Terrestrosin D ameliorates skin lesions in an imiquimod-induced psoriasis-like murine model by inhibiting the interaction between Substance P and Dendritic cells.

BACKGROUND: Psoriasis is a psychosomatic immune skin disease with psychological factors contributing to the disease. Substance P (SP) is highly expressed in the psoriatic lesions of patients and is involved in pathological disease progression. Tribulus terrestris L. has been used as a Chinese herbal medicine for disease prevention for thousands of years. Terrestrosin D (TED) has been identified as the effective monomeric component of Tribulus terrestris L.. PURPOSE: We investigated whether TED could reverse imiquimod-induced psoriatic lesions, and then, investigated its potential mechanism of action both in vivo and in vitro. METHODS: 5% imiquimod cream was applied onto the backs of mice for 6 days to induce psoriasis-like skin lesions. The psoriatic area and severity index (PASI) was then used for scoring disease severity. Pathological changes and Ki-67 expression levels in skin lesions were measured using hematoxylin and eosin (H&E) and immunofluorescence staining after TED administration. The in vivo and in vitro expression levels of inflammatory cytokines, the ratio of DCs, and SP were measured using ProcartaPlex Mouse Cytokine panels, flow cytometry, and western blotting. Behavioral assessments were determined using the open field and elevated plus-maze (EPM) test. RESULTS: TED decreased PASI scores, epidermal thickness, Ki-67 expression levels, the ratio of DCs in the spleen, and secretion of IL-12p70, IL-18, and TNF-α in imiquimod-induced psoriasis-like murine models. Furthermore, TED increased IL-10 secretion levels, improved behavior, and down-regulated the expression levels of SP. Additionally, TED inhibited the in vitro maturation and activation of SP-induced CD11c+ DCs and the release of IL-12p70 and IL-23. CONCLUSION: TED reduced DCs maturation, down-regulated the expression levels of inflammatory factors, and improved skin lesions and behavior of psoriasis-like murine models by inhibiting the interaction between Substance P and Dendritic cells.