Tear proteomic analysis of Sjögren syndrome patients with dry eye syndrome by two-dimensional-nano-liquid chromatography coupled with tandem mass spectrometry

We examined the tear film proteome of patients with Sjögren's syndrome (SS) and dry eye syndrome (group A), patients with dry eye symptoms (group B) and normal volunteers (group C). Tear samples were pooled from 8 subjects from each group and were subjected to two-dimensional-nano-liquid chromatography coupled with tandem mass spectrometry (2D-nano-LC-MS/MS). The tear breakup time for group A was significantly reduced compared with group B and C (P < 0.001). Group A (Schirmer I test, 2.13 ± 2.38 mm/5 min) had markedly lower tear volume than group B (5.94 ± 4.75 mm/5 min) and C (14.44 ± 6.57 mm/5 min) (P < 0.001). Group A had significantly higher normalized tear protein content (1.8291 ± 0.2241 μg/mm) than group B (1.0839 ± 0.1120 μg/mm) (P = 0.001) and C (0.2028 ± 0.0177 μg/mm) (P = 0.001). The 2D-nano-LC-MS/MS analysis identified a total of 435 proteins, including 182 (54.8%), 247 (74.4%) and 278 (83.7%) in group A, B, and C, respectively, with 56 (16.7%) proteins including defensin α1, clusterin and lactotransferrin unique to group A. In conclusion, dry eye syndrome in SS patients is associated with an altered proteomic profile with dysregulated expression of proteins involved in a variety of important cellular process including inflammation, immunity, and oxidative stress.