Background:Acitretin and matrine have been used in the treatment of psoriasis in China.This study was designed to investigate the role and related mechanisms of matrine alone and in combination with acitretin in the treatment of psoriasis in vitro and in vivo.Methods:HaCaT cells were treated with matrine at different concentrations of 0 (blank control),0.2,0.4,0.8,and 1.6 mg/mL for 24,48,72h,respectively.3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium cell viability assay was used to assess the growth and proliferation of HaCaT cells.Cell cycle and apoptosis were detected by flow cytometry.Expression of protein was detected by West blotting.Autophagy was observed by transmission electron microscopy.Then HaCaT cells were assigned to normal saline (NS) control group,matrine (0.4 mg/mL) group,acittetin (10 μmol/L) group,and matrine plus acitretin group,and the above methods were repeated.In animal experiments,the cumulative score (erythema,scaling,thickening) as a measure of the severity of inflammation was used to measure the skin performance of mice after treated with matrine 50 mg/kg,acitretin 4.5 mg/kg or combination of the two drugs on the psoriasis-like mouse models,respectively.Pathological findings of the lesions were observed,and the protein expressions in the lesions were detected by immunohistochemistry.Results:Cell proliferation inhibition was seen in HaCaT cells with treatment of matrine in a dose-and time-dependent manner (P ＜ 0.01,respectively).Cell cycle G0/G1 phase arrest was observed in a dose-dependent way (P ＜ 0.01).The expression of p21 (P ＜ 0.05),LC3Ⅱ/Ⅰ (P ＜ 0.01),and Beclin 1 (P ＜ 0.01) increased and the expression of cyclin D1 (P ＜ 0.05) decreased with increasing doses of matrine.Compared with the blank control,more autophagosomes were seen in HaCaT cells treated with matrine at 0.4 mg/mL by transmission electron microscopy (2.667 ± 1.202 vs.21.33 ± 1.453,t =9.899,P ＜ 0.01).Cell proliferation inhibition and degree of the G0/G1 phase arrest was significantly higher in matrine plus acitretin group than those in matrine,acitretin,or the NS control group (P ＜ 0.01,respectively).Compared with matrine or acitretin group,the expression of p21 (P ＜ 0.05,P ＜ 0.05) and LC3Ⅱ/Ⅰ (P ＜ 0.01,P ＜ 0.05) in matrine plus acitretin group increased significantly and the expression of cyclin D1 (P ＜ 0.01,P ＜ 0.05) and p62 (P ＜ 0.05,P ＜ 0.05) was reduced significantly.Compared with matrine or acitretin,matrine plus acitretin significantly down-regulated the phosphorylation of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) pathway (P ＜ 0.05) and its downstream p-p70S6K (P ＜ 0.05).In addition,the cumulative score of mice in the matrine plus acitretin group was significantly better than that in the matrine or acitretin group (1.480 ± 0.230 vs.2.370 ± 0.241,P ＜ 0.01;1.480 ± 0.230 vs.2.888 ± 0.341,P ＜ 0.01).The expression of LC3 protein in the matrine plus acitretin group was also higher than that in the matrine,acitretin,or the NS control group (P ＜ 0.05,respectively).Conclusions:Matrine has therapeutic potentials for psoriasis.Matrine and acitretin show synergistic effect via cell cycle arrest and autophagy induction by PI3K/Akt/mTOR pathway.