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Experimental assessment of a myocyte-based multiscale model of cardiac contractile dysfunction. J Theor Biol 2018; 456:16-28. [PMID: 30063925 DOI: 10.1016/j.jtbi.2018.07.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 07/09/2018] [Accepted: 07/27/2018] [Indexed: 12/22/2022]
Abstract
Cardiac contractile dysfunction (CD) is a multifactorial syndrome caused by different acute or progressive diseases which hamper assessing the role of the underlying mechanisms characterizing a defined pathological condition. Mathematical modeling can help to understand the processes involved in CD and analyze their relative impact in the overall response. The aim of this study was thus to use a myocyte-based multiscale model of the circulatory system to simulate the effects of halothane, a volatile anesthetic which at high doses elicits significant acute CD both in isolated myocytes and intact animals. Ventricular chambers built using a human myocyte model were incorporated into a whole circulatory system represented by resistances and capacitances. Halothane-induced decreased sarco(endo)plasmic reticulum Ca2+ (SERCA2a) reuptake pump, transient outward K+ (Ito), Na+-Ca2+ exchanger (INCX) and L-type Ca2+ channel (ICaL) currents, together with ryanodine receptor (RyR2) increased open probability (Po) and reduced myofilament Ca2+ sensitivity, reproduced equivalent decreased action potential duration at 90% repolarization and intracellular Ca2+ concentration at the myocyte level reported in the literature. In the whole circulatory system, model reduction in mean arterial pressure, cardiac output and regional wall thickening fraction was similar to experimental results in open-chest sheep subjected to acute halothane overdose. Effective model performance indicates that the model structure could be used to study other changes in myocyte targets eliciting CD.
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2
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Kon N, Abe N, Miyazaki M, Mushiake H, Kazama I. Partial exposure of frog heart to high-potassium solution: an easily reproducible model mimicking ST segment changes. J Vet Med Sci 2018; 80:578-582. [PMID: 29503350 PMCID: PMC5938182 DOI: 10.1292/jvms.18-0010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
By simply inducing burn injuries on the bullfrog heart, we previously reported a simple
model of abnormal ST segment changes observed in human ischemic heart disease. In the
present study, instead of inducing burn injuries, we partially exposed the surface of the
frog heart to high-potassium (K+) solution to create a concentration gradient
of the extracellular K+ within the myocardium. Dual recordings of ECG and the
cardiac action potential demonstrated significant elevation of the ST segment and the
resting membrane potential, indicating its usefulness as a simple model of heart injury.
Additionally, from our results, Na+/K+-ATPase activity was thought
to be primarily responsible for generating the K+ concentration gradient and
inducing the ST segment changes in ECG.
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Affiliation(s)
- Nobuaki Kon
- Department of Physiology, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Nozomu Abe
- Department of Physiology, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan.,Department of Anesthesiology, Tohoku University Hospital, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Masahiro Miyazaki
- Department of Physiology, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Hajime Mushiake
- Department of Physiology, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Itsuro Kazama
- School of Nursing, Miyagi University, Gakuen, Taiwa-cho, Kurokawa-gun, Miyagi 981-3298, Japan.,Department of Physiology, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
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Abstract
KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.
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Affiliation(s)
- Monique N Foster
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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Kazama I. Burn-induced subepicardial injury in frog heart: a simple model mimicking ST segment changes in ischemic heart disease. J Vet Med Sci 2015; 78:313-6. [PMID: 26346747 PMCID: PMC4785125 DOI: 10.1292/jvms.15-0440] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
To mimic ischemic heart disease in humans, several animal models have been created, mainly in rodents by
surgically ligating their coronary arteries. In the present study, by simply inducing burn injuries on the
bullfrog heart, we reproduced abnormal ST segment changes in the electrocardiogram (ECG), mimicking those
observed in ischemic heart disease, such as acute myocardial infarction and angina pectoris. The “currents of
injury” created by a voltage gradient between the intact and damaged areas of the myocardium, negatively
deflected the ECG vector during the diastolic phase, making the ST segment appear elevated during the systolic
phase. This frog model of heart injury would be suitable to explain the mechanisms of ST segment changes
observed in ischemic heart disease.
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Affiliation(s)
- Itsuro Kazama
- Department of Physiology I, Tohoku University Graduate School of Medicine, Seiryo-cho, Aoba-ku, Sendai, Miyagi 980-8575, Japan
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Rautaharju PM, Zhang ZM, Haisty WK, Kucharska-Newton AM, Rosamond WD, Soliman EZ. Electrocardiographic repolarization-related predictors of coronary heart disease and sudden cardiac deaths in men and women with cardiovascular disease in the Atherosclerosis Risk in Communities (ARIC) study. J Electrocardiol 2015; 48:101-11. [DOI: 10.1016/j.jelectrocard.2014.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Indexed: 11/28/2022]
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Fahrenbach JP, Stoller D, Kim G, Aggarwal N, Yerokun B, Earley JU, Hadhazy M, Shi NQ, Makielski JC, McNally EM. Abcc9 is required for the transition to oxidative metabolism in the newborn heart. FASEB J 2014; 28:2804-15. [PMID: 24648545 DOI: 10.1096/fj.13-244459] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The newborn heart adapts to postnatal life by shifting from a fetal glycolytic metabolism to a mitochondrial oxidative metabolism. Abcc9, an ATP-binding cassette family member, increases expression concomitant with this metabolic shift. Abcc9 encodes a membrane-associated receptor that partners with a potassium channel to become the major potassium-sensitive ATP channel in the heart. Abcc9 also encodes a smaller protein enriched in the mitochondria. We now deleted exon 5 of Abcc9 to ablate expression of both plasma membrane and mitochondria-associated Abcc9-encoded proteins, and found that the myocardium failed to acquire normal mature metabolism, resulting in neonatal cardiomyopathy. Unlike wild-type neonatal cardiomyocytes, mitochondria from Ex5 cardiomyocytes were unresponsive to the KATP agonist diazoxide, consistent with loss of KATP activity. When exposed to hydrogen peroxide to induce cell stress, Ex5 neonatal cardiomyocytes displayed a rapid collapse of mitochondria membrane potential, distinct from wild-type cardiomyocytes. Ex5 cardiomyocytes had reduced fatty acid oxidation, reduced oxygen consumption and reserve. Morphologically, Ex5 cardiac mitochondria exhibited an immature pattern with reduced cross-sectional area and intermitochondrial contacts. In the absence of Abcc9, the newborn heart fails to transition normally from fetal to mature myocardial metabolism.-Fahrenbach, J. P., Stoller, D., Kim, G., Aggarwal, N., Yerokun, B., Earley, J. U., Hadhazy, M., Shi, N.-Q., Makielski, J. C., McNally, E. M. Abcc9 is required for the transition to oxidative metabolism in the newborn heart.
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Affiliation(s)
| | - Douglas Stoller
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Gene Kim
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Nitin Aggarwal
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | | | - Judy U Earley
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Michele Hadhazy
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Nian-Qing Shi
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | - Jonathan C Makielski
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | - Elizabeth M McNally
- Department of Medicine, Division of Cardiovascular Medicine, and Department of Human Genetics, The University of Chicago, Chicago, Illinois, USA; and
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Lascano EC, Negroni JA, del Valle HF. Early preconditioning protection against stunning in conscious sheep. Role of KATP channels. Mol Cell Biochem 2009; 331:247-57. [DOI: 10.1007/s11010-009-0166-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/21/2009] [Indexed: 01/24/2023]
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Ross JL, Howlett SE. Beta-adrenoceptor stimulation exacerbates detrimental effects of ischemia and reperfusion in isolated guinea pig ventricular myocytes. Eur J Pharmacol 2008; 602:364-72. [PMID: 19056376 DOI: 10.1016/j.ejphar.2008.11.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 10/20/2008] [Accepted: 11/17/2008] [Indexed: 10/21/2022]
Abstract
We investigated whether beta-adrenoceptor stimulation exacerbates detrimental effects of ischemia and reperfusion on electrical and contractile function and on intracellular Ca(2+) homeostasis in isolated guinea pig ventricular myocytes. Myocytes were exposed to 20 min of simulated ischemia (37 degrees C) in the absence or presence of isoproterenol (10 nM, applied prior to and during ischemia) and reperfused with Tyrode's solution for 30 min. Unloaded cell shortening, Ca(2+) transients (fura-2), and cell viability were recorded at 5 min intervals in field-stimulated cells (2 Hz). In experiments using microelectrodes, membrane potentials, contractions, and transmembrane currents also were recorded at 5 min intervals. In the absence of ischemia, 10 nM isoproterenol had little effect on either contractile function or Ca(2+) homeostasis. In contrast, when cells were exposed to ischemia, isoproterenol increased the size of contractions and Ca(2+) transients and augmented the increase in diastolic Ca(2+) concentration during ischemia in field-stimulated myocytes. Exposure to isoproterenol also promoted contractile depression in reperfusion. In voltage clamp experiments, isoproterenol abolished the decrease in the magnitude of L-type Ca(2+) current caused by ischemia. Isoproterenol also increased the incidence of abnormal contractile activity and induced delayed afterdepolarizations and the arrhythmogenic transient inward current in ischemia. Additionally, the decline in cell viability in ischemia and reperfusion was exacerbated by isoproterenol. This study shows that beta-adrenoceptor stimulation strongly potentiates adverse effects of ischemia and reperfusion on electrical and contractile function. These adverse effects of isoproterenol are likely caused by an increase in intracellular Ca(2+) accumulation during ischemia.
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Affiliation(s)
- Jenna L Ross
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
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Mykytenko J, Reeves JG, Kin H, Wang NP, Zatta AJ, Jiang R, Guyton RA, Vinten-Johansen J, Zhao ZQ. Persistent beneficial effect of postconditioning against infarct size: role of mitochondrial K(ATP) channels during reperfusion. Basic Res Cardiol 2008; 103:472-84. [PMID: 18600365 DOI: 10.1007/s00395-008-0731-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Accepted: 05/02/2008] [Indexed: 10/21/2022]
Abstract
UNLABELLED This study tested the hypothesis that inhibition of myocardial injury and modulation of mitochondrial dysfunction by postconditioning (Postcon) after 24 h of reperfusion is associated with activation of K(ATP) channels. Thirty dogs undergoing 60 min of ischemia and 24 h of reperfusion (R) were randomly divided into four groups: CONTROL no intervention at R; Postcon: three cycles of 30 s R alternating with 30 s re-occlusion were applied at R; 5-hydroxydecanoate (5-HD): the mitochondrial K(ATP) channel blocker was infused 5 min before Postcon; HMR1098: the sarcolemmal K(ATP) channel blocker was administered 5 min before Postcon. After 24 h of R, infarct size was smaller in Postcon relative to CONTROL (27 +/- 4%* Vs. 39 +/- 2% of area at risk), consistent with a reduction in CK activity (66 +/- 7* Vs. 105 +/- 7 IU/g). The infarct-sparing effect of Postcon was blocked by 5-HD (48 +/- 5%(dagger)), but was not altered by HMR1098 (29 +/- 3%*), consistent with the change in CK activity (102 +/- 8(dagger) in 5-HD and 71 +/- 6* IU/g in HMR1098). In H9c2 cells exposed to 8 h hypoxia and 3 h of reoxygenation, Postcon up-regulated expression of mito-K(ATP) channel Kir6.1 protein, maintained mitochondrial membrane potential and inhibited mitochondrial permeability transition pore (mPTP) opening evidenced by preserved fluorescent TMRE and calcein staining. The protective effects were blocked by 5-HD, but not by HMR1098. These data suggest that in a clinically relevant model of ischemia-reperfusion (1) Postcon reduces infarct size and decreases CK activity after prolonged reperfusion; (2) protection by Postcon is achieved by opening mitochondrial K(ATP) channels and inhibiting mPTP opening. *P < 0.05 Vs. CONTROL; P < 0.05 Vs. Postcon.
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Affiliation(s)
- James Mykytenko
- Carlyle Fraser Heart Center, Emory Crawford Long Hospital, Emory University, Atlanta, GA 30308-2225, USA
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Tang L, Deng C, Long M, Tang A, Wu S, Dong Y, Saravolatz LD, Gardin JM. Thrombin receptor and ventricular arrhythmias after acute myocardial infarction. Mol Med 2008; 14:131-40. [PMID: 18224254 DOI: 10.2119/2007-00097.tang] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 01/08/2008] [Indexed: 11/06/2022] Open
Abstract
The mechanism mediating the development of ventricular arrhythmia (VA) after acute myocardial infarction (AMI) is still uncertain. Thrombin receptor (TR) activation has been proven to be arrhythmogenic in many other situations, and we hypothesize that it may participate in the genesis of post-AMI VA. Using a left coronary artery ligation rat model of AMI, we found that a local injection of hirudin into the left ventricle (LV) significantly reduced the ratio of VA durations to infarction sizing, whereas injection of thrombin receptor-activating peptide (TRAP) increased the ratios of VA duration to infarction sizing. The effects of TR activation on whole-cell currents were investigated in isolated myocytes. TRAP increased a glibenclamide-sensitive outward current. Pretreatment of rats with glibenclamide (4 mg/kg intraperitoneally) eliminated the effects of a local injection of TRAP on the ratios of VA durations to infarction sizing. TR mRNA and protein expression in the ischemic left ventricle had reached its peak by 20 min postligation in the rat AMI model (P < 0.05). TR-immunoreactive myocytes were observed in infarcted LV but were seldom seen in the right ventricle or in the normal heart. By 60 min, TR transcript levels had returned to control levels. We conclude that increased TR activation and expression in the infarcted LV after AMI may contribute to VA through a mechanism involving glibenclamide-sensitive potassium channels.
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Affiliation(s)
- Lilong Tang
- Department of Cardiovascular Diseases, The First Affiliated Hospital to Sun Yat-sen University, Guangzhou, Guangdong, China.
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11
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Gumina RJ, O'Cochlain DF, Kurtz CE, Bast P, Pucar D, Mishra P, Miki T, Seino S, Macura S, Terzic A. KATP channel knockout worsens myocardial calcium stress load in vivo and impairs recovery in stunned heart. Am J Physiol Heart Circ Physiol 2006; 292:H1706-13. [PMID: 17189350 DOI: 10.1152/ajpheart.01305.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gene knockout of the KCNJ11-encoded Kir6.2 ATP-sensitive K(+) (K(ATP)) channel implicates this stress-response element in the safeguard of cardiac homeostasis under imposed demand. K(ATP) channels are abundant in ventricular sarcolemma, where subunit expression appears to vary between the sexes. A limitation, however, in establishing the full significance of K(ATP) channels in the intact organism has been the inability to monitor in vivo the contribution of the channel to intracellular calcium handling and the superimposed effect of sex that ultimately defines heart function. Here, in vivo manganese-enhanced cardiac magnetic resonance imaging revealed, under dobutamine stress, a significantly greater accumulation of calcium in both male and female K(ATP) channel knockout (Kir6.2-KO) mice compared with sex- and age-matched wild-type (WT) counterparts, with greatest calcium load in Kir6.2-KO females. This translated, poststress, into a sustained contracture manifested by reduced end-diastolic volumes in K(ATP) channel-deficient mice. In response to ischemia-induced stunning, male and female Kir6.2-KO hearts demonstrated accelerated time to contracture and increased peak contracture compared with WT. The outcome on reperfusion, in both male and female Kir6.2-KO hearts, was a transient reduction in systolic performance, measured as rate-pressure product compared with WT, with protracted increase in left ventricular end-diastolic pressure, exaggerated in female knockout hearts, despite comparable leakage of creatine kinase across groups. Kir6.2-KO hearts were rescued from diastolic dysfunction by agents that target alternative pathways of calcium handling. Thus K(ATP) channel deficit confers a greater susceptibility to calcium overload in vivo, accentuated in female hearts, impairing contractile recovery under various conditions of high metabolic demand.
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Affiliation(s)
- Richard J Gumina
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Departments of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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Lascano EC, Del Valle HF, Negroni JA. Role of the cyclooxygenase pathway in the protection against postischemic stunning in conscious sheep. Mol Cell Biochem 2006; 289:91-100. [PMID: 16691312 DOI: 10.1007/s11010-006-9152-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Accepted: 12/01/2004] [Indexed: 10/24/2022]
Abstract
OBJECTIVE There are controversial reports in conscious animals regarding the role of cyclooxygenase-2 in late preconditioning (LP). This study analyzed the effect of COX-2 involvement in non-preconditioned hearts (NP) and in mediation of LP protection against stunning in conscious sheep submitted to a prolonged reversible ischemia. METHODS Six groups were considered: NP: 12 min ischemia and 120 min reperfusion; LP consisting of six periods of 5 min-ischemia-5 min reperfusion 24 h before the 12 min ischemia; NP and LP with either the non-selective COX-1 and COX-2 inhibitor, aspirin (20 mg/kg), or the specific COX-2 inhibitor, celecoxib (3 mg/kg) before the 12 min ischemic period. RESULTS Mean postischemic wall thickening fraction (as % of preischemic values) improved from 49.6 +/- 4.0% in NP to 72.5 +/- 3.5% in LP (p < 0.01) and a similar protection was obtained with aspirin and celecoxib in NP hearts (p < 0.01). Neither aspirin nor celecoxib administration prior to the prolonged ischemia on day 2 abrogated LP improvement of postischemic dysfunction. Moreover, LP with aspirin improved the protective response (80.7 +/- 2.6%) over that obtained with aspirin in NP hearts (66.6 +/- 4.7%, p < 0.05). This effect was not obtained with celecoxib. CONCLUSIONS Aspirin and celecoxib showed that COX-2 has a detrimental effect on mechanical cardioprotection in NP hearts of conscious sheep submitted to a prolonged reversible ischemia, and does not seem to participate as mediator of LP. Aspirin revealed a similar COX-1 deleterious action, since only when both COX-1 and COX-2 were inhibited, LP was put in evidence adding functional improvement over that obtained in NP hearts treated with aspirin.
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Affiliation(s)
- Elena C Lascano
- Department of Physiology, Pharmacology and Biochemistry, Universidad Favaloro Buenos Aires, Buenos Aires, Argentina.
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Wang Y, Haider HK, Ahmad N, Ashraf M. Mechanisms by which KATP channel openers produce acute and delayed cardioprotection. Vascul Pharmacol 2005; 42:253-64. [PMID: 15922258 DOI: 10.1016/j.vph.2005.02.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Mitochondria are being increasingly studied for their critical role in cell survival. Multiple diverse signaling pathways have been shown to converge on the K+-sensitive ATP channels as the effectors of cytoprotection against necrosis and apoptosis. The role of potassium channel openers in regulation and transformation of cell membrane excitability, action potential and electrolyte transfer has been extensively studied. Cardiac mitoK(ATP) channels are the key effectors in cardioprotection during ischemic preconditioning, as yet with an undefined mechanism. They have been hypothesized to couple myocardial metabolism with membrane electrical activity and provide an excellent target for drug therapy. A number of K(ATP) channel openers have been characterized for their beneficial effects on the myocardium against ischemic injury. This review updates recent progress in understanding the physiological role of K(ATP) channels in cardiac protection induced by preconditioning and highlights relevant questions and controversies in the light of published data.
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Affiliation(s)
- Yigang Wang
- Department of Pathology and Laboratory Medicine, University of Cincinnati Medical Center, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0529, USA
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Budas GR, Jovanovic S, Crawford RM, Jovanovic A. Hypoxia-induced preconditioning in adult stimulated cardiomyocytes is mediated by the opening and trafficking of sarcolemmal KATP channels. FASEB J 2004; 18:1046-8. [PMID: 15084521 PMCID: PMC2128706 DOI: 10.1096/fj.04-1602fje] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The opening of sarcolemmal and mitochondrial ATP-sensitive K(+) (KATP) channels in the heart is believed to mediate ischemic preconditioning, a phenomenon whereby brief periods of ischemia/reperfusion protect the heart against myocardial infarction. Here, we have applied digital epifluorescent microscopy, immunoprecipitation and Western blotting, perforated patch clamp electrophysiology, and immunofluorescence/laser confocal microscopy to examine the involvement of KATP channels in cardioprotection afforded by preconditioning. We have shown that adult, stimulated-to-beat, guinea-pig cardiomyocytes survived in sustained hypoxia for approximately 17 min. An episode of 5-min-long hypoxia/5-min-long reoxygenation before sustained hypoxia dramatically increased the duration of cellular survival. Experiments with different antagonists of KATP channels, applied at different times during the experimental protocol, suggested that the opening of sarcolemmal KATP channels at the beginning of sustained hypoxia mediate preconditioning. This conclusion was supported by perforated patch clamp experiments that revealed activation of sarcolemmal KATP channels by preconditioning. Immunoprecipitation and Western blotting as well as immunofluorescence and laser confocal microscopy showed that the preconditioning is associated with the increase in KATP channel proteins in sarcolemma. Inhibition of trafficking of KATP channel subunits prevented preconditioning without affecting sensitivity of cardiomyocytes to hypoxia in the absence of preconditioning. We conclude that the preconditioning is mediated by the activation and trafficking of sarcolemmal KATP channels.
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Affiliation(s)
- Grant R Budas
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital & Medical School, University of Dundee, Dundee, Scotland, UK
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