Inula japonica Thunb. and its active compounds ameliorate airway inflammation by suppressing JAK-STAT signaling.

Asthma, a chronic inflammatory disease, remains a global health challenge due to its complex pathophysiology and the limited treatment efficacy. This study explored the effect of Inula japonica Thunb. water extract (IJW) on asthma and its protective mechanisms. To assess the effects of IJW, we established an experimental asthma model in BALB/c mice using ovalbumin (OVA). Airway hyper-responsiveness (AHR) in response to methacholine was measured. We quantified inflammatory cell infiltration and cytokine and chemokine levels in bronchoalveolar lavage fluid (BALF), as well as total IgE levels in serum. Staining with hematoxylin and eosin and periodic acid-Schiff was used to examine the impact of IJW on lung pathology. We performed RNA sequencing to identify differentially expressed genes, which were subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses. We used interleukin (IL)-4/IL-13-treated human bronchial epithelial (HBE) cells to explore the associated mechanisms. IJW showed therapeutic effects against OVA-induced asthma by alleviating AHR, peribronchial inflammation, mucus hypersecretion, and collagen fiber deposition. It reduced total IgE levels in the serum and IL-4, IL-5, IL-13, eotaxin, macrophage-derived chemokines, and periostin levels in BALF. In IL-4/IL-13-treated HBE cells, IJW and its components suppressed the Janus kinase-signal transducer and activator of the transcription (JAK-STAT) signaling. These findings support IJW's potential as a pharmacological agent for allergic airway inflammation and asthma.