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J. Y. Huang, K. Xu, C. S. Chen, F.-S. X. Yu; High Glucose Exacerbates UVB-Induced Damage in Human Corneal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1960. doi: https://doi.org/.
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UVB rays can cause damage to the cornea by inducing corneal epithelial cell death and delayed regeneration and wound healing. The effect of UVB rays to the cornea of individuals with diabetes mellitus is not well understood. This study sought to investigate whether high glucose (HG) exacerbates UVB induced cell damage to corneal epithelial cells in vitro.
Telomerase-immortalized human corneal epithelial (HUCL) cells were cultured in Defined Keratinocyte Serum Free Medium containing normal D-glucose (NG, 5mM) and high D-glucose (HG, 25mM) and irradiated with 30, 50, 60, 90, 100, 200 mJ/cm2 of UVB (~312nm). Cell apoptosis was determined by TUNEL staining, caspase-3 fluorometric enzyme assay and immunoblotting of PARP cleavage. PI3K-AKT activation was determined by immunocytochemistry. IL-8 cytokine release was examined by ELISA. Effects of UVB exposure and high glucose on cell migration and cell proliferation were determined by in vitro scratch wound healing assay and by BrdU incorporation, respectively.
HUCL cells cultured in HG irradiated with 200mJ/cm2 UVB resulted in significantly more TUNEL-positive apoptotic cells (62/mm2 ± 19) when compared with cells cultured in NG (19/mm2 ± 12). Moreover, 100mJ/cm2 UVB irradiation induced a 28-fold increase in caspase-3 enzyme activity in both HG and NG cells after 24hrs. In addition, after 100mJ/cm2 UVB irradiation, PARP cleavage appeared at 3hrs in HG cells, but did not occur until 6hrs in NG cells. Accordingly, a pronounced decrease in the intensity of phospho-AKT immunostaining was found in HG cells after UVB irradiation. IL-8 cytokine secretion after UVB irradiation was found to be significantly decreased in cells cultured in HG than in NG. Furthermore, a cell monolayer cultured in HG had a UVB dose-dependent delay in epithelial wound closure and attenuation in BrdU incorporation as compared to cells in NG.
Cells cultured in HG exhibited greater sensitivity to UVB irradiation, resulting in an increase in cell apoptosis, a decrease in growth signaling and cytokine production, and impairment in cell proliferation and migration in human corneal epithelial cells. Understanding the additive effects of UVB irradiation and high glucose conditions may help prevent unnecessary corneal damage in individuals with diabetes mellitus.
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