N-terminal fragment of cardiac myosin binding protein-C triggers pro-inflammatory responses in vitro.

Myocardial infarction (MI) leads to loss and degradation of contractile cardiac tissue followed by sterile inflammation of the myocardium through activation and recruitment of innate and adaptive cells of the immune system. Recently, it was shown that cardiac myosin binding protein-C (cMyBP-C), a protein of the cardiac sarcomere, is degraded following MI, releasing a predominant N-terminal 40-kDa fragment (C0C1f) into myocardial tissue and the systemic circulation. We hypothesized that early release of C0C1f contributes to the initiation of inflammation and plays a key role in recruitment and activation of immune cells. Therefore, we investigated the role of C0C1f on macrophage/monocyte activation using both mouse bone marrow-derived macrophages and human monocytes. Here we demonstrate that C0C1f leads to macrophage/monocyte activation in vitro. Furthermore, C0C1f induces strong upregulation of pro-inflammatory cytokines (interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and interleukin-1ß (IL-1ß)) in cultured murine macrophages and human monocytes, resulting in a pro-inflammatory phenotype. We identified the toll-like receptor 4 (TLR4), toll-like receptor 2 (TLR2), and Advanced Glycosylation End Product-Specific Receptor (RAGE) as potential receptors for C0C1f whose activation leads to mobilization of the NFκB signaling pathway, a central mediator of the pro-inflammatory signaling cascade. Thus, C0C1f appears to be a key player in the initiation of inflammatory processes and might also play an important role upon MI.

Release kinetics of inflammatory biomarkers in a clinical model of acute myocardial infarction.

RATIONALE: Inflammation in the setting of acute myocardial infarction (MI) has been linked to risk stratification; however, the release kinetics of inflammatory biomarkers in patients with acute MI has been difficult to establish. OBJECTIVE: The aim of this study was to determine the kinetics of changes in the levels of several biomarkers specifically linked to inflammation after transcoronary ablation of septal hypertrophy, a procedure that mimics acute MI. METHODS AND RESULTS: We analyzed release kinetics of C-reactive protein, high-sensitivity C-reactive protein, interleukin-6, soluble CD40 ligand, and peripheral blood leukocyte subsets in patients (n=21) undergoing transcoronary ablation of septal hypertrophy. Blood samples were collected before transcoronary ablation of septal hypertrophy and at various times after transcoronary ablation of septal hypertrophy. Serum levels of C-reactive protein were increased at 24 hours (1.0 mg/dL [interquartile range [IQR], 0.7-1.75] versus 0.2 mg/dL [IQR, 0.1-1.05] at baseline [BL]; P<0.001), whereas high-sensitivity C-reactive protein increased as early as 8 hours (2.68 mg/L [IQR, 1.23-11.80] versus 2.17 mg/L [IQR, 1.15-5.06] at BL; P=0.002). Interleukin-6 was significantly increased at 45 minutes (2.59 pg/mL [IQR, 1.69-5.0] versus 1.5 pg/mL [IQR, 1.5-2.21] at BL; P=0.002), and soluble CD40 ligand was significantly decreased at 60 minutes (801.6 pg/mL [IQR, 675.0-1653.5] versus 1750.0 pg/mL [IQR, 1151.0-2783.0] at BL; P=0.016). Elevated counts of polymorphonuclear neutrophils were detectable at 15 minutes, with a significant increase at 2 hours (6415 cells/µL [IQR, 5288-7827] versus 4697 cells/µL [IQR, 2892-5620] at BL; P=0.004). Significant monocytosis was observed at 24 hours (729 cells/µL [IQR, 584-1344] versus 523 cells/µL [IQR, 369-701] at BL; P=0.015). CONCLUSIONS: Interleukin-6 and neutrophil granulocytes showed a continuous rise at all prespecified time points after induction of MI. Our results provide valuable additional evidence of the diagnostic value of inflammatory biomarkers in the setting of early acute MI.