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Roseborough AD, Ollen-Bittle N, Whitehead SN. Using microglia-derived extracellular vesicles to capture diversity of microglial activation phenotypes following neurological injury. Neural Regen Res 2024; 19:1633-1634. [PMID: 38103216 PMCID: PMC10960273 DOI: 10.4103/1673-5374.389632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/14/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023] Open
Affiliation(s)
- Austyn D. Roseborough
- Vulnerable Brain Laboratory, Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, London, OH, Canada
| | - Nikita Ollen-Bittle
- Vulnerable Brain Laboratory, Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, London, OH, Canada
| | - Shawn N. Whitehead
- Vulnerable Brain Laboratory, Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, London, OH, Canada
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2
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Che J, Wang H, Dong J, Wu Y, Zhang H, Fu L, Zhang J. Human umbilical cord mesenchymal stem cell-derived exosomes attenuate neuroinflammation and oxidative stress through the NRF2/NF-κB/NLRP3 pathway. CNS Neurosci Ther 2024; 30:e14454. [PMID: 37697971 PMCID: PMC10916441 DOI: 10.1111/cns.14454] [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: 04/04/2023] [Revised: 05/19/2023] [Accepted: 08/16/2023] [Indexed: 09/13/2023] Open
Abstract
AIMS We investigated whether human umbilical cord mesenchymal stem cell (hUC-MSC)-derived exosomes bear therapeutic potential against lipopolysaccharide (LPS)-induced neuroinflammation. METHODS Exosomes were isolated from hUC-MSC supernatant by ultra-high-speed centrifugation and characterized by transmission electron microscopy and western blotting. Inflammatory responses were induced by LPS in BV-2 cells, primary microglial cultures, and C57BL/6J mice. H2 O2 was also used to induce inflammation and oxidative stress in BV-2 cells. The effects of hUC-MSC-derived exosomes on inflammatory cytokine expression, oxidative stress, and microglia polarization were studied by immunofluorescence and western blotting. RESULTS Treatment with hUC-MSC-derived exosomes significantly decreased the LPS- or H2 O2 -induced oxidative stress and expression of pro-inflammatory cytokines (IL-6 and TNF-α) in vitro, while promoting an anti-inflammatory (classical M2) phenotype in an LPS-treated mouse model. Mechanistically, the exosomes increased the NRF2 levels and inhibited the LPS-induced NF-κB p65 phosphorylation and NLRP3 inflammasome activation. In contrast, the reactive oxygen species scavenger NAC and NF-κB inhibitor BAY 11-7082 also inhibited the LPS-induced NLRP3 inflammasome activation and switched to the classical M2 phenotype. Treatment with the NRF2 inhibitor ML385 abolished the anti-inflammatory and anti-oxidative effects of the exosomes. CONCLUSION hUC-MSC-derived exosomes ameliorated LPS/H2 O2 -induced neuroinflammation and oxidative stress by inhibiting the microglial NRF2/NF-κB/NLRP3 signaling pathway.
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Affiliation(s)
- Ji Che
- Department of AnesthesiologyFudan University Shanghai Cancer CenterShanghaiChina
- Department of Oncology, Shanghai Medical CollegeFudan UniversityShanghaiChina
| | - Hui Wang
- Department of AnesthesiologyFudan University Shanghai Cancer CenterShanghaiChina
- Department of Oncology, Shanghai Medical CollegeFudan UniversityShanghaiChina
| | - Jing Dong
- Department of AnesthesiologyFudan University Shanghai Cancer CenterShanghaiChina
- Department of Oncology, Shanghai Medical CollegeFudan UniversityShanghaiChina
| | - Yuanyuan Wu
- Department of AnesthesiologyFudan University Shanghai Cancer CenterShanghaiChina
- Department of Oncology, Shanghai Medical CollegeFudan UniversityShanghaiChina
| | - Haichao Zhang
- Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong HospitalFudan UniversityShanghaiChina
| | - Lei Fu
- Shanghai Key Laboratory of Clinical Geriatric Medicine, Huadong HospitalFudan UniversityShanghaiChina
| | - Jun Zhang
- Department of AnesthesiologyFudan University Shanghai Cancer CenterShanghaiChina
- Department of Oncology, Shanghai Medical CollegeFudan UniversityShanghaiChina
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3
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Grovola MR, Jinich A, Paleologos N, Arroyo EJ, Browne KD, Swanson RL, Duda JE, Cullen DK. Persistence of Hyper-Ramified Microglia in Porcine Cortical Gray Matter after Mild Traumatic Brain Injury. Biomedicines 2023; 11:1960. [PMID: 37509599 PMCID: PMC10377269 DOI: 10.3390/biomedicines11071960] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/20/2023] [Accepted: 07/01/2023] [Indexed: 07/30/2023] Open
Abstract
Traumatic brain injury (TBI) is a major contributor to morbidity and mortality in the United States as several million people visit the emergency department every year due to TBI exposures. Unfortunately, there is still no consensus on the pathology underlying mild TBI, the most common severity sub-type of TBI. Previous preclinical and post-mortem human studies have detailed the presence of diffuse axonal injury following TBI, suggesting that white matter pathology is the predominant pathology of diffuse brain injury. However, the inertial loading produced by TBI results in strain fields in both gray and white matter. In order to further characterize gray matter pathology in mild TBI, our lab used a pig model (n = 25) of closed-head rotational acceleration-induced TBI to evaluate blood-brain barrier disruptions, neurodegeneration, astrogliosis, and microglial reactivity in the cerebral cortex out to 1 year post-injury. Immunohistochemical staining revealed the presence of a hyper-ramified microglial phenotype-more branches, junctions, endpoints, and longer summed process length-at 30 days post injury (DPI) out to 1 year post injury in the cingulate gyrus (p < 0.05), and at acute and subacute timepoints in the inferior temporal gyrus (p < 0.05). Interestingly, we did not find neuronal loss or astroglial reactivity paired with these chronic microglia changes. However, we observed an increase in fibrinogen reactivity-a measure of blood-brain barrier disruption-predominately in the gray matter at 3 DPI (p = 0.0003) which resolved to sham levels by 7 DPI out to chronic timepoints. Future studies should employ gene expression assays, neuroimaging, and behavioral assays to elucidate the effects of these hyper-ramified microglia, particularly related to neuroplasticity and responses to potential subsequent insults. Further understanding of the brain's inflammatory activity after mild TBI will hopefully provide understanding of pathophysiology that translates to clinical treatment for TBI.
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Affiliation(s)
- Michael R Grovola
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alan Jinich
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nicholas Paleologos
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Edgardo J Arroyo
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physical Medicine and Rehabilitation, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kevin D Browne
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Randel L Swanson
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Physical Medicine and Rehabilitation, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - John E Duda
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Parkinson's Disease Research, Education and Clinical Center, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
| | - D Kacy Cullen
- Center for Neurotrauma, Neurodegeneration & Restoration, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA
- Center for Brain Injury & Repair, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
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Wang X, Xie Y, Niu Y, Wan B, Lu Y, Luo Q, Zhu L. CX3CL1/CX3CR1 signal mediates M1-type microglia and accelerates high-altitude-induced forgetting. Front Cell Neurosci 2023; 17:1189348. [PMID: 37234914 PMCID: PMC10206058 DOI: 10.3389/fncel.2023.1189348] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 04/24/2023] [Indexed: 05/28/2023] Open
Abstract
Introduction Hypoxia-induced neuronal damage is the primary cause of cognitive impairment induced by high-altitude exposure. Microglia play a crucial regulatory role in the central nervous system (CNS) homeostasis and synaptic plasticity. M1-type polarized microglia are suspected to be responsible for CNS injury under hypoxic conditions, but the exact molecular mechanism is still unelucidated. Methods CX3CR1 knock out and wide type mice were exposed to a simulated plateau at 7000 m for 48 h to construct the model of hypobaric hypoxia-induced memory impairment. The memory impairment of mice was assessed by Morris water maze. The dendritic spine density in the hippocampus was examined by Golgi staining. The synapses in the CA1 region and the number of neurons in the DG region were examined by immunofluorescence staining. The synapses in microglia activation and phagocytosis were examined by immunofluorescence. The levels of CX3CL1/CX3CR1 and their downstream proteins were detected. CX3CR1 knockout primary microglia were treated with CX3CL1 combined with 1% O2. The levels of proteins related to microglial polarization, the uptake of synaptosome and phagocytotic ability of microglia were detected. Results In this study, mice exposed to a simulated 7000 m altitude for 48 h developed significant amnesia for recent memories, but no significant change in their anxiety levels was observed. Hypobaric hypoxia exposure (7000 m altitude above sea level for 48 h) resulted in synapse loss in the CA1 region of the hippocampus, but no significant changes occurred in the total number of neurons. Meanwhile, microglia activation, increased phagocytosis of synapses by microglia, and CX3CL1/CX3CR1 signal activation were observed under hypobaric hypoxic exposure. Further, we found that after hypobaric hypoxia exposure, CX3CR1-deficient mice showed less amnesia, less synaptic loss in the CA1 region, and less increase in M1 microglia, compared to their wildtype siblings. CX3CR1-deficient microglia did not exhibit M1-type polarization in response to either hypoxia or CX3CL1 induction. Both hypoxia and CX3CL1 induced the phagocytosis of synapses by microglia through the upregulation of microglial phagocytosis. Discussion The current study demonstrates that CX3CL1/CX3CR1 signal mediates the M1-type polarization of microglia under high-altitude exposure and upregulates microglial phagocytosis, which increases the phagocytosis of synapses in the CA1 region of the hippocampus, causing synaptic loss and inducing forgetting.
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Doust YV, Bindoff A, Holloway OG, Wilson R, King AE, Ziebell JM. Temporal changes in the microglial proteome of male and female mice after a diffuse brain injury using label-free quantitative proteomics. Glia 2023; 71:880-903. [PMID: 36468604 PMCID: PMC10952308 DOI: 10.1002/glia.24313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 11/22/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022]
Abstract
Traumatic brain injury (TBI) triggers neuroinflammatory cascades mediated by microglia, which promotes tissue repair in the short-term. These cascades may exacerbate TBI-induced tissue damage and symptoms in the months to years post-injury. However, the progression of the microglial function across time post-injury and whether this differs between biological sexes is not well understood. In this study, we examined the microglial proteome at 3-, 7-, or 28-days after a midline fluid percussion injury (mFPI) in male and female mice using label-free quantitative proteomics. Data are available via ProteomeXchange with identifier PXD033628. We identified a reduction in microglial proteins involved with clearance of neuronal debris via phagocytosis at 3- and 7-days post-injury. At 28 days post-injury, pro-inflammatory proteins were decreased and anti-inflammatory proteins were increased in microglia. These results indicate a reduction in microglial clearance of neuronal debris in the days post-injury with a shift to anti-inflammatory function by 28 days following TBI. The changes in the microglial proteome that occurred across time post-injury did not differ between biological sexes. However, we did identify an increase in microglial proteins related to pro-inflammation and phagocytosis as well as insulin and estrogen signaling in males compared with female mice that occurred with or without a brain injury. Although the microglial response was similar between males and females up to 28 days following TBI, biological sex differences in the microglial proteome, regardless of TBI, has implications for the efficacy of treatment strategies targeting the microglial response post-injury.
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Affiliation(s)
- Yasmine V. Doust
- Wicking Dementia Research and Education Centre, College of Health and MedicineUniversity of TasmaniaHobartTasmaniaAustralia
| | - Aidan Bindoff
- Wicking Dementia Research and Education Centre, College of Health and MedicineUniversity of TasmaniaHobartTasmaniaAustralia
| | - Olivia G. Holloway
- Wicking Dementia Research and Education Centre, College of Health and MedicineUniversity of TasmaniaHobartTasmaniaAustralia
| | - Richard Wilson
- Central Science Laboratory (CSL)University of TasmaniaHobartTasmaniaAustralia
| | - Anna E. King
- Wicking Dementia Research and Education Centre, College of Health and MedicineUniversity of TasmaniaHobartTasmaniaAustralia
| | - Jenna M. Ziebell
- Wicking Dementia Research and Education Centre, College of Health and MedicineUniversity of TasmaniaHobartTasmaniaAustralia
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Tsur N, Talmy T, Radomislensky I, Almog O, Gendler S. Traumatic maxillofacial injuries: Patterns, outcomes, and long-term follow-up of a military cohort. Dent Traumatol 2023; 39:147-156. [PMID: 36345164 DOI: 10.1111/edt.12801] [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: 08/23/2022] [Revised: 10/21/2022] [Accepted: 10/21/2022] [Indexed: 11/10/2022]
Abstract
BACKGROUND/AIMS Maxillofacial trauma poses a distinct challenge on the modern battlefield, and data on its long-term implications are scarce. The aim of this study was to investigate maxillofacial injury characteristics, outcomes, and complications along the continuum of care among hospitalized military personnel from the pre-hospital setting through long-term rehabilitation. MATERIALS AND METHODS A registry-based study was undertaken of three national trauma and rehabilitation registries: The Israel Defense Forces Trauma Registry (IDF-TR), which records pre-hospital data. The Israeli National Trauma Registry for in-hospital data and the Israel Ministry of Defense Rehabilitation Department (MOD-RD) registry contain long-term disability data. The cohort comprised IDF soldiers who suffered maxillofacial injuries between 1997 and 2020. RESULTS A total of 672 patients with maxillofacial injuries were included in the study, and 6.4% of all trauma admissions were related to maxillofacial injuries. Of these, 366 (54%) were injured in non-military (NMC) circumstances, and 306 (46%) were wounded in military circumstances (MC). The mechanisms of injury were mainly traffic-related among the NMC group compared with an explosion in the MC group. Maxillofacial fractures were frequently associated with traumatic brain injuries with higher rates in the NMC group than in the MC group (55% vs. 30%, p < .001). In a multivariate analysis, zygomatic and orbital fractures were associated with higher odds of concomitant head injury. The most common categories of long-term disability included central nervous system disorders, skull injuries, epilepsy, hearing impairment, ophthalmologic conditions, and post-traumatic stress disorder. CONCLUSIONS Maxillofacial injuries are often associated with concomitant traumatic brain injury. Long-term disabilities associated with these injuries included the central nervous system, hearing, ophthalmologic impairments, and post-traumatic stress disorder.
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Affiliation(s)
- Nir Tsur
- The Trauma and Combat Medicine Branch, Surgeon General's, Headquarters, Israel Defense Forces, Ramat Gan, Israel.,Department of Otolaryngology-Head and Neck Surgery, Rabin Medical Center, Tel Aviv University, Tel Aviv, Israel
| | - Tomer Talmy
- The Trauma and Combat Medicine Branch, Surgeon General's, Headquarters, Israel Defense Forces, Ramat Gan, Israel
| | - Irina Radomislensky
- The National Center for Trauma & Emergency Medicine Research, Gertner Institute, Tel HaShomer, Israel
| | - Ofer Almog
- The Trauma and Combat Medicine Branch, Surgeon General's, Headquarters, Israel Defense Forces, Ramat Gan, Israel.,The Hebrew University of Jerusalem Faculty of Medicine, Jerusalem, Israel
| | - Sami Gendler
- The Trauma and Combat Medicine Branch, Surgeon General's, Headquarters, Israel Defense Forces, Ramat Gan, Israel
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Ibeh S, Bakkar NMZ, Ahmad F, Nwaiwu J, Barsa C, Mekhjian S, Reslan MA, Eid AH, Harati H, Nabha S, Mechref Y, El-Yazbi AF, Kobeissy F. High fat diet exacerbates long-term metabolic, neuropathological, and behavioral derangements in an experimental mouse model of traumatic brain injury. Life Sci 2023; 314:121316. [PMID: 36565814 DOI: 10.1016/j.lfs.2022.121316] [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: 10/20/2022] [Revised: 12/13/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
AIMS Traumatic brain injury (TBI) constitutes a serious public health concern. Although TBI targets the brain, it can exert several systemic effects which can worsen the complications observed in TBI subjects. Currently, there is no FDA-approved therapy available for its treatment. Thus, there has been an increasing need to understand other factors that could modulate TBI outcomes. Among the factors involved are diet and lifestyle. High-fat diets (HFD), rich in saturated fat, have been associated with adverse effects on brain health. MAIN METHODS To study this phenomenon, an experimental mouse model of open head injury, induced by the controlled cortical impact was used along with high-fat feeding to evaluate the impact of HFD on brain injury outcomes. Mice were fed HFD for a period of two months where several neurological, behavioral, and molecular outcomes were assessed to investigate the impact on chronic consequences of the injury 30 days post-TBI. KEY FINDINGS Two months of HFD feeding, together with TBI, led to a notable metabolic, neurological, and behavioral impairment. HFD was associated with increased blood glucose and fat-to-lean ratio. Spatial learning and memory, as well as motor coordination, were all significantly impaired. Notably, HFD aggravated neuroinflammation, oxidative stress, and neurodegeneration. Also, cell proliferation post-TBI was repressed by HFD, which was accompanied by an increased lesion volume. SIGNIFICANCE Our research indicated that chronic HFD feeding can worsen functional outcomes, predispose to neurodegeneration, and decrease brain recovery post-TBI. This sheds light on the clinical impact of HFD on TBI pathophysiology and rehabilitation as well.
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Affiliation(s)
- Stanley Ibeh
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Nour-Mounira Z Bakkar
- Department of Pharmacology and Toxicology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Fatima Ahmad
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon; Neuroscience Research Center, Lebanese University, Beirut, Lebanon
| | - Judith Nwaiwu
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon; Deparment of Chemistry, Texas Tech University, Lubbock, TX, USA
| | - Chloe Barsa
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Sarine Mekhjian
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Mohammad Amine Reslan
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Ali H Eid
- Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar
| | - Hayat Harati
- Neuroscience Research Center, Lebanese University, Beirut, Lebanon
| | - Sanaa Nabha
- Neuroscience Research Center, Lebanese University, Beirut, Lebanon
| | - Yehia Mechref
- Deparment of Chemistry, Texas Tech University, Lubbock, TX, USA
| | - Ahmed F El-Yazbi
- Department of Pharmacology and Toxicology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon; Deparment of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt; Faculty of Pharmacy, Alamein International University, Al-Alamein, Egypt.
| | - Firas Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon; Morehouse School of Medicine, Department of Neurobiology, Center for Neurotrauma, Multiomics & Biomarkers (CNMB), 720 Westview Dr. SW, Atlanta, GA 30310, USA.
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Honig MG, Del Mar NA, Henderson DL, O'Neal D, Doty JB, Cox R, Li C, Perry AM, Moore BM, Reiner A. Raloxifene Modulates Microglia and Rescues Visual Deficits and Pathology After Impact Traumatic Brain Injury. Front Neurosci 2021; 15:701317. [PMID: 34776838 PMCID: PMC8585747 DOI: 10.3389/fnins.2021.701317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 09/07/2021] [Indexed: 11/29/2022] Open
Abstract
Mild traumatic brain injury (TBI) involves widespread axonal injury and activation of microglia, which initiates secondary processes that worsen the TBI outcome. The upregulation of cannabinoid type-2 receptors (CB2) when microglia become activated allows CB2-binding drugs to selectively target microglia. CB2 inverse agonists modulate activated microglia by shifting them away from the harmful pro-inflammatory M1 state toward the helpful reparative M2 state and thus can stem secondary injury cascades. We previously found that treatment with the CB2 inverse agonist SMM-189 after mild TBI in mice produced by focal cranial blast rescues visual deficits and the optic nerve axon loss that would otherwise result. We have further shown that raloxifene, which is Food and Drug Administration (FDA)-approved as an estrogen receptor modulator to treat osteoporosis, but also possesses CB2 inverse agonism, yields similar benefit in this TBI model through its modulation of microglia. As many different traumatic events produce TBI in humans, it is widely acknowledged that diverse animal models must be used in evaluating possible therapies. Here we examine the consequences of TBI created by blunt impact to the mouse head for visual function and associated pathologies and assess raloxifene benefit. We found that mice subjected to impact TBI exhibited decreases in contrast sensitivity and the B-wave of the electroretinogram, increases in light aversion and resting pupil diameter, and optic nerve axon loss, which were rescued by daily injection of raloxifene at 5 or 10 mg/ml for 2 weeks. Raloxifene treatment was associated with reduced M1 activation and/or enhanced M2 activation in retina, optic nerve, and optic tract after impact TBI. Our results suggest that the higher raloxifene dose, in particular, may be therapeutic for the optic nerve by enhancing the phagocytosis of axonal debris that would otherwise promote inflammation, thereby salvaging less damaged axons. Our current work, together with our prior studies, shows that microglial activation drives secondary injury processes after both impact and cranial blast TBI and raloxifene mitigates microglial activation and visual system injury in both cases. The results thus provide a strong basis for phase 2 human clinical trials evaluating raloxifene as a TBI therapy.
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Affiliation(s)
- Marcia G Honig
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Nobel A Del Mar
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Desmond L Henderson
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Dylan O'Neal
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - John B Doty
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Rachel Cox
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Chunyan Li
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Aaron M Perry
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Bob M Moore
- Department of Pharmaceutical Sciences, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Anton Reiner
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Ophthalmology, The University of Tennessee Health Science Center, Memphis, TN, United States
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