Differential urine proteome analysis of a bovine IRBP induced uveitis rat model by discovery and parallel reaction monitoring proteomics

Uveitis, a group of intraocular inflammatory diseases, is one of the major causes of severe visual impairment among working age population. Urine is a promising resource for biomarker research, which could sensitively reflect the changes of the body. This study was designed to explore urinary protein biomarkers for diagnosis and/or monitoring of uveitis. Experimental autoimmune uveitis (EAU) rat model induced by bovine interphotoreceptor retinoid-binding protein (IRBP) was used to mimic the uveitis. In the discovery phase, urine samples from EAU and control rats were analyzed by data independent acquisition (DIA) approach combined with high-resolution mass spectrometry. Overall, 704 high confidential proteins were identified, of which 100 were differentially expressed (37, 33, 37, and 44 on day 5, 8, 12, and 16, respectively, after bovine IRBP immunization) (1.5-fold change, P<0.05). Gene Ontology analysis of the dysregulated proteins showed that chronic inflammatory response, neutrophil aggregation and immune system processes were significantly enriched. Finally, parallel reaction monitoring (PRM) approach was used for further validation. A total of 12 urinary proteins (MMP8, NGAL, HPT, UROM, RISC, A1AG, TTHY, KNT1, C9, PTER, CBG, and FUCA1) changed significantly, even when there is no clinical manifestations and histopathological ocular damages in the EAU rats. Our findings represent the first step towards urinary protein diagnostic biomarkers for uveitis.\n\nBiological SignificanceThis is the first study investigating urinary protein candidate biomarkers for uveitis using data independent acquisition (DIA) combined with parallel reaction monitoring (PRM) in experimental autoimmune uveitis (EAU) rats. The results revealed that urine is a promising resource for early diagnostics of uveitis. Further research including clinical urine samples is needed to determine the sensitivity and specificity of these candidate biomarkers for uveitis.