Psoriasis is a chronic inflammatory skin disease accompanied by excessive keratinocyte proliferation. Corticosteroids, vitamin D3 analogs, and calcineurin inhibitors, which are used to treat psoriasis, have diverse adverse effects, whereas natural products are popular due to their high efficiency and relatively low toxicity. The roots of the Cudrania tricuspidata (C. tricuspidata) are known to have diverse pharmacological effects, among which the anti-inflammatory effect is reported as a potential therapeutic agent in skin cells. Nevertheless, its effectiveness against skin diseases, especially psoriasis, is not fully elucidated. Here, we investigated the effect of cudraxanthone D (CD), extracted from the roots the C. tricuspidata Bureau, on psoriasis using an imiquimod (IMQ)-induced mouse model and the tumor necrosis factor (TNF)-α/interferon (IFN)-γ-activated keratinocytes. IMQ was topically applied to the back skin of C57BL/6 mice for seven consecutive days, and the mice were orally administered with CD. This resulted in reduced psoriatic characteristics, such as the skin thickness and Psoriasis Area Severity Index score, and the infiltration of neutrophils in IMQ-induced skin. CD inhibited the serum levels of TNF-α, immunoglobulin G2a, and myeloperoxidase, and the expression of Th1/Th17 cells in splenocytes. In TNF-α/IFN-γ-activated keratinocytes, CD reduced the expressions of CCL17, IL-1β, IL-6, and IL-8 by inhibiting the phosphorylation of STAT1 and the nuclear translocation of NF-kB. Taken together, these results suggest that CD could be a potential drug candidate for the treatment of psoriasis.

The extracts of Schisandra chinensis (Turcz.) Baill. (Schisandraceae) have various therapeutic effects, including inflammation and allergy. In this study, gomisin M2 (GM2) was isolated from S. chinensis and its beneficial effects were assessed against atopic dermatitis (AD). We evaluated the therapeutic effects of GM2 on 2,4-dinitrochlorobenzene (DNCB) and Dermatophagoides farinae extract (DFE)-induced AD-like skin lesions with BALB/c mice ears and within the tumor necrosis factor (TNF)-α and interferon (IFN)-γ-stimulated keratinocytes. The oral administration of GM2 resulted in reduced epidermal and dermal thickness, infiltration of tissue eosinophils, mast cells, and helper T cells in AD-like lesions. GM2 suppressed the expression of IL-1β, IL-4, IL-5, IL-6, IL-12a, and TSLP in ear tissue and the expression of IFN-γ, IL-4, and IL-17A in auricular lymph nodes. GM2 also inhibited STAT1 and NF-κB phosphorylation in DNCB/DFE-induced AD-like lesions. The oral administration of GM2 reduced levels of IgE (DFE-specific and total) and IgG2a in the mice sera, as well as protein levels of IL-4, IL-6, and TSLP in ear tissues. In TNF-α/IFN-γ-stimulated keratinocytes, GM2 significantly inhibited IL-1β, IL-6, CXCL8, and CCL22 through the suppression of STAT1 phosphorylation and the nuclear translocation of NF-κB. Taken together, these results indicate that GM2 is a biologically active compound that exhibits inhibitory effects on skin inflammation and suggests that GM2 might serve as a remedy in inflammatory skin diseases, specifically on AD.