1
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Garcia-Bermudez J, Badgley MA, Prasad S, Baudrier L, Liu Y, La K, Soula M, Williams RT, Yamaguchi N, Hwang RF, Taylor LJ, de Stanchina E, Rostandy B, Alwaseem H, Molina H, Bar-Sagi D, Birsoy K. Adaptive stimulation of macropinocytosis overcomes aspartate limitation in cancer cells under hypoxia. Nat Metab 2022; 4:724-738. [PMID: 35726024 PMCID: PMC9678334 DOI: 10.1038/s42255-022-00583-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 05/10/2022] [Indexed: 12/24/2022]
Abstract
Stress-adaptive mechanisms enable tumour cells to overcome metabolic constraints under nutrient and oxygen shortage. Aspartate is an endogenous metabolic limitation under hypoxic conditions, but the nature of the adaptive mechanisms that contribute to aspartate availability and hypoxic tumour growth are poorly understood. Here we identify GOT2-catalysed mitochondrial aspartate synthesis as an essential metabolic dependency for the proliferation of pancreatic tumour cells under hypoxic culture conditions. In contrast, GOT2-catalysed aspartate synthesis is dispensable for pancreatic tumour formation in vivo. The dependence of pancreatic tumour cells on aspartate synthesis is bypassed in part by a hypoxia-induced potentiation of extracellular protein scavenging via macropinocytosis. This effect is mutant KRAS dependent, and is mediated by hypoxia-inducible factor 1 (HIF1A) and its canonical target carbonic anhydrase-9 (CA9). Our findings reveal high plasticity of aspartate metabolism and define an adaptive regulatory role for macropinocytosis by which mutant KRAS tumours can overcome nutrient deprivation under hypoxic conditions.
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Affiliation(s)
- Javier Garcia-Bermudez
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
- Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Michael A Badgley
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Sheela Prasad
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Lou Baudrier
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Yuyang Liu
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Konnor La
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Mariluz Soula
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Robert T Williams
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Norihiro Yamaguchi
- Laboratory of Systems Cancer Biology, The Rockefeller University, New York, NY, USA
| | - Rosa F Hwang
- Department of Breast Surgical Oncology, Division of Surgery, MD Anderson Cancer Center, University of Texas, Houston, TX, USA
| | - Laura J Taylor
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Elisa de Stanchina
- Antitumor Assessment Core Facility, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Bety Rostandy
- The Proteomics Resource Center, The Rockefeller University, New York, NY, USA
| | - Hanan Alwaseem
- The Proteomics Resource Center, The Rockefeller University, New York, NY, USA
| | - Henrik Molina
- The Proteomics Resource Center, The Rockefeller University, New York, NY, USA
| | - Dafna Bar-Sagi
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
| | - Kıvanç Birsoy
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA.
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2
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Nesci S, Trombetti F, Pagliarani A, Ventrella V, Algieri C, Tioli G, Lenaz G. Molecular and Supramolecular Structure of the Mitochondrial Oxidative Phosphorylation System: Implications for Pathology. Life (Basel) 2021; 11:242. [PMID: 33804034 PMCID: PMC7999509 DOI: 10.3390/life11030242] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/09/2021] [Accepted: 03/11/2021] [Indexed: 02/07/2023] Open
Abstract
Under aerobic conditions, mitochondrial oxidative phosphorylation (OXPHOS) converts the energy released by nutrient oxidation into ATP, the currency of living organisms. The whole biochemical machinery is hosted by the inner mitochondrial membrane (mtIM) where the protonmotive force built by respiratory complexes, dynamically assembled as super-complexes, allows the F1FO-ATP synthase to make ATP from ADP + Pi. Recently mitochondria emerged not only as cell powerhouses, but also as signaling hubs by way of reactive oxygen species (ROS) production. However, when ROS removal systems and/or OXPHOS constituents are defective, the physiological ROS generation can cause ROS imbalance and oxidative stress, which in turn damages cell components. Moreover, the morphology of mitochondria rules cell fate and the formation of the mitochondrial permeability transition pore in the mtIM, which, most likely with the F1FO-ATP synthase contribution, permeabilizes mitochondria and leads to cell death. As the multiple mitochondrial functions are mutually interconnected, changes in protein composition by mutations or in supercomplex assembly and/or in membrane structures often generate a dysfunctional cascade and lead to life-incompatible diseases or severe syndromes. The known structural/functional changes in mitochondrial proteins and structures, which impact mitochondrial bioenergetics because of an impaired or defective energy transduction system, here reviewed, constitute the main biochemical damage in a variety of genetic and age-related diseases.
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Affiliation(s)
- Salvatore Nesci
- Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, 40064 Ozzano Emilia, Italy; (F.T.); (V.V.); (C.A.)
| | - Fabiana Trombetti
- Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, 40064 Ozzano Emilia, Italy; (F.T.); (V.V.); (C.A.)
| | - Alessandra Pagliarani
- Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, 40064 Ozzano Emilia, Italy; (F.T.); (V.V.); (C.A.)
| | - Vittoria Ventrella
- Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, 40064 Ozzano Emilia, Italy; (F.T.); (V.V.); (C.A.)
| | - Cristina Algieri
- Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, 40064 Ozzano Emilia, Italy; (F.T.); (V.V.); (C.A.)
| | - Gaia Tioli
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum University of Bologna, 40138 Bologna, Italy;
| | - Giorgio Lenaz
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum University of Bologna, 40138 Bologna, Italy;
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3
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Ducsay CA, Goyal R, Pearce WJ, Wilson S, Hu XQ, Zhang L. Gestational Hypoxia and Developmental Plasticity. Physiol Rev 2018; 98:1241-1334. [PMID: 29717932 PMCID: PMC6088145 DOI: 10.1152/physrev.00043.2017] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.
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Affiliation(s)
- Charles A. Ducsay
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
| | - Ravi Goyal
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
| | - William J. Pearce
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
| | - Sean Wilson
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
| | - Xiang-Qun Hu
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
| | - Lubo Zhang
- The Lawrence D. Longo, MD Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, California
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4
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Garcia-Bermudez J, Baudrier L, La K, Zhu XG, Fidelin J, Sviderskiy VO, Papagiannakopoulos T, Molina H, Snuderl M, Lewis CA, Possemato RL, Birsoy K. Aspartate is a limiting metabolite for cancer cell proliferation under hypoxia and in tumours. Nat Cell Biol 2018; 20:775-781. [PMID: 29941933 PMCID: PMC6030478 DOI: 10.1038/s41556-018-0118-z] [Citation(s) in RCA: 272] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 05/09/2018] [Indexed: 12/27/2022]
Abstract
As oxygen is essential for many metabolic pathways, tumour hypoxia may impair cancer cell proliferation1-4. However, the limiting metabolites for proliferation under hypoxia and in tumours are unknown. Here, we assessed proliferation of a collection of cancer cells following inhibition of the mitochondrial electron transport chain (ETC), a major metabolic pathway requiring molecular oxygen5. Sensitivity to ETC inhibition varied across cell lines, and subsequent metabolomic analysis uncovered aspartate availability as a major determinant of sensitivity. Cell lines least sensitive to ETC inhibition maintain aspartate levels by importing it through an aspartate/glutamate transporter, SLC1A3. Genetic or pharmacologic modulation of SLC1A3 activity markedly altered cancer cell sensitivity to ETC inhibitors. Interestingly, aspartate levels also decrease under low oxygen, and increasing aspartate import by SLC1A3 provides a competitive advantage to cancer cells at low oxygen levels and in tumour xenografts. Finally, aspartate levels in primary human tumours negatively correlate with the expression of hypoxia markers, suggesting that tumour hypoxia is sufficient to inhibit ETC and, consequently, aspartate synthesis in vivo. Therefore, aspartate may be a limiting metabolite for tumour growth, and aspartate availability could be targeted for cancer therapy.
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Affiliation(s)
- Javier Garcia-Bermudez
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Lou Baudrier
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Konnor La
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Xiphias Ge Zhu
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Justine Fidelin
- Proteomics Resource Center, The Rockefeller University, New York, NY, USA
| | | | | | - Henrik Molina
- Proteomics Resource Center, The Rockefeller University, New York, NY, USA
| | - Matija Snuderl
- Department of Pathology, New York University School of Medicine, New York, NY, USA
| | | | - Richard L Possemato
- Department of Pathology, New York University School of Medicine, New York, NY, USA
| | - Kıvanç Birsoy
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA.
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5
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Lim TKY, Rone MB, Lee S, Antel JP, Zhang J. Mitochondrial and bioenergetic dysfunction in trauma-induced painful peripheral neuropathy. Mol Pain 2015; 11:58. [PMID: 26376783 PMCID: PMC4574230 DOI: 10.1186/s12990-015-0057-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 08/26/2015] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Mitochondrial dysfunction is observed in various neuropathic pain phenotypes, such as chemotherapy induced neuropathy, diabetic neuropathy, HIV-associated neuropathy, and in Charcot-Marie-Tooth neuropathy. To investigate whether mitochondrial dysfunction is present in trauma-induced painful mononeuropathy, a time-course of mitochondrial function and bioenergetics was characterized in the mouse partial sciatic nerve ligation model. RESULTS Traumatic nerve injury induces increased metabolic indices of the nerve, resulting in increased oxygen consumption and increased glycolysis. Increased metabolic needs of the nerve are concomitant with bioenergetic and mitochondrial dysfunction. Mitochondrial dysfunction is characterized by reduced ATP synthase activity, reduced electron transport chain activity, and increased futile proton cycling. Bioenergetic dysfunction is characterized by reduced glycolytic reserve, reduced glycolytic capacity, and increased non-glycolytic acidification. CONCLUSION Traumatic peripheral nerve injury induces persistent mitochondrial and bioenergetic dysfunction which implies that pharmacological agents which seek to normalize mitochondrial and bioenergetic dysfunction could be expected to be beneficial for pain treatment. Increases in both glycolytic acidification and non-glycolytic acidification suggest that pH sensitive drugs which preferentially act on acidic tissue will have the ability to preferential act on injured nerves without affecting healthy tissues.
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Affiliation(s)
- Tony K Y Lim
- Neurology and Neurosurgery, McGill University, Montreal, QC, H3A 2B4, Canada. .,Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200, Montreal, QC, H3A 0G1, Canada.
| | - Malena B Rone
- Neurology and Neurosurgery, McGill University, Montreal, QC, H3A 2B4, Canada.
| | - Seunghwan Lee
- Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200, Montreal, QC, H3A 0G1, Canada. .,Faculty of Dentistry, McGill University, Montreal, QC, H3A 0C7, Canada.
| | - Jack P Antel
- Neurology and Neurosurgery, McGill University, Montreal, QC, H3A 2B4, Canada.
| | - Ji Zhang
- Neurology and Neurosurgery, McGill University, Montreal, QC, H3A 2B4, Canada. .,Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200, Montreal, QC, H3A 0G1, Canada. .,Faculty of Dentistry, McGill University, Montreal, QC, H3A 0C7, Canada.
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6
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Schumacker PT, Gillespie MN, Nakahira K, Choi AMK, Crouser ED, Piantadosi CA, Bhattacharya J. Mitochondria in lung biology and pathology: more than just a powerhouse. Am J Physiol Lung Cell Mol Physiol 2014; 306:L962-74. [PMID: 24748601 DOI: 10.1152/ajplung.00073.2014] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
An explosion of new information about mitochondria reveals that their importance extends well beyond their time-honored function as the "powerhouse of the cell." In this Perspectives article, we summarize new evidence showing that mitochondria are at the center of a reactive oxygen species (ROS)-dependent pathway governing the response to hypoxia and to mitochondrial quality control. The potential role of the mitochondrial genome as a sentinel molecule governing cytotoxic responses of lung cells to ROS stress also is highlighted. Additional attention is devoted to the fate of damaged mitochondrial DNA relative to its involvement as a damage-associated molecular pattern driving adverse lung and systemic cell responses in severe illness or trauma. Finally, emerging strategies for replenishing normal populations of mitochondria after damage, either through promotion of mitochondrial biogenesis or via mitochondrial transfer, are discussed.
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Affiliation(s)
- Paul T Schumacker
- Northwestern University Feinberg School of Medicine, Department of Pediatrics, Chicago, Illinois
| | - Mark N Gillespie
- University of South Alabama College of Medicine, Department of Pharmacology, Mobile, Alabama;
| | - Kiichi Nakahira
- Weill Cornell Medical College, Department of Medicine, New York, New York
| | - Augustine M K Choi
- Weill Cornell Medical College, Department of Medicine, New York, New York
| | - Elliott D Crouser
- The Ohio State University College of Medicine, Department of Internal Medicine, Columbus, Ohio
| | - Claude A Piantadosi
- Duke University School of Medicine, Department of Medicine, Durham, North Carolina, and
| | - Jahar Bhattacharya
- Columbia University Medical Center, Department of Physiology and Cellular Biophysics, New York, New York
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7
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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8
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Mitochondrial bioenergetics of metastatic breast cancer cells in response to dynamic changes in oxygen tension: effects of HIF-1α. PLoS One 2013; 8:e68348. [PMID: 23840849 PMCID: PMC3696014 DOI: 10.1371/journal.pone.0068348] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 05/28/2013] [Indexed: 11/19/2022] Open
Abstract
Solid tumors are characterized by regions of low oxygen tension (OT), which play a central role in tumor progression and resistance to therapy. Low OT affects mitochondrial function and for the cells to survive, mitochondria must functionally adapt to low OT to maintain the cellular bioenergetics. In this study, a novel experimental approach was developed to examine the real-time bioenergetic changes in breast cancer cells (BCCs) during adaptation to OT (from 20% to <1% oxygen) using sensitive extracellular flux technology. Oxygen was gradually removed from the medium, and the bioenergetics of metastatic BCCs (MDA-MB-231 and MCF10CA clones) was compared with non-tumorigenic (MCF10A) cells. BCCs, but not MCF10A, rapidly responded to low OT by stabilizing HIF-1α and increasing HIF-1α responsive gene expression and glucose uptake. BCCs also increased extracellular acidification rate (ECAR), which was markedly lower in MCF10A. Interestingly, BCCs exhibited a biphasic response in basal respiration as the OT was reduced from 20% to <1%. The initial stimulation of oxygen consumption is found to be due to increased mitochondrial respiration. This effect was HIF-1α-dependent, as silencing HIF-1α abolished the biphasic response. During hypoxia and reoxygenation, BCCs also maintained oxygen consumption rates at specific OT; however, HIF-1α silenced BCC were less responsive to changes in OT. Our results suggest that HIF-1α provides a high degree of bioenergetic flexibility under different OT which may confer an adaptive advantage for BCC survival in the tumor microenvironment and during invasion and metastasis. This study thus provides direct evidence for the cross-talk between HIF-1α and mitochondria during adaptation to low OT by BCCs and may be useful in identifying novel therapeutic agents that target the bioenergetics of BCCs in response to low OT.
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Site-specific antioxidative therapy for prevention of atherosclerosis and cardiovascular disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:796891. [PMID: 23738041 PMCID: PMC3657429 DOI: 10.1155/2013/796891] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/09/2013] [Indexed: 02/07/2023]
Abstract
Oxidative stress has been implicated in pathophysiology of aging and age-associated disease. Antioxidative medicine has become a practice for prevention of atherosclerosis. However, limited success in preventing cardiovascular disease (CVD) in individuals with atherosclerosis using general antioxidants has prompted us to develop a novel antioxidative strategy to prevent atherosclerosis. Reducing visceral adipose tissue by calorie restriction (CR) and regular endurance exercise represents a causative therapy for ameliorating oxidative stress. Some of the recently emerging drugs used for the treatment of CVD may be assigned as site-specific antioxidants. CR and exercise mimetic agents are the choice for individuals who are difficult to continue CR and exercise. Better understanding of molecular and cellular biology of redox signaling will pave the way for more effective antioxidative medicine for prevention of CVD and prolongation of healthy life span.
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10
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Levett DZ, Radford EJ, Menassa DA, Graber EF, Morash AJ, Hoppeler H, Clarke K, Martin DS, Ferguson-Smith AC, Montgomery HE, Grocott MPW, Murray AJ. Acclimatization of skeletal muscle mitochondria to high-altitude hypoxia during an ascent of Everest. FASEB J 2011; 26:1431-41. [PMID: 22186874 DOI: 10.1096/fj.11-197772] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ascent to high altitude is associated with a fall in the partial pressure of inspired oxygen (hypobaric hypoxia). For oxidative tissues such as skeletal muscle, resultant cellular hypoxia necessitates acclimatization to optimize energy metabolism and restrict oxidative stress, with changes in gene and protein expression that alter mitochondrial function. It is known that lowlanders returning from high altitude have decreased muscle mitochondrial densities, yet the underlying transcriptional mechanisms and time course are poorly understood. To explore these, we measured gene and protein expression plus ultrastructure in muscle biopsies of lowlanders at sea level and following exposure to hypobaric hypoxia. Subacute exposure (19 d after initiating ascent to Everest base camp, 5300 m) was not associated with mitochondrial loss. After 66 d at altitude and ascent beyond 6400 m, mitochondrial densities fell by 21%, with loss of 73% of subsarcolemmal mitochondria. Correspondingly, levels of the transcriptional coactivator PGC-1α fell by 35%, suggesting down-regulation of mitochondrial biogenesis. Sustained hypoxia also decreased expression of electron transport chain complexes I and IV and UCP3 levels. We suggest that during subacute hypoxia, mitochondria might be protected from oxidative stress. However, following sustained exposure, mitochondrial biogenesis is deactivated and uncoupling down-regulated, perhaps to improve the efficiency of ATP production.
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Affiliation(s)
- Denny Z Levett
- Centre for Altitude, Space, and Extreme Environment Medicine, University College London (UCL) Institute of Child Health, University College London, London, UK
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11
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Carchman EH, Rao J, Loughran PA, Rosengart MR, Zuckerbraun BS. Heme oxygenase-1-mediated autophagy protects against hepatocyte cell death and hepatic injury from infection/sepsis in mice. Hepatology 2011; 53:2053-62. [PMID: 21437926 PMCID: PMC9976293 DOI: 10.1002/hep.24324] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 03/16/2011] [Indexed: 12/12/2022]
Abstract
UNLABELLED Adaptive responses to sepsis are necessary to prevent organ failure and death. Cellular signaling responses that limit cell death and structural damage allow a cell to withstand insult from sepsis to prevent irreversible organ dysfunction. One such protective pathway to reduce hepatocellular injury is the up-regulation of heme oxygenase-1 (HO-1) signaling. HO-1 is up-regulated in the liver in response to multiple stressors, including sepsis and lipopolysaccharide (LPS), and has been shown to limit cell death. Another recently recognized rudimentary cellular response to injury is autophagy. The aim of these investigations was to test the hypothesis that HO-1 protects against hepatocyte cell death in experimental sepsis in vivo or LPS in vitro via induction of autophagy. These data demonstrate that both HO-1 and autophagy are up-regulated in the liver after cecal ligation and puncture (CLP) in C57BL/6 mice or in primary mouse hepatocytes after treatment with LPS (100 ng/mL). CLP or LPS results in minimal hepatocyte cell death. Pharmacological inhibition of HO-1 activity using tin protoporphyrin or knockdown of HO-1 prevents the induction of autophagic signaling in these models and results in increased hepatocellular injury, apoptosis, and death. Furthermore, inhibition of autophagy using 3-methyladenine or small interfering RNA specific to VPS34, a class III phosphoinositide 3-kinase that is an upstream regulator of autophagy, resulted in hepatocyte apoptosis in vivo or in vitro. LPS induced phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), in part, via HO-dependent signaling. Moreover, inhibition of p38 MAPK prevented CLP- or LPS-induced autophagy. CONCLUSION Sepsis or LPS-induced autophagy protects against hepatocellular death, in part via an HO-1 p38 MAPK-dependent signaling. Further investigations are needed to elucidate how autophagic signaling prevents apoptosis and cell death.
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Affiliation(s)
- Evie H. Carchman
- VA Pittsburgh Healthcare System, University of Pittsburgh School of Medicine, Pittsburgh, PA.,Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Jayashree Rao
- VA Pittsburgh Healthcare System, University of Pittsburgh School of Medicine, Pittsburgh, PA.,Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Patricia A. Loughran
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Matthew R. Rosengart
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Brian S. Zuckerbraun
- VA Pittsburgh Healthcare System, University of Pittsburgh School of Medicine, Pittsburgh, PA.,Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
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12
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Abstract
Adaptation to lowering oxygen levels (hypoxia) requires coordinated downregulation of metabolic demand and supply to prevent a mismatch in ATP utilization and production that might culminate in a bioenergetic collapse. Hypoxia diminishes ATP utilization by downregulating protein translation and the activity of the Na-K-ATPase. Hypoxia diminishes ATP production in part by lowering the activity of the electron transport chain through activation of the transcription factor hypoxia-inducible factor-1. The decrease in electron transport limits the overproduction of reactove oxygen species during hypoxia and slows the rate of oxygen depletion to prevent anoxia. In this review, we discuss these mechanisms that diminish metabolic supply and demand for adaptation to hypoxia.
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Affiliation(s)
- William W Wheaton
- Division of Pulmonary & Critical Care Medicine, 240 East Huron Ave., McGraw M-334, Chicago, IL 60611-2909, USA
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13
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Presley T, Vedam K, Velayutham M, Zweier JL, Ilangovan G. Activation of Hsp90-eNOS and increased NO generation attenuate respiration of hypoxia-treated endothelial cells. Am J Physiol Cell Physiol 2008; 295:C1281-91. [PMID: 18787079 DOI: 10.1152/ajpcell.00550.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hypoxia induces various adoptive signaling in cells that can cause several physiological changes. In the present work, we have observed that exposure of bovine aortic endothelial cells (BAECs) to extreme hypoxia (1-5% O(2)) attenuates cellular respiration by a mechanism involving heat shock protein 90 (Hsp90) and endothelial nitric oxide (NO) synthase (eNOS), so that the cells are conditioned to consume less oxygen and survive in prolonged hypoxic conditions. BAECs, exposed to 1% O(2), showed a reduced respiration compared with 21% O(2)-maintained cells. Western blot analysis showed an increase in the association of Hsp90-eNOS and enhanced NO generation on hypoxia exposure, whereas there was no significant accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha). The addition of inhibitors of Hsp90, phosphatidylinositol 3-kinase, and NOS significantly alleviated this hypoxia-induced attenuation of respiration. Thus we conclude that hypoxia-induced excess NO and its derivatives such as ONOO(-) cause inhibition of the electron transport chain and attenuate O(2) demand, leading to cell survival at extreme hypoxia. More importantly, such an attenuation is found to be independent of HIF-1alpha, which is otherwise thought to be the key regulator of respiration in hypoxia-exposed cells, through a nonphosphorylative glycolytic pathway. The present mechanistic insight will be helpful to understand the difference in the magnitude of endothelial dysfunction.
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Affiliation(s)
- Tennille Presley
- Rm. 392, Biomedical Research Tower, Ohio State Univ., 420 West 12th Ave., Columbus, OH 43210, USA
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14
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Abstract
The existence of hypoxia-induced reactive oxygen species (ROS) production remains controversial. However, numerous observations with a variety of methods and in many cells and tissue types are supportive of this idea. Skeletal muscle appears to behave much like heart in that in the early stages of hypoxia there is a transient elevation in ROS, whereas in chronic exposure to very severe hypoxia there is evidence of ongoing oxidative stress. Important remaining questions that are addressed in this review include the following. Are there levels of PO2 in skeletal muscle, typical of physiological or mildly pathophysiological conditions, that are low enough to induce significant ROS production? Does the ROS associated with muscle contractile activity reflect imbalances in oxygen uptake and demand that drive the cell to a more reduced state? What are the possible molecular mechanisms by which ROS may be elevated in hypoxic skeletal muscle? Is the production of ROS in hypoxia of physiological significance, both with respect to cell signaling pathways promoting cell function and with respect to damaging effects of long-term exposure? Discussion of these and other topics leads to general conclusions that hypoxia-induced ROS may be a normal physiological response to imbalance in oxygen supply and demand or environmental stress and may play a yet undefined role in normal response mechanisms to these stimuli. However, in chronic and extreme hypoxic exposure, muscles may fail to maintain a normal redox homeostasis, resulting in cell injury or dysfunction.
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Affiliation(s)
- Thomas L Clanton
- Department of Internal Medicine, The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University College of Medicine, 473 W. 12th, Columbus, OH 43210, USA.
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15
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Zuckerbraun BS, Chin BY, Bilban M, d'Avila JDC, Rao J, Billiar TR, Otterbein LE. Carbon monoxide signals via inhibition of cytochrome c oxidase and generation of mitochondrial reactive oxygen species. FASEB J 2007; 21:1099-106. [PMID: 17264172 DOI: 10.1096/fj.06-6644com] [Citation(s) in RCA: 249] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Carbon monoxide (CO), which is produced endogenously in the breakdown of heme, has been recognized as an important physiological second messenger similar to NO. Additionally, pharmacological delivery of CO is protective in numerous models of injury, including ischemia/reperfusion, transplantation, hemorrhagic shock, and endotoxemia. However, the mechanism of action of CO is only partially elucidated focused primarily on how it modulates the cellular response to stress. The purpose of these investigations is to test the hypothesis that CO acts via inhibition of cytochrome c oxidase leading to the generation of low levels of reactive oxygen species (ROS) that in turn mediate subsequent adaptive signaling. We show here that CO increases ROS generation in RAW 264.7 cells, which is inhibited by antimycin A and is absent in respiration-deficient rho0 cells. CO inhibits cytochrome c oxidase, while maintaining cellular ATP levels and increasing mitochondrial membrane potential. The addition of antioxidants or inhibition of complex III of the electron transport chain by antimycin A attenuates the inhibitory effects of CO on lipopolysaccharide (LPS)-induced TNF-alpha and blocked CO-induced p38 MAPK phosphorylation, which we previously have shown to be important in the anti-inflammatory effects of CO.
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Affiliation(s)
- Brian S Zuckerbraun
- Department of Surgery, University of Pittsburgh School of Medicine, NW653 MUH, 3459 Fifth Ave., Pittsburgh, PA 15213, USA.
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16
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Prabu SK, Anandatheerthavarada HK, Raza H, Srinivasan S, Spear JF, Avadhani NG. Protein kinase A-mediated phosphorylation modulates cytochrome c oxidase function and augments hypoxia and myocardial ischemia-related injury. J Biol Chem 2005; 281:2061-70. [PMID: 16303765 PMCID: PMC4271455 DOI: 10.1074/jbc.m507741200] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have investigated the effects of hypoxia and myocardial ischemia/reperfusion on the structure and function of cytochrome c oxidase (CcO). Hypoxia (0.1% O(2) for 10 h) and cAMP-mediated inhibition of CcO activity were accompanied by hyperphosphorylation of subunits I, IVi1, and Vb and markedly increased reactive O(2) species production by the enzyme complex in an in vitro system that uses reduced cytochrome c as an electron donor. Both subunit phosphorylation and enzyme activity were effectively reversed by 50 nm H89 or 50 nm myristoylated peptide inhibitor (MPI), specific inhibitors of protein kinase A, but not by inhibitors of protein kinase C. In rabbit hearts subjected to global and focal ischemia, CcO activity was inhibited in a time-dependent manner and was accompanied by hyperphosphorylation as in hypoxia. Additionally, CcO activity and subunit phosphorylation in the ischemic heart were nearly completely reversed by H89 or MPI added to the perfusion medium. Hyperphosphorylation of subunits I, IVi1, and Vb was accompanied by reduced subunit contents of the immunoprecipitated CcO complex. Most interestingly, both H89 and MPI added to the perfusion medium dramatically reduced the ischemia/reperfusion injury to the myocardial tissue. Our results pointed to an exciting possibility of using CcO activity modulators for controlling myocardial injury associated with ischemia and oxidative stress conditions.
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Affiliation(s)
| | | | | | | | | | - Narayan G. Avadhani
- To whom correspondence should be addressed: Dept. of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce St., Philadelphia, PA 19104. Tel.: 215-898-8819; Fax: 215-573-6651;
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17
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Abstract
Pregnancy is a state of oxidative stress arising from increased placental mitochondrial activity and production of reactive oxygen species (ROS), mainly superoxide anion. The placenta also produces other ROS including nitric oxide, carbon monoxide, and peroxynitrite which have pronounced effects on placental function including trophoblast proliferation and differentiation and vascular reactivity. Excessive production of ROS may occur at certain windows in placental development and in pathologic pregnancies, such as those complicated by preeclampsia and/or IUGR, overpowering antioxidant defenses with deleterious outcome. In the first trimester, establishment of blood flow into the intervillous space is associated with a burst of oxidative stress. The inability to mount an effective antioxidant defense against this results in early pregnancy loss. In late gestation increased oxidative stress is seen in pregnancies complicated by diabetes, IUGR, and preeclampsia in association with increased trophoblast apoptosis and deportation and altered placental vascular reactivity. Evidence for this oxidative stress includes increased lipid peroxides and isoprostanes and decreased expression and activity of antioxidants. The interaction of nitric oxide and superoxide produces peroxynitrite, a powerful prooxidant with diverse deleterious effects including nitration of tyrosine residues on proteins thus altering function. Nitrative stress, subsequent to oxidative stress is seen in the placenta in preeclampsia and diabetes in association with altered placental function.
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Affiliation(s)
- Leslie Myatt
- Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, PO Box 670526, Cincinnati, OH 45267-0526, USA.
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18
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Turcotte ML, Parliament M, Franko A, Allalunis-Turner J. Variation in mitochondrial function in hypoxia-sensitive and hypoxia-tolerant human glioma cells. Br J Cancer 2002; 86:619-24. [PMID: 11870546 PMCID: PMC2375290 DOI: 10.1038/sj.bjc.6600087] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2001] [Revised: 09/20/2001] [Accepted: 11/19/2001] [Indexed: 11/18/2022] Open
Abstract
We have shown previously that human glioblastoma multiforme cells vary in their ability to survive under hypoxic conditions. Under oxygen limiting conditions, hypoxia-tolerant cells decrease their oxygen consumption rate whereas hypoxia-sensitive cells continue to consume oxygen at a relatively steady rate until the oxygen supply becomes exhausted. We now show that hypoxia-tolerant and hypoxia-sensitive cells exhibit distinct patterns of mitochondrial function in response to hypoxic challenge. Hypoxia-tolerant cell lines retain stable mitochondrial membrane potential and ATP concentration when incubated under oxygen limiting conditions. In addition, hypoxia-tolerant cell lines are consistently more sensitive to a wide spectrum of inhibitors of mitochondrial function than are hypoxia-sensitive cells. In contrast, the hypoxia-sensitive cells are unable to maintain stable mitochondrial membrane potential and ATP levels when incubated at reduced oxygen tension. These results demonstrate significant differences in the mitochondrial function between these two phenotypes and reinforce previous data that suggest a regulatory role for mitochondria in the development of hypoxia tolerance.
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Affiliation(s)
- M L Turcotte
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
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Shin CY, Choi JW, Jang ES, Ryu JH, Kim WK, Kim HC, Ko KH. Glucocorticoids exacerbate peroxynitrite mediated potentiation of glucose deprivation-induced death of rat primary astrocytes. Brain Res 2001; 923:163-71. [PMID: 11743984 DOI: 10.1016/s0006-8993(01)03212-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Glucocorticoids have been implicated in the exacerbation of several types of neurotoxicity in various neuropathological situations. In this study, we investigated the effect of a glucocorticoid dexamethasone on glucose deprivation induced cell death of immunostimulated rat primary astrocytes, which is dependent on the production of peroxynitrite from the immunostimulated cells [Choi et al. Glia, 31(2001) 155-164; J. Neuroimmunol. 112 (2001) 55-62]. Glucose deprivation in immunostimulated rat primary astrocytes results in the release of lactate dehydrogenase (LDH) after 5 h and co-treatment with dexamethasone (1-1000 nM) dose-dependently increased LDH release. Treatment of the exogenous peroxynitrite generator SIN-1 (20 microM), plus glucose deprivation, also increased LDH release after 6 h and co-treatment with dexamethasone dose-dependently increased LDH release. A glucocorticoid receptor antagonist, RU-486, reversed the potentiation of cell death by dexamethasone. Glucose deprivation in immunostimulated cells decreased the intracellular ATP levels, which preceded LDH release from the cell, and co-treatment with dexamethasone dose-dependently potentiated the depletion of intracellular ATP levels. In addition, dexamethasone further deteriorated SIN-1 plus glucose deprivation-induced decrease in mitochondrial transmembrane potential in rat primary astrocytes, which was reversed by RU-486. The results from the present study suggest that glucocorticoids may be detrimental to astrocytes in situations where activation of glial cells are observed, including ischemia and Alzheimer's disease, by mechanisms involving depletion of intracellular ATP levels and deterioration of mitochondrial transmembrane potentials.
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Affiliation(s)
- C Y Shin
- Department of Pharmacology, College of Pharmacy, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-742, South Korea
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20
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Camougrand N, Rigoulet M. Aging and oxidative stress: studies of some genes involved both in aging and in response to oxidative stress. RESPIRATION PHYSIOLOGY 2001; 128:393-401. [PMID: 11718766 DOI: 10.1016/s0034-5687(01)00314-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aging is a complex physiological phenomenon and several theories have been developed about its origin. Among such theories, the 'mitochondrial theory of aging' has been supported by numerous studies and reviews. Cell oxidative damage, in particular the accumulation of mtDNA mutations, is determined by the rate of reactive oxygen species production and degradation induced by the antioxidant defense systems. In this review, data from our laboratory and from the recent literature have been examined to provide arguments that reinforce the crucial role of mitochondria in aging. Various genes that affect life span have been described in numerous organisms. Some of them encode signal transduction proteins and participate in the regulation of mitochondrial metabolism.
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Affiliation(s)
- N Camougrand
- Institut de Biochimie et Genetique Cellulaires du CNRS, 1 rue Camille Saint Saëns, 33077 Cedex, Bordeaux, France.
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21
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Chandel NS, Schumacker PT. Cellular oxygen sensing by mitochondria: old questions, new insight. J Appl Physiol (1985) 2000; 88:1880-9. [PMID: 10797153 DOI: 10.1152/jappl.2000.88.5.1880] [Citation(s) in RCA: 257] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxia elicits a variety of adaptive responses at the tissue level, at the cellular level, and at the molecular level. A physiological response to hypoxia requires the existence of an O(2) sensor coupled to a signal transduction system, which in turn activates the functional response. Although much has been learned about the signaling systems activated by hypoxia, no consensus exists regarding the nature of the underlying O(2) sensor or whether multiple sensors exist. Among previously considered mechanisms, heme proteins have been suggested to undergo allosteric modification in response to O(2) binding or release at different PO(2) levels. Other studies suggest that ion channels may change conductance as a function of PO(2), allowing them to signal the onset of hypoxia. Still other studies suggest that NADPH oxidase may decrease its generation of reactive O(2) species (ROS) during hypoxia. Recent data suggest that mitochondria may function as O(2) sensors by increasing their generation of ROS during hypoxia. These oxidant signals appear to act as second messengers in the adaptive responses to hypoxia in a variety of cell types. Such observations contribute to a growing awareness that mitochondria do more than just generate ATP, in that they initiate signaling cascades involved in adaptive responses to hypoxia and that they participate in the control of cell death pathways.
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Affiliation(s)
- N S Chandel
- The University of Chicago, Pulmonary and Critical Care Medicine, Chicago, Illinois 60637, USA
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22
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Chandel NS, Maltepe E, Goldwasser E, Mathieu CE, Simon MC, Schumacker PT. Mitochondrial reactive oxygen species trigger hypoxia-induced transcription. Proc Natl Acad Sci U S A 1998; 95:11715-20. [PMID: 9751731 PMCID: PMC21706 DOI: 10.1073/pnas.95.20.11715] [Citation(s) in RCA: 1470] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transcriptional activation of erythropoietin, glycolytic enzymes, and vascular endothelial growth factor occurs during hypoxia or in response to cobalt chloride (CoCl2) in Hep3B cells. However, neither the mechanism of cellular O2 sensing nor that of cobalt is fully understood. We tested whether mitochondria act as O2 sensors during hypoxia and whether hypoxia and cobalt activate transcription by increasing generation of reactive oxygen species (ROS). Results show (i) wild-type Hep3B cells increase ROS generation during hypoxia (1. 5% O2) or CoCl2 incubation, (ii) Hep3B cells depleted of mitochondrial DNA (rho0 cells) fail to respire, fail to activate mRNA for erythropoietin, glycolytic enzymes, or vascular endothelial growth factor during hypoxia, and fail to increase ROS generation during hypoxia; (iii) rho0 cells increase ROS generation in response to CoCl2 and retain the ability to induce expression of these genes; and (iv) the antioxidants pyrrolidine dithiocarbamate and ebselen abolish transcriptional activation of these genes during hypoxia or CoCl2 in wild-type cells, and abolish the response to CoCl2 in rho degrees cells. Thus, hypoxia activates transcription via a mitochondria-dependent signaling process involving increased ROS, whereas CoCl2 activates transcription by stimulating ROS generation via a mitochondria-independent mechanism.
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Affiliation(s)
- N S Chandel
- Department of Medicine, The University of Chicago, Chicago, IL 60637, USA
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23
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Simon N, Jolliet P, Morin C, Zini R, Urien S, Tillement JP. Glucocorticoids decrease cytochrome c oxidase activity of isolated rat kidney mitochondria. FEBS Lett 1998; 435:25-8. [PMID: 9755852 DOI: 10.1016/s0014-5793(98)01033-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The importance of mitochondria is rising as a target in pathologic processes such as ischemia. We have investigated the effects of hydrocortisone, prednisolone, dexamethasone and triamcinolone on oxidative phosphorylation, Ca2+ fluxes, swelling and membrane potentials in isolated kidney mitochondria. The measurement of respiration state 3 showed a significant decrease in presence of glucocorticoids whereas the other respiration states were not modified. When mitochondria were uncoupled and either the complexes III and IV or the complex IV were stimulated, the O2 consumption was decreased by glucocorticoids. These results suggest the cytochrome c oxidase is a target of the glucocorticoid effect on the respiratory chain. Indeed, the other mitochondrial functions investigated were unchanged, ruling out a direct effect on Ca2+ fluxes or swelling. A regulation of cytochrome c oxidase activity by glucocorticoids will be of particular interest in pathology involving metabolic insult.
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Affiliation(s)
- N Simon
- Départment de Pharmacologie, Faculté de Médecine de Paris XII, Créteil, France
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Cooper CE, Springett R. Measurement of cytochrome oxidase and mitochondrial energetics by near-infrared spectroscopy. Philos Trans R Soc Lond B Biol Sci 1997; 352:669-76. [PMID: 9232854 PMCID: PMC1691958 DOI: 10.1098/rstb.1997.0048] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Cytochrome oxidase is the terminal electron acceptor of the mitochondrial respiratory chain. It is responsible for the vast majority of oxygen consumption in the body and essential for the efficient generation of cellular ATP. The enzyme contains four redox active metal centres; one of these, the binuclear CuA centre, has a strong absorbance in the near-infrared that enables it to be detectable in vivo by near-infrared spectroscopy. However, the fact that the concentration of this centre is less than 10% of that of haemoglobin means that its detection is not a trivial matter. Unlike the case with deoxyhaemoglobin and oxyhaemoglobin, concentration changes of the total cytochrome oxidase protein occur very slowly (over days) and are therefore not easily detectable by near-infrared spectroscopy. However, the copper centre rapidly accepts and donates an electron, and can thus change its redox state quickly; this redox change is detectable by near-infrared spectroscopy. Many factors can affect the CuA redox state in vivo (Cooper et al. 1994), but most significant is likely to be the molecular oxygen concentration (at low oxygen tensions, electrons build up on CuA as reduction of oxygen by the enzyme starts to limit the steady-state rate of electron transfer). The factors underlying haemoglobin oxygenation, deoxygenation and blood volume changes are, in general, well understood by the clinicians and physiologists who perform near-infrared spectroscopy measurements. In contrast, the factors that control the steady-state redox level of CuA in cytochrome oxidase are still a matter of active debate, even amongst biochemists studying the isolated enzyme and mitochondria. Coupled with the difficulties of accurate in vivo measurements it is perhaps not surprising that the field of cytochrome oxidase near-infrared spectroscopy has a somewhat chequered past. Too often papers have been written with insufficient information to enable the measurements to be repeated and few attempts have been made to test the algorithms in vivo. In recent years a number of research groups and commercial spectrometer manufacturers have made a concerted attempt to not only say how they are attempting to measure cytochrome oxidase by near-infrared spectroscopy but also to demonstrate that they are really doing so. We applaud these attempts, which in general fall into three areas: first, modelling of data can be performed to determine what problems are likely to derail cytochrome oxidase detection algorithms (Matcher et al. 1995); secondly haemoglobin concentration changes can be made by haemodilution (using saline or artificial blood substitutes) in animals (Tamura 1993) or patients (Skov & Greisen 1994); and thirdly, the cytochrome oxidase redox state can be fixed by the use of mitochondrial inhibitors and then attempts make to cause spurious cytochrome changes by dramatically varying haemoglobin oxygenation, haemoglobin concentration and light scattering (Cooper et al. 1997). We have previously written reviews covering the difficulties of measuring the cytochrome near-infrared spectroscopy signal in vivo (Cooper et al. 1997) and the factors affecting the oxidation state of cytochrome oxidase CuA (Cooper et al. 1994). In this article we would like to strike a somewhat more optimistic note--we will stress the usefulness this measurement may have in the clinical environment, as well as describing conditions under which we can have confidence that we are measuring real changes in the CuA redox state.
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Affiliation(s)
- C E Cooper
- Department of Biological and Chemical Sciences, University of Essex, Colchester, UK
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