reperfusion injury through transient mitochondrial permeability transition pore opening

reperfusion injury through transient mitochondrial permeability transition pore opening

ABSTRACTS / Journal of Molecular and Cellular Cardiology 45 (2008) S1–S35 ance. Otherwise, allogenic SMB transplantation was not acceptable because i...

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ABSTRACTS / Journal of Molecular and Cellular Cardiology 45 (2008) S1–S35

ance. Otherwise, allogenic SMB transplantation was not acceptable because it did not show enough therapeutic effect. Keywords: Acute myocardial Infarction; Cell Therapy; Allogenic doi:10.1016/j.yjmcc.2008.09.657

P-A-28 Regulation of coronary vascular tone via redox modulation in the alpha1-adrenergic-angiotensin-endothelin axis of the myocardium Osamu Yamaguchi, Shu-ichi Saitoh, Takashi Kaneshiro, Toshiyuki Ishibashi, Yasuchika Takeishi First Department of Internal Medicine, Fukushima medical university We hypothesized that α1-adrenoceptor stimulation on the cardiac myocytes results in the production of an endothelin-releasing factor, which stimulates the coronary vasculature to release endothelin, and by manipulating the redox state of cardiac and vascular cells, may influence the extent of α1-adrenergic-endothelin-1-vasoconstriction. Relative dihydroethidium (DHE) and dichloro-dihydrofluorescein (DCF) intensities were increased by phenylephrine stimulation in isolated rat cardiac myocytes, which was enhanced by a mitochondrial ETc-complex I inhibitor rotenone, but not by a NADPH oxidase inhibitor apocynin. Olmesartan, an angiotensin II type 1 receptor antagonist, and enalaprilate, an angiotensin converting enzyme inhibitor, did not change DHE and DCF intensities by phenylephrine. Next, we measured vasoconstriction of isolated, pressurized rat coronary arteriole (74 ± 8 μm, diameter) response to supernatant collected from isolated cardiac myocytes. Addition of supernatant from phenylephrinestimulated myocytes to a 2-ml vessel bath caused volume-dependent vasoconstriction (500 μl: -14.8 ± 2.2%). Olmesartan and TA0201, endothelin type-A receptor antagonist, converted vasoconstriction into vasodilation (8.5 ± 1.2%, 10.5 ± 0.5%, P < 0.01) in response to the supernatant from phenylephrine-stimulated myocytes, which was eliminated with catalase. Vasoconstriction was weakened using supernatant from phenylephrine with rotenone- or antioxidant Nacetylcysteine-treated myocytes. Treatment of arterioles with apocynin to the myocyte supernatant converted vasoconstriction into vasodilation (7.8 ± 0.8%, P < 0.01).These results suggest that α1-adrenergic stimulation in cardiac myocytes produces angiotensin I and hydrogen peroxide, and that angiotensin releases endothelin-1 through NADPH oxidase in coronary arterioles. Thus, coronary vasoconstriction via the α-adrenergic-angiotensin-endothelin axis appears to require redox-mediated signaling in cardiac and vascular cells. Keywords: α1-adrenoceptor; reactive oxygen species; coronary vasomotion doi:10.1016/j.yjmcc.2008.09.658

P-A-29 Downregulation of ferritin heavy chain increases labile iron pool, oxidative stress and cell death in cardimyocytes Shigemiki Omiya, Shungo Hikoso, Kinya Otsu Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine Background: Ferritin heavy chain (FHC) regulates the cellular availability of iron, which induces generation of reactive oxygen species. However, the role of FHC in the pathogenesis of heart failue has not been elucidated. Methods and Results: We examined the FHC expression level in murine failing hearts. FHC protein had significantly reduced in failing hearts after both myocardial infarction and transverse aortic constriction compared with corresponding sham-operated hearts (36.6 ± 5.3% and 37.6 ± 4.5% of sham-operated hearts, respectively, p < 0.05). Iron deposition and oxidative stress had increased in failing

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hearts. To clarify the functional significance of FHC downregulation in hearts, we infected rat neonatal cardiomyocytes with adenovirus expressing short hairpin RNA targeted to FHC (Ad-FHC-RNAi). Knockdown of FHC by Ad-FHC-RNAi had significantly increased the number of iron deposition positive cells and 4-hydroxy-2-nonenal positive cells (Ad-nonspecific-RNAi infected vs. Ad-FHC-RNAi infected cells, 15.5 ± 2.1% vs. 49.8 ± 1.2%, 21.4 ± 2.9% vs. 48.9 ± 4.0%, respectively, p < 0.05), and resulted in significant reduction in cell viability (45.6 ± 8.6% of Ad-nonspecific-RNAi infected cells, p < 0.05). Reduced cell viability by Ad-FHC-RNAi was significantly attenuated with desferrioxamine treatment, an iron chelator. Conclusions: These findings indicate that increase in free iron mediated through downregulation of FHC induces cardiomyocyte death, and may play an important role in the progression of heart failure. Keywords: Ferritin heavy chain; Cardiomyocyte death doi:10.1016/j.yjmcc.2008.09.659

P-A-30 Hydrogen peroxide protects myocardium from ischemia/ reperfusion injury through transient mitochondrial permeability transition pore opening Masao Saotome, Takamitsu Tanaka, Mamoru Nobuhara, Hideki Katoh, Yasuhiro Yaguchi, Tsuyoshi Urusida, Hiroshi Satoh, Hideharu Hayashi Division of Cardiology, Internal Medicine III, Hamamatsu University School of Medicine Reactive oxygen species (ROS) generation during ischemia/ reperfusion has been considered as a critical factor of myocardial injury. However previous reports have claimed that the repetitive pretreatment of ROS can mimicked the ischemic preconditioning (IPC) and protect myocardium against ishcemia/reperfusion injury. Here we investigated the mechanisms in the ROS-induced cardioprotection against ischemia/reperfusion injury, and tested the hypothesis that the transient opening of mitochondrial permeability transition pore (mPTP) may be involved in this mechanism. Langendorff-perfused hearts were subjected to 35 min of ischemia and 40 min reperfusion, and the pretreatment with hydrogen peroxide (H2O2; 2 μM) significantly improved the post-ischemic recoveries in left ventricular developed pressure (LVDP), intracellular phosphocreatine and ATP levels. A specific mPTP inhibitor cyclosporin A (CsA; 0.2 μM) abolished these H2O2-induced benefits. In single permeabilized myocytes, H2O2 (1 μM) accelerated the calcein leakage from mitochondria in a CsA-sensitive manner, indicating the opening of mPTP. Although H2O2 did not alter mitochondrial membrane potential (ΔΨm), H2O2 decreased mitochondrial Ca2+ concentration ([Ca2+]m) by accelerating the mitochondrial Ca2+ extrusion via an mPTP. We conclude that the transient mPTP opening is involved in the H2O2-mediated cardioprotection against reperfusion injury, and that the reduction in [Ca2+]m without altering ΔΨm might be a possible mechanism for the cardiac protection. Keywords: ischemic preconditioning; Reactive oxygen species; mitochondrial permeability transition pore doi:10.1016/j.yjmcc.2008.09.660

P-A-31 Changes in mitochondrial energy-producing ability in the right ventricular muscle of monocrotaline-induced pulmonary hypertensive rats Takuya Daicho, Tatsuya Yagi, Yohei Abe, Meiko Ohara, Yoriko Daisho, Tetsuro Marunouchi, Satoshi Takeo, Kouichi Tanonaka Department of Molecular and Cellular Pharmacology, Tokyo University of Pharmacy and Life Sciences