Tissue Inhibitor of Metalloproteinase-1 Levels in Bronchoalveolar Lavage Fluid from Asthmatic Subjects

Airway remodeling is a well-recognized feature in patients with chronic asthma. The accumulation in the submucosa of fibrous proteins that are substrates of matrix metalloproteinases (MMP), and the demonstration of increased levels of MMP-9 in bronchoalveolar lavage fluid, prompted us to determine whether there was an imbalance between MMPs and tissue inhibitors of metalloproteinase (TIMP) in such patients. We investigated the presence of TIMPs and other MMPs. TIMP levels were compared with those of all MMPs and inflammatory cytokines. Adults with stable asthma, either untreated or treated with glucocorticoids (GCs), were enrolled. Healthy nonsmokers served as a control population. MMPs and TIMPs were identified through zymography or immunoblotting. TIMPs, MMPs, and cytokines were measured with enzyme immunoassays. TIMP-1 levels were significantly higher in untreated asthmatic subjects than in GC-treated subjects or controls (p < 0.0001), and were far greater than those of MMP-1, MMP-2, MMP-3, and MMP-9 combined. TIMP-2 was undetectable. TIMP-1 levels were correlated with levels of interleukin-6 (p < 0.012) and the number of alveolar macrophages recovered (p < 0.005). This observation has important implications, since an excess of TIMP-1 could lead to airway fibrosis, a hallmark of airway remodelling in patients with chronic asthma.