title: Quantitative retinal protein analysis after optic nerve transection reveals a neuroprotective role for hepatoma-derived growth factor on injured retinal ganglion cells.
abstract: OBJECTIVE
  Retinal ganglion cell (RGC) degeneration is an important cause of visual impairment and can be modeled by optic nerve transection, which causes the death of 90% of RGCs within 14 days postaxotomy. We performed a proteomic study to identify and quantify proteins in the rat retina after optic nerve transection. Our goal was to isolate potential targets for therapeutic intervention to prevent RGC degeneration.
  
  
  METHODS
  iTRAQ proteomics was used to analyze adult rat retinas at 1, 3, 4, 7, 14, and 21 days postaxotomy. Hepatoma-derived growth factor (HDGF), a target identified by iTRAQ, was delivered by intraocular injections. Wortmannin or PD98059 were coadministered with HDGF to determine if the protective effects of HDGF are dependent on PI3 kinase or MAP kinase activity, respectively.
  
  
  RESULTS
  At a false-discovery rate of 5%, 216 proteins were identified by iTRAQ proteomics, 71 of which showed changes in expression (<0.7× or >1.3×) at one time point after injury: 52 proteins had expression peaks, whereas 19 showed downward expression spikes. Levels of GAPDH did not change after axotomy. Among these differentially expressed proteins was HDGF. HDGF delivery significantly increased RGC survival compared with control treatments, and increased Akt phosphorylation in the retina at 24 hours after intraocular injection. RGC rescue by HDGF was dependent on both MAP kinase and PI3 kinase activity in the retina.
  
  
  CONCLUSIONS
  We have identified numerous proteins that are differentially regulated at key time points after axotomy, and how the temporal profiles of their expression parallel RGC death. Using these data, we showed that HDGF is a potent neuroprotective factor for injured adult RGCs.
authors.affiliation: Division of Anatomy, Department of Surgery, University of Toronto, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Hollander
authors.forename: Philippe M
authors.initials: PM
authors.lastname: D'Onofrio
authors.forename: Mark M
authors.initials: MM
authors.lastname: Magharious
authors.forename: Meghan D
authors.initials: MD
authors.lastname: Lysko
authors.forename: Paulo D
authors.initials: PD
authors.lastname: Koeberle
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D005136:Eye Proteins / Q000032:analysis*; D005260:Female; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009900:Optic Nerve / Q000378:metabolism* / Q000473:pathology; D020221:Optic Nerve Injuries / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012162:Retinal Degeneration / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction
chemical_list: D005136:Eye Proteins; D036341:Intercellular Signaling Peptides and Proteins; D018696:Neuroprotective Agents; C051610:hepatoma-derived growth factor