Persistent expression of cytokine in the chronic stage of viral myocarditis in mice

Innate and adaptive immunity in acute myocarditis

Acute myocarditis is an acute inflammatory cardiomyopathy associated with cardiac damage triggered by a virus or a pathological immune activation. It may present with a wide range of clinical presentations, ranging from mild symptoms to severe forms like fulminant myocarditis, characterized by hemodynamic compromise and cardiogenic shock. The immune system plays a central role in the pathogenesis of myocarditis. In fact, while its function is primarily protective, aberrant responses can be detrimental. In this context, both innate and adaptive immunity play pivotal roles; notably, the innate system offers a non-specific and immediate defense, while the adaptive provides specialized protection with immunological memory. However, dysregulation in these systems can misidentify cardiac tissue, triggering autoimmune reactions and possibly leading to significant cardiac tissue damage. This review highlights the importance of innate and adaptive immune responses in the progression and treatment of acute myocarditis.

Role of immune cells in the pathogenesis of myocarditis

Myocarditis is an inflammatory heart disease that mostly affects young people. Myocarditis involves a complex immune network; however, its detailed pathogenesis is currently unclear. The diversity and plasticity of immune cells, either in the peripheral blood or in the heart, have been partially revealed in a number of previous studies involving patients and several kinds of animal models with myocarditis. It is the complexity of immune cells, rather than one cell type that is the culprit. Thus, recognizing the individual intricacies within immune cells in the context of myocarditis pathogenesis and finding the key intersection of the immune network may help in the diagnosis and treatment of this condition. With the vast amount of cell data gained on myocarditis and the recent application of single-cell sequencing, we summarize the multiple functions of currently recognized key immune cells in the pathogenesis of myocarditis to provide an immune background for subsequent investigations.

The Role of Pro-Inflammatory Cytokines in the Pathogenesis of Cardiovascular Disease

With cardiovascular disease (CVD) being a primary source of global morbidity and mortality, it is crucial that we understand the molecular pathophysiological mechanisms at play. Recently, numerous pro-inflammatory cytokines have been linked to several different CVDs, which are now often considered an adversely pro-inflammatory state. These cytokines most notably include interleukin-6 (IL-6),tumor necrosis factor (TNF)α, and the interleukin-1 (IL-1) family, amongst others. Not only does inflammation have intricate and complex interactions with pathophysiological processes such as oxidative stress and calcium mishandling, but it also plays a role in the balance between tissue repair and destruction. In this regard, pre-clinical and clinical evidence has clearly demonstrated the involvement and dynamic nature of pro-inflammatory cytokines in many heart conditions; however, the clinical utility of the findings so far remains unclear. Whether these cytokines can serve as markers or risk predictors of disease states or act as potential therapeutic targets, further extensive research is needed to fully understand the complex network of interactions that these molecules encompass in the context of heart disease. This review will highlight the significant advances in our understanding of the contributions of pro-inflammatory cytokines in CVDs, including ischemic heart disease (atherosclerosis, thrombosis, acute myocardial infarction, and ischemia-reperfusion injury), cardiac remodeling (hypertension, cardiac hypertrophy, cardiac fibrosis, cardiac apoptosis, and heart failure), different cardiomyopathies as well as ventricular arrhythmias and atrial fibrillation. In addition, this article is focused on discussing the shortcomings in both pathological and therapeutic aspects of pro-inflammatory cytokines in CVD that still need to be addressed by future studies.

Nuclear Factor-κB is a Prime Candidate for the Diagnosis and Control of Inflammatory Cardiovascular Disease

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is responsible for the regulation of genes involved in inflammation and immune responses. NF-κB may play an important role in cardiovascular diseases (CVDs), atherosclerosis and diabetes. Several therapeutic agents used for the treatment of CVDs and diabetes, such as pimobendan and sodium-glucose cotransporter 2 inhibitors, exert anti-inflammatory effects by inhibiting NF-κB activation; anti-inflammatory therapy may have beneficial effects in CVDs and diabetes. Several pharmacological agents and natural compounds may inhibit NF-κB, and these agents alone or in combination may be used to treat various inflammatory diseases. Immunoglobulin-free light chains could be surrogate biomarkers of NF-κB activation and may be useful for evaluating the efficacy of these agents. This review discusses recent advances in our understanding of how the NF-κB signalling pathway controls inflammation, metabolism and immunity, and how improved knowledge of these pathways may lead to better diagnostics and therapeutics for various human diseases.

Roles of inflammasomes in viral myocarditis

Viral myocarditis (VMC), characterized by viral infection-induced inflammation, is a life-threatening disease associated with dilated cardiomyopathy or heart failure. Innate immunity plays a crucial role in the progression of inflammation, in which inflammasomes provide a platform for the secretion of cytokines and mediate pyroptosis. Inflammasomes are rising stars gaining increasing attention. The nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, the caspase recruitment domain-containing protein 8 (CARD8) inflammasome, and the caspase-11 inflammasome are three inflammasomes that were reported to affect the process and prognosis of VMC. These inflammasomes can be activated by a wide range of cellular events. Accumulating evidence has suggested that inflammasomes are involved in different stages of VMC, including the trigger and progression of myocardial injury and remodeling after infection. In this review, we summarized the pathways involving inflammasomes in VMC and discussed the potential therapies targeting inflammasomes and related pathways.

PCSK9: A emerging participant in heart failure

Heart failure (HF) is a complex clinical syndrome caused by various cardiovascular diseases. Its main pathogenesis includes cardiomyocyte loss, myocardial energy metabolism disorder, and activation of cardiac inflammation. Due to the clinically unsatisfactory treatment of heart failure, different mechanisms need to be explored to provide new targets for the treatment of this disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene mainly related to familial hypercholesterolemia, was discovered in 2003. Aside from regulating lipid metabolism, PCSK9 may be involved in other biological processes such as apoptosis, autophagy, pyroptosis, inflammation, and tumor immunity and related to diabetes and neurodegenerative diseases. Recently, clinical data have shown that the circulating PCSK9 level is significantly increased in patients with heart failure, and it is related to the prognosis for heart failure. Furthermore, in animal models and patients with myocardial infarction, PCSK9 in the infarct margin area was also found to be significantly increased, which further suggested that PCSK9 might be closely related to heart failure. However, the specific mechanism of how PCSK9 participates in heart failure remains to be further explored. The purpose of this review is to summarize the potential mechanism of PCSK9's involvement in heart failure, thereby providing a new treatment strategy for heart failure.

Mechanisms and Therapeutic Strategies of Viral Myocarditis Targeting Autophagy

Viral myocarditis is caused by infection with viruses or bacteria, including coxsackievirus B3 (CVB3), and is characterized by acute or chronic inflammatory responses in the heart. The mortality associated with severe viral myocarditis is considerable. In some patients, viral myocarditis may develop into dilated cardiomyopathy or heart failure. Autophagy is involved in a wide range of physiological processes, including viral infection and replication. In the present review, we focus on the responses of cardiac tissues, cardiomyocytes, and cardiac fibroblasts to CVB3 infection. Subsequently, the effects of altered autophagy on the development of viral myocarditis are discussed. Finally, this review also examined and assessed the use of several popular autophagy modulating drugs, such as metformin, resveratrol, rapamycin, wortmannin, and 3-methyladenine, as alternative treatment strategies for viral myocarditis.

The Roles of Cardiac Fibroblasts and Endothelial Cells in Myocarditis

In myocarditis caused by various etiologies, activated immune cells and the immune regulatory factors released by them play important roles. But in this complex microenvironment, non-immune cells and non-cardiomyocytes in the heart, such as cardiomyocytes (CMs), cardiac fibroblasts (CFs) and endothelial cells (ECs), play the role of “sentinel”, amplify inflammation, and interact with the cardiomyocytes. The complex interactions between them are rarely paid attention to. This review will re-examine the functions of CFs and ECs in the pathological conditions of myocarditis and their direct and indirect interactions with CMs, in order to have a more comprehensive understanding of the pathogenesis of myocarditis and better guide the drug development and clinical treatment of myocarditis.

Myeloid-Derived Suppressor Cells Restrain Natural Killer Cell Activity in Acute Coxsackievirus B3-Induced Myocarditis

Murine models of coxsackievirus B3 (CVB3)-induced myocarditis well represent the different outcomes of this inflammatory heart disease. Previously, we found that CVB3-infected A.BY/SnJ mice, susceptible for severe acute and chronic myocarditis, have lower natural killer (NK) cell levels than C57BL/6 mice, with mild acute myocarditis. There is evidence that myeloid-derived suppressor cells (MDSC) may inhibit NK cells, influencing the course of myocarditis. To investigate the MDSC/NK interrelationship in acute myocarditis, we used CVB3-infected A.BY/SnJ mice. Compared to non-infected mice, we found increased cell numbers of MDSC in the spleen and heart of CVB3-infected A.BY/SnJ mice. In parallel, S100A8 and S100A9 were increased in the heart, spleen, and especially in splenic MDSC cells compared to non-infected mice. In vitro experiments provided evidence that MDSC disrupt cytotoxic NK cell function upon co-culturing with MDSC. MDSC-specific depletion by an anti-Ly6G antibody led to a significant reduction in the virus load and injury in hearts of infected animals. The decreased cardiac damage in MDSC-depleted mice was associated with fewer Mac3⁺ macrophages and CD3⁺ T lymphocytes and a reduced cardiac expression of S100A8, S100A9, IL-1β, IL-6, and TNF-α. In conclusion, impairment of functional NK cells by MDSC promotes the development of chronic CVB3 myocarditis in A.BY/SnJ mice.

Interleukin-1 and Systemic Sclerosis: Getting to the Heart of Cardiac Involvement

Systemic sclerosis (SSc) is rare, severe connective tissue disease characterized by endothelial and vascular damage, immune activation, and resulting in inflammation and fibrosis of skin and internal organs, including the heart. SSc is associated with high morbidity and mortality. Cardiac involvement is frequent in SSc patients, even though often asymptomatic at early stages, and represents one of the major causes of SSc-related mortality. Heart involvement has a variable clinical presentation, and its pathogenesis is not completely understood. Myocardial fibrosis is traditionally considered the immunopathologic hallmark of heart involvement in SSc. This unique histological feature is paralleled by distinctive clinical and prognostic features. The so-called "vascular hypothesis" represents the most credited hypothesis to explain myocardial fibrosis. More recently, the prominent role of an inflammatory myocardial process has been identified as a cardinal event in the evolution to fibrosis, thus also delineating an "inflammation-driven pathway to fibrosis". The pro-inflammatory cytokine interleukin (IL)-1 has an apical and cardinal role in the myocardial inflammatory cascade and in cardiac dysfunction. The primary aim of this perspective article is: to present the emerging evidence on the role of IL-1 and inflammasome in both SSc and heart inflammation, to review the complex interplay between cellular metabolism and inflammasome activation, and to discuss the rationale for targeted inhibition of IL-1 for the treatment of SSc-heart involvement, providing preliminary experimental and clinical data to support this hypothesis.

Inflammatory Cytokines and Chemokines as Therapeutic Targets in Heart Failure

Heart failure exhibits remarkable pathophysiologic heterogeneity. A large body of evidence suggests that regardless of the underlying etiology, heart failure is associated with induction of cytokines and chemokines that may contribute to the pathogenesis of adverse remodeling, and systolic and diastolic dysfunction. The pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 have been extensively implicated in the pathogenesis of heart failure. Inflammatory cytokines modulate phenotype and function of all myocardial cells, suppressing contractile function in cardiomyocytes, inducing inflammatory activation in macrophages, stimulating microvascular inflammation and dysfunction, and promoting a matrix-degrading phenotype in fibroblasts. Moreover, cytokine-induced growth factor synthesis may exert chronic fibrogenic actions contributing to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). In addition to their role in adverse cardiac remodeling, some inflammatory cytokines may also exert protective actions on cardiomyocytes under conditions of stress. Chemokines, such as CCL2, are also upregulated in failing hearts and may stimulate recruitment of pro-inflammatory leukocytes, promoting myocardial injury, fibrotic remodeling, and dysfunction. Although experimental evidence suggests that cytokine and chemokine targeting may hold therapeutic promise in heart failure, clinical translation remains challenging. This review manuscript summarizes our knowledge on the role of TNF-α, IL-1, IL-6, and CCL2 in the pathogenesis of heart failure, and discusses the promises and challenges of targeted anti-cytokine therapy. Dissection of protective and maladaptive cellular actions of cytokines in the failing heart, and identification of patient subsets with overactive or dysregulated myocardial inflammatory responses are required for design of successful therapeutic approaches.

Immunoglobulin free light chains as an inflammatory biomarker of heart failure with myocarditis

BACKGROUND

In this study, we measured immunoglobulin free light chains (FLC), a biomarker of inflammation in the sera of patients with heart failure due to myocarditis.

METHODS

FLC kappa and FLC lambda were assayed in stored serum samples from patients with heart failure with myocarditis from the US myocarditis treatment trial by a competitive-inhibition multiplex Luminex® assay.

RESULTS

The median concentration of circulating FLC kappa/lambda ratio was significantly lower in the sera from patients with heart failure with myocarditis than in healthy controls, and FLC kappa/lambda ratio had good diagnostic ability for identification of heart failure with myocarditis. Further, FLC kappa/lambda ratio was an independent prognostic factor for overall survival, and allowed creation of three prognostic groups by combining with N-terminal pro-B-type natriuretic peptide.

CONCLUSIONS

This study suggests that FLC kappa/lambda ratio is a promising biomarker of heart failure with myocarditis.

Dysregulated CD4+ T Cells and microRNAs in Myocarditis

Myocarditis is a polymorphic disease complicated with indeterminate etiology and pathogenesis, and represents one of the most challenging clinical problems lacking specific diagnosis and effective therapy. It is caused by a complex interplay of environmental and genetic factors, and causal links between dysregulated microribonucleic acids (miRNAs) and myocarditis have also been supported by recent epigenetic researches. Both dysregulated CD4+ T cells and miRNAs play critical roles in the pathogenesis of myocarditis, and the classic triphasic model of its pathogenesis consists of the acute infectious, subacute immune, and recovery/chronic myopathic phase. CD4+ T cells are key pathogenic factors underlying the development and progression of myocarditis, and the effector and regulatory subsets, respectively, promote and inhibit autoimmune responses. Furthermore, the reciprocal interplay of these subsets influences the pathogenesis as well. Dysregulated miRNAs along with their mRNA and protein targets have been identified in heart biopsies (intracellular miRNAs) and body fluids (circulating miRNAs) during myocarditis. These miRNAs show phase-dependent changes, and correlate with viral infection, immune status, fibrosis, destruction of cardiomyocytes, arrhythmias, cardiac functions, and outcomes. Thus, miRNAs are promising diagnostic markers and therapeutic targets in myocarditis. In this review, we review myocarditis with an emphasis on its pathogenesis, and present a summary of current knowledge of dysregulated CD4+ T cells and miRNAs in myocarditis.

Interleukin-10 delivered by mesenchymal stem cells attenuates experimental autoimmune myocarditis

BACKGROUNDS

Autoimmune myocarditis is characterized by over-activated immune system attacking the cardiomyocytes, resulting in heart function decline. In the current study, we investigated the therapeutic advantages of delivering Interleukin-10 (IL-10) by mesenchymal stem cells (MSCs), both of which had immune suppression functions, in treating experimental autoimmune myocarditis.

METHODS

The mouse model of autoimmune myocarditis was established by subcutaneous injection of troponin I in A/J mice. Mouse bone marrow derived mesenchymal stem cells (BM-MSCs) with or without IL-10 overexpression, or the recombinant IL-10 protein were delivered into the mice via tail-vein injection. The inflammation and fibrosis levels of the heart were evaluated with qPCR, ELISA and histological staining. Serum level of anti-troponin-I was assessed by ELISA. Heart function analysis was conducted with echocardiography.

RESULTS

BM-MSCs overexpressing IL-10 had enhanced immune suppression functions. They also showed improved therapeutic effects from the perspective of heart function and cardiac fibrosis. The anti-troponin-I level was significantly reduced by MSCs overexpressing IL-10 when comparing with the MSCs or IL-10 protein injection.

CONCLUSION

IL-10 delivered by MSCs showed therapeutic advantages in treating experimental autoimmune myocarditis.

IL-1β reduces cardiac lymphatic muscle contraction via COX-2 and PGE2 induction: Potential role in myocarditis

The role of lymphatic vessels in myocarditis is largely unknown, while it has been shown to play a key role in other inflammatory diseases. We aimed to investigate the role of lymphatic vessels in myocarditis using in vivo model induced with Theiler's murine encephalomyelitis virus (TMEV) and in vitro model with rat cardiac lymphatic muscle cells (RCLMC). In the TMEV model, we found that upregulation of a set of inflammatory mediator genes, including interleukin (IL)-1β, tumor necrosis factor (TNF)-αand COX-2 were associated with disease activity. Thus, using in vitro collagen gel contraction assays, we decided to clarify the role(s) of these mediators by testing contractility of RCLMC in response to IL-1β and TNF-α individually and in combination, in the presence or absence of: IL-1 receptor antagonist (Anakinra); cyclooxygenase (COX) inhibitors inhibitors (TFAP, diclofenac and DuP-697). IL-1β impaired RCLMC contractility dose-dependently, while co-incubation with both IL-1β and TNF-α exhibited synergistic effects in decreasing RCLMC contractility with increased COX-2 expression. Anakinra maintained RCLMC contractility; Anakinra blocked the mobilization of COX-2 induced by IL-1β with or without TNF-α. COX-2 inhibition blocked the IL-1β-mediated decrease in RCLMC contractility. Mechanistically, we found that IL-1β increased prostaglandin (PG) E₂ release dose-dependently, while Anakinra blocked IL-1β mediated PGE₂ release. Using prostaglandin E receptor 4 (EP4) receptor antagonist, we demonstrated that EP4 receptor blockade maintained RCLMC contractility following IL-1β exposure. Our results indicate that IL-1β reduces RCLMC contractility via COX-2/PGE₂ signaling with synergistic cooperation by TNF-α. These pathways may help provoke inflammatory mediator accumulation within the heart, driving progression from acute myocarditis into dilated cardiomyopathy.

Elevation of Serum APE1/Ref-1 in Experimental Murine Myocarditis

Myocarditis is an inflammatory disease of the myocardium that causes cardiogenic shock and death. However, endomyocardial biopsy that is, the gold standard for a diagnosis is limited. Apurinic/apyrimidinic endonuclease 1/redox effector factor-1 (APE1/Ref-1) is a multifunctional protein, which is involved in DNA-based excision repair pathway, and in redox signaling, its changes are observed in various cardiovascular diseases including hypertension and coronary artery disease. We analyzed serum APE1/Ref-1 in experimental murine myocarditis. To induce myocarditis, coxsackievirus B3 was injected intraperitoneally to BALB/c mice. The serum APE1/Ref-1, N-terminal pro-B-type natriuretic peptide (NT-proBNP) and troponin I were measured. The histology and virus titers measurements were performed. The troponin I and inflammation were significantly elevated at day 3, peaked to day 7 and decreased at day 10. The NT-proBNP and virus titers were significantly peaked at day 3, and dropped at day 7 and 10. The serum APE1/Ref-1 was gradually raised and its elevation is still maintained until a later time, namely day 10. Also, its level was positively correlated with myocardial inflammation, reflecting severity of myocardial injury. We suggest that serum APE1/Ref-1 can be used to assess for myocardial injury in viral myocarditis without endomyocardial biopsy.

Interleukin-13 reduces cardiac injury and prevents heart dysfunction in viral myocarditis via enhanced M2 macrophage polarization

Viral myocarditis is one of the major causes of congestive heart failure and dilated cardiomyopathy. Recent reports have demonstrated an essential role of cytokines, like interleukin-13 (IL-13), in the pathogenesis of viral myocarditis, while the underlying mechanisms remain poorly defined. Here, using a coxsackie virus B3 (CVB3)-infection model in BALB/C mice, we showed that IL-13 protected mouse heart function in viral myocarditis, seemingly through reduction in T lymphocyte immunity and induction of M2 macrophage polarization. Adoptive transfer to M2 macrophages mimicked the effects of IL-13 on protection from myocarditis, suggesting that the effects of IL-13 may be primarily through regulation of macrophage polarization. Together, our data suggest that application of IL-13 treatment may reduce cardiac Injury and protect heart function in viral myocarditis via enhanced M2 macrophage polarization.

Absence of kynurenine 3-monooxygenase reduces mortality of acute viral myocarditis in mice

Infection of the encephalomyocarditis virus (EMCV) in mice is an established model for viral myocarditis. Previously, we have demonstrated that indoleamine 2,3-dioxygenase (IDO), an L-tryptophan - kynurenine pathway (KP) enzyme, affects acute viral myocarditis. However, the roles of KP metabolites in EMCV infection remain unclear. Kynurenine 3-monooxygenase (KMO) is one of the key regulatory enzymes, which metabolizes kynurenine to 3-hydroxykynurenine in the KP. Therefore, we examined the role of KMO in acute viral infection by comparing between KMO^-/- mice and KMO^+/+ mice. KMO deficiency resulted in suppressed mortality after EMCV infection. The number of infiltrating cells and F4/80⁺ cells in KMO^-/- mice was suppressed compared with those in KMO^+/+ mice. KMO^-/- mice showed significantly increased levels of serum KP metabolites, and induction of KMO expression upon EMCV infection was involved in its effect on mortality through EMCV suppression. Furthermore, KMO^-/- mice showed significantly suppression of CCL2, CCL3 and CCL4 on day 2 and CXCL1 on day 4 after infection. These results suggest that increased KP metabolites reduced chemokine production, resulting in suppressed mortality upon KMO knockdown in EMCV infection. KP metabolites may thus provide an effective strategy for treating acute viral myocarditis.

Endotoxin-activated cultured neonatal rat cardiomyocytes express functional surface-associated interleukin-1α

Interleukin-1 (IL-1) is a potent regulator of cardiovascular proliferation, apoptosis, contraction or production of inflammatory mediators. Thus, we investigated expression and function of IL-1 in cultured neonatal rat heart cells upon endotoxin stimulation. We show that cultured neonatal rat cardiomyocytes expressed IL—1α and IL—1β mRNA. The cells expressed functional cell-associated IL—1 activity and a specific anti-IL—1α-antibody inhibited the activity. Biologically active IL—1α was present at the cell surface of the cardiomyocytes, as indicated in co-culture experiments. Immunohistochemistry showed IL—1α-staining of the neonatal cardiomyocytes. Although the cells also expressed IL—1β mRNA, we did not detect IL—1β in the supernatants of cultured cardiomyocytes by ELISA or in immunohistochemical staining. Furthermore, neonatal and adult rat heart tissues expressed IL—1α mRNA, whereas fetal, but not adult, human cardiac tissues expressed detectable IL—1α mRNA. In contrast, IL-1β mRNA was present in rat and human fetal and adult samples. Furthermore, in patients with dilated or ischemic cardiomyopathy, we measured IL—1β, but not IL—1α, mRNA. These results provide evidence for the presence of functionally active IL—1α on the cell surface of neonatal rat cardiomyocytes and may suggest a differential role of IL—1α in regulation of cellular functions during development, aging and disease in rat and human heart cells.

Remodeling and dedifferentiation of adult cardiomyocytes during disease and regeneration

Cardiomyocytes continuously generate the contractile force to circulate blood through the body. Imbalances in contractile performance or energy supply cause adaptive responses of the heart resulting in adverse rearrangement of regular structures, which in turn might lead to heart failure. At the cellular level, cardiomyocyte remodeling includes (1) restructuring of the contractile apparatus; (2) rearrangement of the cytoskeleton; and (3) changes in energy metabolism. Dedifferentiation represents a key feature of cardiomyocyte remodeling. It is characterized by reciprocal changes in the expression pattern of "mature" and "immature" cardiomyocyte-specific genes. Dedifferentiation may enable cardiomyocytes to cope with hypoxic stress by disassembly of the energy demanding contractile machinery and by reduction of the cellular energy demand. Dedifferentiation during myocardial repair might provide cardiomyocytes with additional plasticity, enabling survival under hypoxic conditions and increasing the propensity to enter the cell cycle. Although dedifferentiation of cardiomyocytes has been described during tissue regeneration in zebrafish and newts, little is known about corresponding mechanisms and regulatory circuits in mammals. The recent finding that the cytokine oncostatin M (OSM) is pivotal for cardiomyocyte dedifferentiation and exerts strong protective effects during myocardial infarction highlights the role of cytokines as potent stimulators of cardiac remodeling. Here, we summarize the current knowledge about transient dedifferentiation of cardiomyocytes in the context of myocardial remodeling, and propose a model for the role of OSM in this process.

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.

Control of inflammatory heart disease by CD4+ T cells

This review focuses on autoimmune myocarditis and its sequela, inflammatory dilated cardiomyopathy (DCMI), and the inflammatory and immune mechanisms underlying the pathogenesis of these diseases. Several mouse models of myocarditis and DCMI have improved our knowledge of the pathogenesis of these diseases, informing more general problems of cardiac remodeling and heart failure. CD4(+) T cells are critical in driving the pathogenesis of myocarditis. We discuss in detail the role of T helper cell subtypes in the pathogenesis of myocarditis, the biology of T cell-derived effector cytokines, and the participation of other leukocytic effectors in mediating disease pathophysiology. We discuss interactions between these subsets in both suppressive and collaborative fashions. These findings indicate that cardiac inflammatory disease, and autoimmunity in general, may be more diverse in divergent effector mechanisms than has previously been appreciated.

Immunomodulatory effects of mesenchymal stromal cells revisited in the context of inflammatory cardiomyopathy

Myocarditis is a common inflammatory cardiomyopathy, associated with cardiomyocyte apoptosis, which can lead to chronic left ventricular dysfunction. Under conventional heart failure therapy, inflammatory cardiomyopathy typically has a progressive course, indicating a need for alternative therapeutic strategies to improve long-term outcomes. Experimental and clinical studies consistently support the application of cellular transplantation as a strategy to improve myocardial function. Mesenchymal stromal cells (MSCs) mediate distinct paracrine effects supporting endogenous regeneration, but most important are their remarkable immunoregulatory properties. In this review, an overview of current knowledge on immunopathology in myocarditis will be given. Furthermore, current research regarding the immunomodulatory properties of MSCs in the context of myocarditis will be discussed. Finally, the impact of MSC priming by the environment on their functionality and the advantages of systemic administration of MSCs under myocarditis are outlined.

Interferon-γ causes cardiac myocyte atrophy via selective degradation of myosin heavy chain in a model of chronic myocarditis

Interferon-γ (IFN-γ), a proinflammatory cytokine, has been implicated in the pathogenesis of a number of forms of heart disease including myocarditis and congestive heart failure. In fact, overexpression of IFN-γ in mice causes dilated cardiomyopathy. However, the direct effects of IFN-γ on cardiac myocytes and the mechanism by which it causes cardiac dysfunction have not been described. Here, we present the molecular pathology of IFN-γ exposure and its effect on myofibrillar proteins in isolated neonatal rat ventricular myocytes. Treatment with IFN-γ caused cardiac myocyte atrophy attributable to a specific decrease in myosin heavy chain protein. This selective degradation of myosin heavy chain was not accompanied by a decrease in total protein synthesis or by an increase in total protein degradation. IFN-γ increased both proteasome and immunoproteasome activity in cardiac myocytes and their inhibition blocked myosin heavy chain loss and myocyte atrophy, whereas inhibition of the lysosome or autophagosome did not. Collectively, these results provide a mechanism by which IFN-γ causes cardiac pathology in the setting of chronic inflammatory diseases.

Viral kinetics are associated with changes in cytokines and chemokines in serum and target organs of SSM-CVB3-infected macaques

OBJECTIVE

To determine the relationship between viral kinetics and the expression patterns for different cytokines and chemokines in the serum and organs of coxsackievirus B3 (SSM-CVB3)-infected macaques over the course of infection.

METHODS

SSM-CVB3 levels in serum and organs were measured using the Spearman-Karber 50% tissue culture infectious dose (TCID(50)) method. Cytokine and chemokine levels in the serum and organs were measured by indirect-ELISA.

RESULTS

Low viral titers were detected in the serum samples on the first day post-inoculation (p.i.) and peaked at 6 to 10 days p.i. in the serum samples from five macaques. Serum levels of IL-1β, IL-2, IL-6, IL-12p40, IL-17α, IFN-γ, TNF-α, MCP-1 and MIP-1β were detected each day and, similar to the viral titers, peaked at 6 to 10 days. IL-10 was only detected on days 10 to 14 p.i. Additionally, higher viral titers and relative viral mRNA levels were associated with higher cytokine and chemokine levels in selected tissues from infected macaques including heart, liver, spleen, lung, kidney and brain.

CONCLUSION

The results indicate that patterns of cytokine and chemokine response are associated with viral kinetics in the serum and target organs of SSM-CVB3-infected macaques, suggesting that the changes in cytokines and chemokines could help further our understanding of the progress of CVB3 infections in clinical settings.

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.

The encephalomyocarditis virus

The encephalomyocarditis virus (EMCV) is a small non-enveloped single-strand RNA virus, the causative agent of not only myocarditis and encephalitis, but also neurological diseases, reproductive disorders and diabetes in many mammalian species. EMCV pathogenesis appears to be viral strain- and host-specific, and a better understanding of EMCV virulence factors is increasingly required. Indeed, EMCV is often used as a model for diabetes and viral myocarditis, and is also widely used in immunology as a double-stranded RNA stimulus in the study of Toll-like as well as cytosolic receptors. However, EMCV virulence and properties have often been neglected. Moreover, EMCV is able to infect humans albeit with a low morbidity. Progress on xenografts, such as pig heart transplantation in humans, has raised safety concerns that need to be explored. In this review we will highlight the biology of EMCV and all known and potential virulence factors.

Virus Infection of the Heart – Unmet Therapeutic Needs

For over 50 years, viral infection has been recognized as an important trigger of acute myocarditis, inflammatory dilated cardiomyopathy (DCM) and congestive heart failure. Nevertheless, viral heart disease remains challenging to diagnose and treat. Improved diagnostic methods for myocarditis have led to a better understanding of its pathophysiology. The recognition of virus-mediated damage, inflammation and autoimmune dysregulation in these patients highlights the importance of differentiating between virus-positive and virus-negative inflammatory DCM. These insights have led to the development of novel treatment strategies, including intravenous immunoglobulin and interferon therapy for virus-positive patients. This article will focus on the pathogenesis of viral myocarditis, especially parvovirus B19-induced, its progression to inflammatory DCM and future treatment strategies.

Oncostatin M is a major mediator of cardiomyocyte dedifferentiation and remodeling

Cardiomyocyte remodeling, which includes partial dedifferentiation of cardiomyocytes, is a process that occurs during both acute and chronic disease processes. Here, we demonstrate that oncostatin M (OSM) is a major mediator of cardiomyocyte dedifferentiation and remodeling during acute myocardial infarction (MI) and in chronic dilated cardiomyopathy (DCM). Patients suffering from DCM show a strong and lasting increase of OSM expression and signaling. OSM treatment induces dedifferentiation of cardiomyocytes and upregulation of stem cell markers and improves cardiac function after MI. Conversely, inhibition of OSM signaling suppresses cardiomyocyte remodeling after MI and in a mouse model of DCM, resulting in deterioration of heart function after MI but improvement of cardiac performance in DCM. We postulate that dedifferentiation of cardiomyocytes initially protects stressed hearts but fails to support cardiac structure and function upon continued activation. Manipulation of OSM signaling provides a means to control the differentiation state of cardiomyocytes and cellular plasticity.

Animal models of cardiac disease and stem cell therapy

Animal models that mimic cardiovascular diseases are indispensable tools for understanding the mechanisms underlying the diseases at the cellular and molecular level. This review focuses on various methods in preclinical research to create small animal models of cardiac diseases, such as myocardial infarction, dilated cardiomyopathy, heart failure, myocarditis and cardiac hypertrophy, and the related stem cell treatment for these diseases.

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.

Effects of angiotensin-II receptor blockers on experimental autoimmune myocarditis

BACKGROUND

The effects of angiotensin-II type 1 receptor blockers (ARBs) on the treatment of hypertension, heart failure, and other cardiovascular diseases have been confirmed extensively. However, recent studies have emphasized the nonhemodynamic effects of these drugs. The purpose of this study was to investigate the effects of ARBs on the development of experimental autoimmune myocarditis (EAM), and to clarify the mechanisms involved.

METHODS

EAM model was induced in Lewis rats by injection of porcine cardiac myosin subcutaneously. We administered valsartan (a new ARB) to rats with EAM and measured blood pressure regularly. Echocardiography was performed to examine the cardiac function and heart structure of the rats. The severity of myocarditis was detected by histopathological evaluation. We evaluated antigen-specific T-cell proliferation responses to cardiac myosin by the lymphocyte proliferation assay and measured serum levels of Th1 and Th2 cytokines by enzyme-linked immunosorbent assay.

RESULTS

There was no significant difference in the blood pressure (BP) level between the groups and cardiac function of valsartan-treated rats was significantly improved compared with untreated rats. Valsartan markedly reduced the severity of myocardial lesions and suppressed lymphocyte proliferation in rats immunized with myosin. After drug administration, Th1 cytokines (IFN-gamma and IL-2) were significantly down-regulated, while Th2 cytokines (IL-4 and IL-10) were detected to undergo up-regulation.

CONCLUSIONS

The results suggest that valsartan can ameliorate EAM independent of BP-lowering effects. Some of the beneficial effects of ARBs may be due to their immunomodulatory reactions in the modification of helper T-cell balance.

TGF-beta and fibrosis in different organs - molecular pathway imprints

The action of transforming-growth-factor (TGF)-beta following inflammatory responses is characterized by increased production of extracellular matrix (ECM) components, as well as mesenchymal cell proliferation, migration, and accumulation. Thus, TGF-beta is important for the induction of fibrosis often associated with chronic phases of inflammatory diseases. This common feature of TGF-related pathologies is observed in many different organs. Therefore, in addition to the description of the common TGF-beta-pathway, this review focuses on TGF-beta-related pathogenetic effects in different pathologies/organs, i. e., arthritis, diabetic nephropathy, colitis/Crohn's disease, radiation-induced fibrosis, and myocarditis (including their similarities and dissimilarities). However, TGF-beta exhibits both exacerbating and ameliorating features, depending on the phase of disease and the site of action. Due to its central role in severe fibrotic diseases, TGF-beta nevertheless remains an attractive therapeutic target, if targeted locally and during the fibrotic phase of disease.

Nifedipine inhibits the activation of inflammatory and immune reactions in viral myocarditis

AIMS

The aim of study is to investigate the effect of nifedipine on viral myocarditis in an animal model.

MAIN METHODS

Four-week-old male DBA/2 mice were inoculated with 2 pfu of encephalomyocarditis virus (EMCV) and randomized to nifedipine (n=10) or control (n=10) group. The control group was fed by regular chow and the nifedipine group contained 0.01% of nifedipine. Mast cell density was counted, and expressions of messenger RNAs of stem cell factor (SCF), matrix metalloproteinases (MMPs), pro-collagen I, mast cell proteases, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were evaluated by RT-PCR.

KEY FINDINGS

The area of myocardial necrosis was smaller in the nifedipine vs the control group (mean+/-SD, 1.2+/-1.3% vs 3.8+/-1.8%, respectively, P<0.005). The mast cell density (count/mm(2)) was lower in the nifedipine vs the control group (mean+/-SD, 0.23+/-0.16 vs 1.08+/-0.45, respectively, P<0.0005). The expressions of MMPs, mast cell proteases, TNF-alpha, IL-6, SCF and pro-collagen I were lower in the nifedipine group than in the control group (P<0.05).

SIGNIFICANCE

Nifedipine inhibited the activation of various participants in inflammatory and immune reactions in EMCV myocarditis.

The role of IL-1 in the pathogenesis of heart disease

Interleukin (IL)-1 consists of two distinct ligands, IL-1alpha and IL-1beta, with indistinguishable biological activities that signal through the IL-1 type I receptor (IL-1RI). A naturally occurring IL-1 receptor antagonist (IL-1Ra) binds to IL-1RI without initiating signal transduction and prevents IL-1 signaling, competitively inhibiting IL-1-mediated responses. Emerging evidence suggests that the balance between IL-1 agonists and antagonists plays an essential role in a variety of cardiovascular conditions. IL-1 may play a role in atherothrombotic disease by promoting the formation of atheromatous lesions, enhancing vascular inflammation, and triggering plaque destabilization. Following myocardial infarction, IL-1 critically regulates the inflammatory response and is involved in the development of adverse remodeling by enhancing expression of matrix metalloproteinases. IL-1 signaling may also be an essential mediator in the pathogenesis of heart failure by suppressing cardiac contractility, promoting myocardial hypertrophy, and inducing cardiomyocyte apoptosis. The present review summarizes current available data showing the significant role of IL-1 signaling in heart disease and raising the possibility that IL-1 inhibitors (such as anakinra, a nonglycosylated recombinant human IL-1Ra) may be clinically useful agents in patients with certain cardiovascular conditions.

Cardiac cell-specific apoptotic and cytokine responses to reovirus infection: determinants of myocarditic phenotype

BACKGROUND

The pathophysiologic mechanisms underlying viral myocarditis are not well defined. As a result, effective treatments do not exist and viral myocarditis remains a potentially lethal infection of the heart.

METHODS AND RESULTS

We used cultured rat cardiac myocytes and fibroblasts to investigate apoptosis and cytokine production in response to infection by myocarditic vs. non-myocarditic strains of reovirus. Myocarditic reovirus strain 8B and non-myocarditic strain DB188 replicate comparably in each cardiac cell type. However, strain 8B and related myocarditic reoviruses preferentially increase apoptosis of myocytes relative to fibroblasts, whereas DB188 and nonmyocarditic strains preferentially increase fibroblast apoptosis. Infection of cardiac fibroblasts with the nonmyocarditic strain DB188 elicits substantial increases in a panel of cytokines compared to fibroblasts infected with strain 8B or mock-infected controls. Analysis of culture supernatants using cytometric bead arrays revealed that DB188 enhanced release of interleukin (IL)-1beta, IL-4, IL-6, IL-10, IL-12(p70), GRO-KC, tumor necrosis factor-alpha, and MCP-1 relative to 8B or mock-infected controls (all P < .05).

CONCLUSION

We hypothesize that differential cytokine production and cell-specific apoptosis are important determinants of myocarditic potential of reoviral strains. Therapies that target the beneficial effects of cytokines in limiting cytopathic damage may offer an effective and novel treatment approach to viral myocarditis.

Acute viral myocarditis

Acute myocarditis is one of the most challenging diagnosis in cardiology. At present, no diagnostic gold standard is generally accepted, due to the insensitivity of traditional diagnostic tests. This leads to the need for new diagnostic approaches, which resulted in the emergence of new molecular tests and a more detailed immunohistochemical analysis of endomyocardial biopsies. Recent findings using these new diagnostic tests resulted in increased interest in inflammatory cardiomyopathies and a better understanding of its pathophysiology, the recognition in overlap of virus-mediated damage, inflammation, and autoimmune dysregulation. Novel results also pointed towards a broader spectrum of viral genomes responsible for acute myocarditis, indicating a shift of enterovirus and adenovirus to parvovirus B19 and human herpes virus 6. The present review proposes a general diagnostic approach, focuses on the viral aetiology and associated autoimmune processes, and reviews treatment options for patients with acute viral myocarditis.

Altered interleukin-1 receptor antagonist and interleukin-18 mRNA expression in myocardial tissues of patients with dilatated cardiomyopathy

Interleukin-1 (IL-1) is a potent regulator of cell proliferation, inflammation, and contraction of cardiovascular cells. It has been proposed that the IL-1/IL-1ra (IL-1 receptor antagonist) ratio influences these functions. Other members of the IL-1 family and the related caspase-1 also contribute to regulation of IL-1-mediated functions. We determined the mRNA expression of caspase-1, caspase-3, IL-1alpha , IL-1beta , IL-18, IL-1 receptor type I (IL-1-RI), and IL-1ra in left ventricle tissue of hearts from patients with ischemic or dilated cardiomyopathy (ICM or DCM) and in control tissues from unused donor transplant hearts in RT-PCR experiments. We show that the expression of caspase-1, caspase-3, IL-1beta , and IL-1-RI mRNA was not different between patients and control tissues. Furthermore, we did not find detectable amounts of IL-1alpha mRNA in any of these adult myocardial tissues. On the other hand, expression of IL-18 RNA was lower in myocardium of both patient groups compared with control hearts. Furthermore, IL-1ra mRNA expression was significantly lower in tissues of DCM patients compared with ICM patients and controls. This was in line with a trend towards lower IL-1ra protein levels in myocardial tissues of DCM patients. In contrast with the adult tissues discussed above, which did not express IL-1alpha mRNA, commercially available human fetal tissue expressed IL-1alpha mRNA. On the other hand IL-1beta mRNA was present in fetal and in adult human heart tissue. Our data provide evidence for an altered ratio of IL-1/IL-1ra in DCM patients. This dysregulation may contribute to pathogenesis and/or progression of heart disease by modulating the otherwise balanced IL-1-mediated functions in cardiovascular cells.

Interferon-gamma induces chronic active myocarditis and cardiomyopathy in transgenic mice

Chronic heart failure is associated with an activation of the immune system characterized among other factors by the cardiac synthesis and serum expression of proinflammatory cytokines. There is unequivocal clinical and experimental evidence that the cytokine tumor necrosis factor-alpha is involved in the development of chronic heart failure, but a putative cardiotoxic potential of the proinflammatory cytokine interferon (IFN)-gamma remains primarily unknown. To investigate this issue we analyzed the cardiac phenotype of SAP-IFN-gamma transgenic mice, which constitutively express IFN-gamma in their livers and hence exhibit high circulating serum levels of this cytokine. SAP-IFN-gamma mice spontaneously developed chronic active myocarditis, characterized by the infiltration of not only CD4(+) and CD8(+) T cells but also Mac2(+) (galectin 3(+)) macrophages and CD11c(+) dendritic cells, eventually culminating in cardiomyopathy. Echocardiographic analyses exhibited a left ventricular dilation and impaired systolic function induced by IFN-gamma overexpression. IFN-gamma-mediated cardiotoxicity was associated with high-level cardiac transcription of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-12 and the macrophage-attracting chemokines MCP1 and MIP1-alpha. Myotoxic IFN-gamma effects could not be detected in smooth or striated muscle tissue, suggesting cardiomyocellular specificity of the toxic IFN-gamma effect. The precise mechanism of IFN-gamma cardiotoxicity remains to be elucidated.

Leptin induces elongation of cardiac myocytes and causes eccentric left ventricular dilatation with compensation

One of the major manifestations of obesity is an increased production of the adipocyte-derived 16-kDa peptide leptin, which acts mainly on hypothalamic leptin receptors. Leptin receptors are widely distributed in various tissues, including the heart. Whereas increased plasma leptin levels have been reported in patients with congestive heart failure, systemic alterations induced by obesity can affect cardiac hypertrophy, and the direct effects of leptin on cardiac structure and function still remain to be determined. We first exposed primary cardiac myocytes from neonatal rats to leptin for 48 h. This resulted in a significant increase in myocyte long-axis length ( P < 0.05 at 50 ng/ml) but not in the short-axis width. Leptin induced the rapid phosphorylation of STAT3 and its DNA binding in cardiac myocytes. Administration of a JAK2 inhibitor, AG-490, completely inhibited all of these effects by leptin. Furthermore, we examined the effect of continuous infusion of leptin for 4 wk following myocardial infarction in mice. Echocardiography demonstrated that left ventricular fractional shortening in the leptin-infused group (28.4 ± 2.8%) was significantly higher than that in the PBS-infused group (18.4 ± 2.2%) following myocardial infarction. Interestingly, left ventricular diastolic dimension in the leptin-infused group (4.56 ± 0.12 mm) was also higher than that in the PBS-infused group (4.13 ± 0.09 mm). These results demonstrate that leptin induces the elongation of cardiac myocytes via a JAK/STAT pathway and chronic leptin infusion causes eccentric dilatation with augmented systolic function after myocardial infarction.

Anti-viral treatment in patients with virus-induced cardiomyopathy

Ongoing viral persistence in the myocardium is associated with an adverse prognosis of cardiomyopathy eventually resulting in a reduced capacity for work and thus it is associated with enormous social costs. Experimental and clinical data highlight that an imbalance of the cytokine network and a defect in the cytokine-induced immune response may constitute major causes leading to the development of virus persistence and progression of myocardial dysfunction. Reversibility of cardiac impairment during the early stages of the disease and the arising chance of specific treatment options demand early diagnosis and treatment of the disease. Our pilot data on anti-viral treatment using INF-beta showed beneficial clinical effects and suggest that some of the ventricular dysfunction and wall motion abnormalities resolved after elimination of the responsible agents. The data also suggest that elimination of cardiotropic viruses and associated clinical effects may occur even in DCM patients presenting with a long history.

Immunomodulation by interleukin-4 suppresses matrix metalloproteinases and improves cardiac function in murine myocarditis

Immune response is critically involved in determining the course of viral myocarditis and immunomodulation. Different cytokines may have either deleterious or protective effects. Following acute Coxsackievirus B3 infection, intramyocardial inflammation is associated with altered myocardial matrix metalloproteinase (MMP) expression and left ventricular dysfunction. In this study, we evaluated the effect of exogenous interleukin-4 treatment on myocardial inflammation, MMPs and left ventricular function in Coxsackievirus B3-induced acute murine myocarditis. Eight-week-old inbred male BALB/c (H-2d) mice (The Jackson Laboratory, Bar Harbor, Maine, USA) were used. Myocardial inflammation was measured by immunohistochemical detection of CD3(+)-, CD8a(+)-T-lymphocytes, and CD11b+ macrophages. In situ hybridization was used to detect enteroviral genome in the myocardium. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was employed to detect cytokine and MMP mRNA. MMP activity was quantified by zymography analysis. Detection of myocytolysis was performed by Luxol fast blue staining. In the early acute phase, in comparison to infected mice without treatment, interleukin-4 administration (200 ng daily) reduced intramyocardial inflammation (CD3+ lymphocytes: 55.3+/-7.0 vs. 72.1+/-13.7 cells/mm2, P < 0.05; CD8a+ lymphocytes: 31.7+/-3.6 vs. 64.2+/-7.7 cells/mm2, P < 0.05; CD11b+ macrophages: 5.1+/-2.3 vs. 13.2+/-2.5 cells/mm2, P < 0.05). It also down-regulated interleukin-2 (IL) (1.7-fold, P < 0.001) but increased transforming growth factor-beta1 (TGF) (1.5-fold, P < 0.001) and IL-4 (1.4-fold, P < 0.001). IL-4 suppressed MMP-2/-3/-9 transcription and activity. These biochemical alterations were accompanied by a significant improvement of left ventricular function as assessed by Milar tip catheter (left ventricular endsystolic pressure, 1.3-fold, P < 0.01; dP/dt max, 1.5-fold, P < 0.01). Immunomodulation by exogenous IL-4 treatment may lead to an anti-inflammatory effect with the inhibition of Th1 cell phenotypic response, which may further mediate the down-regulation of MMPs. A significant suppression of MMPs may mainly contribute to an improvement of left ventricular dysfunction in acute murine CVB3-induced myocarditis.

Histopathological Examination and Analysis of Mortality in DBA/2 Mouse Vasculitis Induced with CAWS, a Water-soluble Extracellular Polysaccharide Fraction Obtained from Candida albicans

CAWS, a water-soluble extracellular polysaccharide fraction obtained from the culture supernatant of Candida albicans, is one of the fungal pathogen-associated molecular patterns (PAMPs). It has been reported to show potent activity inducing arteritis and coronaritis in mice. Especially, CAWS-induced arteritis has a 100% incidence and severe mortality in the DBA/2 mouse strain. This artificial vasculitis was reported to provide a good murine model of Kawasaki disease and other inflammatory vascular disease. However, severe mortality was observed only in DBA/2 mice, which is a CAWS-sensitive strain. In this study, to clarify the mechanisms of CAWS-induced arteritis and mortality, we investigated microscopic histopathological changes in cardiovascular tissues in DBA/2 mice. Severe inflammatory infiltration was observed from the external elastic lamina in the aorta and proximal coronary arteries within 1 week after CAWS administration. Severe stenosis of the aorta and coronary arteries was observed more than 3 weeks after CAWS administration. Fibrinoid necrosis was observed in these vessel walls. All CAWS-treated mice died between the fifth and twelfth week after administration. Severe inflammatory change with aortic valve transformation suggested that CAWS-treated mice died of valvular endocarditis or cardiac dysfunction. Based on the simple induction method and complete incidence, these data suggest that CAWS-induced arteritis is a good model of not only Kawasaki disease but also other cardiovascular diseases such as valvular endocarditis.

TNFR-Fc fusion protein expressed by in vivo electroporation improves survival rates and myocardial injury in coxsackievirus induced murine myocarditis

Tumor necrosis factor-alpha (TNF-alpha) is one of the major cytokines that modulate the immune response in viral myocarditis, but its role has not yet been thoroughly evaluated. We antagonized TNF-alpha using the expressed soluble p75 TNF receptor linked to the Fc portion of the human IgG1 gene (sTNFR:Fc) by in vivo electroporation, and evaluated its effects on experimental coxsackieviral B3 (CVB3) myocarditis. A plasmid DNA encoding sTNFR:Fc (15microg/mouse) was injected into the gastrocnemius muscles of Balb/C male mice followed by electroporation (day -1). Control mice were injected with an empty vector. One day after electroporation, mice were infected with CVB3 (day 0). Serum levels of sTNFR:Fc increased from day 2 and peaked at day 5 following electroporation. The heart virus titers of sTNFR:Fc mice were higher than those of controls at day 3. However, subsequent to day 12, the survival rates of the sTNFR:Fc mice were significantly higher than those of the controls (36% versus 0% at day 27, P<0.01). Histopathological examination indicated that inflammation and myocardial fibrosis were significantly decreased in sTNFR:Fc mice at day 12. The expressed sTNFR:Fc could modulate the inflammatory process during the post-viremic phase of viral myocarditis.