Effect of total glucosides of paeony on the expression of interleukin-18 in human HaCaT keratinocytes and its related signaling pathways / 中华皮肤科杂志

ABSTRACT

Objective To evaluate the effect of total glucosides of paeony (TGP) on the expression of interleukin-18 (IL-18) in human HaCaT keratinocytes,and to explore the roles of extracelluar signal-regulated protein kinase1/2 (ERK1/2) and c-Jun N-terminal kinase 1/2 (JNK1/2) signaling pathways in the effect.Methods Some cultured human HaCaT keratinocytes were classified into three groupscontrol group treated with dimethyl sulfoxide (0.031％),TGP groups treated with 6 different concentrations (0.5,2.5,12.5,62.5,125.0 and 312.5 mg/L) of TGP respectively,inhibitor groups treated with TGP of 125 mg/L after 2-hour pretreatment with PD98059 (an ERK1/2 inhibitor) and SP600125 (a JNK1/2 inhibitor) of 10 μmol/L respectively.After additional culture for 48 hours,reverse transcription (RT)-PCR was performed to measure the mRNA expression level of IL-18,and enzymelinked immunosorbent assay (ELISA) to determine the level of IL-18 protein in the culture supematant of HaCaT cells.Some HaCaT keratinocytes were classified into two groups to be treated with TGP of 125 mg/L for 15,30 and 60 minutes with or without the pretreatment with PD98059 and SP600125 of 10 μmol/L; then,Western blot was carried out to determine the phosphorylation levels of ERK1/2 and JNK1/2 in HaCaT cells.Results The levels of IL-18 mRNA and protein in culture supernatant were significantly increased by TGP of 0.5 and 2.5 mg/L,but decreased by TGP of 62.5 and 125.0 mg/L,and TGP of 125.0 mg/L showed the strongest inhibitory effect.After treatment with TGP of 125.0 mg/L,the level of phosphorylated ERK1/2 in HaCaT cells peaked at 15 minutes (0.448 ± 0.018),decreased to 0.213 ± 0.005 at 30 minutes and 0.217 ± 0.005 at 60 minutes,with significant differences between TGP-treated and untreated cells at 15 minutes (0.448 ± 0.018 vs.0.204 ± 0.005,P＜ 0.05) but not at 30 or 60 minutes (both P ＞ 0.05).The phosphorylation level of ERK1/2 was 0.237 ± 0.010 in HaCaT cells pretreated with PD98059 prior to the treatment with TGP,significantly different from that in HaCaT cells treated with TGP only (P ＜0.01).TGP of 125.0 mg/L had no obvious effect on JNK phosphorylation,and there was no significant difference in the level of phosphorylated JNK1/2 between HaCaT cells untreated and those treated with TGP of 125.0 mg/L for different durations (all P ＞ 0.05).Conclusions TGP can inhibit the expression of IL-18 mRNA and protein in HaCaT cells,likely through the ERK1/2 signaling pathway.