Figure 3.

Association between MMP-9/TIMP-1 ratio and the development of airflow limitation.

Notes: Spirometry and bronchoscopy were performed during the recruitment, and spirometry was repeated 5 years later. AMs from 21 smokers, including 13 AHR − S and 8 AHR + S, were incubated for 24 h. The level of MMP-9 and TIMP-1 in the culture supernatants was determined by enzyme-linked immunosorbent assays. The MMP-9/TIMP-1 ratio was less related to the reduction in FEV₁/FVC (A) but was positively associated with the annualized reduction in FEV₁%pred (B), FVC%pred (C), and MMEF%pred (D). AHR − S, smokers without AHR; AHR + S, smokers with AHR.

Abbreviations: AHR, airway hyperresponsiveness; AMs, alveolar macrophages; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; MMEF, maximal mid-expiratory flow; MMP-9, matrix metalloproteinase-9; %pred, percentage of the predicted value; TIMP-1, tissue inhibitor of metalloproteinase-1.