Polymorphisms in CFH, HTRA1 and CX3CR1 confer risk to exudative age-related macular degeneration in Han Chinese

Relationship between rs1410996 polymorphism of CFH gene and essential hypertension patients of Han from Yunnan Province

OBJECTIVE

To explore the relationship between rs1410996 polymorphism of CFH gene and essential hypertension (EH) in the Yunnan Han population.

METHODS

rs1410996 of CFH gene was genotyped based on the collected clinical phenotypes of the EH patients (n = 520) and healthy people (n = 494).

RESULTS

On the genotype model and dominance model, there was no relationship between rs1410996 of CFH gene and EH after adjustment (P > 0.05). On the dominance model of male EH patients, the pulse pressure (PP) level of CC genotype carriers was higher than that of (CT + TT) genotype carriers after adjustment (P < 0.05).

CONCLUSION

rs1410996 of CFH gene has no correlation with the genetic susceptibility to EH in the Yunnan Han population, but it is related to the PP level in male patients.

Genetic factors associated with age-related macular degeneration modulating plasma inflammatory biomarker levels in patients with AIDS

INTRODUCTION

Patients with the acquired immunodeficiency syndrome (AIDS) have an increased prevalence and incidence of intermediate-stage age-related macular degeneration (AMD). Several elevated plasma inflammatory biomarkers are associated with increased incidence of intermediate-stage AMD in this population. We evaluated the association between AMD risk alleles and plasma inflammatory biomarker levels in persons with AIDS.

MATERIALS AND METHODS

Cryopreserved plasma specimens of 229 non-Hispanic White and 252 non-Hispanic blacks from the Longitudinal Study of the Ocular Complications of AIDS cohort were assayed for plasma levels of soluble tumor necrosis factor receptor (sTNFR) 2, interleukin (IL)-18, C × 3motif chemokine ligand 1 (CX3CL1), C-reactive protein (CRP), and soluble CD14 (sCD14). Genotyping included AMD-associated variants rs10801553 and rs800292 for complement factor H (CFH) rs9332739 and rs547154 for complement factor 2 (C2), rs2230199 for C3, rs2285714 for CFI, and rs3732379 and rs3732378 for C × 3motif chemokine receptor 1 (CX3CR1).

RESULTS

In Whites, AMD low-risk CX3CR1 variants (V249I and T280M) were associated with reduced plasma levels of IL-18. In Blacks, AMD low-risk C3 R102G and low-risk CX3CR1 T280M variants were associated with reduced CRP levels.

CONCLUSIONS

Genetic variants in AMD-associated immune genes may influence AMD-associated systemic plasma inflammatory biomarker levels in patients with AIDS.

Association of the Complement Factor H Y402H Polymorphism and Response to Anti-Vascular Endothelial Growth Factor Treatment in Age-Related Macular Degeneration: An Updated Meta-Analysis

INTRODUCTION

Anti-vascular endothelial growth factor (anti-VEGF) agents have a variable effect on patients with age-related macular degeneration (AMD) that has been attributed to several causes, including genetic factors. We evaluated the effects of Complement Factor H (CFH) rs1061170/Y402H polymorphism on the response to anti-VEGF therapy among AMD patients.

METHODS

PubMed, Scopus, EMBASE, Web of Science, and Google Scholar were used for a literature search. Pooled odds ratios (ORs) and their 95% confidence intervals (CIs) were estimated to assess the effects of CFH Y402H polymorphism on the response to anti-VEGF therapy in AMD. I2 was used to present the amount of heterogeneity. We used STATA version 14.0 software.

RESULTS

Twenty-five papers reporting data for 4,681 patients were included in this study. Better response to anti-VEGF therapy was seen in T over C (OR = 1.25, 95% CI = 1.04-1.50), TT over CC (OR = 1.60, 95% CI = 1.06-2.4), and TT + TC over CC (OR = 1.68, 95% CI = 1.23-2.28) genotypes. There was no significant difference in the three other genetic models (TT vs. TC, TT vs. TC + CC, TC vs. TT + CC). In Asians, no significant difference was observed in all six genetic models. Ranibizumab and bevacizumab had similar efficacy; however, conbercept was more effective in homozygous genotypes. The literature indicated that TT and TC genotypes and T allele were associated with a better functional response, while the CC genotype and C alleles had a better anatomical response. The combination of risk alleles in ARMS2 A69S (rs10490924), VEGF-A (rs699947), and VEGF-A (rs833069) with Y420H is a predictor of non-respondents.

CONCLUSION

In patients with AMD, the CFH Y402H is a predictor of the response to anti-VEGF agents and should be considered in the treatment plan.

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.

Biomarkers as Predictive Factors of Anti-VEGF Response

Age-related macular degeneration is the main cause of irreversible vision in developed countries, and intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections are the current gold standard treatment today. Although anti-VEGF treatment results in important improvements in the course of this disease, there is a considerable number of patients not responding to the standardized protocols. The knowledge of how a patient will respond or how frequently retreatment might be required would be vital in planning treatment schedules, saving both resource utilization and financial costs, but today, there is not an ideal biomarker to use as a predictive response to ranibizumab therapy. Whole blood and blood mononuclear cells are the samples most studied; however, few reports are available on other important biofluid samples for studying this disease, such as aqueous humor. Moreover, the great majority of studies carried out to date were focused on the search for SNPs in genes related to AMD risk factors, but miRNAs, proteomic and metabolomics studies have rarely been conducted in anti-VEGF-treated samples. Here, we propose that genomic, proteomic and/or metabolomic markers could be used not alone but in combination with other methods, such as specific clinic characteristics, to identify patients with a poor response to anti-VEGF treatment to establish patient-specific treatment plans.

Association of the HtrA1 rs11200638 Polymorphism with Neovascular Age-Related Macular Degeneration in Indonesia

Introduction

The aim of this study was to investigate the association of the HtrA1 rs11200638 polymorphism with neovascular age-related macular degeneration (nAMD) in Indonesia.

Methods

This case–control study included 80 patients with nAMD and 85 controls. Demographic parameters and whole blood were collected from each participant. Genomic DNA was extracted and used to assess the rs11200638 genotype by PCR and restriction enzyme digestion. Associations between the HtrA1 rs11200638 polymorphism and other risk factors for susceptibility to nAMD were assessed using the logistic regression model.

Results

Significant allelic associations between the HtrA1 polymorphism and nAMD were detected (odds ratio [OR] 8.67; 95% confidence interval [CI] 4.88–15.41; P < 0.001). Genotype analysis showed a statistical difference between the nAMD group and the control group (P < 0.001). In the multiple adjusted logistic regression model, people with the AA genotype were more likely to have nAMD although there was a wide confidence interval (OR 19.65; 95% CI 4.52–85.38; P < 0.001).

Conclusion

Our findings show that the risk of nAMD increased in the presence of risk alleles of HtrA1 rs11200638.

CX3CL1/CX3CR1 signaling targets for the treatment of neurodegenerative diseases

Neuroinflammation was initially thought of as a consequence of neurodegenerative disease pathology, but more recently it is becoming clear that it plays a significant role in the development and progression of disease. Thus, neuroinflammation is seen as a realistic and valuable therapeutic target for neurodegeneration. Neuroinflammation can be modulated by neuron-glial signaling through various soluble factors, and one such critical modulator is Fractalkine or C-X3-C Motif Chemokine Ligand 1 (CX3CL1). CX3CL1 is produced in neurons and is a unique chemokine that is initially translated as a transmembrane protein but can be proteolytically processed to generate a soluble chemokine. CX3CL1 has been shown to signal through its sole receptor CX3CR1, which is located on microglial cells within the central nervous system (CNS). Although both the membrane bound and soluble forms of CX3CL1 appear to interact with CX3CR1, they do seem to have different signaling capabilities. It is believed that the predominant function of CX3CL1 within the CNS is to reduce the proinflammatory response and many studies have shown neuroprotective effects. However, in some cases CX3CL1 appears to be promoting neurodegeneration. This review focusses on presenting a comprehensive overview of the complex nature of CX3CL1/CX3CR1 signaling in neurodegeneration and how it may present as a therapeutic in some neurodegenerative diseases but not others. The role of CX3CL1/CXCR1 is reviewed in the context of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), ischemia, retinopathies, spinal cord and neuropathic pain, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, and epilepsy.

HTRA1 rs11200638 variant and AMD risk from a comprehensive analysis about 15,316 subjects

BACKGROUND

The high-temperature requirement factor A1 (HTRA1) gene located at 10q26 locus has been associated with age-related macular degenerative (AMD), with the significantly related polymorphism being (rs11200638, -625G/A), however, above association is not consistent. We investigated a comprehensive analysis to evaluate the correlations between rs11200638 polymorphism and AMD susceptibility thoroughly addressing this issue.

METHODS

An identification was covered from the PubMed and Wanfang databases until 27th Jan, 2020. Odds ratios (OR) with 95% confidence intervals (CI) were applied to evaluate the associations. After a thorough and meticulous search, 35 different articles (33 case-control studies with HWE, 22 case-control studies about wet/dry AMD) were retrieved.

RESULTS

Individuals carrying A-allele or AA genotype may have an increased risk to be AMD disease. For example, there has a significantly increased relationship between rs11200638 polymorphism and AMD both for Asians (OR: 2.51, 95%CI: 2.22-2.83 for allelic contrast) and Caucasians [OR (95%CI) = 2.63(2.29-3.02) for allelic contrast]. Moreover, a similar trend in the source of control was detected. To classify the type of AMD, increased association was also observed in both wet (OR: 3.40, 95%CI: 2.90-3.99 for dominant model) and dry (OR: 2.08, 95%CI: 1.24-3.48 for dominant model) AMD. Finally, based on the different genotyping methods, increased relationships were identified by sequencing, TaqMan, PCR-RFLP and RT-PCR.

CONCLUSIONS

Our meta-analysis demonstrated that HTRA1 rs11200638 polymorphism may be related to the AMD development, especially about individuals carrying A-allele or AA genotype, who may be as identified targets to detect and intervene in advance. Further studies using Larger sample size studies, including information about gene-environment interactions will be necessary to carry out.

Plasma fractalkine levels are associated with renal inflammation and outcomes in immunoglobulin A nephropathy

BACKGROUND

A recognized noninvasive biomarker to improve risk stratification of immunoglobulin A nephropathy (IgAN) patients is scarce. Fractalkine has been shown to play a key role in glomerular disease as chemoattractant, adhesion and even fibrosis factor. The current study assessed the possibility of plasma fractalkine as a novel biomarker in IgAN patients.

METHODS

Plasma fractalkine was measured in 229 patients with renal biopsy consistent IgAN from 2012 to 2014, and clinical, pathological and prognostic relationships were analyzed.

RESULTS

The plasma fractalkine levels in IgAN patients were significantly correlated with the creatinine level and 24-h urine protein by both univariate and multivariate analysis. Mesangial hypercellularity was still significantly correlated with the plasma fractalkine levels even after adjustment for other potential predictor variables by multivariate analysis. In addition, the counts of CD20+ B cells or CD68+ macrophage in renal biopsies of IgAN patients were significantly correlated with the plasma fractalkine levels, but not CD4+ and CD8+ T cells. Finally, we concluded that patients with higher plasma fractalkine levels had higher risk of poor renal outcome compared with those with lower plasma fractalkine levels. No association was observed between the CX3CR1 polymorphisms and clinical parameters including plasma fractalkine levels and prognosis. Recombinant fractalkine induced mesangial cells extracellular matrix synthesis and promoted the migration of microphage cells RAW264.7.

CONCLUSIONS

Plasma fractalkine levels were associated with creatinine level, 24-h urine protein, mesangial hypercellularity pathological damage, the CD68+ macrophage and CD20+ B cell infiltration in renal tissue and renal outcome in IgAN patients. Plasma fractalkine might be a potential prognosis novel predictor in Chinese patients with IgAN.

The association between complement factor H rs1061170 polymorphism and age-related macular degeneration: a comprehensive meta-analysis stratified by stage of disease and ethnicity

PURPOSE

The strength of association between complement factor H (CFH) rs1061170 polymorphism and age-related macular degeneration (AMD) differs between AMD subtypes and ethnicities. The main aim was to provide a systematic review and an updated meta-analysis stratified by stage of disease and ethnicity.

METHODS

A literature search in the PubMed-Medline, EMBASE and Web of Science databases was conducted to identify epidemiological studies, published before September 2017, that included at least twp comparison groups (a control group with no signs of AMD and a case group of AMD patients). Genotype distribution, phenotype of the cases, ethnicity, mean age and gender ratio were collected. Odds ratios (ORs) and 95%CIs were estimated under the allelic, homozygous and heterozygous models. Sensitivity and subgroup analyses, by AMD subtype and ethnicity, were performed.

RESULTS

The meta-analysis included data of 27 418 AMD patients and 32 843 controls from 76 studies. In Caucasians, the rs1061170 showed a significant association with early AMD (OR: 1.44; 95%CI 1.27-1.63), dry AMD (OR: 2.90; 95%CI 1.89-4.47) and wet AMD (OR: 2.46; 95%CI 2.15-2.83), under an allelic model. In Asians, the rs1061170 showed a significant association with advanced AMD (OR: 2.09; 95%CI 1.67-2.60), especially wet AMD (OR: 2.24; 95%CI 1.81-2.77).

CONCLUSION

Our work provides a more comprehensive meta-analysis of studies investigating the effect of the CFH rs1061170 polymorphism on AMD risk. These findings not only improve the assessment of disease risk associated with the polymorphism, but also constitute a scientific background to be translated into clinical practice for AMD prevention.

Analysis of genetic polymorphisms for age-related macular degeneration (AMD) in Chinese Tujia ethnic minority group

Background

Age-related macular degeneration (AMD) can cause vision loss or blindness in elderly. The associations between single nucleotide polymorphism (SNP) and AMD in Chinese Tujia ethnic minority group are still unclear.

Methods

A total of 2122 Tujia volunteers were recruited and 197 of them were diagnosed with AMD (either dry or wet type).Then the blood specimens of these 197 AMD patients and 404 controls from the remaining 1925 normal Tujia volunteers were collected to detect the frequencies of 39 chosen SNPs. The Bonferroni method was used to correct the P values from the Fisher’s exact test.

Results

The mean age of the 197 AMD patients(113 males and 84 females) was 68.4197 years old. No significant differences in allelic and genotypic frequencies were found for all the 39 SNPs between the patients and controls. However, weak correlations between 10 SNPs (CFH rs1329428 TT genotype, CFH rs3753394 CC genotype and T allele, CFH rs1410996 AA genotype, CFH rs800292 AA genotype, CFH rs800292 A allele, VEGF rs833061 TT genotype and C allele, VEGF rs2010963 CG genotype, VEGFR2 rs1531289 TT genotype, ARMS2 rs10490924 TT genotype, KCTD10 rs238104 GC genotype, rs1531289 T allele and ARMS2 rs10490924 T allele) and AMD were shown.

Conclusions

The effects of 39 SNPs have found no associations with the morbidity of AMD in Chinese Tujia ethnic minority group.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0756-4) contains supplementary material, which is available to authorized users.

Polymorphisms in the microglial marker molecule CX3CR1 affect the blood volume of the human brain

AIM

CX3CR1, a G-protein-coupled receptor, is involved in various inflammatory processes. Two non-synonymous single nucleotide polymorphisms, V249I (rs3732379) and T280M (rs3732378), are located in the sixth and seventh transmembrane domains of the CX3CR1 protein, respectively. Previous studies have indicated significant associations between T280M and leukocyte functional characteristics, including adhesion, signaling, and chemotaxis, while the function of V249I is unclear. In the brain, microglia are the only proven and widely accepted CX3CR1-expressing cells. This study aimed to specify whether there were specific brain regions on which these two single nucleotide polymorphisms exert their biological impacts through their functional effects on microglia.

METHODS

Associations between the single nucleotide polymorphisms and brain characteristics, including gray and white matter volumes, white matter integrity, resting arterial blood volume, and cerebral blood flow, were evaluated among 1300 healthy Japanese individuals.

RESULTS

The major allele carriers (V249 and T280) were significantly associated with an increased total arterial blood volume of the whole brain, especially around the bilateral precuneus, left posterior cingulate cortex, and left posterior parietal cortex. There were no significant associations between the genotypes and other brain structural indicators.

CONCLUSION

This finding suggests that the CX3CR1 variants may affect arterial structures in the brain, possibly via interactions between microglia and brain microvascular endothelial cells.

Polymorphisms in Selected Genes and Their Association with Age-Related Macular Degeneration in a Chinese Population

Background

Increasing evidence shows that polymorphisms in a number of genes can influence age-related macular degeneration (AMD) risk. This study aimed to investigate the association of CX3CR1 839C/T, CX3CR1 745G/A, PLEKHA1 958A/G, VEGFA +674C/T, and VEGFA +936C/T polymorphisms with AMD risk among Chinese.

Material/Methods

The polymorphisms were genotyped on 827 AMD patients and 827 controls, and the odds ratios (ORs) were calculated under allele, additive, recessive, and dominant genetic models. Logistic regression analysis was performed to control for potential confounders (age, sex, and smoking status).

Results

We showed that all the 5 polymorphisms showed a significant association with AMD risk under the additive model (for homozygous mutant genotype) and at least 1 other genetic model, both before and after adjustment for the potential confounders. PLEKHA1 958A/G polymorphism was associated with a decreased AMD risk (additive model: aOR=0.722, 95% CI=0.450–0.979, P=0.019; allele model: aOR=0.883, 95% CI=0.736–0.992, P=0.014), while all other polymorphisms were associated with an increased AMD risk (CX3CR1 839C/T, additive model: aOR=2.682, 95% CI=1.119–5.709, P=0.022, recessive model: aOR=2.729, 95% CI=1.141–6.048, P=0.010; CX3CR1 745G/A, additive model: aOR=2.614, 95% CI=1.231–6.012, P=0.020, recessive model: aOR=2.340, 95% CI=1.227–5.993, P=0.011; VEGFA +674C/T, additive model: aOR=1.601, 95% CI=1.253–2.179, P<0.001, dominant model: aOR=1.287, 95% CI=1.058–1.570, P<0.001, allele model: OR=1.220, 95% CI=1.118–1.427, P<0.001; VEGFA +936C/T, additive model: aOR=1.509, 95% CI=1.105–2.311, P<0.001, recessive model: aOR=1.432, 95% CI=1.027–2.192, P=0.009, dominant model: aOR=1.207, 95% CI=1.031–1.514, P0.001, allele model: aOR=1.216, 95% CI=1.062–1.408, P<0.001).

Conclusions

We conclude that the 5 polymorphisms could serve as biomarkers for AMD susceptibility.

[The role of inflammation in Age-related Macular Degeneration]

Age-related Macular Degeneration (AMD) is a multifactorial disease that occurs only in senior population. According to Harman's theory (1956), senescence happens due to excessive accumulation and reduced elimination of free radicals in tissues. At the young age, intensive metabolic processes in the outer layers of the retina and pigment epithelium do not lead to the disease because the pigment epithelium itself and the antioxidant protection function well. If they do not work, the immune system becomes involved. Macrophages, microglia, complement system all contribute to the removal of toxic products. R. Medzhidov in 2008 proposed to call this phenomenon 'para-inflammation'. With aging, this protection may fail, especially if there is a genetic predisposition or aggravating environmental factors. Although AMD cannot be truly called an inflammatory disease, the factors of chronic inflammation are present in it. This is especially true for the alternative complement pathway. People carrying polymorphism of the H gene that normally blocks excessive complement activity are reliably known to have AMD more often. The normal functioning of the complement system contributes to para-inflammation, while its hyperactivation leads to more tissue damage inducing the disease. The impairment of the hemo-ophthalmic barrier caused by the defeat of RPE makes antigens of the outer layers of the retina accessible. Depending on the genetic characteristics of the patient, these antigens are represented differently to his immune system, and since they do not have immune tolerance, varying degrees of autoimmune reaction should be expected. The treatment should be aimed at reduction of the oxidative stress, and injection of inhibitors of vascular endothelial growth factors, glucocorticoids, etc. The study of para-inflammation and inflammation in AMD will help create a new generation of effective drugs that affect the key links in these processes.

MiR-2964a-5p binding site SNP regulates ATM expression contributing to age-related cataract risk

This study was to explore the involvement of DNA repair genes in the pathogenesis of age-related cataract (ARC). We genotyped nine single nucleotide polymorphisms (SNPs) of genes responsible to DNA double strand breaks (DSBs) in 804 ARC cases and 804 controls in a cohort of eye diseases in Chinese population and found that the ataxia telangiectasia mutated (ATM) gene-rs4585:G>T was significantly associated with ARC risk. An in vitro functional test found that miR-2964a-5p specifically down-regulated luciferase reporter expression and ATM expression in the cell lines transfected with rs4585 T allele compared to rs4585 G allele. The molecular assay on human tissue samples discovered that ATM expression was down-regulated in majority of ARC tissues and correlated with ATM genotypes. In addition, the Comet assay of cellular DNA damage of peripheral lymphocytes indicated that individuals carrying the G allele (GG/GT) of ATM-rs4585 had lower DNA breaks compared to individuals with TT genotype. These findings suggested that the SNP rs4585 in ATM might affect ARC risk through modulating the regulatory affinity of miR-2964a-5p. The reduced DSBs repair might be involved in ARC pathogenesis.

Functional SNP in 3'-UTR MicroRNA-Binding Site of ZNF350 Confers Risk for Age-Related Cataract

Many studies have suggested that individual susceptibility to age-related cataract (ARC) may be associated with DNA sequence polymorphisms affecting gene regulation. As DNA repair is implicated in ARC pathogenesis and single-nucleotide polymorphisms (SNPs) in the 3'-terminal untranslated region (3'-UTR) targeted by microRNAs (miRNAs) can alter the gene function, we hypothesize that the miRNA-binding SNPs (miRSNPs) in DNA double-strand break repair (DSBR) and nucleotide excision repair (NER) pathways might associate with ARC risk. We genotyped nine miRSNPs of eight genes in DSBR and NER pathways in Chinese population and found that ZNF350- rs2278414:G>A was significantly associated with ARC risk. Even though the Comet assay of cellular DNA damage indicated that all the subtypes of ARC patients had more DNA breaks in peripheral lymphocytes than the controls independent of rs2278414 genotypes, individuals carrying the variant A allele (AA and AG) had lower ZNF350 mRNA levels compared with individuals with GG genotype. Moreover, the in vitro experiment indicated that miR-21-3p and miR-150-5p specifically downregulated luciferase reporter expression in the cell lines transfected with rs2278414 A allele compared with rs2278414 G. These results suggested that the association of SNP rs2278414 with ARC might involve an altered miRNA regulation of ZNF350.

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.

Inflammation and its role in age-related macular degeneration

Inflammation is a cellular response to factors that challenge the homeostasis of cells and tissues. Cell-associated and soluble pattern-recognition receptors, e.g. Toll-like receptors, inflammasome receptors, and complement components initiate complex cellular cascades by recognizing or sensing different pathogen and damage-associated molecular patterns, respectively. Cytokines and chemokines represent alarm messages for leukocytes and once activated, these cells travel long distances to targeted inflamed tissues. Although it is a crucial survival mechanism, prolonged inflammation is detrimental and participates in numerous chronic age-related diseases. This article will review the onset of inflammation and link its functions to the pathogenesis of age-related macular degeneration (AMD), which is the leading cause of severe vision loss in aged individuals in the developed countries. In this progressive disease, degeneration of the retinal pigment epithelium (RPE) results in the death of photoreceptors, leading to a loss of central vision. The RPE is prone to oxidative stress, a factor that together with deteriorating functionality, e.g. decreased intracellular recycling and degradation due to attenuated heterophagy/autophagy, induces inflammation. In the early phases, accumulation of intracellular lipofuscin in the RPE and extracellular drusen between RPE cells and Bruch's membrane can be clinically detected. Subsequently, in dry (atrophic) AMD there is geographic atrophy with discrete areas of RPE loss whereas in the wet (exudative) form there is neovascularization penetrating from the choroid to retinal layers. Elevations in levels of local and systemic biomarkers indicate that chronic inflammation is involved in the pathogenesis of both disease forms.

Four complement factor H gene polymorphisms in association with AMD: A meta-analysis

AIM

To investigate the possible association between CFH gene polymorphisms -543G>A (rs1410996), A473A (rs2274700), -257C>T (rs3753394), IVS15 (rs1329428) and AMD risk.

METHODS

We searched the published literature in the Medline and Scopus from inception to May 2015. A meta-analysis was performed by the programs RevMan 5.1 and Stata 12.0, and the Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated in fixed or random effect model based on heterogeneity test among studies.

RESULTS

Nineteen studies with a total of 10,676 subjects were included in the present meta-analysis. A statistical significant association was observed between AMD risk and CFH -543G>A polymorphism with OR of 1.77 (95% CI, 1.47-2.12), 2.24 (95% CI, 1.71-2.94), 0.49 (95% CI, 0.38-0.62) and 0.25 (95% CI, 0.18-0.37) in additive, dominant, recessive and codominant models, respectively. Similar results were obtained in polymorphisms A473A, -257C>T, IVS15. Furthermore, stratified analysis for ethnicity showed a significantly strong association between -543G>A, A473A polymorphisms and AMD risk.

CONCLUSION

The present meta-analysis suggested that CFH -543G>A, A473A, -257C>T, and IVS15 polymorphisms might be moderately associated with AMD risk. This conclusion warrants confirmation by further studies.

Association of Two Polymorphisms, rs1061170 and rs1410996, in Complement Factor H with Age-Related Macular Degeneration in an Asian Population: A Meta-Analysis

BACKGROUND

With the increasing number of studies indicating that two single-nucleotide polymorphisms (SNPs), rs1061170 and rs1410996, in complement factor H (CFH) might be associated with the susceptibility to age-related macular degeneration (AMD), the exact association still remains uncertain. Thus, we conducted a meta-analysis to systematically summarize and clarify the association between the two SNPs and the AMD risk particularly in an Asian population.

METHODS

A systematic search of studies on the association of two SNPs with the susceptibility to AMD was conducted in PubMed, Embase and Web of Science. Summary odds ratios (ORs) and 95% confidence intervals (CIs) of allele contrast and genotype contrast were estimated using the random or fixed effects model. The Q statistic test was used to identify heterogeneity, and the funnel plot was adopted to evaluate publication bias. A total of 19 case-control studies on rs1061170 and 8 studies on rs1410996 were included.

RESULTS

Clearly a significantly increased trend of AMD was observed with the rs1061170 (T vs. C: OR = 1.91, 95% CI = 1.71-2.13, pH = 0.029; TC vs. CC: OR = 2.11, 95% CI = 1.30-3.42, pH = 0.792; TT vs. CC: OR = 3.90, 95% CI = 2.45-6.22, pH = 0.774). Similarly, the rs1410996 polymorphism also showed a rising AMD tendency (T vs. C: OR = 1.48, 95% CI = 1.17-1.87, pH < 0.001; TC vs. CC: OR = 1.52, 95% CI = 1.13-2.04, pH = 0.002; TT vs. CC: OR = 2.10, 95% CI = 1.27-3.49, pH < 0.001). What is more, subgroup analysis revealed that both polymorphisms indicated a high risk of nAMD (neovascular AMD) in Asian populations.

CONCLUSIONS

This meta-analysis suggested that CFH rs1061170 and rs1410996 polymorphisms were associated with AMD risk, both of which demonstrated a higher susceptibility to AMD, especially to nAMD. However, the results of rs1410996 should be interpreted with caution due to the limited sample and heterogeneity. Large-scale and well-designed studies are needed to validate our findings.

Association of CX3CR1 (V249I and T280M) polymorphisms with age-related macular degeneration: a meta-analysis

OBJECTIVE

Studies investigating the associations between CX3CR1 genetic polymorphisms and age-related macular degeneration (AMD) have reported controversial results. Therefore, this meta-analysis aims to clarify the effects of CX3CR1 T280M and V249I polymorphisms on AMD risk.

DESIGN

Meta-analysis.

PARTICIPANTS

Results from six studies were pooled in the meta-analysis.

METHODS

Relevant studies were selected through an extensive search of PubMed, EMBASE, and the Web of Science databases. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using random-effects model.

RESULTS

Six studies with were included in this systematic review and meta-analysis. There was no significant association between CX3CR1 T280M polymorphism and risk of AMD under all genetic models (TT vs

CC/CT

OR = 1.57, 95% CI = 0.87-2.84; CC vs TT/CT: OR = 0.75, 95% CI = 0.54-1.06; TT vs CC: OR = 0.58, 95% CI = 0.30-1.144; CT vs CC: OR = 1.25, 95% CI = 0.91-1.70). The CX3CR1 V249I polymorphism also did not significantly affect the AMD risk (AA vs

GG/AG

OR = 1.23, 95% CI = 0.98-1.55; AG/AA vs GG: OR = 0.56, 95% CI = 0.29-1.07; AA vs GG: OR = 1.43, 95% CI = 0.97-2.09; AG vs GG: OR = 1.07, 95% CI = 0.85-1.36).

CONCLUSIONS

This meta-analysis suggested that CX3CR1 T280M and V249I polymorphisms may not be associated with an increased risk of AMD based on current published data. Given the limited sample size, the finding on CX3CR1 polymorphisms needs further investigation.

CFH polymorphisms in a Northern Spanish population with neovascular and dry forms of age-related macular degeneration

PURPOSE

To elucidate the potential role of single-nucleotide polymorphisms (SNPs) in complement factor H (CFH) gene in Northern Spanish patients with age-related macular degeneration (AMD).

METHODS

A case-control study of 130 unrelated native Northern Spanish diagnosed with AMD (46 dry, 35 neovascular and 49 mixed) and 96 healthy controls matched by age and ethnicity were enrolled. DNA was isolated from peripheral blood and genotyped for AMD-associated SNPs (rs3753394, rs529825, rs800292, rs3766404, rs203674, rs10671170, rs3753396 and rs1065489) using TaqMan probes and restriction fragment length polymorphism (RFLP). The association study was performed using the HaploView 4.0 software.

RESULTS

The allelic frequency analysis revealed that rs529825, rs800292, rs203674 and rs10671170 were significantly associated with an increased risk for AMD. The haplotypes CGG (rs3753394, rs529825 and rs800292) and GCAG (rs203674, rs1061170, rs3753396 and rs1065489) were significantly associated with AMD while the haplotypes CAA (rs3753394, rs529825 and rs800292) and TTAG (rs203674, rs1061170, rs3753396 and rs1065489) were found to be protective. Small differ-ences in allelic frequencies were found between dry and neovascular cases; however, these differences were not significant and did not distinguish one form the other.

CONCLUSIONS

This study found significant association of SNPs rs529825, rs800292, rs203674 and rs1061170 in the CFH gene with susceptibility to AMD. We identified haplotypes that confer protection or increased risk of AMD but not specific genetic variants in CFH capable to distinguish the different clinical forms of AMD in this cohort. Collectively, our results confirmed that CFH represents a strong genetic risk factor for this disease in the Northern Spanish population.

Identification of genome-wide SNP-SNP and SNP-clinical Boolean interactions in age-related macular degeneration

We propose here a methodology to uncover modularities in the network of SNP-SNP interactions most associated with disease. We start by computing all possible Boolean binary SNP interactions across the whole genome. By constructing a weighted graph of the most relevant interactions and via a combinatorial optimization approach, we find the most highly interconnected SNPs. We show that the method can be easily extended to find SNP/environment interactions. Using a modestly sized GWAS dataset of age-related macular degeneration (AMD), we identify a group of only 19 SNPs, which include those in previously reported regions associated to AMD. We also uncover a larger set of loci pointing to a matrix of key processes and functions that are affected. The proposed integrative methodology extends and overlaps traditional statistical analysis in a natural way. Combinatorial optimization techniques allow us to find the kernel of the most central interactions, complementing current methods of GWAS analysis and also enhancing the search for gene-environment interaction.

Prospective study of common variants in CX3CR1 and risk of macular degeneration: pooled analysis from 5 long-term studies

IMPORTANCE

The CX3CR1 gene is implicated as a candidate gene for age-related macular degeneration (AMD) through several lines of evidence. There is uncertainty, however, as to whether common genetic variants in CX3CR1 alter risk of AMD, since prior studies have been inconsistent and mostly limited to evaluation of 2 nonsynonymous variants, T280M (rs3732378) and V249I (rs3732379).

OBJECTIVE

To determine if common variants in CX3CR1 predict future risk of AMD.

DESIGN, SETTING, AND PARTICIPANTS

Prospective nested case-control study within 5 large study populations with long-term follow-up. We measured genotypes for T280M, V249I, and 13 other common single-nucleotide polymorphisms (SNPs) of the CX3CR1 gene among people who developed AMD (n = 1110, including 369 with neovascular AMD) and 2532 age- and sex-matched controls.

MAIN OUTCOMES AND MEASURES

We determined the incidence rate ratios (RR) and 95% CIs for incidence of AMD for each variant and examined interactions with other AMD-associated variants and modifiable risk factors.

RESULTS

In additive genetic models, we identified nonsignificant associations with AMD for T280M (RR, 0.87; P = .07) and 3 other SNPs, rs2853707 (RR, 0.88; P = .07), rs12636547 (RR, 0.85; P = .10), and rs1877563 (RR, 0.84; P = .06), 1 of which, rs2853707, is positioned in the CX3CR1 promoter region and was associated with neovascular AMD (RR, 0.75; P = .03). We observed that a recessive model was a better fit to the data for some SNPs, with associations between rs11715522 and AMD (RR, 1.27; P = .03) and between rs2669845 (RR, 3.10; P = .04), rs2853707 (RR, 0.48; P = .050), and rs9868689 (RR, 0.31; P = .02) and neovascular AMD. Moreover, in exploratory analyses, we identified a number of possible interactions including between V249I and rs2669845 and dietary intake of ω-3 fatty acids (P = .004 and P = .009, respectively) for AMD; between rs2669845 and obesity (P = .03) for neovascular AMD; between T280M and complement component 3 (C3) R102G for AMD (P = .03); between rs2669845 and Y402H in complement factor H for AMD (P = .04); and between rs2669845, rs2853707, and V249I and C3 R102G for neovascular AMD (P = .008; .04; and .002, respectively).

CONCLUSIONS AND RELEVANCE

This study failed to identify significant associations between common CX3CR1 variants and AMD after considering the number of SNPs analyzed and multiple comparisons. However, we observed evidence consistent with recessive modes of association and that an effect of CX3CR1 variants may depend on other factors including dietary intake of ω-3 fatty acids, obesity, and genotypes at CFH Y402H and C3 R102G. If replicated in other populations, these findings would support a role for CX3CR1 in AMD but also suggest that its role may involve mechanisms that are independent of the T280M/V249I variations.

Association between complement factor H Val62Ile polymorphism and age-related macular degeneration susceptibility: a meta-analysis

BACKGROUND

An increasing body of studies has assessed the contribution of Val62Ile polymorphism to age-related macular degeneration (AMD) risk, but the exact association still remains uncertain. This meta-analysis was undertaken in order to further characterize the potential association between Val62Ile polymorphism and AMD risk in four different ethnic populations.

METHODS

A meta-analysis was performed using data available from 16 case-control studies evaluating correlation between the Val62Ile polymorphism and AMD in Caucasian, Chinese, Japanese and South Korean populations. Data extraction and study quality assessment were performed in duplicate. Summary odds ratios (ORs) and 95% confidence intervals (CIs) of allele contrast and genotype contrast were estimated using the random-effects model. The Q-statistic test was used to identify heterogeneity, and the funnel plot was adopted to evaluate publication bias.

RESULTS

Sixteen studies involving a total of 11,400 subjects based on the search criteria were included in the meta-analysis. In overall populations, the Val62Ile polymorphism seemed to be associated with AMD (ORAA vs. GG=0.40, 95% CI=0.28-0.59; ORAA+GA vs. GG=0.72, 95% CI=0.64-0.80; ORAA vs. GC+GG=0.50, 95% CI=0.36-0.70; ORA vs. G=0.68, 95% CI=0.58-0.78; ORGA vs. GG=0.71, 95% CI=0.65-0.77). Similarly, subgroup analysis also revealed that this polymorphism was related to AMD in all ethnicities.

CONCLUSIONS

This meta-analysis suggested that Val62Ile polymorphism was associated with susceptibility to AMD.

Association of single nucleotide polymorphisms in CFH, ARMS2 and HTRA1 genes with risk of age-related macular degeneration in Egyptian patients

BACKGROUND

Age-related macular degeneration (AMD) is one of the leading causes of blindness in the elderly worldwide. Several single nucleotide polymorphisms (SNPs) have been linked to the risk of developing AMD. We aimed to examine the association between AMD and SNPs on CFH, ARMS2 and HTRA1 in Egyptians, a previously unstudied population.

MATERIALS AND METHODS

Genomic DNA was extracted from 26 AMD patients and 20 controls. Genotyping was performed using PCR followed by allele-specific restriction digestion and direct sequencing.

RESULTS

CFH rs1061170 was significantly associated with AMD with the frequency of the risk C allele being 0.53 in patients and 0.17 in controls (p < 0.017). The odds ratio (OR) for the TC genotype was 5.5 (95% CI: 1.1-26.4) and for combined TC + CC genotypes was 8 (95% CI: 1.7-37.1). ARMS2 rs10490924 was also significantly associated with the risk allele T found at a frequency of 0.5 in AMD and 0.15 in controls (p < 0.017, χ(2) test). The OR for the TG genotype was 4.667 (95% CI: 1.2-18.4) and for combined TG + TT genotypes was 7 (95% CI: 1.8-26.5). HTRA1 rs11200638 also was significantly associated, with the risk allele A found at a frequency of 0.44 in patients and 0.17 in controls (p < 0.017, χ(2) test). OR for GA genotype was 5 (95% CI: 1.2-20.9) and for the combined GA + AA genotypes was 6 (95% CI: 1.4-24.7).

CONCLUSIONS

Our data demonstrates significant association between AMD and rs1061170 on CFH, rs10490924 on ARMS2 and rs11200638 on HTRA1 in Egyptian patients. These findings are in agreement with previous findings in Caucasians.

CCR2(+) monocytes infiltrate atrophic lesions in age-related macular disease and mediate photoreceptor degeneration in experimental subretinal inflammation in Cx3cr1 deficient mice

Atrophic age-related macular degeneration (AMD) is associated with the subretinal accumulation of mononuclear phagocytes (MPs). Their role in promoting or inhibiting retinal degeneration is unknown. We here show that atrophic AMD is associated with increased intraocular CCL2 levels and subretinal CCR2⁺ inflammatory monocyte infiltration in patients. Using age- and light-induced subretinal inflammation and photoreceptor degeneration in Cx3cr1 knockout mice, we show that subretinal Cx3cr1 deficient MPs overexpress CCL2 and that both the genetic deletion of CCL2 or CCR2 and the pharmacological inhibition of CCR2 prevent inflammatory monocyte recruitment, MP accumulation and photoreceptor degeneration in vivo. Our study shows that contrary to CCR2 and CCL2, CX3CR1 is constitutively expressed in the retina where it represses the expression of CCL2 and the recruitment of neurotoxic inflammatory CCR2⁺ monocytes. CCL2/CCR2 inhibition might represent a powerful tool for controlling inflammation and neurodegeneration in AMD.

Association of complement factor H tyrosine 402 histidine genotype with posterior involvement in sarcoid-related uveitis

PURPOSE

To determine whether the complement factor H (CFH) tyrosine 402 histidine (Y402H) variant, recently shown to be associated with age-related macular degeneration (AMD) and multifocal choroiditis, is associated with specific ocular sarcoidosis clinical phenotypes in black and white persons.

DESIGN

Case-control study.

METHODS

The CFH Y402H polymorphism (rs1061170) was genotyped in 41 subjects with ocular sarcoidosis and 393 control subjects. Allele frequencies in the ocular sarcoidosis cases were compared with controls using chi-square score tests. Genotypic model-based (dominant, recessive, and additive) associations of the rs1061170 allele were tested using multivariate logistic regression. Bayesian information criteria were used to formalize model selection. Genotypes were correlated with disease characteristics and severity of ocular inflammation.

RESULTS

The C allele (rs1061170) was found in 35% of controls, but occurred with a significantly higher frequency (48.7%) in ocular sarcoidosis cases (odds ratio, 1.72; 95% confidence interval, 1.09 to 2.78; P = .018). Logistic regression demonstrated an association between rs1061170 and ocular sarcoidosis in 2 of 3 genetic models (additive, P = .0078; recessive, P = .0018). Posterior uveitis and panuveitis were overrepresented significantly in cases with the homozygous variant genotype (CC, 91%; P = .047). The population-attributable risk related to this CFH risk variant was 20%.

CONCLUSIONS

The Y402H polymorphism of CFH seems to be associated with ocular sarcoidosis in black and white persons. Carriage of the CFH Y402H polymorphism in both alleles is associated with an increased risk for posterior uveitis and panuveitis presentation. The prognostic importance of this genotype will require prolonged follow-up studies.

Early degeneration of photoreceptor synapse in Ccl2/Cx3cr1-deficient mice on Crb1(rd8) background

Photoreceptor ribbon synapse releases glutamate to postsynaptic targets. The synaptic ribbon may play multiple roles in ribbon synapse development, synaptic vesicle recycling, and synaptic transmission. Age-related macular degeneration (AMD) patients appear to have fewer or no detectable synaptic ribbons as well as abnormal swelling in the photoreceptor terminals in the macula. However, reports on changes of photoreceptor synapses in AMD are scarce and photoreceptor type and quantity affected in early AMD is still unclear. Here, we employed multiple anatomical techniques to investigate these questions in Ccl2⁻/⁻/Cx3cr1⁻/⁻ mouse on Crb1(rd8) background (DKO rd8) at one month of age. We found that approximately 17% of photoreceptors over the focal lesion were lost. Immunostaining for synapse-associated proteins (CtBP2, synaptophysin, and vesicular glutamate transporter 1) showed significantly reduced expression and ectopic localization. Cone opsins demonstrated dramatic reduction in expression (S-opsins) and extensive mislocalization (M-opsins). Quantitative ultrastructural analysis confirmed a significant decrease in the number of cone terminals and nuclei, numerous vacuoles in remaining cone terminals, reduction in the number of synaptic ribbons in photoreceptor terminals, and ectopic rod ribbon synapses. In addition, glutamate receptor immunoreactivity on aberrant sprouting of rod bipolar cells and horizontal cells were identified at the ectopic synapses. These results indicate that synaptic alterations occur at the early stages of disease and cones are likely more susceptible to damage caused by DKO rd8 mutation. They provide a new insight into potential mechanism of vision function lost due to synaptic degeneration before cell death in the early stages of AMD.

Age- and light-dependent development of localised retinal atrophy in CCL2(-/-)CX3CR1(GFP/GFP) mice

Previous studies have shown that CCL2/CX3CR1 deficient mice on C57BL/6N background (with rd8 mutation) have an early onset (6 weeks) of spontaneous retinal degeneration. In this study, we generated CCL2^−/−CX3CR1^GFP/GFP mice on the C57BL/6J background. Retinal degeneration was not detected in CCL2^−/−CX3CR1^GFP/GFP mice younger than 6 months. Patches of whitish/yellowish fundus lesions were observed in 17∼60% of 12-month, and 30∼100% of 18-month CCL2^−/−CX3CR1^GFP/GFP mice. Fluorescein angiography revealed no choroidal neovascularisation in these mice. Patches of retinal pigment epithelium (RPE) and photoreceptor damage were detected in 30% and 50% of 12- and 18-month CCL2^−/−CX3CR1^GFP/GFP mice respectively, but not in wild-type mice. All CCL2^−/−CX3CR1^GFP/GFP mice exposed to extra-light (∼800lux, 6 h/day, 6 months) developed patches of retinal atrophy, and only 20–25% of WT mice which underwent the same light treatment developed atrophic lesions. In addition, synaptophysin expression was detected in the outer nucler layer (ONL) of area related to photoreceptor loss in CCL2^−/−CX3CR1^GFP/GFP mice. Markedly increased rhodopsin but reduced cone arrestin expression was observed in retinal outer layers in aged CCL2^−/−CX3CR1^GFP/GFP mice. GABA expression was reduced in the inner retina of aged CCL2^−/−CX3CR1^GFP/GFP mice. Significantly increased Müller glial and microglial activation was observed in CCL2^−/−CX3CR1^GFP/GFP mice compared to age-matched WT mice. Macrophages from CCL2^−/−CX3CR1^GFP/GFP mice were less phagocytic, but expressed higher levels of iNOS, IL-1β, IL-12 and TNF-α under hypoxia conditions. Our results suggest that the deletions of CCL2 and CX3CR1 predispose mice to age- and light-mediated retinal damage. The CCL2/CX3CR1 deficient mouse may thus serve as a model for age-related atrophic degeneration of the RPE, including the dry type of macular degeneration, geographic atrophy.

670 nm LED ameliorates inflammation in the CFH(-/-) mouse neural retina

Para-inflammation in the neural retina is thought to contribute to the onset of some age-related retinal diseases. Continuous innate immune system activation, manifests in progressive chronic inflammation, macrophage invasion and cell loss, resulting in visual loss. We have previously shown that mitochondrial function is augmented following 670 nm LED exposure, leading to reduced retinal inflammation. Here, it was asked whether 670 nm LED regulates para-inflammation in an aged-related macular degeneration mouse model. Mutant CFH(-/-) mice were exposed to four 90 s exposures over 2 days for 1 week and 8 weeks. These regimes significantly reduced activated macrophage number, TNF-alpha and MIF protein expression levels. Immuno-reactivity to C3, C3b and calcitonin, all markers of inflammatory status were also altered. Finally, innate immune proteins, TLR 2 and 4, showed a marked decrease in protein expression. These findings support the notion that 670 nm LED regulates innate immunity, alleviating inflammation in the neural retina of an age-related macular degeneration mouse model.

Association of sequence variation in the CX3CR1 gene with geographic atrophy age-related macular degeneration in a Greek population

PURPOSE

To explore the association of two single nucleotide polymorphisms (SNPs) in the CX3CR1 gene with grades of age-related macular degeneration (AMD) in a population-based setting.

METHODS

The Thessaloniki Eye study is a cross-sectional population-based epidemiologic study of chronic eye diseases in Thessaloniki, Greece. A total of 371 subjects were included and classified according to their AMD status. Subjects with AMD Grades 0-1 (n = 188) were compared to those with AMD Grades 2-3 (n = 138), to those with AMD Grade 4 (geographic atrophy) (n = 20) and to those with AMD Grade 5 (neovascular AMD) (n = 25) with regard to the presence of CX3CR1 polymorphisms (V249I and T280M). Polychotomous logistic regression analysis adjusted for age, gender, and smoking was conducted and the log-additive allelic model was preferred.

RESULTS

Participants with AMD Grade 4 were approximately three times more likely to carry the VI249 and nine times more likely to carry the II249 alleles, compared to those with AMD Grades 0-1, whereas those with AMD Grades 2-3 or Grade 5 did not differ. The T280M polymorphism was not associated with either AMD Grades 2-3 or AMD Grades 4 or 5.

CONCLUSION

In this Greek population, after adjusting for known risk factors, increased risk of geographic atrophy (GA) AMD among the carriers of the V249I polymorphism in the CX3CR1 gene was found. Our study failed to reveal any association with the T280M polymorphism reported in previous studies. Additional studies in different ethnic populations using standardized methodology are needed in order to confirm this association.

Genetics of immunological and inflammatory components in age-related macular degeneration

Age-related macular degeneration (AMD), affecting 30 to 50 million elder individuals worldwide, is a disease affecting the macular retina and choroid that can lead to irreversible central vision loss and blindness. Recent findings support a role for immunologic processes in AMD pathogenesis, including generation of inflammatory related molecules in the Bruch's membrane, recruitment of macrophages, complement activation, microglial activation and accumulation in the macular lesions. Pro-inflammatory effects of chronic inflammation and oxidative stress can result in abnormal retinal pigment epithelium, photoreceptor atrophy and choroidal neovascularization. The associations of immunological and inflammatory genes, in particular the genes related to innate immunity with AMD support the involvement of various immunological pathways in the AMD pathogenesis. We review the literature on the involvements of inflammatory genes in AMD, highlight recent genetic discoveries, and discuss the potential application of such knowledge in the management of patients with AMD.

Animal models of age related macular degeneration

Age related macular degeneration (AMD) is the leading cause of vision loss of those over the age of 65 in the industrialized world. The prevalence and need to develop effective treatments for AMD has lead to the development of multiple animal models. AMD is a complex and heterogeneous disease that involves the interaction of both genetic and environmental factors with the unique anatomy of the human macula. Models in mice, rats, rabbits, pigs and non-human primates have recreated many of the histological features of AMD and provided much insight into the underlying pathological mechanisms of this disease. In spite of the large number of models developed, no one model yet recapitulates all of the features of human AMD. However, these models have helped reveal the roles of chronic oxidative damage, inflammation and immune dysregulation, and lipid metabolism in the development of AMD. Models for induced choroidal neovascularization have served as the backbone for testing new therapies. This article will review the diversity of animal models that exist for AMD as well as their strengths and limitations.

Stochastic model search with binary outcomes for genome-wide association studies

Objective

The spread of case–control genome-wide association studies (GWASs) has stimulated the development of new variable selection methods and predictive models. We introduce a novel Bayesian model search algorithm, Binary Outcome Stochastic Search (BOSS), which addresses the model selection problem when the number of predictors far exceeds the number of binary responses.

Materials and methods

Our method is based on a latent variable model that links the observed outcomes to the underlying genetic variables. A Markov Chain Monte Carlo approach is used for model search and to evaluate the posterior probability of each predictor.

Results

BOSS is compared with three established methods (stepwise regression, logistic lasso, and elastic net) in a simulated benchmark. Two real case studies are also investigated: a GWAS on the genetic bases of longevity, and the type 2 diabetes study from the Wellcome Trust Case Control Consortium. Simulations show that BOSS achieves higher precisions than the reference methods while preserving good recall rates. In both experimental studies, BOSS successfully detects genetic polymorphisms previously reported to be associated with the analyzed phenotypes.

Discussion

BOSS outperforms the other methods in terms of F-measure on simulated data. In the two real studies, BOSS successfully detects biologically relevant features, some of which are missed by univariate analysis and the three reference techniques.

Conclusion

The proposed algorithm is an advance in the methodology for model selection with a large number of features. Our simulated and experimental results showed that BOSS proves effective in detecting relevant markers while providing a parsimonious model.

Association between complementary factor H Y402H polymorphisms and age-related macular degeneration in Chinese: Systematic review and meta-analysis

AIM

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world and complement factor H (CFH) polymorphism has been found to associate with the AMD. To investigate whether the Y402H variant in CFH is associated with AMD in Chinese populations, a systematic review and meta-analysis were performed to estimate the magnitude of the gene effect and the possible mode of action.

METHODS

A meta-analysis was performed using data available from ten case-control studies assessing association between the CFH Y402H polymorphism and AMD in Chinese populations involving 1538 AMD. Data extraction and study quality assessment were performed in duplicate. Summary odds ratios (ORs) and 95% confidence intervals (CIs) an allele contrast and genotype contrast were estimated using fixed- effects models. The Q-statistic test was used to assess heterogeneity, and Funnel plot was used to evaluate publication bias.

RESULTS

Seven of ten case-control studies were neovascular AMD, and few studies came from west and north of China. There was strong evidence for association between CFH and AMD in Chinese population, with those having risk allele C 2.35 times more likely to have AMD than subjects with T allele. Evidence of publication bias was not observed in our meta-analysis.

CONCLUSION

[corrected] This meta-analysis summarizes the strong evidence for an association between CFH and AMD in Chinese and indicates each C allele increasing the odds of AMD by 2.33-fold.But more evidences about the relation between CFH polymorphism and different type of Chinese AMD from various district were needed.

Today and future of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 in developed countries. Understanding of the pathologic process, genetic mechanisms, and risk factors of this disease has the benefit of seeking newer and more effective treatment options. Current clinical therapy for AMD shows a dramatic change from a decade ago. Anti-VEGF drug therapy is regarded as the more effective treatment for neovascular AMD now, especially combining PDT therapy. In the future, the genetic and biochemical therapies may be the promising treatments for AMD. This paper will focus on the progress of pathology, candidate genes of AMD, risk factors, and the existing drugs or surgical therapies available, in order to present some new directions of care with the prospect of improved vision in many patients suffered from AMD.

Age-related macular degeneration-susceptibility single nucleotide polymorphisms in a han chinese control population

PURPOSE

Our study aimed to detect the frequency of age-related macular degeneration (AMD)-susceptibility single nucleotide polymorphisms (SNPs) in control subjects of Han Chinese in a population-based study.

METHODS

A total of 419 subjects of Han Chinese without AMD were recruited from our population-based Nantong Eye Study. Nine AMD-susceptibility SNPs were genotyped. The allele/genotype frequencies were compared with the data from the literature and NCBI Reference Assembly.

RESULTS

The call rates of genotyping were > 98%. All tested SNPs except for HTRA1 rs11200638 were in Hardy-Weinberg Equilibrium (HWE). The allele distributions of some AMD-susceptibility SNPs were different from the records for the Chinese population in the National Center for Biotechnology Information (NCBI) Reference Assembly. Compared to those in a Caucasian population, the frequency of minor alleles of CFH rs800292 (48% vs. 19.2%) and HTRA1 rs11200638 were much higher (47% vs. 25%), while the frequency of minor alleles of CFH rs1061170 (9% vs. 35%), CX3CR1 rs3732379 (3% vs. 21%), CX3CR1 rs3732378 (3% vs. 11%) and SERPING1 rs2511989 (11% vs. 48%) were much lower in the Han Chinese population. Minor differences were observed in the frequency of minor alleles of CFB rs4151667, C2 rs547154 and TLR3 rs3775291. The allele/genotype frequencies of CFH rs1061170 and HTRA1 rs11200638, two well-confirmed AMD-susceptible SNPs, were close to each other in the Han Chinese and Japanese population.

CONCLUSION

The distribution of AMD-susceptibility SNPs shows ethnicity specificity. Substantial differences of the SNPs' distribution were noted from study to study, even within the same ethnic group. The genotype data will be used for longitudinal observation of AMD onset in the follow-up of the cohort.

No association between the T280M polymorphism of the CX3CR1 gene and exudative AMD

Major genetic factors for age-related macular degeneration (AMD) have recently been identified as susceptibility risk factors. The CX3CR1 gene has been shown to be associated with AMD in some studies. Our purpose was to analyze the role of the T280M polymorphism of the CX3CR1 gene in a large French population, in a case-control study. 1093 patients with exudative AMD and 396 controls have been recruited and genotyped for the Y402H of CFH, rs10490924 of ARMS2 and T280M of the CX3CR1 gene. The distribution of the Y402H of CFH and of the rs10490924 of ARMS2 was significantly different between cases and controls (p < 0.0001). The distribution of the T280M genotypes was not significantly different in the AMD patients compared to controls (p = 0.99). The Odds Ratio compared to TT individuals was 1.0 (95% CI 0.8-1.3) for TM individuals and 1.0 (95% CI 0.5-2.1) for MM individuals. The M allele frequency was 0.157 in cases and 0.154 in controls (p = 0.87). Our study exclude an association between the T280M of the CX3CR1 gene and exudative AMD in a French population.

Copy number variations in candidate genes in neovascular age-related macular degeneration

PURPOSE

The pathogenesis of age-related macular degeneration (AMD) is strongly influenced by genetic factors, and single nucleotide polymorphisms have been consistently linked to AMD. Copy number variation (CNV), or variation in the number of copies of a particular segment of DNA, may also contribute to AMD pathogenesis. This study evaluated CNVs in candidate genes that have been reported to be linked to AMD.

METHODS

Study participants were 131 patients with neovascular AMD and 103 elderly persons without AMD who were evaluated by retinal specialists at the National Eye Institute. DNA was collected from peripheral whole blood, and duplex RT-PCR based copy number (CN) assays were performed for the genes CCR3, CFH, CX3CR1, ERCC6, HTRA1, and VEGF. Quantitative CNs (CN = 0, 1, 2, or 3+) were determined.

RESULTS

Novel CNVs were discovered in CCR3, CX3CR1, and ERCC6. The unadjusted data suggested that CN = 3+ for CX3CR1 might be mildly protective against AMD, but this trend did not persist after adjustment for age. AMD patients appeared to have an elevated mean CFH CN relative to controls (2.13 [95% confidence interval (CI), 2.05-2.21] vs. 2.01 [95% CI, 1.92-2.09 copies]; P = 0.05). No significant associations between CNV and AMD were observed for the remaining genes.

CONCLUSIONS

The methods described are suitable for quantitative characterization of CNV in candidate genes. The authors identified CNVs in AMD-associated genes but did not find strong evidence for a link with neovascular AMD.

Amyloid beta enhances migration of endothelial progenitor cells by upregulating CX3CR1 in response to fractalkine, which may be associated with development of choroidal neovascularization

OBJECTIVE

Deposits that accumulate beneath retinal pigment epithelium, called drusen, are early signs of age-related macular degeneration (AMD). We have shown that amyloid β (Aβ) is present in drusen, and Aβ may be involved in AMD development. We have also shown that endothelial progenitor cells (EPCs) may contribute to the development of choroidal neovascularization (CNV). Thus, the purpose of this study was to investigate the role played by CX3CR1, a chemokine receptor, in EPC migration and CNV formation.

METHODS AND RESULTS

EPCs collected from human umbilical cords were found to express higher levels of CX3CR1 than human umbilical vein endothelial cells, and exposure of EPCs to Aβ caused further upregulation of CX3CR1. This upregulation was decreased by blocking fractalkine, a ligand of CX3CR1. Exposure of EPCs to fractalkine increased their migration, but pretreatment with Aβ enhanced the migration. The fractalkine-induced EPC migration was more inhibited by EPCs derived from CX3CR1(-/-) mice than wild-type mice. The area of laser-induced CNV was significantly smaller in wild-type mice that received bone marrow transplantation from CX3CR1(-/-) mice than in those that received transplantation from wild-type mice.

CONCLUSIONS

These data suggest that Aβ enhances EPC migration through the upregulation of CX3CR1. This upregulation might play a role in development of CNV.

[Role of chemokines in the development of age-related macular degeneration]

Age-related macular degeneration (AMD) is the main cause of irreversible blindness in industrialized nations. Recent research has emphasized the importance of inflammatory processes in pathogenesis of this disease. Chemotactic cytokines also named chemokines are important mediators of inflammation and might have a role in development of this disease. They appear to be crucial in the subretinal microglia / macrophage accumulation observed in AMD and may participate in the development of retinal degeneration and in choroidal neovascularization. This paper reviews the possible implication of chemokines in the development of AMD.

CCL2/CCR2 and CX3CL1/CX3CR1 chemokine axes and their possible involvement in age-related macular degeneration

The causes of age-related macular degeneration (AMD) are not well understood. Due to demographic shifts in the industrialized world a growing number of people will develop AMD in the coming decades. To develop treatments it is essential to characterize the disease's pathogenic process. Over the past few years, numerous studies have focused on the role of chemotactic cytokines, also known as chemokines. Certain chemokines, such as CCL2 and CX3CL1, appear to be crucial in subretinal microglia and macrophage accumulation observed in AMD, and participate in the development of retinal degeneration as well as in choroidal neovascularization. This paper reviews the possible implications of CCL2 and CX3CL1 signaling in AMD. Expression patterns, single nucleotide polymorphisms (SNPs) association studies, chemokine and chemokine receptor knockout models are discussed. Future AMD treatments could target chemokines and/or their receptors.