Modulation of the acute defence reaction by eplerenone prevents cardiac disease progression in viral myocarditis.

AIMS: Left ventricular (LV) dysfunction in viral myocarditis is attributed to myocardial inflammation and fibrosis, inducing acute and long-time cardiac damage. Interventions are not established. On the basis of the link between inflammation, fibrosis, aldosterone, and extracellular matrix regulation, we aimed to investigate the effect of an early intervention with the mineralocorticoid receptor antagonist (MRA) eplerenone on cardiac remodelling in a murine model of persistent coxsackievirus B3 (CVB3)-induced myocarditis. METHODS AND RESULTS: SWR/J mice were infected with 5 × 104 plaque-forming units of CVB3 (Nancy strain) and daily treated either with eplerenone (200 mg/kg body weight) or with placebo starting from Day 1. At Day 8 or 28 post infection, mice were haemodynamically characterized and subsequently sacrificed for immunohistological and molecular biology analyses. Eplerenone did not influence CVB3 load. Already at Day 8, 1.8-fold (P < 0.05), 1.4-fold (P < 0.05), 3.2-fold (P < 0.01), and 2.1-fold (P < 0.001) reduction in LV intercellular adhesion molecule 1 expression, presence of monocytes/macrophages, oxidative stress, and apoptosis, respectively, was observed in eplerenone-treated vs. untreated CVB3-infected mice. In vitro, eplerenone led to 1.4-fold (P < 0.01) and 1.2-fold (P < 0.01) less CVB3-induced cardiomyocyte oxidative stress and apoptosis. Furthermore, collagen production was 1.1-fold (P < 0.05) decreased in cardiac fibroblasts cultured with medium of eplerenone-treated vs. untreated CVB3-infected HL-1 cardiomyocytes. These ameliorations were in vivo translated into prevention of cardiac fibrosis, as shown by 1.4-fold (P < 0.01) and 2.1-fold (P < 0.001) lower collagen content in the LV of eplerenone-treated vs. untreated CVB3-infected mice at Days 8 and 28, respectively. This resulted in an early and long-lasting improvement of LV dimension and function, as indicated by reduced LV end-systolic volume and end-diastolic volume, and an increase in LV contractility (dP/dtmax ) and LV relaxation (dP/dtmin ), respectively (P < 0.05). CONCLUSIONS: Early intervention with the MRA eplerenone modulates the acute host and defence reaction and prevents cardiac disease progression in experimental CVB3-induced myocarditis without aggravation of viral load. The findings advocate for an initiation of therapy of viral myocarditis as early as possible, even before the onset of inflammation-induced myocardial dysfunction. This may also have implications for coronavirus disease-19 therapy.

Left ventricular enlargement in coxsackievirus-B3 induced chronic myocarditis--ongoing inflammation and an imbalance of the matrix degrading system.

Enteroviruses, especially Coxsackie B3 virus (CVB-3), cause acute viral myocarditis, but the detailed mechanisms leading to chronic left ventricular dysfunction and dilatation remain elusive. Myocardial tissues of CVB-3 infected and sham infected male swr/J mice were analyzed after hemodynamic evaluation on days 4, 7, and 28 p.i. by RT-PCR, gelatin zymography, ELISA, immunohistochemistry, sirius red staining, and luxol fast blue staining. In the early phase after infection an abnormal diastolic function was the main hemodynamic finding. CVB-3 infection caused impairment of left ventricular function combined with ventricular dilatation 7 and 28days post-infection. These hemodynamic findings were associated with relevant upregulation of different cytokines (IL-1beta, IL-6, IL-10, INF-gamma, and TNF-alpha) in the acute phase with persistent over-expression of IL-6, IL-10, and INF-gamma in the chronic phase. This virus induced myocardial inflammation was linked to a significant induced MMP/TIMP system (MMP-2,-3,-8, TIMP-1, uPA, tPA-mRNA expression, and MMP-2-activity) in the acute and chronic phase leading to imbalance in the MMP/TIMP-ratio at day 28. This imbalance in the MMP/TIMP system was significantly correlated to the development of ventricular dilatation. Viral persistence induces chronic myocardial inflammation and an imbalance of the matrix degrading system, associated with the development of left ventricular dysfunction and dilatation in chronic murine myocarditis.

Contributions of inflammation and cardiac matrix metalloproteinase activity to cardiac failure in diabetic cardiomyopathy: the role of angiotensin type 1 receptor antagonism.

We investigated the effect of the angiotensin type 1 (AT-1) receptor antagonist, irbesartan, on matrix metalloproteinase (MMP) activity and cardiac cytokines in an animal model of diabetic cardiomyopathy. Diabetes was induced in 20 C57/bl6 mice by injection of streptozotocin (STZ). These animals were treated with irbesartan or placebo and were compared with nondiabetic controls. Left ventricular (LV) function was measured by pressure-volume loops with parameters for systolic function (end systolic elastance [Ees]) and diastolic function (cardiac stiffness) 8 weeks after STZ treatment. The cardiac protein content of interleukin (IL)1beta and transforming growth factor (TGF)beta1 were measured by enzyme-linked immunosorbent assay. The total cardiac collagen content and collagen type 1 and 3 were measured by histochemistry, and MMP-2 activity was measured by gelatin zymography. LV dysfunction was documented by impaired Ees and diastolic stiffness in STZ mice compared with controls. This was accompanied by increased TGFbeta, IL1beta, and fibrosis and decreased MMP-2 activity. Treatment with irbesartan attenuated LV dysfunction, IL1beta, TGFbeta, and cardiac fibrosis compared with untreated diabetic animals and normalized MMP activity. These findings present evidence that AT-1 receptor antagonists attenuate cardiac failure by decreasing cardiac inflammation and normalizing MMP activity, leading to normalized cardiac fibrosis in STZ-induced diabetic cardiomyopathy.

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.

Inhibition of urokinase-type plasminogen activator or matrix metalloproteinases prevents cardiac injury and dysfunction during viral myocarditis.

BACKGROUND: Acute viral myocarditis is an important cause of cardiac failure in young adults for which there is no effective treatment apart from general heart failure therapy. The present study tested the hypothesis that increased expression of the proteinases urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs) is implicated in cardiac inflammation, injury, and subsequent failure during Coxsackievirus-B3 (CVB3)-induced myocarditis. METHODS AND RESULTS: First, we showed increased expression and activity of uPA and MMP-9 in wild-type mice at 7 days of CVB3-induced myocarditis. Targeted deletion of uPA, which resulted in reduced MMP activity and cytokine expression or inhibition of MMPs by adenoviral gene overexpression of tissue inhibitor of metalloproteinases-1, decreased cardiac inflammation and reduced myocardial necrosis at 7 days and decreased cardiac fibrosis at 35 days after CVB3 infection. Importantly, loss of uPA or MMP activity prevented CVB3-induced cardiac dilatation and dysfunction, as determined by serial echocardiography. CONCLUSIONS: Loss of uPA or MMP activity reduces the cardiac inflammatory response after CVB3 infection, thereby protecting against cardiac injury, dilatation, and failure during CVB3-induced myocarditis.

Myocardial proteases and matrix remodeling in inflammatory heart disease.

Recently, it has been demonstrated that myocardial inflammation plays a pivotal role in the development and progression of congestive heart failure. The myocardial inflammatory reaction not only affects myocardial hypertrophy and apoptosis, but it has a major influence on the regulation of extracellular matrix turnover. The balance between collagen synthesis and degradation is of crucial relevance in maintaining the structural integrity of the heart. Therefore, the overwhelming inflammatory response, as seen in acute myocarditis or inflammatory cardiomyopathy, could lead to a breakdown of this tightly regulated system. This is an additional key factor in the development and progression of heart failure. This review summarizes the importance of myocardial inflammation in respect to extracellular matrix remodeling and its possible patho-physiological role in the development and progression of left ventricular dysfunction in inflammatory heart disease.

Diltiazem treatment prevents diastolic heart failure in mice with familial hypertrophic cardiomyopathy.

BACKGROUND: The cardiac troponin T I79N mutation, linked to familial hypertrophic cardiomyopathy, carries a high risk of sudden cardiac death even in the absence of significant cardiac hypertrophy. The pathology underlying this mechanism has not yet been identified. AIMS: To study the underlying mechanism of this phenomenon we characterized the left ventricular (LV) performance of transgenic mice carrying the human troponin T mutation I79N under basal and isoproterenol-induced stress conditions. METHODS AND RESULTS: LV function was analyzed by recording pressure-volume loops using a microconductance catheter. Despite a hypercontractile systolic function under basal conditions TnT-I79N mice showed a diastolic dysfunction indicated by an increase in end-diastolic pressure-volume relationship (EDPVR), a load-independent factor of LV stiffness (0.06+/-0.01 vs. 0.02+/-0.01; P<0.05), when compared to mice expressing human wild-type troponin T (TnT-WT). TnT-I79N mutants developed severe diastolic heart failure and cardiac sudden death under isoproterenol stress. This was prevented after pretreatment with the L-type Ca2+ channel inhibitor diltiazem. CONCLUSIONS: Diastolic dysfunction due to increased LV stiffness in TnT-I79N mice leads to severe primary diastolic heart failure and finally to cardiac sudden death, which can be prevented by diltiazem.

Carvedilol improves left ventricular function in murine coxsackievirus-induced acute myocarditis association with reduced myocardial interleukin-1beta and MMP-8 expression and a modulated immune response.

BACKGROUND: Proinflammatory cytokines induce the expression of matrix metalloproteinases that play a crucial role in myocardial remodeling. Beta-adrenergic receptor stimulation influences the production of cytokines heralding the possibility of modulating cytokine production by beta-adrenergic blockers. METHODS AND RESULTS: In a coxsackievirus B3 murine myocarditis model (BALB/c), effects of carvedilol and metoprolol on myocardial cytokine expression, inflammatory cell infiltration and MMP/TIMP profiles were investigated. In carvedilol-treated mice, a significant improvement in left ventricular function was documented 10 days post infection. In infected mice (n=10), IL-1beta, TNF-alpha, TGF-beta(1) and IL-10 myocardial mRNA abundance were increased significantly (240%, 200%, 161%, and 230%) compared to controls (n=10), while IL-15 mRNA was markedly reduced (70%). Infected mice showed significantly increased infiltrations with CD3-, CD4- and CD8-T-lymphocytes (730%, 1110%, 380%). In the infected mice, myocardial MMP/TIMP profiles presented a significant upregulation of membrane type-1 MMP, MMP-9, MMP-8 and MMP-3 (150%, 160%, 340%, and 270%) and a significant decrease in TIMP-4 levels (75%). Carvedilol attenuated over-expression of myocardial TGF-beta(1), IL-1beta and MMP-8 mRNA expression significantly and induced a relevant IL-10 mRNA expression in the infected mice (n=10). By an unchanged infiltration with CD3-T-lymphocytes, carvedilol showed a representative reduction in CD4-T-lymphocytes. CONCLUSION: Carvedilol treatment in experimental myocarditis leads to reduced expression of proinflammatory cytokines and MMPs, which contributes to reduced matrix degradation and ultimately to improved structural integrity of the heart. Besides the antiadrenergic potential, carvedilol is beneficial due to a wide range of biological activities (antiinflammatory, antifibrotic, antioxidative and immunomodulatory).

Hemodynamic characterization of left ventricular function in experimental coxsackieviral myocarditis: effects of carvedilol and metoprolol.

BACKGROUND: Carvedilol, a vasodilating nonselective beta-adrenoceptor antagonist, but not metoprolol, a selective beta1-adrenoceptor antagonist, has been shown to increase the production of cardiac antiinflammatory cytokines in experimental myocarditis. However, the hemodynamic consequences of these differences had not been investigated until today. Therefore, we determined the effects of carvedilol and metoprolol on left ventricular function in a murine model of coxsackievirus B3 (CVB3)-induced myocarditis. METHODS: BALB/c mice were inoculated with the coxsackie-B3 virus. Four and 10 days after infection, left ventricular function was investigated using a conductance micromanometer system. Additional groups were treated starting 24 h after infection using equipotent doses of carvedilol and metoprolol and studied on day 10. RESULTS: On day 4, infected mice manifested increased afterload-enhanced contractility and abnormal diastolic function. On day 10, contractile function of untreated mice was impaired. Carvedilol significantly improved cardiac index and most systolic indices, whereas metoprolol was substantially less effective. Diastolic dysfunction was not influenced by either of the beta-adrenoceptor antagonists. CONCLUSIONS: These hemodynamic data indicate that not only beta1-adrenoceptor blockade but also pleiotropic effects are involved in the cardioprotective effects of carvedilol on the pathophysiology of acute viral myocarditis.

Collagen degradation in a murine myocarditis model: relevance of matrix metalloproteinase in association with inflammatory induction.

OBJECTIVE: Myocardial collagen degradation is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinase (TIMPs). The possible relevance of MMPs in association with the inflammatory induction was investigated in a murine coxsackievirus B3 myocarditis model. METHODS: Hearts from viral infected and sham-infected BALB/c mice were analyzed by semi-quantitative RT-PCR, picrosirius red staining, Western blot analysis, and immunohistochemistry. RESULTS: In viral infected mice, both mRNA and protein abundance for collagen type I remained unaltered. In addition, picrosirius red staining showed the unchanged total collagen content. However, degraded soluble fraction of collagen type I protein was increased. Moreover, the mRNA abundance for MMP-3 and MMP-9 was upregulated, whereas the mRNAs for TIMP-1 and TIMP-4 were downregulated, respectively. The upregulation of MMP-3/MMP-9 and downregulation of TIMP-4 were confirmed at the protein level, and were associated with significantly increased mRNA levels of interleukin 1beta, tumor necrosis factor-alpha, transforming growth factor-beta1 and interleukin-4. CONCLUSION: The increment of MMPs in the absence of counterbalance by TIMPs may lead to a functional defect of the myocardial collagen network by posttranslational mechanisms. This may contribute significantly to the development of left ventricular dysfunction in murine viral myocarditis. The inflammatory response with induction of cytokines may mediate the dysregulation of the myocardial MMP/TIMP systems.