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Department Introduction

Department Introduction

Ischemia Heart Disease Group

(9) Molecular Cardiology

Our current main research interests have focused on the mechanisms of heart failure due to ventricular remodeling following myocardial infarction or pressure-overload induced ventricular hypertrophy. Our aim is to develop new treatment strategies to protect hearts from the development of heart failure.

1.Evaluation of Intracellular Signal Transduction in the Process of Post-infarction Ventricular Remodeling in Humans Using Nuclear Imaging Techniques

In recent years, cellular and molecular basic research has made remarkable progress in the area of cardiovascular medicine. However, clinical application of what has been learned requires non-invasive methods for the assessment of intracellular signal transduction in the heart. Nuclear cardiology techniques are very suitable for this purpose. Metabolic pathways of diacylglycerol exist at the downstream of angiotensin II receptor-mediated signaling, which plays an important role in the progression of cardiac hypertrophy and failure. We for the first time showed that diacylglycerol kinase ε and ζ are expressed in rat myocardium, that the expression of diacylglycerol kinase ε are suppressed in the process of post-infarction ventricular remodeling, and that an angiotensin converting enzyme inhibitor elicits the recovery of the expression of this enzyme and the amelioration of ventricular remodeling (Circ Res 2001). We then applied 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol developed by Dr. Yoshio Imahori at Kyoto Prefectural Medical University as a positron labeled diacylglycerol to positron emission CT (PET) (Figure 1). First, we performed animal experiments to confirm that the accumulation of 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol in rat myocardium well reflects the activity of phosphoinositide metabolism (J Nucl Med 2000, Eur J Nucl Med 2002). Using PET we then demonstrated that the accumulation of 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol in viable myocardium in post-infarction patients was significantly correlated with both the enlargement of left ventricle and deterioration of its systolic performance (J Nucl Med 2005) (Figure 2). While only a part of the intracellular signal transduction, we for the first time succeeded in its evaluation non-invasively using PET.

Fig. 1: Receptor binding of angiotensin II activates phospholipase C (PLC) to produce diacylglycerol (DAG) and IP3 from phosphatidylinositol bisphosphate (PIP2). The DAG then activates protein kinase C (PKC) to induce cardiac hypertrophy and accelerate ventricular remodeling through a series of phosphorylation cascades. IP3 promotes Ca2+ release from the intracellular Ca2+ store. Intravenous administration of 11C labeled diacylglycerol (DAG*) is incorporated into the phosphoiositide metabolic turnover, radioactively labeled various phosphoinositides accumulated in the cell membrane, which makes the imaging possible. Fig. 1

Fig. 2: Positron CT images using 11C labeled diacylglycerol in a healthy volunteer (left) and patients with chronic phase of myocardial infarction suffering from minor ventricular remodeling (middle) and advanced ventricular remodeling (right). A high accumulation in the viable myocardium of the patient with advanced ventricular remodeling is shown (left). Fig. 2

2.Protective Roles of Erythropoietin in Myocardium

Cardiovascular events are frequent in patients with chronic kidney disease, and patients with both chronic heart failure and chronic kidney disease have poorer prognosis. Heart diseases and kidney diseases therefore are closely related to each other with regard to the development of cardiovascular events. This pathological condition is called cardio-renal syndrome. Endogenous erythropoietin (Epo)-Epo receptor system is down-regulated in chronic kidney disease, which is a cause of anemia occasionally associated with such patients. Recently, roles of anemia in the cardio-renal syndrome have also been paid an attention. Actually, recombinant human Epo has been shown to improve exercise tolerance capacity and quality of life in chronic heart failure patients with anemia. Epo is a cytokine produced by the kidney, which plays a pivotal role in the development and differentiation of erythroid progenitor cells. In recent years, it has been shown that Epo receptor is expressed not only in erythroid cells but also in many organs including the cardiovascular system. Furthermore, the administration of recombinant human Epo has been shown to reduce the size of infraction and improve cardiac function in animal experiments.

  1. 1. Roles of Endogenous Erythropoietin in Myocardial Ischemic/Reperfusion in Humans
    We investigated serum erythropoietin (Epo) levels in patients with acute myocardial infarction who underwent successful primary percutaneous coronary intervention, and found that the patients with high serum Epo levels had a significantly smaller infarct size compared to those with low serum Epo levels. Multivariate analysis revealed for the first time that the serum Epo level predicts a smaller infarct size independently of other factors such as anemia (Namiuchi S., Kagaya Y., et al., J Am Coll Cardiol 2005). These data suggest that endogenous Epo plays a protective role in myocardial ischemia and reperfusion in humans.

  2. Roles of Erythropoietin Receptors in Non-erythroid Cells
    To understand roles of erythropoietin (Epo) receptors in non-erythroid cells in cardiovascular diseases, Epo receptor knockout mice might be useful. However, these mice die during the embryonic stage due to severe anemia. By crossing the hetero-type of this mouse with the mouse that expresses transgene-derived Epo receptors only in erythroid cells, we are able to obtain mice that express Epo receptors only in the erythroid cells. Those mice show normal erythropoiesis that rescues them from death due to severe anemia (EpoR-/- rescued). EpoR-/- rescued mice were developed by Professor Masayuki Yamamoto at the Tsukuba Advanced Research Alliance (TARA) (currently Professor of Medical Chemistry at Tohoku University Graduate School of Medicine) and Dr. Norio Suzuki at the University of Tsukuba.

EpoR-/- rescued mice underwent 30-minute myocardial ischemia and 24-hour reperfusion. Myocardial infarct size was significantly increased in the EpoR-/- rescued mice compared with wild-type mice. Compared to the wild-type mice, the EpoR-/- rescued mice showed suppressed p38 and JNK phosphorylations in myocardium. Echocardiography performed 3 weeks later revealed that EpoR-/- rescued mice showed significantly accelerated ventricular remodeling compared to wild-type mice (Cardiovasc Res 2006). These data suggest that the Epo-Epo receptor system in non-erythroid cells plays a protective role against myocardial ischemic/reperfusion injury.

EpoR-/- rescued mice were underwent transverse aortic constriction to induce left ventricular hypertrophy due to pressure-overload. After 1 week of banding, the EpoR-/- rescued mice showed remarkable left ventricular dilation, deteriorated left ventricular systolic function, and increased mortality rate compared with wild-type mice (Figure 3). In addition, the phosphorylations of STAT3 and p38, the expression level of vascular endothelial growth factor, and myocardial angiogenesis were all suppressed in EpoR-/- rescued mice compared with wild type mice. These data suggest that the endogenous Epo-Epo receptor system plays an important protective role against the development of heart failure induced by pressure overload at least in part by coronary angiogenesis (Figure 4).

Fig. 3: Deterioration of survival after transverse aortic constriction in mouse lacking erythropoietin receptors in the non-erythroid cells.

Fig. 3

Fig. 4: Endogenous Epo-Epo receptor system in the heart plays a protective role against pressure-overload induced left ventricular dysfunction at least in part by coronary angiogenesis, an adaptive response to cardiac hypertrophy. Fig. 4

3. Possibility of Clinical Application of Erythropoietin for Heart Failure

The results from the above clinical and basic pieces of research suggest that erythropoietin provides protective effects on the diseased hearts and that recombinant human Epo can be used to treat patients with a variety of heart diseases. We will conduct further research to confirm the most beneficial way to administer Epo to patients with myocardial infarction and chronic heart failure while avoiding excessive hematopoiesis.

( Text by Yutaka Kagawa )

4. Role of the Rho-kinase Pathway in Hypertrophic Hearts

We have shown that the Rho-kinase pathway plays an important role in vascular smooth muscle constriction in coronary spastic angina, hypertension, and pulmonary hypertension. This pathway does not work on normal blood vessels but on abnormally constrictive blood vessels including microvessels, but the same mechanism exists in diastolic heart failure where the myocardial cells have constricted, so this is considered to possibly contribute to inhibiting the dilation of myocytes. In addition, left ventricular fibrosis strongly contributes to left ventricular diastolic dysfunction and we are examining the role of Rho-kinase pathway in left ventricular diastolic dysfunction.

( Text by Yoshihiro Fukumoto )

5. Publications (since 2000)
  1. Fukui S, Fukumoto Y, Suzuki J, Saji K, Nawata J, Tawara S, Shinozaki T, Kagaya Y, Shimokawa H. Long-term Inhibition of Rho-kinase Ameliorates Diastolic Heart Failure in Hypertensive Rats. J Cardiovasc Pharmacol. 2008 ;51:317-326.
  2. Oi K, Fukumoto Y, Ito K, Uwatoku T, Abe K, Hizume T, Shimokawa H. Extracorporeal shock wave therapy ameliorates hindlimb ischemia in rabbits. Tohoku J Exp Med. 2008 ;214:151-8.
  3. Onoue N, Nawata J, Tada T, Zhulanqiqige D, Wang H, Sugimura K, Fukumoto Y, Shirato K, Shimokawa H. Increased Static Pressure Promotes Migration of Vascular Smooth Muscle Cells: Involvement of the Rho-kinase Pathway. J Cardiovasc Pharmacol. 2008 ;51:55-61.
  4. Saji K, Fukumoto Y, Suzuki J, Fukui S, Nawata J, Shimokawa H. Colchicine, a microtubule depolymerizing agent, inhibits myocardial apoptosis in rats. Tohoku J Exp Med. 2007 ;213:139-48.
  5. Tawara S, Fukumoto Y, Shimokawa H. Effects of Combined Therapy With a Rho-Kinase Inhibitor and Prostacyclin on Monocrotaline-Induced Pulmonary Hypertension in Rats. J Cardiovasc Pharmacol. 2007 ;50:195-200.
  6. Asaumi Y, Kagaya Y, Takeda M, Yamaguchi N, Tada H, Ito K, Ohta J, Shiroto T, Shirato K, Minegishi N, Shimokawa H. Protective role of endogenous erythropoietin system in non-hematopoietic cells against pressure overload-induced left ventricular dysfunction in mice. Circulation. 2007;115:2022-2032.
  7. Nakano M, Satoh K, Fukumoto Y, Ito Y, Kagaya Y, Ishii N, Sugamura K, Shimokawa H. Important role of erythropoietin receptor to promote VEGF expression and angiogenesis in peripheral ischemia in mice. Circ Res .2007;100:662-669.
  8. Minatoya Y, Ito K, Kagaya Y, Asaumi Y, Takeda M, Nakayama M, Takahashi J, Iguchi A, Shirato K, Shimokawa H. Depressed contractile reserve and impaired calcium handling of cardiac myocytes from chronically unloaded hearts are ameliorated with the administration of physiological treatment dose of T3 in rats. Acta Physiol .2007;189:221-231.
  9. Tada H, Kagaya K, Takeda M, Ohta J, Asaumi Y, Satoh K, Ito K, Karibe A, Shirato K, Minegishi N, Shimokawa H. Endogenous erythropoietin system in non-hematopoietic lineage cells plays a protective role in myocardial ischemia/reperfusion. Cardiovasc Res .2006;71:466-477.
  10. Satoh K, Kagaya Y, Nakano M, Ito Y, Ohta J, Tada H, Karibe A, Minegishi N, Suzuki N, Yamamoto M, Ono M, Watanabe J, Shirao K, Ishii N, Sugamura K, Shimokawa H. Important role of endogenous erythropoietin system in recruitment of endothelial progenitor cells in hypoxia-induced pulmonary hypertension in mice. Circulation .2006;113:1442-1450.
  11. Watanabe J, Shinozaki T, Shiba N, Fukahori K, Koseki Y, Karibe A, Sakuma M, Miura M, Kagaya Y, Shirato K. Accumulation of risk markers predicts the incidence of sudden death in patients with chronic heart failure. Eur J Heart Fail. 2006;8:237-242.
  12. Oikawa M, Kagaya Y, Otani H, Sakuma M, Demachi J, Suzuki J, Takahashi T, Nawata J, Ido T, Watanabe J, Shirato K. Increased [18F]fluorodeoxyglucose accumulation in right ventricular free wall in patients with pulmonary hypertension and the effect of epoprostenol. J Am Coll Cardiol. 2005;45:1849-1855.
  13. Yahagi H, Takeda M, Asaumi Y, Okumura K, Takahashi R, Takahashi J, Ohta J, Tada H, Minatoya Y, Sakuma M, Watanabe J, Goto K, Shirato K, Kagaya Y. Differential regulation of diacylglycerol kinase isozymes in cardiac hypertrophy. Biochem Biophys Res Commun. 2005;332:101-108.
  14. Namiuchi S, Kagaya Y, Ohta J, Shiba N, Sugi M, Oikawa M, Kunii H, Yamao H, Komatsu N, Yui M, Tada H, Sakuma M, Watanabe J, Ichihara T, Shirato K. High serum erythropoietin level is associated with smaller infarct size in patients with acute myocardial infarction who undergo successful primary percutaneous coronary intervention. J Am Coll Cardiol. 2005;45:1406-1412.
  15. Otani H, Kagaya Y, Imahori Y, Yasuda S, Fujii R, Chida M, Namiuchi S, Takeda M, Sakuma M, Watanabe J, Ido T, Nonogi H, Shirato K. Myocardial [C-11] labeled diacylglycerol accumulation and left ventricular remodeling in post myocardial infarction patients. J Nucl Med. 2005;46:553-559.
  16. Watanabe J, Shiba N, Shinozaki T, Koseki Y, Karibe A, Komaru T, Miura M, Fukuchi M, Fukahori K, Sakuma M, Kagaya Y, Shirato K. Prognostic value of plasma brain natriuretic peptide combined with left ventricular dimensions in predicting sudden death of patients with chronic heart failure. J Cardiac Fail. 2005;11:50-55.
  17. Demachi J, Kagaya Y, Watanabe J, Sakuma M, Ikeda J, Kakuta Y, Motoyoshi I, Kohnosu T, Sakuma H, Shimazaki S, Sakai H, Kimpara T, Takahashi T, Omura K, Okada M, Saito H, Shirato K. Characteristics of the increase in plasma brain natriuretic peptide level in left ventricular systolic dysfunction associated with muscular dystrophy in comparison with idiopathic dilated cardiomyopathy. Neuromuscul Disord. 2004;14:732-739.
  18. Takahashi J, Kagaya Y, Kato I, Ohta J, Isoyama S, Miura M, Sugai Y, Hirose M, Wakayama Y, Ninomiya M, Watanabe J, Takasawa S, Okamoto H, Shirato K. Deficit of CD38/cyclic ADP-ribose is differentially compensated in hearts by genders. Biochem Biophys Res Commun . 2003;312:434-440.
  19. Sugie T, Kagaya Y, Takeda M, Yahagi H, Takahashi C, Takahashi J, Ninomiya M, Watanabe J, Ichinohasama R, Tezuka F, Shirato K. Should increasing the dose or adding AT1 receptor blocker follow a relatively low dose of ACE inhibitor initiated in acute myocardial infarction Cardiovasc Res. 2003;58:611-620.
  20. Kagaya Y, Chida M, Imahori Y, Fujii R, Namiuchi S, Takeda M, Yamane Y, Otani H, Watanabe J, Fukuchi M, Tezuka F, Ido T, Shirato K. Effect of angiotensin converting enzyme inhibition on myocardial phosphoinositide metabolism visualized with 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol in myocardial infarction in the rat. Eur J Nucl Med Mol Imaging. 2002;29:1516-1522.
  21. Kaneta T, Takai Y, Kagaya Y, Yamane Y, Wada H, Yuki M, Iwata R, Tsujitani M, Takahashi S, Yamada S. Imaging of ischemic but viable myocardium using a new [18F]labeled 2-nitroimidazole analog, [18F]FRP170. J Nucl Med. 2002; 43:109-116.
  22. Chida M, Kagaya Y, Nagata S, Mukoyoshi M, Namiuchi S, Yamane Y, Ishide N, Watanabe J, Takahashi T, Ido T, Shirato K. [18F] labeled diacylglycerol analogue as a potential agent to trace myocardial phosphoinositide metabolism. Nucl Med Biol . 2001 ;28:815-819.
  23. Takeda M, Kagaya Y, Takahashi J, Sugie T, Ohta J, Watanabe J, Shirato K, Kondo H, Goto K. Gene expression and in situ localization of diacylglycerolkinase isozymes in normal and infarcted rat hearts: Effects of captopril treatment. Circ Res. 2001; 89: 265-272.
  24. Nozaki T, Kagaya Y, Ishide N, Kitada S, Miura M, Nawata J, Ohno I, Watanabe J, Shirato K. Interaction between sarcomere and mitochondrial length in normoxic and hypoxic rat ventricular papillary muscles. Cardiovasc Pathol. 2001; 10: 125-132.
  25. Takahashi C, Kagaya Y, Namiuchi S, Takeda M, Fukuchi M, Otani H, Ninomiya M, Yamane Y, Kohzuki M, Watanabe J, Shirato K. Non selective ET receptor antagonist initiated soon after the onset of myocardial infarction may deteriorate 24-hour survival. J Cardiovasc Pharmacol. 2001; 38:29-38.
  26. Chida M, Kagaya Y, Imahori Y, Namiuchi S, Fujii R, Fukuchi M, Takahashi C, Tezuka F, Ido T, Shirato K. Visualization of Myocardial Phosphoinositide Turnover with 1-[1-11C]-butyryl-2-palmitoyl-rac-glycerol in rats with myocardial infarction. J Nucl Med. 2000; 41:2063-2068.
  27. Otani H, Kagaya Y, Yamane Y, Chida M, Ito K, Namiuchi S, Shiba N, Koseki Y, Ninomiya M, Ikeda J, Saito H, Maruoka M, Fujiwara T, Ido T, Ishide N, Shirato K. Long-term right ventricular volume overload increases myocardial FDG uptake in the interventricular septum in patients with atrial septal defect. Circulation . 2000; 101:1686-1692.
  28. Namiuchi S, Kagaya Y, Chida M, Yamane Y, Takahashi C, Fukuchi M, Tezuka F, Watanabe J, Ido T, Shirato K. Regional and temporal profiles of phorbol 12, 13 - dibutyrate binding after myocardial infarction in rats: Effects of captopril treatment. J Cardiovasc Pharmacol. 2000;35:353-360.

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