Protease-Activated Receptor-2 Regulates the Innate Immune Response to Viral Infection in a Coxsackievirus B3–Induced Myocarditis

Abstract

Objectives This study sought to evaluate the role of protease-activated receptor-2 (PAR2) in coxsackievirus B3 (CVB3)–induced myocarditis. Background An infection with CVB3 leads to myocarditis. PAR2 modulates the innate immune response. Toll-like receptor-3 (TLR3) is crucial for the innate immune response by inducing the expression of the antiviral cytokine interferon-beta (IFNβ). Methods To induce myocarditis, wild-type (wt) and PAR2 knockout (ko) mice were infected with 105 plaque-forming units CVB3. Mice underwent hemodynamic measurements with a 1.2-F microconductance catheter. Wt and PAR2ko hearts and cardiac cells were analyzed for viral replication and immune response with plaque assay, quantitative polymerase chain reaction, Western blot, and immunohistochemistry. Results Compared with wt mice, PAR2ko mice and cardiomyocytes exhibited a reduced viral load and developed no myocarditis after infection with CVB3. Hearts and cardiac fibroblasts from PAR2ko mice expressed higher basal levels of IFNβ than wt mice did. Treatment with CVB3 and polyinosinic:polycytidylic acid led to higher IFNβ expression in PAR2ko than in wt fibroblasts and reduced virus replication in PAR2ko fibroblasts was abrogated by neutralizing IFNβ antibody. Overexpression of PAR2 reduced the basal IFNβ expression. Moreover, a direct interaction between PAR2 and Toll-like receptor 3 was observed. PAR2 expression in endomyocardial biopsies of patients with nonischemic cardiomyopathy was positively correlated with myocardial inflammation and negatively with IFNβ expression and left ventricular ejection fraction. Conclusions PAR2 negatively regulates the innate immune response to CVB3 infection and contributes to myocardial dysfunction. The antagonism of PAR2 is of therapeutic interest to strengthen the antiviral response after an infection with a cardiotropic virus.

Multiple roles of the coagulation protease cascade during virus infection

“…45 We found that murine embryonic CFs lacking PAR2 expressed higher levels of IFN-b and CCL5 expression after poly I:C stimulation compared with wild-type (WT) fibroblasts (Figure 4). 42 Taken together, these results indicate that PAR2 suppresses For personal use only. on April 29, 2019. by guest www.bloodjournal.org From TLR3-dependent expression of the antiviral pathway in both epithelial cells and CFs.…”

“…42 In vitro studies demonstrated that PAR2ko CFs either infected with CVB3 or stimulated with poly I:C expressed more IFN-b and CCL5 compared with WT cells. 42 Furthermore, activation of PAR2 inhibited poly I:C-induced phosphorylation of Stat1, which is activated downstream of IFN-b binding to its receptors. 42 These data suggest that is PAR2 suppresses the TLR3-TRIF-IFN-b pathway.…”

“…42 Furthermore, activation of PAR2 inhibited poly I:C-induced phosphorylation of Stat1, which is activated downstream of IFN-b binding to its receptors. 42 These data suggest that is PAR2 suppresses the TLR3-TRIF-IFN-b pathway. These results are consistent with previous studies by the Vogel …”

“…We found that PAR2ko mice exhibited strikingly less CVB3-induced myocarditis compared with WT mice (Table 1). 42 Interestingly, infected PAR2ko mice expressed increased levels of cardiac IFN-b compared with infected WT mice, which may explain the reduced levels of CVB3 in the heart. 42 In vitro studies demonstrated that PAR2ko CFs either infected with CVB3 or stimulated with poly I:C expressed more IFN-b and CCL5 compared with WT cells.…”

“…42 Interestingly, infected PAR2ko mice expressed increased levels of cardiac IFN-b compared with infected WT mice, which may explain the reduced levels of CVB3 in the heart. 42 In vitro studies demonstrated that PAR2ko CFs either infected with CVB3 or stimulated with poly I:C expressed more IFN-b and CCL5 compared with WT cells. 42 Furthermore, activation of PAR2 inhibited poly I:C-induced phosphorylation of Stat1, which is activated downstream of IFN-b binding to its receptors.…”