Propolis Protects Human Keratinocyte HaCaT Cells against UV-induced Apoptosis

Propolis, a natural product derived from plant resins collected by honeybees, has been reported to exert a wide spectrum of biological functions. Although it has been reported that propolis and its active constituents inhibited the proliferation and growth of tumor cells by inducing apoptosis, the effect of propolis on cell death and growth is still controversial. This research aimed at investigating the effect of propolis on UV-induced apoptosis of human keratinocyte HaCaT cells. Phase contrast microscope showed that pretreatment of HaCaT cells with propolis (1~3μg/ml) protected UV-induced cell damage. Using Hoechst staining, it was demonstrated that propolis significantly inhibited the apoptosis of HaCaT cells induced by UV-irradiation. To investigate the role of ROS in UV-induced apoptosis and protection by propolis, the generation of ROS was determined in cells by using ROSdetecting fluorescent dye DCF-DA. The results showed that although the generation of ROS was markedly increased in UV-irradiated HaCaT cells, it was significantly reduced in cells pretreated with propolis (1~3μg/ml). Consequently, propolis protected human keratinocyte HaCaT cells against UVinduced apoptosis, which might be related to the reduction of ROS generation by UV-irradiation.