Synthesis of Findings, Current Investigations, and Future Directions: Operation Brain Trauma Therapy

Traumatic Brain Injury in the Long-COVID Era

Major determinants of the biological background or reserve, such as age, biological sex, comorbidities (diabetes, hypertension, obesity, etc.), and medications (e.g., anticoagulants), are known to affect outcome after traumatic brain injury (TBI). With the unparalleled data richness of coronavirus disease 2019 (COVID-19; ∼375,000 and counting!) as well as the chronic form, long-COVID, also called post-acute sequelae SARS-CoV-2 infection (PASC), publications (∼30,000 and counting) covering virtually every aspect of the diseases, pathomechanisms, biomarkers, disease phases, symptomatology, etc., have provided a unique opportunity to better understand and appreciate the holistic nature of diseases, interconnectivity between organ systems, and importance of biological background in modifying disease trajectories and affecting outcomes. Such a holistic approach is badly needed to better understand TBI-induced conditions in their totality. Here, I briefly review what is known about long-COVID/PASC, its underlying-suspected-pathologies, the pathobiological changes induced by TBI, in other words, the TBI endophenotypes, discuss the intersection of long-COVID/PASC and TBI-induced pathobiologies, and how by considering some of the known factors affecting the person's biological background and the inclusion of mechanistic molecular biomarkers can help to improve the clinical management of TBI patients.

Advances in neuroproteomics for neurotrauma: unraveling insights for personalized medicine and future prospects

Neuroproteomics, an emerging field at the intersection of neuroscience and proteomics, has garnered significant attention in the context of neurotrauma research. Neuroproteomics involves the quantitative and qualitative analysis of nervous system components, essential for understanding the dynamic events involved in the vast areas of neuroscience, including, but not limited to, neuropsychiatric disorders, neurodegenerative disorders, mental illness, traumatic brain injury, chronic traumatic encephalopathy, and other neurodegenerative diseases. With advancements in mass spectrometry coupled with bioinformatics and systems biology, neuroproteomics has led to the development of innovative techniques such as microproteomics, single-cell proteomics, and imaging mass spectrometry, which have significantly impacted neuronal biomarker research. By analyzing the complex protein interactions and alterations that occur in the injured brain, neuroproteomics provides valuable insights into the pathophysiological mechanisms underlying neurotrauma. This review explores how such insights can be harnessed to advance personalized medicine (PM) approaches, tailoring treatments based on individual patient profiles. Additionally, we highlight the potential future prospects of neuroproteomics, such as identifying novel biomarkers and developing targeted therapies by employing artificial intelligence (AI) and machine learning (ML). By shedding light on neurotrauma's current state and future directions, this review aims to stimulate further research and collaboration in this promising and transformative field.

Revert total protein normalization method offers a reliable loading control for mitochondrial samples following TBI

Owing to evidence that mitochondrial dysfunction plays a dominant role in the traumatic brain injury (TBI) pathophysiology, the Western blot (WB) based immunoblotting method is widely employed to identify changes in the mitochondrial protein expressions after neurotrauma. In WB method, the housekeeping proteins (HKPs) expression is routinely used as an internal control for sample normalization. However, the traditionally employed HKPs can be susceptible to complex cascades of TBI pathogenesis, leading to their inconsistent expression. Remarkably, our data illustrated here that mitochondrial HKPs, including Voltage-dependent anion channels (VDAC), Complex-IV, Cytochrome C and Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) yielded altered expressions following penetrating TBI (PTBI) as compared to Sham. Therefore, our goal was to identify more precise normalization procedure in WB. Adult male Sprague Dawley rats (N = 6 rats/group) were used to perform PTBI, and the novel REVERT Total Protein (RTP) method was used to quantify mitochondrial protein load consistency between samples at 6 h and 24 h post-injury. Notably, the RTP method displayed superior protein normalization compared to HKPs method with higher sensitivity at both time-points between experimental groups. Our data favors application of RTP based normalization to accurately quantify protein expression where inconsistent HKPs may be evident in neuroscience research.

Comprehensive evaluation of mitochondrial redox profile, calcium dynamics, membrane integrity and apoptosis markers in a preclinical model of severe penetrating traumatic brain injury

Traumatic Brain Injury (TBI) is caused by the external physical assaults damages the brain. It is a heterogeneous disorder that remains a leading cause of death and disability in the military and civilian population of the United States. Preclinical investigations of mitochondrial responses in TBI have ascertained that mitochondrial dysfunction is an acute indicator of cellular damage and plays a pivotal role in long-term injury progression through cellular excitotoxicity. The current study was designed to provide an in-depth evaluation of mitochondrial endpoints with respect to redox and calcium homeostasis, and cell death responses following penetrating TBI (PTBI). To evaluate these pathological cascades, anesthetized adult male rats (N = 6/group) were subjected to either 10% unilateral PTBI or Sham craniectomy. Animals were euthanized at 24 h post-PTBI, and purified mitochondrial fractions were isolated from the brain injury core and perilesional areas. Overall, increased reactive oxygen and nitrogen species (ROS/RNS) production, and elevated oxidative stress markers such as 4-hydroxynonenal (4-HNE), 3-nitrotyrosine (3-NT), and protein carbonyls (PC) were observed in the PTBI group compared to Sham. Mitochondrial antioxidants such as glutathione, peroxiredoxin (PRX-3), thioredoxin (TRX), nicotinamide adenine dinucleotide phosphate (NADPH), superoxide dismutase (SOD), and catalase (CAT) levels were significantly decreased after PTBI. Likewise, PTBI mitochondria displayed significant loss of Ca²⁺ homeostasis, early opening of mitochondrial permeability transition pore (mPTP), and increased mitochondrial swelling. Both, outer and inner mitochondrial membrane integrity markers, such as voltage-dependent anion channels (VDAC) and cytochrome c (Cyt C) expression were significantly decreased following PTBI. The apoptotic cell death was evidenced by significantly decreased B-cell lymphoma-2 (Bcl-2) and increased glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression after PTBI. Collectively, current results highlight the comprehensive picture of mitochondria-centric acute pathophysiological responses following PTBI, which may be utilized as novel prognostic indicators of disease progression and theragnostic indicators for evaluating neuroprotection therapeutics following TBI.

Characterization of the lncRNA-miRNA-mRNA regulatory network to reveal potential functional competing endogenous RNAs in traumatic brain injury

Traumatic brain injury (TBI) is one of the most common acute central nervous system injury diseases. Given the medical and socio-economic burdens of TBI patients, the pathogenesis in TBI and the latent intervention targets needed to be further illuminated. Long non-coding RNAs (lncRNAs) had been revealed to play a vital role in the regulation of pathogenesis after TBI. However, the mutual communication and adjustment of lncRNA associated competing for endogenous RNA (ceRNA) networks in TBI have not been explored to date. In this study, we systematically sequenced the whole transcriptome of lncRNAs, miRNAs, and mRNAs between sham and TBI groups and a total of 939 differentially expressed (DE) lncRNAs, 46 DE miRNAs, and 1,951 DE mRNAs were obtained. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein interaction relationship analyses were conducted for DE mRNAs to identify hub DE genes in TBI. Based on the criteria of bioinformatics prediction, the lncRNA associated ceRNA network covering 201 lncRNAs, 22 miRNAs, and 79 mRNAs was constructed. This study provides a novel perspective on the molecular mechanism of lncRNA in TBI and identifies certain lncRNAs as potential therapeutic targets against TBI.

High arterial oxygen levels and supplemental oxygen administration in traumatic brain injury: insights from CENTER-TBI and OzENTER-TBI

PURPOSE

The effect of high arterial oxygen levels and supplemental oxygen administration on outcomes in traumatic brain injury (TBI) is debated, and data from large cohorts of TBI patients are limited. We investigated whether exposure to high blood oxygen levels and high oxygen supplementation is independently associated with outcomes in TBI patients admitted to the intensive care unit (ICU) and undergoing mechanical ventilation.

METHODS

This is a secondary analysis of two multicenter, prospective, observational, cohort studies performed in Europe and Australia. In TBI patients admitted to ICU, we describe the arterial partial pressure of oxygen (PaO₂) and the oxygen inspired fraction (FiO₂). We explored the association between high PaO₂ and FiO₂ levels within the first week with clinical outcomes. Furthermore, in the CENTER-TBI cohort, we investigate whether PaO₂ and FiO₂ levels may have differential relationships with outcome in the presence of varying levels of brain injury severity (as quantified by levels of glial fibrillary acidic protein (GFAP) in blood samples obtained within 24 h of injury).

RESULTS

The analysis included 1084 patients (11,577 measurements) in the CENTER-TBI cohort, of whom 55% had an unfavorable outcome, and 26% died at a 6-month follow-up. Median PaO₂ ranged from 93 to 166 mmHg. Exposure to higher PaO₂ and FiO₂ in the first seven days after ICU admission was independently associated with a higher mortality rate. A trend of a higher mortality rate was partially confirmed in the OzENTER-TBI cohort (n = 159). GFAP was independently associated with mortality and functional neurologic outcome at follow-up, but it did not modulate the outcome impact of high PaO₂ levels, which remained independently associated with 6-month mortality.

CONCLUSIONS

In two large prospective multicenter cohorts of critically ill patients with TBI, levels of PaO₂ and FiO₂ varied widely across centers during the first seven days after ICU admission. Exposure to high arterial blood oxygen or high supplemental oxygen was independently associated with 6-month mortality in the CENTER-TBI cohort, and the severity of brain injury did not modulate this relationship. Due to the limited sample size, the findings were not wholly validated in the external OzENTER-TBI cohort. We cannot exclude the possibility that the worse outcomes associated with higher PaO₂ were due to use of higher FiO₂ in patients with more severe injury or physiological compromise. Further, these findings may not apply to patients in whom FiO₂ and PaO₂ are titrated to brain tissue oxygen monitoring (PbtO₂) levels. However, at minimum, these findings support the need for caution with oxygen therapy in TBI, particularly since titration of supplemental oxygen is immediately applicable at the bedside.

Exploring serum glycome patterns after moderate to severe traumatic brain injury: A prospective pilot study

BACKGROUND

Glycans play essential functional roles in the nervous system and their pathobiological relevance has become increasingly recognized in numerous brain disorders, but not fully explored in traumatic brain injury (TBI). We investigated longitudinal glycome patterns in patients with moderate to severe TBI (Glasgow Coma Scale [GCS] score ≤12) to characterize glyco-biomarker signatures and their relation to clinical features and long-term outcome.

METHODS

This prospective single-center observational study included 51 adult patients with TBI (GCS ≤12) admitted to the neurosurgical unit of the University Hospital of Pecs, Pecs, Hungary, between June 2018 and April 2019. We used a high-throughput liquid chromatography-tandem mass spectrometry platform to assess serum levels of N-glycans up to 3 days after injury. Outcome was assessed using the Glasgow Outcome Scale-Extended (GOS-E) at 12 months post-injury. Multivariate statistical techniques, including principal component analysis and orthogonal partial least squares discriminant analysis, were used to analyze glycomics data and define highly influential structures driving class distinction. Receiver operating characteristic analyses were used to determine prognostic accuracy.

FINDINGS

We identified 94 N-glycans encompassing all typical structural types, including oligomannose, hybrid, and complex-type entities. Levels of high mannose, hybrid and sialylated structures were temporally altered (p<0·05). Four influential glycans were identified. Two brain-specific structures, HexNAc5Hex3DeoxyHex0NeuAc0 and HexNAc5Hex4DeoxyHex0NeuAc1, were substantially increased early after injury in patients with unfavorable outcome (GOS-E≤4) (area under the curve [AUC]=0·75 [95%CI 0·59-0·90] and AUC=0·71 [0·52-0·89], respectively). Serum levels of HexNAc7Hex7DeoxyHex1NeuAc2 and HexNAc8Hex6DeoxyHex0NeuAc0 were persistently increased in patients with favorable outcome, but undetectable in those with unfavorable outcome. Levels of HexNAc5Hex4DeoxyHex0NeuAc1 were acutely elevated in patients with mass lesions and in those requiring decompressive craniectomy.

INTERPRETATION

In spite of the exploratory nature of the study and the relatively small number of patients, our results provide to the best of our knowledge initial evidence supporting the utility of glycomics approaches for biomarker discovery and patient phenotyping in TBI. Further larger multicenter studies will be required to validate our findings and to determine their pathobiological value and potential applications in practice.

FUNDING

This work was funded by the Italian Ministry of Health (grant number GR-2013-02354960), and also partially supported by a NIH grant (1R01GM112490-08).

Developing a National Trauma Research Action Plan: Results from the Neurotrauma Research Panel Delphi Survey

BACKGROUND

In 2016, the National Academies of Science, Engineering and Medicine called for the development of a National Trauma Research Action Plan. The Department of Defense funded the Coalition for National Trauma Research to generate a comprehensive research agenda spanning the continuum of trauma and burn care. Given the public health burden of injuries to the central nervous system, neurotrauma was one of 11 panels formed to address this recommendation with a gap analysis and generation of high-priority research questions.

METHODS

We recruited interdisciplinary experts to identify gaps in the neurotrauma literature, generate research questions, and prioritize those questions using a consensus-driven Delphi survey approach. We conducted four Delphi rounds in which participants generated key research questions and then prioritized the importance of the questions on a 9-point Likert scale. Consensus was defined as 60% or greater of panelists agreeing on the priority category. We then coded research questions using an National Trauma Research Action Plan taxonomy of 118 research concepts, which were consistent across all 11 panels.

RESULTS

Twenty-eight neurotrauma experts generated 675 research questions. Of these, 364 (53.9%) reached consensus, and 56 were determined to be high priority (15.4%), 303 were deemed to be medium priority (83.2%), and 5 were low priority (1.4%). The research topics were stratified into three groups-severe traumatic brain injury (TBI), mild TBI (mTBI), and spinal cord injury. The number of high-priority questions for each subtopic was 46 for severe TBI (19.7%), 3 for mTBI (4.3%) and 7 for SCI (11.7%).

CONCLUSION

This Delphi gap analysis of neurotrauma research identified 56 high-priority research questions. There are clear areas of focus for severe TBI, mTBI, and spinal cord injury that will help guide investigators in future neurotrauma research. Funding agencies should consider these gaps when they prioritize future research.

LEVEL OF EVIDENCE

Diagnostic Test or Criteria, Level IV.

Advances in Traumatic Brain Injury Biomarkers

Traumatic brain injury (TBI) is increasingly a major cause of disability across the globe. The current methods of diagnosis are inadequate at classifying patients and prognosis. TBI is a diagnostic and therapeutic challenge. There is no Food and Drug Administration (FDA)-approved treatment for TBI yet. It took about 16 years of preclinical research to develop accurate and objective diagnostic measures for TBI. Two brain-specific protein biomarkers, namely, ubiquitin C-terminal hydrolase-L1 and glial fibrillary acidic protein, have been extensively characterized. Recently, the two biomarkers were approved by the FDA as the first blood-based biomarker, Brain Trauma Indicator™ (BTI™), via the Breakthrough Devices Program. This scoping review presents (i) TBI diagnosis challenges, (ii) the process behind the FDA approval of biomarkers, and (iii) known unknowns in TBI biomarker biology. The current lag in TBI incidence and hospitalization can be reduced if digital biomarkers such as hard fall detection are standardized and used as a mechanism to alert paramedics to an unresponsive trauma patient.

Etifoxine Restores Mitochondrial Oxidative Phosphorylation and Improves Cognitive Recovery Following Traumatic Brain Injury

The opening of the mitochondrial permeability transition pore (mPTP) has emerged as a pivotal event following traumatic brain injury (TBI). Evidence showing the impact of the translocator protein (TSPO) over mPTP activity has prompted several studies exploring the effect of TSPO ligands, including etifoxine, on the outcome of traumatic brain injury (TBI). Mitochondrial respiration was assessed by respirometry in isolated rat brain mitochondria (RBM) by measurements of oxidative phosphorylation capacity (OXPHOS). The addition of calcium to RBM was used to induce mitochondrial injury and resulted in significant OXPHOS reduction that could be reversed by preincubation of RBM with etifoxine. Sensorimotor and cognitive functions were assessed following controlled cortical impact and compared in vehicle and etifoxine-treated animals. There was no difference between the vehicle and etifoxine groups for sensorimotor functions as assessed by rotarod. In contrast, etifoxine resulted in a significant improvement of cognitive functions expressed by faster recovery in Morris water maze testing. The present findings show a significant neuroprotective effect of etifoxine in TBI through restoration of oxidative phosphorylation capacity associated with improved behavioral and cognitive outcomes. Since etifoxine is a registered drug used in common clinical practice, implementation in a phase II study may represent a reasonable step forward.

Kollidon VA64 Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Loss of plasmalemmal integrity may mediate cell death after traumatic brain injury (TBI). Prior studies in controlled cortical impact (CCI) indicated that the membrane resealing agent Kollidon VA64 improved histopathological and functional outcomes. Kollidon VA64 was therefore selected as the seventh therapy tested by the Operation Brain Trauma Therapy consortium, across three pre-clinical TBI rat models: parasagittal fluid percussion injury (FPI), CCI, and penetrating ballistic-like brain injury (PBBI). In each model, rats were randomized to one of four exposures (7-15/group): (1) sham; (2) TBI+vehicle; (3) TBI+Kollidon VA64 low-dose (0.4 g/kg); and (4) TBI+Kollidon VA64 high-dose (0.8 g/kg). A single intravenous VA64 bolus was given 15 min post-injury. Behavioral, histopathological, and serum biomarker outcomes were assessed over 21 days generating a 22-point scoring matrix per model. In FPI, low-dose VA64 produced zero points across behavior and histopathology. High-dose VA64 worsened motor performance compared with TBI-vehicle, producing -2.5 points. In CCI, low-dose VA64 produced intermediate benefit on beam balance and the Morris water maze (MWM), generating +3.5 points, whereas high-dose VA64 showed no effects on behavior or histopathology. In PBBI, neither dose altered behavior or histopathology. Regarding biomarkers, significant increases in glial fibrillary acidic protein (GFAP) levels were seen in TBI versus sham at 4 h and 24 h across models. Benefit of low-dose VA64 on GFAP was seen at 24 h only in FPI. Ubiquitin C-terminal hydrolase-L1 (UCH-L1) was increased in TBI compared with vehicle across models at 4 h but not at 24 h, without treatment effects. Overall, low dose VA64 generated +4.5 points (+3.5 in CCI) whereas high dose generated -2.0 points. The modest/inconsistent benefit observed reduced enthusiasm to pursue further testing.

Omega-3 Fatty Acids and Vitamin D Decrease Plasma T-Tau, GFAP, and UCH-L1 in Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) results in neuronal, axonal and glial damage. Interventions targeting neuroinflammation to enhance recovery from TBI are needed. Exercise is known to improve cognitive function in TBI patients. Omega-3 fatty acids and vitamin D reportedly reduce inflammation, and in combination, might improve TBI outcomes. This study examined how an anti-inflammatory diet affected plasma TBI biomarkers, voluntary exercise and behaviors following exposure to mild TBI (mTBI). Adult, male rats were individually housed in cages fitted with running wheels and daily running distance was recorded throughout the study. A modified weight drop method induced mTBI, and during 30 days post-injury, rats were fed diets supplemented with omega-3 fatty acids and vitamin D₃ (AIDM diet), or non-supplemented AIN-76A diets (CON diet). Behavioral tests were periodically conducted to assess functional deficits. Plasma levels of Total tau (T-tau), glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1) and neurofilament light chain (NF-L) were measured at 48 h, 14 days, and 30 days post-injury. Fatty acid composition of food, plasma, and brain tissues was determined. In rats exposed to mTBI, NF-L levels were significantly elevated at 48 h post-injury (P < 0.005), and decreased to levels seen in uninjured rats by 14 days post-injury. T-tau, GFAP, and UCH-L1 plasma levels did not change at 48 h or 14 days post-injury. However, at 30 days post-injury, T-tau, GFAP and UCH-L1 all significantly increased in rats exposed to mTBI and fed CON diets (P < 0.005), but not in rats fed AIDM diets. Behavioral tests conducted post-injury showed that exercise counteracted cognitive deficits associated with mTBI. The AIDM diets significantly increased docosahexaenoic acid levels in plasma and brain tissue (P < 0.05), and in serum levels of vitamin D (P < 0.05). The temporal response of the four injury biomarkers examined is consistent with studies by others demonstrating acute and chronic neural tissue damage following exposure to TBI. The anti-inflammatory diet significantly altered the temporal profiles of plasma T-tau, GFAP, and UCH-L1 following mTBI. Voluntary exercise protected against mTBI-induced cognitive deficits, but had no impact on plasma levels of neurotrauma biomarkers. Thus, the prophylactic effect of exercise, when combined with an anti-inflammatory diet, may facilitate recovery in patients with mTBI.

A 3-month-delayed treatment with anatabine improves chronic outcomes in two different models of repetitive mild traumatic brain injury in hTau mice

To date, an overwhelming number of preclinical studies have addressed acute treatment in mild TBI (mTBI) and repetitive mTBI (r-mTBI), whereas, in humans, there often exists a significant time gap between the injury and the first medical intervention. Our study focused on a delayed treatment with anatabine, an anti-inflammatory compound, in hTau mice using two different models of r-mTBI. The rationale for using two models of the same impact but different frequencies (5 hit mTBI over 9 days and 24 hit mTBI over 90 days) was chosen to address the heterogeneity of r-mTBI in clinical population. Following the last injury in each model, three months elapsed before the initiation of treatment. Anatabine was administered in drinking water for 3 months thereafter. Our data demonstrated that a 3-month delayed treatment with anatabine mitigated astrogliosis in both TBI paradigms but improved cognitive functions only in more-frequently-injured mice (24 hit mTBI). We also found that anatabine decreased the phosphorylation of tau protein and NFκB, which were increased after r-mTBI in both models. The ability of anatabine to suppress these mechanisms suggests that delayed treatment can be effective for clinical population of r-mTBI. The discrepancy between the two models with regard to changes in cognitive performance suggests that r-mTBI heterogeneity may influence treatment efficiency and should be considered in therapeutic development.

Rebuilding Microbiome for Mitigating Traumatic Brain Injury: Importance of Restructuring the Gut-Microbiome-Brain Axis

Traumatic brain injury (TBI) is a damage to the brain from an external force that results in temporary or permanent impairment in brain functions. Unfortunately, not many treatment options are available to TBI patients. Therefore, knowledge of the complex interplay between gut microbiome (GM) and brain health may shed novel insights as it is a rapidly expanding field of research around the world. Recent studies show that GM plays important roles in shaping neurogenerative processes such as blood-brain-barrier (BBB), myelination, neurogenesis, and microglial maturation. In addition, GM is also known to modulate many aspects of neurological behavior and cognition; however, not much is known about the role of GM in brain injuries. Since GM has been shown to improve cellular and molecular functions via mitigating TBI-induced pathologies such as BBB permeability, neuroinflammation, astroglia activation, and mitochondrial dysfunction, herein we discuss how a dysbiotic gut environment, which in fact, contributes to central nervous system (CNS) disorders during brain injury and how to potentially ward off these harmful effects. We further opine that a better understanding of GM-brain (GMB) axis could help assist in designing better treatment and management strategies in future for the patients who are faced with limited options.

Operation Brain Trauma Therapy: An Exploratory Study of Levetiracetam Treatment Following Mild Traumatic Brain Injury in the Micro Pig

Operation brain trauma therapy (OBTT) is a drug- and biomarker-screening consortium intended to improve the quality of preclinical studies and provide a rigorous framework to increase the translational potential of experimental traumatic brain injury (TBI) treatments. Levetiracetam (LEV) is an antiepileptic agent that was the fifth drug tested by OBTT in three independent rodent models of moderate to severe TBI. To date, LEV has been the most promising drug tested by OBTT and was therefore advanced to testing in the pig. Adult male micro pigs were subjected to a mild central fluid percussion brain injury followed by a post-injury intravenous infusion of either 170 mg/kg LEV or vehicle. Systemic physiology was assessed throughout the post-injury period. Serial serum samples were obtained pre-injury as well as at 1 min, 30 min, 1 h, 3 h, and 6 h post-injury for a detailed analysis of the astroglial biomarker glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1. Tissue was collected 6 h following injury for histological assessment of diffuse axonal injury using antibodies against the amyloid precursor protein (APP). The animals showed significant increases in circulating GFAP levels from baseline to 6 h post-injury; however, LEV treatment was associated with greater GFAP increases compared to the vehicle. There were no differences in the numbers of APP+ axonal swellings within the pig thalamus with LEV treatment; however, significant alterations in the morphological properties of the APP+ axonal swellings, including reduced swelling area and increased swelling roundness, were observed. Additionally, expression of the neurite outgrowth marker, growth-associated protein 43, was reduced in axonal swellings following LEV treatment, suggesting potential effects on axonal outgrowth that warrant further investigation.

Glibenclamide Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Glibenclamide (GLY) is the sixth drug tested by the Operation Brain Trauma Therapy (OBTT) consortium based on substantial pre-clinical evidence of benefit in traumatic brain injury (TBI). Adult Sprague-Dawley rats underwent fluid percussion injury (FPI; n = 45), controlled cortical impact (CCI; n = 30), or penetrating ballistic-like brain injury (PBBI; n = 36). Efficacy of GLY treatment (10-μg/kg intraperitoneal loading dose at 10 min post-injury, followed by a continuous 7-day subcutaneous infusion [0.2 μg/h]) on motor, cognitive, neuropathological, and biomarker outcomes was assessed across models. GLY improved motor outcome versus vehicle in FPI (cylinder task, p < 0.05) and CCI (beam balance, p < 0.05; beam walk, p < 0.05). In FPI, GLY did not benefit any other outcome, whereas in CCI, it reduced 21-day lesion volume versus vehicle (p < 0.05). On Morris water maze testing in CCI, GLY worsened performance on hidden platform latency testing versus sham (p < 0.05), but not versus TBI vehicle. In PBBI, GLY did not improve any outcome. Blood levels of glial fibrillary acidic protein and ubiquitin carboxyl terminal hydrolase-1 at 24 h did not show significant treatment-induced changes. In summary, GLY showed the greatest benefit in CCI, with positive effects on motor and neuropathological outcomes. GLY is the second-highest-scoring agent overall tested by OBTT and the only drug to reduce lesion volume after CCI. Our findings suggest that leveraging the use of a TBI model-based phenotype to guide treatment (i.e., GLY in contusion) might represent a strategic choice to accelerate drug development in clinical trials and, ultimately, achieve precision medicine in TBI.

Paths to Successful Translation of New Therapies for Severe Traumatic Brain Injury in the Golden Age of Traumatic Brain Injury Research: A Pittsburgh Vision

New neuroprotective therapies for severe traumatic brain injury (TBI) have not translated from pre-clinical to clinical success. Numerous explanations have been suggested in both the pre-clinical and clinical arenas. Coverage of TBI in the lay press has reinvigorated interest, creating a golden age of TBI research with innovative strategies to circumvent roadblocks. We discuss the need for more robust therapies. We present concepts for traditional and novel approaches to defining therapeutic targets. We review lessons learned from the ongoing work of the pre-clinical drug and biomarker screening consortium Operation Brain Trauma Therapy and suggest ways to further enhance pre-clinical consortia. Biomarkers have emerged that empower choice and assessment of target engagement by candidate therapies. Drug combinations may be needed, and it may require moving beyond conventional drug therapies. Precision medicine may also link the right therapy to the right patient, including new approaches to TBI classification beyond the Glasgow Coma Scale or anatomical phenotyping-incorporating new genetic and physiologic approaches. Therapeutic breakthroughs may also come from alternative approaches in clinical investigation (comparative effectiveness, adaptive trial design, use of the electronic medical record, and big data). The full continuum of care must also be represented in translational studies, given the important clinical role of pre-hospital events, extracerebral insults in the intensive care unit, and rehabilitation. TBI research from concussion to coma can cross-pollinate and further advancement of new therapies. Misconceptions can stifle/misdirect TBI research and deserve special attention. Finally, we synthesize an approach to deliver therapeutic breakthroughs in this golden age of TBI research.

Circulating GFAP and Iba-1 levels are associated with pathophysiological sequelae in the thalamus in a pig model of mild TBI

Serum biomarkers are promising tools for evaluating patients following traumatic brain injury (TBI). However, their relationship with diffuse histopathology remains unclear. Additionally, translatability is a focus of neurotrauma research, however, studies using translational animal models are limited. Here, we evaluated associations between circulating biomarkers and acute thalamic histopathology in a translational micro pig model of mTBI. Serum samples were collected pre-injury, and 1 min-6 h following mTBI. Markers of neuronal injury (Ubiquitin Carboxy-terminal Hydrolase L1 [UCH-L1]), microglial/macrophage activation (Ionized calcium binding adaptor molecule-1 [Iba-1]) and interleukin-6 [IL-6]) and astrogliosis/astrocyte damage (glial fibrillary acidic protein [GFAP]) were measured. Axonal injury and histological features of neurons and glia were also investigated using immunofluorescent labeling and correlated to serum levels of the associated biomarkers. Consistent with prior experimental and human studies, GFAP, was highest at 6 h post-injury, while no substantial changes were observed in UCH-L1, Iba-1 or IL-6 over 6 h. This study also found promising associations between thalamic glial histological signatures and ensuing release of Iba-1 and GFAP into the circulation. Our findings suggest that in diffuse injury, monitoring serum Iba-1 and GFAP levels can provide clinically relevant insight into the underlying acute pathophysiology and biomarker release kinetics following mTBI, providing previously underappreciated diagnostic capability.

BabaoDan cures hepatic encephalopathy by decreasing ammonia levels and alleviating inflammation in rats

ETHNOPHARMACOLOGICAL RELEVANCE

BabaoDan (BBD) is a famous traditional Chinese formula frequently used in TCM clinics to eliminate jaundice and treat infectious viral hepatitis. This paper assesses BBD's preventive and therapeutic effects on hepatic encephalopathy after liver cirrhosis (CHE) and acute liver failure (AHE) in rats and explains its possible mechanism of action.

METHODS

CHE rat model was established by injection of carbon tetrachloride (CCl4) twice a week for a total of 9 weeks and then by injection of thioacetamide (TAA) to induce hepatic encephalopathy. AHE rat model was established by injection of TAA once a day for a total of 3 days. In CHE rat model, BBD was gavaged once a day at the end of the 6th week until the experiment ended. In AHE rat model,BBD was gavaged once a day 3 days before TAA injection until the experiment ended. The preventive and therapeutic effects of BBD on brain dysfunction, as well as liver injury, pathology and fibrosis were evaluated in vivo. The role of BBD in the regulation of inflammatory factors and myeloid differentiation factor 88/Toll-like receptor 4/nuclear factor kappa-B (TLR4/MyD88/NK-κ B) pathway was detected in both liver and brain in vivo. The rat bone marrow derived macrophages (BMDMs) were activated by Lipopolysaccharide (LPS), and the role of BBD in the regulation of inflammatory factors and NK-κ B pathway were detected in vitro.

RESULTS

In CHE rat model: BBD significantly improved the total distance as well as the activity rate of rats. BBD also improved the learning and memory abilities of rats compared with the control group. In addition, BBD effectively decreased ammonia levels and significantly decreased the levels of alanine aminotransferase (ALT), aspartate transaminase (AST), total bilirubin (TBil) and total bile acid (TBA), as well as improved the levels of total protein (TP) and albumin (Alb). In the liver, BBD not only inhibited the gene expressions of tumor necrosis factor alpha (TNF-α), interleukini-6 (IL-6), TLR4, MyD88, and NF-κ B but also inhibited the protein expressions of TLR4, MyD88, NK-κ B and TNF-α. In the brain, BBD inhibited the gene expressions of iNOS, IL-6, TNF-α, TLR-4, MyD88, and NF-κ B, as well as inhibited the protein expressions of TLR4, MyD88, P65 TNF-α and ionized calcium binding adapter molecule 1 (Iba-1). BBD also decreased NO and TNF-α in the blood.

IN AHE RAT MODEL

BBD improved neurological scores, blood ammonia levels and the brain inflammatory gene expressions of iNOS, TNF-α and IL-1β. BBD also improved liver function biomarkers such as ALT, TBil, TBA, TP, ALB and inflammatory and apoptotic gene expressions of TNF-α, IL-1β, IL-6, Bax, Bcl-2, caspase-9, caspase-3 and NF-κ B. In LPS-activated rat BMDMs, BBD decreased NO and TNF-α production in BMDM culture supernatant. In addition, BBD inhibited the gene expressions of TNF-α, IL-1 β and IL-6 as well as the phosphorylation of P65.

CONCLUSION

BBD can prevent and cure hepatic encephalopathy (HE) derived from both chronic and acute liver diseases. BBD can reduce hyperammonemia as well as the systematic and neurological inflammation. Inflammation is likely an important target of BBD to treat HE. The anti-inflammatory role of BBD may lie in its regulation of the TLR4/MyD88/NF-κ B pathways.

Sarm1 loss reduces axonal damage and improves cognitive outcome after repetitive mild closed head injury

One of the consistent pathologies associated with both clinical and experimental traumatic brain injury is axonal injury, especially following mild traumatic brain injury (or concussive injury). Several lines of experimental evidence have demonstrated a role for NAD+ metabolism in axonal degeneration. One of the enzymes that metabolizes NAD+ in axons is Sarm1 (Sterile Alpha and TIR Motif Containing 1), and its activity is thought to play a key role in axonal degeneration. Using a Sarm1 knock-out mouse, we examined if loss of Sarm1 offers axonal injury protection and improves cognitive outcome after repeated mild closed head injury (rmCHI). Our results indicate that rmCHI caused white matter damage that can be observed in the corpus callosum, cingulum bundle, alveus of the hippocampus, and fimbria of the fornix of wild-type mice. These pathological changes were markedly reduced in injured Sarm1^-/- mice. Interestingly, the activation of astrocytes and microglia was also attenuated in the areas with white matter damage, suggesting reduced inflammation. Associated with these improved pathological outcomes, injured Sarm1^-/- mice performed significantly better in both motor and cognitive tasks. Taken together, our results suggest that strategies aimed at inhibiting Sarm1 and/or restoring NAD+ levels in injured axons may have therapeutic utility.

Role of Sulfonylurea Receptor 1 and Glibenclamide in Traumatic Brain Injury: A Review of the Evidence

Cerebral edema and contusion expansion are major determinants of morbidity and mortality after TBI. Current treatment options are reactive, suboptimal and associated with significant side effects. First discovered in models of focal cerebral ischemia, there is increasing evidence that the sulfonylurea receptor 1 (SUR1)-Transient receptor potential melastatin 4 (TRPM4) channel plays a key role in these critical secondary injury processes after TBI. Targeted SUR1-TRPM4 channel inhibition with glibenclamide has been shown to reduce edema and progression of hemorrhage, particularly in preclinical models of contusional TBI. Results from small clinical trials evaluating glibenclamide in TBI have been encouraging. A Phase-2 study evaluating the safety and efficacy of intravenous glibenclamide (BIIB093) in brain contusion is actively enrolling subjects. In this comprehensive narrative review, we summarize the molecular basis of SUR1-TRPM4 related pathology and discuss TBI-specific expression patterns, biomarker potential, genetic variation, preclinical experiments, and clinical studies evaluating the utility of treatment with glibenclamide in this disease.

Gut Microbiota as a Therapeutic Target to Ameliorate the Biochemical, Neuroanatomical, and Behavioral Effects of Traumatic Brain Injuries

Current efficacious treatments for traumatic brain injury (TBI) are lacking. Establishment of a protective gut microbiota population offers a compelling therapeutic avenue, as brain injury induces disruptions in the composition of the gut microbiota, i.e., gut dysbiosis, which has been shown to contribute to TBI-related neuropathology and impaired behavioral outcomes. The gut microbiome is involved in the modulation of a multitude of cellular and molecular processes fundamental to the progression of TBI-induced pathologies including neuroinflammation, blood brain barrier permeability, immune system response, microglial activation, and mitochondrial dysfunction, as well as intestinal motility and permeability. Additionally, gut dysbiosis further aggravates behavioral impairments in animal models of TBI and spinal cord injury, as well as negatively affects health outcomes in murine stroke models. Recent studies indicate that microbiota transplants and probiotics ameliorate neuroanatomical damage and functional impairments in animal models of stroke and spinal cord injury. In addition, probiotics have been shown to reduce the rate of infection and time spent in intensive care of hospitalized patients suffering from brain trauma. Perturbations in the composition of the gut microbiota and its metabolite profile may also serve as potential diagnostic and theragnostic biomarkers for injury severity and progression. This review aims to address the etiological role of the gut microbiome in the biochemical, neuroanatomical, and behavioral/cognitive consequences of TBI, as well as explore the potential of gut microbiome manipulation in the form of probiotics as an effective therapeutic to ameliorate TBI-induced pathology and symptoms.

The complexity of neuroinflammation consequent to traumatic brain injury: from research evidence to potential treatments

This review recounts the definitions and research evidence supporting the multifaceted roles of neuroinflammation in the injured brain following trauma. We summarise the literature fluctuating from the protective and detrimental properties that cytokines, leukocytes and glial cells play in the acute and chronic stages of TBI, including the intrinsic factors that influence cytokine responses and microglial functions relative to genetics, sex, and age. We elaborate on the pros and cons that cytokines, chemokines, and microglia play in brain repair, specifically neurogenesis, and how such conflicting roles may be harnessed therapeutically to sustain the survival of new neurons. With a brief review of the clinical and experimental findings demonstrating early and chronic inflammation impacts on outcomes, we focus on the clinical conditions that may be amplified by neuroinflammation, ranging from acute seizures to chronic epilepsy, neuroendocrine dysfunction, dementia, depression, post-traumatic stress disorder and chronic traumatic encephalopathy. Finally, we provide an overview of the therapeutic agents that have been tested to reduce inflammation-driven secondary pathological cascades and speculate the future promise of alternative drugs.

Operation Brain Trauma Therapy: 2016 Update

Operation brain trauma therapy (OBTT) is a multi-center, pre-clinical drug and biomarker screening consortium for traumatic brain injury (TBI). Therapies are screened across three rat models (parasagittal fluid percussion injury, controlled cortical impact [CCI], and penetrating ballistic-like brain injury). Operation brain trauma therapy seeks to define therapies that show efficacy across models that should have the best chance in randomized clinical trials (RCTs) and/or to define model-dependent therapeutic effects, including TBI protein biomarker responses, to guide precision medicine-based clinical trials in targeted pathologies. The results of the first five therapies tested by OBTT (nicotinamide, erythropoietin, cyclosporine [CsA], simvastatin, and levetiracetam) were published in the Journal of Neurotrauma. Operation brain trauma therapy now describes preliminary results on four additional therapies (glibenclamide, kollidon-VA64, AER-271, and amantadine). To date, levetiracetam was beneficial on cognitive outcome, histology, and/or biomarkers in two models. The second most successful drug, glibenclamide, improved motor function and histology in CCI. Other therapies showed model-dependent effects (amantadine and CsA). Critically, glial fibrillary acidic protein levels predicted treatment effects. Operation brain trauma therapy suggests that levetiracetam merits additional pre-clinical and clinical evaluation and that glibenclamide and amantadine merit testing in specific TBI phenotypes. Operation brain trauma therapy has established that rigorous, multi-center consortia could revolutionize TBI therapy and biomarker development.

Cortical Spreading Depression Denotes Concussion Injury

Cortical spreading depression (CSD) has been described after moderate-to-severe traumatic brain injury (TBI). It is uncertain, however, whether CSD occurs after mild, concussive TBI and whether it relates to brain pathology and functional outcome. Male C57BL6/J mice (n = 62) were subjected to closed head TBI with a 25 g weight (n = 11), 50 g weight (n = 45), or sham injury (n = 6). Laser Doppler flowmetry and optical intrinsic signal imaging were used to determine cerebral blood flow dynamics after concussive CSD. Functional deficits were assessed at baseline, 2 h, 24 h, and 48 h. TUNEL and Prussian blue staining were used to determine cell death and presence of cerebral microbleeds at 48 h. No CSD was observed in mice subjected to a 25 g weight drop whereas 58.9% of mice subjected to a 50 g weight drop developed a CSD. Mice with concussive CSD displayed significantly greater numbers of apoptotic cell profiles in the ipsilesional hemisphere compared with mice without a CSD that underwent the same 50 g weight drop paradigm (p < 0.05, each). All investigated animals had at least one cerebral microbleed (range 1 to 24). Compared with mice without a CSD, mice with a CSD had significantly more microbleeds in the traumatized hemisphere (p < 0.05, each) and showed impaired functional recovery (p < 0.05). Incidence of CSD after mild TBI depended on impact severity and was associated with histological and behavioral outcomes. These observations indicate that concussive CSD may serve as viable marker for concussion severity and provide novel avenues for outcome prediction and therapeutic decision making.

Evaluation of taurine neuroprotection in aged rats with traumatic brain injury

Despite higher rates of hospitalization and mortality following traumatic brain injury (TBI) in patients over 65 years old, older patients remain underrepresented in drug development studies. Worse outcomes in older individuals compared to younger adults could be attributed to exacerbated injury mechanisms including oxidative stress, inflammation, blood-brain barrier disruption, and bioenergetic dysfunction. Accordingly, pleiotropic treatments are attractive candidates for neuroprotection. Taurine, an endogenous amino acid with antioxidant, anti-inflammatory, anti-apoptotic, osmolytic, and neuromodulator effects, is neuroprotective in adult rats with TBI. However, its effects in the aged brain have not been evaluated. We subjected aged male rats to a unilateral controlled cortical impact injury to the sensorimotor cortex, and randomized them into four treatment groups: saline or 25 mg/kg, 50 mg/kg, or 200 mg/kg i.p. taurine. Treatments were administered 20 min post-injury and daily for 7 days. We assessed sensorimotor function on post-TBI days 1-14 and tissue loss on day 14 using T2-weighted magnetic resonance imaging. Experimenters were blinded to the treatment group for the duration of the study. We did not observe neuroprotective effects of taurine on functional impairment or tissue loss in aged rats after TBI. These findings in aged rats are in contrast to previous reports of taurine neuroprotection in younger animals. Advanced age is an important variable for drug development studies in TBI, and further research is required to better understand how aging may influence mechanisms of taurine neuroprotection.

Enduring Neuroprotective Effect of Subacute Neural Stem Cell Transplantation After Penetrating TBI

Traumatic brain injury (TBI) is the largest cause of death and disability of persons under 45 years old, worldwide. Independent of the distribution, outcomes such as disability are associated with huge societal costs. The heterogeneity of TBI and its complicated biological response have helped clarify the limitations of current pharmacological approaches to TBI management. Five decades of effort have made some strides in reducing TBI mortality but little progress has been made to mitigate TBI-induced disability. Lessons learned from the failure of numerous randomized clinical trials and the inability to scale up results from single center clinical trials with neuroprotective agents led to the formation of organizations such as the Neurological Emergencies Treatment Trials (NETT) Network, and international collaborative comparative effectiveness research (CER) to re-orient TBI clinical research. With initiatives such as TRACK-TBI, generating rich and comprehensive human datasets with demographic, clinical, genomic, proteomic, imaging, and detailed outcome data across multiple time points has become the focus of the field in the United States (US). In addition, government institutions such as the US Department of Defense are investing in groups such as Operation Brain Trauma Therapy (OBTT), a multicenter, pre-clinical drug-screening consortium to address the barriers in translation. The consensus from such efforts including “The Lancet Neurology Commission” and current literature is that unmitigated cell death processes, incomplete debris clearance, aberrant neurotoxic immune, and glia cell response induce progressive tissue loss and spatiotemporal magnification of primary TBI. Our analysis suggests that the focus of neuroprotection research needs to shift from protecting dying and injured neurons at acute time points to modulating the aberrant glial response in sub-acute and chronic time points. One unexpected agent with neuroprotective properties that shows promise is transplantation of neural stem cells. In this review we present (i) a short survey of TBI epidemiology and summary of current care, (ii) findings of past neuroprotective clinical trials and possible reasons for failure based upon insights from human and preclinical TBI pathophysiology studies, including our group's inflammation-centered approach, (iii) the unmet need of TBI and unproven treatments and lastly, (iv) present evidence to support the rationale for sub-acute neural stem cell therapy to mediate enduring neuroprotection.

Pre-Clinical Testing of Therapies for Traumatic Brain Injury

Despite the large number of promising neuroprotective agents identified in experimental traumatic brain injury (TBI) studies, none has yet shown meaningful improvements in long-term outcome in clinical trials. To develop recommendations and guidelines for pre-clinical testing of pharmacological or biological therapies for TBI, the Moody Project for Translational Traumatic Brain Injury Research hosted a symposium attended by investigators with extensive experience in pre-clinical TBI testing. The symposium participants discussed issues related to pre-clinical TBI testing including experimental models, therapy and outcome selection, study design, data analysis, and dissemination. Consensus recommendations included the creation of a manual of standard operating procedures with sufficiently detailed descriptions of modeling and outcome measurement procedures to permit replication. The importance of the selection of clinically relevant outcome variables, especially related to behavior testing, was noted. Considering the heterogeneous nature of human TBI, evidence of therapeutic efficacy in multiple, diverse (e.g., diffuse vs. focused) rodent models and a species with a gyrencephalic brain prior to clinical testing was encouraged. Basing drug doses, times, and routes of administration on pharmacokinetic and pharmacodynamic data in the test species was recommended. Symposium participants agreed that the publication of negative results would reduce costly and unnecessary duplication of unsuccessful experiments. Although some of the recommendations are more relevant to multi-center, multi-investigator collaborations, most are applicable to pre-clinical therapy testing in general. The goal of these consensus guidelines is to increase the likelihood that therapies that improve outcomes in pre-clinical studies will also improve outcomes in TBI patients.

Neurotherapeutic capacity of P7C3 agents for the treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant public health problem around the world. A promising area of research is the characterization of small, drug-like molecules that have potent clinical properties. One pharmacotherapeutic agent in particular, an aminopropyl carbazole called P7C3, was discovered using an in vivo screen to identify new agents that augmented the net magnitude of adult hippocampal neurogenesis. P7C3 greatly enhanced neurogenesis by virtue of increasing survival rates of immature neurons. The potent neuroprotective efficacy of P7C3 is likely due to enhanced nicotinamide phosphoribosyltransferase (NAMPT) activity, which supports critical cellular processes. The scaffold of P7C3 was found to have favorable pharmacokinetic properties, good bioavailability, and was nontoxic. Preclinical studies have shown that administration of the P7C3-series of neuroprotective compounds after TBI can rescue and reverse detrimental cellular events leading to improved functional recovery. In several TBI models and across multiple species, P7C3 and its analogues have produced significant neuroprotection, axonal preservation, robust increases in the net magnitude of adult neurogenesis, protection from injury-induced LTP deficits, and improvement in neurological functioning. This review will elucidate the exciting and diverse therapeutic findings of P7C3 administration in the presence of a complex and multifactorial set of cellular and molecular challenges brought forth by experimental TBI. The clinical potential and broad therapeutic applicability of P7C3 warrants much needed investigation into whether these remedial effects can be replicated in the clinic. P7C3 may serve as an important step forward in the design, understanding, and implementation of pharmacotherapies for treating patients with TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Multi-Center Pre-clinical Consortia to Enhance Translation of Therapies and Biomarkers for Traumatic Brain Injury: Operation Brain Trauma Therapy and Beyond

Current approaches have failed to yield success in the translation of neuroprotective therapies from the pre-clinical to the clinical arena for traumatic brain injury (TBI). Numerous explanations have been put forth in both the pre-clinical and clinical arenas. Operation Brain Trauma Therapy (OBTT), a pre-clinical therapy and biomarker screening consortium has, to date, evaluated 10 therapies and assessed three serum biomarkers in nearly 1,500 animals across three rat models and a micro pig model of TBI. OBTT provides a unique platform to exploit heterogeneity of TBI and execute the research needed to identify effective injury specific therapies toward precision medicine. It also represents one of the first multi-center pre-clinical consortia for TBI, and through its work has yielded insight into the challenges and opportunities of this approach. In this review, important concepts related to consortium infrastructure, modeling, therapy selection, dosing and target engagement, outcomes, analytical approaches, reproducibility, and standardization will be discussed, with a focus on strategies to embellish and improve the chances for future success. We also address issues spanning the continuum of care. Linking the findings of optimized pre-clinical consortia to novel clinical trial designs has great potential to help address the barriers in translation and produce successes in both therapy and biomarker development across the field of TBI and beyond.

Interleukin-1 Receptor 1 Deletion in Focal and Diffuse Experimental Traumatic Brain Injury in Mice

Important differences in the biology of focal and diffuse traumatic brain injury (TBI) subtypes may result in unique pathophysiological responses to shared molecular mechanisms. Interleukin-1 (IL-1) signaling has been tested as a potential therapeutic target in preclinical models of cerebral contusion and diffuse TBI, and in a phase II clinical trial, but no published studies have examined IL-1 signaling in an impact/acceleration closed head injury (CHI) model. We hypothesized that genetic deletion of IL-1 receptor-1 (IL-1R1 KO) would be beneficial in focal (contusion) and CHI in mice. Wild type and IL-1R1 KO mice were subjected to controlled cortical impact (CCI), or to CHI. CCI produced brain leukocyte infiltration, HMGB1 translocation and release, edema, cell death, and cognitive deficits. CHI induced peak rotational acceleration of 9.7 × 10⁵ ± 8.1 × 10⁴ rad/s², delayed time to righting reflex, and robust Morris water maze deficits without deficits in tests of anxiety, locomotion, sensorimotor function, or depression. CHI produced no discernable acute plasmalemma damage or cell death, blood-brain barrier permeability to IgG, or brain edema and only a modest increase in brain leukocyte infiltration at 72 h. In both models, mature (17 kDa) interleukin-1 beta (IL-1β) was induced by 24 h in CD31+ endothelial cells isolated from injured brain but was not induced in CD11b⁺ cells in either model. High mobility group box protein-1 was released from injured brain cells in CCI but not CHI. Surprisingly, cognitive outcome in mice with global deletion of IL-1R1 was improved in CHI, but worse after CCI without affecting lesion size, edema, or infiltration of CD11b⁺/CD45⁺ leukocytes in CCI. IL-1R1 may induce unique biological responses, beneficial or detrimental to cognitive outcome, after TBI depending on the pathoanatomical subtype. Brain endothelium is a hitherto unrecognized source of mature IL-1β in both models.

Preclinical Models of Traumatic Brain Injury: Emerging Role of Glutamate in the Pathophysiology of Depression

More than 10 million people worldwide incur a traumatic brain injury (TBI) each year, with two million cases occurring in the United States. TBI survivors exhibit long-lasting cognitive and affective sequelae that are associated with reduced quality of life and work productivity, as well as mental and emotional disturbances. While TBI-related disabilities often manifest physically and conspicuously, TBI has been linked with a "silent epidemic" of psychological disorders, including major depressive disorder (MDD). The prevalence of MDD post-insult is approximately 50% within the 1st year. Furthermore, given they are often under-reported when mild, TBIs could be a significant overall cause of MDD in the United States. The emergence of MDD post-TBI may be rooted in widespread disturbances in the modulatory role of glutamate, such that glutamatergic signaling becomes excessive and deleterious to neuronal integrity, as reported in both clinical and preclinical studies. Following this acute glutamatergic storm, regulators of glutamatergic function undergo various manipulations, which include, but are not limited to, alterations in glutamatergic subunit composition, release, and reuptake. This review will characterize the glutamatergic functional and signaling changes that emerge and persist following experimental TBI, utilizing evidence from clinical, molecular, and rodent behavioral investigations. Special care will be taken to speculate on how these manipulations may correlate with the development of MDD following injury in the clinic, as well as pharmacotherapies to date. Indisputably, TBI is a significant healthcare issue that warrants discovery and subsequent refinement of therapeutic strategies to improve neurobehavioral recovery and mental health.

Conference Report: 6th Annual International Symposium on Regenerative Rehabilitation

The 6th International Symposium on Regenerative Rehabilitation, hosted by the Alliance for Regenerative Rehabilitation Research and Training (AR³T), included a preconference meeting of institutional representatives of the International Consortium of Regenerative Rehabilitation, keynote talks from distinguished scientists, platform and poster presentations from experts and trainees, panel discussions and postconference workshops. The following priorities were identified: increasing rigor in basic, preclinical and clinical studies, especially the use of better controls; developing better outcome measures for preclinical and clinical trials; focusing on developing more tissue-based interventions versus cell-based interventions; including regenerative rehabilitation in curricula of professional programs like occupational and physical therapy; and developing better instruments to quantify rehabilitative interventions.

The case for introducing pre-registered confirmatory pharmacological pre-clinical studies

When evaluating the design of pre-clinical studies in the field of traumatic brain injury, we found substantial differences compared to phase III clinical trials, which in part may explain the difficulties in translating promising experimental drugs into approved treatments. By using network analysis, we also found cases where a large proportion of the studies evaluating a pre-clinical treatment was performed by inter-related researchers, which is potentially problematic. Subjecting all pre-clinical trials to the rigor of a phase III clinical trial is, however, likely not practically achievable. Instead, we repeat the call for a distinction to be made between exploratory and confirmatory pre-clinical studies.

Pre-clinical models in pediatric traumatic brain injury-challenges and lessons learned

PURPOSE

Despite the enormity of the problem and the lack of new therapies, research in the pre-clinical arena specifically using pediatric traumatic brain injury (TBI) models is limited. In this review, some of the key models addressing both the age spectrum of pediatric TBI and its unique injury mechanisms will be highlighted. Four topics will be addressed, namely, (1) unique facets of the developing brain important to TBI model development, (2) a description of some of the most commonly used pre-clinical models of severe pediatric TBI including work in both rodents and large animals, (3) a description of the pediatric models of mild TBI and repetitive mild TBI that are relatively new, and finally (4) a discussion of challenges, gaps, and potential future directions to further advance work in pediatric TBI models.

METHODS

This narrative review on the topic of pediatric TBI models was based on review of PUBMED/Medline along with a synthesis of information on key factors in pre-clinical and clinical developmental brain injury that influence TBI modeling.

RESULTS

In the contemporary literature, six types of models have been used in rats including weight drop, fluid percussion injury (FPI), impact acceleration, controlled cortical impact (CCI), mechanical shaking, and closed head modifications of CCI. In mice, studies are largely restricted to CCI. In large animals, FPI and rotational injury have been used in piglets and shake injury has also been used in lambs. Most of the studies have been in severe injury models, although more recently, studies have begun to explore mild and repetitive mild injuries to study concussion.

CONCLUSIONS

Given the emerging importance of TBI in infants and children, the morbidity and mortality that is produced, along with its purported link to the development of chronic neurodegenerative diseases, studies in these models merit greater systematic investigations along with consortium-type approaches and long-term follow-up to translate new therapies to the bedside.

Treatment options for severe traumatic brain injuries in children: current therapies, challenges, and future prospects

INTRODUCTION

Severe traumatic brain injury (TBI) afflicts many children and adults worldwide, resulting in high rates of morbidity and mortality. Recent therapeutic advances have focused on both surgical and medical treatment options, but none have been proven to reduce overall morbidity and mortality in this population. Areas covered: Several emerging therapies are addressed that focus on treating related secondary injuries and other clinical sequelae post-TBI during the acute injury phase (defined by authors as up to four weeks post-injury). Information and data were obtained from a PubMed search of recent literature and through reputable websites (e.g. Centers for Disease Control, ClinicalTrials.gov). Peer-reviewed original articles, review articles, and clinical guidelines were included. Expert commentary: The ongoing challenges related to conducting rigorous clinical trials in TBI have led to largely inconclusive findings regarding emerging beneficial therapies.

Effects of the dimeric PSD-95 inhibitor UCCB01-144 on functional recovery after fimbria-fornix transection in rats

Pharmacological inhibition of PSD-95 is a promising therapeutic strategy in the treatment of stroke, and positive effects of monomeric and dimeric PSD-95 inhibitors have been reported in numerous studies. However, whether therapeutic effects will generalize to other types of acute brain injury such as traumatic brain injury (TBI), which has pathophysiological mechanisms in common with stroke, is currently uncertain. We have previously found a lack of neuroprotective effects of dimeric PSD-95 inhibitors in the controlled cortical impact model of TBI in rats. However, as no single animal model is currently able to mimic the complex and heterogeneous pathophysiology of TBI, it is necessary to assess treatment effects across a range of models. In this preliminary study we investigated the neuroprotective abilities of the dimeric PSD-95 inhibitor UCCB01-144 after fimbria-fornix (FF) transection in rats. UCCB01-144 or saline was injected into the lateral tail vein of rats immediately after sham surgery or FF-transection, and effects on spatial delayed alternation in a T-maze were assessed over a 28-day period. Task acquisition was significantly impaired in FF-transected animals, but there were no significant effects of UCCB01-144 on spatial delayed alternation after FF-transection or sham surgery, although decelerated learning curves were seen after treatment with UCCB01-144 in FF-transected animals. The results of the present study are consistent with previous research showing a lack of neuroprotective effects of PSD-95 inhibition in experimental models of TBI.

Rethinking Neuroprotection in Severe Traumatic Brain Injury: Toward Bedside Neuroprotection

Neuroprotection after traumatic brain injury (TBI) is an important goal pursued strenuously in the last 30 years. The acute cerebral injury triggers a cascade of biochemical events that may worsen the integrity, function, and connectivity of the brain cells and decrease the chance of functional recovery. A number of molecules acting against this deleterious cascade have been tested in the experimental setting, often with preliminary encouraging results. Unfortunately, clinical trials using those candidate neuroprotectants molecules have consistently produced disappointing results, highlighting the necessity of improving the research standards. Despite repeated failures in pharmacological neuroprotection, TBI treatment in neurointensive care units has achieved outcome improvement. It is likely that intensive treatment has contributed to this progress offering a different kind of neuroprotection, based on a careful prevention and limitations of intracranial and systemic threats. The natural course of acute brain damage, in fact, is often complicated by additional adverse events, like the development of intracranial hypertension, brain hypoxia, or hypoperfusion. All these events may lead to additional brain damage and worsen outcome. An approach designed for early identification and prompt correction of insults may, therefore, limit brain damage and improve results.

Severe traumatic brain injury: targeted management in the intensive care unit

Severe traumatic brain injury (TBI) is currently managed in the intensive care unit with a combined medical-surgical approach. Treatment aims to prevent additional brain damage and to optimise conditions for brain recovery. TBI is typically considered and treated as one pathological entity, although in fact it is a syndrome comprising a range of lesions that can require different therapies and physiological goals. Owing to advances in monitoring and imaging, there is now the potential to identify specific mechanisms of brain damage and to better target treatment to individuals or subsets of patients. Targeted treatment is especially relevant for elderly people-who now represent an increasing proportion of patients with TBI-as preinjury comorbidities and their therapies demand tailored management strategies. Progress in monitoring and in understanding pathophysiological mechanisms of TBI could change current management in the intensive care unit, enabling targeted interventions that could ultimately improve outcomes.

'Spreading depression of Leão' and its emerging relevance to acute brain injury in humans

A new research field in translational neuroscience has opened as a result of the recognition since 2002 that "spreading depression of Leão" can be detected in many patients with acute brain injury, whether vascular and spontaneous, or traumatic in origin, as well as in those many individuals experiencing the visual (or sensorimotor) aura of migraine. In this review, we trace from their first description in rabbits through to their detection and study in migraine and the injured human brain, and from our personal perspectives, the evolution of understanding of the importance of spread of mass depolarisations in cerebral grey matter. Detection of spontaneous depolarisations occurring and spreading in the periphery or penumbra of experimental focal cortical ischemic lesions and of their adverse effects on the cerebral cortical microcirculation and on the tissue glucose and oxygen pools has led to clearer concepts of how ischaemic and traumatic lesions evolve in the injured human brain, and of how to seek to improve clinical management and outcome. Recognition of the likely fundamental significance of spreading depolarisations for this wide range of serious acute encephalopathies in humans provides a powerful case for a fresh examination of neuroprotection strategies.

Translational obstacles with off-label drug use in acute traumatic brain injury

Traumatic brain injury results in significant morbidity and mortality, and there is an urgent need for neuroprotective medications that can prevent the persisting symptoms and disabilities following injury. Several existing pharmacotherapies have been targeted for off-label benefit in traumatic brain injury, as these agents are well characterized and commercially available, easing the process of clinical trial development. Despite promising results in animal models, clinical trials have demonstrated minimal benefit. One possible reason for these failed translations could be that drug selection, characterization and dosing are not routinely established in the appropriate early phase trials before larger scale testing. Examining how recent trials may have bypassed these steps may help future trials to more definitively determine the efficacy of potential therapeutics.

Traumatic Brain Injury Advances

There have been many recent advances in the management of traumatic brain injury (TBI). Research regarding established and novel therapies is ongoing. Future research must not only focus on development of new strategies but determine the long-term benefits or disadvantages of current strategies. In addition, the impact of these advances on varying severities of brain injury must not be ignored. It is hoped that future research strategies in TBI will prioritize large-scale trials using common data elements to develop large registries and databases, and leverage international collaborations.

Microdialysis Monitoring in Clinical Traumatic Brain Injury and Its Role in Neuroprotective Drug Development

Injuries to the central nervous system continue to be vast contributors to morbidity and mortality; specifically, traumatic brain injury (TBI) is the most common cause of death during the first four decades of life. Several modalities are used to monitor patients suffering from TBI in order to prevent detrimental secondary injuries. The microdialysis (MD) technique, introduced during the 1990s, presents the treating physician with a robust monitoring tool for brain chemistry in addition to conventional intracranial pressure monitoring. Nevertheless, some limitations remain, such as limited spatial resolution. Moreover, while there have been several attempts to develop new potential pharmacological therapies in TBI, there are currently no available drugs which have shown clinical efficacy that targets the underlying pathophysiology, despite various trials investigating a plethora of pharmaceuticals. Specifically in the brain, MD is able to demonstrate penetration of the drug through the blood-brain barrier into the brain extracellular space at potential site of action. In addition, the downstream effects of drug action can be monitored directly. In the future, clinical MD, together with other monitoring modalities, can identify specific pathological substrates which require tailored treatment strategies for patients suffering from TBI.

Insight into Pre-Clinical Models of Traumatic Brain Injury Using Circulating Brain Damage Biomarkers: Operation Brain Trauma Therapy

Operation Brain Trauma Therapy (OBTT) is a multicenter pre-clinical drug screening consortium testing promising therapies for traumatic brain injury (TBI) in three well-established models of TBI in rats--namely, parasagittal fluid percussion injury (FPI), controlled cortical impact (CCI), and penetrating ballistic-like brain injury (PBBI). This article presents unique characterization of these models using histological and behavioral outcomes and novel candidate biomarkers from the first three treatment trials of OBTT. Adult rats underwent CCI, FPI, or PBBI and were treated with vehicle (VEH). Shams underwent all manipulations except trauma. The glial marker glial fibrillary acidic protein (GFAP) and the neuronal marker ubiquitin C-terminal hydrolase (UCH-L1) were measured by enzyme-linked immunosorbent assay in blood at 4 and 24 h, and their delta 24-4 h was calculated for each marker. Comparing sham groups across experiments, no differences were found in the same model. Similarly, comparing TBI + VEH groups across experiments, no differences were found in the same model. GFAP was acutely increased in injured rats in each model, with significant differences in levels and temporal patterns mirrored by significant differences in delta 24-4 h GFAP levels and neuropathological and behavioral outcomes. Circulating GFAP levels at 4 and 24 h were powerful predictors of 21 day contusion volume and tissue loss. UCH-L1 showed similar tendencies, albeit with less robust differences between sham and injury groups. Significant differences were also found comparing shams across the models. Our findings (1) demonstrate that TBI models display specific biomarker profiles, functional deficits, and pathological consequence; (2) support the concept that there are different cellular, molecular, and pathophysiological responses to TBI in each model; and (3) advance our understanding of TBI, providing opportunities for a successful translation and holding promise for theranostic applications. Based on our findings, additional studies in pre-clinical models should pursue assessment of GFAP as a surrogate histological and/or theranostic end-point.

Nicotinamide Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Nicotinamide (vitamin B3) was the first drug selected for cross-model testing by the Operation Brain Trauma Therapy (OBTT) consortium based on a compelling record of positive results in pre-clinical models of traumatic brain injury (TBI). Adult male Sprague-Dawley rats were exposed to either moderate fluid percussion injury (FPI), controlled cortical impact injury (CCI), or penetrating ballistic-like brain injury (PBBI). Nicotinamide (50 or 500 mg/kg) was delivered intravenously at 15 min and 24 h after injury with subsequent behavioral, biomarker, and histopathological outcome assessments. There was an intermediate effect on balance beam performance with the high (500 mg/kg) dose in the CCI model, but no significant therapeutic benefit was detected on any other motor task across the OBTT TBI models. There was an intermediate benefit on working memory with the high dose in the FPI model. A negative effect of the low (50 mg/kg) dose, however, was observed on cognitive outcome in the CCI model, and no cognitive improvement was observed in the PBBI model. Lesion volume analysis showed no treatment effects after either FPI or PBBI, but the high dose of nicotinamide resulted in significant tissue sparing in the CCI model. Biomarker assessments included measurements of glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl-terminal hydrolase-1 (UCH-L1) in blood at 4 or 24 h after injury. Negative effects (both doses) were detected on biomarker levels of GFAP after FPI and on biomarker levels of UCH-L1 after PBBI. The high dose of nicotinamide, however, reduced GFAP levels after both PBBI and CCI. Overall, our results showed a surprising lack of benefit from the low dose nicotinamide. In contrast, and partly in keeping with the literature, some benefit was achieved with the high dose. The marginal benefits achieved with nicotinamide, however, which appeared sporadically across the TBI models, has reduced enthusiasm for further investigation by the OBTT Consortium.

Cyclosporine Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Operation Brain Trauma Therapy (OBTT) is a consortium of investigators using multiple pre-clinical models of traumatic brain injury (TBI) to bring acute therapies to clinical trials. To screen therapies, we used three rat models (parasagittal fluid percussion injury [FPI], controlled cortical impact [CCI], and penetrating ballistic-like brain injury [PBBI]). We report results of the third therapy (cyclosporin-A; cyclosporine; [CsA]) tested by OBTT. At each site, rats were randomized to treatment with an identical regimen (TBI + vehicle, TBI + CsA [10 mg/kg], or TBI + CsA [20 mg/kg] given intravenously at 15 min and 24 h after injury, and sham). We assessed motor and Morris water maze (MWM) tasks over 3 weeks after TBI and lesion volume and hemispheric tissue loss at 21 days. In FPI, CsA (10 mg/kg) produced histological protection, but 20 mg/kg worsened working memory. In CCI, CsA (20 mg/kg) impaired MWM performance; surprisingly, neither dose showed benefit on any outcome. After PBBI, neither dose produced benefit on any outcome, and mortality was increased (20 mg/kg) partly caused by the solvent vehicle. In OBTT, CsA produced complex effects with histological protection at the lowest dose in the least severe model (FPI), but only deleterious effects as model severity increased (CCI and PBBI). Biomarker assessments included measurements of glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase-L1 (UCH-L1) in blood at 4 or 24 h after injury. No positive treatment effects were seen on biomarker levels in any of the models, whereas significant increases in 24 h UCH-L1 levels were seen with CsA (20 mg/kg) after CCI and 24 h GFAP levels in both CsA treated groups in the PBBI model. Lack of behavioral protection in any model, indicators of toxicity, and a narrow therapeutic index reduce enthusiasm for clinical translation.

Peptide Pharmacological Approaches to Treating Traumatic Brain Injury: a Case for Arginine-Rich Peptides

Traumatic brain injury (TBI) has a devastating effect on victims and their families, and has profound negative societal and economic impacts, a situation that is further compounded by the lack of effective treatments to minimise injury after TBI. The current strategy for managing TBI is partly through preventative measures and partly through surgical and rehabilitative interventions. Secondary brain damage remains the principal focus for the development of a neuroprotective therapeutic. However, the complexity of TBI pathophysiology has meant that single-action pharmacological agents have been largely unsuccessful in combatting the associated brain injury cascades, while combination therapies to date have proved equally ineffective. Peptides have recently emerged as promising lead agents for the treatment of TBI, especially those rich in the cationic amino acid, arginine. Having been shown to lessen the impact of ischaemic stroke in animal models, there are reasonable grounds to believe that arginine-rich peptides may have neuroprotective therapeutic potential in TBI. Here, we review a range of peptides previously examined as therapeutic agents for TBI. In particular, we focus on cationic arginine-rich peptides -- a new class of agents that growing evidence suggests acts through multiple neuroprotective mechanisms.

Approach to Modeling, Therapy Evaluation, Drug Selection, and Biomarker Assessments for a Multicenter Pre-Clinical Drug Screening Consortium for Acute Therapies in Severe Traumatic Brain Injury: Operation Brain Trauma Therapy

Traumatic brain injury (TBI) was the signature injury in both the Iraq and Afghan wars and the magnitude of its importance in the civilian setting is finally being recognized. Given the scope of the problem, new therapies are needed across the continuum of care. Few therapies have been shown to be successful. In severe TBI, current guidelines-based acute therapies are focused on the reduction of intracranial hypertension and optimization of cerebral perfusion. One factor considered important to the failure of drug development and translation in TBI relates to the recognition that TBI is extremely heterogeneous and presents with multiple phenotypes even within the category of severe injury. To address this possibility and attempt to bring the most promising therapies to clinical trials, we developed Operation Brain Trauma Therapy (OBTT), a multicenter, pre-clinical drug screening consortium for acute therapies in severe TBI. OBTT was developed to include a spectrum of established TBI models at experienced centers and assess the effect of promising therapies on both conventional outcomes and serum biomarker levels. In this review, we outline the approach to TBI modeling, evaluation of therapies, drug selection, and biomarker assessments for OBTT, and provide a framework for reports in this issue on the first five therapies evaluated by the consortium.