CHAC1 Is Differentially Expressed in Normal and Cystic Fibrosis Bronchial Epithelial Cells and Regulates the Inflammatory Response Induced by Pseudomonas aeruginosa

Perra, Léa; Balloy, Viviane; Foussignière, Tobias; Moissenet, Didier; Petat, Hortense; Mungrue, Imran N.; Touqui, Lhousseine; Corvol, Harriet; Chignard, Michel; Guillot, Loic

CHAC1 is a component of the ER stress pathway, and a link between ER stress and the inflammatory response has already been described in the context of CF (12) . Therefore, we investigated the role of CHAC1 in the inflammatory response induced by LPS or flagellin. Transfection with CHAC1 siRNA induced around 50% reduction in CHAC1 mRNA expression (Figure 5A) . We then examined different inflammatory parameters, particularly the secretion of IL-8, IL-6, and PGE2. As expected, we observed that 1 µg/mL LPS, 50 ng/mL flagellin, and the combination of both (LPS+flagellin) induced significant increases in both IL-8 and IL-6 secretion and tended to increase PGE 2 secretion (Figures 5B-D) . Under these stimulation conditions, when CHAC1 mRNA expression was decreased using siRNA, greater significant increases in IL-8 secretion ( Figure 5B ) and PGE 2 secretion ( Figure 5D ) were observed. In contrast, in the presence of CHAC1 siRNA, we observed significant inhibition of IL-6 secretion ( Figure 5C ) in cells stimulated with LPS (80% inhibition), flagellin (30% inhibition), or the combination of both virulence factors (80% inhibition). We obtained similar results for the mRNA expression of IL-8 and IL-6 (Supplementary Figures 4A,C) . CCL2 mRNA expression was also modulated similar to IL-8 expression under these experimental conditions (not detectable by ELISA; Supplementary Figure 4B ).