Neutrophil Extracellular Traps in ST-Segment Elevation Myocardial Infarction: Reduced by Tocilizumab and Associated With Infarct Size

Background Interleukin-6-receptor inhibition with tocilizumab improves myocardial salvage in patients with ST-segment elevation myocardial infarction (STEMI). Reduced levels of neutrophil extracellular traps (NETs), which consist of nuclear material studded with proteins released upon neutrophil activation, might contribute to this effect. Objectives The purpose of this study was to evaluate the effect of tocilizumab on NETs and investigate the association between NETs and myocardial injury in patients with STEMI. Methods In the ASSAIL-MI study, 199 patients with STEMI were randomized to tocilizumab or placebo during percutaneous coronary intervention. In this substudy, we analyzed blood levels of the NET markers double-stranded deoxyribonucleic acid (dsDNA), myeloperoxidase-DNA, and citrullinated histone 3 (H3Cit) at admission and after 24 hours and 3 to 7 days. In a subgroup of patients, we assessed regulation of transcripts related to the formation of NETs. We also investigated associations between NET markers and the myocardial salvage index (MSI). Results All NET markers were lower in the tocilizumab group than in the placebo group at 3 to 7 days (all P < 0.04). Several NET-related pathways were downregulated in the tocilizumab group. The beneficial effect of tocilizumab on the MSI seemed to be partly dependent on reduction of NETs (structural equation modeling: 0.05, P = 0.001 [dsDNA] and 0.02, P = 0.055 [H3Cit]). Patients with NETs in the 3 lowest quartiles had higher MSI than patients in quartile 4 (β = 10.9 [95% CI: 4.0-15.0] [dsDNA] and β = 8.9 [95% CI: 2.0-15.9] [H3Cit], both P = 0.01). Conclusions NETs were reduced by tocilizumab and associated with myocardial injury. The effect of tocilizumab on MSI might be mediated through reduced NETs. (ASSessing the Effect of Anti-IL-6 Treatment in Myocardial Infarction: The ASSAIL-MI Trial [ASSAIL-MI]; NCT03004703)