Formononetin ameliorates airway inflammation by suppressing ESR1/NLRP3/Caspase-1 signaling in asthma

Since inhaled glucocorticoids are the first-line treatment for asthma, asthma management becomes extremely difficult when asthma does not react well to glucocorticoids. Formononetin, a bioactive isoflavone and typical phytoestrogen, has been shown to have an anti-inflammatory impact while alleviating epithelial barrier dysfunction, which plays a role in the pathogenesis of allergic illnesses like asthma. However, the biological mechanisms behind this impact are unknown. As a result, we set out to investigate the effects of formononetin on airway inflammation and epithelial barrier repair in house dust mite (HDM)-induced asthmatic mice. We further expanded on formononetin's putative mode of action in reducing airway inflammation by modifying epithelial barrier dysfunction. In the current study, researchers discovered that formononetin significantly lowered total IgE levels in serum and interleukin (IL)-4, IL-6, and IL-17A levels in bronchoalveolar lavage fluid (BALF) in HDM-challenged asthmatic mice. Experiments on cell proliferation, migration, and apoptosis were performed in vitro to determine the effect of formononetin on bronchial epithelial barrier repair. Furthermore, in lipopolysaccharide (LPS)-stimulated 16HBE cells, formononetin increased cell proliferation and migration while preventing apoptosis and lowering the Bax/Bcl-2 ratio. In vitro and in vivo, formononetin significantly inhibited toll-like receptor 4 (TLR4) and estrogen receptor (ESR1)/Nod-like receptor family pyrin domain-containing protein 3 (NLRP3)/Caspase-1 signaling. These findings show that formononetin can reduce airway inflammation in HDM-challenged asthmatic mice by promoting epithelial barrier repair and possibly by inhibiting ESR1/NLRP3/Caspase-1 signaling as the underlying mechanism; formononetin could be a promising alternative treatment for asthma.