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Interferon-gamma and polyunsaturated fatty acids increase the binding of lipopolysaccharide to macrophages
H Darmani1, J Parton, J L Harwood
1Department of Medical Microbiology, University of Wales College of Medicine, Cardiff, UK.
Abstract:
We have previously shown that interferon-gamma (IFN-gamma) increases the polyunsaturated fatty acid content of membrane phospholipids in cells that were sensitive to endotoxin. In this study, IFN-gamma was found to stimulate the binding of endotoxin to the murine macrophage cell line J774.2 and the human monocyte cell line U937. Interferon-gamma-activated J774.2 cells showed a 66% increase in fluoresceine isothiocyanate (FITC) labelled LPS binding (P < 0.0005 vs control cells) and a 49% increase in tritium labelled LPS binding (P < 0.0001 vs control cells). Interferon-gamma also induced a 35% increase in binding of FITC-LPS in U937 cells (P < 0.0001 vs control cells). In contrast, pretreatment of J774.2 cells with interferon-beta (IFN-beta) had no effect on binding of FITC-LPS. Preincubation with exogenously supplied polyunsaturated fatty acids, linoleic and arachidonic acids, resulted in increases of 74% and 69% in FITC-LPS binding, respectively (both P < 0.0005 vs control cells). On the other hand, pretreatment with the saturated fatty acid, palmitic acid, had no effect on FITC-LPS binding. We propose that IFN-gamma-induced changes in the membrane phospholipid fatty acid composition of macrophage-like cells influence the binding of endotoxin.
Insights
Interferon-gamma (IFN-gamma) enhances endotoxin binding to immune cells by increasing membrane polyunsaturated fatty acids. This discovery offers new insights into endotoxin-lipopolysaccharide interactions and immune responses.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Interferon-gamma (IFN-gamma) previously shown to increase polyunsaturated fatty acids in endotoxin-sensitive cells.
- Endotoxin lipopolysaccharide (LPS) is a key component of Gram-negative bacteria, triggering potent immune responses.
Purpose of the Study:
- To investigate the effect of IFN-gamma on endotoxin binding to macrophage and monocyte cell lines.
- To explore the role of membrane phospholipid fatty acid composition in IFN-gamma-mediated endotoxin binding.
Main Methods:
- Utilized murine macrophage (J774.2) and human monocyte (U937) cell lines.
- Assessed endotoxin (LPS) binding using fluorescent (FITC) and tritium-labeled LPS.
- Investigated the impact of fatty acid supplementation (linoleic, arachidonic, palmitic acids) and interferon-beta (IFN-beta) pretreatment.
Main Results:
- IFN-gamma significantly increased FITC-LPS binding by 66% in J774.2 cells and 35% in U937 cells.
- IFN-gamma also increased tritium-labeled LPS binding by 49% in J774.2 cells.
- Exogenous polyunsaturated fatty acids (linoleic, arachidonic) mimicked IFN-gamma's effect, while saturated fatty acids (palmitic acid) did not. IFN-beta had no effect.
Conclusions:
- IFN-gamma stimulates endotoxin binding to macrophage and monocyte cell lines.
- Changes in membrane phospholipid polyunsaturated fatty acid content induced by IFN-gamma are crucial for enhancing endotoxin binding.