Increased serum N-terminal pro-B-type natriuretic peptide and left ventricle diastolic dysfunction in patients with hepatitis C virus infection.

Prior studies demonstrated that patients with hepatitis C virus (HCV) infection had higher plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, which may indicate the presence of a subclinical cardiac dysfunction. However, there are few data regarding the echocardiographic assessment in HCV-infected patients. The objectives of this study were to investigate changes in the left ventricle (LV) with echocardiography and to identify echocardiographic correlates of serum NT-proBNP levels in HCV-infected patients. Ninety HCV-infected patients and 90 age and gender-matched healthy controls were included. The level of serum NT-proBNP was higher in the patient group (P < 0.001). The proportion of patients whose serum NT-proBNP levels were higher than 125 pg/mL was greater than that of controls (15.56%vs 3.33%, P = 0.011). Echocardiography did not show any significant difference of cardiac structural abnormalities between groups. In the patient group, E, E' and E/A were lower, and E/E' was higher. The proportion of patients (13, 14.44%) with impaired diastolic filling (E/A ≤ 0.75; 0.75 < E/A < 1.5 and E/E' ≥ 10) was greater than that of the control group (3, 3.33%; P = 0.018). Simple regression analysis demonstrated a statistically significant linear correlation between NT-proBNP levels and left ventricular diastolic diameter (LVDd) (r = 0.178, P = 0.013), left ventricular posterior wall diastolic thickness (LVPWd) (r = 0.147, P = 0.023) and mitral E/E' (r = 0.414, P = 0.027). Independent correlates of NT-proBNP levels (R(2) = 0.34) were older age (ß' = 0.034, P = 0.011) and E/E' ratio (ß' = 0.026, P = 0.018). In conclusion, the combined analysis of NT-proBNP and echocardiography showed a possible subclinical left ventricular diastolic dysfunction as evidence of a pathogenic link between HCV and CVD.

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.

Autoimmune dilated cardiomyopathy in PD-1 receptor-deficient mice.

Dilated cardiomyopathy is a severe pathology of the heart with poorly understood etiology. Disruption of the gene encoding the negative immunoregulatory receptor PD-1 in BALB/c mice, but not in BALB/c RAG-2-/- mice, caused dilated cardiomyopathy with severely impaired contraction and sudden death by congestive heart failure. Affected hearts showed diffuse deposition of immunoglobulin G (IgG) on the surface of cardiomyocytes. All of the affected PD-1-/- mice exhibited high-titer circulating IgG autoantibodies reactive to a 33-kilodalton protein expressed specifically on the surface of cardiomyocytes. These results indicate that PD-1 may be an important factor contributing to the prevention of autoimmune diseases.

HLA-DPbeta chain may confer the susceptibility to hepatitis C virus-associated hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a heart muscle disease characterized by hypertrophy and diastolic dysfunction of cardiac ventricles. It is suggested that one possible aetiology of HCM is the hepatitis C virus (HCV) infection, but molecular mechanisms underlying development of HCV-associated HCM (HCV-HCM) remains unknown. Because the human leucocyte antigen (HLA) molecule is involved in the control of progression/suppression of viral infection, extensive HLA allelic diversity may modulate the post-infectious course of HCV and pathogenesis of HCV-HCM. Here we undertook a case-control study with 38 patients with HCV-HCM and 132 unrelated healthy controls to reveal the potential impact of polymorphisms in seven classical and two non-classical HLA genes on the pathogenesis of HCV-HCM. It was found that DPB1*0401 and DPB1*0901 were significantly associated with increased risk to HCV-HCM in dominant model (P < 0.028, OR = 3.94, 95% confidence interval (CI) = 1.19, 13.02) and in recessive model (P < 0.007, OR = 9.85, 95% CI = 1.83, 53.04), respectively. The disparity in the gene-dose effect by two susceptible DPB1 alleles may be attributable to the difference between the susceptible (36 A and 55 A) and resistant (8L, 9F, 11G, 57E and 76M) residue-combination consisting of DPbeta anchor pocket for antigenic peptide-binding. These results implied that the HLA-DP molecules with specificity pocket appropriate for HCV antigen(s) might confer the progressive process of HCM among the HCV-infected individuals.

Treatment of virus-induced myocardial injury with a novel immunomodulating agent, vesnarinone. Suppression of natural killer cell activity and tumor necrosis factor-alpha production.

Controversy still exists concerning the therapy for viral myocarditis which manifests a wide variety of clinical symptoms. Vesnarinone, a quinolinone derivative that was developed as a positive inotropic agent with complex actions, including phosphodiesterase inhibition and cation channel modification, has recently been confirmed to improve the prognosis of patients with chronic heart failure. However, the precise mechanism of this beneficial effect is not yet clearly understood. In this study, using a murine model of acute viral myocarditis resulting from encephalomyocarditis virus infection, survival and myocardial damage were markedly improved by treatment with vesnarinone. In contrast, survival was not improved by treatment with amrinone, a phosphodiesterase inhibitor. Although vesnarinone did not inhibit viral replication or protect myocytes from viral direct cell injury, it did inhibit the increase in natural killer cell activity after viral infection. On the other hand, amrinone failed to inhibit natural killer cell activity. Both vesnarinone and amrinone suppressed the production of tumor necrosis factor-alpha. Therefore, we postulate that vesnarinone exerted its beneficial effects through an inhibition of natural killer cell activity, and that it serves as an immunomodulator providing new therapeutic possibilities for the treatment of viral myocarditis and/or immunological disorders.

Activation of Ca-permeable cation channels by myocarditis-associated antibody in guinea pig ventricular myocytes.

The pathogenesis of myocarditis and dilated cardiomyopathy is though to involve autoimmunological processes and myocardial calcium overload. Serum containing antiheart antibodies associated with a murine model of myocarditis increased [Ca2+]i in guinea pig ventricular myocytes only in the presence of extracellular Ca2+. The antiheart antibody-positive serum activated Ca(2+)-permeable cation channels that were insensitive to dihydropyridines and membrane stretch. The permeability sequence was Ba2+ > Ca2+ > Na+ approximately K+, and the single-channel conductance to Ba2+ was 12 pS. The channel was activated by extracellular application of the serum during on-cell recording, which suggests that a soluble intracellular messenger may be involved. The antibody-positive serum did not alter voltage-gated Ca2+ currents. We propose that excess Ca entry in myocarditis and dilated cardiomyopathy results from activation of a Ca(2+)-permeable cationic channel by the autoantibodies.

Enhanced expression of superoxide dismutase messenger RNA in viral myocarditis. An SH-dependent reduction of its expression and myocardial injury.

The oxygen free radical system has been reported to be activated by influenza virus infection in the lungs. However, the involvement of oxygen radicals in viral myocarditis is still unknown. Captopril, an angiotensin-converting enzyme (ACE) inhibitor and potent free radical scavenger with a sulfhydryl group, was effective for the treatment of viral myocarditis, while enalapril, an ACE inhibitor without a sulfhydryl group, was not effective against acute myocarditis. In this study, we investigated the role of oxygen radicals in the pathogenesis of viral myocarditis and the therapeutic effects of agents with a sulfhydryl group. 4-wk-old BALB/c mice were inoculated with the encephalomyocarditis virus, and treated with captopril or N,2-mercapto-propionyl glycine (MPG), a sulfhydryl-containing amino acid derivative without ACE inhibiting property, from days 4 to 14. On day 14, captopril and MPG significantly improved survival of mice and myocardial injury (necrosis, cellular infiltration, and calcification) in a dose-dependent manner compared with the infected control group. Thus, captopril and MPG were effective for the treatment of virus-induced myocarditis. Furthermore, a striking induction of manganese superoxide dismutase (Mn-SOD) and copper/zinc SOD (Cu/Zn-SOD) mRNAs in infected hearts was found (8-13-fold for Mn-SOD and 4-11-fold for Cu/Zn-SOD) when compared with age-matched uninfected mice hearts. MPG completely inhibited the increase of both mRNAs, even when treatment was started on day 4. Thus, oxygen radicals may play an important role in the pathogenesis of viral myocarditis, and a therapeutic approach by eliminating oxygen radicals seems possible.

Role of hepatitis C virus in cardiomyopathies.

Virus infection was conventionally considered to cause myocarditis, which resulted in development of dilated cardiomyopathy. Recent studies suggest that hepatitis C virus (HCV) is involved in the development of dilated cardiomyopathy, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy in addition to myocarditis. Furthermore, left ventricular aneurysm represents the same morbid state not only after myocardial infarction but also after myocarditis. There were wide variations in the frequency of detection of HCV genomes in cardiomyopathies in different regions or in different populations. Major histocompatibility complex class II genes may play a role in the susceptibility to HCV infection, and may influence the development of different phenotypes of cardiomyopathies. If it is the fact that the myocardial damage is caused by HCV, it might be expected that interferon (IFN) treatment would be useful for its treatment. Patients receiving IFN treatment of hepatitis were screened by thallium myocardial scintigraphy, and an abnormality was discovered in half of patients. Treatment with IFN resulted in disappearance of the image abnormality. It has thus been suggested that mild myocarditis and myocardial damage may be cured with IFN. We have recently found that high concentrations of circulating cardiac troponin T are a specific marker of cardiac involvement in HCV infection. By measuring cardiac troponin T in patients with HCV infection, the prevalence of cardiac involvement in hepatitis C virus infection will be clarified. We are proposing a collaborative work on global network on myocarditis/cardiomyopathies due to HCV infection.

Treatment of experimental viral myocarditis with interleukin-10.

BACKGROUND: The T helper cell type 2-associated cytokine interleukin (IL)-10 has a variety of immunomodulatory properties. However, the effects of the cytokine on viral myocarditis remain unclear. METHODS AND RESULTS: We studied the effects of recombinant human IL-10 (rhIL-10) fully active on mouse cells in a murine experimental model of acute viral myocarditis caused by the encephalomyocarditis virus (EMCV). Four-week-old DBA/2 mice were inoculated with EMCV (day 0). rhIL-10 (10 microg/mouse) was administered once daily, starting on day 0, and control mice received vehicle only. Survival rates were determined on day 14. Myocardial histopathology, cytokine levels in the heart by ELISA assay, and myocardial virus concentration were examined on day 6, and the expression levels of myocardial inducible nitric oxide synthase (iNOS) mRNA were measured by competitive polymerase chain reaction. The 14-day survival in mice treated with rhIL-10 was significantly higher (80%) than in the control group (30%, n=10 in each, P<0.05). rhIL-10 treatment significantly attenuated myocardial lesions and suppressed tumor necrosis factor-alpha and IL-2 in the heart. rhIL-10 treatment had little effect on myocardial virus concentration. The expression levels of myocardial iNOS mRNA were significantly decreased in the group treated with rhIL-10 (8.6+/-4.7 amol/mg total RNA in treated versus 26.5+/-7.1 amol/mg total RNA in control mice, P<0.05). CONCLUSIONS: These findings provide new insights into the in vivo effects of IL-10 on viral infection and suggest a therapeutic effect of IL-10 on viral myocarditis.

Contribution of endothelin-1 to myocardial injury in a murine model of myocarditis: acute effects of bosentan, an endothelin receptor antagonist.

BACKGROUND: Endothelin (ET) is one of the most important contributing factors in the pathophysiology of cardiovascular diseases. However, little is known about its role in myocarditis. METHODS AND RESULTS: Four-week-old DBA/2 mice were inoculated with the encephalomyocarditis virus. Expression levels of ET-converting enzyme-1 (ECE-1) and prepro-ET-1 mRNA were significantly increased at 7 and 14 days after virus inoculation. Plasma and myocardial ET-1 levels were significantly higher in infected than noninfected mice between 5 and 14 days after virus inoculation. Immunohistochemical analyses revealed that not only endothelial cells and myocytes but also infiltrating mononuclear cells produced ET-1 protein at 7 days. Oral bosentan, a mixed ET-1 receptor antagonist, was administered after virus inoculation in doses of 0 (control group), 10, or 100 mg. kg(-1). d(-1), and the animals were killed on day 14. Mean heart weight/body weight ratios were 8.3+/-1.8 versus 11.2+/-2.4 versus 10. 8+/-2.4 in the bosentan 100 mg. kg(-1). d(-1) versus 10 mg. kg(-1). d(-1) versus control groups, respectively (P<0.05). Corresponding histological scores for myocardial necrosis were 2.0+/-0.2 versus 2. 9+/-0.3 versus 3.0+/-0.4 (P<0.05), and cellular infiltration scores were 2.3+/-0.3 versus 2.9+/-0.4 versus 3.3+/-0.4 (P<0.05). Animals killed on day 5 had significantly smaller necrotic areas after treatment with bosentan 100 mg. kg(-1). d(-1) than the group treated with a lower dose or the control group, despite the absence of differences in virus titers. CONCLUSIONS: This study suggests that ET-1 plays an important pathophysiological role in viral myocarditis. Treatment with bosentan had a cardioprotective effect without modifying viral replication.

FTY720, a new immunosuppressant, promotes long-term graft survival and inhibits the progression of graft coronary artery disease in a murine model of cardiac transplantation.

Background-Effective immunosuppression is a critical determinant of organ and patient survival in cardiac transplantation. The present study was designed to determine the potency of FTY720, a new synthesized immunosuppressant, and examine its clinical potential as an immunosuppressant. Methods and Results-Hearts of DBA/2 mice were transplanted heterotopically in C57BL/6 mice. Recipients were treated with oral FTY720 in doses of 0.3, 1, 3, or 10 mg. kg(-1). d(-1) or with 40 mg. kg(-1). d(-1) of cyclosporin A (CsA) as a comparative treatment. The median graft survival time (MST) was significantly prolonged by treatment with FTY720 10 mg. kg(-1). d(-1). MST was not prolonged by FTY720 1 mg. kg(-1). d(-1) or CsA. However, FTY720 1 mg. kg(-1). d(-1) combined with CsA 40 mg. kg(-1). d(-1) resulted in a significant prolongation of MST. Histopathological studies performed 5 days after transplantation demonstrated remarkable suppression of inflammatory response by treatment with FTY720 10 mg. kg(-1). d(-1). Interleukin (IL)-2 and interferon (IFN)-gamma production was not suppressed; however, cytotoxic T lymphocyte activity was strongly suppressed in vitro. In addition, IL-2-stimulated T-cell proliferation and class I and class II MHC antigen expression on IFN-gamma-stimulated macrophages were strongly inhibited by FTY720. Histopathological studies 60 days after transplantation (DBA/2-B10.D2) demonstrated a beneficial effect on graft atherosclerosis. Conclusions-FTY720 promoted long-term cardiac graft survival and strongly inhibited the progression of graft atherosclerosis. These observations suggest that FTY720 has a promising clinical potential in cardiac transplantation.

Persistently increased serum concentrations of cardiac troponin t in patients with idiopathic dilated cardiomyopathy are predictive of adverse outcomes.

BACKGROUND: The measurement of serum concentrations of cardiac troponin T (TnT) is a simple, useful method to detect myocyte injury that may be repeated multiple times to follow patients without interobserver variability. METHODS AND RESULTS: Multiple measurements of TnT with a second-generation assay were performed in 60 patients with dilated cardiomyopathy confirmed by coronary angiography and endomyocardial biopsy between April 1996 and December 1999. Three evolutionary patterns of TnT concentrations were identified. Thirty-three patients had concentrations of TnT <0.02 ng/mL throughout the follow-up period (group 1). The remaining 27 patients had high initial serum concentrations of TnT (>/=0.02 ng/mL). In 10 of these 27 patients, TnT decreased to <0.02 ng/mL during follow-up (group 2), whereas 17 had persistently high serum TnT concentrations despite being conventionally treated for chronic congestive heart failure (group 3). Although the initial echocardiographic left ventricular diastolic dimension (LVDd) and left ventricular ejection fraction (LVEF) were not significantly different among the 3 groups, follow-up echocardiography showed significantly decreased LVDd and increased LVEF in group 1 (each P:<0.01) and group 2 (each P:<0.05) compared with increased LVDd and decreased LVEF in group 3 (each P:<0.05). The cardiac event-free rate was significantly lower in group 3 than in groups 1 and 2 (each P:<0.001), and the survival rate was lower in group 3 than in group 1 (P:<0.05). CONCLUSIONS: Persistently increased TnT concentrations in dilated cardiomyopathy suggest ongoing subclinical myocyte degeneration associated with deterioration of the patients' clinical status.

Mast cells cause apoptosis of cardiomyocytes and proliferation of other intramyocardial cells in vitro.

BACKGROUND: Mast cells are multifunctional cells containing various mediators such as cytokines, proteases, and histamine. They are found in the human heart and have been implicated in ventricular hypertrophy and heart failure. However, their roles in pathogenesis of these diseases are unknown. METHODS AND RESULTS: Cultured cardiomyocytes from neonatal rats were incubated with mast cell granules (MCGs) for 24 hours. The highest concentration of diluted MCGs caused the death of approximately 70% of cardiomyocytes. This cell death was proved to be apoptosis, as quantified by electron microscopy and biochemical criteria. MCG-mediated cytotoxicity was prevented by pretreatment of MCGs with protease inhibitors or a neutralizing antibody against rat mast cell chymase 1 (RMCP 1). RMCP 1 by itself was proved to induce cell death of cardiomyocytes. These results suggest that RMCP 1 contained in MCGs causes the death of cardiomyocytes. In contrast, MCGs induced the proliferation of intramyocardial cells other than myocytes. RMCP 1 was also proved to induce their proliferation. CONCLUSIONS: Mast cells cause apoptosis of cardiomyocytes and proliferation of other intramyocardial cells via the activity of RMCP 1. Our results suggest that mast cell chymase may play a role in the progression of heart failure, because loss of cardiomyocytes and proliferation of nonmyocardial cells exaggerate its pathophysiology.

Prevention of viral myocarditis with recombinant human leukocyte interferon alpha A/D in a murine model.

Effects of recombinant human leukocyte interferon alpha A/D on experimental myocarditis due to encephalomyocarditis virus were investigated. Plaque reduction assays revealed that 50% of plaque formation in vitro in human amnion (FL) cells was inhibited by interferon alpha A/D (9.7 U/ml) when it was administered 24 hours before infection with the encephalomyocarditis virus. Four week old male DBA/2 mice were inoculated intraperitoneally with 10 plaque-forming units (pfu) of encephalomyocarditis virus. Interferon alpha A/D was administered subcutaneously (10(2) U/g body weight per day in Group 1, 10(3) U/g per day in Group 2 and 10(4) U/g per day in Group 3) starting 1 day before infection. It was also administered starting the same day in Group 4 and 1 day after virus inoculation in Group 5 (10(4) U/g per day in both groups). Control mice were injected with saline solution. Each group consisted of 10 mice; they were killed on day 4 for evaluation. Myocardial virus titers were significantly lower in Group 3 (8.2 +/- 25.2 X 10(2) pfu/mg, p less than 0.05) and Group 4 (3.0 +/- 5.5 X 10(3) pfu/mg, p less than 0.05) than in control mice (5.6 +/- 4.1 X 10(4) pfu/mg). Histologic examination showed extensive myocardial necrosis and cellular infiltration in all control mice, but no myocardial necrosis or cellular infiltration in Group 3 and less severe necrosis and infiltration in Group 4. There were no significant differences in myocardial virus titers or histologic changes between control mice and Group 1, 2 or 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prednisolone on acute viral myocarditis in mice.

The effect of prednisolone on viral myocarditis was studied in BALB/c mice with encephalomyocarditis virus myocarditis. Prednisolone was injected intramuscularly, 10 mg/kg once a day, on days 4 to 13 (experiment 1) and on days 8 to 17 (experiment 2). The control mice in each experiment received injections of distilled water. In experiment 1, myocardial virus titers were maximal but neutralizing antibodies were rarely present on day 4, and viral titers were still elevated and antibody titers were high on day 8. The survival rate of the prednisolone group was significantly lower (p less than 0.05) than that of the control group on days 21, 22 and 23. On day 10, the antibody titers of the prednisolone group were significantly lower (p less than 0.01) than those of the control group, and viral titers of the prednisolone group remained significantly elevated (p less than 0.01), whereas viruses were rarely isolated in the control group. In experiment 2, the survival rate and antibody titers were not significantly different in the prednisolone and control groups. In both experiments, no viruses were isolated on day 14. The present study suggests that corticosteroids given in the early stage aggravate the course of acute viral myocarditis, and that they may not have detrimental effects if given when neutralizing antibody titer levels are high, although they are not expected to have a beneficial effect.

Myocardial catecholamines in hypertrophic and dilated (congestive) cardiomyopathy: a biopsy study.

A high performance liquid chromatographic method was used to determine myocardial norepinephrine and epinephrine concentrations in 66 biopsy specimens obtained from the right or left ventricle during routine diagnostic cardiac catheterization of 45 patients with dilated (congestive) or hypertrophic cardiomyopathy, or with heart disease other than cardiomyopathy, such as acute perimyocarditis, postmyocarditis and constrictive pericarditis. The validity of catecholamine determination in a 2 to 6 mg biopsy specimen to assess overall ventricular myocardial catecholamines was demonstrated. Norepinephrine concentrations in the myocardium were inversely correlated with the grade of hypertrophy in patients with congestive cardiomyopathy or heart disease other than cardiomyopathy, but not in patients with hypertrophic cardiomyopathy. The fact that the myocardial norepinephrine concentration was always lower in the left than in the right ventricle of the same patient may be explained by the simple dilution of sympathetic nerve endings in the left ventricle. There were some cases of hypertrophic cardiomyopathy in which the concentration of myocardial norepinephrine was exceptionally high, although its mean value was not significantly higher than that in patients with other types of heart disease who served as a control group without cardiomyopathy. Some patients with dilated cardiomyopathy had lower levels of myocardial norepinephrine than would be expected for the degree of interstitial fibrosis and the severity of heart failure. The mean plasma norepinephrine and epinephrine levels were significantly elevated in patients with dilated cardiomyopathy.

Electrocardiographic findings in experimental myocarditis in DBA/2 mice: complete atrioventricular block in the acute stage, low voltage of the QRS complex in the subacute stage and arrhythmias in the chronic stage.

To determine whether arrhythmias persist in the chronic stage of myocarditis, serial electrocardiograms were studied in DBA/2 mice with experimentally induced myocarditis. After baseline electrocardiograms with standard limb and two precordial leads were recorded, 52 mice were inoculated intraperitoneally with 0.1 ml of the myocardiotropic variant of encephalomyocarditis in a viral suspension containing 10(2) TCD50 (50% tissue culture infective dose). Electrocardiograms were recorded every day on days 3 to 18 and, thereafter, once every 10 to 20 days until day 220. The cumulative incidence rate of myocarditis was 90.4% (47 of 52). No arrhythmias were found on baseline electrocardiograms. Serial electrocardiograms showed atrial and ventricular premature complexes and complete atrioventricular (AV) block, respectively, in 6 (12.8%), 8 (17.0%) and 25 (53.2%) of 47 mice with myocarditis. Myocardial lesions were found in the heart of mice with these ectopic complexes. Mononuclear cell infiltrations into the His bundle were noted in the conduction system of mice with complete AV block. Heart rate began to increase after day 11 (638 +/- 105 beats/min, n = 16 versus control rate 557 +/- 57 beats/min, n = 47, mean +/- standard deviation, p less than 0.01) and reached a maximum on day 15 (40 +/- 22 beats/min, n = 8, p less than 0.01). The sum of QRS voltage in eight leads began to decrease after day 6 (62.1 +/- 18.8 mm, n = 24 versus control value 80.0 +/- 14.7 mm, n = 47, p less than 0.01) and reached a minimum on day 13 (32.5 +/- 7.5 mm, n = 8, p less than 0.01) when myocardial necrosis and congestion of the lungs and liver were most prominent.(ABSTRACT TRUNCATED AT 250 WORDS)

Denopamine, a beta1-adrenergic agonist, prolongs survival in a murine model of congestive heart failure induced by viral myocarditis: suppression of tumor necrosis factor-alpha production in the heart.

OBJECTIVES: This study was designed to examine the effects of denopamine, a selective beta1-adrenergic agonist, in a murine model of congestive heart failure (CHF) due to viral myocarditis. BACKGROUND: Positive inotropic agents are used to treat severe heart failure due to myocarditis. However, sympathomimetic agents have not been found beneficial in animal models of myocarditis. METHODS: In vitro: The effects of denopamine on lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-alpha) production was studied in murine spleen cells. In vivo: Four-week-old DBA/2 mice were inoculated with the encephalomyocarditis virus (day 0). Denopamine (14 micromol/kg), denopamine (14 micromol/kg) with a selective beta1-blocker metoprolol (42 micromol/kg), or denopamine (14 micromol/kg) with metoprolol (84 micromol/kg) was given daily, and control mice received the vehicle only. Survival and myocardial histology on day 14 and TNF-alpha levels in the heart on day 6 were examined. RESULTS: In the in vitro study, TNF-alpha levels in treated cells were significantly lower than in controls (p < 0.05). In the in vivo study treatment with denopamine significantly improved the survival of the animals (14 of 25 (56%) treated, vs 5 of 25 (20%) control mice), attenuated myocardial lesions, and suppressed TNF-alpha production (66.5+/-7.5 pg/mg of heart in treated mice vs 113.5+/-15.1 pg/mg of heart in control mice, mean+/-SE). There was a strong linear relationship between mortality and TNF-alpha levels (r=0.98, n=4, p < 0.05). These in vitro and in vivo effects of denopamine were significantly inhibited by metoprolol. CONCLUSIONS: These results suggest that denopamine may exert its beneficial effects, in part, by suppressing the production of TNF-alpha via beta1-adrenoceptors.

Therapeutic effects of FTY720, a new immunosuppressive agent, in a murine model of acute viral myocarditis.

OBJECTIVES: This study examines the efficacy of FTY720 (FTY), a new immunosuppressor, in the treatment of acute viral myocarditis in a murine model. BACKGROUND: Immunosuppressive agents have no proven therapeutic efficacy in experimental or clinical myocarditis. METHODS: Encephalomyocarditis virus was inoculated i.p. in DBA/2 mice on day 0. Postinoculation treatment consisted of FTY 10 mg/kg/day p.o. (FTY group), or cyclosporine A (CsA) 40 mg/kg/day p.o. (CsA group) or distilled water p.o. only (control group). Survival until day 14, as well as cardiac histopathology, virus concentrations, cytokines (interleukin [IL]-2, IL-12, interferon [IFN]-gamma and tumor necrosis factor [TNF]-alpha) and nitric oxide (NO) on day 5 were examined. RESULTS: In the control and CsA groups, all mice died within 10 and 7 days, respectively. However, in the FTY group, 27% of the animals survived up to day 14. Compared with the control group, 1) histological scores were significantly lower in the FTY group but unchanged in the CsA group; 2) virus concentration was significantly higher in the CsA group but not in the FTY group; 3) expressions of IL-2, IL-12 and IFN-gamma in the heart were suppressed in both the FTY and CsA groups, though suppression was weaker in the FTY group; 4) TNF-alpha and NO were significantly increased in the CsA group but not in the FTY group. CONCLUSIONS: FTY720 had a significant therapeutic effect in acute experimental myocarditis without inducing excessive virus replication. This report is the first to describe a beneficial effect by an immunosuppressive agent in the treatment of acute viral myocarditis.

Pharmacokinetics of indium-111-labeled antimyosin monoclonal antibody in murine experimental viral myocarditis.

The pharmacokinetics of indium-111-labeled antimyosin monoclonal antibody Fab were investigated with use of murine experimental viral myocarditis as a model. The biodistribution of indium-111-labeled antimyosin antibody Fab on days 3, 5, 7, 14, 21 and 28 after encephalomyocarditis virus inoculation demonstrated that myocardial uptake increased significantly on days 5, 7 and 14 (maximum on day 7) in infected versus uninfected mice (p less than 0.001). In vivo kinetics in infected mice on day 7 demonstrated that the heart to blood ratio reached a maximum 48 h after the intravenous administration of indium-111-labeled antimyosin Fab, which was considered to be the optimal time for scintigraphy. The scintigraphic images obtained with indium-111-labeled antimyosin Fab demonstrated positive uptake in the cardiac lesion in infected mice. The pathologic study demonstrated that myocardial uptake correlated well with pathologic grades of myocardial necrosis. High performance liquid chromatography revealed the presence of an antigen-antibody complex in the circulation of infected mice after the injection of indium-111-labeled antimyosin Fab. This antigen bound to indium-111-labeled antimyosin Fab in the circulation might be whole myosin and this complex may decrease myocardial uptake and increase liver uptake. It is concluded that indium-111-labeled antimyosin monoclonal antibody Fab accumulates selectively in damaged heart tissue in mice with acute myocarditis and that indium-111-labeled antimyosin Fab scintigraphy may be a useful method for the visualization of acute myocarditis.