[New exploration of treatment target for proliferative diabetic retinopathy based on iTRAQ LC-MS/MS Proteomics]

Objective: To identify differentially expressed proteins between the patients with proliferative diabetic retinopathy (PDR) and vitreous floaters, and explore treatment target for PDR based on isobaric tags for relative and absolute quantification (iTRAQ) LC-MS/MS Proteomics. Method: Vitreous samples were collected from 28 eyes of patients with PDR and 4 eyes with vitreous floaters, which served as controls. For quantitative proteomics, vitreous samples were combined and proteins extracted and labeled with iTRAQ peptide-tagging reagents. Samples were fractionated by liquid chromatography (LC), analyzed by tandem mass spectrometry (MS/MS) and Gene Ontology (GO) analyses performed on differentially expressed proteins identified in the PDR samples. Results: In the PDR vitreous, 26 proteins were identified that were differentially expressed when compared to the controls. Of these, 7 showed a significant increase (P<0.05) and 19 a significant decrease (P<0.05)in expression in PDR patients. These included some high abundance proteins including Retinoic acid receptor reactive protein 2 (PDR 1=85.0, PDR 2=83.0, Control 1=119.6, Control 2=120.2, FC=0.710, P=0.001), Semaphorin-4B(PDR 1=64.4, PDR 2=68.8, Control 1=135.4, Control 2=146.0, FC=0.473, P=0.023), Apolipoprotein B (PDR 1=104.4, PDR 2=106.6, Control 1=89.0, Control 2=85.3, FC=1.211, P=0.024), and Heat shock protein 70 (PDR 1=69.3, PDR 2=75.0, Control 1=137.7, Control 2=138.3, FC=0.523, P=0.026), which are closely related to the pathological mechanism of PDR. GO analysis clustered the differentially expressed genes into three major functional domains: Biological Processes, Molecular Function and Cellular Component. Differential gene expression was found in the categories of cellular metabolism, organonitrogen compound and carbohydrate derivative metabolic processes, transferase activity and transmembrane signaling receptor activity. KEGG Pathway analysis indicate that Chemerin signaling through Akt, Sema4B signaling via PI3K, and HIF-1α signal pathways were all altered in the PDR samples. Conclusions: In this study we identified variations in expression of genes extensively involved in key biological processes in the retina including neovascularization, cellular metabolism and transmembrane signaling, which provide new insights into the pathophysiology of PDR. Extracellular matrix was degraded and endothelial cell migration was induced by Chemerin, in addition, the destruction of blood-retinal barrier and neuronal apoptosis were induced by ApoB. Chemerin and ApoB accelerated the development of PDR. Sema 4B participated in vascular protection, HSP70 conducted anti-apoptosis. These two cytokines protected the retinal neurovascular in PDR patients. Therefore, Chemerin, Sema 4B, ApoB and HSP70 may be the treatment target for PDR. (Chin J Ophthalmol, 2019, 55:769-776).