Elevation of serum oxidative stress in patients with retina vein occlusions

Longevity factor FOXO3a: A potential therapeutic target for age-related ocular diseases

The forkhead box protein O3 (FOXO3a) belongs to the subgroup O of the forkhead transcription factor family and plays an important role in regulating the aging process by participating in the regulation of various life processes, including cell cycle arrest, apoptosis, autophagy, oxidative stress, and DNA repair. The eye is an organ that is affected by aging earlier. However, the functional role and potential clinical applications of FOXO3a in age-related eye diseases have not received widespread attention and lacked comprehensive and clear clarification. In this review, we demonstrated the relationship between FOXO3a and visual system health, summarized the functional roles of FOXO3a in various eye diseases, and potential ocular-related therapies and drugs targeting FOXO3a in visual system diseases through a review and summary of relevant literature. This review indicates that FOXO3a is an important factor in maintaining the normal function of various tissues in the eye, and is closely related to the occurrence and development of ophthalmic-related diseases. Based on its vital role in the normal function of the visual system, FOXO3a has potential clinical application value in related ophthalmic diseases. At present, multiple molecules and drugs targeting FOXO3a have been reported to have the potential for the treatment of related ophthalmic diseases, but further clinical trials are needed. In conclusion, this review can facilitate us to grasp the role of FOXO3a in the visual system and provide new views and bases for the treatment strategy research of age-related eye diseases.

Deciphering the interplay of gut microbiota and metabolomics in retinal vein occlusion

This study aims to explore the link between retinal vein occlusion (RVO), a blinding ocular condition, and alterations in gut microbiota composition, to offer insights into the pathogenesis of RVO. Fecal samples from 25 RVO patients and 11 non-RVO individuals were analyzed using 16S rRNA sequencing and liquid chromatography-mass spectrometry (LC-MS). Significant differences in the abundance of gut microbial species were noted between RVO and non-RVO groups. At the phylum level, the RVO group showed an elevation in the ratio of Firmicutes to Bacteroidetes. At the genus level, the RVO group showed higher abundance in Escherichia_Shigella (P < 0.05) and less abundance in Parabacteroides (P < 0.01) than the non-RVO group. Functional predictions indicated reduced folate synthesis, biotin metabolism, and oxidative phosphorylation, with an increase in butyric acid metabolism in the RVO group. LC-MS analysis showed significant differences in purine metabolism, ABC transporters, and naphthalene degradation pathways, especially purine metabolism. Pearson correlation analysis revealed significant associations between bacterial genera and fecal metabolites. Enrichment analysis highlighted connections between specific metabolites and bacterial genera. The findings showed that the dysregulation of gut microbiota was observed in RVO patients, suggesting the gut microbiota as a potential therapeutic target. Modulating the gut microbiota could be a novel strategy for managing RVO and improving patient outcomes. Furthermore, the study findings suggest the involvement of gut microbial dysbiosis in RVO development, underscoring the significance of understanding its pathogenesis for effective treatment development.

IMPORTANCE

Retinal vein occlusion (RVO) is a blinding ocular condition, and understanding its pathogenesis is crucial for developing effective treatments. This study demonstrates significant differences in gut microbiota composition between RVO patients and non-RVO individuals, implicating the involvement of gut microbial dysbiosis in RVO development. Functional predictions and metabolic profiling provide insights into the underlying mechanisms, highlighting potential pathways for therapeutic intervention. These findings suggest that modulating the gut microbiota might be a promising strategy for managing RVO and improving patient outcomes.

Injectable, Antioxidative, and Tissue-Adhesive Nanocomposite Hydrogel as a Potential Treatment for Inner Retina Injuries

Reactive oxygen species (ROS) have been recognized as prevalent contributors to the development of inner retinal injuries including optic neuropathies such as glaucoma, non-arteritic anterior ischemic optic neuropathy, traumatic optic neuropathy, and Leber hereditary optic neuropathy, among others. This underscores the pivotal significance of oxidative stress in the damage inflicted upon retinal tissue. To combat ROS-related challenges, this study focuses on creating an injectable and tissue-adhesive hydrogel with tailored antioxidant properties for retinal applications. GelCA, a gelatin-modified hydrogel with photo-crosslinkable and injectable properties, is developed. To enhance its antioxidant capabilities, curcumin-loaded polydopamine nanoparticles (Cur@PDA NPs) are incorporated into the GelCA matrix, resulting in a multifunctional nanocomposite hydrogel referred to as Cur@PDA@GelCA. This hydrogel exhibits excellent biocompatibility in both in vitro and in vivo assessments, along with enhanced tissue adhesion facilitated by NPs in an in vivo model. Importantly, Cur@PDA@GelCA demonstrates the potential to mitigate oxidative stress when administered via intravitreal injection in retinal injury models such as the optic nerve crush model. These findings underscore its promise in advancing retinal tissue engineering and providing an innovative strategy for acute neuroprotection in the context of inner retinal injuries.

Oxidative stress in the eye and its role in the pathophysiology of ocular diseases

Oxidative stress occurs through an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms of cells. The eye is particularly exposed to oxidative stress because of its permanent exposure to light and due to several structures having high metabolic activities. The anterior part of the eye is highly exposed to ultraviolet (UV) radiation and possesses a complex antioxidant defense system to protect the retina from UV radiation. The posterior part of the eye exhibits high metabolic rates and oxygen consumption leading subsequently to a high production rate of ROS. Furthermore, inflammation, aging, genetic factors, and environmental pollution, are all elements promoting ROS generation and impairing antioxidant defense mechanisms and thereby representing risk factors leading to oxidative stress. An abnormal redox status was shown to be involved in the pathophysiology of various ocular diseases in the anterior and posterior segment of the eye. In this review, we aim to summarize the mechanisms of oxidative stress in ocular diseases to provide an updated understanding on the pathogenesis of common diseases affecting the ocular surface, the lens, the retina, and the optic nerve. Moreover, we discuss potential therapeutic approaches aimed at reducing oxidative stress in this context.

Flavoprotein fluorescence elevation is a marker of mitochondrial oxidative stress in patients with retinal disease

Purpose

Recent studies of glaucoma, age-related macular degeneration, and diabetic retinopathy have demonstrated that flavoprotein fluorescence (FPF) can be utilized non-invasively as an indicator of mitochondrial oxidative stress in the retina. However, a comprehensive assessment of the validity and reliability of FPF in differentiating between healthy and diseased eyes across multiple disease states is lacking. Here, we evaluate the sensitivity and specificity of FPF in discriminating between healthy and diseased eyes in four leading causes of visual impairment worldwide, one of which has not been previously evaluated using FPF. We also evaluate the association between FPF and visual acuity.

Methods

A total of 88 eyes [21 eyes of 21 unaffected controls, 20 eyes from 20 retinal vein occlusion (RVO) patients, 20 eyes from 20 diabetic retinopathy (DR) patients, 17 eyes from 17 chronic exudative age-related macular degeneration (exudative AMD) patients, and 10 eyes from 10 central serous retinopathy (CSR) patients] were included in the present cross-sectional observational study. Eyes were imaged non-invasively using a specially configured fundus camera OcuMet Beacon® (OcuSciences, Ann Arbor, MI). The macula was illuminated using a narrow bandwidth blue light (455 - 470 nm) and fluorescence was recorded using a narrow notch filter to match the peak emission of flavoproteins from 520 to 540 nm. AUROC analysis was used to determine the sensitivity of FPF in discriminating between diseased eyes and healthy eyes. Nonparametric Kruskal-Wallis Tests with post-hoc Mann Whitney U tests with the Holm-Bonferroni correction were performed to assess differences in FPF intensity, FPF heterogeneity, and best corrected visual acuity (BCVA) between the five groups. Spearman rank correlation coefficients were calculated to assess the relationship between FPF and BCVA.

Results

AUROC analysis indicated that FPF intensity is highly sensitive for detecting disease, particularly for exudative AMD subjects (0.989; 95% CI = 0.963 - 1.000, p=3.0 x 107). A significant difference was detected between the FPF intensity, FPF heterogeneity, and BCVA in all four disease states compared to unaffected controls (Kruskal-Wallis Tests, p = 1.06 x 10-8, p = 0.002, p = 5.54 x 10-8, respectively). Compared to healthy controls, FPF intensity values were significantly higher in RVO, DR, exudative AMD, and CSR (p < 0.001, p < 0.001, p < 0.001, and p = 0.001, respectively). Spearman rank correlation coefficient between FPF intensity and BCVA was ρ = 0.595 (p = 9.62 x 10-10).

Conclusions

Despite variations in structural retinal findings, FPF was found to be highly sensitive for detecting retinal disease. Significant FPF elevation were seen in all four disease states, with the exudative AMD patients exhibiting the highest FPF values compared to DR, CSR, and RVO subjects. This is consistent with the hypothesis that there is elevated oxidative stress in all of these conditions as previously demonstrated by blood studies. FPF intensity is moderately correlated with the late-in disease-marker BCVA, which suggests that the degree of FPF elevation can be used as a metabolic indicator of disease severity.

ceRNA network construction and identification of hub genes as novel therapeutic targets for age-related cataracts using bioinformatics

Background

The aim of this study is to investigate the genetic and epigenetic mechanisms involved in the pathogenesis of age-related cataract (ARC).

Methods

We obtained the transcriptome datafile of th ree ARC samples and three healthy, age-matched samples and used differential expression analyses to identify the differentially expressed genes (DEGs). The differential lncRNA-associated competing endogenous (ceRNA) network, and the protein-protein network (PPI) were constructed using Cytoscape and STRING. Cluster analyses were performed to identify the underlying molecular mechanisms of the hub genes affecting ARC progression. To verify the immune status of the ARC patients, immune-associated analyses were also conducted.

Results

The PPI network identified the FOXO1 gene as the hub gene with the highest score, as calculated by the Maximal Clique Centrality (MCC) algorithm. The ceRNA network identified lncRNAs H19, XIST, TTTY14, and MEG3 and hub genes FOXO1, NOTCH3, CDK6, SPRY2, and CA2 as playing key roles in regulating the pathogenesis of ARC. Additionally, the identified hub genes showed no significant correlation with an immune response but were highly correlated with cell metabolism, including cysteine, methionine, and galactose.

Discussion

The findings of this study may provide clues toward ARC pathogenic mechanisms and may be of significance for future therapeutic research.

Review: The Development of Risk Factors and Cytokines in Retinal Vein Occlusion

Retinal vein occlusion (RVO) is the second most prevalent retinal disease. Despite this, the pathogenic mechanisms and risk factors are not entirely clear. In this article, we review recent publications on the classification, pathogenesis, risk factors, ischemic changes, cytokines, and vital complications of RVO. Risk factors and cytokines are important for exploring the mechanisms and new treatment targets. Furthermore, risk factors are interrelated, making RVO mechanisms more complex. Cytokines act as powerful mediators of pathological conditions, such as inflammation, neovascularization, and macular edema. This review aims to summarize the updated knowledge on risk factors, cytokines of RVO and signaling in order to provide valuable insight on managing the disease.

Metabolite Changes in the Aqueous Humor of Patients With Retinal Vein Occlusion Macular Edema: A Metabolomics Analysis

Macular edema (ME) is the main cause of visual impairment in patients with retinal vein occlusion (RVO). The degree of ME affects the prognosis of RVO patients, while it lacks objective laboratory biomarkers. We aimed to compare aqueous humor samples from 28 patients with retinal vein occlusion macular edema (RVO-ME) to 27 age- and sex-matched controls by ultra-high-performance liquid chromatography equipped with quadrupole time-of-flight mass spectrometry, so as to identify the key biomarkers and to increase the understanding of the mechanism of RVO-ME at the molecular level. Through univariate and multivariate statistical analyses, we identified 60 metabolites between RVO-ME patients and controls and 40 differential metabolites in mild RVO-ME [300 μm ≤ central retinal thickness (CRT) < 400 μm] patients compared with severe RVO-ME (CRT ≥ 400 μm). Pathway enrichment analysis showed that valine, leucine, and isoleucine biosynthesis; ascorbate and aldarate metabolism; and pantothenate and coenzyme A biosynthesis were significantly altered in RVO-ME in comparison with controls. Compared with mild RVO-ME, degradation and biosynthesis of valine, leucine, and isoleucine; histidine metabolism; beta-alanine metabolism; and pantothenate and coenzyme A biosynthesis were significantly changed in severe RVO-ME. Furthermore, the receiver operating characteristic (ROC) curve analysis revealed that adenosine, threonic acid, pyruvic acid, and pyro-L-glutaminyl-l-glutamine could differentiate RVO-ME from controls with an area under the curve (AUC) of >0.813. Urocanic acid, diethanolamine, 8-butanoylneosolaniol, niacinamide, paraldehyde, phytosphingosine, 4-aminobutyraldehyde, dihydrolipoate, and 1-(beta-D-ribofuranosyl)-1,4-dihydronicotinamide had an AUC of >0.848 for distinguishing mild RVO-ME from severe RVO-ME. Our study expanded the understanding of metabolomic changes in RVO-ME, which could help us to have a good understanding of the pathogenesis of RVO-ME.

Different Sources of Dietary Magnesium Supplementation Reduces Oxidative Stress by Regulation Nrf2 and NF-κB Signaling Pathways in High-Fat Diet Rats

Magnesium (Mg) is an essential mineral required for many physiological processes, including ionic balances in ocular tissues. We compared the effects of different Mg-chelates (Mg oxide, MgO vs. Mg picolinate, MgPic) on retinal function in a high-fat diet (HFD) rats. Forty-two rats were divided into six groups and treated orally for 8 weeks as follows: Control, MgO, MgPic, HFD, HFD + MgO, and HFD + MgPic. Mg was administered at 500 mg of elemental Mg/kg of diet. HFD intake increased the levels of retinal MDA and NF-κB, INOS, ICAM, and VEGF but downregulated Nrf2. However, in rats supplemented with MgO and MgPic, the retinal MDA level was decreased, compared with the control and HFD rats. Activities of antioxidant enzymes (SOD, CAT, and GPx) were increased in HFD animals given Mg-chelates (p < 0.001), MgPic being the most effective. Mg supplementation significantly decreased the expression levels of NF-κB, INOS, ICAM, and VEGF in HFD rats while increasing the level of Nrf2 (p < 0.001). Mg supplementation significantly decreased the levels of NF-κB, INOS, ICAM, and VEGF and increased Nrf2 level in HFD rats (p < 0.001), with stronger effects seen from MgPic. Mg attenuated retinal oxidative stress and neuronal inflammation and could be considered as an effective treatment for ocular diseases.

SERUM LEVELS OF ANTIBODIES AGAINST OXIDATION-SPECIFIC EPITOPES ARE DECREASED IN PATIENTS WITH RETINAL VEIN OCCLUSION

PURPOSE

Oxidative stress and inflammation have been implicated in the development of retinal vein occlusion (RVO). Oxidation-specific epitopes (OSEs) represent products of oxidative stress that can trigger vascular inflammation and thrombosis. Natural occurring antibodies have been shown to bind oxidation-specific epitopes thereby inhibiting their inflammatory potential and promoting their removal.

METHODS

This prospective cross-sectional study included 270 patients with RVO and 81 in-hospital control patients. We measured three types of serum levels of oxidation-specific epitope-specific immunoglobulin M and immunoglobulin G antibodies (anti-copper-oxidized LDL [CuOx-LDL], antiphosphocholine [PC], anti-malondialdehyde-modified LDL [MDA-LDL]). History of arterial hypertension, hyperlipidemia, myocardial infarction, diabetes mellitus, stroke, smoking status, and several laboratory parameters were determined to control for potential confounders.

RESULTS

Compared with controls, patients with RVO had significantly lower levels of immunoglobulin M and immunoglobulin G antibodies against CuOx-LDL and PC, and significantly lower levels of immunoglobulin G but not immunoglobulin M antibodies against MDA-LDL. The association between RVO patients and lower levels of these antibodies prevailed upon multivariable adjustment.

CONCLUSION

These prospective data show that antibodies against oxidation-specific epitope are lower in patients with RVO compared with control patients and support the concept that oxidative stress and inflammation play key roles in the development and subsequent complications in RVO.

Oral administration of NSP-116, a free radical scavenger, suppresses the symptoms of retinal vein occlusion in the murine model

Retinal vein occlusion (RVO) is an intractable eye disease that results in reduced visual acuity, associated with retinal ischemia, hemorrhage, and edema. RVO results in excessive ROS production in the retina, causing inflammation and retinal edema. A free radical scavenger, 4-(4-acetylpiperazin-1-yl)-2-(1H-imidazole-1-yl) aniline (NSP-116), has been reported to demonstrate antioxidative effects and prevent ROS production in the retina. Therefore, NSP-116 may represent a useful drug for treating the pathological symptoms of RVO, such as retinal edema and ischemic symptoms. This study aimed to investigate the effects of NSP-116 in a murine model of RVO. We evaluated the thickness of the retinal layer and the size of the non-perfused area following the oral administration of NSP-116. Moreover, we used western blot analysis to examine the expression levels of vascular endothelial growth factor (VEGF) and tumor necrosis factor (TNF)-α, after NSP-116 administration, and examined the localization of 8-hydroxy-2'-deoxyguanosine (8-OHdG), by immunostaining. The findings indicate that NSP-116 suppressed retinal edema and expansion the non-perfused area by suppressing the increased expression of VEGF, TNF-α, and 8-OHdG in the murine RVO model. In conclusion, the oral administration of NSP-116 may serve as an effective pharmacological treatment for the pathological symptoms of RVO.

Establishment of a pigmented murine model abundant with characteristics of retinal vein occlusion

Retinal vein occlusion (RVO) is a vascular disease that represents characteristic retinal hemorrhage and dilated retinal veins. Despite its clinical importance, its pathogenesis remains largely unknown because of limited opportunities to acquire human retinal samples. Therefore, an animal model that reproduces the clinical features of RVO patients is required for further investigation. In this study, we established a pigmented murine RVO model that reproduced characteristic fundus appearances similar to human RVO findings. Retinal edema in this model was observed in both optical coherence tomography and histological analysis, which is a clinically important outcome. With quantitative real-time PCR analysis on retinal samples, we revealed that the mRNA level of vascular endothelial growth factor (VEGF) increased in the retina induced RVO. Moreover, this retinal edema was reduced by intravitreal injection of anti-VEGF antibody. These results were consistent with human clinical knowledge and suggested that this model could be a useful tool for research into new therapeutic approaches.

Polyethylene microbeads are more critically toxic to the eyes and reproduction than the kidneys or growth in medaka, Oryzias latipes

Many studies using experimental and wild animals have reported negative effects of microplastic beads (MPs) ingestion. However, data regarding the lowest observed adverse effect levels (LOAELs) of MPs remain limited. Our aim was to evaluate the adverse effect levels of polyethylene MPs (10-63 μm diameter) with respect to growth, reproduction, and the eyes and kidneys of medaka (Oryzias latipes) under breeding conditions to contribute to future research involving LOAEL determinations. Fish were exposed to 0.009 mg-MPs (approximately 1000 particles)/L to 0.32 mg-MPs (approximately 40,000 particles)/L for 12 weeks. The eyes and kidneys were evaluated by histopathologic analysis. Although histologic analyses indicated an absence of MPs in the tissues, the eyes and kidneys as well as reproduction were adversely affected by increasing MP concentrations. The number of spawned eggs decreased, and changes were noted in the eyes of fish exposed to ≥0.032 mg-MPs/L under breeding conditions. The eyes exhibited thinning of the optic nerve fiber layer and dilatation of retinal capillaries compared with medaka not treated with MPs. Changes in the kidneys were observed in fish exposed to ≥0.065 mg-MPs/L. The mesangial matrix in the glomerulus of the kidneys was expanded compared with non-treated medaka, suggesting a deterioration in renal function. Analyses of an oxidative stress marker in the tissues indicated that lesion progression was associated with increased oxidative stress. Furthermore, a comparison of adverse effect levels suggested that MPs were more toxic to the eyes and reproduction than the kidneys or growth. Our data should prove useful for determining the LOAELs of polyethylene beads on vertebrates and enhance understanding of the mechanism underlying the biological toxicity of polyethylene MPs.

Changes in the Systemic Expression of Sirtuin-1 and Oxidative Stress after Intravitreal Anti-Vascular Endothelial Growth Factor in Patients with Retinal Vein Occlusion

OBJECTIVES

Retinal vein occlusions (RVO) are associated with systemic risk factors. However, the ocular occlusive events might also influence a patient's systemic condition. This study tried to investigate serum biomarkers associated with oxidative stress, before and after intravitreal anti-vascular endothelial growth factor (aVEGF) therapy in patients with RVOs.

METHODS

Newly-onset RVO patients were categorized into two groups: comorbid with macular edema requiring aVEGF therapy (treatment group) and no edema (observation group). Age and sex-matched patients (who received cataract surgery) were included as the control group. Intravitreal ranibizumab with a pro-re-nata regimen were administered. Serum samples were collected prior to treatment, at 6 and 12 months after therapy/observation and were collected once before controls who received cataract surgery. mRNA expression of sirtuin-1, its downstream genes, anti-oxidative biomarkers, and proinflammatory cytokines were measured.

RESULTS

There were 32, 26, and 34 patients enrolled in the treatment, observation, and control groups, respectively. The expressions of sirtuin-1 and its downstream genes were significantly lower in patients with RVO compared with the control group. Sirtuin-1 gene expression increased after 1 year of aVEGF therapy in the treatment group but remained unchanged in the observation group. Biomarkers of oxidative stress and proinflammatory cytokines were reduced after 1 year of aVEGF therapy. These biomarkers remained with no changes in the observation group.

CONCLUSIONS

Our study showed that the systemic oxidative stress increased in RVO patients. The aVEGF therapy could alter the gene expression of anti-oxidative proteins and reduce systemic oxidative stress in these patients.

Results from the Population-Based Gutenberg Health Study Revealing Four Altered Autoantibodies in Retinal Vein Occlusion Patients

Purpose

Retinal vein occlusion (RVO) is the second most common retinal vascular disease and a major cause of visual impairment. In this study, we aimed to observe whether RVO cases have different antibody profiles as a new potential risk factor and whether a conversion of retinal vein occlusion (RVO) to neovascular glaucoma (NVG), one of the major complications, is occurring within a 5-year timeframe.

Methods

We performed a nested case-control study (1 : 4) within the Gutenberg Health Study (GHS), a population-based, prospective cohort study in the Rhine-Main Region of Germany including 15,010 participants. RVO subjects (n = 59) were identified by grading of fundus photographs. Optic nerves of RVO subjects and age- and sex-matched controls (n = 229) at baseline and their follow-up examination after 5 years were analyzed for glaucomatous alterations. Of all RVO subjects and controls, serum autoantibody profiles were measured using in-house manufactured antigen-antibody microarrays.

Results

Of the 59 RVO patients, 3 patients (5%) showed glaucomatous optic disc alterations at baseline, whereas no new glaucoma case was detected at 5-year follow-up. Four of the autoantibodies measured (against dermcidin, neurotrophin-3, superoxide dismutase 1, and signal recognition particle 14 kDa protein) were significantly increased in the serum of RVO patients (p < 0.001). Multivariable conditional logistic regression analysis showed that 3 of these 4 antibodies were independent of cardiovascular risk factors.

Conclusions

We found several autoantibodies associated with RVO, targeting proteins and structures possibly involved in RVO pathogenesis.