1
|
Amorim MR, Wang X, Aung O, Bevans-Fonti S, Anokye-Danso F, Ribeiro C, Escobar J, Freire C, Pho H, Dergacheva O, Branco LGS, Ahima RS, Mendelowitz D, Polotsky VY. Leptin signaling in the dorsomedial hypothalamus couples breathing and metabolism in obesity. Cell Rep 2023; 42:113512. [PMID: 38039129 PMCID: PMC10804286 DOI: 10.1016/j.celrep.2023.113512] [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: 05/14/2023] [Revised: 10/25/2023] [Accepted: 11/14/2023] [Indexed: 12/03/2023] Open
Abstract
Mismatch between CO2 production (Vco2) and respiration underlies the pathogenesis of obesity hypoventilation. Leptin-mediated CNS pathways stimulate both metabolism and breathing, but interactions between these functions remain elusive. We hypothesized that LEPRb+ neurons of the dorsomedial hypothalamus (DMH) regulate metabolism and breathing in obesity. In diet-induced obese LeprbCre mice, chemogenetic activation of LEPRb+ DMH neurons increases minute ventilation (Ve) during sleep, the hypercapnic ventilatory response, Vco2, and Ve/Vco2, indicating that breathing is stimulated out of proportion to metabolism. The effects of chemogenetic activation are abolished by a serotonin blocker. Optogenetic stimulation of the LEPRb+ DMH neurons evokes excitatory postsynaptic currents in downstream serotonergic neurons of the dorsal raphe (DR). Administration of retrograde AAV harboring Cre-dependent caspase to the DR deletes LEPRb+ DMH neurons and abolishes metabolic and respiratory responses to leptin. These findings indicate that LEPRb+ DMH neurons match breathing to metabolism through serotonergic pathways to prevent obesity-induced hypoventilation.
Collapse
Affiliation(s)
- Mateus R Amorim
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA.
| | - Xin Wang
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - O Aung
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Shannon Bevans-Fonti
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA
| | | | - Caitlin Ribeiro
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Joan Escobar
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Carla Freire
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Huy Pho
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Olga Dergacheva
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Luiz G S Branco
- University of São Paulo, Ribeirão Preto, São Paulo 14040-904, Brazil
| | - Rexford S Ahima
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - David Mendelowitz
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Vsevolod Y Polotsky
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA; Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA.
| |
Collapse
|
2
|
Carbon dioxide levels in neonates: what are safe parameters? Pediatr Res 2022; 91:1049-1056. [PMID: 34230621 PMCID: PMC9122818 DOI: 10.1038/s41390-021-01473-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 03/01/2021] [Accepted: 03/02/2021] [Indexed: 02/01/2023]
Abstract
There is no consensus on the optimal pCO2 levels in the newborn. We reviewed the effects of hypercapnia and hypocapnia and existing carbon dioxide thresholds in neonates. A systematic review was conducted in accordance with the PRISMA statement and MOOSE guidelines. Two hundred and ninety-nine studies were screened and 37 studies included. Covidence online software was employed to streamline relevant articles. Hypocapnia was associated with predominantly neurological side effects while hypercapnia was linked with neurological, respiratory and gastrointestinal outcomes and Retinpathy of prematurity (ROP). Permissive hypercapnia did not decrease periventricular leukomalacia (PVL), ROP, hydrocephalus or air leaks. As safe pCO2 ranges were not explicitly concluded in the studies chosen, it was indirectly extrapolated with reference to pCO2 levels that were found to increase the risk of neonatal disease. Although PaCO2 ranges were reported from 2.6 to 8.7 kPa (19.5-64.3 mmHg) in both term and preterm infants, there are little data on the safety of these ranges. For permissive hypercapnia, parameters described for bronchopulmonary dysplasia (BPD; PaCO2 6.0-7.3 kPa: 45.0-54.8 mmHg) and congenital diaphragmatic hernia (CDH; PaCO2 ≤ 8.7 kPa: ≤65.3 mmHg) were identified. Contradictory findings on the effectiveness of permissive hypercapnia highlight the need for further data on appropriate CO2 parameters and correlation with outcomes. IMPACT: There is no consensus on the optimal pCO2 levels in the newborn. There is no consensus on the effectiveness of permissive hypercapnia in neonates. A safe range of pCO2 of 5-7 kPa was inferred following systematic review.
Collapse
|
3
|
Phelan DE, Mota C, Lai C, Kierans SJ, Cummins EP. Carbon dioxide-dependent signal transduction in mammalian systems. Interface Focus 2021; 11:20200033. [PMID: 33633832 PMCID: PMC7898142 DOI: 10.1098/rsfs.2020.0033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/15/2022] Open
Abstract
Carbon dioxide (CO2) is a fundamental physiological gas known to profoundly influence the behaviour and health of millions of species within the plant and animal kingdoms in particular. A recent Royal Society meeting on the topic of 'Carbon dioxide detection in biological systems' was extremely revealing in terms of the multitude of roles that different levels of CO2 play in influencing plants and animals alike. While outstanding research has been performed by leading researchers in the area of plant biology, neuronal sensing, cell signalling, gas transport, inflammation, lung function and clinical medicine, there is still much to be learned about CO2-dependent sensing and signalling. Notably, while several key signal transduction pathways and nodes of activity have been identified in plants and animals respectively, the precise wiring and sensitivity of these pathways to CO2 remains to be fully elucidated. In this article, we will give an overview of the literature relating to CO2-dependent signal transduction in mammalian systems. We will highlight the main signal transduction hubs through which CO2-dependent signalling is elicited with a view to better understanding the complex physiological response to CO2 in mammalian systems. The main topics of discussion in this article relate to how changes in CO2 influence cellular function through modulation of signal transduction networks influenced by pH, mitochondrial function, adenylate cyclase, calcium, transcriptional regulators, the adenosine monophosphate-activated protein kinase pathway and direct CO2-dependent protein modifications. While each of these topics will be discussed independently, there is evidence of significant cross-talk between these signal transduction pathways as they respond to changes in CO2. In considering these core hubs of CO2-dependent signal transduction, we hope to delineate common elements and identify areas in which future research could be best directed.
Collapse
Affiliation(s)
- D. E. Phelan
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - C. Mota
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - C. Lai
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - S. J. Kierans
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - E. P. Cummins
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| |
Collapse
|
4
|
Hypoxia Inducible Factor 1A Supports a Pro-Fibrotic Phenotype Loop in Idiopathic Pulmonary Fibrosis. Int J Mol Sci 2021; 22:ijms22073331. [PMID: 33805152 PMCID: PMC8078165 DOI: 10.3390/ijms22073331] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 03/18/2021] [Accepted: 03/22/2021] [Indexed: 12/11/2022] Open
Abstract
Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with poor prognosis. The IPF-conditioned matrix (IPF-CM) system enables the study of matrix–fibroblast interplay. While effective at slowing fibrosis, nintedanib has limitations and the mechanism is not fully elucidated. In the current work, we explored the underlying signaling pathways and characterized nintedanib involvement in the IPF-CM fibrotic process. Results were validated using IPF patient samples and bleomycin-treated animals with/without oral and inhaled nintedanib. IPF-derived primary human lung fibroblasts (HLFs) were cultured on Matrigel and then cleared using NH4OH, creating the IPF-CM. Normal HLF-CM served as control. RNA-sequencing, PCR and western-blots were performed. HIF1α targets were evaluated by immunohistochemistry in bleomycin-treated rats with/without nintedanib and in patient samples with IPF. HLFs cultured on IPF-CM showed over-expression of ‘HIF1α signaling pathway’ (KEGG, p < 0.0001), with emphasis on SERPINE1 (PAI-1), VEGFA and TIMP1. IPF patient samples showed high HIF1α staining, especially in established fibrous tissue. PAI-1 was overexpressed, mainly in alveolar macrophages. Nintedanib completely reduced HIF1α upregulation in the IPF-CM and rat-bleomycin models. IPF-HLFs alter the extracellular matrix, thus creating a matrix that further propagates an IPF-like phenotype in normal HLFs. This pro-fibrotic loop includes the HIF1α pathway, which can be blocked by nintedanib.
Collapse
|
5
|
Meshchaninov V, Shcherbakov D, Zvezdina E, Gavrilov I. Use of dry carbonic acid gas baths to correct human biological age. BIO WEB OF CONFERENCES 2020. [DOI: 10.1051/bioconf/20202201012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Relevance. The physiotherapy method of dry carbonic acid gas baths (DCAGB) mediated through the effects of carbon dioxide (CO2) is a minimally invasive treatment and prevention method of many human diseases. However, the CO2 effect on the rate of human aging has not been sufficiently studied. Therefore, it is relevant to study the effect of dry carbonic acid gas baths (DCAGB) physiotherapy method on peripheral blood indicators and biological age. Purpose. To assess the effect of carbon dioxide in dry carbonic acid gas baths condition on peripheral blood indicators and biological age in patients of different age groups. Patients and methods. An interventional single center controlled clinical trial was conducted on 140 male patients. Within 1 day before the DCAGB sessions course start (10 sessions 40 minutes each) and 1 day after course completion, patients’ peripheral blood samples were studied, as well as biological and cardiopulmonal age on the patented method was determined.
Results. DCAGB course reduced biological age in young and middle-aged patients by 5.5 years (p<0.001), elderly and old patients – by 4.7 years (p<0.001), elderly and old patients had a decrease in cardiopulmonal bio age by 8.6 years (p<0.01).
Conclusion. The course of DCAGB sessions slowed the aging rate of the human body from young to old age, which was probably associated with antihypoxic, antitoxic, antioxidant effects of carbon dioxide, as well as possibly with erythropoiesis activation.
Collapse
|
6
|
Cummins EP, Strowitzki MJ, Taylor CT. Mechanisms and Consequences of Oxygen and Carbon Dioxide Sensing in Mammals. Physiol Rev 2019; 100:463-488. [PMID: 31539306 DOI: 10.1152/physrev.00003.2019] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Molecular oxygen (O2) and carbon dioxide (CO2) are the primary gaseous substrate and product of oxidative phosphorylation in respiring organisms, respectively. Variance in the levels of either of these gasses outside of the physiological range presents a serious threat to cell, tissue, and organism survival. Therefore, it is essential that endogenous levels are monitored and kept at appropriate concentrations to maintain a state of homeostasis. Higher organisms such as mammals have evolved mechanisms to sense O2 and CO2 both in the circulation and in individual cells and elicit appropriate corrective responses to promote adaptation to commonly encountered conditions such as hypoxia and hypercapnia. These can be acute and transient nontranscriptional responses, which typically occur at the level of whole animal physiology or more sustained transcriptional responses, which promote chronic adaptation. In this review, we discuss the mechanisms by which mammals sense changes in O2 and CO2 and elicit adaptive responses to maintain homeostasis. We also discuss crosstalk between these pathways and how they may represent targets for therapeutic intervention in a range of pathological states.
Collapse
Affiliation(s)
- Eoin P Cummins
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Moritz J Strowitzki
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Cormac T Taylor
- UCD Conway Institute, Systems Biology Ireland and the School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| |
Collapse
|
7
|
Strowitzki MJ, Cummins EP, Taylor CT. Protein Hydroxylation by Hypoxia-Inducible Factor (HIF) Hydroxylases: Unique or Ubiquitous? Cells 2019; 8:cells8050384. [PMID: 31035491 PMCID: PMC6562979 DOI: 10.3390/cells8050384] [Citation(s) in RCA: 131] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/24/2019] [Accepted: 04/24/2019] [Indexed: 02/07/2023] Open
Abstract
All metazoans that utilize molecular oxygen (O2) for metabolic purposes have the capacity to adapt to hypoxia, the condition that arises when O2 demand exceeds supply. This is mediated through activation of the hypoxia-inducible factor (HIF) pathway. At physiological oxygen levels (normoxia), HIF-prolyl hydroxylases (PHDs) hydroxylate proline residues on HIF-α subunits leading to their destabilization by promoting ubiquitination by the von-Hippel Lindau (VHL) ubiquitin ligase and subsequent proteasomal degradation. HIF-α transactivation is also repressed in an O2-dependent way due to asparaginyl hydroxylation by the factor-inhibiting HIF (FIH). In hypoxia, the O2-dependent hydroxylation of HIF-α subunits by PHDs and FIH is reduced, resulting in HIF-α accumulation, dimerization with HIF-β and migration into the nucleus to induce an adaptive transcriptional response. Although HIFs are the canonical substrates for PHD- and FIH-mediated protein hydroxylation, increasing evidence indicates that these hydroxylases may also have alternative targets. In addition to PHD-conferred alterations in protein stability, there is now evidence that hydroxylation can affect protein activity and protein/protein interactions for alternative substrates. PHDs can be pharmacologically inhibited by a new class of drugs termed prolyl hydroxylase inhibitors which have recently been approved for the treatment of anemia associated with chronic kidney disease. The identification of alternative targets of HIF hydroxylases is important in order to fully elucidate the pharmacology of hydroxylase inhibitors (PHI). Despite significant technical advances, screening, detection and verification of alternative functional targets for PHDs and FIH remain challenging. In this review, we discuss recently proposed non-HIF targets for PHDs and FIH and provide an overview of the techniques used to identify these.
Collapse
Affiliation(s)
- Moritz J Strowitzki
- UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Eoin P Cummins
- UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Cormac T Taylor
- UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
- School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
- Systems Biology Ireland, University College Dublin, Belfield, Dublin 4, Ireland.
| |
Collapse
|
8
|
Cummins EP. Physiological gases in health and disease - key regulatory factors, not just a lot of hot air. J Physiol 2018; 595:2421-2422. [PMID: 28406542 DOI: 10.1113/jp274042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Eoin P Cummins
- School of Medicine and Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
| |
Collapse
|
9
|
Silva TM, Chaar LJ, Silva RC, Takakura AC, Câmara NO, Antunes VR, Moreira TS. Minocycline alters expression of inflammatory markers in autonomic brain areas and ventilatory responses induced by acute hypoxia. Exp Physiol 2018. [DOI: 10.1113/ep086780] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Talita M. Silva
- Department of Physiology and Biophysics; University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Laiali J. Chaar
- Department of Physiology and Biophysics; University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Reinaldo C. Silva
- Department of Immunology; University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Ana C. Takakura
- Department of Pharmacology; Institute of Biomedical Sciences, University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Niels O. Câmara
- Department of Immunology; University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Vagner R. Antunes
- Department of Physiology and Biophysics; University of São Paulo; 05508-000 São Paulo SP Brazil
| | - Thiago S. Moreira
- Department of Physiology and Biophysics; University of São Paulo; 05508-000 São Paulo SP Brazil
| |
Collapse
|
10
|
Keogh CE, Scholz CC, Rodriguez J, Selfridge AC, von Kriegsheim A, Cummins EP. Carbon dioxide-dependent regulation of NF-κB family members RelB and p100 gives molecular insight into CO 2-dependent immune regulation. J Biol Chem 2017; 292:11561-11571. [PMID: 28507099 DOI: 10.1074/jbc.m116.755090] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 05/12/2017] [Indexed: 12/31/2022] Open
Abstract
CO2 is a physiological gas normally produced in the body during aerobic respiration. Hypercapnia (elevated blood pCO2 >≈50 mm Hg) is a feature of several lung pathologies, e.g. chronic obstructive pulmonary disease. Hypercapnia is associated with increased susceptibility to bacterial infections and suppression of inflammatory signaling. The NF-κB pathway has been implicated in these effects; however, the molecular mechanisms underpinning cellular sensitivity of the NF-κB pathway to CO2 are not fully elucidated. Here, we identify several novel CO2-dependent changes in the NF-κB pathway. NF-κB family members p100 and RelB translocate to the nucleus in response to CO2 A cohort of RelB protein-protein interactions (e.g. with Raf-1 and IκBα) are altered by CO2 exposure, although others are maintained (e.g. with p100). RelB is processed by CO2 in a manner dependent on a key C-terminal domain located in its transactivation domain. Loss of the RelB transactivation domain alters NF-κB-dependent transcriptional activity, and loss of p100 alters sensitivity of RelB to CO2 Thus, we provide molecular insight into the CO2 sensitivity of the NF-κB pathway and implicate altered RelB/p100-dependent signaling in the CO2-dependent regulation of inflammatory signaling.
Collapse
Affiliation(s)
- Ciara E Keogh
- From the School of Medicine and Conway Institute and
| | - Carsten C Scholz
- Systems Biology Ireland, University College Dublin, Dublin 4, Ireland.,the Institute of Physiology, University of Zürich, CH-8057 Zürich, Switzerland
| | - Javier Rodriguez
- Systems Biology Ireland, University College Dublin, Dublin 4, Ireland.,the Edinburgh Cancer Research Centre, Edinburgh EH4 2XR, Scotland, United Kingdom, and
| | | | - Alexander von Kriegsheim
- Systems Biology Ireland, University College Dublin, Dublin 4, Ireland.,the Edinburgh Cancer Research Centre, Edinburgh EH4 2XR, Scotland, United Kingdom, and
| | | |
Collapse
|
11
|
Fagundes RR, Taylor CT. Determinants of hypoxia-inducible factor activity in the intestinal mucosa. J Appl Physiol (1985) 2017; 123:1328-1334. [PMID: 28408694 DOI: 10.1152/japplphysiol.00203.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 03/28/2017] [Accepted: 04/07/2017] [Indexed: 12/16/2022] Open
Abstract
The intestinal mucosa is exposed to fluctuations in oxygen levels due to constantly changing rates of oxygen demand and supply and its juxtaposition with the anoxic environment of the intestinal lumen. This frequently results in a state of hypoxia in the healthy mucosa even in the physiologic state. Furthermore, pathophysiologic hypoxia (which is more severe and extensive) is associated with chronic inflammatory diseases including inflammatory bowel disease (IBD). The hypoxia-inducible factor (HIF), a ubiquitously expressed regulator of cellular adaptation to hypoxia, is central to both the adaptive and the inflammatory responses of cells of the intestinal mucosa in IBD patients. In this review, we discuss the microenvironmental factors which influence the level of HIF activity in healthy and inflamed intestinal mucosae and the consequences that increased HIF activity has for tissue function and disease progression.
Collapse
Affiliation(s)
- Raphael R Fagundes
- Graduate School of Medical Sciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; and.,UCD Conway Institute, Systems Biology Ireland and School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Cormac T Taylor
- UCD Conway Institute, Systems Biology Ireland and School of Medicine, University College Dublin, Belfield, Dublin, Ireland
| |
Collapse
|
12
|
Otulakowski G, Engelberts D, Arima H, Hirate H, Bayir H, Post M, Kavanagh BP. α-Tocopherol transfer protein mediates protective hypercapnia in murine ventilator-induced lung injury. Thorax 2017; 72:538-549. [PMID: 28159772 DOI: 10.1136/thoraxjnl-2016-209501] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 12/27/2022]
Abstract
RATIONALE Hypercapnia is common in mechanically ventilated patients. Experimentally, 'therapeutic hypercapnia' can protect, but it can also cause harm, depending on the mechanism of injury. Hypercapnia suppresses multiple signalling pathways. Previous investigations have examined mechanisms that were known a priori, but only a limited number of pathways, each suppressed by CO2, have been reported. OBJECTIVE Because of the complexity and interdependence of processes in acute lung injury, this study sought to fill in knowledge gaps using an unbiased screen, aiming to identify a specifically upregulated pathway. METHODS AND RESULTS Using genome-wide gene expression analysis in a mouse model of ventilator-induced lung injury, we discovered a previously unsuspected mechanism by which CO2 can protect against injury: induction of the transporter protein for α-tocopherol, α-tocopherol transfer protein (αTTP). Pulmonary αTTP was induced by inspired CO2 in two in vivo murine models of ventilator-induced lung injury; the level of αTTP expression correlated with degree of lung protection; and, absence of the αTTP gene significantly reduced the protective effects of CO2. α-Tocopherol is a potent antioxidant and hypercapnia increased lung α-tocopherol in wild-type mice, but this did not alter superoxide generation or expression of NRF2-dependent antioxidant response genes in wild-type or in αTTP-/- mice. In concordance with a regulatory role for α-tocopherol in lipid mediator synthesis, hypercapnia attenuated 5-lipoxygenase activity and this was dependent on the presence of αTTP. CONCLUSIONS Inspired CO2 upregulates αTTP which increases lung α-tocopherol levels and inhibits synthesis of a pathogenic chemoattractant.
Collapse
Affiliation(s)
- Gail Otulakowski
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada
| | - Doreen Engelberts
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada
| | - Hajime Arima
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Critical Care Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Anesthesiology and Intensive Care Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Hiroyuki Hirate
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Critical Care Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Anesthesiology and Intensive Care Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Hülya Bayir
- Department of Environmental and Occupational Health, Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Critical Care Medicine, Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Martin Post
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada
| | - Brian P Kavanagh
- Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Critical Care Medicine, Hospital for Sick Children, Toronto, Canada.,Department of Anesthesia, University of Toronto, Toronto, Canada
| |
Collapse
|
13
|
McLoughlin P, Tipton M. A time of change: out with the old. Exp Physiol 2017; 102:1-2. [PMID: 28044404 DOI: 10.1113/ep086163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Paul McLoughlin
- School of Medicine, University College Dublin, Dublin D4, Ireland
| | - Michael Tipton
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, UK
| |
Collapse
|