Immunological protein expression profile in Ccl2/Cx3cr1 deficient mice with lesions similar to age-related macular degeneration

Exp Eye Res. 2008 Apr;86(4):675-83. doi: 10.1016/j.exer.2008.01.014. Epub 2008 Jan 25.

Abstract

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.

MeSH terms

  • Animals
  • Autoantibodies / blood
  • Bruch Membrane / immunology
  • CX3C Chemokine Receptor 1
  • Capillaries / immunology
  • Chemokine CCL2 / deficiency*
  • Chemokine CCL2 / immunology
  • Chemokine CCL2 / physiology
  • Choroid / blood supply
  • Complement C3 / biosynthesis
  • Complement C3 / genetics
  • Complement C3d / metabolism
  • Disease Models, Animal*
  • Gene Expression
  • Macrophages / immunology
  • Macular Degeneration / immunology*
  • Mice
  • Mice, Knockout
  • Microglia / immunology
  • Pigment Epithelium of Eye / immunology
  • Polymorphism, Single Nucleotide
  • RNA, Messenger / genetics
  • Receptors, Chemokine / deficiency*
  • Receptors, Chemokine / immunology
  • Receptors, Chemokine / physiology
  • Toll-Like Receptor 4 / metabolism
  • Uveitis / immunology

Substances

  • Autoantibodies
  • CX3C Chemokine Receptor 1
  • Ccl2 protein, mouse
  • Chemokine CCL2
  • Complement C3
  • Cx3cr1 protein, mouse
  • RNA, Messenger
  • Receptors, Chemokine
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Complement C3d