Regulation of normal and cystic fibrosis airway epithelial repair processes by TNF-α after injury

Abstract

Chronic infection and inflammation have been associated with progressive airway epithelial damage in patients with cystic fibrosis (CF). However, the effect of inflammatory products on the repair capacity of respiratory epithelia is unclear. Our objective was to study the regulation of repair mechanisms by tumor necrosis factor-α (TNF-α), a major component of inflammation in CF, in a model of mechanical wounding, in two bronchial cell lines, non-CF NuLi and CF CuFi. We observed that TNF-α enhanced the NuLi and CuFi repair rates. Chronic exposure (24-48 h) to TNF-α augmented this stimulation as well as the migration rate during repair. The cellular mechanisms involved in this stimulation were then evaluated. First, we discerned that TNF-α induced metalloproteinase-9 release, epidermal growth factor (EGF) shedding, and subsequent EGF receptor transactivation. Second, TNF-α-induced stimulation of the NuLi and CuFi wound-closure rates was prevented by GM6001 (metalloproteinase inhibitor), EGF antibody (to titrate secreted EGF), and EGF receptor tyrosine kinase inhibitors. Furthermore, we recently reported a relationship between the EGF response and K(+) channel function, both controlling bronchial repair. We now show that TNF-α enhances KvLQT1 and K(ATP) currents, while their inhibition abolishes TNF-α-induced repair stimulation. These results indicate that the effect of TNF-α is mediated, at least in part, through EGF receptor transactivation and K(+) channel stimulation. In contrast, cell proliferation during repair was slowed by TNF-α, suggesting that TNF-α could exert contrasting actions on repair mechanisms of CF airway epithelia. Finally, the stimulatory effect of TNF-α on airway wound repair was confirmed on primary airway epithelial cells, from non-CF and CF patients.

Lipoxin A4-mediated KATP potassium channel activation results in cystic fibrosis airway epithelial repair

“…Exaggerated inflammation is a common factor that contributes to matrix destruction, cellular senescence, and nonhealing in a variety of disease processes, including defective airway epithelial repair in CF (16,27,(43)(44)(45). Epithelial repair involves cell spreading, migration, and proliferation to recover the denuded area created through injury (42, 51, 52), followed by differentiation of the epithelium (11).…”

“…Among the more than 30 different K ϩ channels detected in the respiratory epithelium, few have been described to be involved in cell migration, proliferation, and wound repair (27,44,45). The voltage-gated KCNQ1 potassium channel, the inwardly rectifying KCNJ8 potassium channel (K6.1, K ATP subunit), which is responsible for a major part of basolateral K ϩ permeability, has been reported as essential in respiratory epithelial repair processes (44,45).…”

“…Repeated insults to the airway epithelium result in damage and remodeling of the airway, resulting in a decline in lung function (33,34). Epithelial repair is triggered to restore the epithelial airway architecture; however, recent research suggests that this process is impaired in CF epithelial cells (16,27,44,45).…”

Deleterious impact ofPseudomonas aeruginosaon cystic fibrosis transmembrane conductance regulator function and rescue in airway epithelial cells

“…For CFTR [28] and epidermal growth factor receptor (EGFR) [30] detection, the upper section of the membrane was incubated with the polyclonal anti-CFTR 596 antibody (CFFT) or anti-EGFR antibody (anti-erbB1; Cell Signaling Technology, Danvers, MA, USA); whereas the bottom section was incubated with purified mouse anti-β-actin monoclonal antibody (Cedarlane Laboratory, Burlington, ON, Canada) to ensure equivalent loading. The expression of CFTR was reported as percentage relative to cells with LB, after normalisation to β-actin signal.…”

“…Short-circuit currents (Isc) [30][31][32] were measured through CFBE and primary airway cells [28] that had been cultured on coated permeant filters until they reached an air-liquid interface and formed a polarised epithelium with high resistance [33,34]. Measurements were performed (see supplementary material for details) on intact monolayers or through apical membranes after permeabilisation of the basolateral side with 7.5 µM amphotericin B (Sigma-Aldrich), in the presence of a symmetrical physiological solution or a chloride (Cl − ) gradient, as indicated in figure legends.…”