Andrographolide alleviates nasal mucosal inflammation in allergic rhinitis mice by inhibiting the IL-17/NF-κB pathway and downregulating MUC5AC expression.

ETHNOPHARMACOLOGICAL RELEVANCE: Andrographolide (Andro), the major bioactive constituent of the traditional Chinese medicinal herb Andrographis paniculata (Burm.f.) Wall. ex Nees, possesses prominent pharmacological activities including anti-inflammatory and immunomodulatory effects. Clinically, it has been applied as a supplementary therapy for inflammatory respiratory conditions., yet its intervention efficacy in allergic rhinitis (AR) and its multidimensional molecular mechanisms involving "anti-inflammatory-barrier protection" remain poorly elucidated.

AIM OF THE STUDY: To explore the mechanism by which Andro alleviates AR, evaluate its safety, and predict its potential therapeutic targets.

MATERIALS AND METHODS: Public bioinformatic databases were applied to forecast the potential targets and signaling pathways. An OVA-induced mouse model of AR was established, and Andro was administered by intraperitoneal injection. In vitro, an inflammatory injury model was established by stimulating human nasal epithelial RPMI-2650 cells with IL-4/IL-13, and functional blockade experiments were performed using the IL-17-specific inhibitor ixekizumab. Nasal mucosa was collected for transcriptome sequencing, and differentially expressed genes (DEGs) were screened and further analyzed with predicted targets. Pathological changes, inflammatory factors, tight junction proteins, immune cell subsets and key pathway-related proteins were evaluated by immunofluorescence, ELISA, RT-qPCR, IHC, flow cytometry and WB.

RESULTS: Network pharmacology analysis indicated that the IL-17 signaling pathway served as the core pathway of Andro against AR. Molecular docking and dynamics simulations show the stable binding between Andro and IL-17A. As demonstrated by a series of in vivo experiments, the administration of Andro resulted in a significant alleviation of nasal symptoms in AR mice. Furthermore, the serum levels of IgE, IL-17A, IL-6, and TNF-α were reduced, and the proportion of splenic CD4+IL-17A+ Th17 cells was dose-dependently decreased as determined by flow cytometry, and inflammatory cells infiltration in the nasal mucosa was suppressed. Meanwhile, Andro significantly inhibited goblet cell hyperplasia and MUC5AC overexpression, while dose-dependently restoring the expression of tight junction proteins ZO-1 and Occludin. In vitro experiments confirmed that Andro dose-dependently reversed IL-4/IL-13-induced inflammatory cytokine secretion, mucus hypersecretion and epithelial barrier damage in RPMI-2650 cells. Combined treatment with Andro and ixekizumab produced no additional additive effect, indicating that the protective effect of Andro may be dependent on the inhibition of the IL-17 signaling pathway. Mechanistically, Andro downregulated the transcription and protein expression of IL-17A, IL-17RA, and Act1, inhibited the phosphorylation of NF-κB p65, and blocked IL-17/NF-κB-mediated mucus hypersecretion and epithelial barrier damage.

CONCLUSIONS: The therapeutic mechanism of Andro against AR involves suppressing nasal mucosal inflammation and repairing epithelial barrier function by inhibiting key protein expression in the IL-17/NF-κB pathway and downregulating MUC5AC expression. This targeted regulation effectively ameliorates pathological injury in AR.