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Lyu Y, Thai PN, Ren L, Timofeyev V, Jian Z, Park S, Ginsburg KS, Overton J, Bossuyt J, Bers DM, Yamoah EN, Chen-Izu Y, Chiamvimonvat N, Zhang XD. Beat-to-beat dynamic regulation of intracellular pH in cardiomyocytes. iScience 2022; 25:103624. [PMID: 35005560 PMCID: PMC8718820 DOI: 10.1016/j.isci.2021.103624] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/10/2021] [Accepted: 12/10/2021] [Indexed: 11/20/2022] Open
Abstract
The mammalian heart beats incessantly with rhythmic mechanical activities generating acids that need to be buffered to maintain a stable intracellular pH (pHi) for normal cardiac function. Even though spatial pHi non-uniformity in cardiomyocytes has been documented, it remains unknown how pHi is regulated to match the dynamic cardiac contractions. Here, we demonstrated beat-to-beat intracellular acidification, termed pHi transients, in synchrony with cardiomyocyte contractions. The pHi transients are regulated by pacing rate, Cl-/HCO3 - transporters, pHi buffering capacity, and β-adrenergic signaling. Mitochondrial electron-transport chain inhibition attenuates the pHi transients, implicating mitochondrial activity in sculpting the pHi regulation. The pHi transients provide dynamic alterations of H+ transport required for ATP synthesis, and a decrease in pHi may serve as a negative feedback to cardiac contractions. Current findings dovetail with the prevailing three known dynamic systems, namely electrical, Ca2+, and mechanical systems, and may reveal broader features of pHi handling in excitable cells.
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Affiliation(s)
- Yankun Lyu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Phung N. Thai
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Lu Ren
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Valeriy Timofeyev
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Kenneth S. Ginsburg
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - James Overton
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Julie Bossuyt
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
| | - Xiao-Dong Zhang
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
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2
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Bou-Teen D, Kaludercic N, Weissman D, Turan B, Maack C, Di Lisa F, Ruiz-Meana M. Mitochondrial ROS and mitochondria-targeted antioxidants in the aged heart. Free Radic Biol Med 2021; 167:109-124. [PMID: 33716106 DOI: 10.1016/j.freeradbiomed.2021.02.043] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 02/14/2021] [Accepted: 02/26/2021] [Indexed: 12/12/2022]
Abstract
Excessive mitochondrial ROS production has been causally linked to the pathophysiology of aging in the heart and other organs, and plays a deleterious role in several age-related cardiac pathologies, including myocardial ischemia-reperfusion injury and heart failure, the two worldwide leading causes of death and disability in the elderly. However, ROS generation is also a fundamental mitochondrial function that orchestrates several signaling pathways, some of them exerting cardioprotective effects. In cardiac myocytes, mitochondria are particularly abundant and are specialized in subcellular populations, in part determined by their relationships with other organelles and their cyclic calcium handling activity necessary for adequate myocardial contraction/relaxation and redox balance. Depending on their subcellular location, mitochondria can themselves be differentially targeted by ROS and display distinct age-dependent functional decline. Thus, precise mitochondria-targeted therapies aimed at counteracting unregulated ROS production are expected to have therapeutic benefits in certain aging-related heart conditions. However, for an adequate design of such therapies, it is necessary to unravel the complex and dynamic interactions between mitochondria and other cellular processes.
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Affiliation(s)
- Diana Bou-Teen
- Hospital Universitari Vall d'Hebron, Department of Cardiology, Vall d'Hebron Institut de Recerca (VHIR),Universitat Autonoma de Barcelona, 08035, Barcelona, Spain
| | - Nina Kaludercic
- Neuroscience Institute, National Research Council of Italy (CNR), via Ugo Bassi 58/B, 35131, Padova, Italy; Fondazione Istituto di Ricerca Pediatrica Città della Speranza (IRP), 35129, Padova, Italy
| | - David Weissman
- Comprehensive Heart Failure Center, University Clinic Würzburg, 97080, Würzburg, Germany
| | - Belma Turan
- Departments of Biophysics, Faculty of Medicine, Lokman Hekim University, Ankara, Turkey
| | - Christoph Maack
- Comprehensive Heart Failure Center, University Clinic Würzburg, 97080, Würzburg, Germany
| | - Fabio Di Lisa
- Neuroscience Institute, National Research Council of Italy (CNR), via Ugo Bassi 58/B, 35131, Padova, Italy; Department of Biomedical Sciences, University of Padova, via Ugo Bassi 58/B, 35131, Padova, Italy
| | - Marisol Ruiz-Meana
- Hospital Universitari Vall d'Hebron, Department of Cardiology, Vall d'Hebron Institut de Recerca (VHIR),Universitat Autonoma de Barcelona, 08035, Barcelona, Spain; Centro de Investigación Biomédica en Red-CV, CIBER-CV, Spain.
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3
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Zhou X, Li A, Lin PH, Zhou J, Ma J. TRIC-A regulates intracellular Ca 2+ homeostasis in cardiomyocytes. Pflugers Arch 2021; 473:547-556. [PMID: 33474637 PMCID: PMC7940156 DOI: 10.1007/s00424-021-02513-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/14/2020] [Accepted: 01/04/2021] [Indexed: 01/26/2023]
Abstract
Trimeric intracellular cation (TRIC) channels have been identified as monovalent cation channels that are located in the ER/SR membrane. Two isoforms discovered in mammals are TRIC-A (TMEM38a) and TRIC-B (TMEM38b). TRIC-B ubiquitously expresses in all tissues, and TRIC-B-/- mice is lethal at the neonatal stage. TRIC-A mainly expresses in excitable cells. TRIC-A-/- mice survive normally but show abnormal SR Ca2+ handling in both skeletal and cardiac muscle cells. Importantly, TRIC-A mutations have been identified in human patients with stress-induced arrhythmia. In the past decade, important discoveries have been made to understand the structure and function of TRIC channels, especially its role in regulating intracellular Ca2+ homeostasis. In this review article, we focus on the potential roles of TRIC-A in regulating cardiac function, particularly its effects on intracellular Ca2+ signaling of cardiomyocytes and discuss the current knowledge gaps.
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Affiliation(s)
- Xinyu Zhou
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA
| | - Ang Li
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, 76019, USA
| | - Pei-Hui Lin
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA
| | - Jingsong Zhou
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, 76019, USA
| | - Jianjie Ma
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA.
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4
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Su Y, Ahn B, Macpherson PCD, Ranjit R, Claflin DR, Van Remmen H, Brooks SV. Transgenic expression of SOD1 specifically in neurons of Sod1 deficient mice prevents defects in muscle mitochondrial function and calcium handling. Free Radic Biol Med 2021; 165:299-311. [PMID: 33561489 PMCID: PMC8026109 DOI: 10.1016/j.freeradbiomed.2021.01.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 01/09/2021] [Accepted: 01/25/2021] [Indexed: 01/21/2023]
Abstract
Aging is accompanied by loss of muscle mass and force, known as sarcopenia. Muscle atrophy, weakness, and neuromuscular junction (NMJ) degeneration reminiscent of normal muscle aging are observed early in adulthood for mice deficient in Cu, Zn-superoxide dismutase (SOD, Sod1-/-). Muscles of Sod1-/- mice also display impaired mitochondrial ATP production and increased mitochondrial reactive oxygen species (ROS) generation implicating oxidative stress in sarcopenia. Restoration of CuZnSOD specifically in neurons of Sod1-/- mice (SynTgSod1-/-) prevents muscle atrophy and loss of force, but whether muscle mitochondrial function is preserved is not known. To establish links among CuZnSOD expression, mitochondrial function, and sarcopenia, we examined contractile properties, mitochondrial function and ROS production, intracellular calcium transients (ICT), and NMJ morphology in lumbrical muscles of 7-9 month wild type (WT), Sod1-/-, and SynTgSod1-/- mice. Compared with WT values, mitochondrial ROS production was increased 2.9-fold under basal conditions and 2.2-fold with addition of glutamate and malate in Sod1-/- muscle fibers while oxygen consumption was not significantly altered. In addition, NADH recovery was blunted following contraction and the peak of the ICT was decreased by 25%. Mitochondrial function, ROS generation and calcium handling were restored to WT values in SynTgSod1-/- mice, despite continued lack of CuZnSOD in muscle. NMJ denervation and fragmentation were also fully rescued in SynTgSod1-/- mice suggesting that muscle mitochondrial and calcium handling defects in Sod1-/- mice are secondary to neuronal oxidative stress and its effects on the NMJ rather than the lack of muscle CuZnSOD. We conclude that intact neuronal function and innervation are key to maintaining excitation-contraction coupling and muscle mitochondrial function.
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Affiliation(s)
- Yu Su
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA; Department of Orthopedics, Second Xiangya Hospital, Central South University, Changsha, PR China
| | - Bumsoo Ahn
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Peter C D Macpherson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Rojina Ranjit
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Dennis R Claflin
- Department of Surgery, Section of Plastic Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Holly Van Remmen
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA; Department of Physiology, Oklahoma University Health Science Center, Oklahoma City, OK, USA; VA Medical Center, Oklahoma City, OK, USA
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
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5
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Boyman L, Karbowski M, Lederer WJ. Regulation of Mitochondrial ATP Production: Ca 2+ Signaling and Quality Control. Trends Mol Med 2019; 26:21-39. [PMID: 31767352 DOI: 10.1016/j.molmed.2019.10.007] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/16/2019] [Accepted: 10/23/2019] [Indexed: 02/06/2023]
Abstract
Cardiac ATP production primarily depends on oxidative phosphorylation in mitochondria and is dynamically regulated by Ca2+ levels in the mitochondrial matrix as well as by cytosolic ADP. We discuss mitochondrial Ca2+ signaling and its dysfunction which has recently been linked to cardiac pathologies including arrhythmia and heart failure. Similar dysfunction in other excitable and long-lived cells including neurons is associated with neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Central to this new understanding is crucial Ca2+ regulation of both mitochondrial quality control and ATP production. Mitochondria-associated membrane (MAM) signaling from the sarcoplasmic reticulum (SR) and the endoplasmic reticulum (ER) to mitochondria is discussed. We propose future research directions that emphasize a need to define quantitatively the physiological roles of MAMs, as well as mitochondrial quality control and ATP production.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Mariusz Karbowski
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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6
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Abstract
In heart failure, alterations of Na+ and Ca2+ handling, energetic deficit, and oxidative stress in cardiac myocytes are important pathophysiological hallmarks. Mitochondria are central to these processes because they are the main source for ATP, but also reactive oxygen species (ROS), and their function is critically controlled by Ca2+ During physiological variations of workload, mitochondrial Ca2+ uptake is required to match energy supply to demand but also to keep the antioxidative capacity in a reduced state to prevent excessive emission of ROS. Mitochondria take up Ca2+ via the mitochondrial Ca2+ uniporter, which exists in a multiprotein complex whose molecular components were identified only recently. In heart failure, deterioration of cytosolic Ca2+ and Na+ handling hampers mitochondrial Ca2+ uptake and the ensuing Krebs cycle-induced regeneration of the reduced forms of NADH (nicotinamide adenine dinucleotide) and NADPH (nicotinamide adenine dinucleotide phosphate), giving rise to energetic deficit and oxidative stress. ROS emission from mitochondria can trigger further ROS release from neighboring mitochondria termed ROS-induced ROS release, and cross talk between different ROS sources provides a spatially confined cellular network of redox signaling. Although low levels of ROS may serve physiological roles, higher levels interfere with excitation-contraction coupling, induce maladaptive cardiac remodeling through redox-sensitive kinases, and cell death through mitochondrial permeability transition. Targeting the dysregulated interplay between excitation-contraction coupling and mitochondrial energetics may ameliorate the progression of heart failure.
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Affiliation(s)
- Edoardo Bertero
- From the Comprehensive Heart Failure Center, University Clinic Würzburg, Germany
| | - Christoph Maack
- From the Comprehensive Heart Failure Center, University Clinic Würzburg, Germany.
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7
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Optical Metabolic Imaging for Assessment of Radiation-Induced Injury to Rat Kidney and Mitigation by Lisinopril. Ann Biomed Eng 2019; 47:1564-1574. [PMID: 30963380 DOI: 10.1007/s10439-019-02255-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/26/2019] [Indexed: 12/17/2022]
Abstract
The kidney is one of the most radiosensitive organs; it is the primary dose-limiting organ in radiotherapies for upper abdominal cancers. The role of mitochondrial redox state in the development and treatment of renal radiation injury, however, remains ill-defined. This study utilizes 3D optical cryo-imaging to quantify renal mitochondrial bioenergetics dysfunction after 13 Gy leg-out partial body irradiation (PBI). Furthermore, the mitigating effects of lisinopril (lisino), an anti-hypertensive angiotensin converting enzyme inhibitor, is assessed in renal radiation-induced injuries. Around day 150 post-irradiation, kidneys are harvested for cryo-imaging. The 3D images of the metabolic indices (NADH, nicotinamide adenine dinucleotide, and FAD, flavin adenine dinucleotide) are acquired, and the mitochondrial redox states of the irradiated and irradiated + lisino kidneys are quantified by calculating the volumetric mean redox ratio (NADH/FAD). PBI oxidized renal mitochondrial redox state by 78%. The kidneys from the irradiated + lisino rats showed mitigation of mitochondrial redox state by 93% compared to the PBI group. The study provides evidence for an altered bioenergetics and energy metabolism in the rat model of irradiation-induced kidney damage. In addition, the results suggest that lisinopril mitigates irradiation damage by attenuating the oxidation of mitochondria leading to increase redox ratio.
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8
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Wüst RCI, Stienen GJM. Successive contractile periods activate mitochondria at the onset of contractions in intact rat cardiac trabeculae. J Appl Physiol (1985) 2018; 124:1003-1011. [PMID: 29357483 DOI: 10.1152/japplphysiol.01010.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rate of oxidative phosphorylation depends on the contractile activity of the heart. Cardiac mitochondrial oxidative phosphorylation is determined by free ADP concentration, mitochondrial Ca2+ accumulation, mitochondrial enzyme activities, and Krebs cycle intermediates. The purpose of the present study was to examine the factors that limit oxidative phosphorylation upon rapid changes in contractile activity in cardiac muscle. We tested the hypotheses that prior contractile performance enhances the changes in NAD(P)H and FAD concentration upon an increase in contractile activity and that this mitochondrial "priming" depends on pyruvate dehydrogenase activity. Intact rat cardiac trabeculae were electrically stimulated at 0.5 Hz for at least 30 min. Thereafter, two equal bouts at elevated stimulation frequency of 1, 2, or 3 Hz were applied for 3 min with 3 min of 0.5-Hz stimulation in between. No discernible time delay was observed in the changes in NAD(P)H and FAD fluorescence upon rapid changes in contractile activity. The amplitudes of the rapid changes in fluorescence upon an increase in stimulation frequency (the on-transients) were smaller than upon a decrease in stimulation frequency (the off-transients). A first bout in glucose-containing superfusion solution resulted, during the second bout, in an increase in the amplitudes of the on-transients, but the off-transients remained the same. No such priming effect was observed after addition of 10 mM pyruvate. These results indicate that mitochondrial priming can be observed in cardiac muscle in situ and that pyruvate dehydrogenase activity is critically involved in the mitochondrial adaptation to increases in contractile performance. NEW & NOTEWORTHY Mitochondrial respiration increases with increased cardiac contractile activity. Similar to mitochondrial "priming" in skeletal muscle, we hypothesized that cardiac mitochondrial activity is altered upon successive bouts of contractions and depends on pyruvate dehydrogenase activity. We found altered bioenergetics upon repeated contractile periods, indicative of mitochondrial priming in rat myocardium. No effect was seen when pyruvate was added to the perfusate. As such, pyruvate dehydrogenase activity is involved in the mitochondrial adaptation to increased contractile performance.
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Affiliation(s)
- Rob C I Wüst
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center , Amsterdam , The Netherlands.,Laboratory Genetic Metabolic Diseases, Academic Medical Center , Amsterdam , The Netherlands
| | - Ger J M Stienen
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center , Amsterdam , The Netherlands.,Faculty of Science, Department of Physics and Astronomy, VU University , Amsterdam , The Netherlands
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9
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Moreno A, Kuzmiak-Glancy S, Jaimes R, Kay MW. Enzyme-dependent fluorescence recovery of NADH after photobleaching to assess dehydrogenase activity of isolated perfused hearts. Sci Rep 2017; 7:45744. [PMID: 28361886 PMCID: PMC5374639 DOI: 10.1038/srep45744] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 03/02/2017] [Indexed: 01/09/2023] Open
Abstract
Reduction of NAD+ by dehydrogenase enzymes to form NADH is a key component of cellular metabolism. In cellular preparations and isolated mitochondria suspensions, enzyme-dependent fluorescence recovery after photobleaching (ED-FRAP) of NADH has been shown to be an effective approach for measuring the rate of NADH production to assess dehydrogenase enzyme activity. Our objective was to demonstrate how dehydrogenase activity could be assessed within the myocardium of perfused hearts using NADH ED-FRAP. This was accomplished using a combination of high intensity UV pulses to photobleach epicardial NADH. Replenishment of epicardial NADH fluorescence was then imaged using low intensity UV illumination. NADH ED-FRAP parameters were optimized to deliver 23.8 mJ of photobleaching light energy at a pulse width of 6 msec and a duty cycle of 50%. These parameters provided repeatable measurements of NADH production rate during multiple metabolic perturbations, including changes in perfusate temperature, electromechanical uncoupling, and acute ischemia/reperfusion injury. NADH production rate was significantly higher in every perturbation where the energy demand was either higher or uncompromised. We also found that NADH production rate remained significantly impaired after 10 min of reperfusion after global ischemia. Overall, our results indicate that myocardial NADH ED-FRAP is a useful optical non-destructive approach for assessing dehydrogenase activity.
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Affiliation(s)
- Angel Moreno
- Department of Biomedical Engineering, The George Washington University, Washington, DC 20052, USA
| | - Sarah Kuzmiak-Glancy
- Department of Biomedical Engineering, The George Washington University, Washington, DC 20052, USA
| | - Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University, Washington, DC 20052, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, DC 20052, USA
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10
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Ranji M, Motlagh MM, Salehpour F, Sepehr R, Heisner JS, Dash RK, Camara AKS. Optical Cryoimaging Reveals a Heterogeneous Distribution of Mitochondrial Redox State in ex vivo Guinea Pig Hearts and Its Alteration During Ischemia and Reperfusion. IEEE JOURNAL OF TRANSLATIONAL ENGINEERING IN HEALTH AND MEDICINE-JTEHM 2016; 4:1800210. [PMID: 27574574 PMCID: PMC4993131 DOI: 10.1109/jtehm.2016.2570219] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 04/21/2016] [Accepted: 04/26/2016] [Indexed: 12/16/2022]
Abstract
Oxidation of substrates to generate ATP in mitochondria is mediated by redox reactions of NADH and FADH2. Cardiac ischemia and reperfusion (IR) injury compromises mitochondrial oxidative phosphorylation. We hypothesize that IR alters the metabolic heterogeneity of mitochondrial redox state of the heart that is only evident in the 3-D optical cryoimaging of the perfused heart before, during, and after IR. The study involved four groups of hearts: time control (TC: heart perfusion without IR), global ischemia (Isch), global ischemia followed by reperfusion (IR) and TC with PCP (a mitochondrial uncoupler) perfusion. Mitochondrial NADH and FAD autofluorescence signals were recorded spectrofluorometrically online in guinea pig ex vivo-perfused hearts in the Langendorff mode. At the end of each specified protocol, hearts were rapidly removed and snap frozen in liquid N2 for later 3-D optical cryoimaging of the mitochondrial NADH, FAD, and NADH/FAD redox ratio (RR). The TC hearts revealed a heterogeneous spatial distribution of NADH, FAD, and RR. Ischemia and IR altered the spatial distribution and caused an overall increase and decrease in the RR by 55% and 64%, respectively. Uncoupling with PCP resulted in the lowest level of the RR (73% oxidation) compared with TC. The 3-D optical cryoimaging of the heart provides novel insights into the heterogeneous distribution of mitochondrial NADH, FAD, RR, and metabolism from the base to the apex during ischemia and IR. This 3-D information of the mitochondrial redox state in the normal and ischemic heart was not apparent in the dynamic spectrofluorometric data.
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Affiliation(s)
- Mahsa Ranji
- Department of Electrical EngineeringUniversity of Wisconsin-MilwaukeeMilwaukeeWI53211USA; Biotechnology and Bioengineering CenterMedical College of WisconsinMilwaukeeWI53226USA
| | | | - Fahimeh Salehpour
- Department of Electrical Engineering University of Wisconsin-Milwaukee Milwaukee WI 53211 USA
| | - Reyhaneh Sepehr
- Department of Electrical Engineering University of Wisconsin-Milwaukee Milwaukee WI 53211 USA
| | - James S Heisner
- Department of Anesthesiology Medical College of Wisconsin Milwaukee WI 53226 USA
| | - Ranjan K Dash
- Department of PhysiologyMedical College of WisconsinMilwaukeeWI53226USA; Biotechnology and Bioengineering CenterMedical College of WisconsinMilwaukeeWI53226USA; Cardiovascular Research CenterMedical College of WisconsinMilwaukeeWI53226USA
| | - Amadou K S Camara
- Cardiovascular Research CenterMedical College of WisconsinMilwaukeeWI53226USA; Department of AnesthesiologyMedical College of WisconsinMilwaukeeWI53226USA
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11
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Jaimes R, Kuzmiak-Glancy S, Brooks DM, Swift LM, Posnack NG, Kay MW. Functional response of the isolated, perfused normoxic heart to pyruvate dehydrogenase activation by dichloroacetate and pyruvate. Pflugers Arch 2015; 468:131-142. [PMID: 26142699 DOI: 10.1007/s00424-015-1717-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 06/17/2015] [Accepted: 06/22/2015] [Indexed: 12/19/2022]
Abstract
Dichloroacetate (DCA) and pyruvate activate pyruvate dehydrogenase (PDH), a key enzyme that modulates glucose oxidation and mitochondrial NADH production. Both compounds improve recovery after ischemia in isolated hearts. However, the action of DCA and pyruvate in normoxic myocardium is incompletely understood. We measured the effect of DCA and pyruvate on contraction, mitochondrial redox state, and intracellular calcium cycling in isolated rat hearts during normoxic perfusion. Normalized epicardial NADH fluorescence (nNADH) and left ventricular developed pressure (LVDP) were measured before and after administering DCA (5 mM) or pyruvate (5 mM). Optical mapping of Rhod-2AM was used to measure cytosolic calcium kinetics. DCA maximally activated PDH, increasing the ratio of active to total PDH from 0.48 ± 0.03 to 1.03 ± 0.03. Pyruvate sub-maximally activated PDH to a ratio of 0.75 ± 0.02. DCA and pyruvate increased LVDP. When glucose was the only exogenous fuel, pyruvate increased nNADH by 21.4 ± 2.9 % while DCA reduced nNADH by 21.4 ± 6.1 % and elevated the incidence of premature ventricular contractions (PVCs). When lactate, pyruvate, and glucose were provided together as exogenous fuels, nNADH increased with DCA, indicating that PDH activation with glucose as the only exogenous fuel depletes PDH substrate. Calcium transient time-to-peak was shortened by DCA and pyruvate and SR calcium re-uptake was 30 % longer. DCA and pyruvate increased SR calcium load in myocyte monolayers. Overall, during normoxia when glucose is the only exogenous fuel, DCA elevates SR calcium, increases LVDP and contractility, and diminishes mitochondrial NADH. Administering DCA with plasma levels of lactate and pyruvate mitigates the drop in mitochondrial NADH and prevents PVCs.
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Affiliation(s)
- Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Sarah Kuzmiak-Glancy
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Daina M Brooks
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Luther M Swift
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA
| | - Nikki G Posnack
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA.
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA.
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12
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Wüst RCI, Helmes M, Stienen GJM. Rapid changes in NADH and flavin autofluorescence in rat cardiac trabeculae reveal large mitochondrial complex II reserve capacity. J Physiol 2015; 593:1829-40. [PMID: 25640645 DOI: 10.1113/jphysiol.2014.286153] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 01/27/2015] [Indexed: 12/17/2022] Open
Abstract
KEY POINTS A photometry-based technique was developed to measure nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) autofluorescence and contractile properties simultaneously in intact rat trabeculae at a high time resolution. This provides insight into the function of mitochondrial complex I and II. Maximal complex I and complex II activities were determined in saponin-permeabilized right ventricular tissue by respirometry. In trabeculae, complex II function was considerably smaller than the maximal complex II activity, suggesting large complex II reserve capacity. Up-down asymmetry in NADH and FAD kinetics suggests a complex interaction between mitochondrial and contractile function. These data show that simultaneous measurement of contractile properties and NADH and FAD kinetics in cardiac trabeculae provides a mean to study the differences in complex I and II function in intact preparations in health and disease. ABSTRACT The functional properties of cardiac mitochondria in intact preparations have been mainly studied by measurements of nicotinamide adenine dinucleotide (NADH) autofluorescence, which reflects mitochondrial complex I function. To assess complex II function, we extended this method by measuring flavin adenine dinucleotide (FAD)-related autofluorescence in electrically stimulated cardiac trabeculae isolated from the right ventricle from the rat at 27°C. NADH and FAD autofluorescence and tension responses were measured when stimulation frequency was increased from 0.5 Hz to 1, 2 or 3 Hz for 3 min, and thereafter decreased to 0.5 Hz. Maximal complex I and complex II activity in vitro were determined in saponin-permeabilized right ventricular tissue by respirometry. NADH responses upon an increase in stimulation frequency showed a rapid decline, followed by a slow recovery towards the initial level. FAD responses followed a similar time course, but in the opposite direction. The amplitudes of early rapid changes in the NADH and FAD concentration correlated well with the change in tension time integral per second (R(2) = 0.833 and 0.660 for NADH and FAD, respectively), but with different slopes for the up and down transient. Maximal velocity of the increase in FAD concentration (16 ± 4 μm s(-1) ), measured upon an increase in stimulation frequency from 0.5 to 3 Hz was considerably smaller than that of the decrease in NADH (78 ± 13 μm s(-1) ). The respiration measurements indicated that the maximal velocity of NADH utilization (143 ± 14 μm s(-1) ) was 2 times smaller than that of FADH2 (291 ± 19 μm s(-1) ). This indicates that in cardiac mitochondria considerable complex II activity reserve is present.
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Affiliation(s)
- Rob C I Wüst
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, the Netherlands
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Claflin DR, Jackson MJ, Brooks SV. Age affects the contraction-induced mitochondrial redox response in skeletal muscle. Front Physiol 2015; 6:21. [PMID: 25698975 PMCID: PMC4316701 DOI: 10.3389/fphys.2015.00021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 01/14/2015] [Indexed: 01/17/2023] Open
Abstract
Compromised mitochondrial respiratory function is associated with advancing age. Damage due to an increase in reactive oxygen species (ROS) with age is thought to contribute to the mitochondrial deficits. The coenzyme nicotinamide adenine dinucleotide in its reduced (NADH) and oxidized (NAD+) forms plays an essential role in the cyclic sequence of reactions that result in the regeneration of ATP by oxidative phosphorylation in mitochondria. Monitoring mitochondrial NADH/NAD+ redox status during recovery from an episode of high energy demand thus allows assessment of mitochondrial function. NADH fluoresces when excited with ultraviolet light in the UV-A band and NAD+ does not, allowing NADH/NAD+ to be monitored in real time using fluorescence microscopy. Our goal was to assess mitochondrial function by monitoring the NADH fluorescence response following a brief period of high energy demand in muscle from adult and old wild-type mice. This was accomplished by isolating whole lumbrical muscles from the hind paws of 7- and 28-month-old mice and making simultaneous measurements of force and NADH fluorescence responses during and after a 5 s maximum isometric contraction. All muscles exhibited fluorescence oscillations that were qualitatively similar and consisted of a brief transient increase followed by a longer transient period of reduced fluorescence and, finally, an increase that included an overshoot before recovering to resting level. Compared with the adult mice, muscles from the 28 mo mice exhibited a delayed peak during the first fluorescence transient and an attenuated recovery following the second transient. These findings indicate an impaired mitochondrial capacity to maintain NADH/NAD+ redox homeostasis during contractile activity in skeletal muscles of old mice.
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Affiliation(s)
- Dennis R Claflin
- Department of Biomedical Engineering, University of Michigan Ann Arbor, MI, USA ; Department of Surgery, Section of Plastic Surgery, University of Michigan Ann Arbor, MI, USA
| | - Malcolm J Jackson
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool Liverpool, UK
| | - Susan V Brooks
- Department of Biomedical Engineering, University of Michigan Ann Arbor, MI, USA ; Department of Molecular and Integrative Physiology, University of Michigan Ann Arbor, MI, USA
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Near-IR Triggered Photon Upconversion. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/b978-0-444-63481-8.00273-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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15
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Williams GSB, Boyman L, Lederer WJ. Mitochondrial calcium and the regulation of metabolism in the heart. J Mol Cell Cardiol 2014; 78:35-45. [PMID: 25450609 DOI: 10.1016/j.yjmcc.2014.10.019] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 10/28/2014] [Accepted: 10/30/2014] [Indexed: 01/28/2023]
Abstract
Consumption of adenosine triphosphate (ATP) by the heart can change dramatically as the energetic demands increase from a period of rest to strenuous activity. Mitochondrial ATP production is central to this metabolic response since the heart relies largely on oxidative phosphorylation as its source of intracellular ATP. Significant evidence has been acquired indicating that Ca(2+) plays a critical role in regulating ATP production by the mitochondria. Here the evidence that the Ca(2+) concentration in the mitochondrial matrix ([Ca(2+)]m) plays a pivotal role in regulating ATP production by the mitochondria is critically reviewed and aspects of this process that are under current active investigation are highlighted. Importantly, current quantitative information on the bidirectional Ca(2+) movement across the inner mitochondrial membrane (IMM) is examined in two parts. First, we review how Ca(2+) influx into the mitochondrial matrix depends on the mitochondrial Ca(2+) channel (i.e., the mitochondrial calcium uniporter or MCU). This discussion includes how the MCU open probability (PO) depends on the cytosolic Ca(2+) concentration ([Ca(2+)]i) and on the mitochondrial membrane potential (ΔΨm). Second, we discuss how steady-state [Ca(2+)]m is determined by the dynamic balance between this MCU-based Ca(2+) influx and mitochondrial Na(+)/Ca(2+) exchanger (NCLX) based Ca(2+) efflux. These steady-state [Ca(2+)]m levels are suggested to regulate the metabolic energy supply due to Ca(2+)-dependent regulation of mitochondrial enzymes of the tricarboxylic acid cycle (TCA), the proteins of the electron transport chain (ETC), and the F1F0 ATP synthase itself. We conclude by discussing the roles played by [Ca(2+)]m in influencing mitochondrial responses under pathological conditions. This article is part of a Special Issue entitled "Mitochondria: From BasicMitochondrial Biology to Cardiovascular Disease."
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Affiliation(s)
- George S B Williams
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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Bay J, Kohlhaas M, Maack C. Intracellular Na⁺ and cardiac metabolism. J Mol Cell Cardiol 2013; 61:20-7. [PMID: 23727097 DOI: 10.1016/j.yjmcc.2013.05.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 12/13/2022]
Abstract
In heart failure, alterations of excitation-contraction underlie contractile dysfunction. One important defect is an elevation of the intracellular Na(+) concentration in cardiac myocytes ([Na(+)]i), which has an important impact on cytosolic and mitochondrial Ca(2+) homeostasis. While elevated [Na(+)]i is thought to compensate for decreased Ca(2+) load of the sarcoplasmic reticulum (SR), it yet negatively affects energy supply-and-demand matching and can even induce mitochondrial oxidative stress. Here, we review the mechanisms underlying these pathophysiological changes. The chain of events may constitute a vicious cycle of ion dysregulation, oxidative stress and energetic deficit, resembling characteristic cellular deficits that are considered key hallmarks of the failing heart. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Johannes Bay
- Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes, Homburg, Germany
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Staniszewski K, Audi SH, Sepehr R, Jacobs ER, Ranji M. Surface fluorescence studies of tissue mitochondrial redox state in isolated perfused rat lungs. Ann Biomed Eng 2013; 41:827-36. [PMID: 23238793 PMCID: PMC3606690 DOI: 10.1007/s10439-012-0716-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 11/28/2012] [Indexed: 12/24/2022]
Abstract
We designed a fiber-optic-based optoelectronic fluorometer to measure emitted fluorescence from the auto-fluorescent electron carriers NADH and FAD of the mitochondrial electron transport chain (ETC). The ratio of NADH to FAD is called the redox ratio (RR = NADH/FAD) and is an indicator of the oxidoreductive state of tissue. We evaluated the fluorometer by measuring the fluorescence intensities of NADH and FAD at the surface of isolated, perfused rat lungs. Alterations of lung mitochondrial metabolic state were achieved by the addition of rotenone (complex I inhibitor), potassium cyanide (KCN, complex IV inhibitor) and/or pentachlorophenol (PCP, uncoupler) into the perfusate recirculating through the lung. Rotenone- or KCN-containing perfusate increased RR by 21 and 30%, respectively. In contrast, PCP-containing perfusate decreased RR by 27%. These changes are consistent with the established effects of rotenone, KCN, and PCP on the redox status of the ETC. Addition of blood to perfusate quenched NADH and FAD signal, but had no effect on RR. This study demonstrates the capacity of fluorometry to detect a change in mitochondrial redox state in isolated perfused lungs, and suggests the potential of fluorometry for use in in vivo experiments to extract a sensitive measure of lung tissue health in real-time.
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Affiliation(s)
- Kevin Staniszewski
- Biophotonics Lab, Department of Electrical Engineering, University of Wisconsin Milwaukee, 3200 N Cramer St., Milwaukee, WI 53211
| | - Said H. Audi
- Department of Biomedical Engineering, Marquette University, 1515 West Wisconsin Avenue, Milwaukee, WI, 53233
| | - Reyhaneh Sepehr
- Biophotonics Lab, Department of Electrical Engineering, University of Wisconsin Milwaukee, 3200 N Cramer St., Milwaukee, WI 53211
| | - Elizabeth R. Jacobs
- Associate Chief of Staff, Research and Development, Clement J. Zablocki VA Medical Center, 5000 W. National Avenue Milwaukee, WI 5329 and Associate Dean Research, Medical College of Wisconsin
| | - Mahsa Ranji
- Biophotonics Lab, Department of Electrical Engineering, University of Wisconsin Milwaukee, 3200 N Cramer St., Milwaukee, WI 53211
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Boelens AD, Pradhan RK, Blomeyer CA, Camara AKS, Dash RK, Stowe DF. Extra-matrix Mg2+ limits Ca2+ uptake and modulates Ca2+ uptake-independent respiration and redox state in cardiac isolated mitochondria. J Bioenerg Biomembr 2013; 45:203-18. [PMID: 23456198 DOI: 10.1007/s10863-013-9500-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 01/24/2013] [Indexed: 12/20/2022]
Abstract
Cardiac mitochondrial matrix (m) free Ca(2+) ([Ca(2+)]m) increases primarily by Ca(2+) uptake through the Ca(2+) uniporter (CU). Ca(2+) uptake via the CU is attenuated by extra-matrix (e) Mg(2+) ([Mg(2+)]e). How [Ca(2+)]m is dynamically modulated by interacting physiological levels of [Ca(2+)]e and [Mg(2+)]e and how this interaction alters bioenergetics are not well understood. We postulated that as [Mg(2+)]e modulates Ca(2+) uptake via the CU, it also alters bioenergetics in a matrix Ca(2+)-induced and matrix Ca(2+)-independent manner. To test this, we measured changes in [Ca(2+)]e, [Ca(2+)]m, [Mg(2+)]e and [Mg(2+)]m spectrofluorometrically in guinea pig cardiac mitochondria in response to added CaCl2 (0-0.6 mM; 1 mM EGTA buffer) with/without added MgCl2 (0-2 mM). In parallel, we assessed effects of added CaCl2 and MgCl2 on NADH, membrane potential (ΔΨm), and respiration. We found that ≥0.125 mM MgCl2 significantly attenuated CU-mediated Ca(2+) uptake and [Ca(2+)]m. Incremental [Mg(2+)]e did not reduce initial Ca(2+)uptake but attenuated the subsequent slower Ca(2+) uptake, so that [Ca(2+)]m remained unaltered over time. Adding CaCl2 without MgCl2 to attain a [Ca(2+)]m from 46 to 221 nM enhanced state 3 NADH oxidation and increased respiration by 15 %; up to 868 nM [Ca(2+)]m did not additionally enhance NADH oxidation or respiration. Adding MgCl2 did not increase [Mg(2+)]m but it altered bioenergetics by its direct effect to decrease Ca(2+) uptake. However, at a given [Ca(2+)]m, state 3 respiration was incrementally attenuated, and state 4 respiration enhanced, by higher [Mg(2+)]e. Thus, [Mg(2+)]e without a change in [Mg(2+)]m can modulate bioenergetics independently of CU-mediated Ca(2+) transport.
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Affiliation(s)
- Age D Boelens
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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20
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Influence of ethanol extract of Ginkgo biloba leaves on the isolated rat heart work and mitochondria functions. J Cardiovasc Pharmacol 2012; 59:450-7. [PMID: 22240914 DOI: 10.1097/fjc.0b013e318249171d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
In this study, we attempted to elucidate whether the effects of ethanol extract of Ginkgo biloba leaves (GBE) observed previously on isolated rat heart mitochondria may be realized in situ (in case of isolated heart perfused under normal conditions and under ischemia-reperfusion). We found that GBE at low concentrations (0.01, 0.05, and 0.1 μL/mL) does not affect the heart rate and parameters of electrocardiogram (ECG) but produces a small increase in the coronary flow. Higher concentration of GBE (0.2 and 0.3 μL/mL) diminished the heart rate, decreased the coronary flow, and tended to enhance the parameters of ECG. The contractility of isolated rat heart and mitochondrial nicotinamide adenine dinucleotide reduced form fluorescence decreased in a GBE concentration-dependent manner. Mitochondria isolated from hearts pre-perfused with GBE (0.05 μL/mL) for 20 minutes before nonflow global ischemia-reperfusion (45 min/15 min) showed higher respiratory rates with pyruvate + malate in state 2 and state 3, higher respiratory control index, and diminished H₂O₂ generation compared with untreated group. Higher GBE concentration, 0.4 μL/mL, had no effect on H2O2 generation and did not prevent the ischemia-reperfusion-induced decrease of pyruvate + malate oxidation in state 3 but even enhanced it. However, in the case of nonischemic perfusions, this GBE concentration had no significant effect on these parameters of respiratory functions of isolated heart mitochondria.
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Abstract
Since 1929, when it was discovered that ATP is a substrate for muscle contraction, the knowledge about this purine nucleotide has been greatly expanded. Many aspects of cell metabolism revolve around ATP production and consumption. It is important to understand the concepts of glucose and oxygen consumption in aerobic and anaerobic life and to link bioenergetics with the vast amount of reactions occurring within cells. ATP is universally seen as the energy exchange factor that connects anabolism and catabolism but also fuels processes such as motile contraction, phosphorylations, and active transport. It is also a signalling molecule in the purinergic signalling mechanisms. In this review, we will discuss all the main mechanisms of ATP production linked to ADP phosphorylation as well the regulation of these mechanisms during stress conditions and in connection with calcium signalling events. Recent advances regarding ATP storage and its special significance for purinergic signalling will also be reviewed.
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Dedkova EN, Blatter LA. Measuring mitochondrial function in intact cardiac myocytes. J Mol Cell Cardiol 2011; 52:48-61. [PMID: 21964191 DOI: 10.1016/j.yjmcc.2011.08.030] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 07/30/2011] [Accepted: 08/09/2011] [Indexed: 12/01/2022]
Abstract
Mitochondria are involved in cellular functions that go beyond the traditional role of these organelles as the power plants of the cell. Mitochondria have been implicated in several human diseases, including cardiac dysfunction, and play a role in the aging process. Many aspects of our knowledge of mitochondria stem from studies performed on the isolated organelle. Their relative inaccessibility imposes experimental difficulties to study mitochondria in their natural environment-the cytosol of intact cells-and has hampered a comprehensive understanding of the plethora of mitochondrial functions. Here we review currently available methods to study mitochondrial function in intact cardiomyocytes. These methods primarily use different flavors of fluorescent dyes and genetically encoded fluorescent proteins in conjunction with high-resolution imaging techniques. We review methods to study mitochondrial morphology, mitochondrial membrane potential, Ca(2+) and Na(+) signaling, mitochondrial pH regulation, redox state and ROS production, NO signaling, oxygen consumption, ATP generation and the activity of the mitochondrial permeability transition pore. Where appropriate we complement this review on intact myocytes with seminal studies that were performed on isolated mitochondria, permeabilized cells, and in whole hearts.
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Affiliation(s)
- Elena N Dedkova
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL 60612, USA
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Aldakkak M, Camara AKS, Heisner JS, Yang M, Stowe DF. Ranolazine reduces Ca2+ overload and oxidative stress and improves mitochondrial integrity to protect against ischemia reperfusion injury in isolated hearts. Pharmacol Res 2011; 64:381-92. [PMID: 21741479 DOI: 10.1016/j.phrs.2011.06.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 06/21/2011] [Accepted: 06/22/2011] [Indexed: 10/18/2022]
Abstract
Ranolazine is a clinically approved drug for treating cardiac ventricular dysrhythmias and angina. Its mechanism(s) of protection is not clearly understood but evidence points to blocking the late Na+ current that arises during ischemia, blocking mitochondrial complex I activity, or modulating mitochondrial metabolism. Here we tested the effect of ranolazine treatment before ischemia at the mitochondrial level in intact isolated hearts and in mitochondria isolated from hearts at different times of reperfusion. Left ventricular (LV) pressure (LVP), coronary flow (CF), and O2 metabolism were measured in guinea pig isolated hearts perfused with Krebs-Ringer's solution; mitochondrial (m) superoxide (O2·-), Ca2+, NADH/FAD (redox state), and cytosolic (c) Ca2+ were assessed on-line in the LV free wall by fluorescence spectrophotometry. Ranolazine (5 μM), infused for 1 min just before 30 min of global ischemia, itself did not change O2·-, cCa2+, mCa2+ or redox state. During late ischemia and reperfusion (IR) O2·- emission and m[Ca2+] increased less in the ranolazine group vs. the control group. Ranolazine decreased c[Ca2+] only during ischemia while NADH and FAD were not different during IR in the ranolazine vs. control groups. Throughout reperfusion LVP and CF were higher, and ventricular fibrillation was less frequent. Infarct size was smaller in the ranolazine group than in the control group. Mitochondria isolated from ranolazine-treated hearts had mild resistance to permeability transition pore (mPTP) opening and less cytochrome c release than control hearts. Ranolazine may provide functional protection of the heart during IR injury by reducing cCa2+ and mCa2+ loading secondary to its effect to block the late Na+ current. Subsequently it indirectly reduces O2·- emission, preserves bioenergetics, delays mPTP opening, and restricts loss of cytochrome c, thereby reducing necrosis and apoptosis.
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Affiliation(s)
- Mohammed Aldakkak
- Department of Anesthesiology, The Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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Aldakkak M, Stowe DF, Heisner JS, Riess ML, Camara AKS. Adding ROS quenchers to cold K+ cardioplegia reduces superoxide emission during 2-hour global cold cardiac ischemia. J Cardiovasc Pharmacol Ther 2011; 17:93-101. [PMID: 21282477 DOI: 10.1177/1074248410389815] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We reported that the combination of reactive oxygen species (ROS) quenchers Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), catalase, and glutathione (MCG) given before 2 hours cold ischemia better protected cardiac mitochondria against cold ischemia and warm reperfusion (IR)-induced damage than MnTBAP alone. Here, we hypothesize that high K(+) cardioplegia (CP) plus MCG would provide added protection of mitochondrial bioenergetics and cardiac function against IR injury. Using fluorescence spectrophotometry, we monitored redox balance, ie reduced nicotinamide adenine dinucleotide and flavin adenine dinucleotide (NADH/FAD), superoxide (O(2) (•-)), and mitochondrial Ca(2+) (m[Ca(2+)]) in the left ventricular free wall. Guinea pig isolated hearts were perfused with either Krebs Ringer's (KR) solution, CP, or CP + MCG, before and during 27°C perfusion followed immediately by 2 hours of global ischemia at 27°C. Drugs were washed out with KR at the onset of 2 hours 37°C reperfusion. After 120 minutes warm reperfusion, myocardial infarction was lowest in the CP + MCG group and highest in the KR group. Developed left ventricular pressure recovery was similar in CP and CP + MCG and was better than in the KR group. O(2) (•-), m[Ca(2+)], and NADH/FAD were significantly different between the treatment and KR groups. O(2) (•-) was lower in CP + MCG than in the CP group. This study suggests that CP and ROS quenchers act in parallel to improve mitochondrial function and to provide protection against IR injury at 27°C.
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Affiliation(s)
- Mohammed Aldakkak
- Department of Anesthesiology, The Medical College of Wisconsin, Milwaukee, WI, USA
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Modulation of mitochondrial bioenergetics in the isolated Guinea pig beating heart by potassium and lidocaine cardioplegia: implications for cardioprotection. J Cardiovasc Pharmacol 2010; 54:298-309. [PMID: 19620879 DOI: 10.1097/fjc.0b013e3181b2b842] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mitochondria are damaged by cardiac ischemia/reperfusion (I/R) injury but can contribute to cardioprotection. We tested if hyperkalemic cardioplegia (CP) and lidocaine (LID) differently modulate mitochondrial (m) bioenergetics and protect hearts against I/R injury. Guinea pig hearts (n = 71) were perfused with Krebs Ringer's solution before perfusion for 1 minute just before ischemia with either CP (16 mM K) or LID (1 mM) or Krebs Ringer's (control, 4 mM K). The 1-minute perfusion period assured treatment during ischemia but not on reperfusion. Cardiac function, NADH, FAD, m[Ca], and superoxide (reactive oxygen species) were assessed at baseline, during the 1-minute perfusion, and continuously during I/R. During the brief perfusion before ischemia, CP and LID decreased reactive oxygen species and increased NADH without changing m[Ca]. Additionally, CP decreased FAD. During ischemia, NADH was higher and reactive oxygen species was lower after CP and LID, whereas m[Ca] was lower only after LID. On reperfusion, NADH and FAD were more normalized, and m[Ca] and reactive oxygen species remained lower after CP and LID. Better functional recovery and smaller infarct size after CP and LID were accompanied by better mitochondrial function. These results suggest that mitochondria may be implicated, directly or indirectly, in protection by CP and LID against I/R injury.
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Abstract
Reactive oxygen/nitrogen species (ROS/RNS) have been increasingly recognized as important mediators and play a number of critical roles in cell injury, metabolism, disease pathology, diagnosis, and clinical treatment. Electron paramagnetic resonance (EPR) spectroscopy enables the spectral information at certain spatial position, and, from the observed line-width and signal intensity, the localized tissue oxygenation, and tissue redox status can be determined. We applied in vivo EPR oximetry and redoximetry technique and implemented its physiological/pathophysiological applications, along with the use of biocompatible lithium pthalocyanine (liPc) and nitroxide redox sensitive probes, on in vivo tissue oxygenation and redox profile of the ischemic and reperfused heart in living animals. We have observed that the hypoxia during myocardial ischemia limited mitochondrial respiration and caused a shift of tissue redox status to a more reduced state. ROS/RNS generated at the beginning of reperfusion not only caused a shift of redox status to a more oxidized state which may contribute to the postischemic myocardial injury, but also a marked suppression of in vivo tissue O(2) consumption in the postischemic heart through modulation of mitochondrial respiration based on alterations in enzyme activity and mRNA expression of NADH dehydrogenase (NADH-DH) and cytochrome c oxidase (CcO). In addition, ischemic preconditioning was found to be able to markedly attenuate postischemic myocardial hyperoxygenation with less ROS/RNS generation and preservation of mitochondrial O(2) metabolism, due to conserved NADH-DH and CcO activities. These studies have demonstrated that EPR oximetry and redoximetry techniques have advanced to a stage that enables in-depth insight in the process of ischemia reperfusion injury.
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Affiliation(s)
- Guanglong He
- The Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute and Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine, Columbus, OH, USA.
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Mitochondrial calcium transport in the heart: Physiological and pathological roles. J Mol Cell Cardiol 2009; 46:789-803. [DOI: 10.1016/j.yjmcc.2009.03.001] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 02/28/2009] [Accepted: 03/03/2009] [Indexed: 12/20/2022]
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Tiede L, Steyger PS, Nichols MG, Hallworth R. Metabolic imaging of the organ of corti--a window on cochlea bioenergetics. Brain Res 2009; 1277:37-41. [PMID: 19272358 DOI: 10.1016/j.brainres.2009.02.052] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Revised: 02/16/2009] [Accepted: 02/23/2009] [Indexed: 11/28/2022]
Abstract
Hair cell loss is a major cause of sensorineural hearing loss. We have developed a method to examine metabolic events in hair cells in response to stimuli known to cause hair cell loss, such as acoustic trauma and aminoglycoside administration. The method employs two-photon excitation of the metabolic intermediate, reduced nicotinamide adenine dinucleotide (NADH), in hair cell mitochondria in an explanted mouse cochlea. Using this method, we show evidence that the aminoglycoside gentamicin selectively affects the level of mitochondrial NADH in outer hair cells, but not inner hair cells, within minutes of administration.
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Affiliation(s)
- LeAnn Tiede
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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Griffiths EJ, Rutter GA. Mitochondrial calcium as a key regulator of mitochondrial ATP production in mammalian cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1324-33. [PMID: 19366607 DOI: 10.1016/j.bbabio.2009.01.019] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 01/23/2009] [Accepted: 01/27/2009] [Indexed: 12/30/2022]
Abstract
Mitochondrial Ca(2+) transport was initially considered important only in buffering of cytosolic Ca(2+) by acting as a "sink" under conditions of Ca(2+) overload. The main regulator of ATP production was considered to be the relative concentrations of high energy phosphates. However, work by Denton and McCormack in the 1970s and 1980s showed that free intramitochondrial Ca(2+) ([Ca(2+)](m)) activated dehydrogenase enzymes in mitochondria, leading to increased NADH and hence ATP production. This leads them to propose a scheme, subsequently termed a "parallel activation model" whereby increases in energy demand, such as hormonal stimulation or increased workload in muscle, produced an increase in cytosolic [Ca(2+)] that was relayed by the mitochondrial Ca(2+) transporters into the matrix to give an increase in [Ca(2+)](m). This then stimulated energy production to meet the increased energy demand. With the development of methods for measuring [Ca(2+)](m) in living cells that proved [Ca(2+)](m) changed over a dynamic physiological range rather than simply soaking up excess cytosolic [Ca(2+)], this model has now gained widespread acceptance. However, work by ourselves and others using targeted probes to measure changes in both [Ca(2+)] and [ATP] in different cell compartments has revealed variations in the interrelationships between these two in different tissues, suggesting that metabolic regulation by Ca(2+) is finely tuned to the demands and function of the individual organ.
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Affiliation(s)
- Elinor J Griffiths
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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Mitochondrial Ca2+ uptake: tortoise or hare? J Mol Cell Cardiol 2008; 46:767-74. [PMID: 19162034 DOI: 10.1016/j.yjmcc.2008.12.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 12/04/2008] [Accepted: 12/04/2008] [Indexed: 11/20/2022]
Abstract
Mitochondria are equipped with an efficient machinery for Ca(2+) uptake and extrusion and are capable of storing large amounts of Ca(2+). Furthermore, key steps of mitochondrial metabolism (ATP production) are Ca(2+)-dependent. In the field of cardiac physiology and pathophysiology, two main questions have dominated the thinking about mitochondrial function in the heart: 1) how does mitochondrial Ca(2+) buffering shape cytosolic Ca(2+) levels and affect excitation-contraction coupling, particularly the Ca(2+) transient, on a beat-to-beat basis, and 2) how does mitochondrial Ca(2+) homeostasis influence cardiac energy metabolism. To answer these questions, a thorough understanding of the kinetics of mitochondrial Ca(2+) transport and buffer capacity is required. Here, we summarize the role of mitochondrial Ca(2+) signaling in the heart, discuss the evidence either supporting or arguing against the idea that Ca(2+) can be taken up rapidly by mitochondria during excitation-contraction coupling and highlight some interesting new areas for further investigation.
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Enhanced Na+/H+ exchange during ischemia and reperfusion impairs mitochondrial bioenergetics and myocardial function. J Cardiovasc Pharmacol 2008; 52:236-44. [PMID: 18806604 DOI: 10.1097/fjc.0b013e3181831337] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Inhibition of Na+/H+ exchange (NHE) during ischemia reduces cardiac injury due to reduced reverse mode Na+/Ca2+ exchange. We hypothesized that activating NHE-1 at buffer pH 8 during ischemia increases mitochondrial oxidation, Ca2+ overload, and reactive O2 species (ROS) levels and worsens functional recovery in isolated hearts and that NHE inhibition reverses these effects. Guinea pig hearts were perfused with buffer at pH 7.4 (control) or pH 8 +/- NHE inhibitor eniporide for 10 minutes before and for 10 minutes after 35- minute ischemia and then for 110 minutes with pH 7.4 buffer alone. Mitochondrial NADH and FAD, [Ca2+], and superoxide were measured by spectrophotofluorometry. NADH and FAD were more oxidized, and cardiac function was worse throughout reperfusion after pH 8 versus pH 7.4, Ca2+ overload was greater at 10-minute reperfusion, and superoxide generation was higher at 30-minute reperfusion. The pH 7.4 and eniporide groups exhibited similar mitochondrial function, and cardiac performance was most improved after pH 7.4+eniporide. Cardiac function on reperfusion after pH 8+eniporide was better than after pH 8. Percent infarction was largest after pH 8 and smallest after pH 7.4+eniporide. Activation of NHE with pH 8 buffer and the subsequent decline in redox state with greater ROS and Ca2+ loading underlie the poor functional recovery after ischemia and reperfusion.
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32
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García-Pérez C, Hajnóczky G, Csordás G. Physical coupling supports the local Ca2+ transfer between sarcoplasmic reticulum subdomains and the mitochondria in heart muscle. J Biol Chem 2008; 283:32771-80. [PMID: 18790739 DOI: 10.1074/jbc.m803385200] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In many cell types, transfer of Ca(2+) released via ryanodine receptors (RyR) to the mitochondrial matrix is locally supported by high [Ca(2+)] microdomains at close contacts between the sarcoplasmic reticulum (SR) and mitochondria. Here we studied whether the close contacts were secured via direct physical coupling in cardiac muscle using isolated rat heart mitochondria (RHMs). "Immuno-organelle chemistry" revealed RyR2 and calsequestrin-positive SR particles associated with mitochondria in both crude and Percoll-purified "heavy" mitochondrial fractions (cRHM and pRHM), to a smaller extent in the latter one. Mitochondria-associated vesicles were also visualized by electron microscopy in the RHMs. Western blot analysis detected greatly reduced presence of SR markers (calsequestrin, SERCA2a, and phospholamban) in pRHM, suggesting that the mitochondria-associated particles represented a small subfraction of the SR. Fluorescence calcium imaging in rhod2-loaded cRHM revealed mitochondrial matrix [Ca(2+)] ([Ca(2+)](m)) responses to caffeine-induced Ca(2+) release that were prevented when thapsigargin was added to predeplete the SR or by mitochondrial Ca(2+) uptake inhibitors. Importantly, caffeine failed to increase [Ca(2+)] in the large volume of the incubation medium, suggesting that local Ca(2+) transfer between the SR particles and mitochondria mediated the [Ca(2+)](m) signal. Despite the substantially reduced SR presence, pRHM still displayed a caffeine-induced [Ca(2+)](m) rise comparable with the one recorded in cRHM. Thus, a relatively small fraction of the total SR is physically coupled and transfers Ca(2+) locally to the mitochondria in cardiac muscle. The transferred Ca(2+) stimulates dehydrogenase activity and affects mitochondrial membrane permeabilization, indicating the broad significance of the physical coupling in mitochondrial function.
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Affiliation(s)
- Cecilia García-Pérez
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Grünwald I, Stahn RM, Kindt CM, Pfeifer L, Hetzer R. Criteria for the multiple use of isolated perfused hearts in electrophysiological and metabolic experiments / Kriterien für die Mehrfachnutzung von isoliert perfundierten Schweineherzen für elektrophysiologische und metabolische Untersuchungen. BIOMED ENG-BIOMED TE 2008; 53:16-24. [DOI: 10.1515/bmt.2008.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Maack C, O'Rourke B. Excitation-contraction coupling and mitochondrial energetics. Basic Res Cardiol 2007; 102:369-92. [PMID: 17657400 PMCID: PMC2785083 DOI: 10.1007/s00395-007-0666-z] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 06/12/2007] [Accepted: 06/13/2007] [Indexed: 12/20/2022]
Abstract
Cardiac excitation-contraction (EC) coupling consumes vast amounts of cellular energy, most of which is produced in mitochondria by oxidative phosphorylation. In order to adapt the constantly varying workload of the heart to energy supply, tight coupling mechanisms are essential to maintain cellular pools of ATP, phosphocreatine and NADH. To our current knowledge, the most important regulators of oxidative phosphorylation are ADP, Pi, and Ca2+. However, the kinetics of mitochondrial Ca2+-uptake during EC coupling are currently a matter of intense debate. Recent experimental findings suggest the existence of a mitochondrial Ca2+ microdomain in cardiac myocytes, justified by the close proximity of mitochondria to the sites of cellular Ca2+ release, i. e., the ryanodine receptors of the sarcoplasmic reticulum. Such a Ca2+ microdomain could explain seemingly controversial results on mitochondrial Ca2+ uptake kinetics in isolated mitochondria versus whole cardiac myocytes. Another important consideration is that rapid mitochondrial Ca2+ uptake facilitated by microdomains may shape cytosolic Ca2+ signals in cardiac myocytes and have an impact on energy supply and demand matching. Defects in EC coupling in chronic heart failure may adversely affect mitochondrial Ca2+ uptake and energetics, initiating a vicious cycle of contractile dysfunction and energy depletion. Future therapeutic approaches in the treatment of heart failure could be aimed at interrupting this vicious cycle.
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Affiliation(s)
- Christoph Maack
- Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes, 66421, Homburg/Saar, Germany.
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35
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Pfeifer L, Gruenwald I, Welker A, Stahn RM, Stein K, Rex A. Fluorimetric characterisation of metabolic activity of ex vivo perfused pig hearts. BIOMED ENG-BIOMED TE 2007; 52:193-9. [PMID: 17408379 DOI: 10.1515/bmt.2007.036] [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] [Indexed: 11/15/2022]
Abstract
Autofluorescence of tissues and organs is an indicator of the physiological state of cells. The aim of the study was to investigate whether fluorimetric determination of the redox state of the ex vivo perfused pig heart can provide fast online detection of progressive changes in heart muscle tissue. Measurements on six organs perfused in a four-chamber working heart model were performed using a spectroscopic method exploiting the specific and different fluorescence lifetimes of intrinsic fluorophores such as NADH and flavins and providing a means of internal signal referencing. It was shown that the redox potential of heart muscle tissue can be assessed by fluorescence measurement. In the steady-state phase of the beating heart, spectroscopic measurements revealed a change in redox state from an initial constant level to a continuous decrease, accompanied by a decrease in heart performance and indications of changes in electrolyte equilibrium (K(+) concentration). At the same time, troponin I levels in the perfusate increased. The results indicate that fluorimetric determination of heart muscle metabolic activity yields reliable information about the functional status of the ex vivo heart and may be advantageous for the optimisation of ex vivo organ models.
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Affiliation(s)
- Lutz Pfeifer
- IOM Innovative Optische Messtechnik GmbH, Berlin, Germany.
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Kim KH, Antkiewicz DS, Yan L, Eliceiri KW, Heideman W, Peterson RE, Lee Y. Lrrc10 is required for early heart development and function in zebrafish. Dev Biol 2007; 308:494-506. [PMID: 17601532 PMCID: PMC2048587 DOI: 10.1016/j.ydbio.2007.06.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 05/15/2007] [Accepted: 06/06/2007] [Indexed: 11/15/2022]
Abstract
Leucine-rich Repeat Containing protein 10 (LRRC10) has recently been identified as a cardiac-specific factor in mice. However, the function of this factor remains to be elucidated. In this study, we investigated the developmental roles of Lrrc10 using zebrafish as an animal model. Knockdown of Lrrc10 in zebrafish embryos (morphants) using morpholinos caused severe cardiac morphogenic defects including a cardiac looping failure accompanied by a large pericardial edema, and embryonic lethality between day 6 and 7 post fertilization. The Lrrc10 morphants exhibited cardiac functional defects as evidenced by a decrease in ejection fraction and cardiac output. Further investigations into the underlying mechanisms of the cardiac defects revealed that the number of cardiomyocyte was reduced in the morphants. Expression of two cardiac genes was deregulated in the morphants including an increase in atrial natriuretic factor, a hallmark for cardiac hypertrophy and failure, and a decrease in cardiac myosin light chain 2, an essential protein for cardiac contractility in zebrafish. Moreover, a reduced fluorescence intensity from NADH in the morphant heart was observed in live zebrafish embryos as compared to control. Taken together, the present study demonstrates that Lrrc10 is necessary for normal cardiac development and cardiac function in zebrafish embryos, which will enhance our understanding of congenital heart defects and heart disease.
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Affiliation(s)
- Ki-Hyun Kim
- Department of Anatomy, School of Medicine and Public Health, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA
| | - Dagmara S. Antkiewicz
- Molecular and Environmental Toxicology Center, School of Pharmacy, University of Wisconsin, Madison, WI 53705, USA
| | - Long Yan
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53706, USA
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin, Madison, WI 53706, USA
| | - Kevin W. Eliceiri
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin, Madison, WI 53706, USA
| | - Warren Heideman
- Molecular and Environmental Toxicology Center, School of Pharmacy, University of Wisconsin, Madison, WI 53705, USA
| | - Richard E. Peterson
- Molecular and Environmental Toxicology Center, School of Pharmacy, University of Wisconsin, Madison, WI 53705, USA
| | - Youngsook Lee
- Department of Anatomy, School of Medicine and Public Health, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA
- Corresponding author. Fax: +1 608 262 7306., E-mail address: (Y. Lee)
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Korzeniewski B. Regulation of oxidative phosphorylation through parallel activation. Biophys Chem 2007; 129:93-110. [PMID: 17566629 DOI: 10.1016/j.bpc.2007.05.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 05/22/2007] [Accepted: 05/23/2007] [Indexed: 11/21/2022]
Abstract
When the mechanical work intensity in muscle increases, the elevated ATP consumption rate must be matched by the rate of ATP production by oxidative phosphorylation in order to avoid a quick exhaustion of ATP. The traditional mechanism of the regulation of oxidative phosphorylation, namely the negative feedback involving [ADP] and [Pi] as regulatory signals, is not sufficient to account for various kinetic properties of the system in intact skeletal muscle and heart in vivo. Theoretical studies conducted using a dynamic computer model of oxidative phosphorylation developed previously strongly suggest the so-called each-step-activation (or parallel activation) mechanism, due to which all oxidative phosphorylation complexes are directly activated by some cytosolic factor/mechanism related to muscle contraction in parallel with the activation of ATP usage and substrate dehydrogenation by calcium ions. The present polemic article reviews and discusses the growing evidence supporting this mechanism and compares it with alternative mechanisms proposed in the literature. It is concluded that only the each-step-activation mechanism is able to explain the rich set of various experimental results used as a reference for estimating the validity and applicability of particular mechanisms.
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Kraków, Poland.
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38
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Zhu X, Zuo L, Cardounel AJ, Zweier JL, He G. Characterization of in vivo tissue redox status, oxygenation, and formation of reactive oxygen species in postischemic myocardium. Antioxid Redox Signal 2007; 9:447-55. [PMID: 17280486 DOI: 10.1089/ars.2006.1389] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The current study aims to characterize the alterations of in vivo tissue redox status, oxygenation, formation of reactive oxygen species (ROS), and their effects on the postischemic heart. Mouse heart was subjected to 30 min LAD occlusion, followed by 60 min reperfusion. In vivo myocardial redox status and oxygenation were measured with electron paramagnetic resonance (EPR). In vivo tissue NAD(P)H and formation of ROS were monitored with fluorometry. Tissue glutathione/glutathione disulfide (GSH/GSSG) levels were detected with high-performance liquid chromatography (HPLC). These experiments demonstrated that tissue reduction rate of nitroxide was increased 100% during ischemia and decreased 33% after reperfusion compared to the nonischemic tissue. There was an overshoot of tissue oxygenation after reperfusion. Tissue NAD(P)H levels were increased during and after ischemia. There was a burst formation of ROS at the beginning of reperfusion. Tissue GSH/GSSG level showed a 48% increase during ischemia and 29% decrease after reperfusion. In conclusion, the hypoxia during ischemia limited mitochondrial respiration and caused a shift of tissue redox status to a more reduced state. ROS generated at the beginning of reperfusion caused a shift of redox status to a more oxidized state, which may contribute to the postischemic myocardial injury.
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Affiliation(s)
- Xuehai Zhu
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
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Nguyen MHT, Dudycha SJ, Jafri MS. Effect of Ca2+ on cardiac mitochondrial energy production is modulated by Na+ and H+ dynamics. Am J Physiol Cell Physiol 2007; 292:C2004-20. [PMID: 17344315 DOI: 10.1152/ajpcell.00271.2006] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The energy production of mitochondria in heart increases during exercise. Several works have suggested that calcium acts at multiple control points to activate net ATP production in what is termed "parallel activation". To study this, a computational model of mitochondrial energy metabolism in the heart has been developed that integrates the Dudycha-Jafri model for the tricarboxylic acid cycle with the Magnus-Keizer model for mitochondrial energy metabolism and calcium dynamics. The model improves upon the previous formulation by including an updated formulation for calcium dynamics, and new descriptions of sodium, hydrogen, phosphate, and ATP balance. To this end, it incorporates new formulations for the calcium uniporter, sodium-calcium exchange, sodium-hydrogen exchange, the F(1)F(0)-ATPase, and potassium-hydrogen exchange. The model simulates a wide range of experimental data, including steady-state and simulated pacing protocols. The model suggests that calcium is a potent activator of net ATP production and that as pacing increases energy production due to calcium goes up almost linearly. Furthermore, it suggests that during an extramitochondrial calcium transient, calcium entry and extrusion cause a transient depolarization that serve to increase NADH production by the tricarboxylic acid cycle and NADH consumption by the respiration driven proton pumps. The model suggests that activation of the F(1)F(0)-ATPase by calcium is essential to increase ATP production. In mitochondria very close to the release sites, the depolarization is more severe causing a temporary loss of ATP production. However, due to the short duration of the depolarization the net ATP production is also increased.
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Affiliation(s)
- My-Hanh T Nguyen
- Dept. of Bioinformatics and Computational Biology, George Mason University, Manassas, VA 20110, USA
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40
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Camara AKS, Aldakkak M, Heisner JS, Rhodes SS, Riess ML, An J, Heinen A, Stowe DF. ROS scavenging before 27 degrees C ischemia protects hearts and reduces mitochondrial ROS, Ca2+ overload, and changes in redox state. Am J Physiol Cell Physiol 2007; 292:C2021-31. [PMID: 17287367 DOI: 10.1152/ajpcell.00231.2006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have shown that cold perfusion of hearts generates reactive oxygen and nitrogen species (ROS/RNS). In this study, we determined 1) whether ROS scavenging only during cold perfusion before global ischemia improves mitochondrial and myocardial function, and 2) which ROS leads to compromised cardiac function during ischemia and reperfusion (I/R) injury. Using fluorescence spectrophotometry, we monitored redox balance (NADH and FAD), O(2)(*-) levels and mitochondrial Ca(2+) (m[Ca(2+)]) at the left ventricular wall in 120 guinea pig isolated hearts divided into control (Con), MnTBAP (a superoxide dismutase 2 mimetic), MnTBAP (M) + catalase (C) + glutathione (G) (MCG), C+G (CG), and N(G)-nitro-L-arginine methyl ester (L-NAME; a nitric oxide synthase inhibitor) groups. After an initial period of warm perfusion, hearts were treated with drugs before and after at 27 degrees C. Drugs were washed out before 2 h at 27 degrees C ischemia and 2 h at 37 degrees C reperfusion. We found that on reperfusion the MnTBAP group had the worst functional recovery and largest infarction with the highest m[Ca(2+)], most oxidized redox state and increased ROS levels. The MCG group had the best recovery, the smallest infarction, the lowest ROS level, the lowest m[Ca(2+)], and the most reduced redox state. CG and L-NAME groups gave results intermediate to those of the MnTBAP and MCG groups. Our results indicate that the scavenging of cold-induced O(2)(*-) species to less toxic downstream products additionally protects during and after cold I/R by preserving mitochondrial function. Because MnTBAP treatment showed the worst functional return along with poor preservation of mitochondrial bioenergetics, accumulation of H(2)O(2) and/or hydroxyl radicals during cold perfusion may be involved in compromised function during subsequent cold I/R injury.
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Affiliation(s)
- Amadou K S Camara
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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41
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Bonnet S, Archer SL, Allalunis-Turner J, Haromy A, Beaulieu C, Thompson R, Lee CT, Lopaschuk GD, Puttagunta L, Bonnet S, Harry G, Hashimoto K, Porter CJ, Andrade MA, Thebaud B, Michelakis ED. A mitochondria-K+ channel axis is suppressed in cancer and its normalization promotes apoptosis and inhibits cancer growth. Cancer Cell 2007; 11:37-51. [PMID: 17222789 DOI: 10.1016/j.ccr.2006.10.020] [Citation(s) in RCA: 1141] [Impact Index Per Article: 67.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Revised: 07/12/2006] [Accepted: 10/18/2006] [Indexed: 02/06/2023]
Abstract
The unique metabolic profile of cancer (aerobic glycolysis) might confer apoptosis resistance and be therapeutically targeted. Compared to normal cells, several human cancers have high mitochondrial membrane potential (DeltaPsim) and low expression of the K+ channel Kv1.5, both contributing to apoptosis resistance. Dichloroacetate (DCA) inhibits mitochondrial pyruvate dehydrogenase kinase (PDK), shifts metabolism from glycolysis to glucose oxidation, decreases DeltaPsim, increases mitochondrial H2O2, and activates Kv channels in all cancer, but not normal, cells; DCA upregulates Kv1.5 by an NFAT1-dependent mechanism. DCA induces apoptosis, decreases proliferation, and inhibits tumor growth, without apparent toxicity. Molecular inhibition of PDK2 by siRNA mimics DCA. The mitochondria-NFAT-Kv axis and PDK are important therapeutic targets in cancer; the orally available DCA is a promising selective anticancer agent.
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Affiliation(s)
- Sébastien Bonnet
- Pulmonary Hypertension Program and Vascular Biology Group, Department of Physiology, University of Alberta, Edmonton, AB T6G 2B7, Canada
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Stoner JD, Clanton TL, Aune SE, Angelos MG. O2 delivery and redox state are determinants of compartment-specific reactive O2 species in myocardial reperfusion. Am J Physiol Heart Circ Physiol 2006; 292:H109-16. [PMID: 17028160 DOI: 10.1152/ajpheart.00925.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Reperfusion of the ischemic myocardium leads to a burst of reactive O(2) species (ROS), which is a primary determinant of postischemic myocardial dysfunction. We tested the hypothesis that early O(2) delivery and the cellular redox state modulate the initial myocardial ROS production at reperfusion. Isolated buffer-perfused rat hearts were loaded with the fluorophores dihydrofluorescein or Amplex red to detect intracellular and extracellular ROS formation using surface fluorometry at the left ventricular wall. Hearts were made globally ischemic for 20 min and then reperfused with either 95% or 20% O(2)-saturated perfusate. The same protocol was repeated in hearts loaded with dihydrofluorescein and perfused with either 20 or 5 mM glucose-buffered solution to determine relative changes in NADH and FAD. Myocardial O(2) delivery during the first 5 min of reperfusion was 84.7 +/- 4.2 ml O(2)/min with 20% O(2)-saturated buffer and 354.4 +/- 22.8 ml O(2)/min with 95% O(2) (n = 8/group, P < 0.001). The fluorescein signal (intracellular ROS) was significantly increased in hearts reperfused with 95% O(2) compared with 20% O(2). However, the resorufin signal (extracellular ROS) was significantly increased with 20% O(2) compared with 95% O(2) during reperfusion. Perfusion of hearts with 20 mM glucose reduced the (.)NADH during ischemia (P < 0.001) and the (.)ROS at reperfusion (P < 0.001) compared with 5.5 mM-perfused glucose hearts. In conclusion, initial O(2) delivery to the ischemic myocardium modulates a compartment-specific ROS response at reperfusion such that high O(2) delivery promotes intracellular ROS and low O(2) delivery promotes extracellular ROS. The redox state that develops during ischemia appears to be an important precursor for reperfusion ROS production.
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Affiliation(s)
- Jason D Stoner
- Dept. of Emergency Medicine, The Ohio State Univ., 146 Means Hall, 1654 Upham Dr., Columbus, OH 43210, USA
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43
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Bell CJ, Bright NA, Rutter GA, Griffiths EJ. ATP regulation in adult rat cardiomyocytes: time-resolved decoding of rapid mitochondrial calcium spiking imaged with targeted photoproteins. J Biol Chem 2006; 281:28058-67. [PMID: 16882672 DOI: 10.1074/jbc.m604540200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanisms that enable the heart to rapidly increase ATP supply in line with increased demand have not been fully elucidated. Here we used an adenoviral system to express the photoproteins luciferase and aequorin, targeted to the mitochondria or cytosol of adult cardiomyocytes, to investigate the interrelationship between ATP and Ca(2+) in these compartments. In neither compartment were changes in free [ATP] observed upon increased workload (addition of isoproterenol) in myocytes that were already beating. However, when myocytes were stimulated to beat rapidly from rest, in the presence of isoproterenol, a significant but transient drop in mitochondrial [ATP] ([ATP](m)) occurred (on average to 10% of the initial signal). Corresponding changes in cytosolic [ATP] ([ATP](c)) were much smaller (<5%), indicating that [ATP](c) was effectively buffered in this compartment. Although mitochondrial [Ca(2+)] ([Ca(2+)](m)) is an important regulator of respiratory chain activity and ATP production in other cells, the kinetics of mitochondrial Ca(2+) transport are controversial. Parallel experiments in cells expressing mitochondrial aequorin showed that the drop in [ATP](m) occurred over the same time scale as average [Ca(2+)](m) was increasing. Conversely, in the absence or presence of isoproterenol, clear beat-to-beat peaks in [Ca(2+)](m) were observed at 0.9 or 1.3 mum, respectively, concentrations similar to those observed in the cytosol. These results suggest that mitochondrial Ca(2+) transients occur during the contractile cycle and are translated into a time-averaged increase in mitochondrial ATP production that keeps pace with increased cytosolic demand.
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Affiliation(s)
- Christopher J Bell
- Bristol Heart Institute, University of Bristol, Bristol BS8 1TD, United Kingdom
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44
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Korzeniewski B. Oxygen consumption and metabolite concentrations during transitions between different work intensities in heart. Am J Physiol Heart Circ Physiol 2006; 291:H1466-74. [PMID: 16679405 DOI: 10.1152/ajpheart.00004.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Steady-state metabolite (ADP, ATP, P(i), PCr, and NADH) concentrations usually differ little between different workloads with significantly different oxygen consumption rates in the heart. However, during transitions between steady states, metabolite concentrations may in some cases change transiently, exhibiting a significant overshoot or undershoot, whereas in other cases they approach near-exponentially new steady-state values. Oxygen consumption rate usually reaches the new steady-state value very quickly (within a few seconds). The present in silico studies, performed using a previously developed computer model of oxidative phosphorylation in the heart, demonstrate that such a behavior of the oxidative phosphorylation system can be reproduced only under the assumption that ATP usage, substrate dehydrogenation, and (particular steps of) oxidative phosphorylation are directly activated to a similar extend by some cytosolic factor/mechanism during transition from low work to high work (the so-called parallel-activation mechanism). Computer simulations show that some differences observed between different experimental systems can be explained by a slightly different balance of the activation of particular components of the system and/or by a delay in time of the activation/inactivation of substrate dehydrogenation and oxidative phosphorylation during low-to-high and high-to-low work transitions. Thus the presented theoretical approach offers a general idea that is able to unify, at least semiquantitatively, different experimental data available in the literature.
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Kraków, Poland.
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45
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Jo H, Noma A, Matsuoka S. Calcium-mediated coupling between mitochondrial substrate dehydrogenation and cardiac workload in single guinea-pig ventricular myocytes. J Mol Cell Cardiol 2006; 40:394-404. [PMID: 16480740 DOI: 10.1016/j.yjmcc.2005.12.012] [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] [Received: 08/30/2005] [Revised: 11/23/2005] [Accepted: 12/19/2005] [Indexed: 11/29/2022]
Abstract
We measured mitochondrial NADH autofluorescence or Ca(2+) using Rhod-2, simultaneously with cell shortening in isolated guinea-pig ventricular myocytes. When both frequency and amplitude of twitch shortening (work intensity) were increased by raising stimulus frequency in incremental steps from 0.1 to 3.3 Hz, the steady level of NADH signal increased in a frequency-dependent manner. Mitochondrial Ca(2+) also increased with increasing work intensity. Applying Ru360, an inhibitor of mitochondrial Ca(2+) uniporter, largely attenuated the response of both NADH fluorescence and mitochondrial Ca(2+). The increase in mitochondrial Ca(2+) was slow with t(1/2)=~12 s and no obvious cyclic changes were observed in the NADH signal. When a step change from 0.1 to 3.3 Hz stimulation was applied, the NADH signal first decreased to 83% and then increased to 155% of the control level. Upon returning to 0.1 Hz, the NADH signal showed an overshoot before declining to the control level. The biphasic onset time course was well explained by the delayed Ca(2+) activation of the substrate dehydrogenation superimposed on the feedback control of the ATP synthesis, while the offset time course with a delayed deactivation of dehydrogenation. A computer simulation using an oxidative phosphorylation linked to the cardiac excitation contraction model well reconstructed the response of NADH. This model simulation predicts that the activation of substrate dehydrogenation provides ~23% of driving force of the ATP synthesis to meet the increased workload induced by the jump of stimulus from 0.1 to 3.3 Hz, and remaining ~77% is supplied by the feedback control.
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Affiliation(s)
- Hikari Jo
- Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine, Yoshida-konoe, Sakyo-ku, Kyoto 606-8501, Japan
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46
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An J, Camara AKS, Riess ML, Rhodes SS, Varadarajan SG, Stowe DF. Improved mitochondrial bioenergetics by anesthetic preconditioning during and after 2 hours of 27 degrees C ischemia in isolated hearts. J Cardiovasc Pharmacol 2006; 46:280-7. [PMID: 16116332 DOI: 10.1097/01.fjc.0000175238.18702.40] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We examined if sevoflurane given before cold ischemia of intact hearts (anesthetic preconditioning, APC) affords additional protection by further improving mitochondrial energy balance and if this is abolished by a mitochondrial KATP blocker. NADH and FAD fluorescence was measured within the left ventricular wall of 5 groups of isolated guinea pig hearts: (1) hypothermia alone; (2) hypothermia+ischemia; (3) APC (4.1% sevoflurane)+cold ischemia; (4) 5-HD+cold ischemia, and (5) APC+5-HD+cold ischemia. Hearts were exposed to sevoflurane for 15 minutes followed by 15 minutes of washout at 37 degrees C before cooling, 2 hours of 27 degrees C ischemia, and 2 hours of 37 degrees C reperfusion. The KATP channel inhibitor 5-HD was perfused before and after sevoflurane. Ischemia caused a rapid increase in NADH and a decrease in FAD that waned over 2 hours. Warm reperfusion led to a decrease in NADH and an increase in FAD. APC attenuated the changes in NADH and FAD and further improved postischemic function and reduced infarct size. 5-HD blocked the cardioprotective effects of APC but not APC-induced alterations of NADH and FAD. Thus, APC improves redox balance and has additive cardioprotective effects with mild hypothermic ischemia. 5-HD blocks APC-induced cardioprotective effects but not improvements in mitochondrial bioenergetics. This suggests that mediation of protection by KATP channel opening during cold ischemia and reperfusion is downstream from the APC-induced improvement in redox state or that these changes in redox state are not attenuated by KATP channel antagonism.
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Affiliation(s)
- Jianzhong An
- Anesthesiology Research Laboratory, Department of Anesthesiology, Medical College of Wisconsin, and Veterans Affairs Medical Center, Milwaukee, Wisconsin 53226, USA
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47
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Rhodes SS, Ropella KM, Camara AKS, Chen Q, Riess ML, Pagel PS, Stowe DF. Ischemia-reperfusion injury changes the dynamics of Ca2+-contraction coupling due to inotropic drugs in isolated hearts. J Appl Physiol (1985) 2005; 100:940-50. [PMID: 16282437 DOI: 10.1152/japplphysiol.00285.2005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Positive inotropic drugs may attenuate or exacerbate the deleterious effects of ischemia and reperfusion (IR) injury on excitation-contraction coupling in hearts. We 1) quantified the phase-space relationship between simultaneously measured myoplasmic Ca2+ concentration ([Ca2+]) and isovolumetric left ventricular pressure (LVP) using indexes of loop area, orientation, and position; and 2) quantified cooperativity by linearly modeling the phase-space relationship between [Ca2+] and rate of LVP development in intact hearts during administration of positive inotropic drugs before and after global IR injury. Unpaced, isolated guinea pig hearts were perfused at a constant pressure with Krebs-Ringer solution (37 degrees C, 1.25 mM CaCl2). [Ca2+] was measured ratiometrically by indo 1 fluorescence by using a fiber-optic probe placed at the left ventricular free wall. LVP was measured by using a saline-filled latex balloon and transducer. Drugs were infused for 2 min, 30 min before, and for 2 min, 30 min after 30-min global ischemia. IR injury worsened Ca2+-contraction coupling, as seen from decreased orientation and repositioning of the loop rightward and downward and reduced cooperativity of contraction and relaxation with or without drugs. Dobutamine (4 microM) worsened, whereas dopamine (8 microM) improved Ca2+-contraction coupling before and after IR injury. Dobutamine and dopamine improved cooperativity of contraction and relaxation after IR injury, whereas only dopamine increased cooperativity of relaxation before IR injury. Digoxin (1 microM) improved Ca2+-contraction coupling and cooperativity of contraction after but not before ischemia. Levosimendan (1 microM) did not alter Ca2+-contraction coupling or cooperativity, despite producing concomitant increases in contractility, relaxation, and Ca2+ flux before and after ischemia. Dynamic indexes based on LVP-[Ca2+] diagrams (area, shape, position) can be used to identify and measure alterations in Ca2+-contraction coupling during administration of positive inotropic drugs in isolated hearts before and after IR injury.
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Affiliation(s)
- Samhita S Rhodes
- Department of Anesthesiology, M4280, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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48
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Cabrera ME, Zhou L, Stanley WC, Saidel GM. Regulation of cardiac energetics: role of redox state and cellular compartmentation during ischemia. Ann N Y Acad Sci 2005; 1047:259-70. [PMID: 16093502 DOI: 10.1196/annals.1341.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The heart is capable of altering its metabolic rate during exercise or ischemia. Under most state transitions, the heart maintains the concentration of adenosine triphosphate (ATP) at relatively constant values, in spite of large fluctuations in metabolic rate or in the delivery of fuels and oxygen. However, the mechanisms responsible for the regulation of cardiac energetics under conditions of increased demand or reduced supply are still under debate. To improve quantitative understanding of the regulation of glycolysis and oxidative phosphorylation under physiological and pathological conditions, it is essential to assess the dynamics of cytosolic and mitochondrial nicotinamide adenine dinucleotide (NAD(+)) and its reduced form (NADH) during stress (e.g., ischemia, exercise). However, at present there are no reliable methods to measure the dynamics of redox state in vivo in these subcellular compartments. In the present study, computer simulations with a mathematical model of myocardial energy metabolism are used to investigate the role of cytosolic and mitochondrial redox states in regulating cardiac energetics during reduced myocardial blood flow.
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Affiliation(s)
- Marco E Cabrera
- Department of Pediatrics, Case Western Reserve University, 11100 Euclid Avenue, RBC-389, Cleveland, OH 44106-6011, USA.
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Matsuoka S, Jo H, Sarai N, Noma A. An in silico study of energy metabolism in cardiac excitation-contraction coupling. ACTA ACUST UNITED AC 2005; 54:517-22. [PMID: 15760483 DOI: 10.2170/jjphysiol.54.517] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The heart produces and uses ATP at a high rate. Each step involved in ATP metabolism has been extensively studied. However, functional coupling between ATP production and membrane excitation-contraction coupling, which is the main ATP consumption process, is not yet fully understood because of complicated interactions and the lack of quantitative data obtained in vivo. Computer simulation is a powerful tool for integrating experimental data and for solving their complicated interactions. To investigate the mechanisms underlying cardiac excitation-contraction-energy metabolism coupling, we have developed a computer model of cardiac excitation-contraction coupling (Kyoto model) that includes the major processes of ATP production, such as oxidative phosphorylation that was originally developed for skeletal muscle by Korzeniewski and Zoladz [Biophys Chem 92: 17-34, 2001], creatine kinase, and adenylate kinase. In this review, we briefly summarize cardiac energy metabolism and discuss the regulation of mitochondrial ATP synthesis, using the Kyoto model.
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Affiliation(s)
- Satoshi Matsuoka
- Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
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50
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Riess ML, Kevin LG, McCormick J, Jiang MT, Rhodes SS, Stowe DF. Anesthetic preconditioning: the role of free radicals in sevoflurane-induced attenuation of mitochondrial electron transport in Guinea pig isolated hearts. Anesth Analg 2005; 100:46-53. [PMID: 15616050 DOI: 10.1213/01.ane.0000139346.76784.72] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cardioprotection by anesthetic preconditioning (APC) can be abolished by nitric oxide (NO*) synthase inhibitors or by reactive oxygen species (ROS) scavengers. We previously reported attenuated mitochondrial electron transport (ET) and increased ROS generation during preconditioning sevoflurane exposure as part of the triggering mechanism of APC. We hypothesized that NO* and other ROS mediate anesthetic-induced ET attenuation. Cardiac function and reduced nicotinamide adenine dinucleotide (NADH) fluorescence, an index of mitochondrial ET, were measured online in 68 Langendorff-prepared guinea pig hearts. Hearts underwent 30 min of global ischemia and 120 min of reperfusion. Before ischemia, hearts were temporarily perfused with superoxide dismutase, catalase, and glutathione to scavenge ROS or N(G)-nitro-L-arginine-methyl-ester (L-NAME) to inhibit NO* synthase in the presence or absence of 1.3 mM sevoflurane (APC). APC temporarily increased NADH before ischemia, i.e., it attenuated mitochondrial ET. Both this NADH increase and the cardioprotection by APC on reperfusion were prevented by superoxide dismutase, catalase, and glutathione and by N(G)-nitro-L-arginine-methyl-ester. Thus, ROS and NO*, or reaction products including peroxynitrite, mediate sevoflurane-induced ET attenuation. This may lead to a positive feedback mechanism with augmented ROS generation to trigger APC secondary to altered mitochondrial function.
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Affiliation(s)
- Matthias L Riess
- *Anesthesiology Research Laboratories, Departments of Anesthesiology and §Physiology and ∥Cardiovascular Research Center, ‡Medical College of Wisconsin, Milwaukee, Wisconsin; †Westfälische-Wilhelms-Universität, Münster, Germany; and ¶Veterans Affairs Medical Center Research Service and #Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin
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