Yinxieling decoction ameliorates psoriasis by regulating the differentiation and functions of Langerhans cells via TGF-β1/PU.1/IL-23 signal axis

Langerhans cells(LCs) play a critical role in skin immune responses and the development of psoriasis. Yinxieling(YXL) is a representative herbal medicine formula for the treatment of psoriasis in South China. It was confirmed to improve psoriasis without obvious side effects in the clinic. Here we attempted to clarify whether and how YXL regulates the differentiation and functions of LCs in Imiquimod(IMQ)-induced psoriasis-like C57BL/6 mouse model in vivo, and induced LCs in vitro. The Psoriasis Area Severity Index (PASI) score was used to evaluate efficacy of YXL for IMQ-induced psoriasis-like mice. Flow cytometry was utilized to analyze the effects of YXL to regulate the differentiation, migration, mature and antigen presentation of LCs. The results show that YXL significantly alleviated skin inflammation, as reduced in PASI score and classic psoriatic characteristics in pathological sections. Although there was not any effect on the proportion of total DCs in the skin draining lymph nodes, the expression of epidermal LCs and its transcription factor PU.1 was significantly inhibited, and its migration to draining lymph nodes and maturation were also inhibited. Further data showed that the number of antigen-carrying LC in the epidermis increased, indicating that YXL could effectively inhibit the antigen presentation of LCs. YXL also significantly inhibited the differentiation of LC in vitro. Further data showed that YXL decreaded the relatve expression of TGFβmRNA and IL-23 mRNA. Thus, YXL allievates psoriasis by regualting differentiation, migration, maturation and antigen presentation via TGFβ/ PU.1/IL-23 signal axis.