Enhanced Exhalation of Matrix Metalloproteinase-9 and Tissue Inhibitor of Metalloproteinase-1 in Patients with COPD Exacerbation: A Prospective Study

Abstract

Background: Matrix metalloproteinase-9 (MMP-9) and its inhibitor tissue inhibitor of metalloproteinase-1 (TIMP-1) are involved in the pathogenesis of airway inflammation in patients with chronic obstructive pulmonary disease (COPD). However, no study so far has addressed their value as noninvasive biomarkers of airways inflammation. Objective: To evaluate MMP-9 and TIMP-1 concentrations in the exhaled breath condensate (EBC) of patients with stable COPD and also during the exacerbation episode. Methods: EBC and serum samples were collected in 17 stable-phase COPD patients who were current smokers as well as during their first exacerbation episode, and in 22 asymptomatic smokers. EBC and serum levels of MMP-9 and TIMP-1 were measured with ELISA kit. Results: Mean EBC MMP-9 and TIMP-1 levels were higher in patients with stable COPD than in asymptomatic smokers. Exacerbation of COPD increased 2-fold the exhalation of MMP-9 (18.5 ± 10.1 ng/ml vs. 8.9 ± 6.2 ng/ml, p = 0.01) and TIMP-1 (to 41.1 ± 20.4 ng/ml vs. 16.4 ± 6.8 ng/ml, p < 0.001). Both, MMP-9 and TIMP-1 in EBC correlated negatively with FEV₁ (% predicted) at baseline (r = –0.78, p < 0.001 and r = –0.73, p < 0.001) and during the exacerbation episode (r = –0.57, p = 0.02 and r = –0.65, p = 0.005). Similar negative correlations were noted with FVC (% predicted), except for MMP-9 in EBC at exacerbation. Exhaled MMP-9 and TIMP-1 did not correlate with serum concentrations in COPD patients, either at baseline or during exacerbation. Conclusion: Exhaled MMP-9 and TIMP-1 increased during COPD exacerbation and was negatively correlated with spirometric variables, which suggests the usefulness of their measurement in EBC for the monitoring of airways inflammation. However, to better assess their diagnostic or prognostic value larger studies are necessary.