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G. Pachigolla, J.C. Welch, W. Farley, L. Luo, L.Z. Chen, M.E. Stern, S.C. Pflugfelder; The Effects of Experimental Dry Eye on Corneal Epithelial Tight Junctions in Two Strains of Mice . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3803.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate and compare the effects of experimental dry eye on the expression of the corneal epithelial tight junction proteins, occludin and ZO–1 in two strains of mice. Methods: Dry eye was induced in 6– to 8–week–old Balb–c and C57BL6 mice with subcutaneous injections of 2.5mg/ml scopolamine 4 times per day and exposure to an air draft and low humidity for 4 to 12 days. Untreated mice were used as controls. Laser scanning confocal microscopy was performed on excised corneas to immunolocalize ZO–1 and occludin. Western blots for occludin, ZO–1 and phosphorylated–ERK (p–ERK) were performed on corneal epithelial cell lysates. Gelatinase activity in corneal sections was assessed by in–situ gelatin zymography. Results: A honeycomb pattern of ZO–1 staining was observed in both strains of untreated and dry eye mice. Increased levels of ZO–1 protein were noted in the cornea epithelia of both mouse strains, after 5 days of treatment. Dryness induced a diffuse intracellular redistribution of occludin protein in both strains with more pronounced changes in C57BL6 mice. Focal loss of cell membrane occludin staining was also noted in C57BL6 mice. Compared to untreated eyes, there was an increase in 50kDa degraded occludin in immunoblots of corneal epithelia of C57BL6 mice after 5 days of treatment. Levels of p–ERK increased in 5 day treated corneas in both stains, but to a greater extent in C57BL6 mice. In–situ gelatin zymography revealed increased gelatinase activity by day 2 of treatment in both mouse stains. This progressively decreased to near pre–treatment levels by day 12 in Balb–c mice, but it remained elevated up to day 12 in C57BL6 mice. Conclusions: These findings suggest that experimental murine dry eye induces changes in corneal epithelial tight junctions with intracellular redistribution and proteolytic degradation of occludin protein and increased levels of ZO–1 protein. These changes may be related to increased levels of activated MAPK and gelatinase activity. Balb–c and C57BL6 mouse strains showed a different response to dry eye treatment.
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