Abstract 19779: Nod2 Knock Down Improves Left Ventricular Function and Attenuates Pathophysiological Key Mechanisms in Experimental Coxsackievirus B3-induced Myocarditis

Abstract

Introduction: Nucleotide binding oligomerization domain 2 (NOD2) is a cytoplasmatic pattern recognition receptor belonging to the NOD-like receptor family, which is part of the innate immune system. Hypothesis: Since NOD2 recognises ssRNA and Coxsackievirus B3 (CVB3) is a ssRNA virus, we hypothesised that NOD2 regulates cardiac inflammatory signaling in CVB3-induced myocarditis. Methods: Gene expression was analyzed on endomyocardial biopsies (EMBs) taken from ejection fraction- and age-matched CVB3+ (n=10) and CVB3- control (n=7) patients and on EMBs from CVB3+patients who spontaneously eliminated CVB3 (n=6). NOD2 -/- mice and wild-type (wt) C57BL/6 mice were i.p. infected with 5 x 105 p.f.u. of CVB3. Seven days after infection, mice were hemodynamically characterized, and left ventricles (LV) were isolated. Results: NOD2 mRNA expression was 3.7-fold (p<0.05) increased in CVB3+ vs CVB3- control patients. Interestingly, NOD2 and Nrlp3 mRNA expression significantly dropped in EMBs of CVB3+ patients who spontaneously eliminated CVB3. In addition, LV NOD2 mRNA expession was increased in CVB3 vs wt mice. NOD2-/- CVB3 mice showed an improved LV function compared to CVB3 wt mice. In parallel, infiltration of CD4-, CD8-, CD11b- and CD68-positive cells was less pronounced in CVB3-infected NOD2-/- mice compared to CVB3 wt mice. Concomitantly, LV mRNA levels for TNF-alpha, IL-1ß, IFN-gamma, IFN-ß, TLR4, and MyD88 were 3.9-fold, 2.9-fold, 5.3-fold, 8.0-fold, 1.4-fold and 2.0-fold reduced in CVB3 NOD2-/- vs CVB3 wt mice, respectively (p<0.05). LV viral copy number was lower in CVB3 NOD2-/- vs CVB3 wt mice. CVB3-infected NOD2-/- mice exhibited less pronounced cardiac fibrosis, as indicated by lower collagen I and III mRNA expression and a 2.7-fold (p<0.0005) lower collagen I/III protein ratio. NOD2 knockdown in HL-1 cardiomyocytes was associated with a decreased inflammatory response, a 1.4-fold (p<0.05) lower CVB3 copy number, and a 3.4-fold (p<0.005) reduced TLR4 protein expression and underlying signaling. Conclusions: NOD2 knock down improves LV function and attenuates pathophysiological key mechanisms in acute CVB3-induced myocarditis mice. Modulation of NOD2 might represent a promising therapeutic strategy to treat viral myocarditis.