Minoru Hongo

Inflammasome Activation of Cardiac Fibroblasts Is Essential for Myocardial Ischemia/Reperfusion Injury

Background— Inflammation plays a key role in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury; however, the mechanism by which myocardial I/R induces inflammation remains unclear. Recent evidence indicates that a sterile inflammatory response triggered by tissue damage is mediated through a multiple-protein complex called the inflammasome. Therefore, we hypothesized that the inflammasome is an initial sensor for danger signal(s) in myocardial I/R injury. Methods and Results— We demonstrate that inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, is crucially involved in the initial inflammatory response after myocardial I/R injury. We found that inflammasomes are formed by I/R and that its subsequent activation of inflammasomes leads to interleukin-1&bgr; production, resulting in inflammatory responses such as inflammatory cell infiltration and cytokine expression in the heart. In mice deficient for apoptosis-associated speck-like adaptor protein and caspase-1, these inflammatory responses and subsequent injuries, including infarct development and myocardial fibrosis and dysfunction, were markedly diminished. Bone marrow transplantation experiments with apoptosis-associated speck-like adaptor protein–deficient mice revealed that inflammasome activation in bone marrow cells and myocardial resident cells such as cardiomyocytes or cardiac fibroblasts plays an important role in myocardial I/R injury. In vitro experiments revealed that hypoxia/reoxygenation stimulated inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, and that hypoxia/reoxygenation–induced activation was mediated through reactive oxygen species production and potassium efflux. Conclusions— Our results demonstrate the molecular basis for the initial inflammatory response after I/R and suggest that the inflammasome is a potential novel therapeutic target for preventing myocardial I/R injury.

Human amniotic mesenchymal cells have some characteristics of cardiomyocytes

Background. Cellular cardiomyoplasty (CCM) is a major method for the treatment of heart failure because adult cardiomyocytes do not regenerate after ischemic injury, which results in heart failure. There is a great deal of interest in finding suitable new cell sources for use in CCM. Here, we report that human amniotic mesenchymal cells (hAMC), which are multipotent cells derived from fetal mesoderm, may be a suitable cell source for CCM. Methods. Freshly isolated hAMC were examined to detect the expression of cardiac-specific genes by reverse-transcription polymerase chain reaction and immunocytochemistry. hAMC were cocultivated with neonatal rat heart explants and transplanted into myocardial infarcts in the rat heart. Results. hAMC expressed cardiac-specific transcription factor GATA4, cardiac-specific genes, such as myosin light chain (MLC)-2a, MLC-2v, cTnI, and cTnT, and the &agr;-subunits of the cardiac-specific L-type calcium channel (&agr;1c) and the transient outward potassium channel (Kv4.3). After stimulation with basic fibroblast growth factor (bFGF) or activin A, hAMC expressed Nkx2.5, a specific transcription factor for the cardiomyocyte and cardiac-specific marker atrial natriuretic peptide. In addition, the cardiac-specific gene &agr;-myosin heavy chain was detected after treatment with activin A. Coculture experiments confirmed that hAMC were able to both integrate into cardiac tissues and differentiate into cardiomyocyte-like cells. After transplantation into the myocardial infarcts in rat hearts, hAMC survived in the scar tissue for at least 2 months and differentiated into cardiomyocyte-like cells. Conclusion. The results of the present study suggest that hAMC possess some characteristics of cardiomyocytes.

Cardiac Overexpression of Monocyte Chemoattractant Protein-1 in Transgenic Mice Prevents Cardiac Dysfunction and Remodeling After Myocardial Infarction

Myocardial infarction (MI) is accompanied by inflammatory responses that lead to the recruitment of leukocytes and subsequent myocardial damage, healing, and scar formation. Because monocyte chemoattractant protein-1 (MCP-1) (also known as CCL2) regulates monocytic inflammatory responses, we investigated the effect of cardiac MCP-1 overexpression on left ventricular (LV) dysfunction and remodeling in a murine MI model. Transgenic mice expressing the mouse JE-MCP-1 gene under the control of the α-cardiac myosin heavy chain promoter (MHC/MCP-1 mice) were used for this purpose. MHC/MCP-1 mice had reduced infarct area and scar formation and improved LV dysfunction after MI. These mice also showed induction of macrophage infiltration and neovascularization; however, few bone marrow-derived endothelial cells were detected in MHC/MCP-1 mice whose bone marrow was replaced with that of Tie2/LacZ transgenic mice. Flow cytometry analysis showed no increase in endothelial progenitor cells (CD34+/Flk-1+ cells) in MHC/MCP-1 mice. Marked myocardial interleukin (IL)-6 secretion, STAT3 activation, and LV hypertrophy were observed after MI in MHC/MCP-1 mice. Furthermore, cardiac myofibroblasts accumulated after MI in MHC/MCP-1 mice. In vitro experiments revealed that a combination of IL-6 with MCP-1 synergistically stimulated and sustained STAT3 activation in cardiomyocytes. MCP-1, IL-6, and hypoxia directly promoted the differentiation of cardiac fibroblasts into myofibroblasts. Our results suggest that cardiac overexpression of MCP-1 induced macrophage infiltration, neovascularization, myocardial IL-6 secretion, and accumulation of cardiac myofibroblasts, thereby resulting in the prevention of LV dysfunction and remodeling after MI. They also provide a new insight into the role of cardiac MCP-1 in the pathophysiology of MI.

Progressive cardiac dysfunction and fibrosis in the cardiomyopathic hamster and effects of growth hormone and angiotensin-converting enzyme inhibition.

BACKGROUND Growth hormone (GH) improves cardiac function in the rat with myocardial infarction, but its effects in a model of primary dilated cardiomyopathy have not been reported. GH effects were examined at early (4 months) and late (10 months) phases of disease in the cardiomyopathic (CM) hamster, and the combination of GH with chronic ACE inhibition was assessed in late-phase heart failure. METHODS AND RESULTS CM hamsters (CHF 147 line) at 4 months showed severe systolic left ventricular (LV) dysfunction with normal LV filling pressure, and at 10 months there was more severe systolic as well as diastolic dysfunction with increasing myocardial fibrosis. Recombinant human GH alone for 3 weeks at age 4 months increased LV wall thickness and reduced systolic wall stress without altering diastolic wall stress, whereas at 10 months, wall stress and fractional shortening did not improve. The LV dP/dt(max) was enhanced at both ages by GH, which at 4 months reflected increased contractility, but at 10 months was most likely caused by elevation of the LV filling pressure. The increasing degree of fibrosis correlated inversely with LV function but was unaffected by GH. In other CM hamsters, high-dose ACE inhibition alone (quinapril), started at 8 months and continued for 11 weeks, improved LV function and inhibited unfavorable remodeling, but the addition of GH for 3 weeks at age 10 months produced increased wall thickness with little additional functional benefit and increased the LV filling pressure and diastolic wall stress. CONCLUSIONS GH treatment alone improved LV dysfunction at 4 months of age in CM hamsters by increasing contractility and reducing wall stress but had few beneficial effects at 10 months in severe LV failure. After chronic ACE inhibition, addition of GH at 10 months had no additional beneficial effects and further increased LV diastolic pressure. These differing effects of GH may relate to the progressive increase of LV fibrosis in the CM hamster.

Iodine-123 Metaiodobenzylguanidine Scintigraphic Assessment of Myocardial Sympathetic Innervation in Patients With Familial Amyloid Polyneuropathy☆

OBJECTIVES This study attempted to assess myocardial sympathetic innervation using iodine-123 (I-123) metaidobenzylguanidine (MIBG) imaging in patients with familial amyloid polyneuropathy. BACKGROUND Signs and symptoms of cardiac autonomic dysfunction are commonly seen in patients with cardiac amyloidosis. However, the incidence and magnitude of abnormalities in myocardial sympathetic nerve function by means of I-123 MIBG imaging and their relation to clinical findings, cardiac function and the results of thallium-201 (Tl-201) and technetium-99m pyrophosphate (Tc-99m PYP) myocardial scanning have not yet been clarified. METHODS We performed M-mode, two-dimensional and Doppler echocardiography and I-123 MIBG, Tl-201 and Tc-99m PYP imaging of the heart in 12 patients with familial amyloid polyneuropathy and biopsy-proved cardiac amyloidosis. RESULTS Ten of 12 patients had no clinical evidence of overt heart disease, but left ventricular (LV) wall thickening was observed in 4 of these 10. Left ventricular percent fractional shortening and Doppler transmitral flow velocity patterns were found to be normal in all 12 patients. Eight of 12 patients showed no myocardial MIBG accumulation, with limited uptake in the remaining 4 demonstrated only in the LV anterior wall. Diffuse but mild myocardial uptake of Tc-99m PYP occurred in only 4 of 12 patients, and all 12 had normal results on Tl-201 myocardial scanning. Complete defects on myocardial MIBG scans were found in five of eight patients with negative findings on Tc-99m PYP myocardial scanning. The incidence and magnitude of myocardial uptake of MIBG were independent of clinical findings, extent of endomyocardial amyloid deposition, electrocardiographic QRS voltage and ventricular wall thickness. CONCLUSIONS Patients with familial amyloid polyneuropathy show a high incidence of myocardial adrenergic denervation with viable myocardium that can be identified very early in cardiac amyloidosis, before the development of clinically apparent heart disease, ventricular wall thickening, significant LV systolic and diastolic dysfunction and positive findings on Tc-99m PYP myocardial scanning.

Coronary microvascular response to intracoronary administration of nicorandil

Nicorandil is an antianginal drug that causes potent coronary vasodilation of both epicardial and resistance vessels. To measure the dose-response kinetics of bolus injections of intracoronary nicorandil and to compare the vasodilatory response to nicorandil with that of intracoronary papaverine in humans, coronary blood flow velocity was measured in 30 patients using a 3Fr intravascular Doppler catheter. Continuous intravenous nitroglycerin 6 to 8 micrograms/min was infused to achieve maximal vasodilation of the epicardial vessels. Bolus doses of nicorandil dissolved in warmed saline solution were injected into the left (0.1, 0.2, 0.5, 1.0, 1.5, and 2.0 mg) and right (0.1, 0.2, 0.4, 0.8, 1.0, and 1.5 mg) coronary arteries. Intracoronary nicorandil caused a dose-dependent increase in coronary flow velocity and a decrease in coronary vascular resistance. Maximal vasodilatory effects equivalent to those obtained with 12 +/- 2 mg of intracoronary papaverine were induced with nicorandil 1.5 mg in the left coronary artery, and effects similar to those of 10 +/- 2 mg of papaverine were produced with nicorandil 1.0 mg in the right coronary artery. The time from injection of nicorandil to the onset of maximal hyperemia and duration of hyperemia were significantly shorter after nicorandil than after papaverine in both coronary arteries. Each dose of nicorandil produced no clinical symptoms and fewer changes in systemic hemodynamics and electrocardiographic QT intervals than did papaverine. These results suggest that a bolus administration of intracoronary nicorandil can safely, quickly, and reliably induce maximal coronary hyperemia comparable to that achieved with intracoronary papaverine in humans.

Relation of phasic coronary flow velocity profile to clinical and hemodynamic characteristics of patients with aortic valve disease.

BACKGROUND Our objective was to assess phasic coronary blood flow and velocity characteristics of the proximal portion of the left anterior descending artery and to evaluate their relation to the clinical and hemodynamic manifestations in patients with aortic valve disease. METHODS AND RESULTS We examined 26 patients with chronic aortic regurgitation (AR), 12 patients with predominant aortic stenosis (AS), and 11 control subjects using an intravascular Doppler catheter with spectral analysis. Angiographic assessment of AR identified 10 patients with mild regurgitation and 16 with severe regurgitation. The resting systolic coronary flow velocity-time integral (VTI) was significantly higher and the diastolic VTI was slightly but significantly higher in patients with severe regurgitation than in those with mild regurgitation (11.8 +/- 4.2 vs 4.1 +/- 1.1 cm, P < .001; 18.5 +/- 5.8 vs 13.2 +/- 3.2 cm, P < .05) and control subjects (4.0 +/- 1.0 cm, P < .001 and 13.3 +/- 3.6 cm, P < .05), respectively. Patients with AS had a slightly lower resting systolic VTI (3.8 +/- 1.4 cm) and a higher diastolic VTI (14.6 +/- 3.7 cm) than control subjects. Resting coronary blood flow was greater in patients with aortic valve disease than in control subjects. There was a significant correlation between the ratio of the resting systolic to diastolic VTI (S/D ratio) and the ratio of the aortic systolic to diastolic pressure (r = .75, P < .001) in patients with AR. The S/D ratio was inversely correlated with left ventricular systolic pressure (r = -.92, P < .001) and positively correlated with the ratio of the aortic systolic to diastolic pressure (r = .68, P < .05) in patients with AS. CONCLUSIONS Our results indicate that hemodynamic changes related to aortic valve disease contribute to alterations in the resting phasic coronary blood flow and velocity profiles observed in these patients.

Effects of heart rate on phasic coronary blood flow pattern and flow reserve in patients with normal coronary arteries : a study with an intravascular Doppler catheter and spectral analysis

To assess the effects of pacing-induced tachycardia on phasic coronary blood flow pattern and flow reserve of left anterior descending artery, we examined 16 patients with chest pain and angiographically normal coronary arteries by using an intravascular Doppler catheter with spectral analysis of the velocity signal. The heart rate was increased from a mean of 68 +/- 11 beats/min during sinus rhythm to 100 beats/min and again to 120 beats/min. Cross-sectional area of the epicardial artery and resting systolic and diastolic coronary blood flows increased progressively, resulting in an elevation of total coronary flow from 142 +/- 54 ml/min during sinus rhythm to 190 +/- 66 ml/min at 100 beats/min (p < 0.05) and to 219 +/- 69 ml/min at 120 beats/min (p < 0.01). During maximal hyperemia with intracoronary injection of 10 to 12 mg of papaverine, there was an increase in the systolic coronary blood flow with a decrease in the diastolic flow, resulting in no significant change in the total flow. These alterations led to progressive reductions in coronary flow reserve from 3.9 +/- 0.7 during sinus rhythm to 2.9 +/- 0.9 at 100 beats/min (p < 0.01) and to 2.3 +/- 0.3 at 120 beats/min (p < 0.001). Thus careful consideration should be given to the effects of heart rate when phasic coronary blood flow pattern and flow reserve are assessed.

Vagus nerve and celiac ganglion lesions in generalized amyloidosis: A correlative study of familial amyloid polyneuropathy and AL-amyloidosis

To clarify the cause of gastrointestinal disorders in systemic amyloidosis we made pathologic and morphometric studies of vagus nerves, celiac ganglia, stomach and rectum in three autopsied cases with type 1 familial amyloid polyneuropathy (FAP) and two with nonhereditary generalized amyloidosis (AL-amyloidosis). The gastric and rectal walls in all cases were affected in the same way by amyloid deposition. On the other hand, there was a great difference between the two diseases in the severity of vagus nerve and celiac ganglion lesions: the vagus nerves in FAP showed very extensive endoneurial deposition of amyloid with severe loss of myelinated nerve fibers, but in AL-amyloidosis there was no loss of myelinated nerve fibers and only slight amyloid deposition in the endoneurium. Similarly, in the celiac ganglion, intraganglionic deposition of amyloid was prominent in FAP and slight in AL-amyloidosis. It is known that bowel symptoms frequently occur in type I FAP and are less prominent in AL-amyloidosis. This study demonstrated that the gastrointestinal autonomic nerves were more markedly disturbed by amyloid in the former than in the latter, and disorder in neural control of the digestive tract may be responsible for the bowel symptoms in systemic amyloidosis, especially in type I FAP.

Early identification of amyloid heart disease by technetium-99m-pyrophosphate scintigraphy: A study with familial amyloid polyneuropathy

To determine whether technetium-99m-pyrophosphate (Tc-99m-PYP) scanning or two-dimensional echocardiography can detect amyloid heart disease in an earlier stage of familial amyloid polyneuropathy, 15 patients were examined. Although 10 of the 15 patients had no clinical evidence of congestive heart failure, as well as normal ventricular wall thickness and normal values for left ventricular systolic function, five (50%) of them showed mild or moderate myocardial uptake. On the other hand, none had characteristic highly refractile myocardial echoes on the two-dimensional echocardiographic images (p less than 0.01), and values for diastolic function were reduced in four of the five and normal in the remaining one. In 85 control subjects, diffuse positive pyrophosphate scans of the heart were found in four (5%) of them (three with dilated cardiomyopathy and one with sarcoidosis), and highly refractile granular sparkling echoes were observed in nine (11%) (five with hypertrophic cardiomyopathy, three with aortic stenosis, and one with hypereosinophilic syndrome). We conclude that Tc-99m-PYP scanning is a more sensitive and specific method and may have the potential ability to detect amyloid heart disease in the earlier stage of familial amyloid polyneuropathy than two-dimensional echocardiography.