Effect of neutrophil elastase and its inhibitor EPI-hNE4 on transepithelial sodium transport across normal and cystic fibrosis human nasal epithelial cells

Abstract

BackgroundHyperactivity of the epithelial sodium (Na+) channel (ENaC) and increased Na+ absorption by airway epithelial cells leading to airway surface liquid dehydration and impaired mucociliary clearance are thought to play an important role in the pathogenesis of cystic fibrosis (CF) pulmonary disease. In airway epithelial cells, ENaC is constitutively activated by endogenous trypsin-like serine proteases such as Channel-Activating Proteases (CAPs). It was recently reported that ENaC activity could also be stimulated by apical treatment with human neutrophil elastase (hNE) in a human airway epithelial cell line, suggesting that hNE inhibition could represent a novel therapeutic approach for CF lung disease. However, whether hNE can also activate Na+ reabsorption in primary human nasal epithelial cells (HNEC) from control or CF patients is currently unknown.MethodsWe evaluated by short-circuit current (Isc) measurements the effects of hNE and EPI-hNE4, a specific hNE inhibitor, on ENaC activity in primary cultures of HNEC obtained from control (9) and CF (4) patients.ResultsNeither hNE nor EPI-hNE4 treatments did modify Isc in control and CF HNEC. Incubation with aprotinin, a Kunitz-type serine protease inhibitor that blocks the activity of endogenous CAPs, decreased Isc by 27.6% and 54% in control and CF HNEC, respectively. In control and CF HNEC pretreated with aprotinin, hNE did significantly stimulate Isc, an effect which was blocked by EPI-hNE4.ConclusionsThese results indicate that hNE does activate ENaC and transepithelial Na+ transport in both normal and CF HNEC, on condition that the activity of endogenous CAPs is first inhibited. The potent inhibitory effect of EPI-hNE4 on hNE-mediated ENaC activation observed in our experiments highlights that the use of EPI-hNE4 could be of interest to reduce ENaC hyperactivity in CF airways.

The Role of Neutrophil Elastase Inhibitors in Lung Diseases

“…has also been tested, but little information is available. 55,56 Human Studies With NE Inhibitors AZD9668, a reversible and selective inhibitor of human NE, was tested in a randomized, double-blind, placebocontrolled, parallel-group, phase IIa study in CF. 57 Patients were assigned treatment with oral AZD9668 or placebo (28 days).…”

Mechanism of Action of Novel Lung Edema Therapeutic AP301 by Activation of the Epithelial Sodium Channel

“…Experiments were performed with human nasal epithelial cells (RPMI-2650) cells, which express ENaC (Prulière-Escabasse et al, 2010). A lysine residue in the g subunit of ENaC (gK181) has been identified for the activation of near-silent channels in the plasma membrane by extracellular trypsin, chymotrypsin, or human neutrophil elastase (hNE) (Diakov et al, 2008).…”

“…Our experiments indicate that the amiloride-sensitive Na 1 current-enhancing effect of AP301 requires ENaC that has been proteolytically cleaved and released from Na 1 -dependent self-inhibition. The majority of channels in the RPMI-2650 cell membrane are closed or in a quiescent, nonconducting state (Prulière-Escabasse et al, 2010). Nonconducting or quiescent ENaC may be poorly accessible to AP301.…”

2-O, 3-O-Desulfated Heparin Inhibits Neutrophil Elastase–Induced HMGB-1 Secretion and Airway Inflammation

“…Recent studies suggest that NE also disables CF transmembrane conductance regulator (CFTR) function in vitro and in vivo, exacerbating this functional defect in CF lung disease (4). Furthermore, the epithelial Na( 1 ) channel that mediates regulated Na( 1 ) reabsorption by epithelial cells in the lungs can be activated by NE (5)(6)(7)(8). Increased levels of NE at airway surfaces are a predictor of early bronchiectasis and CF lung disease progression (9,10).…”