Epigallocatechin gallate inhibits the proliferation and apoptosis of keratinocytes induced by interleukin-17

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 expression levels of IL-6, IL-23 and IL-8, and Western-blot analysis to determine protein expressions 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 expressions 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 expression, cell proliferation rate and IL-6, IL-23 and IL-8 expression levels (all P < 0.05) . However, compared with the IL-17+EGCG group, the IL-17+EGCG+anisomycin group showed significantly increased protein expression of P-JNK, cell proliferation rate and IL-6, IL-23 and IL-8 expression 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. Key words: Keratinocytes; Catechin; Interleukin-17; Cell proliferation; Apoptosis; Epigallo-catechin gallate