Evidence for an inflammatory process in age-related macular degeneration gains new support

Role of immune inflammation regulated by macrophage in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) can lead to irreversible impairment of visual function, and the number of patients with AMD has been increasing globally. The immunoinflammatory theory is an important pathogenic mechanism of AMD, with macrophages serving as the primary inflammatory infiltrating cells in AMD lesions. Its powerful immunoinflammatory regulatory function has attracted considerable attention. Herein, we provide an overview of the involvement of macrophage-regulated immunoinflammation in different stages of AMD. Additionally, we summarize novel therapeutic approaches for AMD, focusing on targeting macrophages, such as macrophage/microglia modulators, reduction of macrophage aggregation in the subretinal space, modulation of macrophage effector function, macrophage phenotypic alterations, and novel biomimetic nanocomposites development based on macrophage-associated functional properties. We aimed to provide a basis and reference for the further exploration of AMD pathogenesis, developmental influences, and new therapeutic approaches.

Age-Related Macular Degeneration With Visual Disability Is Associated With Cardiovascular Disease Risk in the Korean Nationwide Cohort

Background Age-related macular degeneration (AMD) is the leading cause of visual disability. AMD shares some risk factors with the pathogenesis of cardiovascular disease (CVD). However, previous studies examining the association between AMD and the risk of CVD provide conflicting results. Hence, we investigated the association between AMD, visual disability, and the risk of CVD. Methods and Results This is a nationwide cohort study using data from the Korean National Health Insurance System database (2009-2019) on subjects who underwent a national health screening program in 2009. A total of 3 789 963 subjects were categorized by the presence of AMD and visual disability. Visual disability was defined as a best-corrected visual acuity of ≤20/100 by validated documentation from a specialist physician. Cox regression hazard model was used to examine the hazard ratios (HRs) of CVD, including myocardial infarction and ischemic stroke, after adjusting for potential confounders. During a mean 9.77 years of follow-up, AMD was associated with a 5% higher risk of myocardial infarction (adjusted HR [aHR], 1.05 [95% CI, 1.01-1.10]) but not associated with increased risk of overall CVD (aHR, 1.02 [95% CI, 1.00-1.05]) or ischemic stroke (aHR, 1.02 [95% CI, 0.98-1.06]). However, when AMD was accompanied by visual disability, there was increased risk of CVD (aHR, 1.17 [95% CI, 1.06-1.29]), myocardial infarction (aHR, 1.18 [95% CI, 1.01-1.37]), and ischemic stroke (aHR, 1.20 [95% CI, 1.06-1.35]). These trends were more evident in women and subjects with cardiometabolic comorbidities. Conclusions AMD with visual disability, but not all AMD, was associated with an increased risk of CVD. Patients with AMD who have visual disability should be targeted for CVD prevention.

Extracellular vesicles released by human retinal pigment epithelium mediate increased polarised secretion of drusen proteins in response to AMD stressors

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. Drusen are key contributors to the etiology of AMD and the ability to modulate drusen biogenesis could lead to therapeutic strategies to slow or halt AMD progression. The mechanisms underlying drusen biogenesis, however, remain mostly unknown. Here we demonstrate that under homeostatic conditions extracellular vesicles (EVs) secreted by retinal pigment epithelium (RPE) cells are enriched in proteins associated with mechanisms involved in AMD pathophysiology, including oxidative stress, immune response, inflammation, complement system and drusen composition. Furthermore, we provide first evidence that drusen-associated proteins are released as cargo of extracellular vesicles secreted by RPE cells in a polarised apical:basal mode. Notably, drusen-associated proteins exhibited distinctive directional secretion modes in homeostatic conditions and, differential modulation of this directional secretion in response to AMD stressors. These observations underpin the existence of a finely-tuned mechanism regulating directional apical:basal sorting and secretion of drusen-associated proteins via EVs, and its modulation in response to mechanisms involved in AMD pathophysiology. Collectively, our results strongly support an active role of RPE-derived EVs as a key source of drusen proteins and important contributors to drusen development and growth.

Fatty Acids and Lipid Derivatives Protecting Photooxidative Attack in Age-related Macular Degeneration

The objective is the systematic review of studies published in Scielo, Redalyc, Dialnet, Web of Science, Scopus and Pubmed, related to the inclusion of fatty acids and lipid derivatives in the daily diet to prevent or delay the appearance or progression of Age-Related Macular Degeneration (AMD). The analysis of the research results consulted shows that AMD is one of the most frequent causes of blindness in subjects over 55 years of age. AMD is characterized by decreased vision, metamorphopsia, macropsies, micropsies, and central scotoma. Disease that must be diagnosed early as it can lead to irreversible blindness. Among the components of the diet that in numerous epidemiological studies have shown an association in the treatment of AMD and that are reviewed in this work are fatty acids, vitamins and carotenoids. There is ample evidence that fatty acids and lipid derivatives can be included in the diet plans of subjects with AMD.

RETINAL ARTERIAL DILATION IS IMPAIRED IN EYES WITH DRUSEN AND RETICULAR PSEUDODRUSEN

PURPOSE

To analyze static characteristics and dynamic functionality of retinal vessels in eyes with drusen and reticular pseudodrusen (RPD) using dynamic vessel analyzer.

METHODS

Patients with clinical diagnosis of isolated RPD or medium-large drusen and healthy controls were enrolled in the study between July 2016 and May 2018. Participants underwent complete ophthalmologic examination, including enhanced depth imaging structural optical coherence tomography, dynamic retinal vessel analysis, and static retinal vessel analysis.

RESULTS

Twenty-eight eyes of 23 patients with drusen (9 men, mean age 77 ± 6 years), 22 eyes of 16 patients with RPD (7 men, mean age: 76 ± 6 years), and 22 eyes of 22 control subjects (11 men, mean age of 75 ± 6 years) were enrolled. Static retinal vessel analysis did not show any significant difference between the three groups for the central retinal artery equivalent (P = 0.11), the central retinal vein equivalent (P = 0.27), and the arteriovenous ratio (P = 0.30). Dynamic vessel analysis showed significantly reduced arterial dilation in eyes with drusen (P = 0.0001) and RPD (P = 0.015) compared with control subjects. No significant difference was seen between drusen and RPD groups (P = 0.32). Dynamic vessel analysis of retinal veins showed no differences between the three groups (P = 0.10).

CONCLUSION

Dynamic vessel analysis in eyes with drusen and RPD revealed an impaired retinal arterial dilation in response to flicker light stimulation, which further supports the relationship between cardiovascular risk and age-related macular degeneration.

C5 Inhibitor Avacincaptad Pegol for Geographic Atrophy Due to Age-Related Macular Degeneration: A Randomized Pivotal Phase 2/3 Trial

PURPOSE

The complement pathway may play a key role in the pathogenesis of age-related macular degeneration (AMD). The safety and efficacy of avacincaptad pegol (Zimura, IVERIC bio Inc, New York, NY), a C5 inhibitor, were assessed in participants with geographic atrophy (GA) secondary to AMD (GATHER1 Study).

DESIGN

International, prospective, randomized, double-masked, sham-controlled, pivotal phase 2/3 clinical trial.

PARTICIPANTS

A total of 286 participants with GA secondary to AMD.

MAIN OUTCOME MEASURES

The primary efficacy endpoint was the mean rate of change in GA over 12 months measured by fundus autofluorescence (FAF) at 3 timepoints: baseline, month 6, and month 12.

RESULTS

The reduction in the mean rate of GA growth (square root transformation) over 12 months was 27.4% (P = 0.0072) for the avacincaptad pegol 2 mg cohort and 27.8% (P = 0.0051) for the avacincaptad pegol 4 mg cohort compared with their corresponding sham cohorts. The results for both dose groups were statistically significant. Avacincaptad pegol was generally well tolerated after monthly administration over 12 months. There were no avacincaptad pegol-related adverse events (AEs) or inflammation. Further, there were no ocular serious AEs (SAEs) and no cases of endophthalmitis. The most frequent ocular AEs were related to the injection procedure.

CONCLUSIONS

Intravitreal administration of avacincaptad pegol 2 mg and 4 mg led to a significant reduction of GA growth in eyes with AMD over a 12-month period. Because C5 inhibition theoretically preserves C3 activity, it may offer additional safety advantages. A second confirmatory pivotal clinical trial is underway to confirm the efficacy and safety of avacincaptad pegol in slowing the GA growth (GATHER2 Study).

Photoprotection role of melanin in the human retinal pigment epithelium. Imaging techniques for retinal melanin

The human eye is made up of multiple layers of pigmented tissues that have in componence melanin. In the eye, one can separate melanosomes from various embryonic origins. The pigment-producing cells in the stroma of the iris, ciliary body and the choroid (uveal melanocytes) are neural crest derivatives. On the other hand, ciliary, iris and retinal pigment epithelial cells are developed from the neural ectoderm. One universally accepted role of melanin is to react as neutral-density filter in scattering light. Melanin acts as a free radical stabilizer and has the ability to absorb near-infrared, visible light and UV radiation. This paper reviews the current knowledge on ocular melanin, including ocular melanogenesis, roles of melanin in retinal metabolic processes and some imaging techniques that identify melanin in the retina.

Two distinct conformations of factor H regulate discrete complement-binding functions in the fluid phase and at cell surfaces

Factor H (FH) is the major regulator of C3b in the alternative pathway of the complement system in immunity. FH comprises 20 short complement regulator (SCR) domains, including eight glycans, and its Y402H polymorphism predisposes those who carry it to age-related macular degeneration. To better understand FH complement binding and self-association, we have studied the solution structures of both the His-402 and Tyr-402 FH allotypes. Analytical ultracentrifugation revealed that up to 12% of both FH allotypes self-associate, and this was confirmed by small-angle X-ray scattering (SAXS), MS, and surface plasmon resonance analyses. SAXS showed that monomeric FH has a radius of gyration (Rg ) of 7.2-7.8 nm and a length of 25 nm. Starting from known structures for the SCR domains and glycans, the SAXS data were fitted using Monte Carlo methods to determine atomistic structures of monomeric FH. The analysis of 29,715 physically realistic but randomized FH conformations resulted in 100 similar best-fit FH structures for each allotype. Two distinct molecular structures resulted that showed either an extended N-terminal domain arrangement with a folded-back C terminus or an extended C terminus and a folded-back N terminus. These two structures are the most accurate to date for glycosylated full-length FH. To clarify FH functional roles in host protection, crystal structures for the FH complexes with C3b and C3dg revealed that the extended N-terminal conformation accounted for C3b fluid-phase regulation, the extended C-terminal conformation accounted for C3d binding, and both conformations accounted for bivalent FH binding to glycosaminoglycans on the target cell surface.

RPE phagocytic function declines in age-related macular degeneration and is rescued by human umbilical tissue derived cells

Background

Age-related macular degeneration (AMD) is a leading cause of blindness among the elderly characterized by retinal pigment epithelium (RPE) degeneration with accumulation of abnormal intracellular deposits (lipofuscin) and photoreceptor death. RPE is vital for the retina and integrity of photoreceptors through its phagocytic function which is closely linked to formation of lipofuscin through daily phagocytosis of discarded photoreceptor outer segments (POS). Although phagocytosis has been implicated in AMD, it has not been directly shown to be altered in AMD. RPE phagocytic defect was previously shown to be rescued by subretinal injection of human umbilical tissue derived cells (hUTC) in a rodent model of retinal degeneration (RCS rat) through receptor tyrosine kinase (RTK) ligands and bridge molecules. Here, we examined RPE phagocytic function directly in the RPE from AMD patients and the ability and mechanisms of hUTC to affect phagocytosis in the human RPE.

Methods

Human RPE was isolated from the post-mortem eyes of normal and AMD-affected subjects and cultured. RPE phagocytic function was measured in vitro using isolated POS. The effects of hUTC conditioned media, recombinant RTK ligands brain-derived neurotrophic factor (BDNF), hepatocyte growth factor (HGF), and glial cell-derived neurotrophic factor (GDNF), as well as bridge molecules milk-fat-globule-EGF-factor 8 (MFG-E8), thrombospondin (TSP)-1, and TSP-2 on phagocytosis were also examined in phagocytosis assays using isolated POS. RNA was isolated from normal and AMD RPE treated with hUTC conditioned media and subjected to transcriptome profiling by RNA-Seq and computational analyses.

Results

RPE phagocytosis, while showing a moderate decline with age, was significantly reduced in AMD RPE, more than expected for age. hUTC conditioned media stimulated phagocytosis in the normal human RPE and significantly rescued the phagocytic dysfunction in the AMD RPE. RTK ligands and bridge molecules duplicated the rescue effect. Moreover, multiple molecular pathways involving phagocytosis, apoptosis, oxidative stress, inflammation, immune activation, and cholesterol transport were affected by hUTC in the RPE.

Conclusions

We demonstrated for the first time RPE phagocytic dysfunction in AMD, highlighting its likely importance in AMD, and the ability of hUTC to correct this dysfunction, providing insights into the therapeutic potential of hUTC for AMD.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1434-6) contains supplementary material, which is available to authorized users.

Induced pluripotent stem cell-based therapy for age-related macular degeneration

INTRODUCTION

In age-related macular degeneration (AMD), stem cells could possibly replace or regenerate disrupted pathologic retinal pigment epithelium (RPE), and produce supportive growth factors and cytokines such as brain-derived neurotrophic factor.  Induced pluripotent stem cells (iPSCs)-derived RPE was first subretinally transplanted in a neovascular AMD patient in 2014. Areas covered: Induced PSCs are derived from the introduction of transcription factors to adult cells under specific cell culture conditions, followed by differentiation into RPE cells. Induced PSC-derived RPE cells exhibit ion transport, membrane potential, polarized VEGF secretion and gene expression that is similar to native RPE. Despite having similar in vitro function, morphology, immunostaining and microscopic analysis, it remains to be seen if iPSC-derived RPE can replicate the myriad of in vivo functions, including immunomodulatory effects, of native RPE cells.  Historically, adjuvant RPE transplantation during CNV resections were technically difficult and complicated by immune rejection. Autologous iPSCs are hypothesized to reduce the risk of immune rejection, but their production is time-consuming and expensive.  Alternatively, allogenic transplantation using human leukocyte antigen (HLA)-matched iPSCs, similar to HLA-matched organ transplantation, is currently being investigated. Expert opinion: Challenges to successful transplantation with iPSCs include surgical technique, a pathologic subretinal microenvironment, possible immune rejection, and complications of immunosuppression.

C-reactive protein and complement factor H polymorphism interaction in advanced exudative age-related macular degeneration

PURPOSE

To determine the association of C-reactive protein (CRP) and complement factor H (CFH) gene with exudative age-related macular degeneration (AMD) and any possible interaction among these factors.

METHODS

In this case-control study, 139 unrelated patients with exudative AMD and 123 non-AMD controls were recruited. Blood sample was taken for analysis of the CRP levels and DNA testing. DNA fragments of CFH gene variants containing 4 single nucleotide polymorphisms including rs800292, rs1061170, rs2274700, and rs3753395 were assessed. A CRP level of ≥3 mg/L was considered as elevated. The association of elevated CRP and CFH gene variants polymorphism with exudative AMD was compared between the groups.

RESULTS

Mean age was 72.6 ± 6.4 for controls and 74.9 ± 7.4 for case group (P = 0.006). The difference between CRP levels in cases and controls was not statistically significant (P = 0.055). However, Y402H variant of CFH in both homozygous and heterozygous carriers C allele was significantly more frequent among exudative AMD patients than controls, 32.1 versus 6.5 % (P < 0.001). Evaluating various CRP levels in patients with CC and non-CC genotypes disclosed that in CC genotype group, higher CRP level (>3 mg/L) was associated with higher risk of developing exudative AMD (OR = 12.0, CI: 1.5-98.8) compared with the control group.

CONCLUSION

This study disclosed no difference in CRP levels per se between exudative AMD patients with control group. However, higher levels of CRP in the presence of C allele of Y402H might confer more risk for the development of exudative AMD.

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.

Association of age-related macular degeneration and reticular macular disease with cardiovascular disease

Age-related macular degeneration is the leading cause of adult blindness in the developed world. Thus, major endeavors to understand the risk factors and pathogenesis of this disease have been undertaken. Reticular macular disease is a proposed subtype of age-related macular degeneration correlating histologically with subretinal drusenoid deposits located between the retinal pigment epithelium and the inner segment ellipsoid zone. Reticular lesions are more prevalent in females and in older age groups and are associated with a higher mortality rate. Risk factors for developing age-related macular degeneration include hypertension, smoking, and angina. Several genes related to increased risk for age-related macular degeneration and reticular macular disease are also associated with cardiovascular disease. Better understanding of the clinical and genetic risk factors for age-related macular degeneration and reticular macular disease has led to the hypothesis that these eye diseases are systemic. A systemic origin may help to explain why reticular disease is diagnosed more frequently in females as males suffer cardiovascular mortality at an earlier age, before the age of diagnosis of reticular macular disease and age-related macular degeneration.

Brain-derived neurotrophic factor in patients with advanced age-related macular degeneration

AIM

To investigate the serum level of the brain-derived neurotrophic factor (BDNF) in age-related macular degeneration (AMD) and healthy control subjects. The disruption in the tight balance of neuroinflammatory and neuroprotective processes in an immune-privileged site like retina is proposed to contribute to the pathogenesis of AMD. One of the main neuroprotective mediators in the central nervous system is BDNF with its serum level notably affected in several neurodegenerative disorders.

METHODS

Thirty-six patients with AMD and 36 age-matched controls were enrolled in this study. The serum level of BDNF was measured using the enzyme-linked immunosorbent assay method. Results were analyzed to compare case and control values. Comparisons were also made between the BDNF level of wet- vs dry-AMD, and male vs female patients and controls. Analysis of variance (ANOVA) and Student's t-test were employed to analyze the data.

RESULTS

The mean BDNF levels in AMD group were significantly higher than the control group. Furthermore, our analysis revealed greater BDNF values in all AMD subgroups compared to controls (P=0.004, 0.005, 0.001 and 0.02 for male wet-AMD, male dry-AMD, female wet-AMD and female dry-AMD vs controls, respectively). The BDNF level however did not vary between wet- and dry-AMD patients (P=0.74). While within-group comparisons in males and females of AMD and control groups did not show any difference in BDNF (P=0.16, 0.64 and 0.85 for wet-AMD, dry-AMD and control groups, respectively), between-group data showed a higher mean BDNF in both male and female AMD subjects than their peer controls.

CONCLUSION

This study demonstrated that the serum BDNF level is different in patients with AMD as compared to subjects without AMD. Future attempts should be done to unravel beneficial or deleterious effect of this neurotrophin in the pathogenesis of AMD.

Inflammation and Cell Death in Age-Related Macular Degeneration: An Immunopathological and Ultrastructural Model

The etiology of Age-related Macular Degeneration (AMD) remains elusive despite the characterization of many factors contributing to the disease in its late-stage phenotypes. AMD features an immune system in flux, as shown by changes in macrophage polarization with age, expression of cytokines and complement, microglial accumulation with age, etc. These point to an allostatic overload, possibly due to a breakdown in self vs. non-self when endogenous compounds and structures acquire the appearance of non-self over time. The result is inflammation and inflammation-mediated cell death. While it is clear that these processes ultimately result in degeneration of retinal pigment epithelium and photoreceptor, the prevalent type of cell death contributing to the various phenotypes is unknown. Both molecular studies as well as ultrastructural pathology suggest pyroptosis, and perhaps necroptosis, are the predominant mechanisms of cell death at play, with only minimal evidence for apoptosis. Herein, we attempt to reconcile those factors identified by experimental AMD models and integrate these data with pathology observed under the electron microscope—particularly observations of mitochondrial dysfunction, DNA leakage, autophagy, and cell death.

Retinal phagocytes in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in industrial countries. Vision loss caused by AMD results from geographic atrophy (dry AMD) and/or choroidal neovascularization (wet AMD). Presently, the etiology and pathogenesis of AMD is not fully understood and there is no effective treatment. Oxidative stress in retinal pigment epithelial (RPE) cells is considered to be one of the major factors contributing to the pathogenesis of AMD. Also retinal glia, as scavengers, are deeply related with diseases and could play a role. Therefore, therapeutic approaches for microglia and Müller glia, as well as RPE, may lead to new strategies for AMD treatment. This review summarizes the pathological findings observed in RPE cells, microglia and Müller glia of AMD murine models.

Gossypol Acetic Acid Prevents Oxidative Stress-Induced Retinal Pigment Epithelial Necrosis by Regulating the FoxO3/Sestrin2 Pathway

The late stage of dry age-related macular degeneration (AMD), or geographic atrophy (GA), is characterized by extensive retinal pigment epithelial (RPE) cell death, and a cure is not available currently. We have recently demonstrated that RPE cells die from necrosis in response to oxidative stress, providing a potential novel mechanism for RPE death in AMD. In this study, we screened U.S. Food and Drug Administration-approved natural compounds and identified gossypol acetic acid (GAA) as a potent inhibitor of oxidative stress-induced RPE cell death. GAA induces antioxidative response and inhibits accumulation of excessive reactive oxygen species in cells, through which it prevents the activation of intrinsic necrotic pathway in response to oxidative stress. Sestrin2 (SESN2) is found to mediate GAA function in antioxidative response and RPE survival upon oxidative stress. Moreover, Forkhead box O3 transcription factor (FoxO3) is further found to be required for GAA-mediated SESN2 expression and RPE survival. Mechanistically, GAA promotes FoxO3 nuclear translocation and binding to the SESN2 enhancer, which in turn increases its transcriptional activity. Taken together, we have identified GAA as a potent inhibitor of oxidative stress-induced RPE necrosis by regulating the FoxO3/SESN2 pathway. This study may have significant implications in the therapeutics of age-related diseases, especially GA.

Lutein supplementation leads to decreased soluble complement membrane attack complex sC5b-9 plasma levels

PURPOSE

The purpose of this study was to investigate the effect of lutein on systemic complement activation in elderly individuals.

METHODS

Seventy patients with signs of early age-related macular degeneration (AMD) were included in this study. All subjects were randomly assigned to receive a 10 mg daily dose of lutein or a placebo for a time period of 1 year. EDTA blood was collected before and at various time-points during the study (0, 4, 8 and 12 months). The plasma level of the soluble complement membrane attack complex sC5b-9 was measured by ELISA.

RESULTS

We found a significant 1.1 ng/ml monthly decrease in the plasma sC5b-9 concentration in the lutein group (p<0.001), resulting in a decrease from 60.3 ng/ml at baseline to 46.3 ng/ml at 12 months. For the placebo group, we found a significant 0.6 ng/ml monthly increase in plasma sC5b-9 concentration (p=0.001), resulting in an increase from 51.6 ng/ml at baseline to 58.4 ng/ml at 12 months.

CONCLUSIONS

Lutein supplementation inhibits the systemic activation of the complement system, which provides further functional evidence for the reported beneficial effects of this carotenoid in the management of AMD.

Age-related macular degeneration: insights into inflammatory genes

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease that affects approximately 8.7% of elderly people worldwide (>55 years old). AMD is characterized by a multifactorial aetiology that involves several genetic and environmental risk factors (genes, ageing, smoking, family history, dietary habits, oxidative stress, and hypertension). In particular, ageing and cigarette smoking (including oxidative compounds and reactive oxygen species) have been shown to significantly increase susceptibility to the disease. Furthermore, different genes (CFH, CFI, C2, C3, IL-6, IL-8, and ARMS2) that play a crucial role in the inflammatory pathway have been associated with AMD risk. Several genetic and molecular studies have indicated the participation of inflammatory molecules (cytokines and chemokines), immune cells (macrophages), and complement proteins in the development and progression of the disease. Taking into consideration the genetic and molecular background, this review highlights the genetic role of inflammatory genes involved in AMD pathogenesis and progression.

Neuroprotectin D1 is synthesized in the cone photoreceptor cell line 661W and elicits protection against light-induced stress

Docosahexaenoic acid (DHA), an omega-3 fatty acid family member, is obtained by diet or synthesized from dietary essential omega-3 linolenic acid and delivered systemically to the choriocapillaris, from where it is taken up by the retinal pigment epithelium (RPE). DHA is then transported to the inner segments of photoreceptors, where it is incorporated in phospholipids during the biogenesis of outer segment disk and plasma membranes. As apical photoreceptor disks are gradually shed and phagocytized by the RPE, DHA is retrieved and recycled back to photoreceptor inner segments for reassembly into new disks. Under uncompensated oxidative stress, the docosanoid neuroprotectin D1 (NPD1), a potent mediator derived from DHA, is formed by the RPE and displays its bioactivity in an autocrine and paracrine fashion. The purpose of this study was to determine whether photoreceptors have the ability to synthesize NPD1, and whether or not this lipid mediator exerts bioactivity on these cells. For this purpose, 661W cells (mouse-derived photoreceptor cells) were used. First we asked whether these cells have the ability to form NPD1 by incubating cells with deuterium (d4)-labeled DHA exposed to dark and bright light treatments, followed by LC-MS/MS-based lipidomic analysis to identify and quantify d4-NPD1. The second question pertains to the potential bioactivity of these lipids. Therefore, cells were incubated with 9-cis-retinal in the presence of bright light that triggers cell damage and death. Following 9-cis-retinal loading, DHA, NPD1, or vehicle were added to the media and the 661W cells maintained either in darkness or under bright light. DHA and NPD1 were then quantified in cells and media. Regardless of lighting conditions, 661W cells acquired DHA from the media and synthesized 4-9 times as much d4-NPD1 under bright light treatment in the absence and presence of 9-cis-retinal compared to cells in darkness. Viability assays of 9-cis-retinal-treated cells demonstrated that 34 % of the cells survived without DHA or NPD1. However, after bright light exposure, DHA protected 23 % above control levels and NPD1 increased protection by 32 %. In conclusion, the photoreceptor cell line 661W has the capability to synthesize NPD1 from DHA when under stress, and, in turn, can be protected from stress-induced apoptosis by DHA or NPD1, indicating that photoreceptors effectively contribute to endogenous protective signaling mediated by NPD1 under stressful conditions.

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).

Mediator lipidomics in ophthalmology: targets for modulation in inflammation, neuroprotection and nerve regeneration

Studies in the central nervous system (CNS) and retina have revealed the significance of docosahexaenoic acid (DHA), an essential omega-3, 22 carbon 6 double bond (22:6), fatty acid. DHA is necessary for various functions in the CNS, including neuronal membrane bio- and synaptogenesis in memory and vision, and it is the precursor for docosanoids and neuroprotectin D1 (NPD1; 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z hexaenoic acid), a DHA bio-derivative with neuroprotective properties. This review covers three targets in ophthalmology for mediator lipidomics, a subgroup within the field of metabolomics: inflammation, neuroprotection and nerve regeneration. It also discusses the role DHA, NPD1 and other lipid mediators play in these three areas.

Preparation of naringenin/ β-cyclodextrin complex and its more potent alleviative effect on choroidal neovascularization in rats

Choroidal neovascularization (CNV) is characterized by abnormal blood vessels growing from the choroid. Current remedies for CNV have not shown favorable therapeutic efficacy. It is urgent to identify and develop more safe and potent anti-CNV agents via multiple technologies. We previously showed that the natural product naringenin attenuated CNV. However, naringenin has poor water solubility and low bioavailability. Here, we prepared the β-cyclodextrin (β-CD) complex of naringenin and characterized it using infrared spectra and X-ray diffraction analyses. Determination of content and solubility in the complex showed that naringenin accounted for 20.53% in the complex and its solubility was increased by more than 10-fold. Using a laser-induced CNV model in rats we demonstrated that naringenin/β-CD complex more significantly reduced CNV area than naringenin alone in rats. Furthermore, naringenin and its β-CD complex significantly inhibited the mRNA and protein expression of VEGF, COX-2, PI3K, p38MAPK, MMP-2, and MMP-9 in retina and choroid tissues. Naringenin/β-CD complex showed more significant inhibitory effect on VEGF and COX-2 expression than naringenin. These results collectively indicated that naringenin/β-CD complex could be a promising therapeutic option for CNV and that the beneficial effects could be linked to the anti-inflammatory properties of naringenin.

Should I stay or should I go? Trafficking of sub-lytic MAC in the retinal pigment epithelium

Assembly of sub-lytic C5b-9 membrane attack complexes (MAC) on the plasma membrane of retinal pigment epithelial cells contributes to the pathogenesis of age-related macular degeneration. C5b-9 pores induce calcium influx, which activates signaling pathways that compromise cell function. Mechanisms that limit sub-lytic MAC activity include: cell surface complement regulatory proteins CD46, CD55, and CD59 that inhibit specific steps of MAC formation; elimination of assembled MAC by exocytosis of membrane vesicles or by endocytosis and subsequent lysosomal degradation; and rapid resealing of pores by the exocytosis of lysosomes. Aging in the post-mitotic retinal pigment epithelium is characterized by the accumulation of cellular debris called lipofuscin, which has also been associated with retinal diseases such as age-related macular degeneration. Lipofuscin has been shown to activate complement components both in vitro and in vivo, suggesting that it could contribute complement-mediated dysfunction in the retinal pigment epithelium. Here, we discuss emerging evidence that vesicular trafficking in the retinal pigment epithelium is critical for efficient removal of MAC from the cell surface and for limiting inflammation in the outer retina.

Complement factor B polymorphism (rs641153) and susceptibility to age-related macular degeneration: evidence from published studies

AIM

To determine whether single nucleotide polymorphism (SNP) rs641153 is associated with the risk of age-related macular degeneration (AMD), we performed a systematic meta-analysis of 15 eligible studies. SNP in the complement factor B (CFB) gene is considered to have significant association with AMD susceptibility, but there is great discrepancy in these results.

METHODS

The eligible studies were identified by searching the databases of PubMed, EMBASE, and Web of Science. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association. All data were analyzed using Stata software.

RESULTS

The association between rs641153 and AMD risk was statistically significant under the homozygous model (AA vs GG:OR=0.26, 95%CI=0.15-0.45, P h=0.973, I (2)=0.0%, fixed effects), dominant model (AA+GA vs GG:OR=0.49, 95%CI=0.40-0.59, P h=0.004, I (2)=56.4%, random effects) and recessive model (AA vs GA+GG:OR=0.30, 95%CI=0.17-0.51, P h=0.983, I (2)=0.0%, fixed effects). The same results were also observed in the stratified analyses by ethnicity, source of control and sample size.

CONCLUSION

Our meta-analysis suggests that rs641153 in the CFB gene may play a protective role in AMD susceptibility, the late AMD in particular, both in Caucasians and in Asians.

Age-dependent changes in FasL (CD95L) modulate macrophage function in a model of age-related macular degeneration

PURPOSE

We examined the effect of aging on Fas ligand (FasL) function in a mouse model of choroidal neovascularization (CNV).

METHODS

Young and aged mice were laser treated to induce CNV. Bone marrow chimeras were performed between young and aged mice. FasL protein expression was examined in the eye and soluble FasL (sFasL) was measured in the blood. Young and aged mice were treated with a matrix metalloprotease (MMP) inhibitor and systemic sFasL was neutralized by antibody treatment. Macrophages from young and aged mice were tested for sFasL-mediated cytokine production and migration.

RESULTS

The elevated CNV response observed with aging was dependent on bone marrow-derived cells. FasL expression in the eye was increased with age, but decreased following laser treatment. Aged mice had higher levels of sFasL in the blood compared to young mice. Systemic treatment with an MMP inhibitor decreased bloodborne sFasL, and reduced CNV in young and aged mice. Systemic neutralization of sFasL reduced CNV only in aged mice. sFasL increased cytokine production in aged macrophages and proangiogenic M2 macrophages. Aged M2 macrophages had elevated Fas (CD95) expression and displayed increased migration in response to sFasL compared to M1 macrophages derived from young animals.

CONCLUSIONS

Age modulates FasL function where increased MMP cleavage leads to a loss of function in the eye. The released form of FasL (sFasL) preferentially induces the migration of proangiogenic M2 macrophages into the laser lesions and increases proangiogenic cytokines promoting CNV. FasL may be a viable target for therapeutic intervention in aged-related neovascular disease.

Zinc-induced self-association of complement C3b and Factor H: implications for inflammation and age-related macular degeneration

The sub-retinal pigment epithelial deposits that are a hallmark of age-related macular degeneration contain both C3b and millimolar levels of zinc. C3 is the central protein of complement, whereas C3u is formed by the spontaneous hydrolysis of the thioester bridge in C3. During activation, C3 is cleaved to form active C3b, then C3b is inactivated by Factor I and Factor H to form the C3c and C3d fragments. The interaction of zinc with C3 was quantified using analytical ultracentrifugation and x-ray scattering. C3, C3u, and C3b associated strongly in >100 μM zinc, whereas C3c and C3d showed weak association. With zinc, C3 forms soluble oligomers, whereas C3u and C3b precipitate. We conclude that the C3, C3u, and C3b association with zinc depended on the relative positions of C3d and C3c in each protein. Computational predictions showed that putative weak zinc binding sites with different capacities exist in all five proteins, in agreement with experiments. Factor H forms large oligomers in >10 μM zinc. In contrast to C3b or Factor H alone, the solubility of the central C3b-Factor H complex was much reduced at 60 μM zinc and even more so at >100 μM zinc. The removal of the C3b-Factor H complex by zinc explains the reduced C3u/C3b inactivation rates by zinc. Zinc-induced precipitation may contribute to the initial development of sub-retinal pigment epithelial deposits in the retina as well as reducing the progression to advanced age-related macular degeneration in higher risk patients.

Family-based genome-wide copy number scan identifies five new genes of dyslexia involved in dendritic spinal plasticity

Genome-wide screening for copy number variations (CNVs) in ten Indian dyslexic families revealed the presence of five de novo CNVs in regions harboring GABARAP, NEGR1, ACCN1, DCDC5, and one in already known candidate gene CNTNAP2. These genes are located on regions of chromosomes 17p13.1, 1p31.1, 17q11.21, 11p14.1 and 7q35, respectively, and are implicated in learning, cognition and memory processes through dendritic spinal plasticity, though not formally associated with dyslexia. Molecular network analysis of these and other dyslexia-related module genes suggests them to be associated with synaptic transmission, axon guidance and cell adhesion. Thus, we suggest that dyslexia may also be caused by neuronal disconnection in addition to the earlier view that it is due to neuronal migrational disorder.

Parainflammation associated with advanced glycation endproduct stimulation of RPE in vitro: implications for age-related degenerative diseases of the eye

Age related macular degeneration (AMD) is one of the leading causes of blindness in Western society. A hallmark of early stage AMD are drusen, extracellular deposits that accumulate in the outer retina. Advanced glycation endproducts (AGE) accumulate with aging and are linked to several age-related diseases such as Alzheimer's disease, osteoarthritis, atherosclerosis and AMD. AGE deposits are found in drusen and in Bruch's membrane of the eye and several studies have suggested its role in promoting oxidative stress, apoptosis and lipofuscin accumulation. Recently, complement activation and chronic inflammation have been implicated in the pathogenesis of AMD. While AGEs have been shown to promote inflammation in other diseases, whether it plays a similar role in AMD is not known. This study investigates the effects of AGE stimulation on pro- and anti-inflammatory pathways in primary culture of human retinal pigment epithelial cells (RPE). Differential gene expression studies revealed a total of 41 up- and 18 down-regulated RPE genes in response to AGE stimulation. These genes fell into three categories as assessed by gene set enrichment analysis (GSEA). The main categories were inflammation (interferon-induced, immune response) and proteasome degradation, followed by caspase signaling. Using suspension array technology, protein levels of secreted cytokines and growth factors were also examined. Anti-inflammatory cytokines including IL10, IL1ra and IL9 were all overexpressed. Pro-inflammatory cytokines including IL4, IL15 and IFN-γ were overexpressed, while other pro-inflammatory cytokines including IL8, MCP1, IP10 were underexpressed after AGE stimulation, suggesting a para-inflammation state of the RPE under these conditions. Levels of mRNA of chemokine, CXCL11, and viperin, RSAD2, were up-regulated and may play a role in driving the inflammatory response via the NF-kB and JAK-STAT pathways. CXCL11 was strongly immunoreactive and associated with drusen in the AMD eye. The pathways and novel genes identified here highlight inflammation as a key response to AGE stimulation in primary culture of human RPE, and identify chemokine CXCL11 as putative novel agent associated with the pathogenesis of AMD.

Plasma levels of complement proteins from the alternative pathway in patients with age-related macular degeneration are independent of Complement Factor H Tyr⁴⁰²His polymorphism

PURPOSE

To investigate the influence of the Factor H (CFH) Tyr⁴⁰²His polymorphism on the plasma levels of the alternative pathway proteins CFH, C3, Factor B (FB), Factor D (FD), and Factor I (FI) and the inflammatory marker C-reactive protein (CRP) in 119 patients with age-related macular degeneration (AMD) and 152 unrelated control individuals.

METHODS

Patients with AMD and the control group were separated according to CFH polymorphism, age, and gender. Plasma complement proteins and CRP concentrations were determined with enzyme-linked immunosorbent assay, immunodiffusion, or nephelometry.

RESULTS

Significant differences in the concentrations of FD and FI were observed between the patients with AMD and the control individuals. We observed significantly reduced FD plasma levels in patients with AMD. We also identified a significant decrease in CFH plasma levels in female patients with AMD in relation to female controls. Plasma FI levels were significantly increased in patients with AMD compared to the control group. Regarding gender, a significant increase in FI plasma levels was observed in male patients. Finally, we found no significant correlation between the CFH Tyr(402)His polymorphism and the CFH, C3, FB, FD, FI, and CRP plasma levels.

CONCLUSIONS

Patients with AMD present altered levels of FD and FI in a manner independent of this CFH polymorphism, and gender apparently contributes to the plasma levels of these two proteins in patients with AMD and control individuals.

Regulation of VEGF expression in human retinal cells by cytokines: implications for the role of inflammation in age-related macular degeneration

Chronic inflammation is implicated in the pathogenesis of age-related macular degeneration (AMD). Choroidal neovascularization (CNV) observed in exudative form of AMD results in vision loss. Human retinal pigment epithelial cell (HRPE) layer and choroidal tissue are the primary pathological sites in AMD. Pathological and therapeutic evidences have strongly indicated the vascular endothelial growth factor (VEGF) molecules as critical components in CNV pathogenesis. In these studies, we used human primary HRPE and choroidal fibroblast cells (HCHF) prepared from adult donor eyes. The effects of inflammatory cytokine (IFN-γ+ TNF-α+IL-1β) mix (ICM) on global gene expression profiles in HRPE cells, revealed 10- and 9-fold increase in VEGF-A and VEGF-C expression, respectively. The microarray results were validated by quantitative RT-PCR and secretion of VEGFs proteins. IL-1β is the most potent in inducing VEGFs secretion followed by IFN-γ and TNF-α, and the secretion was more effective in the presence of 2 and 3 cytokines. NF-κB and JAK-STAT pathway, but not HIF-1α, Sp-1, Sp-3, and STAT-3, transcription factors were upregulated and translocated to nucleus by ICM treatment. The mRNA levels of VEGF-A and VEGF-C and secretion of these proteins were also significantly enhanced by ICM in HCHF cells. The secretion of other angiogenic molecules, PEDF, SDF-1α, endostatin, and angiopoietins was not affected by ICM. Our results show that the inflammatory cytokines enhance secretion of VEGF-A and VEGF-C by HRPE and HCHF cells. These studies indicate that VEGFs secreted by these cells initiate and promote pathological choroidal and retinal noevascularization processes in AMD.

A rare variant in CFH directly links age-related macular degeneration with rare glomerular nephropathies

A careful analysis of risk haplotypes in relation to age-related macular degeneration (AMD) susceptibility has led to the identification of a rare, high-penetrance variant in the complement factor H (CFH) gene that is also causally associated with atypical hemolytic uremic syndrome (aHUS) and related glomerulopathies. This finding provides a convincing causal mechanism linking the two diseases and develops a paradigm for the genetic architecture of a common and complex disease.

A review and meta-analysis of the association between C-reactive protein and age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 60 in western countries. Inflammatory markers have been implicated in the development and progression of AMD. C-reactive protein (CRP) is an inflammatory marker known to be associated with cardiovascular disease, and a link between AMD and CRP has been suggested. In this systematic review we summarize the currently available evidence from clinic-based and population-based studies investigating this association. A meta-analysis of evidence from eleven studies (41,690 study participants) shows that high serum levels (>3 mg/L) of CRP are associated with a two-fold likelihood of late onset AMD, compared to low levels (<1mg/L). Sub-group meta-analyses show a higher association in studies using ophthalmoscopic examination, compared to those using photographic grading (pooled odds ratio 3.83 vs 1.36), to determine AMD status, or in clinic-based samples compared to population-based studies.

Zinc binding to the Tyr402 and His402 allotypes of complement factor H: possible implications for age-related macular degeneration

The Tyr402His polymorphism of complement factor H (FH) with 20 short complement regulator (SCR) domains is associated with age-related macular degeneration (AMD). How FH contributes to disease pathology is not clear. Both FH and high concentrations of zinc are found in drusen deposits, the key feature of AMD. Heterozygous FH is inhibited by zinc, which causes FH to aggregate. Here, zinc binding to homozygous FH was studied. By analytical ultracentrifugation, large amounts of oligomers were observed with both the native Tyr402 and the AMD-risk His402 homozygous allotypes of FH and both the recombinant SCR-6/8 allotypes with Tyr/His402. X-ray scattering also showed that both FH and SCR-6/8 allotypes strongly aggregated at > 10 μM zinc. The SCR-1/5 and SCR-16/20 fragments were less likely to bind zinc. These observations were supported by bioinformatics predictions. Starting from known zinc binding sites in crystal structures, we predicted 202 putative partial surface zinc binding sites in FH, most of which were in SCR-6. Metal site prediction web servers also suggested that SCR-6 and other domains bind zinc. Predicted SCR-6/8 dimer structures showed that zinc binding sites could be formed at the protein–protein interface that would lead to daisy-chained oligomers. It was concluded that zinc binds weakly to FH at multiple surface locations, most probably within the functionally important SCR-6/8 domains, and this explains why zinc inhibits FH activity. Given the high pathophysiological levels of bioavailable zinc present in subretinal deposits, we discuss how zinc binding to FH may contribute to deposit formation and inflammation associated with AMD.

Age-related macular degeneration: genetic and clinical findings

Age-related macular degeneration (AMD) is a sight threatening eye disease that affects millions of humans over the age of 65 years. It is considered to be the major cause of irreversible blindness in the elderly population in the developed world. The disease is prevalent in Europe and the United States, which has a large number of individuals of European descent. AMD is characterized by a progressive loss of central vision attributable to degenerative and neovascular changes that occur in the interface between the neural retina and the underlying choroid. This location contains the retinal photoreceptors, the retinal pigmented epithelium, a basement membrane complex known as Bruch's membrane and a network of choroidal capillaries. AMD is increasingly recognized as a complex genetic disorder where one or more genes contribute to an individual's susceptibility to development of the condition, while the prevailing view is that the disease stems from the interaction of multiple genetic and environmental factors. Although it has been proposed that a threshold event occurs during normal aging, the sequelae of biochemical, cellular, and molecular events leading to AMD are not fully understood. Here, we review the clinical aspects of AMD and summarize the genes which have been reported to have a positive association with the disease.

Subtoxic levels hydrogen peroxide-induced production of interleukin-6 by retinal pigment epithelial cells

PURPOSE

To study the effect of subtoxic levels of hydrogen peroxide (H(2)O(2)) on the expression and release of interleukin-6 (IL-6) by cultured retinal pigment epithelial (RPE) cells and to explore the relevant signal pathways.

METHODS

Cultured human RPE cells were stimulated with various subtoxic concentrations of H(2)O(2) for different periods. Conditioned medium and cells were collected. IL-6 in the medium and IL-6 mRNA in the collected cells were measured using an IL-6 enzyme-linked immunosorbent assay kit and reverse transcriptase polymerase chain reaction, respectively. Nuclear factor-kappaB (NF-κB) in nuclear extracts and phosphorylated p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinases (JNK) in cells cultured with and without H(2)O(2) were measured by NF-κB and MAPK enzyme-linked immunosorbent assay kits. Inhibitors of p38 (SB203580), ERK (UO1026), JNK (SP600125), and NF-κB (BAY11-7082) were added to the cultures before the addition of H(2)O(2) to test their effects(.)

RESULTS

Subtoxic levels of H(2)O(2) (100 µM and less) increased the IL-6 mRNA level and the release of IL-6 protein by the cultured human RPE cells in a dose- and time-dependent manner. This was accompanied by an increase of NF-κB in nuclear extracts and phosphorylated p38 MAPK, ERK, and JNK in cell lysates, particularly in the p38 and NF-κB. The NF-κB inhibitor decreased the H(2)O(2)-induced expression of IL-6. The p38 inhibitor, but not the ERK or JNK inhibitor, completely abolished H(2)O(2)-induced expression of IL-6 by RPE cells. The p38 inhibitor also abolished the increase of NF-κB in nuclear extracts in cells treated with H(2)O(2).

CONCLUSIONS

H(2)O(2) stimulated the production of IL-6, a key factor in the modulation of immune responses, inflammatory processes, and the occurrence of autoimmune diseases, which recently has been documented to be increased in age-related macular degeneration (AMD). This may be a molecular linkage for the oxidative stress and inflammatory/autoimmune reactions in AMD and may provide a novel target for the treatment of AMD.

Rescue and repair during photoreceptor cell renewal mediated by docosahexaenoic acid-derived neuroprotectin D1

Retinal degenerative diseases result in retinal pigment epithelial (RPE) and photoreceptor cell loss. These cells are continuously exposed to the environment (light) and to potentially pro-oxidative conditions, as the retina's oxygen consumption is very high. There is also a high flux of docosahexaenoic acid (DHA), a PUFA that moves through the blood stream toward photoreceptors and between them and RPE cells. Photoreceptor outer segment shedding and phagocytosis intermittently renews photoreceptor membranes. DHA is converted through 15-lipoxygenase-1 into neuroprotectin D1 (NPD1), a potent mediator that evokes counteracting cell-protective, anti-inflammatory, pro-survival repair signaling, including the induction of anti-apoptotic proteins and inhibition of pro-apoptotic proteins. Thus, NPD1 triggers activation of signaling pathway/s that modulate/s pro-apoptotic signals, promoting cell survival. This review provides an overview of DHA in photoreceptors and describes the ability of RPE cells to synthesize NPD1 from DHA. It also describes the role of neurotrophins as agonists of NPD1 synthesis and how photoreceptor phagocytosis induces refractoriness to oxidative stress in RPE cells, with concomitant NPD1 synthesis.

The immune privileged retina mediates an alternative activation of J774A.1 cells

PURPOSE

We have previously found that retinal pigment epithelial (RPE) cells suppressed endotoxin-stimulated macrophages; moreover, it induced expression of anti-inflammatory cytokines. We further assessed the possibility that the RPE is alternatively activating macrophages.

METHODS

J774A.1 cells were stimulated with endotoxin and treated with the conditioned media (CM) of RPE, or neuroretinal eyecups from healthy mouse eyes. The supernatant was assayed for IL-1 beta, TNF-alpha, IL-6, IL-12(p70), and IL-10, and for nitric-oxide generation. The RPE conditioned media (RPE CM) was absorbed of known soluble factors to identify the factor that augments nitric-oxide generation.

RESULTS

We found the RPE CM suppressed all cytokine production except IL-10, and augmented nitric-oxide generation. The augmented nitric-oxide levels were mediated by RPE derived alpha-melanocyte stimulating hormone (alpha-MSH).

CONCLUSIONS

Healthy RPE not only suppresses inflammatory activity, it promotes an alternative activation of macrophages that can further promote immune privilege.

Neuroprotectin D1/protectin D1 stereoselective and specific binding with human retinal pigment epithelial cells and neutrophils

Retinal pigment epithelial (RPE) cells, derived from the neuroectoderm, biosynthesize the novel lipid mediator neuroprotectin D1 (NPD1) from docosahexaenoic acid (DHA) in response to oxidative stress or to neurotrophins, and in turn, elicits cytoprotection. Here, we report the identification of a 16,17-epoxide-containing intermediate in the biosynthesis of NPD1 in ARPE-19 cells from 17S-hydro-(peroxy)-docosahexaenoic acid. We prepared and isolated tritium-labeled NPD1 ([(3)H]-NPD1) and demonstrate specific and high-affinity stereoselective binding to ARPE-19 cells (K(d)=31.3+/-13.1 pmol/mg of cell protein). The stereospecific NPD1 interactions with these cells in turn gave potent protection against oxidative stress-induced apoptosis, and other structurally related compounds were weak competitors of NPD1 specific binding. This [(3)H]-NPD1/PD1 also displayed specific and selective high affinity binding with isolated human neutrophils (K(d) approximately 25 nM). Neither resolvin E1 nor lipoxin A(4) competed for [(3)H]-NPD1/PD1 specific binding with human neutrophils. Together, these results provide evidence for stereoselective specific binding of NPD1/PD1 with retinal pigment epithelial cells as well as human neutrophils. Moreover, they suggest specific receptors for this novel mediator in both the immune and visual systems.