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Demchenko IT, Suliman HB, Zhilyaey SY, Alekseeva OS, Platonova TF, Makowski MS, Piantadosi CA, Gasier HG. GAT inhibition preserves cerebral blood flow and reduces oxidant damage to mitochondria in rodents exposed to extreme hyperbaric oxygen. Front Mol Neurosci 2023; 15:1062410. [PMID: 36704328 PMCID: PMC9871636 DOI: 10.3389/fnmol.2022.1062410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/22/2022] [Indexed: 01/11/2023] Open
Abstract
Oxygen breathing at elevated partial pressures (PO2's) at or more than 3 atmospheres absolute (ATA) causes a reduction in brain γ-aminobutyric acid (GABA) levels that impacts the development of central nervous system oxygen toxicity (CNS-OT). Drugs that increase brain GABA content delay the onset of CNS-OT, but it is unknown if oxidant damage is lessened because brain tissue PO2 remains elevated during hyperbaric oxygen (HBO2) exposures. Experiments were performed in rats and mice to measure brain GABA levels with or without GABA transporter inhibitors (GATs) and its influence on cerebral blood flow, oxidant damage, and aspects of mitochondrial quality control signaling (mitophagy and biogenesis). In rats pretreated with tiagabine (GAT1 inhibitor), the tachycardia, secondary rise in mean arterial blood pressure, and cerebral hyperemia were prevented during HBO2 at 5 and 6 ATA. Tiagabine and the nonselective GAT inhibitor nipecotic acid similarly extended HBO2 seizure latencies. In mice pretreated with tiagabine and exposed to HBO2 at 5 ATA, nuclear and mitochondrial DNA oxidation and astrocytosis was attenuated in the cerebellum and hippocampus. Less oxidant injury in these regions was accompanied by reduced conjugated microtubule-associated protein 1A/1B-light chain 3 (LC3-II), an index of mitophagy, and phosphorylated cAMP response element binding protein (pCREB), an initiator of mitochondrial biogenesis. We conclude that GABA prevents cerebral hyperemia and delays neuroexcitation under extreme HBO2, limiting oxidant damage in the cerebellum and hippocampus, and likely lowering mitophagy flux and initiation of pCREB-initiated mitochondrial biogenesis.
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Affiliation(s)
- Ivan T. Demchenko
- The Duke Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, United States,Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Hagir B. Suliman
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Sergey Y. Zhilyaey
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Olga S. Alekseeva
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Tatyana F. Platonova
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Matthew S. Makowski
- The Duke Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, United States
| | - Claude A. Piantadosi
- The Duke Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, United States
| | - Heath G. Gasier
- The Duke Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, United States,*Correspondence: Heath G. Gasier, ✉
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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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