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Yang RZ, Wang DD, Li SM, Liu PP, Kang JS. Development and Application of a Mitochondrial Genetically Encoded Voltage Indicator in Narcosis. Neurosci Bull 2024:10.1007/s12264-024-01235-w. [PMID: 38829505 DOI: 10.1007/s12264-024-01235-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 01/11/2024] [Indexed: 06/05/2024] Open
Abstract
Mitochondrial membrane potential (MMP) plays a crucial role in the function of cells and organelles, involving various cellular physiological processes, including energy production, formation of reactive oxygen species (ROS), unfolded protein stress, and cell survival. Currently, there is a lack of genetically encoded fluorescence indicators (GEVIs) for MMP. In our screening of various GEVIs for their potential monitoring MMP, the Accelerated Sensor of Action Potentials (ASAP) demonstrated optimal performance in targeting mitochondria and sensitivity to depolarization in multiple cell types. However, mitochondrial ASAPs also displayed sensitivity to ROS in cardiomyocytes. Therefore, two ASAP mutants resistant to ROS were generated. A double mutant ASAP3-ST exhibited the highest voltage sensitivity but weaker fluorescence. Overall, four GEVIs capable of targeting mitochondria were obtained and named mitochondrial potential indicators 1-4 (MPI-1-4). In vivo, fiber photometry experiments utilizing MPI-2 revealed a mitochondrial depolarization during isoflurane-induced narcosis in the M2 cortex.
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Affiliation(s)
- Run-Zhou Yang
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
| | - Dian-Dian Wang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, China
| | - Sen-Miao Li
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, China
| | - Pei-Pei Liu
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Jian-Sheng Kang
- Clinical Systems Biology Laboratories, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
- The Academy of Medical Sciences, Zhengzhou University, Zhengzhou, 450052, China.
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2
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Yamasaki H, Itoh RD, Mizumoto KB, Yoshida YS, Otaki JM, Cohen MF. Spatiotemporal Characteristics Determining the Multifaceted Nature of Reactive Oxygen, Nitrogen, and Sulfur Species in Relation to Proton Homeostasis. Antioxid Redox Signal 2024. [PMID: 38407968 DOI: 10.1089/ars.2023.0544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Significance: Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) act as signaling molecules, regulating gene expression, enzyme activity, and physiological responses. However, excessive amounts of these molecular species can lead to deleterious effects, causing cellular damage and death. This dual nature of ROS, RNS, and RSS presents an intriguing conundrum that calls for a new paradigm. Recent Advances: Recent advancements in the study of photosynthesis have offered significant insights at the molecular level and with high temporal resolution into how the photosystem II oxygen-evolving complex manages to prevent harmful ROS production during the water-splitting process. These findings suggest that a dynamic spatiotemporal arrangement of redox reactions, coupled with strict regulation of proton transfer, is crucial for minimizing unnecessary ROS formation. Critical Issues: To better understand the multifaceted nature of these reactive molecular species in biology, it is worth considering a more holistic view that combines ecological and evolutionary perspectives on ROS, RNS, and RSS. By integrating spatiotemporal perspectives into global, cellular, and biochemical events, we discuss local pH or proton availability as a critical determinant associated with the generation and action of ROS, RNS, and RSS in biological systems. Future Directions: The concept of localized proton availability will not only help explain the multifaceted nature of these ubiquitous simple molecules in diverse systems but also provide a basis for new therapeutic strategies to manage and manipulate these reactive species in neural disorders, pathogenic diseases, and antiaging efforts.
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Affiliation(s)
- Hideo Yamasaki
- Faculty of Science, University of the Ryukyus, Okinawa, Japan
| | - Ryuuichi D Itoh
- Faculty of Science, University of the Ryukyus, Okinawa, Japan
| | | | - Yuki S Yoshida
- Faculty of Science, University of the Ryukyus, Okinawa, Japan
| | - Joji M Otaki
- Faculty of Science, University of the Ryukyus, Okinawa, Japan
| | - Michael F Cohen
- University of California Cooperative Extension, Santa Clara County, San Jose, California, USA
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3
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Layton AT. A comparative modeling study of the mitochondrial function of the proximal tubule and thick ascending limb cells in the rat kidney. Am J Physiol Renal Physiol 2024; 326:F189-F201. [PMID: 37994410 DOI: 10.1152/ajprenal.00290.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 11/09/2023] [Accepted: 11/16/2023] [Indexed: 11/24/2023] Open
Abstract
To reabsorb >99% of the glomerular filtrate, the metabolic demand of the kidney is high. Interestingly, renal blood flow distribution exhibits marked inhomogeneity, with typical tissue oxygen tension (Po2) of 50-60 mmHg in the well-perfused cortex and 10-20 mmHg in the inner medulla. Cellular fluid composition and acidity also varies substantially. To understand how different renal epithelial cells adapt to their local environment, we have developed and applied computational models of mitochondrial function of proximal convoluted tubule cell (baseline Po2 = 50 mmHg, cytoplasmic pH = 7.20) and medullary thick ascending limb (mTAL) cell (baseline Po2 = 10 mmHg, cytoplasmic pH = 6.85). The models predict key cellular quantities, including ATP generation, P/O (phosphate/oxygen) ratio, proton motive force, electrical potential gradient, oxygen consumption, the redox state of key electron carriers, and ATP consumption. Model simulations predict that close to their respective baseline conditions, the proximal tubule and mTAL mitochondria exhibit qualitatively similar behaviors. Nonetheless, because the mTAL mitochondrion has adapted to a much lower Po2, it can sustain a sufficiently high ATP production at Po2 as low as 4-5 mmHg, whereas the proximal tubule mitochondria would not. Also, because the mTAL cytosol is already acidic under baseline conditions, the proton motive force (pmf) exhibits higher sensitivity to further acidification. Among the different pathways that lead to oxidative phosphorylation impairment, the models predict that both the proximal tubule and mTAL mitochondria are most sensitive to reductions in Complex III activity.NEW & NOTEWORTHY Tissue fluid composition varies substantially within the mammalian kidney. The renal cortex is well perfused and pH neutral, whereas some medullary regions are hypoxic and acidic. How do these environments affect the mitochondrial function of proximal convoluted tubule and medullary thick ascending limb cells, which reside in the cortex and medulla, respectively? This computational modeling study demonstrates that these mitochondria can adapt to their contrasting environments and exhibit different sensitivities to perturbations to local environments.
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Affiliation(s)
- Anita T Layton
- Department of Applied Mathematics, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
- Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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4
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Gushi S, Balis V. Mitochondrial Inherited Disorders and their Correlation with Neurodegenerative Diseases. Endocr Metab Immune Disord Drug Targets 2024; 24:381-393. [PMID: 37937560 DOI: 10.2174/0118715303250271231018103202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 07/13/2023] [Accepted: 09/15/2023] [Indexed: 11/09/2023]
Abstract
Mitochondria are essential organelles for the survival of a cell because they produce energy. The cells that need more mitochondria are neurons because they perform a variety of tasks that are necessary to support brain homeostasis. The build-up of abnormal proteins in neurons, as well as their interactions with mitochondrial proteins, or MAM proteins, cause serious health issues. As a result, mitochondrial functions, such as mitophagy, are impaired, resulting in the disorders described in this review. They are also due to mtDNA mutations, which alter the heritability of diseases. The topic of disease prevention, as well as the diagnosis, requires further explanation and exploration. Finally, there are treatments that are quite promising, but more detailed research is needed.
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Affiliation(s)
- Sofjana Gushi
- Department of Health Science and Biomedical Science, Metropolitan College - Thessaloniki Campus, Thessaloniki, Greece
| | - Vasileios Balis
- Department of Health Science and Biomedical Science, Metropolitan College - Thessaloniki Campus, Thessaloniki, Greece
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5
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Xu Y, Chiang YH, Ho PC, Vannini N. Mitochondria Dictate Function and Fate of HSCs and T Cells. Cancer Immunol Res 2023; 11:1303-1313. [PMID: 37789763 DOI: 10.1158/2326-6066.cir-22-0685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 01/23/2023] [Accepted: 08/16/2023] [Indexed: 10/05/2023]
Abstract
Hematopoietic stem cells (HSC) and T cells are intimately related, lineage-dependent cell populations that are extensively used as therapeutic products for the treatment of hematologic malignancies and certain types of solid tumors. These cellular therapies can be life-saving treatments; however, their efficacies are often limited by factors influencing their activity and cellular properties. Among these factors is mitochondrial metabolism, which influences the function and fate commitment of both HSCs and T cells. Mitochondria, besides being the "cellular powerhouse," provide metabolic intermediates that are used as substrates for epigenetic modifications and chromatin remodeling, thus, driving cell fate decisions during differentiation. Moreover, mitochondrial fitness and mitochondrial quality control mechanisms are closely related to cellular function, and impairment of these mitochondrial properties associates with cellular dysfunction due to factors such as T-cell exhaustion and aging. Here, we give an overview of the role of mitochondria in shaping the behavior of these lineage-related cell populations. Moreover, we discuss the potential of novel mitochondria-targeting strategies for enhancing HSC- and T cell-based cancer immunotherapies and highlight how design and application of such approaches requires consideration of the metabolic similarities and differences between HSCs and T cells. See related article on p. 1302.
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Affiliation(s)
- Yingxi Xu
- Department of Fundamental Oncology, University of Lausanne, Lausanne, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland
| | - Yi-Hsuan Chiang
- Department of Fundamental Oncology, University of Lausanne, Lausanne, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland
| | - Ping-Chih Ho
- Department of Fundamental Oncology, University of Lausanne, Lausanne, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland
| | - Nicola Vannini
- Department of Fundamental Oncology, University of Lausanne, Lausanne, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland
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6
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Vianello C, Dal Bello F, Shin SH, Schiavon S, Bean C, Magalhães Rebelo AP, Knedlík T, Esfahani EN, Costiniti V, Lacruz RS, Covello G, Munari F, Scolaro T, Viola A, Rampazzo E, Persano L, Zumerle S, Scorrano L, Gianelle A, Giacomello M. High-Throughput Microscopy Analysis of Mitochondrial Membrane Potential in 2D and 3D Models. Cells 2023; 12:cells12071089. [PMID: 37048162 PMCID: PMC10093082 DOI: 10.3390/cells12071089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/24/2023] [Accepted: 04/03/2023] [Indexed: 04/08/2023] Open
Abstract
Recent proteomic, metabolomic, and transcriptomic studies have highlighted a connection between changes in mitochondria physiology and cellular pathophysiological mechanisms. Secondary assays to assess the function of these organelles appear fundamental to validate these -omics findings. Although mitochondrial membrane potential is widely recognized as an indicator of mitochondrial activity, high-content imaging-based approaches coupled to multiparametric to measure it have not been established yet. In this paper, we describe a methodology for the unbiased high-throughput quantification of mitochondrial membrane potential in vitro, which is suitable for 2D to 3D models. We successfully used our method to analyze mitochondrial membrane potential in monolayers of human fibroblasts, neural stem cells, spheroids, and isolated muscle fibers. Moreover, by combining automated image analysis and machine learning, we were able to discriminate melanoma cells from macrophages in co-culture and to analyze the subpopulations separately. Our data demonstrated that our method is a widely applicable strategy for large-scale profiling of mitochondrial activity.
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Affiliation(s)
- Caterina Vianello
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | - Federica Dal Bello
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | - Sang Hun Shin
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | - Sara Schiavon
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | - Camilla Bean
- Department of Medicine, University of Udine, Piazzale Kolbe, 33100 Udine, Italy
| | | | - Tomáš Knedlík
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | | | - Veronica Costiniti
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010, USA
| | - Rodrigo S. Lacruz
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010, USA
| | - Giuseppina Covello
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
| | - Fabio Munari
- Department of Biomedical Sciences, Via Ugo Bassi 58B, 35131 Padova, Italy
- Pediatric Research Institute, Città della Speranza Foundation, Corso Stati Uniti 4 F, 35127 Padova, Italy
| | - Tommaso Scolaro
- Pediatric Research Institute, Città della Speranza Foundation, Corso Stati Uniti 4 F, 35127 Padova, Italy
- Laboratory of Tumor Inflammation and Angiogenesis, Center for Cancer Biology, Department of Oncology, KU Leuven, B3000 Leuven, Belgium
| | - Antonella Viola
- Department of Biomedical Sciences, Via Ugo Bassi 58B, 35131 Padova, Italy
- Pediatric Research Institute, Città della Speranza Foundation, Corso Stati Uniti 4 F, 35127 Padova, Italy
| | - Elena Rampazzo
- Pediatric Research Institute, Città della Speranza Foundation, Corso Stati Uniti 4 F, 35127 Padova, Italy
- Oncohematology, Department of Women’s and Children’s Health, University of Padova, Via Giustiniani 3, 35128 Padova, Italy
| | - Luca Persano
- Pediatric Research Institute, Città della Speranza Foundation, Corso Stati Uniti 4 F, 35127 Padova, Italy
- Oncohematology, Department of Women’s and Children’s Health, University of Padova, Via Giustiniani 3, 35128 Padova, Italy
| | - Sara Zumerle
- Department of Medicine, University of Padova, Via Giustiniani 2, 35128 Padova, Italy
- Veneto Institute of Molecular Medicine, Via Giuseppe Orus 2, 35128 Padova, Italy
| | - Luca Scorrano
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
- Veneto Institute of Molecular Medicine, Via Giuseppe Orus 2, 35128 Padova, Italy
| | - Alessio Gianelle
- National Institute for Nuclear Physics, Padova Division, Via Marzolo 8, 35131 Padova, Italy
| | - Marta Giacomello
- Department of Biology, University of Padova, Via Ugo Bassi 58B, 35131 Padova, Italy
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7
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Targeting mitochondrial impairment for the treatment of cardiovascular diseases: From hypertension to ischemia-reperfusion injury, searching for new pharmacological targets. Biochem Pharmacol 2023; 208:115405. [PMID: 36603686 DOI: 10.1016/j.bcp.2022.115405] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 12/26/2022] [Accepted: 12/28/2022] [Indexed: 01/03/2023]
Abstract
Mitochondria and mitochondrial proteins represent a group of promising pharmacological target candidates in the search of new molecular targets and drugs to counteract the onset of hypertension and more in general cardiovascular diseases (CVDs). Indeed, several mitochondrial pathways result impaired in CVDs, showing ATP depletion and ROS production as common traits of cardiac tissue degeneration. Thus, targeting mitochondrial dysfunction in cardiomyocytes can represent a successful strategy to prevent heart failure. In this context, the identification of new pharmacological targets among mitochondrial proteins paves the way for the design of new selective drugs. Thanks to the advances in omics approaches, to a greater availability of mitochondrial crystallized protein structures and to the development of new computational approaches for protein 3D-modelling and drug design, it is now possible to investigate in detail impaired mitochondrial pathways in CVDs. Furthermore, it is possible to design new powerful drugs able to hit the selected pharmacological targets in a highly selective way to rescue mitochondrial dysfunction and prevent cardiac tissue degeneration. The role of mitochondrial dysfunction in the onset of CVDs appears increasingly evident, as reflected by the impairment of proteins involved in lipid peroxidation, mitochondrial dynamics, respiratory chain complexes, and membrane polarization maintenance in CVD patients. Conversely, little is known about proteins responsible for the cross-talk between mitochondria and cytoplasm in cardiomyocytes. Mitochondrial transporters of the SLC25A family, in particular, are responsible for the translocation of nucleotides (e.g., ATP), amino acids (e.g., aspartate, glutamate, ornithine), organic acids (e.g. malate and 2-oxoglutarate), and other cofactors (e.g., inorganic phosphate, NAD+, FAD, carnitine, CoA derivatives) between the mitochondrial and cytosolic compartments. Thus, mitochondrial transporters play a key role in the mitochondria-cytosol cross-talk by leading metabolic pathways such as the malate/aspartate shuttle, the carnitine shuttle, the ATP export from mitochondria, and the regulation of permeability transition pore opening. Since all these pathways are crucial for maintaining healthy cardiomyocytes, mitochondrial carriers emerge as an interesting class of new possible pharmacological targets for CVD treatments.
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8
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Malas KM, Lambert DS, Heisner JS, Camara AKS, Stowe DF. Time and charge/pH-dependent activation of K + channel-mediated K + influx and K +/H + exchange in guinea pig heart isolated mitochondria; role in bioenergetic stability. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148908. [PMID: 35961396 DOI: 10.1016/j.bbabio.2022.148908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 07/17/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
Mitochondria play an important role not only in producing energy for the cell but also for regulating mitochondrial and cell function depending on the cell's needs and environment. Uptake of cations, anions, and substrates requires a stable, polarized transmembrane charge potential (ΔΨm). Chemiosmosis requires ion exchangers to remove Na+, K+, Ca2+, PO43-, and other charged species that enter mitochondria. Knowledge of the kinetics of mitochondrial (m) cation channels and exchangers is important in understanding their roles in regulating mitochondrial chemiosmosis and bioenergetics. The influx/efflux of K+, the most abundant mitochondrial cation, alters mitochondrial volume and shape by bringing in anions and H2O by osmosis. The effects of K+ uptake through ligand-specific mK+ channels stimulated/inhibited by agonists/antagonists on mitochondrial volume (swelling/contraction) are well known. However, a more important role for K+ influx is likely its effects on H+ cycling and bioenergetics facilitated by mitochondrial (m) K+/H+ exchange (mKHE), though the kinetics and consequences of K+ efflux by KHE are not well described. We hypothesized that a major role of K+ influx/efflux is stimulation of respiration via the influx of H+ by KHE. We proposed to modulate KHE activity by energizing guinea pig heart isolated mitochondria and by altering the mK+ cycle to capture changes in mitochondrial volume, pHm, ΔΨm, and respiration that would reflect a role for H+ influx via KHE to regulate bioenergetics. To test this, mitochondria were suspended in a 150 mM K+ buffer at pH 6.9, or in a 140 mM Cs+ buffer at pH 7.6 or 6.9 with added 10 mM K+, minimal Ca2+ and free of Na+. O2 content was measured by a Clark electrode, and pHm, ΔΨm, and volume, were measured by fluorescence spectrophotometry and light-scattering. Adding pyruvic acid (PA) alone caused increases in volume and respiration and a rapid decrease in the transmembrane pH gradient (ΔpHm = pHin-pHext) at pHext 6.9> > 7.6, so that ΔΨm was charged and maintained. BKCa agonist NS1619 and antagonist paxilline modified these effects, and KHE inhibitor quinine and K+ ionophore valinomycin depolarized ΔΨm. We postulate that K+ efflux-induced H+ influx via KHE causes an inward H+ leak that stimulates respiration, but at buffer pH 6.9 also utilizes the energy of ΔpHm, the smaller component of the overall proton motive force, ΔμH+. Thus ΔpHm establishes and maintains the ΔΨm required for utilization of substrates, entry of all cations, and for oxidative phosphorylation. Thus, K+ influx/efflux appears to play a pivotal role in regulating energetics while maintaining mitochondrial ionic balance and volume homeostasis.
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Affiliation(s)
- Kareem M Malas
- Department of Anesthesiology, Research Division, Medical College of Wisconsin, Milwaukee, WI, USA
| | - David S Lambert
- Department of Anesthesiology, Research Division, Medical College of Wisconsin, Milwaukee, WI, USA
| | - James S Heisner
- Department of Anesthesiology, Research Division, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Amadou K S Camara
- Department of Anesthesiology, Research Division, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA; Cancer Center, Medical College of Wisconsin, Milwaukee, WI, USA
| | - David F Stowe
- Department of Anesthesiology, Research Division, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA; Departments of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Milwaukee, WI, USA; Zablocki Veterans Administration, Research Service, Milwaukee, WI, USA.
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9
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Gottschalk B, Koshenov Z, Waldeck-Weiermair M, Radulović S, Oflaz FE, Hirtl M, Bachkoenig OA, Leitinger G, Malli R, Graier WF. MICU1 controls spatial membrane potential gradients and guides Ca 2+ fluxes within mitochondrial substructures. Commun Biol 2022; 5:649. [PMID: 35778442 PMCID: PMC9249747 DOI: 10.1038/s42003-022-03606-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 06/17/2022] [Indexed: 01/19/2023] Open
Abstract
Mitochondrial ultrastructure represents a pinnacle of form and function, with the inner mitochondrial membrane (IMM) forming isolated pockets of cristae membrane (CM), separated from the inner-boundary membrane (IBM) by cristae junctions (CJ). Applying structured illumination and electron microscopy, a novel and fundamental function of MICU1 in mediating Ca2+ control over spatial membrane potential gradients (SMPGs) between CM and IMS was identified. We unveiled alterations of SMPGs by transient CJ openings when Ca2+ binds to MICU1 resulting in spatial cristae depolarization. This Ca2+/MICU1-mediated plasticity of the CJ further provides the mechanistic bedrock of the biphasic mitochondrial Ca2+ uptake kinetics via the mitochondrial Ca2+ uniporter (MCU) during intracellular Ca2+ release: Initially, high Ca2+ opens CJ via Ca2+/MICU1 and allows instant Ca2+ uptake across the CM through constantly active MCU. Second, MCU disseminates into the IBM, thus establishing Ca2+ uptake across the IBM that circumvents the CM. Under the condition of MICU1 methylation by PRMT1 in aging or cancer, UCP2 that binds to methylated MICU1 destabilizes CJ, disrupts SMPGs, and facilitates fast Ca2+ uptake via the CM.
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Affiliation(s)
- Benjamin Gottschalk
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Zhanat Koshenov
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Markus Waldeck-Weiermair
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Snježana Radulović
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria
| | - Furkan E. Oflaz
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Martin Hirtl
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Olaf A. Bachkoenig
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Gerd Leitinger
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria
| | - Roland Malli
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria ,grid.452216.6BioTechMed Graz, Graz, Austria
| | - Wolfgang F. Graier
- grid.11598.340000 0000 8988 2476Gottfried Schatz Research Center: Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria ,grid.452216.6BioTechMed Graz, Graz, Austria
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10
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Dhokne K, Pandey J, Yadav RM, Ramachandran P, Rath JR, Subramanyam R. Change in the photochemical and structural organization of thylakoids from pea (Pisum sativum) under salt stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2022; 177:46-60. [PMID: 35255419 DOI: 10.1016/j.plaphy.2022.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/02/2022] [Accepted: 02/07/2022] [Indexed: 06/14/2023]
Abstract
Salt can induce adverse effects, primarily on the photosynthetic process, ultimately influencing plant productivity. Still, the impact of salt on the photosynthesis process in terms of supercomplexes organization of thylakoid structure and function is not understood in Pea (Pisum sativum). To understand the structure and function in the leaves and thylakoids under salt (NaCl) treatment, we used various biophysical and biochemical techniques like infrared gas analyzer, chlorophyll a fluorescence, circular dichroism, electron microscopy, blue native gels, and western blots. The net photosynthetic rate, transpiration rate, and stomatal conductance were reduced significantly, whereas the water use efficiency was enhanced remarkably under high salt conditions (200 mM NaCl). The photochemical efficiency of both photosystem (PS) I and II was reduced in high salt by inhibiting their donor and acceptor sides. Interestingly the non-photochemical quenching (NPQ) is reduced in high salt; however, the non-regulated energy dissipation (NO) of PSII increased, leading to inactivation of PSII. The obtained results exhibit inhibition of NAD(P)H dehydrogenase (NDH) mediated pathway-dependent cyclic electron transport under salinity caused a decrease in proton motive force of ΔpH and Δψ. Further, the electron micrographs show the disorganization of grana thylakoids under salt stress. Furthermore, the macro-organization and supercomplexes of thylakoids were significantly affected by high salt. Specifically, the mega complexes, PSII-LHCII, PSI-LHCI, and NDH complexes were notably reduced, ultimately altering the electron transport. The reaction center proteins of oxygen-evolving complexes, D1 and D2 proteins were affected to high salt indicating changes in photochemical activities.
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Affiliation(s)
- Kunal Dhokne
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India; Department of Botany, Shri Vitthal Rukmini College, Sawana, Yavatmal, 445001, India
| | - Jayendra Pandey
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Ranay Mohan Yadav
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Pavithra Ramachandran
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Jyoti Ranjan Rath
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India.
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11
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Zeviani M, Carelli V. Mitochondrial Retinopathies. Int J Mol Sci 2021; 23:210. [PMID: 35008635 PMCID: PMC8745158 DOI: 10.3390/ijms23010210] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/14/2021] [Accepted: 12/18/2021] [Indexed: 12/13/2022] Open
Abstract
The retina is an exquisite target for defects of oxidative phosphorylation (OXPHOS) associated with mitochondrial impairment. Retinal involvement occurs in two ways, retinal dystrophy (retinitis pigmentosa) and subacute or chronic optic atrophy, which are the most common clinical entities. Both can present as isolated or virtually exclusive conditions, or as part of more complex, frequently multisystem syndromes. In most cases, mutations of mtDNA have been found in association with mitochondrial retinopathy. The main genetic abnormalities of mtDNA include mutations associated with neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) sometimes with earlier onset and increased severity (maternally inherited Leigh syndrome, MILS), single large-scale deletions determining Kearns-Sayre syndrome (KSS, of which retinal dystrophy is a cardinal symptom), and mutations, particularly in mtDNA-encoded ND genes, associated with Leber hereditary optic neuropathy (LHON). However, mutations in nuclear genes can also cause mitochondrial retinopathy, including autosomal recessive phenocopies of LHON, and slowly progressive optic atrophy caused by dominant or, more rarely, recessive, mutations in the fusion/mitochondrial shaping protein OPA1, encoded by a nuclear gene on chromosome 3q29.
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Affiliation(s)
- Massimo Zeviani
- Department of Neurosciences, The Clinical School, University of Padova, 35128 Padova, Italy
- Veneto Institute of Molecular Medicine, Via Orus 2, 35128 Padova, Italy
| | - Valerio Carelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40139 Bologna, Italy
- Programma di Neurogenetica, IRCCS Istituto delle Scienze Neurologiche di Bologna, Via Altura 6, 40139 Bologna, Italy
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12
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Song Y, Villeneuve DL. AOP Report: Uncoupling of Oxidative Phosphorylation Leading to Growth Inhibition via Decreased Cell Proliferation. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2021; 40:2959-2967. [PMID: 34416019 PMCID: PMC10620627 DOI: 10.1002/etc.5197] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 08/18/2021] [Indexed: 05/22/2023]
Abstract
This report describes a novel adverse outcome pathway (AOP) on uncoupling of oxidative phosphorylation (OXPHOS) leading to growth inhibition via decreased adenosine triphosphate (ATP) pool and cell proliferation (AOPWiki, AOP263). Oxidative phosphorylation is a major metabolic process that produces the primary form of energy (ATP) supporting various biological functions. Uncoupling of OXPHOS is a widely recognized mode of action of many chemicals and is known to affect growth via different biological processes. Capturing these events in an AOP can greatly facilitate mechanistic understanding and hazard assessment of OXPHOS uncouplers and growth regulators in eukaryotes. The four proposed key events in this AOP are intentionally generalized to cover a wide range of organisms and stressors. Three out of four events can be measured using in vitro high-throughput bioassays, whereas for most organisms, growth inhibition can also be measured in a high-throughput format using standard in vivo toxicity test protocols. The key events and key event relationships in this AOP are further assessed for weight of evidence using evolved Bradford-Hill considerations. The overall confidence levels range from moderate to high with only a few uncertainties and inconsistencies. The chemical applicability domain of the AOP mainly contains protonophores uncouplers, which can be predicated using the quantitative structure-activity relationship (QSAR) approach and validated using in vitro high-throughput bioassays. The biological domain of the AOP basically covers all eukaryotes. The AOP described in this report is part of a larger AOP network linking uncoupling of OXPHOS to growth inhibition, and is considered highly relevant and applicable to both human health and ecological risk assessments.
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Affiliation(s)
- You Song
- Norwegian Institute for Water Research, Oslo, Norway
| | - Daniel L. Villeneuve
- Great Lakes Toxicology and Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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13
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Zunica ERM, Axelrod CL, Cho E, Spielmann G, Davuluri G, Alexopoulos SJ, Beretta M, Hoehn KL, Dantas WS, Stadler K, King WT, Pergola K, Irving BA, Langohr IM, Yang S, Hoppel CL, Gilmore LA, Kirwan JP. Breast cancer growth and proliferation is suppressed by the mitochondrial targeted furazano[3,4-b]pyrazine BAM15. Cancer Metab 2021; 9:36. [PMID: 34627389 PMCID: PMC8502397 DOI: 10.1186/s40170-021-00274-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 09/22/2021] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Enhanced metabolic plasticity and diversification of energy production is a hallmark of highly proliferative breast cancers. This contributes to poor pharmacotherapy efficacy, recurrence, and metastases. We have previously identified a mitochondrial-targeted furazano[3,4-b]pyrazine named BAM15 that selectively reduces bioenergetic coupling efficiency and is orally available. Here, we evaluated the antineoplastic properties of uncoupling oxidative phosphorylation from ATP production in breast cancer using BAM15. METHODS The anticancer effects of BAM15 were evaluated in human triple-negative MDA-MB-231 and murine luminal B, ERα-negative EO771 cells as well as in an orthotopic allograft model of highly proliferative mammary cancer in mice fed a standard or high fat diet (HFD). Untargeted transcriptomic profiling of MDA-MB-231 cells was conducted after 16-h exposure to BAM15. Additionally, oxidative phosphorylation and electron transfer capacity was determined in permeabilized cells and excised tumor homogenates after treatment with BAM15. RESULTS BAM15 increased proton leak and over time, diminished cell proliferation, migration, and ATP production in both MDA-MB-231 and EO771 cells. Additionally, BAM15 decreased mitochondrial membrane potential, while inducing apoptosis and reactive oxygen species accumulation in MDA-MB-231 and EO771 cells. Untargeted transcriptomic profiling of MDA-MB-231 cells further revealed inhibition of signatures associated with cell survival and energy production by BAM15. In lean mice, BAM15 lowered body weight independent of food intake and slowed tumor progression compared to vehicle-treated controls. In HFD mice, BAM15 reduced tumor growth relative to vehicle and calorie-restricted weight-matched controls mediated in part by impaired cell proliferation, mitochondrial respiratory function, and ATP production. LC-MS/MS profiling of plasma and tissues from BAM15-treated animals revealed distribution of BAM15 in adipose, liver, and tumor tissue with low abundance in skeletal muscle. CONCLUSIONS Collectively, these data indicate that mitochondrial uncoupling may be an effective strategy to limit proliferation of aggressive forms of breast cancer. More broadly, these findings highlight the metabolic vulnerabilities of highly proliferative breast cancers which may be leveraged in overcoming poor responsiveness to existing therapies.
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Affiliation(s)
- Elizabeth R M Zunica
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Department of Nutrition, Case Western Reserve University, Cleveland, OH, 44109, USA.,Clinical Oncology and Metabolism, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Christopher L Axelrod
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Department of Translational Services, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Eunhan Cho
- School of Kinesiology, Louisiana State University, Baton Rouge, LA, USA
| | | | - Gangarao Davuluri
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Sarcopenia and Malnutrition Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Stephanie J Alexopoulos
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Martina Beretta
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Kyle L Hoehn
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia
| | - Wagner S Dantas
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA
| | - Krisztian Stadler
- Department of Oxidative Stress and Disease, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - William T King
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Department of Translational Services, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Kathryn Pergola
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Department of Translational Services, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Brian A Irving
- School of Kinesiology, Louisiana State University, Baton Rouge, LA, USA
| | - Ingeborg M Langohr
- Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Shengping Yang
- Department of Biostatistics, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Charles L Hoppel
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA.,Department of Pharmacology, Case Western Reserve University, Cleveland, OH, 44109, USA
| | - L Anne Gilmore
- Clinical Oncology and Metabolism, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA.,Department of Clinical Nutrition, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - John P Kirwan
- Integrated Physiology and Molecular Medicine Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. .,Department of Nutrition, Case Western Reserve University, Cleveland, OH, 44109, USA. .,Department of Translational Services, Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA.
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14
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Cytotoxic activity of cholesterol oxidase produced by Streptomyces sp. AKHSS against cancerous cell lines: mechanism of action in HeLa cells. World J Microbiol Biotechnol 2021; 37:141. [PMID: 34287712 DOI: 10.1007/s11274-021-03076-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 05/20/2021] [Indexed: 11/27/2022]
Abstract
Re-occurrence of cancer is the major drawback for the currently available anticancer therapies. Therefore, study of an efficient enzyme, cholesterol oxidase produced by various kinds of microbes especially obtained from unexplored marine actinobacterial species against human cancer cell lines and understanding its mechanism of action helps to identify an irreversible and potent anticancer agent. The cytotoxic potential of cholesterol oxidase produced by a marine Streptomyces sp. AKHSS against four different human cancer cell lines was demonstrated through MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. Fluorescent confocal microscopy and flow cytometry based experiments were performed to understand the efficiency of the enzymatic action on HeLa cells. Further, the apoptotic related proteins were detected through western blotting. Interestingly, the enzyme exhibited potent cytotoxicity at very low concentrations (0.093-0.327 µM) against all the cells tested. Fluorescent confocal microscopy revealed the morphological variations induced by the enzyme on cancer cell lines such as the formation of lipid droplets and condensation of nuclei. The enzyme treated cell-free extracts of HeLa cells analyzed through gas chromatography mass spectrometry showed the depletion of membrane cholesterol and the presence of substituted enzyme oxidized product, cholest-4-ene-3-one. The enzyme had induced significant inhibitory effects on the cell viability such as cell cycle arrest (G1 phase), apoptosis and rise of reactive oxygen species as evident through flow cytometry. Besides, hyperpolarization of mitochondrial membrane, reduced rates of phosphorylation of pAkt and the expression of apoptotic death markers like Fas, Fas L, caspases (8 and 3) and PARP-1 were recorded in the enzyme treated HeLa cells. Thus, cholesterol oxidase purified from a marine Streptomyces sp. AKHSS exhibits potent cytotoxicity at very low concentrations against human cancer cell lines. All the ex vivo experiments portrayed the substantial inhibitory effect of the enzyme on HeLa cells suggesting that cholesterol oxidase of Streptomyces sp. AKHSS could be a prominent cancer chemotherapeutic agent.
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15
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Ouillon N, Sokolov EP, Otto S, Rehder G, Sokolova IM. Effects of variable oxygen regimes on mitochondrial bioenergetics and reactive oxygen species production in a marine bivalve, Mya arenaria. J Exp Biol 2021; 224:jeb.237156. [PMID: 33436367 DOI: 10.1242/jeb.237156] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 01/06/2021] [Indexed: 12/12/2022]
Abstract
Estuarine and coastal benthic organisms often experience fluctuations in oxygen levels that can negatively impact their mitochondrial function and aerobic metabolism. To study these impacts, we exposed a common sediment-dwelling bivalve, the soft-shell clam Mya arenaria, for 21 days to chronic hypoxia (P O2 ∼4.1 kPa), cyclic hypoxia (P O2 ∼12.7-1.9 kPa, mean 5.7 kPa) or normoxia (P O2 ∼21.1 kPa). pH was manipulated to mimic the covariation in CO2/pH and oxygen levels in coastal hypoxic zones. Mitochondrial respiration, including proton leak, the capacity for oxidative phosphorylation (OXPHOS), the maximum activity of the electron transport system (ETS), reactive oxygen species (ROS) production, and activity and oxygen affinity of cytochrome c oxidase (CCO) were assessed. Acclimation to constant hypoxia did not affect the studied mitochondrial traits except for a modest decrease in the OXPHOS coupling efficiency. Cyclic hypoxia had no effect on OXPHOS or ETS capacity, but increased proton leak and lowered mitochondrial OXPHOS coupling efficiency. Furthermore, mitochondria of clams acclimated to cyclic hypoxia had higher rates of ROS generation compared with the clams acclimated to normoxia or chronic hypoxia. CCO activity was upregulated under cyclic hypoxia, but oxygen affinity of CCO did not change. These findings indicate that long-term cyclic hypoxia has a stronger impact on the mitochondria of M. arenaria than chronic hypoxia and might lead to impaired ATP synthesis, higher costs of mitochondrial maintenance and oxidative stress. These changes might negatively affect populations of M. arenaria in the coastal Baltic Sea under increasing hypoxia pressure.
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Affiliation(s)
- Natascha Ouillon
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, Rostock 18057, Germany
| | - Eugene P Sokolov
- Leibniz Institute for Baltic Research, Leibniz Science Campus Phosphorus Research Rostock, Rostock 18119, Germany
| | - Stefan Otto
- Department of Marine Chemistry, Leibniz Institute for Baltic Research, Rostock 18119, Germany
| | - Gregor Rehder
- Department of Marine Chemistry, Leibniz Institute for Baltic Research, Rostock 18119, Germany
| | - Inna M Sokolova
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, Rostock 18057, Germany .,Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
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16
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Hou C, Metcalfe NB, Salin K. Is mitochondrial reactive oxygen species production proportional to oxygen consumption? A theoretical consideration. Bioessays 2021; 43:e2000165. [PMID: 33543487 DOI: 10.1002/bies.202000165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 12/19/2020] [Accepted: 01/12/2021] [Indexed: 11/07/2022]
Abstract
It has been assumed that at the whole organismal level, the mitochondrial reactive oxygen species (ROS) production is proportional to the oxygen consumption. Recently, a number of researchers have challenged this assumption, based on the observation that the ROS production per unit oxygen consumed in the resting state of mitochondrial respiration is much higher than that in the active state. Here, we develop a simple model to investigate the validity of the assumption and the challenge of it. The model highlights the significance of the time budget that mitochondria operate in the different respiration states. The model suggests that under three physiologically possible conditions, the difference in ROS production per unit oxygen consumed between the respiration states does not upset the proportionality between the whole animal ROS production and oxygen consumption. The model also shows that mitochondrial uncoupling generally enhances the proportionality.
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Affiliation(s)
- Chen Hou
- Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri, USA
| | - Neil B Metcalfe
- Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr Building, University of Glasgow, Glasgow, UK
| | - Karine Salin
- Department of Environment and Resources, Institut français de recherche pour l'exploitation de la mer, Plouzané, France
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17
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Raven JA. Determinants, and implications, of the shape and size of thylakoids and cristae. JOURNAL OF PLANT PHYSIOLOGY 2021; 257:153342. [PMID: 33385618 DOI: 10.1016/j.jplph.2020.153342] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/25/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Thylakoids are flattened sacs isolated from other membranes; cristae are attached to the rest of the inner mitochondrial membrane by the crista junction, but the crista lumen is separated from the intermembrane space. The shape of thylakoids and cristae involves membranes with small (5-30 nm) radii of curvature. While the mechanism of curvature is not entirely clear, it seems to be largely a function of Curt proteins in thylakoids and Mitochondrial Organising Site and Crista Organising Centre proteins and oligomeric FOF1 ATP synthase in cristae. A subordinate, or minimal, role is attributable to lipids with areas of their head group area greater (convex leaflet) or smaller (concave leaflet) than the area of the lipid tail; examples of the latter group are monogalactosyldiglyceride in thylakoids and cardiolipin in cristae. The volume per unit area on the lumen side of the membrane is less than that of the chloroplast stroma or cyanobacterial cytosol for thylakoids, and mitochondrial matrix for cristae. A low volume per unit area of thylakoids and cristae means a small lumen width that is the average of wider spaces between lipid parts of the membranes and the narrower gaps dominated by extra-membrane components of transmembrane proteins. These structural constraints have important implications for the movement of the electron carriers plastocyanin and cytochrome c6 (thylakoids) and cytochrome c (cristae) and hence the separation of the membrane-associated electron donors to, and electron acceptors from, these water-soluble electron carriers. The donor/acceptor pairs, are the cytochrome fb6Fenh complex and P700+ in thylakoids, and Complex III and Complex IV of cristae. The other energy flux parallel to the membranes is that of the proton motive force generated by redox-powered H+ pumps into the lumen to the proton motive force use in ATP synthesis by H+ flux from the lumen through the ATP synthase. For both the electron transport and proton motive force movement, concentration differences of reduced and oxidised electron carriers and protonated and deprotonated pH buffers are involved. The need for diffusion along a congested route of these energy transfer agents may limit the separation of sources and sinks parallel to the membranes of thylakoids and cristae.
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Affiliation(s)
- John A Raven
- Division of Plant Science, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK; University of Technology, Sydney, Climate Change Cluster, Faculty of Science, Sydney, Ultimo, NSW, 2007, Australia; School of Biological Sciences, University of Western Australia, Crawley, WA, 6009, Australia.
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18
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Lin J, Wang L. Oxidative Stress in Oocytes and Embryo Development: Implications for In Vitro Systems. Antioxid Redox Signal 2020; 34:1394-1406. [PMID: 33115254 DOI: 10.1089/ars.2020.8209] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Significance: To improve the outcomes of in vitro culture of human oocytes and embryos, the dynamic balance and roles of reactive oxygen species (ROS) in folliculogenesis and embryo development merit further consideration. Recent Advances: ROS have been demonstrated to participate in various signaling processes and act as mediators in various physiological events in germ cells. An imbalance between pro-oxidants and antioxidants seems to explain the high failure rate of assisted reproduction. Critical Issues: Oxidative stress induced by excessive ROS or insufficient antioxidant protection can cause detrimental effects on both male and female reproduction. In this study, oxidative stress in folliculogenesis and embryo development are summarized and the multiple modifiable factors of in vitro culture systems in relation to ROS are discussed. Future Directions: More studies are needed to establish an optimal redox state in in vitro culture systems for human oocytes and embryos.
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Affiliation(s)
- Jing Lin
- Laboratory for Reproductive Immunology, Hospital and Institute of Obstetrics and Gynecology, Shanghai Medical College, Fudan University, Shanghai, China
- Academy of Integrative Medicine, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Female Reproductive Endocrine-Related Diseases, Shanghai, China
| | - Ling Wang
- Laboratory for Reproductive Immunology, Hospital and Institute of Obstetrics and Gynecology, Shanghai Medical College, Fudan University, Shanghai, China
- Academy of Integrative Medicine, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Female Reproductive Endocrine-Related Diseases, Shanghai, China
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19
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Response to "Molecular-level understanding of biological energy coupling and transduction: Response to "Chemiosmotic misunderstandings"". Biophys Chem 2020; 269:106512. [PMID: 33307371 DOI: 10.1016/j.bpc.2020.106512] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 11/15/2020] [Accepted: 11/24/2020] [Indexed: 01/31/2023]
Abstract
The most recent contribution by Sunil Nath in these pages is, mostly, a repetition of his previous claims regarding failures of the chemiosmotic hypotheses, supplemented with some fresh misunderstandings of the points I had sought to clarify in my previous critique. Considerable portions rehash 50-60 years-old controversies, with no apparent understanding that the current chemiosmotic hypothesis, while birthed by Mitchell, differs from Mitchell's details in many respects. As such, Nath has devoted much time dealing with a few errors (or wrong hypotheses) by Mitchell (in a few places I would almost venture to say "typographical mistakes in typesetting") and presents the ensuing conclusions as "refutations" of the chemiosmotic paradigm, completely neglecting that such details (such as the precise H+/ATP or H+:O ratios) are completely irrelevant to the reality (or not) of an electron-transport chain that uses the free energy liberated by electron-transfer to remove H+ from a compartment, to which it returns through and ATP synthase which uses the energy in that spontaneous return to drive ATP synthesis. The thermodynamical mistakes and misunderstandings of the relevant literature present in Nath's new contribution are so numerous, though, that I feel forced to call the attention of the readers of "Biophysical Chemistry" to them.
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20
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Li T, Liu C, Zhen X, Yu Y, Qiao J. Actinomycin D causes oocyte maturation failure by inhibiting chromosome separation and spindle assembly†. Biol Reprod 2020; 104:94-105. [PMID: 33106855 DOI: 10.1093/biolre/ioaa170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 06/08/2020] [Accepted: 09/21/2020] [Indexed: 11/12/2022] Open
Abstract
Actinomycin D (ActD) has been considered as one of the most effective and safe chemotherapeutic medications for treating a number of cancers. Although ActD has been used in the treatment of gynecological tumors and pediatric tumors for more than 50 years, the toxic effects of ActD on mammalian oocytes remain unknown. In this study, the influence of ActD on mouse and human oocyte maturation and the possible mechanisms were investigated. Notably, ActD inhibited oocyte maturation and arrested oocytes at the metaphase I (MI) stage in a dose-dependent manner. In addition, ActD arrested oocyte maturation when the oocytes were treated at different successive stages, including the germinal vesicle (GV), germinal vesicle breakdown, and MI stages. In ActD-treated oocytes, disordered chromosome condensation and irregular spindle assembly occurred, resulting in incomplete chromosome segregation and oocytes arresting at the MI phase; these results possibly occurred because ActD triggered the formation of reactive oxygen species, resulting in DNA damage and decreased ATP in mouse GV oocytes. Besides, in vivo treatment with ActD also inhibited mouse oocyte maturation. Similar effects were seen in human oocytes. Collectively, our results indicated that ActD exposure disrupted oocyte maturation by increasing DNA damage, which is a finding that might help with optimizing future methods for female fertility preservation before undergoing chemotherapy.
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Affiliation(s)
- Tianjie Li
- Department of Obstetrics and Gynecology, Beijing Key laboratory of Reproductive Endocrinology and Assisted Reproductive Technology and Key Laboratory of Assisted Reproduction, Ministry of Education, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China.,Department of Obstetrics and Gynecology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Changyu Liu
- Department of Obstetrics and Gynecology, Beijing Key laboratory of Reproductive Endocrinology and Assisted Reproductive Technology and Key Laboratory of Assisted Reproduction, Ministry of Education, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China
| | - Xiumei Zhen
- Department of Obstetrics and Gynecology, Beijing Key laboratory of Reproductive Endocrinology and Assisted Reproductive Technology and Key Laboratory of Assisted Reproduction, Ministry of Education, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China
| | - Yang Yu
- Department of Obstetrics and Gynecology, Beijing Key laboratory of Reproductive Endocrinology and Assisted Reproductive Technology and Key Laboratory of Assisted Reproduction, Ministry of Education, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China
| | - Jie Qiao
- Department of Obstetrics and Gynecology, Beijing Key laboratory of Reproductive Endocrinology and Assisted Reproductive Technology and Key Laboratory of Assisted Reproduction, Ministry of Education, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China
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21
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Mitochondrial electron transport chain: Oxidative phosphorylation, oxidant production, and methods of measurement. Redox Biol 2020; 37:101674. [PMID: 32811789 PMCID: PMC7767752 DOI: 10.1016/j.redox.2020.101674] [Citation(s) in RCA: 474] [Impact Index Per Article: 118.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/24/2020] [Accepted: 07/31/2020] [Indexed: 12/14/2022] Open
Abstract
The mitochondrial electron transport chain utilizes a series of electron transfer reactions to generate cellular ATP through oxidative phosphorylation. A consequence of electron transfer is the generation of reactive oxygen species (ROS), which contributes to both homeostatic signaling as well as oxidative stress during pathology. In this graphical review we provide an overview of oxidative phosphorylation and its inter-relationship with ROS production by the electron transport chain. We also outline traditional and novel translational methodology for assessing mitochondrial energetics in health and disease.
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22
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Halder A, Yadav K, Aggarwal A, Singhal N, Sandhir R. Activation of TNFR1 and TLR4 following oxygen glucose deprivation promotes mitochondrial fission in C6 astroglial cells. Cell Signal 2020; 75:109714. [PMID: 32693013 DOI: 10.1016/j.cellsig.2020.109714] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 06/30/2020] [Accepted: 07/12/2020] [Indexed: 12/14/2022]
Abstract
Astrocytes have emerged as active players in the innate immune response triggered by various types of insults. Recent literature suggests that mitochondria are key participants in innate immunity. The present study investigates the role of ischemia-induced innate immune response on p65/PGC-1α mediated mitochondrial dynamics in C6 astroglial cells. OGD conditions induced astroglial differentiation in C6 cells and increased the expression of hypoxia markers; HIF-1α, HO-1 and Cox4i2. OGD conditions resulted in induction of innate immune response in terms of expression of TNFR1 and TLR4 along with increase in IL-6 and TNF-α levels. OGD conditions resulted in decreased expression of I-κB with a concomitant increase in phos-p65 levels. The expression of PGC-1α, a key regulator of mitochondrial biogenesis, was also increased. Immunochemical staining suggested that phos-p65 and PGC-1α was co-localized. Studies on mitochondrial fusion (Mfn-1) and fission (DRP1) markers revealed shift toward fission. In addition, mitochondrial membrane potential decreased with increased DNA degradation and apoptosis confirming mitochondrial fission under OGD conditions. However, inhibition of phos-p65 by MG132 reduced the co-localization of phos-p65/ PGC-1α and significantly increased the Mfn-1 expression. The findings demonstrate the involvement of TNFR1 and TLR4 mediated immune response followed by interaction between phos-p65 and PGC-1α in promoting fission in C6 cells under hypoxic condition.
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Affiliation(s)
- Avishek Halder
- Department of Biochemistry, Basic Medical Science Block II, Panjab University, Chandigarh, India
| | - Kamalendra Yadav
- National Agri-Food Biotechnology Institute, Sector 81, Mohali, Punjab, India
| | - Aanchal Aggarwal
- National Agri-Food Biotechnology Institute, Sector 81, Mohali, Punjab, India
| | - Nitin Singhal
- National Agri-Food Biotechnology Institute, Sector 81, Mohali, Punjab, India
| | - Rajat Sandhir
- Department of Biochemistry, Basic Medical Science Block II, Panjab University, Chandigarh, India.
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23
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Silva PJ. Chemiosmotic misunderstandings. Biophys Chem 2020; 264:106424. [PMID: 32717593 DOI: 10.1016/j.bpc.2020.106424] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 06/19/2020] [Accepted: 06/21/2020] [Indexed: 02/04/2023]
Abstract
Recent publications have questioned the appropriateness of the chemiosmotic theory, a key tenet of modern bioenergetics originally described by Mitchell and since widely improved upon and applied. In one of them, application of Gauss' law to a model charge distribution in mitochondria was argued to refute the possibility of ATP generation through H+ movement in the absence of a counterion, whereas a different author advocated, for other reasons, the impossibility of chemiosmosis and proposed that a novel energy-generation scheme (referred to as "murburn") relying on superoxide-catalyzed (or superoxide-promoted) ADP phosphorylation would operate instead. In this letter, those proposals are critically examined and found to be inconsistent with established experimental data and new theoretical calculations.
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Affiliation(s)
- Pedro J Silva
- FP-ENAS/Fac. de Ciências da Saúde, Universidade Fernando Pessoa, Porto, Portugal; UCIBIO@REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina, Universidade do Porto, Porto, Portugal.
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24
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Kinetic coupling of the respiratory chain with ATP synthase, but not proton gradients, drives ATP production in cristae membranes. Proc Natl Acad Sci U S A 2020; 117:2412-2421. [PMID: 31964824 DOI: 10.1073/pnas.1917968117] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Mitochondria have a characteristic ultrastructure with invaginations of the inner membrane called cristae that contain the protein complexes of the oxidative phosphorylation system. How this particular morphology of the respiratory membrane impacts energy conversion is currently unknown. One proposed role of cristae formation is to facilitate the establishment of local proton gradients to fuel ATP synthesis. Here, we determined the local pH values at defined sublocations within mitochondria of respiring yeast cells by fusing a pH-sensitive GFP to proteins residing in different mitochondrial subcompartments. Only a small proton gradient was detected over the inner membrane in wild type or cristae-lacking cells. Conversely, the obtained pH values did barely permit ATP synthesis in a reconstituted system containing purified yeast F1F0 ATP synthase, although, thermodynamically, a sufficiently high driving force was applied. At higher driving forces, where robust ATP synthesis was observed, a P-side pH value of 6 increased the ATP synthesis rate 3-fold compared to pH 7. In contrast, when ATP synthase was coreconstituted with an active proton-translocating cytochrome oxidase, ATP synthesis readily occurred at the measured, physiological pH values. Our study thus reveals that the morphology of the inner membrane does not influence the subcompartmental pH values and is not necessary for robust oxidative phosphorylation in mitochondria. Instead, it is likely that the dense packing of the oxidative phosphorylation complexes in the cristae membranes assists kinetic coupling between proton pumping and ATP synthesis.
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25
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Edwards A, Palm F, Layton AT. A model of mitochondrial O 2 consumption and ATP generation in rat proximal tubule cells. Am J Physiol Renal Physiol 2019; 318:F248-F259. [PMID: 31790302 DOI: 10.1152/ajprenal.00330.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxygen tension in the kidney is mostly determined by O2 consumption (Qo2), which is, in turn, closely linked to tubular Na+ reabsorption. The objective of the present study was to develop a model of mitochondrial function in the proximal tubule (PT) cells of the rat renal cortex to gain more insight into the coupling between Qo2, ATP formation (GATP), ATP hydrolysis (QATP), and Na+ transport in the PT. The present model correctly predicts in vitro and in vivo measurements of Qo2, GATP, and ATP and Pi concentrations in PT cells. Our simulations suggest that O2 levels are not rate limiting in the proximal convoluted tubule, absent large metabolic perturbations. The model predicts that the rate of ATP hydrolysis and cytoplasmic pH each substantially regulate the GATP-to-Qo2 ratio, a key determinant of the number of Na+ moles actively reabsorbed per mole of O2 consumed. An isolated increase in QATP or in cytoplasmic pH raises the GATP-to-Qo2 ratio. Thus, variations in Na+ reabsorption and pH along the PT may, per se, generate axial heterogeneities in the efficiency of mitochondrial metabolism and Na+ transport. Our results also indicate that the GATP-to-Qo2 ratio is strongly impacted not only by H+ leak permeability, which reflects mitochondrial uncoupling, but also by K+ leak pathways. Simulations suggest that the negative impact of increased uncoupling in the diabetic kidney on mitochondrial metabolic efficiency is partly counterbalanced by increased rates of Na+ transport and ATP consumption. This model provides a framework to investigate the role of mitochondrial dysfunction in acute and chronic renal diseases.
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Affiliation(s)
- Aurélie Edwards
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Fredrik Palm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Anita T Layton
- Departments of Mathematics, Biomedical Engineering, and Medicine, Duke University, Durham, North Carolina.,Departments of Applied Mathematics and Biology, School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada
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26
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Wei-LaPierre L, Dirksen RT. Isolating a reverse-mode ATP synthase-dependent mechanism of mitoflash activation. J Gen Physiol 2019; 151:708-713. [PMID: 31010808 PMCID: PMC6571996 DOI: 10.1085/jgp.201912358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Wei-LaPierre and Dirksen discuss new work investigating the molecular events underlying mitoflash biogenesis.
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Affiliation(s)
- Lan Wei-LaPierre
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
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27
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Haumann J, Camara AKS, Gadicherla AK, Navarro CD, Boelens AD, Blomeyer CA, Dash RK, Boswell MR, Kwok WM, Stowe DF. Slow Ca 2+ Efflux by Ca 2+/H + Exchange in Cardiac Mitochondria Is Modulated by Ca 2+ Re-uptake via MCU, Extra-Mitochondrial pH, and H + Pumping by F OF 1-ATPase. Front Physiol 2019; 9:1914. [PMID: 30804812 PMCID: PMC6378946 DOI: 10.3389/fphys.2018.01914] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 12/18/2018] [Indexed: 02/04/2023] Open
Abstract
Mitochondrial (m) Ca2+ influx is largely dependent on membrane potential (ΔΨm), whereas mCa2+ efflux occurs primarily via Ca2+ ion exchangers. We probed the kinetics of Ca2+/H+ exchange (CHEm) in guinea pig cardiac muscle mitochondria. We tested if net mCa2+ flux is altered during a matrix inward H+ leak that is dependent on matrix H+ pumping by ATPm hydrolysis at complex V (FOF1-ATPase). We measured [Ca2+]m, extra-mitochondrial (e) [Ca2+]e, ΔΨm, pHm, pHe, NADH, respiration, ADP/ATP ratios, and total [ATP]m in the presence or absence of protonophore dinitrophenol (DNP), mitochondrial uniporter (MCU) blocker Ru360, and complex V blocker oligomycin (OMN). We proposed that net slow influx/efflux of Ca2+ after adding DNP and CaCl2 is dependent on whether the ΔpHm gradient is/is not maintained by reciprocal outward H+ pumping by complex V. We found that adding CaCl2 enhanced DNP-induced increases in respiration and decreases in ΔΨm while [ATP]m decreased, ΔpHm gradient was maintained, and [Ca2+]m continued to increase slowly, indicating net mCa2+ influx via MCU. In contrast, with complex V blocked by OMN, adding DNP and CaCl2 caused larger declines in ΔΨm as well as a slow fall in pHm to near pHe while [Ca2+]m continued to decrease slowly, indicating net mCa2+ efflux in exchange for H+ influx (CHEm) until the ΔpHm gradient was abolished. The kinetics of slow mCa2+ efflux with slow H+ influx via CHEm was also observed at pHe 6.9 vs. 7.6 by the slow fall in pHm until ΔpHm was abolished; if Ca2+ reuptake via the MCU was also blocked, mCa2+ efflux via CHEm became more evident. Of the two components of the proton electrochemical gradient, our results indicate that CHEm activity is driven largely by the ΔpHm chemical gradient with H+ leak, while mCa2+ entry via MCU depends largely on the charge gradient ΔΨm. A fall in ΔΨm with excess mCa2+ loading can occur during cardiac cell stress. Cardiac cell injury due to mCa2+ overload may be reduced by temporarily inhibiting FOF1-ATPase from pumping H+ due to ΔΨm depolarization. This action would prevent additional slow mCa2+ loading via MCU and permit activation of CHEm to mediate efflux of mCa2+. HIGHLIGHTSWe examined how slow mitochondrial (m) Ca2+ efflux via Ca2+/H+ exchange (CHEm) is triggered by matrix acidity after a rapid increase in [Ca2+]m by adding CaCl2 in the presence of dinitrophenol (DNP) to permit H+ influx, and oligomycin (OMN) to block H+ pumping via FOF1-ATP synthase/ase (complex V). Declines in ΔΨm and pHm after DNP and added CaCl2 were larger when complex V was blocked. [Ca2+]m slowly increased despite a fall in ΔΨm but maintained pHm when H+ pumping by complex V was permitted. [Ca2+]m slowly decreased and external [Ca2+]e increased with declines in both ΔΨm and pHm when complex V was blocked. ATPm hydrolysis supports a falling pHm and redox state and promotes a slow increase in [Ca2+]m. After rapid Ca2+ influx due to a bolus of CaCl2, slow mCa2+ efflux by CHEm occurs directly if pHe is low.
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Affiliation(s)
- Johan Haumann
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Amadou K S Camara
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Ashish K Gadicherla
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Christopher D Navarro
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Age D Boelens
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Christoph A Blomeyer
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Ranjan K Dash
- Department of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, WI, United States
| | - Michael R Boswell
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Wai-Meng Kwok
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States.,Cancer Center, Medical College of Wisconsin, Milwaukee, WI, United States.,Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - David F Stowe
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States.,Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United States.,Department of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, WI, United States.,Research Service, Veterans Affairs Medical Center, Milwaukee, WI, United States
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28
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Pan S, Conaway S, Deshpande DA. Mitochondrial regulation of airway smooth muscle functions in health and pulmonary diseases. Arch Biochem Biophys 2019; 663:109-119. [PMID: 30629957 DOI: 10.1016/j.abb.2019.01.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/28/2018] [Accepted: 01/04/2019] [Indexed: 12/24/2022]
Abstract
Mitochondria are important for airway smooth muscle physiology due to their diverse yet interconnected roles in calcium handling, redox regulation, and cellular bioenergetics. Increasing evidence indicates that mitochondria dysfunction is intimately associated with airway diseases such as asthma, IPF and COPD. In these pathological conditions, increased mitochondrial ROS, altered bioenergetics profiles, and calcium mishandling contribute collectively to changes in cellular signaling, gene expression, and ultimately changes in airway smooth muscle contractile/proliferative properties. Therefore, understanding the basic features of airway smooth muscle mitochondria and their functional contribution to airway biology and pathology are key to developing novel therapeutics for airway diseases. This review summarizes the recent findings of airway smooth muscle mitochondria focusing on calcium homeostasis and redox regulation, two key determinants of physiological and pathological functions of airway smooth muscle.
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Affiliation(s)
- Shi Pan
- Center for Translational Medicine, Jane and Leonard Korman Lung Center, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Stanley Conaway
- Center for Translational Medicine, Jane and Leonard Korman Lung Center, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Deepak A Deshpande
- Center for Translational Medicine, Jane and Leonard Korman Lung Center, Thomas Jefferson University, Philadelphia, PA, 19107, USA.
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29
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Lu T, Shi JW, Sun ZP, Qi MF, Liu YF, Li TL. Response of linear and cyclic electron flux to moderate high temperature and high light stress in tomato. J Zhejiang Univ Sci B 2018; 18:635-648. [PMID: 28681588 DOI: 10.1631/jzus.b1600286] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To evaluate the possible photoprotection mechanisms of cyclic and linear electron flux (CEF and LEF) under specific high temperature and high light (HH) stress. METHODS Six-leaf-stage tomato seedlings ("Liaoyuanduoli", n=160) were divided into four parts: Part 1, served as control under 25 °C, 500 µmol/(m2·s); Part 2, spayed with distilled water (H2O) under 35 °C, 1000 µmol/(m2·s) (HH); Part 3, spayed with 100 µmol/L diuron (DCMU, CEF inhibitor) under HH; Part 4, spayed with 60 µmol/L methyl viologen (MV, LEF inhibitor) under HH. Energy conversion, photosystem I (PSI), and PSII activity, and trans-thylakoid membrane proton motive force were monitored during the treatment of 5 d and of the recovering 10 d. RESULTS HH decreased photochemical reaction dissipation (P) and the maximal photochemical efficiency of PSII (Fv/Fm), and increased the excitation energy distribution coefficient of PSII (β); DCMU and MV aggravated the partition imbalance of the excitation energy (γ) and the photoinhibition degree. With prolonged DCMU treatment time, electron transport rate and quantum efficiency of PSI (ETRI and YI) significantly decreased whereas acceptor and donor side limitation of PSI (YNA and YND) increased. MV led to a significant decline and accession of yield of regulated and non-regulated energy YNPQ and YNO, respectively. Membrane integrity and ATPase activity were reduced by HH stress, and DCMU and MV enhanced inhibitory actions. CONCLUSIONS The protective effects of CEF and LEF were mediated to a certain degree by meliorations in energy absorption and distribution as well as by maintenance of thylakoid membrane integrity and ATPase activity.
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Affiliation(s)
- Tao Lu
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
| | - Jie-Wei Shi
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
| | - Zhou-Ping Sun
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
| | - Ming-Fang Qi
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
| | - Yu-Feng Liu
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
| | - Tian-Lai Li
- College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.,Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang 110866, China.,Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang 110866, China
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30
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In Mitochondria ?-Actin Regulates mtDNA Transcription and Is Required for Mitochondrial Quality Control. iScience 2018; 3:226-237. [PMID: 30428323 PMCID: PMC6137402 DOI: 10.1016/j.isci.2018.04.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 03/27/2018] [Accepted: 04/26/2018] [Indexed: 12/11/2022] Open
Abstract
In eukaryotic cells, actin regulates both cytoplasmic and nuclear functions. However, whether actin-based structures are present in the mitochondria and are involved in mitochondrial functions has not been investigated. Here, using wild-type ?-actin +/+ and knockout (KO) ?-actin ?/? mouse embryonic fibroblasts we show evidence for the defect in maintaining mitochondrial membrane potential (MMP) in ?-actin-null cells. MMP defects were associated with impaired mitochondrial DNA (mtDNA) transcription and nuclear oxidative phosphorylation (OXPHOS) gene expression. Using super-resolution microscopy we provided direct evidence on the presence of ?-actin-containing structures inside mitochondria. Large aggregates of TFAM-stained nucleoids were observed in bulb-shaped mitochondria in KO cells, suggesting defects in mitochondrial nucleoid segregation without ?-actin. The observation that mitochondria-targeted ?-actin rescued mtDNA transcription and MMP suggests an indispensable functional role of a mitochondrial ?-actin pool necessary for mitochondrial quality control.
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31
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You DG, Lee HR, Kim WK, Kim HJ, Lee GY, Yoo YD. Hepatitis C virus p7 induces mitochondrial depolarization of isolated liver mitochondria. Mol Med Rep 2017; 16:9533-9538. [PMID: 29039530 DOI: 10.3892/mmr.2017.7809] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/20/2017] [Indexed: 11/06/2022] Open
Abstract
Hepatitis C virus (HCV)‑encoded protein p7 is a viroporin that acts as an ion channel and is indispensable for HCV particle production. Although the main target of HCV p7 is the endoplasmic reticulum, it also targets mitochondria. HCV‑infected cells show mitochondrial depolarization and ATP depletion; however, the function of HCV p7 in mitochondria is not fully understood. The present study demonstrated that treatment of isolated mouse liver mitochondria with the synthesized HCV p7 protein induced mitochondrial dysfunction. It also demonstrated that HCV p7 targeted isolated mouse liver mitochondria and induced mitochondrial depolarization. In addition, HCV p7 triggered matrix acidification and, ultimately, a decrease in ATP synthesis in isolated mitochondria. These findings indicate that targeting of mitochondria by HCV p7 in infected cells causes mitochondrial dysfunction to support HCV particle production. The present study provided evidence for the role of HCV p7 in mitochondria, and may lead to the development of novel strategies for HCV therapy.
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Affiliation(s)
- Deok-Gyun You
- Laboratory of Molecular Cell Biology, Graduate School of Medicine, College of Medicine, Korea University, Seoul 02841, Republic of Korea
| | - Hye-Ra Lee
- Laboratory of Molecular Cell Biology, Graduate School of Medicine, College of Medicine, Korea University, Seoul 02841, Republic of Korea
| | - Won-Ki Kim
- Department of Neuroscience, College of Medicine, Korea University, Seoul 02841, Republic of Korea
| | - Hyung Jung Kim
- Department of Internal Medicine, Yonsei University College of Medicine, Yonsei University Health System, Seoul 03722, Republic of Korea
| | - Gi Young Lee
- Laboratory of Molecular Cell Biology, Graduate School of Medicine, College of Medicine, Korea University, Seoul 02841, Republic of Korea
| | - Young Do Yoo
- Laboratory of Molecular Cell Biology, Graduate School of Medicine, College of Medicine, Korea University, Seoul 02841, Republic of Korea
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32
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Biomarkers of chondriome topology and function: implications for the extension of healthy aging. Biogerontology 2016; 18:201-215. [PMID: 28028686 DOI: 10.1007/s10522-016-9673-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Accepted: 12/19/2016] [Indexed: 12/27/2022]
Abstract
Multiple theories of aging (e.g., free radical, error catastrophe, mitochondrial) are complementary but fail to provide adequate models that comprehensively predict lifelong aging processes and that are valid across species. Hayflick (PLoS Genet 3(12):2351-2354, 2007) described six universal characteristics of aging that focus upon post-reproductive molecular entropy. Here we present a thermodynamic potential model of aging in which the energetic and topological properties of the mitochondrion drive functional and structural stabilities within living systems. Using multivariate regressions of physiological assessments from the National Health and Nutrition Examination Survey, VO2 max consistently declined with age regardless of gender or race, although it had a significantly greater decline for African American females. Percent fat (negative), hematocrit (negative), and urine creatinine (negative) were strongly and significantly associated with VO2 max and male aging, although cholesterol (positive) was an additional factor for African American males. Bioenergetic measures such as VO2 max can be useful for physical assessments to promote healthy aging.
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33
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Saito R, Takeuchi A, Himeno Y, Inagaki N, Matsuoka S. A simulation study on the constancy of cardiac energy metabolites during workload transition. J Physiol 2016; 594:6929-6945. [PMID: 27530892 DOI: 10.1113/jp272598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 08/03/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The cardiac energy metabolites such as ATP, phosphocreatine, ADP and NADH are kept relatively constant during physiological cardiac workload transition. How this is accomplished is not yet clarified, though Ca2+ has been suggested to be one of the possible mechanisms. We constructed a detailed mathematical model of cardiac mitochondria based on experimental data and studied whether known Ca2+ -dependent regulation mechanisms play roles in the metabolite constancy. Model simulations revealed that the Ca2+ -dependent regulation mechanisms have important roles under the in vitro condition of isolated mitochondria where malate and glutamate were mitochondrial substrates, while they have only a minor role and the composition of substrates has marked influence on the metabolite constancy during workload transition under the simulated in vivo condition where many substrates exist. These results help us understand the regulation mechanisms of cardiac energy metabolism during physiological cardiac workload transition. ABSTRACT The cardiac energy metabolites such as ATP, phosphocreatine, ADP and NADH are kept relatively constant over a wide range of cardiac workload, though the mechanisms are not yet clarified. One possible regulator of mitochondrial metabolism is Ca2+ , because it activates several mitochondrial enzymes and transporters. Here we constructed a mathematical model of cardiac mitochondria, including oxidative phosphorylation, substrate metabolism and ion/substrate transporters, based on experimental data, and studied whether the Ca2+ -dependent activation mechanisms play roles in metabolite constancy. Under the in vitro condition of isolated mitochondria, where malate and glutamate were used as mitochondrial substrates, the model well reproduced the Ca2+ and inorganic phosphate (Pi ) dependences of oxygen consumption, NADH level and mitochondrial membrane potential. The Ca2+ -dependent activations of the aspartate/glutamate carrier and the F1 Fo -ATPase, and the Pi -dependent activation of Complex III were key factors in reproducing the experimental data. When the mitochondrial model was implemented in a simple cardiac cell model, simulation of workload transition revealed that cytoplasmic Ca2+ concentration ([Ca2+ ]cyt ) within the physiological range markedly increased NADH level. However, the addition of pyruvate or citrate attenuated the Ca2+ dependence of NADH during the workload transition. Under the simulated in vivo condition where malate, glutamate, pyruvate, citrate and 2-oxoglutarate were used as mitochondrial substrates, the energy metabolites were more stable during the workload transition and NADH level was almost insensitive to [Ca2+ ]cyt . It was revealed that mitochondrial substrates have a significant influence on metabolite constancy during cardiac workload transition, and Ca2+ has only a minor role under physiological conditions.
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Affiliation(s)
- Ryuta Saito
- Biology Research Laboratories, Mitsubishi Tanabe Pharma Corporation, Saitama, 335-8505, Japan.,Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Ayako Takeuchi
- Department of Integrative and Systems Physiology, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.,Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Yukiko Himeno
- Department of Life Science, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Satoshi Matsuoka
- Department of Integrative and Systems Physiology, Faculty of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan.,Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
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34
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Normoyle KP, Kim M, Farahvar A, Llano D, Jackson K, Wang H. The emerging neuroprotective role of mitochondrial uncoupling protein-2 in traumatic brain injury. Transl Neurosci 2015; 6:179-186. [PMID: 28123803 PMCID: PMC4936626 DOI: 10.1515/tnsci-2015-0019] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/20/2015] [Indexed: 12/11/2022] Open
Abstract
Traumatic brain injury (TBI) is a multifaceted disease with intrinsically complex heterogeneity and remains a significant clinical challenge to manage. TBI model systems have demonstrated many mechanisms that contribute to brain parenchymal cell death, including glutamate and calcium toxicity, oxidative stress, inflammation, and mitochondrial dysfunction. Mitochondria are critically regulated by uncoupling proteins (UCP), which allow protons to leak back into the matrix and thus reduce the mitochondrial membrane potential by dissipating the proton motive force. This uncoupling of oxidative phosphorylation from adenosine triphosphate (ATP) synthesis is potentially critical for protection against cellular injury as a result of TBI and stroke. A greater understanding of the underlying mechanism or mechanisms by which uncoupling protein-2 (UCP2) functions to maintain or optimize mitochondrial function, and the conditions which precipitate the failure of these mechanisms, would inform future research and treatment strategies. We posit that UCP2-mediated function underlies the physiological response to neuronal stress associated with traumatic and ischemic injury and that clinical development of UCP2-targeted treatment would significantly impact these patient populations. With a focus on clinical relevance in TBI, we synthesize current knowledge concerning UCP2 and its potential neuroprotective role and apply this body of knowledge to current and potential treatment modalities.
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Affiliation(s)
- Kieran P Normoyle
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA; College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Child Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Miri Kim
- College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Arash Farahvar
- Department of Neurosurgery, Carle Foundation Hospital, Urbana, IL, USA
| | - Daniel Llano
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Department of Neurology, Carle Foundation Hospital, Urbana, IL, USA; The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Kevin Jackson
- The Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Thermal Neuroscience Laboratory (TNL), Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Huan Wang
- Department of Neurology, Carle Foundation Hospital, Urbana, IL, USA; Thermal Neuroscience Laboratory (TNL), Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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35
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Pätsi J, Kervinen M, Kytövuori L, Majamaa K, Hassinen IE. Effects of pathogenic mutations in membrane subunits of mitochondrial Complex I on redox activity and proton translocation studied by modeling in Escherichia coli. Mitochondrion 2015; 22:23-30. [PMID: 25747201 DOI: 10.1016/j.mito.2015.02.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 02/19/2015] [Accepted: 02/24/2015] [Indexed: 01/12/2023]
Abstract
Effects of Complex I mutations were studied by modeling in NuoH, NuoJ or NuoK subunits of Escherichia coli NDH-1 by simultaneous optical monitoring of deamino-NADH oxidation and proton translocation and fitting to the data a model equation of transmembrane proton transport. A homolog of the ND1-E24 LHON/MELAS mutation caused 95% inhibition of d-NADH oxidation and proton translocation. The NuoJ-Y59F replacement decreased proton translocation. The NuoK-E72Q mutation lowered the enzyme activity, but proton pumping could be rescued by the double mutation NuoK-E72Q/I39D. Moving the NuoK-E72/E36 pair one helix turn towards the periplasm did not affect redox activity but decreased proton pumping.
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Affiliation(s)
- Jukka Pätsi
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland.
| | - Marko Kervinen
- Department of Ophthalmology and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland.
| | - Laura Kytövuori
- Department of Neurology and Medical Research Center, Oulu University Hospital and University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland.
| | - Kari Majamaa
- Department of Neurology and Medical Research Center, Oulu University Hospital and University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland.
| | - Ilmo E Hassinen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland.
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Padmaraj D, Pande R, Miller JH, Wosik J, Zagozdzon-Wosik W. Mitochondrial membrane studies using impedance spectroscopy with parallel pH monitoring. PLoS One 2014; 9:e101793. [PMID: 25010497 PMCID: PMC4091947 DOI: 10.1371/journal.pone.0101793] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/11/2014] [Indexed: 11/18/2022] Open
Abstract
A biological microelectromechanical system (BioMEMS) device was designed to study complementary mitochondrial parameters important in mitochondrial dysfunction studies. Mitochondrial dysfunction has been linked to many diseases, including diabetes, obesity, heart failure and aging, as these organelles play a critical role in energy generation, cell signaling and apoptosis. The synthesis of ATP is driven by the electrical potential across the inner mitochondrial membrane and by the pH difference due to proton flux across it. We have developed a tool to study the ionic activity of the mitochondria in parallel with dielectric measurements (impedance spectroscopy) to gain a better understanding of the properties of the mitochondrial membrane. This BioMEMS chip includes: 1) electrodes for impedance studies of mitochondria designed as two- and four-probe structures for optimized operation over a wide frequency range and 2) ion-sensitive field effect transistors for proton studies of the electron transport chain and for possible monitoring other ions such as sodium, potassium and calcium. We have used uncouplers to depolarize the mitochondrial membrane and disrupt the ionic balance. Dielectric spectroscopy responded with a corresponding increase in impedance values pointing at changes in mitochondrial membrane potential. An electrical model was used to describe mitochondrial sample’s complex impedance frequency dependencies and the contribution of the membrane to overall impedance changes. The results prove that dielectric spectroscopy can be used as a tool for membrane potential studies. It can be concluded that studies of the electrochemical parameters associated with mitochondrial bioenergetics may render significant information on various abnormalities attributable to these organelles.
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Affiliation(s)
- Divya Padmaraj
- Electrical and Computer Engineering Department, University of Houston, Houston, Texas, United States of America
- Texas Center for Superconductivity, University of Houston, Houston, Texas, United States of America
| | - Rohit Pande
- Electrical and Computer Engineering Department, University of Houston, Houston, Texas, United States of America
- Texas Center for Superconductivity, University of Houston, Houston, Texas, United States of America
| | - John H. Miller
- Texas Center for Superconductivity, University of Houston, Houston, Texas, United States of America
- Physics Department, University of Houston, Houston, Texas, United States of America
| | - Jarek Wosik
- Electrical and Computer Engineering Department, University of Houston, Houston, Texas, United States of America
- Texas Center for Superconductivity, University of Houston, Houston, Texas, United States of America
| | - Wanda Zagozdzon-Wosik
- Electrical and Computer Engineering Department, University of Houston, Houston, Texas, United States of America
- * E-mail:
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Bociąga-Jasik M, Polus A, Góralska J, Czech U, Gruca A, Śliwa A, Garlicki A, Mach T, Dembińska-Kieć A. Metabolic effects of the HIV protease inhibitor--saquinavir in differentiating human preadipocytes. Pharmacol Rep 2014; 65:937-50. [PMID: 24145088 DOI: 10.1016/s1734-1140(13)71075-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Revised: 03/12/2013] [Indexed: 11/30/2022]
Abstract
BACKGROUND The iatrogenic, HIV-related lipodystrophy is associated with development of the significant metabolic and cardiovascular complications. The underlying mechanisms of antiretroviral (ARV) drugs are not completely explored. METHODS The aim of the study was to characterize effects of the protease inhibitor (PI)--saquinavir (SQV) on metabolic functions, and gene expression during differentiation in cells (Chub-S7) culture. RESULTS SQV in concentrations observed during antiretroviral therapy (ART) significantly decreased mitochondrial membrane potential (MMP), oxygen consumption and ATP generation. The effects were greater in already differentiated cells. This was accompanied by characteristic changes in the expression of the genes involved in endoplasmic reticulum (ER) stress, and differentiation (lipid droplet formation) process such as: WNT10a, C/EBPa, AFT4, CIDEC, ADIPOQ, LPIN1. CONCLUSIONS The results indicate that SQV affects not only metabolic (mitochondrial) activity of adipocytes, but affects the expression of genes related to differentiation and to a lesser extent to cell apoptosis.
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Affiliation(s)
- Monika Bociąga-Jasik
- Chair of Gastroenterology, Hepatology and Infectious Diseases, Department of Infectious Diseases, Jagiellonian University, Collegium Medicum, Sniadeckich 5, PL 31-501 Kraków, Poland.
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Modulation of mitochondrial bioenergetics in a skeletal muscle cell line model of mitochondrial toxicity. Redox Biol 2014; 2:224-33. [PMID: 24494197 PMCID: PMC3909783 DOI: 10.1016/j.redox.2013.12.028] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 12/24/2013] [Accepted: 12/24/2013] [Indexed: 12/03/2022] Open
Abstract
Mitochondrial toxicity is increasingly being implicated as a contributing factor to many xenobiotic-induced organ toxicities, including skeletal muscle toxicity. This has necessitated the need for predictive in vitro models that are able to sensitively detect mitochondrial toxicity of chemical entities early in the research and development process. One such cell model involves substituting galactose for glucose in the culture media. Since cells cultured in galactose are unable to generate sufficient ATP from glycolysis they are forced to rely on mitochondrial oxidative phosphorylation for ATP generation and consequently are more sensitive to mitochondrial perturbation than cells grown in glucose. The aim of this study was to characterise cellular growth, bioenergetics and mitochondrial toxicity of the L6 rat skeletal muscle cell line cultured in either high glucose or galactose media. L6 myoblasts proliferated more slowly when cultured in galactose media, although they maintained similar levels of ATP. Galactose cultured L6 cells were significantly more sensitive to classical mitochondrial toxicants than glucose-cultured cells, confirming the cells had adapted to galactose media. Analysis of bioenergetic function with the XF Seahorse extracellular flux analyser demonstrated that oxygen consumption rate (OCR) was significantly increased whereas extracellular acidification rate (ECAR), a measure of glycolysis, was decreased in cells grown in galactose. Mitochondria operated closer to state 3 respiration and had a lower mitochondrial membrane potential and basal mitochondrial O2•– level compared to cells in the glucose model. An antimycin A (AA) dose response revealed that there was no difference in the sensitivity of OCR to AA inhibition between glucose and galactose cells. Importantly, cells in glucose were able to up-regulate glycolysis, while galactose cells were not. These results confirm that L6 cells are able to adapt to growth in a galactose media model and are consequently more susceptible to mitochondrial toxicants. L6 cells grown in glucose and galactose as model to detect skeletal muscle mitochondrial toxicity. L6 cells grown in galactose rely on mitochondrial oxidative phosphorylation for ATP production. Galactose cells are unable to use glycolysis to produce ATP following mitochondrial inhibition.
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Key Words
- AA, antimycin A
- ANT, adenine nucleotide translocase
- CPD, cumulative population doublings
- ECAR, extracellular acidification rate
- ETC, electron transport chain
- Extracellular flux analysis
- FCCP, Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone
- FSC, forward scatter
- Galactose
- Mitochondria
- O2•–, superoxide
- OCR, oxygen consumption rate
- OXPHOS, oxidative phosphorylation
- Oligo, oligomycin
- PD, population doublings
- PPP, pentose phosphate pathway
- RCR, respiratory control ratio
- SSC, side scatter
- Skeletal muscle toxicity
- TCA, tricarboxylic acid cycle
- UCPs, uncoupling proteins
- XF, extracellular flux
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Ivanina AV, Sokolova IM. Interactive effects of pH and metals on mitochondrial functions of intertidal bivalves Crassostrea virginica and Mercenaria mercenaria. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2013; 144-145:303-309. [PMID: 24211794 DOI: 10.1016/j.aquatox.2013.10.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 10/11/2013] [Accepted: 10/16/2013] [Indexed: 06/02/2023]
Abstract
Intertidal bivalves experience broad fluctuations of environmental temperature, pH and oxygen content which could change their intracellular pH. They are also exposed to trace metals such as cadmium (Cd) and copper (Cu) that accumulate in their tissues and may negatively affect mitochondrial functions and bioenergetics. We determined the interactive effects of pH and trace metals (25 μM Cd or Cu) on mitochondrial functions (including respiration and membrane potentials in both ADP-stimulated (state 3) and resting (state 4) states) of two common marine bivalves, the hard clams (Mercenaria mercenaria) and eastern oysters (Crassostrea virginica). In the absence of the trace metals, mitochondrial functions of C. virginica and M. mercenaria were insensitive to pH in a broad physiologically relevant range (6.6-7.8). Mitochondrial respiration was generally suppressed by 25 μM Cd or Cu (with the stronger effects observed for ADP-stimulated compared to the resting respiration) while the mitochondrial membrane potential was unaffected. pH modulated the effects of Cu and Cd on mitochondrial respiration of the bivalves. In oysters, Cu suppressed ADP-stimulated mitochondrial respiration at high and low pH values (6.6 and 7.8, respectively), but had no effect in the intermediate pH range (7.0-7.4). In clams, the negative effect of Cu on ADP-stimulated respiration was only observed at extremely high pH (7.8). A decrease in pH was also protective against Cd in mitochondria of clams and oysters. In clams, 25 μM Cd suppressed ADP-stimulated respiration at all pH; however, at low pH (6.6-7.0) this suppression was paralleled by a decrease in the rates of proton leak thereby effectively restoring mitochondrial coupling. In oysters, the inhibitory effects of Cd on ADP-stimulated respiration were fully abolished at low pH (6.6-7.0). This indicates that moderate acidosis (such as occurs during exposure to air, extreme salinities or elevated CO2 levels in the intertidal zone) may have a beneficial side-effect of protecting mitochondria of clams and oysters against the toxic effects of trace metals in polluted estuaries.
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Affiliation(s)
- Anna V Ivanina
- Department of Biology, University of North Carolina at Charlotte, Charlotte, NC, USA
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Korzeniewski B. Regulation of oxidative phosphorylation during work transitions results from its kinetic properties. J Appl Physiol (1985) 2013; 116:83-94. [PMID: 24157529 DOI: 10.1152/japplphysiol.00759.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The regulation of oxidative phosphorylation (OXPHOS) during work transitions in skeletal muscle and heart is still not well understood. Different computer models of this process have been developed that are characterized by various kinetic properties. In the present research-polemic theoretical study it is argued that models belonging to one group (Model A), which predict that among OXPHOS complexes complex III keeps almost all of the metabolic control over oxygen consumption (Vo2) and involve a strong complex III activation by inorganic phosphate (Pi), lead to the conclusion that an increase in Pi is the main mechanism responsible for OXPHOS activation (feedback-activation mechanism). Models belonging to another group (Model B), which were developed to take into account an approximately uniform distribution of metabolic control over Vo2 among particular OXPHOS complexes (complex I, complex III, complex IV, ATP synthase, ATP/ADP carrier, phosphate carrier) encountered in experimental studies in isolated mitochondria, predict that all OXPHOS complexes are directly activated in parallel with ATP usage and NADH supply by some external cytosolic factor/mechanism during rest-to-work or low-to-high work transitions in skeletal muscle and heart ("each-step-activation" mechanism). Model B demonstrates that different intensities of each-step activation can account for the very different (slopes of) phenomenological Vo2-ADP relationships observed in various skeletal muscles and heart. Thus they are able to explain the differences in the regulation of OXPHOS during work transitions between skeletal muscle (where moderate changes in ADP take place) and intact heart in vivo (where ADP is essentially constant).
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
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Deng C, Zhang D, Pan X, Chang F, Wang S. Toxic effects of mercury on PSI and PSII activities, membrane potential and transthylakoid proton gradient in Microsorium pteropus. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2013; 127:1-7. [PMID: 23920143 DOI: 10.1016/j.jphotobiol.2013.07.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 07/10/2013] [Accepted: 07/11/2013] [Indexed: 10/26/2022]
Abstract
Mercury (Hg) is one of the top toxic metals in environment and it poses a great risk to organisms. This study aimed to elucidate the toxic effects of Hg(2+) on energy conversion of photosystem I (PSI) and photosystem II (PSII), membrane potential and proton gradient of Microsorium pteropus (an aquatic plant species). Contents of chlorophyll a, chlorophyll b and carotenoids, quantum yield and electron transfer of PSI and PSII of M. pteropus exposed to various concentrations of Hg(2+) were measured. With increasing Hg(2+) concentration, quantum yield and electron transport of PSI [Y(I) and ETR(I)] and PSII [Y(II) and ETR(II)] decreased whereas limitation of donor side of PSI [Y(ND)] increased. At ⩾165μgL(-1) Hg(2+), quantum yield of non-light-induced non-photochemical fluorescence quenching in PSII [Y(NO)] significantly increased but quantum yield of light-induced non-photochemical fluorescence quenching [Y(NPQ)] decreased. Membrane potential (Δψ) and proton gradient (ΔpH) of M. pteropus were reduced significantly at 330μg L(-1) Hg(2+) compared to control. Mercury exposure affected multiple sites in PSII and PSI of M. pteropus.
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Affiliation(s)
- Chunnuan Deng
- Key Lab of Plateau Lake Ecology & Global Change, College of Tourism and Geographic Science, Yunnan Provincial Key Laboratory of Plateau Geographical Process and Environmental Change, Yunnan Normal University, Kunming 650500, China; Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
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Ripple MO, Kim N, Springett R. Mammalian complex I pumps 4 protons per 2 electrons at high and physiological proton motive force in living cells. J Biol Chem 2013; 288:5374-80. [PMID: 23306206 DOI: 10.1074/jbc.m112.438945] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial complex I couples electron transfer between matrix NADH and inner-membrane ubiquinone to the pumping of protons against a proton motive force. The accepted proton pumping stoichiometry was 4 protons per 2 electrons transferred (4H(+)/2e(-)) but it has been suggested that stoichiometry may be 3H(+)/2e(-) based on the identification of only 3 proton pumping units in the crystal structure and a revision of the previous experimental data. Measurement of proton pumping stoichiometry is challenging because, even in isolated mitochondria, it is difficult to measure the proton motive force while simultaneously measuring the redox potentials of the NADH/NAD(+) and ubiquinol/ubiquinone pools. Here we employ a new method to quantify the proton motive force in living cells from the redox poise of the bc(1) complex measured using multiwavelength cell spectroscopy and show that the correct stoichiometry for complex I is 4H(+)/2e(-) in mouse and human cells at high and physiological proton motive force.
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Affiliation(s)
- Maureen O Ripple
- Department of Radiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA
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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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Korzeniewski B. Computer-aided studies on the regulation of oxidative phosphorylation during work transitions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:274-85. [DOI: 10.1016/j.pbiomolbio.2011.08.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 07/12/2011] [Accepted: 08/06/2011] [Indexed: 11/30/2022]
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Cha CY, Nakamura Y, Himeno Y, Wang J, Fujimoto S, Inagaki N, Earm YE, Noma A. Ionic mechanisms and Ca2+ dynamics underlying the glucose response of pancreatic β cells: a simulation study. ACTA ACUST UNITED AC 2011; 138:21-37. [PMID: 21708953 PMCID: PMC3135323 DOI: 10.1085/jgp.201110611] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To clarify the mechanisms underlying the pancreatic β-cell response to varying glucose concentrations ([G]), electrophysiological findings were integrated into a mathematical cell model. The Ca2+ dynamics of the endoplasmic reticulum (ER) were also improved. The model was validated by demonstrating quiescent potential, burst–interburst electrical events accompanied by Ca2+ transients, and continuous firing of action potentials over [G] ranges of 0–6, 7–18, and >19 mM, respectively. These responses to glucose were completely reversible. The action potential, input impedance, and Ca2+ transients were in good agreement with experimental measurements. The ionic mechanisms underlying the burst–interburst rhythm were investigated by lead potential analysis, which quantified the contributions of individual current components. This analysis demonstrated that slow potential changes during the interburst period were attributable to modifications of ion channels or transporters by intracellular ions and/or metabolites to different degrees depending on [G]. The predominant role of adenosine triphosphate–sensitive K+ current in switching on and off the repetitive firing of action potentials at 8 mM [G] was taken over at a higher [G] by Ca2+- or Na+-dependent currents, which were generated by the plasma membrane Ca2+ pump, Na+/K+ pump, Na+/Ca2+ exchanger, and TRPM channel. Accumulation and release of Ca2+ by the ER also had a strong influence on the slow electrical rhythm. We conclude that the present mathematical model is useful for quantifying the role of individual functional components in the whole cell responses based on experimental findings.
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Affiliation(s)
- Chae Young Cha
- Biosimulation Project, Ritsumeikan University, Kusatsu, Shiga, Japan
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Role of mitochondrial phosphate carrier in metabolism-secretion coupling in rat insulinoma cell line INS-1. Biochem J 2011; 435:421-30. [PMID: 21265734 DOI: 10.1042/bj20101708] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In pancreatic β-cells, glucose-induced mitochondrial ATP production plays an important role in insulin secretion. The mitochondrial phosphate carrier PiC is a member of the SLC25 (solute carrier family 25) family and transports Pi from the cytosol into the mitochondrial matrix. Since intramitochondrial Pi is an essential substrate for mitochondrial ATP production by complex V (ATP synthase) and affects the activity of the respiratory chain, Pi transport via PiC may be a rate-limiting step for ATP production. We evaluated the role of PiC in metabolism-secretion coupling in pancreatic β-cells using INS-1 cells manipulated to reduce PiC expression by siRNA (small interfering RNA). Consequent reduction of the PiC protein level decreased glucose (10 mM)-stimulated insulin secretion, the ATP:ADP ratio in the presence of 10 mM glucose and elevation of intracellular calcium concentration in response to 10 mM glucose without affecting the mitochondrial membrane potential (Δψm) in INS-1 cells. In experiments using the mitochondrial fraction of INS-1 cells in the presence of 1 mM succinate, PiC down-regulation decreased ATP production at various Pi concentrations ranging from 0.001 to 10 mM, but did not affect Δψm at 3 mM Pi. In conclusion, the Pi supply to mitochondria via PiC plays a critical role in ATP production and metabolism-secretion coupling in INS-1 cells.
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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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Fridlyand LE, Phillipson LH. Mechanisms of glucose sensing in the pancreatic β-cell: A computational systems-based analysis. Islets 2011; 3:224-30. [PMID: 21814042 PMCID: PMC3219158 DOI: 10.4161/isl.3.5.16409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Pancreatic β-cells respond to rising blood glucose by increasing oxidative metabolism, leading to an increased ATP/ADP ratio in the cytoplasm with a subsequent influx of calcium and the eventual secretion of insulin. The mechanisms of glucose sensing in the pancreatic β-cell involve the coupling of cytoplasmic and mitochondrial processes. Our analysis, based on mathematical models of data from multiple sources has implications for β-cell function and the treatment of type 2 diabetes (Fridlyand and Philipson, 2010). This β-cell glucose response model correctly predicts changes in the ATP/ADP ratio, cytoplasmic and mitochondrial calcium levels, and other metabolic parameters in response to alterations in substrate delivery at steady-state and during cytoplasmic calcium oscillations. Here we consider how peculiarities of β-cell pathways that result in dysfunction can be a consequence of specific mechanisms of glucose sensitivity, using our computational systems-based analysis. We found that the mitochondrial membrane potential must be relatively low in β-cells compared with other cell types to permit precise mitochondrial regulation of the cytoplasmic ATP/ADP ratio. This key difference may follow from a relative reduction in cellular respiratory activity. Our analysis additionally demonstrates how activity of lactate dehydrogenase, uncoupling proteins, and the redox shuttles all working in concert can regulate β-cell function. We further show that a decreased mitochondrial membrane potential may lead to a low rate of production of reactive oxygen species in β-cells under physiological conditions. This computational systems analysis aids in providing a more complete understanding of the complex process of β-cell glucose sensing.
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Onizuka S, Tamura R, Hosokawa N, Kawasaki Y, Tsuneyoshi I. Local anesthetics depolarize mitochondrial membrane potential by intracellular alkalization in rat dorsal root ganglion neurons. Anesth Analg 2010; 111:775-83. [PMID: 20686005 DOI: 10.1213/ane.0b013e3181e9f03b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Although it has been reported that local anesthetics, especially lidocaine, are cytotoxic, the mechanism is unclear. Depolarization of the mitochondrial membrane potential (DeltaPsim), one of the markers of mitochondrial failure, is regulated by the proton electrochemical gradient (Delta H(+)). Therefore, intracellular pH ([pH]in) and mitochondrial pH ([pH]m) are important factors for modifying DeltaPsim. However, the effects of local anesthetics on [pH]in and [pH]m are unclear. To investigate mitochondrial responses to local anesthetics, we simultaneously measured [pH]m and [pH]in, along with DeltaPsim. METHODS The ratiometric fluorescent probe JC-1 and HPTS were used for the simultaneous measurements of DeltaPsim with [pH]in in rat dorsal root ganglion neurons. A carboxy-SNARF-1 fluorescent probe was used to measure [pH]m. Lidocaine, mepivacaine, bupivacaine, procaine, QX-314, a charged form of lidocaine, and ammonium chloride (NH(4)Cl) were evaluated. RESULTS DeltaPsim was depolarized and [pH]in was increased by lidocaine, mepivacaine, bupivacaine, and procaine in a dose-dependent manner. Significantly, a relationship between DeltaPsim and [pH]in was observed for lidocaine, mepivacaine, bupivacaine, procaine, and NH(4)Cl perfusion. In contrast, QX-314 did not change DeltaPsim or [pH]in. In low-pH saline (pH6) and in the presence of a weak acid, lidocaine failed to increase [pH]in or depolarize DeltaPsim. The [pH]m was also increased by lidocaine, mepivacaine, bupivacaine, procaine, and NH(4)Cl. CONCLUSION These results demonstrate that uncharged (base) forms of local anesthetics induce DeltaPsim depolarization. One of the causes is intracellular and mitochondrial alkalization.
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Affiliation(s)
- Shin Onizuka
- Department of Anesthesiology and Faculty of Medicine, University of Miyazaki, Kiyotake, Miyazaki 889-1692, Japan
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Fridlyand LE, Philipson LH. Glucose sensing in the pancreatic beta cell: a computational systems analysis. Theor Biol Med Model 2010; 7:15. [PMID: 20497556 PMCID: PMC2896931 DOI: 10.1186/1742-4682-7-15] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 05/24/2010] [Indexed: 12/29/2022] Open
Abstract
Background Pancreatic beta-cells respond to rising blood glucose by increasing oxidative metabolism, leading to an increased ATP/ADP ratio in the cytoplasm. This leads to a closure of KATP channels, depolarization of the plasma membrane, influx of calcium and the eventual secretion of insulin. Such mechanism suggests that beta-cell metabolism should have a functional regulation specific to secretion, as opposed to coupling to contraction. The goal of this work is to uncover contributions of the cytoplasmic and mitochondrial processes in this secretory coupling mechanism using mathematical modeling in a systems biology approach. Methods We describe a mathematical model of beta-cell sensitivity to glucose. The cytoplasmic part of the model includes equations describing glucokinase, glycolysis, pyruvate reduction, NADH and ATP production and consumption. The mitochondrial part begins with production of NADH, which is regulated by pyruvate dehydrogenase. NADH is used in the electron transport chain to establish a proton motive force, driving the F1F0 ATPase. Redox shuttles and mitochondrial Ca2+ handling were also modeled. Results The model correctly predicts changes in the ATP/ADP ratio, Ca2+ and other metabolic parameters in response to changes in substrate delivery at steady-state and during cytoplasmic Ca2+ oscillations. Our analysis of the model simulations suggests that the mitochondrial membrane potential should be relatively lower in beta cells compared with other cell types to permit precise mitochondrial regulation of the cytoplasmic ATP/ADP ratio. This key difference may follow from a relative reduction in respiratory activity. The model demonstrates how activity of lactate dehydrogenase, uncoupling proteins and the redox shuttles can regulate beta-cell function in concert; that independent oscillations of cytoplasmic Ca2+ can lead to slow coupled metabolic oscillations; and that the relatively low production rate of reactive oxygen species in beta-cells under physiological conditions is a consequence of the relatively decreased mitochondrial membrane potential. Conclusion This comprehensive model predicts a special role for mitochondrial control mechanisms in insulin secretion and ROS generation in the beta cell. The model can be used for testing and generating control hypotheses and will help to provide a more complete understanding of beta-cell glucose-sensing central to the physiology and pathology of pancreatic β-cells.
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Affiliation(s)
- Leonid E Fridlyand
- Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
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