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

BackgroundPseudomonas 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. MethodsAir-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)-1 beta, tumor necrosis factor (TNF)-alpha, and IL-6 were measured after stimulation by lipopolysaccharide or flagellin and responses were compared between CRS and healthy control patients. ResultsHSNECs were weakly responsive to lipopolysaccharide, whereas flagellin stimulated a profound innate immune response dominated by TNF-alpha, IL-1 beta, 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-alpha secretion coupled with reduced IL-6 secretion. ConclusionsFlagellin 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-alpha secretion.