Excessive accumulation of active neutrophil elastase (NE) in pulmonary fluids and tissues of patients with cystic fibrosis (CF) is thought to act on the lungs, compromising their structure and function. The aim of this study was to investigate the in vitro and in vivo protective effect of a new, rapidly acting, potent (Ki = 5.45 x 10(-12) M and Kon = 8 x 10(6) M(-1) s(-1)) and specific human NE inhibitor, EPI-HNE-4, engineered from the Kunitz domain. The results demonstrated that this inhibitor was able to (i) effectively inhibit in vitro the high levels of active NE present in a medium as complex as sputum from children with CF, with a measured IC(50) equal or close to the calculated IC(50) in 60% of cases, and (ii) almost completely block (91%) the N-formyl-methionine-leucine-phenylalanine-induced migration of purified human neutrophils across a Matrigel basement membrane. Intratracheal administration (250, 175, or 100 microg per rat) of the inhibitor 5 min before instillation of pure human NE (HNE) (150 microg per rat) to rats induced effective, dose-dependent protection of the lungs, 4 h later, from hemorrhage, serum albumin leakage, residual active NE, and discrete neutrophil influx in air spaces induced by instillation of pure HNE. Intravenous administration (3 mg per rat) of EPI-HNE-4, 15 min before instillation of the soluble fraction of pooled sputum (delivering 120 microg of active NE per rat) from children with CF, effectively reduced (64%), 4 h later, the massive neutrophil influx induced by sputum instillation. Overall, these data strongly suggest that associated aerosol and systemic administration of EPI-HNE-4 would be beneficial in the treatment of CF.

Retinoic acid (RA) has been shown to induce human neuroblastoma SKNBE cell differentiation into a neuronal phenotype. Whether this neuronal differentiation is associated with modulation of matrix gelatinase [matrix metalloproteinase (MMP)-2 and MMP-9] expression was investigated in SKNBE cell cultures exposed to RA for 14 days.

Neutropenia recovery can worsen acute lung injury, and this effect is exacerbated by granulocyte colony-stimulating factor.