Oxidation and age-related macular degeneration: insights from molecular biology. Expert Rev Mol Med. 2010;12:e34. [PMID: 20959033 DOI: 10.1017/s146239941000164x]

Antioxidants and Mechanistic Insights for Managing Dry Age-Related Macular Degeneration

Age-related macular degeneration (AMD) severely affects central vision due to progressive macular degeneration and its staggering prevalence is rising globally, especially in the elderly population above 55 years. Increased oxidative stress with aging is considered an important contributor to AMD pathogenesis despite multifaceted risk factors including genetic predisposition and environmental agents. Wet AMD can be managed with routine intra-vitreal injection of angiogenesis inhibitors, but no satisfactory medicine has been approved for the successful management of the dry form. The toxic carbonyls due to photo-oxidative degradation of accumulated bisretinoids within lysosomes initiate a series of events including protein adduct formation, impaired autophagy flux, complement activation, and chronic inflammation, which is implicated in dry AMD. Therapy based on antioxidants has been extensively studied for its promising effect in reducing the impact of oxidative stress. This paper reviews the dry AMD pathogenesis, delineates the effectiveness of dietary and nutrition supplements in clinical studies, and explores pre-clinical studies of antioxidant molecules, extracts, and formulations with their mechanistic insights.

Understanding the Impact of the Sirtuin 1 (SIRT1) Gene on Age-related Macular Degeneration: A Comprehensive Study

Age-related macular degeneration (AMD) is a prevalent and incurable condition affecting the central retina and posing a significant risk to vision, particularly in individuals over the age of 60. As the global population ages, the prevalence of AMD is expected to rise, leading to substantial socioeconomic impacts and increased healthcare costs. The disease manifests primarily in two forms, neovascular and non-neovascular, with genetic, environmental and lifestyle factors playing a pivotal role in disease susceptibility and progression. This review article involved conducting an extensive search across various databases, including Google Scholar, PubMed, Web of Science, ScienceDirect, Scopus and EMBASE, to compile relevant case-control studies and literature reviews from online published articles extracted using search terms related to the work. SIRT1, a key member of the sirtuin family, influences cellular processes such as ageing, metabolism, DNA repair and stress response. Its dysregulation is linked to retinal ageing and ocular conditions like AMD. This review discusses the role of SIRT1 in AMD pathology, its association with genetic variants and its potential as a biomarker, paving the way for targeted interventions and personalised treatment strategies. In addition, it highlights the findings of case-control studies investigating the relationship between SIRT1 gene polymorphisms and AMD risk. These studies collectively revealed a significant association between certain SIRT1 gene variants and AMD risk. Further studies with larger sample sizes are required to validate these findings. As the prevalence of AMD grows, understanding the role of SIRT1 and other biomarkers becomes increasingly vital for improving diagnosis, treatment and, ultimately, patient outcomes.

Natural compounds efficacy in Ophthalmic Diseases: A new twist impacting ferroptosis

Ferroptosis, a distinct form of cell death, is characterized by the iron-mediated oxidation of lipids and is finely controlled by multiple cellular metabolic pathways. These pathways encompass redox balance, iron regulation, mitochondrial function, as well as amino acid, lipid, and sugar metabolism. Additionally, various disease-related signaling pathways also play a role in the regulation of ferroptosis. In recent years, with the introduction of the concept of ferroptosis and the deepening of research on its mechanism, ferroptosis is closely related to various biological conditions of eye diseases, including eye organ development, aging, immunity, and cancer. This article reviews the development of the concept of ferroptosis, the mechanism of ferroptosis, and its latest research progress in ophthalmic diseases and reviews the research on ferroptosis in ocular diseases within the framework of metabolism, active oxygen biology, and iron biology. Key regulators and mechanisms of ferroptosis in ocular diseases introduce important concepts and major open questions in the field of ferroptosis and related natural compounds. It is hoped that in future research, further breakthroughs will be made in the regulation mechanism of ferroptosis and the use of ferroptosis to promote the treatment of eye diseases. At the same time, natural compounds may be the direction of new drug development for the potential treatment of ferroptosis in the future. Open up a new way for clinical ophthalmologists to research and prevent diseases.

A narrative review on dietary components and patterns and age-related macular degeneration

Age-related macular degeneration (AMD) is one of the most prevalent eye diseases among the ageing population worldwide. It is a leading cause of blindness in individuals over 55, particularly in industrialised Western countries. The prevalence of AMD increases with age, and genetic factors and environmental influences are believed to contribute to its development. Among the environmental factors, diet plays a significant role in AMD. This review explores the association between dietary components, dietary patterns and AMD. Various nutrients, non-nutrient substances and dietary models that have the potential to counteract oxidative stress and inflammation, which are underlying mechanisms of AMD, are discussed. Consuming fruits, vegetables, fish and seafood, whole grains, olive oil, nuts and low-glycaemic-index foods has been highlighted as beneficial for reducing the risk of AMD. Adhering to the Mediterranean diet, which encompasses these elements, can be recommended as a dietary pattern for AMD. Furthermore, the modulation of the gut microbiota through dietary interventions and probiotics has shown promise in managing AMD.

Smoking, dietary factors and major age-related eye disorders: an umbrella review of systematic reviews and meta-analyses

BACKGROUND

There is accumulating evidence of the associations between age-related eye diseases (AREDs) and smoking or dietary factors. We aimed to provide an umbrella review of the published literature pertaining to smoking or dietary intake as risk factors for major AREDs including cataract, glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy.

METHODS

We searched for pertinent systematic reviews or meta-analyses in PubMed and Web of Science until 16 April 2022. We reperformed the meta-analysis of each association using random effects models. The heterogeneity and 95% prediction interval were calculated. The presence of small-study effect or excess significance bias was also assessed.

RESULTS

In total, 64 associations from 25 meta-analyses and 41 associations from 10 qualitative systematic reviews were evaluated. There was convincing (class I) evidence for only one association, namely current smoking and cataract. Two factors had highly suggestive (class II) evidence, namely ever smoking associated with cataract and fish consumption associated with AMD. We also found suggestive (class III) evidence for associations between the dietary intake of omega-3 polyunsaturated fatty acid, lutein, zeaxanthin, vitamin C and the risk of cataract.

CONCLUSIONS

Smoking as a risk factor for cataract was the most robust association we identified. We also identified several dietary elements associated with AREDs. Large prospective studies are warranted to further examine the associations discussed in this review.

PROSPERO REGISTRATION NUMBER

CRD42022339082.

Epidemiology of geographic atrophy and its precursor features of intermediate age-related macular degeneration

Globally age-related macular degeneration (AMD) is a leading cause of blindness with a significant impact on quality of life. Geographic atrophy (GA) is the atrophic late form of AMD and its prevalence increases markedly with age with around 1 in 5 persons aged 85 and above having GA in at least one eye. Bilateral GA leads to severe visual impairment thus posing a significant burden on patients, careers and health providers. The incidence and prevalence of GA varies across different geographic regions, with the highest rates in those of European ancestry. Although heterogeneity in definitions of GA and reporting strategy can explain some of the discrepancies, the data overall are consistent in showing a lower prevalence in other ethnicities such as those of Asian heritage. This is at present unexplained but thought to be due to the existence of protective factors such as differences in eye pigmentation, diet, environmental exposures and genetic variability. This review covers key aspects of the prevalence and incidence of the ocular precursor features of GA (large drusen, pigmentary abnormalities and reticular pseudo-drusen), the late stage of GA and factors that have been known to be associated with modifying risk including systemic, demographic, environment, genetic and ocular. Understanding the global epidemiology scenario is crucial for the prevention of and management of patients with GA.

Mechanistic Insight into Age-Related Macular Degeneration (AMD): Anatomy, Epidemiology, Genetics, Pathogenesis, Prevention, Implications, and Treatment Strategies to Pace AMD Management

One of the most complicated eye disorders is age-related macular degeneration (AMD) which is the leading cause of irremediable blindness all over the world in the elderly. AMD is classified as early stage to late stage (advanced AMD), in which this stage is divided into the exudative or neovascular form (wet AMD) and the nonexudative or atrophic form (dry AMD). Clinically, AMD primarily influences the central area of retina known as the macula. Importantly, the wet form is generally associated with more severe vision loss. AMD has a systemic component, where many factors, like aging, genetic, environment, autoimmune and non-autoimmune disorders are associated with this disease. Additionally, healthy lifestyles, regular exercise, maintaining a normal lipid profile and weight are crucial to decreasing the risk of AMD. Furthermore, therapeutic strategies for limiting AMD should encompass a variety of factors to avoid and improve drug interventions, and also need to take into account personalized genetic information. In conclusion, with the development of technology and research progress, visual impairment and legal blindness from AMD have been substantially reduced in incidence. This review article is focused on identifying and developing the knowledge about the association between genetics, and etiology with AMD. We hope that this review will encourage researchers and lecturers, open new discussions, and contribute to a better understanding of AMD that improves patients' visual acuity, and upgrades the quality of life of AMD patients.

Endogenous and Exogenous Regulation of Redox Homeostasis in Retinal Pigment Epithelium Cells: An Updated Antioxidant Perspective

The retinal pigment epithelium (RPE) performs a range of necessary functions within the neural layers of the retina and helps ensure vision. The regulation of pro-oxidative and antioxidant processes is the basis for maintaining RPE homeostasis and preventing retinal degenerative processes. Long-term stable changes in the redox balance under the influence of endogenous or exogenous factors can lead to oxidative stress (OS) and the development of a number of retinal pathologies associated with RPE dysfunction, and can eventually lead to vision loss. Reparative autophagy, ubiquitin-proteasome utilization, the repair of damaged proteins, and the maintenance of their conformational structure are important interrelated mechanisms of the endogenous defense system that protects against oxidative damage. Antioxidant protection of RPE cells is realized as a result of the activity of specific transcription factors, a large group of enzymes, chaperone proteins, etc., which form many signaling pathways in the RPE and the retina. Here, we discuss the role of the key components of the antioxidant defense system (ADS) in the cellular response of the RPE against OS. Understanding the role and interactions of OS mediators and the components of the ADS contributes to the formation of ideas about the subtle mechanisms in the regulation of RPE cellular functions and prospects for experimental approaches to restore RPE functions.

DAPL1 deficiency in mice impairs antioxidant defenses in the RPE and leads to retinal degeneration with AMD-like features

The decreased antioxidant capacity in the retinal pigment epithelium (RPE) is the hallmark of retinal degenerative diseases including age-related macular degeneration (AMD). Nevertheless, the exact regulatory mechanisms underlying the pathogenesis of retinal degenerations remain largely unknown. Here we show in mice that deficiencies in Dapl1, a susceptibility gene for human AMD, impair the antioxidant capacity of the RPE and lead to age-related retinal degeneration in the 18-month-old mice homozygous for a partial deletion of Dapl1. Dapl1-deficiency is associated with a reduction of the RPE's antioxidant capacity, and experimental re-expression of Dapl1 reverses this reduction and protects the retina from oxidative damage. Mechanistically, DAPL1 directly binds the transcription factor E2F4 and inhibits the expression of MYC, leading to upregulation of the transcription factor MITF and its targets NRF2 and PGC1α, both of which regulate the RPE's antioxidant function. When MITF is experimentally overexpressed in the RPE of DAPL1 deficient mice, antioxidation is restored and retinas are protected from degeneration. These findings suggest that the DAPL1-MITF axis functions as a novel regulator of the antioxidant defense system of the RPE and may play a critical role in the pathogenesis of age-related retinal degenerative diseases.

Risk of developing age-related macular degeneration in patients with osteoporosis: a population-based, longitudinal follow-up study

Osteoporosis was suggested to be associated with higher odds of age-related macular degeneration. However, the temporal relationship between osteoporosis and age-related macular degeneration has not been explored. This population-based longitudinal follow-up study showed an increased risk of age-related macular degeneration in both men and women with osteoporosis.

PURPOSE

To investigate the long-term risk of age-related macular degeneration (AMD) in patients with osteoporosis.

METHODS

This is a retrospective cohort study using the Longitudinal Health Insurance Database 2005, a subset of Taiwan's National Health Insurance research database. A total of 23,611 individuals aged 50 to 79 who were diagnosed with osteoporosis between January 1, 2002 and December 31, 2006, were enrolled in the osteoporosis group. An exactly equal number of propensity score-matched individuals without osteoporosis comprised the comparison group. The variables used in propensity score matching included age, sex, comorbidities, and socioeconomic status. Cox proportional hazard regression analysis was used to evaluate the association between osteoporosis and AMD. The main outcome measure is the occurrence of newly diagnosed AMD.

RESULTS

The hazard ratio (HR) of AMD in the osteoporosis group was 1.34 times higher than in the comparison group (95% confidence interval [CI] 1.22-1.47, p < 0.05). The AMD-free survival rate of the osteoporosis group was significantly lower than that of the comparison group (p < 0.0001). Sex-stratified analysis revealed a significantly increased risk of AMD in both osteoporotic men (HR 1.45; 95% CI 1.20-1.76, p = 0.0002) and women (HR 1.31; 95% CI 1.17-1.46, p < 0.0001) compared with their non-osteoporotic counterparts.

CONCLUSION

This longitudinal follow-up study revealed an increased risk of developing AMD in both men and women with osteoporosis.

Hydrogen sulfide protects retinal pigment epithelium cells against ferroptosis through the AMPK- and p62-dependent non-canonical NRF2-KEAP1 pathway

Oxidative stress-induced ferroptosis of retinal pigment epithelium (RPE) cells contributes to retinal degenerative diseases. The antioxidant molecule hydrogen sulfide (H₂S) regulates oxidative stress response, but its effect on the ferroptosis of RPE cells is unclear. In this study, sodium hydrosulfide (NaHS) was used as an exogenous H₂S donor to intervene tert-butyl hydroperoxide (t-BHP)-induced ferroptosis of APRE-19 cells. We found that NaHS pretreatment attenuates t-BHP-induced oxidative stress and ferroptosis. Analysis of mRNA-sequencing coupled with FerrDb database identified nuclear factor erythroid-2-related factor 2 (NRF2) as a primary target for the cytoprotective role of H₂S. NRF2 inhibitor ML385 reverses the effects of H₂S on ferroptosis. Biochemical analysis revealed that H₂S stabilizes NRF2. H₂S decreases the interaction between NRF2 and KEAP1, but enhances the interaction between KEAP1 and p62. These results suggest that H₂S activates the non-canonical NRF2-KEAP1 pathway. Further study demonstrated that H₂S stimulates AMPK to interact and phosphorylate p62. Additionally, inhibiting AMPK or knocking down p62 blocks the effects of H₂S. We speculate that targeting the non-canonical NRF2-KEAP1 pathway by H₂S-based drug may benefit the treatment of retinal degenerative diseases.

Understanding Ischemic Retinopathies: The Role of Succinate and Its Receptor in Retinal Pigment Epithelium

Retinopathy is the general name for all condition of the eyes in which blood vessels that supply oxygen to the retina are damaged. These include diabetic retinopathy, retinopathy of prematurity, hypertensive retinopathy, and arteriosclerotic retinopathy. Although the initial trigger that leads to insufficient perfusion of the retina may be different, once a critical level of ischemia is achieved, all types of retinopathies seem to follow a common sequence-oxidative stress, followed by hypoxia-induced formation of morphologically abnormal vessels. This preretinal vascular growth is the most severe aspect of the retinopathy, as the outcome is often retinal detachment and eventually blindness. Regardless of which therapy strategy is followed, a deeper understanding of both normal retinal growth and the underlying molecular mechanisms of retinopathies is needed in order to come up with more effective therapies. This chapter focuses on the citric acid cycle intermediate succinate and its G protein-coupled receptor SUCNR1 in ischemic retinopathies, which were identified as potent mediators of vessel growth in the settings of both normal retinal development and proliferative ischemic retinopathies.

A critical review on air pollutant exposure and age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairments and blindness worldwide in the elderly and its incidence strongly increases with ages. The etiology of AMD is complex and attributed to the genetic modifiers, environmental factors and gene-environment interactions. Recently, the impacts of air pollution on the development of eye diseases have become the new area of focus, and disordered air exposure combined with inadequate health management has caused problems for the eye health, such as dry eye, glaucoma, and retinopathy, while its specific role in the occurrence of AMD is still not well understood. In order to summarize the progress of this research field, we performed a critical review to summarize the epidemiological and mechanism evidence on the association between air pollutants exposure and AMD. This review documented that exposure to air pollutants will accelerate or worsen the morbidity and prevalence of AMD. Air pollutants exposure may change the homeostasis, interfere with the inflammatory response, and take direct action on the lipid metabolism and oxidative stress in the macula. More attention should be given to understanding the impact of ambient air pollution on AMD worldwide.

Osteoarthritis Is Associated With an Increased Risk of Age-Related Macular Degeneration: A Population-Based Longitudinal Follow-Up Study

Aims

To investigate the long-term risk of age-related macular degeneration (AMD) in persons with osteoarthritis (OA).

Methods

This retrospective cohort study first enrolled 71,609 subjects diagnosed with OA, and 236,169 without such a diagnosis between January 1, 2002 and December 31, 2005, from the Longitudinal Health Insurance Database 2005. All were aged 40–69. After excluding subjects who had pre-existing AMD and/or who had missing socioeconomic data, frequency matching by sex and age was performed. This resulted in there being 60,274 subjects in each of the final matched OA and non-OA groups. The study participants were followed up to the occurrence of AMD, death, or the end of 2011. We used Cox proportional-hazards regression to estimate the impact of OA on the risk of developing AMD, and performed subgroup analyses stratified by sex and age.

Results

The median follow-up time was 8.9 years, with an interquartile range of 1.4 years. The incidence rate of AMD in the OA group was 2.77 per 1,000 person-years [95% confidence interval (CI), 2.62–2.92], and in the non-OA group, 2.06 per 1,000 person-years (95% CI, 1.94–2.19). The adjusted hazard ratio (HR) of AMD for the OA group was therefore 1.30 (95% CI, 1.20–1.41). In the subgroup analysis stratified by sex for the OA group, the adjusted HRs of AMD were 1.29 in the women's stratum and 1.31 in the men's. When stratified by age, the adjusted HRs of AMD for the younger (40–54 years) and older (55–69 years) strata were 1.28 and 1.31, respectively.

Conclusions

Persons with OA have an increased risk of developing AMD, regardless of age and sex.

Mitochondrial-Targeted Antioxidant Peptide SS31 Prevents RPE Cell Death under Oxidative Stress

This work aims at investigating the protective effects of the mitochondria-targeted peptide SS31, on mitochondria function, preventing human retinal pigment epithelial cell-19 (ARPE-19) cell apoptosis. The ARPE-19 cells were subjected to 24 h of intervention with H2O2 of various concentrations (0, 100, 150, 200, 250, 300, and 500 μmol/L). Various concentrations of SS31 (10 nM, 100 nM, and 1 μmol/L) pretreated the cells for 2 h. The MTT assay determined cell viability. ARPE-19 cell apoptosis was observed by 4',6-diamidino-2-phenylindole (DAPI) staining under fluorescence microscope and detected by Annexin-V/PI staining under flow cytometry. The measurement of reactive oxygen species (ROS) release level used MitoSOX Red (a mitochondrial superoxide indicator) and the probe 2'-7'dichlorofluorescin diacetate (DCFH-DA). And with the use of a JC-1 probe, the mitochondrial membrane potential (MMP; ΔΨm) was analyzed. Reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR were responsible for measuring the levels of apoptosis related genes (Bcl-2, Bax, and Caspase-3). The cell viability increased significantly with SS31 pretreated (P < 0.05). In the SS31 + H2O2 group, the fluorescence of the cell nuclei with DAPI staining was weaker than H2O2 along group accordance with the decreased ratio of apoptotic cells (P < 0.05). The ROS generation decreased in SS31 pretreated group, with the increased ΔΨm. The RT-PCR result showed decreased Bax gene and Caspase-3 gene expression with SS31 pretreatment, while increased antiapoptotic gene Bcl-2 (P < 0.05). We provide evidence that SS31 promotes resilience of RPE cells to oxidative stress by stabilizing mitochondrial function.

Physical Activity, Incidence, and Progression of Age-Related Macular Degeneration: A Multicohort Study

PURPOSE

To investigate the impact of physical activity (PA) on the incidence or progression of age-related macular degeneration (AMD) in the general population.

DESIGN

Meta-analysis of longitudinal cohort studies.

METHODS

We included 14,630 adults with no or early AMD at baseline from 7 population-based studies and examined associations of PA with AMD incidence and progression using multistate models (MSM) per study and subsequent random effects meta-analysis. Age effects were assessed using meta-regression. The main outcome measure was the hazard ratio (HR) for incident early or progression to late AMD.

RESULTS

At baseline, mean age was 60.7 ± 6.9 to 76.4 ± 4.3 years, and prevalence of early AMD was 7.7% (range, 3.6%-16.9%) between cohorts. During follow-up, 1461 and 189 events occurred for early and late AMD, respectively. In meta-analyses, no or low to moderate PA (high PA as reference) was associated with an increased risk for incident early AMD (HR, 1.19; 95% CI, 1.01-1.40; P = .04), but not for late AMD. In subsequent meta-regression, we found no association of age with the effect of PA on incident AMD.

CONCLUSIONS

Our study suggests high levels of PA to be protective for the development of early AMD across several population-based cohort studies. Our results establish PA as a modifiable risk factor for AMD and inform further AMD prevention strategies to reduce its public health impact.

The Age-Related Macular Degeneration (AMD)-Preventing Mechanism of Natural Products

Age-related macular degeneration (AMD) is related to central visual loss in elderly people and, based on the increment in the percentage of the aging population, the number of people suffering from AMD could increase. AMD is initiated by retinal pigment epithelium (RPE) cell death, finally leading to neovascularization in the macula lutea. AMD is an uncurable disease, but the symptom can be suppressed. The current therapy of AMD can be classified into four types: device-based treatment, anti-inflammatory drug treatment, anti-vascular endothelial growth factor treatment, and natural product treatment. All these therapies have adverse effects, however early AMD therapy used with products has several advantages, as it can prevent RPE cell apoptosis in safe doses. Cell death (apoptosis) is caused by various factors, such as oxidative stress, inflammation, carbonyl stress, and a deficiency in essential components for cells, and RPE cell death is related to oxidative stress, inflammation, and carbonyl stress. Some natural products have anti-oxidative effects, anti-inflammation effects, and/or anti-carbonylation effects. The AMD preventive mechanism of natural products varies, with some natural products activating one or more anti-apoptotic pathways, such as the Nrf2/HO-1 anti-oxidative pathway, the anti-inflammasome pathway, and the anti-carbonyl pathway. As AMD drug candidates from natural products effectively inhibit RPE cell death, they have the potential to be developed as drugs for preventing early (dry) AMD.

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

Age-related macular degeneration: Epidemiology, genetics, pathophysiology, diagnosis, and targeted therapy

Age-related macular degeneration (AMD) is a complex eye disorder and is the leading cause of incurable blindness worldwide in the elderly. Clinically, AMD initially affects the central area of retina known as the macula and it is classified as early stage to late stage (advanced AMD). The advanced AMD is classified into the nonexudative or atrophic form (dry AMD) and the exudative or neovascular form (wet AMD). More severe vision loss is typically associated with the wet form. Multiple genetic factors, lipid metabolism, oxidative stress and aging, play a role in the etiology of AMD. Dysregulation in genetic to AMD is established to 46%-71% of disease contribution, with CFH and ARMS2/HTRA1 to be the two most notable risk loci among the 103 identified AMD associated loci so far. Chronic cigarette smoking is the most proven consistently risk living habits for AMD. Deep learning algorithm has been developed based on image recognition to distinguish wet AMD and normal macula with high accuracy. Currently, anti-vascular endothelial growth factor (VEGF) therapy is highly effective at treating wet AMD. Several new generation AMD drugs and iPSC-derived RPE cell therapy are in the clinical trial stage and are promising to improve AMD treatment in the near future.

The Association of Objective and Subjective Vision Impairment With Self-Reported Time Spent in Sedentary Behaviors in Low- and Middle-Income Countries

BACKGROUND

There is a scarcity of studies on the relationship between visual impairment (VI) and time spent in sedentary behavior (SB), especially from low- and middle-income countries (LMICs). Thus, we investigated the association of objectively and subjectively measured VI with SB in adults aged ≥18 years across 6 LMICs.

METHODS

Cross-sectional data from the WHO Study on global AGEing and adult health (SAGE) were analyzed. Objective and subjective visual acuity were measured. Information on self-reported SB was also collected. Multivariable multinomial logistic regression analysis was conducted to assess associations with time spent in SB as the outcome.

RESULTS

The sample consisted of 42,489 individuals (mean age = 43.8 [14.4] y; 50.1% females). Only severe objective VI (vs no VI) was significantly associated with ≥11 hours per day of SB (vs <4 h/d) (odds ratio = 4.50; 95% confidence interval, 1.57-12.92). Increasing severity of subjective VI was associated with greater odds for ≥8 hours per day of SB (vs <4 h/d) dose dependently.

CONCLUSIONS

The present study identified an association of both objectively and subjectively measured VI with time spent in SB in adults residing in LMICs, with subjectively measured VI being a stronger predictor of time spent in SB. Targeted interventions to decrease SB especially in those who perceive themselves to have VI are needed in LMICs.

Association of Smoking, Alcohol Consumption, Blood Pressure, Body Mass Index, and Glycemic Risk Factors With Age-Related Macular Degeneration: A Mendelian Randomization Study

IMPORTANCE

Advanced age-related macular degeneration (AMD) is a leading cause of blindness in Western countries. Causal, modifiable risk factors need to be identified to develop preventive measures for advanced AMD.

OBJECTIVE

To assess whether smoking, alcohol consumption, blood pressure, body mass index, and glycemic traits are associated with increased risk of advanced AMD.

DESIGN, SETTING, PARTICIPANTS

This study used 2-sample mendelian randomization. Genetic instruments composed of variants associated with risk factors at genome-wide significance (P < 5 × 10-8) were obtained from published genome-wide association studies. Summary-level statistics for these instruments were obtained for advanced AMD from the International AMD Genomics Consortium 2016 data set, which consisted of 16 144 individuals with AMD and 17 832 control individuals. Data were analyzed from July 2020 to September 2021.

EXPOSURES

Smoking initiation, smoking cessation, lifetime smoking, age at smoking initiation, alcoholic drinks per week, body mass index, systolic and diastolic blood pressure, type 2 diabetes, glycated hemoglobin, fasting glucose, and fasting insulin.

MAIN OUTCOMES AND MEASURES

Advanced AMD and its subtypes, geographic atrophy (GA), and neovascular AMD.

RESULTS

A 1-SD increase in logodds of genetically predicted smoking initiation was associated with higher risk of advanced AMD (odds ratio [OR], 1.26; 95% CI, 1.13-1.40; P < .001), while a 1-SD increase in logodds of genetically predicted smoking cessation (former vs current smoking) was associated with lower risk of advanced AMD (OR, 0.66; 95% CI, 0.50-0.87; P = .003). Genetically predicted increased lifetime smoking was associated with increased risk of advanced AMD (OR per 1-SD increase in lifetime smoking behavior, 1.32; 95% CI, 1.09-1.59; P = .004). Genetically predicted alcohol consumption was associated with higher risk of GA (OR per 1-SD increase of log-transformed alcoholic drinks per week, 2.70; 95% CI, 1.48-4.94; P = .001). There was insufficient evidence to suggest that genetically predicted blood pressure, body mass index, and glycemic traits were associated with advanced AMD.

CONCLUSIONS AND RELEVANCE

This study provides genetic evidence that increased alcohol intake may be a causal risk factor for GA. As there are currently no known treatments for GA, this finding has important public health implications. These results also support previous observational studies associating smoking behavior with risk of advanced AMD, thus reinforcing existing public health messages regarding the risk of blindness associated with smoking.

Medication Trends for Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is central vision loss with aging, was the fourth main cause of blindness in 2015, and has many risk factors, such as cataract surgery, cigarette smoking, family history, hypertension, obesity, long-term smart device usage, etc. AMD is classified into three categories: normal AMD, early AMD, and late AMD, based on angiogenesis in the retina, and can be determined by bis-retinoid N-retinyl-N-retinylidene ethanolamine (A2E)-epoxides from the reaction of A2E and blue light. During the reaction of A2E and blue light, reactive oxygen species (ROS) are synthesized, which gather inflammatory factors, induce carbonyl stress, and finally stimulate the death of retinal pigment epitheliums (RPEs). There are several medications for AMD, such as device-based therapy, anti-inflammatory drugs, anti-VEGFs, and natural products. For device-based therapy, two methods are used: prophylactic laser therapy (photocoagulation laser therapy) and photodynamic therapy. Anti-inflammatory drugs consist of corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs). Anti-VEGFs are classified antibodies for VEGF, aptamer, soluble receptor, VEGF receptor-1 and -2 antibody, and VEGF receptor tyrosine kinase inhibitor. Finally, additional AMD drug candidates are derived from natural products. For each medication, there are several and severe adverse effects, but natural products have a potency as AMD drugs, as they have been used as culinary materials and/or traditional medicines for a long time. Their major application route is oral administration, and they can be combined with device-based therapy, anti-inflammatory drugs, and anti-VEGFs. In general, AMD drug candidates from natural products are more effective at treating early and intermediate AMD. However, further study is needed to evaluate their efficacy and to investigate their therapeutic mechanisms.

Mitochondria dynamics in the aged mice eye and the role in the RPE phagocytosis

Aging is a predominant risk factor for various eye diseases. Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, and its etiology remains unclear. Fragmented and dysfunctional mitochondria are associated with age-related diseases. The retinal pigment epithelium (RPE), a polarized cell layer that functions in visual pigment recycling and degeneration, is suspected as the primary region site of AMD. In the present study, we investigated the relationship between mitochondrial dysfunction and RPE aging. Compared to young mice, aged pigmented mice (C57BL/6J, 12-month-old) exhibit decreased visual function without retinal thinning. Consistently, the rhodopsin expression level decreased in the outer segment of aged mice. Moreover, the cell volume of the RPE increased in aged animals. Interestingly, the expression of mitochondria dynamics-related proteins, including Drp1, was altered in the RPE-choroid complex but not in the neural retina after aging. Electron microscopy revealed that mitochondrial size decreased and cristae width increased in aged RPE. The photoreceptor outer segment (POS) treatment of ARPE-19 cells causes Drp1 activation. Furthermore, pharmacological suppression of mitochondrial fission improved the phagocytosis of the POS. These findings indicate that mitochondrial dysfunction and fission in RPE impede phagocytosis and cause retardation of the visual cycle, which can be one of the age-related defects in the retina that may contribute to the onset of AMD.

Dietary omega-3 polyunsaturated fatty acids and fish intake and risk of age-related macular degeneration

BACKGROUND & AIMS

Epidemiologic studies are inconsistent regarding the association of dietary omega-3 polyunsaturated fatty acids (PUFA) and/or fish intake with risk of age-related macular degeneration (AMD) incidence and progression. The objective was to determine these associations by conducting a meta-analysis of available studies.

METHODS

Three electronic databases were searched for studies that quantified dietary omega-3 PUFA and/or fish intake from inception to December 2020 without language restriction. Three investigators independently assessed for inclusion and extracted data. Study-specific risk estimates were combined using random-effects model. Potential dose-response associations were explored with the use of generalized least-squares trend estimation.

RESULTS

21 studies were included in the meta-analysis. Higher dietary intakes of omega-3 PUFA was significantly associated with 14% (relative risk [RR]: 0.86, 95% confidence interval [CI]: 0.77, 0.96) and 29% (RR: 0.71, 95% CI: 0.55, 0.91) lower risk of early and late AMD, respectively. The dose-response analysis showed a 6% and 22% decrease in the risk of early and late AMD for each additional 1  g/d omega-3 PUFA intake. For individual omega-3 PUFA, the intake of eicosapentaenoic acid and docosahexaenoic acid was inversely associated with lower AMD risk, whereas no association was found for the alpha-linolenic acid. Consistent inverse associations were also found between fish intake and AMD. The pooled RRs comparing extreme categories of fish intake were 0.79 (95% CI: 0.70, 0.90) and 0.71 (95% CI: 0.60, 0.85) for early and late AMD risk, respectively. Every 15 g/d of fish consumption was associated with 13% and 14% lower early and late AMD. In addition, fish intake was associated with a significantly reduced risk of AMD progression (RR: 0.73, 95% CI: 0.53, 1.00).

CONCLUSIONS

A high intake of dietary omega-3 PUFA or fish was associated with a reduced risk of developing of AMD, which further supports that consumption of omega-3 PUFA-rich foods may be a new avenue nutritional approach to preventing AMD.

Evaluation of the effect of high-intensity interval training on macular microcirculation via swept-source optical coherence tomography angiography in young football players

Purpose:

This study was conducted to evaluate the effect of high intensity interval training (HIIT) on macular microcirculation, measured by swept source optical coherence tomography angiography (ss OCTA) in young football players.

Methods:

Football players between 18–20 years old were included. After a detailed ophthalmological examination, physiological parameters, including height, body weight, body fat, systemic blood pressure, hematocrit values, oxygen saturation, and heart rate, were recorded. Intraocular pressure and ss OCTA parameters were measured one day before and the day after the high intensity interval training program using DRI OCT Triton (Topcon, Tokyo, Japan) between 11:00 am and 1:00 pm.

Results:

Fifteen participants completed the study. All were males with a mean age of 18.1 ± 0.4 years. Systolic and diastolic blood pressure and oxygen saturation did not change significantly (P > 0.05), while hematocrit levels increased remarkably (P = 0.049) after the HIIT program. Heart rates and intraocular pressure decreased (P = 0.003, P = 0.017, respectively). There was a significant increase in the central vessel density in deep capillary plexus (before: 18.7 ± 3.8%, after: 21.1 ± 4.5%) and central vessel density in choriocapillaris (before: 54.5 ± 2.8%, after 56.9 ± 2.2%) (P = 0.02, P = 0.02, respectively), although no changes were observed in other ss OCTA or in the central macular thickness and subfoveal choroidal thickness.

Conclusion:

A 6 week, high intensity interval training program with three exercise sessions per week seems not to alter mean superficial vascular densities, deep foveal avascular zone, and superficial foveal avascular zones, central macular thickness, or subfoveal choroidal thickness, while the central deep vascular density and central choriocapillaris vascular density increased remarkably among ss OCTA parameters.

Prevention of the Onset of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) represents the leading cause of irreversible blindness in elderly people, mostly after the age of 65. The progressive deterioration of visual function in patients affected by AMD has a significant impact on quality of life and has also high social costs. The current therapeutic options are only partially able to slow down the natural course of the disease, without being capable of stopping its progression. Therefore, better understanding of the possibilities to prevent the onset of the disease is needed. In this regard, a central role is played by the identification of risk factors, which might participate to the development of the disease. Among these, the most researched are dietary risk factors, lifestyle, and light exposure. Many studies showed that a higher dietary intake of nutrients, such as lutein, zeaxanthin, beta carotene, omega-3 fatty acids and zinc, reduced the risk of early AMD. Regarding lifestyle habits, the association between smoking and AMD is currently accepted. Finally, retinal damage caused by ultraviolet rays and blue light is also worthy of attention. The scope of this review is to summarize the present knowledge focusing on the measures to adopt in order to prevent the onset of AMD.

Anti-Inflammatory and Anti-Oxidative Synergistic Effect of Vitamin D and Nutritional Complex on Retinal Pigment Epithelial and Endothelial Cell Lines against Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by dysfunction of retinal pigmented epithelial (RPE) and loss of photoreceptor cells under oxidative stress and inflammatory conditions. Vitamin D and antioxidants have beneficial effects against retinal degenerative diseases, such as AMD. We investigated the impact of associating vitamin D (ND) with a nutritional antioxidant complex (Nutrof Total^®; N) on oxidative stress and inflammation-like induced conditions by H₂O₂ and LPS, respectively, in human retinal epithelial (ARPE-19) and human retinal endothelial (HREC) cells. Application of either N or ND treatments to H₂O₂-induced media in ARPE-19 cells counteracted late apoptosis, attenuated oxidative DNA damage, and increased cell proliferation. Significant reduction in the expression levels of MCP1, IL-8, and IL6 cytokines was observed following application of either N or ND treatments under LPS-induced conditions in ARPE-19 cells and in MCP-1 and IL12p70 cytokine levels in HREC cells. ND and not N revealed significant downregulation of IFNγ in ARPE-19 cells, and of IL-6 and IL-18 in HREC cells. In conclusion, adding vitamin D to Nutrof Total^® protects in a synergistic way against oxidative and inflammatory stress-induced conditions in retinal epithelial and endothelial cells.

Therapeutic Potential of Hispidin-Fungal and Plant Polyketide

There is a large number of bioactive polyketides well-known for their anticancer, antibiotic, cholesterol-lowering, and other therapeutic functions, and hispidin is among them. It is a highly abundant secondary plant and fungal metabolite, which is investigated in research devoted to cancer, metabolic syndrome, cardiovascular, neurodegenerative, and viral diseases. This review summarizes over 20 years of hispidin studies of its antioxidant, anti-inflammatory, anti-apoptotic, antiviral, and anti-cancer cell activity.

Iron Accumulation and Lipid Peroxidation in the Aging Retina: Implication of Ferroptosis in Age-Related Macular Degeneration

Iron is an essential component in many biological processes in the human body. It is critical for the visual phototransduction cascade in the retina. However, excess iron can be toxic. Iron accumulation and reduced efficiency of intracellular antioxidative defense systems predispose the aging retina to oxidative stress-induced cell death. Age-related macular degeneration (AMD) is characterized by retinal iron accumulation and lipid peroxidation. The mechanisms underlying AMD include oxidative stress-mediated death of retinal pigment epithelium (RPE) cells and subsequent death of retinal photoreceptors. Understanding the mechanism of the disruption of iron and redox homeostasis in the aging retina and AMD is crucial to decipher these mechanisms of cell death and AMD pathogenesis. The mechanisms of retinal cell death in AMD are an area of active investigation; previous studies have proposed several types of cell death as major mechanisms. Ferroptosis, a newly discovered programmed cell death pathway, has been associated with the pathogenesis of several neurodegenerative diseases. Ferroptosis is initiated by lipid peroxidation and is characterized by iron-dependent accumulation. In this review, we provide an overview of the mechanisms of iron accumulation and lipid peroxidation in the aging retina and AMD, with an emphasis on ferroptosis.

MicroRNA-100 Mediates Hydrogen Peroxide-Induced Apoptosis of Human Retinal Pigment Epithelium ARPE-19 Cells

This study investigated the regulatory role of microRNA 100 (miR-100) in hydrogen peroxide (H₂O₂)-induced apoptosis of human retinal pigment epithelial ARPE-19 cells. H₂O₂ induced oxidative cell death of cultured ARPE-19 cells was measured by cytotoxicity assay. qRT-PCR was used to quantify cytosolic and extracellular contents of miR-100. Kinase and miR-100 inhibition treatments were applied to determine the regulatory signaling pathways involved in cell death regulation. H₂O₂ dose-dependently reduced viability of ARPE-19 cells and simultaneously upregulated miR-100 levels in both cytosolic and extracellular compartments. Western blotting detection indicated that H₂O₂ elicited hyperphosphorylation of PI3K/Akt, ERK1/2, JNK, p38 MAPK, and p65 NF-κB. Further kinase inhibition experiments demonstrated that PI3K, p38 MAPK, and NF-κB activities were involved in oxidative-stress-induced miR-100 upregulation in ARPE-19 cells, while blockade of PI3K, JNK, and NF-κB signaling significantly attenuated the oxidative cell death. Intriguingly, MiR-100 antagomir treatment exerted a cytoprotective effect against the H₂O₂-induced oxidative cell death through attenuating the oxidation-induced AMPK hyperphosphorylation, restoring cellular mTOR and p62/SQSTM1 levels and upregulating heme oxygenase-1 expression. These findings support that miR-100 at least in part mediates H₂O₂-induced cell death of ARPE-19 cells and can be regarded as a preventive and therapeutic target for retinal degenerative disease.

Age-Related Macular Degeneration: Role of Oxidative Stress and Blood Vessels

Age-related macular degeneration (AMD) is a common irreversible ocular disease characterized by vision impairment among older people. Many risk factors are related to AMD and interact with each other in its pathogenesis. Notably, oxidative stress and choroidal vascular dysfunction were suggested to be critically involved in AMD pathogenesis. In this review, we give an overview on the factors contributing to the pathophysiology of this multifactorial disease and discuss the role of reactive oxygen species and vascular function in more detail. Moreover, we give an overview on therapeutic strategies for patients suffering from AMD.

Leukemia inhibitory factor protects photoreceptor cone cells against oxidative damage through activating JAK/STAT3 signaling

Background

The present study aimed to investigate the protective role of leukemia inhibitory factor (LIF) against oxidative damage in photoreceptor cone cells.

Methods

In vivo, dark-adapted mice were injected with LIF or phosphate-buffered saline (PBS) intravitreously prior to being exposed to 5,000 lux bright light to determine the protective effect of LIF against light damage in cone cells. Oxidative damage to cone cells was analyzed using electroretinograms, immunostaining, Western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR). In vitro, 661W cells were pretreated with 5 ng/mL of LIF with or without 50 µM of signal transducer and activator of transcription 3 (STAT3) inhibitor S3I201 for 1 h prior to treatment with 1 mM H₂O₂; cell survival, apoptosis, the oxidative stress index, and the activation of STAT3, extracellular signal-regulated kinase (ERK1/2), and AKT were subsequently determined.

Results

In vivo, light induction damaged the function and morphology of cone cells, and LIF was observed to protect cone cells from this light damage. Moreover, the activation of the Janus tyrosine kinase (JAK)/STAT3 signaling pathway and the subsequent changes in apoptosis and proliferation-related genes were found to be involved in the protective effect of LIF against light-induced retinal damage. In the H₂O₂-induced 661W cell model, H₂O₂ increased cellular apoptosis rates, the expression levels of Bcl-2–associated X-protein (BAX) and cleaved caspase 3, reactive oxygen species (ROS) production, and malondialdehyde content, while decreasing the cell viability, and Bcl-2, superoxide dismutase, catalase, and glutathione peroxidase activity. LIF was observed to block these events; however, the administration of the STAT3 inhibitor S3I201 reversed the beneficial effects of LIF on H₂O₂-triggered apoptosis and ROS production.

Conclusions

In conclusion, the present study suggested that LIF may relieve oxidative damage in cone cells through suppressing apoptosis and oxidative stress by targeting the STAT3 signaling pathway.

Not All Stressors Are Equal: Mechanism of Stressors on RPE Cell Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness among the elderly population. Dysfunction and degeneration of the retinal pigment epithelial (RPE) layer in the retina underscore the pathogenesis of both dry and wet AMD. Advanced age, cigarette smoke and genetic factors have been found to be the prominent risk factors for AMD, which point to an important role for oxidative stress and aging in AMD pathogenesis. However, the mechanisms whereby oxidative stress and aging lead to RPE cell degeneration are still unclear. As cell senescence and cell death are the major outcomes from oxidative stress and aging, here we review the mechanisms of RPE cell senescence and different kinds of cell death, including apoptosis, necroptosis, pyroptosis, ferroptosis, with an aim to clarify how RPE cell degeneration could occur in response to AMD-related stresses, including H₂O₂, 4-Hydroxynonenal (4-HNE), N-retinylidene-N-retinyl-ethanolamine (A2E), Alu RNA and amyloid β (Aβ). Besides those, sodium iodate (NaIO₃) induced RPE cell degeneration is also discussed in this review. Although NaIO₃ itself is not related to AMD, this line of study would help understand the mechanism of RPE degeneration.

Interplay between reactive oxygen species and autophagy in the course of age-related macular degeneration

Pathological biomolecules such as lipofuscin, methylglyoxal-modified proteins (the major precursors of advanced glycationend products), misfolding protein deposits and dysfunctional mitochondria are source of oxidative stress and act as strong autophagic stimulators in age-related macular degeneration. Disturbed autophagy accelerates progression of the disease, since it leads to retinal cells' death and activates inflammation by the interplay with the NLRP3 inflammasome complex. Vascular dysfunction and hypoxia, as well as circulating autoantibodies against autophagy regulators (anti-S100A9, anti-ANXA5, and anti-HSPA8, A9 and B4) compromise an autophagy-mediated mechanism as well. Metformin, the autophagic stimulator, may act as a senostatic drug to inhibit the senescent phenotype in the age-related macular degeneration. PGC-1α , Sirt1 and AMPK represent new therapeutic targets for interventions in this disease.

Controlled release of anti-VEGF by redox-responsive polydopamine nanoparticles

Reactive oxidative species (ROS) are the primary mediator of angiogenesis by upregulating the expression of vascular endothelial growth factor (VEGF) in the development of wet age-related macular degeneration (AMD). However, the current treatment of AMD currently relies on monthly intravitreal injection of anti-angiogenic therapeutics to inhibit new choroidal angiogenesis. However, repeated injections have been associated with side-effects, are costly, and may lower patient compliance. Moreover, the intraocular oxidative stress-dependent angiogenesis is not alleviated by current treatments, which limits the overall efficacy of the treatment strategy. Recently, nanoparticle-based devices present potential in sustained delivery of angiogenesis inhibitors and excellent capability of scavenging reactive oxygen species (ROS). Nevertheless, limited efforts have been dedicated to the treatment of oxidative stress-related diseases via a combined anti-angiogenesis and anti-oxidization pathway. For this purpose, we developed anti-angiogenetic protein-loaded polydopamine (PDA) nanoparticles for the enhanced treatment of AMD. Remarkably, the PDA nanoparticles could efficiently scavenge ROS to reduce the expression of angiogenic agents. In parallel, the particles were able to controllably release loaded anti-angiogenic drugs in response to oxidative stress.

Tribulus terrestris Ameliorates Oxidative Stress-Induced ARPE-19 Cell Injury through the PI3K/Akt-Nrf2 Signaling Pathway

Oxidative stress on retinal pigment epithelial (RPE) cells has been confirmed to play a crucial role in the development and progression of age-related macular degeneration (AMD) or other retinal degenerative diseases. Tribulus terrestris (TT) is a Chinese traditional herb medicine, which has been used for the treatment of ocular diseases for many centuries. In this study, we investigated the underlying mechanisms of TT and examined its ability to protect and restore the human retinal pigment epithelial cells (ARPE-19) against H₂O₂-induced oxidative stress. Our data show that 200 μg/mL of ethanol extract of Tribulus terrestris (EE-TT) significantly increased the cell viability and prevented the apoptosis of H₂O₂-treated ARPE-19 cells through the regulation of Bcl2, Bax, cleaved caspase-3, and caspase-9. Treatment with EE-TT also significantly decreased the upregulated reactive oxygen species (ROS) activities and increased the downregulated superoxide dismutase (SOD) activities induced by H₂O₂ in ARPE-19 cells. Additionally, H₂O₂ at 1 mM significantly decreased the mRNA expression levels of Nrf2, CAT, SOD1, SOD2, HO-1, GST-pi, NQO1, and GLCM in ARPE-19 cells; however, treatment with EE-TT reversed the downregulated mRNA expression levels of all these genes induced by H₂O₂. Furthermore, treatment with 200 μg/mL EE-TT alone for 24 h significantly increased Nrf2, HO-1, NQO1, and GCLM mRNA expressions in ARPE-19 cells when compared with untreated control cells. Pretreatment with the inhibitor of PI3K/Akt signaling (LY294002) completely blocked these EE-TT-upregulated mRNA expressions and abolished the improvement of cell viability in H₂O₂-treated ARPE-19 cells. These findings all suggest that Tribulus terrestris has significant antioxidant effects on oxidative stressed ARPE-19 cells through regulating PI3K/Akt-Nrf2 signaling pathway.

An in vitro model of chronic wounding and its implication for age-related macular degeneration

Degeneration of the retinal pigment epithelium (RPE) plays a central role in age-related macular degeneration (AMD). Throughout life, RPE cells are challenged by a variety of cytotoxic stressors, some of which are cumulative with age and may ultimately contribute to drusen and lipofuscin accumulation. Stressors such as these continually damage RPE cells resulting in a state of chronic wounding. Current cell-based platforms that model a state of chronic RPE cell wounding are limited, and the RPE cellular response is not entirely understood. Here, we used the electric cell-substrate impedance sensing (ECIS) system to induce a state of acute or chronic wounding on differentiated human fetal RPE cells to analyze changes in the wound repair response. RPE cells surrounding the lesioned area employ both cell migration and proliferation to repair wounds but fail to reestablish their original cell morphology or density after repetitive wounding. Chronically wounded RPE cells develop phenotypic AMD characteristics such as loss of cuboidal morphology, enlarged size, and multinucleation. Transcriptomic analysis suggests a systemic misregulation of RPE cell functions in bystander cells, which are not directly adjacent to the wound. Genes associated with the major RPE cell functions (LRAT, MITF, RDH11) significantly downregulate after wounding, in addition to differential expression of genes associated with the cell cycle (CDK1, CDC6, CDC20), inflammation (IL-18, CCL2), and apoptosis (FAS). Interestingly, repetitive wounding resulted in prolonged misregulation of genes, including FAS, LRAT, and PEDF. The use of ECIS to induce wounding resulted in an over-representation of AMD-associated genes among those dysregulated genes, particularly genes associated with advanced AMD. This simple system provides a new model for further investigation of RPE cell wound response in AMD pathogenesis.

Blue light-emitting diode irradiation promotes transcription factor EB-mediated lysosome biogenesis and lysosomal cell death in murine photoreceptor-derived cells

Exposure to blue light from light-emitting diodes (LEDs) is a source of damage for human eyes in today's modern life. Although it is well known that blue light can cause cellular damage and death, the molecular mechanism underlying this is still not fully understood. Here, we demonstrated that exposure to blue LED light increased lysosome levels and perinuclear cluster formation in 661W murine photoreceptor-derived cells. Irradiation with blue LED light promoted the nuclear transport of transcription factor EB (TFEB) and a subsequent increase in lysosomal-related gene expression. Moreover, blue LED light induced morphological changes in lysosomal structure and lysosomal membrane permeabilization (LMP). These effects were suppressed by an antioxidant, N-acetylcysteine (NAC). Finally, a calcium ion chelator, BAPTA-AM, attenuated blue LED light-induced lysosomal biogenesis and cell death. Taken together, these findings suggest that oxidative stress under blue LED light increases lysosome levels via the TFEB pathway in a calcium-dependent manner, resulting in the accumulation of damaged lysosomes and subsequently lysosomal cell death. Our results imply that lysosomal homeostasis plays a key role in the maintenance of eye function and the progression of retinal diseases.

Protection of human retinal pigment epithelial cells from oxidative damage using cysteine prodrugs

Age-related macular degeneration (AMD) is one of the major causes of vision loss in the elderly in most developed countries. Among other causes, oxidative stress in the retinal pigment epithelium (RPE) has been hypothesized to be a major driving force of AMD pathology. Oxidative stress could be treated by antioxidant administration into the RPE cells. However, to achieve high in-vivo efficacy of an antioxidant, it is imperative that the agent be able to penetrate the tissues and cells. Evidence suggests that lipophilicity governs cellular penetrance. Out of many antioxidant candidates, N-acetyl-L-cysteine (a prodrug of L-cysteine) (NAC) is a potent antioxidant as the bioavailability of the parent drug, L-cysteine, determines the production of glutathione; the universal antioxidant that regulates ROS. To increase the lipophilicity, four ester derivatives of N-acetylcysteine: N-acetylcysteine methyl ester, N-acetylcysteine ethyl ester, N-acetylcysteine propyl ester, and N-acetylcysteine butyl ester were synthesized. To mimic in vitro AMD conditions, hydroquinone, a component of cigarette smoke, was used as the oxidative insult. Cytosolic and mitochondrial protection against oxidative stress were tested using cytosolic and mitochondrial specific assays. The results provide evidence that these lipophilic cysteine prodrugs provide increased protection against oxidative stress in human RPE cells compared with NAC.

MITF protects against oxidative damage-induced retinal degeneration by regulating the NRF2 pathway in the retinal pigment epithelium

Oxidative damage is one of the major contributors to retinal degenerative diseases such as age-related macular degeneration (AMD), while RPE mediated antioxidant defense plays an important role in preventing retinopathies. However, the regulatory mechanisms of antioxidant signaling in RPE cells are poorly understood. Here we show that transcription factor MITF regulates the antioxidant response in RPE cells, protecting the neural retina from oxidative damage. In the oxidative stress-induced retinal degeneration mouse model, retinal degeneration in Mitf+/- mice is significantly aggravated compared to WT mice. In contrast, overexpression of Mitf in Dct-Mitf transgenic mice and AAV mediated overexpression in RPE cells protect the neural retina against oxidative damage. Mechanistically, MITF both directly regulates the transcription of NRF2, a master regulator of antioxidant signaling, and promotes its nuclear translocation. Furthermore, specific overexpression of NRF2 in Mitf+/- RPE cells activates antioxidant signaling and partially protects the retina from oxidative damage. Taken together, our findings demonstrate the regulation of NRF2 by MITF in RPE cells and provide new insights into potential therapeutic approaches for prevention of oxidative damage diseases.

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MITF haploinsufficiency exacerbates oxidative stress-induced retinal degeneration.

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Specific overexpression of MITF in RPE cells protects retinas from oxidative damage in vivo.

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MITF directly regulates the transcription and nuclear translocation of NRF2.

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Partial rescue of retinal oxidative damage in Mitf ±mice by gene transfer mediated RPE cell specific expression of NRF2.

Signaling lipids as diagnostic biomarkers for ocular surface cicatrizing conjunctivitis

Abstract

Metabolomics has been applied to diagnose diseases, predict disease progression, and design therapeutic strategies in various areas of medicine. However, it remains to be applied to the ocular surface diseases, where biological samples are often of limited quantities. We successfully performed proof-of-concept metabolomics assessment of volume-limited cytology samples from a clinical form of chronic inflammatory cicatrizing conjunctivitis, i.e., ocular MMP and discovered metabolic changes of signaling lipid mediators upon disease onset and progression. The metabolomics assessment revealed active oxylipins, lysophospholipids, fatty acids, and endocannabinoids alterations, from which potential biomarkers linked to inflammatory processes were identified. Possible underlying mechanisms such as dysregulated enzyme activities (e.g., lipoxygenases, cytochrome P450, and phospholipases) were suggested which may be considered as potential therapeutic targets in future studies.

Key messages

Metabolic profile of the ocular surface can be measured using impression cytology samples.

Metabolomics analysis of ocular pemphigoid is presented for the first time.

The metabolomics assessment of OCP patients revealed active oxylipins, lysophospholipids, fatty acids, and endocannabinoids alterations.

Several oxylipins are identified as diagnostic biomarkers for OCP.

Cathepsin B pH-Dependent Activity Is Involved in Lysosomal Dysregulation in Atrophic Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is characterized by retinal pigment epithelial (RPE) cell dysfunction beginning at early stages of the disease. The lack of an appropriate in vitro model is a major limitation in understanding the mechanisms leading to the occurrence of AMD. This study compared human-induced pluripotent stem cell- (hiPSC-) RPE cells derived from atrophic AMD patients (77 y/o ± 7) to hiPSC-RPE cells derived from healthy elderly individuals with no drusen or pigmentary alteration (62.5 y/o ± 17.5). Control and AMD hiPSC-RPE cell lines were characterized by immunofluorescence, flow cytometry, and electronic microscopy. The toxicity level of iron after Fe-NTA treatment was evaluated by an MTT test and by the detection of dichloro-dihydro-fluorescein diacetate. Twelve hiPSC-RPE cell lines (6 AMD and 6 controls) were used for the experiment. Under basal conditions, all hiPSC-RPE cells expressed a phenotypic profile of senescent cells with rounded mitochondria at passage 2. However, the treatment with Fe-NTA induced higher reactive oxygen species production and cell death in hiPSC-RPE AMD cells than in hiPSC-RPE Control cells. Interestingly, functional analysis showed differences in lysosomal activity between the two populations. Indeed, Cathepsin B activity was higher in hiPSC-RPE AMD cells compared to hiPSC-RPE Control cells in basal condition and link to a pH more acidic in this cell population. Moreover, oxidative stress exposure leads to an increase of Cathepsin D immature form levels in both populations, but in a higher proportion in hiPSC-RPE AMD cells. These findings could demonstrate that hiPSC-RPE AMD cells have a typical disease phenotype compared to hiPSC-RPE Control cells.

The Protective Effect of Hispidin against Hydrogen Peroxide-Induced Oxidative Stress in ARPE-19 Cells via Nrf2 Signaling Pathway

Hispidin, a polyphenol compound isolated from Phellinus linteus, has been reported to possess antioxidant activities. In this study, we aimed to investigate the mechanisms underlying the protective effect of hispidin against hydrogen peroxide (H₂O₂)-induced oxidative stress on Adult Retinal Pigment Epithelial cell line-19 (ARPE-19) cells. Hispidin was not cytotoxic to ARPE-19 cells at concentrations of less than 50 μM. The levels of intracellular reactive oxygen species (ROS) were analyzed by dichlorofluorescin diacetate (DCFDA) staining. Hispidin significantly restored H₂O₂-induced cell death and reduced the levels of intracellular ROS. The expression levels of antioxidant enzymes, such as NAD(P)H:Quinine oxidoreductase-1 (NQO-1), heme oxygenase-1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC), and glutamate-cysteine ligase modifier subunit (GCLM) were examined using real-time PCR and Western blotting. Our results showed that hispidin markedly enhanced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), HO-1, NQO-1, GCLM, and GCLC in a dose-dependent manner. Furthermore, knockdown experiments revealed that transfection with Nrf2 siRNA successfully suppresses the hispidin activated Nrf2 signaling in ARPE-19 cells. Moreover, activation of the c-Jun N-terminal kinase (JNK) pathway is involved in mediating the protective effects of hispidin on the ARPE-19 cells. Thus, the present study demonstrated that hispidin provides protection against H₂O₂-induced damage in ARPE-19 cells via activation of Nrf2 signaling and up-regulation of its downstream targets, including Phase II enzymes, which might be associated with the activation of the JNK pathway.

Transcriptome-wide analysis of differentially expressed chemokine receptors, SNPs, and SSRs in the age-related macular degeneration

Background

Age-related macular degeneration (AMD) is the most common, progressive, and polygenic cause of irreversible visual impairment in the world. The molecular pathogenesis of the primary events of AMD is poorly understood. We have investigated a transcriptome-wide analysis of differential gene expression, single-nucleotide polymorphisms (SNPs), indels, and simple sequence repeats (SSRs) in datasets of the human peripheral retina and RPE-choroid-sclera control and AMD.

Methods and results

Adaptors and unbiased components were removed and checked to ensure the quality of the data sets. Molecular function, biological process, cellular component, and pathway analyses were performed on differentially expressed genes. Analysis of the gene expression datasets identified 5011 upregulated genes, 11,800 downregulated genes, 42,016 SNPs, 1141 indels, and 6668 SRRs between healthy controls and AMD donor material. Enrichment categories for gene ontology included chemokine activity, cytokine activity, cytokine receptor binding, immune system process, and signal transduction respectively. A functional pathways analysis identified that chemokine receptors bind chemokines, complement cascade genes, and create cytokine signaling in immune system pathway genes (p value < 0.001). Finally, allele-specific expression was found to be significant for Chemokine (C-C motif) ligand (CCL) 2, 3, 4, 13, 19, 21; C-C chemokine receptor (CCR) 1, 5; chemokine (C-X-C motif) ligand (CXCL) 9, 10, 16; C-X-C chemokine receptor type (CXCR) 6; as well as atypical chemokine receptor (ACKR) 3,4 and pro-platelet basic protein (PPBP).

Conclusions

Our results improve our overall understanding of the chemokine receptors’ signaling pathway in AMD conditions, which may lead to potential new diagnostic and therapeutic targets.

Electronic supplementary material

The online version of this article (10.1186/s40246-019-0199-1) contains supplementary material, which is available to authorized users.

Celastrol protects human retinal pigment epithelial cells against hydrogen peroxide mediated oxidative stress, autophagy, and apoptosis through sirtuin 3 signal pathway

Age-related macular degeneration (AMD), one of the most common causes of visual impairment, often occurrs in the elderly in developed countries. Oxidative stress, autophagy, and apoptosis of retinal pigment epithelial (RPE) cells play roles in the pathogenesis of AMD. In the current study, the protective effect of celastrol against hydrogen peroxide (H₂ O₂ )-induced oxidative stress and apoptosis was investigated using a human RPE cell line (ARPE-19). H₂ O₂ inhibited ARPE-19 cells' survival and autophagy and induced their oxidative stress and apoptosis. Compared with the H₂ O₂ group, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay showed that celastrol increased ARPE-19 cells' survival in a dose- and time-dependent manner. Further, studies have suggested that celastrol has antioxidative stress and antiapoptosis effects in H₂ O₂ -treated ARPE-19 cells. Also, cell autophagy is activated by celastrol in H₂ O₂ -treated ARPE-19 cells. Reverse transcription polymerase chain reaction and Western blot showed that celastrol elevated the messenger RNA (mRNA) and protein expression of sirtuin 3 (SIRT3) in H₂ O₂ -induced ARPE-19 cells. Inhibition of the level of SIRT3 by SIRT3 small interfering RNA (siRNA) reversed the effects of celastrol on oxidative stress, autophagy, and apoptosis in H₂ O₂ -induced ARPE-19 cells. In conclusion, these observations suggest that celastrol activates the SIRT3 pathway in RPE cells and protects against H₂ O₂ -induced oxidative stress and apoptosis.

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

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

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

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

PEDF protects human retinal pigment epithelial cells against oxidative stress via upregulation of UCP2 expression

To investigate the protective function of pigment epithelium-derived factor (PEDF) against oxidative stress (OS) in ARPE-19 cells, ARPE-19 cells were divided into different OS groups and treated with various concentrations of H₂O₂ (0, 75, 150 and 200 µmol/l) for 24 h. To establish the protective group, 200 ng/ml of PEDF was administered to ARPE-19 cells. Cell Counting Kit-8 assays and cell growth curve experiments were performed to determine levels of cell viability; lactate dehydrogenase and propidium iodide (PI) staining assays were also performed. The expression levels of genes associated with apoptosis as well as uncoupling protein 2 (UCP2) were detected by reverse transcription-quantitative, or semi-quantitative polymerase chain reaction. Furthermore, an OS injury animal model was established in both C57BL/6 and BALB/c mice via injection of 5 µg of PEDF in the vitreous cavity and subsequent injection of 150 µM H₂O₂ following a 24 h time interval. Hematoxylin and eosin (H&E) staining, as well as UCP2 immunofluorescent labeling were also performed. One-way analysis of variance was used to determine statistically significant differences, followed by multiple comparison analysis using the Newman Keuls method. The results of cell viability assays demonstrated that the numbers of apoptotic cells were increased following treatment with H₂O₂ in a dose-dependent manner; however, this effect was reversed following treatment with PEDF. The expression levels of caspase 3 and B cell lymphoma (Bcl2) associated X genes associated with apoptosis were inhibited, whereas levels of the anti-apoptotic gene Bcl2 were enhanced following treatment with PEDF in different passages of ARPE-19 cells. Significant differences were demonstrated in the levels of UCP2 gene expression between the PEDF+ H₂O₂ treated group and cells treated with H₂O₂ alone. Labeling of the UCP2 detector in the confocal images demonstrated decreased UCP2 protein staining in the retinal pigment epithelium (RPE) cells and RPE layers following H₂O₂ injury; however, this effect was inhibited following treatment with PEDF. H&E staining was performed to investigate the thickness of the RPE layers, and the results revealed that thicknesses were significantly increased in sections treated with PEDF during OS, due to increased numbers of RPE cells. Furthermore, PEDF was demonstrated to increase UCP2 gene expression in ARPE-19 cells and animal RPE layers under OS, which suggested that PEDF may protect RPE cells and tissues during oxidative injury.