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Yuichi Uchino, Jerome Mauris, Julia Dieckow, Ashley Woodward, Francisco Amparo, Reza Dana, Flavio Mantelli, Pablo Argueso; Role of galectin-3 in dry eye disease. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2666.
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Galectin-3, a multimeric carbohydrate-binding protein expressed by the ocular surface epithelia, provides barrier function under physiological conditions through interaction with transmembrane mucins on the apical glycocalyx. Here, we investigated whether galectin-3 is altered on the ocular surface of dry eye patients and/or modulates cytokine receptor activation in corneal epithelial cells.
Galectin-3 in tear fluid collected from the inferior fornix of normal subjects (n=11) and patients with dry eye (n=20) was analyzed by quantitative Western blot with recombinant protein as calibration standards. siRNA targeting galectin-3 and scramble control were introduced into stratified cultures of human corneal-limbal epithelial (HCLE) cells by lipofectamine-mediated transfection. Stratified HCLE cell cultures were treated for 2 h with serum-free growth-media alone or with recombinant human IL-1β (10 ng/ml). Secreted IL-8, IL-1 receptor 1 (IL1R1), and GAPDH were quantified by Western blot.
The levels of galectin-3 detected in normal tear samples were 0.12±0.14 ng/µg total protein (range, 0.00-0.41). In dry eye, there was a significant increase in galectin-3 content in tears (0.38±0.37 ng/µg total protein; range, 0.04-1.36). In vitro, we found that galectin-3 mediates inflammatory responses in corneal epithelial cells. As expected, IL-8 protein levels were increased in the culture media of control HCLE cells treated with IL-1β. However, IL-8 secretion was impaired in HCLE cells treated with IL-1β after galectin-3 siRNA knockdown, indicating that galectin-3 mediates IL1R1 activation. The amount of IL1R1 in total cell protein extracts was not affected by either IL-1β stimulation or galectin-3 knockdown.
Increased levels of galectin-3 in the tear fluid may reflect alterations of the ocular surface glycocalyx barrier in dry eye patients. Galectin-3 regulates IL-1-mediated inflammatory responses on the ocular surface epithelia, but the molecular mechanisms of this regulation remain to be elucidated.
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