Myeloid related proteins activate Toll-like receptor 4 in human acute coronary syndromes

Atherosclerosis. 2011 Oct;218(2):486-92. doi: 10.1016/j.atherosclerosis.2011.06.020. Epub 2011 Jun 17.

Abstract

Introduction: We previously reported increased expression of TLR4 on monocytes in thrombi from patients with acute coronary syndromes (ACS). In mice, myeloid related protein (MRP) 8 and MRP14, cytoplasmic proteins of neutrophils and monocytes, activate Toll-like receptor (TLR) 4 during sepsis. In human ACS, we investigated now whether the pro-inflammatory action of MRPs occurs through TLR4 in monocytes derived from thrombi.

Methods: Coronary thrombi and peripheral blood of 27 ACS patients were analyzed. CD14(+) monocytes were isolated and incubated with TLR2 ligand PM3SKA, TLR4 ligand lipopolysaccharide (LPS), MRP8, MRP14, or MRP8/14 heterocomplex. Anti-TLR4 antibodies (HTA125) were used to block TLR4 and polymyxin B (PMB) was employed to inhibit endotoxins. Before and after stimulation, the release of TNFα was measured by ELISA and the expression of TLR4 on CD14(+) monocytes was determined by flow cytometry. Further, selected pathways of downstream signaling were analyzed.

Results: MRP8 and MRP8/14 increased release of TNFα in cultures of CD14(+) monocytes, more in cells derived from thrombi compared with matched peripheral blood cells (p<0.001). LPS, MRP8, and MRP8/14, but much less PM3SKA and MRP14 alone, stimulated TNFα release, which can be inhibited by HTA125. MRP8/14 enhanced TLR4 expression on monocytes from thrombi (p<0.001), but not on monocytes from peripheral blood of the same patients.

Conclusion: In ACS, MRP8 and MRP8/14 complex are specific ligands of TLR4, which induce the release of TNFα and probably other pro-inflammatory agents from monocytes. This specific MRP8/14-dependent pathway with striking similarities to sepsis increasing expression of TLR4 in thrombi appears to be involved in the pathogenesis of coronary occlusion and may represent a novel therapeutic target in ACS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Coronary Syndrome / metabolism*
  • Aged
  • Calgranulin A / metabolism
  • Calgranulin B / metabolism
  • Cytoplasm / metabolism
  • Endotoxins / metabolism
  • Female
  • Humans
  • Inflammation
  • Lipopolysaccharide Receptors / biosynthesis
  • Male
  • Middle Aged
  • Monocytes / cytology
  • Myeloid Cells / cytology*
  • Sepsis / metabolism
  • Signal Transduction
  • Thrombosis / metabolism
  • Toll-Like Receptor 2 / metabolism
  • Toll-Like Receptor 4 / metabolism*
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Calgranulin A
  • Calgranulin B
  • Endotoxins
  • Lipopolysaccharide Receptors
  • TLR2 protein, human
  • TLR4 protein, human
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Tumor Necrosis Factor-alpha