Takuya Miyamoto

Toll-Like Receptor-2 Modulates Ventricular Remodeling After Myocardial Infarction

Background—Toll-like receptors (TLRs) are members of the interleukin-1 receptor family and transduce similar signals as interleukin-1 receptor in response to exogenous pathogens. Recent studies have demonstrated that TLRs are activated by endogenous signals, such as heat shock proteins and oxidative stress, that may contribute to ventricular remodeling after myocardial infarction. In this study, we determined whether TLR-2 was involved in cardiac remodeling after myocardial infarction. Methods and Results—Myocardial infarction was induced by surgical left anterior descending coronary artery ligation on wild-type (WT) mice and TLR-2–knockout (KO) mice. The survival rate was significantly higher in KO mice than in WT mice 4 weeks after myocardial infarction (65% versus 43%, P <0.03). Infarct size and degree of inflammatory cell infiltration in infarct area were similar between WT and KO mice. However, myocardial fibrosis in the noninfarct area of KO mice was much less than in WT mice (P <0.01) and was accompanied by reduced transforming growth factor-&bgr;1 and collagen type 1 mRNA expressions (P <0.01 and P <0.05, respectively). Left ventricular dimensions at end diastole were smaller in KO mice than in WT mice at 1 week (P <0.05) and 4 weeks (P <0.01) after surgery. Furthermore, fractional shortening was higher (27.7±2.5% versus 21.2±2.6%, P <0.05, at 1 week, and 24.3±2.0% versus 16.6±2.5%, P <0.01, at 4 weeks) in KO mice compared with WT mice. Conclusions—These data suggest that TLR-2 plays an important role in ventricular remodeling after myocardial infarction.

Apatite-forming ability of carboxyl group-containing polymer gels in a simulated body fluid

Carboxymethylated chitin, gellan gum, and curdlan gels were soaked in a simulated body fluid (SBF) having ion concentrations nearly equal to those of human blood plasma. Some of the gels had been soaked in a saturated Ca(OH)(2) solution, while others had not. The carboxymethylated chitin and gellan gum gels have carboxyl groups, while the curdlan gel has hydroxyl groups. None of the gels formed apatite on their surfaces in the SBF when they had not been subjected to the Ca(OH)(2) treatment, whereas the carboxymethylated chitin and gellan gum gels formed apatite on their surfaces when they had been subjected to the Ca(OH)(2) treatment. The curdlan gel did not form an apatite deposit even after the Ca(OH)(2) treatment. Apatite formation on the carboxymethylated chitin and gellan gum gels was attributed to the catalytic effect of their carboxyl groups for apatite nucleation, and acceleration of apatite nucleation from released Ca(2+) ions. This result provides a guiding principle for obtaining apatite-organic polymer fiber composites. This composite is expected to have an analogous structure to that of natural bone.

Reactive oxygen species regulate FLICE inhibitory protein (FLIP) and susceptibility to Fas-mediated apoptosis in cardiac myocytes

OBJECTIVE Fas ligand (FasL) is a key cytokine which initiates apoptosis when FasL binds to its receptor, Fas. Cardiac myocytes are generally resistant to Fas-induced apoptosis. However, sublethal dose of doxorubicin (Dox) can sensitize cardiac myocytes to Fas-induced apoptosis. We investigated the molecular mechanism by which Dox sensitizes cardiac myocytes to Fas-induced apoptosis. FLICE inhibitory protein (FLIP) is a key molecule for blocking Fas-induced apoptosis by functioning as a caspase-8 dominant negative. METHODS AND RESULTS FLIP was constitutively expressed in cultured neonatal rat cardiac myocytes. FLIP protein levels were markedly down-regulated by Dox in a time-dependent and dose-dependent manner. Next, we examined the relation of reactive oxygen species (ROS) by Dox to the expression of FLIP. Both of N-acetylcysteine (NAC) and the combination of superoxide dismutase and catalase restored the decreased FLIP in Dox-treated cardiac myocytes to the basal level. NAC also restored the increased formation of thiobarbituric acid-reactive substance after Dox-treatment. Concurrently, the susceptibility to Fas-mediated apoptosis disappeared with the treatments of the antioxidant agents. Hydrogen peroxide down-regulated FLIP in a dose-dependent fashion and also sensitized cardiac myocytes to Fas-induced apoptosis. CONCLUSIONS FLIP, an inhibitor of apoptosis induced by cytokines of TNF family, contributes at least partly to Dox-induced sensitization to Fas-mediated apoptosis in cardiac myocytes. The expression of FLIP in cardiac myocytes is regulated by ROS.

The prognostic importance of objective nutritional indexes in patients with chronic heart failure

BACKGROUND Although malnutrition indicates an unfavorable prognosis in some clinical settings, the association between nutritional indexes and outcomes for patients with chronic heart failure (CHF) is unclear. METHODS AND RESULTS All the previously established objective nutritional indexes were evaluated. The controlling nutritional status score (CONUT), prognostic nutritional index (PNI), and geriatric nutritional risk index (GNRI) were determined for 388 consecutive patients with CHF (mean age 69.6±12.3 years). The prevalence of malnutrition in this cohort was 60-69%. Patients were followed prospectively, with the endpoints being death due to a cardiovascular event or re-hospitalization. There were 130 events, including 33 deaths and 97 re-hospitalizations, during a mean follow-up period of 28.4 months. Patients experiencing cardiovascular events showed impaired nutritional status, higher CONUT scores, lower PNI scores, and lower GNRI scores, compared with those who did not experience cardiovascular events. CONUT score [hazard ratio 40.9, 95% confidence interval (CI) 10.8-154.8], PNI score (hazard ratio 6.4, 95% CI 5.4-25.1), and GNRI score (hazard ratio 11.6, 95% CI 3.7-10.0) were independently associated with cardiovascular events. Kaplan-Meier analysis showed that there was a significantly higher incidence of cardiovascular events in patients who were malnourished than in those who were not. CONCLUSION Malnutrition was common in patients with CHF. Evaluation of nutritional status may provide additional prognostic information in patients with CHF.

Activation of distinct signal transduction pathways in hypertrophied hearts by pressure and volume overload

Abstract.ObjectiveTwo types of hemodynamic overload, pressure and volume overload, result in morphologically distinct types of cardiac remodeling. We explored the possibility that distinct hemodynamic overload may differentially activate the signal transduction pathway.MethodsPressure and volume overload were induced by thoracic aortic banding and carotid–jugular shunt formation in rabbits, respectively. Phosphorylation activities of mitogen–activated protein (MAP) kinase families, Akt, and signal transducer and activator of transcription (STAT) 3 in the left ventricular myocardium were determined by Western blotting using phospho–specific antibodies and were compared between hypertrophied hearts by pressure and volume overload.ResultsPressure and volume overload produced concentric and eccentric cardiac hypertrophy in rabbits, respectively. In pressure–overloaded hearts, extracellular signal–regulated kinase (ERK) 1/2, p38 MAP kinase, and STAT3 were transiently activated prior to hypertrophic changes. In contrast, activation of ERK1/2, but not p38 MAP kinase and STAT3, was observed only at 12 weeks after shunt surgery. Pressure overload evoked short and biphasic activation of Akt at 15 min and 1 day after aortic banding. In contrast, volume overload induced sustained activation of Akt from 1 day to 1 week. Concordant phosphorylation of downstream targets of Akt, glycogen synthase kinase–3β (GSK–3β) and p70 ribosomal S6 kinase (p70S6K), in response to Akt activation was observed at 15 min after pressure overload. However in volume–overloaded hearts, phosphorylation of GSK-3β and p70S6K was observed at 6 weeks and at 6 and 12 weeks, respectively, and was not coincident with Akt activation. These findings suggest that phosphorylation of GSK-3β and p70S6K is regulated by an alternative pathway other than Akt in volume–overloaded hearts.ConclusionPressure and volume overload–induced cardiac hypertrophy is associated with distinct patterns of activation of signal transduction pathways. These data may suggest that stimulus–specific heterogeneity in the signaling pathway plays a role in determining the type of cardiac hypertrophy.

Signal Transduction and Ca2+ Signaling in Contractile Regulation Induced by Crosstalk Between Endothelin-1 and Norepinephrine in Dog Ventricular Myocardium

Abstract— In certain cardiovascular disorders, such as congestive heart failure and ischemic heart disease, several endogenous regulators, including norepinephrine (NE) and endothelin-1 (ET-1), are released from various types of cell. Because plasma levels of these regulators are elevated, it seems likely that cardiac contraction might be regulated by crosstalk among these endogenous regulators. We studied the regulation of cardiac contractile function by crosstalk between ET-1 and NE and its relationship to Ca2+ signaling in canine ventricular myocardium. ET-1 alone did not affect the contractile function. However, in the presence of NE at subthreshold concentrations (0.1 to 1 nmol/L), ET-1 had a positive inotropic effect (PIE). In the presence of NE at higher concentrations (100 to 1000 nmol/L), ET-1 had a negative inotropic effect. ET-1 had a biphasic inotropic effect in the presence of NE at an intermediate concentration (10 nmol/L). The PIE of ET-1 was associated with an increase in myofilament sensitivity to Ca2+ ions and a small increase in Ca2+ transients, which required the simultaneous activation of protein kinase A (PKA) and PKC. ET-1 elicited translocation of PKC&egr; from cytosolic to membranous fraction, which was inhibited by the PKC inhibitor GF 109203X. Whereas the Na+-H+ exchange inhibitor Hoe 642 suppressed partially the PIE of ET-1, detectable alteration of pHi did not occur during application of ET-1 and NE. The negative inotropic effect of ET-1 was associated with a pronounced decrease in Ca2+ transients, which was mediated by pertussis toxin-sensitive G proteins, activation of protein kinase G, and phosphatases. When the inhibitory pathway was suppressed, ET-1 had a PIE even in the absence of NE. Our results indicate that the myocardial contractility is regulated either positively or negatively by crosstalk between ET-1 and NE through different signaling pathways whose activation depends on the concentration of NE in the dog.

Cardiac nuclear high mobility group box 1 prevents the development of cardiac hypertrophy and heart failure

Aims High mobility group box 1 (HMGB1) is an abundant and ubiquitous nuclear DNA-binding protein that has multiple functions dependent on its cellular location. HMGB1 binds to DNA, facilitating numerous nuclear functions including maintenance of genome stability, transcription, and repair. However, little is known about the effects of nuclear HMGB1 on cardiac hypertrophy and heart failure. The aim of this study was to examine whether nuclear HMGB1 plays a role in the development of cardiac hypertrophy induced by pressure overload. Methods and results Analysis of human biopsy samples by immunohistochemistry showed decreased nuclear HMGB1 expression in failing hearts compared with normal hearts. Nuclear HMGB1 decreased in response to both endothelin-1 (ET-1) and angiotensin II (Ang II) stimulation in neonatal rat cardiomyocytes, where nuclear HMGB1 was acetylated and translocated to the cytoplasm. Overexpression of nuclear HMGB1 attenuated ET-1 induced cardiomyocyte hypertrophy. Thoracic transverse aortic constriction (TAC) was performed in transgenic mice with cardiac-specific overexpression of HMGB1 (HMGB1-Tg) and wild-type (WT) mice. Cardiac hypertrophy after TAC was attenuated in HMGB1-Tg mice and the survival rate after TAC was higher in HMGB1-Tg mice than in WT mice. Induction of foetal cardiac genes was decreased in HMGB1-Tg mice compared with WT mice. Nuclear HMGB1 expression was preserved in HMGB1-Tg mice compared with WT mice and significantly attenuated DNA damage after TAC was attenuated in HMGB1-TG mice. Conclusion These results suggest that the maintenance of stable nuclear HMGB1 levels prevents hypertrophy and heart failure by inhibiting DNA damage.

Impact of serum omentin-1 levels on cardiac prognosis in patients with heart failure

BackgroundVarious adipokines are reported to be associated with the development of heart failure (HF) through insulin resistance and chronic inflammation. Omentin-1 is a novel adipokine and is associated with incident coronary artery disease. However, it remains unclear whether serum omentin-1 levels are associated with cardiac prognosis in patients with HF.MethodsWe measured serum omentin-1 levels at admission in 136 consecutive patients with HF, and 20 control subjects without signs of significant heart disease. We prospectively followed patients with HF to endpoints of cardiac death or re-hospitalization for worsening HF.ResultsSerum omentin-1 levels were markedly lower in HF patients with cardiac events compared with to without. The patients who were in New York Heart Association (NYHA) functional class IV showed significantly lower serum omentin-1 levels compared to those in class II and III, whereas serum omentin-1 levels did not correlate with serum brain natriuretic peptide levels (r = 0.217, P = 0.011). We divided the HF patients into three groups based on the tertiles of serum omentin-1 level (low T1, middle T2, and high T3). Multivariate Cox hazard analysis showed that the lowest serum omentin-1 level (T1) was independently associated with cardiac events after adjustment for confounding factors (hazard ratio 5.78, 95% confidence interval 1.20-12.79). We divided the HF patients into two groups according to the median serum omentin-1 levels. Kaplan-Meier analysis revealed that the patients with low serum omentin-1 levels had a higher risk of cardiac events compared with those with high serum omentin-1 levels (log-rank test p < 0.001).ConclusionDecreased serum omentin-1 levels were associated with a poor cardiac outcome in patients with HF.

Apatite-forming ability of alginate fibers treated with calcium hydroxide solution.

Calcium alginate fibers were prepared by extruding an aqueous sodium alginate solution into an aqueous calcium chloride solution. The fibers were treated with a saturated aqueous calcium hydroxide solution for various periods and their apatite-forming ability was examined in a simulated body fluid (SBF). The calcium alginate fibers were treated with the aqueous calcium hydroxide solution for periods longer than five days formed apatite on their surfaces in SBF, and their apatite-forming ability improved with increasing calcium hydroxide treatment time. The amount of calcium ions released from the fibers also increased with increasing calcium hydroxide treatment time, resulting in acceleration of nucleation and growth of apatite on the fiber surfaces. The resultant apatite–alginate fiber composite is expected to be useful as a flexible bioactive bone-repairing material.

Elevated plasma brain natriuretic peptide levels predict left atrial appendage dysfunction in patients with acute ischemic stroke.

BACKGROUND It is well known that left atrial appendage (LAA) dysfunction plays an important role in the occurrence of cardioembolic stroke. The atrium is the main source of brain natriuretic peptide (BNP) in patients with atrial fibrillation (AF). We hypothesized that the plasma BNP level would be a sensitive predictor of LAA dysfunction in patients with acute ischemic stroke. METHODS AND RESULTS Transesophageal echocardiography was performed and plasma BNP levels were measured in 223 patients (145 males, age 69 ± 14 years), within 7 days after the onset of acute ischemic stroke. None of the patients had a history of congestive heart failure. LAA thrombus was detected in 23 of 77 (30%) patients with AF. Plasma BNP levels were markedly higher in patients with cardioembolic stroke compared to those without (144 pg/ml vs. 35 pg/ml, p<0.05). Plasma BNP levels were significantly correlated with LAA emptying flow velocity regardless of sinus rhythm (R=-0.352) or AF (R=-0.436). Furthermore, among patients with cardioembolic stroke, plasma BNP levels were markedly higher in patients with cardiogenic stroke, as diagnosed by transesophageal echocardiography, than in those with cryptogenic stroke (193 pg/ml vs. 14 pg/ml, p<0.05). Multivariate logistic regression analysis showed that a BNP concentration >90 pg/ml was an independent predictor of cardiogenic stroke (odds ratio 41.39, 95% confidence interval 1.28-138; p=0.0358). CONCLUSION Elevated plasma BNP concentrations may be a reliable surrogate marker for the prediction of LAA dysfunction and cardiogenic stroke in patients with acute ischemic stroke.