Introduction to the multi-author review on macular degeneration

The impact of NF-κB on inflammatory and angiogenic processes in age-related macular degeneration

Age-related macular degeneration (AMD) is a prominent cause of vision loss, characterized by two different types, dry (atrophic) and wet (neovascular). Dry AMD is distinguished by the progressive deterioration of retinal cells, which ultimately causes a decline in vision. In contrast, wet AMD is defined by the abnormal development of blood vessels underneath the retina, leading to a sudden and severe vision impairment. The course of AMD is primarily driven by chronic inflammation and pathological angiogenesis, in which the NF-κB signaling pathway plays a crucial role. The activation of NF-κB results in the generation of pro-inflammatory cytokines, chemokines, and angiogenic factors like VEGF, which contribute to inflammation and the formation of new blood vessels in AMD. This review analyzes the intricate relationship between NF-κB signaling, inflammation, and angiogenesis in AMD and assesses the possibility of using NF-κB as a target for therapy. The evaluation involves a comprehensive examination of preclinical and clinical evidence that substantiates the effectiveness of NF-κB inhibitors in treating AMD by diminishing inflammation and pathological angiogenesis.

Rationale, Design and Methodology of a Population-Based Ocular Study in a Suburbanization Region in Tianjin, China: The Beichen Eye Study

PURPOSE

The urbanization of suburbs has a significant impact on ocular health, however, the effect of this phenomenon on the epidemiology of eye diseases in the sub-urbanization region of China remains unclear. In this context, the population-based Beichen Eye Study (BCES) was conducted in the Beichen District of Tianjin, China. This article aims to summarize the background, design scheme and operation process of the study. The Chinese Clinical Trial Registry number was ChiCTR2000032280.

METHODS

In total, 8218 participants were randomly selected by a multi-stage sampling method. After their qualification was confirmed, participants were mainly invited to a centralized clinic via telephone interviews after promotion of the study in the community. Examinations included a standardized interview, anthropometric assessment, autorefraction, ocular biometry, visual acuity, anterior and posterior segment examinations, dry eye disease (DED), intra-ocular pressure, visual field testing, gonioscopy, and imaging of anterior segment, posterior segment, fundus, and optic disc. A peripheral venous blood sample was also collected for biochemical testing. For observational purposes, a community-based type II diabetes mellitus management mode was created and assessed for its effect in preventing the progression of diabetic retinopathy (DR).

RESULTS

Of the 8,218 residents, 7,271 were eligible for inclusion, and 5,840 (80.32%) subjects were enrolled in the BCES. Most of the participants were female (64.38%) with a median age of 63 years, and 98.23% representing Han Chinese descent. Conclusions: This study provides insights into the epidemiological characteristics of major ocular diseases and their moderators in a suburbanized region of China.

Recent advances of exosomes in age-related macular degeneration

Exosomes are 30-150 nm extracellular vesicles that are secreted by almost all types of cells. Exosomes contain a variety of biologically active substances, such as proteins, nucleic acids, and lipids, and are important in the intercellular communication of biological mediators involved in nerve injury and repair, vascular regeneration, immune response, fibrosis formation, and many other pathophysiological processes. Although it has been extensively studied in the field of cancer, the exploration of ocular diseases has only just begun. Here, we discuss the latest developments in exosomes for age-related macular degeneration (AMD), including the pathogenesis of exosomes in age-related macular degeneration, their potential as diagnostic markers, and therapeutic vectors of the disease. Finally, the study of exosomes in age-related macular degeneration is still relatively few, and more detailed basic research and clinical trials are needed to verify its application in treatment and diagnosis, so as to adopt more personalized diagnosis and treatment strategies to stop the progression of age-related macular degeneration.

Matrix Metalloproteinase 10 Contributes to Choroidal Neovascularisation

Age-related macular degeneration (AMD) is currently the main cause of severe visual loss among older adults in developed countries. The pathophysiology has not been clarified, but oxidative stress is believed to play a major role. Matrix metalloproteinases (MMP) may play a prominent role in several steps of the pathophysiology of AMD, especially in its neovascular form; therefore, there is of great interest in understanding their role in choroidal neovascularisation. This study aimed to elucidate the role of MMP10 in the development of choroidal neovascularisation (CNV). We have demonstrated that MMP10 was expressed by retinal pigment epithelium cells and endothelial cells of the neovascular membrane, in cell culture, mouse and human retina. MMP10 expression and activity increased under oxidative stress conditions in ARPE-19 cells. MMP10-/- mice developed smaller laser-induced areas of CNV. Furthermore, to exclude a systemic MMP10 imbalance in these patients, plasma MMP10 concentrations were assessed in an age- and sex-matched sample of 52 control patients and 52 patients with neovascular AMD and no significant differences were found between the groups, demonstrating that MMP10 induction is a local phenomenon. Our findings suggest that MMP10 participates in the development of choroidal neovascularisation and promotes MMP10 as a possible new therapeutic target.

Real-life results in treating neovascular age-related macular degeneration with anti-VEGF therapy. Analysis of 122 patients from a single centre

BACKGROUND

The prognosis of age-related macular degeneration (AMD) has improved significantly since the advent of antiangiogenic treatments. However, several «real life» studies have shown lower number of injections and a markedly worse visual prognosis than pivotal clinical trials.

OBJECTIVE

To assess the effectiveness and safety of the treatment of neovascular AMD and analyse clinical factors related to the functional and structural prognosis in routine clinical practice.

MATERIAL AND METHODS

Retrospective, observational, single-centre study that included 143 eyes of 122 patients diagnosed with neovascular AMD between the years 2015 and 2016, who received treatment with antiangiogenic drugs and were followed up for two or more years.

RESULTS

Visual acuity improved in 45% of patients after two years of treatment. The mean decrease in central macular thickness was 85 μm (p < 0.001) and the mean number of injections was 13. Retinal pigment epithelium rupture was present in 3.5%. Ranibizumab was the drug most used as a first option, although 79 patients (55.2%) required a change in treatment, most being switched to aflibercept. A greater number of visits (p < 0.001) and a lower number of injections (p < 0.01) were predictors of worse structural outcome. The number of visits was associated with better visual acuity (p < 0.001).

CONCLUSIONS

The treatment has demonstrated its efficacy by improving visual acuity and central macular thickness. However, the number of injections performed has generally been higher than in other real-life studies.

Decorin Protects Retinal Pigment Epithelium Cells from Oxidative Stress and Apoptosis via AMPK-mTOR-Regulated Autophagy

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss among the elderly worldwide with unidentified pathogenesis and limited therapeutic options. Oxidative stress-induced damage to the retinal pigment epithelium (RPE) is central in the development and progression of AMD. Decorin (DCN), a small leucine-rich proteoglycan, possesses powerful antifibrotic, anti-inflammatory, and antiangiogenic properties. DCN has also been reported to serve a cytoprotective role in various cell types, but its protective effects against H₂O₂-induced oxidative stress and apoptosis in ARPE-19 cells remain unclear. In this study, we showed that DCN significantly attenuated the increase in cell viability loss, apoptosis rate, and reactive oxygen species (ROS) levels in ARPE-19 cells induced by H₂O₂. Furthermore, DCN activated the AMPK/mTOR pathway to promote autophagy while genetic inhibition of autophagy-related gene 5 (ATG5) hindered autophagic process and diminished the protective role of DCN against oxidative stress in ARPE-19 cells. Collectively, these results suggest that DCN could protect RPE cells from H₂O₂-induced oxidative stress and apoptosis via autophagy promotion, thus providing the therapeutic potential for AMD prevention and treatment.

The interplay of autophagy and oxidative stress in the pathogenesis and therapy of retinal degenerative diseases

Oxidative stress is mainly caused by intracellular reactive oxygen species (ROS) production, which is highly associated with normal physiological homeostasis and the pathogenesis of diseases, particularly ocular diseases. Autophagy is a self-clearance pathway that removes oxidized cellular components and regulates cellular ROS levels. ROS can modulate autophagy activity through transcriptional and posttranslational mechanisms. Autophagy further triggers transcription factor activation and degrades impaired organelles and proteins to eliminate excessive ROS in cells. Thus, autophagy may play an antioxidant role in protecting ocular cells from oxidative stress. Nevertheless, excessive autophagy may cause autophagic cell death. In this review, we summarize the mechanisms of interaction between ROS and autophagy and their roles in the pathogenesis of several ocular diseases, including glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and optic nerve atrophy, which are major causes of blindness. The autophagy modulators used to treat ocular diseases are further discussed. The findings of the studies reviewed here might shed light on the development and use of autophagy modulators for the future treatment of ocular diseases.

The Evaluation of oxidative stress, 3-nitrotyrosine, and HMGB-1 levels in patients with Wet Type Age-Related Macular Degeneration

Background

This study aims to compare serum HMGB-1, 3-nitrotyrosine (3-NT), TAS, TOS, and OSI levels in Wettype Age-Related Macular Degeneration (wAMD) patients and healthy controls to determine the correlation of these parameters with each other.

Methods

Thirty patients with Wet-type Age-Related Macular Degeneration (wAMD) and 27 healthy adults, as controls were enrolled in the study. We determined the TAS and TOS levels in serum samples of both groups using commercial kits on a microplate reader. Serum HMGB-1 and 3-NT levels were measured with the enzyme-linked immunosorbent assay method.

Results

HMGB-1 levels were significantly higher in the patient group (137.51 pg/mL, p=0.001), while there was no difference between the two groups in serum 3-NT levels (p=0.428). A statistically significant difference found in the levels of TOS and OSI (p=0.001 and p=0.045, respectively) between the patients and controls, however, no significant difference was observed between the groups in terms of TAS levels (p=0.228).

Conclusions

Oxidative stress and HMGB-1 levels were increased in wAMD patients and enhanced oxidative stress may be associated with increased tissue necrosis and inflammation. Thus administration of antioxidant treatment in addition to routine therapy should be considered in wAMD.

Differential Expression of Inflammasome-Related Genes in Induced Pluripotent Stem-Cell-Derived Retinal Pigment Epithelial Cells with or without History of Age-Related Macular Degeneration

Inflammation is a key underlying factor of age-related macular degeneration (AMD) and inflammasome activation has been linked to disease development. Induced pluripotent stem-cell-derived retinal pigment epithelial cells (iPSC-RPE) are an attractive novel model system that can help to further elucidate disease pathways of this complex disease. Here, we analyzed the effect of dysfunctional protein clearance on inflammation and inflammasome activation in iPSC-RPE cells generated from a patient suffering from age-related macular degeneration (AMD) and an age-matched control. We primed iPSC-RPE cells with IL-1α and then inhibited both proteasomal degradation and autophagic clearance using MG-132 and bafilomycin A1, respectively, causing inflammasome activation. Subsequently, we determined cell viability, analyzed the expression levels of inflammasome-related genes using a PCR array, and measured the levels of pro-inflammatory cytokines IL-1β, IL-6, IL-8, and MCP-1 secreted into the medium. Cell treatments modified the expression of 48 inflammasome-related genes and increased the secretion of mature IL-1β, while reducing the levels of IL-6 and MCP-1. Interestingly, iPSC-RPE from an AMD donor secreted more IL-1β and expressed more Hsp90 prior to the inhibition of protein clearance, while MCP-1 and IL-6 were reduced at both protein and mRNA levels. Overall, our results suggest that cellular clearance mechanisms might already be dysfunctional, and the inflammasome activated, in cells with a disease origin.

The polyp regression rate and treatment prognosis of different interventions for polypoidal choroidal vasculopathy: a systematic review and meta-analysis

PURPOSE

To estimate the polyp regression rate and treatment prognosis of different interventions for polypoidal choroidal vasculopathy (PCV) and clarify its baseline characteristics.

METHODS

The PubMed, EMBASE, and Ovid were searched up to January 2020 to identify related studies. R software version 3.6.3 was used to perform the statistical analyses. Results in proportion with 95% confidence interval (CI) were calculated by means of the Freeman-Tukey variant of arcsine square transformation. Chi-squared test and I² statistics were used to evaluate the statistical heterogeneity. Sensitivity analysis and subgroup analyses were performed to identify the source of heterogeneity.

RESULTS

This meta-analysis included 104 studies with 5816 patients. The pooling results indicated the general rate of complete polyp regression at post-treatment 12 months was 64% (95% CI [57~71%]), 89% (95% CI [81~95%]) for photodynamic therapy (PDT) monotherapy, 78% (95% CI [68~86%]) for PDT plus anti-vascular endothelial growth factor (anti-VEGF), and 42% (95% CI [35~49%]) for anti-VEGF monotherapy; PDT plus anti-VEGF showed the best efficacy in visual improvement and achieved the highest rate of dry macula (91%, 95% CI [78~99%]), while anti-VEGF monotherapy achieved the lowest polyp recurrence rate (14%, 95% CI [8~20%]); PDT monotherapy showed the best efficacy in pigment epithelial detachment regression (66%, 95% CI [58~83%]). Additionally, the baseline characteristics of PCV were also well described.

CONCLUSION

PDT plus anti-VEGF is still valuable for the management of PCV; it could achieve not only satisfactory anatomical outcomes like dry macula rate and polyp regression rate but also ideal visual prognosis like BCVA improvement.

Metformin Protects ARPE-19 Cells from Glyoxal-Induced Oxidative Stress

The protective effects and mechanisms of metformin against oxidative stress were evaluated both in vivo and in vitro. ARPE-19 cells comprised the normal group, the glyoxal-treated group (0.5 mM glyoxal), and the glyoxal+metformin group (0.5 mM glyoxal and 0.1 mM metformin). In the in vitro model, differences in cell viability, ROS production, NO products, cellular apoptosis, and the expressions of phospho-AMPKα, total-AMPKα, Sirt1, Nrf2, TXNIP, ZO-1, and Occludin were assessed. In the glyoxal-treated group, cell viability and NO production were decreased, while ROS production and cell apoptosis were increased (p < 0.05), compared with the control group. These changes were prevented by metformin treatment. Protein expressions of phospho-AMPKα, Sirt1, TXNIP, ZO-1, and Occludin, but not Nrf2, were decreased significantly in the glyoxal-treated group compared to normal controls. Metformin treatment significantly increased the above protein expressions and slightly increased TXNIP expression. Immunofluorescence showed that metformin prevented the glyoxal-induced, disorganized tight junctions in ARPE-19 cells. To confirm metformin's protection, Sprague-Dawley rats were injected intravenously with sodium iodate (SI) to induce oxidative stress in the retinal pigment epithelium (RPE). Metformin was then delivered intraperitoneally or intravitreally. One day and three days after SI and metformin treatments, the RPE-Bruch's membrane-choriocapillaris complex was isolated and immune-stained with ZO-1 antibodies. The morphology of the RPE showed enlarged cellular bodies and disorganized ZO-1 staining in SI-treated rats. Metformin treatment prevented these changes. The results indicated that metformin maintained the barrier functions of RPE cells both in vivo and in vitro. Metformin exerted its protection against oxidative stress possibly via activating AMPK/Sirt1 and increasing TXNIP. Metformin has been proposed as a candidate drug for age-related macular degeneration (AMD) by both preclinical and clinical studies. The cellular and animal models used in this study might be useful for the interpretation of the molecular mechanisms involved in the drug activity.