Modifying levels of factors associated with age-related macular degeneration (AMD) may decrease the risk for visual impairment in older persons.Objective
To examine the relationships of markers of inflammation, oxidative stress, and endothelial dysfunction to the 20-year cumulative incidence of early AMD.Design, Setting, and Participants
This longitudinal population-based cohort study involved a random sample of 975 persons in the Beaver Dam Eye Study without signs of AMD who participated in the baseline examination in 1988-1990 and up to 4 follow-up examinations in 1993-1995, 1998-2000, 2003-2005, and 2008-2010.Exposures
Serum markers of inflammation (high-sensitivity C-reactive protein, tumor necrosis factor–α receptor 2, interleukin-6, and white blood cell count), oxidative stress (8-isoprostane and total carbonyl content), and endothelial dysfunction (soluble vascular cell adhesion molecule–1 and soluble intercellular adhesion molecule–1) were measured. Interactions with complement factor H (rs1061170), age-related maculopathy susceptibility 2 (rs10490924), complement component 3 (rs2230199), and complement component 2/complement factor B (rs4151667) were examined using multiplicative models. Age-related macular degeneration was assessed from fundus photographs.Main Outcomes and Measures
Early AMD defined by the presence of any size drusen and the presence of pigmentary abnormalities or by the presence of large-sized drusen (≥125-μm diameter) in the absence of late AMD.Results
The 20-year cumulative incidence of early AMD was 23.0%. Adjusting for age, sex, and other risk factors, high-sensitivity C-reactive protein (odds ratio comparing fourth with first quartile, 2.18; P = .005), tumor necrosis factor–α receptor 2 (odds ratio, 1.78; P = .04), and interleukin-6 (odds ratio, 1.78; P = .03) were associated with the incidence of early AMD. Increased incidence of early AMD was associated with soluble vascular cell adhesion molecule–1 (odds ratio per SD on the logarithmic scale, 1.21; P = .04).Conclusions and Relevance
We found modest evidence of relationships of serum high-sensitivity C-reactive protein, tumor necrosis factor–α receptor 2, interleukin-6, and soluble vascular cell adhesion molecule–1 to the 20-year cumulative incidence of early AMD independent of age, smoking status, and other factors. It is not known whether these associations represent a cause and effect relationship or whether other unknown confounders accounted for the findings. Even if inflammatory processes are a cause of early AMD, it is not known whether interventions that reduce systemic inflammatory processes will reduce the incidence of early AMD.
"Interestingly, APOA-I and APOE can also extract membrane cholesterol from lipid rafts, activate the innate immunity receptor cluster in the absence of TLR ligands, and induce several inflammatory cytokines including IL-6 (shown for APOA-I) (Smoak et al, 2010). Recently, it has been shown that increased IL-6 levels are associated with AMD incidence (Klein et al, 2014) and with late AMD (Seddon et al, 2005; Klein et al, 2008). It is currently not clear how APOE and IL-6 participate in AMD patho- genesis. "
[Show abstract][Hide abstract] ABSTRACT: Physiologically, the retinal pigment epithelium (RPE) expresses immunosuppressive signals such as FAS ligand (FASL), which prevents the accumulation of leukocytes in the subretinal space. Age-related macular degeneration (AMD) is associated with a breakdown of the subretinal immunosuppressive environment and chronic accumulation of mononuclear phagocytes (MPs). We show that subretinal MPs in AMD patients accumulate on the RPE and express high levels of APOE. MPs of Cx3cr1−/− mice that develop MP accumulation on the RPE, photoreceptor degeneration, and increased choroidal neovascularization similarly express high levels of APOE. ApoE deletion in Cx3cr1−/− mice prevents pathogenic age- and stress-induced subretinal MP accumulation. We demonstrate that increased APOE levels induce IL-6 in MPs via the activation of the TLR2-CD14-dependent innate immunity receptor cluster. IL-6 in turn represses RPE FasL expression and prolongs subretinal MP survival. This mechanism may account, in part, for the MP accumulation observed in Cx3cr1−/− mice. Our results underline the inflammatory role of APOE in sterile inflammation in the immunosuppressive subretinal space. They provide rationale for the implication of IL-6 in AMD and open avenues toward therapies inhibiting pathogenic chronic inflammation in late AMD.
EMBO Molecular Medicine 01/2015; 7(2). DOI:10.15252/emmm.201404524 · 8.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Delayed rod-mediated dark adaptation (DA) is characteristic of early age-related macular degeneration (AMD) and also can be observed in some older adults in normal macular health. We examine cross-sectional associations between rod-mediated DA and risk factors for AMD in older adults in normal macular health.
The sample consisted of adults aged ≥60 years old in normal macular health per grading of fundus photos using an established disease classification system. Rod-mediated DA was measured psychophysically following a photobleach using a computer-automated dark adaptometer with targets centered at 5° on the inferior vertical meridian. The speed of DA was characterized by the rod-intercept value, with abnormal DA defined as rod-intercept ≥ 12.3 minutes. We assessed several health and functional characteristics that the literature has suggested increase AMD risk (e.g., smoking, alcohol use, inflammatory markers, apolipoproteins, low luminance visual acuity, chronic medical conditions, body mass, family history).
Among 381 participants (mean age, 68.5 years; SD, 5.5), 78% had normal and 22% had abnormal DA, with the prevalence of abnormal DA increasing with age. After age-adjustment, abnormal DA was associated with increased odds of elevated C-reactive protein (CRP), heavy use of or abstention from alcohol, high blood pressure, and drop in visual acuity under mesopic conditions.
Despite having normal macular health according to accepted definitions of AMD presence, approximately one-quarter of older adults recruited from primary eye care clinics had abnormal DA, which was associated with known risk factors for AMD, including elevated CRP.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
This study evaluates the potential of serum pro-inflammatory cytokines as AMD biomarkers.
Serum samples from 30 age-related macular degeneration (AMD) patients and 15 age-matched controls were examined for 16 inflammatory cytokines using multiplex ELISA. Patients were divided into three subgroups (improvement/no change/deterioration during anti-VEGF treatment) by OCT and funduscopy, and correlated to the cytokine levels.
Serum concentrations of IL-1α, IL-1β, IL-4, IL-5, IL-10, IL-13, and IL-17 were significantly higher in AMD patients than in controls. None of the co-variables expressed a significant effect on the tested cytokines. Only IL-1a and IL-17 showed a statistically significant difference between groups (improved, unchanged, deteriorated) as determined by one-way ANOVA. Patients with increased macular thickness during treatment showed significantly lower levels of IL-17 compared to improved cases and to unchanged cases (p = 0.004, 0.03 respectively, Dunnett's T3 post hoc multiple test). TNF-α was significantly higher in improved cases compared to deteriorated cases (p =0.03, Dunnett's T3 post hoc multiple test). IL-17 was a significant predictor for macular oedema using linear regression (β = -0.888, p <0.05).
Elevation of IL-1α, IL-1β, IL-4, IL-5, IL-10, IL-13, and IL-17 in the serum of AMD patients supports the hypothesis of AMD as an inflammatory disease. Patients with high IL-17 and TNF-α serum levels were more likely to have a favourable course under VEGF therapy. These cytokines may be used as easy-to-obtain biomarkers.
Albrecht von Graæes Archiv für Ophthalmologie 07/2014; 253(5). DOI:10.1007/s00417-014-2738-8 · 1.91 Impact Factor
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