Masaharu Okada

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.

Cyclic Stretch Upregulates Production of Interleukin-8 and Monocyte Chemotactic and Activating Factor/Monocyte Chemoattractant Protein-1 in Human Endothelial Cells

In vivo, vascular walls are exposed to mechanical stretch, which may promote atherogenesis. This study was designed to investigate the effect of mechanical stretch on the production and gene expression of cytokines in endothelial cells (ECs) of human umbilical veins. ECs were cultured on flexible silicone membranes and exposed to cyclic mechanical stretch. Although the secretion levels of interleukin (IL)-1beta, tumor necrosis factor-alpha, IL-6, granulocyte (G) -colony stimulating factor (CSF), G and macrophage (M) -CSF, and M-CSF were not affected by cyclic stretch over 24 hours, the levels of IL-8 and monocyte chemotactic and activating factor (MCAF)/monocyte chemoattractant protein-1 (MCP-1) were significantly increased by cyclic stretch. Northern blot analysis indicated that the mRNA levels of IL-8 and MCAF/MCP-1 were upregulated by cyclic stretch as a function of its intensity. Cytochalasin D, which disrupts the actin cytoskeleton, abolished the stretch-induced gene expression of IL-8 and MCAF/MCP-1. In contrast, neither inhibition of stretch-activated ion channels nor disruption of microtubules affected the induction of these chemokines by cyclic stretch. Northern blot analysis using enzyme inhibitors showed that phospholipase C, protein kinase C, and tyrosine kinase were involved in the stretch-induced gene expression of IL-8 and MCAF/MCP-1, whereas cAMP- or cGMP-dependent protein kinase was not. In conclusion, cyclic stretch enhanced the secretion and gene expression of IL-8 and MCAF/MCP-1 in a stretch-dependent fashion, and the integrity of the actin cytoskeleton and activities of phospholipase C, protein kinase C, and tyrosine kinase may be essential in the process of stretch-induced gene induction of IL-8 and MCAF/MCP-1.

Long-Term (>10 Years) Clinical Outcomes of First-in-Human Biodegradable Poly-l-Lactic Acid Coronary Stents Igaki-Tamai Stents

Background— The purpose of this study was to evaluate the long-term safety of the Igaki-Tamai stent, the first-in-human fully biodegradable coronary stent made of poly-l-lactic acid. Methods and Results— Between September 1998 and April 2000, 50 patients with 63 lesions were treated electively with 84 Igaki-Tamai stents. Overall clinical follow-up (>10 years) of major adverse cardiac events and rates of scaffold thrombosis was analyzed together with the results of angiography and intravascular ultrasound. Major adverse cardiac events included all-cause death, nonfatal myocardial infarction, and target lesion revascularization/target vessel revascularization. During the overall clinical follow-up period (121±17 months), 2 patients were lost to follow-up. There were 1 cardiac death, 6 noncardiac deaths, and 4 myocardial infarctions. Survival rates free of all-cause death, cardiac death, and major adverse cardiac events at 10 years were 87%, 98%, and 50%, respectively. The cumulative rates of target lesion revascularization (target vessel revascularization) were 16% (16%) at 1 year, 18% (22%) at 5 years, and 28% (38%) at 10 years. Two definite scaffold thromboses (1 subacute, 1 very late) were recorded. The latter case was related to a sirolimus-eluting stent, which was implanted for a lesion proximal to an Igaki-Tamai stent. From the analysis of intravascular ultrasound data, the stent struts mostly disappeared within 3 years. The external elastic membrane area and stent area did not change. Conclusion— Acceptable major adverse cardiac events and scaffold thrombosis rates without stent recoil and vessel remodeling suggested the long-term safety of the Igaki-Tamai stent.

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.

Role of p38 Mitogen-Activated Protein Kinase in Neointimal Hyperplasia After Vascular Injury

Abstract—p38 mitogen-activated protein kinase (MAPK) is involved in intracellular signals that regulate a variety of cellular responses during inflammation. However, the role of p38 MAPK in atherosclerosis, a chronic inflammatory disorder, remains uncertain. The aim of the present study was to examine the role of p38 MAPK in the development of neointimal hyperplasia in balloon-injured rat carotid arteries. Immunohistochemical studies indicated that p38 MAPK was rapidly activated in the majority of medial cells in injured arterial walls. Rats treated with FR167653, a selective inhibitor of p38 MAPK, at a dosage of 10 mg · kg–1 · d–1, had a 29.4% lower intima-to-media ratio than the untreated controls at 14 days after balloon injury (P <0.05). The percentage of proliferating nuclear antigen–positive cells in the media at 48 hours was significantly lower in the FR167653-treated group than in the control group. Quantitative competitive reverse transcription–polymerase chain reaction analysis revealed that interleukin-1&bgr; mRNA expression in arteries was significantly inhibited by FR167653 (to 18.1% of control, P <0.05) at 8 hours after balloon injury. Moreover, p38 MAPK activation and interleukin-1&bgr; production by lipopolysaccharide-stimulated vascular smooth muscle cells were inhibited by FR167653 in a concentration-dependent manner in vitro. These results indicate that p38 MAPK is activated in vascular walls after injury and promotes neointimal formation and suggest that selective inhibition of p38 MAPK may be effective in the prevention of restenosis after percutaneous transluminal coronary angioplasty.

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.

Histopathological findings of new in‐stent lesions developed beyond five years

We analyzed 14 cases of new lesions inside implanted bare‐metal stents. In every case, there was no angiographic restenosis within 3 years, but a new lesion was observed inside a stented segment at long‐term follow‐up (>5 years). Fourteen cases were evaluated: 9 with Wiktor stents, 2 with Palmaz‐Schatz stents, and 3 with ACS Multilink stents. The interval from stent implantation to follow‐up angiography was 63–147 months (89 ± 23). Thirteen lesions were treated by percutaneous coronary intervention (PCI) and stenotic tissue was obtained by directional coronary atherectomy (DCA) in 10 cases. All retrieved samples were composed of newly developed atherosclerosis facing the healed neointimal layer, and four samples showed histopathological findings of acute coronary syndrome. Stent struts were retrieved in four cases and no inflammation was observed surrounding them. Qualitative and quantitative analysis of stent struts was performed in two cases that showed no metal corrosion. These findings suggest that new atherosclerotic progression occurred inside the implanted stent without peristrut inflammation.

New technique for superior guiding catheter support during advancement of a balloon in coronary angioplasty: The anchor technique

To get superior guiding catheter support, we tried a new method called the anchor technique. By inflating a balloon in a nontarget vessel and holding its shaft with backward force while advancing another balloon, the anchor effect for the guiding catheter could be obtained and it appeared to be helpful for a balloon or a stent to cross the target lesion. Cathet Cardiovasc Intervent 2003;59:482–488.

Pimobendan inhibits the production of proinflammatory cytokines and gene expression of inducible nitric oxide synthase in a murine model of viral myocarditis.

OBJECTIVES This study was designed to examine the effects of pimobendan in a murine model of viral myocarditis in relation to proinflammatory cytokine production and nitric oxide (NO) synthesis by inducible NO synthase (iNOS) in the heart. BACKGROUND Pimobendan has been recently confirmed to improve both acute and chronic heart failure. Since the modulation of myocardial necrosis and contractile dysfunction by various proinflammatory cytokines may be partially mediated by the production of nitric oxide, the effects of pimobendan on the production ofproinflammatory cytokines and NO were investigated in an animal model of viral myocarditis involving heart failure. METHODS DBA/2 mice were inoculated with the encephalomyocarditis virus. To observe its effect on survival up to 14 days, pimobendan (0.1 mg/kg or 1 mg/kg) or vehicles were given from the day of virus inoculation (day 0) orally once daily. The effects of pimobendan on histological changes, cytokine production, NO production and iNOS gene expression in the heart were studied in mice treated either with pimobendan, 1 mg/kg or with vehicles only, and sacrificed seven days after virus inoculation. RESULTS The survival of mice improved in a dose-dependent fashion such that a significant difference (p < 0.02) was found between the higher-dose pimobendan group (20 of 30 [66.7%]) and the control group (11 of 30 [36.7%]). Histological scores for cellular infiltration (1.1+/-0.1 vs. 2.0+/-0.0, p < 0.001), intracardiac tumor necrosis factor (TNF)-alpha (18.2+/-1.8 vs. 35.8+/-4.2 pg/mg heart, p < 0.001) and interleukin (IL)-1beta (9.3 +/-1.2 vs. 26.6+/-7.1 pg/mg heart, p < 0.01) were significantly lower in the mice given pimobendan versus those of the control mice. Interleukin-6 levels (7.1+/-0.8 vs. 9.2+/-1.9 pg/mg heart) were also lower in the mice treated with pimobendan. Furthermore, intracardiac NO production was significantly (p < 0.001) less in the pimobendan group (0.165+/-0.004 nmol/mg heart) than in the control group (0.291+/-0.051 nmol/mg heart), and intracardiac iNOS gene expression in the mice given pimobendan was 74% lower than it was in the control animals (p < 0.01). CONCLUSIONS These findings suggest that the beneficial effects of pimobendan in viral myocarditis are partially mediated by the inhibition of both proinflammatory cytokine production and NO synthesis by iNOS.