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Ojeda J, Vergara M, Ávila A, Henríquez JP, Fehlings M, Vidal PM. Impaired communication at the neuromotor axis during Degenerative Cervical Myelopathy. Front Cell Neurosci 2024; 17:1316432. [PMID: 38269114 PMCID: PMC10806149 DOI: 10.3389/fncel.2023.1316432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024] Open
Abstract
Degenerative Cervical Myelopathy (DCM) is a progressive neurological condition characterized by structural alterations in the cervical spine, resulting in compression of the spinal cord. While clinical manifestations of DCM are well-documented, numerous unanswered questions persist at the molecular and cellular levels. In this study, we sought to investigate the neuromotor axis during DCM. We use a clinically relevant mouse model, where after 3 months of DCM induction, the sensorimotor tests revealed a significant reduction in both locomotor activity and muscle strength compared to the control group. Immunohistochemical analyses showed alterations in the gross anatomy of the cervical spinal cord segment after DCM. These changes were concomitant with the loss of motoneurons and a decrease in the number of excitatory synaptic inputs within the spinal cord. Additionally, the DCM group exhibited a reduction in the endplate surface, which correlated with diminished presynaptic axon endings in the supraspinous muscles. Furthermore, the biceps brachii (BB) muscle exhibited signs of atrophy and impaired regenerative capacity, which inversely correlated with the transversal area of remnants of muscle fibers. Additionally, metabolic assessments in BB muscle indicated an increased proportion of oxidative skeletal muscle fibers. In line with the link between neuromotor disorders and gut alterations, DCM mice displayed smaller mucin granules in the mucosa layer without damage to the epithelial barrier in the colon. Notably, a shift in the abundance of microbiota phylum profiles reveals an elevated Firmicutes-to-Bacteroidetes ratio-a consistent hallmark of dysbiosis that correlates with alterations in gut microbiota-derived metabolites. Additionally, treatment with short-chain fatty acids stimulated the differentiation of the motoneuron-like NSC34 cell line. These findings shed light on the multifaceted nature of DCM, resembling a synaptopathy that disrupts cellular communication within the neuromotor axis while concurrently exerting influence on other systems. Notably, the colon emerges as a focal point, experiencing substantial perturbations in both mucosal barrier integrity and the delicate balance of intestinal microbiota.
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Affiliation(s)
- Jorge Ojeda
- Neuroimmunology and Regeneration of the Central Nervous System Unit, Biomedical Science Research Laboratory, Basic Sciences Department, Faculty of Medicine, Universidad Católica de la Santísima Concepción, Concepción, Chile
| | - Mayra Vergara
- Neuroimmunology and Regeneration of the Central Nervous System Unit, Biomedical Science Research Laboratory, Basic Sciences Department, Faculty of Medicine, Universidad Católica de la Santísima Concepción, Concepción, Chile
| | - Ariel Ávila
- Developmental Neurobiology Unit, Biomedical Science Research Laboratory, Basic Sciences Department, Faculty of Medicine, Universidad Católica de la Santísima Concepción, Concepción, Chile
| | - Juan Pablo Henríquez
- Neuromuscular Studies Lab (NeSt Lab), Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile
| | - Michael Fehlings
- Department of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Spinal Program, University Health Network, Toronto Western Hospital, Toronto, ON, Canada
| | - Pia M. Vidal
- Neuroimmunology and Regeneration of the Central Nervous System Unit, Biomedical Science Research Laboratory, Basic Sciences Department, Faculty of Medicine, Universidad Católica de la Santísima Concepción, Concepción, Chile
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Arkhipov AY, Fedorov NS, Nurullin LF, Khabibrakhmanov AN, Mukhamedyarov MA, Samigullin DV, Malomouzh AI. Activation of TRPV1 Channels Inhibits the Release of Acetylcholine and Improves Muscle Contractility in Mice. Cell Mol Neurobiol 2023; 43:4157-4172. [PMID: 37689594 DOI: 10.1007/s10571-023-01403-y] [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: 05/04/2023] [Accepted: 08/22/2023] [Indexed: 09/11/2023]
Abstract
TRPV1 represents a non-selective transient receptor potential cation channel found not only in sensory neurons, but also in motor nerve endings and in skeletal muscle fibers. However, the role of TRPV1 in the functioning of the neuromuscular junction has not yet been fully established. In this study, the Levator Auris Longus muscle preparations were used to assess the effect of pharmacological activation of TRPV1 channels on neuromuscular transmission. The presence of TRPV1 channels in the nerve terminal and in the muscle fiber was confirmed by immunohistochemistry. It was verified by electrophysiology that the TRPV1 channel agonist capsaicin inhibits the acetylcholine release, and this effect was completely absent after preliminary application of the TRPV1 channel blocker SB 366791. Nerve stimulation revealed an increase of amplitude of isometric tetanic contractions upon application of capsaicin which was also eliminated after preliminary application of SB 366791. Similar data were obtained during direct muscle stimulation. Thus, pharmacological activation of TRPV1 channels affects the functioning of both the pre- and postsynaptic compartment of the neuromuscular junction. A moderate decrease in the amount of acetylcholine released from the motor nerve allows to maintain a reserve pool of the mediator to ensure a longer signal transmission process, and an increase in the force of muscle contraction, in its turn, also implies more effective physiological muscle activity in response to prolonged stimulation. This assumption is supported by the fact that when muscle was indirect stimulated with a fatigue protocol, muscle fatigue was attenuated in the presence of capsaicin.
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Affiliation(s)
- Arsenii Y Arkhipov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of Russian Academy of Sciences, 2/31 Lobachevsky Street, Box 261, Kazan, Russia, 420111
| | - Nikita S Fedorov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of Russian Academy of Sciences, 2/31 Lobachevsky Street, Box 261, Kazan, Russia, 420111
- Kazan Federal University, 18 Kremlyovskaya Street, Kazan, Russia, 420008
| | - Leniz F Nurullin
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of Russian Academy of Sciences, 2/31 Lobachevsky Street, Box 261, Kazan, Russia, 420111
- Kazan State Medical University, 49 Butlerova Street, Kazan, Russia, 420012
| | | | | | - Dmitry V Samigullin
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of Russian Academy of Sciences, 2/31 Lobachevsky Street, Box 261, Kazan, Russia, 420111
- A.N. Tupolev Kazan National Research Technical University, 10, K. Marx Street, Kazan, Russia, 420111
| | - Artem I Malomouzh
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center, Kazan Scientific Center of Russian Academy of Sciences, 2/31 Lobachevsky Street, Box 261, Kazan, Russia, 420111.
- A.N. Tupolev Kazan National Research Technical University, 10, K. Marx Street, Kazan, Russia, 420111.
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Durbin RJ, Heredia DJ, Gould TW, Renden RB. Postsynaptic Calcium Extrusion at the Mouse Neuromuscular Junction Alkalinizes the Synaptic Cleft. J Neurosci 2023; 43:5741-5752. [PMID: 37474311 PMCID: PMC10423045 DOI: 10.1523/jneurosci.0815-23.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 07/07/2023] [Accepted: 07/14/2023] [Indexed: 07/22/2023] Open
Abstract
Neurotransmission is shaped by extracellular pH. Alkalization enhances pH-sensitive transmitter release and receptor activation, whereas acidification inhibits these processes and can activate acid-sensitive conductances in the synaptic cleft. Previous work has shown that the synaptic cleft can either acidify because of synaptic vesicular release and/or alkalize because of Ca2+ extrusion by the plasma membrane ATPase (PMCA). The direction of change differs across synapse types. At the mammalian neuromuscular junction (NMJ), the direction and magnitude of pH transients in the synaptic cleft during transmission remain ambiguous. We set out to elucidate the extracellular pH transients that occur at this cholinergic synapse under near-physiological conditions and identify their sources. We monitored pH-dependent changes in the synaptic cleft of the mouse levator auris longus using viral expression of the pseudoratiometric probe pHusion-Ex in the muscle. Using mice from both sexes, a significant and prolonged alkalization occurred when stimulating the connected nerve for 5 s at 50 Hz, which was dependent on postsynaptic intracellular Ca2+ release. Sustained stimulation for a longer duration (20 s at 50 Hz) caused additional prolonged net acidification at the cleft. To investigate the mechanism underlying cleft alkalization, we used muscle-expressed GCaMP3 to monitor the contribution of postsynaptic Ca2+ Activity-induced liberation of intracellular Ca2+ in muscle positively correlated with alkalization of the synaptic cleft, whereas inhibiting PMCA significantly decreased the extent of cleft alkalization. Thus, cholinergic synapses of the mouse NMJ typically alkalize because of cytosolic Ca2+ liberated in muscle during activity, unless under highly strenuous conditions where acidification predominates.SIGNIFICANCE STATEMENT Changes in synaptic cleft pH alter neurotransmission, acting on receptors and channels on both sides of the synapse. Synaptic acidification has been associated with a myriad of diseases in the central and peripheral nervous system. Here, we report that in near-physiological recording conditions the cholinergic neuromuscular junction shows use-dependent bidirectional changes in synaptic cleft pH-immediate alkalinization and a long-lasting acidification under prolonged stimulation. These results provide further insight into physiologically relevant changes at cholinergic synapses that have not been defined previously. Understanding and identifying synaptic pH transients during and after neuronal activity provides insight into short-term synaptic plasticity synapses and may identify therapeutic targets for diseases.
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Affiliation(s)
- Ryan J Durbin
- Integrative Neuroscience Graduate Program, University of Nevada, Reno, Reno, Nevada 89557
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557
| | - Dante J Heredia
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557
| | - Thomas W Gould
- Integrative Neuroscience Graduate Program, University of Nevada, Reno, Reno, Nevada 89557
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557
| | - Robert B Renden
- Integrative Neuroscience Graduate Program, University of Nevada, Reno, Reno, Nevada 89557
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557
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Negro S, Lauria F, Stazi M, Tebaldi T, D’Este G, Pirazzini M, Megighian A, Lessi F, Mazzanti CM, Sales G, Romualdi C, Fillo S, Lista F, Sleigh JN, Tosolini AP, Schiavo G, Viero G, Rigoni M. Hydrogen peroxide induced by nerve injury promotes axon regeneration via connective tissue growth factor. Acta Neuropathol Commun 2022; 10:189. [PMID: 36567321 PMCID: PMC9791753 DOI: 10.1186/s40478-022-01495-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 12/12/2022] [Indexed: 12/26/2022] Open
Abstract
Regeneration of the neuromuscular junction (NMJ) leverages on extensive exchange of factors released from motor axon terminals (MATs), muscle fibers and perisynaptic Schwann cells (PSCs), among which hydrogen peroxide (H2O2) is a major pro-regenerative signal. To identify critical determinants of NMJ remodeling in response to injury, we performed temporal transcriptional profiling of NMJs from 2 month-old mice during MAT degeneration/regeneration, and cross-referenced the differentially expressed genes with those elicited by H2O2 in SCs. We identified an enrichment in extracellular matrix (ECM) transcripts, including Connective Tissue Growth Factor (Ctgf), which is usually expressed during development. We discovered that Ctgf levels are increased in a Yes-associated protein (YAP)-dependent fashion in response to rapid, local H2O2 signaling generated by stressed mitochondria in the injured sciatic nerve, a finding highlighting the importance of signals triggered by mechanical force to motor nerve repair. Through sequestration of Ctgf or inactivation of H2O2, we delayed the recovery of neuromuscular function by impairing SC migration and, in turn, axon-oriented re-growth. These data indicate that H2O2 and its downstream effector Ctgf are pro-regenerative factors that enable axonal growth, and reveal a striking ECM remodeling process during nerve regeneration upon local H2O2 signaling. Our study identifies key transcriptomic changes at the regenerating NMJ, providing a rich source of pro-regenerative factors with potential for alleviating the consequences of peripheral nerve injuries.
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Affiliation(s)
- Samuele Negro
- grid.5608.b0000 0004 1757 3470Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy ,grid.5608.b0000 0004 1757 3470U.O.C. Clinica Neurologica, Azienda Ospedale, University of Padua, 35128 Padua, Italy
| | - Fabio Lauria
- grid.419463.d0000 0004 1756 3731Institute of Biophysics, CNR Unit at Trento, 38123 Povo, Italy
| | - Marco Stazi
- grid.5608.b0000 0004 1757 3470Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy
| | - Toma Tebaldi
- grid.11696.390000 0004 1937 0351Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, 38123 Povo, Italy ,grid.47100.320000000419368710Section of Hematology, Department of Internal Medicine, Yale Comprehensive Cancer Center, Yale University School of Medicine, New Haven, CT 06520 USA
| | - Giorgia D’Este
- grid.5608.b0000 0004 1757 3470Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy
| | - Marco Pirazzini
- grid.5608.b0000 0004 1757 3470Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy ,grid.5608.b0000 0004 1757 3470Myology Center (CIR-Myo), University of Padua, 35129 Padua, Italy
| | - Aram Megighian
- grid.5608.b0000 0004 1757 3470Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy ,grid.5608.b0000 0004 1757 3470Padua Neuroscience Center, University of Padua, 35131 Padua, Italy
| | - Francesca Lessi
- Laboratory of Genomics, Pisa Science Foundation, 56017 San Giuliano Terme, Italy
| | - Chiara M. Mazzanti
- Laboratory of Genomics, Pisa Science Foundation, 56017 San Giuliano Terme, Italy
| | - Gabriele Sales
- grid.5608.b0000 0004 1757 3470Department of Biology, University of Padua, 35131 Padua, Italy
| | - Chiara Romualdi
- grid.5608.b0000 0004 1757 3470Department of Biology, University of Padua, 35131 Padua, Italy
| | - Silvia Fillo
- grid.470599.60000 0004 1760 920XCenter of Medical and Veterinary Research of the Ministry of Defence, 00184 Rome, Italy
| | - Florigio Lista
- grid.470599.60000 0004 1760 920XCenter of Medical and Veterinary Research of the Ministry of Defence, 00184 Rome, Italy
| | - James N. Sleigh
- grid.83440.3b0000000121901201Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College London, London, WC1N 3BG UK ,grid.83440.3b0000000121901201UCL Queen Square Motor Neuron Disease Centre, University College London, London, WC1N 3BG UK ,grid.83440.3b0000000121901201UK Dementia Research Institute, University College London, London, WC1E 6BT UK
| | - Andrew P. Tosolini
- grid.83440.3b0000000121901201Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College London, London, WC1N 3BG UK ,grid.83440.3b0000000121901201UCL Queen Square Motor Neuron Disease Centre, University College London, London, WC1N 3BG UK
| | - Giampietro Schiavo
- grid.83440.3b0000000121901201Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College London, London, WC1N 3BG UK ,grid.83440.3b0000000121901201UCL Queen Square Motor Neuron Disease Centre, University College London, London, WC1N 3BG UK ,grid.83440.3b0000000121901201UK Dementia Research Institute, University College London, London, WC1E 6BT UK
| | - Gabriella Viero
- grid.419463.d0000 0004 1756 3731Institute of Biophysics, CNR Unit at Trento, 38123 Povo, Italy
| | - Michela Rigoni
- Department of Biomedical Sciences, University of Padua, 35131, Padua, Italy. .,Myology Center (CIR-Myo), University of Padua, 35129, Padua, Italy.
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5
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Bermedo-García F, Zelada D, Martínez E, Tabares L, Henríquez JP. Functional regeneration of the murine neuromuscular synapse relies on long-lasting morphological adaptations. BMC Biol 2022; 20:158. [PMID: 35804361 PMCID: PMC9270767 DOI: 10.1186/s12915-022-01358-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 05/05/2022] [Indexed: 12/04/2022] Open
Abstract
Background In a broad variety of species, muscle contraction is controlled at the neuromuscular junction (NMJ), the peripheral synapse composed of a motor nerve terminal, a muscle specialization, and non-myelinating terminal Schwann cells. While peripheral nerve damage leads to successful NMJ reinnervation in animal models, muscle fiber reinnervation in human patients is largely inefficient. Interestingly, some hallmarks of NMJ denervation and early reinnervation in murine species, such as fragmentation and poly-innervation, are also phenotypes of aged NMJs or even of unaltered conditions in other species, including humans. We have reasoned that rather than features of NMJ decline, such cellular responses could represent synaptic adaptations to accomplish proper functional recovery. Here, we have experimentally tackled this idea through a detailed comparative study of the short- and long-term consequences of irreversible (chronic) and reversible (partial) NMJ denervation in the convenient cranial levator auris longus muscle. Results Our findings reveal that irreversible muscle denervation results in highly fragmented postsynaptic domains and marked ectopic acetylcholine receptor clustering along with significant terminal Schwann cells sprouting and progressive detachment from the NMJ. Remarkably, even though reversible nerve damage led to complete reinnervation after 11 days, we found that more than 30% of NMJs are poly-innervated and around 65% of postsynaptic domains are fragmented even 3 months after injury, whereas synaptic transmission is fully recovered two months after nerve injury. While postsynaptic stability was irreversibly decreased after chronic denervation, this parameter was only transiently affected by partial NMJ denervation. In addition, we found that a combination of morphometric analyses and postsynaptic stability determinations allows discriminating two distinct forms of NMJ fragmentation, stable-smooth and unstable-blurred, which correlate with their regeneration potential. Conclusions Together, our data unveil that reversible nerve damage imprints a long-lasting reminiscence in the NMJ that results in the rearrangement of its cellular components. Instead of being predictive of NMJ decline, these traits may represent an efficient adaptive response for proper functional recovery. As such, these features are relevant targets to be considered in strategies aimed to restore motor function in detrimental conditions for peripheral innervation. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01358-4.
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Affiliation(s)
- Francisca Bermedo-García
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Diego Zelada
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Esperanza Martínez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, Universidad de Sevilla, Sevilla, Spain
| | - Juan Pablo Henríquez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile.
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6
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Lopez-Manzaneda M, Fuentes-Moliz A, Tabares L. Presynaptic Mitochondria Communicate With Release Sites for Spatio-Temporal Regulation of Exocytosis at the Motor Nerve Terminal. Front Synaptic Neurosci 2022; 14:858340. [PMID: 35645766 PMCID: PMC9133601 DOI: 10.3389/fnsyn.2022.858340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/07/2022] [Indexed: 11/13/2022] Open
Abstract
Presynaptic Ca2+ regulation is critical for accurate neurotransmitter release, vesicle reloading of release sites, and plastic changes in response to electrical activity. One of the main players in the regulation of cytosolic Ca2+ in nerve terminals is mitochondria, which control the size and spread of the Ca2+ wave during sustained electrical activity. However, the role of mitochondria in Ca2+ signaling during high-frequency short bursts of action potentials (APs) is not well known. Here, we studied spatial and temporal relationships between mitochondrial Ca2+ (mCa2+) and exocytosis by live imaging and electrophysiology in adult motor nerve terminals of transgenic mice expressing synaptophysin-pHluorin (SypHy). Our results show that hot spots of exocytosis and mitochondria are organized in subsynaptic functional regions and that mitochondria start to uptake Ca2+ after a few APs. We also show that mitochondria contribute to the regulation of the mode of fusion (synchronous and asynchronous) and the kinetics of release and replenishment of the readily releasable pool (RRP) of vesicles. We propose that mitochondria modulate the timing and reliability of neurotransmission in motor nerve terminals during brief AP trains.
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7
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Preliminary Observations on Skeletal Muscle Adaptation and Plasticity in Homer 2 -/- Mice. Metabolites 2021; 11:metabo11090642. [PMID: 34564458 PMCID: PMC8469648 DOI: 10.3390/metabo11090642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/16/2021] [Accepted: 09/18/2021] [Indexed: 01/05/2023] Open
Abstract
Homer represents a diversified family of scaffold and transduction proteins made up of several isoforms. Here, we present preliminary observations on skeletal muscle adaptation and plasticity in a transgenic model of Homer 2-/- mouse using a multifaceted approach entailing morphometry, quantitative RT-PCR (Reverse Transcription PCR), confocal immunofluorescence, and electrophysiology. Morphometry shows that Soleus muscle (SOL), at variance with Extensor digitorum longus muscle (EDL) and Flexor digitorum brevis muscle (FDB), displays sizable reduction of fibre cross-sectional area compared to the WT counterparts. In SOL of Homer 2-/- mice, quantitative RT-PCR indicated the upregulation of Atrogin-1 and Muscle ring finger protein 1 (MuRF1) genes, and confocal immunofluorescence showed the decrease of neuromuscular junction (NMJ) Homer content. Electrophysiological measurements of isolated FDB fibres from Homer 2-/- mice detected the exclusive presence of the adult ε-nAChR isoform excluding denervation. As for NMJ morphology, data were not conclusive, and further work is needed to ascertain whether the null Homer 2 phenotype induces any endplate remodelling. Within the context of adaptation and plasticity, the present data show that Homer 2 is a co-regulator of the normotrophic status in a muscle specific fashion.
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8
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Zelada D, Barrantes FJ, Henríquez JP. Lithium causes differential effects on postsynaptic stability in normal and denervated neuromuscular synapses. Sci Rep 2021; 11:17285. [PMID: 34446751 PMCID: PMC8390761 DOI: 10.1038/s41598-021-96708-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 08/06/2021] [Indexed: 11/12/2022] Open
Abstract
Lithium chloride has been widely used as a therapeutic mood stabilizer. Although cumulative evidence suggests that lithium plays modulatory effects on postsynaptic receptors, the underlying mechanism by which lithium regulates synaptic transmission has not been fully elucidated. In this work, by using the advantageous neuromuscular synapse, we evaluated the effect of lithium on the stability of postsynaptic nicotinic acetylcholine receptors (nAChRs) in vivo. We found that in normally innervated neuromuscular synapses, lithium chloride significantly decreased the turnover of nAChRs by reducing their internalization. A similar response was observed in CHO-K1/A5 cells expressing the adult muscle-type nAChRs. Strikingly, in denervated neuromuscular synapses, lithium led to enhanced nAChR turnover and density by increasing the incorporation of new nAChRs. Lithium also potentiated the formation of unstable nAChR clusters in non-synaptic regions of denervated muscle fibres. We found that denervation-dependent re-expression of the foetal nAChR γ-subunit was not altered by lithium. However, while denervation inhibits the distribution of β-catenin within endplates, lithium-treated fibres retain β-catenin staining in specific foci of the synaptic region. Collectively, our data reveal that lithium treatment differentially affects the stability of postsynaptic receptors in normal and denervated neuromuscular synapses in vivo, thus providing novel insights into the regulatory effects of lithium on synaptic organization and extending its potential therapeutic use in conditions affecting the peripheral nervous system.
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Affiliation(s)
- Diego Zelada
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, CMA Bio-Bio, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Francisco J Barrantes
- Pontificia Universidad Católica Argentina (UCA)-Scientific and Technological Research Council of Argentina (CONICET), Buenos Aires, Argentina
| | - Juan Pablo Henríquez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, CMA Bio-Bio, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
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9
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Villarroel-Campos D, Schiavo G, Sleigh JN. Dissection, in vivo imaging and analysis of the mouse epitrochleoanconeus muscle. J Anat 2021; 241:1108-1119. [PMID: 34121181 PMCID: PMC9558155 DOI: 10.1111/joa.13478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/07/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
Analysis of rodent muscles affords an opportunity to glean key insights into neuromuscular development and the detrimental impact of disease‐causing genetic mutations. Muscles of the distal leg, for instance the gastrocnemius and tibialis anterior, are commonly used in such studies with mice and rats. However, thin and flat muscles, which can be dissected, processed and imaged without major disruption to muscle fibres and nerve‐muscle contacts, are more suitable for accurate and detailed analyses of the peripheral motor nervous system. One such wholemount muscle is the predominantly fast twitch epitrochleoanconeus (ETA), which is located in the upper forelimb, innervated by the radial nerve, and contains relatively large and uniformly flat neuromuscular junctions (NMJs). To facilitate incorporation of the ETA into the experimental toolkit of the neuromuscular disease field, here, we describe a simple method for its rapid isolation (<5 min), supported by high‐resolution videos and step‐by‐step images. Furthermore, we outline how the ETA can be imaged in live, anaesthetised mice, to enable examination of dynamic cellular processes occurring at the NMJ and within intramuscular axons, including transport of organelles, such as mitochondria and signalling endosomes. Finally, we present reference data on wild‐type ETA fibre‐type composition in young adult, male C57BL6/J mice. Comparative neuroanatomical studies of different muscles in rodent models of disease can generate critical insights into pathogenesis and pathology; dissection of the wholemount ETA provides the possibility to diversify the repertoire of muscles analysed for this endeavour.
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Affiliation(s)
- David Villarroel-Campos
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Giampietro Schiavo
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| | - James N Sleigh
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
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10
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Tereshenko V, Dotzauer DC, Maierhofer U, Festin C, Luft M, Laengle G, Politikou O, Klein HJ, Blumer R, Aszmann OC, Bergmeister KD. Selective Denervation of the Facial Dermato-Muscular Complex in the Rat: Experimental Model and Anatomical Basis. Front Neuroanat 2021; 15:650761. [PMID: 33828465 PMCID: PMC8019738 DOI: 10.3389/fnana.2021.650761] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/01/2021] [Indexed: 11/13/2022] Open
Abstract
The facial dermato-muscular system consists of highly specialized muscles tightly adhering to the overlaying skin and thus form a complex morphological conglomerate. This is the anatomical and functional basis for versatile facial expressions, which are essential for human social interaction. The neural innervation of the facial skin and muscles occurs via branches of the trigeminal and facial nerves. These are also the most commonly pathologically affected cranial nerves, often requiring surgical treatment. Hence, experimental models for researching these nerves and their pathologies are highly relevant to study pathophysiology and nerve regeneration. Experimental models for the distinctive investigation of the complex afferent and efferent interplay within facial structures are scarce. In this study, we established a robust surgical model for distinctive exploration of facial structures after complete elimination of afferent or efferent innervation in the rat. Animals were allocated into two groups according to the surgical procedure. In the first group, the facial nerve and in the second all distal cutaneous branches of the trigeminal nerve were transected unilaterally. All animals survived and no higher burden was caused by the procedures. Whisker pad movements were documented with video recordings 4 weeks after surgery and showed successful denervation. Whole-mount immunofluorescent staining of facial muscles was performed to visualize the innervation pattern of the neuromuscular junctions. Comprehensive quantitative analysis revealed large differences in afferent axon counts in the cutaneous branches of the trigeminal nerve. Axon number was the highest in the infraorbital nerve (28,625 ± 2,519), followed by the supraorbital nerve (2,131 ± 413), the mental nerve (3,062 ± 341), and the cutaneous branch of the mylohyoid nerve (343 ± 78). Overall, this surgical model is robust and reliable for distinctive surgical deafferentation or deefferentation of the face. It may be used for investigating cortical plasticity, the neurobiological mechanisms behind various clinically relevant conditions like facial paralysis or trigeminal neuralgia as well as local anesthesia in the face and oral cavity.
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Affiliation(s)
- Vlad Tereshenko
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Dominik C Dotzauer
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria
| | - Udo Maierhofer
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Christopher Festin
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Matthias Luft
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Gregor Laengle
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Olga Politikou
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Holger J Klein
- Department of Plastic Surgery and Hand Surgery, University Hospital Zurich, Zurich, Switzerland
| | - Roland Blumer
- Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | - Oskar C Aszmann
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria
| | - Konstantin D Bergmeister
- Clinical Laboratory for Bionic Extremity Reconstruction, Department of Plastic, Reconstructive and Aesthetic Surgery, Medical University of Vienna, Vienna, Austria.,Department of Plastic, Aesthetic and Reconstructive Surgery, University Hospital St. Poelten, Karl Landsteiner University of Health Sciences, Krems, Austria.,Department of Plastic, Aesthetic and Reconstructive Surgery, University Hospital St. Poelten, Krems, Austria
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