IL-17A mediates pyroptosis via the ERK pathway and contributes to steroid resistance in CRSwNP.

Background: Pyroptosis is closely related to inflammation. However, the molecular mechanisms and pathologic contributions of pyroptotic epithelial cell are not yet fully understood.

Objective: This study aimed to explore the function and molecular mechanisms of IL-17A on human nasal epithelial cell (hNEC) pyroptosis.

Methods: The expression of pyroptosis-related biomarkers and IL-17A was assessed in sinonasal mucosa from control individuals, patients with chronic rhinosinusitis without nasal polyps, and patients with chronic rhinosinusitis with nasal polyps (CRSwNP) by using quantitative RT-PCR. Their localization was analyzed via immunohistochemistry and immunofluorescence. The ultrastructural characteristics of IL-17A-induced pyroptosis in hNECs were visualized by using electron microscopy. IL-17A functional assays were performed on hNECs and airway epithelial cell lines. Cytokine levels were quantified via ELISA. The signaling pathways involved in IL-17A-induced pyroptosis were studied via unbiased RNA sequencing and Western blotting.

Results: The expression of IL-17A and the pyroptotic biomarkers NOD-like receptor family, pyrin domain containing 3 (NLRP3), caspase-1, gasdermin D, and IL-1β was increased in nasal mucosa from patients with CRSwNP compared with in those with chronic rhinosinusitis without nasal polyps and the control subjects. IL-17A was positively correlated and colocalized with the pyroptotic biomarkers. IL-17A treatment induced pyroptosis in the hNECs and cell lines analyzed, primarily through the extracellular signal-regulated kinase (ERK)-NLRP3/caspase-1 signaling pathway, and increased IL-1β and IL-18 secretion in hNECs. Moreover, IL-17A-induced pyroptosis contributed to steroid resistance by affecting glucocorticoid receptor-α and glucocorticoid receptor-β expression, and the inhibition of pyroptotic proteins partially abolished IL-17A-induced steroid resistance in hNECs.

Conclusion: Elevated IL-17A level promotes pyroptosis in hNECs through the ERK-NLRP3/caspase-1 signaling pathway and contributes to glucocorticoid resistance by affecting glucocorticoid receptor homeostasis in patients with CRSwNP.