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Adzigbli L, Ponsuksili S, Sokolova I. Mitochondrial responses to constant and cyclic hypoxia depend on the oxidized fuel in a hypoxia-tolerant marine bivalve Crassostrea gigas. Sci Rep 2024; 14:9658. [PMID: 38671046 PMCID: PMC11053104 DOI: 10.1038/s41598-024-60261-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 04/21/2024] [Indexed: 04/28/2024] Open
Abstract
Sessile benthic organisms like oysters inhabit the intertidal zone, subject to alternating hypoxia and reoxygenation (H/R) episodes during tidal movements, impacting respiratory chain activities and metabolome compositions. We investigated the effects of constant severe hypoxia (90 min at ~ 0% O2 ) followed by 10 min reoxygenation, and cyclic hypoxia (5 cycles of 15 min at ~ 0% O2 and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of Crassostrea gigas respiring on pyruvate, palmitate, or succinate. Constant hypoxia suppressed oxidative phosphorylation (OXPHOS), particularly during Complex I-linked substrates oxidation. It had no effect on mitochondrial reactive oxygen species (ROS) efflux but increased fractional electron leak (FEL). In mitochondria oxidizing Complex I substrates, exposure to cyclic hypoxia prompted a significant drop after the first H/R cycle. In contrast, succinate-driven respiration only showed significant decline after the third to fifth H/R cycle. ROS efflux saw little change during cyclic hypoxia regardless of the oxidized substrate, but Complex I-driven FEL tended to increase with each subsequent H/R cycle. These observations suggest that succinate may serve as a beneficial stress fuel under H/R conditions, aiding in the post-hypoxic recovery of oysters by reducing oxidative stress and facilitating rapid ATP re-synthesis. The impacts of constant and cyclic hypoxia of similar duration on mitochondrial respiration and oxidative lesions in the proteins were comparable indicating that the mitochondrial damage is mostly determined by the lack of oxygen and mitochondrial depolarization. The ROS efflux in the mitochondria of oysters was minimally affected by oxygen fluctuations indicating that tight regulation of ROS production may contribute to robust mitochondrial phenotype of oysters and protect against H/R induced stress.
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Affiliation(s)
- Linda Adzigbli
- Institute for Farm Animal Biology, Institute of Genome Biology, Dummerstorf, Germany
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany
| | - Siriluck Ponsuksili
- Institute for Farm Animal Biology, Institute of Genome Biology, Dummerstorf, Germany
| | - Inna Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany.
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany.
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2
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Kadamani KL, Logan SM, Pamenter ME. Does hypometabolism constrain innate immune defense? Acta Physiol (Oxf) 2024; 240:e14091. [PMID: 38288574 DOI: 10.1111/apha.14091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 11/30/2023] [Accepted: 01/01/2024] [Indexed: 02/24/2024]
Abstract
Many animals routinely make energetic trade-offs to adjust to environmental demands and these trade-offs often have significant implications for survival. For example, environmental hypoxia is commonly experienced by many organisms and is an energetically challenging condition because reduced oxygen availability constrains aerobic energy production, which can be lethal. Many hypoxia-tolerant species downregulate metabolic demands when oxygen is limited; however, certain physiological functions are obligatory and must be maintained despite the need to conserve energy in hypoxia. Of particular interest is immunity (including both constitutive and induced immune functions) because mounting an immune response is among the most energetically expensive physiological processes but maintaining immune function is critical for survival in most environments. Intriguingly, physiological responses to hypoxia and pathogens share key molecular regulators such as hypoxia-inducible factor-1α, through which hypoxia can directly activate an immune response. This raises an interesting question: do hypoxia-tolerant species mount an immune response during periods of hypoxia-induced hypometabolism? Unfortunately, surprisingly few studies have examined interactions between immunity and hypometabolism in such species. Therefore, in this review, we consider mechanistic interactions between metabolism and immunity, as well as energetic trade-offs between these two systems, in hypoxia-tolerant animals but also in other models of hypometabolism, including neonates and hibernators. Specifically, we explore the hypothesis that such species have blunted immune responses in hypometabolic conditions and/or use alternative immune pathways when in a hypometabolic state. Evidence to date suggests that hypoxia-tolerant animals do maintain immunity in low oxygen conditions, but that the sensitivity of immune responses may be blunted.
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Affiliation(s)
- Karen L Kadamani
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Samantha M Logan
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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3
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Pohl F, Germann AL, Mao J, Hou S, Bakare B, Kong Thoo Lin P, Yates K, Nonet ML, Akk G, Kornfeld K, Held JM. UNC-49 is a redox-sensitive GABA A receptor that regulates the mitochondrial unfolded protein response cell nonautonomously. SCIENCE ADVANCES 2023; 9:eadh2584. [PMID: 37910615 PMCID: PMC10619936 DOI: 10.1126/sciadv.adh2584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 09/29/2023] [Indexed: 11/03/2023]
Abstract
The γ-aminobutyric acid-mediated (GABAergic) system participates in many aspects of organismal physiology and disease, including proteostasis, neuronal dysfunction, and life-span extension. Many of these phenotypes are also regulated by reactive oxygen species (ROS), but the redox mechanisms linking the GABAergic system to these phenotypes are not well defined. Here, we report that GABAergic redox signaling cell nonautonomously activates many stress response pathways in Caenorhabditis elegans and enhances vulnerability to proteostasis disease in the absence of oxidative stress. Cell nonautonomous redox activation of the mitochondrial unfolded protein response (mitoUPR) proteostasis network requires UNC-49, a GABAA receptor that we show is activated by hydrogen peroxide. MitoUPR induction by a spinocerebellar ataxia type 3 (SCA3) C. elegans neurodegenerative disease model was similarly dependent on UNC-49 in C. elegans. These results demonstrate a multi-tissue paradigm for redox signaling in the GABAergic system that is transduced via a GABAA receptor to function in cell nonautonomous regulation of health, proteostasis, and disease.
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Affiliation(s)
- Franziska Pohl
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Allison L. Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Jack Mao
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Sydney Hou
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Bayode Bakare
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Paul Kong Thoo Lin
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Kyari Yates
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Michael L. Nonet
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Kerry Kornfeld
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Jason M. Held
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, USA
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4
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Falfushynska H, Sokolova IM. Intermittent hypoxia differentially affects metabolic and oxidative stress responses in two species of cyprinid fish. Biol Open 2023; 12:bio060069. [PMID: 37670684 PMCID: PMC10537972 DOI: 10.1242/bio.060069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 08/24/2023] [Indexed: 09/07/2023] Open
Abstract
Oxygen fluctuations are common in freshwater habitats and aquaculture and can impact ecologically and economically important species of fish like cyprinids. To gain insight into the physiological responses to oxygen fluctuations in two common cyprinid species, we evaluated the impact of short-term intermittent hypoxia on oxidative stress and metabolic parameters (including levels of prooxidants and oxidative lesions, antioxidants, mitochondrial enzyme activities, mitochondrial swelling, markers of apoptosis, autophagy and cytotoxicity) in silver carp Hypophthalmichthys molitrix and gibel carp Carassius gibelio. During hypoxia, gibel carp showed higher baseline levels of antioxidants and less pronounced changes in oxidative and metabolic biomarkers in the tissues than silver carp. Reoxygenation led to a strong shift in metabolic and redox-related parameters and tissue damage, indicating high cost of post-hypoxic recovery in both species. Species-specific differences were more strongly associated with oxidative stress status, whereas metabolic indices and nitrosative stress parameters were more relevant to the response to hypoxia-reoxygenation. Overall, regulation of energy metabolism appears more critical than the regulation of antioxidants in the response to oxygen deprivation in the studied species. Further research is needed to establish whether prioritizing metabolic over redox regulation during hypoxia-reoxygenation stress is common in freshwater cyprinids.
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Affiliation(s)
- Halina Falfushynska
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock 18059, Germany
- Department of Electrical, Mechanical and Industrial Engineering, Anhalt University for Applied Sciences, Köthen 06366, Germany
| | - Inna M. Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock 18059, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock 18059, Germany
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5
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Cheng H, Perkins GA, Ju S, Kim K, Ellisman MH, Pamenter ME. Enhanced mitochondrial buffering prevents Ca 2+ overload in naked mole-rat brain. J Physiol 2023:10.1113/JP285002. [PMID: 37668020 PMCID: PMC10912373 DOI: 10.1113/jp285002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/16/2023] [Indexed: 09/06/2023] Open
Abstract
Deleterious Ca2+ accumulation is central to hypoxic cell death in the brain of most mammals. Conversely, hypoxia-mediated increases in cytosolic Ca2+ are retarded in hypoxia-tolerant naked mole-rat brain. We hypothesized that naked mole-rat brain mitochondria have an enhanced capacity to buffer exogenous Ca2+ and examined Ca2+ handling in naked mole-rat cortical tissue. We report that naked mole-rat brain mitochondria buffer >2-fold more exogenous Ca2+ than mouse brain mitochondria, and that the half-maximal inhibitory concentration (IC50 ) at which Ca2+ inhibits aerobic oxidative phosphorylation is >2-fold higher in naked mole-rat brain. The primary driving force of Ca2+ uptake is the mitochondrial membrane potential (Δψm ), and the IC50 at which Ca2+ decreases Δψm is ∼4-fold higher in naked mole-rat than mouse brain. The ability of naked mole-rat brain mitochondria to safely retain large volumes of Ca2+ may be due to ultrastructural differences that support the uptake and physical storage of Ca2+ in mitochondria. Specifically, and relative to mouse brain, naked mole-rat brain mitochondria are larger and have higher crista density and increased physical interactions between adjacent mitochondrial membranes, all of which are associated with improved energetic homeostasis and Ca2+ management. We propose that excessive Ca2+ influx into naked mole-rat brain is buffered by physical storage in large mitochondria, which would reduce deleterious Ca2+ overload and may thus contribute to the hypoxia and ischaemia-tolerance of naked mole-rat brain. KEY POINTS: Unregulated Ca2+ influx is a hallmark of hypoxic brain death; however, hypoxia-mediated Ca2+ influx into naked mole-rat brain is markedly reduced relative to mice. This is important because naked mole-rat brain is robustly tolerant against in vitro hypoxia, and because Ca2+ is a key driver of hypoxic cell death in brain. We show that in hypoxic naked mole-rat brain, oxidative capacity and mitochondrial membrane integrity are better preserved following exogenous Ca2+ stress. This is due to mitochondrial buffering of exogenous Ca2+ and is driven by a mitochondrial membrane potential-dependant mechanism. The unique ultrastructure of naked mole-rat brain mitochondria, as a large physical storage space, may support increased Ca2+ buffering and thus hypoxia-tolerance.
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Affiliation(s)
- Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Guy A Perkins
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, CA, USA
| | - Saeyeon Ju
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, CA, USA
| | - Keunyoung Kim
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, CA, USA
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, CA, USA
- Department of Neurosciences, University of California at San Diego School of Medicine, San Diego, CA, USA
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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Harford AR, Devaux JBL, Hickey AJR. Dynamic defence? Intertidal triplefin species show better maintenance of mitochondrial membrane potential than subtidal species at low oxygen pressures. J Exp Biol 2023; 226:jeb245926. [PMID: 37498237 DOI: 10.1242/jeb.245926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 07/14/2023] [Indexed: 07/28/2023]
Abstract
Oxygen is essential for most eukaryotic lifeforms, as it supports mitochondrial oxidative phosphorylation to supply ∼90% of cellular adenosine triphosphate (ATP). Fluctuations in O2 present a major stressor, with hypoxia leading to a cascade of detrimental physiological changes that alter cell operations and ultimately induce death. Nonetheless, some species episodically tolerate near-anoxic environments, and have evolved mechanisms to sustain function even during extended hypoxic periods. While mitochondria are pivotal in central metabolism, their role in hypoxia tolerance remains ill defined. Given the vulnerability of the brain to hypoxia, mitochondrial function was tested in brain homogenates of three closely related triplefin species with varying degrees of hypoxia tolerance (Bellapiscis medius, Forsterygion lapillum and Forsterygion varium). High-resolution respirometry coupled with fluorometric measurements of mitochondrial membrane potential (mtMP) permitted assessment of differences in mitochondrial function and integrity in response to intermittent hypoxia and anoxia. Traditional steady-state measures of respiratory flux and mtMP showed no differences among species. However, in the transition into anoxia, the tolerant species B. medius and F. lapillum maintained mtMP at O2 pressures 7- and 4.4-fold lower, respectively, than that of the hypoxia-sensitive F. varium and exhibited slower rates of membrane depolarisation. The results indicate that dynamic oxic-hypoxic mitochondria transitions underlie hypoxia tolerance in these intertidal fish.
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Affiliation(s)
- Alice R Harford
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
| | - Jules B L Devaux
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
| | - Anthony J R Hickey
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
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7
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Steffen JBM, Sokolov EP, Bock C, Sokolova IM. Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas. J Exp Biol 2023; 226:jeb246164. [PMID: 37470191 PMCID: PMC10445735 DOI: 10.1242/jeb.246164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 07/12/2023] [Indexed: 07/21/2023]
Abstract
Coastal environments commonly experience fluctuations in salinity and hypoxia-reoxygenation (H/R) stress that can negatively affect mitochondrial functions of marine organisms. Although intertidal bivalves are adapted to these conditions, the mechanisms that sustain mitochondrial integrity and function are not well understood. We determined the rates of respiration and reactive oxygen species (ROS) efflux in the mitochondria of oysters, Crassostrea gigas, acclimated to high (33 psu) or low (15 psu) salinity, and exposed to either normoxic conditions (control; 21% O2) or short-term hypoxia (24 h at <0.01% O2) and subsequent reoxygenation (1.5 h at 21% O2). Further, we exposed isolated mitochondria to anoxia in vitro to assess their ability to recover from acute (∼10 min) oxygen deficiency (<0.01% O2). Our results showed that mitochondria of oysters acclimated to high or low salinity did not show severe damage and dysfunction during H/R stress, consistent with the hypoxia tolerance of C. gigas. However, acclimation to low salinity led to improved mitochondrial performance and plasticity, indicating that 15 psu might be closer to the metabolic optimum of C. gigas than 33 psu. Thus, acclimation to low salinity increased mitochondrial oxidative phosphorylation rate and coupling efficiency and stimulated mitochondrial respiration after acute H/R stress. However, elevated ROS efflux in the mitochondria of low-salinity-acclimated oysters after acute H/R stress indicates a possible trade-off of higher respiration. The high plasticity and stress tolerance of C. gigas mitochondria may contribute to the success of this invasive species and facilitate its further expansion into brackish regions such as the Baltic Sea.
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Affiliation(s)
- Jennifer B. M. Steffen
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18059 Rostock, Germany
| | - Eugene P. Sokolov
- Leibniz Institute for Baltic Research, Leibniz Science Campus Phosphorus Research Rostock, 18119 Warnemünde, Germany
| | - Christian Bock
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
| | - Inna M. Sokolova
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18059 Rostock, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, 18059 Rostock, Germany
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8
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Ackerly KL, Negrete B, Dichiera AM, Esbaugh AJ. Hypoxia acclimation improves mitochondrial efficiency in the aerobic swimming muscle of red drum (Sciaenops ocellatus). Comp Biochem Physiol A Mol Integr Physiol 2023; 282:111443. [PMID: 37201653 DOI: 10.1016/j.cbpa.2023.111443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 05/11/2023] [Accepted: 05/13/2023] [Indexed: 05/20/2023]
Abstract
Environmental hypoxia (low dissolved oxygen) is a significant threat facing fishes. As fishes require oxygen to efficiently produce ATP, hypoxia can significantly limit aerobic capacity. However, some fishes show respiratory flexibility that rescues aerobic performance, including plasticity in mitochondrial performance. This plasticity may result in increased mitochondrial efficiency (e.g., less proton leak), increased oxygen storage capacity (increased myoglobin), and oxidative capacity (e.g., higher citrate synthase activity) under hypoxia. We acclimated a hypoxia-tolerant fish, red drum (Sciaenops ocellatus), to 8-days of constant hypoxia to induce a hypoxic phenotype. Fish were terminally sampled for cardiac and red muscle tissue to quantify oxidative phosphorylation, proton leak, and maximum respiration in tissue from both hypoxia-acclimated and control fish. Tissue was also collected to assess the plasticity of citrate synthase enzyme activity and mRNA expression for select oxygen storage and antioxidant pathway transcripts. We found that mitochondrial respiration rates were not affected by hypoxia exposure in cardiac tissue, though citrate synthase activity and myoglobin expression were higher following hypoxia acclimation. Interestingly, measures of mitochondrial efficiency in red muscle significantly improved in hypoxia-acclimated individuals. Hypoxia-acclimated fish had significantly higher OXPHOS Control Efficiency, OXPHOS Capacity and Coupling Control Ratios (i.e., LEAK/OXPHOS). There was no significant change to citrate synthase activity or myoglobin expression in red muscle. Overall, these results suggest that red muscle mitochondria of hypoxia-acclimated fish more efficiently utilize oxygen, which may explain previous reports in red drum of improved aerobic swimming performance in the absence of improved maximum metabolic rate following hypoxia acclimation.
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Affiliation(s)
- Kerri Lynn Ackerly
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA.
| | - Benjamin Negrete
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA
| | - Angelina M Dichiera
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Andrew J Esbaugh
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA
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Li J, Yang Z, Yan J, Zhang K, Ning X, Wang T, Ji J, Zhang G, Yin S, Zhao C. Multi-omics analysis revealed the brain dysfunction induced by energy metabolism in Pelteobagrus vachelli under hypoxia stress. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 254:114749. [PMID: 36907096 DOI: 10.1016/j.ecoenv.2023.114749] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/21/2023] [Accepted: 03/06/2023] [Indexed: 06/18/2023]
Abstract
Hypoxia in water environment has become increasingly frequent and serious due to global warming and environmental pollution. Revealing the molecular mechanism of fish hypoxia adaptation will help to develop markers of environmental pollution caused by hypoxia. Here, we used a multi-omics method to identify the hypoxia-associated mRNA, miRNA, protein, and metabolite involved in various biological processes in Pelteobagrus vachelli brain. The results showed that hypoxia stress caused brain dysfunction by inhibiting energy metabolism. Specifically, the biological processes involved in energy synthesis and energy consumption are inhibited in P. vachelli brain under hypoxia, such as oxidative phosphorylation, carbohydrate metabolism and protein metabolism. Brain dysfunction is mainly manifested as blood-brain barrier injury accompanied by neurodegenerative diseases and autoimmune diseases. In addition, compared with previous studies, we found that P. vachelli has tissue specificity in response to hypoxia stress and the muscle suffers more damage than the brain. This is the first report to the integrated analysis of the transcriptome, miRNAome, proteome, and metabolome in fish brain. Our findings could provide insights into the molecular mechanisms of hypoxia, and the approach could also be applied to other fish species. DATA AVAILABILITY: The raw data of transcriptome has been uploaded to NCBI database (ID: SUB7714154 and SUB7765255). The raw data of proteome has been uploaded to ProteomeXchange database (PXD020425). The raw data of metabolome has been uploaded to Metabolight (ID: MTBLS1888).
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Affiliation(s)
- Jie Li
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Zhiru Yang
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China
| | - Jie Yan
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Kai Zhang
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Xianhui Ning
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Tao Wang
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Jie Ji
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China
| | - Guosong Zhang
- Key Laboratory for Physiology Biochemistry and Application, Heze University, Heze 274015, China
| | - Shaowu Yin
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China.
| | - Cheng Zhao
- College of Marine Science and Engineering, College of Life Science, Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology, Nanjing Normal University, Nanjing, Jiangsu 210023, China; Co-Innovation Center for Marine Bio-Industry Technology, Lian Yungang 222005, China.
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10
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Marks de Chabris NC, Sabir S, Perkins G, Cheng H, Ellisman MH, Pamenter ME. Short communication: Acute hypoxia does not alter mitochondrial abundance in naked mole-rats. Comp Biochem Physiol A Mol Integr Physiol 2023; 276:111343. [PMID: 36379380 DOI: 10.1016/j.cbpa.2022.111343] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 10/20/2022] [Accepted: 11/08/2022] [Indexed: 11/15/2022]
Abstract
Hypoxia poses a significant energetic challenge and most species exhibit metabolic remodelling when exposed to prolonged hypoxia. One component of this remodelling is mitochondrial biogenesis/mitophagy, which alter mitochondrial abundance and helps to adjust metabolic throughput to match changes in energy demands in hypoxia. However, how acute hypoxia impacts mitochondrial abundance in hypoxia-tolerant species is poorly understood. To help address this gap, we exposed hypoxia-tolerant naked mole-rats to 3 h of normoxia or acute hypoxia (5% O2) and measured changes in mitochondrial abundance using two well-established markers: citrate synthase (CS) enzyme activity and mitochondrial DNA (mtDNA) abundance. We found that neither marker changed with hypoxia in brain, liver, or kidney, suggesting that mitochondrial biogenesis is not initiated during acute hypoxia in these tissues. Conversely in skeletal muscle, the ratio of CS activity to total protein decreased 50% with hypoxia. However, this change was likely driven by an increase in soluble protein density in hypoxia because CS activity was unchanged relative to wet tissue weight and the mtDNA copy number was unchanged. To confirm this, we examined skeletal muscle mitochondria using transmission electron microscopy and found no change in mitochondrial volume density. Taken together with previous studies of mitochondrial respiratory function, our present findings suggest that naked mole-rats primarily rely on tissue-specific functional remodelling of metabolic pathways and mitochondrial respiratory throughput, and not physical changes in mitochondrial number or volume, to adjust to short-term hypoxic exposure.
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Affiliation(s)
| | - Soulene Sabir
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Guy Perkins
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Marc H Ellisman
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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11
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Cerra MC, Filice M, Caferro A, Mazza R, Gattuso A, Imbrogno S. Cardiac Hypoxia Tolerance in Fish: From Functional Responses to Cell Signals. Int J Mol Sci 2023; 24:ijms24021460. [PMID: 36674975 PMCID: PMC9866870 DOI: 10.3390/ijms24021460] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 01/14/2023] Open
Abstract
Aquatic animals are increasingly challenged by O2 fluctuations as a result of global warming, as well as eutrophication processes. Teleost fish show important species-specific adaptability to O2 deprivation, moving from intolerance to a full tolerance of hypoxia and even anoxia. An example is provided by members of Cyprinidae which includes species that are amongst the most tolerant hypoxia/anoxia teleosts. Living at low water O2 requires the mandatory preservation of the cardiac function to support the metabolic and hemodynamic requirements of organ and tissues which sustain whole organism performance. A number of orchestrated events, from metabolism to behavior, converge to shape the heart response to the restricted availability of the gas, also limiting the potential damages for cells and tissues. In cyprinids, the heart is extraordinarily able to activate peculiar strategies of functional preservation. Accordingly, by using these teleosts as models of tolerance to low O2, we will synthesize and discuss literature data to describe the functional changes, and the major molecular events that allow the heart of these fish to sustain adaptability to O2 deprivation. By crossing the boundaries of basic research and environmental physiology, this information may be of interest also in a translational perspective, and in the context of conservative physiology, in which the output of the research is applicable to environmental management and decision making.
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12
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Eaton L, Pamenter ME. What to do with low O 2: Redox adaptations in vertebrates native to hypoxic environments. Comp Biochem Physiol A Mol Integr Physiol 2022; 271:111259. [PMID: 35724954 DOI: 10.1016/j.cbpa.2022.111259] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 06/11/2022] [Accepted: 06/14/2022] [Indexed: 01/05/2023]
Abstract
Reactive oxygen species (ROS) are important cellular signalling molecules but sudden changes in redox balance can be deleterious to cells and lethal to the whole organism. ROS production is inherently linked to environmental oxygen availability and many species live in variable oxygen environments that can range in both severity and duration of hypoxic exposure. Given the importance of redox homeostasis to cell and animal viability, it is not surprising that early studies in species adapted to various hypoxic niches have revealed diverse strategies to limit or mitigate deleterious ROS changes. Although research in this area is in its infancy, patterns are beginning to emerge in the suites of adaptations to different hypoxic environments. This review focuses on redox adaptations (i.e., modifications of ROS production and scavenging, and mitigation of oxidative damage) in hypoxia-tolerant vertebrates across a range of hypoxic environments. In general, evidence suggests that animals adapted to chronic lifelong hypoxia are in homeostasis, and do not encounter major oxidative challenges in their homeostatic environment, whereas animals exposed to seasonal chronic anoxia or hypoxia rapidly downregulate redox balance to match a hypometabolic state and employ robust scavenging pathways during seasonal reoxygenation. Conversely, animals adapted to intermittent hypoxia exposure face the greatest degree of ROS imbalance and likely exhibit enhanced ROS-mitigation strategies. Although some progress has been made, research in this field is patchy and further elucidation of mechanisms that are protective against environmental redox challenges is imperative for a more holistic understanding of how animals survive hypoxic environments.
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Affiliation(s)
- Liam Eaton
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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13
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Hawrysh PJ, Myrka AM, Buck LT. Review: A history and perspective of mitochondria in the context of anoxia tolerance. Comp Biochem Physiol B Biochem Mol Biol 2022; 260:110733. [PMID: 35288242 DOI: 10.1016/j.cbpb.2022.110733] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/07/2022] [Accepted: 03/07/2022] [Indexed: 01/01/2023]
Abstract
Symbiosis is found throughout nature, but perhaps nowhere is it more fundamental than mitochondria in all eukaryotes. Since mitochondria were discovered and mechanisms of oxygen reduction characterized, an understanding gradually emerged that these organelles were involved not just in the combustion of oxygen, but also in the sensing of oxygen. While multiple hypotheses exist to explain the mitochondrial involvement in oxygen sensing, key elements are developing that include potassium channels and reactive oxygen species. To understand how mitochondria contribute to oxygen sensing, it is informative to study a model system which is naturally adapted to survive extended periods without oxygen. Amongst air-breathing vertebrates, the most highly adapted are western painted turtles (Chrysemys picta bellii), which overwinter in ice-covered and anoxic water bodies. Through research of this animal, it was postulated that metabolic rate depression is key to anoxic survival and that mitochondrial regulation is a key aspect. When faced with anoxia, excitatory neurotransmitter receptors in turtle brain are inhibited through mitochondrial calcium release, termed "channel arrest". Simultaneously, inhibitory GABAergic signalling contributes to the "synaptic arrest" of excitatory action potential firing through a pathway dependent on mitochondrial depression of ROS generation. While many pathways are implicated in mitochondrial oxygen sensing in turtles, such as those of adenosine, ATP turnover, and gaseous transmitters, an apparent point of intersection is the mitochondria. In this review we will explore how an organelle that was critical for organismal complexity in an oxygenated world has also become a potentially important oxygen sensor.
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Affiliation(s)
- Peter John Hawrysh
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Alexander Morley Myrka
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Leslie Thomas Buck
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.
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14
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Acute pH alterations do not impact cardiac mitochondrial respiration in naked mole-rats or mice. Comp Biochem Physiol A Mol Integr Physiol 2022; 268:111185. [PMID: 35278722 DOI: 10.1016/j.cbpa.2022.111185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/06/2022] [Accepted: 03/06/2022] [Indexed: 01/04/2023]
Abstract
Energetically demanding conditions such as hypoxia and exercise favour anaerobic metabolism (glycolysis), which leads to acidification of the cellular milieu from ATP hydrolysis and accumulation of the anaerobic end-product, lactate. Cellular acidification may damage mitochondrial proteins and/or alter the H+ gradient across the mitochondrial inner membrane, which may in turn impact mitochondrial respiration and thus aerobic ATP production. Naked mole-rats are among the most hypoxia-tolerant mammals, and putatively experience intermittent environmental and systemic hypoxia while resting and exercising in their underground burrows. Previous studies in naked mole-rat brain, heart, and skeletal muscle mitochondria have demonstrated adaptations that favour improved efficiency in hypoxic conditions; however, the impact of cellular acidification on mitochondrial function has not been explored. We hypothesized that, relative to hypoxia-intolerant mice, naked mole-rat cardiac mitochondrial respiration is less sensitive to cellular pH changes. To test this, we used high-resolution respirometry to measure mitochondrial respiration by permeabilized cardiac muscle fibres from naked mole-rats and mice exposed in vitro to a pH range from 6.6 to 7.6. Surprisingly, we found that acute pH changes do not impact cardiac mitochondrial respiration or compromise mitochondrial integrity in either species. Our results suggest that acute alterations of cellular pH have minimal impact on cardiac mitochondrial respiration.
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15
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Epigenetic and post-transcriptional repression support metabolic suppression in chronically hypoxic goldfish. Sci Rep 2022; 12:5576. [PMID: 35368037 PMCID: PMC8976842 DOI: 10.1038/s41598-022-09374-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 03/21/2022] [Indexed: 12/03/2022] Open
Abstract
Goldfish enter a hypometabolic state to survive chronic hypoxia. We recently described tissue-specific contributions of membrane lipid composition remodeling and mitochondrial function to metabolic suppression across different goldfish tissues. However, the molecular and especially epigenetic foundations of hypoxia tolerance in goldfish under metabolic suppression are not well understood. Here we show that components of the molecular oxygen-sensing machinery are robustly activated across tissues irrespective of hypoxia duration. Induction of gene expression of enzymes involved in DNA methylation turnover and microRNA biogenesis suggest a role for epigenetic transcriptional and post-transcriptional suppression of gene expression in the hypoxia-acclimated brain. Conversely, mechanistic target of rapamycin-dependent translational machinery activity is not reduced in liver and white muscle, suggesting this pathway does not contribute to lowering cellular energy expenditure. Finally, molecular evidence supports previously reported chronic hypoxia-dependent changes in membrane cholesterol, lipid metabolism and mitochondrial function via changes in transcripts involved in cholesterol biosynthesis, β-oxidation, and mitochondrial fusion in multiple tissues. Overall, this study shows that chronic hypoxia robustly induces expression of oxygen-sensing machinery across tissues, induces repressive transcriptional and post-transcriptional epigenetic marks especially in the chronic hypoxia-acclimated brain and supports a role for membrane remodeling and mitochondrial function and dynamics in promoting metabolic suppression.
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Sandra I, Verri T, Filice M, Barca A, Schiavone R, Gattuso A, Cerra MC. Shaping the cardiac response to hypoxia: NO and its partners in teleost fish. Curr Res Physiol 2022; 5:193-202. [PMID: 35434651 PMCID: PMC9010694 DOI: 10.1016/j.crphys.2022.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 03/14/2022] [Accepted: 03/31/2022] [Indexed: 12/12/2022] Open
Abstract
The reduced availability of dissolved oxygen is a common stressor in aquatic habitats that affects the ability of the heart to ensure tissue oxygen supply. Among key signalling molecules activated during cardiac hypoxic stress, nitric oxide (NO) has emerged as a central player involved in the related adaptive responses. Here, we outline the role of the nitrergic control in modulating tolerance and adaptation of teleost heart to hypoxia, as well as major molecular players that participate in the complex NO network. The purpose is to provide a framework in which to depict how the heart deals with limitations in oxygen supply. In this perspective, defining the relational interplay between the multiple (sets of) proteins that, due to the gene duplication events that occurred during the teleost fish evolutive radiation, do operate in parallel with similar functions in the (different) heart (districts) and other body districts under low levels of oxygen supply, represents a next goal of the comparative research in teleost fish cardiac physiology. The flexibility of the teleost heart to O2 limitations is illustrated by using cyprinids as hypoxia tolerance models. Major molecular mediators of the teleost cardiac response are discussed with a focus on the nitrergic system. A comparative analysis of gene duplication highlights conserved targets which may orchestrate the cardiac response to hypoxia.
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17
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Abstract
ABSTRACT
Hypoxia is one of the strongest environmental drivers of cellular and physiological adaptation. Although most mammals are largely intolerant of hypoxia, some specialized species have evolved mitigative strategies to tolerate hypoxic niches. Among the most hypoxia-tolerant mammals are naked mole-rats (Heterocephalus glaber), a eusocial species of subterranean rodent native to eastern Africa. In hypoxia, naked mole-rats maintain consciousness and remain active despite a robust and rapid suppression of metabolic rate, which is mediated by numerous behavioural, physiological and cellular strategies. Conversely, hypoxia-intolerant mammals and most other hypoxia-tolerant mammals cannot achieve the same degree of metabolic savings while staying active in hypoxia and must also increase oxygen supply to tissues, and/or enter torpor. Intriguingly, recent studies suggest that naked mole-rats share many cellular strategies with non-mammalian vertebrate champions of anoxia tolerance, including the use of alternative metabolic end-products and potent pH buffering mechanisms to mitigate cellular acidification due to upregulation of anaerobic metabolic pathways, rapid mitochondrial remodelling to favour increased respiratory efficiency, and systemic shifts in energy prioritization to maintain brain function over that of other tissues. Herein, I discuss what is known regarding adaptations of naked mole-rats to a hypoxic lifestyle, and contrast strategies employed by this species to those of hypoxia-intolerant mammals, closely related African mole-rats, other well-studied hypoxia-tolerant mammals, and non-mammalian vertebrate champions of anoxia tolerance. I also discuss the neotenic theory of hypoxia tolerance – a leading theory that may explain the evolutionary origins of hypoxia tolerance in mammals – and highlight promising but underexplored avenues of hypoxia-related research in this fascinating model organism.
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Affiliation(s)
- Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7. University of Ottawa, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
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18
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Adzigbli L, Sokolov EP, Ponsuksili S, Sokolova IM. Tissue- and substrate-dependent mitochondrial responses to acute hypoxia-reoxygenation stress in a marine bivalve Crassostrea gigas (Thunberg, 1793). J Exp Biol 2021; 225:273950. [PMID: 34904172 DOI: 10.1242/jeb.243304] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 12/07/2021] [Indexed: 11/20/2022]
Abstract
Hypoxia is a major stressor for aquatic organisms, yet intertidal organisms like the oyster Crassostrea gigas are adapted to frequent oxygen fluctuations by metabolically adjusting to shifts in oxygen and substrate availability during hypoxia-reoxygenation (H/R). We investigated the effects of acute H/R stress (15 min at ∼0% O2, and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of C. gigas respiring on different substrates (pyruvate, glutamate, succinate, palmitate and their mixtures). Gill mitochondria showed better capacity for amino acid and fatty acid oxidation compared to the mitochondria from the digestive gland. Mitochondrial responses to H/R stress strongly depended on the substrate and the activity state of mitochondria. In mitochondria oxidizing NADH-linked substrates exposure to H/R stress suppressed oxygen consumption and ROS generation in the resting state, whereas in the ADP-stimulated state, ROS production increased despite little change in respiration. As a result, electron leak (measured as H2O2 to O2 ratio) increased after H/R stress in the ADP-stimulated mitochondria with NADH-linked substrates. In contrast, H/R exposure stimulated succinate-driven respiration without an increase in electron leak. Reverse electron transport (RET) did not significantly contribute to succinate-driven ROS production in oyster mitochondria except for a slight increase in the OXPHOS state during post-hypoxic recovery. A decrease in NADH-driven respiration and ROS production, enhanced capacity for succinate oxidation and resistance to RET might assist in post-hypoxic recovery of oysters mitigating oxidative stress and supporting rapid ATP re-synthesis during oxygen fluctuations such as commonly observed in estuaries and intertidal zones.
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Affiliation(s)
- Linda Adzigbli
- Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Dummerstorf, Germany.,Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany
| | - Eugene P Sokolov
- Leibniz Institute for Baltic Sea Research, Leibniz Science Campus Phosphorus Research, Warnemünde, Rostock, Germany
| | - Siriluck Ponsuksili
- Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Dummerstorf, Germany
| | - Inna M Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany.,Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
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19
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Thoral E, Farhat E, Roussel D, Cheng H, Guillard L, Pamenter ME, Weber JM, Teulier L. Different patterns of chronic hypoxia lead to hierarchical adaptative mechanisms in goldfish metabolism. J Exp Biol 2021; 225:273673. [PMID: 34881781 DOI: 10.1242/jeb.243194] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 12/02/2021] [Indexed: 11/20/2022]
Abstract
Some hypoxia-tolerant species, such as goldfish, experience intermittent and severe hypoxia in their natural habitat causing them to develop multiple physiological adaptations. However, in fish, the metabolic impact of regular hypoxic exposure on swimming performance in normoxia is less well understood. Therefore, we experimentally tested whether chronic exposure to constant (30 days at 10% air saturation) or intermittent hypoxia (3hrs in normoxia and 21hrs in hypoxia, 5 days a week) would result in similar metabolic and swimming performance benefits after reoxygenation. Moreover, half of the normoxic and intermittent hypoxic fish were put on a 20-day normoxic training regime. After these treatments, metabolic rate (standard and maximum metabolic rates: SMR and MMR) and swimming performance (critical swimming speed [Ucrit] and cost of transport [COT]) were assessed. In addition, enzyme activities (citrate synthase CS, cytochrome c oxidase COX and lactate dehydrogenase LDH) and mitochondrial respiration were examined in red muscle fibres. We found that acclimation to constant hypoxia resulted in (1) metabolic suppression (-45% SMR, and -27% MMR), (2) increased anaerobic capacity (+117% LDH), (3) improved swimming performance (+80% Ucrit, -71% COT) and (4) no changes at the mitochondrial level. Conversely, the enhancement of swimming performance was reduced following acclimation to intermittent hypoxia (+45% Ucrit, -41% COT), with a 55% decrease in aerobic scope, despite a significant increase in oxidative metabolism (+201% COX, +49% CS). This study demonstrates that constant hypoxia leads to the greatest benefit in swimming performance and that mitochondrial metabolic adjustments only provide minor help in coping with hypoxia.
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Affiliation(s)
- Elisa Thoral
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Elie Farhat
- Biology Department, University of Ottawa, Ottawa, ON, Canada
| | - Damien Roussel
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Hang Cheng
- Biology Department, University of Ottawa, Ottawa, ON, Canada
| | - Ludovic Guillard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Matthew E Pamenter
- Biology Department, University of Ottawa, Ottawa, ON, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
| | | | - Loïc Teulier
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
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20
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Isei MO, Chinnappareddy N, Stevens D, Kamunde C. Anoxia-reoxygenation alters H 2O 2 efflux and sensitivity of redox centers to copper in heart mitochondria. Comp Biochem Physiol C Toxicol Pharmacol 2021; 248:109111. [PMID: 34146700 DOI: 10.1016/j.cbpc.2021.109111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 06/07/2021] [Accepted: 06/09/2021] [Indexed: 11/20/2022]
Abstract
Mitochondrial reactive oxygen species (ROS) have been implicated in organ damage caused by environmental stressors, prompting studies on the effect of oxygen deprivation and metal exposure on ROS metabolism. However, how anoxia and copper (Cu) jointly influence heart mitochondrial ROS metabolism is not understood. We used rainbow trout heart mitochondria to probe the effects of anoxia-reoxygenation and Cu on hydrogen peroxide (H2O2) emission during oxidation of palmitoylcarnitine (PC), succinate, or glutamate-malate. In addition, we examined the influence of anoxia-reoxygenation and Cu on site-specific H2O2 emission capacities and key antioxidant enzymes, glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). Results showed that anoxia-reoxygenation suppressed H2O2 emission regardless of substrate type or duration of anoxia. Anoxia-reoxygenation reduced mitochondrial sensitivity to Cu during oxidation of succinate or glutamate-malate whereas high Cu concentration additively stimulated H2O2 emission in mitochondria oxidizing PC. Prolonged anoxia-reoxygenation stimulated H2O2 emission from sites OF and IF, inhibited emission from sites IQ, IIF and IIIQo, and disparately altered the sensitivity of the sites to Cu. Interestingly, anoxia-reoxygenation increased GPx and TrxR activities, more prominently when reoxygenation followed a short duration of anoxia. Cu did not alter GPx but reduced TrxR activity in normoxic and anoxic-reoxygenated mitochondria. Overall, our study revealed potential mechanisms that may reduce oxidative damage associated with anoxia-reoxygenation and Cu exposure in heart mitochondria. The increased and decreased H2O2 emission from NADH/NAD+ and QH2/Q isopotential sites, respectively, may represent a balance between H2O2 required for oxygen deprivation-induced signaling and prevention of ROS burst associated with anoxia-reoxygenation.
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Affiliation(s)
- Michael O Isei
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown C1A 4P3, PE, Canada
| | - Nirmala Chinnappareddy
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown C1A 4P3, PE, Canada
| | - Don Stevens
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown C1A 4P3, PE, Canada
| | - Collins Kamunde
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown C1A 4P3, PE, Canada.
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21
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Country MW, Jonz MG. Mitochondrial KATP channels stabilize intracellular Ca2+ during hypoxia in retinal horizontal cells of goldfish (Carassius auratus). J Exp Biol 2021; 224:271844. [PMID: 34402511 DOI: 10.1242/jeb.242634] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 08/11/2021] [Indexed: 01/20/2023]
Abstract
Neurons of the retina require oxygen to survive. In hypoxia, neuronal ATP production is impaired, ATP-dependent ion pumping is reduced, transmembrane ion gradients are dysregulated, and intracellular Ca2+ concentration ([Ca2+]i) increases enough to trigger excitotoxic cell death. Central neurons of the common goldfish (Carassius auratus) are hypoxia tolerant, but little is known about how goldfish retinas withstand hypoxia. To study the cellular mechanisms of hypoxia tolerance, we isolated retinal interneurons (horizontal cells; HCs), and measured [Ca2+]i with Fura-2. Goldfish HCs maintained [Ca2+]i throughout 1 h of hypoxia, whereas [Ca2+]i increased irreversibly in HCs of the hypoxia-sensitive rainbow trout (Oncorhynchus mykiss) with just 20 min of hypoxia. Our results suggest mitochondrial ATP-dependent K+ channels (mKATP) are necessary to stabilize [Ca2+]i throughout hypoxia. In goldfish HCs, [Ca2+]i increased when mKATP channels were blocked with glibenclamide or 5-hydroxydecanoic acid, whereas the mKATP channel agonist diazoxide prevented [Ca2+]i from increasing in hypoxia in trout HCs. We found that hypoxia protects against increases in [Ca2+]i in goldfish HCs via mKATP channels. Glycolytic inhibition with 2-deoxyglucose increased [Ca2+]i, which was rescued by hypoxia in a mKATP channel-dependent manner. We found no evidence of plasmalemmal KATP channels in patch-clamp experiments. Instead, we confirmed the involvement of KATP in mitochondria with TMRE imaging, as hypoxia rapidly (<5 min) depolarized mitochondria in a mKATP channel-sensitive manner. We conclude that mKATP channels initiate a neuroprotective pathway in goldfish HCs to maintain [Ca2+]i and avoid excitotoxicity in hypoxia. This model provides novel insight into the cellular mechanisms of hypoxia tolerance in the retina.
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Affiliation(s)
- Michael W Country
- Department of Biology, University of Ottawa, Ottawa, ON, CanadaK1N 6N5
| | - Michael G Jonz
- Department of Biology, University of Ottawa, Ottawa, ON, CanadaK1N 6N5.,Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, CanadaK1H 8M5
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22
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Cheng H, Pamenter ME. Naked mole-rat brain mitochondria tolerate in vitro ischaemia. J Physiol 2021; 599:4671-4685. [PMID: 34472099 DOI: 10.1113/jp281942] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/31/2021] [Indexed: 11/08/2022] Open
Abstract
Naked mole-rats (NMRs; Heterocephalus glaber) are among the most hypoxia-tolerant mammals. There is evidence that the NMR brain tolerates in vitro hypoxia and NMR brain mitochondria exhibit functional plasticity following in vivo hypoxia; however, if and how these organelles tolerate ischaemia and how ischaemic stress impacts mitochondrial energetics and redox regulation is entirely unknown. We hypothesized that mitochondria fundamentally contribute to in vitro ischaemia resistance in the NMR brain. To test this, we treated NMR and CD-1 mouse cortical brain sheets with an in vitro ischaemic mimic and evaluated mitochondrial respiration capacity and redox regulation following 15 or 30 min of ischaemia or ischaemia/reperfusion (I/R). We found that, relative to mice, the NMR brain largely retains mitochondrial function and redox balance post-ischaemia and I/R. Specifically: (i) ischaemia reduced complex I and II-linked respiration ∼50-70% in mice, vs. ∼20-40% in NMR brain, (ii) NMR but not mouse brain maintained relatively steady respiration control ratios and robust mitochondrial membrane integrity, (iii) electron leakage post-ischaemia was lesser in NMR than mouse brain and NMR brain retained higher coupling efficiency, and (iv) free radical generation during and following ischaemia and I/R was lower from NMR brains than mice. Taken together, our results indicate that NMR brain mitochondria are more tolerant of ischaemia and I/R than mice and retain respiratory capacity while avoiding redox derangements. Overall, these findings support the hypothesis that hypoxia-tolerant NMR brain is also ischaemia-tolerant and suggest that NMRs may be a natural model of ischaemia tolerance in which to investigate evolutionarily derived solutions to ischaemic pathology. KEY POINTS: Ischaemia is highly deleterious to the mammalian brain and this damage is largely mediated by mitochondrial dysfunction. Naked mole-rats are among the most hypoxia-tolerant mammals and their brain tolerates ischaemia ex vivo, but the impact of ischaemia on mitochondrial function is unknown. Naked mole-rat but not mouse brain mitochondria retain respiratory capacity and membrane integrity following ischaemia or ischaemia/reperfusion. Differences in free radical management and respiratory pathway control between species may mediate this tolerance. These results help us understand how natural models of hypoxia tolerance also tolerate ischaemia in the brain.
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Affiliation(s)
- Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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23
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Filice M, Imbrogno S, Gattuso A, Cerra MC. Hypoxic and Thermal Stress: Many Ways Leading to the NOS/NO System in the Fish Heart. Antioxidants (Basel) 2021; 10:1401. [PMID: 34573033 PMCID: PMC8471457 DOI: 10.3390/antiox10091401] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 12/22/2022] Open
Abstract
Teleost fish are often regarded with interest for the remarkable ability of several species to tolerate even dramatic stresses, either internal or external, as in the case of fluctuations in O2 availability and temperature regimes. These events are naturally experienced by many fish species under different time scales, but they are now exacerbated by growing environmental changes. This further challenges the intrinsic ability of animals to cope with stress. The heart is crucial for the stress response, since a proper modulation of the cardiac function allows blood perfusion to the whole organism, particularly to respiratory organs and the brain. In cardiac cells, key signalling pathways are activated for maintaining molecular equilibrium, thus improving stress tolerance. In fish, the nitric oxide synthase (NOS)/nitric oxide (NO) system is fundamental for modulating the basal cardiac performance and is involved in the control of many adaptive responses to stress, including those related to variations in O2 and thermal regimes. In this review, we aim to illustrate, by integrating the classic and novel literature, the current knowledge on the NOS/NO system as a crucial component of the cardiac molecular mechanisms that sustain stress tolerance and adaptation, thus providing some species, such as tolerant cyprinids, with a high resistance to stress.
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Affiliation(s)
| | - Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Arcavacata di Rende, Italy; (M.F.); (M.C.C.)
| | - Alfonsina Gattuso
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Arcavacata di Rende, Italy; (M.F.); (M.C.C.)
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24
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Farhat E, Weber JM. Hypometabolic Responses to Chronic Hypoxia: A Potential Role for Membrane Lipids. Metabolites 2021; 11:503. [PMID: 34436444 PMCID: PMC8399526 DOI: 10.3390/metabo11080503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 07/26/2021] [Accepted: 07/29/2021] [Indexed: 02/06/2023] Open
Abstract
Metabolic suppression is an essential strategy to cope with chronic hypoxia. This review examines the physiological processes used to survive in low oxygen environments. It proposes a novel mechanism-the remodeling of membrane lipids-to suppress ATP use and production. Temperature (homeoviscous adaptation), diet (natural doping in migrant birds) and body mass (membrane pacemaker of metabolism) have an impact on the lipid composition of membranes, which, in turn, modulates metabolic capacity. Vertebrate champions of hypoxia tolerance show extensive changes in membrane lipids upon in vivo exposure to low oxygen. These changes and those observed in hibernating mammals can promote the downregulation of ion pumps (major ATP consumers), ion channels, mitochondrial respiration capacity (state 3, proton leak, cytochrome c oxidase), and energy metabolism (β-oxidation and glycolysis). A common membrane signal regulating the joint inhibition of ion pumps and channels could be an exquisite way to preserve the balance between ATP supply and demand in hypometabolic states. Membrane remodeling together with more traditional mechanisms could work in concert to cause metabolic suppression.
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Affiliation(s)
| | - Jean-Michel Weber
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada;
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Farhat E, Cheng H, Romestaing C, Pamenter M, Weber JM. Goldfish Response to Chronic Hypoxia: Mitochondrial Respiration, Fuel Preference and Energy Metabolism. Metabolites 2021; 11:187. [PMID: 33809959 PMCID: PMC8004290 DOI: 10.3390/metabo11030187] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/10/2021] [Accepted: 03/17/2021] [Indexed: 12/16/2022] Open
Abstract
Hypometabolism is a hallmark strategy of hypoxia tolerance. To identify potential mechanisms of metabolic suppression, we have used the goldfish to quantify the effects of chronically low oxygen (4 weeks; 10% air saturation) on mitochondrial respiration capacity and fuel preference. The responses of key enzymes from glycolysis, β-oxidation and the tricarboxylic acid (TCA) cycle, and Na+/K+-ATPase were also monitored in various tissues of this champion of hypoxia tolerance. Results show that mitochondrial respiration of individual tissues depends on oxygen availability as well as metabolic fuel oxidized. All the respiration parameters measured in this study (LEAK, OXPHOS, Respiratory Control Ratio, CCCP-uncoupled, and COX) are affected by hypoxia, at least for one of the metabolic fuels. However, no common pattern of changes in respiration states is observed across tissues, except for the general downregulation of COX that may help metabolic suppression. Hypoxia causes the brain to switch from carbohydrates to lipids, with no clear fuel preference in other tissues. It also downregulates brain Na+/K+-ATPase (40%) and causes widespread tissue-specific effects on glycolysis and beta-oxidation. This study shows that hypoxia-acclimated goldfish mainly promote metabolic suppression by adjusting the glycolytic supply of pyruvate, reducing brain Na+/K+-ATPase, and downregulating COX, most likely decreasing mitochondrial density.
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Affiliation(s)
- Elie Farhat
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
| | - Hang Cheng
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
| | - Caroline Romestaing
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
- Univ Lyon, Université Claude Bernard Lyon1, CNRS, ENTPE, UMR 5023, LEHNA, F 69622 Villeurbanne, France
| | - Matthew Pamenter
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
- Faculty of Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jean-Michel Weber
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
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Cheng H, Munro D, Huynh K, Pamenter ME. Naked mole-rat skeletal muscle mitochondria exhibit minimal functional plasticity in acute or chronic hypoxia. Comp Biochem Physiol B Biochem Mol Biol 2021; 255:110596. [PMID: 33757832 DOI: 10.1016/j.cbpb.2021.110596] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/11/2021] [Accepted: 03/15/2021] [Indexed: 01/10/2023]
Abstract
Oxidative phosphorylation is compromised in hypoxia, but many organisms live and exercise in low oxygen environments. Hypoxia-driven adaptations at the mitochondrial level are common and may enhance energetic efficiency or minimize deleterious reactive oxygen species (ROS) generation. Mitochondria from various hypoxia-tolerant animals exhibit robust functional changes following in vivo hypoxia and we hypothesized that similar plasticity would occur in naked mole-rat skeletal muscle. To test this, we exposed adult subordinate naked mole-rats to normoxia (21% O2) or acute (4 h, 7% O2) or chronic hypoxia (4-6 weeks, 11% O2) and then isolated skeletal muscle mitochondria. Using high-resolution respirometry and a fluorescent indicator of ROS production, we then probed for changes in: i) lipid- (palmitoylcarnitine-malate), ii) carbohydrate- (pyruvate-malate), and iii) succinate-fueled metabolism, and also iv) complex IV electron transfer capacity, and v) H2O2 production. Compared to normoxic values, a) lipid-fueled uncoupled respiration was reduced ~15% during acute and chronic hypoxia, b) complex I-II capacity and the rate of ROS efflux were both unaffected, and c) complex II and IV uncoupled respiration were supressed ~16% following acute hypoxia. Notably, complex II-linked H2O2 efflux was 33% lower after acute hypoxia, which may reduce deleterious ROS bursts during reoxygenation. These mild changes in lipid- and carbohydrate-fueled respiratory capacity may reflect the need for this animal to exercise regularly in highly variable and intermittently hypoxic environments in which more robust plasticity may be energetically expensive.
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Affiliation(s)
- Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Daniel Munro
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Kenny Huynh
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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Pamenter ME, Hall JE, Tanabe Y, Simonson TS. Cross-Species Insights Into Genomic Adaptations to Hypoxia. Front Genet 2020; 11:743. [PMID: 32849780 PMCID: PMC7387696 DOI: 10.3389/fgene.2020.00743] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 06/22/2020] [Indexed: 12/13/2022] Open
Abstract
Over millions of years, vertebrate species populated vast environments spanning the globe. Among the most challenging habitats encountered were those with limited availability of oxygen, yet many animal and human populations inhabit and perform life cycle functions and/or daily activities in varying degrees of hypoxia today. Of particular interest are species that inhabit high-altitude niches, which experience chronic hypobaric hypoxia throughout their lives. Physiological and molecular aspects of adaptation to hypoxia have long been the focus of high-altitude populations and, within the past decade, genomic information has become increasingly accessible. These data provide an opportunity to search for common genetic signatures of selection across uniquely informative populations and thereby augment our understanding of the mechanisms underlying adaptations to hypoxia. In this review, we synthesize the available genomic findings across hypoxia-tolerant species to provide a comprehensive view of putatively hypoxia-adaptive genes and pathways. In many cases, adaptive signatures across species converge on the same genetic pathways or on genes themselves [i.e., the hypoxia inducible factor (HIF) pathway). However, specific variants thought to underlie function are distinct between species and populations, and, in most cases, the precise functional role of these genomic differences remains unknown. Efforts to standardize these findings and explore relationships between genotype and phenotype will provide important clues into the evolutionary and mechanistic bases of physiological adaptations to environmental hypoxia.
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Affiliation(s)
- Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
- Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - James E. Hall
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, San Diego, CA, United States
| | - Yuuka Tanabe
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, San Diego, CA, United States
| | - Tatum S. Simonson
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, School of Medicine, University of California, San Diego, San Diego, CA, United States
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Gerber L, Clow KA, Katan T, Emam M, Leeuwis RHJ, Parrish CC, Gamperl AK. Cardiac mitochondrial function, nitric oxide sensitivity and lipid composition following hypoxia acclimation in sablefish. ACTA ACUST UNITED AC 2019; 222:jeb.208074. [PMID: 31645375 DOI: 10.1242/jeb.208074] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/21/2019] [Indexed: 01/02/2023]
Abstract
In fishes, the effect of O2 limitation on cardiac mitochondrial function remains largely unexplored. The sablefish (Anoplopoma fimbria) encounters considerable variations in environmental oxygen availability, and is an interesting model for studying the effects of hypoxia on fish cardiorespiratory function. We investigated how in vivo hypoxia acclimation (6 months at 40% then 3 weeks at 20% air saturation) and in vitro anoxia-reoxygenation affected sablefish cardiac mitochondrial respiration and reactive oxygen species (ROS) release rates using high-resolution fluorespirometry. Further, we investigated how hypoxia acclimation affected the sensitivity of mitochondrial respiration to nitric oxide (NO), and compared mitochondrial lipid and fatty acid (FA) composition between groups. Hypoxia acclimation did not alter mitochondrial coupled or uncoupled respiration, or respiratory control ratio, ROS release rates, P 50 or superoxide dismutase activity. However, it increased citrate synthase activity (by ∼20%), increased the sensitivity of mitochondrial respiration to NO inhibition (i.e., the NO IC50 was 25% lower), and enhanced the recovery of respiration (by 21%) and reduced ROS release rates (by 25-30%) post-anoxia. In addition, hypoxia acclimation altered mitochondrial FA composition [increasing arachidonic acid (20:4ω6) and eicosapentaenoic acid (20:5ω3) proportions by 11 and 14%, respectively], and SIMPER analysis revealed that the phospholipid:sterol ratio was the largest contributor (24%) to the dissimilarity between treatments. Overall, these results suggest that hypoxia acclimation may protect sablefish cardiac bioenergetic function during or after periods of O2 limitation, and that this may be related to alterations in mitochondrial sensitivity to NO and to adaptive changes in membrane composition (fluidity).
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Affiliation(s)
- Lucie Gerber
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
| | - Kathy A Clow
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
| | - Tomer Katan
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
| | - Mohamed Emam
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
| | - Robine H J Leeuwis
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
| | | | - Anthony K Gamperl
- Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada
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Munro D, Pamenter ME. Comparative studies of mitochondrial reactive oxygen species in animal longevity: Technical pitfalls and possibilities. Aging Cell 2019; 18:e13009. [PMID: 31322803 PMCID: PMC6718592 DOI: 10.1111/acel.13009] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 06/03/2019] [Accepted: 06/30/2019] [Indexed: 11/30/2022] Open
Abstract
The mitochondrial oxidative theory of aging has been repeatedly investigated over the past 30 years by comparing the efflux of hydrogen peroxide (H2O2) from isolated mitochondria of long‐ and short‐lived species using horseradish peroxidase‐based assays. However, a clear consensus regarding the relationship between H2O2 production rates and longevity has not emerged. Concomitantly, novel insights into the mechanisms of reactive oxygen species (ROS) handling by mitochondria themselves should have raised concerns about the validity of this experimental approach. Here, we review pitfalls of the horseradish peroxidase/amplex red detection system for the measurement of mitochondrial ROS formation rates, with an emphasis on longevity studies. Importantly, antioxidant systems in the mitochondrial matrix are often capable of scavenging H2O2 faster than mitochondria produce it. As a consequence, as much as 84% of the H2O2 produced by mitochondria may be consumed before it diffuses into the reaction medium, where it can be detected by the horseradish peroxidase/amplex red system, this proportion is likely not consistent across species. Furthermore, previous studies often used substrates that elicit H2O2 formation at a much higher rate than in physiological conditions and at sites of secondary importance in vivo. Recent evidence suggests that the activity of matrix antioxidants may correlate with longevity instead of the rate of H2O2 formation. We conclude that past studies have been methodologically insufficient to address the putative relationship between longevity and mitochondrial ROS. Thus, novel methodological approaches are required that more accurately encompass mitochondrial ROS metabolism.
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Affiliation(s)
- Daniel Munro
- Department of Biology University of Ottawa Ottawa Ontario Canada
| | - Matthew E. Pamenter
- Department of Biology University of Ottawa Ottawa Ontario Canada
- University of Ottawa Brain and Mind Research Institute Ottawa Ontario Canada
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Genome-Wide Association Analysis of Anoxia Tolerance in Drosophila melanogaster. G3-GENES GENOMES GENETICS 2019; 9:2989-2999. [PMID: 31311780 PMCID: PMC6723132 DOI: 10.1534/g3.119.400421] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
As the genetic bases to variation in anoxia tolerance are poorly understood, we used the Drosophila Genetics Reference Panel (DGRP) to conduct a genome-wide association study (GWAS) of anoxia tolerance in adult and larval Drosophila melanogaster Survival ranged from 0-100% in adults exposed to 6 h of anoxia and from 20-98% for larvae exposed to 1 h of anoxia. Anoxia tolerance had a broad-sense heritability of 0.552 in adults and 0.433 in larvae. Larval and adult phenotypes were weakly correlated but the anoxia tolerance of adult males and females were strongly correlated. The GWA identified 180 SNPs in adults and 32 SNPs in larvae associated with anoxia tolerance. Gene ontology enrichment analysis indicated that many of the 119 polymorphic genes associated with adult anoxia-tolerance were associated with ionic transport or immune function. In contrast, the 22 polymorphic genes associated with larval anoxia-tolerance were mostly associated with regulation of transcription and DNA replication. RNAi of mapped genes generally supported the hypothesis that disruption of these genes reduces anoxia tolerance. For two ion transport genes, we tested predicted directional and sex-specific effects of SNP alleles on adult anoxia tolerance and found strong support in one case but not the other. Correlating our phenotype to prior DGRP studies suggests that genes affecting anoxia tolerance also influence stress-resistance, immune function and ionic balance. Overall, our results provide evidence for multiple new potential genetic influences on anoxia tolerance and provide additional support for important roles of ion balance and immune processes in determining variation in anoxia tolerance.
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Hawrysh PJ, Buck LT. Oxygen-sensitive interneurons exhibit increased activity and GABA release during ROS scavenging in the cerebral cortex of the western painted turtle. J Neurophysiol 2019; 122:466-479. [PMID: 31141433 DOI: 10.1152/jn.00104.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The western painted turtle (Chrysemys picta bellii) has the unique ability of surviving several months in the absence of oxygen, which is termed anoxia. One major protective strategy that the turtle employs during anoxia is a reduction in neuronal electrical activity, which may result from a natural reduction in reactive oxygen species (ROS). We previously linked a reduction in ROS levels to an increase in γ-amino butyric acid (GABA) receptor currents. The purpose of this study is to understand how fast-spiking, GABA-releasing neurons respond to reductions in ROS and how this affects GABA release. Using a fluorescence-coupled enzymatic microplate assay for GABA, we found that anoxia, the ROS scavenger N-(2-mercaptopriopionyl)glycine (MPG), or the mitochondria-specific ROS scavenger MitoTEMPO resulted in a 2.5-, 2.0-, and 2.5-fold increase in extracellular GABA concentration, respectively. This phenomenon could be blocked with TTX, indicating that it is activity dependent. Using whole cell patch-clamping techniques, we found that fast-spiking, burst-firing GABAergic turtle neurons increase the duration and number of action potentials per burst by 26% and 42%, respectively, in response to ROS scavenging via MPG. These results suggest that the reduction in mitochondrially produced ROS that occurs during anoxia leads to increased GABA release, which promotes postsynaptic inhibitory activity through activation of GABA receptors.NEW & NOTEWORTHY This is a novel study examining the response of cerebral cortical stellate interneurons to anoxia and mitochondrial reactive oxygen species (ROS) scavenging with MitoTEMPO. Under both conditions burst firing increases in these cells, and we show that extracellular GABA release increases in the presence of the ROS scavenger. We conclude that in the anoxia-tolerant painted turtle brain, a decrease in ROS levels is an important low oxygen signal.
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Affiliation(s)
- Peter John Hawrysh
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Leslie Thomas Buck
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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Devaux JBL, Hedges CP, Birch N, Herbert N, Renshaw GMC, Hickey AJR. Acidosis Maintains the Function of Brain Mitochondria in Hypoxia-Tolerant Triplefin Fish: A Strategy to Survive Acute Hypoxic Exposure? Front Physiol 2019; 9:1941. [PMID: 30713504 PMCID: PMC6346031 DOI: 10.3389/fphys.2018.01941] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/22/2018] [Indexed: 11/13/2022] Open
Abstract
The vertebrate brain is generally very sensitive to acidosis, so a hypoxia-induced decrease in pH is likely to have an effect on brain mitochondria (mt). Mitochondrial respiration (JO2) is required to generate an electrical gradient (ΔΨm) and a pH gradient to power ATP synthesis, yet the impact of pH modulation on brain mt function remains largely unexplored. As intertidal fishes within rock pools routinely experience hypoxia and reoxygenation, they would most likely experience changes in cellular pH. We hence compared four New Zealand triplefin fish species ranging from intertidal hypoxia-tolerant species (HTS) to subtidal hypoxia-sensitive species (HSS). We predicted that HTS would tolerate acidosis better than HSS in terms of sustaining mt structure and function. Using respirometers coupled to fluorimeters and pH electrodes, we titrated lactic-acid to decrease the pH of the media, and simultaneously recorded JO2, ΔΨm, and H+ buffering capacities within permeabilized brain and swelling of mt isolated from non-permeabilized brains. We then measured ATP synthesis rates in the most HTS (Bellapiscus medius) and the HSS (Forsterygion varium) at pH 7.25 and 6.65. Mitochondria from HTS brain did have greater H+ buffering capacities than HSS mt (∼10 mU pH.mgprotein -1). HTS mt swelled by 40% when exposed to a decrease of 1.5 pH units, and JO2 was depressed by up to 15% in HTS. However, HTS were able to maintain ΔΨm near -120 mV. Estimates of work, in terms of charges moved across the mt inner-membrane, suggested that with acidosis, HTS mt may in part harness extra-mt H+ to maintain ΔΨm, and could therefore support ATP production. This was confirmed with elevated ATP synthesis rates and enhanced P:O ratios at pH 6.65 relative to pH 7.25. In contrast, mt volumes and ΔΨm decreased downward pH 6.9 in HSS mt and paradoxically, JO2 increased (∼25%) but ATP synthesis and P:O ratios were depressed at pH 6.65. This indicates a loss of coupling in the HSS with acidosis. Overall, the mt of these intertidal fish have adaptations that enhance ATP synthesis efficiency under acidic conditions such as those that occur in hypoxic or reoxygenated brain.
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Affiliation(s)
- Jules B L Devaux
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Christopher P Hedges
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Nigel Birch
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Neill Herbert
- Institute of Marine Science, The University Auckland, Auckland, New Zealand
| | - Gillian M C Renshaw
- School of Allied Health Sciences, Griffith University, Gold Coast, QLD, Australia
| | - Anthony J R Hickey
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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Abstract
Therapeutic hypothermia is a strategy that reduces metabolic rate and brain damage during clinically-relevant hypoxic events. Mitochondrial respiration is compromised by hypoxia, with deleterious consequences for the mammalian brain; however, little is known about the effects of reduced temperature on mitochondrial metabolism. Therefore, we examined how mitochondrial function is impacted by temperature using high resolution respirometry to assess electron transport system (ETS) function in saponin-permeabilized mouse brain at 28 and 37°C. Respirometric analysis revealed that, at the colder temperature, ETS respiratory flux was ~ 40–75% lower relative to the physiological temperature in all respiratory states and for all fuel substrates tested. In whole brain tissue, the enzyme maximum respiratory rates for complexes I-V were similarly reduced by between 37–88%. Complexes II and V were particularly temperature-sensitive; a temperature-mediated decrease in complex II activity may support a switch to complex I mediated ATP-production, which is considerably more oxygen-efficient. Finally, the mitochondrial H+-gradient was more tightly coupled, indicating that mitochondrial respiration is more efficient at the colder temperature. Taken together, our results suggest that improvements in mitochondrial function with colder temperatures may contribute to energy conservation and enhance cellular viability in hypoxic brain.
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Houlahan CR, Kirby AM, Dzal YA, Fairman GD, Pamenter ME. Divergent behavioural responses to acute hypoxia between individuals and groups of naked mole rats. Comp Biochem Physiol B Biochem Mol Biol 2018; 224:38-44. [DOI: 10.1016/j.cbpb.2018.01.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 12/28/2017] [Accepted: 01/10/2018] [Indexed: 11/30/2022]
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The hypoxia-tolerant vertebrate brain: Arresting synaptic activity. Comp Biochem Physiol B Biochem Mol Biol 2018; 224:61-70. [DOI: 10.1016/j.cbpb.2017.11.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/23/2017] [Accepted: 11/30/2017] [Indexed: 01/16/2023]
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Lefevre S, Stecyk JAW, Torp MK, Løvold LY, Sørensen C, Johansen IB, Stensløkken KO, Couturier CS, Sloman KA, Nilsson GE. Re-oxygenation after anoxia induces brain cell death and memory loss in the anoxia-tolerant crucian carp. ACTA ACUST UNITED AC 2018; 220:3883-3895. [PMID: 29093186 DOI: 10.1242/jeb.165118] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 09/01/2017] [Indexed: 01/15/2023]
Abstract
Crucian carp (Carassius carassius) survive without oxygen for several months, but it is unknown whether they are able to protect themselves from cell death normally caused by the absence, and particularly return, of oxygen. Here, we quantified cell death in brain tissue from crucian carp exposed to anoxia and re-oxygenation using the terminal deoxy-nucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen (PCNA) as well as PCNA mRNA expression. We also measured mRNA and protein expression of the apoptosis executer protease caspase 3, in laboratory fish exposed to anoxia and re-oxygenation and fish exposed to seasonal anoxia and re-oxygenation in their natural habitat over the year. Finally, a behavioural experiment was used to assess the ability to learn and remember how to navigate in a maze to find food, before and after exposure to anoxia and re-oxygenation. The number of TUNEL-positive cells in the telencephalon increased after 1 day of re-oxygenation following 7 days of anoxia, indicating increased cell death. However, there were no consistent changes in whole-brain expression of caspase 3 in either laboratory-exposed or naturally exposed fish, indicating that cell death might occur via caspase-independent pathways or necrosis. Re-oxygenated crucian carp appeared to have lost the memory of how to navigate in a maze (learnt prior to anoxia exposure), while the ability to learn remained intact. PCNA mRNA was elevated after re-oxygenation, indicating increased neurogenesis. We conclude that anoxia tolerance involves not only protection from damage but also repair after re-oxygenation.
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Affiliation(s)
- Sjannie Lefevre
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Jonathan A W Stecyk
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - May-Kristin Torp
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Lisa Y Løvold
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Christina Sørensen
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Ida B Johansen
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Kåre-Olav Stensløkken
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Christine S Couturier
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
| | - Katherine A Sloman
- Institute of Biomedical and Environmental Health Research, School of Science and Sport, University of the West of Scotland, PA1 2BE, UK
| | - Göran E Nilsson
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
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Gattuso A, Garofalo F, Cerra MC, Imbrogno S. Hypoxia Tolerance in Teleosts: Implications of Cardiac Nitrosative Signals. Front Physiol 2018; 9:366. [PMID: 29706897 PMCID: PMC5906588 DOI: 10.3389/fphys.2018.00366] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/26/2018] [Indexed: 12/18/2022] Open
Abstract
Changes in environmental oxygen (O2) are naturally occurring phenomena which ectotherms have to face on. Many species exhibit a striking capacity to survive and remain active for long periods under hypoxia, even tolerating anoxia. Some fundamental adaptations contribute to this capacity: metabolic suppression, tolerance of pH and ionic unbalance, avoidance and/or repair of free-radical-induced cell injury during reoxygenation. A remarkable feature of these species is their ability to preserve a normal cardiovascular performance during hypoxia/anoxia to match peripheral (tissue pO2) requirements. In this review, we will refer to paradigms of hypoxia- and anoxia-tolerant teleost fish to illustrate cardiac physiological strategies that, by involving nitric oxide and its metabolites, play a critical role in the adaptive responses to O2 limitation. The information here reported may contribute to clarify the molecular and cellular mechanisms underlying heart vulnerability vs. resistance in relation to O2 availability.
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Affiliation(s)
- Alfonsina Gattuso
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Filippo Garofalo
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Maria C Cerra
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
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Pamenter ME, Lau GY, Richards JG, Milsom WK. Naked mole rat brain mitochondria electron transport system flux and H + leak are reduced during acute hypoxia. ACTA ACUST UNITED AC 2018; 221:jeb.171397. [PMID: 29361591 DOI: 10.1242/jeb.171397] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 12/19/2017] [Indexed: 01/02/2023]
Abstract
Mitochondrial respiration and ATP production are compromised by hypoxia. Naked mole rats (NMRs) are among the most hypoxia-tolerant mammals and reduce metabolic rate in hypoxic environments; however, little is known regarding mitochondrial function during in vivo hypoxia exposure in this species. To address this knowledge gap, we asked whether the function of NMR brain mitochondria exhibits metabolic plasticity during acute hypoxia. Respirometry was utilized to assess whole-animal oxygen consumption rates and high-resolution respirometry was utilized to assess electron transport system (ETS) function in saponin-permeabilized NMR brain. We found that NMR whole-animal oxygen consumption rate reversibly decreased by ∼85% in acute hypoxia (4 h at 3% O2). Similarly, relative to untreated controls, permeabilized brain respiratory flux through the ETS was decreased by ∼90% in acutely hypoxic animals. Relative to carbonyl cyanide p-trifluoro-methoxyphenylhydrazone-uncoupled total ETS flux, this functional decrease was observed equally across all components of the ETS except for complex IV (cytochrome c oxidase), at which flux was further reduced, supporting a regulatory role for this enzyme during acute hypoxia. The maximum enzymatic capacities of ETS complexes I-V were not altered by acute hypoxia; however, the mitochondrial H+ gradient decreased in step with the decrease in ETS respiration. Taken together, our results indicate that NMR brain ETS flux and H+ leak are reduced in a balanced and regulated fashion during acute hypoxia. Changes in NMR mitochondrial metabolic plasticity mirror whole-animal metabolic responses to hypoxia.
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Affiliation(s)
- Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N5 .,Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada
| | - Gigi Y Lau
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Jeffrey G Richards
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Dhillon RS, Denu JM. Using comparative biology to understand how aging affects mitochondrial metabolism. Mol Cell Endocrinol 2017; 455:54-61. [PMID: 28025033 DOI: 10.1016/j.mce.2016.12.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/24/2016] [Accepted: 12/16/2016] [Indexed: 02/06/2023]
Abstract
Lifespan varies considerably among even closely related species, as exemplified by rodents and primates. Despite these disparities in lifespan, most studies have focused on intra-specific aging pathologies, primarily within a select few systems. While mice have provided much insight into aging biology, it is unclear if such a short-lived species lack defences against senescence that may have evolved in related longevous species. Many age-related diseases have been linked to mitochondrial dysfunction that are measured by decreased energy generation, structural damage to cellular components, and even cell death. Post translational modifications (PTMs) orchestrate many of the pathways associated with cellular metabolism, and are thought to be a key regulator in biological senescence. We propose hyperacylation as one such modification that may be implicated in numerous mitochondrial impairments affecting energy metabolism.
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Affiliation(s)
- Rashpal S Dhillon
- Department of Biomolecular Chemistry, University of Wisconsin- Madison, Madison, WI 53715, USA.
| | - John M Denu
- Department of Biomolecular Chemistry, University of Wisconsin- Madison, Madison, WI 53715, USA
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Ivanina AV, Nesmelova I, Leamy L, Sokolov EP, Sokolova IM. Intermittent hypoxia leads to functional reorganization of mitochondria and affects cellular bioenergetics in marine molluscs. ACTA ACUST UNITED AC 2017; 219:1659-74. [PMID: 27252455 DOI: 10.1242/jeb.134700] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Accepted: 03/14/2016] [Indexed: 12/11/2022]
Abstract
Fluctuations in oxygen (O2) concentrations represent a major challenge to aerobic organisms and can be extremely damaging to their mitochondria. Marine intertidal molluscs are well-adapted to frequent O2 fluctuations, yet it remains unknown how their mitochondrial functions are regulated to sustain energy metabolism and prevent cellular damage during hypoxia and reoxygenation (H/R). We used metabolic control analysis to investigate the mechanisms of mitochondrial responses to H/R stress (18 h at <0.1% O2 followed by 1 h of reoxygenation) using hypoxia-tolerant intertidal clams Mercenaria mercenaria and hypoxia-sensitive subtidal scallops Argopecten irradians as models. We also assessed H/R-induced changes in cellular energy balance, oxidative damage and unfolded protein response to determine the potential links between mitochondrial dysfunction and cellular injury. Mitochondrial responses to H/R in scallops strongly resembled those in other hypoxia-sensitive organisms. Exposure to hypoxia followed by reoxygenation led to a strong decrease in the substrate oxidation (SOX) and phosphorylation (PHOS) capacities as well as partial depolarization of mitochondria of scallops. Elevated mRNA expression of a reactive oxygen species-sensitive enzyme aconitase and Lon protease (responsible for degradation of oxidized mitochondrial proteins) during H/R stress was consistent with elevated levels of oxidative stress in mitochondria of scallops. In hypoxia-tolerant clams, mitochondrial SOX capacity was enhanced during hypoxia and continued rising during the first hour of reoxygenation. In both species, the mitochondrial PHOS capacity was suppressed during hypoxia, likely to prevent ATP wastage by the reverse action of FO,F1-ATPase. The PHOS capacity recovered after 1 h of reoxygenation in clams but not in scallops. Compared with scallops, clams showed a greater suppression of energy-consuming processes (such as protein turnover and ion transport) during hypoxia, indicated by inactivation of the translation initiation factor EIF-2α, suppression of 26S proteasome activity and a dramatic decrease in the activity of Na(+)/K(+)-ATPase. The steady-state levels of adenylates were preserved during H/R exposure and AMP-dependent protein kinase was not activated in either species, indicating that the H/R exposure did not lead to severe energy deficiency. Taken together, our findings suggest that mitochondrial reorganizations sustaining high oxidative phosphorylation flux during recovery, combined with the ability to suppress ATP-demanding cellular functions during hypoxia, may contribute to high resilience of clams to H/R stress and help maintain energy homeostasis during frequent H/R cycles in the intertidal zone.
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Affiliation(s)
- Anna V Ivanina
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Irina Nesmelova
- Department of Physics, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Larry Leamy
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Eugene P Sokolov
- Department of General Surgery, Carolinas Medical Center, Charlotte, NC 28232, USA
| | - Inna M Sokolova
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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Pamenter ME, Gomez CR, Richards JG, Milsom WK. Mitochondrial responses to prolonged anoxia in brain of red-eared slider turtles. Biol Lett 2017; 12:20150797. [PMID: 26763217 DOI: 10.1098/rsbl.2015.0797] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mitochondria are central to aerobic energy production and play a key role in neuronal signalling. During anoxia, however, the mitochondria of most vertebrates initiate deleterious cell death cascades. Nonetheless, a handful of vertebrate species, including some freshwater turtles, are remarkably tolerant of low oxygen environments and survive months of anoxia without apparent damage to brain tissue. This tolerance suggests that mitochondria in the brains of such species are adapted to withstand prolonged anoxia, but little is known about potential neuroprotective responses. In this study, we address such mechanisms by comparing mitochondrial function between brain tissues isolated from cold-acclimated red-eared slider turtles (Trachemys scripta elegans) exposed to two weeks of either normoxia or anoxia. We found that brain mitochondria from anoxia-acclimated turtles exhibited a unique phenotype of remodelling relative to normoxic controls, including: (i) decreased citrate synthase and F1FO-ATPase activity but maintained protein content, (ii) markedly reduced aerobic capacity, and (iii) mild uncoupling of the mitochondrial proton gradient. These data suggest that turtle brain mitochondria respond to low oxygen stress with a unique suite of changes tailored towards neuroprotection.
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Affiliation(s)
- Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Crisostomo R Gomez
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Jeffrey G Richards
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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Ballinger MA, Schwartz C, Andrews MT. Enhanced oxidative capacity of ground squirrel brain mitochondria during hibernation. Am J Physiol Regul Integr Comp Physiol 2017; 312:R301-R310. [PMID: 28077389 DOI: 10.1152/ajpregu.00314.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 01/06/2017] [Accepted: 01/08/2017] [Indexed: 11/22/2022]
Abstract
During hibernation, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) regularly cycle between bouts of torpor and interbout arousal (IBA). Most of the brain is electrically quiescent during torpor but regains activity quickly upon arousal to IBA, resulting in extreme oscillations in energy demand during hibernation. We predicted increased functional capacity of brain mitochondria during hibernation compared with spring to accommodate the variable energy demands of hibernation. To address this hypothesis, we examined mitochondrial bioenergetics in the ground squirrel brain across three time points: spring (SP), torpor (TOR), and IBA. Respiration rates of isolated brain mitochondria through complex I of the electron transport chain were more than twofold higher in TOR and IBA than in SP (P < 0.05). We also found a 10% increase in membrane potential between hibernation and spring (P < 0.05), and that proton leak was lower in TOR and IBA than in SP. Finally, there was a 30% increase in calcium loading in SP brain mitochondria compared with TOR and IBA (P < 0.01). To analyze brain mitochondrial abundance between spring and hibernation, we measured the ratio of copy number in a mitochondrial gene (ND1) vs. a nuclear gene (B2M) in frozen cerebral cortex samples. No significant differences were observed in DNA copies between SP and IBA. These data show that brain mitochondrial bioenergetics are not static across the year and suggest that brain mitochondria function more effectively during the hibernation season, allowing for rapid production of energy to meet demand when extreme physiological changes are occurring.
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Affiliation(s)
- Mallory A Ballinger
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota; and
| | - Christine Schwartz
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota; and.,Department of Biology, University of Wisconsin-La Crosse, La Crosse, Wisconsin
| | - Matthew T Andrews
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota; and
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Pamenter ME, Powell FL. Time Domains of the Hypoxic Ventilatory Response and Their Molecular Basis. Compr Physiol 2016; 6:1345-85. [PMID: 27347896 DOI: 10.1002/cphy.c150026] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ventilatory responses to hypoxia vary widely depending on the pattern and length of hypoxic exposure. Acute, prolonged, or intermittent hypoxic episodes can increase or decrease breathing for seconds to years, both during the hypoxic stimulus, and also after its removal. These myriad effects are the result of a complicated web of molecular interactions that underlie plasticity in the respiratory control reflex circuits and ultimately control the physiology of breathing in hypoxia. Since the time domains of the physiological hypoxic ventilatory response (HVR) were identified, considerable research effort has gone toward elucidating the underlying molecular mechanisms that mediate these varied responses. This research has begun to describe complicated and plastic interactions in the relay circuits between the peripheral chemoreceptors and the ventilatory control circuits within the central nervous system. Intriguingly, many of these molecular pathways seem to share key components between the different time domains, suggesting that varied physiological HVRs are the result of specific modifications to overlapping pathways. This review highlights what has been discovered regarding the cell and molecular level control of the time domains of the HVR, and highlights key areas where further research is required. Understanding the molecular control of ventilation in hypoxia has important implications for basic physiology and is emerging as an important component of several clinical fields. © 2016 American Physiological Society. Compr Physiol 6:1345-1385, 2016.
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Affiliation(s)
| | - Frank L Powell
- Physiology Division, Department of Medicine, University of California San Diego, La Jolla, California, USA
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Pamenter ME, Dzal YA, Milsom WK. Adenosine receptors mediate the hypoxic ventilatory response but not the hypoxic metabolic response in the naked mole rat during acute hypoxia. Proc Biol Sci 2016; 282:20141722. [PMID: 25520355 DOI: 10.1098/rspb.2014.1722] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Naked mole rats are the most hypoxia-tolerant mammals identified; however, the mechanisms underlying this tolerance are poorly understood. Using whole-animal plethysmography and open-flow respirometry, we examined the hypoxic metabolic response (HMR), hypoxic ventilatory response (HVR) and hypoxic thermal response in awake, freely behaving naked mole rats exposed to 7% O₂ for 1 h. Metabolic rate and ventilation each reversibly decreased 70% in hypoxia (from 39.6 ± 2.9 to 12.1 ± 0.3 ml O₂ min(-1) kg(-1), and 1412 ± 244 to 417 ± 62 ml min(-1) kg(-1), respectively; p < 0.05), whereas body temperature was unchanged and animals remained awake and active. Subcutaneous injection of the general adenosine receptor antagonist aminophylline (AMP; 100 mg kg(-1), in saline), but not control saline injections, prevented the HVR but had no effect on the HMR. As a result, AMP-treated naked mole rats exhibited extreme hyperventilation in hypoxia. These animals were also less tolerant to hypoxia, and in some cases hypoxia was lethal following AMP injection. We conclude that in naked mole rats (i) hypoxia tolerance is partially dependent on profound hypoxic metabolic and ventilatory responses, which are equal in magnitude but occur independently of thermal changes in hypoxia, and (ii) adenosine receptors mediate the HVR but not the HMR.
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Affiliation(s)
- Matthew E Pamenter
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Yvonne A Dzal
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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