title: Myeloid related proteins activate Toll-like receptor 4 in human acute coronary syndromes.
abstract: BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Cardiology, CardioVascular Center, University Hospital Zurich, Switzerland.
authors.forename: Keiko
authors.initials: K
authors.lastname: Yonekawa
authors.forename: Michel
authors.initials: M
authors.lastname: Neidhart
authors.forename: Lukas A
authors.initials: LA
authors.lastname: Altwegg
authors.forename: Christophe A
authors.initials: CA
authors.lastname: Wyss
authors.forename: Roberto
authors.initials: R
authors.lastname: Corti
authors.forename: Thomas
authors.initials: T
authors.lastname: Vogl
authors.forename: Mariam
authors.initials: M
authors.lastname: Grigorian
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Lüscher
authors.forename: Willibald
authors.initials: W
authors.lastname: Maier
mesh_terms: D054058:Acute Coronary Syndrome / Q000378:metabolism*; D000368:Aged; D040501:Calgranulin A / Q000378:metabolism; D040502:Calgranulin B / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004731:Endotoxins / Q000378:metabolism; D005260:Female; D006801:Humans; D007249:Inflammation; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology; D022423:Myeloid Cells / Q000166:cytology*; D018805:Sepsis / Q000378:metabolism; D015398:Signal Transduction; D013927:Thrombosis / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D040501:Calgranulin A; D040502:Calgranulin B; D004731:Endotoxins; D018950:Lipopolysaccharide Receptors; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha