QZLX gel alleviates psoriasiform inflammation through immunomodulatory effects involving PD-1/PD-L1/SHP2 signaling axis.

ETHNOPHARMACOLOGICAL RELEVANCE: A gel preparation derived from the traditional Chinese medicine formula QinZhuLiangXue (QZLX), a herbal formula for clinical psoriasis treatment, was developed as a potential alternative to existing topical treatments for psoriasis and to meet clinical expectations. Nonetheless, the exact mechanisms of its action against this condition remain to be clarified.

AIM OF THE STUDY: Investigation of the potential molecular and cellular mechanisms associated with the effects of QZLX gel on psoriasis, with a focus on the PD-1/PD-L1/SHP2-related PI3K-AKT signaling pathway.

MATERIALS AND

METHODS

A 15% concentration was chosen from in vivo gradient screening for animal investigations, while the appropriate in vitro concentration (2.5 mg/mL) was ascertained using parallel gradient screening. The anti-psoriasis effect of 15% QZLX gel was tested in mouse models triggered by Imiquimod. Pathological changes in the epidermis were shown by H&E. The content of IL-17A, IL-22, IL-6, and TNF-α in the model samples was analyzed by ELISA. The critical ingredients and targets were predicted by using network pharmacology analysis, and the binding affinities between key compounds and candidate targets were preliminarily evaluated via molecular docking. IHC analysis was used to compare the percentage of positive area for PD-1 and PD-L1 in the epidermis and dermis. mRNA expression of IL-1β and CXCL8 was analyzed using qRT-PCR. The interaction between PD-1 and PD-L1/SHP2 was evaluated by Co-IP, and the interactions were further validated in a DC-T cell co-culture system following QZLX treatment. WB was performed to analyze the expression levels of PD-1 in T cells, PD-L1 in DCs, and PI3K, AKT, p-PI3K, and p-AKT after QZLX intervention.

RESULTS

A 15% QZLX gel markedly alleviated psoriasis-like phenotypes and histopathological changes, alongside a significant decrease in the content of IL-17A, IL-22, IL-6, and TNF-α. The quercetin, kaempferol, and porphyrin were screened as candidate active ingredients for QZLX gel. The PD-1/PD-L1 pathway was identified as a significantly enriched immune checkpoint pathway associated with the therapeutic action of QZLX. QZLX gel treatment significantly upregulated PD-1 and PD-L1 levels in the dermis, but no discernible alterations in their expression levels were noted in the epidermal layer. The 2.5 mg/mL solution of QZLX markedly decreased IL-1β and CXCL8 levels. Co-IP analysis confirmed the association of PD-1 with PD-L1 and SHP2, as evidenced by enhanced PD-L1 and SHP2 signals in PD-1 immunoprecipitates. Moreover, QZLX treatment further increased these interactions in the T cell-DC co-culture system. According to the WB results, the 2.5 mg/mL QZLX solution elevated PD-1 levels in T-cell lysates and levels of PD-L1 in dendritic cells, while promoting the interaction between PD-1 and PD-L1. Moreover, the PI3K-AKT signaling pathway was markedly suppressed after QZLX gel administration.

CONCLUSIONS

Our study demonstrates that QZLX gel alleviates psoriasis-like inflammation and skin symptoms, and these effects are associated with modulation of the PD-1/PD-L1/SHP2 axis and PI3K-AKT signaling pathway activity.