Neutrophil Elastase Degrades Cystic Fibrosis Transmembrane Conductance Regulator via Calpains and Disables Channel Function In Vitro and In Vivo

Rationale: Cystic fibrosis transmembrane conductance regulator (CFTR) protein is a chloride channel regulating fluid homeostasis at epithelial surfaces. Its loss of function induces hypohydration, mucus accumulation, and bacterial infections in CF and potentially other lung chronic diseases. Objectives: To test whether neutrophil elastase (NE) and neutrophil-mediated inflammation negatively impact CFTR structure and function, in vitro and in vivo. Methods: Using an adenovirus-CFTR overexpression approach, we showed that NE degrades wild-type (WT)- and Delta F508-CFTR in vitro and WT-CFTR in mice through a new pathway involving the activation of intracellular calpains. Measurements and Main Results: CFTR degradation triggered a loss of function, as measured in vitro by channel patch-clamp and in vivo by nasal potential recording in mice. Importantly, this mechanism was also shown to be operative in a Pseudomonas aeruginosa lung infection murine model, and was NE-dependent, because CFTR integrity was significantly protected in NE-/- mice compared with WT mice. Conclusions: These data provide a new mechanism and show for the first time a link between NE-calpains activation and CFTR loss of function in bacterial lung infections relevant to CF and to other chronic inflammatory lung conditions.