CFTR mutation leads to intrinsic dysfunction in neutrophils from people with Cystic Fibrosis

Abstract

Cystic fibrosis (CF), a common genetic disease, is caused by a defective CF-transmembrane conductance regulator (CFTR). People with CF (pwCF) are prone to develop infections by opportunistic pathogens, including Burkholderia cenocepacia, leading to chronic inflammation and lung function loss. Neutrophils, the most abundant cells in the chronically inflamed lungs of pwCF, release granular proteins and oxidative products that contribute to tissue damage. The CFTR modulators are a new treatment for pwCF aiming to correct the subcellular location and function of the CFTR ion channel. The triple modulator combination of Elexacaftor, Tezacaftor, and Ivacaftor (ETI) or Trikafta(R) has significantly improved clinical symptoms and overall provided a better quality of life for pwCF. The mechanism by which the CFTR modulators help to restore the antimicrobial functions of neutrophils is unknown. The present study demonstrates that neutrophils functionally express CFTR and reveals how ETI modifies subcellular CFTR trafficking in CF neutrophils. In addition, ETI treatment reduces intracellular chloride levels in human neutrophils, indicating activation of CFTR-dependent chloride efflux (outflow). Finally, ETI treatment also reestablished the intracellular antimicrobial killing of CF neutrophils by potentiating NADPH oxidase activity and producing Neutrophil Extracellular Traps (NETs). Together, our findings suggest that CFTR has an essential role in controlling neutrophil functions and that the CFTR modulators improve the health of pwCF by restoring the antimicrobial functions of CF neutrophils. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/656500v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@8469b5org.highwire.dtl.DTLVardef@1380609org.highwire.dtl.DTLVardef@1145117org.highwire.dtl.DTLVardef@d7c0a2_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract.C_FLOATNO (A) The F508del defective CFTR protein cannot reach the plasma membrane in CF neutrophils, which increases the intracellular concentrations of Cl- ions, and allows other ions to be internalized, including Na+ and Ca2+. This ionic imbalance affects the NADPH oxidase, leading to a reduced preactivation response and consequently impacting NADPH oxidase-dependent antimicrobial mechanisms, including intracellular antimicrobial killing and NETosis. (B) Treating with ETI restores the CFTR expression in the plasma membrane of CF neutrophils, increasing the Cl- efflux and regulating the intracellular levels of Na+ and Ca2+, leading to correcting the NADPH oxidase, which results in potentiating the intracellular antimicrobial killing and NETosis. BiorenderTM tools generated the images. C_FIG