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Xie Y, Qin P, Guo T, Al Abed A, Lovell NH, Tsai D. Modulating individual axons and axonal populations in the peripheral nerve using transverse intrafascicular multichannel electrodes. J Neural Eng 2023; 20:046032. [PMID: 37536318 DOI: 10.1088/1741-2552/aced20] [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: 02/13/2023] [Accepted: 08/03/2023] [Indexed: 08/05/2023]
Abstract
Objective.A transverse intrafascicular multichannel electrode (TIME) may offer advantages over more conventional cuff electrodes including higher spatial selectivity and reduced stimulation charge requirements. However, the performance of TIME, especially in the context of non-conventional stimulation waveforms, remains relatively unexplored. As part of our overarching goal of investigating stimulation efficacy of TIME, we developed a computational toolkit that automates the creation and usage ofin siliconerve models with TIME setup, which solves nerve responses using cable equations and computes extracellular potentials using finite element method.Approach.We began by implementing a flexible and scalable Python/MATLAB-based toolkit for automatically creating models of nerve stimulation in the hybrid NEURON/COMSOL ecosystems. We then developed a sciatic nerve model containing 14 fascicles with 1,170 myelinated (A-type, 30%) and unmyelinated (C-type, 70%) fibers to study fiber responses over a variety of TIME arrangements (monopolar and hexapolar) and stimulation waveforms (kilohertz stimulation and cathodic ramp modulation).Main results.Our toolkit obviates the conventional need to re-create the same nerve in two disparate modeling environments and automates bi-directional transfer of results. Our population-based simulations suggested that kilohertz stimuli provide selective activation of targeted C fibers near the stimulating electrodes but also tended to activate non-targeted A fibers further away. However, C fiber selectivity can be enhanced by hexapolar TIME arrangements that confined the spatial extent of electrical stimuli. Improved upon prior findings, we devised a high-frequency waveform that incorporates cathodic DC ramp to completely remove undesirable onset responses.Conclusion.Our toolkit allows agile, iterative design cycles involving the nerve and TIME, while minimizing the potential operator errors during complex simulation. The nerve model created by our toolkit allowed us to study and optimize the design of next-generation intrafascicular implants for improved spatial and fiber-type selectivity.
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Affiliation(s)
- Yuyang Xie
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Peijun Qin
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
- Tyree Institute of Health Engineering (IHealthE), UNSW Sydney, NSW 2052, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
- School of Electrical Engineering & Telecommunications, UNSW Sydney, NSW 2052, Australia
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2
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Hopper AJ, Beswick‐Jones H, Brown AM. Resilience of compound action potential peaks to high-frequency firing in the mouse optic nerve. Physiol Rep 2023; 11:e15606. [PMID: 36807847 PMCID: PMC9937793 DOI: 10.14814/phy2.15606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/16/2023] [Accepted: 01/23/2023] [Indexed: 02/19/2023] Open
Abstract
Action potential conduction in axons triggers trans-membrane ion movements, where Na+ enters and K+ leaves axons, leading to disruptions in resting trans-membrane ion gradients that must be restored for optimal axon conduction, an energy dependent process. The higher the stimulus frequency, the greater the ion movements and the resulting energy demand. In the mouse optic nerve (MON), the stimulus evoked compound action potential (CAP) displays a triple peaked profile, consistent with subpopulations of axons classified by size producing the distinct peaks. The three CAP peaks show differential sensitivity to high-frequency firing, with the large axons, which contribute to the 1st peak, more resilient than the small axons, which produce the 3rd peak. Modeling studies predict frequency dependent intra-axonal Na+ accumulation at the nodes of Ranvier, sufficient to attenuate the triple peaked CAP. Short bursts of high-frequency stimulus evoke transient elevations in interstitial K+ ([K+ ]o ), which peak at about 50 Hz. However, powerful astrocytic buffering limits the [K+ ]o increase to levels insufficient to cause CAP attenuation. A post-stimulus [K+ ]o undershoot below baseline coincides with a transient increase in the amplitudes of all three CAP peaks. The volume specific scaling relating energy expenditure to increasing axon size dictates that large axons are more resilient to high-frequency firing than small axons.
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Affiliation(s)
- Amy J. Hopper
- School of Life SciencesUniversity of NottinghamNottinghamUK
| | | | - Angus M. Brown
- School of Life SciencesUniversity of NottinghamNottinghamUK
- Department of Neurology, School of MedicineUniversity of WashingtonSeattleWashingtonUSA
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3
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Deck M, Van Hameren G, Campbell G, Bernard-Marissal N, Devaux J, Berthelot J, Lattard A, Médard JJ, Gautier B, Guelfi S, Abbou S, Quintana P, Chao de la Barca JM, Reynier P, Lenaers G, Chrast R, Tricaud N. Physiology of PNS axons relies on glycolytic metabolism in myelinating Schwann cells. PLoS One 2022; 17:e0272097. [PMID: 36194565 PMCID: PMC9531822 DOI: 10.1371/journal.pone.0272097] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 07/12/2022] [Indexed: 11/18/2022] Open
Abstract
While lactate shuttle theory states that glial cells metabolize glucose into lactate to shuttle it to neurons, how glial cells support axonal metabolism and function remains unclear. Lactate production is a common occurrence following anaerobic glycolysis in muscles. However, several other cell types, including some stem cells, activated macrophages and tumor cells, can produce lactate in presence of oxygen and cellular respiration, using Pyruvate Kinase 2 (PKM2) to divert pyruvate to lactate dehydrogenase. We show here that PKM2 is also upregulated in myelinating Schwann cells (mSC) of mature mouse sciatic nerve versus postnatal immature nerve. Deletion of this isoform in PLP-expressing cells in mice leads to a deficit of lactate in mSC and in peripheral nerves. While the structure of myelin sheath was preserved, mutant mice developed a peripheral neuropathy. Peripheral nerve axons of mutant mice failed to maintain lactate homeostasis upon activity, resulting in an impaired production of mitochondrial ATP. Action potential propagation was not altered but axonal mitochondria transport was slowed down, muscle axon terminals retracted and motor neurons displayed cellular stress. Additional reduction of lactate availability through dichloroacetate treatment, which diverts pyruvate to mitochondrial oxidative phosphorylation, further aggravated motor dysfunction in mutant mice. Thus, lactate production through PKM2 enzyme and aerobic glycolysis is essential in mSC for the long-term maintenance of peripheral nerve axon physiology and function.
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Affiliation(s)
- Marie Deck
- INM, INSERM, Université de Montpellier, Montpellier, France
- * E-mail: (NT); (MD)
| | | | | | | | - Jérôme Devaux
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jade Berthelot
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Alise Lattard
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jean-Jacques Médard
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Benoît Gautier
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Sophie Guelfi
- INM, INSERM, Université de Montpellier, Montpellier, France
| | | | | | - Juan Manuel Chao de la Barca
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Pascal Reynier
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Guy Lenaers
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Roman Chrast
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Nicolas Tricaud
- I-Stem, UEVE/UPS U861, INSERM, AFM, Corbeil-Essonnes, France
- * E-mail: (NT); (MD)
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4
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Cury J, Smets H, Bouzin C, Doguet P, Vanhoestenberghe A, Delbeke J, Tahry RE, Nonclercq A, Gorza SP. Optical birefringence changes in myelinated and unmyelinated nerves: A comparative study. JOURNAL OF BIOPHOTONICS 2022; 15:e202200028. [PMID: 35703916 DOI: 10.1002/jbio.202200028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 05/30/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
The measurement of birefringence variations related to nerve activity is a promising label-free technique for sensing compound neural action potentials (CNAPs). While widely applied in crustaceans, little is known about its efficiency on mammal peripheral nerves. In this work, birefringence recordings to detect CNAPs, and Stokes parameters measurements were performed in rat and lobster nerves. While single-trial detection of nerve activity in crustaceans was achieved successfully, no optical signal was detected in rats, even after extensive signal filtering and averaging. The Stokes parameters showed that a high degree of polarization of light is maintained in lobster sample, whereas an almost complete light depolarization occurs in rat nerve. Our results indicate that depolarization itself is not sufficient to explain the absence of birefringence signals in rats. We hypothesize that this absence comes from the myelin sheets, which constraint the birefringence changes to only take place at the nodes of Ranvier.
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Affiliation(s)
- Joaquín Cury
- Opera-photonics, Université Libre de Bruxelles, Brussels, Belgium
- Bio-, Electro- and Mechanical Systems (BEAMS), Université Libre de Bruxelles, Brussels, Belgium
| | - Hugo Smets
- Bio-, Electro- and Mechanical Systems (BEAMS), Université Libre de Bruxelles, Brussels, Belgium
| | - Caroline Bouzin
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), IREC Imaging Platform (2IP), Brussels, Belgium
| | | | - Anne Vanhoestenberghe
- Aspire Centre for Rehabilitation Engineering and Assistive Technology, University College of London, London, UK
| | - Jean Delbeke
- Department of Neurology, Institute of Neurosciences (IONS), Université Catholique de Louvain, Cliniques Universitaires Saint Luc, Brussels, Belgium
| | - Riëm El Tahry
- Department of Neurology, Institute of Neurosciences (IONS), Université Catholique de Louvain, Cliniques Universitaires Saint Luc, Brussels, Belgium
| | - Antoine Nonclercq
- Bio-, Electro- and Mechanical Systems (BEAMS), Université Libre de Bruxelles, Brussels, Belgium
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5
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Rich LR, Ransom BR, Brown AM. Energy Metabolism in Mouse Sciatic Nerve A Fibres during Increased Energy Demand. Metabolites 2022; 12:metabo12060505. [PMID: 35736438 PMCID: PMC9227381 DOI: 10.3390/metabo12060505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 05/29/2022] [Accepted: 05/30/2022] [Indexed: 11/16/2022] Open
Abstract
The ability of sciatic nerve A fibres to conduct action potentials relies on an adequate supply of energy substrate, usually glucose, to maintain necessary ion gradients. Under our ex vivo experimental conditions, the absence of exogenously applied glucose triggers Schwann cell glycogen metabolism to lactate, which is transported to axons to fuel metabolism, with loss of the compound action potential (CAP) signalling glycogen exhaustion. The CAP failure is accelerated if tissue energy demand is increased by high-frequency stimulation (HFS) or by blocking lactate uptake into axons using cinnemate (CIN). Imposing HFS caused CAP failure in nerves perfused with 10 mM glucose, but increasing glucose to 30 mM fully supported the CAP and promoted glycogen storage. A combination of glucose and lactate supported the CAP more fully than either substrate alone, indicating the nerve is capable of simultaneously metabolising each substrate. CAP loss resulting from exposure to glucose-free artificial cerebrospinal fluid (aCSF) could be fully reversed in the absence of glycogen by addition of glucose or lactate when minimally stimulated, but imposing HFS resulted in only partial CAP recovery. The delayed onset of CAP recovery coincided with the release of lactate by Schwann cells, suggesting that functional Schwann cells are a prerequisite for CAP recovery.
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Affiliation(s)
- Laura R. Rich
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK;
| | - Bruce R. Ransom
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA 98195, USA;
- Department of Neuroscience, City University of Hong Kong, Hong Kong
| | - Angus M. Brown
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK;
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA 98195, USA;
- Correspondence: ; Tel.: +0115-823-0173
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6
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Jia L, Liao M, Mou A, Zheng Q, Yang W, Yu Z, Cui Y, Xia X, Qin Y, Chen M, Xiao B. Rheb-regulated mitochondrial pyruvate metabolism of Schwann cells linked to axon stability. Dev Cell 2021; 56:2980-2994.e6. [PMID: 34619097 DOI: 10.1016/j.devcel.2021.09.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/12/2021] [Accepted: 09/10/2021] [Indexed: 02/05/2023]
Abstract
The metabolic coupling of Schwann cells (SCs) and peripheral axons is poorly understood. Few molecules in SCs are known to regulate axon stability. Using SC-specific Rheb knockout mice, we demonstrate that Rheb-regulated mitochondrial pyruvate metabolism is critical for SC-mediated non-cell-autonomous regulation of peripheral axon stability. Rheb knockout suppresses pyruvate dehydrogenase (PDH) activity (independently of mTORC1) and shifts pyruvate metabolism toward lactate production in SCs. The increased lactate causes age-dependent peripheral axon degeneration, affecting peripheral nerve function. Lactate, as an energy substrate and a potential signaling molecule, enhanced neuronal mitochondrial metabolism and energy production of peripheral nerves. Albeit beneficial to injured peripheral axons in the short term, we show that persistently increased lactate metabolism of neurons enhances ROS production, eventually damaging mitochondria, neuroenergetics, and axon stability. This study highlights the complex roles of lactate metabolism to peripheral axons and the importance of lactate homeostasis in preserving peripheral nerves.
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Affiliation(s)
- Lanlan Jia
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Maoxing Liao
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Aidi Mou
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Quanzhen Zheng
- Shenzhen Key Laboratory of Gene Regulation and Systems Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518005, People's Republic of China; Department of Biology, School of Life Sciences, Brain Research Center, Southern University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Wanchun Yang
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Zongyan Yu
- Shenzhen Key Laboratory of Gene Regulation and Systems Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518005, People's Republic of China; Department of Biology, School of Life Sciences, Brain Research Center, Southern University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Yiyuan Cui
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Xiaoqiang Xia
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China; Department of Biology, School of Life Sciences, Brain Research Center, Southern University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Yue Qin
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Mina Chen
- Neuroscience & Metabolism Research, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Bo Xiao
- Shenzhen Key Laboratory of Gene Regulation and Systems Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518005, People's Republic of China; Department of Biology, School of Life Sciences, Brain Research Center, Southern University of Science and Technology, Shenzhen 518000, People's Republic of China.
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7
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A method for reducing animal use whilst maintaining statistical power in electrophysiological recordings from rodent nerves. Heliyon 2020; 6:e04143. [PMID: 32529085 PMCID: PMC7281824 DOI: 10.1016/j.heliyon.2020.e04143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 11/21/2019] [Accepted: 06/02/2020] [Indexed: 12/29/2022] Open
Abstract
The stimulus evoked compound action potential, recorded from ex vivo nerve trunks such as the rodent optic and sciatic nerve, is a popular model system used to study aspects of nervous system metabolism. This includes (1) the role of glycogen in supporting axon conduction, (2) the injury mechanisms resulting from metabolic insults, and (3) to test putative benefits of clinically relevant neuroprotective strategies. We demonstrate the benefit of simultaneously recording from pairs of nerves in the same superfusion chamber compared with conventional recordings from single nerves. Experiments carried out on mouse optic and sciatic nerves demonstrate that our new recording configuration decreased the relative standard deviation from samples when compared with recordings from an equivalent number of individually recorded nerves. The new method reduces the number of animals required to produce equivalent Power compared with the existing method, where single nerves are used. Adopting this method leads to increased experimental efficiency and productivity. We demonstrate that reduced animal use and increased Power can be achieved by recording from pairs of rodent nerve trunks simultaneously.
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8
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Bouçanova F, Chrast R. Metabolic Interaction Between Schwann Cells and Axons Under Physiological and Disease Conditions. Front Cell Neurosci 2020; 14:148. [PMID: 32547370 PMCID: PMC7274022 DOI: 10.3389/fncel.2020.00148] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 05/04/2020] [Indexed: 12/24/2022] Open
Abstract
Recent research into axon-glial interactions in the nervous system has made a compelling case that glial cells have a relevant role in the metabolic support of axons, and that, in the case of myelinating cells, this role is independent of myelination itself. In this mini-review article, we summarize some of those observations and focus on Schwann cells (SC), drawing parallels between glia of the central and peripheral nervous systems (PNS), pointing out limitations in current knowledge, and discussing its potential clinical relevance. First, we introduce SC, their development and main roles, and follow with an evolutionary perspective of glial metabolic function. Then we provide evidence of the myelin-independent aspects of axonal support and their coupling to neuronal metabolism. Finally, we address the opportunity to use SC-axon metabolic interactions as therapeutic targets to treat peripheral neuropathies.
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Affiliation(s)
- Filipa Bouçanova
- Department of Neuroscience, KarolinskaInstitutet, Stockholm, Sweden.,Department of Clinical Neuroscience, KarolinskaInstitutet, Stockholm, Sweden
| | - Roman Chrast
- Department of Neuroscience, KarolinskaInstitutet, Stockholm, Sweden.,Department of Clinical Neuroscience, KarolinskaInstitutet, Stockholm, Sweden
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Sepsis Activates the TLR4/MyD88 Pathway in Schwann Cells to Promote Infiltration of Macrophages, Thereby Impeding Neuromuscular Function. Shock 2020; 55:90-99. [PMID: 32433207 DOI: 10.1097/shk.0000000000001557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
INTRODUCTION Sepsis is a kind of maladjustment response to bacterial infection and activation of coagulation, which can induce neuromuscular dysfunction. However, there is scarce of experimental evidence about the relationship between Schwann cells (SCs) and sepsis in neuromuscular dysfunction. We therefore set out to identify the potential role of SCs in sepsis-induced neuromuscular dysfunction and to explore the underlying molecular mechanism. METHODS Primary SCs were isolated from the left hind limb sciatic nerve of sepsis mice, which was constructed by cecal ligation and puncture. Then, the SCs were infected with adenovirus encoding toll-like receptor 4 (TLR4), MyD88, or IL-1R (with lipopolysaccharide stimulation), and the Raw 264.7 macrophages were injected with adenovirus with CCR2 silencing (with mMCP-1 stimulation). Further investigation of the interleukin 1 beta (IL-1β) and macrophage cationic peptide 1 (MCP-1) expressions, we followed reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay techniques, the F4/80 and Ki67 expressions was observed by immunofluorescence staining, while the expressions of CCR2, FAK/p-FAK, nuclear factor-κB (NFκB)/p-NFκB, and ERK1/2/p-ERK1/2 were determined by Western blot analysis. Last, but not the least, the cell migration ability and cell proliferation ability were detected by Transwell assay and Flow cytometry respectively. RESULTS Our results showed that in sepsis mice, the TLR4/MyD88/ERK pathway was activated in SCs, which triggered the cells to secrete IL-1β and MCP-1. The secreted IL-1β bound with IL-1β receptor on the surface of SCs, thereby activating the IL-1β/IL-1R/MyD88/ERK pathway and further promoting the secretion of MCP-1 by SCs. MCP-1 was found to bind to CCR2 on the surface of Raw264.7 macrophages to activate the TLR4/MyD88/ERK pathway which caused the inhibition of neuromuscular function. CONCLUSION Sepsis significantly promotes the infiltration of macrophages by activating the TLR4/MyD88 pathway in SCs, thereby impeding neuromuscular function. Consistently, our study provides a novel concept in the area of neuromuscular dysfunction therapeutics following sepsis.
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Fledrich R, Kungl T, Nave KA, Stassart RM. Axo-glial interdependence in peripheral nerve development. Development 2019; 146:146/21/dev151704. [PMID: 31719044 DOI: 10.1242/dev.151704] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
During the development of the peripheral nervous system, axons and myelinating Schwann cells form a unique symbiotic unit, which is realized by a finely tuned network of molecular signals and reciprocal interactions. The importance of this complex interplay becomes evident after injury or in diseases in which aspects of axo-glial interaction are perturbed. This Review focuses on the specific interdependence of axons and Schwann cells in peripheral nerve development that enables axonal outgrowth, Schwann cell lineage progression, radial sorting and, finally, formation and maintenance of the myelin sheath.
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Affiliation(s)
- Robert Fledrich
- Institute of Anatomy, Leipzig University, 04103 Leipzig, Germany .,Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Theresa Kungl
- Institute of Anatomy, Leipzig University, 04103 Leipzig, Germany.,Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Ruth M Stassart
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany .,Department of Neuropathology, University Clinic Leipzig, 04103 Leipzig, Germany
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11
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Stassart RM, Möbius W, Nave KA, Edgar JM. The Axon-Myelin Unit in Development and Degenerative Disease. Front Neurosci 2018; 12:467. [PMID: 30050403 PMCID: PMC6050401 DOI: 10.3389/fnins.2018.00467] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 06/19/2018] [Indexed: 12/15/2022] Open
Abstract
Axons are electrically excitable, cable-like neuronal processes that relay information between neurons within the nervous system and between neurons and peripheral target tissues. In the central and peripheral nervous systems, most axons over a critical diameter are enwrapped by myelin, which reduces internodal membrane capacitance and facilitates rapid conduction of electrical impulses. The spirally wrapped myelin sheath, which is an evolutionary specialisation of vertebrates, is produced by oligodendrocytes and Schwann cells; in most mammals myelination occurs during postnatal development and after axons have established connection with their targets. Myelin covers the vast majority of the axonal surface, influencing the axon's physical shape, the localisation of molecules on its membrane and the composition of the extracellular fluid (in the periaxonal space) that immerses it. Moreover, myelinating cells play a fundamental role in axonal support, at least in part by providing metabolic substrates to the underlying axon to fuel its energy requirements. The unique architecture of the myelinated axon, which is crucial to its function as a conduit over long distances, renders it particularly susceptible to injury and confers specific survival and maintenance requirements. In this review we will describe the normal morphology, ultrastructure and function of myelinated axons, and discuss how these change following disease, injury or experimental perturbation, with a particular focus on the role the myelinating cell plays in shaping and supporting the axon.
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Affiliation(s)
- Ruth M. Stassart
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
- Department of Neuropathology, University Medical Center Leipzig, Leipzig, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
| | - Julia M. Edgar
- Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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