A variety of triggers contribute to mucin production, including allergic inflammation, environmental pollutants, viral exposure and bacterial products, and various mechanisms have been implicated in the regulation of mucin production, including signaling via the epidermal growth factor receptor, the Notch pathway and purinergic signaling following extracellular release of adenosine 5'-triphosphate (ATP) (Boucherat et al., 2013; Krishn et al., 2018). Here, MUC5AC is linked to inflammation.