Protective Activity of Silk Sericin against UV Radiation-Induced Skin Damage by Downregulating Oxidative Stress

Topical delivery of potential antioxidants protects the skin against ultraviolet (UV) radiation-induced oxidative damage through maintaining redox balance. Sericin, one of the major components of silk, possesses antioxidant property along with skin-protective activity against UVB radiation-induced damage. However, the protective activity of silk sericin (SS) extracted from different sources has not been explored against UVA and UVB radiation-induced oxidative damage. In the present study, we have systematically investigated the protective activity of sericin against UVA and UVB radiation-induced skin damage. MTT and neutral red assays showed that Philosamia ricini sericin (PRS) and Antheraea assamensis sericin (AAS) (10 mu g/mL) treatment prior to UVA (12 J/cm(2)) and UVB (120 mJ/cm(2)) irradiations enhanced the viability of human keratinocytes. Examination of cell cycle arrest and apoptotic/necrotic cell death using flow cytometry showed that sericin treatment before UVA and UVB irradiation protected the cells from apoptotic cell death by arresting the cell cycle at G1 phase. Sericin pretreatment downregulated the interleukin (IL)-6 and IL-8, upregulated p53 and decrease the dysregulation of Bcl-2/Bax gene expression. AAS treatment prior to UVB irradiation significantly reduced skin inflammation, DNA fragmentation, and lipid peroxidation in the female SKH-1 hairless mouse skin. Altogether, our results substantiate the use of AAS in effectively ameliorating UVA and UVB radiation-induced skin damage, which holds prospects as a potent antioxidant supplement in the preparation of skin care products.