Abstract
Purpose :
The tear film is a protein-rich multilayer fluid that coats the corneal and conjunctival epithelia. Dry eye disease (DED), a multifactorial inflammatory disease of the ocular surface, is characterized by tear film instability. DED diagnostic methods are limited, and there is an urgent need for objective biomarkers. We analyzed human tear fluid to identify potential proteomic biomarkers associated with DED.
Methods :
Tear samples were collected via Schirmer strips from 41 DED patients and 41 healthy controls. Proteomic analysis was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). To ensure proteomic changes did not derive from confounding factors, multivariate regression analysis was performed, adjusting for age, sex, and race. Targeted parallel reaction monitoring (PRM) analysis was used to confirm the changes of 15 selected proteins.
Results :
A total of 3288 unique proteins were identified in 82 tear samples. 89 of the 500 proteins detected in at least 50% of the samples were significantly altered in DED patients. 76 of the altered proteins were extracellular exosome proteins, and 28 were glycoproteins. The altered proteins are implicated in retinal homeostasis, cell-cell adhesion, proteolysis, receptor-mediated endocytosis, innate immune response, antibacterial humoral response, phagocytosis, and the complement pathway. The levels of lipocalin-1 (LCN1: 0.12-fold), lactoperoxidase (LPO: 0.15-fold), mesothelin (MSLN: 0.16-fold), heparan sulfate proteoglycan (HSPG2: 0.19-fold), nucleobindin-2 (NUCB2: 0.22-fold), zinc-alpha-2-glycoprotein (AZGP1: 0.33-fold), cystatin-C (CST3: 0.39-fold), polymeric immunoglobulin receptor (PIGR: 0.41-fold), and antileukoproteinase (SLP1: 0.43-fold) were decreased in DED patients, while the levels of serpin B5 (SERPINB5: 3.29-fold), calpain-2 catalytic subunit (CAPN2: 3.27-fold), complement factor H (CFH: 3.18-fold), protein S100-A8 (S100A8: 3.14-fold), and ubiquitin-like modifier-activating enzyme 1 (UBA1: 2.90-fold) were increased.
Conclusions :
Using a shotgun approach, we found that the levels of 89 tear proteins were altered in DED patients. Targeted PRM analysis of 15 selected proteins confirmed the changes of 14 proteins in DED patients (9 decreased and 5 increased). These findings demonstrate the potential of tear protein levels as biomarkers for DED, and the pathways involving these proteins may further our understanding of the mechanisms underlying DED.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.