The role of MMPs in the inflammatory process of acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) manifests as non-cardiogenic pulmonary oedema, respiratory distress, hypoxemia and results from various processes that directly or indirectly injure the lung (e.g., during sepsis). The innate inflammatory response of the lung to infection, which triggers a cascade of events, including release of proinflammatory cytokines, influx of polymorphonuclear neutrophils in the lung tissue, and production of proteinases, such as matrix metalloproteinases, is central to host defence processes. However, in disease conditions, this chronic inflammatory response can become detrimental to the airways, causing degradation of the extracellular matrix in the lung. Matrix metalloproteinases are thought to play a critical role in this degradation, and has been the subject of intense research. In an attempt to prevent or control disease progression there has been great interest in the development of MMP inhibitors. However, to date, there are no effective therapeutic agents; hence, researchers continue to further elucidate the complex role of these proteinases.