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Witkin JM, Shafique H, Cerne R, Smith JL, Marini AM, Lipsky RH, Delery E. Mechanistic and therapeutic relationships of traumatic brain injury and γ-amino-butyric acid (GABA). Pharmacol Ther 2024; 256:108609. [PMID: 38369062 DOI: 10.1016/j.pharmthera.2024.108609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 01/18/2024] [Accepted: 02/01/2024] [Indexed: 02/20/2024]
Abstract
Traumatic brain injury (TBI) is a highly prevalent medical condition for which no medications specific for the prophylaxis or treatment of the condition as a whole exist. The spectrum of symptoms includes coma, headache, seizures, cognitive impairment, depression, and anxiety. Although it has been known for years that the inhibitory neurotransmitter γ-amino-butyric acid (GABA) is involved in TBI, no novel therapeutics based upon this mechanism have been introduced into clinical practice. We review the neuroanatomical, neurophysiological, neurochemical, and neuropharmacological relationships of GABA neurotransmission to TBI with a view toward new potential GABA-based medicines. The long-standing idea that excitatory and inhibitory (GABA and others) balances are disrupted by TBI is supported by the experimental data but has failed to invent novel methods of restoring this balance. The slow progress in advancing new treatments is due to the complexity of the disorder that encompasses multiple dynamically interacting biological processes including hemodynamic and metabolic systems, neurodegeneration and neurogenesis, major disruptions in neural networks and axons, frank brain lesions, and a multitude of symptoms that have differential neuronal and neurohormonal regulatory mechanisms. Although the current and ongoing clinical studies include GABAergic drugs, no novel GABA compounds are being explored. It is suggested that filling the gap in understanding the roles played by specific GABAA receptor configurations within specific neuronal circuits could help define new therapeutic approaches. Further research into the temporal and spatial delivery of GABA modulators should also be useful. Along with GABA modulation, research into the sequencing of GABA and non-GABA treatments will be needed.
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Affiliation(s)
- Jeffrey M Witkin
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent Hospital, Indianapolis, IN, USA; Departments of Neuroscience and Trauma Research, Ascension St. Vincent Hospital, Indianapolis, IN, USA; RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA.
| | | | - Rok Cerne
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent Hospital, Indianapolis, IN, USA; RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA; Department of Anatomy and Cell Biology, Indiana University/Purdue University, Indianapolis, IN, USA
| | - Jodi L Smith
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent Hospital, Indianapolis, IN, USA
| | - Ann M Marini
- Department of Neurology, Program in Neuroscience, and Molecular and Cellular Biology Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Robert H Lipsky
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Elizabeth Delery
- College of Osteopathic Medicine, Marian University, Indianapolis, IN, USA.
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Chen WH, Chiu CH, Farn SS, Cheng KH, Huang YR, Lee SY, Fang YC, Lin YH, Chang KW. Identification of the Hepatic Metabolites of Flumazenil and their Kinetic Application in Neuroimaging. Pharmaceuticals (Basel) 2023; 16:ph16050764. [PMID: 37242547 DOI: 10.3390/ph16050764] [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: 04/14/2023] [Revised: 05/08/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
Studies of the neurobiological causes of anxiety disorders have suggested that the γ-aminobutyric acid (GABA) system increases synaptic concentrations and enhances the affinity of GABAA (type A) receptors for benzodiazepine ligands. Flumazenil antagonizes the benzodiazepine-binding site of the GABA/benzodiazepine receptor (BZR) complex in the central nervous system (CNS). The investigation of flumazenil metabolites using liquid chromatography (LC)-tandem mass spectrometry will provide a complete understanding of the in vivo metabolism of flumazenil and accelerate radiopharmaceutical inspection and registration. The main goal of this study was to investigate the use of reversed-phase high performance liquid chromatography (PR-HPLC), coupled with electrospray ionization triple-quadrupole tandem mass spectrometry (ESI-QqQ MS), to identify flumazenil and its metabolites in the hepatic matrix. Carrier-free nucleophilic fluorination with an automatic synthesizer for [18F]flumazenil, combined with nano-positron emission tomography (NanoPET)/computed tomography (CT) imaging, was used to predict the biodistribution in normal rats. The study showed that 50% of the flumazenil was biotransformed by the rat liver homogenate in 60 min, whereas one metabolite (M1) was a methyl transesterification product of flumazenil. In the rat liver microsomal system, two metabolites were identified (M2 and M3), as their carboxylic acid and hydroxylated ethyl ester forms between 10 and 120 min, respectively. A total of 10-30 min post-injection of [18F]flumazenil showed an immediate decreased in the distribution ratio observed in the plasma. Nevertheless, a higher ratio of the complete [18F]flumazenil compound could be used for subsequent animal studies. [18F] According to in vivo nanoPET/CT imaging and ex vivo biodistribution assays, flumazenil also showed significant effects on GABAA receptor availability in the amygdala, prefrontal cortex, cortex, and hippocampus in the rat brain, indicating the formation of metabolites. We reported the completion of the biotransformation of flumazenil by the hepatic system, as well as [18F]flumazenil's potential as an ideal ligand and PET agent for the determination of the GABAA/BZR complex for multiplex neurological syndromes at the clinical stage.
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Affiliation(s)
- Wei-Hsi Chen
- Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan City 325207, Taiwan
| | - Chuang-Hsin Chiu
- Department of Nuclear Medicine, Tri-Service General Hospital, Taipei 114202, Taiwan
| | - Shiou-Shiow Farn
- Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan City 325207, Taiwan
| | - Kai-Hung Cheng
- Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan City 325207, Taiwan
| | - Yuan-Ruei Huang
- Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan City 325207, Taiwan
| | - Shih-Ying Lee
- Isotope Application Division, Institute of Nuclear Energy Research, Taoyuan City 325207, Taiwan
| | - Yao-Ching Fang
- Taipei Neuroscience Institute, Taipei Medical University, Taipei 110301, Taiwan
| | - Yu-Hua Lin
- Laboratory Animal Center, Taipei Medical University, Taipei 110301, Taiwan
| | - Kang-Wei Chang
- Taipei Neuroscience Institute, Taipei Medical University, Taipei 110301, Taiwan
- Laboratory Animal Center, Taipei Medical University, Taipei 110301, Taiwan
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Wang X, Wang T, Fan X, Zhang Z, Wang Y, Li Z. A Molecular Toolbox of Positron Emission Tomography Tracers for General Anesthesia Mechanism Research. J Med Chem 2023; 66:6463-6497. [PMID: 37145921 DOI: 10.1021/acs.jmedchem.2c01965] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
With appropriate radiotracers, positron emission tomography (PET) allows direct or indirect monitoring of the spatial and temporal distribution of anesthetics, neurotransmitters, and biomarkers, making it an indispensable tool for studying the general anesthesia mechanism. In this Perspective, PET tracers that have been recruited in general anesthesia research are introduced in the following order: 1) 11C/18F-labeled anesthetics, i.e., PET tracers made from inhaled and intravenous anesthetics; 2) PET tracers targeting anesthesia-related receptors, e.g., neurotransmitters and voltage-gated ion channels; and 3) PET tracers for studying anesthesia-related neurophysiological effects and neurotoxicity. The radiosynthesis, pharmacodynamics, and pharmacokinetics of the above PET tracers are mainly discussed to provide a practical molecular toolbox for radiochemists, anesthesiologists, and those who are interested in general anesthesia.
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Affiliation(s)
- Xiaoxiao Wang
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Tao Wang
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Xiaowei Fan
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Zhao Zhang
- Department of Anesthesiology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yingwei Wang
- Department of Anesthesiology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Zijing Li
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
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Automated Synthesis of [18F]Flumazenil Application in GABAA Receptor Neuroimaging Availability for Rat Model of Anxiety. Pharmaceuticals (Basel) 2023; 16:ph16030417. [PMID: 36986516 PMCID: PMC10058208 DOI: 10.3390/ph16030417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/03/2023] [Accepted: 03/07/2023] [Indexed: 03/12/2023] Open
Abstract
Clinical studies have demonstrated that the γ-aminobutyric acid type A (GABAA) receptor complex plays a central role in the modulation of anxiety. Conditioned fear and anxiety-like behaviors have many similarities at the neuroanatomical and pharmacological levels. The radioactive GABA/BZR receptor antagonist, fluorine-18-labeled flumazenil, [18F]flumazenil, behaves as a potential PET imaging agent for the evaluation of cortical damage of the brain in stroke, alcoholism, and for Alzheimer disease investigation. The main goal of our study was to investigate a fully automated nucleophilic fluorination system, with solid extraction purification, developed to replace traditional preparation methods, and to detect underlying expressions of contextual fear and characterize the distribution of GABAA receptors in fear-conditioned rats by [18F]flumazenil. A carrier-free nucleophilic fluorination method using an automatic synthesizer with direct labeling of a nitro-flumazenil precursor was implemented. The semi-preparative high-performance liquid chromatography (HPLC) purification method (RCY = 15–20%) was applied to obtain high purity [18F]flumazenil. Nano-positron emission tomography (NanoPET)/computed tomography (CT) imaging and ex vivo autoradiography were used to analyze the fear conditioning of rats trained with 1–10 tone-foot-shock pairings. The anxiety rats had a significantly lower cerebral accumulation (in the amygdala, prefrontal cortex, cortex, and hippocampus) of fear conditioning. Our rat autoradiography results also supported the findings of PET imaging. Key findings were obtained by developing straightforward labeling and purification procedures that can be easily adapted to commercially available modules for the high radiochemical purity of [18F]flumazenil. The use of an automatic synthesizer with semi-preparative HPLC purification would be a suitable reference method for new drug studies of GABAA/BZR receptors in the future.
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Malatesta M. Molecular Imaging in Nanomedical Research. Int J Mol Sci 2022; 23:ijms23084207. [PMID: 35457025 PMCID: PMC9027711 DOI: 10.3390/ijms23084207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 03/24/2022] [Accepted: 03/29/2022] [Indexed: 01/27/2023] Open
Affiliation(s)
- Manuela Malatesta
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, I-37134 Verona, Italy
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Holzgreve A, Pötter D, Brendel M, Orth M, Weidner L, Gold L, Kirchner MA, Bartos LM, Unterrainer LM, Unterrainer M, Steiger K, von Baumgarten L, Niyazi M, Belka C, Bartenstein P, Riemenschneider MJ, Lauber K, Albert NL. Longitudinal [ 18F]GE-180 PET Imaging Facilitates In Vivo Monitoring of TSPO Expression in the GL261 Glioblastoma Mouse Model. Biomedicines 2022; 10:biomedicines10040738. [PMID: 35453488 PMCID: PMC9030822 DOI: 10.3390/biomedicines10040738] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 03/17/2022] [Accepted: 03/21/2022] [Indexed: 02/01/2023] Open
Abstract
The 18 kDa translocator protein (TSPO) is increasingly recognized as an interesting target for the imaging of glioblastoma (GBM). Here, we investigated TSPO PET imaging and autoradiography in the frequently used GL261 glioblastoma mouse model and aimed to generate insights into the temporal evolution of TSPO radioligand uptake in glioblastoma in a preclinical setting. We performed a longitudinal [18F]GE-180 PET imaging study from day 4 to 14 post inoculation in the orthotopic syngeneic GL261 GBM mouse model (n = 21 GBM mice, n = 3 sham mice). Contrast-enhanced computed tomography (CT) was performed at the day of the final PET scan (±1 day). [18F]GE-180 autoradiography was performed on day 7, 11 and 14 (ex vivo: n = 13 GBM mice, n = 1 sham mouse; in vitro: n = 21 GBM mice; n = 2 sham mice). Brain sections were also used for hematoxylin and eosin (H&E) staining and TSPO immunohistochemistry. [18F]GE-180 uptake in PET was elevated at the site of inoculation in GBM mice as compared to sham mice at day 11 and later (at day 14, TBRmax +27% compared to sham mice, p = 0.001). In GBM mice, [18F]GE-180 uptake continuously increased over time, e.g., at day 11, mean TBRmax +16% compared to day 4, p = 0.011. [18F]GE-180 uptake as depicted by PET was in all mice co-localized with contrast-enhancement in CT and tissue-based findings. [18F]GE-180 ex vivo and in vitro autoradiography showed highly congruent tracer distribution (r = 0.99, n = 13, p < 0.001). In conclusion, [18F]GE-180 PET imaging facilitates non-invasive in vivo monitoring of TSPO expression in the GL261 GBM mouse model. [18F]GE-180 in vitro autoradiography is a convenient surrogate for ex vivo autoradiography, allowing for straightforward identification of suitable models and scan time-points on previously generated tissue sections.
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Affiliation(s)
- Adrien Holzgreve
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Dennis Pötter
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Matthias Brendel
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Michael Orth
- Department of Radiation Oncology, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (M.O.); (M.N.); (C.B.); (K.L.)
| | - Lorraine Weidner
- Department of Neuropathology, Regensburg University Hospital, 93053 Regensburg, Germany; (L.W.); (M.J.R.)
| | - Lukas Gold
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Maximilian A. Kirchner
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Laura M. Bartos
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Lena M. Unterrainer
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
| | - Marcus Unterrainer
- Department of Radiology, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany;
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
| | - Katja Steiger
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
- Institute of Pathology, TUM School of Medicine, Technical University of Munich, 81675 Munich, Germany
| | - Louisa von Baumgarten
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
- Department of Neurosurgery, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany
| | - Maximilian Niyazi
- Department of Radiation Oncology, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (M.O.); (M.N.); (C.B.); (K.L.)
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
| | - Claus Belka
- Department of Radiation Oncology, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (M.O.); (M.N.); (C.B.); (K.L.)
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
| | - Peter Bartenstein
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
| | - Markus J. Riemenschneider
- Department of Neuropathology, Regensburg University Hospital, 93053 Regensburg, Germany; (L.W.); (M.J.R.)
| | - Kirsten Lauber
- Department of Radiation Oncology, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (M.O.); (M.N.); (C.B.); (K.L.)
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
| | - Nathalie L. Albert
- Department of Nuclear Medicine, University Hospital, Ludwig Maximilian University of Munich (LMU Munich), 81377 Munich, Germany; (A.H.); (D.P.); (M.B.); (L.G.); (M.A.K.); (L.M.B.); (L.M.U.); (P.B.)
- German Cancer Consortium (DKTK), Partner Site Munich, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (K.S.); (L.v.B.)
- Correspondence:
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