Low-dose UVB irradiation prevents MMP2-induced skin hyperplasia by inhibiting inflammation and ROS.

Skin cancer is one of the most common types of malignancy in the world. UV radiation is known as the primary environmental carcinogen responsible for skin cancer development. However, UV radiation is a ubiquitous substance existing in the environment and the physiological effect of UV radiation is consistently ignored. Therefore, in the present study, the physiological effect of UV radiation on inhibition of skin cancer was investigated. Normal mouse skin was processing by no pre-radiation or pre-radiation of low-dose UV before a medium or high dose of UV radiation. We found that the low-dose pre-radiated mouse skin tissue exhibited low skin inflammation, skin ROS production and consequently low skin epithelial hyperplasia after the medium-dose UV radiation compared with the no pre-radiated mouse. However, this inhibition was not indicated in the high-dose UV radiation group after low-dose pre-radiation. Furthermore, western blot analysis and gelatin zymography showed low expression and activation of MMP2 in the skin tissues processed following medium-dose radiation, but not in tissues treated with high-dose radiation after a low-dose pre-radiation. Further investigation of MMP2 inhibitors of TIMP2/TIMP4 showed an upregulated TIMP2 expression, but not TIMP4. Collectively, these data indicate that low-dose pre-radiation attenuates the skin inflammation and ROS production induced by medium-dose UV radiation and also elevates TIMP2 to withstand MMP2, therefore suppressing skin hyperplasia. The present study indicates a novel concept or prophylactic function of moderate UV radiation as a preventative strategy.