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Biswas S, Shahriar S, Bachay G, Arvanitis P, Jamoul D, Brunken WJ, Agalliu D. Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/β-catenin signaling. Neuron 2024; 112:1978-1996.e6. [PMID: 38599212 PMCID: PMC11189759 DOI: 10.1016/j.neuron.2024.03.011] [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: 07/11/2023] [Revised: 01/15/2024] [Accepted: 03/11/2024] [Indexed: 04/12/2024]
Abstract
Interactions among neuronal, glial, and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Although synaptic dysfunction precedes vascular abnormalities in many retinal pathologies, how neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA sequencing (scRNA-seq), and functional validation, we show that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1-/- retinas where neurons fail to release glutamate. By contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1-/- retinas, where constitutively depolarized rods release excessive glutamate. Norrin expression and endothelial Norrin/β-catenin signaling are downregulated in Vglut1-/- retinas and upregulated in Gnat1-/- retinas. Pharmacological activation of endothelial Norrin/β-catenin signaling in Vglut1-/- retinas rescues defects in deep plexus angiogenesis and paracellular BRB maturation. Our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating endothelial Norrin/β-catenin signaling.
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Affiliation(s)
- Saptarshi Biswas
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA.
| | - Sanjid Shahriar
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; Wyss Institute for Biologically Inspired Engineering, Boston, MA 02115, USA
| | - Galina Bachay
- Department of Ophthalmology and Visual Sciences, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Panos Arvanitis
- Warren Alpert Medical School, Brown University, Providence, RI 02903, USA
| | - Danny Jamoul
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA; John Jay College of Criminal Justice, City University of New York, New York, NY 10019, USA
| | - William J Brunken
- Department of Ophthalmology and Visual Sciences, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Dritan Agalliu
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA.
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2
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Ormel L, Lauritzen KH, Schreiber R, Kunzelmann K, Gundersen V. GABA, but Not Bestrophin-1, Is Localized in Astroglial Processes in the Mouse Hippocampus and the Cerebellum. Front Mol Neurosci 2020; 13:135. [PMID: 32848599 PMCID: PMC7399226 DOI: 10.3389/fnmol.2020.00135] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 07/07/2020] [Indexed: 11/13/2022] Open
Abstract
GABA is proposed to act as a gliotransmitter in the brain. Differences in GABA release from astroglia are thought to underlie differences in tonic inhibition between the cerebellum and the CA1 hippocampus. Here we used quantitative immunogold cytochemistry to localize and compare the levels of GABA in astroglia in these brain regions. We found that the density of GABA immunogold particles was similar in delicate processes of Bergman glia in the cerebellum and astrocytes in the CA1 hippocampus. The astrocytic GABA release is proposed to be mediated by, among others, the Ca2+ activated Cl- channel bestrophin-1. The bestrophin-1 antibodies did not show any significant bestrophin-1 signal in the brain of wt mice, nor in bestrophin-1 knockout mice. The bestrophin-1 signal was low both on Western blots and immunofluorescence laser scanning microscopic images. These results suggest that GABA is localized in astroglia, but in similar concentrations in the cerebellum and CA1 hippocampus, and thus cannot account for differences in tonic inhibition between these brain regions. Furthermore, our data seem to suggest that the GABA release from astroglia previously observed in the hippocampus and cerebellum occurs via mechanisms other than bestrophin-1.
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Affiliation(s)
- Lasse Ormel
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Department of Neurology, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Knut H Lauritzen
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Vidar Gundersen
- Section of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Section for Movement Disorders, Department of Neurology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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3
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Patel DC, Tewari BP, Chaunsali L, Sontheimer H. Neuron-glia interactions in the pathophysiology of epilepsy. Nat Rev Neurosci 2019; 20:282-297. [PMID: 30792501 DOI: 10.1038/s41583-019-0126-4] [Citation(s) in RCA: 219] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Epilepsy is a neurological disorder afflicting ~65 million people worldwide. It is caused by aberrant synchronized firing of populations of neurons primarily due to imbalance between excitatory and inhibitory neurotransmission. Hence, the historical focus of epilepsy research has been neurocentric. However, the past two decades have enjoyed an explosion of research into the role of glia in supporting and modulating neuronal activity, providing compelling evidence of glial involvement in the pathophysiology of epilepsy. The mechanisms by which glia, particularly astrocytes and microglia, may contribute to epilepsy and consequently could be harnessed therapeutically are discussed in this Review.
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Affiliation(s)
- Dipan C Patel
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Bhanu P Tewari
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Lata Chaunsali
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA
| | - Harald Sontheimer
- Fralin Biomedical Research Institute, Glial Biology in Health, Disease, and Cancer Center, Roanoke, VA, USA. .,School of Neuroscience, Virginia Tech, Blacksburg, VA, USA.
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4
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Dodds KN, Beckett EAH, Evans SF, Hutchinson MR. Spinal Glial Adaptations Occur in a Minimally Invasive Mouse Model of Endometriosis: Potential Implications for Lesion Etiology and Persistent Pelvic Pain. Reprod Sci 2018; 26:357-369. [PMID: 29730970 DOI: 10.1177/1933719118773405] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Glial adaptations within the central nervous system are well known to modulate central sensitization and pain. Recently, it has been suggested that activity of glial-related proinflammatory cytokines may potentiate peripheral inflammation, via central neurogenic processes. However, a role for altered glial function has not yet been investigated in the context of endometriosis, a chronic inflammatory condition in women associated with peripheral lesions, often manifesting with persistent pelvic pain. Using a minimally invasive mouse model of endometriosis, we investigated associations between peripheral endometriosis-like lesions and adaptations in central glial reactivity. Spinal cords (T13-S1) from female C57BL/6 mice with endometriosis-like lesions (ENDO) were imaged via fluorescent immunohistochemistry for the expression of glial fibrillary acidic protein (GFAP; astrocytes) and CD11b (microglia) in the dorsal horn (n = 5). Heightened variability ( P = .02) as well as an overall increase ( P = .04) in the mean area of GFAP immunoreactivity was found in ENDO versus saline-injected control animals. Interestingly, spinal levels showing the greatest alterations in GFAP immunoreactivity appeared to correlate with the spatial location of lesions within the abdominopelvic cavity. A subtle but significant increase in the mean area of CD11b immunostaining was also observed in ENDO mice compared to controls ( P = .02). This is the first study to describe adaptations in nonneuronal, immune-like cells of the central nervous system attributed to the presence of endometriosis-like lesions.
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Affiliation(s)
- Kelsi N Dodds
- 1 Discipline of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Elizabeth A H Beckett
- 1 Discipline of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Susan F Evans
- 2 Discipline of Pharmacology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Mark R Hutchinson
- 1 Discipline of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia.,3 Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, South Australia, Australia
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5
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Kalitin KY, Grechko OY, Spasov AA, Sukhov AG, Anisimova VA, Matukhno AE. GABAergic Mechanism of Anticonvulsive Effect of Chemical Agent RU-1205. Bull Exp Biol Med 2018; 164:629-635. [PMID: 29582204 DOI: 10.1007/s10517-018-4047-4] [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: 05/27/2015] [Indexed: 11/27/2022]
Abstract
The study examined the effect of 9-(2-morpholinoethyl)-2-(4-fluorophenyl)imidazo[1,2-α] benzimidazole dihydrochloride (RU-1205) on the latency of seizures provoked by corazol, bicuculline, or picrotoxin. This agent (10 and 20 mg/kg) increased the seizure latency in the experimental models of epileptogenesis. The blockers of GABAA and GABA A -ρ receptors picrotoxin and (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid, respectively, were employed to study the effects of RU-1205 on electrical activity of somatosensory cortical neurons and on formation of pathological rhythms in the rat brain. RU-1205 inhibited the focal background rhythm and eliminated the epileptiform activity, which can be mediated by interaction with GABAA receptors.
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Affiliation(s)
- K Yu Kalitin
- Department of Pharmacology, Volgograd State Medical University, Volgograd, Russia.
| | - O Yu Grechko
- Department of Pharmacology, Volgograd State Medical University, Volgograd, Russia
| | - A A Spasov
- Department of Pharmacology, Volgograd State Medical University, Volgograd, Russia.,Volgograd Medical Science Center, Volgograd, Russia
| | - A G Sukhov
- Laboratory of Experimental Neurobiology, D. I. Ivanovsky Academy of Biology and Biotechnology, Rostov-on-Don, Russia
| | - V A Anisimova
- Research Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don, Russia
| | - A E Matukhno
- Laboratory of Experimental Neurobiology, D. I. Ivanovsky Academy of Biology and Biotechnology, Rostov-on-Don, Russia
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6
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Dong W, Todd AC, Bröer A, Hulme SR, Bröer S, Billups B. PKC-Mediated Modulation of Astrocyte SNAT3 Glutamine Transporter Function at Synapses in Situ. Int J Mol Sci 2018; 19:ijms19040924. [PMID: 29561757 PMCID: PMC5979592 DOI: 10.3390/ijms19040924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/07/2018] [Accepted: 03/15/2018] [Indexed: 01/13/2023] Open
Abstract
Astrocytes are glial cells that have an intimate physical and functional association with synapses in the brain. One of their main roles is to recycle the neurotransmitters glutamate and gamma-aminobutyric acid (GABA), as a component of the glutamate/GABA-glutamine cycle. They perform this function by sequestering neurotransmitters and releasing glutamine via the neutral amino acid transporter SNAT3. In this way, astrocytes regulate the availability of neurotransmitters and subsequently influence synaptic function. Since many plasma membrane transporters are regulated by protein kinase C (PKC), the aim of this study was to understand how PKC influences SNAT3 glutamine transport in astrocytes located immediately adjacent to synapses. We studied SNAT3 transport by whole-cell patch-clamping and fluorescence pH imaging of single astrocytes in acutely isolated brainstem slices, adjacent to the calyx of the Held synapse. Activation of SNAT3-mediated glutamine transport in these astrocytes was reduced to 77 ± 6% when PKC was activated with phorbol 12-myristate 13-acetate (PMA). This effect was very rapid (within ~20 min) and eliminated by application of bisindolylmaleimide I (Bis I) or 7-hydroxystaurosporine (UCN-01), suggesting that activation of conventional isoforms of PKC reduces SNAT3 function. In addition, cell surface biotinylation experiments in these brain slices show that the amount of SNAT3 in the plasma membrane is reduced by a comparable amount (to 68 ± 5%) upon activation of PKC. This indicates a role for PKC in dynamically controlling the trafficking of SNAT3 transporters in astrocytes in situ. These data demonstrate that PKC rapidly regulates the astrocytic glutamine release mechanism, which would influence the glutamine availability for adjacent synapses and control levels of neurotransmission.
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Affiliation(s)
- Wuxing Dong
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
| | - Alison C Todd
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
- Centre for Discovery Brain Sciences, School of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
| | - Angelika Bröer
- Research School of Biology, The Australian National University, Linnaeus Way 134, Canberra ACT 2601, Australia.
| | - Sarah R Hulme
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
| | - Stefan Bröer
- Research School of Biology, The Australian National University, Linnaeus Way 134, Canberra ACT 2601, Australia.
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra ACT 2601, Australia.
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7
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Liu T, He Z, Tian X, Kamal GM, Li Z, Liu Z, Liu H, Xu F, Wang J, Xiang H. Specific patterns of spinal metabolites underlying α-Me-5-HT-evoked pruritus compared with histamine and capsaicin assessed by proton nuclear magnetic resonance spectroscopy. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1222-1230. [PMID: 28344131 DOI: 10.1016/j.bbadis.2017.03.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 03/22/2017] [Accepted: 03/22/2017] [Indexed: 12/29/2022]
Abstract
The mechanism behind itching is not well understood. Proton nuclear magnetic resonance (1H-NMR) spectroscopic analysis of spinal cord extracts provides a quick modality for evaluating the specific metabolic activity of α-Me-5-HT-evoked pruritus mice. In the current study, four groups of young adult male C57Bl/6 mice were investigated; one group treated with saline, while the other groups intradermally injected with α-Me-5-HT (histamine independent pruritogen), histamine (histamine dependent pruritogen) and capsaicin (algogenic substance), respectively. The intradermal microinjection of α-Me-5-HT and histamine resulted in a dramatic increase in the itch behavior. Furthermore, the results of NMR studies of the spinal cord extracts revealed that the metabolites show very different patterns for these different drugs, especially when comparing α-Me-5-HT and capsaicin. All the animals in the groups of α-Me-5-HT and capsaicin were completely separated using the metabolite parameters and principal component analysis. For α-Me-5-HT, the concentrations of glutamate, GABA, glycine and aspartate increased significantly, especially for GABA (increased 17.2%, p=0.008). Furthermore, the concentration of NAA increased, but there was no significant difference (increased 11.3%, p=0.191) compared to capsaicin (decreased 29.1%, p=0.002). Thus the application of magnetic resonance spectroscopy technique, coupled with statistical analysis, could further explain the mechanism behind itching evoked by α-Me-5-HT or other drugs. It can thus improve our understanding of itch pathophysiology and pharmacological therapies which may contribute to itch relief.
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Affiliation(s)
- Taotao Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China; Department of Anesthesiology, Peking University Third Hospital, Beijing 100191, China
| | - Zhigang He
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Xuebi Tian
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Ghulam Mustafa Kamal
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Zhixiao Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China
| | - Zeyuan Liu
- College of Life Science, Wuhan University, Wuhan, Hubei 430076, PR China
| | - Huili Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China
| | - Fuqiang Xu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Jie Wang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
| | - Hongbing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, PR China.
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8
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Todd AC, Marx MC, Hulme SR, Bröer S, Billups B. SNAT3-mediated glutamine transport in perisynaptic astrocytesin situis regulated by intracellular sodium. Glia 2017; 65:900-916. [DOI: 10.1002/glia.23133] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 01/12/2017] [Accepted: 02/08/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Alison C. Todd
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
- Centre for Integrative Physiology, School of Biomedical Sciences; University of Edinburgh; Edinburgh EH8 9XD United Kingdom
| | - Mari-Carmen Marx
- Department of Pharmacology; University of Cambridge; Tennis Court Road Cambridge CB2 1BT United Kingdom
| | - Sarah R. Hulme
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
| | - Stefan Bröer
- Research School of Biology; The Australian National University; Linnaeus Way 134 Canberra ACT 2601 Australia
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
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9
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Yan X, Maixner DW, Li F, Weng HR. Chronic pain and impaired glial glutamate transporter function in lupus-prone mice are ameliorated by blocking macrophage colony-stimulating factor-1 receptors. J Neurochem 2017; 140:963-976. [PMID: 28072466 DOI: 10.1111/jnc.13952] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/22/2016] [Accepted: 01/05/2017] [Indexed: 12/20/2022]
Abstract
Systemic lupus erythematosus (SLE) is a multi-organ disease of unknown etiology in which the normal immune responses are directed against the body's own healthy tissues. Patients with SLE often suffer from chronic pain. Currently, no animal studies have been reported about the mechanisms underlying pain in SLE. In this study, the development of chronic pain in MRL lupus-prone (MRL/lpr) mice, a well-established lupus mouse model, was characterized for the first time. We found that female MRL/lpr mice developed thermal hyperalgesia at the age of 13 weeks, and mechanical allodynia at the age of 16 weeks. MRL/lpr mice with chronic pain had activation of microglia and astrocytes, over-expression of macrophage colony-stimulating factor-1 (CSF-1) and interleukin-1 beta (IL-1β), as well as suppression of glial glutamate transport function in the spinal cord. Intrathecal injection of either the CSF-1 blocker or IL-1 inhibitor attenuated thermal hyperalgesia in MRL/lpr mice. We provide evidence that the suppressed activity of glial glutamate transporters in the spinal dorsal horn in MRL/lpr mice is caused by activation of the CSF-1 and IL-1β signaling pathways. Our findings suggest that targeting the CSF-1 and IL-1β signaling pathways or the glial glutamate transporter in the spinal cord is an effective approach for the management of chronic pain caused by SLE.
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Affiliation(s)
- Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia, USA.,Department of Cardiovascular Medicine, The Third Hospital of Wuhan, Wuhan, Hubei, China
| | - Dylan W Maixner
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia, USA
| | - Fen Li
- Department of Neurology, The Third Hospital of Wuhan, Wuhan, Hubei, China
| | - Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia College of Pharmacy, Athens, Georgia, USA
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10
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Sajjad J, Felice VD, Golubeva AV, Cryan JF, O’Mahony SM. Sex-dependent activity of the spinal excitatory amino acid transporter: Role of estrous cycle. Neuroscience 2016; 333:311-9. [DOI: 10.1016/j.neuroscience.2016.07.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 06/28/2016] [Accepted: 07/20/2016] [Indexed: 02/07/2023]
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11
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Dodds KN, Beckett EAH, Evans SF, Grace PM, Watkins LR, Hutchinson MR. Glial contributions to visceral pain: implications for disease etiology and the female predominance of persistent pain. Transl Psychiatry 2016; 6:e888. [PMID: 27622932 PMCID: PMC5048206 DOI: 10.1038/tp.2016.168] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 07/14/2016] [Accepted: 07/22/2016] [Indexed: 12/27/2022] Open
Abstract
In the central nervous system, bidirectional signaling between glial cells and neurons ('neuroimmune communication') facilitates the development of persistent pain. Spinal glia can contribute to heightened pain states by a prolonged release of neurokine signals that sensitize adjacent centrally projecting neurons. Although many persistent pain conditions are disproportionately common in females, whether specific neuroimmune mechanisms lead to this increased susceptibility remains unclear. This review summarizes the major known contributions of glia and neuroimmune interactions in pain, which has been determined principally in male rodents and in the context of somatic pain conditions. It is then postulated that studying neuroimmune interactions involved in pain attributed to visceral diseases common to females may offer a more suitable avenue for investigating unique mechanisms involved in female pain. Further, we discuss the potential for primed spinal glia and subsequent neurogenic inflammation as a contributing factor in the development of peripheral inflammation, therefore, representing a predisposing factor for females in developing a high percentage of such persistent pain conditions.
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Affiliation(s)
- K N Dodds
- Discipline of Physiology, School of Medicine, University of Adelaide, Adelaide, SA, Australia
| | - E A H Beckett
- Discipline of Physiology, School of Medicine, University of Adelaide, Adelaide, SA, Australia
| | - S F Evans
- Discipline of Pharmacology, School of Medicine, University of Adelaide, Adelaide, SA, Australia
- Pelvic Pain SA, Norwood, SA, Australia
| | - P M Grace
- Discipline of Pharmacology, School of Medicine, University of Adelaide, Adelaide, SA, Australia
- Department of Psychology and Neuroscience, Center for Neuroscience, University of Colorado Boulder, Boulder, CO, USA
| | - L R Watkins
- Department of Psychology and Neuroscience, Center for Neuroscience, University of Colorado Boulder, Boulder, CO, USA
| | - M R Hutchinson
- Discipline of Physiology, School of Medicine, University of Adelaide, Adelaide, SA, Australia
- ARC Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, SA, Australia
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12
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Glia plasma membrane transporters: Key players in glutamatergic neurotransmission. Neurochem Int 2016; 98:46-55. [DOI: 10.1016/j.neuint.2016.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/07/2016] [Accepted: 04/06/2016] [Indexed: 12/27/2022]
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13
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Bjørn-Yoshimoto WE, Underhill SM. The importance of the excitatory amino acid transporter 3 (EAAT3). Neurochem Int 2016; 98:4-18. [PMID: 27233497 DOI: 10.1016/j.neuint.2016.05.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 05/09/2016] [Accepted: 05/17/2016] [Indexed: 12/21/2022]
Abstract
The neuronal excitatory amino acid transporter 3 (EAAT3) is fairly ubiquitously expressed in the brain, though it does not necessarily maintain the same function everywhere. It is important in maintaining low local concentrations of glutamate, where its predominant post-synaptic localization can buffer nearby glutamate receptors and modulate excitatory neurotransmission and synaptic plasticity. It is also the main neuronal cysteine uptake system acting as the rate-limiting factor for the synthesis of glutathione, a potent antioxidant, in EAAT3 expressing neurons, while on GABAergic neurons, it is important in supplying glutamate as a precursor for GABA synthesis. Several diseases implicate EAAT3, and modulation of this transporter could prove a useful therapeutic approach. Regulation of EAAT3 could be targeted at several points for functional modulation, including the level of transcription, trafficking and direct pharmacological modulation, and indeed, compounds and experimental treatments have been identified that regulate EAAT3 function at different stages, which together with observations of EAAT3 regulation in patients is giving us insight into the endogenous function of this transporter, as well as the consequences of altered function. This review summarizes work done on elucidating the role and regulation of EAAT3.
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Affiliation(s)
- Walden E Bjørn-Yoshimoto
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 København Ø, Denmark
| | - Suzanne M Underhill
- National Institute of Mental Health, National Institutes of Health, 35 Convent Drive Room 3A: 210 MSC3742, Bethesda, MD 20892-3742, USA.
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14
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Maixner DW, Yan X, Hooks SB, Weng HR. AMPKα1 knockout enhances nociceptive behaviors and spinal glutamatergic synaptic activities via production of reactive oxygen species in the spinal dorsal horn. Neuroscience 2016; 326:158-169. [PMID: 27058143 DOI: 10.1016/j.neuroscience.2016.03.061] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/25/2016] [Accepted: 03/28/2016] [Indexed: 12/15/2022]
Abstract
Emerging studies have shown that pharmacological activation of adenosine monophosphate-activated protein kinase (AMPK) produces potent analgesic effects in different animal pain models. Currently, the spinal molecular and synaptic mechanism by which AMPK regulates the pain signaling system remains unclear. To address this issue, we utilized the Cre-LoxP system to conditionally knockout the AMPKα1 gene in the nervous system of mice. We demonstrated that AMPKα1 is imperative for maintaining normal nociception, and mice deficient for AMPKα1 exhibit mechanical allodynia. This is concomitantly associated with increased glutamatergic synaptic activities in neurons located in the superficial spinal dorsal horn, which results from the increased glutamate release from presynaptic terminals and function of ligand-gated glutamate receptors at the postsynaptic neurons. Additionally, AMPKα1 knockout mice have increased activities of extracellular signal-regulated kinases (ERK) and p38 mitogen-activated protein kinases (p38), as well as elevated levels of interleukin-1β (IL-1β), reactive oxygen species (ROS), and heme oxygenase 1 (HO-1) in the spinal dorsal horn. Systemic administration of a non-specific ROS scavenger (phenyl-N-tert-butylnitrone, PBN) or a HO-1 activator (Cobalt protoporphyrin IX, CoPP) attenuated allodynia in AMPKα1 knockout mice. Bath-perfusion of the ROS scavenger or HO-1 activator effectively attenuated the increased ROS levels and glutamatergic synaptic activities in the spinal dorsal horn. Our findings suggest that ROS are the key down-stream signaling molecules mediating the behavioral hypersensitivity in AMPKα1 knockout mice. Thus, targeting AMPKα1 may represent an effective approach for the treatment of pathological pain conditions associated with neuroinflammation at the spinal dorsal horn.
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Affiliation(s)
- Dylan W Maixner
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia 30602, USA
| | - Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia 30602, USA.,Department of Cardiovascular Medicine, The Third Hospital of Wuhan, Wuhan 430074, Hubei Province, China.,Department of Endocrinology and Metabolism, Shanghai Tenth People's hospital, Tongji University School of Medicine, Shanghai 200072, China
| | - Shelley B Hooks
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia 30602, USA
| | - Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia 30602, USA
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15
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Pun H, Awamleh L, Lee JC, Avivi-Arber L. Decreased face primary motor cortex (face-M1) excitability induced by noxious stimulation of the rat molar tooth pulp is dependent on the functional integrity of medullary astrocytes. Exp Brain Res 2015; 234:645-57. [DOI: 10.1007/s00221-015-4448-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 09/18/2015] [Indexed: 02/03/2023]
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Adenosine Monophosphate-activated Protein Kinase Regulates Interleukin-1β Expression and Glial Glutamate Transporter Function in Rodents with Neuropathic Pain. Anesthesiology 2015; 122:1401-13. [PMID: 25710409 DOI: 10.1097/aln.0000000000000619] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Neuroinflammation and dysfunctional glial glutamate transporters (GTs) in the spinal dorsal horn are implicated in the genesis of neuropathic pain. The authors determined whether adenosine monophosphate-activated protein kinase (AMPK) in the spinal dorsal horn regulates these processes in rodents with neuropathic pain. METHODS Hind paw withdrawal responses to radiant heat and mechanical stimuli were used to assess nociceptive behaviors. Spinal markers related to neuroinflammation and glial GTs were determined by Western blotting. AMPK activities were manipulated pharmacologically and genetically. Regulation of glial GTs was determined by measuring protein expression and activities of glial GTs. RESULTS AMPK activities were reduced in the spinal dorsal horn of rats (n = 5) with thermal hyperalgesia induced by nerve injury, which were accompanied with the activation of astrocytes, increased production of interleukin-1β and activities of glycogen synthase kinase 3β, and suppressed protein expression of glial glutamate transporter-1. Thermal hyperalgesia was reversed by spinal activation of AMPK in neuropathic rats (n = 10) and induced by inhibiting spinal AMPK in naive rats (n = 7 to 8). Spinal AMPKα knockdown (n = 6) and AMPKα1 conditional knockout (n = 6) induced thermal hyperalgesia and mechanical allodynia. These genetic alterations mimicked the changes of molecular markers induced by nerve injury. Pharmacological activation of AMPK enhanced glial GT activity in mice with neuropathic pain (n = 8) and attenuated glial glutamate transporter-1 internalization induced by interleukin-1β (n = 4). CONCLUSIONS These findings suggest that enhancing spinal AMPK activities could be an effective approach for the treatment of neuropathic pain.
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Yadav R, Yan X, Maixner DW, Gao M, Weng HR. Blocking the GABA transporter GAT-1 ameliorates spinal GABAergic disinhibition and neuropathic pain induced by paclitaxel. J Neurochem 2015; 133:857-69. [PMID: 25827582 DOI: 10.1111/jnc.13103] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 03/02/2015] [Accepted: 03/05/2015] [Indexed: 11/24/2022]
Abstract
Paclitaxel is a chemotherapeutic agent widely used for treating carcinomas. Patients receiving paclitaxel often develop neuropathic pain and have a reduced quality of life which hinders the use of this life-saving drug. In this study, we determined the role of GABA transporters in the genesis of paclitaxel-induced neuropathic pain using behavioral tests, electrophysiology, and biochemical techniques. We found that tonic GABA receptor activities in the spinal dorsal horn were reduced in rats with neuropathic pain induced by paclitaxel. In normal controls, tonic GABA receptor activities were mainly controlled by the GABA transporter GAT-1 but not GAT-3. In the spinal dorsal horn, GAT-1 was expressed at presynaptic terminals and astrocytes while GAT-3 was only expressed in astrocytes. In rats with paclitaxel-induced neuropathic pain, the protein expression of GAT-1 was increased while GAT-3 was decreased. This was concurrently associated with an increase in global GABA uptake. The paclitaxel-induced attenuation of GABAergic tonic inhibition was ameliorated by blocking GAT-1 but not GAT-3 transporters. Paclitaxel-induced neuropathic pain was significantly attenuated by the intrathecal injection of a GAT-1 inhibitor. These findings suggest that targeting GAT-1 transporters for reversing disinhibition in the spinal dorsal horn may be a useful approach for treating paclitaxel-induced neuropathic pain. Patients receiving paclitaxel for cancer therapy often develop neuropathic pain and have a reduced quality of life. In this study, we demonstrated that animals treated with paclitaxel develop neuropathic pain, have enhancements of GABA transporter-1 protein expression and global GABA uptake, as well as suppression of GABAergic tonic inhibition in the spinal dorsal horn. Pharmacological inhibition of GABA transporter-1 ameliorates the paclitaxel-induced suppression of GABAergic tonic inhibition and neuropathic pain. Thus, targeting GAT-1 transporters for reversing GABAergic disinhibition in the spinal dorsal horn could be a useful approach for treating paclitaxel-induced neuropathic pain.
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Affiliation(s)
- Ruchi Yadav
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA
| | - Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA.,Department of Cardiovascular Medicine, the Third Hospital of Wuhan, Wuhan, Hubei Province, China
| | - Dylan W Maixner
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA
| | - Mei Gao
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA
| | - Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA
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18
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Austin PJ, Bembrick AL, Denyer GS, Keay KA. Injury-Dependent and Disability-Specific Lumbar Spinal Gene Regulation following Sciatic Nerve Injury in the Rat. PLoS One 2015; 10:e0124755. [PMID: 25905723 PMCID: PMC4408097 DOI: 10.1371/journal.pone.0124755] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 03/06/2015] [Indexed: 12/23/2022] Open
Abstract
Allodynia, hyperalgesia and spontaneous pain are cardinal sensory signs of neuropathic pain. Clinically, many neuropathic pain patients experience affective-motivational state changes, including reduced familial and social interactions, decreased motivation, anhedonia and depression which are severely debilitating. In earlier studies we have shown that sciatic nerve chronic constriction injury (CCI) disrupts social interactions, sleep-wake-cycle and endocrine function in one third of rats, a subgroup reliably identified six days after injury. CCI consistently produces allodynia and hyperalgesia, the intensity of which was unrelated either to the altered social interactions, sleep-wake-cycle or endocrine changes. This decoupling of the sensory consequences of nerve injury from the affective-motivational changes is reported in both animal experiments and human clinical data. The sensory changes triggered by CCI are mediated primarily by functional changes in the lumbar dorsal horn, however, whether lumbar spinal changes may drive different affective-motivational states has never been considered. In these studies, we used microarrays to identify the unique transcriptomes of rats with altered social behaviours following sciatic CCI to determine whether specific patterns of lumbar spinal adaptations characterised this subgroup. Rats underwent CCI and on the basis of reductions in dominance behaviour in resident-intruder social interactions were categorised as having Pain & Disability, Pain & Transient Disability or Pain alone. We examined the lumbar spinal transcriptomes two and six days after CCI. Fifty-four ‘disability-specific’ genes were identified. Sixty-five percent were unique to Pain & Disability rats, two-thirds of which were associated with neurotransmission, inflammation and/or cellular stress. In contrast, 40% of genes differentially regulated in rats without disabilities were involved with more general homeostatic processes (cellular structure, transcription or translation). We suggest that these patterns of gene expression lead to either the expression of disability, or to resilience and recovery, by modifying local spinal circuitry at the origin of ascending supraspinal pathways.
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Affiliation(s)
- Paul J. Austin
- School of Medical Sciences (Anatomy & Histology), The University of Sydney, Sydney, NSW, Australia
| | - Alison L. Bembrick
- School of Medical Sciences (Anatomy & Histology), The University of Sydney, Sydney, NSW, Australia
| | - Gareth S. Denyer
- School of Molecular Bioscience, The University of Sydney, Sydney, NSW, Australia
| | - Kevin A. Keay
- School of Medical Sciences (Anatomy & Histology), The University of Sydney, Sydney, NSW, Australia
- * E-mail:
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Patel AB, de Graaf RA, Rothman DL, Behar KL. Effects of γ-Aminobutyric acid transporter 1 inhibition by tiagabine on brain glutamate and γ-Aminobutyric acid metabolism in the anesthetized rat In vivo. J Neurosci Res 2015; 93:1101-8. [PMID: 25663257 DOI: 10.1002/jnr.23548] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 11/14/2014] [Accepted: 12/02/2014] [Indexed: 12/24/2022]
Abstract
γ-Aminobutyric acid (GABA) clearance from the extracellular space after release from neurons involves reuptake into terminals and astrocytes through GABA transporters (GATs). The relative flows through these two pathways for GABA released from neurons remains unclear. This study determines the effect of tiagabine, a selective inhibitor of neuronal GAT-1, on the rates of glutamate (Glu) and GABA metabolism and GABA resynthesis via the GABA-glutamine (Gln) cycle. Halothane-anesthetized rats were administered tiagabine (30 mg/kg, i.p.) and 45 min later received an intravenous infusion of either [1,6-(13)C2]glucose (in vivo) or [2-(13)C]acetate (ex vivo). Nontreated rats served as controls. Metabolites and (13)C enrichments were measured with (1)H-[(13)C]-nuclear magnetic resonance spectroscopy and referenced to their corresponding endpoint values measured in extracts from in situ frozen brain. Metabolic flux estimates of GABAergic and glutamatergic neurons were determined by fitting a metabolic model to the (13)C turnover data measured in vivo during [1,6-(13)C2]glucose infusion. Tiagabine-treated rats were indistinguishable (P > 0.05) from controls in tissue amino acid levels and in (13)C enrichments from [2-(13)C]acetate. Tiagabine reduced average rates of glucose oxidation and neurotransmitter cycling in both glutamatergic neurons (↓18%, CMR(glc(ox)Glu): control, 0.27 ± 0.05 vs. tiagabine, 0.22 ± 0.04 µmol/g/min; ↓11%, V(cyc(Glu-Gln)): control 0.23 ± 0.05 vs. tiagabine 0.21 ± 0.04 µmol/g/min and GABAergic neurons (↓18-25%, CMR(glc(ox)GABA): control 0.09 ± 0.02 vs. tiagabine 0.07 ± 0.03 µmol/g/min; V(cyc(GABA-Gln)): control 0.08 ± 0.02 vs. tiagabine 0.07 ± 0.03 µmol/g/min), but the changes in glutamatergic and GABAergic fluxes were not significant (P > 0.10). The results suggest that any reduction in GABA metabolism by tiagabine might be an indirect response to reduced glutamatergic drive rather than direct compensatory effects.
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Affiliation(s)
- Anant B Patel
- Department of Diagnostic Radiology and the Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India
| | - Robin A de Graaf
- Department of Diagnostic Radiology and the Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut
| | - Douglas L Rothman
- Department of Diagnostic Radiology and the Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut
| | - Kevin L Behar
- Department of Psychiatry and the Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, Connecticut
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20
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Marx MC, Billups D, Billups B. Maintaining the presynaptic glutamate supply for excitatory neurotransmission. J Neurosci Res 2015; 93:1031-44. [PMID: 25648608 DOI: 10.1002/jnr.23561] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/04/2015] [Accepted: 01/05/2015] [Indexed: 01/09/2023]
Abstract
Glutamate released from synapses during excitatory neurotransmission must be rapidly recycled to maintain neuronal communication. This review evaluates data from physiological experiments at hippocampal CA3 to CA1 synapses and the calyx of Held synapse in the brainstem to analyze quantitatively the rates of release and resupply of glutamate required to sustain neurotransmission. We calculate that, without efficient recycling, the presynaptic glutamate supply will be exhausted within about a minute of normal synaptic activity. We also discuss replenishment of the presynaptic pool by diffusion from the soma, direct uptake of glutamate back into the presynaptic terminal, and uptake of glutamate precursor molecules. Diffusion of glutamate from the soma is calculated to be fast enough to resupply presynaptic glutamate in the hippocampus but not at the calyx of Held. However, because the somatic cytoplasm will also quickly run out of glutamate and synapses can function continually even if the presynaptic axon is severed, mechanisms other than diffusion must be present to resupply glutamate for release. Direct presynaptic uptake of glutamate is not present at the calyx of Held but may play a role in glutamate recycling in the hippocampus. Alternatively, glutamine or tricarboxylic acid cycle intermediates released from glia can serve as a precursor for glutamate in synaptic terminals, and we calculate that the magnitude of presynaptic glutamine uptake is sufficient to supply enough glutamate to sustain neurotransmission. The nature of these mechanisms, their relative abundance, and the co-ordination between them remain areas of intensive investigation.
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Affiliation(s)
- Mari-Carmen Marx
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Daniela Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
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21
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Yan X, Jiang E, Weng HR. Activation of toll like receptor 4 attenuates GABA synthesis and postsynaptic GABA receptor activities in the spinal dorsal horn via releasing interleukin-1 beta. J Neuroinflammation 2015; 12:222. [PMID: 25571780 PMCID: PMC4302431 DOI: 10.1186/s12974-014-0222-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 12/13/2014] [Indexed: 12/26/2022] Open
Abstract
Toll like receptor 4 (TLR4) is an innate immune pattern recognition receptor, expressed predominantly on microglia in the CNS. Activation of spinal TLR4 plays a critical role in the genesis of pathological pain induced by nerve injury, bone cancer, and tissue inflammation. Currently, it remains unknown how synaptic activities in the spinal dorsal horn are regulated by TLR4 receptors. Through recording GABAergic currents in neurons and glial glutamate transporter currents in astrocytes in rodent spinal slices, we determined whether and how TLR4 modulates GABAergic synaptic activities in the superficial spinal dorsal horn. We found that activation of TLR4 by lipopolysaccharide (LPS) reduces GABAergic synaptic activities through both presynaptic and postsynaptic mechanisms. Specifically, LPS causes the release of IL-1β from microglia. IL-1β in turn suppresses GABA receptor activities at the postsynaptic site through activating protein kinase C (PKC) in neurons. GABA synthesis at the presynaptic site is reduced upon activation of TLR4. Glial glutamate transporter activities are suppressed by IL-1β and PKC activation induced by LPS. The suppression of glial glutamate transporter activities leads to a deficiency of glutamine supply, which results in an attenuation of the glutamate-glutamine cycle-dependent GABA synthesis. These findings shed light on understanding synaptic plasticity induced by activation of TLR4 under neuroinflammation and identify GABA receptors, glial glutamate transporters, IL-1β and PKC as therapeutic targets to abrogate abnormal neuronal activities following activation of TLR4 in pathological pain conditions.
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Affiliation(s)
- Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, 240 West Green Street, Athens, GA, 30602, USA. .,Department of Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA. .,Department of Cardiovascular Medicine, the Third Hospital of Wuhan, Wuhan, Hubei Province, China.
| | - Enshe Jiang
- Department of Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA. .,Institute of Public Hygiene, Henan University Nursing School, Kaifeng, China.
| | - Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, 240 West Green Street, Athens, GA, 30602, USA. .,Department of Pain Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
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Abstract
The multifunctional properties of astrocytes signify their importance in brain physiology and neurological function. In addition to defining the brain architecture, astrocytes are primary elements of brain ion, pH and neurotransmitter homoeostasis. GS (glutamine synthetase), which catalyses the ATP-dependent condensation of ammonia and glutamate to form glutamine, is an enzyme particularly found in astrocytes. GS plays a pivotal role in glutamate and glutamine homoeostasis, orchestrating astrocyte glutamate uptake/release and the glutamate-glutamine cycle. Furthermore, astrocytes bear the brunt of clearing ammonia in the brain, preventing neurotoxicity. The present review depicts the central function of astrocytes, concentrating on the importance of GS in glutamate/glutamine metabolism and ammonia detoxification in health and disease.
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23
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Yan X, Yadav R, Gao M, Weng HR. Interleukin-1 beta enhances endocytosis of glial glutamate transporters in the spinal dorsal horn through activating protein kinase C. Glia 2014; 62:1093-109. [PMID: 24677092 DOI: 10.1002/glia.22665] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 03/12/2014] [Accepted: 03/12/2014] [Indexed: 01/01/2023]
Abstract
Excessive activation of glutamate receptors in spinal dorsal horn neurons is a key mechanism leading to abnormal neuronal activation in pathological pain conditions. Previous studies have shown that activation of glutamate receptors in the spinal dorsal horn is enhanced by impaired glial glutamate transporter functions and proinflammatory cytokines including interleukin-1 beta (IL-1β). In this study, we for the first time revealed that spinal glial glutamate transporter activities in the neuropathic animals are attenuated by endogenous IL-1β. Specifically, we demonstrated that nerve injury results in an increased expression of IL-1β and activation of PKC in the spinal dorsal horn as well as suppression of glial glutamate uptake activities. We provided evidence that the nerve-injury induced suppression of glial glutamate uptake is at least in part ascribed to endogenous IL-1β and activation of PKC in the spinal dorsal horn. IL-1β reduces glial glutamate transporter activities through enhancing the endocytosis of both GLT-1 and GLAST glial glutamate transporters. The IL-1β induced trafficking of glial glutamate transporters is through the calcium/PKC signaling pathway, and the dynamin-dependent endocytosis, which is dependent on the integrity of actin filaments. The signaling pathway regulating glial glutamate transporters revealed in this study provides novel targets to attenuate aberrant activation of glutamate receptors in the spinal dorsal horn, which could ultimately help the development of analgesics.
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Affiliation(s)
- Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia; Department of Cardiovascular Medicine, The Third Hospital of Wuhan, Wuhan, Hubei Province, China
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Weng HR, Gao M, Maixner DW. Glycogen synthase kinase 3 beta regulates glial glutamate transporter protein expression in the spinal dorsal horn in rats with neuropathic pain. Exp Neurol 2013; 252:18-27. [PMID: 24275526 DOI: 10.1016/j.expneurol.2013.11.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 10/07/2013] [Accepted: 11/13/2013] [Indexed: 12/30/2022]
Abstract
Dysfunctional glial glutamate transporters and over production of pro-inflammatory cytokines (including interleukin-1β, IL-1β) are two prominent mechanisms by which glial cells enhance neuronal activities in the spinal dorsal horn in neuropathic pain conditions. Endogenous molecules regulating production of IL-1β and glial glutamate functions remain poorly understood. In this study, we revealed a dynamic alteration of GSK3β activities and its role in regulating glial glutamate transporter 1 (GLT-1) protein expression in the spinal dorsal horn and nociceptive behaviors following the nerve injury. Specifically, GSK3β was expressed in both neurons and astrocytes in the spinal dorsal horn. GSK3β activities were suppressed on day 3 but increased on day 10 following the nerve injury. In parallel, protein expression of GLT-1 in the spinal dorsal horn was enhanced on day 3 but reduced on day 10. In contrast to these time-dependent changes, the activation of astrocytes and over-production of IL-1β were found on both day 3 and day 10. Meanwhile, thermal hyperalgesia was observed from day 2 through day 10 and mechanical allodynia from day 4 through day 10. Pre-emptive pharmacological inhibition of GSK3β activities significantly ameliorated thermal hyperalgesia and mechanical allodynia at the late stage but did not have effects at the early stage. These were accompanied with the suppression of GSK3β activities, prevention of decreased GLT-1 protein expression, inhibition of astrocytic activation, and reduction of IL-1β in the spinal dorsal horn on day 10. These data indicate that the increased GSK3β activity in the spinal dorsal horn is attributable to the downregulation of GLT-1 protein expression in neuropathic rats at the late stage. Further, we also demonstrated that the nerve-injury-induced thermal hyperalgesia on day 10 was transiently suppressed by pharmacological inhibition of GSK3β. Our study suggests that GSK3β may be a potential target for the development of analgesics for chronic neuropathic pain.
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Affiliation(s)
- Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA.
| | - Mei Gao
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA
| | - Dylan W Maixner
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA
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Gao M, Yan X, Weng HR. Inhibition of glycogen synthase kinase 3β activity with lithium prevents and attenuates paclitaxel-induced neuropathic pain. Neuroscience 2013; 254:301-11. [PMID: 24070631 DOI: 10.1016/j.neuroscience.2013.09.033] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/20/2013] [Accepted: 09/16/2013] [Indexed: 12/21/2022]
Abstract
Paclitaxel (taxol) is a first-line chemotherapy-drug used to treat many types of cancers. Neuropathic pain and sensory dysfunction are the major toxicities, which are dose-limiting and significantly reduce the quality of life in patients. Two known critical spinal mechanisms underlying taxol-induced neuropathic pain are an increased production of pro-inflammatory cytokines including interleukin-1β (IL-1β) and suppressed glial glutamate transporter activities. In this study, we uncovered that increased activation of glycogen synthase kinase 3beta (GSK3β) in the spinal dorsal horn was concurrently associated with increased protein expressions of GFAP, IL-1β and a decreased protein expression of glial glutamate transporter 1 (GLT-1), as well as the development and maintenance of taxol-induced neuropathic pain. The enhanced GSK3β activities were supported by the concurrently decreased AKT and mTOR activities. The changes of all these biomarkers were basically prevented when animals received pre-emptive lithium (a GSK3β inhibitor) treatment, which also prevented the development of taxol-induced neuropathic pain. Further, chronic lithium treatment, which began on day 11 after the first taxol injection, reversed the existing mechanical and thermal allodynia induced by taxol. The taxol-induced increased GSK3β activities and decreased AKT and mTOR activities in the spinal dorsal horn were also reversed by lithium. Meanwhile, protein expressions of GLT-1, GFAP and IL-1β in the spinal dorsal horn were improved. Hence, suppression of spinal GSK3β activities is a key mechanism used by lithium to reduce taxol-induced neuropathic pain, and targeting spinal GSK3β is an effective approach to ameliorate GLT-1 expression and suppress the activation of astrocytes and IL-1β over-production in the spinal dorsal horn.
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Affiliation(s)
- M Gao
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, GA 30602, USA
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Maixner DW, Weng HR. The Role of Glycogen Synthase Kinase 3 Beta in Neuroinflammation and Pain. ACTA ACUST UNITED AC 2013; 1:001. [PMID: 25309941 DOI: 10.13188/2327-204x.1000001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Neuroinflammation is a crucial mechanism related to many neurological diseases. Extensive studies in recent years have indicated that dysregulation of Glycogen Synthase Kinase 3 Beta (GSK3β) contributes to the development and progression of these disorders through regulating the neuroinflammation processes. Inhibitors of GSK3β have been shown to be beneficial in many neuroinflammatory disease models including Alzheimer's disease, multiple sclerosis and AIDS dem entia complex. Glial activation and elevated pro-inflammation cytokines (signs of neuroinflammation) in the spinal cord have been widely recognized as a pivotal mechanism underlying the development and maintenance of many types of pathological pain. The role of GSK3β in the pathogenesis of pain has recently emerged. In this review, we will first review the GSK3β structure, regulation, and mechanisms by which GSK3βregulates inflammation. We will then describe neuroinflammationin general and in specific types of neurological diseases and the potential beneficial effects induced by inhibiting GSK3β. Finally, we will provide new evidence linking aberrant levels of GSK3β in the development of pathological pain.
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Affiliation(s)
- Dylan Warren Maixner
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, 30606, USA
| | - Han-Rong Weng
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, 30606, USA
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