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N. Kato, S. Shimmura, T. Kawakita, H. Miyashita, S. Yoshida, K. Tsubota; Reactive Oxigen Species Produced by Uva Causes Epithelial-Mesenchymal Transition-Like Changes in Corneal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1963.
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We previously reported epithelial cells at the leading edge of pterygial head showed epithelial-mesenchymal transition (EMT) (Kato et al, IOVS 2007). Since pteryium is known to correlate with cumulative ultraviolet exposure on the corneal limbus, we speculated that oxidative stress generated by ultraviolet exposure may induce EMT in the pterygial epithelium. In the present study, we assessed the characteristical changes of the corneal epithelial cells after UVA irradiation.
TKE2 cells (mouse corneal epithelial cell line) were cultured in 5% CO2 at 37°C using the defined KSFM medium. When the cells grew semi-confluent, cells were irradiated with UVA (370 nm). The elevation of EMT-related factors and phosphorylation of mitogen-actiated protein kinases (MAPK) were assessed.
TKE2 cells that exposed by 15 J of UVA for 3 days showed upregulation of a transcription factor, snail in the cells exposed to UVA by RT-PCR and western blotting. Upregulation of αSMA, a representative mesenchymal marker, and downregulation of E-cadherin, a representative epithelial marker, were also confirmed. Immunofluorescence showed decline of membrane staining and increase of intranuclear staining of β-catenin. By 1 hour of UVA irradiation, p38 were shown to be phosphorylated, and translocated into the cell nucleous, and this change was downregulated by add of N-acetylcystein.
UVA irradiation induced EMT-like changes in cultured corneal epithelial cells, probably due to increase of intracellular reaction oxygen species. The present results may indicate that intracellular oxidative stress generated by ultraviolet irradiation may cause EMT in the pathogenesis of pterygium. P38 MAPK may be involved in the signal transduction of the EMT-like changes after UVA irradiation in the TKE2 cells.
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