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Brandenburg JE, Fogarty MJ, Zhan WZ, Kopper LA, Sieck GC. Postnatal survival of phrenic motor neurons is promoted by BDNF/TrkB.FL signaling. J Appl Physiol (1985) 2024; 136:1113-1121. [PMID: 38511211 DOI: 10.1152/japplphysiol.00911.2023] [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: 12/22/2023] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 03/22/2024] Open
Abstract
The number of motor neurons (MNs) declines precipitously during the final trimester before birth. Thereafter, the number of MNs remains relatively stable, with their connections to skeletal muscle dependent on neurotrophins, including brain-derived neurotrophic factor (BDNF) signaling through its high-affinity full-length tropomyosin-related kinase receptor subtype B (TrkB.FL) receptor. As a genetic knockout of BDNF leads to extensive MN loss and postnatal death within 1-2 days after birth, we tested the hypothesis that postnatal inhibition of BDNF/TrkB.FL signaling is important for postnatal phrenic MN (PhMN) survival. In the present study, we used a 1NMPP1-sensitive TrkBF616A mutant mouse to evaluate the effects of inhibition of TrkB kinase activity on phrenic MN (PhMN) numbers and diaphragm muscle (DIAm) fiber cross-sectional area (CSA). Pups were exposed to 1NMPP1 or vehicle (DMSO) from birth to 21 days old (weaning) via the mother's ingestion in the drinking water. Following weaning, the right phrenic nerve was exposed in the neck and the proximal end dipped in a rhodamine solution to retrogradely label PhMNs. After 24 h, the cervical spinal cord and DIAm were excised. Labeled PhMNs were imaged using confocal microscopy, whereas DIAm strips were frozen at ∼1.5× resting length, cryosectioned, and stained with hematoxylin and eosin to assess CSA. We observed an ∼34% reduction in PhMN numbers and increased primary dendrite numbers in 1NMPP1-treated TrkBF616A mice. The distribution of PhMN size (somal surface area) DIAm fiber cross-sectional areas did not differ. We conclude that survival of PhMNs during early postnatal development is sensitive to BDNF/TrkB.FL signaling.NEW & NOTEWORTHY During early postnatal development, BDNF/TrkB signaling promotes PhMN survival. Inhibition of BDNF/TrkB signaling in early postnatal development does not impact PhMN size. Inhibition of BDNF/TrkB signaling in early postnatal development does not impact the number or CSA of DIAm fibers.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota, United States
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Leo A Kopper
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
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2
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Fogarty MJ, Dasgupta D, Khurram OU, Sieck GC. Chemogenetic inhibition of TrkB signalling reduces phrenic motor neuron survival and size. Mol Cell Neurosci 2023; 125:103847. [PMID: 36958643 PMCID: PMC10247511 DOI: 10.1016/j.mcn.2023.103847] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 03/07/2023] [Accepted: 03/16/2023] [Indexed: 03/25/2023] Open
Abstract
Brain derived neurotrophic factor (BDNF) signalling through its high-affinity tropomyosin receptor kinase B (TrkB) is known to have potent effects on motor neuron survival and morphology during development and in neurodegenerative diseases. Here, we employed a novel 1NMPP1 sensitive TrkBF616 rat model to evaluate the effect of 14 days inhibition of TrkB signalling on phrenic motor neurons (PhMNs). Adult female and male TrkBF616 rats were divided into 1NMPP1 or vehicle treated groups. Three days prior to treatment, PhMNs in both groups were initially labeled via intrapleural injection of Alexa-Fluor-647 cholera toxin B (CTB). After 11 days of treatment, retrograde axonal uptake/transport was assessed by secondary labeling of PhMNs by intrapleural injection of Alexa-Fluor-488 CTB. After 14 days of treatment, the spinal cord was excised 100 μm thick spinal sections containing PhMNs were imaged using two-channel confocal microscopy. TrkB inhibition reduced the total number of PhMNs by ∼16 %, reduced the mean PhMN somal surface areas by ∼25 %, impaired CTB uptake 2.5-fold and reduced the estimated PhMN dendritic surface area by ∼38 %. We conclude that inhibition of TrkB signalling alone in adult TrkBF616 rats is sufficient to lead to PhMN loss, morphological degeneration and deficits in retrograde axonal uptake/transport.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Debanjali Dasgupta
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Obaid U Khurram
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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3
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Bolívar S, Udina E. Preferential regeneration and collateral dynamics of motor and sensory neurons after nerve injury in mice. Exp Neurol 2022; 358:114227. [PMID: 36108714 DOI: 10.1016/j.expneurol.2022.114227] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 08/26/2022] [Accepted: 09/08/2022] [Indexed: 11/04/2022]
Abstract
Specificity in regeneration after peripheral nerve injuries is a major determinant of functional recovery. Unfortunately, regenerating motor and sensory axons rarely find their original pathways to reinnervate appropriate target organs. Although a preference of motor axons to regenerate towards the muscle has been described, little is known about the specificity of the heterogeneous sensory populations. Here, we propose the comparative study of regeneration in different neuron subtypes. Using female and male reporter mice, we assessed the regenerative preference of motoneurons (ChAT-Cre/Ai9), proprioceptors (PV-Cre/Ai9), and cutaneous mechanoreceptors (Npy2r-Cre/Ai9). The femoral nerve of these animals was transected above the bifurcation and repaired with fibrin glue. Regeneration was assessed by applying retrograde tracers in the distal branches of the nerve 1 or 8 weeks after the lesion and counting the retrotraced somas and the axons in the branches. We found that cutaneous mechanoreceptors regenerated faster than other populations, followed by motoneurons and, lastly, proprioceptors. All neuron types had an early preference to regenerate into the cutaneous branch whereas, at long term, all neurons regenerated more through their original branch. Finally, we found that myelinated neurons extend more regenerative sprouts in the cutaneous than in the muscle branch of the femoral nerve and, particularly, that motoneurons have more collaterals than proprioceptors. Our findings reveal novel differences in regeneration dynamics and specificity, which indicate distinct regenerative mechanisms between neuron subtypes that can be potentially modulated to improve functional recovery after nerve injury.
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Affiliation(s)
- Sara Bolívar
- Institute of Neurosciences, Department Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
| | - Esther Udina
- Institute of Neurosciences, Department Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain.
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4
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Davis LA, Fogarty MJ, Brown A, Sieck GC. Structure and Function of the Mammalian Neuromuscular Junction. Compr Physiol 2022; 12:3731-3766. [PMID: 35950651 PMCID: PMC10461538 DOI: 10.1002/cphy.c210022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The mammalian neuromuscular junction (NMJ) comprises a presynaptic terminal, a postsynaptic receptor region on the muscle fiber (endplate), and the perisynaptic (terminal) Schwann cell. As with any synapse, the purpose of the NMJ is to transmit signals from the nervous system to muscle fibers. This neural control of muscle fibers is organized as motor units, which display distinct structural and functional phenotypes including differences in pre- and postsynaptic elements of NMJs. Motor units vary considerably in the frequency of their activation (both motor neuron discharge rate and duration/duty cycle), force generation, and susceptibility to fatigue. For earlier and more frequently recruited motor units, the structure and function of the activated NMJs must have high fidelity to ensure consistent activation and continued contractile response to sustain vital motor behaviors (e.g., breathing and postural balance). Similarly, for higher force less frequent behaviors (e.g., coughing and jumping), the structure and function of recruited NMJs must ensure short-term reliable activation but not activation sustained for a prolonged period in which fatigue may occur. The NMJ is highly plastic, changing structurally and functionally throughout the life span from embryonic development to old age. The NMJ also changes under pathological conditions including acute and chronic disease. Such neuroplasticity often varies across motor unit types. © 2022 American Physiological Society. Compr Physiol 12:1-36, 2022.
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Affiliation(s)
- Leah A. Davis
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew J. Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Alyssa Brown
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C. Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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5
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Franco ML, García-Carpio I, Comaposada-Baró R, Escribano-Saiz JJ, Chávez-Gutiérrez L, Vilar M. TrkA-mediated endocytosis of p75-CTF prevents cholinergic neuron death upon γ-secretase inhibition. Life Sci Alliance 2021; 4:4/4/e202000844. [PMID: 33536237 PMCID: PMC7898468 DOI: 10.26508/lsa.202000844] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 01/11/2021] [Accepted: 01/11/2021] [Indexed: 12/13/2022] Open
Abstract
The findings shed light into the adverse effects of GSIs observed in the Alzheimer’s field and explain, at least in part, the unexpected worsening in cognition observed in the semagacestat Phase 3 trial. γ-secretase inhibitors (GSI) were developed to reduce the generation of Aβ peptide to find new Alzheimer’s disease treatments. Clinical trials on Alzheimer’s disease patients, however, showed several side effects that worsened the cognitive symptoms of the treated patients. The observed side effects were partially attributed to Notch signaling. However, the effect on other γ-secretase substrates, such as the p75 neurotrophin receptor (p75NTR) has not been studied in detail. p75NTR is highly expressed in the basal forebrain cholinergic neurons (BFCNs) during all life. Here, we show that GSI treatment induces the oligomerization of p75CTF leading to the cell death of BFCNs, and that this event is dependent on TrkA activity. The oligomerization of p75CTF requires an intact cholesterol recognition sequence (CRAC) and the constitutive binding of TRAF6, which activates the JNK and p38 pathways. Remarkably, TrkA rescues from cell death by a mechanism involving the endocytosis of p75CTF. These results suggest that the inhibition of γ-secretase activity in aged patients, where the expression of TrkA in the BFCNs is already reduced, could accelerate cholinergic dysfunction and promote neurodegeneration.
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Affiliation(s)
- María Luisa Franco
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Irmina García-Carpio
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Raquel Comaposada-Baró
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Juan J Escribano-Saiz
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
| | - Lucía Chávez-Gutiérrez
- Vlaams Instituut voor Biotechnologie Katholieke Universiteit (VIB-KU) Leuven Center for Brain and Disease, Leuven, Belgium
| | - Marçal Vilar
- Molecular Basis of Neurodegeneration Unit, Institute of Biomedicine of València (IBV-CSIC), València, Spain
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6
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Pérez V, Bermedo-Garcia F, Zelada D, Court FA, Pérez MÁ, Fuenzalida M, Ábrigo J, Cabello-Verrugio C, Moya-Alvarado G, Tapia JC, Valenzuela V, Hetz C, Bronfman FC, Henríquez JP. The p75 NTR neurotrophin receptor is required to organize the mature neuromuscular synapse by regulating synaptic vesicle availability. Acta Neuropathol Commun 2019; 7:147. [PMID: 31514753 PMCID: PMC6739937 DOI: 10.1186/s40478-019-0802-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 09/01/2019] [Indexed: 02/07/2023] Open
Abstract
The coordinated movement of organisms relies on efficient nerve-muscle communication at the neuromuscular junction. After peripheral nerve injury or neurodegeneration, motor neurons and Schwann cells increase the expression of the p75NTR pan-neurotrophin receptor. Even though p75NTR targeting has emerged as a promising therapeutic strategy to delay peripheral neuronal damage progression, the effects of long-term p75NTR inhibition at the mature neuromuscular junction have not been elucidated. We performed quantitative neuroanathomical analyses of the neuromuscular junction in p75NTR null mice by laser confocal and electron microscopy, which were complemented with electromyography, locomotor tests, and pharmacological intervention studies. Mature neuromuscular synapses of p75NTR null mice show impaired postsynaptic organization and ultrastructural complexity, which correlate with altered synaptic function at the levels of nerve activity-induced muscle responses, muscle fiber structure, force production, and locomotor performance. Our results on primary myotubes and denervated muscles indicate that muscle-derived p75NTR does not play a major role on postsynaptic organization. In turn, motor axon terminals of p75NTR null mice display a strong reduction in the number of synaptic vesicles and active zones. According to the observed pre and postsynaptic defects, pharmacological acetylcholinesterase inhibition rescued nerve-dependent muscle response and force production in p75NTR null mice. Our findings revealing that p75NTR is required to organize mature neuromuscular junctions contribute to a comprehensive view of the possible effects caused by therapeutic attempts to target p75NTR.
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Affiliation(s)
- Viviana Pérez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile
| | - Francisca Bermedo-Garcia
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile
| | - Diego Zelada
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile
| | - Felipe A Court
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor; FONDAP Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
| | - Miguel Ángel Pérez
- Laboratory of Neural Plasticity, Center for Neurobiology and Integrative Physiology, Faculty of Sciences, Institute of Physiology, Universidad de Valparaíso, Valparaíso, Chile
- Present Address: Health Sciences School, Universidad de Viña del Mar, Viña del Mar, Chile
| | - Marco Fuenzalida
- Laboratory of Neural Plasticity, Center for Neurobiology and Integrative Physiology, Faculty of Sciences, Institute of Physiology, Universidad de Valparaíso, Valparaíso, Chile
| | - Johanna Ábrigo
- Laboratory of Muscle Pathologies, Fragility and Aging, Department of Biological Sciences, Faculty of Life Sciences, Millennium Institute on Immunology and Immunotherapy, Universidad Andrés Bello, Santiago, Chile
| | - Claudio Cabello-Verrugio
- Laboratory of Muscle Pathologies, Fragility and Aging, Department of Biological Sciences, Faculty of Life Sciences, Millennium Institute on Immunology and Immunotherapy, Universidad Andrés Bello, Santiago, Chile
| | - Guillermo Moya-Alvarado
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Carlos Tapia
- Department of Biomedical Sciences, Faculty of Health Sciences, Universidad de Talca, Talca, Chile
| | - Vicente Valenzuela
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile
- Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Claudio Hetz
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile
- Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
- Buck Institute for Research on Aging, Novato, CA, 94945, USA
| | - Francisca C Bronfman
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile.
- Center for Aging and Regeneration (CARE), Institute of Biomedical Sciences (ICB), Faculty of Medicine and Faculty of Life Sciences, Universidad Andrés Bello, Santiago, Chile.
| | - Juan Pablo Henríquez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile.
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7
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McGregor CE, English AW. The Role of BDNF in Peripheral Nerve Regeneration: Activity-Dependent Treatments and Val66Met. Front Cell Neurosci 2019; 12:522. [PMID: 30687012 PMCID: PMC6336700 DOI: 10.3389/fncel.2018.00522] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/14/2018] [Indexed: 11/29/2022] Open
Abstract
Despite the ability of peripheral nerves to spontaneously regenerate after injury, recovery is generally very poor. The neurotrophins have emerged as an important modulator of axon regeneration, particularly brain derived neurotrophic factor (BDNF). BDNF regulation and signaling, as well as its role in activity-dependent treatments including electrical stimulation, exercise, and optogenetic stimulation are discussed here. The importance of a single nucleotide polymorphism in the BDNF gene, Val66Met, which is present in 30% of the human population and may hinder the efficacy of these treatments in enhancing regeneration after injury is considered. Preliminary data are presented on the effectiveness of one such activity-dependent treatment, electrical stimulation, in enhancing axon regeneration in mice expressing the met allele of the Val66Met polymorphism.
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Affiliation(s)
- Claire Emma McGregor
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Arthur W English
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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8
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Feter N, Penny J, Freitas M, Rombaldi A. Effect of physical exercise on hippocampal volume in adults: Systematic review and meta-analysis. Sci Sports 2018. [DOI: 10.1016/j.scispo.2018.02.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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9
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Abstract
Age-dependent declines in muscle function are observed across species. The loss of mobility resulting from the decline in muscle function represents an important health issue and a key determinant of quality of life for the elderly. It is believed that changes in the structure and function of the neuromuscular junction are important contributors to the observed declines in motor function with increased age. Numerous studies indicate that the aging muscle is an important contributor to the deterioration of the neuromuscular junction but the cellular and molecular mechanisms driving the degeneration of the synapse remain incompletely described. Importantly, growing data from both animal models and humans indicate that exercise can rejuvenate the neuromuscular junction and improve motor function. In this review we will focus on the role of muscle-derived neurotrophin signaling in the rejuvenation of the aged neuromuscular junction in response to exercise.
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Affiliation(s)
- Tabita Kreko-Pierce
- Department of Cellular and Integrative Physiology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.,Barshoph Institute of Longevity and Aging Studies, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA
| | - Benjamin A Eaton
- Department of Cellular and Integrative Physiology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA.,Barshoph Institute of Longevity and Aging Studies, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas, USA
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10
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p75NTR and TROY: Uncharted Roles of Nogo Receptor Complex in Experimental Autoimmune Encephalomyelitis. Mol Neurobiol 2018; 55:6329-6336. [PMID: 29294247 DOI: 10.1007/s12035-017-0841-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 12/14/2017] [Indexed: 12/11/2022]
Abstract
Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), have been on the forefront of drug discovery for most of the myelin inhibitory molecules implicated in axonal regenerative process. Nogo-A along with its putative receptor NgR and co-receptor LINGO-1 has paved the way for the production of pharmaceutical agents such as monoclonal antibodies, which are already put into handful of clinical trials. On the other side, little progress has been made towards clarifying the role of neurotrophin receptor p75 (p75NTR) and TROY in disease progression, other key players of the Nogo receptor complex. Previous work of our lab has shown that their exact location and type of expression is harmonized in a phase-dependent manner. Here, in this review, we outline their façade in normal and diseased central nervous system (CNS) and suggest a role for p75NTR in chronic axonal regeneration whereas TROY in acute inflammation of EAE intercourse.
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11
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Benítez-Temiño B, Davis-López de Carrizosa MA, Morcuende S, Matarredona ER, de la Cruz RR, Pastor AM. Functional Diversity of Neurotrophin Actions on the Oculomotor System. Int J Mol Sci 2016; 17:E2016. [PMID: 27916956 PMCID: PMC5187816 DOI: 10.3390/ijms17122016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/24/2016] [Accepted: 11/25/2016] [Indexed: 11/16/2022] Open
Abstract
Neurotrophins play a principal role in neuronal survival and differentiation during development, but also in the maintenance of appropriate adult neuronal circuits and phenotypes. In the oculomotor system, we have demonstrated that neurotrophins are key regulators of developing and adult neuronal properties, but with peculiarities depending on each neurotrophin. For instance, the administration of NGF (nerve growth factor), BDNF (brain-derived neurotrophic factor) or NT-3 (neurotrophin-3) protects neonatal extraocular motoneurons from cell death after axotomy, but only NGF and BDNF prevent the downregulation in ChAT (choline acetyltransferase). In the adult, in vivo recordings of axotomized extraocular motoneurons have demonstrated that the delivery of NGF, BDNF or NT-3 recovers different components of the firing discharge activity of these cells, with some particularities in the case of NGF. All neurotrophins have also synaptotrophic activity, although to different degrees. Accordingly, neurotrophins can restore the axotomy-induced alterations acting selectively on different properties of the motoneuron. In this review, we summarize these evidences and discuss them in the context of other motor systems.
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Affiliation(s)
- Beatriz Benítez-Temiño
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | | | - Sara Morcuende
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Esperanza R Matarredona
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
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12
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Greising SM, Stowe JM, Sieck GC, Mantilla CB. Role of TrkB kinase activity in aging diaphragm neuromuscular junctions. Exp Gerontol 2015; 72:184-91. [PMID: 26517952 DOI: 10.1016/j.exger.2015.10.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/23/2015] [Accepted: 10/26/2015] [Indexed: 11/30/2022]
Abstract
Brain derived neurotrophic factor (BDNF) acting through the tropomyosin-related kinase receptor B (TrkB) enhances neuromuscular transmission in the diaphragm muscle of adult mice, reflecting presynaptic effects. With aging, BDNF enhancement of neuromuscular transmission is lost. We hypothesize that disrupting BDNF/TrkB signaling in early old age will reveal a period of susceptibility evident by morphological changes at neuromuscular junctions (NMJ). Adult, male TrkB(F616A) mice (n=25) at 6 and 18 months of age, were used to examine the structural properties of diaphragm muscle NMJs (n=1097). Confocal microscopy was used to compare pre- and post-synaptic morphology and denervation following a 7 day treatment with the phosphoprotein phosphatase-1 derivative 1NMPP1, which inhibits TrkB kinase activity in TrkB(F616A) mice vs. vehicle treatment. In early old age (18 months), presynaptic terminal volume decreased compared to 6 month old diaphragm NMJs (~20%). Inhibition of TrkB kinase activity significantly decreased the presynaptic terminal volume (~20%) and motor end-plate 2D planar area (~10%), independent of age group. Inhibition of TrkB kinase activity in early old age significantly reduced overlap of pre- and post-synaptic structures and increased the proportion of denervated NMJs (to ~20%). Collectively these results support a period of susceptibility in early old age when BDNF/TrkB signaling at diaphragm NMJs supports the maintenance of NMJs structure and muscle innervation.
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Affiliation(s)
- Sarah M Greising
- Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | - Jessica M Stowe
- Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA; Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA; Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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13
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Meeker RB, Williams KS. The p75 neurotrophin receptor: at the crossroad of neural repair and death. Neural Regen Res 2015; 10:721-5. [PMID: 26109945 PMCID: PMC4468762 DOI: 10.4103/1673-5374.156967] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2015] [Indexed: 12/14/2022] Open
Abstract
The strong repair and pro-survival functions of neurotrophins at their primary receptors, TrkA, TrkB and TrkC, have made them attractive candidates for treatment of nervous system injury and disease. However, difficulties with the clinical implementation of neurotrophin therapies have prompted the search for treatments that are stable, easier to deliver and allow more precise regulation of neurotrophin actions. Recently, the p75 neurotrophin receptor (p75NTR) has emerged as a potential target for pharmacological control of neurotrophin activity, supported in part by studies demonstrating 1) regulation of neural plasticity in the mature nervous system, 2) promotion of adult neurogenesis and 3) increased expression in neurons, macrophages, microglia, astrocytes and/or Schwann cells in response to injury and neurodegenerative diseases. Although the receptor has no intrinsic catalytic activity it interacts with and modulates the function of TrkA, TrkB, and TrkC, as well as sortilin and the Nogo receptor. This provides substantial cellular and molecular diversity for regulation of neuron survival, neurogenesis, immune responses and processes that support neural function. Upregulation of the p75NTR under pathological conditions places the receptor in a key position to control numerous processes necessary for nervous system recovery. Support for this possibility has come from recent studies showing that small, non-peptide p75NTR ligands can selectively modify pro-survival and repair functions. While a great deal remains to be discovered about the wide ranging functions of the p75NTR, studies summarized in this review highlight the immense potential for development of novel neuroprotective and neurorestorative therapies.
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Affiliation(s)
- Rick B Meeker
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA
| | - Kimberly S Williams
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, USA
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14
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Greising SM, Ermilov LG, Sieck GC, Mantilla CB. Ageing and neurotrophic signalling effects on diaphragm neuromuscular function. J Physiol 2014; 593:431-40. [PMID: 25630263 DOI: 10.1113/jphysiol.2014.282244] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/23/2014] [Indexed: 12/22/2022] Open
Abstract
The age-related mechanisms underlying sarcopenia are largely unknown. We hypothesize that age-related neuromuscular changes depend on brain-derived neurotrophic factor (BDNF) acting through the tropomyosin-related kinase receptor B (TrkB). Maximal specific force and neuromuscular transmission failure were assessed at 6, 18 and 24 months following control, BDNF or phosphoprotein phosphatase 1 derivative (1NMPP1) treatment in male TrkB(F616A) mice. Phosphoprotein phosphatase-1 derivatives such as 1NMPP1 inhibit TrkB kinase activity as a result of this single amino acid mutation in the ATP binding domain. Maximal twitch and isometric tetanic force were reduced at 24 months compared to 6 and 18 months (P < 0.001). Neuromuscular transmission failure significantly increased at 18 and 24 months compared to 6 months (age × treatment interaction: P < 0.001). Neuromuscular transmission was improved following BDNF at 6 and 18 months and was impaired only at 6 months following 1NMPP1 treatment. Age and inhibition of TrkB kinase activity had similar effects on neuromuscular transmission failure, supporting a critical role for BDNF/TrkB signalling on neuromuscular changes in ageing. These results suggest that an age-related loss of endogenous BDNF precedes reductions in TrkB kinase activity in the diaphragm muscle.
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Affiliation(s)
- Sarah M Greising
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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15
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McCullough MJ, Gyorkos AM, Spitsbergen JM. Short-term exercise increases GDNF protein levels in the spinal cord of young and old rats. Neuroscience 2013; 240:258-68. [PMID: 23500094 DOI: 10.1016/j.neuroscience.2013.02.063] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/12/2013] [Accepted: 02/27/2013] [Indexed: 12/29/2022]
Abstract
Neurotrophic factors may play a role in exercise-induced neuroprotective effects, however it is not known if exercise mediates changes in glial cell line-derived neurotrophic factor (GDNF) protein levels in the spinal cord. The aim of the current study was to determine if 2 weeks of exercise alters GDNF protein content in the lumbar spinal cord of young and old rats. GDNF protein was quantified via an enzyme-linked immunosorbent assay and Western blot. Immunohistochemical analysis localized GDNF in choline acetyltransferase (ChAT)-positive motor neurons and cell body areas were measured. Involuntary running in the young animals appeared to elicit the greatest increase in GDNF protein content (sixfold increase), followed by swimming (threefold increase) and voluntary running (twofold increase); however there was no significant difference between the modalities of exercise. Low-intensity running of the old animals significantly increased GDNF protein content in the spinal cord. Both young and old exercised animals showed a doubling in ChAT-positive motor neuron cell body areas. These results suggest that GDNF protein content in the spinal cord is modulated by exercise.
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Affiliation(s)
- M J McCullough
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI 49008-5410, USA.
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16
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Taylor AR, Gifondorwa DJ, Robinson MB, Strupe JL, Prevette D, Johnson JE, Hempstead BL, Oppenheim RW, Milligan CE. Motoneuron programmed cell death in response to proBDNF. Dev Neurobiol 2012; 72:699-712. [PMID: 21834083 PMCID: PMC3233653 DOI: 10.1002/dneu.20964] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Motoneurons (MN) as well as most neuronal populations undergo a temporally and spatially specific period of programmed cell death (PCD). Several factors have been considered to regulate the survival of MNs during this period, including availability of muscle-derived trophic support and activity. The possibility that target-derived factors may also negatively regulate MN survival has been considered, but not pursued. Neurotrophin precursors, through their interaction with p75(NTR) and sortilin receptors have been shown to induce cell death during development and following injury in the CNS. In this study, we find that muscle cells produce and secrete proBDNF. ProBDNF through its interaction with p75(NTR) and sortilin, promotes a caspase-dependent death of MNs in culture. We also provide data to suggest that proBDNF regulates MN PCD during development in vivo.
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Affiliation(s)
- AR Taylor
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - DJ Gifondorwa
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - MB Robinson
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - JL Strupe
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - D Prevette
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - JE Johnson
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
| | - BL Hempstead
- Department of Medicine Cornell University Medical Center, NY
| | - RW Oppenheim
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
- Interdisciplinary Neuroscience Program, Wake Forest University School of Medicine Winston-Salem, NC
- ALS Center, Wake Forest University School of Medicine Winston-Salem, NC
| | - CE Milligan
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine Winston-Salem, NC
- Interdisciplinary Neuroscience Program, Wake Forest University School of Medicine Winston-Salem, NC
- ALS Center, Wake Forest University School of Medicine Winston-Salem, NC
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17
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Morcuende S, Matarredona ER, Benítez-Temiño B, Muñoz-Hernández R, Pastor AM, de la Cruz RR. Differential regulation of the expression of neurotrophin receptors in rat extraocular motoneurons after lesion. J Comp Neurol 2011; 519:2335-52. [PMID: 21456016 DOI: 10.1002/cne.22630] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Neurotrophins acting through high-affinity tyrosine kinase receptors (trkA, trkB, and trkC) play a crucial role in regulating survival and maintenance of specific neuronal functions after injury. Adult motoneurons supplying extraocular muscles survive after disconnection from the target, but suffer dramatic changes in morphological and physiological properties, due in part to the loss of their trophic support from the muscle. To investigate the dependence of the adult rat extraocular motoneurons on neurotrophins, we examined trkA, trkB, and trkC mRNA expression after axotomy by in situ hybridization. trkA mRNA expression was detectable at low levels in unlesioned motoneurons, and its expression was downregulated 1 and 3 days after injury. Expression of trkB and trkC mRNAs was stronger, and after axotomy a simultaneous, but inverse regulation of both receptors was observed. Thus, whereas a considerable increase in trkB expression was seen about 2 weeks after axotomy, the expression of trkC mRNA had decreased at the same post-lesion period. Injured extraocular motoneurons also experienced an initial induction in expression of calcitonin gene-related peptide and a transient downregulation of cholinergic characteristics, indicating a switch in the phenotype from a transmitter-specific to a regenerative state. These results suggest that specific neurotrophins may contribute differentially to the survival and regenerative responses of extraocular motoneurons after lesion.
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Affiliation(s)
- Sara Morcuende
- Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
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18
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Schaser AJ, Stang K, Connor NP, Behan M. The effect of age and tongue exercise on BDNF and TrkB in the hypoglossal nucleus of rats. Behav Brain Res 2011; 226:235-41. [PMID: 21951697 DOI: 10.1016/j.bbr.2011.09.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 09/14/2011] [Indexed: 11/30/2022]
Abstract
Age-associated changes in tongue musculature may contribute to dysphagia. One possible treatment is tongue exercise. Exercise induces synaptic plasticity by increasing neurotrophic factors in spinal cord and limb musculature. However, effects of exercise on neurotrophic factors in the cranial sensorimotor system are unknown. Our purpose was to examine the effects of age and exercise on brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the rat hypoglossal nucleus. Young, middle-aged, and old rats were assigned to exercise or no-exercise control conditions. Exercise animals were trained to perform a tongue press task for 8 weeks. Samples from the hypoglossal nucleus were analyzed for BDNF and TrkB immunoreactivity. Baseline maximum tongue forces were similar in all age groups and increased significantly following exercise. BDNF immunoreactivity did not show a significant decrease with age in control group. However, in the exercise group, BDNF was significantly increased in young animals. TrkB immunoreactivity decreased significantly with age in control group, but did not change with exercise. BDNF and TrkB immunoreactivity levels were positively correlated with exercise in young and middle aged animals, but were negatively or weakly correlated with exercise in old animals and with a lack of exercise in no-exercise controls. Tongue exercise was associated with increased tongue forces in rats at all ages. While increases in BDNF and TrkB levels associated with exercise may play a role in mechanisms contributing to increased tongue forces in young and middle-aged rats, other mechanisms may be involved in increased tongue forces observed in old rats.
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Affiliation(s)
- Allison J Schaser
- Department of Surgery, University of Wisconsin-Madison, WI 53706, USA.
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19
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Petruska JC, Kitay B, Boyce VS, Kaspar BK, Pearse DD, Gage FH, Mendell LM. Intramuscular AAV delivery of NT-3 alters synaptic transmission to motoneurons in adult rats. Eur J Neurosci 2010; 32:997-1005. [PMID: 20849530 DOI: 10.1111/j.1460-9568.2010.07392.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We examined whether elevating levels of neurotrophin-3 (NT-3) in the spinal cord and dorsal root ganglion (DRG) would alter connections made by muscle spindle afferent fibers on motoneurons. Adeno-associated virus (AAV) serotypes AAV1, AAV2 and AAV5, selected for their tropism profile, were engineered with the NT-3 gene and administered to the medial gastrocnemius muscle in adult rats. ELISA studies in muscle, DRG and spinal cord revealed that NT-3 concentration in all tissues peaked about 3 months after a single viral injection; after 6 months NT-3 concentration returned to normal values. Intracellular recording in triceps surae motoneurons revealed complex electrophysiological changes. Moderate elevation in cord NT-3 resulted in diminished segmental excitatory postsynaptic potential (EPSP) amplitude, perhaps as a result of the observed decrease in motoneuron input resistance. With further elevation in NT-3 expression, the decline in EPSP amplitude was reversed, indicating that NT-3 at higher concentration could increase EPSP amplitude. No correlation was observed between EPSP amplitude and NT-3 concentration in the DRG. Treatment with control viruses could elevate NT-3 levels minimally resulting in measurable electrophysiological effects, perhaps as a result of inflammation associated with injection. EPSPs elicited by stimulation of the ventrolateral funiculus underwent a consistent decline in amplitude independent of NT-3 level. These novel correlations between modified NT-3 expression and single-cell electrophysiological parameters indicate that intramuscular administration of AAV(NT-3) can exert long-lasting effects on synaptic transmission to motoneurons. This approach to neurotrophin delivery could be useful in modifying spinal function after injury.
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Affiliation(s)
- Jeffrey C Petruska
- Department of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794, USA
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20
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Nerve growth factor regulates the firing patterns and synaptic composition of motoneurons. J Neurosci 2010; 30:8308-19. [PMID: 20554882 DOI: 10.1523/jneurosci.0719-10.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Target-derived neurotrophins exert powerful synaptotrophic actions in the adult brain and are involved in the regulation of different forms of synaptic plasticity. Target disconnection produces a profound synaptic stripping due to the lack of trophic support. Consequently, target reinnervation leads to synaptic remodeling and restoration of cellular functions. Extraocular motoneurons are unique in that they normally express the TrkA neurotrophin receptor in the adult, a feature not seen in other cranial or spinal motoneurons, except after lesions such as axotomy or in neurodegenerative diseases like amyotrophic lateral sclerosis. We investigated the effects of nerve growth factor (NGF) by retrogradely delivering this neurotrophin to abducens motoneurons of adult cats. Axotomy reduced the density of somatic boutons and the overall tonic and phasic firing modulation. Treatment with NGF restored synaptic inputs and firing modulation in axotomized motoneurons. When K252a, a selective inhibitor of tyrosine kinase activity, was applied to specifically test TrkA effects, the NGF-mediated restoration of synapses and firing-related parameters was abolished. Discharge variability and recruitment threshold were, however, increased by NGF compared with control or axotomized motoneurons. Interestingly, these parameters returned to normal following application of REX, an antibody raised against neurotrophin receptor p75 (p75(NTR)). In conclusion, NGF, acting retrogradely through TrkA receptors, supports afferent boutons and regulates the burst and tonic signals correlated with eye movements. On the other hand, p75(NTR) activation regulates recruitment threshold, which impacts on firing regularity. To our knowledge, this is the first report showing powerful synaptotrophic effects of NGF on motoneurons in vivo.
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21
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Verhovshek T, Cai Y, Osborne MC, Sengelaub DR. Androgen regulates brain-derived neurotrophic factor in spinal motoneurons and their target musculature. Endocrinology 2010; 151:253-61. [PMID: 19880806 PMCID: PMC2803156 DOI: 10.1210/en.2009-1036] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Trophic factors maintain motoneuron morphology and function in adulthood. Brain-derived neurotrophic factor (BDNF) interacts with testosterone to maintain dendritic morphology of spinal motoneurons. In addition, testosterone regulates BDNF's receptor (trkB) in motoneurons innervating the quadriceps muscles as well as in motoneurons of the highly androgen-sensitive spinal nucleus of the bulbocavernosus (SNB). Given these interactive effects, we examined whether androgen might also regulate BDNF in quadriceps and SNB motoneurons and their corresponding target musculature. In both motoneuron populations, castration of males reduced BDNF immunolabeling, and this effect was prevented with testosterone replacement. ELISA for BDNF in the target musculature of quadriceps (vastus lateralis, VL) and SNB (bulbocavernosus, BC) motoneurons revealed that BDNF in the VL and BC muscles was also regulated by androgen. However, although castration significantly decreased BDNF concentration in the VL muscle, BDNF concentration in the BC muscle was significantly increased in castrates. Treatment of castrated males with testosterone maintained BDNF levels at those of intact males in both sets of muscles. Together, these results demonstrate that androgens regulate BDNF in both a sexually dimorphic, highly androgen-sensitive neuromuscular system as well as a more typical somatic neuromuscular system. Furthermore, in addition to the regulation of trkB, these studies provide another possible mechanism for the interactive effects of testosterone and BDNF on motoneuron morphology. More importantly, by examining both the motoneurons and the muscles they innervate, these results demonstrate that within a neural system, BDNF levels in different components are differentially affected by androgen manipulation.
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Affiliation(s)
- Tom Verhovshek
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, USA
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22
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The role of brain-derived neurotrophic factor in different animal models of neuropathic pain. Eur J Pain 2009; 14:473.e1-9. [PMID: 19959385 DOI: 10.1016/j.ejpain.2009.09.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 09/22/2009] [Accepted: 09/29/2009] [Indexed: 12/20/2022]
Abstract
Even in present day pain therapy, neuropathic pain remains a challenge for clinicians to treat and a challenge for researchers to investigate. Different animal models have been developed to mimic neuropathic pain. Neurotrophins such as nerve growth factor, brain-derived neurotrophic factor and neurotrophin 3 have been studied extensively in these models, yet few review articles concerning brain-derived neurotrophic factor have been published. This article reassesses the literature concerning brain-derived neurotrophic factor expression in the sciatic nerve chronic constriction injury model, the sciatic nerve transection model, the spinal nerve ligation model and the spinal nerve transection model and discusses differences in regulation of brain-derived neurotrophic factor between these models and their causality with neuropathic pain.
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23
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Receptor tyrosine kinases and respiratory motor plasticity. Respir Physiol Neurobiol 2009; 164:242-51. [PMID: 18634908 DOI: 10.1016/j.resp.2008.06.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 06/13/2008] [Accepted: 06/18/2008] [Indexed: 11/23/2022]
Abstract
Protein kinases are a family of enzymes that transfer a phosphate group from adenosine tri-phosphate to an amino acid residue on a protein. The receptor tyrosine kinases (RTKs) are expressed on the outer cell membrane, bind extracellular protein ligands, and phosphorylate tyrosine residues on other proteins-essentially permitting communication between cells. Such activity regulates multiple aspects of cellular physiology including cell growth and differentiation, adhesion, motility, cell death, and morphological and synaptic plasticity. This review will focus on the role of RTKs in respiratory motor plasticity, with particular emphasis on long-term changes in respiratory motoneuron function. Reflecting the predominant literature, specific attention will be devoted to the role of tropomyosin-related kinase type B (TrkB) activation on phrenic motoneuron activity. However, many RTKs share similar patterns of expression and mechanisms of ligand-induced activation and downstream signaling. Thus, a perspective based on TrkB-induced phrenic motor plasticity may provide insight into the potential roles of other RTKs in the neural control of breathing. Finally, understanding how different RTKs affect respiratory motor output in the long-term may provide future avenues for pharmacological development with the goal of increasing respiratory motor output in disorders such as obstructive sleep apnea and after spinal cord injury. This is best illustrated in recent studies where we have used small, highly diffusible molecules to transactivate TrkB receptors near phrenic motoneurons to improve breathing after cervical spinal cord injury.
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24
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Keast JR, Kepper ME. Differential regulation of trkA and p75 in noradrenergic pelvic autonomic ganglion cells after deafferentation of their cholinergic neighbours. Eur J Neurosci 2008. [DOI: 10.1111/j.1460-9568.2001.01374.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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25
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Li H, Costantini C, Scrable H, Weindruch R, Puglielli L. Egr-1 and Hipk2 are required for the TrkA to p75(NTR) switch that occurs downstream of IGF1-R. Neurobiol Aging 2008; 30:2010-20. [PMID: 18378044 DOI: 10.1016/j.neurobiolaging.2008.02.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 02/14/2008] [Accepted: 02/14/2008] [Indexed: 02/07/2023]
Abstract
The aging program mediated by IGF1-R is responsible for a naturally occurring TrkA to p75(NTR) switch that leads to activation of the second messenger ceramide and increased production of the Alzheimer's disease amyloid beta-peptide. Biochemical and genetic approaches that target IGF1-R signaling, p75(NTR), or ceramide are able to block the above events. Here, we show that the transcription factors Egr-1 and Hipk2 are required elements for the TrkA to p75(NTR) switch downstream of IGF1-R signaling. Specifically, Egr-1 is required for the upregulation of p75(NTR), whereas Hipk2 is required for the downregulation of TrkA. In fact, gene silencing of Egr-1 abolished the ability of IGF1 to upregulate p75(NTR), whereas similar approaches directed against Hipk2 blocked the downregulation of TrkA. In addition, IGF1 treatment favored binding of Egr-1 and Hipk2 to the promoter of p75(NTR) and TrkA, respectively. Finally, the expression levels of both Egr-1 and Hipk2 are upregulated in an age-dependent fashion. Such an event is opposed by caloric restriction, a model of delayed aging, and favored by the p44 transgene in p44(+/+) animals, a model of accelerated aging.
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Affiliation(s)
- Hui Li
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
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26
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Edström E, Altun M, Bergman E, Johnson H, Kullberg S, Ramírez-León V, Ulfhake B. Factors contributing to neuromuscular impairment and sarcopenia during aging. Physiol Behav 2007; 92:129-35. [PMID: 17585972 DOI: 10.1016/j.physbeh.2007.05.040] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Motor disturbances and wasting of skeletal muscles (sarcopenia) causes significant impairment of daily life activities and is a major underlying cause for hospitalization in senescence. Herein we review data and present new findings on aging-specific changes in motoneurons, skeletal muscle and the interplay between motoneurons and target muscle fibers. Although many of the changes occurring during aging may be specific to motoneurons and myofibers, respectively, evidence indicates that myofiber regeneration in sarcopenic muscle is halted at the point where reinnervation is critical for the final differentiation into mature myofibers. Combined, evidence suggests that sarcopenia to a significant extent depend on a decreased capacity among motoneurons to innervate regenerating fibers. There are also conspicuous changes in the expression of several cytokines known to play important roles in establishing and maintaining neuromuscular connectivity during development and adulthood. We also present data showing the usefulness of rodent models in studies of successful and unsuccessful patterns of aging. Finally, we show that not only dietary restriction (DR) but also activity and social environment may modulate the pattern of aging.
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Affiliation(s)
- Erik Edström
- Karolinska Institutet, Department of Neuroscience, Retzius Laboratory, S-171 77 Stockholm, Sweden
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27
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Osborne MC, Verhovshek T, Sengelaub DR. Androgen regulates trkB immunolabeling in spinal motoneurons. J Neurosci Res 2007; 85:303-9. [PMID: 17131419 DOI: 10.1002/jnr.21122] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Neurotrophic factors and steroid hormones have been shown to have neuroprotective/neurotherapeutic effects, and it has been shown previously that brain-derived neurotrophic factor (BDNF) and testosterone have a combinatorial effect in the maintenance of motoneurons. Given that gonadal hormones regulate the BDNF receptor, tyrosine receptor kinase B (trkB), we hypothesized that such a regulatory effect could mediate the interactive effects of BDNF and testosterone. Using immunohistochemical methods, we examined the frequency of cells immunolabeled for trkB receptors in two populations of spinal motoneurons, the hormone-sensitive, sexually dimorphic motoneurons of the spinal nucleus of the bulbocavernosus (SNB) and the nondimorphic motoneurons innervating the muscles of the quadriceps. In both the highly androgen-sensitive SNB motoneurons and the more typical somatic motoneurons innervating the quadriceps, the frequency of motoneurons intensely immunolabeled for trkB receptors was regulated by the presence of testosterone. Castrated animals deprived of testosterone showed a reduced frequency of intensely labeled motoneurons compared with intact animals or castrated animals given testosterone replacement. This finding suggests that the combinatorial effect of BDNF and testosterone in the maintenance of motoneurons could occur at least in part through an androgen-mediated expression of the BDNF receptor.
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Affiliation(s)
- M C Osborne
- Department of Psychological and Brain Sciences and Program in Neuroscience, Indiana University, Bloomington, Indiana 47405, USA
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28
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Puglielli L. Aging of the brain, neurotrophin signaling, and Alzheimer's disease: is IGF1-R the common culprit? Neurobiol Aging 2007; 29:795-811. [PMID: 17313996 PMCID: PMC2387053 DOI: 10.1016/j.neurobiolaging.2007.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 09/21/2006] [Accepted: 01/13/2007] [Indexed: 12/26/2022]
Abstract
The last decade has revealed that the lifespan of an organism can be modulated by the signaling pathway that acts downstream of the insulin/insulin-like growth factor 1 receptors (IR/IGF1-R), indicating that there is a "program" that drives the process of aging. New results have now linked the same pathway to the neurogenic capacities of the aging brain, to neurotrophin signaling, and to the molecular pathogenesis of Alzheimer's disease. Therefore, a common signaling cascade now seems to link aging to age-associated pathologies of the brain, suggesting that pharmacologic approaches aimed at the modulation of this pathway can serve to delay the onset of age-associated disorders and improve the quality of life. Work from a wide range of fields performed with different approaches has already identified some of the signaling molecules that act downstream of IGF1-R, and has revealed that a delicate checkpoint exists to balance excessive growth/"immortality" and reduced growth/"senescence" of a cell. Future research will determine how far the connection goes and how much of it we can influence.
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Affiliation(s)
- Luigi Puglielli
- Department of Medicine, University of Wisconsin-Madison, and Geriatric Research Education Clinical Center, VA Medical Center, VAH-GRECC 11G, 2500 Overlook Terrace, Madison, WI 53705, USA.
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29
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Sohrabji F, Lewis DK. Estrogen-BDNF interactions: implications for neurodegenerative diseases. Front Neuroendocrinol 2006; 27:404-14. [PMID: 17069877 PMCID: PMC1828910 DOI: 10.1016/j.yfrne.2006.09.003] [Citation(s) in RCA: 213] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2006] [Revised: 07/24/2006] [Accepted: 09/01/2006] [Indexed: 01/08/2023]
Abstract
Since its' discovery over 20 years ago, BDNF has been shown to play a key role in neuronal survival, in promoting neuronal regeneration following injury, regulating transmitter systems and attenuating neural-immune responses. Estrogen's actions in the young and mature brain, and its role in neurodegenerative diseases in many cases overlaps with those observed for BDNF. Reduced estrogen and BDNF are observed in patients with Parkinson's disease and Alzheimer's disease, while high estrogen levels are a risk factor for development of multiple sclerosis. Estrogen receptors, which transduce the actions of estrogen, colocalize to cells that express BDNF and its receptor trkB, and estrogen further regulates the expression of this neurotrophin system. This review describes the distribution of BDNF and trkB expressing cells in the forebrain, and the roles of estrogen and the BDNF-trkB neurotrophin system in Parkinson's disease, Alzheimer's disease and multiple sclerosis.
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Affiliation(s)
- Farida Sohrabji
- Department of Neuroscience and Experimental Therapeutics, TAMU Health Science Center, College Station, TX 77843-1114, USA.
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30
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Costantini C, Weindruch R, Della Valle G, Puglielli L. A TrkA-to-p75NTR molecular switch activates amyloid beta-peptide generation during aging. Biochem J 2006; 391:59-67. [PMID: 15966860 PMCID: PMC1237139 DOI: 10.1042/bj20050700] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Aging is the single most important risk factor for AD (Alzheimer's disease). However, the molecular events that connect normal aging to AD are mostly unknown. The abnormal accumulation of Abeta (amyloid beta-peptide) in the form of senile plaques is one of the main characteristics of AD. In the present study, we show that two members of the neurotrophin receptor superfamily, TrkA (tyrosine kinase receptor A) and p75NTR (p75 neurotrophin receptor), differentially regulate the processing of APP (amyloid precursor protein): TrkA reduces, whereas p75NTR activates, beta-cleavage of APP. The p75NTR-dependent effect requires NGF (nerve growth factor) binding and activation of the second messenger ceramide. We also show that normal aging activates Abeta generation in the brain by 'switching' from the TrkA to the p75NTR receptor system. Such an effect is abolished in p75NTR 'knockout' animals, and can be blocked by both caloric restriction and inhibitors of nSMase (neutral sphingomyelinase). In contrast with caloric restriction, which prevents the age-associated up-regulation of p75NTR expression, nSMase inhibitors block the activation of ceramide. When taken together, these results indicate that the p75NTR-ceramide signalling pathway activates the rate of Abeta generation in an age-dependent fashion, and provide a new target for both the understanding and the prevention of late-onset AD.
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Affiliation(s)
- Claudio Costantini
- *Department of Medicine, University of Wisconsin-Madison, Wm. S. Middleton Memorial Veteran's Hospital, Madison, WI 53705, U.S.A
| | - Richard Weindruch
- *Department of Medicine, University of Wisconsin-Madison, Wm. S. Middleton Memorial Veteran's Hospital, Madison, WI 53705, U.S.A
| | | | - Luigi Puglielli
- *Department of Medicine, University of Wisconsin-Madison, Wm. S. Middleton Memorial Veteran's Hospital, Madison, WI 53705, U.S.A
- To whom correspondence should be addressed (email )
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Barrett GL, Greferath U, Barker PA, Trieu J, Bennie A. Co-expression of the P75 neurotrophin receptor and neurotrophin receptor-interacting melanoma antigen homolog in the mature rat brain. Neuroscience 2005; 133:381-92. [PMID: 15878242 DOI: 10.1016/j.neuroscience.2005.01.067] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2003] [Revised: 11/02/2004] [Accepted: 01/19/2005] [Indexed: 12/26/2022]
Abstract
The p75 neurotrophin receptor (p75(NTR)) is involved in the regulation of neuronal survival and phenotype, but its signal transduction mechanisms are poorly understood. Recent evidence has implicated the cytoplasmic protein NRAGE (neurotrophin receptor-interacting MAGE (from Melanoma AntiGEn) homolog) in p75(NTR) signaling. To gain further insight into the role of NRAGE, we investigated the co-expression of NRAGE and p75(NTR) in mature rat brain. In all areas examined, NRAGE appeared to be confined to neurons. In the basal forebrain cholinergic complex, NRAGE immunoreactivity was evident in all p75(NTR)-positive neurons. There were many more NRAGE-positive than p75(NTR)-positive neurons in these regions, however. NRAGE was also expressed in areas of the basal forebrain that did not express p75(NTR), including the lateral septal nucleus and the nucleus accumbens. A finding in marked contrast to previous studies was the presence of p75(NTR) immunoreactivity in neuronal cell bodies in the hippocampus. Hippocampal p75(NTR) immunoreactivity was apparent in rats 6 months and older, and was localized to the dentate gyrus and stratum oriens. All p75(NTR)-positive neurons in the dentate gyrus and hippocampal formation were positive for NRAGE. The majority of granular cells of the dentate gyrus and pyramidal cells in the hippocampal formation were positive for NRAGE and negative for p75(NTR). NRAGE was also present in some neuronal populations that express p75(NTR) after injury, including striatal cholinergic interneurons, and motor neurons. A region of marked disparity was the cerebral cortex, in which NRAGE immunoreactivity was widespread whereas p75(NTR) was absent. The results are consistent with an important role for NRAGE in p75(NTR) signaling, as all cells that expressed p75(NTR) also expressed NRAGE. The wider distribution of NRAGE expression suggests that NRAGE may also participate in other signaling processes.
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Affiliation(s)
- G L Barrett
- Department of Physiology, University of Melbourne, Parkville 3010, Australia.
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Jiang X, Edstrom E, Altun M, Ulfhake B. Differential regulation of Shc adaptor proteins in skeletal muscle, spinal cord and forebrain of aged rats with sensorimotor impairment. Aging Cell 2003; 2:47-57. [PMID: 12882334 DOI: 10.1046/j.1474-9728.2003.00030.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The Shc family of proteins participates in mitogenic and survival signalling through binding to receptor tyrosine kinases. We report here on the expression of Shc in forebrain, spinal cord and hind limb muscles from 30-month-old rats with different degrees of sensorimotor impairment. ShcA (mRNA and protein) is up-regulated in skeletal muscles and spinal cord of aged rats, and this change relates to biological age, i.e. degree of behavioural incapacitation, rather than to chronological age. Western blot and RT-PCR revealed that the increase in ShcA selectively affected the p46 isoform in the spinal cord, whereas in muscle tissue a robust increase of p66(ShcA) was also evident. Furthermore, in parallel with the up-regulation of ShcA, an increase of p75(NTR) mRNA in the aged animals was observed. ShcB mRNA showed a tendency for down-regulation in both spinal cord and skeletal muscles, whereas the expression of ShcC was unaltered. Our data show that the regulation of Shc mRNAs in senescence is region as well as isoform specific. The regulatory changes may reflect changes in mitogenic/survival signalling induced by age-related cell and tissue damage. The coup-regulation of p66(ShcA) and p75(NTR) is interesting since both molecules have been associated with apoptosis.
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Affiliation(s)
- Xiaogang Jiang
- Experimental Neurogerontology, Department of Neuroscience, Retzius Laboratory, Karolinska Institutet, 171 77 Stockholm, Sweden
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Abstract
Impaired sensory perception is a well-established stigma of aging and whereas loss of dorsal root ganglion (DRG) neurons is marginal there is a specific pattern of reduced peripheral sensory innervation. To resolve if similar regressive processes occur in the central innervation, peripheral nerves were injected with markers for unmyelinated (isolectin B4) or myelinated (cholera toxin B subunit; CTB) DRG neurons. The results were a dramatic decrease of primary sensory endings in the spinal cord of aged rats following transganglionic labeling with CTB, and also to a lesser degree with B4. Profile counting and frequency estimates showed that the reduction of CTB labeled profiles not was caused by impaired axonal uptake, slowed axonal transport of CTB, or by a loss of myelinated fibers in the peripheral nerve. At the ultrastructural level, peripheral nerves showed the classical hallmarks of aging, with more pronounced alterations in myelinated than unmyelinated axons. Taken together, sensory deprivation in senescence appears to be a distal process in DRG neurons involving both peripheral and central target disconnection. Finally, preliminary data indicates that the substantial reduction in mechanoreceptive input to the central nervous system co-varies with the degree of sensorimotor impairment of the aged individuals.
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Affiliation(s)
- Esbjörn Bergman
- Department of Neuroscience, Karolinska Institutet, S-171 77, Stockholm, Sweden.
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Simon M, Mann D, Coulton G, Terenghi G. Differential tyrosine kinase C mRNA distribution in extensor digitorum longus and soleus motoneurons in adult rats: effect of axotomy and neurotrophin-3 treatment. Neurosci Lett 2002; 320:9-12. [PMID: 11849751 DOI: 10.1016/s0304-3940(02)00007-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Delivery of neurotrophin-3 (NT-3) to severed sciatic nerves results in specific normalization of atrophied fast 2b gastrocnemius muscle fibres, and promotes preferential neuromuscular junction maturation of fast extensor digitorum longus (EDL). To investigate the selective influence on fast muscle reinnervation due to NT-3 delivery, we analyzed tyrosine kinase C (trkC) mRNA differential expression in EDL and slow soleus motor pools of unoperated rats and at 1-week post-axotomy. Motoneurons (Mns) were identified using retrograde tracers. TrkC mRNA quantification was estimated by silver grain counting. TrkC mRNA expression was higher in EDL than in soleus Mns in unoperated rats. Axotomy decreased trkC mRNA expression only in EDL Mns, this downregulation being prevented by NT-3. These results suggest that differential expression of trkC receptor is the morphological correlate of the preferential effect of NT-3 upon EDL Mns.
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MESH Headings
- Animals
- Axotomy
- Cell Communication/drug effects
- Cell Communication/physiology
- Down-Regulation/drug effects
- Down-Regulation/physiology
- Male
- Motor Neurons/cytology
- Motor Neurons/drug effects
- Motor Neurons/metabolism
- Muscle Fibers, Fast-Twitch/cytology
- Muscle Fibers, Fast-Twitch/enzymology
- Muscle Fibers, Slow-Twitch/cytology
- Muscle Fibers, Slow-Twitch/enzymology
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/innervation
- Nerve Regeneration/drug effects
- Nerve Regeneration/physiology
- Neuromuscular Junction/cytology
- Neuromuscular Junction/drug effects
- Neuromuscular Junction/enzymology
- Neurotrophin 3/metabolism
- Neurotrophin 3/pharmacology
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred Lew
- Receptor, trkC/genetics
- Sciatic Nerve/cytology
- Sciatic Nerve/drug effects
- Sciatic Nerve/metabolism
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Affiliation(s)
- Magda Simon
- Blond McIndoe Centre, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, UK
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Viidik A. Experimental gerontology in the Nordic countries. Exp Gerontol 2001; 36:383-401. [PMID: 11250112 DOI: 10.1016/s0531-5565(00)00251-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Research in geriatric medicine developed in the Nordic countries in the 1950s, following the tradition from the United Kingdom. Quite early, longitudinal epidemiological studies of 'normal' ageing emerged. Now there are chairs in geriatric medicine at many of the medical schools. Experimental gerontology came much later, typically scattered in a variety of medical school departments. There is only one chair in gerontology (in Tampere). Two major research undertakings have emerged in recent years, the Danish Centre for Molecular Gerontology, and a cluster of research groups at the Division of Geriatrics at the Karolinska Institutet. Other research groups are found in Denmark at the universities in Aarhus, Copenhagen and Odense; in Finland at the universities in Jyväskylä, Kuopio, Tampere and Turku; and in Norway at the university in Trondheim. These activities are reviewed country-wise.
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Affiliation(s)
- A Viidik
- Institute of Anatomy, University of Aarhus, Universitetsparken, Bygning 230, DK-8000 C, Aarhus, Denmark.
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Keast JR, Kepper ME. Differential regulation of trkA and p75 in noradrenergic pelvic autonomic ganglion cells after deafferentation of their cholinergic neighbours. Eur J Neurosci 2001. [DOI: 10.1046/j.1460-9568.2001.01374.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Ulfhake B, Bergman E, Edstrom E, Fundin BT, Johnson H, Kullberg S, Ming Y. Regulation of neurotrophin signaling in aging sensory and motoneurons: dissipation of target support? Mol Neurobiol 2000; 21:109-35. [PMID: 11379795 DOI: 10.1385/mn:21:3:109] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A hallmark of senescence is sensorimotor impairment, involving locomotion and postural control as well as fine-tuned movements. Sensory and motoneurons are not lost to any significant degree with advancing age, but do show characteristic changes in gene-expression pattern, morphology, and connectivity. This review covers recent experimental findings corroborating that alterations in trophic signaling may induce several of the phenotypic changes seen in primary sensory and motoneurons during aging. Furthermore, the data suggests that target failure, and/or breakdown of neuron-target interaction, is a critical event in the aging process of sensory and motoneurons.
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Affiliation(s)
- B Ulfhake
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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Ming Y, Bergman E, Edström E, Ulfhake B. Reciprocal changes in the expression of neurotrophin mRNAs in target tissues and peripheral nerves of aged rats. Neurosci Lett 1999; 273:187-90. [PMID: 10515190 DOI: 10.1016/s0304-3940(99)00655-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
trk receptors are downregulated in both dorsal root ganglion (DRG) and spinal motoneurons of aged rats with behavioral sensorimotor deficits. Here we provide evidence, using reverse transcription-polymerase chain reaction (RT-PCR), of decreased levels of neurotrophin (nerve growth factor, NGF; brain-derived neurotrophic factor, BDNF; neurotrophin-3, NT-3; and neurotrophin-4, NT-4) mRNAs in target muscles. Moreover, the degree of neurotrophin mRNA decrease in target muscles seems to co-vary with the extent of sensorimotor disturbances. In contrast, the peripheral nerve of aged rats showed a reciprocal regulation of neurotrophins, with increased levels of NGF, BDNF, and NT-4 mRNAs. Taken together, evidence suggest an aging-related attenuation of neurotrophin signaling between target tissues, on one hand, and DRG and motoneurons, on the other, and, furthermore, that target-derived neurotrophins regulate the expression levels of trk mRNAs in both DRG and motoneurons.
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Affiliation(s)
- Y Ming
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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