title: Analysis of complement expression in light-induced retinal degeneration: synthesis and deposition of C3 by microglia/macrophages is associated with focal photoreceptor degeneration.
abstract: OBJECTIVE
  To investigate the expression and localization of complement system mRNA and protein in a light-induced model of progressive retinal degeneration.
  
  
  METHODS
  Sprague-Dawley (SD) rats were exposed to 1000 lux of bright continuous light (BCL) for up to 24 hours. At time points during (1-24 hours) and after (3 and 7 days) exposure, the animals were euthanatized and the retinas processed. Differential expression of complement genes at 24 hours of exposure was assessed using microarray analysis. Expression of complement genes was validated by quantitative PCR, and expression of selected genes was investigated during and after BCL exposure. Photoreceptor apoptosis was assessed using TUNEL and C3 was further investigated by spatiotemporal analysis using in situ hybridization and immunohistochemistry.
  
  
  RESULTS
  Exposure to 24 hours of BCL induced differential expression of a suite of complement system genes, including classic and lectin components, regulators, and receptors. C1qr1, MCP, Daf1, and C1qTNF6 all modulated in concert with photoreceptor death and AP-1 expression, which reached a peak at 24 hours exposure. C1s and C4a reached peak expression at 3 days after exposure, while expression of C3, C3ar1, and C5r1 were maximum at 7 days after exposure. C3 mRNA was detected in ED1- and IBA1-positive microglia/macrophages, in the retinal vessels and optic nerve head and in the subretinal space, particularly at the margins of the emerging lesion.
  
  
  CONCLUSIONS
  The data indicate that BCL induces the prolonged expression of a range of complement genes and show that microglia/macrophages synthesize C3 and deposit it in the ONL after BCL injury. These findings have relevance to the role of complement in progressive retinal degeneration, including atrophic AMD.
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia. matt.rutar@rsbs.anu.edu.au
authors.forename: Matt
authors.initials: M
authors.lastname: Rutar
authors.forename: Riccardo
authors.initials: R
authors.lastname: Natoli
authors.forename: Peter
authors.initials: P
authors.lastname: Kozulin
authors.forename: Krisztina
authors.initials: K
authors.lastname: Valter
authors.forename: Paul
authors.initials: P
authors.lastname: Gatenby
authors.forename: Jan M
authors.initials: JM
authors.lastname: Provis
mesh_terms: D000818:Animals; D017209:Apoptosis; D003176:Complement C3 / Q000235:genetics*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D008027:Light / Q000009:adverse effects; D008264:Macrophages / Q000378:metabolism*; D017628:Microglia / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000235:genetics* / Q000378:metabolism
chemical_list: D003176:Complement C3; D012333:RNA, Messenger