Immunohistochemical analysis of histone H3 acetylation and methylation--evidence for altered epigenetic signaling following traumatic brain injury in immature rats

Extracellular cold-inducible RNA-binding protein mediated neuroinflammation and neuronal apoptosis after traumatic brain injury

Background

Extracellular cold-inducible RNA-binding protein (eCIRP) plays a vital role in the inflammatory response during cerebral ischaemia. However, the potential role and regulatory mechanism of eCIRP in traumatic brain injury (TBI) remain unclear. Here, we explored the effect of eCIRP on the development of TBI using a neural-specific CIRP knockout (KO) mouse model to determine the contribution of eCIRP to TBI-induced neuronal injury and to discover novel therapeutic targets for TBI.

Methods

TBI animal models were generated in mice using the fluid percussion injury method. Microglia or neuron lines were subjected to different drug interventions. Histological and functional changes were observed by immunofluorescence and neurobehavioural testing. Apoptosis was examined by a TdT-mediated dUTP nick end labelling assay in vivo or by an annexin-V assay in vitro. Ultrastructural alterations in the cells were examined via electron microscopy. Tissue acetylation alterations were identified by non-labelled quantitative acetylation via proteomics. Protein or mRNA expression in cells and tissues was determined by western blot analysis or real-time quantitative polymerase chain reaction. The levels of inflammatory cytokines and mediators in the serum and supernatants were measured via enzyme-linked immunoassay.

Results

There were closely positive correlations between eCIRP and inflammatory mediators, and between eCIRP and TBI markers in human and mouse serum. Neural-specific eCIRP KO decreased hemispheric volume loss and neuronal apoptosis and alleviated glial cell activation and neurological function damage after TBI. In contrast, eCIRP treatment resulted in endoplasmic reticulum disruption and ER stress (ERS)-related death of neurons and enhanced inflammatory mediators by glial cells. Mechanistically, we noted that eCIRP-induced neural apoptosis was associated with the activation of the protein kinase RNA-like ER kinase-activating transcription factor 4 (ATF4)-C/EBP homologous protein signalling pathway, and that eCIRP-induced microglial inflammation was associated with histone H3 acetylation and the α7 nicotinic acetylcholine receptor.

Conclusions

These results suggest that TBI obviously enhances the secretion of eCIRP, thereby resulting in neural damage and inflammation in TBI. eCIRP may be a biomarker of TBI that can mediate the apoptosis of neuronal cells through the ERS apoptotic pathway and regulate the inflammatory response of microglia via histone modification.

Traumatic brain injury-associated epigenetic changes and the risk for neurodegenerative diseases

Epidemiological studies have shown that traumatic brain injury (TBI) increases the risk for developing neurodegenerative diseases (NDs). However, molecular mechanisms that underlie this risk are largely unidentified. TBI triggers widespread epigenetic modifications. Similarly, NDs such as Alzheimer's or Parkinson's are associated with numerous epigenetic changes. Although epigenetic changes can persist after TBI, it is unresolved if these modifications increase the risk of later ND development and/or dementia. We briefly review TBI-related epigenetic changes, and point out putative feedback loops that might contribute to long-term persistence of some modifications. We then focus on evidence suggesting persistent TBI-associated epigenetic changes may contribute to pathological processes (e.g., neuroinflammation) which may facilitate the development of specific NDs - Alzheimer's disease, Parkinson's disease, or chronic traumatic encephalopathy. Finally, we discuss possible directions for TBI therapies that may help prevent or delay development of NDs.

Treatment of Status Epilepticus after Traumatic Brain Injury Using an Antiseizure Drug Combined with a Tissue Recovery Enhancer Revealed by Systems Biology

We tested a hypothesis that in silico-discovered compounds targeting traumatic brain injury (TBI)-induced transcriptomics dysregulations will mitigate TBI-induced molecular pathology and augment the effect of co-administered antiseizure treatment, thereby alleviating functional impairment. In silico bioinformatic analysis revealed five compounds substantially affecting TBI-induced transcriptomics regulation, including calpain inhibitor, chlorpromazine, geldanamycin, tranylcypromine, and trichostatin A (TSA). In vitro exposure of neuronal-BV2-microglial co-cultures to compounds revealed that TSA had the best overall neuroprotective, antioxidative, and anti-inflammatory effects. In vivo assessment in a rat TBI model revealed that TSA as a monotherapy (1 mg/kg/d) or in combination with the antiseizure drug levetiracetam (LEV 150 mg/kg/d) mildly mitigated the increase in plasma levels of the neurofilament subunit pNF-H and cortical lesion area. The percentage of rats with seizures during 0-72 h post-injury was reduced in the following order: TBI-vehicle 80%, TBI-TSA (1 mg/kg) 86%, TBI-LEV (54 mg/kg) 50%, TBI-LEV (150 mg/kg) 40% (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 30% (p < 0.05). Cumulative seizure duration was reduced in the following order: TBI-vehicle 727 ± 688 s, TBI-TSA 898 ± 937 s, TBI-LEV (54 mg/kg) 358 ± 715 s, TBI-LEV (150 mg/kg) 42 ± 64 (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 109 ± 282 s (p < 0.05). This first preclinical intervention study on post-TBI acute seizures shows that a combination therapy with the tissue recovery enhancer TSA and LEV was safe but exhibited no clear benefit over LEV monotherapy on antiseizure efficacy. A longer follow-up is needed to confirm the possible beneficial effects of LEV monotherapy and combination therapy with TSA on chronic post-TBI structural and functional outcomes, including epileptogenesis.

Acute metabolic alterations in the hippocampus are associated with decreased acetylation after blast induced TBI

INTRODUCTION

Blast induced Traumatic brain injury (BI-TBI) is common among military personnels as well as war affected civilians. In the war zone, people can also encounter repeated exposure of blast wave, which may affect their cognition and metabolic alterations.

OBJECTIVE

In this study we assess the metabolic and histological changes in the hippocampus of rats at 24 h post injury.

METHOD

Rats were divided into four groups: (i) Sham; (ii) Mild TBI (mi); (iii) Moderate TBI (mo); and (iv) Repetitive mild TBI (rm TBI) and then subjected to different intensities of blast exposure. Hippocampal tissues were collected after 24 h of injury for proton nuclear magnetic resonance spectroscopy (1H NMR spectroscopy) and immunohistochemical (IHC) analysis.

RESULTS

The metabolic alterations were found in the hippocampal tissue samples and these alterations showed significant change in glutamate, N-Acetylaspartic acid (NAA), acetate, creatine, phosphoethanolamine (PE), ethanolamine and PC/choline concentrations in rmTBI rats only. IHC studies revealed that AH3 (Acetyl histone) positive cells were decreased in rm TBI tissue samples in comparison to other TBI groups and sham rats. This might reflect an epigenetic alteration due to repeated blast exposure at 24 h post injury. Additionally, astrogliosis was observed in miTBI and moTBI hippocampal tissue while no change was observed in rmTBI tissues.

CONCLUSION

The present study reports altered acetylation in the presence of altered metabolism in hippocampal tissue of blast induced rmTBI at 24 h post injury. Mechanistic understanding of these intertwined processes may help in the development of better therapeutic pathways and agents for blast induced TBI in near future.

Traumatic Brain Injury Leads to Alterations in Contusional Cortical miRNAs Involved in Dementia

There is compelling evidence that head injury is a significant environmental risk factor for Alzheimer's disease (AD) and that a history of traumatic brain injury (TBI) accelerates the onset of AD. Amyloid-β plaques and tau aggregates have been observed in the post-mortem brains of TBI patients; however, the mechanisms leading to AD neuropathology in TBI are still unknown. In this study, we hypothesized that focal TBI induces changes in miRNA expression in and around affected areas, resulting in the altered expression of genes involved in neurodegeneration and AD pathology. For this purpose, we performed a miRNA array in extracts from rats subjected to experimental TBI, using the controlled cortical impact (CCI) model. In and around the contusion, we observed alterations of miRNAs associated with dementia/AD, compared to the contralateral side. Specifically, the expression of miR-9 was significantly upregulated, while miR-29b, miR-34a, miR-106b, miR-181a and miR-107 were downregulated. Via qPCR, we confirmed these results in an additional group of injured rats when compared to naïve animals. Interestingly, the changes in those miRNAs were concomitant with alterations in the gene expression of mRNAs involved in amyloid generation and tau pathology, such as β-APP cleaving enzyme (BACE1) and Glycogen synthase-3-β (GSK3β). In addition increased levels of neuroinflammatory markers (TNF-α), glial activation, neuronal loss, and tau phosphorylation were observed in pericontusional areas. Therefore, our results suggest that the secondary injury cascade in TBI affects miRNAs regulating the expression of genes involved in AD dementia.

Epigenetic Modifications and Their Potential Contribution to Traumatic Brain Injury Pathobiology and Outcome

Epigenetic information is not permanently encoded in the DNA sequence, but rather consists of reversible, heritable modifications that regulate the gene expression profile of a cell. Epigenetic modifications can result in cellular changes that can be long lasting and include DNA methylation, histone methylation, histone acetylation, and RNA methylation. As epigenetic modifications are reversible, the enzymes that add (epigenetic writers), the proteins that decode (epigenetic readers), and the enzymes that remove (epigenetic erasers) these modifications can be targeted to alter cellular function and disease biology. While epigenetic modifications and their contributions are intense topics of current research in the context of a number of diseases, including cancer, inflammatory diseases, and Alzheimer disease, the study of epigenetics in the context of traumatic brain injury (TBI) is in its infancy. In this review, we will summarize the experimental and clinical findings demonstrating that TBI triggers epigenetic modifications, with a focus on changes in DNA methylation, histone methylation, and the translational utility of the universal methyl donor S-adenosylmethionine (SAM). Finally, we will review the evidence for using methyl donors as possible treatments for TBI-associated pathology and outcome.

Extracellular signal-regulated kinase-dependent phosphorylation of histone H3 serine 10 is involved in the pathogenesis of traumatic brain injury

Traumatic brain injury (TBI) induces a series of epigenetic changes in brain tissue, among which histone modifications are associated with the deterioration of TBI. In this study, we explored the role of histone H3 modifications in a weight-drop model of TBI in rats. Screening for various histone modifications, immunoblot analyses revealed that the phosphorylation of histone H3 serine 10 (p-H3S10) was significantly upregulated after TBI in the brain tissue surrounding the injury site. A similar posttraumatic regulation was observed for phosphorylated extracellular signal-regulated kinase (p-ERK), which is known to phosphorylate H3S10. In support of the hypothesis that ERK-mediated phosphorylation of H3S10 contributes to TBI pathogenesis, double immunofluorescence staining of brain sections showed high levels and colocalization of p-H3S10 and p-ERK predominantly in neurons surrounding the injury site. To test the hypothesis that inhibition of ERK-H3S10 signaling ameliorates TBI pathogenesis, the mitogen-activated protein kinase–extracellular signal-regulated kinase kinase (MEK) 1/2 inhibitor U0126, which inhibits ERK phosphorylation, was administered into the right lateral ventricle of TBI male and female rats via intracerebroventricular cannulation for 7 days post trauma. U0126 administration indeed prevented H3S10 phosphorylation and improved motor function recovery and cognitive function compared to vehicle treatment. In agreement with our findings in the rat model of TBI, immunoblot and double immunofluorescence analyses of brain tissue specimens from patients with TBI demonstrated high levels and colocalization of p-H3S10 and p-ERK as compared to control specimens from non-injured individuals. In conclusion, our findings indicate that phosphorylation-dependent activation of ERK-H3S10 signaling participates in the pathogenesis of TBI and can be targeted by pharmacological approaches.

A Double-Blind Placebo-Controlled, Randomized Trial of Divalproex Sodium for Posttraumatic Irritability Greater Than 1 Year After Mild to Moderate Traumatic Brain Injury

OBJECTIVE

Posttraumatic irritability after traumatic brain injury (TBI) may become a chronic problem and contribute to impaired everyday function, either alone or in combination with alcohol use disorder. The authors hypothesized that divalproex sodium (VPA) would improve posttraumatic irritability and result in lessened alcohol use.

METHODS

This randomized, placebo-controlled double-blind clinical trial recruited participants with an index TBI occurring 1 or more years prior to enrollment, a history of alcohol use disorder, and posttraumatic irritability corroborated by a knowledgeable informant. An 8-item subset of the Agitated Behavior Scale served as the primary outcome measure of VPA efficacy. Doses of VPA were titrated to standard serum concentrations of 50 µg/ml to 100 µg/ml.

RESULTS

Forty-eight persons completed this clinical trial (VPA, N=22; placebo, N=26). At baseline, participants rated their posttraumatic irritability as less severe than did their informants (p<0.05). During the trial, informants reported significant and sustained reduction of posttraumatic irritability (p=0.03) in the study participants. Biweekly averages during drug exposure confirmed this (p<0.03, Cohen's d=0.44). Treatment efficacy was not related to measures of anxiety, posttraumatic stress disorder, sedation, or veteran versus nonveteran status. Alcohol use did not change as a result of treatment. There were no serious adverse events.

CONCLUSIONS

This study demonstrated an effect of VPA on posttraumatic irritability, and VPA was well tolerated. Further definition of treatment efficacy and safety requires a large-scale multisite trial, using a randomized, double-blind placebo-controlled design.

Decreased DNA Methylation of RGMA is Associated with Intracranial Hypertension After Severe Traumatic Brain Injury: An Exploratory Epigenome-Wide Association Study

BACKGROUND

Cerebral edema and intracranial hypertension are major contributors to unfavorable prognosis in traumatic brain injury (TBI). Local epigenetic changes, particularly in DNA methylation, may influence gene expression and thus host response/secondary injury after TBI. It remains unknown whether DNA methylation in the central nervous system is associated with cerebral edema severity or intracranial hypertension post TBI. We sought to identify epigenome-wide DNA methylation patterns associated with these forms of secondary injury after TBI.

METHODS

We obtained genome-wide DNA methylation profiles of DNA extracted from ventricular cerebrospinal fluid samples at three different postinjury time points from a prospective cohort of patients with severe TBI (n = 89 patients, 254 samples). Cerebral edema and intracranial pressure (ICP) measures were clustered to generate composite end points of cerebral edema and ICP severity. We performed an unbiased epigenome-wide association study (EWAS) to test associations between DNA methylation at 419,895 cytosine-phosphate-guanine (CpG) sites and cerebral edema/ICP severity categories. Given inflated p values, we conducted permutation tests for top CpG sites to filter out potential false discoveries.

RESULTS

Our data-driven hierarchical clustering across six cerebral edema and ICP measures identified two groups differing significantly in ICP based on the EWAS-identified CpG site cg22111818 in RGMA (Repulsive guidance molecule A, permutation p = 4.20 × 10-8). At 3-4 days post TBI, patients with severe intracranial hypertension had significantly lower levels of methylation at cg22111818.

CONCLUSIONS

We report a novel potential relationship between intracranial hypertension after TBI and an acute, nonsustained reduction in DNA methylation at cg22111818 in the RGMA gene. To our knowledge, this is the largest EWAS in severe TBI. Our findings are further strengthened by previous findings that RGMA modulates axonal repair in other central nervous system disorders, but a role in intracranial hypertension or TBI has not been previously identified. Additional work is warranted to validate and extend these findings, including assessment of its possible role in risk stratification, identification of novel druggable targets, and ultimately our ability to personalize therapy in TBI.

Progress Toward a Multiomic Understanding of Traumatic Brain Injury: A Review

Traumatic brain injury (TBI) is not a single disease state but describes an array of conditions associated with insult or injury to the brain. While some individuals with TBI recover within a few days or months, others present with persistent symptoms that can cause disability, neuropsychological trauma, and even death. Understanding, diagnosing, and treating TBI is extremely complex for many reasons, including the variable biomechanics of head impact, differences in severity and location of injury, and individual patient characteristics. Because of these confounding factors, the development of reliable diagnostics and targeted treatments for brain injury remains elusive. We argue that the development of effective diagnostic and therapeutic strategies for TBI requires a deep understanding of human neurophysiology at the molecular level and that the framework of multiomics may provide some effective solutions for the diagnosis and treatment of this challenging condition. To this end, we present here a comprehensive review of TBI biomarker candidates from across the multiomic disciplines and compare them with known signatures associated with other neuropsychological conditions, including Alzheimer’s disease and Parkinson’s disease. We believe that this integrated view will facilitate a deeper understanding of the pathophysiology of TBI and its potential links to other neurological diseases.

Functional and transcriptional profiling of microglial activation during the chronic phase of TBI identifies an age-related driver of poor outcome in old mice

Elderly patients with traumatic brain injury (TBI) have greater mortality and poorer outcomes than younger individuals. The extent to which old age alters long-term recovery and chronic microglial activation after TBI is unknown, and evidence for therapeutic efficacy in aged mice is sorely lacking. The present study sought to identify potential inflammatory mechanisms underlying age-related outcomes late after TBI. Controlled cortical impact was used to induce moderate TBI in young and old male C57BL/6 mice. At 12 weeks post-injury, aged mice exhibited higher mortality, poorer functional outcomes, larger lesion volumes, and increased microglial activation. Transcriptomic analysis identified age- and TBI-specific gene changes consistent with a disease-associated microglial signature in the chronically injured brain, including those involved with complement, phagocytosis, and autophagy pathways. Dysregulation of phagocytic and autophagic function in microglia was accompanied by increased neuroinflammation in old mice. As proof-of-principle that these pathways have functional importance, we administered an autophagic enhancer, trehalose, in drinking water continuously for 8 weeks after TBI. Old mice treated with trehalose showed enhanced functional recovery and reduced microglial activation late after TBI compared to the sucrose control group. Our data indicate that microglia undergo chronic changes in autophagic regulation with both normal aging and TBI that are associated with poorer functional outcome. Enhancing autophagy may therefore be a promising clinical therapeutic strategy for TBI, especially in older patients.

Post-Traumatic Epilepsy and Comorbidities: Advanced Models, Molecular Mechanisms, Biomarkers, and Novel Therapeutic Interventions

Post-traumatic epilepsy (PTE) is one of the most devastating long-term, network consequences of traumatic brain injury (TBI). There is currently no approved treatment that can prevent onset of spontaneous seizures associated with brain injury, and many cases of PTE are refractory to antiseizure medications. Post-traumatic epileptogenesis is an enduring process by which a normal brain exhibits hypersynchronous excitability after a head injury incident. Understanding the neural networks and molecular pathologies involved in epileptogenesis are key to preventing its development or modifying disease progression. In this article, we describe a critical appraisal of the current state of PTE research with an emphasis on experimental models, molecular mechanisms of post-traumatic epileptogenesis, potential biomarkers, and the burden of PTE-associated comorbidities. The goal of epilepsy research is to identify new therapeutic strategies that can prevent PTE development or interrupt the epileptogenic process and relieve associated neuropsychiatric comorbidities. Therefore, we also describe current preclinical and clinical data on the treatment of PTE sequelae. Differences in injury patterns, latency period, and biomarkers are outlined in the context of animal model validation, pathophysiology, seizure frequency, and behavior. Improving TBI recovery and preventing seizure onset are complex and challenging tasks; however, much progress has been made within this decade demonstrating disease modifying, anti-inflammatory, and neuroprotective strategies, suggesting this goal is pragmatic. Our understanding of PTE is continuously evolving, and improved preclinical models allow for accelerated testing of critically needed novel therapeutic interventions in military and civilian persons at high risk for PTE and its devastating comorbidities.

Epigenetics of Neurotrauma

Epigenetic changes have been linked to a host of disease states. Besides the physiological function of epigenetic changes in regulating cellular function, recent data indicates that key changes in epigenetic activity also play an important pathophysiologic role following neurotrauma specifically. Such manifestations occur through the activation or silencing of different genes. Histone methylation has emerged as a critical component of this process and can be selectively modulated after injury. Pre-clinical studies have resulted in key discoveries regarding specific methylation sites of interest. This focused review highlights some of these early findings and their relationship to clinical outcomes. These findings suggest areas of future investigation and discovery in the quest to develop ideal biomarkers and methods to utilize them in developing therapeutic interventions.

Epigenetic Regulations of Microglia/Macrophage Polarization in Ischemic Stroke

Ischemic stroke is one of the leading causes of death and disability worldwide. Microglia/macrophages (MMs)-mediated neuroinflammation contributes significantly to the pathological process of ischemic brain injury. Microglia, serving as resident innate immune cells in the central nervous system, undergo pro-inflammatory phenotype or anti-inflammatory phenotype in response to the microenvironmental changes after cerebral ischemia. Emerging evidence suggests that epigenetics modifications, reversible modifications of the phenotype without changing the DNA sequence, could play a pivotal role in regulation of MM polarization. However, the knowledge of the mechanism of epigenetic regulations of MM polarization after cerebral ischemia is still limited. In this review, we present the recent advances in the mechanisms of epigenetics involved in regulating MM polarization, including histone modification, non-coding RNA, and DNA methylation. In addition, we discuss the potential of epigenetic-mediated MM polarization as diagnostic and therapeutic targets for ischemic stroke. It is valuable to identify the underlying mechanisms between epigenetics and MM polarization, which may provide a promising treatment strategy for neuronal damage after cerebral ischemia.

Acute Brain-Derived Neurotrophic Factor DNA Methylation Trajectories in Cerebrospinal Fluid and Associations With Outcomes Following Severe Traumatic Brain Injury in Adults

Background. Epigenetic biomarkers have the potential to explain outcome heterogeneity following traumatic brain injury (TBI) but are largely unexplored. Objective. This exploratory pilot study characterized brain-derived neurotrophic factor (BDNF) DNA methylation trajectories following severe TBI. Methods. Brain-derived neurotrophic factor DNA methylation trajectories in cerebrospinal fluid (CSF) over the first 5 days following severe TBI in 112 adults were examined in association with 3- and 12-month outcomes. Results. Group-based trajectory analysis revealed low and high DNA methylation groups at two BDNF cytosine-phosphate-guanine (CpG) targets that showed suggestive associations (P < .05) with outcomes. Membership in the high DNA methylation groups was associated with better outcomes after controlling for age, sex, and injury severity. Associations of age × trajectory group interactions with outcomes at a third CpG site revealed a pattern of the same or better outcomes with higher ages in the high DNA methylation group and worse outcomes with higher ages in the low DNA methylation group. Conclusions. Although no observed associations met the empirical significance threshold after correcting for multiple comparisons, suggestive associations of the main effect models were consistent in their direction of effect and were observed across two CpG sites and two outcome time points. Results suggest that higher acute CSF BDNF DNA methylation may promote recovery following severe TBI in adults, and this effect may be more robust with higher age. While the results require replication in larger and racially diverse independent samples, BDNF DNA methylation may serve as an early postinjury biomarker helping to explain outcome heterogeneity following TBI.

The Biological Significance of Targeting Acetylation-Mediated Gene Regulation for Designing New Mechanistic Tools and Potential Therapeutics

The molecular interplay between nucleosomal packaging and the chromatin landscape regulates the transcriptional programming and biological outcomes of downstream genes. An array of epigenetic modifications plays a pivotal role in shaping the chromatin architecture, which controls DNA access to the transcriptional machinery. Acetylation of the amino acid lysine is a widespread epigenetic modification that serves as a marker for gene activation, which intertwines the maintenance of cellular homeostasis and the regulation of signaling during stress. The biochemical horizon of acetylation ranges from orchestrating the stability and cellular localization of proteins that engage in the cell cycle to DNA repair and metabolism. Furthermore, lysine acetyltransferases (KATs) modulate the functions of transcription factors that govern cellular response to microbial infections, genotoxic stress, and inflammation. Due to their central role in many biological processes, mutations in KATs cause developmental and intellectual challenges and metabolic disorders. Despite the availability of tools for detecting acetylation, the mechanistic knowledge of acetylation-mediated cellular processes remains limited. This review aims to integrate molecular and structural bases of KAT functions, which would help design highly selective tools for understanding the biology of KATs toward developing new disease treatments.

"Omics" in traumatic brain injury: novel approaches to a complex disease

BACKGROUND

To date, there is neither any pharmacological treatment with efficacy in traumatic brain injury (TBI) nor any method to halt the disease progress. This is due to an incomplete understanding of the vast complexity of the biological cascades and failure to appreciate the diversity of secondary injury mechanisms in TBI. In recent years, techniques for high-throughput characterization and quantification of biological molecules that include genomics, proteomics, and metabolomics have evolved and referred to as omics.

METHODS

In this narrative review, we highlight how omics technology can be applied to potentiate diagnostics and prognostication as well as to advance our understanding of injury mechanisms in TBI.

RESULTS

The omics platforms provide possibilities to study function, dynamics, and alterations of molecular pathways of normal and TBI disease states. Through advanced bioinformatics, large datasets of molecular information from small biological samples can be analyzed in detail and provide valuable knowledge of pathophysiological mechanisms, to include in prognostic modeling when connected to clinically relevant data. In such a complex disease as TBI, omics enables broad categories of studies from gene compositions associated with susceptibility to secondary injury or poor outcome, to potential alterations in metabolites following TBI.

CONCLUSION

The field of omics in TBI research is rapidly evolving. The recent data and novel methods reviewed herein may form the basis for improved precision medicine approaches, development of pharmacological approaches, and individualization of therapeutic efforts by implementing mathematical "big data" predictive modeling in the near future.

A new ketogenic formulation improves functional outcome and reduces tissue loss following traumatic brain injury in adult mice

Rationale: Traumatic brain injury (TBI) leads to neurological impairment, with no satisfactory treatments available. Classical ketogenic diets (KD), which reduce reliance on carbohydrates and provide ketones as fuel, have neuroprotective potential, but their high fat content reduces compliance, and experimental evidence suggests they protect juvenile brain against TBI, but not adult brain, which would strongly limit their applicability in TBI. Methods: We designed a new-KD with a fat to carbohydrate plus protein ratio of 2:1, containing medium chain triglycerides (MCT), docosahexaenoic acid (DHA), low glycaemic index carbohydrates, fibres and the ketogenic amino acid leucine, and evaluated its neuroprotective potential in adult TBI. Adult male C57BL6 mice were injured by controlled cortical impact (CCI) and assessed for 70 days, during which they received a control diet or the new-KD. Results: The new-KD, that markedly increased plasma Beta-hydroxybutyrate (β-HB), significantly attenuated sensorimotor deficits and corrected spatial memory deficit. The lesion size, perilesional inflammation and oxidation were markedly reduced. Oligodendrocyte loss appeared to be significantly reduced. TBI activated the mTOR pathway and the new-KD enhanced this increase and increased histone acetylation and methylation. Conclusion: The behavioural improvement and tissue protection provide proof of principle that this new formulation has therapeutic potential in adult TBI.

Epigenetic Effects on Pediatric Traumatic Brain Injury Recovery (EETR): An Observational, Prospective, Longitudinal Concurrent Cohort Study Protocol

Introduction: Unexplained heterogeneity in outcomes following pediatric traumatic brain injury (TBI) is one of the most critical barriers to the development of effective prognostic tools and therapeutics. The addition of personal biological factors to our prediction models may account for a significant portion of unexplained variance and advance the field toward precision rehabilitation medicine. The overarching goal of the Epigenetic Effects on Pediatric Traumatic Brain Injury Recovery (EETR) study is to investigate an epigenetic biomarker involved in both childhood adversity and postinjury neuroplasticity to better understand heterogeneity in neurobehavioral outcomes following pediatric TBI. Our primary hypothesis is that childhood adversity will be associated with worse neurobehavioral recovery in part through an epigenetically mediated reduction in brain-derived neurotrophic factor (BDNF) expression in response to TBI. Methods and analysis: EETR is an observational, prospective, longitudinal concurrent cohort study of children aged 3-18 years with either TBI (n = 200) or orthopedic injury (n = 100), recruited from the UPMC Children's Hospital of Pittsburgh. Participants complete study visits acutely and at 6 and 12 months postinjury. Blood and saliva biosamples are collected at all time points-and cerebrospinal fluid (CSF) when available acutely-for epigenetic and proteomic analysis of BDNF. Additional measures assess injury characteristics, pre- and postinjury child neurobehavioral functioning, childhood adversity, and potential covariates/confounders. Recruitment began in July 2017 and will occur for ~6 years, with data collection complete by mid-2023. Analyses will characterize BDNF DNA methylation and protein levels over the recovery period and investigate this novel biomarker as a potential biological mechanism underlying the known association between childhood adversity and worse neurobehavioral outcomes following pediatric TBI. Ethics and dissemination: The study received ethics approval from the University of Pittsburgh Institutional Review Board. Participants and their parents provide informed consent/assent. Research findings will be disseminated via local and international conference presentations and manuscripts submitted to peer-reviewed journals. Trial Registration: The study is registered with clinicaltrials.org (ClinicalTrials.gov Identifier: NCT04186429).

Adenosine kinase inhibition promotes proliferation of neural stem cells after traumatic brain injury

Traumatic brain injury (TBI) is a major public health concern and remains a leading cause of disability and socio-economic burden. To date, there is no proven therapy that promotes brain repair following an injury to the brain. In this study, we explored the role of an isoform of adenosine kinase expressed in the cell nucleus (ADK-L) as a potential regulator of neural stem cell proliferation in the brain. The rationale for this hypothesis is based on coordinated expression changes of ADK-L during foetal and postnatal murine and human brain development indicating a role in the regulation of cell proliferation and plasticity in the brain. We first tested whether the genetic disruption of ADK-L would increase neural stem cell proliferation after TBI. Three days after TBI, modelled by a controlled cortical impact, transgenic mice, which lack ADK-L (ADK^Δneuron) in the dentate gyrus (DG) showed a significant increase in neural stem cell proliferation as evidenced by significant increases in doublecortin and Ki67-positive cells, whereas animals with transgenic overexpression of ADK-L in dorsal forebrain neurons (ADK-L^tg) showed an opposite effect of attenuated neural stem cell proliferation. Next, we translated those findings into a pharmacological approach to augment neural stem cell proliferation in the injured brain. Wild-type C57BL/6 mice were treated with the small molecule adenosine kinase inhibitor 5-iodotubercidin for 3 days after the induction of TBI. We demonstrate significantly enhanced neural stem cell proliferation in the DG of 5-iodotubercidin-treated mice compared to vehicle-treated injured animals. To rule out the possibility that blockade of ADK-L has any effects in non-injured animals, we quantified baseline neural stem cell proliferation in ADK^Δneuron mice, which was not altered, whereas baseline neural stem cell proliferation in ADK-L^tg mice was enhanced. Together these findings demonstrate a novel function of ADK-L involved in the regulation of neural stem cell proliferation after TBI.

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

Epigenetic modifications are emerging as major players in the pathogenesis of neurodegenerative disorders and susceptibility to acute brain injury. DNA and histone modifications act together with non-coding RNAs to form a complex gene expression machinery that adapts the brain to environmental stressors and injury response. These modifications influence cell-level operations like neurogenesis and DNA repair to large, intricate processes such as brain patterning, memory formation, motor function and cognition. Thus, epigenetic imbalance has been shown to influence the progression of many neurological disorders independent of aberrations in the genetic code. This review aims to highlight ways in which epigenetics applies to several commonly researched neurodegenerative diseases and forms of acute brain injury as well as shed light on the benefits of epigenetics-based treatments.

Artificial Intelligence and the detection of pediatric concussion using epigenomic analysis

Concussion, also referred to as mild traumatic brain injury (mTBI) is the most common type of traumatic brain injury. Currently concussion is an area ofintensescientific interest to better understand the biological mechanisms and for biomarker development. We evaluated whole genome-wide blood DNA cytosine ('CpG') methylation in 17 pediatric concussion isolated cases and 18 unaffected controls using Illumina Infinium MethylationEPIC assay. Pathway analysis was performed using Ingenuity Pathway Analysis to help elucidate the epigenetic and molecular mechanisms of the disorder. Area under the receiver operating characteristics (AUC) curves and FDR p-values were calculated for mTBI detection based on CpG methylation levels. Multiple Artificial Intelligence (AI) platforms including Deep Learning (DL), the newest form of AI, were used to predict concussion based on i) CpG methylation markers alone, and ii) combined epigenetic, clinical and demographic predictors. We found 449 CpG sites (473 genes), those were statistically significantly methylated in mTBI compared to controls. There were four CpGs with excellent individual accuracy (AUC ≥ 0.90-1.00) while 119 displayed good accuracy (AUC ≥ 0.80-0.89) for the prediction of mTBI. The CpG methylation changes ≥10% were observed in many CpG loci after concussion suggesting biological significance. Pathway analysis identified several biologically important neurological pathways that were perturbed including those associated with: impaired brain function, cognition, memory, neurotransmission, intellectual disability and behavioral change and associated disorders. The combination of epigenomic and clinical predictors were highly accurate for the detection of concusion using AI techniques. Using DL/AI, a combination of epigenomic and clinical markers had sensitivity and specificity ≧95% for prediction of mTBI. In this novel study, we identified significant methylation changes in multiple genes in response to mTBI. Gene pathways that were epigenetically dysregulated included several known to be involved in neurological function, thus giving biological plausibility to our findings.

A Repeated Measures Pilot Comparison of Trajectories of Fluctuating Endogenous Hormones in Young Women with Traumatic Brain Injury, Healthy Controls

Objective

To compare baseline and 72-hour hormone levels in women with traumatic brain injury (TBI) and controls.

Setting

Hospital emergency department.

Participants

21 women ages 18-35 with TBI and 21 controls.

Design

Repeated measures.

Main Measures

Serum samples at baseline and 72 hours; immunoassays for estradiol (E2), progesterone (PRO), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and cortisol (CORT); and health history.

Results

Women with TBI had lower E2 (p = 0.042) and higher CORT (p = 0.028) levels over time. Lower Glasgow Coma Scale (GSC) and OCs were associated with lower FSH (GCS p = 0.021; OCs p = 0.016) and higher CORT (GCS p = 0.001; OCs p = 0.008).

Conclusion

Acute TBI may suppress E2 and increase CORT in young women. OCs appeared to independently affect CORT and FSH responses. Future work is needed with a larger sample to characterize TBI effects on women's endogenous hormone response to injury and OC use's effects on post-TBI stress response and gonadal function, as well as secondary injury.

Apolipoprotein E DNA methylation and posttraumatic stress disorder are associated with plasma ApoE level: A preliminary study

Mild traumatic brain injury (mTBI) occurred in 15-30% of Veterans returning from Iraq and Afghanistan. We examined whether DNA methylation of the apolipoprotein E (APOE) gene promoter region or plasma ApoE protein levels are altered in mTBI. APOE promoter region DNA methylation, APOE genotype, and plasma ApoE concentration were determined in 87 Veterans with or without mTBI who were recruited from 2010-2014. Plasma ApoE concentration was found to be associated with Posttraumatic Stress Disorder (PTSD) symptom severity ratings by hierarchical linear regression (p = .013) and ANCOVA (p = .007). Hierarchical linear regression revealed that plasma ApoE concentration was associated with APOE-ε4 genotype status (p=.022). Higher ApoE plasma levels were found in ε3/ε3 Veterans than in APOE-ε4 carriers (p = .031). Furthermore, plasma ApoE concentration was associated experiment-wise with DNA methylation at CpG sites -877 (p = .021), and -775 (p = .014). The interaction between APOE-ε4 genotype and having a PTSD diagnosis was associated with DNA methylation at CpG site -675 (p = .009).

Traumatic Brain Injury Disrupts Pain Signaling in the Brainstem and Spinal Cord

Chronic pain is a common consequence of traumatic brain injury (TBI) that can increase the suffering of a patient and pose a significant challenge to rehabilitative efforts. Unfortunately, the mechanisms linking TBI to pain are poorly understood, and specific treatments for TBI-related pain are still lacking. Our laboratory has shown that TBI causes pain sensitization in areas distant to the site of primary injury, and that changes in spinal gene expression may underlie this sensitization. The aim of this study was to examine the roles that pain modulatory pathways descending from the brainstem play in pain after TBI. Deficiencies in one type of descending inhibition, diffuse noxious inhibitory control (DNIC), have been suggested to be responsible for the development of chronic pain by allowing excess and uncontrolled afferent nociceptive inputs. Here we expand our knowledge of pain after TBI in two ways: (1) by outlining the neuropathology in pain-related centers of the brain and spinal cord involved in DNIC using the rat lateral fluid percussion (LFP) model of TBI, and (2) by evaluating the effects of a potent histone acetyl transferase inhibitor, anacardic acid (AA), on LFP-induced pain behaviors and neuropathology when administered for several days after TBI. The results revealed that TBI induces transient mechanical allodynia and a chronic persistent loss of DNIC. Further, while short-term AA treatment can block acute nociceptive sensitization and some early neuropathological changes, this treatment neither prevented the loss of DNIC nor did it alter long-term neuropathological changes in the brain or spinal cord.

Genetic Variation in the Vesicular Monoamine Transporter: Preliminary Associations With Cognitive Outcomes After Severe Traumatic Brain Injury

INTRODUCTION

Traumatic brain injury (TBI) frequently results in impaired cognition, a function that can be modulated by monoaminergic signaling. Genetic variation among monoaminergic genes may affect post-TBI cognitive performance. The vesicular monoamine transporter-2 (VMAT2) gene may be a novel source of genetic variation important for cognitive outcomes post-TBI given VMAT2's role in monoaminergic neurotransmission.

OBJECTIVE

To evaluate associations between VMAT2 variability and cognitive outcomes post-TBI.

METHODS

We evaluated 136 white adults with severe TBI for variation in VMAT2 using a tagging single nucleotide polymorphism (tSNP) approach (rs363223, rs363226, rs363251, and rs363341). We show genetic variation interacts with assessed cognitive impairment (cognitive composite [Comp-Cog] T-scores) to influence functional cognition (functional independence measure cognitive [FIM-Cog] subscale] 6 and 12 months postinjury.

RESULTS

Multivariate analyses at 6 months postinjury showed rs363226 genotype was associated with Comp-Cog (P = .040) and interacted with Comp-Cog to influence functional cognition (P < .001). G-homozygotes had the largest cognitive impairment, and their cognitive impairment had the greatest adverse effect on functional cognition.

DISCUSSION

We provide the first evidence that genetic variation within VMAT2 is associated with cognitive outcomes after TBI. Further work is needed to validate this finding and elucidate mechanisms by which genetic variation affects monoaminergic signaling, mediating differences in cognitive outcomes.

HDAC1 Silence Promotes Neuroprotective Effects of Human Umbilical Cord-Derived Mesenchymal Stem Cells in a Mouse Model of Traumatic Brain Injury via PI3K/AKT Pathway

Stem cell transplantation is a promising therapy for traumatic brain injury (TBI), but low efficiency of survival and differentiation of transplanted stem cells limits its clinical application. Histone deacetylase 1 (HDAC1) plays important roles in self-renewal of stem cells as well as the recovery of brain disorders. However, little is known about the effects of HDAC1 on the survival and efficacy of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) in vivo. In this study, our results showed that HDAC1 silence promoted hUC-MSCs engraftment in the hippocampus and increased the neuroprotective effects of hUC-MSCs in TBI mouse model, which was accompanied by improved neurological function, enhanced neurogenesis, decreased neural apoptosis, and reduced oxidative stress in the hippocampus. Further mechanistic studies revealed that the expressions of phosphorylated PTEN (p-PTEN), phosphorylated Akt (p-Akt), and phosphorylated GSK-3β (p-GSK-3β) were upregulated. Intriguingly, the neuroprotective effects of hUC-MSCs with HDAC1 silence on behavioral performance of TBI mice was markedly attenuated by LY294002, an inhibitor of the PI3K/AKT pathway. Taken together, our findings suggest that hUC-MSCs transplantation with HDAC1 silence may provide a potential strategy for treating TBI in the future.

Epigenetic interventions for epileptogenesis: A new frontier for curing epilepsy

This article highlights the emerging therapeutic potential of specific epigenetic modulators as promising antiepileptogenic or disease-modifying agents for curing epilepsy. Currently, there is an unmet need for antiepileptogenic agents that truly prevent the development of epilepsy in people at risk. There is strong evidence that epigenetic signaling, which exerts high fidelity regulation of gene expression, plays a crucial role in the pathophysiology of epileptogenesis and chronic epilepsy. These modifications are not hard-wired into the genome and are constantly reprogrammed by environmental influences. The potential epigenetic mechanisms, including histone modifications, DNA methylation, microRNA-based transcriptional control, and bromodomain reading activity, can drastically alter the neuronal gene expression profile by exerting their summative effects in a coordinated fashion. Such an epigenetic intervention appears more rational strategy for preventing epilepsy because it targets the primary pathway that initially triggers the numerous downstream cellular and molecular events mediating epileptogenesis. Among currently approved epigenetic drugs, the majority are anticancer drugs with well-established profiles in clinical trials and practice. Evidence from preclinical studies supports the premise that these drugs may be applied to a wide range of brain disorders. Targeting histone deacetylation by inhibiting histone deacetylase enzymes appears to be one promising epigenetic therapy since certain inhibitors have been shown to prevent epileptogenesis in animal models. However, developing neuronal specific epigenetic modulators requires rational, pathophysiology-based optimization to efficiently intercept the upstream pathways in epileptogenesis. Overall, epigenetic agents have been well positioned as new frontier tools towards the national goal of curing epilepsy.

Pore-Forming Proteins as Mediators of Novel Epigenetic Mechanism of Epilepsy

Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures. In the last two decades, numerous gene defects underlying different forms of epilepsy have been identified with most of these genes encoding ion channel proteins. Despite these developments, the etiology of majority of non-familial epilepsies has no known associated genetic mutations and cannot be explained by defects in identified ion channels alone. We hypothesize that de novo formation of ion channels by naturally unfolded proteins (NUPs) increases neuronal excitability. Altered ionic homeostasis may initiate/contribute to cellular cascades related to epileptogenesis in susceptible individuals. Here, we consider two small proteins, namely, α-synuclein and stefin B, as prototypical candidates to illustrate the underlying mechanism(s). Previous work points to an association between epilepsy and α-synuclein or stefin B, but the mechanism(s) underlying such association remains elusive. We review the evidence to link the structure-function of these proteins with disease processes. Epigenetic mechanisms unrelated to altered DNA sequence(s) that may affect epileptogenesis include transcriptional or posttranscriptional regulation. Such epigenetic mechanisms or their combination(s) enhance the levels of these proteins and as a result the ability to form annular structures, which upon incorporation into membrane form novel ion channels and disturb intracellular ion homeostasis. Alternative epigenetic mechanisms may change amyloidogenic proteins by posttranslational modifications, thereby increasing their propensity to form channels. Further research elucidating the details about the formation of ion channels through these mechanisms and their role in epileptogenesis may define new molecular targets and guide the development of new drug targets.

Astrocyte Reactivity Following Blast Exposure Involves Aberrant Histone Acetylation

Blast induced neurotrauma (BINT) is a prevalent injury within military and civilian populations. The injury is characterized by persistent inflammation at the cellular level which manifests as a multitude of cognitive and functional impairments. Epigenetic regulation of transcription offers an important control mechanism for gene expression and cellular function which may underlie chronic inflammation and result in neurodegeneration. We hypothesize that altered histone acetylation patterns may be involved in blast induced inflammation and the chronic activation of glial cells. This study aimed to elucidate changes to histone acetylation occurring following injury and the roles these changes may have within the pathology. Sprague Dawley rats were subjected to either a 10 or 17 psi blast overpressure within an Advanced Blast Simulator (ABS). Sham animals underwent the same procedures without blast exposure. Memory impairments were measured using the Novel Object Recognition (NOR) test at 2 and 7 days post-injury. Tissues were collected at 7 days for Western blot and immunohistochemistry (IHC) analysis. Sham animals showed intact memory at each time point. The novel object discrimination decreased significantly between two and 7 days for each injury group (p < 0.05). This is indicative of the onset of memory impairment. Western blot analysis showed glial fibrillary acidic protein (GFAP), a known marker of activated astrocytes, was elevated in the prefrontal cortex (PFC) following blast exposure for both injury groups. Analysis of histone protein extract showed no changes in the level of any total histone proteins within the PFC. However, acetylation levels of histone H2b, H3, and H4 were decreased in both groups (p < 0.05). Co-localization immunofluorescence was used to further investigate any potential correlation between decreased histone acetylation and astrocyte activation. These experiments showed a similar decrease in H3 acetylation in astrocytes exposed to a 17 psi blast but not a 10 psi blast. Further investigation of gene expression by polymerase chain reaction (PCR) array, showed dysregulation of several cytokine and cytokine receptors that are involved in neuroinflammatory processes. We have shown aberrant histone acetylation patterns involved in blast induced astrogliosis and cognitive impairments. Further understanding of their role in the injury progression may lead to novel therapeutic targets.

Epigenetic changes following traumatic brain injury and their implications for outcome, recovery and therapy

Traumatic brain injury (TBI) contributes to nearly a third of all injury-related deaths in the United States. For survivors of TBI, depending on severity, patients can be left with devastating neurological disabilities that include impaired cognition or memory, movement, sensation, or emotional function. Despite the efforts to identify novel therapeutics, the only strategy to combat TBI is risk reduction (helmets, seatbelts, removal of fall hazards, etc.). Enormous heterogeneity exists within TBI, and it depends on the severity, the location, and whether the injury was focal or diffuse. Evidence from recent studies support the involvement of epigenetic mechanisms such as DNA methylation, chromatin post-translational modification, and miRNA regulation of gene expression in the post-injured brain. In this review, we discuss studies that have assessed epigenetic changes and mechanisms following TBI, how epigenetic changes might not only be limited to the nucleus but also impact the mitochondria, and the implications of these changes with regard to TBI recovery.

Traumatic Brain Injury Alters Methionine Metabolism: Implications for Pathophysiology

Methionine is an essential proteinogenic amino acid that is obtained from the diet. In addition to its requirement for protein biosynthesis, methionine is metabolized to generate metabolites that play key roles in a number of cellular functions. Metabolism of methionine via the transmethylation pathway generates S-adenosylmethionine (SAM) that serves as the principal methyl (−CH₃) donor for DNA and histone methyltransferases (MTs) to regulate epigenetic changes in gene expression. SAM is also required for methylation of other cellular proteins that serve various functions and phosphatidylcholine synthesis that participate in cellular signaling. Under conditions of oxidative stress, homocysteine (which is derived from SAM) enters the transsulfuration pathway to generate glutathione, an important cytoprotective molecule against oxidative damage. As both experimental and clinical studies have shown that traumatic brain injury (TBI) alters DNA and histone methylation and causes oxidative stress, we examined if TBI alters the plasma levels of methionine and its metabolites in human patients. Blood samples were collected from healthy volunteers (HV; n = 20) and patients with mild TBI (mTBI; GCS > 12; n = 20) or severe TBI (sTBI; GCS < 8; n = 20) within the first 24 h of injury. The levels of methionine and its metabolites in the plasma samples were analyzed by either liquid chromatography-mass spectrometry or gas chromatography-mass spectrometry (LC-MS or GC-MS). sTBI decreased the levels of methionine, SAM, betaine and 2-methylglycine as compared to HV, indicating a decrease in metabolism through the transmethylation cycle. In addition, precursors for the generation of glutathione, cysteine and glycine were also found to be decreased as were intermediate metabolites of the gamma-glutamyl cycle (gamma-glutamyl amino acids and 5-oxoproline). mTBI also decreased the levels of methionine, α-ketobutyrate, 2 hydroxybutyrate and glycine, albeit to lesser degrees than detected in the sTBI group. Taken together, these results suggest that decreased levels of methionine and its metabolic products are likely to alter cellular function in multiple organs at a systems level.

Intimate Partner Violence and Traumatic Brain Injury: State of the Science and Next Steps

Women who receive traumatic brain injuries (TBI) from intimate partner violence (IPV) are gaining attention; however, research studies are lacking in this area. A review of literature conducted on TBI from IPV found prevalence of 60% to 92% of abused women obtaining a TBI directly correlated with IPV. Adverse overlapping health outcomes are associated with both TBI and IPV. Genetic predisposition and epigenetic changes can occur after TBI and add increased vulnerability to receiving and inflicting a TBI. Health care providers and community health workers need awareness of the link between IPV/TBI to provide appropriate treatment and improve the health of women and families.

IL-1β associations with posttraumatic epilepsy development: A genetics and biomarker cohort study

OBJECTIVE

Posttraumatic epilepsy (PTE) is a significant complication following traumatic brain injury (TBI), yet the role of genetic variation in modulating PTE onset is unclear. We hypothesized that TBI-induced inflammation likely contributes to seizure development. We assessed whether genetic variation in the interleukin-1beta (IL-1β) gene, Il-1β levels in cerebral spinal fluid (CSF) and serum, and CSF/serum IL-1β ratios would predict PTE development post-TBI.

METHODS

We investigated PTE development in 256 Caucasian adults with moderate-to-severe TBI. IL-1β tagging and functional single nucleotide polymorphisms (SNPs) were genotyped. Genetic variance and PTE development were assessed. Serum and CSF IL-1β levels were collected from a subset of subjects (n = 59) during the first week postinjury and evaluated for their associations with IL-1β gene variants, and also PTE. Temporally matched CSF/serum IL-1β ratios were also generated to reflect the relative contribution of serum IL-1β to CSF IL-1β.

RESULTS

Multivariate analysis showed that higher CSF/serum IL-1β ratios were associated with increased risk for PTE over time (p = 0.008). Multivariate analysis for rs1143634 revealed an association between the CT genotype and increased PTE risk over time (p = 0.005). The CT genotype group also had lower serum IL-1β levels (p = 0.014) and higher IL-1β CSF/serum ratios (p = 0.093).

SIGNIFICANCE

This is the first report implicating IL-1β gene variability in PTE risk and linking (1) IL-1β gene variation with serum IL-1β levels observed after TBI and (2) IL-1β ratios with PTE risk. Given these findings, we propose that genetic and IL-1β ratio associations with PTE may be attributable to biologic variability with blood-brain barrier integrity during TBI recovery. These results provide a rationale for further studies (1) validating the impact of genetic variability on IL-1β production after TBI, (2) assessing genetically mediated signaling mechanisms that contribute to IL-1β CSF/serum associations with PTE, and (3) evaluating targeted IL-1β therapies that reduce PTE. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Genetic variation in the adenosine regulatory cycle is associated with posttraumatic epilepsy development

OBJECTIVE

Determine if genetic variation in enzymes/transporters influencing extracellular adenosine homeostasis, including adenosine kinase (ADK), [ecto-5'-nucleotidase (NT5E), cluster of differentiation 73 (CD73)], and equilibrative nucleoside transporter type-1 (ENT-1), is significantly associated with epileptogenesis and posttraumatic epilepsy (PTE) risk, as indicated by time to first seizure analyses.

METHODS

Nine ADK, three CD73, and two ENT-1 tagging single nucleotide polymorphisms (SNPs) were genotyped in 162 white adults with moderate/severe traumatic brain injury (TBI) and no history of premorbid seizures. Kaplan-Meier models were used to screen for genetic differences in time to first seizure occurring >1 week post-TBI. SNPs remaining significant after correction for multiple comparisons were examined using Cox proportional hazards analyses, adjusting for subdural hematoma, injury severity score, and isolated TBI status. SNPs significant in multivariate models were then entered simultaneously into an adjusted Cox model.

RESULTS

Comparing Kaplan-Meier curves, rs11001109 (ADK) rare allele homozygosity and rs9444348 (NT5E) heterozygosity were significantly associated with shorter time to first seizure and an increased seizure rate 3 years post-TBI. Multivariate Cox proportional hazard models showed that these genotypes remained significantly associated with increased PTE hazard up to 3 years post-TBI after controlling for variables of interest (rs11001109: hazard ratio (HR) 4.47, 95% confidence interval (CI) 1.27-15.77, p = 0.020; rs9444348: HR 2.95, 95% CI 1.19-7.31, p = 0.019) .

SIGNIFICANCE

Genetic variation in ADK and NT5E may help explain variability in time to first seizure and PTE risk, independent of previously identified risk factors, after TBI. Once validated, identifying genetic variation in adenosine regulatory pathways relating to epileptogenesis and PTE may facilitate exploration of therapeutic targets and pharmacotherapy development.

Sodium selenate reduces hyperphosphorylated tau and improves outcomes after traumatic brain injury

Traumatic brain injury is a common and serious neurodegenerative condition that lacks a pharmaceutical intervention to improve long-term outcome. Hyperphosphorylated tau is implicated in some of the consequences of traumatic brain injury and is a potential pharmacological target. Protein phosphatase 2A is a heterotrimeric protein that regulates key signalling pathways, and protein phosphatase 2A heterotrimers consisting of the PR55 B-subunit represent the major tau phosphatase in the brain. Here we investigated whether traumatic brain injury in rats and humans would induce changes in protein phosphatase 2A and phosphorylated tau, and whether treatment with sodium selenate-a potent PR55 activator-would reduce phosphorylated tau and improve traumatic brain injury outcomes in rats. Ninety young adult male Long-Evans rats were administered either a fluid percussion injury or sham-injury. A proportion of rats were killed at 2, 24, and 72 h post-injury to assess acute changes in protein phosphatase 2A and tau. Other rats were given either sodium selenate or saline-vehicle treatment that was continuously administered via subcutaneous osmotic pump for 12 weeks. Serial magnetic resonance imaging was acquired prior to, and at 1, 4, and 12 weeks post-injury to assess evolving structural brain damage and axonal injury. Behavioural impairments were assessed at 12 weeks post-injury. The results showed that traumatic brain injury in rats acutely reduced PR55 expression and protein phosphatase 2A activity, and increased the expression of phosphorylated tau and the ratio of phosphorylated tau to total tau. Similar findings were seen in post-mortem brain samples from acute human traumatic brain injury patients, although many did not reach statistical significance. Continuous sodium selenate treatment for 12 weeks after sham or fluid percussion injury in rats increased protein phosphatase 2A activity and PR55 expression, and reduced the ratio of phosphorylated tau to total tau, attenuated brain damage, and improved behavioural outcomes in rats given a fluid percussion injury. Notably, total tau levels were decreased in rats 12 weeks after fluid percussion injury, and several other factors, including the use of anaesthetic, the length of recovery time, and that some brain injury and behavioural dysfunction still occurred in rats treated with sodium selenate must be considered in the interpretation of this study. However, taken together these data suggest protein phosphatase 2A and hyperphosphorylated tau may be involved in the neurodegenerative cascade of traumatic brain injury, and support the potential use of sodium selenate as a novel traumatic brain injury therapy.

IL-1β associations with posttraumatic epilepsy development: a genetics and biomarker cohort study

OBJECTIVE

Posttraumatic epilepsy (PTE) is a significant complication following traumatic brain injury (TBI), yet the role of genetic variation in modulating PTE onset is unclear. We hypothesized that TBI-induced inflammation likely contributes to seizure development. We assessed whether genetic variation in the interleukin-1beta (IL-1β) gene, IL-1β levels in cerebrospinal fluid (CSF) and serum, and CSF/serum IL-1β ratios would predict PTE development post-TBI.

METHODS

We investigated PTE development in 256 Caucasian adults with moderate-to-severe TBI. IL-1β tagging and functional single nucleotide polymorphisms (SNPs) were genotyped. Genetic variance and PTE development were assessed. Serum and CSF IL-1β levels were collected from a subset of subjects (n = 59) during the first week postinjury and evaluated for their associations with IL-1β gene variants, and also PTE. Temporally matched CSF/serum IL-1β ratios were also generated to reflect the relative contribution of serum IL-1β to CSF IL-1β.

RESULTS

Multivariate analysis showed that higher CSF/serum IL-1β ratios were associated with increased risk for PTE over time (p = 0.008). Multivariate analysis for rs1143634 revealed an association between the CT genotype and increased PTE risk over time (p = 0.005). The CT genotype group also had lower serum IL-1β levels (p = 0.014) and higher IL-1β CSF/serum ratios (p = 0.093).

SIGNIFICANCE

This is the first report implicating IL-1β gene variability in PTE risk and linking (1) IL-1β gene variation with serum IL-1β levels observed after TBI and (2) IL-1β ratios with PTE risk. Given these findings, we propose that genetic and IL-1β ratio associations with PTE may be attributable to biologic variability with blood-brain barrier integrity during TBI recovery. These results provide a rationale for further studies (1) validating the impact of genetic variability on IL-1β production after TBI, (2) assessing genetically mediated signaling mechanisms that contribute to IL-1β CSF/serum associations with PTE, and (3) evaluating targeted IL-1β therapies that reduce PTE.

Epilepsy related to traumatic brain injury

Post-traumatic epilepsy accounts for 10-20% of symptomatic epilepsy in the general population and 5% of all epilepsy. During the last decade, an increasing number of laboratories have investigated the molecular and cellular mechanisms of post-traumatic epileptogenesis in experimental models. However, identification of critical molecular, cellular, and network mechanisms that would be specific for post-traumatic epileptogenesis remains a challenge. Despite of that, 7 of 9 proof-of-concept antiepileptogenesis studies have demonstrated some effect on seizure susceptibility after experimental traumatic brain injury, even though none of them has progressed to clinic. Moreover, there has been some promise that new clinically translatable imaging approaches can identify biomarkers for post-traumatic epileptogenesis. Even though the progress in combating post-traumatic epileptogenesis happens in small steps, recent discoveries kindle hope for identification of treatment strategies to prevent post-traumatic epilepsy in at-risk patients.

Histone deacetylase inhibitors are neuroprotective and preserve NGF-mediated cell survival following traumatic brain injury

Acute traumatic brain injury (TBI) is associated with long-term cognitive and behavioral dysfunction. In vivo studies have shown histone deacetylase inhibitors (HDACis) to be neuroprotective following TBI in rodent models. HDACis are intriguing candidates because they are capable of provoking widespread genetic changes and modulation of protein function. By using known HDACis and a unique small-molecule pan-HDACi (LB-205), we investigated the effects and mechanisms associated with HDACi-induced neuroprotection following CNS injury in an astrocyte scratch assay in vitro and a rat TBI model in vivo. We demonstrate the preservation of sufficient expression of nerve growth factor (NGF) and activation of the neurotrophic tyrosine kinase receptor type 1 (TrkA) pathway following HDACi treatment to be crucial in stimulating the survival of CNS cells after TBI. HDACi treatment up-regulated the expression of NGF, phospho-TrkA, phospho-protein kinase B (p-AKT), NF-κB, and B-cell lymphoma 2 (Bcl-2) cell survival factors while down-regulating the expression of p75 neurotrophin receptor (NTR), phospho-JNK, and Bcl-2-associated X protein apoptosis factors. HDACi treatment also increased the expression of the stem cell biomarker nestin, and decreased the expression of reactive astrocyte biomarker GFAP within damaged tissue following TBI. These findings provide further insight into the mechanisms by which HDACi treatment after TBI is neuroprotective and support the continued study of HDACis following acute TBI.

Administration of MS-275 improves cognitive performance and reduces cell death following traumatic brain injury in rats

AIMS

The MS-275 is a selective inhibitor of class I histone deacetylases (HDACs), which has been reported as a potential strategy in some central nervous system diseases associated with neurodegeneration and disturbed learning. However, its role in traumatic brain injury is not well defined. In this study, we examined the behavioral-cognitive performance as well as histology outcome in adult rats to evaluate whether postinjury administration of MS-275 (15 and 45 mg/kg) would provide neuroprotection benefits and ameliorate cognitive deficits following fluid percussion injury.

METHODS

Traumatic brain injury (˜2.15 ATMs) was produced using a fluid percussion device with the lateral orientation. MS-275 was administered (15 and 45 mg/kg) systemically once daily for 7 days starting at 30 min after lateral fluid percussion TBI. Acquisition of spatial learning and memory retention was assessed using the Morris water maze (MWM) on days 10-14 after TBI. Brain tissues were collected and stained with Fluoro-Jade B histofluorescence (for degenerating neurons) at 24 h after injury and cresyl violet (for long-term neuronal survival) on day 14 postinjury.

RESULTS

Behavioral outcome after TBI revealed MS-275 treatment groups, at all doses examined, performed significantly better in the Morris Water Maze (P < 0.001). Acute histology analysis demonstrated that 45 mg/kg MS-275 significantly reduced the number of degenerating neurons in the ipsilateral CA2-3 hippocampus at 24 h postinjury (P = 0.007). There was a trend for MS-275 to increase the survival of neurons in the CA2-3 hippocampus on 14 days after TBI (P = 0.164).

CONCLUSION

Our present data highlight the fact that MS-275 may provide neuroprotective effect and improve cognitive performance after TBI. We concluded that MS-275 is a potential novel treatment and will have an ameliorative effect on some of the pathological features associated with TBI.

Role of epigenetic regulatory mechanisms in neonatal hypoxic-ischemic brain injury

BACKGROUND

DNA methylation and histone modifications are the most identified modifications that selectively activate or inactivate genes that control cell growth, proliferation, and apoptosis.

AIM

We hypothesized that alterations in gene expression due to hypoxic-ischemic brain damage was regulated by epigenetic mechanisms including DNA methylation and histone methylation.

STUDY DESIGN

To test this hypothesis, we established a rat model of HIE. Three groups were defined as hypoxic-ischemic, sham-operated, and control group.

OUTCOME MEASUREMENTS

The validity of the HIE model used in this study was confirmed by histological and immunohistochemical tests. Gene expressions related with apoptosis and angiogenesis were studied at 0.5, 3, 6 and 24h after HI or sham operation. DNA and histone methylation status was studied in the genes showing significant change in expression.

RESULTS AND CONCLUSIONS

Most of the genes related with apoptosis and angiogenesis (Epo, Epor, Hif 1α, Hif3α, VEGFa, VEGFc, Casp1, Casp9, and Casp8ap2) induced early after HI (30min). All of these genes were unmethylated at the beginning of the insult and in the control group. DNA methylation percentage and histone methylation (H3K36) levels were not correlated with gen expression levels. To our knowledge this is the first study evaluating the role of epigenetic mechanisms in HIE model, therefore the absence of similar studies don't allow us to compare the present results. Further studies investigating different epigenetic mechanisms are needed.

Morris water maze function and histologic characterization of two age-at-injury experimental models of controlled cortical impact in the immature rat

PURPOSE

Controlled cortical impact (CCI) is commonly used in adult animals to study focal traumatic brain injury (TBI). Our study aims to further study injury mechanisms in children and variable models of pathology in the developing brain.

METHODS

Develop a focal injury model of experimental TBI in the immature, postnatal days (PND) 7 and 17 rats that underwent a CCI at varying depths of deflection, 1.5-2.5 mm compared with sham and then tested using the Morris water maze (MWM) beginning on post-injury day (PID) 11. Histopathologic analysis was performed at PID 1 and 28.

RESULTS

In PND 7, the 1.75- and 2.0-mm deflections (diameter (d) = 3 mm; velocity = 4 m/s; and duration = 500 ms) resulted in significant MWM deficits while the 1.5-mm injury did not produce MWM deficits vs. sham controls. In PND 17, all injury levels resulted in significant MWM deficits vs. sham controls with a graded response; the 1.5-mm deflection (d = 6 mm; velocity = 4 m/s; and duration = 500 ms) produced significantly less deficits as compared WITH the 2.0- and 2.5-mm injuries. Histologically, a graded injury response was also seen in both ages at injury with cortical and more severe injuries, hippocampal damage. Cortical contusion volume increased in most injury severities from PID 1 to 28 in both ages at injury while hippocampal volumes subsequently decreased.

CONCLUSIONS

CCI in PND 7 and 17 rat results in significant MWM deficits and cortical histopathology providing two different and unique experimental models of TBI in immature rats that may be useful in further investigations into the mechanisms and treatments of pediatric TBI.

Scriptaid, a novel histone deacetylase inhibitor, protects against traumatic brain injury via modulation of PTEN and AKT pathway : scriptaid protects against TBI via AKT

Traumatic brain injury (TBI) is a leading cause of motor and cognitive deficits in young adults for which there is no effective therapy. The present study characterizes the protective effect of a new histone deacetylase inhibitor, Scriptaid (Sigma-Aldrich Corporation, St. Louis, MO), against injury from controlled cortical impact (CCI). Scriptaid elicited a dose-dependent decrease in lesion size at 1.5 to 5.5 mg/kg and a concomitant attenuation in motor and cognitive deficits when delivered 30 minutes postinjury in a model of moderate TBI. Comparable protection was achieved even when treatment was delayed to 12 h postinjury. Furthermore, the protection of motor and cognitive functions was long lasting, as similar improvements were detected 35 days postinjury. The efficacy of Scriptaid (Sigma-Aldrich Corporation) was manifested as an increase in surviving neurons, as well as the number/length of their processes within the CA3 region of the hippocampus and the pericontusional cortex. Consistent with other histone deacetylase inhibitors, Scriptaid treatment prevented the decrease in phospho-AKT (p-AKT) and phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (p-PTEN) induced by TBI in cortical and CA3 hippocampal neurons. Notably, the p-AKT inhibitor LY294002 attenuated the impact of Scriptaid, providing mechanistic evidence that Scriptaid functions partly by modulating the prosurvival AKT signaling pathway. As Scriptaid offers long-lasting neuronal and behavioral protection, even when delivered 12 h after controlled cortical impact, it is an excellent new candidate for the effective clinical treatment of TBI.

Genetic variability in glutamic acid decarboxylase genes: associations with post-traumatic seizures after severe TBI

Post traumatic seizures (PTS) occur frequently after traumatic brain injury (TBI). Since gamma-amino butyric acid (GABA) neurotransmission is central to excitotoxicity and seizure development across multiple models, we investigated how genetic variability for glutamic acid decarboxylase (GAD) influences risk for PTS. Using both a tagging and functional single nucleotide polymorphism (SNP) approach, we genotyped the GAD1 and GAD2 genes and linked them with PTS data, regarding time to first seizure, obtained for 257 adult subjects with severe TBI. No significant associations were found for GAD2. In the GAD1 gene, the tagging SNP (tSNP) rs3828275 was associated with an increased risk for PTS occurring <1 wk. The tSNP rs769391 and the functional SNP rs3791878 in the GAD1 gene were associated with increased PTS risk occurring 1 wk-6 mo post-injury. Both risk variants conferred an increased susceptibility to PTS compared to subjects with 0-1 risk variant. Also, those with haplotypes having both risk variants had a higher PTS risk 1 wk-6 mo post-injury than those without these haplotypes. Similarly, diplotype analysis showed those with 2 copies of the haplotype containing both risk alleles were at the highest PTS risk. These results implicate genetic variability within the GABA system in modulating the development of PTS.