Abstract
BACKGROUND: A dacryolith mainly contains organic material, but its specific protein content is unknown. We observed a unique dacryolith formation in patients with long-term use of rebamipide eye drops and tried to identify the differences in protein compositions of dacryoliths from patients with or without use of rebamipide eye drops using novel proteomic analysis. METHODS: Dacryolith samples were obtained from 7 patients (4 samples were without rebamipide usage, 3 were with rebamipide usage) who underwent endo-dacryocystorhinostomy or lacrimal endoscopic surgery and were subjected to protein identification and metaproteomic analysis. RESULTS: The proteomic analysis revealed that most core proteins of dacryoliths are involved in immune and inflammatory responses and rebamipide-related proteins participated in several biological processes, including immune response, receptor-mediated endocytosis, and negative regulation of endopeptidase activity. Metaproteomic analysis of taxonomic diversity of dacryolith proteomes suggested less involvement of bacterial infections in dacryoliths from patients with long-term use of rebamipide. CONCLUSION: This is the first report to clinically detect the different features of dacryoliths related with long-term use of rebamipide eye drops with proteomic analysis. It is possible that lacrimal protein alteration may be accelerated by topical rebamipide treatment with less bacterial infection involvement, but this requires further study. Long-term rebamipide eye drop use may be restricted in patients with nasolacrimal duct obstruction.