Resveratrol reduces oxidation and proliferation of human retinal pigment epithelial cells via extracellular signal-regulated kinase inhibition

Retinoprotective Effect of SkQ1, Visomitin Eye Drops, Is Associated with Suppression of P38 MAPK and ERK1/2 Signaling Pathways Activity

Visomitin eye drops are the first and, so far, the only drug based on SkQ1 - the mitochondria-targeted antioxidant 10-(6'-plastoquinonyl) decyltriphenylphosphonium, developed in the laboratories of Moscow State University under the leadership of Academician V. P. Skulachev. SkQ1 is considered as a potential tool to combat the aging program. We have previously shown that it is able to prevent and/or suppress development of all manifestations of accelerated senescence in OXYS rats, including retinopathy, similar to the age-related macular degeneration (AMD). Here, we assessed the effect of Visomitin instillations on progression of the AMD-like pathology and p38 MAPK and ERK1/2 activity in the OXYS rat retina (from the age of 9 to 12 months). Wistar and OXYS rats treated with placebo (composition identical to Visomitin with the exception of SkQ1) were used as controls. Ophthalmological examination showed that in the OXYS rats receiving placebo, retinopathy progressed and severity of clinical manifestations did not differ from the intact OXYS rats. Visomitin suppressed progression of the AMD-like pathology in the OXYS rats and significantly improved structural and functional parameters of the retinal pigment epithelium cells and state of microcirculation in the choroid, which, presumably, contributed to preservation of photoreceptors, associative and ganglion neurons. It was found that the activity of p38 MAPK and ERK1/2 in the retina of 12-month-old OXYS rats is higher than that of the Wistar rats of the same age, as indicated by the increased content of phosphorylated forms of p38 MAPK and ERK1/2 and their target protein tau (at position T181 and S396). Visomitin decreased phosphorylation of p38 MAPK, ERK1/2, and tau indicating suppression of activity of these MAPK signaling cascades. Thus, Visomitin eye drops are able to suppress progression of the AMD-like pathology in the OXYS rats and their effect is associated with the decrease in activity of the MAPK signaling cascades.

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.

Plant bioactive compounds alleviate photoinduced retinal damage and asthenopia: Mechanisms, synergies, and bioavailability

The retina, an important tissue of the eye, is essential in visual transmission and sustaining adequate eyesight. However, oxidative stress and inflammatory reactions can harm retinal structure and function. Recent studies have demonstrated that exposure to light can induce oxidative stress and inflammatory reactions in retinal cells, thereby facilitating the progression of retinal damage-related diseases and asthenopia. Plant bioactive compounds such as anthocyanin, curcumin, resveratrol, lutein, zeaxanthin, epigallocatechin gallate, and quercetin are effective in alleviating retinal damage and asthenopia. Their strong oxidation resistance and unique chemical structure can prevent the retina from producing reactive oxygen species and regulating eye muscle relaxation, thus alleviating retinal damage and asthenopia. Additionally, the combination of these active ingredients produces a stronger antioxidant effect. Consequently, understanding the mechanism of retinal damage caused by light and the regulation mechanism of bioactive compounds can better protect the retina and reduce asthenopia.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Effects of Resveratrol on Vascular Function in Retinal Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) events are involved in the development of various ocular pathologies, e.g., retinal artery or vein occlusion. We tested the hypothesis that resveratrol is protective against I/R injury in the murine retina. Intraocular pressure (IOP) was elevated in anaesthetized mice to 110 mm Hg for 45 min via a micropipette placed in the anterior chamber to induce ocular ischemia. In the fellow eye, which served as control, IOP was kept at a physiological level. One group received resveratrol (30 mg/kg/day p.o. once daily) starting one day before the I/R event, whereas the other group of mice received vehicle solution only. On day eight after the I/R event, mice were sacrificed and retinal wholemounts were prepared and immuno-stained using a Brn3a antibody to quantify retinal ganglion cells. Reactivity of retinal arterioles was measured in retinal vascular preparations using video microscopy. Reactive oxygen species (ROS) and nitrogen species (RNS) were quantified in ocular cryosections by dihydroethidium and anti-3-nitrotyrosine staining, respectively. Moreover, hypoxic, redox and nitric oxide synthase gene expression was quantified in retinal explants by PCR. I/R significantly diminished retinal ganglion cell number in vehicle-treated mice. Conversely, only a negligible reduction in retinal ganglion cell number was observed in resveratrol-treated mice following I/R. Endothelial function and autoregulation were markedly reduced, which was accompanied by increased ROS and RNS in retinal blood vessels of vehicle-exposed mice following I/R, whereas resveratrol preserved vascular endothelial function and autoregulation and blunted ROS and RNS formation. Moreover, resveratrol reduced I/R-induced mRNA expression for the prooxidant enzyme, nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2). Our data provide evidence that resveratrol protects from I/R-induced retinal ganglion cell loss and endothelial dysfunction in the murine retina by reducing nitro-oxidative stress possibly via suppression of NOX2 upregulation.

Pharmacological Therapy of Proliferative Vitreoretinopathy: Systematic In Vitro Comparison of 36 Pharmacological Agents

Purpose: Proliferative vitreoretinopathy (PVR) is currently treated surgically. Reliable pharmaceutical options would be desirable, and numerous drugs have been proposed. This in vitro study is intended to systematically compare and determine the most promising candidates for the treatment of PVR. Methods: A structured literature review was conducted in the "PubMed" database to identify previously published agents proposed for medical treatment of PVR -36 substances that met the inclusion criteria. Toxicity and antiproliferative effects were evaluated on primary human retinal pigment epithelial (hRPE) using colorimetric viability assays. The seven substances with the widest therapeutic range between toxicity and no longer detectable antiproliferative effect were then validated with a bromodeoxyuridine assay and a scratch wound healing assay using primary cells derived from surgically excised human PVR membranes (hPVR). Results: Among 36 substances, 12 showed no effect on hRPE at all. Seventeen substances had a significant (P < 0.05) toxic effect of which nine did not have an antiproliferative effect. Fifteen substances significantly reduced hRPE proliferation (P < 0.05). The seven most promising drugs with the highest difference between toxicity and antiproliferative effects on hRPE were dasatinib, methotrexate, resveratrol, retinoic acid, simvastatin, tacrolimus, and tranilast. Whereof resveratrol, simvastatin, and tranilast additionally showed antiproliferative and dasatinib, resveratrol, and tranilast antimigratory effects on hPVR (P < 0.05). Conclusion: This study presents a systematic comparison of drugs that have been proposed for PVR treatment in a human disease model. Dasatinib, resveratrol, simvastatin, and tranilast seem to be promising and are well-characterized in human use.

Resveratrol: Its Path from Isolation to Therapeutic Action in Eye Diseases

Due to the confirmed therapeutic potential of resveratrol (Rv) for eye diseases, namely its powerful anti-angiogenic and antioxidant effects, this molecule must be studied more deeply. Nowadays, the pharmaceutic and pharmacokinetic available studies offer a troubling picture because of its low stability and bioavailability. To overcome this problem, researchers started to design and create different delivery systems that could improve the delivery amount of Rv. Therefore, this review aims to shed light on the proper and efficient techniques to isolate, purify and quantify the Rv molecule, and how this therapeutic molecule can be a part of a delivery system. The Rv great impact on aspects regarding its stability, bioavailability and absorption are also debated here, based on the existent literature on in vitro and in vivo human and animal studies. Moreover, after its absorption the Rv influence at the molecular level in ocular pathologies is described. In addition, the present review summarizes the available literature about Rv, hoping that Rv will gain more attention to investigate its unexplored side.

The Role of Resveratrol in Eye Diseases—A Review of the Literature

Resveratrol (3,5,4′-trans-trihydroxystilbene) is a polyphenolic phytoalexin belonging to the stilbene family. It is commonly found in grape skins and seeds, as well as other plant-based foods. Oxidative stress and inflammation play a key role in the initiation and progression of age-related eye disorders (glaucoma, cataracts, diabetic retinopathy, and macular degeneration) that lead to a progressive loss of vision and blindness. Even though the way resveratrol affects the human body and the course of many diseases is still the subject of ongoing scientific research, it has been shown that the broad spectrum of anti-inflammatory and neuroprotective properties of resveratrol has a beneficial effect on eye tissues. In our research, we decided to analyze the current scientific literature on resveratrol, its possible mechanisms of action, and its therapeutic application in order to assess its effectiveness in eye diseases.

Role of Mitochondria in Retinal Pigment Epithelial Aging and Degeneration

Retinal pigment epithelial (RPE) cells form a monolayer between the neuroretina and choroid. It has multiple important functions, including acting as outer blood-retina barrier, maintaining the function of neuroretina and photoreceptors, participating in the visual cycle and regulating retinal immune response. Due to high oxidative stress environment, RPE cells are vulnerable to dysfunction, cellular senescence, and cell death, which underlies RPE aging and age-related diseases, including age-related macular degeneration (AMD). Mitochondria are the powerhouse of cells and a major source of cellular reactive oxygen species (ROS) that contribute to mitochondrial DNA damage, cell death, senescence, and age-related diseases. Mitochondria also undergo dynamic changes including fission/fusion, biogenesis and mitophagy for quality control in response to stresses. The role of mitochondria, especially mitochondrial dynamics, in RPE aging and age-related diseases, is still unclear. In this review, we summarize the current understanding of mitochondrial function, biogenesis and especially dynamics such as morphological changes and mitophagy in RPE aging and age-related RPE diseases, as well as in the biological processes of RPE cellular senescence and cell death. We also discuss the current preclinical and clinical research efforts to prevent or treat RPE degeneration by restoring mitochondrial function and dynamics.

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.

Dietary Supplementation of Olive Mill Waste Water Polyphenols in Rabbits: Evaluation of the Potential Effects on Hepatic Apoptosis, Inflammation and Metabolism through RT-qPCR Approach

Agro-industrial processing for the production of food or non-food products generates a wide range of by-products and residues rich in bioactive compounds including polyphenols. The concentration of these by-products is sometimes higher than in the original raw material as in the case of olive mill waste water (OMWW), one of the main by-products of olive oil extraction. Polyphenols are secondary plant metabolites that regulate the expression of specific inflammatory genes, transcriptional factors and pro/anti-apoptotic molecules, thus modulating the signaling pathways essential for cell health and homeostasis. The liver plays a key role in regulating homeostasis by responding to dietary changes in order to maintain nutritional and physiological states. In this study a nutrigenomic approach was adopted, which focuses on the effects of diet-health-gene interactions and the modulation of cellular processes, in order to evaluate the expression of the genes (AGER, BAX, COX2, IL1B, PPARA, PPARG, SIRT1, TNFA) involved in these interactions in the livers of rabbits fed with a diet supplemented with OMWW (POL) or without supplements (control, CTR). The RT-qPCR analysis showed the down-regulation of SIRT1, TNFA, AGER, BAX and PPARA transcripts in the POL group compared to the CTR group. These results show that OMWW dietary supplementation prevents cell death and tissue deterioration in rabbits.

Mitochondrial Dysfunction and Endoplasmic Reticulum Stress in Age Related Macular Degeneration, Role in Pathophysiology, and Possible New Therapeutic Strategies

Age related macular degeneration (AMD) is the main cause of legal blindness in developed countries. It is a multifactorial disease in which a combination of genetic and environmental factors contributes to increased risk of developing this vision-incapacitating condition. Oxidative stress plays a central role in the pathophysiology of AMD and recent publications have highlighted the importance of mitochondrial dysfunction and endoplasmic reticulum stress in this disease. Although treatment with vascular endothelium growth factor inhibitors have decreased the risk of blindness in patients with the exudative form of AMD, the search for new therapeutic options continues to prevent the loss of photoreceptors and retinal pigment epithelium cells, characteristic of late stage AMD. In this review, we explain how mitochondrial dysfunction and endoplasmic reticulum stress participate in AMD pathogenesis. We also discuss a role of several antioxidants (bile acids, resveratrol, melatonin, humanin, and coenzyme Q10) in amelioration of AMD pathology.

The Present and Future of Mitochondrial-Based Therapeutics for Eye Disease

Translational Relevance

Mitochondria are viable therapeutic targets for a broad spectrum of ocular diseases.

Tetrandrine Enhances H2O2-Induced Apoptotic Cell Death Through Caspase-dependent Pathway in Human Keratinocytes

BACKGROUND

Tetrandrine, a bis-benzylisoquinoline alkaloid, induces apoptosis of many types of human cancer cell. Hydrogen peroxide (H₂O₂) is a reactive oxygen species inducer; however, there are no reports to show whether pre-treatment of tetrandrine with H₂O₂ induces more cell apoptosis than H₂O₂ alone. Thus, the present study investigated the effects of tetrandrine on H₂O₂-induced cell apoptosis of human keratinocytes, HaCaT, in vitro.

MATERIALS AND METHODS

HaCaT cells were pre-treated with and without tetrandrine for 1 h, and then treated with H₂O₂ for examining cell morphological changes and cell viability using contrast-phase microscopy and propidium iodide (PI) exclusion assay, respectively. Cells were measured apoptotic cell death by using annexin V/PI double staining and further analyzed by flow cytometer. Cells were further assessed for DNA condensation using 2-(4-amidinophenyl)-6-indolecarbamidine staining. Western blotting was used to measure expression of apoptosis-associated proteins and confocal laser microscopy was used to measure the protein expression and nuclear translocation from the cytoplasm to nuclei.

RESULTS

Pre-treatment of tetrandrine for 1 h and treatment with H₂O₂ enhanced H₂O₂-induced cell morphological changes and reduced cell viability, whilst increasing apoptotic cell death and DNA condensation. Furthermore, tetrandrine significantly increased expression of reactive oxygen species-associated proteins such as superoxide dismutase (Cu/Zn) and superoxide dismutase (Mn) but significantly reduced the level of catalase, which was also confirmed by confocal laser microscopy. It also increased expression of DNA repair-associated proteins ataxia telangiectasia mutated, ataxia-telangectasia and Rad3-related, phospho-P53, P53 and phosphorylated histone H2AX, and of pro-apoptotic proteins BCL2 apoptosis regulator-associated X-protein, caspase-3, caspase-8, caspase-9 and poly ADP ribose polymerase in HaCaT cells.

CONCLUSION

These are the first and novel findings showing tetrandrine enhances H₂O₂-induced apoptotic cell death of HaCaT cells and may provide a potent approach for the treatment of proliferated malignant keratinocytes.

Nutraceutical Supplementation Ameliorates Visual Function, Retinal Degeneration, and Redox Status in rd10 Mice

Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies characterized by progressive degeneration of photoreceptor cells. Ocular redox status is altered in RP suggesting oxidative stress could contribute to their progression. In this study, we investigated the effect of a mixture of nutraceuticals with antioxidant properties (NUT) on retinal degeneration in rd10 mice, a model of RP. NUT was orally administered to rd10 mice from postnatal day (PD) 9 to PD18. At PD18 retinal function and morphology were examined by electroretinography (ERG) and histology including TUNEL assay, immunolabeling of microglia, Müller cells, and poly ADP ribose polymers. Retinal redox status was determined by measuring the activity of antioxidant enzymes and some oxidative stress markers. Gene expression of the cytokines IL-6, TNFα, and IL-1β was assessed by real-time PCR. NUT treatment delayed the loss of photoreceptors in rd10 mice partially preserving their electrical responses to light stimuli. Moreover, it ameliorated redox status and reduced inflammation including microglia activation, upregulation of cytokines, reactive gliosis, and PARP overactivation. NUT ameliorated retinal functionality and morphology at early stages of RP in rd10 mice. This formulation could be useful as a neuroprotective approach for patients with RP in the future.

Effects of Dietary Polyphenols from Olive Mill Waste Waters on Inflammatory and Apoptotic Effectors in Rabbit Ovary

The aim of this study was to evaluate the effect of dietary polyphenols on the expression of the effectors involved in inflammation and apoptosis in rabbit ovary. New Zealand White female rabbits were fed a basal control diet (CTR), or the same diet supplemented with a polyphenolic concentrate (POL, 282.4 mg/kg) obtained from olive mill waste waters. The follicle counts and the relative mRNA (RT-qPCR) and protein (immunohistochemistry) expression of the effectors involved in inflammation (cyclooxygenase-2; interleukin-1beta; tumor necrosis factor-alpha, TNFA) and apoptosis (BCL2-associated X protein, BAX), detected in the ovaries of both groups, were examined. The POL diet increased the primary and total follicles number. Cyclooxygenase-2 gene expression was higher (p < 0.05) in the POL group than in the CTR group, whereas BAX was lower (p < 0.05) in POL than CTR. Immunohistochemistry revealed the presence of all the proteins examined, with weaker (p < 0.05) COX2 and BAX signals in POL. No differences between the CTR and POL groups were observed for IL1B and TNFA gene and protein expression. These preliminary findings show that dietary polyphenols modulate inflammatory and apoptotic activities in rabbit ovary, regulating cyclooxygenase-2 and BAX expression, thus suggesting a functional involvement of these dietary compounds in mammalian reproduction.

Antioxidants for the Treatment of Retinal Disease: Summary of Recent Evidence

Retinal tissue is prone to oxidant burden and oxidative stress secondary to the generation of reactive oxygen species from high metabolic demand. The formation of reactive oxygen species occurs primarily from the mitochondrial respiratory chain as well as several enzymatic and oxidation reactions that occur in the neurosensory retina and retinal pigment epithelium. This oxidative stress has been implicated in the pathogenesis of several retinal diseases and the role of antioxidants as a therapeutic treatment shows promise in slowing the progression of certain diseases. The aim of this narrative review is to describe the mechanisms of retinal oxidative stress and summarize the current available evidence for antioxidants as a treatment for vitreoretinal disorders.

New Highlights of Resveratrol: A Review of Properties against Ocular Diseases

Eye diseases are currently a major public health concern due to the growing number of cases resulting from both an aging of populations and exogenous factors linked to our lifestyles. Thus, many treatments including surgical pharmacological approaches have emerged, and special attention has been paid to prevention, where diet plays a preponderant role. Recently, potential antioxidants such as resveratrol have received much attention as potential tools against various ocular diseases. In this review, we focus on the mechanisms of resveratrol against ocular diseases, in particular age-related macular degeneration, glaucoma, cataract, diabetic retinopathy, and vitreoretinopathy. We analyze, in relation to the different steps of each disease, the resveratrol properties at multiple levels, such as cellular and molecular signaling as well as physiological effects. We show and discuss the relationship to reactive oxygen species, the regulation of inflammatory process, and how resveratrol can prevent ocular diseases through a potential epigenetic action by the activation of sirtuin-1. Lastly, various new forms of resveratrol delivery are emerging at the same time as some clinical trials are raising more questions about the future of resveratrol as a potential tool for prevention or in therapeutic strategies against ocular diseases. More preclinical studies are required to provide further insights into RSV's potential adjuvant activity.

Swertiamarin from Enicostemma littorale, counteracts PD associated neurotoxicity via enhancement α-synuclein suppressive genes and SKN-1/NRF-2 activation through MAPK pathway

The elusive targets and the multifactorial etiology of Parkinson's disease (PD) have hampered the discovery of a potent drug for PD. Furthermore, the presently available medications provide only symptomatic relief and have failed to mitigate the pathogenesis associated with PD. Therefore, the current study was aimed to evaluate the prospective of swertiamarin (SW), a secoiridoid glycoside isolated from a traditional medicinal plant, Enicostemma littorale Blume to ameliorate the characteristic features of PD in Caenorhabditis elegans. SW (25 μM) administration decreased the α-synuclein (α-syn) deposition, inhibited apoptosis and increased dopamine level mediated through upregulating the expression of genes linked to ceramide synthesis, mitochondrial morphology and function regulation, fatty acid desaturase genes along with stress responsive MAPK (mitogen-activated protein kinase) pathway genes. The neuroprotective effect of SW was evident from the robust reduction of 6-hydroxydopamine (6-OHDA) induced dopaminergic neurodegeneration independent of dopamine transporter (dat-1). SW mediated translational regulation of MAPK pathway genes was observed through increase expression of SKN-1 and GST-4. Further, in-silico molecular docking analysis of SW with C. elegans MEK-1 showed a promising binding affinity affirming the in-vivo results. Overall, these novel finding supports that SW is a possible lead for drug development against the multi- factorial PD pathologies.

Oral administration of resveratrol or lactic acid bacterium improves lens elasticity

A decrease in the elasticity of the ocular lens during aging is associated with loss of the accommodative ability of the eye, leading to presbyopia. Although near vision impairment is a social issue affecting the length of healthy life expectancy and productivity of elderly people, an effective treatment to improve near vision has not yet become available. Here we examined the effect of Enterococcus faecium WB2000, Lactobacillus pentosus TJ515, and resveratrol on lens elasticity in rats, where the stiffness of the ocular lens increases exponentially during the aging process. A combination of WB2000 and resveratrol improved lens elasticity not only in the long term but also with just short-term treatment. In addition, TJ515 decreased stiffness in the eye lens with long-term treatment. Therefore, the oral administration of WB2000 and resveratrol or TJ515 may be a potential approach for managing the progression of near vision impairment.

New lipophenols prevent carbonyl and oxidative stresses involved in macular degeneration

Dry age-related macular degeneration and Stargardt disease undergo a known toxic mechanism caused by carbonyl and oxidative stresses (COS). This is responsible for accumulation in the retinal pigment epithelium (RPE) of A2E, a main toxic pyridinium bis-retinoid lipofuscin component. Previous studies have shown that carbonyl stress in retinal cells could be reduced by an alkyl-phloroglucinol-DHA conjugate (lipophenol). Here, we performed a rational design of different families of lipophenols to conserve anti-carbonyl stress activities and improve antioxidant properties. Five synthetic pathways leading to alkyl-(poly)phenol derivatives, with phloroglucinol, resveratrol, catechin and quercetin as the main backbone, linked to poly-unsaturated fatty acid, are presented. These lipophenols were evaluated in ARPE-19 cell line for their anti-COS properties and a structure-activity relationship study is proposed. Protection of ARPE-19 cells against A2E toxicity was assessed for the four best candidates. Finally, interesting anti-COS properties of the most promising quercetin lipophenol were confirmed in primary RPE cells.

Hydrogen Sulfide Protects Retinal Pigment Epithelial Cells from Oxidative Stress-Induced Apoptosis and Affects Autophagy

Age-related macular degeneration (AMD) is a major cause of visual impairment and blindness among the elderly. AMD is characterized by retinal pigment epithelial (RPE) cell dysfunction. However, the pathogenesis of AMD is still unclear, and there is currently no effective treatment. Accumulated evidence indicates that oxidative stress and autophagy play a crucial role in the development of AMD. H2S is an antioxidant that can directly remove intracellular superoxide anions and hydrogen peroxide. The purpose of this study is to investigate the antioxidative effect of H2S in RPE cells and its role in autophagy. The results show that exogenous H2S (NaHS) pretreatment effectively reduces H2O2-induced oxidative stress, oxidative damage, apoptosis, and inflammation in ARPE-19 cells. NaHS pretreatment also decreased autophagy levels raised by H2O2, increased cell viability, and ameliorated cell morphological damage. Interestingly, the suppression of autophagy by its inhibitor 3-MA showed an increase of cell viability, amelioration of morphology, and a decrease of apoptosis. In summary, oxidative stress causes ARPE-19 cell injury by inducing cell autophagy. However exogenous H2S is shown to attenuate ARPE-19 cell injury, decrease apoptosis, and reduce the occurrence of autophagy-mediated by oxidative stress. These findings suggest that autophagy might play a crucial role in the development of AMD, and exogenous H2S has a potential value in the treatment of AMD.

Nanodelivery of Resveratrol-Loaded PLGA Nanoparticles for Age-Related Macular Degeneration

Age-related macular degeneration, precisely neovascular form, is the leading cause of vision loss and the key treatment includes intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents. A method to increase local concentration of drug at posterior segment of the eye and to reduce the frequency of intravitreal injections is an unmet need. Resveratrol, a naturally occurring antioxidant and anti-inflammatory polyphenol, was loaded in PLGA polymeric nanoparticles to study their sustained release property and effectiveness in reducing expression of VEGF protein in vitro. Nanoparticles were characterized using FTIR, DSC, size, encapsulation efficiency, TEM, and in vitro drug release studies. Using MTT assay, the cytotoxicity of formulation was evaluated on ARPE-19 cells. The cellular uptake and VEGF expression levels were also evaluated in in vitro settings. The optimized formulation had a particle size of 102.7 nm with - 47.30 mV of zeta potential. Entrapment efficiency was found to be 65.21%. The cell viability results suggested compatibility of developed formulation. Cellular uptake and VEGF expression levels for the formulated nanoparticles specified that the developed formulation showed potential cellular uptake and had displayed anti-angiogenic property by inhibiting VEGF expression in vitro. The results showed successful development of resveratrol-loaded nanoparticles which may be used for neovascular AMD treatment alone or in combination with anti-VEGF agents.

The retina revolution: signaling pathway therapies, genetic therapies, mitochondrial therapies, artificial intelligence

PURPOSE OF REVIEW

The aim of this article is to review and discuss the history, current state, and future implications of promising biomedical offerings in the field of retina.

RECENT FINDINGS

The technologies discussed are some of the more recent promising biomedical developments within the field of retina. There is a US Food and Drug Administration-approved gene therapy product and artificial intelligence device for retina, with many other offerings in the pipeline.

SUMMARY

Signaling pathway therapies, genetic therapies, mitochondrial therapies, and artificial intelligence have shaped retina care as we know it and are poised to further impact the future of retina care. Retina specialists have the privilege and responsibility of shaping this future for the visual health of current and future generations.

Cytoprotective Effects of Natural Highly Bio-Available Vegetable Derivatives on Human-Derived Retinal Cells

Retinal pigment epithelial cells are crucial for retina maintenance, making their cytoprotection an excellent way to prevent or slow down retinal degeneration. In addition, oxidative stress, inflammation, apoptosis, neovascularization, and/or autophagy are key pathways involved in degenerative mechanisms. Therefore, here we studied the effects of curcumin, lutein, and/or resveratrol on human retinal pigment epithelial cells (ARPE-19). Cells were incubated with individual or combined agent(s) before induction of (a) H₂O₂-induced oxidative stress, (b) staurosporin-induced apoptosis, (c) CoCl₂-induced hypoxia, or (d) a LED-autophagy perturbator. Metabolic activity, cellular survival, caspase 3/7 activity (casp3/7), cell morphology, VEGF levels, and autophagy process were assessed. H₂O₂ provoked a reduction in cell survival, whereas curcumin reduced metabolic activity which was not associated with cell death. Cell death induced by H₂O₂ was significantly reduced after pre-treatment with curcumin and lutein, but not resveratrol. Staurosporin increased caspase-3/7 activity (689%) and decreased cell survival by 32%. Curcumin or lutein protected cells from death induced by staurosporin. Curcumin, lutein, and resveratrol were ineffective on the increase of caspase 3/7 induced by staurosporin. Pre-treatment with curcumin or lutein prevented LED-induced blockage of autophagy flux. Basal-VEGF release was significantly reduced by lutein. Therefore, lutein and curcumin showed beneficial protective effects on human-derived retinal cells against several insults.

Cytoprotective effect of crocin and trans-resveratrol on photodamaged primary human retinal pigment epithelial cells

PURPOSE

Light-induced damage to retinal pigment epithelium during pars plana vitrectomy remains a hot topic in ophthalmology. Improvements in technology led to a change of light sources, selective filters, and shorter light exposure time. Currently, there is no satisfying solution to the problem. The aim of the study was to investigate the cytoprotective effects of crocin and resveratrol on light-induced damage to primary human retinal pigment epithelial cells in vitro.

METHODS

Primary human retinal pigment epithelial cells were exposed to light analogous to the illumination during pars plana vitrectomy. To evaluate the cytoprotective effects and potential toxicity of resveratrol and crocin, human retinal pigment epithelial cells were incubated with varying concentrations of both before 3-[4,5-dimethylthiazol-2-yl] tetrazolium bromide (MTT) viability assay. Furthermore, glutathione levels were measured to investigate synergistic antioxidant potential. Apoptosis of human retinal pigment epithelial cells was determined by a nucleosome detection enzyme-linked immunosorbent assay.

RESULTS

Crocin and resveratrol improved cell viability in photodamaged human retinal pigment epithelial cells significantly from 40.65 ± 21.99% in illuminated human retinal pigment epithelial cells and reached a peak viability of 85.64 ± 11.37% in crocin and resveratrol pretreated cells (for all: p < 0.001). In line, the combination of the supplements increased glutathione levels significantly from 39.35 ± 21.96% to 80.74 ± 10.32% (p = 0.017). No toxic effects were detected (p > 0.99). However, no change in apoptosis rates could be observed following pretreatment with crocin and resveratrol (p > 0.99).

CONCLUSION

Crocin and trans-resveratrol revealed cytoprotective effects on human retinal pigment epithelial cells supporting both supplement's development as potential perioperative treatments in light-induced retinal pigment epithelial damage.

Caffeic Acid Alkyl Amide Derivatives Ameliorate Oxidative Stress and Modulate ERK1/2 and AKT Signaling Pathways in a Rat Model of Diabetic Retinopathy

The purpose of this study was to examine the neuroprotective effects of caffeic acid hexyl (CAF6) and dodecyl (CAF12) amide derivatives on the early stage of retinopathy in streptozotocin-induced diabetic rats. Animals were divided in five groups (n=8/group); one group consisted of non-diabetic rats as control, while the other four were diabetic animals either non-treated or treated with CAF6, CAF12 or resveratrol intravitreally for four weeks. Retinal superoxide dismutase (SOD) activity and 8-iso-prostaglandin F_2α (iPF_2α ) levels were evaluated by an ELISA assay. Phosphorylation of ERK1/2 and AKT was determined by immunoblotting in retinal homogenates. Retinal morphology was also examined using light microscopy. Treatment with CAF6 and CAF12 increased retinal SOD activity, while it decreased iPF_2α levels in diabetic rats. Phosphorylation of ERK1/2 was increased, while AKT phosphorylation was decreased in diabetic rats compared to normal control and these alterations were significantly reversed in diabetic rats treated with CAF6 and CAF12. Furthermore, thickness of the whole retinal layer, outer nuclear layer, and ganglion cell count were decreased in diabetic rats compared to control and CAF6 and CAF12 treatments prevented these changes. CAF6 and CAF12 seem to be effective agents for treatment of diabetic retinopathy via attenuation of retinal oxidative stress and improvement of neuronal survival signaling.

Toxic effects of A2E in human ARPE-19 cells were prevented by resveratrol: a potential nutritional bioactive for age-related macular degeneration treatment

Age-related macular degeneration (AMD) is a late-onset retinal disease and the leading cause of central vision loss in the elderly. Degeneration of retinal pigment epithelial cells (RPE) is a crucial contributing factor responsible for the onset and progression of AMD. The toxic fluorophore N-retinyl-N-retinylidene ethanolamine (A2E), a major lipofuscin component, accumulates in RPE cells with age. Phytochemicals with antioxidant properties may have a potential role in both the prevention and treatment of this age-related ocular disease. Particularly, there is an increased interest in the therapeutic effects of resveratrol (RSV), a naturally occurring polyphenol (3,4',5-trihydroxystilbene). However, the underlying mechanism of the RSV antioxidative effect in ocular diseases has not been well explored. We hypothesized that this bioactive compound may have beneficial effects for AMD. To this end, to investigate the potential profits of RSV against A2E-provoked oxidative damage, we used human RPE cell line (ARPE-19). RSV (25 µM) attenuates the cytotoxicity and the typical morphological characteristics of apoptosis observed in 25 µM A2E-laden cells. RSV pretreatment strengthened cell monolayer integrity through the preservation of the transepithelial electrical resistance and reduced the fluorescein isothiocyanate (FITC)-dextran diffusion rate as well as cytoskeleton architecture. In addition, RSV exhorts protective effects against A2E-induced modifications in the intracellular redox balance. Finally, RSV also prevented A2E-induced mitochondrial network fragmentation. These findings reinforce the idea that RSV represents an attractive bioactive for therapeutic intervention against ocular diseases associated with oxidative stress such as AMD.

Loss of NAMPT in aging retinal pigment epithelium reduces NAD+ availability and promotes cellular senescence

Retinal pigment epithelium (RPE) performs numerous functions critical to retinal health and visual function. RPE senescence is a hallmark of aging and degenerative retinal disease development. Here, we evaluated the temporal expression of key nicotinamide adenine dinucleotide (NAD⁺)-biosynthetic genes and associated levels of NAD⁺, a principal regulator of energy metabolism and cellular fate, in mouse RPE. NAD⁺ levels declined with age and correlated directly with decreased nicotinamide phosphoribosyltransferase (NAMPT) expression, increased expression of senescence markers (p16^INK4a, p21^Waf/Cip1, ApoJ, CTGF and β-galactosidase) and significant reductions in SIRT1 expression and activity. We simulated in vitro the age-dependent decline in NAD⁺ and the related increase in RPE senescence in human (ARPE-19) and mouse primary RPE using the NAMPT inhibitor FK866 and demonstrated the positive impact of NAD⁺-enhancing therapies on RPE cell viability. This, we confirmed in vivo in the RPE of mice injected sub-retinally with FK866 in the presence or absence of nicotinamide mononucleotide. Our data confirm the importance of NAD⁺ to RPE cell biology normally and in aging and demonstrate the potential utility of therapies targeting NAMPT and NAD⁺ biosynthesis to prevent or alleviate consequences of RPE senescence in aging and/or degenerative retinal diseases in which RPE dysfunction is a crucial element.

Dietary Polyphenols in Age-Related Macular Degeneration: Protection against Oxidative Stress and Beyond

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by degeneration and loss of photoreceptors and retinal pigment epithelium (RPE) cells with oxidative stress playing a role in its pathology. Although systematic reviews do not support the protective role of diet rich in antioxidants against AMD, dietary polyphenols (DPs) have been reported to have beneficial effects on vision. Some of them, such as quercetin and cyanidin-3-glucoside, can directly scavenge reactive oxygen species (ROS) due to the presence of two hydroxyl groups in their B ring structure. Apart from direct ROS scavenging, DPs can lower oxidative stress in several other pathways. Many DPs induce NRF2 (nuclear factor, erythroid 2-like 2) activation and expression of phase II enzymes that are under transcriptional control of this factor. DPs can inhibit A2E photooxidation in RPE cells, which is a source of oxidative stress. Anti-inflammatory action of DPs in RPE cells is associated with regulation of various interleukins and signaling pathways, including IL-6/JAK2 (Janus kinase 2)/STAT3. Some DPs can improve impaired cellular waste clearance, including AMD-specific deficient phagocytosis of the Aβ42 peptide and autophagy.

A derivative of betulinic acid protects human Retinal Pigment Epithelial (RPE) cells from cobalt chloride-induced acute hypoxic stress

The Retinal Pigment Epithelium (RPE) is a monolayer of cells located above the choroid. It mediates human visual cycle and nourishes photoreceptors. Hypoxia-induced oxidative stress to RPE is a vital cause of retinal degeneration such as the Age-related Macular Degeneration. Most of these retinal diseases are irreversible with no efficient treatment, therefore protecting RPE cells from hypoxia stress is an important way to prevent or slow down the progression of retinal degeneration. Betulinic acid (BA) and betulin (BE) are pentacyclic triterpenoids with anti-oxidative property, but little is known about their effect on RPE cells. We investigated the protective effect of BA, BE and their derivatives against cobalt chloride-induced hypoxia stress in RPE cells. Human ARPE-19 cells were exposed to BA, BE and their eighteen derivatives (named as H3H20) that we customized through replacing moieties at C3 and C28 positions. We found that cobalt chloride reduced cell viability, increased Reactive Oxygen Species (ROS) production as well as induced apoptosis and necrosis in ARPE-19 cells. Interestingly, the pretreatment of 3-O-acetyl-glycyl- 28-O-glycyl-betulinic acid effectively protected cells from acute hypoxia stress induced by cobalt chloride. Our immunoblotting results suggested that this derivative attenuated the cobalt chloride-induced activation of Akt, Erk and JNK pathways. All findings were further validated in human primary RPE cells. In summary, this BA derivate has protective effect against the acute hypoxic stress in human RPE cells and may be developed into a candidate agent effective in the prevention of prevalent retinal diseases.

Reduced sirtuin 1/adenosine monophosphate-activated protein kinase in amyotrophic lateral sclerosis patient-derived mesenchymal stem cells can be restored by resveratrol

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motor neuron system. Our previous study has shown that bone marrow-mesenchymal stem cells (BM-MSCs) from ALS patients have functional limitations in releasing neurotrophic factors and exhibit the senescence phenotype. In this study, we examined sirtuin 1/adenosine monophosphate-activated protein kinase (SIRT1/AMPK) activities and identified significant decreases in the ALS-MSCs compared with normal healthy control originated BM-MSCs. This decline was restored by pretreatment with resveratrol (RSV), measured using quantitative polymerase chain reaction, NAD/NADH assay, and immunoblot analysis. Neuroprogenitor markers were increased in RSV-treated ALS-MSCs (RSV/ALS-MSCs). The differentiated ALS-MSCs (ALS-dMSCs) exhibited a cell body and dendritic shape similar to neurons. RSV/ALS-MSCs showed significantly increased differentiation rate as compared with the untreated ALS-dMSCs. The neurite numbers and lengths were also significantly increased. This was confirmed with immunoblot analysis using neuron specific markers such as nestin, NF-M, Tuj-1, and Map-2 in RSV/ALS-dMSCs. Thus, this study shows that ALS-MSCs showed down-regulation of AMPK/SIRT1 signalling, which was recovered by treatment with RSV. This data suggest that RSV can be one of the candidate agents for improving therapeutic efficacy of ALS patients' originated MSCs.

Protection of Kaempferol on Oxidative Stress-Induced Retinal Pigment Epithelial Cell Damage

The protection of retinal pigment epithelium (RPE) injury plays an important role in the prevention of or in delaying the pathological progress of retinal degeneration diseases, like age-related macular degeneration (AMD), diabetic retinopathy, and retinitis pigmentosa. Oxidative stress has been identified as a major inducer of RPE injury, which eventually could lead to a loss of vision. Kaempferol is a natural flavonoid widely distributed in many edible plants, fruits, and traditional medicines and has been reported to have antioxidant, anti-inflammatory, anticancer, and antimicrobial activities. The present study demonstrates that the total antioxidant capacity of kaempferol is approximately two times stronger than that of lutein which is also a natural antioxidant that is widely used in the prevention or treatment of AMD. Our data indicates that kaempferol protects human RPE cells (ARPE-19) from hydrogen peroxide- (H₂O₂-) induced oxidative cell damage and apoptosis through the signaling pathways involving Bax/Bcl-2 and caspase-3 molecules proofed by real-time PCR and Western blot results. Kaempferol also inhibits the upregulated vascular endothelial growth factor (VEGF) mRNA expression levels induced by H₂O₂ in ARPE-19 cells and affects the oxidation and antioxidant imbalanced system in ARPE-19 cells treated by H₂O₂ through the regulations of both the activities of reactive oxygen species (ROS) and superoxide dismutase (SOD). Furthermore, our in vivo experimental results show that in sodium iodate-induced retinal degeneration rat model, kaempferol could protect sodium iodate-induced pathological changes of retina tissue and retinal cells apoptosis as well as the upregulated VEGF protein expression in RPE cells. In summary, these novel findings demonstrate that kaempferol could protect oxidative stressed-human RPE cell damage through its antioxidant activity and antiapoptosis function, suggesting that kaempferol has a potential role in the prevention and therapeutic treatment of AMD or other retinal diseases mediated by oxidative stress.

Reactive Oxygen Species-Mediated Damage of Retinal Neurons: Drug Development Targets for Therapies of Chronic Neurodegeneration of the Retina

The significance of oxidative stress in the development of chronic neurodegenerative diseases of the retina has become increasingly apparent in recent years. Reactive oxygen species (ROS) are free radicals produced at low levels as a result of normal cellular metabolism that are ultimately metabolized and detoxified by endogenous and exogenous mechanisms. In the presence of oxidative cellular stress, ROS are produced in excess, resulting in cellular injury and death and ultimately leading to tissue and organ dysfunction. Recent studies have investigated the role of excess ROS in the pathogenesis and development of chronic neurodegenerative diseases of the retina including glaucoma, diabetic retinopathy, and age-related macular degeneration. Findings from these studies are promising insofar as they provide clear rationales for innovative treatment and prevention strategies of these prevalent and disabling diseases where currently therapeutic options are limited. Here, we briefly outline recent developments that have contributed to our understanding of the role of ROS in the pathogenesis of chronic neurodegenerative diseases of the retina. We then examine and analyze the peer-reviewed evidence in support of ROS as targets for therapy development in the area of chronic neurodegeneration of the retina.

Therapeutic Role of Resveratrol and Quercetin on Aortic Fibroblasts of Psammomys obesus After Oxidative Stress by Hydrogen Peroxide

In our study, we propose to analyze the effects of resveratrol (RES) and quercetin (QRC) on proliferation markers, oxidative stress, apoptosis, and inflammation of aortic fibroblasts of Psammomys obesus after induced oxidative stress by hydrogen peroxide (H2O2). Fibroblasts were incubated in RES 375 μM and QRC 0.083 μM for 24 hours after exposure to H2O2 1.2 mM for 6 hours. We performed the proliferation rate, cells viability, morphological analyses, cytochrome c, Akt, ERK1/2, and p38 MAPK quantification. The redox status was achieved by proportioning of malondialdehyde, nitric monoxide, advanced oxidation protein products, carbonyl proteins, catalase, and superoxide dismutase activity. The inflammation was measured by TNFα, MCP1, and NF-kB assay. The extracellular matrix (ECM) remodeling was performed by SDS-PAGE. Stressed fibroblasts showed a decrease of cell proliferation and viability, hypertrophy and oncosis, chromatin hypercondensation and increase of cytochrome c release characteristic of apoptosis, activation of ERK1/2 and Akt pathway, and decreases in p38 MAPK pathways marking the cellular resistance. The redox state was disrupted by increased malondialdehyde, nitric monoxide, advanced oxidation protein products, carbonyl protein production, catalase and superoxide dismutase activity, and a decreased production of proteins including collagens. Inflammation state was marked by MCP-1, TNFα, and NF-kB increase. Treatment of fibroblasts stressed by RES and QRC inverted the oxidative stress situation decreasing apoptosis and inflammation, and improving the altered redox status and rearrangement of disorders observed in extracellular matrix. H2O2 induced biochemical and morphological alterations leading to apoptosis. An improved general condition is observed after treatment with RES and QRC; this explains the antioxidant and antiapoptotic effects of polyphenols.

Protective Effect of Melatonin against Oxidative Stress-Induced Apoptosis and Enhanced Autophagy in Human Retinal Pigment Epithelium Cells

Age-related macular degeneration (AMD) affects the retinal macula and results in loss of vision, and AMD is the primary cause of blindness and severe visual impairment among elderly people worldwide. AMD is characterized by the accumulation of drusen in the Bruch's membrane and dysfunction of retinal pigment epithelial (RPE) cells and photoreceptors. The pathogenesis of AMD remains unclear, and no effective treatment exists. Accumulating evidence indicates that oxidative stress plays a critical role in RPE cell degeneration and AMD. Melatonin is an antioxidant that scavenges free radicals, and it has anti-inflammatory, antitumor, and antiangiogenic effects. This study investigated the antioxidative, antiapoptotic, and autophagic effects of melatonin on oxidative damage to RPE cells. We used hydrogen peroxide (H₂O₂) to stimulate reactive oxygen species production to cause cell apoptosis in ARPE-19 cell lines. Our findings revealed that treatment with melatonin significantly inhibited H₂O₂-induced RPE cell damage, decreased the apoptotic rate, increased the mitochondrial membrane potential, and increased the autophagy effect. Furthermore, melatonin reduced the Bax/Bcl-2 ratio and the expression levels of the apoptosis-associated proteins cytochrome c and caspase 7. Additionally, melatonin upregulated the expression of the autophagy-related proteins LC3-II and Beclin-1 and downregulated the expression of p62. Thus, melatonin's effects on autophagy and apoptosis can protect against H₂O₂-induced oxidative damage in human RPE cells. Melatonin may have multiple protective effects on human RPE cells against H₂O₂-induced oxidative damage.

Improvement of Storage Medium for Cultured Human Retinal Pigment Epithelial Cells Using Factorial Design

Storage of human retinal pigment epithelium (hRPE) can contribute to the advancement of cell-based RPE replacement therapies. The present study aimed to improve the quality of stored hRPE cultures by identifying storage medium additives that, alone or in combination, contribute to enhancing cell viability while preserving morphology and phenotype. hRPE cells were cultured in the presence of the silk protein sericin until pigmentation. Cells were then stored for 10 days in storage medium plus sericin and either one of 46 different additives. Individual effects of each additive on cell viability were assessed using epifluorescence microscopy. Factorial design identified promising additive combinations by extrapolating their individual effects. Supplementing the storage medium with sericin combined with adenosine, L-ascorbic acid and allopurinol resulted in the highest cell viability (98.6 ± 0.5%) after storage for three days, as measured by epifluorescence microscopy. Flow cytometry validated the findings. Proteomics identified 61 upregulated and 65 downregulated proteins in this storage group compared to the unstored control. Transmission electron microscopy demonstrated the presence of melanosomes after storage in the optimized medium. We conclude that the combination of adenosine, L-ascorbic acid, allopurinol and sericin in minimal essential medium preserves RPE pigmentation while maintaining cell viability during storage.

Kinsenoside Ameliorates Oxidative Stress-Induced RPE Cell Apoptosis and Inhibits Angiogenesis via Erk/p38/NF-κB/VEGF Signaling

The pathological superoxidative condition that retinal pigment epithelium (RPE) cells experience contributed to the advancement of age-related macular degeneration (AMD), which was accompanied by significant neovascularization. Therefore, the discovery of novel pharmacological candidates to ameliorate oxidative damage (H₂O₂) against RPE cells and inhibit the following angiogenesis simultaneously is urgently needed. Herein, we found that kinsenoside (Kin), an active component derived from Anoectochilus roxburghii, was able to protect RPE cells effectively and attenuate subsequent angiogenesis. In this study, H₂O₂-induced oxidative injury reduced RPE cell viability and increased cell apoptosis, which was significantly rescued by the treatment with Kin. Compared with H₂O₂ alone, Kin decreased the levels of Bax and increased the production of Bcl-2 in RPE cells. H₂O₂-stimulated VEGF up-regulation was inhibited by Kin treatment. Human umbilical vein endothelial cell (HUVEC) neovascularization induced by conditioned medium (CM) from H₂O₂-stimulated RPE cells was attenuated by treatment with Kin, VEGF antagonist, NF-κB, Erk-MAPK, and p38-MAPK inhibitors. Additionally, H₂O₂-activated phosphorylated expression of IκBα, p65, Erk, and p38 in RPE cells was inhibited by treatment with Kin. Taken together, Kin protected RPE from apoptosis against oxidative stress while simultaneously decreasing apoptosis-related neovascularization. This could be ascribed to the inhibition of Erk/p38/NF-κB signaling by Kin that contributed to the resulting decreased VEGF expression in H₂O₂-treated RPE cells.

Effects of resveratrol on memory performance, hippocampus connectivity and microstructure in older adults - A randomized controlled trial

INTRODUCTION

The polyphenol resveratrol has been suggested to exert beneficial effects on memory and the aging hippocampus due to calorie-restriction mimicking effects. However, the evidence based on human interventional studies is scarce. We therefore aimed to determine the effects of resveratrol on memory performance, and to identify potential underlying mechanisms using a broad array of blood-based biomarkers as well as hippocampus connectivity and microstructure assessed with ultra-high field magnetic resonance imaging (UHF-MRI).

METHODS

In this double-blind, randomized controlled trial, 60 elderly participants (60-79 years) with a wide body-mass index (BMI) range of 21-37 kg/m² were randomized to receive either resveratrol (200 mg/day) or placebo for 26 weeks (registered at ClinicalTrials.gov: NCT02621554). Baseline and follow-up assessments included the California Verbal Learning Task (CVLT, main outcome), the ModBent task, anthropometry, markers of glucose and lipid metabolism, inflammation and neurotrophins derived from fasting blood, multimodal neuroimaging at 3 and 7 T, and questionnaires to assess confounding factors.

RESULTS

Multivariate repeated-measures ANOVA did not detect significant time by group effects for CVLT performance. There was a trend for preserved pattern recognition memory after resveratrol, while performance decreased in the placebo group (n.s., p = 0.07). Further exploratory analyses showed increases in both groups over time in body fat, cholesterol, fasting glucose, interleukin 6, high sensitive C-reactive protein, tumor necrosis factor alpha and in mean diffusivity of the subiculum and presubiculum, as well as decreases in physical activity, brain-derived neurotrophic factor and insulin-like growth factor 1 at follow-up, which were partly more pronounced after resveratrol.

DISCUSSION

This interventional study failed to show significant improvements in verbal memory after 6 months of resveratrol in healthy elderly with a wide BMI range. A non-significant trend emerged for positive effects on pattern recognition memory, while possible confounding effects of unfavorable changes in lifestyle behavior, neurotrophins and inflammatory markers occurred. Our findings also indicate the feasibility to detect (un)healthy aging-related changes in measures of hippocampus microstructure after 6 months using 7T diffusion MRI. More studies incorporating a longer duration and larger sample size are needed to determine if resveratrol enhances memory performance in healthy older adults.

Modulated release from implantable ocular silicone oil tamponade drug reservoirs

Complicated cases of retinal detachment can be treated with silicone oil tamponades. There is the potential for silicone oil tamponades to have adjunctive drug releasing behaviour within the eye, however the lipophilic nature of silicone oil limits the number of drugs that are suitable, and drug release from the hydrophobic reservoir is uncontrolled. Here, a radiometric technique was developed to accurately measure drug solubility in silicone oil and measure release into culture media. All-trans retinoic acid (atRA), a lipophilic drug known to act as an anti-proliferative within the eye, was used throughout this work. Chain-end modification of polydimethylsiloxane with atRA produced a polydimethylsiloxane retinoate (PDMS-atRA), which was used as an additive to silicone oil to modify the solvent environment within the silicone oil and the distribution coefficient. Blends of PDMS-atRA and silicone oil containing different concentrations of free atRA were produced. The presence of PDMS-atRA in silicone oil had a positive effect on atRA solubility and the longevity of release in vitro. The drug release period was independent of atRA starting concentration and dependent on the PDMS-atRA concentration in the blend. A clinically relevant release period of atRA over 7 weeks from a silicone oil blend with PDMS-atRA was observed. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 938-946.

Polyphenols protect against age-associated apoptosis in female rat cochleae

Dietary antioxidants, polyphenols, have been found to be beneficial in protecting against the generation of oxidative stress in various diseases associated with aging. Age-related hearing loss (AHL) is the number one neurodegenerative disorder on our aged population. Sprague-Dawley rats divided into five groups according to their age (3, 6, 12, 18 and 24 months old) and treated with 100 mg/day/kg body weight of polyphenols were used. Then, cochleae were harvested to measure caspase activities (- 3, - 8 and - 9), caspase-3 gene expression, ATP levels, Bax, BcL-2 and p53 levels. 8-OHdG levels (marker of DNA oxidative damage) and annexin-V were also measured in cochleae. Increased levels of caspase-3 and 9 in cochlea were observed with age and this effect was attenuated by polyphenol treatment. In addition, ATP and Bcl-2 levels in older rats were recovered after administration of polyphenols, while Bax and p53 levels protein decreased. Oral supplementation with polyphenols also reduces DNA oxidative damage of cochlear cell. Treatment with polyphenols inhibits the activation of age-related apoptotic signaling by decreasing oxidative stress inside the rat cochlea.

Photoprotective effects of cranberry juice and its various fractions against blue light-induced impairment in human retinal pigment epithelial cells

CONTEXT

Cranberry has numerous biological activities, including antioxidation, anticancer, cardioprotection, as well as treatment of urinary tract infection (UTI), attributed to abundant phenolic contents.

OBJECTIVE

The current study focused on the effect of cranberry juice (CJ) on blue light exposed human retinal pigment epithelial (ARPE-19) cells which mimic age-related macular degeneration (AMD).

MATERIALS AND METHODS

Preliminary phytochemical and HPLC analysis, as well as total antioxidant capacity and scavenging activity of cranberry ethyl acetate extract and different CJ fractions (condensed tannins containing fraction), were evaluated. In cell line model, ARPE-19 were irradiated with blue light at 450 nm wavelength for 10 h (mimic AMD) and treated with different fractions of CJ extract at different doses (5-50 μg/mL) by assessing the cell viability or proliferation rate using MTT assay (repairing efficacy).

RESULTS

Phytochemical and HPLC analysis reveals the presence of several phenolic compounds (flavonoids, proanthocyanidin, quercetin) in ethyl acetate extract and different fractions of CJ. However, the condensed tannin containing fraction of ethyl acetate extract of CJ displayed the greater (p < 0.05) scavenging activity especially at the dose of 1 mg/mL. Similarly, the condensed tannin containing fraction at 50 μg/mL presented better (p < 0.05) repairing ability (increased cell viability). Furthermore, the oligomeric condensed tannin containing fraction display the best (p < 0.05) repairing efficiency at 50 μg/mL.

DISCUSSION AND CONCLUSION

In conclusion, this study distinctly proved that condensed tannin containing fraction of CJ probably exhibits better free radicals scavenging activity and thereby effectively protected the ARPE-19 cells and thus, hampers the progress of AMD.

Resveratrol reverses the adverse effects of bevacizumab on cultured ARPE-19 cells

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (PDR) are one of the major causes of blindness caused by neo-vascular changes in the retina. Intravitreal anti-VEGF injections are widely used in the treatment of wet-AMD and PDR. A significant percentage of treated patients have complications of repeated injections. Resveratrol (RES) is a polyphenol phytoalexin with anti-oxidative, anti-inflammatory and anti-proliferative properties. Hence, we hypothesized that if RES is used in combination with bevacizumab (BEV, anti-VEGF), it could reverse the adverse effects that precipitate fibrotic changes, drusen formation, tractional retinal detachment and so on. Human retinal pigment epithelial cells were treated with various combinations of BEV and RES. There was partial reduction in secreted VEGF levels compared to untreated controls. Epithelial-mesenchymal transition was lower in BEV + RES treated cultures compared to BEV treated cultures. The proliferation status was similar in BEV + RES as well as BEV treated cultures both groups. Phagocytosis was enhanced in the presence of BEV + RES compared to BEV. Furthermore, we observed that notch signaling was involved in reversing the adverse effects of BEV. This study paves way for a combinatorial strategy to treat as well as prevent adverse effects of therapy in patients with wet AMD and PDR.

Resveratrol (3,5,4'-trihydroxystilbene) and its properties in oral diseases

Health promotion strategies and lifestyle changes are important in disease prevention. Oral health has received a large amount of attention previously as it is a fundamental component of general health and it contributes to the quality of life. Therefore, the study of associations between diet, health and the presence of bioactive compounds in food is receiving a substantial amount of attention. In the present review the effects and targets of a natural polyohenolic stilbenoid compound; resveratrol (3,5,4'-trihydroxystilbene; RSV) is assessed, and the future prospects for RSV in promoting oral health are considered. RSV is a phytoalexin, synthesized by a wide range of plants and abundantly extracted in grape skin, it has been purported to exert a multiplicity of anti-inflammatory, anti-viral, anti-microbial, estrogenic, anticancer, cardioprotective, neuroprotective and immunomodulatory functions. In this review, following an introduction documenting the biochemistry of RSV and RSV glucosides, the bioavailability and pharmacokinetics of RSV are described. Considering its multiple properties, the present review has focused on the potential benefits of RSV as an antioxidant and chemopreventive agent.

Resveratrol inhibits transforming growth factor-β2-induced epithelial-to-mesenchymal transition in human retinal pigment epithelial cells by suppressing the Smad pathway

Proliferative vitreoretinopathy (PVR) is the main cause of failure following retinal detachment surgery. Transforming growth factor (TGF)-β2-induced epithelial-to-mesenchymal transition (EMT) plays an important role in the development of PVR, and EMT inhibition decreases collagen gel contraction and fibrotic membrane formation, resulting in prevention of PVR. Resveratrol is naturally found in red wine and has inhibitory effects on EMT. Resveratrol is widely used in cardioprotection, neuroprotection, chemotherapy, and antiaging therapy. The purpose of this study was to investigate the effects of resveratrol on TGF-β2-induced EMT in ARPE-19 cells in vitro. We found that resveratrol suppressed the decrease of zona occludens-1 (ZO-1) and caused an increase of alpha-smooth muscle actin expression in TGF-β2-treated ARPE-19 cells, assessed using Western blots; moreover, it also suppressed the decrease in ZO-1 and the increase of vimentin expression, observed using immunocytochemistry. Resveratrol attenuated TGF-β2-induced wound closure and cell migration in ARPE-19 cells in a scratch wound test and modified Boyden chamber assay, respectively. We also found that resveratrol reduced collagen gel contraction - assessed by collagen matrix contraction assay - and suppressed the phosphorylation of Smad2 and Smad3 in TGF-β2-treated ARPE-19 cells. These results suggest that resveratrol mediates anti-EMT effects, which could be used in the prevention of PVR.

Protective effects of resveratrol and its analogs on age-related macular degeneration in vitro

Damage of retinal pigment epithelial (RPE) cells by A2E may be critical for age-related macular degeneration (AMD) management. Accumulation and photooxidation of A2E are known to be one of the critical causes in AMD. Here, we evaluated the protective effect of resveratrol (RES), piceatannol (PIC) and RES glycones on blue-light-induced RPE cell death caused by A2E photooxidation. A2E treatment followed by blue light exposure caused significant damages on human RPE cells (ARPE-19). But the damages were attenuated by post- and pre-treatment of RES and PIC in our in vitro models. The results of cell free system and FAB-MS analysis clearly showed that the reduction of A2E by blue light exposure was significantly rescued, and that oxidized forms of A2E were significantly reduced by RES or PIC treatment. Besides, RES or PIC inhibited the intracellular accumulation of A2E. Not only RES and PIC but RES glycones showed protection of ARPE-19 cells against A2E and blue-light-induced photo-damage. These findings demonstrate that RES and its analogs may have protective effects against A2E and blue-light-induced ARPE-19 cell death through regulation of A2E accumulation as well as photooxidation of A2E. Thus RES and its analogs may be beneficial for AMD treatment.

Convergent Effects of Resveratrol and PYK2 on Prostate Cells

Resveratrol, a dietary polyphenol, is under consideration as chemopreventive and chemotherapeutic agent for several diseases, including cancer. However, its mechanisms of action and its effects on non-tumor cells, fundamental to understand its real efficacy as chemopreventive agent, remain largely unknown. Proline-rich tyrosine kinase 2 (PYK2), a non-receptor tyrosine kinase acting as signaling mediator of different stimuli, behaves as tumor-suppressor in prostate. Since, PYK2 and RSV share several fields of interaction, including oxidative stress, we have investigated their functional relationship in human non-transformed prostate EPN cells and in their tumor-prone counterpart EPN-PKM, expressing a PYK2 dead-kinase mutant. We show that RSV has a strong biological activity in both cell lines, decreasing ROS production, inducing morphological changes and reversible growth arrest, and activating autophagy but not apoptosis. Interestingly, the PYK2 mutant increases basal ROS and autophagy levels, and modulates the intensity of RSV effects. In particular, the anti-oxidant effect of RSV is more potent in EPN than in EPN-PKM, whereas its anti-proliferative and pro-autophagic effects are more significant in EPN-PKM. Consistently, PYK2 depletion by RNAi replicates the effects of the PKM mutant. Taken together, our results reveal that PYK2 and RSV act on common cellular pathways and suggest that RSV effects on prostate cells may depend on mutational-state or expression levels of PYK2 that emerges as a possible mediator of RSV mechanisms of action. Moreover, the observation that resveratrol effects are reversible and not associated to apoptosis in tumor-prone EPN-PKM cells suggests caution for its use in humans.

Resveratrol alleviates endotoxemia-associated adrenal insufficiency by suppressing oxidative/nitrative stress

We have recently demonstrated that endotoxin causes oxidative stress and overproduction of nitric oxide in adrenal glands, thereby leading to adrenocortical insufficiency. The aim of this study is to investigate the effects of resveratrol, a natural plant polyphenol with anti-oxidant and anti-nitrative properties, on endotoxemia-associated adrenocortical insufficiency. Resveratrol was administered immediately before injection of lipopolysaccharide (LPS). Twenty four hours later, the adrenocorticotropic hormone (ACTH) stimulation tests was been performed to measure the plasma corticosterone level and the adrenal gland tissues were collected for histopathologic examination, and determination of malondialdehyde (MDA), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity, inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) and peroxynitrite production. Treatment with resveratrol significantly inhibited endotoxemia-induced iNOS expression, NO production, and peroxynitrite formation and also attenuated LPS-induced oxidative stress in the adrenal gland, as evidenced by the decrease of pro-oxidant biomarker (MDA), and the increases of anti-oxidant biomarkers (T-AOC, CAT and SOD activity). H&E staining demonstrated that administration of LPS resulted in increased into the adrenal gland. H&E-stained sections of adrenal glands demonstrated signs of leukocyte infiltration and hemorrhage during endotoxemia, which were significantly improved by resveratrol treatment. In addition, resveratrol reversed the LPS-induced downregulation of ACTH receptor and silent information regulator 1 (SIRT1) in adrenal gland, as well as adrenocortical hyporesponsiveness to ACTH. Resveratrol exerts protective effects against endotoxemia-associated adrenocortical insufficiency by suppressing oxidative/nitrative stress. These findings support the potential for resveratrol as a possible pharmacological agent to improve adrenocortical insufficiency resulting from oxidative/nitrative damage.

Resveratrol and Ophthalmic Diseases

Resveratrol, a naturally occurring plant polyphenol found in grapes, is the principal biologically active component in red wine. Clinical studies have shown that resveratrol due to its potent anti-oxidant and anti-inflammatory properties are cardio-protective, chemotherapeutic, neuroprotective, and display anti-aging effects. Oxidative stress and inflammation play a critical role in the initiation and progression of age-related ocular diseases (glaucoma, cataract, diabetic retinopathy and macular degeneration) that lead to progressive loss of vision and blindness. In vitro and in vivo (animal model) experimental studies performed so far have provided evidence for the biological effects of resveratrol on numerous pathways including oxidative stress, inflammation, mitochondrial dysfunction, apoptosis, pro-survival or angiogenesis that are implicated in the pathogenesis of these age-related ocular disorders. In this review, we provide a brief overview of current scientific literature on resveratrol, its plausible mechanism(s) of action, its potential use and current limitations as a nutritional therapeutic intervention in the eye and its related disorders.