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Mahoney KJ, Bowie JS, Ford AE, Perera N, Sekiguchi Y, Fothergill DM, Lee EC. Plasma Proteomics-Based Discovery of Mechanistic Biomarkers of Hyperbaric Stress and Pulmonary Oxygen Toxicity. Metabolites 2023; 13:970. [PMID: 37755249 PMCID: PMC10534745 DOI: 10.3390/metabo13090970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/31/2023] [Accepted: 08/01/2023] [Indexed: 09/28/2023] Open
Abstract
Our aim was to identify proteins that reflect an acute systemic response to prolonged hyperbaric stress and discover potential biomarker pathways for pulmonary O2 toxicity. The study was a double-blind, randomized, crossover design in trained male Navy diver subjects. Each subject completed two dry resting hyperbaric chamber dives separated by a minimum of one week. One dive exposed the subject to 6.5 h of 100% oxygen (O2) at 2ATA. The alternate dive exposed the subjects to an enhanced air nitrox mixture (EAN) containing 30.6% O2 at the same depth for the same duration. Venous blood samples collected before (PRE) and after (POST) each dive were prepared and submitted to LC-MS/MS analysis (2 h runs). A total of 346 total proteins were detected and analyzed. A total of 12 proteins were significantly increased at EANPOST (vs. EANPRE), including proteins in hemostasis and immune signaling and activation. Significantly increased proteins at O2PRE (vs. O2POST) included neural cell adhesion molecule 1, glycoprotein Ib, catalase, hemoglobin subunit beta, fibulin-like proteins, and complement proteins. EANPOST and O2POST differed in biomarkers related to coagulation, immune signaling and activation, and metabolism. Of particular interest is (EANPOST vs. O2POST), which is protective against oxidative stress.
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Affiliation(s)
- Kyle J. Mahoney
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
| | - Jacob S. Bowie
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
| | - Austin E. Ford
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
| | - Neranjan Perera
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
| | - Yasuki Sekiguchi
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
| | | | - Elaine C. Lee
- Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA; (K.J.M.); (J.S.B.); (N.P.)
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2
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Arieli R. The pulmonary oxygen toxicity index. Respir Physiol Neurobiol 2023; 315:104114. [PMID: 37460079 DOI: 10.1016/j.resp.2023.104114] [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: 05/30/2023] [Revised: 07/03/2023] [Accepted: 07/14/2023] [Indexed: 07/29/2023]
Abstract
Pulmonary oxygen toxicity (POT) is a major risk in diving while breathing hyperoxic gas and is also considered in clinical hyperbaric oxygen treatment. The POTindex calculated by the power equation K = t2 × PO24.57 with the recovery form Ktr = Ke × e - [- 0.42 + 0.384 × (PO2)ex] × tr which are based on chemical and physiological principles, have a better prediction power than other suggested approaches. Reduction of vital capacity as well as incidence of POT are well predicted by the POTindex. Both the cumulative pulmonary toxic effect and concomitant recovery were suggested to operate at the lower toxic range of PO2 used in saturation diving K = t2 × PO24.57 × e-0.0135 × t, and further experimental support is supplied. The recovery time constant for the full range of PO2 is presented. POTindex is suggested to replace the old method of UPTD for safe diving. Many diving clubs and diving institutes already adopted the POTindex.
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Affiliation(s)
- R Arieli
- Israel Naval Medical Institute, Haifa, Israel; Eliachar Research Laboratory, Western Galilee Medical Center, Nahariya, Israel.
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3
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Dean JB, Stavitzski NM. The O2-sensitive brain stem, hyperoxic hyperventilation, and CNS oxygen toxicity. Front Physiol 2022; 13:921470. [PMID: 35957982 PMCID: PMC9360621 DOI: 10.3389/fphys.2022.921470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
Central nervous system oxygen toxicity (CNS-OT) is a complex disorder that presents, initially, as a sequence of cardio-respiratory abnormalities and nonconvulsive signs and symptoms (S/Sx) of brain stem origin that culminate in generalized seizures, loss of consciousness, and postictal cardiogenic pulmonary edema. The risk of CNS-OT and its antecedent “early toxic indications” are what limits the use of hyperbaric oxygen (HBO2) in hyperbaric and undersea medicine. The purpose of this review is to illustrate, based on animal research, how the temporal pattern of abnormal brain stem responses that precedes an “oxtox hit” provides researchers a window into the early neurological events underlying seizure genesis. Specifically, we focus on the phenomenon of hyperoxic hyperventilation, and the medullary neurons presumed to contribute in large part to this paradoxical respiratory response; neurons in the caudal Solitary complex (cSC) of the dorsomedial medulla, including putative CO2 chemoreceptor neurons. The electrophysiological and redox properties of O2-/CO2-sensitive cSC neurons identified in rat brain slice experiments are summarized. Additionally, evidence is summarized that supports the working hypothesis that seizure genesis originates in subcortical areas and involves cardio-respiratory centers and cranial nerve nuclei in the hind brain (brainstem and cerebellum) based on, respectively, the complex temporal pattern of abnormal cardio-respiratory responses and various nonconvulsive S/Sx that precede seizures during exposure to HBO2.
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Hinojo CM, Ciarlone GE, D'Agostino DP, Dean JB. Exogenous ketone salts inhibit superoxide production in the rat caudal solitary complex during exposure to normobaric and hyperbaric hyperoxia. J Appl Physiol (1985) 2021; 130:1936-1954. [PMID: 33661724 DOI: 10.1152/japplphysiol.01071.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The use of hyperbaric oxygen (HBO2) in hyperbaric and undersea medicine is limited by the risk of seizures [i.e., central nervous system (CNS) oxygen toxicity, CNS-OT] resulting from increased production of reactive oxygen species (ROS) in the CNS. Importantly, ketone supplementation has been shown to delay onset of CNS-OT in rats by ∼600% in comparison with control groups (D'Agostino DP, Pilla R, Held HE, Landon CS, Puchowicz M, Brunengraber H, Ari C, Arnold P, Dean JB. Am J Physiol Regu Integr Comp Physiol 304: R829-R836, 2013). We have tested the hypothesis that ketone body supplementation inhibits ROS production during exposure to hyperoxygenation in rat brainstem cells. We measured the rate of cellular superoxide ([Formula: see text]) production in the caudal solitary complex (cSC) in rat brain slices using a fluorogenic dye, dihydroethidium (DHE), during exposure to control O2 (0.4 ATA) followed by 1-2 h of normobaric oxygen (NBO2) (0.95 ATA) and HBO2 (1.95, and 4.95 ATA) hyperoxia, with and without a 50:50 mixture of ketone salts (KS) dl-β-hydroxybutyrate + acetoacetate. All levels of hyperoxia tested stimulated [Formula: see text] production similarly in cSC cells and coexposure to 5 mM KS during hyperoxia significantly blunted the rate of increase in DHE fluorescence intensity during exposure to hyperoxia. Not all cells tested produced [Formula: see text] at the same rate during exposure to control O2 and hyperoxygenation; cells that increased [Formula: see text] production by >25% during hyperoxia in comparison with baseline were inhibited by KS, whereas cells that did not reach that threshold during hyperoxia were unaffected by KS. These findings support the hypothesis that ketone supplementation decreases the steady-state concentrations of superoxide produced during exposure to NBO2 and HBO2 hyperoxia.NEW & NOTEWORTHY Exposure of rat medullary tissue slices to levels of O2 that mimic those that cause seizures in rats stimulates cellular superoxide ([Formula: see text]) production to varying degrees. Cellular [Formula: see text] generation in the caudal solitary complex is variable during exposure to control O2 and hyperoxia and significantly decreases during ketone supplementation. Our findings support the theory that ketone supplementation delays onset of central nervous system oxygen toxicity in mammals, in part, by decreasing [Formula: see text] production in O2-sensitive neurons.
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Affiliation(s)
- Christopher M Hinojo
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, MDC 8, University of South Florida, Tampa, Florida
| | - Geoffrey E Ciarlone
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, MDC 8, University of South Florida, Tampa, Florida
| | - Dominic P D'Agostino
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, MDC 8, University of South Florida, Tampa, Florida.,Institute of Human and Machine Cognition, Ocala, Florida
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, MDC 8, University of South Florida, Tampa, Florida
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5
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Zhang Y, You B, Chen Y, Yang J, Xie C, Huang G, Li R, Hu P. Effect of Transcriptional Regulatory Factor FoxO3a on Central Nervous System Oxygen Toxicity. Front Physiol 2021; 11:596326. [PMID: 33391015 PMCID: PMC7775677 DOI: 10.3389/fphys.2020.596326] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/24/2020] [Indexed: 11/23/2022] Open
Abstract
Central nervous system (CNS) oxygen toxicity (CNS-OT) is a toxic reaction that appears after the inhalation of gas at an excessive oxygen partial pressure during underwater operation or hyperbaric oxygen (HBO) treatment. The mechanism of CNS-OT has not been clearly characterized. Though it has been attributed to the excessive oxidative stress induced by HBO, evidences against this hypothesis have been reported. Here we find that Forkhead box protein O3 (FoxO3a) is important for CNS-OT protection. FoxO3a knock-out (KO) mice had a shorter latency to develop convulsions and greater number of seizures within a certain period of time. The acute lung injury (ALI) induced by CNS-OT was also more severe in FoxO3a KO mice. Further analysis reveals a significant decrease in the activity of catalase (CAT), an antioxidant enzyme and a significant increase in the content of malondialdehyde (MDA), an oxidative product, in brain tissues of FoxO3a KO mice. Short-time HBO exposure could increase FoxO3a expression level and trigger its nuclear translocation. The level of nuclear localized FoxO3a peaked at 8 h after exposure. Our results demonstrate that the activity of FoxO3a is highly sensitive to HBO exposure and FoxO3a plays important roles in protecting CNS-OT. Further mechanic analysis reveals that FoxO3a protects CNS-OT via activating antioxidative signaling pathway.
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Affiliation(s)
- Yanan Zhang
- Department of Diving and Hyperbaric Medicine, Naval Special Medical Center, Navy Medical University, Shanghai, China
| | - Benming You
- Department of Pharmacy, Changhai Hospital, Navy Medical University, Shanghai, China
| | - Yuliang Chen
- Department of Nautical and Aviation Medicine Center, The Sixth Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Junlin Yang
- Xinhua Hospital, Shangahai Jiao Tong University, Shanghai, China
| | - Chengwei Xie
- Department of Diving and Hyperbaric Medicine, Naval Special Medical Center, Navy Medical University, Shanghai, China
| | - Guoyang Huang
- Department of Diving and Hyperbaric Medicine, Naval Special Medical Center, Navy Medical University, Shanghai, China
| | - Runping Li
- Department of Diving and Hyperbaric Medicine, Naval Special Medical Center, Navy Medical University, Shanghai, China
| | - Ping Hu
- State Key Laboratory of Cell Biology, Center of Excellence in Molecular and Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.,Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China.,Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory), Guangzhou, China.,Xinhua Hospital, Shangahai Jiao Tong University, Shanghai, China.,Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
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6
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Platonova TF, Zhilyaev SY, Alekseeva OS, Nikitina ER, Demchenko IT. Blockade of Brain Adrenoreceptors
Delays Seizure Development during Hyperbaric Oxygen Breathing. J EVOL BIOCHEM PHYS+ 2020. [DOI: 10.1134/s0022093020050051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Zhilyaev SY, Platonova TF, Alekseeva OS, Nikitina ER, Demchenko IT. Adaptive Mechanisms of Baroreflectory Regulation of the Cardiovascular System in Extreme Hyperoxia. J EVOL BIOCHEM PHYS+ 2019. [DOI: 10.1134/s002209301905003x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Ciarlone GE, Hinojo CM, Stavitzski NM, Dean JB. CNS function and dysfunction during exposure to hyperbaric oxygen in operational and clinical settings. Redox Biol 2019; 27:101159. [PMID: 30902504 PMCID: PMC6859559 DOI: 10.1016/j.redox.2019.101159] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 02/20/2019] [Accepted: 03/01/2019] [Indexed: 12/26/2022] Open
Abstract
Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is the acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms, many of which appear to be of brainstem origin involving cranial nerve nuclei and autonomic and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate as generalized tonic-clonic seizures. The initial safe latent period makes the use of HBO2 practical in hyperbaric and undersea medicine; however, the latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure are highly conservative. This review examines the disorder of CNS-OT and summarizes current ideas on its underlying pathophysiology, including specific areas of the CNS and fundamental neural and redox signaling mechanisms that are thought to be involved in seizure genesis and propagation. In addition, conditions that accelerate the onset of seizures are discussed, as are current mitigation strategies under investigation for neuroprotection against redox stress while breathing HBO2 that extend the latent period, thus enabling safer and longer exposures for diving and medical therapies.
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Affiliation(s)
- Geoffrey E Ciarlone
- Undersea Medicine Department, Naval Medical Research Center, 503 Robert Grant Ave., Silver Spring, MD, USA
| | - Christopher M Hinojo
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Nicole M Stavitzski
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
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9
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Wilson DF, Matschinsky FM. Hyperbaric oxygen toxicity in brain: A case of hyperoxia induced hypoglycemic brain syndrome. Med Hypotheses 2019; 132:109375. [PMID: 31454640 DOI: 10.1016/j.mehy.2019.109375] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 08/09/2019] [Accepted: 08/18/2019] [Indexed: 12/25/2022]
Abstract
Hyperbaric oxygen exposure is a recent hazzard for higher animals that originated as humans began underwater construction, exploration, and sports. Exposure can lead to abnormal brain EEG, convulsions, and death, the time to onset of each stage of pathology decreasing with increase in oxygen pressure. We provide evidence that hyperoxia, through oxidative phosphorylation, increases the energy state ([ATP]/[ADP][Pi]) of cells critical to providing glucose to cells behind the blood brain barrier (BBB). Brain cells without an absolute dependence on glucose metabolism; i.e. those having sufficient ATP synthesis using lactate and glutamate as oxidizable substrates, are not themselves very adversely affected by hyperoxia. The increased energy state and decrease in free [AMP], however, suppress glucose transport through the blood brain barrier (BBB) and into cells behind the BBB. Glucose has to pass in sequence through three steps of transport by facilitated diffusion and transporter activity for each step is regulated in part by AMP dependent protein kinase. The physiological role of this regulation is to increase glucose transport in response to hypoxia and/or systemic hypoglycemia. Hyperoxia, however, through unphysiological decrease in free [AMP] suppresses 1) glucose transport through the BBB (endothelial GLUT1 transporters) into cerebrospinal fluid (CSF); 2) glucose transport from CSF into cells behind the BBB (GLUT3 transporters) and (GLUT4 transporters). Cumulative suppression of glucose transport results in local regions of hypoglycemia and induces hypoglycemic failure. It is suggested that failure is initiated at axons and synapses with insufficient mitochondria to meet their energy requirements.
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Affiliation(s)
- David F Wilson
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Franz M Matschinsky
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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10
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Demchenko IT, Zhilyaev SY, Alekseeva OS, Krivchenko AI, Piantadosi CA, Gasier HG. Increased Antiseizure Effectiveness with Tiagabine Combined with Sodium Channel Antagonists in Mice Exposed to Hyperbaric Oxygen. Neurotox Res 2019; 36:788-795. [PMID: 31148118 DOI: 10.1007/s12640-019-00063-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 04/24/2019] [Accepted: 05/09/2019] [Indexed: 10/26/2022]
Abstract
Hyperbaric oxygen (HBO2) is acutely toxic to the central nervous system, culminating in EEG spikes and tonic-clonic convulsions. GABA enhancers and sodium channel antagonists improve seizure latencies in HBO2 when administered individually, while combining antiepileptic drugs from different functional classes can provide greater seizure latency. We examined the combined effectiveness of GABA enhancers (tiagabine and gabapentin) with sodium channel antagonists (carbamazepine and lamotrigine) in delaying HBO2-induced seizures. A series of experiments in C57BL/6 mice exposed to 100% oxygen at 5 atmospheres absolute (ATA) were performed. We predicted equally effective doses from individual drug-dose response curves, and the combinations of tiagabine + carbamazepine or lamotrigine were tested to determine the maximally effective combined doses to be used in subsequent experiments designed to identify the type of pharmacodynamic interaction for three fixed-ratio combinations (1:3, 1:1, and 3:1) using isobolographic analysis. For both combinations, the maximally effective combined doses increased seizure latency over controls > 5-fold and were determined to interact synergistically for fixed ratios 1:1 and 3:1, additive for 1:3. These results led us to explore whether the benefits of these drug combinations could be extended to the lungs, since a centrally mediated mechanism is believed to mediate hyperoxic-induced cardiogenic lung injury. Indeed, both combinations attenuated bronchoalveolar lavage protein content by ~ 50%. Combining tiagabine with carbamazepine or lamotrigine not only affords greater antiseizure protection in HBO2 but also allows for lower doses to be used, minimizing side effects, and attenuating acute lung injury.
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Affiliation(s)
- Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, USA.,Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Sergei Yu Zhilyaev
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Olga S Alekseeva
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexander I Krivchenko
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Claude A Piantadosi
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, USA.,Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA.,Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Heath G Gasier
- Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
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11
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Yi H, Yu S, Zhang Y, Li R, Zhang D, Zhang D, Xu W. Preventive effects of ketone ester BD-AcAc 2 on central nervous system oxygen toxicity and concomitant acute lung injury. Diving Hyperb Med 2019; 48:235-240. [PMID: 30517956 DOI: 10.28920/dhm48.4.235-240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 10/28/2018] [Indexed: 02/01/2023]
Abstract
BACKGROUND Recent studies indicated that ketone ester R,S-1,3-butanediol acetoacetate diester (BD-AcAc2) may be effective in preventing central nervous system oxygen toxicity (CNS-OT) and concomitant acute lung injury, a serious medical problem to be faced when breathing hyperbaric oxygen (HBO). This study aimed to further investigate the protective effects of BD-AcAc2 against CNS-OT and concomitant acute lung injury (ALI) in mice. METHODS Mice were treated with BD-AcAc2 in peanut oil vehicle (2.5, 5.0 or 10.0 g·kg⁻² body weight) by gavage 20 minutes before 600 kPa HBO exposure. Control mice received the vehicle only. Seizure latency was recorded. Malondialdehyde content in brain and lung tissues, total protein level in bronchoalveolar lavage fluid (BLF) and lung water content were measured 60 minutes after the hyperbaric exposure. Histopathology of lung tissue was undertaken. RESULTS Compared with the vehicle alone, BD-AcAc2 prolonged seizure latency in a dose-dependent manner (P < 0.01). The HBO-induced increase in brain malondialdehyde, BLF protein and lung water were significantly reduced by BD-AcAc2 (P < 0.01). CONCLUSION Oral administration of the ketone ester BD-AcAc2 significantly protected against CNS-OT and concomitant ALI. Alleviation of oxidative stress may be one underlying mechanism providing this effect.
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Affiliation(s)
- Hongjie Yi
- Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai, P R China
| | - Shichong Yu
- Department of Organic Chemistry, Naval Medical University, Shanghai
| | - Yanan Zhang
- Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai, P R China
| | - Runping Li
- Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai, P R China
| | - Dazhi Zhang
- Department of Organic Chemistry, Naval Medical University, Shanghai
| | - Dazhi Zhang
- Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai, P R China
| | - Weigang Xu
- Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai, P R China.,Corresponding author: Department of Diving and Hyperbaric Medicine, Naval Medical University, Shanghai 200433, China,
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12
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Xie CW, Wang ZZ, Zhang YN, Chen YL, Li RP, Zhang JD. Effect of Interaction between Adenosine and Nitric Oxide on Central Nervous System Oxygen Toxicity. Neurotox Res 2019; 36:193-203. [PMID: 30927242 DOI: 10.1007/s12640-019-00025-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 03/11/2019] [Accepted: 03/13/2019] [Indexed: 11/26/2022]
Abstract
The metabolism of adenosine (ADO) and nitric oxide (NO) in brain tissues is closely associated with the change of oxygen content. They have contrary effects in the onset of hyperbaric oxygen (HBO)-induced central nervous system oxygen toxicity (CNS OT): ADO can suppress the onset, while NO promotes it. We adopted the ADO-augmenting measure and NO-inhibiting measure in this study and found the combined use had a far superior preventive and therapeutic effect in protecting against CNS OT compared with the use of either measure alone. So we hypothesized that there is an interaction between ADO and NO which has an important impact on the onset of CNS OT. On this basis, we administered ADO-augmenting or ADO-inhibiting drugs to rats. After exposure to HBO, the onset of CNS OT was evaluated, followed by the measurement of NO content in brain tissues. In another experiment, rats were administered NO-augmenting or NO-inhibiting drugs. After exposure to HBO, the onset of CNS OT was evaluated, followed by measurement of the activities of ADO metabolism-related enzymes in brain tissues. The results showed that, following ADO augmentation, the content of NO and its metabolite was significantly reduced, and the onset of CNS OT significantly improved. After ADO inhibition, just the opposite was observed. NO promotion resulted in a decrease in the activity of ADO-producing enzyme, an increase in the activity of ADO-decomposing enzyme, and an aggravation in CNS OT. The above results were all reversed after an inhibition in NO content. Studies have shown that exposure to HBO has a significant impact on the content of ADO and NO in brain tissues as well as their biological effects, and ADO and NO might have an intense interaction, which might generate an important effect on the onset of CNS OT. The prophylaxis and treatment effects of CNS OT can be greatly enhanced by augmenting ADO and inhibiting NO.
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Affiliation(s)
- Cheng-Wei Xie
- Department of Diving Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, 200433, China
| | - Zhong-Zhuang Wang
- Department of Pharmacy, Changhai Hospital, Second Military Medical University, Shanghai, 200433, China
| | - Ya-Nan Zhang
- Department of Diving Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, 200433, China
| | - Yu-Liang Chen
- Nautical and Aviation Medicine Center, Navy General Hospital of PLA, Beijing, 10048, China
| | - Run-Ping Li
- Department of Diving Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, 200433, China.
| | - Jun-Dong Zhang
- Tenth People's Hospital of Tongji University, Shanghai, 200072, China.
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13
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Gasier HG, Demchenko IT, Zhilyaev SY, Moskvin AN, Krivchenko AI, Piantadosi CA. Adrenoceptor blockade modifies regional cerebral blood flow responses to hyperbaric hyperoxia: Protection against CNS oxygen toxicity. J Appl Physiol (1985) 2018; 125:1296-1304. [PMID: 30024340 DOI: 10.1152/japplphysiol.00540.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exposure to extreme-hyperbaric oxygen (HBO2), > 5-6 atmospheres absolute (ATA), produces baroreflex impairment, sympathetic hyperactivation, hypertension, tachycardia, and cerebral hyperemia, known as Phase II, culminating in seizures. We hypothesized that attenuation of the effects of high sympathetic outflow would preserve regional cerebral blood flow (rCBF) and protect against HBO2-induced seizures. To explore this possibility, we tested four adrenoceptor antagonists in conscious and anesthetized rats exposed to HBO2 at 5 and 6 ATA, respectively: phentolamine (nonselective α1 and 2), prazosin (selective α1), propranolol (nonselective β1 and 2) and atenolol (selective β1). In conscious rats, 4 drug-doses were administered to rats prior to HBO2 exposures, and seizure latencies were recorded. Drug-doses that provided similar protection against seizures were administered before HBO2 exposures in anesthetized rats to determine the effects of adrenoceptor blockade on mean arterial pressure, heart rate, rCBF and EEG spikes. All four drugs modified cardiovascular and rCBF responses in HBO2 that aligned with epileptiform discharges, but only phentolamine and propranolol effectively increased EEG spike latencies by ~20 and 36 min, respectively. When phentolamine and propranolol were delivered during HBO2 at the onset of phase II, only propranolol led to sustained reductions in heart rate and rCBF, preventing the appearance of epileptiform discharges. The enhanced effectiveness of propranolol may extend beyond β-adrenoceptor blockade, i.e. membrane stability and reduced metabolic activity. These results indicate that adrenoceptor drug pre-treatment will minimize the effects of excessive sympathetic outflow on rCBF and extend HBO2 exposure time.
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Affiliation(s)
- Heath G Gasier
- Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, United States
| | - Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University, United States
| | - Sergei Yu Zhilyaev
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexander N Moskvin
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexander I Krivchenko
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Claude A Piantadosi
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University, United States
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14
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Freiberger JJ, Derrick BJ, Natoli MJ, Akushevich I, Schinazi EA, Parker C, Stolp BW, Bennett PB, Vann RD, Dunworth SAS, Moon RE. Assessment of the interaction of hyperbaric N2, CO2, and O2 on psychomotor performance in divers. J Appl Physiol (1985) 2016; 121:953-964. [PMID: 27633739 DOI: 10.1152/japplphysiol.00534.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/02/2016] [Indexed: 11/22/2022] Open
Abstract
Diving narcosis results from the complex interaction of gases, activities, and environmental conditions. We hypothesized that these interactions could be separated into their component parts. Where previous studies have tested single cognitive tasks sequentially, we varied inspired partial pressures of CO2, N2, and O2 in immersed, exercising subjects while assessing multitasking performance with the Multi-Attribute Task Battery II (MATB-II) flight simulator. Cognitive performance was tested under 20 conditions of gas partial pressure and exercise in 42 male subjects meeting U.S. Navy age and fitness profiles. Inspired nitrogen (N2) and oxygen (O2) partial pressures were 0, 4.5, and 5.6 ATA and 0.21, 1.0, and 1.22 ATA, respectively, at rest and during 100-W immersed exercise with and without 0.075-ATA CO2 Linear regression modeled the association of gas partial pressure with task performance while controlling for exercise, hypercapnic ventilatory response, dive training, video game frequency, and age. Subjects served as their own controls. Impairment of memory, attention, and planning, but not motor tasks, was associated with N2 partial pressures >4.5 ATA. Sea level O2 at 0.925 ATA partially rescued motor and memory reaction time impaired by 0.075-ATA CO2; however, at hyperbaric pressures an unexpectedly strong interaction between CO2, N2, and exercise caused incapacitating narcosis with amnesia, which was augmented by O2 Perception of narcosis was not correlated with actual scores. The relative contributions of factors associated with diving narcosis will be useful to predict the effects of gas mixtures and exercise conditions on the cognitive performance of divers. The O2 effects are consistent with O2 narcosis or enhanced O2 toxicity.
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Affiliation(s)
- J J Freiberger
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - B J Derrick
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - M J Natoli
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - I Akushevich
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - E A Schinazi
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - C Parker
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - B W Stolp
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - P B Bennett
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - R D Vann
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - S A S Dunworth
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - R E Moon
- Duke Center for Hyperbaric Medicine and Environmental Physiology and Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
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15
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Abstract
In saturation diving, divers stay under pressure until most of their tissues are saturated with breathing gas. Divers spend a long time in isolation exposed to increased partial pressure of oxygen, potentially toxic gases, bacteria, and bubble formation during decompression combined with shift work and long periods of relative inactivity. Hyperoxia may lead to the production of reactive oxygen species (ROS) that interact with cell structures, causing damage to proteins, lipids, and nucleic acid. Vascular gas-bubble formation and hyperoxia may lead to dysfunction of the endothelium. The antioxidant status of the diver is an important mechanism in the protection against injury and is influenced both by diet and genetic factors. The factors mentioned above may lead to production of heat shock proteins (HSP) that also may have a negative effect on endothelial function. On the other hand, there is a great deal of evidence that HSPs may also have a "conditioning" effect, thus protecting against injury. As people age, their ability to produce antioxidants decreases. We do not currently know the capacity for antioxidant defense, but it is reasonable to assume that it has a limit. Many studies have linked ROS to disease states such as cancer, insulin resistance, diabetes mellitus, cardiovascular diseases, and atherosclerosis as well as to old age. However, ROS are also involved in a number of protective mechanisms, for instance immune defense, antibacterial action, vascular tone, and signal transduction. Low-grade oxidative stress can increase antioxidant production. While under pressure, divers change depth frequently. After such changes and at the end of the dive, divers must follow procedures to decompress safely. Decompression sickness (DCS) used to be one of the major causes of injury in saturation diving. Improved decompression procedures have significantly reduced the number of reported incidents; however, data indicate considerable underreporting of injuries. Furthermore, divers who are required to return to the surface quickly are under higher risk of serious injury as no adequate decompression procedures for such situations are available. Decompression also leads to the production of endothelial microparticles that may reduce endothelial function. As good endothelial function is a documented indicator of health that can be influenced by regular exercise, regular physical exercise is recommended for saturation divers. Nowadays, saturation diving is a reasonably safe and well controlled method for working under water. Until now, no long-term impact on health due to diving has been documented. However, we still have limited knowledge about the pathophysiologic mechanisms involved. In particular we know little about the effect of long exposure to hyperoxia and microparticles on the endothelium.
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Affiliation(s)
- Alf O Brubakk
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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16
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Demchenko IT, Gasier HG, Zhilyaev SY, Moskvin AN, Krivchenko AI, Piantadosi CA, Allen BW. Baroreceptor afferents modulate brain excitation and influence susceptibility to toxic effects of hyperbaric oxygen. J Appl Physiol (1985) 2014; 117:525-34. [PMID: 24994889 DOI: 10.1152/japplphysiol.00435.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Unexplained adjustments in baroreflex sensitivity occur in conjunction with exposures to potentially toxic levels of hyperbaric oxygen. To investigate this, we monitored central nervous system, autonomic and cardiovascular responses in conscious and anesthetized rats exposed to hyperbaric oxygen at 5 and 6 atmospheres absolute, respectively. We observed two contrasting phases associated with time-dependent alterations in the functional state of the arterial baroreflex. The first phase, which conferred protection against potentially neurotoxic doses of oxygen, was concurrent with an increase in baroreflex sensitivity and included decreases in cerebral blood flow, heart rate, cardiac output, and sympathetic drive. The second phase was characterized by baroreflex impairment, cerebral hyperemia, spiking on the electroencephalogram, increased sympathetic drive, parasympatholysis, and pulmonary injury. Complete arterial baroreceptor deafferentation abolished the initial protective response, whereas electrical stimulation of intact arterial baroreceptor afferents prolonged it. We concluded that increased afferent traffic attributable to arterial baroreflex activation delays the development of excessive central excitation and seizures. Baroreflex inactivation or impairment removes this protection, and seizures may follow. Finally, electrical stimulation of intact baroreceptor afferents extends the normal delay in seizure development. These findings reveal that the autonomic nervous system is a powerful determinant of susceptibility to sympathetic hyperactivation and seizures in hyperbaric oxygen and the ensuing neurogenic pulmonary injury.
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Affiliation(s)
- Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, and Departments of Anesthesiology and Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Heath G Gasier
- Center for Hyperbaric Medicine and Environmental Physiology, and Departments of Anesthesiology and
| | - Sergei Yu Zhilyaev
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexander N Moskvin
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Alexander I Krivchenko
- Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Claude A Piantadosi
- Center for Hyperbaric Medicine and Environmental Physiology, and Departments of Anesthesiology and Medicine, Duke University Medical Center, Durham, North Carolina
| | - Barry W Allen
- Center for Hyperbaric Medicine and Environmental Physiology, and Departments of Anesthesiology and
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17
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Eynan M, Krinsky N, Biram A, Arieli Y, Arieli R. A comparison of factors involved in the development of central nervous system and pulmonary oxygen toxicity in the rat. Brain Res 2014; 1574:77-83. [PMID: 24928619 DOI: 10.1016/j.brainres.2014.05.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 05/09/2014] [Accepted: 05/30/2014] [Indexed: 10/25/2022]
Abstract
Central nervous system oxygen toxicity (CNS-OT) can occur in humans at pressures above 2atmospheres absolute (ATA), and above 4.5ATA in the rat. Pulmonary oxygen toxicity appears at pressures above 0.5ATA. We hypothesized that exposure to mild HBO following extreme exposure might provide protection against CNS, but not pulmonary oxygen toxicity. We measured the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and nitrotyrosine and nNOS levels in the brain and lung in the following groups: (1) Sham rats, no pressure exposure (SHAM); (2) Exposure to 6ATA oxygen for 60% of latency to CNS-OT (60%LT); (3) Exposure to 6ATA for 60% of latency to CNS-OT, followed by 20min at 2.5ATA for recovery (REC); (4) Exposure to 6ATA for 60% of latency to CNS-OT, followed by 20min at 2.5ATA oxygen and a subsequent increase in pressure to 6ATA until the appearance of convulsions (CONV); (5) Control rats exposed to 6ATA until the appearance of convulsions (C). SOD and CAT activity were reduced in both brain and lung in the REC group. GPX activity was reduced in the hippocampus in the REC group, but not in the cortex or the lung. nNOS levels were reduced in the hippocampus in the REC group. Contrary to our hypothesis, no difference was observed between the brain and the lung for the factors investigated. We suggest that at 2.5ATA and above, CNS and pulmonary oxygen toxicity may share similar mechanisms.
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Affiliation(s)
- Mirit Eynan
- Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Box 22, Rambam Health Care Campus, P.O. Box 9602, 3109601 Haifa, Israel.
| | - Nitzan Krinsky
- Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Box 22, Rambam Health Care Campus, P.O. Box 9602, 3109601 Haifa, Israel.
| | - Adi Biram
- Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Box 22, Rambam Health Care Campus, P.O. Box 9602, 3109601 Haifa, Israel.
| | - Yehuda Arieli
- Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Box 22, Rambam Health Care Campus, P.O. Box 9602, 3109601 Haifa, Israel.
| | - Ran Arieli
- Israel Naval Medical Institute, Israel Defense Forces Medical Corps, Box 22, Rambam Health Care Campus, P.O. Box 9602, 3109601 Haifa, Israel.
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Herold S, Gabrielli NM, Vadász I. Novel concepts of acute lung injury and alveolar-capillary barrier dysfunction. Am J Physiol Lung Cell Mol Physiol 2013; 305:L665-81. [PMID: 24039257 DOI: 10.1152/ajplung.00232.2013] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this review we summarize recent major advances in our understanding on the molecular mechanisms, mediators, and biomarkers of acute lung injury (ALI) and alveolar-capillary barrier dysfunction, highlighting the role of immune cells, inflammatory and noninflammatory signaling events, mechanical noxae, and the affected cellular and molecular entities and functions. Furthermore, we address novel aspects of resolution and repair of ALI, as well as putative candidates for treatment of ALI, including pharmacological and cellular therapeutic means.
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Affiliation(s)
- Susanne Herold
- Dept. of Internal Medicine, Justus Liebig Univ., Universities of Giessen and Marburg Lung Center, Klinikstrasse 33, 35392 Giessen, Germany.
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19
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Demchenko IT, Zhilyaev SY, Moskvin AN, Krivchenko AI, Piantadosi CA, Allen BW. Baroreflex-mediated cardiovascular responses to hyperbaric oxygen. J Appl Physiol (1985) 2013; 115:819-28. [PMID: 23823147 DOI: 10.1152/japplphysiol.00625.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The cardiovascular system responds to hyperbaric hyperoxia (HBO2) with vasoconstriction, hypertension, bradycardia, and reduced cardiac output (CO). We tested the hypothesis that these responses are linked by a common mechanism-activation of the arterial baroreflex. Baroreflex function in HBO2 was assessed in anesthetized and conscious rats after deafferentation of aortic or carotid baroreceptors or both. Cardiovascular and autonomic responses to HBO2 in these animals were compared with those in intact animals at 2.5 ATA for conscious rats and at 3 ATA for anesthetized rats. During O2 compression, hypertension was greater after aortic or carotid baroreceptor deafferentation and was significantly more severe if these procedures were combined. Similarly, the hyperoxic bradycardia observed in intact animals was diminished after aortic or carotid baroreceptor deafferentation and replaced by a slight tachycardia after complete baroreceptor deafferentation. We found that hypertension, bradycardia, and reduced CO--the initial cardiovascular responses to moderate levels of HBO2--are coordinated through a baroreflex-mediated mechanism initiated by HBO2-induced vasoconstriction. Furthermore, we have shown that baroreceptor activation in HBO2 inhibits sympathetic outflow and can partially reverse an O2-dependent increase in arterial pressure.
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Affiliation(s)
- Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, North Carolina
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20
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Pilla R, Landon CS, Dean JB. A potential early physiological marker for CNS oxygen toxicity: hyperoxic hyperpnea precedes seizure in unanesthetized rats breathing hyperbaric oxygen. J Appl Physiol (1985) 2013; 114:1009-20. [PMID: 23429869 DOI: 10.1152/japplphysiol.01326.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Hyperbaric oxygen (HBO(2)) stimulates presumptive central CO2-chemoreceptor neurons, increases minute ventilation (V(min)), decreases heart rate (HR) and, if breathed sufficiently long, produces central nervous system oxygen toxicity (CNS-OT; i.e., seizures). The risk of seizures when breathing HBO(2) is variable between individuals and its onset is difficult to predict. We have tested the hypothesis that a predictable pattern of cardiorespiration precedes an impending seizure when breathing HBO2. To test this hypothesis, 27 adult male Sprague-Dawley rats were implanted with radiotelemetry transmitters to assess diaphragmatic/abdominal electromyogram, electrocardiogram, and electroencephalogram. Seven days after surgery, each rat was placed in a sealed, continuously ventilated animal chamber inside a hyperbaric chamber. Both chambers were pressurized in parallel using poikilocapnic 100% O(2) (animal chamber) and air (hyperbaric chamber) to 4, 5, or 6 atmospheres absolute (ATA). Breathing 1 ATA O(2) initially decreased V(min) and HR (Phase 1 of the compound hyperoxic ventilatory response). With continued exposure to normobaric hyperoxia, however, V(min) began increasing toward the end of exposure in one-third of the animals tested. Breathing HBO2 induced an early transient increase in V(min) (Phase 2) and HR during the chamber pressurization, followed by a second significant increase of V(min) ≤8 min prior to seizure (Phase 3). HR, which subsequently decreased during sustained hyperoxia, showed no additional changes prior to seizure. We conclude that hyperoxic hyperpnea (Phase 3 of the compound hyperoxic ventilatory response) is a predictor of an impending seizure while breathing poikilocapnic HBO(2) at rest in unanesthetized rats.
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Affiliation(s)
- Raffaele Pilla
- Department of Molecular Pharmacology & Physiology, Hyperbaric Biomedical Research Laboratory, University of South Florida, Morsani College of Medicine, Tampa, FL 33612, USA
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21
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Demchenko IT, Moskvin AN, Krivchenko AI, Piantadosi CA, Allen BW. Nitric oxide-mediated central sympathetic excitation promotes CNS and pulmonary O₂ toxicity. J Appl Physiol (1985) 2012; 112:1814-23. [PMID: 22442027 PMCID: PMC3379151 DOI: 10.1152/japplphysiol.00902.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 03/16/2012] [Indexed: 01/29/2023] Open
Abstract
In hyperbaric oxygen (HBO(2)) at or above 3 atmospheres absolute (ATA), autonomic pathways link central nervous system (CNS) oxygen toxicity to pulmonary damage, possibly through a paradoxical and poorly characterized relationship between central nitric oxide production and sympathetic outflow. To investigate this possibility, we assessed sympathetic discharges, catecholamine release, cardiopulmonary hemodynamics, and lung damage in rats exposed to oxygen at 5 or 6 ATA. Before HBO(2) exposure, either a selective inhibitor of neuronal nitric oxide synthase (NOS) or a nonselective NOS inhibitor was injected directly into the cerebral ventricles to minimize effects on the lung, heart, and peripheral circulation. Experiments were performed on both anesthetized and conscious rats to differentiate responses to HBO(2) from the effects of anesthesia. EEG spikes, markers of CNS toxicity in anesthetized animals, were approximately four times as likely to develop in control rats than in animals with central NOS inhibition. In inhibitor-treated animals, autonomic discharges, cardiovascular pressures, catecholamine release, and cerebral blood flow all remained below baseline throughout exposure to HBO(2). In control animals, however, initial declines in these parameters were followed by significant increases above their baselines. In awake animals, central NOS inhibition significantly decreased the incidence of clonic-tonic convulsions or delayed their onset, compared with controls. The novel findings of this study are that NO produced by nNOS in the periventricular regions of the brain plays a critical role in the events leading to both CNS toxicity in HBO(2) and to the associated sympathetic hyperactivation involved in pulmonary injury.
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Affiliation(s)
- Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC 27710, USA
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