Oxidative stress and its downstream signaling in aging eyes

Nutrition and diet for dry eye disease: Insights toward holistic management

Dry eye disease (DED) is one of the most common eye problems in the aging population. Hyperosmolarity triggers the immune response in DED and consequently activates the self-perpetuating immune cycle, leading to chronic damage of the ocular surface. This event causes symptoms such as a burning sensation, irritation, redness, photophobia, and blurred vision in DED patients. Subsequently, the quality of life gets significantly affected. The rising demand for DED management and treatment solutions, and the desirable outcomes from innovative therapies that draw global interest provide evidence to demonstrate the role of diet and nutrition in DED. Nutritional deficiency and a Westernized diet contribute to the chronic systemic progression of DED symptoms. It has been revealed in several published studies that the use of nutrients and dietary supplements improves the ocular surface and acts as a protective factor against DED. - We reviewed nutrition and dietary aspects in managing DED and its associated consequences, based on published studies, and reached an evidence-based conclusion.

Dielectrophoretic characterization of peroxidized retinal pigment epithelial cells as a model of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a prevalent ocular pathology affecting mostly the elderly population. AMD is characterized by a progressive retinal pigment epithelial (RPE) cell degeneration, mainly caused by an impaired antioxidative defense. One of the AMD therapeutic procedures involves injecting healthy RPE cells into the subretinal space, necessitating pure, healthy RPE cell suspensions. This study aims to electrically characterize RPE cells to demonstrate a possibility using simulations to separate healthy RPE cells from a mixture of healthy/oxidized cells by dielectrophoresis.

METHODS

BPEI-1 rat RPE cells were exposed to hydrogen peroxide to create an in-vitro AMD cellular model. Cell viability was evaluated using various methods, including microscopic imaging, impedance-based real-time cell analysis, and the MTS assay. Healthy and oxidized cells were characterized by recording their dielectrophoretic spectra, and electric cell parameters (crossover frequency, membrane conductivity and permittivity, and cytoplasm conductivity) were computed. A COMSOL simulation was performed on a theoretical microfluidic-based dielectrophoretic separation chip using these parameters.

RESULTS

Increasing the hydrogen peroxide concentration shifted the first crossover frequency toward lower values, and the cell membrane permittivity progressively increased. These changes were attributed to progressive membrane peroxidation, as they were diminished when measured on cells treated with the antioxidant N-acetylcysteine. The changes in the crossover frequency were sufficient for the efficient separation of healthy cells, as demonstrated by simulations.

CONCLUSIONS

The study demonstrates that dielectrophoresis can be used to separate healthy RPE cells from oxidized ones based on their electrical properties. This method could be a viable approach for obtaining pure, healthy RPE cell suspensions for AMD therapeutic procedures.

Rheumatoid arthritis and diabetic retinopathy: A two-sample Mendelian randomization study

Diabetic retinopathy (DR) is a common and highly blinding disease. Many clinical studies have shown a causal relationship between Rheumatoid arthritis (RA) and DR, but the results are contradictory. In addition, some clinical results and pathological inferences have certain paradoxes, and the influence of RA on the pathogenesis and development of DR Is unclear. Our research assessed the causal association between RA and the development of DR using a 2-sample Mendelian randomization method. Single nucleotide polymorphisms (SNPs) relevant to the study were extracted and filtered from genome-wide association study (GWAS) data. A DR GWAS with a sample size of 190,594 and an RA GWAS with a sample size of 58,284 were obtained. Inverse variance weighted (IVW) method was used to analyze the results, and Mendelian randomization (MR)-Egger regression method and weighted median method were used to evaluate the robustness. Sensitivity analysis was performed using pleiotropy test, heterogeneity test, leave-one-out test to ensure that the results were unbiased. Confounding factors were eliminated to ensure robustness. A total of 83 related SNPs were screened. IVW method showed a positive correlation between RA and the increased relative risk of diabetic retinopathy (OR = 1.06, 95%CI: 1.04-1.23). The same trend was shown by MR-Egger regression method and weighted median method. Sensitivity analysis showed that there was no heterogeneity in SNPs, and the results were less likely to be affected by potential bias. After removing SNPs linked to confounders, the MR results remained significant and stable in direction. There is a positive causal association between rheumatoid arthritis and diabetic retinopathy. It is important to strengthen retina-related screening and prevention in diabetic patients with RA to reduce the risk of DR In RA patients.

Ferroptosis in Glaucoma: A Promising Avenue for Therapy

Glaucoma, a blind-leading disease largely since chronic pathological intraocular high pressure (ph-IOP). Hitherto, it is reckoned incurable for irreversible neural damage and challenges in managing IOP. Thus, it is significant to develop neuroprotective strategies. Ferroptosis, initially identified as an iron-dependent regulated death that triggers Fenton reactions and culminates in lipid peroxidation (LPO), has emerged as a focal point in multiple tumors and neurodegenerative diseases. Researches show that iron homeostasis play critical roles in the optic nerve (ON) and retinal ganglion cells (RGCs), suggesting targeted treatments could be effective. In glaucoma, apart from neural lesions, disrupted metal balance and increased oxidative stress in trabecular meshwork (TM) are observed. These disturbances lead to extracellular matrix excretion disorders, known as sclerotic mechanisms, resulting in refractory blockages. Importantly, oxidative stress, a significant downstream effect of ferroptosis, is also a key factor in cell senescence. It plays a crucial role in both the etiology and risk of glaucoma. Moreover, ferroptosis also induces non-infectious inflammation, which exacerbate glaucomatous injury. Therefore, the relevance of ferroptosis in glaucoma is extensive and multifaceted. In this review, the study delves into the current understanding of ferroptosis mechanisms in glaucoma, aiming to provide clues to inform clinical therapeutic practices.

Association of dietary intake of B vitamins with glaucoma

This cross-sectional study investigated the association between glaucoma and B vitamin dietary intake. A total of 5025 enrolled individuals participated in self-reported glaucoma questionnaire and 3264 participated in International Society Geographical and Epidemiological Ophthalmology (ISGEO) criteria. In self-reported glaucoma, the risk of having self-reported glaucoma was lower in the third quartile of vitamin B1 intake (odds ratio [odds ratio [OR] 0.63, 95% confidence interval [CI] 0.40-0.97), and P trend (P trend = 0.004) for vitamin B12 was significant; in males, the third quartile of vitamin B1 intake (OR 0.44, 95% CI 0.24-0.83) and the fourth quartile of vitamin B2 intake (OR 0.39, 95% CI 0.17-0.89) were associated with a lower risk. In glaucoma based on ISGEO criteria, the increase of niacin intake (OR 0.94, 95% CI 0.89-0.99) was negatively associated with the odds of self-reported glaucoma. After sex-stratified analysis, the third quartile of vitamin B6 intake (OR 0.21, 95% CI 0.08-0.60) in males were associated with reduced odds of glaucoma. The restricted cubic spline analysis revealed a nonlinear association of vitamin B2 (p for nonlinearity = 0.04) and B9 (p for nonlinearity = 0.024) intake with glaucoma diagnosed by ISGEO criteria in females.

Association between dietary antioxidant indices and glaucoma in the National Health and Nutrition Examination Survey

OBJECTIVE

To explore the relationship between dietary antioxidant indices (DAI) and glaucoma using the data from the 2005 to 2008 National Health and Nutrition Examination Survey (NHANES).

METHODS

Our study comprised participants who completed the NHANES dietary intake interview and visual health questionnaire at age 40 or older. The intakes of the vitamins A, C, and E as well as of zinc, selenium, and magnesium were used to generate the DAI, which represents the overall antioxidant qualities. The self-report method for glaucoma diagnosis (ever been told by an eye doctor) was used. Survey logistic regression analyses were employed to investigate the association between DAI and glaucoma.

RESULTS

A total of 6,128 participants were included in our study. The unadjusted model's findings revealed a negative correlation between dietary antioxidant indices and self-reported glaucoma [0.93 (0.90, 0.96), p < 0.0001]. For every unit increase in dietary antioxidant indices, the risks of self-reported glaucoma in model 1 (adjusted for age, sex, race, marital status and PIR) decreased by 5% [0.95 (0.90, 0.99), p = 0.02]. After adjusting all the covariates (model 2), the risks of self-reported glaucoma decreased by 6% [0.94 (0.90, 0.99), p = 0.02] for each unit increase of dietary antioxidant indices. After converting DAI into classified variables (tertile), the same trend was found (p = 0.001).

CONCLUSION

In this analysis of the NHANES database, we found higher dietary antioxidant indices were associated with lower risk of glaucoma.

Nanomaterial-based ophthalmic drug delivery

The low bioavailability and side effects of conventional drugs for eye disease necessitate the development of efficient drug delivery systems. Accompanying the developments of nanofabrication techniques, nanomaterials have been recognized as promising tools to overcome these challenges due to their flexible and programmable properties. Given the advances achieved in material science, a broad spectrum of functional nanomaterials capable of overcoming various ocular anterior and posterior segment barriers have been explored to satisfy the demands for ocular drug delivery. In this review, we first highlight the unique functions of nanomaterials suitable for carrying and transporting ocular drugs. Then, various functionalization strategies are emphasized to endow nanomaterials with superior performance in enhanced ophthalmic drug delivery. The rational design of several affecting factors is essential for ideal nanomaterial candidates and is depicted as well. Lastly, we introduce the current applications of nanomaterial-based delivery systems in the therapy of different ocular anterior and posterior segment diseases. The limitations of these delivery systems as well as potential solutions are also discussed. This work will inspire innovative design thinking for the development of nanotechnology-mediated strategies for advanced drug delivery and treatment toward ocular diseases.

Lipid peroxidation in osteoarthritis: focusing on 4-hydroxynonenal, malondialdehyde, and ferroptosis

Osteoarthritis (OA) is a multifactorial and increasingly prevalent degenerative disease that affects the whole joint. The pathogenesis of OA is poorly understood and there is a lack of therapeutic interventions to reverse the pathological process of this disease. Accumulating studies have shown that the overproduction of reactive oxygen species (ROS) and ROS-induced lipid peroxidation are involved in the pathogenesis of OA. 4-Hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) have received considerable attention for their role in cartilage degeneration and subchondral bone remodeling during OA development. Ferroptosis is a form of cell death characterized by a lack of control of membrane lipid peroxidation and recent studies have suggested that chondrocyte ferroptosis contributes to OA progression. In this review, we aim to discuss lipid peroxidation-derived 4-HNE and MDA in the progression of OA. In addition, the therapeutic potential for OA by controlling the accumulation of lipid peroxidation and inhibiting chondrocyte ferroptosis are discussed.

Biochemical-molecular-genetic biomarkers in the tear film, aqueous humor, and blood of primary open-angle glaucoma patients

Introduction

Glaucoma is a chronic neurodegenerative disease, which is the leading cause of irreversible blindness worldwide. As a response to high intraocular pressure, the clinical and molecular glaucoma biomarkers indicate the biological state of the visual system. Classical and uncovering novel biomarkers of glaucoma development and progression, follow-up, and monitoring the response to treatment are key objectives to improve vision outcomes. While the glaucoma imaging field has successfully validated biomarkers of disease progression, there is still a considerable need for developing new biomarkers of early glaucoma, that is, at the preclinical and initial glaucoma stages. Outstanding clinical trials and animal-model study designs, innovative technology, and analytical approaches in bioinformatics are essential tools to successfully uncover novel glaucoma biomarkers with a high potential for translation into clinical practice.

Methods

To better understand the clinical and biochemical-molecular-genetic glaucoma pathogenesis, we conducted an analytical, observational, and case-comparative/control study in 358 primary open-angle glaucoma (POAG) patients and 226 comparative-control individuals (CG) to collect tears, aqueous humor, and blood samples to be processed for identifying POAG biomarkers by exploring several biological pathways, such as inflammation, neurotransmitter/neurotrophin alteration, oxidative stress, gene expression, miRNAs fingerprint and its biological targets, and vascular endothelial dysfunction, Statistics were done by using the IBM SPSS 25.0 program. Differences were considered statistically significant when p ≤ 0.05.

Results

Mean age of the POAG patients was 70.03 ± 9.23 years, and 70.62 ± 7.89 years in the CG. Malondialdehyde (MDA), nitric oxide (NO), interleuquin (IL)-6, endothelin-1 (ET-1), and 5 hydroxyindolacetic acid (5-HIAA), displayed significantly higher levels in the POAG patients vs. the CG (p < 0.001). Total antioxidant capacity (TAC), brain derived neurotrophic factor (BDNF), 5-hydroxy tryptamine (5-HT), solute carrier family 23-nucleobase transporters-member 2 (SLC23A2) gene, and the glutathione peroxidase 4 (GPX4) gene, showed significantly lower levelsin the POAG patients than in the CG (p < 0.001). The miRNAs that differentially expressed in tear samples of the POAG patients respect to the CG were the hsa miR-26b-5p (involved in cell proliferation and apoptosis), hsa miR-152-3p (regulator of cell proliferation, and extracellular matrix expression), hsa miR-30e-5p (regulator of autophagy and apoptosis), and hsa miR-151a-3p (regulator of myoblast proliferation).

Discussion

We are incredibly enthusiastic gathering as much information as possible on POAG biomarkers to learn how the above information can be used to better steer the diagnosis and therapy of glaucoma to prevent blindness in the predictable future. In fact, we may suggest that the design and development of blended biomarkers is a more appropriate solution in ophthalmological practice for early diagnosis and to predict therapeutic response in the POAG patients.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Innate immunity dysregulation in aging eye and therapeutic interventions

The prevalence of eye diseases increases considerably with age, resulting in significant vision impairment. Although the pathobiology of age-related eye diseases has been studied extensively, the contribution of immune-related changes due to aging remains elusive. In the eye, tissue-resident cells and infiltrating immune cells regulate innate responses during injury or infection. But due to aging, these cells lose their protective functions and acquire pathological phenotypes. Thus, dysregulated ocular innate immunity in the elderly increases the susceptibility and severity of eye diseases. Herein, we emphasize the impact of aging on the ocular innate immune system in the pathogenesis of infectious and non-infectious eye diseases. We discuss the role of age-related alterations in cellular metabolism, epigenetics, and cellular senescence as mechanisms underlying altered innate immune functions. Finally, we describe approaches to restore protective innate immune functions in the aging eye. Overall, the review summarizes our current understanding of innate immune functions in eye diseases and their dysregulation during aging.

Melanin-like Nanoparticles as an Alternative to Natural Melanin in Retinal Pigment Epithelium Cells and Their Therapeutic Effects against Age-Related Macular Degeneration

Melanin is a natural pigment that is widely distributed in many parts of the human body, such as the skin and retinal pigment epithelium (RPE) in eyes. In contrast to skin melanin, which is being constantly synthesized by the epidermal melanocytes, melanin in the RPE does not regenerate. Melanin is known to function as a potential radical scavenger and photoprotective agent. However, the protective effects of melanin against oxidative stress decline with increasing age. This phenomenon has been correlated with the pathogenesis of age-related macular degeneration (AMD). To increase the potential antioxidant and photoprotective characteristics of melanin, we designed a therapeutic strategy for replenishment of melanin using PEGylated synthetic melanin-like nanoparticles (MNPs) in the RPE for the treatment of AMD. We performed experiments using AMD-like cellular and mouse models and demonstrated that MNPs are biocompatible and selectively target reactive oxygen species (ROS) with powerful antioxidant properties. MNPs can traffic and accumulate in the RPE and are exclusively located in cytosol, but not the nucleus and mitochondria of the cells, for at least 3 months after a single-dose intravitreal injection. Our findings demonstrate that MNPs are able to substitute for natural melanin in the RPE and suggest the potential efficacy of MNPs as a natural radical scavenger against oxidative stress in ROS-related diseases, such as AMD.

Impact of Systemic Comorbidities on Ocular Hypertension and Open-Angle Glaucoma, in a Population from Spain and Portugal

Open-angle glaucoma (OAG), the most prevalent clinical type of glaucoma, is still the main cause of irreversible blindness worldwide. OAG is a neurodegenerative illness for which the most important risk factor is elevated intraocular pressure (IOP). Many questions remain unanswered about OAG, such as whether nutritional or toxic habits, other personal characteristics, and/or systemic diseases influence the course of glaucoma. As such, in this study, we performed a multicenter analytical, observational, case–control study of 412 participants of both sexes, aged 40–80 years, that were classified as having ocular hypertension (OHT) or OAG. Our primary endpoint was to investigate the relationship between specific lifestyle habits; anthropometric and endocrine–metabolic, cardiovascular, and respiratory events; and commonly used psychochemicals, with the presence of OHT or OAG in an ophthalmologic population from Spain and Portugal. Demographic, epidemiological, and ocular/systemic clinical data were recorded from all participants. Data were analyzed using the R Statistics v4.1.2 and RStudio v2021.09.1 programs. The mean age was 62 ± 15 years, with 67–80 years old comprising the largest subgroup sample of participants in both study groups. The central corneal thickness (ultrasound pachymetry)-adjusted IOP (Goldman tonometry) in each eye was 20.46 ± 2.35 and 20.1 ± 2.73 mmHg for the OHT individuals, and 15.8 ± 3.83 and 16.94 ± 3.86 mmHg for the OAG patients, with significant differences between groups (both p = 0.001). The highest prevalence of the surveyed characteristics in both groups was for overweight/obesity and daily coffee consumption, followed by psychochemical drug intake, migraine, and peripheral vasospasm. Our data show that overweight/obesity, migraine, asthma, and smoking are major risk factors for conversion from OHT to OAG in this Spanish and Portuguese population.

Bidirectional association between visual impairment and frailty among community-dwelling older adults: a longitudinal study

Background

Vision impairment is common among older adults, and it may be related to frailty. However, the longitudinal relationship between visual impairment and frailty is still unclear.

Methods

We used data from Round 1 to Round 5 from the National Health and Aging Trend Study. Two samples were community-dwelling older adults, sample 1 (without visual impairment) was classified according to whether they have pre-frailty/frailty at R1 (N = 3013) and sample 2 (without pre-frailty/frailty) was classified according to whether they have visual impairment at R1 (N = 1422), respectively. Frailty was measured using five criteria: experiencing exhaustion, unintentional weight loss, low physical activity, slow gait, and weak grip strength. Visual impairment was assessed by asking participants if they had any visual impairment. Generalized estimating equation models were used to examine the concurrent and lagged association between visual impairment and frailty.

Results

The participants were on average 76 ± 7 years old, female (59%), non-Hispanic white (74%) with less than bachelor educated (73%), and 44% were pre-frail/frail in the older adults without visual impairment. Approximately 5% of participants had visual impairment at R1, and they tended to be female and non-Hispanic White in the older adults without frailty. The concurrent (OR, 95% CI = 1.55, 1.17-2.02) and lagged (OR, 95% CI = 1.79, 1.25-2.59) associations between frailty and visual impairment were significantly after controlling the covariates. Similarly, the concurrent (OR, 95% CI = 1.63, 1.32-2.04) and lagged (OR, 95% CI = 1.49, 1.20-1.87) associations between visual impairment and frailty were also significant.

Conclusions

Overall, this study provides evidence for a longitudinal, bidirectional association between self-reported visual impairment and frailty. Future intervention programs to delay frailty progression should include strategies that may reduce the incidence of visual impairment.

Switching of Redox Signaling by Prdx6 Expression Decides Cellular Fate by Hormetic Phenomena Involving Nrf2 and Reactive Oxygen Species

Changes in intracellular reactive oxygen species (ROS) levels due to remodeling of antioxidant defense can affect the status of biological homeostasis in aging/oxidative stress. Peroxiredoxin 6 (Prdx6), an antioxidant gene downstream target for the Nrf2 pathway, plays a role in regulating ROS homeostasis. Using aging human (h) lens epithelial cells (LECs) or Prdx6-deficient (Prdx6^-/-) mouse (m) LECs, here we showed that dichlorofluorescein (DCF) oxidation or H₂O₂ were strictly controlled by Prdx6. We observed that a moderate degree of oxidative stress augmented Nrf2-mediated Prdx6 expression, while higher doses of H₂O₂ (≥100 µM) caused a dramatic loss of Prdx6 expression, resulting in increased DCF oxidation and H₂O₂ amplification and cell death. Mechanistically, at increased oxidative stress, Nrf2 upregulated transcriptional factor Klf9, and that Klf9 bound to the promoter and repressed the Prdx6 gene. Similarly, cells overexpressing Klf9 displayed Klf9-dependent Prdx6 suppression and DCF oxidation with H₂O₂ amplification, while ShKlf9 reversed the process. Our data revealed that H₂O₂ and DCF oxidation levels play a hormetical role, and the Nrf2-Klf9-Prdx6 pathway is pivotal for the phenomena under the conditions of oxidative load/aging. On the whole, the results demonstrate that oxidative hormetical response is essentially based on levels of oxidative triggering and the status of Klf9-Prdx6 pathway activation; thus, Klf9 can be considered as a therapeutic target for hormetic shifting of cellular defense to improve protective resilience to oxidative stress.

Cellular stress signaling and the unfolded protein response in retinal degeneration: mechanisms and therapeutic implications

Background

The retina, as part of the central nervous system (CNS) with limited capacity for self-reparation and regeneration in mammals, is under cumulative environmental stress due to high-energy demands and rapid protein turnover. These stressors disrupt the cellular protein and metabolic homeostasis, which, if not alleviated, can lead to dysfunction and cell death of retinal neurons. One primary cellular stress response is the highly conserved unfolded protein response (UPR). The UPR acts through three main signaling pathways in an attempt to restore the protein homeostasis in the endoplasmic reticulum (ER) by various means, including but not limited to, reducing protein translation, increasing protein-folding capacity, and promoting misfolded protein degradation. Moreover, recent work has identified a novel function of the UPR in regulation of cellular metabolism and mitochondrial function, disturbance of which contributes to neuronal degeneration and dysfunction. The role of the UPR in retinal neurons during aging and under disease conditions in age-related macular degeneration (AMD), retinitis pigmentosa (RP), glaucoma, and diabetic retinopathy (DR) has been explored over the past two decades. Each of the disease conditions and their corresponding animal models provide distinct challenges and unique opportunities to gain a better understanding of the role of the UPR in the maintenance of retinal health and function.

Method

We performed an extensive literature search on PubMed and Google Scholar using the following keywords: unfolded protein response, metabolism, ER stress, retinal degeneration, aging, age-related macular degeneration, retinitis pigmentosa, glaucoma, diabetic retinopathy.

Results and conclusion

We summarize recent advances in understanding cellular stress response, in particular the UPR, in retinal diseases, highlighting the potential roles of UPR pathways in regulation of cellular metabolism and mitochondrial function in retinal neurons. Further, we provide perspective on the promise and challenges for targeting the UPR pathways as a new therapeutic approach in age- and disease-related retinal degeneration.

Vitreous Humor Proteome: Targeting Oxidative Stress, Inflammation, and Neurodegeneration in Vitreoretinal Diseases

Oxidative stress is defined as an unbalance between pro-oxidants and antioxidants, as evidenced by an increase in reactive oxygen and reactive nitrogen species production over time. It is important in the pathophysiology of retinal disorders such as diabetic retinopathy, age-related macular degeneration, retinal detachment, and proliferative vitreoretinopathy, which are the focus of this article. Although the human organism's defense mechanisms correct autoxidation caused by endogenous or exogenous factors, this may be insufficient, causing an imbalance in favor of excessive ROS production or a weakening of the endogenous antioxidant system, resulting in molecular and cellular damage. Furthermore, modern lifestyles and environmental factors contribute to increased chemical exposure and stress induction, resulting in oxidative stress. In this review, we discuss the current information about oxidative stress and the vitreous proteome with a special focus on vitreoretinal diseases. Additionally, we explore therapies using antioxidants in an attempt to rescue the body from oxidation, restore balance, and maximize healthy body function, as well as new investigational therapies that have shown significant therapeutic potential in preclinical studies and clinical trial outcomes, along with their goals and strategic approaches to combat oxidative stress.

FUNDC1 induces apoptosis and autophagy under oxidative stress via PI3K/Akt/mTOR pathway in cataract lens cells

OBJECTIVE

This purpose of the study is to explore the mRNA and protein expression of FUNDC1 in cataract cells and tissues, clarify the function and mechanism of FUNDC1 in cataract cells under oxidative stress.

METHODS

We used bioinformatic analysis to screen DEGs in cataract from GSE153933. The expression of FUNDC1 in cataract specimens and cells was measured by RT-qPCR and western blotting. MethPrimer was used to predict CpG island of FUNDC1 promoter. The methylation of FUNDC1 in cataract specimens and cells was determined by MSP assay. Flow cytometry assay was used to measure cell apoptosis in FUNDC1-knockdown and -overexpression SRA01/04 cells. The expression of LC3 was analyzed by immunofluorescence assay. The expression of apoptosis related proteins, autophagy and PI3K/Akt/mTOR related proteins was determined by western blotting.

RESULTS

The results of bioinformatic analysis revealed that FUNDC1 was upregulation in cataract. FUNDC1 was further high expression in SRA01/04 cells with H₂O₂ treatment whereas hypomethylation of FUNDC1 in cataract lens cells under oxidative stress. Knockdown of FUNDC1 decreased cell apoptosis and autophagy compared with negative control of SRA01/04 cells. While overexpression of FUNDC1 elevated cell apoptosis and autophagy compared to empty vector group in SRA01/04 cells. Mechanically, FUNDC1 reduced the phosphorylation of PI3K/Akt/mTOR pathway under oxidative stress in SRA01/04 cells.

CONCLUSION

Our study suggested that FUNDC1 deficiency restrains cell apoptosis and autophagy through inhibiting PI3K/Akt/mTOR signal pathway.

Effects of Daily Melatonin Supplementation on Visual Loss, Circadian Rhythms, and Hepatic Oxidative Damage in a Rodent Model of Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases characterized by a progressive loss of visual function that primarily affect photoreceptors, resulting in the complete disorganization and remodeling of the retina. Progression of the disease is enhanced by increased oxidative stress in the retina, aqueous humor, plasma, and liver of RP animal models and patients. Melatonin has beneficial effects against age-related macular degeneration, glaucoma, and diabetic retinopathy, in which oxidative stress plays a key role. In the present study, we used the P23HxLE rat as an animal model of RP. Melatonin treatment (10 mg/kg b.w. daily in drinking water for 6 months) improved the parameters of visual function and decreased the rate of desynchronization of the circadian rhythm, both in P23HxLE and wild-type rats. Melatonin reduced oxidative stress and increased antioxidant defenses in P23HxLE animals. In wild-type animals, melatonin did not modify any of the oxidative stress markers analyzed and reduced the levels of total antioxidant defenses. Treatment with melatonin improved visual function, circadian synchronization, and hepatic oxidative stress in P23HxLE rats, an RP model, and had beneficial effects against age-related visual damage in wild-type rats.

Comparison of Medical Comorbidity between Patients with Normal-Tension Glaucoma and Primary Open-Angle Glaucoma: A Population-Based Study in Taiwan

The objective was to investigate different comorbidities developed in normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG) patients. This was a case-control study, with 1489 people in the NTG group and 5120 people in the POAG group. Patient data were obtained from the Longitudinal Health Insurance Database 2010 (LHID2010) of Taiwan for the 2008-2013 period. The chi-square test was used to compare categorical variables, such as gender, income and urbanisation level, between NTG and POAG patients, and the two-tailed t test was used to compare continuity between the two groups. We use a multivariate logic regression model to assess the risk of each participant. The results are expressed in terms of odds ratio (OR) and 95% confidence intervals (CI). Patients with NTG had significantly higher proportions of hypotension (adjusted OR, 1.984; 95% CI, 1.128-3.490), sleep disturbances (adjusted OR, 1.323; 95% CI, 1.146-1.528), peptic ulcers (adjusted OR, 1.383; 95% CI, 1.188-1.609) and allergic rhinitis (adjusted OR, 1.484; 95% CI, 1.290-1.707) than those with POAG. Conversely, arterial hypertension (adjusted OR, 0.767; 95% CI, 0.660-0.893), diabetes (adjusted OR, 0.850; 95% CI, 0.728-0.993) and atopic dermatitis (adjusted OR, 0.869; 95% CI, 0.763-0.990) had a lower risk in the NTG group than in the POAG group. We found that comorbidities such a hypotension, sleep disturbances and peptic ulcer and allergic rhinitis are more highly associated to NTG than POAG.

Objectively measured far vision impairment and sarcopenia among adults aged ≥ 65 years from six low- and middle-income countries

BACKGROUND

There are currently no studies on visual impairment and sarcopenia. We investigated the cross-sectional association between objectively measured far vision impairment and sarcopenia in a nationally representative sample of older adults aged 65 years and over from six low- and middle-income countries (LMICs).

METHODS

Cross-sectional, community-based data from the study on global ageing and adult health (SAGE) were analyzed. Far vision acuity was measured using the tumbling E LogMAR chart and classified as: no vision impairment (6/12 or better); mild vision impairment (6/18 or better but worse than 6/12); moderate vision impairment (6/60 or better but worse than 6/18); severe vision impairment (worse than 6/60). Sarcopenia was defined as having low skeletal muscle mass and either a slow gait speed or a weak handgrip strength. Associations were assessed with multivariable logistic regression.

RESULTS

Fourteen thousand five hundred and eighty five individuals aged ≥ 65 years were included in the analysis [mean (SD) age 72.6 (11.5) years; 54.1% females]. After adjustment for multiple potential confounders, compared to those with no vision impairment, the OR (95% CI) for sarcopenia in those with mild, moderate, and severe vision impairment were 1.10 (0.87-1.40), 1.69 (1.25-2.27), and 3.38 (1.69-6.77), respectively. The estimates for females and males were similar.

CONCLUSIONS

The odds for sarcopenia increased with increasing severity of far vision impairment among older people in LMICs. The mere co-occurrence of these conditions is concerning, and it may be prudent to implement interventions to address/prevent sarcopenia in those with far vision impairment through the promotion of physical activity and appropriate nutrition.

Retinal and Choroidal Pathologies in Aged BALB/c Mice Following Systemic Neonatal Murine Cytomegalovirus Infection

Although pathologies associated with acute virus infections have been extensively studied, the effects of long-term latent virus infections are less well understood. Human cytomegalovirus, which infects 50% to 80% of humans, is usually acquired during early life and persists in a latent state for the lifetime. The purpose of this study was to determine whether systemic murine cytomegalovirus (MCMV) infection acquired early in life disseminates to and becomes latent in the eye and if ocular MCMV can trigger in situ inflammation and occurrence of ocular pathology. This study found that neonatal infection of BALB/c mice with MCMV resulted in dissemination of virus to the eye, where it localized principally to choroidal endothelia and pericytes and less frequently to the retinal pigment epithelium (RPE) cells. MCMV underwent ocular latency, which was associated with expression of multiple virus genes and from which MCMV could be reactivated by immunosuppression. Latent ocular infection was associated with significant up-regulation of several inflammatory/angiogenic factors. Retinal and choroidal pathologies developed in a progressive manner, with deposits appearing at both basal and apical aspects of the RPE, RPE/choroidal atrophy, photoreceptor degeneration, and neovascularization. The pathologies induced by long-term ocular MCMV latency share features of previously described human ocular diseases, such as age-related macular degeneration.

Antioxidant Bioactivity of Extracts from Beach Cast Leaves of Posidonia oceanica (L.) Delile

The marine environment is a generous source of biologically active compounds useful for human health. In 50 years, about 25,000 bioactive marine compounds have been identified, with an increase of 5% per year. Peculiar feature of algae and plants is the production of secondary metabolites, such as polyphenols, synthesized as a form of adaptation to environmental stress. Posidonia oceanica is a Mediterranean endemic and dominant seagrass and represents a biologically, ecologically and geologically important marine ecosystem. Within this study, methanolic and ethanolic extracts were generated from fresh and dried Posidonia oceanica leaves, with the aim to employ and valorize the beach cast leaves. The best yield and antioxidant activity (polyphenols content equal to 19.712 ± 0.496 mg GAE/g and DPPH IC50 of 0.090 µg/µL.) were recorded in 70% ethanol extracts (Gd-E4) obtained from leaves dried for two days at 60 °C and ground four times. HPLC analyses revealed the presence of polyphenols compounds (the most abundant of which was chicoric acid) with antioxidant and beneficial properties. Bioactive properties of the Gd-E4 extracts were evaluated in vitro using fibroblast cells line (HS-68), subjected to UV induced oxidative stress. Pre-treatment of cells with Gd-E4 extracts led to significant protection against oxidative stress and mortality associated with UV exposure, thus highlighting the beneficial properties of antioxidants compounds produced by these marine plants against photo damage, free radicals and associated negative cellular effects. Beach cast leaves selection, processing and extraction procedures, and the in vitro assay results suggested the potentiality of a sustainable approach for the biotechnological exploitation of this resource and could serve a model for other marine resources.

Impact of dorzolamide, benzalkonium-preserved dorzolamide and benzalkonium-preserved brinzolamide on selected biomarkers of oxidative stress in the tear film

Background

Long-term use of topical, especially benzalkonium chloride (BAC)-preserved, antiglaucoma medications can cause a negative impact on the ocular surface. The aim of the study was to assess the effect of topical carbonic anhydrase inhibitors (CAIs) on selected oxidative stress biomarkers in the tear film.

Methods

The patients were divided into four sex-matched groups: group C (n = 25) – control group – subjects who did not use topical antiglaucoma medications, group DL (n = 14) – patients using preservative-free dorzolamide, group DL + BAC (n = 16) – patients using topical BAC-preserved dorzolamide, group BL + BAC (n = 17) – patients using BAC-preserved brinzolamide. Subjects in all the study groups have been using the eye drops two times daily for 6–12 months. The oxidative stress biomarkers in the tear film samples were measured: total protein (TP) concentration, advanced oxidation protein products (AOPP) content, total sulfhydryl (-SH) groups content, the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as Total Oxidant Status (TOS), Total Antioxidant Response (TAR), and Oxidative Stress Index (OSI).

Results

The advanced oxidation protein products content, Total Oxidant Status as well as superoxide dismutase and catalase activities in the group DL + BAC and BL + BAC were higher in comparison with the group C. The total sulfhydryl groups content was lower in the group DL + BAC and BL + BAC when compared to group C. Oxidative Stress Index was higher in the groups DL + BAC and BL + BAC in comparison with the groups DL and C.

Conclusions

Use of topical benzalkonium chloride-preserved carbonic anhydrase inhibitors increases oxidative stress in the tear film.

Nutraceutical Strategy to Counteract Eye Neurodegeneration and Oxidative Stress in Drosophila melanogaster Fed with High-Sugar Diet

Aberrant production of reactive oxygen species (ROS) is a common feature of damaged retinal neurons in diabetic retinopathy, and antioxidants may exert both preventive and therapeutic action. To evaluate the beneficial and antioxidant properties of food supplementation with Lisosan G, a powder of bran and germ of grain (Triticum aestivum) obtained by fermentation with selected lactobacillus and natural yeast strains, we used an in vivo model of hyperglycemia-induced retinal damage, the fruit fly Drosophila melanogaster fed with high-sucrose diet. Lisosan G positively affected the visual system of hyperglycemic flies at structural/functional level, decreased apoptosis, and reactivated protective autophagy at the retina internal network. Also, in high sucrose-fed Drosophila, Lisosan G reduced the levels of brain ROS and retina peroxynitrite. The analysis of oxidative stress-related metabolites suggested 7,8-dihydrofolate, uric acid, dihydroorotate, γ-L-glutamyl-L-cysteine, allantoin, cysteinyl-glycine, and quinolate as key mediators of Lisosan G-induced inhibition of neuronal ROS, along with the upregulation of glutathione system. Of note, Lisosan G may impact oxidative stress and the ensuing retinal cell death, also independently from autophagy, although the autophagy-ROS cross-talk is critical. This study demonstrated that the continuous supplementation with the alimentary integrator Lisosan G exerts a robust and multifaceted antioxidant effect on retinal neurons, thus providing efficacious neuroprotection of hyperglycemic eye.

Searching for the Antioxidant, Anti-Inflammatory, and Neuroprotective Potential of Natural Food and Nutritional Supplements for Ocular Health in the Mediterranean Population

Adherence to a healthy diet offers a valuable intervention to compete against the increasing cases of ocular diseases worldwide, such as dry eye disorders, myopia progression, cataracts, glaucoma, diabetic retinopathy, or age macular degeneration. Certain amounts of micronutrients must be daily provided for proper functioning of the visual system, such as vitamins, carotenoids, trace metals and omega-3 fatty acids. Among natural foods, the following have to be considered for boosting eye/vision health: fish, meat, eggs, nuts, legumes, citrus fruits, nuts, leafy green vegetables, orange-colored fruits/vegetables, olives-olive oil, and dairy products. Nutritional supplements have received much attention as potential tools for managing chronic-degenerative ocular diseases. A systematic search of PubMed, Web of Science, hand-searched publications and historical archives were performed by the professionals involved in this study, to include peer-reviewed articles in which natural food, nutrient content, and its potential relationship with ocular health. Five ophthalmologists and two researchers collected the characteristics, quality and suitability of the above studies. Finally, 177 publications from 1983 to 2021 were enclosed, mainly related to natural food, Mediterranean diet (MedDiet) and nutraceutic supplementation. For the first time, original studies with broccoli and tigernut (chufa de Valencia) regarding the ocular surface dysfunction, macular degeneration, diabetic retinopathy and glaucoma were enclosed. These can add value to the diet, counteract nutritional defects, and help in the early stages, as well as in the course of ophthalmic pathologies. The main purpose of this review, enclosed in the Special Issue "Health Benefits and Nutritional Quality of Fruits, Nuts and Vegetables," is to identify directions for further research on the role of diet and nutrition in the eyes and vision, and the potential antioxidant, anti-inflammatory and neuroprotective effects of natural food (broccoli, saffron, tigernuts and walnuts), the Mediterranean Diet, and nutraceutic supplements that may supply a promising and highly affordable scenario for patients at risk of vision loss. This review work was designed and carried out by a multidisciplinary group involved in ophthalmology and ophthalmic research and especially in nutritional ophthalmology.

Correcting QUEST Magnetic Resonance Imaging-Sensitive Free Radical Production in the Outer Retina In Vivo Does Not Correct Reduced Visual Performance in 24-Month-Old C57BL/6J Mice

Purpose

To test the hypothesis that acutely correcting a sustained presence of outer retina free radicals measured in vivo in 24-month-old mice corrects their reduced visual performance.

Methods

Male C57BL/6J mice two and 24 months old were noninvasively evaluated for unremitted production of paramagnetic free radicals based on whether 1/T1 in retinal laminae are reduced after acute antioxidant administration (QUEnch-assiSTed [QUEST] magnetic resonance imaging [MRI]). Superoxide production was measured in freshly excised retina (lucigenin assay). Combining acute antioxidant administration with optical coherence tomography (i.e., QUEST OCT) tested for excessive free radical–induced shrinkage of the subretinal space volume. Combining antioxidant administration with optokinetic tracking tested for a contribution of uncontrolled free radical production to cone-based visual performance declines.

Results

At two months, antioxidants had no effect on 1/T1 in vivo in any retinal layer. At 24 months, antioxidants reduced 1/T1 only in superior outer retina. No age-related change in retinal superoxide production was measured ex vivo, suggesting that free radical species other than superoxide contributed to the positive QUEST MRI signal at 24 months. Also, subretinal space volume did not show evidence for age-related shrinkage and was unresponsive to antioxidants. Finally, visual performance declined with age and was not restored by antioxidants that were effective per QUEST MRI.

Conclusions

An ongoing uncontrolled production of outer retina free radicals as measured in vivo in 24 mo C57BL/6J mice appears to be insufficient to explain reductions in visual performance.

Role of Oral Antioxidant Supplementation in the Current Management of Diabetic Retinopathy

Oxidative stress has been postulated as an underlying pathophysiologic mechanism of diabetic retinopathy (DR), the main cause of avoidable blindness in working-aged people. This review addressed the current daily clinical practice of DR and the role of antioxidants in this practice. A systematic review of the studies on antioxidant supplementation in DR patients was presented. Fifteen studies accomplished the inclusion criteria. The analysis of these studies concluded that antioxidant supplementation has a IIB level of recommendation in adult Type 1 and Type 2 diabetes mellitus subjects without retinopathy or mild-to-moderate nonproliferative DR without diabetic macular oedema as a complementary therapy together with standard medical care.

Microfluidic and Microscale Assays to Examine Regenerative Strategies in the Neuro Retina

Bioengineering systems have transformed scientific knowledge of cellular behaviors in the nervous system (NS) and pioneered innovative, regenerative therapies to treat adult neural disorders. Microscale systems with characteristic lengths of single to hundreds of microns have examined the development and specialized behaviors of numerous neuromuscular and neurosensory components of the NS. The visual system is comprised of the eye sensory organ and its connecting pathways to the visual cortex. Significant vision loss arises from dysfunction in the retina, the photosensitive tissue at the eye posterior that achieves phototransduction of light to form images in the brain. Retinal regenerative medicine has embraced microfluidic technologies to manipulate stem-like cells for transplantation therapies, where de/differentiated cells are introduced within adult tissue to replace dysfunctional or damaged neurons. Microfluidic systems coupled with stem cell biology and biomaterials have produced exciting advances to restore vision. The current article reviews contemporary microfluidic technologies and microfluidics-enhanced bioassays, developed to interrogate cellular responses to adult retinal cues. The focus is on applications of microfluidics and microscale assays within mammalian sensory retina, or neuro retina, comprised of five types of retinal neurons (photoreceptors, horizontal, bipolar, amacrine, retinal ganglion) and one neuroglia (Müller), but excludes the non-sensory, retinal pigmented epithelium.

Esculetin protects human corneal epithelial cells from oxidative stress through Nrf-2 signaling pathway

Dry eye formation often originates from oxidative damage to the ocular surface, which can be caused by external environment or internal pathologic factors. Esculetin (6, 7-dihydroxycoumarin) is a natural product found in many plants, and has been reported to have multiple pharmacological activities. The objective of our present study is to investigate if esculetin could protect the corneal epithelial cells from oxidative damages and its underlying antioxidant molecular mechanisms. Our experimental results demonstrated that pretreatment with esculetin markedly increased the cell viability while decreased the apoptosis in H₂O₂-treated human corneal epithelial (HCE) cells, by regulating Bcl-2, Bax and caspase-3 protein expressions and by altering the imbalance of activities of intracellular reactive oxygen species (ROS) and superoxide dismutase (SOD). Our data revealed that esculetin played an antioxidant role not only through its antioxidant activity, but also by highly inducing Nrf-2 translocation to the nucleus, which in turn, enhanced Nrf2 signaling regulated antioxidant genes (HO-1, NQO1, GCLM, SOD1 and SOD2) mRNA expression levels in H₂O₂-treated HCE cells. In the present study, the protective effects of esculetin on the corneal epithelium were also confirmed by a murine desiccating stress induced dry eye model in vivo. These data illustrated, for the first time, that esculetin may have the ability to protect human corneal epithelial cells from oxidative damages through its scavenging of free radical properties and through the activation of Nrf2 signaling.

Clinical and Molecular-Genetic Insights into the Role of Oxidative Stress in Diabetic Retinopathy: Antioxidant Strategies and Future Avenues

Reactive oxygen species (ROS) overproduction and ROS-signaling pathways activation attack the eyes. We evaluated the oxidative stress (OS) and the effects of a daily, core nutritional supplement regimen containing antioxidants and omega 3 fatty acids (A/ω3) in type 2 diabetics (T2DM). A case-control study was carried out in 480 participants [287 T2DM patients with (+)/without (-) diabetic retinopathy (DR) and 193 healthy controls (CG)], randomly assigned to a daily pill of A/ω3. Periodic evaluation through 38 months allowed to outline patient characteristics, DR features, and classic/OS blood parameters. Statistics were performed by the SPSS 24.0 program. Diabetics displayed significantly higher circulating pro-oxidants (p = 0.001) and lower antioxidants (p = 0.0001) than the controls. Significantly higher plasma malondialdehyde/thiobarbituric acid reactive substances (MDA/TBARS; p = 0.006) and lower plasma total antioxidant capacity (TAC; p = 0.042) and vitamin C (0.020) was found in T2DM + DR versus T2DM-DR. The differential expression profile of solute carrier family 23 member 2 (SLC23A2) gene was seen in diabetics versus the CG (p = 0.001), and in T2DM + DR versus T2DM - DR (p < 0.05). The A/ω3 regime significantly reduced the pro-oxidants (p < 0.05) and augmented the antioxidants (p < 0.05). This follow-up study supports that a regular A/ω3 supplementation reduces the oxidative load and may serve as a dietary prophylaxis/adjunctive intervention for patients at risk of diabetic blindness.

Modulation of Oxidative Stress and Inflammation in the Aged Lacrimal Gland

Inflammation and oxidative stress accompany aging. This study investigated the interplay between oxidative stress and inflammation in the lacrimal gland. C57BL/6 mice were used at 2 to 3, 12, and 24 months of age. Nuclear factor erythroid derived-2-related factor 2 (Nrf2)^-/- and corresponding wild-type mice were used at 2 to 3 and 12 to 13 months of age. A separate group of 15.5 to 17 months of age C57BL/6 mice received a diet containing an Nrf2 inducer (Oltipraz) for 8 weeks. Aged C57BL/6 lacrimal glands showed significantly greater lymphocytic infiltration, higher levels of MHC II, IFN-γ, IL-1β, TNF-α, and cathepsin S (Ctss) mRNA transcripts, and greater nitrotyrosine and 4-hydroxynonenal protein. Young Nrf2^-/- mice showed an increase in IL-1β, IFN-γ, MHC II, and Ctss mRNA transcripts compared with young wild-type mice and greater age-related changes at 12 to 13 months of age. Oltipraz diet significantly decreased nitrotyrosine and 4-hydroxynonenal and decreased the expression of IL-1β and TNF-α mRNA transcripts, while decreasing the frequency of CD45⁺CD4⁺ cells in lacrimal glands and significantly increasing conjunctival goblet cell density compared with a standard diet. The findings provide novel insight into the development of chronic, low-grade inflammation and oxidative stress in age-related dry eye. New therapies targeting oxidative stress pathways will be valuable in treating age-related dry eye.

Inflammation in Glaucoma: From the back to the front of the eye, and beyond

The pathophysiology of glaucoma is complex, multifactorial and not completely understood. Elevated intraocular pressure (IOP) and/or impaired retinal blood flow may cause initial optic nerve damage. In addition, age-related oxidative stress in the retina concurrently with chronic mechanical and vascular stress is crucial for the initiation of retinal neurodegeneration. Oxidative stress is closely related to cell senescence, mitochondrial dysfunction, excitotoxicity, and neuroinflammation, which are involved in glaucoma progression. Accumulating evidence from animal glaucoma models and from human ocular samples suggests a dysfunction of the para-inflammation in the retinal ganglion cell layer and the optic nerve head. Moreover, quite similar mechanisms in the anterior chamber could explain the trabecular meshwork dysfunction and the elevated IOP in primary open-angle glaucoma. On the other hand, ocular surface disease due to topical interventions is the most prominent and visible consequence of inflammation in glaucoma, with a negative impact on filtering surgery failure, topical treatment efficacy, and possibly on inflammation in the anterior segment. Consequently, glaucoma appears as an outstanding eye disease where inflammatory changes may be present to various extents and consequences along the eye structure, from the ocular surface to the posterior segment, and the visual pathway. Here we reviewed the inflammatory processes in all ocular structures in glaucoma from the back to the front of the eye and beyond. Our approach was to explain how para-inflammation is necessary to maintain homoeostasis, and to describe abnormal inflammatory findings observed in glaucomatous patients or in animal glaucoma models, supporting the hypothesis of a dysregulation of the inflammatory balance toward a pro-inflammatory phenotype. Possible anti-inflammatory therapeutic approaches in glaucoma are also discussed.

Computational Analysis of Clinical and Molecular Markers and New Theranostic Possibilities in Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is a paramount cause of irreversible visual disability worldwide. We focus on identifying clinical and molecular facts that may help elucidating the pathogenic mechanisms of the disease. By using ophthalmological approaches (biomicroscopy, ocular fundus, optical coherence tomography, and perimetry) and experimental tests (enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC), and Western blot/immunoblotting) directed to evaluate the oxidative stress, inflammation, apoptosis, and neurodegeneration processes, we gather information to build a network of data to perform a computational bioinformatics analysis. Our results showed strong interaction of the above players and its downstream effectors in POAG pathogenesis. In conclusion, specific risk factors were identified, and molecules involved in multiple pathways were found in relation to anterior and posterior eye segment glaucoma changes, pointing to new theranostic challenges for better managing POAG progression.

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

Diabetic retinopathy is one of the leading causes of visual impairment and morbidity worldwide, being the number one cause of blindness in people between 27 and 75 years old. It is estimated that ~191 million people will be diagnosed with this microvascular complication by 2030. Its pathogenesis is due to alterations in the retinal microvasculature as a result of a high concentration of glucose in the blood for a long time which generates numerous molecular changes like oxidative stress. Therefore, this narrative review aims to approach various biomarkers associated with the development of diabetic retinopathy. Focusing on the molecules showing promise as detection tools, among them we consider markers of oxidative stress (TAC, LPO, MDA, 4-HNE, SOD, GPx, and catalase), inflammation (IL-6, IL-1ß, IL-8, IL-10, IL-17A, TNF-α, and MMPs), apoptosis (NF-kB, cyt-c, and caspases), and recently those that have to do with epigenetic modifications, their measurement in different biological matrices obtained from the eye, including importance, obtaining process, handling, and storage of these matrices in order to have the ability to detect the disease in its early stages.

Increased Antioxidant Capacity and Pro-Homeostatic Lipid Mediators in Ocular Hypertension-A Human Experimental Model

The main risk factor for primary open-angle glaucoma (POAG) is increased intraocular pressure (IOP). It is of interest that about half of the patients have an IOP within the normal range (normal-tension glaucoma, NTG). Additionally, there is a group of patients with a high IOP but no glaucomatous neurodegeneration (ocular hypertension, OHT). Therefore, risk factors other than IOP are involved in the pathogenesis of glaucoma. Since the retina has a very high oxygen-demand, decreased autoregulation and a fluctuating oxygen supply to the retina have been linked to glaucomatous neurodegeneration. To assess the significance of these mechanisms, we have utilized a human experimental model, in which we stress participants with a fluctuating oxygen supply. Levels of oxidative stress molecules, antioxidants, and lipid mediators were measured in the plasma. Patients with NTG, OHT, and control subjects were found to have similar levels of oxidative stress markers. In contrast, patients with OHT had a higher level of total antioxidant capacity (TAC) and pro-homeostatic lipid mediators. Thus, we suggest that OHT patients manage fluctuating oxygen levels more efficiently and, thus, are less susceptible to glaucomatous neurodegenerations, due to enhanced systemic antioxidant protection.

[Antioxidant nutraceuticals for glaucoma]

Glaucoma is the leading cause of irreversible blindness in the world. Intraocular pressure (IOP) is currently the only proven modifiable risk factor for POAG. IOP-independent mechanisms contributing to the development of glaucomatous neurodegeneration include oxidative stress, excitotoxicity, mitochondrial dysfunction, and impaired ocular blood flow. In this regard, there has recently been growing interest in the use of various antioxidant dietary supplements as neuroprotective therapy for glaucoma. The issue of the effectiveness and safety of these biologically active additives is an urgent scientific problem reflected in numerous studies. This article reviews current concepts of oxidative/nitrosative stress, the role of reactive oxygen species (ROS)/reactive nitrogen (Nr) and their participation in the development of POAG, as well as experimental models and clinical studies using essential fatty acids, natural compounds and a number of other antioxidant substances that can counteract oxidative stress in glaucoma.

Clock Protein Bmal1 and Nrf2 Cooperatively Control Aging or Oxidative Response and Redox Homeostasis by Regulating Rhythmic Expression of Prdx6

Many disorders of aging, including blinding-diseases, are associated with deficiency of brain and muscle arnt-like protein 1 (Bmal1) and, thereby, dysregulation of antioxidant-defense pathway. However, knowledge is limited regarding the role of Bmal1 regulation of antioxidant-pathway in the eye lens/lens epithelial cells (LECs) at the molecular level. We found that, in aging human (h)LECs, a progressive decline of nuclear factor erythroid 2-related factor 2 (Nrf2)/ARE (antioxidant response element)-mediated antioxidant genes was connected to Bmal1-deficiency, leading to accumulation of reactive oxygen species (ROS) and cell-death. Bmal1-depletion disrupted Nrf2 and expression of its target antioxidant genes, like Peroxiredoxin 6 (Prdx6). DNA binding and transcription assays showed that Bmal1 controlled expression by direct binding to E-Box in Prdx6 promoter to regulate its transcription. Mutation at E-Box or ARE reduced promoter activity, while disruption of both sites diminished the activity, suggesting that both sites were required for peak Prdx6-transcription. As in aging hLECs, ROS accumulation was increased in Bmal1-deficient cells and the cells were vulnerable to death. Intriguingly, Bmal1/Nrf2/Prdx6 and PhaseII antioxidants showed rhythmic expression in mouse lenses in vivo and were reciprocally linked to ROS levels. We propose that Bmal1 is pivotal for regulating oxidative responses. Findings also reveal a circadian control of antioxidant-pathway, which is important in combating lens/LECs damage induced by aging or oxidative stress.

Epigallocatechin Gallate Slows Retinal Degeneration, Reduces Oxidative Damage, and Modifies Circadian Rhythms in P23H Rats

Retinitis pigmentosa (RP) includes a group of genetic disorders that involve the loss of visual function due to mutations mainly in photoreceptors but also in other retinal cells. Apoptosis, retinal disorganization, and inflammation are common in the progression of the disease. Epigallocatechin gallate (EGCG) has been proved as beneficial in different eye diseases. Pigmented heterozygous P23H rat was used as an animal model of RP. Visual function was assessed by optomotor and electroretinogram (ERG) and circadian rhythms were evaluated by telemetry. Hepatic oxidative damage and antioxidant defenses were assessed using biochemical tests. The visual function of the EGCG P23H group was preserved, with a deterioration in the activity period and lower values in the interdaily stability parameter. Control rats treated with EGCG were less active than the sham group. EGCG increased antioxidant levels in P23H rats but reduced total hepatic antioxidant capacity by almost 42% in control rats compared to the sham group. We conclude that treatment with EGCG improves visual function and antioxidant status in P23H rats but diminishes antioxidant defenses in wild-type control animals, and slightly worsens activity circadian rhythms. Further studies are necessary to clarify the beneficial effects in disease conditions and in healthy organisms.

Effects of Eurya japonica extracts on human corneal epithelial cells and experimental dry eye

Eurya japonica (EJ) leaves have been indicated to exert anti-oxidative and anti-inflammatory effects. Dry eye disease (DED) is a chronic inflammatory disease and oxidative stress is closely associated with DED. The aim of the present study was to analyze the therapeutic efficacy of EJ in DED using human corneal epithelial (HCE) cells and a mouse model of experimental dry eye (EDE). EJ extracts (0.001, 0.01 and 0.1%) were used to treat HCE cells. Cell viability and mitochondrial function were detected using a EZ-Cytox cell viability assay kit and mitochondrial membrane potential assays. Dichlorofluorescein diacetate (DCF-DA) assay was used to measure cellular reactive oxygen species (ROS) levels. Subsequently, eye drops consisting of BSS or 0.001%, 0.01 and 0.1% EJ extracts were applied for treatment of EDE. At 7 days, conjunctival ROS production was measured using a DCF-DA assay. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, 10 kDa interferon gamma-induced protein 10 (IP-10) and monokine induced by interferon-γ (MIG) levels in the conjunctiva were analyzed using a multiplex immunobead assay. Tear film and ocular surface parameters were measured. Treatment with EJ extracts in HCE cells effectively improved cell viability, ROS levels and mitochondrial function. Mice treated with 0.01 and 0.1% EJ extracts indicated a significant decrease in ROS, TNF-α, IL-1β, IP-10 and MIG levels compared with the EDE or BSS groups. Furthermore, a significant improvement in all clinical parameters was observed in the 0.01 and 0.1% EJ extract groups. EJ extracts could decrease cytotoxicity and ROS production in HCE cells. Additionally, topical EJ extracts reduced oxidative damage and inflammation and improved clinical signs of EDE, suggesting that EJ extracts may be used as an adjunctive therapy for DED.

A Novel Selective 11β-HSD1 Inhibitor, (E)-4-(2-(6-(2,6-Dichloro-4-(Trifluoromethyl)Phenyl)-4-Methyl-1,1-Dioxido-1,2,6-Thiadiazinan-2-yl)Acetamido)Adamantan-1-Carboxamide (KR-67607), Prevents BAC-Induced Dry Eye Syndrome

Dry eye syndrome is the most common eye disease and it is caused by various reasons. As the balance of the tear film that protects the eyes is broken due to various causes, it becomes impossible to properly protect the eyes. In this study, the protective effects and underlying mechanisms of topical (E)-4-(2-(6-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-methyl-1,1-dioxido-1,2,6-thiadiazinan-2-yl)acetamido)adamantan-1-carboxamide (KR-67607), a novel selective 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) inhibitor, were investigated in benzalkonium chloride (BAC)-induced dry eye syndrome. BAC-treated rat eyes induced significant increases in ocular surface damage, decreased corneal thickness, corneal basement membrane destruction in the conjunctival epithelium, and expression of pro-inflammatory cytokines tumor necrosis factor-α and 11β-HSD1. These effects of BAC were reversed by topical KR-67607 treatment. Furthermore, KR-67607 decreased 4-hydroxynonenal expression and increased antioxidant and mucus secretion in BAC-treated rat eyes. Taken together, a novel selective 11β-HSD1 inhibitor can prevent BAC-induced dry eye syndrome by inhibiting pro-inflammatory cytokine and reactive oxygen species expression via the inhibition of both 11β-HSD1 activity and expression.

Protective effects of carnosic acid on retinal ganglion cells in acute ocular hypertension rats

OBJECTIVE

To observe the protective effects of carnosic acid on rat retinal ganglion cells (RGCs) among acute ocular hypertension rats.

METHODS

Sixty male SPF (specific-pathogen-free) SD rats (10 weeks) were randomly assigned to untreated group, carnosic-acid-treated group and hypertensive group with 20 rats for each. The acute ocular hypertension animal model was induced by the perfusion of normal saline solution into anterior chamber of eyes to elevate the intraocular pressure (IOP) to 110 mmHg for 60 min in the rats of the carnosic-acid-treated group and hypertensive group. Then, the carnosic acid dissolving in dimethyl sulfoxide (DMSO) was intraperitoneally injected for consecutive 7 days in the carnosic-acid-treated group, and only DMSO was used in the same way in the hypertensive group. The rats were killed 2 weeks after experiment, and retinal sections were prepared for histopathological and apoptotic retinal ganglion cells (RGCs) examination by hemotoxylin and eosin staining and TUNEL staining. Use immunofluorescence employed to examine the survival of RGCs. This study protocol was approved by the Ethic Committee for Experimental Animal of Three Gorges University.

RESULTS

The retinal morphology and structure were clear in the untreated group. The edema of retinal tissue, loosely arranged RGCs and swollen nucleus were seen in the hypertensive group. In the carnosic-acid-treated group, the retinal morphology and structure were regular. The retinal nerve fiber layer (RNFL) thickness was (32.96 ± 1.63), (58.96 ± 1.57) and (50.11 ± 2.37) μm, and the apoptotic cell number was (6.92 ± 2.96), (29.85 ± 6.40) and (14.69 ± 2.98)/field, and the survived cell number was (2363.17 ± 148.45), (1308.67 ± 106.02) and (1614.17 ± 96.39)/0.235 mm² in the untreated group, hypertensive group and carnosic-acid-treated group, respectively, showing significant differences among groups (F = 339.284, 81.583, 122.68, all at P < 0.01). Compared with the untreated group, the RNFL thickness was thickened, the number of apoptotic RGCs was much more, and the number of survived RGCs was decreased in the hypertensive group. In the carnosic-acid-treated group, the RNFL thickness was thinner, the number of apoptotic RGCs was reduced, and the number of survived RGCs was increased in comparison with the untreated group (all at P < 0.01).

CONCLUSIONS

Carnosic acid plays a protective effect on RGCs by inhibiting the cell apoptosis in acute ocular hypertension rats.

The Role of Nutrition and Nutritional Supplements in Ocular Surface Diseases

Dry eye disease (DED) is a multifactorial disease of the ocular surface system whose chore mechanisms are tear film instability, inflammation, tear hyperosmolarity and epithelial damage. In recent years, novel therapies specifically targeting inflammation and oxidative stress are being investigated and used in this field. Therefore, an increasing body of evidence supporting the possible role of different micronutrients and nutraceutical products for the treatment of ocular surface diseases is now available. In the present review, we analyzed in detail the effects on ocular surface of omega-3 fatty acids, vitamins A, B12, C, D, selenium, curcumin and flavonoids. Among these, the efficacy of omega-3 fatty acid supplementation in ameliorating DED signs and symptoms is supported by robust scientific evidence. Further long-term clinical trials are warranted to confirm the safety and efficacy of the supplementation of the other micronutrients and nutraceuticals.

Let-7c-3p Regulates Autophagy under Oxidative Stress by Targeting ATG3 in Lens Epithelial Cells

Background

Oxidative stress is an important factor during age-related cataract formation. Apoptosis and autophagy induced by oxidative stress have been reported as key factors in age-related cataract. In our research, we investigated the role of let-7c-3p in the regulation of autophagy and apoptosis during the formation of age-related cataract. Material and Methods. Real-time PCR and western blot were employed to detect the expression of let-7c-3p in the tissues of age-related cataract. Human lens epithelial cells (LECs) were treated with H₂O₂ as an age-related cataract model. The extent of apoptosis was measured by flow cytometry and western blot. To detect autophagy, immunofluorescence was used to analyze the spot number of LC3, and western blot was used to detect the expression of LC3-II/I and ATG3. The molecular mechanisms of let-7c-3p regulating autophagy via ATG3 under oxidative stress were performed by a luciferase report gene assay and rescue experiment.

Results

Downregulation of let-7c-3p was found in the age-related cataract group aged >65 years relative to the age-related cataract group aged ≤65 years. Consistently, the expression of let-7c-3p was also lower under oxidative stress. The activities of LEC apoptosis and autophagy induced by oxidative stress were inhibited by let-7c-3p. By the bioinformatics database and the luciferase reporter assay, ATG3 was found to be a direct target of let-7c-3p. Let-7c-3p reduced the ATG3-mediated autophagy level, which was induced by oxidative stress in LECs.

Conclusion

Let-7c-3p inhibits autophagy by targeting ATG3 in LECs in age-related cataract.

Autophagy and Age-Related Eye Diseases

Background

Autophagy is a catabolic process that depends on the lysosome. It is usually used to maintain cellular homeostasis, survival and development by degrading abnormal substances and dysfunctional organelles, especially when the cell is exposed to starvation or other stresses. Increasing studies have reported that autophagy is associated with various eye diseases, of which aging is one of the important factors.

Objective

To summarize the functional and regulatory role of autophagy in ocular diseases with aging, and discuss the possibility of autophagy-targeted therapy in age-related diseases.

Methods

PubMed searches were performed to identify relevant articles published mostly in the last 5 years. The key words were used to retrieve including “autophagy”, “aging”, “oxidative stress AND autophagy”, “dry eye AND autophagy”, “corneal disease AND autophagy”, “glaucoma AND autophagy”, “cataract AND autophagy”, “AMD AND autophagy”, “cardiovascular diseases AND autophagy”, “diabetes AND autophagy”. After being classified and assessed, the most relevant full texts in English were chosen.

Results

Apart from review articles, more than two research articles for each age-related eye diseases related to autophagy were retrieved. We only included the most relevant and recent studies for summary and discussion.

Conclusion

Autophagy has both protective and detrimental effects on the progress of age-related eye diseases. Different types of studies based on certain situations in vitro showed distinct results, which do not necessarily coincide with the actual situation in human bodies completely. It means the exact role and regulatory function of autophagy in ocular diseases remains largely unknown. Although autophagy as a potential therapeutic target has been proposed, many problems still need to be solved before it applies to clinical practice.

Oxidative stress in corneal injuries of different origin: Utilization of 3D human corneal epithelial tissue model

The purpose of the current work was to utilize a three dimensional (3D) corneal epithelial tissue model to study dry eye disease and oxidative stress-related corneal epithelial injuries for the advancement of ocular therapeutics. Air-liquid interface cultures of normal human corneal epithelial cells were used to produce 3D corneal epithelial tissues appropriate for physiologically relevant exposure to environmental factors. Oxidative stress was generated by exposing the tissues to non-toxic doses of ultraviolet radiation (UV), hydrogen peroxide, vesicating agent nitrogen mustard, or desiccating conditions that stimulated morphological, cellular, and molecular changes relevant to dry eye disease. Corneal specific responses, including barrier function, tissue viability, reactive oxygen species (ROS) accumulation, lipid peroxidation, cytokine release, histology, and gene expression were evaluated. 3D corneal epithelial tissue model structurally and functionally reproduced key features of molecular responses of various types of oxidative stress-induced ocular damage. The most pronounced effects for different treatments were: UV irradiation - intracellular ROS accumulation; hydrogen peroxide exposure - barrier impairment and IL-8 release; nitrogen mustard exposure - lipid peroxidation and IL-8 release; desiccating conditions - tissue thinning, a decline in mucin expression, increased lipid peroxidation and IL-8 release. Utilizing a PCR gene array, we compared the effects of corneal epithelial damage on the expression of 84 oxidative stress-responsive genes and found specific molecular responses for each type of damage. The topical application of lubricant eye drops improved tissue morphology while decreasing lipid peroxidation and IL-8 release from tissues incubated at desiccating conditions. This model is anticipated to be a valuable tool to study molecular mechanisms of corneal epithelial damage and aid in the development of therapies against dry eye disease, oxidative stress- and vesicant-induced ocular injuries.

Antioxidant status in rabbit aqueous humor after instillation of ascorbyl laurate-based nanostructures

BACKGROUND

The aim of this work was evaluate the antioxidant effect of ascorbyl laurate (ASC12) based nanostructures applied topically to the cornea of ocular normotensive and hypertensive rabbits. The ASC12 was chosen for its capacity to form liquid lyotropic crystal and keeps its free radical trapping power.

METHODS

The hypertension model was performed in six rabbits and was obtained by the application of intracameral injections of alpha-chymotrypsin in the right eye. A single 50 ml dose of ascorbyl laurate coagel 2% w/v (COA-ASC12) was applied topically to the cornea of six normotensive and six hypertensive rabbits. The aqueous humor samples were obtained before and after instillation of COA-ASC12 at different times (2 h and 4 h). Antioxidant capacity was determined via the reduction reaction with iron and tripyridyltriazine (FRAP) and the total proteins were measured using the Bradford reagent.

RESULTS

The kinetic antioxidant capacity in the aqueous humor of normotensive and hypertensive rabbits showed a maxim increment at 4 h instillation. Also, the antioxidant capacity in the aqueous humor of hypertensive rabbits was ten times lower than in normotensive rabbits.

CONCLUSION

This type of nanostructures has the potential to significantly improve the topical formulation for the prophylaxis and treatment of several eye diseases.

Saffron (Crocus sativus L.) in Ocular Diseases: A Narrative Review of the Existing Evidence from Clinical Studies

Saffron (Crocus sativus L.) and its main constituents, i.e., crocin and crocetin, are natural carotenoid compounds, which have been reported to possess a wide spectrum of properties and induce pleiotropic anti-inflammatory, anti-oxidative, and neuroprotective effects. An increasing number of experimental, animal, and human studies have investigated the effects and mechanistic pathways of these compounds in order to assess their potential therapeutic use in ocular diseases (e.g., in age related macular degeneration, glaucoma, and diabetic maculopathy). This narrative review presents the key findings of published clinical studies that examined the effects of saffron and/or its constituents in the context of ocular disease, as well as an overview of the proposed underlying mechanisms mediating these effects.

Changes in conjunctival epithelial cells after treatment with 0.2% xanthan gum eye drops in mild-moderate dry eye

PURPOSE

To study the effects of xanthan gum eye drops on the ocular surface and conjunctival cytology of patients with mild-moderate dry eye.

METHODS

This prospective, double-masked, controlled trial included 30 patients (age > 60 and Ocular Surface Disease Index score >12 and <33), divided into two groups of 15 subjects and treated with 0.2% xanthan gum eye drops (group 1) or 0.5% carboxymethylcellulose (group 2) qid. After a run-in period with saline qid, patients were evaluated by Ocular Surface Disease Index questionnaire, clinical assessment, and impression cytology at baseline (T0) and after 1 month (T1). For impression cytology, cellularity, cell-to-cell contacts, nucleus/cytoplasm ratio, chromatin aspect, goblet cells distribution, keratinization, and the presence of inflammatory cells were considered. Parameters were scored from 0 (no alterations) to 3 (evident alterations). For statistical analysis, Student's t-test, Wilcoxon rank-sum test, and Mann-Whitney U-test were used.

RESULTS

Clinically, after 1 month of treatment, group 1 showed an improvement of corneal stain (T0 = 1.1 ± 1.4; T1 = 0.5 ± 0.7; p = 0.03) and a reduction of Schirmer I test (T0 = 9.8 ± 6.1; T1 = 5.9 ± 4.1; p = 0.001). In group 2, no differences were found between T0 and T1 for all the clinical tests. For impression cytology, in group 1 cellularity (T0 = 0.6 ± 0.5; T1 = 0.3 ± 0.5; p = 0.05), chromatin aspect (T0 = 1.2 ± 0.4; T1 = 0.8 ± 0.5; p = 0.01), keratinization (T0 = 1 ± 0.7; T1 = 0.5 ± 0.5; p = 0.03), and total score (T0 = 5.8 ± 1.3; T1 = 3.6 ± 1.7; p = 0.003) were significantly ameliorated, while in group 2 only total score improved significantly (T0 = 5 ± 1.4; T1 = 4.3 ± 1.5; p = 0.01). The comparison between groups showed significant amelioration for keratinization in group 1 at T1 (p = 0.02).

CONCLUSION

The treatment with xanthan gum, a molecule with anti-oxidant and mucoadhesive properties, ameliorated conjunctival epithelium of mild-moderate dry eye patients better than carboxymethylcellulose.