1. A neutrophil intrinsic impairment affecting Rab27a and degranulation in cystic fibrosis is corrected by CFTR potentiator therapy.
- Author
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Pohl K, Hayes E, Keenan J, Henry M, Meleady P, Molloy K, Jundi B, Bergin DA, McCarthy C, McElvaney OJ, White MM, Clynes M, Reeves EP, and McElvaney NG
- Subjects
- Adult, Aminophenols therapeutic use, Cell Degranulation drug effects, Cell Degranulation genetics, Cells, Cultured, Chlorides metabolism, Cystic Fibrosis drug therapy, Cystic Fibrosis genetics, Cystic Fibrosis Transmembrane Conductance Regulator genetics, Electrophoresis, Gel, Two-Dimensional, Female, Homeostasis genetics, Humans, Immunoblotting, Magnesium metabolism, Male, Mutation, Neutrophils drug effects, Neutrophils physiology, Protein Transport drug effects, Proteome genetics, Proteome metabolism, Proteomics methods, Quinolones therapeutic use, Sodium metabolism, Tumor Necrosis Factor-alpha pharmacology, Young Adult, rab27 GTP-Binding Proteins, Cystic Fibrosis metabolism, Cystic Fibrosis Transmembrane Conductance Regulator metabolism, Neutrophils metabolism, rab GTP-Binding Proteins metabolism
- Abstract
Studies have endeavored to reconcile whether dysfunction of neutrophils in people with cystic fibrosis (CF) is a result of the genetic defect or is secondary due to infection and inflammation. In this study, we illustrate that disrupted function of the CF transmembrane conductance regulator (CFTR), such as that which occurs in patients with ∆F508 and/or G551D mutations, correlates with impaired degranulation of antimicrobial proteins. We demonstrate that CF blood neutrophils release less secondary and tertiary granule components compared with control cells and that activation of the low-molecular-mass GTP-binding protein Rab27a, involved in the regulation of granule trafficking, is defective. The mechanism leading to impaired degranulation involves altered ion homeostasis caused by defective CFTR function with increased cytosolic levels of chloride and sodium, yet decreased magnesium measured in CF neutrophils. Decreased magnesium concentration in vivo and in vitro resulted in significantly decreased levels of GTP-bound Rab27a. Treatment of G551D patients with the ion channel potentiator ivacaftor resulted in normalized neutrophil cytosolic ion levels and activation of Rab27a, thereby leading to increased degranulation and bacterial killing. Our results confirm that intrinsic alterations of circulating neutrophils from patients with CF are corrected by ivacaftor, thus illustrating additional clinical benefits for CFTR modulator therapy., (© 2014 by The American Society of Hematology.)
- Published
- 2014
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