Effects of Fungus‐Derived Compound N9 on Airway Mucus Secretion: In Vitro and In Vivo Studies

Abstract

Asthma is a heterogeneous chronic airway inflammatory disease affecting more than 250 million people worldwide. It is characterized by airway inflammation, smooth muscle contraction, and mucus hypersecretion. The current treatment of asthma includes inhibition of the first two characteristics with little attention being paid for modulation of mucus secretion. In fact, mucus dysregulation is a main contributor to airway obstruction in fatal asthma. Since N9 inhibited TMEM16A chloride channel required for airway mucus secretion, we hypothesized that N9 might be a negative modulator for mucus secretion in asthma. Interestingly, we found that N9 at 10 µM impaired Ca2+‐induced mucin depletion in cytokine‐treated airway epithelial (Calu‐3) cell monolayers as analyzed by immunofluorescence staining of intracellular MUC5AC, a pathologic mucin protein, suggesting that N9 inhibited mucin secretion. Intraperitoneal administration of N9 at 20 mg/kg inhibited OVA‐induced mucus secretion as analyzed by ELISA for detection of MUC5AC in bronchoalveolar lavage of BALB/c mice. Conversely, N9 did not reduce inflammatory score in H&E‐stained lung slides or inflammatory cells in bronchoalveolar lavage with dexamethasone (5 mg/kg) being a positive control. These results suggest that N9 specifically targets mucin secretion without compromising immune function. Taken together, N9 represents the first class of fungus‐derived inhibitor of mucus secretion which might be useful for the treatment of asthma and other airway diseases with mucus hypersecretion being the main pathogenesis.