Preventive effects of Eucommia ulmoides leaf extract and its components on UVB-induced immunosuppression in mice

Ultraviolet (UV) irradiation is a well known photo-immunosuppressant. To determine the effect of Eucommia ulmoides leaf extract (ELE) components (chlorogenic acid, geniposidic acid, and asperuloside) on UVB induced immunosuppression, we examined mice that were contact hypersensitized. Systemic immunosuppression was induced in the C57BL/6j mice that were sensitized with 0.5% oxazolone through the skin by a single exposure to UVB. Consecutive oral administration of ELE, chlorogenic acid, or geniposidic acid significantly reduced UVB-induced suppression of the contact hypersensitivity (CHS) response. The treatment with chlorogenic acid or geniposidic acid decreased the serum interleukin-10 levels in the sensitized mice after UVB irradiation. Additionally, the level of plasma reactive oxygen species and the expression of skin mast cells decreased in the chlorogenic acid-treated mice. Contrarily, the expression of regulatory T cell in the skin decreased in the geniposidic acid-treated mice. These results suggest that chlorogenic and geniposidic acids prevent the photo-immunosuppression of the CHS response.