Murine Ccl2/Cx3cr1 Deficiency Results in Retinal Lesions Mimicking Human Age-Related Macular Degeneration

Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-1857, USA.
Investigative Ophthalmology &amp Visual Science (Impact Factor: 3.4). 09/2007; 48(8):3827-36. DOI: 10.1167/iovs.07-0051
Source: PubMed

ABSTRACT Senescent Ccl2(-/-) mice are reported to develop cardinal features of human age-related macular degeneration (AMD). Loss-of-function single-nucleotide polymorphisms within CX3CR1 are also found to be associated with AMD. The authors generated Ccl2(-/-)/Cx3cr1(-/-) mice to establish a more characteristic and reproducible AMD model.
Single Ccl2- and Cx3cr1-deficient mice were crossbred to obtain Ccl2(-/-)/Cx3cr1(-/-) mice. Funduscopy, histopathology, retinal A2E quantification, proteomics, RT-PCR gene expression assay, immunochemistry, and Western blotting were used to examine the retina and to evaluate gene expression within the retinal tissue.
By 6 weeks of age, all Ccl2(-/-)/Cx3cr1(-/-) mice developed AMD-like retinal lesions, including drusen, retinal pigment epithelium alteration, and photoreceptor degeneration. Furthermore, choroidal neovascularization occurred in 15% of the mice. These degenerative lesions progressed with age. A2E, a major lipofuscin fluorophore that accumulated during AMD progression, was significantly higher in the Ccl2(-/-)/Cx3cr1(-/-) retina than in the wild-type retina. Complement cofactor was higher in the Ccl2(-/-)/Cx3cr1(-/-) RPE. Proteomics data indicated that four proteins were differentially expressed in Ccl2(-/-)/Cx3cr1(-/-) retina compared with control. One of these proteins, ERp29, an endoplasmic reticulum protein, functions as an escort chaperone and in protein folding.
The authors concluded that Ccl2(-/-)/Cx3cr1(-/-) mice develop a broad spectrum of AMD abnormalities with early onset and high penetrance. These observations implicate certain chemokines and endoplasmic reticulum proteins in AMD pathogenesis. Similar to the mechanism of neurodegeneration caused by dysfunction of endoplasmic reticulum proteins, decreased chaperoning may cause misfolded protein accumulation, leading to drusen formation and retinal degeneration.

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Available from: Jeffrey A Kowalak, Sep 26, 2015
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    • "Cx3cr1 -/mice displayed photoreceptor degeneration and subretinal deposit of microglial cells and lipid containing cells. The Ccl2 -/-/Cx3cr1 -/-mouse model demonstrated early onset of the AMD phenotype with high penetrance (Tuo et al., 2007). Ccl2 -/-/Cx3cr1 -/-mice began exhibiting drusen-like lesions by fundoscopy as early as 4–6 weeks of age. "
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    ABSTRACT: Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly. The underlying mechanism of non-neovascular AMD (dry AMD), also named geographic atrophy (GA) remains unclear and the mechanism of retinal pigment epithelial (RPE) cell death in AMD is controversial. We review the history and recent progress in understanding the mechanism of RPE cell death induced by oxidative stress, in AMD mouse models, and in AMD patients. Due to the limitation of toolsets to distinguish between apoptosis and necroptosis (or necrosis), most previous research concludes that apoptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD. Recent studies suggest necroptosis as a major mechanism of RPE cell death in response to oxidative stress. Moreover, ultrastructural and histopathological studies support necrosis as major mechanism of RPE cells death in AMD. In this review, we discuss the mechanism of RPE cell death in response to oxidative stress, in AMD mouse models, and in human AMD patients. Based on the literature, we hypothesize that necroptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD.
    Ageing Research Reviews 09/2015; DOI:10.1016/j.arr.2015.09.002 · 4.94 Impact Factor
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    • "MCP-1/CCL2 interact with the chemokine receptors type 1 and 2 (CX3CR1 and CCR2, resp.) [106, 107]. Macrophages induce granulomatous inflammatory reactions in Bruch's membrane [46, 51, 108]. "
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    ABSTRACT: 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).
    Mediators of Inflammation 08/2014; 2014:930671. DOI:10.1155/2014/930671 · 3.24 Impact Factor
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    • "A significant limitation in studying AMD in rodents is the length of time needed to house animals, with many of the reported signs only developing in aged mice, often well over the age of 12 months. Tuo et al.47 reported an accelerated model of AMD created by crossing Cx3cr1-null and Ccl2-null mice. They observed thickening of the Bruch membrane, RPE changes, photoreceptor loss, and CNV from 6 to 12 weeks.47 "
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    ABSTRACT: Over the recent years, there have been tremendous advances in our understanding of the genetic and environmental factors associated with the development of age-related macular degeneration (AMD). Examination of retinal changes in various animals has aided our understanding of the pathogenesis of the disease. Notably, mouse strains, carrying genetic anomalies similar to those affecting humans, have provided a foundation for understanding how various genetic risk factors affect retinal integrity. However, to date, no single mouse strain that develops all the features of AMD in a progressive age-related manner has been identified. In addition, a mutation present in some background strains has clouded the interpretation of retinal phenotypes in many mouse strains. The aim of this perspective was to describe how animals can be used to understand the significance of each sign of AMD, as well as key genetic risk factors.This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License, where it is permissible to download and share thework providedit is properly cited. The work cannot be changed in any way or used commercially.
    Optometry and vision science: official publication of the American Academy of Optometry 06/2014; 91(8). DOI:10.1097/OPX.0000000000000322 · 1.60 Impact Factor
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