18β-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), 18 beta-glycyrrhetinic acid (18 beta-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 18 beta-GA and GLB prevented direct and indirect DNA damage avoiding apoptosis activation. Conclusion: 18 beta-glycyrrhetinic acid and glabridin are potent antioxidants that prevent oxidative DNA fragmentation and the activation of apoptosis-associated proteins in human keratinocytes.