Introduction: Cardiac myosin binding protein-C (cMyBP-C) is detectable early after cardiac injury and has been described as a novel biomarker for cardiovascular diseases. Recently, it was shown that cMyBP-C is degraded following ischemia/reperfusion (I/R) injury. C0-C1f, the 40-kDa fragment of cMyBP-C consisting of C0 and C1 domains and the first 17 residues of the M-domain (amino acids 1-271), is cleaved and released from cardiomyocytes within the first 30 min upon I/R injury. An essential component of cardiac diseases is inflammation that is associated with cardiac injury and the cardiac regeneration process. The initiation process of inflammation and the precise mechanisms involved are still unclear.
Hypothesis: Our hypothesis is that C0-C1f is involved in the initiation of inflammatory processes upon MI.
Methods and Results: Multiple cell types from mouse or human origin were treated with various N-terminal fragments of cMyBP-C as well as the cardiovascular biomarker cardiac troponin I in vitro. We observed that only C0-C1f specifically activates human monocytes and murine macrophages resulting in an increase of pro-inflammatory cytokines such as IL-6 (mRNA: 303 ± 90 fold), TNFα (mRNA: 12.4 ± 2.8 fold), and IL-1β (mRNA: 91 ± 30 fold) as well as adhesion molecules. We observed the activation of MAPKs such as ERK1/2 and p38 that were phosphorylated within 30 and 10 min upon treatment, respectively. Furthermore, we identified NFκB as the central mediator in the pro-inflammatory signaling cascade, as the inflammatory response was abrogated by the NFκB inhibitor Bay 11-7082. By using various inhibitors, we identified toll-like receptor 4 (TLR4) and TLR2 as well as advanced glycosylation end product-specific receptor (RAGE) as potential receptors for C0C1f.
Conclusions: Here we report evidence that C0-C1f is important for the initiation of inflammatory signaling arising from cardiac injury. We demonstrate that C0-C1f activates macrophages and blood monocytes via various receptors and identified the NFκB signaling pathway as central mediator. We currently examine the role of cMyBP-C in eliciting immune responses that cause inflammation in vivo post-MI. This information paves the way for examining C0-C1f as a potential target for future drug development.