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Serum amyloid A, an acute-phase protein, modulates proteoglycan synthesis in cultured murine peritoneal macrophages
R Elliott-Bryant1, J E Silbert, G Sugumaran
1Edith Nourse Rogers Memorial Veterans Hospital, Bedford, Massachusetts, 01730, USA.
Abstract:
Cultured peritoneal macrophages obtained from azocasein-injected mice were found to produce several fold more cell-associated and medium proteoglycans than peritoneal macrophages from untreated mice. Since serum amyloid A (an acute-phase protein) is also upregulated following injections of azocasein, we questioned whether its production was the immediate agent stimulating proteoglycan formation. Cultured peritoneal macrophages from untreated mice were then incubated with varying concentrations of SAA, resulting in a similar dose-dependent several fold increase in proteoglycan production. Of particular note was a disproportionate increase in cell-associated heparan sulfate proteoglycans in both experimental groups and of dermatan sulfate and chondroitin sulfate proteoglycans when cells were incubated in the presence of SAA in the culture medium. These results indicate a potentially important function of SAA in directing specific modifications in inflammatory conditions where increase in macrophage proteoglycans may play direct roles.
Insights
Serum amyloid A (SAA) significantly increases proteoglycan production in macrophages during inflammation. This acute-phase protein influences specific proteoglycan types, suggesting a key role in inflammatory responses.
Area of Science:
- Immunology
- Biochemistry
- Cell Biology
Background:
- Macrophages play a crucial role in inflammatory responses.
- Proteoglycans are important extracellular matrix components involved in cell signaling and tissue remodeling.
- Serum amyloid A (SAA) is an acute-phase protein upregulated during inflammation.
Purpose of the Study:
- To investigate the effect of azocasein injection on proteoglycan production by peritoneal macrophages.
- To determine if serum amyloid A (SAA) is the mediator of increased proteoglycan synthesis in macrophages.
- To elucidate the specific types of proteoglycans affected by SAA.
Main Methods:
- Culturing peritoneal macrophages from azocasein-injected and untreated mice.
- Incubating macrophages with varying concentrations of purified SAA.
- Quantifying cell-associated and medium proteoglycans, including specific glycosaminoglycan chains.
Main Results:
- Azocasein-injected mice macrophages produced significantly more proteoglycans than controls.
- Incubation with SAA dose-dependently increased proteoglycan production in macrophages.
- SAA disproportionately increased cell-associated heparan sulfate proteoglycans and also dermatan sulfate and chondroitin sulfate proteoglycans.
Conclusions:
- Serum amyloid A (SAA) directly stimulates macrophages to increase proteoglycan production.
- SAA influences the synthesis of specific proteoglycan types, notably heparan sulfate proteoglycans.
- SAA may play a significant role in modulating macrophage function and tissue modification during inflammatory conditions.