Inflammation In Myocarditis Research Articles

Inflammation of conduction tissue is a major determinant of electrical instability in patients with arrhythmic phenotype of myocarditis

Abstract Background Arrhythmic presentation of myocarditis can be life-threatening although often associated with a preserved cardiac dimension and function. The involvement of conduction tissue (CT) has been suggested as pro-arrhythmic factor, but its role has not conclusively supported. Purpose CT inflammation in myocarditis with arrhythmic presentation. Methods We retrospectively enrolled consecutive patients from January 2010 to June 2021 with acute myocarditis (< 1 month from the onset of symptoms). Patients were categorized according to clinical presentation in arrhythmic [frequent premature ventricular beats, non-sustained or sustained ventricular tachycardia (VT) and survivors of ventricular fibrillation, associated to preserved cardiac contractility –LVEF ≥ 50%] (Group A) and cardiomyopathy phenotype (signs and symptoms of heart failure with LVEF≤ 45%) (Group B). All patients had a normal coronary network at angiography and an unremarkable valvular pattern at 2D-Echo.They all underwent a LV endomyocardial biopsy; sections of CT (Purkinje fibres) were identified by morphologic (Ashoff and Monkeberg criteria) findings and positive immunohistochemistry for HCN4. CT infiltration was demonstrated by the presence of CD45Ro+ T lymphocytes and the necrosis of adjacent small and loosely arranged myocytes. The extent of myocardial fibrosis, the rate of vasculitis and CT inflammation was compared between the two groups. Results Among 217 consecutive pts with biopsy-proven diagnosis of myocarditis, 107 (49.3%) had an arrhythmic presentation (Group A). CT was observed in 33 (30.8%) patients in the Group A and 31 (28.2%) of Group B. In patients with biopsy-evidence of CT, no significant difference was reported in the mean age (51.2±16.8 vs 53.7±14.7; p-value: 0.53) . Inflamed CT was documented in 2 (6.5%) cases in Group B and in 33 (100%) in Group A (p-value< 0.001). No statistically difference was observed between Group A and B regarding the presence of vasculitis (4 vs 1; p-value: 0.36) and myocardial fibrosis (8.8±4.2% vs 9.5±4.3%; p-value: 0.50). Conclusion CT inflammation is a major determinant of electrical instability in human myocarditis with arrhythmic presentation. Figure Legend Sustained ventricular tachycardia (A) associated to severe infiltration by CD45Ro T lymphocytes of CT in an acute myocarditis with arrhythmic presentation.

Non-invasive contrast enhanced ultrasound molecular imaging of inflammation in autoimmune myocarditis for prediction of left ventricular fibrosis and remodeling.

BackgroundMyocarditis can lead to myocyte loss and myocardial fibrosis resulting in dilated cardiomyopathy (DCMP). Currently employed methods for assessing the risk for development of DCMP are inaccurate or rely on invasive myocardial biopsies. We hypothesized that molecular imaging of tissue inflammation with contrast enhanced ultrasound during peak inflammation in myocarditis could predict development of fibrosis and impaired left ventricular function.Methods and resultsExperimental autoimmune myocarditis (EAM) was induced in Balbc mice by injection of the α-myosin heavy chain peptide. Contrast enhanced ultrasound (CEU) using microbubbles targeted to leukocytes (MBLc), to CD4+ lymphocytes (MBCD4), and to the endothelial cell adhesion molecule P-selectin (MBPSel) was performed during the expected EAM peak inflammatory activity 21 days after induction. High resolution ultrasound, invasive hemodynamic measurements and fibrosis quantification were done 63 days after EAM assessment. All tested microbubbles correlated to fibrosis (MBLc spearman r 0.28, p 0.047, MBCD4 r 0.44, p 0.01, MBPSel r 0.73, p 0.02), however, correlations were weak overall and the spread of data was considerable. Also, targeted CEU data on day 21 did not correlate to hemodynamic and functional data on day 63.ConclusionsUltrasound molecular imaging using targeted microbubbles during the peak inflammatory activity of myocarditis correlates weakly with later development of fibrosis but not with hemodynamic or left ventricular functional parameters.

4323Detection of early inflammation in myocarditis by molecular magnetic resonance imaging of activated platelets

Abstract Introduction A noninvasive imaging strategy for diagnosis and localization of early myocarditis would be of great clinical interest. However, resolution of current imaging techniques is limited. Platelets play an important role in inflammatory processes but the role in myocarditis is unknown. Therefore, the aim of this project was to examine the role of platelets in myocarditis and establish a sensitive non-invasive molecular MRI in-vivo imaging strategy for diagnosis of myocarditis with a contrast agent against activated platelets in mice. Methods Myocarditis was induced by subcutaneous injection of an emulsion of porcine cardiac myosin and complete freud's adjuvant (CFA) in Balb/c mice. Inflammatory activity was targeted with a contrast agent against activated platelets consisting of microparticles of iron oxide (MPIO) conjugated to a single chain antibody directed against ligand-induced binding sites (LIBS) on activated glycoprotein IIb/IIIa (=LIBS-MPIO). In comparison, we applied an unspecific control antibody linked to microparticles of iron oxide (control-MPIO) and injected LIBS-MPIO to mice subjected to incomplete freud's adjuvant (iCFA). All imaging results were correlated to immunohistochemistry findings. Results Histological evaluation showed significantly higher binding of LIBS-MPIOs to platelet enriched, CD41-positive inflamed myocardium two days after induction of myocarditis in comparison to later time points (7d, 14d, 21d) (p<0.05) and control-MPIO (p<0.05) injection. In iCFA injected mice no significant LIBS-MPIO binding was found (p<0.05). In 3D in-vivo MRI we could specifically detect focal signal effects in LIBS-MPIO injected mice 2 days after induction of myocarditis, whereas in control-MPIO injected mice no signal effect was visible. Quantification of the myocardial MRI signal confirmed a signal decrease after LIBS-MPIO injection and significant fewer signals in comparison to control-MPIO injection (p<0.05). As a perspective, we also found CD41 positive areas in histology of human myocarditis specimens. Conclusions Platelets are involved in the inflammation of myocarditis. Molecular MRI with LIBS-MPIO can image them at an early time point. This noninvasive imaging strategy is of clinical interest for both diagnostic and prognostic purposes, and highlights the potential of molecular MRI for characterization of cardiovascular pathologies such as myocardial inflammation.

Self-reactive CD4+ IL-3+ T cells amplify autoimmune inflammation in myocarditis by inciting monocyte chemotaxis

Acquisition of self-reactive effector CD4+ T cells is a major component of the autoimmune response that can occur during myocarditis, an inflammatory form of cardiomyopathy. Although the processes by which self-reactive T cells gain effector function have received considerable attention, how these T cells contribute to effector organ inflammation and damage is less clear. Here, we identified an IL-3-dependent amplification loop that exacerbates autoimmune inflammation. In experimental myocarditis, we show that effector organ-accumulating autoreactive IL-3+ CD4+ T cells stimulate IL-3R+ tissue macrophages to produce monocyte-attracting chemokines. The newly recruited monocytes differentiate into antigen-presenting cells that stimulate local IL-3+ CD4+ T cell proliferation, thereby amplifying organ inflammation. Consequently, Il3 -/- mice resist developing robust autoimmune inflammation and myocardial dysfunction, whereas therapeutic IL-3 targeting ameliorates disease. This study defines a mechanism that orchestrates inflammation in myocarditis, describes a previously unknown function for IL-3, and identifies IL-3 as a potential therapeutic target in patients with myocarditis.

Role of Toll-like receptors and interferon regulatory factors in different experimental heart failure models of diverse etiology: IRF7 as novel cardiovascular stress-inducible factor

Heart failure (HF) is a leading cause of morbidity and mortality in the western world. Although optimal medical care and treatment is widely available, the prognosis of patients with HF is still poor.Toll-like receptors (TLRs) are important compartments of the innate immunity. Current studies have identified TLRs as critical mediators in cardiovascular diseases. In the present study, we investigated the involvement of TLRs and interferon (IFN) regulatory factors (IRFs) in different experimental HF models including viral myocarditis, myocardial ischemia, diabetes mellitus, and cardiac hypertrophy. In addition, we investigated for the first time comprehensive TLR and IRF gene and protein expression under basal conditions in murine and human cardiac tissue. We found that Tlr4, Tlr9 and Irf7 displayed highest gene expression under basal conditions, indicating their significant role in first-line defense in the murine and human heart. Moreover, induction of TLRs and IRFs clearly differs between the various experimental HF models of diverse etiology and the concomitant inflammatory status. In the HF model of acute viral-induced myocarditis, TLR and IRF activation displayed the uppermost gene expression in comparison to the remaining experimental HF models, indicating the highest amount of myocardial inflammation in myocarditis. In detail, Irf7 displayed by far the highest gene expression during acute viral infection. Interestingly, post myocardial infarction TLR and IRF gene expression was almost exclusively increased in the infarct zone after myocardial ischemia (Tlr2, Tlr3, Tlr6, Tlr7, Tlr9, Irf3, Irf7). With one exception, Irf3 showed a decreased gene expression in the remote zone post infarction. Finally, we identified Irf7 as novel cardiovascular stress-inducible factor in the pathologically stressed heart. These findings on TLR and IRF function in the inflamed heart highlight the complexity of inflammatory immune response and raise more interesting questions for future investigation.

Mesenchymal stromal cells inhibit NLRP3 inflammasome activation in a model of Coxsackievirus B3-induced inflammatory cardiomyopathy

Inflammation in myocarditis induces cardiac injury and triggers disease progression to heart failure. NLRP3 inflammasome activation is a newly identified amplifying step in the pathogenesis of myocarditis. We previously have demonstrated that mesenchymal stromal cells (MSC) are cardioprotective in Coxsackievirus B3 (CVB3)-induced myocarditis. In this study, MSC markedly inhibited left ventricular (LV) NOD2, NLRP3, ASC, caspase-1, IL-1β, and IL-18 mRNA expression in CVB3-infected mice. ASC protein expression, essential for NLRP3 inflammasome assembly, increased upon CVB3 infection and was abrogated in MSC-treated mice. Concomitantly, CVB3 infection in vitro induced NOD2 expression, NLRP3 inflammasome activation and IL-1β secretion in HL-1 cells, which was abolished after MSC supplementation. The inhibitory effect of MSC on NLRP3 inflammasome activity in HL-1 cells was partly mediated via secretion of the anti-oxidative protein stanniocalcin-1. Furthermore, MSC application in CVB3-infected mice reduced the percentage of NOD2-, ASC-, p10- and/or IL-1β-positive splenic macrophages, natural killer cells, and dendritic cells. The suppressive effect of MSC on inflammasome activation was associated with normalized expression of prominent regulators of myocardial contractility and fibrosis to levels comparable to control mice. In conclusion, MSC treatment in myocarditis could be a promising strategy limiting the adverse consequences of cardiac and systemic NLRP3 inflammasome activation.

Acute focal Myocarditis with Preserved Ventricular Function Masquerading as Acute ST-elevation Inferior Wall Myocardial Infarction

Myocarditis is a pathological inflammatory condition which can result in significant damage to the myocardium and more specifically the myocytes. Acute myocarditis can present similarly to myocardial infarction, and can rise to the top of the differential diagnosis when chest pain, cardiac enzymes, and ECG that suggest myocardial infarction are followed by a normal coronary angiogram. The gold standard of diagnosis for myocarditis is an endomyocardial biopsy as a positive biopsy is very specific; however, the inflammation of myocarditis may be diffuse or focal, limiting the biopsy’s sensitivity. We present a case of a 19 year old man with acute focal myocarditis masquerading as an acute ST-elevation inferior wall myocardial infarction on ECG with elevated troponin I. This is an unusual presentation as the patient’s echocardiogram and cardiac catheterization did not show ventricular dysfunction. Our diagnosis was confirmed by cardiac MRI rather than endomyocardial biopsy, due to the high risk of adverse events associated with the latter. Acute myocarditis that mimicks a myocardial infarction in presentation is a rare, but well known occurrence [1]. Acute myocarditis typically presents with a less distinct prodromal illness period, in contrast with fulminant myocarditis, which has a more defined viral prodrome and associated with more severe cardiovascular compromise. Acute myocarditis is also more likely to present in those patients with established ventricular dysfunction, with the potential to progress to dilated cardiomyopathy [2].

Endothelin receptor antagonist exacerbates autoimmune myocarditis in mice

AimsMyocarditis and subsequent dilated cardiomyopathy are major causes of heart failure in young adults. Experimental autoimmune myocarditis (EAM) is a mouse model of post-infectious myocarditis and inflammatory cardiomyopathy. The pathological role of endothelin (ET) in myocarditis has not been elucidated. Main methodsEAM was induced by immunization of cardiac myosin peptide with complete Freund's adjuvant on days 0 and 7 in BALB/c mice. An ETA/ETB dual receptor antagonist, SB209670, was administered by a continuous infusion from a subcutaneous pump for 2weeks. Key findingsAn increase in the heart-to-body weight ratio was observed in SB209670-treated mice compared with vehicle-treated mice. Heart pathology in SB209670-treated mice was remarkable for gross inflammatory infiltration, in contrast to the lesser inflammation in the hearts of vehicle-treated mice. We found that an ET blockade decreased the number of Foxp3+ regulatory T cells in the heart. The ET blockade also inhibited the expression of the suppressor of cytokine signaling 3 that plays a key role in the negative regulation of both Toll-like receptor- and cytokine receptor-mediated signaling. EAM is a CD4+ T cell-mediated disease. CD4+ T cells isolated from SB209670-treated EAM mice produced less IL-10 and more inflammatory cytokines, IL-6 and IL-17, than those isolated from vehicle-treated mice. SignificanceThe ET receptor antagonist exacerbated autoimmune myocarditis in mice. Our novel findings suggest that ET may play an important role in the regulation of inflammation in myocarditis.

Imaging of the binding of ET-1 and of linear ET-1 in rat mesenteric resistance arteries

Background: Experimental autoimmune myocarditis (EAM) is a mouse model of inflammatory cardiomyopathy. The amount of endothelin (ET) increases according to the disease progression; however, the pathological role of ET in myocarditis has not been elucidated. Methods and results: EAM was induced by immunization of cardiac myosin peptide with complete Freund's adjuvant on days 0 and 7 in BALB/c mice. ET-A/-B dual receptor antagonist SB209670 was administered by continuous infusion from a subcutaneous pump for 3 weeks. An increase in heart-to-body weight ratio was observed in SB209670-treated mice compared with vehicle-treated mice. The heart pathology in SB209670-treated mice was remarkable for gross inflammatory infiltration, in contrast to the smaller inflammation in the hearts of vehicle-treated mice. We found that ET blockade decreased the number of Foxp3+ regulatory T cells and inhibited the production of immunoregulatory cytokine IL-10 in the heart. ET blockade also inhibited the expression of suppressor of cytokine signaling 3 (SOCS3) that plays a key role in the negative regulation of both Toll-like receptor (TLR)and cytokine receptor-mediated signaling. EAM is a CD4+ T cell-mediated disease. CD4+ T cells isolated from SB209670-treated EAM mice produced less IL-10 and more inflammatory cytokines IFN-γ and IL-17 than those isolated from vehicle-treated mice. Conclusions: ET receptor antagonist exacerbated autoimmune myocarditis in mice. ET may play an important role in the regulation of inflammation in myocarditis.

Lessons learned from experimental myocarditis

We have developed murine models of viral myocarditis induced by encephalomyocarditis (EMC) virus in which severe myocarditis, congestive heart failure and dilated cardiomyopathy occur in high incidence. From these models, we have learned the natural history and pathogenesis and assessed not only new diagnostic methods but also therapeutic and preventive interventions. Autoantibodies against cardiac troponin I appeared in spontaneously developing autoimmune myocarditis in PD-1 deficient mice, who lack the T-cell receptor costimulatory molecule PD-1. The passive transfer of this antibody induced myocardial dysfunction. Later, this autoantibody was found in patients with myocarditis. Mast cell deficiency had beneficial effects in the viral myocarditis model, and anti-allergic agents prevented viral myocarditis. Angiotensin-converting enzyme inhibitors, angiotensin II receptor blocker and an aldosterone receptor antagonist improved viral myocarditis, suggesting that the renin-angiotension-aldosterone system may play an important role in the pathogenesis of viral myocarditis. Differential modulation of cytokine production was seen with various calcium channel blockers, and some calcium channel blocker improved viral myocarditis. Viral infection could lead to increased synthesis of immunoglobulin light chains (FLC). Serum levels of FLC were increased in myocarditis, and exogenously given FLC inhibited viral replication and improved myocarditis. We suggest that a strategy of drug development specifically addressing inflammation in myocarditis may provide increased benefit in terms of target organ damage.

Abstract 129: Suppressor of Cytokine Signaling 1 in Dendritic Cells Inhibits Myocardial Inflammation in Experimental Autoimmune Myocarditis

Introduction: Autoimmunity is considered to play an important role in the development of myocarditis and dilated cardiomyopathy. Recent reports have indicated that a subgroup of myocarditis patients may benefit from immune-targeted therapies. Suppressor of cytokine signaling1 (SOCS1) is an intracellular, cytokine-inducible protein that regulates the responses of immune cells to cytokines. We therefore hypothesized that overexpression of SOCS1 may inhibit the inflammation of myocarditis and cardiomyopathy. Methods and Results: Myocarditis was induced by subcutaneous immunization with cardiac specific peptides derived from α-myosin heavy chain in BALB/c mice on days 0 and 7. Plasmid DNA encoding SOCS1 (pSOCS1) was injected intraperitoneally into mice on days 0, 5 and 10. pSOCS1 treatment significantly decreased heart-to-body weight ratios and the number of infiltrating cells in the heart. Echocardiography showed preserved contractile function in pSOCS1-treated mice. Although autoimmune myocarditis is a CD4+ T cell-mediated disease, pSOCS1 treatment does not have a direct suppressive effect on autoreactive T-cell activation. The introduced pSOCS1 suppressed proinflammatory cytokine production and STAT1 phosphorylation in dendritic cells (DCs). In addition, the proliferative responses of autoreactive CD4+ T cells co-cultured with DCs from pSOCS1-treated mice were much weaker than those of cells cultured with DCs from control plasmid-injected mice. These results suggested that the inoculated pSOCS1 may have been transfected into DCs and impaired DC function in vivo. Conclusion: The administration of pSOCS1 protected mice from the development of experimental autoimmune myocarditis, which was mediated by the inhibition of DC function that in turn reduced the activation of autoreactive CD4+ T cells.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

721 Meta-analysis on the immunohistological and histological proof of intramyocardial inflammation in myocarditis and dilated cardiomyopathy

721 Meta-analysis on the immunohistological and histological proof of intramyocardial inflammation in myocarditis and dilated cardiomyopathy

P1069 Meta-analysis on the histological and immunohistological proof of intramyocardial inflammation in myocarditis and dilated cardiomyopathy

P1069 Meta-analysis on the histological and immunohistological proof of intramyocardial inflammation in myocarditis and dilated cardiomyopathy