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.

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.

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.

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.

The haplotype block, NFKBIL1-ATP6V1G2-BAT1-MICB-MICA, within the class III-class I boundary region of the human major histocompatibility complex may control susceptibility to hepatitis C virus-associated dilated cardiomyopathy.

Cardiomyopathy is a heart muscle disease with impaired stretch response that can result in severe heart failure and sudden death. A small proportion of hepatitis C virus (HCV)-infected patients may be predisposed to develop dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). The molecular mechanisms involved in the predisposition remain unknown due in part to the lack of information on their genetic background. Because the human leukocyte antigen (HLA) region has a pivotal role in controlling the susceptibility to HCV-induced liver disease, we hypothesized that particular HLA alleles and/or non-HLA gene alleles within the human major histocompatibility complex (MHC) genomic region might control the predisposition to HCV-associated DCM (HCV-DCM) and/or HCV-associated HCM (HCV-HCM). Here, we present mapping results of the MHC-related susceptibility gene locus for HCV-associated cardiomyopathy by analyzing microsatellite and single nucleotide polymorphism markers. To delineate the susceptibility locus, we genotyped 44 polymorphic markers scattered across the entire MHC region in a total of 59 patients (21 HCV-DCM and 38 HCV-HCM) and 120 controls. We mapped HCV-DCM susceptibility to a non-HLA gene locus spanning from NFKBIL1 to MICA gene loci within the MHC class III-class I boundary region. Our results showed that HCV-DCM was more strongly associated with alleles of the non-HLA genes rather than the HLA genes themselves. In addition, no significant association was found between the MHC markers and HCV-HCM. This marked difference in the MHC-related disease susceptibility for HCV- associated cardiomyopathy strongly suggests that the development of HCV- DCM and HCV-HCM is under the control of different pathogenic mechanisms.

Gene transfer of Fc-fusion cytokine by in vivo electroporation: application to gene therapy for viral myocarditis.

Among a number of techniques for gene transfer in vivo, the direct injection of plasmid DNA into muscle is simple, inexpensive and safe. Although combining direct DNA injection with in vivo electroporation increases the efficiency of gene transfer into muscle, applications of this method have remained limited because of the relatively low expression level. To overcome this problem, we developed a plasmid vector that expresses a secretory protein as a fusion protein with the noncytolytic immunoglobulin Fc portion and used it for electroporation-mediated viral interleukin 10 (vIL-10) expression in vivo. The fusion cytokine vIL-10/mutFc was successfully expressed and the peak serum concentration of vIL-10 was almost 100-fold (195 ng/ml) higher than with a non-fusion vIL-10 expression plasmid. The expressed fusion cytokine suppressed the phytohemagglutinin-induced IFN-gamma production by human peripheral blood mononuclear cells and decreased the mortality in a mouse viral myocarditis model as effectively as vIL-10 expression. These results demonstrate that the transfer of plasmid DNA expressing a noncytolytic Fc-fusion cytokine is useful to deliver enhanced levels of cytokine without altering general biological activities. This simple and efficient system should provide a new approach to gene therapy for human diseases and prove very useful for investigating the function of newly discovered secretory protein genes.

Epidemiology of idiopathic cardiomyopathy in Japan: results from a nationwide survey.

OBJECTIVE: To estimate the total number of patients with idiopathic cardiomyopathy in Japan and the prevalence of the disorder. DESIGN: A nationwide epidemiological survey. SETTING: Hospitals selected randomly from among all hospitals in Japan. PATIENTS: Patients presenting with any of the three types of idiopathic cardiomyopathy: dilated cardiomyopathy, hypertrophic cardiomyopathy, and restrictive cardiomyopathy. MAIN OUTCOME MEASURES: The total number of patients in Japan was estimated using the sampling and response rates in each stratum with respect to hospital size. The second survey was conducted for patients reported in the first survey in order to obtain detailed information, including age, sex, and specific clinical data. RESULTS: Estimated patient totals and 95% confidence intervals (CI) were 17 700 (95% CI 16 500 to 18 800) for dilated cardiomyopathy, 21 900 (95% CI 20 600 to 23 200) for hypertrophic cardiomyopathy, and 300 (95% CI 250 to 350) for restrictive cardiomyopathy. Crude prevalence per 100 000 population was estimated as 14.0 for dilated cardiomyopathy, 17.3 for hypertrophic cardiomyopathy, and 0.2 for restrictive cardiomyopathy; crude incidence per 100 000 person-years was estimated as 3.58, 4.14, and 0.06, respectively. CONCLUSIONS: The total number and prevalence of patients with idiopathic cardiomyopathy in Japan are estimated for the first time in a nationwide survey. The prevalence of dilated cardiomyopathy in Japan appears to be about half that of Western populations, while that of hypertrophic cardiomyopathy is about the same.

Neutralization of interleukin-1beta in the acute phase of myocardial infarction promotes the progression of left ventricular remodeling.

OBJECTIVES: We sought to examine the role of the pro-inflammatory cytokine, interleukin-1-beta (IL-1beta), in the process of left ventricular (LV) remodeling in the early phase after myocardial infarction (MI). BACKGROUND: Studies have shown that pro-inflammatory cytokines are closely related to the progression of LV remodeling after MI. METHODS: Mice underwent coronary artery ligation, and the time course of LV remodeling was followed up to 20 weeks. The gene expression level of IL-1beta was examined. In a second set of experiments, the mice underwent coronary artery ligation followed by treatment with anti-IL-1beta antibody (100 microg, intravenously), versus control immunoglobulin G (100 microg, intravenously) immediately after the operation. RESULTS: Rapid hypertrophy of noninfarcted myocardium was observed by four weeks, and interstitial fibrosis progressed steadily up to 20 weeks. Anti-IL-1beta treatment increased the occurrence of ventricular rupture and suppressed collagen accumulation in the infarct-related area. At four and eight weeks after the operation, total heart weight and LV end-diastolic dimension were significantly greater in the anti-IL-1beta-treated mice than in the other groups. In the infarct-related area, collagen accumulation was suppressed, whereas in the noninfarcted area, pro-collagen gene expression levels, particularly type III, were decreased in the anti-IL-1beta-treated mice. CONCLUSIONS: Anti-IL-1beta treatment suppressed pro-collagen gene expression and delayed wound healing mechanisms-properties that are likely to lead to progression of LV remodeling. In the acute phase of MI, IL-1beta appears to play a protective role.

Serial evaluation of fatty acid metabolism in rats with myocardial infarction by pinhole SPECT.

BACKGROUND: Iodine 123-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) is mainly trapped in the myocardium as triglyceride, depending on the adenosine triphosphate level. Ten percent to 20% of it is metabolized through alpha-oxidation after beta-oxidation; however, the precise mechanism of the regulatory pathways of BMIPP is yet to be clarified. METHODS AND RESULTS: A brief left coronary artery occlusion (10-30 minutes) was performed in 28 male Wistar-Kyoto rats. Dual single photon emission computed tomography images of BMIPP and thallium 201 were obtained 3 days and 24 days after the operation. The activities of 3-hydroxyacyl-coenzyme A dehydrogenase (HAD), citrate synthase (CS), and alpha-glycerol-phosphate dehydrogenase (GPD) were then measured in both ischemic and nonischemic regions. BMIPP and Tl-201 chloride severity scores were also evaluated conventionally. CS and HAD levels were significantly lower in the ischemic region than in the nonischemic region in the chronic group (CS, 102.9 +/- 28.1 vs 138.7 +/- 33.7 micromol/g/min, respectively, P =.0051; HAD, 54.7 +/- 20.1 vs 78.6 +/- 18.7 micromol/g/min, respectively, P =.0031). There was no difference in GPD between the ischemic and nonischemic regions. The BMIPP severity score had closer inverse relations with HAD (acute, r = -0.82; chronic, r = -0.80) and CS (acute, r = -0.87; chronic, r = -0.81), but not with GPD, than did Tl-201 chloride severity score. CONCLUSIONS: BMIPP imaging correlates well with the activities of HAD and CS, suggesting that a decrease in BMIPP uptake reflects deterioration of both fatty acid metabolism and citrate cycle and shows information other than regional myocardial perfusion.

Cytokine gene therapy for myocarditis by in vivo electroporation.

Cytokines are important pathophysiologic and pathogenic factors in cardiovascular disorders, including viral myocarditis. We attempted to treat viral myocarditis with cytokine gene therapy by transferring an inhibitory cytokine, IL-1 receptor antagonist (IL-1ra) or viral IL-10 (vIL-10), by in vivo electroporation, a new method for gene transfer into muscle. Four-week-old male DBA/2 mice were inoculated intraperitoneally with 10 PFU of encephalomyocarditis virus. Immediately after virus inoculation, an expression plasmid carrying IL-1ra or vIL-10 was injected into tibialis anterior muscles followed by electroporation. Serum levels of IL1ra and vIL-10 reached 10.5 and 2.3 ng/ml, respectively, on day 5, when gene expression reached its peak. Histopathological examination showed that myocardial cellular infiltration was improved in mice treated with IL-1ra or vIL-10 compared with the control group. On day 14 after the onset of myocarditis, transfer of IL1ra or vIL-10 expression plasmid had significantly improved the survival rates of the animals. The expression of TNF-alpha was decreased to 0.60-fold (p < 0.005) and inducible nitric oxide synthase (iNOS) 0.43-fold (p < 0.005) by IL-1ra treatment, and the expression of IFN-gamma in the heart was decreased to 0.35-fold (p < 0.05), and iNOS 0.21-fold (p < 0.005), by vIL-10 relative to the controls. These results show that gene therapy with IL-1ra or vIL-10 expression plasmid was effective in the treatment of viral myocarditis, and in vivo electroporation may be a useful method by which to deliver cytokine therapy in cardiovascular diseases.

ESDN, a novel neuropilin-like membrane protein cloned from vascular cells with the longest secretory signal sequence among eukaryotes, is up-regulated after vascular injury.

A novel cDNA has been isolated from primary culture of human coronary arterial cells by a signal sequence trap method, and designated ESDN (endothelial and smooth muscle cell-derived neuropilin-like molecule). ESDN is a type-I transmembrane protein with the longest cleavable secretory signal sequence among eukaryotes. ESDN contains a CUB domain and a coagulation factor V/VIII homology domain, which reminds us of the structure of neuropilins. ESDN also harbors an LCCL domain, which is shared by Limulus factor C and Coch. Mouse and rat counterparts were also identified revealing >84% amino acid identity with human ESDN. The human ESDN gene was mapped between D3S1552 and D3S1271. Northern blot analysis showed that ESDN mRNA was expressed in various tissues; particularly highly expressed in cultured vascular smooth muscle cells. The ESDN expression was up-regulated in platelet-derived growth factor-BB-stimulated vascular smooth muscle cells in vitro and neointima of the balloon-injured carotid artery in vivo. Overexpression of ESDN in 293T cells suppressed their bromodeoxyuridine uptake. In addition, ESDN protein was strongly expressed in nerve bundles in rodents. Thus, ESDN is considered to play a role in regulation of vascular cell growth and may have a wide variety of functions in other tissues including the nervous system, like neuropilins.

Proinflammatory cytokine inhibitor prolongs the survival of rats with heart failure induced by pressure overload.

Although an increased expression of proinflammatory cytokines has been reported in cardiac tissue samples from patients with congestive heart failure (CHF) and in various animal models of CHF, the role of these cytokines in the disease remains to be determined. Dahl salt-sensitive (DS) rats fed a high salt diet develop hypertension, cardiac hypertrophy and eventually CHF. In the present study, DS rats were treated with FR167653 (1-[7-(4-fluorophenyl)-1,2,3,4-tetrahydro-8-(4-pyridyl)pyrazolo[5,1-c][1,2,4]triazin-2-yl]-2-phenylethanedione sulfate monohydrate), a new low molecular weight inflammatory cytokine inhibitor. Treatment with 10 mg/kg per day of FR167653 significantly prolonged the survival of the animals and also prevented the bodyweight loss associated with heart failure. In conclusion, a non-peptide proinflammatory cytokine inhibitor improved the survival of animals with heart failure.

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.

The role of inflammatory mediators in the failing heart: immunomodulation of cytokines in experimental models of heart failure.

Congestive heart failure may be produced by a variety of disorders, including dilated cardiomyopathy, hypertension, and ischemic heart disease. We have developed experimental models of these diseases, and found gene expressions of proinflammatory cytokines increased in the hearts of these animals. Various drugs for heart failure modulate the production of cytokines in experimental models of heart failure. Pimobendan, an inhibitor of phosphodiesterase III prolonged survival, attenuated inflammatory lesions, and decreased the production of cytokines and nitric oxide. Recent studies have shown that these inhibitory effects are due to inhibition of activation of NF-kappaB. In contrast, digitalis increased the production of cytokines and exacerbated myocarditis. Interleukin-10 prolonged survival, attenuated myocardial injury, and appears promising as a treatment of heart failure due to viral myocarditis. Endothelin-1 plays an important pathophysiological role in heart failure, and treatment with an endothelin antagonist had a cardioprotective effect in experimental models of heart failure.

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.

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.