Protective effects of Sosihotang extract against ultraviolet B-induced skin photoageing in hairless mice

Abstract Objectives Sosihotang (SSH) is an herbal medicine traditionally used against the common cold, and hepatic and gastric diseases, in Northeast Asia. In this study, we investigated whether SSH extract can protect against UVB-induced skin damage and photoageing. Methods HaCaT cells were treated with SSH extract and exposed UVB irradiation at 20 mJ/cm2. Hairless mice were orally administered SSH extract (100 mg/kg per mouse) as UVB irradiation was increased from 60 to 120 mJ/cm2 over the course of 12 weeks. Key findings Treatment with SSH extract inhibited the upregulation of MMP-1 and MMP-9 expression in UVB-irradiated HaCaT cells. In UVB-irradiated hairless mice, treatment with SSH extract restored the levels of factors instrumental in skin hydration (TEWL, capacitance, HA and TGF-β) and those regulating collagen content (procollagen, MMP-1 and MMP-9). This activity inhibited epidermal thickening and disorganization of collagen fibres. Administration of SSH extract also ameliorated the expression of UVB-induced pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and phosphorylation of MAPK family members (MEK, JNK, ERK and p38) by upregulating the activity of antioxidant enzymes (SOD, CAT, Nrf-2, HO-1 and NQO-1). Conclusions These results indicate that SSH extract can be used therapeutically for the treatment of UVB-induced skin damage and photoageing.