The Role of Matrix Metalloproteinase Inhibitors in Ischemia-Reperfusion Injury in the Liver

Liver ischemia-reperfusion injury is characterized by cell necrosis and apoptosis and by profound modifications in the extracellular matrix (ECM). During the complex series of events that take place both during ischemia and when normal blood flow is restored (reperfusion), a concerted regulation of release and activation of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) mainly by stellate cells, Kupffer cells and inflammatory cells leads first to endothelial cell injury and subsequent infiltration of neutrophils into the wounded area. Later, MMP activation causes degradation of extracellular matrix components of the liver, mainly collagen and fibronectin, altering tissue architecture. The fibrosis that can result after liver injury is also dependent on the imbalance between MMPs and TIMPs and to new collagen deposition. Several experimental models of liver ischemia-reperfusion injury have demonstrated protective effects of MMP inhibitors in terms of cell necrosis, apoptosis and rearrangement of the extracellular matrix. This review summarizes current knowledge of MMP biology, with particular attention to the most recent evidence of novel, non-extracellular matrix MMP substrates involved in inflammation and cell cycle regulation. An overview of MMP and TIMP expression and activation in hepatic ischemia- reperfusion injury is provided. The analysis of such provides a rational basis for MMP inhibition as a viable strategy to prevent liver injury.