1
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Antonijevic M, Sopkova-de Oliveira Santos J, Dallemagne P, Rochais C. Discovery of a pocket network on the domain 5 of the TrkB receptor - A potential new target in the quest for the new ligands. Mol Inform 2024; 43:e202400043. [PMID: 38619318 DOI: 10.1002/minf.202400043] [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: 02/01/2024] [Revised: 03/06/2024] [Accepted: 03/26/2024] [Indexed: 04/16/2024]
Abstract
The important role that the neurotrophin tyrosine kinase receptor - TrkB has in the pathogenesis of several neurodegenerative conditions such are Alzheimer's disease, Parkinson's disease, Huntington's disease, has been well described. This shouldn't be a surprise, since in the physiological conditions, once activated by brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5), the TrkB receptor promotes neuronal survival, differentiation and synaptic function. Considering that the natural ligands for TrkB receptor are large proteins, it is a challenge to discover small molecule capable to mimic their effects. Even though, the surface of receptor that is interacting with BDNF or NT-4/5 is known, there was always a question which pocket and interaction is responsible for activation of it. In order to answer this challenging question, we have used molecular dynamic (MD) simulations and Pocketron algorithm which enabled us to detect, for the first time, a pocket network existing in the interacting domain (d5) of the receptor; to describe them and to see how they are communicating with each other. This new discovery gave us potential new areas on receptor that can be targeted and used for structure-based drug design approach in the development of the new ligands.
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2
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Qiao LY. Satellite Glial Cells Bridge Sensory Neuron Crosstalk in Visceral Pain and Cross-Organ Sensitization. J Pharmacol Exp Ther 2024; 390:213-221. [PMID: 38777604 PMCID: PMC11264254 DOI: 10.1124/jpet.123.002061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 05/07/2024] [Accepted: 05/08/2024] [Indexed: 05/25/2024] Open
Abstract
Following colonic inflammation, the uninjured bladder afferent neurons are also activated. The mechanisms and pathways underlying this sensory neuron cross-activation (from injured neurons to uninjured neurons) are not fully understood. Colonic and bladder afferent neurons reside in the same spinal segments and are separated by satellite glial cells (SGCs) and extracellular matrix in dorsal root ganglia (DRG). SGCs communicate with sensory neurons in a bidirectional fashion. This review summarizes the differentially regulated genes/proteins in the injured and uninjured DRG neurons and explores the role of SGCs in regulation of sensory neuron crosstalk in visceral cross-organ sensitization. The review also highlights the paracrine pathways in mediating neuron-SGC and SGC-neuron coupling with an emphasis on the neurotrophins and purinergic systems. Finally, I discuss the results from recent RNAseq profiling of SGCs to reveal useful molecular markers for characterization, functional study, and therapeutic targets of SGCs. SIGNIFICANCE STATEMENT: Satellite glial cells (SGCs) are the largest glial subtypes in sensory ganglia and play a critical role in mediating sensory neuron crosstalk, an underlying mechanism in colon-bladder cross-sensitization. Identification of novel and unique molecular markers of SGCs can advance the discovery of therapeutic targets in treatment of chronic pain including visceral pain comorbidity.
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Affiliation(s)
- Liya Y Qiao
- Department of Physiology and Biophysics, Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, Virginia
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3
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Antonijevic M, Charou D, Davis A, Curel T, Valcarcel M, Ramos I, Villacé P, Claeysen S, Dallemagne P, Gravanis A, Charalampopoulos I, Rochais C. Development of Pleiotropic TrkB and 5-HT 4 Receptor Ligands as Neuroprotective Agents. Molecules 2024; 29:515. [PMID: 38276593 PMCID: PMC10819171 DOI: 10.3390/molecules29020515] [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: 12/14/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 01/27/2024] Open
Abstract
One common event that is the most detrimental in neurodegenerative disorders, even though they have a complex pathogenesis, is the increased rate of neuronal death. Endogenous neurotrophins consist of the major neuroprotective factors, while brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine kinase receptor TrkB are described in a number of studies for their important neuronal effects. Normal function of this receptor is crucial for neuronal survival, differentiation, and synaptic function. However, studies have shown that besides direct activation, the TrkB receptor can be transactivated via GPCRs. It has been proven that activation of the 5-HT4 receptor and transactivation of the TrkB receptor have a positive influence on neuronal differentiation (total dendritic length, number of primary dendrites, and branching index). Because of that and based on the main structural characteristics of LM22A-4, a known activator of the TrkB receptor, and RS67333, a partial 5-HT4 receptor agonist, we have designed and synthesized a small data set of novel compounds with potential dual activities in order to not only prevent neuronal death, but also to induce neuronal differentiation in neurodegenerative disorders.
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Affiliation(s)
- Mirjana Antonijevic
- Normandie University, Unicaen, Centre d’Etudes et de Recherche sur le Médicament de Normandie (CERMN), 14000 Caen, France; (M.A.); (A.D.); (P.D.)
| | - Despoina Charou
- Department of Pharmacology, Medical School, University of Crete, 70013 Heraklion, Greece; (D.C.); (A.G.); (I.C.)
- Institute of Molecular Biology & Biotechnology, Foundation of Research & Technology-Hellas, 70013 Heraklion, Greece
| | - Audrey Davis
- Normandie University, Unicaen, Centre d’Etudes et de Recherche sur le Médicament de Normandie (CERMN), 14000 Caen, France; (M.A.); (A.D.); (P.D.)
| | - Thomas Curel
- IGF, Univ Montpellier, CNRS, INSERM, 34000 Montpellier, France; (T.C.); (S.C.)
| | | | - Isbaal Ramos
- Innoprot S.L, 48160 Derio, Spain; (M.V.); (I.R.); (P.V.)
| | | | - Sylvie Claeysen
- IGF, Univ Montpellier, CNRS, INSERM, 34000 Montpellier, France; (T.C.); (S.C.)
| | - Patrick Dallemagne
- Normandie University, Unicaen, Centre d’Etudes et de Recherche sur le Médicament de Normandie (CERMN), 14000 Caen, France; (M.A.); (A.D.); (P.D.)
| | - Achille Gravanis
- Department of Pharmacology, Medical School, University of Crete, 70013 Heraklion, Greece; (D.C.); (A.G.); (I.C.)
- Institute of Molecular Biology & Biotechnology, Foundation of Research & Technology-Hellas, 70013 Heraklion, Greece
| | - Ioannis Charalampopoulos
- Department of Pharmacology, Medical School, University of Crete, 70013 Heraklion, Greece; (D.C.); (A.G.); (I.C.)
- Institute of Molecular Biology & Biotechnology, Foundation of Research & Technology-Hellas, 70013 Heraklion, Greece
| | - Christophe Rochais
- Normandie University, Unicaen, Centre d’Etudes et de Recherche sur le Médicament de Normandie (CERMN), 14000 Caen, France; (M.A.); (A.D.); (P.D.)
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4
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Wang Y, Liang J, Xu B, Yang J, Wu Z, Cheng L. TrkB/BDNF signaling pathway and its small molecular agonists in CNS injury. Life Sci 2024; 336:122282. [PMID: 38008209 DOI: 10.1016/j.lfs.2023.122282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 10/19/2023] [Accepted: 11/18/2023] [Indexed: 11/28/2023]
Abstract
As one of the most prevalent neurotrophic factors in the central nervous system (CNS), brain-derived neurotrophic factor (BDNF) plays a significant role in CNS injury by binding to its specific receptor Tropomyosin-related kinase receptor B (TrkB). The BDNF/TrkB signaling pathway is crucial for neuronal survival, structural changes, and plasticity. BDNF acts as an axonal growth and extension factor, a pro-survival factor, and a synaptic modulator in the CNS. BDNF also plays an important role in the maintenance and plasticity of neuronal circuits. Several studies have demonstrated the importance of BDNF in the treatment and recovery of neurodegenerative and neurotraumatic disorders. By undertaking in-depth study on the mechanism of BDNF/TrkB function, important novel therapeutic strategies for treating neuropsychiatric disorders have been discovered. In this review, we discuss the expression patterns and mechanisms of the TrkB/BDNF signaling pathway in CNS damage and introduce several intriguing small molecule TrkB receptor agonists produced over the previous several decades.
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Affiliation(s)
- Yujin Wang
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China; Medical School, Tongji University, Shanghai 200433, China
| | - Jing Liang
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China; School of Stomatology, Tongji University, Shanghai 200072, China
| | - Boyu Xu
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China; Medical School, Tongji University, Shanghai 200433, China
| | - Jin Yang
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China; Medical School, Tongji University, Shanghai 200433, China
| | - Zhourui Wu
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China.
| | - Liming Cheng
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China; Key Laboratory of Spine and Spinal cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai 200072, China.
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5
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Liao GY, Xu H, Shumate J, Scampavia L, Spicer T, Xu B. High throughput assay for compounds that boost BDNF expression in neurons. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2023; 28:88-94. [PMID: 36842668 PMCID: PMC10759152 DOI: 10.1016/j.slasd.2023.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/30/2023] [Accepted: 02/21/2023] [Indexed: 02/27/2023]
Abstract
Deficiencies in brain-derived neurotrophic factor (BDNF) have been linked to several brain disorders, making compounds that can boost neuronal BDNF synthesis attractive as potential therapeutics. However, a sensitive and quantitative BDNF assay for high-throughput screening (HTS) is still missing. Here we report the generation of a new mouse Bdnf allele, BdnfNLuc, in which the sequence encoding nano luciferase (NLuc) is inserted into the Bdnf locus immediately before the stop codon so that the allele will produce a BDNF-NLuc fusion protein. BDNF-NLuc protein appears to function like BDNF as BdnfNLuc/NLuc homozygous mice grew and behaved almost normally. We were able to establish and optimize cultures of cortical and hippocampal BdnfNLuc/+ neurons isolated from mouse embryos in 384-well plates. We used the cultures as a phenotypic assay to detect the ability of 10 mM KCl to stimulate BDNF synthesis and achieved a reproducible Z' factor > 0.50 for the assay, a measure considered suitable for HTS. We successfully scaled up the assay to screen the 1280-compound LOPAC library (Library of Pharmacologically Active Compounds). The screen identified several BDNF-boosting compounds, one of which is Bay K8644, a L-type voltage-gated calcium channel (L-VGCC) agonist, which was previously shown to stimulate BDNF synthesis. These results indicate that our phenotypic neuronal assay is ready for HTS to identify novel BDNF-boosting compounds.
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Affiliation(s)
- Guey-Ying Liao
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Haifei Xu
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Justin Shumate
- Department of Molecular Medicine, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Louis Scampavia
- Department of Molecular Medicine, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Timothy Spicer
- Department of Molecular Medicine, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Baoji Xu
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, University of Florida, 130 Scripps Way, Jupiter, FL 33458, USA.
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6
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Antonijevic M, Charou D, Ramos I, Valcarcel M, Gravanis A, Villace P, Callizot N, Since M, Dallemagne P, Charalampopoulos I, Rochais C. Design, synthesis and biological characterization of novel activators of the TrkB neurotrophin receptor. Eur J Med Chem 2023; 248:115111. [PMID: 36645981 DOI: 10.1016/j.ejmech.2023.115111] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 01/07/2023] [Accepted: 01/08/2023] [Indexed: 01/11/2023]
Abstract
Numerous studies have been published about the implication of the neurotrophin brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the pathogenesis of several neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, Multiple Sclerosis and motor neuron disease. BDNF activates the TrkB receptor with high potency and specificity, promoting neuronal survival, differentiation and synaptic plasticity. Based on the main structural characteristics of LM22A-4, a previously published small molecule that acts as activator of the TrkB receptor, we have designed and synthesized a small data set of compounds. The lead idea for the design of the new compounds was to modify the third position of the LM22A-4, by introducing different substitutions in order to obtain compounds which will have not only better physicochemical properties but selective activity as well. ADME and toxicity profiles of molecules have been evaluated as well as their biological properties through the TrkB receptor and affinity to promote neurite differentiation.
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Affiliation(s)
| | - Despoina Charou
- Department of Pharmacology, Medical School, University of Crete, Heraklion, Greece; Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology-Hellas (IMBB-FORTH), Heraklion, Greece
| | | | | | - Achille Gravanis
- Department of Pharmacology, Medical School, University of Crete, Heraklion, Greece; Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology-Hellas (IMBB-FORTH), Heraklion, Greece
| | | | | | - Marc Since
- Normandie Univ., UNICAEN, CERMN, 14000, Caen, France
| | | | - Ioannis Charalampopoulos
- Department of Pharmacology, Medical School, University of Crete, Heraklion, Greece; Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology-Hellas (IMBB-FORTH), Heraklion, Greece
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7
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Hsiang HW, Girard BM, Ratkovits L, Campbell SE, Vizzard MA. Effects of pharmacological neurotrophin receptor inhibition on bladder function in female mice with cyclophosphamide-induced cystitis. FRONTIERS IN UROLOGY 2022; 2:1037511. [PMID: 37701182 PMCID: PMC10494527 DOI: 10.3389/fruro.2022.1037511] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Interstitial cystitis/bladder pain syndrome is a chronic inflammatory pelvic pain syndrome of unknown etiology characterized by a number of lower urinary tract symptoms, including increased urinary urgency and frequency, bladder discomfort, decreased bladder capacity, and pelvic pain. While its etiology remains unknown, a large body of evidence suggests a role for changes in neurotrophin signaling, particularly that of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Here, we evaluated the effects of pharmacological inhibition of the NGF receptor TrkA, BDNF receptor TrkB, and pan-neurotrophin receptor p75NTR on bladder function in acute (4-hour) and chronic (8-day) mouse models of cyclophosphamide (CYP)-induced cystitis. TrkA inhibition via ARRY-954 significantly increased intermicturition interval and bladder capacity in control and acute and chronic CYP-treatment conditions. TrkB inhibition via ANA-12 significantly increased intermicturition interval and bladder capacity in acute, but not chronic, CYP-treatment conditions. Interestingly, intermicturition interval and bladder capacity significantly increased following p75NTR inhibition via LM11A-31 in the acute CYP-treatment condition, but decreased in the chronic condition, potentially due to compensatory changes in neurotrophin signaling or increased urothelial barrier dysfunction in the chronic condition. Our findings demonstrate that these receptors represent additional potent therapeutic targets in mice with cystitis and may be useful in the treatment of interstitial cystitis and other inflammatory disorders of the bladder.
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Affiliation(s)
- Harrison W. Hsiang
- The Larner College of Medicine, Department of Neurological Sciences, The University of Vermont, Burlington, VT, United States
| | - Beatrice M. Girard
- The Larner College of Medicine, Department of Neurological Sciences, The University of Vermont, Burlington, VT, United States
| | - Lexi Ratkovits
- The Larner College of Medicine, Department of Neurological Sciences, The University of Vermont, Burlington, VT, United States
| | - Susan E. Campbell
- The Larner College of Medicine, Department of Neurological Sciences, The University of Vermont, Burlington, VT, United States
| | - Margaret A. Vizzard
- The Larner College of Medicine, Department of Neurological Sciences, The University of Vermont, Burlington, VT, United States
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8
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Brain-Derived Neurotrophic Factor and Nerve Growth Factor Therapeutics for Brain Injury: The Current Translational Challenges in Preclinical and Clinical Research. Neural Plast 2022; 2022:3889300. [PMID: 35283994 PMCID: PMC8906958 DOI: 10.1155/2022/3889300] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/04/2022] [Indexed: 01/11/2023] Open
Abstract
Ischemic stroke and traumatic brain injury (TBI) are among the leading causes of death and disability worldwide with impairments ranging from mild to severe. Many therapies are aimed at improving functional and cognitive recovery by targeting neural repair but have encountered issues involving efficacy and drug delivery. As a result, therapeutic options for patients are sparse. Neurotrophic factors are one of the key mediators of neural plasticity and functional recovery. Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) serve as potential therapeutic options to increase neural repair and recovery as they promote neuroprotection and regeneration. BDNF and NGF have demonstrated the ability to improve functional recovery in preclinical and to a lesser extent clinical studies. Direct and indirect methods to increase levels of neurotrophic factors in animal models have been successful in improving postinjury outcome measures. However, the translation of these studies into clinical trials has been limited. Preclinical experiments have largely failed to result in significant impacts in clinical research. This review will focus on the administration of these neurotrophic factors in preclinical and clinical stroke and TBI and the challenges in translating these therapies from the bench to the clinic.
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9
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Wollet M, Kim JH. Brain-Derived Neurotrophic Factor Is Involved in Activity-Dependent Tonotopic Refinement of MNTB Neurons. Front Neural Circuits 2022; 16:784396. [PMID: 35185479 PMCID: PMC8850952 DOI: 10.3389/fncir.2022.784396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/07/2022] [Indexed: 01/21/2023] Open
Abstract
In the mammalian brain, auditory brainstem nuclei are arranged topographically according to acoustic frequency responsiveness. During postnatal development, the axon initial segment (AIS) of principal neurons undergoes structural refinement depending on location along the tonotopic axis within the medial nucleus of the trapezoid body (MNTB). However, the molecular mechanisms underlying the structural refinement of the AIS along the tonotopic axis in the auditory brainstem have not been explored. We tested the hypothesis that brain-derived neurotrophic factor (BDNF) is a molecular mediator of the structural development of the MNTB in an activity-dependent manner. Using BDNF heterozygous mutant (BDNF+/- ) mice, we examined the impact of global BDNF reduction on structural and functional development of MNTB neurons by assessing AIS structure and associated intrinsic neuronal properties. BDNF reduction inhibits the structural and functional differentiation of principal neurons along the tonotopic axis in the MNTB. Augmented sound input during the critical period of development has been shown to enhance the structural refinement of the AIS of MNTB neurons. However, in BDNF +/- mice, MNTB neurons did not show this activity-dependent structural modification of the AIS following repeated sound stimulation. In addition, BDNF+/- mice lacked a defined isofrequency band of neuronal activity following exposure to 16 kHz sound, suggesting degradation of tonotopy. Taken together, structural development and functional refinement of auditory brainstem neurons require physiological levels of BDNF to establish proper tonotopic gradients.
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Affiliation(s)
| | - Jun Hee Kim
- Department of Cellular and Integrative Physiology, UT Health San Antonio, San Antonio, TX, United States
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10
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Driving effect of BDNF in the spinal dorsal horn on neuropathic pain. Neurosci Lett 2021; 756:135965. [PMID: 34022262 DOI: 10.1016/j.neulet.2021.135965] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/30/2021] [Accepted: 05/11/2021] [Indexed: 12/11/2022]
Abstract
Neuropathic pain (NP) is caused by direct or indirect damage to the nervous system and is a common symptom of many diseases. The mechanisms underlying the onset and persistence of NP are unclear. Therefore, research concerning these mechanisms has become an important focus in the medical field. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophic factor family of signaling molecules. BDNF is an important regulator of neuronal development, synaptic transmission, and cellular and synaptic plasticity, which are essential for nerve maintenance and repair. However, BDNF is upregulated in the spinal dorsal horn and can promote NP by activating glial cells, reducing inhibitory functions and enhancing excitement after nociceptive stimulation. This review considers the relationship between NP and BDNF signaling in the spinal dorsal horn and discusses potentially related pathological mechanisms.
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11
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Kulkarni K, Kelderman J, Coleman H, Aguilar MI, Parkington H, Del Borgo M. Self-assembly of trifunctional tripeptides to form neural scaffolds. J Mater Chem B 2021; 9:4475-4479. [PMID: 34036977 DOI: 10.1039/d0tb02959a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Peptide self-assembly has been exploited to generate a multitude of biomaterials that exhibit biocompatibility due to their similarity to naturally occurring proteins. Previously, we have shown that β-tripeptides self-assemble despite containing sterically bulky, functional sidechains. Herein, we describe the synthesis of a novel β-amino acid to allow for the synthesis of a trifunctional β-tripeptide that remarkably maintains self-assembly and acts as a bioactive neuronal scaffold. These scaffolds show promise for studies involving neuronal cell growth and development.
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Affiliation(s)
- Ketav Kulkarni
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, 3800, VIC, Australia
| | - Jenisi Kelderman
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, 3800, VIC, Australia
| | - Harold Coleman
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia
| | - Marie-Isabel Aguilar
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, 3800, VIC, Australia
| | - Helena Parkington
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia
| | - Mark Del Borgo
- Department of Pharmacology, Monash University, Clayton, VIC 3800, Australia.
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12
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Barker PA, Mantyh P, Arendt-Nielsen L, Viktrup L, Tive L. Nerve Growth Factor Signaling and Its Contribution to Pain. J Pain Res 2020; 13:1223-1241. [PMID: 32547184 PMCID: PMC7266393 DOI: 10.2147/jpr.s247472] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nerve growth factor (NGF) is a neurotrophic protein essential for the growth, differentiation, and survival of sympathetic and sensory afferent neurons during development. A substantial body of evidence, based on both animal and human studies, demonstrates that NGF plays a pivotal role in modulation of nociception in adulthood. This has spurred development of a variety of novel analgesics that target the NGF signaling pathway. Here, we present a narrative review designed to summarize how NGF receptor activation and downstream signaling alters nociception through direct sensitization of nociceptors at the site of injury and changes in gene expression in the dorsal root ganglion that collectively increase nociceptive signaling from the periphery to the central nervous system. This review illustrates that NGF has a well-known and multifunctional role in nociceptive processing, although the precise signaling pathways downstream of NGF receptor activation that mediate nociception are complex and not completely understood. Additionally, much of the existing knowledge derives from studies performed in animal models and may not accurately represent the human condition. However, available data establish a role for NGF in the modulation of nociception through effects on the release of inflammatory mediators, nociceptive ion channel/receptor activity, nociceptive gene expression, and local neuronal sprouting. The role of NGF in nociception and the generation and/or maintenance of chronic pain has led to it becoming a novel and attractive target of pain therapeutics for the treatment of chronic pain conditions.
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Affiliation(s)
- Philip A Barker
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Patrick Mantyh
- Department of Pharmacology, University of Arizona, Tucson, AZ, USA
| | - Lars Arendt-Nielsen
- Department of Health Science and Technology and the Center for Sensory-Motor Interaction/Center for Neuroplasticity and Pain, Aalborg University, Aalborg, Denmark
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Boakye PA, Rancic V, Whitlock KH, Simmons D, Longo FM, Ballanyi K, Smith PA. Receptor dependence of BDNF actions in superficial dorsal horn: relation to central sensitization and actions of macrophage colony stimulating factor 1. J Neurophysiol 2019; 121:2308-2322. [PMID: 30995156 DOI: 10.1152/jn.00839.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Peripheral nerve injury elicits an enduring increase in the excitability of the spinal dorsal horn. This change, which contributes to the development of neuropathic pain, is a consequence of release and prolonged exposure of dorsal horn neurons to various neurotrophins and cytokines. We have shown in rats that nerve injury increases excitatory synaptic drive to excitatory neurons but decreases drive to inhibitory neurons. Both effects, which contribute to an increase in dorsal horn excitability, appear to be mediated by microglia-derived BDNF. We have used multiphoton Ca2+ imaging and whole cell recording of spontaneous excitatory postsynaptic currents in defined-medium organotypic cultures of GAD67-GFP+ mice spinal cord to determine the receptor dependence of these opposing actions of BDNF. In mice, as in rats, BDNF enhances excitatory transmission onto excitatory neurons. This is mediated via presynaptic TrkB and p75 neurotrophin receptors and exclusively by postsynaptic TrkB. By contrast with findings from rats, in mice BDNF does not decrease excitation of inhibitory neurons. The cytokine macrophage colony-stimulating factor 1 (CSF-1) has also been implicated in the onset of neuropathic pain. Nerve injury provokes its de novo synthesis in primary afferents, its release in spinal cord, and activation of microglia. We now show that CSF-1 increases excitatory drive to excitatory neurons via a BDNF-dependent mechanism and decreases excitatory drive to inhibitory neurons via BDNF-independent processes. Our findings complete missing steps in the cascade of events whereby peripheral nerve injury instigates increased dorsal horn excitability in the context of central sensitization and the onset of neuropathic pain. NEW & NOTEWORTHY Nerve injury provokes synthesis of macrophage colony-stimulating factor 1 (CSF-1) in primary afferents and its release in the dorsal horn. We show that CSF-1 increases excitatory drive to excitatory dorsal horn neurons via BDNF activation of postsynaptic TrkB and presynaptic TrkB and p75 neurotrophin receptors. CSF-1 decreases excitatory drive to inhibitory neurons via a BDNF-independent processes. This completes missing steps in understanding how peripheral injury instigates central sensitization and the onset of neuropathic pain.
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Affiliation(s)
- Paul A Boakye
- Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada
| | - Vladimir Rancic
- Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada.,Department of Physiology, University of Alberta , Edmonton , Canada
| | - Kerri H Whitlock
- Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada
| | - Danielle Simmons
- Department of Neurology and Neurological Sciences, Stanford University , Stanford, California
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University , Stanford, California
| | - Klaus Ballanyi
- Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada.,Department of Physiology, University of Alberta , Edmonton , Canada
| | - Peter A Smith
- Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada.,Department of Pharmacology, University of Alberta , Edmonton , Canada
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Shimizu T, Majima T, Suzuki T, Shimizu N, Wada N, Kadekawa K, Takai S, Takaoka E, Kwon J, Kanai AJ, de Groat WC, Tyagi P, Saito M, Yoshimura N. Nerve growth factor-dependent hyperexcitability of capsaicin-sensitive bladder afferent neurones in mice with spinal cord injury. Exp Physiol 2018; 103:896-904. [PMID: 29603450 DOI: 10.1113/ep086951] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 03/20/2018] [Indexed: 01/03/2023]
Abstract
NEW FINDINGS What is the central question of this study? Nerve growth factor (NGF) is reportedly a mediator inducing urinary bladder dysfunction. Is NGF directly involved in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent pathways after spinal cord injury (SCI)? What is the main finding and its importance? Neutralization of NGF by anti-NGF antibody treatment reversed the SCI-induced increase in the number of action potentials and the reduction in spike thresholds and A-type K+ current density in mouse capsaicin-sensitive bladder afferent neurones. Thus, NGF plays an important and direct role in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent neurones attributable to the reduction in A-type K+ channel activity in SCI. ABSTRACT Nerve growth factor (NGF) has been implicated as an important mediator in the induction of C-fibre bladder afferent hyperexcitability, which contributes to the emergence of neurogenic lower urinary tract dysfunction after spinal cord injury (SCI). In this study, we determined whether NGF immunoneutralization using an anti-NGF antibody (NGF-Ab) normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fibre bladder afferent neurones in female C57BL/6 mice. The spinal cord was transected at the Th8/Th9 level. Two weeks later, continuous administration of NGF-Ab (10 μg kg-1 h-1 , s.c. for 2 weeks) was started. Bladder afferent neurones were labelled with Fast-Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3 weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurones were prepared. Whole-cell patch-clamp recordings were then performed in FB-labelled neurones. After recording action potentials or voltage-gated K+ currents, the sensitivity of each neurone to capsaicin was evaluated. In capsaicin-sensitive FB-labelled neurones, SCI significantly reduced the spike threshold and increased the number of action potentials during membrane depolarization for 800 ms. These SCI-induced changes were reversed by NGF-Ab. Densities of slow-decaying A-type K+ (KA ) and sustained delayed rectifier-type K+ currents were significantly reduced by SCI. The NGF-Ab treatment reversed the SCI-induced reduction in the KA current density. These results indicate that NGF plays an important role in hyperexcitability of mouse capsaicin-sensitive C-fibre bladder afferent neurones attributable to a reduction in KA channel activity. Thus, NGF-targeting therapies could be effective for treatment of afferent hyperexcitability and neurogenic lower urinary tract dysfunction after SCI.
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Affiliation(s)
- Takahiro Shimizu
- Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku, Kochi, 783-8505, Japan.,Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Tsuyoshi Majima
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Takahisa Suzuki
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Nobutaka Shimizu
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Naoki Wada
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Katsumi Kadekawa
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Shun Takai
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Eiichiro Takaoka
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Joonbeom Kwon
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Anthony J Kanai
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - William C de Groat
- Department of Pharmacology & Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Pradeep Tyagi
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Motoaki Saito
- Department of Pharmacology, Kochi Medical School, Kochi University, Nankoku, Kochi, 783-8505, Japan
| | - Naoki Yoshimura
- Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA.,Department of Pharmacology & Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
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15
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Guo Y, Su ZJ, Chen YK, Chai Z. Brain-derived neurotrophic factor/neurotrophin 3 regulate axon initial segment location and affect neuronal excitability in cultured hippocampal neurons. J Neurochem 2017; 142:260-271. [DOI: 10.1111/jnc.14050] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 04/07/2017] [Accepted: 04/18/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Yu Guo
- State Key Laboratory of Membrane Biology; College of Life Sciences; Peking University; Beijing China
| | - Zi-jun Su
- State Key Laboratory of Membrane Biology; College of Life Sciences; Peking University; Beijing China
| | - Yi-kun Chen
- State Key Laboratory of Membrane Biology; College of Life Sciences; Peking University; Beijing China
| | - Zhen Chai
- State Key Laboratory of Membrane Biology; College of Life Sciences; Peking University; Beijing China
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Garcia‐Gil M, Pierucci F, Vestri A, Meacci E. Crosstalk between sphingolipids and vitamin D3: potential role in the nervous system. Br J Pharmacol 2017; 174:605-627. [PMID: 28127747 PMCID: PMC6398521 DOI: 10.1111/bph.13726] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/16/2016] [Accepted: 01/18/2017] [Indexed: 12/14/2022] Open
Abstract
Sphingolipids are both structural and bioactive compounds. In particular, ceramide and sphingosine 1-phosphate regulate cell fate, inflammation and excitability. 1-α,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ) is known to play an important physiological role in growth and differentiation in a variety of cell types, including neural cells, through genomic actions mediated by its specific receptor, and non-genomic effects that result in the activation of specific signalling pathways. 1,25(OH)2 D3 and sphingolipids, in particular sphingosine 1-phosphate, share many common effectors, including calcium regulation, growth factors and inflammatory cytokines, but it is still not known whether they can act synergistically. Alterations in the signalling and concentrations of sphingolipids and 1,25(OH)2 D3 have been found in neurodegenerative diseases and fingolimod, a structural analogue of sphingosine, has been approved for the treatment of multiple sclerosis. This review, after a brief description of the role of sphingolipids and 1,25(OH)2 D3 , will focus on the potential crosstalk between sphingolipids and 1,25(OH)2 D3 in neural cells.
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Affiliation(s)
- Mercedes Garcia‐Gil
- Department of BiologyUniversity of PisaPisaItaly
- Interdepartmental Research Center Nutrafood ‘Nutraceuticals and Food for Health’University of PisaPisaItaly
| | - Federica Pierucci
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
| | - Ambra Vestri
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
| | - Elisabetta Meacci
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
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Xia C, Shen S, Hashmi F, Qiao LY. Colitis-induced bladder afferent neuronal activation is regulated by BDNF through PLCγ pathway. Exp Neurol 2015; 285:126-135. [PMID: 26687970 DOI: 10.1016/j.expneurol.2015.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 11/14/2015] [Accepted: 12/10/2015] [Indexed: 02/08/2023]
Abstract
Patients with inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS) often experience increased sensory responsiveness in the urinary bladder reflecting neurogenic bladder overactivity. Here we demonstrate that colitis-induced up-regulation of the phospholipase C gamma (PLCγ) pathway downstream of brain-derived neurotrophic factor (BDNF) in bladder afferent neurons in the dorsal root ganglia (DRG) plays essential roles in activating these neurons thereby leading to bladder hyperactivity. Upon induction of colitis with 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats, we found that the phosphorylation (activation) level of cAMP responsive element-binding (p-CREB) protein, a molecular switch of neuronal plasticity, was increased in specifically labeled bladder afferent neurons in the thoracolumbar and lumbosacral DRGs. In rats having reduced levels of BDNF (BDNF+/-), colitis failed to elevate CREB protein activity in bladder afferent neurons. Physiological examination also demonstrated that colitis-induced urinary frequency was not shown in BDNF+/- rats, implicating an essential role of BDNF in mediating colon-to-bladder sensory cross-sensitization. We further implemented in vivo and in vitro studies and demonstrated that BDNF-mediated colon-to-bladder sensory cross-activation involved the TrkB-PLCγ-calcium/calmodulin-dependent protein kinase II (CaMKII) cascade. In contrast, the PI3K/Akt pathway was not activated in bladder afferent neurons during colitis and was not involved in BDNF action in the DRG. Our results suggest that colon-to-bladder sensory cross-sensitization is regulated by specific signal transduction initiated by the up-regulation of BDNF in the DRG.
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Affiliation(s)
- Chunmei Xia
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Shanwei Shen
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Fiza Hashmi
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Li-Ya Qiao
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
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18
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Abstract
Neurotrophins (NTs) belong to a family of trophic factors that regulate the survival, growth and programmed cell death of neurons. In mammals, there are four structurally and functionally related NT proteins, viz. nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 and neurotrophin 4. Most research on NTs to date has focussed on the effects of NGF and BDNF signalling via their respective cognate high affinity neurotrophic tyrosine kinase viz TrkA and TrkB receptors. Apart from the key physiologic roles of NGF and BDNF in peripheral and central nervous system function, NGF and BDNF signalling via TrkA and TrkB receptors respectively have been implicated in mechanisms underpinning neuropathic pain. Additionally, NGF and BDNF signalling via the low-affinity pan neurotrophin receptor at 75 kDa (p75NTR) may also contribute to the pathobiology of neuropathic pain. In this review, we critically assess the role of neurotrophins signalling via their cognate high affinity receptors as well as the low affinity p75NTR in the pathophysiology of peripheral neuropathic and central neuropathic pain. We also identify knowledge gaps to guide future research aimed at generating novel insight on how to optimally modulate NT signalling for discovery of novel therapeutics to improve neuropathic pain relief.
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19
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Smith PA. BDNF: No gain without pain? Neuroscience 2014; 283:107-23. [DOI: 10.1016/j.neuroscience.2014.05.044] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 05/16/2014] [Accepted: 05/21/2014] [Indexed: 12/22/2022]
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20
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Plotkin JL, Day M, Peterson JD, Xie Z, Kress GJ, Rafalovich I, Kondapalli J, Gertler TS, Flajolet M, Greengard P, Stavarache M, Kaplitt MG, Rosinski J, Chan CS, Surmeier DJ. Impaired TrkB receptor signaling underlies corticostriatal dysfunction in Huntington's disease. Neuron 2014; 83:178-88. [PMID: 24991961 DOI: 10.1016/j.neuron.2014.05.032] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2014] [Indexed: 12/28/2022]
Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. The debilitating choreic movements that plague HD patients have been attributed to striatal degeneration induced by the loss of cortically supplied brain-derived neurotrophic factor (BDNF). Here, we show that in mouse models of early symptomatic HD, BDNF delivery to the striatum and its activation of tyrosine-related kinase B (TrkB) receptors were normal. However, in striatal neurons responsible for movement suppression, TrkB receptors failed to properly engage postsynaptic signaling mechanisms controlling the induction of potentiation at corticostriatal synapses. Plasticity was rescued by inhibiting p75 neurotrophin receptor (p75NTR) signaling or its downstream target phosphatase-and-tensin-homolog-deleted-on-chromosome-10 (PTEN). Thus, corticostriatal synaptic dysfunction early in HD is attributable to a correctable defect in the response to BDNF, not its delivery.
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Affiliation(s)
- Joshua L Plotkin
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Michelle Day
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Jayms D Peterson
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Zhong Xie
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Geraldine J Kress
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Igor Rafalovich
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Jyothisri Kondapalli
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Tracy S Gertler
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Marc Flajolet
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10065, USA
| | - Paul Greengard
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10065, USA
| | - Mihaela Stavarache
- Department of Neurological Surgery, Weill Cornell Medical College, New York, NY 10028, USA
| | - Michael G Kaplitt
- Department of Neurological Surgery, Weill Cornell Medical College, New York, NY 10028, USA
| | - Jim Rosinski
- CHDI Management/CHDI Foundation, Princeton, NJ 08540, USA
| | - C Savio Chan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - D James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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21
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Pettersson LME, Geremia NM, Ying Z, Verge VMK. Injury-associated PACAP expression in rat sensory and motor neurons is induced by endogenous BDNF. PLoS One 2014; 9:e100730. [PMID: 24968020 PMCID: PMC4072603 DOI: 10.1371/journal.pone.0100730] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 05/28/2014] [Indexed: 11/19/2022] Open
Abstract
Peripheral nerve injury results in dramatic upregulation in pituitary adenylate cyclase activating polypeptide (PACAP) expression in adult rat dorsal root ganglia and spinal motor neurons mirroring that described for the neurotrophin brain derived neurotrophic factor (BDNF). Thus, we posited that injury-associated alterations in BDNF expression regulate the changes in PACAP expression observed in the injured neurons. The role of endogenous BDNF in induction and/or maintenance of PACAP mRNA expression in injured adult rat motor and sensory neurons was examined by intrathecally infusing or intraperitoneally injecting BDNF-specific antibodies or control IgGs immediately at the time of L4-L6 spinal nerve injury, or in a delayed fashion one week later for 3 days followed by analysis of impact on PACAP expression. PACAP mRNA in injured lumbar sensory and motor neurons was detected using in situ hybridization, allowing quantification of relative changes between experimental groups, with ATF-3 immunofluorescence serving to identify the injured subpopulation of motor neurons. Both the incidence and level of PACAP mRNA expression were dramatically reduced in injured sensory and motor neurons in response to immediate intrathecal anti-BDNF treatment. In contrast, neither intraperitoneal injections nor delayed intrathecal infusions of anti-BDNF had any discernible impact on PACAP expression. This impact on PACAP expression in response to BDNF immunoneutralization in DRG was confirmed using qRT-PCR or by using BDNF selective siRNAs to reduce neuronal BDNF expression. Collectively, our findings support that endogenous injury-associated BDNF expression is critically involved in induction, but not maintenance, of injury-associated PACAP expression in sensory and motor neurons.
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Affiliation(s)
- Lina M. E. Pettersson
- CMSNRC & Department of Anatomy & Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada
- * E-mail:
| | - Nicole M. Geremia
- CMSNRC & Department of Anatomy & Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Zhengxin Ying
- CMSNRC & Department of Anatomy & Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Valerie M. K. Verge
- CMSNRC & Department of Anatomy & Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada
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Abstract
Neurotrophin family are traditionally recognized for their nerve growth promoting function and are recently identified as crucial factors in regulating neuronal activity in the central and peripheral nervous systems. The family members including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are reported to have distinct roles in the development and maintenance of sensory phenotypes in normal states and in the modulation of sensory activity in disease. This paper highlights receptor tyrosine kinase (Trk) -mediated signal transduction by which neurotrophins regulate neuronal activity in the visceral sensory reflex pathways with emphasis on the distinct roles of NGF and BDNF signaling in physiologic and pathophysiological processes. Viscero-visceral cross-organ sensitization exists widely in human diseases. The role of neurotrophins in mediating neural cross talk and interaction in primary afferent neurons in the dorsal root ganglia (DRG) and neurotrophin signal transduction in the context of cross-organ sensitization are also discussed.
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Affiliation(s)
- Li-Ya Qiao
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
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Takeda M, Takahashi M, Matsumoto S. Inflammation enhanced brain-derived neurotrophic factor-induced suppression of the voltage-gated potassium currents in small-diameter trigeminal ganglion neurons projecting to the trigeminal nucleus interpolaris/caudalis transition zone. Neuroscience 2014; 261:223-31. [DOI: 10.1016/j.neuroscience.2013.12.048] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 12/12/2013] [Accepted: 12/20/2013] [Indexed: 12/30/2022]
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Fon D, Zhou K, Ercole F, Fehr F, Marchesan S, Minter MR, Crack PJ, Finkelstein DI, Forsythe JS. Nanofibrous scaffolds releasing a small molecule BDNF-mimetic for the re-direction of endogenous neuroblast migration in the brain. Biomaterials 2014; 35:2692-712. [PMID: 24406218 DOI: 10.1016/j.biomaterials.2013.12.016] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 12/10/2013] [Indexed: 01/19/2023]
Abstract
Brain tissue engineering has the potential to harness existing elements of neurogenesis within the adult brain to overcome a microenvironment that is otherwise inhibitory to regeneration, especially following severe tissue damage. This study investigates the ability of electrospun poly ε-caprolactone (PCL) to re-direct the migratory pathway of endogenous neuroblasts from the disrupted subventricular zone (SVZ). A small molecule non-peptide ligand (BDNF-mimetic) that mimicked the trophic properties of brain-derived neurotrophic factor (BDNF) was incorporated into electrospun PCL scaffolds to improve neuroblast survival and promote neuroblast migration towards the implant. PCL scaffolds were able to support neuroblast infiltration and migration along the implant tract. In the presence of the BDNF-mimetic, neuroblasts were able to migrate towards the implant via the parenchyma, and their persistence within the implants was prolonged. In addition, the BDNF-mimetic improved implant integration and increased local neuronal plasticity by increasing neurite sprouting at the tissue-implant interface. SMI32+ neurites were observed inside scaffolds at 21 days but not 8 days post implantation, indicating that at least some of the infiltrated neuroblasts had differentiated into neurons.
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Affiliation(s)
- Deniece Fon
- Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia; Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Kun Zhou
- Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Francesca Ercole
- Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Friederike Fehr
- CSIRO Materials Science and Engineering, Clayton, VIC 3053, Australia
| | - Silvia Marchesan
- CSIRO Materials Science and Engineering, Clayton, VIC 3053, Australia
| | - Myles R Minter
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Peter J Crack
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC 3010, Australia
| | - David I Finkelstein
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3010, Australia.
| | - John S Forsythe
- Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia.
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25
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Bernard-Gauthier V, Boudjemeline M, Rosa-Neto P, Thiel A, Schirrmacher R. Towards tropomyosin-related kinase B (TrkB) receptor ligands for brain imaging with PET: radiosynthesis and evaluation of 2-(4-[(18)F]fluorophenyl)-7,8-dihydroxy-4H-chromen-4-one and 2-(4-([N-methyl-(11)C]-dimethylamino)phenyl)-7,8-dihydroxy-4H-chromen-4-one. Bioorg Med Chem 2013; 21:7816-29. [PMID: 24183588 DOI: 10.1016/j.bmc.2013.10.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 10/01/2013] [Accepted: 10/10/2013] [Indexed: 12/11/2022]
Abstract
The interaction of tropomyosin-related kinase B (TrkB) with the cognate ligand brain-derived neurotrophic factor (BDNF) mediates fundamental pathways in the development of the nervous system. TrkB signaling alterations are linked to numerous neurodegenerative diseases and conditions. Herein we report the synthesis, biological evaluation and radiosynthesis of the first TrkB radioligands based on the recently identified 7,8-dihydroxyflavone chemotype. 2-(4-[(18)F]fluorophenyl)-7,8-dihydroxy-4H-chromen-4-one ([(18)F]10b) was synthesized in high radiochemical yields via an efficient SNAr radiofluorination involving a para-Michael acceptor substituted aryl followed by BBr3-promoted double demethylation. Selective N-[(11)C]methylation afforded 2-(4-([N-methyl-(11)C]-dimethylamino)phenyl)-7,8-dihydroxy-4H-chromen-4-one ([(11)C]10c) from the fully deprotected catechol-bearing normethyl precursor 13 with [(11)C]MeOTf. In vitro autoradiography of [(18)F]10b with transverse rat brain sections revealed high specific binding in the cortex, striatum, hippocampus and thalamus in accordance with expected TrkB distribution. Blockade experiments with both 7,8-dihydroxyflavone (1a) and TrkB cognate ligand, BDNF, led to decreases of 80% and 85% of radioligand binding strongly supporting the hypothesis that 7,8-dihydroxyflavones exert their effect on TrkB phosphorylation via direct TrkB extracellular domain (ECD) binding. Positron emission tomography (PET) studies revealed that [(18)F]10b and [(11)C]10c brain uptake is minimal and that they are rapidly eliminated from the plasma (effective plasma half-life 5-10 min) via hepatic secretion. Nevertheless, the high specific binding and TrkB specificity derived from in vitro experiments suggests that the 7,8-disubstituted flavone chemotype represents a promising scaffold for the development of TrkB radiotracers for PET.
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Affiliation(s)
- Vadim Bernard-Gauthier
- Department of Chemistry, Université de Montréal, PO Box 6128, Station Downtown, QC H3C 3J7, Canada; McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
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Khodorova A, Nicol GD, Strichartz G. The p75NTR signaling cascade mediates mechanical hyperalgesia induced by nerve growth factor injected into the rat hind paw. Neuroscience 2013; 254:312-23. [PMID: 24095693 DOI: 10.1016/j.neuroscience.2013.09.046] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 09/13/2013] [Accepted: 09/24/2013] [Indexed: 01/25/2023]
Abstract
Nerve growth factor (NGF) augments the excitability of isolated rat sensory neurons through activation of the p75 neurotrophin receptor (p75(NTR)) and its downstream sphingomyelin signaling cascade, wherein neutral sphingomyelinase(s) (nSMase), ceramide, and the atypical protein-kinase C (aPKC), protein-kinase M zeta (PKMζ), are key mediators. Here we examined these same receptor-pathways in vivo for their role in mechanical hyperalgesia from exogenous NGF. Mechanical sensitivity was tested by the number of paw withdrawals in response to 10 stimuli (PWF=n/10) by a 4-g von Frey hair (VFH, testing "allodynia") and by 10 and 15g VFHs (testing "hyperalgesia"). NGF (500ng/10μL) injected into the male rat's plantar hind paw induced long-lasting ipsilateral mechanical hypersensitivity. Mechano-hypersensitivity, relative to baseline responses and to those of the contralateral paw, developed by 0.5-1.5h and remained elevated at least for 21-24h, Acute intraplantar pre-treatment with nSMase inhibitors, glutathione (GSH) or GW4869, prevented the acute hyperalgesia from NGF (at 1.5h) but not that at 24h. A single injection of N-acetyl sphingosine (C2-ceramide), simulating the ceramide produced by nSMase activity, induced ipsilateral allodynia that persisted for 24h, and transient hyperalgesia that resolved by 2h. Intraplantar injection of hydrolysis-resistant mPro-NGF, selective for the p75(NTR) over the tyrosine kinase (TrkA) receptor, gave very similar results to NGF and was susceptible to the same inhibitors. Hyperalgesia from both NGF and mPro-NGF was prevented by paw pre-injection with blocking antibodies to rat p75(NTR) receptor. Finally, intraplantar (1day before NGF) injection of mPSI, the myristolated pseudosubstrate inhibitor of PKCζ/PKMζ, decreased the hyperalgesia resulting from NGF or C2-ceramide, although scrambled mPSI was ineffective. The findings indicate that mechano-hypersensitivity from peripheral NGF involves the sphingomyelin signaling cascade activated via p75(NTR), and that a peripheral aPKC is essential for this sensitization.
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Affiliation(s)
- A Khodorova
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, USA
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Brain-derived neurotrophic factor enhances the excitability of small-diameter trigeminal ganglion neurons projecting to the trigeminal nucleus interpolaris/caudalis transition zone following masseter muscle inflammation. Mol Pain 2013; 9:49. [PMID: 24073832 PMCID: PMC3849633 DOI: 10.1186/1744-8069-9-49] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/24/2013] [Indexed: 12/29/2022] Open
Abstract
Background The trigeminal subnuclei interpolaris/caudalis transition zones (Vi/Vc) play an important role in orofacial deep pain, however, the role of primary afferent projections to the Vi/Vc remains to be determined. This study investigated the functional significance of hyperalgesia to the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (trkB) signaling system in trigeminal ganglion (TRG) neurons projecting to the Vi/Vc transition zone following masseter muscle (MM) inflammation. Results The escape threshold from mechanical stimulation applied to skin above the inflamed MM was significantly lower than in naïve rats. Fluorogold (FG) labeling was used to identify the TRG neurons innervating the MM, while microbeads (MB) were used to label neurons projecting to the Vi/Vc region. FG/MB-labeled TRG neurons were immunoreactive (IR) for BDNF and trkB. The mean number of BDNF/trkB-IR small/medium-diameter TRG neurons was significantly higher in inflamed rats than in naïve rats. In whole-cell current-clamp experiments, the majority of dissociated small-diameter TRG neurons showed a depolarization response to BDNF that was associated with spike discharge, and the concentration of BDNF that evoked a depolarizing response was significantly lower in the inflamed rats. In addition, the relative number of BDNF-induced spikes during current injection was significantly higher in inflamed rats. The BDNF-induced changes in TRG neuron excitability was abolished by tyrosine kinase inhibitor, K252a. Conclusion The present study provided evidence that BDNF enhances the excitability of the small-diameter TRG neurons projecting onto the Vi/Vc following MM inflammation. These findings suggest that ganglionic BDNF-trkB signaling is a therapeutic target for the treatment of trigeminal inflammatory hyperalgesia.
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Callaghan CK, Kelly ÁM. Neurotrophins play differential roles in short and long-term recognition memory. Neurobiol Learn Mem 2013; 104:39-48. [DOI: 10.1016/j.nlm.2013.04.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 12/25/2022]
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Zhang YH, Khanna R, Nicol GD. Nerve growth factor/p75 neurotrophin receptor-mediated sensitization of rat sensory neurons depends on membrane cholesterol. Neuroscience 2013; 248:562-70. [PMID: 23811397 DOI: 10.1016/j.neuroscience.2013.06.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 06/14/2013] [Accepted: 06/18/2013] [Indexed: 12/31/2022]
Abstract
Nerve growth factor (NGF) is an important mediator in the initiation of the inflammatory response and NGF via activation of the p75 neurotrophin receptor (p75(NTR)) and downstream sphingomyelin signaling leads to significant enhancement of the excitability of small-diameter sensory neurons. Because of the interaction between sphingomyelin and cholesterol in creating membrane liquid-ordered domains known as membrane or lipid rafts, we examined whether neuronal NGF-induced sensitization via p75(NTR) was dependent on the integrity of membrane rafts. Here, we demonstrate that the capacity of NGF to enhance the excitability of sensory neurons may result from the interaction of p75(NTR) with its downstream signaling partner(s) in membrane rafts. Two agents known to disrupt membrane rafts, edelfosine and methyl-β-cyclodextrin (MβCD), block the increase in excitability produced by NGF. In contrast, treatment with MβCD containing saturated amounts of cholesterol does not alter the capacity of NGF to augment excitability. In addition, adding back MβCD with cholesterol restored the NGF-induced sensitization in previously cholesterol-depleted neurons, suggesting that cholesterol and the structural integrity of rafts are key to promoting NGF-mediated sensitization. Using established protocols to isolate detergent-resistant membranes, both p75(NTR) and the neuronal membrane raft marker, flotillin, localize to raft fractions. These results suggest that downstream signaling partners interacting with p75(NTR) in sensory neurons are associated with membrane raft signaling platforms.
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Affiliation(s)
- Y H Zhang
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - R Khanna
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - G D Nicol
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN 46202, USA.
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Tian J, Tep C, Zhu MX, Yoon SO. Changes in Spontaneous firing patterns of cerebellar Purkinje cells in p75 knockout mice. CEREBELLUM (LONDON, ENGLAND) 2013; 12:300-3. [PMID: 23307658 PMCID: PMC3643992 DOI: 10.1007/s12311-012-0439-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The p75 neurotrophin receptor is highly expressed in the developing nervous system and is required for neuronal survival, growth, and synaptic transmission. In young mice, p75 is present in both granular cells and Purkinje cells of the cerebellum. Although p75 has been implicated in modulation of neuronal excitability in several neuronal types, whether and how it affects the excitability of cerebellar Purkinje neurons remained unclear. Using extracellular recordings of spontaneous firing of Purkinje neurons in cerebellar slices prepared from wild type and p75 knockout mice, we measured intrinsic firing properties in the presence of fast synaptic blockers of more than 200 Purkinje cells, each for a period of 5 min, for each genotype. We detected a significant increase in the mean firing frequency in p75(-/-) neurons comparing to the wild type littermates. Upon separating tonically firing from phasically firing cells, i.e., cells with firing pauses of longer than 300 ms, we observed that the change mainly arose from phasic firing cells and can be explained by an increase in the firing/silence ratio and a decrease in the number of long pauses during the 5-min recording period. We conclude that p75 plays an important role in regulating the firing-to-silence transition during the phasic firing period of the spontaneous firing of Purkinje cells. Thus, p75 exerts a modulatory function on Purkinje cell firing patterns, through which it may act as a key player in motor coordination and other cerebellum-regulated activities since Purkinje cells represent the sole neuronal output of the cerebellar cortex.
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Affiliation(s)
- Jinbin Tian
- Department of Neuroscience, The Ohio State University, Columbus, OH 43210
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Chhavy Tep
- Department of Molecular & Cellular Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
| | - Michael X. Zhu
- Department of Neuroscience, The Ohio State University, Columbus, OH 43210
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Sung Ok Yoon
- Department of Molecular & Cellular Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
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TrkB receptor signalling: implications in neurodegenerative, psychiatric and proliferative disorders. Int J Mol Sci 2013; 14:10122-42. [PMID: 23670594 PMCID: PMC3676832 DOI: 10.3390/ijms140510122] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 04/27/2013] [Accepted: 04/28/2013] [Indexed: 02/06/2023] Open
Abstract
The Trk family of receptors play a wide variety of roles in physiological and disease processes in both neuronal and non-neuronal tissues. Amongst these the TrkB receptor in particular has attracted major attention due to its critical role in signalling for brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT3) and neurotrophin-4 (NT4). TrkB signalling is indispensable for the survival, development and synaptic plasticity of several subtypes of neurons in the nervous system. Substantial evidence has emerged over the last decade about the involvement of aberrant TrkB signalling and its compromise in various neuropsychiatric and degenerative conditions. Unusual changes in TrkB signalling pathway have also been observed and implicated in a range of cancers. Variations in TrkB pathway have been observed in obesity and hyperphagia related disorders as well. Both BDNF and TrkB have been shown to play critical roles in the survival of retinal ganglion cells in the retina. The ability to specifically modulate TrkB signalling can be critical in various pathological scenarios associated with this pathway. In this review, we discuss the mechanisms underlying TrkB signalling, disease implications and explore plausible ameliorative or preventive approaches.
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Zhu W, Frost EE, Begum F, Vora P, Au K, Gong Y, MacNeil B, Pillai P, Namaka M. The role of dorsal root ganglia activation and brain-derived neurotrophic factor in multiple sclerosis. J Cell Mol Med 2012; 16:1856-65. [PMID: 22050733 PMCID: PMC3822697 DOI: 10.1111/j.1582-4934.2011.01481.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Multiple sclerosis (MS) is characterized by focal destruction of the white matter of the brain and spinal cord. The exact mechanisms underlying the pathophysiology of the disease are unknown. Many studies have shown that MS is predominantly an autoimmune disease with an inflammatory phase followed by a demyelinating phase. Recent studies alongside current treatment strategies, including glatiramer acetate, have revealed a potential role for brain-derived neurotrophic factor (BDNF) in MS. However, the exact role of BDNF is not fully understood. We used the experimental autoimmune encephalomyelitis (EAE) model of MS in adolescent female Lewis rats to identify the role of BDNF in disease progression. Dorsal root ganglia (DRG) and spinal cords were harvested for protein and gene expression analysis every 3 days post-disease induction (pdi) up to 15 days. We show significant increases in BDNF protein and gene expression in the DRG of EAE animals at 12 dpi, which correlates with peak neurological disability. BDNF protein expression in the spinal cord was significantly increased at 12 dpi, and maintained at 15 dpi. However, there was no significant change in mRNA levels. We show evidence for the anterograde transport of BDNF protein from the DRG to the dorsal horn of the spinal cord via the dorsal roots. Increased levels of BDNF within the DRG and spinal cord in EAE may facilitate myelin repair and neuroprotection in the CNS. The anterograde transport of DRG-derived BDNF to the spinal cord may have potential implications in facilitating central myelin repair and neuroprotection.
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Affiliation(s)
- Wenjun Zhu
- Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba, Canada
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Exogenous BDNF enhances the integration of chronically injured axons that regenerate through a peripheral nerve grafted into a chondroitinase-treated spinal cord injury site. Exp Neurol 2012; 239:91-100. [PMID: 23022460 DOI: 10.1016/j.expneurol.2012.09.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 08/03/2012] [Accepted: 09/20/2012] [Indexed: 12/20/2022]
Abstract
Although axons lose some of their intrinsic capacity for growth after their developmental period, some axons retain the potential for regrowth after injury. When provided with a growth-promoting substrate such as a peripheral nerve graft (PNG), severed axons regenerate into and through the graft; however, they stop when they reach the glial scar at the distal graft-host interface that is rich with inhibitory chondroitin sulfate proteoglycans. We previously showed that treatment of a spinal cord injury site with chondroitinase (ChABC) allows axons within the graft to traverse the scar and reinnervate spinal cord, where they form functional synapses. While this improvement in outgrowth was significant, it still represented only a small percentage (<20%) of axons compared to the total number of axons that regenerated into the PNG. Here we tested whether providing exogenous brain-derived neurotrophic factor (BDNF) via lentivirus in tissue distal to the PNG would augment regeneration beyond a ChABC-treated glial interface. We found that ChABC treatment alone promoted axonal regeneration but combining ChABC with BDNF-lentivirus did not increase the number of axons that regenerated back into spinal cord. Combining BDNF with ChABC did increase the number of spinal cord neurons that were trans-synaptically activated during electrical stimulation of the graft, as indicated by c-Fos expression, suggesting that BDNF overexpression improved the functional significance of axons that did reinnervate distal spinal cord tissue.
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Purcell EK, Yang A, Liu L, Velkey JM, Morales MM, Duncan RK. BDNF profoundly and specifically increases KCNQ4 expression in neurons derived from embryonic stem cells. Stem Cell Res 2012; 10:29-35. [PMID: 23089626 DOI: 10.1016/j.scr.2012.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 08/15/2012] [Accepted: 08/27/2012] [Indexed: 01/10/2023] Open
Abstract
Neurons resembling the spiral ganglion neurons (SGNs) of the auditory nerve can be generated from embryonic stem cells through induced overexpression of the transcription factor Neurogenin-1 (Neurog1). While recapitulating this developmental pathway produces glutamatergic, bipolar neurons reminiscent of SGNs, these neurons are functionally immature, being characterized by a depolarized resting potential and limited excitability. We explored the effects of two neurotrophins known to be present in the inner ear, brain derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), on the electrophysiology of neurons following Neurog1 induction. Our data reveal a significant reduction in resting membrane potential (RMP) following neurotrophin exposure, with BDNF producing a more robust effect than NT-3. This effect was accompanied by a profound and specific upregulation of the KCNQ4 subtype, where a 9-fold increase was observed with quantitative PCR. The other neuronally expressed KCNQ subtypes (2, 3, and 5) exhibited upregulation which was 3-fold or less in magnitude. Quantitative immunohistochemistry confirmed the increase in KCNQ4 expression at the protein level. The present data show a novel link between BDNF and KCNQ4 expression, yielding insight into the restricted expression pattern of a channel known to play special roles in setting the resting potential of auditory cells and in the etiology of progressive high-frequency hearing loss.
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35
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Callaghan CK, Kelly ÁM. Differential BDNF signaling in dentate gyrus and perirhinal cortex during consolidation of recognition memory in the rat. Hippocampus 2012; 22:2127-35. [PMID: 22573708 DOI: 10.1002/hipo.22033] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2012] [Indexed: 01/16/2023]
Abstract
Consolidation of long-term memory is dependent on synthesis of new proteins in the hippocampus and associated cortical regions. The neurotrophin brain-derived neurotrophic factor (BDNF) is tightly regulated by activity-dependent cellular processes and is strongly linked with mechanisms underlying learning and memory. BDNF activation of tyrosine receptor kinase (TrkB) stimulates intracellular signaling cascades implicated in plasticity, including the extracellular-signal related kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and the phosphatidylinositide-3-kinase (PI3K)/Akt pathway. Here, we investigate the role of BDNF, ERK/MAPK, and PI3K/AKT signaling cascade in recognition memory in the rat. We report that recognition memory was associated with increased release of BDNF in the dentate gyrus and perirhinal cortex. This was associated with significant increases in p44ERK activation and c-fos expression in the dentate gyrus and PI3K activation and c-fos expression in the perirhinal cortex. Furthermore, both recognition memory and the associated cell signaling events in dentate gyrus and perirhinal cortex were blocked by intraperitoneal injection of the Trk receptor inhibitor tyrphostin AG879. These data are consistent with the hypothesis that BDNF-stimulated intracellular signaling plays a role in consolidation of recognition memory in the rat.
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Affiliation(s)
- Charlotte K Callaghan
- Department of Physiology, School of Medicine and Trinity College Institute of Neuroscience, University of Dublin, Trinity College, Dublin, Ireland
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36
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Ndong C, Landry RP, DeLeo JA, Romero-Sandoval EA. Mitogen activated protein kinase phosphatase-1 prevents the development of tactile sensitivity in a rodent model of neuropathic pain. Mol Pain 2012; 8:34. [PMID: 22540262 PMCID: PMC3460752 DOI: 10.1186/1744-8069-8-34] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 04/27/2012] [Indexed: 12/30/2022] Open
Abstract
Background Neuropathic pain due to nerve injury is one of the most difficult types of pain to treat. Following peripheral nerve injury, neuronal and glial plastic changes contribute to central sensitization and perpetuation of mechanical hypersensitivity in rodents. The mitogen activated protein kinase (MAPK) family is pivotal in this spinal cord plasticity. MAPK phosphatases (MKPs) limit inflammatory processes by dephosphorylating MAPKs. For example, MKP-1 preferentially dephosphorylates p-p38. Since spinal p-p38 is pivotal for the development of chronic hypersensitivity in rodent models of pain, and p-p38 inhibitors have shown clinical potential in acute and chronic pain patients, we hypothesize that induction of spinal MKP-1 will prevent the development of peripheral nerve-injury-induced hypersensitivity and p-p38 overexpression. Results We cloned rat spinal cord MKP-1 and optimize MKP-1 cDNA in vitro using transfections to BV-2 cells. We observed that in vitro overexpression of MKP-1 blocked lipopolysaccharide-induced phosphorylation of p38 (and other MAPKs) as well as release of pro-algesic effectors (i.e., cytokines, chemokines, nitric oxide). Using this cDNA MKP-1 and a non-viral, in vivo nanoparticle transfection approach, we found that spinal cord overexpression of MKP-1 prevented development of peripheral nerve-injury-induced tactile hypersensitivity and reduced pro-inflammatory cytokines and chemokines and the phosphorylated form of p38. Conclusions Our results indicate that MKP-1, the natural regulator of p-p38, mediates resolution of the spinal cord pro-inflammatory milieu induced by peripheral nerve injury, resulting in prevention of chronic mechanical hypersensitivity. We propose that MKP-1 is a potential therapeutic target for pain treatment or prevention.
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Affiliation(s)
- Christian Ndong
- Dartmouth Medical School, Department of Anesthesiology, Lebanon, NH, USA
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Ashpole NM, Song W, Brustovetsky T, Engleman EA, Brustovetsky N, Cummins TR, Hudmon A. Calcium/calmodulin-dependent protein kinase II (CaMKII) inhibition induces neurotoxicity via dysregulation of glutamate/calcium signaling and hyperexcitability. J Biol Chem 2012; 287:8495-506. [PMID: 22253441 DOI: 10.1074/jbc.m111.323915] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Aberrant glutamate and calcium signalings are neurotoxic to specific neuronal populations. Calcium/calmodulin-dependent kinase II (CaMKII), a multifunctional serine/threonine protein kinase in neurons, is believed to regulate neurotransmission and synaptic plasticity in response to calcium signaling produced by neuronal activity. Importantly, several CaMKII substrates control neuronal structure, excitability, and plasticity. Here, we demonstrate that CaMKII inhibition for >4 h using small molecule and peptide inhibitors induces apoptosis in cultured cortical neurons. The neuronal death produced by prolonged CaMKII inhibition is associated with an increase in TUNEL staining and caspase-3 cleavage and is blocked with the translation inhibitor cycloheximide. Thus, this neurotoxicity is consistent with apoptotic mechanisms, a conclusion that is further supported by dysregulated calcium signaling with CaMKII inhibition. CaMKII inhibitory peptides also enhance the number of action potentials generated by a ramp depolarization, suggesting increased neuronal excitability with a loss of CaMKII activity. Extracellular glutamate concentrations are augmented with prolonged inhibition of CaMKII. Enzymatic buffering of extracellular glutamate and antagonism of the NMDA subtype of glutamate receptors prevent the calcium dysregulation and neurotoxicity associated with prolonged CaMKII inhibition. However, in the absence of CaMKII inhibition, elevated glutamate levels do not induce neurotoxicity, suggesting that a combination of CaMKII inhibition and elevated extracellular glutamate levels results in neuronal death. In sum, the loss of CaMKII observed with multiple pathological states in the central nervous system, including epilepsy, brain trauma, and ischemia, likely exacerbates programmed cell death by sensitizing vulnerable neuronal populations to excitotoxic glutamate signaling and inducing an excitotoxic insult itself.
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Affiliation(s)
- Nicole M Ashpole
- Stark Neuroscience Research Institute, Indiana University of School of Medicine, Indianapolis, Indiana 46202, USA
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Zhang YH, Kays J, Hodgdon KE, Sacktor TC, Nicol GD. Nerve growth factor enhances the excitability of rat sensory neurons through activation of the atypical protein kinase C isoform, PKMζ. J Neurophysiol 2011; 107:315-35. [PMID: 21975456 DOI: 10.1152/jn.00030.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our previous work showed that nerve growth factor (NGF) increased the excitability of small-diameter capsaicin-sensitive sensory neurons by activating the p75 neurotrophin receptor and releasing sphingolipid-derived second messengers. Whole cell patch-clamp recordings were used to establish the signaling pathways whereby NGF augments action potential (AP) firing (i.e., sensitization). Inhibition of MEK1/2 (PD-98059), PLC (U-73122, neomycin), or conventional/novel isoforms of PKC (bisindolylmaleimide I) had no effect on the sensitization produced by NGF. Pretreatment with a membrane-permeable, myristoylated pseudosubstrate inhibitor of atypical PKCs (aPKCs: PKMζ, PKCζ, and PKCλ/ι) blocked the NGF-induced increase in AP firing. Inhibitors of phosphatidylinositol 3-kinase (PI3K) also blocked the sensitization produced by NGF. Isolated sensory neurons were also treated with small interfering RNA (siRNA) targeted to PKCζ. Both Western blots and quantitative real-time PCR established that PKMζ, but neither full-length PKCζ nor PKCλ/ι, was significantly reduced after siRNA exposure. Treatment with these labeled siRNA prevented the NGF-induced enhancement of excitability. Furthermore, consistent with the high degree of catalytic homology for aPKCs, internal perfusion with active recombinant PKCζ or PKCι augmented excitability, recapitulating the sensitization produced by NGF. Internal perfusion with recombinant PKCζ suppressed the total potassium current and enhanced the tetrodotoxin-resistant sodium current. Pretreatment with the myristoylated pseudosubstrate inhibitor blocked the increased excitability produced by ceramide or internal perfusion with recombinant PKCζ. These results demonstrate that NGF leads to the activation of PKMζ that ultimately enhances the capacity of small-diameter capsaicin-sensitive sensory neurons to fire APs through a PI3K-dependent signaling cascade.
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Affiliation(s)
- Y H Zhang
- Dept. of Pharmacology and Toxicology, Indiana Univ. School of Medicine, Indianapolis, IN 46202, USA
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Mantyh PW, Koltzenburg M, Mendell LM, Tive L, Shelton DL. Antagonism of nerve growth factor-TrkA signaling and the relief of pain. Anesthesiology 2011; 115:189-204. [PMID: 21602663 PMCID: PMC3121917 DOI: 10.1097/aln.0b013e31821b1ac5] [Citation(s) in RCA: 237] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nerve growth factor (NGF) was originally discovered as a neurotrophic factor essential for the survival of sensory and sympathetic neurons during development. However, in the adult NGF has been found to play an important role in nociceptor sensitization after tissue injury. The authors outline mechanisms by which NGF activation of its cognate receptor, tropomyosin-related kinase A receptor, regulates a host of ion channels, receptors, and signaling molecules to enhance acute and chronic pain. The authors also document that peripherally restricted antagonism of NGF-tropomyosin-related kinase A receptor signaling is effective for controlling human pain while appearing to maintain normal nociceptor function. Understanding whether there are any unexpected adverse events and how humans may change their behavior and use of the injured/degenerating tissue after significant pain relief without sedation will be required to fully appreciate the patient populations that may benefit from these therapies targeting NGF.
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Affiliation(s)
- Patrick W Mantyh
- Department of Pharmacology, University of Arizona, Tucson, Arizona, USA.
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Ho R, Minturn JE, Simpson AM, Iyer R, Light JE, Evans AE, Brodeur GM. The effect of P75 on Trk receptors in neuroblastomas. Cancer Lett 2011; 305:76-85. [PMID: 21419569 DOI: 10.1016/j.canlet.2011.02.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 02/09/2011] [Accepted: 02/10/2011] [Indexed: 01/04/2023]
Abstract
Neuroblastomas (NBs) with favorable outcome usually express TrkA, whereas unfavorable NBs frequently express TrkB and its cognate ligand BDNF. P75 (p75(LNTR), NGFR, TNFRSF16) binds NGF-related neurotrophins with low affinity and usually is coexpressed with Trk receptors in NBs. Here, we investigated the importance of p75 coexpression with Trk receptors in NBs. We transfected p75 into two Trk-null NB cell lines, SH-SY5Y and NLF that were also engineered to stably express TrkA or TrkB. Cell numbers were compared between single (Trk alone) and double (Trk+p75) transfectants, and proliferation was assessed by flow cytometry. P75 coexpression had little effect on cell growth in Trk NB cells in the absence of ligand, but it increased sensitivity and greatly enhanced the effect of cognate ligand. Exogenous NGF induced greater phosphorylation of TrkA and AKT. This was associated with increased cell number in TrkA/p75 cells compared to TrkA cells (p<0.01), which was due to increased proliferation in TrkA/p75 cells (p<0.05), followed by differentiation. Exogenous BDNF also increased cell number in TrkB/p75 compared to TrkB cells (p<0.01), due to an increase in proliferation, but without differentiation. Coexpression of p75 also increased specificity of Trk-expressing cells to ligand. NT3-induced phosphorylation of TrkA and AKT was reduced in TrkA/p75 cells. NT3-induced phosphorylation of TrkB (as well as AKT and MAPK) was also reduced with p75 coexpression. Our results suggest that p75 plays an important role in enhancing both the sensitivity of Trk receptors to low levels of ligand, as well as increasing the specificity of Trks to their cognate ligands. It also enhances ligand-induced differentiation in TrkA/p75 but not TrkB/p75 cells.
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Affiliation(s)
- Ruth Ho
- Division of Oncology, The Children's Hospital of Philadelphia, PA 19104, United States
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Pain mechanisms in chronic pancreatitis: of a master and his fire. Langenbecks Arch Surg 2010; 396:151-60. [PMID: 21153480 PMCID: PMC3026929 DOI: 10.1007/s00423-010-0731-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 11/24/2010] [Indexed: 12/13/2022]
Abstract
BACKGROUND Unraveling the mechanisms of pain in chronic pancreatitis (CP) remains a true challenge. The rapid development of pancreatic surgery in the twentieth century, usage of advanced molecular biological techniques, and emergence of clinician-scientists have enabled the elucidation of several mechanisms that lead to the chronic, complicated neuropathic pain syndrome in CP. However, the proper analysis of pain in CP should include three main arms of mechanisms: "peripheral nociception," "peripheral/pancreatic neuropathy and neuroplasticity," and "central neuropathy and neuroplasticity." DISCUSSION According to our current knowledge, pain in CP involves sustained sensitization of pancreatic peripheral nociceptors by neurotransmitters and neurotrophic factors following neural damage. This peripheral pancreatic neuropathy leads to intrapancreatic neuroplastic alterations that involve a profound switch in the autonomic innervation of the human pancreas via "neural remodeling." Furthermore, this neuropathy entails a hyperexcitability of spinal sensory second-order neurons, which are subject to modulation from the brainstem via descending facilitation. Finally, viscerosensory cortical areas react to this central sensitization via spatial reorganization and thus a central neuroplasticity. The present review summarizes the current findings in these arms of mechanisms and introduces a novel concept to consistently describe pain in CP as a "predominantly neuropathic," "mixed-type" pain.
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Norman E, Cutler RG, Flannery R, Wang Y, Mattson MP. Plasma membrane sphingomyelin hydrolysis increases hippocampal neuron excitability by sphingosine-1-phosphate mediated mechanisms. J Neurochem 2010; 114:430-9. [PMID: 20456020 DOI: 10.1111/j.1471-4159.2010.06779.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Proteins that control the excitability of neurons, including voltage-dependent ion channels and neurotransmitter receptors, reside in a membrane lipid environment that includes sphingomyelin, but the influence of the metabolism of this lipid on excitability is unknown. Sphingomyelin in the plasma membrane can be cleaved by neutral sphingomyelinases (nSMase) to generate ceramides and sphingosine-1-phosphate (S1P) which have been shown to play a variety of roles in cellular signaling processes. We found that application of nSMase to hippocampal slices results in a selective enhancement in the population spike amplitude, resulting in fEPSP-PS potentiation of the CA3-CA1 schaeffer collateral synapse. Single cell recordings showed that nSMase activity increases action potential frequency in CA1 neurons in a reversible manner. Additional current clamp recordings showed that nSMase reduces the slow after-hyperpolarization after a burst of action potentials. Mass spectrometry-based measurements demonstrated that nSMase activity induces a rapid increase in the levels of ceramides and S1P in cells in hippocampal slices. The ability of nSMase to increase CA1 neuron excitability was blocked by an inhibitor of sphingosine kinase, the enzyme that converts ceramide to S1P. Moreover, direct intracellular application of S1P to CA1 neurons increased action potential firing. Our findings suggest roles for sphingomyelin metabolism and S1P in the positive regulation of the excitability of hippocampal neurons.
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Affiliation(s)
- Eric Norman
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, NIH Biomedical Research Center, Baltimore, Maryland 21224, USA
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Massa SM, Yang T, Xie Y, Shi J, Bilgen M, Joyce JN, Nehama D, Rajadas J, Longo FM. Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents. J Clin Invest 2010; 120:1774-85. [PMID: 20407211 DOI: 10.1172/jci41356] [Citation(s) in RCA: 303] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 02/17/2010] [Indexed: 02/01/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) activates the receptor tropomyosin-related kinase B (TrkB) with high potency and specificity, promoting neuronal survival, differentiation, and synaptic function. Correlations between altered BDNF expression and/or function and mechanism(s) underlying numerous neurodegenerative conditions, including Alzheimer disease and traumatic brain injury, suggest that TrkB agonists might have therapeutic potential. Using in silico screening with a BDNF loop-domain pharmacophore, followed by low-throughput in vitro screening in mouse fetal hippocampal neurons, we have efficiently identified small molecules with nanomolar neurotrophic activity specific to TrkB versus other Trk family members. Neurotrophic activity was dependent on TrkB and its downstream targets, although compound-induced signaling activation kinetics differed from those triggered by BDNF. A selected prototype compound demonstrated binding specificity to the extracellular domain of TrkB. In in vitro models of neurodegenerative disease, it prevented neuronal degeneration with efficacy equal to that of BDNF, and when administered in vivo, it caused hippocampal and striatal TrkB activation in mice and improved motor learning after traumatic brain injury in rats. These studies demonstrate the utility of loop modeling in drug discovery and reveal what we believe to be the first reported small molecules derived from a targeted BDNF domain that specifically activate TrkB.We propose that these compounds constitute a novel group of tools for the study of TrkB signaling and may provide leads for developing new therapeutic agents for neurodegenerative diseases.
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Affiliation(s)
- Stephen M Massa
- Department of Neurology and Laboratory for Computational Neurochemistry and Drug Discovery, UCSF, San Francisco, California, USA
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Takeda M, Kitagawa J, Nasu M, Takahashi M, Iwata K, Matsumoto S. Glial cell line-derived neurotrophic factor acutely modulates the excitability of rat small-diameter trigeminal ganglion neurons innervating facial skin. Brain Behav Immun 2010; 24:72-82. [PMID: 19679180 DOI: 10.1016/j.bbi.2009.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 07/14/2009] [Accepted: 08/05/2009] [Indexed: 12/31/2022] Open
Abstract
Glial cell line-derived neurotrophic factor (GDNF) plays an important role in adult sensory neuron function. However, the acute effects of GDNF on primary sensory neuron excitability remain to be elucidated. The aim of the present study was to investigate whether GDNF acutely modulates the excitability of adult rat trigeminal ganglion (TRG) neurons that innervate the facial skin by using perforated-patch clamping, retrograde-labeling and immunohistochemistry techniques. Fluorogold (FG) retrograde labeling was used to identify the TRG neurons innervating the facial skin. The FG-labeled small- and medium-diameter GDNF immunoreactive TRG neurons, and most of these neurons also expressed the GDNF family receptor alpha-1 (GFRalpha-1). In whole-cell voltage-clamp mode, GDNF application significantly inhibited voltage-gated K(+) transient (I(A)) and sustained (I(K)) currents in most dissociated FG-labeled small-diameter TRG neurons. This effect was concentration-dependent and was abolished by co-application of the protein tyrosine kinase inhibitor, K252b. Under current-clamp conditions, the repetitive firing during a depolarizing pulse were significantly increased by GDNF application. GDNF application also increased the duration of the repolarization phase and decreased the duration of the depolarization phase of the action potential, and these characteristic effects were also abolished by co-application of K252b. These results suggest that acute application of GDNF enhances the neuronal excitability of adult rat small-diameter TRG neurons innervating the facial skin, via activation of GDNF-induced intracellular signaling pathway. We therefore conclude that a local release of GDNF from TRG neuronal soma and/or nerve terminals may regulate normal sensory function, including nociception.
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Affiliation(s)
- Mamoru Takeda
- Department of Physiology, School of Life Dentistry at Tokyo, Nippon Dental University, 1-9-20, Fujimi-cho, Chiyoda-ku, Tokyo 102-8159, Japan.
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Luther JA, Birren SJ. Neurotrophins and target interactions in the development and regulation of sympathetic neuron electrical and synaptic properties. Auton Neurosci 2009; 151:46-60. [PMID: 19748836 DOI: 10.1016/j.autneu.2009.08.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The electrical and synaptic properties of neurons are essential for determining the function of the nervous system. Thus, understanding the mechanisms that control the appropriate developmental acquisition and maintenance of these properties is a critical problem in neuroscience. A great deal of our understanding of these developmental mechanisms comes from studies of soluble growth factor signaling between cells in the peripheral nervous system. The sympathetic nervous system has provided a model for studying the role of these factors both in early development and in the establishment of mature properties. In particular, neurotrophins produced by the targets of sympathetic innervation regulate the synaptic and electrophysiological properties of postnatal sympathetic neurons. In this review we examine the role of neurotrophin signaling in the regulation of synaptic strength, neurotransmitter phenotype, voltage-gated currents and repetitive firing properties of sympathetic neurons. Together, these properties determine the level of sympathetic drive to target organs such as the heart. Changes in this sympathetic drive, which may be linked to dysfunctions in neurotrophin signaling, are associated with devastating diseases such as high blood pressure, arrhythmias and heart attack. Neurotrophins appear to play similar roles in modulating the synaptic and electrical properties of other peripheral and central neuronal systems, suggesting that information provided from studies in the sympathetic nervous system will be widely applicable for understanding the neurotrophic regulation of neuronal function in other systems.
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Affiliation(s)
- Jason A Luther
- Department of Biology, National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA.
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Lu VB, Colmers WF, Smith PA. Long-term effects of brain-derived neurotrophic factor on the frequency of inhibitory synaptic events in the rat superficial dorsal horn. Neuroscience 2009; 161:1135-43. [PMID: 19376198 DOI: 10.1016/j.neuroscience.2009.04.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 04/10/2009] [Accepted: 04/10/2009] [Indexed: 02/05/2023]
Abstract
Chronic constriction injury (CCI) of rat sciatic nerve produces a specific pattern of electrophysiological changes in the superficial dorsal horn that lead to central sensitization that is associated with neuropathic pain. These changes can be recapitulated in spinal cord organotypic cultures by long term (5-6 days) exposure to brain-derived neurotrophic factor (BDNF) (200 ng/ml). Certain lines of evidence suggest that both CCI and BDNF increase excitatory synaptic drive to putative excitatory neurons while reducing that to putative inhibitory interneurons. Because BDNF slows the rate of discharge of synaptically-driven action potentials in inhibitory neurons, it should also decrease the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) throughout the superficial dorsal horn. To test this possibility, we characterized superficial dorsal horn neurons in organotypic cultures according to five electrophysiological phenotypes that included tonic, delay and irregular firing neurons. Five to 6 days of treatment with 200 ng/ml BDNF decreased sIPSC frequency in tonic and irregular neurons as might be expected if BDNF selectively decreases excitatory synaptic drive to inhibitory interneurons. The frequency of sIPSCs in delay neurons was however increased. Further analysis of the action of BDNF on tetrodotoxin-resistant miniature inhibitory postsynaptic currents (mIPSC) showed that the frequency was increased in delay neurons, unchanged in tonic neurons and decreased in irregular neurons. BDNF may thus reduce action potential frequency in those inhibitory interneurons that project to tonic and irregular neurons but not in those that project to delay neurons.
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Affiliation(s)
- V B Lu
- Department of Pharmacology and Centre for Neuroscience, 9.75 Medical Sciences Building, University of Alberta, Edmonton, AB T6G3E7, Canada
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