Inhibitory effects of Rumex japonicus Houtt. on the development of atopic dermatitis-like skin lesions in NC/Nga mice

Background Rumex japonicus Houtt. (RJH) is one of the herbs used in Eastern countries for the treatment of atopic dermatitis (AD). It has been shown to have an antioxidative effect in human skin disease. Objectives To examine whether RJH extract (RJH-E) suppresses the development of AD-like skin lesions in NC/Nga mice, which are induced by the repeated application of picryl chloride (PC). Methods The efficacy of RJH-E in NC/Nga mice was assessed by measuring symptom severity, scratching behaviour, Staphylococcus aureus numbers on an ear, and serum levels of IgE, interleukin (IL)-4 and interferon (IFN)-gamma. Results Oral administration of RJH-E to NC/Nga mice treated with PC inhibited the development of AD-like skin lesions as exemplified by a significant decrease in total skin symptom severity scores, and a decrease in hypertrophy, hyperkeratosis and infiltration of inflammatory cells in the skin. The scratching behaviour and numbers of S. aureus, which are known to be exacerbated in AD, were also significantly reduced by RJH-E. No significant change was observed in the serum levels of IFN-gamma, whereas IgE and IL-4 levels were significantly reduced by RJH-E. Conclusions These results suggest that RJH-E inhibits the development of AD-like skin lesions in NC/Nga mice by suppressing the T-helper 2 cell response. Our results indicate that RJH treatment could provide an effective alternative therapy for the management of AD.