Lipopolysaccharide-induced modulation of human monocyte urokinase production and activity.
Cells of the monocyte/macrophage lineage are known to produce urokinase type plasminogen activator (u-PA) and are active participants in the inflammatory response. Modulation of cellular u-PA production, for instance in response to LPS, may have an important impact on the evolution of inflammatory lesions. A definitive picture of how monocyte u-PA production and activity are regulated by LPS is lacking. We addressed this issue directly by measuring u-PA Ag and activity in mononuclear cell cultures. By using a competition ELISA to quantitate u-PA Ag, we found that LPS-stimulated mononuclear cells in culture increased u-PA production in a dose-dependent manner and that all the u-PA detected was attributable to the monocytes therein. Increasing amounts of u-PA were secreted into the medium, bound to the cell surface, and found intracellularly. Although the absolute amounts of u-PA varied from donor to donor, the increases seen with LPS stimulation were a consistent and statistically significant finding. Only the cell-surface-bound u-PA was fibrinolytically active, however, with this activity increasing upon LPS stimulation. All monocyte cell-surface-associated fibrinolytic activity was attributed to u-PA, as shown by plasminogen dependence, neutralization by antibodies to u-PA, and identification of fibrinolytically active molecules eluted from the cell surface. The surface bound u-PA was not inhibited by its physiologic inhibitors, PAI-1 or PAI-2, whereas free u-PA was. Hence LPS stimulation results in monocytes exhibiting increased cell-surface-associated u-PA Ag and fibrinolytic activity, in spite of concomitant high levels of plasminogen activator inhibitor type 2 production. This surface-bound enzymatic activity may influence the ability of monocytes to migrate in and interact with an inflammatory microenvironment.
Manchanda
N
N
Department of Medicine, University of Wisconsin, Madison 53706.
Schwartz
B S
BS
D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008262:Macrophage Activation; D009000:Monocytes / Q000201:enzymology*; D015849:Plasminogen Inactivators / Q000494:pharmacology; D013499:Surface Properties; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors / Q000378:metabolism*
D008070:Lipopolysaccharides; D015849:Plasminogen Inactivators; D014568:Urokinase-Type Plasminogen Activator