18beta-glycyrrhetinic acid and glabridin prevent oxidative DNA fragmentation in UVB-irradiated human keratinocyte cultures.

BACKGROUND: UVB radiation is the major etiological factor in the pathogenesis of skin aging and cancer development. New approaches to prevent and reverse UVB damage are needed to reduce sunlight-induced skin cancer. This study aimed to investigate a possible protective activity of liquorice root extracts glycyrrhizin (GL), 18ß-glycyrrhetinic acid (18ß-GA) and glabridin (GLB) against UVB radiation damage in human keratinocyte cultures. MATERIALS AND METHODS: The MTT test was performed to assess cell viability. DNA damage was evaluated by comet assay, whereas generation of intracellular reactive oxygen species (ROS) was measured by fluorescent 2'7'-dichlorodihydrofluorescein diacetate assay. In addition, the activation of p53, regulation of BCL-2 and PARP cleavage were analyzed by Western blot analysis. RESULTS: The treatment of human keratinocytes with 18ß-GA and GLB prevented direct and indirect DNA damage avoiding apoptosis activation. CONCLUSION: 18ß-glycyrrhetinic acid and glabridin are potent antioxidants that prevent oxidative DNA fragmentation and the activation of apoptosis-associated proteins in human keratinocytes.