Masatake Hara

Evidence for a Role of Mast Cells in the Evolution to Congestive Heart Failure

Mast cells are believed to be involved in the pathophysiology of heart failure, but their precise role in the process is unknown. This study examined the role of mast cells in the progression of heart failure, using mast cell-deficient (WBB6F1-W/Wv) mice and their congenic controls (wild-type [WT] mice). Systolic pressure overload was produced by banding of the abdominal aorta, and cardiac function was monitored over 15 wk. At 4 wk after aortic constriction, cardiac hypertrophy with preserved left ventricular performance (compensated hypertrophy) was observed in both W/Wv and WT mice. Thereafter, left ventricular performance gradually decreased in WT mice, and pulmonary congestion became apparent at 15 wk (decompensated hypertrophy). In contrast, decompensation of cardiac function did not occur in W/Wv mice; left ventricular performance was preserved throughout, and pulmonary congestion was not observed. Perivascular fibrosis and upregulation of mast cell chymase were all less apparent in W/Wv mice. Treatment with tranilast, a mast cell–stabilizing agent, also prevented the evolution from compensated hypertrophy to heart failure. These observations suggest that mast cells play a critical role in the progression of heart failure. Stabilization of mast cells may represent a new approach in the management of heart failure.

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

Abstract OBJECTIVES We sought to examine the role of the pro-inflammatory cytokine, interleukin-1-beta (IL-1β), 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-1β was examined. In a second set of experiments, the mice underwent coronary artery ligation followed by treatment with anti–IL-1β antibody (100 μg, intravenously), versus control immunoglobulin G (100 μg, 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-1β 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-1β-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-1β-treated mice. CONCLUSIONS Anti–IL-1β 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-1β appears to play a protective role.

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.

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.

Mast Cell Tryptase in Mast Cell Granules Enhances MCP-1 and Interleukin-8 Production in Human Endothelial Cells

Objective—Recent studies have highlighted the pathogenetic importance of chronic inflammation in cardiovascular disorders such as congestive heart failure and atherosclerosis. Mast cells release a wide variety of immune mediators that may initiate inflammatory responses, whereas endothelial cells (ECs) play a prominent role in the pathogenesis of cardiovascular diseases by secreting cytokines. The purpose of this study was to clarify the role of mast cells as an activator of ECs. Methods and Results—ECs harvested from human umbilical cord veins were stimulated with mast cell granules (MCGs) prepared from sonicated human leukemic mast cells. The supernatants and total RNA from cells were collected. Levels of interleukin (IL)-1β, tumor necrosis factor-α, and granulocyte colony-stimulating factor remained unchanged up to 24 hours. In contrast, levels of monocyte chemoattractant protein-1 (MCP-1) and IL-8 increased significantly within 6 hours. Northern blot analysis revealed an increase in MCP-1 and IL-8 mRNA expression in MCG-treated ECs. Induction of these chemokines was attenuated by antitryptase neutralizing antibody. Furthermore, MCP-1 and IL-8 were induced in ECs by incubation with human mast cell tryptase, but not with chymase. Conclusions—These results indicate that the production of MCP-1 and IL-8 in ECs was induced by MCG and amplified by tryptase.

Mast Cells Play a Critical Role in the Pathogenesis of Viral Myocarditis

Background— Mast cells are powerful producers of multiple cytokines and chemical mediators playing a pivotal role in the pathogenesis of various cardiovascular diseases. We examined the role of mast cells in murine models of heart failure due to viral myocarditis, using 2 strains of mast cell–deficient mice. Methods and Results— Two strains of mast cell–deficient mice, WBB6F1-KitW/KitW-v (W/WV) and WCB6F1-KitlSl/KitlSl-d (Sl/Sld), were inoculated with 10 plaque-forming units of the encephalomyocarditis virus intraperitoneally. On day 14 after inoculation, survival of W/WV mice was significantly higher than that of their control littermates (77% versus 31%; P=0.03; n=13). On histological examination on day 7, myocardial necrosis and cellular infiltration were significantly less pronounced in W/WV and Sl/Sld mice than in their control littermates (area of infiltration, 7.6±3.5% versus 29.3±15.6%; P=0.002; area of necrosis, 7.6±3.5% versus 30.0±17.2%; P=0.003; n=10). Histological examination showed more severe changes in mast cell–reconstituted than in –nonreconstituted W/WV and Sl/Sld mice. The gene expressions of mast cell proteases were upregulated in the acute phase of viral myocarditis and rose further in the subacute phase of heart failure. Their activation coincided with the development of myocardial necrosis and fibrosis and correlated with the upregulation of gene expression of matrix metalloproteinase-9. The histamine H1-receptor antagonist bepotastine improved encephalomyocarditis viral myocarditis. Conclusions— These observations suggest that mast cells participate in the acute inflammatory reaction and the onset of ventricular remodeling associated with acute viral myocarditis and that the inhibition of their function may be therapeutic in this disease.

Suppression of cytokines and nitric oxide production, and protection against lethal endotoxemia and viral myocarditis by a new NF-κB inhibitor

Nuclear factor kappa B (NF‐κB) is activated by several factors, which increase the inflammatory response, and this activation, in turn, leads to the expression of several genes such as cytokines, and may play an important role in cardiovascular diseases.

Preformed angiotensin II is present in human mast cells.

SummaryPurpose The density of mast cells increases in the myocardium of patients suffering from heart failure. However, their function remains unclear. In this study, preformed angiotensin II (ANG II), a potent growth factor, was found to be contained in, and released by, human mast cells.Methods: The human mast cell line (HMC-1) was incubated with 0 to 10−6 M calcitonin gene-related peptide (CGRP) or culture medium. The expression of renin-angiotensin system mRNA was examined using RT-PCR analysis. ELISA and immunohistochemistry with monoclonal antibody against human ANG II were performed to detect the presence of ANG II in HMC-1. The effect of CGRP on the expression of angiotensinogen mRNA was examined by quantitative RT-PCR analysis.Results: Preformed ANG II was detected in a human mast cell line (HMC-1) which is a neoplastic cell line of mast cells by ELISA and immunohistochemistry. Presence of mRNA of angiotensinogen and renin was confirmed by polymerase chain reaction in HMC-1, while mRNA of angiotensin converting enzyme (ACE) was undetectable. Since myocardial mast cells are interfaced with nerve fibers and functionally associated with CGRP, the effect of CGRP on ANG II release from HMC-1 was examined. CGRP induced the release of ANG II and increased angiotensinogen mRNA in HMC-1.Conclusions The presence of preformed ANG II and gene expression of the renin-angiotensin system were detected in human mast cells. The release and synthesis of ANG II in mast cells was regulated by CGRP.

The Key Role of Mast Cells in the Evolution to Congestive Heart Failure

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 disorders are unknown. To clarify the roles of mast cells, cultured cardiomyocytes from neonatal rats were incubated with mast cell granules (MCGs) for 24 h. We found that mast cells cause apoptosis of cardiomyocytes and proliferation of other intramyocardial cells. These observations suggest that mast cell chymase plays a role in the progression of heart failure, since loss of cardiomyocytes and proliferation of non-myocardial cells both amplify its pathophysiology. Therefore, we examined the role of mast cells in the progression of heart failure, using mast cell-deficient WBB6F1-W/Wv mice and their congenic contorls (WT mice). Systolic pressure overload was produced by banding of the abdominal aorta, and cardiac function was monitored by serial echocardiography over 15 weeks. Left ventricular performance gradually decreased in WT mice, and pulmonary congestion became apparent at 15 weeks (decompensated hypertrophy). In contrast, decompensation of cardiac function did not occur in W/Wv mice; left ventricular performance was preserved thoughout, and pulmonary congestion was not observed. Perivascular fibrosis and upregulation of mast cell chymase were all less apparent in W/Wv mice. Treatment with tranilast, a mast cell-stabilizing agent, also prevented the evolution from compensated hypertrophy to heart failure. These observations suggest that mast cells playa critical role in the progression of heart failure. Stabilization of mast cells may represent a new approach in the management of heart failure.