Bradykinin and α-Thrombin Increase Human Umbilical Vein Endothelial Macromolecular Permeability by Different Mechanisms

Bradykinin and α-thrombin both increase endothelial macromolecular permeability, however the mechanism for this effect is unclear. Human umbilical vein endothelial cell (HUVEC) permeability to human serum albumin was increased by 1 μM α-thrombin (AT) or bradykinin (BK), but the kinetics of the permeability response were different. Intracellular calcium mobilization of HUVEC by AT was increased, yet BK had no effect on intracellular calcium. Distribution of F-actin and content was increased by AT as early as 10 minutes after administration, yet BK had no affect on F-actin when compared to control. We hypothesized that BK may increase HUVEC permeability by producing matrix metalloproteinase-2 (MMP-2). The AT-treated HUVEC produced an intermediate 64 kDa MMP-2, whereas BK-treated HUVEC increased the intermediate 64 kDa MMP-2 and also an active 62 kDa MMP-2. Pre-treatment of the HUVEC with tissue inhibitor of matrix metalloproteinase-2 slightly decreased the AT-induced increase in macromolecular permeability and completely inhibited the BK-induced increase in macromolecular permeability.