Background-ST2 is an interleukin (IL)-1 receptor family member with membrane-bound (ST2L) and soluble (sST2) isoforms, and sST2 is a biomarker for poor outcome in patients with myocardial infarction (MI). IL-33, the recently discovered ligand for ST2, activates nuclear factor B and thus may regulate apoptotic cell death. We tested the hypothesis that IL-33 is cardioprotective after MI through ST2 signaling. Methods and Results-IL-33 protected cultured cardiomyocytes from hypoxia-induced apoptosis, and this cardioprotection was partially inhibited by sST2. IL-33 induced expression of the antiapoptotic factors XIAP, cIAP1, and survivin. To define the cardioprotective role of IL-33 in vivo, we performed a blinded and randomized study of ischemia/reperfusion in rats. IL-33 reduced cardiomyocyte apoptosis, suppressed caspase-3 activity, and increased expression of IAP family member proteins. IL-33 decreased both infarct and fibrosis volumes at 15 days; furthermore, both echocardiographic and hemodynamic studies revealed that IL-33 improved ventricular function. To determine whether cardioprotection by IL-33 is mediated through ST2 signaling, a randomized and blinded study of ST2

OBJECTIVE We investigated the prognostic performance of ST2 with respect to cardiovascular death (CVD) and heart failure (HF) in patients with non–ST-elevation acute coronary syndrome (NSTE-ACS) in a large multinational trial. BACKGROUND Myocytes that are subjected to mechanical stress secrete ST2, a soluble interleukin-1 receptor family member that is associated with HF after STE-ACS. METHODS We measured ST2 with a high-sensitivity assay in all available baseline samples (N = 4426) in patients enrolled in the Metabolic Efficiency With Ranolazine for Less Ischemia in the Non–ST-Elevation Acute Coronary Syndrome Thrombolysis in Myocar-dial Infarction 36 (MERLIN-TIMI 36), a placebo-controlled trial of ranolazine in NSTE-ACS. All events, including cardiovascular death and new or worsening HF, were adjudicated by an independent events committee. RESULTS Patients with ST2 concentrations in the top quartile (>35 μg/L) were more likely to be older and male and have diabetes and renal dysfunction. ST2 was only weakly correlated with troponin and B-type natriuretic peptide. High ST2 was associated with increased risk for CVD/HF at 30 days (6.6% vs 1.6%, P <0.0001) and 1 year (12.2% vs 5.2%, P <0.0001). The risk associated with ST2 was significant after adjustment for clinical covariates and biomarkers (adjusted hazard ratio CVD/HF 1.90, 95% CI 1.15–3.13 at 30 days, P = 0.012; 1.51, 95% CI 1.15–1.98 at 1 year, P = 0.003), with a significant integrated discrimination improvement (P < 0.0001). No significant interaction was found between ST2 and ranolazine (Pinteraction = 0.15). CONCLUSIONS ST2 correlates weakly with biomarkers of acute injury and hemodynamic stress but is strongly associated with the risk of HF after NSTE-ACS. This biomarker and related pathway merit further investigation as potential therapeutic targets for patients with ACS at risk for cardiac remodeling.

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