Tumor Necrosis Factor Regulation of Endothelial Cell Extracellular Proteolysis: The Role of Urokinase Plasminogen Activator

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Abstract
Morphological and functional changes in the endothelial cell phenotype which may be central to proinflammatory processes can be elicited by tumor necrosis factor alpha (TNF). Recent observations have indicated that TNF can promote the expression, synthesis and secretion of urokinase plasminogen activator (uPA) in low passage human umbilical vein endothelial cells which normally synthesize little uPA. To further address this issue, we evaluated the ability of TNF to regulate: 1) PA and plasminogen activator inhibitor (PAI-1) mRNA expression and 2) endothelial cell surface associated PA and PAI-1. TNF (100 U/ml) treatment of endothelial cultures induced steady state levels of uPA and PAI-1 mRNA following a 18 hr treatment both 6-fold and 2-fold, respectively utilizing northern analysis. In accord with Northern analyses, TNF stimulated a time and dose dependent increase in cell surface associated uPA antigen as determined by a cell based ELISA assay and immunofluorescence in conjunction with flow cytometry. Treatment of endothelial cell cultures with 100 U/ml of TNF resulted in a 3-fold increase in cell surface uPA antigen levels which peaked at 8 hr. In contrast, no changes in tissue-PA (tPA) and PAI-1 cell surface antigen expression were evident under analogous conditions over a 24 hr period. The TNF mediated increase in both uPA mRNA and cell surface uPA expression correlated with the increased ability of endothelial cells to invade matrix and organize into tube-like structures when cultured on Matrigel.(ABSTRACT TRUNCATED AT 250 WORDS)