Macrophage-Specific Coxsackievirus and Adenovirus Receptor Deletion Enhances Macrophage M1 Polarity in CVB3-Induced Myocarditis.

The coxsackievirus and adenovirus receptor (CAR) is very well known as an epithelial tight junction and cardiac intercalated disc protein; it mediates attachment and infection via the coxsackievirus B3 (CVB3) and type 5 adenovirus. Macrophages play important roles in early immunity during viral infections. However, the role of CAR in macrophages is not well studied in relation to CVB3 infection. In this study, the function of CAR was observed in the Raw264.7 mouse macrophage cell line. CAR expression was stimulated by treatment with lipopolysaccharide (LPS) and tumor necrosis factor-α (TNF-α). In thioglycollate-induced peritonitis, the peritoneal macrophage was activated and CAR expression was increased. The macrophage-specific CAR conditional knockout mice (KO) were generated from lysozyme Cre mice. The expression of inflammatory cytokine (IL-1ß and TNF-α) was attenuated in the KO mice's peritoneal macrophage after LPS treatment. In addition, the virus was not replicated in CAR-deleted macrophages. The organ virus replication was not significantly different in both wild-type (WT) and KO mice at days three and seven post-infection (p.i). However, the inflammatory M1 polarity genes (IL-1ß, IL-6, TNF-α and MCP-1) were significantly increased, with increased rates of myocarditis in the heart of KO mice compared to those of WT mice. In contrast, type1 interferon (IFN-α and ß) was significantly decreased in the heart of KO mice. Serum chemokine CXCL-11 was increased in the KO mice at day three p.i. compared to the WT mice. The attenuation of IFN-α and ß in macrophage CAR deletion induced higher levels of CXCL-11 and more increased CD4 and CD8 T cells in KO mice hearts compared to those of WT mice at day seven p.i. These results demonstrate that macrophage-specific CAR deletion increased the macrophage M1 polarity and myocarditis in CVB3 infection. In addition, chemokine CXCL-11 expression was increased, and stimulated CD4 and CD8 T cell activity. Macrophage CAR may be important for the regulation of innate-immunity-induced local inflammation in CVB3 infection.

Protein Kinase B2 (PKB2/AKT2) Is Essential for Host Protection in CVB3-Induced Acute Viral Myocarditis.

Protein kinase B2 (AKT2) is involved in various cardiomyocyte signaling processes, including those important for survival and metabolism. Coxsackievirus B3 (CVB3) is one of the most common pathogens that cause myocarditis in humans. The role of AKT2 in CVB3 infection is not yet well understood. We used a cardiac-specific AKT2 knockout (KO) mouse to determine the role of AKT2 in CVB3-mediated myocarditis. CVB3 was injected intraperitoneally into wild-type (WT) and KO mice. The mice's survival rate was recorded: survival in KO mice was significantly decreased compared with WT mice (WT vs. KO: 73.3 vs. 27.1%). Myocardial damage and inflammation were significantly increased in the hearts of KO mice compared with those of WT mice. Moreover, from surface ECG, AKT2 KO mice showed a prolonged atria and ventricle conduction time (PR interval, WT vs. KO: 47.27 ± 1.17 vs. 64.79 ± 7.17 ms). AKT2 deletion induced severe myocarditis and cardiac dysfunction due to CVB3 infection. According to real-time PCR, the mRNA level of IL-1, IL-6, and TNF-α decreased significantly in KO mice compared with WT mice on Days 5 after infection. In addition, innate immune response antiviral effectors, Type I interferon (interferon-α and ß), and p62, were dramatically suppressed in the heart of KO mice. In particular, the adult cardiac myocytes isolated from the heart showed high induction of TLR4 protein in KO mice in comparison with WT. AKT2 deletion suppressed the activation of Type I interferon and p62 transcription in CVB3 infection. In cardiac myocytes, AKT2 is a key signaling molecule for the heart from damage through the activation of innate immunity during acute myocarditis.

Vascular Endothelial Integrity Affects the Severity of Enterovirus-Mediated Cardiomyopathy.

Coxsackievirus and adenovirus receptor (CAR) is present in epithelial and vascular endothelial cell junctions. We have previously shown a hemorrhagic phenotype in germ-line CAR knock-out mouse embryos; we have also found that CAR interacts with ZO-1 and ß-catenin. However, the role of CAR in vascular endothelial junction permeability has not been proven. To understand the roles of CAR in the vascular endothelial junctions, we generated endothelium-specific CAR knockout (CAR-eKO) mice. In the absence of CAR, the endothelial cell layer showed an increase in transmembrane electrical resistance (TER, Ω) and coxsackievirus permeability. Evans blue dye and 70 kDa dextran-FITC were delivered by tail vein injection. We observed increased vascular permeability in the hearts of adult CAR-eKO mice compare with wild-type (WT) mice. There was a marked increase in monocyte and macrophage penetration into the peritoneal cavity caused by thioglycolate-induced peritonitis. We found that CAR ablation in endothelial cells was not significantly increased coxsackievirus B3 (CVB3) induced myocarditis in murine model. However, tissue virus titers were significantly higher in CAR-eKO mice compared with WT. Moreover, CVB3 was detected in the brain of CAR-eKO mice. Endothelial CAR deletion affects the expression of major endothelial junction proteins, such as cadherin and platelet endothelial cell adhesion molecule-1 (PECAM-1) in the cultured endothelial cells as well as liver vessel. We suggest that CAR expression is required for normal vascular permeability and endothelial tight junction homeostasis. Furthermore, CVB3 organ penetration and myocarditis severities were dependent on the endothelial CAR level.

Inhibition of RNA Helicase Activity Prevents Coxsackievirus B3-Induced Myocarditis in Human iPS Cardiomyocytes.

AIMS: Coxsackievirus B3 (CVB3) is known to be an important cause of myocarditis and dilated cardiomyopathy. Enterovirus-2C (E2C) is a viral RNA helicase. It inhibits host protein synthesis. Based on these facts, we hypothesize that the inhibition of 2C may suppress virus replication and prevent enterovirus-mediated cardiomyopathy. METHODS AND RESULTS: We generated a chemically modified enterovirus-2C inhibitor (E2CI). From the in vitro assay, E2CI was showed strong antiviral effects. For in vivo testing, mice were treated with E2CI intraperitoneally injected daily for three consecutive days at a dose of 8mg/kg per day, after CVB3 post-infection (p.i) (CVB3 + E2CI, n = 33). For the infected controls (CVB3 only, n = 35), mice were injected with PBS (phosphate buffered saline) in a DBA/2 strain to establish chronic myocarditis. The four-week survival rate of E2CI-treated mice was significantly higher than that of controls (92% vs. 71%; p < 0.05). Virus titers and myocardial damage were significantly reduced in the E2CI treated group. In addition, echocardiography indicated that E2CI administration dramatically maintained mouse heart function compared to control at day 28 p.i chronic stage (LVIDD, 3.1 ± 0.08 vs. 3.9 ± 0.09, p < 0.01; LVDS, 2.0 ± 0.07 vs. 2.5 ± 0.07, p < 0.001; FS, 34.8 ± 1.6% vs. 28.5 ± 1.5%; EF, 67. 9 ± 2.9% vs. 54.7 ± 4.7%, p < 0.05; CVB3 + E2CI, n = 6 vs. CVB3, n = 4). Moreover, E2CI is effectively worked in human iPS (induced pluripotent stem cell) derived cardiomyocytes. CONCLUSION: Enterovirus-2C inhibitor (E2CI) was significantly reduced viral replication, chronic myocardium damage, and CVB3-induced mortality in DBA/2 mice. These results suggested that E2CI is a novel therapeutic agent for the treatment of enterovirus-mediated diseases.