Serum autoantibody biomarkers for age-related macular degeneration and possible regulators of neovascularization

Altered Elastin Turnover, Immune Response, and Age-Related Retinal Thinning in a Transgenic Mouse Model With RPE-Specific HTRA1 Overexpression

Purpose

A single-nucleotide polymorphism in HTRA1 has been linked to age-related macular degeneration (AMD). Here we investigated the potential links between age-related retinal changes, elastin turnover, elastin autoantibody production, and complement C3 deposition in a mouse model with RPE-specific human HTRA1 overexpression.

Methods

HTRA1 transgenic mice and age-matched CD1 wild-type mice were analyzed at 6 weeks and 4, 6, and 12 to 14 months of age using in vivo retinal imaging by optical coherence tomography (OCT) and fundus photography, as well as molecular readouts, focusing on elastin and elastin-derived peptide quantification, antielastin autoantibody, and total Ig antibody measurements and immunohistochemistry to examine elastin, IgG, and C3 protein levels in retinal sections.

Results

OCT imaging indicated thinning of inner nuclear layer as an early phenotype in HTRA1 mice, followed by age and age/genotype-related thinning of the photoreceptor layer, RPE, and total retina. HTRA1 mice exhibited reduced elastin protein levels in the RPE/choroid and increased elastin breakdown products in the retina and serum. A corresponding age-dependent increase of serum antielastin IgG and IgM autoantibodies and total Ig antibody levels was observed. In the RPE/choroid, these changes were associated with an age-related increase of IgG and C3 deposition.

Conclusions

Our results confirm that RPE-specific overexpression of human HTRA1 induces certain AMD-like phenotypes in mice. This includes altered elastin turnover, immune response, and complement deposition in the RPE/choroid in addition to age-related outer retinal and photoreceptor layer thinning. The identification of elastin-derived peptides and corresponding antielastin autoantibodies, together with increased C3 deposition in the RPE/choroid, provides a rationale for an overactive complement system in AMD irrespective of the underlying genetic risk.

Age-Related Macular Degeneration: A Disease of Cellular Senescence and Dysregulated Immune Homeostasis

Age-related macular degeneration (AMD) is a degenerative ocular disease primarily affecting central vision in the elderly. Its pathogenesis is complex, involving cellular senescence and immune homeostasis dysregulation. This review investigates the interaction between these two critical biological processes in AMD pathogenesis and their impact on disease progression. Initially, cellular senescence is analyzed, with particular emphasis on retinal damage induced by senescent retinal pigment epithelial cells. Subsequently, the occurrence of immune homeostasis dysregulation within the retina and its mechanistic role in AMD areis explored. Furthermore, the paper also discusses in detail the interplay between cellular senescence and immune responses, forming a vicious cycle that exacerbates retinal damage and may influence treatment outcomes. In summary, a deeper understanding of the interrelation between cellular senescence and immune dysregulation is vital for the developing innovative therapeutic strategies for AMD.

Pluripotent stem cell-derived models of retinal disease: Elucidating pathogenesis, evaluating novel treatments, and estimating toxicity

Blindness poses a growing global challenge, with approximately 26% of cases attributed to degenerative retinal diseases. While gene therapy, optogenetic tools, photosensitive switches, and retinal prostheses offer hope for vision restoration, these high-cost therapies will benefit few patients. Understanding retinal diseases is therefore key to advance effective treatments, requiring in vitro models replicating pathology and allowing quantitative assessments for drug discovery. Pluripotent stem cells (PSCs) provide a unique solution given their limitless supply and ability to differentiate into light-responsive retinal tissues encompassing all cell types. This review focuses on the history and current state of photoreceptor and retinal pigment epithelium (RPE) cell generation from PSCs. We explore the applications of this technology in disease modelling, experimental therapy testing, biomarker identification, and toxicity studies. We consider challenges in scalability, standardisation, and reproducibility, and stress the importance of incorporating vasculature and immune cells into retinal organoids. We advocate for high-throughput automation in data acquisition and analyses and underscore the value of advanced micro-physiological systems that fully capture the interactions between the neural retina, RPE, and choriocapillaris.

Bioinformatics and Network Pharmacology Explore the Role of Immune Cells in the Occurrence of Anti-Vascular Endothelial Growth Factor (VEGF) Resistance in Patients with Neovascular Age-Related Macular Degeneration(nAMD) and the Application of Complementary Medicine Treatment

PURPOSE

This study explores the immune cells' role in anti-VEGF resistance in nAMD patients, and the potential of Zi-Yin-Jiang-Huo-Tang (ZYJHT), a Traditional Chinese Medicine formula, as complementary therapy.

METHODS

Aqueous humor proteomics data from 10 nAMD patients with anti-VEGF resistance and 10 nAMD patients without anti-VEGF resistance were analyzed, investigating immune cells's role in anti-VEGF resistance and its underlying mechanism. Network pharmacology methods are employed to analyze the active ingredients in ZYJHT that contribute to therapeutic effects and their mechanisms. Real-time PCR (polymerase chain reaction) was used to detect changes in the expression of SOD1 (superoxide dismutase 1) after treatment with compounds targeting SOD1 in ARPE-19 cells.

RESULTS

nAMD patients with anti-VEGF resistance showed enhancement of biological processes linked to the positive regulation of immune function, along with decreased cellular resistance to oxidative stress. Infiltration of B cells memory, plasma cells, CD8+and γδ-T cells were higher in nAMD patients with anti-VEGF resistance. SOD1 was identified as a hub gene in the occurrence of anti-VEGF resistance and a core therapeutic target of ZYJHT, negatively correlated with B and T cell infiltration. Compounds diosgenin, naringenin, and liquiritin in ZYJHT can bind to SOD1 and upregulating SOD1 expression in ARPE-19 cells.

Immune System, Inflammation and Autoantigens in Wet Age-Related Macular Degeneration: Pathological Significance and Therapeutic Importance

Wet age-related macular degeneration (wAMD) is a chronic inflammation-associated neurodegenerative disease affecting the posterior part of the eye in the aging population. Aging results in the reduced functionality of cells and tissues, including the cells of the retina. Initiators of a chronic inflammatory and pathologic state in wAMD may be a result of the accumulation of inevitable metabolic injuries associated with the maintenance of tissue homeostasis from a young age to over 50. Apart from this, risk factors like smoking, genetic predisposition, and failure to repair the injuries that occur, alongside attempts to rescue the hypoxic outer retina may also contribute to the pathogenesis. Aging of the immune system (immunosenescence) and a compromised outer blood retinal barrier (BRB) result in the exposure of the privileged milieu of the retina to the systemic immune system, further increasing the severity of the disease. When immune-privileged sites like the retina are under pathological stress, certain age- and disease-related conditions may necessitate assistance from cells distant from the resident ones to help restore the functionality of the tissue. As a necessary part of tissue repair, inflammation is a major response to disease and recruits immune cells to the site of damage. We suspect that the specific reparative inflammatory responses are controlled by an autoantigen-T cell-mediated mechanism, a process that may be hindered in wAMD.

Beyond the Complement Cascade: Insights into Systemic Immunosenescence and Inflammaging in Age-Related Macular Degeneration and Current Barriers to Treatment

Landmark genetic studies have revealed the effect of complement biology and its regulation on the pathogenesis of age-related macular degeneration (AMD). Limited phase 3 clinical trial data showing a benefit of complement inhibition in AMD raises the prospect of more complex mediators at play. Substantial evidence supports the role of para-inflammation in maintaining homeostasis in the retina and choroid. With increasing age, a decline in immune system regulation, known as immunosenescence, has been shown to alter the equilibrium maintained by para-inflammation. The altered equilibrium results in chronic, sterile inflammation with aging, termed 'inflammaging', including in the retina and choroid. The chronic inflammatory state in AMD is complex, with contributions from cells of the innate and adaptive branches of the immune system, sometimes with overlapping features, and the interaction of their secretory products with retinal cells such as microglia and retinal pigment epithelium (RPE), extracellular matrix and choroidal vascular endothelial cells. In this review, the chronic inflammatory state in AMD will be explored by immune cell type, with a discussion of factors that will need to be overcome in the development of curative therapies.

Exploring the Therapeutic Potential of Elastase Inhibition in Age-Related Macular Degeneration in Mouse and Human

Abnormal turnover of the extracellular matrix (ECM) protein elastin has been linked to AMD pathology. Elastin is a critical component of Bruch's membrane (BrM), an ECM layer that separates the retinal pigment epithelium (RPE) from the underlying choriocapillaris. Reduced integrity of BrM's elastin layer corresponds to areas of choroidal neovascularization (CNV) in wet AMD. Serum levels of elastin-derived peptides and anti-elastin antibodies are significantly elevated in AMD patients along with the prevalence of polymorphisms of genes regulating elastin turnover. Despite these results indicating significant associations between abnormal elastin turnover and AMD, very little is known about its exact role in AMD pathogenesis. Here we report on results that suggest that elastase enzymes could play a direct role in the pathogenesis of AMD. We found significantly increased elastase activity in the retinas and RPE cells of AMD mouse models, and AMD patient-iPSC-derived RPE cells. A1AT, a protease inhibitor that inactivates elastase, reduced CNV lesion sizes in mouse models. A1AT completely inhibited elastase-induced VEGFA expression and secretion, and restored RPE monolayer integrity in ARPE-19 monolayers. A1AT also mitigated RPE thickening, an early AMD phenotype, in HTRA1 overexpressing mice, HTRA1 being a serine protease with elastase activity. Finally, in an exploratory study, examining archival records from large patient data sets, we identified an association between A1AT use, age and AMD risk. Our results suggest that repurposing A1AT may have therapeutic potential in modifying the progression to AMD.

Correlation of photoreceptor damage with anti-retina antibodies level in aqueous humor in macular edema patients

This study aimed to investigate the correlation between the severity of photoreceptor damage and the level of anti-retina antibodies (ARAs) in aqueous humor, including recoverin, CA II and enolase-α IgG antibody of macular edema patients. Aqueous humor samples were collected from macular edema patients and from cataract patients. Patients were divided into three groups according to the severity of discontinuity of ellipsoid zone (EZ) shown on optical coherence tomography (OCT) imaging: cataract patients with intact EZ, macular edema patients with mild EZ damage, and macular edema patients with severe EZ damage. The level of ARAs was determined with enzyme-linked immunosorbent assay (ELISA). The correlation between the level of ARAs and the degree of photoreceptor damage was analyzed. The level of ARAs of the intact EZ group was significantly lower than that in the severely damaged group (P < 0.05). The level of recoverin IgG of the intact EZ group was significantly lower than mildly damaged group (P = 0.030). In a subgroup analysis, the level of recoverin IgG of DME patients was correlated with their central retinal thickness (CRT) (r = 0.462, P = 0.035). The level of ARAs in aqueous humor of patients with DME and RVO-ME was correlated with the degree of photoreceptor damage.

Recent Advances in Proteomics-Based Approaches to Studying Age-Related Macular Degeneration: A Systematic Review

Age-related macular degeneration (AMD) is a common ocular disease characterized by degeneration of the central area of the retina in the elderly population. Progression and response to treatment are influenced by genetic and non-genetic factors. Proteomics is a powerful tool to study, at the molecular level, the mechanisms underlying the progression of the disease, to identify new therapeutic targets and to establish biomarkers to monitor progression and treatment effectiveness. In this work, we systematically review the use of proteomics-based approaches for the study of the molecular mechanisms underlying the development of AMD, as well as the progression of the disease and on-treatment patient monitoring. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) reporting guidelines were followed. Proteomic approaches have identified key players in the onset of the disease, such as complement components and proteins involved in lipid metabolism and oxidative stress, but also in the progression to advanced stages, including factors related to extracellular matrix integrity and angiogenesis. Although anti-vascular endothelial growth factor (anti-VEGF)-based therapy has been crucial in the treatment of neovascular AMD, it is necessary to deepen our understanding of the underlying disease mechanisms to move forward to next-generation therapies for later-stage forms of this multifactorial disease.

C1q and the classical complement cascade in geographic atrophy secondary to age-related macular degeneration

Geographic atrophy (GA) secondary to age-related macular degeneration (AMD) is a retinal neurodegenerative disorder. Human genetic data support the complement system as a key component of pathogenesis in AMD, which has been further supported by pre-clinical and recent clinical studies. However, the involvement of the different complement pathways (classical, lectin, alternative), and thus the optimal complement inhibition target, has yet to be fully defined. There is evidence that C1q, the initiating molecule of the classical pathway, is a key driver of complement activity in AMD. C1q is expressed locally by infiltrating phagocytic cells and C1q-activating ligands are present at disease onset and continue to accumulate with disease progression. The accumulation of C1q on photoreceptor synapses with age and disease is consistent with its role in synapse elimination and neurodegeneration that has been observed in other neurodegenerative disorders. Furthermore, genetic deletion of C1q, local pharmacologic inhibition within the eye, or genetic deletion of downstream C4 prevents photoreceptor cell damage in mouse models. Hence, targeting the classical pathway in GA could provide a more specific therapeutic approach with potential for favorable efficacy and safety.

Genetic Aspects of Age-Related Macular Degeneration and Their Therapeutic Potential

Age-related macular degeneration (AMD) is a complex and multifactorial disease, resulting from the interaction of environmental and genetic factors. The continuous discovery of associations between genetic polymorphisms and AMD gives reason for the pivotal role attributed to the genetic component to its development. In that light, genetic tests and polygenic scores have been created to predict the risk of development and response to therapy. Still, none of them have yet been validated. Furthermore, there is no evidence from a clinical trial that the determination of the individual genetic structure can improve treatment outcomes. In this comprehensive review, we summarize the polymorphisms of the main pathogenetic ways involved in AMD development to identify which of them constitutes a potential therapeutic target. As complement overactivation plays a major role, the modulation of targeted complement proteins seems to be a promising therapeutic approach. Herein, we summarize the complement-modulating molecules now undergoing clinical trials, enlightening those in an advanced phase of trial. Gene therapy is a potential innovative one-time treatment, and its relevance is quickly evolving in the field of retinal diseases. We describe the state of the art of gene therapies now undergoing clinical trials both in the field of complement-suppressors and that of anti-VEGF.

Elastin turnover in ocular diseases: A special focus on age-related macular degeneration

The extracellular matrix (ECM) and its turnover play a crucial role in the pathogenesis of several inflammatory diseases, including age-related macular degeneration (AMD). Elastin, a critical protein component of the ECM, not only provides structural and mechanical support to tissues, but also mediates several intracellular and extracellular molecular signaling pathways. Abnormal turnover of elastin has pathological implications. In the eye elastin is a major structural component of Bruch's membrane (BrM), a critical ECM structure separating the retinal pigment epithelium (RPE) from the choriocapillaris. Reduced integrity of macular BrM elastin, increased serum levels of elastin-derived peptides (EDPs), and elevated elastin antibodies have been reported in AMD. Existing reports suggest that elastases, the elastin-degrading enzymes secreted by RPE, infiltrating macrophages or neutrophils could be involved in BrM elastin degradation, thus contributing to AMD pathogenesis. EDPs derived from elastin degradation can increase inflammatory and angiogenic responses in tissues, and the elastin antibodies are shown to play roles in immune cell activity and complement activation. This review summarizes our current understanding on the elastases/elastin fragments-mediated mechanisms of AMD pathogenesis.

Novel Possible Protein Targets in Neovascular Age-Related Macular Degeneration: A Pilot Study Experiment

Age-related macular degeneration (AMD) is among the world's leading causes of blindness. In its neovascular form (nAMD), around 25% of patients present further anatomical and visual deterioration due to persistence of neovascular activity, despite gold-standard treatment protocols using intravitreal anti-VEGF medications. Thus, to comprehend, the molecular pathways that drive choroidal neoangiogenesis, associated with the vascular endothelial growth factor (VEGF), are important steps to elucidate the mechanistic events underneath the disease development. This is a pilot study, a prospective, translational experiment, in a real-life context aiming to evaluate the protein profiles of the aqueous humor of 15 patients divided into three groups: group 1, composed of patients with nAMD, who demonstrated a good response to anti-VEGF intravitreal injections during follow-up (good responsive); group 2, composed of patients with anti-VEGF-resistant nAMD, who demonstrated choroidal neovascularization activity during follow-up (poor/non-responsive); and group 3, composed of control patients without systemic diseases or signs of retinopathy. For proteomic characterization of the groups, mass spectrometry (label-free LC-MS/MS) was used. A total of 2,336 proteins were identified, of which 185 were distinctly regulated and allowed the differentiation of the clinical conditions analyzed. Among those, 39 proteins, including some novel ones, were analyzed as potential disease effectors through their pathophysiological implications in lipid metabolism, oxidative stress, complement system, inflammatory pathways, and angiogenesis. So, this study suggests the participation of other promising biomarkers in neovascular AMD, in addition to the known VEGF.

Specific Autoantibodies in Neovascular Age-Related Macular Degeneration: Evaluation of Morphological and Functional Progression over Five Years

(1) Background: Altered levels of autoantibodies (aab) and their networks have been identified as biomarkers for various diseases. Neovascular age-related macular degeneration (nAMD) is a leading cause for central vision loss worldwide with highly variable inter- and intraindividual disease courses. Certain aab networks could help in daily routine to identify patients with a high disease activity who need to be visited and treated more regularly. (2) Methods: We analyzed levels of aab against Angiotensin II receptor type 1 (AT1-receptor), Protease-activated receptors (PAR1), vascular endothelial growth factor (VEGF) -A, VEGF-B, and VEGF-receptor 2 in sera of 164 nAMD patients. In a follow-up period of five years, we evaluated changes in functional and morphological characteristics. Using correlation analyses, multiple regression models, and receiver operator characteristics, we assessed whether the five aab have a clinical significance as biomarkers that correspond to the clinical properties. (3) Results: Neither the analyzed aab individually nor taken together as a network showed statistically significant results that would allow us to draw conclusions on the clinical five-year course in nAMD patients. (4) Conclusions: The five aab that we analyzed do not correspond to the clinical five-year course of nAMD patients. However, larger, prospective studies should reevaluate different and more aab to gain deeper insights.

Peptide-based immunotherapy against oxidized elastin ameliorates pathology in mouse model of smoke-induced ocular injury

PURPOSE

Age-related macular degeneration (AMD), the leading cause of blindness in western populations, is associated with an overactive complement system, and an increase in circulating antibodies against certain epitopes, including elastin. As loss of the elastin layer of Bruch's membrane (BrM) has been reported in aging and AMD, we previously showed that immunization with elastin peptide oxidatively modified by cigarette smoke (ox-elastin), exacerbated ocular pathology in the smoke-induced ocular pathology (SIOP) model. Here we asked whether ox-elastin peptide-based immunotherapy (PIT) ameliorates damage.

METHODS

C57BL/6J mice were injected with ox-elastin peptide at two doses via weekly subcutaneous administration, while exposed to cigarette smoke for 6 months. FcγR-/- and uninjected C57BL/6J mice served as controls. Retinal morphology was assessed by electron microscopy, and complement activation, antibody deposition and mechanisms of immunological tolerance were assessed by Western blotting and ELISA.

RESULTS

Elimination of Fcγ receptors, preventing antigen/antibody-dependent cytotoxicity, protected against SIOP. Mice receiving PIT with low dose ox-elastin (LD-PIT) exhibited reduced humoral immunity, reduced complement activation and IgG/IgM deposition in the RPE/choroid, and largely a preserved BrM. While there is no direct evidence of ox-elastin pathogenicity, LD-PIT reduced IFNγ and increased IL-4 within RPE/choroid. High dose PIT was not protective.

CONCLUSIONS

These data further support ox-elastin role in ocular damage in part via elastin-specific antibodies, and support the corollary that PIT with ox-elastin attenuates ocular pathology. Overall, damage is associated with complement activation, antibody-dependent cell-mediated cytotoxicity, and altered cytokine signature.

Biomarkers for Nonexudative Age-Related Macular Degeneration and Relevance for Clinical Trials: A Systematic Review

TOPIC

The purpose of the review was to identify structural, functional, blood-based, and other types of biomarkers for early, intermediate, and late nonexudative stages of age-related macular degeneration (AMD) and summarize the relevant data for proof-of-concept clinical trials.

CLINICAL RELEVANCE

AMD is a leading cause of blindness in the aging population, yet no treatments exist for its most common nonexudative form. There are limited data on the diagnosis and progression of nonexudative AMD compared to neovascular AMD. Our objective was to provide a comprehensive, systematic review of recently published biomarkers (molecular, structural, and functional) for early AMD, intermediate AMD, and geographic atrophy and to evaluate the relevance of these biomarkers for use in future clinical trials.

METHODS

A literature search of PubMed, ScienceDirect, EMBASE, and Web of Science from January 1, 1996 to November 30, 2020 and a patent search were conducted. Search terms included "early AMD," "dry AMD," "intermediate AMD," "biomarkers for nonexudative AMD," "fundus autofluorescence patterns," "color fundus photography," "dark adaptation," and "microperimetry." Articles were assessed for bias and quality with the Mixed-Methods Appraisal Tool. A total of 94 articles were included (61,842 individuals).

RESULTS

Spectral-domain optical coherence tomography was superior at highlighting detailed structural changes in earlier stages of AMD. Fundus autofluorescence patterns were found to be most important in estimating progression of geographic atrophy. Delayed rod intercept time on dark adaptation was the most widely recommended surrogate functional endpoint for early AMD, while retinal sensitivity on microperimetry was most relevant for intermediate AMD. Combinational studies accounting for various patient characteristics and machine/deep-learning approaches were best suited for assessing individualized risk of AMD onset and progression.

CONCLUSION

This systematic review supports the use of structural and functional biomarkers in early AMD and intermediate AMD, which are more reproducible and less invasive than the other classes of biomarkers described. The use of deep learning and combinational algorithms will gain increasing importance in future clinical trials of nonexudative AMD.

Natural immunoglobulin M-based delivery of a complement alternative pathway inhibitor in mouse models of retinal degeneration

PURPOSE

Age-related macular degeneration is a slowly progressing disease. Studies have tied disease risk to an overactive complement system. We have previously demonstrated that pathology in two mouse models, the choroidal neovascularization (CNV) model and the smoke-induced ocular pathology (SIOP) model, can be reduced by specifically inhibiting the alternative complement pathway (AP). Here we report on the development of a novel injury-site targeted inhibitor of the alternative pathway, and its characterization in models of retinal degeneration.

METHODS

Expression of the danger associated molecular pattern, a modified annexin IV, in injured ARPE-19 cells was confirmed by immunohistochemistry and complementation assays using B4 IgM mAb. Subsequently, a construct was prepared consisting of B4 single chain antibody (scFv) linked to a fragment of the alternative pathway inhibitor, fH (B4-scFv-fH). ARPE-19 cells stably expressing B4-scFv-fH were microencapsulated and administered intravitreally or subcutaneously into C57BL/6 J mice, followed by CNV induction or smoke exposure. Progression of CNV was analyzed using optical coherence tomography, and SIOP using structure-function analyses. B4-scFv-fH targeting and AP specificity was assessed by Western blot and binding experiments.

RESULTS

B4-scFv-fH was secreted from encapsulated RPE and inhibited complement in RPE monolayers. B4-scFv-fH capsules reduced CNV and SIOP, and western blotting for breakdown products of C3α, IgM and IgG confirmed a reduction in complement activation and antibody binding in RPE/choroid.

CONCLUSIONS

Data supports a role for natural antibodies and neoepitope expression in ocular disease, and describes a novel strategy to target AP-specific complement inhibition to diseased tissue in the eye.

PRECIS

AMD risk is tied to an overactive complement system, and ocular injury is reduced by alternative pathway (AP) inhibition in experimental models. We developed a novel inhibitor of the AP that targets an injury-specific danger associated molecular pattern, and characterized it in disease models.

Protein Microarrays for Ocular Diseases

The eye is a multifaceted organ organized in several compartments with particular properties that reflect their diverse functions. The prevalence of ocular diseases is increasing, mainly because of its relationship with aging and of generalized lifestyle changes. However, the pathogenic molecular mechanisms of many common eye pathologies remain poorly understood. Considering the unquestionable importance of proteins in cellular processes and disease progression, proteomic techniques, such as protein microarrays, represent a valuable approach to analyze pathophysiological protein changes in the ocular environment. This technology enables to perform multiplex high-throughput protein expression profiling with minimal sample volume requirements broadening our knowledge of ocular proteome network in eye diseases.In this review, we present a brief summary of the main types of protein microarrays (antibody microarrays, reverse-phase protein microarrays, and protein microarrays) and their application for protein change detection in chronic ocular diseases such as dry eye, age-related macular degeneration, diabetic retinopathy, and glaucoma. The validation of these specific protein changes in eye pathologies may lead to the identification of new biomarkers, depiction of ocular disease pathways, and assistance in the diagnosis, prognosis, and development of new therapeutic options for eye pathologies.

Immunization Against Oxidized Elastin Exacerbates Structural and Functional Damage in Mouse Model of Smoke-Induced Ocular Injury

Purpose

Age-related macular degeneration (AMD) is the leading cause of blindness in Western populations. While an overactive complement system has been linked to pathogenesis, mechanisms contributing to its activation are largely unknown. In aged and AMD eyes, loss of the elastin layer (EL) of Bruch's membrane (BrM) has been reported. Elastin antibodies are elevated in patients with AMD, the pathogenic significance of which is unclear. Here we assess the role of elastin antibodies using a mouse model of smoke-induced ocular pathology (SIOP), which similarly demonstrates EL loss.

Methods

C57BL/6J mice were immunized with elastin or elastin peptide oxidatively modified by cigarette smoke (ox-elastin). Mice were then exposed to cigarette smoke or air for 6 months. Visual function was assessed by optokinetic response, retinal morphology by spectral-domain optical coherence tomography and electron microscopy, and complement activation and antibody deposition by Western blot.

Results

Ox-elastin IgG and IgM antibodies were elevated in ox-elastin immunized mice following 6 months of smoke, whereas elastin immunization had a smaller effect. Ox-elastin immunization exacerbated smoke-induced vision loss, with thicker BrM and more damaged retinal pigment epithelium (RPE) mitochondria compared with mice immunized with elastin or nonimmunized controls. These changes were correlated with increased levels of IgM, IgG2, IgG3, and complement activation products in RPE/choroid.

Conclusions

These data demonstrate that SIOP mice generate elastin-specific antibodies and that immunization with ox-elastin exacerbates ocular pathology. Elastin antibodies represented complement fixing isotypes that, together with the increased presence of complement activation seen in immunized mice, suggest that elastin antibodies exert pathogenic effects through mediating complement activation.

The Inhibitory Effects of Gold Nanoparticles on VEGF-A-Induced Cell Migration in Choroid-Retina Endothelial Cells

Background: Vascular endothelial growth factor (VEGF) is upregulated by hypoxia and is a crucial stimulator for choroidal neovascularization (CNV) in age-related macular degeneration and pathologic myopia, as well as retinal neovascularization in proliferative diabetic retinopathy. Retinal and choroidal endothelial cells play key roles in the development of retinal and CNV, and subsequent fibrosis. At present, the effects of gold nanoparticles (AuNPs) on the VEGF-induced choroid-retina endothelial (RF/6A) cells are still unknown. In our study, we investigated the effects of AuNPs on RF/6A cell viabilities and cell adhesion to fibronectin, a major ECM protein of fibrovascular membrane. Furthermore, the inhibitory effects of AuNPs on RF/6A cell migration induced by VEGF and its signaling were studied. Methods: The cell viability assay was used to determine the viability of cells treated with AuNPs. The migration of RF/6A cells was assessed by the Transwell migration assay. The cell adhesion to fibronectin was examined by an adhesion assay. The VEGF-induced signaling pathways were determined by western blotting. Results: The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay revealed no cytotoxicity of AuNPs on RF/6A cells. AuNPs inhibited VEGF-induced RF/6A cell migration in a concentration-dependent manner but showed no significant effects on RF/6A cell adhesion to fibronectin. Inhibitory effects of AuNPs on VEGF-induced Akt/eNOS were found. Conclusions: These results suggest that AuNPs are an effective inhibitor of VEGF-induced RF/6A cell migration through the Akt/eNOS pathways, but they have no effects on their cell viabilities and cell adhesion to fibronectin.

Protein Microarrays: Valuable Tools for Ocular Diseases Research

The eye is a complex organ comprised of several compartments with exclusive and specialized properties that reflect their diverse functions. Although the prevalence of eye pathologies is increasing, mainly because of its correlation with aging and of generalized lifestyle changes, the pathogenic molecular mechanisms of many common ocular diseases remain poorly understood. Therefore, there is an unmet need to delve into the pathogenesis, diagnosis, and treatment of eye diseases to preserve ocular health and reduce the incidence of visual impairment or blindness. Proteomics analysis stands as a valuable tool for deciphering protein profiles related to specific ocular conditions. In turn, such profiles can lead to real breakthroughs in the fields of ocular science and ophthalmology. Among proteomics techniques, protein microarray technology stands out by providing expanded information using very small volumes of samples. In this review, we present a brief summary of the main types of protein microarrays and their application for the identification of protein changes in chronic ocular diseases such as dry eye, glaucoma, age-related macular degeneration, or diabetic retinopathy. The validation of these specific protein alterations could provide new biomarkers, disclose eye diseases pathways, and help in the diagnosis and development of novel therapies for eye pathologies.

Pleiotropic Effects of Risk Factors in Age-Related Macular Degeneration and Seemingly Unrelated Complex Diseases

Age-related macular degeneration (AMD) is a complex disease with both environmental and genetic factors influencing disease risk. Genome-wide case-control association studies, candidate gene analyses, and epidemiological studies reinforced the notion that AMD is predominantly a disease of an impaired complement system and an altered high-density lipoprotein (HDL) metabolism. Recent reports demonstrated the pleiotropic role of the complement system and HDL in complex diseases such as cardiovascular disease, autoimmune disorders, cancer, and Alzheimer's disease. In light of these findings, we explore current evidence for a shared genetic and environmental risk of AMD and unrelated complex diseases based on epidemiological studies. Shared risk factors may indicate common pathways in disease pathology and thus may have implications for novel treatment options of AMD pathology.

Gut bacterial peptides with autoimmunity potential as environmental trigger for late onset complex diseases: In-silico study

Recent evidences suggest that human gut microbiota with major component as bacteria can induce immunity. It is also known that gut lining depletes with ageing and that there is increased risk of autoimmune and inflammatory disorders with ageing. It is therefore likely that both may be correlated as depletion of gut lining exposes the gut bacterial antigens to host immune mechanisms, which may induce immunity to certain bacterial proteins, but at the same time such immunity may also be auto-immunogenic to host. This autoimmunity may make a protein molecule nonfunctional and thereby may be involved in late onset metabolic, autoimmune and inflammatory disorders such as, Diabetes, Rheumatoid Arthritis, Hyperlipidemias and Cancer. In this in-silico study we found a large number of peptides identical between human and gut bacteria which were binding to HLA-II alleles, and hence, likely to be auto-immunogenic. Further we observed that such autoimmune candidates were enriched in bacterial species belonging to Firmicutes and Proteobacteria phyla, which lead us to conclude that these phyla may have higher disease impact in genetically predisposed individuals. Functional annotation of human proteins homologous to candidate gut-bacterial peptides showed significant enrichment in metabolic processes and pathways. Cognitive trait, Ageing, Alzheimer, Type 2 diabetes, Chronic Kidney Failure (CKF), Chronic Obstructive Pulmonary Disease (COPD) and various Cancers were the major diseases represented in the dataset. This dataset provides us with gut bacterial autoimmune candidates which can be studied for their clinical significance in late onset diseases.

The link between morphology and complement in ocular disease

The complement system is a vital component of the immune-priveliged human eye that is always active at a low-grade level, preventing harmful intraocular injuries caused by accumulation of turnover products and controlling pathogens to preserve eye homeostasis and vision. The complement system is a double-edged sword that is essential for protection but may also become harmful and contribute to eye pathology. Here, we review the evidence for the involvement of complement system dysregulation in age-related macular degeneration, glaucoma, uveitis, and neuromyelitis optica, highlighting the relationship between morphogical changes and complement system protein expression and regulation in these diseases. The potential benefits of complement inhibition in age-related macular degeneration, glaucoma, uveitis, and neuromyelitis optica are abundant, as are those of further research to improve our understanding of complement-mediated injury in these diseases.

Systemic and ocular fluid compounds as potential biomarkers in age-related macular degeneration

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

Cell-based therapeutic strategies for replacement and preservation in retinal degenerative diseases

Cell-based therapeutics offer diverse options for treating retinal degenerative diseases, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP). AMD is characterized by both genetic and environmental risks factors, whereas RP is mainly a monogenic disorder. Though treatments exist for some patients with neovascular AMD, a majority of retinal degenerative patients have no effective therapeutics, thus indicating a need for universal therapies to target diverse patient populations. Two main cell-based mechanistic approaches are being tested in clinical trials. Replacement therapies utilize cell-derived retinal pigment epithelial (RPE) cells to supplant lost or defective host RPE cells. These cells are similar in morphology and function to native RPE cells and can potentially supplant the responsibilities of RPE in vivo. Preservation therapies utilize supportive cells to aid in visual function and photoreceptor preservation partially by neurotrophic mechanisms. The goal of preservation strategies is to halt or slow the progression of disease and maintain remaining visual function. A number of clinical trials are testing the safety of replacement and preservation cell therapies in patients; however, measures of efficacy will need to be further evaluated. In addition, a number of prevailing concerns with regards to the immune-related response, longevity, and functionality of the grafted cells will need to be addressed in future trials. This review will summarize the current status of cell-based preclinical and clinical studies with a focus on replacement and preservation strategies and the obstacles that remain regarding these types of treatments.

Can innate and autoimmune reactivity forecast early and advance stages of age-related macular degeneration?

Age-related macular degeneration (AMD) is a major cause of central vision loss in persons over 55years of age in developed countries. AMD is a complex disease in which genetic, environmental and inflammatory factors influence its onset and progression. Elevation in serum anti-retinal autoantibodies, plasma and local activation of complement proteins of the alternative pathway, and increase in secretion of proinflammatory cytokines have been seen over the course of disease. Genetic studies of AMD patients confirmed that genetic variants affecting the alternative complement pathway have a major influence on AMD risk. Because the heterogeneity of this disease, there is no sufficient strategy to identify the disease onset and progression sole based eye examination, thus identification of reliable serological biomarkers for diagnosis, prognosis and response to treatment by sampling patient's blood is necessary. This review provides an outline of the current knowledge on possible serological (autoantibodies, complement factors, cytokines, chemokines) and related genetic biomarkers relevant to the pathology of AMD, and discusses their application for prediction of disease activity and prognosis in AMD.

Risk factors and biomarkers of age-related macular degeneration

A biomarker can be a substance or structure measured in body parts, fluids or products that can affect or predict disease incidence. As age-related macular degeneration (AMD) is the leading cause of blindness in the developed world, much research and effort has been invested in the identification of different biomarkers to predict disease incidence, identify at risk individuals, elucidate causative pathophysiological etiologies, guide screening, monitoring and treatment parameters, and predict disease outcomes. To date, a host of genetic, environmental, proteomic, and cellular targets have been identified as both risk factors and potential biomarkers for AMD. Despite this, their use has been confined to research settings and has not yet crossed into the clinical arena. A greater understanding of these factors and their use as potential biomarkers for AMD can guide future research and clinical practice. This article will discuss known risk factors and novel, potential biomarkers of AMD in addition to their application in both academic and clinical settings.

Connecting the innate and adaptive immune responses in mouse choroidal neovascularization via the anaphylatoxin C5a and γδT-cells

Neovascular age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). An overactive complement system is associated with AMD pathogenesis, and serum pro-inflammatory cytokines, including IL-17, are elevated in AMD patients. IL-17 is produced by complement C5a-receptor-expressing T-cells. In murine CNV, infiltrating γδT- rather than Th17-cells produce the IL-17 measurable in lesioned eyes. Here we asked whether C5a generated locally in response to CNV recruits IL-17-producing T-cells to the eye. CNV lesions were generated using laser photocoagulation and quantified by imaging; T-lymphocytes were characterized by QRT-PCR. CNV resulted in an increase in splenic IL-17-producing γδT- and Th17-cells; yet in the CNV eye, only elevated levels of γδT-cells were observed. Systemic administration of anti-C5- or anti-C5a-blocking antibodies blunted the CNV-induced production of splenic Th17- and γδT-cells, reduced CNV size and eliminated ocular γδT-cell infiltration. In ARPE-19 cell monolayers, IL-17 triggered a pro-inflammatory state; and splenocyte proliferation was elevated in response to ocular proteins. Thus, we demonstrated that CNV lesions trigger a systemic immune response, augmenting local ocular inflammation via the infiltration of IL-17-producing γδT-cells, which are presumably recruited to the eye in a C5a-dependent manner. Understanding the complexity of complement-mediated pathological mechanisms will aid in the development of an AMD treatment.

Phosphatidylserine (PS) Is Exposed in Choroidal Neovascular Endothelium: PS-Targeting Antibodies Inhibit Choroidal Angiogenesis In Vivo and Ex Vivo

PURPOSE

Choroidal neovascularization (CNV) accounts for 90% of cases of severe vision loss in patients with advanced age-related macular degeneration. Identifying new therapeutic targets for CNV may lead to novel combination therapies to improve outcomes and reduce treatment burden. Our goal was to test whether phosphatidylserine (PS) becomes exposed in the outer membrane of choroidal neovascular endothelium, and whether this could provide a new therapeutic target for CNV.

METHODS

Choroidal neovascularization was induced in C57BL/6J mice using laser photocoagulation. Choroidal neovascularization lesions costained for exposed PS and for intercellular adhesion molecule 2 (or isolectin B4) were imaged in flat mounts and in cross sections. The laser CNV model and a choroidal sprouting assay were used to test the effect of PS-targeting antibodies on choroidal angiogenesis. Choroidal neovascularization lesion size was determined by intercellular adhesion molecule 2 (ICAM-2) staining of flat mounts.

RESULTS

We found that PS was exposed in CNV lesions and colocalized with vascular endothelial staining. Treatment with PS-targeting antibodies led to a 40% to 80% reduction in CNV lesion area when compared to treatment with a control antibody. The effect was the same as that seen using an equal dose of an anti-VEGF antibody. Results were confirmed using the choroid sprouting assay, an ex vivo model of choroidal angiogenesis.

CONCLUSIONS

We demonstrated that PS is exposed in choroidal neovascular endothelium. Furthermore, targeting this exposed PS with antibodies may be of therapeutic value in CNV.

Hypersensitivity toward bacterial stimuli in patients with age-related macular degeneration

Although the pathogenesis of age-related macular degeneration (AMD) is unclear, genetic screening has revealed that polymorphisms in the complement system may be associated with AMD development. Production of autoantibodies was also found in AMD patients. In this study, we analyzed the antibody response in AMD patients. We found that purified B cells from AMD patients tended to respond to lower concentrations of bacterial antigen stimulation, and produced higher amounts of antibodies, especially in IgM and IgA secretions. When examining clinical symptoms, patients with more severe wet-form AMD tended to exhibit higher sensitivity to bacterial antigens and secreted more IgM and IgA antibodies than those with less severe dry-form cases. In conclusion, our study discovered an altered B-cell antibody production in response to bacterial antigens in AMD patients, which potentially contributes to AMD pathogenesis.

Increased serum IgA concentration and plasmablast frequency in patients with age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness among senior citizens of developed countries, with currently unknown etiology. Despite the close associations between AMD development and inhibitory complement factor H mutations, the first step of complement activation, which is the antibody response in AMD patients, has not been studied. Here, we obtained blood and tear samples from AMD patients and Non-AMD controls. We found that compared to Non-AMD controls, AMD subjects had increased IgA titers in serum and tear, and had elevated levels of circulating antibody-secreting plasmablasts. The increase in antibody titer was limited to the IgA isotype, since no significant differences were observed in IgM and IgG isotypes between AMD patients and Non-AMD controls. Interestingly, this increased antibody response in AMD patients was correlated with disease severity, as late AMD patients had increased IgA titers in serum and tear, as well as elevated plasmablast frequency after staphylococcal enterotoxin B stimulation, compared to early AMD patients. Together, our results implicated a role of overreactive IgA responses in AMD pathogenesis.

Circulating Autoantibodies in Age-Related Macular Degeneration Recognize Human Macular Tissue Antigens Implicated in Autophagy, Immunomodulation, and Protection from Oxidative Stress and Apoptosis

BACKGROUND

We investigated sera from elderly subjects with and without age-related macular degeneration (AMD) for presence of autoantibodies (AAbs) against human macular antigens and characterized their identity.

METHODS

Sera were collected from participants in the Age-Related Maculopathy Ancillary (ARMA) Study, a cross-sectional investigation ancillary to the Health ABC Study, enriched with participants from the general population. The resulting sample (mean age: 79.2±3.9 years old) included subjects with early to advanced AMD (n = 131) and controls (n = 231). Sera were tested by Western blots for immunoreactive bands against human donor macular tissue homogenates. Immunoreactive bands were identified and graded, and odds ratios (OR) calculated. Based on these findings, sera were immunoprecipitated, and subjected to 2D gel electrophoresis (GE). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify the targets recognized by circulating AAbs seen on 2D-GE, followed by ELISAs with recombinant proteins to confirm LC-MS/MS results, and quantify autoreactivities.

RESULTS

In AMD, 11 immunoreactive bands were significantly more frequent and 13 were significantly stronger than in controls. Nine of the more frequent bands also showed stronger reactivity. OR estimates ranged between 4.06 and 1.93, and all clearly excluded the null value. Following immunoprecipitation, 2D-GE and LC-MS/MS, five of the possible autoreactivity targets were conclusively identified: two members of the heat shock protein 70 (HSP70) family, HSPA8 and HSPA9; another member of the HSP family, HSPB4, also known as alpha-crystallin A chain (CRYAA); Annexin A5 (ANXA5); and Protein S100-A9, also known as calgranulin B that, when complexed with S100A8, forms calprotectin. ELISA testing with recombinant proteins confirmed, on average, significantly higher reactivities against all targets in AMD samples compared to controls.

CONCLUSIONS

Consistent with other evidence supporting the role of inflammation and the immune system in AMD pathogenesis, AAbs were identified in AMD sera, including early-stage disease. Identified targets may be mechanistically linked to AMD pathogenesis because the identified proteins are implicated in autophagy, immunomodulation, and protection from oxidative stress and apoptosis. In particular, a role in autophagy activation is shared by all five autoantigens, raising the possibility that the detected AAbs may play a role in AMD via autophagy compromise and downstream activation of the inflammasome. Thus, we propose that the detected AAbs provide further insight into AMD pathogenesis and have the potential to contribute to disease biogenesis and progression.

Molecular response of chorioretinal endothelial cells to complement injury: implications for macular degeneration

Age-related macular degeneration (AMD) is a common, blinding disease of the elderly in which macular photoreceptor cells, retinal pigment epithelium and choriocapillaris endothelial cells ultimately degenerate. Recent studies have found that degeneration of the choriocapillaris occurs early in this disease and that endothelial cell drop-out is concomitant with increased deposition of the complement membrane attack complex (MAC) at the choroidal endothelium. However, the impact of MAC injury to choroidal endothelial cells is poorly understood. To model this event in vitro, and to study the downstream consequences of MAC injury, endothelial cells were exposed to complement from human serum, compared to heat-inactivated serum, which lacks complement components. Cells exposed to complement components in human serum showed increased labelling with antibodies directed against the MAC, time- and dose-dependent cell death, as assessed by lactate dehydrogenase assay and increased permeability. RNA-Seq analysis following complement injury revealed increased expression of genes associated with angiogenesis including matrix metalloproteinase (MMP)-3 and -9, and VEGF-A. The MAC-induced increase in MMP9 RNA expression was validated using C5-depleted serum compared to C5-reconstituted serum. Increased levels of MMP9 were also established, using western blot and zymography. These data suggest that, in addition to cell lysis, complement attack on choroidal endothelial cells promotes an angiogenic phenotype in surviving cells.

Immune mechanisms in inflammatory and degenerative eye disease

It has recently been recognized that pathology of age-associated degenerative eye diseases such as adult macular degeneration (AMD), glaucoma and diabetic retinopathy, have strong immunological underpinnings. Attempts have been made to extrapolate to age-related degenerative disease insights from inflammatory processes associated with non-infectious uveitis, but these have not yet been sufficiently informative. Here we review recent findings on the immune processes underlying uveitis and those that have been shown to contribute to AMD, discussing in this context parallels and differences between overt inflammation and para-inflammation in the eye. We propose that mechanisms associated with ocular immune privilege, in combination with paucity of age-related antigen(s) within the target tissue, dampen what could otherwise be overt inflammation and result in the para-inflammation that characterizes age-associated neurodegenerative disease.

Genomic regulation of senescence and innate immunity signaling in the retinal pigment epithelium

The tumor suppressor p53 is a major regulator of genes important for cell cycle arrest, senescence, apoptosis, and innate immunity, and has recently been implicated in retinal aging. In this study we sought to identify the genetic networks that regulate p53 function in the retina using quantitative trait locus (QTL) analysis. First we examined age-associated changes in the activation and expression levels of p53; known p53 target proteins and markers of innate immune system activation in primary retinal pigment epithelial (RPE) cells that were harvested from young and aged human donors. We observed increased expression of p53, activated caspase-1, CDKN1A, CDKN2A (p16INK4a), TLR4, and IFNα in aged primary RPE cell lines. We used the Hamilton Eye Institute (HEI) retinal dataset ( www.genenetwork.org ) to identify genomic loci that modulate expression of genes in the p53 pathway in recombinant inbred BXD mouse strains using a QTL systems biology-based approach. We identified a significant trans-QTL on chromosome 1 (region 172-177 Mb) that regulates the expression of Cdkn1a. Many of the genes in this QTL locus are involved in innate immune responses, including Fc receptors, interferon-inducible family genes, and formin 2. Importantly, we found an age-related increase in FCGR3A and FMN2 and a decrease in IFI16 levels in RPE cultures. There is a complex multigenic innate immunity locus that controls expression of genes in the p53 pathway in the RPE, which may play an important role in modulating age-related changes in the retina.

Seeing through VEGF: innate and adaptive immunity in pathological angiogenesis in the eye

The central role of vascular endothelial growth factor (VEGF) signaling in regulating normal vascular development and pathological angiogenesis has been documented in multiple studies. Ocular anti-VEGF therapy is highly effective for treating a subset of patients with blinding eye disorders such as diabetic retinopathy and neovascular age-related macular degeneration (AMD). However, chronic VEGF suppression can lead to adverse effects associated with poor visual outcomes due to the loss of prosurvival and neurotrophic capacities of VEGF. In this review, we discuss emerging evidence for immune-related mechanisms that regulate ocular angiogenesis in a VEGF-independent manner. These novel molecular and cellular pathways may provide potential therapeutic avenues for a multitarget strategy, preserving the neuroprotective functions of VEGF in those patients whose disease is unresponsive to VEGF neutralization.

Prevalence of anti-retinal autoantibodies in different stages of Age-related macular degeneration

Background

Age-related macular degeneration (AMD) is the leading cause of central vision loss in older adults. Anti-retinal autoantibodies (AAbs) have been found in individuals with AMD. The goal of the study was to determine the AAb specificity in different stages of AMD, and determine whether there is a prevalent AAb signature.

Methods

Sera of 134 participants in the Age-related Eye Disease Study were analyzed for anti-retinal AAbs by western blotting. The subjects were classified by diagnostic subgroups based upon their clinical classification: No AMD, Intermediate AMD, and Late AMD - geographic atrophy (GA) and Late AMD - neovascular (NV).

Results

The presence of anti-retinal AAb was detected in 58% patients with Intermediate and Late AMD, and 54% of those with no AMD. AAbs bound to fifteen different retinal antigens. Most individuals had 1 specific AAbs (67%), with the remainder having 2 to 4 different AAbs. Over 40% of patients with Intermediate AMD, and 46% of those with GA had anti-enolase AAbs, compared with 29% of individuals with NV and 29% with no AMD. Different AAbs signatures related to NV as compared to GA and/or Intermediate AMD were distinguished. Anti-40-kDa (10%) and 42-kDa (16%) autoantibodies were associated with Intermediate AMD, while anti-30-kDa AAbs (23%) were primarily present in GA. Anti-32-kDa (12%), 35-kDa (21%), and 60-kDa (8%) AAbs were more frequent in NV AMD.

Conclusions

A unique AAb pattern for each of the disease subgroups was present when AMD progressed from the intermediate to the late forms of severity. Differences in the frequency of specific AAbs between AMD subgroups suggested that they may participate in pathogenicity of AMD. Further studies are necessary to confirm these observations in the larger cohort and individual AMD patients over time.

Age-related macular degeneration in the aspect of chronic low-grade inflammation (pathophysiological parainflammation)

The products of oxidative stress trigger chronic low-grade inflammation (pathophysiological parainflammation) process in AMD patients. In early AMD, soft drusen contain many mediators of chronic low-grade inflammation such as C-reactive protein, adducts of the carboxyethylpyrrole protein, immunoglobulins, and acute phase molecules, as well as the complement-related proteins C3a, C5a, C5, C5b-9, CFH, CD35, and CD46. The complement system, mainly alternative pathway, mediates chronic autologous pathophysiological parainflammation in dry and exudative AMD, especially in the Y402H gene polymorphism, which causes hypofunction/lack of the protective complement factor H (CFH) and facilitates chronic inflammation mediated by C-reactive protein (CRP). Microglial activation induces photoreceptor cells injury and leads to the development of dry AMD. Many autoantibodies (antibodies against alpha beta crystallin, alpha-actinin, amyloid, C1q, chondroitin, collagen I, collagen III, collagen IV, elastin, fibronectin, heparan sulfate, histone H2A, histone H2B, hyaluronic acid, laminin, proteoglycan, vimentin, vitronectin, and aldolase C and pyruvate kinase M2) and overexpression of Fcc receptors play role in immune-mediated inflammation in AMD patients and in animal model. Macrophages infiltration of retinal/choroidal interface acts as protective factor in early AMD (M2 phenotype macrophages); however it acts as proinflammatory and proangiogenic factor in advanced AMD (M1 and M2 phenotype macrophages).

Immune responses in age-related macular degeneration and a possible long-term therapeutic strategy for prevention

PURPOSE

To describe the immune alterations associated with age-related macular degeneration (AMD); and, based on these findings, to offer an approach to possibly prevent the expression of late disease.

DESIGN

Perspective.

METHODS

Review of the existing literature dealing with epidemiology, models, and immunologic findings in patients.

RESULTS

Significant genetic associations have been identified and reported, but environmentally induced (including epigenetic) changes are also an important consideration. Immune alterations include a strong interleukin 17 family signature as well as marked expression of these molecules in the eye. Oxidative stress as well as other homeostatic altering mechanisms occur throughout life. With this immune dysregulation there is a rationale for considering immunotherapy. Indeed, immunotherapy has been shown to affect the late stages of AMD.

CONCLUSION

Immune dysregulation appears to be an underlying alteration in AMD, as in other diseases thought to be degenerative and attributable to aging. Para-inflammation and immunosenescence may importantly contribute to the development of disease. The role of complement factor H still needs to be better defined, but in light of its association with ocular inflammatory conditions such as sarcoidosis, it does not appear to be unique to AMD but rather may be a marker for retinal pigment epithelium function. With the strong interleukin 17 family signature and the need to treat early on in the disease process, oral tolerance may be considered to prevent disease progression.

Proteomics of vitreous humor of patients with exudative age-related macular degeneration

BACKGROUND

There is absence of specific biomarkers and an incomplete understanding of the pathophysiology of exudative age-related macular degeneration (AMD).

METHODS AND FINDINGS

Eighty-eight vitreous samples (73 from patients with treatment naïve AMD and 15 control samples from patients with idiopathic floaters) were analyzed with capillary electrophoresis coupled to mass spectrometry in this retrospective case series to define potential candidate protein markers of AMD. Nineteen proteins were found to be upregulated in vitreous of AMD patients. Most of the proteins were plasma derived and involved in biological (ion) transport, acute phase inflammatory reaction, and blood coagulation. A number of proteins have not been previously associated to AMD including alpha-1-antitrypsin, fibrinogen alpha chain and prostaglandin H2-D isomerase. Alpha-1-antitrypsin was validated in vitreous of an independent set of AMD patients using Western blot analysis. Further systems biology analysis of the data indicated that the observed proteomic changes may reflect upregulation of immune response and complement activity.

CONCLUSIONS

Proteome analysis of vitreous samples from patients with AMD, which underwent an intravitreal combination therapy including a core vitrectomy, steroids and bevacizumab, revealed apparent AMD-specific proteomic changes. The identified AMD-associated proteins provide some insight into the pathophysiological changes associated with AMD.

Potential Sources and Roles of Adaptive Immunity in Age-Related Macular Degeneration: Shall We Rename AMD into Autoimmune Macular Disease?

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly throughout the industrialized world. Its most prominent pathologic features are lesions involving the retinal pigment epithelium (RPE) the Bruch's membrane, the degeneration of photoreceptors, and, in the most aggressive cases, choroidal neovascularization. Genetic associations between the risk of developing AMD and polymorphism within components of the complement system, as well as chemokine receptors expressed on microglial cells and macrophages, have linked retinal degeneration and choroidal neovascularization to innate immunity (inflammation). In addition to inflammation, players of the adaptive immunity including cytokines, chemokines, antibodies, and T cells have been detected in animal models of AMD and in patients suffering from this pathology. These observations suggest that adaptive immunity might play a role in different processes associated with AMD such as RPE atrophy, neovascularization, and retinal degeneration. To this date however, the exact roles (if any) of autoantibodies and T cells in AMD remain unknown. In this review we discuss the potential effects of adaptive immune responses in AMD pathogenesis.

T cells and macrophages responding to oxidative damage cooperate in pathogenesis of a mouse model of age-related macular degeneration

Age-related macular degeneration (AMD) is a major disease affecting central vision, but the pathogenic mechanisms are not fully understood. Using a mouse model, we examined the relationship of two factors implicated in AMD development: oxidative stress and the immune system. Carboxyethylpyrrole (CEP) is a lipid peroxidation product associated with AMD in humans and AMD-like pathology in mice. Previously, we demonstrated that CEP immunization leads to retinal infiltration of pro-inflammatory M1 macrophages before overt retinal degeneration. Here, we provide direct and indirect mechanisms for the effect of CEP on macrophages, and show for the first time that antigen-specific T cells play a leading role in AMD pathogenesis. In vitro, CEP directly induced M1 macrophage polarization and production of M1-related factors by retinal pigment epithelial (RPE) cells. In vivo, CEP eye injections in mice induced acute pro-inflammatory gene expression in the retina and human AMD eyes showed distinctively diffuse CEP immunolabeling within RPE cells. Importantly, interferon-gamma (IFN-γ) and interleukin-17 (IL-17)-producing CEP-specific T cells were identified ex vivo after CEP immunization and promoted M1 polarization in co-culture experiments. Finally, T cell immunosuppressive therapy inhibited CEP-mediated pathology. These data indicate that T cells and M1 macrophages activated by oxidative damage cooperate in AMD pathogenesis.

Fcγ receptor upregulation is associated with immune complex inflammation in the mouse retina and early age-related macular degeneration

PURPOSE

Several lines of evidence suggest the involvement of antibodies and immune complex inflammation in AMD, a blinding disease with a strong inflammatory component. To examine this further, we developed a novel experimental mouse model of retinal inflammation and evaluated whether inflammation associated with immune complex formation was present in eyes of AMD donors.

METHODS

A localized immune complex-mediated reaction was induced in the retina of wild-type (WT), Fc receptor γ chain-deficient (γ(-/-)), and C1q-deficient (C1q(-/-)) mice, and donor eyes were obtained after death from donors with early or wet AMD and from healthy control subjects. The presence of immune complexes, Fcγ receptors (FcγRs), and markers of macrophage/microglia activation was investigated by immunohistochemistry.

RESULTS

In WT and C1q(-/-) mice, immune complex deposition in the retina led to a robust inflammatory response with activation of microglia, recruitment of myeloid cells, and increased expression of FcγRI through FcγRIV and major histocompatibility complex class II. This response was not observed in γ(-/-) mice lacking activating FcγRs. We found that early AMD was associated with deposition of IgG, C1q, and membrane attack complex in the choriocapillaris and with increased numbers of CD45+ cells expressing FcγRIIa and FcγRIIb. Furthermore, FcγRIIa and FcγRIIb were observed in eyes of donors with wet AMD.

CONCLUSIONS

Our studies suggest that immune complexes may contribute to AMD pathogenesis through interaction of IgG with FcγRs and might inform about possible adverse effects associated with therapeutic antibodies.

The role of the immune response in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries; with the aging population, the negative health impacts and costs of the disease will increase dramatically over the next decade. Although the exact cause of AMD is unknown, genetic studies have implicated the complement system as well as other immune responses in disease pathogenesis and severity. Furthermore, histologic studies have shown the presence of macrophages, lymphocytes, and mast cells, as well as fibroblasts, in both atrophic lesions and with retinal neovascularization. This review summarizes discussions from the fifth annual conference of the Arnold and Mabel Beckman Initiative for Macular Research by the Inflammation and Immune Response Task Force. These deliberations focused on the role of inflammatory immune responses, including complement, inflammasomes, adaptive immune responses, and para-inflammation, unanswered questions and studies to address these questions, and potential immune-related therapeutic targets for AMD.

Phenotypic expression of Bardet-Biedl syndrome in patients homozygous for the common M390R mutation in the BBS1 gene

PURPOSE

To characterize the phenotype of Bardet-Biedl syndrome (BBS) patients homozygous for the BBS1 M390R mutation.

METHODS

Three patients [PT1, F, 27 years old (yo) at last examination, 14-year follow-up (F/U) PT2, F, 15-yo PT3, M, 15-yo, both 1-year F/U] underwent eye exams, Goldmann visual fields (GVFs), dark- (DA) and light-adapted (LA) electroretinograms (ERGs), spectral domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF). Vision and systemic history were also collected.

RESULTS

All patients had night blindness, hyperopic astigmatism, ptosis or mild blepharospasm, foot polydactyly, 5th finger clinodactyly, history of headaches, and variable, diet-responsive obesity. Two had asthma, PT1 was developmentally delayed, PT2 had Asperger-like symptoms, and PT3 had normal cognition. At age 14, acuity was 20/100 in PT1, who had nystagmus since age 2, 20/40 in PT2 and 20/30 in PT3. By 27yo PT1 progressed to 20/320, by 15 yo PT2 was 20/60 and PT3 remained stable. PT1 had well preserved peripheral GVFs, with minimal progression over 10 years of F/U. PT2 and PT3 presented with ring scotomas and I4e<5°. All patients had severe generalized visual sensitivity depression. ERGs were consistently recordable (also rod ERG in PT3 after 60 min DA), but progressed to non-recordable in PT1. Mixed DA ERGs exhibited electronegativity. In PT3, this was partly due to a bleaching effect during bright-flash DA averaging, partly to ON≫OFF LA response compromise. PT2 and 3 had, on SD-OCTs, generalized macular thinning, normal retinal lamination, and widespread photoreceptor outer/inner segment attenuation except foveally, and multiple rings of abnormal FAF configuring a complex bull's eye-pattern. PT1 had macular atrophy. All patients also had peripapillary nerve fiber layer thickening.

CONCLUSIONS

The observed phenotype matches very closely that reported in patients by Azari et al. (IOVS 2006) and in the Bbs1-M390R knock-in mouse model, and expands it to the characterization of important ERG response characteristics that provide insight in the pathogenesis of retinopathy in these patients. Our findings confirm the consistent pathogenicity of the BBS1 M390R mutation.