Evidence for regulation of endothelial plasminogen-activating system by polymorphonuclear leukocyte elastase

Incubation of unstimulated polymorphonuclear leukocytes with cultured bovine pulmonary artery endothelial cells increased the activity of endothelial plasminogen activator. On the other hand, polymorphonuclear leukocytes stimulated by serum-opsonized zymosan decreased the plasminogen activator activity. A specific elastase inhibitor increased the enhancing effect of the unstimulated polymorphonuclear leukocytes and reversed the suppressing effect of the stimulated polymorphonuclear leukocytes. Catalytically active elastase suppressed the plasminogen activator activity and increased the activity of plasminogen activator inhibitor. In contrast, inactivated elastase enhanced the activity of plasminogen activator. Both, active and inactive forms of elastase bound to the endothelial cells. These findings suggest that elastase modulates the endothelial plasminogen-activating system, apparently by binding to the endothelial cells.