1
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Negrete B, Ackerly KL, Esbaugh AJ. Hypoxia-acclimation adjusts skeletal muscle anaerobic metabolism and burst swim performance in a marine fish. Comp Biochem Physiol A Mol Integr Physiol 2024; 297:111734. [PMID: 39216551 DOI: 10.1016/j.cbpa.2024.111734] [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: 06/17/2024] [Revised: 08/26/2024] [Accepted: 08/28/2024] [Indexed: 09/04/2024]
Abstract
Red drum, Sciaenops ocellatus, are a marine teleost native to the Gulf of Mexico that routinely experiences periods of low oxygen (hypoxia). Recent work has demonstrated this species has the capacity to improve aerobic performance in hypoxia through respiratory acclimation. However, it remains unknown how hypoxia acclimation impacts anaerobic metabolism in red drum, and the consequences of exhaustive exercise and recovery. Juvenile fish were acclimated to normoxia (n = 15, DO 90.4 ± 6.42 %) or hypoxia (n = 15, DO 33.6 ± 7.2 %) for 8 days then sampled at three time points: at rest, after exercise, and after a 3 h recovery period. The resting time point was used to characterize the acclimated phenotype, while the remaining time points demonstrate how this phenotype responds to exhaustive exercise. Whole blood, red muscle, white muscle, and heart tissues were sampled for metabolites and enzyme activity. The resting phenotype was characterized by lower pHe and changes to skeletal muscle ATP. Exhaustive exercise increased muscle lactate, and decreased phosphocreatine and ATP with no effect of acclimation. Interestingly, hypoxia-acclimated fish had higher pHe and pHi than control in all exercise time points. Red muscle ATP was lower in hypoxia-acclimated fish versus control at each sample period. Moreover, acclimated fish increased lactate dehydrogenase activity in the red muscle. Hypoxia acclimation increased white muscle ATP and hexokinase activity, a glycolytic enzyme. In a gait-transition swim test, hypoxia-acclimated fish recruited anaerobic-powered burst swimming at lower speeds in normoxia compared to control fish. These data suggest that acclimation increases reliance on anaerobic metabolism, and does not benefit recovery from exhaustive exercise.
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Affiliation(s)
- Benjamin Negrete
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA; Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Kerri Lynn Ackerly
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA. https://twitter.com/KerriAckerlyPhD
| | - Andrew J Esbaugh
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA
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2
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Bundgaard A, Borowiec BG, Lau GY. Are reactive oxygen species always bad? Lessons from hypoxic ectotherms. J Exp Biol 2024; 227:jeb246549. [PMID: 38533673 DOI: 10.1242/jeb.246549] [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] [Indexed: 03/28/2024]
Abstract
Oxygen (O2) is required for aerobic energy metabolism but can produce reactive oxygen species (ROS), which are a wide variety of oxidant molecules with a range of biological functions from causing cell damage (oxidative distress) to cell signalling (oxidative eustress). The balance between the rate and amount of ROS generated and the capacity for scavenging systems to remove them is affected by several biological and environmental factors, including oxygen availability. Ectotherms, and in particular hypoxia-tolerant ectotherms, are hypothesized to avoid oxidative damage caused by hypoxia, although it is unclear whether this translates to an increase in ecological fitness. In this Review, we highlight the differences between oxidative distress and eustress, the current mechanistic understanding of the two and how they may affect ectothermic physiology. We discuss the evidence of occurrence of oxidative damage with hypoxia in ectotherms, and that ectotherms may avoid oxidative damage through (1) high levels of antioxidant and scavenging systems and/or (2) low(ering) levels of ROS generation. We argue that the disagreements in the literature as to how hypoxia affects antioxidant enzyme activity and the variable metabolism of ectotherms makes the latter strategy more amenable to ectotherm physiology. Finally, we argue that observed changes in ROS production and oxidative status with hypoxia may be a signalling mechanism and an adaptive strategy for ectotherms encountering hypoxia.
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Affiliation(s)
- Amanda Bundgaard
- University of Cologne, CECAD, Joseph-Stelzmann-Straße 26, DE-50931 Köln, Germany
- Aarhus University, Department of Biology, CF Moellers Alle 3, DK-8000 Aarhus C, Denmark
| | - Brittney G Borowiec
- Wilfrid Laurier University, Department of Biology, 75 University Ave. W., Waterloo, ON, Canada, N2L 3C5
| | - Gigi Y Lau
- University of British Columbia, Department of Zoology, 6270 University Blvd, Vancouver, BC, Canada, V6T 1Z4
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3
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Duffy BM, Hayward L, Staples JF. Torpid 13-lined ground squirrel liver mitochondria resist anoxia-reoxygenation despite high levels of protein damage. J Comp Physiol B 2023; 193:715-728. [PMID: 37851102 DOI: 10.1007/s00360-023-01515-3] [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: 04/17/2023] [Revised: 08/27/2023] [Accepted: 09/05/2023] [Indexed: 10/19/2023]
Abstract
Hibernation confers resistance to ischemia-reperfusion injury in tissue, but the underlying mechanisms remain unclear. Suppression of mitochondrial respiration during torpor may contribute to this tolerance. To explore this concept, we subjected isolated liver mitochondria from torpid, interbout euthermic (IBE) and summer 13-lined ground squirrels (Ictidomys tridecemlineatus) to 5 min of anoxia, followed by reoxygenation (A/R). We also included rat liver mitochondria as a non-hibernating comparison group. Maximum respiration rates of mitochondria from torpid ground squirrels were not affected by A/R, but in IBE and summer, these rates decreased by 50% following A/R and in rats they decreased by 80%. Comparing net ROS production rates among groups, revealed seasonal differences; mitochondria from IBE and torpor produced 75% less ROS than summer ground squirrels and rats. Measurements of oxidative damage to these mitochondria, both freshly isolated, as well as pre- and post-A/R, demonstrated elevated damage to protein, but not lipids, in all groups. Hibernation likely generates oxidative stress, as freshly isolated mitochondria had greater protein damage in torpor and IBE than in summer and rats. When comparing markers of damage pre- and post-A/R, we found that when RET was active, rat macromolecules were more damaged than when RET is inhibited, but in TLGS markers of damage were similar. This result suggests that suppression of RET during hibernation, both in torpor and IBE, lessens oxidative stress produced during arousal. Taken together our study suggests that ischemia-reperfusion tolerance at the mitochondrial level is associated with metabolically suppressed oxidative phosphorylation during hibernation.
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Affiliation(s)
- Brynne M Duffy
- University of Western Ontario, (Biology), London, ON, Canada.
| | - Leah Hayward
- University of Western Ontario, (Biology), London, ON, Canada
- McMaster University, (Hamilton Health Sciences), Hamilton, ON, Canada
| | - James F Staples
- University of Western Ontario, (Biology), London, ON, Canada
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4
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Bundgaard A, Gruszczyk AV, Prag HA, Williams C, McIntyre A, Ruhr IM, James AM, Galli GLJ, Murphy MP, Fago A. Low production of mitochondrial reactive oxygen species after anoxia and reoxygenation in turtle hearts. J Exp Biol 2023; 226:jeb245516. [PMID: 37066839 PMCID: PMC10184768 DOI: 10.1242/jeb.245516] [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: 01/11/2023] [Accepted: 04/03/2023] [Indexed: 04/18/2023]
Abstract
Extremely anoxia-tolerant animals, such as freshwater turtles, survive anoxia and reoxygenation without sustaining tissue damage to their hearts. In contrast, for mammals, the ischemia-reperfusion (IR) injury that leads to tissue damage during a heart attack is initiated by a burst of superoxide (O2·-) production from the mitochondrial respiratory chain upon reperfusion of ischemic tissue. Whether turtles avoid oxidative tissue damage because of an absence of mitochondrial superoxide production upon reoxygenation, or because the turtle heart is particularly protected against this damage, is unclear. Here, we investigated whether there was an increase in mitochondrial O2·- production upon the reoxygenation of anoxic red-eared slider turtle hearts in vivo and in vitro. This was done by measuring the production of H2O2, the dismutation product of O2·-, using the mitochondria-targeted mass-spectrometric probe in vivo MitoB, while in parallel assessing changes in the metabolites driving mitochondrial O2·- production, succinate, ATP and ADP levels during anoxia, and H2O2 consumption and production rates of isolated heart mitochondria. We found that there was no excess production of in vivo H2O2 during 1 h of reoxygenation in turtles after 3 h anoxia at room temperature, suggesting that turtle hearts most likely do not suffer oxidative injury after anoxia because their mitochondria produce no excess O2·- upon reoxygenation. Instead, our data support the conclusion that both the low levels of succinate accumulation and the maintenance of ADP levels in the anoxic turtle heart are key factors in preventing the surge of O2·- production upon reoxygenation.
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Affiliation(s)
- Amanda Bundgaard
- CECAD, University of Cologne, 50931 Cologne, Germany
- Department of Biology, Aarhus University, DK-8000 Aarhus, Denmark
| | - Anja V. Gruszczyk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Hiran A. Prag
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | | | - Angela McIntyre
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Ilan M. Ruhr
- Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9PL, UK
| | - Andrew M. James
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Gina L. J. Galli
- Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9PL, UK
| | - Michael P. Murphy
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Angela Fago
- Department of Biology, Aarhus University, DK-8000 Aarhus, Denmark
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5
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Johansen A, Thiede B, Anonsen JH, Nilsson GE. Surviving without oxygen involves major tissue specific changes in the proteome of crucian carp ( Carassius carassius). PeerJ 2023; 11:e14890. [PMID: 36915662 PMCID: PMC10007964 DOI: 10.7717/peerj.14890] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 01/23/2023] [Indexed: 03/10/2023] Open
Abstract
The crucian carp (Carassius carassius) can survive complete oxygen depletion (anoxia) for several months at low temperatures, making it an excellent model for studying molecular adaptations to anoxia. Still, little is known about how its global proteome responds to anoxia and reoxygenation. By applying mass spectrometry-based proteome analyses on brain, heart and liver tissue from crucian carp exposed to normoxia, five days anoxia, and reoxygenation, we found major changes in particularly cardiac and hepatic protein levels in response to anoxia and reoxygenation. These included tissue-specific differences in mitochondrial proteins involved in aerobic respiration and mitochondrial membrane integrity. Enzymes in the electron transport system (ETS) decreased in heart and increased massively in liver during anoxia and reoxygenation but did not change in the brain. Importantly, the data support a special role for the liver in succinate handling upon reoxygenation, as suggested by a drastic increase of components of the ETS and uncoupling protein 2, which could allow for succinate metabolism without excessive formation of reactive oxygen species (ROS). Also during reoxygenation, the levels of proteins involved in the cristae junction organization of the mitochondria changed in the heart, possibly functioning to suppress ROS formation. Furthermore, proteins involved in immune (complement) system activation changed in the anoxic heart compared to normoxic controls. The results emphasize that responses to anoxia are highly tissue-specific and related to organ function.
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Affiliation(s)
| | - Bernd Thiede
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Jan Haug Anonsen
- Department of Biosciences, University of Oslo, Oslo, Norway
- Climate & Environment Department, NORCE, Norwegian Research Centre AS, Stavanger, Norway
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6
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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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7
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Galli GLJ, Shiels HA, White E, Couturier CS, Stecyk JAW. The air-breathing Alaska blackfish (Dallia pectoralis) suppresses brain mitochondrial reactive oxygen species to survive cold hypoxic winters. Comp Biochem Physiol A Mol Integr Physiol 2023; 276:111355. [PMID: 36529208 DOI: 10.1016/j.cbpa.2022.111355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 12/13/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022]
Abstract
The Alaska blackfish (Dallia pectoralis) is the only air-breathing fish in the Arctic. In the summer, a modified esophagus allows the fish to extract oxygen from the air, but this behavior is not possible in the winter because of ice and snow cover. The lack of oxygen (hypoxia) and near freezing temperatures in winter is expected to severely compromise metabolism, and yet remarkably, overwintering Alaska blackfish remain active. To maintain energy balance in the brain and limit the accumulation of reactive oxygen species (ROS), we hypothesized that cold hypoxic conditions would trigger brain mitochondrial remodeling in the Alaska blackfish. To address this hypothesis, fish were acclimated to warm (15 °C) normoxia, cold (5 °C) normoxia or cold hypoxia (5 °C, 2.1-4.2 kPa; no air access) for 5-8 weeks. Mitochondrial respiration, ADP affinity and H202 production were measured at 10 °C in isolated brain homogenates with an Oroboros respirometer. Cold acclimation and chronic hypoxia had no effects on mitochondrial aerobic capacity or ADP affinity. However, cold acclimation in normoxia led to a suppression of brain mitochondrial H202 production, which persisted and became more pronounced in the cold hypoxic fish. Overall, our study suggests cold acclimation supresses ROS production in Alaska blackfish, which may protect the fish from oxidative stress when oxygen becomes limited during winter.
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Affiliation(s)
- Gina L J Galli
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, 46 Grafton Street, Manchester M13 9NT, United Kingdom.
| | - Holly A Shiels
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, 46 Grafton Street, Manchester M13 9NT, United Kingdom
| | - Ed White
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Christine S Couturier
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America
| | - Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America
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8
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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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9
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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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10
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Fago A. New insights into survival strategies to oxygen deprivation in anoxia-tolerant vertebrates. Acta Physiol (Oxf) 2022; 235:e13841. [PMID: 35548887 PMCID: PMC9287066 DOI: 10.1111/apha.13841] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 05/09/2022] [Accepted: 05/09/2022] [Indexed: 11/23/2022]
Abstract
Hypoxic environments pose a severe challenge to vertebrates and even short periods of oxygen deprivation are often lethal as they constrain aerobic ATP production. However, a few ectotherm vertebrates are capable of surviving long‐term hypoxia or even anoxia with little or no damage. Among these, freshwater turtles and crucian carp are the recognized champions of anoxia tolerance, capable of overwintering in complete oxygen deprivation for months at freezing temperatures by entering a stable hypometabolic state. While all steps of the oxygen cascade are adjusted in response to oxygen deprivation, this review draws from knowledge of freshwater turtles and crucian carp to highlight mechanisms regulating two of these steps, namely oxygen transport in the blood and oxygen utilization in mitochondria during three sequential phases: before anoxia, when hypoxia develops, during anoxia, and after anoxia at reoxygenation. In cold hypoxia, reduced red blood cell concentration of ATP plays a crucial role in increasing blood oxygen affinity and/or reducing oxygen unloading to tissues, to adjust aerobic metabolism to decrease ambient oxygen. In anoxia, metabolic rewiring of oxygen utilization keeps largely unaltered NADH/NAD+ ratios and limits ADP degradation and succinate buildup. These critical adjustments make it possible to restart mitochondrial respiration and energy production with little generation of reactive oxygen species at reoxygenation when oxygen is again available. Inhibition of key metabolic enzymes seems to play crucial roles in these responses, in particular mitochondrial complex V, although identifying the nature of such inhibition(s) in vivo remains a challenge for future studies.
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Affiliation(s)
- Angela Fago
- Department of Biology Aarhus University Aarhus Denmark
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11
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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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12
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Huynh KW, Pamenter ME. Lactate inhibits naked mole-rat cardiac mitochondrial respiration. J Comp Physiol B 2022; 192:501-511. [PMID: 35181821 DOI: 10.1007/s00360-022-01430-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 01/13/2022] [Accepted: 01/29/2022] [Indexed: 12/25/2022]
Abstract
In aerobic conditions, the proton-motive force drives oxidative phosphorylation (OXPHOS) and the conversion of ADP to ATP. In hypoxic environments, OXPHOS is impaired, resulting in energy shortfalls and the accumulation of protons and lactate. This results in cellular acidification, which may impact the activity and/or integrity of mitochondrial enzymes and in turn negatively impact mitochondrial respiration and thus aerobic ATP production. Naked mole-rats (NMRs) are among the most hypoxia-tolerant mammals and putatively experience intermittent hypoxia in their underground burrows. However, if and how NMR cardiac mitochondria are impacted by lactate accumulation in hypoxia is unknown. We predicted that lactate alters mitochondrial respiration in NMR cardiac muscle. To test this, we used high-resolution respirometry to measure mitochondrial respiration in permeabilized cardiac muscle fibres from NMRs exposed to 4 h of in vivo normoxia (21% O2) or hypoxia (7% O2). We found that: (1) cardiac mitochondria cannot directly oxidize lactate, but surprisingly, (2) lactate inhibits mitochondrial respiration, and (3) decreases complex IV maximum respiratory capacity. Finally, (4) in vivo hypoxic exposure decreases the magnitude of lactate-mediated inhibition of mitochondrial respiration. Taken together, our results suggest that lactate may retard electron transport system function in NMR cardiac mitochondria, particularly in normoxia, and that NMR hearts may be primed for anaerobic metabolism.
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Affiliation(s)
- Kenny W Huynh
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt., Ottawa, ON, K1N 6N5, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt., Ottawa, ON, K1N 6N5, Canada. .,University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
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13
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Okoye CN, Chinnappareddy N, Stevens D, Kamunde C. Anoxia-reoxygenation modulates cadmium-induced liver mitochondrial reactive oxygen species emission during oxidation of glycerol 3-phosphate. Comp Biochem Physiol C Toxicol Pharmacol 2022; 252:109227. [PMID: 34728389 DOI: 10.1016/j.cbpc.2021.109227] [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: 07/14/2021] [Revised: 10/20/2021] [Accepted: 10/27/2021] [Indexed: 11/03/2022]
Abstract
Aquatic organisms are frequently exposed to multiple stressors including low dissolved oxygen (O2) and metals such as cadmium (Cd). Reduced O2 concentration and Cd exposure alter cellular function in part by impairing energy metabolism and dysregulating reactive oxygen species (ROS) homeostasis. However, little is known about the role of mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) in ROS homeostasis in fish and its response to environmental stress. In this study, mGPDH activity and the effects of anoxia-reoxygenation (A-RO) and Cd on ROS (as hydrogen peroxide, H2O2) emission in rainbow trout liver mitochondria during oxidation of glycerol 3-phosphate (G3P) were probed. Trout liver mitochondria exhibited low mGPDH activity that supported a low respiratory rate but substantial H2O2 emission rate. Cd evoked a low concentration stimulatory-high concentration inhibitory H2O2 emission pattern that was blunted by A-RO. At specific redox centers, Cd suppressed H2O2 emission from site IQ, but stimulated emission from sites IIIQo and GQ. In contrast, A-RO stimulated H2O2 emission from site IQ following 15 min exposure and augmented Cd-stimulated emission from site IIF after 30 min exposure but did not alter the rate of H2O2 emission from sites IIIQo and GQ. Additionally, Cd neither altered the activities of catalase, glutathione peroxidase, or thioredoxin reductase nor the concentrations of total glutathione, reduced glutathione, or oxidized glutathione. Overall, this study indicates that oxidation of G3P drives ROS production from mGPDH and complexes I, II and III, whereas Cd directly modulates redox sites but not antioxidant defense systems to alter mitochondrial H2O2 emission.
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Affiliation(s)
- Chidozie N Okoye
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada
| | - Nirmala Chinnappareddy
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada
| | - Don Stevens
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada
| | - Collins Kamunde
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
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14
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Sartori MR, Navarro CDC, Castilho RF, Vercesi AE. Enhanced resistance to Ca2+-induced mitochondrial permeability transition in the long-lived red-footed tortoise Chelonoidis carbonaria. J Exp Biol 2022; 225:jeb243532. [PMID: 34904632 DOI: 10.1242/jeb.243532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 12/08/2021] [Indexed: 11/20/2022]
Abstract
The interaction between supraphysiological cytosolic Ca2+ levels and mitochondrial redox imbalance mediates the mitochondrial permeability transition (MPT). The MPT is involved in cell death, diseases and aging. This study compared the liver mitochondrial Ca2+ retention capacity and oxygen consumption in the long-lived red-footed tortoise (Chelonoidis carbonaria) with those in the rat as a reference standard. Mitochondrial Ca2+ retention capacity, a quantitative measure of MPT sensitivity, was remarkably higher in tortoises than in rats. This difference was minimized in the presence of the MPT inhibitors ADP and cyclosporine A. However, the Ca2+ retention capacities of tortoise and rat liver mitochondria were similar when both MPT inhibitors were present simultaneously. NADH-linked phosphorylating respiration rates of tortoise liver mitochondria represented only 30% of the maximal electron transport system capacity, indicating a limitation imposed by the phosphorylation system. These results suggested underlying differences in putative MPT structural components [e.g. ATP synthase, adenine nucleotide translocase (ANT) and cyclophilin D] between tortoises and rats. Indeed, in tortoise mitochondria, titrations of inhibitors of the oxidative phosphorylation components revealed a higher limitation of ANT. Furthermore, cyclophilin D activity was approximately 70% lower in tortoises than in rats. Investigation of critical properties of mitochondrial redox control that affect MPT demonstrated that tortoise and rat liver mitochondria exhibited similar rates of H2O2 release and glutathione redox status. Overall, our findings suggest that constraints imposed by ANT and cyclophilin D, putative components or regulators of the MPT pore, are associated with the enhanced resistance to Ca2+-induced MPT in tortoises.
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Affiliation(s)
- Marina R Sartori
- Department of Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, SP 13083-887, Brazil
| | - Claudia D C Navarro
- Department of Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, SP 13083-887, Brazil
| | - Roger F Castilho
- Department of Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, SP 13083-887, Brazil
| | - Anibal E Vercesi
- Department of Pathology, Faculty of Medical Sciences, University of Campinas, Campinas, SP 13083-887, Brazil
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15
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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: 14] [Impact Index Per Article: 4.7] [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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16
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Heinrichs-Caldas W, de Almeida-Val VMF. Hypoxia tolerance in two amazon cichlids: mitochondrial respiration and cellular metabolism adjustments are result of species environmental preferences and distribution. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1759-1775. [PMID: 34480679 DOI: 10.1007/s10695-021-01000-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 08/08/2021] [Indexed: 06/13/2023]
Abstract
The amazon fishes' responses to hypoxia seem to be related to the Amazon basin diversity of aquatic environments, which present drastic daily and seasonal variations in the dissolved oxygen concentration. Among these fishes' adaptation to hypoxia, behavioral, metabolic, physiological, and biochemical responses are well known for some species. In this work, we aimed to identify how two different aquatic environments, normoxic forest streams and hypoxic lakes, dictate the responses to hypoxia for two cichlid species, Mesonauta festivus and Aequidens pallidus. In our results, we found that A. pallidus is less tolerant to hypoxia, which seems to be related to this animal's natural normoxic environment. Even though this species modulated the mitochondrial respiration in order to improve the oxygen use, it also showed a lower decrease in metabolic rate when exposed to hypoxia and no activation of the anaerobic metabolism. Instead, M. festivus showed a higher decrease in metabolic rate and an activation of the anaerobic metabolism. Our data reveal that the natural dissolved oxygen influences the hypoxia tolerance and the species' tolerance is related to its ability to perform metabolic depression. The interest results are the absence of mitochondrial respiration influences in these processes. The results observed with A. pallidus bring to light also the importance of preserving the forests, in which streams hold very specialized species acclimated to normoxia and lower temperature. The importance of hypoxia tolerance is, thus, important to keep fish assemblage and is thought to be a strong driver of fish biodiversity.
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Affiliation(s)
- Waldir Heinrichs-Caldas
- LEEM - Laboratório de Ecofisiologia e Evolução Molecular, Instituto Nacional de Pesquisas da Amazônia, Campus I, Manaus, Amazonas, Brazil.
| | - Vera Maria Fonseca de Almeida-Val
- LEEM - Laboratório de Ecofisiologia e Evolução Molecular, Instituto Nacional de Pesquisas da Amazônia, Campus I, Manaus, Amazonas, Brazil
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17
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Steffen JBM, Haider F, Sokolov EP, Bock C, Sokolova IM. Mitochondrial capacity and reactive oxygen species production during hypoxia and reoxygenation in the ocean quahog, Arctica islandica. J Exp Biol 2021; 224:272605. [PMID: 34697625 DOI: 10.1242/jeb.243082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/06/2021] [Indexed: 11/20/2022]
Abstract
Oxygen fluctuations are common in marine waters, and hypoxia-reoxygenation (H-R) stress can negatively affect mitochondrial metabolism. The long-lived ocean quahog, Arctica islandica, is known for its hypoxia tolerance associated with metabolic rate depression, yet the mechanisms that sustain mitochondrial function during oxygen fluctuations are not well understood. We used top-down metabolic control analysis (MCA) to determine aerobic capacity and control over oxygen flux in the mitochondria of quahogs exposed to short-term hypoxia (24 h <0.01% O2) and subsequent reoxygenation (1.5 h 21% O2) compared with normoxic control animals (21% O2). We demonstrated that flux capacity of the substrate oxidation and proton leak subsystems were not affected by hypoxia, while the capacity of the phosphorylation subsystem was enhanced during hypoxia associated with a depolarization of the mitochondrial membrane. Reoxygenation decreased the oxygen flux capacity of all three mitochondrial subsystems. Control over oxidative phosphorylation (OXPHOS) respiration was mostly exerted by substrate oxidation regardless of H-R stress, whereas control by the proton leak subsystem of LEAK respiration increased during hypoxia and returned to normoxic levels during reoxygenation. During hypoxia, reactive oxygen species (ROS) efflux was elevated in the LEAK state, whereas it was suppressed in the OXPHOS state. Mitochondrial ROS efflux returned to normoxic control levels during reoxygenation. Thus, mitochondria of A. islandica appear robust to hypoxia by maintaining stable substrate oxidation and upregulating phosphorylation capacity, but remain sensitive to reoxygenation. This mitochondrial phenotype might reflect adaptation of A. islandica to environments with unpredictable oxygen fluctuations and its behavioural preference for low oxygen levels.
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Affiliation(s)
- Jennifer B M Steffen
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18059 Rostock, Germany
| | - Fouzia Haider
- 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, Warnemünde, 18119 Rostock, 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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18
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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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19
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Alderman SL, Riggs CL, Bullingham OMN, Gillis TE, Warren DE. Cold acclimation induces life stage-specific responses in the cardiac proteome of western painted turtles (Chrysemys picta bellii): implications for anoxia tolerance. J Exp Biol 2021; 224:271114. [PMID: 34328184 DOI: 10.1242/jeb.242387] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 06/24/2021] [Indexed: 12/18/2022]
Abstract
Western painted turtles (Chrysemys picta bellii) are the most anoxia-tolerant tetrapod. Survival time improves at low temperature and during ontogeny, such that adults acclimated to 3°C survive far longer without oxygen than either warm-acclimated adults or cold-acclimated hatchlings. As protein synthesis is rapidly suppressed to save energy at the onset of anoxia exposure, this study tested the hypothesis that cold acclimation would evoke preparatory changes in protein expression to support enhanced anoxia survival in adult but not hatchling turtles. To test this, adult and hatchling turtles were acclimated to either 20°C (warm) or 3°C (cold) for 5 weeks, and then the heart ventricles were collected for quantitative proteomic analysis. The relative abundance of 1316 identified proteins was compared between temperatures and developmental stages. The effect of cold acclimation on the cardiac proteome was only evident in the context of an interaction with life stage, suggesting that ontogenic differences in anoxia tolerance may be predicated on successful maturation of the heart. The main differences between the hatchling and adult cardiac proteomes reflect an increase in metabolic scope with age that included more myoglobin and increased investment in both aerobic and anaerobic energy pathways. Mitochondrial structure and function were key targets of the life stage- and temperature-induced changes to the cardiac proteome, including reduced Complex II proteins in cold-acclimated adults that may help down-regulate the electron transport system and avoid succinate accumulation during anoxia. Therefore, targeted cold-induced changes to the cardiac proteome may be a contributing mechanism for stage-specific anoxia tolerance in turtles.
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Affiliation(s)
- Sarah L Alderman
- Department of Integrative Biology, University of Guelph, ON, Canada, N1G 2W1
| | - Claire L Riggs
- Department of Biology, Saint Louis University, St Louis, MO 63103, USA.,Division of Rheumatology, Inflammation, and Immunity, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Todd E Gillis
- Department of Integrative Biology, University of Guelph, ON, Canada, N1G 2W1
| | - Daniel E Warren
- Department of Biology, Saint Louis University, St Louis, MO 63103, USA
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20
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Galli GLJ, Ruhr IM, Crossley J, Crossley DA. The Long-Term Effects of Developmental Hypoxia on Cardiac Mitochondrial Function in Snapping Turtles. Front Physiol 2021; 12:689684. [PMID: 34262478 PMCID: PMC8273549 DOI: 10.3389/fphys.2021.689684] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 06/03/2021] [Indexed: 01/05/2023] Open
Abstract
It is well established that adult vertebrates acclimatizing to hypoxic environments undergo mitochondrial remodeling to enhance oxygen delivery, maintain ATP, and limit oxidative stress. However, many vertebrates also encounter oxygen deprivation during embryonic development. The effects of developmental hypoxia on mitochondrial function are likely to be more profound, because environmental stress during early life can permanently alter cellular physiology and morphology. To this end, we investigated the long-term effects of developmental hypoxia on mitochondrial function in a species that regularly encounters hypoxia during development-the common snapping turtle (Chelydra serpentina). Turtle eggs were incubated in 21% or 10% oxygen from 20% of embryonic development until hatching, and both cohorts were subsequently reared in 21% oxygen for 8 months. Ventricular mitochondria were isolated, and mitochondrial respiration and reactive oxygen species (ROS) production were measured with a microrespirometer. Compared to normoxic controls, juvenile turtles from hypoxic incubations had lower Leak respiration, higher P:O ratios, and reduced rates of ROS production. Interestingly, these same attributes occur in adult vertebrates that acclimatize to hypoxia. We speculate that these adjustments might improve mitochondrial hypoxia tolerance, which would be beneficial for turtles during breath-hold diving and overwintering in anoxic environments.
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Affiliation(s)
- Gina L. J. Galli
- Faculty of Biology, Medicine, and Health, School of Medical Sciences, The University of Manchester, Manchester, United Kingdom
| | - Ilan M. Ruhr
- Faculty of Biology, Medicine, and Health, School of Medical Sciences, The University of Manchester, Manchester, United Kingdom
| | - Janna Crossley
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, United States
| | - Dane A. Crossley
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, United States
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21
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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: 11] [Impact Index Per Article: 3.7] [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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22
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Bundgaard A, Jensen BS, Jensen FB, Fago A. Exploring pathways of NO and H2S signaling in metabolic depression: The case of anoxic turtles. Comp Biochem Physiol A Mol Integr Physiol 2021; 253:110857. [DOI: 10.1016/j.cbpa.2020.110857] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/24/2020] [Accepted: 11/24/2020] [Indexed: 02/06/2023]
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23
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Cox GK, Gillis TE. Surviving anoxia: the maintenance of energy production and tissue integrity during anoxia and reoxygenation. J Exp Biol 2020; 223:223/13/jeb207613. [DOI: 10.1242/jeb.207613] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
ABSTRACT
The development of anoxia within tissues represents a significant challenge to most animals because of the decreased capacity for aerobic ATP production, the associated loss of essential cellular functions and the potential for detrimental tissue oxidation upon reoxygenation. Despite these challenges, there are many animals from multiple phyla that routinely experience anoxia and can fully recover. In this Review, we integrate knowledge gained from studies of anoxia-tolerant species across many animal taxa. We primarily focus on strategies used to reduce energy requirements, minimize the consequences of anaerobic ATP production and reduce the adverse effects of reactive oxygen species, which are responsible for tissue damage with reoxygenation. We aim to identify common strategies, as well as novel solutions, to the challenges of anoxia exposure. This Review chronologically examines the challenges faced by animals as they enter anoxia, as they attempt to maintain physiological function during prolonged anoxic exposure and, finally, as they emerge from anoxia. The capacity of animals to survive anoxia is also considered in relation to the increasing prevalence of anoxic zones within marine and freshwater environments, and the need to understand what limits survival.
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Affiliation(s)
- Georgina K. Cox
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Todd E. Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1
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24
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Bundgaard A, Ruhr IM, Fago A, Galli GL. Metabolic adaptations to anoxia and reoxygenation: New lessons from freshwater turtles and crucian carp. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/j.coemr.2020.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Sokolova IM, Sokolov EP, Haider F. Mitochondrial Mechanisms Underlying Tolerance to Fluctuating Oxygen Conditions: Lessons from Hypoxia-Tolerant Organisms. Integr Comp Biol 2020; 59:938-952. [PMID: 31120535 DOI: 10.1093/icb/icz047] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oxygen (O2) is essential for most metazoan life due to its central role in mitochondrial oxidative phosphorylation (OXPHOS), which generates >90% of the cellular adenosine triphosphate. O2 fluctuations are an ultimate mitochondrial stressor resulting in mitochondrial damage, energy deficiency, and cell death. This work provides an overview of the known and putative mechanisms involved in mitochondrial tolerance to fluctuating O2 conditions in hypoxia-tolerant organisms including aquatic and terrestrial vertebrates and invertebrates. Mechanisms of regulation of the mitochondrial OXPHOS and electron transport system (ETS) (including alternative oxidases), sulphide tolerance, regulation of redox status and mitochondrial quality control, and the potential role of hypoxia-inducible factor (HIF) in mitochondrial tolerance to hypoxia are discussed. Mitochondrial phenotypes of distantly related animal species reveal common features including conservation and/or anticipatory upregulation of ETS capacity, suppression of reactive oxygen species (ROS)-producing electron flux through ubiquinone, reversible suppression of OXPHOS activity, and investment into the mitochondrial quality control mechanisms. Despite the putative importance of oxidative stress in adaptations to hypoxia, establishing the link between hypoxia tolerance and mitochondrial redox mechanisms is complicated by the difficulties of establishing the species-specific concentration thresholds above which the damaging effects of ROS outweigh their potentially adaptive signaling function. The key gaps in our knowledge about the potential mechanisms of mitochondrial tolerance to hypoxia include regulation of mitochondrial biogenesis and fusion/fission dynamics, and HIF-dependent metabolic regulation that require further investigation in hypoxia-tolerant species. Future physiological, molecular and genetic studies of mitochondrial responses to hypoxia, and reoxygenation in phylogenetically diverse hypoxia-tolerant species could reveal novel solutions to the ubiquitous and metabolically severe problem of O2 deficiency and would have important implications for understanding the evolution of hypoxia tolerance and the potential mitigation of pathological states caused by O2 fluctuations.
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Affiliation(s)
- Inna M Sokolova
- Department of Marine Biology, University of Rostock, Rostock, Germany.,Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
| | - Eugene P Sokolov
- Leibniz Institute for Baltic Sea Research, Leibniz ScienceCampus Phosphorus Research Rostock, Warnemünde, Germany
| | - Fouzia Haider
- Department of Marine Biology, University of Rostock, Rostock, Germany
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26
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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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27
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Lau GY, Milsom WK, Richards JG, Pamenter ME. Heart mitochondria from naked mole-rats (Heterocephalus glaber) are more coupled, but similarly susceptible to anoxia-reoxygenation stress than in laboratory mice (Mus musculus). Comp Biochem Physiol B Biochem Mol Biol 2019; 240:110375. [PMID: 31678269 DOI: 10.1016/j.cbpb.2019.110375] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/17/2019] [Accepted: 10/25/2019] [Indexed: 11/30/2022]
Abstract
Naked mole-rats (Heterocephalus glaber; NMRs) are among the most hypoxia-tolerant mammals described to date and exhibit plastic responses during hypoxia exposure. The goal of the present study was to determine if heart mitochondria from NMRs functionally differ from those of hypoxia-intolerant common laboratory mice (Mus musculus). We assessed heart mitochondrial respiratory flux, proton leak kinetics, responses to in vitro anoxia-recovery, and maximal complex enzyme activities. When investigated at their respective body temperatures (28 °C for NMR and 37 °C for mice), NMR heart mitochondria had lower respiratory fluxes relative to mice, particularly for state 2 and oligomycin-induced state 4 leak respiration rates. When leak respiration rates were standardized to the same membrane potential, NMR mitochondria had lower complex II-stimulated state 2 respiration rates than mice. Both mice and NMRs responded similarly to an in vitro anoxia-recovery challenge and decreased state 3 respiration rate post-anoxia. Finally, NMRs had overall lower maximal complex enzyme activities compared with mice, but the magnitude of the difference did not correspond with observed differences in respiratory fluxes. Overall, heart mitochondria from NMRs appear more coupled than those of mice, but in both species the heart appears equally susceptible to ischemic-reperfusion injury.
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Affiliation(s)
- G Y Lau
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - W K Milsom
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J G Richards
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - M E Pamenter
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
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Bundgaard A, Qvortrup K, Rasmussen LJ, Fago A. Turtles maintain mitochondrial integrity but reduce mitochondrial respiratory capacity in the heart after cold acclimation and anoxia. ACTA ACUST UNITED AC 2019; 222:jeb.200410. [PMID: 31097599 DOI: 10.1242/jeb.200410] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 05/11/2019] [Indexed: 12/21/2022]
Abstract
Mitochondria are important to cellular homeostasis, but can become a dangerous liability when cells recover from hypoxia. Anoxia-tolerant freshwater turtles show reduced mitochondrial respiratory capacity and production of reactive oxygen species (ROS) after prolonged anoxia, but the mechanisms are unclear. Here, we investigated whether this mitochondrial suppression originates from downregulation of mitochondrial content or intrinsic activity by comparing heart mitochondria from (1) warm (25°C) normoxic, (2) cold-acclimated (4°C) normoxic and (3) cold-acclimated anoxic turtles. Transmission electron microscopy of heart ventricle revealed that these treatments did not affect mitochondrial volume density and morphology. Furthermore, neither enzyme activity, protein content nor supercomplex distribution of electron transport chain (ETC) enzymes changed significantly. Instead, our data imply that turtles inhibit mitochondrial respiration rate and ROS production by a cumulative effect of slight inhibition of ETC complexes. Together, these results show that maintaining mitochondrial integrity while inhibiting overall enzyme activities are important aspects of anoxia tolerance.
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Affiliation(s)
- Amanda Bundgaard
- Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
| | - Klaus Qvortrup
- Department of Biomedical Sciences/CFIM, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Lene Juel Rasmussen
- Center for Healthy Aging, Department of Cellular and Molecular medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Angela Fago
- Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
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Wang Y, Zhao J, Liu X, Li W, Ouyang S, Zhu X. Identification of SNPs and copy number variations in mitochondrial genes related to the reproductive capacity of the cultured Asian yellow pond turtle (Mauremys mutica). Anim Reprod Sci 2019; 205:78-87. [DOI: 10.1016/j.anireprosci.2019.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 04/13/2019] [Accepted: 04/22/2019] [Indexed: 01/20/2023]
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Cadiz L, Bundgaard A, Malte H, Fago A. Hypoxia enhances blood O 2 affinity and depresses skeletal muscle O 2 consumption in zebrafish (Danio rerio). Comp Biochem Physiol B Biochem Mol Biol 2019; 234:18-25. [PMID: 31075501 DOI: 10.1016/j.cbpb.2019.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/24/2019] [Accepted: 05/01/2019] [Indexed: 12/13/2022]
Abstract
Zebrafish (Danio rerio) are widely used animal models. Nevertheless, the mechanisms underlying hypoxia tolerance in this species have remained poorly understood. In the present study, we have determined the effects of hypoxia on blood-O2 transport properties and mitochondrial respiration rate in permeabilized muscle fibres of adult zebrafish exposed to either 1) a gradual decrease in O2 levels until fish lost equilibrium (~1 h, acute hypoxia), or 2) severe hypoxia (PO2 ∼ 15 Torr) for 48 h (prolonged hypoxia). Acute, short-term hypoxia caused an increase in hemoglobin (Hb) O2 affinity (decrease in P50), due to a decrease in erythrocyte ATP after erythrocyte swelling. No changes in isoHb expression patterns were observed between hypoxic and normoxic treatments. Prolonged hypoxia elicited additional reponses on O2 consumption: lactate accumulated in the blood, indicating that zebrafish relied on glycolysis for ATP production, and mitochondrial respiration of skeletal muscle was overall significantly inhibited. In addition, male zebrafish had higher hypoxia tolerance (measured as time to loss of equilibrium) than females. The present study contributes to our understanding of the adaptive mechanisms that allow zebrafish, and by inference other fish species, to cope with low O2 levels.
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Affiliation(s)
- Laura Cadiz
- Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Amanda Bundgaard
- Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Hans Malte
- Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Angela Fago
- Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark.
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31
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Effect of hypothermia on the functional activity of liver mitochondria of grass snake (Natrix natrix): inhibition of succinate-fueled respiration and K + transport, ROS-induced activation of mitochondrial permeability transition. J Bioenerg Biomembr 2019; 51:219-229. [PMID: 30982206 DOI: 10.1007/s10863-019-09796-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 04/04/2019] [Indexed: 12/16/2022]
Abstract
The article considers the comparative analysis of the functional activity of mitochondria isolated from the liver of grass snakes, Natrix natrix (Linnaeus, 1758) that were kept at different temperatures (23-26 °C and 4-5 °C). It was found that liver mitochondria of hypothermia-exposed grass snakes are characterized by weak coupling of oxidative phosphorylation as compared to mitochondria of active animals which is caused by inhibition of succinate-fuelled respiration in ADP-stimulated state, as well as by activation of basal non-phosphorylating rate. Inhibition of mitochondrial respiration in hibernating animals is associated with a decrease in the activity of the respiratory chain complexes of organelles. A significant decrease in the rate of K+ transport in the liver mitochondria of hibernating animals has been established. Under these conditions, a decrease in the calcium capacity of the organelles was also revealed, which indicates a decrease in the resistance of the mitochondria of hibernating animals to the induction of the Ca2+-dependent mitochondrial pore. All these changes in the functional activity of mitochondria are observed on the background of increasing H2O2 production as well as increasing the proportion of polyunsaturated fatty acids in phospholipid composition of mitochondrial membranes, which are the targets of reactive oxygen species. It can lead to increased formation of lipid peroxides and activation of destructive processes associated with the induction of Ca2+-dependent mitochondrial pore.
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32
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Kirby AR, Cox GK, Nelson D, Heuer RM, Stieglitz JD, Benetti DD, Grosell M, Crossley DA. Acute crude oil exposure alters mitochondrial function and ADP affinity in cardiac muscle fibers of young adult Mahi-mahi (Coryphaena hippurus). Comp Biochem Physiol C Toxicol Pharmacol 2019; 218:88-95. [PMID: 30658134 DOI: 10.1016/j.cbpc.2019.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mitochondrial function is critical to support aerobic metabolism through the production of ATP, and deficiencies in mitochondrial bioenergetics will directly impact the performance capacity of highly aerobic tissues such as the myocardium. Cardiac function in fish has been shown to be negatively affected by crude oil exposure, however, the mechanism for this adverse response is largely unexplored. We hypothesized that lipophilic polycyclic aromatic hydrocarbons (PAHs) found in crude oil disrupt the electron transport system (ETS) ultimately leading to mitochondrial dysfunction. In this study, mitochondrial respiration and ADP affinity we measured using high resolution respirometery in permeabilized cardiac muscle fibers of young adult Mahi-mahi (Coryphaena hippurus) after an acute (24 h) whole animal crude oil exposure. Oil exposure reduced both complex I-fueled ADP stimulated respiration (OXPHOSCI) and complex I,II-fueled ADP stimulated respiration (OXPHOSCI, CII) by 33%,while complex II-fueled ADP stimulated respiration (OXPHOSCII) was reduced by 25%. These changes were found without changes in enzyme activity or mitochondrial density between control and oil exposed Mahi. Additionally, mitochondrial affinity for ADP was decreased three-fold after acute exposure to crude oil. We purpose that acute crude oil exposure selectively impairs mitochondrial complexes of the electron transport system and ATP supply to the cell. This limited ATP supply could present several challenges to a predatory animal like the mahi; including a reliance on anaerobic metabolism and ultimately cell or tissue death as metabolic substrates are rapidly depleted. However, the impact of this impairment may only be evident under periods of increased aerobic metabolic demand.
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Affiliation(s)
- Amanda Reynolds Kirby
- Developmental and Integrative Biology Division, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Georgina K Cox
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149-1098, United States
| | - Derek Nelson
- Developmental and Integrative Biology Division, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Rachael M Heuer
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149-1098, United States
| | - John D Stieglitz
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149-1098, United States
| | - Daniel D Benetti
- Department of Marine Ecosystems and Society, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149-1098, United States
| | - Martin Grosell
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149-1098, United States
| | - Dane A Crossley
- Developmental and Integrative Biology Division, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States.
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33
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Hawrysh PJ, Buck LT. Mitochondrial matrix pH acidifies during anoxia and is maintained by the F 1F o-ATPase in anoxia-tolerant painted turtle cortical neurons. FEBS Open Bio 2019; 9:571-581. [PMID: 30984533 PMCID: PMC6443863 DOI: 10.1002/2211-5463.12612] [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: 06/08/2018] [Revised: 01/18/2019] [Accepted: 02/05/2019] [Indexed: 12/19/2022] Open
Abstract
The western painted turtle (Chrysemys picta bellii) can survive extended periods of anoxia via a series of mechanisms that serve to reduce its energetic needs. Central to these mechanisms is the response of mitochondria, which depolarize in response to anoxia in turtle pyramidal neurons due to an influx of K+. It is currently unknown how mitochondrial matrix pH is affected by this response and we hypothesized that matrix pH acidifies during anoxia due to increased K+/H+ exchanger activity. Inhibition of K+/H+ exchange via quinine led to a collapse of mitochondrial membrane potential (Ψm) during oxygenated conditions in turtle cortical neurons, as indicated by rhodamine‐123 fluorescence, and this occurred twice as quickly during anoxia which indicates an elevation in K+ conductance. Mitochondrial matrix pH acidified during anoxia, as indicated by SNARF‐1 fluorescence imaged via confocal microscopy, and further acidification occurred during anoxia when the F1Fo‐ATPase was inhibited with oligomycin‐A, indicating that ΔpH collapse is prevented during anoxic conditions. Collectively, these results indicate that the mitochondrial proton electrochemical gradient is actively preserved during anoxia to prevent a collapse of Ψm and ΔpH.
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Affiliation(s)
| | - Leslie Thomas Buck
- Department of Cell and Systems Biology University of Toronto Canada.,Department of Ecology and Evolutionary Biology University of Toronto Canada
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34
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Bundgaard A, James AM, Gruszczyk AV, Martin J, Murphy MP, Fago A. Metabolic adaptations during extreme anoxia in the turtle heart and their implications for ischemia-reperfusion injury. Sci Rep 2019; 9:2850. [PMID: 30808950 PMCID: PMC6391391 DOI: 10.1038/s41598-019-39836-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 01/30/2019] [Indexed: 02/01/2023] Open
Abstract
ATP depletion and succinate accumulation during ischemia lead to oxidative damage to mammalian organs upon reperfusion. In contrast, freshwater turtles survive weeks of anoxia at low temperatures without suffering from oxidative damage upon reoxygenation, but the mechanisms are unclear. To determine how turtles survive prolonged anoxia, we measured ~80 metabolites in hearts from cold-acclimated (5 °C) turtles exposed to 9 days anoxia and compared the results with those for normoxic turtles (25 °C) and mouse hearts exposed to 30 min of ischemia. In turtles, ATP and ADP decreased to new steady-state levels during fasting and cold-acclimation and further with anoxia, but disappeared within 30 min of ischemia in mouse hearts. High NADH/NAD+ ratios were associated with succinate accumulation in both anoxic turtles and ischemic mouse hearts. However, succinate concentrations and succinate/fumarate ratios were lower in turtle than in mouse heart, limiting the driving force for production of reactive oxygen species (ROS) upon reoxygenation in turtles. Furthermore, we show production of ROS from succinate is prevented by re-synthesis of ATP from ADP. Thus, maintenance of an ATP/ADP pool and low succinate accumulation likely protects turtle hearts from anoxia/reoxygenation injury and suggests metabolic interventions as a therapeutic approach to limit ischemia/reperfusion injury in mammals.
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Affiliation(s)
- Amanda Bundgaard
- Department of Bioscience, Aarhus University, Aarhus, Denmark
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Andrew M James
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Anja V Gruszczyk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Jack Martin
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Michael P Murphy
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK.
| | - Angela Fago
- Department of Bioscience, Aarhus University, Aarhus, Denmark.
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35
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Chen BJ, Zhang WY, Niu CJ, Li WJ, Jia H, Storey KB. Antioxidant response to acute cold exposure and following recovery in juvenile Chinese soft-shelled turtles, Pelodiscus sinensis. J Exp Biol 2019; 222:jeb.197863. [DOI: 10.1242/jeb.197863] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 12/27/2018] [Indexed: 01/28/2023]
Abstract
The antioxidant defense protects turtles from oxidative stress caused by adverse environment conditions, such as acute thermal fluctuations. However, how these defenses work remains unclear. The present study examined changes in key enzymes of the enzymatic antioxidant system and the glutathione (GSH) system at both the mRNA and enzyme activity levels during acute cold exposure and following recovery in juvenile Chinese soft-shelled turtles, Pelodiscus sinensis. Transcript levels of the upstream regulator NF-E2 related factor 2 (Nrf2) were also measured. Turtles were acclimated at 28oC (3 wks), then given acute cold exposure (8oC, 12 h) and finally placed in recovery (28oC, 24 h). The mRNA levels of cerebral and hepatic Nrf2 and of downstream antioxidant enzyme genes did not change, whereas nephric Nrf2, Manganese superoxide dismutase (MnSOD) and glutathione peroxidase 4 (GPx4) mRNAs decreased in cold exposure. During recovery, Nrf2 mRNA remained stable in all three tissues, hepatic Cu/ZnSOD, MnSOD and catalase (CAT) mRNA levels increased, and nephric MnSOD and GPx4 mRNAs did not change from the values during cold exposure. In the GSH system, mRNA levels of most enzymes remained constant during cold exposure and recovery. Unmatched with changes in mRNA level, high and stable constitutive antioxidant enzyme activities were maintained throughout whereas GPx activity significantly reduced in kidney during cold exposure and in liver and kidney during recovery. Our results suggest that the antioxidant defense regulation in response to acute cold exposure in P. sinensis may not be achieved at the transcriptional level, but may rely mainly on high constitutive antioxidant enzyme activities.
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Affiliation(s)
- Bo-jian Chen
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, P.R. China
- College of Animal Science and Technology, Northwest A and F University, Yangling 712100, P.R. China
| | - Wen-yi Zhang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, P.R. China
| | - Cui-juan Niu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, P.R. China
| | - Wen-jie Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, P.R. China
| | - Hui Jia
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, P.R. China
| | - Kenneth B. Storey
- Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
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36
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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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37
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O'Brien KM, Rix AS, Egginton S, Farrell AP, Crockett EL, Schlauch K, Woolsey R, Hoffman M, Merriman S. Cardiac mitochondrial metabolism may contribute to differences in thermal tolerance of red- and white-blooded Antarctic notothenioid fishes. J Exp Biol 2018; 221:jeb177816. [PMID: 29895681 PMCID: PMC6104818 DOI: 10.1242/jeb.177816] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 06/04/2018] [Indexed: 12/18/2022]
Abstract
Studies in temperate fishes provide evidence that cardiac mitochondrial function and the capacity to fuel cardiac work contribute to thermal tolerance. Here, we tested the hypothesis that decreased cardiac aerobic metabolic capacity contributes to the lower thermal tolerance of the haemoglobinless Antarctic icefish, Chaenocephalus aceratus, compared with that of the red-blooded Antarctic species, Notothenia coriiceps. Maximal activities of citrate synthase (CS) and lactate dehydrogenase (LDH), respiration rates of isolated mitochondria, adenylate levels and changes in mitochondrial protein expression were quantified from hearts of animals held at ambient temperature or exposed to their critical thermal maximum (CTmax). Compared with C. aceratus, activity of CS, ATP concentration and energy charge were higher in hearts of N. coriiceps at ambient temperature and CTmax While state 3 mitochondrial respiration rates were not impaired by exposure to CTmax in either species, state 4 rates, indicative of proton leakage, increased following exposure to CTmax in C. aceratus but not N. coriiceps The interactive effect of temperature and species resulted in an increase in antioxidants and aerobic metabolic enzymes in N. coriiceps but not in C. aceratus Together, our results support the hypothesis that the lower aerobic metabolic capacity of C. aceratus hearts contributes to its low thermal tolerance.
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Affiliation(s)
- Kristin M O'Brien
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Anna S Rix
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | | | - Karen Schlauch
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV 89557, USA
| | - Rebekah Woolsey
- Nevada Proteomics Center, University of Nevada, Reno, NV 89557, USA
| | - Megan Hoffman
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Sean Merriman
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
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38
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Bundgaard A, James AM, Joyce W, Murphy MP, Fago A. Suppression of reactive oxygen species generation in heart mitochondria from anoxic turtles: the role of complex I S-nitrosation. J Exp Biol 2018; 221:jeb174391. [PMID: 29496783 PMCID: PMC5963835 DOI: 10.1242/jeb.174391] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 02/26/2018] [Indexed: 12/12/2022]
Abstract
Freshwater turtles (Trachemys scripta) are among the very few vertebrates capable of tolerating severe hypoxia and re-oxygenation without suffering from damage to the heart. As myocardial ischemia and reperfusion causes a burst of mitochondrial reactive oxygen species (ROS) in mammals, the question arises as to whether, and if so how, this ROS burst is prevented in the turtle heart. We find that heart mitochondria isolated from turtles acclimated to anoxia produce less ROS than mitochondria from normoxic turtles when consuming succinate. As succinate accumulates in the hypoxic heart and is oxidized when oxygen returns, this suggests an adaptation to lessen ROS production. Specific S-nitrosation of complex I can lower ROS in mammals and here we show that turtle complex I activity and ROS production can also be strongly depressed in vitro by S-nitrosation. We detect in vivo endogenous S-nitrosated complex I in turtle heart mitochondria, but these levels are unaffected upon anoxia acclimation. Thus, while heart mitochondria from anoxia-acclimated turtles generate less ROS and have a lower aerobic capacity than those from normoxic turtles, this is not due to decreases in complex I activity or expression levels. Interestingly, in-gel activity staining reveals that most complex I of heart mitochondria from normoxic and anoxic turtles forms stable super-complexes with other respiratory enzymes and, in contrast to mammals, these are not disrupted by dodecyl maltoside. Taken together, these results show that although S-nitrosation of complex I is a potent mechanism to prevent ROS formation upon re-oxygenation after anoxia in vitro, this is not a major cause of the suppression of ROS production by anoxic turtle heart mitochondria.
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Affiliation(s)
- Amanda Bundgaard
- Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Andrew M James
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK
| | - William Joyce
- Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Michael P Murphy
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, UK
| | - Angela Fago
- Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark
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39
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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: 36] [Impact Index Per Article: 6.0] [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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40
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Gomez CR, Richards JG. Mitochondrial responses to anoxia exposure in red eared sliders (Trachemys scripta). Comp Biochem Physiol B Biochem Mol Biol 2018; 224:71-78. [PMID: 29402754 DOI: 10.1016/j.cbpb.2018.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 01/15/2018] [Accepted: 01/16/2018] [Indexed: 11/29/2022]
Abstract
When deprived oxygen, mitochondria from most vertebrates transform from the main site of ATP production to the dominant site of cellular ATP use due to the reverse functioning of the F1FO-ATPase (complex V). The anoxia-tolerant freshwater turtle Trachemys scripta however, has previously been shown to inhibit complex V activity in heart and brain in response to anoxia exposure, but the regulatory mechanism is unknown. To gain insight into the putative regulatory mechanisms underlying the anoxia-induced inhibition of complex V in T. scripta, we examined the effects of two weeks anoxia exposure at 4 °C on the mitochondrial proteome and candidate mechanisms that have been shown to regulate complex V in other organisms. In T. scripta, we confirmed that anoxia exposure resulted in a >80% inhibition of complex V in heart, brain and liver. Incubation of mitochondria with the nitric oxide donor, s-nitrosoglutathione, did not affect complex V activity despite showing the expected inhibition in mice. Proteomics analysis showed anoxia-induced decreases in three peripheral stalk subunits of complex V, possibly pointing to a unique site of regulation. Proteomics analysis also revealed differential expression of numerous enzymes involved with the electron transport system, the tricarboxylic acid cycle, as well as lipid and amino acid metabolism in response to anoxia exposure.
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Affiliation(s)
- Crisostomo R Gomez
- Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver V6T 1Z4, British Columbia, Canada
| | - Jeffrey G Richards
- Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver V6T 1Z4, British Columbia, Canada.
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Dhillon RS, Richards JG. Hypoxia induces selective modifications to the acetylome in the brain of zebrafish (Danio rerio). Comp Biochem Physiol B Biochem Mol Biol 2018; 224:79-87. [PMID: 29309913 DOI: 10.1016/j.cbpb.2017.12.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 12/18/2017] [Accepted: 12/20/2017] [Indexed: 10/18/2022]
Abstract
Reversible protein acetylation is an important regulatory mechanism for modulating protein function. The cellular protein acetylome is in large part dictated by the cellular redox balance, and in particular [NAD+]. While the relationship between hypoxia, redox balance, energy charge and resulting mitochondrial dysfunction has been examined in the context of hypoxia-linked pathologies, little is known about the direct effects of decreases in environmental oxygen on reversible lysine acetylation, and the resulting modifications to mitochondrial metabolism. To address this knowledge gap, we exposed zebrafish (Danio rerio) to 16 h of hypoxia (2.21 kPa) and quantified acetylation levels of 1220 proteins using whole-cell proteomics in samples of brain taken from normoxic and hypoxic zebrafish. In addition, we examined the effects of hypoxia on cytoplasmic and mitochondrial redox status, whole-cell energetics, the activity of the mitochondrial NAD+-dependent deacetylase SIRT3, and electron transport chain complex activities to determine if there is an association between hypoxia-induced metabolic disturbances, protein acetylation, and mitochondrial function. Our results (1) reveal several key changes in the acetylation status of proteins in the brain, primarily within the mitochondria; (2) show significant fluctuations in cytoplasmic and mitochondrial redox status within the brain during hypoxia exposure; and (3) provide evidence that lysine acetylation may be related to large changes in electron transport and ATP-synthase complex activities and adenylate status in zebrafish exposed to hypoxic stress. Together, these data provide new insights into the role of protein modifications in mitochondrial metabolism during hypoxia.
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Affiliation(s)
- Rashpal S Dhillon
- Wisconsin Institute for Discovery, Department of Biomolecular Chemistry, University of Wisconsin-Madison, 330 North Orchard Street, Madison, WI 53715, USA; Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada.
| | - Jeffrey G Richards
- Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada
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Lau GY, Richards JG. Interspecific variation in brain mitochondrial complex I and II capacity and ROS emission in marine sculpins. J Exp Biol 2018; 222:jeb.189407. [DOI: 10.1242/jeb.189407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 11/29/2018] [Indexed: 12/29/2022]
Abstract
Environmental hypoxia presents a metabolic challenge for animals because it inhibits mitochondrial respiration and can lead to the generation of reactive oxygen species (ROS). We investigated the interplay between O2 use for aerobic respiration and ROS generation among sculpin fishes (Cottidae, Actinopterygii) that are known to vary in whole-animal hypoxia tolerance. We hypothesized that mitochondria from hypoxia tolerant sculpins would show more efficient O2 use with a higher phosphorylation efficiency and lower ROS emission. We showed that brain mitochondria from more hypoxia tolerant sculpins had lower complex I and higher complex II flux capacities compared with less hypoxia tolerant sculpins, but these differences were not related to variation in phosphorylation efficiency (ADP/O) or mitochondrial coupling (respiratory control ratio). The hypoxia tolerant sculpin had higher mitochondrial H2O2 emission per O2 consumed (H2O2/O2) under oligomycin-induced state 4 conditions compared to less hypoxia tolerant sculpin. An in vitro redox challenge experiment revealed species differences in how well mitochondria defend their glutathione redox status when challenged with high levels of reduced glutathione, but the redox challenge elicited the same H2O2/O2 in all species. Furthermore, in vitro anoxia-recovery lowered absolute H2O2 emission (H2O2/mg mitochondrial protein) in all species and negatively impacted state 3 respiration rates in some species, but the responses were not related to hypoxia tolerance. Overall, we clearly demonstrate a relationship between hypoxia tolerance and complex I and II flux capacities in sculpins, but the differences in complex flux capacity do not appear to be directly related to variation in ROS metabolism.
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Affiliation(s)
- Gigi Y. Lau
- Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, B.C., Canada, V6T 1Z4
| | - Jeffrey G. Richards
- Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, B.C., Canada, V6T 1Z4
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Escalona T, Weadick CJ, Antunes A. Adaptive Patterns of Mitogenome Evolution Are Associated with the Loss of Shell Scutes in Turtles. Mol Biol Evol 2017; 34:2522-2536. [PMID: 28591857 PMCID: PMC6298445 DOI: 10.1093/molbev/msx167] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The mitochondrial genome encodes several protein components of the oxidative phosphorylation (OXPHOS) pathway and is critical for aerobic respiration. These proteins have evolved adaptively in many taxa, but linking molecular-level patterns with higher-level attributes (e.g., morphology, physiology) remains a challenge. Turtles are a promising system for exploring mitochondrial genome evolution as different species face distinct respiratory challenges and employ multiple strategies for ensuring efficient respiration. One prominent adaptation to a highly aquatic lifestyle in turtles is the secondary loss of keratenized shell scutes (i.e., soft-shells), which is associated with enhanced swimming ability and, in some species, cutaneous respiration. We used codon models to examine patterns of selection on mitochondrial protein-coding genes along the three turtle lineages that independently evolved soft-shells. We found strong evidence for positive selection along the branches leading to the pig-nosed turtle (Carettochelys insculpta) and the softshells clade (Trionychidae), but only weak evidence for the leatherback (Dermochelys coriacea) branch. Positively selected sites were found to be particularly prevalent in OXPHOS Complex I proteins, especially subunit ND2, along both positively selected lineages, consistent with convergent adaptive evolution. Structural analysis showed that many of the identified sites are within key regions or near residues involved in proton transport, indicating that positive selection may have precipitated substantial changes in mitochondrial function. Overall, our study provides evidence that physiological challenges associated with adaptation to a highly aquatic lifestyle have shaped the evolution of the turtle mitochondrial genome in a lineage-specific manner.
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Affiliation(s)
- Tibisay Escalona
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Porto, Portugal.,Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal
| | - Cameron J Weadick
- School of Life Science, Evolution, Behaviour and Environment Group, University of Sussex, Brighton, United Kingdom
| | - Agostinho Antunes
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Porto, Portugal.,Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal
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Comparative biochemistry of cytochrome c oxidase in animals. Comp Biochem Physiol B Biochem Mol Biol 2017; 224:170-184. [PMID: 29180239 DOI: 10.1016/j.cbpb.2017.11.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 11/06/2017] [Accepted: 11/07/2017] [Indexed: 12/19/2022]
Abstract
Cytochrome c oxidase (COX), the terminal enzyme of the electron transport system, is central to aerobic metabolism of animals. Many aspects of its structure and function are highly conserved, yet, paradoxically, it is also an important model for studying the evolution of the metabolic phenotype. In this review, part of a special issue honouring Peter Hochachka, we consider the biology of COX from the perspective of comparative and evolutionary biochemistry. The approach is to consider what is known about the enzyme in the context of conventional biochemistry, but focus on how evolutionary researchers have used this background to explore the role of the enzyme in biochemical adaptation of animals. In synthesizing the conventional and evolutionary biochemistry, we hope to identify synergies and future research opportunities. COX represents a rare opportunity for researchers to design studies that span the breadth of biology: molecular genetics, protein biochemistry, enzymology, metabolic physiology, organismal performance, evolutionary biology, and phylogeography.
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Intraspecific variation and plasticity in mitochondrial oxygen binding affinity as a response to environmental temperature. Sci Rep 2017; 7:16238. [PMID: 29176558 PMCID: PMC5701142 DOI: 10.1038/s41598-017-16598-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/15/2017] [Indexed: 01/19/2023] Open
Abstract
Mitochondrial function has been suggested to underlie constraints on whole-organism aerobic performance and associated hypoxia and thermal tolerance limits, but most studies have focused on measures of maximum mitochondrial capacity. Here we investigated whether variation in mitochondrial oxygen kinetics could contribute to local adaptation and plasticity in response to temperature using two subspecies of the Atlantic killifish (Fundulus heteroclitus) acclimated to a range of temperatures (5, 15, and 33 °C). The southern subspecies of F. heteroclitus, which has superior thermal and hypoxia tolerances compared to the northern subspecies, exhibited lower mitochondrial O2 P50 (higher O2 affinity). Acclimation to thermal extremes (5 or 33 °C) altered mitochondrial O2 P50 in both subspecies consistent with the effects of thermal acclimation on whole-organism thermal tolerance limits. We also examined differences between subspecies and thermal acclimation effects on whole-blood Hb O2-P50 to assess whether variation in oxygen delivery is involved in these responses. In contrast to the clear differences between subspecies in mitochondrial O2-P50 there were no differences in whole-blood Hb-O2 P50 between subspecies. Taken together these findings support a general role for mitochondrial oxygen kinetics in differentiating whole-organism aerobic performance and thus in influencing species responses to environmental change.
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Gorr TA. Hypometabolism as the ultimate defence in stress response: how the comparative approach helps understanding of medically relevant questions. Acta Physiol (Oxf) 2017; 219:409-440. [PMID: 27364602 DOI: 10.1111/apha.12747] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 01/28/2016] [Accepted: 06/28/2016] [Indexed: 12/22/2022]
Abstract
First conceptualized from breath-hold diving mammals, later recognized as the ultimate cell autonomous survival strategy in anoxia-tolerant vertebrates and burrowing or hibernating rodents, hypometabolism is typically recruited by resilient organisms to withstand and recover from otherwise life-threatening hazards. Through the coordinated down-regulation of biosynthetic, proliferative and electrogenic expenditures at times when little ATP can be generated, a metabolism turned 'down to the pilot light' allows the re-balancing of energy demand with supply at a greatly suppressed level in response to noxious exogenous stimuli or seasonal endogenous cues. A unifying hallmark of stress-tolerant organisms, the adaptation effectively prevents lethal depletion of ATP, thus delineating a marked contrast with susceptible species. Along with disengaged macromolecular syntheses, attenuated transmembrane ion shuttling and PO2 -conforming respiration rates, the metabolic slowdown in tolerant species usually culminates in a non-cycling, quiescent phenotype. However, such a reprogramming also occurs in leading human pathophysiologies. Ranging from microbial infections through ischaemia-driven infarcts to solid malignancies, cells involved in these disorders may again invoke hypometabolism to endure conditions non-permissive for growth. At the same time, their reduced activities underlie the frequent development of a general resistance to therapeutic interventions. On the other hand, a controlled induction of hypometabolic and/or hypothermic states by pharmacological means has recently stimulated intense research aimed at improved organ preservation and patient survival in situations requiring acutely administered critical care. The current review article therefore presents an up-to-date survey of concepts and applications of a coordinated and reversibly down-regulated metabolic rate as the ultimate defence in stress responses.
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Affiliation(s)
- T. A. Gorr
- Institute of Veterinary Physiology; Vetsuisse Faculty; University of Zurich; Zurich Switzerland
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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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Galli GLJ, Crossley J, Elsey RM, Dzialowski EM, Shiels HA, Crossley DA. Developmental plasticity of mitochondrial function in American alligators, Alligator mississippiensis. Am J Physiol Regul Integr Comp Physiol 2016; 311:R1164-R1172. [PMID: 27707718 PMCID: PMC5256979 DOI: 10.1152/ajpregu.00107.2016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 10/03/2016] [Accepted: 10/03/2016] [Indexed: 12/22/2022]
Abstract
The effect of hypoxia on cellular metabolism is well documented in adult vertebrates, but information is entirely lacking for embryonic organisms. The effect of hypoxia on embryonic physiology is particularly interesting, as metabolic responses during development may have life-long consequences, due to developmental plasticity. To this end, we investigated the effects of chronic developmental hypoxia on cardiac mitochondrial function in embryonic and juvenile American alligators (Alligator mississippiensis). Alligator eggs were incubated in 21% or 10% oxygen from 20 to 90% of embryonic development. Embryos were either harvested at 90% development or allowed to hatch and then reared in 21% oxygen for 3 yr. Ventricular mitochondria were isolated from embryonic/juvenile alligator hearts. Mitochondrial respiration and enzymatic activities of electron transport chain complexes were measured with a microrespirometer and spectrophotometer, respectively. Developmental hypoxia induced growth restriction and increased relative heart mass, and this phenotype persisted into juvenile life. Embryonic mitochondrial function was not affected by developmental hypoxia, but at the juvenile life stage, animals from hypoxic incubations had lower levels of Leak respiration and higher respiratory control ratios, which is indicative of enhanced mitochondrial efficiency. Our results suggest developmental hypoxia can have life-long consequences for alligator morphology and metabolic function. Further investigations are necessary to reveal the adaptive significance of the enhanced mitochondrial efficiency in the hypoxic phenotype.
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Affiliation(s)
- Gina L J Galli
- Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom;
| | - Janna Crossley
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, Texas; and
| | - Ruth M Elsey
- Rockefeller Wildlife Refuge, Grand Chenier, Louisiana
| | - Edward M Dzialowski
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, Texas; and
| | - Holly A Shiels
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Dane A Crossley
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, Texas; and
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Sappal R, Fast M, Purcell S, MacDonald N, Stevens D, Kibenge F, Siah A, Kamunde C. Copper and hypoxia modulate transcriptional and mitochondrial functional-biochemical responses in warm acclimated rainbow trout (Oncorhynchus mykiss). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 211:291-306. [PMID: 26774776 DOI: 10.1016/j.envpol.2015.11.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 11/26/2015] [Accepted: 11/27/2015] [Indexed: 06/05/2023]
Abstract
To survive in changing environments fish utilize a wide range of biological responses that require energy. We examined the effect of warm acclimation on the electron transport system (ETS) enzymes and transcriptional responses to hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperatures for 3 weeks followed by exposure to Cu, hypoxia or both for 24 h. Activities of ETS enzyme complexes I-IV (CI-CIV) were measured in liver and gill mitochondria. Analyses of transcripts encoding for proteins involved in mitochondrial respiration (cytochrome c oxidase subunits 4-1 and 2: COX4-1 and COX4-2), metal detoxification/stress response (metallothioneins A and B: MT-A and MT-B) and energy sensing (AMP-activated protein kinase α1: AMPKα1) were done in liver mitochondria, and in whole liver and gill tissues by RT-qPCR. Warm acclimation inhibited activities of ETS enzymes while effects of Cu and hypoxia depended on the enzyme and thermal acclimation status. The genes encoding for COX4-1, COX4-2, MT-A, MT-B and AMPKα1 were strongly and tissue-dependently altered by warm acclimation. While Cu and hypoxia clearly increased MT-A and MT-B transcript levels in all tissues, their effects on COX4-1, COX4-2 and AMPKα1 mRNA levels were less pronounced. Importantly, warm acclimation differentially altered COX4-2/COX4-1 ratio in liver mitochondria and gill tissue. The three stressors showed both independent and joint actions on activities of ETS enzymes and transcription of genes involved in energy metabolism, stress response and metals homeostasis. Overall, we unveiled novel interactive effects that should not be overlooked in real world situations wherein fish normally encounter multiple stress factors.
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Affiliation(s)
- Ravinder Sappal
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada; Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Mark Fast
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Sara Purcell
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Nicole MacDonald
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Don Stevens
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Fred Kibenge
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada
| | - Ahmed Siah
- British Columbia Centre for Aquatic Health Sciences, 871A Island Highway, Campbell River, BC V9W 2C2, Canada
| | - Collins Kamunde
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
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