P5443NOD2 knock down worsens diastolic dysfunction in murine angiotensin II-induced heart failure

Abstract

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.