Cigarette smoking, oxidative stress, the anti-oxidant response through Nrf2 signaling, and Age-related Macular Degeneration

Immunogenetic and Environmental Factors in Age-Related Macular Disease

Age-related macular degeneration (AMD) is a chronic disease, which often develops in older people, but this is not the rule. AMD pathogenesis changes include the anatomical and functional complex. As a result of damage, it occurs, in the retina and macula, among other areas. These changes may lead to partial or total loss of vision. This disease can occur in two clinical forms, i.e., dry (progression is slowly and gradually) and exudative (wet, progression is acute and severe), which usually started as dry form. A coexistence of both forms is possible. AMD etiology is not fully understood. Extensive genetic studies have shown that this disease is multifactorial and that genetic determinants, along with environmental and metabolic-functional factors, are important risk factors. This article reviews the impact of heavy metals, macro- and microelements, and genetic factors on the development of AMD. We present the current state of knowledge about the influence of environmental factors and genetic determinants on the progression of AMD in the confrontation with our own research conducted on the Polish population from Kuyavian-Pomeranian and Lubusz Regions. Our research is concentrated on showing how polluted environments of large agglomerations affects the development of AMD. In addition to confirming heavy metal accumulation, the growth of risk of acute phase factors and polymorphism in the genetic material in AMD development, it will also help in the detection of new markers of this disease. This will lead to a better understanding of the etiology of AMD and will help to establish prevention and early treatment.

Inhibition of oxidative stress-induced epithelial-mesenchymal transition in retinal pigment epithelial cells of age-related macular degeneration model by suppressing ERK activation

INTRODUCTION

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is related to the pathogenesis of various retinopathies including age-related macular degeneration (AMD). Oxidative stress is the major factor that induces degeneration of RPE cells associated with the etiology of AMD.

OBJECTIVES

Sodium iodate (NaIO3) generates intracellular reactive oxygen species (ROS) and is widely used to establish a model of AMD due to the selective induction of retinal degeneration. This study was performed to clarify the effects of multiple NaIO3-stimulated signaling pathways on EMT in RPE cells.

METHODS

The EMT characteristics in NaIO3-treated human ARPE-19 cells and RPE cells of the mouse eyes were analyzed. Multiple oxidative stress-induced modulators were investigated and the effects of pre-treatment with Ca2+ chelator, extracellular signal-related kinase (ERK) inhibitor, or epidermal growth factor receptor (EGFR) inhibitor on NaIO3-induced EMT were determined. The efficacy of post-treatment with ERK inhibitor on the regulation of NaIO3-induced signaling pathways was dissected and its role in retinal thickness and morphology was evaluated by using histological cross-sections and spectral domain optical coherence tomography.

RESULTS

We found that NaIO3 induced EMT in ARPE-19 cells and in RPE cells of the mouse eyes. The intracellular ROS, Ca2+, endoplasmic reticulum (ER) stress marker, phospho-ERK, and phospho-EGFR were increased in NaIO3-stimulated cells. Our results showed that pre-treatment with Ca2+ chelator, ERK inhibitor, or EGFR inhibitor decreased NaIO3-induced EMT, interestingly, the inhibition of ERK displayed the most prominent effect. Furthermore, post-treatment with FR180204, a specific ERK inhibitor, reduced intracellular ROS and Ca2+ levels, downregulated phospho-EGFR and ER stress marker, attenuated EMT of RPE cells, and prevented structural disorder of the retina induced by NaIO3.

CONCLUSIONS

ERK is a crucial regulator of multiple NaIO3-induced signaling pathways that coordinate EMT program in RPE cells. Inhibition of ERK may be a potential therapeutic strategy for the treatment of AMD.

The Role of Glutathione in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a chronic disease that usually develops in older people. Pathogenetic changes in this disease include anatomical and functional complexes. Harmful factors damage the retina and macula. These changes may lead to partial or total loss of vision. The disease can occur in two clinical forms: dry (the progression is slow and gentle) and exudative (wet-progression is acute and severe), which usually starts in the dry form; however, the coexistence of both forms is possible. The etiology of AMD is not fully understood, and the precise mechanisms of the development of this illness are still unknown. Extensive genetic studies have shown that AMD is a multi-factorial disease and that genetic determinants, along with external and internal environmental and metabolic-functional factors, are important risk factors. This article reviews the role of glutathione (GSH) enzymes engaged in maintaining the reduced form and polymorphism in glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase mu-1 (GSTM1) in the development of AMD. We only chose papers that confirmed the influence of the parameters on the development of AMD. Because GSH is the most important antioxidant in the eye, it is important to know the influence of the enzymes and genetic background to ensure an optimal level of glutathione concentration. Numerous studies have been conducted on how the glutathione system works till today. This paper presents the current state of knowledge about the changes in GSH, GST, GR, and GPx in AMD. GST studies clearly show increased activity in ill people, but for GPx, the results relating to activity are not so clear. Depending on the research, the results also suggest higher and lower GPx activity in patients with AMD. The analysis of polymorphisms in GST genes confirmed that mutations lead to weaker antioxidant barriers and may contribute to the development of AMD; unfortunately, a meta-analysis and some research did not confirm that connection. Unspecific results of many of the parameters that make up the glutathione system show many unknowns. It is so important to conduct further research to understand the exact mechanism of defense functions of glutathione against oxidative stress in the human eye.

Pathologic vs. protective roles of hypoxia-inducible factor 1 in RPE and photoreceptors in wet vs. dry age-related macular degeneration

It has previously been reported that antioxidant vitamins can help reduce the risk of vision loss associated with progression to advanced age-related macular degeneration (AMD), a leading cause of visual impairment among the elderly. Nonetheless, how oxidative stress contributes to the development of choroidal neovascularization (CNV) in some AMD patients and geographic atrophy (GA) in others is poorly understood. Here, we provide evidence demonstrating that oxidative stress cooperates with hypoxia to synergistically stimulate the accumulation of hypoxia-inducible factor (HIF)-1α in the retinal pigment epithelium (RPE), resulting in increased expression of the HIF-1-dependent angiogenic mediators that promote CNV. HIF-1 inhibition blocked the expression of these angiogenic mediators and prevented CNV development in an animal model of ocular oxidative stress, demonstrating the pathological role of HIF-1 in response to oxidative stress stimulation in neovascular AMD. While human-induced pluripotent stem cell (hiPSC)-derived RPE monolayers exposed to chemical oxidants resulted in disorganization and disruption of their normal architecture, RPE cells proved remarkably resistant to oxidative stress. Conversely, equivalent doses of chemical oxidants resulted in apoptosis of hiPSC-derived retinal photoreceptors. Pharmacologic inhibition of HIF-1 in the mouse retina enhanced-while HIF-1 augmentation reduced-photoreceptor apoptosis in two mouse models for oxidative stress, consistent with a protective role for HIF-1 in photoreceptors in patients with advanced dry AMD. Collectively, these results suggest that in patients with AMD, increased expression of HIF-1α in RPE exposed to oxidative stress promotes the development of CNV, but inadequate HIF-1α expression in photoreceptors contributes to the development of GA.

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

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

The Role of Nrf2/sMAF Signalling in Retina Ageing and Retinal Diseases

Age-related diseases, such as Parkinson's disease, Alzheimer's disease, cardiovascular diseases, cancers, and age-related macular disease, have become increasingly prominent as the population ages. Oxygen is essential for living organisms, but it may also cause disease when it is transformed into reactive oxygen species via biological processes in cells. Most of the production of ROS occurs in mitochondrial complexes I and III. The accumulation of ROS in cells causes oxidative stress, which plays a crucial role in human ageing and many diseases. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key antioxidant transcription factor that plays a central role in many diseases and ageing in general. It regulates many downstream antioxidative enzymes when cells are exposed to oxidative stress. A basic-region leucine zipper (bZIP) transcription factor, MAF, specifically the small MAF subfamily (sMAFs), forms heterodimers with Nrf2, which bind with Maf-recognition elements (MAREs) in response to oxidative stress. The role of this complex in the human retina remains unclear. This review summarises the current knowledge about Nrf2 and its downstream signalling, especially its cofactor-MAF, in ageing and diseases, with a focus on the retina. Since Nrf2 is the master regulator of redox homeostasis in cells, we hypothesise that targeting Nrf2 is a promising therapeutic approach for many age-related diseases.

Mitophagy initiates retrograde mitochondrial-nuclear signaling to guide retinal pigment cell heterogeneity

Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without treatment for early disease. Degenerative retinal pigment epithelial (RPE) cell heterogeneity is a well-recognized but understudied pathogenic factor. Due to the daily phagocytosis of photoreceptor outer segments, unique photo-oxidative stress, and high metabolism for maintaining vision, the RPE has robust macroautophagy/autophagy, and mitochondrial and antioxidant networks. However, the autophagy subtype, mitophagy, in the RPE and AMD is understudied. Here, we found decreased PINK1 (PTEN induced kinase 1) in perifoveal RPE of early AMD eyes. PINK1-deficient RPE have impaired mitophagy and mitochondrial function that triggers death-resistant epithelial-mesenchymal transition (EMT). This reprogramming is mediated by novel retrograde mitochondrial-nuclear signaling (RMNS) through superoxide, NFE2L2 (NFE2 like bZIP transcription factor 2), TXNRD1 (thioredoxin reductase 1), and phosphoinositide 3-kinase (PI3K)-AKT (AKT serine/threonine kinase) that induced canonical transcription factors ZEB1 (zinc finger E-box binding homeobox 1) and SNAI1 (Snail family transcriptional repressor 1) and an EMT transcriptome. NFE2L2 deficiency disrupted RMNS that paradoxically normalized morphology but decreased function and viability. Thus, RPE heterogeneity is defined by the interaction of two cytoprotective pathways that is triggered by mitophagy function. By neutralizing the consequences of impaired mitophagy, an antioxidant dendrimer tropic for the RPE and mitochondria, EMT (a recognized AMD alteration) was abrogated to offer potential therapy for early AMD, a stage without treatment.Abbreviations: ACTB: actin beta; AKT: AKT serine/threonine kinase; AMD: age-related macular degeneration; CCCP: cyanide m-chlorophenyl hydrazone; CDH1: cadherin 1; DAVID: Database for Annotation, Visualization and Integrated Discovery; DHE: dihydroethidium; D-NAC: N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; ECAR: extracellular acidification rate; EMT: epithelial-mesenchymal transition; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GSEA: Gene Set Enrichment Analysis; HSPD1: heat shock protein family D (Hsp60) member 1; IVT: intravitreal; KD: knockdown; LMNA, lamin A/C; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MMP: mitochondrial membrane potential; NAC: N-acetyl-l-cysteine; NQO1: NAD(P)H quinone dehydrogenase 1; NFE2L2: NFE2 like bZIP transcription factor 2; O2-: superoxide anion; OCR: oxygen consumption rate; PI3K: phosphoinositide 3-kinase; PINK1: PTEN induced kinase 1; RMNS: retrograde mitochondrial-nuclear signaling; ROS: reactive oxygen species; RPE: retinal pigment epithelium; SNAI1: snail family transcriptional repressor 1; TJP1: tight junction protein 1; TPP-D-NAC: triphenyl phosphinium and N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; Trig: trigonelline; TXNRD1: thioredoxin reductase 1; VIM: vimentin; WT: wild-type; ZEB1: zinc finger E-box binding homeobox 1.

Oxidative stress alters transcript localization of disease-associated genes in the retinal pigment epithelium

PURPOSE

Nuclear retention is a mechanism whereby excess RNA transcripts are stored in the event that a cell needs to quickly respond to a stimulus; maintaining proper nuclear-to-cytoplasmic balance is important for cellular homeostasis and cell function. There are many mechanisms that are employed to determine whether to retain a transcript or export it to the cytoplasm, although the extent to which tissue or cell type, internal and external stressors, and disease pathogenesis affect this process is not yet clear. As the most biochemically active tissue in the body, the retina must mitigate endogenous and exogenous stressors to maintain cell health and tissue function. Oxidative stress, believed to contribute to the pathogenesis or progression of age-related macular degeneration (AMD) and inherited retinal dystrophies (IRDs), is produced both internally from biochemical processes as well as externally from environmental insult. Here, we evaluate the effect of oxidative stress on transcript localization in the retinal pigment epithelium (RPE), with specific focus on transcripts related to RPE function and disease.

METHODS

We performed poly(A) RNA sequencing on nuclear and cytoplasmic fractions from human induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) cells exposed to hydrogen peroxide (H₂O₂), as well as on untreated controls.

RESULTS

Under normal conditions, the number of mRNA transcripts retained in the nucleus exceeded that found in studies on other tissues. Further, the nuclear-to-cytoplasmic ratio of transcripts was altered following oxidative stress, as was the retention of genes associated with AMD and IRDs, as well as those that are important for RPE physiology.

CONCLUSIONS

These results provide a localization catalog of all expressed mRNA in iPSC-RPE under normal conditions and after exposure to H₂O₂, shedding light on the extent to which H₂O₂ alters transcript localization and potentially offering insight into one mechanism through which oxidative stress may contribute to the progression of visual disorders.

The effect of a chrysanthemum water extract in protecting the retina of mice from light damage

Background

Oxidative stress can induce age-related diseases. Age-related retinal diseases, such as age-related macular degeneration (AMD), are difficult to cure owing to their complicated mechanisms. Although anti-neovascular therapeutics are used to treat wet AMD, vision cannot always be completely restored, and disease progression cannot always be inhibited. Therefore, determining a method to prevent or slow retinal damage is important. This study aimed to investigate the protective effect of a chrysanthemum water extract rich in flavone on the oxidatively stressed retina of mice.

Methods

Light damage was induced to establish oxidative stress mouse models. For in vitro experiments, ARPE-19 cells were cultured and divided into four groups: control, light-damaged, and low- and high-dose chrysanthemum extract. No treatment was administered in the control group. The light-damaged and low- and high-dose chrysanthemum extract groups were exposed to a similar white light level. The chrysanthemum extract was added at a low dose of 0.4 mg/mL or a high dose of 1.0 mg/mL before cell exposure to 2500-lx white light. Reactive oxygen species (ROS) level and cellular viability were measured using MTT and immunofluorescence staining. For in vivo experiments, C57BL/6 J mice were divided into the same four groups. Low- (0.23 g/kg/day) and high-dose (0.38 g/kg/day) chrysanthemum extracts were continuously intragastrically administered for 8 weeks before mouse exposure to 10,000-lx white light. Retinal function was evaluated using electroretinography. In vivo optical coherence tomography and in vitro haematoxylin and eosin staining were performed to observe the pathological retinal changes in each group after light damage. Fluorescein fundus angiography of the arteriovenous vessel was performed, and the findings were analysed using the AngioTool software. TUNEL immunofluorescence staining was used to assess isolated retinal apoptosis.

Results

In vitro, increased ROS production and decreased ARPE-19 cell viability were found in the light-damaged group. Improved ARPE-19 cell viability and reduced ROS levels were observed in the chrysanthemum extract treatment groups. In vivo, dysfunctional retinas and abnormal retinal structures were found in the light-damaged group, as well as increased apoptosis in the retinal ganglion cells (RGCs) and inner and outer nuclear layers. The apoptosis rate in the same layers was lower in the chrysanthemum extract treatment groups than in the light-damaged group. The production of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), increased in the treatment groups. NF-κB in the nucleus and TNF-α were more highly expressed in the light-damaged group than in the low- and high-dose chrysanthemum extract groups.

Conclusions

Light damage-induced retinal oxidative stress can lead to ROS accumulation in the retinal tissues. Herein, RGC and photoreceptor layer apoptosis was triggered, and NF-κB in the nucleus and TNF-α were highly expressed in the light-damaged group. Preventive chrysanthemum extract administration decreased ROS production by increasing SOD, CAT, and GSH-Px activities and reversing the negative changes, demonstrating a potential protective effect on the retina.

Exploring the lncRNA localization landscape within the retinal pigment epithelium under normal and stress conditions

Background

Long noncoding RNAs (lncRNAs) are emerging as a class of genes whose importance has yet to be fully realized. It is becoming clear that the primary function of lncRNAs is to regulate gene expression, and they do so through a variety of mechanisms that are critically tied to their subcellular localization. Although most lncRNAs are poorly understood, mapping lncRNA subcellular localization can provide a foundation for understanding these mechanisms.

Results

Here, we present an initial step toward uncovering the localization landscape of lncRNAs in the human retinal pigment epithelium (RPE) using high throughput RNA-Sequencing (RNA-Seq). To do this, we differentiated human induced pluripotent stem cells (iPSCs) into RPE, isolated RNA from nuclear and cytoplasmic fractions, and performed RNA-Seq on both. Furthermore, we investigated lncRNA localization changes that occur in response to oxidative stress. We discovered that, under normal conditions, most lncRNAs are seen in both the nucleus and the cytoplasm to a similar degree, but of the transcripts that are highly enriched in one compartment, far more are nuclear than cytoplasmic. Interestingly, under oxidative stress conditions, we observed an increase in lncRNA localization in both nuclear and cytoplasmic fractions. In addition, we found that nuclear localization was partially attributable to the presence of previously described nuclear retention motifs, while adenosine to inosine (A-to-I) RNA editing appeared to play a very minimal role.

Conclusions

Our findings map lncRNA localization in the RPE and provide two avenues for future research: 1) how lncRNAs function in the RPE, and 2) how one environmental factor, in isolation, may potentially play a role in retinal disease pathogenesis through altered lncRNA localization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08777-1.

Effect of Photobiomodulation in Suppression of Oxidative Stress on Retinal Pigment Epithelium

As the world undergoes aging, the number of age-related diseases has increased. One of them is disease related to retinal pigment epithelium (RPE) degeneration, such as age-related macular degeneration, causing vision loss without physical damage in the ocular system. It is the leading cause of blindness, with no cure. Although the exact pathogenesis is still unknown, the research shows that oxidative stress is one of the risk factors. Various molecules have been reported as anti-oxidative materials; however, the disease has not yet been conquered. Here, we would like to introduce photobiomodulation (PBM). PBM is a non-invasive treatment based on red and near-infrared light and has been used to cure various diseases by regulating cellular functions. Furthermore, recent studies showed its antioxidant effect, and due to this reason, PBM is arising as a new treatment for ocular disease. In this study, we confirm the antioxidant effect of PBM in retinal pigment epithelium via an RPE model with hypoxia. The function of RPE is protected by PBM against damage from hypoxia. Furthermore, we observed the protective mechanism of PBM by its suppression effect on reactive oxygen species generation. These results indicate that PBM shows great potential to cure RPE degeneration to help patients with blindness.

Bisphenol A induced apoptosis via oxidative stress generation involved Nrf2/HO-1 pathway and mitochondrial dependent pathways in human retinal pigment epithelium (ARPE-19) cells

Bisphenol A (BPA) is an estrogen-like compound, and an environmental hormone, that is commonly used in daily life. Therefore, it may enter the human body through food or direct contact, causing BPA residues in blood and urine. Because most studies focused on the analysis of BPA in reproductive cells or tissues, regarding evidence the effect of BPA on human retinal pigment epithelium (ARPE-19) cells unavailable. Accordingly, the present study explored the cytotoxicity of BPA on ARPE-19 cells. After BPA treatment, the expression of Bcl-XL an antiapoptotic protein, in the mitochondria decreased, and the expression of Bax, a proapoptotic protein increased. Then the mitochondrial membrane potential was affected. BPA changed in mitochondrial membrane potential led to the release of cytochrome C, which activated caspase-9 to promote downstream caspase-3 leading to cytotoxicity. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase 1 (HO-1) pathway play a major role in age-related macular degeneration. Our results showed that expression of HO-1 and Nrf2 suppressed by BPA. Superoxide dismutase and catalase, which Nrf2 downstream antioxidants, were degraded by BPA. AMP-activated kinase (AMPK), which can regulate the phosphorylation of Nrf2, and the phosphorylation of AMPK expression was reduced by BPA. Finally, BPA-induced ROS generation and cytotoxicity were reduced by N-acetyl-l-cysteine. Taken together, these results suggest that BPA induced ARPE-19 cells via oxidative stress, which was associated with down regulated Nrf2/HO-1 pathway, and the mitochondria dependent apoptotic signaling pathway.

Pinosylvin Extract Retinari™ Sustains Electrophysiological Function, Prevents Thinning of Retina, and Enhances Cellular Response to Oxidative Stress in NFE2L2 Knockout Mice

Chronic oxidative stress eventually leads to protein aggregation in combination with impaired autophagy, which has been observed in age-related macular degeneration. We have previously shown an effective age-related macular degeneration disease model in mice with nuclear factor-erythroid 2-related factor-2 (NFE2L2) knockout. We have also shown pinosylvin, a polyphenol abundant in bark waste, to increase human retinal pigment epithelium cell viability in vitro. In this work, the effects of commercial natural pinosylvin extract, Retinari™, were studied on the electroretinogram, optical coherence tomogram, autophagic activity, antioxidant capacity, and inflammation markers. Wild-type and NFE2L2 knockout mice were raised until the age of 14.8 ± 3.8 months. They were fed with either regular or Retinari™ chow (141 ± 17.0 mg/kg/day of pinosylvin) for 10 weeks before the assays. Retinari™ treatment preserved significant retinal function with significantly preserved a- and b-wave amplitudes in the electroretinogram responses. Additionally, the treatment prevented thinning of the retina in the NFE2L2 knockout mice. The NFE2L2 knockout mice showed reduced ubiquitin-tagged protein accumulation in addition to local upregulation of complement factor H and antioxidant enzymes superoxide dismutase 1 and catalase. Therefore, the treatment in the NFE2L2 KO disease model led to reduced chronic oxidative stress and sustained retinal function and morphology. Our results demonstrate that pinosylvin supplementation could potentially lower the risk of age-related macular degeneration onset and slow down its progression.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

Complement factor H deficiency combined with smoking promotes retinal degeneration in a novel mouse model

Age-related macular degeneration is the leading cause of blindness in the elderly. The Y402H polymorphism in complement factor H promotes disease-like pathogenesis, and a Cfh^+/- murine model can replicate this phenotype, but only after two years. We reasoned that by combining CFH deficiency with cigarette smoke exposure, we might be able to accelerate disease progression to facilitate preclinical research in this disease. Wild-type and Cfh^+/- mice were exposed to nose-only cigarette smoke for three months. Retinal tissue morphology and visual function were evaluated by optical coherence tomography, fundus photography and autofluorescence, and electroretinogram. Retinal pigment epithelial cell phenotype and ultrastructure were evaluated by immunofluorescence staining and transmission electron microscopy. Cfh^+/- smoking mice showed a dome-like protruding lesion at the ellipsoid zone (drusen-like deposition), many retinal hyper-autofluorescence spots, and a marked decrease in A- and B-wave amplitudes. Compared with non-smoking mice, wild-type and Cfh^+/- smoking mice showed sub-retinal pigment epithelium complement protein 3 deposition, activation of microglia, metabolic waste accumulation, and impairment of tight junctions. Microglia cells migrated into the photoreceptor outer segment layer in Cfh^+/- smoking mice showed increased activation. Our results suggest that exposing Cfh^+/- mice to smoking leads to earlier onset of age-related macular degeneration than in other animal models, which may facilitate preclinical research into the pathophysiology and treatment of this disease.

Ongoing controversies and recent insights of the ARMS2-HTRA1 locus in age-related macular degeneration

Age-related macular degeneration (AMD) is the most common cause of central vision loss among elderly populations in industrialized countries. Genome-wide association studies have consistently associated two genomic loci with progression to late-stage AMD: the complement factor H (CFH) locus on chromosome 1q31 and the age-related maculopathy susceptibility 2-HtrA serine peptidase 1 (ARMS2-HTRA1) locus on chromosome 10q26. While the CFH risk variant has been shown to alter complement activity, the ARMS2-HTRA1 risk haplotype remains enigmatic due to high linkage disequilibrium and inconsistent functional findings spanning two genes that are plausibly causative for AMD risk. In this review, we detail the genetic and functional evidence used to support either ARMS2 or HTRA1 as the causal gene for AMD risk, emphasizing both the historical development and the current understanding of the ARMS2-HTRA1 locus in AMD pathogenesis. We conclude by summarizing the evidence in favor of HTRA1 and present our hypothesis whereby HTRA1-derived ECM fragments mediate AMD pathogenesis.

Oxidative and Nitrosative Stress in Age-Related Macular Degeneration: A Review of Their Role in Different Stages of Disease

Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered expression of the different isoforms of NO synthases could be involved in choroidal microvascular changes leading to neovascularization. The purpose of this review was to investigate the different pathways activated by oxidative/nitrosative stress in the pathogenesis of AMD, focusing on the mechanisms leading to neovascularization and on the possible protective role of anti-vascular endothelial growth factor agents in this context.

Histopathology of Age-Related Macular Degeneration and Implications for Pathogenesis and Therapy

Aging is associated with a number of histological changes in the choroid, Bruch's membrane, RPE, and neuroretina. Outside of the normal physiologic aging spectrum of changes, abnormal deposits such as basal laminar deposits, basal linear deposits, and soft drusen are known to be associated with AMD. Progression of AMD to advanced stages involving geographic atrophy, choroidal neovascularization, and/or disciform scars can result in debilitating vision loss. Knowledge of the angiogenic pathway and its components that stimulate neovascularization has led to the development of a new paradigm of intravitreal anti-VEGF pharmacotherapy in the management of neovascular AMD. Currently however, there are no available treatments for the modification of disease progression in non-neovascular AMD, or for the treatment of geographic atrophy. Further understanding of the histopathology of AMD and the molecular mechanisms that contribute to pathogenesis of the disease may reveal additional therapeutic targets.

Nanotechnology: revolutionizing the delivery of drugs to treat age-related macular degeneration

Introduction: Age-related macular degeneration (AMD) is a progressive retinal disease that degrades the eye's ability to grasp visual acuity. The antivascular endothelial growth factor (VEGF) therapies have made significant strides in improving the quality of life, and there is a continued opportunity to improve delivery, outcomes, and patient convenience and compliance. The treatments available could gain better clinical outcome from novel therapeutics through nanotechnology application.Areas covered: This review summarizes AMD biology and the pathophysiology of the disease along with the successes and limitations of available therapies. It further discusses the promising nanotechnology modalities that could become the cornerstone of future AMD research for improving delivery and reducing frequency of administration thus, enabling development of novel therapeutics.Expert opinion: The robust translation from preclinical work to clinical outcome for AMD remains an unmet need. Continuing to investigate in deeper understanding of biology and advancing high-quality targets into the clinic in combination with the application of advanced nanotechnology to design patient-centric offerings for both dry and wet AMD is needed. Because of the lack of regulatory precedence, and challenging manufacturing and supply chain need, the future of nano-enabled technologies is challenging but presents exciting treatment options for AMD.

Role of Retinal Amyloid-β in Neurodegenerative Diseases: Overlapping Mechanisms and Emerging Clinical Applications

Amyloid-β (Aβ) accumulations have been identified in the retina for neurodegeneration-associated disorders like Alzheimer's disease (AD), glaucoma, and age-related macular degeneration (AMD). Elevated retinal Aβ levels were associated with progressive retinal neurodegeneration, elevated cerebral Aβ accumulation, and increased disease severity with a decline in cognition and vision. Retinal Aβ accumulation and its pathological effects were demonstrated to occur prior to irreversible neurodegeneration, which highlights its potential in early disease detection and intervention. Using the retina as a model of the brain, recent studies have focused on characterizing retinal Aβ to determine its applicability for population-based screening of AD, which warrants a further understanding of how Aβ manifests between these disorders. While current treatments directly targeting Aβ accumulations have had limited results, continued exploration of Aβ-associated pathological pathways may yield new therapeutic targets for preserving cognition and vision. Here, we provide a review on the role of retinal Aβ manifestations in these distinct neurodegeneration-associated disorders. We also discuss the recent applications of retinal Aβ for AD screening and current clinical trial outcomes for Aβ-associated treatment approaches. Lastly, we explore potential future therapeutic targets based on overlapping mechanisms of pathophysiology in AD, glaucoma, and AMD.

Exacerbation of AMD Phenotype in Lasered CNV Murine Model by Dysbiotic Oral Pathogens

Emerging evidence underscores an association between age-related macular degeneration (AMD) and periodontal disease (PD), yet the biological basis of this linkage and the specific role of oral dysbiosis caused by PD in AMD pathophysiology remains unclear. Furthermore, a simple reproducible model that emulates characteristics of both AMD and PD has been lacking. Hence, we established a novel AMD+PD murine model to decipher the potential role of oral infection (ligature-enhanced) with the keystone periodontal pathogen Porphyromonas gingivalis, in the progression of neovasculogenesis in a laser-induced choroidal-neovascularization (Li-CNV) mouse retina. By a combination of fundus photography, optical coherence tomography, and fluorescein angiography, we documented inflammatory drusen-like lesions, reduced retinal thickness, and increased vascular leakage in AMD+PD mice retinae. H&E further confirmed a significant reduction of retinal thickness and subretinal drusen-like deposits. Immunofluorescence microscopy revealed significant induction of choroidal/retinal vasculogenesis in AMD+PD mice. qPCR identified increased expression of oxidative-stress, angiogenesis, pro-inflammatory mediators, whereas antioxidants and anti-inflammatory genes in AMD+PD mice retinae were notably decreased. Through qPCR, we detected Pg and its fimbrial 16s-RrNA gene expression in the AMD+PD mice retinae. To sum-up, this is the first in vivo study signifying a role of periodontal infection in augmentation of AMD phenotype, with the aid of a pioneering AMD+PD murine model established in our laboratory.

Immunological Aspects of Age-Related Macular Degeneration

Increasing evidence over the past two decades points to a pivotal role for immune mechanisms in age-related macular degeneration (AMD) pathobiology. In this chapter, we will explore immunological aspects of AMD, with a specific focus on how immune mechanisms modulate clinical phenotypes of disease and severity and how components of the immune system may serve as triggers for disease progression in both dry and neovascular AMD. We will briefly review the biology of the immune system, defining the role of immune mechanisms in chronic degenerative disease and differentiating from immune responses to acute injury or infection. We will explore current understanding of the roles of innate immunity (especially macrophages), antigen-specific immunity (T cells, B cells, and autoimmunity), immune amplifications systems, especially complement activity and the NLRP3 inflammasome, in the pathogenesis of both dry and neovascular AMD, reviewing data from pathology, experimental animal models, and clinical studies of AMD patients. We will also assess how interactions between the immune system and infectious pathogens could potentially modulate AMD pathobiology via alterations in in immune effector mechanisms. We will conclude by reviewing the paradigm of "response to injury," which provides a means to integrate various immunologic mechanisms along with nonimmune mechanisms of tissue injury and repair as a model to understand the pathobiology of AMD.

Curcumin Metabolite Tetrahydrocurcumin in the Treatment of Eye Diseases

Curcumin is one of the most valuable natural products due to its pharmacological activities. However, the low bioavailability of curcumin has long been a problem for its medicinal use. Large studies have been conducted to improve the use of curcumin; among these studies, curcumin metabolites have become a relatively new research focus over the past few years. Additionally, accumulating evidence suggests that curcumin or curcuminoid metabolites have similar or better biological activity than the precursor of curcumin. Recent studies focus on the protective role of plasma tetrahydrocurcumin (THC), a main metabolite of curcumin, against tumors and chronic inflammatory diseases. Nevertheless, studies of THC in eye diseases have not yet been conducted. Since ophthalmic conditions play a crucial role in worldwide public health, the prevention and treatment of ophthalmic diseases are of great concern. Therefore, the present study investigated the antioxidative, anti-inflammatory, antiangiogenic, and neuroprotective effects of THC on four major ocular diseases: age-related cataracts, glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR). While this study aimed to show curcumin as a promising potential solution for eye conditions and discusses the involved mechanistic pathways, further work is required for the clinical application of curcumin.

Beyond AREDS Formulations, What Is Next for Intermediate Age-Related Macular Degeneration (iAMD) Treatment? Potential Benefits of Antioxidant and Anti-inflammatory Apocarotenoids as Neuroprotectors

Age-related macular degeneration (AMD) is the commonest cause of severe visual loss and blindness in developed countries among individuals aged 60 and older. AMD slowly progresses from early AMD to intermediate AMD (iAMD) and ultimately late-stage AMD. Late AMD encompasses either neovascular AMD (nAMD) or geographic atrophy (GA). nAMD is defined by choroidal neovascularization (CNV) and hemorrhage in the subretinal space at the level of the macula. This induces a rapid visual impairment caused by the death of photoreceptor cells. Intravitreal injection of anti-vascular endothelial growth factor (VEGF) antibodies is the standard treatment of nAMD but adds to the burden of patient care. GA is characterized by slowly expanding photoreceptor, and retinal pigment epithelium (RPE) degeneration patches progressively leading to blindness. There is currently no therapy to cure GA. Late AMD continues to be an unmet medical need representing a major health problem with millions of patients worldwide. Oxidative stress and inflammation are recognized as some of the main risk factors to developing late AMD. The antioxidant formulation AREDS (Age-Related Eye Disease Studies), contains β-carotene, which has been replaced by lutein and zeaxanthin in AREDS2, are given to patients with iAMD but have a limited effect on the incidence of nAMD and GA. Thus, to avoid or slowdown the development of late stages of AMD (nAMD or GA), new therapies targeting iAMD are needed such as crocetin obtained through hydrolysis of crocin, an important component of saffron (Crocus sativus L.), and norbixin derived from bixin extracted from Bixa orellana seeds. We have shown that these apocarotenoids preserved more effectively RPE cells against apoptosis following blue light exposure in the presence of A2E than lutein and zeaxanthin. In this review, we will discuss the potential use of apocarotenoids to slowdown the progression of iAMD, to reduce the incidence of both forms of late AMD.

Evolution of oxidative stress, inflammation and neovascularization in the choroid and retina in a subretinal lipid induced age-related macular degeneration model

Oxidative stress, inflammation and neovascularization are the key pathological events that are implicated in human age-related macular degeneration (AMD). There are a limited number of animal models available for evaluating and developing new therapies. Most models represent late exudative or neovascular AMD (nAMD) but there is a relative paucity of models that mimic early events in AMD. The purpose of this study is to characterize the evolution of oxidative stress, inflammation, retinal degeneration and neovascularization in a rat model of AMD, created by subretinal injection of human lipid hydroperoxide (HpODE) that found in the sub-macular region in aged and AMD patients. Subretinal HpODE induced retinal pigment epithelium (RPE) and retinal degeneration resulting in loss of RPE cells, photoreceptors and retinal thinning. RPE degeneration and atrophy were detected by day 5, followed by neural tissue degeneration at day 12 with robust TUNEL positive cells. Western blot analysis confirmed an increase in pro-apoptotic Bak protein at day 12 in retinal tissues. Oxidative damage biomarkers (4-hydroxynonenal, malondialdehyde, 8-hydroxy-2'-deoxyguanosine, and nitrotyrosine) increased in retinal tissue from days 5-12. Müller glial activation was observed in the HpODE injected area at day 5 followed by its remodeling and migration in the outer retina by day 20. RT-qPCR analysis further indicated upregulation of pro-inflammatory genes (TNF-α, IL-1β and IL-6) both in retinal and RPE/choroidal tissue as early as day 2 and persisted until day 12. Upregulation of oxidative stress markers such as NADPH oxidase (NOX and DOUX family) was detected early in retinal tissue by day 2 followed by its upregulation in choroidal tissue at day 5. Neovascularization was demonstrated from day 12 to day 20 post HpODE injection in choroidal tissue. The results from this study indicate that subretinal HpODE induces advanced AMD phenotypes comprising many aspects of both dry/early and late) and neovascular/late AMD as observed in humans. Within 3 weeks via oxidative damage, upregulation of reactive oxygen species and pro-inflammatory genes, pro-apoptotic Bak and pro-angiogenic VEGF upregulation occurs leading to CNV formation. This experimental model of subretinal HpODE is an appropriate model for the study of AMD and provides an important platform for translational and basic research in developing new therapies particularly for early/dry AMD where currently no viable therapies are available.

Oxidative stress and mitochondrial transfer: A new dimension towards ocular diseases

Ocular cells like, retinal pigment epithelium (RPE) is a highly specialized pigmented monolayer of post-mitotic cells, which is located in the posterior segment of the eye between neuro sensory retina and vascular choroid. It functions as a selective barrier and nourishes retinal visual cells. As a result of high-level oxygen consumption of retinal cells, RPE cells are vulnerable to chronic oxidative stress and an increased level of reactive oxygen species (ROS) generated from mitochondria. These oxidative stress and ROS generation in retinal cells lead to RPE degeneration. Various sources including mtDNA damage could be an important factor of oxidative stress in RPE. Gene therapy and mitochondrial transfer studies are emerging fields in ocular disease research. For retinal degenerative diseases stem cell-based transplantation methods are developed from basic research to preclinical and clinical trials. Translational research contributions of gene and cell therapy would be a new strategy to prevent, treat and cure various ocular diseases. This review focuses on the effect of oxidative stress in ocular cell degeneration and recent translational researches on retinal degenerative diseases to cure blindness.

Protective Effects and Molecular Signaling of n-3 Fatty Acids on Oxidative Stress and Inflammation in Retinal Diseases

Oxidative stress and inflammation play crucial roles in the development and progression of retinal diseases. Retinal damage by various etiologies can result in retinopathy of prematurity (ROP), diabetic retinopathy (DR), and age-related macular degeneration (AMD). n-3 fatty acids are essential fatty acids and are necessary for homeostasis. They are important retinal membrane components and are involved in energy storage. n-3 fatty acids also have antioxidant and anti-inflammatory properties, and their suppressive effects against ROP, DR, and AMD have been previously evaluated. α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and their metabolites have been shown to alleviate retinal oxidative stress and inflammation involving various biological signaling pathways. In this review, we summarize the current understanding of the n-3 fatty acids effects on the mechanisms of these retinal diseases and how they exert their therapeutic effects, focusing on ALA, EPA, DHA, and their metabolites. This knowledge may provide new remedial strategies for n-3 fatty acids in the prevention and treatment of retinal diseases associated with oxidative stress and inflammation.

Oxidative stress as a therapeutic target for the prevention and treatment of early age-related macular degeneration

Age-related macular degeneration, the leading cause of irreversible visual loss among older adults in developed countries, is a chronic, multifactorial, and progressive disease with the development of painless, central vision loss. Retinal pigment epithelial cell dysfunction is a core change in age-related macular degeneration that results from aging and the accumulated effects of genetic and environmental factors that, in part, is both caused by and leads to oxidative stress. In this review, we describe the role of oxidative stress, the cytoprotective oxidative stress pathways, and the impact of oxidative stress on critical cellular processes involved in age-related macular degeneration pathobiology. We also offer targeted therapy that may define how antioxidant therapy can either prevent or improve specific stages of age-related macular degeneration.

Retinal pigment epithelium transcriptome analysis in chronic smoking reveals a suppressed innate immune response and activation of differentiation pathways

Cigarette smoking, a powerful mixture of chemical oxidants, is the strongest environmental risk factor for developing age-related macular degeneration (AMD), the most common cause of blindness among the elderly in western societies. Despite intensive study, the full impact of smoking on the retinal pigment epithelium (RPE), a central cell type involved in AMD pathobiology, remains unknown. The relative contribution of the known dysfunctional pathways to AMD, at what stage they are most pathogenic, or whether other processes are relevant, is poorly understood, and furthermore, whether smoking activates them, is unknown. We performed global RNA-sequencing of the RPE from C57BL/6J mice exposed to chronic cigarette smoke for 6 months to identify potential pathogenic and cytoprotective pathways. The RPE transcriptome induced by chronic cigarette smoking exhibited a mixed response of marked suppression of the innate immune response including type I and II interferons and upregulation of cell differentiation and morphogenic gene clusters, suggesting an attempt by the RPE to maintain its differentiated state despite smoke-induced injury. Given that mice exposed to chronic smoke develop early features of AMD, these novel findings are potentially relevant to the transition from aging to AMD.

Functional imaging of mitochondria in retinal diseases using flavoprotein fluorescence

Mitochondria are critical for cellular energy production and homeostasis. Oxidative stress and associated mitochondrial dysfunction are integral components of the pathophysiology of retinal diseases, including diabetic retinopathy (DR), age-related macular degeneration, and glaucoma. Within mitochondria, flavoproteins are oxidized and reduced and emit a green autofluorescence when oxidized following blue light excitation. Recently, a noninvasive imaging device was developed to measure retinal flavoprotein fluorescence (FPF). Thus, oxidized FPF can act as a biomarker of mitochondrial dysfunction. This review article describes the literature surrounding mitochondrial FPF imaging in retinal disease. The authors describe the role of mitochondrial dysfunction in retinal diseases, experiments using FPF as a marker of mitochondrial dysfunction in vitro, the three generations of retinal FPF imaging devices, and the peer-reviewed publications that have examined FPF imaging in patients. Finally, the authors report their own study findings. Goals were to establish normative reference levels for FPF intensity and heterogeneity in healthy eyes, to compare between healthy eyes and eyes with diabetes and DR, and to compare across stages of DR. The authors present methods to calculate a patient's expected FPF values using baseline characteristics. FPF intensity and heterogeneity were elevated in diabetic eyes compared to age-matched control eyes, and in proliferative DR compared to diabetic eyes without retinopathy. In diabetic eyes, higher FPF heterogeneity was associated with poorer visual acuity. In conclusion, while current retinal imaging modalities frequently focus on structural features, functional mitochondrial imaging shows promise as a metabolically targeted tool to evaluate retinal disease.

Autophagy Upregulation by the TFEB Inducer Trehalose Protects against Oxidative Damage and Cell Death Associated with NRF2 Inhibition in Human RPE Cells

Trehalose is a natural dietary molecule that has shown antiaging and neuroprotective effects in several animal models of neurodegenerative diseases. The role of trehalose in the management of age-related macular degeneration (AMD) is yet to be investigated and whether trehalose could be a remedy for the treatment of diseases linked to oxidative stress and NRF2 dysregulation. Here, we showed that incubation of human retinal pigment epithelial (RPE) cells with trehalose enhanced the mRNA and protein expressions of TFEB, autophagy genes ATG5 and ATG7, as well as protein expressions of macroautophagy markers, LC3B and p62/SQTM1, and the chaperone-mediated autophagy (CMA) receptor LAMP2. Cathepsin D, a hydrolytic lysosomal enzyme, was also increased by trehalose, indicating higher proteolytic activity. Moreover, trehalose upregulated autophagy flux evident by an increase in the endogenous LC3B level, and accumulation of GFP-LC3B puncta and free GFP fragments in GFP-LC3 - expressing cells in the presence of chloroquine. In addition, the mRNA levels of key molecular targets implicated in RPE damage and AMD, such as vascular endothelial growth factor- (VEGF-) A and heat shock protein 27 (HSP27), were downregulated, whereas NRF2 was upregulated by trehalose. Subsequently, we mimicked in vitro AMD conditions using hydroquinone (HQ) as the oxidative insult on RPE cells and evaluated the cytoprotective effect of trehalose compared to vehicle treatment. HQ depleted NRF2, increased oxidative stress, and reduced the viability of cells, while trehalose pretreatment protected against HQ-induced toxicity. The cytoprotection by trehalose was dependent on autophagy but not NRF2 activation, since autophagy inhibition by shRNA knockdown of ATG5 led to a loss of the protective effect. The results support the transcriptional upregulation of TFEB and autophagy by trehalose and its protection against HQ-induced oxidative damage in RPE cells. Further investigation is, therefore, warranted into the therapeutic value of trehalose in alleviating AMD and retinal diseases associated with impaired NRF2 antioxidant defense.

The Relevance of Oxidative Stress in the Pathogenesis and Therapy of Retinal Dystrophies

Retinal cell survival requires an equilibrium between oxygen, reactive oxygen species, and antioxidant molecules that counteract oxidative stress damage. Oxidative stress alters cell homeostasis and elicits a protective cell response, which is most relevant in photoreceptors and retinal ganglion cells, neurons with a high metabolic rate that are continuously subject to light/oxidative stress insults. We analyze how the alteration of cellular endogenous pathways for protection against oxidative stress leads to retinal dysfunction in prevalent (age-related macular degeneration, glaucoma) as well as in rare genetic visual disorders (Retinitis pigmentosa, Leber hereditary optic neuropathy). We also highlight some of the key molecular actors and discuss potential therapies using antioxidants agents, modulators of gene expression and inducers of cytoprotective signaling pathways to treat damaging oxidative stress effects and ameliorate severe phenotypic symptoms in multifactorial and rare retinal dystrophies.

Mouse Models of Inherited Retinal Degeneration with Photoreceptor Cell Loss

Inherited retinal degeneration (RD) leads to the impairment or loss of vision in millions of individuals worldwide, most frequently due to the loss of photoreceptor (PR) cells. Animal models, particularly the laboratory mouse, have been used to understand the pathogenic mechanisms that underlie PR cell loss and to explore therapies that may prevent, delay, or reverse RD. Here, we reviewed entries in the Mouse Genome Informatics and PubMed databases to compile a comprehensive list of monogenic mouse models in which PR cell loss is demonstrated. The progression of PR cell loss with postnatal age was documented in mutant alleles of genes grouped by biological function. As anticipated, a wide range in the onset and rate of cell loss was observed among the reported models. The analysis underscored relationships between RD genes and ciliary function, transcription-coupled DNA damage repair, and cellular chloride homeostasis. Comparing the mouse gene list to human RD genes identified in the RetNet database revealed that mouse models are available for 40% of the known human diseases, suggesting opportunities for future research. This work may provide insight into the molecular players and pathways through which PR degenerative disease occurs and may be useful for planning translational studies.

Cell-based approaches towards treating age-related macular degeneration

Age-related macular degeneration as one of the most common causes of worldwide vision loss needs a proper approach for treatment. Therein, cell therapy and regenerative medicine can hold a great promise to be an effective approach. Accordingly, some preclinical and clinical studies were conducted to search around the therapeutic influence of stem cells in Age-related macular degeneration models and subjects. Hereupon, the purpose of the current review is to discuss the mechanisms of age-related macular degeneration, appropriate animal models along with suitable dosage and route of stem cell administration for its treatment.

Structure based modification of chalcone analogue activates Nrf2 in the human retinal pigment epithelial cell line ARPE-19

Oxidative stress-induced degeneration of retinal pigment epithelial (RPE) cells is known to be a key contributor to the development of age-related macular degeneration (AMD). Activation of the nuclear factor-(erythroid-derived 2)-related factor-2 (Nrf2)-mediated cellular defense system is believed to be a valid therapeutic approach. In the present study, we designed and synthesized a novel chalcone analogue, 1-(2,3,4-trimethoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-acrylketone (Tak), as a Nrf2 activator. The potency of Tak was measured in RPE cells by the induction of the Nrf2-dependent antioxidant genes HO-1, NQO-1, GCLc, and GCLm, which were regulated through the Erk pathway. We also showed that Tak could protect RPE cells against oxidative stress-induced cell death and mitochondrial dysfunction. Furthermore, by modifying the α, β unsaturated carbonyl entity in Tak, we showed that the induction of antioxidant genes was abolished, indicating that this unique feature in Tak was responsible for the Nrf2 activation. These results suggest that Tak is a potential candidate for clinical application against AMD.

Inhibition of the Keap1-Nrf2 protein-protein interaction protects retinal cells and ameliorates retinal ischemia-reperfusion injury

The Nrf2-Keap1 pathway regulates transcription of a wide array of antioxidant and cytoprotective genes and offers critical protection against oxidative stress. This pathway has demonstrated benefit for a variety of retinal conditions. Retinal ischemia plays a pivotal role in many vision threatening diseases. Retinal vascular endothelial cells are an important participant in ischemic injury. In this setting, Nrf2 provides a protective pathway via amelioration of oxidative stress and inflammation. In this study, we investigated a potent small molecule inhibitor of the Nrf2-Keap1 protein-protein interaction (PPI), CPUY192018, for its therapeutic potential in retinal cells and retinal ischemia-reperfusion injury. In human retinal endothelial cells (HREC), treatment with CPUY192018 increased Nrf2 protein levels and nuclear translocation, stimulated Nrf2-ARE-induced transcriptional capacity, and induced Nrf2 target gene expression. Furthermore, CPUY192018 protected HREC against oxidative stress and inflammatory activation. CPUY192018 also activated Nrf2 and suppressed inflammatory response in macrophages. In the retinal ischemia-reperfusion (I/R) model, administration of CPUY192018 induced Nrf2 target gene activation in the retina. Both systemic and topical treatment with CPUY192018 rescued visual function after ischemia-reperfusion injury. Taken together, these findings indicate that small molecule Keap1-Nrf2 PPI inhibitors can activate the Nrf2 pathway in the retina and provide protection against retinal ischemic and inflammatory injury, suggesting Keap1-Nrf2 PPI inhibition in the treatment of retinal conditions.

Remodeling of the Basal Labyrinth of Retinal Pigment Epithelial Cells With Osmotic Challenge, Age, and Disease

Purpose

The basal surface of the retinal pigment epithelium (RPE) is folded into a complex basal labyrinth thought to facilitate solute and water transport. We aimed to analyze and define the structural organization of the basal labyrinth of the RPE to enable quantitative analysis of structural changes in age and disease and to better understand the relationship between basal labyrinth structure and efficiency of transepithelial transport.

Methods

Conventional transmission and serial block-face scanning electron microscopy and electron tomography were used to examine the structure of the basal labyrinth in mouse eyes of different ages and genotypes and with and without osmotic shock before fixation.

Results

We identified structurally distinct zones (stacked and ribbon-like) within the RPE basal labyrinth that are largely organelle free and cisternal elements that make contact with the endoplasmic reticulum (ER) and mitochondria. These zones are lost in a hierarchic fashion with age and prematurely in a model of the progressive retinal degenerative disease, choroideremia. Junctional complexes crosslink closely opposed infoldings. Spacing between the basal infoldings was affected by subtle osmotic changes while osmotic shock induced dramatic remodeling of the infoldings.

Conclusions

The basal labyrinth has complex but ordered structural elements that break down with age and in choroideremia. The geometry of these elements and site of contact with ER and mitochondria likely facilitate the ion transport that drives water transport across the basal RPE surface. Changes in structure in response to local osmotic variation may allow transport to be modulated in order to maintain RPE volume.

Synthesis and Anticancer Activity of CDDO and CDDO-Me, Two Derivatives of Natural Triterpenoids

Triterpenoids are natural compounds synthesized by plants through cyclization of squalene, known for their weak anti-inflammatory activity. 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), and its C28 modified derivative, methyl-ester (CDDO-Me, also known as bardoxolone methyl), are two synthetic derivatives of oleanolic acid, synthesized more than 20 years ago, in an attempt to enhance the anti-inflammatory behavior of the natural compound. These molecules have been extensively investigated for their strong ability to exert antiproliferative, antiangiogenic, and antimetastatic activities, and to induce apoptosis and differentiation in cancer cells. Here, we discuss the chemical properties of natural triterpenoids, the pathways of synthesis and the biological effects of CDDO and its derivative CDDO-Me. At nanomolar doses, CDDO and CDDO-Me have been shown to protect cells and tissues from oxidative stress by increasing the transcriptional activity of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). At doses higher than 100 nM, CDDO and CDDO-Me are able to modulate the differentiation of a variety of cell types, both tumor cell lines or primary culture cell, while at micromolar doses these compounds exert an anticancer effect in multiple manners; by inducing extrinsic or intrinsic apoptotic pathways, or autophagic cell death, by inhibiting telomerase activity, by disrupting mitochondrial functions through Lon protease inhibition, and by blocking the deubiquitylating enzyme USP7. CDDO-Me demonstrated its efficacy as anticancer drugs in different mouse models, and versus several types of cancer. Several clinical trials have been started in humans for evaluating CDDO-Me efficacy as anticancer and anti-inflammatory drug; despite promising results, significant increase in heart failure events represented an obstacle for the clinical use of CDDO-Me.

Light-induced Nrf2-/- mice as atrophic age-related macular degeneration model and treatment with nanoceria laden injectable hydrogel

Elevated oxidative stress and associated reactive oxygen species (ROS) accumulation are hallmarks in the induction and progression of age-related macular degeneration (AMD). By exposing nuclear factor erythroid 2-related factor (Nrf2) knockout (Nrf2-/-) mice to mild white light, we were able to generate a new dry-AMD like murine model to the study. This animal model developed phenotypes of photoreceptor degeneration, retinal function impairment, ROS accumulation, and inflammation reaction in a relatively shorter time. In the treatment of this animal model we utilized an antioxidative and water soluble nanoparticle known as glycol chitosan coated cerium oxide nanoparticles (GCCNP). The delivery of GCCNP protected retina against progressive retinal oxidative damage. Further combination of GCCNP with alginate-gelatin based injectable hydrogel provided synergistic antioxidant effects and achieved a more rapid recovery of the retinal pigment epithelium and photoreceptor cells. This combined treatment technique has the potential to translate into a clinical intervention for the treatment of AMD.

Ramadan diurnal intermittent fasting modulates SOD2, TFAM, Nrf2, and sirtuins (SIRT1, SIRT3) gene expressions in subjects with overweight and obesity

AIM

A growing body of evidence supports the impact of intermittent fasting on normalizing body metabolism and lowering oxidative stress and inflammation. Mounting evidence confirms that oxidative stress and chronic inflammation trigger the way for the development of metabolic diseases, such as diabetes. This research was conducted to evaluate the impact of Ramadan intermittent fasting (RIF) on the expression of cellular metabolism (SIRT1 and SIRT3) and antioxidant genes (TFAM, SOD2, and Nrf2).

METHODS

Fifty-six (34 males and 22 females) overweight and obese subjects and six healthy body weight controls were recruited and monitored before and after Ramadan.

RESULTS

Results showed that the relative gene expressions in obese subjects in comparison to counterpart expressions of controls for the antioxidant genes (TFAM, SOD2, and Nrf2) were significantly increased at the end of Ramadan, with percent increments of 90.5%, 54.1% and 411.5% for the three genes, respectively. However, the metabolism-controlling gene (SIRT3) showed a highly significant (P < 0.001) downregulation accompanied with a trend for reduction in SIRT1 gene at the end of Ramadan month, with percent decrements of 61.8% and 10.4%, respectively. Binary regression analysis revealed significant positive correlation (P < 0.05) between high energy intake (>2000 Kcal/day vs. <2000 Kcal/day) and expressions of SOD2 and TFAM (r = 0.84 and r = 0.9, respectively).

CONCLUSION

Results suggest that RIF ameliorates the genetic expression of antioxidant and anti-inflammatory, and metabolic regulatory genes. Thus, RIF presumably may entail a protective impact against oxidative stress and its adverse metabolic-related derangements in non-diabetic obese patients.

A Mouse Model of Retinal Recovery From Photo-Oxidative/Photo-Inflammatory Injury: Nrf2, SOD1, DJ-1, and Parkin Are Not Essential to Recovery

Purpose

To determine if there is structural and functional recovery of the retina from light induced retinal degeneration, and to evaluate the role of the oxidative stress response elements Nrf2, SOD1, DJ-1, and Parkin in such a recovery process.

Methods

Eyes from C57BL/6J (B6J) mice and from oxidative stress response-deficient strains of mice were treated with intense light using the fundus camera-delivered light-induced retinal degeneration (FCD-LIRD) model. Fundus photographs, optical coherence tomography (OCT) images, and electroretinography (ERG) responses were obtained before the injury, during the "maximal injury phase" (days 4-7) and during the "recovery phase" (days 14-16) post light exposure and were evaluated for retinal damage and assessed for evidence of recovery from the injury.

Results

We demonstrate that mice treated with a sub-lethal FCD-LIRD protocol show an initial acute retina injury phase peaking between days 4 to 7 followed by a recovery phase in which the outer retinal thickness/volume and retinal function partially recover. These observations are reproduced in B6J mice and in mice lacking oxidative stress response enzymes (SOD1, DJ-1, and Parkin) or the oxidative stress response master regulator Nrf2.

Conclusions

Our data indicate that retinal recovery from injury can proceed via pathways that are independent from the common oxidative stress response elements Nrf2, SOD1, DJ-1, and Parkin. Furthermore, the model of retinal recovery from injury that we describe here mimics changes seen in a variety of clinical entities and may provide an excellent platform for dissecting general pathways of retinal recovery from sub-lethal injury.

Nuclear Factor (Erythroid-Derived 2)-Like 2 (Nrf2) Contributes to the Neuroprotective Effects of Histone Deacetylase Inhibitors In Retinal Ischemia-Reperfusion Injury

Histone deacetylase inhibitors (HDACis) have displayed neuroprotective effects in animal models of retinal ischemia/reperfusion (I/R) injury. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a redox-sensitive transcription factor responds to oxidative damage. We investigated the role of Nrf2 in retinal I/R injury, and further explored the mechanisms underlying Nrf2-mediated neuroprotection exerted by HDACi. High intraocular pressure was used to establish retinal I/R model in wild type (WT) and Nrf2 knockout (KO) mice. Nrf2 KO mice displayed more severe retinal damage after I/R. Trichostatin A (TSA) was administered to both WT and Nrf2 KO mice with retinal I/R damage. TSA significantly diminished the retinal ganglion cell degeneration in WT mice but offered no notable protection in Nrf2 KO mice. TSA markedly promoted Nrf2 nuclear translocation and its acetylation. In addition, TSA upregulated Nrf2 downstream proteins, such as Ho-1 and Nqo1, in retinal tissues. In the retinal neuronal cell line 661W, TSA reduced the expression of proinflammatory cytokines, Il-1β, Il-6, Tnf-α and Mmp-9, and it upregulated Bdnf under oxidative stress. However, this trend was not continued after silencing Nrf2. Chromatin immunoprecipitation assay demonstrated that Nrf2 at the Ho-1 promoter significantly increased transcriptional activity after oxidative stress induction. Nrf2, which is dispensable in HDACi-mediated neuroprotection, plays a major neuroprotective role in retinal I/R injury.

Expression of a CARD Slows the Retinal Degeneration of a Geographic Atrophy Mouse Model

Age-related macular degeneration (AMD) has been linked to oxidative damage and para-inflammation, an activation of inflammasome signaling in the retinal pigment epithelium (RPE) and the underlying choriocapillaris. Herein, we tested the efficacy of a gene-delivered caspase-1 inhibitor in controlling the retinal degeneration observed in two models of RPE-choroid oxidative damage. In an acute model of oxidative stress (NaIO3 injection), eyes pre-treated with the sGFP-TatCARD (trans-activator of transcription; caspase activation and recruitment domain) vector demonstrated a recovery of retinal function and partial protection of RPE structure 1 month after damage, in contrast with control-treated eyes. In a model of chronic oxidative stress (RPE-specific deletion of Sod2), eyes treated with the sGFP-TatCARD vector after the onset of degeneration had a significantly slower decline in retinal function when compared to control-treated eyes. Earlier treatment of this model with the same adeno-associated virus (AAV) vector resulted in a greater protection of RPE function in eyes treated with the TatCARD when compared to control-treated eyes. Our results demonstrate that intravitreal delivery of sGFP-TatCARD reduces inflammation and can protect the retina from both acute and sustained oxidative damage within the RPE and choroid. Therefore, gene therapy with a cell-penetrating inflammasome inhibitor such as CARD may stem the progression of AMD.

Potential Role of Oxidative Stress in Ocular Surface Inflammation and Dry Eye Disease

Reactive oxygen species (ROS) are produced as a by-product during the mitochondrial respiration of the oxygen and potentially able to damage the tissues. Oxidative stress occurs as a result of the disruption of the balance between the anti-oxidant system and the pro-oxidant system found in cells. It has been accepted that overexpression of ROS can be induced in the ocular surface as a result of many acute and chronic diseases and even in normal aging. Recent studies demonstrated that oxidative stress damages the ocular surface and plays an important role in the mechanism of dry eye disease. There is a need to investigate the therapeutic modalities employing topical/systemic use of antioxidants in dry eye disease. This review will summarize the recent studies showing the important relationship between oxidative stress and dry eye disease.