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ABSTRACT: Although adenosine is an important mediator of ischemic preconditioning (IPC), its relative contribution to IPC remains unknown. Because adenosine is formed through the hydrolysis of ATP, the present study investigated the role of ATP and adenosine in IPC. Isolated and buffer-perfused rat hearts underwent IPC by three cycles of 5-min ischemia and 5-min reperfusion before 25 min of global ischemia. The rate-pressure product (RPP) 30 min after reperfusion was taken as an endpoint of functional protection. Interstitial fluid (ISF) adenine nucleotides and adenosine were measured by cardiac microdialysis techniques. Inhibition of IPC-induced recovery of RPP was partial by the adenosine receptor antagonist 8-(p-sulfophenyl)theophylline (SPT; 100 microM) or by the structurally distinct P2Y purinoceptor antagonists suramin (300 microM) or reactive blue (RB; 10 microM) but was additive when SPT was given with suramin or RB. The P2X antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid tetrasodium (50 microM) had no effect on functional protection. The improved functional recovery was not significantly affected by an ecto-5'-nucleotidase inhibitor, alpha,beta-methylene adenosine diphosphate (AMP-CP; 100 microM), alone but was inhibited by AMP-CP plus SPT, suramin, or RB. ISF ATP and adenosine increased temporarily by 10-fold during IPC. AMP-CP augmented the increase in ISF ATP associated with the decrease in ISF adenosine. There was a reciprocal correlation between the ISF concentration of ATP and adenosine in preconditioned hearts. In addition, there was a significant correlation between ISF adenosine and ATP and the inhibitory potency of SPT and suramin or RB against functional protection conferred by IPC. These results suggest that extracellular ATP and adenosine play a complementary role in IPC through P2Y purinoceptors and adenosine receptors, respectively.
AJP Heart and Circulatory Physiology 06/2002; 282(5):H1810-20. · 3.71 Impact Factor
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ABSTRACT: A modern experimental strategy for treating myocardial ischemia is to induce neovascularization of the heart by the use of "angiogens", mediators that induce the formation of blood vessels, or angiogenesis. Studies demonstrated that coronary collateral vessels protect ischemic myocardium after coronary obstruction; therefore we sought to examine a novel method of stimulating myocardial angiogenesis through hypoxic preconditioning at both capillary (using anti-CD31) and arteriolar (using anti- alpha smooth muscle actin) levels and also investigate whether such treatments could preserve left ventricular contractile functional reserve and regional blood flow by increasing vascular endothelial growth factor (VEGF). Male Sprague-Dawley rats were randomly divided into four groups: normoxia+sham surgery (CS), normoxia+permanent left anterior descending coronary artery (LAD) occlusion (CMI), hypoxic preconditioning+sham surgery (HS) and hypoxic preconditioning+permanent LAD occlusion (HMI). Rats in the preconditioned groups were subjected to systemic hypoxemic hypoxic exposure (10+/-0.4% O(2)) for 4 h followed by a 24 h period of normoxic reoxygenation prior to undergoing LAD occlusion. Rats in the normoxia group were time matched with the preconditioned group and maintained under normoxic conditions for a 28 h period prior to LAD occlusion. Western blot analysis was performed to measure VEGF expression and TUNEL staining with endothelial cell-specific antibody, anti-VWF, was used to examine endothelial apoptosis. One, two and three weeks after the LAD occlusion, baseline left ventricular pressures were monitored and recorded. Pharmacological stress tests with dobutamine infusion in progressively increasing doses revealed significantly elevated contractile reserve at each dose point in the HMI group compared to the CMI group. The HMI group displayed statistically significant increases in capillary as well as arteriolar density after 1, 2 and 3 weeks post-operation. Blood flow was also significantly elevated in the HMI groups when compared to the CMI group. The extent of endothelial cell apoptosis was found to be inversely proportional to VEGF expression. It was concluded that hypoxic preconditioning stimulates myocardial angiogenesis to an extent sufficient to exert significant cardioprotection in a rat model of myocardial infarction progressing to heart failure as evidenced by increased capillary/arteriolar density and enhanced ventricular contractile functional reserve.
Journal of Molecular and Cellular Cardiology 04/2002; 34(3):335-48. · 5.17 Impact Factor
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ABSTRACT: SUMMARY1. Na+/H+ exchange has been implicated in the mechanism of reperfusion injury. We examined the effects of the cardiac-specific Na+/H+ exchange inhibitor cariporide (HOE 642) on postischaemic recovery of cardiac function and cardiomyocyte cell death (i.e. necrosis and apoptosis).2. Rat isolated and buffer-perfused hearts were subjected to 25 min normothermic global ischaemia followed by 120 min reperfusion. Cariporide (10 μmol/L) or its vehicle (0.01% dimethylsulphoxide) was administered for 15 min before ischaemia and for the first 30 min after reperfusion.3. Cariporide significantly improved the recovery of isovolumic left ventricular function (heart rate, left ventricular developed pressure and left ventricular end-diastolic pressure) and coronary flow throughout reperfusion. Creatine kinase release during reperfusion was significantly less in the cariporide-treated heart. In situ terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL)- positive cardiomyocytes were also significantly less in the cariporide-treated heart after 120 min reperfusion. Electron microscopy showed necrotic changes without typical apoptotic features in cardiomyocytes after reperfusion. Such necrotic changes were mitigated by cariporide. Simultaneous detection of necrotic and apoptotic cardiomyocytes using propidium iodide (PI) and Annexin V revealed that cardiomyocytes in the infarct area were stained with only PI or both PI and Annexin V. Cariporide did not alter the pattern of cardiomyocyte staining with PI and Annexin V, although the number of cardiomyocytes stained with PI or PI plus Annexin V was less than that in vehicle-treated hearts.4. These results suggest that apoptosis is not a major manifestation of cardiomyocyte cell death in the ischaemic– reperfused myocardium and a cariporide-sensitive mechanism of reperfusion injury promotes both necrotic and apoptotic processes of cell death.
Clinical and Experimental Pharmacology and Physiology 04/2000; 27(5‐6):387 - 393. · 1.85 Impact Factor
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ABSTRACT: A 1-day-old male infant with critical aortic valvular stenosis underwent balloon aortic valvuloplasty (BAV) under echocardiographic
guidance during cardiopulmonary bypass. Left ventricular function dramatically improved after BAV. This technique combined
with a surgical approach was safe and efficient.
CardioVascular and Interventional Radiology 04/1996; 19(5):374-376. · 2.09 Impact Factor
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ABSTRACT: Bone marrow-derived cells (BMCs) are critically involved in inflammation and regeneration after myocardial infarction (MI). However, the participation of BMCs in the reconstruction of infarcted myocardium remains unclear. In this study, we investigated phenotypic modulation of BMCs and their turnover in the heart following MI.
MI was produced in rats with intra-bone marrow-bone marrow transplantation from the syngenic rats expressing green fluorescence protein (GFP). The number of GFP-positive BMCs recruited to the infarcted myocardium peaked at 3 days after MI, and the majority of BMCs recruited to the heart after MI underwent turnover within 2 weeks. This turnover rate was unchanged for up to 16 weeks after MI, although the number of BMCs recruited to the infarcted myocardium rapidly decreased between 2 and 8 weeks after MI. A small number of BMCs recruited to the heart were positive for CD31 and α-smooth muscle actin, and the majority of these were positive for vimentin at 3 days and 4 weeks after MI. None of BMCs expressed α-actinin or von Willebrand factor 4 weeks after MI.
These results suggest that BMCs recruited to the heart underwent phenotypic modulation to a fibroblastic cell type and turnover within 2 weeks after MI without differentiating into cardiomyocytes or endothelial cells, and that although the number of BMCs in the infarcted myocardium decreased over time, the rate of turnover remained relatively constant during the chronic phase of MI.
Cardiovascular pathology: the official journal of the Society for Cardiovascular Pathology 20(3):146-55. · 1.63 Impact Factor
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ABSTRACT: Therapeutic angiogenesis achieved either through the use of discreet angiogenic proteins or by gene therapy is fast emerging as a highly attractive treatment modality for ischemic heart disease. Herein we examine a novel method of stimulating myocardial angiogenesis by hypoxic preconditioning at both capillary and arteriolar levels, and the potential role of NF κ B in mediating such a response. We also investigate the functional relevance of such treatment by assessing whether the induced neovascularization can help preserve left ventricular contractile functional reserve in the setting of developing heart failure secondary to myocardial infarction. Male Sprague–Dawley rats were randomly divided into eight groups: normoxia+sham surgery (NS), normoxia+permanent left anterior descending coronary artery (LAD) occlusion (NMI), hypoxic preconditioning+sham surgery (HS), hypoxic preconditioning+permanent LAD occlusion (HMI), PDTC (NF κ B inhibitor)+hypoxic preconditioning+LAD occlusion (PHMI), PDTC+normoxia+LAD occlusion (PNMI), PDTC+hypoxic preconditioning+sham surgery (PHS) and PDTC+normoxia+sham surgery (PNS). Rats in the preconditioned groups were subjected to systemic hypoxemic hypoxic exposure (10±0.4% O2) for 4 h followed by a 24-h period of normoxic reoxygenation prior to undergoing LAD occlusion. Rats in the normoxia groups were time matched with the preconditioned group and maintained under normoxic conditions for the 28-h period prior to LAD occlusion. The HMI group displayed significant increases in capillary as well as arteriolar density after 2, 4 and 7 days post-operation compared to the NMI. Prior PDTC administration prevented such increases in the PHMI group and effectively abolished the pro-angiogenic effect of hypoxic preconditioning (HP). One week after sham surgery or LAD occlusion, rats underwent a pharmacological stress test with dobutamine in progressively increasing doses which revealed significantly elevated values of dp/dtmaxat each dose point in the HMI group compared to the NMI or PHMI groups. Hypoxic preconditioning also decreases endothelial cell injury as determined by the extent of endothelial cell apoptosis using anti-VWF factor labelling and TUNEL assay. The results suggest that HP stimulates myocardial angiogenesis via redox-regulated transcription factor, NF κ B-dependent pathway to an extent sufficient to exert significant preservation of contractile functional reserve in a rat model of myocardial infarction progressing to heart failure.
Journal of Molecular and Cellular Cardiology.
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ABSTRACT: Phosphoinositide metabolism is known to be associated with neuronal or humoral stimulation of excitable cells. The present study examined whether the phosphoinositide response is involved in such events using isolated rat papillary muscles labeled with [3H]inositol. It was found that neither increase in the stimulation frequencies (0–2 Hz) nor prolongation of the pulse duration (10–70 msec) altered the labeling of phosphoinositides and the accumulation of [3H]inositol phosphates in this preparation. However, phenylephrine, a known α1-agonist, was capable of provoking the breakdown of phosphoinositides associated with a positive inotropic effect in this preparation. We report the evidence that phosphoinositide response is mediated by α1-adrenoceptor stimulation, but not linked with excitation-contraction coupling in cardiac muscle.
Biochemical and Biophysical Research Communications.
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ABSTRACT: Background. Although fibrin sealant (Beriplast, Aventis Behring, Marburg, Germany) has been widely used as a supplementary measure for hemostasis during cardiac surgery in Europe and is becoming popular in the United States, the pharmocokinetics of fibrin sealant applied in pericardial space has not been elucidated.Methods. A small incision was made on the epicardial surface of the left ventricle of a rat, and the incision was sutured. Total 0.2 ml of fibrin sealant containing iodine 125 (125I)-labeled fibrinogen, aprotinin, blood coagulation factor XIII and thrombin was applied to the area around the suture line.Results. Distributions of 125I-labeled fibrinogen in the heart on postoperative days 1, 3, 7, and 14 were 48.2% ± 1.8%, 20.7% ± 2.2%, 0.15% ± 0.02%, and 0.01% ± 0.02%, respectively. The radioactivity was negligible in the blood, liver, spleen, and kidney except for the thyroid in which the radioactivity increased to 7.9% ± 0.7% and 4.3% ± 0.4%, respectively, on postoperative days 7 and 14. Iodine 125-labeled fibrinogen concentrations of the heart and other organs showed a similar change in the time course of distribution. Dense and thick fibrin network, observed on postoperative day 1, had dissipated and was thinner with collagen formation by postoperative day 7.Conclusions. Fibrin sealant applied to the pericardial cavity regresses rapidly and plays an important role in wound healing.
The Annals of Thoracic Surgery.
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ABSTRACT: Thioredoxin (Trx-1), a key mediator of cellular redox homeostasis and cell survival, is implicated in redox signaling in the ischemic myocardium. To investigate further its mechanism of action, Trx expression in rat heart was suppressed by direct injection of small hairpin RNA against Trx-1 (shRNA-Trx-1). Forty-eight hours after treatment, hearts were excised for isolated working-heart preparation. A group of hearts was preconditioned (PC) by subjecting them to four cyclic episodes of 5-min ischemia, each followed by 10 min of reperfusion. All the hearts, PC or non-PC, were subjected to 30-min ischemia followed by 2 h of reperfusion. As expected, the PC hearts exhibited improved ventricular function, reduced infarct size, and cardiomyocyte apoptosis. Also in PC hearts, an increase was noted in Trx-1 and other cardioprotective and redox-regulated proteins like Ref-1, phospho-Akt, and NF-kappaB DNA-binding activity. PC also caused nuclear translocation of Trx-1 and Ref-1 followed by their association. However, in hearts treated with shRNA-Trx 1, the cardioprotective effects of PC were abolished along with a concomitant decrease in nuclear localized Trx-1 and Ref-1, along with a decrease in phospho-Akt and NF-kappaB. These results demonstrate that PC triggers translocation of Trx-1 into the nucleus, where it becomes associated with Ref-1 and performs redox signaling through the activation of NF-kappaB and an increase in prosurvival signal inducer phospho-Akt.
Antioxidants and Redox Signaling 8(11-12):2101-9. · 8.46 Impact Factor
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ABSTRACT: We investigated the role of oxidative/nitrosative stress in the tolerance to ischemia/reperfusion (I/R) injury in BIO14.6 cardiomyopathy hamster hearts at 6 weeks of age. These hearts showed no significant morphologic change and left ventricular (LV) dysfunction. However, expression and activity of iNOS, nitrotyrosine (NT) formation, and protein kinase C (PKC)-epsilon activity were increased in these hearts. When the BIO14.6 hamster hearts were isolated and subjected to 40 min of global ischemia, they showed smaller myocardial necrosis and greater recovery of LV function during reperfusion compared with the control hamster heart. All of these effects were abrogated by prolonged treatment with the antioxidant, 2-mercaptopropionylglycine (MPG). Brief preischemic treatment with MPG or the iNOS inhibitor 1400W also abrogated NT formation and activation of PKC-epsilon and inhibited the tolerance to I/R injury in the BIO14.6 hamster heart. Brief preischemic treatment with the PKC inhibitor chelerythrine or the K(ATP) channel blockers, 5-hydroxydecanoate (5-HD) and glibenclamide, had no effect on iNOS activation and NT formation but inhibited the tolerance to I/R injury in the cardiomyopathic heart. These results suggest that oxidative/nitrosative stress plays a role in the tolerance to I/R injury in the cardiomyopathic heart through activation of PKC and the downstream effectors, K(ATP) channels.
Antioxidants and Redox Signaling 8(7-8):1351-61. · 8.46 Impact Factor
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ABSTRACT: 1. Activation of mitochondrial KATP (mitoKATP) channels and protein kinase C (PKC) has been implicated in cardioprotective mechanisms of ischaemic preconditioning (IPC). However, the exact role of these events in early IPC remains unclear. 2. Isolated and perfused rat hearts underwent IPC with three cycles of 5 min ischaemia and 5 min reperfusion. The heart was subjected to 30 min global ischaemia followed by 120 min reperfusion. Flavoprotein oxidation was monitored to assess mitoKATP channel activity. Cardioprotection was evaluated by recovery of isovolumic left ventricular (LV) function and infarct size. 3. Diazoxide (50 mgr;mol/L) increased flavoprotein oxidation and conferred cardioprotection in a manner sensitive to the selective mitoKATP channel blocker 5-hydroxydecanoate (5-HD; 0.5 mmol/L). 4. Pretreatment with 0.5 mmol/L 5-HD abrogated IPC-induced flavoprotein oxidation and cardioprotection, whereas late treatment with 5-HD after IPC required a higher dose (2 mmol/L) to abolish flavoprotein oxidation and cardioprotection afforded by IPC. 5. Pretreatment with the PKC inhibitors Ro318425 (1 micro mol/L) and chelerythrine (5 micro mol/L) abolished IPC-induced flavoprotein oxidation and cardioprotection, whereas late treatment with Ro318425 required a higher dose (4 micro mol/L) to abolish flavoprotein oxidation and cardioprotection. 6. In conclusion, these results suggest that activation of mitoKATP channels is the trigger and the mediator of IPC and that PKC plays a crucial role in both phases of mitoKATP channel activation, although mitoKATP channels and PKC may be more activated during the mediator phase.
Clinical and Experimental Pharmacology and Physiology 30(5-6):426-36. · 1.85 Impact Factor
