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Jerome Mauris, Flavio Mantelli, Noorjahan A. Panjwani, Pablo Argueso; Modulation of Ocular Surface Barrier Function by Galectin-3. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1842.
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Efficient topical drug delivery into the anterior segment of the eye requires good corneal penetration. We previously reported that O-glycans on transmembrane mucins bind the ß-galactoside-binding protein galectin-3 on the apical corneal epithelium to maintain ocular surface barrier function. Here, we evaluated whether inhibition of galectin-3 binding could potentially be used to modulate barrier function at the ocular surface.
Human corneal-limbal epithelial (HCLE) cells were grown in conditions that induce stratification and mucin biosynthesis. Rose bengal barrier function assays were performed on cells treated with one of the following: siRNA targeting galectin-3; recombinant galectin-3 (rGal3); competitive inhibitors of galectin-3 binding, including a dominant negative inhibitor of galectin-3 lacking the N-terminal domain (rGal3C), ß-lactose, or modified citrus pectin (MCP). Cell surface galectin-3 was detected using biotinylation assays and western blot. Rose bengal uptake was also evaluated in corneas of galectin-3 null and wild type mice.
Use of siRNA significantly reduced the levels of galectin-3 protein in stratified cultures of HCLE cells while increasing rose bengal uptake as compared to scramble control. Addition of rGal3C, but not rGal3, to cell culture media disrupted epithelial barrier function. Similarly, addition of ß-lactose and MCP increased dye penetrance and reduced the levels of cell surface galectin-3. Interestingly, the abrogation of barrier function was transient, as both dye penetrance and cell surface galectin-3 returned to basal levels within 4 h. Corneas of galectin-3 null mice showed increased dye penetrance as compared to wild-type.
Competitive inhibition of galectin-3 binding results in transient disruption of the corneal epithelial barrier. It is, therefore, possible that galectin-3 binding inhibitors could be used therapeutically to enhance topical drug delivery.
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