Promotion of transendothelial neutrophil passage by human thrombin

Abstract

Thrombin has been reported to elicit two temporally different effects on neutrophil-endothelial interaction, categorically described as ‘neutrophil adhesion’: one expressed within a few minutes, the other after several hours of endothelial preincubation. Prolonged activation resulted in often elongated, tightly interacting neutrophils in contact with human umbilical vein endothelial cells (HUVE) mainly at the intercellular region. In contrast, the neutrophil-endothelial interaction due to short-time priming with thrombin was dominated by round, randomly distributed neutrophils, loosely adhering on the endothelial surface. Sheer stress, introduced to characterize these morphological entities in a quantitative manner, clearly defined the neutrophil response due to short time priming as sheer stresslabile compared to the sheer stress-resistant interaction expressed after prolonged preincubation of HUVE with thrombin. Quantitative determination of neutrophil transendothelial migration served to demonstrate the relevance of such differences in neutrophil binding with respect to subsequent layer penetration. Dependent upon endothelial protein synthesis and inhibited by antithrombin-III-heparin and hirudin, neutrophil layer penetration only occurred after prolonged activation of HUVE whereas the neutrophil-endothelial interaction due to short time priming with thrombin was limited to superficial neutrophil adhesion. We conclude that thrombin can be added to the list of activators capable of inducing the neutrophil passage-guiding principle, an effect that has recently been detected as closely related to neutrophil adhesion to endothelial ligands expressed upon activation with interleukin-1 and tumor necrosis factor. This biological activity, which can be separated from superficial attachment of polymorphonuclear leukocytes (PMN) to endothelial cells, is a catalytic site-dependent and late phase-specific effect of thrombin on HUVE.