Molecular mechanism through which Tripterygium hypoglaucum (Lévl.) Hutch alleviates psoriasis.

Tripterygium hypoglaucum (Lévl.) Hutch rhizome (THH) is mainly used in the clinical setting for the treatment of autoimmune diseases such as rheumatoid arthritis. In total, four active compounds were isolated from THH methanol extract （THH-MeOH）and identified. The HPLC results showed that the proportions of the active ingredients in THH-MeOH (i.e., celastrol, triptolide, and 3-O-acetyloleanolic acid) were 0.79 ‰, 0.46 ‰, and 0.76 ‰, respectively. THH-MeOH attenuated the M5-induced hyperproliferation of HaCaT cells, decreased the mRNA expression levels of inflammatory cytokines, and inhibited the phosphorylation of IκBα, NF-κB p65, MAPK, and STAT3/JAK2. Furthermore, THH-MeOH significantly reduced PASI scores in mice; reduced the level of Ki67 expression in skin tissues; decreased the expression of inflammatory cytokines in the skin lesions and serum; and ameliorated the IMQ-induced imbalance in the RORγt/Foxp3 ratio. The extract can attenuate psoriasis-like lesions by inhibiting cellular hyperproliferation, ameliorating inflammatory reactions, and modulating immune responses. Our work provides a theoretical basis to support the use of THH for treating psoriasis.