A Novel Neutrophil Elastase Inhibitor Prevents Elastase Activation and Surface Cleavage of the Epithelial Sodium Channel Expressed in Xenopus laevis Oocytes

摘要: The amiloride-sensitive epithelial sodium channel (ENaC) constitutes a limiting step in reabsorption across distal airway epithelium and controlling mucociliary clearance. ENaC is activated by serine proteases secreted the extracellular milieu. In cystic fibrosis lungs, high concentrations of neutrophil elastase (NE) are observed. hNE could activate contribute to further decreased aims this study were (i) test ability an engineered human inhibitor (EPI-hNE4) specifically inhibit activation ENaC-mediated currents (I(Na)) (ii) examine effect on cell surface expression its cleavage pattern (exogenous proteolysis). Oocytes exposed (10-100 microg/ml) and/or trypsin (10 for 2-5 min presence or absence EPI-hNE4 (0.7 microm). I(Na) 3.6-fold (p < 0.001) relative non-treated hENaC-injected oocytes. fully inhibited hNE-activated but had no trypsin- prostasin-activated I(Na). co-activation was not additive. Biotinylation experiments revealed that gamma (but alpha beta ENaC) 2 cleaved (as 67-kDa fragment) correlated with increased elastase-induced exogenous proteolysis distinct from endogenous induced upon preferential assembly, suggesting causal relationship between activation, taking place at plasma membrane.