Liangxue Jiedu formula improves imiquimod-induced psoriasiform dermatitis with circadian desynchrony by regulating Th17 cell differentiation based on network pharmacological analysis

Liangxue Jiedu formula (LXJDF) is an effective traditional Chinese medicine (TCM) formula for treating psoriasis of blood-heat syndrome and has been used in clinics for decades.This study aimed to discover the mechanism of LXJDF in psoriasis and the circadian clock by network pharmacology and experimental studies.The compounds of LXJDF were obtained from the TCMSP and BATMAN-TCM databases. The genes related to psoriasis and circadian rhythm/clock were identified by the OMIM and GeneCards databases. Then, target genes were integrated by Venn and analyzed by the String, CytoNCA, DAVID (GO and KEGG) databases, and the network was constructed using Cytoscape. Mice were raised under light disturbance for fourteen days. On the eighth day, mouse dorsal skin was shaved and smeared with 62.5 mg 5% imiquimod at 8:00 (ZT0) for six successive days. Mice were randomly divided into the model, LXJDF-H (49.2 g/kg·bw), LXJDF-L (24.6 g/kg·bw), and positive drug (dexamethasone) groups. Other mice were smeared with Vaseline under the normal light cycle as the control. The drug of each group was administered at 10:00 (ZT2) and 22:00 (ZT14). The skin lesions were observed, and PASI was scored daily. HE and immunofluorescence were used to measure pathological morphology. Th17 cytokines in serum and skin were measured by flow cytometry and qPCR. Circadian clock gene and protein expression levels were determined by qPCR and Western blotting.We found 34 potential targets of LXJDF in the treatment of psoriasis and circadian rhythm and confirmed their importance by topology analysis. KEGG pathway analysis revealed that the two major pathways were Th17 cell differentiation and the HIF-1 signaling pathway. At ZT2 and ZT14, LXJDF improved IMQ-induced light disturbance mouse skin lesions, including alleviating scales, erythema, and infiltration, reducing PASI, and inhibiting keratinocyte hyperproliferation and parakeratosis. LXJDF reduced IL-17A, IL-17F, TNF-α, and IL-6 in serum at ZT2 and increased IL-10 at ZT2 and ZT14. LXJDF downregulated the expression of IL-17A and IL-17F in skin. At ZT2, LXJDF significantly upregulated CLOCK and REV-ERBα expression and downregulated HIF-1α expression. At ZT14, LXJDF decreased HIF-1α and RORγt expression and significantly increased REV-ERBα expression.LXJDF improves psoriasis dermatitis with circadian rhythm disorders by regulating Th17 cell differentiation.