The Role of Matrix Metalloproteinases in Chronic Pulmonary Diseases: Relevance of the Airway Epithelium

Pulmonary structural changes that lead to decreased airway function are the cardinal features of chronic diseases such as asthma and chronic obstructive pulmonary disease (COPD). Matrix metalloproteinases (MMPs) are a family of zinc-dependent enzymes that can alter lung architecture by inducing tissue damage and modifying repair mechanisms. The activity of these enzymes is regulated by a group of proteins called tissue inhibitors of matrix metalloproteinases (TIMPs, classes 1-4). Because MMP activities are induced following exposure to allergens and environmental toxins, it is crucial to evaluate potential cellular sources for these proteins. This review specifically focuses on the relevance of the pulmonary epithelium to produce this family of proteins and propagate pulmonary inflammation, destroy parenchymal tissue, and affect repair mechanisms. Data from human and animal studies are reviewed, and the relevance of MMPs and TIMPs in chronic respiratory diseases is discussed.