Extracellular oxidation in cystic fibrosis airway epithelium causes enhanced EGFR/ADAM17 activity

Abstract

The EGF receptor (EGFR)/a disintegrin and metalloproteinase 17 (ADAM17) signaling pathway mediates the shedding of growth factors and secretion of cytokines and is involved in chronic inflammation and tissue remodeling. Since these are hallmarks of cystic fibrosis (CF) lung disease, we hypothesized that CF transmembrane conductance regulator (CFTR) deficiency enhances EGFR/ADAM17 activity in human bronchial epithelial cells. In CF bronchial epithelial CFBE41o cells lacking functional CFTR (iCFTR) cultured at air-liquid interface (ALI) we found enhanced ADAM17-mediated shedding of the EGFR ligand amphiregulin (AREG) compared with genetically identical cells with induced CFTR expression (iCFTR). Expression of the inactive G551D-CFTR did not have this effect, suggesting that active CFTR reduces EGFR/ADAM17 activity. This was confirmed in CF compared with normal differentiated primary human bronchial epithelial cells (HBEC-ALI). ADAM17-mediated AREG shedding was tightly regulated by the EGFR/MAPK pathway. Compared with iCFTR cells, iCFTR cells displayed enhanced apical presentation and phosphorylation of EGFR, in accordance with enhanced EGFR/ADAM17 activity in CFTR-deficient cells. The nonpermeant natural antioxidant glutathione (GSH) strongly inhibited AREG release in iCFTR and in primary HBEC-ALI, suggesting that ADAM17 activity is directly controlled by extracellular redox potentials in differentiated airway epithelium. Furthermore, the fluorescent redox probe glutaredoxin 1-redox-sensitive green fluorescent protein-glycosylphosphatidylinositol (Grx1-roGFP-GPI) indicated more oxidized conditions in the extracellular space of iCFTR cells, consistent with the role of CFTR in GSH transport. Our data suggest that in CFTR-deficient airway epithelial cells a more oxidized state of the extracellular membrane, likely caused by defective GSH secretion, leads to enhanced activity of the EGFR/ADAM17 signaling axis. In CF lungs this could contribute to tissue remodeling and hyperinflammation.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) in Human Lung Microvascular Endothelial Cells Controls Oxidative Stress, Reactive Oxygen-Mediated Cell Signaling and Inflammatory Responses

“…Inhibition of airway epithelial CFTR increased VEGF expression, an effect that was dependent on EGFR activity and inhibited by the receptor tyrosine kinase inhibitor AG1478 (Martin et al, 2013). Further, CF airway epithelial cells have increased EGFR activity and phosphorylation compared to normal cells (Stolarczyk et al, 2018). Thus it was suggested that EGFR tyrosine kinase inhibitors, such as AG1478, might be useful in the treatment of CF.…”

Human Cellular Models for the Investigation of Lung Inflammation and Mucus Production in Cystic Fibrosis

“…The role of CFTR in the EGFR/ADAM17 axis has been investigated with an immortalized CF cell model (iCFTR CFBE) that allows inducible expression of CFTR in ALI culture [71], avoiding invalid comparisons of genetically distinct populations of immortalized cells. In ALI cultures, where they assume a low cuboidal morphology, not-induced iCFTR CFBE cells showed an enhancement of ADAM17-dependent shedding of amphiregulin, which, in turn, regulates EGFR activity, as compared with CFTR-expressing cells [108]. Importantly, these results were replicated in primary bronchial epithelial cells in ALI culture as well and allowed understanding that extracellular oxidative stress, likely related to deficiency in GSH transport, enhances the basal activity of the EGFR/ADAM17 axis through the ADAM17-dependent shedding of EGFR agonists causing enhanced EGFR activity [109].…”

OM-85 Broncho-Vaxom®, a Bacterial Lysate, Reduces SARS-CoV-2 Binding Proteins on Human Bronchial Epithelial Cells

“…Treatment with human recombinant soluble ACE2 (sACE2) has been suggested as a scavenger therapy to trap SARS-CoV-2 before binding to the mACE2 [ 7 ]. The generation of sACE2 is mainly controlled by the activity of ADAM17 (a disintergrin and metalloproteinase 17), which is also expressed on the membrane of epithelial cells [ 8 , 9 ]. ADAM17 expression is sensitive to viral infection including influenza and SARS-CoV-2 [ 8 , 10 ].…”