1
|
Lazarov NE, Atanasova DY. Mechanisms of Chemosensory Transduction in the Carotid Body. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2023; 237:49-62. [PMID: 37946077 DOI: 10.1007/978-3-031-44757-0_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The mammalian carotid body (CB) is a polymodal chemoreceptor, which is activated by blood-borne stimuli, most notably hypoxia, hypercapnia and acidosis, thus ensuring an appropriate cellular response to changes in physical and chemical parameters of the blood. The glomus cells are considered the CB chemosensory cells and the initial site of chemoreceptor transduction. However, the molecular mechanisms by which they detect changes in blood chemical levels and how these changes lead to transmitter release are not yet well understood. Chemotransduction mechanisms are by far best described for oxygen and acid/carbon dioxide sensing. A few testable hypotheses have been postulated including a direct interaction of oxygen with ion channels in the glomus cells (membrane hypothesis), an indirect interface by a reversible ligand like a heme (metabolic hypothesis), or even a functional interaction between putative oxygen sensors (chemosome hypothesis) or the interaction of lactate with a highly expressed in the CB atypical olfactory receptor, Olfr78, (endocrine model). It is also suggested that sensory transduction in the CB is uniquely dependent on the actions and interactions of gaseous transmitters. Apparently, oxygen sensing does not utilize a single mechanism, and later observations have given strong support to a unified membrane model of chemotransduction.
Collapse
Affiliation(s)
- Nikolai E Lazarov
- Department of Anatomy and Histology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria.
| | | |
Collapse
|
2
|
Mitochondrial Succinate Metabolism and Reactive Oxygen Species Are Important but Not Essential for Eliciting Carotid Body and Ventilatory Responses to Hypoxia in the Rat. Antioxidants (Basel) 2021; 10:antiox10060840. [PMID: 34070267 PMCID: PMC8225218 DOI: 10.3390/antiox10060840] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/18/2021] [Accepted: 05/21/2021] [Indexed: 01/31/2023] Open
Abstract
Reflex increases in breathing in response to acute hypoxia are dependent on activation of the carotid body (CB)—A specialised peripheral chemoreceptor. Central to CB O2-sensing is their unique mitochondria but the link between mitochondrial inhibition and cellular stimulation is unresolved. The objective of this study was to evaluate if ex vivo intact CB nerve activity and in vivo whole body ventilatory responses to hypoxia were modified by alterations in succinate metabolism and mitochondrial ROS (mitoROS) generation in the rat. Application of diethyl succinate (DESucc) caused concentration-dependent increases in chemoafferent frequency measuring approximately 10–30% of that induced by severe hypoxia. Inhibition of mitochondrial succinate metabolism by dimethyl malonate (DMM) evoked basal excitation and attenuated the rise in chemoafferent activity in hypoxia. However, approximately 50% of the response to hypoxia was preserved. MitoTEMPO (MitoT) and 10-(6′-plastoquinonyl) decyltriphenylphosphonium (SKQ1) (mitochondrial antioxidants) decreased chemoafferent activity in hypoxia by approximately 20–50%. In awake animals, MitoT and SKQ1 attenuated the rise in respiratory frequency during hypoxia, and SKQ1 also significantly blunted the overall hypoxic ventilatory response (HVR) by approximately 20%. Thus, whilst the data support a role for succinate and mitoROS in CB and whole body O2-sensing in the rat, they are not the sole mediators. Treatment of the CB with mitochondrial selective antioxidants may offer a new approach for treating CB-related cardiovascular–respiratory disorders.
Collapse
|
3
|
Gattuso A, Garofalo F, Cerra MC, Imbrogno S. Hypoxia Tolerance in Teleosts: Implications of Cardiac Nitrosative Signals. Front Physiol 2018; 9:366. [PMID: 29706897 PMCID: PMC5906588 DOI: 10.3389/fphys.2018.00366] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/26/2018] [Indexed: 12/18/2022] Open
Abstract
Changes in environmental oxygen (O2) are naturally occurring phenomena which ectotherms have to face on. Many species exhibit a striking capacity to survive and remain active for long periods under hypoxia, even tolerating anoxia. Some fundamental adaptations contribute to this capacity: metabolic suppression, tolerance of pH and ionic unbalance, avoidance and/or repair of free-radical-induced cell injury during reoxygenation. A remarkable feature of these species is their ability to preserve a normal cardiovascular performance during hypoxia/anoxia to match peripheral (tissue pO2) requirements. In this review, we will refer to paradigms of hypoxia- and anoxia-tolerant teleost fish to illustrate cardiac physiological strategies that, by involving nitric oxide and its metabolites, play a critical role in the adaptive responses to O2 limitation. The information here reported may contribute to clarify the molecular and cellular mechanisms underlying heart vulnerability vs. resistance in relation to O2 availability.
Collapse
Affiliation(s)
- Alfonsina Gattuso
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Filippo Garofalo
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Maria C Cerra
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| | - Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
| |
Collapse
|
4
|
Wang F, Chen ZH, Shabala S. Hypoxia Sensing in Plants: On a Quest for Ion Channels as Putative Oxygen Sensors. PLANT & CELL PHYSIOLOGY 2017; 58:1126-1142. [PMID: 28838128 DOI: 10.1093/pcp/pcx079] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 05/22/2017] [Indexed: 05/18/2023]
Abstract
Over 17 million km2 of land is affected by soil flooding every year, resulting in substantial yield losses and jeopardizing food security across the globe. A key step in resolving this problem and creating stress-tolerant cultivars is an understanding of the mechanisms by which plants sense low-oxygen stress. In this work, we review the current knowledge about the oxygen-sensing and signaling pathway in mammalian and plant systems and postulate the potential role of ion channels as putative oxygen sensors in plant roots. We first discuss the definition and requirements for the oxygen sensor and the difference between sensing and signaling. We then summarize the literature and identify several known candidates for oxygen sensing in the mammalian literature. This includes transient receptor potential (TRP) channels; K+-permeable channels (Kv, BK and TASK); Ca2+ channels (RyR and TPC); and various chemo- and reactive oxygen species (ROS)-dependent oxygen sensors. Identified key oxygen-sensing domains (PAS, GCS, GAF and PHD) in mammalian systems are used to predict the potential plant counterparts in Arabidopsis. Finally, the sequences of known mammalian ion channels with reported roles in oxygen sensing were employed to BLAST the Arabidopsis genome for the candidate genes. Several plasma membrane and tonoplast ion channels (such as TPC, AKT and KCO) and oxygen domain-containing proteins with predicted oxygen-sensing ability were identified and discussed. We propose a testable model for potential roles of ion channels in plant hypoxia sensing.
Collapse
Affiliation(s)
- Feifei Wang
- School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Zhong-Hua Chen
- School of Science and Health, Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Sergey Shabala
- School of Land and Food, University of Tasmania, Hobart, Tasmania 7001, Australia
| |
Collapse
|
5
|
Jurcsisn JG, Pye RL, Ali J, Barr BL, Wyatt CN. The CamKKβ Inhibitor STO609 Causes Artefacts in Calcium Imaging and Selectively Inhibits BKCa in Mouse Carotid Body Type I Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 860:17-24. [DOI: 10.1007/978-3-319-18440-1_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
|
6
|
Turner PJ, Buckler KJ. Oxygen and mitochondrial inhibitors modulate both monomeric and heteromeric TASK-1 and TASK-3 channels in mouse carotid body type-1 cells. J Physiol 2013; 591:5977-98. [PMID: 24042502 DOI: 10.1113/jphysiol.2013.262022] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In rat arterial chemoreceptors, background potassium channels play an important role in maintaining resting membrane potential and promoting depolarization and excitation in response to hypoxia or acidosis. It has been suggested that these channels are a heterodimer of TASK-1 and TASK-3 based on their similarity to heterologously expressed TASK-1/3 fusion proteins. In this study, we sought to confirm the identity of these channels through germline ablation of Task-1 (Kcnk3) and Task-3 (Kcnk9) in mice. Background K-channels were abundant in carotid body type-1 cells from wild-type mice and comparable to those previously described in rat type-1 cells with a main conductance state of 33 pS. This channel was absent from both Task-1(-/-) and Task-3(-/-) cells. In its place we observed a larger (38 pS) K(+)-channel in Task-1(-/-) cells and a smaller (18 pS) K(+)-channel in Task-3(-/-) cells. None of these channels were observed in Task-1(-/-)/Task-3(-/-) double knock-out mice. We therefore conclude that the predominant background K-channel in wild-type mice is a TASK-1/TASK-3 heterodimer, whereas that in Task-1(-/-) mice is TASK-3 and, conversely, that in Task-3(-/-) mice is TASK-1. All three forms of TASK channel in type-1 cells were inhibited by hypoxia, cyanide and the uncoupler FCCP, but the greatest sensitivity was seen in TASK-1 and TASK-1/TASK-3 channels. In summary, the background K-channel in type-1 cells is predominantly a TASK-1/TASK-3 heterodimer. Although both TASK-1 and TASK-3 are able to couple to the oxygen and metabolism sensing pathways present in type-1 cells, channels containing TASK-1 appear to be more sensitive.
Collapse
Affiliation(s)
- Philip J Turner
- K. J. Buckler: Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
| | | |
Collapse
|
7
|
Carroll JL, Agarwal A, Donnelly DF, Kim I. Purinergic modulation of carotid body glomus cell hypoxia response during postnatal maturation in rats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 758:249-53. [PMID: 23080169 DOI: 10.1007/978-94-007-4584-1_34] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Carotid body (CB) glomus cells respond to hypoxia by releasing neurotransmitters, such as ATP, which are believed to stimulate excitatory receptors on apposed nerve endings of the carotid sinus nerves as well as bind to autoreceptors on the glomus cell membrane to modulate response magnitude. The CB response to hypoxia is small at birth and increases during postnatal maturation in mammals. As ATP has been shown to inhibit the glomus cell response to hypoxia via an autoreceptor mechanism, we hypothesized that ATP-mediated inhibition may vary with age and play a role in postnatal development of the hypoxia response magnitude. The effects of ATP on CB glomus cell intracellular calcium ([Ca(2+)](i)) responses to hypoxia were studied at two ages, P0-1 and P14-18. The inhibitory effect of ATP or a stable ATP analog on the glomus cell response to hypoxia was greater in newborn rats compared to the more mature age group. Use of selective P2Y receptor agonists and antagonists suggests that the inhibitory effect of ATP on the glomus cell [Ca(2+)](i) response to hypoxia may be mediated by a P2Y12 receptor. Thus, developmental changes in ATP-mediated glomus cell inhibition may play a role in carotid chemoreceptor postnatal maturation.
Collapse
Affiliation(s)
- John L Carroll
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA.
| | | | | | | |
Collapse
|
8
|
Zhang R, Sun H, Liao C, Yang H, Zhao B, Tian J, Dong S, Zhang Z, Jiao J. Chronic hypoxia in cultured human podocytes inhibits BKCa channels by upregulating its β4-subunit. Biochem Biophys Res Commun 2012; 420:505-10. [DOI: 10.1016/j.bbrc.2012.03.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 03/07/2012] [Indexed: 01/30/2023]
|
9
|
Evans AM, Peers C, Wyatt CN, Kumar P, Hardie DG. Ion channel regulation by the LKB1-AMPK signalling pathway: the key to carotid body activation by hypoxia and metabolic homeostasis at the whole body level. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 758:81-90. [PMID: 23080146 DOI: 10.1007/978-94-007-4584-1_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Our recent investigations provide further support for the proposal that, consequent to inhibition of mitochondrial oxidative phosphorylation, activation of AMP-activated protein kinase (AMPK) mediates carotid body excitation by hypoxia. Consistent with the effects of hypoxia, intracellular dialysis from a patch pipette of an active (thiophosphorylated) recombinant AMPK heterotrimer (α2β2γ1) or application of the AMPK activators AICAR and A769662: (1) Inhibited BK(Ca) currents and TASK K(+) currents in rat carotid body type I cells; (2) Inhibited whole-cell currents carried by KCa1.1 and TASK3, but not TASK1 channels expressed in HEK293 cells; (3) Triggered carotid body activation. Furthermore, preliminary studies using mice with conditional knockout in type I cells of the primary upstream kinase that activates AMPK in response to metabolic stresses, LKB1, appear to confirm our working hypothesis. Studies on mice with knockout of the catalytic α1 subunit and α2 subunits of AMPK, respectively, have proved equally consistent. Accumulating evidence therefore suggests that the LKB1-AMPK signalling pathway is necessary for hypoxia-response coupling by the carotid body, and serves to regulate oxygen and therefore energy supply at the whole body level.
Collapse
Affiliation(s)
- A Mark Evans
- College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK.
| | | | | | | | | |
Collapse
|
10
|
Kajimura M, Fukuda R, Bateman RM, Yamamoto T, Suematsu M. Interactions of multiple gas-transducing systems: hallmarks and uncertainties of CO, NO, and H2S gas biology. Antioxid Redox Signal 2010; 13:157-92. [PMID: 19939208 PMCID: PMC2925289 DOI: 10.1089/ars.2009.2657] [Citation(s) in RCA: 219] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The diverse physiological actions of the "biologic gases," O2, CO, NO, and H2S, have attracted much interest. Initially viewed as toxic substances, CO, NO, and H2S play important roles as signaling molecules. The multiplicity of gas actions and gas targets and the difficulty in measuring local gas concentrations obscures detailed mechanisms whereby gases exert their actions, and many questions remain unanswered. It is now readily apparent, however, that heme-based proteins play central roles in gas-generation/reception mechanisms and provide a point where multiple gases can interact. In this review, we consider a number of key issues related to "gas biology," including the effective tissue concentrations of these gases and the importance and significance of the physical proximity of gas-producing and gas-receptor/sensors. We also take an integrated approach to the interaction of gases by considering the physiological significance of CO, NO, and H2S on mitochondrial cytochrome c oxidase, a key target and central mediator of mitochondrial respiration. Additionally, we consider the effects of biologic gases on mitochondrial biogenesis and "suspended animation." By evaluating gas-mediated control functions from both in vitro and in vivo perspectives, we hope to elaborate on the complex multiple interactions of O2, NO, CO, and H2S.
Collapse
Affiliation(s)
- Mayumi Kajimura
- Department of Biochemistry and Integrative Medical Biology, School of Medicine, Keio University , Tokyo, Japan.
| | | | | | | | | |
Collapse
|
11
|
Teppema LJ, Dahan A. The Ventilatory Response to Hypoxia in Mammals: Mechanisms, Measurement, and Analysis. Physiol Rev 2010; 90:675-754. [DOI: 10.1152/physrev.00012.2009] [Citation(s) in RCA: 257] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The respiratory response to hypoxia in mammals develops from an inhibition of breathing movements in utero into a sustained increase in ventilation in the adult. This ventilatory response to hypoxia (HVR) in mammals is the subject of this review. The period immediately after birth contains a critical time window in which environmental factors can cause long-term changes in the structural and functional properties of the respiratory system, resulting in an altered HVR phenotype. Both neonatal chronic and chronic intermittent hypoxia, but also chronic hyperoxia, can induce such plastic changes, the nature of which depends on the time pattern and duration of the exposure (acute or chronic, episodic or not, etc.). At adult age, exposure to chronic hypoxic paradigms induces adjustments in the HVR that seem reversible when the respiratory system is fully matured. These changes are orchestrated by transcription factors of which hypoxia-inducible factor 1 has been identified as the master regulator. We discuss the mechanisms underlying the HVR and its adaptations to chronic changes in ambient oxygen concentration, with emphasis on the carotid bodies that contain oxygen sensors and initiate the response, and on the contribution of central neurotransmitters and brain stem regions. We also briefly summarize the techniques used in small animals and in humans to measure the HVR and discuss the specific difficulties encountered in its measurement and analysis.
Collapse
Affiliation(s)
- Luc J. Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| |
Collapse
|
12
|
Nurse CA. Neurotransmitter and neuromodulatory mechanisms at peripheral arterial chemoreceptors. Exp Physiol 2010; 95:657-67. [PMID: 20360424 DOI: 10.1113/expphysiol.2009.049312] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The control of breathing depends critically on sensory inputs to the central pattern generator of the brainstem, arising from peripheral arterial chemoreceptors located principally in the carotid bodies (CBs). The CB receptors, i.e. glomus or type I cells, are excited by chemical stimuli in arterial blood, particularly hypoxia, hypercapnia, acidosis and low glucose, which initiate corrective reflex cardiorespiratory and cardiovascular adjustments. Type I cells occur in clusters and are innervated by petrosal afferent fibres. Synaptic specializations (both chemical and electrical) occur between type I cells and petrosal terminals, and between neighbouring type I cells. This, together with the presence of a wide array of neurotransmitters and neuromodulators linked to both ionotropic and metabotropic receptors, allows for a complex modulation of CB sensory output. Studies in several laboratories over the last 20 years have provided much insight into the transduction mechanisms. More recent studies, aided by the development of a co-culture model of the rat CB, have shed light on the role of neurotransmitters and neuromodulators in shaping the afferent response. This review highlights some of these developments, which have contributed to our current understanding of information processing at CB chemoreceptors.
Collapse
Affiliation(s)
- Colin A Nurse
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.
| |
Collapse
|
13
|
Gariépy JF, Missaghi K, Dubuc R. The interactions between locomotion and respiration. PROGRESS IN BRAIN RESEARCH 2010; 187:173-88. [DOI: 10.1016/b978-0-444-53613-6.00012-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
14
|
Perry S, Jonz M, Gilmour K. Chapter 5 Oxygen Sensing And The Hypoxic Ventilatory Response. FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(08)00005-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
15
|
Olson KR. Hydrogen sulfide and oxygen sensing: implications in cardiorespiratory control. ACTA ACUST UNITED AC 2008; 211:2727-34. [PMID: 18723529 DOI: 10.1242/jeb.010066] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Although all cells are variously affected by oxygen, a few have the responsibility of monitoring oxygen tensions and initiating key homeostatic responses when P(O2) falls to critical levels. These ;oxygen-sensing' cells include the chemoreceptors in the gills (neuroepithelial cells), airways (neuroepithelial bodies) and vasculature (carotid bodies) that initiate cardiorespiratory reflexes, oxygen sensitive chromaffin cells associated with systemic veins or adrenal glands that regulate the rate of catecholamine secretion, and vascular smooth muscle cells capable of increasing blood flow to systemic tissues, or decreasing it through the lungs. In spite of intense research, and enormous clinical applicability, there is little, if any, consensus regarding the mechanism of how these cells sense oxygen and transduce this into the appropriate physiological response. We have recently proposed that the metabolism of hydrogen sulfide (H2S) may serve as an 'oxygen sensor' in vertebrate vascular smooth muscle and preliminary evidence suggests it has similar activity in gill chemoreceptors. In this proposed mechanism, the cellular concentration of H2S is determined by the simple balance between constitutive H2S production in the cytoplasm and H2S oxidation in the mitochondria; when tissue oxygen levels fall the rate of H2S oxidation decreases and the concentration of biologically active H2S in the tissue increases. This commentary briefly describes the oxygen-sensitive tissues in fish and mammals, delineates the current hypotheses of oxygen sensing by these tissues, and then critically evaluates the evidence for H2S metabolism in oxygen sensing.
Collapse
Affiliation(s)
- Kenneth R Olson
- Indiana University School of Medicine, South Bend Center, South Bend, Indiana 46617, USA.
| |
Collapse
|
16
|
Olson KR, Healy MJ, Qin Z, Skovgaard N, Vulesevic B, Duff DW, Whitfield NL, Yang G, Wang R, Perry SF. Hydrogen sulfide as an oxygen sensor in trout gill chemoreceptors. Am J Physiol Regul Integr Comp Physiol 2008; 295:R669-80. [PMID: 18565835 DOI: 10.1152/ajpregu.00807.2007] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
O2 chemoreceptors elicit cardiorespiratory reflexes in all vertebrates, but consensus on O2-sensing signal transduction mechanism(s) is lacking. We recently proposed that hydrogen sulfide (H2S) metabolism is involved in O2 sensing in vascular smooth muscle. Here, we examined the possibility that H2S is an O2 sensor in trout chemoreceptors where the first pair of gills is a primary site of aquatic O2 sensing and the homolog of the mammalian carotid body. Intrabuccal injection of H2S in unanesthetized trout produced a dose-dependent bradycardia and increased ventilatory frequency and amplitude similar to the hypoxic response. Removal of the first, but not second, pair of gills significantly inhibited H2S-mediated bradycardia, consistent with the loss of aquatic chemoreceptors. mRNA for H2S-synthesizing enzymes, cystathionine beta-synthase and cystathionine gamma-lyase, was present in branchial tissue. Homogenized gills produced H2S enzymatically, and H2S production was inhibited by O2, whereas mitochondrial H2S consumption was O2 dependent. Ambient hypoxia did not affect plasma H2S in unanesthetized trout, but produced a PO2-dependent increase in a sulfide moiety suggestive of increased H2S production. In isolated zebrafish neuroepithelial cells, the putative chemoreceptive cells of fish, both hypoxia and H2S, produced a similar approximately 10-mV depolarization. These studies are consistent with H2S involvement in O2 sensing/signal transduction pathway(s) in chemoreceptive cells, as previously demonstrated in vascular smooth muscle. This novel mechanism, whereby H2S concentration ([H2S]) is governed by the balance between constitutive production and oxidation, tightly couples tissue [H2S] to PO2 and may provide an exquisitely sensitive, yet simple, O2 sensor in a variety of tissues.
Collapse
Affiliation(s)
- Kenneth R Olson
- Indiana University School of Medicine-South Bend, 1234 Notre Dame Ave., South Bend, IN 46617, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Kumar P, Prabhakar N. Sensing hypoxia: Carotid body mechanisms and reflexes in health and disease. Respir Physiol Neurobiol 2007; 157:1-3. [PMID: 17368118 DOI: 10.1016/j.resp.2007.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 02/03/2007] [Accepted: 02/05/2007] [Indexed: 11/22/2022]
|