Lipopolysaccharides from atherosclerosis-associated bacteria antagonize TLR4, induce formation of TLR2/1/CD36 complexes in lipid rafts and trigger TLR2-induced inflammatory responses in human vascular endothelial cells

Authors

  • Martha Triantafilou,

    1. Infection and Immunity Group, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
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  • Frederick G. J. Gamper,

    1. Infection and Immunity Group, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
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  • Philipp M. Lepper,

    1. Department of Intensive Care Medicine, University of Bern, Inselspital, Bern, Switzerland.
    2. Department of Internal Medicine II, University of Ulm, 89075 Ulm, Germany.
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  • Marios Angelos Mouratis,

    1. Infection and Immunity Group, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
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  • Christian Schumann,

    1. Department of Internal Medicine II, University of Ulm, 89075 Ulm, Germany.
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  • Evlambia Harokopakis,

    1. Center for Oral Health and Systemic Disease and Departments of Periodontics and Microbiology/Immunology and of Orthodontics/Pedodontics, University of Louisville Health Sciences Center, Louisville, KY 40292, USA.
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  • Robert E. Schifferle,

    1. Department of Oral Biology, University at Buffalo, NY 14214, USA.
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  • George Hajishengallis,

    1. Center for Oral Health and Systemic Disease and Departments of Periodontics and Microbiology/Immunology and of Orthodontics/Pedodontics, University of Louisville Health Sciences Center, Louisville, KY 40292, USA.
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  • Kathy Triantafilou

    Corresponding author
    1. Infection and Immunity Group, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
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*E-mail K.Triantafilou@sussex.ac.uk; Tel. (+44) 1273 678362; Fax (+44) 1273 678362.

Summary

Infection with bacteria such as Chlamydia pneumonia, Helicobacter pylori or Porphyromonas gingivalis may be triggering the secretion of inflammatory cytokines that leads to atherogenesis. The mechanisms by which the innate immune recognition of these pathogens could lead to atherosclerosis remain unclear. In this study, using human vascular endothelial cells or HEK-293 cells engineered to express pattern-recognition receptors (PRRs), we set out to determine Toll-like receptors (TLRs) and functionally associated PRRs involved in the innate recognition of and response to lipopolysaccharide (LPS) from H. pylori or P. gingivalis. Using siRNA interference or recombinant expression of cooperating PRRs, we show that H. pylori and P. gingivalis LPS-induced cell activation is mediated through TLR2. Human vascular endothelial cell activation was found to be lipid raft-dependent and to require the formation of heterotypic receptor complexes comprising of TLR2, TLR1, CD36 and CD11b/CD18. In addition, we report that LPS from these bacterial strains are able to antagonize TLR4. This antagonistic activity of H. pylori or P. gingivalis LPS, as well as their TLR2 activation capability may be associated with their ability to contribute to atherosclerosis.

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