1
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Elmansi AM, Miller RA. Oxidative Phosphorylation and Fatty Acid Oxidation in Slow-Aging Mice. Free Radic Biol Med 2024:S0891-5849(24)00605-1. [PMID: 39153667 DOI: 10.1016/j.freeradbiomed.2024.08.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 08/06/2024] [Accepted: 08/09/2024] [Indexed: 08/19/2024]
Abstract
Oxidative metabolism declines with aging in humans leading to multiple metabolic ailments and subsequent inflammation. In mice, there is evidence of age-related suppression of fatty acid oxidation and oxidative phosphorylation in the liver, heart, and muscles. Many interventions that extend healthy lifespan of mice have been developed, including genetic, pharmacological, and dietary interventions. In this article, we review the literature on oxidative metabolism changes in response to those interventions. We also discuss the molecular pathways that mediate those changes, and their potential as targets for future longevity interventions.
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Affiliation(s)
- Ahmed M Elmansi
- Department of Pathology, University of Michigan School of Medicine, Ann Arbor, MI, USA; University of Michigan Geriatrics Center, Ann Arbor, MI, USA
| | - Richard A Miller
- Department of Pathology, University of Michigan School of Medicine, Ann Arbor, MI, USA; University of Michigan Geriatrics Center, Ann Arbor, MI, USA.
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2
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Kruglov AG, Romshin AM, Nikiforova AB, Plotnikova A, Vlasov II. Warm Cells, Hot Mitochondria: Achievements and Problems of Ultralocal Thermometry. Int J Mol Sci 2023; 24:16955. [PMID: 38069275 PMCID: PMC10707128 DOI: 10.3390/ijms242316955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 11/27/2023] [Accepted: 11/28/2023] [Indexed: 12/18/2023] Open
Abstract
Temperature is a crucial regulator of the rate and direction of biochemical reactions and cell processes. The recent data indicating the presence of local thermal gradients associated with the sites of high-rate thermogenesis, on the one hand, demonstrate the possibility for the existence of "thermal signaling" in a cell and, on the other, are criticized on the basis of thermodynamic calculations and models. Here, we review the main thermometric techniques and sensors developed for the determination of temperature inside living cells and diverse intracellular compartments. A comparative analysis is conducted of the results obtained using these methods for the cytosol, nucleus, endo-/sarcoplasmic reticulum, and mitochondria, as well as their biological consistency. Special attention is given to the limitations, possible sources of errors and ambiguities of the sensor's responses. The issue of biological temperature limits in cells and organelles is considered. It is concluded that the elaboration of experimental protocols for ultralocal temperature measurements that take into account both the characteristics of biological systems, as well as the properties and limitations of each type of sensor is of critical importance for the generation of reliable results and further progress in this field.
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Affiliation(s)
- Alexey G. Kruglov
- Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences, 142290 Pushchino, Russia;
| | - Alexey M. Romshin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia;
| | - Anna B. Nikiforova
- Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences, 142290 Pushchino, Russia;
| | - Arina Plotnikova
- Institute for Physics and Engineering in Biomedicine, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute MEPhI), 115409 Moscow, Russia;
| | - Igor I. Vlasov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia;
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3
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JEDLIČKA J, TŮMA Z, RAZAK K, KUNC R, KALA A, PEÑA SPROSKAUER, LERCHNER T, JEŽEK K, KUNCOVÁ J. Impact of aging on mitochondrial respiration in various organs. Physiol Res 2022; 71:S227-S236. [PMID: 36647911 PMCID: PMC9906668 DOI: 10.33549/physiolres.934995] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Mitochondria are considered central regulator of the aging process; however, majority of studies dealing with the impact of age on mitochondrial oxygen consumption focused on skeletal muscle concluding (although not uniformly) a general declining trend with advancing age. In addition, gender related differences in mitochondrial respiration have not been satisfactorily described yet. The aim of the present study was to evaluate mitochondrial oxygen consumption in various organs of aging male and female Fischer 344 rats at the ages of 6, 12 and 24 months. Mitochondrial respiration of homogenized (skeletal muscle, left and right heart ventricle, hippocampus, cerebellum, kidney cortex), gently mechanically permeabilized (liver) tissue or intact cells (platelets) was determined using high-resolution respirometry (oxygraphs O2k, Oroboros, Austria). The pattern of age-related changes differed in each tissue: in the skeletal muscle and kidney cortex of both sexes and in female heart, parameters of mitochondrial respiration significantly declined with age. Resting respiration of intact platelets displayed an increasing trend and it did not correlate with skeletal muscle respiratory states. In the heart of male rats and brain tissues of both sexes, respiratory states remained relatively stable over analyzed age categories with few exceptions of lower mitochondrial oxygen consumption at the age of 24 months. In the liver, OXPHOS capacity was higher in females than in males with either no difference between the ages of 6 and 24 months or even significant increase at the age of 24 months in the male rats. In conclusion, the results of our study indicate that the concept of general pattern of age-dependent decline in mitochondrial oxygen consumption across different organs and tissues could be misleading. Also, the statement of higher mitochondrial respiration in females seems to be conflicting, since the gender-related differences may vary with the tissue studied, combination of substrates used and might be better detectable at younger ages than in old animals.
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Affiliation(s)
- Jan JEDLIČKA
- Institute of Physiology, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Zdeněk TŮMA
- Biomedical Centre, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Karim RAZAK
- Institute of Physiology, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Radovan KUNC
- Institute of Physiology, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic,Institute of Social Medicine, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Annu KALA
- Biomedical Centre, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | | | - Tobias LERCHNER
- Institute of Physiology, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Karel JEŽEK
- Biomedical Centre, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
| | - Jitka KUNCOVÁ
- Institute of Physiology, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic,Biomedical Centre, Faculty of Medicine in Plzeň, Charles University, Plzeň, Czech Republic
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4
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Mookerjee SA, Gerencser AA, Watson MA, Brand MD. Controlled power: how biology manages succinate-driven energy release. Biochem Soc Trans 2021; 49:2929-2939. [PMID: 34882231 PMCID: PMC8786295 DOI: 10.1042/bst20211032] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/08/2021] [Accepted: 11/22/2021] [Indexed: 12/13/2022]
Abstract
Oxidation of succinate by mitochondria can generate a higher protonmotive force (pmf) than can oxidation of NADH-linked substrates. Fundamentally, this is because of differences in redox potentials and gearing. Biology adds kinetic constraints that tune the oxidation of NADH and succinate to ensure that the resulting mitochondrial pmf is suitable for meeting cellular needs without triggering pathology. Tuning within an optimal range is used, for example, to shift ATP consumption between different consumers. Conditions that overcome these constraints and allow succinate oxidation to drive pmf too high can cause pathological generation of reactive oxygen species. We discuss the thermodynamic properties that allow succinate oxidation to drive pmf higher than NADH oxidation, and discuss the evidence for kinetic tuning of ATP production and for pathologies resulting from substantial succinate oxidation in vivo.
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Affiliation(s)
- Shona A. Mookerjee
- Department of Biological and Pharmaceutical Sciences, Touro University California College of Pharmacy, Vallejo, CA, U.S.A
- Buck Institute for Research on Aging, Novato, CA, U.S.A
| | | | | | - Martin D. Brand
- Department of Biological and Pharmaceutical Sciences, Touro University California College of Pharmacy, Vallejo, CA, U.S.A
- Buck Institute for Research on Aging, Novato, CA, U.S.A
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5
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Effects of aging on protein expression in mice brain microvessels: ROS scavengers, mRNA/protein stability, glycolytic enzymes, mitochondrial complexes, and basement membrane components. GeroScience 2021; 44:371-388. [PMID: 34708300 PMCID: PMC8811117 DOI: 10.1007/s11357-021-00468-1] [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: 07/30/2021] [Accepted: 09/23/2021] [Indexed: 12/25/2022] Open
Abstract
Differentially expressed (DE) proteins in the cortical microvessels (MVs) of young, middle-aged, and old male and female mice were evaluated using discovery-based proteomics analysis (> 4,200 quantified proteins/group). Most DE proteins (> 90%) showed no significant differences between the sexes; however, some significant DE proteins showing sexual differences in MVs decreased from young (8.3%), to middle-aged (3.7%), to old (0.5%) mice. Therefore, we combined male and female data for age-dependent comparisons but noted sex differences for examination. Key proteins involved in the oxidative stress response, mRNA or protein stability, basement membrane (BM) composition, aerobic glycolysis, and mitochondrial function were significantly altered with aging. Relative abundance of superoxide dismutase-1/-2, catalase and thioredoxin were reduced with aging. Proteins participating in either mRNA degradation or pre-mRNA splicing were significantly increased in old mice MVs, whereas protein stabilizing proteins decreased. Glycolytic proteins were not affected in middle age, but the relative abundance of these proteins decreased in MVs of old mice. Although most of the 41 examined proteins composing mitochondrial complexes I–V were reduced in old mice, six of these proteins showed a significant reduction in middle-aged mice, but the relative abundance increased in fourteen proteins. Nidogen, collagen, and laminin family members as well as perlecan showed differing patterns during aging, indicating BM reorganization starting in middle age. We suggest that increased oxidative stress during aging leads to adverse protein profile changes of brain cortical MVs that affect mRNA/protein stability, BM integrity, and ATP synthesis capacity.
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6
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Rodríguez E, Hakkou M, Hagen TM, Lemieux H, Blier PU. Divergences in the Control of Mitochondrial Respiration Are Associated With Life-Span Variation in Marine Bivalves. J Gerontol A Biol Sci Med Sci 2021; 76:796-804. [PMID: 33257932 DOI: 10.1093/gerona/glaa301] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Indexed: 12/31/2022] Open
Abstract
The role played by mitochondrial function in the aging process has been a subject of intense debate in the past few decades, as part of the efforts to understand the mechanistic basis of longevity. The mitochondrial oxidative stress theory of aging suggests that a progressive decay of this organelle's function leads to an exacerbation of oxidative stress, with a deleterious impact on mitochondrial structure and DNA, ultimately promoting aging. Among the traits suspected to be associated with longevity is the variation in the regulation of oxidative phosphorylation, potentially affecting the management of oxidative stress. Longitudinal studies using the framework of metabolic control analysis have shown age-related differences in the flux control of respiration, but this approach has seldom been taken on a comparative scale. Using 4 species of marine bivalves exhibiting a large range of maximum life span (from 28 years to 507 years), we report life-span-related differences in flux control at different steps of the electron transfer system. Increased longevity was characterized by a lower control by NADH (complex I-linked) and Succinate (complex II-linked) pathways, while respiration was strongly controlled by complex IV when compared to shorter-lived species. Complex III exerted strong control over respiration in all species. Furthermore, high longevity was associated with higher citrate synthase activity and lower ATP synthase activity. Relieving the control exerted by the electron entry pathways could be advantageous for reaching higher longevity, leading to increased control by complex IV, the final electron acceptor in the electron transfer system.
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Affiliation(s)
- Enrique Rodríguez
- Département de Biologie, Université du Québec, Rimouski, Québec, Canada
| | - Mohammed Hakkou
- Département de Biologie, Université du Québec, Rimouski, Québec, Canada
| | - Tory M Hagen
- Linus Pauling Institute, Oregon State University, Corvallis, Oregon, USA
| | - Hélène Lemieux
- Faculty Saint-Jean, Department of Medicine, Women and Children Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Pierre U Blier
- Département de Biologie, Université du Québec, Rimouski, Québec, Canada
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7
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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: 33] [Impact Index Per Article: 11.0] [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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8
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Lee YY, Choi YS, Kim DW, Cheong JY, Song KY, Ryu MS, Lim IK. Mitochondrial nucleoid remodeling and biogenesis are regulated by the p53-p21 WAF1-PKCζ pathway in p16 INK4a-silenced cells. Aging (Albany NY) 2020; 12:6700-6732. [PMID: 32330121 PMCID: PMC7202532 DOI: 10.18632/aging.103029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 02/22/2020] [Indexed: 11/25/2022]
Abstract
Mitochondrial dysfunction is linked to age-related senescence phenotypes. We report here the pathway increasing nucleoid remodeling and biogenesis in mitochondria during the senescence of foreskin human diploid fibroblasts (fs-HDF) and WI-38 cells. Replicative senescence in fs-HDF cells increased mitochondrial nucleoid remodeling as indicated by 5-bromo-2'-deoxyuridine (BrdU) incorporation and mitochondrial transcription factor A (TFAM) expression in enlarged and fused mitochondria. Mitochondrial nucleoid remodeling was accompanied by mitochondrial biogenesis in old cells, and the expression levels of OXPHOS complex-I, -IV and -V subunits, PGC-1α and NRF1 were greatly increased compared to young cells. Activated protein kinase C zeta (PKCζ) increased mitochondrial activity and expressed phenotypes of delayed senescence in fs-HDF cells, but not in WI-38 cells. The findings were reproduced in the doxorubicin-induced senescence of young fs-HDF and WI-38 cells via the PKCζ-LKB1-AMPK signaling pathway, which was regulated by the p53-p21WAF1 pathway when p16INK4a was silenced. The signaling enhanced PGC-1α-NRF1-TFAM axis in mitochondria, which was demonstrated by Ingenuity Pathway Analysis of young and old fs-HDF cells. Activation of the p53-p21WAF1 pathway and silencing of p16INK4a are responsible for mitochondrial reprogramming in senescent cells, which may be a compensatory mechanism to promote cell survival under senescence stress.
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Affiliation(s)
- Yun Yeong Lee
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Otolaryngology, Ajou University School of Medicine, Suwon 16499, Korea
| | - Yeon Seung Choi
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon 16499, Korea
| | - Do Wan Kim
- Omics Center, Ajou University School of Medicine, Suwon 16499, Korea
| | - Jae Youn Cheong
- Omics Center, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Gastroenterology, Ajou University of Medicine, Suwon 16499, Korea
| | - Kye Yong Song
- Department of Pathology, Chung-Ang University College of Medicine, Seoul 156-756, Korea
| | - Min Sook Ryu
- Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon 16499, Korea
| | - In Kyoung Lim
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon 16499, Korea
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9
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Bucladesine Attenuates Spatial Learning and Hippocampal Mitochondrial Impairments Induced by 3, 4-Methylenedioxymethamphetamine (MDMA). Neurotox Res 2020; 38:38-49. [PMID: 32103463 DOI: 10.1007/s12640-020-00183-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/07/2020] [Accepted: 02/14/2020] [Indexed: 12/14/2022]
Abstract
Neurotoxic effects of systemic administration of 3, 4- methylenedioxymethamphetamine (MDMA) has been attributed to MDMA and its metabolites. However, the role of the parent compound in MDMA-induced mitochondrial and memory impairment has not yet been investigated. Moreover, it is not yet studied that analogs of 3', 5'-cyclic adenosine monophosphate (cAMP) could decrease these neurotoxic effects of MDMA. We wished to investigate the effects of the central administration of MDMA on spatial memory and mitochondrial function as well as the effects of bucladesine, a membrane-permeable analog of cAMP, on these effects of MDMA. We assessed the effects of pre-training bilateral intrahippocampal infusion of MDMA (0.01, 0.1, 0.5, and 1 μg/side), bucladesine (10 and 100 μM) or combination of them on spatial memory, and different parameters of hippocampal mitochondrial function including the level of reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP), mitochondrial swelling, mitochondrial outer membrane damage, the amount of cytochrome c release as well as hippocampal ADP/ATP ratio. The results showed that MDMA caused spatial memory impairments as well as mitochondrial dysfunction as evidenced by the marked increase in hippocampal ADP/ATP ratio, ROS level, the collapse of MMP, mitochondrial swelling, and mitochondrial outer membrane damage leading to cytochrome c release from the mitochondria. The current study also found that bucladesine markedly reduced the destructive effects of MDMA. These results provide evidence of the role of the parent compound (MDMA) in MDMA-induced memory impairments through mitochondrial dysfunction. This study highlights the role of cAMP/PKA signaling in MDMA-induced memory and mitochondrial defects.
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10
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Killen MJ, Giorgi-Coll S, Helmy A, Hutchinson PJ, Carpenter KL. Metabolism and inflammation: implications for traumatic brain injury therapeutics. Expert Rev Neurother 2019; 19:227-242. [PMID: 30848963 DOI: 10.1080/14737175.2019.1582332] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Traumatic Brain Injury (TBI) is a leading cause of death and disability in young people, affecting 69 million people annually, worldwide. The initial trauma disrupts brain homeostasis resulting in metabolic dysfunction and an inflammatory cascade, which can then promote further neurodegenerative effects for months or years, as a 'secondary' injury. Effective targeting of the cerebral inflammatory system is challenging due to its complex, pleiotropic nature. Cell metabolism plays a key role in many diseases, and increased disturbance in the TBI metabolic state is associated with poorer patient outcomes. Investigating critical metabolic pathways, and their links to inflammation, can potentially identify supplements which alter the brain's long-term response to TBI and improve recovery. Areas covered: The authors provide an overview of literature on metabolism and inflammation following TBI, and from relevant pre-clinical and clinical studies, propose therapeutic strategies. Expert opinion: There is still no specific active drug treatment for TBI. Changes in metabolic and inflammatory states have been reported after TBI and appear linked. Understanding more about abnormal cerebral metabolism following TBI, and its relationship with cerebral inflammation, will provide essential information for designing therapies, with implications for neurocritical care and for alleviating long-term disability and neurodegeneration in post-TBI patients.
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Affiliation(s)
- Monica J Killen
- a Division of Neurosurgery, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK
| | - Susan Giorgi-Coll
- a Division of Neurosurgery, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK
| | - Adel Helmy
- a Division of Neurosurgery, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK
| | - Peter Ja Hutchinson
- a Division of Neurosurgery, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK.,b Wolfson Brain Imaging Centre, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK
| | - Keri Lh Carpenter
- a Division of Neurosurgery, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK.,b Wolfson Brain Imaging Centre, Department of Clinical Neurosciences , University of Cambridge , Cambridge , UK
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11
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Nitric Oxide and Mitochondrial Function in Neurological Diseases. Neuroscience 2018; 376:48-71. [DOI: 10.1016/j.neuroscience.2018.02.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 01/20/2018] [Accepted: 02/09/2018] [Indexed: 12/17/2022]
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12
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Bryan K, McGivney BA, Farries G, McGettigan PA, McGivney CL, Gough KF, MacHugh DE, Katz LM, Hill EW. Equine skeletal muscle adaptations to exercise and training: evidence of differential regulation of autophagosomal and mitochondrial components. BMC Genomics 2017; 18:595. [PMID: 28793853 PMCID: PMC5551008 DOI: 10.1186/s12864-017-4007-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 08/02/2017] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND A single bout of exercise induces changes in gene expression in skeletal muscle. Regular exercise results in an adaptive response involving changes in muscle architecture and biochemistry, and is an effective way to manage and prevent common human diseases such as obesity, cardiovascular disorders and type II diabetes. However, the biomolecular mechanisms underlying such responses still need to be fully elucidated. Here we performed a transcriptome-wide analysis of skeletal muscle tissue in a large cohort of untrained Thoroughbred horses (n = 51) before and after a bout of high-intensity exercise and again after an extended period of training. We hypothesized that regular high-intensity exercise training primes the transcriptome for the demands of high-intensity exercise. RESULTS An extensive set of genes was observed to be significantly differentially regulated in response to a single bout of high-intensity exercise in the untrained cohort (3241 genes) and following multiple bouts of high-intensity exercise training over a six-month period (3405 genes). Approximately one-third of these genes (1025) and several biological processes related to energy metabolism were common to both the exercise and training responses. We then developed a novel network-based computational analysis pipeline to test the hypothesis that these transcriptional changes also influence the contextual molecular interactome and its dynamics in response to exercise and training. The contextual network analysis identified several important hub genes, including the autophagosomal-related gene GABARAPL1, and dynamic functional modules, including those enriched for mitochondrial respiratory chain complexes I and V, that were differentially regulated and had their putative interactions 're-wired' in the exercise and/or training responses. CONCLUSION Here we have generated for the first time, a comprehensive set of genes that are differentially expressed in Thoroughbred skeletal muscle in response to both exercise and training. These data indicate that consecutive bouts of high-intensity exercise result in a priming of the skeletal muscle transcriptome for the demands of the next exercise bout. Furthermore, this may also lead to an extensive 're-wiring' of the molecular interactome in both exercise and training and include key genes and functional modules related to autophagy and the mitochondrion.
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Affiliation(s)
- Kenneth Bryan
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Beatrice A. McGivney
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Gabriella Farries
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Paul A. McGettigan
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Charlotte L. McGivney
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Katie F. Gough
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
| | - David E. MacHugh
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
- UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Lisa M. Katz
- UCD School of Veterinary Medicine, University College Dublin, Belfield, D04 V1W8 Ireland
| | - Emmeline W. Hill
- UCD School of Agriculture and Food Science, University College Dublin, Belfield, D04 V1W8 Ireland
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13
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The biological foundation of the genetic association of TOMM40 with late-onset Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2973-2986. [PMID: 28768149 DOI: 10.1016/j.bbadis.2017.07.031] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 07/13/2017] [Accepted: 07/28/2017] [Indexed: 02/06/2023]
Abstract
A variable-length poly-T variant in intron 6 of the TOMM40 gene, rs10524523, is associated with risk and age-of-onset of sporadic (late-onset) Alzheimer's disease. In Caucasians, the three predominant alleles at this locus are Short (S), Long (L) or Very long (VL). On an APOE ε3/3 background, the S/VL and VL/VL genotypes are more protective than S/S. The '523 poly-T has regulatory properties, in that the VL poly-T results in higher expression than the S poly-T in luciferase expression systems. The aim of the current work was to identify effects on cellular bioenergetics of increased TOM40 protein expression. MitoTracker Green fluorescence and autophagic vesicle staining was the same in control and over-expressing cells, but TOM40 over-expression was associated with increased expression of TOM20, a preprotein receptor of the TOM complex, the mitochondrial chaperone HSPA9, and PDHE1a, and increased activities of the oxidative phosphorylation complexes I and IV and of the TCA member α-ketoglutaric acid dehydrogenase. Consistent with the complex I findings, respiration was more sensitive to inhibition by rotenone in control cells than in the TOM40 over-expressing cells. In the absence of inhibitors, total cellular ATP, the mitochondrial membrane potential, and respiration were elevated in the over-expressing cells. Spare respiratory capacity was greater in the TOM40 over-expressing cells than in the controls. TOM40 over-expression blocked Ab-elicited decreases in the mitochondrial membrane potential, cellular ATP levels, and cellular viability in the control cells. These data suggest elevated expression of TOM40 may be protective of mitochondrial function.
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Kiprowska MJ, Stepanova A, Todaro DR, Galkin A, Haas A, Wilson SM, Figueiredo-Pereira ME. Neurotoxic mechanisms by which the USP14 inhibitor IU1 depletes ubiquitinated proteins and Tau in rat cerebral cortical neurons: Relevance to Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1157-1170. [PMID: 28372990 DOI: 10.1016/j.bbadis.2017.03.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Revised: 03/14/2017] [Accepted: 03/27/2017] [Indexed: 12/14/2022]
Abstract
In Alzheimer's disease proteasome activity is reportedly downregulated, thus increasing it could be therapeutically beneficial. The proteasome-associated deubiquitinase USP14 disassembles polyubiquitin-chains, potentially delaying proteasome-dependent protein degradation. We assessed the protective efficacy of inhibiting or downregulating USP14 in rat and mouse (Usp14axJ) neuronal cultures treated with prostaglandin J2 (PGJ2). IU1 concentrations (HIU1>25μM) reported by others to inhibit USP14 and be protective in non-neuronal cells, reduced PGJ2-induced Ub-protein accumulation in neurons. However, HIU1 alone or with PGJ2 is neurotoxic, induces calpain-dependent Tau cleavage, and decreases E1~Ub thioester levels and 26S proteasome assembly, which are energy-dependent processes. We attribute the two latter HIU1 effects to ATP-deficits and mitochondrial Complex I inhibition, as shown herein. These HIU1 effects mimic those of mitochondrial inhibitors in general, thus supporting that ATP-depletion is a major mediator of HIU1-actions. In contrast, low IU1 concentrations (LIU1≤25μM) or USP14 knockdown by siRNA in rat cortical cultures or loss of USP14 in cortical cultures from ataxia (Usp14axJ) mice, failed to prevent PGJ2-induced Ub-protein accumulation. PGJ2 alone induces Ub-protein accumulation and decreases E1~Ub thioester levels. This seemingly paradoxical result may be attributed to PGJ2 inhibiting some deubiquitinases (such as UCH-L1 but not USP14), thus triggering Ub-protein stabilization. Overall, IU1-concentrations that reduce PGJ2-induced accumulation of Ub-proteins are neurotoxic, trigger calpain-mediated Tau cleavage, lower ATP, E1~Ub thioester and E1 protein levels, and reduce proteasome activity. In conclusion, pharmacologically inhibiting (with low or high IU1 concentrations) or genetically down-regulating USP14 fail to enhance proteasomal degradation of Ub-proteins or Tau in neurons.
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Affiliation(s)
- Magdalena J Kiprowska
- Department of Biological Sciences, Hunter College, Biology and Biochemistry Programs, Graduate Center, The City University of New York, New York, NY 10065, USA
| | - Anna Stepanova
- School of Biological Sciences, Queen's University Belfast, Belfast BT9 7BL, United Kingdom; N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Dustin R Todaro
- Department of Biochemistry and Molecular Biology, LSU Health Sciences Center, New Orleans, LA 70112, USA
| | - Alexander Galkin
- School of Biological Sciences, Queen's University Belfast, Belfast BT9 7BL, United Kingdom; Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY 10065, USA
| | - Arthur Haas
- Department of Biochemistry and Molecular Biology, LSU Health Sciences Center, New Orleans, LA 70112, USA
| | - Scott M Wilson
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Maria E Figueiredo-Pereira
- Department of Biological Sciences, Hunter College, Biology and Biochemistry Programs, Graduate Center, The City University of New York, New York, NY 10065, USA.
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15
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Lower Serum Albumin Shortly After Admission Predicts Prolonged Hospital Stay in Younger Burn Patients. J Burn Care Res 2016; 37:e145-53. [PMID: 26594861 DOI: 10.1097/bcr.0000000000000326] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The purpose of this study was to assess whether albumin levels could be used to aid in the prediction of hospital stay in adult burn patients. A retrospective review of burn patients from 2009 to 2014 was used. Demographic, injury details, albumin levels within 72 hours of admission, and clinical outcomes were recorded. The abbreviated burn severity index (ABSI) was calculated for each patient. Hospital stay >3 weeks was defined as "prolonged stay." Since albumin showed a significant interaction with age, patients were divided into two groups based on a median age of 40 years. Albumin, total BSA, and ABSI were each used as predictors, and the area under the curve (AUC) of a receiver operating characteristic curve was calculated. A composite score was created for the ≤ 40 years age group using ABSI and albumin levels to predict an increased length of stay. Thirty-eight of 198 (19.2%) patients had a stay >3 weeks. The AUCs for albumin level, total BSA, and ABSI alone in younger patients were 0.97, 0.97, and 0.96, respectively. Among patients older than 40, the AUC values were substantially lower indicating lower predictive value. The probability of prolonged stay for patients with albumin level ≥ 2.4 g/dl was low (.8%) compared with those with albumin level <2.4 g/dl (96.5%). Adding ABSI to this model increased predictive accuracy. Albumin level obtained within 72 hours of admission was an effective predictor of prolonged hospital stay in adult burn patients ≤ 40 years.
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Pollard AK, Craig EL, Chakrabarti L. Mitochondrial Complex 1 Activity Measured by Spectrophotometry Is Reduced across All Brain Regions in Ageing and More Specifically in Neurodegeneration. PLoS One 2016; 11:e0157405. [PMID: 27333203 PMCID: PMC4917223 DOI: 10.1371/journal.pone.0157405] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/27/2016] [Indexed: 01/11/2023] Open
Abstract
Mitochondrial function, in particular complex 1 of the electron transport chain (ETC), has been shown to decrease during normal ageing and in neurodegenerative disease. However, there is some debate concerning which area of the brain has the greatest complex 1 activity. It is important to identify the pattern of activity in order to be able to gauge the effect of age or disease related changes. We determined complex 1 activity spectrophotometrically in the cortex, brainstem and cerebellum of middle aged mice (70-71 weeks), a cerebellar ataxic neurodegeneration model (pcd5J) and young wild type controls. We share our updated protocol on the measurements of complex1 activity and find that mitochondrial fractions isolated from frozen tissues can be measured for robust activity. We show that complex 1 activity is clearly highest in the cortex when compared with brainstem and cerebellum (p<0.003). Cerebellum and brainstem mitochondria exhibit similar levels of complex 1 activity in wild type brains. In the aged brain we see similar levels of complex 1 activity in all three-brain regions. The specific activity of complex 1 measured in the aged cortex is significantly decreased when compared with controls (p<0.0001). Both the cerebellum and brainstem mitochondria also show significantly reduced activity with ageing (p<0.05). The mouse model of ataxia predictably has a lower complex 1 activity in the cerebellum, and although reductions are measured in the cortex and brain stem, the remaining activity is higher than in the aged brains. We present clear evidence that complex 1 activity decreases across the brain with age and much more specifically in the cerebellum of the pcd5j mouse. Mitochondrial impairment can be a region specific phenomenon in disease, but in ageing appears to affect the entire brain, abolishing the pattern of higher activity in cortical regions.
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Affiliation(s)
- Amelia Kate Pollard
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, United Kingdom
| | - Emma Louise Craig
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, United Kingdom
| | - Lisa Chakrabarti
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, United Kingdom
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Zhang W, Hou L, Wang T, Lu W, Tao Y, Chen W, Du X, Huang Y. The expression characteristics of mt-ND2 gene in chicken. Mitochondrial DNA A DNA Mapp Seq Anal 2015; 27:3787-92. [PMID: 26332376 DOI: 10.3109/19401736.2015.1079904] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Subunit 2 of NADH dehydrogenase (ND2) is encoded by the mt-ND2 gene and plays a critical role in controlling the production of the mitochondrial reactive oxygen species. Our study focused on exploring the mt-ND2 tissue expression patterns and the effects of energy restriction and dietary fat (linseed oil, corn oil, sesame oil or lard) level (2.5% and 5%) on its expression in chicken. The results showed that mt-ND2 gene was expressed in the 15 tissues of hybrid chickens with the highest level in heart and lowest level in pancreas tissue; 30% energy restriction did not significantly affect mt-ND2 mRNA level in chicken liver tissue. Both the mt-ND2 mRNA levels in chicken pectoralis (p < 0.05) and hepatic tissues (p < 0.05) at 42 d-old were affected by the type of dietary fats in 5% level, while not in abdominal fat tissues. The expression of mt-ND2 in hepatic tissues was down-regulated with chicken age (p < 0.01). The interactive effect of dietary fat types with chicken age (p < 0.05) was significant on mt-ND2 mRNA level. The study demonstrated that mt-ND2 gene was extensively expressed in tissues, and the expression was affected by dietary fat types and chicken age.
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Affiliation(s)
- Wenwen Zhang
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
| | - Lingling Hou
- b Animal Science College, Sichuan Agricultural University , Ya'an, Sichuan China
| | - Ting Wang
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
| | - Weiwei Lu
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
| | - Yafei Tao
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
| | - Wen Chen
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
| | - Xiaohui Du
- b Animal Science College, Sichuan Agricultural University , Ya'an, Sichuan China
| | - Yanqun Huang
- a College of Livestock Husbandry and Veterinary Engineering, Henan Agricultural University , Zhengzhou, Henan , China and
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Abstract
SIGNIFICANCE The molecular mechanism of aging is still vigorously debated, although a general consensus exists that mitochondria are significantly involved in this process. However, the previously postulated role of mitochondrial-derived reactive oxygen species (ROS) as the damaging agents inducing functional loss in aging has fallen out of favor in the recent past. In this review, we critically examine the role of ROS in aging in the light of recent advances on the relationship between mitochondrial structure and function. RECENT ADVANCES The functional mitochondrial respiratory chain is now recognized as a reflection of the dynamic association of respiratory complexes in the form of supercomplexes (SCs). Besides providing kinetic advantage (channeling), SCs control ROS generation by the respiratory chain, thus providing a means to regulate ROS levels in the cell. Depending on their concentration, these ROS are either physiological signals essential for the life of the cell or toxic species that damage cell structure and functions. CRITICAL ISSUES We propose that under physiological conditions the dynamic nature of SCs reversibly controls the generation of ROS as signals involved in mitochondrial-nuclear communication. During aging, there is a progressive loss of control of ROS generation so that their production is irreversibly enhanced, inducing a vicious circle in which signaling is altered and structural damage takes place. FUTURE DIRECTIONS A better understanding on the forces affecting SC association would allow the manipulation of ROS generation, directing these species to their physiological signaling role.
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Affiliation(s)
- Maria Luisa Genova
- Dipartimento di Scienze Biomediche e Neuromotorie, Alma Mater Studiorum-Università di Bologna , Bologna, Italy
| | - Giorgio Lenaz
- Dipartimento di Scienze Biomediche e Neuromotorie, Alma Mater Studiorum-Università di Bologna , Bologna, Italy
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Sgarbi G, Matarrese P, Pinti M, Lanzarini C, Ascione B, Gibellini L, Dika E, Patrizi A, Tommasino C, Capri M, Cossarizza A, Baracca A, Lenaz G, Solaini G, Franceschi C, Malorni W, Salvioli S. Mitochondria hyperfusion and elevated autophagic activity are key mechanisms for cellular bioenergetic preservation in centenarians. Aging (Albany NY) 2014; 6:296-310. [PMID: 24799450 PMCID: PMC4032796 DOI: 10.18632/aging.100654] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mitochondria have been considered for long time as important determinants of cell aging because of their role in the production of reactive oxygen species. In this study we investigated the impact of mitochondrial metabolism and biology as determinants of successful aging in primary cultures of fibroblasts isolated from the skin of long living individuals (LLI) (about 100 years old) compared with those from young (about 27 years old) and old (about 75 years old) subjects. We observed that fibroblasts from LLI displayed significantly lower complex I-driven ATP synthesis and higher production of H2O2 in comparison with old subjects. Despite these changes, bioenergetics of these cells appeared to operate normally. This lack of functional consequences was likely due to a compensatory phenomenon at the level of mitochondria, which displayed a maintained supercomplexes organization and an increased mass. This appears to be due to a decreased mitophagy, induced by hyperfused, elongated mitochondria. The overall data indicate that longevity is characterized by a preserved bioenergetic function likely attained by a successful mitochondria remodeling that can compensate for functional defects through an increase in mass, i.e. a sort of mitochondrial “hypertrophy”.
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Affiliation(s)
- Gianluca Sgarbi
- DIBINEM, Department of Biomedical and Neuromotor Sciences University of Bologna, 40126 Bologna, Italy
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Age modulates Fe3O4 nanoparticles liver toxicity: dose-dependent decrease in mitochondrial respiratory chain complexes activities and coupling in middle-aged as compared to young rats. BIOMED RESEARCH INTERNATIONAL 2014; 2014:474081. [PMID: 24949453 PMCID: PMC4032731 DOI: 10.1155/2014/474081] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/03/2014] [Accepted: 04/04/2014] [Indexed: 12/17/2022]
Abstract
We examined the effects of iron oxide nanoparticles (IONPs) on mitochondrial respiratory chain complexes activities and mitochondrial coupling in young (3 months) and middle-aged (18 months) rat liver, organ largely involved in body iron detoxification. Isolated liver mitochondria were extracted using differential centrifugations. Maximal oxidative capacities (Vmax, complexes I, III, and IV activities), Vsucc (complexes II, III, and IV activities), and Vtmpd, (complex IV activity), together with mitochondrial coupling (Vmax/V0) were determined in controls conditions and after exposure to 250, 300, and 350 μg/ml Fe3O4 in young and middle-aged rats. In young liver mitochondria, exposure to IONPs did not alter mitochondrial function. In contrast, IONPs dose-dependently impaired all complexes of the mitochondrial respiratory chain in middle-aged rat liver: Vmax (from 30 ± 1.6 to 17.9 ± 1.5; P < 0.001), Vsucc (from 33.9 ± 1.7 to 24.3 ± 1.0; P < 0.01), Vtmpd (from 43.0 ± 1.6 to 26.3 ± 2.2 µmol O2/min/g protein; P < 0.001) using Fe3O4 350 µg/ml. Mitochondrial coupling also decreased. Interestingly, 350 μg/ml Fe3O4 in the form of Fe3+ solution did not impair liver mitochondrial function in middle-aged rats. Thus, IONPs showed a specific toxicity in middle-aged rats suggesting caution when using it in old age.
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Molecular mechanism and physiological role of active-deactive transition of mitochondrial complex I. Biochem Soc Trans 2014; 41:1325-30. [PMID: 24059527 PMCID: PMC3990385 DOI: 10.1042/bst20130088] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The unique feature of mitochondrial complex I is the so-called A/D transition (active–deactive transition). The A-form catalyses rapid oxidation of NADH by ubiquinone (k ~104 min−1) and spontaneously converts into the D-form if the enzyme is idle at physiological temperatures. Such deactivation occurs in vitro in the absence of substrates or in vivo during ischaemia, when the ubiquinone pool is reduced. The D-form can undergo reactivation given both NADH and ubiquinone availability during slow (k ~1–10 min−1) catalytic turnover(s). We examined known conformational differences between the two forms and suggested a mechanism exerting A/D transition of the enzyme. In addition, we discuss the physiological role of maintaining the enzyme in the D-form during the ischaemic period. Accumulation of the D-form of the enzyme would prevent reverse electron transfer from ubiquinol to FMN which could lead to superoxide anion generation. Deactivation would also decrease the initial burst of respiration after oxygen reintroduction. Therefore the A/D transition could be an intrinsic protective mechanism for lessening oxidative damage during the early phase of reoxygenation. Exposure of Cys39 of mitochondrially encoded subunit ND3 makes the D-form susceptible for modification by reactive oxygen species and nitric oxide metabolites which arrests the reactivation of the D-form and inhibits the enzyme. The nature of thiol modification defines deactivation reversibility, the reactivation timescale, the status of mitochondrial bioenergetics and therefore the degree of recovery of the ischaemic tissues after reoxygenation.
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Babot M, Birch A, Labarbuta P, Galkin A. Characterisation of the active/de-active transition of mitochondrial complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1083-92. [PMID: 24569053 PMCID: PMC4331042 DOI: 10.1016/j.bbabio.2014.02.018] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 02/14/2014] [Accepted: 02/17/2014] [Indexed: 12/12/2022]
Abstract
Oxidation of NADH in the mitochondrial matrix of aerobic cells is catalysed by mitochondrial complex I. The regulation of this mitochondrial enzyme is not completely understood. An interesting characteristic of complex I from some organisms is the ability to adopt two distinct states: the so-called catalytically active (A) and the de-active, dormant state (D). The A-form in situ can undergo de-activation when the activity of the respiratory chain is limited (i.e. in the absence of oxygen). The mechanisms and driving force behind the A/D transition of the enzyme are currently unknown, but several subunits are most likely involved in the conformational rearrangements: the accessory subunit 39 kDa (NDUFA9) and the mitochondrially encoded subunits, ND3 and ND1. These three subunits are located in the region of the quinone binding site. The A/D transition could represent an intrinsic mechanism which provides a fast response of the mitochondrial respiratory chain to oxygen deprivation. The physiological role of the accumulation of the D-form in anoxia is most probably to protect mitochondria from ROS generation due to the rapid burst of respiration following reoxygenation. The de-activation rate varies in different tissues and can be modulated by the temperature, the presence of free fatty acids and divalent cations, the NAD+/NADH ratio in the matrix, the presence of nitric oxide and oxygen availability. Cysteine-39 of the ND3 subunit, exposed in the D-form, is susceptible to covalent modification by nitrosothiols, ROS and RNS. The D-form in situ could react with natural effectors in mitochondria or with pharmacological agents. Therefore the modulation of the re-activation rate of complex I could be a way to ameliorate the ischaemia/reperfusion damage. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. Guest Editors: Manuela Pereira and Miguel Teixeira. The potential mechanism of complex I A/D transition is discussed. An —SH group exposed in the D-form is susceptible to covalent modification. The role of A/D transition in tissue response to ischaemia is proposed.
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Affiliation(s)
- Marion Babot
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Amanda Birch
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Paola Labarbuta
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Alexander Galkin
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
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Gorenkova N, Robinson E, Grieve DJ, Galkin A. Conformational change of mitochondrial complex I increases ROS sensitivity during ischemia. Antioxid Redox Signal 2013; 19:1459-68. [PMID: 23419200 PMCID: PMC3797456 DOI: 10.1089/ars.2012.4698] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
AIMS Myocardial ischemia/reperfusion (I/R) is associated with mitochondrial dysfunction and subsequent cardiomyocyte death. The generation of excessive quantities of reactive oxygen species (ROS) and resultant damage to mitochondrial enzymes is considered an important mechanism underlying reperfusion injury. Mitochondrial complex I can exist in two interconvertible states: active (A) and deactive or dormant (D). We have studied the active/deactive (A/D) equilibrium in several tissues under ischemic conditions in vivo and investigated the sensitivity of both forms of the heart enzyme to ROS. RESULTS We found that in the heart, t½ of complex I deactivation during ischemia was 10 min, and that reperfusion resulted in the return of A/D equilibrium to its initial level. The rate of superoxide generation by complex I was higher in ischemic samples where content of the D-form was higher. Only the D-form was susceptible to inhibition by H2O2 or superoxide, whereas turnover-dependent activation of the enzyme resulted in formation of the A-form, which was much less sensitive to ROS. The mitochondrial-encoded subunit ND3, most likely responsible for the sensitivity of the D-form to ROS, was identified by redox difference gel electrophoresis. INNOVATION A combined in vivo and biochemical approach suggests that sensitivity of the mitochondrial system to ROS during myocardial I/R can be significantly affected by the conformational state of complex I, which may therefore represent a new therapeutic target in this setting. CONCLUSION The presented data suggest that transition of complex I into the D-form in the absence of oxygen may represent a key event in promoting cardiac injury during I/R.
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Affiliation(s)
- Natalia Gorenkova
- 1 Medical Biology Centre, School of Biological Sciences, Queen's University Belfast , Belfast, United Kingdom
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24
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Bakala H, Ladouce R, Baraibar MA, Friguet B. Differential expression and glycative damage affect specific mitochondrial proteins with aging in rat liver. Biochim Biophys Acta Mol Basis Dis 2013; 1832:2057-67. [PMID: 23906978 DOI: 10.1016/j.bbadis.2013.07.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/19/2013] [Accepted: 07/22/2013] [Indexed: 01/07/2023]
Abstract
Aging is accompanied by the gradual deterioration of cell functions. Particularly, mitochondrial dysfunction, associated with an accumulation of damaged proteins, is of key importance due to the central role of these organelles in cellular metabolism. However, the detailed molecular mechanisms involved in such impairment have not been completely elucidated. In the present study, proteomic analyses looking at both changes at the expression level as well as to glycative modifications of the mitochondrial proteome were performed. Two-dimensional difference gel electrophoresis analysis revealed 16 differentially expressed proteins with aging. Thirteen exhibited a decreased expression and are crucial enzymes related to OXPHOS chain complex I/V components, TCA cycle or fatty acid β-oxidation reaction. On the other hand, 2 enzymes involved in fatty acid β-oxidation cycle were increased in aged mitochondria. Immunodetection and further identification of glycated proteins disclosed a set of advanced glycation end product-modified proteins, including 6 enzymes involved in the fatty acid β-oxidation process, and 2 enzymes of the TCA/urea cycles. A crucial antioxidant enzyme, catalase, was among the most strongly glycated proteins. In addition, several AGE-damaged enzymes (aldehyde dehydrogenase 2, medium chain acyl-CoA dehydrogenase and 3-ketoacyl-CoA dehydrogenase) exhibited a decreased activity with age. Taken together, these data suggest that liver mitochondria in old rats suffer from a decline in their capacity for energy production, due to (i) decreased expression of OXPHOS complex I/V components and (ii) glycative damage to key fatty acid β-oxidation and TCA/urea cycle enzymes.
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Affiliation(s)
- Hilaire Bakala
- Université Paris Diderot-Paris 7, Sorbonne Paris Cité, UFR SDV, 75205 Paris Cedex 13, France; Laboratoire de Biologie Cellulaire du Vieillissement, UR4-UPMC, IFR 83, Université Pierre et Marie Curie-Paris 6, 75252 Paris Cedex 05, France.
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25
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Dorszewska J. Cell biology of normal brain aging: synaptic plasticity-cell death. Aging Clin Exp Res 2013; 25:25-34. [PMID: 23740630 DOI: 10.1007/s40520-013-0004-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 01/23/2012] [Indexed: 11/25/2022]
Abstract
Senescence of the brain seems to be related to increased levels of free oxygen radical (FOR). FOR may damage macromolecular compounds such as: proteins, lipids, and DNA. In the aging brain, increased FOR levels damage DNA, mitochondrial DNA (mtDNA), and nuclear DNA (nDNA). In DNA they damage single and double strands, leading to mutations in mtDNA and nDNA. Damage to mtDNA seems to result in decay of mitochondria, decreased production of ATP, and in the activation of the apoptotic process. In the aging brain, apoptosis does not seem to be activated in wild-type p53-expressing cells because the elevated levels of the p53 protein are no longer accompanied by decreased levels of the Bcl-2 protein and increased levels of the Bax protein. It seems that, in the aging brain, changes in the metabolism of neurons may lead to their decreased numbers in the cerebral and cerebellar cortex, hippocampus, basal nucleus of Meynert, locus ceruleus, and substantia nigra, as well as to decreased numbers of synapses and disturbed stimulation of synaptic plasticity in the senescent brain. Simultaneously, a decrease in neurogenesis in the aging brain may lead to a decline in the maintenance of tissue integrity, function, and regenerative response. Environmental enrichment and physical activity may improve hippocampal neurogenesis and induce neuronal plasticity. The morphological lesions in the senescent brain are undoubtedly followed by a disturbed balance between various types of neurons in the CNS. Nevertheless, the high plasticity of the CNS in humans most probably does not allow for the development of abnormalities in higher functions.
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Affiliation(s)
- Jolanta Dorszewska
- Laboratory of Neurobiology, Department of Neurology, Poznan University of Medical Sciences, 49, Przybyszewskiego St, 60-355, Poznan, Poland.
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Nitric oxide inactivation mechanisms in the brain: role in bioenergetics and neurodegeneration. Int J Cell Biol 2012; 2012:391914. [PMID: 22719764 PMCID: PMC3376480 DOI: 10.1155/2012/391914] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 04/18/2012] [Indexed: 10/28/2022] Open
Abstract
During the last decades nitric oxide ((•)NO) has emerged as a critical physiological signaling molecule in mammalian tissues, notably in the brain. (•)NO may modify the activity of regulatory proteins via direct reaction with the heme moiety, or indirectly, via S-nitrosylation of thiol groups or nitration of tyrosine residues. However, a conceptual understanding of how (•)NO bioactivity is carried out in biological systems is hampered by the lack of knowledge on its dynamics in vivo. Key questions still lacking concrete and definitive answers include those related with quantitative issues of its concentration dynamics and diffusion, summarized in the how much, how long, and how far trilogy. For instance, a major problem is the lack of knowledge of what constitutes a physiological (•)NO concentration and what constitutes a pathological one and how is (•)NO concentration regulated. The ambient (•)NO concentration reflects the balance between the rate of synthesis and the rate of breakdown. Much has been learnt about the mechanism of (•)NO synthesis, but the inactivation pathways of (•)NO has been almost completely ignored. We have recently addressed these issues in vivo on basis of microelectrode technology that allows a fine-tuned spatial and temporal measurement (•)NO concentration dynamics in the brain.
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Brown-Borg HM, Bartke A. GH and IGF1: roles in energy metabolism of long-living GH mutant mice. J Gerontol A Biol Sci Med Sci 2012; 67:652-60. [PMID: 22466316 PMCID: PMC3348496 DOI: 10.1093/gerona/gls086] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Of the multiple theories to explain exceptional longevity, the most robust of these has centered on the reduction of three anabolic protein hormones, growth hormone (GH), insulin-like growth factor, and insulin. GH mutant mice live 50% longer and exhibit significant differences in several aspects of energy metabolism as compared with wild-type mice. Mitochondrial metabolism is upregulated in the absence of GH, whereas in GH transgenic mice and dwarf mice treated with GH, multiple aspects of these pathways are suppressed. Core body temperature is markedly lower in dwarf mice, yet whole-body metabolism, as measured by indirect calorimetry, is surprisingly higher in Ames dwarf and Ghr-/- mice compared with normal controls. Elevated adiponectin, a key antiinflammatory cytokine, is also very likely to contribute to longevity in these mice. Thus, several important components related to energy metabolism are altered in GH mutant mice, and these differences are likely critical in aging processes and life-span extension.
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Affiliation(s)
- Holly M Brown-Borg
- Department of Pharmacology, Physiology & Therapeutics, School of Medicine & Health Sciences, University of North Dakota, 501 North Columbia Road, Grand Forks, ND 58202-9037, USA.
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Brown-Borg HM, Johnson WT, Rakoczy SG. Expression of oxidative phosphorylation components in mitochondria of long-living Ames dwarf mice. AGE (DORDRECHT, NETHERLANDS) 2012; 34:43-57. [PMID: 21327718 PMCID: PMC3260352 DOI: 10.1007/s11357-011-9212-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 01/24/2011] [Indexed: 05/30/2023]
Abstract
Reduced signaling of the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) pathway is associated with extended life span in several species. Ames dwarf mice are GH-deficient and live >50% longer than wild-type littermates. Previously, we have shown that tissues from Ames mice exhibit elevated levels of antioxidative enzymes, less H(2)O(2) production, and lower oxidative damage suggesting that mitochondrial function may differ between genotypes. To explore the relationship between hormone deficiency and mitochondria in mice with extended longevity, we evaluated activity, protein, and gene expression of oxidative phosphorylation components in dwarf and wild-type mice at varying ages. Liver complex I + III activity was higher in dwarf mice compared to wild-type mice. The activity of I + III decreased between 3 and 20 months of age in both genotypes with greater declines in wild-type mice in liver and skeletal muscle. Complex IV activities in the kidney were elevated in 3- and 20-month-old dwarf mice relative to wild-type mice. In Ames mice, protein levels of the 39 kDa complex I subunit were elevated at 20 months of age when compared to wild-type mouse mitochondria for every tissue examined. Kidney and liver mitochondria from 20-month-old dwarf mice had elevated levels of both mitochondrially-encoded and nuclear-encoded complex IV proteins compared to wild-type mice (p < 0.05). Higher liver ANT1 and PGC-1α mRNA levels were also observed in dwarf mice. Overall, we found that several components of the oxidative phosphorylation (OXPHOS) system were elevated in Ames mice. Mitochondrial to nuclear DNA ratios were not different between genotypes despite the marked increase in PGC-1α levels in dwarf mice. The increased OXPHOS activities, along with lower ROS production in dwarf mice, predict enhanced mitochondrial function and efficiency, two factors likely contributing to long-life in Ames mice.
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Affiliation(s)
- Holly M Brown-Borg
- Department of Pharmacology, Physiology and Therapeutics, University of North Dakota School of Medicine and Health Sciences, 501 N. Columbia Rd, Grand Forks, ND 58203, USA.
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Arese M, Magnifico MC, Mastronicola D, Altieri F, Grillo C, Blanck TJJ, Sarti P. Nanomolar melatonin enhances nNOS expression and controls HaCaT-cells bioenergetics. IUBMB Life 2012; 64:251-8. [PMID: 22271455 DOI: 10.1002/iub.603] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 11/12/2011] [Indexed: 01/08/2023]
Abstract
A novel role of melatonin was unveiled, using immortalized human keratinocyte cells (HaCaT) as a model system. Within a time window compatible with its circadian rhythm, melatonin at nanomolar concentration raised both the expression level of the neuronal nitric oxide synthase mRNA and the nitric oxide oxidation products, nitrite and nitrate. On the same time scale, a depression of the mitochondrial membrane potential was detected together with a decrease of the oxidative phosphorylation efficiency, compensated by glycolysis as testified by an increased production of lactate. The melatonin concentration, ∼ nmolar, inducing the bioenergetic effects and their time dependence, both suggest that the observed nitric oxide-induced mitochondrial changes might play a role in the metabolic pathways characterizing the circadian melatonin chemistry.
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Affiliation(s)
- Marzia Arese
- Department of Biochemical Sciences, Sapienza University of Rome, Italy
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Mitochondrial Oxidative Stress due to Complex I Dysfunction Promotes Fibroblast Activation and Melanoma Cell Invasiveness. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:684592. [PMID: 22272371 PMCID: PMC3261495 DOI: 10.1155/2012/684592] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 09/22/2011] [Indexed: 12/12/2022]
Abstract
Increased ROS (cellular reactive oxygen species) are characteristic of both fibrosis and tumour development. ROS induce the trans-differentiation to myofibroblasts, the activated form of fibroblasts able to promote cancer progression. Here, we report the role of ROS produced in response to dysfunctions of mitochondrial complex I, in fibroblast activation and in tumour progression. We studied human fibroblasts with mitochondrial dysfunctions of complex I, leading to hyperproduction of ROS. We demonstrated that ROS level produced by the mutated fibroblasts correlates with their activation. The increase of ROS in these cells provides a greater ability to remodel the extracellular matrix leading to an increased motility and invasiveness. Furthermore, we evidentiated that in hypoxic conditions these fibroblasts cause HIF-1α stabilization and promote a proinvasive phenotype of human melanoma cells through secretion of cytokines. These data suggest a possible role of deregulated mitochondrial ROS production in fibrosis evolution as well as in cancer progression and invasion.
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Lenaz G, Genova ML. Supramolecular Organisation of the Mitochondrial Respiratory Chain: A New Challenge for the Mechanism and Control of Oxidative Phosphorylation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 748:107-44. [DOI: 10.1007/978-1-4614-3573-0_5] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Papa S, Martino PL, Capitanio G, Gaballo A, De Rasmo D, Signorile A, Petruzzella V. The oxidative phosphorylation system in mammalian mitochondria. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:3-37. [PMID: 22399416 DOI: 10.1007/978-94-007-2869-1_1] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The chapter provides a review of the state of art of the oxidative phosphorylation system in mammalian mitochondria. The sections of the paper deal with: (i) the respiratory chain as a whole: redox centers of the chain and protonic coupling in oxidative phosphorylation (ii) atomic structure and functional mechanism of protonmotive complexes I, III, IV and V of the oxidative phosphorylation system (iii) biogenesis of oxidative phosphorylation complexes: mitochondrial import of nuclear encoded subunits, assembly of oxidative phosphorylation complexes, transcriptional factors controlling biogenesis of the complexes. This advanced knowledge of the structure, functional mechanism and biogenesis of the oxidative phosphorylation system provides a background to understand the pathological impact of genetic and acquired dysfunctions of mitochondrial oxidative phosphorylation.
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Affiliation(s)
- Sergio Papa
- Department of Basic Medical Sciences, University of Bari, Bari, Italy.
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Lenaz G. Mitochondria and reactive oxygen species. Which role in physiology and pathology? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:93-136. [PMID: 22399420 DOI: 10.1007/978-94-007-2869-1_5] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Oxidative stress is among the major causes of toxicity due to interaction of Reactive Oxygen Species (ROS) with cellular macromolecules and structures and interference with signal transduction pathways. The mitochondrial respiratory chain, specially from Complexes I and III, is considered the main origin of ROS particularly under conditions of high membrane potential, but several other sources may be important for ROS generation, such as mitochondrial p66(Shc), monoamine oxidase, α-ketoglutarate dehydogenase, besides redox cycling of redox-active molecules. ROS are able to oxidatively modify lipids, proteins, carbohydrates and nucleic acids in mitochondria and to activate/inactivate signalling pathways by oxidative modification of redox-active factors. Cells are endowed with several defence mechanisms including repair or removal of damaged molecules, and antioxidant systems, either enzymatic or non-enzymatic. Oxidative stress is at the basis of ageing and many pathological disorders, such as ischemic diseases, neurodegenerative diseases, diabetes, and cancer, although the underlying mechanisms are not always completely understood.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica, Università di Bologna, Bologna, Italy.
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Petruzzella V, Sardanelli AM, Scacco S, Panelli D, Papa F, Trentadue R, Papa S. Dysfunction of mitochondrial respiratory chain complex I in neurological disorders: genetics and pathogenetic mechanisms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:371-84. [PMID: 22399432 DOI: 10.1007/978-94-007-2869-1_17] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
This chapter covers genetic and biochemical aspects of mitochondrial bioenergetics dysfunction in neurological disorders associated with complex I defects. Complex I formation and functionality in mammalian cells depends on coordinated expression of nuclear and mitochondrial genes, post-translational subunit modifications, mitochondrial import/maturation of nuclear encoded subunits, subunits interaction and stepwise assembly, and on proteolytic processing. Examples of complex I dysfunction are herein presented: homozygous mutations in the nuclear NDUFS1 and NDUFS4 genes for structural components of complex I; an autosomic recessive form of encephalopathy associated with enhanced proteolytic degradation of complex I; familial cases of Parkinson associated to mutations in the PINK1 and Parkin genes, in particular, homoplasmic mutations in the ND5 and ND6 mitochondrial genes of the complex I, coexistent with mutation in the PINK1 gene. This knowledge, besides clarifying molecular aspects of the pathogenesis of hereditary diseases, can also provide hints for understanding the involvement of complex I in neurological disorders, as well as for developing therapeutical strategies.
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Affiliation(s)
- Vittoria Petruzzella
- Department of Basic Medical Sciences, University of Bari, Policlinico, Bari, Italy
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Hughes BG, Hekimi S. A mild impairment of mitochondrial electron transport has sex-specific effects on lifespan and aging in mice. PLoS One 2011; 6:e26116. [PMID: 22028811 PMCID: PMC3189954 DOI: 10.1371/journal.pone.0026116] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 09/19/2011] [Indexed: 11/29/2022] Open
Abstract
Impairments of various aspects of mitochondrial function have been associated with increased lifespan in various model organisms ranging from Caenorhabditis elegans to mice. For example, disruption of the function of the 'Rieske' iron-sulfur protein (RISP) of complex III of the mitochondrial electron transport chain can result in increased lifespan in the nematode worm C. elegans. However, the mechanisms by which impaired mitochondrial function affects aging remain under investigation, including whether or not they require decreased electron transport. We have generated knock-in mice with a loss-of-function Risp mutation that is homozygous lethal. However, heterozygotes (Risp(+/P224S)) were viable and had decreased levels of RISP protein and complex III enzymatic activity. This decrease was sufficient to impair mitochondrial respiration and to decrease overall metabolic rate in males, but not females. These defects did not appear to exert an overtly deleterious effect on the health of the mutants, since young Risp(+/P224S) mice are outwardly normal, with unaffected performance and fertility. Furthermore, biomarkers of oxidative stress were unaffected in both young and aged animals. Despite this, the average lifespan of male Risp(+/P224S) mice was shortened and aged Risp(+/P224S) males showed signs of more rapidly deteriorating health. In spite of these differences, analysis of Gompertz mortality parameters showed that Risp heterozygosity decreased the rate of increase of mortality with age and increased the intrinsic vulnerability to death in both sexes. However, the intrinsic vulnerability was increased more dramatically in males, which resulted in their shortened lifespan. For females, the slower acceleration of age-dependent mortality results in significantly increased survival of Risp(+/P224S) mice in the second half of lifespan. These results demonstrate that even relatively small perturbations of the mitochondrial electron transport chain can have significant physiological effects in mammals, and that the severity of those effects can be sex-dependent.
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Papa S, Rasmo DD, Technikova-Dobrova Z, Panelli D, Signorile A, Scacco S, Petruzzella V, Papa F, Palmisano G, Gnoni A, Micelli L, Sardanelli AM. Respiratory chain complex I, a main regulatory target of the cAMP/PKA pathway is defective in different human diseases. FEBS Lett 2011; 586:568-77. [PMID: 21945319 DOI: 10.1016/j.febslet.2011.09.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 09/08/2011] [Accepted: 09/13/2011] [Indexed: 12/15/2022]
Abstract
In mammals, complex I (NADH-ubiquinone oxidoreductase) of the mitochondrial respiratory chain has 31 supernumerary subunits in addition to the 14 conserved from prokaryotes to humans. Multiplicity of structural protein components, as well as of biogenesis factors, makes complex I a sensible pace-maker of mitochondrial respiration. The work reviewed here shows that the cAMP/PKA pathway regulates the biogenesis, assembly and catalytic activity of complex I and mitochondrial oxygen superoxide production. The structural, functional and regulatory complexity of complex I, renders it particularly vulnerable to genetic and sporadic pathological factors. Complex I dysfunction has, indeed, been found, to be associated with several human diseases. Knowledge of the pathogenetic mechanisms of these diseases can help to develop new therapeutic strategies.
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Affiliation(s)
- Sergio Papa
- Department of Basic Medical Sciences, Section of Medical Biochemistry, University of Bari Aldo Moro, Bari, Italy.
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Genova ML, Lenaz G. New developments on the functions of coenzyme Q in mitochondria. Biofactors 2011; 37:330-54. [PMID: 21989973 DOI: 10.1002/biof.168] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 04/06/2011] [Indexed: 12/12/2022]
Abstract
The notion of a mobile pool of coenzyme Q (CoQ) in the lipid bilayer has changed with the discovery of respiratory supramolecular units, in particular the supercomplex comprising complexes I and III; in this model, the electron transfer is thought to be mediated by tunneling or microdiffusion, with a clear kinetic advantage on the transfer based on random collisions. The CoQ pool, however, has a fundamental function in establishing a dissociation equilibrium with bound quinone, besides being required for electron transfer from other dehydrogenases to complex III. The mechanism of CoQ reduction by complex I is analyzed regarding recent developments on the crystallographic structure of the enzyme, also in relation to the capacity of complex I to generate superoxide. Although the mechanism of the Q-cycle is well established for complex III, involvement of CoQ in proton translocation by complex I is still debated. Some additional roles of CoQ are also examined, such as the antioxidant effect of its reduced form and the capacity to bind the permeability transition pore and the mitochondrial uncoupling proteins. Finally, a working hypothesis is advanced on the establishment of a vicious circle of oxidative stress and supercomplex disorganization in pathological states, as in neurodegeneration and cancer.
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Mota MP, Peixoto FM, Soares JF, Figueiredo PA, Leitão JC, Gaivão I, Duarte JA. Influence of aerobic fitness on age-related lymphocyte DNA damage in humans: relationship with mitochondria respiratory chain and hydrogen peroxide production. AGE (DORDRECHT, NETHERLANDS) 2010; 32:337-346. [PMID: 20640548 PMCID: PMC2926856 DOI: 10.1007/s11357-010-9138-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 02/22/2010] [Indexed: 05/29/2023]
Abstract
The aim of this study was to analyze the influence of aerobic fitness (AF) on age-related lymphocyte DNA damage in humans, giving special attention to the role of the mitochondrial respiratory chain and hydrogen peroxide production. Considering age and AF (as assessed by VO(2)max), 66 males (19-59 years old) were classified as high fitness (HF) or low fitness (LF) and distributed into one of the following groups: young adults (19-29 years old), adults (30-39 years old), and middle-aged adults (over 40 years old). Peripheral lymphocytes obtained at rest were used to assess DNA damage (strand breaks and formamidopyrimidine DNA glycosylase (FPG) sites through the comet assay), activity of mitochondrial complexes I and II (polarographically measured), and the hydrogen peroxide production rate (assayed by fluorescence). Results revealed a significant interaction between age groups and AF for DNA strand breaks (F = 8.415, p = .000), FPG sites (F = 11.766, p = .000), mitochondrial complex I activity (F = 7.555, p = .000), and H(2)O(2) production (F = 7.500, p = .000). Except for mitochondrial complex II activity, the age variation of the remaining parameters was significantly attenuated by HF. Considering each AF level, an increase in DNA strand breaks and FPG sites with age (r = 0.655, p = 0.000, and r = 0.738, p = 0.000, respectively) was only observed in LF. Moreover, decreased mitochondrial complex I activity with age (r = -.470, p = .009) was reported in LF. These results allow the conclusion that high AF seems to play a key role in attenuating the biological aging process.
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Affiliation(s)
- Maria Paula Mota
- University of Trás-os-Montes and Alto Douro, Centro de Investigação em Desporto, Saúde e Desenvolvimento Humano, Vila Real, Portugal.
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Lenaz G, Baracca A, Barbero G, Bergamini C, Dalmonte ME, Del Sole M, Faccioli M, Falasca A, Fato R, Genova ML, Sgarbi G, Solaini G. Mitochondrial respiratory chain super-complex I–III in physiology and pathology. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:633-40. [DOI: 10.1016/j.bbabio.2010.01.025] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 01/20/2010] [Accepted: 01/20/2010] [Indexed: 11/27/2022]
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Expression of the yeast NADH dehydrogenase Ndi1 in Drosophila confers increased lifespan independently of dietary restriction. Proc Natl Acad Sci U S A 2010; 107:9105-10. [PMID: 20435911 DOI: 10.1073/pnas.0911539107] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mutations in mitochondrial oxidative phosphorylation complex I are associated with multiple pathologies, and complex I has been proposed as a crucial regulator of animal longevity. In yeast, the single-subunit NADH dehydrogenase Ndi1 serves as a non-proton-translocating alternative enzyme that replaces complex I, bringing about the reoxidation of intramitochondrial NADH. We have created transgenic strains of Drosophila that express yeast NDI1 ubiquitously. Mitochondrial extracts from NDI1-expressing flies displayed a rotenone-insensitive NADH dehydrogenase activity, and functionality of the enzyme in vivo was confirmed by the rescue of lethality resulting from RNAi knockdown of complex I. NDI1 expression increased median, mean, and maximum lifespan independently of dietary restriction, and with no change in sirtuin activity. NDI1 expression mitigated the aging associated decline in respiratory capacity and the accompanying increase in mitochondrial reactive oxygen species production, and resulted in decreased accumulation of markers of oxidative damage in aged flies. Our results support a central role of mitochondrial oxidative phosphorylation complex I in influencing longevity via oxidative stress, independently of pathways connected to nutrition and growth signaling.
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Lenaz G, Genova ML. Structure and organization of mitochondrial respiratory complexes: a new understanding of an old subject. Antioxid Redox Signal 2010; 12:961-1008. [PMID: 19739941 DOI: 10.1089/ars.2009.2704] [Citation(s) in RCA: 186] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The enzymatic complexes of the mitochondrial respiratory chain have been extensively investigated in their structural and functional properties. A clear distinction is possible today between three complexes in which the difference in redox potential allows proton translocation (complexes I, III, and IV) and those having the mere function to convey electrons to the respiratory chain. We also have a clearer understanding of the structure and function of most respiratory complexes, of their biogenesis and regulation, and of their capacity to generate reactive oxygen species. Past investigations led to the conclusion that the complexes are randomly dispersed and functionally connected by diffusion of smaller redox components, coenzyme Q and cytochrome c. More-recent investigations by native gel electrophoresis and single-particle image processing showed the existence of supramolecular associations. Flux-control analysis demonstrated that complexes I and III in mammals and I, III, and IV in plants kinetically behave as single units, suggesting the existence of substrate channeling. This review discusses conditions affecting the formation of supercomplexes that, besides kinetic advantage, have a role in the stability and assembly of the individual complexes and in preventing excess oxygen radical formation. Disruption of supercomplex organization may lead to functional derangements responsible for pathologic changes.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica "G. Moruzzi," Alma Mater Studiorum, Università di Bologna, Bologna, Italy.
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42
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Production of reactive oxygen species by the mitochondrial electron transport chain in Drosophila melanogaster. J Bioenerg Biomembr 2010; 42:135-42. [PMID: 20300811 DOI: 10.1007/s10863-010-9281-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 02/17/2010] [Indexed: 12/19/2022]
Abstract
Mitochondrial free radicals and in particular mitochondrial Reactive Oxygen Species (mtROS) are considered to be totally or partially responsible for several different diseases including Parkinson, diabetes or cancer. Even more importantly, mtROS have also been proposed as the main driving force behind the aging process. Thus, in the last decade, there has been a growing interest in the role of free radicals as signalling molecules. Collectively this makes understanding mechanisms controlling free radical production extremely important. There is extensive published literature on mammalian models (essentially rat, mouse and guinea pig) however; this is not the case in Drosophila melanogaster. Drosophila is an excellent model to study different physiological and pathological processes. Additionally a robust method to study mtROS is extremely useful. In the present article, we describe a simple--but extremely sensitive--method to study mtROS production in Drosophila. We have performed various experiments to determine which specific respiratory complexes produce free radicals in the electron transport chain of Drosophila melanogaster. Complex I is the main generator of ROS in Drosophila mitochondria, leaking electrons either in the forward or reverse direction. The production of ROS during reverse electron transport can be prevented either by rotenone or by the oxidation of NADH by complex I. These results clearly show that Drosophila mitochondria function in a very similar way to mammalian mitochondria, and therefore are a very relevant experimental model for biochemical studies related to ageing.
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Yun JW, Lee TR, Kim CW, Park YH, Chung JH, Lee YS, Kang KS, Lim KM. Predose Blood Gene Expression Profiles Might Identify the Individuals Susceptible to Carbon Tetrachloride–Induced Hepatotoxicity. Toxicol Sci 2010; 115:12-21. [DOI: 10.1093/toxsci/kfq037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Wen JJ, Garg NJ. Mitochondrial complex III defects contribute to inefficient respiration and ATP synthesis in the myocardium of Trypanosoma cruzi-infected mice. Antioxid Redox Signal 2010; 12:27-37. [PMID: 19624257 PMCID: PMC2821147 DOI: 10.1089/ars.2008.2418] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this study, we conducted a thorough analysis of mitochondrial bioenergetic function as well as the biochemical and molecular factors that are deregulated and contribute to compromised adenosine triphosphate (ATP) production in the myocardium during Trypanosoma cruzi infection. We show that ADP-stimulated state 3 respiration and ATP synthesis supported by pyruvate/malate (provides electrons to complex I) and succinate (provides electrons to complex II) substrates were significantly decreased in left ventricular tissue and isolated cardiac mitochondria of infected mice. The decreased mitochondrial ATP synthesis in infected murine hearts was not a result of uncoupling between the electron-transport chain and oxidative phosphorylation and decreased availability of the intermediary metabolites (e.g., NADH). The observed decline in the activities of complex-I, -IV, and -V was not physiologically relevant and did not contribute to compromised respiration and ATP synthesis in infected myocardium. Instead, complex III activity was decreased above the threshold level and contributed to respiratory-chain inefficiency and the resulting decline in mitochondrial ATP synthesis in infected myocardium. The loss in complex III activity occurred as a consequence of cytochrome b depletion. Treatment of infected mice with phenyl-alpha-tert-butyl nitrone (PBN, antioxidant) was beneficial in preserving the mtDNA-encoded cytochrome b expression, and subsequently resulted in improved complex III activity, mitochondrial respiration, and ATP production in infected myocardium. Overall, we provide novel data on the mechanism(s) involved in cardiac bioenergetic inefficiency during T. cruzi infection.
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Affiliation(s)
- Jian-Jun Wen
- Department of Microbiology & Immunology, The Center for Biodefense & Emerging Infectious Diseases, and The Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas 77555-1070, USA
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45
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Lenaz G, Genova ML. Structural and functional organization of the mitochondrial respiratory chain: a dynamic super-assembly. Int J Biochem Cell Biol 2009; 41:1750-1772. [PMID: 19711505 DOI: 10.1016/j.biocel.2009.04.003] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The structural organization of the mitochondrial oxidative phosphorylation (OXPHOS) system has received large attention in the past and most investigations led to the conclusion that the respiratory enzymatic complexes are randomly dispersed in the lipid bilayer of the inner membrane and functionally connected by fast diffusion of smaller redox components, Coenzyme Q and cytochrome c. More recent investigations by native gel electrophoresis, however, have shown the existence of supramolecular associations of the respiratory complexes, confirmed by electron microscopy analysis and single particle image processing. Flux control analysis has demonstrated that Complexes I and III in mammalian mitochondria and Complexes I, III, and IV in plant mitochondria kinetically behave as single units with control coefficients approaching unity for each single component, suggesting the existence of substrate channelling within the supercomplexes. The reasons why the presence of substrate channelling for Coenzyme Q and cytochrome c was overlooked in the past are analytically discussed. The review also discusses the forces and the conditions responsible for the formation of the supramolecular units. The function of the supercomplexes appears not to be restricted to kinetic advantages in electron transfer: we discuss evidence on their role in the stability and assembly of the individual complexes and in preventing excess oxygen radical formation. Finally, there is increasing evidence that disruption of the supercomplex organization leads to functional derangements responsible for pathological changes.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica G. Moruzzi, Università di Bologna, Via Irnerio 48, 40126 Bologna, Italy.
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Lenaz G, Genova ML. Mobility and function of Coenzyme Q (ubiquinone) in the mitochondrial respiratory chain. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:563-73. [DOI: 10.1016/j.bbabio.2009.02.019] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 02/23/2009] [Accepted: 02/23/2009] [Indexed: 11/29/2022]
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Stowe DF, Camara AKS. Mitochondrial reactive oxygen species production in excitable cells: modulators of mitochondrial and cell function. Antioxid Redox Signal 2009; 11:1373-414. [PMID: 19187004 PMCID: PMC2842133 DOI: 10.1089/ars.2008.2331] [Citation(s) in RCA: 341] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 01/12/2009] [Accepted: 01/13/2009] [Indexed: 12/14/2022]
Abstract
The mitochondrion is a major source of reactive oxygen species (ROS). Superoxide (O(2)(*-)) is generated under specific bioenergetic conditions at several sites within the electron-transport system; most is converted to H(2)O(2) inside and outside the mitochondrial matrix by superoxide dismutases. H(2)O(2) is a major chemical messenger that, in low amounts and with its products, physiologically modulates cell function. The redox state and ROS scavengers largely control the emission (generation scavenging) of O(2)(*-). Cell ischemia, hypoxia, or toxins can result in excess O(2)(*-) production when the redox state is altered and the ROS scavenger systems are overwhelmed. Too much H(2)O(2) can combine with Fe(2+) complexes to form reactive ferryl species (e.g., Fe(IV) = O(*)). In the presence of nitric oxide (NO(*)), O(2)(*-) forms the reactant peroxynitrite (ONOO(-)), and ONOOH-induced nitrosylation of proteins, DNA, and lipids can modify their structure and function. An initial increase in ROS can cause an even greater increase in ROS and allow excess mitochondrial Ca(2+) entry, both of which are factors that induce cell apoptosis and necrosis. Approaches to reduce excess O(2)(*-) emission include selectively boosting the antioxidant capacity, uncoupling of oxidative phosphorylation to reduce generation of O(2)(*-) by inducing proton leak, and reversibly inhibiting electron transport. Mitochondrial cation channels and exchangers function to maintain matrix homeostasis and likely play a role in modulating mitochondrial function, in part by regulating O(2)(*-) generation. Cell-signaling pathways induced physiologically by ROS include effects on thiol groups and disulfide linkages to modify posttranslationally protein structure to activate/inactivate specific kinase/phosphatase pathways. Hypoxia-inducible factors that stimulate a cascade of gene transcription may be mediated physiologically by ROS. Our knowledge of the role played by ROS and their scavenging systems in modulation of cell function and cell death has grown exponentially over the past few years, but we are still limited in how to apply this knowledge to develop its full therapeutic potential.
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Affiliation(s)
- David F Stowe
- Anesthesiology Research Laboratories, Department of Anesthesiology, The Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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Pathogenetic mechanisms in hereditary dysfunctions of complex I of the respiratory chain in neurological diseases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:502-17. [DOI: 10.1016/j.bbabio.2008.12.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Revised: 12/23/2008] [Accepted: 12/30/2008] [Indexed: 12/21/2022]
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Control and regulation of integrated mitochondrial function in metabolic and transport networks. Int J Mol Sci 2009; 10:1500-1513. [PMID: 19468321 PMCID: PMC2680629 DOI: 10.3390/ijms10041500] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2009] [Revised: 03/26/2009] [Accepted: 03/30/2009] [Indexed: 12/03/2022] Open
Abstract
The pattern of flux and concentration control coefficients in an integrated mitochondrial energetics model is examined by applying a generalized matrix method of control analysis to calculate control coefficients, as well as response coefficients The computational model of Cortassa et al. encompasses oxidative phosphorylation, the TCA cycle, and Ca2+ dynamics. Control of ATP synthesis, TCA cycle, and ANT fluxes were found to be distributed among various mitochondrial processes. Control is shared by processes associated with ATP/ADP production and transport, as well as by Ca2+ dynamics. The calculation also analyzed the control of the concentrations of key regulatory ions and metabolites (Ca2+, NADH, ADP). The approach we have used demonstrates how properties of integrated systems may be understood through applications of computational modeling and control analysis.
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Cortassa S, O'Rourke B, Winslow RL, Aon MA. Control and regulation of mitochondrial energetics in an integrated model of cardiomyocyte function. Biophys J 2009; 96:2466-78. [PMID: 19289071 PMCID: PMC2989151 DOI: 10.1016/j.bpj.2008.12.3893] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 12/01/2008] [Indexed: 01/14/2023] Open
Abstract
Understanding the regulation and control of complex networks of reactions requires analytical tools that take into account the interactions between individual network components controlling global network function. Here, we apply a generalized matrix method of control analysis to calculate flux and concentration control coefficients, as well as response coefficients, in an integrated model of excitation-contraction (EC) coupling and mitochondrial energetics (ECME model) in the cardiac ventricular myocyte. Control and regulation of oxygen consumption (V(O2)) was first assessed in a mitochondrion model, and then in the integrated cardiac myocyte model under resting and working conditions. The results demonstrate that in the ECME model, control of respiration is distributed among cytoplasmic ATPases and mitochondrial processes. The magnitude of control by cytoplasmic ATPases increases under working conditions. The model prediction that the respiratory chain exerts strong positive control on V(O2) (control coefficient 0.89) was corroborated experimentally in cardiac trabeculae utilizing the inhibitor titration method. In the model, mitochondrial respiration displayed the highest response coefficients with respect to the concentration of cytoplasmic ATP. This was due to the high elasticity of ANT flux toward ATP in the cytoplasm. The analysis reveals the complex interdependence of sarcolemmal, cytoplasmic, and mitochondrial processes that contribute to the control of energy supply and demand in the heart. Moreover, by visualizing the structure of control of the metabolic network of the myocyte, we provide support for the emerging concept of control by diffuse loops, in which action on the network (e.g., by a pharmacological agent) may bring about changes in processes without obvious direct mechanistic links between them.
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Affiliation(s)
- Sonia Cortassa
- Division of Cardiology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
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