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Henning Y, Adam K, Gerhardt P, Begall S. Hypoxic and hypercapnic burrow conditions lead to downregulation of free triiodothyronine and hematocrit in Ansell's mole-rats (Fukomys anselli). J Comp Physiol B 2024; 194:33-40. [PMID: 38059996 PMCID: PMC10940439 DOI: 10.1007/s00360-023-01526-0] [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: 09/04/2023] [Revised: 11/01/2023] [Accepted: 11/08/2023] [Indexed: 12/08/2023]
Abstract
African mole-rats live in self-dug burrow systems under hypoxic and hypercapnic conditions. Adaptations to hypoxia include suppression of resting metabolic rate (RMR) and core body temperature (Tb). Because the thyroid hormones (THs) thyroxine (T4) and triiodothyronine (T3) are positive regulators of RMR and Tb, we hypothesized that serum TH concentrations would also be downregulated under hypoxic conditions. To test this hypothesis, we kept Ansell's mole-rats (Fukomys anselli) in terraria filled with soil in which they were allowed to construct underground burrows to achieve chronic intermittent hypoxia and hypercapnia. The animals stayed in these hypoxic and hypercapnic burrows voluntarily, although given the choice to stay aboveground. We collected blood samples before and after treatment to measure serum T4 and T3 concentrations as well as hematological parameters. The free fraction of the transcriptionally-active T3 was significantly decreased after treatment, indicating that cellular TH signaling was downregulated via peripheral mechanisms, consistent with the assumption that aerobic metabolism is downregulated under hypoxic conditions. Furthermore, we found that hematocrit and hemoglobin concentrations were also downregulated after treatment, suggesting that oxygen demand decreases under hypoxia, presumably due to the metabolic shift towards anaerobic metabolism. Taken together, we have identified a potential upstream regulator of physiological adaptations to hypoxia in these highly hypoxia-tolerant animals.
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Affiliation(s)
- Yoshiyuki Henning
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany.
| | - Kamilla Adam
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Patricia Gerhardt
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
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2
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Zhao Y, Zheng Z, Zhang Z, Xu Y, Hillpot E, Lin YS, Zakusilo FT, Lu JY, Ablaeva J, Biashad SA, Miller RA, Nevo E, Seluanov A, Gorbunova V. Evolution of high-molecular-mass hyaluronic acid is associated with subterranean lifestyle. Nat Commun 2023; 14:8054. [PMID: 38052795 PMCID: PMC10698142 DOI: 10.1038/s41467-023-43623-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 11/15/2023] [Indexed: 12/07/2023] Open
Abstract
Hyaluronic acid is a major component of extracellular matrix which plays an important role in development, cellular response to injury and inflammation, cell migration, and cancer. The naked mole-rat (Heterocephalus glaber) contains abundant high-molecular-mass hyaluronic acid in its tissues, which contributes to this species' cancer resistance and possibly to its longevity. Here we report that abundant high-molecular-mass hyaluronic acid is found in a wide range of subterranean mammalian species, but not in phylogenetically related aboveground species. These subterranean mammalian species accumulate abundant high-molecular-mass hyaluronic acid by regulating the expression of genes involved in hyaluronic acid degradation and synthesis and contain unique mutations in these genes. The abundant high-molecular-mass hyaluronic acid may benefit the adaptation to subterranean environment by increasing skin elasticity and protecting from oxidative stress due to hypoxic conditions. Our work suggests that high-molecular-mass hyaluronic acid has evolved with subterranean lifestyle.
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Affiliation(s)
- Yang Zhao
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
- Department of Physiology and Department of Hepatobiliary and Pancreatic Surgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 301158, China
| | - Zhizhong Zheng
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Zhihui Zhang
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Yandong Xu
- Department of Physiology and Department of Hepatobiliary and Pancreatic Surgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 301158, China
| | - Eric Hillpot
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Yifei S Lin
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Frances T Zakusilo
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - J Yuyang Lu
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Julia Ablaeva
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Seyed Ali Biashad
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Richard A Miller
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Eviatar Nevo
- Institute of Evolution, University of Haifa, Haifa, 3498838, Israel
| | - Andrei Seluanov
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA.
- Department of Medicine, University of Rochester School of Medicine, Rochester, NY, 14627, USA.
| | - Vera Gorbunova
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA.
- Department of Medicine, University of Rochester School of Medicine, Rochester, NY, 14627, USA.
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3
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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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4
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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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5
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Zhao Y, Zheng Z, Zhang Z, Hillpot E, Lin YS, Zakusilo FT, Lu JY, Ablaeva J, Miller RA, Nevo E, Seluanov A, Gorbunova V. Evolution of High-Molecular-Mass Hyaluronic Acid is Associated with Subterranean Lifestyle. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.08.539764. [PMID: 37215017 PMCID: PMC10197608 DOI: 10.1101/2023.05.08.539764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hyaluronic acid (HA) is a major component of extracellular matrix (ECM) which plays an important role in development, cellular response to injury and inflammation, cell migration, and cancer. The naked mole-rat (NMR, Heterocephalus glaber ) contains abundant high-molecular-mass HA (HMM-HA) in its tissues, which contributes to this species' cancer resistance and possibly longevity. Here we report that abundant HMM-HA is found in a wide range of subterranean mammalian species, but not in phylogenetically related aboveground species. These species accumulate abundant HMM-HA by regulating the expression of genes involved in HA degradation and synthesis and contain unique mutations in these genes. The abundant high molecular weight HA may benefit the adaptation to subterranean environment by increasing skin elasticity and protecting from oxidative stress due to hypoxic subterranean environment. HMM-HA may also be coopted to confer cancer resistance and longevity to subterranean mammals. Our work suggests that HMM-HA has evolved with subterranean lifestyle.
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6
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Li M, Peng Y, Chen W, Gao Y, Yang M, Li J, He J. Active Nrf2 signaling flexibly regulates HO-1 and NQO-1 in hypoxic Gansu Zokor (Eospalax cansus). Comp Biochem Physiol B Biochem Mol Biol 2023; 264:110811. [PMID: 36372272 DOI: 10.1016/j.cbpb.2022.110811] [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: 06/08/2022] [Revised: 11/03/2022] [Accepted: 11/07/2022] [Indexed: 11/13/2022]
Abstract
Gansu zokor (Eospalax cansus) is a typical subterranean rodent species with resistance to ambient hypoxia. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling plays a key role in regulating redox homeostasis. However, little is known about the regulation of Nrf2 signaling in Gansu zokor. We exposed Gansu zokors and SD rats to chronic hypoxia (44 h at 10.5% O2) or acute hypoxia (6 h at 6.5% O2) andmeasured the activities of heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO-1),gene expression of HO-1, NQO-1, Nrf2, Kelch-like ECH-associated protein-1 (KEAP1), and β-transducin repeat-containing protein (β-TRCP) in the brain and liver. We found that Gansu zokor increased the NQO-1 protein content and activity, HO-1 protein content in the brain, and increased HO-1 activity and mRNA level, NQO-1 activity and protein content in the liver by up regulating Nrf2 gene expression under chronic hypoxia. Although acute hypoxia enhanced the expression of Nrf2 gene, only the level of HO-1 mRNA in the liver increased. Besides, the HO-1 and NQO-1 genes in the brain, HO-1 genes and NQO-1 mRNA in the Gansu zokor liver were significantly higher than those in SD rats under normoxia. Negative regulators of Nrf2 signaling were tissue specific: KEAP1 protein decreased in the brain, and β-TRCP decreased in the liver. The Nrf2 signaling and expression of downstream antioxidant enzymes were different under different oxygen concentrations, reflecting the flexible characteristics of Gansu zokor to deal with the hypoxic environment.
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Affiliation(s)
- Meng Li
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Yifan Peng
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Wenjun Chen
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Yongjiao Gao
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Maohong Yang
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Jingang Li
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China
| | - Jianping He
- National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest China, Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Science, Shaanxi Normal University, Xi'an, China.
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7
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Yap KN, Wong HS, Ramanathan C, Rodriguez-Wagner CA, Roberts MD, Freeman DA, Buffenstein R, Zhang Y. Naked mole-rat and Damaraland mole-rat exhibit lower respiration in mitochondria, cellular and organismal levels. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148582. [PMID: 35667393 DOI: 10.1016/j.bbabio.2022.148582] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Naked mole-rats (NMR) and Damaraland mole-rats (DMR) exhibit extraordinary longevity for their body size, high tolerance to hypoxia and oxidative stress and high reproductive output; these collectively defy the concept that life-history traits should be negatively correlated. However, when life-history traits share similar underlying physiological mechanisms, these may be positively associated with each other. We propose that one such potential common mechanism might be the bioenergetic properties of mole-rats. Here, we aim to characterize the bioenergetic properties of two African mole-rats. We adopted a top-down perspective measuring the bioenergetic properties at the organismal, cellular, and molecular level in both species and the biological significance of these properties were compared with the same measures in Siberian hamsters and C57BL/6 mice, chosen for their similar body size to the mole-rat species. We found mole-rats shared several bioenergetic properties that differed from their comparison species, including low basal metabolic rates, a high dependence on glycolysis rather than on oxidative phosphorylation for ATP production, and low proton conductance across the mitochondrial inner membrane. These shared mole-rat features could be a result of evolutionary adaptation to tolerating variable oxygen atmospheres, in particular hypoxia, and may in turn be one of the molecular mechanisms underlying their extremely long lifespans.
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Affiliation(s)
- Kang Nian Yap
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, United States of America; Department of Biology, Norwegian University of Science and Technology, Trondheim 7491, Norway
| | - Hoi Shan Wong
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America
| | - Chidambaram Ramanathan
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America
| | | | - Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, AL 36849, United States of America
| | - David A Freeman
- Department of Biological Science, University of Memphis, Memphis, TN 38152, United States of America
| | - Rochelle Buffenstein
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America.
| | - Yufeng Zhang
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America.
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8
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Avoiding the effects of translocation on the estimates of the metabolic rates across an elevational gradient. J Comp Physiol B 2022; 192:659-668. [DOI: 10.1007/s00360-022-01448-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 05/30/2022] [Accepted: 06/24/2022] [Indexed: 10/17/2022]
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9
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Wong HS, Freeman DA, Zhang Y. Not just a cousin of the naked mole-rat: Damaraland mole-rats offer unique insights into biomedicine. Comp Biochem Physiol B Biochem Mol Biol 2022; 262:110772. [PMID: 35710053 PMCID: PMC10155858 DOI: 10.1016/j.cbpb.2022.110772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/07/2022] [Accepted: 06/09/2022] [Indexed: 11/26/2022]
Abstract
Evolutionary medicine has been a fast-growing field of biological research in the past decade. One of the strengths of evolutionary medicine is to use non-traditional model organisms which often exhibit unusual characteristics shaped by natural selection. Studying these unusual traits could provide valuable insight to understand biomedical questions, since natural selection likely discovers solutions to those complex biological problems. Because of many unusual traits, the naked mole-rat (NMR) has attracted attention from different research areas such as aging, cancer, and hypoxia- and hypercapnia-related disorders. However, such uniqueness of NMR physiology may sometimes make the translational study to human research difficult. Damaraland mole-rat (DMR) shares multiple characteristics in common with NMR, but shows higher degree of similarity with human in some aspects of their physiology. Research on DMR could therefore offer alternative insights and might bridge the gap between experimental findings from NMR to human biomedical research. In this review, we discuss studies of DMR as an extension of the current set of model organisms to help better understand different aspects of human biology and disease. We hope to encourage researchers to consider studying DMR together with NMR. By studying these two similar but evolutionarily distinct species, we can harvest the power of convergent evolution and avoid the potential biased conclusions based on life-history of a single species.
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Affiliation(s)
- Hoi-Shan Wong
- Nine Square Therapeutics, South San Francisco, CA 94080, United States of America.
| | - David A Freeman
- Department of Biological Sciences, The University of Memphis, Memphis, TN 38152, United States of America
| | - Yufeng Zhang
- College of Health Sciences, The University of Memphis, Memphis, TN 38152, United States of America.
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10
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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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11
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Shi L, Chen B, Wang X, Huang M, Qiao C, Wang J, Wang Z. Antioxidant response to severe hypoxia in Brandt's vole Lasiopodomys brandtii. Integr Zool 2021; 17:581-595. [PMID: 34713576 DOI: 10.1111/1749-4877.12602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The antioxidant defense system is essential for animals to cope with homeostasis disruption and overcome oxidative stress caused by adverse environmental conditions such as hypoxia. However, our understanding of how this system works in subterranean rodents remains limited. In this study, Brandt's vole Lasiopodomys brandtii was exposed to normoxia (21% O2 ) or hypoxia (mild or severe hypoxia: 10% or 5% O2 ) for 6 h. Changes in key enzymes of the classic enzymatic antioxidant system at both mRNA and enzyme activity levels, and tissue antioxidant levels of the low-molecular-weight antioxidant system were determined in brain, liver, and kidney. Transcript levels of the upstream regulator NF-E2-related factor 2 (Nrf2) were also measured. We found that the mRNA expression of Nrf2 and its downstream antioxidant enzyme genes in L. brandtii were relatively conserved in response to hypoxia in most tissues and genes tested, except in the liver. Hepatic Nrf2, Cu/Zn SOD, GPx1, and GPx3 levels were significantly upregulated in response to mild hypoxia, whereas Mn SOD level decreased significantly in severe hypoxia. Unmatched with changes at the RNA level, constitutively high and relatively stable antioxidant enzyme activities were maintained throughout. For the low-molecular-weight antioxidant system, an abrupt increase of cerebral ascorbic acid (AA) levels in hypoxia indicated a tissue-specific antioxidant response. Although hypoxia did not cause significant oxidative damage in most tissues tested, the significant decrease in antioxidant enzyme activities (GPX and GR) and increase in lipid peroxidation in the kidney suggest that prolonged hypoxia may pose a critical threat to this species.
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Affiliation(s)
- Luye Shi
- School of Life Sciences, Zhengzhou University, Zhengzhou, China.,State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Bojian Chen
- College of Environmental Science and Engineering, Tongji University, Shanghai, China.,Jiaxing-Tongji Environmental Research Institute, Jiaxing, China
| | - Xinrui Wang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Maolin Huang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Congcong Qiao
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Jingou Wang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Zhenlong Wang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China.,Centre for Nutritional Ecology, Zhengzhou University, Zhengzhou, China
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12
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Luna F, Okrouhlík J, McKechnie AE, Bennett NC, Šumbera R. Non‐shivering thermogenesis in four species of African mole‐rats differing in their sociality. J Zool (1987) 2021. [DOI: 10.1111/jzo.12892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- F. Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento Instituto de Investigaciones Marinas y Costeras (IIMyC) CONICET‐UNMdP Mar del Plata Argentina
| | - J. Okrouhlík
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - A. E. McKechnie
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
| | - N. C. Bennett
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - R. Šumbera
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
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13
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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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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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