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Toader AE, Fukuda M, Vazquez AL. Evaluation of calibrated and uncalibrated optical imaging approaches for relative cerebral oxygen metabolism measurements in awake mice. Physiol Meas 2024; 45:045007. [PMID: 38569522 DOI: 10.1088/1361-6579/ad3a2d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 04/03/2024] [Indexed: 04/05/2024]
Abstract
Objective. The continuous delivery of oxygen is critical to sustain brain function, and therefore, measuring brain oxygen consumption can provide vital physiological insight. In this work, we examine the impact of calibration and cerebral blood flow (CBF) measurements on the computation of the relative changes in the cerebral metabolic rate of oxygen consumption (rCMRO2) from hemoglobin-sensitive intrinsic optical imaging data. Using these data, we calculate rCMRO2, and calibrate the model using an isometabolic stimulus.Approach. We used awake head-fixed rodents to obtain hemoglobin-sensitive optical imaging data to test different calibrated and uncalibrated rCMRO2models. Hypercapnia was used for calibration and whisker stimulation was used to test the impact of calibration.Main results. We found that typical uncalibrated models can provide reasonable estimates of rCMRO2with differences as small as 7%-9% compared to their calibrated models. However, calibrated models showed lower variability and less dependence on baseline hemoglobin concentrations. Lastly, we found that supplying the model with measurements of CBF significantly reduced error and variability in rCMRO2change calculations.Significance. The effect of calibration on rCMRO2calculations remains understudied, and we systematically evaluated different rCMRO2calculation scenarios that consider including different measurement combinations. This study provides a quantitative comparison of these scenarios to evaluate trade-offs that can be vital to the design of blood oxygenation sensitive imaging experiments for rCMRO2calculation.
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Affiliation(s)
- A E Toader
- Departments of Radiology, University of Pittsburgh, Pittsburgh PA 15217, United States of America
| | - M Fukuda
- Departments of Radiology, University of Pittsburgh, Pittsburgh PA 15217, United States of America
| | - A L Vazquez
- Departments of Radiology, University of Pittsburgh, Pittsburgh PA 15217, United States of America
- Bioengineering, University of Pittsburgh, Pittsburgh PA 15217, United States of America
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Kowalewska PM, Milkovich SL, Goldman D, Sandow SL, Ellis CG, Welsh DG. Capillary oxygen regulates demand-supply coupling by triggering connexin40-mediated conduction: Rethinking the metabolic hypothesis. Proc Natl Acad Sci U S A 2024; 121:e2303119121. [PMID: 38349880 PMCID: PMC10895355 DOI: 10.1073/pnas.2303119121] [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: 02/26/2023] [Accepted: 12/21/2023] [Indexed: 02/15/2024] Open
Abstract
Coupling red blood cell (RBC) supply to O2 demand is an intricate process requiring O2 sensing, generation of a stimulus, and signal transduction that alters upstream arteriolar tone. Although actively debated, this process has been theorized to be induced by hypoxia and to involve activation of endothelial inwardly rectifying K+ channels (KIR) 2.1 by elevated extracellular K+ to trigger conducted hyperpolarization via connexin40 (Cx40) gap junctions to upstream resistors. This concept was tested in resting healthy skeletal muscle of Cx40-/- and endothelial KIR2.1-/- mice using state-of-the-art live animal imaging where the local tissue O2 environment was manipulated using a custom gas chamber. Second-by-second capillary RBC flow responses were recorded as O2 was altered. A stepwise drop in PO2 at the muscle surface increased RBC supply in capillaries of control animals while elevated O2 elicited the opposite response; capillaries were confirmed to express Cx40. The RBC flow responses were rapid and tightly coupled to O2; computer simulations did not support hypoxia as a driving factor. In contrast, RBC flow responses were significantly diminished in Cx40-/- mice. Endothelial KIR2.1-/- mice, on the other hand, reacted normally to O2 changes, even when the O2 challenge was targeted to a smaller area of tissue with fewer capillaries. Conclusively, microvascular O2 responses depend on coordinated electrical signaling via Cx40 gap junctions, and endothelial KIR2.1 channels do not initiate the event. These findings reconceptualize the paradigm of blood flow regulation in skeletal muscle and how O2 triggers this process in capillaries independent of extracellular K+.
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Affiliation(s)
- Paulina M Kowalewska
- Robarts Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5B7, Canada
| | - Stephanie L Milkovich
- Robarts Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
| | - Daniel Goldman
- Department of Medical Biophysics, University of Western Ontario, London, ON N6A 5B7, Canada
| | - Shaun L Sandow
- School of Health, University of the Sunshine Coast, Maroochydore, QLD 4556, Australia
- School of Clinical Medicine, University of Queensland, St. Lucia, QLD 4072, Australia
| | - Christopher G Ellis
- Robarts Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
- Department of Medical Biophysics, University of Western Ontario, London, ON N6A 5B7, Canada
| | - Donald G Welsh
- Robarts Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5B7, Canada
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3
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Carannante V, Wiklund M, Önfelt B. In vitro models to study natural killer cell dynamics in the tumor microenvironment. Front Immunol 2023; 14:1135148. [PMID: 37457703 PMCID: PMC10338882 DOI: 10.3389/fimmu.2023.1135148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 06/05/2023] [Indexed: 07/18/2023] Open
Abstract
Immunotherapy is revolutionizing cancer therapy. The rapid development of new immunotherapeutic strategies to treat solid tumors is posing new challenges for preclinical research, demanding novel in vitro methods to test treatments. Such methods should meet specific requirements, such as enabling the evaluation of immune cell responses like cytotoxicity or cytokine release, and infiltration into the tumor microenvironment using cancer models representative of the original disease. They should allow high-throughput and high-content analysis, to evaluate the efficacy of treatments and understand immune-evasion processes to facilitate development of new therapeutic targets. Ideally, they should be suitable for personalized immunotherapy testing, providing information for patient stratification. Consequently, the application of in vitro 3-dimensional (3D) cell culture models, such as tumor spheroids and organoids, is rapidly expanding in the immunotherapeutic field, coupled with the development of novel imaging-based techniques and -omic analysis. In this paper, we review the recent advances in the development of in vitro 3D platforms applied to natural killer (NK) cell-based cancer immunotherapy studies, highlighting the benefits and limitations of the current methods, and discuss new concepts and future directions of the field.
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Affiliation(s)
- Valentina Carannante
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Martin Wiklund
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Björn Önfelt
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
- Center for Infectious Medicine, Department of Medicine Huddinge, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden
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Samandarsangari M, Kozina DO, Sokolov VV, Komarova AD, Shirmanova MV, Kritchenkov IS, Tunik SP. Biocompatible Phosphorescent O 2 Sensors Based on Ir(III) Complexes for In Vivo Hypoxia Imaging. BIOSENSORS 2023; 13:680. [PMID: 37504079 PMCID: PMC10377268 DOI: 10.3390/bios13070680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/12/2023] [Accepted: 06/22/2023] [Indexed: 07/29/2023]
Abstract
In this work, we obtained three new phosphorescent iridium complexes (Ir1-Ir3) of general stoichiometry [Ir(N^C)2(N^N)]Cl decorated with oligo(ethylene glycol) fragments to make them water-soluble and biocompatible, as well as to protect them from aggregation with biomolecules such as albumin. The major photophysical characteristics of these phosphorescent complexes are determined by the nature of two cyclometallating ligands (N^C) based on 2-pyridine-benzothiophene, since quantum chemical calculations revealed that the electronic transitions responsible for the excitation and emission are localized mainly at these fragments. However, the use of various diimine ligands (N^N) proved to affect the quantum yield of phosphorescence and allowed for changing the complexes' sensitivity to oxygen, due to the variations in the steric accessibility of the chromophore center for O2 molecules. It was also found that the N^N ligands made it possible to tune the biocompatibility of the resulting compounds. The wavelengths of the Ir1-Ir3 emission maxima fell in the range of 630-650 nm, the quantum yields reached 17% (Ir1) in a deaerated solution, and sensitivity to molecular oxygen, estimated as the ratio of emission lifetime in deaerated and aerated water solutions, displayed the highest value, 8.2, for Ir1. The obtained complexes featured low toxicity, good water solubility and the absence of a significant effect of biological environment components on the parameters of their emission. Of the studied compounds, Ir1 and Ir2 were chosen for in vitro and in vivo biological experiments to estimate oxygen concentration in cell lines and tumors. These sensors have demonstrated their effectiveness for mapping the distribution of oxygen and for monitoring hypoxia in the biological objects studied.
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Affiliation(s)
- Mozhgan Samandarsangari
- Institute of Chemistry, St. Petersburg State University, Universitetskaya Embankment 7-9, 199034 St. Petersburg, Russia
| | - Daria O Kozina
- Institute of Chemistry, St. Petersburg State University, Universitetskaya Embankment 7-9, 199034 St. Petersburg, Russia
| | - Victor V Sokolov
- Institute of Chemistry, St. Petersburg State University, Universitetskaya Embankment 7-9, 199034 St. Petersburg, Russia
| | - Anastasia D Komarova
- Institute of Experimental Oncology and Biomedical Technologies, Privolzhskiy Research Medical University, Minin and Pozharsky Sq. 10/1, 603005 Nizhny Novgorod, Russia
- Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod, Gagarina Av., 23, 603950 Nizhny Novgorod, Russia
| | - Marina V Shirmanova
- Institute of Experimental Oncology and Biomedical Technologies, Privolzhskiy Research Medical University, Minin and Pozharsky Sq. 10/1, 603005 Nizhny Novgorod, Russia
| | - Ilya S Kritchenkov
- Institute of Chemistry, St. Petersburg State University, Universitetskaya Embankment 7-9, 199034 St. Petersburg, Russia
| | - Sergey P Tunik
- Institute of Chemistry, St. Petersburg State University, Universitetskaya Embankment 7-9, 199034 St. Petersburg, Russia
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Brooks GA, Osmond AD, Arevalo JA, Duong JJ, Curl CC, Moreno-Santillan DD, Leija RG. Lactate as a myokine and exerkine: drivers and signals of physiology and metabolism. J Appl Physiol (1985) 2023; 134:529-548. [PMID: 36633863 PMCID: PMC9970662 DOI: 10.1152/japplphysiol.00497.2022] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
No longer viewed as a metabolic waste product and cause of muscle fatigue, a contemporary view incorporates the roles of lactate in metabolism, sensing and signaling in normal as well as pathophysiological conditions. Lactate exists in millimolar concentrations in muscle, blood, and other tissues and can rise more than an order of magnitude as the result of increased production and clearance limitations. Lactate exerts its powerful driver-like influence by mass action, redox change, allosteric binding, and other mechanisms described in this article. Depending on the condition, such as during rest and exercise, following carbohydrate nutrition, injury, or pathology, lactate can serve as a myokine or exerkine with autocrine-, paracrine-, and endocrine-like functions that have important basic and translational implications. For instance, lactate signaling is: involved in reproductive biology, fueling the heart, muscle adaptation, and brain executive function, growth and development, and a treatment for inflammatory conditions. Lactate also works with many other mechanisms and factors in controlling cardiac output and pulmonary ventilation during exercise. Ironically, lactate can be disruptive of normal processes such as insulin secretion when insertion of lactate transporters into pancreatic β-cell membranes is not suppressed, and in carcinogenesis when factors that suppress carcinogenesis are inhibited, whereas factors that promote carcinogenesis are upregulated. Lactate signaling is important in areas of intermediary metabolism, redox biology, mitochondrial biogenesis, neurobiology, gut physiology, appetite regulation, nutrition, and overall health and vigor. The various roles of lactate as a myokine and exerkine are reviewed.NEW & NOTEWORTHY Lactate sensing and signaling is a relatively new and rapidly changing field. As a physiological signal lactate works both independently and in concert with other signals. Lactate operates via covalent binding and canonical signaling, redox change, and lactylation of DNA. Lactate can also serve as an element of feedback loops in cardiopulmonary regulation. From conception through aging lactate is not the only a myokine or exerkine, but it certainly deserves consideration as a physiological signal.
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Affiliation(s)
- George A Brooks
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Adam D Osmond
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Jose A Arevalo
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Justin J Duong
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Casey C Curl
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Diana D Moreno-Santillan
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
| | - Robert G Leija
- Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California, United States
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Pilotto AM, Adami A, Mazzolari R, Brocca L, Crea E, Zuccarelli L, Pellegrino MA, Bottinelli R, Grassi B, Rossiter HB, Porcelli S. Near-infrared spectroscopy estimation of combined skeletal muscle oxidative capacity and O 2 diffusion capacity in humans. J Physiol 2022; 600:4153-4168. [PMID: 35930524 PMCID: PMC9481735 DOI: 10.1113/jp283267] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 07/27/2022] [Indexed: 01/05/2023] Open
Abstract
The final steps of the O2 cascade during exercise depend on the product of the microvascular-to-intramyocyteP O 2 ${P}_{{{\rm{O}}}_{\rm{2}}}$ difference and muscle O2 diffusing capacity (D m O 2 $D{{\rm{m}}}_{{{\rm{O}}}_2}$ ). Non-invasive methods to determineD m O 2 $D{{\rm{m}}}_{{{\rm{O}}}_2}$ in humans are currently unavailable. Muscle oxygen uptake (mV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ ) recovery rate constant (k), measured by near-infrared spectroscopy (NIRS) using intermittent arterial occlusions, is associated with muscle oxidative capacity in vivo. We reasoned that k would be limited byD m O 2 $D{{\rm{m}}}_{{{\rm{O}}}_2}$ when muscle oxygenation is low (kLOW ), and hypothesized that: (i) k in well oxygenated muscle (kHIGH ) is associated with maximal O2 flux in fibre bundles; and (ii) ∆k (kHIGH - kLOW ) is associated with capillary density (CD). Vastus lateralis k was measured in 12 participants using NIRS after moderate exercise. The timing and duration of arterial occlusions were manipulated to maintain tissue saturation index within a 10% range either below (LOW) or above (HIGH) half-maximal desaturation, assessed during sustained arterial occlusion. Maximal O2 flux in phosphorylating state was 37.7 ± 10.6 pmol s-1 mg-1 (∼5.8 ml min-1 100 g-1 ). CD ranged 348 to 586 mm-2 . kHIGH was greater than kLOW (3.15 ± 0.45 vs. 1.56 ± 0.79 min-1 , P < 0.001). Maximal O2 flux was correlated with kHIGH (r = 0.80, P = 0.002) but not kLOW (r = -0.10, P = 0.755). Δk ranged -0.26 to -2.55 min-1 , and correlated with CD (r = -0.68, P = 0.015). mV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ k reflects muscle oxidative capacity only in well oxygenated muscle. ∆k, the difference in k between well and poorly oxygenated muscle, was associated with CD, a mediator ofD m O 2 $D{{\rm{m}}}_{{{\rm{O}}}_2}$ . Assessment of muscle k and ∆k using NIRS provides a non-invasive window on muscle oxidative and O2 diffusing capacity. KEY POINTS: We determined post-exercise recovery kinetics of quadriceps muscle oxygen uptake (mV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ ) measured by near-infrared spectroscopy (NIRS) in humans under conditions of both non-limiting (HIGH) and limiting (LOW) O2 availability, for comparison with biopsy variables. The mV ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ recovery rate constant in HIGH O2 availability was hypothesized to reflect muscle oxidative capacity (kHIGH ) and the difference in k between HIGH and LOW O2 availability (∆k) was hypothesized to reflect muscle O2 diffusing capacity. kHIGH was correlated with phosphorylating oxidative capacity of permeabilized muscle fibre bundles (r = 0.80). ∆k was negatively correlated with capillary density (r = -0.68) of biopsy samples. NIRS provides non-invasive means of assessing both muscle oxidative and oxygen diffusing capacity in vivo.
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Affiliation(s)
- Andrea M. Pilotto
- Department of MedicineUniversity of UdineUdineItaly
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
| | - Alessandra Adami
- Department of KinesiologyUniversity of Rhode IslandKingstonRIUSA
| | - Raffaele Mazzolari
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
- Department of Physical Education and SportUniversity of the Basque Country (UPV/EHU)Vitoria‐GasteizSpain
| | - Lorenza Brocca
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
| | - Emanuela Crea
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
| | | | - Maria A. Pellegrino
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
- Interdipartimental Centre for Biology and Sport MedicineUniversity of PaviaPaviaItaly
| | - Roberto Bottinelli
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
- Interdipartimental Centre for Biology and Sport MedicineUniversity of PaviaPaviaItaly
| | - Bruno Grassi
- Department of MedicineUniversity of UdineUdineItaly
| | - Harry B. Rossiter
- Division of Respiratory and Critical Care Physiology and MedicineThe Lundquist Institute for Biomedical Innovation at Harbor–UCLA Medical CenterTorranceCAUSA
| | - Simone Porcelli
- Department of Molecular MedicineInstitute of PhysiologyUniversity of PaviaPaviaItaly
- Institute of Biomedical TechnologiesNational Research CouncilMilanItaly
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Kritchenkov IS, Mikhnevich VG, Stashchak VS, Solomatina AI, Kozina DO, Sokolov VV, Tunik SP. Novel NIR-Phosphorescent Ir(III) Complexes: Synthesis, Characterization and Their Exploration as Lifetime-Based O2 Sensors in Living Cells. Molecules 2022; 27:molecules27103156. [PMID: 35630633 PMCID: PMC9144934 DOI: 10.3390/molecules27103156] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
A series of [Ir(N^C)2(N^N)]+ NIR-emitting orthometalated complexes (1–7) has been prepared and structurally characterized using elemental analysis, mass-spectrometry, and NMR spectroscopy. The complexes display intense phosphorescence with vibrationally structured emission bands exhibiting the maxima in the range 713–722 nm. The DFT and TD DFT calculations showed that the photophysical characteristics of these complexes are largely determined by the properties of the metalating N^C ligands, with their major contribution into formation of the lowest S1 and T1 excited states responsible for low energy absorption and emission, respectively. Emission lifetimes of 1–7 in degassed methanol solution vary from 1.76 to 5.39 µs and show strong quenching with molecular oxygen to provide an order of magnitude lifetime reduction in aerated solution. The photophysics of two complexes (1 and 7) were studied in model physiological media containing fetal bovine serum (FBS) and Dulbecco’s Modified Eagle Medium (DMEM) to give linear Stern-Volmer calibrations with substantially lower oxygen-quenching constants compared to those obtained in methanol solution. These observations were interpreted in terms of the sensors’ interaction with albumin, which is an abundant component of FBS and cell media. The studied complexes displayed acceptable cytotoxicity and preferential localization, either in mitochondria (1) or in lysosomes (7) of the CHO-K1 cell line. The results of the phosphorescence lifetime imaging (PLIM) experiments demonstrated considerable variations of the sensors’ lifetimes under normoxia and hypoxia conditions and indicated their applicability for semi-quantitative measurements of oxygen concentration in living cells. The complexes’ emission in the NIR domain and the excitation spectrum, extending down to ca. 600 nm, also showed that they are promising for use in in vivo studies.
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Oxygen flux from capillary to mitochondria: integration of contemporary discoveries. Eur J Appl Physiol 2022; 122:7-28. [PMID: 34940908 PMCID: PMC8890444 DOI: 10.1007/s00421-021-04854-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/18/2021] [Indexed: 01/03/2023]
Abstract
Resting humans transport ~ 100 quintillion (1018) oxygen (O2) molecules every second to tissues for consumption. The final, short distance (< 50 µm) from capillary to the most distant mitochondria, in skeletal muscle where exercising O2 demands may increase 100-fold, challenges our understanding of O2 transport. To power cellular energetics O2 reaches its muscle mitochondrial target by dissociating from hemoglobin, crossing the red cell membrane, plasma, endothelial surface layer, endothelial cell, interstitial space, myocyte sarcolemma and a variable expanse of cytoplasm before traversing the mitochondrial outer/inner membranes and reacting with reduced cytochrome c and protons. This past century our understanding of O2's passage across the body's final O2 frontier has been completely revised. This review considers the latest structural and functional data, challenging the following entrenched notions: (1) That O2 moves freely across blood cell membranes. (2) The Krogh-Erlang model whereby O2 pressure decreases systematically from capillary to mitochondria. (3) Whether intramyocyte diffusion distances matter. (4) That mitochondria are separate organelles rather than coordinated and highly plastic syncytia. (5) The roles of free versus myoglobin-facilitated O2 diffusion. (6) That myocytes develop anoxic loci. These questions, and the intriguing notions that (1) cellular membranes, including interconnected mitochondrial membranes, act as low resistance conduits for O2, lipids and H+-electrochemical transport and (2) that myoglobin oxy/deoxygenation state controls mitochondrial oxidative function via nitric oxide, challenge established tenets of muscle metabolic control. These elements redefine muscle O2 transport models essential for the development of effective therapeutic countermeasures to pathological decrements in O2 supply and physical performance.
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Chelushkin PS, Shakirova JR, Kritchenkov IS, Baigildin VA, Tunik SP. Phosphorescent NIR emitters for biomedicine: applications, advances and challenges. Dalton Trans 2021; 51:1257-1280. [PMID: 34878463 DOI: 10.1039/d1dt03077a] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Application of NIR (near-infrared) emitting transition metal complexes in biomedicine is a rapidly developing area of research. Emission of this class of compounds in the "optical transparency windows" of biological tissues and the intrinsic sensitivity of their phosphorescence to oxygen resulted in the preparation of several commercial oxygen sensors capable of deep (up to whole-body) and quantitative mapping of oxygen gradients suitable for in vivo experimental studies. In addition to this achievement, the last decade has also witnessed the increased growth of successful alternative applications of NIR phosphors that include (i) site-specific in vitro and in vivo visualization of sophisticated biological models ranging from 3D cell cultures to intact animals; (ii) sensing of various biologically relevant analytes, such as pH, reactive oxygen and nitrogen species, RedOx agents, etc.; (iii) and several therapeutic applications such as photodynamic (PDT), photothermal (PTT), and photoactivated cancer (PACT) therapies as well as their combinations with other therapeutic and imaging modalities to yield new variants of combined therapies and theranostics. Nevertheless, emerging applications of these compounds in experimental biomedicine and their implementation as therapeutic agents practically applicable in PDT, PTT, and PACT face challenges related to a critically important improvement of their photophysical and physico-chemical characteristics. This review outlines the current state of the art and achievements of the last decade and stresses the most promising trends, major development prospects, and challenges in the design of NIR phosphors suitable for biomedical applications.
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Affiliation(s)
- Pavel S Chelushkin
- Institute of Chemistry, St. Petersburg State University, Universitetskii pr., 26, 198504, St. Petersburg, Russia.
| | - Julia R Shakirova
- Institute of Chemistry, St. Petersburg State University, Universitetskii pr., 26, 198504, St. Petersburg, Russia.
| | - Ilya S Kritchenkov
- Institute of Chemistry, St. Petersburg State University, Universitetskii pr., 26, 198504, St. Petersburg, Russia.
| | - Vadim A Baigildin
- Institute of Chemistry, St. Petersburg State University, Universitetskii pr., 26, 198504, St. Petersburg, Russia.
| | - Sergey P Tunik
- Institute of Chemistry, St. Petersburg State University, Universitetskii pr., 26, 198504, St. Petersburg, Russia.
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Olson KR. A Case for Hydrogen Sulfide Metabolism as an Oxygen Sensing Mechanism. Antioxidants (Basel) 2021; 10:antiox10111650. [PMID: 34829521 PMCID: PMC8615108 DOI: 10.3390/antiox10111650] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 12/30/2022] Open
Abstract
The ability to detect oxygen availability is a ubiquitous attribute of aerobic organisms. However, the mechanism(s) that transduce oxygen concentration or availability into appropriate physiological responses is less clear and often controversial. This review will make the case for oxygen-dependent metabolism of hydrogen sulfide (H2S) and polysulfides, collectively referred to as reactive sulfur species (RSS) as a physiologically relevant O2 sensing mechanism. This hypothesis is based on observations that H2S and RSS metabolism is inversely correlated with O2 tension, exogenous H2S elicits physiological responses identical to those produced by hypoxia, factors that affect H2S production or catabolism also affect tissue responses to hypoxia, and that RSS efficiently regulate downstream effectors of the hypoxic response in a manner consistent with a decrease in O2. H2S-mediated O2 sensing is then compared to the more generally accepted reactive oxygen species (ROS) mediated O2 sensing mechanism and a number of reasons are offered to resolve some of the confusion between the two.
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Affiliation(s)
- Kenneth R Olson
- Department of Physiology, Indiana University School of Medicine-South Bend, South Bend, IN 46617, USA
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11
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Pant A, Chittayil Krishnakumar K, Chakkalaparambil Dileep N, Yamana M, Meenakshisundaran Alamelu N, Paithankar K, Amash V, Amere Subbarao S. Hsp90 and its mitochondrial homologue TRAP-1 independently regulate hypoxia adaptations in Caenorhabditis elegans. Mitochondrion 2021; 60:101-111. [PMID: 34365052 DOI: 10.1016/j.mito.2021.08.002] [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: 06/07/2021] [Revised: 07/28/2021] [Accepted: 08/03/2021] [Indexed: 11/30/2022]
Abstract
Mitochondrial adaptations to various environmental cues contribute to cellular and organismal adaptations across multiple model organisms. Due to increased complexity, a direct connection between mitochondrial integrity and oxygen fluctuations, and survival fitness was not demonstrated. Here, using C. elegans as a model system, we studied the role of HIF-1, Hsp90, and TRAP-1 in mitochondrial adaptations during chemical hypoxia. We show that Hsp90mt (Hsp90 mutant) but not HIF-1mt (HIF-1 mutant) affects hypoxia adaptation in nematodes. TRAP-1KD (TRAP-1 knockdown) interfered with the survival and fecundity of worms. Compared to Hsp90mt, TRAP-1KD has induced a significant decrease in mitochondrial integrity and oxygen consumption rate. The complex I inhibitor rotenone did not affect ATP levels in Hsp90mt worms. However, ATP levels were decreased in TRAP-1KD worms under similar conditions. The glucose restriction has reduced, and glucose supplementation has increased the survival rate in Hsp90mt worms. Neither glucose restriction nor glucose supplementation has significantly affected the survival of TRAP-1KD worms in response to hypoxia. However, TRAP-1 inhibition using a nanocarrier drug has dramatically reduced the survival rate in response to hypoxia. Our results suggest that Hsp90 and TRAP-1 independently regulate hypoxia adaptations and metabolic plasticity in C. elegans. Considering the emerging roles of TRAP-1 in altered energy metabolism and cellular adaptations, our findings gain importance.
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Affiliation(s)
- Aakanksha Pant
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
| | | | | | - Meghana Yamana
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India
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12
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Glancy B, Kane DA, Kavazis AN, Goodwin ML, Willis WT, Gladden LB. Mitochondrial lactate metabolism: history and implications for exercise and disease. J Physiol 2021; 599:863-888. [PMID: 32358865 PMCID: PMC8439166 DOI: 10.1113/jp278930] [Citation(s) in RCA: 85] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 03/25/2020] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial structures were probably observed microscopically in the 1840s, but the idea of oxidative phosphorylation (OXPHOS) within mitochondria did not appear until the 1930s. The foundation for research into energetics arose from Meyerhof's experiments on oxidation of lactate in isolated muscles recovering from electrical contractions in an O2 atmosphere. Today, we know that mitochondria are actually reticula and that the energy released from electron pairs being passed along the electron transport chain from NADH to O2 generates a membrane potential and pH gradient of protons that can enter the molecular machine of ATP synthase to resynthesize ATP. Lactate stands at the crossroads of glycolytic and oxidative energy metabolism. Based on reported research and our own modelling in silico, we contend that lactate is not directly oxidized in the mitochondrial matrix. Instead, the interim glycolytic products (pyruvate and NADH) are held in cytosolic equilibrium with the products of the lactate dehydrogenase (LDH) reaction and the intermediates of the malate-aspartate and glycerol 3-phosphate shuttles. This equilibrium supplies the glycolytic products to the mitochondrial matrix for OXPHOS. LDH in the mitochondrial matrix is not compatible with the cytoplasmic/matrix redox gradient; its presence would drain matrix reducing power and substantially dissipate the proton motive force. OXPHOS requires O2 as the final electron acceptor, but O2 supply is sufficient in most situations, including exercise and often acute illness. Recent studies suggest that atmospheric normoxia may constitute a cellular hyperoxia in mitochondrial disease. As research proceeds appropriate oxygenation levels should be carefully considered.
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Affiliation(s)
- Brian Glancy
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Daniel A. Kane
- Department of Human Kinetics, St. Francis Xavier University, NS B2G 2W5, Antigonish, Canada
| | | | - Matthew L. Goodwin
- Department of Orthopaedic Surgery, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Wayne T. Willis
- College of Medicine, Department of Medicine, University of Arizona, Tucson, AZ 85724-5099, USA
| | - L. Bruce Gladden
- School of Kinesiology, Auburn University, Auburn, AL 36849-5323, USA
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13
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Poole DC, Rossiter HB, Brooks GA, Gladden LB. The anaerobic threshold: 50+ years of controversy. J Physiol 2020; 599:737-767. [PMID: 33112439 DOI: 10.1113/jp279963] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 10/16/2020] [Indexed: 12/23/2022] Open
Abstract
The anaerobic threshold (AT) remains a widely recognized, and contentious, concept in exercise physiology and medicine. As conceived by Karlman Wasserman, the AT coalesced the increase of blood lactate concentration ([La- ]), during a progressive exercise test, with an excess pulmonary carbon dioxide output ( V ̇ C O 2 ). Its principal tenets were: limiting oxygen (O2 ) delivery to exercising muscle→increased glycolysis, La- and H+ production→decreased muscle and blood pH→with increased H+ buffered by blood [HCO3 - ]→increased CO2 release from blood→increased V ̇ C O 2 and pulmonary ventilation. This schema stimulated scientific scrutiny which challenged the fundamental premise that muscle anoxia was requisite for increased muscle and blood [La- ]. It is now recognized that insufficient O2 is not the primary basis for lactataemia. Increased production and utilization of La- represent the response to increased glycolytic flux elicited by increasing work rate, and determine the oxygen uptake ( V ̇ O 2 ) at which La- accumulates in the arterial blood (the lactate threshold; LT). However, the threshold for a sustained non-oxidative contribution to exercise energetics is the critical power, which occurs at a metabolic rate often far above the LT and separates heavy from very heavy/severe-intensity exercise. Lactate is now appreciated as a crucial energy source, major gluconeogenic precursor and signalling molecule but there is no ipso facto evidence for muscle dysoxia or anoxia. Non-invasive estimation of LT using the gas exchange threshold (non-linear increase of V ̇ C O 2 versus V ̇ O 2 ) remains important in exercise training and in the clinic, but its conceptual basis should now be understood in light of lactate shuttle biology.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Harry B Rossiter
- Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, and The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - George A Brooks
- Department of Integrative Biology, Exercise Physiology Laboratory, University of California, Berkeley, CA, USA
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14
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Goulding RP, Okushima D, Marwood S, Poole DC, Barstow TJ, Lei TH, Kondo N, Koga S. Impact of supine exercise on muscle deoxygenation kinetics heterogeneity: mechanistic insights into slow pulmonary oxygen uptake dynamics. J Appl Physiol (1985) 2020; 129:535-546. [PMID: 32702271 DOI: 10.1152/japplphysiol.00213.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Oxygen uptake (V̇o2) kinetics are slowed in the supine (S) position purportedly due to impaired muscle O2 delivery ([Formula: see text]); however, these conclusions are predicated on single-site measurements in superficial muscle using continuous-wave near-infrared spectroscopy (NIRS). This study aimed to determine the impact of body position [i.e., upright (U) versus S] on deep and superficial muscle deoxygenation (deoxy[heme]) using time-resolved (TR-) NIRS, and how these relate to slowed pulmonary V̇o2 kinetics. Seventeen healthy men completed constant power tests during 1) S heavy-intensity exercise and 2) U exercise at the same absolute work rate, with a subset of 10 completing additional tests at the same relative work rate as S. Pulmonary V̇o2 was measured breath-by-breath and, deoxy- and total[heme] were resolved via TR-NIRS in the superficial and deep vastus lateralis and superficial rectus femoris. The fundamental phase V̇o2 time constant was increased during S compared with U (S: 36 ± 10 vs. U: 27 ± 8 s; P < 0.001). The deoxy[heme] amplitude (S: 25-28 vs. U: 13-18 µM; P < 0.05) and total[heme] amplitude (S: 17-20 vs. U: 9-16 µM; P < 0.05) were greater in S compared with U and were consistent for the same absolute (above data) and relative work rates (n = 10, all P < 0.05). The greater deoxy- and total[heme] amplitudes in S vs. U supports that reduced perfusive [Formula: see text] in S, even within deep muscle, necessitated a greater reliance on fractional O2 extraction and diffusive [Formula: see text]. The slower V̇o2 kinetics in S versus U demonstrates that, ultimately, these adjustments were insufficient to prevent impairments in whole body oxidative metabolism.NEW & NOTEWORTHY We show that supine exercise causes a greater degree of muscle deoxygenation in both deep and superficial muscle and increases the spatial heterogeneity of muscle deoxygenation. Therefore, this study suggests that any O2 delivery gradient toward deep versus superficial muscle is insufficient to mitigate impairments in oxidative function in response to reduced whole muscle O2 delivery. More heterogeneous muscle deoxygenation is associated with slower V̇o2 kinetics.
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Affiliation(s)
- Richie P Goulding
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan.,International Research Fellow of Japan Society for Promotion of Sciences, Tokyo, Japan
| | - Dai Okushima
- Osaka International University, Moriguchi, Japan
| | - Simon Marwood
- School of Health Sciences, Liverpool Hope University, Liverpool, Merseyside, United Kingdom
| | - David C Poole
- Departments of Anatomy and Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Thomas J Barstow
- Departments of Anatomy and Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
| | - Tze-Huan Lei
- International Research Fellow of Japan Society for Promotion of Sciences, Tokyo, Japan.,Applied Physiology Laboratory, Kobe University, Kobe, Japan
| | - Narihiko Kondo
- Applied Physiology Laboratory, Kobe University, Kobe, Japan
| | - Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
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15
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Manganese Porphyrin-Based SOD Mimetics Produce Polysulfides from Hydrogen Sulfide. Antioxidants (Basel) 2019; 8:antiox8120639. [PMID: 31842297 PMCID: PMC6943712 DOI: 10.3390/antiox8120639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/04/2019] [Accepted: 12/06/2019] [Indexed: 02/07/2023] Open
Abstract
Manganese-centered porphyrins (MnPs), MnTE-2-PyP5+ (MnTE), MnTnHex-2-PyP5+ (MnTnHex), and MnTnBuOE-2-PyP5+ (MnTnBuOE) have received considerable attention because of their ability to serve as superoxide dismutase (SOD) mimetics thereby producing hydrogen peroxide (H2O2), and oxidants of ascorbate and simple aminothiols or protein thiols. MnTE-2-PyP5+ and MnTnBuOE-2-PyP5+ are now in five Phase II clinical trials warranting further exploration of their rich redox-based biology. Previously, we reported that SOD is also a sulfide oxidase catalyzing the oxidation of hydrogen sulfide (H2S) to hydrogen persulfide (H2S2) and longer-chain polysulfides (H2Sn, n = 3–7). We hypothesized that MnPs may have similar actions on sulfide metabolism. H2S and polysulfides were monitored in fluorimetric assays with 7-azido-4-methylcoumarin (AzMC) and 3′,6′-di(O-thiosalicyl)fluorescein (SSP4), respectively, and specific polysulfides were further identified by mass spectrometry. MnPs concentration-dependently consumed H2S and produced H2S2 and subsequently longer-chain polysulfides. This reaction appeared to be O2-dependent. MnP absorbance spectra exhibited wavelength shifts in the Soret and Q bands characteristic of sulfide-mediated reduction of Mn. Taken together, our results suggest that MnPs can become efficacious activators of a variety of cytoprotective processes by acting as sulfide oxidation catalysts generating per/polysulfides.
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16
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Zuniga-Hertz JP, Patel HH. The Evolution of Cholesterol-Rich Membrane in Oxygen Adaption: The Respiratory System as a Model. Front Physiol 2019; 10:1340. [PMID: 31736773 PMCID: PMC6828933 DOI: 10.3389/fphys.2019.01340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/08/2019] [Indexed: 12/14/2022] Open
Abstract
The increase in atmospheric oxygen levels imposed significant environmental pressure on primitive organisms concerning intracellular oxygen concentration management. Evidence suggests the rise of cholesterol, a key molecule for cellular membrane organization, as a cellular strategy to restrain free oxygen diffusion under the new environmental conditions. During evolution and the increase in organismal complexity, cholesterol played a pivotal role in the establishment of novel and more complex functions associated with lipid membranes. Of these, caveolae, cholesterol-rich membrane domains, are signaling hubs that regulate important in situ functions. Evolution resulted in complex respiratory systems and molecular response mechanisms that ensure responses to critical events such as hypoxia facilitated oxygen diffusion and transport in complex organisms. Caveolae have been structurally and functionally associated with respiratory systems and oxygen diffusion control through their relationship with molecular response systems like hypoxia-inducible factors (HIF), and particularly as a membrane-localized oxygen sensor, controlling oxygen diffusion balanced with cellular physiological requirements. This review will focus on membrane adaptations that contribute to regulating oxygen in living systems.
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Affiliation(s)
- Juan Pablo Zuniga-Hertz
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
| | - Hemal H Patel
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
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17
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Lazarus LS, Simons CR, Arcidiacono A, Benninghoff AD, Berreau LM. Extracellular vs Intracellular Delivery of CO: Does It Matter for a Stable, Diffusible Gasotransmitter? J Med Chem 2019; 62:9990-9995. [PMID: 31577143 DOI: 10.1021/acs.jmedchem.9b01254] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Carbon monoxide (CO) is a gasotransmitter produced in humans. An essential unanswered question in the design of carbon monoxide releasing molecules (CORMs) is whether the delivery molecule should be localized extra- or intracellularly to produce desired biological effects. Herein we show that extracellular CO release is less toxic and is sufficient to produce an anti-inflammatory effect similar to that of intracellular CO release at nanomolar concentrations. This information is valuable for the design of CORMs.
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Affiliation(s)
- Livia S Lazarus
- Department of Chemistry & Biochemistry , Utah State University , Logan , Utah 84322-0300 , United States
| | - Casey R Simons
- Department of Chemistry & Biochemistry , Utah State University , Logan , Utah 84322-0300 , United States
| | - Ashley Arcidiacono
- Department of Chemistry & Biochemistry , Florida State University , Tallahassee , Florida 32306-4390 , United States
| | - Abby D Benninghoff
- Department of Animal, Dairy and Veterinary Sciences , Utah State University , Logan , Utah 84322-4815 , United States
| | - Lisa M Berreau
- Department of Chemistry & Biochemistry , Utah State University , Logan , Utah 84322-0300 , United States
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18
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Poole DC. Edward F. Adolph Distinguished Lecture. Contemporary model of muscle microcirculation: gateway to function and dysfunction. J Appl Physiol (1985) 2019; 127:1012-1033. [PMID: 31095460 DOI: 10.1152/japplphysiol.00013.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This review strikes at the very heart of how the microcirculation functions to facilitate blood-tissue oxygen, substrate, and metabolite fluxes in skeletal muscle. Contemporary evidence, marshalled from animals and humans using the latest techniques, challenges iconic perspectives that have changed little over the past century. Those perspectives include the following: the presence of contractile or collapsible capillaries in muscle, unitary control by precapillary sphincters, capillary recruitment at the onset of contractions, and the notion of capillary-to-mitochondrial diffusion distances as limiting O2 delivery. Today a wealth of physiological, morphological, and intravital microscopy evidence presents a completely different picture of microcirculatory control. Specifically, capillary red blood cell (RBC) and plasma flux is controlled primarily at the arteriolar level with most capillaries, in healthy muscle, supporting at least some flow at rest. In healthy skeletal muscle, this permits substrate access (whether carried in RBCs or plasma) to a prodigious total capillary surface area. Pathologies such as heart failure or diabetes decrease access to that exchange surface by reducing the proportion of flowing capillaries at rest and during exercise. Capillary morphology and function vary disparately among tissues. The contemporary model of capillary function explains how, following the onset of exercise, muscle O2 uptake kinetics can be extremely fast in health but slowed in heart failure and diabetes impairing contractile function and exercise tolerance. It is argued that adoption of this model is fundamental for understanding microvascular function and dysfunction and, as such, to the design and evaluation of effective therapeutic strategies to improve exercise tolerance and decrease morbidity and mortality in disease.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, Kansas
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19
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Clanton TL. Managing the power grid: how myoglobin can regulate PO2 and energy distribution in skeletal muscle. J Appl Physiol (1985) 2019; 126:787-790. [DOI: 10.1152/japplphysiol.00614.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Affiliation(s)
- Thomas L. Clanton
- Department of Applied Physiology and Kinesiology, the University of Florida Gainesville, Florida
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20
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Hirai DM, Colburn TD, Craig JC, Hotta K, Kano Y, Musch TI, Poole DC. Skeletal muscle interstitial O 2 pressures: bridging the gap between the capillary and myocyte. Microcirculation 2018; 26:e12497. [PMID: 30120845 DOI: 10.1111/micc.12497] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/26/2018] [Accepted: 08/13/2018] [Indexed: 01/18/2023]
Abstract
The oxygen transport pathway from air to mitochondria involves a series of transfer steps within closely integrated systems (pulmonary, cardiovascular, and tissue metabolic). Small and finite O2 stores in most mammalian species require exquisitely controlled changes in O2 flux rates to support elevated ATP turnover. This is especially true for the contracting skeletal muscle where O2 requirements may increase two orders of magnitude above rest. This brief review focuses on the mechanistic bases for increased microvascular blood-myocyte O2 flux (V̇O2 ) from rest to contractions. Fick's law dictates that V̇O2 elevations driven by muscle contractions are produced by commensurate changes in driving force (ie, O2 pressure gradients; ΔPO2 ) and/or effective diffusing capacity (DO2 ). While previous evidence indicates that increased DO2 helps modulate contracting muscle O2 flux, up until recently the role of the dynamic ΔPO2 across the capillary wall was unknown. Recent phosphorescence quenching investigations of both microvascular and novel interstitial PO2 kinetics in health have resolved an important step in the O2 cascade between the capillary and myocyte. Specifically, the significant transmural ΔPO2 at rest was sustained (but not increased) during submaximal contractions. This supports the contention that the blood-myocyte interface provides a substantial effective resistance to O2 diffusion and underscores that modulations in erythrocyte hemodynamics and distribution (DO2 ) are crucial to preserve the driving force for O2 flux across the capillary wall (ΔPO2 ) during contractions. Investigation of the O2 transport pathway close to muscle mitochondria is key to identifying disease mechanisms and develop therapeutic approaches to ameliorate dysfunction and exercise intolerance.
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Affiliation(s)
- Daniel M Hirai
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Trenton D Colburn
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Jesse C Craig
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - Kazuki Hotta
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Timothy I Musch
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
| | - David C Poole
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, Kansas
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21
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Abstract
The surgical patient population is increasingly elderly and comorbid and poses challenges to perioperative physicians. Accurate preoperative risk stratification is important to direct perioperative care. Reduced aerobic fitness is associated with increased postoperative morbidity and mortality. Cardiopulmonary exercise testing is an integrated and dynamic test that gives an objective measure of aerobic fitness or functional capacity and identifies the cause of exercise intolerance. Cardiopulmonary exercise testing provides an individualized estimate of patient risk that can be used to predict postoperative morbidity and mortality. This technology can therefore be used to inform collaborative decision-making and patient consent, to triage the patient to an appropriate perioperative care environment, to diagnose unexpected comorbidity, to optimize medical comorbidities preoperatively, and to direct individualized preoperative exercise programs. Functional capacity, evaluated as the anaerobic threshold and peak oxygen uptake ([Formula: see text]o2peak) predicts postoperative morbidity and mortality in the majority of surgical cohort studies. The ventilatory equivalents for carbon dioxide (an index of gas exchange efficiency), is predictive of surgical outcome in some cohorts. Prospective cohort studies are needed to improve the precision of risk estimates for different patient groups and to clarify the best combination of variables to predict outcome. Early data suggest that preoperative exercise training improves fitness, reduces the debilitating effects of neoadjuvant chemotherapy, and may improve clinical outcomes. Further research is required to identify the most effective type of training and the minimum duration required for a positive effect.
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22
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Levett D, Jack S, Swart M, Carlisle J, Wilson J, Snowden C, Riley M, Danjoux G, Ward S, Older P, Grocott M. Perioperative cardiopulmonary exercise testing (CPET): consensus clinical guidelines on indications, organization, conduct, and physiological interpretation. Br J Anaesth 2018; 120:484-500. [DOI: 10.1016/j.bja.2017.10.020] [Citation(s) in RCA: 253] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 10/20/2017] [Accepted: 10/22/2017] [Indexed: 01/09/2023] Open
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23
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Gandra PG, Shiah AA, Nogueira L, Hogan MC. A mitochondrial-targeted antioxidant improves myofilament Ca 2+ sensitivity during prolonged low frequency force depression at low PO2. J Physiol 2018; 596:1079-1089. [PMID: 29334129 DOI: 10.1113/jp275470] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 01/08/2018] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Skeletal muscle contractile activity is associated with an enhanced reactive oxygen species (ROS) generation. At very low PO2, ROS generation by mitochondria can be elevated in intact cells. An elevated intracellular oxidant activity may affect muscle force development and recovery from fatigue. We treated intact single muscle fibres with a mitochondrial antioxidant and stimulated the fibres to contract at a low extracellular PO2 that is similar to the intracellular PO2 that is observed during moderate to intense exercise in vivo. The mitochondrial antioxidant prevented a sustained decrease in the myofibrillar Ca2+ sensitivity and improved muscle submaximal force development after fatigue at low extracellular PO2. ABSTRACT Skeletal muscle can develop a prolonged low frequency-stimulation force depression (PLFFD) following fatigue-inducing contractions. Increased levels of reactive oxygen species (ROS) have been implicated in the development of PLFFD. During exercise the skeletal muscle intracellular PO2 decreases to relatively low levels, and can be further decreased when there is an impairment in O2 diffusion or availability, such as in certain chronic diseases and during exercise at high altitude. Since ROS generation by mitochondria is elevated at very low PO2 in cells, we tested the hypothesis that treatment of muscle fibres with a mitochondrial-targeted antioxidant at a very low, near hypoxic, PO2 can attenuate PLFFD. We treated intact single fibres from mice with the mitochondrial-specific antioxidant SS31, and measured force development and intracellular [Ca2+ ] 30 min after fatigue at an extracellular PO2 of ∼5 Torr. After 30 min following the end of the fatiguing contractions, fibres treated with SS31 showed significantly less impairment in force development compared to untreated fibres at submaximal frequencies of stimulation. The cytosolic peak [Ca2+ ] transients (peak [Ca2+ ]c ) were equally decreased in both groups compared to pre-fatigue values. The combined force and peak [Ca2+ ]c data demonstrated that myofibrillar Ca2+ sensitivity was diminished in the untreated fibres 30 min after fatigue compared to pre-fatigue values, but Ca2+ sensitivity was unaltered in the SS31 treated fibres. These results demonstrate that at a very low PO2, treatment of skeletal muscle fibres with a mitochondrial antioxidant prevents a decrease in the myofibrillar Ca2+ sensitivity, which alleviates the fatigue induced PLFFD.
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Affiliation(s)
- Paulo G Gandra
- Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (Unicamp), Campinas, Brazil.,Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Amy A Shiah
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Leonardo Nogueira
- Institute of Medical Biochemistry Leopoldo de Meis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.,Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Michael C Hogan
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
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24
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Hirai DM, Craig JC, Colburn TD, Eshima H, Kano Y, Sexton WL, Musch TI, Poole DC. Skeletal muscle microvascular and interstitial PO2 from rest to contractions. J Physiol 2018; 596:869-883. [PMID: 29288568 DOI: 10.1113/jp275170] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 12/01/2017] [Indexed: 01/21/2023] Open
Abstract
KEY POINTS Oxygen pressure gradients across the microvascular walls are essential for oxygen diffusion from blood to tissue cells. At any given flux, the magnitude of these transmural gradients is proportional to the local resistance. The greatest resistance to oxygen transport into skeletal muscle is considered to reside in the short distance between red blood cells and myocytes. Although crucial to oxygen transport, little is known about transmural pressure gradients within skeletal muscle during contractions. We evaluated oxygen pressures within both the skeletal muscle microvascular and interstitial spaces to determine transmural gradients during the rest-contraction transient in anaesthetized rats. The significant transmural gradient observed at rest was sustained during submaximal muscle contractions. Our findings support that the blood-myocyte interface provides substantial resistance to oxygen diffusion at rest and during contractions and suggest that modulations in microvascular haemodynamics and red blood cell distribution constitute primary mechanisms driving increased transmural oxygen flux with contractions. ABSTRACT Oxygen pressure (PO2) gradients across the blood-myocyte interface are required for diffusive O2 transport, thereby supporting oxidative metabolism. The greatest resistance to O2 flux into skeletal muscle is considered to reside between the erythrocyte surface and adjacent sarcolemma, although this has not been measured during contractions. We tested the hypothesis that O2 gradients between skeletal muscle microvascular (PO2 mv ) and interstitial (PO2 is ) spaces would be present at rest and maintained or increased during contractions. PO2 mv and PO2 is were determined via phosphorescence quenching (Oxyphor probes G2 and G4, respectively) in the exposed rat spinotrapezius during the rest-contraction transient (1 Hz, 6 V; n = 8). PO2 mv was higher than PO2 is in all instances from rest (34.9 ± 6.0 versus 15.7 ± 6.4) to contractions (28.4 ± 5.3 versus 10.6 ± 5.2 mmHg, respectively) such that the mean PO2 gradient throughout the transient was 16.9 ± 6.6 mmHg (P < 0.05 for all). No differences in the amplitude of PO2 fall with contractions were observed between the microvasculature and interstitium (10.9 ± 2.3 versus 9.0 ± 3.5 mmHg, respectively; P > 0.05). However, the speed of the PO2 is fall during contractions was slower than that of PO2 mv (time constant: 12.8 ± 4.7 versus 9.0 ± 5.1 s, respectively; P < 0.05). Consistent with our hypothesis, a significant transmural gradient was sustained (but not increased) from rest to contractions. This supports that the blood-myocyte interface is the site of a substantial PO2 gradient driving O2 diffusion during metabolic transients. Based on Fick's law, elevated O2 flux with contractions must thus rely primarily on modulations in effective diffusing capacity (mainly erythrocyte haemodynamics and distribution) as the PO2 gradient is not increased.
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Affiliation(s)
- Daniel M Hirai
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Jesse C Craig
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Trenton D Colburn
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Hiroaki Eshima
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Tokyo, Japan
| | - William L Sexton
- Department of Physiology, A.T. Still University of Health Sciences, Kirksville, MO, USA
| | - Timothy I Musch
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
| | - David C Poole
- Departments of Anatomy & Physiology, Kinesiology, Kansas State University, Manhattan, KS, USA
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25
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Ferguson BS, Rogatzki MJ, Goodwin ML, Kane DA, Rightmire Z, Gladden LB. Lactate metabolism: historical context, prior misinterpretations, and current understanding. Eur J Appl Physiol 2018; 118:691-728. [PMID: 29322250 DOI: 10.1007/s00421-017-3795-6] [Citation(s) in RCA: 186] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 12/22/2017] [Indexed: 02/07/2023]
Abstract
Lactate (La-) has long been at the center of controversy in research, clinical, and athletic settings. Since its discovery in 1780, La- has often been erroneously viewed as simply a hypoxic waste product with multiple deleterious effects. Not until the 1980s, with the introduction of the cell-to-cell lactate shuttle did a paradigm shift in our understanding of the role of La- in metabolism begin. The evidence for La- as a major player in the coordination of whole-body metabolism has since grown rapidly. La- is a readily combusted fuel that is shuttled throughout the body, and it is a potent signal for angiogenesis irrespective of oxygen tension. Despite this, many fundamental discoveries about La- are still working their way into mainstream research, clinical care, and practice. The purpose of this review is to synthesize current understanding of La- metabolism via an appraisal of its robust experimental history, particularly in exercise physiology. That La- production increases during dysoxia is beyond debate, but this condition is the exception rather than the rule. Fluctuations in blood [La-] in health and disease are not typically due to low oxygen tension, a principle first demonstrated with exercise and now understood to varying degrees across disciplines. From its role in coordinating whole-body metabolism as a fuel to its role as a signaling molecule in tumors, the study of La- metabolism continues to expand and holds potential for multiple clinical applications. This review highlights La-'s central role in metabolism and amplifies our understanding of past research.
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Affiliation(s)
- Brian S Ferguson
- College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Matthew J Rogatzki
- Department of Health and Exercise Science, Appalachian State University, Boone, NC, USA
| | - Matthew L Goodwin
- Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA.,Huntsman Cancer Institute, Salt Lake City, UT, USA
| | - Daniel A Kane
- Department of Human Kinetics, St. Francis Xavier University, Antigonish, Canada
| | - Zachary Rightmire
- School of Kinesiology, Auburn University, 301 Wire Road, Auburn, AL, 36849, USA
| | - L Bruce Gladden
- School of Kinesiology, Auburn University, 301 Wire Road, Auburn, AL, 36849, USA.
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26
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Poole DC, Richardson RS, Haykowsky MJ, Hirai DM, Musch TI. Exercise limitations in heart failure with reduced and preserved ejection fraction. J Appl Physiol (1985) 2017; 124:208-224. [PMID: 29051336 DOI: 10.1152/japplphysiol.00747.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The hallmark symptom of chronic heart failure (HF) is severe exercise intolerance. Impaired perfusive and diffusive O2 transport are two of the major determinants of reduced physical capacity and lowered maximal O2 uptake in patients with HF. It has now become evident that this syndrome manifests at least two different phenotypic variations: heart failure with preserved or reduced ejection fraction (HFpEF and HFrEF, respectively). Unlike HFrEF, however, there is currently limited understanding of HFpEF pathophysiology, leading to a lack of effective pharmacological treatments for this subpopulation. This brief review focuses on the disturbances within the O2 transport pathway resulting in limited exercise capacity in both HFpEF and HFrEF. Evidence from human and animal research reveals HF-induced impairments in both perfusive and diffusive O2 conductances identifying potential targets for clinical intervention. Specifically, utilization of different experimental approaches in humans (e.g., small vs. large muscle mass exercise) and animals (e.g., intravital microscopy and phosphorescence quenching) has provided important clues to elucidating these pathophysiological mechanisms. Adaptations within the skeletal muscle O2 delivery-utilization system following established and emerging therapies (e.g., exercise training and inorganic nitrate supplementation, respectively) are discussed. Resolution of the underlying mechanisms of skeletal muscle dysfunction and exercise intolerance is essential for the development and refinement of the most effective treatments for patients with HF.
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27
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Isenberg JS, Adams JC. Gaso-transmitters: expanding the kinetic universe of cell signaling. Am J Physiol Cell Physiol 2016; 312:C1-C2. [PMID: 27834197 PMCID: PMC5283899 DOI: 10.1152/ajpcell.00323.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Jeffrey S Isenberg
- Heart, Lung, Blood and Vascular Medicine Institute, Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Josephine C Adams
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
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28
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Garcia-Heredia JM, Carnero A. Decoding Warburg's hypothesis: tumor-related mutations in the mitochondrial respiratory chain. Oncotarget 2016; 6:41582-99. [PMID: 26462158 PMCID: PMC4747175 DOI: 10.18632/oncotarget.6057] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 09/23/2015] [Indexed: 01/13/2023] Open
Abstract
Otto Warburg observed that cancer cells derived their energy from aerobic glycolysis by converting glucose to lactate. This mechanism is in opposition to the higher energy requirements of cancer cells because oxidative phosphorylation (OxPhos) produces more ATP from glucose. Warburg hypothesized that this phenomenon occurs due to the malfunction of mitochondria in cancer cells. The rediscovery of Warburg's hypothesis coincided with the discovery of mitochondrial tumor suppressor genes that may conform to Warburg's hypothesis along with the demonstrated negative impact of HIF-1 on PDH activity and the activation of HIF-1 by oncogenic signals such as activated AKT. This work summarizes the alterations in mitochondrial respiratory chain proteins that have been identified and their involvement in cancer. Also discussed is the fact that most of the mitochondrial mutations have been found in homoplasmy, indicating a positive selection during tumor evolution, thereby supporting their causal role.
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Affiliation(s)
- Jose M Garcia-Heredia
- Instituto de Biomedicina de Sevilla (IBIS), HUVR/CSIC/Universidad de Sevilla, Sevilla, Spain.,Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Sevilla, Spain
| | - Amancio Carnero
- Instituto de Biomedicina de Sevilla (IBIS), HUVR/CSIC/Universidad de Sevilla, Sevilla, Spain
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29
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Singh M, Devi U, Roy S, Gupta PS, Saraf SA, Kaithwas G. Prolyl hydroxylase mediated inhibition of fatty acid synthase to combat tumor growth in mammary gland carcinoma. Breast Cancer 2016; 23:820-829. [PMID: 26951539 DOI: 10.1007/s12282-016-0683-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/24/2016] [Indexed: 12/12/2022]
Abstract
Cancer is a group of cells which grow in an uncontrolled manner and invades to the adjacent organs to form malignant tumors. Tumor hypoxia results due to contrast between the cellular oxygen expenditure and oxygen supply to the cells. Hypoxia inducible factor (HIF) is a heterodimeric transcription factor encompass of oxygen sensitive α subunit and constitutively expressed β subunit both of which are basic helix-loop-helix protein. The stability of HIF is primarily regulated by post translational prolyl hydroxylation, catalyzed by prolyl hydroxylase 2 (Phd-2). Phd-2 is a group of enzymes that acts as an oxygen sensor. Cancer cells have altered metabolism as they fulfil their energy needs through glycolysis and lipid biogenesis. HIF-1α is known to upregulate glycolysis by activating the transcription of enzymes on the glycolytic pathway and through lipogenesis. Cancer cells have over expressed fatty acid synthase owing to altered glycolytic pathway. Considering the above, it is hypothesized that chemical activation of Phd-2 can curtail down HIF-1α and subsequently fatty acid synthase expression.
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Affiliation(s)
- Manjari Singh
- Department of Pharmaceutical Sciences, School of Biosciences and Biotechnology, Babasaheb Bhimrao Ambedkar University (A Central University), Vidya Vihar, Raebareli Road, Lucknow, 226025, India
| | - Uma Devi
- Department of Pharmaceutical Sciences, Faculty of Health Medical Sciences Indigenous and Alternative Medicine, SHIATS-Deemed to be University, Naini, Allahabad, Uttar Pradesh, India
| | - Subhadeep Roy
- Department of Pharmaceutical Sciences, School of Biosciences and Biotechnology, Babasaheb Bhimrao Ambedkar University (A Central University), Vidya Vihar, Raebareli Road, Lucknow, 226025, India
| | - Pushpraj S Gupta
- Department of Pharmaceutical Sciences, Faculty of Health Medical Sciences Indigenous and Alternative Medicine, SHIATS-Deemed to be University, Naini, Allahabad, Uttar Pradesh, India
| | - Shubhini A Saraf
- Department of Pharmaceutical Sciences, School of Biosciences and Biotechnology, Babasaheb Bhimrao Ambedkar University (A Central University), Vidya Vihar, Raebareli Road, Lucknow, 226025, India
| | - Gaurav Kaithwas
- Department of Pharmaceutical Sciences, School of Biosciences and Biotechnology, Babasaheb Bhimrao Ambedkar University (A Central University), Vidya Vihar, Raebareli Road, Lucknow, 226025, India.
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30
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Integrative Conductance of Oxygen During Exercise at Altitude. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 903:395-408. [PMID: 27343110 DOI: 10.1007/978-1-4899-7678-9_26] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the oxygen (O2) cascade downstream steps can never achieve higher flows of O2 than the preceding ones. At the lung the transfer of O2 is determined by the O2 gradient between the alveolar space and the lung capillaries and the O2 diffusing capacity (DLO2). While DLO2 may be increased several times during exercise by recruiting more lung capillaries and by increasing the oxygen carrying capacity of blood due to higher peripheral extraction of O2, the capacity to enhance the alveolocapillary PO2 gradient is more limited. The transfer of oxygen from the alveolar space to the hemoglobin (Hb) must overcome first the resistance offered by the alveolocapillary membrane (1/DM) and the capillary blood (1/θVc). The fractional contribution of each of these two components to DLO2 remains unknown. During exercise these resistances are reduced by the recruitment of lung capillaries. The factors that reduce the slope of the oxygen dissociation curve of the Hb (ODC) (i.e., lactic acidosis and hyperthermia) increase 1/θVc contributing to limit DLO2. These effects are accentuated in hypoxia. Reducing the size of the active muscle mass improves pulmonary gas exchange during exercise and reduces the rightward shift of the ODC. The flow of oxygen from the muscle capillaries to the mitochondria is pressumably limited by muscle O2 conductance (DmcO2) (an estimation of muscle oxygen diffusing capacity). However, during maximal whole body exercise in normoxia, a higher flow of O2 is achieved at the same pressure gradients after increasing blood [Hb], implying that in healthy humans exercising in normoxia there is a functional reserve in DmcO2. This conclusion is supported by the fact that during small muscle exercise in chronic hypoxia, peak exercise DmcO2 is similar to that observed during exercise in normoxia despite a markedly lower O2 pressure gradient driving diffusion.
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31
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Lages YM, Nascimento JM, Lemos GA, Galina A, Castilho LR, Rehen SK. Low oxygen alters mitochondrial function and response to oxidative stress in human neural progenitor cells. PeerJ 2015; 3:e1486. [PMID: 26713239 PMCID: PMC4690376 DOI: 10.7717/peerj.1486] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 11/18/2015] [Indexed: 12/11/2022] Open
Abstract
Oxygen concentration should be carefully regulated in all living tissues, beginning at the early embryonic stages. Unbalances in oxygen regulation can lead to cell death and disease. However, to date, few studies have investigated the consequences of variations in oxygen levels for fetal-like cells. Therefore, in the present work, human neural progenitor cells (NPCs) derived from pluripotent stem cells grown in 3% oxygen (v/v) were compared with NPCs cultured in 21% (v/v) oxygen. Low oxygen concentrations altered the mitochondrial content and oxidative functions of the cells, which led to improved ATP production, while reducing generation of reactive oxygen species (ROS). NPCs cultured in both conditions showed no differences in proliferation and glucose metabolism. Furthermore, antioxidant enzymatic activity was not altered in NPCs cultured in 3% oxygen under normal conditions, however, when exposed to external agents known to induce oxidative stress, greater susceptibility to DNA damage was observed. Our findings indicate that the management of oxygen levels should be considered for in vitro models of neuronal development and drug screening.
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Affiliation(s)
- Yury M Lages
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro , Rio de Janeiro, RJ , Brazil
| | | | - Gabriela A Lemos
- Institute of Medical Biochemistry Leopoldo De Meis, Federal University of Rio de Janeiro , Rio de Janeiro, RJ , Brazil
| | - Antonio Galina
- Institute of Medical Biochemistry Leopoldo De Meis, Federal University of Rio de Janeiro , Rio de Janeiro, RJ , Brazil
| | - Leda R Castilho
- COPPE, Chemical Engineering Program, Federal University of Rio de Janeiro , Rio de Janeiro, RJ , Brazil
| | - Stevens K Rehen
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro , Rio de Janeiro, RJ , Brazil ; IDOR, D'Or Institute for Research and Education , Rio de Janeiro, RJ , Brazil
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32
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Cai H, Tatiyaborworntham N, Yin J, Richards MP. Assessing Low Redox Stability of Myoglobin Relative to Rapid Hemin Loss from Hemoglobin. J Food Sci 2015; 81:C42-8. [DOI: 10.1111/1750-3841.13159] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 10/22/2015] [Indexed: 11/29/2022]
Affiliation(s)
- He Cai
- Dept. of Animal Sciences; Meat Science and Muscle Biology Laboratory; Univ. of Wisconsin-Madison; Madison Wiss. 53706 U.S.A
| | - Nantawat Tatiyaborworntham
- Dept. of Animal Sciences; Meat Science and Muscle Biology Laboratory; Univ. of Wisconsin-Madison; Madison Wiss. 53706 U.S.A
| | - Jie Yin
- Dept. of Animal Sciences; Meat Science and Muscle Biology Laboratory; Univ. of Wisconsin-Madison; Madison Wiss. 53706 U.S.A
| | - Mark P. Richards
- Dept. of Animal Sciences; Meat Science and Muscle Biology Laboratory; Univ. of Wisconsin-Madison; Madison Wiss. 53706 U.S.A
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33
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Boushel R, Gnaiger E, Larsen FJ, Helge JW, González-Alonso J, Ara I, Munch-Andersen T, van Hall G, Søndergaard H, Saltin B, Calbet JAL. Maintained peak leg and pulmonary VO2despite substantial reduction in muscle mitochondrial capacity. Scand J Med Sci Sports 2015; 25 Suppl 4:135-43. [DOI: 10.1111/sms.12613] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2015] [Indexed: 01/12/2023]
Affiliation(s)
- R. Boushel
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- School of Kinesiology; University of British Columbia; Vancouver BC Canada
| | - E. Gnaiger
- Department of Visceral, Transplant and Thoracic Surgery; D. Swarovski Research Laboratory; Medical University of Innsbruck; Innsbruck Austria
| | - F. J. Larsen
- Åstrand Laboratory; The Swedish School of Sport and Health Sciences; Stockholm Sweden
| | - J. W. Helge
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- X-Lab; Department of Biomedical Sciences; University of Copenhagen; Copenhagen Denmark
| | - J. González-Alonso
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- Centre for Sports Medicine and Human Performance; Brunel University, London; Uxbridge UK
| | - I. Ara
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- GENUD Toledo Research Group; Universidad de Castilla-La Mancha (UCLM); Spain
| | | | - G. van Hall
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- Biomedical Sciences, Health & Medical Sciences; University of Copenhagen & Clinical Biochemistry, Rigshospitalet; Copenhagen Denmark
| | - H. Søndergaard
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
| | - B. Saltin
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
| | - J. A. L. Calbet
- The Copenhagen Muscle Research Centre; Copenhagen Denmark
- Department of Physical Education, and Research Institute of Biomedical and Health Sciences (IUIBS); University of Las Palmas de Gran Canaria; Las Palmas Spain
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34
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Kagawa Y, Miyahara H, Ota Y, Tsuneda S. System for measuring oxygen consumption rates of mammalian cells in static culture under hypoxic conditions. Biotechnol Prog 2015; 32:189-97. [PMID: 26558344 DOI: 10.1002/btpr.2202] [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: 07/30/2015] [Revised: 10/28/2015] [Indexed: 01/30/2023]
Abstract
Estimating the oxygen consumption rates (OCRs) of mammalian cells in hypoxic environments is essential for designing and developing a three-dimensional (3-D) cell culture system. However, OCR measurements under hypoxic conditions are infrequently reported in the literature. Here, we developed a system for measuring OCRs at low oxygen levels. The system injects nitrogen gas into the environment and measures the oxygen concentration by an optical oxygen microsensor that consumes no oxygen. The developed system was applied to HepG2 cells in static culture. Specifically, we measured the spatial profiles of the local dissolved oxygen concentration in the medium, then estimated the OCRs of the cells. The OCRs, and also the pericellular oxygen concentrations, decreased nonlinearly as the oxygen partial pressure in the environment decreased from 19% to 1%. The OCRs also depended on the culture period and the matrix used for coating the dish surface. Using this system, we can precisely estimate the OCRs of various cell types under environments that mimic 3-D culture conditions, contributing crucial data for an efficient 3-D culture system design.
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Affiliation(s)
- Yuki Kagawa
- Inst. for Nanoscience and Nanotechnology, Waseda University, 2-2 Wakamatsu-Cho, Shinjuku, Tokyo, 162-8480, Japan
| | - Hirotaka Miyahara
- Dept. of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-Cho, Shinjuku, Tokyo, 162-8480, Japan
| | - Yuri Ota
- Dept. of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-Cho, Shinjuku, Tokyo, 162-8480, Japan
| | - Satoshi Tsuneda
- Inst. for Nanoscience and Nanotechnology, Waseda University, 2-2 Wakamatsu-Cho, Shinjuku, Tokyo, 162-8480, Japan.,Dept. of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-Cho, Shinjuku, Tokyo, 162-8480, Japan
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35
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Zhdanov AV, Golubeva AV, Okkelman IA, Cryan JF, Papkovsky DB. Imaging of oxygen gradients in giant umbrella cells: an ex vivo PLIM study. Am J Physiol Cell Physiol 2015; 309:C501-9. [DOI: 10.1152/ajpcell.00121.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 08/03/2015] [Indexed: 12/29/2022]
Abstract
O2 plays a pivotal role in aerobic metabolism and regulation of cell and tissue function. Local differences and fluctuations in tissue O2 levels are well documented; however, the physiological significance of O2 microgradients, particularly at the subcellular level, remains poorly understood. Using the cell-penetrating phosphorescent O2 probe Pt-Glc and confocal fluorescence microscopy, we visualized O2 distribution in individual giant (>100-μm) umbrella cells located superficially in the urinary bladder epithelium. We optimized conditions for in vivo phosphorescent staining of the inner surface of the mouse bladder and subsequent ex vivo analysis of excised live tissue. Imaging experiments revealed significant (≤85 μM) and heterogeneous deoxygenation within respiring umbrella cells, with radial O2 gradients of up to 40 μM across the cell, or ∼0.6 μM/μm. Deeply deoxygenated (5–15 μM O2) regions were seen to correspond to the areas enriched with polarized mitochondria. Pharmacological activation of mitochondrial respiration decreased oxygenation and O2 gradients in umbrella cells, while inhibition with antimycin A dissipated the gradients and caused gradual reoxygenation of the tissue to ambient levels. Detailed three-dimensional maps of O2 distribution potentially can be used for the modeling of intracellular O2-dependent enzymatic reactions and downstream processes, such as hypoxia-inducible factor signaling. Further ex vivo and in vivo studies on intracellular and tissue O2 gradients using confocal imaging can shed light on the molecular mechanisms regulating O2-dependent (patho)physiological processes in the bladder and other tissues.
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Affiliation(s)
- A. V. Zhdanov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - A. V. Golubeva
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; and
| | - I. A. Okkelman
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - J. F. Cryan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland; and
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - D. B. Papkovsky
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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36
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Morales-Alamo D, Losa-Reyna J, Torres-Peralta R, Martin-Rincon M, Perez-Valera M, Curtelin D, Ponce-González JG, Santana A, Calbet JAL. What limits performance during whole-body incremental exercise to exhaustion in humans? J Physiol 2015; 593:4631-48. [PMID: 26250346 DOI: 10.1113/jp270487] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 07/29/2015] [Indexed: 12/13/2022] Open
Abstract
To determine the mechanisms causing task failure during incremental exercise to exhaustion (IE), sprint performance (10 s all-out isokinetic) and muscle metabolites were measured before (control) and immediately after IE in normoxia (P(IO2) 143 mmHg) and hypoxia (P(IO2): 73 mmHg) in 22 men (22 ± 3 years). After IE, subjects recovered for either 10 or 60 s, with open circulation or bilateral leg occlusion (300 mmHg) in random order. This was followed by a 10 s sprint with open circulation. Post-IE peak power output (W(peak)) was higher than the power output reached at exhaustion during IE (P < 0.05). After 10 and 60 s recovery in normoxia, W(peak) was reduced by 38 ± 9 and 22 ± 10% without occlusion, and 61 ± 8 and 47 ± 10% with occlusion (P < 0.05). Following 10 s occlusion, W(peak) was 20% higher in hypoxia than normoxia (P < 0.05), despite similar muscle lactate accumulation ([La]) and phosphocreatine and ATP reduction. Sprint performance and anaerobic ATP resynthesis were greater after 60 s compared with 10 s occlusions, despite the higher [La] and [H(+)] after 60 s compared with 10 s occlusion recovery (P < 0.05). The mean rate of ATP turnover during the 60 s occlusion was 0.180 ± 0.133 mmol (kg wet wt)(-1) s(-1), i.e. equivalent to 32% of leg peak O2 uptake (the energy expended by the ion pumps). A greater degree of recovery is achieved, however, without occlusion. In conclusion, during incremental exercise task failure is not due to metabolite accumulation or lack of energy resources. Anaerobic metabolism, despite the accumulation of lactate and H(+), facilitates early recovery even in anoxia. This points to central mechanisms as the principal determinants of task failure both in normoxia and hypoxia, with lower peripheral contribution in hypoxia.
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Affiliation(s)
- David Morales-Alamo
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - José Losa-Reyna
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - Rafael Torres-Peralta
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - Marcos Martin-Rincon
- Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Department of Sports and Informatics, Pablo de Olavide University, Seville, Spain
| | - Mario Perez-Valera
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
| | - David Curtelin
- Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Emergency Medicine Department, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain
| | - Jesús Gustavo Ponce-González
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain
| | - Alfredo Santana
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.,Clinical Genetics Unit, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima, del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain
| | - José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain
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37
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Calbet JAL, Losa-Reyna J, Torres-Peralta R, Rasmussen P, Ponce-González JG, Sheel AW, de la Calle-Herrero J, Guadalupe-Grau A, Morales-Alamo D, Fuentes T, Rodríguez-García L, Siebenmann C, Boushel R, Lundby C. Limitations to oxygen transport and utilization during sprint exercise in humans: evidence for a functional reserve in muscle O2 diffusing capacity. J Physiol 2015; 593:4649-64. [PMID: 26258623 DOI: 10.1113/jp270408] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 08/05/2015] [Indexed: 12/14/2022] Open
Abstract
To determine the contribution of convective and diffusive limitations to V̇(O2peak) during exercise in humans, oxygen transport and haemodynamics were measured in 11 men (22 ± 2 years) during incremental (IE) and 30 s all-out cycling sprints (Wingate test, WgT), in normoxia (Nx, P(IO2): 143 mmHg) and hypoxia (Hyp, P(IO2): 73 mmHg). Carboxyhaemoglobin (COHb) was increased to 6-7% before both WgTs to left-shift the oxyhaemoglobin dissociation curve. Leg V̇(O2) was measured by the Fick method and leg blood flow (BF) with thermodilution, and muscle O2 diffusing capacity (D(MO2)) was calculated. In the WgT mean power output, leg BF, leg O2 delivery and leg V̇(O2) were 7, 5, 28 and 23% lower in Hyp than Nx (P < 0.05); however, peak WgT D(MO2) was higher in Hyp (51.5 ± 9.7) than Nx (20.5 ± 3.0 ml min(-1) mmHg(-1), P < 0.05). Despite a similar P(aO2) (33.3 ± 2.4 and 34.1 ± 3.3 mmHg), mean capillary P(O2) (16.7 ± 1.2 and 17.1 ± 1.6 mmHg), and peak perfusion during IE and WgT in Hyp, D(MO2) and leg V̇(O2) were 12 and 14% higher, respectively, during WgT than IE in Hyp (both P < 0.05). D(MO2) was insensitive to COHb (COHb: 0.7 vs. 7%, in IE Hyp and WgT Hyp). At exhaustion, the Y equilibration index was well above 1.0 in both conditions, reflecting greater convective than diffusive limitation to the O2 transfer in both Nx and Hyp. In conclusion, muscle V̇(O2) during sprint exercise is not limited by O2 delivery, O2 offloading from haemoglobin or structure-dependent diffusion constraints in the skeletal muscle. These findings reveal a remarkable functional reserve in muscle O2 diffusing capacity.
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Affiliation(s)
- José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - José Losa-Reyna
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Rafael Torres-Peralta
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Peter Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Jesús Gustavo Ponce-González
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jaime de la Calle-Herrero
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Amelia Guadalupe-Grau
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - David Morales-Alamo
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain.,Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Canary Islands, Spain
| | - Teresa Fuentes
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Lorena Rodríguez-García
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, Las Palmas de Gran Canaria, Canary Islands, 35017, Spain
| | - Christoph Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Robert Boushel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.,Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Carsten Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
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38
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Harrison DK, Fasching M, Fontana-Ayoub M, Gnaiger E. Cytochrome redox states and respiratory control in mouse and beef heart mitochondria at steady-state levels of hypoxia. J Appl Physiol (1985) 2015; 119:1210-8. [PMID: 26251509 DOI: 10.1152/japplphysiol.00146.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 08/03/2015] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial control of cellular redox states is a fundamental component of cell signaling in the coordination of core energy metabolism and homeostasis during normoxia and hypoxia. We investigated the relationship between cytochrome redox states and mitochondrial oxygen consumption at steady-state levels of hypoxia in mitochondria isolated from beef and mouse heart (BHImt, MHImt), comparing two species with different cardiac dynamics and local oxygen demands. A low-noise, rapid spectrophotometric system using visible light for the measurement of cytochrome redox states was combined with high-resolution respirometry. Monophasic hyperbolic relationships were observed between oxygen consumption, JO2, and oxygen partial pressure, Po2, within the range <1.1 kPa (8.3 mmHg; 13 μM). P50j (Po2 at 0.5·Jmax) was 0.015 ± 0.0004 and 0.021 ± 0.003 kPa (0.11 and 0.16 mmHg) for BHImt and MHImt, respectively. Maximum oxygen consumption, Jmax, was measured at saturating ADP levels (OXPHOS capacity) with Complex I-linked substrate supply. Redox states of cytochromes aa3 and c were biphasic hyperbolic functions of Po2. The relationship between cytochrome oxidation state and oxygen consumption revealed a separation of distinct phases from mild to severe and deep hypoxia. When cytochrome c oxidation increased from fully reduced to 45% oxidized at 0.1 Jmax, Po2 was as low as 0.002 kPa (0.02 μM), and trace amounts of oxygen are sufficient to partially oxidize the cytochromes. At higher Po2 under severe hypoxia, respiration increases steeply, whereas redox changes are small. Under mild hypoxia, the steep slope of oxidation of cytochrome c when flux remains more stable represents a cushioning mechanism that helps to maintain respiration high at the onset of hypoxia.
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Affiliation(s)
- David K Harrison
- OROBOROS INSTRUMENTS, Innsbruck, Austria; Microvascular Measurements, St Lorenzen, Italy; and
| | | | | | - Erich Gnaiger
- OROBOROS INSTRUMENTS, Innsbruck, Austria; D Swarowski Research Laboratory, Department of Visceral Transplant and Thoracic Surgery, Medical University of Innsbruck, Austria
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39
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Lu H, Wang R, Xiong J, Xie H, Kayser B, Jia Z. In search for better pharmacological prophylaxis for acute mountain sickness: looking in other directions. Acta Physiol (Oxf) 2015; 214:51-62. [PMID: 25778288 DOI: 10.1111/apha.12490] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 02/23/2015] [Accepted: 03/11/2015] [Indexed: 12/15/2022]
Abstract
Despite decades of research, the exact pathogenic mechanisms underlying acute mountain sickness (AMS) are still poorly understood. This fact frustrates the search for novel pharmacological prophylaxis for AMS. The prevailing view is that AMS results from an insufficient physiological response to hypoxia and that prophylaxis should aim at stimulating the response. Starting off from the opposite hypothesis that AMS may be caused by an initial excessive response to hypoxia, we suggest that directly or indirectly blunting-specific parts of the response might provide promising research alternatives. This reasoning is based on the observations that (i) humans, once acclimatized, can climb Mt Everest experiencing arterial partial oxygen pressures (PaO2) as low as 25 mmHg without AMS symptoms; (ii) paradoxically, AMS usually develops at much higher PaO2 levels; and (iii) several biomarkers, suggesting initial activation of specific pathways at such PaO2, are correlated with AMS. Apart from looking for substances that stimulate certain hypoxia triggered effects, such as the ventilatory response to hypoxia, we suggest to also investigate pharmacological means aiming at blunting certain other specific hypoxia-activated pathways, or stimulating their agonists, in the quest for better pharmacological prophylaxis for AMS.
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Affiliation(s)
- H. Lu
- Key Laboratory of the Plateau of Environmental Damage Control; Lanzhou General Hospital of Lanzhou Military Command; Lanzhou China
| | - R. Wang
- Key Laboratory of the Plateau of Environmental Damage Control; Lanzhou General Hospital of Lanzhou Military Command; Lanzhou China
| | - J. Xiong
- Key Laboratory of the Plateau of Environmental Damage Control; Lanzhou General Hospital of Lanzhou Military Command; Lanzhou China
| | - H. Xie
- Key Laboratory of the Plateau of Environmental Damage Control; Lanzhou General Hospital of Lanzhou Military Command; Lanzhou China
| | - B. Kayser
- Institute of Sports Sciences and Department of Physiology; University of Lausanne; Lausanne Switzerland
| | - Z.P. Jia
- Key Laboratory of the Plateau of Environmental Damage Control; Lanzhou General Hospital of Lanzhou Military Command; Lanzhou China
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40
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Dmitriev RI, Papkovsky DB. Intracellular probes for imaging oxygen concentration: how good are they? Methods Appl Fluoresc 2015; 3:034001. [DOI: 10.1088/2050-6120/3/3/034001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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41
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Levine AP, Duchen MR, de Villiers S, Rich PR, Segal AW. Alkalinity of neutrophil phagocytic vacuoles is modulated by HVCN1 and has consequences for myeloperoxidase activity. PLoS One 2015; 10:e0125906. [PMID: 25885273 PMCID: PMC4401748 DOI: 10.1371/journal.pone.0125906] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/21/2015] [Indexed: 12/03/2022] Open
Abstract
The NADPH oxidase of neutrophils, essential for innate immunity, passes electrons across the phagocytic membrane to form superoxide in the phagocytic vacuole. Activity of the oxidase requires that charge movements across the vacuolar membrane are balanced. Using the pH indicator SNARF, we measured changes in pH in the phagocytic vacuole and cytosol of neutrophils. In human cells, the vacuolar pH rose to ~9, and the cytosol acidified slightly. By contrast, in Hvcn1 knock out mouse neutrophils, the vacuolar pH rose above 11, vacuoles swelled, and the cytosol acidified excessively, demonstrating that ordinarily this channel plays an important role in charge compensation. Proton extrusion was not diminished in Hvcn1-/- mouse neutrophils arguing against its role in maintaining pH homeostasis across the plasma membrane. Conditions in the vacuole are optimal for bacterial killing by the neutral proteases, cathepsin G and elastase, and not by myeloperoxidase, activity of which was unphysiologically low at alkaline pH.
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Affiliation(s)
- Adam P. Levine
- Division of Medicine, University College London, London, United Kingdom
| | - Michael R. Duchen
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Simon de Villiers
- Glynn Laboratory of Bioenergetics, Department of Biology, University College London, London, United Kingdom
| | - Peter R. Rich
- Glynn Laboratory of Bioenergetics, Department of Biology, University College London, London, United Kingdom
| | - Anthony W. Segal
- Division of Medicine, University College London, London, United Kingdom
- * E-mail:
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42
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Woolcott OO, Ader M, Bergman RN. Glucose homeostasis during short-term and prolonged exposure to high altitudes. Endocr Rev 2015; 36:149-73. [PMID: 25675133 PMCID: PMC4399271 DOI: 10.1210/er.2014-1063] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Most of the literature related to high altitude medicine is devoted to the short-term effects of high-altitude exposure on human physiology. However, long-term effects of living at high altitudes may be more important in relation to human disease because more than 400 million people worldwide reside above 1500 m. Interestingly, individuals living at higher altitudes have a lower fasting glycemia and better glucose tolerance compared with those who live near sea level. There is also emerging evidence of the lower prevalence of both obesity and diabetes at higher altitudes. The mechanisms underlying improved glucose control at higher altitudes remain unclear. In this review, we present the most current evidence about glucose homeostasis in residents living above 1500 m and discuss possible mechanisms that could explain the lower fasting glycemia and lower prevalence of obesity and diabetes in this population. Understanding the mechanisms that regulate and maintain the lower fasting glycemia in individuals who live at higher altitudes could lead to new therapeutics for impaired glucose homeostasis.
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Affiliation(s)
- Orison O Woolcott
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048
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Abstract
SIGNIFICANCE Although oxygen (O2)-sensing cells and tissues have been known for decades, the identity of the O2-sensing mechanism has remained elusive. Evidence is accumulating that O2-dependent metabolism of hydrogen sulfide (H2S) is this enigmatic O2 sensor. RECENT ADVANCES The elucidation of biochemical pathways involved in H2S synthesis and metabolism have shown that reciprocal H2S/O2 interactions have been inexorably linked throughout eukaryotic evolution; there are multiple foci by which O2 controls H2S inactivation, and the effects of H2S on downstream signaling events are consistent with those activated by hypoxia. H2S-mediated O2 sensing has been demonstrated in a variety of O2-sensing tissues in vertebrate cardiovascular and respiratory systems, including smooth muscle in systemic and respiratory blood vessels and airways, carotid body, adrenal medulla, and other peripheral as well as central chemoreceptors. CRITICAL ISSUES Information is now needed on the intracellular location and stoichometry of these signaling processes and how and which downstream effectors are activated by H2S and its metabolites. FUTURE DIRECTIONS Development of specific inhibitors of H2S metabolism and effector activation as well as cellular organelle-targeted compounds that release H2S in a time- or environmentally controlled way will not only enhance our understanding of this signaling process but also provide direction for future therapeutic applications.
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Affiliation(s)
- Kenneth R Olson
- Department of Physiology, Indiana University School of Medicine-South Bend , South Bend, India na
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44
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García-Heredia JM, Felipe-Abrio B, Cano DA, Carnero A. Genetic modification of hypoxia signaling in animal models and its effect on cancer. Clin Transl Oncol 2014; 17:90-102. [PMID: 25351170 DOI: 10.1007/s12094-014-1236-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 09/24/2014] [Indexed: 12/19/2022]
Abstract
Conditions that cause hypoxemia or generalized tissue hypoxia, which can last for days, months, or even years, are very common in the human population and are among the leading causes of morbidity, disability, and mortality. Therefore, the molecular pathophysiology of hypoxia and its potential deleterious effects on human health are important issues at the forefront of biomedical research. Generalized hypoxia is a consequence of highly prevalent medical disorders that can severely reduce the capacity for O2 exchange between the air and pulmonary capillaries. In recent years, some of the key O2-dependent signaling pathways have been characterized at the molecular level. In particular, the prolyl hydroxylase (PHD)-hypoxia-inducible factor (HIF) cascade has emerged as the master regulator of a general gene expression program involved in cell/tissue/organ adaptation to hypoxia. Hypoxia has emerged as a critical factor in cancer because it can promote tumor initiation, progression, and resistance to therapy. Beyond its role in neovascularization as a mechanism of tumor adaptation to nutrient and O2 deprivation, hypoxia has been linked to prolonged cellular lifespan and immortalization, the generation of "oncometabolites", deregulation of stem cell proliferation, and inflammation, among other tumor hallmarks. Hypoxia may contribute to cancer through several independent pathways, the inter-connections of which have yet to be elucidated. Furthermore, the relevance of chronic hypoxemia in the initiation and progression of cancer has not been studied in depth in the whole organism. Therefore, we explore here the contributions of hypoxia to the whole organism by reviewing studies on genetically modified mice with alterations in the key molecular factors regulating hypoxia.
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Affiliation(s)
- J M García-Heredia
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, 41013, Seville, Spain
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45
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Pires NJ, Lay BS, Rubenson J. Joint-level mechanics of the walk-to-run transition in humans. ACTA ACUST UNITED AC 2014; 217:3519-27. [PMID: 25104752 DOI: 10.1242/jeb.107599] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two commonly proposed mechanical explanations for the walk-to-run transition (WRT) include the prevention of muscular over-exertion (effort) and the minimization of peak musculoskeletal loads and thus injury risk. The purpose of this study was to address these hypotheses at a joint level by analysing the effect of speed on discrete lower-limb joint kinetic parameters in humans across a wide range of walking and running speeds including walking above and running below the WRT speed. Joint work, peak instantaneous joint power, and peak joint moments in the sagittal and frontal plane of the ankle, knee and hip from eight participants were collected for 10 walking speeds (30-120% of their WRT) and 10 running speeds (80-170% of their WRT) on a force plate instrumented treadmill. Of the parameters analysed, three satisfied our statistical criteria of the 'effort-load' hypothesis of the WRT. Mechanical parameters that provide an acute signal (peak moment and peak power) were more strongly associated with the gait transition than parameters that reflect the mechanical function across a portion of the stride. We found that both the ankle (peak instantaneous joint power during swing) and hip mechanics (peak instantaneous joint power and peak joint moments in stance) can influence the transition from walking to running in human locomotion and may represent a cascade of mechanical events beginning at the ankle and leading to an unfavourable compensation at the hip. Both the ankle and hip mechanisms may contribute to gait transition by lowering the muscular effort of running compared with walking at the WRT speed. Although few of the examined joint variables satisfied our hypothesis of the WRT, most showed a general marked increase when switching from walking to running across all speeds where both walking and running are possible, highlighting the fundamental differences in the mechanics of walking and running. While not eliciting the WRT per se, these variables may initiate the transition between stable walking and running patterns. Those variables that were invariant of gait were predominantly found in the swing phase.
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Affiliation(s)
- Neville J Pires
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA 6009, Australia
| | - Brendan S Lay
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA 6009, Australia
| | - Jonas Rubenson
- School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, WA 6009, Australia
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46
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Oxidative phosphorylation in Debaryomyces hansenii: physiological uncoupling at different growth phases. Biochimie 2014; 102:124-36. [PMID: 24657599 DOI: 10.1016/j.biochi.2014.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/03/2014] [Indexed: 12/31/2022]
Abstract
Physiological uncoupling of mitochondrial oxidative phosphorylation (OxPhos) was studied in Debaryomyces hansenii. In other species, such as Yarrowia lipolytica and Saccharomyces cerevisiae, OxPhos can be uncoupled through differential expression of branched respiratory chain enzymes or by opening of a mitochondrial unspecific channel (ScMUC), respectively. However D. hansenii mitochondria, which contain both a branched respiratory chain and a mitochondrial unspecific channel (DhMUC), selectively uncouple complex I-dependent rate of oxygen consumption in the stationary growth phase. The uncoupled complex I-dependent respiration was only 20% of the original activity. Inhibition was not due to inactivation of complex I, lack of protein expression or to differential expression of alternative oxidoreductases. Furthermore, all other respiratory chain activities were normal. Decrease of complex I-dependent respiration was due to NAD(+) loss from the matrix, probably through an open of DhMUC. When NAD(+) was added back, coupled complex I-activity was recovered. NAD(+) re-uptake was independent of DhMUC opening and seemed to be catalyzed by a NAD(+)-specific transporter, which was sensitive to bathophenanthroline, bromocresol purple or pyridoxal-5'-phosphate as described for S. cerevisiae mitochondrial NAD(+) transporters. Loss of NAD(+) from the matrix through an open MUC is proposed as an additional mechanism to uncouple OxPhos.
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47
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Ghodbane R, Raoult D, Drancourt M. Dramatic reduction of culture time of Mycobacterium tuberculosis. Sci Rep 2014; 4:4236. [PMID: 24577292 PMCID: PMC3937792 DOI: 10.1038/srep04236] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 02/03/2014] [Indexed: 11/25/2022] Open
Abstract
Mycobacterium tuberculosis culture, a critical technique for routine diagnosis of tuberculosis, takes more than two weeks. Here, step-by-step improvements in the protocol including a new medium, microaerophlic atmosphere or ascorbic-acid supplement and autofluorescence detection dramatically shortened this delay. In the best case, primary culture and rifampicin susceptibility testing were achieved in 72 hours when specimens were inoculated directly on the medium supplemented by antibiotic at the beginning of the culture.
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Affiliation(s)
- Ramzi Ghodbane
- Aix Marseille Université, URMITE UMR CNRS 7278, IRD 198, Inserm 1095, 13005, Marseille, France
| | - Didier Raoult
- Aix Marseille Université, URMITE UMR CNRS 7278, IRD 198, Inserm 1095, 13005, Marseille, France
| | - Michel Drancourt
- Aix Marseille Université, URMITE UMR CNRS 7278, IRD 198, Inserm 1095, 13005, Marseille, France
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48
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Burggren WW, Christoffels VM, Crossley DA, Enok S, Farrell AP, Hedrick MS, Hicks JW, Jensen B, Moorman AFM, Mueller CA, Skovgaard N, Taylor EW, Wang T. Comparative cardiovascular physiology: future trends, opportunities and challenges. Acta Physiol (Oxf) 2014; 210:257-76. [PMID: 24119052 DOI: 10.1111/apha.12170] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/16/2013] [Accepted: 09/12/2013] [Indexed: 12/23/2022]
Abstract
The inaugural Kjell Johansen Lecture in the Zoophysiology Department of Aarhus University (Aarhus, Denmark) afforded the opportunity for a focused workshop comprising comparative cardiovascular physiologists to ponder some of the key unanswered questions in the field. Discussions were centred around three themes. The first considered function of the vertebrate heart in its various forms in extant vertebrates, with particular focus on the role of intracardiac shunts, the trabecular ('spongy') nature of the ventricle in many vertebrates, coronary blood supply and the building plan of the heart as revealed by molecular approaches. The second theme involved the key unanswered questions in the control of the cardiovascular system, emphasizing autonomic control, hypoxic vasoconstriction and developmental plasticity in cardiovascular control. The final theme involved poorly understood aspects of the interaction of the cardiovascular system with the lymphatic, renal and digestive systems. Having posed key questions around these three themes, it is increasingly clear that an abundance of new analytical tools and approaches will allow us to learn much about vertebrate cardiovascular systems in the coming years.
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Affiliation(s)
- W. W. Burggren
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - V. M. Christoffels
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
| | - D. A. Crossley
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - S. Enok
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - A. P. Farrell
- Department of Zoology and Faculty of Land and Food Systems; University of British Columbia; Vancouver BC Canada
| | - M. S. Hedrick
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - J. W. Hicks
- Department of Ecology and Evolutionary Biology; University of California; Irvine CA USA
| | - B. Jensen
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - A. F. M. Moorman
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
| | - C. A. Mueller
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - N. Skovgaard
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - E. W. Taylor
- School of Biosciences; University of Birmingham; Birmingham UK
| | - T. Wang
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
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49
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Welc SS, Judge AR, Clanton TL. Skeletal muscle interleukin-6 regulation in hyperthermia. Am J Physiol Cell Physiol 2013; 305:C406-13. [DOI: 10.1152/ajpcell.00084.2013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously reported that IL-6 production is acutely elevated in skeletal muscles exposed to ≥41°C, but the regulatory pathways are poorly understood. The present study characterizes the heat-induced transcriptional control of IL-6 in C2C12 muscle fibers. Hyperthermia exposure (42°C for 1 h) induced transcription from an IL-6 promoter-luciferase reporter plasmid. Heat shock factor-1 (HSF-1), a principal mediator of the heat shock response, was then tested for its role in IL-6 regulation. Overexpression of a constitutively active HSF-1 construct increased basal (37°C) promoter activity, whereas overexpression of a dominant negative HSF-1 reduced IL-6 promoter activity during basal and hyperthermia conditions. Since hyperthermia also induces stress-activated protein kinase (SAPK) signaling, we tested whether mutation of a transcription site downstream of SAPK, (i.e., activator protein-1, AP-1) influences IL-6 transcription in hyperthermia. The mutation had no effect on baseline reporter activity but completely inhibited heat-induced activity. We then tested whether pharmacologically induced states of protein stress, characteristic of cellular responses to hyperthermia and known to induce SAPKs and HSF-1, would induce IL-6 production in the absence of heat. The proteasome was inhibited with MG-132 in one set of experiments, and the unfolded protein response was stimulated with dithiothreitol, thapsigargin, tunicamycin, or castanospermine in other experiments. All treatments stimulated IL-6 protein secretion in the absence of hyperthermia. These studies demonstrate that IL-6 regulation in hyperthermia is directly controlled by HSF-1 and AP-1 signaling and that the IL-6 response in C2C12 myotubes is sensitive to categories of protein stress that reflect accumulation of damaged or unfolded proteins.
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Affiliation(s)
- Steven S. Welc
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, Florida; and
| | - Andrew R. Judge
- Department of Physical Therapy, College of Health and Health Professions, University of Florida, Gainesville, Florida
| | - Thomas L. Clanton
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, Florida; and
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