IL-17 family members exert an autocrine pro-inflammatory loop in CF respiratory epithelial cells ex vivo

Background: Lungs of people with Cystic Fibrosis (pwCF) are characterized by chronic inflammation and infection with P. aeruginosa. High levels of IL-17 A and F have been observed in sputum of pwCF and the interleukin-17(IL-17) family (A-to-F) has been suggested to play a key role in CF pulmonary disease. Methods: We measured mRNA levels of IL-17 receptors (IL-17R) by RT-qPCR in CF bronchial epithelial (CFBE) cultured cells upon infection with P. aeruginosa PAO1 strain or clinical exoproducts (EXO) isolated from pwCF. We measured IL-17 mRNA expression by RT-qPCR and the release of cytokines by ELISA and Bioplex from CF primary nasal epithelial (HNE) cultured cells. Results: Infection of CFBE cells with PAO1 or EXO isolated from 15 pwCF significantly increased mRNA expression of all IL-17R, except IL-17RD. Infection of HNE cells with EXO isolated from the correspondent donor significantly increased the mRNA levels of all the IL-17 cytokines and receptors, except for IL-17D and IL-17RD, and the release of the cytokines IL-17 A, IL-17B, IL-17C, IL-17E and IL-17F. HNE exposed to IL-17 A and F were induced to release pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), neutrophil chemokines (IL-8, G-CSF) and cytokines known to be involved in chloride and bicarbonate secretion, together with mucin upregulation (IL-4, IL-13). Conclusion: These results highlight a wider expression of IL-17 family member in respiratory epithelial cells, which can play a role as an autocrine inflammatory amplification loop in CF airways. These in-vitro studies using patient-derived cultures underline the relevant role of IL-17 family members in CF pulmonary immune response.