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Expression of procoagulant activity in a human monocyte-like cell line
Abstract:
Peripheral blood monocytes generate the potent membrane-bound procoagulant TF in response to a number of immune-related stimuli. Although the contribution of the monocyte/macrophage and its soluble mediators to the immune response has been recognized, the role of macrophage procoagulant in the pathogenesis of this response is less certain. Previous studies have suggested that MTF generation is important in the pathogenesis of fibrin deposition in the inflammatory response. In order to pursue this relationship, we have studied the activation of a procoagulant in a human monocyte-like cell line, the U937. The U937 procoagulant has been characterized as TF by the following criteria: the PCA requires factors VII and X for expression; the PCA is not due to serine protease activity; PCA is neutralized by a monospecific antibody to purified bovine TF. The expression of TF in these cells was amplified after stimulation with LPS, a potent activator of peripheral blood MTF expression, and was inhibited by actinomycin D and cycloheximide. Cytosine arabinoside, an inhibitor of cell division, failed to affect U937 TF generation. The U937 cell line appears to be a useful in vitro model for the study of the activation of MTF.
Insights
Peripheral blood monocytes produce tissue factor (TF), a procoagulant crucial in inflammation. Researchers used the U937 cell line to model TF activation, finding it a viable in vitro system for studying this process.
Area of Science:
- Immunology
- Hematology
- Cell Biology
Background:
- Monocytes generate tissue factor (TF), a membrane-bound procoagulant, upon immune stimulation.
- The role of macrophage-derived TF in inflammatory pathogenesis and fibrin deposition remains under investigation.
Purpose of the Study:
- To characterize and study the activation of procoagulant activity in the human monocyte-like U937 cell line.
- To establish U937 cells as a reliable in vitro model for investigating monocyte TF (MTF) activation.
Main Methods:
- Characterization of U937 procoagulant activity using criteria for TF, including dependence on factors VII and X, lack of serine protease activity, and neutralization by anti-TF antibody.
- Stimulation of U937 cells with lipopolysaccharide (LPS) to assess TF expression.
- Inhibition studies using actinomycin D, cycloheximide, and cytosine arabinoside to determine the mechanisms of TF generation.
Main Results:
- The procoagulant activity in U937 cells was confirmed as TF.
- LPS stimulation amplified TF expression in U937 cells.
- TF generation was inhibited by actinomycin D and cycloheximide, indicating a requirement for protein synthesis, but was unaffected by cytosine arabinoside.
Conclusions:
- The U937 cell line serves as a valuable in vitro model for studying the activation of monocyte tissue factor.
- Understanding MTF activation in models like U937 can elucidate its role in inflammatory responses and fibrin deposition.