Immunological protein expression profile in Ccl2/Cx3cr1 deficient mice with lesions similar to age-related macular degeneration.
Age-related macular degeneration (AMD) is the leading cause of blindness in the United States. Ccl2 knock-out (KO) mice sporadically develop the cardinal features of AMD in their senescent stage. Humans bearing a loss of function variant or single nucleotide polymorphism (SNP) in CX3CR1 are at increased risk of developing AMD. We recently developed Ccl2(-/-)/Cx3cr1(-/-) mice, which consistently develop retinal degeneration with many AMD features. Since there is strong evidence for an immunological role in AMD pathogenesis, we examined ocular immune protein expression levels in Ccl2(-/-)/Cx3cr1(-/-), Ccl2(-/-), Cx3cr1(-/-), and age-matched wild-type (WT) mice. Immunohistochemistry revealed increased complement C3d in Bruch's membrane, retinal pigment epithelium (RPE), choroidal capillaries, and particularly drusen of the Ccl2(-/-)/Cx3cr1(-/-) mice relative to the WT controls. No change was detected in single KO mice. Real-time RT-PCR revealed a 2.5-fold increase in C3 expression in the Ccl2(-/-)/Cx3cr1(-/-). While the retinas of four month old WT and Ccl2(-/-) showed minimal immunoreactivity for markers of macrophages and microglia, infiltrates of these mononuclear phagocytic cells were detected in the Ccl2(-/-)/Cx3cr1(-/-)retinal lesions and a few foci in the Cx3cr1(-/-) retina. The Ccl2(-/-)/Cx3cr1(-/-) had reduced toll-like receptor 4 (TLR4) expression in the RPE. Following LPS injection, the Ccl2(-/-)/Cx3cr1(-/-) had significantly reduced endotoxin-induced uveitis scores and showed a diminished increase in Tlr4 mRNA expression. No changes in TLR4 expression were detected in either single KO. Autoantibodies against the retina and photoreceptors were also detected in the Ccl2(-/-)/Cx3cr1(-/-) serum. Real-time RT-PCR revealed significant increases in Ccl5 transcript in the Ccl2(-/-)/Cx3cr1(-/-) relative to the WT. These results suggest that innate immunity and possibly adaptive immunity play an important role in Ccl2(-/-)/Cx3cr1(-/-) retinal degeneration. Moreover, since human AMD patients show similar immunopathological profiles, these results support the Ccl2(-/-)/Cx3cr1(-/-) as a suitable model for human AMD.
Ross
Robert J
RJ
Section of Immunopathology, Laboratory of Immunology, National Eye Institute, Bethesda, MD 20892, USA.
Zhou
Min
M
Shen
Defen
D
Fariss
Robert N
RN
Ding
Xiaoyan
X
Bojanowski
Christine M
CM
Tuo
Jingsheng
J
Chan
Chi-Chao
CC
D000818:Animals; D001323:Autoantibodies / Q000097:blood; D016570:Bruch Membrane / Q000276:immunology; D000073883:CX3C Chemokine Receptor 1; D002196:Capillaries / Q000276:immunology; D018932:Chemokine CCL2 / Q000172:deficiency* / Q000276:immunology / Q000502:physiology; D002829:Choroid / Q000098:blood supply; D003176:Complement C3 / Q000096:biosynthesis / Q000235:genetics; D015933:Complement C3d / Q000378:metabolism; D004195:Disease Models, Animal; D015870:Gene Expression; D008264:Macrophages / Q000276:immunology; D008268:Macular Degeneration / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000276:immunology; D010857:Pigment Epithelium of Eye / Q000276:immunology; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000235:genetics; D019707:Receptors, Chemokine / Q000172:deficiency* / Q000276:immunology / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014605:Uveitis / Q000276:immunology
D001323:Autoantibodies; D000073883:CX3C Chemokine Receptor 1; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D003176:Complement C3; C471885:Cx3cr1 protein, mouse; D012333:RNA, Messenger; D019707:Receptors, Chemokine; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D015933:Complement C3d