GAT inhibition preserves cerebral blood flow and reduces oxidant damage to mitochondria in rodents exposed to extreme hyperbaric oxygen.

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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Published Version (Please cite this version)

10.3389/fnmol.2022.1062410

Publication Info

Demchenko, Ivan T, Hagir B Suliman, Sergey Y Zhilyaey, Olga S Alekseeva, Tatyana F Platonova, Matthew S Makowski, Claude A Piantadosi, Heath G Gasier, et al. (2022). GAT inhibition preserves cerebral blood flow and reduces oxidant damage to mitochondria in rodents exposed to extreme hyperbaric oxygen. Frontiers in molecular neuroscience, 15. p. 1062410. 10.3389/fnmol.2022.1062410 Retrieved from https://hdl.handle.net/10161/26693.

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Scholars@Duke

Gasier

Heath Gasier

Associate Professor in Anesthesiology

I am a physiologist who joined Duke University in 2019 after retiring from military service. My research has focused on understanding how oxidant stress impacts cellular and systems physiology. Initially, I studied in humans how hyperbaric oxygen (HBO2) within the therapeutic range and high altitude influence nitric oxide production, antioxidant defenses, tissue oxygenation and muscle performance. This work sparked my interest in redox biology and led me to train under Dr. Claude A. Piantadosi at Duke University. Here, I began to study in mice and rats the impact of extreme HBO2 on the central nervous system (CNS). The objectives were to identify in rodents the origin and mechanisms of CNS oxygen toxicity, and test targeted pharmacological intervention strategies. It was during this time that I became interested in heme oxygenase 1 (HO-1). During my final military assignment, I continued to work on HBO2 and CNS oxygen toxicity related research (pharmacological intervention) and initiated new studies examining how HO-1 induction influences musculoskeletal health in diet-induced obesity. These studies led to follow-on work aimed at determining the mechanisms of HO-1 induction and mitochondrial dynamic regulation in an in vitro model of diet-induced obesity. In addition, I was involved in research aimed at understanding how antioxidants influence skeletal muscle mitochondrial dynamics in rodents and cells exposed heat stress and extreme high altitude.

Since returning to Duke University, I continue to conduct research focused on understanding how oxidant stress induced by HBO2 and obesity influences mitochondrial dynamic regulation in the brain, lung and skeletal muscle. I am now studying how sarcopenia and gender influence these responses. I am also involved (Co-I) in research testing the efficacy of a home-based high intensity interval training program in COVID-19 critical illness and early parenteral nutrition in abdominal trauma victims. In both of these studies, my efforts will be directed towards measuring inflammation and mitochondrial quality control responses to the interventions, which are linked to HO-1 activation.


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