DC-SIGN and Toll-like receptor 4 mediate oxidized low-density lipoprotein-induced inflammatory responses in macrophages

Sci Rep. 2017 Jun 12;7(1):3296. doi: 10.1038/s41598-017-03740-7.

Abstract

The regulation of inflammatory responses by innate immune receptors is recognized as a crucial step in the development of atherosclerosis, although the precise molecular mechanisms remain to be elucidated. This study focused on illustrating the roles of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN)- and Toll-like receptor 4 (TLR4)-regulated inflammatory responses in macrophages. We found that DC-SIGN expression levels were increased in macrophages of atherosclerotic plaques. Oxidized low-density lipoprotein (oxLDL) significantly enhanced DC-SIGN protein expression levels after a short-term exposure. Knockdown of DC-SIGN decreased expression and secretion of interleukin 1-β (IL1-β), monocyte chemo-attractant protein 1 (MCP-1), tumor necrosis factor-α (TNFα) and matrix metalloproteinase-9 (MMP-9). Immunofluorescence studies demonstrated that DC-SIGN and TLR4 co-localized in regions of the plaques. Moreover, DC-SIGN was co-expressed with TLR4 on the plasma membrane after oxLDL stimulation. The presence of an endogenous interaction and the results of the in vitro pull-down assays revealed that DC-SIGN binds directly with TLR4. We also present evidence that DC-SIGN mediates TLR4-regulated NFκB activation but not activation of p38 and JNK. Our results suggest an essential role of DC-SIGN/TLR4 signaling in macrophages in the pathogenesis of atherosclerosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Atherosclerosis / metabolism
  • Atherosclerosis / pathology
  • Cell Adhesion Molecules / metabolism*
  • Cytokines / metabolism
  • Female
  • Gene Knockdown Techniques
  • HEK293 Cells
  • Humans
  • Inflammation / pathology*
  • Inflammation Mediators / metabolism
  • Lectins, C-Type / metabolism*
  • Lipoproteins, LDL / metabolism*
  • Macrophages / metabolism*
  • Macrophages / pathology*
  • Male
  • Middle Aged
  • Plaque, Atherosclerotic / pathology
  • Protein Binding
  • Receptors, Cell Surface / metabolism*
  • Toll-Like Receptor 4 / metabolism*
  • Transcription Factor RelA / metabolism

Substances

  • Cell Adhesion Molecules
  • Cytokines
  • DC-specific ICAM-3 grabbing nonintegrin
  • Inflammation Mediators
  • Lectins, C-Type
  • Lipoproteins, LDL
  • Receptors, Cell Surface
  • Toll-Like Receptor 4
  • Transcription Factor RelA
  • oxidized low density lipoprotein