Protection of human keratinocytes from UVB-induced inflammation using root extract of Lithospermum erythrorhizon.

UVB irradiation is an important inducer of biological changes in skin and can activate inflammatory reactions and apoptotic pathways, leading to skin damage. A root extract of Lithospermum erythrorhizon (SK), which has naphthoquinone pigments containing shikonin and shikonin derivatives, is known for its anti-inflammatory, anti-bacterial, and anti-tumor activity, and for its scavenging of reactive oxygen species. However, the effect of SK against UV damage is not clear. The aim of this study was to evaluate the efficacy of SK against UVB induced damage in normal human epidermal keratinocytes (NHEK). UVB-irradiated NHEK showed decreased cell viability, increased production of interleukin (IL)-1alpha, IL-6, IL-8, and tumor necrosis factor-alpha, and induced apoptosis. In an apoptosis pathway assay, UVB-irradiated NHEK showed increased caspase-3 activity, p53 and its phosphorylation at serine 15 compared with non-irradiated cells. All these effects induced by UVB irradiation were clearly inhibited by treatment with SK before and after UVB irradiation for 24 h. It is suggested that SK can protect epidermal cells against harmful effects of UVB irradiation and that SK treatment is probably beneficial for photoprotection of the skin.