A 96-KDA GELATINASE INDUCED BY TNF-ALPHA CONTRIBUTES TO INCREASED MICROVASCULAR ENDOTHELIAL PERMEABILITY

Tumor necrosis factor-alpha (TNF-alpha) may increase vascular endothel ial permeability through alteration of the extracellular matrix (ECM). Incubation of bovine pulmonary microvascular endothelial (BPMVE) cell s grown to confluence on microporous filters with 10(4) U/ml TNF-alpha for 24 h increased monolayer permeability to I-125-labeled albumin tw o- to threefold. TNF-alpha treatment also induced expression of a 96-k Da gelatinolytic metalloproteinase that was present in the medium and bound to the ECM. The induced 96-kDa metalloproteinase was purified fr om conditioned medium and found to cleave fibronectin, laminin, types IV and V collagens, and gelatins from types I and III collagens, sugge sting identity as a type IV collagenase-gelatinase. Incubation of BPMV E cells with the 96-kDa gelatinase increased monolayer permeability, a n effect prevented by inclusion of either tissue inhibitor of metallop roteinase (TIMP) or 1,10-phenanthroline. When BPMVE cells were incubat ed with the 96-kDa gelatinase or 10(4) U/ml TNF-alpha and then strippe d from the filters, the remaining ECM displayed increased permeability to I-125-albumin compared with matrix from untreated BPMVE. The ECM e xtracts from both TNF-alpha- and enzyme-treated cells were found to co ntain less fibronectin, whereas their total protein contents were simi lar to those of untreated controls. These results suggest that the 96- kDa metalloproteinase induced by TNF-alpha contributes to increased va scular endothelial permeability through the degradation of specific ex tracellular matrix components.