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Uchino E, Kusumoto-Yoshida I, Kashiwadani H, Kanmura Y, Matsunaga A, Kuwaki T. Identification of hypothermia-inducing neurons in the preoptic area and activation of them by isoflurane anesthesia and central injection of adenosine. J Physiol Sci 2024; 74:33. [PMID: 38867187 PMCID: PMC11167735 DOI: 10.1186/s12576-024-00927-2] [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: 03/02/2024] [Accepted: 06/05/2024] [Indexed: 06/14/2024]
Abstract
Hibernation and torpor are not passive responses caused by external temperature drops and fasting but are active brain functions that lower body temperature. A population of neurons in the preoptic area was recently identified as such active torpor-regulating neurons. We hypothesized that the other hypothermia-inducing maneuvers would also activate these neurons. To test our hypothesis, we first refined the previous observations, examined the brain regions explicitly activated during the falling phase of body temperature using c-Fos expression, and confirmed the preoptic area. Next, we observed long-lasting hypothermia by reactivating torpor-tagged Gq-expressing neurons using the activity tagging and DREADD systems. Finally, we found that about 40-60% of torpor-tagged neurons were activated by succeeding isoflurane anesthesia and by icv administration of an adenosine A1 agonist. Isoflurane-induced and central adenosine-induced hypothermia is, at least in part, an active process mediated by the torpor-regulating neurons in the preoptic area.
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Affiliation(s)
- Erika Uchino
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan
- Department of Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Ikue Kusumoto-Yoshida
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan
| | - Hideki Kashiwadani
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan
| | - Yuichi Kanmura
- Department of Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Akira Matsunaga
- Department of Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Tomoyuki Kuwaki
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima, 890-8544, Japan.
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2
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Jia J, Chen T, Chen C, Si T, Gao C, Fang Y, Sun J, Wang J, Zhang Z. Astrocytes in preoptic area regulate acute nociception-induced hypothermia through adenosine receptors. CNS Neurosci Ther 2024; 30:e14726. [PMID: 38715251 PMCID: PMC11076694 DOI: 10.1111/cns.14726] [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: 01/02/2024] [Revised: 02/27/2024] [Accepted: 04/01/2024] [Indexed: 05/12/2024] Open
Abstract
AIMS The preoptic area (POA) of the hypothalamus, crucial in thermoregulation, has long been implicated in the pain process. However, whether nociceptive stimulation affects body temperature and its mechanism remains poorly studied. METHODS We used capsaicin, formalin, and surgery to induce acute nociceptive stimulation and monitored rectal temperature. Optical fiber recording, chemical genetics, confocal imaging, and pharmacology assays were employed to confirm the role and interaction of POA astrocytes and extracellular adenosine. Immunofluorescence was utilized for further validation. RESULTS Acute nociception could activate POA astrocytes and induce a decrease in body temperature. Manipulation of astrocytes allowed bidirectional control of body temperature. Furthermore, acute nociception and astrocyte activation led to increased extracellular adenosine concentration within the POA. Activation of adenosine A1 or A2A receptors contributed to decreased body temperature, while inhibition of these receptors mitigated the thermo-lowering effect of astrocytes. CONCLUSION Our results elucidate the interplay between acute nociception and thermoregulation, specifically highlighting POA astrocyte activation. This enriches our understanding of physiological responses to painful stimuli and contributes to the analysis of the anatomical basis involved in the process.
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Affiliation(s)
- Junke Jia
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Ting Chen
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Chang Chen
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Tengxiao Si
- Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanChina
| | - Chenyi Gao
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Yuanyuan Fang
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Jiahui Sun
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
| | - Jie Wang
- Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanChina
- Institute of Neuroscience and Brain Diseases, Xiangyang Central HospitalAffiliated Hospital of Hubei University of Arts and ScienceXiangyangChina
- Shanghai Key Laboratory of Emotions and Affective Disorders, Shanghai Jiao Tong University School of MedicineSongjiang Hospital and Songjiang Research InstituteShanghaiChina
| | - Zongze Zhang
- Department of Anesthesiology, Zhongnan HospitalWuhan UniversityWuhanChina
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3
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Yamaguchi H, Murphy KR, Fukatsu N, Sato K, Yamanaka A, de Lecea L. Dorsomedial and preoptic hypothalamic circuits control torpor. Curr Biol 2023; 33:5381-5389.e4. [PMID: 37992720 DOI: 10.1016/j.cub.2023.10.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/25/2023] [Accepted: 10/31/2023] [Indexed: 11/24/2023]
Abstract
Endotherms can survive low temperatures and food shortage by actively entering a hypometabolic state known as torpor. Although the decrease in metabolic rate and body temperature (Tb) during torpor is controlled by the brain, the specific neural circuits underlying these processes have not been comprehensively elucidated. In this study, we identify the neural circuits involved in torpor regulation by combining whole-brain mapping of torpor-activated neurons, cell-type-specific manipulation of neural activity, and viral tracing-based circuit mapping. We find that Trpm2-positive neurons in the preoptic area and Vgat-positive neurons in the dorsal medial hypothalamus are activated during torpor. Genetic silencing shows that the activity of either cell type is necessary to enter the torpor state. Finally, we show that these cells receive projections from the arcuate and suprachiasmatic nucleus and send projections to brain regions involved in thermoregulation. Our results demonstrate an essential role of hypothalamic neurons in the regulation of Tb and metabolic rate during torpor and identify critical nodes of the torpor regulatory network.
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Affiliation(s)
- Hiroshi Yamaguchi
- Department of Neural Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601, Japan; PRESTO, Japan Science and Technology Agency (JST), Tokyo, Japan.
| | - Keith R Murphy
- Department of Psychiatry and Behavioral Sciences, Stanford University, 1201 Welch Road, Stanford, CA 94305, USA
| | - Noriaki Fukatsu
- Department of System Biology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 464-8601, Japan; Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 464-8601, Japan
| | - Kazuhide Sato
- Institute for Advanced Research, Nagoya University, Nagoya, Aichi 466-8550, Japan
| | | | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University, 1201 Welch Road, Stanford, CA 94305, USA.
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4
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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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5
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Scott KA, Tan Y, Johnson DN, Elsaafien K, Baumer-Harrison C, Eikenberry SA, Sa JM, de Lartigue G, de Kloet AD, Krause EG. Mechanosensation of the heart and gut elicits hypometabolism and vigilance in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.29.547073. [PMID: 37425814 PMCID: PMC10327188 DOI: 10.1101/2023.06.29.547073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Interoception broadly refers to awareness of one's internal milieu. Vagal sensory afferents monitor the internal milieu and maintain homeostasis by engaging brain circuits that alter physiology and behavior. While the importance of the body-to-brain communication that underlies interoception is implicit, the vagal afferents and corresponding brain circuits that shape perception of the viscera are largely unknown. Here, we use mice to parse neural circuits subserving interoception of the heart and gut. We determine vagal sensory afferents expressing the oxytocin receptor, hereafter referred to as NDGOxtr, send projections to the aortic arch or stomach and duodenum with molecular and structural features indicative of mechanosensation. Chemogenetic excitation of NDGOxtr significantly decreases food and water consumption, and remarkably, produces a torpor-like phenotype characterized by reductions in cardiac output, body temperature, and energy expenditure. Chemogenetic excitation of NDGOxtr also creates patterns of brain activity associated with augmented hypothalamic-pituitary-adrenal axis activity and behavioral indices of vigilance. Recurrent excitation of NDGOxtr suppresses food intake and lowers body mass, indicating that mechanosensation of the heart and gut can exert enduring effects on energy balance. These findings suggest that the sensation of vascular stretch and gastrointestinal distention may have profound effects on whole body metabolism and mental health.
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Affiliation(s)
- Karen A. Scott
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Yalun Tan
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Dominique N. Johnson
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Khalid Elsaafien
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Caitlin Baumer-Harrison
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Sophia A. Eikenberry
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | - Jessica M. Sa
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
| | | | - Annette D. de Kloet
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - Eric G. Krause
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32611, USA
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL 32611, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
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6
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Yang Y, Yuan J, Field RL, Ye D, Hu Z, Xu K, Xu L, Gong Y, Yue Y, Kravitz AV, Bruchas MR, Cui J, Brestoff JR, Chen H. Induction of a torpor-like hypothermic and hypometabolic state in rodents by ultrasound. Nat Metab 2023; 5:789-803. [PMID: 37231250 PMCID: PMC10229429 DOI: 10.1038/s42255-023-00804-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 04/11/2023] [Indexed: 05/27/2023]
Abstract
Torpor is an energy-conserving state in which animals dramatically decrease their metabolic rate and body temperature to survive harsh environmental conditions. Here, we report the noninvasive, precise and safe induction of a torpor-like hypothermic and hypometabolic state in rodents by remote transcranial ultrasound stimulation at the hypothalamus preoptic area (POA). We achieve a long-lasting (>24 h) torpor-like state in mice via closed-loop feedback control of ultrasound stimulation with automated detection of body temperature. Ultrasound-induced hypothermia and hypometabolism (UIH) is triggered by activation of POA neurons, involves the dorsomedial hypothalamus as a downstream brain region and subsequent inhibition of thermogenic brown adipose tissue. Single-nucleus RNA-sequencing of POA neurons reveals TRPM2 as an ultrasound-sensitive ion channel, the knockdown of which suppresses UIH. We also demonstrate that UIH is feasible in a non-torpid animal, the rat. Our findings establish UIH as a promising technology for the noninvasive and safe induction of a torpor-like state.
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Affiliation(s)
- Yaoheng Yang
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Jinyun Yuan
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Rachael L Field
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Dezhuang Ye
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Zhongtao Hu
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Kevin Xu
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Lu Xu
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Yan Gong
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Yimei Yue
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Alexxai V Kravitz
- Department of Psychiatry, Washington University School of Medicine, Saint Louis, MO, USA
| | - Michael R Bruchas
- Departments of Anesthesiology and Pain Medicine, Pharmacology, and Bioengineering, Center for Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, WA, USA
| | - Jianmin Cui
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA
| | - Jonathan R Brestoff
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Hong Chen
- Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, USA.
- Department of Radiation Oncology, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Neurosurgery, Washington University School of Medicine, St. Louis, MO, USA.
- Division of Neurotechnology, Washington University School of Medicine, Saint Louis, MO, USA.
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7
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Ma WX, Yuan PC, Zhang H, Kong LX, Lazarus M, Qu WM, Wang YQ, Huang ZL. Adenosine and P1 receptors: Key targets in the regulation of sleep, torpor, and hibernation. Front Pharmacol 2023; 14:1098976. [PMID: 36969831 PMCID: PMC10036772 DOI: 10.3389/fphar.2023.1098976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 02/27/2023] [Indexed: 03/12/2023] Open
Abstract
Graphical AbstractAdenosine mediates sleep, torpor and hibernation through P1 receptors. Recent reasearch has shown that P1 receptors play a vital role in the regulation of sleep-wake, torpor and hibernation-like states. In this review, we focus on the roles and neurobiological mechanisms of the CNS adenosine and P1 receptors in these three states. Among them, A1 and A2A receptors are key targets for sleep-wake regulation, A1Rs and A3Rs are very important for torpor induction, and activation of A1Rs is sufficient for hibernation-like state.
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Affiliation(s)
- Wei-Xiang Ma
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Pharmacology, School of Basic Medical Sciences, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Ping-Chuan Yuan
- Anhui Provincial Engineering Research Center for Polysaccharide Drugs, Provincial Engineering Laboratory for Screening and Re-evaluation of Active Compounds of Herbal Medicines in Southern Anhui, School of Pharmacy, Wannan Medical College, Wuhu, China
| | - Hui Zhang
- Anhui Provincial Engineering Research Center for Polysaccharide Drugs, Provincial Engineering Laboratory for Screening and Re-evaluation of Active Compounds of Herbal Medicines in Southern Anhui, School of Pharmacy, Wannan Medical College, Wuhu, China
| | - Ling-Xi Kong
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Pharmacology, School of Basic Medical Sciences, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Michael Lazarus
- International Institute for Integrative Sleep Medicine (WPI-IIIS) and Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Wei-Min Qu
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Pharmacology, School of Basic Medical Sciences, Institutes of Brain Science, Fudan University, Shanghai, China
- *Correspondence: Wei-Min Qu, ; Yi-Qun Wang, ; Zhi-Li Huang,
| | - Yi-Qun Wang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Pharmacology, School of Basic Medical Sciences, Institutes of Brain Science, Fudan University, Shanghai, China
- *Correspondence: Wei-Min Qu, ; Yi-Qun Wang, ; Zhi-Li Huang,
| | - Zhi-Li Huang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Pharmacology, School of Basic Medical Sciences, Institutes of Brain Science, Fudan University, Shanghai, China
- *Correspondence: Wei-Min Qu, ; Yi-Qun Wang, ; Zhi-Li Huang,
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8
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HORII Y, OKADERA K, MIYAWAKI S, SHIINA T, SHIMIZU Y. <i>Suncus murinus</i> as a novel model animal that is suitable for elucidating the mechanism of daily torpor. Biomed Res 2022; 43:53-57. [DOI: 10.2220/biomedres.43.53] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yuuki HORII
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Kanako OKADERA
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Shingo MIYAWAKI
- Laboratory of Veterinary Surgery, Faculty of Applied Biological Sciences, Gifu University
| | - Takahiko SHIINA
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Yasutake SHIMIZU
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2022; 6:313. [PMID: 35087956 PMCID: PMC8764563 DOI: 10.12688/wellcomeopenres.17379.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2022] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to review the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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Affiliation(s)
- Michael Ambler
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Timna Hitrec
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Anthony Pickering
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
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10
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2021; 6:313. [DOI: 10.12688/wellcomeopenres.17379.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2021] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to take a critical view of the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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11
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Adenosine 5'-Monophosphate Protects from Hypoxia by Lowering Mitochondrial Metabolism and Oxygen Demand. Shock 2021; 54:237-244. [PMID: 31460871 DOI: 10.1097/shk.0000000000001440] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ischemia and reperfusion injury following severe trauma or cardiac arrest are major causes of organ damage in intensive care patients. The brain is particularly vulnerable because hypoxia rapidly damages neurons due to their heavy reliance on oxidative phosphorylation. Therapeutic hypothermia can reduce ischemia-induced brain damage, but cooling procedures are slow and technically difficult to perform in critical care settings. It has been previously reported that injection of naturally occurring adenosine 5'-monophosphate (AMP) can rapidly induce hypothermia in mice. We studied the underlying mechanisms and found that AMP transiently reduces the heart rate, respiratory rate, body temperature, and the consciousness of adult male and female C57BL/6J mice. Adding AMP to mouse or human neuronal cell cultures dose-dependently reduced the membrane potential (ΔΨm) and Ca signaling of mitochondria in these cells. AMP treatment increased intracellular AMP levels and activated AMP-activated protein kinase, which resulted in the inhibition of mammalian target of rapamycin complex 1 (mTORC1) and of mitochondrial and cytosolic Ca signaling in resting and stimulated neurons. Pretreatment with an intraperitoneal injection of AMP almost doubled the survival time of mice under hypoxic (6% O2) or anoxic (<1% O2) conditions when compared to untreated mice. These findings suggest that AMP induces a hypometabolic state that slows mitochondrial respiration, reduces oxygen demand, and delays the processes that damage mitochondria in the brain and other organs following hypoxia and reperfusion. Further examination of these mechanisms may lead to new treatments that preserve organ function in critical care patients.
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12
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Ouchi Y, Yamato M, Chowdhury VS, Bungo T. Adenosine 5'-monophosphate induces hypothermia and alters gene expressions in the brain and liver of chicks. Brain Res Bull 2021; 172:14-21. [PMID: 33862124 DOI: 10.1016/j.brainresbull.2021.04.008] [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: 01/19/2021] [Revised: 04/05/2021] [Accepted: 04/10/2021] [Indexed: 10/21/2022]
Abstract
The adenosine A1 receptor is important for body temperature regulation in mammals; however, little is known about its function in avian species. In this study, we investigated the effects of the adenosine A1 receptor agonist and antagonist (adenosine 5'-monophosphate [5'-AMP] and 8 p-sulfophenyl theophylline [8-SPT], respectively) on thermoregulation in chickens. Male chicks were used in this study. After administration of 5'-AMP and 8-SPT, the rectal temperature, plasma metabolites, and gene expressions in the hypothalamus and liver were measured. The rectal temperature was reduced by peripheral administration of 5'-AMP, and the hypothermic effect of 5'-AMP was attenuated by central injection of 8-SPT in chicks. In the hypothalamus, the mRNA level of the agouti-related protein (AgRP) was increased by 5'-AMP administration, whereas it was suppressed by 8-SPT. The plasma levels of free fatty acid were elevated in 5'-AMP-treated chicks and that elevation was suppressed by the 8-SPT treatment. The gene expression of proopiomelanocortin in the hypothalamus was affected by 8-SPT. Nevertheless, the gene expressions of the thermoregulation-related genes, such as the thyrotropin-releasing hormone, were not affected by 5'-AMP and 8-SPT. Hepatic gene expressions related to lipid intake and metabolism were suppressed by 5'-AMP. However, the gene expression of the uncoupling protein was upregulated by 5'-AMP. Based on these results, birds, like mammals, will undergo adenosine A1 receptor-induced hypothermia. In conclusion, it is suggested that 5'-AMP-mediated hypothermia via the adenosine A1 receptor may affect the central melanocortin system and suppress hepatic lipid metabolism in chickens.
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Affiliation(s)
- Yoshimitsu Ouchi
- Laboratory of Animal Behavior and Physiology, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi, Hiroshima, 739-8528, Japan
| | - Miko Yamato
- Faculty of Applied Biological Science, Hiroshima University, Higashi, Hiroshima, 739-8528, Japan
| | | | - Takashi Bungo
- Laboratory of Animal Behavior and Physiology, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi, Hiroshima, 739-8528, Japan.
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13
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Province HS, Xiao C, Mogul AS, Sahoo A, Jacobson KA, Piñol RA, Gavrilova O, Reitman ML. Activation of neuronal adenosine A1 receptors causes hypothermia through central and peripheral mechanisms. PLoS One 2020; 15:e0243986. [PMID: 33326493 PMCID: PMC7743955 DOI: 10.1371/journal.pone.0243986] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 12/01/2020] [Indexed: 12/12/2022] Open
Abstract
Extracellular adenosine, a danger signal, can cause hypothermia. We generated mice lacking neuronal adenosine A1 receptors (A1AR, encoded by the Adora1 gene) to examine the contribution of these receptors to hypothermia. Intracerebroventricular injection of the selective A1AR agonist (Cl-ENBA, 5'-chloro-5'-deoxy-N6-endo-norbornyladenosine) produced hypothermia, which was reduced in mice with deletion of A1AR in neurons. A non-brain penetrant A1AR agonist [SPA, N6-(p-sulfophenyl) adenosine] also caused hypothermia, in wild type but not mice lacking neuronal A1AR, suggesting that peripheral neuronal A1AR can also cause hypothermia. Mice expressing Cre recombinase from the Adora1 locus were generated to investigate the role of specific cell populations in body temperature regulation. Chemogenetic activation of Adora1-Cre-expressing cells in the preoptic area did not change body temperature. In contrast, activation of Adora1-Cre-expressing dorsomedial hypothalamus cells increased core body temperature, concordant with agonism at the endogenous inhibitory A1AR causing hypothermia. These results suggest that A1AR agonism causes hypothermia via two distinct mechanisms: brain neuronal A1AR and A1AR on neurons outside the blood-brain barrier. The variety of mechanisms that adenosine can use to induce hypothermia underscores the importance of hypothermia in the mouse response to major metabolic stress or injury.
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Affiliation(s)
- Haley S. Province
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Cuiying Xiao
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Allison S. Mogul
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Ankita Sahoo
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Kenneth A. Jacobson
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Ramón A. Piñol
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
| | - Marc L. Reitman
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, Maryland, United States of America
- * E-mail:
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14
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Shi Z, Qin M, Huang L, Xu T, Chen Y, Hu Q, Peng S, Peng Z, Qu LN, Chen SG, Tuo QH, Liao DF, Wang XP, Wu RR, Yuan TF, Li YH, Liu XM. Human torpor: translating insights from nature into manned deep space expedition. Biol Rev Camb Philos Soc 2020; 96:642-672. [PMID: 33314677 DOI: 10.1111/brv.12671] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 11/09/2020] [Accepted: 11/17/2020] [Indexed: 12/12/2022]
Abstract
During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (Tb ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.
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Affiliation(s)
- Zhe Shi
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China.,Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China.,State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China.,Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200030, China
| | - Meng Qin
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China
| | - Lu Huang
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, 510632, China
| | - Tao Xu
- Department of Anesthesiology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, China
| | - Ying Chen
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China
| | - Qin Hu
- College of Life Sciences and Bio-Engineering, Beijing University of Technology, Beijing, 100024, China
| | - Sha Peng
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Zhuang Peng
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Li-Na Qu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Shan-Guang Chen
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Qin-Hui Tuo
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Duan-Fang Liao
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Xiao-Ping Wang
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China
| | - Ren-Rong Wu
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China
| | - Ti-Fei Yuan
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200030, China.,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226000, China
| | - Ying-Hui Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Xin-Min Liu
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China.,State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China.,Research Center for Pharmacology and Toxicology, Institute of Medicinal Plant Development (IMPLAD), Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100193, China
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15
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Frare C, Jenkins M, McClure KM, Drew K. Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N 6 -cyclohexyladenosine-induced hibernation in the Arctic ground squirrel (Urocitellus parryii). J Neurochem 2019; 151:316-335. [PMID: 31273780 PMCID: PMC6819227 DOI: 10.1111/jnc.14814] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/12/2019] [Accepted: 07/01/2019] [Indexed: 01/07/2023]
Abstract
Hibernation is a seasonal phenomenon characterized by a drop in metabolic rate and body temperature. Adenosine A1 receptor agonists promote hibernation in different mammalian species, and the understanding of the mechanism inducing hibernation will inform clinical strategies to manipulate metabolic demand that are fundamental to conditions such as obesity, metabolic syndrome, and therapeutic hypothermia. Adenosine A1 receptor agonist-induced hibernation in Arctic ground squirrels is regulated by an endogenous circannual (seasonal) rhythm. This study aims to identify the neuronal mechanism underlying the seasonal difference in response to the adenosine A1 receptor agonist. Arctic ground squirrels were implanted with body temperature transmitters and housed at constant ambient temperature (2°C) and light cycle (4L:20D). We administered CHA (N6 -cyclohexyladenosine), an adenosine A1 receptor agonist in euthermic-summer phenotype and euthermic-winter phenotype and used cFos and phenotypic immunoreactivity to identify cell groups affected by season and treatment. We observed lower core and subcutaneous temperature in winter animals and CHA produced a hibernation-like response in winter, but not in summer. cFos-ir was greater in the median preoptic nucleus and the raphe pallidus in summer after CHA. CHA administration also resulted in enhanced cFos-ir in the nucleus tractus solitarius and decreased cFos-ir in the tuberomammillary nucleus in both seasons. In winter, cFos-ir was greater in the supraoptic nucleus and lower in the raphe pallidus than in summer. The seasonal decrease in the thermogenic response to CHA and the seasonal increase in vasoconstriction, assessed by subcutaneous temperature, reflect the endogenous seasonal modulation of the thermoregulatory systems necessary for CHA-induced hibernation. Cover Image for this issue: doi: 10.1111/jnc.14528.
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Affiliation(s)
- C. Frare
- Department of Chemistry and Biochemistry University of Alaska Fairbanks 900 Yukon Drive Rm. 194 Fairbanks, AK 99775-6160, USA,Institute of Arctic Biology University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK 99775-7000 USA
| | - M.E. Jenkins
- Department of Chemistry and Biochemistry University of Alaska Fairbanks 900 Yukon Drive Rm. 194 Fairbanks, AK 99775-6160, USA
| | - K. M. McClure
- Department of Veterinary Medicine, Colorado State University, 1601 Campus Delivery, Fort Collins, Colorado 80523-160, USA
| | - K.L. Drew
- Department of Chemistry and Biochemistry University of Alaska Fairbanks 900 Yukon Drive Rm. 194 Fairbanks, AK 99775-6160, USA,Institute of Arctic Biology University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK 99775-7000 USA
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16
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Nordeen CA, Martin SL. Engineering Human Stasis for Long-Duration Spaceflight. Physiology (Bethesda) 2019; 34:101-111. [PMID: 30724130 DOI: 10.1152/physiol.00046.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Suspended animation for deep-space travelers is moving out of the realm of science fiction. Two approaches are considered: the first elaborates the current medical practice of therapeutic hypothermia; the second invokes the cascade of metabolic processes naturally employed by hibernators. We explore the basis and evidence behind each approach and argue that mimicry of natural hibernation will be critical to overcome the innate limitations of human physiology for long-duration space travel.
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Affiliation(s)
- Claire A Nordeen
- Department of Emergency Medicine, Harborview Medical Center, University of Washington , Seattle, Washington
| | - Sandra L Martin
- Department of Cell and Developmental Biology, University of Colorado School of Medicine , Aurora, Colorado
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17
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Silvani A, Cerri M, Zoccoli G, Swoap SJ. Is Adenosine Action Common Ground for NREM Sleep, Torpor, and Other Hypometabolic States? Physiology (Bethesda) 2019; 33:182-196. [PMID: 29616880 DOI: 10.1152/physiol.00007.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This review compares two states that lower energy expenditure: non-rapid eye movement (NREM) sleep and torpor. Knowledge on mechanisms common to these states, and particularly on the role of adenosine in NREM sleep, may ultimately open the possibility of inducing a synthetic torpor-like state in humans for medical applications and long-term space travel. To achieve this goal, it will be important, in perspective, to extend the study to other hypometabolic states, which, unlike torpor, can also be experienced by humans.
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Affiliation(s)
- Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Matteo Cerri
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy.,National Institute of Nuclear Physics (INFN), Section of Bologna, Bologna , Italy
| | - Giovanna Zoccoli
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Steven J Swoap
- Department of Biology, Williams College , Williamstown, Massachusetts
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18
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Shimaoka H, Kawaguchi T, Morikawa K, Sano Y, Naitou K, Nakamori H, Shiina T, Shimizu Y. Induction of hibernation-like hypothermia by central activation of the A1 adenosine receptor in a non-hibernator, the rat. J Physiol Sci 2018; 68:425-430. [PMID: 28508339 PMCID: PMC10717028 DOI: 10.1007/s12576-017-0543-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 05/10/2017] [Indexed: 11/30/2022]
Abstract
Central adenosine A1-receptor (A1AR)-mediated signals play a role in the induction of hibernation. We determined whether activation of the central A1AR enables rats to maintain normal sinus rhythm even after their body temperature has decreased to less than 20 °C. Intracerebroventricular injection of an adenosine A1 agonist, N6-cyclohexyladenosine (CHA), followed by cooling decreased the body temperature of rats to less than 20 °C. Normal sinus rhythm was fundamentally maintained during the extreme hypothermia. In contrast, forced induction of hypothermia by cooling anesthetized rats caused cardiac arrest. Additional administration of pentobarbital to rats in which hypothermia was induced by CHA also caused cardiac arrest, suggesting that the operation of some beneficial mechanisms that are not activated under anesthesia may be essential to keep heart beat under the hypothermia. These results suggest that central A1AR-mediated signals in the absence of anesthetics would provide an appropriate condition for maintaining normal sinus rhythm during extreme hypothermia.
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Affiliation(s)
- Hiroki Shimaoka
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takayuki Kawaguchi
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Kahori Morikawa
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yuuki Sano
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Kiyotada Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroyuki Nakamori
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
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19
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Involvement of orexin neurons in fasting- and central adenosine-induced hypothermia. Sci Rep 2018; 8:2717. [PMID: 29426934 PMCID: PMC5807529 DOI: 10.1038/s41598-018-21252-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 01/31/2018] [Indexed: 01/04/2023] Open
Abstract
We examined whether orexin neurons might play a protective role against fasting- and adenosine-induced hypothermia. We first measured body temperature (BT) in orexin neuron-ablated (ORX-AB) mice and wild-type (WT) controls during 24 hours of fasting. As expected, the magnitude of BT drop and the length of time suffering from hypothermia were greater in ORX-AB mice than in WT mice. Orexin neurons were active just before onset of hypothermia and during the recovery period as revealed by calcium imaging in vivo using G-CaMP. We next examined adenosine-induced hypothermia via an intracerebroventricular administration of an adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA), which induced hypothermia in both ORX-AB and WT mice. The dose of CHA required to initiate a hypothermic response in ORX-AB mice was more than 10 times larger than the dose for WT mice. Once hypothermia was established, the recovery was seemingly slower in ORX-AB mice. Activation of orexin neurons during the recovery phase was confirmed by immunohistochemistry for c-Fos. We propose that orexin neurons play dual roles (enhancer in the induction phase and compensator during the recovery phase) in adenosine-induced hypothermia and a protective/compensatory role in fasting-induced hypothermia.
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20
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Abstract
Mice subjected to cold or caloric deprivation can reduce body temperature and metabolic rate and enter a state of torpor. Here we show that administration of pyruvate, an energy-rich metabolic intermediate, can induce torpor in mice with diet-induced or genetic obesity. This is associated with marked hypothermia, decreased activity, and decreased metabolic rate. The drop in body temperature correlates with the degree of obesity and is blunted by housing mice at thermoneutrality. Induction of torpor by pyruvate in obese mice relies on adenosine signaling and is accompanied by changes in brain levels of hexose bisphosphate and GABA as detected by mass spectroscopy-based imaging. Pyruvate does not induce torpor in lean mice but results in the activation of brown adipose tissue (BAT) with an increase in the level of uncoupling protein-1 (UCP1). Denervation of BAT in lean mice blocks this increase in UCP1 and allows the pyruvate-induced torpor phenotype. Thus, pyruvate administration induces torpor in obese mice by pathways involving adenosine and GABA signaling and a failure of normal activation of BAT.
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21
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Horii Y, Shiina T, Shimizu Y. The Mechanism Enabling Hibernation in Mammals. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1081:45-60. [PMID: 30288703 DOI: 10.1007/978-981-13-1244-1_3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Some rodents including squirrels and hamsters undergo hibernation. During hibernation, body temperature drops to only a few degrees above ambient temperature. The suppression of whole-body energy expenditure is associated with regulated, but not passive, reduction of cellular metabolism. The heart retains the ability to beat constantly, although body temperature drops to less than 10 °C during hibernation. Cardiac myocytes of hibernating mammals are characterized by reduced Ca2+ entry into the cell membrane and a concomitant enhancement of Ca2+ release from and reuptake by the sarcoplasmic reticulum. These adaptive changes would help in preventing excessive Ca2+ entry and its overload and in maintaining the resting levels of intracellular Ca2+. Adaptive changes in gene expression in the heart prior to hibernation may be indispensable for acquiring cold resistance. In addition, protective effects of cold-shock proteins are thought to have an important role. We recently reported the unique expression pattern of cold-inducible RNA-binding protein (CIRP) in the hearts of hibernating hamsters. The CIRP mRNA is constitutively expressed in the heart of a nonhibernating euthermic hamster with several different forms probably due to alternative splicing. The short product contained the complete open reading frame for full-length CIRP, while the long product had inserted sequences containing a stop codon, suggesting production of a C-terminal deletion isoform of CIRP. In contrast to nonhibernating hamsters, only the short product was found in hibernating animals. Thus, these results indicate that CIRP expression in the hamster heart is regulated at the level of alternative splicing, which would permit a rapid increment of functional CIRP when entering hibernation. We will summarize the current understanding of the cold-resistant property of the heart in hibernating animals.
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Affiliation(s)
- Yuuki Horii
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan.
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22
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Morrison SF. Efferent neural pathways for the control of brown adipose tissue thermogenesis and shivering. HANDBOOK OF CLINICAL NEUROLOGY 2018; 156:281-303. [PMID: 30454595 DOI: 10.1016/b978-0-444-63912-7.00017-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The fundamental central neural circuits for thermoregulation orchestrate behavioral and autonomic repertoires that maintain body core temperature during thermal challenges that arise from either the ambient or the internal environment. This review summarizes our understanding of the neural pathways within the fundamental thermoregulatory reflex circuitry that comprise the efferent (i.e., beyond thermosensory) control of brown adipose tissue (BAT) and shivering thermogenesis: the motor neuron systems consisting of the BAT sympathetic preganglionic neurons and BAT sympathetic ganglion cells, and the alpha- and gamma-motoneurons; the premotor neurons in the region of the rostral raphe pallidus, and the thermogenesis-promoting neurons in the dorsomedial hypothalamus/dorsal hypothalamic area. Also included are inputs to, and neurochemical modulators of, these efferent neuronal populations that could influence their activity during thermoregulatory responses. Signals of metabolic status can be particularly significant for the energy-hungry thermoeffectors for heat production.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, United States.
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23
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Choudhary RC, Jia X. Hypothalamic or Extrahypothalamic Modulation and Targeted Temperature Management After Brain Injury. Ther Hypothermia Temp Manag 2017; 7:125-133. [PMID: 28467285 PMCID: PMC5610405 DOI: 10.1089/ther.2017.0003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Targeted temperature management (TTM) has been recognized to protect tissue function and positively influence neurological outcomes after brain injury. While shivering during hypothermia nullifies the beneficial effect of TTM, traditionally, antishivering drugs or paralyzing agents have been used to reduce the shivering. The hypothalamic area of the brain helps in controlling cerebral temperature and body temperature through interactions between different brain areas. Thus, modulation of different brain areas either pharmacologically or by electrical stimulation may contribute in TTM; although, very few studies have shown that TTM might be achieved by activation and inhibition of neurons in the hypothalamic region. Recent studies have investigated potential pharmacological methods of inducing hypothermia for TTM by aiming to maintain the TTM and reduce the shivering effect without using antiparalytic drugs. Better survival and neurological outcome after brain injury have been reported after pharmacologically induced TTM. This review discusses the mechanisms and modulation of the hypothalamus with other brain areas that are involved in inducing hypothermia through which TTM may be achieved and provides therapeutic strategies for TTM after brain injury.
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Affiliation(s)
| | - Xiaofeng Jia
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland
- Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland
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24
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Bailey IR, Laughlin B, Moore LA, Bogren LK, Barati Z, Drew KL. Optimization of Thermolytic Response to A 1 Adenosine Receptor Agonists in Rats. J Pharmacol Exp Ther 2017; 362:424-430. [PMID: 28652388 DOI: 10.1124/jpet.117.241315] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 06/22/2017] [Indexed: 12/13/2022] Open
Abstract
Cardiac arrest is a leading cause of death in the United States, and, currently, therapeutic hypothermia, now called targeted temperature management (TTM), is the only recent treatment modality proven to increase survival rates and reduce morbidity for this condition. Shivering and subsequent metabolic stress, however, limit application and benefit of TTM. Stimulating central nervous system A1 adenosine receptors (A1AR) inhibits shivering and nonshivering thermogenesis in rats and induces a hibernation-like response in hibernating species. In this study, we investigated the pharmacodynamics of two A1AR agonists in development as antishivering agents. To optimize body temperature (Tb) control, we evaluated the influence of every-other-day feeding, dose, drug, and ambient temperature (Ta) on the Tb-lowering effects of N6-cyclohexyladenosine (CHA) and the partial A1AR agonist capadenoson in rats. The highest dose of CHA (1.0 mg/kg, i.p.) caused all ad libitum-fed animals tested to reach our target Tb of 32°C, but responses varied and some rats overcooled to a Tb as low as 21°C at 17.0°C Ta Dietary restriction normalized the response to CHA. The partial agonist capadenoson (1.0 or 2.0 mg/kg, i.p.) produced a more consistent response, but the highest dose decreased Tb by only 1.6°C. To prevent overcooling after CHA, we studied continuous i.v. administration in combination with dynamic surface temperature control. Results show that after CHA administration control of surface temperature maintains desired target Tb better than dose or ambient temperature.
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Affiliation(s)
- Isaac R Bailey
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
| | - Bernard Laughlin
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
| | - Lucille A Moore
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
| | - Lori K Bogren
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
| | - Zeinab Barati
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
| | - Kelly L Drew
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., L.A.M., L.K.B., Z.B., K.L.D.); and Departments of Chemistry and Biochemisty, University of Alaska Fairbanks, Fairbanks, Alaska (I.R.B., B.L., K.L.D.)
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Central activation of the A 1 adenosine receptor in fed mice recapitulates only some of the attributes of daily torpor. J Comp Physiol B 2017; 187:835-845. [PMID: 28378088 DOI: 10.1007/s00360-017-1084-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/02/2016] [Accepted: 03/07/2017] [Indexed: 01/23/2023]
Abstract
Mice enter bouts of daily torpor, drastically reducing metabolic rate, core body temperature (T b), and heart rate (HR), in response to reduced caloric intake. Because central adenosine activation has been shown to induce a torpor-like state in the arctic ground squirrel, and blocking the adenosine-1 (A1) receptor prevents daily torpor, we hypothesized that central activation of the A1 adenosine receptors would induce a bout of natural torpor in mice. To test the hypothesis, mice were subjected to four different hypothermia bouts: natural torpor, forced hypothermia (FH), isoflurane-anesthesia, and an intracerebroventricular injection of the selective A1 receptor agonist N6-cyclohexyladenosine (CHA). All conditions induced profound hypothermia. T b fell more rapidly in the FH, isoflurane-anesthesia, and CHA conditions compared to torpor, while mice treated with CHA recovered at half the rate of torpid mice. FH, isoflurane-anesthesia, and CHA-treated mice exhibited a diminished drop in HR during entry into hypothermia as compared to torpor. Mice in all conditions except CHA shivered while recovering from hypothermia, and only FH mice shivered substantially while entering hypothermia. Circulating lactate during the hypothermic bouts was not significantly different between the CHA and torpor conditions, both of which had lower than baseline lactate levels. Arrhythmias were largely absent in the FH and isoflurane-anesthesia conditions, while skipped beats were observed in natural torpor and periodic extended (>1 s) HR pauses in the CHA condition. Lastly, the hypothermic bouts showed distinct patterns of gene expression, with torpor characterized by elevated hepatic and cardiac Txnip expression and all other hypothermic states characterized by elevated c-Fos and Egr-1 expression. We conclude that CHA-induced hypothermia and natural torpor are largely different physiological states.
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26
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Tupone D, Cano G, Morrison SF. Thermoregulatory inversion: a novel thermoregulatory paradigm. Am J Physiol Regul Integr Comp Physiol 2017; 312:R779-R786. [PMID: 28330964 DOI: 10.1152/ajpregu.00022.2017] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/01/2017] [Accepted: 03/15/2017] [Indexed: 01/06/2023]
Abstract
To maintain core body temperature in mammals, the normal central nervous system (CNS) thermoregulatory reflex networks produce an increase in brown adipose tissue (BAT) thermogenesis in response to skin cooling and an inhibition of the sympathetic outflow to BAT during skin rewarming. In contrast, these normal thermoregulatory reflexes appear to be inverted in hibernation/torpor; thermogenesis is inhibited during exposure to a cold environment, allowing dramatic reductions in core temperature and metabolism, and thermogenesis is activated during skin rewarming, contributing to a return of normal body temperature. Here, we describe two unrelated experimental paradigms in which rats, a nonhibernating/torpid species, exhibit a "thermoregulatory inversion," which is characterized by an inhibition of BAT thermogenesis in response to skin cooling, and a switch in the gain of the skin cooling reflex transfer function from negative to positive values. Either transection of the neuraxis immediately rostral to the dorsomedial hypothalamus in anesthetized rats or activation of A1 adenosine receptors within the CNS of free-behaving rats produces a state of thermoregulatory inversion in which skin cooling inhibits BAT thermogenesis, leading to hypothermia, and skin warming activates BAT, supporting an increase in core temperature. These results reflect the existence of a novel neural circuit that mediates inverted thermoregulatory reflexes and suggests a pharmacological mechanism through which a deeply hypothermic state can be achieved in nonhibernating/torpid mammals, possibly including humans.
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Affiliation(s)
- Domenico Tupone
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon; and
| | - Georgina Cano
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaun F Morrison
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon; and
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Carlin JL, Jain S, Gizewski E, Wan TC, Tosh DK, Xiao C, Auchampach JA, Jacobson KA, Gavrilova O, Reitman ML. Hypothermia in mouse is caused by adenosine A 1 and A 3 receptor agonists and AMP via three distinct mechanisms. Neuropharmacology 2017; 114:101-113. [PMID: 27914963 PMCID: PMC5183552 DOI: 10.1016/j.neuropharm.2016.11.026] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/02/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022]
Abstract
Small mammals have the ability to enter torpor, a hypothermic, hypometabolic state, allowing impressive energy conservation. Administration of adenosine or adenosine 5'-monophosphate (AMP) can trigger a hypothermic, torpor-like state. We investigated the mechanisms for hypothermia using telemetric monitoring of body temperature in wild type and receptor knock out (Adora1-/-, Adora3-/-) mice. Confirming prior data, stimulation of the A3 adenosine receptor (AR) induced hypothermia via peripheral mast cell degranulation, histamine release, and activation of central histamine H1 receptors. In contrast, A1AR agonists and AMP both acted centrally to cause hypothermia. Commonly used, selective A1AR agonists, including N6-cyclopentyladenosine (CPA), N6-cyclohexyladenosine (CHA), and MRS5474, caused hypothermia via both A1AR and A3AR when given intraperitoneally. Intracerebroventricular dosing, low peripheral doses of Cl-ENBA [(±)-5'-chloro-5'-deoxy-N6-endo-norbornyladenosine], or using Adora3-/- mice allowed selective stimulation of A1AR. AMP-stimulated hypothermia can occur independently of A1AR, A3AR, and mast cells. A1AR and A3AR agonists and AMP cause regulated hypothermia that was characterized by a drop in total energy expenditure, physical inactivity, and preference for cooler environmental temperatures, indicating a reduced body temperature set point. Neither A1AR nor A3AR was required for fasting-induced torpor. A1AR and A3AR agonists and AMP trigger regulated hypothermia via three distinct mechanisms.
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Affiliation(s)
- Jesse Lea Carlin
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Shalini Jain
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Elizabeth Gizewski
- Department of Pharmacology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Tina C Wan
- Department of Pharmacology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Dilip K Tosh
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Cuiying Xiao
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - John A Auchampach
- Department of Pharmacology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Marc L Reitman
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA.
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Muzzi M, Buonvicino D, Chiarugi A. Therapeutic hypothermia: Turning humans into cold-blooded ectotherms via adenosine receptors. Neuropharmacology 2017; 116:441-443. [PMID: 28089845 DOI: 10.1016/j.neuropharm.2016.12.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2016] [Indexed: 10/20/2022]
Affiliation(s)
- Mirko Muzzi
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Daniela Buonvicino
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Alberto Chiarugi
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy.
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Drew KL, Frare C, Rice SA. Neural Signaling Metabolites May Modulate Energy Use in Hibernation. Neurochem Res 2017; 42:141-150. [PMID: 27878659 PMCID: PMC5284051 DOI: 10.1007/s11064-016-2109-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 10/05/2016] [Accepted: 11/11/2016] [Indexed: 12/23/2022]
Abstract
Despite an epidemic in obesity and metabolic syndrome limited means exist to effect adiposity or metabolic rate other than life style changes. Here we review evidence that neural signaling metabolites may modulate thermoregulatory pathways and offer novel means to fine tune energy use. We extend prior reviews on mechanisms that regulate thermogenesis and energy use in hibernation by focusing primarily on the neural signaling metabolites adenosine, AMP and glutamate.
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Affiliation(s)
- Kelly L Drew
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA.
| | - Carla Frare
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Sarah A Rice
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
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30
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Sunagawa GA, Takahashi M. Hypometabolism during Daily Torpor in Mice is Dominated by Reduction in the Sensitivity of the Thermoregulatory System. Sci Rep 2016; 6:37011. [PMID: 27845399 PMCID: PMC5109469 DOI: 10.1038/srep37011] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/21/2016] [Indexed: 01/20/2023] Open
Abstract
Some mammals enter a hypometabolic state either daily torpor (minutes to hours in length) or hibernation (days to weeks), when reducing metabolism would benefit survival. Hibernators demonstrate deep torpor by reducing both the sensitivity (H) and the theoretical set-point temperature (TR) of the thermogenesis system, resulting in extreme hypothermia close to ambient temperature. However, these properties during daily torpor remain poorly understood due to the very short steady state of the hypometabolism and the large variation among species and individuals. To overcome these difficulties in observing and evaluating daily torpor, we developed a novel torpor-detection algorithm based on Bayesian estimation of the basal metabolism of individual mice. Applying this robust method, we evaluated fasting induced torpor in various ambient temperatures (TAs) and found that H decreased 91.5% during daily torpor while TR only decreased 3.79 °C in mice. These results indicate that thermogenesis during daily torpor shares a common property of sensitivity reduction with hibernation while it is distinct from hibernation by not lowering TR. Moreover, our findings support that mice are suitable model animals to investigate the regulation of the heat production during active hypometabolism, thus suggesting further study of mice may provide clues to regulating hypometabolism in mammals.
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Affiliation(s)
- Genshiro A Sunagawa
- Laboratory for Retinal Regeneration, RIKEN Center for Developmental Biology, 2-2-3 Minatojimaminami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Masayo Takahashi
- Laboratory for Retinal Regeneration, RIKEN Center for Developmental Biology, 2-2-3 Minatojimaminami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
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Abstract
Autonomic thermoregulation is a recently acquired function, as it appears for the first time in mammals and provides the brain with the ability to control energy expenditure. The importance of such control can easily be highlighted by the ability of a heterogeneous group of mammals to actively reduce metabolic rate and enter a condition of regulated hypometabolism known as torpor. The central neural circuits of thermoregulatory cold defense have been recently unraveled and could in theory be exploited to reduce energy expenditure in species that do not normally use torpor, inducing a state called synthetic torpor. This approach may represent the first steps toward the development of a technology to induce a safe and reversible state of hypometabolism in humans, unlocking many applications ranging from new medical procedures to deep space travel.
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Affiliation(s)
- Matteo Cerri
- Department of Biomedical and Neuromotor Sciences, Physiology Division, Alma Mater Studiorum, University of Bologna, 40126 Bologna, Italy;
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32
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Abstract
Central neural circuits orchestrate the behavioral and autonomic repertoire that maintains body temperature during environmental temperature challenges and alters body temperature during the inflammatory response and behavioral states and in response to declining energy homeostasis. This review summarizes the central nervous system circuit mechanisms controlling the principal thermoeffectors for body temperature regulation: cutaneous vasoconstriction regulating heat loss and shivering and brown adipose tissue for thermogenesis. The activation of these thermoeffectors is regulated by parallel but distinct efferent pathways within the central nervous system that share a common peripheral thermal sensory input. The model for the neural circuit mechanism underlying central thermoregulatory control provides a useful platform for further understanding of the functional organization of central thermoregulation, for elucidating the hypothalamic circuitry and neurotransmitters involved in body temperature regulation, and for the discovery of novel therapeutic approaches to modulating body temperature and energy homeostasis.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA
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Pamenter ME, Dzal YA, Milsom WK. Adenosine receptors mediate the hypoxic ventilatory response but not the hypoxic metabolic response in the naked mole rat during acute hypoxia. Proc Biol Sci 2016; 282:20141722. [PMID: 25520355 DOI: 10.1098/rspb.2014.1722] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Naked mole rats are the most hypoxia-tolerant mammals identified; however, the mechanisms underlying this tolerance are poorly understood. Using whole-animal plethysmography and open-flow respirometry, we examined the hypoxic metabolic response (HMR), hypoxic ventilatory response (HVR) and hypoxic thermal response in awake, freely behaving naked mole rats exposed to 7% O₂ for 1 h. Metabolic rate and ventilation each reversibly decreased 70% in hypoxia (from 39.6 ± 2.9 to 12.1 ± 0.3 ml O₂ min(-1) kg(-1), and 1412 ± 244 to 417 ± 62 ml min(-1) kg(-1), respectively; p < 0.05), whereas body temperature was unchanged and animals remained awake and active. Subcutaneous injection of the general adenosine receptor antagonist aminophylline (AMP; 100 mg kg(-1), in saline), but not control saline injections, prevented the HVR but had no effect on the HMR. As a result, AMP-treated naked mole rats exhibited extreme hyperventilation in hypoxia. These animals were also less tolerant to hypoxia, and in some cases hypoxia was lethal following AMP injection. We conclude that in naked mole rats (i) hypoxia tolerance is partially dependent on profound hypoxic metabolic and ventilatory responses, which are equal in magnitude but occur independently of thermal changes in hypoxia, and (ii) adenosine receptors mediate the HVR but not the HMR.
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Affiliation(s)
- Matthew E Pamenter
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Yvonne A Dzal
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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34
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Morrison SF, Madden CJ. Central nervous system regulation of brown adipose tissue. Compr Physiol 2015; 4:1677-713. [PMID: 25428857 DOI: 10.1002/cphy.c140013] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Thermogenesis, the production of heat energy, in brown adipose tissue is a significant component of the homeostatic repertoire to maintain body temperature during the challenge of low environmental temperature in many species from mouse to man and plays a key role in elevating body temperature during the febrile response to infection. The sympathetic neural outflow determining brown adipose tissue (BAT) thermogenesis is regulated by neural networks in the CNS which increase BAT sympathetic nerve activity in response to cutaneous and deep body thermoreceptor signals. Many behavioral states, including wakefulness, immunologic responses, and stress, are characterized by elevations in core body temperature to which central command-driven BAT activation makes a significant contribution. Since energy consumption during BAT thermogenesis involves oxidation of lipid and glucose fuel molecules, the CNS network driving cold-defensive and behavioral state-related BAT activation is strongly influenced by signals reflecting the short- and long-term availability of the fuel molecules essential for BAT metabolism and, in turn, the regulation of BAT thermogenesis in response to metabolic signals can contribute to energy balance, regulation of body adipose stores and glucose utilization. This review summarizes our understanding of the functional organization and neurochemical influences within the CNS networks that modulate the level of BAT sympathetic nerve activity to produce the thermoregulatory and metabolic alterations in BAT thermogenesis and BAT energy expenditure that contribute to overall energy homeostasis and the autonomic support of behavior.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon
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35
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Jinka TR, Combs VM, Drew KL. Translating drug-induced hibernation to therapeutic hypothermia. ACS Chem Neurosci 2015; 6:899-904. [PMID: 25812681 DOI: 10.1021/acschemneuro.5b00056] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Therapeutic hypothermia (TH) improves prognosis after cardiac arrest; however, thermoregulatory responses such as shivering complicate cooling. Hibernators exhibit a profound and safe reversible hypothermia without any cardiovascular side effects by lowering the shivering threshold at low ambient temperatures (Ta). Activation of adenosine A1 receptors (A1ARs) in the central nervous system (CNS) induces hibernation in hibernating species and a hibernation-like state in rats, principally by attenuating thermogenesis. Thus, we tested the hypothesis that targeted activation of the central A1AR combined with a lower Ta would provide a means of managing core body temperature (Tb) below 37 °C for therapeutic purposes. We targeted the A1AR within the CNS by combining systemic delivery of the A1AR agonist (6)N-cyclohexyladenosine (CHA) with 8-(p-sulfophenyl)theophylline (8-SPT), a nonspecific adenosine receptor antagonist that does not readily cross the blood-brain barrier. Results show that CHA (1 mg/kg) and 8-SPT (25 mg/kg), administered intraperitoneally every 4 h for 20 h at a Ta of 16 °C, induce and maintain the Tb between 29 and 31 °C for 24 h in both naïve rats and rats subjected to asphyxial cardiac arrest for 8 min. Faster and more stable hypothermia was achieved by continuous infusion of CHA delivered subcutaneously via minipumps. Animals subjected to cardiac arrest and cooled by CHA survived better and showed less neuronal cell death than normothermic control animals. Central A1AR activation in combination with a thermal gradient shows promise as a novel and effective pharmacological adjunct for inducing safe and reversible targeted temperature management.
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Affiliation(s)
- Tulasi R. Jinka
- University of Alaska Fairbanks, 902 North Koyukuk Drive, Fairbanks, Alaska 99775-7000, United States
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Velva M. Combs
- University of Alaska Fairbanks, 902 North Koyukuk Drive, Fairbanks, Alaska 99775-7000, United States
| | - Kelly L. Drew
- University of Alaska Fairbanks, 902 North Koyukuk Drive, Fairbanks, Alaska 99775-7000, United States
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37
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Drew KL, Romanovsky AA, Stephen TKL, Tupone D, Williams RH. Future approaches to therapeutic hypothermia: a symposium report. Temperature (Austin) 2015; 2:168-71. [PMID: 27227020 PMCID: PMC4843898 DOI: 10.4161/23328940.2014.976512] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 10/09/2014] [Accepted: 10/09/2014] [Indexed: 12/22/2022] Open
Key Words
- A1AR
- AGS, arctic ground squirrel
- CE, capillary electrophoresis
- EEG,electroencephalogram
- FSCV, Fast scan cyclic voltammetry
- HPLC, high performance liquid chromatography
- ICV, intracerebroventricular
- TRPM8
- Tb, core body temperature
- adenosine
- capillary electrophoresis
- hibernation
- nNOS, neuronal nitric oxide synthase; NTS, nucleus tractus solitarii; TH, therapeutic hypothermia; TRP, transient receptor potential [channel(s)]; TRPM8, TRP melastatin-8
- nNOS/NK1
- targeted temperature management
- therapeutic hypothermia
- torpor
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Affiliation(s)
- Kelly L Drew
- Institute of Arctic Biology; University of Alaska Fairbanks; Fairbanks, AK, USA
| | - Andrej A Romanovsky
- Systemic Inflammation Laboratory (Fever Lab); Trauma Research, St. Joseph's Hospital and Medical Center; Phoenix, AZ, USA
| | - Terilyn KL Stephen
- Department of Chemistry and Biochemistry; University of Alaska Fairbanks; Fairbanks, AK, USA
| | - Domenico Tupone
- Department of Neurological Surgery; Oregon Health & Science University; Portland, OR, USA
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Shylo AV. Dynamics of the Electrographic Indices in Rats and Hamsters Recovering from Artificial and Natural Hypometabolic States. NEUROPHYSIOLOGY+ 2015. [DOI: 10.1007/s11062-015-9502-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Zhang M, Wang H, Zhao J, Chen C, Leak RK, Xu Y, Vosler P, Chen J, Gao Y, Zhang F. Drug-induced hypothermia in stroke models: does it always protect? CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2014; 12:371-80. [PMID: 23469851 DOI: 10.2174/1871527311312030010] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 11/06/2012] [Accepted: 11/11/2012] [Indexed: 12/19/2022]
Abstract
Ischemic stroke is a common neurological disorder lacking a cure. Recent studies show that therapeutic hypothermia is a promising neuroprotective strategy against ischemic brain injury. Several methods to induce therapeutic hypothermia have been established; however, most of them are not clinically feasible for stroke patients. Therefore, pharmacological cooling is drawing increasing attention as a neuroprotective alternative worthy of further clinical development. We begin this review with a brief introduction to the commonly used methods for inducing hypothermia; we then focus on the hypothermic effects of eight classes of hypothermia-inducing drugs: the cannabinoids, opioid receptor activators, transient receptor potential vanilloid, neurotensins, thyroxine derivatives, dopamine receptor activators, hypothermia-inducing gases, adenosine, and adenine nucleotides. Their neuroprotective effects as well as the complications associated with their use are both considered. This article provides guidance for future clinical trials and animal studies on pharmacological cooling in the setting of acute stroke.
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Affiliation(s)
- Meijuan Zhang
- Department of Neurology, University of Pittsburgh School of Medicine, 3500 Terrace Street, Pittsburgh, PA 15213, USA
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40
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Quinones QJ, Ma Q, Zhang Z, Barnes BM, Podgoreanu MV. Organ protective mechanisms common to extremes of physiology: a window through hibernation biology. Integr Comp Biol 2014; 54:497-515. [PMID: 24848803 DOI: 10.1093/icb/icu047] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Supply and demand relationships govern survival of animals in the wild and are also key determinants of clinical outcomes in critically ill patients. Most animals' survival strategies focus on the supply side of the equation by pursuing territory and resources, but hibernators are able to anticipate declining availability of nutrients by reducing their energetic needs through the seasonal use of torpor, a reversible state of suppressed metabolic demand and decreased body temperature. Similarly, in clinical medicine the majority of therapeutic interventions to care for critically ill or trauma patients remain focused on elevating physiologic supply above critical thresholds by increasing the main determinants of delivery of oxygen to the tissues (cardiac output, perfusion pressure, hemoglobin concentrations, and oxygen saturation), as well as increasing nutritional support, maintaining euthermia, and other general supportive measures. Techniques, such as induced hypothermia and preconditioning, aimed at diminishing a patient's physiologic requirements as a short-term strategy to match reduced supply and to stabilize their condition, are few and underutilized in clinical settings. Consequently, comparative approaches to understand the mechanistic adaptations that suppress metabolic demand and alter metabolic use of fuel as well as the application of concepts gleaned from studies of hibernation, to the care of critically ill and injured patients could create novel opportunities to improve outcomes in intensive care and perioperative medicine.
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Affiliation(s)
- Quintin J Quinones
- *Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA
| | - Qing Ma
- *Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA
| | - Zhiquan Zhang
- *Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA
| | - Brian M Barnes
- *Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA
| | - Mihai V Podgoreanu
- *Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA*Department of Anesthesiology, Systems Modeling of Perioperative Organ Injury Laboratory, Duke University, Box 3094, Durham, NC 27710, USA; Institute for Arctic Biology, University of Alaska, Fairbanks, AK, USA
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Abstract
We have demonstrated that 5'-adenosine-monophosphate (5'-AMP) can be used to induce deep hypometabolism in mice and other non-hibernating mammals. This reversible 5'-AMP induced hypomatabolism (AIHM) allows mice to maintain a body temperature about 1°C above the ambient temperature for several hours before spontaneous reversal to euthermia. Our biochemical and gene expression studies suggested that the molecular processes involved in AIHM behavior most likely occur at the metabolic interconversion level, rather than the gene or protein expression level. To understand the metabolic processes involved in AIHM behavior, we conducted a non-targeted comparative metabolomics investigation at multiple stages of AIHM in the plasma, liver and brain of animals that underwent AIHM. Dozens of metabolites representing many important metabolic pathways were detected and measured using a metabolite profiling platform combining both LC-MS and GC-MS. Our findings indicate that there is a widespread suppression of energy generating metabolic pathways but lipid metabolism appears to be minimally altered. Regulation of carbohydrate metabolites appears to be the major way the animal utilizes energy in AIHM and during the following recovery process. The 5'-AMP administered has largely been catabolized by the time the animals have entered AIHM. During AIHM, the urea cycle appears to be functional, helping to avoid ammonia toxicity. Of all tissues studied, brain's metabolite flux is the least affected by AIHM.
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Affiliation(s)
- Zhaoyang Zhao
- Department of Biochemistry and Molecular Biology, Medical School, University of Texas, Health Science Center (UTHealth), Houston, Texas, USA
| | - Anita Van Oort
- Department of Biochemistry and Molecular Biology, Medical School, University of Texas, Health Science Center (UTHealth), Houston, Texas, USA
| | - Zhenyin Tao
- Department of Biochemistry and Molecular Biology, Medical School, University of Texas, Health Science Center (UTHealth), Houston, Texas, USA
| | - William G O'Brien
- Department of Biochemistry and Molecular Biology, Medical School, University of Texas, Health Science Center (UTHealth), Houston, Texas, USA
| | - Cheng Chi Lee
- Department of Biochemistry and Molecular Biology, Medical School, University of Texas, Health Science Center (UTHealth), Houston, Texas, USA
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42
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Central activation of the A1 adenosine receptor (A1AR) induces a hypothermic, torpor-like state in the rat. J Neurosci 2013; 33:14512-25. [PMID: 24005302 DOI: 10.1523/jneurosci.1980-13.2013] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Since central activation of A1 adenosine receptors (A1ARs) plays an important role in the induction of the hypothermic and hypometabolic torpid state in hibernating mammals, we investigated the potential for the A1AR agonist N6-cyclohexyladenosine to induce a hypothermic, torpor-like state in the (nonhibernating) rat. Core and brown adipose tissue temperatures, EEG, heart rate, and arterial pressure were recorded in free-behaving rats, and c-fos expression in the brain was analyzed, following central administration of N6-cyclohexyladenosine. Additionally, we recorded the sympathetic nerve activity to brown adipose tissue; expiratory CO2 and skin, core, and brown adipose tissue temperatures; and shivering EMGs in anesthetized rats following central and localized, nucleus of the solitary tract, administration of N6-cyclohexyladenosine. In rats exposed to a cool (15°C) ambient temperature, central A1AR stimulation produced a torpor-like state similar to that in hibernating species and characterized by a marked fall in body temperature due to an inhibition of brown adipose tissue and shivering thermogenesis that is mediated by neurons in the nucleus of the solitary tract. During the induced hypothermia, EEG amplitude and heart rate were markedly reduced. Skipped heartbeats and transient bradycardias occurring during the hypothermia were vagally mediated since they were eliminated by systemic muscarinic receptor blockade. These findings demonstrate that a deeply hypothermic, torpor-like state can be pharmacologically induced in a nonhibernating mammal and that recovery of normothermic homeostasis ensues upon rewarming. These results support the potential for central activation of A1ARs to be used in the induction of a hypothermic, therapeutically beneficial state in humans.
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Olson JM, Jinka TR, Larson LK, Danielson JJ, Moore JT, Carpluck J, Drew KL. Circannual rhythm in body temperature, torpor, and sensitivity to A₁ adenosine receptor agonist in arctic ground squirrels. J Biol Rhythms 2013; 28:201-7. [PMID: 23735499 DOI: 10.1177/0748730413490667] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A₁ adenosine receptor (A₁AR) activation within the central nervous system induces torpor, but in obligate hibernators such as the arctic ground squirrel (AGS; Urocitellus parryii), A₁AR stimulation induces torpor only during the hibernation season, suggesting a seasonal increase in sensitivity to A₁AR signaling. The purpose of this research was to investigate the relationship between body temperature (Tb) and sensitivity to an adenosine A1 receptor agonist in AGS. We tested the hypothesis that increased sensitivity in A₁AR signaling would lead to lower Tb in euthermic animals during the hibernation season when compared with the summer season. We further predicted that if a decrease in euthermic Tb reflects increased sensitivity to A₁AR activation, then it should likewise predict spontaneous torpor. We used subcutaneous IPTT-300 transponders to monitor Tb in AGS housed under constant ambient conditions (12:12 L:D, 18 °C) for up to 16 months. These animals displayed an obvious rhythm in euthermic Tb that cycled with a period of approximately 8 months. Synchrony in the Tb rhythm within the group was lost after several months of constant L:D conditions; however, individual rhythms in Tb continued to show clear sine wave-like waxing and waning. AGS displayed spontaneous torpor only during troughs in euthermic Tb. To assess sensitivity to A₁AR activation, AGS were administered the A₁AR agonist N(6)-cyclohexyladenosine (CHA, 0.1 mg/kg, ip), and subcutaneous Tb was monitored. AGS administered CHA during a seasonal minimum in euthermic Tb showed a greater drug-induced decrease in Tb (1.6 ± 0.3 °C) than did AGS administered CHA during a peak in euthermic Tb (0.4 ± 0.3 °C). These results provide evidence for a circannual rhythm in Tb that is associated with increased sensitivity to A₁AR signaling and correlates with the onset of torpor.
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Affiliation(s)
- Jasmine M Olson
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA
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Grimpo K, Kutschke M, Kastl A, Meyer CW, Heldmaier G, Exner C, Jastroch M. Metabolic depression during warm torpor in the Golden spiny mouse (Acomys russatus) does not affect mitochondrial respiration and hydrogen peroxide release. Comp Biochem Physiol A Mol Integr Physiol 2013; 167:7-14. [PMID: 24021912 DOI: 10.1016/j.cbpa.2013.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 09/03/2013] [Accepted: 09/03/2013] [Indexed: 01/08/2023]
Abstract
Small mammals actively decrease metabolism during daily torpor and hibernation to save energy. Recently, depression of mitochondrial substrate oxidation in isolated liver mitochondria was observed and associated to hypothermic/hypometabolic states in Djungarian hamsters, mice and hibernators. We aimed to clarify whether hypothermia or hypometabolism causes mitochondrial depression during torpor by studying the Golden spiny mouse (Acomys russatus), a desert rodent which performs daily torpor at high ambient temperatures of 32°C. Notably, metabolic rate but not body temperature is significantly decreased under these conditions. In isolated liver, heart, skeletal muscle or kidney mitochondria we found no depression of respiration. Moderate cold exposure lowered torpor body temperature but had minor effects on minimal metabolic rate in torpor. Neither decreased body temperature nor metabolic rate impacted mitochondrial respiration. Measurements of mitochondrial proton leak kinetics and determination of P/O ratio revealed no differences in mitochondrial efficiency. Hydrogen peroxide release from mitochondria was not affected. We conclude that interspecies differences of mitochondrial depression during torpor do not support a general relationship between mitochondrial respiration, body temperature and metabolic rate. In Golden spiny mice, reduction of metabolic rate at mild temperatures is not triggered by depression of substrate oxidation as found in liver mitochondria from other cold-exposed rodents.
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Affiliation(s)
- Kirsten Grimpo
- Philipps-Universität Marburg, Faculty of Biology, Department of Animal Physiology, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany
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