ISG15 blocks cardiac glycolysis and ensures sufficient mitochondrial energy production during Coxsackievirus B3 infection

AIMS

Virus infection triggers inflammation and, may impose nutrient shortage to the heart. Supported by type I interferon (IFN) signalling, cardiomyocytes counteract infection by various effector processes, with the IFN-stimulated gene of 15 kDa (ISG15) system being intensively regulated and protein modification with ISG15 protecting mice Coxsackievirus B3 (CVB3) infection. The underlying molecular aspects how the ISG15 system affects the functional properties of respective protein substrates in the heart are unknown.

METHODS AND RESULTS

Based on the protective properties due to protein ISGylation, we set out a study investigating CVB3-infected mice in depth and found cardiac atrophy with lower cardiac output in ISG15-/- mice. By mass spectrometry, we identified the protein targets of the ISG15 conjugation machinery in heart tissue and explored how ISGylation affects their function. The cardiac ISGylome showed a strong enrichment of ISGylation substrates within glycolytic metabolic processes. Two control enzymes of the glycolytic pathway, hexokinase 2 (HK2) and phosphofructokinase muscle form (PFK1), were identified as bona fide ISGylation targets during infection. In an integrative approach complemented with enzymatic functional testing and structural modelling, we demonstrate that protein ISGylation obstructs the activity of HK2 and PFK1. Seahorse-based investigation of glycolysis in cardiomyocytes revealed that, by conjugating proteins, the ISG15 system prevents the infection-/IFN-induced up-regulation of glycolysis. We complemented our analysis with proteomics-based advanced computational modelling of cardiac energy metabolism. Our calculations revealed an ISG15-dependent preservation of the metabolic capacity in cardiac tissue during CVB3 infection. Functional profiling of mitochondrial respiration in cardiomyocytes and mouse heart tissue by Seahorse technology showed an enhanced oxidative activity in cells with a competent ISG15 system.

CONCLUSION

Our study demonstrates that ISG15 controls critical nodes in cardiac metabolism. ISG15 reduces the glucose demand, supports higher ATP production capacity in the heart, despite nutrient shortage in infection, and counteracts cardiac atrophy and dysfunction.

Loss of TRIM29 mitigates viral myocarditis by attenuating PERK-driven ER stress response in male mice

Viral myocarditis, an inflammatory disease of the myocardium, is a significant cause of sudden death in children and young adults. The current coronavirus disease 19 pandemic emphasizes the need to understand the pathogenesis mechanisms and potential treatment strategies for viral myocarditis. Here, we found that TRIM29 was highly induced by cardiotropic viruses and promoted protein kinase RNA-like endoplasmic reticulum kinase (PERK)-mediated endoplasmic reticulum (ER) stress, apoptosis, and reactive oxygen species (ROS) responses that promote viral replication in cardiomyocytes in vitro. TRIM29 deficiency protected mice from viral myocarditis by promoting cardiac antiviral functions and reducing PERK-mediated inflammation and immunosuppressive monocytic myeloid-derived suppressor cells (mMDSC) in vivo. Mechanistically, TRIM29 interacted with PERK to promote SUMOylation of PERK to maintain its stability, thereby promoting PERK-mediated signaling pathways. Finally, we demonstrated that the PERK inhibitor GSK2656157 mitigated viral myocarditis by disrupting the TRIM29-PERK connection, thereby bolstering cardiac function, enhancing cardiac antiviral responses, and curbing inflammation and immunosuppressive mMDSC in vivo. Our findings offer insight into how cardiotropic viruses exploit TRIM29-regulated PERK signaling pathways to instigate viral myocarditis, suggesting that targeting the TRIM29-PERK axis could mitigate disease severity.

Enterovirus-Cardiomyocyte Interactions: Impact of Terminally Deleted Genomic RNAs on Viral and Host Functions

Group B enteroviruses, including coxsackievirus B3 (CVB3), can persistently infect cardiac tissue and cause dilated cardiomyopathy. Persistence is linked to 5' terminal deletions of viral genomic RNAs that have been detected together with minor populations of full-length genomes in human infections. In this study, we explored the functions and interactions of the different viral RNA forms found in persistently infected patients and their putative role(s) in pathogenesis. Since enterovirus cardiac pathogenesis is linked to the viral proteinase 2A, we investigated the effect of different terminal genomic RNA deletions on 2A activity. We discovered that 5' terminal deletions in CVB3 genomic RNAs decreased the levels of 2A proteinase activity but could not abrogate it. Using newly generated viral reporters encoding nano-luciferase, we found that 5' terminal deletions resulted in decreased levels of viral protein and RNA synthesis in singly transfected cardiomyocyte cultures. Unexpectedly, when full-length and terminally deleted forms were cotransfected into cardiomyocytes, a cooperative interaction was observed, leading to increased viral RNA and protein production. However, when viral infections were carried out in cells harboring 5' terminally deleted CVB3 RNAs, a decrease in infectious particle production was observed. Our results provide a possible explanation for the necessity of full-length viral genomes during persistent infection, as they would stimulate efficient viral replication compared to that of the deleted genomes alone. To avoid high levels of viral particle production that would trigger cellular immune activation and host cell death, the terminally deleted RNA forms act to limit the production of viral particles, possibly as trans-dominant inhibitors. IMPORTANCE Enteroviruses like coxsackievirus B3 are able to initiate acute infections of cardiac tissue and, in some cases, to establish a long-term persistent infection that can lead to serious disease sequelae, including dilated cardiomyopathy. Previous studies have demonstrated the presence of 5' terminally deleted forms of enterovirus RNAs in heart tissues derived from patients with dilated cardiomyopathy. These deleted RNAs are found in association with very low levels of full-length enterovirus genomic RNAs, an interaction that may facilitate continued persistence while limiting virus particle production. Even in the absence of detectable infectious virus particle production, these deleted viral RNA forms express viral proteinases at levels capable of causing viral pathology. Our studies provide mechanistic insights into how full-length and deleted forms of enterovirus RNA cooperate to stimulate viral protein and RNA synthesis without stimulating infectious viral particle production. They also highlight the importance of targeting enteroviral proteinases to inhibit viral replication while at the same time limiting the long-term pathologies they trigger.

Functional Effects of Cardiomyocyte Injury in COVID-19

COVID-19 affects multiple organs. Clinical data from the Mount Sinai Health System show that substantial numbers of COVID-19 patients without prior heart disease develop cardiac dysfunction. How COVID-19 patients develop cardiac disease is not known. We integrated cell biological and physiological analyses of human cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs) infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the presence of interleukins (ILs) with clinical findings related to laboratory values in COVID-19 patients to identify plausible mechanisms of cardiac disease in COVID-19 patients. We infected hiPSC-derived cardiomyocytes from healthy human subjects with SARS-CoV-2 in the absence and presence of IL-6 and IL-1β. Infection resulted in increased numbers of multinucleated cells. Interleukin treatment and infection resulted in disorganization of myofibrils, extracellular release of troponin I, and reduced and erratic beating. Infection resulted in decreased expression of mRNA encoding key proteins of the cardiomyocyte contractile apparatus. Although interleukins did not increase the extent of infection, they increased the contractile dysfunction associated with viral infection of cardiomyocytes, resulting in cessation of beating. Clinical data from hospitalized patients from the Mount Sinai Health System show that a significant portion of COVID-19 patients without history of heart disease have elevated troponin and interleukin levels. A substantial subset of these patients showed reduced left ventricular function by echocardiography. Our laboratory observations, combined with the clinical data, indicate that direct effects on cardiomyocytes by interleukins and SARS-CoV-2 infection might underlie heart disease in COVID-19 patients. IMPORTANCE SARS-CoV-2 infects multiple organs, including the heart. Analyses of hospitalized patients show that a substantial number without prior indication of heart disease or comorbidities show significant injury to heart tissue, assessed by increased levels of troponin in blood. We studied the cell biological and physiological effects of virus infection of healthy human iPSC-derived cardiomyocytes in culture. Virus infection with interleukins disorganizes myofibrils, increases cell size and the numbers of multinucleated cells, and suppresses the expression of proteins of the contractile apparatus. Viral infection of cardiomyocytes in culture triggers release of troponin similar to elevation in levels of COVID-19 patients with heart disease. Viral infection in the presence of interleukins slows down and desynchronizes the beating of cardiomyocytes in culture. The cell-level physiological changes are similar to decreases in left ventricular ejection seen in imaging of patients' hearts. These observations suggest that direct injury to heart tissue by virus can be one underlying cause of heart disease in COVID-19.

Robotic high-throughput biomanufacturing and functional differentiation of human pluripotent stem cells

Efficient translation of human induced pluripotent stem cells (hiPSCs) requires scalable cell manufacturing strategies for optimal self-renewal and functional differentiation. Traditional manual cell culture is variable and labor intensive, posing challenges for high-throughput applications. Here, we established a robotic platform and automated all essential steps of hiPSC culture and differentiation under chemically defined conditions. This approach allowed rapid and standardized manufacturing of billions of hiPSCs that can be produced in parallel from up to 90 different patient- and disease-specific cell lines. Moreover, we established automated multi-lineage differentiation and generated functional neurons, cardiomyocytes, and hepatocytes. To validate our approach, we compared robotic and manual cell culture operations and performed comprehensive molecular and cellular characterizations (e.g., single-cell transcriptomics, mass cytometry, metabolism, electrophysiology) to benchmark industrial-scale cell culture operations toward building an integrated platform for efficient cell manufacturing for disease modeling, drug screening, and cell therapy.

Highly Efficient SARS-CoV-2 Infection of Human Cardiomyocytes: Spike Protein-Mediated Cell Fusion and Its Inhibition

Severe cardiovascular complications can occur in coronavirus disease of 2019 (COVID-19) patients. Cardiac damage is attributed mostly to the aberrant host response to acute respiratory infection. However, direct infection of cardiac tissue by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) also occurs. We examined here the cardiac tropism of SARS-CoV-2 in spontaneously beating human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). These cardiomyocytes express the angiotensin-converting enzyme 2 (ACE2) receptor but not the transmembrane protease serine 2 (TMPRSS2) that mediates spike protein cleavage in the lungs. Nevertheless, SARS-CoV-2 infection of hiPSC-CMs was prolific; viral transcripts accounted for about 88% of total mRNA. In the cytoplasm of infected hiPSC-CMs, smooth-walled exocytic vesicles contained numerous 65- to 90-nm particles with canonical ribonucleocapsid structures, and virus-like particles with knob-like spikes covered the cell surface. To better understand how SARS-CoV-2 spreads in hiPSC-CMs, we engineered an expression vector coding for the spike protein with a monomeric emerald-green fluorescent protein fused to its cytoplasmic tail (S-mEm). Proteolytic processing of S-mEm and the parental spike were equivalent. Live cell imaging tracked spread of S-mEm cell-to-cell and documented formation of syncytia. A cell-permeable, peptide-based molecule that blocks the catalytic site of furin and furin-like proteases abolished cell fusion. A spike mutant with the single amino acid change R682S that disrupts the multibasic furin cleavage motif was fusion inactive. Thus, SARS-CoV-2 replicates efficiently in hiPSC-CMs and furin, and/or furin-like-protease activation of its spike protein is required for fusion-based cytopathology. This hiPSC-CM platform enables target-based drug discovery in cardiac COVID-19. IMPORTANCE Cardiac complications frequently observed in COVID-19 patients are tentatively attributed to systemic inflammation and thrombosis, but viral replication has occasionally been confirmed in cardiac tissue autopsy materials. We developed an in vitro model of SARS-CoV-2 spread in myocardium using induced pluripotent stem cell-derived cardiomyocytes. In these highly differentiated cells, viral transcription levels exceeded those previously documented in permissive transformed cell lines. To better understand the mechanisms of SARS-CoV-2 spread, we expressed a fluorescent version of its spike protein that allowed us to characterize a fusion-based cytopathic effect. A mutant of the spike protein with a single amino acid mutation in the furin/furin-like protease cleavage site lost cytopathic function. Of note, the fusion activities of the spike protein of other coronaviruses correlated with the level of cardiovascular complications observed in infections with the respective viruses. These data indicate that SARS-CoV-2 may cause cardiac damage by fusing cardiomyocytes.

Cardiomyocytes recruit monocytes upon SARS-CoV-2 infection by secreting CCL2

Heart injury has been reported in up to 20% of COVID-19 patients, yet the cause of myocardial histopathology remains unknown. Here, using an established in vivo hamster model, we demonstrate that SARS-CoV-2 can be detected in cardiomyocytes of infected animals. Furthermore, we found damaged cardiomyocytes in hamsters and COVID-19 autopsy samples. To explore the mechanism, we show that both human pluripotent stem cell-derived cardiomyocytes (hPSC-derived CMs) and adult cardiomyocytes (CMs) can be productively infected by SARS-CoV-2, leading to secretion of the monocyte chemoattractant cytokine CCL2 and subsequent monocyte recruitment. Increased CCL2 expression and monocyte infiltration was also observed in the hearts of infected hamsters. Although infected CMs suffer damage, we find that the presence of macrophages significantly reduces SARS-CoV-2-infected CMs. Overall, our study provides direct evidence that SARS-CoV-2 infects CMs in vivo and suggests a mechanism of immune cell infiltration and histopathology in heart tissues of COVID-19 patients.

COVID-19-related cardiac complications from clinical evidences to basic mechanisms: opinion paper of the ESC Working Group on Cellular Biology of the Heart

The pandemic of coronavirus disease (COVID)-19 is a global threat, causing high mortality, especially in the elderly. The main symptoms and the primary cause of death are related to interstitial pneumonia. Viral entry also into myocardial cells mainly via the angiotensin converting enzyme type 2 (ACE2) receptor and excessive production of pro-inflammatory cytokines, however, also make the heart susceptible to injury. In addition to the immediate damage caused by the acute inflammatory response, the heart may also suffer from long-term consequences of COVID-19, potentially causing a post-pandemic increase in cardiac complications. Although the main cause of cardiac damage in COVID-19 remains coagulopathy with micro- (and to a lesser extent macro-) vascular occlusion, open questions remain about other possible modalities of cardiac dysfunction, such as direct infection of myocardial cells, effects of cytokines storm, and mechanisms related to enhanced coagulopathy. In this opinion paper, we focus on these lesser appreciated possibilities and propose experimental approaches that could provide a more comprehensive understanding of the cellular and molecular bases of cardiac injury in COVID-19 patients. We first discuss approaches to characterize cardiac damage caused by possible direct viral infection of cardiac cells, followed by formulating hypotheses on how to reproduce and investigate the hyperinflammatory and pro-thrombotic conditions observed in the heart of COVID-19 patients using experimental in vitro systems. Finally, we elaborate on strategies to discover novel pathology biomarkers using omics platforms.

Human embryonic stem cell-derived cardiomyocyte platform screens inhibitors of SARS-CoV-2 infection

Patients with cardiovascular comorbidities are more susceptible to severe infection with SARS-CoV-2, known to directly cause pathological damage to cardiovascular tissue. We outline a screening platform using human embryonic stem cell-derived cardiomyocytes, confirmed to express the protein machinery critical for SARS-CoV-2 infection, and a SARS-CoV-2 spike-pseudotyped virus system. The method has allowed us to identify benztropine and DX600 as novel inhibitors of SARS-CoV-2 infection in a clinically relevant stem cell-derived cardiomyocyte line. Discovery of new medicines will be critical for protecting the heart in patients with SARS-CoV-2, and for individuals where vaccination is contraindicated.

SARS-CoV-2 infection of human iPSC-derived cardiac cells reflects cytopathic features in hearts of patients with COVID-19

Although coronavirus disease 2019 (COVID-19) causes cardiac dysfunction in up to 25% of patients, its pathogenesis remains unclear. Exposure of human induced pluripotent stem cell (iPSC)-derived heart cells to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) revealed productive infection and robust transcriptomic and morphological signatures of damage, particularly in cardiomyocytes. Transcriptomic disruption of structural genes corroborates adverse morphologic features, which included a distinct pattern of myofibrillar fragmentation and nuclear disruption. Human autopsy specimens from patients with COVID-19 reflected similar alterations, particularly sarcomeric fragmentation. These notable cytopathic features in cardiomyocytes provide insights into SARS-CoV-2-induced cardiac damage, offer a platform for discovery of potential therapeutics, and raise concerns about the long-term consequences of COVID-19 in asymptomatic and severe cases.

COVID-19 and Cardiovascular Disease: From Bench to Bedside

A pandemic of historic impact, coronavirus disease 2019 (COVID-19) has potential consequences on the cardiovascular health of millions of people who survive infection worldwide. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), the etiologic agent of COVID-19, can infect the heart, vascular tissues, and circulating cells through ACE2 (angiotensin-converting enzyme 2), the host cell receptor for the viral spike protein. Acute cardiac injury is a common extrapulmonary manifestation of COVID-19 with potential chronic consequences. This update provides a review of the clinical manifestations of cardiovascular involvement, potential direct SARS-CoV-2 and indirect immune response mechanisms impacting the cardiovascular system, and implications for the management of patients after recovery from acute COVID-19 infection.

MicroRNA-30a-5p silencing polarizes macrophages toward M2 phenotype to alleviate cardiac injury following viral myocarditis by targeting SOCS1

Viral myocarditis (VMC) is a life-threatening disease characterized by severe cardiac inflammation generally caused by coxsackievirus B3 (CVB3) infection. Several microRNAs (miRNAs or miRs) are known to play crucial roles in the pathogenesis of VMC. The study aimed to decipher the role of miR-30a-5p in the underlying mechanisms of VMC pathogenesis. We first quantified miR-30a-5p expression in a CVB3-induced mouse VMC model. The physiological characteristics of mouse cardiac tissues were then detected by hematoxylin and eosin (HE) and Picrosirius red staining. We established the correlation between miR-30a-5p and SOCS1, using dual-luciferase gene assay and Pearson's correlation coefficient. The expression of inflammatory factors (IFN-γ, IL-6, IL-10, and IL-13), M1 polarization markers [TNF-α, inducible nitric oxide synthase (iNOS)], M2 polarization markers (Arg-1, IL-10), and myocardial hypertrophy markers [atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)] was detected by RT-qPCR and Western blot analysis. miR-30a-5p was found to be highly expressed in VMC mice. Silencing of miR-30a-5p improved the cardiac function index and reduced heart weight-to-body weight ratio, myocardial tissue pathological changes and fibrosis degree, serological indexes, as well as proinflammatory factor levels, while enhancing anti-inflammatory factor levels in VMC mice. Furthermore, silencing of miR-30a-5p inhibited M1 polarization of macrophages while promoting M2 polarization in vivo and in vitro. SOCS1 was a target gene of miR-30a-5p, and the aforementioned cardioprotective effects of miR-30a-5p silencing were reversed upon silencing of SOCS1. Overall, this study shows that silencing of miR-30a-5p may promote M2 polarization of macrophages and improve cardiac injury following VMC via SOCS1 upregulation, constituting a potential therapeutic target for VMC treatment.NEW & NOTEWORTHY We found in this study that microRNA (miR)-30a-5p inhibition might improve cardiac injury following viral myocarditis (VMC) by accelerating M2 polarization of macrophages via SOCS1 upregulation. Furthermore, the anti-inflammatory mechanisms of miR-30a-5p inhibition may contribute to the development of new therapeutic strategies for VMC.

Network pharmacology and RNA-sequencing reveal the molecular mechanism of Xuebijing injection on COVID-19-induced cardiac dysfunction

BACKGROUND

Coronavirus disease 2019 (COVID-19) is an emerging infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Up to 20%-30% of patients hospitalized with COVID-19 have evidence of cardiac dysfunction. Xuebijing injection is a compound injection containing five traditional Chinese medicine ingredients, which can protect cells from SARS-CoV-2-induced cell death and improve cardiac function. However, the specific protective mechanism of Xuebijing injection on COVID-19-induced cardiac dysfunction remains unclear.

METHODS

The therapeutic effect of Xuebijing injection on COVID-19 was validated by the TCM Anti COVID-19 (TCMATCOV) platform. RNA-sequencing (RNA-seq) data from GSE150392 was used to find differentially expressed genes (DEGs) from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) infected with SARS-CoV-2. Data from GSE151879 was used to verify the expression of Angiotensin I Converting Enzyme 2 (ACE2) and central hub genes in both human embryonic-stem-cell-derived cardiomyocytes (hESC-CMs) and adult human CMs with SARS-CoV-2 infection.

RESULTS

A total of 97 proteins were identified as the therapeutic targets of Xuebijing injection for COVID-19. There were 22 DEGs in SARS-CoV-2 infected hiPSC-CMs overlapped with the 97 therapeutic targets, which might be the therapeutic targets of Xuebijing injection on COVID-19-induced cardiac dysfunction. Based on the bioinformatics analysis, 7 genes (CCL2, CXCL8, FOS, IFNB1, IL-1A, IL-1B, SERPINE1) were identified as central hub genes and enriched in pathways including cytokines, inflammation, cell senescence and oxidative stress. ACE2, the receptor of SARS-CoV-2, and the 7 central hub genes were differentially expressed in at least two kinds of SARS-CoV-2 infected CMs. Besides, FOS and quercetin exhibited the tightest binding by molecular docking analysis.

CONCLUSION

Our study indicated the underlying protective effect of Xuebijing injection on COVID-19, especially on COVID19-induced cardiac dysfunction, which provided the theoretical basis for exploring the potential protective mechanism of Xuebijing injection on COVID19-induced cardiac dysfunction.

SARS-CoV-2 Infects Human Pluripotent Stem Cell-Derived Cardiomyocytes, Impairing Electrical and Mechanical Function

COVID-19 patients often develop severe cardiovascular complications, but it remains unclear if these are caused directly by viral infection or are secondary to a systemic response. Here, we examine the cardiac tropism of SARS-CoV-2 in human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) and smooth muscle cells (hPSC-SMCs). We find that that SARS-CoV-2 selectively infects hPSC-CMs through the viral receptor ACE2, whereas in hPSC-SMCs there is minimal viral entry or replication. After entry into cardiomyocytes, SARS-CoV-2 is assembled in lysosome-like vesicles and egresses via bulk exocytosis. The viral transcripts become a large fraction of cellular mRNA while host gene expression shifts from oxidative to glycolytic metabolism and upregulates chromatin modification and RNA splicing pathways. Most importantly, viral infection of hPSC-CMs progressively impairs both their electrophysiological and contractile function, and causes widespread cell death. These data support the hypothesis that COVID-19-related cardiac symptoms can result from a direct cardiotoxic effect of SARS-CoV-2.

Human influenza A virus causes myocardial and cardiac-specific conduction system infections associated with early inflammation and premature death

AIMS

Human influenza A virus (hIAV) infection is associated with important cardiovascular complications, although cardiac infection pathophysiology is poorly understood. We aimed to study the ability of hIAV of different pathogenicity to infect the mouse heart, and establish the relationship between the infective capacity and the associated in vivo, cellular and molecular alterations.

METHODS AND RESULTS

We evaluated lung and heart viral titres in mice infected with either one of several hIAV strains inoculated intranasally. 3D reconstructions of infected cardiac tissue were used to identify viral proteins inside mouse cardiomyocytes, Purkinje cells, and cardiac vessels. Viral replication was measured in mouse cultured cardiomyocytes. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to confirm infection and study underlying molecular alterations associated with the in vivo electrophysiological phenotype. Pathogenic and attenuated hIAV strains infected and replicated in cardiomyocytes, Purkinje cells, and hiPSC-CMs. The infection was also present in cardiac endothelial cells. Remarkably, lung viral titres did not statistically correlate with viral titres in the mouse heart. The highly pathogenic human recombinant virus PAmut showed faster replication, higher level of inflammatory cytokines in cardiac tissue and higher viral titres in cardiac HL-1 mouse cells and hiPSC-CMs compared with PB2mut-attenuated virus. Correspondingly, cardiac conduction alterations were especially pronounced in PAmut-infected mice, associated with high mortality rates, compared with PB2mut-infected animals. Consistently, connexin43 and NaV1.5 expression decreased acutely in hiPSC-CMs infected with PAmut virus. YEM1L protease also decreased more rapidly and to lower levels in PAmut-infected hiPSC-CMs compared with PB2mut-infected cells, consistent with mitochondrial dysfunction. Human IAV infection did not increase myocardial fibrosis at 4-day post-infection, although PAmut-infected mice showed an early increase in mRNAs expression of lysyl oxidase.

CONCLUSION

Human IAV can infect the heart and cardiac-specific conduction system, which may contribute to cardiac complications and premature death.

Mitigated viral myocarditis in A/J mice by the immunoproteasome inhibitor ONX 0914 depends on inhibition of systemic inflammatory responses in CoxsackievirusB3 infection

A preclinical model of troponin I-induced myocarditis (AM) revealed a prominent role of the immunoproteasome (ip), the main immune cell-resident proteasome isoform, in heart-directed autoimmunity. Viral infection of the heart is a known trigger of cardiac autoimmunity, with the ip enhancing systemic inflammatory responses after infection with a cardiotropic coxsackievirusB3 (CV). Here, we used ip-deficient A/J-LMP7-/- mice to investigate the role of ip-mediated effects on adaptive immunity in CV-triggered myocarditis and found no alteration of the inflammatory heart tissue damage or cardiac function in comparison to wild-type controls. Aiming to define the impact of the systemic inflammatory storm under the control of ip proteolysis during CV infection, we targeted the ip in A/J mice with the inhibitor ONX 0914 after the first cycle of infection, when systemic inflammation has set in, well before cardiac inflammation. During established acute myocarditis, the ONX 0914 treatment group had the same reduction in cardiac output as the controls, with inflammatory responses in heart tissue being unaffected by the compound. Based on these findings and with regard to the known anti-inflammatory role of ONX 0914 in CV infection, we conclude that the efficacy of ip inhibitors for CV-triggered myocarditis in A/J mice relies on their immunomodulatory effects on the systemic inflammatory reaction.

Coxsackievirus B3 Infection Early in Pregnancy Induces Congenital Heart Defects Through Suppression of Fetal Cardiomyocyte Proliferation

Background Coxsackievirus B (CVB) is the most common cause of viral myocarditis. It targets cardiomyocytes through coxsackie and adenovirus receptor, which is highly expressed in the fetal heart. We hypothesized CVB3 can precipitate congenital heart defects when fetal infection occurs during critical window of gestation. Methods and Results We infected C57Bl/6 pregnant mice with CVB3 during time points in early gestation (embryonic day [E] 5, E7, E9, and E11). We used different viral titers to examine possible dose-response relationship and assessed viral loads in various fetal organs. Provided viral exposure occurred between E7 and E9, we observed characteristic features of ventricular septal defect (33.6%), abnormal myocardial architecture resembling noncompaction (23.5%), and double-outlet right ventricle (4.4%) among 209 viable fetuses examined. We observed a direct relationship between viral titers and severity of congenital heart defects, with apparent predominance among female fetuses. Infected dams remained healthy; we did not observe any maternal heart or placental injury suggestive of direct viral effects on developing heart as likely cause of congenital heart defects. We examined signaling pathways in CVB3-exposed hearts using RNA sequencing, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, and immunohistochemistry. Signaling proteins of the Hippo, tight junction, transforming growth factor-β1, and extracellular matrix proteins were the most highly enriched in CVB3-infected fetuses with ventricular septal defects. Moreover, cardiomyocyte proliferation was 50% lower in fetuses with ventricular septal defects compared with uninfected controls. Conclusions We conclude prenatal CVB3 infection induces congenital heart defects. Alterations in myocardial proliferate capacity and consequent changes in cardiac architecture and trabeculation appear to account for most of observed phenotypes.

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.

Antiviral activity and safety of remdesivir against SARS-CoV-2 infection in human pluripotent stem cell-derived cardiomyocytes

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is considered as the most significant global public health crisis of the century. Several drug candidates have been suggested as potential therapeutic options for COVID-19, including remdesivir, currently the only authorized drug for use under an Emergency Use Authorization. However, there is only limited information regarding the safety profiles of the proposed drugs, in particular drug-induced cardiotoxicity. Here, we evaluated the antiviral activity and cardiotoxicity of remdesivir using cardiomyocytes-derived from human pluripotent stem cells (hPSC-CMs) as an alternative source of human primary cardiomyocytes (CMs). In this study, remdesivir exhibited up to 60-fold higher antiviral activity in hPSC-CMs compared to Vero E6 cells; however, it also induced moderate cardiotoxicity in these cells. To gain further insight into the drug-induced arrhythmogenic risk, we assessed QT interval prolongation and automaticity of remdesivir-treated hPSC-CMs using a multielectrode array (MEA). As a result, the data indicated a potential risk of QT prolongation when remdesivir is used at concentrations higher than the estimated peak plasma concentration. Therefore, we conclude that close monitoring of the electrocardiographic/QT interval should be advised in SARS-CoV-2-infected patients under remdesivir medication, in particular individuals with pre-existing heart conditions.

MicroRNAs targeting the SARS-CoV-2 entry receptor ACE2 in cardiomyocytes

The World Health Organization (WHO) declared coronavirus disease 2019 (COVID-19) as a public health emergency of international concern as more than 15 million cases were reported by 24th July 2020. Angiotensin-converting enzyme 2 (ACE2) is a COVID-19 entry receptor regulating host cell infection. A recent study reported that ACE2 is expressed in cardiomyocytes. In this study, we aimed to explore if there are microRNA (miRNA) molecules which target ACE2 and which may be exploited to regulate the SARS-CoV-2 receptor. Our data reveal that both Ace2 mRNA and Ace2 protein levels are inhibited by miR-200c in rat primary cardiomyocytes and importantly, in human iPSC-derived cardiomyocytes. We report the first miRNA candidate that can target ACE2 in cardiomyocytes and thus may be exploited as a preventive strategy to treat cardiovascular complications of COVID-19.

Characterization of zika virus infection of human fetal cardiac mesenchymal stromal cells

Zika virus (ZIKV) is a single-stranded RNA virus belonging to the family Flaviviridae. ZIKV predominantly enters cells using the TAM-family protein tyrosine kinase receptor AXL, which is expressed on a range of cell types, including neural progenitor cells, keratinocytes, dendritic cells, and osteoblasts. ZIKV infections have been associated with fetal brain damage, which prompted the World Health Organization to declare a public health emergency in 2016. ZIKV infection has also been linked to birth defects in other organs. Several studies have reported congenital heart defects (CHD) in ZIKV infected infants and cardiovascular complications in adults infected with ZIKV. To develop a better understanding of potential causes for these pathologies at a cellular level, we characterized ZIKV infection of human fetal cardiac mesenchymal stromal cells (fcMSCs), a cell type that is known to contribute to both embryological development as well as adult cardiac physiology. Total RNA, supernatants, and/or cells were collected at various time points post-infection to evaluate ZIKV replication, cell death, and antiviral responses. We found that ZIKV productively infected fcMSCs with peak (~70%) viral mRNA detected at 48 h. Use of an antibody blocking the AXL receptor decreased ZIKV infection (by ~50%), indicating that the receptor is responsible to a large extent for viral entry into the cell. ZIKV also altered protein expression of several mesenchymal cell markers, which suggests that ZIKV could affect fcMSCs’ differentiation process. Gene expression analysis of fcMSCs exposed to ZIKV at 6, 12, and 24 h post-infection revealed up-regulation of genes/pathways associated with interferon-stimulated antiviral responses. Stimulation of TLR3 (using poly I:C) or TLR7 (using Imiquimod) prior to ZIKV infection suppressed viral replication in a dose-dependent manner. Overall, fcMSCs can be a target for ZIKV infection, potentially resulting in CHD during embryological development and/or cardiovascular issues in ZIKV infected adults.

Extracellular SPARC increases cardiomyocyte contraction during health and disease

Secreted protein acidic and rich in cysteine (SPARC) is a non-structural extracellular matrix protein that regulates interactions between the matrix and neighboring cells. In the cardiovascular system, it is expressed by cardiac fibroblasts, endothelial cells, and at lower levels by ventricular cardiomyocytes. SPARC expression levels are increased upon myocardial injury and also during hypertrophy and fibrosis. We have previously shown that SPARC improves cardiac function after myocardial infarction by regulating post-synthetic procollagen processing, however whether SPARC directly affects cardiomyocyte contraction is still unknown. In this study we demonstrate a novel inotropic function for extracellular SPARC in the healthy heart as well as in the diseased state after myocarditis-induced cardiac dysfunction. We demonstrate SPARC presence on the cardiomyocyte membrane where it is co-localized with the integrin-beta1 and the integrin-linked kinase. Moreover, extracellular SPARC directly increases cardiomyocyte cell shortening ex vivo and cardiac function in vivo, both in healthy myocardium and during coxsackie virus-induced cardiac dysfunction. In conclusion, we demonstrate a novel inotropic function for SPARC in the heart, with a potential therapeutic application when myocyte contractile function is diminished such as that caused by a myocarditis-related cardiac injury.

Development of selective cytotoxic viral vectors for concentration of undifferentiated cells in cardiomyocytes derived from human induced pluripotent stem cells

Cell-processed therapeutic products (CTPs) derived from human pluripotent stem cells (hPSCs) have innovative applications in regenerative medicine. However, undifferentiated hPSCs possess tumorigenic potential; thus, sensitive methods for the detection of residual undifferentiated hPSCs are essential for the clinical use of hPSC-derived CTPs. The detection limit of the methods currently available is 1/105 (0.001%, undifferentiated hPSCs/differentiated cells) or more, which could be insufficient for the detection of residual hPSCs when CTPs contain more than 1 × 105 cells. In this study, we developed a novel approach to overcome this challenge, using adenovirus and adeno-associated virus (AdV and AAV)-based selective cytotoxic vectors. We constructed AdV and AAV vectors that possess a suicide gene, iCaspase 9 (iCasp9), regulated by the CMV promoter, which is dormant in hPSCs, for the selective expression of iCasp9 in differentiated cells. As expected, AdV/CMV-iCasp9 and AAV/CMV-iCasp9 exhibited cytotoxicity in cardiomyocytes but not in human induced pluripotent stem cells (hiPSCs). The vectors also induced apoptosis in hiPSC-derived cardiomyocytes, and the surviving cells exhibited higher levels of hPSC marker expression. These results indicate that the AdV- and AAV-based cytotoxic vectors concentrate cells expressing the undifferentiated cell markers in hiPSC-derived products and are promising biological tools for verifying the quality of CTPs.

ADAR1p150 Forms a Complex with Dicer to Promote miRNA-222 Activity and Regulate PTEN Expression in CVB3-Induced Viral Myocarditis

Adenosine deaminases acting on RNA (ADAR) are enzymes that regulate RNA metabolism through post-transcriptional mechanisms. ADAR1 is involved in a variety of pathological conditions including inflammation, cancer, and the host defense against viral infections. However, the role of ADAR1p150 in vascular disease remains unclear. In this study, we examined the expression of ADAR1p150 and its role in viral myocarditis (VMC) in a mouse model. VMC mouse cardiomyocytes showed significantly higher expression of ADAR1p150 compared to the control samples. Coimmunoprecipitation verified that ADAR1p150 forms a complex with Dicer in VMC. miRNA-222, which is involved in many cardiac diseases, is highly expressed in cardiomyocytes in VMC. In addition, the expression of miRNA-222 was promoted by ADAR1p150/Dicer. Among the target genes of miRNA-222, the expression of phosphatase-and-tensin (PTEN) protein was significantly reduced in VMC. By using a bioinformatics tool, we found a potential binding site of miRNA-222 on the PTEN gene’s 3′-UTR, suggesting that miRNA-222 might play a regulatory role. In cultured cells, miR-222 suppressed PTEN expression. Our findings suggest that ADAR1p150 plays a key role in complexing with Dicer and promoting the expression of miRNA-222, the latter of which suppresses the expression of the target gene PTEN during VMC. Our work reveals a previously unknown role of ADAR1p150 in gene expression in VMC.

Cathepsin B aggravates coxsackievirus B3-induced myocarditis through activating the inflammasome and promoting pyroptosis

Cathepsin B (CatB) is a cysteine proteolytic enzyme widely expressed in various cells and mainly located in the lysosomes. It contributes to the pathogenesis and development of many diseases. However, the role of CatB in viral myocarditis (VMC) has never been elucidated. Here we generated the VMC model by intraperitoneal injection of coxsackievirus B3 (CVB3) into mice. At day 7 and day 28, we found CatB was significantly activated in hearts from VMC mice. Compared with the wild-type mice receiving equal amount of CVB3, genetic ablation of CatB (Ctsb^-/-) significantly improved survival, reduced inflammatory cell infiltration, decreased serum level of cardiac troponin I, and ameliorated cardiac dysfunction, without altering virus titers in hearts. Conversely, genetic deletion of cystatin C (Cstc^-/-), which markedly enhanced CatB levels in hearts, distinctly increased the severity of VMC. Furthermore, compared with the control, we found the inflammasome was activated in the hearts of wild-type mice with VMC, which was attenuated in the hearts of Ctsb^-/- mice but was further enhanced in Cstc^-/- mice. Consistently, the inflammasome-initiated pyroptosis was reduced in Ctsb^-/- mice hearts and further increased in Cstc^-/- mice. These results suggest that CatB aggravates CVB3-induced VMC probably through activating the inflammasome and promoting pyroptosis. This finding might provide a novel strategy for VMC treatment.

Severe VMC could lead to sudden cardiac death especially in youths, and is also the most common cause of secondary dilated cardiomyopathy. However, we still lack effective and specific clinical treatments currently. Therefore, further exploration of the pathogenesis and new therapeutic targets are urgently needed. Our results implied that CatB, a cysteine protease mainly located in the lysosome, is activated in the hearts of mice with VMC induced by intraperitoneal injection of CVB3. Genetic deletion of CatB significantly improves survival, attenuates cardiac inflammation, decreases serum cardiac troponin I levels and alleviates cardiac dysfunction, without altering virus titers in hearts. However, ablation of its main endogenous inhibitor, cystatin C, distinctly exaggerates the disease severity. Mechanistically, we found that CatB influences VMC probably by activating the NLRP3 inflammasome and promoting caspase-1-induced pyroptosis. This may provide a potential new therapeutic strategy for VMC.

Establishment and characterization of a heart-derived cell line from goldfish (Carassius auratus)

The goldfish Carassius auratus, a freshwater fish in the family Cyprinidae, was one of the earliest fish to be domesticated for ornamental purposes. A cell line was established from goldfish heart (GH) tissue to create a biological monitoring tool for viral diseases. The GH cell line was optimally maintained at 25 °C in M199 medium supplemented with 10-20% fetal bovine serum. A chromosomal analysis indicated that the cell line remained diploid, with a mean chromosomal count of 100. In viral inoculation assays, significant cytopathic effects (CPEs) were caused by epizootic hematopoietic necrosis virus (EHNV), Andrias davidianus iridovirus (ADIV), and Bohle iridovirus (BIV) infections in the fish cells and the viral titers (average value) of EHNV, ADIV, and BIV in GH cells reached 10^5.0, 10^4.5, and 10^5.0 TCID₅₀/0.1 mL, respectively, within 7 days. However, no CPE was observed in the cells infected with viral hemorrhagic septicemia virus (VHSV), infectious hematopoietic necrosis virus (IHNV), spring viremia of carp virus (SVCV), infectious pancreatic necrosis virus (IPNV), channel catfish virus (CCV), or grass carp reovirus (GCRV). These results suggest that the GH cell line is a valuable tool for studying viral pathogenesis.

Electrophysiological alterations in a murine model of chronic coxsackievirus B3 myocarditis

INTRODUCTION

Coxsackievirus B3 (CVB3) is known to induce acute and chronic myocarditis. Most infections are clinically unapparent but some patients suffer from ventricular arrhythmias (VA) and sudden cardiac death (SCD). Studies showed that acute CVB3 infection may cause impaired function of cardiac ion channels, creating a proarrhythmic substrate. However, it is unknown whether low level CVB3+ expression in myocytes may cause altered cardiac electrophysiology leading to VA.

METHODS

Cellular electrophysiology was used to analyze cellular action potentials (APs) and occurrence of afterdepolarizations from isolated cardiomyocytes of wildtype (WT) and transgenic CVB3ΔVP0 (CVB3+) mice. Further, we studied surface ECGs, monophasic APs, ventricular effective refractory period (VERP) and inducibility of VAs in Langendorff-perfused whole hearts. All used cardiomyocytes and whole hearts originated from male mice.

RESULTS

Cellular action potential duration (APD) in WT and CVB3+ myocytes was unchanged. No difference in mean occurrence or amplitude of afterdepolarizations in WT and CVB3+ myocytes was found. Interestingly, resting membrane potential in CVB3+ myocytes was significantly hyperpolarized (WT: -90.0±2.2 mV, n = 7; CVB3+: -114.1±3.0 mV, n = 14; p<0.005). Consistently, in Langendorff-perfused hearts, APDs were also not different between WT and CVB3+ whole hearts. Within both groups, we found a heart rate dependent shortening of ADP90 with increasing heart rate in Langendorff-perfused hearts. VERP was significantly prolonged in CVB3+ hearts compared to WT (WT: 36.0±2.7 ms, n = 5; CVB3+: 47.0±2.0 ms, n = 7; p = 0.018). Resting heart rate (HR) in Langendorff-perfused hearts was not significantly different between both genotypes. Electrical pacing protocols induced no VA in WT and CVB3+ hearts.

CONCLUSION

In CVB3+ mice, prolonged ventricular refractoriness and hyperpolarized resting membrane potentials in presence of unchanged APD were observed, suggesting that low level CVB3 expression does not promote VA by altered cardiac electrophysiology in this type of chronic myocarditis. These findings may suggest that other mechanisms such as chronic myocardial inflammation or fibrosis may account for arrhythmias observed in patients with chronic enteroviral myocarditis.

NF-κB activation is cell type-specific in the heart

Viral myocarditis is common and can progress to cardiac failure. Cardiac cell pro-inflammatory responses are critical for viral clearance, however sustained inflammatory responses contribute to cardiac damage. The transcription factor NF-κB regulates expression of many pro-inflammatory cytokines, but basal and induced activation of NF-κB in different cardiac cell types have not been compared. Here, we used primary cultures of cardiac myocytes and cardiac fibroblasts to identify cardiac cell type-specific events. We show that while viral infection readily stimulates activation of NF-κB in cardiac fibroblasts, cardiac myocytes are largely recalcitrant to activation of NF-κB. Moreover, we show that cardiac myocyte subpopulations differ in their NF-κB subcellular localization and identify the cis-Golgi as a cardiac myocyte-specific host compartment. Together, results indicate that NF-κB-dependent signaling in the heart is cardiac cell type-specific, likely reflecting mechanisms that have evolved to balance responses that can be either protective or damaging to the heart.

[Effect of total flavonoids of astragalus on endoplasmic reticulum chaperone, calumenin and connecxin 43 in suckling mouse myocardium with myocarditis caused by coxsackievirus B3]

OBJECTIVE

To investigate the effect of total flavonoids of astragalus on the expression of endoplasmic reticulum chaperone, calumenin and connecxin 43 (CX43) in suckling mouse myocardium with myocarditis caused by coxsackievirus B3 (CVB3).

METHODS

The primary culture of suckling mouse myocardium cells were randomly divided into control group, CVB3 infected group and total flavonoids of astragalus group. Firstly, to confirm the identity of the suckling mouse myocardium, α-SMA was monitored by immunohistochemistry method. Then the protein expression changes of endoplasmic reticulum chaperone-glucose regulatory protein 78 ( GRP78), calumenin and CX43 were detected by Western blot.

RESULTS

(1) Compared with that of the control group, the GRP78 expression level in CVB3 infected group was improved, the expression levels of calumenin and CX43 were all reduced. (2) Compared with that of CVB3 infected group, GRP78 expression level was decreased, and the expression levels of calumenin and CX43 were increased in total flavonoids of astragalus group.

CONCLUSION

CVB3 infection may cause endoplasmic reticulum stress of rat myocardium cells by increasing the expression of GRP78 and decreasing the expression of calumenin and CX43. On the other hand, total flavonoids of astragalus can reduce the expression of GRP78 and increase the expression of calumenin and CX43.The results of this experiment may be closely related to the effects of anti-arrhythmia with viral myocarditis caused by CVB3.

Adenoviral transduction of FRET-based biosensors for cAMP in primary adult mouse cardiomyocytes

Genetically encoded biosensors that make use of fluorescence resonance energy transfer (FRET) are important tools for the study of compartmentalized cyclic nucleotide signaling in living cells. With the advent of germ line and tissue-specific transgenic technologies, the adult mouse represents a useful tool for the study of cardiovascular pathophysiology. The use of FRET-based genetically encoded biosensors coupled with this animal model represents a powerful combination for the study of cAMP signaling in live primary cardiomyocytes. In this chapter, we describe the steps required during the isolation, viral transduction, and culture of cardiomyocytes from an adult mouse to obtain reliable expression of genetically encoded FRET biosensors for the study of cAMP signaling in living cells.

Mutations in the 5' NTR and the Non-Structural Protein 3A of the Coxsackievirus B3 Selectively Attenuate Myocarditogenicity

The 5’ non-translated region (NTR) is an important molecular determinant that controls replication and virulence of coxsackievirus B (CVB)3. Previous studies have reported many nucleotide (nt) sequence differences in the Nancy strain of the virus, including changes in the 5’ NTR with varying degrees of disease severity. In our studies of CVB3-induced myocarditis, we sought to generate an infectious clone of the virus for routine in vivo experimentation. By determining the viral nt sequence, we identified three new nt substitutions in the clone that differed from the parental virus strain: C97U in the 5’ NTR; a silent mutation, A4327G, in non-structural protein 2C; and C5088U (resulting in P1449L amino acid change) in non-structural protein 3A of the virus leading us to evaluate the role of these changes in the virulence properties of the virus. We noted that the disease-inducing ability of the infectious clone-derived virus in three mouse strains was restricted to pancreatitis alone, and the incidence and severity of myocarditis were significantly reduced. We then reversed the mutations by creating three new clones, representing 1) U97C; 2) G4327A and U5088C; and 3) their combination together in the third clone. The viral titers obtained from all the clones were comparable, but the virions derived from the third clone induced myocarditis comparable to that induced by wild type virus; however, the pancreatitis-inducing ability remained unaltered, suggesting that the mutations described above selectively influence myocarditogenicity. Because the accumulation of mutations during passages is a continuous process in RNA viruses, it is possible that CVB3 viruses containing such altered nts may evolve naturally, thus favoring their survival in the environment.

Establishment of a new cell line from the heart of giant grouper, Epinephelus lanceolatus (Bloch), and its application in toxicology and virus susceptibility

A new marine fish cell line, derived from the heart of giant grouper, Epinephelus lanceolatus (Bloch), was established and characterized. The cell line was designated as ELGH and subcultured with more than 60 passages. The ELGH cells were mainly composed of fibroblast-like cells and multiplied well in Leibovitz's L-15 medium supplemented with 10% foetal bovine serum (FBS) at 28 °C. Chromosome analysis indicated that the modal chromosome number was 48. The fluorescent signals were detected in ELGH when transfected with green fluorescent protein reporter plasmids. The 50% cytotoxic concentration (CC50 ) of the extracellular products (ECPs) from Streptococcus iniae and Vibrio alginolyticus E333 on ELGH cells was 60.02 and 12.49 μg mL(-1), respectively. Moreover, the ELGH cells showed susceptibility to Singapore grouper iridovirus (SGIV), but not to soft-shelled turtle iridovirus (STIV), red-spotted grouper nervous necrosis virus (RGNNV) and spring viremia of carp virus (SVCV), which was demonstrated by the presence of a severe cytopathic effect (CPE) and increased viral titres. In addition, electron microscopy observation showed that abundant virus particles were present in the infected cells. Taken together, our data above provided the potential utility of ELGH cells for transgenic and genetic manipulation, as well as cytotoxicity testing and virus pathogenesis.

HIV-1 subtype C unproductively infects human cardiomyocytes in vitro and induces apoptosis mitigated by an anti-Gp120 aptamer

HIV-associated cardiomyopathy (HIVCM) is of clinical concern in developing countries because of a high HIV-1 prevalence, especially subtype C, and limited access to highly active antiretroviral therapy (HAART). For these reasons, we investigated the direct and indirect effects of HIV-1 subtype C infection of cultured human cardiomyocytes and the mechanisms leading to cardiomyocytes damage; as well as a way to mitigate the damage. We evaluated a novel approach to mitigate HIVCM using a previously reported gp120 binding and HIV-1 neutralizing aptamer called UCLA1. We established a cell-based model of HIVCM by infecting human cardiomyocytes with cell-free HIV-1 or co-culturing human cardiomyocytes with HIV-infected monocyte derived macrophages (MDM). We discovered that HIV-1 subtype C unproductively (i.e. its life cycle is arrested after reverse transcription) infects cardiomyocytes. Furthermore, we found that HIV-1 initiates apoptosis of cardiomyocytes through caspase-9 activation, preferentially via the intrinsic or mitochondrial initiated pathway. CXCR4 receptor-using viruses were stronger inducers of apoptosis than CCR5 utilizing variants. Importantly, we discovered that HIV-1 induced apoptosis of cardiomyocytes was mitigated by UCLA1. However, UCLA1 had no protective effective on cardiomyocytes when apoptosis was triggered by HIV-infected MDM. When HIV-1 was treated with UCLA1 prior to infection of MDM, it failed to induce apoptosis of cardiomyocytes. These data suggest that HIV-1 causes a mitochondrial initiated apoptotic cascade, which signal through caspase-9, whereas HIV-1 infected MDM causes apoptosis predominantly via the death-receptor pathway, mediated by caspase-8. Furthermore the data suggest that UCLA1 protects cardiomyocytes from caspase-mediated apoptosis, directly by binding to HIV-1 and indirectly by preventing infection of MDM.

Cardiac fibroblasts aggravate viral myocarditis: cell specific coxsackievirus B3 replication

Myocarditis is an inflammatory disease caused by viral infection. Different subpopulations of leukocytes enter the cardiac tissue and lead to severe cardiac inflammation associated with myocyte loss and remodeling. Here, we study possible cell sources for viral replication using three compartments of the heart: fibroblasts, cardiomyocytes, and macrophages. We infected C57BL/6j mice with Coxsackievirus B3 (CVB3) and detected increased gene expression of anti-inflammatory and antiviral cytokines in the heart. Subsequently, we infected cardiac fibroblasts, cardiomyocytes, and macrophages with CVB3. Due to viral infection, the expression of TNF-α, IL-6, MCP-1, and IFN-β was significantly increased in cardiac fibroblasts compared to cardiomyocytes or macrophages. We found that in addition to cardiomyocytes cardiac fibroblasts were infected by CVB3 and displayed a higher virus replication (132-fold increase) compared to cardiomyocytes (14-fold increase) between 6 and 24 hours after infection. At higher virus concentrations, macrophages are able to reduce the viral copy number. At low virus concentration a persistent virus infection was determined. Therefore, we suggest that cardiac fibroblasts play an important role in the pathology of CVB3-induced myocarditis and are another important contributor of virus replication aggravating myocarditis.

Cardiac fibroblasts recruit Th17 cells infiltration into myocardium by secreting CCL20 in CVB3-induced acute viral myocarditis

AIMS

Th17 cells contributed to myocardial inflammatory injury in acute viral myocarditis (AVMC), and the migration of these cells were mainly mediated by CCL20-secreting inflammatory cells. However, whether and how the resident cells such as cardiomyocytes and cardiac fibroblasts could mediate Th17 cell migration into the heart remains unclear in AVMC.

METHODS

The effect of CCL20 on the dynamic alterations of intracardiac Th17 cells and disease severity were investigated through the neutralization of CCL20 in AVMC mice. The key cells releasing CCL20 in the heart and the effects of CCL20-secreting cells on Th17 cell arrest, migration and differentiation were detected in vitro.

RESULTS

Neutralization of CCL20 efficiently repressed the myocardial inflammation along with the reduction of Th17 cell infiltrations in the course of AVMC. In vitro, after stimulations of TNF-α, IL-1β and IL-17, cardiac fibroblasts rather than cardiomyocytes could be dominantly induced for CCL20 production. CCL20-secreting cardiac fibroblasts boosted Th17 cell arrest on endothelium, and induce Th17 cell migration. However, CCL20 produced by cardiac fibroblasts had no effect on Th17 cell differentiation and IL-17 production.

CONCLUSIONS

It firstly suggested that cardiac fibroblasts could recruit Th17 cells infiltration into myocardium by secreting CCL20 in AVMC.

Coxsackievirus-induced miR-21 disrupts cardiomyocyte interactions via the downregulation of intercalated disk components

Intercalated disks (ICDs) are substantial connections maintaining cardiac structures and mediating signal communications among cardiomyocytes. Deficiency in ICD components such as desmosomes, fascia adherens and gap junctions leads to heart dysfunction. Coxsackievirus B3 (CVB3) infection induces cardiac failure but its pathogenic effect on ICDs is unclear. Here we show that CVB3-induced miR-21 expression affects ICD structure, i.e., upregulated miR-21 targets YOD1, a deubiquitinating enzyme, to enhance the K48-linked ubiquitination and degradation of desmin, resulting in disruption of desmosomes. Inhibition of miR-21 preserves desmin during CVB3 infection. Treatment with proteasome inhibitors blocks miR-21-mediated desmin degradation. Transfection of miR-21 or knockdown of YOD1 triggers co-localization of desmin with proteasomes. We also identified K108 and K406 as important sites for desmin ubiquintination and degradation. In addition, miR-21 directly targets vinculin, leading to disturbed fascia adherens evidenced by the suppression and disorientation of pan-cadherin and α-E-catenin proteins, two fascia adherens-components. Our findings suggest a new mechanism of miR-21 in modulating cell-cell interactions of cardiomyocytes during CVB3 infection.

Coxsackievirus B3 (CVB3) is one of most common causes of heart inflammation and failure. However, the mechanism by which CVB3 induces cardiac damage has not been fully elucidated. Particularly, the involvement of microRNAs (miRNAs), a family of small RNAs controlling the progression of a wide range of diseases, in CVB3 infection is still unclear. These small RNAs are essential to understand the CVB3-caused heart muscle cell injury and have great potential to serve therapeutic purposes. Here, we systematically analyzed the miRNA changes during CVB3 infection and found that miR-21 is increased by viral infection. We further demonstrated that the CVB3-induced miR-21 triggers heart muscle cell damage by interfering with the cell-cell interactions. miR-21 suppresses the levels of components in cell-cell interactions by either promoting the degradation of those proteins or directly inhibiting the protein production. Inhibition of miR-21 can reduce the host injury caused by CVB3 infection. Our findings will shed new lights on the pathogenesis of CVB3-induced heart failure.

CCR5 inhibition prevents cardiac dysfunction in the SIV/macaque model of HIV

Background

Diastolic dysfunction is a highly prevalent cardiac abnormality in asymptomatic as well as ART‐treated human immunodeficiency virus (HIV) patients. Although the mechanisms underlying depressed cardiac function remain obscure, diastolic dysfunction in SIV‐infected rhesus macaques is highly correlated with myocardial viral load. As cardiomyocytes are not productively infected, damage may be an indirect process attributable to a combination of pro‐inflammatory mediators and viral proteins.

Methods and Results

Given the diverse roles of CCR5 in mediating recruitment of leukocytes to inflammatory sites and serving as a receptor for HIV entry into cells, we investigated the role of CCR5 in the SIV/macaque model of diastolic dysfunction. We found that in SIV‐infected macaques, CCR5 inhibition dramatically impacted myocardial viral load measured by qRT‐PCR and prevented diastolic dysfunction measured by echocardiography. Complementary in vitro experiments using fluorescence microscopy showed that CCR5 ligands impaired contractile function of isolated cardiomyocytes, thus identifying CCR5 signaling as a novel mediator of impaired cardiac mechanical function.

Conclusions

Together, these findings incriminate SIV/HIV gp120‐CCR5 as well as chemokine‐CCR5 interactions in HIV‐associated cardiac dysfunction. These findings also have important implications for the treatment of HIV‐infected individuals: in addition to antiviral properties and reduced chemokine‐mediated recruitment and activation of inflammatory cells, CCR5 inhibition may provide a cardioprotective benefit by preventing cardiomyocyte CCR5 signaling.

Targeting matrix metalloproteinase activity and expression for the treatment of viral myocarditis

Infectious agents including viruses can infect the heart muscle, resulting in the development of heart inflammation called myocarditis. Chronic myocarditis can lead to dilated cardiomyopathy (DCM). DCM develops from the extensive extracellular matrix (ECM) remodeling caused by myocarditis and may result in heart failure. Epidemiological data for viral myocarditis has long suggested a worse pathology in males, with more recent data demonstrating sex-dependent pathogenesis in DCM as well. Matrix metalloproteinases (MMPs), long known modulators of the extracellular matrix, have important roles in mediating heart inflammation and remodeling during disease and in convalescence. This ability of MMPs to control both the inflammatory response and ECM remodeling during myocarditis makes them potential drug targets. In this review, we analyze the role of MMPs in mediating myocarditis/DCM disease progression, their sex-dependent expression, and their potential as drug targets during viral myocarditis and DCM.

Inhibition of Coxsackievirus-associated dystrophin cleavage prevents cardiomyopathy

Heart failure in children and adults is often the consequence of myocarditis associated with Coxsackievirus (CV) infection. Upon CV infection, enteroviral protease 2A cleaves a small number of host proteins including dystrophin, which links actin filaments to the plasma membrane of muscle fiber cells (sarcolemma). It is unknown whether protease 2A-mediated cleavage of dystrophin and subsequent disruption of the sarcolemma play a role in CV-mediated myocarditis. We generated knockin mice harboring a mutation at the protease 2A cleavage site of the dystrophin gene, which prevents dystrophin cleavage following CV infection. Compared with wild-type mice, we found that mice expressing cleavage-resistant dystrophin had a decrease in sarcolemmal disruption and cardiac virus titer following CV infection. In addition, cleavage-resistant dystrophin inhibited the cardiomyopathy induced by cardiomyocyte-restricted expression of the CV protease 2A transgene. These findings indicate that protease 2A-mediated cleavage of dystrophin is critical for viral propagation, enteroviral-mediated cytopathic effects, and the development of cardiomyopathy.

X-linked inhibitor of apoptosis protein-mediated attenuation of apoptosis, using a novel cardiac-enhanced adeno-associated viral vector

Successful amelioration of cardiac dysfunction and heart failure through gene therapy approaches will require a transgene effective at attenuating myocardial injury, and subsequent remodeling, using an efficient and safe delivery vehicle. Our laboratory has established a well-curated, high-quality repository of human myocardial tissues that we use as a discovery engine to identify putative therapeutic transgene targets, as well as to better understand the molecular basis of human heart failure. By using this rare resource we were able to examine age- and sex-matched left ventricular samples from (1) end-stage failing human hearts and (2) nonfailing human hearts and were able to identify the X-linked inhibitor of apoptosis protein (XIAP) as a novel target for treating cardiac dysfunction. We demonstrate that XIAP is diminished in failing human hearts, indicating that this potent inhibitor of apoptosis may be central in protecting the human heart from cellular injury culminating in heart failure. Efforts to ameliorate heart failure through delivery of XIAP compelled the design of a novel adeno-associated viral (AAV) vector, termed SASTG, that achieves highly efficient transduction in mouse heart and in cultured neonatal rat cardiomyocytes. Increased XIAP expression achieved with the SASTG vector inhibits caspase-3/7 activity in neonatal cardiomyocytes after induction of apoptosis through three common cardiac stresses: protein kinase C-γ inhibition, hypoxia, or β-adrenergic receptor agonist. These studies demonstrate the potential benefit of XIAP to correct heart failure after highly efficient delivery to the heart with the rationally designed SASTG AAV vector.

[Role of triggering receptor expressed on myeloid cells-1 on coxsackievirus B3-induced inflammation and cardiomyocyte injury]

OBJECTIVE

To determine the expression of TREM-1 (triggering receptor expressed on myeloid cells-1) in macrophages after coxsackievirus B3 (CVB3) infection and the cardiomyocytes viability after culturing with supernatant of macrophages in the absence and presence of TREM-1 inhibitor LP-17 to explore if TREM-1 is involved in the pathogenesis of CVB3 infection induced inflammation and cardiomyocytes injury.

METHODS

TREM-1 mRNA and TREM-1 and DAP-12 protein expression in macrophages were detected by Real-time PCR at 0, 1, 4, 8 and 12 h and by Western blot at 0, 16, 24 and 48 h post CVB3 infection. TNF-α secretion of macrophages was measure by ELISA, vitality and the apoptosis degree of cardiomyocytes was assessed by CCK8 and Annexin V-FITC after the cardiomyocytes were cultured with the supernatant of macrophages in normal control group, CVB3 infection group and LP-17 pretreated CVB3 infection group.

RESULTS

TREM-1 mRNA expression was significantly upregulated at 4, 8, and 12 h (peaked at 8 h) and TREM-1 protein expression was significantly upregulated at 16 and 24 h and returned to baseline level at 48 h after CVB3 infection. The protein expression of DAP-12, a direct downstream signaling molecule of TREM-1, also significantly increased at 24 and 48 h post CVB3 infection (P < 0.01). Level of macrophages secreted TNF-α post CVB3 infection was significantly reduced in LP-17 pretreated cells (P < 0.01), LP-17 pretreatment also significantly improved viability and significantly reduced apoptosis of cardiomyocytes cultured with supernatant of CVB3 infected macrophages (P < 0.01).

CONCLUSION

TREM-1 might be an important mediator post CVB3 infection and a major player on inducing excess macrophages-related inflammation and resulting in an indirect injury to cardiomyocytes.

[The diagnostics of arrhythmogenic right ventricular dysplasia by an endomiocardial biopsy and the role of viruses in the pathogenesis of disease]

The comparative histologic, morphometric and immunohistochemical investigation of a right ventricular myocardium from 3 groups of patients has been carried out. The first group has included 12 patients with an arrythmogenic right ventricular dysplasia (ARVD) confirmed by an endomyocardial biopsy. The second group has consisted of 7 healthy people died a violent death. The third group has included 7 patients with a chronic alcoholism died from an acute alcoholic intoxication. The patients with ARVD and a chronic alcoholism have had an evident adiposis, a moderate fibrosis, and muscle atrophy with only 65% of cardiac hystiocytes. The patients with a chronic alcoholism have had only dystonia of intramural arteries. The cardiac hystiocytes of patients with ARVD have infected by enteroviruses (100%), parvoviruses B19 (58%), adenoviruses (25%), and hepatitis virus C (16%). 83% of observations have had a mixed viral infections.

Establishment, characterization of a new cell line from heart of half smooth tongue sole (Cynoglossus semilaevis)

A new cell line was established from the heart of a cultured marine fish, half smooth tongue sole (Cynoglossus semilaevis), designated as CSH (Cynoglossus semilaevis heart cell line). The CSH cells grow over 400 days in minimum essential medium (MEM) supplemented with 10% fetal bovine serum (FBS) and 2 ng/ml basic fibroblast growth factor (bFGF). The suitable temperature for the cell growth was 24-30°C with the optimum growth at 24°C and a reduced growth at 12 and 30°C. FBS and bFGF concentration were the two important components for CSH cells proliferation. Twenty percent FBS in the medium was found to be the optimum concentration and bFGF promoted the growth of CSH cells. The double time of the cells at 24°C was determined to 73.39 h. Chromosome analysis revealed that 44% of the cells maintained a normal diploid chromosome number (2n=42) in the CSH cells at Passage 58. The fluorescent signals were observed in CSH after the cells were transfected with green fluorescent protein (GFP) reporter plasmids. CSH cells showed the cytopathic effect (CPE) after infection with lymphosystis disease virus (LCDV). Moreover, the LCDV particles can be observed in the cytoplasm of virus-infected cells by electron microscopy, and a segment of MCP gene for major capsid protein of LCDV was found by PCR amplification DNA of virus-infected cells.

[Protective effects of tetramethylpyrazine on rat myocardial cells infected by Coxsackie virus B3 and its signal transduction mechanism]

OBJECTIVE

To study the protective effects of tetramethylpyrazine (TMPZ) on rat myocardial cells infected by Coxsackie virus B3 (CVB3) and its signal transduction mechanism.

METHODS

The cultured myocardial cells of neonatal Sprague-Dawley rats were randomly treated with CVB3, CVB3+TMPZ (100 micromol/L), TMPZ (100 micromol/L) (negative control) or DMEM (blank control). After treatment, the beating rate of myocardial cells and the LDH activity in the culture fluid were measured. Cell viability was ascertained with MTT assay. Western blot was used to study the expression of nuclear factor kappa-B (NF-kappaB) protein in myocardial cells.

RESULTS

The beating rate of myocardial cells in the untreated CVB3 infection group was significantly lower than that in the TMPZ-treated CVB3 infection group (32.0+/-3.6 bpm vs 84.3+/-3.5 bpm, P<0.01). The LDH activity and NF-kappaB expression in the TMPZ-treated CVB3 infection group was significantly reduced when compared with untreated CVB3 infection group (P<0.05, P<0.01, respectively). Cell viability 7 days after CVB3 infection in the TMPZ-treated group was higher than that in the untreated CVB3 infection group (86.7+/-2.7% vs 35.3+/-3.4%; P<0.01).

CONCLUSIONS

TMPZ can provide protective effects on rat myocardial cells infected by CVB3, possibly by an inhibition of the activity of NF-kappaB in myocardial cells.

A myocardium tropic adeno-associated virus (AAV) evolved by DNA shuffling and in vivo selection

To engineer gene vectors that target striated muscles after systemic delivery, we constructed a random library of adeno-associated virus (AAV) by shuffling the capsid genes of AAV serotypes 1 to 9, and screened for muscle-targeting capsids by direct in vivo panning after tail vein injection in mice. After 2 rounds of in vivo selection, a capsid gene named M41 was retrieved mainly based on its high frequency in the muscle and low frequency in the liver. Structural analyses revealed that the AAVM41 capsid is a recombinant of AAV1, 6, 7, and 8 with a mosaic capsid surface and a conserved capsid interior. AAVM41 was then subjected to a side-by-side comparison to AAV9, the most robust AAV for systemic heart and muscle gene delivery; to AAV6, a parental AAV with strong muscle tropism. After i.v. delivery of reporter genes, AAVM41 was found more efficient than AAV6 in the heart and muscle, and was similar to AAV9 in the heart but weaker in the muscle. In fact, the myocardium showed the highest gene expression among all tissues tested in mice and hamsters after systemic AAVM41 delivery. However, gene transfer in non-muscle tissues, mainly the liver, was dramatically reduced. AAVM41 was further tested in a genetic cardiomyopathy hamster model and achieved efficient long-term delta-sarcoglycan gene expression and rescue of cardiac functions. Thus, direct in vivo panning of capsid libraries is a simple tool for the de-targeting and retargeting of viral vector tissue tropisms facilitated by acquisition of desirable sequences and properties.