, N-acetyl-L-cysteine (NAC), in protecting RPE from oxidative damage. To test this idea, primary cultures of RPE from human donors with AMD (n = 32) or without AMD (No AMD, n = 21) were examined for expression of NADPH oxidase (NOX) genes, a source of reactive oxygen species (ROS). Additionally, the cells were pretreated with NAC for 2 hours and then treated with either hydrogen peroxide (H₂O₂) or tert-butyl hydroperoxide (t-BHP) to induce cellular oxidation. Twenty-four hours after treatment, ROS production, cell survival, the content of glutathione (GSH) and adenosine triphosphate (ATP), and cellular bioenergetics were measured. We found increased expression of p22phox, a NOX regulator, in AMD cells compared to No AMD cells (p = 0.02). In both AMD and No AMD cells, NAC pretreatment reduced t-BHP-induced ROS production and protected from H₂O₂-induced cell death and ATP depletion. In the absence of oxidation, NAC treatment improved mitochondrial function in both groups (p < 0.01). Conversely, the protective response exhibited by NAC was disease-dependent for some parameters. In the absence of oxidation, NAC significantly reduced ROS production (p < 0.001) and increased GSH content (p = 0.02) only in RPE from AMD donors. Additionally, NAC-mediated protection from H₂O₂-induced GSH depletion (p = 0.04) and mitochondrial dysfunction (p < 0.05) was more pronounced in AMD cells compared with No AMD cells. These results demonstrate the therapeutic benefit of NAC by mitigating oxidative damage in RPE. Additionally, the favorable outcomes observed for AMD RPE support NAC's relevance and the potential therapeutic value in treating AMD.

Reduction of Aging-Induced Oxidative Stress and Activation of Autophagy by Bilberry Anthocyanin Supplementation via the AMPK-mTOR Signaling Pathway in Aged Female Rats

Oxidative-stress-induced senescence constitutes a great risk factor for chronic diseases. Therefore, ameliorating oxidative-stress-induced senescence is expected to prevent chronic diseases. The beneficial effects of bilberry anthocyanin (BA) on healthy aging were evaluated using 12 month old, aging female SD rats in this study. The experimental results suggested that consumption of a middle-dose of BA (MBA) appreciably increased the relative liver mass by 7.34% when compared with that of the AC group. Furthermore, BA significantly increased the total antioxidant capacity, total superoxide dismutase activity, and catalase activities; decreased malondialdehyde, serum low-density lipoprotein cholesterol (LDL-C), serum total cholesterol (TC), serum triglyceride (TG), and glycated serum protein (GSP) levels; and reduced TC/high-density lipoprotein cholesterol (HDL-C) and LDL-C/HDL-C ratios. In addition, MBA decreased the activity of fecal bacterial enzymes and increased the content of fecal short-chain fatty acids. The Western blot results showed that MBA significantly upregulated the expression of OCLN, ZO-1, and autophagy-related proteins (ATP6 V0C, ATG4D, and CTSB) in aging rats. Moreover, it also showed that MBA induced the phosphorylation of AMPK and FOXO3a and inhibited the phosphorylation of mTOR, which indicated that bilberry anthocyanin induced autophagy via the AMPK-mTOR signaling pathways. This induction of autophagy further promoted oxidative stress resistance effects and intestinal epithelial barrier function of bilberry anthocyanin in aging female rats.

Lutein and Zeaxanthin Isomers Reduce Photoreceptor Degeneration in the Pde6b rd10 Mouse Model of Retinitis Pigmentosa

PURPOSE

Lutein, RR-zeaxanthin, and RS-zeaxanthin (L-Z) are antioxidants which can reduce endoplasmic reticulum stress (ERS) and oxidative stress (OS), and ameliorate neurodegenerative diseases. However, their treatment effect in the Pde6b rd10 (rd10) mouse model of retinitis pigmentosa (RP) and the underlying cellular mechanisms have not been studied. ERS is an important factor which causes photoreceptor apoptosis. The aim of the current project is to test the treatment effect of L-Z in rd10 mice and to investigate the underlying molecular mechanisms of ERS.

METHODS

L-Z (Lutemax 2020, 10 mg/kg) diluted in sunflower oil (SFO, 1 mg/ml) or the same volume of SFO was administrated via gavage from postnatal day 6 (P6) to P20 daily in L-Z group (n=5) or SFO group (n=6) of rd10 mice. At P21, electroretinography (ERG) was performed to show the functional change of retinas. 78 kDa glucose-regulated protein (GRP78) and endoplasmic reticulum protein 29 (ERp29) were tested by western blot and immunostaining.

RESULTS

The ERG amplitudes were larger in the L-Z group than those of the SFO group in all flash luminances of dark-adapted and light-adapted ERG (all p < 0.01). Western blot revealed that GRP78 in the retinas of the L-Z group was significantly downregulated compared to that of the SFO group (p < 0.01). Meanwhile, the retinal ERp29 protein was significantly upregulated in the L-Z treatment group than that of the SFO group (p < 0.01).

CONCLUSIONS

L-Z provide protection to the photoreceptors of rd10 mouse model of RP, which is probably associated with the reduction of ERS.

Bilberry extract and anthocyanins suppress unfolded protein response induced by exposure to blue LED light of cells in photoreceptor cell line

Purpose

The purpose of this study was to investigate the effects of bilberry extract with its anthocyanins on retinal photoreceptor cell damage and on the endoplasmic reticulum (ER) stress induced by exposure to blue light-emitting diode (LED) light.

Methods

Cultured murine photoreceptor cells (661W) were exposed to blue LED light with or without bilberry extract or its anthocyanins in the culture media. Aggregated short-wavelength opsin (S-opsin) in murine photoreceptor cells was observed with immunostaining. The expression of factors involved in the unfolded protein response was examined with immunoblot analysis and quantitative real-time reverse transcription (RT)-PCR. Furthermore, cell death was observed with double staining with Hoechst 33342 and propidium iodide after dithiothreitol (DTT) treatment.

Results

Bilberry extract and anthocyanins suppressed the aggregation of S-opsin, activation of ATF4, and expression of the mRNA of the factors associated with the unfolded protein response (UPR). In addition, bilberry extract and the anthocyanins inhibited the death of photoreceptor cells induced by DTT, an ER stress inducer.

Conclusions

These findings suggest that bilberry extract containing anthocyanins can alter the effects of blue LED light and DTT-induced retinal photoreceptor cell damage. These effects were achieved by modulating the activation of ATF4 and through the suppression of the abnormal aggregation of S-opsin.

Chrysin Ameliorates Malfunction of Retinoid Visual Cycle through Blocking Activation of AGE-RAGE-ER Stress in Glucose-Stimulated Retinal Pigment Epithelial Cells and Diabetic Eyes

Diabetes-associated visual cycle impairment has been implicated in diabetic retinopathy, and chronic hyperglycemia causes detrimental effects on visual function. Chrysin, a naturally occurring flavonoid found in various herbs, has anti-inflammatory, antioxidant, and neuroprotective properties. The goal of the current study was to identify the retinoprotective role of chrysin in maintaining robust retinoid visual cycle-related components. The in vitro study employed human retinal pigment epithelial (RPE) cells exposed to 33 mM of glucose or advanced glycation end products (AGEs) in the presence of 1–20 μM chrysin for three days. In the in vivo study, 10 mg/kg of chrysin was orally administrated to db/db mice. Treating chrysin reversed the glucose-induced production of vascular endothelial growth factor, insulin-like growth factor-1, and pigment epithelium-derived factor (PEDF) in RPE cells. The outer nuclear layer thickness of chrysin-exposed retina was enhanced. The oral gavage of chrysin augmented the levels of the visual cycle enzymes of RPE65, lecithin retinol acyltransferase (LRAT), retinol dehydrogenase 5 (RDH5), and rhodopsin diminished in db/db mouse retina. The diabetic tissue levels of the retinoid binding proteins and the receptor of the cellular retinol-binding protein, cellular retinaldehyde-binding protein-1, interphotoreceptor retinoid-binding protein and stimulated by retinoic acid 6 were restored to those of normal mouse retina. The presence of chrysin demoted AGE secretion and AGE receptor (RAGE) induction in glucose-exposed RPE cells and diabetic eyes. Chrysin inhibited the reduction of PEDF, RPE 65, LRAT, and RDH5 in 100 μg/mL of AGE-bovine serum albumin-exposed RPE cells. The treatment of RPE cells with chrysin reduced the activation of endoplasmic reticulum (ER) stress. Chrysin inhibited the impairment of the retinoid visual cycle through blocking ER stress via the AGE-RAGE activation in glucose-stimulated RPE cells and diabetic eyes. This is the first study demonstrating the protective effects of chrysin on the diabetes-associated malfunctioned visual cycle.

Lutein and Zeaxanthin Isomers Protect against Light-Induced Retinopathy via Decreasing Oxidative and Endoplasmic Reticulum Stress in BALB/cJ Mice

Oxidative stress (OS) and endoplasmic reticulum stress (ERS) are the major factors underlying photoreceptor degeneration. Lutein, RR-zeaxanthin (3R,3’R-zeaxanthin) and RS (meso)-zeaxanthin (3R,3’S-RS- zeaxanthin) (L/Zi) could protect against cell damage by ameliorating OS in retina. In this study, we examined the effect of L/Zi supplementation in a mouse model of photoreceptor degeneration and investigated whether the treatment of L/Zi ameliorated OS and ERS. BALB/cJ mice after light exposure were used as the animal model. The protective effects of L/Zi were observed by electroretinography (ERG) and terminal deoxyuridine triphosphate nick-end labeling (TUNEL) analysis. The underlying mechanisms related to OS and ERS were explored by Western blotting. After L/Zi treatment, the ERG amplitudes were significantly higher, and the number of TUNEL-positive cells was significantly reduced compared to that of the vehicle group. Western blotting results revealed that OS was ameliorated according to the significant downregulation of phosphorylated c-Jun N-terminal kinase (p-JNK), and significant upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). In addition, ERS was reduced according to the significant downregulation of 78 kDa glucose-regulated protein (GRP78), phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), activating transcription factor 4 (ATF4) and activating transcription factor (ATF6). Our data shows that L/Zi provided functional and morphological preservation of photoreceptors against light damage, which is probably related to its mitigation of oxidative and endoplasmic reticulum stress.

Protective Effect of Highly Polymeric A-Type Proanthocyanidins from Seed Shells of Japanese Horse Chestnut (Aesculus turbinata BLUME) against Light-Induced Oxidative Damage in Rat Retina

Retinal tissue is exposed to oxidative stress caused by visible light. Light-damaged rat used in age-related macular degeneration (AMD) studies clarified that antioxidants decrease retinal light damage. Albino rats were exposed to 5000 Lux light for 12 h with oral administration of the polyphenolic compounds fraction (PF) from the seed shells of Japanese horse chestnut (30 mg/kg, 100 mg/kg, and 300 mg/kg body weight: BW). To evaluate the protective effects against light damage, electroretinograms (ERGs), the outer nuclear layer (ONL) thickness, the antioxidant activity of plasma, oxidized retinal lipids, and the detection of apoptosis were examined. To reveal their active compounds, PF were separated into an A-type proanthocyanidin (PAF) and a flavonol O-glycosides fraction. The protective effects of these fractions against light damage were compared by measuring the thickness of the ERGs and ONL. Compared with the negative control, the PF group (100 mg/kg and 300 mg/kg BW) significantly suppressed the decrease of the ERG amplitudes and ONL thickness. PF (300 mg/kg BW) induced the elevation of in vivo antioxidant activity, and the suppression of retinal lipid oxidation. PF administration also suppressed apoptotic cell death. The protective effects against light damage were attributable to the antioxidant activity of PAF. The light-induced damage of retinas was protected by oral administration of PF and PAF. Taken together, these compounds are potentially useful for the prevention of the disease caused by light exposure. Highlights: The protective effects of retinal damage by light exposure were evaluated using polyphenolic compounds from the seed shells of Japanese horse chestnut (Aesculus turbinata BLUME) as an antioxidant. Decreases in the electroretinographic amplitude and outer nuclear layer thickness were suppressed by the polyphenolic compounds of the seed shells. Polyphenolic compounds from the seed shells of Japanese horse chestnut inhibited the oxidation of retinal lipids. Highly polymeric A-type proanthocyanidin from the seed shells protected the rat retina from light exposure damage by inhibiting oxidative stress and apoptotic mechanisms.

Neuroprotective role of retinal SIRT3 against acute photo-stress

SIRT3 is a key regulator of mitochondrial reactive oxygen species as well as mitochondrial function. The retina is one of the highest energy-demanding tissues, in which the regulation of reactive oxygen species is critical to prevent retinal neurodegeneration. Although previous reports have demonstrated that SIRT3 is highly expressed in the retina and important in neuroprotection, function of SIRT3 in regulating reactive oxygen species in the retina is largely unknown. In this study, we investigated the role of retinal SIRT3 in a light-induced retinal degeneration model using SIRT3 knockout mice. We demonstrate that SIRT3 deficiency causes acute reactive oxygen species accumulation and endoplasmic reticulum stress in the retina after the light exposure, which leads to increased photoreceptor death, retinal thinning, and decreased retinal function. Using a photoreceptor-derived cell line, we revealed that reactive oxygen species were the upstream initiators of endoplasmic reticulum stress. Under SIRT3 knockdown condition, we demonstrated that decreased superoxide dismutase 2 activity led to elevated intracellular reactive oxygen species. These studies have helped to elucidate the critical role of SIRT3 in photoreceptor neuronal survival, and suggest that SIRT3 might be a therapeutic target for oxidative stress-induced retinal disorders.