Overexpression of interleukin-6 aggravates viral myocarditis: impaired increase in tumor necrosis factor-alpha

Current understanding and management of cardiovascular involvement in rheumatic immune-mediated inflammatory diseases

Immune-mediated inflammatory diseases (IMIDs) are a spectrum of disorders of overlapping immunopathogenesis, with a prevalence of up to 10% in Western populations and increasing incidence in developing countries. Although targeted treatments have revolutionized the management of rheumatic IMIDs, cardiovascular involvement confers an increased risk of mortality and remains clinically under-recognized. Cardiovascular pathology is diverse across rheumatic IMIDs, ranging from premature atherosclerotic cardiovascular disease (ASCVD) to inflammatory cardiomyopathy, which comprises myocardial microvascular dysfunction, vasculitis, myocarditis and pericarditis, and heart failure. Epidemiological and clinical data imply that rheumatic IMIDs and associated cardiovascular disease share common inflammatory mechanisms. This concept is strengthened by emergent trials that indicate improved cardiovascular outcomes with immune modulators in the general population with ASCVD. However, not all disease-modifying therapies that reduce inflammation in IMIDs such as rheumatoid arthritis demonstrate equally beneficial cardiovascular effects, and the evidence base for treatment of inflammatory cardiomyopathy in patients with rheumatic IMIDs is lacking. Specific diagnostic protocols for the early detection and monitoring of cardiovascular involvement in patients with IMIDs are emerging but are in need of ongoing development. This Review summarizes current concepts on the potentially targetable inflammatory mechanisms of cardiovascular pathology in rheumatic IMIDs and discusses how these concepts can be considered for the diagnosis and management of cardiovascular involvement across rheumatic IMIDs, with an emphasis on the potential of cardiovascular imaging for risk stratification, early detection and prognostication.

Investigating the virulence of coxsackievirus B6 strains and antiviral treatments in a neonatal murine model

Coxsackievirus B6 (CVB6), a member of the human enterovirus family, is associated with severe diseases such as myocarditis in children. However, to date, only a limited number of CVB6 strains have been identified, and their characterization in animal models has been lacking. To address this gap, in this study, a neonatal murine model of CVB6 infection was established to compare the replication and virulence of three infectious-clone-derived CVB6 strains in vivo. The results showed that following challenge with a lethal dose of CVB6 strains, the neonatal mice rapidly exhibited a series of clinical signs, such as weight loss, limb paralysis, and death. For the two high-virulence CVB6 strains, histological examination revealed myocyte necrosis in skeletal and cardiac muscle, and immunohistochemistry confirmed the expression of CVB6 viral protein in these tissues. Real-time PCR assay also revealed higher viral loads in the skeletal and cardiac muscle than in other tissues at different time points post infection. Furthermore, the protective effect of passive immunization with antisera and a neutralizing monoclonal antibody against CVB6 infection was evaluated in the neonatal mouse model. This study should provide insights into the pathogenesis of CVB6 and facilitate further research in the development of vaccines and antivirals against CVBs.

Effect of Astragalus injection on inflammatory mediators in patients with viral myocarditis: A systematic review and meta-analysis

BACKGROUND

To explore the therapeutic effect and mechanism of Astragalus injection on viral myocarditis, we conducted a systematic review and meta-analysis to identify the influence of Astragalus injection on inflammatory mediators and overall efficiency in patients undergoing viral myocarditis.

METHODS

EMBASE, Cochrane Library, PubMed, Chinese Biomedical Literature, Chinese National Knowledge Infrastructure (CNKI), and Wanfang databases were searched to screen randomized controlled trials (RCTs) published before July 3, 2022. The quality of participating studies was assessed by the Cochrane Collaboration Risk of Bias tool. The calculation of qualitative data used a risk ratio (RR) with a 95% confidence interval (95% CI), and quantitative data had standardized mean differences (SMDs) with a 95% CI. The heterogeneity among trials was quantified with Cochran's Q test and the I² statistic. Confounding factors were estimated by sensitivity analysis, meta-regression, and subgroup analysis. The publication bias of participating articles was evaluated by funnel plot and Egger's test. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was recommended for assessing the strength of evidence.

RESULTS

Nineteen available studies were included in our present meta-analysis, all of which were conducted in China. The outcomes expose that Astragalus injection dramatically decreased the levels of pro-inflammatory TNF-α (SMD=-2.271, 95% CI=-2.802 to -1.739, p<0.001, I²=90.6%), IL-6 (SMD=-1.501, 95% CI=-1.872 to -1.130, p<0.001, I²=83.2%), IL-17 (SMD=-3.194, 95% CI=-4.569 to -1.818, p<0.001, I²=88.9%), 1L-8 (SMD=-6.133, 95% CI=-9.938 to -2.328, p = 0.002, I²=97%), 1L-1 (SMD=-1.814, 95% CI=-2.557 to -1.070, p<0.001, I²=92.1%), CRP (SMD=-2.020, 95% CI=-3.107 to -0.932, p<0.001, I²=92.7%), and IFN-γ (SMD=-1.512, 95% CI=-2.771 to -0.253, p = 0.019, I²=92%) and increased the total effective rate of treatment (RR=1.225, 95% CI=1.17 to 1.29, p<0.001, I²=0.0%) in patients with viral myocarditis.

CONCLUSION

Astragalus injection can play a therapeutic role in patients with viral myocarditis through immunomodulatory effects. Outcomes were treated with caution due to significant heterogeneity among studies. Large-scale RCTs should be performed to support these conclusions.

Beta2 -agonist increases skeletal muscle interleukin 6 production and release in response to resistance exercise in men

OBJECTIVE

Several tissues produce and release interleukin-6 (IL-6) in response to beta₂ -adrenergic stimulation with selective agonists (beta₂ -agonists). Moreover, exercise stimulates muscle IL-6 production, but whether beta₂ -agonists regulate skeletal muscle production and release of IL-6 in humans in association with exercise remains to be clarified. Thus, we investigated leg IL-6 release in response to beta₂ -agonist salbutamol in lean young men at rest and in recovery from resistance exercise.

DESIGN

The study employed a randomized controlled crossover design, where 12 men ingested either salbutamol (16 mg) or placebo for 4 days, followed by the last dose (24 mg) administered 1½ h before exercise. Arterial and femoral venous plasma IL-6 as well as femoral artery blood flow was measured before and ½-5 h in recovery from quadriceps muscle resistance exercise. Furthermore, vastus lateralis muscle biopsies were collected ½ and 5 h after exercise for determination of mRNA levels of IL-6 and Tumor Necrosis Factor (TNF)-α.

RESULTS

Average leg IL-6 release was 1.7-fold higher (p = 0.01) for salbutamol than placebo, being 138 ± 76 and 79 ± 66 pg min^-1 (mean ± SD) for salbutamol and placebo, respectively, but IL-6 release was not significantly different between treatments within specific sampling points at rest and after exercise. Muscle IL-6 mRNA was 1.5- and 1.7-fold higher (p = 0.001) for salbutamol than placebo ½ and 5 h after exercise, respectively, whereas no significant treatment differences were observed for TNF-α mRNA.

CONCLUSIONS

Beta₂ -adrenergic stimulation with high doses of the selective beta₂ -agonist salbutamol, preceeded by 4 consecutive daily doses, induces transcription of IL-6 in skeletal muscle in response to resistance exercise, and increases muscle IL-6 release in lean individuals.

COVID-19-Associated Myocarditis: An Evolving Concern in Cardiology and Beyond

Simple Summary

Coronavirus disease-2019 (COVID-19) affects many organs in the body, including the heart. One complication of particular concern is inflammation of the heart muscle, called myocarditis. This paper presents updated research data on COVID-19-associated myocarditis. Specifically, we review the incidence, potential mechanisms, blood and imaging tests that can be used to detect the disease. We emphasize that, in contrast with early reports, recent data suggest that myocarditis in the setting of COVID-19 is relatively uncommon, yet infected individuals are at a substantially increased risk for poor outcomes. It is important to continue research in this area.

Abstract

The direct and indirect adverse effects of SARS-CoV-2 infection on the cardiovascular system, including myocarditis, are of paramount importance. These not only affect the disease course but also determine clinical outcomes and recovery. In this review, the authors aimed at providing an update on the incidence of Coronavirus disease-2019 (COVID-19)-associated myocarditis. Our knowledge and experience relevant to this area continues to evolve rapidly since the beginning of the pandemic. It is crucial for the scientific and medical community to stay abreast of current information. Contrasting early reports, recent data suggest that the overall incidence of SARS-CoV-2-associated myocarditis is relatively low, yet infected individuals are at a substantially increased risk. Therefore, understanding the pathophysiology and diagnostic evaluation, including the use of serum biomarkers and imaging modalities, remain important. This review aims to summarize the most recent data in these areas as they relate to COVID-19-associated myocarditis. Given its increasing relevance, a brief update is included on the proposed mechanisms of myocarditis in COVID-19 vaccine recipients.

The Role of Interleukin-6 Family Members in Cardiovascular Diseases

Cardiovascular disease is one of the main causes of human mortality. Cytokines play crucial roles in the development of cardiovascular disease. Interleukin (IL)-6 family members are a series of cytokines, including IL-6, IL-11, IL-30, IL-31, OSM, LIF, CNTF, CT-1, CT-2, and CLC, that regulate multiple biological effects. Experimental and clinical evidence shows that IL-6 family members are closely related to cardiovascular diseases such as atherosclerosis, hypertension, aortic dissection, cardiac fibrosis, and cardiomyopathy. This review mainly discusses the role of IL-6 family members in cardiovascular disease for the sake of identifying possible intervention targets for cardiovascular disease prevention and treatment.

Viruses in the Heart: Direct and Indirect Routes to Myocarditis and Heart Failure

Viruses are an underappreciated cause of heart failure. Indeed, several types of viral infections carry cardiovascular risks. Understanding shared and unique mechanisms by which each virus compromises heart function is critical to inform on therapeutic interventions. This review describes how the key viruses known to lead to cardiac dysfunction operate. Both direct host-damaging mechanisms and indirect actions on the immune systems are discussed. As viral myocarditis is a key pathologic driver of heart failure in infected individuals, this review also highlights the role of cytokine storms and inflammation in virus-induced cardiomyopathy.

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.

Pathological and clinical effects of interleukin-6 on human myocarditis

BACKGROUND

Numerous basic studies have shown a relationship between interleukin-6 (IL-6) and the development or severity of myocarditis. However, there has been no study in which the effect of IL-6 levels in patients with myocarditis was evaluated.

METHODS

We enrolled control patients (n = 12) and consecutive patients with acute myocarditis (n = 13), including lymphocytic, eosinophilic, and giant cell myocarditis, and investigated the pathological and clinical effects of IL-6 on human myocarditis.

RESULTS

The serum IL-6 level in patients with myocarditis (16.7 [9.9, 103.8] pg/mL) was significantly higher than that in the control patients (1.4 [1.0, 1.9] pg/mL) (P<0.001). Immunohistochemical analysis showed that IL-6 was expressed in infiltrating inflammatory cells of endomyocardial biopsy samples from all patients with myocarditis. Moreover, the log-transformed value of serum IL-6 level showed significant positive correlations with serum creatine kinase (CK) level, CK-MB level, peak CK level, peak CK-MB level and C-reactive protein level (all P ≤ 0.005) and a negative correlation with the left ventricular (LV) ejection fraction (p = 0.014). We divided the patients with myocarditis into a low IL-6 group (9.9 [4.5, 14.2] pg/dL, n = 7) and a high IL-6 group (108.9 [51.1, 130.9] pg/dL, n = 6). The degree of infiltration of IL-6-expressing inflammatory cells in myocardial samples obtained from patients in the high IL-6 group was significantly more severe than that in samples obtained from patients in the low IL-6 group. Furthermore, patients in the high IL-6 group significantly more frequently received catecholamine therapy (P = 0.005), venoarterial extracorporeal membrane oxygenation (P = 0.029), and artificial respirator support (P = 0.021) in the acute phase of myocarditis.

CONCLUSION

The results suggest that there is a strong impact of IL-6 on cardiac injury and dysfunction in patients with myocarditis.

Interleukin-6 knockout reverses macrophage differentiation imbalance and alleviates cardiac dysfunction in aging mice

Several interleukins (ILs) have been shown to be involved in aging, but the effects of IL-6 on aging-related cardiac dysfunction remain unknown. In this study, the expression and sources of cardiac IL-6 in aging hearts were investigated for the first time. The results showed that cardiac IL-6 expression in mice gradually increased with age, and the expression at 16 months, 20 months and 25 months was higher than that at 3 months. In addition, cardiac macrophages (Møs) were shown to be the main sources of IL-6 in aging mice. IL-6 knockout (KO) significantly alleviated cardiac dysfunction, increased M2 macrophage (Mø2) differentiation, reduced M1 macrophage (Mø1) differentiation and protected against cardiomyocyte apoptosis in aging mice. IL-6 KO also reversed the stimulatory effect of doxorubicin (DOX) treatment on Mø1s and the inhibitory effect of DOX treatment on Mø2s in vitro. Furthermore, the mRNA expression of both aging markers and apoptosis-related markers was markedly inhibited by IL-6 KO. Our results suggest that aging can be significantly reversed by IL-6 KO and that the mechanisms of this effect are related to alleviation of Mø1/Mø2 imbalance and protection against apoptosis in cardiomyocytes.

Protective functions of myricetin in LPS-induced cardiomyocytes H9c2 cells injury by regulation of MALAT1

BACKGROUND

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a crucial mediator in response to inflammation. Myricetin protects cardiomyocytes against inflammatory injury. However, it's still unexplored whether myricetin exerted anti-inflammatory properties via MALAT1. The purpose of our study was to validate the cardio-protective function of myricetin against myocarditis and its underlying mechanism in vitro.

METHODS

H9c2 cells were pre-incubated with myricetin before stimulation with lipopolysaccharide (LPS). Enforced silence of MALAT1 was achieved by transducing short hairpin (sh)-MALAT1 into H9c2 cells. Next, cell viability and apoptotic cells were detected with cell counting kit-8 (CCK-8) and Annexin V-fluorescein isothiocyanate/propidium iodide (Annexin V-FITC/PI) apoptosis detection kit, respectively. Western blot assay was conducted to examine apoptosis-relative proteins, pro-inflammatory factors, and signaling regulators. Quantitative real-time PCR (qRT-PCR) was performed to quantify pro-inflammatory factors and MALAT1 at mRNA levels. Enzyme-linked immune sorbent assay (ELISA) was employed to determine protein concentration of pro-inflammatory factors.

RESULTS

Myricetin ameliorated LPS-elicited reduction of cell viability, augment of apoptosis, and overexpression of monocyte chemo-attractant protein-1 (MCP-1) and interleukin-6 (IL-6) in H9c2 cells. Meanwhile, phosphorylation of p65 and inhibitor of nuclear factor kappa B alpha (IκBα) were suppressed. Besides, myricetin enhanced the expression of MALAT1 which was originally down-regulated by LPS. However, the protective effects of myricetin against LPS-caused inflammatory lesions were abrogated in MALAT1-deficiency cells, with the restored phosphorylation of p65 and IκBα.

CONCLUSION

Myricetin possessed an anti-inflammatory function against LPS-induced lesions in cardiomyocytes. Mechanically, myricetin up-regulated MALAT1, blocked LPS-evoked activation of nuclear factor-κB (NF-κB) inflammatory pathway, and, finally, exerted cardio-protective effects.

Dpep2 Emerging as a Modulator of Macrophage Inflammation Confers Protection Against CVB3-Induced Viral Myocarditis

Overwhelming cardiac inflammation has been reported to be the pathogenic mechanism of Coxsackievirus B3 (CVB3)-induced viral myocarditis (VMC), while the detailed molecular mechanisms remain unknown. Membrane-bound dipeptidases (MBD, also known as Dpep) have been shown to be involved in inflammatory diseases. However, the clear and direct evidence of their impacts on inflammation is still lacking. In this study, our results revealed that Dpep2 expression was remarkably increased during CVB3 infection, and primarily produced by the cardiac tissue-infiltrating macrophages instead of constitutive cardiomyocytes. Macrophages have been reported to play an important pathological role in driving VMC. Interestingly, macrophage-specific Dpep2 deletion robustly aggravated CVB3-induced cardiac inflammation, evidenced by augmented expression of TNF-α, IL-6, and MCP-1 in heart tissue. In addition, Dpep2-deficient bone-marrow derived macrophages (BMDMs) generated more TNF-α, IL-6, and MCP-1 after CVB3 stimulation compared with the control BMDMs. Moreover, this suppressive effect of Dpep2 on macrophages relied on its repression on NF-κB signaling pathway, but not on its conventional hydrolysate LTE4. Taken together, this study revealed that Dpep2 could protect against CVB3-induced VMC by acting as a suppressor of macrophage inflammation. Better understanding how macrophage Dpep2 dampened the cardiac inflammation would provide us with insights for the efficient control of CVB3-induced VMC.

Inhibition of endogenous hydrogen sulfide production improves viral elimination in CVB3-infected myocardium in mice

BACKGROUND

To find whether administration of hydrogen sulfide has interaction with coxsackie virus B3 (CVB3) replication and spread.

METHODS

Six-week-old inbred male Balb/c mice were injected intraperitoneally with CVB3. Mice were randomized to four groups (n = 10 for each group): group N (sham infection + vehicle), group C (virus + vehicle), group P (virus + DL-proparglygylcine (PAG)), and group S (virus + sodium hydrogen sulfide (NaHS)). PAG and NaHS were administered intraperitoneally daily and mice were killed on day 4 after viral inoculation. Serum specimens were obtained to assay tumor necrosis factor-α (TNFα) level, and heart specimens were harvested for histological examination, 50% tissue culture infection dose (TCID50) assay, reverse transcription-polymerase chain reaction and Western blot analysis.

RESULTS

The ratio of heart-weight to body-weight and inflammatory scores showed no significant difference between infected groups. The circulatory and local concentrations of TNFα, nitric oxide synthase 2 messenger RNA, and protein were higher in group P, and were lower in group S compared to those in group C. Mice treated with PAG and NaHS had significantly lower and higher viral stocks than those inoculated with CVB3 only, respectively.

CONCLUSION

Inhibition of endogenous hydrogen sulfide production contributed to viral clearance in acute viremia of CVB3-induced myocarditis.

Pseudomonas aeruginosa Invades Human Aortic Endothelial Cells and Induces Cell Damage in vitro

BACKGROUND

Cardiovascular diseases such as endocarditis are the second most common cause of death worldwide. Infective Endocarditis (IE) is the most severe infection of the heart associated with significant mortality and morbidity. The binding and invasion of Human Aortic Endothelial Cells (HAECs) by pathogenic microbes can play an important role in the pathogenesis of IE.

OBJECTIVE

Pseudomonas aeruginosa is an emerging pathogen that has been associated with IE. However, it is not known whether P. aeruginosa can bind and interact with HAECs. The aim of this study was to determine whether P. aeruginosa can bind and colonize HAECs.

METHODS

The invasion of HAECs by P. aeruginosa was assessed by gentamicin protection assay. Cytokine levels were determined by enzyme-linked Immunosorbent Assay (ELISA) kits. Cell damage was determined by Lactate Dehydrogenase (LDH) assay.

RESULTS

P. aeruginosa can bind and invade HAECs. Infection of HAECs with P. aeruginosa induces TNF-α IL-1β, IL-6 and IL-8 cytokine production leading to the generation of inflammatory milieu that can cause tissue damage as observed in human clinical cases of IE. We also observed that P. aeruginosa induces cell damage in HAECs.

CONCLUSION

In this study, we demonstrate for first time that P. aeruginosa can invade and survive inside HAECs. This cell culture model can be of immense importance to determine the efficacy of drug targets against IE.

Viral Infection of the Heart: Pathogenesis and Diagnosis

Viral infections of the heart cause serious clinical problems, either as infectious myocarditis, which usually is a consequence of acute infection or as idiopathic dilated cardiomyopathy, resulting rather from a chronic infection. This minireview presents an up-to-date view on pathomechanisms of viral infection of the heart tissues, the role of immune system in controlling infectious process at its various stages and current possibilities of recognizing viral infection of the heart with use of both cardiological and virological methods. Our goal was to present the variety of known viral agents causing heart infection, level of complexity in mutual virus-cell interactions, and consequent clinical scenarios.

β1-Adrenergic Receptor Contains Multiple IAk and IEk Binding Epitopes That Induce T Cell Responses with Varying Degrees of Autoimmune Myocarditis in A/J Mice

Myocarditis/dilated cardiomyopathy (DCM) patients can develop autoantibodies to various cardiac antigens and one major antigen is β1-adrenergic receptor (β₁AR). Previous reports indicate that animals immunized with a β₁AR fragment encompassing, 197–222 amino acids for a prolonged period can develop DCM by producing autoantibodies, but existence of T cell epitopes, if any, were unknown. Using A/J mice that are highly susceptible to lymphocytic myocarditis, we have identified β₁AR 171–190, β₁AR 181–200, and β₁AR 211–230 as the major T cell epitopes that bind major histocompatibility complex class II/IA^k or IE^k alleles, and by creating IA^k and IE^k dextramers, we demonstrate that the CD4 T cell responses to be antigen-specific. Of note, all the three epitopes were found also to stimulate CD8 T cells suggesting that they can act as common epitopes for both CD4 and CD8 T cells. While, all epitopes induced only mild myocarditis, the disease-incidence was enhanced in animals immunized with all the three peptides together as a cocktail. Although, antigen-sensitized T cells produced mainly interleukin-17A, their transfer into naive animals yielded no disease. But, steering for T helper 1 response led the T cells reacting to one epitope, β₁AR 181–200 to induce severe myocarditis in naive mice. Finally, we demonstrate that all three β₁AR epitopes to be unique for T cells as none of them induced antibody responses. Conversely, animals immunized with a non-T cell activator, β₁AR 201–220, an equivalent of β₁AR 197–222, had antibodies comprising of all IgG isotypes and IgM except, IgA and IgE. Thus, identification of T cell and B cell epitopes of β₁AR may be helpful to determine β₁AR-reactive autoimmune responses in various experimental settings in A/J mice.

Transmissible endoplasmic reticulum stress from myocardiocytes to macrophages is pivotal for the pathogenesis of CVB3-induced viral myocarditis

Infiltrating macrophages have been proven as a pivotal pathological inflammatory cell subset in coxsackievirus B3 (CVB3) induced viral myocarditis. However, the mechanisms underlying the initiation and promotion of macrophage pro-inflammatory responses are still blur. We previously reported that cardiac ER stress contributed to CVB3-induced myocarditis by augmenting inflammation. In this study, we focused on the influence of ER stress on the macrophage inflammatory responses in the viral myocarditis. We found that ER stress was robustly induced in the cardiac infiltrating macrophages from CVB3-infected mice, and robustly facilitated the production of pro-inflammatory cytokines (IL-6, IL-12, MCP-1 and IP-10). Consistently, adoptive transfer of ER stressed macrophages significantly worsened the viral myocarditis; while transfer of ER stress-inhibited macrophages obviously alleviated the myocarditis. To our surprise, this significantly activated ER stress was not directly caused by the virus stimulation, but was transferred from the CVB3-infected, ER stressed myocardiocytes via soluble molecules in a TLR2, 4-independent way. In the present study, we reported that the transmissible ER stress from the infected myocardiocytes to macrophages could augment the pro-inflammatory responses and promoted the pathogenesis of viral myocarditis. Blocking ER stress transmission, instead of inhibiting its initiation, may represent novel therapeutic strategies against viral myocarditis.

Gene expression profiling reveals genes and transcription factors associated with dilated and ischemic cardiomyopathies

AIMS

Dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM) can cause heart failure, and this study aims to identify genes and transcription factors (TFs) associated with DCM and ICM.

METHODS

Gene expression dataset GSE42955 was generated from GEO database, and it contained 12 DCM, 12 ICM, and 5 control samples. Differentially expressed genes (DEGs) were identified between DCM (or ICM) and controls. Gene functions were investigated, and their associations were analyzed using Enrichmentmap plugin in Cytoscape. Protein-protein interactions (PPIs) between DEGs were determined, and DEGs with high degree were defined as key DEGs. Potential TFs of key DEGs were predicted using iRegulon plugin. Common DEGs were found, and their functional interactions were investigated using GeneMANIA.

RESULTS

A total of 362 and 300 DEGs were respectively identified for DCM and ICM in comparison with controls, and these DEGs mainly participated in similar functions about extracellular region, membrane, immune process, and defense response. PPI networks were respectively constructed for DCM and ICM, and 26 key DEGs (e.g. CXCL10, IL6, TLR3, and VCAM1) were found, which might be targeted by 35 TFs (e.g. IRF1). Besides, 47 common up-regulated DEGs were found, which participated in 14 pathways like Apoptosis, Collagen formation, as well as 127 common down-regulated DEGs that involved in 20 pathways like Adaptive immune system, Interferon γ signaling (e.g. IRF1, VCAM1), and Toll-like receptor signaling pathway (e.g. CXCL10, IL6, TLR3).

CONCLUSION

DCM and ICM may share similar mechanism, and TFs (e.g. IRF1) play crucial roles in their development via regulating gene expression.

Usefulness of Subepicardial Hyperemia on Contrast-Enhanced First-Pass Magnetic Resonance Perfusion Imaging for Diagnosis of Acute Myocarditis

Hyperemia is a major criterion for the diagnosis of acute myocarditis on cardiac magnetic resonance imaging but its assessment is challenging and time consuming. We evaluated the usefulness of the contrast-enhanced first-pass perfusion (FPP) on magnetic resonance imaging for detecting subepicardial hyperemia in acute myocarditis. Forty-seven consecutive patients (mean age: 42 ± 15.6 years; 35 men) with a definite diagnosis of acute myocarditis according to the state-of-the-art guidelines were included and compared with 16 control subjects. FPP was evaluated by 2 blinded observers and compared with the reference late gadolinium enhancement. Detection of hyperemia was performed on both qualitative and quantitative methods. Relative increased signal intensity (SI) in the subepicardial hyperemic layer was measured with SI ratio (SI of the subepicardial layer/SI of the immediately adjacent subendocardial layer). Twenty-four patients (51%) with acute myocarditis exhibited subepicardial hyperemia, detected with a good interobserver reproducibility (kappa coefficient: 0.75). The SI in the myocardium of myocarditis patients was increased compared with controls (1.08 ± 0.03 vs 0.945 ± 0.04, p = 0.03) and the SI in myocarditis patients with hyperemia compared with those without hyperemia (1.22 ± 0.04 vs 0.94 ± 0.04, p <0.0001). Sensitivity, specificity, positive predictive, and negative predictive values of FPP for detecting hyperemia were 85%, 94%, 85%, and 93%, respectively. In conclusion, contrast-enhanced first-pass magnetic resonance imaging is a fast and useful method for assessing myocardial hyperemia in patients with acute myocarditis.

Nicotine inhibits the production of proinflammatory cytokines of mice infected with coxsackievirus B3

AIMS

Although excessive sympathetic activation in viral myocarditis and the protective effects of sympathetic inhibition with β-blockers are clear, the effects of enhancing vagal tone on viral myocarditis remain unclear. In several models, vagus nerve activation with the α7 nicotinic acetylcholine receptor (α7-nAChR) agonists has been demonstrated to ameliorate inflammation. This study was therefore designed to examine the effects of cholinergic stimulation with α7-nAChR agonist nicotine in a murine model of acute viral myocarditis.

MATERIALS AND METHODS

BALB/C mice were infected by an intraperitoneally injection with coxsackievirus B3. Nicotine and methyllycaconitine (an α7-nAChR antagonist) were administered at doses of 0.4mg/kg and 0.8mg/kg three times per day for 7 or 14 consecutive days, respectively. The effects of nicotine and methyllycaconitine on survival rate, myocardial histopathological changes, cardiac function, cytokine levels, viral RNA, malondialdehyde, and superoxide dismutase contents were investigated.

KEY FINDINGS

Nicotine significantly increased survival rate of the infected mice, decreased myocardial inflammation, and improved the impairment of left ventricular function in murine coxsackievirus B3-induced myocarditis compared with methyllycaconitine. The proinflammatory cytokines TNF-α, IL-1β, IL-6 and IL-17A were significantly decreased in the infected mice treated with nicotine compared with methyllycaconitine. Nicotine had no significant anti-oxidative and antiviral effects in coxsackievirus B3-infected mice.

SIGNIFICANCE

The results indicate that cholinergic stimulation with nicotine significantly reduced the severity of viral myocarditis in mice. The findings suggest that alpha7 nAChR agonists may be a promising new strategy for patients with myocarditis.

Dose-dependent protective effect of nicotine in a murine model of viral myocarditis induced by coxsackievirus B3

The alpha 7 nicotinic acetylcholine receptor (alpha7 nAChR) was recently described as an anti-inflammatory target in various inflammatory diseases. The aim of this study was to investigate the dose-related effects of nicotine, an alpha7 nAChR agonist, in murine model of viral myocarditis. BALB/C mice were infected by an intraperitoneally injection with coxsackievirus B3. Nicotine was administered at doses of 0.1, 0.2 or 0.4 mg/kg three times per day for 7 or 14 consecutive days. The effects of nicotine on survival, myocardial histopathological changes, cardiac function, and cytokine levels were studied. The survival rate on day 14 increased in a dose-dependent fashion and was markedly higher in the 0.2 and 0.4 mg/kg nicotine groups than in the infected untreated group. Treatment with high-dose nicotine reduced the myocardial inflammation and improved the impaired left ventricular function in infected mice. The mRNA expressions and protein levels of TNF-α, IL-1β, IL-6, and IL-17A were significantly downregulated in dose-dependent manners in the nicotine treatment groups compared to the infected untreated group. Nicotine dose-dependently reduced the severity of viral myocarditis through inhibiting the production of proinflammatory cytokines. The findings suggest that alpha7 nAChR agonists may be a promising new strategy for patients with viral myocarditis.

Interleukin-6 receptor inhibition modulates the immune reaction and restores titin phosphorylation in experimental myocarditis

Increased levels of interleukin-6 (IL-6) have been observed in patients with acute myocarditis and are associated with poor prognosis. This study was designed to examine whether treatment with anti-IL-6 receptor antibody improves cardiac dysfunction and left ventricular (LV) remodeling in experimental Coxsackie virus B3 (CVB3)-induced myocarditis. C57BL6/J mice were subjected to acute CVB3 infection. One day after viral infection mice were treated with a single injection of an anti-IL-6 receptor antibody (MR16-1, tocilizumab) or control IgG. Seven days after viral infection, LV function was examined by conductance catheter technique, cardiac remodeling assessed by estimation of titin phosphorylation, cardiac fibrosis, and inflammatory and antiviral response by immunohistochemistry, RT-PCR and cell culture experiments. Compared to controls, infected mice displayed an impaired systolic and diastolic LV function associated with an increase in cardiac inflammation, fibrosis and impaired titin phosphorylation. IL-6 receptor blockade led to a shift of the immune response to a Th1 direction and significant reduction of viral load. In addition, cardiac immune response, extracellular matrix regulation and titin function improved, resulting in a preserved LV function. IL-6 receptor blockade exerts cardiac beneficial effects by antiviral and immunomodulatory actions after induction of an acute murine CVB3 virus myocarditis.

Early expression of local cytokines during systemic Candida albicans infection in a murine intravenous challenge model

Local cytokine production is a significant indicator for disease pathogenesis or progression. Previous studies on cytokine production during systemic Candida albicans (C. albicans) infection were solely on kidney or single cell type interaction with C. albicans. Therefore, the present study aimed to assess the early cytokine expression of various target organs (kidney, spleen and brain) over a 72-h time course during systemic C. albicans infection. The local cytokine profiles of the target organs during systemic C. albicans infection were measured by cytometric bead array and ELISA analysis. The results demonstrated that interleukin-6 (IL-6) and IL-2 were statistically significant (P<0.05) in the spleen at 24 and 72 h post-infection, whereas in the kidney, IL-6 and tumor necrosis factor-α (TNF-α) were statistically significant (P<0.05) at 24 and 72 h post-infection and CXCL-1 and transforming growth factor-β (TGF-β) were statistically significant (P<0.05) at 72 h post-infection. In the brain, IL-6 and TNF-α were statistically significant (P<0.05) at 24 and 72 h post-infection, whereas TGF-β was statistically significant (P<0.05) at 72 h post-infection. These findings demonstrate that host immune responses were varied among target organs during systemic C. albicans infection. This could be important for designing targeted immunotherapy against this pathogen through immunomodulatory approaches in future exploratory research.

Circulating angiogenic and inflammatory cytokine responses to acute aerobic exercise in trained and sedentary young men

PURPOSE

Endurance exercise training can ameliorate many cardiovascular and metabolic disorders and attenuate responses to inflammatory stimuli. The purpose of this study was to determine whether the angiogenic and pro-inflammatory cytokine response to acute endurance exercise differs between endurance-trained and sedentary young men.

METHODS

Ten endurance-trained and ten sedentary healthy young men performed 30 min of treadmill running at 75 % VO2max with blood sampling before and after exercise. Plasma concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, IL-6, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), placental growth factor (PlGF), and soluble VEGF receptor-1 (sFlt-1) were measured by multiplex ELISA.

RESULTS

Acute exercise increased IL-6 by 165 % (P < 0.05), IL-8 by 32 % (P < 0.05), PlGF by ~16 % (P < 0.05), sFlt-1 by 36 % (P < 0.001), and tended to increase bFGF by ~25 % (P = 0.06) in main effects analyses. TNF-α and VEGF did not change significantly with exercise in either group. Contrary to our hypothesis, there were no significant differences in TNF-α, IL-6, VEGF, bFGF, PlGF, or sFlt-1 between groups before or after acute exercise; however, there was a tendency for IL-8 concentrations to be higher in endurance-trained subjects compared to sedentary subjects (P = 0.06).

CONCLUSIONS

These results indicate that 30 min of treadmill running at 75 % VO2max produces a systemic angiogenic and inflammatory reaction, but endurance exercise training does not appear to significantly alter these responses in healthy young men.

Myocyte signalling in leucocyte recruitment to the heart

Myocardial damage, by different noxious causes, triggers an inflammatory reaction driving post-injury repair mechanisms and chronic remodelling processes that are largely detrimental to cardiac function. Cardiomyocytes have recently emerged as key players in orchestrating this inflammatory response. Injured cardiomyocytes release damage-associated molecular pattern molecules, such as high-mobility group box 1 (HMGB1), DNA fragments, heat shock proteins, and matricellular proteins, which instruct surrounding healthy cadiomyocytes to produce inflammatory mediators. These mediators, mainly interleukin (IL)-1β, IL-6, macrophage chemoattractant protein (MCP)-1, and tumour necrosis factor α (TNF-α), in turn activate versatile signalling networks within surviving cardiomyocytes and trigger leucocyte activation and recruitment. In this review, we will focus on recently characterized signalling pathways activated in cardiomyocytes that mediate inflammatory responses during myocardial infarction, hypertensive heart disease, and myocarditis.

Effects of carvedilol treatment on cardiac cAMP response element binding protein expression and phosphorylation in acute coxsackievirus B3-induced myocarditis

Background

The role of β-adrenergic stimulation on viral myocarditis has been investigated in animal models of viral myocarditis. Excess stimulation of β-adrenergic receptors by catecholamines causes phosphorylation/activation of cAMP response element binding protein (CREB) by the cAMP signaling pathway. CREB as an important regulator of gene expression mediates the cardiovascular remodeling process and promotes anti-inflammatory immune responses. However, the CREB expression and phosphorylation have not been studied, and the effects of carvedilol (a nonselective β-adrenoceptor antagonist) on the CREB has not been investigated in the setting of acute viral myocarditis.

Methods

This study was therefore designed to examine the effects of carvedilol on the transcriptional factor CREB in a murine model of acute viral myocarditis. In a coxsackievirus B3 murine myocarditis model (Balb/c), effects of carvedilol on plasma noradrenaline, heart rate and blood pressure, myocardial histopathological changes and fibrosis, cardiomyocyte apoptosis, cardiac CREB and phosphorylated CREB, cytokine levels, and viral RNA were studied.

Results

The expression and phosphorylation of CREB were decreased with concomitant increase of IL-6 and TNF-α in murine coxsackievirus-induced acute viral myocarditis. The levels of IL-6 and TNF-α were correlated with the expression of CREB or phosphorylated CREB. Carvedilol increased the cardiac CREB expression and phosphorylation and decreased the plasma catecholamine levels and the production of IL-6 and TNF-α with amelioration of acute viral myocarditis.

Conclusion

These results show that CREB may be involved in the pathophysiology of viral myocarditis and carvedilol exerts some of its beneficial effects by increasing the CREB expression and phosphorylation.

Side effects of TNF-α blockers in patients with psoriatic arthritis: evidences from literature studies

Psoriatic arthritis is an inflammatory rheumatic disorder, which occurs in patients with skin and/or nail psoriasis. In psoriatic arthritis, the importance of biologic mediators modulating inflammatory reaction, such as tumor necrosis factor, and the knowledge on their role in the pathogenesis of psoriatic arthritis influence the therapeutic choices. In the last years, the introduction of biologic drugs has greatly changed the treatment of psoriasis and psoriatic arthritis. In fact, tumor necrosis factor-α blockers demonstrated an effective action in the treatment of both skin and joint manifestations of psoriatic arthritis, but they have some adverse effects. The aim of this review is to revisit the literature data on adverse effects of tumor necrosis factor-α blockers in patients with psoriatic arthritis.

Chronic inflammation and low-dose glucocorticoid effects on glucose metabolism in premenopausal females with rheumatoid arthritis free of conventional metabolic risk factors

Chronic systemic inflammation is associated with increased cardiovascular mortality in patients with rheumatoid arthritis (RA). The aim of our study was to investigate association of glucose metabolism and inflammatory markers in a group of patients with rheumatoid arthritis free of other metabolic risk factors. Twenty-two premenopausal RA females (11 patients on low-dose GC (<8.5 mg/day of prednisone or equivalent), 11 patients without glucocorticoid therapy) and 15 age- and BMI-matched healthy females underwent the oral glucose tolerance test. The insulin sensitivity indices according Matsuda (ISI(MAT)) and Cederholm (ISI(CED)) as well as HOMA2 %S were calculated. Cytokines, lipid profile, non-esterified fatty acids (NEFA) and plasminogen activator inhibitor-1 (PAI-1) were measured in baseline blood samples. Despite elevated interleukin IL-6 and TNF alpha, glucose, insulin and C-peptide responses to oral glucose load as well as ISI(MAT), ISI(CED), PAI-1 and NEFA were comparable in both RA groups and healthy controls. HOMA2 %S correlated with disease activity. In conclusions, low-dose glucocorticoid treatment does not lead to glucose metabolism impairment in RA patients without other metabolic risk factors. Increased cardiovascular mortality and morbidity is probably due to a direct effect of systemic inflammation on myocardium and/or blood vessels.

Effect of prophylactically applied CpG ODN on the development of myocarditis in mice infected with Coxsackievirus B3

Coxsackievirus B3 was one of the major pathogens causing viral myocarditis. Toll-like receptor 9 activation contributed to the innate immune response in the process of CVB3-induced myocarditis. In order to find out how CpG oligodeoxynucleotide, known as a TLR-9 agonist, would affect the CVB3-induced myocarditis, we chose a C-type CpG oligodeoxynucleotide (YW002) injected to the mice one day before CVB3 challenge. On day 4 post CVB3 infection, 3 mice in each group were randomly sacrificed and their hearts were isolated to detect CVB3 replication. On day 10, the CVB3 neutralizing antibody and inflammatory change of the hearts were detected. The results indicated that the CVB3-induced myocarditis was aggravated with the declining body weight of mice, decreasing neutralizing antibody, and uncontrolling virus replication by injecting 20 μg YW002 per mouse. When adjusted the amount at 10 μg YW002 per mouse, there were no signs of aggravation in myocarditis. Plus, the mortality of the infected mice was reduced, the neutralizing antibody level was raised and the replication of virus was restrained. These results suggested that a proper amount of CpG oligodeoxynucleotide application could help to inhibit CVB3 infection.

Comparison of effects of ivabradine versus carvedilol in murine model with the Coxsackievirus B3-induced viral myocarditis

BACKGROUND

Elevated heart rate is associated with increased cardiovascular morbidity. The selective I(f) current inhibitor ivabradine reduces heart rate without affecting cardiac contractility, and has been shown to be cardioprotective in the failing heart. Ivabradine also exerts some of its beneficial effects by decreasing cardiac proinflammatory cytokines and inhibiting peroxidants and collagen accumulation in atherosclerosis or congestive heart failure. However, the effects of ivabradine in the setting of acute viral myocarditis and on the cytokines, oxidative stress and cardiomyocyte apoptosis have not been investigated.

METHODOLOGY/PRINCIPAL FINDINGS

The study was designed to compare the effects of ivabradine and carvedilol in acute viral myocarditis. In a coxsackievirus B3 murine myocarditis model (Balb/c), effects of ivabradine and carvedilol (a nonselective β-adrenoceptor antagonist) on myocardial histopathological changes, cardiac function, plasma noradrenaline, cytokine levels, cardiomyocyte apoptosis, malondialdehyde and superoxide dismutase contents were studied. Both ivabradine and carvedilol similarly and significantly reduced heart rate, attenuated myocardial lesions and improved the impairment of left ventricular function. In addition, ivabradine treatment as well as carvedilol treatment showed significant effects on altered myocardial cytokines with a decrease in the amount of plasma noradrenaline. The increased myocardial MCP-1, IL-6, and TNF-α. in the infected mice was significantly attenuated in the ivabradine treatment group. Only carvedilol had significant anti-oxidative and anti-apoptoic effects in coxsackievirus B3-infected mice.

CONCLUSIONS/SIGNIFICANCE

These results show that the protective effects of heart rate reduction with ivabradine and carvedilol observed in the acute phase of coxsackievirus B3 murine myocarditis may be due not only to the heart rate reduction itself but also to the downregulation of inflammatory cytokines.

Role of the cholinergic antiinflammatory pathway in murine autoimmune myocarditis

RATIONALE

This study was performed to gain insights into novel therapeutic approaches for the treatment of autoimmune myocarditis.

OBJECTIVE

Chemical stimulation of the efferent arm of the vagus nerve through activation of nicotinic acetylcholine receptor subtype-7α (α7-nAChR) has been shown to be protective in several models of inflammatory diseases. In the present study, we investigated the potentially protective effect of vagus nerve stimulation on myocarditis.

METHODS AND RESULTS

A/J mice were immunized with cardiac troponin I (TnI) to induce autoimmune myocarditis. Mice were exposed to drinking water that contained nicotine in different concentrations and for different time periods (for 3 days at 12.5 mg/L; 3 days at 125 mg/L; 21 days at 12.5 mg/L; and 21 days at 125 mg/L after first immunization). TnI-immunized mice with no pharmacological treatment showed extensive myocardial inflammation and fibrosis and significantly elevated levels of interleukin-6 and tumor necrosis factor-α. Furthermore, elevated levels of mRNA transcripts of proinflammatory chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and RANTES) and chemokine receptors (CCR1, CCR2, and CCR5) were found. Oral nicotine administration reduced inflammation within the myocardium, decreased the production of interleukin-6 and tumor necrosis factor-α, and downregulated the expression of monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, RANTES, CCR1, CCR2, and CCR5. In addition, nicotine treatment resulted in decreased expression of matrix metalloproteinase-14, natriuretic peptide precursor B, tissue inhibitor of metalloproteinase-1, and osteopontin, proteins that are commonly involved in heart failure. Finally, we found that nicotine reduced levels of pSTAT3 (phosphorylated signal transducer and activator of transcription 3) protein expression within the myocardium. Neostigmine treatment did not affect the progression of myocarditis.

CONCLUSIONS

We showed that activation of the cholinergic antiinflammatory pathway with nicotine reduces inflammation in autoimmune myocarditis. Our results may open new possibilities in the therapeutic management of autoimmune myocarditis.

Sustained high levels of interleukin-6 contribute to the pathogenesis of enterovirus 71 in a neonate mouse model

Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD) in young children and has been consistently associated with the most severe complications of the disease, including central nervous system inflammation and pulmonary edema. Increasing frequency and amplitude of EV71 outbreaks have raised awareness and concerns worldwide. Previous reports proposed that overwhelming virus replication combined with the induction of massive proinflammatory cytokines is responsible for the pathogenicity of EV71. Specifically, elevated interleukin-6 (IL-6) levels were observed consistently in patients and strongly correlated with disease severity. In this study, we show in the neonate mouse model that sustained high levels of IL-6 produced upon EV71 infection lead to severe tissue damage and eventually death of the animals. Administration of anti-IL-6 neutralizing antibodies after the onset of the clinical symptoms successfully improved the survival rates and clinical scores of the infected hosts. Compared to untreated infected controls, anti-IL-6-treated mice displayed reduced tissue damage, absence of splenic atrophy, and increased immune cell activation. In addition, markedly elevated systemic levels of IL-10 were measured in the protected animals. Furthermore, there was no significant difference in virus titers between anti-IL-6-treated mice and untreated mice, indicating that the anti-IL-6 antibody-mediated protection is independent of the virus load. Our findings thus demonstrate that IL-6 plays a major role in EV71-induced immunopathogenesis. As there is still neither vaccine nor treatment available against EV71, anti-IL-6 antibody treatment represents a potential therapeutic approach to providing protection from the most severe complications of the disease.

Experimental encephalomyocarditis virus infection in small laboratory rodents

Encephalomyocarditis virus (EMCV) is a cardiovirus that belongs to the family Picornaviridae. EMCV is an important cause of acute myocarditis in piglets and of fetal death or abortion in pregnant sows. Small rodents, especially rats, have been suspected to be reservoir hosts or carriers. This virus also induces type 1 diabetes mellitus, encephalomyelitis, myocarditis, orchitis and/or sialodacryoadenitis in small laboratory rodents. This paper reviews the pathology and pathogenesis of experimental infection with EMCV in small laboratory rodents.

Interleukin-17A is dispensable for myocarditis but essential for the progression to dilated cardiomyopathy

RATIONALE

One-third of myocarditis cases progresses to dilated cardiomyopathy (DCM), but the mechanisms controlling this process are largely unknown. CD4(+) T helper (Th)17 cells have been implicated in the pathogenesis of autoimmune diseases, but the role of Th17-produced cytokines during inflammation-induced cardiac remodeling has not been previously studied.

OBJECTIVE

We examined the importance of interleukin (IL)-17A in the progression of myocarditis to DCM using a mouse model.

METHODS AND RESULTS

Immunization of mice with myocarditogenic peptide in complete Freund's adjuvant induced the infiltration of IL-17A-producing Th17 cells into the inflamed heart. Unexpectedly, IL-17A-deficient mice developed myocarditis with similar incidence and severity compared to wild-type mice. Additionally, IL-17A deficiency did not ameliorate the severe myocarditis of interferon (IFN)gamma-deficient mice, suggesting that IL-17A plays a minimal role during acute myocarditis. In contrast, IL-17A-deficient mice were protected from postmyocarditis remodeling and did not develop DCM. Flow cytometric and cytokine analysis revealed an important role for IL-17A in heart-specific upregulation of IL-6, TNFalpha, and IL-1beta and the recruitment of CD11b(+) monocyte and Gr1(+) granulocyte populations into the heart. Furthermore, IL-17A-deficient mice had reduced interstitial myocardial fibrosis, downregulated expression of matrix metalloproteinase-2 and -9 and decreased gelatinase activity. Treatment of BALB/c mice with anti-IL-17A monoclonal antibody administered after the onset of myocarditis abrogated myocarditis-induced cardiac fibrosis and preserved ventricular function.

CONCLUSIONS

Our findings reveal a critical role for IL-17A in postmyocarditis cardiac remodeling and the progression to DCM. Targeting IL-17A may be an attractive therapy for patients with inflammatory dilated cardiomyopathy.

Activation of PI 3-kinase/Akt/NF-kappaB and Stat3 signaling by avian reovirus S1133 in the early stages of infection results in an inflammatory response and delayed apoptosis

Avian reovirus (ARV) strain S1133 causes apoptosis in host cells in the middle to late stages of infection. This study investigated the early-stage biological response and intracellular signaling in ARV S1133-infected Vero and chicken cells. Treatment with conditioned medium from ARV S1133-infected cells increased the chemotactic activity of U937 cells. Neutralizing antibodies against IL-1beta and IL-6 showed that both cytokines contribute to viral-induced inflammation but neither affect cell survival. Inhibition of Akt, NF-kappaB, and Stat3 released the chemotactic activity and anti-apoptotic effect elicited by ARV S1133. ARV S1133 activated PI 3-kinase-dependent Akt/NF-kappaB and p70 S6 kinase, as well as Stat3; however, p70 S6 kinase was not involved in ARV S1133-mediated effects. DF1 cells over-expressing constitutively active PI 3-kinase and Stat3 showed association with enhancement of anti-apoptotic activity. In conclusion, in the early stages of ARV S1133 infection, activation of cell survival signals contributes to virus-induced inflammation and anti-apoptotic response.

Lack of IL-6 during coxsackievirus infection heightens the early immune response resulting in increased severity of chronic autoimmune myocarditis

BACKGROUND

Chronic myocarditis is often initiated by viral infection, the most common of which is coxsackievirus infection. The precise mechanism by which viral infection leads to chronic autoimmune pathology is poorly understood, however it is clear that the early immune response plays a critical role. Previous results have shown that the inflammatory cytokine interleukin (IL)-6 is integral to the development of experimental-induced autoimmune myocarditis. However, the function of IL-6 during viral-mediated autoimmunity has yet to be elucidated.

METHODS AND RESULTS

To address the requirement of IL-6 during disease induction, IL-6 deficient mice were infected with coxsackievirus B3 (CB3). Following infection, mice lacking IL-6 developed increased chronic autoimmune disease pathology compared to wild type controls without a corresponding change in the level of viral replication in the heart. This increase in disease severity was accompanied by elevated levels of TNF-alpha, MCP-1, IL-10, activated T cells and cardiac infiltrating macrophage/monocytes. Injection of recombinant IL-6 early following infection in the IL-6 deficient mice was sufficient to lower the serum cytokines TNF-alpha and IL-10 as well as the serum chemokines MCP-1, MIP-1beta, RANTES and MIG with a corresponding decrease in the chronic disease pathology strongly suggests an important regulatory role for IL-6 during the early response.

CONCLUSIONS

While IL-6 plays a pathogenic role in experimental-induced autoimmune disease, its function following viral-induced autoimmunity is not reprised. By regulating the early immune response and thereby controlling the severity of chronic disease, IL-6 directs the outcome of chronic autoimmune myocarditis.

Role of the innate immune system in acute viral myocarditis

Although the adaptive immune system is thought to play an important role in the pathogenesis of viral myocarditis, the role of the innate immune system has not been well defined. To address this deficiency, we employed a unique line of mice that harbor a genomic "knock in" of a mutated TNF gene lacking the AU rich element (TNF(ARE/ARE)) that is critical for TNF mRNA stability and translation, in order to examine the contribution of the innate immune system in encephalomyocarditis-induced myocarditis (EMCV). Heterozygous mice (TNF(ARE/+)) were infected with 500 plaque-forming units of EMCV. TNF(ARE/+)mice had a significantly higher 14-day mortality and myocardial inflammation when compared to littermate control mice. Virologic studies showed that the viral load at 14 days was significantly lower in the hearts of TNF(ARE/+) mice. TNF(ARE/+) mice had an exaggerated proinflammatory cytokine and chemokine response in the heart following EMCV infection. Modulation of the innate immune response in TNF(ARE/+) mice by the late administration of prednisolone resulted in a significant improvement in survival and decreased cardiac inflammation, whereas early administration of prednisolone resulted in a blunted innate response and increased mortality in littermate control mice. Viewed together, these data suggest that the duration and degree of activation of the innate immune system plays a critical role in determining host outcomes in experimental viral myocarditis.

Role of gp130-mediated signalling pathways in the heart and its impact on potential therapeutic aspects

IL-6-type cytokines bind to plasma membrane receptor complexes containing the common signal transducing receptor chain gp130 that is ubiquitously expressed in most tissues including the heart. The two major signalling cascades activated by the gp130 receptor, SHP2/ERK and STAT pathways, have been demonstrated to play important roles in cardiac development, hypertrophy, protection and remodelling in response to physiological and pathophysiological stimuli. Experimental data, both in vivo and in vitro, imply beneficial effects of gp130 signalling on cardiomyocytes in terms of growth and survival. In contrast, it has been reported that elevated serum levels of IL-6 cytokines and gp130 proteins are strong prognostic markers for morbidity and mortality in patients with heart failure or after myocardial infarction. Moreover, it has been shown that the local gp130 receptor system is altered in failing human hearts. In the present review, we summarize the basic principles of gp130 signalling, which requires simultaneous activation of STAT and ERK pathways under the tight control of positive and negative intracellular signalling modulators to provide a balanced biological outcome. Furthermore, we highlight the key role of the gp130 receptor and its major downstream effectors in the heart in terms of development and regeneration and in response to various physiological and pathophysiological stress situations. Finally, we comment on tissue-specific diversity and challenges in targeted pharmacological interference with components of the gp130 receptor system.

Survival pathways in hypertrophy and heart failure: the gp130-STAT3 axis

Circulating levels of interleukin (IL)-6 and related cytokines are elevated in patients with congestive heart failure and after myocardial infarction. Serum IL-6 concentrations are related to decreasing functional status of these patients and provide important prognostic information.Moreover, in the failing human heart, multiple components of the IL-6- glycoprotein (gp)130 receptor system are impaired, implicating an important role of this system in cardiac pathophysiology.Experimental studies have shown that the common receptor subunit of IL-6 cytokines is phosphorylated in response to pressure overload and myocardial infarction and that it subsequently activates at least three different downstream signaling pathways, the signal transducers and activators of transcription 1 and 3 (STAT1/3), the Src-homology tyrosine phosphatase 2 (SHP2)-Ras-ERK, and the PI3K-Akt system. Gp130 receptor mediated signaling promotes cardiomyocyte survival, induces hypertrophy, modulates cardiac extracellular matrix and cardiac function. In this regard, the gp130 receptor system and its main downstream mediator STAT3 play a key role in cardioprotection. This review summarizes the current knowledge of IL-6 cytokines, gp130 receptor and STAT3 signaling in the heart exposed to physiological (aging, pregnancy) and pathophysiological stress (ischemia, pressure overload, inflammation and cardiotoxic agents) with a special focus on the potential role of individual IL-6 cytokines.

TLR ligands act directly upon T cells to restore proliferation in the absence of protein kinase C-theta signaling and promote autoimmune myocarditis

The serine/threonine kinase, protein kinase C-theta (PKC-theta), plays a central role in the activation and differentiation of Th2 cells while being redundant in CD4+ and CD8+ antiviral responses. Recent evidence indicates that PKC-theta may however be required for some T cell-driven autoimmune responses. We have investigated the role of PKC-theta in the induction of autoimmune myocarditis induced by either Coxsackie B3 virus infection or immunization with alpha-myosin/CFA (experimental autoimmune myocarditis (EAM)). PKC-theta-deficient mice did not develop EAM as shown by impaired inflammatory cell infiltration into the heart, reduced CD4+ T cell IL-17 production, and the absence of a myosin-specific Ab response. Comparatively, PKC-theta was not essential for both early and late-phase Coxsackie virus-induced myocarditis. We sought to find alternate pathways of immune stimulation that might reconcile the differential requirements for PKC-theta in these two disease models. We found systemic administration of the TLR ligand CpG restored EAM in PKC-theta-deficient mice. CpG could act directly upon TLR9-expressing T cells to restore proliferation and up-regulation of Bcl-x(L), but exogenous IL-6 and TGF-beta was required for Th17 cell differentiation. Taken together, these results indicate that TLR-mediated activation of T cells can directly overcome the requirement for PKC-theta signaling and, combined with the dendritic cell-derived cytokine milieu, can promote the development of autoimmunity.

Early inflammatory responses direct chronic autoimmunity development in the heart following coxsackievirus infection

Coxsackievirus infections are a major cause of chronic autoimmune myocarditis, a known precursor to dilated cardiomyopathy. Dilated cardiomyopathy leads to heart failure and is responsible for nearly half of all heart transplant cases. The induction of chronic autoimmunity following coxsackievirus infection is governed by the interplay of several genetic and immunological factors. In this review, we will focus on how the innate immune response to viral infection directs a cascade of events that ultimately results in chronic autoimmune heart disease.

Differential regulation of IL-6 and TNF-α via calcineurin in human skeletal muscle cells

Interleukin-6 increases in skeletal muscle during exercise, and evidence points to Ca2+ as an initiator of IL-6 production. However, the signalling pathway whereby this occurs is unknown. One candidate for Ca2+ -mediated IL-6 induction is calcineurin, an activator of NF-AT. Here we investigated whether skeletal myocytes produce IL-6 in a Ca2+/calcineurin-dependent manner, and whether TNF-alpha, an inducer of IL-6, is affected by these stimuli. Human skeletal muscle cell cultures were stimulated with ionomycin time-and dose-dependently to elevate intracellular Ca2+ levels, with or without addition of cyclosporin A (CSA); a calcineurin inhibitor. mRNA was extracted from myocytes and analysed for IL-6 and TNF-alpha gene expression. IL-6 mRNA increased time- and dose-dependently with ionomycin stimulation, an effect that was blunted by approximately 75% in the presence of CSA. In contrast, TNF-alpha gene expression was decreased by approximately 70% in response to ionomycin treatment, but increased in response to addition of CSA. These data demonstrate that IL-6 and TNF-alpha are regulated differentially in skeletal muscle cells in response to a Ca2+ stimulus. Blocking the calcineurin pathway resulted in inhibition of the IL-6 response to ionomycin, whereas TNF-alpha increased by addition of CSA, further indicating a differential regulation of IL-6 and TNF-alpha in human skeletal myocytes.

Toll-like receptor 3 is an essential component of the innate stress response in virus-induced cardiac injury

Enterovirus-induced myocardial injury can lead to severe heart failure. To date, little is known about the early innate stress response that contributes to host defense in the heart. Toll-like receptor 3 (TLR3) is important in the initiation of the innate antiviral response. We investigated the involvement of TLR3, which recognizes viral double-stranded RNA, on encephalomyocarditis virus (EMCV) infection. To examine the contribution of TLR3 in protection from EMCV infection, we infected mice deficient in TLR3 with 50 plaque-forming units of EMCV. TLR3-deficient (TLR3(-/-)) mice were more susceptible to EMCV infection and had a significantly higher viral load in the heart compared with TLR3(+/+) mice. Histopathological examination showed that the inflammatory changes of the myocardium were less marked in TLR3(-/-) than in TLR3(+/+)mice. TLR3(-/-) mice had impaired proinflammatory cytokine and chemokine expression in the heart following EMCV infection. However, the expression of interferon-beta was not impaired in EMCV-infected TLR3(-/-) mice. EMCV infection leads to a TLR3-dependent innate stress response, which is involved in mediating protection against virus-induced myocardial injury.