1
|
Fedotova EI, Dolgacheva LP, Abramov AY, Berezhnov AV. Lactate and Pyruvate Activate Autophagy and Mitophagy that Protect Cells in Toxic Model of Parkinson's Disease. Mol Neurobiol 2021; 59:177-190. [PMID: 34642892 DOI: 10.1007/s12035-021-02583-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 09/27/2021] [Indexed: 11/24/2022]
Abstract
Intracellular quality control regulated by autophagy process is important for maintenance of cellular homeostasis. Deregulation of autophagy and more specifically mitophagy leads to accumulation of the misfolded proteins and damaged mitochondria that in turn leads to the cell loss. Alteration of autophagy and mitophagy has shown to be involved in the number of disorders including neurodegenerative diseases. Autophagy and mitophagy could be activated by short-time acidification of the cytosol; however, most of the compounds which can induce it are toxic. Here, we tested several organic compounds which are involved in cellular metabolism on their ability to change intracellular pH and induce mitophagy/autophagy. We have found that lactate and pyruvate are able to reduce intracellular pH in non-toxic concentrations. Short-term (2 h) and long-term (24 h) incubation of the cells with lactate and pyruvateinduced mitophagy and autophagy. Incubation of the SH-SY5Y cells or primary neurons and astrocytes with lactate or pyruvate also activated mitophagy and autophagy after MPP + treatment that led to recovery of mitochondrial function and protection of these cells against apoptotic and necrotic death. Thus, pyruvate- or lactate-induced acidification of cytosol activates cell protective mitophagy and autophagy.
Collapse
Affiliation(s)
- Evgeniya I Fedotova
- Institute of Cell Biophysics of the Russian Academy of Sciences, 3 Institutskaya St., 142290, Pushchino, Russia.,Cell Physiology and Pathology Laboratory, Orel State University, 29 Naugorskoe Highway, 302020, Orel, Russia
| | - Ludmila P Dolgacheva
- Institute of Cell Biophysics of the Russian Academy of Sciences, 3 Institutskaya St., 142290, Pushchino, Russia
| | - Andrey Y Abramov
- Cell Physiology and Pathology Laboratory, Orel State University, 29 Naugorskoe Highway, 302020, Orel, Russia.,Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Alexey V Berezhnov
- Institute of Cell Biophysics of the Russian Academy of Sciences, 3 Institutskaya St., 142290, Pushchino, Russia. .,Cell Physiology and Pathology Laboratory, Orel State University, 29 Naugorskoe Highway, 302020, Orel, Russia.
| |
Collapse
|
2
|
Connexins in the Heart: Regulation, Function and Involvement in Cardiac Disease. Int J Mol Sci 2021; 22:ijms22094413. [PMID: 33922534 PMCID: PMC8122935 DOI: 10.3390/ijms22094413] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/12/2021] [Accepted: 04/20/2021] [Indexed: 12/20/2022] Open
Abstract
Connexins are a family of transmembrane proteins that play a key role in cardiac physiology. Gap junctional channels put into contact the cytoplasms of connected cardiomyocytes, allowing the existence of electrical coupling. However, in addition to this fundamental role, connexins are also involved in cardiomyocyte death and survival. Thus, chemical coupling through gap junctions plays a key role in the spreading of injury between connected cells. Moreover, in addition to their involvement in cell-to-cell communication, mounting evidence indicates that connexins have additional gap junction-independent functions. Opening of unopposed hemichannels, located at the lateral surface of cardiomyocytes, may compromise cell homeostasis and may be involved in ischemia/reperfusion injury. In addition, connexins located at non-canonical cell structures, including mitochondria and the nucleus, have been demonstrated to be involved in cardioprotection and in regulation of cell growth and differentiation. In this review, we will provide, first, an overview on connexin biology, including their synthesis and degradation, their regulation and their interactions. Then, we will conduct an in-depth examination of the role of connexins in cardiac pathophysiology, including new findings regarding their involvement in myocardial ischemia/reperfusion injury, cardiac fibrosis, gene transcription or signaling regulation.
Collapse
|
3
|
Hoeker GS, James CC, Tegge AN, Gourdie RG, Smyth JW, Poelzing S. Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium. Am J Physiol Heart Circ Physiol 2020; 319:H396-H409. [PMID: 32678707 DOI: 10.1152/ajpheart.00112.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during nonsimulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering preischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n = 49) were Langendorff perfused with 145 or 153 mM Na+ and 1.25 or 2.0 mM Ca2+ and optically mapped during 30 min of no-flow ischemia. Altering Na+ and Ca2+ did not substantially affect baseline conduction. Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, whereas increasing Ca2+ narrowed perinexal width (Wp). A least squares mean estimate revealed that reduced perfusate Na+ and Ca2+ resulted in the most severe conduction slowing during ischemia. Increasing Na+ alone modestly attenuated conduction slowing, yet significantly delayed the median time to conduction block (10 to 16 min). Increasing both Na+ and Ca2+ selectively widened Wp during ischemia (22.7 vs. 15.7 nm) and attenuated conduction slowing to the greatest extent. Neither repolarization nor levels of total or phosphorylated connexin43 correlated with conduction slowing or block. Thus, perfusate-dependent widening of the perinexus preserved ischemic conduction and may be an adaptive response to ischemic stress.NEW & NOTEWORTHY Conduction slowing during acute ischemia creates an arrhythmogenic substrate. We have shown that extracellular ionic concentrations can alter conduction by modulating ephaptic coupling. Here, we demonstrate increased extracellular sodium and calcium significantly attenuate conduction slowing during no-flow ischemia. This effect was associated with selective widening of the perinexus, an intercalated disc nanodomain and putative cardiac ephapse. These findings suggest that acute changes in ephaptic coupling may serve as an adaptive response to ischemic stress.
Collapse
Affiliation(s)
- Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Carissa C James
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia
| | - Allison N Tegge
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - James W Smyth
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Steven Poelzing
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| |
Collapse
|
4
|
Berezhnov AV, Soutar MPM, Fedotova EI, Frolova MS, Plun-Favreau H, Zinchenko VP, Abramov AY. Intracellular pH Modulates Autophagy and Mitophagy. J Biol Chem 2016; 291:8701-8. [PMID: 26893374 DOI: 10.1074/jbc.m115.691774] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Indexed: 12/15/2022] Open
Abstract
The specific autophagic elimination of mitochondria (mitophagy) plays the role of quality control for this organelle. Deregulation of mitophagy leads to an increased number of damaged mitochondria and triggers cell death. The deterioration of mitophagy has been hypothesized to underlie the pathogenesis of several neurodegenerative diseases, most notably Parkinson disease. Although some of the biochemical and molecular mechanisms of mitochondrial quality control are described in detail, physiological or pathological triggers of mitophagy are still not fully characterized. Here we show that the induction of mitophagy by the mitochondrial uncoupler FCCP is independent of the effect of mitochondrial membrane potential but dependent on acidification of the cytosol by FCCP. The ionophore nigericin also reduces cytosolic pH and induces PINK1/PARKIN-dependent and -independent mitophagy. The increase of intracellular pH with monensin suppresses the effects of FCCP and nigericin on mitochondrial degradation. Thus, a change in intracellular pH is a regulator of mitochondrial quality control.
Collapse
Affiliation(s)
- Alexey V Berezhnov
- From the Department of Intracellular Signaling, Institute of Cell Biophysics Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russian Federation and
| | - Marc P M Soutar
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Evgeniya I Fedotova
- From the Department of Intracellular Signaling, Institute of Cell Biophysics Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russian Federation and
| | - Maria S Frolova
- From the Department of Intracellular Signaling, Institute of Cell Biophysics Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russian Federation and
| | - Helene Plun-Favreau
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Valery P Zinchenko
- From the Department of Intracellular Signaling, Institute of Cell Biophysics Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russian Federation and
| | - Andrey Y Abramov
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
| |
Collapse
|
5
|
Toldo S, Mezzaroma E, Mauro AG, Salloum F, Van Tassell BW, Abbate A. The inflammasome in myocardial injury and cardiac remodeling. Antioxid Redox Signal 2015; 22:1146-61. [PMID: 25330141 DOI: 10.1089/ars.2014.5989] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
SIGNIFICANCE An inflammatory response follows an injury of any nature, and while such a response is an attempt to promote healing, it may, itself, result in further injury. RECENT ADVANCES The inflammasome is a macromolecular structure recently recognized as a central mediator in the acute inflammatory response. The inflammasome senses the injury and it amplifies the response by leading to the release of powerful pro-inflammatory cytokines, interleukin-1β (IL-1β) and IL-18. CRITICAL ISSUES The activation of the inflammasome in the heart during ischemic and nonischemic injury represents an exaggerated response to sterile injury and promotes adverse cardiac remodeling and failure. FUTURE DIRECTIONS Pilot clinical trials have explored blockade of the inflammasome-derived IL-1β and have shown beneficial effects on cardiac function. Additional clinical studies testing this approach are warranted. Moreover, specific inflammasome inhibitors that are ready for clinical use are currently lacking.
Collapse
Affiliation(s)
- Stefano Toldo
- 1 VCU Pauley Heart Center, Virginia Commonwealth University , Richmond, Virginia
| | | | | | | | | | | |
Collapse
|
6
|
Del Rio CL, Clymer BD, Billman GE. Myocardial electrotonic response to submaximal exercise in dogs with healed myocardial infarctions: evidence for β-adrenoceptor mediated enhanced coupling during exercise testing. Front Physiol 2015; 6:25. [PMID: 25698976 PMCID: PMC4318283 DOI: 10.3389/fphys.2015.00025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/15/2015] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION Autonomic neural activation during cardiac stress testing is an established risk-stratification tool in post-myocardial infarction (MI) patients. However, autonomic activation can also modulate myocardial electrotonic coupling, a known factor to contribute to the genesis of arrhythmias. The present study tested the hypothesis that exercise-induced autonomic neural activation modulates electrotonic coupling (as measured by myocardial electrical impedance, MEI) in post-MI animals shown to be susceptible or resistant to ventricular fibrillation (VF). METHODS Dogs (n = 25) with healed MI instrumented for MEI measurements were trained to run on a treadmill and classified based on their susceptibility to VF (12 susceptible, 9 resistant). MEI and ECGs were recorded during 6-stage exercise tests (18 min/test; peak: 6.4 km/h @ 16%) performed under control conditions, and following complete β-adrenoceptor (β-AR) blockade (propranolol); MEI was also measured at rest during escalating β-AR stimulation (isoproterenol) or overdrive-pacing. RESULTS Exercise progressively increased heart rate (HR) and reduced heart rate variability (HRV). In parallel, MEI decreased gradually (enhanced electrotonic coupling) with exercise; at peak exercise, MEI was reduced by 5.3 ± 0.4% (or -23 ± 1.8Ω, P < 0.001). Notably, exercise-mediated electrotonic changes were linearly predicted by the degree of autonomic activation, as indicated by changes in either HR or in HRV (P < 0.001). Indeed, β-AR blockade attenuated the MEI response to exercise while direct β-AR stimulation (at rest) triggered MEI decreases comparable to those observed during exercise; ventricular pacing had no significant effects on MEI. Finally, animals prone to VF had a significantly larger MEI response to exercise. CONCLUSIONS These data suggest that β-AR activation during exercise can acutely enhance electrotonic coupling in the myocardium, particularly in dogs susceptible to ischemia-induced VF.
Collapse
Affiliation(s)
- Carlos L Del Rio
- Department of Physiology and Cell Biology, The Ohio State University Columbus, OH, USA ; Department of Electrical and Computer Engineering, The Ohio State University Columbus, OH, USA ; Safety Pharmacology, QTest Labs Columbus, OH, USA
| | - Bradley D Clymer
- Department of Electrical and Computer Engineering, The Ohio State University Columbus, OH, USA ; Biomedical Engineering, The Ohio State University Columbus, OH, USA
| | - George E Billman
- Department of Physiology and Cell Biology, The Ohio State University Columbus, OH, USA ; Davis Heart and Lung Research Institute, The Ohio State University Columbus, OH, USA
| |
Collapse
|
7
|
Waits CMK, Barr RC, Pollard AE. Sensor spacing affects the tissue impedance spectra of rabbit ventricular epicardium. Am J Physiol Heart Circ Physiol 2014; 306:H1660-8. [PMID: 24778170 DOI: 10.1152/ajpheart.00661.2013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was designed to test the hypothesis that a complex composite impedance spectra develops when stimulation and recording of cardiac muscle with sufficiently fine spatial resolution in a four-electrode configuration is used. With traditional (millimeter scale) separations, the ratio between the recorded interstitial central potential difference and total supplied interstitial current is constant at all frequencies. This occurs because the fraction of supplied current that redistributes to the intracellular compartment depends on effective membrane resistance between electrodes, which is low, to a much greater extent than effective membrane capacitance. The spectra should therefore change with finer separations at which effective membrane resistance increases, as supplied current will remain primarily interstitial at lower frequencies and redistribute between compartments at higher frequencies. To test this hypothesis, we built arrays with sensors separated (d) by 804 μm, 452 μm, and 252 μm; positioned those arrays across myocyte axes on rabbit ventricular epicardium; and resolved spectra in terms of resistivity (ρt) and reactivity (χt) over the 10 Hz to 4,000 Hz range. With all separations, we measured comparable spectra with predictions from passive membrane simulations that used a three-dimensional structural framework in which intracellular, interstitial, and membrane properties were prescribed based on the limited data available from the literature. At the finest separation, we found mean ρt at 100 Hz and 4,000 Hz that lowered from 395 Ω-cm to 236 Ω-cm, respectively, with maximal mean χt of 160 Ω-cm. This experimental confirmation of spectra development in whole heart experiments is important because such development is central to achieve measurements of intracellular and interstitial passive electrical properties in cardiac electrophysiological experiments using only interstitial access.
Collapse
Affiliation(s)
- Charlotte Mae K Waits
- Department of Biomedical Engineering, Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Roger C Barr
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Andrew E Pollard
- Department of Biomedical Engineering, Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham, Birmingham, Alabama;
| |
Collapse
|
8
|
Pollard AE, Barr RC. A new approach for resolution of complex tissue impedance spectra in hearts. IEEE Trans Biomed Eng 2013; 60:2494-503. [PMID: 23625349 DOI: 10.1109/tbme.2013.2258917] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This study was designed to test the feasibility of using sinusoidal approximation in combination with a new instrumentation approach to resolve complex impedance (uCI) spectra from heart preparations. To assess that feasibility, we applied stimuli in the 10-4000 Hz range and recorded potential differences (uPDs) in a four-electrode configuration that allowed identification of probe constants (Kp) during calibration that were in turn used to measure total tissue resistivity ρt from rabbit ventricular epicardium. Simultaneous acquisition of a signal proportional to the supplied current (Vstim) with uPD allowed identification of the V- I ratio needed for ρt measurement, as well as the phase shift from Vstim to uPD needed for uCI spectra resolution. Performance with components integrated to reduce noise in cardiac electrophysiologic experiments, in particular, and provide accurate electrometer-based measurements, in general, was first characterized in tests using passive loads. Load tests showed accurate uCI recovery with mean uPD SNRs between 10 (1) and 10 (3) measured with supplied currents as low as 10 nA. Comparable performance characteristics were identified during calibration of nine arrays built with 250 μm Ag/AgCl electrodes, with uCIs that matched analytic predictions and no apparent effect of frequency ( F = 0.12, P = 0.99). The potential ability of parasitic capacitance in the presence of the electrode-electrolyte interface associated with the small sensors to influence the uCI spectra was therefore limited by the instrumentation. Resolution of uCI spectra in rabbit ventricle allowed measurement of ρt = 134 ± 53 Ω· cm. The rapid identification available with this strategy provides an opportunity for new interpretations of the uCI spectra to improve quantification of disease-, region-, tissue-, and species-dependent intercellular uncoupling in hearts.
Collapse
|
9
|
Electrophysiology of single and aggregate Cx43 hemichannels. PLoS One 2012; 7:e47775. [PMID: 23112846 PMCID: PMC3480394 DOI: 10.1371/journal.pone.0047775] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/17/2012] [Indexed: 11/20/2022] Open
Abstract
Connexin43 (Cx43) is the most ubiquitous gap junction protein in the human body and is essential for cell-to-cell communication in a variety of organs and organ systems. As a result, Cx43 is responsible for mediating both electrical and chemical signals, passing dissolved solutes and small signaling molecules between cells in a coordinated fashion. Here, we explore the electrophysiological properties of hemichannels formed from Cx43 and Cx43 fused to eGFP (Cx43eGFP) and their interactions in a planar lipid membrane (BLM). Unlike in vivo patch clamp experiments, Cx43 was purified and isolated from other membrane constituents allowing elucidation of individual protein responses to various electrical and chemical stimuli. Using this system, we examined hemichannel electrophysiology and the roles of several well-known gap junction blockers, namely: lanthanum, heptanol, carbenoxalone and lindane. We also observed a critical number of hemichannels required for an accelerated conductance increase, an emergent electrical signature indicative of plaque formation.
Collapse
|
10
|
Mao HJ, Chen BP, Ren GY, Jin JS, Fan FY, Gao Q, Bruce I, Xia Q. The Effects of Heptanol on Electrical Coupling during Ischemia in the Perfused Isolated Rat Heart. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2012; 2006:122-5. [PMID: 17282126 DOI: 10.1109/iembs.2005.1616357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The aims of the present study were to examine the effect of heptanol on electrical coupling during ischemia, and to assess whether changes in electrical coupling by heptanol is associated with its cardiac protection. Perfused isolated rat hearts were subjected to a 24 min infusion of heptanol (0.05, 0.1, 0.5 or 1.0 mmol/L) followed by 70 min of global no-flow ischemia or by 20 min of regional ischemia and 60 min of reperfusion. Heptanol markedly decreased arrhythmia scores during ischemia and reperfusion as well as reduced infarct size to a degree similar to that induced by ischemic preconditioning. In the prolonged ischemia model, heptanol delayed the onset of uncoupling, increased time to plateau, and decreased the maximal rate of uncoupling during ischemia. Ischemic preconditioning had similar effects on these parameters. These results demonstrate that treatment with the gap junction uncoupler heptanol confers cardioprotection against ischemia, and this effect is related to delayed electrical uncoupling during prolonged ischemia.
Collapse
Affiliation(s)
- Hong-Jiao Mao
- Dept. of Physiol., Zhejiang Univ. Sch. of Med., Hangzhou
| | | | | | | | | | | | | | | |
Collapse
|
11
|
How ischaemic region shape affects ST potentials in models of cardiac tissue. Math Biosci 2012; 239:213-21. [DOI: 10.1016/j.mbs.2012.05.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 11/19/2022]
|
12
|
Bitter T, Westerheide N, Prinz C, Hossain MS, Vogt J, Langer C, Horstkotte D, Oldenburg O. Cheyne-Stokes respiration and obstructive sleep apnoea are independent risk factors for malignant ventricular arrhythmias requiring appropriate cardioverter-defibrillator therapies in patients with congestive heart failure. Eur Heart J 2010; 32:61-74. [PMID: 20846992 DOI: 10.1093/eurheartj/ehq327] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Thomas Bitter
- Department of Cardiology, Heart and Diabetes Centre North Rhine-Westphalia, Ruhr University Bochum, Georgstasse 11, Bad Oeynhausen, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Ponsaerts R, De Vuyst E, Retamal M, D'hondt C, Vermeire D, Wang N, De Smedt H, Zimmermann P, Himpens B, Vereecke J, Leybaert L, Bultynck G. Intramolecular loop/tail interactions are essential for connexin 43-hemichannel activity. FASEB J 2010; 24:4378-95. [PMID: 20634352 DOI: 10.1096/fj.09-153007] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Connexin-assembled gap junctions (GJs) and hemichannels coordinate intercellular signaling processes. Although the regulation of connexins in GJs has been well characterized, the molecular determinants controlling connexin-hemichannel activity are unresolved. Here we investigated the regulation of Cx43-hemichannel activity by actomyosin contractility and intracellular [Ca(2+)] ([Ca(2+)](i)) using plasma membrane-permeable TAT peptides (100 μM) designed to interfere with interactions between the cytoplasmic loop (CL) and carboxy-terminal (CT) in primary bovine corneal endothelial cells and HeLa, C6 glioma, and Xenopus oocytes ectopically expressing Cx43. Peptides corresponding to the last 10 CT aa (TAT-Cx43CT) prevented the inhibition of Cx43-hemichannel activity by contractility/high [Ca(2+)](i), whereas a reverse peptide (TAT-Cx43CTrev) did not. These effects were independent of zonula occludens-1, a cytoskeletal-associated Cx43-binding protein. In contrast, peptides corresponding to CL (TAT-L2) inhibited Cx43-hemichannel responses, whereas a mutant peptide (TAT-L2(H126K/I130N)) did not inhibit. In these assays, TAT-Cx43CT acted as a scaffold for TAT-L2 and vice versa, a finding supported by surface plasmon resonance measurements. Loop/tail interactions appeared essential for Cx43-hemichannel activity, because TAT-Cx43CT restored the activity of nonfunctional hemichannels, consisting of either Cx43 lacking the C-terminal tail (Cx43(M239)) or intact Cx43 ectopically expressed in Xenopus oocytes. We conclude that intramolecular loop/tail interactions control Cx43-hemichannel activity, laying the basis for developing hemichannel-specific blockers.
Collapse
Affiliation(s)
- Raf Ponsaerts
- Department Molecular Cell Biology, KU Leuven, Leuven, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Chen BP, Mao HJ, Fan FY, Bruce IC, Xia Q. Delayed uncoupling is related to cardioprotection induced by κ-agonist U-50,488H in rat heart. SCAND CARDIOVASC J 2009; 39:375-82. [PMID: 16352491 DOI: 10.1080/14017430500293056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVES To determine whether the kappa-opioid receptor agonist U50,488H affects electrical uncoupling during prolonged ischemia and, if so, whether the changes are associated with its cardioprotective action. DESIGN The isolated rat heart was perfused in a Langendorff apparatus. Formazan content, lactate dehydrogenase (LDH) and hemodynamic parameters were measured to confirm the cardioprotective effect of U50,488H. The effects of U50,488H on electrical coupling during prolonged ischemia were also measured. RESULTS U50,488H concentration-dependently increased formazan content and reduced LDH release, and the ameliorating effect of 10(-5) mol/L U50,488H was abolished by 5 x 10(-6) mol/L nor-binaltorphimine (nor-BNI), a selective kappa-opioid receptor antagonist, or 10(-4) mol/L 5-hydroxydecanoate (5-HD), a selective mitochondrial ATP-sensitive K(+) (K(ATP)) channel blocker. The onset of electrical uncoupling during prolonged ischemia was delayed by U50,488H, and the delay was not only abolished, but also advanced by nor-BNI or 5-HD relative to the control group. CONCLUSIONS These results demonstrate that delayed uncoupling during prolonged ischemia is associated with the cardioprotection of U50,488H, and these effects of U50,488H are mediated by mitochondrial K(ATP) channels.
Collapse
Affiliation(s)
- Bao-Ping Chen
- Department of Physiology, Shaoxing University School of Medicine, Shaoxing, 312000, China
| | | | | | | | | |
Collapse
|
15
|
Del Rio CL, Dawson TA, Clymer BD, Paterson DJ, Billman GE. Effects of acute vagal nerve stimulation on the early passive electrical changes induced by myocardial ischaemia in dogs: heart rate-mediated attenuation. Exp Physiol 2008; 93:931-44. [PMID: 18376003 DOI: 10.1113/expphysiol.2007.041558] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Parasympathetic activity during acute coronary artery occlusion (CAO) can protect against ischaemia-induced malignant arrhythmias; nonetheless, the mechanism mediating this protection remains unclear. During CAO, myocardial electrotonic uncoupling is associated with autonomically mediated immediate (i.e. type 1A) arrhythmias and can modulate pro-arrhythmic dispersion of repolarization. Therefore, the effects of acutely enhanced or decreased cardiac parasympathetic activity on early electrotonic coupling during CAO, as measured by myocardial electrical impedance (MEI), were investigated. Anaesthetized dogs were instrumented for MEI measurements, and left circumflex coronary arterial occlusions were performed in intact (CTRL) and vagotomized (VAG) animals. The CAO was followed by either vagotomy (CTRL) or vagal nerve stimulation (VNS, 10 Hz, 10 V) in the VAG dogs. Vagal nerve stimulation was studied in two additional sets of animals. In one set heart rate (HR) was maintained by pacing (220 beats min(-1)), while in the other set bilateral stellectomy preceded CAO. The MEI increased after CAO in all animals. A larger MEI increase was observed in vagotomized animals (+85 +/- 9 Omega, from 611 +/- 24 Omega, n = 16) when compared with intact control dogs (+43 +/- 5 Omega, from 620 +/- 20 Omega, n = 7). Acute vagotomy during ischaemia abruptly increased HR (from 155 +/- 11 to 193 +/- 15 beats min(-1)) and MEI (+12 +/- 1.1 Omega, from 663 +/- 18 Omega). In contrast, VNS during ischaemia (n = 11) abruptly reduced HR (from 206 +/- 6 to 73 +/- 9 beats min(-1)) and MEI (-16 +/- 2 Omega, from 700 +/- 44 Omega). These effects of VNS were eliminated by pacing but not by bilateral stellectomy. Vagal nerve stimulation during CAO also attenuated ECG-derived indices of ischaemia (e.g. ST segment, 0.22 +/- 0.03 versus 0.15 +/- 0.03 mV) and of rate-corrected repolarization dispersion [terminal portion of T wave (TPEc), 84.5 +/- 4.2 versus 65.8 +/- 5.9 ms; QTc, 340 +/- 8 versus 254 +/- 16 ms]. Vagal nerve stimulation during myocardial ischaemia exerts negative chronotropic effects, limiting early ischaemic electrotonic uncoupling and dispersion of repolarization, possibly via a decreased myocardial metabolic demand.
Collapse
Affiliation(s)
- Carlos L Del Rio
- Department of Physiology and Cell Biology, The Ohio State University, 1645 Neil Avenue, 305 Hamilton Hall, Columbus, OH 43210, USA
| | | | | | | | | |
Collapse
|
16
|
Yu J, Bippes CA, Hand GM, Muller DJ, Sosinsky GE. Aminosulfonate Modulated pH-induced Conformational Changes in Connexin26 Hemichannels. J Biol Chem 2007; 282:8895-904. [PMID: 17227765 DOI: 10.1074/jbc.m609317200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gap junction channels regulate cell-cell communication by passing metabolites, ions, and signaling molecules. Gap junction channel closure in cells by acidification is well documented; however, it is unknown whether acidification affects connexins or modulating proteins or compounds that in turn act on connexins. Protonated aminosulfonates directly inhibit connexin channel activity in an isoform-specific manner as shown in previously published studies. High-resolution atomic force microscopy of force-dissected connexin26 gap junctions revealed that in HEPES buffer, the pore was closed at pH < 6.5 and opened reversibly by increasing the pH to 7.6. This pH effect was not observed in non-aminosulfonate buffers. Increasing the protonated HEPES concentration did not close the pore, indicating that a saturation of the binding sites occurs at 10 mM HEPES. Analysis of the extracellular surface topographs reveals that the pore diameter increases gradually with pH. The outer connexon diameter remains unchanged, and there is a approximately 6.5 degrees rotation in connexon lobes. These observations suggest that the underlying mechanism closing the pore is different from an observed Ca2+-induced closure.
Collapse
Affiliation(s)
- Jinshu Yu
- BioTechnological Center, University of Technology Dresden, Tatzberg 47-51, 01307 Dresden, Germany
| | | | | | | | | |
Collapse
|
17
|
Chen BP, Fan FY, Ren GY, Jin JS, Mao HJ, Wu LP, Bruce I, Xia Q. The Effects of κ-Opioid Receptor Stimulation on Electrical Coupling during Ischemia in the Perfused Isolated Rat Heart. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:126-9. [PMID: 17282127 DOI: 10.1109/iembs.2005.1616358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Two series of experiments were performed in the perfused isolated rat heart to determine whether stimulation of κ-opioid receptor with U50,488H, a selective κ-opioid receptor agonist, produces any changes in electrical coupling during prolonged ischemia and whether these changes in electrical coupling is associated with the cardioprotection induced by U50,488H. It was found that U50,488H concentration dependently increased formazan content and reduced lactate dehydrogenase (LDH) release induced by 30 min of ischemia and 120 min of reperfusion, and the ameliorating effect of 10<sup>-5</sup>mol/L U50,488H was abolished by 5x10<sup>-6</sup>mol/L nor-binaltorphimine (nor-BNI), a selective Κ-opioid receptor antagonist, or 10<sup>-4</sup>mol/L 5-hydroxydecanoate (5-HD), a selective mitochondrial ATP-sensitive K<sup>+</sup>(K<inf>ATP</inf>) channels blocker. The onset of electrical uncoupling during prolonged ischemia was delayed by U50,488H, and delaying effect was not only abolished, but also advanced by nor-BNI or 5-HD compared with control group. These results demonstrate that delayed electrical uncoupling is associated with the cardioprotection induced by U50,488H. These effects of U50,488H are mediated by mitochondrial K<inf>ATP</inf>channels.
Collapse
Affiliation(s)
- Bao-Ping Chen
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, china; Department of Physiology, Shaoxing University School of Medicine, Shaoxing, china
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Li HL, Qu YJ, Lu YC, Bondarenko VE, Wang S, Skerrett IM, Morales MJ. DPP10 is an inactivation modulatory protein of Kv4.3 and Kv1.4. Am J Physiol Cell Physiol 2006; 291:C966-76. [PMID: 16738002 DOI: 10.1152/ajpcell.00571.2005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Voltage-gated K+ channels exist in vivo as multiprotein complexes made up of pore-forming and ancillary subunits. To further our understanding of the role of a dipeptidyl peptidase-related ancillary subunit, DPP10, we expressed it with Kv4.3 and Kv1.4, two channels responsible for fast-inactivating K+ currents. Previously, DPP10 has been shown to effect Kv4 channels. However, Kv1.4, when expressed with DPP10, showed many of the same effects as Kv4.3, such as faster time to peak current and negative shifts in the half-inactivation potential of steady-state activation and inactivation. The exception was recovery from inactivation, which is slowed by DPP10. DPP10 expressed with Kv4.3 caused negative shifts in both steady-state activation and inactivation of Kv4.3, but no significant shifts were detected when DPP10 was expressed with Kv4.3 + KChIP2b (Kv channel interacting protein). DPP10 and KChIP2b had different effects on closed-state inactivation. At −60 mV, KChIP2b nearly abolishes closed-state inactivation in Kv4.3, whereas it developed to a much greater extent in the presence of DPP10. Finally, expression of a DPP10 mutant consisting of its transmembrane and cytoplasmic 58 amino acids resulted in effects on Kv4.3 gating that were nearly identical to those of wild-type DPP10. These data show that DPP10 and KChIP2b both modulate Kv4.3 inactivation but that their primary effects are on different inactivation states. Thus DPP10 may be a general modulator of voltage-gated K+ channel inactivation; understanding its mechanism of action may lead to deeper understanding of the inactivation of a broad range of K+ channels.
Collapse
Affiliation(s)
- Hong-Ling Li
- Dept. of Physiology and Biophysics, University at Buffalo-SUNY, Buffalo, NY 14214, USA
| | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
PURPOSE OF REVIEW This article reviews mechanisms and available therapeutic options for arrhythmias leading to sudden cardiac death in patients with coronary artery disease. RECENT FINDINGS Intensive efforts have led to a better understanding of the pathophysiology and various treatments of sudden cardiac death. Antiarrhythmic medications have not demonstrated a survival benefit. Beta-adrenergic blocking agents have been revalidated in recent studies to improve survival and reduce risk of sudden cardiac death in patients with myocardial infarction. Angiotensin-converting enzyme inhibitors and aldosterone antagonists should also be used in these patients. Data from randomized trials demonstrate significant survival benefit with an implantable cardioverter-defibrillator and indications have expanded. Patients with established ischemic cardiomyopathy do not require electrophysiologic studies for induction of tachyarrhythmias based on these trials. One recent trial did not demonstrate mortality reduction with implantable defibrillators in patients with recent myocardial infarction. Devices may not provide survival benefit in patients with advanced New York Heart Association class IV heart failure. SUMMARY The incidence of arrhythmia-related sudden death in the general population remains relatively high. Better risk stratification tools are needed to identify high-risk patients in the general population and in those with known coronary disease and to exclude low-risk patients.
Collapse
MESH Headings
- Adrenergic beta-Antagonists/therapeutic use
- Angiotensin-Converting Enzyme Inhibitors/therapeutic use
- Anti-Arrhythmia Agents/therapeutic use
- Arrhythmias, Cardiac/complications
- Arrhythmias, Cardiac/etiology
- Arrhythmias, Cardiac/physiopathology
- Arrhythmias, Cardiac/therapy
- Coronary Artery Disease/complications
- Coronary Artery Disease/physiopathology
- Death, Sudden, Cardiac/etiology
- Death, Sudden, Cardiac/pathology
- Death, Sudden, Cardiac/prevention & control
- Defibrillators, Implantable
- Fatty Acids, Omega-3/therapeutic use
- Humans
- Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use
- Mineralocorticoid Receptor Antagonists/therapeutic use
Collapse
Affiliation(s)
- Adnan Siddiqui
- Main Line Health Heart Center and the Lankenau Hospital and Institute for Medical Research, Main Line Health Systems, Wynnewood, Pennsylvania 19096, USA.
| | | |
Collapse
|
20
|
Stinstra JG, Shome S, Hopenfeld B, MacLeod RS. Modelling passive cardiac conductivity during ischaemia. Med Biol Eng Comput 2005; 43:776-82. [PMID: 16594306 DOI: 10.1007/bf02430957] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The results of a geometric model of cardiac tissue, used to compute the bidomain conductivity tensors during three phases of ischaemia, are described. Ischaemic conditions were simulated by model parameters being changed to match the morphological and electrical changes of three phases of ischaemia reported in literature. The simulated changes included collapse of the interstitial space, cell swelling and the closure of gap junctions. The model contained 64 myocytes described by 2 million tetrahedral elements, to which an external electric field was applied, and then the finite element method was used to compute the associated current density. In the first case, a reduction in the amount of interstitial space led to a reduction in extracellular longitudinal conductivity by about 20%, which is in the range of reported literature values. Moderate cell swelling in the order of 10-20% did not affect extracellular conductivity considerably. To match the reported drop in total tissue conductance reported in experimental studies during the third phase of ischaemia, a ten fold increase in the gap junction resistance was simulated. This ten-fold increase correlates well with the reported changes in gap junction densities in the literature.
Collapse
Affiliation(s)
- J G Stinstra
- Scientific Computing & Imaging Institute, University of Utah, Salt Lake City, USA.
| | | | | | | |
Collapse
|
21
|
del Rio CL, McConnell PI, Clymer BD, Dzwonczyk R, Michler RE, Billman GE, Howie MB. Early time course of myocardial electrical impedance during acute coronary artery occlusion in pigs, dogs, and humans. J Appl Physiol (1985) 2005; 99:1576-81. [PMID: 15961608 DOI: 10.1152/japplphysiol.00830.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Changes in myocardial electrical impedance (MEI) and physiological end points have been correlated during acute ischemia. However, the importance of MEI's early time course is not clear. This study evaluates such significance, by comparing the temporal behavior of MEI during acute total occlusion of the left anterior descending coronary artery in anesthetized humans, dogs, and pigs. Here, interspecies differences in three MEI parameters (baseline, time to plateau onset, and plateau value normalized by baseline) were evaluated using Kruskal-Wallis ANOVA and post hoc tests ( P < 0.05). Noteworthy differences in the MEI time to plateau onset were observed: In dogs, MEI ischemic plateau was reached after 46.3 min (SD 12.9) min of occlusion, a significantly longer period compared with that of pigs and humans [4.7 (SD 1.2) and 4.1 min (SD 1.9), respectively]. However, no differences could be observed between both animal species regarding the normalized MEI ischemic plateau value (15.3% (SD 4.7) in pigs, vs. 19.6% (SD 2.6) in dogs). For all studied MEI parameters, only swine values resembled those of humans. The severity of myocardial supply ischemia, resulting from coronary artery occlusion, is known to be dependent on collateral flow. Thus, because dogs possess a well-developed collateral system (unlike humans or pigs), they have shown superior resistance to occlusion of a coronary artery. Here, the early MEI time course after left anterior descending coronary artery occlusion, represented by the time required to reach ischemic plateau, was proven to reflect such interspecies differences.
Collapse
Affiliation(s)
- Carlos L del Rio
- Department of Anesthesiology, The Ohio State University, Columbus, 43210, USA.
| | | | | | | | | | | | | |
Collapse
|
22
|
Wang S, Bondarenko VE, Qu YJ, Bett GCL, Morales MJ, Rasmusson RL, Strauss HC. Time- and voltage-dependent components of Kv4.3 inactivation. Biophys J 2005; 89:3026-41. [PMID: 16100281 PMCID: PMC1366800 DOI: 10.1529/biophysj.105.059378] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kv4.3 inactivation is a complex multiexponential process, which can occur from both closed and open states. The fast component of inactivation is modulated by the N-terminus, but the mechanisms mediating the other components of inactivation are controversial. We studied inactivation of Kv4.3 expressed in Xenopus laevis oocytes, using the two-electrode voltage-clamp technique. Inactivation during 2000 ms pulses at potentials positive to the activation threshold was described by three exponents (46 +/- 3, 152 +/- 13, and 930 +/- 50 ms at +50 mV, n = 7) whereas closed-state inactivation (at potentials below threshold) was described by two exponents (1079 +/- 119 and 3719 +/- 307 ms at -40 mV, n = 9). The fast component of open-state inactivation was dominant at potentials positive to -20 mV. Negative to -30 mV, the intermediate and slow components dominated inactivation. Inactivation properties were dependent on pulse duration. Recovery from inactivation was strongly dependent on voltage and pulse duration. We developed an 11-state Markov model of Kv4.3 gating that incorporated a direct transition from the open-inactivated state to the closed-inactivated state. Simulations with this model reproduced open- and closed-state inactivation, isochronal inactivation relationships, and reopening currents. Our data suggest that inactivation can proceed primarily from the open state and that multiple inactivation components can be identified.
Collapse
Affiliation(s)
- Shimin Wang
- Department of Physiology and Biophysics, University at Buffalo, The State University of New York, School of Medicine and Biomedical Sciences, Buffalo, NY, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
Chen BP, Mao HJ, Fan FY, Bruce IC, Xia Q. DELAYED UNCOUPLING CONTRIBUTES TO THE PROTECTIVE EFFECT OF HEPTANOL AGAINST ISCHAEMIA IN THE RAT ISOLATED HEART. Clin Exp Pharmacol Physiol 2005; 32:655-62. [PMID: 16120193 DOI: 10.1111/j.0305-1870.2005.04246.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. It is known that infusion of the gap junction uncoupler heptanol, before ischaemia or during reperfusion, limits myocardial infarct size. However, whether this cardiac effect is linked to the effect of heptanol on communication across gap junctions has not been elucidated. The aims of the present study were to examine the effect of heptanol on infarct size, arrhythmias and myocardial tissue resistance and to assess whether changes in electrical coupling correlate with cardiac protection. 2. Rat isolated, perfused hearts were subjected to a 24 min infusion of heptanol (0.05, 0.1, 0.5 or 1.0 mmol/L) followed by 20 min regional ischaemia and 60 min reperfusion, or by 70 min global no-flow ischaemia. The effective refractory period, action potential and conduction velocity were measured in papillary muscles from the right ventricle. Heptanol markedly decreased arrhythmia scores during ischaemia and reperfusion, as well as reducing infarct size to a degree similar to that induced by ischaemic preconditioning. In the prolonged ischaemia model, heptanol delayed the onset of uncoupling, increased time to plateau and decreased the maximal rate of uncoupling during ischaemia. Ischaemic preconditioning had similar effects on these parameters. In papillary muscle, heptanol reduced the conduction velocity of the action potential in a dose-dependent manner, but had no significant effect on resting potential, action potential amplitude, action potential duration, maximal upstroke of depolarization or effective refractory period. 3. These results demonstrate that treatment with the gap junction uncoupler heptanol confers cardioprotection against ischaemia and this effect is related to delayed electrical uncoupling during prolonged ischaemia.
Collapse
Affiliation(s)
- Bao-Ping Chen
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, China
| | | | | | | | | |
Collapse
|
24
|
Stoyanovsky DA, Schor NF, Nylander KD, Salama G. Effects of pH on the Cytotoxicity of Sodium Trioxodinitrate (Angeli's Salt). J Med Chem 2003; 47:210-7. [PMID: 14695834 DOI: 10.1021/jm030192j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tumor tissues have an acidic microenvironment with a pH from 6.0 to 7.0, whereas the intra- and extracellular milieu of normal cells is 7.4. We have found that the hydrolysis of sodium trioxodinitrate (Angeli's salt; 1) to hydroxyl radical (*OH) was 10 times higher at pH = 6.0 than at pH = 7.4. It is hypothesized that the formation of *OH in solutions of 1 reflects the hydrolysis of the latter compound to nitroxyl (HNO) which dimerizes to cis-hyponitrous acid (HO-N=N-OH; 3) with concomitant azo-type homolytic fission to N(2) and *OH. In weakly acidified solutions, 1 exhibited strong toxicity to cancer cells that was inhibited by scavengers of hydroxyl radical, whereas no toxicity was observed at pH = 7.4. In a subcutaneous xenograft model of pheochromocytoma, 1 markedly inhibited tumor growth at a dose that was nontoxic to nude mice. These data suggest that the H(+)-amplified production of *OH from 1, and maybe other precursors of HNO, could be a selective mechanism for destruction cells with an acidic intra- or extracellular microenvironment.
Collapse
Affiliation(s)
- Detcho A Stoyanovsky
- Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
| | | | | | | |
Collapse
|
25
|
Padilla F, Garcia-Dorado D, Rodríguez-Sinovas A, Ruiz-Meana M, Inserte J, Soler-Soler J. Protection afforded by ischemic preconditioning is not mediated by effects on cell-to-cell electrical coupling during myocardial ischemia-reperfusion. Am J Physiol Heart Circ Physiol 2003; 285:H1909-16. [PMID: 12869372 DOI: 10.1152/ajpheart.00438.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The end-effectors of ischemic preconditioning (IPC) are not well known. It has been recently shown that transgenic mice underexpressing the gap junction protein connexin43 (Cx43) cannot be preconditioned. Because gap junctions allow spreading of cell death during ischemia-reperfusion in different tissues, including myocardium, we hypothesized that the protection afforded by IPC is mediated by effects on gap junction-mediated intercellular communication. To test this hypothesis, we analyzed the effect of IPC (5 min ischemia-5 min reperfusion x 2) on the changes in electrical impedance (four electrode probe) and impulse propagation velocity (transmembrane action potential) induced by ischemia (60 min) and reperfusion (60 min) in isolated rat hearts. IPC (n = 8) reduced reperfusion-induced lactate dehydrogenase release by 65.8% with respect to control hearts (n = 9) (P = 0.04) but had no effect on the time of onset of rigor contracture (increase in diastolic tension), electrical uncoupling (sharp changes in tissue resistivity and phase angle in impedance recordings), or block of impulse propagation during ischemia. Normalization of electrical impedance during reperfusion was also unaffected by IPC. The lack of effect of IPC on ischemic rigor contracture and on changes in tissue impedance during ischemia-reperfusion were validated under in vivo conditions in pigs submitted to 48 min of coronary occlusion and 120 min of reperfusion. IPC (n = 12) reduced infarct size (triphenyltetrazolium) by 64.9% (P = 0.01) with respect to controls (n = 17). We conclude that the protection afforded by IPC is not mediated by effects on electrical coupling. This result is consistent with recent findings suggesting that Cx43 could have effects on cell survival independent on changes in cell-to-cell communication.
Collapse
Affiliation(s)
- Ferran Padilla
- Laboratorio de Cardiología Experimental, Servicio de Cardiología, Hospital Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain
| | | | | | | | | | | |
Collapse
|
26
|
Ivanova J, Salama G, Clancy RM, Schor NF, Nylander KD, Stoyanovsky DA. Formation of nitroxyl and hydroxyl radical in solutions of sodium trioxodinitrate: effects of pH and cytotoxicity. J Biol Chem 2003; 278:42761-8. [PMID: 12920123 DOI: 10.1074/jbc.m305544200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite its negative redox potential, nitroxyl (HNO) can trigger reactions of oxidation. Mechanistically, these reactions were suggested to occur with the intermediate formation of either hydroxyl radical (.OH) or peroxynitrite (ONOO-). In this work, we present further experimental evidence that HNO can generate.OH. Sodium trioxodinitrate (Na2N2O3), a commonly used donor of HNO, oxidized phenol and Me2SO to benzene diols and.CH3, respectively. The oxidation of Me2SO was O2-independent, suggesting that this process reflected neither the intermediate formation of ONOO- nor a redox cycling of transition metal ions that could initiate Fenton-like reactions. In solutions of phenol, Na2N2O3 yielded benzene-1,2-diol and benzene-1,4-diol at a ratio of 2:1, which is consistent with the generation of free.OH. Ethanol and Me2SO, which are efficient scavengers of.OH, impeded the hydroxylation of phenol. A mechanism for the hydrolysis of Na2N2O3 is proposed that includes dimerization of HNO to cis-hyponitrous acid (HO-N=N-OH) with a concomitant azo-type homolytic fission of the latter to N2 and.OH. The HNO-dependent production of.OH was with 1 order of magnitude higher at pH 6.0 than at pH 7.4. Hence, we hypothesized that HNO can exert selective toxicity to cells subjected to acidosis. In support of this thesis, Na2N2O3 was markedly more toxic to human fibroblasts and SK-N-SH neuroblastoma cells at pH 6.2 than at pH 7.4. Scavengers of.OH impeded the cytotoxicity of Na2N2O3. These results suggest that the formation of HNO may be viewed as a toxicological event in tissues subjected to acidosis.
Collapse
Affiliation(s)
- Juliana Ivanova
- Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
| | | | | | | | | | | |
Collapse
|
27
|
London B, Baker LC, Lee JS, Shusterman V, Choi BR, Kubota T, McTiernan CF, Feldman AM, Salama G. Calcium-dependent arrhythmias in transgenic mice with heart failure. Am J Physiol Heart Circ Physiol 2003; 284:H431-41. [PMID: 12388316 DOI: 10.1152/ajpheart.00431.2002] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Transgenic mice overexpressing the inflammatory cytokine tumor necrosis factor (TNF)-alpha (TNF-alpha mice) in the heart develop a progressive heart failure syndrome characterized by biventricular dilatation, decreased ejection fraction, atrial and ventricular arrhythmias on ambulatory telemetry monitoring, and decreased survival compared with nontransgenic littermates. Programmed stimulation in vitro with single extra beats elicits reentrant ventricular arrhythmias in TNF-alpha (n = 12 of 13 hearts) but not in control hearts. We performed optical mapping of voltage and Ca(2+) in isolated perfused ventricles of TNF-alpha mice to study the mechanisms that lead to the initiation and maintenance of the arrhythmias. When compared with controls, hearts from TNF-alpha mice have prolonged of action potential durations (action potential duration at 90% repolarization: 23 +/- 2 ms, n = 7, vs. 18 +/- 1 ms, n = 5; P < 0.05), no increased dispersion of refractoriness between apex and base, elevated diastolic and depressed systolic [Ca(2+)], and prolonged Ca(2+) transients (72 +/- 6 ms, n = 10, vs. 54 +/- 5 ms, n = 8; P < 0.01). Premature beats have diminished action potential amplitudes and conduct in a slow, heterogeneous manner. Lowering extracellular [Ca(2+)] normalizes conduction and prevents inducible arrhythmias. Thus both action potential prolongation and abnormal Ca(2+) handling may contribute to the initiation of reentrant arrhythmias in this heart failure model by mechanisms distinct from enhanced dispersion of refractoriness or triggered activity.
Collapse
Affiliation(s)
- Barry London
- Cardiovascular Institute, University of Pittsburgh, Pennsylvania 15213, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Schaefer M, Gross W, Ackemann J, Gebhard MM. The complex dielectric spectrum of heart tissue during ischemia. Bioelectrochemistry 2002; 58:171-80. [PMID: 12414323 DOI: 10.1016/s1567-5394(02)00152-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Because of the variety of tissue structures, the interpretation of the passive complex dielectric permittivity spectrum epsilon (omega) of the heart is still a problem. The aim of this work was to correlate epsilon (omega) of heart tissue with physical processes on cellular level. METHODS epsilon (omega) of canine hearts was continuously measured in the range from 10 Hz to 400 MHz during cardioplegic perfusion and during following ischemia. Cardioplegic perfusion was performed with HTK (Custodiol) without or with heptanol, in order to produce electrical cell uncoupling via the closure of gap junctions. To analyse epsilon (omega), we present two heart models which consider cell shape, electrical cell coupling, and dielectric polarisation of cell membranes and membranes of intracellular structures. RESULTS epsilon (omega) of heart tissue shows an alpha-, beta-, and gamma-dispersion. epsilon (omega) remains unchanged during cardioplegic perfusion with HTK, but if heptanol is added, there is an immediate decrease in the region of alpha-dispersion and an increase in the low frequency part of beta-dispersion. Similar changes are observed during ischemia following HTK perfusion without heptanol; additionally, the beta-dispersion shifts to higher frequencies. Using our models, we obtain analogue changes of epsilon (omega) by fitting model parameters which describe water content, water distribution, extra- and intracellular conductivity, and gap junction resistance. DISCUSSION Changes of these tissue properties as calculated by our models based on the measurement of epsilon (omega) are consistent with intraischemic changes of heart tissue known from immunohistochemical, biochemical, and histological investigations. The next step will be to use our models for the prognosis of irreversible tissue damage.
Collapse
Affiliation(s)
- M Schaefer
- Department of Experimental Surgery, University of Heidelberg, INF 365, D-69120 Heidelberg, Germany.
| | | | | | | |
Collapse
|
29
|
Huang JL, Ting CT, Chen YT, Chen SA. Mechanisms of ventricular fibrillation during coronary angioplasty: increased incidence for the small orifice caliber of the right coronary artery. Int J Cardiol 2002; 82:221-8. [PMID: 11911909 DOI: 10.1016/s0167-5273(01)00596-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Ventricular fibrillation (VF) is not an infrequent complication of percutaneous transluminal coronary angioplasty (PTCA). However, it is not clear why there is a marked discrepancy in the higher incidence of VF during right coronary artery (RCA) approach. METHODS AND RESULTS We analyzed in detail every case of VF occurring in 905 consecutive PTCA procedures to investigate possible mechanisms. Sixteen patients (M/F=15/1, mean age: 71 +/- 8 years) with VF during PTCA for the RCA as Group I. Those 51 patients (M/F=48/3, mean age: 70 +/- 9 years) without VF during PTCA for the RCA engagement were designated as Group II. Patients were equipped with cardiac event recorder (CardioCall, Reynolds Medical, UK) before the PTCA, and we set the time period 1 min before and after the event. The lead II was selected to check the QRS width, QTc interval, ST segment change and RR interval before and after event. A total of 905 PTCA procedures were included. There were 561 procedures for the left coronary artery and three events (0.5%) with spontaneous VF. However, there were 16 events (4.6%) of VF during 344 PTCA procedures for the right coronary artery. The incidence of VF for the right side PTCA was significantly higher than for the left side. The orifice of RCA in Group I was smaller than Group II (orifice of RCA in Group I vs. Group II - 2.7+/-0.8 vs. 4.1+/-1.2 mm, P<0.001). Most cases (68.7%) presented with ST segment depression before the onset of VF. CONCLUSION A small caliber of RCA and associated ST segment changes played important roles in the patients with VF during the PTCA.
Collapse
Affiliation(s)
- Jin Long Huang
- Division of Cardiology, Department of Medicine, Institute of Clinical Medicine, and Cardiovascular Research Center, National Yang-Ming University, Taichung Veterans General Hospital, Taichung, Taiwan, ROC
| | | | | | | |
Collapse
|
30
|
Gramatikov B, Brinker J, Yi-chun S, Thakor NV. Wavelet analysis and time-frequency distributions of the body surface ECG before and after angioplasty. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2000; 62:87-98. [PMID: 10764935 DOI: 10.1016/s0169-2607(00)00060-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In a pilot study, electrocardiographic (ECG) recordings of patients with left and right coronary stenosis taken before and after angioplasty were analyzed using the continuous wavelet transform. Time-frequency distributions were obtained for different leads in order to examine the dynamics of the QRS-spectrum and establish features specific of ischemia in the time-frequency domain. We found relevant changes in the mid-frequency range, reflecting the ECG's response to percutaneous transluminal coronary angioplasty (PTCA). The changes appeared in ECG leads close to ischemic zones of the myocardium. Time-frequency distributions of the ECG during the QRS may thus become another electrocardiographic indicator of ischemia, alternative to ST-level in standard ECG or body surface mapping. The paper demonstrates the ability of the continuous wavelet transform to detect short lasting events of low amplitude superimposed on large signal deflections.
Collapse
Affiliation(s)
- B Gramatikov
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
| | | | | | | |
Collapse
|
31
|
Rodríguez-Sinovas A, Cinca J. [Sudden death (II). Myocardial ischemia and ventricular arrhythmias in experimental models: triggering mechanisms]. Rev Esp Cardiol 1999; 52:851-9. [PMID: 10563159 DOI: 10.1016/s0300-8932(99)75012-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metabolic and electrolytic alterations generated in the acute ischemic myocardium, such as an increase in extracellular potassium or acidosis, are responsible for the occurrence of ventricular arrhythmias. In the first 5-10 minutes following coronary occlusion, reentry seems to have an important role, although not in the next 15 minutes. If the patient survives, a subacute arrhythmia period appears, 6 to 72 hours after the onset of ischemia, probably due to abnormal automaticity in the surviving Purkinje fibers. Finally, reentry in the epicardial border zone is the most likely mechanism for chronic arrhythmias. In this review we focus on the studies dealing with the mechanisms of ischemia-induced arrhythmias, with special reference to those conducted in experimental models.
Collapse
Affiliation(s)
- A Rodríguez-Sinovas
- Laboratorio A de Cardiología Experimental, Hospitals Vall d'Hebron, Barcelona.
| | | |
Collapse
|
32
|
Silomon M, Rose S. Effect of sodium bicarbonate infusion on hepatocyte Ca2+ overload during resuscitation from hemorrhagic shock. Resuscitation 1998; 37:27-32. [PMID: 9667335 DOI: 10.1016/s0300-9572(98)00029-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ischemia/reperfusion events alter the cellular ion homeostasis by intracellular acidosis and a subsequent rise of sodium and calcium concentrations. Since disturbance of intracellular Ca2+ signaling pathways impairs cellular function, we investigated the effect of sodium bicarbonate infusion on hepatocellular Ca2+ dysregulation induced by resuscitation from hemorrhagic shock. Anesthetized Sprague-Dawley rats were bled to a mean arterial blood pressure of 40 mmHg for 60 min. Rats were resuscitated by retransfusion of shed blood (60%) in 20 min and three-fold the bleed out volume as lactated Ringers' during 60 min and received either a bolus infusion of sodium bicarbonate (2 mval/kg body weight) or an equal volume of sodium chloride (0.9%). After hepatocyte isolation by portal collagenase perfusion, the rate of Ca2+ influx (Ca2+in) in the absence and presence of epinephrine (100 nM), cellular Ca2+ uptake (Ca2+up) and membrane Ca2+ flux (Ca2+flux) were determined using 45Ca2+ incubation techniques. Hemorrhage/resuscitation substantially increased hepatocyte Ca2+up (3.44 +/- 0.2 nmol/mg protein) and Ca2+flux (32.8 +/- 5 pmol/mg protein x min) compared to sham-operated controls (2.57 +/- 0.1 and 15.2 +/- 3.5; P < 0.05). Resuscitation with sodium bicarbonate significantly prevented altered hepatocyte Ca2+ regulation (2.31 +/- 0.1 and 14.4 +/- 4.6; P < 0.05). These findings suggested that postischemic hepatocyte Ca2+ overload could partly be due to enhanced membrane Ca2+ movements to correct for altered intracellular pH homeostasis.
Collapse
Affiliation(s)
- M Silomon
- Department of Anesthesiology and Critical Care Medicine, University of Saarland, Homburg/Saar, Germany
| | | |
Collapse
|
33
|
Watanabe I, Kanda A, Engle CL, Gettes LS. Comparison of the effects of regional ischemia and hyperkalemia on the membrane action potentials of the in situ pig heart. Experimental Cardiology Group, University of North Carolina at Chapel Hill. J Cardiovasc Electrophysiol 1997; 8:1229-36. [PMID: 9395164 DOI: 10.1111/j.1540-8167.1997.tb01012.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
INTRODUCTION This study was designed to determine the role of increased extracellular potassium [K+]e on action potential duration (APD) in the in situ porcine heart during acute regional no-flow ischemia. METHODS AND RESULTS In open chest, anesthetized swine, an arterial shunt from the carotid artery to the mid-left anterior descending coronary artery was created through which a solution of KCl was infused to raise [K+]e. Myocardial [K+]e was determined by potassium-sensitive electrodes, and transmembrane action potential was recorded by floating glass microelectrode. During the first 2 minutes of ischemia, APD at 90% repolarization (APD90) lengthened by 31.2 +/- 1.1 msec (P < 0.05). The comparable increase in [K+]e alone shortened APD90. During the next 6 minutes of ischemia, [K+]e rose to 11.3 +/- 0.3 mM and APD90 showed a decrease. However, the comparable increase in [K+]e by infusion of KCl caused further shortening of APD90 at similar levels of [K+]e. CONCLUSIONS Acutely ischemic myocardium showed a brief increase in APD90 during the first 2 minutes of ischemia, followed by a fall in APD90 after 2 minutes of ischemia, but the shortening is less than anticipated by the rise in [K+]e. Thus, we hypothesize that other component(s) of ischemia may inhibit action potential repolarization.
Collapse
|