Abstract
Ultraviolet (UV) irradiation induces skin dryness, largely by disruption of the epidermal barrier. In a search for dietary and plant compounds that would protect against skin dryness, we investigated the dietary effect of red ginseng (the steamed root of Panax ginseng C.A. Meyer) on epidermal levels of hydration and ceramides, the most important lipids for maintaining the epidermal barrier, in UV-irradiated mice. Albino hairless mice were fed either control diets (group UV [UV-irradiated control]) or diets with 0.5% (group H0.5) or 1% (group H1.0) red ginseng extract for 5 weeks in parallel with UV irradiation. A normal control group (group C) was fed a control diet without UV irradiation for 5 weeks. Skin dryness in group UV, as assessed by epidermal levels of hydration and ceramides, was significantly lower than those in group C. With no differences in food intake and weight gains among groups, epidermal levels of hydration and ceramides in group H0.5 were similar to those in group C. In addition, protein expression of serine palmitoyltransferase (SPT), a key enzyme involved in de novo ceramide synthesis, was increased in group H0.5. However, epidermal levels of hydration and ceramides in group H1.0 did not differ from those in group UV, in which ceramidase, an enzyme involved in ceramide degradation, was highly expressed. In conclusion, we demonstrate that dietary supplementation of 0.5% red ginseng protects skin from UV-induced dryness with an accumulation of ceramides due to elevated expression of SPT protein.