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Verduzco-Mendoza A, Mota-Rojas D, Olmos-Hernández A, Avila-Luna A, García-García K, Gálvez-Rosas A, Hidalgo-Bravo A, Ríos C, Parra-Cid C, Montes S, García-López J, Ramos-Languren LE, Pérez-Severiano F, González-Piña R, Bueno-Nava A. Changes in Noradrenergic Synthesis and Dopamine Beta-Hydroxylase Activity in Response to Oxidative Stress after Iron-induced Brain Injury. Neurochem Res 2024:10.1007/s11064-024-04222-9. [PMID: 39105899 DOI: 10.1007/s11064-024-04222-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2024] [Revised: 07/22/2024] [Accepted: 07/25/2024] [Indexed: 08/07/2024]
Abstract
Noradrenaline (NA) levels are altered during the first hours and several days after cortical injury. NA modulates motor functional recovery. The present study investigated whether iron-induced cortical injury modulated noradrenergic synthesis and dopamine beta-hydroxylase (DBH) activity in response to oxidative stress in the brain cortex, pons and cerebellum of the rat. Seventy-eight rats were divided into two groups: (a) the sham group, which received an intracortical injection of a vehicle solution; and (b) the injured group, which received an intracortical injection of ferrous chloride. Motor deficits were evaluated for 20 days post-injury. On the 3rd and 20th days, the rats were euthanized to measure oxidative stress indicators (reactive oxygen species (ROS), reduced glutathione (GSH) and oxidized glutathione (GSSG)) and catecholamines (NA, dopamine (DA)), plus DBH mRNA and protein levels. Our results showed that iron-induced brain cortex injury increased noradrenergic synthesis and DBH activity in the brain cortex, pons and cerebellum at 3 days post-injury, predominantly on the ipsilateral side to the injury, in response to oxidative stress. A compensatory increase in contralateral noradrenergic activity was observed, but without changes in the DBH mRNA and protein levels in the cerebellum and pons. In conclusion, iron-induced cortical injury increased the noradrenergic response in the brain cortex, pons and cerebellum, particularly on the ipsilateral side, accompanied by a compensatory response on the contralateral side. The oxidative stress was countered by antioxidant activity, which favored functional recovery following motor deficits.
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Affiliation(s)
- Antonio Verduzco-Mendoza
- Programa de Doctorado en Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, Ciudad de México, Mexico
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Daniel Mota-Rojas
- División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana CBS, Unidad Xochimilco, Ciudad de México, Mexico
| | - Adriana Olmos-Hernández
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Alberto Avila-Luna
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Karla García-García
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Arturo Gálvez-Rosas
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Alberto Hidalgo-Bravo
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Camilo Ríos
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
- División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana CBS, Unidad Xochimilco, Ciudad de México, Mexico
| | - Carmen Parra-Cid
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Sergio Montes
- Unidad Académica Multidisciplinaria Reynosa-Aztlán, Universidad Autónoma de Tamaulipas, calle 16 y lago de Chapala, Aztlán, Tamaulipas, Mexico
| | - Julieta García-López
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico
| | - Laura E Ramos-Languren
- Facultad de Psicología, División de Estudios Profesionales, Universidad Nacional Autónoma de Mexico, Av. Universidad 3040, Col, Copilco Universidad Alcaldía Coyoacán, Ciudad de México, Mexico
| | - Francisca Pérez-Severiano
- Laboratorio de Neurofarmacología Molecular y Nanotecnología, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, SSa, Insurgentes Sur 3877, Ciudad de México, Mexico
| | - Rigoberto González-Piña
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Salvador Díaz Mirón esq. Plan de San Luis S/N, Miguel Hidalgo, Casco de Santo Tomas, 11340, Ciudad de México, Mexico
- Clínica de Rehabilitación del Daño Cerebral CLIREDACE "Dr. Hugo Iván González Gutiérrez", Monterrey 243, Col. Roma Sur, Alcaldía Cuauhtémoc, Ciudad de México, Mexico
| | - Antonio Bueno-Nava
- Dirección de Investigación, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calzada México-Xochimilco 289, Arenal de Guadalupe, Ciudad de México, Mexico.
- Laboratorio de Neurofisiología Química de la Discapacidad, Coordinación de Neurociencias Básica, Arenal de Guadalupe, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, SSa, Calz. México-Xochimilco 289, Ciudad de México, 14389, Mexico.
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Hu S, Exner C, Sienel RI, When AC, Seker FB, Boldoczki FM, Guo Y, Duering M, Pasternak O, Plesnila N, Schwarzmaier SM. Characterization of Vasogenic and Cytotoxic Brain Edema Formation After Experimental Traumatic Brain Injury by Free Water Diffusion Magnetic Resonance Imaging. J Neurotrauma 2024; 41:393-406. [PMID: 37776177 PMCID: PMC10908318 DOI: 10.1089/neu.2023.0222] [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] [Indexed: 10/01/2023] Open
Abstract
Brain edema formation is a key factor for secondary tissue damage after traumatic brain injury (TBI), however, the type of brain edema and the temporal profile of edema formation are still unclear. We performed free water imaging, a bi-tensor model based diffusion MRI analysis, to characterize vasogenic brain edema (VBE) and cytotoxic edema (CBE) formation up to 7 days after experimental TBI. Male C57/Bl6 mice were subjected to controlled cortical impact (CCI) or sham surgery and investigated by MRI 4h, 1, 2, 3, 5, and 7 days thereafter (n = 8/group). We determined mean diffusivity (MD) and free water (FW) in contusion, pericontusional area, ipsi- and contralateral brain tissue. Free (i.e., non-restricted) water was interpreted as VBE, restricted water as CBE. To verify the results, VBE formation was investigated by in-vivo 2-Photon Microscopy (2-PM) 48h after surgery. We found that MD and FW values decreased for 48h within the contusion, indicating the occurrence of CBE. In pericontusional tissue, MD and FW indices were increased at all time points, suggesting the formation of VBE. This was consistent with our results obtained by 2-PM. Taken together, CBE formation occurs for 48h after trauma and is restricted to the contusion, while VBE forms in pericontusional tissue up to 7 days after TBI. Our results indicate that free water magnetic resonance imaging may represent a promising tool to investigate vasogenic and cytotoxic brain edema in the laboratory and in patients.
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Affiliation(s)
- Senbin Hu
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Carina Exner
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Rebecca Isabella Sienel
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Antonia Clarissa When
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Fatma Burcu Seker
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Fanni Magdane Boldoczki
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Yinghuimin Guo
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Marco Duering
- Medical Image Analysis Center (MIAC) and Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Ofer Pasternak
- Neuroscience Image Computing, Harvard Medical School, Boston, Massachusetts, USA
| | - Nikolaus Plesnila
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Susanne M. Schwarzmaier
- Institute for Stroke and Dementia Research (ISD)and Ludwig-Maximilians University (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
- Department of Anesthesiology, Ludwig-Maximilians University (LMU), Munich, Germany
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Zhang Y, Li Z, Wang H, Pei Z, Zhao S. Molecular biomarkers of diffuse axonal injury: recent advances and future perspectives. Expert Rev Mol Diagn 2024; 24:39-47. [PMID: 38183228 DOI: 10.1080/14737159.2024.2303319] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 12/18/2023] [Indexed: 01/07/2024]
Abstract
INTRODUCTION Diffuse axonal injury (DAI), with high mortality and morbidity both in children and adults, is one of the most severe pathological consequences of traumatic brain injury. Currently, clinical diagnosis, disease assessment, disability identification, and postmortem diagnosis of DAI is mainly limited by the absent of specific molecular biomarkers. AREAS COVERED In this review, we first introduce the pathophysiology of DAI, summarized the reported biomarkers in previous animal and human studies, and then the molecular biomarkers such as β-Amyloid precursor protein, neurofilaments, S-100β, myelin basic protein, tau protein, neuron-specific enolase, Peripherin and Hemopexin for DAI diagnosis is summarized. Finally, we put forward valuable views on the future research direction of diagnostic biomarkers of DAI. EXPERT OPINION In recent years, the advanced technology has ultimately changed the research of DAI, and the numbers of potential molecular biomarkers was introduced in related studies. We summarized the latest updated information in such studies to provide references for future research and explore the potential pathophysiological mechanism on diffuse axonal injury.
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Affiliation(s)
- Youyou Zhang
- Department of Geriatrics Neurology, the Second Affiliated Hospital of Xi'an Jiao Tong University, Xi'an Jiaotong University, Xi'an, Shaanxi, China
- Linfen People's Hosiptal, the Seventh Clinical Medical College of Shanxi Medical University, Linfen, Shanxi, China
| | - Zhaoyang Li
- Department of Occupational and Environmental Health, School of Public Health, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Hui Wang
- Department of Geriatrics Neurology, the Second Affiliated Hospital of Xi'an Jiao Tong University, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Zhiyong Pei
- Linfen People's Hosiptal, the Seventh Clinical Medical College of Shanxi Medical University, Linfen, Shanxi, China
| | - Shuquan Zhao
- Department of Forensic Pathology, Zhongshan School of Medicine Sun Yat-sen University, Guangzhou, Guangdong, China
- Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Sun Yat-sen University, Guangzhou, Guangdong, China
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Krieg JL, Leonard AV, Turner RJ, Corrigan F. Identifying the Phenotypes of Diffuse Axonal Injury Following Traumatic Brain Injury. Brain Sci 2023; 13:1607. [PMID: 38002566 PMCID: PMC10670443 DOI: 10.3390/brainsci13111607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 11/15/2023] [Accepted: 11/17/2023] [Indexed: 11/26/2023] Open
Abstract
Diffuse axonal injury (DAI) is a significant feature of traumatic brain injury (TBI) across all injury severities and is driven by the primary mechanical insult and secondary biochemical injury phases. Axons comprise an outer cell membrane, the axolemma which is anchored to the cytoskeletal network with spectrin tetramers and actin rings. Neurofilaments act as space-filling structural polymers that surround the central core of microtubules, which facilitate axonal transport. TBI has differential effects on these cytoskeletal components, with axons in the same white matter tract showing a range of different cytoskeletal and axolemma alterations with different patterns of temporal evolution. These require different antibodies for detection in post-mortem tissue. Here, a comprehensive discussion of the evolution of axonal injury within different cytoskeletal elements is provided, alongside the most appropriate methods of detection and their temporal profiles. Accumulation of amyloid precursor protein (APP) as a result of disruption of axonal transport due to microtubule failure remains the most sensitive marker of axonal injury, both acutely and chronically. However, a subset of injured axons demonstrate different pathology, which cannot be detected via APP immunoreactivity, including degradation of spectrin and alterations in neurofilaments. Furthermore, recent work has highlighted the node of Ranvier and the axon initial segment as particularly vulnerable sites to axonal injury, with loss of sodium channels persisting beyond the acute phase post-injury in axons without APP pathology. Given the heterogenous response of axons to TBI, further characterization is required in the chronic phase to understand how axonal injury evolves temporally, which may help inform pharmacological interventions.
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Affiliation(s)
- Justin L Krieg
- Translational Neuropathology Laboratory, School of Biomedicine, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide 5000, Australia
| | - Anna V Leonard
- Translational Neuropathology Laboratory, School of Biomedicine, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide 5000, Australia
| | - Renée J Turner
- Translational Neuropathology Laboratory, School of Biomedicine, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide 5000, Australia
| | - Frances Corrigan
- Translational Neuropathology Laboratory, School of Biomedicine, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide 5000, Australia
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Freire MAM, Rocha GS, Bittencourt LO, Falcao D, Lima RR, Cavalcanti JRLP. Cellular and Molecular Pathophysiology of Traumatic Brain Injury: What Have We Learned So Far? BIOLOGY 2023; 12:1139. [PMID: 37627023 PMCID: PMC10452099 DOI: 10.3390/biology12081139] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023]
Abstract
Traumatic brain injury (TBI) is one of the leading causes of long-lasting morbidity and mortality worldwide, being a devastating condition related to the impairment of the nervous system after an external traumatic event resulting in transitory or permanent functional disability, with a significant burden to the healthcare system. Harmful events underlying TBI can be classified into two sequential stages, primary and secondary, which are both associated with breakdown of the tissue homeostasis due to impairment of the blood-brain barrier, osmotic imbalance, inflammatory processes, oxidative stress, excitotoxicity, and apoptotic cell death, ultimately resulting in a loss of tissue functionality. The present study provides an updated review concerning the roles of brain edema, inflammation, excitotoxicity, and oxidative stress on brain changes resulting from a TBI. The proper characterization of the phenomena resulting from TBI can contribute to the improvement of care, rehabilitation and quality of life of the affected people.
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Affiliation(s)
- Marco Aurelio M. Freire
- Graduate Program in Physiological Sciences, University of the State of Rio Grande do Norte, Mossoró 59607-360, RN, Brazil
| | - Gabriel Sousa Rocha
- Graduate Program in Biochemistry and Molecular Biology, University of the State of Rio Grande do Norte, Mossoró 59607-360, RN, Brazil
| | - Leonardo Oliveira Bittencourt
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará, Belém 66075-900, PA, Brazil
| | - Daniel Falcao
- VCU Health Systems, Virginia Commonwealth University, 23219 Richmond, VA, USA
| | - Rafael Rodrigues Lima
- Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará, Belém 66075-900, PA, Brazil
| | - Jose Rodolfo Lopes P. Cavalcanti
- Graduate Program in Physiological Sciences, University of the State of Rio Grande do Norte, Mossoró 59607-360, RN, Brazil
- Graduate Program in Biochemistry and Molecular Biology, University of the State of Rio Grande do Norte, Mossoró 59607-360, RN, Brazil
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Song H, McEwan PP, Ameen-Ali KE, Tomasevich A, Kennedy-Dietrich C, Palma A, Arroyo EJ, Dolle JP, Johnson VE, Stewart W, Smith DH. Concussion leads to widespread axonal sodium channel loss and disruption of the node of Ranvier. Acta Neuropathol 2022; 144:967-985. [PMID: 36107227 PMCID: PMC9547928 DOI: 10.1007/s00401-022-02498-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 09/08/2022] [Accepted: 09/08/2022] [Indexed: 01/26/2023]
Abstract
Despite being a major health concern, little is known about the pathophysiological changes that underly concussion. Nonetheless, emerging evidence suggests that selective damage to white matter axons, or diffuse axonal injury (DAI), disrupts brain network connectivity and function. While voltage-gated sodium channels (NaChs) and their anchoring proteins at the nodes of Ranvier (NOR) on axons are key elements of the brain's network signaling machinery, changes in their integrity have not been studied in context with DAI. Here, we utilized a clinically relevant swine model of concussion that induces evolving axonal pathology, demonstrated by accumulation of amyloid precursor protein (APP) across the white matter. Over a two-week follow-up post-concussion with this model, we found widespread loss of NaCh isoform 1.6 (Nav1.6), progressive increases in NOR length, the appearance of void and heminodes and loss of βIV-spectrin, ankyrin G, and neurofascin 186 or their collective diffusion into the paranode. Notably, these changes were in close proximity, yet distinct from APP-immunoreactive swollen axonal profiles, potentially representing a unique, newfound phenotype of axonal pathology in DAI. Since concussion in humans is non-fatal, the clinical relevance of these findings was determined through examination of post-mortem brain tissue from humans with higher levels of acute traumatic brain injury. Here, a similar loss of Nav1.6 and changes in NOR structures in brain white matter were observed as found in the swine model of concussion. Collectively, this widespread and progressive disruption of NaChs and NOR appears to be a form of sodium channelopathy, which may represent an important substrate underlying brain network dysfunction after concussion.
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Affiliation(s)
- Hailong Song
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - Przemyslaw P McEwan
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - Kamar E Ameen-Ali
- School of Neuroscience and Psychology, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Alexandra Tomasevich
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | | | - Alexander Palma
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - Edgardo J Arroyo
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - Jean-Pierre Dolle
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - Victoria E Johnson
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA
| | - William Stewart
- School of Neuroscience and Psychology, University of Glasgow, Glasgow, G12 8QQ, UK
- Department of Neuropathology, Queen Elizabeth University Hospital, Glasgow, G51 4TF, UK
| | - Douglas H Smith
- Department of Neurosurgery, Center for Brain Injury and Repair, University of Pennsylvania, 3320 Smith Walk, 105 Hayden Hall, Philadelphia, PA, 19104, USA.
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Purkinje cell vulnerability induced by diffuse traumatic brain injury is linked to disruption of long-range neuronal circuits. Acta Neuropathol Commun 2022; 10:129. [PMID: 36064443 PMCID: PMC9446851 DOI: 10.1186/s40478-022-01435-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/22/2022] [Indexed: 11/10/2022] Open
Abstract
Cerebellar dysfunction is commonly observed following traumatic brain injury (TBI). While direct impact to the cerebellum by TBI is rare, cerebellar pathology may be caused by indirect injury via cortico-cerebellar pathways. To address the hypothesis that degeneration of Purkinje cells (PCs), which constitute the sole output from the cerebellum, is linked to long-range axonal injury and demyelination, we used the central fluid percussion injury (cFPI) model of widespread traumatic axonal injury in mice. Compared to controls, TBI resulted in early PC loss accompanied by alterations in the size of pinceau synapses and levels of non-phosphorylated neurofilament in PCs. A combination of vDISCO tissue clearing technique and immunohistochemistry for vesicular glutamate transporter type 2 show that diffuse TBI decreased mossy and climbing fiber synapses on PCs. At 2 days post-injury, numerous axonal varicosities were found in the cerebellum supported by fractional anisotropy measurements using 9.4 T MRI. The disruption and demyelination of the cortico-cerebellar circuits was associated with poor performance of brain-injured mice in the beam-walk test. Despite a lack of direct input from the injury site to the cerebellum, these findings argue for novel long-range mechanisms causing Purkinje cell injury that likely contribute to cerebellar dysfunction after TBI.
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