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Gottwald EM, Schuh CD, Drücker P, Haenni D, Pearson A, Ghazi S, Bugarski M, Polesel M, Duss M, Landau EM, Kaech A, Ziegler U, Lundby AKM, Lundby C, Dittrich PS, Hall AM. The iron chelator Deferasirox causes severe mitochondrial swelling without depolarization due to a specific effect on inner membrane permeability. Sci Rep 2020; 10:1577. [PMID: 32005861 PMCID: PMC6994599 DOI: 10.1038/s41598-020-58386-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 01/15/2020] [Indexed: 12/13/2022] Open
Abstract
The iron chelator Deferasirox (DFX) causes severe toxicity in patients for reasons that were previously unexplained. Here, using the kidney as a clinically relevant in vivo model for toxicity together with a broad range of experimental techniques, including live cell imaging and in vitro biophysical models, we show that DFX causes partial uncoupling and dramatic swelling of mitochondria, but without depolarization or opening of the mitochondrial permeability transition pore. This effect is explained by an increase in inner mitochondrial membrane (IMM) permeability to protons, but not small molecules. The movement of water into mitochondria is prevented by altering intracellular osmotic gradients. Other clinically used iron chelators do not produce mitochondrial swelling. Thus, DFX causes organ toxicity due to an off-target effect on the IMM, which has major adverse consequences for mitochondrial volume regulation.
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Affiliation(s)
| | - Claus D Schuh
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Patrick Drücker
- Department of Biosystems Science and Engineering, ETH Zurich, Zurich, Switzerland
| | - Dominik Haenni
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Adam Pearson
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Susan Ghazi
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Milica Bugarski
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | | | - Michael Duss
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Ehud M Landau
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Urs Ziegler
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Anne K M Lundby
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Carsten Lundby
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Petra S Dittrich
- Department of Biosystems Science and Engineering, ETH Zurich, Zurich, Switzerland
| | - Andrew M Hall
- Institute of Anatomy, University of Zurich, Zurich, Switzerland. .,Department of Nephrology, University Hospital Zurich, Zurich, Switzerland.
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2
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Daniele JR, Heydari K, Dillin A. Mitochondrial Subtype Identification and Characterization. CURRENT PROTOCOLS IN CYTOMETRY 2018; 85:e41. [PMID: 29944197 PMCID: PMC6039279 DOI: 10.1002/cpcy.41] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Healthy, functional mitochondria are central to many cellular and physiological phenomena, including aging, metabolism, and stress resistance. A key feature of healthy mitochondria is a high membrane potential (Δψ) or charge differential (i.e., proton gradient) between the matrix and inner mitochondrial membrane. Mitochondrial Δψ has been extensively characterized via flow cytometry of intact cells, which measures the average membrane potential within a cell. However, the characteristics of individual mitochondria differ dramatically even within a single cell, and thus interrogation of mitochondrial features at the organelle level is necessary to better understand and accurately measure heterogeneity. Here we describe a new flow cytometric methodology that enables the quantification and classification of mitochondrial subtypes (via their Δψ, size, and substructure) using the small animal model C. elegans. Future application of this methodology should allow research to discern the bioenergetic and mitochondrial component in a number of human disease and aging models, including, C. elegans, cultured cells, small animal models, and human biopsy samples. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
- Joseph R. Daniele
- Department of Molecular & Cellular Biology, University of
California, Berkeley, Berkeley, CA 94720
| | - Kartoosh Heydari
- LKS Flow Cytometry Core, Cancer Research Laboratory, University of
California, Berkeley, Berkeley, CA 94720
| | - Andrew Dillin
- Department of Molecular & Cellular Biology, University of
California, Berkeley, Berkeley, CA 94720
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3
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DGAT1-Dependent Lipid Droplet Biogenesis Protects Mitochondrial Function during Starvation-Induced Autophagy. Dev Cell 2017; 42:9-21.e5. [PMID: 28697336 DOI: 10.1016/j.devcel.2017.06.003] [Citation(s) in RCA: 318] [Impact Index Per Article: 45.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 04/25/2017] [Accepted: 06/02/2017] [Indexed: 01/22/2023]
Abstract
Lipid droplets (LDs) provide an "on-demand" source of fatty acids (FAs) that can be mobilized in response to fluctuations in nutrient abundance. Surprisingly, the amount of LDs increases during prolonged periods of nutrient deprivation. Why cells store FAs in LDs during an energy crisis is unknown. Our data demonstrate that mTORC1-regulated autophagy is necessary and sufficient for starvation-induced LD biogenesis. The ER-resident diacylglycerol acyltransferase 1 (DGAT1) selectively channels autophagy-liberated FAs into new, clustered LDs that are in close proximity to mitochondria and are lipolytically degraded. However, LDs are not required for FA delivery to mitochondria but instead function to prevent acylcarnitine accumulation and lipotoxic dysregulation of mitochondria. Our data support a model in which LDs provide a lipid buffering system that sequesters FAs released during the autophagic degradation of membranous organelles, reducing lipotoxicity. These findings reveal an unrecognized aspect of the cellular adaptive response to starvation, mediated by LDs.
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Daniele JR, Heydari K, Arriaga EA, Dillin A. Identification and Characterization of Mitochondrial Subtypes in Caenorhabditis elegans via Analysis of Individual Mitochondria by Flow Cytometry. Anal Chem 2016; 88:6309-16. [PMID: 27210103 DOI: 10.1021/acs.analchem.6b00542] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mitochondrial bioenergetics has been implicated in a number of vital cellular and physiological phenomena, including aging, metabolism, and stress resistance. Heterogeneity of the mitochondrial membrane potential (Δψ), which is central to organismal bioenergetics, has been successfully measured via flow cytometry in whole cells but rarely in isolated mitochondria from large animal models. Similar studies in small animal models, such as Caenorhabditis elegans (C. elegans), are critical to our understanding of human health and disease but lack analytical methodologies. Here we report on new methodological developments that make it possible to investigate the heterogeneity of Δψ in C. elegans during development and in tissue-specific studies. The flow cytometry methodology described here required an improved collagenase-3-based mitochondrial isolation procedure and labeling of mitochondria with the ratiometric fluorescent probe JC-9. To demonstrate feasibility of tissue-specific studies, we used C. elegans strains expressing blue-fluorescent muscle-specific proteins, which enabled identification of muscle mitochondria among mitochondria from other tissues. This methodology made it possible to observe, for the first time, critical changes in Δψ during C. elegans larval development and provided direct evidence of the elevated bioenergetic status of muscle mitochondria relative to their counterparts in the rest of the organism. Further application of these methodologies can help tease apart bioenergetics and other biological complexities in C. elegans and other small animal models used to investigate human disease and aging.
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Affiliation(s)
- Joseph R Daniele
- Department of Molecular and Cellular Biology, University of California, Berkeley , Berkeley, California 94720, United States
| | - Kartoosh Heydari
- LKS Flow Cytometry Core, Cancer Research Laboratory, University of California, Berkeley , Berkeley, California 94720, United States
| | - Edgar A Arriaga
- Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Andrew Dillin
- Department of Molecular and Cellular Biology, University of California, Berkeley , Berkeley, California 94720, United States
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Eder AR, Arriaga EA. Capillary electrophoresis monitors enhancement in subcellular reactive oxygen species production upon treatment with doxorubicin. Chem Res Toxicol 2006; 19:1151-9. [PMID: 16978019 PMCID: PMC2626132 DOI: 10.1021/tx060083i] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study investigated the role of doxorubicin (DOX) accumulation in reactive oxygen species (ROS) production detected in individually electrophoresed organelles, including mitochondria, acidic organelles, and peroxisomes. While bulk measurements of ROS production in cells and organelles are not capable of discriminating between the effects of preparative procedures on measured ROS production, capillary electrophoresis with dual laser-induced detection of individual organelles demonstrated a difference in the measured ROS production as a result of various preparative procedures. Using this technique, the three different types of detected organelles (i) produce ROS and do not have detectable levels of DOX, (ii) contain detectable DOX but do not produce ROS, or (iii) produce ROS and accumulate DOX. The third type displays two subpopulations of organelles, one of which demonstrated a direct relationship between DOX uptake and subsequent ROS production, corresponding most likely to mitochondria, and a second one with low DOX uptake but large variation in ROS production, corresponding most likely to acidic organelles.
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Affiliation(s)
| | - Edgar A Arriaga
- *Author to whom correspondence should be addressed. Tel.: +1 612 624 8024; fax +1, 612 626 7541. E-mail address:
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Lifshitz J, Janmey PA, McIntosh TK. Photon correlation spectroscopy of brain mitochondrial populations: Application to traumatic brain injury. Exp Neurol 2006; 197:318-29. [PMID: 16289540 DOI: 10.1016/j.expneurol.2005.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 08/29/2005] [Accepted: 10/12/2005] [Indexed: 01/27/2023]
Abstract
Mitochondrial dysfunction and pathology that contribute to a host of neurodegenerative diseases are deduced from changes in ultrastructure, routinely examined by a host of optical techniques. We adapted the technique of photon correlation spectroscopy (PCS) to evaluate calcium-induced structural alterations in isolated viable cortical and hippocampal mitochondria. In detecting calcium-induced reductions in light intensity, PCS was more sensitive than absorbance across varying calcium concentrations. Mitochondrial populations encompass a broad distribution of sizes, confirmed by ultrastructural profiles, both which remain unaffected by calcium exposure. Cortical and hippocampal populations show fractional calcium-induced reductions in light scatter compared to subsequent maximal alamethicin-induced reductions. Although reductions in light scatter (refractive index) have been interpreted as mitochondrial swelling, PCS quantification of the mean mitochondrial radius demonstrates that mitochondrial size is unaffected by calcium exposure, but not alamethicin. Likewise, the population distribution histograms remain stable with calcium exposure, but shift to larger radii after alamethicin exposure. Furthermore, hippocampal mitochondrial populations from a neurodegenerative model of traumatic brain injury, lateral fluid percussion, demonstrate greater calcium-induced reductions in scatter intensity, which are associated with an initial population of large mitochondria becoming smaller. The disparate responses to calcium and subsequent alamethicin of mitochondria at 3 and 24 h after injury attest to an acute disruption of membrane permeability in mitochondria from injured brain. PCS provides quantitative indices of refractive index and size in isolated mitochondrial populations, aiding the evaluation of mitochondria in degenerative diseases.
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Affiliation(s)
- Jonathan Lifshitz
- Traumatic Brain Injury Laboratory, Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA.
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7
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Mattiasson G. Flow cytometric analysis of isolated liver mitochondria to detect changes relevant to cell death. ACTA ACUST UNITED AC 2004; 60:145-54. [PMID: 15290715 DOI: 10.1002/cyto.a.20024] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Mitochondria are key players in many forms of cell death, and mitochondrial production of reactive oxygen species (ROS), membrane depolarization, permeability changes, and release of apoptogenic proteins are involved in these processes. Flow cytometric analysis of isolated mitochondria enables parallel analysis of mitochondrial structure and function in individual mitochondria, and small mitochondrial samples are sufficient for analysis. This article describes a well-characterized protocol for flow cytometric analysis of isolated liver mitochondria that can be used to detect mitochondrial alterations relevant to cell death. METHODS Fluorescent probes were used to selectively stain mitochondria (nonyl acridine orange), and to measure membrane potential (tetramethylrhodamine-methyl-ester, 1,1',3,3,3',3'-hexamethylindodicarbocyanine-iodide), as well as production of ROS (2',7'-dichlorodihydrofluorescein-diacetate). Calcium-induced mitochondrial swelling was detected as a decrease in SSC. To ensure optimal concentrations of all probes, the effect on mitochondrial respiration was evaluated. RESULTS This protocol can be used to determine the purity of the mitochondrial preparation, to detect calcium-induced morphological changes, small mitochondrial de- and hyperpolarizations, as well as physiological changes in ROS generation. CONCLUSIONS Flow cytometry is a very useful tool to simultaneously analyze several mitochondrial parameters that are important in the induction of mitochondria-mediated cell death.
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Affiliation(s)
- Gustav Mattiasson
- Laboratory for Experimental Brain Research, Wallenberg Neuroscience Center, Lund University, Lund, Sweden.
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Mattiasson G, Friberg H, Hansson M, Elmér E, Wieloch T. Flow cytometric analysis of mitochondria from CA1 and CA3 regions of rat hippocampus reveals differences in permeability transition pore activation. J Neurochem 2003; 87:532-44. [PMID: 14511130 DOI: 10.1046/j.1471-4159.2003.02026.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Mitochondria are important in the pathophysiology of several neurodegenerative diseases, and mitochondrial production of reactive oxygen species (ROS), membrane depolarization, permeability changes and release of apoptogenic proteins are involved in these processes. Following brain insults, cell death often occurs in discrete regions of the brain, such as the subregions of the hippocampus. To analyse mitochondrial structure and function in such subregions, only small amounts of mitochondria are available. We developed a protocol for flow cytometric analysis of very small samples of isolated brain mitochondria, and analysed mitochondrial swelling and formation of ROS in mitochondria from the CA1 and CA3 regions of the hippocampus. Calcium-induced mitochondrial swelling was measured, and fluorescent probes were used to selectively stain mitochondria (nonyl acridine orange), to measure membrane potential (tetramethylrhodamine-methyl-ester, 1,1',3,3,3',3'-hexamethylindodicarbocyanine-iodide) and to measure production of ROS (2',7'-dichlorodihydrofluorescein-diacetate). We found that formation of ROS and mitochondrial permeability transition pore activation were higher in mitochondria from the CA1 than from the CA3 region, and propose that differences in mitochondrial properties partly underlie the selective vulnerability of the CA1 region to brain insults. We also conclude that flow cytometry is a useful tool to analyse the role of mitochondria in cell death processes.
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Affiliation(s)
- Gustav Mattiasson
- Laboratory for Experimental Brain Research, Wallenberg Neuroscience Center, Lund University, Lund, Sweden.
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9
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Boustany NN, Drezek R, Thakor NV. Calcium-induced alterations in mitochondrial morphology quantified in situ with optical scatter imaging. Biophys J 2002; 83:1691-700. [PMID: 12202392 PMCID: PMC1302265 DOI: 10.1016/s0006-3495(02)73937-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Optical scatter imaging (OSI), a technique we developed recently, was used to measure the ratio of wide-to-narrow angle scatter (OSIR) within endothelial cells subjected to calcium overload (1.6 mM) after permeabilization by ionomycin. Within a few minutes of calcium overload, the mitochondria, which started as elongated organelles, rounded up into spherically shaped particles. This change in morphology was accompanied by a statistically significant 14% increase in OSIR in the cells' cytoplasm. Mitochondrial rounding and OSIR increase were suppressed by cyclosporin A (25 microM), implying that the observed geometrical and scattering changes were directly attributable to the mitochondrial permeability transition. The angular scattering properties of a long mitochondrion rounding up were approximated by numerical simulations of light scatter from an ellipsoid rounding up into a sphere. The simulations predicted a relative increase in OSIR comparable to that measured experimentally for the case where the shape transition takes place with little or no volume increase. The simulations also suggested that mitochondrial refractive index changes could not account for the OSIR changes observed. Our data show that changes in OSIR correlate with mitochondrial morphology change in situ. OSI provides a new tool for subcellular imaging and complements other microscopy methods, such as fluorescence.
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Affiliation(s)
- Nada N Boustany
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205, USA.
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10
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von Ahsen O, Renken C, Perkins G, Kluck RM, Bossy-Wetzel E, Newmeyer DD. Preservation of mitochondrial structure and function after Bid- or Bax-mediated cytochrome c release. J Cell Biol 2000; 150:1027-36. [PMID: 10973993 PMCID: PMC2175243 DOI: 10.1083/jcb.150.5.1027] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2000] [Accepted: 07/13/2000] [Indexed: 11/22/2022] Open
Abstract
Proapoptotic members of the Bcl-2 protein family, including Bid and Bax, can activate apoptosis by directly interacting with mitochondria to cause cytochrome c translocation from the intermembrane space into the cytoplasm, thereby triggering Apaf-1-mediated caspase activation. Under some circumstances, when caspase activation is blocked, cells can recover from cytochrome c translocation; this suggests that apoptotic mitochondria may not always suffer catastrophic damage arising from the process of cytochrome c release. We now show that recombinant Bid and Bax cause complete cytochrome c loss from isolated mitochondria in vitro, but preserve the ultrastructure and protein import function of mitochondria, which depend on inner membrane polarization. We also demonstrate that, if caspases are inhibited, mitochondrial protein import function is retained in UV-irradiated or staurosporine-treated cells, despite the complete translocation of cytochrome c. Thus, Bid and Bax act only on the outer membrane, and lesions in the inner membrane occurring during apoptosis are shown to be secondary caspase-dependent events.
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Affiliation(s)
- Oliver von Ahsen
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Christian Renken
- Biology Department, San Diego State University, San Diego, California 92182
| | - Guy Perkins
- Department of Neurosciences, University of California San Diego, San Diego, California 92093
| | - Ruth M. Kluck
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Ella Bossy-Wetzel
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Donald D. Newmeyer
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
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11
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Kluck RM, Esposti MD, Perkins G, Renken C, Kuwana T, Bossy-Wetzel E, Goldberg M, Allen T, Barber MJ, Green DR, Newmeyer DD. The pro-apoptotic proteins, Bid and Bax, cause a limited permeabilization of the mitochondrial outer membrane that is enhanced by cytosol. J Cell Biol 1999; 147:809-22. [PMID: 10562282 PMCID: PMC2156156 DOI: 10.1083/jcb.147.4.809] [Citation(s) in RCA: 256] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/1999] [Accepted: 10/12/1999] [Indexed: 01/01/2023] Open
Abstract
During apoptosis, an important pathway leading to caspase activation involves the release of cytochrome c from the intermembrane space of mitochondria. Using a cell-free system based on Xenopus egg extracts, we examined changes in the outer mitochondrial membrane accompanying cytochrome c efflux. The pro-apoptotic proteins, Bid and Bax, as well as factors present in Xenopus egg cytosol, each induced cytochrome c release when incubated with isolated mitochondria. These factors caused a permeabilization of the outer membrane that allowed the corelease of multiple intermembrane space proteins: cytochrome c, adenylate kinase and sulfite oxidase. The efflux process is thus nonspecific. None of the cytochrome c-releasing factors caused detectable mitochondrial swelling, arguing that matrix swelling is not required for outer membrane permeability in this system. Bid and Bax caused complete release of cytochrome c but only a limited permeabilization of the outer membrane, as measured by the accessibility of inner membrane-associated respiratory complexes III and IV to exogenously added cytochrome c. However, outer membrane permeability was strikingly increased by a macromolecular cytosolic factor, termed PEF (permeability enhancing factor). We hypothesize that PEF activity could help determine whether cells can recover from mitochondrial cytochrome c release.
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Affiliation(s)
- Ruth M. Kluck
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Mauro Degli Esposti
- Department of Biochemistry and Molecular Biology, University of South Florida, College of Medicine, Tampa, Florida 33612
| | - Guy Perkins
- Department of Neurosciences, University of California San Diego, San Diego, California 92093
| | - Christian Renken
- Biology Department, San Diego State University, San Diego, California 92182
| | - Tomomi Kuwana
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Ella Bossy-Wetzel
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Martin Goldberg
- Paterson Institute, Christie Hospital NHS Trust, Manchester M20 9BX, United Kingdom
| | - Terry Allen
- Paterson Institute, Christie Hospital NHS Trust, Manchester M20 9BX, United Kingdom
| | - Michael J. Barber
- Department of Biochemistry and Molecular Biology, University of South Florida, College of Medicine, Tampa, Florida 33612
| | - Douglas R. Green
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Donald D. Newmeyer
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
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12
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Abstract
There is a widespread need for commercial instrumentation for the rapid and inexpensive detection of microbial contamination of food, industrial waste water and clinical samples. A large number of detection methods have been developed utilizing the optical, electrochemical, biochemical and physical properties of microorganisms. The need for a device which can produce a rapid, accurate, sensitive, real-time analysis for clinical, industrial and environmental applications has led to considerable progress being achieved in recent years in the development of biosensors for microbial detection. This intense research has resulted in the commercialization of several instruments. Techniques used for the quantification of microorganisms are reviewed under the general categories of non-bioelectrochemical and bioelectrochemical methods.
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Affiliation(s)
- N S Hobson
- Biotechnology Centre, Cranfield University, Bedford, UK
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13
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Petit PX, O'Connor JE, Grunwald D, Brown SC. Analysis of the membrane potential of rat- and mouse-liver mitochondria by flow cytometry and possible applications. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 194:389-97. [PMID: 2269275 DOI: 10.1111/j.1432-1033.1990.tb15632.x] [Citation(s) in RCA: 194] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Washed and purified rat- or mouse-liver mitochondria exhibiting high membrane integrity and metabolic activity were studied by flow cytometry. The electrophoretic accumulation/redistribution of cationic lipophilic probes, rhodamine 123, safranine O and a cyanine derivative, 3,3'-dihexyloxadicarbocyanine iodide, during the energization process was studied and was consistent with the generation of a negative internal membrane potential. An exception to this was nonylacridine orange which spontaneously bound to the mitochondrial membrane by hydrophobic interactions via its hydrocarbon chain. Energized purified mitochondria stained with potentiometric dyes exhibited both higher fluorescence and population homogeneity than the non-energized or deenergized (nigericin plus valinomycin) mitochondria. By contrast, under non-energized or deenergized conditions, the mitochondrial population exhibited fluorescence intensity heterogeneity related to the residual membrane potential; two subpopulations were evident, one of low fluorescence which may be related to the autofluorescence of the mitochondria (plus non-specific dye binding) and a second population which exhibited high fluorescence. Flow cytometry of the unpurified, simply washed, rat-liver mitochondria stained with rhodamine 123, a classically used dye, provided evidence of their heterogeneity in terms of light-scattering properties and membrane-potential-related fluorescence. One third of the washed mitochondria were found to be non-functional by such assays. The fluorescence of purified rat-liver mitochondria due to the membrane potential built up by endogenous substrates indicates heterogeneity of the mitochondrial population with respect to levels of endogenous substrates. The low-angle light scattering increases upon energization and provides some original information about the shape and modification of the inner mitochondrial conformation accompanying the energization. The heterogeneity of the rat liver mitochondrial population, from a structural, metabolic (existence of endogenous substrates) and functional (active and non-active mitochondrial population dispersion) point of view could thus be demonstrated by flow-cytometry analysis. Two animal models were examined with regard to the alteration of the mitochondrial membrane potential under the effects of drugs (rat-liver mitochondria), and the effects of ammonium toxicity (mouse-liver mitochondria). These results are promising and open new perspectives in the study of mitochondriopathies.
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Affiliation(s)
- P X Petit
- Centre National de la Recherche Scientifique, Biosystèmes Membranaires, Gif-sur-Yvette, France
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14
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Wiggins PM, MacClement BA. Two states of water found in hydrophobic clefts: their possible contribution to mechanisms of cation pumps and other enzymes. INTERNATIONAL REVIEW OF CYTOLOGY 1987; 108:249-303. [PMID: 2959632 DOI: 10.1016/s0074-7696(08)61440-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- P M Wiggins
- Department of Medicine, University of Auckland School of Medicine, New Zealand
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15
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AZZONE GIOVANNIFELICE, PIETROBON DANIELA, ZORATTI MARIO. Determination of the Proton Electrochemical Gradient across Biological Membranes. CURRENT TOPICS IN BIOENERGETICS 1984. [DOI: 10.1016/b978-0-12-152513-2.50008-8] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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16
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Sholtz KF, Gorskaya IA, Kotelnikova AV. The stoichiometry of proton translocation through H+-ATPase of rat-liver mitochondria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 136:129-34. [PMID: 6311544 DOI: 10.1111/j.1432-1033.1983.tb07715.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The ratio of the number of protons transported directly by H+-ATPase of intact mitochondria and that of the hydrolyzed ATP (the proton translocation quotient) is determined. A special kinetic method which makes possible determination of ATPase and H+-translocase activities in the same experiment has been used to estimate the proton translocation quotient for mitochondrial H+-ATPase. The quotient is found to be, on average, equal to 3.31 mol/mol. It is shown that the protonophore 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile can greatly decrease the proton translocation quotient. This supports our assumption concerning a labile coupling between H+-translocase and ATPase in mitochondria [I. A. Gorskaya, K. F. Sholtz, S. A. Moreva, A. V. Kotelnikova (1979) Biochemistry (Engl. Transl. Biokhimiya) 44, 765-770]. A decrease in the translocation quotient in the presence of the protonophore is likely to be due to the ability of this uncoupler to take back the translocated protons into the mitochondrial matrix before their release into the medium. An electrostatic model of the molecular mechanism of H+-translocase and ATPase coupling in the H+-ATPase complex is discussed. The model is in agreement with the results obtained: transport of more than two protons per each hydrolyzed ATP molecule, and variable efficiency of the process.
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