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Yuichi Uchino, Ashley M Woodward, Jerome Mauris, Julia Dieckow, Francisco Amparo, Reza Dana, Flavio Mantelli, Pablo Argueso; Alteration of Galectin-3 in Tears of Dry Eye Patients. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1306.
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Galectin-3 is a multimeric carbohydrate-binding protein known to be upregulated under several pathological conditions, such as inflammation and cancer. Proteolytic cleavage of galectin-3 by matrix metalloproteinases (MMPs) has been associated with abrogation of the biological properties of the lectin and with the progression of the disease. Here, we investigated the secretion and cleavage of galectin-3 in tears of dry eye patients.
Tear fluid and conjunctival impression cytology specimens were collected from normal subjects (n=11) and patients with non-Sjögren’s dry eye (n=20). Galectin-3 content in tears was analyzed by quantitative Western blot, using recombinant galectin-3 protein as the calibration standard. The relative expression of MMP9 mRNA in conjunctival impression cytology specimens was evaluated using quantitative PCR (qPCR). Galectin-3 cleavage and inhibition assays were performed in vitro using activated recombinant MMP9.
The level of galectin-3 was significantly higher in tears of dry eye patients (Ave. 0.38 ng/µg total protein, range 0.04-1.36) compared to controls (Ave. 0.12 ng/µg total protein, range 0.00-0.41)(p<0.01). By Western blot, all tear samples from normal subjects were characterized by the presence of a single band corresponding to full-length galectin-3, whereas 50% of dry eye patients contained both full-length and cleaved galectin-3. Analyses of conjunctival epithelium by qPCR revealed increased MMP9 mRNA expression in dry eye patients. Importantly, we demonstrated that active MMP9 can cleave full-length galectin-3 from recombinant origin and from tear fluid. These effects were abrogated by use of the broad-spectrum MMP inhibitor GM6001.
Tear fluid of patients with dry eye contains increased levels of galectin-3. Proteolytic cleavage of galectin-3 by MMP9 may lead to ocular surface barrier dysfunction and be potentially used to monitor inflammation in dry eye disease.
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