Human Endothelial Cell Damage by Neutrophil-Derived Cathepsin G: Role of Cytoskeleton Rearrangement and Matrix-Bound Plasminogen Activator Inhibitor-1

Abstract Cathepsin G, a major protease released by activated neutrophils, induces functional and morphological damage to human endothelial cells. We studied the mechanisms involved and ways to reverse this damage. Cathepsin G induced a concentration- and time-dependent injury to human umbilical vein endothelial cell (HUVEC) morphology simultaneous with cytoskeleton rearrangement. Preincubation of the endothelial monolayer with phallacidin completely prevented damage to cell morphology by cathepsin G, whereas preincubation with cytochalasin B potentiated its activity. Damage to cell shape and F-actin cytoskeleton were prevented by eglin C, an inhibitor of the active site of cathepsin G. Furthermore, cathepsin G increased transcellular permeability to albumin and induced a time-dependent detachment of PAI-1 from the extracellular matrix of a cell-free system. The inhibition of matrix-bound PAI-1 activity by specific antibodies induced changes in HUVEC monolayers similar to those observed after cathepsin G. However, although stabilization of F-actin microfilaments by phallacidin prevented changes in cell shape, it did not prevent the ability of cathepsin G to increase cell permeability and release matrix PAI-1. The damage of cathepsin G to cell morphology and cytoskeleton arrangement was reversed within 12 hours if the deendothelialization area was