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Arora P, Sharma A, Trivedi R, Sharma P, Padhy S, Shah S, Dutta SK, Manda K, Rana P. Lipidomic Analysis Reveals Systemic Alterations in Servicemen Exposed to Repeated Occupational Low-Level Blast Waves. Mil Med 2024:usae268. [PMID: 38776149 DOI: 10.1093/milmed/usae268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/02/2024] [Accepted: 05/06/2024] [Indexed: 05/24/2024] Open
Abstract
INTRODUCTION Occupational exposure to blast is a prevalent risk experienced by military personnel. While low-level exposure may not manifest immediate signs of illness, prolonged and repetitive exposure may result in neurophysiological dysfunction. Such repeated exposure to occupational blasts has been linked to structural and functional modifications in the brain, adversely affecting the performance of servicemen in the field. These neurological changes can give rise to symptoms resembling concussion and contribute to the development of post-traumatic stress disorder. MATERIALS AND METHODS To understand long-term effects of blast exposure, the study was conducted to assess memory function, serum circulatory protein and lipid biomarkers, and associated concussive symptomology in servicemen. Concussion-like symptoms were assessed using the Rivermead Post-Concussion Symptoms Questionnaire (RPSQ) along with memory function using PGI memory scale. The serum protein biomarkers were quantified using a sandwich ELISA assay, and the serum lipid profile was measured using liquid chromatography-mass spectrometer. RESULTS The findings revealed that repeated low-level blast exposure resulted in impaired memory function, accompanied by elevated levels of serum neurofilament light chain (neuroaxonal injury) and C-reactive protein. Furthermore, alterations in the lipid profile were observed, with an increase in lipid species associated with immune activation. These changes collectively point to systemic inflammation, neuronal injury, and memory dysfunction as pathological characteristics of repeated low-level blast exposure. CONCLUSION The results of our preliminary investigation offer valuable insights for further large-scale study and provide a guiding principle that necessitates a suitable mitigation approach to safeguard the health of personnel against blast overpressure.
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Affiliation(s)
- Palkin Arora
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
| | - Apoorva Sharma
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
| | - Richa Trivedi
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
| | - Priyanka Sharma
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
| | - Sankarsan Padhy
- RADAR and Sensor Wing, Proof and Experimental Establishment (PXE), DRDO, Chandipur, Balasore, Odisha 756025, India
| | - Shahnawaj Shah
- RADAR and Sensor Wing, Proof and Experimental Establishment (PXE), DRDO, Chandipur, Balasore, Odisha 756025, India
| | - Suman K Dutta
- Military Wing, Proof and Experimental Establishment (PXE), DRDO, Chandipur, Balasore, Odisha 756025, India
| | - Kailash Manda
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
| | - Poonam Rana
- Radiological, Nuclear and Imaging Sciences (RNAIS), Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi 110054, India
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Kocik VI, Dengler BA, Rizzo JA, Ma Moran M, Willis AM, April MD, Schauer SG. A Narrative Review of Existing and Developing Biomarkers in Acute Traumatic Brain Injury for Potential Military Deployed Use. Mil Med 2024; 189:e1374-e1380. [PMID: 37995274 DOI: 10.1093/milmed/usad433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/31/2023] [Indexed: 11/25/2023] Open
Abstract
INTRODUCTION Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in both adult civilian and military populations. Currently, diagnostic and prognostic methods are limited to imaging and clinical findings. Biomarker measurements offer a potential method to assess head injuries and help predict outcomes, which has a potential benefit to the military, particularly in the deployed setting where imaging modalities are limited. We determine how biomarkers such as ubiquitin C-terminal hydrolase-L1 (UCH-L1), glial fibrillary acidic protein (GFAP), S100B, neurofilament light chain (NFL), and tau proteins can offer important information to guide the diagnosis, acute management, and prognosis of TBI, specifically in military personnel. MATERIALS AND METHODS We performed a narrative review of peer-reviewed literature using online databases of Google Scholar and PubMed. We included articles published between 1988 and 2022. RESULTS We screened a total of 73 sources finding a total of 39 original research studies that met inclusion for this review. We found five studies that focused on GFAP, four studies that focused on UCH-L1, eight studies that focused on tau proteins, six studies that focused on NFL, and eight studies that focused on S100B. The remainder of the studies included more than one of the biomarkers of interest. CONCLUSIONS TBI occurs frequently in the military and civilian settings with limited methods to diagnose and prognosticate outcomes. We highlighted several promising biomarkers for these purposes including S100B, UCH-L1, NFL, GFAP, and tau proteins. S100B and UCH-L1 appear to have the strongest data to date, but further research is necessary. The robust data that explain the optimal timing and, more importantly, trending of these biomarker measurements are necessary before widespread application.
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Affiliation(s)
| | - Bradley A Dengler
- Walter Reed National Military Medical Center, Bethesda, MD, USA
- Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
| | - Julie A Rizzo
- Brooke Army Medical Center, JBSA Fort Sam Houston, TX, USA
- Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
| | | | | | - Michael D April
- Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
- 14th Field Hospital, Fort Stewart, GA 31314, USA
| | - Steven G Schauer
- Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
- Departments of Anesthesiology and Emergency Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA
- Center for Combat and Battlefield (COMBAT) Research, University of Colorado School of Medicine, Aurora, CO 80045, USA
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Lippa SM, Bailie JM, French LM, Brickell TA, Lange RT. Lifetime blast exposure is not related to cognitive performance or psychiatric symptoms in US military personnel. Clin Neuropsychol 2024:1-23. [PMID: 38494345 DOI: 10.1080/13854046.2024.2328881] [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: 09/25/2023] [Accepted: 03/05/2024] [Indexed: 03/19/2024]
Abstract
Objective: The present study aimed to examine the impact of lifetime blast exposure (LBE) on neuropsychological functioning in service members and veterans (SMVs). Method: Participants were 282 SMVs, with and without history of traumatic brain injury (TBI), who were prospectively enrolled in a Defense and Veterans Brain Injury Center (DVBIC)-Traumatic Brain Injury Center of Excellence (TBICoE) Longitudinal TBI Study. A cross-sectional analysis of baseline data was conducted. LBE was based on two factors: Military Occupational Speciality (MOS) and SMV self-report. Participants were divided into three groups based on LBE: Blast Naive (n = 61), Blast + Low Risk MOS (n = 96), Blast + High Risk MOS (n = 125). Multivariate analysis of variance (MANOVA) was used to examine group differences on neurocognitive domains and the Minnesota Multiphasic Personality Inventory-2 Restructured Form. Results: There were no statistically significant differences in attention/working memory, processing speed, executive functioning, and memory (Fs < 1.75, ps > .1, ηp2s < .032) or in General Cognition (Fs < 0.95, ps > .3, ηp2s < .008). Prior to correction for covariates, lifetime blast exposure was related to Restructured Clinical (F(18,542) = 1.77, p = .026, ηp2 = .055), Somatic/Cognitive (F(10,550) = 1.99, p = .033, ηp2 = .035), and Externalizing Scales (F(8,552) = 2.17, p = .028, ηp2 = .030); however, these relationships did not remain significant after correction for covariates (Fs < 1.53, ps > .145, ηp2s < .032). Conclusions: We did not find evidence of a relationship between LBE and neurocognitive performance or psychiatric symptoms. This stands in contrast to prior studies demonstrating an association between lifetime blast exposure and highly sensitive blood biomarkers and/or neuroimaging. Overall, findings suggest the neuropsychological impact of lifetime blast exposure is minimal in individuals remaining in or recently retired from military service.
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Affiliation(s)
- Sara M Lippa
- National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Jason M Bailie
- Traumatic Brain Injury Center of Excellence, Bethesda, MD, USA
- Naval Hospital Camp Pendleton, Oceanside, CA, USA
- General Dynamics Information Technology, Fairfax, VA, USA
| | - Louis M French
- National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
- Traumatic Brain Injury Center of Excellence, Bethesda, MD, USA
| | - Tracey A Brickell
- National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
- Traumatic Brain Injury Center of Excellence, Bethesda, MD, USA
- General Dynamics Information Technology, Fairfax, VA, USA
| | - Rael T Lange
- National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD, USA
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
- Traumatic Brain Injury Center of Excellence, Bethesda, MD, USA
- General Dynamics Information Technology, Fairfax, VA, USA
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
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Elder GA, Gama Sosa MA, De Gasperi R, Perez Garcia G, Perez GM, Abutarboush R, Kawoos U, Zhu CW, Janssen WGM, Stone JR, Hof PR, Cook DG, Ahlers ST. The Neurovascular Unit as a Locus of Injury in Low-Level Blast-Induced Neurotrauma. Int J Mol Sci 2024; 25:1150. [PMID: 38256223 PMCID: PMC10816929 DOI: 10.3390/ijms25021150] [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: 12/12/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/24/2024] Open
Abstract
Blast-induced neurotrauma has received much attention over the past decade. Vascular injury occurs early following blast exposure. Indeed, in animal models that approximate human mild traumatic brain injury or subclinical blast exposure, vascular pathology can occur in the presence of a normal neuropil, suggesting that the vasculature is particularly vulnerable. Brain endothelial cells and their supporting glial and neuronal elements constitute a neurovascular unit (NVU). Blast injury disrupts gliovascular and neurovascular connections in addition to damaging endothelial cells, basal laminae, smooth muscle cells, and pericytes as well as causing extracellular matrix reorganization. Perivascular pathology becomes associated with phospho-tau accumulation and chronic perivascular inflammation. Disruption of the NVU should impact activity-dependent regulation of cerebral blood flow, blood-brain barrier permeability, and glymphatic flow. Here, we review work in an animal model of low-level blast injury that we have been studying for over a decade. We review work supporting the NVU as a locus of low-level blast injury. We integrate our findings with those from other laboratories studying similar models that collectively suggest that damage to astrocytes and other perivascular cells as well as chronic immune activation play a role in the persistent neurobehavioral changes that follow blast injury.
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Affiliation(s)
- Gregory A. Elder
- Neurology Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY 10468, USA
- Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029, USA;
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029, USA; (M.A.G.S.); (R.D.G.)
- Mount Sinai Alzheimer’s Disease Research Center and the Ronald M. Loeb Center for Alzheimer’s Disease, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (C.W.Z.); (P.R.H.)
| | - Miguel A. Gama Sosa
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029, USA; (M.A.G.S.); (R.D.G.)
- General Medical Research Service, James J. Peters Department of Veterans Affairs Medical Center, Bronx, NY 10468, USA
| | - Rita De Gasperi
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029, USA; (M.A.G.S.); (R.D.G.)
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY 10468, USA;
| | - Georgina Perez Garcia
- Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029, USA;
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY 10468, USA;
| | - Gissel M. Perez
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY 10468, USA;
| | - Rania Abutarboush
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical ResearchCommand, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA; (R.A.); (U.K.); (S.T.A.)
- The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, MD 20817, USA
| | - Usmah Kawoos
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical ResearchCommand, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA; (R.A.); (U.K.); (S.T.A.)
- The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, MD 20817, USA
| | - Carolyn W. Zhu
- Mount Sinai Alzheimer’s Disease Research Center and the Ronald M. Loeb Center for Alzheimer’s Disease, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (C.W.Z.); (P.R.H.)
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY 10468, USA;
- Department of Geriatrics and Palliative Care, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - William G. M. Janssen
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA;
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - James R. Stone
- Department of Radiology and Medical Imaging, University of Virginia, 480 Ray C Hunt Drive, Charlottesville, VA 22903, USA;
| | - Patrick R. Hof
- Mount Sinai Alzheimer’s Disease Research Center and the Ronald M. Loeb Center for Alzheimer’s Disease, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (C.W.Z.); (P.R.H.)
- Department of Geriatrics and Palliative Care, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA;
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - David G. Cook
- Geriatric Research Education and Clinical Center, VA Puget Sound Health Care System, 1660 S Columbian Way, Seattle, WA 98108, USA;
- Department of Medicine, University of Washington, 1959 NE Pacific St., Seattle, WA 98195, USA
| | - Stephen T. Ahlers
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical ResearchCommand, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA; (R.A.); (U.K.); (S.T.A.)
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Brokaw EB, S Brungart D, M Byrne R, A Flamme G, Gupta R, Jokel CR, Kujawa SG, Lalis L, L McKinley R, Murphy WJ, W Spencer R, J Smalt C, F Zagadou B. Recommendations for a Military Health System Auditory Blast Injury Prevention Standard. Mil Med 2023; 188:176-184. [PMID: 37948248 DOI: 10.1093/milmed/usad078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/06/2023] [Accepted: 03/22/2023] [Indexed: 11/12/2023] Open
Abstract
INTRODUCTION Although existing auditory injury prevention standards benefit warfighters, the Department of Defense could do more to understand and address auditory injuries (e.g., hearing loss, tinnitus, and central processing deficits) among service members. The Blast Injury Prevention Standards Recommendation (BIPSR) Process is designed to address the needs of all the Military Services for biomedically valid Military Health System (MHS) Blast Injury Prevention Standards. MATERIALS AND METHODS Through the BIPSR Process, stakeholders provided their intended uses and requested functionalities for an MHS Blast Injury Prevention Standard. The BIPSR Process established a broad-based, non-advocacy panel of auditory injury Subject Matter Expert (SME) Panel with members drawn from industry, academia, and government. The SME Panel selected evaluation factors, weighted priorities, and then evaluated the resulting candidate MHS Auditory Blast Injury Prevention Standards against the evaluation criteria. The SME Panel members provided rationales for their decisions, documented discussions, and used iterative rounds of feedback to promote consensus building among members. The BIPSR Process used multi-attribute utility theory to combine members' evaluations and compare the candidate standards. RESULTS The SME Panel identified and collated information about existing auditory injury datasets to identify gaps and promote data sharing and comprehensive evaluations of standards for preventing auditory blast injury. The panel evaluated the candidate standards and developed recommendations for an MHS Blast Injury Prevention Standard. CONCLUSIONS The BIPSR Process illuminated important characteristics, capabilities, and limitations of candidate standards and existing datasets (e.g., limited human exposure data to evaluate the validity of injury prediction) for auditory blast injury prevention. The evaluation resulted in the recommendation to use the 8-hour Equivalent Level (LAeq8hr) as the interim MHS Auditory Blast Injury Prevention Standard while the community performs additional research to fill critical knowledge gaps.
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Affiliation(s)
| | | | | | - Greg A Flamme
- Stephenson and Stephenson Research and Consulting, LLC, Forest Grove, OR 97116, USA
| | - Raj Gupta
- U.S. Army Medical Research and Development Command, Frederick, MD 21702-501, USA
| | - Charles R Jokel
- Defense Centers for Public Health-Aberdeen, Aberdeen Proving Ground, MD 21010-5403, USA
| | | | - Lisa Lalis
- The MITRE Corporation, McLean, VA 22102, USA
| | | | - William J Murphy
- Stephenson and Stephenson Research and Consulting, LLC, Forest Grove, OR 97116, USA
| | | | - Christopher J Smalt
- Massachusetts Institute of Technology Lincoln Laboratory, 244 Wood St, Lexington, Massachusetts 02421, USA
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Rao HM, McGuire SM, Halford E, Smalt CJ. Changes in Eye Tracking Features Across Periods of Overpressure Exposure. Mil Med 2023; 188:e3398-e3406. [PMID: 37192128 DOI: 10.1093/milmed/usad147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/22/2023] [Accepted: 04/25/2023] [Indexed: 05/18/2023] Open
Abstract
INTRODUCTION Repetitive exposure to blast overpressure waves can be a part of routine military and law enforcement training. However, our understanding of the effects of that repetitive exposure on human neurophysiology remains limited. To link an individual's cumulative exposure with their neurophysiological effects, overpressure dosimetry needs to be concurrently collected with relevant physiological signals. Eye tracking has shown promise for providing insight into neurophysiological change because of neural injury, but video-based technology limits usage to a laboratory or clinic. In the present work, we show capability for using electrooculography-based eye tracking to enable physiological assessment in the field during activities involved repetitive blast exposures. MATERIALS AND METHODS Overpressure dosimetry was accomplished by using a body-worn measurement system that captures continuous sound pressure levels as well as pressure waveforms of blast event in the range of 135-185 dB peak (0.1-36 kPa). Electrooculography eye tracking was performed using a commercial Shimmer Sensing system, which captured horizontal eye movements of both the left and right eyes, as well as vertical eye movements of the right eye, from which blinks can also be extracted. Data were collected during breaching activities that included repetitive use of explosives. Participants in the study were U.S. Army Special Operators and Federal Bureau of Investigations special agents. Approval for research was received by the Massachucetts Institute of Technology Committee on the Use of Humans as Experimental Subjects, the Air Force Human Research Protections Office, and the Federal Bureau of Investigations Institutional Review Board. RESULTS The energy from overpressure events was accumulated and summarized into an 8-hour equivalent of sound pressure level (i.e., LZeq8hr). The total exposure in a single day, i.e., the LZeq8hr, ranged from 110 to 160 dB. Oculomotor features, such as blink and saccade rate, as well as variance in blink waveforms, show changes across the period of overpressure exposure. However, the features that showed significant change across the population were not necessarily the ones that showed significant correlation with the levels of overpressure exposure. A regression model built to predict overpressure levels from oculomotor features alone showed a significant association (R = 0.51, P < .01). Investigation of the model indicates that changes in the saccade rate and blink waveforms are driving the relationship. CONCLUSIONS This study successfully demonstrated that eye tracking can be performed during training activities, such as explosive breaching, and that the modality may provide insight into neurophysiological change across periods of overpressure exposure. The results presented herein show that electrooculography-based eye tracking may be a useful method of assessing individualized physiological effects of overpressure exposure in the field. Future work is focused on time-dependent modeling to assess continuous changes in eye movements as this will enable building dose-response curves.
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Affiliation(s)
- Hrishikesh M Rao
- Human Health & Performance Systems Group, MIT Lincoln Laboratory, Lexington, MA 02420 USA
| | - Sarah M McGuire
- Human Health & Performance Systems Group, MIT Lincoln Laboratory, Lexington, MA 02420 USA
| | | | - Christopher J Smalt
- Human Health & Performance Systems Group, MIT Lincoln Laboratory, Lexington, MA 02420 USA
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Heyburn L, Dahal S, Abutarboush R, Reed E, Urioste R, Batuure A, Wilder D, Ahlers ST, Long JB, Sajja VS. Differential effects on TDP-43, piezo-2, tight-junction proteins in various brain regions following repetitive low-intensity blast overpressure. Front Neurol 2023; 14:1237647. [PMID: 37877029 PMCID: PMC10593467 DOI: 10.3389/fneur.2023.1237647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 09/15/2023] [Indexed: 10/26/2023] Open
Abstract
Introduction Mild traumatic brain injury (mTBI) caused by repetitive low-intensity blast overpressure (relBOP) in military personnel exposed to breaching and heavy weapons is often unrecognized and is understudied. Exposure to relBOP poses the risk of developing abnormal behavioral and psychological changes such as altered cognitive function, anxiety, and depression, all of which can severely compromise the quality of the life of the affected individual. Due to the structural and anatomical heterogeneity of the brain, understanding the potentially varied effects of relBOP in different regions of the brain could lend insights into the risks from exposures. Methods In this study, using a rodent model of relBOP and western blotting for protein expression we showed the differential expression of various neuropathological proteins like TDP-43, tight junction proteins (claudin-5, occludin, and glial fibrillary acidic protein (GFAP)) and a mechanosensitive protein (piezo-2) in different regions of the brain at different intensities and frequency of blast. Results Our key results include (i) significant increase in claudin-5 after 1x blast of 6.5 psi in all three regions and no definitive pattern with higher number of blasts, (ii) significant increase in piezo-2 at 1x followed by significant decrease after multiple blasts in the cortex, (iii) significant increase in piezo-2 with increasing number of blasts in frontal cortex and mixed pattern of expression in hippocampus and (iv) mixed pattern of TDP-3 and GFAP expression in all the regions of brain. Discussion These results suggest that there are not definitive patterns of changes in these marker proteins with increase in intensity and/or frequency of blast exposure in any particular region; the changes in expression of these proteins are different among the regions. We also found that the orientation of blast exposure (e.g. front vs. side exposure) affects the altered expression of these proteins.
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Affiliation(s)
- Lanier Heyburn
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Shataakshi Dahal
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
- The Geneva Foundation, Tacoma, WA, United States
| | | | - Eileen Reed
- Naval Medical Research Center, Silver Spring, MD, United States
| | - Rodrigo Urioste
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Andrew Batuure
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Donna Wilder
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | | | - Joseph B. Long
- Blast Induced Neurotrauma Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
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Campos-Pires R, Ong BE, Koziakova M, Ujvari E, Fuller I, Boyles C, Sun V, Ko A, Pap D, Lee M, Gomes L, Gallagher K, Mahoney PF, Dickinson R. Repetitive, but Not Single, Mild Blast TBI Causes Persistent Neurological Impairments and Selective Cortical Neuronal Loss in Rats. Brain Sci 2023; 13:1298. [PMID: 37759899 PMCID: PMC10526452 DOI: 10.3390/brainsci13091298] [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: 07/31/2023] [Revised: 08/29/2023] [Accepted: 09/04/2023] [Indexed: 09/29/2023] Open
Abstract
Exposure to repeated mild blast traumatic brain injury (mbTBI) is common in combat soldiers and the training of Special Forces. Evidence suggests that repeated exposure to a mild or subthreshold blast can cause serious and long-lasting impairments, but the mechanisms causing these symptoms are unclear. In this study, we characterise the effects of single and tightly coupled repeated mbTBI in Sprague-Dawley rats exposed to shockwaves generated using a shock tube. The primary outcomes are functional neurologic function (unconsciousness, neuroscore, weight loss, and RotaRod performance) and neuronal density in brain regions associated with sensorimotor function. Exposure to a single shockwave does not result in functional impairments or histologic injury, which is consistent with a mild or subthreshold injury. In contrast, exposure to three tightly coupled shockwaves results in unconsciousness, along with persistent neurologic impairments. Significant neuronal loss following repeated blast was observed in the motor cortex, somatosensory cortex, auditory cortex, and amygdala. Neuronal loss was not accompanied by changes in astrocyte reactivity. Our study identifies specific brain regions particularly sensitive to repeated mbTBI. The reasons for this sensitivity may include exposure to less attenuated shockwaves or proximity to tissue density transitions, and this merits further investigation. Our novel model will be useful in elucidating the mechanisms of sensitisation to injury, the temporal window of sensitivity and the evaluation of new treatments.
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Affiliation(s)
- Rita Campos-Pires
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
- Royal British Legion Centre for Blast Injury Studies, Imperial College London, London SW7 2AZ, UK
| | - Bee Eng Ong
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Mariia Koziakova
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Eszter Ujvari
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Isobel Fuller
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Charlotte Boyles
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Valerie Sun
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Andy Ko
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Daniel Pap
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Matthew Lee
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Lauren Gomes
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Kate Gallagher
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
| | - Peter F. Mahoney
- Royal British Legion Centre for Blast Injury Studies, Imperial College London, London SW7 2AZ, UK
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Robert Dickinson
- Anaesthetics, Pain Medicine and Intensive Care Division, Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK
- Royal British Legion Centre for Blast Injury Studies, Imperial College London, London SW7 2AZ, UK
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9
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Wu L, Cui F, Zhang S, Ding X, Gao W, Chen L, Ma J, Niu P. Associations between multiple heavy metals exposure and neural damage biomarkers in welders: A cross-sectional study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 869:161812. [PMID: 36706997 DOI: 10.1016/j.scitotenv.2023.161812] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 01/15/2023] [Accepted: 01/20/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND Both occupational and environmental exposure to heavy metals are associated with various neurodegenerative diseases. However, limited evidence is available on the potential effects of exposure to metallic mixtures and neural damage. OBJECTIVES This study aimed to evaluate the association between metal mixtures in urine and neural damage biomarkers in welders. METHODS In this cross-sectional study, a total of 186 workers were recruited from steel mills. Twenty-three metals in urine were measured by inductively coupled plasma mass spectrometry. Serum neural damage biomarkers, including neurofilament light chain (NfL), sphingosine-1-phosphate (S1P), prolactin (PRL), and dopamine (DA) were detected using enzyme-linked immunosorbent assay kits. Multivariable linear regression, Bayesian kernel machine regression (BKMR), and Quantile g-computation (QG-C) were employed to estimate the association between metals exposure and neural damage biomarkers. RESULTS Inverted u-shaped associations of nickel with NfL, S1P, and DA were observed in the BKMR model. A non-linear relationship was also found between Fe and PRL. Urinary cobalt was positively associated with serum PRL and had the strongest positive weights in the QG-C model. Urinary lead was associated with higher serum S1P levels. We also found the interaction among nickel, zinc, arsenic, strontium, iron, and lead with the neural damage biomarkers. CONCLUSION This study provides new evidence of a direct association between metal mixture exposure and the serum biomarkers of neural damage. Several metals Ni, Co, Pb, Sr, As and Fe, may have adverse effects on the nervous system, while Zn may have neuroprotective effects.
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Affiliation(s)
- Luli Wu
- Department of Occupational Health and Environmental Health, School of Public Health, Capital Medical University, 100069 Beijing, China; Beijing Key Laboratory of Environmental Toxicology, School of Public Health, Capital Medical University, 100069 Beijing, China
| | - Fengtao Cui
- Occupational Disease Prevention and Control Hospital of Huaibei Mining Co., Ltd, Huaibei, Anhui Province 235000, China
| | - Shixuan Zhang
- Department of Occupational Health and Environmental Health, School of Public Health, Capital Medical University, 100069 Beijing, China; Beijing Key Laboratory of Environmental Toxicology, School of Public Health, Capital Medical University, 100069 Beijing, China
| | - Xinping Ding
- Occupational Disease Prevention and Control Hospital of Huaibei Mining Co., Ltd, Huaibei, Anhui Province 235000, China
| | - Wei Gao
- Occupational Disease Prevention and Control Hospital of Huaibei Mining Co., Ltd, Huaibei, Anhui Province 235000, China
| | - Li Chen
- Experimental Teaching Center, School of Public Health, Capital Medical University, Beijing 100069, China
| | - Junxiang Ma
- Department of Occupational Health and Environmental Health, School of Public Health, Capital Medical University, 100069 Beijing, China; Beijing Key Laboratory of Environmental Toxicology, School of Public Health, Capital Medical University, 100069 Beijing, China.
| | - Piye Niu
- Department of Occupational Health and Environmental Health, School of Public Health, Capital Medical University, 100069 Beijing, China; Beijing Key Laboratory of Environmental Toxicology, School of Public Health, Capital Medical University, 100069 Beijing, China.
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10
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Woodall JLA, Sak JA, Cowdrick KR, Bove Muñoz BM, McElrath JH, Trimpe GR, Mei Y, Myhre RL, Rains JK, Hutchinson CR. Repetitive Low-level Blast Exposure and Neurocognitive Effects in Army Ranger Mortarmen. Mil Med 2023; 188:e771-e779. [PMID: 34557921 DOI: 10.1093/milmed/usab394] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/03/2021] [Accepted: 09/20/2021] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION Occupational exposure to repetitive, low-level blasts in military training and combat has been tied to subconcussive injury and poor health outcomes for service members. Most low-level blast studies to date have focused on explosive breaching and firing heavy weapon systems; however, there is limited research on the repetitive blast exposure and physiological effects that mortarmen experience when firing mortar weapon systems. Motivated by anecdotal symptoms of mortarmen, the purpose of this paper is to characterize this exposure and its resulting neurocognitive effects in order to provide preliminary findings and actionable recommendations to safeguard the health of mortarmen. MATERIALS AND METHODS In collaboration with the U.S. Army Rangers at Fort Benning, blast exposure, symptoms, and pupillary light reflex were measured during 3 days of firing 81 mm and 120 mm mortars in training. Blast exposure analysis included the examination of the blast overpressure (BOP) and cumulative exposure by mortarman position, as well as comparison to the 4 psi safety threshold. Pupillary light reflex responses were analyzed with linear mixed effects modeling. All neurocognitive results were compared between mortarmen (n = 11) and controls (n = 4) and cross-compared with blast exposure and blast history. RESULTS Nearly 500 rounds were fired during the study, resulting in a high cumulative blast exposure for all mortarmen. While two mortarmen had average BOPs exceeding the 4 psi safety limit (Fig. 2), there was a high prevalence of mTBI-like symptoms among all mortarmen, with over 70% experiencing headaches, ringing in the ears, forgetfulness/poor memory, and taking longer to think during the training week (n ≥ 8/11). Mortarmen also had smaller and slower pupillary light reflex responses relative to controls, with significantly slower dilation velocity (P < 0.05) and constriction velocity (P < 0.10). CONCLUSION Mortarmen experienced high cumulative blast exposure coinciding with altered neurocognition that is suggestive of blast-related subconcussive injury. These neurocognitive effects occurred even in mortarmen with average BOP below the 4 psi safety threshold. While this study was limited by a small sample size, its results demonstrate a concerning health risk for mortarmen that requires additional study and immediate action. Behavioral changes like ducking and standing farther from the mortar when firing can generally help reduce mortarmen BOP exposure, but we recommend the establishment of daily cumulative safety thresholds and daily firing limits in training to reduce cumulative blast exposure, and ultimately, improve mortarmen's quality of life and longevity in service.
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Affiliation(s)
- Julia L A Woodall
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Jordyn A Sak
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Kyle R Cowdrick
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Brady M Bove Muñoz
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Jessica H McElrath
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Grace R Trimpe
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Yajun Mei
- H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | | | - James K Rains
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
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11
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Varghese N, Morrison B. Partial Depletion of Microglia Attenuates Long-Term Potentiation Deficits following Repeated Blast Traumatic Brain Injury in Organotypic Hippocampal Slice Cultures. J Neurotrauma 2023; 40:547-560. [PMID: 36508265 PMCID: PMC10081725 DOI: 10.1089/neu.2022.0284] [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] [Indexed: 12/14/2022] Open
Abstract
Blast-induced traumatic brain injury (bTBI) has been a health concern in both military and civilian populations due to recent military and geopolitical conflicts. Military service members are frequently exposed to repeated bTBI throughout their training and deployment. Our group has previously reported compounding functional deficits as a result of increased number of blast exposures. In this study, we further characterized the decrease in long-term potentiation (LTP) by varying the blast injury severity and the inter-blast interval between two blast exposures. LTP deficits were attenuated with increasing inter-blast intervals. We also investigated changes in microglial activation; expression of CD68 was increased and expression of CD206 was decreased after multiple blast exposures. Expression of macrophage inflammatory protein (MIP)-1α, interleukin (IL)-1β, monocyte chemoattractant protein (MCP)-1, interferon gamma-inducible protein (IP)-10, and regulated on activation, normal T cell expressed and secreted (RANTES) increased, while expression of IL-10 decreased in the acute period after both single and repeated bTBI. By partially depleting microglia prior to injury, LTP deficits after injury were significantly reduced. Treatment with the novel drug, MW-189, prevented LTP deficits when administered immediately following a repeated bTBI and even when administered only for an acute period (24 h) between two blast injuries. These findings could inform the development of therapeutic strategies to treat the neurological deficits of repeated bTBI suggesting that microglia play a major role in functional neuronal deficits and may be a viable therapeutic target to lessen the neurophysiological deficits after bTBI.
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Affiliation(s)
- Nevin Varghese
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
| | - Barclay Morrison
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
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12
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Gharahi H, Garimella HT, Chen ZJ, Gupta RK, Przekwas A. Mathematical model of mechanobiology of acute and repeated synaptic injury and systemic biomarker kinetics. Front Cell Neurosci 2023; 17:1007062. [PMID: 36814869 PMCID: PMC9939777 DOI: 10.3389/fncel.2023.1007062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 01/10/2023] [Indexed: 02/09/2023] Open
Abstract
Background Blast induced Traumatic Brain Injury (bTBI) has become a signature casualty of military operations. Recently, military medics observed neurocognitive deficits in servicemen exposed to repeated low level blast (LLB) waves during military heavy weapons training. In spite of significant clinical and preclinical TBI research, current understanding of injury mechanisms and short- and long-term outcomes is limited. Mathematical models of bTBI biomechanics and mechanobiology of sensitive neuro-structures such as synapses may help in better understanding of injury mechanisms and in the development of improved diagnostics and neuroprotective strategies. Methods and results In this work, we formulated a model of a single synaptic structure integrating the dynamics of the synaptic cell adhesion molecules (CAMs) with the deformation mechanics of the synaptic cleft. The model can resolve time scales ranging from milliseconds during the hyperacute phase of mechanical loading to minutes-hours acute/chronic phase of injury progression/repair. The model was used to simulate the synaptic injury responses caused by repeated blast loads. Conclusion Our simulations demonstrated the importance of the number of exposures compared to the duration of recovery period between repeated loads on the synaptic injury responses. The paper recognizes current limitations of the model and identifies potential improvements.
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Affiliation(s)
- Hamidreza Gharahi
- Biomedical and Data Sciences Division, CFD Research Corporation, Huntsville, AL, United States,Hamidreza Gharahi,
| | - Harsha T. Garimella
- Biomedical and Data Sciences Division, CFD Research Corporation, Huntsville, AL, United States
| | - Zhijian J. Chen
- Biomedical and Data Sciences Division, CFD Research Corporation, Huntsville, AL, United States
| | - Raj K. Gupta
- Department of Defense Blast Injury Research Program Coordinating Office, U.S. Army Medical Research and Development Command, Fort Detrick, MD, United States
| | - Andrzej Przekwas
- Biomedical and Data Sciences Division, CFD Research Corporation, Huntsville, AL, United States,*Correspondence: Andrzej Przekwas,
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13
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Kulinski D, Dirks C, Carr W, Sheffield B, Kamimori G, Brungart DS. Field assessment of acute auditory responses to environmental exposures in close quarters tactics training. Int J Audiol 2023; 62:138-150. [PMID: 35073491 DOI: 10.1080/14992027.2022.2028023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The purpose of this study was to evaluate auditory performance of military instructors as part of a training course involving noise and blast exposure. Boothless audiometry was used to estimate the test-retest reliability of the auditory measures under realistic field conditions and to determine risk of acute auditory injury during standard training practices. DESIGN AND STUDY SAMPLE Thirteen U.S. Marine instructors participated in study activities. An audiologic testing suite embedded in a noise-attenuating headset was used to test various tone detection tasks on subjects after exposure. Acoustic exposures were captured with sound level meters. RESULTS Boothless audiometry provide highly repeatable results for various tests of auditory performance in the field environment. In this test population, changes in auditory performance pre- and post-noise exposure were minimal for most measures. The notable exception was binaural (NoSπ) tone detection, which showed significant degradations both as a function of pre- and post-noise exposure on the same day and as a result of cumulative noise exposure over the period of the study. CONCLUSIONS Study outcomes are consistent with prior laboratory and epidemiological work and suggest a link between the binaural processes required for NoSπ detection and the hearing-related issues reported by blast-exposed service members.
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Affiliation(s)
- Devon Kulinski
- Audiology and Speech Center, Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - Coral Dirks
- Audiology and Speech Center, Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - Walter Carr
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Benjamin Sheffield
- Audiology and Speech Center, Walter Reed National Military Medical Center, Bethesda, MD, USA.,Army Hering Program, Army Public Health Center, Aberdeen Proving Ground, MD, USA
| | - Gary Kamimori
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Douglas S Brungart
- Audiology and Speech Center, Walter Reed National Military Medical Center, Bethesda, MD, USA
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14
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Snapper DM, Reginauld B, Liaudanskaya V, Fitzpatrick V, Kim Y, Georgakoudi I, Kaplan DL, Symes AJ. Development of a novel bioengineered 3D brain-like tissue for studying primary blast-induced traumatic brain injury. J Neurosci Res 2023; 101:3-19. [PMID: 36200530 DOI: 10.1002/jnr.25123] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 08/04/2022] [Accepted: 08/29/2022] [Indexed: 11/08/2022]
Abstract
Primary blast injury is caused by the direct impact of an overpressurization wave on the body. Due to limitations of current models, we have developed a novel approach to study primary blast-induced traumatic brain injury. Specifically, we employ a bioengineered 3D brain-like human tissue culture system composed of collagen-infused silk protein donut-like hydrogels embedded with human IPSC-derived neurons, human astrocytes, and a human microglial cell line. We have utilized this system within an advanced blast simulator (ABS) to expose the 3D brain cultures to a blast wave that can be precisely controlled. These 3D cultures are enclosed in a 3D-printed surrogate skull-like material containing media which are then placed in a holder apparatus inside the ABS. This allows for exposure to the blast wave alone without any secondary injury occurring. We show that blast induces an increase in lactate dehydrogenase activity and glutamate release from the cultures, indicating cellular injury. Additionally, we observe a significant increase in axonal varicosities after blast. These varicosities can be stained with antibodies recognizing amyloid precursor protein. The presence of amyloid precursor protein deposits may indicate a blast-induced axonal transport deficit. After blast injury, we find a transient release of the known TBI biomarkers, UCHL1 and NF-H at 6 h and a delayed increase in S100B at 24 and 48 h. This in vitro model will enable us to gain a better understanding of clinically relevant pathological changes that occur following primary blast and can also be utilized for discovery and characterization of biomarkers.
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Affiliation(s)
- Dustin M Snapper
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University, Bethesda, Maryland, USA
| | - Bianca Reginauld
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University, Bethesda, Maryland, USA
| | - Volha Liaudanskaya
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - Vincent Fitzpatrick
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - Yeonho Kim
- Preclinical Behavior and Modeling Core, Uniformed Services University, Bethesda, Maryland, USA
| | - Irene Georgakoudi
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - David L Kaplan
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - Aviva J Symes
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University, Bethesda, Maryland, USA
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15
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Boutté AM, Thangavelu B, Anagli J. Opinion: The Potential Role of Amyloid Beta Peptides as Biomarkers of Subconcussion and Concussion. Front Neurol 2022; 13:941151. [PMID: 35903122 PMCID: PMC9315433 DOI: 10.3389/fneur.2022.941151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/10/2022] [Indexed: 11/24/2022] Open
Affiliation(s)
- Angela M. Boutté
- Aries Biotechnologies, Oakland, CA, United States
- *Correspondence: Angela M. Boutté
| | | | - John Anagli
- NeuroTheranostics, Inc., Detroit, MI, United States
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16
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Mannix R, Kawata K, Bazarian JJ. Defining an Approach to Monitoring Brain Health in Individuals Exposed to Repetitive Head Impacts: Lessons Learned from Radiation Safety. J Neurotrauma 2022; 39:897-901. [PMID: 35848096 DOI: 10.1089/neu.2022.29130.rm] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recently, there has been increased concern over the effect of repetitive head impacts (RHIs, both concussive and subconcussive impacts) on long-term brain health. This concern has led researchers and policy makers to consider establishing RHI thresholds in order to mitigate the potential long-term effects of RHI exposure. However, the concept of thresholding relies on twin streams of information: 1) biomedical research relevant to the short and long-term risks of exposure to RHIs, and 2) societal standards for "acceptable risk." In the case of RHI, these streams of information have not been cogently combined to inform sensible policy making. In the current editorial, we discuss how the history of radiation safety provides an instructive example of an approach to ford these two streams to derive actionable clinically relevant policies surrounding RHI exposures.
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Affiliation(s)
- Rebekah Mannix
- Department of Medicine, Division of Emergency Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Keisuke Kawata
- Department of Kinesiology, Indiana University, Bloomington, Indiana, USA
| | - Jeffrey J Bazarian
- Department of Emergency Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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17
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Hubbard WB, Velmurugan GV, Brown EP, Sullivan PG. Resilience of females to acute blood–brain barrier damage and anxiety behavior following mild blast traumatic brain injury. Acta Neuropathol Commun 2022; 10:93. [PMID: 35761393 PMCID: PMC9235199 DOI: 10.1186/s40478-022-01395-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/13/2022] [Indexed: 11/10/2022] Open
Abstract
AbstractLow-level blast exposure can result in neurological impairment for military personnel. Currently, there is a lack of experimental data using sex as a biological variable in neurovascular outcomes following blast exposure. To model mild blast traumatic brain injury (mbTBI), male and female rats were exposed to a single 11 psi static peak overpressure blast wave using the McMillan blast device and cohorts were then euthanized at 6 h, 24 h, 7 d and 14 d post-blast followed by isolation of the amygdala. After mbTBI, animals experience immediate bradycardia, although no changes in oxygen saturation levels or weight loss are observed. Male mbTBI animals displayed significantly higher levels of anxiety-like behavior (open field and elevated plus maze) compared to male sham groups; however, there was no anxiety phenotype in female mbTBI animals. Blast-induced neurovascular damage was explored by measuring expression of tight junction (TJ) proteins (zonula occludens-1 (ZO-1), occludin and claudin-5), glial fibrillary acidic protein (GFAP) and astrocyte end-feet coverage around the blood–brain barrier (BBB). Western blot analysis demonstrates that TJ protein levels were significantly decreased at 6 h and 24 h post-mbTBI in male rats, but not in female rats, compared to sham. Female animals have decreased GFAP at 6 h post-mbTBI while male animals display decreased GFAP expression at 24 h post-mbTBI. By 7 d post-mbTBI, there were no significant differences in TJ or GFAP levels between groups in either sex. At 24 h post-mbTBI, vascular integrity and astrocytic end-feet coverage around the BBB was significantly decreased in males following mbTBI. These results demonstrate that loss of GFAP expression may be due to astrocytic damage at the BBB. Our findings also demonstrate sex differences in acute vascular and behavioral outcomes after single mbTBI. Female animals display a lack of BBB pathology after mbTBI corresponding to improved acute neuropsychological outcomes as compared to male animals.
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18
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Long-Term Effects of Low-Level Blast Exposure and High-Caliber Weapons Use in Military Special Operators. Brain Sci 2022; 12:brainsci12050679. [PMID: 35625065 PMCID: PMC9140026 DOI: 10.3390/brainsci12050679] [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: 04/02/2022] [Revised: 05/03/2022] [Accepted: 05/17/2022] [Indexed: 02/01/2023] Open
Abstract
Chronic low-level blast exposure has been linked with neurological alterations and traumatic brain injury (TBI) biomarkers. Impaired smooth-pursuit eye movements (SPEM) are often associated with TBI. The purpose of this study was to determine whether long-term operators of low-level blast exposure or high-caliber weapons use displayed oculomotor behaviors that differed from controls. Twenty-six members of an elite military unit performed a computerized oculomotor testing task using an eye tracker and completed a concussion assessment questionnaire. The participants were split into a blast exposure group and control group. The blast exposure group had a history of exposure to low-level blasts or high-caliber weapon use. The results revealed significant differences in SPEM, saccades, and fixations between the blast exposure group and control group. The blast exposure group’s eye movements were slower, stopped at more frequent points when following a target, traveled further from the target in terms of both speed and direction, and showed higher rates of variation and inefficiency. Poor oculomotor behavior correlated with a higher symptom severity on the concussion assessment questionnaire. Military special operators exposed to long-term low-level blasts or high-caliber weapons usage displayed an impaired oculomotor behavior in comparison to controls. These findings further our understanding of the impact of long-term low-level blast exposure on the oculomotor behavior of military special operators and may inform practical implications for military training.
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19
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Miller MR, DiBattista A, Patel MA, Daley M, Tenn C, Nakashima A, Rhind SG, Vartanian O, Shiu MY, Caddy N, Garrett M, Saunders D, Smith I, Jetly R, Fraser DD. A Distinct Metabolite Signature in Military Personnel Exposed to Repetitive Low-Level Blasts. Front Neurol 2022; 13:831792. [PMID: 35463119 PMCID: PMC9021419 DOI: 10.3389/fneur.2022.831792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/10/2022] [Indexed: 11/30/2022] Open
Abstract
Military Breachers and Range Staff (MBRS) are subjected to repeated sub-concussive blasts, and they often report symptoms that are consistent with a mild traumatic brain injury (mTBI). Biomarkers of blast injury would potentially aid blast injury diagnosis, surveillance and avoidance. Our objective was to identify plasma metabolite biomarkers in military personnel that were exposed to repeated low-level or sub-concussive blast overpressure. A total of 37 military members were enrolled (18 MBRS and 19 controls), with MBRS having participated in 8–20 breaching courses per year, with a maximum exposure of 6 blasts per day. The two cohorts were similar except that the number of blast exposures were significantly higher in the MBRS, and the MBRS cohort suffered significantly more post-concussive symptoms and poorer health on assessment. Metabolomics profiling demonstrated significant differences between groups with 74% MBRS classification accuracy (CA). Feature reduction identified 6 metabolites that resulted in a MBRS CA of 98%, and included acetic acid (23.7%), formate (22.6%), creatine (14.8%), acetone (14.2%), methanol (12,7%), and glutamic acid (12.0%). All 6 metabolites were examined with individual receiver operating characteristic (ROC) curve analyses and demonstrated areas-under-the-curve (AUCs) of 0.82–0.91 (P ≤ 0.001) for MBRS status. Several parsimonious combinations of three metabolites increased accuracy of ROC curve analyses to AUCs of 1.00 (P < 0.001), while a combination of volatile organic compounds (VOCs; acetic acid, acetone and methanol) yielded an AUC of 0.98 (P < 0.001). Candidate biomarkers for chronic blast exposure were identified, and if validated in a larger cohort, may aid surveillance and care of military personnel. Future point-of-care screening could be developed that measures VOCs from breath, with definitive diagnoses confirmed with plasma metabolomics profiling.
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Affiliation(s)
- Michael R. Miller
- Lawson Health Research Institute, London, ON, Canada
- Department of Pediatrics, Western University, London, ON, Canada
| | - Alicia DiBattista
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Neurolytix Inc., Toronto, ON, Canada
| | - Maitray A. Patel
- Department of Computer Science, Western University, London, ON, Canada
| | - Mark Daley
- Department of Computer Science, Western University, London, ON, Canada
- The Vector Institute for Artificial Intelligence, Toronto, ON, Canada
| | - Catherine Tenn
- Defence Research and Development Canada, Suffield Research Centre, Medicine Hat, AB, Canada
| | - Ann Nakashima
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
| | - Shawn G. Rhind
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
- Faculty of Kinesiology & Physical Education, University of Toronto, Toronto, ON, Canada
| | - Oshin Vartanian
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
- Department of Psychology, University of Toronto, Toronto, ON, Canada
| | - Maria Y. Shiu
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
| | - Norleen Caddy
- Defence Research and Development Canada, Suffield Research Centre, Medicine Hat, AB, Canada
| | - Michelle Garrett
- Defence Research and Development Canada, Suffield Research Centre, Medicine Hat, AB, Canada
| | - Doug Saunders
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
| | - Ingrid Smith
- Defence Research and Development Canada, Toronto Research Centre, Toronto, ON, Canada
| | - Rakesh Jetly
- Canadian Forces Health Services, National Defence Headquarters, Ottawa, ON, Canada
- Department of Psychiatry, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- Department of Psychiatry, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Douglas D. Fraser
- Lawson Health Research Institute, London, ON, Canada
- Department of Pediatrics, Western University, London, ON, Canada
- Neurolytix Inc., Toronto, ON, Canada
- Clinical Neurological Sciences, Western University, London, ON, Canada
- Physiology and Pharmacology, Western University, London, ON, Canada
- *Correspondence: Douglas D. Fraser
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20
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A Pilot Study of Whole-Blood Transcriptomic Analysis to Identify Genes Associated with Repetitive Low-Level Blast Exposure in Career Breachers. Biomedicines 2022; 10:biomedicines10030690. [PMID: 35327492 PMCID: PMC8945695 DOI: 10.3390/biomedicines10030690] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/12/2022] [Accepted: 03/15/2022] [Indexed: 02/06/2023] Open
Abstract
Repetitive low-level blast exposure is one of the major occupational health concerns among US military service members and law enforcement. This study seeks to identify gene expression using microRNA and RNA sequencing in whole-blood samples from experienced breachers and unexposed controls. We performed experimental RNA sequencing using Illumina’s HiSeq 2500 Sequencing System, and microRNA analysis using NanoString Technology nCounter miRNA expression panel in whole-blood total RNA samples from 15 experienced breachers and 14 age-, sex-, and race-matched unexposed controls. We identified 10 significantly dysregulated genes between experienced breachers and unexposed controls, with FDR corrected <0.05: One upregulated gene, LINC00996 (long intergenic non-protein coding RNA 996); and nine downregulated genes, IGLV3-16 (immunoglobulin lambda variable 3-16), CD200 (CD200 molecule), LILRB5 (leukocyte immunoglobulin-like receptor B5), ZNF667-AS1 (ZNF667 antisense RNA 1), LMOD1 (leiomodin 1), CNTNAP2 (contactin-associated protein 2), EVPL (envoplakin), DPF3 (double PHD fingers 3), and IGHV4-34 (immunoglobulin heavy variable 4-34). The dysregulated gene expressions reported here have been associated with chronic inflammation and immune response, suggesting that these pathways may relate to the risk of lasting neurological symptoms following high exposures to blast over a career.
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Daneshvar DH, Alosco ML. In search of cost-effective and non-invasive biomarkers of traumatic brain injury. EBioMedicine 2022; 76:103823. [PMID: 35074628 PMCID: PMC8792432 DOI: 10.1016/j.ebiom.2022.103823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 11/27/2022] Open
Affiliation(s)
- Daniel H Daneshvar
- Department of Physical Medicine and Rehabilitation, Harvard Medical School; Boston, MA; Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Boston, MA; Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Boston, MA
| | - Michael L Alosco
- Boston University Alzheimer's Disease Research Center and Boston University CTE Center, Boston University School of Medicine, Boston, MA; Department of Neurology, Boston University School of Medicine, Boston, MA.
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Siedhoff HR, Chen S, Song H, Cui J, Cernak I, Cifu DX, DePalma RG, Gu Z. Perspectives on Primary Blast Injury of the Brain: Translational Insights Into Non-inertial Low-Intensity Blast Injury. Front Neurol 2022; 12:818169. [PMID: 35095749 PMCID: PMC8794583 DOI: 10.3389/fneur.2021.818169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 12/20/2021] [Indexed: 12/18/2022] Open
Abstract
Most traumatic brain injuries (TBIs) during military deployment or training are clinically "mild" and frequently caused by non-impact blast exposures. Experimental models were developed to reproduce the biological consequences of high-intensity blasts causing moderate to severe brain injuries. However, the pathophysiological mechanisms of low-intensity blast (LIB)-induced neurological deficits have been understudied. This review provides perspectives on primary blast-induced mild TBI models and discusses translational aspects of LIB exposures as defined by standardized physical parameters including overpressure, impulse, and shock wave velocity. Our mouse LIB-exposure model, which reproduces deployment-related scenarios of open-field blast (OFB), caused neurobehavioral changes, including reduced exploratory activities, elevated anxiety-like levels, impaired nesting behavior, and compromised spatial reference learning and memory. These functional impairments associate with subcellular and ultrastructural neuropathological changes, such as myelinated axonal damage, synaptic alterations, and mitochondrial abnormalities occurring in the absence of gross- or cellular damage. Biochemically, we observed dysfunctional mitochondrial pathways that led to elevated oxidative stress, impaired fission-fusion dynamics, diminished mitophagy, decreased oxidative phosphorylation, and compensated cell respiration-relevant enzyme activity. LIB also induced increased levels of total tau, phosphorylated tau, and amyloid β peptide, suggesting initiation of signaling cascades leading to neurodegeneration. We also compare translational aspects of OFB findings to alternative blast injury models. By scoping relevant recent research findings, we provide recommendations for future preclinical studies to better reflect military-operational and clinical realities. Overall, better alignment of preclinical models with clinical observations and experience related to military injuries will facilitate development of more precise diagnosis, clinical evaluation, treatment, and rehabilitation.
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Affiliation(s)
- Heather R. Siedhoff
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO, United States
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, MO, United States
| | - Shanyan Chen
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO, United States
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, MO, United States
| | - Hailong Song
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO, United States
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, MO, United States
| | - Jiankun Cui
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO, United States
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, MO, United States
| | - Ibolja Cernak
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA, United States
| | - David X. Cifu
- Department of Physical Medicine and Rehabilitation, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Ralph G. DePalma
- Office of Research and Development, Department of Veterans Affairs, Washington, DC, United States
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Zezong Gu
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO, United States
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, MO, United States
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Siedhoff HR, Chen S, Balderrama A, Sun GY, Koopmans B, DePalma RG, Cui J, Gu Z. Long-Term Effects of Low-Intensity Blast Non-Inertial Brain Injury on Anxiety-Like Behaviors in Mice: Home-Cage Monitoring Assessments. Neurotrauma Rep 2022; 3:27-38. [PMID: 35141713 PMCID: PMC8820222 DOI: 10.1089/neur.2021.0063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mild traumatic brain injury induced by low-intensity blast (LIB) exposure poses concerns in military personnel. Using an open-field, non-inertial blast model and assessments by conventional behavioral tests, our previous studies revealed early-phase anxiety-like behaviors in LIB-exposed mice. However, the impact of LIB upon long-term anxiety-like behaviors requires clarification. This study applied a highly sensitive automated home-cage monitoring (HCM) system, which minimized human intervention and environmental changes, to assess anxiety-like responses in mice 3 months after LIB exposure. Initial assessment of 72-h spontaneous activities in a natural cage condition over multiple light and dark phases showed altered sheltering behaviors. LIB-exposed mice exhibited a subtle, but significantly decreased, duration of short shelter visits as compared to sham controls. Other measured responses between LIB-exposed mice and sham controls were insignificant. When behavioral assessments were performed in a challenged condition using an aversive spotlight, LIB-exposed mice demonstrated a significantly higher frequency of movements of shorter distance and duration per movement. Taken together, these findings demonstrated the presence of chronic anxiety-like behaviors assessed by the HCM system under both natural and challenged conditions in mice occurring post-LIB exposure. This model thus provides a platform to test for screening and interventions on anxiety disorders occurring after LIB non-inertial brain injury.
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Affiliation(s)
- Heather R. Siedhoff
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, Missouri, USA
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Shanyan Chen
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, Missouri, USA
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Ashley Balderrama
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, Missouri, USA
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Grace Y. Sun
- Department of Biochemistry, University of Missouri School of Medicine, Columbia, Missouri, USA
| | | | - Ralph G. DePalma
- Office of Research and Development, Department of Veterans Affairs, Washington, DC, USA; Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Jiankun Cui
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, Missouri, USA
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Zezong Gu
- Harry S. Truman Memorial Veterans' Hospital Research Service, Columbia, Missouri, USA
- Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri, USA
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24
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Animal model of repeated low-level blast traumatic brain injury displays acute and chronic neurobehavioral and neuropathological changes. Exp Neurol 2021; 349:113938. [PMID: 34863680 DOI: 10.1016/j.expneurol.2021.113938] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 11/04/2021] [Accepted: 11/26/2021] [Indexed: 11/20/2022]
Abstract
Blast-induced neurotrauma (BINT) is not only a signature injury to soldiers in combat field and training facilities but may also a growing concern in civilian population due to recent increases in the use of improvised explosives by insurgent groups. Unlike moderate or severe BINT, repeated low-level blast (rLLB) is different in its etiology as well as pathology. Due to the constant use of heavy weaponry as part of combat readiness, rLLB usually occurs in service members undergoing training as part of combat readiness. rLLB does not display overt pathological symptoms; however, earlier studies report chronic neurocognitive changes such as altered mood, irritability, and aggressive behavior, all of which may be caused by subtle neuropathological manifestations. Current animal models of rLLB for investigation of neurobehavioral and neuropathological alterations have not been adequate and do not sufficiently represent rLLB conditions. Here, we developed a rat model of rLLB by applying controlled low-level blast pressures (<10 psi) repeated successively five times to mimic the pressures experienced by service members. Using this model, we assessed anxiety-like symptoms, motor coordination, and short-term memory as a function of time. We also examined levels of superoxide-producing enzyme NADPH oxidase, microglial activation, and reactive astrocytosis as factors likely contributing to these neurobehavioral changes. Animals exposed to rLLB displayed acute and chronic anxiety-like symptoms, motor and short-term memory impairments. These changes were paralleled by increased microglial activation and reactive astrocytosis. Conversely, animals exposed to a single low-level blast did not display significant changes. Collectively, this study demonstrates that, unlike a single low-level blast, rLLB exerts a cumulative impact on different brain regions and produces chronic neuropathological changes in so doing, may be responsible for neurobehavioral alterations.
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