HUMAN NEUTROPHIL ELASTASE INCREASES PERMEABILITY OF CULTURED PULMONARY ENDOTHELIAL-CELL MONOLAYERS

Polymorphonuclear leukocytes (PMN) contribute to increased pulmonary v ascular permeability in inflammatory lung injury, but the mechanism of their action is complex. In the present study we examined possible ef fects of PMN-derived proteases on the permeability of pulmonary endoth elial cell monolayers,grown on polycarbonate filter membranes and expo sed continuously to a hydrostatic pressure of 10cm H2O. Cell- and seru m free PMN-supernatants (human PMN, stimulated with 30ng/ml phorbol-my ristate acetate for 30min, presence of catalase, were centrifuged, the supernatants were passed through a 0.45 mu m filter) dose-dependently (calculated PMN: endothelial cell ratio of 2:1 and more) increased hy draulic conductivity of endothelial cell monolayers ten- to twentyfold within 20-70min. At the same time the dextran reflection coefficient decreased from 0.8 to 0.1. Phase contrast and scanning electronmicrosc opy showed a widening of intercellular gaps. The effects of the postse cretory PMN-supernatant were blocked dose-dependently by inhibitors of human neutrophil elastase (HNE) but not of cathepsin G. On quantitati ve grounds highly purified HNE was similarly active as postsecretory P MN supernatant. The effects of HNE were inhibited by pretreatment with eglin-c or heat, but not with heparin. The data suggest that HNE is a n effective and sufficient neutrophil-derived mediator to increase end othelial permeability. HNE appears to act primarily enzymatically and not as a cationic protein.