Tear proteomics in evaporative dry eye disease

To analyze tear protein variations in patients suffering from dry eye symptoms in the presence of tear film instability but without epithelial defects.

Five microlitres of non-stimulated tears from 60 patients, suffering from evaporative dry eye (EDE) with a break-up time (BUT) <10 s, and from 30 healthy subjects as control (no symptoms, BUT >10 s) were collected. Tear proteins were separated by mono and bi-dimensional SDS-PAGE electrophoresis and characterized by immunoblotting and enzymatic digestion. Digested peptides were analyzed by liquid chromatography coupled to electrospray ionization quadrupole-time of flight mass spectrometry followed by comparative data analysis into Swiss-Prot human protein database using Mascot. Statistical analysis were performed by applying a t-test for independent data and a Mann-Whitney test for unpaired data (P<0.05).

In EDE patients vscontrols, a significant decrease in levels of lactoferrin (data in %+/-SD): 20.15+/-2.64 vs 24.56+/-3.46 (P=0.001), lipocalin-1: 14.98+/-2.70 vs 17.73+/-2.96 (P=0.0001), and lipophilin A-C: 2.89+/-1.06 vs 3.63+/-1.37 (P=0.006) was revealed, while a significant increase was observed for serum albumin: 9.45+/-1.87 vs 3.46+/-1.87 (P=0.0001). No changes for lysozyme and zinc alpha-2 glycoprotein (P=0.07 and 0.7, respectively) were shown. Proteomic analysis showed a downregulation of lipophilin A and C and lipocalin-1 in patients, which is suggested to be associated with post-translational modifications.

Data show that tear protein changes anticipate the onset of more extensive clinical signs in early stage dry eye disease.