WS09.05Potential antimicrobial effects induced in cultured human bronchial epithelia by IL-17/TNF-alpha

Defective bacterial eradication and inflammation is an hallmark of many respiratory diseases, including cystic fibrosis (CF). In our previous study (Guidone et al., 2022), we found that treatment of human bronchial epithelia (HBE) with IL-17A/TNF-a, an inflammatory stimulus associated with neutrophilic infiltration, impact on cell transcriptome, with upregulation of genes involved in antimicrobial response, neutrophil recruitment and transepithelial ion transport. The consequence of ion transport changes is a hyperviscosity of the airway surface, that is reversed by b-adrenergic stimulation with isoproterenol. The switch from the hyperviscous to fluid state is dependent on CFTR. Our aim was to evaluate how this affects bacteria viability and motility. We deposited on HBE PAO1 and RP73 P. aeruginosa strains on a selected spot of the apical surface. After incubation, we pressed the snapwells on agar plates. Under control conditions, the bacteria were distributed all over the epithelial surface. Instead, in HBE treated with IL-17/TNF-a, bacteria remained in the area in which they were deposited. These findings indicate that the hyperviscosity elicited by the cytokines strongly limits the diffusion of bacteria. To identify antimicrobial molecules released by HBE, we decided to characterize their secretome. Mass spectrometry of fluid collected from the apical surface of epithelia treated with IL-17/TNF-a revealed an increased abundance of many defense molecules and chemoattractants for immune cells (IL-19, CSF3, CXCL17, CCL20). Surprisingly, we also found a specific set of membrane proteins including ATP12A, SLC26A4, DUOX2, SLC5A1, but not CFTR or ENaC. FACS experiments revealed an increased abundance of EVs upon treatment with IL-17A/TNF-a and the presence of EVs markers. We hypothesize that the presence of EVs may be involved in antimicrobial activity or in communication of regulatory stimuli to epithelial and immune cells.

Work supported by FFC#9/2022 and GMRF#1/2024.