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Kadamani KL, Rahnamaie-Tajadod R, Eaton L, Bengtsson J, Ojaghi M, Cheng H, Pamenter ME. What can naked mole-rats teach us about ameliorating hypoxia-related human diseases? Ann N Y Acad Sci 2024. [PMID: 39269277 DOI: 10.1111/nyas.15219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2024]
Abstract
Ameliorating the deleterious impact of systemic or tissue-level hypoxia or ischemia is key to preventing or treating many human diseases and pathologies. Usefully, environmental hypoxia is also a common challenge in many natural habitats; animals that are native to such hypoxic niches often exhibit strategies that enable them to thrive with limited O2 availability. Studying how such species have evolved to tolerate systemic hypoxia offers a promising avenue of discovery for novel strategies to mitigate the deleterious effects of hypoxia in human diseases and pathologies. Of particular interest are naked mole-rats, which are among the most hypoxia-tolerant mammals. Naked mole-rats that tolerate severe hypoxia in a laboratory setting are also protected against clinically relevant mimics of heart attack and stroke. The mechanisms that support this tolerance are currently being elucidated but results to date suggest that metabolic rate suppression, reprogramming of metabolic pathways, and mechanisms that defend against deleterious perturbations of cellular signaling pathways all provide layers of protection. Herein, we synthesize and discuss what is known regarding adaptations to hypoxia in the naked mole-rat cardiopulmonary system and brain, as these systems comprise both the primary means of delivering O2 to tissues and the most hypoxia-sensitive organs in mammals.
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Affiliation(s)
- Karen L Kadamani
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Liam Eaton
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - John Bengtsson
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Mohammad Ojaghi
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Hang Cheng
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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Ojaghi M, Pamenter ME. Hypoxia impairs blood glucose homeostasis in naked mole-rat adult subordinates but not queens. J Exp Biol 2024; 227:jeb247537. [PMID: 38680085 PMCID: PMC11166464 DOI: 10.1242/jeb.247537] [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: 02/16/2024] [Accepted: 04/12/2024] [Indexed: 05/01/2024]
Abstract
Naked mole-rats (NMRs) are among the most hypoxia-tolerant mammals and metabolize only carbohydrates in hypoxia. Glucose is the primary building block of dietary carbohydrates, but how blood glucose is regulated during hypoxia has not been explored in NMRs. We hypothesized that NMRs mobilize glucose stores to support anaerobic energy metabolism in hypoxia. To test this, we treated newborn, juvenile and adult (subordinate and queen) NMRs in normoxia (21% O2) or hypoxia (7, 5 or 3% O2), while measuring metabolic rate, body temperature and blood [glucose]. We also challenged animals with glucose, insulin or insulin-like growth factor-1 (IGF-1) injections and measured the rate of glucose clearance in normoxia and hypoxia. We found that: (1) blood [glucose] increases in moderate hypoxia in queens and pups, but only in severe hypoxia in adult subordinates and juveniles; (2) glucose tolerance is similar between developmental stages in normoxia, but glucose clearance times are 2- to 3-fold longer in juveniles and subordinates than in queens or pups in hypoxia; and (3) reoxygenation accelerates glucose clearance in hypoxic subordinate adults. Mechanistically, (4) insulin and IGF-1 reduce blood [glucose] in subordinates in both normoxia but only IGF-1 impacts blood [glucose] in hypoxic queens. Our results indicate that insulin signaling is impaired by hypoxia in NMRs, but that queens utilize IGF-1 to overcome this limitation and effectively regulate blood glucose in hypoxia. This suggests that sexual maturation impacts blood glucose handling in hypoxic NMR queens, which may allow queens to spend longer periods of time in hypoxic nest chambers.
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Affiliation(s)
- Mohammad Ojaghi
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada, K1H 8M5
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Devereaux MEM, Pamenter ME. Adenosine and γ-aminobutyric acid partially regulate metabolic and ventilatory responses of Damaraland mole-rats to acute hypoxia. J Exp Biol 2023; 226:jeb246186. [PMID: 37694288 PMCID: PMC10565114 DOI: 10.1242/jeb.246186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/01/2023] [Indexed: 09/12/2023]
Abstract
Fossorial Damaraland mole-rats (Fukomys damarensis) mount a robust hypoxic metabolic response (HMR) but a blunted hypoxic ventilatory response (HVR) to acute hypoxia. Although these reflex physiological responses have been described previously, the underlying signalling pathways are entirely unknown. Of particular interest are contributions from γ-aminobutyric acid (GABA), which is the primary inhibitory neurotransmitter in the nervous system of most adult mammals, and adenosine, the accumulation of which increases during hypoxia as a breakdown product of ATP. Therefore, we hypothesized that GABAergic and/or adenosinergic signalling contributes to the blunted HVR and robust HMR in Damaraland mole-rats. To test this hypothesis, we injected adult animals with saline alone (controls), or 100 mg kg-1 aminophylline or 1 mg kg-1 bicuculline, to block adenosine or GABAA receptors, respectively. We then used respirometry, plethysmography and thermal RFID probes to non-invasively measure metabolic, ventilator and thermoregulatory responses, respectively, to acute hypoxia (1 h in 5 or 7% O2) in awake and freely behaving animals. We found that bicuculline had relatively minor effects on metabolism and thermoregulation but sensitized ventilation such that the HVR became manifest at 7% instead of 5% O2 and was greater in magnitude. Aminophylline increased metabolic rate, ventilation and body temperature in normoxia, and augmented the HMR and HVR. Taken together, these findings indicate that adenosinergic and GABAergic signalling play important roles in mediating the robust HMR and blunted HVR in Damaraland mole-rats.
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Affiliation(s)
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
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Devereaux MEM, Chiasson S, Brennan KF, Pamenter ME. The glutamatergic drive to breathe is reduced in severe but not moderate hypoxia in Damaraland mole-rats. J Exp Biol 2023; 226:jeb246185. [PMID: 37589556 PMCID: PMC10565110 DOI: 10.1242/jeb.246185] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/07/2023] [Indexed: 08/18/2023]
Abstract
Damaraland mole-rats (Fukomys damarensis) are a hypoxia-tolerant fossorial species that exhibit a robust hypoxic metabolic response (HMR) and blunted hypoxic ventilatory response (HVR). Whereas the HVR of most adult mammals is mediated by increased excitatory glutamatergic signalling, naked mole-rats, which are closely related to Damaraland mole-rats, do not utilize this pathway. Given their phylogenetic relationship and similar lifestyles, we hypothesized that the signalling mechanisms underlying physiological responses to acute hypoxia in Damaraland mole-rats are like those of naked mole-rats. To test this, we used pharmacological antagonists of glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and N-methyl-d-aspartate receptors (NMDARs), combined with plethysmography, respirometry and thermal RFID chips, to non-invasively evaluate the role of excitatory AMPAR and NMDAR signalling in mediating ventilatory, metabolic and thermoregulatory responses, respectively, to 1 h of 5 or 7% O2. We found that AMPAR or NMDAR antagonism have minimal impacts on the HMR or hypoxia-mediated changes in thermoregulation. Conversely, the 'blunted' HVR of Damaraland mole-rats is reduced by either AMPAR or NMDAR antagonism such that the onset of the HVR occurs in less severe hypoxia. In more severe hypoxia, antagonists have no impact, suggesting that these receptors are already inhibited. Together, these findings indicate that the glutamatergic drive to breathe decreases in Damaraland mole-rats exposed to severe hypoxia. These findings differ from other adult mammals, in which the glutamatergic drive to breathe increases with hypoxia.
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Affiliation(s)
| | - Sarah Chiasson
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Kate F. Brennan
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
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Extracellular Vesicles in Veterinary Medicine. Animals (Basel) 2022; 12:ani12192716. [PMID: 36230457 PMCID: PMC9559303 DOI: 10.3390/ani12192716] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/23/2022] [Accepted: 10/03/2022] [Indexed: 11/16/2022] Open
Abstract
Extracellular vesicles (EVs) are cell-derived membrane-bound vesicles involved in many physiological and pathological processes not only in humans but also in all the organisms of the eukaryotic and prokaryotic kingdoms. EV shedding constitutes a fundamental universal mechanism of intra-kingdom and inter-kingdom intercellular communication. A tremendous increase of interest in EVs has therefore grown in the last decades, mainly in humans, but progressively also in animals, parasites, and bacteria. With the present review, we aim to summarize the current status of the EV research on domestic and wild animals, analyzing the content of scientific literature, including approximately 220 papers published between 1984 and 2021. Critical aspects evidenced through the veterinarian EV literature are discussed. Then, specific subsections describe details regarding EVs in physiology and pathophysiology, as biomarkers, and in therapy and vaccines. Further, the wide area of research related to animal milk-derived EVs is also presented in brief. The numerous studies on EVs related to parasites and parasitic diseases are excluded, deserving further specific attention. The literature shows that EVs are becoming increasingly addressed in veterinary studies and standardization in protocols and procedures is mandatory, as in human research, to maximize the knowledge and the possibility to exploit these naturally produced nanoparticles.
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Peng Y, Nanduri J, Wang N, Khan SA, Pamenter M, Prabhakar NR. Carotid body responses to O 2 and CO 2 in hypoxia-tolerant naked mole rats. Acta Physiol (Oxf) 2022; 236:e13851. [PMID: 35757963 PMCID: PMC9787741 DOI: 10.1111/apha.13851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/09/2022] [Accepted: 06/10/2022] [Indexed: 02/02/2023]
Abstract
AIM Naked mole rats (NMRs) exhibit blunted hypoxic (HVR) and hypercapnic ventilatory responses (HCVR). The mechanism(s) underlying these responses are largely unknown. We hypothesized that attenuated carotid body (CB) sensitivity to hypoxia and hypercapnia contributes to the near absence of ventilatory responses to hypoxia and CO2 in NMRs. METHODS We measured ex vivo CB sensory nerve activity, phrenic nerve activity (an estimation of ventilation), and blood gases in urethane-anesthetized NMRs and C57BL/6 mice breathing normoxic, hypoxic, or hypercapnic gases. CB morphology, carbon monoxide, and H2 S levels were also determined. RESULTS Relative to mice, NMRs had blunted CB and HVR. Morphologically, NMRs have larger CBs, which contained more glomus cells than in mice. Furthermore, NMR glomus cells form a dispersed pattern compared to a clustered pattern in mice. Hemeoxygenase (HO)-1 mRNA was elevated in NMR CBs, and an HO inhibitor increased CB sensitivity to hypoxia in NMRs. This increase was blocked by an H2 S synthesis inhibitor, suggesting that interrupted gas messenger signaling contributes to the blunted CB responses and HVR in NMRs. Regarding hypercapnia, CB and ventilatory responses to CO2 in NMRs were larger than in mice. Carbonic anhydrase (CA)-2 mRNA is elevated in NMR CBs, and a CA inhibitor blocked the augmented CB response to CO2 in NMRs, indicating CA activity regulates augmented CB response to CO2 . CONCLUSIONS Consistent with our hypothesis, impaired CB responses to hypoxia contribute in part to the blunted HVR in NMRs. Conversely, the HCVR and CB are more sensitive to CO2 in NMRs.
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Affiliation(s)
- Ying‐Jie Peng
- Institute for Integrative Physiology and Center for Systems Biology of O2 SensingUniversity of ChicagoChicagoIllinoisUSA
| | - Jayasri Nanduri
- Institute for Integrative Physiology and Center for Systems Biology of O2 SensingUniversity of ChicagoChicagoIllinoisUSA
| | - Ning Wang
- Institute for Integrative Physiology and Center for Systems Biology of O2 SensingUniversity of ChicagoChicagoIllinoisUSA
| | - Shakil A. Khan
- Institute for Integrative Physiology and Center for Systems Biology of O2 SensingUniversity of ChicagoChicagoIllinoisUSA
| | - Matthew E. Pamenter
- Department of BiologyUniversity of OttawaOttawaOntarioCanada,University of Ottawa Brain and Mind Research InstituteOttawaOntarioCanada
| | - Nanduri R. Prabhakar
- Institute for Integrative Physiology and Center for Systems Biology of O2 SensingUniversity of ChicagoChicagoIllinoisUSA
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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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D’Alessio S, Cheng H, Eaton L, Kraev I, Pamenter ME, Lange S. Acute Hypoxia Alters Extracellular Vesicle Signatures and the Brain Citrullinome of Naked Mole-Rats (Heterocephalus glaber). Int J Mol Sci 2022; 23:ijms23094683. [PMID: 35563075 PMCID: PMC9100269 DOI: 10.3390/ijms23094683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 04/20/2022] [Accepted: 04/22/2022] [Indexed: 02/04/2023] Open
Abstract
Peptidylarginine deiminases (PADs) and extracellular vesicles (EVs) may be indicative biomarkers of physiological and pathological status and adaptive responses, including to diseases and disorders of the central nervous system (CNS) and related to hypoxia. While these markers have been studied in hypoxia-intolerant mammals, in vivo investigations in hypoxia-tolerant species are lacking. Naked mole-rats (NMR) are among the most hypoxia-tolerant mammals and are thus a good model organism for understanding natural and beneficial adaptations to hypoxia. Thus, we aimed to reveal CNS related roles for PADs in hypoxia tolerance and identify whether circulating EV signatures may reveal a fingerprint for adaptive whole-body hypoxia responses in this species. We found that following in vivo acute hypoxia, NMR: (1) plasma-EVs were remodelled, (2) whole proteome EV cargo contained more protein hits (including citrullinated proteins) and a higher number of associated KEGG pathways relating to the total proteome of plasma-EVs Also, (3) brains had a trend for elevation in PAD1, PAD3 and PAD6 protein expression, while PAD2 and PAD4 were reduced, while (4) the brain citrullinome had a considerable increase in deiminated protein hits with hypoxia (1222 vs. 852 hits in normoxia). Our findings indicate that circulating EV signatures are modified and proteomic content is reduced in hypoxic conditions in naked mole-rats, including the circulating EV citrullinome, while the brain citrullinome is elevated and modulated in response to hypoxia. This was further reflected in elevation of some PADs in the brain tissue following acute hypoxia treatment. These findings indicate a possible selective role for PAD-isozymes in hypoxia response and tolerance.
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Affiliation(s)
- Stefania D’Alessio
- Tissue Architecture and Regeneration Research Group, School of Life Sciences, College of Liberal Arts and Sciences, University of Westminster, London W1W 6 UW, UK;
| | - Hang Cheng
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (H.C.); (L.E.); (M.E.P.)
| | - Liam Eaton
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (H.C.); (L.E.); (M.E.P.)
| | - Igor Kraev
- Electron Microscopy Suite, Faculty of Science, Technology, Engineering and Mathematics, Open University, Walton Hall, Milton Keynes MK7 6AA, UK;
| | - Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (H.C.); (L.E.); (M.E.P.)
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Sigrun Lange
- Tissue Architecture and Regeneration Research Group, School of Life Sciences, College of Liberal Arts and Sciences, University of Westminster, London W1W 6 UW, UK;
- Correspondence: ; Tel.: +44-(0)-20-7911-5000 (ext. 64832)
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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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Li M, Pan D, Sun H, Zhang L, Cheng H, Shao T, Wang Z. The hypoxia adaptation of small mammals to plateau and underground burrow conditions. Animal Model Exp Med 2021; 4:319-328. [PMID: 34977483 PMCID: PMC8690988 DOI: 10.1002/ame2.12183] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 09/08/2021] [Indexed: 12/19/2022] Open
Abstract
Oxygen is one of the important substances for the survival of most life systems on the earth, and plateau and underground burrow systems are two typical hypoxic environments. Small mammals living in hypoxic environments have evolved different adaptation strategies, which include increased oxygen delivery, metabolic regulation of physiological responses and other physiological responses that change tissue oxygen utilization. Multi-omics predictions have also shown that these animals have evolved different adaptations to extreme environments. In particular, vascular endothelial growth factor (VEGF) and erythropoietin (EPO), which have specific functions in the control of O2 delivery, have evolved adaptively in small mammals in hypoxic environments. Naked mole-rats and blind mole-rats are typical hypoxic model animals as they have some resistance to cancer. This review primarily summarizes the main living environment of hypoxia tolerant small mammals, as well as the changes of phenotype, physiochemical characteristics and gene expression mode of their long-term living in hypoxia environment.
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Affiliation(s)
- Mengke Li
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
| | - Dan Pan
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
| | - Hong Sun
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
- Centre for Nutritional EcologyZhengzhou UniversityZhengzhouP.R. China
| | - Lei Zhang
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
| | - Han Cheng
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
| | - Tian Shao
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
| | - Zhenlong Wang
- School of Life SciencesZhengzhou UniversityZhengzhouP.R. China
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The Idiosyncratic Physiological Traits of the Naked Mole-Rat; a Resilient Animal Model of Aging, Longevity, and Healthspan. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:221-254. [PMID: 34424518 DOI: 10.1007/978-3-030-65943-1_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The subterranean-dwelling naked mole-rat (Heterocephalus glaber) is an extremophilic rodent, able to thrive in the harsh underground conditions of sub-Saharan Northeast Africa. This pelage-free mammal exhibits numerous unusual ecophysiological features including pronounced tolerance of thermolability, hypoxia, hypercapnia and noxious substances. As a mammal, the naked mole-rat provides a proof-of-concept that age-related changes in physiology are avoidable. At ages far beyond their expected lifespans given both their body size and/or the timing of early developmental milestones, naked mole-rats fail to exhibit meaningful changes in physiological health or demographic mortality. Lack of physiological deterioration with age is also evident in lean and fat mass, bone quality, and reproductive capacity. Rather, regardless of age, under basal conditions naked mole-rats appear to "idle on low" with their "shields up" as is manifested by low body temperature, metabolic rate, cardiac output and kidney concentrating ability, enabling better protection of organs and cellular function. When needed, they can nevertheless ramp up these functions, increasing cardiac output and metabolism 2-5 fold. Here we review many unusual aspects of their physiology and examine how these attributes facilitate both tolerance of the diverse suite of hostile conditions encountered in their natural milieu as well as contribute to their extraordinary longevity and resistance to common, age-related chronic diseases.
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12
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Hadj-Moussa H, Chiasson S, Cheng H, Eaton L, Storey KB, Pamenter ME. MicroRNA-mediated inhibition of AMPK coordinates tissue-specific downregulation of skeletal muscle metabolism in hypoxic naked mole-rats. J Exp Biol 2021; 224:271234. [PMID: 34374781 DOI: 10.1242/jeb.242968] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 07/07/2021] [Indexed: 12/15/2022]
Abstract
Naked mole-rats reduce their metabolic requirements to tolerate severe hypoxia. However, the regulatory mechanisms that underpin this metabolic suppression have yet to be elucidated. 5'-AMP-activated protein kinase (AMPK) is the cellular 'master' energy effector and we hypothesized that alterations in the AMPK pathway contribute to metabolic reorganization in hypoxic naked mole-rat skeletal muscle. To test this hypothesis, we exposed naked mole-rats to 4 h of normoxia (21% O2) or severe hypoxia (3% O2), while indirectly measuring whole-animal metabolic rate and fuel preference. We then isolated skeletal muscle and assessed protein expression and post-translational modification of AMPK, and downstream changes in key glucose and fatty acid metabolic proteins mediated by AMPK, including acetyl-CoA carboxylase (ACC1), glycogen synthase (GS) and glucose transporters (GLUTs) 1 and 4. We found that in hypoxic naked mole-rats (1) metabolic rate decreased ∼80% and fuel use switched to carbohydrates, and that (2) levels of activated phosphorylated AMPK and GS, and GLUT4 expression were downregulated in skeletal muscle, while ACC1 was unchanged. To explore the regulatory mechanism underlying this hypometabolic state, we used RT-qPCR to examine 55 AMPK-associated microRNAs (miRNAs), which are short non-coding RNA post-transcriptional silencers. We identified changes in 10 miRNAs (three upregulated and seven downregulated) implicated in AMPK downregulation. Our results suggest that miRNAs and post-translational mechanisms coordinately reduce AMPK activity and downregulate metabolism in naked mole-rat skeletal muscle during severe hypoxia. This novel mechanism may support tissue-specific prioritization of energy for more essential organs in hypoxia.
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Affiliation(s)
- Hanane Hadj-Moussa
- Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada, K1S 5B6
| | - Sarah Chiasson
- Biology Department, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
| | - Hang Cheng
- Biology Department, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
| | - Liam Eaton
- Biology Department, University of Ottawa, Ottawa, ON, Canada, K1N 9A7
| | - Kenneth B Storey
- Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, Canada, K1S 5B6
| | - Matthew E Pamenter
- Biology Department, University of Ottawa, Ottawa, ON, Canada, K1N 9A7.,Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
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Fernandes-Junior SA, Oliveira LM, Czeisler CM, Mo X, Roy S, Somogyi A, Zhang L, Moreira TS, Otero JJ, Takakura AC. Stimulation of retrotrapezoid nucleus Phox2b-expressing neurons rescues breathing dysfunction in an experimental Parkinson's disease rat model. Brain Pathol 2020; 30:926-944. [PMID: 32497400 DOI: 10.1111/bpa.12868] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 04/17/2020] [Accepted: 05/11/2020] [Indexed: 01/10/2023] Open
Abstract
Emerging evidence from multiple studies indicates that Parkinson's disease (PD) patients suffer from a spectrum of autonomic and respiratory motor deficiencies in addition to the classical motor symptoms attributed to substantia nigra degeneration of dopaminergic neurons. Animal models of PD show a decrease in the resting respiratory rate as well as a decrease in the number of Phox2b-expressing retrotrapezoid nucleus (RTN) neurons. The aim of this study was to determine the extent to which substantia nigra pars compact (SNc) degeneration induced RTN biomolecular changes and to identify the extent to which RTN pharmacological or optogenetic stimulations rescue respiratory function following PD-induction. SNc degeneration was achieved in adult male Wistar rats by bilateral striatal 6-hydroxydopamine injection. For proteomic analysis, laser capture microdissection and pressure catapulting were used to isolate the RTN for subsequent comparative proteomic analysis and Ingenuity Pathway Analysis (IPA). The respiratory parameters were evaluated by whole-body plethysmography and electromyographic analysis of respiratory muscles. The results confirmed reduction in the number of dopaminergic neurons of SNc and respiratory rate in the PD-animals. Our proteomic data suggested extensive RTN remodeling, and that pharmacological or optogenetic stimulations of the diseased RTN neurons promoted rescued the respiratory deficiency. Our data indicate that despite neuroanatomical and biomolecular RTN pathologies, that RTN-directed interventions can rescue respiratory control dysfunction.
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Affiliation(s)
- Silvio A Fernandes-Junior
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil.,Department of Pathology, School of Medicine, The Ohio State University (OSU), Columbus, OH
| | - Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Catherine M Czeisler
- Department of Pathology, School of Medicine, The Ohio State University (OSU), Columbus, OH
| | - Xiaokui Mo
- Department of Biostatistics and Bioinformatics, The Ohio State University (OSU), Columbus, OH
| | - Sashwati Roy
- Departments of Surgery and Molecular and Cellular Biochemistry, The Ohio State University (OSU), Columbus, OH
| | - Arpad Somogyi
- Mass Spectrometry and Proteomics Facility, The Ohio State University (OSU), Columbus, OH
| | - Liewn Zhang
- Mass Spectrometry and Proteomics Facility, The Ohio State University (OSU), Columbus, OH
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - José J Otero
- Department of Pathology, School of Medicine, The Ohio State University (OSU), Columbus, OH
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
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14
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Devereaux MEM, Pamenter ME. Fossorial giant Zambian mole-rats have blunted ventilatory responses to environmental hypoxia and hypercapnia. Comp Biochem Physiol A Mol Integr Physiol 2020; 243:110672. [PMID: 32032753 DOI: 10.1016/j.cbpa.2020.110672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/28/2020] [Accepted: 02/02/2020] [Indexed: 10/25/2022]
Abstract
Fossorial giant Zambian mole-rats are believed to live in a hypoxic and hypercapnic subterranean environment but their physiological responses to these challenges are entirely unknown. To investigate this, we exposed awake and freely-behaving animals to i) 6 h of normoxia, ii) acute graded normocapnic hypoxia (21, 18, 15, 12, 8, and 5% O2, 0% CO2, balance N2; 1 h each), or iii) acute graded normoxic hypercapnia (0, 2, 5, 7, 9, and 10% CO2, 21% O2, balance N2; 1 h each), followed by a 1 h normoxic normocapnic recovery period, while non-invasively measuring ventilation, metabolic rate, and body temperature (Tb). We found that these mole-rats had a blunted hypoxic ventilatory response that manifested at 12% inhaled O2, a robust hypoxic metabolic response (up to a 68% decrease, starting at 15% O2), and decreased Tb (at or below 8% O2). Upon reoxygenation, metabolic rate increased 52% above normoxic levels, suggesting the paying off of an O2 debt. Ventilation was less sensitive to environmental hypercapnia than to environmental hypoxia and animals also exhibited a blunted hypercapnic ventilatory response that did not manifest below 9% inhaled CO2. Conversely, metabolism and Tb were not affected by hypercapnia. Taken together, these results indicate that, like most other fossorial rodents, giant Zambian mole-rats have blunted hypoxic and hypercapnic ventilatory responses and employ metabolic suppression to tolerate acute hypoxia. Blunted physiological responses to hypoxia and hypercapnia likely reflect the subterranean lifestyle of this mammal, wherein intermittent but severe hypoxia and/or hypercapnia may be common challenges.
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Affiliation(s)
| | - 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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15
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Ivy CM, Sprenger RJ, Bennett NC, Jaarsveld B, Hart DW, Kirby AM, Yaghoubi D, Storey KB, Milsom WK, Pamenter ME. The hypoxia tolerance of eight related African mole-rat species rivals that of naked mole-rats, despite divergent ventilatory and metabolic strategies in severe hypoxia. Acta Physiol (Oxf) 2020; 228:e13436. [PMID: 31885213 DOI: 10.1111/apha.13436] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/11/2019] [Accepted: 12/25/2019] [Indexed: 12/21/2022]
Abstract
AIMS Burrowing mammals tend to be more hypoxia tolerant than non-burrowing mammals and rely less on increases in ventilation and more on decreases in metabolic rate to tolerate hypoxia. Naked mole-rats (Heterocephalus glaber, NMRs), eusocial mammals that live in large colonies, are among the most hypoxia-tolerant mammals, and rely almost solely on decreases in metabolism with little change in ventilation during hypoxia. We hypothesized that the remarkable hypoxia tolerance of NMRs is an evolutionarily conserved trait derived from repeated exposure to severe hypoxia owing to their burrow environment and eusocial colony organization. METHODS We used whole-body plethysmography and indirect calorimetry to measure the hypoxic ventilatory and metabolic responses of eight mole-rat species closely related to the NMR. RESULTS We found that all eight species examined had a strong tolerance to hypoxia, with most species tolerating 3 kPa O2 , Heliophobius emini tolerating 2 kPa O2 and Bathyergus suillus tolerating 5 kPa O2 . All species examined employed a combination of increases in ventilation and decreases in metabolism in hypoxia, a response midway between that of the NMR and that of other fossorial species (larger ventilatory responses, lesser reductions in metabolism). We found that eusociality is not fundamental to the physiological response to hypoxia of NMRs as Fukomys damarensis, another eusocial species, was among this group. CONCLUSIONS Our data suggest that, while the NMR is unique in the pattern of their physiological response to hypoxia, eight closely related mole-rat species share the ability to tolerate hypoxia like the current "hypoxia-tolerant champion," the NMR.
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Affiliation(s)
| | - Ryan J. Sprenger
- Department of Zoology University of British Columbia Vancouver BC Canada
| | - Nigel C. Bennett
- Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Barry Jaarsveld
- Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Daniel W. Hart
- Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | | | | | | | - William K. Milsom
- Department of Zoology University of British Columbia Vancouver BC Canada
| | - Matthew E. Pamenter
- Department of Biology University of Ottawa Ottawa ON Canada
- Ottawa Brain and Mind Research Institute University of Ottawa Ottawa ON Canada
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16
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Clayson MS, Devereaux MEM, Pamenter ME. Neurokinin-1 receptor activation is sufficient to restore the hypercapnic ventilatory response in the Substance P-deficient naked mole-rat. Am J Physiol Regul Integr Comp Physiol 2020; 318:R712-R721. [PMID: 31967860 DOI: 10.1152/ajpregu.00251.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Naked mole-rats (NMRs) live in large colonies within densely populated underground burrows. Their collective respiration generates significant metabolic carbon dioxide (CO2) that diffuses slowly out of the burrow network, creating a hypercapnic environment. Currently, the physiological mechanisms that underlie the ability of NMRs to tolerate environmental hypercapnia are largely unknown. To address this, we used whole-body plethysmography and respirometry to elucidate the hypercapnic ventilatory and metabolic responses of awake, freely behaving NMRs to 0%-10% CO2. We found that NMRs have a blunted hypercapnic ventilatory response (HCVR): ventilation increased only in 10% CO2. Conversely, metabolism was unaffected by hypercapnia. NMRs are insensitive to cutaneous acid-based pain caused by modified substance P (SP)-mediated peripheral neurotransmission, and SP is also an important neuromodulator of ventilation. Therefore, we re-evaluated physiological responses to hypercapnia in NMRs after an intraperitoneal injection of exogenous substance P (2 mg/kg) or a long-lived isoform of substance P {[pGlu5-MePhe8-MeGly9]SP(5-11), DiMe-C7; 40-400 μg/kg}. We found that both drugs restored hypercapnia sensitivity and unmasked an HCVR in animals breathing 2%-10% CO2. Taken together, our findings indicate that NMRs are remarkably tolerant of hypercapnic environments and have a blunted HCVR; however, the signaling network architecture required for a "normal" HCVR is retained but endogenously inactive. This muting of chemosensitivity likely suits the ecophysiology of this species, which presumably experiences hypercapnia regularly in their underground niche.
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Affiliation(s)
- Maxwell S Clayson
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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17
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Al-Attar R, Childers CL, Nguyen VC, Pamenter ME, Storey KB. Differential protein phosphorylation is responsible for hypoxia-induced regulation of the Akt/mTOR pathway in naked mole rats. Comp Biochem Physiol A Mol Integr Physiol 2020; 242:110653. [PMID: 31926299 DOI: 10.1016/j.cbpa.2020.110653] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 12/25/2019] [Accepted: 01/06/2020] [Indexed: 12/21/2022]
Abstract
Naked mole rats (NMRs, Heterocephalus glaber) are among the most hypoxia-tolerant mammals known. They can reduce their metabolic rate (>85%) under severe hypoxia, remain moderately active and recover with no obvious signs of damage. Hence, NMRs are an excellent model for studying mammalian hypoxia tolerance. The current study characterized the involvement of posttranslational modifications in regulating the Akt/mTOR pathway that regulates protein synthesis, and the responses of key ribosomal proteins in order to assess tissue-specific responses to 4 h exposure to 7% O2 (compared to controls at 21% O2). Results showed a tissue-specific regulation of the Akt/mTOR pathway via differential phosphorylation. Relative amounts of p-TSC(S939) in brain and of p-TSC(S939), p-Akt(473) and p-PTEN(S380) in liver increased under hypoxia, whereas levels of IGF1R(Y1135/1136) in liver decreased. In skeletal muscle, levels of p-Akt(S473) and p-PTEN(S380) decreased during hypoxia, whereas lungs showed an increase in p-mTOR(S2884) content but a decrease in p-RPS6(S235-236) under the same conditions. Analysis of the phosphorylation states of ribosomal proteins revealed increases in p-4E-BP1(T37/46) content in brain and lungs under hypoxia, as well as a rise in total 4E-BP1 protein level in liver. Phosphorylated eIF-4B(S422) content also increased in liver while levels of p-eIF-2α(S51), and eIF-4E(S209) decreased during hypoxia in liver. Overall, hypoxia altered the Akt/mTOR pathway, which correlated with a general decrease in activity of the ribosomal protein biosynthesis machinery in muscle, lung, and brain of NMRs. However, the increase in eIF-4B in liver suggests the potential promotion of cap-independent mRNA translation mechanism operating under hypoxic stress.
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Affiliation(s)
- Rasha Al-Attar
- Department of Biology, Carleton University, Ottawa, ON, Canada
| | | | - Vu C Nguyen
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Matthew E Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada; uOttawa Brain and Mind Research Institute, Canada
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18
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Postnatal changes in O2 and CO2 sensitivity in rodents. Respir Physiol Neurobiol 2020; 272:103313. [DOI: 10.1016/j.resp.2019.103313] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/31/2019] [Accepted: 10/02/2019] [Indexed: 02/06/2023]
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19
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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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20
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Vandewint AL, Zhu-Pawlowsky AJ, Kirby A, Tattersall GJ, Pamenter ME. Evaporative cooling and vasodilation mediate thermoregulation in naked mole-rats during normoxia but not hypoxia. J Therm Biol 2019; 84:228-235. [DOI: 10.1016/j.jtherbio.2019.07.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/02/2019] [Accepted: 07/02/2019] [Indexed: 12/20/2022]
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21
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Zhang SY, Pamenter ME. Ventilatory, metabolic, and thermoregulatory responses of Damaraland mole rats to acute and chronic hypoxia. J Comp Physiol B 2019; 189:319-334. [DOI: 10.1007/s00360-019-01206-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 01/13/2019] [Accepted: 01/27/2019] [Indexed: 01/22/2023]
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