Alleviation effects of Rubus coreanus Miquel root extract on skin symptoms and inflammation in chronic atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disease characterized by chronic inflammatory dermatitis with immunological manifestations. The aim of this study was to investigate the effects of polyphenol-containing Rubus coreanus Miquel root extract on skin allergy and AD. The protective effects of R. coreanus root ethanol extract against AD were investigated using the human keratinocyte cell line HaCaT, human mast cell line HMC-1, and the 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin NC/Nga mouse model. Treatment with R. coreanus root ethanol extracts reduced beta-hexosaminidase and histamine release from HMC-1 cells stimulated with compound 48/80 compared to treatment with R. coreanus fruit ethanol extract. Furthermore, topical application of R. coreanus root ethanol extract dramatically reduced the severity of skin symptoms and the thickening and swelling of the dorsal skin and ear in DNCB-treated NC/Nga mice. The protein and mRNA expression of several cytokines (IL-4, IL-5, IL-12, IFN-gamma, TNF-alpha, and TARC) and IgE was significantly lowered upon application of the R. coreanus root ethanol extract. The promising candidate for the active ingredient of R. coreanus root polyphenols was revealed to be ellagic acid. These findings clearly indicate that the R. coreanus root polyphenols show strong anti-allergic effects and suppress the symptoms of AD. Therefore, polyphenol-containing R. coreanus root ethanol extract could be a novel therapeutic candidate for the treatment of allergy and AD.