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Homocysteine induces monocyte chemoattractant protein-1 expression by activating NF-kappaB in THP-1 macrophages
1Department of Pharmacology and Institute of Cardiovascular Science and Medicine, Faculty of Medicine, University of Hong Kong, Hong Kong, China.
Insights
High homocysteine levels increase cardiovascular risk by boosting monocyte chemoattractant protein-1 (MCP-1) in macrophages. This occurs through activating the NF-kappaB pathway, promoting monocyte migration in atherosclerosis.
Area of Science:
- Cardiovascular Science
- Immunology
- Molecular Biology
Background:
- Homocysteine is a risk factor for cardiovascular disorders.
- Monocyte recruitment is key in atherogenesis.
- Monocyte chemoattractant protein-1 (MCP-1) drives monocyte migration into arterial walls.
Purpose of the Study:
- To investigate homocysteine's effect on MCP-1 expression in macrophages.
- To elucidate the mechanism behind homocysteine-induced MCP-1 expression.
Main Methods:
- Human monocytic THP-1 cells differentiated into macrophages.
- Incubation with varying concentrations of homocysteine (0.05-0.2 mM).
- Nuclease protection assay and ELISA to quantify MCP-1 mRNA and protein levels.
- Assessment of NF-kappaB pathway activation (IkappaB-alpha phosphorylation and mRNA expression).
Main Results:
- Homocysteine significantly enhanced MCP-1 mRNA (up to 2.6-fold) and protein (up to 4.8-fold) expression.
- Homocysteine-induced MCP-1 led to increased monocyte chemotaxis.
- Activation of NF-kappaB was observed, indicated by increased IkappaB-alpha phosphorylation and reduced IkappaB-alpha mRNA.
Conclusions:
- Pathological concentrations of homocysteine stimulate MCP-1 expression in macrophages.
- This stimulation occurs via the activation of the NF-kappaB signaling pathway.
- Findings highlight a mechanism linking homocysteine to atherogenesis through MCP-1 and NF-kappaB.
Abstract:
Homocysteinemia is an independent risk factor for cardiovascular disorders. The recruitment of monocytes is an important event in atherogenesis. Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that stimulates monocyte migration into the intima of arterial walls. The objective of the present study was to investigate the effect of homocysteine on MCP-1 expression in macrophages and the underlying mechanism of such effect. Human monocytic cell (THP-1)-derived macrophages were incubated with homocysteine. By nuclease protection assay and ELISA, homocysteine (0.05-0.2 mM) was shown to significantly enhance the expression of MCP-1 mRNA (up to 2.6-fold) and protein (up to 4.8-fold) in these cells. Homocysteine-induced MCP-1 expression resulted in increased monocyte chemotaxis. The increase in MCP-1 expression was associated with activation of nuclear factor (NF)-kappaB due to increased phosphorylation of the inhibitory protein (IkappaB-alpha) as well as reduced expression of IkappaB-alpha mRNA in homocysteine-treated cells. In conclusion, our results demonstrate that homocysteine, at pathological concentration, stimulates MCP-1 expression in THP-1 macrophages via NF-kappaB activation.