Abstract: Zheng Yuxin, Min Min, Zhu Ziyu, Yang Xiaohong, Cao Yi, Zheng Min Zhejiang Chinese Medical University, Hangzhou 310053, China （Zheng YX, Zhu ZY, Yang XH, Cao Y）; Department of Dermatology, The First People′s Hospital of Changzhou, Changzhou 213003, Jiangsu, China （Min M）; Department of Dermatology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310009, China （Zheng M） Corresponding author: Cao Yi, Email: caoyi1965@163.com 【Abstract】 Objective To preliminarily evaluate the effect of glycyrrhetinic acid on the proliferation and apoptosis of keratinocytes in patients with psoriasis, and to explore its possible mechanisms. Methods Keratinocytes were isolated from patients with psoriasis, and subjected to a primary culture in vitro. After 2 - 3 passages, the keratinocytes were divided into several groups to be treated with glycyrrhetinic acid at final concentrations of 0 （control group）, 1, 2, 4, 8 and 10 mg/L （glycyrrhetinic acid groups）, respectively. After 24 - 72 hours of treatment, MTS assay was performed to evaluate the effect of glycyrrhetinic acid on the proliferation of keratinocytes, and flow cytometry was conducted to detect the apoptosis of keratinocytes after 24-hour treatment with glycyrrhetinic acid at different concentrations. Real-time fluorescence-based PCR was performed to determine the expression of miR-21 in keratinocytes. Results After 24 - 72 hours of treatment with 1 - 10 mg/L glycyrrhetinic acid, the proliferation activity of keratinocytes significantly decreased along with the increase in the treatment duration and concentrations of glycyrrhizinic acid. After 24-hour treatment with 1, 2, 4, 8, 10 mg/L glycyrrhetinic acid, the apoptosis rates of keratinocytes increased to （9.64 ± 0.86）%, （25.24 ± 2.93）%, （27.68 ± 3.70）%, （35.55 ± 4.23）% and （38.89 ± 2.31）% respectively. As LSD-t test showed, the apoptosis rates of keratinocytes were significantly higher in all the glycyrrhetinic acid groups than in the control group （10.09% ± 0.69%, all P < 0.01）, except the 1 mg/L glycyrrhetinic acid group. After 24-hour treatment with 1, 2 and 4 mg/L glycyrrhetinic acid, the miR-21 expression （2-ΔΔCt） significantly decreased （0.24 ± 0.04, 0.22 ± 0.07, 0.17 ± 0.05, respectively） compared with the control group （0.92 ± 0.12, F = 213.10, P < 0.05）. After 18-, 24- and 48-hour treatment with 2 mg/L glycyrrhetinic acid, the miR-21 expression significantly decreased （0.55 ± 0.02, 0.22 ± 0.06 and 0.15 ± 0.06 respectively） compared with the control group （0.98 ± 0.02, F = 238.10, P < 0.05）. Conclusion Glycyrrhetinic acid can inhibit the proliferation of keratinocytes from psoriatic patients, but promote the apoptosis, likely by down-regulation of miR-21 expression.

Key words: Psoriasis, Glycyrrhetinic acid, Keratinocytes, Cell proliferation, Apoptosis, MicroRNAs, miR?21