Publications by authors named "Yukio Kuramochi"

14 Publications

  • Page 1 of 1

Inhibition of ErbB2 by receptor tyrosine kinase inhibitors causes myofibrillar structural damage without cell death in adult rat cardiomyocytes.

Exp Cell Res 2009 Apr 12;315(7):1302-12. Epub 2009 Feb 12.

Swiss Cardiovascular Center, Bern University Hospital, Bern, Switzerland.

Inhibition of ErbB2 (HER2) with monoclonal antibodies, an effective therapy in some forms of breast cancer, is associated with cardiotoxicity, the pathophysiology of which is poorly understood. Recent data suggest, that dual inhibition of ErbB1 (EGFR) and ErbB2 signaling is more efficient in cancer therapy, however, cardiac safety of this therapeutic approach is unknown. We therefore tested an ErbB1-(CGP059326) and an ErbB1/ErbB2-(PKI166) tyrosine kinase inhibitor in an in-vitro system of adult rat ventricular cardiomyocytes and assessed their effects on 1. cell viability, 2. myofibrillar structure, 3. contractile function, and 4. MAPK- and Akt-signaling alone or in combination with Doxorubicin. Neither CGP nor PKI induced cardiomyocyte necrosis or apoptosis. PKI but not CGP caused myofibrillar structural damage that was additive to that induced by Doxorubicin at clinically relevant doses. These changes were associated with an inhibition of excitation-contraction coupling. PKI but not CGP decreased p-Erk1/2, suggesting a role for this MAP-kinase signaling pathway in the maintenance of myofibrils. These data indicate that the ErbB2 signaling pathway is critical for the maintenance of myofibrillar structure and function. Clinical studies using ErbB2-targeted inhibitors for the treatment of cancer should be designed to include careful monitoring for cardiac dysfunction.
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http://dx.doi.org/10.1016/j.yexcr.2009.02.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991362PMC
April 2009

Anticonvulsants for protracted seizures in children.

Lancet 2006 Aug;368(9535):576; author reply 577

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http://dx.doi.org/10.1016/S0140-6736(06)69190-3DOI Listing
August 2006

Telithromycin in acute exacerbations of asthma.

N Engl J Med 2006 Jul;355(1):97; author reply 97-8

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July 2006

Neuregulin activates erbB2-dependent src/FAK signaling and cytoskeletal remodeling in isolated adult rat cardiac myocytes.

J Mol Cell Cardiol 2006 Aug;41(2):228-35

Center for Molecular Stress Response, Whitaker Cardiovascular Institute, Department of Medicine, Boston University Medical Center, MA 02118, USA.

Cardiac myocyte erbB2 expression is required for maintenance of normal cardiac structure and function, though its role in cardiac cellular physiology is incompletely understood. We tested the hypothesis that erbB2 signaling modulates focal adhesion formation via activation of a src/FAK pathway using adult rat ventricular myocytes in primary culture. The erbB ligand neuregulin-1Beta (NRG-1Beta) induced phosphorylation of Src at Y416 and Y215, and FAK at Y861. Using antibody and pharmacological inhibitor strategies, we found that FAK activation was erbB2- and Src-dependent, but independent of PI3-kinase/Akt pathway. Furthermore, NRG-1Beta stimulated the formation of a multiprotein complex between erbB2, FAK, p130(CAS) and paxillin within 30 min, and induced lamellipodia with longitudinal elongation of the myocytes within days. The extension of lamellipodia resulted in restoration of cell-to-cell contact between isolated myocytes, allowing for synchronous beating. These effects of NRG-1Beta were prevented by a src inhibitor as well as an antibody to erbB2. These results suggest the potential role of NRG-1Beta/erbB2/Src/FAK signaling in the maintenance and repair of electrical and mechanical coupling in cardiomyocytes.
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http://dx.doi.org/10.1016/j.yjmcc.2006.04.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1847613PMC
August 2006

Rapid electrical stimulation induces early activation of kinase signal transduction pathways and apoptosis in adult rat ventricular myocytes.

Exp Physiol 2006 Jul 4;91(4):773-80. Epub 2006 May 4.

Molecular Stress Response Unit, Whitaker Cardiovascular Institute, Department of Medicine, Boston University Medical Center, Boston, MA 02118, USA.

Chronic tachycardia in patients and rapid pacing in animal models induce myocardial dysfunction and initiate a cascade of compensatory adaptations that are ultimately unsustainable, leading to ventricular enlargement and failure. The molecular pathogenesis during the early stages of tachycardia-induced cardiomyopathy, however, remains unclear. We utilized our previously reported cell culture pacing system to directly assess phosphatidylinositol-3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK) signalling of adult rat ventricular myocytes (ARVM) in response to rapid electrical stimulation. Freshly isolated ARVMs were maintained quiescent (0 Hz), or continuously stimulated at 5 (normofrequency) and 8 Hz (rapid frequency). Pacing resulted in an increase in mitochondrial respiration, assessed by mitochondrial uptake of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) at 48 h. Rapid pacing at 8 Hz significantly increased cell injury and death as assessed by Trypan Blue uptake, creatine phosphokinase release, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay. Pacing at 5 Hz induced early, but weak, activation of Akt and protein kinase 38 (p38). Rapid pacing further augmented the early activation of Akt and p38, and induced extracellular signal-related kinase (Erk) and c-jun amino terminal kinase (JNK) activation. Incubation of ARVM with PI3K inhibitor LY294002 resulted in a twofold increase of TUNEL-positive cells under all pacing conditions examined. In conclusion, rapid pacing has immediate and detrimental consequences for cardiomyocyte survival, with pro-apoptotic pathways (e.g. JNK, p38) able to overwhelm antiapoptotic signalling (PI3K/Akt, Erk). The rapid pacing methodology described in this report will be particularly useful in determination of cell signalling pathways associated with tachycardia-induced cardiomyopathy.
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http://dx.doi.org/10.1113/expphysiol.2006.033894DOI Listing
July 2006

Neuregulin-1alpha and beta isoform expression in cardiac microvascular endothelial cells and function in cardiac myocytes in vitro.

Exp Cell Res 2005 Nov 26;311(1):135-46. Epub 2005 Sep 26.

Whitaker Cardiovascular Institute and Molecular Stress Response Unit, Cardiovascular Division, Department of Medicine, Boston University Medical Center, 650 Albany Street, Boston, X-320, MA 02118, USA.

Neuregulins (NRGs) are a family of alternatively spliced growth factors that act through receptor tyrosine kinases of the epidermal growth factor (EGF) receptor family in diverse tissues. The NRG-erbB signaling axis is a critical mediator of cardiac development, and growing evidence supports a role for this system in the intricate cross-talk between the microvascular endothelium and myocytes in the adult heart. The purpose of this study was first to examine the expression of splice variants of the NRG1 gene in adult rat cardiac microvascular endothelial cells and second to compare the function of these variants in cardiac myocytes. We demonstrate that cardiac microvascular endothelial cells in rat culture express multiple Type I NRG1 gene products, including both alpha and beta variants. Comparison of the activity of recombinant NRG1alpha and NRG1beta EGF-like domain proteins in cardiac myocytes shows that the beta ligand is a more potent activator of receptor phosphorylation and intracellular signaling than the alpha ligand, and only the beta ligand stimulated glucose uptake and protein synthesis in these culture conditions. Thus, cardiac microvascular endothelial cells express multiple NRG1 isotypes, but only beta-variants are biologically active on cardiac myocytes.
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http://dx.doi.org/10.1016/j.yexcr.2005.08.017DOI Listing
November 2005

Heat shock protein 90 stabilization of ErbB2 expression is disrupted by ATP depletion in myocytes.

J Biol Chem 2005 Apr 25;280(13):13148-52. Epub 2005 Jan 25.

Whitaker Cardiovascular Institute and Center for Molecular Stress Response, Boston University Medical Center, Boston, Massachusetts 02118, USA.

Heat shock protein (Hsp) 90 is a ubiquitously expressed chaperone that stabilizes expression of multiple signaling kinases involved in growth regulation, including ErbB2, Raf-1, and Akt. The chaperone activity of Hsp90 requires ATP, which binds with approximately 10-fold lower affinity than ADP. This suggests that Hsp90 may be a physiological ATP sensor, regulating the stability of growth signaling cascades in relation to cellular energy charge. Here we show that lowering ATP concentration by inhibiting glycolysis or mitochondrial respiration in isolated myocytes triggers rapid dissociation of Hsp90 from ErbB2 and degradation of ErbB2 along with other client proteins. The effect of disrupting Hsp90 chaperone activity by ATP depletion was similar to the effect of the pharmacological Hsp90 inhibitor geldanamycin. ATP depletion-induced disruption of Hsp90 chaperone activity was associated with cellular resistance to growth factor activation of intracellular signaling. ErbB2 degradation was also induced by the physiological stress of beta-adrenergic receptor stimulation in electrically stimulated cells. These results support a role for Hsp90 as an ATP sensor that modulates tissue growth factor responsiveness under metabolically stressed conditions and provide a novel mechanism by which cellular responsiveness to growth factor stimulation is modulated by cellular energy charge.
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http://dx.doi.org/10.1074/jbc.M410838200DOI Listing
April 2005

Cardiac endothelial cells regulate reactive oxygen species-induced cardiomyocyte apoptosis through neuregulin-1beta/erbB4 signaling.

J Biol Chem 2004 Dec 21;279(49):51141-7. Epub 2004 Sep 21.

Center of Molecular Stress Response, Whitaker Cardiovascular Institute, Department of Medicine, Boston University Medical Center, Boston, Massachusetts 02118, USA.

Neuregulin (NRG)-1beta has a prosurvival effect on cardiac myocytes via the phosphatidylinositol-3-kinase/Akt pathway, but the physiological regulators of this system in the intact heart are unknown. In this study, we tested the hypothesis that reactive oxygen species regulate NRG/erbB signaling. We used isolated adult rat ventricular myocytes (ARVMs) or cardiac microvascular endothelial cells (CMECs) in monoculture, or together in coculture. H2O2 induced NRG-1beta release from CMECs in a concentration-dependent manner, and conditioned medium from H2O2-treated CMEC activated ARVM erbB4. NRG-1beta release occurred via proteolytic cleavage of 115-kDa transmembrane NRG-1beta and was inhibited by the metalloproteinase inhibitor 1,10-phenanthroline. In myocyte monoculture, H2O2 induced erbB4-dependent, but NRG-independent, activation of Akt. To elucidate the bioactivity of CMEC-derived NRG-1beta on ARVMs, we examined H2O2-induced myocyte apoptosis in co-culture using an antibody to NRG-1beta. The percentages of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly higher in the anti-NRG-1beta group than in the control group. The change in apoptosis induced by anti-NRG-1beta in co-culture was similar in magnitude to the protection of myocytes by addition of recombinant NRG-1beta to ARVM monocultures. Activation of NRG/erbB paracrine signaling was also seen in the intact heart subjected to oxidative stress by ischemia-reperfusion injury. Isolated perfused mouse hearts subjected to 15 min of ischemia, followed by 30 min of reperfusion, showed complete proteolytic cleavage of 115-kDa NRG-1beta, with concomitant erbB4 phosphorylation. These results demonstrate that reactive oxygen species activate NRG-1beta/erbB4 paracrine signaling in the heart and suggest that this system is involved in cardiac adaptation to oxidative stress.
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http://dx.doi.org/10.1074/jbc.M408662200DOI Listing
December 2004

Estimation of myocardial hemodynamics before and after intervention in children with Kawasaki disease.

J Am Coll Cardiol 2004 Feb;43(4):653-61

Department of Pediatrics, Nippon Medical School Hospital, Tokyo, Japan.

Objectives: We used myocardial fractional flow reserve (FFR(myo)) and coronary flow reserve (CFR) to estimate cut-off values for assessment of the functional severity of coronary stenosis and myocardial ischemia, and we tested the usefulness of coronary blood hemodynamic measurements before and after plain old balloon angioplasty (POBA) and coronary artery bypass graft surgery (CABG).

Background: Fractional flow reserve and CFR are useful for assessing the functional severity of coronary artery stenosis, coronary microvascular dysfunction, and myocardial ischemia during cardiac catheterization in adults. However, there have been no reports on the use of these measurements in children with Kawasaki disease (KD).

Methods: The study group included 128 patients with 314 coronary branches. The subjects were classified into three groups: normal coronary group, with 206 branches; abnormal coronary artery without ischemia group, with 58 branches; and ischemia group, with 50 branches.

Results: In each branch, CFR and FFR(myo) were significantly lower in the ischemia group than in the other groups. Cut-off values for assessing the functional severity of coronary stenosis and CFR were approximately equal to those obtained for adults (CFR: <2.0; FFR(myo): <0.75). We obtained very high sensitivity and specificity for estimating myocardial ischemia using CFR and FFR(myo) (CFR: 94.0% and 98.5%, respectively; FFR(myo): 95.7% and 99.1%, respectively). Both CFR and FFR(myo) were reliable indicators of coronary hemodynamics before and after POBA and CABG.

Conclusions: Together, CFR and FFR(myo) provide a useful index for assessing the functional severity of coronary artery stenosis and myocardial ischemia and estimating the effectiveness of POBA and CABG in children with KD, the same as they do for adults.
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http://dx.doi.org/10.1016/j.jacc.2003.10.032DOI Listing
February 2004

Neuregulin-1 protects ventricular myocytes from anthracycline-induced apoptosis via erbB4-dependent activation of PI3-kinase/Akt.

J Mol Cell Cardiol 2003 Dec;35(12):1473-9

Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.

We have found that neuregulin-1beta (NRG-1beta) is expressed in the cardiac microvascular endothelium, and promotes the growth and survival of cardiac myocytes in culture through the activation of erbB2 and erbB4 receptor tyrosine kinases. In this study, we examined the role of NRG-1/erbB signaling in protection of cardiac myocytes from anthracycline-induced apoptosis in vitro to determine the coupling between erbB receptor subtypes and cytoprotective signaling. Treatment of neonatal rat ventricular myocytes with NRG-1beta inhibited daunorubicin-induced apoptosis as shown by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining for DNA fragmentation as well as flow cytometric quantification of apoptotic myocytes. Daunorubicin-induced activation of caspase-3 in cardiomyocytes was similarly inhibited by NRG-1beta. The phosphoinositol-3-kinase (PI3-kinase) inhibitor wortmannin prevented the effects of NRG-1beta on daunorubicin-induced apoptosis and activation of caspase-3. NRG-1beta treatment induced rapid activation of Akt/PKB that was inhibited by wortmannin, and adenoviral-mediated overexpression of a dominant-negative Akt prevented the protective effect of NRG-1beta. Akt activation by NRG-1beta was prevented by the tyrphostin AG1478, which we show inhibits erbB4 activation by NRG-1beta. In contrast, the erbB2-specific tyrphostin AG879 had no effect on NRG-1beta activation of Akt. Myocyte treatment with an activating antibody to erbB2 caused phosphorylation of erbB2, and led to activation of Erk but not Akt. Treatment with the erbB2 antibody had no effect on anthracycline-induced apoptosis. Thus, NRG-1beta protects against anthracycline-induced apoptosis via erbB4-dependent activation of the PI3-kinase/Akt pathway.
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http://dx.doi.org/10.1016/j.yjmcc.2003.09.012DOI Listing
December 2003

Myocyte contractile activity modulates norepinephrine cytotoxicity and survival effects of neuregulin-1beta.

Am J Physiol Cell Physiol 2004 Feb 1;286(2):C222-9. Epub 2003 Oct 1.

Whitaker Cardiovascular Institute and Cardiovascular Divisions, Department of Medicine, Boston University Medical Center, Boston, MA 02118, USA.

The purpose of this study is to test the hypothesis that mechanical and electrical activity in adult rat ventricular myocytes (ARVM) alters responses to proapoptotic and prosurvival ligands. The effects of electrical stimulation on myocyte survival, stress signaling, response to beta-adrenergic receptor (beta-AR)-stimulated apoptosis, and neuregulin-1beta (NRG) were examined. Electrical stimulation (6.6 V/cm; 0, 2, and 5 Hz; 2-ms duration; alternating polarity) of ARVM resulted in more than 70% capture. Although ARVM paced for 48 h showed higher mitochondrial uptake of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (P < 0.05, 0 vs. 2 and 5 Hz), electrical stimulation had little effect on cell survival assessed by trypan blue uptake, CPK release, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. Electrical stimulation for 24 h did not induce stress response (heat shock protein 70, 90) nor stress kinase (Erk, JNK, p38) activation. NRG stimulation of Erk and Akt was similar between paced and quiescent cells. Pacing sensitized myocytes to beta-AR-stimulated JNK phosphorylation and cell death with 0.1 microM norepinephrine (NE) in paced myocytes causing equivalent cytotoxicity to 10 microM NE in quiescent cells. NRG suppressed beta-AR-induced apoptosis through a phosphatidylinositol-3-kinase-dependent pathway in both paced and quiescent cells, although it is overwhelmed by high-NE concentration in paced cells. Thus myocyte contractility modulates both NE cytotoxicity as well as the cytoprotective effect of NRG. These results demonstrate the feasibility and importance of using electrically paced cardiomyocytes in primary culture when examining the signaling pathways of cell survival.
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http://dx.doi.org/10.1152/ajpcell.00312.2003DOI Listing
February 2004

Cardiomyocyte regeneration from circulating bone marrow cells in mice.

Pediatr Res 2003 Sep 2;54(3):319-25. Epub 2003 Jul 2.

Department of Pediatrics, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.

We investigated the role of circulating bone marrow cells (BMC) in cardiomyocyte regeneration. BMC, isolated from transgenic mice expressing enhanced green fluorescent protein (GFP), were transplanted into lethally irradiated C57BL6 mice. Five weeks after bone marrow transplantation (BMT), flow cytometric analysis for GFP-positive cells confirmed reconstitution of transplanted bone marrow. Bone marrow transplant mice subsequently underwent left coronary artery ligation (myocardial infarction) or sham-operation, and were killed at 1 mo or 3 mo after operation. Infarct size was similar in bone marrow transplant mice at 1 mo (47.1 +/- 5.9%) and at 3 mo (45.3 +/- 7.8%), and echocardiography at 2 and 8 wk revealed decreasing left ventricular function. In infarcted heart, GFP-positive cells that expressed desmin and troponin T-C were identified by confocal microscopy. GFP and troponin T-C double-positive cells were predominantly in the peri-infarcted region (1 mo, 365 +/- 45 cells/50 sections; 3 mo: 458 +/- 100 cells/50 sections; p < 0.05 versus noninfarct, infarct, and sham-operated regions). Furthermore, BMC mobilization and differentiation into cardiomyocytes was found to be complete within 1 mo after myocardial infarction. These results demonstrate that circulating BMC undergo mobilization and differentiation in cardiac cells after myocardial infarction. Future studies are required to determine the molecular signaling mechanisms responsible for this phenomenon.
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http://dx.doi.org/10.1203/01.PDR.0000078275.14079.77DOI Listing
September 2003

Longitudinal estimation of signal-averaged electrocardiograms in patients with Kawasaki disease.

Pediatr Int 2002 Feb;44(1):12-7

Department of Pediatrics, Nippon Medical School Hospital, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.

Background: Myocarditis associated with Kawasaki (KD) disease is prominent, but rarely detected by conventional methods. The hypothesis of this study is to see if signal-averaged electrocardiogram can detect myocarditis with KD.

Methods: We obtained signal-averaged electrocardiograms from 71 patients with KD (mean age 2.8 +/- 2.9 years) in the acute (1st-4th week), subacute (5-7th week), and chronic (8th week or later) phases (mean study period 3.5 +/- 1.7 years). Sixteen patients who had pericardial effusion, bundle branch block or myocardial ischemia were excluded from this study. The results were compared with those of Holter and 12-lead electrocardiograms, echocardiography and serum myocardial enzymes. They were also contrasted with the course of each patient.

Results: The incidence of abnormal findings on signal-averaged electrocardiogram was 18.2% in the acute phase versus 10.9% in the subacute and chronic phases. It differed significantly higher than the other conventional tests (P < 0.05). Four patients had abnormalities of signal-averaged electrocardiograms through all three phases. Among these four, two had reduced left ventricular contractility. However, these changes were transient and resolved in the subacute phase. All patients had good courses and no residue.

Conclusion: This study shows the possibility that signal-averaged electrocardiogram is more useful to detect myocarditis associated with KD than the other conventional tests. However, we could not define the prognostic value of abnormal signal-averaged electrocardiograms during this study period.
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http://dx.doi.org/10.1046/j.1442-200x.2002.01497.xDOI Listing
February 2002