Protective Effects of Timosaponin AIII against UVB-Radiation Induced Inflammation and DNA Injury in Human Epidermal Keratinocytes

UVB radiation changes several photoaging pathway in the body, thereby prompting skin injury. Besides, chronic UVB radiation leads to photoaging, sustained immunosuppression, and photocarcinogenesis. We investigated the protective effect of Timosaponin AIII (TA-III), a naturally occurring steroidal saponin separated from Anemarrhena asphodeloides, against UVB-induced invasive properties of human epidermal keratinocytes (HEKs) and human dermal fibroblasts (HDF). No cytotoxicity was observed up to 50nM concentration of TA-III. Similarly, TA-III inhibited UVB-induced cyclooxygenase-2 (COX-2), matrix metalloproteinase-9 (MMP-9) transcription level and protein expression in a dose-dependent manner at non-cytotoxic dose. Further, TA-III decreased UVB-induced invasion in primary skin cells. Additionally, TA-III suppressed UVB-stimulates mitogen-activated protein kinase (MAPK) signaling, activator protein-1 (AP-I) and nuclear factor kappa B (NF-kappa B) activation, thereby preventing the overexpression of tumor necrosis factor-a (TNF-alpha), interleukin-6 (IL-6), and COX-2 in human epidermal keratinocytes cells. Furthermore, TA-III prevented UVB-mediated formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and activation of DNA repair enzymes and, cell cycle arrest genes like as proliferating cell nuclear antigen (PCNA), structural maintenance of chromosomes protein 1 (SMCI). This results support that understanding into the molecular action of TA-III, which can be useful for developing photoprotective agents.