Inflammatory mediators ATP and S100A12 activate the NLRP3 inflammasome to induce MUC5AC production in airway epithelial cells.

Danger-associated molecular patterns (DAMPs) play a proinflammatory role in the pathogenesis of airway obstructive diseases such as severe asthma and chronic obstructive pulmonary disease. The NLRP3 inflammasome is a cytosolic multiprotein platform that activates the caspase-1 pathway in response to inflammatory stimuli such as DAMPs. ATP and S100 proteins are newly identified DAMPs that accumulate in inflamed airways. We previously demonstrated that S100A8, S100A9, and S100A12 induce production and secretion of MUC5AC, a major mucin in the conducting airway mucosa. The purpose of this study was to determine the involvement of NLRP3 inflammasome in, and the contribution of ATP to, S100 protein-induced MUC5AC production by NCI-H292 mucoepidermoid carcinoma cells. Stimulation with either S100A12 or ATP led to MUC5AC production at comparable levels. Simultaneous treatment with both stimuli resulted in additive increases in NLRP3, active caspase-1, IL-1β, NLRP3/caspase-1 colocalization, and MUC5AC. NLRP3 siRNA or inhibitors of NF-κB, NLRP3 inflammasome oligomerization, or caspase-1 nearly completely inhibited ATP- and S100A12-mediated MUC5AC production. Furthermore, S100A12-as well as ATP-mediated MUC5AC production was almost equally blunted by both nonspecific and specific antagonists of the purinergic receptor P2X7, a principal receptor mediating NLRP3 inflammasome activation by ATP. Thus, these two danger signals contribute to MUC5AC production in airway epithelial cells through overlapping signaling pathways for NLRP3 inflammasome activation.