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Macrophage cell lines behave as activated macrophages in the production and regulation of plasminogen activator
Abstract:
Seven macrophagelike cell lines, WEHI-3, J774, RAW264, FC-1, P388D-1, PU5-R, and PU5-1.8, commonly used as in vitro models of macrophage function, were studied for their fibrinolytic activity in the presence and absence of purified plasminogen. All cell lines, as well as the freshly harvested peritoneal macrophages, produced plasminogen activator, as indicated by the levels of fibrinolytic activity in the presence of plasminogen. However, fibrinolytic proteolysis was most efficiently measured by direct attachment to 125I-fibrin plates, a method which measures both secreted and cell-membrane-associated plasminogen activator. Other non-plasminogen-dependent fibrinolytic activities were also produced by all cells studied and secreted by WEHI-3, FC-1, RAW-264, and thioglycollate-elicited macrophages. Activation of the thioglycollate-elicited macrophages with macrophage activation factor (MAF) induced threefold higher levels of plasminogen activator production but MAF treatment had no effect on the level of activity produced by macrophagelike cell lines. Indeed, the macrophagelike cell lines produced plasminogen activator at levels seen with MAF-activated thioglycollate-elicited macrophages. We conclude that these cell lines constitutively produce activators of plasminogen and, in their failure to respond to MAF, behave as activated macrophages.
Insights
Seven common macrophage cell lines constitutively produce plasminogen activators. These cell lines mimic activated macrophages by showing high plasminogen activator levels without responding to macrophage activation factor (MAF).
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Macrophage cell lines are vital in vitro models for studying macrophage functions.
- Fibrinolytic activity, involving the breakdown of fibrin, is a key aspect of macrophage function.
- Plasminogen activators play a crucial role in the fibrinolytic system.
Purpose of the Study:
- To investigate the fibrinolytic activity of seven commonly used macrophagelike cell lines.
- To compare the plasminogen activator production of these cell lines with primary macrophages.
- To determine the responsiveness of these cell lines to macrophage activation factor (MAF).
Main Methods:
- Assessing fibrinolytic activity in seven macrophagelike cell lines (WEHI-3, J774, RAW264, FC-1, P388D-1, PU5-R, PU5-1.8) and primary macrophages.
- Measuring plasminogen activator (PA) production in the presence and absence of purified plasminogen.
- Utilizing direct attachment to 125I-fibrin plates to quantify both secreted and cell-membrane-associated PA.
- Treating thioglycollate-elicited macrophages with MAF to assess its effect on PA production.
Main Results:
- All tested macrophagelike cell lines and primary macrophages produced plasminogen activator.
- Direct attachment to 125I-fibrin plates proved most effective for measuring fibrinolytic proteolysis.
- Non-plasminogen-dependent fibrinolytic activities were observed in all cells.
- MAF treatment significantly increased PA production in primary macrophages but not in macrophagelike cell lines.
- Macrophagelike cell lines exhibited PA production levels comparable to MAF-activated primary macrophages.
Conclusions:
- The studied macrophagelike cell lines constitutively produce plasminogen activators.
- These cell lines exhibit characteristics of activated macrophages due to their high, constitutive PA levels and lack of response to MAF.
- The findings suggest these cell lines are valuable models for studying activated macrophage functions related to fibrinolysis.