A 96-kDa gelatinase induced by TNF-alpha contributes to increased microvascular endothelial permeability

Tumor necrosis factor-alpha (TNF-alpha) may increase vascular endothelial permeability through alteration of the extracellular matrix (ECM). Incubation of bovine pulmonary microvascular endothelial (BPMVE) cells grown to confluence on microporous filters with 10(4) U/ml TNF-alpha for 24 h increased monolayer permeability to 125I-labeled albumin two- to threefold. TNF-alpha treatment also induced expression of a 96-kDa gelatinolytic metalloproteinase that was present in the medium and bound to the ECM. The induced 96-kDa metalloproteinase was purified from conditioned medium and found to cleave fibronectin, laminin, types IV and V collagens, and gelatins from types I and III collagens, suggesting identity as a type IV collagenase-gelatinase. Incubation of BPMVE cells with the 96-kDa gelatinase increased monolayer permeability, an effect prevented by inclusion of either tissue inhibitor of metalloproteinase (TIMP) or 1,10-phenanthroline. When BPMVE cells were incubated with the 96-kDa gelatinase or 10(4) U/ml TNF-alpha and then stripped from the filters, the remaining ECM displayed increased permeability to 125I-albumin compared with matrix from untreated BPMVE. The ECM extracts from both TNF-alpha- and enzyme-treated cells were found to contain less fibronectin, whereas their total protein contents were similar to those of untreated controls. These results suggest that the 96-kDa metalloproteinase induced by TNF-alpha contributes to increased vascular endothelial permeability through the degradation of specific extracellular matrix components.