Comparative evaluation of the aqueous humor proteome of primary angle closure and primary open angle glaucomas and age-related cataract eyes.

PURPOSE: To analyze and compare the total proteome of aqueous humor (AH) from patients having primary angle closure glaucoma (PACG), primary open angle glaucoma (POAG) and age-related cataract. MATERIALS AND METHODOLOGY: Aqueous humor was collected from age-matched PACG, POAG and cataract patients who underwent surgery, and it was immediately stored at - 80 °C until analysis. From each sample, 25 µg of total protein was subjected to trypsin digestion and subsequently LC-MS/MS analysis was performed for the deep proteome analysis. The data acquired after the LC-MS/MS analysis were analyzed using Proteome Discoverer 1.4. The identified peptide matches were validated using percolator, at less than 1% false discovery rates. RESULTS: A total of 625, 594 and 636 proteins were identified in PACG, POAG and cataract groups, respectively (n = 9 in each group). The inter-group comparison among all these groups showed that 246 proteins were identified in all the three groups. An average of 236 ± 42, 218 ± 40 and 214 ± 62 proteins from each AH sample of PACG, POAG and cataract, respectively, was identified. There were 53 proteins commonly found in all 9 PACG AH, 59 proteins in POAG AH and 42 proteins in 9 cataracts AH samples. In the individual analysis, there were 28 proteins found in all the samples analyzed representing the "constitutive AH proteome." Spectral counting analysis of 246 proteins identified in all three group types showed significant differences in protein abundance. In proteins unique to PACG AH, 7 proteins viz. ARHGEF12, APC2, WAS, PIK3CG, ITGB1, MSN and PFN1 out of 226 were found in "Regulation of Actin Cytoskeleton" pathway, whereas in POAG 5 out of 206 proteins viz. ADCY2, ITPR1, MAPK3, MAP3K2 and TUBB1 were found in "Gap Junction" pathway. CONCLUSIONS: A qualitative as well as a quantitative comparison of proteomes of AH from PACG, POAG and age-related cataract eyes showed significant differences, thus providing clues to the disease pathophysiology.