INTRODUCTIONIn infl ammatory respiratory diseases, the imbalance between proteases and endogenous protease inhibitors leads to an exacerbated activity of human neutrophil elastase (a protease that destroys the extracellular matrix and stimulates proinfl ammatory cytokine release). Elastase is considered a target in the search for therapeutic treatments for infl ammatory respiratory diseases. Pulmonary surfactant is a promising product for this purpose, because in addition to its biophysical function, it has anti-infl ammatory properties.OBJECTIVE Evaluate eff ect of the Cuban porcine pulmonary surfactant (Surfacen), the rCmPI-II elastase inhibitor, and the Surfacen/rCmPI-II combination on activated neutrophil elastase activity in vitro, and determine if Surfacen's interface property changes in the presence of the inhibitor. METHODSThe anti-elastase eff ect of Surfacen, rCmPI-II and the Surfacen/rCmPI-II combination was evaluated in an in vitro model of activated neutrophils, previously purifi ed from the blood of healthy subjects. The cells were stimulated with LPS/fMLP and were incubated with diff erent concentrations of Surfacen, rCmPI-II and the Surfacen/rCmPI-II combination. Elastase activity was measured. The interface property was determined on a Langmuir surface balance. RESULTSSurfacen at 10 mg/mL inhibited 71% of stimulated neutrophil elastase activity. rCmPI-II at 0.1 μM reduced 20% of elastase activity; at 200 μM-the maximum concentration evaluated-inhibition was 68%. Both products had a dosedependent eff ect. The Surfacen/inhibitor combination (0.5 mg/ mL/80 μM) did not aff ect the surfactant interface property or the inhibitory activity of rCmPI-II against human neutrophil elastase.CONCLUSIONS Surfacen and the rCmPI-II inhibitor have an anti-elastase eff ect on an activated neutrophil model. rCmPI-II does not aff ect Surfacen's interface property and, therefore, both can be evaluated for combined use in treating infl ammatory lung diseases.