Abstract 563: Myeloid Related Protein 8 is a Ligand of Toll-like receptor 4 in Acute Coronary Syndromes
Introduction: Inflammatory and immune cells are involved in acute coronary syndromes (ACS). Toll-like receptors (TLR) play a major role in pathogen recognition and inflammation. Previously, we reported increased TLR4+ monocytes in thrombi from patients with ACS. Recently, myeloid related protein (MRP)8 and MRP14, cytoplasmic proteins of neutrophils and monocytes, have been shown to activate TLR4 by inducing TNFα in a mouse model of sepsis. Thus, we investigated whether MRP8, MRP14, and MRP8/14 complex activate TLR4 in ACS, using lipopolysaccharide (LPS), a known ligand of TLR4, as positive control.
Methods: In 6 patients, thrombi were harvested from the site of coronary occlusion in parallel with sampling of peripheral blood. Thrombi were disrupted and treated with Actilyse for 12 hours in a cell culture medium. Leukocytes were isolated by Ficoll centrifugation. Blood leukocytes (PBL) were treated in the same manner. CD14+ cells from thrombi or blood were isolated with magnetic beads and incubated with PM3SKA (TLR2 ligand), LPS (TLR4 ligand), MRP8, MRP14 or MRP8/14. Monoclonal anti-TLR4 antibodies (HTA125) and Polymyxin B (PMB) were used to inhibit TLR4 and endotoxin, respectively. The release of TNFα in cell culture supernatants was measured by ELISA.
Results: The amount of TNFα from CD14+ cells of thrombi upon incubation with MRP8 was significantly increased (p<0.05) compared to PBL CD14+ cells. Pre-incubation with HTA125 had a similar inhibitory effect on MRP8− as on LPS-induced TNFα release, but not incubation with PM3SKA or MRP14.
Conclusion: In ACS, MRP8 is a ligand of TLR4. Analogous pathways in ACS and sepsis may initiate new diagnostic and therapeutic strategies.