Abstract:

Objective To investigate the protective effect of green tea-based cream at different concentrations on photoaging and photo-immunosuppression. Methods Twenty healthy female volunteers were enrolled into this study with informed consent. Green tea-based cream with a mass fraction of 2%-5% （prepared by adding green tea extracts to an emollient formulation）, excipient or green tea extracts alone were applied to six unexposed sites on the back of these volunteers. Thirty minutes later, these treated sites were subjected to solar-simulated ultraviolet irradiation （ssUVR） with a 1.5-fold minimal erythema dose once a day for 4 days. At 6, 24 and 48 hours after the last irradiation, green tea-based cream were applied repeatedly to the corresponding sites. Biopsy specimens were obtained from the seven sites 72 hours following the last irradiation, and immunohistochemical staining was performed to detect cytokeratin 5/6 and 16 expression, as well as the densities of CD1a- or HLA-DR-positive cells. Results Green tea-based cream at a mass fraction of 2% to 3% could effectively prevent ssUVR-induced obvious erythema and hyperpigmentation. The positivity （+） rates plus strong positivity （++） rates reached 50% and 25% for CK5/6 in the sites treated with ssUVR only and those irradiated and protected with green tea cream at a mass fraction of 3%, respectively, 69% and 31% in the sites treated with ssUVR only and those irradiated and protected with green tea-based cream at a mass fraction of 2%, respectively. Compared with the control site without irradiation or protection, a decrease over 75% was noticed in the density of epidermal CD1a- or HLA-DR- positive Langerhans cells in the irradiated sites without protection, and green tea-based cream, especially those at a mass fraction of 3%, could effectively inhibit the density decrease. Conclusion Green tea extracts could effectively protect skin from photoaging and photo-immunosuppression with the optimal mass fraction at 2% or 3%.

Key words: Green tea extracts;photo-aging;photo immune suppression;Green tea extracts, photo-aging, photo immune suppression