miR-29b-3p regulates cardiomyocytes pyroptosis in CVB3-induced myocarditis through targeting DNMT3A

BACKGROUND

Viral myocarditis (VMC) is a disease resulting from viral infection, which manifests as inflammation of myocardial cells. Until now, the treatment of VMC is still a great challenge for clinicians. Increasing studies indicate the participation of miR-29b-3p in various diseases. According to the transcriptome sequencing analysis, miR-29b-3p was markedly upregulated in the viral myocarditis model. The purpose of this study was to investigate the role of miR-29b-3p in the progression of VMC.

METHODS

We used CVB3 to induce primary cardiomyocytes and mice to establish a model of viral myocarditis. The purity of primary cardiomyocytes was identified by immunofluorescence. The cardiac function of mice was detected by Vevo770 imaging system. The area of inflammatory infiltration in heart tissue was shown by hematoxylin and eosin (H&E) staining. The expression of miR-29b-3p and DNMT3A was detected by quantitative real time polymerase chain reaction (qRT-PCR). The expression of a series of pyroptosis-related proteins was detected by western blot. The role of miR-29b-3p/DNMT3A in CVB3-induced pyroptosis of cardiomyocytes was studied in this research.

RESULTS

Our data showed that the expression of miR-29b-3p was upregulated in CVB3-induced cardiomyocytes and heart tissues in mice. To explore the function of miR-29b-3p in CVB3-induced VMC, we conducted in vivo experiments by knocking down the expression of miR-29b-3p using antagomir. We then assessed the effects on mice body weight, histopathology changes, myocardial function, and cell pyroptosis in heart tissues. Additionally, we performed gain/loss-of-function experiments in vitro to measure the levels of pyroptosis in primary cardiomyocytes. Through bioinformatic analysis, we identified DNA methyltransferases 3A (DNMT3A) as a potential target gene of miR-29b-3p. Furthermore, we found that the expression of DNMT3A can be modulated by miR-29b-3p during CVB3 infection.

CONCLUSIONS

Our results demonstrate a correlation between the expression of DNMT3A and CVB3-induced pyroptosis in cardiomyocytes. These findings unveil a previously unidentified mechanism by which CVB3 induces cardiac injury through the regulation of miR-29b-3p/DNMT3A-mediated pyroptosis.

Synergistic Viro-chemoimmunotherapy in Breast Cancer Enabled by Bioengineered Immunostimulatory Exosomes and Dual-Targeted Coxsackievirus B3

Breast cancer's immunosuppressive environment hinders effective immunotherapy, but oncolytic viruses hold promise for addressing this challenge by targeting tumor cells and altering the microenvironment. Yet, neutralizing antibodies and immune clearance impede their clinical utility. This study explored microRNA-modified coxsackievirus B3 (miR-CVB3), an innovative oncolytic virus, and its potential in breast cancer treatment. It investigated miR-CVB3's impact on immune-related proteins and utilized exosomes as both protective shields and delivery carriers. Results demonstrated miR-CVB3's capacity to reshape immune-related protein profiles toward a more immunostimulatory state and enhance exosome-mediated immune cell activation. Notably, cancer cell-released exosomes encapsulating miR-CVB3 (ExomiR-CVB3) maintained its antitumor cytotoxicity and bolstered its immunostimulatory effects. Moreover, ExomiR-CVB3 shielded miR-CVB3 from neutralizing antibodies and rapid immune clearance when it was systemically administered. Building on these findings, ExomiR-CVB3 was engineered with the AS1411 aptamer and doxorubicin (ExomiR-CVB3/DoxApt), enhancing therapeutic efficacy. This notable approach, combining genomic modification, aptamer surface decoration, and doxorubicin addition, demonstrated safe delivery of CVB3 to cancer cells. Comprehensive in vitro and in vivo analyses revealed selective breast cancer cell targeting, cell death induction, and significant immune cell infiltration within the tumor microenvironment while sparing healthy organs. In summary, this study highlights ExomiR-CVB3/DoxApt as a pioneering breast cancer treatment strategy adaptable for diverse cancer types, offering a potent and versatile approach to reshaping cancer immunotherapy.

Myocardial Mitochondrial DNA Drives Macrophage Inflammatory Response through STING Signaling in Coxsackievirus B3-Induced Viral Myocarditis

Coxsackievirus B3 (CVB3), a single-stranded positive RNA virus, primarily infects cardiac myocytes and is a major causative pathogen for viral myocarditis (VMC), driving cardiac inflammation and organ dysfunction. However, whether and how myocardial damage is involved in CVB3-induced VMC remains unclear. Herein, we demonstrate that the CVB3 infection of cardiac myocytes results in the release of mitochondrial DNA (mtDNA), which functions as an important driver of cardiac macrophage inflammation through the stimulator of interferon genes (STING) dependent mechanism. More specifically, the CVB3 infection of cardiac myocytes promotes the accumulation of extracellular mtDNA. Such myocardial mtDNA is indispensable for CVB3-infected myocytes in that it induces a macrophage inflammatory response. Mechanistically, a CVB3 infection upregulates the expression of the classical DNA sensor STING, which is predominantly localized within cardiac macrophages in VMC murine models. Myocardial mtDNA efficiently triggers STING signaling in those macrophages, resulting in strong NF-kB activation when inducing the inflammatory response. Accordingly, STING-deficient mice are able to resist CVB3-induced cardiac inflammation, exhibiting minimal inflammation with regard to their functional cardiac capacities, and they exhibit higher survival rates. Moreover, our findings pinpoint myocardial mtDNA as a central element driving the cardiac inflammation of CVB3-induced VMC, and we consider the DNA sensor, STING, to be a promising therapeutic target for protecting against RNA viral infections.

Appendectomy Mitigates Coxsackievirus B3-Induced Viral Myocarditis

Appendix has a distinct abundance of lymphatic cells and serves as a reservoir of microbiota which helps to replenish the large intestine with healthy flora. And it is the primary site of IgA induction, which shapes the composition of the intestinal microbiota. Recent population-based cohort studies report that appendectomy is associated with an increased risk of acute myocardial infarction and ischemic heart disease. Here, whether appendectomy has an effect on the occurrence and development of coxsackievirus B3 (CVB3)-induced viral myocarditis is studied. 103 TCID50 CVB3 was inoculated i.p. into appendectomized and sham-operated mice. RNA levels of viral load and pro-inflammatory cytokines in the hearts and the intestine were detected by RT-PCR. Compared to sham-operated mice, appendectomized mice exhibited attenuated cardiac inflammation and improved cardiac function, which is associated with a systemic reduced viral load. Appendectomized mice also displayed a reduction in cardiac neutrophil and macrophage infiltration and pro-inflammatory cytokine production. Mechanistically, we found that CVB3 induced an early and potent IL-10 production in the cecal patch at 2 days post infection. Appendectomy significantly decreased intestinal IL-10 and IL-10+ CD4+ Treg frequency which led to a marked increase in intestinal (primary entry site for CVB3) anti-viral IFN-γ+ CD4+ T and IFN-γ+ CD8+ T response and viral restriction, eventually resulting in improved myocarditis. Our results suggest that appendix modulates cardiac infection and inflammation through regulating intestinal IL-10+ Treg response.

Proteome-wide copy-number estimation from transcriptomics

Protein copy numbers constrain systems-level properties of regulatory networks, but absolute proteomic data remain scarce compared to transcriptomics obtained by RNA sequencing. We addressed this persistent gap by relating mRNA to protein statistically using best-available data from quantitative proteomics-transcriptomics for 4366 genes in 369 cell lines. The approach starts with a central estimate of protein copy number and hierarchically appends mRNA-protein and mRNA-mRNA dependencies to define an optimal gene-specific model that links mRNAs to protein. For dozens of independent cell lines and primary prostate samples, these protein inferences from mRNA outmatch stringent null models, a count-based protein-abundance repository, and empirical protein-to-mRNA ratios. The optimal mRNA-to-protein relationships capture biological processes along with hundreds of known protein-protein interaction complexes, suggesting mechanistic relationships are embedded. We use the method to estimate viral-receptor abundances of CD55-CXADR from human heart transcriptomes and build 1489 systems-biology models of coxsackievirus B3 infection susceptibility. When applied to 796 RNA sequencing profiles of breast cancer from The Cancer Genome Atlas, inferred copy-number estimates collectively reclassify 26% of Luminal A and 29% of Luminal B tumors. Protein-based reassignments strongly involve a pharmacologic target for luminal breast cancer (CDK4) and an α-catenin that is often undetectable at the mRNA level (CTTNA2). Thus, by adopting a gene-centered perspective of mRNA-protein covariation across different biological contexts, we achieve accuracies comparable to the technical reproducibility limits of contemporary proteomics. The collection of gene-specific models is assembled as a web tool for users seeking mRNA-guided predictions of absolute protein abundance (http://janeslab.shinyapps.io/Pinferna).

Pathophysiological Mechanisms of Cardiac Dysfunction in Transgenic Mice with Viral Myocarditis

Viral myocarditis is pathologically associated with RNA viruses such as coxsackievirus B3 (CVB3), or more recently, with SARS-CoV-2, but despite intensive research, clinically proven treatment is limited. Here, by use of a transgenic mouse strain (TG) containing a CVB3ΔVP0 genome we unravel virus-mediated cardiac pathophysiological processes in vivo and in vitro. Cardiac function, pathologic ECG alterations, calcium homeostasis, intracellular organization and gene expression were significantly altered in transgenic mice. A marked alteration of mitochondrial structure and gene expression indicates mitochondrial impairment potentially contributing to cardiac contractile dysfunction. An extended picture on viral myocarditis emerges that may help to develop new treatment strategies and to counter cardiac failure.

Stress Granules Inhibit Coxsackievirus B3-Mediated Cell Death via Reduction of Mitochondrial Reactive Oxygen Species and Viral Extracellular Release

Stress granules (SGs) are cytoplasmic aggregates of RNA-protein complexes that form in response to various cellular stresses and are known to restrict viral access to host translational machinery. However, the underlying molecular mechanisms of SGs during viral infections require further exploration. In this study, we evaluated the effect of SG formation on cellular responses to coxsackievirus B3 (CVB3) infection. Sodium arsenite (AS)-mediated SG formation suppressed cell death induced by tumor necrosis factor-alpha (TNF-a)/cycloheximide (CHX) treatment in HeLa cells, during which G3BP1, an essential SG component, contributed to the modulation of apoptosis pathways. SG formation in response to AS treatment blocked CVB3-mediated cell death, possibly via the reduction of mitochondrial reactive oxygen species. Furthermore, we examined whether AS treatment would affect small extracellular vesicle (sEV) formation and secretion during CVB3 infection and modulate human monocytic cell (THP-1) response. CVB3-enriched sEVs isolated from HeLa cells were able to infect and replicate THP-1 cells without causing cytotoxicity. Interestingly, sEVs from AS-treated HeLa cells inhibited CVB3 replication in THP-1 cells. These findings suggest that SG formation during CVB3 infection modulates cellular response by inhibiting the release of CVB3-enriched sEVs.

Effect of FoxO1 on Cardiomyocyte Apoptosis and Inflammation in Viral Myocarditis via Modultion of the TLR4/NF-κB Signaling Pathway

To investigate the possible effect of FoxO on coxsackievirus B3 (CVB3) -induced cardiomyocyte inflammation and apoptosis via modulation of the TLR4/NF-κB signaling pathway.Viral myocarditis (VMC) models were establied via CVB3 infection both in vivo and in vitro. Western blotting was adopted to detect FoxO1 and TLR4 expressions in myocardial tissues and cells. Cardiomyocytes of suckling mouse were divided into the control, CVB3, CVB3 + pcDNA, CVB3 + pcDNA-FoxO1, CVB3 + TLR4 siRNA, and CVB3 + pcDNA-FoxO1 + TLR4 siRNA groups. Flow cytometry was employed to evaluate cell apoptosis. The expressions of inflammatory factors including TNF-α, IL-1β, and IL-6 were detected via quantitative reverse transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. Then, TLR4/NF-κB pathway-related proteins were determined via Western blotting.VMC mice had increased FoxO1 and TLR4 expressions in myocardial tissues. Cardiomyocytes with CVB3 infection also had upregulated protein expressions of p-FoxO1/FoxO1 and TLR4. Compared with those in the control group, the cardiomyocytes in the CVB3 group were increased in LDH and CK-MB levels, cell apoptosis rate and inflammatory factors (TNF-α, IL-1β and IL-6), as well as protein expressions of TLR4 and p-p65/p65. Compared with those in the CVB3 group, the cardiomyocytes in the CVB3 + pcDNA-FoxO1 group were further upregulated whereas those in the CVB3 +TLR4 siRNA group were downregulated in the aforementioned indicators. Furthermore, TLR4 siRNA can reverse the effect of pcDNA-FoxO1 on the aggravation of cardiomyocyte injury induced by CVB3 infection.FoxO1 can upregulate the TLR4/NF-κB signaling pathway to promote cardiomyocyte apoptosis and inflammatory injury in CVB3-induced VMC.

Stem cell factor/mast cell/CCL2/monocyte/macrophage axis promotes Coxsackievirus B3 myocarditis and cardiac fibrosis by increasing Ly6Chigh monocyte influx and fibrogenic mediators production

Mast cells (MCs), central players in allergy and parasitic infections, play key roles in inflammation and fibrosis. Here, the impact of MCs on the progression of Coxsackievirus B3 (CVB3)-induced viral myocarditis (VMC) and fibrosis was investigated using MC-deficient Kit^W-sh mice. Viral titres, cellular infiltrates and heart pathologies were evaluated and compared with wild-type (WT) mice during acute CVB3 infection of C57BL/6 mice. CVB3 infection induced an increased accumulation and degranulation of MCs in the hearts of mice during acute infection. MC-deficient Kit^W-sh mice had slightly higher viral titres, decreased VMC and cardiac fibrosis and improved cardiac dysfunction compared to WT mice via decreasing cardiac influx of Ly6C^high monocytes/macrophages (Mo/Mφ). While bone marrow-derived MC reconstitution decreased viral titre and worsened improved survival and VMC severity in Wsh mice. MC-fibroblasts co-culture revealed a cardiac MC-fibroblasts crosstalk during early infection: fibroblasts trigger MC degranulation and secretion of CCL2 and tumour necrosis factor alpha (TNF-α) via producing early stem cell factor (SCF); while MCs-fibrogenic mediators (TNF-α) stimulate fibroblasts to increase CCL2, α-smooth muscle actin (SMA), collagen and transforming growth factor beta（TGFβ) expression, thus aggravating cardiac fibrosis. MCs and fibroblast-derived CCL2s are both essential for cardiac Ly6C^high Mo/Mφ influx. Administration of recombinant mouse SCF to CVB3-infected mice aggravates VMC via accelerating MCs accumulation and cardiac influx of Ly6C^hi Mo/Mφ. Collectively, our data highlight an early MC-fibroblast crosstalk and SCF/MC/CCL2/Mo/Mφ axis as important mechanisms required for triggering VMC and myocardial fibrosis. This finding indicates critical roles of MCs in initiating and modulating cardiac innate response to CVB3 and has an implication in developing new and more effective treatments for VMC.

Exploration of IRES Elements within the ORF of the Coxsackievirus B3 Genome

OBJECTIVE

This study aimed to identify internal ribosome entry sites (IRESs) in the open reading frame (ORF) of the Coxsackievirus B3 (CVB3) genome.

METHODS

The sequences of P1, P2, or P3 of the CVB3 genome or the truncated sequences from each antithymocyte globulin (ATG) to the end of the P1, P2, or P3 gene were inserted into the pEGFP-N1 vector. After transfection, possible IRES-dependent green fluorescent protein (GFP)-fused proteins were detected by anti-GFP western blotting. The sequences of possible IRESs were inserted into specific Fluc/Rluc bicistronic vectors, in which the potential IRESs were determined according to the Fluc/Rluc activity ratio. Expression of Fluc and Rluc mRNA of the bicistronic vector was detected by RT-qPCR.

RESULTS

After transfection of full length or truncated sequences of the P1, P2, or P3 plasmids, six GFP-fused protein bands in P1, six bands in P2 and nine bands in P3 were detected through western blotting. Two IRESs in VP2 (1461-1646 nt) and VP1 (2784-2983 nt) of P1; one IRES in 2C (4119-4564 nt) of P2; and two IRESs in 3C (5634-5834 nt) and 3D (6870-7087 nt) of P3 were identified according to Fluc/Rluc activity ratio. The cryptic promoter was also excluded by RT-qPCR.

CONCLUSION

Five IRESs are present in the CVB3 coding region.

HSBP1 Is a Novel Interactor of FIP200 and ATG13 That Promotes Autophagy Initiation and Picornavirus Replication

ATG13 and FIP200 are two subunits of the ULK kinase complex, a key regulatory component of the autophagy machinery. We have previously found that the FIP200-ATG13 subcomplex controls picornavirus replication outside its role in the ULK kinase complex and autophagy. Here, we characterized HSBP1, a very small cytoplasmic coiled-coil protein, as a novel interactor of FIP200 and ATG13 that binds these two proteins via FIP200. HSBP1 is a novel pro-picornaviral host factor since its knockdown or knockout, inhibits the replication of various picornaviruses. The anti-picornaviral function of the FIP200-ATG13 subcomplex was abolished when HSBP1 was depleted, inferring that this subcomplex negatively regulates HSBP1’s pro-picornaviral function during infections. HSBP1depletion also reduces the stability of ULK kinase complex subunits, resulting in an impairment in autophagy induction. Altogether, our data show that HSBP1 interaction with FIP200-ATG13-containing complexes is involved in the regulation of different cellular pathways.

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 β-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.

A food-responsive switch modulates TFEB and autophagy, and determines susceptibility to coxsackievirus infection and pancreatitis

Almost a billion people worldwide are chronically undernourished. Herein, using a mouse model of coxsackievirus B3 (CVB3) infection, we report that a single day of food restriction (FR) markedly increases susceptibility to attenuated enterovirus infection, replication, and disease. These "pro-viral" effects, which are rapidly-reversed by the restoration of food, are mediated by several genes whose expression is altered by FR, and which support CVB3 replication. Central to this is TFEB, a protein whose expression and activation status are rapidly increased by FR. TFEB, which regulates the transcription of >100 genes involved in macroautophagy/autophagy and lysosomal biogenesis, responds similarly to both FR and CVB3 infection and plays a pivotal role in determining host susceptibility to CVB3. We propose that, by upregulating TFEB, FR generates an intracellular environment that is more hospitable to the incoming virus, facilitating its replication. This interplay between nutritional status and enterovirus replication has implications for human health and, perhaps, for the evolution of these viruses.Abbreviations: Atg/ATG: autophagy-related; CAR: Coxsackievirus and adenovirus receptor; Cas9: CRISPR associated protein 9; Cre: recombinase that causes recombination; CRISPR: clustered regularly interspaced short palindromic repeats; Ctsb/CTSB: cathepsin B; CVB3: coxsackievirus B3; DsRedCVB3: a recombinant CVB3 that encodes the Discosoma red fluorescent protein; EL: elastase; FR: food restriction; GFP: green fluorescent protein; gRNA: guide RNA; HBSS: Hanks Buffered Salt Solution; LYNUS: lysosomal nutrient sensing machinery; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MFI: mean fluorescence intensity; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; Nluc: nanoluciferase; NlucCVB3: a recombinant CVB3 encoding nanoluciferase; pfu: plaque-forming unit(s); p.i.: post infection; rCVB: recombinant coxsackievirus B3; RPS6KB/p70S6K: ribosomal protein S6 kinase; RT: room temperature; siRNA: small interfering RNA; TFEB: transcription factor EB; tg: transgenic; TUBB: β-tubulin; UNINF: uninfected; wrt: with respect to; WT: wild type.

MicroRNA-30a Modulates Type I Interferon Responses to Facilitate Coxsackievirus B3 Replication Via Targeting Tripartite Motif Protein 25

Viral myocarditis is caused by a viral infection and characterized by the inflammation of the myocardium. Coxsackievirus B3 (CVB3) infection is one of the most common among the infections caused by this virus. The host's early innate immune response to CVB3 infection particularly depends on the functions of type I interferons (IFNs). In this study, we report that a host microRNA, miR-30a, was upregulated by CVB3 to facilitate its replication. We demonstrated that miR-30a was a potent negative regulator of IFN-I signaling by targeting tripartite motif protein 25 (TRIM25). In addition, we found that TRIM25 overexpression significantly suppressed CVB3 replication, whereas TRIM25 knockdown increased viral titer and VP1 protein expression. MiR-30a inhibits the expression of TRIM25 and TRIM25-mediated retinoic acid-inducible gene (RIG)-I ubiquitination to suppress IFN-β activation and production, thereby resulting in the enhancement of CVB3 replication. These results indicate the proviral role of miR-30a in modulating CVB3 infection for the first time. This not only provides a new strategy followed by CVB3 in order to modulate IFN-I-mediated antiviral immune responses by engaging host miR-30a but also improves our understanding of its pathogenesis.

Effect of Consecutive Alternating Administration of a Triple Combination of Anti-Enteroviral Compounds in Mice Infected with Coxsackievirus B3

A novel approach for treatment of enterovirus infections was characterized. Application of treatment course of consecutive alternating administration (CAA) of triple combination of enterovirus replication inhibitors in experimental infections (20 MLD50) with coxsackievirus B3 (CVB3) strains in newborn mice is presented. It was established that in infection with cardiotropic Woodruff strain the combination of pleconaril, МDL-860 and oxoglaucine (PMO) subjected to the CAA scheme, a significant protective effect was observed. Monotherapeutic courses as well as simultaneously daily applied PMO were without effect. Analogous data were observed at experimental infection with the neurotriopic Nancy strain of CVB3. Following IC50 values of virus samples taken every day from target organs of infected animals during the whole period of study, a drug-resistance was established in monotherapy with compounds-partners in the PMO combination. At courses by the treatment scheme CAA of PMO development of drug-resistance was not established, but an increased susceptibility to the effect of the inhibitor-components in the combination was proven. Toxicity of PMO applied via the CAA scheme and in the monotherapeutic courses in both healthy and CVB3 infected animals was recorded. All data obtained prove the potential of the CAA treatment scheme for development of effective chemotherapy of enterovirus infections.

New RNA Structural Elements Identified in the Coding Region of the Coxsackie B3 Virus Genome

Here we present a set of new structural elements formed within the open reading frame of the virus, which are highly probable, evolutionarily conserved and may interact with host proteins. This work focused on the coding regions of the CVB3 genome (particularly the V4-, V1-, 2C-, and 3D-coding regions), which, with the exception of the cis-acting replication element (CRE), have not yet been subjected to experimental analysis of their structures. The SHAPE technique, chemical modification with DMS and RNA cleavage with Pb²⁺, were performed in order to characterize the RNA structure. The experimental results were used to improve the computer prediction of the structural models, whereas a phylogenetic analysis was performed to check universality of the newly identified structural elements for twenty CVB3 genomes and 11 other enteroviruses. Some of the RNA motifs turned out to be conserved among different enteroviruses. We also observed that the 3'-terminal region of the genome tends to dimerize in a magnesium concentration-dependent manner. RNA affinity chromatography was used to confirm RNA-protein interactions hypothesized by database searches, leading to the discovery of several interactions, which may be important for virus propagation.

Cardiomyocyte-specific deletion of Senp2 contributes to CVB3 viral replication and inflammation

Viral myocarditis (VMC) is characterized by cardiac inflammation and excessive inflammatory responses after viral infection. SENP2, a deSUMO-specific protease, has been reported to regulate antiviral innate immunity. This study aimed to investigate whether SENP2 affects CVB3-induced VMC. We generated a CVB3-induced VMC mouse model in 6-week-old cardiomyocyte-specific Senp2 knockout mice. The mice were sacrificed at days 0, 2, 4 and 6 after CVB3 infection. The survival rate, body weight, myocardial histopathological changes, viral load, cytokine levels and antiviral gene expression in cardiac tissues of both groups were investigated. Our study indicated that the expression of Senp2 in primary cardiomyocytes was upregulated by CVB3 infection. Moreover, deletion of Senp2 in the heart exacerbated CVB3 infection-induced myocarditis, facilitated CVB3 viral replication and downregulated the expression of antiviral proteins. In conclusion, our findings suggest a protective role for SENP2 in CVB3-induced VMC.

Advancement of Mechanisms of Coxsackie Virus B3-Induced Myocarditis Pathogenesis and the Potential Therapeutic Targets

Viral myocarditis is a cardiac disease caused by Group B Coxsackie virus of Enterovirus genus in the Picorna viridae family. It causes heart failure in children, young and adults. Ten Percent (10%) of acute heart failure and 12% of sudden deaths in young and adults who are less than 40 years is due to this viral myocarditis. If treatment action is not taken earlier, the viral disease can develop into chronic myocarditis and Dilated Cardiomyopathy which lead to congestive heart failure. And these eventually result in a reduced cardiac function which finally brings the victim to death. The only treatment option of the disease is heart transplantation once the acute stage of disease develops to chronic and Dilated Cardiomyopathy. Currently, there is a limitation in daily clinical treatments and even some available treatment options are ineffective. Therefore, focusing on search for treatment options through investigation is imperative. Recent studies have reported that biological molecules show a promising role. But their mechanism of pathogenesis is still unclear. A detailed study on identifying the role of biological molecules involved in Coxsackie B3 virus induced myocarditis and their mechanisms of pathogenesis; compiling and disseminating the findings of the investigation to the scientific communities contribute one step forward to the solution. Therefore, this review is aimed at compiling information from findings of current studies on the potential therapeutic role of micro RNA, cytokines and chemokines on the mechanism of pathogenesis of Coxsackie virus B3- induced myocarditis to give brief information for scholars to conduct a detailed study in the area.

The regulatory role of miR-107 in Coxsackie B3 virus replication

Coxsackie B3 virus (CVB3) is a member of small RNA viruses that belongs to the genus Enterovirus of the family Picornaviridae and CVB3 is the main pathogen of acute and chronic viral myocarditis. In this study RT-qPCR was used to determine the expression of miR-107 in CVB3-infected and uninfected HeLa cells. The experimental results show that the level of miR-107 began to rise at 4 h after the infection, and significantly boosted at 6 h. Based on the results of this experiment, we consider that miR-107 expression is related to CVB3 infection. In order to further clarify the effect of miR-107 in the process of CVB3 infection, we studied the effect of miR-107 upstream and downstream target genes on CVB3 replication. Levels of the target RNAs were detected by RT-qPCR after CVB3 infection, and the expression of CVB3 capsid protein VP1 by western blot analysis. Then the virus in the supernatant was quantitated via a viral plaque assay, reflecting the release of the virus. The experimental results showed that miRNA-107 expression is associated with CVB3 replication and proliferation, while KLF4 and BACE1 as the downstream of miR-107 weakened CVB3 replication. Overexpressions of KLF4 and BACE1 negatively regulated CVB3 replication, this effect on CVB3 was completely opposite to that of miR-107. Further experiments revealed that the upstream lncRNA004787, a new lncRNA that had not been reported, was located on chromosome 5, strand - from 37073250 to 37070908 (genome assembly: hg19). We sequenced and studied lncRNA004787 and found that it partially inhibited CVB3 replication. This prompted us to speculate that lncRNA004787 probably impacted the replication by other means. In conclusion, miR-107 interfered with CVB3 replication and release.

Viral myocarditis involves the generation of autoreactive T cells with multiple antigen specificities that localize in lymphoid and non-lymphoid organs in the mouse model of CVB3 infection

Autoreactive T cells may contribute to post-viral myocarditis induced with Coxsackievirus B3 (CVB3), but the underlying mechanisms of their generation are unclear. Here, we have comprehensively analyzed the generation of antigen-specific, autoreactive T cells in the mouse model of CVB3 infection for antigens implicated in patients with myocarditis/dilated cardiomyopathy. First, comparative analysis of CVB3 proteome with five autoantigens led us to identify three mimicry epitopes, one each from adenine nucleotide translocator 1 (ANT), sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) and cardiac troponin I. None of these induced cross-reactive T cell responses. Next, we generated major histocompatibility complex (MHC) class II dextramers to enumerate the frequencies of antigen-specific T cells to determine whether T cells with multiple antigen specificities are generated by CVB3 infection. These analyses revealed appearance of CD4 T cells positive for SERCA2a 971-990, and cardiac myosin heavy chain-α (Myhc) 334-352 dextramers, both in the periphery and also in the hearts of CVB3-infected animals. While ANT 21-40 dextramer⁺ T cells were inconsistently detected, the β1-adrenergic receptor 181-200/211-230 or branched chain α-ketoacid dehydrogenase kinase 111-130 dextramer⁺ cells were absent. Interestingly, SERCA2a 971-990, Myhc 334-352 and ANT 21-40 dextramer⁺ cells were also detected in the liver indicating that they may have a pathogenic role. Finally, we demonstrate that the SERCA2a 971-990-reactive T cells generated in CVB3 infection could transfer disease to naïve mice. The data suggest that CVB3 infection can lead to the generation of autoreactive T cells for multiple antigens indicating a possibility that the autoreactive T cells localized in the liver can potentially circulate and contribute to the development of viral myocarditis.

MG-132 attenuates cardiac deterioration of viral myocarditis via AMPK pathway

BACKGROUND

Coxsackievirus B3 (CVB3) is the primary cause of infectious myocarditis. Aggressive immunological activation and apoptosis of myocytes contributes to progressive dysfunction of cardiac contraction and poor prognosis. MG-132, a proteasome inhibitor, regulates mitochondrial-mediated intrinsic myocardial apoptosis and downregulates NF-κB-mediated inflammation. Here, we determined whether AMPK pathway participates in MG-132-mediated myocardial protection in viral-induced myocarditis.

METHODS AND RESULTS

Acute viral myocarditis models were established by intraperitoneal inoculation of CVB3 in male BALB/c mice. Myocarditis and age-matched control mice were administered MG-132 and/or BML-275 dihydrochloride (BML) (AMPK antagonist) intraperitoneally daily from the day following CVB3 inoculation. MG-132 improved hemodynamics and inhibited the structural remodeling of the ventricle in mice with myocarditis, while BML largely blunted these effects. TUNEL staining and immunochemistry suggested that MG-132 exerts anti-apoptotic and anti-inflammatory effects against CVB3-induced myocardial injuries. BML attenuated the effects of MG-132 on anti-apoptosis and anti-inflammation.

CONCLUSION

MG-132 modulated apoptosis and inflammation, improved hemodynamics, and inhibited the structural remodeling of ventricles in a myocarditis mouse model via regulation of the AMPK signal pathway.

Antiviral Effects of Novel 2-Benzoxyl-Phenylpyridine Derivatives

Coxsackievirus B3 (CVB3) is the most common cause of acute and chronic viral myocarditis, primarily in children, while human adenovirus infections represent a significant cause of morbidity and mortality worldwide, in people of all ages. A series of novel 2-benzoxyl-phenylpyridine derivatives were evaluated for their potential antiviral activities against CVB3 and adenovirus type 7 (ADV7). Preliminary assays indicated that some of these compounds exhibited excellent antiviral effects on both CVB3 and ADV7 viruses; they could effectively inhibit virus-induced cytopathic effects, reduce viral progeny yields, and had similar or superior antiviral activities compared with the control drug, ribavirin. Further, these compounds targeted the early stages of CVB3 replication in cells, including viral RNA replication and protein synthesis, rather than inactivating the virus directly, inhibiting virus adsorption/entry, or affecting viral release from cells. Our data demonstrate that the tested 2-benzoxyl-phenylpyridine derivatives are effective inhibitors of CVB3 and ADV7, raising the possibility that these compounds might be feasible candidates for anti-viral agents.

The protective role of microRNA-21 against coxsackievirus B3 infection through targeting the MAP2K3/P38 MAPK signaling pathway

Background

The P38 mitogen-activated protein kinase (MAPK) pathway plays an essential role in CVB3-induced diseases. We previously demonstrated microRNA-21 has potential inhibitory effect on the MAP2K3 which locates upstream of P38 MAPK and was upregulated in mouse hearts upon CVB3 infection. However, the effect and underlying mechanism of miRNA-21 on CVB3 infection remain unclear.

Methods

We detected continuous changes of cellular miRNA-21 and P38 MAPK proteins expression profiling post CVB3 infection in vitro within 12 h. P38 MAPK signaling was inhibited by the specific inhibitor, small interfering RNA and miRNA-21 mimic in vitro, CVB3 replication, cell apoptosis rate and proliferation were detected. Viral load in the mice heart, cardiomyocyte apoptosis rate and histological of the heart were also detected in the mice model of viral myocarditis pretreated with miRNA-21-lentivirus.

Results

We observed significant upregulation of miRNA-21 expression followed by suppression of the MAP2K3/P38 MAPK signaling in CVB3-infected Hela cells. The inactivation of the MAP2K3/P38 MAPK signaling by P38 MAPK specific inhibitor, small interfering RNA against MAP2K3, or miRNA-21 overexpression significantly inhibited viral progeny release from CVB3-infected cells. Mechanistically, when compared with control miRNA, miRNA-21 showed no effect on capsid protein VP1 expression and viral load within host cells, while significantly reversing CVB3-induced caspase-3 activation and cell apoptosis rate, further promoting proliferation of infected cells, which indicates the inhibitory effect of miRNA-21 on CVB3 progeny release. In the in vivo study, when compared with control miRNA, miRNA-21 pretreatment remarkably inactivated the MAP2K3/P38 MAPK signaling in mice and protected them against CVB3 infection as evidenced by significantly alleviated cell apoptosis rate, reduced viral titers, necrosis in the heart as well as by remarkably prolonged survival time.

Conclusions

miRNA-21 were reverse correlated with P38 MAPK activation post CVB3 infection, miRNA-21 overexpression significantly inhibited viral progeny release and decreased myocytes apoptosis rate in vitro and in vivo, suggesting that miRNA-21 may serve as a potential therapeutic agent against CVB3 infection through targeting the MAP2K3/P38 MAPK signaling.

Cleavage and Sub-Cellular Redistribution of Nuclear Pore Protein 98 by Coxsackievirus B3 Protease 2A Impairs Cardioprotection

Myocarditis, inflammation of the heart muscle, affects all demographics and is a major cause of sudden and unexpected death in young people. It is most commonly caused by viral infections of the heart, with coxsackievirus B3 (CVB3) being among the most prevalent pathogens. To understand the molecular pathogenesis of CVB3 infection and provide strategies for developing treatments, we examined the role of a key nuclear pore protein 98 (NUP98) in the setting of viral myocarditis. NUP98 was cleaved as early as 2 h post-CVB3 infection. This cleavage was further verified through both the ectopic expression of viral proteases and in vitro using purified recombinant CVB3 proteases (2A and 3C), which demonstrated that CVB3 2A but not 3C is responsible for this cleavage. By immunostaining and confocal imaging, we observed that cleavage resulted in the redistribution of NUP98 to punctate structures in the cytoplasm. Targeted siRNA knockdown of NUP98 during infection further increased viral protein expression and viral titer, and reduced cell viability, suggesting a potential antiviral role of NUP98. Moreover, we discovered that expression levels of neuregulin-1 (NRG1), a cardioprotective gene, and presenilin-1 (PSEN1), a cellular protease processing the tyrosine kinase receptor ERBB4 of NRG1, were reliant upon NUP98 and were downregulated during CVB3 infection. In addition, expression of these NUP98 target genes in myocardium tissue not only occurred at an earlier phase of infection, but also appeared in areas away from the initial inflammatory regions. Collectively, CVB3-induced cleavage of NUP98 and subsequent impairment of the cardioprotective NRG1-ERBB4/PSEN1 signaling cascade may contribute to increased myocardial damage in the context of CVB3-induced myocarditis. To our knowledge, this is the first study to demonstrate the link between NUP98 and the NRG1 signaling pathway in viral myocarditis.

Macrophage NLRP3 inflammasome activated by CVB3 capsid proteins contributes to the development of viral myocarditis

Viral myocarditis, mainly caused by enteroviruses specially coxsackievirus B3 (CVB3) infection, is a common clinical cardiovascular disease and characterized by cardiac massive inflammation. Our previous study showed that CVB3-induced myocardial NLRP3 contributed to the development of viral myocarditis. In this study, we found that beside of being up-regulated in myocardiocytes, NLPR3 was also obviously increased in the cardiac infiltrating macrophages. While whether this accumulated NLRP3 influences, macrophage inflammatory responses remains unknown. By adoptive transfer assays, we found that mice receiving NLRP3 up-regulated macrophages showed much more abundant cardiac IL-1β production and more severe myocardial inflammation, while those receiving NLRP3 down-regulated macrophages showed much less IL-1β production and milder myocarditis, indicating that NLRP3 up-regulated macrophages played a pathological role in CVB3-induced myocarditis. In addition, we further found that it was CVB3 capsid proteins VP1 (predominant) and VP2, but not viral RNAs, robustly triggered macrophage NLRP3 up-regulation and activation. Our study demonstrated macrophage NLRP3 inflammasome could be efficiently be activated by CVB3 capsid proteins, and contributed to the pathogenesis of viral myocarditis. It might provide some clues to the development of new therapeutic strategies based on macrophage NLRP3 modulation.

Calpain regulates CVB3 induced viral myocarditis by promoting autophagic flux upon infection

Calpains are calcium-activated neutral cysteine proteases. The dysregulation of calpain activity has been found to be related to cardiovascular diseases, for which calpain inhibition is used as a treatment. Viral myocarditis (VMC) is primarily caused by Coxsackievirus group B3 virus infection (CVB3). CVB3 virus infection induces autophagy and hijacks this process to facilitate its replication. In this study, we found that calpain was significantly activated in hearts affected by VMC. However, pharmacologically inhibiting calpain aggravated VMC symptoms in mice due to myocardial inflammation and cardiac dysfunction. The inhibition of calpain activity in vitro led to the accumulation of LC3-II and increased levels of p62/SQSTM1 protein expression, suggesting that autophagic flux was impaired by calpain inhibition. These effects of calpain inhibition were also observed in capn4-specific myocardial knockout mice in vivo. Furthermore, our results provided evidence that calpain inhibition in VMC, unlike other cardiovascular diseases, exacerbated the disease symptom by impairing CVB3-induced autophagic flux, which may subsequently reduce virus autolysosome degradation. Our findings indicated that calpain inhibition may not be a good treatment for VMC disease in a clinical setting.

Role of neutrophils in CVB3 infection and viral myocarditis

Coxsackievirus B3 (CVB3) is a globally prevalent enterovirus of the Picornaviridae family that is frequently associated with viral myocarditis (VM). Neutrophils, as first responders, may be key cells in determining viral disease outcomes; however, neutrophils have been poorly studied with respect to viral infection. Although neutrophils have been ascribed a relevant role in early cardiac inflammation, their precise role in CVB3 infection has not yet been evaluated. In this study, we aimed to determine if the interaction between human neutrophils and CVB3 could lead to viral replication and/or modulation of neutrophil survival and biological functions, and whether neutrophil depletion in a murine model has a beneficial or harmful effect on CVB3 infection. Our results show that CVB3 interacted with but did not replicate in human neutrophils. Neutrophils recognized CVB3 mainly through endosomal TLR-8, and infection triggered NFκB activation. Virus internalization resulted in increased cell survival, up-regulation of CD11b, enhanced adhesion to fibrinogen and fibronectin, and the secretion of IL-6, IL-1β, TNF-α, and IL-8. Supernatants from infected neutrophils exerted chemotactic activity partly mediated by IL-8. The infected neutrophils released myeloperoxidase and triggered neutrophil extracellular trap formation in the presence of TNF-α. In mice infected with CVB3, viral RNA was detected in neutrophils as well as in mononuclear cells. After neutrophil depletion, mice showed reduced VM reflected by a reduction in viral titers, cell exudates, and CCL-2 mRNA levels, as well as the abrogation of reactive cardiomyocyte hypertrophy. Our results indicate that neutrophils have relevant direct and indirect roles in the pathogenesis of CVB3-induced VM.

Antiviral phenolics from Antenoron filiforme var. neofiliforme

Two new phenolics, 1,3-di-O-p-coumaroyl-2',6'-di-O-acetylsucrose (1) and quercetin 3-O-β-D-apiofuranoyl-(1→2)-α-L-rhamnopyranoside (2), along with nine known compounds (3-11), were isolated from the whole plants of Antenoron filiforme var. neofiliforme. Their chemical structures were characterized on the basis of various spectroscopic techniques. This is the first report of the isolation of phenylpropanoid sucrose (1, 3-4) from the genus Antenoron. The bioassay results showed that compound 11 exhibited antiviral activity against the Coxsackie virus B3 (CVB3).

Immunological and pathological consequences of coxsackievirus RNA persistence in the heart

Type B coxsackieviruses (CVB) can cause myocarditis and dilated cardiomyopathy (DCM), a potentially-fatal sequela that has been correlated to the persistence of viral RNA. Herein, we demonstrate that cardiac RNA persistence can be established even after an inapparent primary infection. Using an inducible Cre/lox mouse model, we ask: (i) Does persistent CVB3 RNA cause ongoing immune activation? (ii) If T1IFN signaling into cardiomyocytes is ablated after RNA persistence is established, is there any change in the abundance of persistent CVB3 RNA and/or does cytopathic infectious virus re-emerge? (iii) Does this loss of T1IFN responsiveness by cardiomyocytes lead to the recurrence/exacerbation of myocarditis? Our findings suggest that persistent enteroviral RNAs probably do not contribute to ongoing myocardial disease, and are more likely to be the fading remnants of a recent, possibly sub-clinical, primary infection which may have set in motion the process that ultimately ends in DCM.

Echovirus plays major roles in the natural recombination of Coxsackievirus B3

Coxsakievirus B3 (CVB3) is a member of enterovirus B (EVB) group, which can cause serious heart diseases such as viral myocarditis. In order to analyze the evolution of CVB3, we performed a recombination analysis of all viral genomes of enterovirus B, and found that there were 19 putative recombination events that produced CVB3. A total of 11 serotypes were found to be involved in the generation of CVB3 progeny virus. These recombination events involved echovirus, EcoV (which includes EcoV6, EcoV9, EcoV14, EcoV15, EcoV17, EcoV21, EcoV24, and EcoV25), CVB4, CVB5, and EVB81, as major or minor parents. The most active, EcoV, which was involved in the 14 of 19 recombination events, acts as one of the parental viruses for CVB3 strains among molecular evolution and recombination events in circulating CVB3. Our study indicates that, EcoV plays major roles in CVB3 recombination, and is involved in the production of 11 new CVB3 recombinant strains.

TRAF6: A player in CVB3-induced myocarditis?

Coxsackievirus B3 (CVB3) is an important inducer of myocarditis, which, in susceptible individuals, can chronify and eventually lead to the development of dilated cardiomyopathy and heart failure. The respective mechanisms are not completely understood. Here, we analyzed expression of the TRAF6 gene, encoding TNF receptor-associated factor 6 (TRAF6), a signal transduction scaffold protein that acts downstream of cytokine receptors, in heart tissue of susceptible and non-susceptible mouse strains. We found that after infection, TRAF6 expression was upregulated in both non-susceptible C57BL/6 wildtype and susceptible A.BY/SnJ and C57BL/6-TLR3 (-/-) mice, however, to different degrees. In infected HeLa cells, we also found moderately elevated TRAF6 levels after infection, in addition, activity of the transcription factor nuclear factor kappa B (NFκB), which can be activated downstream of TRAF6, was strongly enhanced in infected cells. To functionally analyze the role of TRAF6 with regard to infection progression, TRAF6 expression was knocked down in cultured HeLa cells using specific siRNAs. We found that reduction of TRAF6 expression had no effect on NFκB activation in response to infection. Taken together, our data suggest that CVB3 infection enhances TRAF6 levels, however, this induction might not be necessary for infection-induced NFκB activation.

Understanding the Mechanism of the Broad-Spectrum Antiviral Activity of Favipiravir (T-705): Key Role of the F1 Motif of the Viral Polymerase

Favipiravir (T-705) is a broad-spectrum antiviral agent that has been approved in Japan for the treatment of influenza virus infections. T-705 also inhibits the replication of various RNA viruses, including chikungunya virus (CHIKV). We demonstrated earlier that the K291R mutation in the F1 motif of the RNA-dependent RNA polymerase (RdRp) of CHIKV is responsible for low-level resistance to T-705. Interestingly, this lysine is highly conserved in the RdRp of positive-sense single-stranded RNA (+ssRNA) viruses. To obtain insights into the unique broad-spectrum antiviral activity of T-705, we explored the role of this lysine using another +ssRNA virus, namely, coxsackievirus B3 (CVB3). Introduction of the corresponding K-to-R substitution in the CVB3 RdRp (K159R) resulted in a nonviable virus. Replication competence of the K159R variant was restored by spontaneous acquisition of an A239G substitution in the RdRp. A mutagenesis analysis at position K159 identified the K159M variant as the only other viable variant which had also acquired the A239G substitution. The K159 substitutions markedly decreased the processivity of the purified viral RdRp, which was restored by the introduction of the A239G mutation. The K159R A239G and K159M A239G variants proved, surprisingly, more susceptible than the wild-type virus to T-705 and exhibited lower fidelity in polymerase assays. Furthermore, the K159R A239G variant was found to be highly attenuated in mice. We thus demonstrate that the conserved lysine in the F1 motif of the RdRp of +ssRNA viruses is involved in the broad-spectrum antiviral activity of T-705 and that it is a key amino acid for the proper functioning of the enzyme.IMPORTANCE In this study, we report the key role of a highly conserved lysine residue of the viral polymerase in the broad-spectrum antiviral activity of favipiravir (T-705) against positive-sense single-stranded RNA viruses. Substitutions of this conserved lysine have a major negative impact on the functionality of the RdRp. Furthermore, we show that this lysine is involved in the fidelity of the RdRp and that the RdRp fidelity influences the sensitivity of the virus for the antiviral efficacy of T-705. Consequently, these results provide insights into the mechanism of the antiviral activity of T-705 and may lay the basis for the design of novel chemical scaffolds that may be endowed with a more potent broad-spectrum antiviral activity than that of T-705.

Expansion of CD11b+Ly-6C+ myeloid-derived suppressor cells (MDSCs) driven by galectin-9 attenuates CVB3-induced myocarditis

Galectin-9 is known to play a role in the modulation of innate and adaptive immunity to ameliorate CVB3-induced myocarditis. In the present study, we found that galectin-9 induced the expansion of CD11b⁺Ly-6C⁺ myeloid-derived suppressor cells (MDSCs) in the heart from CVB3-infected mice. Adoptive transfer of CD11b⁺Ly-6C⁺ MDSCs significantly alleviated myocarditis accompanied by increased Th2 and Treg frequency and anti-inflammatory cytokines expression in the heart tissue. Moreover, Ly6C⁺ MDSCs, but not Ly6G⁺ cells, expressed Arg-1 and NOS2, and suppressed CD4⁺ T cell proliferation in vitro in an Arg-1-dependent mechanism; an event that was reversed with treatment of either an Arg-1 inhibitor or addition of excess l-arginine. Furthermore, Ly6C⁺ MDSCs co-expressed higher levels of F4/80, Tim-3, and IL-4Rα, and had the plasticity to up-regulate NOS2 or Arg-1 in response to IFN-γ or IL-4 treatment. The present results indicate that galectin-9 expands CD11b⁺Ly-6C⁺ MDSCs to ameliorate CVB3-induced myocarditis.

Vγ1+γδT, early cardiac infiltrated innate population dominantly producing IL-4, protect mice against CVB3 myocarditis by modulating IFNγ+ T response

Viral myocarditis (VMC) is an inflammation of the myocardium closely associated with Coxsackievirus B3 (CVB3) infection. Vγ1⁺γδT cells, one of early cardiac infiltrated innate population, were reported to protect CVB3 myocarditis while the precise mechanism not fully addressed. To explore cytokine profiles and kinetics of Vγ1⁺γδT and mechanism of protection against VMC, flow cytometry was conducted on cardiac Vγ1 cells in C57BL/6 mice following CVB3 infection. The level of cardiac inflammation, transthoracic echocardiography and viral replication were evaluated after monoclonal antibody depletion of Vγ1γδT. We found that Vγ1⁺γδT cells infiltration peaked in the heart at day3 post CVB3 infection and constituted a minor source of IFN-γ but major producers for early IL-4. Vγ1γδT cells were activated earlier holding a higher IL-4-producing efficiency than CD4⁺Th cells in the heart. Depletion of Vγ1⁺γδT resulted in a significantly exacerbated cardiac infiltration, increased T, macrophage and neutrophil population in heart homogenates and worse cardiomyopathy; which was accompanied by a significant expansion of peripheral IFNγ⁺CD4+ and CD8+T cells. Neutralization of IL-4 in mice resulted in an exacerbated acute myocarditis confirming the IL-4-mediated protective mechanism of Vγ1. Our findings identify a unique property of Vγ1⁺γδT cells as one dominant early producers of IL-4 upon CVB3 acute infection which is a key mediator to protect mice against acute myocarditis by modulating IFNγ-secreting T response.

Melittin ameliorates CVB3-induced myocarditis via activation of the HDAC2-mediated GSK-3β/Nrf2/ARE signaling pathway

Viral myocarditis (VMC) is characterized as an inflammatory process of the myocardium and can be fatal in infants and children. Melittin is a major polypeptide in honey bee venom that has been traditionally used against inflammation. However, its effect on VMC and the underlying molecular mechanism has not been reported. In this study, BALB/c mice were intraperitoneally injected with CVB3 to build a VMC model and treated with melittin. The results showed that melittin increased the mice's body weight and inhibited CVB3 replication. HE staining also showed that melittin alleviated myocardial injury in the VMC model. Flow cytometry showed that melittin inhibited myocardial cell apoptosis; in addition, real-time PCR showed that melittin decreased the expression of bax and caspase-3, and increased the expression of bcl-2. The results of echocardiographic examination showed that melittin improved cardiac function. Moreover, melittin decreased the activity of AST, CK, HBDH and LDH, and decreased the production of IL-1β, IL-6, TNF-α and MCP-1 in CVB3-induced myocardial tissues. Finally, we also found that melittin increased the expression of HDAC2 and activated the GSK-3β/Nrf2/ARE signaling pathway, whereas these changes were reversed by inhibition of HDAC2 in VMC model mice. In conclusion, our results suggested that melittin ameliorates CVB3-induced myocarditis via activation of the HDAC2-mediated GSK-3β/Nrf2/ARE signaling pathway.

The novel asymmetric entry intermediate of a picornavirus captured with nanodiscs

Many nonenveloped viruses engage host receptors that initiate capsid conformational changes necessary for genome release. Structural studies on the mechanisms of picornavirus entry have relied on in vitro approaches of virus incubated at high temperatures or with excess receptor molecules to trigger the entry intermediate or A-particle. We have induced the coxsackievirus B3 entry intermediate by triggering the virus with full-length receptors embedded in lipid bilayer nanodiscs. These asymmetrically formed A-particles were reconstructed using cryo-electron microscopy and a direct electron detector. These first high-resolution structures of a picornavirus entry intermediate captured at a membrane with and without imposing icosahedral symmetry (3.9 and 7.8 Å, respectively) revealed a novel A-particle that is markedly different from the classical A-particles. The asymmetric receptor binding triggers minimal global capsid expansion but marked local conformational changes at the site of receptor interaction. In addition, viral proteins extrude from the capsid only at the site of extensive protein remodeling adjacent to the nanodisc. Thus, the binding of the receptor triggers formation of a unique site in preparation for genome release.

Isolation and genetic characterization of enterovirus in patients with febrile rash illness

Measles and rubella virus are usually considered as the causative agents in patients with febrile rash illness (FRI). However, investigators have identified that enteroviruses are also associated with FRI, and the present study was undertaken to investigate this association. In the study, 20 throat swab samples were collected from patients suffering from rash and fever between April and July in 2013. The 20 samples tested negative for measles virus, but all were positive when reverse transcription-polymerase chain reaction was performed using enterovirus universal primers. Specifically, five tested positive for Coxsackie B3 virus (CVB3). The titers of the five CVB3 isolates were 10^6.5, 10^6.4, 10^7.5, 10^6.5 and 10^6.5 tissue culture infectious dose₅₀/100 µl respectively. The partial VP1 sequences of the five CVB3 isolates were identical to each other and were closely associated with the CVB3/MKP and CVB3/Macocy strains, which are known to induce myocarditis and neonatal diseases of the central nervous system. In conclusion, CVB3 may cause symptoms of fever and rash and should be differentiated from measles, rubella and other infectious pathogens. The five CVB3 isolates described in the study were genetically similar to each other and to other local CVB3 strains. The results provide further data on the viral pathogen spectrum associated with FRI.

Remission of CVB3-induced myocarditis with Astragaloside IV treatment requires A20 (TNFAIP3) up-regulation

Viral myocarditis (VMC) most prevalently caused by coxsackievirus B3 (CVB3) infection is characterized by severe cardiac inflammation. Therapeutic options for the disease are still limited. Astragaloside IV (AST-IV), a purified small molecular saponin (C₄₁H₆₈O₁₄, MW 784), is the main active component of Chinese medical herb Astragalus which has been empirically prescribed for the treatment of heart dysfunction for centuries. In this study, we investigated the effect of AST-IV on CVB3-induced myocarditis and explored its possible mechanism involved. The results showed that AST-IV administration alleviated the severity of myocarditis and attenuated cardiac inflammation, which was mediated by inhibition of nuclear factor-kappaB (NF-κB) signalling. Importantly, we further identified that the inhibitory effect of AST-IV on NF-κB signalling was through increasing A20 (TNFAIP3) expression. Moreover, we validated that A20 was critical for the therapeutic efficacy of AST-IV on CVB3-induced myocarditis. Finally, we revealed that AST-IV enhanced A20 expression at post-transcriptional level by stabilization of mRNA. Our findings uncover a previously unknown mechanism for AST-IV in the treatment of VMC because of modulating inflammatory response via increasing A20 expression, which provide a potential target for screening new drugs and are helpful for optimization of the therapeutic strategies for VMC.

The antiviral effect of jiadifenoic acids C against coxsackievirus B3

Coxsackievirus B type 3 (CVB3) is one of the major causative pathogens associated with viral meningitis and myocarditis, which are widespread in the human population and especially prevalent in neonates and children. These infections can result in dilated cardiomyopathy (DCM) and other severe clinical complications. There are no vaccines or drugs approved for the prevention or therapy of CVB3-induced diseases. During screening for anti-CVB3 candidates in our previous studies, we found that jiadifenoic acids C exhibited strong antiviral activities against CVB3 as well as other strains of Coxsackie B viruses (CVBs). The present studies were carried out to evaluate the antiviral activities of jiadifenoic acids C. Results showed that jiadifenoic acids C could reduce CVB3 RNA and proteins synthesis in a dose-dependent manner. Jiadifenoic acids C also had a similar antiviral effect on the pleconaril-resistant variant of CVB3. We further examined the impact of jiadifenoic acids C on the synthesis of viral structural and non-structural proteins, finding that jiadifenoic acids C could reduce VP1 and 3D protein production. A time-course study with Vero cells showed that jiadifenoic acids C displayed significant antiviral activities at 0-6 h after CVB3 inoculation, indicating that jiadifenoic acids C functioned at an early step of CVB3 replication. However, jiadifenoic acids C had no prophylactic effect against CVB3. Taken together, we show that jiadifenoic acids C exhibit strong antiviral activities against all strains of CVB, including the pleconaril-resistant variant. Our study could provide a significant lead for anti-CVB3 drug development.

Antiviral activity of ginsenosides against coxsackievirus B3, enterovirus 71, and human rhinovirus 3

Background

Ginsenosides are the major components responsible for the biochemical and pharmacological actions of ginseng, and have been shown to have various biological activities. In this study, we investigated the antiviral activities of seven ginsenosides [protopanaxatriol (PT) type: Re, Rf, and Rg2; protopanaxadiol (PD) type: Rb1, Rb2, Rc, and Rd)] against coxsackievirus B3 (CVB3), enterovirus 71 (EV71), and human rhinovirus 3 (HRV3).

Methods

Assays of antiviral activity and cytotoxicity were evaluated by the sulforhodamine B method using the cytopathic effect (CPE) reduction assay.

Results

The antiviral assays demonstrated that, of the seven ginsenosides, the PT-type ginsenosides (Re, Rf, and Rg2) possess significant antiviral activities against CVB3 and HRV3 at a concentration of 100 μg/mL. Among the PT-type ginsenosides, only ginsenoside Rg2 showed significant anti-EV71 activity with no cytotoxicity to cells at 100 μg/mL. The PD-type ginsenosides (Rb1, Rb2, Rc, and Rd), by contrast, did not show any significant antiviral activity against CVB3, EV71, and HRV3, and exhibited cytotoxic effects to virus-infected cells. Notably, the antiviral efficacies of PT-type ginsenosides were comparable to those of ribavirin, a commonly used antiviral drug.

Conclusion

Collectively, our findings suggest that the ginsenosides Re, Rf, and Rg2 have the potential to be effective in the treatment of CVB3, EV71, and HRV3 infection.

Single-target RNA interference for the blockade of multiple interacting proinflammatory and profibrotic pathways in cardiac fibroblasts. J Mol Cell Cardiol. 2014;66:141-156. [PMID: 24239602 DOI: 10.1016/j.yjmcc.2013.11.004]

Therapeutic targets of broad relevance are likely located in pathogenic pathways common to disorders of various etiologies. Screening for targets of this type revealed CCN genes to be consistently upregulated in multiple cardiomyopathies. We developed RNA interference (RNAi) to silence CCN2 and found this single-target approach to block multiple proinflammatory and profibrotic pathways in activated primary cardiac fibroblasts (PCFBs). The RNAi-strategy was developed in murine PCFBs and then investigated in "individual" human PCFBs grown from human endomyocardial biopsies (EMBs). Screening of short hairpin RNA (shRNA) sequences for high silencing efficacy and specificity yielded RNAi adenovectors silencing CCN2 in murine or human PCFBs, respectively. Comparison of RNAi with CCN2-modulating microRNA (miR) vectors expressing miR-30c or miR-133b showed higher efficacy of RNAi. In murine PCFBs, CCN2 silencing resulted in strongly reduced expression of stretch-induced chemokines (Ccl2, Ccl7, Ccl8), matrix metalloproteinases (MMP2, MMP9), extracellular matrix (Col3a1), and a cell-to-cell contact protein (Cx43), suggesting multiple signal pathways to be linked to CCN2. Immune cell chemotaxis towards CCN2-depleted PCFBs was significantly reduced. We demonstrate here that this RNAi strategy is technically applicable to "individual" human PCFBs, too, but that these display individually strikingly different responses to CCN2 depletion. Either genomically encoded factors or stable epigenetic modification may explain different responses between individual PCFBs. The new RNAi approach addresses a key regulator protein induced in cardiomyopathies. Investigation of this and other molecular therapies in individual human PCBFs may help to dissect differential pathogenic processes between otherwise similar disease entities and individuals.

Maladaptive immune and inflammatory pathways lead to cardiovascular insulin resistance

Insulin resistance is a hallmark of obesity, the cardiorenal metabolic syndrome and type 2 diabetes mellitus (T2DM). The progression of insulin resistance increases the risk for cardiovascular disease (CVD). The significance of insulin resistance is underscored by the alarming rise in the prevalence of obesity and its associated comorbidities in the Unites States and worldwide over the last 40-50 years. The incidence of obesity is also on the rise in adolescents. Furthermore, premenopausal women have lower CVD risk compared to men, but this protection is lost in the setting of obesity and insulin resistance. Although systemic and cardiovascular insulin resistance is associated with impaired insulin metabolic signaling and cardiovascular dysfunction, the mechanisms underlying insulin resistance and cardiovascular dysfunction remain poorly understood. Recent studies show that insulin resistance in obesity and diabetes is linked to a metabolic inflammatory response, a state of systemic and tissue specific chronic low grade inflammation. Evidence is also emerging that there is polarization of macrophages and lymphocytes towards a pro-inflammatory phenotype that contributes to progression of insulin resistance in obesity, cardiorenal metabolic syndrome and diabetes. In this review, we provide new insights into factors, such as, the renin-angiotensin-aldosterone system, sympathetic activation and incretin modulators (e.g., DPP-4) and immune responses that mediate this inflammatory state in obesity and other conditions characterized by insulin resistance.

Protease-activated receptor-2 regulates the innate immune response to viral infection in a coxsackievirus B3-induced myocarditis

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 10(5) 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.