Bacterial Lipopolysaccharide Activates NF-κB through Toll-like Receptor 4 (TLR-4) in Cultured Human Dermal Endothelial Cells

By E. Faure, O. Equils, P. Sieling, L. Thomas, Frank X. Zhang, C. Kirschning, N. Polentarutti, M. Muzio, M. Arditi. Journal of Biological Chemistry, 2000

608 citations recorded by the source corpus.

A missense mutation in the cytoplasmic domain of the Toll-like receptor-4 (TLR-4) has been identified as the defect responsible for lipopolysaccharide (LPS) hyporesponsiveness in C3H/HeJ mice. TLR-4 and TLR-2 have recently been implicated in LPS signaling in studies where these receptors were overexpressed in LPS non-responsive 293 human embryonic kidney cells. However, the signaling role of TLR-4 or TLR-2 in human cells with natural LPS response remains largely undefined. Here we show that human dermal microvessel endothelial cells (HMEC) and human umbilical vein endothelial cells express predominantly TLR-4 but very weak TLR-2 and respond vigorously to LPS but not toMycobacterium tuberculosis 19-kDa lipoprotein. Transient transfection of non-signaling mutant forms of TLR-4 and anti-TLR-4 monoclonal antibody inhibited LPS-induced NF-κB activation in HMEC, while a monoclonal antibody against TLR-2 was ineffective. In contrast to LPS responsiveness, the ability of HMEC to respond to 19-kDa lipoprotein correlated with the expression of TLR-2. Transfection of TLR-2 into HMEC conferred responsiveness to 19-kDa lipoprotein. These data indicate that TLR-4 is the LPS signaling receptor in HMEC and that human endothelial cells (EC) express predominantly TLR-4 and weak TLR-2, which may explain why they do not respond to 19-kDa lipoprotein. The differential expression of TLRs on human EC may have important implications in the participation of vascular EC in innate immune defense mechanisms against various infectious pathogens, which may use different TLRs to signal.

Subfields: Immunology

View Paper: https://www.semanticscholar.org/paper/3d83eaeae2c7ec1ede1a4f0cefc5e4de4c77886c

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In Immunology

1. M. Abreu
2. Yuanqing Liu
3. E. Cario
4. S. Michalek
5. D. Podolsky
6. Céline Vaure

Citations in the corpus

• Differential Alteration in Intestinal Epithelial Cell Expression of Toll-Like Receptor 3 (TLR3) and TLR4 in Inflammatory Bowel Disease (2000, background): “Downstream, LPS-induced signaling through TLRs rapidly leads to NF-kB activation and cytokine expression in monocytes (7, 10).”
• A Comparative Review of Toll-Like Receptor 4 Expression and Functionality in Different Animal Species (2014, background): “Human dermal microvessel endothelial cells (HMEC) and human umbilical vein endothelial cells (HUVEC) express TLR4 (68).”
• Signaling by Toll-Like Receptor 2 and 4 Agonists Results in Differential Gene Expression in Murine Macrophages (2001, background): “Faure et al. ( 6 ) reported recently that human dermal microvessel or umbilical vein endothelial cells express predominantly TLR4 but very weakly TLR2 and respond vigorously to E. coli LPS but not to Mycobacterium tuberculosis 19-kDa lipoprotein, a TLR2 ligand.”
• Lipopolysaccharide-binding protein: a possible diagnostic marker for Gram-negative bacteremia in neutropenic cancer patients (2003, positive): “Recently it was demonstrated that the LPS-LBP-CD14 complex binds to the Toll-like receptor 2 and 4 on effector cells, leading to production of inflammatory cytokines [5, 6].”
• Decreased Expression of Toll-Like Receptor-4 and MD-2 Correlates with Intestinal Epithelial Cell Protection Against Dysregulated Proinflammatory Gene Expression in Response to Bacterial Lipopolysaccharide1 (2001, methodology): “We investigated the mRNA expression profile of TLR4 and MD-2 by RTPCR in these representative intestinal cell lines and used HMEC, an LPS-responsive cell line (24) as a control.”