Study protocol: Identifying transcriptional regulatory alterations of chronic effects of blast and disturbed sleep in United States Veterans.

Injury related to blast exposure dramatically rose during post-911 era military conflicts in Iraq and Afghanistan. Mild traumatic brain injury (mTBI) is among the most common injuries following blast, an exposure that may not result in a definitive physiologic marker (e.g., loss of consciousness). Recent research suggests that exposure to low level blasts and, more specifically repetitive blast exposure (RBE), which may be subconcussive in nature, may also impact long term physiologic and psychological outcomes, though findings have been mixed. For military personnel, blast-related injuries often occur in chaotic settings (e.g., combat), which create challenges in the immediate assessment of related-injuries, as well as acute and post-acute sequelae. As such, alternate means of identifying blast-related injuries are needed. Results from previous work suggest that epigenetic markers, such as DNA methylation, may provide a potential stable biomarker of cumulative blast exposure that can persist over time. However, more research regarding blast exposure and associations with short- and long-term sequelae is needed. Here we present the protocol for an observational study that will be completed in two phases: Phase 1 will address blast exposure among Active Duty Personnel and Phase 2 will focus on long term sequelae and biological signatures among Veterans who served in the recent conflicts and were exposed to repeated blast events as part of their military occupation. Phase 2 will be the focus of this paper. We hypothesize that Veterans will exhibit similar differentially methylated regions (DMRs) associated with changes in sleep and other psychological and physical metrics, as observed with Active Duty Personnel. Additional analyses will be conducted to compare DMRs between Phase 1 and 2 cohorts, as well as self-reported psychological and physical symptoms. This comparison between Service Members and Veterans will allow for exploration regarding the natural history of blast exposure in a quasi-longitudinal manner. Findings from this study are expected to provide additional evidence for repetitive blast-related physiologic changes associated with long-term neurobehavioral symptoms. It is expected that findings will provide foundational data for the development of effective interventions following RBE that could lead to improved long-term physical and psychological health.

Association of Blast Exposure in Military Breaching with Intestinal Permeability Blood Biomarkers Associated with Leaky Gut.

Injuries and subclinical effects from exposure to blasts are of significant concern in military operational settings, including tactical training, and are associated with self-reported concussion-like symptomology and physiological changes such as increased intestinal permeability (IP), which was investigated in this study. Time-series gene expression and IP biomarker data were generated from "breachers" exposed to controlled, low-level explosive blast during training. Samples from 30 male participants at pre-, post-, and follow-up blast exposure the next day were assayed via RNA-seq and ELISA. A battery of symptom data was also collected at each of these time points that acutely showed elevated symptom reporting related to headache, concentration, dizziness, and taking longer to think, dissipating ~16 h following blast exposure. Evidence for bacterial translocation into circulation following blast exposure was detected by significant stepwise increase in microbial diversity (measured via alpha-diversity p = 0.049). Alterations in levels of IP protein biomarkers (i.e., Zonulin, LBP, Claudin-3, I-FABP) assessed in a subset of these participants (n = 23) further evidenced blast exposure associates with IP. The observed symptom profile was consistent with mild traumatic brain injury and was further associated with changes in bacterial translocation and intestinal permeability, suggesting that IP may be linked to a decrease in cognitive functioning. These preliminary findings show for the first time within real-world military operational settings that exposures to blast can contribute to IP.

Investigating neuropathological changes and underlying neurobiological mechanisms in the early stages of primary blast-induced traumatic brain injury: Insights from a rat model.

The utilization of explosives and chemicals has resulted in a rise in blast-induced traumatic brain injury (bTBI) in recent times. However, there is a dearth of diagnostic biomarkers and therapeutic targets for bTBI due to a limited understanding of biological mechanisms, particularly in the early stages. The objective of this study was to examine the early neuropathological characteristics and underlying biological mechanisms of primary bTBI. A total of 83 Sprague Dawley rats were employed, with their heads subjected to a blast shockwave of peak overpressure ranging from 172 to 421 kPa in the GI, GII, and GIII groups within a closed shock tube, while the body was shielded. Neuromotor dysfunctions, morphological changes, and neuropathological alterations were detected through modified neurologic severity scores, brain water content analysis, MRI scans, histological, TUNEL, and caspase-3 immunohistochemical staining. In addition, label-free quantitative (LFQ)-proteomics was utilized to investigate the biological mechanisms associated with the observed neuropathology. Notably, no evident damage was discernible in the GII and GI groups, whereas mild brain injury was observed in the GIII group. Neuropathological features of bTBI were characterized by morphologic changes, including neuronal injury and apoptosis, cerebral edema, and cerebrovascular injury in the shockwave's path. Subsequently, 3153 proteins were identified and quantified in the GIII group, with subsequent enriched neurological responses consistent with pathological findings. Further analysis revealed that signaling pathways such as relaxin signaling, hippo signaling, gap junction, chemokine signaling, and sphingolipid signaling, as well as hub proteins including Prkacb, Adcy5, and various G-protein subunits (Gnai2, Gnai3, Gnao1, Gnb1, Gnb2, Gnb4, and Gnb5), were closely associated with the observed neuropathology. The expression of hub proteins was confirmed via Western blotting. Accordingly, this study proposes signaling pathways and key proteins that exhibit sensitivity to brain injury and are correlated with the early pathologies of bTBI. Furthermore, it highlights the significance of G-protein subunits in bTBI pathophysiology, thereby establishing a theoretical foundation for early diagnosis and treatment strategies for primary bTBI.

Cutaneous burn injury represents a major risk factor for the development of traumatic ectopic bone formation following blast-related extremity injury.

Blast-related traumatic heterotopic ossification (tHO) impacts clinical outcomes in combat-injured patients, leading to delayed wound healing, inflammatory complications, and reduced quality of life. Blast injured patients often have significant burns. This study investigated whether a partial thickness thermal burn injury exacerbates blast-related tHO in a clinically relevant polytrauma animal model. Adult male Sprague Dawley rats were subjected to an established model involving a whole-body blast overpressure exposure (BOP), complex extremity trauma followed by hind limb amputation (CET) followed by the addition of a 10 % total body surface area (TBSA) second degree thermal burn (BU). Micro-CT scans on post-operative day 56 showed a significant increase in HO volume in the CET + BU as compared to the CET alone injury group (p < .0001; 22.83 ± 3.41 mm3 vs 4.84 ± 5.77 mm3). Additionally, CET + BU concomitant with BOP significantly increased HO (p < .0001; 34.95 ± 7.71 mm3) as compared to CET + BU alone, confirming BOP has a further synergistic effect. No HO was detectable in rats in the absence of CET. Serum analysis revealed similar significant elevated (p < .0001) levels of pro-inflammatory markers (Cxcl1 and Il6) at 6 h post-injury (hpi) in the CET + BU and BOP + CET + BU injury groups as compared to naïve baseline values. Real-time qPCR demonstrated similar levels of chondrogenic and osteogenic gene expression in muscle tissue at the site of injury at 168 hpi in both the CET + BU and BOP+CET + BU injury groups. These results support the hypothesis that a 10 % TBSA thermal burn markedly enhances tHO following acute musculoskeletal extremity injury in the presence and absence of blast overpressure. Furthermore, the influence of BOP on tHO cannot be accounted for either in regards to systemic inflammation induced from remote injury or inflammatory-osteo-chondrogenic expression changes local to the musculoskeletal trauma, suggesting that another mechanism beyond BOP and BU synergistic effects are at play. Therefore, these findings warrant future investigations to explore other mechanisms by which blast and burn influence tHO, and testing prophylactic measures to mitigate the local and systemic inflammatory effects of these injuries on development of HO.

Model matters: Differential outcomes in traumatic optic neuropathy pathophysiology between blunt and blast-wave mediated head injuries.

Over 3 million people in the United States live with long-term disability because of a traumatic brain injury (TBI). The purpose of this study was to characterize and compare two different animal models of TBI (blunt head trauma and blast TBI) to determine common and divergent characteristics of these models. With recent literature reviews noting the prevalence of visual system injury in animal models of TBI, coupled with clinical estimates of 50-75% of all TBI cases, we decided to assess commonalities, if they existed, through visual system injury. A unilateral (left directed) blast and repeat blast model injury with coup-contra-coup injury patterns were compared to a midline blunt injury. Injuries were induced in adult male mice to observe and quantify visual deficits. Retinal ganglion cell loss and axonal degeneration in the optic tract, superior colliculus, and lateral geniculate nuclei were examined to trace injury outcomes throughout major vision-associated areas. Optokinetic response, immunohistochemistry, and western blots were analyzed. Where a single blunt injury produces significant visual deficits a single blast injury appears to have less severe visual consequences. Visual deficits after repeat blasts are similar to a single blast. Single blast injury induces contralateral damage to the right optic chiasm and tract whereas bilateral injury follows a single blunt TBI. Repeat blast injuries are required to see degeneration patterns in downstream regions similar to the damage seen in a single blunt injury. This finding is further supported by amyloid precursor protein (APP) staining in injured cohorts. Blunt injured groups present with staining 1.2 mm ahead of the optic nerve, indicating axonal breakage closer to the optic chiasm. In blast groups, APP was identifiable in a bilateral pattern only in the geniculate nucleus. Evidence for unilateral neuronal degeneration in brain tissue with bilateral axonal ruptures are pivotal discoveries in this model differentiation. Analysis of the two injury models suggests that there is a significant difference in the histological outcomes dependent on injury type, though visual system injury is likely present in more cases than are currently diagnosed clinically.

Metabotropic Glutamate Receptor 2 Expression Is Chronically Elevated in Male Rats With Post-Traumatic Stress Disorder Related Behavioral Traits Following Repetitive Low-Level Blast Exposure.

Many military veterans who experienced blast-related traumatic brain injuries in the conflicts in Iraq and Afghanistan currently suffer from chronic cognitive and mental health problems that include depression and post-traumatic stress disorder (PTSD). Male rats exposed to repetitive low-level blast develop cognitive and PTSD-related behavioral traits that are present for more than 1 year after exposure. We previously reported that a group II metabotropic receptor (mGluR2/3) antagonist reversed blast-induced behavioral traits. In this report, we explored mGluR2/3 expression following blast exposure in male rats. Western blotting revealed that mGluR2 protein (but not mGluR3) was increased in all brain regions studied (anterior cortex, hippocampus, and amygdala) at 43 or 52 weeks after blast exposure but not at 2 weeks or 6 weeks. mGluR2 RNA was elevated at 52 weeks while mGluR3 was not. Immunohistochemical staining revealed no changes in the principally presynaptic localization of mGluR2 by blast exposure. Administering the mGluR2/3 antagonist LY341495 after behavioral traits had emerged rapidly reversed blast-induced effects on novel object recognition and cued fear responses 10 months following blast exposure. These studies support alterations in mGluR2 receptors as a key pathophysiological event following blast exposure and provide further support for group II metabotropic receptors as therapeutic targets in the neurobehavioral effects that follow blast injury.

High Lifetime Blast Exposure Using the Blast Exposure Threshold Survey Is Associated With Worse Warfighter Brain Health Following Mild Traumatic Brain Injury.

The purpose of this study was to extend previous research by examining the relationship between lifetime blast exposure and neurobehavioral functioning after mild TBI (MTBI) by (a) using a comprehensive measure of lifetime blast exposure, and (b) controlling for the influence of post-traumatic stress disorder (PTSD). Participants were 103 United States service members and veterans (SMVs) with a medically documented diagnosis of MTBI, recruited from three military treatment facilities (74.8%) and community-based recruitment initiatives (25.2%, e.g., social media, flyers). Participants completed a battery of neurobehavioral measures 12 or more months post-injury (Neurobehavioral Symptom Inventory, PTSD-Checklist PCLC, TBI-Quality of Life), including the Blast Exposure Threshold Survey (BETS). The sample was classified into two lifetime blast exposure (LBE) groups: High (n = 57) and Low (n = 46) LBE. In addition, the sample was classified into four LBE/PTSD subgroups: High PTSD/High LBE (n = 38); High PTSD/Low LBE (n = 19); Low PTSD/High LBE (n = 19); and Low PTSD/Low LBE (n = 27). The High LBE group had consistently worse scores on all neurobehavioral measures compared with the Low LBE group. When controlling for the influence of PTSD (using ANCOVA), however, only a handful of group differences remained. When comparing measures across the four LBE/PTSD subgroups, in the absence of clinically meaningful PTSD symptoms (i.e., Low PTSD), participants with High LBE had worse scores on the majority of neurobehavioral measures (e.g., post-concussion symptoms, sleep, fatigue). When examining the total number of clinically elevated measures, the High LBE subgroup consistently had a greater number of clinically elevated scores compared with the Low LBE subgroup for the majority of comparisons (i.e., four to 15 or more elevated symptoms). In contrast, in the presence of clinically meaningful PTSD symptoms (i.e., High PTSD), there were no differences between High versus Low LBE subgroups for all measures. When examining the total number of clinically elevated measures, however, there were meaningful differences between High versus Low LBE subgroups for those comparisons that included a high number of clinically elevated scores (i.e., six to 10 or more), but not for a low number of clinically elevated scores (i.e., one to five or more). High LBE, as quantified using a more comprehensive measure than utilized in past research (i.e., BETS), was associated with worse overall neurobehavioral functioning after MTBI. This study extends existing literature showing that lifetime blast exposure, that is largely subconcussive, may negatively impact warfighter brain health and readiness beyond diagnosable brain injury.

Combat Deployed Service Members by Blast TBI and Service Separation Status 5-years Post-deployment: Comparison of Cognitive, Neurobehavioral, and Psychological Profiles of Those Who Left vs. Those Still Serving.

INTRODUCTION: Longitudinal research regarding the pre- and post-separation experience has been relatively limited, despite its potential as a major life transition. Separating from the military and re-integration to civilian life is noted to be a period of increased risk of significant adjustment challenges, which impacts a service member in a multitude of areas. Active duty service members with combat-related physical or mental health or pre-existing adjustment conditions may be more likely to separate from service and more at risk for post-military service adjustment problems. MATERIALS AND METHODS: This is a secondary data analysis from a prospective, observational, longitudinal, multicohort study involving deployed service members originally enrolled between 2008 and 2013 in combat or following medical evacuation to Landstuhl, Germany. Two combat-deployed cohorts were examined: non-head-injured control without blast exposure (n = 109) and combat-related concussion arising from blast (n = 165). Comprehensive clinical evaluations performed at 1 year and 5 year follow-up included identical assessment batteries for neurobehavioral, psychiatric, and cognitive outcomes. In addition to demographics collected at each study visit, the current analysis leveraged the Glasgow Outcome Scale Extended (GOS-E), a measure of overall global disability. For neurobehavioral impairment, the Neurobehavioral Rating Scale-Revised (NRS) was used as well as the Headache Impact Test (HIT-6) to assess headache burden. To compare psychiatric symptom burden between those separated to those still serving, the Clinician-Administered PTSD Scale for DSM-IV (CAPS) and Montgomery-Asberg Depression Rating Scale (MADRS) for depression were used as well as the Michigan Alcohol Screening Test (MAST) to be able to compare alcohol misuse across groups. Overall cognitive function/performance was defined for each service member by aggregating the 19 neuropsychological measures. RESULTS: Overall comparisons following adjustment by linear regression and correction for multiple comparisons by separation status subgroup for non-blast control or blast traumatic brain injury (TBI) identified significant differences at 5 years post-enrollment in measures of global disability, neurobehavioral impairment, and psychiatric symptom burden. Those who separated had worse global disability, worse neurobehavioral symptoms, worse Post-Traumatic Stress Disorder symptoms, and worse depression symptoms than active duty service members. While service members who sustain a mild blast TBI during combat are more likely to separate from service within 5 years, there is a proportion of those non-injured who also leave during this time frame. Clinical profiles of both groups suggest service members who separated have elevated psychiatric and neurobehavioral symptoms but not cognitive dysfunction. Interestingly, the symptom load in these same domains is lower for those without blast TBI who separated during this time frame. CONCLUSIONS: These results appear to support previous research depicting that, for some service members, transitioning out of the military and re-integrating into civilian life can be a challenging adjustment. Many factors, including personal and social circumstances, prior mental or emotional difficulties, availability of social or community support or resources, can influence the adjustment outcomes of veterans. Service members with prior adjustment difficulties and/or those with blast TBI history (and ongoing neurobehavioral symptoms) may find the transition from military to civilian life even more challenging, given the potential substantial changes in lifestyle, structure, identity, and support.

Local Firework Restrictions and Ocular Trauma.

Importance: Fireworks can cause vision-threatening injuries, but the association of local legislation with the mitigation of these injuries is unclear. Objective: To evaluate the odds of firework-related ocular trauma among residents of areas where fireworks are permitted vs banned. Design, Setting, and Participants: This case-control study was conducted at a level 1 trauma center in Seattle, Washington, among 230 patients presenting with ocular trauma in the 2 weeks surrounding the Independence Day holiday, spanning June 28 to July 11, over an 8-year period (2016-2022). Exposures: Firework ban status of patient residence. Main Outcomes and Measures: Odds of firework-related injuries among residents of areas where fireworks are legal vs where they are banned, calculated as odds ratios (ORs) and 95% CIs. Results: Of 230 consultations for ocular trauma during the study period, 94 patients (mean [SD] age, 25 [14] years; 86 male patients [92%]) sustained firework-related injuries, and 136 (mean [SD] age, 43 [23] years; 104 male patients [77%]) sustained non-firework-related injuries. The odds of firework-related ocular trauma were higher among those living in an area where fireworks were legal compared with those living in an area where fireworks were banned (OR, 2.0 [95% CI, 1.2-3.5]; P = .01). In addition, the odds of firework injuries were higher for patients younger than 18 years (OR, 3.1 [95% CI, 1.7-5.8]; P < .001) and for male patients (OR, 3.3 [95% CI, 1.5-7.1]; P = .004). Firework injuries were more likely to be vision threatening (54 of 94 [57%]) compared with non-firework-related injuries (54 of 136 [40%]; OR, 2.1 [95% CI, 1.2-3.5]; P = .01). Conclusions and Relevance: This case-control study suggests that the odds of firework-related ocular trauma were slightly higher among residents of areas where fireworks were legal compared with residents of areas where fireworks were banned. Although these results suggest that local firework bans may be associated with a small reduction in the odds of firework-related ocular trauma, additional studies are warranted to assess what actions might lead to greater reductions.

Proteomic Changes in the Hippocampus after Repeated Explosive-Driven Blasts.

Repeated blast-traumatic brain injury (blast-TBI) has been hypothesized to cause persistent and unusual neurological and psychiatric symptoms in service members returning from war zones. Blast-wave primary effects have been supposed to induce damage and molecular alterations in the brain. However, the mechanisms through which the primary effect of an explosive-driven blast wave generate brain lesions and induce brain consequences are incompletely known. Prior findings from rat brains exposed to two consecutive explosive-driven blasts showed molecular changes (hyperphosphorylated-Tau, AQP4, S100ß, PDGF, and DNA-polymerase-ß) that varied in magnitude and direction across different brain regions. We aimed to compare, in an unbiased manner, the proteomic profile in the hippocampus of double blast vs sham rats using mass spectrometry (MS). Data showed differences in up- and down-regulation for protein abundances in the hippocampus of double blast vs sham rats. Tandem mass tag (TMT)-MS results showed 136 up-regulated and 94 down-regulated proteins between the two groups (10.25345/C52B8VP0X). These TMT-MS findings revealed changes never described before in blast studies, such as increases in MAGI3, a scaffolding protein at cell-cell junctions, which were confirmed by Western blotting analyses. Due to the absence of behavioral and obvious histopathological changes as described in our previous publications, these proteomic data further support the existence of an asymptomatic blast-induced molecular altered status (ABIMAS) associated with specific protein changes in the hippocampus of rats repeatedly expsosed to blast waves generated by explosive-driven detonations.

Prevalence and Risk Factors of Self-reported Dizziness in Post-9/11 Service Members and Veterans.

INTRODUCTION: Dizziness is prevalent in the general population, but little is known about its prevalence in the U.S. military population. Dizziness is commonly associated with blast exposure and traumatic brain injury (TBI), but the potential independent contributions of blast and TBI have yet to be evaluated. This study's goal was to estimate the prevalence of dizziness among post-9/11 service members and Veterans and to examine independent and joint associations between military TBI history, blast exposure, and self-reported dizziness. MATERIALS AND METHODS: The study sample consisted of service members (n = 424) and recently separated (< ∼2.5 years) Veterans (n = 492) enrolled in the Noise Outcomes in Service members Epidemiology (NOISE) Study. We examined associations between self-reported history of probable TBI and blast exposure and recent dizziness using logistic regression. Models were stratified by service member versus Veteran status and adjusted to account for potentially confounding demographic and military characteristics. RESULTS: Overall, 22% of service members and 31% of Veterans self-reported dizziness. Compared to those with neither TBI nor blast exposure history, both service members and Veterans with TBI (with or without blast) were three to four times more likely to self-report dizziness. Those with blast exposure but no TBI history were not more likely to self-report dizziness. There was no evidence of an interaction effect between blast exposure and a history of TBI on the occurrence of dizziness. CONCLUSION: Self-reported dizziness was prevalent in this sample of service members and Veterans. Probable TBI history, with or without blast exposure, was associated with dizziness, but blast exposure without TBI history was not. This suggests that treatment guidelines for TBI-related dizziness may not need to be tailored to the injury mechanism. However, future efforts should be directed toward the understanding of the pathophysiology of TBI on self-reported dizziness, which is fundamental to the design of treatment strategies.

Acute Hearing Deficits associated with Weapons Exposure in Section 734 Blast Overpressure Study (BOS).

INTRODUCTION: This prospective, multi-site, observational study describes ongoing efforts in support of the Fiscal Year 2018 National Defense Authorization Act (NDAA) Section 734 Blast Overpressure Study (BOS) to identify the acute effects impulse and blast exposure have on hearing abilities of the Warfighter in various military training environments. MATERIALS AND METHODS: Hearing thresholds, a binaural tone detection task, and auditory symptoms were collected before and immediately following weapons exposure across nine military training environments from January 2020 to October 2022. An additional 25 non-exposed control participants also completed the behavioral test battery. A boothless audiometer was used to measure hearing ability in the field. Sound level meters were attached on-body to record the exposure environment throughout training. RESULTS: Mean threshold change for the blast-exposed group was worse than the control group. Of the 188 blast-exposed participants, 23 experienced a temporary threshold shift (TTS) acutely after exposure. A decrease in binaural tone detection performance and increased symptom severity was found when comparing blast-exposed participants with a TTS versus those without a significant change in hearing. A complex but consistent relationship between measured exposure level (LAeq8hr) and the magnitude of the resulting TTS is suggested in the available data. CONCLUSIONS: Recent discussions on Section 734 studies examining the effects of repetitive blast exposure have indicated that hearing-related issues were a critical problem that needed additional research. Study outcomes provide highly repeatable results across various weapons systems with hazardous blast exposure. This standardized set of hearing assessment tools for evaluating acute effects of noise under field conditions has been critically important in improving our understanding of TTS in prospective human subject research.

Blast Lung Injury in Children: Injury Patterns and Associated Organ Injuries.

BACKGROUND: Bombings are the most common cause of civilian deaths in wars, and unfortunately, a large proportion of civilian victims are children. OBJECTIVE: This study aimed to evaluate the frequency of blast lung injury (BLI), to evaluate lung injury patterns on tomographic images, and to document the relationship between blast lung and mortality in children exposed to the blast effect. METHODS: Thirty-six children (25.3% of pediatric patients brought to our hospital with blast injury) with BLI were included in the study. The pediatric trauma score evaluations made in the emergency department in the first admission were recorded. Lung injury findings in the computed tomography images of the patients were examined, and injuries detected in other systems were recorded. RESULTS: The most common lung injury pattern was contusion (right: 69.4%, left: 80.6%). The incidence of brain damage (52.4%) and intra-abdominal injury (76.2%) in children with low pediatric trauma score value was statistically significantly higher ( P = 0.049, P = 0.017, respectively). There was no statistically significant correlation between the presence of lung injury, injury patterns, and mortality. The incidence of brain damage in deceased patients (61.5%) was statistically significantly higher than the incidence of brain damage in surviving patients (26.1%) ( P = 0.036). Low pediatric trauma score was observed in 11 (84.6%) of the deceased children and in 10 (43.5%) of the survivors ( P = 0.016). The mean age of children with hemothorax in the right lung was statistically significantly lower than those without ( P = 0.014). CONCLUSION: Our findings revealed that pediatric BLI is common after a blast, that it is associated with other system injuries, and that a multimodal radiological approach is required in child victims.

Systemic inflammation induced from remote extremity trauma is a critical driver of secondary brain injury.

Blast exposure, commonly experienced by military personnel, can cause devastating life-threatening polysystem trauma. Despite considerable research efforts, the impact of the systemic inflammatory response after major trauma on secondary brain injury-inflammation is largely unknown. The aim of this study was to identify markers underlying the susceptibility and early onset of neuroinflammation in three rat trauma models: (1) blast overpressure exposure (BOP), (2) complex extremity trauma (CET) involving femur fracture, crush injury, tourniquet-induced ischemia, and transfemoral amputation through the fracture site, and (3) BOP+CET. Six hours post-injury, intact brains were harvested and dissected to obtain biopsies from the prefrontal cortex, striatum, neocortex, hippocampus, amygdala, thalamus, hypothalamus, and cerebellum. Custom low-density microarray datasets were used to identify, interpret and visualize genes significant (p < 0.05 for differential expression [DEGs]; 86 neuroinflammation-associated) using a custom python-based computer program, principal component analysis, heatmaps and volcano plots. Gene set and pathway enrichment analyses of the DEGs was performed using R and STRING for protein-protein interaction (PPI) to identify and explore key genes and signaling networks. Transcript profiles were similar across all regions in naïve brains with similar expression levels involving neurotransmission and transcription functions and undetectable to low-levels of inflammation-related mediators. Trauma-induced neuroinflammation across all anatomical brain regions correlated with injury severity (BOP+CET > CET > BOP). The most pronounced differences in neuroinflammatory-neurodegenerative gene regulation were between blast-associated trauma (BOP, BOP+CET) and CET. Following BOP, there were few DEGs detected amongst all 8 brain regions, most were related to cytokines/chemokines and chemokine receptors, where PPI analysis revealed Il1b as a potential central hub gene. In contrast, CET led to a more excessive and diverse pro-neuroinflammatory reaction in which Il6 was identified as the central hub gene. Analysis of the of the BOP+CET dataset, revealed a more global heightened response (Cxcr2, Il1b, and Il6) as well as the expression of additional functional regulatory networks/hub genes (Ccl2, Ccl3, and Ccl4) which are known to play a critical role in the rapid recruitment and activation of immune cells via chemokine/cytokine signaling. These findings provide a foundation for discerning pathophysiological consequences of acute extremity injury and systemic inflammation following various forms of trauma in the brain.

Late chronic local inflammation, synaptic alterations, vascular remodeling and arteriovenous malformations in the brains of male rats exposed to repetitive low-level blast overpressures.

In the course of military operations in modern war theaters, blast exposures are associated with the development of a variety of mental health disorders associated with a post-traumatic stress disorder-related features, including anxiety, impulsivity, insomnia, suicidality, depression, and cognitive decline. Several lines of evidence indicate that acute and chronic cerebral vascular alterations are involved in the development of these blast-induced neuropsychiatric changes. In the present study, we investigated late occurring neuropathological events associated with cerebrovascular alterations in a rat model of repetitive low-level blast-exposures (3 × 74.5 kPa). The observed events included hippocampal hypoperfusion associated with late-onset inflammation, vascular extracellular matrix degeneration, synaptic structural changes and neuronal loss. We also demonstrate that arteriovenous malformations in exposed animals are a direct consequence of blast-induced tissue tears. Overall, our results further identify the cerebral vasculature as a main target for blast-induced damage and support the urgent need to develop early therapeutic approaches for the prevention of blast-induced late-onset neurovascular degenerative processes.

Early Brain Amyloid Accumulation at PET in Military Instructors Exposed to Subconcussive Blast Injuries.

Background Traumatic brain injury (TBI) is the leading cause of disability in young adults. Recurrent TBI is associated with a range of neurologic sequelae, but the contributing factors behind the development of such chronic encephalopathy are poorly understood. Purpose To quantify early amyloid ß deposition in the brain of otherwise healthy adult men exposed to repeated subconcussive blast injury using amyloid PET. Materials and Methods In this prospective study from January 2020 to December 2021, military instructors who were routinely exposed to repeated blast events were evaluated at two different points: baseline (before blast exposure from breacher or grenade) and approximately 5 months after baseline (after blast exposure). Age-matched healthy control participants not exposed to blasts and without a history of brain injury were evaluated at similar two points. Neurocognitive evaluation was performed with standard neuropsychologic testing in both groups. Analysis of PET data consisted of standardized uptake value measurements in six relevant brain regions and a whole-brain voxel-based statistical approach. Results Participants were men (nine control participants [median age, 33 years; IQR, 32-36 years] and nine blast-exposed participants [median age, 33 years; IQR, 30-34 years]; P = .82). In the blast-exposed participants, four brain regions showed significantly increased amyloid deposition after blast exposure: inferomedial frontal lobe (P = .004), precuneus (P = .02), anterior cingulum (P = .002), and superior parietal lobule (P = .003). No amyloid deposition was observed in the control participants. Discriminant analysis on the basis of regional changes of amyloid accumulation correctly classified the nine healthy control participants as healthy control participants (100%), and seven of the nine blast-exposed participants (78%) were correctly classified as blast exposed. Based on the voxel-based analysis, whole-brain parametric maps of early abnormal early amyloid uptake were obtained. Conclusion Early brain amyloid accumulation was identified and quantified at PET in otherwise healthy adult men exposed to repetitive subconcussive traumatic events. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Haller in this issue.

Triage and Evaluation of Blast-Injured Patients in Wenling Liquefied Petroleum Gas Tanker Explosion.

On June 13, 2020, a liquefied petroleum gas tanker exploded in Wenling. Here, the authors describe the mass casualty emergency response to the explosion. The authors collected the medical records of 176 inpatients at 8 hospitals in Taizhou and Hangzhou. The 176 inpatients with blast injuries comprised 70 females and 106 males, with an average age of 45.48 ± 19.96 years, and more than half of the patients were farmers. They were transported to six hospitals distributed around the explosion site in Taizhou in the initial rescue period and were grouped according to their new injury severity score as having mild, moderate, severe, or extremely severe injuries. Most patients with severe and extremely severe injuries were admitted to a superior hospital for postsecondary triage. Forty-four patients experienced primary blast injuries, 137 experienced secondary blast injuries, 37 experienced tertiary blast injuries, and 40 patients experienced quaternary blast injuries. Multiple blast injuries were suffered by 62 patients. Most patients (95.45%) suffered external injuries, with the chest, extremities, and face as the main affected areas. Burns were diagnosed in 26 adults, of whom 15.38%, 19.23%, 7.70%, and 57.69% suffered mild, moderate, severe, and extremely severe cases. Sixteen burn patients suffered from burn-blast injuries. Upper limbs and the head/face/neck area, as exposed areas, were more likely to experience a burn injury. Inhalation was the main accompanying injury. Of the eight patients who died in the prehospital session, seven had burn injuries. This report on the accident and injury characteristics of an open-air LPG-related explosion will facilitate responses to subsequent catastrophes.

Validation of Military Occupational Specialty as a Proxy for Blast Exposure Using the Salisbury Blast Interview.

Abstract Evaluating large data sets precludes the ability to directly measure individual experiences, instead relying on proxies to infer certain constructs. Blast exposure is a construct of study currently in its infancy, resulting in diverse definitions and measurements across studies. The purpose of the present study was to validate military occupational specialty (MOS) as a proxy for blast exposure in combat veterans. A total of 256 veterans (86.33% male) completed the Salisbury Blast Interview (SBI) and Mid-Atlantic Mental Illness Research Education and Clinical Center (MIRECC) Assessment of Traumatic Brain Injury (MMA-TBI). MOS was collected through record review and categorized into low and high risk for blast exposure. Chi-square analyses and t tests compared SBI metrics between MOS categories. Receiver operating characteristic (ROC) analyses evaluated the diagnostic accuracy of MOS category in determining blast exposure severity. Veterans in high-risk MOS were more likely to have experienced blast and deployment TBI (ps < 0.001) than were those in low-risk MOS. ROC analyses indicated good specificity (81.29-88.00) for blast and deployment TBI outcomes, suggesting that low-risk MOS is generally associated with an absence of blast and deployment TBI outcomes. Sensitivity was low (36.46-51.14), indicating that MOS risk level was not a good predictor of the presence of these outcomes. Results demonstrate that high-risk MOSs will identify individuals with blast exposure and deployment TBI history whereas low-risk MOSs will capture a highly variable group. Accuracy of MOS categorization was not acceptable for diagnostic-level tests; however, results support its use as a screening measure for a history of exposure to blast, use in epidemiological studies, and considerations for military policy.

The Impact of Blast Exposure-With or Without Traumatic Brain Injury-on Metabolic Abnormalities in Post-9/11 Veterans.

OBJECTIVE: The primary aim included explorations of: (1) the associations between the history of blast exposure (BE), close blast exposure (CBE), and blast-related traumatic brain injury (bTBI) and metabolic abnormality; and (2) the potential mediating effect of comorbid psychological and somatic conditions on these associations. The secondary aim explored the association of dose-response impact of BE, CBE, and bTBI and metabolic abnormality. SETTING: Data were collected by the Translational Research Center for TBI and Stress Disorders (TRACTS). PARTICIPANTS: Post-9/11 veterans from the TRACTS baseline sample who had conflict-zone deployment experience ( N = 734). DESIGN: Cross-sectional secondary data analysis. We computed relative risks (RRs) and 95% CI using modified Poisson regression. We quantified the impact of co-occurring psychological and somatic conditions on this association using mediation analyses. MAIN MEASURES: Exposures included BE (<100 m), CBE (<10 m), and bTBI. Metabolic abnormality outcomes included (1) overweight/obesity (defined by abnormal waist-hip ratio [WHR] and abnormal waist circumference [WC]); (2) glucose dysregulation; and (3) meeting criteria for cardiometabolic syndrome (defined by guidelines). RESULTS: The sample was majority male (91%) and White (68%), with a mean age of 34.6 years (SD = 8.99). Most participants had 1 or more BE (83%); 48% experienced 1 or more CBE. Overweight/obesity was highly prevalent in the sample (51% had abnormal WHR and 60% abnormal WC). There was no significant direct or indirect association between BE, CBE, and bTBI and metabolic abnormalities (RRs: 0.70-1.51; P 's > .05). CONCLUSION: Future research is needed to investigate the association of BE with metabolic abnormalities with larger, more targeted sample selection, and longer follow-up. Effective and sustainable weight management and metabolic health prevention interventions for this veteran cohort are needed.

GABAA receptor subunit modulation reversed electrophysiological network alterations after blast exposure in rat organotypic hippocampal slice cultures.

Throughout training and deployment, some military service members are frequently exposed to shock waves due to blasts, and some complain of myriad neurological symptoms. In rat organotypic hippocampal slice cultures (OHSCs), blast-induced traumatic brain injury (bTBI) causes deficits in some electrophysiological measures, like long term potentiation, a neuronal correlate for learning and memory. In this study, we further characterized the alterations in the hippocampal network of OHSCs following a single moderate blast exposure. Connectivity and clustering coefficients were reduced across the hippocampal network following bTBI, despite the lack of changes in the firing rate, spike amplitude, spike duration, or inter-spike interval. However, interrogation with the GABAA receptor antagonist, bicuculline, revealed additional significant differences between injured and control slices in measures of spike amplitude, spike duration, connectivity, and clustering. bTBI also significantly reduced expression of the α1 and α5 GABAA receptor subunits. Treatment with the FDA-approved histone deacetylase inhibitor suberanilohydroxamic acid (SAHA) restored the α1 subunit and attenuated deficits in network measures, like connectivity and clustering coefficients. These findings suggest that GABAA receptors may be implicated in neuronal network changes in OHSCs following bTBI, and their recovery may be a viable therapeutic intervention to mitigate injury-induced neurological symptoms.