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), 18β-glycyrrhetinic acid (18β-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 18β-GA and GLB prevented direct and indirect DNA damage avoiding apoptosis activation. Conclusion: 18β-glycyrrhetinic acid and glabridin are potent antioxidants that prevent oxidative DNA fragmentation and the activation of apoptosis- associated proteins in human keratinocytes. The UV component of sunlight is now recognized as a major environmental factor deleterious to human health. In particular, UVB activates various signal transduction pathways and induces the expression of several specific genes (1). Such radiation may cause tumour initiation by inducing chromosome alterations and DNA damage and its promoting activity includes the transcriptional modulation of