Abstract
Purpose: :
To identify proteomic signatures in serum following acute retinal injury.
Methods: :
We used laser photocoagulation (532 nm; continuous) as a model of acute retinal injury in Rhesus macaques. In a paired-control study, we collected serum from each animal at 4 hours, 1 day, 3 days, and 1 week following both a mock procedure and then a treatment with 15 macula sparing laser spots that produced either Grade 2 (moderately severe; GII, n=6) or minimally visible lesions (mild; MVL, n=6). Serum samples were fractionated by isoelectric focusing, digested with trypsin, and analyzed by liquid chromatography/tandem mass spectrometry. Relative protein abundances were determined by spectral counting. Statistical significance was determined using the G-test followed by Holm-Sidak correction for multiple comparison testing. Proteins with an adjusted p-value <0.05 were considered significant.
Results: :
A total of 19 and 17 proteins in sera following MVL and GII injury respectively, were identified as being significantly more abundant compared with control (p<0.05). None of these proteins were common to both MVL and GII injury. However, among the 36 proteins, irrespective of injury severity, most were membrane or intracellular proteins with roles in signaling, inflammatory, and apoptotic pathways. Although most differences following either grade injury were unique to one time point, 4 proteins (Keratin 18, Phosphoglycerate kinase 1, Lewis alpha-3-fucosyltransferase, and Ephrin receptor A2) with MVL and 1 protein (DEAD box protein 17) with GII showed differences at two time points between 4 hours and 3 days after laser treatment. For these proteins detected at multiple time points, maximal protein elevation occurred at 1-3 days post-treatment and decreased to basal levels within 1 week.
Conclusions: :
A serum biomarker response was demonstrated and panels of candidate proteins were identified for both GII and MVL retinal laser injury. The proteomic signature was unique for each grade of injury. The proteins detected with highest differences were increased within 1-3 days and the change was transient. Significantly elevated proteins were ontologically similar in cellular localization and function. Increased abundance of these proteins in serum may be indicative of acute retinal injury.
Keywords: proteomics • laser • retina