Abstract: Zhang Hongying*, Wang Xiaoyan, Chen Xingyu, Pang Mingjie, Shi Tongxin. *Department of Dermatology, Qingdao Municipal Hospital, Qingdao 266011, China Corresponding author: Shi Tongxin, Email: shitx2006@163.com 【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 groups: control 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 enzyme-linked immunosorbent assay（ELISA） to determine the level of IL-18 protein in the culture supernatant 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．

Key words: RADIX PAEONIAE ALBA, Keratinocytes, Interleukin-18, Mitogen-activated protein kinases