Abstract 15323: Par2 Deficiency Protects the Heart Against Cvb3-Induced Myocarditis Via Upregulation of Toll-Like Receptor-3 Mediated INFβ Expression
Introduction: The protease activated receptor 2 (PAR2) is activated by serine proteases, such as the complex of tissue factor (TF)/ factor VII (FVII) and factor X (FX). Its proteolytic cleavage leads to the expression of proinflammatory cytokines and reduction of antiviral cytokines such as interferon (INF) β. In this study, the role of PAR2 for the antiviral and inflammatory response upon infection with Coxsackievirus B3 was examined with a special focus on the pathogenesis of myocarditis and cardiac remodelling.
Methods: To investigate the specific role of the PAR2 receptor in viral induced myocarditis, wt and PAR2 Knock-out mice were infected with CVB3. Eight days post infection (p.i.) the animals were sacrificed and hearts were collected. Plaque assays and real time PCR (qPCR) were performed. Fibroblasts were isolated from embryonic mouse hearts (E12.5) and infected with CVB3 or stimulated with a specific Toll-like-receptor (TLR) - 3 agonist and analysis performed thereafter.
Results: PAR2 ko mice exhibited almost no myocarditis after infection with CVB3 compared to wt mice. Virus replication and virus titre were reduced in PAR2ko compared to wt hearts (virus titre wt: 6.8E+06 PfU/ml vs PAR2ko 6.3E+05 PfU/ml, p<0.003). Myocardial inflammation was increased in wt compared to PAR2 ko mice (x-fold increase for IFNβ mRNA: 7.07±1.50 wt vs. 2.67±2.41 PAR2ko, p<0.01 and for RANTES mRNA 437±127 vs 65±22, p<0.05). The endogenous antiviral IFNβ expression was 5 times higher in PAR2ko hearts. Stat1 phosphorylation was significantly increased in PAR2 deficient hearts and fibroblasts. Fibroblasts lacking PAR2 exhibited an increased expression of Toll-like receptors. In line, the IFNβ production upon CVB3 infection and upon stimulation with a specific TLR-3 agonist (poly(I:C)) was significantly increased in PAR2ko fibroblasts (p<0.05). The co-stimulation of PAR2 with a specific PAR2 agonist led to an inhibition of the poly(I:C) induced Stat1 phosphorylation in fibroblasts overexpressing PAR2.
Conclusion: The expression and activation of PAR2 is crucial for the development of CVB3 induced viral myocarditis. PAR2 deficiency increases the Toll-like receptor-3 mediated INFß expression and release from cardiac fibroblasts.
- © 2011 by American Heart Association, Inc.