Effects of cystic fibrosis transmembrane conductance regulator and ΔF508CFTR on inflammatory response, ER stress, and Ca2+of airway epithelia

Abstract

We tested whether cystic fibrosis (CF) airway epithelia have larger innate immune responses than non-CF or cystic fibrosis transmembrane conductance regulator (CFTR)-corrected cells, perhaps resulting from ER stress due to retention of ΔF508CFTR in the endoplasmic reticulum (ER) and activation of cytosolic Ca2+(Cai) and nuclear factor (NF)-κB signaling. Adenovirus infections of a human CF (ΔF508/ΔF508) nasal cell line (CF15) provided isogenic comparisons of wild-type (wt) CFTR and ΔF508CFTR. In the absence of bacteria, there were no or only small differences among CF15, CF15-lacZ (β-galactosidase-expressing), CF15-wtCFTR (wtCFTR-corrected), and CF15-ΔF508CFTR (to test ER retention of ΔF508CFTR) cells in NF-κB activity, interleukin (IL)-8 secretion, Cairesponses, and ER stress. Non-CF and CF primary cultures of human bronchial epithelial cells (HBE) secreted IL-8 equivalently. Upon infection with Pseudomonas aeruginosa (PA) or flagellin (key activator for airway epithelia), CF15, CF15-lacZ, CF15-wtCFTR, and CF15ΔF508CFTR cells exhibited equal PA binding, NF-κB activity, and IL-8 secretion; cells also responded similarly to flagellin when both CFTR (forskolin) and Caisignaling (ATP) were activated. CF and non-CF HBE responded similarly to flagellin + ATP. Thapsigargin (Tg, releases ER Ca2+) increased flagellin-stimulated NF-κB and ER stress similarly in all cells. We conclude that ER stress, Cai, and NF-κB signaling and IL-8 secretion were unaffected by wt- or ΔF508CFTR in control and during exposure to PA, flagellin, flagellin + ATP, or flagellin + ATP + forskolin. Tg, but not wt- or ΔF508CFTR, triggered ER stress. Previous measurements showing hyperinflammatory responses in CF airway epithelia may have resulted from cell-specific, rather than CFTR- or ΔF508CFTR-specific effects.