Role of Coxsackievirus B3-Induced Immune Responses in the Transition from Myocarditis to Dilated Cardiomyopathy and Heart Failure

SAR Analysis of Novel Coxsackie virus A9 Capsid Binders

Enterovirus infections are common in humans, yet there are no approved antiviral treatments. In this study we concentrated on inhibition of one of the Enterovirus B (EV-B), namely Coxsackievirus A9 (CVA9), using a combination of medicinal chemistry, virus inhibition assays, structure determination from cryogenic electron microscopy and molecular modeling, to determine the structure activity relationships for a promising class of novel N-phenylbenzylamines. Of the new 29 compounds synthesized, 10 had half maximal effective concentration (EC50) values between 0.64-10.46 μM, and of these, 7 had 50% cytotoxicity concentration (CC50) values higher than 200 μM. In addition, this new series of compounds showed promising physicochemical properties and act through capsid stabilization, preventing capsid expansion and subsequent release of the genome.

N6-Methyladenosine Positively Regulates Coxsackievirus B3 Replication

Enteroviruses such as coxsackievirus B3 are identified as a common cause of viral myocarditis, but the potential mechanism of its replication and pathogenesis are largely unknown. The genomes of a variety of viruses contain N6-methyladenosine (m6A), which plays important roles in virus replication. Here, by using the online bioinformatics tools SRAMP and indirect immunofluorescence assay (IFA), we predict that the CVB3 genome contains m6A sites and found that CVB3 infection could alter the expression and cellular localization of m6A-related proteins. Moreover, we found that 3-deazaadenosine (3-DAA), an m6A modification inhibitor, significantly decreased CVB3 replication. We also observed that the m6A methyltransferases methyltransferase-like protein 3 (METTL3) and METTL14 play positive roles in CVB3 replication, whereas m6A demethylases fat mass and obesity-associated protein (FTO) or AlkB homolog 5 (ALKBH5) have opposite effects. Knockdown of the m6A binding proteins YTH domain family protein 1 (YTHDF1), YTHDF2 and YTHDF3 strikingly decreased CVB3 replication. Finally, the m6A site mutation in the CVB3 genome decreased the replication of CVB3 compared with that in the CVB3 wild-type (WT) strain. Taken together, our results demonstrated that CVB3 could exploit m6A modification to promote viral replication, which provides new insights into the mechanism of the interaction between CVB3 and the host.

Role of TGFβ-producing regulatory T cells in scleroderma and end-stage organ failure

Regulatory T cells (Tregs) are crucial immune cells that initiate a tolerable immune response. Transforming growth factor-beta (TGFβ) is a key cytokine produced by Tregs and plays a significant role in stimulating tissue fibrosis. Systemic sclerosis, an autoimmune disease characterized by organ fibrosis, is associated with an overrepresentation of regulatory T cells. This review aims to identify Treg-dominant tolerable host immune reactions and discuss their association with scleroderma and end-stage organ failure. End-stage organ failures, including heart failure, liver cirrhosis, uremia, and pulmonary fibrosis, are frequently linked to tissue fibrosis. This suggests that TGFβ-producing Tregs are involved in the pathogenesis of these conditions. However, the exact significance of TGFβ and the mechanisms through which it induces tolerable immune reactions during end-stage organ failure remain unclear. A deeper understanding of these mechanisms could lead to improved preventive and therapeutic strategies for these severe diseases.

Baicalein suppresses Coxsackievirus B3 replication by inhibiting caspase-1 and viral protease 2A

Myocarditis is an inflammatory disease of the cardiac muscle and one of the primary causes of dilated cardiomyopathy. Group B coxsackievirus (CVB) is one of the leading causative pathogens of viral myocarditis, which primarily affects children and young adults. Due to the lack of vaccines, the development of antiviral medicines is crucial to controlling CVB infection and the progression of myocarditis. In this study, we investigated the antiviral effect of baicalein, a flavonoid extracted from Scutellaria baicaleinsis. Our results demonstrated that baicalein treatment significantly reduced cytopathic effect and increased cell viability in CVB3-infected cells. In addition, significant reductions in viral protein 3D, viral RNA, and viral particles were observed in CVB3-infected cells treated with baicalein. We found that baicalein exerted its inhibitory effect in the early stages of CVB3 infection. Baicalein also suppressed viral replication in the myocardium and effectively alleviated myocarditis induced by CVB3 infection. Our study revealed that baicalein exerts its antiviral effect by inhibiting the activity of caspase-1 and viral protease 2A. Taken together, our findings demonstrate that baicalein has antiviral activity against CVB3 infection and may serve as a potential therapeutic option for the myocarditis caused by enterovirus infection.

Baicalein alleviates cardiomyocyte death in EAM mice by inhibiting the JAK-STAT1/4 signalling pathway

BACKGROUND

The experimental autoimmune myocarditis (EAM) model is valuable for investigating myocarditis pathogenesis. M1-type macrophages and CD4+T cells exert key pathogenic effects on EAM initiation and progression. Baicalein (5,6,7-trihydroxyflavone, C15H10O5, BAI), which is derived from the Scutellaria baicalensis root, is a primary bioactive compound with potent anti-inflammatory and antioxidant properties. BAI exerts good therapeutic effects against various autoimmune diseases; however, its effect in EAM has not been thoroughly researched.

PURPOSE

This study aimed to explore the possible inhibitory effect of BAI on M1 macrophage polarisation and CD4+T cell differentiation into Th1 cells via modulation of the JAK-STAT1/4 signalling pathway, which reduces the secretion of pro-inflammatory factors, namely, TNF-α and IFN-γ, and consequently inhibits TNF-α- and IFN-γ-triggered apoptosis in cardiomyocytes of the EAM model mice.

STUDY DESIGN AND METHODS

Flow cytometry, immunofluorescence, real-time quantitative polymerase chain reaction (q-PCR), and western blotting were performed to determine whether BAI alleviated M1/Th1-secreted TNF-α- and IFN-γ-induced myocyte death in the EAM model mice through the inhibition of the JAK-STAT1/4 signalling pathway.

RESULTS

These results indicate that BAI intervention in mice resulted in mild inflammatory infiltrates. BAI inhibited JAK-STAT1 signalling in macrophages both in vivo and in vitro, which attenuated macrophage polarisation to the M1 type and reduced TNF-α secretion. Additionally, BAI significantly inhibited the differentiation of CD4+T cells to Th1 cells and IFN-γ secretion both in vivo and in vitro by modulating the JAK-STAT1/4 signalling pathway. This ultimately led to decreased TNF-α and IFN-γ levels in cardiac tissues and reduced myocardial cell apoptosis.

CONCLUSION

This study demonstrates that BAI alleviates M1/Th1-secreted TNF-α- and IFN-γ-induced cardiomyocyte death in EAM mice by inhibiting the JAK-STAT1/4 signalling pathway.

Complement components regulates ferroptosis in CVB3 viral myocarditis by interatction with TFRC

BACKGROUND

Dysregulated cell death machinery and an excessive inflammatory response in Coxsackievirus B3(CVB3)-infected myocarditis are hallmarks of an abnormal host response. Complement C4 and C3 are considered the central components of the classical activation pathway and often participate in the response process in the early stages of virus infection.

METHODS

In our study, we constructed a mouse model of CVB3-related viral myocarditis via intraperitoneal injection of Fer-1 and detected myocarditis and ferroptosis markers in the mouse myocardium. Then, we performed co-IP and protein mass spectrometry analyses to explore which components interact with the ferroptosis gene transferrin receptor (TFRC). Finally, functional experiments were conducted to verify the role of complement components in regulating ferroptosis in CVB3 infection.

RESULTS

It showed that the ferroptosis inhibitor Fer-1 could alleviate the inflammation in viral myocarditis as well as ferroptosis. Mechanistically, during CVB3 infection, the key factor TFRC was activated and inhibited by Fer-1. Fer-1 effectively prevented the consumption of complement C3 and overload of the complement product C4b. Interestingly, we found that TFRC directly interacts with complement C4, leading to an increase in the product of C4b and a decrease in the downstream complement C3. Functional experiments have also confirmed that regulating the complement C4/C3 pathway can effectively rescue cell ferroptosis caused by CVB3 infection.

CONCLUSIONS

In this study, we found that ferroptosis occurs through crosstalk with complement C4 in viral myocarditis through interaction with TFRC and that regulating the complement C4/C3 pathway may rescue ferroptosis in CVB3-infected cardiomyocytes.