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Lombardi AM, Wong H, Bower ME, Milstead R, Borski C, Schmitt E, Griffioen M, LaPlante L, Ehringer MA, Stitzel J, Hoeffer CA. AKT2 modulates astrocytic nicotine responses in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.31.596856. [PMID: 38854016 PMCID: PMC11160815 DOI: 10.1101/2024.05.31.596856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
A better understanding of nicotine neurobiology is needed to reduce or prevent chronic addiction, ameliorate the detrimental effects of nicotine withdrawal, and increase successful cessation of use. Nicotine binds and activates two astrocyte-expressed nicotinic acetylcholine receptors (nAChRs), α4β2 and α7. We recently found that Protein kinase B-β (Pkb-β or Akt2) expression is restricted to astrocytes in mice and humans. To determine if AKT2 plays a role in astrocytic nicotinic responses, we generated astrocyte-specific Akt2 conditional knockout (cKO) and full Akt2 KO mice for in vivo and in vitro experiments. For in vivo studies, we examined mice exposed to chronic nicotine for two weeks in drinking water (200 μg/mL) and following acute nicotine challenge (0.09, 0.2 mg/kg) after 24 hrs. Our in vitro studies used cultured mouse astrocytes to measure nicotine-dependent astrocytic responses. We validated our approaches using lipopolysaccharide (LPS) exposure inducing astrogliosis. Sholl analysis was used to measure glial fibrillary acidic protein responses in astrocytes. Our data show that wild-type (WT) mice exhibit increased astrocyte morphological complexity during acute nicotine exposure, with decreasing complexity during chronic nicotine use, whereas Akt2 cKO mice showed increased astrocyte morphology complexity. In culture, we found that 100μM nicotine was sufficient for morphological changes and blocking α7 or α4β2 nAChRs prevented observed morphologic changes. Finally, we performed conditioned place preference (CPP) in Akt2 cKO mice and found that astrocytic AKT2 deficiency reduced nicotine preference compared to controls. These findings show the importance of nAChRs and Akt2 signaling in the astrocytic response to nicotine.
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Affiliation(s)
- Andrew M. Lombardi
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
| | - Helen Wong
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Myra E. Bower
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Ryan Milstead
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Curtis Borski
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Emily Schmitt
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
| | - Mina Griffioen
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Lauren LaPlante
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Marissa A. Ehringer
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Jerry Stitzel
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
| | - Charles A. Hoeffer
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80303
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309
- Linda Crnic Institute, Anschutz Medical Center, Aurora, CO 80045
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Ma L, Wu Q, You Y, Zhang P, Tan D, Liang M, Huang Y, Gao Y, Ban Y, Chen Y, Yuan J. Neuronal small extracellular vesicles carrying miR-181c-5p contribute to the pathogenesis of epilepsy by regulating the protein kinase C-δ/glutamate transporter-1 axis in astrocytes. Glia 2024; 72:1082-1095. [PMID: 38385571 DOI: 10.1002/glia.24517] [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: 09/25/2023] [Revised: 01/17/2024] [Accepted: 02/05/2024] [Indexed: 02/23/2024]
Abstract
Information exchange between neurons and astrocytes mediated by extracellular vesicles (EVs) is known to play a key role in the pathogenesis of central nervous system diseases. A key driver of epilepsy is the dysregulation of intersynaptic excitatory neurotransmitters mediated by astrocytes. Thus, we investigated the potential association between neuronal EV microRNAs (miRNAs) and astrocyte glutamate uptake ability in epilepsy. Here, we showed that astrocytes were able to engulf epileptogenic neuronal EVs, inducing a significant increase in the glutamate concentration in the extracellular fluid of astrocytes, which was linked to a decrease in glutamate transporter-1 (GLT-1) protein expression. Using sequencing and gene ontology (GO) functional analysis, miR-181c-5p was found to be the most significantly upregulated miRNA in epileptogenic neuronal EVs and was linked to glutamate metabolism. Moreover, we found that neuronal EV-derived miR-181c-5p interacted with protein kinase C-delta (PKCδ), downregulated PKCδ and GLT-1 protein expression and increased glutamate concentrations in astrocytes both in vitro and in vivo. Our findings demonstrated that epileptogenic neuronal EVs carrying miR-181c-5p decrease the glutamate uptake ability of astrocytes, thus promoting susceptibility to epilepsy.
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Affiliation(s)
- Limin Ma
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
- Department of Neurology, Chongqing University Three Gorges Hospital, Chongqing, China
| | - Qingyuan Wu
- Department of Neurology, Chongqing University Three Gorges Hospital, Chongqing, China
| | - Yu You
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Peng Zhang
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Dandan Tan
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Minxue Liang
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yunyi Huang
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yuan Gao
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yuenan Ban
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yangmei Chen
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jinxian Yuan
- Department of Neurology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
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Jeong KH, Zhu J, Park S, Kim WJ. Transient Receptor Potential Vanilloid 6 Modulates Aberrant Axonal Sprouting in a Mouse Model of Pilocarpine-Induced Epilepsy. Mol Neurobiol 2024; 61:2839-2853. [PMID: 37940780 DOI: 10.1007/s12035-023-03748-3] [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: 09/05/2023] [Accepted: 10/26/2023] [Indexed: 11/10/2023]
Abstract
Transient receptor potential vanilloid 6 (TRPV6) is a highly selective calcium-ion channel that belongs to the TRPV family. TRPV6 is widely distributed in the brain, but its role in neurological diseases such as epilepsy remains unknown. Here, we report for the first time that TRPV6 expression is upregulated in the hippocampus of a pilocarpine-induced status epilepticus model, mainly in the suprapyramidal bundle of the mossy fiber (MF) projection of the hippocampal CA3 regions. We found that TRPV6 overexpression via viral vector transduction attenuated abnormal MF sprouting (MFS), whereas TRPV6 knockdown aggravated the development of MFS and the incidence of recurrent seizures during epileptogenic progression. In the in vitro experiments, our results showed that modulation of TRPV6 expression resulted in a change in axonal formation in cultured hippocampal neurons. In addition, we found that TRPV6 was implicated in the regulation of Akt-glycogen synthase kinase-3-β activity, which is closely related to the cellular mechanism of axonal outgrowth. Therefore, these findings suggest that TRPV6 may regulate the formation of aberrant synaptic circuits during epileptogenesis.
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Affiliation(s)
- Kyoung Hoon Jeong
- Epilepsy Research Institute, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea.
| | - Jing Zhu
- Department of Neurology, Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea
| | - Soojin Park
- Department of Neurology, Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea
| | - Won-Joo Kim
- Department of Neurology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, 06273, Republic of Korea.
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Li M, Yu J, Deng H, Xie S, Li Q, Zhao Y, Yin S, Ji YF. Upregulation of glutamate transporter 1 by mTOR/Akt pathway in astrocyte culture during oxygen-glucose deprivation and reoxygenation. Exp Brain Res 2023; 241:201-209. [PMID: 36436003 DOI: 10.1007/s00221-022-06514-4] [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: 05/04/2022] [Accepted: 11/16/2022] [Indexed: 11/28/2022]
Abstract
Astrocyte-specific glutamate transporter subtype 1 (GLT-1) plays an important role in influencing glutamate excitatory toxicity and preventing the death of excitatory toxic neurons. Although the mammalian target of rapamycin (mTOR)/protein kinase B(Akt)/nuclear factor kappa B signaling cascade is involved in the upregulation of astrocytic GLT-1 in oxygen-glucose deprivation (OGD), it is unclear whether the mTOR/Akt pathway is involved in astrocytic GLT-1 upregulation in OGD and reoxygenation (OGD/R). In this study, we found that the treatment of cultured astrocytes with rapamycin and triciribine led to the decreased astrocytes' protrusions, smaller nuclei, and an increased apoptotic rate. The inhibitors of mTOR complex 1 significantly increased the expression levels of phosphorylated Akt-Ser473 (p-Akt), phosphorylated Akt-Thr308(p-Akt), and GLT-1, while Akt-specific inhibitors blocked GLT-1 expression, suggesting that the mTOR/Akt pathway is involved in GLT-1 upregulation. We further demonstrated that astrocytes under OGD/R adapted to environmental changes through the mTOR/Akt pathway, mainly by altering cell morphology and apoptosis and upregulating the expression levels of p-Akt and GLT-1. Our results suggested that astrocytes may adapt to short-term ischemic-reperfusion injury by regulating cell morphology, apoptosis and GLT-1 upregulation.
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Affiliation(s)
- Mi Li
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
- Department of Neurology, Yilong County People's Hospital, Nanchong, Sichuan, People's Republic of China
| | - Jingmei Yu
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Huan Deng
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Shansha Xie
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Qiuling Li
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Yuping Zhao
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Shubin Yin
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China
| | - Yi-Fei Ji
- Department of Neurology, Second Clinical College, North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.
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Li Q, Chen Y, Feng W, Cai J, Gao J, Ge F, Zhou T, Wang Z, Ding F, Marshall C, Sheng C, Zhang Y, Sun M, Shi J, Xiao M. Drainage of senescent astrocytes from brain via meningeal lymphatic routes. Brain Behav Immun 2022; 103:85-96. [PMID: 35427759 DOI: 10.1016/j.bbi.2022.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 03/16/2022] [Accepted: 04/10/2022] [Indexed: 12/30/2022] Open
Abstract
Recent progress on the central lymphatic system has greatly increased our understanding of how the brain maintains its own waste homeostasis. Here, we showed that perivascular spaces and meningeal lymphatic vessels form a functional route for clearance of senescent astrocytes from the aging brain. Blocking meningeal lymphatic drainage by ligation of the deep cervical lymph nodes impaired clearance of senescent astrocytes from brain parenchyma, subsequently increasing neuroinflammation in aged mice. By contrast, enhancing meningeal lymphatic vessel diameter by a recombinant adeno-associated virus encoding mouse vascular endothelial growth factor-C (VEGF-C) improved clearance of senescent astrocytes and mitigated neuroinflammation. Mechanistically, VEGF-C was highly expressed in senescent astrocytes, contributing themselves to migrate across lymphatic vessels along C-C motif chemokine ligand 21 (CCL21) gradient by interacting with VEGF receptor 3. Moreover, intra-cisternal injection of antibody against CCL21 hampered senescent astrocytes into the lymphatic vessels and exacerbated short memory defects of aged mice. Together, these findings reveal a new perspective for the meningeal lymphatics in the removal of senescent astrocytes, thus offering a valuable target for therapeutic intervention.
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Affiliation(s)
- Qian Li
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China; Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China; Center for Global Health, Nanjing Medical University, Nanjing, 211166, China
| | - Yan Chen
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China; Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China; Center for Global Health, Nanjing Medical University, Nanjing, 211166, China
| | - Weixi Feng
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China; Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China; Center for Global Health, Nanjing Medical University, Nanjing, 211166, China
| | - Jiachen Cai
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China
| | - Junying Gao
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China; Department of Anatomy, Nanjing Medical University, Nanjing, 211166, China
| | - Feifei Ge
- Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Tiantian Zhou
- Department of Anesthesia, Nanjing Integrated Traditional Chinese and Western Medicine Hospital, Nanjing, 210028, China
| | - Ze Wang
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China
| | - Fengfei Ding
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China; Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, NY, 14642, United States
| | - Charles Marshall
- Department of Physical Therapy, University of Kentucky Center of Excellence in Rural Health, Hazard, KY, 41701, USA
| | - Chengyu Sheng
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China
| | - Yongjie Zhang
- Department of Anatomy, Nanjing Medical University, Nanjing, 211166, China
| | - Mingkuan Sun
- Department of Toxicology, Nanjing Medical University, Nanjing, 211166, China
| | - Jingping Shi
- Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Ming Xiao
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, 211166, China; Department of Neurology, the Affiliated Nanjing Brain Hospital of Nanjing Medical University, Nanjing, 210029, China; Center for Global Health, Nanjing Medical University, Nanjing, 211166, China.
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Park S, Zhu J, Jeong KH, Kim WJ. Adjudin prevents neuronal damage and neuroinflammation via inhibiting mTOR activation against pilocarpine-induced status epilepticus. Brain Res Bull 2022; 182:80-89. [PMID: 35182690 DOI: 10.1016/j.brainresbull.2022.02.009] [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: 11/05/2021] [Revised: 01/23/2022] [Accepted: 02/14/2022] [Indexed: 11/02/2022]
Abstract
Inflammatory responses in the brain play an etiological role in the development of epilepsy, suggesting that finding novel molecules for controlling neuroinflammation may have clinical value in developing the disease-modifying strategies for epileptogenesis. Adjudin, a multi-functional small molecule compound, has pleiotropic effects, including anti-inflammatory properties. In the present study, we aimed to investigate the effects of adjudin on pilocarpine-induced status epilepticus (SE) and its role in the regulation of reactive gliosis and neuroinflammation. SE was induced in male C57BL/6 mice that were then treated with adjudin (50mg/kg) for 3 days after SE onset. Immunofluorescence staining, terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and western blot analysis were used to evaluate the effects of adjudin treatment in the hippocampus after SE. Our results showed that adjudin treatment significantly mitigated apoptotic cell death in the hippocampus after SE onset. Moreover, adjudin treatment suppressed SE-induced glial activation and activation of mammalian target of rapamycin signaling in the hippocampus. Concomitantly, adjudin treatment significantly reduced SE-induced inflammatory processes, as confirmed by changes in the expression of inflammatory mediators such as tumor necrosis factor-α, interleukin-1β, and arginase-1. In conclusion, these findings suggest that adjudin may serve as a potential neuroprotective agent for preventing pathological mechanisms implicated in epileptogenesis.
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Affiliation(s)
- Soojin Park
- Department of Neurology, Yonsei University College of Medicine, Seoul, Republic of Korea; Brain Korea 21 Plus Project for Medical Science, Yonsei University, Seoul, Republic of Korea
| | - Jing Zhu
- Department of Neurology, Yonsei University College of Medicine, Seoul, Republic of Korea; Brain Korea 21 Plus Project for Medical Science, Yonsei University, Seoul, Republic of Korea
| | - Kyoung Hoon Jeong
- Department of Neurology, Yonsei University College of Medicine, Seoul, Republic of Korea; Epilepsy Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
| | - Won-Joo Kim
- Department of Neurology, Yonsei University College of Medicine, Seoul, Republic of Korea; Department of Neurology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
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Twible C, Abdo R, Zhang Q. Astrocyte Role in Temporal Lobe Epilepsy and Development of Mossy Fiber Sprouting. Front Cell Neurosci 2021; 15:725693. [PMID: 34658792 PMCID: PMC8514632 DOI: 10.3389/fncel.2021.725693] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
Epilepsy affects approximately 50 million people worldwide, with 60% of adult epilepsies presenting an onset of focal origin. The most common focal epilepsy is temporal lobe epilepsy (TLE). The role of astrocytes in the presentation and development of TLE has been increasingly studied and discussed within the literature. The most common histopathological diagnosis of TLE is hippocampal sclerosis. Hippocampal sclerosis is characterized by neuronal cell loss within the Cornu ammonis and reactive astrogliosis. In some cases, mossy fiber sprouting may be observed. Mossy fiber sprouting has been controversial in its contribution to epileptogenesis in TLE patients, and the mechanisms surrounding the phenomenon have yet to be elucidated. Several studies have reported that mossy fiber sprouting has an almost certain co-existence with reactive astrogliosis within the hippocampus under epileptic conditions. Astrocytes are known to play an important role in the survival and axonal outgrowth of central and peripheral nervous system neurons, pointing to a potential role of astrocytes in TLE and associated cellular alterations. Herein, we review the recent developments surrounding the role of astrocytes in the pathogenic process of TLE and mossy fiber sprouting, with a focus on proposed signaling pathways and cellular mechanisms, histological observations, and clinical correlations in human patients.
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Affiliation(s)
- Carolyn Twible
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada
| | - Rober Abdo
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Anatomy and Cell Biology, Western University, London, ON, Canada
| | - Qi Zhang
- Department of Pathology and Lab Medicine, Western University, London, ON, Canada.,Department of Pathology and Lab Medicine, London Health Sciences Centre, University Hospital, London, ON, Canada
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Green JL, Dos Santos WF, Fontana ACK. Role of glutamate excitotoxicity and glutamate transporter EAAT2 in epilepsy: Opportunities for novel therapeutics development. Biochem Pharmacol 2021; 193:114786. [PMID: 34571003 DOI: 10.1016/j.bcp.2021.114786] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 12/21/2022]
Abstract
Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.
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Affiliation(s)
- Jennifer Leigh Green
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, 19102, United States
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Brewster AL. Relationship Status Update on Astrocytic VEGFR-3 and mTOR Signaling: It's Complicated. Epilepsy Curr 2021; 21:117-119. [PMID: 34025288 PMCID: PMC8010874 DOI: 10.1177/1535759720988541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Vascular Endothelial Growth Factor Receptor-3 Regulates Astroglial Glutamate Transporter-1 Expression via mTOR Activation in Reactive Astrocytes Following Pilocarpine-Induced Status Epilepticus Jeong KH, Cho KO, Lee MY, Kim SY, Kim WJ. Glia. 2021;69(2):296-309. doi:10.1002/glia.23897. PMID: 32835451. Recent evidence has shown that the vascular endothelial growth factor (VEGF) system plays a crucial role in several neuropathological processes. We previously reported an upregulation of VEGF-C and its receptor, VEGFR-3, in reactive astrocytes after the onset of status epilepticus (SE). However, it remains unknown, which molecules act as downstream signals following VEGFR-3 upregulation and are involved in astrogliosis after SE. Therefore, we investigated whether VEGFR-3 upregulation within reactive astrocytes is associated with the activation of mammalian target of rapamycin (mTOR) signaling, which we confirmed by assaying for the phosphorylated form of S6 protein (pS6), and whether VEGFR-3-mediated mTOR activation induces astroglial glutamate transporter-1 (GLT-1) expression in the hippocampus after pilocarpine-induced SE. We found that spatiotemporal expression of pS6 was consistent with VEGFR-3 expression in the hippocampus after SE and that both pS6 and VEGFR-3 were highly expressed in SE-induced reactive astrocytes. Treatment with the mTOR inhibitor rapamycin decreased astroglial VEGFR-3 expression and GLT-1 expression after SE. Treatment with a selective inhibitor for VEGFR-3 attenuated astroglial pS6 expression as well as suppressed GLT-1 expression and astroglial reactivity in the hippocampus after SE. These findings demonstrate that VEGFR-3-mediated mTOR activation could contribute to the regulation of GLT-1 expression in reactive astrocytes during the subacute phase of epilepsy. In conclusion, the present study suggests that VEGFR-3 upregulation in reactive astrocytes may play a role in preventing hyperexcitability induced by continued seizure activity.
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