N-Acetyl cysteine effectively alleviates Coxsackievirus B-Induced myocarditis through suppressing viral replication and inflammatory response

Viral myocarditis: From molecular mechanisms to therapeutic prospects

Myocarditis is characterized as local or diffuse inflammatory lesions in the myocardium, primarily caused by viruses and other infections. It is a common cause of sudden cardiac death and dilated cardiomyopathy. In recent years, the global prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the widespread vaccination have coincided with a notable increase in the number of reported cases of myocarditis. In light of the potential threat that myocarditis poses to global public health, numerous studies have sought to elucidate the pathogenesis of this condition. However, despite these efforts, effective treatment strategies remain elusive. To collate the current research advances in myocarditis, and thereby provide possible directions for further research, this review summarizes the mechanisms involved in viral invasion of the organism and primarily focuses on how viruses trigger excessive inflammatory responses and in result in different types of cell death. Furthermore, this article outlines existing therapeutic approaches and potential therapeutic targets for the acute phase of myocarditis. In particular, immunomodulatory treatments are emphasized and suggested as the most extensively studied and clinically promising therapeutic options.

COVID-19 vaccine adverse events: Evaluating the pathophysiology with an emphasis on sulfur metabolism and endotheliopathy

In this narrative review, we assess the pathophysiology of severe adverse events that presented after vaccination with DNA and mRNA vaccines against COVID-19. The focus is on the perspective of an undersulfated and degraded glycocalyx, considering its impact on immunomodulation, inflammatory responses, coagulation and oxidative stress. The paper explores various factors that lead to glutathione and inorganic sulfate depletion and their subsequent effect on glycocalyx sulfation and other metabolites, including hormones. Components of COVID-19 vaccines, such as DNA and mRNA material, spike protein antigen and lipid nanoparticles, are involved in possible cytotoxic effects. The common thread connecting these adverse events is endotheliopathy or glycocalyx degradation, caused by depleted glutathione and inorganic sulfate levels, shear stress from circulating nanoparticles, aggregation and formation of protein coronas; leading to imbalanced immune responses and chronic release of pro-inflammatory cytokines, ultimately resulting in oxidative stress and systemic inflammatory response syndrome. By understanding the underlying pathophysiology of severe adverse events, better treatment options can be explored.

N-Acetylcysteine Inhibits Coxsackievirus B3 Replication by Downregulating Eukaryotic Translation Elongation Factor 1 Alpha 1

Group B Coxsackieviruses (CVB) are one of the causative pathogens of myocarditis, which may progress to cardiomyopathy. The pathogenesis of CVB is not fully understood, and effective antiviral therapy is not available. N-acetylcysteine (NAC), the classic antioxidant, has been used in clinical practice for several decades to treat various medical conditions. In this study, the anti-CVB effect of NAC was investigated. We show that NAC dramatically suppressed viral replication and alleviated cardiac injury induced by CVB3. To further study the antiviral mechanism of NAC, RNA-sequencing was performed for CVB3-infected cells with NAC treatment. We found that eukaryotic elongation factor 1 alpha 1 (EEF1A1) is one of the most upregulated genes in CVB3-infected cells. However, EEF1A2, the highly homologous isoform of EEF1A1, remains unchanged. EEF1A1 expression was significantly suppressed by NAC treatment in CVB3-infected cells, while EEF1A2 was not affected. eEF1A1 knockdown significantly inhibited CVB3 replication, implicating that eEF1A1 facilitates viral replication. Importantly, we show that eEF1A1, which was not expressed in the myocardia of newborn mice, was significantly upregulated by CVB3 infection. NAC markedly downregulated the expression of eEF1A1 but not eEF1A2 in the myocardia of CVB3-infected mice. Furthermore, NAC accelerated eEF1A1 degradation by promoting autophagy in CVB3-infected cells. We show that p62, one of the critical adaptors of autophagic targets, interacts with eEF1A1 and was downregulated in CVB3-infected cells upon NAC treatment. Taken together, this study demonstrated that NAC shows a potent anti-CVB effect through the downregulation of eEF1A1.

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.

Leucoverdazyls as Novel Potent Inhibitors of Enterovirus Replication

Enteroviruses (EV) are important pathogens causing human disease with various clinical manifestations. To date, treatment of enteroviral infections is mainly supportive since no vaccination or antiviral drugs are approved for their prevention or treatment. Here, we describe the antiviral properties and mechanisms of action of leucoverdazyls-novel heterocyclic compounds with antioxidant potential. The lead compound, 1a, demonstrated low cytotoxicity along with high antioxidant and virus-inhibiting activity. A viral strain resistant to 1a was selected, and the development of resistance was shown to be accompanied by mutation of virus-specific non-structural protein 2C. This resistant virus had lower fitness when grown in cell culture. Taken together, our results demonstrate high antiviral potential of leucoverdazyls as novel inhibitors of enterovirus replication and support previous evidence of an important role of 2C proteins in EV replication.

Anisomycin inhibits Coxsackievirus B replication by promoting the lysosomal degradation of eEF1A1

Group B Coxsackieviruses (CVB) are non-enveloped small RNA viruses in the genus Enterovirus, family Picornaviridae. CVB infection causes diverse conditions from common cold to myocarditis, encephalitis, and pancreatitis. No specific antiviral is available for the treatment of CVB infection. Anisomycin, a pyrrolidine-containing antibiotic and translation inhibitor, was reported to inhibit the replication of some picornaviruses. However, it is unknown if anisomycin can act as an antiviral against CVB infection. Here we observed that anisomycin showed potent inhibition on CVB type 3 (CVB3) infection with negligible cytotoxicity when applied at the early stage of virus infection. Mice infected with CVB3 showed markedly alleviated myocarditis with reduced viral replication. We found that CVB3 infection significantly increased the transcription of eukaryotic translation elongation factor 1 alpha 1 (eEF1A1). CVB3 replication was suppressed by EEF1A1 knockdown, while elevated by EEF1A1 overexpression. Similar to the effect of CVB3 infection, EEF1A1 transcription was increased in response to anisomycin treatment. However, eEF1A1 protein level was decreased with anisomycin treatment in a dose-dependent manner in CVB3-infected cells. Moreover, anisomycin promoted eEF1A1 degradation, which was inhibited by the treatment of chloroquine but not MG132. We demonstrated that eEF1A1 interacted with the heat shock cognate protein 70 (HSP70), and eEF1A1 degradation was inhibited by LAMP2A knockdown, implicating that eEF1A1 is degraded through chaperone-mediated autophagy. Taken together, we demonstrated that anisomycin, which inhibits CVB replication through promoting the lysosomal degradation of eEF1A1, could be a potential antiviral candidate for the treatment of CVB infection.

Antiviral Activity of trans-Hexenoic Acid against Coxsackievirus B and Enterovirus A71

Enterovirus infections are life-threatening viral infections which occur mainly among children and are possible causes of viral outbreak. Until now, treatment and management of infections caused by members of the genus Enterovirus largely depended on supportive care, and no antiviral medications are currently approved for the treatment of most of these infections. The urgency of discovering new therapeutic options for the treatment of enterovirus infection is increasing. In the present study, we identified that trans-2-hexenoic acid (THA), a natural product from a dietary source, possesses antiviral activity against coxsackievirus B (CVB) and enterovirus A71 (EV-A71) in a dose-dependent manner. We found that THA possesses antiviral activity at 50% effective concentrations (EC50) of 2.9 μM and 3.21 μM against CVB3 and EV-A71 infections, respectively. The time of addition assay revealed that THA inhibits both CVB3 and EV-A71 replication at the entry stage of infection. Additional results from this study further suggest that THA inhibits viral replication by blocking viral entry. Given that THA has received approval as a food additive, treatment of enterovirus infections with THA might be a safe therapeutic option or could pave the way for semisynthetic manufacturing of more antiviral drugs in the future.

Direct-Acting Antivirals and Host-Targeting Approaches against Enterovirus B Infections: Recent Advances

Enterovirus B (EV-B)-related diseases, which can be life threatening in high-risk populations, have been recognized as a serious health problem, but their clinical treatment is largely supportive, and no selective antivirals are available on the market. As their clinical relevance has become more serious, efforts in the field of anti-EV-B inhibitors have greatly increased and many potential antivirals with very high selectivity indexes and promising in vitro activities have been discovered. The scope of this review encompasses recent advances in the discovery of new compounds with anti-viral activity against EV-B, as well as further progress in repurposing drugs to treat these infections. Current progress and future perspectives in drug discovery against EV-Bs are briefly discussed and existing gaps are spotlighted.

N-Acetyl-L-Cysteine Protects Airway Epithelial Cells during Respiratory Syncytial Virus Infection against Mucin Synthesis, Oxidative Stress, and Inflammatory Response and Inhibits HSPA6 Expression

Objective. Respiratory syncytial virus (RSV) infection is an important cause of hospitalization of children worldwide, leading to significant morbidity and mortality. RSV infection leads to increasing inflammatory and apoptosis events in the airway epithelium through mechanisms involving ROS generation. The antioxidant N-acetyl-L-cysteine (NAC) has been shown to inhibit influenza virus replication and to reduce the secretion of inflammatory and apoptotic mediators during virus infection. The study aims to investigate the effects of NAC on human bronchial epithelial cells BEAS-2B and HSPA6 expression during RSV infection. Methods. CCK-8 assays were performed to evaluate cell survival. The production of proinflammatory factors, TNF-α, IL-6, IL-1β, IL-18, and MUC5AC was examined by quantitative real-time PCR and ELISA. Oxidative stress was determined by reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH)/glutathione disulfide (GSSG) ratio. Immunoblotting analysis of epidermal growth factor receptor (EGFR) and its phosphorylation was performed. The antiviral effect of NAC was assessed by determining viral titers using plaque assay. Results. RSV infection reduced cell survival, promoted the release of proinflammatory factors, increased the ROS production and MDA concentration, and diminished the SOD activity and GSH/GSSG ratio, all which were attenuated by NAC treatment. Accordingly, NAC treatment inhibited the activation of EGFR and MUC5AC in BEAS-2B cells with RSV infection. Furthermore, NAC administration resulted in a marked decrease in RSV-induced HSPA6 expression in BEAS-2B cells. Concomitantly, EPB treatment led to an evident inhibition of RSV fusion gene and viral replication in RSV-infected BEAS-2B cells. Conclusion. This work supports the use of NAC to exert antimucin synthesis, anti-inflammatory, antioxidant, and antiviral effects on airway epithelium during RSV infection.

Novel Antiviral Activity of Ethyl 3-Hydroxyhexanoate Against Coxsackievirus B Infection

Coxsackievirus group B (CVB) is a member of the genus Enterovirus in the family Picornaviridae. CVB infection has been implicated as a major etiologic agent of viral myocarditis, dilated cardiomyopathy, meningitis, and pancreatitis among children and young adults. Until date, no antiviral agent has been licensed for the treatment of Coxsackievirus infection. In an effort to identify antiviral agents against diseases caused by the CVB, we found that ethyl 3-hydroxyhexanoate (EHX), a volatile compound present in fruits and food additives, is a potent antiviral compound. In this study, we demonstrated that EHX treatment significantly inhibits CVB replication both in vivo and in vitro. Furthermore, EHX possesses antiviral activity at 50% effective concentration (EC₅₀) of 1.2 μM and 50% cytotoxicity (CC₅₀) of 25.6 μM, yielding a selective index (SI) value as high as 20.8. Insights into the mechanism of antiviral activity of EHX showed that it acts at the step of viral RNA replication. Since EHX has received approval as food additives, treatment of CVB-related infections with EHX might be a safe therapeutic option and may be a promising strategy for the development of semi-synthetic antiviral drugs for viral diseases.

Mono-macrophage-Derived MANF Alleviates Bacterial Myocarditis by Inhibiting NF-kappaB Activation and Myocardial Inflammation

Bacterial myocarditis is a key cause leading to myocardial damage and cardiac dysfunction. Mesencephalic astrocyte-derived neurotrophic factor (MANF) has been found to be an anti-inflammatory factor. This study is to explore the effect of MANF on LPS-induced myocardial inflammation and macrophage differentiation. The myocarditis mouse model was constructed by LPS treatment. Myocardial damage and serum inflammatory factors were evaluated by ELISA. RT-qPCR was used to detect mRNA of M1/M2 macrophage markers. Western blot, immunohistochemical, and immunofluorescent staining were used to examine myocardial M1/M2 macrophages and NF-κB activation. Mono-macrophage-derived MANF deficiency enhanced LPS-induced inflammatory response and increased M1 macrophages in myocardium tissues, further causing more severe myocardial injury and lower survival rate of mice. Also, LPS-induced myocardial NF-κB activation was strengthened after mono-macrophage-derived MANF knockout. Mono-macrophage-derived MANF inhibits bacterial myocarditis and myocardial M1 macrophage differentiation, which is potential to be used for bacterial myocarditis treatment clinically.