Mechanisms of age-related macular degeneration and therapeutic opportunities

Implantable anti-angiogenic scaffolds for treatment of neovascular ocular pathologies

The retinal physiology can accrue oxidative damage and inflammatory insults due to age and metabolic irregularities. Two notable diseases that involve retinal and choroidal neovascularization are proliferative diabetic retinopathy and wet age-related macular degeneration. Currently, these diseases are mainly treated with anti-VEGF drugs (VEGF = vascular endothelial growth factor), generally on a monthly dosage scheme. We discuss recent developments for the treatment of these diseases, including bioactive tissue-engineered materials, which may reduce frequency of dosage and propose a path forward for improving patient outcomes. Graphical abstract Development of materials for long-term intravitreal delivery for management of posterior segment diseases.

The Role of Inflammation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a blinding eye disease which incidence gradually increases with age. Inflammation participates in AMD pathogenesis, including choroidal neovascularization and geographic atrophy. It is also a kind of self-protective regulation from injury for the eyes. In this review, we described inflammation in AMD pathogenesis, summarized the roles played by inflammation-related cytokines, including pro-inflammatory and anti-inflammatory cytokines, as well as leukocytes (macrophages, dendritic cells, neutrophils, T lymphocytes and B lymphocytes) in the innate or adaptive immunity in AMD. Possible clinical applications such as potential diagnostic biomarkers and anti-inflammatory therapies were also discussed. This review overviews the inflammation as a target of novel effective therapies in treating AMD.

DS-7080a, a Selective Anti-ROBO4 Antibody, Shows Anti-Angiogenic Efficacy with Distinctly Different Profiles from Anti-VEGF Agents

Purpose

Neovascular age-related macular degeneration (nAMD) results from choroidal neovascularization (CNV) and causes severe vision loss. Intravitreal anti-vascular endothelial growth factor (VEGF) therapies have significantly improved therapeutic outcomes; however, a substantial number of patients experience disease progression. Roundabout 4 (ROBO4) has been reported to be a vascular-specific protein that stabilizes vasculature in ocular pathological angiogenesis. To explore ROBO4 targeting as a novel treatment against neovascularization, we generated a humanized anti-human ROBO4 antibody, DS-7080a, and evaluated its efficacy.

Methods

ROBO4 mRNA in human whole eye cross-sections was examined by in situ hybridization. Human umbilical vein endothelial cell (HUVEC) migration was measured in the presence of VEGF, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), or conditioned medium of primary human retinal pigment epithelial (HRPE) cells. CNV was induced in cynomolgus monkeys by laser irradiation. Vascular leakage was measured by fluorescein angiography, and pathological changes were determined by histology.

Results

ROBO4 mRNA was detected in choroidal vessels of nAMD patients. DS-7080a suppressed HGF- or bFGF-induced HUVEC migration in addition to that induced by VEGF. Further, HUVEC migration induced by HRPE-conditioned medium was inhibited by either DS-7080a or ranibizumab in a similar manner, and the combination of these showed further inhibition. In a laser-induced CNV monkey model, single intravitreous administration of 1.1 mg/eye of DS-7080a reduced the incidence of grade 4 leakage from 44.45% in control eyes to 1.85% (P < 0.05 by Dunnett's test).

Conclusions

Anti-ROBO4 antibody DS-7080a suppressed HUVEC migration in a distinctly different fashion from anti-VEGF agents and improved laser-induced CNV in non-human primates.

Translational Relevance

DS-7080a may be a novel treatment option for nAMD.

Cerebral Modifications and Visual Pathway Reorganization in Maculopathy: A Systematic Review

Background

Macular degeneration (MD) is one of the most frequent causes of visual deficit, resulting in alterations affecting not only the retina but also the entire visual pathway up to the brain areas. This would seem related not just to signal deprivation but also to a compensatory neuronal reorganization, having significant implications in terms of potential rehabilitation of the patient and therapeutic perspectives.

Objective

This paper aimed to outline, by analyzing the existing literature, the current understanding of brain structural and functional changes detected with neuroimaging techniques in subjects affected by juvenile and age-related maculopathy.

Methods

Articles using various typologies of central nervous system (CNS) imaging in at least six patients affected by juvenile or age-related maculopathy were considered. A total of 142 were initially screened. Non-pertinent articles and duplicates were rejected. Finally, 19 articles, including 649 patients, were identified.

Results

In these sources, both structural and functional modifications were found in MD subjects' CNS. Changes in visual cortex gray matter volume were observed in both age-related MD (AMD) and juvenile MD (JMD); in particular, an involvement of not only its posterior part but also the anterior one suggests further causes besides an input-deprivation mechanism only. White matter degeneration was also found, more severe in JMD than in AMD. Moreover, functional analysis revealed differences in cortical activation patterns between MD and controls, suggesting neuronal circuit reorganization. Interestingly, attention and oculomotor training allowed better visual performances and correlated to a stronger cortical activation, even of the area normally receiving inputs from lesioned macula.

Conclusion

In MD, structural and functional changes in cerebral circuits and visual pathway can happen, involving both cerebral volume and activation patterns. These modifications, possibly due to neuronal plasticity (already observed and described for several brain areas), can allow patients to compensate for macular damage and gives therapeutic perspectives which could be achievable through an association between oculomotor training and biochemical stimulation of neuronal plasticity.

Celastrol Protects RPE Cells from Oxidative Stress-Induced Cell Death via Activation of Nrf2 Signaling Pathway

PURPOSE

Oxidative stress to retinal pigment epithelial (RPE) cells and inflammation are closely related to the pathogenesis of age-related macular degeneration (AMD). Celastrol is a natural compound isolated from the root of Tripterygium wilfordii. Celastrol has been shown to have potent anti-inflammatory and anti-tumor effects in multiple disease models. The objective of this study was to test the anti-oxidative effects of celastrol in RPE cells and to investigate the underlying mechanisms.

METHODS

ARPE-19 cells were treated with hydrogen peroxide (H2O2) and menadione alone or in combination with celastrol. Cell viability and apoptosis were examined by CCK-8 and TUNEL assay, respectively. The expression of Nrf2 and its target genes, such as GCLM and HO-1 was determined by Western blotting. The knockdown of Nrf2 was done by transfecting ARPE-19 cells with lentivirus encoding shRNA against Nrf2. The knockdown efficiency was determined by real-time quantitative PCR and Western blotting.

RESULTS

Treatment of ARPE-19 cells with celastrol significantly attenuated the toxic effects of both H2O2 and menadione. Treatment with celastrol enhanced the expression of transcription factor Nrf2 and its targets, GCLM and HO-1. Knockdown of Nrf2 expression by shRNA partially abolished the protective effects of celastrol. Chemical inhibition of glutathione synthesis by L-buthionine-S,R-sulfoximine (BSO) completely abolished the protective effects of celastrol against H2O2 and menadione-induced damage. However, chemical inhibition of HO-1 activity by ZnPPIX did not reduce the protective effects of celastrol.

CONCLUSION

This study provides evidence that treatment of RPE cells with celastrol shows potent protective effects against oxidative insults via activation of Nrf2 signaling pathway and upregulation of GCLM expression. This finding suggests that celastrol might be used as a potential therapeutic agent for oxidative stress-related eyes diseases, such as AMD.

Melatonin: Implications for Ocular Disease and Therapeutic Potential

Melatonin, an indoleamine secreted mainly by the pineal gland, is known to modulate a wide range of circadian functions. However, this neurohormone is also synthesized within the eye and acts directly on ocular structures to mediate a variety of physiological processes. This review is focused on the role and therapeutic potential of melatonin in ocular diseases. We summarize data indicating that melatonin may represent a powerful tool to counteract ocular dysfunctions such as uveitis, glaucoma, age-related macular degeneration, and diabetic retinopathy. A search strategy was conducted to identify studies in PubMed (January 1990 to September 2017). In particular, we included experimental studies, clinical trials, and reviews to provide suitable insights and elucidations regarding the action of melatonin on age-related ocular disorders. Literature data suggest that melatonin could potentially protect ocular tissues by decreasing the production of free radicals and pro-inflammatory mediators. Additionally, melatonin appears to be safe and well-tolerated, even at high doses, and no adverse/side effects were reported. Although this topic remains under intense investigation, we can conclude that melatonin, as a single agent or in combination with other drugs, is an attractive pharmacological candidate for age-related ocular diseases.

The potential health benefits of dietary natural plant products in age related eye diseases

In the past decade, there has been a tremendous increase in the number of cases of age-related eye diseases such as age-related macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. These diseases are the leading causes of visual impairment and blindness all over the world and are associated with many pathological risk factors such as aging, pollution, high levels of glucose (hyperglycaemia), high metabolic rates, and light exposure. These risk factors lead to the generation of uncontrollable reactive oxygen species (ROS), which causes oxidative stress. Oxidative stress plays a crucial role in the pathogenesis of age-related eye diseases through the activation of nuclear factor kappa B (NF-κB), vascular endothelial growth factor (VEGF), and lipid peroxidation, which leads to the production of inflammatory cytokines, angiogenesis, protein and DNA damages, apoptosis that causes macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. This review provides updated information on the beneficial effects of dietary natural plant products (DPNPs) against age-related eye diseases. In this review, supplementation of DPNPs demonstrated preventive and therapeutic effects on people at risk of or with age-related eye diseases due to their capacity to scavenge free radicals, ameliorate inflammatory molecules, neutralize the oxidation reaction that occurs in photoreceptor cells, decrease vascular endothelial growth factor and the blood-retinal barrier and increase the antioxidant defence system. However, further experiments and clinical trials are required to establish the daily doses of DPNPs that will safely and effectively prevent age-related eye diseases.

NEI-Supported Age-Related Macular Degeneration Research: Past, Present, and Future

Purpose

To review past and current National Eye Institute (NEI)–supported age-related macular degeneration (AMD) activities and initiatives and preview upcoming coordinated efforts for studying AMD.

Methods

We conducted and summarized a portfolio analysis and literature review of NEI intramural and extramural AMD activities.

Results

The NEI supports a broad range of AMD research, both by individual independent investigators as well as through networks and consortia. The International AMD Genomics Consortium, Age-Related Eye Disease Study, Age-Related Eye Disease Study 2 (AREDS2), and Comparison of AMD Treatments Trial legacy work probed the complex genetics, clinical presentation, and standards of patient care, respectively. The NEI AMD Pathobiology Working Group identified gaps and opportunities for future research efforts. The AMD Ryan Initiative Study and clinical trials testing the efficacies of minocycline to modulate retinal microglia activity and induced pluripotent stem cells–derived retinal pigmented epithelium (RPE) patch implants to rescue photoreceptor cell death are among the future directions for NEI-supported AMD research. Finally, NEI commissioned the creation of AREDS2 participant-derived induced pluripotent stem cell (iPSC) lines linked to their associated genomic and phenotypic datasets. These datasets will also be linked to the data obtained using their associated iPSC-derived cells (RPE, retina, choroid) and made publicly available.

Conclusions

Investments by NEI for AMD research will continue to provide invaluable resources to investigators committed to addressing this complex blinding disease and other retinal degenerative diseases.

Translational Relevance

NEI now stands poised to expand the resources available to clinical investigators to uncover disease mechanisms and move experimental therapies into clinical trials.

New frontiers and clinical implications in the pathophysiology of age-related macular degeneration

Age-related macular degeneration (AMD) involves progressive degeneration of the central retina, termed the macula, which provides high-acuity vision needed to recognize faces, drive, etc. AMD is the leading cause of blindness in the aging population. A plethora of paradigm-shifting perspectives regarding AMD's multifaceted pathophysiology is emerging. This review will endeavor to gather novel insights and attempts to identify translational implications and new areas of research. The concept of aberrant inflammation being at the center of age-related diseases, particularly AMD, is being received with increasing credence. Retinal angiogenesis, at the forefront of the neovascular complications of AMD (nAMD), is now being understood as an imbalance between trophic factors released by retinal cells secretome. Additionally, mechanisms involving oxidative stress and inflammatory complement pathways have also been identified, along with genetic and other risk factors that play a key role in AMD's onset and progression. Associations have been drawn with AMD and other degenerative deposit diseases such as Alzheimer's disease, atherosclerosis, and glomerulonephritis, which are providing further insight into this maculopathy.

Loss of Complement Factor H impairs antioxidant capacity and energy metabolism of human RPE cells

Polymorphisms in the Complement Factor H (CFH) gene, coding for the Factor H protein (FH), can increase the risk for age-related macular degeneration (AMD). AMD-associated CFH risk variants, Y402H in particular, impair FH function leading to complement overactivation. Whether this alone suffices to trigger AMD pathogenesis remains unclear. In AMD, retinal homeostasis is compromised due to the dysfunction of retinal pigment epithelium (RPE) cells. To investigate the impact of endogenous FH loss on RPE cell balance, we silenced CFH in human hTERT-RPE1 cells. FH reduction led to accumulation of C3, at both RNA and protein level and increased RPE vulnerability toward oxidative stress. Mild hydrogen-peroxide exposure in combination with CFH knock-down led to a reduction of glycolysis and mitochondrial respiration, paralleled by an increase in lipid peroxidation, which is a key aspect of AMD pathogenesis. In parallel, cell viability was decreased. The perturbations of energy metabolism were accompanied by transcriptional deregulation of several glucose metabolism genes as well as genes modulating mitochondrial stability. Our data suggest that endogenously produced FH contributes to transcriptional and metabolic homeostasis and protects RPE cells from oxidative stress, highlighting a novel role of FH in AMD pathogenesis.

Employing Nanostructured Scaffolds to Investigate the Mechanical Properties of Adult Mammalian Retinae Under Tension

Numerous eye diseases are linked to biomechanical dysfunction of the retina. However, the underlying forces are almost impossible to quantify experimentally. Here, we show how biomechanical properties of adult neuronal tissues such as porcine retinae can be investigated under tension in a home-built tissue stretcher composed of nanostructured TiO₂ scaffolds coupled to a self-designed force sensor. The employed TiO₂ nanotube scaffolds allow for organotypic long-term preservation of adult tissues ex vivo and support strong tissue adhesion without the application of glues, a prerequisite for tissue investigations under tension. In combination with finite element calculations we found that the deformation behavior is highly dependent on the displacement rate which results in Young’s moduli of (760–1270) Pa. Image analysis revealed that the elastic regime is characterized by a reversible shear deformation of retinal layers. For larger deformations, tissue destruction and sliding of retinal layers occurred with an equilibration between slip and stick at the interface of ruptured layers, resulting in a constant force during stretching. Since our study demonstrates how porcine eyes collected from slaughterhouses can be employed for ex vivo experiments, our study also offers new perspectives to investigate tissue biomechanics without excessive animal experiments.

Development of a therapeutic anti-HtrA1 antibody and the identification of DKK3 as a pharmacodynamic biomarker in geographic atrophy

Genetic polymorphisms in the region of the trimeric serine hydrolase high-temperature requirement 1 (HTRA1) are associated with increased risk of age-related macular degeneration (AMD) and disease progression, but the precise biological function of HtrA1 in the eye and its contribution to disease etiologies remain undefined. In this study, we have developed an HtrA1-blocking Fab fragment to test the therapeutic hypothesis that HtrA1 protease activity is involved in the progression of AMD. Next, we generated an activity-based small-molecule probe (ABP) to track target engagement in vivo. In addition, we used N-terminomic proteomic profiling in preclinical models to elucidate the in vivo repertoire of HtrA1-specific substrates, and identified substrates that can serve as robust pharmacodynamic biomarkers of HtrA1 activity. One of these HtrA1 substrates, Dickkopf-related protein 3 (DKK3), was successfully used as a biomarker to demonstrate the inhibition of HtrA1 activity in patients with AMD who were treated with the HtrA1-blocking Fab fragment. This pharmacodynamic biomarker provides important information on HtrA1 activity and pharmacological inhibition within the ocular compartment.

Melatonin protects the retina from experimental nonexudative age-related macular degeneration in mice

Nonexudative age-related macular degeneration (NE-AMD) represents the leading cause of blindness in the elderly. Currently, there are no available treatments for NE-AMD. We have developed a NE-AMD model induced by superior cervical ganglionectomy (SCGx) in C57BL/6J mice, which reproduces the disease hallmarks. Several lines of evidence strongly support the involvement of oxidative stress in NE-AMD-induced retinal pigment epithelium (RPE) and outer retina damage. Melatonin is a proven and safe antioxidant. Our aim was analysing the effect of melatonin in the RPE/outer retina damage within experimental NE-AMD. The treatment with melatonin starting 48 h after SCGx, which had no effect on the ubiquitous choriocapillaris widening, protected visual functions and avoided Bruch´s membrane thickening, RPE melanin content, melanosome number loss, retinoid isomerohydrolase (RPE65)-immunoreactivity decrease, and RPE and hotoreceptor ultrastructural damage induced within experimental NE-AMD exclusively located at the central temporal (but not nasal) region. Melatonin also prevented the increase in outer retina/RPE oxidative stress markers and a decrease in mitochondrial mass at 6 weeks post-SCGx. Moreover, when the treatment with melatonin started at 4 weeks post-SCGx, it restored visual functions and reversed the decrease in RPE melanin content and RPE65-immunoreactivity. These findings suggest that melatonin could become a promising safe therapeutic strategy for NE-AMD.

Metabolomic Profiling of the Aqueous Humor in Patients with Wet Age-Related Macular Degeneration Using UHPLC-MS/MS

Assessing metabolomic alterations in age-related macular degeneration (AMD) can provide insights into its pathogenesis. We compared the metabolomic profiles of the aqueous humor between wet AMD patients (n = 26) and age- and sex-matched patients undergoing cataract surgery without AMD as controls (n = 20). A global untargeted metabolomics study was performed using ultra-high-performance liquid chromatography tandem mass spectrometry. Univariate analysis after the false discovery correction showed 18 significantly altered metabolites among the 291 metabolites measured. These differential metabolomic profiles pointed to three interconnected metabolic pathways: a compromised carnitine-associated mitochondrial oxidation pathway (carnitine, deoxycarnitine, N6-trimethyl-l-lysine), an altered carbohydrate metabolism pathway (cis-aconitic acid, itaconatic acid, and mesaconic acid), which plays a role in senescence and immunity, and an activated osmoprotection pathway (glycine betaine, creatine), which potentially contributes to the pathogenesis of the disease. These results suggested that metabolic dysfunction in AMD is mitochondrial-centered and may provide new insights into the pathophysiology of wet AMD and novel therapeutic strategies.

Up-regulation of pro-angiogenic pathways and induction of neovascularization by an acute retinal light damage

The light damage (LD) model was mainly used to study some of the main aspects of age related macular degeneration (AMD), such as oxidative stress and photoreceptor death. Several protocols of light-induced retinal degeneration exist. Acute light damage is characterized by a brief exposure (24 hours) to high intensity light (1000 lux) and leads to focal degeneration of the retina which progresses over time. To date there are not experimental data that relate this model to neovascular events. Therefore, the purpose of this study was to characterize the retina after an acute light damage to assess whether the vascularization was affected. Functional, molecular and morphological investigations were carried out. The electroretinographic response was assessed at all recovery times (7, 60, 120 days after LD). Starting from 7 days after light damage there was a significant decrease in the functional response, which remained low up to 120 days of recovery. At 7 days after light exposure, neo-vessels invaded the photoreceptor layer and retinal neovascularization occurred. Remarkably, neoangiogenesis was associated to the up-regulation of VEGF, bFGF and their respective receptors (VEGFR2 and FGFR1) with the progression of degeneration. These important results indicate that a brief exposure to bright light induces the up-regulation of pro-angiogenic pathways with subsequent neovascularization.

Suppressive Effect of Arctium Lappa L. Leaves on Retinal Damage Against A2E-Induced ARPE-19 Cells and Mice

Age-related macular degeneration (AMD) is a major cause of irreversible loss of vision with 80–90% of patients demonstrating dry type AMD. Dry AMD could possibly be prevented by polyphenol-rich medicinal foods by the inhibition of N-retinylidene-N-retinylethanolamine (A2E)-induced oxidative stress and cell damage. Arctium lappa L. (AL) leaves are medicinal and have antioxidant activity. The purpose of this study was to elucidate the protective effects of the extract of AL leaves (ALE) on dry AMD models, including in vitro A2E-induced damage in ARPE-19 cells, a human retinal pigment epithelial cell line, and in vivo light-induced retinal damage in BALB/c mice. According to the total phenolic contents (TPCs), total flavonoid contents (TFCs) and antioxidant activities, ALE was rich in polyphenols and had antioxidant efficacies on 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and 2′,7′-dichlorofluorescin diacetate (DCFDA) assays. The effects of ALE on A2E accumulation and A2E-induced cell death were also monitored. Despite continued exposure to A2E (10 μM), ALE attenuated A2E accumulation in APRE-19 cells with levels similar to lutein. A2E-induced cell death at high concentration (25 μM) was also suppressed by ALE by inhibiting the apoptotic signaling pathway. Furthermore, ALE could protect the outer nuclear layer (ONL) in the retina from light-induced AMD in BALB/c mice. In conclusion, ALE could be considered a potentially valuable medicinal food for dry AMD.

Glucose Metabolic Characterization of Human Aqueous Humor in Relation to Wet Age-Related Macular Degeneration

Purpose

Energy compromise underpins wet age-related macular degeneration (wAMD) pathogenesis, but the relationship between glucose metabolism and the disease remains unclear. Here, we characterized aqueous humor (AH) to elucidate glucose-related metabolic signatures in patients with wAMD.

Methods

In total, 25 eyes of 25 patients with wAMD were divided into phakic (15 eyes), pseudophakic (10 eyes), and intravitreal injections of ranibizumab (13 eyes) wAMD groups. Twenty patients with cataract (21 eyes) served as controls. Ultrahigh-performance liquid chromatography tandem mass spectrometry was used to quantitatively characterize AH.

Results

Twenty-one metabolites related to glucose metabolism were identified in AH from 45 patients. Tricarboxylic acid (TCA)-related metabolic substrates, including citrate, were detected in AH and were significantly increased in AMD (P < 0.01) and AMD pseudophakic groups (P < 0.05). In contrast, α-ketoglutarate levels were decreased in the AMD group (P < 0.05). The α-ketoglutarate/citrate ratio was significantly decreased, corresponding to 71.71% and 93.6% decreases in the AMD (phakic and pseudophakic) groups as compared with controls (P < 0.001), revealing a significant positive correlation with glutamine. A lower mean glutamine and higher glutamate level were detected in AMD cases compared with controls. No significant differences were observed for lactic acid or other Krebs cycle metabolites. Intravitreal injection significantly alleviated mean central foveal thickness but did not significantly alter metabolites.

Conclusions

Compromised glucose TCA cycle and altered glutamine metabolism are implicated in the AH metabolism in wAMD. These findings highlight potential treatments for alleviating wAMD from a metabolic perspective.

Pirfenidone ameliorates the formation of choroidal neovascularization in mice

The formation and development of choroidal neovascularization (CNV) is accompanied by inflammation and fibrosis. Existing treatments are expensive and can cause irreversible complications. Pirfenidone (PFD) exerts anti‑inflammatory and anti‑fibrotic effects; however, its applications in the eye remain unclear. Male C57BL/6J mice (aged 6‑8 weeks) were used to explore whether PFD can inhibit the formation of laser‑induced CNV. The localization of transforming growth factor β2 (TGFβ2) was determined through immunofluorescent staining. After laser photocoagulation, the vehicle and PFD groups were intravitreally injected with 1 µl PBS and 1 µl 0.5% PFD, respectively. At day 7 after intravitreal injection, the expression of TGFβ2 and vascular endothelial growth factor (VEGF) was assessed. Fundus fluorescein angiography was performed to investigate the extent of fluorescence leakage, and the CNV areas were analyzed using a choroidal flat mount. The results demonstrated that, on day 7 after photocoagulation, the expression of TGFβ2 and VEGF was reduced in the experimental group. In addition, fluorescein angiography showed that the leakage area of CNV was significantly smaller in the PFD injection group than those observed in the control and vehicle groups. Moreover, the areas of CNV in the PFD injection group were smaller compared with those reported in the other two injection groups. Histopathological and TUNEL analyses performed on day 28 revealed that there were no notable abnormalities on the layers of the neural retina of PFD‑treated mice. In conclusion, intravitreal injection of PFD inhibited the formation of CNV in mice, likely via the downregulation of VEGF and TGFβ2, which did not cause damage to the mouse retina after 28 days of treatment.

The Nrf2 activator MIND4-17 protects retinal ganglion cells from high glucose-induced oxidative injury

Diabetic retinopathy (DR) is a leading cause of acquired blindness among adults. High glucose (HG) induces oxidative injury and apoptosis in retinal ganglion cells (RGCs), serving as a primary pathological mechanism of DR. MIND4-17 activates nuclear-factor-E2-related factor 2 (Nrf2) signaling via modifying one cysteine (C151) residue of Kelch-like ECH-associated protein 1 (Keap1). The current study tested its effect in HG-treated primary murine RGCs. We show that MIND4-17 disrupted Keap1-Nrf2 association, leading to Nrf2 protein stabilization and nuclear translocation, causing subsequent expression of key Nrf2 target genes, including heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1. Functional studies showed that MIND4-17 pretreatment significantly inhibited HG-induced cytotoxicity and apoptosis in primary murine RGCs. Reactive oxygen species production and oxidative injury in HG-treated murine RGCs were attenuated by MIND4-17. Nrf2 silencing (by targeted small interfering RNA) or knockout (by CRISPR/Cas9 method) abolished MIND4-17-induced RGC cytoprotection against HG. Additionally, Keap1 knockout or silencing mimicked and abolished MIND4-17-induced activity in RGCs. In vivo, MIND4-17 intravitreal injection activated Nrf2 signaling and attenuated retinal dysfunction by light damage in mice. We conclude that MIND4-17 activates Nrf2 signaling to protect murine RGCs from HG-induced oxidative injury.

Different conbercept injection strategies for the treatment of exudative age-related macular degeneration: A retrospective cohort study

Conbercept is a novel anti-vascular endothelial growth factor for the treatment of age-related macular degeneration (AMD). The most optimal injection strategy is unknown. To assess the effectiveness of intravitreal injection of conbercept using the 3 + pro re nata (PRN) and 3 + Q3 M strategies for the treatment of exudative AMD.From January 2015 to January 2018, patients confirmed with exudative AMD at Qilu Hospital of Shandong University were included in this retrospective study. Intravitreal injection of 0.5 mg of conbercept was conducted either with the 3 + PRN or 3 + Q3 M strategy. Best-corrected visual acuity (BCVA), intraocular pressure, and optical coherence tomography were conducted at 1 and 2 weeks, then every month. fundus fluorescein angiography examination was conducted every 3 months.There were 106 eyes from 106 patients. The number of follow-ups (3 + Q3 M: 12.4 ± 1.3 vs 3 + PRN: 12.9 ± 1.6, P = .079) and the follow-up time (3 + Q3 M: 12.7 ± 0.6 vs 3 + PRN: 12.5 ± 0.7 months, P = .121) were similar in the 2 groups. The number of injections was less in 3 + PRN than 3 + Q3 M (5.3 ± 1.0 vs 6.0 ± 0.0, P < .001) The BCVA at months 7 and 9 to 12 in the 3 + Q3 M (n = 51) group were lower than for 3 + PRN (n = 55) (all P < .05). The CRT at months 9 to 12 in the 3 + Q3 M group was lower than in the 3 + PRN group (all P < .05). There were no differences between the 2 groups regarding the exudation area during follow-up. No serious treatment-related ocular complications or serious systemic adverse events were found.The 3 + PRN and 3 + Q3 M strategies of intravitreal injection of conbercept are effective in treating exudative AMD. The 3 + Q3 M strategy needs more injection but is more effective in increasing visual acuity and reducing macular CRT than the 3 + PRN strategy.

LINC00167 Regulates RPE Differentiation by Targeting the miR-203a-3p/SOCS3 Axis

Increasing evidence has indicated that long non-coding RNAs (lncRNAs) play significant roles in various diseases; however, their roles in age-related macular degeneration (AMD) remain unclear. Dedifferentiation and dysfunction of retinal pigment epithelium (RPE) cells have been shown to contribute to AMD etiology in several studies. Herein, we found that lncRNA LINC00167 was downregulated in RPE-choroid samples of AMD patients and dysfunctional RPE cells, and it was consistently upregulated along with RPE differentiation. In vitro study indicated that reduced endogenous LINC00167 expression resulted in RPE dedifferentiation, which was typified by attenuated expression of RPE markers, reduced vascular endothelial growth factor A secretion, accumulation of mitochondrial reactive oxygen species, and interrupted phagocytic ability. Mechanistically, LINC00167 functioned as a sponge for microRNA miR-203a-3p to restore the expression of the suppressor of cytokine signaling 3 (SOCS3), which further inhibited the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway. Taken together, our study demonstrated that LINC00167 showed a protective role in AMD by maintaining RPE differentiation through the LINC00167/miR-203a-3p/SOCS3 axis and might be a potential therapeutic target for AMD.

All-trans-retinal induces autophagic cell death via oxidative stress and the endoplasmic reticulum stress pathway in human retinal pigment epithelial cells

Failure of all-trans-retinal (atRAL) clearance contributes to retina degeneration. However, whether autophagy can be activated by excess atRAL accumulation in retinal pigment epithelial (RPE) cells is not known. This study showed that atRAL provoked mitochondria-associated reactive oxygen species (ROS) production, activated the nuclear factor (erythroid-derived 2)-like 2 and apoptosis in a human RPE cell line, ARPE-19 cells. Moreover, we found that autophagic flux was functionally activated after atRAL treatment. The antioxidant N-acetylcysteine attenuated the expression of autophagy markers, suggesting that ROS triggered atRAL-activated autophagy. In addition, autophagic cell death was observed in atRAL-treated RPE cells, while inhibition of autophagy with 3-methyladenine or LC3, Beclin1, p62 silencing ameliorated atRAL-induced cytotoxicity. Suppression of autophagy quenched mitochondrial ROS and inhibited HO-1 and γ-GCSh expression, indicating that atRAL-activated autophagy enhances intracellular oxidative stress, thereby promoting RPE cell apoptosis. Furthermore, we found that inhibiting endoplasmic reticulum (ER) stress suppressed atRAL-induced mitochondrial ROS generation, subsequently attenuated autophagy and apoptosis in RPE cells. Taken together, these results suggest that atRAL-induced oxidative stress and ER stress modulate autophagy, which may contribute to RPE degeneration. There may be positive feedback regulatory mechanisms between atRAL-induced oxidative stress and autophagy or ER stress.

Effects of lutein supplementation in age-related macular degeneration

The purpose of this meta-analysis was to evaluate the effects of lutein supplementation on macular pigment optical density (MPOD) in randomized controlled trials involving patients with age-related macular degeneration (AMD). A comprehensive search of the literature was performed in PubMed, Cochrane Library, Web of Science, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, and Wan Fang database through December 2018. Nine randomized controlled trials involving 920 eyes (855 with AMD) were included. Meta-analysis suggested that lutein supplementation (10 or 20 mg per day) was associated with an increase in MPOD (mean difference (MD) 0.07; 95% confidence interval (CI) 0.03 to 0.10), visual acuity (MD 0.28; 95%CI 0.06 to 0.50) and contrast sensitivity (MD 0.26; 95%CI 0.22 to 0.30). Stratified analyses showed the increase in MPOD to be faster and greater with higher dose and longer treatment. The available evidence suggests that dietary lutein may be beneficial to AMD patients and the higher dose could make MPOD increase in a shorter time.

Microarray expression profile and functional analysis of circular RNAs in choroidal neovascularization

Choroidal neovascularization (CNV) is a leading cause of visual loss in age-related macular degeneration (AMD). However, the molecular mechanism for CNV progression is still unclear. This study aimed to identify CNV-related circular RNAs (circRNAs), a novel class of non-coding RNAs with diverse functions. A total of 117 circRNAs were differentially expressed in the murine CNV model by microarrays. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to identify the functions of selected circRNAs. The host genes of these circRNAs were predicted to be targeted to neurogenesis (ontology: biological process), proteinaceous extracellular matrix (ECM) (ontology: cellular component), and binding (ontology: molecular function). Differentially expressed circRNAs-mediated regulatory networks were enriched in ECM receptor interaction. Most of the dysregulated circRNAs could potentially bind to five different miRNAs by TargetScan and miRanda. Specifically, circ_15752 was identified in this circRNAs pool which may facilitate vascular endothelial cell proliferation, migration, and tube formation, suggesting a critical role in endothelial angiogenesis. Our work suggests that dysregulated circRNAs may be involved in CNV pathogenesis and serve as potential biomarkers for CNV.

All-trans-retinoic acid generation is an antidotal clearance pathway for all-trans-retinal in the retina

The present study was designed to analyze the metabolites of all-trans-retinal (atRal) and compare the cytotoxicity of atRal versus its derivative all-trans-retinoic acid (atRA) in human retinal pigment epithelial (RPE) cells. We confirmed that atRA was produced in normal pig neural retina and RPE. The amount of all-trans-retinol (atROL) converted from atRal was about 2.7 times that of atRal-derived atRA after incubating RPE cells with 10 μmol/L atRal for 24 h, whereas atRA in medium supernatant is more plentiful (91 vs. 29 pmol/mL), suggesting that atRA conversion facilitates elimination of excess atRal in the retina. Moreover, we found that mRNA expression of retinoic acid-specific hydroxylase CYP26b1 was dose-dependently up-regulated by atRal exposure in RPE cells, indicating that atRA inactivation may be also initiated in atRal-accumulated RPE cells. Our data show that atRA-caused viability inhibition was evidently reduced compared with the equal concentration of its precursor atRal. Excess accumulation of atRal provoked intracellular reactive oxygen species (ROS) overproduction, heme oxygenase-1 (HO-1) expression, and increased cleaved poly(ADP-ribose) polymerase 1 (PARP1) expression in RPE cells. In contrast, comparable dosage of atRA-induced oxidative stress was much weaker, and it could not activate apoptosis in RPE cells. These results suggest that atRA generation is an antidotal metabolism pathway for atRal in the retina. Moreover, we found that in the eyes of ABCA4^-/-RDH8^-/- mice, a mouse model with atRal accumulation in the retina, the atRA content was almost the same as that in the wild type. It is possible that atRal accumulation simultaneously and equally promotes atRA synthesis and clearance in eyes of ABCA4^-/-RDH8^-/- mice, thus inhibiting the further increase of atRA in the retina. Our present study provides further insights into atRal clearance in the retina.

Undertreatment of Neovascular Age-Related Macular Degeneration after 10 Years of Anti-Vascular Endothelial Growth Factor Therapy in the Real World: The Need for A Change of Mindset

PURPOSE

To assess the gap between visual acuity (VA) outcomes with anti-vascular endothelial growth factor (anti-VEGF) therapies in clinical trials and real-world practice, and explore the reasons for this gap.

METHODS

The literature was searched from January 1, 2013, to June 30, 2018, for studies reporting VA gains and injection frequencies in clinical trials and real-world practice.

RESULTS

Clinical trials of anti-VEGF agents and their extension studies demonstrated initial VA gains maintained at 4 years and beyond (up to 7 years) with continuous proactive treatment. Visual outcomes correlated with injection frequency. In real-world practice, patients are usually undertreated, accounting for the VA decline over time. Reasons for undertreatment include the burden of injections and monitoring visits imposed on patients/caregivers. However, another primary reason is the general mindset in the ophthalmological community that sustained benefits with treatment are not possible, leading to poor compliance and creating a vicious circle.

CONCLUSIONS

Initial VA gains can be maintained with more intensive/proactive approaches. Promising new treatments requiring less frequent injections/monitoring will help in the near future; meanwhile, better results could be achieved by changing the community mindset that contributes to undertreatment.

Targeting Keap1 by miR-626 protects retinal pigment epithelium cells from oxidative injury by activating Nrf2 signaling

Activation of the NF-E2-related factor 2 (Nrf2) cascade can offer significant protection against oxidative stress in retinal pigment epithelium (RPE) cells. Here, we identified a novel kelch-like ECH-associated protein 1 (Keap1)-targeting microRNA, microRNA-626 (miR-626) that activates Nrf2 signaling. In ARPE-19 cells and primary human RPE cells, ectopic overexpression of miR-626 targeting the 3'-UTR (3'-untranslated region) of Keap1 downregulated its expression, promoting Nrf2 protein stabilization and nuclear translocation, leading to expression of ARE-dependent genes (HO1, NOQ1 and GCLC). Functional studies showed that miR-626 protected RPE cells from hydrogen peroxide (H₂O₂)-induced oxidative injury. Conversely, miR-626 inhibition induced Keap1 upregulation and Nrf2 cascade inhibition, exacerbating oxidative injury in RPE cells. Further studies demonstrated that miR-626 was ineffective in Keap1-knockout or Nrf2-knockout RPE cells. Importantly, miR-626 also activated Keap1-Nrf2 signaling cascade in human lens epithelial cells (HLECs) and primary human retinal ganglion cells (RGCs), providing protection from H₂O₂. At last, we show that plasma miR-626 levels are significantly downregulated in age-related macular degeneration (AMD) patients than those in the healthy donors. We conclude that targeting Keap1 by miR-626 protects RPE cells and other ophthalmic cells from oxidative injury via activation of Nrf2 signaling cascade.

MicroRNA-24 protects retina from degeneration in rats by down-regulating chitinase-3-like protein 1

MicroRNAs (miRNAs) have been shown to play critical roles in the pathogenesis and progression of degenerative retinal diseases like age-related macular degeneration (AMD). In this study, we first demonstrated that miR-24 plays an important role in maintaining retinal structure and visual function of rats by targeting chitinase-3-like protein 1 (CHI3L1). In the retinal pigment epithelial (RPE) cells of Royal College of Surgeons (RCS) rats, an animal model of genetic retinal degeneration (RD), miR-24 was found lower and CHI3L1 level was higher in comparison with those in Sprague-Dawley (SD) rats. Other changes in the eyes of RCS rats include activated AKT/mTOR and ERK pathways and abnormal autophagy in the RPE cells. Such roles of miR-24 and CHI3L1 were further confirmed in RCS rats by subretinal injection of agomiR-24, which decreased CHI3L1 level and preserved retinal structure and function. Upstream, NF-κB was identified as the regulator of miR-24 in the RPE cells of these rats. On the other hand, in SD rats, intraocular treatment of antagomiR-24 induced pathological changes similar to those in RCS rats. The results revealed the protective roles for miR-24 to RPE cells and a mechanism for RD in RCS rats was proposed: extracellular stress stimuli first activate the NF-κB signaling pathway, which lowers miR-24 expression so that CHI3L1 increased. CHI3L1 sequentially results in aberrant autophagy and RPE dysfunction by activating AKT/mTOR and ERK pathways. Taken together, although the possibility, that the therapeutic effects in RCS rats are caused by other transcriptional changes regulated by miR-24, cannot be excluded, these findings indicate that miR-24 protects rat retina by targeting CHI3L1. Thus, miR-24 and CHI3L1 might be the targets for developing more effective therapy for degenerative retinal diseases like AMD.

Evaluation of retinal function improvement in neovascular age-related macular degeneration after intravitreal aflibercept injections with the use of the assessment of retinal sensitivity: The use of the assessment of retinal sensitivity in anti-VEGF treatment - a STROBE-compliant observational study

This study compares 2 methods of macular function evaluation: the microperimetric examination (mean central retinal sensitivity and fixation stability) and the distance best-corrected visual acuity (BCVA) examination, which is the most frequently used method of assessing macular function in patients with newly diagnosed wet age-related macular degeneration (AMD) who have been treated with anti-vascular endothelial growth factor (VEGF) drug (aflibercept).Prospective analysis was conducted on 44 eyes of 44 patients treated with intravitreal injection of anti-VEGF (aflibercept) because of newly diagnosed neovascular AMD. According to the research protocol, all patients had a 6-month follow-up. The response to treatment was monitored functionallybyMP-1 microperimetry, fixation, and distance BCVA assessment after injection. Improvement of retinal sensitivity and BCVA was found under aflibercept treatment. There was statistically significant improvement in retinal sensitivity in the MP-1 study 3 and 6 months from the beginning of anti-VEGF therapy. Moreover, a significant improvement in retinal sensitivity between 3 and 6 months of observation was demonstrated. At the same time, up to 3 months from the beginning of treatment, BCVA improved significantly compared to the baseline value. In the 6th month of the study BCVA remained stable without further significant improvement.Microperimetric examination with medium sensitivity and fixation stability assessment is a very valuable test determining the retinal function. It is clear that examining the macular morphology itself in modern diagnostics is not enough to assess retinal function. Microperimetry technique is a valuable tool for functional long-term evaluation of retinal function (also for a period of more than 3 months).

Systemic expression of Alu RNA in patients with geographic atrophy secondary to age-related macular degeneration

Geographic atrophy (GA) secondary to age-related macular degeneration (AMD) is characterized by irreversible loss of macular retinal tissue and retinal pigment epithelium (RPE) cells. Several studies have revealed that accumulation of Alu RNA in RPE cell causes RPE cell degeneration in AMD. In the present study, systemic Alu RNA expression levels were determined in 33 subjects with GA and 40 control subjects using a proprietary Alu RNA quantification method. It was observed that the expression level of Alu RNA was not significantly different between GA and Control groups (median = 21.3 in both GA and Control groups, P = 0.251). In addition, the systemic level of Alu RNA was not associated with subject characteristics, such as GA lesion size and SNP profiles of complement factors associated with increased risk of AMD. In conclusion, the usability of systemic Alu RNA expression level as a biomarker of GA secondary to AMD could not be established in this study.

Diagnostic accuracy of optical coherence tomography angiography for choroidal neovascularization: a systematic review and meta-analysis

BACKGROUND

Optical coherence tomography angiography (OCTA), an innovative image technique, renders visualization of ocular neovascularization through non-invasive means, which has been applied in recent years. Therefore, the present study was designed to assess the diagnostic value of OCTA in detecting the choroidal neovascularization (CNV).

METHODS

In brief, PubMed, Web of Science and Cochrane Library databases were systematically searched from January 2014 to June 2019. Afterwards, a meta-analysis was performed to determine the pooled diagnostic accuracy in a random-effects model using STATA 15.1 and Meta-Disc 1.4 software. Quality Assessment of diagnostic Accuracy Version 2 was used to evaluate the risk of bias of each study by Revman 5.3 software. In addition, a meta-regression model was further conducted to explore potential sources of heterogeneity.

RESULTS

According to pre-set inclusion and exclusion criteria, 16 eligible studies were enrolled in this study. A total of 447 CNV eyes and 414 non-CNV eyes were included to investigate the diagnostic accuracy of OCTA. As a result, the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (PLR), diagnostic odds ratio (DOR) and the area under the summary receiver operating characteristic curve (sROC-AUC) were 0.87 (95% CI 0.81-0.92), 0.97 (95% CI 0.92-0.99), 32.7 (95% CI 10.1-105.5), 0.13 (95% CI 0.08-0.20), 252 (95% CI 63-1011) and 0.96 (95% CI 0.94-0.97), respectively.

CONCLUSIONS

In summary, we demonstrated that OCTA was of high diagnostic value for detecting intraocular CNV.

AAV2/8 Anti-angiogenic Gene Therapy Using Single-Chain Antibodies Inhibits Murine Choroidal Neovascularization

While anti-angiogenic therapies for wet age-related macular degeneration (AMD) are effective for many patients, they require multiple injections and are expensive and prone to complications. Gene therapy could be an elegant solution for this problem by providing a long-term source of anti-angiogenic proteins after a single administration. Another potential issue with current therapeutic proteins containing a fragment crystallizable (Fc) domain (such as whole antibodies like bevacizumab) is the induction of an unwanted immune response. In wet AMD, a low level of inflammation is already present, so to avoid exacerbation of disease by the therapeutic protein, we propose single-chain fragment variable (scFv) antibodies, which lack the Fc domain, as a safer alternative. To investigate the feasibility of this, anti-vascular endothelial growth factor (VEGF)-blocking antibodies in two formats were produced and tested in vitro and in vivo. The scFv transgene was then cloned into an adeno-associated virus (AAV) vector. A therapeutic effect in a mouse model of choroidal neovascularization (CNV) was demonstrated with antibodies in both scFv and immunoglobulin G1 (IgG1) formats (p < 0.04). Importantly, the scFv anti-VEGF antibody expressed from an AAV vector also had a significant beneficial effect (p = 0.02), providing valuable preclinical data for future translation to the clinic.

Targeting cullin 3 by miR-601 activates Nrf2 signaling to protect retinal pigment epithelium cells from hydrogen peroxide

Activation of Nrf2 cascade can protect retinal pigment epithelium (RPE) cells from hydrogen peroxide (H₂O₂) and other oxidative injury. The current study identified microRNA-601 (miR-601) as a novel cullin 3 (Cul3)-targeting miRNA that activates Nrf2 cascade. In ARPE-19 cells and primary human RPE cells, forced overexpression of miR-601 significantly inhibited Cul3 3'-UTR activity and downregulated Cul3 mRNA/protein expression, leading to Nrf2 protein stabilization and its nuclear translocation as well as expression of anti-oxidant response elements (ARE)-dependent genes (HO1, NQO1 and GCLC). H₂O₂ treatment increased miR-601 levels in RPE cells. Significantly, ectopic miR-601 overexpression attenuated H₂O₂-induced oxidative injury and apoptosis in RPE cells. In contrast, miR-601 inhibition promoted Cul3 expression, lowered basal Nrf2 activation, and enhanced H₂O₂-induced oxidative stress and apoptosis in RPE cells. In ARPE-19 cells, CRISPC/Cas9-mediated knockout (KO) of Cul3 or Keap1 not only mimicked, but also nullified, miR-601-inudced anti-H₂O₂ actions. Furthermore, Nrf2 silencing by targeted shRNAs abolished miR-601-inudced cytoprotection in H₂O₂-treated ARPE-19 cells. Taken together, we show that miR-601 activates Nrf2 signaling to protect RPE cells from H₂O₂ by targeting Cul3.

Responses of Types 1 and 2 Neovascularization in Age-Related Macular Degeneration to Anti-Vascular Endothelial Growth Factor Treatment: Optical Coherence Tomography Angiography Analysis

Purpose: To compare the responses of types 1 (sub-pigment epithelial) and 2 (subretinal) neovascularization in neovascular age-related macular degeneration (AMD) to anti-vascular endothelial growth factor (VEGF) treatment. Methods: Fifty-five treatment-naïve neovascular AMD eyes (53 patients) were retrospectively included for analysis. All patients were treated with three loading injections of anti-VEGF agent, followed by further injections as required. The lesion size and vascular density of type 1 and 2 lesions before and after treatment for 12 months were analyzed using optical coherence tomography angiography (OCTA). Results: The mean lesion size of the type 1 neovascularization group (42 eyes) showed no significant change from 2.12 ± 1.01 mm² at baseline to 2.08 ± 0.91 mm² at 12 months (P = .682). However, the mean lesion size of type 2 neovascularization significantly decreased from 1.23 ± 0.93 mm² at baseline to 0.79 ± 0.61 mm² at 12 months (P = .022). The proportion of eyes with lesion sizes that decreased by more than 40% from baseline was also significantly higher for the type 2 compared to the type 1 neovascularization group (46.2% versus 11.9%, P = .007). Vascular density showed no significant changes for both groups after treatment and showed no association with the change in lesion size. There was no significant difference between the groups in terms of visual acuity improvement. Conclusion: OCTA analysis revealed different responses to anti-VEGF treatment depending on the location of neovascularization in neovascular AMD. Type 2 neovascularization was significantly regressed compared to type 1 neovascularization after anti-VEGF treatment. However, the changes in vascular density and visual outcome showed no significant differences between groups after 12 months of treatment.

Cyanidin-3-glucoside attenuates 4-hydroxynonenal- and visible light-induced retinal damage in vitro and in vivo

4-Hydroxynonenal (HNE) is a highly reactive end-product of lipid peroxidation reaction that leads to retinal pigment epithelial (RPE) cell damage. Cyanidin-3-glucoside (C3G), the most abundant anthocyanin in the edible parts of plants, is a nutritional supplement used for preventing retinal damage. However, the protective effect of C3G against HNE-induced RPE cell damage remains to be elucidated. The protective mechanisms of C3G on ARPE-19 cells after HNE exposure were investigated in this study. Results showed that compared with HNE-treated cells, the viability of ARPE-19 cells was significantly (P < 0.05) increased after 1 and 5 μM C3G treatment. C3G exhibited a significant (P < 0.05) inhibitory effect on the expression of senescence-associated β-galactosidase in ARPE-19 cells. VEGF levels in the C3G groups were significantly (P < 0.05) decreased relative to those of the HNE-treated group. C3G also regulated the release of two inflammatory mediators, namely monocyte chemoattractant protein 1 and interleukine-8, in ARPE-19 cells after HNE treatment. Furthermore, C3G attenuated retinal cell apoptosis in pigmented rabbits induced by visible light. Therefore, our data showed that C3G has efficient protective effects on HNE-induced apoptosis, angiogenesis, and dysregulated cytokine production in ARPE-19 cells.

microRNA-4532 inhibition protects human lens epithelial cells from ultra-violet-induced oxidative injury via activating SIRT6-Nrf2 signaling

Ultra-violet radiation (UVR) can induce significant oxidative injury to human lens epithelial cells (HLECs). Sirtuin 6 (SIRT6) is shown to directly bind to Nrf2, essential for Nrf2 signaling activation. In the present study, we show that microRNA-4532 (miR-4532) targets SIRT6 to regulate Nrf2 signaling in HLECs. Ectopic overexpression of miR-4532 in HLECs decreased SIRT6 3'-UTR activity, causing SIRT6 downregulation and Nrf2 signaling inhibition. Conversely, miR-4532 inhibition, by a lentiviral construct, enhanced SIRT6 3'-UTR activity, SIRT6 expression and Nrf2 signaling activation. Functional studies show that UVR-induced cytotoxicity and apoptosis in HLECs were potentiated by miR-4532 overexpression, Nrf2 depletion or SIRT6 shRNA. Conversely, miR-4532 inhibition or ectopic SIRT6 overexpression attenuated UVR-induced oxidative injury in HLECs. Importantly, miR-4532 overexpression or inhibition was ineffective in SIRT6-KO or Nrf2-KO HLECs. Taken together, the results show that inhibition of miR-4532 protects HLECs from UVR-induced oxidative injury via activation of SIRT6-Nrf2 pathway. Targeting the miR-4532-SIRT6-Nrf2 pathway could be a novel strategy to protect HLECs from UVR and possible other oxidative stresses.

ERBB2-modulated ATG4B and autophagic cell death in human ARPE19 during oxidative stress

Age-related macular degeneration (AMD) is an ocular disease with retinal degeneration. Retinal pigment epithelium (RPE) degeneration is mainly caused by long-term oxidative stress. Kinase activity could be either protective or detrimental to cells during oxidative stress; however, few reports have described the role of kinases in oxidative stress. In this study, high-throughput screening of kinome siRNA library revealed that erb-b2 receptor tyrosine-protein kinase 2 (ERBB2) knockdown reduced reactive oxygen species (ROS) production in ARPE-19 cells during oxidative stress. Silencing ERBB2 caused an elevation in microtubule associated protein light chain C3-II (MAP1LC3B-II/I) conversion and sequesterone (SQSTM)1 protein level. ERBB2 deprivation largely caused an increase in autophagy-regulating protease (ATG4B) expression, a protease that negatively recycles MAP1LC3-II at the fusion step between the autophagosome and lysosome, suggesting ERBB2 might modulate ATG4B for autophagy induction in oxidative stress-stimulated ARPE-19 cells. ERBB2 knockdown also caused an accumulation of nuclear factor erythroid 2-related factor 2 (NRF2) and enhanced its transcriptional activity. In addition, ERBB2 ablation or treatment with autophagy inhibitors reduced oxidative-induced cytotoxic effects in ARPE-19 cells. Furthermore, ERBB2 silencing had little or no additive effects in ATG5/7-deficient cells. Taken together, our results suggest that ERBB2 may play an important role in modulating autophagic RPE cell death during oxidative stress, and ERBB2 may be a potential target in AMD prevention.

Immunohistochemical localization of NGF, BDNF, and their receptors in a normal and AMD-like rat retina

BACKGROUND

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries, and the molecular pathogenesis of AMD is poorly understood. A large body of evidence has corroborated the key role of neurotrophins in development, proliferation, differentiation, and survival of retinal cells. Neurotrophin deprivation has been proposed to contribute to retinal-cell death associated with neurodegenerative diseases. Little is known about the expression of the immature form of neurotrophins (proneurotrophins) and their mature form [e.g., nerve growth factor (proNGF and mNGF) and brain-derived neurotrophic factor (proBDNF and mBDNF)] in the retina during physiological aging and against the background of AMD. In addition, cell-specific localization of proteins NGF and BDNF in the retina during AMD development is not clear. Here, we evaluated contributions of the age-related alterations in the neurotrophin system to the development of AMD-like retinopathy in OXYS rats.

METHODS

Male OXYS rats at preclinical (20 days), early (3 months), and late (18 months) stages of the disease and age-matched male Wistar rats (as controls) were used. We performed immunohistochemical localization of NGF, BDNF, and their receptors TrkA, TrkB, and p75NTR by fluorescence microscopy in retinal sections from OXYS and Wistar rats.

RESULTS

We found increased NGF staining in Muller cells in 18-month-old OXYS rats (progressive stage of retinopathy). In contrast, we observed only subtle changes in the labeling of mature BDNF (mBDNF) and TrkB during the development of AMD-like retinopathy in OXYS rats. Using colocalization with vimentin and NeuN, we detected a difference in the cell type-specific localization of mBDNF between OXYS and Wistar rats. We showed that the mBDNF protein was located in Muller cells in OXYS rats, whereas in the Wistar retina, mBDNF immunoreactivity was detected in Muller cells and ganglion cells. During the development of AMD-like retinopathy, proBDNF dominated over mBDNF during increasing cell loss in the OXYS retina.

CONCLUSIONS

These data indicate that alterations in the balance of neurotrophic factors in the retina are involved in the development of AMD-like retinopathy in OXYS rats and confirm their participation in the pathogenesis of AMD in humans.

Biomechanical Properties of Bruch's Membrane-Choroid Complex and Their Influence on Optic Nerve Head Biomechanics

Purpose

The purpose of this study was to measure the rupture pressure and the biomechanical properties of porcine Bruch's membrane (BM)-choroid complex (BMCC) and the influences of BM on optic nerve head (ONH) tissues.

Methods

The biomechanical properties of BMCC were extracted through uniaxial tensile tests of 10 BMCC specimens from 10 porcine eyes; the rupture pressures of BMCC were measured through burst tests of 20 porcine eyes; and the influence of BM on IOP-induced ONH deformations were investigated using finite element (FE) analysis.

Results

Uniaxial experimental results showed that the average elastic (tangent) moduli of BMCC samples at 0% and 5% strain were 1.60 ± 0.81 and 2.44 ± 1.02 MPa, respectively. Burst tests showed that, on average, BMCC could sustain an IOP of 82 mm Hg before rupture. FE simulation results predicted that, under elevated IOP, prelamina tissue strains increased with increasing BM stiffness. On the contrary, lamina cribrosa strains showed an opposite trend but the effects were small.

Conclusions

BMCC stiffness is comparable or higher than those of other ocular tissues and can sustain a relatively high pressure before rupture. Additionally, BM may have a nonnegligible influence on IOP-induced ONH deformations.

Activator of G-protein signaling 8 is involved in VEGF-induced choroidal neovascularization

Choroidal neovascularization (CNV) is associated with age-related macular degeneration (AMD), a major cause of vision loss among elderly people. Vascular endothelial cell growth factor (VEGF) is essential for the development and progression of AMD, and VEGF signaling molecules are effective targets for the treatment of AMD. We recently reported that activator of G-protein signaling 8 (AGS8), a receptor-independent Gβγ regulator, is involved in VEGF-induced angiogenesis in cultured endothelial cells (EC); however, the role of AGS8 in CNV is not yet understood. This study aimed to explore the role of AGS8 in CNV in cultured cells, explanted choroid tissue, and laser-induced CNV in a mouse AMD model. AGS8 knockdown in cultured choroidal EC inhibited VEGF-induced VEGFR-2 phosphorylation, cell proliferation, and migration. AGS8 knockdown also downregulated cell sprouting from mouse choroidal tissue in ex vivo culture. A mouse model of laser-induced CNV, created to analyze the roles of AGS8 in vivo, demonstrated that AGS8 mRNA was significantly upregulated in choroidal lesions and AGS8 was specifically expressed in the neovasculature. Local AGS8 knockdown in intravitreal tissue significantly inhibited laser-induced AGS8 upregulation and suppressed CNV, suggesting that AGS8 knockdown in the choroid has therapeutic potential for AMD. Together, these results demonstrate that AGS8 plays critical roles in VEGF-induced CNV.

The association between blood vitamins D and E with age-related macular degeneration: A pilot study

Background

This study was aimed to evaluate the association of serum vitamins D and E level with age-related macular degeneration (AMD).

Methods

This pilot study was performed in two groups of 15 patients in treatment group and 15 patients in control group. Measurements of blood factors [such as C-reactive protein (CRP) and high-density lipoprotein (HDL)] were performed after 12 h of fasting. To measure vitamins D and E, the serum was isolated from 5 cc blood samples.

Results

HDL was higher in the control group as compared with the AMD group. However, no significant difference was found between the two groups (p = 0.08). On the other hand, serum vitamin E in the AMD group was remarkably higher as compared to the control group (p < 0.002). However, no significant difference was found in serum vitamin D levels between the two groups (p = 0.662). Our findings also revealed that there was no statistically significant relationship between BMI and AMD. Moreover, no significant correlation was determined between serum CRP and AMD (p = 0.96).

Conclusions

Our data indicated that none provides evidence for associations between AMD and serum vitamin D levels. The association between vitamin D and AMD requires further investigations in a large population studies, to elucidate whether vitamin D deficiency can be an important risk factor for AMD.

Oxidative stress damage circumscribed to the central temporal retinal pigment epithelium in early experimental non-exudative age-related macular degeneration

Non-exudative age-related macular degeneration (NE-AMD) represents the leading cause of blindness in the elderly. The macular retinal pigment epithelium (RPE) lies in a high oxidative environment because its high metabolic demand, mitochondria concentration, reactive oxygen species levels, and macular blood flow. It has been suggested that oxidative stress-induced damage to the RPE plays a key role in NE-AMD pathogenesis. The fact that the disease limits to the macular region raises the question as to why this area is particularly susceptible. We have developed a NE-AMD model induced by superior cervical ganglionectomy (SCGx) in C57BL/6J mice, which reproduces the disease hallmarks exclusively circumscribed to the temporal region of the RPE/outer retina. The aim of this work was analyzing RPE regional differences that could explain AMD localized susceptibility. Lower melanin content, thicker basal infoldings, higher mitochondrial mass, and higher levels of antioxidant enzymes, were found in the temporal RPE compared with the nasal region. Moreover, SCGx induced a decrease in the antioxidant system, and in mitochondria mass, as well as an increase in mitochondria superoxide, lipid peroxidation products, nuclear Nrf2 and heme oxygenase-1 levels, and in the occurrence of damaged mitochondria exclusively at the temporal RPE. These findings suggest that despite the well-known differences between the human and mouse retina, it might not be NE-AMD pathophysiology which conditions the localization of the disease, but the macular RPE histologic and metabolic specific attributes that make it more susceptible to choroid alterations leading initially to a localized RPE dysfunction/damage, and secondarily to macular degeneration.

Conbercept for Treatment of Neovascular Age-related Macular Degeneration: Results of the Randomized Phase 3 PHOENIX Study

PURPOSE

Age-related macular degeneration (AMD) can cause irreversible vision loss leading to blindness. We aim to evaluate the efficacy and safety of intravitreal injections of 0.5 mg conbercept, a new anti-vascular endothelial growth factor (anti-VEGF) drug, for treatment of AMD on a schedule more manageable for patients.

DESIGN

A prospective, double-masked, multicenter, sham-controlled, phase III randomized trial.

METHODS

Patients: Patients with choroidal neovascularization (CNV) secondary to AMD were enrolled and randomized to the conbercept group or the sham control group.

INTERVENTION

The conbercept group received intravitreal injections of conbercept (0.5 mg) once monthly for the first 3 months, then once quarterly until month 12 (3 + Q3M). The sham group received first 3 monthly sham injections and then 3 monthly injections of conbercept (0.5 mg) followed by quarterly administrations until month 12.

MAIN OUTCOME MEASURES

The primary endpoint was mean change from baseline in best-corrected visual acuity (BCVA) at month 3.

RESULTS

A total of 114 patients (91.9%) from 9 sites in China completed the 12-month study. At the 3-month primary endpoint, the mean changes in BCVA from baseline were +9.20 letters in the conbercept group and +2.02 letters in the sham group, respectively (P < .001). At 12 months, the mean changes from baseline in BCVA letter score were +9.98 letters in the conbercept group and +8.81 letters in the sham group (P = .64). The most common ocular adverse events were associated with intravitreal injections, such as conjunctival hemorrhage, and increased intraocular pressure.

CONCLUSIONS

A conbercept dosing regimen of 3 initial monthly administrations followed by quarterly treatments is effective for treatment of AMD. In previous reports, other anti-VEGF agents were unable to maintain similar clinical benefits with the same regimen.

GEP100/ARF6 regulates VEGFR2 signaling to facilitate high-glucose-induced epithelial-mesenchymal transition and cell permeability in retinal pigment epithelial cells

Cell permeability and epithelial-mesenchymal transition (EMT) were found to be enhanced in diabetic retinopathy, and the aim of this study was to investigate the underlying mechanism. ARPE-19 cell line or primary retinal pigment epithelial (RPE) cells were cultured under high or normal glucose conditions. Specific shRNAs were employed to knock down ADP-ribosylation factor 6 (ARF6), GEP100, or VEGF receptor 2 (VEGFR2) in ARPE-19 or primary RPE cells. Cell migration ability was measured using Transwell assay. Western blotting was used to measure indicated protein levels. RPE cells treated with high glucose showed increased cell migration, paracellular permeability, EMT, and expression of VEGF. Knockdown of VEGFR2 inhibited the high-glucose-induced effects on RPE cells via inactivation of ARF6 and MAPK pathways. Knockdown ARF6 or GEP100 led to inhibition of high-glucose-induced effects via inactivation of VEGFR2 pathway. Knockdown of ARF6, but not GEP100, decreased high-glucose-induced internalization of VEGFR2. High-glucose enhances EMT and cell permeability of RPE cells through activation of VEGFR2 and ARF6/GEP100 pathways, which form a positive feedback loop to maximize the activation of VEGF/VEGFR2 signaling.

Strategies for modifying drug residence time and ocular bioavailability to decrease treatment frequency for back of the eye diseases

INTRODUCTION

Treating posterior eye diseases has become a major area of focus for pharmaceutical and biotechnology companies. Current standard of care for treating posterior eye diseases relies on administration via intravitreal injection. Although effective, this is not without complications and there is great incentive to develop longer-acting therapeutics and/or sustained release delivery systems. Here, we present an overview of emerging technologies for delivery of biologics to the back of the eye.

AREAS COVERED

Posterior eye diseases, intravitreal injection, age-related macular degeneration, anti-VEGF, ocular pharmacokinetics, novel technologies to extend half-life, in vivo models, translation to the clinic, and hurdles to effective patient care.

EXPERT OPINION

Posterior eye diseases are a worldwide public health issue. Although anti-VEGF molecules represent a major advance for treating diseases involving choroidal neovascularization, frequent injection can be burdensome for patients and clinicians. There is a need for effective and patient-friendly treatments for posterior eye diseases. Many technologies that enable long-acting delivery to the back of the eye are being evaluated. However, successful development of novel therapies and delivery technologies is hampered by a multitude of factors, including patient education, translatability of in vitro/in vivo preclinical data to the clinic, and regulatory challenges associated with novel technologies.

PP2A inhibition by LB-100 protects retinal pigment epithelium cells from UV radiation via activation of AMPK signaling

AMP-activated protein kinase (AMPK) signaling activation can inhibit Ultra-violet (UV) radiation (UVR)-induced retinal pigment epithelium (RPE) cell injuries. LB-100 is a novel inhibitor of protein phosphatase 2A (PP2A), the AMPKα1 phosphatase. Here, our results demonstrated that LB-100 significantly inhibited UVR-induced viability reduction, cell death and apoptosis in established ARPE-19 cells and primary murine RPE cells. LB-100 activated AMPK, nicotinamide adenine dinucleotide phosphate (NADPH) and Nrf2 (NF-E2-related factor 2) signalings, inhibiting UVR-induced oxidative injuries and DNA damage in RPE cells. Conversely, AMPK inhibition, by AMPKα1-shRNA, -CRISPR/Cas9 knockout or -T172A mutation, almost blocked LB-100-induced RPE cytoprotection against UVR. Importantly, CRISPR/Cas9-mediated PP2A knockout mimicked and nullified LB-100-induced anti-UVR activity in RPE cells. Collectively, these results show that PP2A inhibition by LB-100 protects RPE cells from UVR via activation of AMPK signaling.