Abstract: SONG Xiu-zu, XU Wen, XIANG Wen-zhong, XU Ai-e. Department of Dermatology, Third People's Hospital of Hangzhou, Hangzhou 310009, China Correponding author：XU Ai-e, Email: xuaiehz@msn.com 【Abstract】 Objective To evaluate the effect of green tea polyphenol epigallocatechin-3-gallate （EGCG） and ultraviolet B （UVB） on the expression of aquaporin 3 and epidermal growth factor receptor （EGFR）/extracellular signal-regulated protein kinase （ERK） signaling pathway in keratinocytes. Methods Twenty healthy human subjects were enrolled in this study. Both legs of each subjects were separated into 4 areas to remain untreated （control area）, be topically treated with 3% and 1% EGCG cream and the vehicle of EGCG cream respectively once a day for 2 weeks followed by the measurement of skin moisture content and trans-epidermal water loss （TEWL）. Cultured keratinocytes were classified into various groups to be irradiated with different doses （10, 20 and 30 mJ/cm2） of UVB, or be pretreated with different concentrations of EGCG （10－7， 10－6，10－5 mol/L） or EGFR/ERK phosphorylation inhibitors for 1 hour followed by irradiation with UVB of 30 mJ/cm2. After various durations of additional culture, Western blot was conducted to quantify the expression of AQP3 and phosphorylated-EGFR （p-EGFR） and -ERK （p-ERK） of keratinocytes. Data were processed by SPSS 10.0 software, and statistical analysis was carried out by t test. Results Skin moisture content was significantly increased, while TEWL was decreased in healthy skin after treatment with 1% and 3% EGCG cream compared with vehicle-treated skin areas and untreated skin areas. Increased AQP3 expression was observed in keratinocytes pretreated with EGCG of 10－7，10－6，10－5 mol/L （172.36 ± 12.42，320.66 ± 15.51 and 368.10 ± 11.39 vs. 100.00, t = 12.16， 26.75 and 38.62 respectively, all P < 0.05） and in those pretreated with the EGFR inhibitor PD153035 of 1.0 μmol/L and ERK inhibitor U0126 of 10 μmol/L（413.85 ± 25.27 and 268.85 ± 16.33 vs. 100.00, t = 35.16, 19.25 respectively, both P < 0.05）compared with those irradiated with UVB of 30 mJ/cm2 alone. UVB irradiation stimulated the phosphorylation of EGFR/ERK in keratinocytes, and the stimulation was markedly inhibited by the pre-treatment with EGCG of 10－7， 10－6 and 10－5 mol/L （all P < 0.05）. Conclusions EGCG can enhance skin barrier function. AQP3 expression is down-regulated by UVB irradiation in keratinoctyes, while EGCG can inhibit the downregulation likely by suppressing the UVB-induced activation of EGFR and ERK. 【Key words】 Skin barrier； Aquaporin 3； Ultraviolet B；EGCG

Key words: aquaporin3, Ultraviolet B, EGCG