Stage Of Myocarditis Research Articles

Blocking the IL-1β signalling pathway prevents chronic viral myocarditis and cardiac remodeling

Coxsackieviruses of group B (CVB) are well-known causes of acute and chronic myocarditis. Chronic myocarditis can evolve into dilated cardiomyopathy (DCM) characterized by fibrosis and cardiac remodeling. Interleukin-1β (IL-1β) plays a decisive role in the induction of the inflammatory response as a consequence of viral replication. In this study, we analyzed the effects of IL-1β neutralization on the transition of acute to chronic myocarditis in a mouse model of CVB3 myocarditis. Mice were treated with an anti-murine IL-1β antibody as a surrogate for Canakinumab at different time points post CVB3 infection. Treatment was performed in the early phase (day 1-14 pi, day 3-14 pi) or at a later stage of myocarditis (day 14-28 pi). Subsequently, the hearts were examined histologically, immunohistochemically and by molecular biology. A significant reduction of viral replication, cardiac damage and inflammation was found after administration of the antibody in the early phase and in the later phase of infection. Furthermore, less collagen I deposition and a considerable reduction of fibrosis were found in antibody-treated mice. Using microarray analysis, a significant upregulation of various extracellular matrix and fibrosis-associated molecules was found in CVB3-infected mice, including TGF-β, TIMP-1 and MMP12, as well as diverse matricellular proteins, whereas, these molecules were significantly downregulated in all IL-1β antibody-treated infected mice. Neutralization of IL-1β at different stages of enteroviral infection prevents the development of chronic viral myocarditis by reducing inflammation, interstitial fibrosis and adverse cardiac remodeling. These findings are relevant for the treatment of patients with acute and chronic myocarditis.

Ferumoxytol-enhanced cardiovascular magnetic resonance detection of early stage acute myocarditis

BackgroundThe diagnostic utility of cardiovascular magnetic resonance (CMR) is limited during the early stages of myocarditis. This study examined whether ferumoxytol-enhanced CMR (FE-CMR) could detect an earlier stage of acute myocarditis compared to gadolinium-enhanced CMR.MethodsLewis rats were induced to develop autoimmune myocarditis. CMR (3 T, GE Signa) was performed at the early- (day 14, n = 7) and the peak-phase (day 21, n = 8) of myocardial inflammation. FE-CMR was evaluated as % myocardial dephasing signal loss on gradient echo images at 6 and 24 h (6 h- & 24 h-FE-CMR) following the administration of ferumoxytol (300μmolFe/kg). Pre- and post-contrast T2* mapping was also performed. Early (EGE) and late (LGE) gadolinium enhancement was obtained after the administration of gadolinium-DTPA (0.5 mmol/kg) on day 14 and 21. Healthy rats were used as control (n = 6).ResultsLeft ventricular ejection fraction (LVEF) was preserved at day 14 with inflammatory cells but no fibrosis seen on histology. EGE and LGE at day 14 both showed limited myocardial enhancement (EGE: 11.7 ± 15.5%; LGE: 8.7 ± 8.7%; both p = ns vs. controls). In contrast, 6 h-FE-CMR detected extensive myocardial signal loss (33.2 ± 15.0%, p = 0.02 vs. EGE and p < 0.01 vs. LGE). At day 21, LVEF became significantly decreased (47.4 ± 16.4% vs control: 66.2 ± 6.1%, p < 0.01) with now extensive myocardial involvement detected on EGE, LGE, and 6 h-FE-CMR (41.6 ± 18.2% of LV). T2* mapping also detected myocardial uptake of ferumoxytol both at day 14 (6 h R2* = 299 ± 112 s− 1vs control: 125 ± 26 s− 1, p < 0.01) and day 21 (564 ± 562 s− 1, p < 0.01 vs control). Notably, the myocardium at peak-phase myocarditis also showed significantly higher pre-contrast T2* (27 ± 5 ms vs control: 16 ± 1 ms, p < 0.001), and the extent of myocardial necrosis had a strong positive correlation with T2* (r = 0.86, p < 0.001).ConclusionsFE-CMR acquired at 6 h enhance detection of early stages of myocarditis before development of necrosis or fibrosis, which could potentially enable appropriate therapeutic intervention.

Heme Oxygenase-1 Mediates Oxidative Stress and Apoptosis in Coxsackievirus B3-Induced Myocarditis

Background: Heme oxygenase-1 (HO-1), which is suggested to play a role in defending the organism against oxidative stress-mediated injuries, can be induced by diverse factors including viruses and iron. As coxsackievirus B3 (CVB3)-infected SWR/J mice susceptible for chronic myocarditis were found to have a significant iron incorporation and HO-1 upregulation in the myocardium, we aimed to investigate the molecular interplay between HO-1 expression and iron homeostasis in the outcome of viral myocarditis. Methods and Results: In susceptible SWR/J mice, but not in resistant C57BL/6 mice, we observed at later stages of CVB3 myocarditis significant iron deposits in macrophages and also in cardiomyocytes, which were spatially associated with oxidative stress, upregulation of HO-1 and caspase-3 activation. HO-1, which is also expressed in cultivated RAW 264.7 macrophages upon incubation with iron and/or CVB3, could be downregulated by inhibition of NO/iNOS using L-NAME. Moreover, specific inhibition of HO-1 by tin mesoporphyrin revealed a suppression of superoxide production in iron and/or CVB3-treated macrophages. The molecular relationship of HO-1 and caspase-3 activation was proven by downregulation with HO-1 siRNA in iron- and/or CVB3-treated cultivated cells. Importantly, iron was found to increase viral replication in vitro. Conclusion: These results indicate that HO-1 induces a paracrine signalling in macrophages via reactive oxygen species production, mediating apoptosis of heart muscle cells at later stages of myocarditis. Notably, in genetically susceptible mice iron potentiates the detrimental effects of CVB3 by the NO/HO-1 pathway, thus increasing cardiac pathogenicity.

The viral genetic background determines the outcome of coxsackievirus B3 infection in outbred NMRI mice

The reasons for the different outcome of coxsackievirus B3 (CVB3)-induced heart disease in humans are not well understood. Since there are no experimental data on the course of disease after infection with genetically different CVB3 in a natural variable population until now, we studied the outcome of virus infection in outbred NMRI mice after inoculation of genetically different CVB3 variants. Adult male mice were inoculated with seven closely related CVB3 variants. The histopathological changes of heart and pancreas tissue, antibody induction, virus titers, and persistence of viral positive- as well as negative-strand RNA in spleen and heart tissue were compared at day 7 or day 28 after infection to detect prerequisites and predictive factors for chronic myocarditis. Six CVB3 variants infected NMRI mice. CVB3 infection (i) did not induce detectable myocardial injury, (ii) caused signs of healing up acute myocarditis or (iii) ongoing chronic myocarditis. Neither IgG antibody responses nor the extent of destruction of exocrine pancreatic tissue or viral RNA load in spleen did correlate with myocardial histopathology. In contrast, a high persistent viral RNA load in heart tissue specimens was characteristic for mice developing chronic myocarditis. The results of the present study corroborate high viral load in the acute stage of myocarditis and high amounts of persisting CVB3 RNA in heart tissue as predictive marker of chronic myocarditis. The outcome of CVB3-induced heart disease in outbred NMRI mice depends strongly on the viral genetic background. In particular an important role of viral capsid proteins is suggested.

Effect of Chinese herbal medicine Xin-kang oral liquid on interferon-induction and its antiviral activity in coxsackievirus B3 infected mice

To investigate the effect of Chinese herbal medicine Xin-kang oral liquid on interferon (IFN)-induction and its antiviral activity in Coxsackievirus B3 virus strain (CVB3) infected mice. The Xin-kang oral liquid was given orally to mice two days prior to the challenge of CVB3 virus to induce myocarditis. Two dosages of Xin-kang oral liquid crude herbal medicine 30 g x kg(-1) x d(-1) and 12 g x kg(-1) x d(-1) were given to the mice of different treatment groups respectively, sterilized water was given to the mice of virus control group. IFN-alpha 10(6) U x kg(-1) x d(-1) S.C was given to the infected mice as positive drug control group. The mice were sacrificed on 5th, 10th and 20th day of infection for evaluation, the levels of serum interferon (IFN) were titrated with vesicular stomatitis virus (VSV) and cardiac tissue was fixed and sectioned. The quantitative histological changes at various stages of myocarditis were observed. In the infected mice fed with 30 g x kg(-1) x d(-1) or 12 g x kg(-1) x d(-1) of Xin-kang oral liquid orally for 5, 10 and 20 days, the mean titer of serum IFN of Xin-Kang oral liquid treated group was markedly higher (29.3 U/0.1 ml) than that of virus control group (12.6 U/0.1 ml). The level of serum IFN in IFN treated positive control mice was lower than that of Xin-kang treatment groups. The histological examination showed extensive myocardial necrosis and cellular infiltration in virus control group, but necrosis and cellular infiltration were less severe in Xin-kang treatment goups of mice. It is demonstrated that there were close correlation between the degree of myocardial lesions and the level of IFN-induction in treated mice. Xin-kang oral liquid could facilitate the induction of endogenous interferon that exerted its antiviral activity in CVB3 infected mice. This can help us to understand better the mechanism of anti-CVB3 effect of Xin-Kang oral liquid.

Cytomegalovirus-associated heart muscle disease.

Human cytomegalovirus (CMV) can persist in many organs after primary infection. Not only is it suspected to cause morbidity during reactivation in patients under immunosuppression, but it may also induce long-term latency by chronic disease, e.g. in the myocardium. Endomyocardial biopsies of 27 patients with active myocarditis, 35 patients with healing, 41 patients with healed and 25 patients with ongoing myocarditis according to the Dallas Criteria and 52 patients with dilated cardiomyopathy (DCM) and the biopsies of 25 healthy heart donors were studied for persisting CMV-DNA by polymerase chain reaction (PCR) and in-situ hybridization (ISH). CMV-DNA could be assessed in 5-14% of patients in the different stages of myocarditis and in 22% of patients with DCM. Although two biopsies of the control group showed a positive result, studies by in-situ hybridization demonstrated that in patients with heart muscle disease CMV persists in all cell types including myocytes, whereas in the controls it is only found in interstitial cells. CMV antigens could not be detected in the myocardium with our methods. It must be assumed that infection by CMV is more a persistent or latent than an active infection.

Editors' comments on the biopsy diagnosis of myocarditis

During the International Symposium on Cardiomyopathy and Myocarditis, which was held in December 12 15, 1984 in Tokyo, Japan, several references were made to the difficulties that exist in making a diagnosis of myocarditis in endomyocardial tissue obtained by bioptome. As part of the planned poster session, a number of photomicrographs were on display throughout the symposium. Examples of the various stages of myocarditis as well as hypertrophic cardiomyopathy and congenital heart disease were presented. All participants were invited to write down their diagnoses. No clinical information was provided. Toward the end of the symposium, the entire display was discussed. There was remarkable agreement with respect to active and resolving (healing) myoearditis. However, difficulties arose with the resolved or healed types. During this discussion, the relevant clinical information was released. To emphasize the problems to the reader, a selection of the photomicrographs is reproduced in Fig. 1. This exercise highlighted several important points, foremost among which was the need for clear concepts and criteria that must be observed and applied. Only by these means can one hope to categorize a patient's condition accurately, which may have important therapeutic implications. We recommend that the Dallas criteria, as discussed in papers [1], [2], and [3], should be used as a basis for uniformity of approach and interpretation of endomyocardial biopsies. Future developments, including improvements in methodology and other technical advances, should result from such an approach and may well necessitate continuous appraisal and refinement as newer techniques emerge.

Right and left ventricular compliance in experimental acute and subacute trypanosomal myocarditis

In order to elucidate the dominance of right ventricular failure in South American trypanosomal myocarditis (Chagas's disease), postmortem ventricular pressure—volume relationships were studied in eight C3H mice with acute experimental myocarditis due to Trypanosoma cruzi and in nine healthy control animals, as well as in seven animals with myocarditis in the subacute stage and eight controls. Pressures and volumes of right and left ventricles, isolated at thoracotomy, were measured within 35 min after death during simultaneous infusion of saline into right and left ventricles. Compliance, defined as the slope of the pressure-volume curve (ΔV/ΔP), was plotted against ventricular pressure over the range from 5 to 20 mm Hg. In the normal and myocarditic C3H mice, right ventricular compliance was always greater than left ventricular compliance. Right ventricular distensibility was maximal during the acute stage of myocarditis and decreased subsequently. Left ventricular distensibility remained unchanged during acute myocarditis, but increased significantly in the subacute stage. It is postulated that the dominance of right ventricular failure in Chagas's disease may be the result of a vicious cycle among inflammation and necrosis, increased compliance with dilatation and increased wall tension in the right ventricle, while the left ventricle remains less compliant.