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Nolte TM. 300-fold higher neuro- and immunotoxicity from low-redox transformation of carbamazepine. Toxicol Rep 2023; 11:319-329. [PMID: 37927955 PMCID: PMC10622881 DOI: 10.1016/j.toxrep.2023.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 11/07/2023] Open
Abstract
Current challenges in (eco)toxicology are in understanding the transformation of (reactive) substances, and how transformation affects toxic modes of action. Empirical assessment of transformation products of, practically an infinite number of substances, via experimentation, is impossible. Predicting transformation products for (benchmarking) compounds from conditions, facilitates risk analyses. This study applied calculus to predict transformation products of an important environmental and medicinal/toxicological marker, carbamazepine. As radicals are ubiquitous in humans and the environment, we looked into radical-mediated transformations of carbamazepine as a benchmark. We calculated proportions of their speciation states as function of redox conditions, which we took as pH and O2 concentration, describing transformation via covalent and ionic interactions. Formation of ring-contracted products with neuro-immunological activity is thermodynamically favored under anaerobic conditions and at low pH. Experimentally observed product distributions and toxicities reflect that pattern. Our predictive method may support toxicity predictions for other substances and conditions 'similar' to the current case study via interpolation. This paves the way for a more coherent, effective and easier risk assessment of transformation products.
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Affiliation(s)
- Tom M. Nolte
- Department of Environmental Science, Institute for Water and Wetland Research, Radboud, University Nijmegen, 6500 GL Nijmegen, the Netherlands
- Eidgenössische Technische Hochschule (ETH) Zurich, Laboratory of Inorganic Chemistry, Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland
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2
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Wang Z, Li Q, Kolls BJ, Mace B, Yu S, Li X, Liu W, Chaparro E, Shen Y, Dang L, Del Águila Á, Bernstock JD, Johnson KR, Yao J, Wetsel WC, Moore SD, Turner DA, Yang W. Sustained overexpression of spliced X-box-binding protein-1 in neurons leads to spontaneous seizures and sudden death in mice. Commun Biol 2023; 6:252. [PMID: 36894627 PMCID: PMC9998612 DOI: 10.1038/s42003-023-04594-8] [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: 06/25/2022] [Accepted: 02/14/2023] [Indexed: 03/11/2023] Open
Abstract
The underlying etiologies of seizures are highly heterogeneous and remain incompletely understood. While studying the unfolded protein response (UPR) pathways in the brain, we unexpectedly discovered that transgenic mice (XBP1s-TG) expressing spliced X-box-binding protein-1 (Xbp1s), a key effector of UPR signaling, in forebrain excitatory neurons, rapidly develop neurologic deficits, most notably recurrent spontaneous seizures. This seizure phenotype begins around 8 days after Xbp1s transgene expression is induced in XBP1s-TG mice, and by approximately 14 days post induction, the seizures evolve into status epilepticus with nearly continuous seizure activity followed by sudden death. Animal death is likely due to severe seizures because the anticonvulsant valproic acid could significantly prolong the lives of XBP1s-TG mice. Mechanistically, our gene profiling analysis indicates that compared to control mice, XBP1s-TG mice exhibit 591 differentially regulated genes (mostly upregulated) in the brain, including several GABAA receptor genes that are notably downregulated. Finally, whole-cell patch clamp analysis reveals a significant reduction in both spontaneous and tonic GABAergic inhibitory responses in Xbp1s-expressing neurons. Taken together, our findings unravel a link between XBP1s signaling and seizure occurrence.
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Affiliation(s)
- Zhuoran Wang
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Qiang Li
- Department of Neurology, Duke University Medical Center, Durham, NC, USA
| | - Brad J Kolls
- Department of Neurology, Duke University Medical Center, Durham, NC, USA
| | - Brian Mace
- Department of Neurology, Duke University Medical Center, Durham, NC, USA
| | - Shu Yu
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Xuan Li
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Wei Liu
- Department of Bioengineering, Duke University, Durham, NC, USA
| | - Eduardo Chaparro
- Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA
| | - Yuntian Shen
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Lihong Dang
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Ángela Del Águila
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Joshua D Bernstock
- National Institute of Neurological Disorders and Stroke, NINDS/NIH, Bethesda, MD, USA
| | - Kory R Johnson
- National Institute of Neurological Disorders and Stroke, NINDS/NIH, Bethesda, MD, USA
| | - Junjie Yao
- Department of Bioengineering, Duke University, Durham, NC, USA
| | - William C Wetsel
- Department of Neurology, Duke University Medical Center, Durham, NC, USA
- Departments of Neurobiology and Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Scott D Moore
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA
| | - Dennis A Turner
- Departments of Neurosurgery, Neurobiology and Biomedical Engineering, Duke University Medical Center, Durham, NC, USA
| | - Wei Yang
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA.
- Department of Neurology, Duke University Medical Center, Durham, NC, USA.
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3
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Kośmider K, Kamieniak M, Czuczwar SJ, Miziak B. Second Generation of Antiepileptic Drugs and Oxidative Stress. Int J Mol Sci 2023; 24:ijms24043873. [PMID: 36835284 PMCID: PMC9964930 DOI: 10.3390/ijms24043873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/10/2023] [Accepted: 02/12/2023] [Indexed: 02/17/2023] Open
Abstract
Epilepsy is a chronic disease of the central nervous system characterized by recurrent epileptic seizures. As a result of epileptic seizure or status epilepticus oxidants are excessively formed, which may be one of the causes of neuronal death. Given the role of oxidative stress in epileptogenesis, as well as the participation of this process in other neurological conditions, we decided to review the latest state of knowledge regarding the relationship between selected newer antiepileptic drugs (AEDs), also known as antiseizure drugs, and oxidative stress. The literature review indicates that drugs enhancing GABA-ergic transmission (e.g., vigabatrin, tiagabine, gabapentin, topiramate) or other antiepileptics (e.g., lamotrigine, levetiracetam) reduce neuronal oxidation markers. In particular, levetiracetam may produce ambiguous effects in this regard. However, when a GABA-enhancing drug was applied to the healthy tissue, it tended to increase oxidative stress markers in a dose-dependent manner. Studies on diazepam have shown that it exerts a neuroprotective effect in a "U-shaped" dose-dependent manner after excitotoxic or oxidative stress. Its lower concentrations are insufficient to protect against neuronal damage, while higher concentrations produce neurodegeneration. Therefore, a conclusion follows that newer AEDs, enhancing GABA-ergic neurotransmission, may act similarly to diazepam, causing neurodegeneration and oxidative stress when used in high doses.
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Demchenko IT, Zhilyaev SY, Platonova TF, Alekseeva OS, Nikitina ER. Inhibition of GABA-Transaminase and GABA-Transporters in the Brain by Vigabatrin and Tiagabine Prevents Seizure Development in Rats Breathing Hyperbaric Oxygen. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021050112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Stavitzski NM, Landon CS, Hinojo CM, Poff AM, Rogers CQ, D'Agostino DP, Dean JB. Exogenous ketone ester delays CNS oxygen toxicity without impairing cognitive and motor performance in male Sprague-Dawley rats. Am J Physiol Regul Integr Comp Physiol 2021; 321:R100-R111. [PMID: 34132115 DOI: 10.1152/ajpregu.00088.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/11/2021] [Indexed: 11/22/2022]
Abstract
Hyperbaric oxygen (HBO2) is breathing >1 atmosphere absolute (ATA; 101.3 kPa) O2 and is used in HBO2 therapy and undersea medicine. What limits the use of HBO2 is the risk of developing central nervous system (CNS) oxygen toxicity (CNS-OT). A promising therapy for delaying CNS-OT is ketone metabolic therapy either through diet or exogenous ketone ester (KE) supplement. Previous studies indicate that KE induces ketosis and delays the onset of CNS-OT; however, the effects of exogeneous KE on cognition and performance are understudied. Accordingly, we tested the hypothesis that oral gavage with 7.5 g/kg induces ketosis and increases the latency time to seizure (LSz) without impairing cognition and performance. A single oral dose of 7.5 g/kg KE increases systemic β-hydroxybutyrate (BHB) levels within 0.5 h and remains elevated for 4 h. Male rats were separated into three groups: control (no gavage), water-gavage, or KE-gavage, and were subjected to behavioral testing while breathing 1 ATA (101.3 kPa) of air. Testing included the following: DigiGait (DG), light/dark (LD), open field (OF), and novel object recognition (NOR). There were no adverse effects of KE on gait or motor performance (DG), cognition (NOR), and anxiety (LD, OF). In fact, KE had an anxiolytic effect (OF, LD). The LSz during exposure to 5 ATA (506.6 kPa) O2 (≤90 min) increased 307% in KE-treated rats compared with control rats. In addition, KE prevented seizures in some animals. We conclude that 7.5 g/kg is an optimal dose of KE in the male Sprague-Dawley rat model of CNS-OT.
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Affiliation(s)
- Nicole M Stavitzski
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Carol S Landon
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Christopher M Hinojo
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Angela M Poff
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Christopher Q Rogers
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Dominic P D'Agostino
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
- Institute of Human Machine and Cognition, Ocala, Florida
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Hyperbaric Biomedical Research Laboratory, Morsani College of Medicine, University of South Florida, Tampa, Florida
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Abstract
PURPOSE OF REVIEW The topic of perioperative hyperoxia remains controversial, with valid arguments on both the 'pro' and 'con' side. On the 'pro' side, the prevention of surgical site infections was a strong argument, leading to the recommendation of the use of hyperoxia in the guidelines of the Center for Disease Control and the WHO. On the 'con' side, the pathophysiology of hyperoxia has increasingly been acknowledged, in particular the pulmonary side effects and aggravation of ischaemia/reperfusion injuries. RECENT FINDINGS Some 'pro' articles leading to the Center for Disease Control and WHO guidelines advocating perioperative hyperoxia have been retracted, and the recommendations were downgraded from 'strong' to 'conditional'. At the same time, evidence that supports a tailored, more restrictive use of oxygen, for example, in patients with myocardial infarction or following cardiac arrest, is accumulating. SUMMARY The change in recommendation exemplifies that despite much work performed on the field of hyperoxia recently, evidence on either side of the argument remains weak. Outcome-based research is needed for reaching a definite recommendation.
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7
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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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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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9
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Bosco G, Rizzato A, Quartesan S, Camporesi E, Mangar D, Paganini M, Cenci L, Malacrida S, Mrakic-Sposta S, Moretti S, Paoli A. Effects of the Ketogenic diet in overweight divers breathing Enriched Air Nitrox. Sci Rep 2018; 8:2655. [PMID: 29422679 PMCID: PMC5805750 DOI: 10.1038/s41598-018-20933-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 01/25/2018] [Indexed: 02/07/2023] Open
Abstract
Central Nervous System Oxygen Toxicity (CNS-OT) is one of the most harmful effects of Enriched Air Nitrox (EAN) diving. Protective factors of the Ketogenic Diet (KD) are antioxidant activity, the prevention of mitochondrial damage and anti-inflammatory mechanisms. We aimed to investigate if a short-term KD may reduce oxidative stress and inflammation during an hyperoxic dive. Samples from six overweight divers (mean ± SD, age: 55.2 ± 4.96 years; BMI: 26.7 ± 0.86 kg/m2) were obtained a) before and after a dive breathing Enriched Air Nitrox and performing 20-minute mild underwater exercise, b) after a dive (same conditions) performed after 7 days of KD. We measured urinary 8-isoprostane and 8-OH-2-deoxyguanosine and plasmatic IL-1β, IL-6 and TNF-α levels. The KD was successful in causing weight loss (3.20 ± 1.31 Kgs, p < 0.01) and in limiting lipid peroxidation (3.63 ± 1.16 vs. 1.11 ± 0.22; p < 0.01) and inflammatory response (IL-1β = 105.7 ± 25.52 vs. 57.03 ± 16.32, p < 0.05; IL-6 = 28.91 ± 4.351 vs. 14.08 ± 1.74, p < 0.001; TNF-α = 78.01 ± 7.69 vs. 64.68 ± 14.56, p < 0.05). A short-term KD seems to be effective in weight loss, in decreasing inflammation and protective towards lipid peroxidation during hyperoxic diving.
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Affiliation(s)
- Gerardo Bosco
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Alex Rizzato
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy.
| | - Silvia Quartesan
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | | | - Matteo Paganini
- Emergency Medicine Residency Program, University of Padova, Padova, Italy
| | - Lorenzo Cenci
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Sandro Malacrida
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | - Sara Moretti
- CNR Institute of Bioimaging and Molecular Physiology, Segrate (Milano), Italy
| | - Antonio Paoli
- Environmental physiology & medicine Lab, Department of Biomedical Sciences, University of Padova, Padova, Italy
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Bosco G, Rizzato A, Moon RE, Camporesi EM. Environmental Physiology and Diving Medicine. Front Psychol 2018; 9:72. [PMID: 29456518 PMCID: PMC5801574 DOI: 10.3389/fpsyg.2018.00072] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/17/2018] [Indexed: 12/12/2022] Open
Abstract
Man's experience and exploration of the underwater environment has been recorded from ancient times and today encompasses large sections of the population for sport enjoyment, recreational and commercial purpose, as well as military strategic goals. Knowledge, respect and maintenance of the underwater world is an essential development for our future and the knowledge acquired over the last few dozen years will change rapidly in the near future with plans to establish secure habitats with specific long-term goals of exploration, maintenance and survival. This summary will illustrate briefly the physiological changes induced by immersion, swimming, breath-hold diving and exploring while using special equipment in the water. Cardiac, circulatory and pulmonary vascular adaptation and the pathophysiology of novel syndromes have been demonstrated, which will allow selection of individual characteristics in order to succeed in various environments. Training and treatment for these new microenvironments will be suggested with description of successful pioneers in this field. This is a summary of the physiology and the present status of pathology and therapy for the field.
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Affiliation(s)
- Gerardo Bosco
- Environmental Physiology and Medicine Lab, Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Alex Rizzato
- Environmental Physiology and Medicine Lab, Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Richard E. Moon
- Center for Hyperbaric Medicine and Environmental Physiology, Department of Anesthesiology, Duke University Medical Center, Durham, NC, United States
| | - Enrico M. Camporesi
- TEAMHealth Research Institute, Tampa General Hospital, Tampa, FL, United States
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Gasier HG, Demchenko IT, Tatro LG, Piantadosi CA. S-nitrosylation of GAD65 is implicated in decreased GAD activity and oxygen-induced seizures. Neurosci Lett 2017; 653:283-287. [PMID: 28579483 DOI: 10.1016/j.neulet.2017.05.067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/22/2017] [Accepted: 05/30/2017] [Indexed: 11/19/2022]
Abstract
Breathing oxygen at partial pressures ≥2.5 atmospheres absolute, which can occur in diving and hyperbaric oxygen (HBO2) therapy, can rapidly become toxic to the central nervous system (CNS). This neurotoxicity culminates in generalized EEG epileptiform discharges, tonic-clonic convulsions and ultimately death. Increased production of neuronal nitric oxide (NO) has been implicated in eliciting hyperoxic seizures by altering the equilibrium between glutamatergic and GABAergic synaptic transmission. Inhibition of glutamic acid decarboxylase (GAD) activity in HBO2 promotes this imbalance; however, the mechanisms by which this occurs is unknown. Therefore, we conducted a series of experiments using mice, a species that is highly susceptible to CNS oxygen toxicity, to explore the possibility that NO modulates GABA metabolism. Mice were exposed to 100% oxygen at 4 ATA for various durations, and brain GAD and GABA transaminase (GABA-T) activity, as well as S-nitrosylation of GAD65 and GAD67 were determined. HBO2 inhibited GAD activity by 50% and this was negatively correlated with S-nitrosylation of GAD65, whereas GABA-T activity and S-nitrosylation of GAD67 were unaltered. These results suggest a new mechanism by which NO alters GABA metabolism, leading to neuroexcitation and seizures in HBO2.
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Affiliation(s)
- Heath G Gasier
- Department of Military and Emergency Medicine, Uniformed Services University of the Health Science, Bethesda, MD, 20814, USA.
| | - Ivan T Demchenko
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lynn G Tatro
- Durham Veterans Affairs Hospital, Durham, NC, 20814, USA
| | - Claude A Piantadosi
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA; Durham Veterans Affairs Hospital, Durham, NC, 20814, USA; Departments of Medicine and Pathology, Duke University Medical Center, Durham, NC, 27710, USA
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