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Modulation of ICAM-1 expression in ECV304 cells by macrophage-released cytokines
A Antonelli1, M Bianchi, R Crinelli
1Istituto di Chimica Biologica G. Fornaini, Università degli Studi di Urbino, Urbino, Italy.
Insights
Targeted dexamethasone delivery to macrophages inhibits tumor necrosis factor-alpha (TNF-alpha) release, reducing intercellular adhesion molecule-1 (ICAM-1) expression on endothelial cells. This approach offers a potential therapeutic strategy for inflammatory conditions.
Area of Science:
- Immunology
- Cell Biology
- Molecular Medicine
Background:
- Transendothelial leukocyte trafficking is crucial during inflammation and relies on adhesion molecules like ICAM-1.
- Endothelial ICAM-1 expression is upregulated by inflammatory mediators, with macrophages releasing key cytokines.
- Macrophages play a central role by releasing proinflammatory cytokines that upregulate endothelial adhesion molecules.
Purpose of the Study:
- To investigate if modulating macrophage activation and cytokine release affects ICAM-1 expression in endothelial cells.
- To explore the role of dexamethasone-mediated inhibition of macrophage activation on ICAM-1 expression.
- To identify the specific cytokines involved in macrophage-induced ICAM-1 expression.
Main Methods:
- Selective delivery of dexamethasone to macrophages using a red blood cell-mediated system.
- Stimulation of macrophages with lipopolysaccharide (LPS) and analysis of NF-kB activation and cytokine release.
- Incubation of endothelial cells (ECV304) with conditioned medium from treated macrophages and assessment of ICAM-1 mRNA and NF-kB activity.
Main Results:
- Dexamethasone treatment inhibited NF-kB activation and TNF-alpha release in LPS-stimulated macrophages.
- Conditioned medium from treated macrophages reduced ICAM-1 mRNA expression by 45% in ECV304 cells.
- Reduced ICAM-1 expression correlated with decreased NF-kB DNA binding and increased IkB(alpha) in endothelial cells, with TNF-alpha identified as the primary mediator.
Conclusions:
- TNF-alpha is the main cytokine from LPS-stimulated macrophages that drives ICAM-1 gene expression in endothelial cells.
- Targeting the NF-kB pathway in macrophages via dexamethasone can inhibit endothelial ICAM-1 expression.
- This modulation presents a potential therapeutic strategy for inflammatory diseases involving leukocyte trafficking.
Abstract:
Transendothelial leukocyte trafficking during inflammation requires the expression of adhesion molecules such as human intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is constitutively expressed on the surface of endothelial cells and its levels increase in response to a variety of inflammatory mediators, including cytokines. Monocyte/macrophage cells play a crucial role in this context because, upon stimulation, they release proinflammatory cytokines which are responsible for the upregulation of adhesion molecules in endothelial cells. In the present study we investigated whether the modulation of macrophage activation and cytokine release is able to modulate ICAM-1 expression in endothelial cells. Dexamethasone was selectively delivered to macrophages by means of a red blood cell-mediated delivery system. Subsequent stimulation of macrophages by lipopolysaccharide (LPS) was found to inhibit NF-kB activation and tumor necrosis factor-alpha (TNF-alpha) release [R. Crinelli, A. Antonelli, M. Bianchi, L. Gentilini, S. Scaramucci, and M. Magnani (2000) Blood Cells Mol. Dis. 26, 211-222]. Incubation with conditioned medium derived from LPS-stimulated macrophages receiving dexamethasone resulted in a 45% inhibition of ICAM-1 mRNA expression in ECV304 cells. In the same experimental system this reduced ICAM-1 expression was paralleled by a reduced NF-kB DNA binding activity and a twofold higher level of IkB(alpha) in the cytosol of endothelial cells. Activation of ICAM-1 expression in ECV304 cells by macrophage-conditioned medium is not due to IFN-gamma stimulation since STAT-1 DNA binding remained unchanged. Furthermore, treatment of the macrophage-conditioned medium with a TNF-alpha-inactivating antibody resulted in the complete abrogation of induced ICAM-1 expression. These results suggest that TNF-alpha is the main cytokine released by LPS-stimulated macrophages able to promote ICAM-1 gene expression in endothelial cells. Modulation of the NF-kB activation pathway in macrophages by targeted delivery of dexamethasone could potentially be used as a therapeutic strategy with which to inhibit the expression of ICAM-1 in endothelial cells.
