In vitro reoxygenation following hypoxia increases MMP-2 and TIMP-2 secretion by human umbilical vein endothelial cells

Endothelial cells lining the inner blood vessel walls play a key role in the response to hypoxia, which is frequently encountered in clinical conditions such as myocardial infarction, renal ischemia and cerebral ischemia. In the present study we investigated the effects of hypoxia and hypoxia/reoxygenation on gelatinases (matrix metalloproteinase-2 and -9), their inhibitor (TIMP-2) and activator (MT1-MMP), in human umbilical vein endothelial (HUVE) cells. HUVE cells were subjected to 4 h of hypoxia or hypoxia followed by 4 and 24 h of reoxygenation. The pro- and active forms of MMP-2 and MMP-9 were analyzed by gelatin zymography; TIMP-2 protein level was assayed using ELISA, while MT1-MMP activity was measured using an activity assay. The secretion of MMP-2 proform increased significantly in cells subjected to 4 h of hypoxia followed by 4 or 24 h of reoxygenation, compared with the normoxic group. TIMP-2 protein level also increased significantly in the hypoxia/reoxygenation groups, compared with the normoxic group. There were no statistically significant differences in the levels of active MT1-MMP in all groups. This study indicates that MMP-2 and TIMP-2 could be regarded as important components of a mechanism in the pathophysiology of ischemic injury following reperfusion