Effects of green tea polyphenol epigallocatechin-3-gallate and ultraviolet B on the expression of aquaporin 3 and EGFR/ERK signaling pathway in keratinocytes / 中华皮肤科杂志

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 transepidermal 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.