INTRODUCTION In inflammatory 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 proinflammatory cytokine release). Elastase is considered a target in the search for therapeutic treatments for inflammatory respiratory diseases. Pulmonary surfactant is a promising product for this purpose, because in addition to its biophysical function, it has anti-inflammatory properties.

OBJECTIVES Evaluate effect 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.

METHODS The anti-elastase effect of Surfacen, rCmPI-II and the Surfacen/rCmPI-II combination was evaluated in an in vitro model of activated neutrophils, previously purified from the blood of healthy subjects. The cells were stimulated with LPS/fMLP and were incubated with different 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.

The new index, called the abdominal adipose deposit index, was obtained by multiplying the subcutaneous fat thickness by visceral fat thickness, both measured by ultrasound. A cutoff point was established that facilitated discernment of an unhealthy phenotype: normal weight but metabolically obese, a cardiometabolic risk factor.

RESULTS Surfacen 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 dose-dependent effect. The Surfacen/inhibitor combination (0.5 mg/mL/80 µM) did not affect 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 effect on an activated neutrophil model. rCmPI-II does not affect Surfacen’s interface property and, therefore, both can be evaluated for combined use in treating inflammatory lung diseases.

KEYWORDS Pulmonary surfactants, elastase inhibitor, drug carriers, neutrophils, Cuba