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Plasminogen activator activity of cultured murine macrophages and effects of isopropylmethylphosphonofluoridate
P Dubois1, D Lison, R Lauwerys
1Unité de Toxicologie Industrielle et Médecine du Travail, Université Catholique de Louvain, Bruxelles, Belgium.
Abstract:
Casein-elicited mouse peritoneal macrophages cultured in the presence of phorbol 12-myristate 13-acetate (PMA) express u-PA. Induction is maximal after 4 hr of stimulation and u-PA activity is mainly recovered with the membrane fraction of the cellular lysate. This enzymatic activity is inhibited by isopropylmethylphosphonofluoridate after stimulation by PMA. The presence of the organophosphorus compound before stimulation does not affect the activity. The results of the present study on the kinetics of u-PA activity in cultured macrophages, its subcellular localization and the effect of an organophosphorus ester are consistent with the concept that the development of pericellular proteolysis proceeds through a series of stages, namely, (a) synthesis of pro-u-PA, (b) binding to membrane receptors, (c) activation to a double-chain u-PA, and (d) conversion of plasminogen into plasmin. The assay procedure developed here provides a sensitive tool to investigate the mechanism of interference of chemicals with several steps of induction of this enzymatic activity in macrophages.
Insights
Mouse macrophages stimulated with phorbol 12-myristate 13-acetate (PMA) express urokinase-type plasminogen activator (u-PA). This enzyme
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- Macrophages play a crucial role in inflammatory and immune responses.
- Urokinase-type plasminogen activator (u-PA) is a key enzyme involved in pericellular proteolysis.
- Understanding u-PA regulation in macrophages is vital for studying inflammatory processes.
Purpose of the Study:
- To investigate the induction and localization of u-PA in macrophages stimulated with phorbol 12-myristate 13-acetate (PMA).
- To examine the effect of an organophosphorus ester on u-PA activity.
- To elucidate the stages of pericellular proteolysis involving u-PA.
Main Methods:
- Culturing mouse peritoneal macrophages.
- Stimulation with phorbol 12-myristate 13-acetate (PMA).
- Assessing u-PA activity and subcellular localization.
- Investigating the effect of isopropylmethylphosphonofluoridate.
Main Results:
- PMA induces u-PA expression in macrophages, peaking at 4 hours.
- u-PA activity is primarily localized to the cell membrane fraction.
- The organophosphorus compound inhibits u-PA activity post-stimulation, not before.
- The findings support a multi-stage model of pericellular proteolysis.
Conclusions:
- Macrophage u-PA induction by PMA involves synthesis, membrane binding, activation, and plasminogen conversion.
- The developed assay is a sensitive tool for studying chemical interference with u-PA induction.
- This research provides insights into the regulation of pericellular proteolysis in macrophages.