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TLR4-mediated inflammatory activation of human coronary artery endothelial cells by LPS
Stefanie Zeuke1, Artur J Ulmer, Shoichi Kusumoto
1Department of Medicine II, Medical University of Luebeck, Ratzeburger Allee 160, Luebeck, Germany.
Insights
Human coronary artery endothelial cells (HCAEC) become inflammatory when exposed to bacterial lipopolysaccharide (LPS), producing cytokines and adhesion molecules. This suggests HCAECs actively contribute to heart failure and coronary artery disease progression.
Area of Science:
- Cardiovascular Biology
- Immunology
- Cellular Inflammation
Background:
- Cytokines are elevated in severe congestive heart failure (CHF) and coronary artery disease (CAD).
- Cardiac cells are known targets of cytokines, but their role as active participants in inflammation is less understood.
Purpose of the Study:
- To investigate if human coronary artery endothelial cells (HCAEC) can act as a source of inflammatory mediators when stimulated.
- To determine the role of Toll-like receptor 4 (TLR4) in HCAEC activation by lipopolysaccharide (LPS).
Main Methods:
- HCAECs were stimulated with LPS.
- Cytokine and adhesion molecule expression was analyzed using ELISA, RT-PCR, and FACS.
- The involvement of TLR4 was investigated.
- The effect of Cerivastatin on IL-6 release was assessed.
Main Results:
- LPS stimulation increased the secretion of IL-6, IL-8, and MCP-1 in HCAECs.
- mRNA expression of IL-1beta and TNF-alpha was upregulated, while IL-10 remained undetectable.
- LPS induced upregulation of ICAM-1, VCAM, and ELAM-1.
- HCAEC activation by LPS was dependent on TLR4.
- Cerivastatin treatment reduced IL-6 release.
Conclusions:
- Activated HCAECs can function as inflammatory cells.
- These findings suggest HCAECs directly contribute to the progression of CHF and CAD.
Objective:
Blood levels of cytokines are commonly elevated in severe congestive heart failure (CHF) and in coronary artery disease (CAD). While the adverse effects of cytokines on contractile function and myocardial cell integrity are well studied, little is known on whether cardiac cells are only targets or active players in these inflammatory reactions.
Methods And Results:
We tested if human coronary artery endothelial cells (HCAEC) may become a source of cytokine and adhesion molecule expression when stimulated with bacterial lipopolysaccharide (LPS). Analysis of HCAEC supernatants by ELISA identified enhanced secretion of IL-6, IL-8, and MCP-1 while endothelin-1 was not increased. IL-1beta, IL-10, or TNF-alpha were not detectable by ELISA while RT-PCR revealed enhanced mRNA expression of IL-1beta and TNF-alpha but not IL-10. FACS analysis showed an LPS-induced upregulation of ICAM-1, VCAM, and ELAM-1. LFA-1 could not be detected. We further characterized receptors involved in LPS-induced signaling. Our results indicate that activation of HCAEC by LPS requires Toll-like receptor (TLR) 4. Pretreating the cells with the 3-hydroxy-3-methylglutaryl CoA (HMG CoA) reductase inhibitor Cerivastatin reduced IL-6 release.
Conclusions:
Taken together, our results indicate that activated HCAEC may act as inflammatory cells and thus directly contribute to the progression of CHF and CAD.