Involvement of Endoplasmic Reticulum Stress-Mediated C/EBP Homologous Protein Activation in Coxsackievirus B3-Induced Acute Viral Myocarditis.

BACKGROUND This study tested the hypothesis whether endoplasmic reticulum (ER) stress/C/EBP homologous protein (CHOP) signaling is linked with coxsackievirus B3 (CVB3)-induced acute viral myocarditis (AVMC) in vivo. METHODS AND RESULTS AVMC was induced by intraperitoneal injection of 1000 tissue culture infectious dose (TCID50) of CVB3 virus in mice. In AVMC mouse hearts (n=11), ER stress and CHOP were significantly activated, and were linked to the induction of proapoptotic signaling including reduction of Bcl-2, activation of Bax and caspase 3, compared with the controls (n=10), whereas these could be markedly blocked by ER stress inhibitor tauroursodeoxycholic acid administration (n=11). Moreover, chemical inhibition of ER stress significantly attenuated cardiomyocytes apoptosis, and prevented cardiac troponin I elevation, ameliorated cardiac dysfunction assessed by both hemodynamic and echocardiographic analysis, reduced viral replication, and increased survival rate after CVB3 inoculation. We further discovered that genetic ablation of CHOP (n=10) suppressed cardiac Bcl-2/Bax ratio reduction and caspase 3 activation, and prevented cardiomyotes apoptosis in vivo, compared with wild-type receiving CVB3 inoculation (n=10). Strikingly, CHOP deficiency exhibited dramatic protective effects on cardiac damage, cardiac dysfunction, viral replication, and promoted survival in CVB3-caused AVMC. CONCLUSIONS Our data imply the involvement of ER stress/CHOP signaling in CVB3-induced AVMC via proapoptotic pathways, and provide a novel strategy for AVMC treatment.