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Sakellariou GK, Jackson MJ, Vasilaki A. Redefining the major contributors to superoxide production in contracting skeletal muscle. The role of NAD(P)H oxidases. Free Radic Res 2013; 48:12-29. [PMID: 23915064 DOI: 10.3109/10715762.2013.830718] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The production of reactive oxygen and nitrogen species (RONS) by skeletal muscle is important as it (i) underlies oxidative damage in many degenerative muscle pathologies and (ii) plays multiple regulatory roles by fulfilling important cellular functions. Superoxide and nitric oxide (NO) are the primary radical species produced by skeletal muscle and studies in the early 1980s demonstrated that their generation is augmented during contractile activity. Over the past 30 years considerable research has been undertaken to identify the major sites that contribute to the increased rate of RONS generation in response to contractions. It is widely accepted that NO is regulated by the nitric oxide synthases, however the sites that modulate changes in superoxide during exercise remain unclear. Despite the initial indications that the mitochondrial electron transport chain was the predominant source of superoxide during activity, with the development of analytical methods a number of alternative potential sites have been identified including the NAD(P)H oxidases, xanthine oxidase, cyclooxygenases, and lipoxygenases linked to the activity of the phospholipase A2 enzymes. In the present review we outline the subcellular sites that modulate intracellular changes in superoxide in skeletal muscle and based on the available experimental evidence in the literature we conclude that the NAD(P)H oxidases are likely to be the major superoxide generating sources in contracting skeletal muscle.
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Affiliation(s)
- G K Sakellariou
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing, Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool , Liverpool , UK
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Bajić A, Spasić M, Andjus PR, Savić D, Parabucki A, Nikolić-Kokić A, Spasojević I. Fluctuating vs. continuous exposure to H₂O₂: the effects on mitochondrial membrane potential, intracellular calcium, and NF-κB in astroglia. PLoS One 2013; 8:e76383. [PMID: 24124554 PMCID: PMC3790680 DOI: 10.1371/journal.pone.0076383] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 08/27/2013] [Indexed: 01/08/2023] Open
Abstract
The effects of H2O2 are widely studied in cell cultures and other in vitro systems. However, such investigations are performed with the assumption that H2O2 concentration is constant, which may not properly reflect in vivo settings, particularly in redox-turbulent microenvironments such as mitochondria. Here we introduced and tested a novel concept of fluctuating oxidative stress. We treated C6 astroglial cells and primary astrocytes with H2O2, using three regimes of exposure - continuous, as well as fluctuating at low or high rate, and evaluated mitochondrial membrane potential and other parameters of mitochondrial activity - respiration, reducing capacity, and superoxide production, as well as intracellular ATP, intracellular calcium, and NF-κB activation. When compared to continuous exposure, fluctuating H2O2 induced a pronounced hyperpolarization in mitochondria, whereas the activity of electron transport chain appears not to be significantly affected. H2O2 provoked a decrease of ATP level and an increase of intracellular calcium concentration, independently of the regime of treatment. However, fluctuating H2O2 induced a specific pattern of large-amplitude fluctuations of calcium concentration. An impact on NF-κB activation was observed for high rate fluctuations, whereas continuous and low rate fluctuating oxidative stress did not provoke significant effects. Presented results outline the (patho)physiological relevance of redox fluctuations.
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Affiliation(s)
- Aleksandar Bajić
- Center for Laser Microscopy, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Mihajlo Spasić
- Department of Physiology, Institute for Biological Research ‘Siniša Stanković’, University of Belgrade, Belgrade, Serbia
| | - Pavle R. Andjus
- Center for Laser Microscopy, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Danijela Savić
- Department of Neurobiology, Institute for Biological Research ‘Siniša Stanković’, University of Belgrade, Belgrade, Serbia
| | - Ana Parabucki
- Department of Neurobiology, Institute for Biological Research ‘Siniša Stanković’, University of Belgrade, Belgrade, Serbia
| | - Aleksandra Nikolić-Kokić
- Department of Physiology, Institute for Biological Research ‘Siniša Stanković’, University of Belgrade, Belgrade, Serbia
| | - Ivan Spasojević
- Life Sciences Department, Institute for Multidisciplinary Research, University of Belgrade, Belgrade, Serbia
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Optical microwell array for large scale studies of single mitochondria metabolic responses. Anal Bioanal Chem 2013; 406:931-41. [PMID: 23892878 DOI: 10.1007/s00216-013-7211-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/27/2013] [Accepted: 07/02/2013] [Indexed: 12/21/2022]
Abstract
Microsystems based on microwell arrays have been widely used for studies on single living cells. In this work, we focused on the subcellular level in order to monitor biological responses directly on individual organelles. Consequently, we developed microwell arrays for the entrapment and fluorescence microscopy of single isolated organelles, mitochondria herein. Highly dense arrays of 3-μm mean diameter wells were obtained by wet chemical etching of optical fiber bundles. Favorable conditions for the stable entrapment of individual mitochondria within a majority of microwells were found. Owing to NADH auto-fluorescence, the metabolic status of each mitochondrion was analyzed at resting state (Stage 1), then following the addition of a respiratory substrate (Stage 2), ethanol herein, and of a respiratory inhibitor (Stage 3), antimycin A. Mean levels of mitochondrial NADH were increased by 29% and 35% under Stages 2 and 3, respectively. We showed that mitochondrial ability to generate higher levels of NADH (i.e., its metabolic performance) is not correlated either to the initial energetic state or to the respective size of each mitochondrion. This study demonstrates that microwell arrays allow metabolic studies on populations of isolated mitochondria with a single organelle resolution.
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Wang X, Fang H, Huang Z, Shang W, Hou T, Cheng A, Cheng H. Imaging ROS signaling in cells and animals. J Mol Med (Berl) 2013; 91:917-27. [PMID: 23873151 PMCID: PMC3730091 DOI: 10.1007/s00109-013-1067-4] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 06/08/2013] [Accepted: 06/17/2013] [Indexed: 11/16/2022]
Abstract
Reactive oxygen species (ROS) act as essential cellular messengers, redox regulators, and, when in excess, oxidative stressors that are widely implicated in pathologies of cancer and cardiovascular and neurodegenerative diseases. Understanding such complexity of the ROS signaling is critically hinged on the ability to visualize and quantify local, compartmental, and global ROS dynamics at high selectivity, sensitivity, and spatiotemporal resolution. The past decade has witnessed significant progress in ROS imaging at levels of intact cells, whole organs or tissues, and even live organisms. In particular, major advances include the development of novel synthetic or genetically encoded fluorescent protein-based ROS indicators, the use of protein indicator-expressing animal models, and the advent of in vivo imaging technology. Innovative ROS imaging has led to important discoveries in ROS signaling—for example, mitochondrial superoxide flashes as elemental ROS signaling events and hydrogen peroxide transients for wound healing. This review aims at providing an update of the current status in ROS imaging, while identifying areas of insufficient knowledge and highlighting emerging research directions.
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Affiliation(s)
- Xianhua Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing 100871, China
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55
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Eisner V, Csordás G, Hajnóczky G. Interactions between sarco-endoplasmic reticulum and mitochondria in cardiac and skeletal muscle - pivotal roles in Ca²⁺ and reactive oxygen species signaling. J Cell Sci 2013; 126:2965-78. [PMID: 23843617 DOI: 10.1242/jcs.093609] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are strategically and dynamically positioned in the cell to spatially coordinate ATP production with energy needs and to allow the local exchange of material with other organelles. Interactions of mitochondria with the sarco-endoplasmic reticulum (SR/ER) have been receiving much attention owing to emerging evidence on the role these sites have in cell signaling, dynamics and biosynthetic pathways. One of the most important physiological and pathophysiological paradigms for SR/ER-mitochondria interactions is in cardiac and skeletal muscle. The contractile activity of these tissues has to be matched by mitochondrial ATP generation that is achieved, at least in part, by propagation of Ca(2+) signals from SR to mitochondria. However, the muscle has a highly ordered structure, providing only limited opportunity for mitochondrial dynamics and interorganellar interactions. This Commentary focuses on the latest advances in the structure, function and disease relevance of the communication between SR/ER and mitochondria in muscle. In particular, we discuss the recent demonstration of SR/ER-mitochondria tethers that are formed by multiple proteins, and local Ca(2+) transfer between SR/ER and mitochondria.
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Affiliation(s)
- Verónica Eisner
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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56
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Superoxide constitutes a major signal of mitochondrial superoxide flash. Life Sci 2013; 93:178-86. [PMID: 23800644 DOI: 10.1016/j.lfs.2013.06.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 06/08/2013] [Accepted: 06/12/2013] [Indexed: 11/21/2022]
Abstract
AIMS Mitochondrial flashes detected with an N- and C-terminal circularly-permuted yellow fluorescent protein (cpYFP) have been thought to represent transient and quantal bursts of superoxide production under physiological, stressful and pathophysiological conditions. However, the superoxide nature of the cpYFP-flash has been challenged, considering the pH-sensitivity of cpYFP and the distinctive regulation of the flash versus the basal production of mitochondrial reactive oxygen species (ROS). Thus, the aim of the study is to further determine the origin of mitochondrial flashes. MAIN METHODS We investigated the origin of the flashes using the widely-used pH-insensitive ROS indicators, mitoSOX, an indicator for superoxide, and 2, 7-dichlorodihydrofluorescein diacetate (DCF), an indicator for H2O2 and other oxidants. KEY FINDINGS Robust, quantal, and stochastic mitochondrial flashes were detected with either mitoSOX or DCF in several cell-types and in mitochondria isolated from the heart. Both mitoSOX-flashes and DCF-flashes showed similar incidence and kinetics to those of cpYFP-flashes, and were equally sensitive to mitochondria-targeted antioxidants. Furthermore, they were markedly decreased by inhibitors or an uncoupler of the mitochondrial electron transport chain, as is the case with cpYFP-flashes. The involvement of the mitochondrial permeability transition pore in DCF-flashes was evidenced by the coincidental loss of mitochondrial membrane potential and matrix-enriched rhod-2, as well as by their sensitivity to cyclosporine A. SIGNIFICANCE These data indicate that all the three types of mitochondrial flashes stem from the common physiological process of bursting superoxide and ensuing H2O2 production in the matrix of single mitochondrion.
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Cao Y, Zhang X, Shang W, Xu J, Wang X, Hu X, Ao Y, Cheng H. Proinflammatory Cytokines Stimulate Mitochondrial Superoxide Flashes in Articular Chondrocytes In Vitro and In Situ. PLoS One 2013; 8:e66444. [PMID: 23840469 PMCID: PMC3686682 DOI: 10.1371/journal.pone.0066444] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 05/05/2013] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE Mitochondria play important roles in many types of cells. However, little is known about mitochondrial function in chondrocytes. This study was undertaken to explore possible role of mitochondrial oxidative stress in inflammatory response in articular chondrocytes. METHODS Chondrocytes and cartilage explants were isolated from wild type or transgenic mice expressing the mitochondrial superoxide biosensor - circularly permuted yellow fluorescent protein (cpYFP). Cultured chondrocytes or cartilage explants were incubated in media containing interleukin-1β (10 ng/ml) or tumor necrosis factor-α (10 ng/ml) to stimulate an inflammatory response. Mitochondrial imaging was carried out by confocal and two-photon microscopy. Mitochondrial oxidative status was evaluated by "superoxide flash" activity recorded with time lapse scanning. RESULTS Cultured chondrocytes contain abundant mitochondria that show active motility and dynamic morphological changes. In intact cartilage, mitochondrial abundance as well as chondrocyte density declines with distance from the surface. Importantly, sudden, bursting superoxide-producing events or "superoxide flashes" occur at single-mitochondrion level, accompanied by transient mitochondrial swelling and membrane depolarization. The superoxide flash incidence in quiescent chondrocytes was ∼4.5 and ∼0.5 events/1000 µm(2)*100 s in vitro and in situ, respectively. Interleukin-1β or tumor necrosis factor-α stimulated mitochondrial superoxide flash activity by 2-fold in vitro and 5-fold in situ, without altering individual flash properties except for reduction in spatial size due to mitochondrial fragmentation. CONCLUSIONS The superoxide flash response to proinflammatory cytokine stimulation in vitro and in situ suggests that chondrocyte mitochondria are a significant source of cellular oxidants and are an important previously under-appreciated mediator in inflammatory cartilage diseases.
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Affiliation(s)
- Yongxing Cao
- Institute of Sports Medicine, Peking University Third Hospital, Beijing, China
| | - Xin Zhang
- Institute of Sports Medicine, Peking University Third Hospital, Beijing, China
| | - Wei Shang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Jiejia Xu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Xianhua Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking University, Beijing, China
| | - Xiaoqing Hu
- Institute of Sports Medicine, Peking University Third Hospital, Beijing, China
| | - Yingfang Ao
- Institute of Sports Medicine, Peking University Third Hospital, Beijing, China
- * E-mail:
| | - Heping Cheng
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking University, Beijing, China
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58
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OPA1 promotes pH flashes that spread between contiguous mitochondria without matrix protein exchange. EMBO J 2013; 32:1927-40. [PMID: 23714779 PMCID: PMC3981180 DOI: 10.1038/emboj.2013.124] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 04/19/2013] [Indexed: 01/13/2023] Open
Abstract
The chemical nature and functional significance of mitochondrial flashes associated with fluctuations in mitochondrial membrane potential is unclear. Using a ratiometric pH probe insensitive to superoxide, we show that flashes reflect matrix alkalinization transients of ∼0.4 pH units that persist in cells permeabilized in ion-free solutions and can be evoked by imposed mitochondrial depolarization. Ablation of the pro-fusion protein Optic atrophy 1 specifically abrogated pH flashes and reduced the propagation of matrix photoactivated GFP (paGFP). Ablation or invalidation of the pro-fission Dynamin-related protein 1 greatly enhanced flash propagation between contiguous mitochondria but marginally increased paGFP matrix diffusion, indicating that flashes propagate without matrix content exchange. The pH flashes were associated with synchronous depolarization and hyperpolarization events that promoted the membrane potential equilibration of juxtaposed mitochondria. We propose that flashes are energy conservation events triggered by the opening of a fusion pore between two contiguous mitochondria of different membrane potentials, propagating without matrix fusion to equilibrate the energetic state of connected mitochondria. Mitochondrial fusion events and transient changes in matrix pH linked to membrane depolarization are found to underlie mitochondrial flashes, whose propagation may help equilibrate energy states between connected mitochondria.
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59
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Suraniti E, Vajrala VS, Goudeau B, Bottari SP, Rigoulet M, Devin A, Sojic N, Arbault S. Monitoring metabolic responses of single mitochondria within poly(dimethylsiloxane) wells: study of their endogenous reduced nicotinamide adenine dinucleotide evolution. Anal Chem 2013; 85:5146-52. [PMID: 23600852 DOI: 10.1021/ac400494e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
It is now demonstrated that mitochondria individually function differently because of specific energetic needs in cell compartments but also because of the genetic heterogeneity within the mitochondrial pool-network of a cell. Consequently, understanding mitochondrial functioning at the single organelle level is of high interest for biomedical research, therefore being a target for analyticians. In this context, we developed easy-to-build platforms of milli- to microwells for fluorescence microscopy of single isolated mitochondria. Poly(dimethylsiloxane) (PDMS) was determined to be an excellent material for mitochondrial deposition and observation of their NADH content. Because of NADH autofluorescence, the metabolic status of each mitochondrion was analyzed following addition of a respiratory substrate (stage 2), ethanol herein, and a respiratory inhibitor (stage 3), Antimycin A. Mean levels of mitochondrial NADH were increased by 32% and 62% under stages 2 and 3, respectively. Statistical studies of NADH value distributions evidenced different types of responses, at least three, to ethanol and Antimycin A within the mitochondrial population. In addition, we showed that mitochondrial ability to generate high levels of NADH, that is its metabolic performance, is not correlated either to the initial energetic state or to the respective size of each mitochondrion.
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60
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Wei-LaPierre L, Gong G, Gerstner BJ, Ducreux S, Yule DI, Pouvreau S, Wang X, Sheu SS, Cheng H, Dirksen RT, Wang W. Respective contribution of mitochondrial superoxide and pH to mitochondria-targeted circularly permuted yellow fluorescent protein (mt-cpYFP) flash activity. J Biol Chem 2013; 288:10567-77. [PMID: 23457298 DOI: 10.1074/jbc.m113.455709] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Superoxide flashes are transient bursts of superoxide production within the mitochondrial matrix that are detected using the superoxide-sensitive biosensor, mitochondria-targeted circularly permuted YFP (mt-cpYFP). However, due to the pH sensitivity of mt-cpYFP, flashes were suggested to reflect transient events of mitochondrial alkalinization. Here, we simultaneously monitored flashes with mt-cpYFP and mitochondrial pH with carboxy-SNARF-1. In intact cardiac myocytes and purified skeletal muscle mitochondria, robust mt-cpYFP flashes were accompanied by only a modest increase in SNARF-1 ratio (corresponding to a pH increase of <0.1), indicating that matrix alkalinization is minimal during an mt-cpYFP flash. Individual flashes were also accompanied by stepwise increases of MitoSOX signal and decreases of NADH autofluorescence, supporting the superoxide origin of mt-cpYFP flashes. Transient matrix alkalinization induced by NH4Cl only minimally influenced flash frequency and failed to alter flash amplitude. However, matrix acidification modulated superoxide flash frequency in a bimodal manner. Low concentrations of nigericin (< 100 nM) that resulted in a mild dissipation of the mitochondrial pH gradient increased flash frequency, whereas a maximal concentration of nigericin (5 μm) collapsed the pH gradient and abolished flash activity. These results indicate that mt-cpYFP flash events reflect a burst in electron transport chain-dependent superoxide production that is coincident with a modest increase in matrix pH. Furthermore, flash activity depends strongly on a combination of mitochondrial oxidation and pH gradient.
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Affiliation(s)
- Lan Wei-LaPierre
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA
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61
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Santo-Domingo J, Demaurex N. Perspectives on: SGP symposium on mitochondrial physiology and medicine: the renaissance of mitochondrial pH. ACTA ACUST UNITED AC 2013; 139:415-23. [PMID: 22641636 PMCID: PMC3362525 DOI: 10.1085/jgp.201110767] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Jaime Santo-Domingo
- Department of Cell Physiology and Metabolism, University of Geneva, CH-1211 Geneva, Switzerland
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62
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Hou T, Zhang X, Xu J, Jian C, Huang Z, Ye T, Hu K, Zheng M, Gao F, Wang X, Cheng H. Synergistic triggering of superoxide flashes by mitochondrial Ca2+ uniport and basal reactive oxygen species elevation. J Biol Chem 2013; 288:4602-12. [PMID: 23283965 DOI: 10.1074/jbc.m112.398297] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mitochondrial superoxide flashes reflect a quantal, bursting mode of reactive oxygen species (ROS) production that arises from stochastic, transient opening of the mitochondrial permeability transition pore (mPTP) in many types of cells and in living animals. However, the regulatory mechanisms and the exact nature of the flash-coupled mPTP remain poorly understood. Here we demonstrate a profound synergistic effect between mitochondrial Ca(2+) uniport and elevated basal ROS production in triggering superoxide flashes in intact cells. Hyperosmotic stress potently augmented the flash activity while simultaneously elevating mitochondrial Ca(2+) and ROS. Blocking mitochondrial Ca(2+) transport by knockdown of MICU1 or MCU, newly identified components of the mitochondrial Ca(2+) uniporter, or scavenging mitochondrial basal ROS markedly diminished the flash response. More importantly, whereas elevating Ca(2+) or ROS production alone was inefficacious in triggering the flashes, concurrent physiological Ca(2+) and ROS elevation served as the most powerful flash activator, increasing the flash incidence by an order of magnitude. Functionally, superoxide flashes in response to hyperosmotic stress participated in the activation of JNK and p38. Thus, physiological levels of mitochondrial Ca(2+) and ROS synergistically regulate stochastic mPTP opening and quantal ROS production in intact cells, marking the flash as a coincidence detector of mitochondrial Ca(2+) and ROS signals.
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Affiliation(s)
- Tingting Hou
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
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Affiliation(s)
- Emilie Quatresous
- Centre National de la Recherche Scientifique (CNRS) UMR 5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, 69622 Villeurbanne, France
| | - Claude Legrand
- Centre National de la Recherche Scientifique (CNRS) UMR 5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, 69622 Villeurbanne, France
| | - Sandrine Pouvreau
- CNRS UMR 5297, Interdisciplinary Institute for Neuroscience, University of Bordeaux, F-33000 Bordeaux, France
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Glutathionylation of UCP2 sensitizes drug resistant leukemia cells to chemotherapeutics. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:80-9. [PMID: 23069211 DOI: 10.1016/j.bbamcr.2012.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/03/2012] [Accepted: 10/04/2012] [Indexed: 01/19/2023]
Abstract
Uncoupling protein-2 (UCP2) is used by cells to control reactive oxygen species (ROS) production by mitochondria. This ability depends on the glutathionylation state of UCP2. UCP2 is often overexpressed in drug resistant cancer cells and therein controls cell ROS levels and limits drug toxicity. With our recent observation that glutathionylation deactivates proton leak through UCP2, we decided to test if diamide, a glutathionylation catalyst, can sensitize drug resistant cells to chemotherapeutic agents. Using drug sensitive HL-60 cells and the drug resistant HL-60 subline, Mx2, we show that chemical induction of glutathionylation selectively deactivates proton leak through UCP2 in Mx2 cells. Chemical glutathionylation of UCP2 disables chemoresistance in the Mx2 cells. Exposure to 200μM diamide led to a significant increase in Mx2 cell death that was augmented when cells were exposed to either menadione or the anthracycline doxorubicin. Diamide also sensitized Mx2 cells to a number of other chemotherapeutics. Proton leak through UCP2 contributed significantly to the energetics of the Mx2 cells. Knockdown of UCP2 led to a significant decrease in both resting and state 4 (i.e., proton leak-dependent) respiration (~43% and 62%, respectively) in Mx2 cells. Similarly diamide inhibited proton leak-dependent respiration by ~64%. In contrast, diamide had very little effect on proton leak in HL-60 cells. Collectively, our observations indicate that manipulation of UCP2 glutathionylation status can serve as a therapeutic strategy for cancer treatment.
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65
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Mitochondrial ‘flashes’: a radical concept repHined. Trends Cell Biol 2012; 22:503-8. [DOI: 10.1016/j.tcb.2012.07.007] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Revised: 07/18/2012] [Accepted: 07/19/2012] [Indexed: 11/23/2022]
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66
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Mailloux RJ, Harper ME. Mitochondrial proticity and ROS signaling: lessons from the uncoupling proteins. Trends Endocrinol Metab 2012; 23:451-8. [PMID: 22591987 DOI: 10.1016/j.tem.2012.04.004] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Revised: 04/09/2012] [Accepted: 04/11/2012] [Indexed: 12/16/2022]
Abstract
Fifty years since Peter Mitchell proposed the theory of chemiosmosis, the transformation of cellular redox potential into ATP synthetic capacity is still a widely recognized function of mitochondria. Mitchell used the term 'proticity' to describe the force and flow of the proton circuit across the inner membrane. When the proton gradient is coupled to ATP synthase activity, the conversion of fuel to ATP is efficient. However, uncoupling proteins (UCPs) can cause proton leaks resulting in poor fuel conversion efficiency, and some UCPs might control mitochondrial reactive oxygen species (ROS) production. Once viewed as toxic metabolic waste, ROS are now implicated in cell signaling and regulation. Here, we discuss the role of mitochondrial proticity in the context of ROS production and signaling.
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Affiliation(s)
- Ryan J Mailloux
- University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology, and Immunology, 451 Smyth Road, Ottawa, Ontario, K1H 8M5, Canada
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67
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Wei L, Dirksen RT. Perspectives on: SGP symposium on mitochondrial physiology and medicine: mitochondrial superoxide flashes: from discovery to new controversies. J Gen Physiol 2012; 139:425-34. [PMID: 22641637 PMCID: PMC3362526 DOI: 10.1085/jgp.201210790] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Lan Wei
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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68
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Wang X, Jian C, Zhang X, Huang Z, Xu J, Hou T, Shang W, Ding Y, Zhang W, Ouyang M, Wang Y, Yang Z, Zheng M, Cheng H. Superoxide flashes: Elemental events of mitochondrial ROS signaling in the heart. J Mol Cell Cardiol 2012; 52:940-8. [DOI: 10.1016/j.yjmcc.2012.02.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 02/21/2012] [Accepted: 02/21/2012] [Indexed: 12/29/2022]
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69
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Zhou L, O'Rourke B. Cardiac mitochondrial network excitability: insights from computational analysis. Am J Physiol Heart Circ Physiol 2012; 302:H2178-89. [PMID: 22427517 DOI: 10.1152/ajpheart.01073.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the heart, mitochondria form a regular lattice and function as a coordinated, nonlinear network to continuously produce ATP to meet the high-energy demand of the cardiomyocytes. Cardiac mitochondria also exhibit properties of an excitable system: electrical or chemical signals can spread within or among cells in the syncytium. The detailed mechanisms by which signals pass among individual elements (mitochondria) across the network are still not completely understood, although emerging studies suggest that network excitability might be mediated by the local diffusion and autocatalytic release of messenger molecules such as reactive oxygen species and/or Ca(2+). In this short review, we have attempted to described recent advances in the field of cardiac mitochondrial network excitability. Specifically, we have focused on how mitochondria communicate with each other through the diffusion and regeneration of messenger molecules to initiate and propagate waves or oscillations, as revealed by computational models of mitochondrial network.
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Affiliation(s)
- Lufang Zhou
- Division of Cardiovascular Disease, Department of Medicine, The University of Alabama at Birmingham, 35294, USA.
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Li K, Zhang W, Fang H, Xie W, Liu J, Zheng M, Wang X, Wang W, Tan W, Cheng H. Superoxide flashes reveal novel properties of mitochondrial reactive oxygen species excitability in cardiomyocytes. Biophys J 2012; 102:1011-21. [PMID: 22404923 DOI: 10.1016/j.bpj.2012.01.044] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Revised: 01/02/2012] [Accepted: 01/27/2012] [Indexed: 11/18/2022] Open
Abstract
Superoxide flash represents quantal and bursting production of mitochondrial reactive oxygen species (ROS) instigated by transient opening of the mitochondrial permeability transition pore (mPTP). Given their critical role in metabolism, ischemia-reperfusion injury, and apoptosis, characterization of flash properties would be valuable to further mechanistic and physiological studies of this newly discovered mitochondrial phenomenon. Here we developed the flash detector FlashSniper based on segmentation of two-dimensional feature maps extracted from time-lapse confocal image stacks, and on the theory for correcting optical distortion of flash-amplitude histograms. Through large-scale analysis of superoxide flashes in cardiomyocytes, we demonstrated uniform mitochondrial ROS excitability among subsarcolemmal and intermyofibrillar mitochondria, and exponential distribution of intervals between consecutive flash events. Flash ignition displayed three different patterns: an abrupt rise from quiescence (44%), a rise with an exponential foot (27%), or a rise occurring after a pedestal precursor (29%), closely resembling action-potential initiation in excitable cells. However, the optical blurring-corrected amplitudes of superoxide flashes were highly variable, as were their durations, indicating stochastic automaticity of single-mitochondrion ROS excitation. Simultaneous measurement of mitochondrial membrane potential revealed that graded, rather than all-or-none, depolarization mirrored the precursor and the primary peak of the flash. We propose that superoxide flash production is a regenerative process dominated by stochastic, autonomous recruitment of a limited number of units (e.g., mPTPs) in single mitochondria.
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Affiliation(s)
- Kaitao Li
- Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Life Sciences, Peking University, Beijing, China
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71
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Azarias G, Chatton JY. Selective ion changes during spontaneous mitochondrial transients in intact astrocytes. PLoS One 2011; 6:e28505. [PMID: 22145050 PMCID: PMC3228761 DOI: 10.1371/journal.pone.0028505] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 11/09/2011] [Indexed: 01/11/2023] Open
Abstract
The bioenergetic status of cells is tightly regulated by the activity of cytosolic enzymes and mitochondrial ATP production. To adapt their metabolism to cellular energy needs, mitochondria have been shown to exhibit changes in their ionic composition as the result of changes in cytosolic ion concentrations. Individual mitochondria also exhibit spontaneous changes in their electrical potential without altering those of neighboring mitochondria. We recently reported that individual mitochondria of intact astrocytes exhibit spontaneous transient increases in their Na+ concentration. Here, we investigated whether the concentration of other ionic species were involved during mitochondrial transients. By combining fluorescence imaging methods, we performed a multiparameter study of spontaneous mitochondrial transients in intact resting astrocytes. We show that mitochondria exhibit coincident changes in their Na+ concentration, electrical potential, matrix pH and mitochondrial reactive oxygen species production during a mitochondrial transient without involving detectable changes in their Ca2+ concentration. Using widefield and total internal reflection fluorescence imaging, we found evidence for localized transient decreases in the free Mg2+ concentration accompanying mitochondrial Na+ spikes that could indicate an associated local and transient enrichment in the ATP concentration. Therefore, we propose a sequential model for mitochondrial transients involving a localized ATP microdomain that triggers a Na+-mediated mitochondrial depolarization, transiently enhancing the activity of the mitochondrial respiratory chain. Our work provides a model describing ionic changes that could support a bidirectional cytosol-to-mitochondria ionic communication.
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Affiliation(s)
- Guillaume Azarias
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
| | - Jean-Yves Chatton
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
- Cellular Imaging Facility, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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72
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Linking flickering to waves and whole-cell oscillations in a mitochondrial network model. Biophys J 2011; 101:2102-11. [PMID: 22067147 DOI: 10.1016/j.bpj.2011.09.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 09/21/2011] [Accepted: 09/23/2011] [Indexed: 11/22/2022] Open
Abstract
It has been shown that transient single mitochondrial depolarizations, known as flickers, tend to occur randomly in space and time. On the other hand, many studies have shown that mitochondrial depolarization waves and whole-cell oscillations occur under oxidative stress. How single mitochondrial flickering events and whole-cell oscillations are mechanistically linked remains unclear. In this study, we developed a Markov model of the inner membrane anion channel in which reactive-oxidative-species (ROS)-induced opening of the inner membrane anion channel causes transient mitochondrial depolarizations in a single mitochondrion that occur in a nonperiodic manner, simulating flickering. We then coupled the individual mitochondria into a network, in which flickers occur randomly and sparsely when a small number of mitochondria are in the state of high superoxide production. As the number of mitochondria in the high-superoxide-production state increases, short-lived or abortive waves due to ROS-induced ROS release coexist with flickers. When the number of mitochondria in the high-superoxide-production state reaches a critical number, recurring propagating waves are observed. The origins of the waves occur randomly in space and are self-organized as a consequence of random flickering and local synchronization. We show that at this critical state, the depolarization clusters exhibit a power-law distribution, a signature of self-organized criticality. In addition, the whole-cell mitochondrial membrane potential changes from exhibiting small random fluctuations to more periodic oscillations as the superoxide production rate increases. These simulation results may provide mechanistic insight into the transition from random mitochondrial flickering to the waves and whole-cell oscillations observed in many experimental studies.
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73
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Superoxide flashes, reactive oxygen species, and the mitochondrial permeability transition pore: potential implications for hematopoietic stem cell function. Curr Opin Hematol 2011; 18:208-13. [PMID: 21537169 DOI: 10.1097/moh.0b013e3283475ffe] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
PURPOSE OF REVIEW Reactive oxygen species (ROS) have an important function in blood cell homeostasis and hematopoietic diseases. Recent discoveries concerning how ROS are generated and regulated in mitochondria via the mitochondrial permeability transition pore (mPTP) and the new phenomenon, superoxide flashes, and ROS-induced ROS release, have not been investigated in hematopoietic stem and progenitor cells, but likely have important implications for their regulation and survival. Here we relate our opinions about these potential implications. RECENT FINDINGS The mPTP has been recently implicated in ROS generation via binding of Stat3 transcription factor to a central component of the pore. SUMMARY The implications of this new information for hematopoiesis regulation and transplantation methodologies could prove to be important, especially as they relate to myeloid neoplasm oncogenesis and potentially new therapeutic targets. New details about ROS production suggest that techniques for bone marrow and umbilical cord blood harvest may benefit from means to downmodulate ROS.
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74
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Mailloux RJ, Harper ME. Uncoupling proteins and the control of mitochondrial reactive oxygen species production. Free Radic Biol Med 2011; 51:1106-15. [PMID: 21762777 DOI: 10.1016/j.freeradbiomed.2011.06.022] [Citation(s) in RCA: 388] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 06/14/2011] [Accepted: 06/16/2011] [Indexed: 12/16/2022]
Abstract
Reactive oxygen species (ROS), natural by-products of aerobic respiration, are important cell signaling molecules, which left unchecked can severely impair cellular functions and induce cell death. Hence, cells have developed a series of systems to keep ROS in the nontoxic range. Uncoupling proteins (UCPs) 1-3 are mitochondrial anion carrier proteins that are purported to play important roles in minimizing ROS emission from the electron transport chain. The function of UCP1 in this regard is highly contentious. However, UCPs 2 and 3 are generally thought to be activated by ROS or ROS by-products to induce proton leak, thus providing a negative feedback loop for mitochondrial ROS production. In our laboratory, we have not only confirmed that ROS activate UCP2 and UCP3, but also demonstrated that UCP2 and UCP3 are controlled by covalent modification by glutathione. Furthermore, the reversible glutathionylation is required to activate/inhibit UCP2 and UCP3, but not UCP1. Hence, our findings are consistent with the notion that UCPs 2 and 3 are acutely activated by ROS, which then directly modulate the glutathionylation status of the UCP to decrease ROS emission and participate in cell signaling mechanisms.
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Affiliation(s)
- Ryan J Mailloux
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa Faculty of Medicine, Ottawa, ON, Canada K1G8M5
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75
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Ma Q, Fang H, Shang W, Liu L, Xu Z, Ye T, Wang X, Zheng M, Chen Q, Cheng H. Superoxide flashes: early mitochondrial signals for oxidative stress-induced apoptosis. J Biol Chem 2011; 286:27573-81. [PMID: 21659534 PMCID: PMC3149349 DOI: 10.1074/jbc.m111.241794] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/29/2011] [Indexed: 11/06/2022] Open
Abstract
Irreversible mitochondrial permeability transition and the resultant cytochrome c release signify the commitment of a cell to apoptotic death. However, the role of transient MPT (tMPT) because of flickering opening of the mitochondrial permeability transition pore remains elusive. Here we show that tMPT and the associated superoxide flashes (i.e. tMPT/superoxide flashes) constitute early mitochondrial signals during oxidative stress-induced apoptosis. Selenite (a ROS-dependent insult) but not staurosporine (a ROS-independent insult) stimulated an early and persistent increase in tMPT/superoxide flash activity prior to mitochondrial fragmentation and a global ROS rise, independently of Bax translocation and cytochrome c release. Selectively targeting tMPT/superoxide flash activity by manipulating cyclophilin D expression or scavenging mitochondrial ROS markedly impacted the progression of selenite-induced apoptosis while exerting little effect on the global ROS response. Furthermore, the tMPT/superoxide flash served as a convergence point for pro- and anti-apoptotic regulation mediated by cyclophilin D and Bcl-2 proteins. These results indicate that tMPT/superoxide flashes act as early mitochondrial signals mediating the apoptotic response during oxidative stress, and provide the first demonstration of highly efficacious local mitochondrial ROS signaling in deciding cell fate.
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Affiliation(s)
- Qi Ma
- From the Joint Laboratory of Apoptosis and Cancer Biology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- the Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huaqiang Fang
- the Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871, China
| | - Wei Shang
- the Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871, China
| | - Lei Liu
- From the Joint Laboratory of Apoptosis and Cancer Biology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- the Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhengshuang Xu
- the Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Tao Ye
- the Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
- the Department of Applied Biology & Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China, and
| | - Xianhua Wang
- the Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871, China
| | - Ming Zheng
- the Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871, China
| | - Quan Chen
- From the Joint Laboratory of Apoptosis and Cancer Biology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
- the Tianjin Key Laboratory of Protein Sciences, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Heping Cheng
- the Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing 100871, China
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76
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The circularly permuted yellow fluorescent protein cpYFP that has been used as a superoxide probe is highly responsive to pH but not superoxide in mitochondria: implications for the existence of superoxide ‘flashes’. Biochem J 2011; 437:381-7. [DOI: 10.1042/bj20110883] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The properties of a cpYFP [circularly permuted YFP (yellow fluorescent protein)] reported to act as a superoxide sensor have been re-examined in Arabidopsis mitochondria. We have found that the probe has high pH sensitivity and that dynamics in the cpYFP signal disappeared when the matrix pH was clamped by nigericin. In contrast, genetic and pharmacological manipulation of matrix superoxide had no detectable effect on the cpYFP signal. These findings question the existence of superoxide flashes in mitochondria.
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77
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Wei L, Salahura G, Boncompagni S, Kasischke KA, Protasi F, Sheu SS, Dirksen RT. Mitochondrial superoxide flashes: metabolic biomarkers of skeletal muscle activity and disease. FASEB J 2011; 25:3068-78. [PMID: 21646399 DOI: 10.1096/fj.11-187252] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mitochondrial superoxide flashes (mSOFs) are stochastic events of quantal mitochondrial superoxide generation. Here, we used flexor digitorum brevis muscle fibers from transgenic mice with muscle-specific expression of a novel mitochondrial-targeted superoxide biosensor (mt-cpYFP) to characterize mSOF activity in skeletal muscle at rest, following intense activity, and under pathological conditions. Results demonstrate that mSOF activity in muscle depended on electron transport chain and adenine nucleotide translocase functionality, but it was independent of cyclophilin-D-mediated mitochondrial permeability transition pore activity. The diverse spatial dimensions of individual mSOF events were found to reflect a complex underlying morphology of the mitochondrial network, as examined by electron microscopy. Muscle activity regulated mSOF activity in a biphasic manner. Specifically, mSOF frequency was significantly increased following brief tetanic stimulation (18.1 ± 1.6 to 22.3 ± 2.0 flashes/1000 μm²·100 s before and after 5 tetani) and markedly decreased (to 7.7 ± 1.6 flashes/1000 μm²·100 s) following prolonged tetanic stimulation (40 tetani). A significant temperature-dependent increase in mSOF frequency (11.9 ± 0.8 and 19.8 ± 2.6 flashes/1000 μm²·100 s at 23°C and 37°C) was observed in fibers from RYR1(Y522S/WT) mice, a mouse model of malignant hyperthermia and heat-induced hypermetabolism. Together, these results demonstrate that mSOF activity is a highly sensitive biomarker of mitochondrial respiration and the cellular metabolic state of muscle during physiological activity and pathological oxidative stress
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Affiliation(s)
- Lan Wei
- University of Rochester Medical Center, Department of Pharmacology and Physiology, Rochester, NY 14642, USA
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Kawamata H, Tiranti V, Magrané J, Chinopoulos C, Manfredi G. adPEO mutations in ANT1 impair ADP-ATP translocation in muscle mitochondria. Hum Mol Genet 2011; 20:2964-74. [PMID: 21586654 DOI: 10.1093/hmg/ddr200] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutations in the heart and muscle isoform of adenine nucleotide translocator 1 (ANT1) are associated with autosomal-dominant progressive external opthalmoplegia (adPEO) clinically characterized by exercise intolerance, ptosis and muscle weakness. The pathogenic mechanisms underlying the mitochondrial myopathy caused by ANT1 mutations remain largely unknown. In yeast, expression of ANT1 carrying mutations corresponding to the human adPEO ones causes a wide range of mitochondrial abnormalities. However, functional studies of ANT1 mutations in mammalian cells are lacking, because they have been hindered by the fact that ANT1 expression leads to apoptotic cell death in commonly utilized replicating cell lines. Here, we successfully express functional ANT1 in differentiated mouse myotubes, which naturally contain high levels of ANT1, without causing cell death. We demonstrate, for the first time in these disease-relevant mammalian cells, that mutant human ANT1 causes dominant mitochondrial defects characterized by decreased ADP-ATP exchange function and abnormal translocator reversal potential. These abnormalities are not due to ANT1 loss of function, because knocking down Ant1 in myotubes causes functional changes different from ANT1 mutants. Under certain physiological conditions, mitochondria consume ATP to maintain membrane potential by reversing the ADP-ATP transport. The modified properties of mutant ANT1 can be responsible for disease pathogenesis in adPEO, because exchange reversal occurring at higher than normal membrane potential can cause excessive energy depletion and nucleotide imbalance in ANT1 mutant muscle cells.
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Affiliation(s)
- Hibiki Kawamata
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10065, USA
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79
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Fang H, Chen M, Ding Y, Shang W, Xu J, Zhang X, Zhang W, Li K, Xiao Y, Gao F, Shang S, Li JC, Tian XL, Wang SQ, Zhou J, Weisleder N, Ma J, Ouyang K, Chen J, Wang X, Zheng M, Wang W, Zhang X, Cheng H. Imaging superoxide flash and metabolism-coupled mitochondrial permeability transition in living animals. Cell Res 2011; 21:1295-304. [PMID: 21556035 DOI: 10.1038/cr.2011.81] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The mitochondrion is essential for energy metabolism and production of reactive oxygen species (ROS). In intact cells, respiratory mitochondria exhibit spontaneous "superoxide flashes", the quantal ROS-producing events consequential to transient mitochondrial permeability transition (tMPT). Here we perform the first in vivo imaging of mitochondrial superoxide flashes and tMPT activity in living mice expressing the superoxide biosensor mt-cpYFP, and demonstrate their coupling to whole-body glucose metabolism. Robust tMPT/superoxide flash activity occurred in skeletal muscle and sciatic nerve of anesthetized transgenic mice. In skeletal muscle, imaging tMPT/superoxide flashes revealed labyrinthine three-dimensional networks of mitochondria that operate synchronously. The tMPT/superoxide flash activity surged in response to systemic glucose challenge or insulin stimulation, in an apparently frequency-modulated manner and involving also a shift in the gating mode of tMPT. Thus, in vivo imaging of tMPT-dependent mitochondrial ROS signals and the discovery of the metabolism-tMPT-superoxide flash coupling mark important technological and conceptual advances for the study of mitochondrial function and ROS signaling in health and disease.
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Affiliation(s)
- Huaqiang Fang
- Institute of Molecular Medicine, College of Life Science, Peking University, Beijing 100871, China
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Kim BS, Jung JS, Jang JH, Kang KS, Kang SK. Nuclear Argonaute 2 regulates adipose tissue-derived stem cell survival through direct control of miR10b and selenoprotein N1 expression. Aging Cell 2011; 10:277-91. [PMID: 21241449 DOI: 10.1111/j.1474-9726.2011.00670.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Argonaute 2 (Ago2) has a leading function in miRNA-induced RNA silencing, a conserved gene regulatory mechanism in cells and organisms. miRNAs are critical for stem cell self-renewal, development, and other functions. Here, we report that nuclear Ago2, by binding to a specific region of functional genes, directly controls adipose tissue-derived stem cell (ATSC) survival in response to a critical dose of reactive oxygen species (ROS)-mediated oxidative cell damage or senescence. The role of nuclear Ago2 has not been previously reported. Here, we show that human ATSCs in which Ago2 was downregulated underwent apoptosis. Silencing of Ago2 in ATSCs significantly induces upregulation of miR10b and miR23b expression. These miRNAs directly interfere with ROS-scavenging gene expression, such as TXNL1 and GPX3. Upregulation of miR10b and miR23b is sufficient to induce ATSC cell apoptosis via p38 MAPK phosphorylation and caspase 3 activation. In addition, Ago2 overexpression or interference by miR10b and miR23b expression in ATSCs partially rescued H(2) O(2) /ROS-mediated apoptotic cell death by upregulating the expression of TXNL2, JUNK, caspase-3, and cytochrome C. Nuclear Ago2-mediated miR10b and miR23b downregulation also allows cells to escape senescence, which results in telomerase reverse transcriptase, stemness overexpression, and improved self-renewal and differentiation through Wnt5a/β-catenin activation. Argonaute 2 expression is critical for stem cells to escape senescence by downregulating miR10b and miR23b. The Ago2-binding gene selenoprotein N1 (SEPN1) was also effectively involved in ATSC survival and self-renewal through ROS-mediated p38 MAPK inactivation.
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Affiliation(s)
- Bong Sun Kim
- Department of Biotechnology, College of Veterinary Medicine, Seoul National University, Seoul, Korea
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