Abstract
Tear is an accessible fluid for exploring biomarkers of dry eye disease. This study describes a fast proteomic method by LC-Q-orbitrap-MS analysis with in-strip digestion and investigates the tear proteome of dry eye patients. Schirmer’s strips were used for collection of tear fluid from patients. These strips were cut into pieces and directly digested with trypsin before mass spectrometry analysis. The data showed that more than 50 proteins were found in tear fluid from dry eye patients. Gene Ontology (GO) annotation showed that most of proteins were transfer/carrier proteins, hydrolyses, enzyme modulators and signaling molecules. Targeted proteomics strategy revealed that 18 proteins were differentially expressed in dry eye patients. Furthermore, it was showed that the common post-translational modification in tear proteins is deamidation of Asn.
Highlights
Human tear is a complex fluid comprised of secretions from different sources including the lacrimal gland, goblet cells, cornea, and vascular sources
We developed a fast pretreatment method for proteomic analysis by liquid chromatography couple quadrupole-orbitrap mass spectrometry (LC-Q-Orbitrap-Mass spectrometry (MS)) and investigated the proteins in tears from moderate dry eye patients
Previous study has proved that more proteins were identified by using Schirmer’s strips than glass capillary tubes [28]
Summary
Human tear is a complex fluid comprised of secretions from different sources including the lacrimal gland, goblet cells, cornea, and vascular sources. Large amounts of tear proteins (close to 2000) have been revealed in human body [6, 7]. The endogenous peptides in human reflex tears were identified. Hayakawa et al [8] have analyzed and identified 30 peptides derived from two different proteins Azkargorta et al [9] have identified 234 peptides derived from 25 proteins in a human basal tear sample. MS-based proteomic analysis of tear fluid can reveal basic biological information for many ocular diseases, such as diabetic retinopathy, keratoconus, thyroid eye disease, vernal keratoconjunctivitis and primary open angle glaucoma [10,11,12,13,14].
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