Epithelial innate immune response to Pseudomonas aeruginosa–derived flagellin in chronic rhinosinusitis

Abstract Background Pseudomonas aeruginosa is a common colonizing pathogen in the upper respiratory tract and is associated with recalcitrant chronic rhinosinusitis (CRS). Herein we sought to characterize the effect of P. aeruginosa– derived flagellin on human sinonasal epithelial cell (HSNEC) immune responses and determine whether these pathways are disrupted in CRS. Methods Air‐liquid interface cultures were established from CRS and healthy control donors. Cells were incubated with P. aeruginosa– derived flagellin for 24 hours and transcriptional changes were assessed using whole transcriptome RNA sequencing. Apical and basolateral secretion of the pro‐inflammatory cytokines in interleukin (IL)‐1β, tumor necrosis factor (TNF)‐α, and IL‐6 were measured after stimulation by lipopolysaccharide or flagellin and responses were compared between CRS and healthy control patients. Results HSNECs were weakly responsive to lipopolysaccharide, whereas flagellin stimulated a profound innate immune response dominated by TNF‐α, IL‐1β, and IL‐17 signaling and activation of the IL‐17C/IL‐23 axis. CRS‐derived HNSECs showed an altered innate immune response to flagellin, characterized by a profound increase in TNF‐α secretion coupled with reduced IL‐6 secretion. Conclusions Flagellin activates a potent innate immune response in HSNECs characterized by pro‐inflammatory mediators and cytokines/chemokines associated with neutrophilic inflammation. HSNECs from CRS patients have a dysregulated innate immune response to flagellin characterized by an imbalance between IL‐6 and TNF‐α secretion.