Abstract:

Fu Dandan, Hu Hua, Sun Min, Li Min, Tian Zhongwei Department of Dermatology and Venereology, The First Affiliated Hospital of Xinxiang Medical University, Weihui 453100, Henan, China Corresponding author: Tian Zhongwei, Email: zhonwt@163.com 【Abstract】 Objective To evaluate the protective effect of epigallocatechin gallate （EGCG） against interleukin （IL）-17-induced injury to keratinocytes, and to explore its mechanism. Methods Some cultured HaCaT cells were divided into 3 groups to be treated with IL-17 alone at concentrations of 50, 70, 90 μg/L, respectively, with those receiving no treatment as the blank control group. Some HaCaT cells were divided into 5 groups: IL-17 group treated with 90 μg/L IL-17 alone, IL-17 + EGCG group treated with 90 μg/L IL-17 and 60 μmol/L EGCG, IL-17 + SP600125 group treated with 90 μg/L IL-17 and SP600125 （a JAK signaling pathway inhibitor）, IL-17+ EGCG + anisomycin group treated with 90 μg/L IL-17, 60 μmol/L EGCG and anisomycin （a Janus kinase signaling pathway activator）, and blank control group receiving no treatment. After different durations of treatment, CCK-8 assay was performed to evaluate cellular proliferative activity, flow cytometry to detect cell apoptosis, enzyme-linked immunosorbent assay （ELISA） to measure levels of IL-6, IL-23 and IL-8, and Western-blot analysis to determine protein s of c-Jun N-terminal kinase （JNK） and phosphorylated JNK （P-JNK）. Results IL-17 promoted cellular proliferation of HaCaT cells, and the proliferation rate, which was correlated with the concentration of IL-17, reached the maximum in the 90-μg/L IL-17 group （P < 0.05）. EGCG at 60 μmol/L significantly inhibited cellular proliferation of, promoted apoptosis in, and reduced IL-6, IL-23 and IL-8 s in, HaCaT cells induced by 90 μg/L IL-17 （all P < 0.05）. Compared with the IL-17 group, the IL-17 + EGCG group and IL-17 + SP600125 group both showed significantly decreased P-JNK , cell proliferation rate and IL-6, IL-23 and IL-8 levels （all P < 0.05）. However, compared with the IL-17 + EGCG group, the IL-17 + EGCG + anisomycin group showed significantly increased protein of P-JNK, cell proliferation rate and IL-6, IL-23 and IL-8 levels （all P < 0.05）. Conclusion EGCG protected against IL-17-induced injury to HaCaT cells, such as abnormal cell proliferation, apoptosis and inflammatory response, likely by inhibiting the JNK signaling pathway.