Antiplatelet and anticoagulant (APAC) heparin proteoglycan mimetic restricts thrombo-inflammation and maintains cardiac function following myocardial injury
Background: Myocardial ischemia-reperfusion injury (IRI) is characterized by thrombo-inflammation, which triggers acute organ damage. Therapies that target both coagulation and cyto-protection to dampen inflammation are likely to provide clinical benefits. APAC, a heparin proteoglycan mimetic, with antiplatelet (for collagen and thrombin) and anticoagulant (APAC) functions, acts at sites of vascular injury. Since both platelet and coagulation activation are intimately associated with inflammation, we studied APAC in a thrombo-inflammatory myocardial injury model.  Methods: WT or Nlrp3A350V mutant mice were either pre-treated (30 minutes before left anterior descending – LAD – coronary artery ligation) or post-treated (at the time of starting reperfusion) with APAC (0.5 mg/kg, intravenously) or PBS (control). After 30 min of ischemia, followed by 24 h of reperfusion (ischemia reperfusion injury, IRI), we examined the infarct size, thrombo-inflammatory biomarkers in blood, and conducted single-nuclei RNA sequencing on hearts and single-cell RNA sequencing on peripheral blood mononuclear cells (PBMCs).   Results: APAC pretreatment efficiently inhibited platelet activation and coagulation, as shown by reductions in plasma thrombin-antithrombin (TAT) and platelet factor 4 (PF4) levels and in infarct size. A decrease in myocardial IRI was associated with reduced infiltration of monocyte-derived macrophage, neutrophils and Nlrp3 inflammasome activation in heart, and circulation . The constitutively active Nlrp3A350V mutation at least partially abolished the effect of APAC, indicating that Nlrp3 suppression is important for APAC-mediated protection against IRI. Additionally, APAC alleviated myocardial fibrosis and improved left ventricular ejection fraction, cardiac output, and stroke volume at 28 days after myocardial IRI, indicating beneficial cardiac effects beyond the effects on acute tissue injury.  Conclusion: APAC restricted myocardial IRI, correlating with reduced infarct size, myocardial myeloid populations, and near-complete disappearance of neutrophils and Nlrp3 inflammasome activation in PBMCs. With its multifunctional vascular injury-targeting, antithrombotic, and anti-inflammatory properties, APAC holds potential for managing myocardial IRI.