Inhibition of the protease activity in tracheobronchial aspirates of horses with chronic obstructive pulmonary disease

Objectives--To clarify the role of proteolytic enzymes in the pathogenesis of chronic obstructive pulmonary disease (COPD) in horses, and to investigate new possibilities for treatment of this disease by interfering in the proteolytic process. Design--Effect of antiproteolytic activity of selected protease inhibitors on tracheal aspirates was studied in vitro, and the inhibition profiles were compared with those of purified proteases. Sample Population-Respiratory tract secretions with antiproteolytic activity from 9 horses with COPD. Procedure-Caseinolytic agar-diffusion assay. Results-The protease-inhibition profile of tracheal aspirates differed from horse to horse. The profiles did not resemble that of any of the pure proteases. Acetylcysteine, pentamidine, and diminazene were most effective in inhibiting proteolytic activity in tracheal aspirates in vitro. Conclusions-A mixed type of proteolytic activity is present in the respiratory tract secretions of horses with COPD. Clinical Relevance-Acetylcysteine, pentamidine, and diminazene seem to have potential to be used in vivo to protect the lungs of horses with COPD from proteolytic damage.