Neutrophil methylmalonic acid promotes microthrombus formation and adverse cardiac remodeling post-myocardial infarction through activating IL-6 signaling pathway-mediated NETosis.

BACKGROUND: Neutrophils contribute critically to adverse cardiac remodeling following acute myocardial infarction (AMI), yet the precise regulatory mechanisms remain unclear. Our previous findings identified methylmalonic acid (MMA) as a novel cardiovascular prognostic biomarker. Thus, we aimed to investigate whether neutrophil-derived MMA mediates neutrophil extracellular trap (NET) formation and subsequent adverse cardiac remodeling post-MI, and to elucidate potential underlying mechanisms. METHODS: Serum and neutrophil MMA levels were measured in humans and mice with AMI. Neutrophil-specific Mmut knockout mice (S100a8(Cre) Mmut(flox/flox)) were treated with GSK484 (PAD4 inhibitor) or DNase I (NET-degrading agent) to evaluate the role of neutrophil-derived MMA in cardiac NET formation and adverse remodeling after MI. High-throughput RNA sequencing was performed on isolated neutrophils to identify molecular mechanisms. RESULTS: Compared with patients with angina, patients with AMI displayed significantly increased MMA levels in serum and neutrophils, particularly pronounced in neutrophils. Elevated NET markers were observed in thrombus tissue from patients with AMI with higher neutrophil MMA. Similarly, Mmut knockout mice exhibited increased NET formation, greater microthrombus burden, and worsened cardiac dysfunction 4 weeks after MI compared with S100a8Cre controls. NETosis-targeted interventions (GSK484 or DNase I) substantially reduced microthrombus formation and adverse cardiac remodeling, especially in Mmut knockout mice. Integrated transcriptomic and multifactorial analyses revealed that activation of the neutrophil IL-6/JAK1/STAT3 signaling pathway plays a key role in MMA-induced NETosis, which was largely compromised by the treatment with an IL-6 neutralizing antibody. Moreover, colchicine, an FDA-approved anti-inflammatory agent, significantly inhibited neutrophilic IL-6 expression, NETosis, and microthrombus formation, thereby attenuating post-MI cardiac remodeling against the hazards of neutrophil MMA elevation. CONCLUSIONS: Neutrophil-derived MMA promotes NETosis and microthrombus formation through IL-6 activation, contributing to maladaptive cardiac remodeling post-MI. These findings identify neutrophil MMA as a novel immunometabolic trigger driving NET-mediated adverse cardiac remodeling and suggest colchicine as a promising therapeutic strategy to prevent heart failure post-MI, particularly in patients with elevated neutrophil MMA contents.