Depelestat

Hyperactivity 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.

We 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.

Neither 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.

These 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 engineered protein inhibitor of human neutrophil elastase, Epi-hNE4, is being developed for the treatment of cystic fibrosis. Like many recombinant proteins, Epi-hNE4 may induce antibodies in pre-clinical species and in humans. The aim of this report was to validate an ELISA to assess its immunogenicity in monkeys. We have designed and optimized a classical ELISA in which Epi-hNE4 was coated directly on microtitre plates and the antibodies were detected using a secondary antibody labelled with peroxidase. We report implementation of the recent recommendations proposed for the validation of immunogenicity assessment. The cut-off point was determined by means of statistical analysis of negative samples. Linearity, reproducibility, stability and specificity were estimated using quality control samples obtained from a pool of positive samples. The method was applied to monkeys given Epi-hNE4 by inhalation. A confirmation test and a neutralization assay were developed in order to further assess positive samples. In conclusion, we present here one of the first examples of validation in application of recent recommendations [A.R. Mire-Sluis, Y.C. Barrett, V. Devanarayan, E. Koren, H. Liu, M. Maia, T. Parish, G. Scott, G. Shankar, E. Shores, S.J. Swanson, G. Taniguchi, D. Wierda, L.A. Zuckerman, J. Immunol. Methods 289 (2004) 1-16].