Abstract Background Heart failure with preserved ejection fraction (HFpEF) is associated with cardiac inflammatory responses, indicating a potential role of the immune system in the pathology of diastolic dysfunction. The cytoplasmatic pattern recognition receptor, nucleotide binding oligomerization domain 2 (NOD2) belongs to the innate immune system and induces among others the NLRP3 inflammasome, known to be involved in myocarditis and coronary heart disease. Purpose The aim of this study was to explore the role of NOD2 in Angiotensin II (AngII)-induced diastolic heart failure. Methods In NOD2−/− knock down and C57Bl6/j-wild type (WT) mice, diastolic dysfunction was induced by subcutaneous administration of 1.4mg/kg*day–1 AngII. Twenty-one days after first AngII administration, left ventricular (LV) function was evaluated by pressure tip catheter. Cardiac fibrosis, inflammation, and the expression of NOD2 and the NLRP3 component Apoptosis-associated speck like protein containing a caspase recruitment domain (ASC) were determined via immunohistochemistry, real-time PCR or Western Blot. Results LV NOD2 mRNA expression was 2.3-fold (p<0.0005) and 1.9-fold (p<0.0005) lower in NOD2−/− control and NOD2−/− AngII mice compared to their respective WT littermates. In parallel, LV protein expression of the downstream NLRP3 component Apoptosis-associated speck like protein containing a caspase recruitment domain (ASC) was 1.5-fold (p<0.05) lower in NOD2−/− AngII mice versus WT AngII mice, whereas LV protein IL-1β levels were unchanged. LV diastolic dysfunction was more pronounced in NOD2−/− AngII mice versus WT AngII mice, as displayed by a 19% (p<0.05) increased LV relaxation time and 24% (p<0.057) impaired dP/dtmin, with no changes in the ejection fraction (EF: NOD2−/− AngII 72.5%±5.4 versus WT AngII 65.6±3.5). In parallel, LV presence of CD68-positive cells was 1.8-fold (p<0.05) higher in NOD2−/− AngII compared to WT AngII mice. Concomitantly, NOD2−/− AngII mice displayed 1.3-fold (p<0.05) and 1.7-fold (p<0.05) higher LV mRNA expression of the chemokine macrophage inflammatory protein (MIP)-2 and monocyte chemotactant protein (MCP)-1 compared to WT AngII mice, respectively. Furthermore, cardiac interstitial fibrosis in NOD2−/− mice with AngII-induced diastolic dysperformance was more pronounced versus the WT AngII group, as indicated by a 2.0-fold (p<0.0005), 2.0-fold, and 1.6-fold (p<0.05) higher LV ColI/ColIII ratio, and TGF-β and TIMP-1 mRNA expression, respectively. Conclusion NOD2−/− deteriorates LV diastolic dysfunction and worsens pathophysiological key mechanisms in mice with AngII-induced diastolic heart failure.

Abstract Background The alarmin S100A8/A9 has been shown to be of importance in several inflammatory cardiovascular disorders. We recently demonstrated the pivotal role of cardiac S100A8/A9 in human and experimental Coxsackievirus B3 (CVB3)-induced myocarditis (MC). Purpose We aimed to evaluate whether serum S100A8/A9 levels are a marker in patients with a recent onset of MC Methods Serum S100A8/A9, hsCRP, and NT pro-BNP levels were analyzed in patients with a recent onset of MC (≤30 days (d), n=29; ejection fraction (EF): 44.3%±13%), dilated cardiomyopathy patients with inflammation (DCMi: n=112; EF: 28.8%±12%) or without inflammation (DCM: n=58; EF: 26.7%±9%), and controls (co: n=25; EF: 68.5%±5%). Blood samples and endomyocardial biopsies (EMB) were collected at time point (T1). In a subgroup, S100A8/A9 serum levels and EMB were available at T1 (n=10) and follow-up (T2, n=10, mean follow-up 8 months). Results MC ≤30 d patients showed a 4.5-fold (p<0.0001), 19.3-fold (p<0.0001), and 4.0-fold (p<0.0001) increase in S100A8/A9, hsCRP, NT pro-BNP levels vs co, respectively. S100A8/A9 levels correlated with the disease activity, displayed by EMB counts of inflammatory cells (CD3: r=0.464, p=0.0128, XY pairs=28, LFA-1: r=0.551, p=0.002, XY pairs=28, Mac-1: r=0.418, p=0.026, XY pairs=28), and the EF (r=0.545, p=0.0027, XY pairs=28). MC ≤30 d patients showed an association between serum S100A8/A9 levels and EMB S100A8 (r=0.482, p=0.060, XY pairs=16), S100A9 (r=0.441, p=0.088, XY pairs=16), nucleotide-binding oligomerization domain containing-protein 2 (NOD2, r=0.55, p=0.035, XY=15), and Nod-like receptor family, pyrin domain-containing 3 protein (NLRP3, r=0.52, p=0.048, XY=15) mRNA levels. Also EMB S100A8 and S100A9 mRNA levels showed a significant correlation with EMB NOD2 and NLRP3 mRNA expression. Serum S100A8/A9 levels were increased by 3.0-fold (p<0.0001) and 1.8-fold (p=0.0005) in DCMi (n=112), and DCM (n=58) patients vs co, respectively. However, the S100A8/A9 levels of DCMi and DCM patients were 1.5-fold (p=0.07) and 2.5-fold (p<0.0001) lower vs MC ≤30 d patients. ROC analyses of S100A8/A9 in MC ≤30 d provided a cut-off of 583 ng/ml with a specificity=92%, sensitivity=86.2%, a PPV=92.6%, a NPV=85.2%, and an AUC=0.934 vs co, which was superior to hsCRP (cut-off=5 mg/l): specificity=95.8%, sensitivity=58.6%, a PPV=94.4%, a NPV=65.7%, AUC=0.885. In the subgroup, S100A8/A9 levels decreased after heart failure medication (T1: 2454±1931 ng/ml vs T2: 934.4±552 ng/ml; p=0.002), reflected by a decrease of EMB inflammatory cells. Baseline serum S100A8/A9 levels predicted the change in EMB CD3 and Mac-1. Conclusions These results support an additional value for S100A8/A9 serum levels as a potential diagnostic biomarker and as a tool to monitor the course of the disease. We provide first evidence that S100A8/A9 is connected to the NOD2-NLRP3 pathway in these patients. Acknowledgement/Funding Novartis

The alarmins S100A8 and S100A9, which preferentially form the S100A8/S100A9 heterodimer, are danger-associated molecular pattern molecules and have been shown to be of importance in several cardiovascular disorders. Their role in myocarditis has not been explored yet. The aim of the present study