A novel role for Livin in the response to ultraviolet B radiation and pterygium development

A pterygium is an inflammatory, invasive and proliferative lesion on the ocular surface, which can decrease visual acuity, damage the ocular surface and affect the appearance of the eye. However, the underlying molecular mechanisms of the pathogenesis remain unclear. In the present study, the role of apoptosis-associated protein Livin in the occurrence and development of pterygium was investigated. Primary samples from quiescent or advanced clinical stages of pterygium and normal human conjunctival tissues were used to assess mRNA and protein expression levels of Livin using reverse transcription-quantitative PCR and immunohistochemistry, respectively. Livin was knocked down in pterygium epithelial cells (PECs) using small interfering RNA (siRNA), to investigate the role of Livin in PEC viability, migration, invasion ability and apoptosis. The cell viability, invasion ability and apoptosis of PECs following ultraviolet B (UVB) radiation alone or in combination with Livin silencing were also analyzed. Expression levels of Livin increased in the pterygium tissues compared with those in the normal conjunctiva at both the mRNA and protein levels. Livin expression levels in advanced pterygium were significantly higher compared with those in quiescent pterygium samples. Knockdown of Livin expression levels significantly reduced cell migration, invasion ability and cell viability, and induced apoptosis of PECs. Inhibition of Livin expression in PECs increased the expression levels of caspase-7, caspase-3 and E-cadherin, whereas expression levels of Snail were downregulated. Cell viability and invasion ability in PECs was enhanced following UVB radiation and Livin expression upregulated. UVB irradiation induced cell invasion ability of PECs and this was attenuated by Livin-silencing. Transfection with Livin siRNA also partially recovered the apoptosis rate of PECs, which was reduced by UVB irradiation. In conclusion, Livin was upregulated in pterygium, and UVB radiation functions in the development of pterygium by inducing Livin expression.