Akira Matsumori

Mutations in the Genes for Cardiac Troponin T and α-Tropomyosin in Hypertrophic Cardiomyopathy

BACKGROUND Familial hypertrophic cardiomyopathy can be caused by mutations in the genes for beta cardiac myosin heavy chain, alpha-tropomyosin, or cardiac troponin T. It is not known how often the disease is caused by mutations in the tropomyosin and troponin genes, and the associated clinical phenotypes have not been carefully studied. METHODS Linkage between polymorphisms of the alpha-tropomyosin gene or the cardiac troponin T gene and hypertrophic cardiomyopathy was assessed in 27 families. In addition, 100 probands were screened for mutations in the alpha-tropomyosin gene, and 26 were screened for mutations in the cardiac troponin T gene. Life expectancy, the incidence of sudden death, and the extent of left ventricular hypertrophy were compared in patients with different mutations. RESULTS Genetic analyses identified only one alpha-tropomyosin mutation, identical to one previously described. Five novel mutations in cardiac troponin were identified, as well as a further example of a previously described mutation. The clinical phenotype of four troponin T mutations in seven unrelated families was similar and was characterized by a poor prognosis (life expectancy, approximately 35 years) and a high incidence of sudden death. The mean (+/- SD) maximal thickness of the left ventricular wall in subjects with cardiac troponin T mutations (16.7 +/- 5.5 mm) was significantly less than that in subjects with beta cardiac myosin heavy-chain mutations (23.7 +/- 7.7 mm, P < 0.001). CONCLUSIONS Mutations in alpha-tropomyosin are a rare cause of familial hypertrophic cardiomyopathy, accounting for approximately 3 percent of cases. Mutations in cardiac troponin T account for approximately 15 percent of cases of familial hypertrophic cardiomyopathy in this referral-center population. These mutations are characterized by relatively mild and sometimes subclinical hypertrophy but a high incidence of sudden death. Genetic testing may therefore be especially important in this group.

Increased circulating cytokines in patients with myocarditis and cardiomyopathy.

OBJECTIVES--To elucidate the potential role of cytokines in the pathogenesis of cardiomyopathy and myocarditis. BACKGROUND--Experimental studies show that certain cytokines depress myocardial contractility and that tumour necrosis factor-alpha plays an important part in the pathogenesis of myocardial injury in animal models of viral and autoimmune myocarditis. METHODS--Plasma interleukin 1-alpha, interleukin 1-beta, interleukin-2, interleukin-6, tumour necrosis factor-alpha, tumour necrosis factor-beta, granulocyte-macrophage colony stimulating factor, granulocyte colony stimulating factor, macrophage colony stimulating factor, interferon-alpha and interferon-gamma were measured in 13 patients with acute myocarditis, 23 patients with dilated cardiomyopathy, 51 patients with hypertrophic cardiomyopathy, nine patients with acute myocardial infarction, 18 patients with angina pectoris, 12 patients with essential hypertension and 17 healthy controls. RESULTS--Increased concentrations of cytokines were not detected in the controls. In patients with acute myocarditis, interleukin 1-alpha was detected in 23% (mean (SD) 25 (11) pg/ml), tumour necrosis factor-alpha in 46% (61 (31) pg/ml), and macrophage colony stimulating factor was 2.5 (1.8) ng/ml (normal 1.9 (0.4)). In patients with dilated cardiomyopathy, tumour necrosis factor-alpha was detected in 35% (402 (555) pg/ml). In patients with hypertrophic cardiomyopathy, interleukin-2 was detectable in 14% (2318 (4738) pg/ml) and tumour necrosis factor-alpha ws detected in 20% (992 (1517) pg/ml). The concentration of macrophage colony stimulating factor was raised in patients with acute myocardial infarction. Granulocyte colony stimulating factor was often increased in myocarditis, cardiomyopathies, acute myocardial infarction, and angina pectoris--suggesting activation of macrophages and/or endothelial cells--but this increase was not specific to these diseases. Increased concentrations of cytokines were not found in patients with essential hypertension. CONCLUSION--These results suggest that cytokines may play a part in the pathogenesis of myocardial injury in myocarditis and cardiomyopathies and that further studies to explore the potential pathogenetic role of cytokines in myocardial diseases may be warranted.

Cytokine Gene Expression After Myocardial Infarction in Rat Hearts Possible Implication in Left Ventricular Remodeling

BACKGROUND A large transmural myocardial infarction may initiate structural and geometric changes in the left ventricle that are commonly referred to as remodeling. Progressive, adverse remodeling of the myocardium may lead to ventricular dilatation and congestive heart failure. Recent studies have highlighted the effects of some cytokines on immune-mediated myocyte injury, postischemic myocardial inflammation, and cardiac function. However, studies of the involvement of cytokines in remodeling of the heart are few. METHODS AND RESULTS In a rat model of myocardial infarction, progressive dilatation of the left ventricular cavity and lack of appropriate hypertrophy of the surviving myocardium were confirmed by transthoracic echocardiography. The relative expression of mRNA for tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 in the infarcted and noninfarcted myocardium of these rats, as well as in a group of sham-operated animals, was assessed by the technique of quantitative polymerase chain reaction amplification. In the infarcted region, TNF-alpha, IL-1beta, and IL-6 gene expression peaked at 1 week after infarction and decreased rapidly thereafter. In contrast, at 20 weeks after infarction, the gene expression levels of these cytokines remained significantly higher in the noninfarcted than in the infarcted zone or in the myocardium of sham-operated animals. Furthermore, the levels of these cytokines in the noninfarcted region correlated with the left ventricular end-diastolic diameter measured at 8 and 20 weeks after infarction. Among these cytokines, IL-1beta expression was highest, and its level correlated well with collagen deposition in the noninfarcted myocardium at 8 and 20 weeks after surgery. At 20 weeks after infarction, immunohistochemical analysis revealed the presence of IL-1beta in macrophages, endothelial cells, and vascular smooth muscle cells in the noninfarcted region, whereas no such immunoreactivity was found in the myocardium of sham-operated animals. CONCLUSIONS These findings suggest the possible involvement of cytokines during the remodeling process of the noninfarcted left ventricular myocardium.

Autoantibodies against cardiac troponin I are responsible for dilated cardiomyopathy in PD-1-deficient mice

We recently reported that mice deficient in the programmed cell death-1 (PD-1) immunoinhibitory coreceptor develop autoimmune dilated cardiomyopathy (DCM), with production of high-titer autoantibodies against a heart-specific, 30-kDa protein. In this study, we purified the 30-kDa protein from heart extract and identified it as cardiac troponin I (cTnI), encoded by a gene in which mutations can cause familial hypertrophic cardiomyopathy (HCM). Administration of monoclonal antibodies to cTnI induced dilatation and dysfunction of hearts in wild-type mice. Monoclonal antibodies to cTnI stained the surface of cardiomyocytes and augmented the voltage-dependent L-type Ca2+ current of normal cardiomyocytes. These findings suggest that antibodies to cTnI induce heart dysfunction and dilatation by chronic stimulation of Ca2+ influx in cardiomyocytes.

Anti–Monocyte Chemoattractant Protein-1/Monocyte Chemotactic and Activating Factor Antibody Inhibits Neointimal Hyperplasia in Injured Rat Carotid Arteries

Monocyte chemoattractant protein-1 (MCP-1)/monocyte chemotactic and activating factor (MCAF) has been suggested to promote atherogenesis. The effects of in vivo neutralization of MCP-1 in a rat model were examined in an effort to clarify the role of MCP-1 in the development of neointimal hyperplasia. Competitive polymerase chain reaction analysis revealed maximum MCP-1 mRNA expression at 4 hours after carotid arterial injury. Increased immunoreactivities of MCP-1 were also detected at 2 and 8 hours after injury. Either anti-MCP-1 antibody or nonimmunized goat IgG (10 mg/kg) was then administered every 12 hours to rats that had undergone carotid arterial injury. Treatment with 3 consecutive doses of anti-MCP-1 antibody within 24 hours (experiment 1) and every 12 hours for 5 days (experiment 2) significantly inhibited neointimal hyperplasia at day 14, resulting in a 27.8% reduction of the mean intima/media ratio (P<0.05) in experiment 1 and a 43.6% reduction (P<0.01) in experiment 2. This effect was still apparent at day 56 (55.6% inhibition; P<0.05). The number of vascular smooth muscle cells in the neointima at day 4 was significantly reduced by anti-MCP-1 treatment, demonstrating the important role of MCP-1 in early neointimal lesion formation. However, recombinant MCP-1 did not stimulate chemotaxis of vascular smooth muscle cells in an in vitro migration assay. These results suggest that MCP-1 promotes neointimal hyperplasia in early neointimal lesion formation and that neutralization of MCP-1 before, and immediately after, arterial injury may be effective in preventing restenosis after angioplasty. Further studies are needed to clarify the mechanism underlying the promotion of neointimal hyperplasia by MCP-1.

Enhanced Expression of Hepatocyte Growth Factor/c-Met by Myocardial Ischemia and Reperfusion in a Rat Model

Background Hepatocyte growth factor (HGF) is a multifunctional factor implicated in tissue regeneration, wound healing, and angiogenesis. Circulating HGF is reportedly elevated during the early stage of myocardial infarction. However, its precise effect on the heart is unknown. To evaluate the regulation of HGF in ischemically damaged myocardium, the production of HGF and its high-affinity receptor, c-Met, was studied in a rat model of myocardial ischemia and reperfusion. Methods and Results The plasma concentration of HGF began to increase within 1 hour of reperfusion after 1 hour of ischemia. The peak level was reached at 3 hours after reperfusion. Northern blotting revealed that HGF mRNA expression in the heart was augmented threefold at 24 and 48 hours and remained elevated by twofold at 120 hours after the myocardium was reperfused. The signal for c-met , high-affinity HGF receptor mRNA, was also upregulated parallel to upregulation for HGF. In the kidney, liver, lung, and spleen, HGF mRNA was also m...

Increased Expression of Interleukin-1β and Monocyte Chemotactic and Activating Factor/Monocyte Chemoattractant Protein-1 in the Hypertrophied and Failing Heart With Pressure Overload

Studies on the effects of proinflammatory cytokines on the heart suggest that they play some roles in the pathogenesis of congestive heart failure (CHF). To determine the involvement of proinflammatory cytokine in cardiac hypertrophy and CHF induced by mechanical overload, we investigated the expression of interleukin (IL)-1 beta and monocyte chemotactic and activating factor (MCAF)/monocyte chemoattractant protein-1 (MCP-1) in the left ventricle (LV) of Dahl salt-sensitive (DS) rats that showed hypertrophy of the LV induced by hypertension and subsequently developed CHF. The IL-1 beta mRNA content in the LV of DS rats increased 3.9-fold when LV hypertrophy developed, and the increase reached 6.2-fold at the CHF stage compared with that of age-matched Dahl salt-resistant (DR) rats. The amount of IL-1 beta in the LV was positively correlated with the LV weight/body weight ratio. Most of the IL-1 beta immunoreactivity was localized in the endothelial cells and interstitial macrophages. The mRNA levels of MCAF in the LV increased 3.6-fold at 11 weeks and reached 4.8-fold at the CHF stage relative to the age-matched DR rats. MCAF protein was localized to the endothelial cells and interstitial macrophages. In DS rats, the number of interstitial macrophages increased diffusely throughout the LV. We suggest that increased chemokine expression, macrophage infiltration, and proinflammatory cytokine expression play some role in the pathogenesis of cardiac hypertrophy and failure induced by chronic mechanical overload.

Persistent expression of cytokine in the chronic stage of viral myocarditis in mice

BACKGROUND Dilated cardiomyopathy (DCM) is one of the most frequent causes of heart failure of unknown origin. One possible cause of DCM is considered to be a sequel to myocarditis. However, the mechanism of progression from viral myocarditis to DCM is still not clear. METHODS AND RESULTS The expression of the immunoregulatory cytokines interferon (IFN)-gamma and interleukin (IL)-2 and the proinflammatory cytokines IL-1 beta and tumor necrosis factor (TNF)-alpha in the heart tissue was studied in a murine model of postmyocarditis DCM induced by encephalomyocarditis virus. IFN-gamma, IL-1 beta, and TNF-alpha mRNA increased 3 days after virus inoculation. IL-2 mRNA was detectable 7 days after inoculation. The peak expression of all cytokine genes examined was seen 7 days after inoculation. The expression of these cytokine genes decreased thereafter but persisted 80 days after inoculation. IL-1 beta gene expression in the chronic stage was relatively high compared with other cytokines and was correlated with the ratio of heart weight to body weight and the extent of fibrotic lesions. Immunohistochemical analysis revealed that some of the mononuclear cells, endothelial cells, and interstitial macrophages were positive for IL-1 beta or TNF-alpha and fibroblasts were positive for IL-1 beta in the heart tissue of mice 80 days after inoculation. CONCLUSIONS Persistent expression of cytokines was seen in a murine model of postmyocarditis DCM. These cytokines may have important implications in the pathogenesis of DCM.

DANCE, a novel secreted RGD protein expressed in developing, atherosclerotic, and balloon-injured arteries.

We have identified and characterized mouse, rat, and human cDNAs that encode a novel secreted protein of 448 amino acids named DANCE (developmental arteries andneural crest epidermal growth factor (EGF)-like). DANCE contains six calcium-binding EGF-like domains, one of which includes an RGD motif. Overexpression studies of recombinant DANCE protein document that DANCE is a secreted 66-kDa protein. DANCE and recently described protein S1–5 comprise a new EGF-like protein family. The human DANCE gene was mapped at chromosome 14q32.1. DANCE mRNA is mainly expressed in heart, ovary, and colon in adult human tissues. Expression profile analysis byin situ hybridization revealed prominent DANCE expression in developing arteries. DANCE is also expressed in neural crest cell derivatives, endocardial cushion tissue, and several other mesenchymal tissues. In adult vessels, DANCE expression is largely diminished but is reinduced in balloon-injured vessels and atherosclerotic lesions, notably in intimal vascular smooth muscle cells and endothelial cells that lose their ability to proliferate in late stage of injury. DANCE protein was shown to promote adhesion of endothelial cells through interaction of integrins and the RGD motif of DANCE. DANCE is thus a novel vascular ligand for integrin receptors and may play a role in vascular development and remodeling.

Dilated Cardiomyopathy Associated With Hepatitis C Virus Infection

BACKGROUND Myocarditis is thought to be commonly caused by various viruses, and accumulating evidence links viral myocarditis with the eventual development of dilated cardiomyopathy. In many cases, however, the evidence is only circumstantial, and direct conclusive proof is not available. Polymerase chain reaction (PCR) has been used to detect enterovirus RNA in myocardial tissue, but the wide discrepancy in results emphasizes the need for further study. METHODS AND RESULTS We investigated hepatitis C virus infection in patients with dilated cardiomyopathy. The presence, type, and quantity of hepatitis C virus RNA were evaluated in the sera, and the presence of positive and negative strands of hepatitis C virus RNA in the heart was investigated with the PCR technique. Anti-hepatitis C virus antibody was present in the sera of 6 of 36 patients (16.7%) with dilated cardiomyopathy and in 1 of 40 patients (2.5%) with ischemic heart disease, showing a statistically significant (P < .05) difference. At an earlier time, acute myocarditis was suspected in 3 patients who had developed acute onset of heart failure, and the diagnosis was confirmed by endomyocardial biopsy in 1 patient. Hepatitis C virus RNA was present in the sera of 4 of the 6 patients, and all 4 had hepatitis C virus type II. The copy number of hepatitis C virus RNA in the serum was 8 x 10(2) to 2 x 10(3) genomes per 1 mL serum. Positive strands of hepatitis C virus were found in the hearts of 3 patients, and negative strands of hepatitis C virus were detected in the heart of 1 patient. CONCLUSIONS The results suggest that hepatitis C virus infection is frequently found in patients with dilated cardiomyopathy and that hepatitis C virus is an important causal agent in the pathogenesis of the disease. Antiviral therapy against hepatitis C virus may be indicated in these patients.