Individuals homozygous for the age-related macular degeneration risk-conferring variant of complement factor H have elevated levels of CRP in the choroid

Proc Natl Acad Sci U S A. 2006 Nov 14;103(46):17456-61. doi: 10.1073/pnas.0606234103. Epub 2006 Nov 1.

Abstract

Polymorphisms in the complement factor H gene (CFH) are associated with a significantly increased risk for, or protection against, the development of age-related macular degeneration (AMD). The most documented risk-conferring single-nucleotide polymorphism results in a tyrosine-to-histidine substitution at position 402 (Y402H) of the CFH protein. In this work, we examined the ocular distributions and relative abundance of CFH, several CFH-binding proteins, and abundant serum proteins in the retinal pigmented epithelium (RPE), Bruch's membrane, and choroid (RPE-choroid) in CFH homozygotes possessing either the "at-risk" 402HH or "normal" 402YY variants. Although CFH immunoreactivity is high in the choroid and in drusen, no differences in CFH-labeling patterns between genotypes are apparent. In contrast, at-risk individuals have significantly higher levels of the CFH-binding protein, C-reactive protein (CRP), in the choroidal stroma. Immunoblots confirm that at-risk individuals have approximately 2.5-fold higher levels of CRP in the RPE-choroid; no significant differences in the levels of CFH or other serum proteins are detected. Similarly, we find no differences in CFH transcription levels in the RPE-choroid nor evidence for local ocular CRP transcription. Increased levels of CRP in the choroid may reflect a state of chronic inflammation that is a by-product of attenuated CFH complement-inhibitory activity in those who possess the CFH at-risk allele. Because the CRP-binding site in CFH lies within the domain containing the Y402H polymorphism, it is also possible that the AMD risk-conferring allele alters the binding properties of CFH, thereby leading to choroidal CRP deposition, contributing to AMD pathogenesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Distribution
  • Aged
  • Aged, 80 and over
  • C-Reactive Protein / genetics
  • C-Reactive Protein / metabolism*
  • Choroid / metabolism*
  • Choroid / pathology*
  • Complement Factor H / genetics
  • Complement Factor H / metabolism
  • Complement Membrane Attack Complex / metabolism
  • Female
  • Genetic Variation / genetics*
  • Homozygote
  • Humans
  • Macular Degeneration / genetics
  • Macular Degeneration / metabolism*
  • Macular Degeneration / pathology*
  • Male
  • Middle Aged
  • Pigment Epithelium of Eye / metabolism
  • Risk Factors
  • Transcription, Genetic / genetics

Substances

  • CFH protein, human
  • Complement Membrane Attack Complex
  • Complement Factor H
  • C-Reactive Protein