1
|
Lumor L, Bock C, Mark FC, Ponsuksili S, Sokolova I. Effects of hypoxia-reoxygenation on the bioenergetics and oxidative stress in the isolated mitochondria of the king scallop, Pecten maximus. J Exp Biol 2025; 228:jeb249870. [PMID: 40289682 PMCID: PMC12091870 DOI: 10.1242/jeb.249870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2024] [Accepted: 04/11/2025] [Indexed: 04/30/2025]
Abstract
The king scallop (Pecten maximus) is a highly aerobic subtidal bivalve species vulnerable to fluctuations in oxygen availability. This study investigated the effects of short-term (15 min) and long-term (90 min) hypoxia-reoxygenation (H/R) stress on substrate-specific mitochondrial functions in the gill and digestive gland tissues of P. maximus, oxidizing substrates that engage mitochondrial Complex I (pyruvate, palmitate) and Complex II (succinate). Under normoxic conditions, scallop mitochondria preferentially oxidized pyruvate. H/R stress induced a significant decline in Complex I-driven ATP synthesis, increased proton leak and dysregulated fatty acid oxidation, indicating mitochondrial vulnerability to H/R stress. Following H/R, both tissues demonstrated a greater capacity for succinate oxidation than for Complex I substrates; however, long-term H/R exposure led to a reduction in respiratory coupling efficiency across all substrates. Notably, gill mitochondria exhibited more effective regulation of reactive oxygen species efflux and electron leak compared with digestive gland mitochondria under H/R stress. Despite these physiological changes, no evidence of oxidative damage was detected, suggesting the presence of a robust mitochondrial antioxidant defense. Collectively, these findings suggest that succinate oxidation plays an important role in stress recovery in P. maximus, providing insights into mitochondrial resilience and the management of oxidative stress during intermittent hypoxia.
Collapse
Affiliation(s)
- Linda Lumor
- Institute for Farm Animal Biology (FBN), Institute of Genome Biology, 18196 Dummerstorf, Germany
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, 18059 Rostock, Germany
| | - Christian Bock
- Integrative Ecophysiology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27515 Bremerhaven, Germany
| | - Felix Christopher Mark
- Integrative Ecophysiology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27515 Bremerhaven, Germany
| | - Siriluck Ponsuksili
- Institute for Farm Animal Biology (FBN), Institute of Genome Biology, 18196 Dummerstorf, Germany
| | - Inna Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, 18059 Rostock, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, 18059 Rostock, Germany
| |
Collapse
|
2
|
Burzawa AM, Potera KB, Sokolov EP, Sokolova IM, Walczyńska A. Temperature-driven trade-off between mitochondrial activity and efficiency in live rotifers representing different thermal histories. J Exp Biol 2025; 228:jeb249338. [PMID: 39989280 DOI: 10.1242/jeb.249338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2024] [Accepted: 02/18/2025] [Indexed: 02/25/2025]
Abstract
Mitochondria generate up to 90% of cellular ATP, making it critical to understand how abiotic factors affect mitochondrial function under varying conditions. Using clones of the rotifer Lecane inermis with known thermal preferences, we investigated mitochondrial bioenergetic responses to four thermal regimes: standard temperature, optimal temperature, low suboptimal temperature and high suboptimal temperature. The study aimed to determine how mitochondrial parameters in intact organisms vary with temperature shifts and whether these responses differ across experimental populations. We assessed key bioenergetic parameters: routine respiration (representing overall metabolic rate), electron transport system capacity (indicative of oxidative phosphorylation potential) and proton leak rates (reflecting the energetic costs of maintaining mitochondrial membrane potential). Our results showed that populations with different thermal preferences displayed distinct mitochondrial responses to temperature changes, particularly at suboptimal temperatures. In contrast, responses were more uniform under standard and optimal conditions. Our findings demonstrated that metabolic plasticity in changing environments often involves trade-offs between mitochondrial efficiency and maintenance. By studying mitochondrial respiration at the whole-organism level, we revealed the complex temperature dependence of bioenergetic traits, providing insights beyond isolated mitochondria studies. This research highlights how a cascade of plastic responses spanning from mitochondrial responses to overall growth patterns is triggered by temperature changes, offering a valuable perspective in the context of global warming and organismal adaptation.
Collapse
Affiliation(s)
- Agata M Burzawa
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
- Doctoral School of Exact and Natural Sciences, Jagiellonian University, Prof. S. Łojasiewicza 11, 30-348 Krakow, Poland
| | - Katarzyna B Potera
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
- Doctoral School of Exact and Natural Sciences, Jagiellonian University, Prof. S. Łojasiewicza 11, 30-348 Krakow, Poland
| | - Eugene P Sokolov
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, A. Einstein Str., 3, Rostock 18055, Germany
| | - Inna M Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, A. Einstein Str., 3, Rostock 18055, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, 18059, Rostock, Germany
| | - Aleksandra Walczyńska
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| |
Collapse
|
3
|
Wiesenthal AA, Timm S, Sokolova IM. Osmotolerance reflected in mitochondrial respiration of Mytilus populations from three different habitat salinities. MARINE ENVIRONMENTAL RESEARCH 2025; 205:106968. [PMID: 39883997 DOI: 10.1016/j.marenvres.2025.106968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2024] [Revised: 01/13/2025] [Accepted: 01/15/2025] [Indexed: 02/01/2025]
Abstract
Mussels from the Mytilus edulis species complex experience a salinity gradient from the North Sea into the Baltic Proper ranging from 32 to 5. As osmoconformers, they adjust their internal osmolarity to match that of their surroundings, which presents a significant challenge to the metabolic machinery, including their mitochondria. We hypothesized that the osmotic optima for the mitochondrial function of mussels matches the prevailing habitat salinity and is accompanied by a population specific metabolite profile. To test this hypothesis, mussels from three populations along the salinity gradient were assessed. We found a population specific shift in the optimal osmolarities for maximal mitochondrial respiration capacity that mirrored the populations' habitat salinity. So, mitochondria from North Sea mussels reached their highest capacity at higher osmotic concentrations than their Baltic Sea congeners. Additionally, Baltic Sea populations appear to have traded off an adaptation to low salinities for a narrower mitochondrial tolerance range resulting in a more specialized mitochondrial phenotype, while North Sea populations have mitochondria with a more general functioning phenotype. The local adaptation to a low salinity habitat was supported by the analysis of gill tissue metabolites via LC-MS/MS. Abundances of metabolites involved in energy generation, osmotic homeostasis or the urea cycle were similar between North Sea and southern Baltic Sea mussels, while northern Baltic Sea mussels seem to follow a different metabolic strategy, which may allow them to inhabit very low salinities. Thus, northern Baltic Sea mussels have adapted to low salinities on a mitochondrial and metabolic level.
Collapse
Affiliation(s)
- Amanda A Wiesenthal
- Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Strasse 3, D - 18059, Rostock, Germany.
| | - Stefan Timm
- Plant Physiology Department, University of Rostock, Albert-Einstein-Strasse 3, D-18059, Rostock, Germany
| | - Inna M Sokolova
- Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Strasse 3, D - 18059, Rostock, Germany; Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Albert-Einstein-Strasse 21, D-18059, Rostock, Germany
| |
Collapse
|
4
|
Sabit H, Arneth B, Abdel-Ghany S, Madyan EF, Ghaleb AH, Selvaraj P, Shin DM, Bommireddy R, Elhashash A. Beyond Cancer Cells: How the Tumor Microenvironment Drives Cancer Progression. Cells 2024; 13:1666. [PMID: 39404428 PMCID: PMC11475877 DOI: 10.3390/cells13191666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2024] [Revised: 10/04/2024] [Accepted: 10/06/2024] [Indexed: 10/19/2024] Open
Abstract
Liver cancer represents a substantial global health challenge, contributing significantly to worldwide morbidity and mortality. It has long been understood that tumors are not composed solely of cancerous cells, but also include a variety of normal cells within their structure. These tumor-associated normal cells encompass vascular endothelial cells, fibroblasts, and various inflammatory cells, including neutrophils, monocytes, macrophages, mast cells, eosinophils, and lymphocytes. Additionally, tumor cells engage in complex interactions with stromal cells and elements of the extracellular matrix (ECM). Initially, the components of what is now known as the tumor microenvironment (TME) were thought to be passive bystanders in the processes of tumor proliferation and local invasion. However, recent research has significantly advanced our understanding of the TME's active role in tumor growth and metastasis. Tumor progression is now known to be driven by an intricate imbalance of positive and negative regulatory signals, primarily influenced by specific growth factors produced by both inflammatory and neoplastic cells. This review article explores the latest developments and future directions in understanding how the TME modulates liver cancer, with the aim of informing the design of novel therapies that target critical components of the TME.
Collapse
Affiliation(s)
- Hussein Sabit
- Department of Medical Biotechnology, College of Biotechnology, Misr University for Science and Technology, Giza P.O. Box 77, Egypt; (H.S.); (E.F.M.)
| | - Borros Arneth
- Institute of Laboratory Medicine and Pathobiochemistry, Molecular Diagnostics, Hospital of the Universities of Giessen and Marburg (UKGM), Philipps University Marburg, Baldinger Str., 35043 Marburg, Germany
- Institute of Laboratory Medicine and Pathobiochemistry, Molecular Diagnostics, Hospital of the Universities of Giessen and Marburg (UKGM), Justus Liebig University Giessen, Feulgenstr. 12, 35392 Giessen, Germany
| | - Shaimaa Abdel-Ghany
- Department of Environmental Biotechnology, College of Biotechnology, Misr University for Science and Technology, Giza P.O. Box 77, Egypt;
| | - Engy F. Madyan
- Department of Medical Biotechnology, College of Biotechnology, Misr University for Science and Technology, Giza P.O. Box 77, Egypt; (H.S.); (E.F.M.)
| | - Ashraf H. Ghaleb
- Department of Surgery, College of Medicine, Misr University for Science and Technology, Giza P.O. Box 77, Egypt;
- Department of Surgery, College of Medicine, Cairo University, Giza 12613, Egypt
| | - Periasamy Selvaraj
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (P.S.); (R.B.)
| | - Dong M. Shin
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA;
| | - Ramireddy Bommireddy
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (P.S.); (R.B.)
| | - Ahmed Elhashash
- Department of Biology, Texas A&M University, 3258 TAMU I, College Station, TX 77843-3258, USA
| |
Collapse
|
5
|
Adzigbli L, Ponsuksili S, Sokolova I. Mitochondrial responses to constant and cyclic hypoxia depend on the oxidized fuel in a hypoxia-tolerant marine bivalve Crassostrea gigas. Sci Rep 2024; 14:9658. [PMID: 38671046 PMCID: PMC11053104 DOI: 10.1038/s41598-024-60261-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 04/21/2024] [Indexed: 04/28/2024] Open
Abstract
Sessile benthic organisms like oysters inhabit the intertidal zone, subject to alternating hypoxia and reoxygenation (H/R) episodes during tidal movements, impacting respiratory chain activities and metabolome compositions. We investigated the effects of constant severe hypoxia (90 min at ~ 0% O2 ) followed by 10 min reoxygenation, and cyclic hypoxia (5 cycles of 15 min at ~ 0% O2 and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of Crassostrea gigas respiring on pyruvate, palmitate, or succinate. Constant hypoxia suppressed oxidative phosphorylation (OXPHOS), particularly during Complex I-linked substrates oxidation. It had no effect on mitochondrial reactive oxygen species (ROS) efflux but increased fractional electron leak (FEL). In mitochondria oxidizing Complex I substrates, exposure to cyclic hypoxia prompted a significant drop after the first H/R cycle. In contrast, succinate-driven respiration only showed significant decline after the third to fifth H/R cycle. ROS efflux saw little change during cyclic hypoxia regardless of the oxidized substrate, but Complex I-driven FEL tended to increase with each subsequent H/R cycle. These observations suggest that succinate may serve as a beneficial stress fuel under H/R conditions, aiding in the post-hypoxic recovery of oysters by reducing oxidative stress and facilitating rapid ATP re-synthesis. The impacts of constant and cyclic hypoxia of similar duration on mitochondrial respiration and oxidative lesions in the proteins were comparable indicating that the mitochondrial damage is mostly determined by the lack of oxygen and mitochondrial depolarization. The ROS efflux in the mitochondria of oysters was minimally affected by oxygen fluctuations indicating that tight regulation of ROS production may contribute to robust mitochondrial phenotype of oysters and protect against H/R induced stress.
Collapse
Affiliation(s)
- Linda Adzigbli
- Institute for Farm Animal Biology, Institute of Genome Biology, Dummerstorf, Germany
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany
| | - Siriluck Ponsuksili
- Institute for Farm Animal Biology, Institute of Genome Biology, Dummerstorf, Germany
| | - Inna Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Rostock, Germany.
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany.
| |
Collapse
|
6
|
Bruhns T, Timm S, Feußner N, Engelhaupt S, Labrenz M, Wegner M, Sokolova IM. Combined effects of temperature and emersion-immersion cycles on metabolism and bioenergetics of the Pacific oyster Crassostrea (Magallana) gigas. MARINE ENVIRONMENTAL RESEARCH 2023; 192:106231. [PMID: 37862760 DOI: 10.1016/j.marenvres.2023.106231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 10/12/2023] [Accepted: 10/14/2023] [Indexed: 10/22/2023]
Abstract
Life on tidal coasts presents physiological major challenges for sessile species. Fluctuations in oxygen and temperature can affect bioenergetics and modulate metabolism and redox balance, but their combined effects are not well understood. We investigated the effects of intermittent hypoxia (12h/12h) in combination with different temperature regimes (normal (15 °C), elevated (30 °C) and fluctuating (15 °C water/30 °C air)) on the Pacific oyster Crassostrea (Magallana) gigas. Fluctuating temperature led to energetic costly metabolic rearrangements and accumulation of proteins in oyster tissues. Elevated temperature led to high (60%) mortality and oxidative damage in survivors. Normal temperature had no major negative effects but caused metabolic shifts. Our study shows high plasticity of oyster metabolism in response to oxygen and temperature fluctuations and indicates that metabolic adjustments to oxygen deficiency are strongly modulated by the ambient temperature. Co-exposure to constant elevated temperature and intermittent hypoxia demonstrates the limits of this adaptive metabolic plasticity.
Collapse
Affiliation(s)
- Torben Bruhns
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18059, Rostock, Germany
| | - Stefan Timm
- Department of Plant Physiology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18059, Rostock, Germany
| | - Nina Feußner
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18059, Rostock, Germany
| | - Sonja Engelhaupt
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18059, Rostock, Germany
| | - Matthias Labrenz
- Leibniz Institute for Baltic Sea Research (IOW), Department of Biological Oceanography, Seestraße 15, 18119, Rostock, Germany
| | - Mathias Wegner
- Alfred Wegener Institut - Helmholtz-Zentrum für Polar- und Meeresforschung, Coastal Ecology, Waddensea Station Sylt, Hafenstraße 43, 25992, List/Sylt, Germany
| | - Inna M Sokolova
- Department of Marine Biology, Institute for Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18059, Rostock, Germany; Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Albert-Einstein-Str. 21, 18059, Rostock, Germany.
| |
Collapse
|
7
|
Steffen JBM, Sokolov EP, Bock C, Sokolova IM. Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas. J Exp Biol 2023; 226:jeb246164. [PMID: 37470191 PMCID: PMC10445735 DOI: 10.1242/jeb.246164] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 07/12/2023] [Indexed: 07/21/2023]
Abstract
Coastal environments commonly experience fluctuations in salinity and hypoxia-reoxygenation (H/R) stress that can negatively affect mitochondrial functions of marine organisms. Although intertidal bivalves are adapted to these conditions, the mechanisms that sustain mitochondrial integrity and function are not well understood. We determined the rates of respiration and reactive oxygen species (ROS) efflux in the mitochondria of oysters, Crassostrea gigas, acclimated to high (33 psu) or low (15 psu) salinity, and exposed to either normoxic conditions (control; 21% O2) or short-term hypoxia (24 h at <0.01% O2) and subsequent reoxygenation (1.5 h at 21% O2). Further, we exposed isolated mitochondria to anoxia in vitro to assess their ability to recover from acute (∼10 min) oxygen deficiency (<0.01% O2). Our results showed that mitochondria of oysters acclimated to high or low salinity did not show severe damage and dysfunction during H/R stress, consistent with the hypoxia tolerance of C. gigas. However, acclimation to low salinity led to improved mitochondrial performance and plasticity, indicating that 15 psu might be closer to the metabolic optimum of C. gigas than 33 psu. Thus, acclimation to low salinity increased mitochondrial oxidative phosphorylation rate and coupling efficiency and stimulated mitochondrial respiration after acute H/R stress. However, elevated ROS efflux in the mitochondria of low-salinity-acclimated oysters after acute H/R stress indicates a possible trade-off of higher respiration. The high plasticity and stress tolerance of C. gigas mitochondria may contribute to the success of this invasive species and facilitate its further expansion into brackish regions such as the Baltic Sea.
Collapse
Affiliation(s)
- Jennifer B. M. Steffen
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18059 Rostock, Germany
| | - Eugene P. Sokolov
- Leibniz Institute for Baltic Research, Leibniz Science Campus Phosphorus Research Rostock, 18119 Warnemünde, Germany
| | - Christian Bock
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
| | - Inna M. Sokolova
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18059 Rostock, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, 18059 Rostock, Germany
| |
Collapse
|
8
|
Sokolova IM. Ectotherm mitochondrial economy and responses to global warming. Acta Physiol (Oxf) 2023; 237:e13950. [PMID: 36790303 DOI: 10.1111/apha.13950] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/24/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023]
Abstract
Temperature is a key abiotic factor affecting ecology, biogeography, and evolution of species. Alterations of energy metabolism play an important role in adaptations and plastic responses to temperature shifts on different time scales. Mitochondrial metabolism affects cellular bioenergetics and redox balance making these organelles an important determinant of organismal performances such as growth, locomotion, or development. Here I analyze the impacts of environmental temperature on the mitochondrial functions (including oxidative phosphorylation, proton leak, production of reactive oxygen species(ROS), and ATP synthesis) of ectotherms and discuss the mechanisms underlying negative shifts in the mitochondrial energy economy caused by supraoptimal temperatures. Owing to the differences in the thermal sensitivity of different mitochondrial processes, elevated temperatures (beyond the species- and population-specific optimal range) cause reallocation of the electron flux and the protonmotive force (Δp) in a way that decreases ATP synthesis efficiency, elevates the relative cost of the mitochondrial maintenance, causes excessive production of ROS and raises energy cost for antioxidant defense. These shifts in the mitochondrial energy economy might have negative consequences for the organismal fitness traits such as the thermal tolerance or growth. Correlation between the thermal sensitivity indices of the mitochondria and the whole organism indicate that these traits experience similar selective pressures but further investigations are needed to establish whether there is a cause-effect relationship between the mitochondrial failure and loss of organismal performance during temperature change.
Collapse
Affiliation(s)
- Inna M Sokolova
- Department of Marine Biology, Institute of Biological Sciences, University of Rostock, Rostock, Germany
- Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|