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

DNA Methylation in Periodontal Disease: A Focus on Folate, Folic Acid, Mitochondria, and Dietary Intervention

Although periodontal disease (PD) is reported to be associated with changes in various genes and proteins in both invading bacteria and the host, its molecular mechanism of pathogenesis remains unclear. Changes in immune and inflammatory genes play a significant role in PD pathogenesis. Some reports relate alterations in cellular epigenetic patterns to PD characteristics, while several high-throughput analyses indicate thousands of differentially methylated genes in both PD patients and controls. Furthermore, changes in DNA methylation patterns in inflammation-related genes have been linked to the efficacy of periodontal therapy, as demonstrated by findings related to the cytochrome C oxidase II gene. Distinct DNA methylation patterns in mesenchymal stem cells from PD patients and controls persisted despite the reversal of phenotypic PD. Methyl groups for DNA methylation are supplied by S-adenosylmethionine, which is synthesized with the involvement of folate, an essential nutrient known to play a role in maintaining mitochondrial homeostasis, reported to be compromised in PD. Folate may benefit PD through its antioxidant action against reactive oxygen and nitrogen species that are overproduced by dysfunctional mitochondria. As such, DNA methylation, dietary folate, and mitochondrial quality control may interact in PD pathogenesis. In this narrative/hypothesis review, we demonstrate how PD is associated with changes in mitochondrial homeostasis, which may, in turn, be improved by folate, potentially altering the epigenetic patterns of immune and inflammatory genes in both the nucleus and mitochondria. Therefore, a folate-based dietary intervention is recommended for PD prevention and as an adjunct therapy. At the same time, further research is needed on the involvement of epigenetic mechanisms in the beneficial effects of folate on PD studies.

Development of BACE2-IN-1/tranylcypromine-based compounds to induce steroidogenesis-dependent neuroprotection

Traumatic brain injury (TBI) constitutes a significant burden on global healthcare systems, especially affecting younger populations, where it is a leading cause of disability and mortality. Current treatments for TBI mainly focus on preventing further brain damage and controlling symptoms. However, despite these approaches, several clinical needs remain unmet. Revelations from single-cell RNA sequencing (scRNA-seq) performed to determine cell-type heterogeneity and gene expression changes in brain tissue indicated that brain trauma increases the expression of lysine-specific demethylase 1 (LSD1) and secretase 2 (BACE2). To capitalize on this finding, a medicinal chemistry campaign was conducted to pragmatically insert tranylcypromine, an LSD1 inhibitor, into a carefully designed BACE2 inhibitory template (BACE2-IN-1). Additionally, tranylcypromine was structurally modified to enhance the effects of LSD1 inhibition in TBI. As a result, a tractable neuroprotective agent, BACE2-IN-1/tranylcypromine-based compound 4, was identified, showing potential to maintain Neuro-2a cell survival by alleviating mitochondrial damage after oxidative stress. Compound 4 also restored TBI-mediated inhibition of the cholesterol biosynthetic pathway (mevalonate pathway) and damage of redox metabolism, increasing neuroprotective effects. Furthermore, behavioral assays, including nest-building and cognitive performance tests, demonstrated significant improvement in mice post-TBI following treatment with compound 4. Taken together, the outcomes of this study validate the favorable effects of inhibiting LSD1 and beta-secretase in mitigating mitochondrial stress and promoting neurometabolic recovery in TBI. These findings pave the way for the development of rationally designed inhibitors as promising neuroprotective agents, potentially addressing unmet clinical needs in TBI treatment.

Comprehensive Transcriptome-Wide Profiling of 5-Methylcytosine Modifications in Long Non-Coding RNAs in a Rat Model of Traumatic Brain Injury

Traumatic brain injury (TBI) poses a major global health challenge, leading to serious repercussions for those affected and imposing considerable financial strains on families and healthcare systems. RNA methylation, especially 5-methylcytosine (m5C), plays a crucial role as an epigenetic modification in regulating RNA at the level of post-transcriptional regulation. However, the impact of TBI on the m5C methylation profile of long non-coding RNAs (lncRNAs) remains unexplored. In the present study, we conducted a thorough transcriptome-wide examination of m5C methylation in lncRNAs in a rat TBI model utilizing MeRIP-Seq. Our results revealed significant differences in the amount and distribution of m5C methylation in lncRNAs between TBI and control groups, indicating profound changes in m5C methylation following TBI. Bioinformatic analyses linked these specifically methylated transcripts to pathways involved in immune response, neural repair, and lipid metabolism, providing insight into possible mechanisms underlying TBI pathology. These findings offer novel perspectives on the post-transcriptional modifications in lncRNA m5C methylation following TBI, which may contribute to understanding the disease mechanisms and developing targeted therapeutic strategies.

Severe traumatic injury is associated with profound changes in DNA methylation

Whether DNA methylation changes follow human physical trauma is uncertain. We aimed to investigate if severe trauma was associated with DNA methylation changes. In a prospective, observational, clinical study, we included severely injured adults and adults undergoing elective surgery (controls). Blood was obtained from trauma patients (n = 60) immediately- and 30-45 days post-trauma, and from surgical patients (n = 57) pre-, post-, and 30-45 days post-surgery. Epigenome-wide DNA methylation profiling was performed and analyzed for significant differentially methylated CpGs and -regions (DMRs) within and between groups. Within the trauma group we identified 10,126 significant differentially methylated CpGs and 1169 DMRs. No significant differential methylation was found in the surgical group. In the trauma group, differentially methylated sites were enriched in genes and pathways involved in blood coagulation and inflammatory response. Severe trauma was associated with profound alterations in the DNA methylome of circulating leucocytes, and differential methylation was located in trauma-relevant genes.

Neuroprotective Mechanism of MOTS-c in TBI Mice: Insights from Integrated Transcriptomic and Metabolomic Analyses

Background

Traumatic brain injury (TBI) is a condition characterized by structural and physiological disruptions in brain function caused by external forces. However, as the highly complex and heterogenous nature of TBI, effective treatments are currently lacking. Mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) has shown notable antinociceptive and anti-inflammatory effects, yet its detailed neuroprotective effects and mode of action remain incompletely understood. This study investigated the neuroprotective effects and the underlying mechanisms of MOTS-c.

Methods

Adult male C57BL/6 mice were randomly divided into three groups: control (CON) group, MOTS-c group and TBI group. Enzyme-linked immunosorbent assay (ELISA) kit method was used to measure the expression levels of MOTS-c in different groups. Behavioral tests were conducted to assess the effects of MOTS-c. Then, transcriptomics and metabolomics were performed to search Differentially Expressed Genes (DEGs) and Differentially Expressed Metabolites (DEMs), respectively. Moreover, the integrated transcriptomics and metabolomics analysis were employed using R packages and online Kyoto Encyclopedia of Genes and Genomes (KEGG) database.

Results

ELISA kit method showed that TBI resulted in a decrease in the expression of MOTS-c. and peripheral administration of MOTS-c could enter the brain tissue after TBI. Behavioral tests revealed that MOTS-c improved memory, learning, and motor function impairments in TBI mice. Additionally, transcriptomic analysis screened 159 differentially expressed genes. Metabolomic analysis identified 491 metabolites with significant differences. Integrated analysis found 14 KEGG pathways, primarily related to metabolic pathways. Besides, several signaling pathways were enriched, including neuroactive ligand-receptor interaction and retrograde endocannabinoid signaling.

Conclusion

TBI reduced the expression of MOTS-c. MOTS-c reduced inflammatory responses, molecular damage, and cell death by down-regulating macrophage migration inhibitory factor (MIF) expression and activating the retrograde endocannabinoid signaling pathway. In addition, MOTS-c alleviated the response to hypoxic stress and enhanced lipid β-oxidation to provide energy for the body following TBI. Overall, our study offered new insights into the neuroprotective mechanisms of MOTS-c in TBI mice.

From powerhouse to regulator: The role of mitoepigenetics in mitochondrion-related cellular functions and human diseases

Beyond their crucial role in energy production, mitochondria harbor a distinct genome subject to epigenetic regulation akin to that of nuclear DNA. This paper delves into the nascent but rapidly evolving fields of mitoepigenetics and mitoepigenomics, exploring the sophisticated regulatory mechanisms governing mitochondrial DNA (mtDNA). These mechanisms encompass mtDNA methylation, the influence of non-coding RNAs (ncRNAs), and post-translational modifications of mitochondrial proteins. Together, these epigenetic modifications meticulously coordinate mitochondrial gene transcription, replication, and metabolism, thereby calibrating mitochondrial function in response to the dynamic interplay of intracellular needs and environmental stimuli. Notably, the dysregulation of mitoepigenetic pathways is increasingly implicated in mitochondrial dysfunction and a spectrum of human pathologies, including neurodegenerative diseases, cancer, metabolic disorders, and cardiovascular conditions. This comprehensive review synthesizes the current state of knowledge, emphasizing recent breakthroughs and innovations in the field. It discusses the potential of high-resolution mitochondrial epigenome mapping, the diagnostic and prognostic utility of blood or tissue mtDNA epigenetic markers, and the promising horizon of mitochondrial epigenetic drugs. Furthermore, it explores the transformative potential of mitoepigenetics and mitoepigenomics in precision medicine. Exploiting a theragnostic approach to maintaining mitochondrial allostasis, this paper underscores the pivotal role of mitochondrial epigenetics in charting new frontiers in medical science.

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.

Mediator complex in neurological disease

Neurological diseases, including traumatic brain injuries, stroke (haemorrhagic and ischemic), and inherent neurodegenerative diseases cause acquired disability in humans, representing a leading cause of death worldwide. The Mediator complex (MED) is a large, evolutionarily conserved multiprotein that facilities the interaction between transcription factors and RNA Polymerase II in eukaryotes. Some MED subunits have been found altered in the brain, although their specific functions in neurodegenerative diseases are not fully understood. Mutations in MED subunits were associated with a wide range of genetic diseases for MED12, MED13, MED13L, MED20, MED23, MED25, and CDK8 genes. In addition, MED12 and MED23 were deregulated in the Alzheimer's Disease. Interestingly, most of the genomic mutations have been found in the subunits of the kinase module. To date, there is only one evidence on MED1 involvement in post-stroke cognitive deficits. Although the underlying neurodegenerative disorders may be different, we are confident that the signal cascades of the biological-cognitive mechanisms of brain adaptation, which begin after brain deterioration, may also differ. Here, we analysed relevant studies in English published up to June 2023. They were identified through a search of electronic databases including PubMed, Medline, EMBASE and Scopus, including search terms such as "Mediator complex", "neurological disease", "brains". Thematic content analysis was conducted to collect and summarize all studies demonstrating MED alteration to understand the role of this central transcriptional regulatory complex in the brain. Improved and deeper knowledge of the regulatory mechanisms in neurological diseases can increase the ability of physicians to predict onset and progression, thereby improving diagnostic care and providing appropriate treatment decisions.

Recent advances in the role of miRNAs in post-traumatic stress disorder and traumatic brain injury

Post-traumatic stress disorder (PTSD) is usually considered a psychiatric disorder upon emotional trauma. However, with the rising number of conflicts and traffic accidents around the world, the incidence of PTSD has skyrocketed along with traumatic brain injury (TBI), a complex neuropathological disease due to external physical force and is also the most common concurrent disease of PTSD. Recently, the overlap between PTSD and TBI is increasingly attracting attention, as it has the potential to stimulate the emergence of novel treatments for both conditions. Of note, treatments exploiting the microRNAs (miRNAs), a well-known class of small non-coding RNAs (ncRNAs), have rapidly gained momentum in many nervous system disorders, given the miRNAs' multitudinous and key regulatory role in various biological processes, including neural development and normal functioning of the nervous system. Currently, a wealth of studies has elucidated the similarities of PTSD and TBI in pathophysiology and symptoms; however, there is a dearth of discussion with respect to miRNAs in both PTSD and TBI. In this review, we summarize the recent available studies of miRNAs in PTSD and TBI and discuss and highlight promising miRNAs therapeutics for both conditions in the future.

Stress-sensitive dynamics of miRNAs and Elba1 in Drosophila embryogenesis

Early-life stress can result in life-long effects that impact adult health and disease risk, but little is known about how such programming is established and maintained. Here, we show that such epigenetic memories can be initiated in the Drosophila embryo before the major wave of zygotic transcription, and higher-order chromatin structures are established. An early short heat shock results in elevated levels of maternal miRNA and reduced levels of a subgroup of zygotic genes in stage 5 embryos. Using a Dicer-1 mutant, we show that the stress-induced decrease in one of these genes, the insulator-binding factor Elba1, is dependent on functional miRNA biogenesis. Reduction in Elba1 correlates with the upregulation of early developmental genes and promotes a sustained weakening of heterochromatin in the adult fly as indicated by an increased expression of the PEV w^m4h reporter. We propose that maternal miRNAs, retained in response to an early embryonic heat shock, shape the subsequent de novo heterochromatin establishment that occurs during early development via direct or indirect regulation of some of the earliest expressed genes, including Elba1.

Cannabidiol's neuroprotective properties and potential treatment of traumatic brain injuries

Cannabidiol (CBD) has numerous pharmacological targets that initiate anti-inflammatory, antioxidative, and antiepileptic properties. These neuroprotective benefits have generated interest in CBD's therapeutic potential against the secondary injury cascade from traumatic brain injury (TBI). There are currently no effective broad treatment strategies for combating the damaging mechanisms that follow the primary injury and lead to lasting neurological consequences or death. However, CBD's effects on different neurotransmitter systems, the blood brain barrier, oxidative stress mechanisms, and the inflammatory response provides mechanistic support for CBD's clinical utility in TBI. This review describes the cascades of damage caused by TBI and CBD's neuroprotective mechanisms to counter them. We also present challenges in the clinical treatment of TBI and discuss important future clinical research directions for integrating CBD in treatment protocols. The mechanistic evidence provided by pre-clinical research shows great potential for CBD as a much-needed improvement in the clinical treatment of TBI. Upcoming clinical trials sponsored by major professional sport leagues are the first attempts to test the efficacy of CBD in head injury treatment protocols and highlight the need for further clinical research.

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.

Epigenetic Alterations in Sports-Related Injuries

It is a well-known fact that physical activity benefits people of all age groups. However, highly intensive training, maladaptation, improper equipment, and lack of sufficient rest lead to contusions and sports-related injuries. From the perspectives of sports professionals and those performing regular–amateur sports activities, it is important to maintain proper levels of training, without encountering frequent injuries. The bodily responses to physical stress and intensive physical activity are detected on many levels. Epigenetic modifications, including DNA methylation, histone protein methylation, acetylation, and miRNA expression occur in response to environmental changes and play fundamental roles in the regulation of cellular activities. In the current review, we summarise the available knowledge on epigenetic alterations present in tissues and organs (e.g., muscles, the brain, tendons, and bones) as a consequence of sports-related injuries. Epigenetic mechanism observations have the potential to become useful tools in sports medicine, as predictors of approaching pathophysiological alterations and injury biomarkers that have already taken place.

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.

Spatial and temporal dynamics of HDACs class IIa following mild traumatic brain injury in adult rats

The fundamental role of epigenetic regulatory mechanisms involved in neuroplasticity and adaptive responses to traumatic brain injury (TBI) is gaining increased recognition. TBI-induced neurodegeneration is associated with several changes in the expression-activity of various epigenetic regulatory enzymes, including histone deacetylases (HDACs). In this study, PET/CT with 6-([18F]trifluoroacetamido)-1- hexanoicanilide ([18F]TFAHA) to image spatial and temporal dynamics of HDACs class IIa expression-activity in brains of adult rats subjected to a weight drop model of diffuse, non-penetrating, mild traumatic brain injury (mTBI). The mTBI model was validated by histopathological and immunohistochemical analyses of brain tissue sections for localization and magnitude of expression of heat-shock protein-70 kDa (HSP70), amyloid precursor protein (APP), cannabinoid receptor-2 (CB2), ionized calcium-binding adapter protein-1 (IBA1), histone deacetylase-4 and -5 (HDAC4 and HDAC5). In comparison to baseline, the expression-activities of HDAC4 and HDAC5 were downregulated in the hippocampus, nucleus accumbens, peri-3rd ventricular part of the thalamus, and substantia nigra at 1-3 days post mTBI, and remained low at 7-8 days post mTBI. Reduced levels of HDAC4 and HDAC5 expression observed in neurons of these brain regions post mTBI were associated with the reduced nuclear and neuropil levels of HDAC4 and HDAC5 with the shift to perinuclear localization of these enzymes. These results support the rationale for the development of therapeutic strategies to upregulate expression-activity of HDACs class IIa post-TBI. PET/CT (MRI) with [18F]TFAHA can facilitate the development and clinical translation of unique therapeutic approaches to upregulate the expression and activity of HDACs class IIa enzymes in the brain after TBI.

Roles of m6A modification in neurological diseases

N6-methyladenosine (m6A) methylation modification is one of the most common epigenetic modifications for eukaryotic mRNA. Under the catalytic regulation of relevant enzymes, m6A participates in the body's pathophysiological processes via mediating RNA transcription, splicing, translation, and decay. In the past, we mainly focused on the regulation of m6A in tumors such as hematological tumors, cervical cancer, breast cancer. In recent years, it has been found that m6A is enriched in mRNAs of neurogenesis, cell cycle, and neuron differentiation. Its regulation in the nervous system is gradually being recognized. When the level of m6A modification and the expression levels of relevant enzyme proteins are changed, it will cause neurological dysfunction and participate in the occurrence and conversion of neurological diseases. Recent studies have found that the m6A modification and its associated enzymes were involved in major depressive disorder, Parkinson's disease, Alzheimer's disease, Fragile X syndrome, amyotrophic lateral sclerosis, and traumatic brain injury, and they also play a key role in the development of neurological diseases and many other neurological diseases. This paper mainly reviewed the recent progress of m6A modification-related enzymes, focusing on the impact of m6A modification and related enzyme-mediated regulation of gene expression on the central nervous system diseases, so as to provide potential targets for the prevention of neurological diseases.

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.

Transcriptional Pathology Evolves over Time in Rat Hippocampus after Lateral Fluid Percussion Traumatic Brain Injury

Traumatic brain injury (TBI) causes acute and lasting impacts on the brain, driving pathology along anatomical, cellular, and behavioral dimensions. Rodent models offer an opportunity to study the temporal progression of disease from injury to recovery. Transcriptomic and epigenomic analysis were applied to evaluate gene expression in ipsilateral hippocampus at 1 and 14 days after sham (n = 2 and 4, respectively per time point) and moderate lateral fluid percussion injury (n = 4 per time point). This enabled the identification of dynamic changes and differential gene expression (differentially expressed genes; DEGs) modules linked to underlying epigenetic response. We observed acute signatures associated with cell death, astrocytosis, and neurotransmission that largely recovered by 2 weeks. Inflammation and immune signatures segregated into upregulated modules with distinct expression trajectories and functions. Whereas most down-regulated genes recovered by 14 days, two modules with delayed and persistent changes were associated with cholesterol metabolism, amyloid beta clearance, and neurodegeneration. Differential expression was paralleled by changes in histone H3 lysine residue 4 trimethylation at the promoters of DEGs at 1 day post-TBI, with the strongest changes observed for inflammation and immune response genes. These results demonstrate how integrated genomics analysis in the pre-clinical setting has the potential to identify stage-specific biomarkers for injury and/or recovery. Though limited in scope here, our general strategy has the potential to capture pathological signatures over time and evaluate treatment efficacy at the systems level.

Repeated mild traumatic brain injuries perturb the mitochondrial biogenesis via DNA methylation in the hippocampus of rat

Mitochondrial biogenesis in the brain is impaired in various neurological disorders including traumatic brain injury (TBI). The long-lasting effects of TBI may be, in part, attributed to epigenetic mechanisms such as DNA methylation. However, the role of DNA methylation on regulatory elements of nuclear and mitochondrial genome in mitochondrial biogenesis is not known. We examined the epigenetic regulation of mitochondrial transcription factor A (TFAM), and further probed its implications in mitochondrial dysfunction in the hippocampus of rats subjected to repeated mild TBI (rMTBI) using weight drop injury paradigm. rMTBI-induced hypermethylation at TFAM promoter resulted in deficits in its protein levels in mitochondria after immediate (48 h) and protracted (30 d) time points. Further, rMTBI also caused hypomethylation of mitochondrial DNA (mtDNA) promoters (HSP1 and HSP2), which further culminated into low binding of TFAM. rMTBI-induced changes weakened mitochondrial biogenesis in terms of reduced mtDNA-encoded rRNA, mRNA, and protein levels leading to shortages of ATP. To verify the potential role of mtDNA methylation in rMTBI-induced persistent mitochondrial dysfunction, rMTBI-induced rats were treated with methionine, a methyl donor. Methionine treatment restored the methylation levels on HSP1 and HSP2 resulting in efficient binding of TFAM and normalized the rRNA, mRNA, and protein levels. These findings suggest the crucial role of DNA methylation at nuclear and mitochondrial promoter regions in mitochondrial gene expression and ATP activity in the hippocampus after rMTBI.

Post-traumatic Neuroinflammation: Relevance to Pediatrics

Both detrimental and beneficial effects of post-traumatic neuroinflammation have become a major research focus as they offer the potential for immediate as well as delayed targeted reparative therapies. Understanding the complex interactions of central and peripheral immunocompetent cells as well as their mediators on brain injury and recovery is complicated by the temporal, regional, and developmental differences in their response to injuries. Microglia, the brain-resident macrophages, have become central in these investigations as they serve a major surveillance function, have the ability to react swiftly to injury, recruit various cellular and chemical mediators, and monitor the reparative/degenerative processes. In this review we describe selected aspects of this burgeoning literature, describing the critical role of cytokines and chemokines, microglia, advances in neuroimaging, genetics and fractal morphology analysis, our research efforts in this area, and selected aspects of pediatric post-traumatic neuroinflammation.

DNA methylation under the major depression pathway predicts pediatric quality of life four-month post-pediatric mild traumatic brain injury

BACKGROUND

Major depression has been recognized as the most commonly diagnosed psychiatric complication of mild traumatic brain injury (mTBI). Moreover, major depression is associated with poor outcomes following mTBI; however, the underlying biological mechanisms of this are largely unknown. Recently, genomic and epigenetic factors have been increasingly implicated in the recovery following TBI.

RESULTS

This study leveraged DNA methylation within the major depression pathway, along with demographic and behavior measures (features used in the clinical model) to predict post-concussive symptom burden and quality of life four-month post-injury in a cohort of 110 pediatric mTBI patients and 87 age-matched healthy controls. The results demonstrated that including DNA methylation markers in the major depression pathway improved the prediction accuracy for quality of life but not persistent post-concussive symptom burden. Specifically, the prediction accuracy (i.e., the correlation between the predicted value and observed value) of quality of life was improved from 0.59 (p = 1.20 × 10^-3) (clinical model) to 0.71 (p = 3.89 × 10^-5); the identified cytosine-phosphate-guanine sites were mainly in the open sea regions and the mapped genes were related to TBI in several molecular studies. Moreover, depression symptoms were a strong predictor (with large weights) for both post-concussive symptom burden and pediatric quality of life.

CONCLUSION

This study emphasized that both molecular and behavioral manifestations of depression symptoms played a prominent role in predicting the recovery process following pediatric mTBI, suggesting the urgent need to further study TBI-caused depression symptoms for better recovery outcome.

Medical Comorbidities Associated With Outcomes in Patients With Traumatic Epidural Hematomas

Background

Traumatic brain injury (TBI) is a frequently encountered neurosurgical pathology with significant morbidity and mortality. One such subtype is the epidural hematoma. Literature regarding the effects of comorbidities in TBI and epidural hematomas is limited.

Methodology

This was a single-center retrospective review of 50 consecutive patients admitted to a level two trauma center with epidural hematomas. Patients were identified using an internal trauma database. Patients were included if they were 18 years of age with a diagnosed epidural hematoma. Outcome variables of Glasgow coma scale (GCS), length of stay in the intensive care unit (ICU) and hospital, and requirement of a neurosurgical procedure were analyzed. Identification of the presence of diagnosed comorbidities was performed including common comorbidities such as obesity, diabetes, hypertension, hyperlipidemia, drug use, tobacco use, cancer, psychiatric disease, and renal disease. Correlations were evaluated using two-sided bivariate analysis (p < 0.05).

Results

A total of 50 patients were included for analysis. Significant correlations with a p-value less of than 0.05 were noted in initial GCS and cancer (r = -0.357, p = 0.011), requirements of an intracranial procedure with a history of gastrointestinal disease (r = 0.377, p = 0.007), and younger age (r = -0.306, p = 0.031). Increased ICU length of stay was related to a history of cancer (r = 0.494, p < 0.001), a history of respiratory disease (r = 0.427, p = 0.002), and a history of psychiatric disease (r = 0.297, p = 0.036). Increased hospital length of stay was related to psychiatric disorders (r = 0.285, p = 0.045). Discharge GCS was negatively associated with a history of hypertension (r = -0.374, p = 0.008), tobacco use (r = -0.417, p = 0.003), drug use (r = -0.294, p = 0.037), and history of cancer (r = -0.303, p = 0.032).

Discussion and Conclusions

In our 50 consecutive patient subset, selected comorbidities demonstrated significant relationships with outcome measures of GCS, need for a procedure, and lengths of stay in the hospital and ICU. Obtaining comorbidity information when available from families can better allow the clinician to optimize treatment and educate loved ones about the potential effects of these comorbidities on the overall health of the patient. Understanding these correlations may allow for a better understanding of the systemic effects of the pathophysiology of injury in epidural hematomas.

The Gene Coexpression Analysis Identifies Functional Modules Dynamically Changed After Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, both in adult and pediatric populations. However, the dynamic changes of gene expression profiles following TBI have not been fully understood. In this study, we identified the differentially expressed genes (DEGs) following TBI. Remarkably, Serpina3n, Asf1b, Folr1, LOC100366216, Clec12a, Olr1, Timp1, Hspb1, Lcn2, and Spp1 were identified as the top 10 with the highest statistical significance. The weighted gene coexpression analysis (WGCNA) identified 12 functional modules from the DEGs, which showed specific expression patterns over time and were characterized by enrichment analysis. Specifically, the black and turquoise modules were mainly involved in energy metabolism and protein translation. The green yellow and yellow modules including Hmox1, Mif, Anxa2, Timp1, Gfap, Cd9, Gja1, Pdpn, and Gpx1 were related to response to wounding, indicating that expression of these genes such as Hmox1, Anxa2, and Timp1 could protect the brains from brain injury. The green yellow module highlighted genes involved in microglial cell activation such as Tyrobp, Cx3cr1, Grn, Trem2, C1qa, and Aif1, suggesting that these genes were responsible for the inflammatory response caused by TBI. The upregulation of these genes has been validated in an independent dataset. These results indicated that the key genes in microglia cell activation may serve as a promising therapeutic target for TBI. In summary, the present study provided a full view of the dynamic gene expression changes following TBI.

Progenitor cell therapy for acquired pediatric nervous system injury: Traumatic brain injury and acquired sensorineural hearing loss

While cell therapies hold remarkable promise for replacing injured cells and repairing damaged tissues, cell replacement is not the only means by which these therapies can achieve therapeutic effect. For example, recent publications show that treatment with varieties of adult, multipotent stem cells can improve outcomes in patients with neurological conditions such as traumatic brain injury and hearing loss without directly replacing damaged or lost cells. As the immune system plays a central role in injury response and tissue repair, we here suggest that multipotent stem cell therapies achieve therapeutic effect by altering the immune response to injury, thereby limiting damage due to inflammation and possibly promoting repair. These findings argue for a broader understanding of the mechanisms by which cell therapies can benefit patients.

"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.

YTHDC1 mitigates ischemic stroke by promoting Akt phosphorylation through destabilizing PTEN mRNA

YTH Domain Containing 1 (YTHDC1) is one of the m⁶A readers that is essential for oocyte development and tumor progression. The role of YTHDC1 in neuronal survival and ischemic stroke is unknown. Here, we found that YTHDC1 was unregulated in the early phase of ischemic stroke. Knockdown of YTHDC1 exacerbated ischemic brain injury and overexpression of YTHDC1 protected rats against brain injury. Mechanistically, YTHDC1 promoted PTEN mRNA degradation to increase Akt phosphorylation, thus facilitating neuronal survival in particular after ischemia. These data identify YTHDC1 as a novel regulator of neuronal survival and modulating m⁶A reader YTHDC1 may provide a potential therapeutic target for ischemic stroke.

Precision Medicine in Acute Brain Injury: A Narrative Review

Over the past few years, the concept of personalized medicine has percolated into the management of different neurological conditions. Improving outcomes after acute brain injury (ABI) continues to be a major challenge. Unrecognized individual multiomic variations in addition to multiple interacting processes may explain why we fail to observe comprehensive improvements in ABI outcomes even when applied treatments appear to be beneficial logically. The provision of clinical care based on a multiomic approach may revolutionize the management of traumatic brain injury, delayed cerebral ischemia after subarachnoid hemorrhage, acute ischemic stroke, and several other neurological diseases. The challenge is to incorporate all the information obtained from genomic studies, other omic data, and individual variability into a practical tool that can be used to assist clinical decision-making. The effective execution of such strategies, which is still far away, requires the development of protocols on the basis of these complex interactions and strict adherence to management protocols. In this review, we will discuss various omics and physiological targets to guide individualized patient management after ABI.

Chronic Regulation of miR-124-3p in the Perilesional Cortex after Experimental and Human TBI

Traumatic brain injury (TBI) dysregulates microRNAs, which are the master regulators of gene expression. Here we investigated the changes in a brain-enriched miR-124-3p, which is known to associate with major post-injury pathologies, such as neuroinflammation. RT-qPCR of the rat tissue sampled at 7 d and 3 months in the perilesional cortex adjacent to the necrotic lesion core (aPeCx) revealed downregulation of miR-124-3p at 7 d (fold-change (FC) 0.13, p < 0.05 compared with control) and 3 months (FC 0.40, p < 0.05) post-TBI. In situ hybridization confirmed the downregulation of miR-124-3p at 7 d and 3 months post-TBI in the aPeCx (both p < 0.01). RT-qPCR confirmed the upregulation of the miR-124-3p target Stat3 in the aPeCx at 7 d post-TBI (7-fold, p < 0.05). mRNA-Seq revealed 312 downregulated and 311 upregulated miR-124 targets (p < 0.05). To investigate whether experimental findings translated to humans, we performed in situ hybridization of miR-124-3p in temporal lobe autopsy samples of TBI patients. Our data revealed downregulation of miR-124-3p in individual neurons of cortical layer III. These findings indicate a persistent downregulation of miR-124-3p in the perilesional cortex that might contribute to post-injury neurodegeneration and inflammation.

Epigenetic Regulation of WNT3A Enhancer during Regeneration of Injured Cortical Neurons

Traumatic brain injury is known to reprogram the epigenome. Chromatin immunoprecipitation-sequencing of histone H3 lysine 27 acetylation (H3K27ac) and tri-methylation of histone H3 at lysine 4 (H3K4me3) marks was performed to address the transcriptional regulation of candidate regeneration-associated genes. In this study, we identify a novel enhancer region for induced WNT3A transcription during regeneration of injured cortical neurons. We further demonstrated an increased mono-methylation of histone H3 at lysine 4 (H3K4me1) modification at this enhancer concomitant with a topological interaction between sub-regions of this enhancer and with promoter of WNT3A gene. Together, this study reports a novel mechanism for WNT3A gene transcription and reveals a potential therapeutic intervention for neuronal regeneration.

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.

Epitranscriptomic profiling of N6-methyladenosine-related RNA methylation in rat cerebral cortex following traumatic brain injury

Background

N6-methyladenosine (m6A) is the most prevalent post-transcriptional modification of eukaryotic mRNA. It has been reported that there is a stimulus-dependent regulation of m6A in the mammalian central nervous system in response to sensory experience, learning, and injury. The mRNA m6A methylation pattern in rat cortex after traumatic brain injury (TBI) has not been investigated.

Results

In this study, we conducted a genome-wide profiling of mRNA m6A methylation in rat cortex via methylated RNA immunoprecipitation sequencing (MeRIP-Seq). After TBI, the expressions of METTL14 and FTO were significantly down-regulated in rat cerebral cortex. Using MeRIP-Seq, we identified a total of 2165 significantly changed peaks, of which 1062 were significantly up-regulated and 1103 peaks were significantly down-regulated. These m6A peaks were located across 1850 genes. The analysis of both m6A peaks and mRNA expression revealed that there were 175 mRNA significantly altered methylation and expression levels after TBI. Moreover, it was found that functional FTO is necessary to repair neurological damage caused by TBI but has no effect on the spatial learning and memory abilities of TBI rats by using FTO inhibitor FB23–2.

Conclusion

This study explored the m6A methylation pattern of mRNA after TBI in rat cortex and identified FTO as possible intervention targets in the epigenetic modification of TBI.

The functional roles of IGF-1 variants in the susceptibility and clinical outcomes of mild traumatic brain injury

BACKGROUND

Insulin-like growth factor 1 (IGF-1) is an important pleiotropic hormone that exerts neuroprotective and neuroreparative effects after a brain injury. However, the roles of IGF-1 variants in mild traumatic brain injury (mTBI) are not yet fully understood. This study attempted to elucidate the effects of IGF-1 variants on the risk and neuropsychiatric outcomes of mTBI.

METHODS

Based on 176 recruited mTBI patients and 1517 control subjects from the Taiwan Biobank project, we first compared the genotypic distributions of IGF-1 variants between the two groups. Then, we analyzed associations of IGF-1 variants with neuropsychiatric symptoms after mTBI, including anxiety, depression, dizziness, and sleep disturbances. Functional annotation of IGF-1 variants was also performed through bioinformatics databases.

RESULTS

The minor allele of rs7136446 was over-represented in mTBI patients compared to community-based control subjects. Patients carrying minor alleles of rs7136446 and rs972936 showed more dizziness and multiple neuropsychiatric symptoms after brain injury.

CONCLUSIONS

IGF-1 variants were associated with the risk and neuropsychiatric symptoms of mTBI. The findings highlight the important role of IGF-1 in the susceptibility and clinical outcomes of mTBI.

Methylene Blue Reduces Neuronal Apoptosis and Improves Blood-Brain Barrier Integrity After Traumatic Brain Injury

Objective: To investigate whether methylene blue (MB) treatment can reverse neuronal mitochondrial dysfunction caused by oxygen glucose deprivation/reoxygenation (OGD) injury and then investigate whether MB treatment can reduce neuronal apoptosis and improve blood-brain barrier (BBB) integrity in traumatic brain injury (TBI) animals. Methods: Reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and adenosine triphosphate (ATP) were used to evaluate mitochondrial function. The terminal deoxynucleotidyl transferase-dUTP nick end labeling (TUNEL) assay was used to assess neuronal apoptosis in vitro. TUNEL and immunofluorescence staining for neuronal nuclei (NeuN) were combined to assess neuronal apoptosis in vivo. An Evans blue (EB) permeability assay and brain water content (BWC) were used to measure BBB permeability in vivo. The Morris water maze (MWM), rotarod test, and modified Neurological Severity Score (mNSS) test were employed to assess the prognosis of TBI mice. Results: MB treatment significantly reversed neuronal mitochondrial dysfunction caused by OGD injury. Both in vitro and in vivo, MB treatment reduced neuronal apoptosis and improved BBB integrity. In TBI animals, treatment with MB not only improved cognitive and motor function caused by TBI but also significantly improved overall neurological function. Conclusions: Our findings suggest that MB is a potential candidate for the treatment of TBI. Future research should focus on other therapeutic effects and mechanisms of MB in secondary brain injury.

The 'Omics' of Epigenetic Modulation by Valproic Acid Treatment in Traumatic Brain Injury-What We Know and What the Future Holds

Traumatic brain injury (TBI) is a heterogeneous injury that is a major cause of morbidity and mortality worldwide. Epigenetic modulation through the alteration of cellular acetylation by valproic acid (VPA) administration has shown promise as a novel pharmacological treatment for TBI. It improves clinical outcomes through multiple mechanisms, many of which are still poorly understood. In recent years, omics technologies have emerged as a promising strategy to detect molecular changes at the cellular level. This review highlights the use of these high throughput technologies in advancing the understanding of epigenetic modulation by VPA in TBI. It also describes the future role of omics techniques in developing a point of care test to guide patient selection for VPA administration.

Mitochondria in migraine pathophysiology - does epigenetics play a role?

The approximately three times higher rate of migraine prevalence in women than men may result from the mitochondrial transmission of this disease. Studies with imaging techniques suggest disturbances in mitochondrial metabolism in specific regions of the brain in migraine patients. Migraine shares some clinical features with several mitochondrial diseases and many other disorders include migraine headaches. Epigenetic regulation of mitochondrial DNA (mtDNA) is a matter of debate and there are some conflicting results, especially on mtDNA methylation. Micro RNAs (miRNAs) and long-noncoding RNA (lncRNAs) have been detected in mitochondria. The regulation of the miRNA-lncRNA axis can be important for mitochondrial physiology and its impairment can result in a disease phenotype. Further studies on the role of mitochondrial epigenetic modifications in migraine are needed, but they require new methods and approaches.

Acupuncture for hearing loss after traumatic brain injury: A protocol for systematic review of randomized controlled trial

BACKGROUND

This study aims to systematically assess the effectiveness and safety of acupuncture on hearing loss (HL) after traumatic brain injury (TBI).

METHODS

In this study, the following databases will be retrieved from inception up to the May 1, 2019: PUBMED, EMBASE, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, Allied and Complementary Medicine Database, and Chinese Biomedical Literature Database. All databases will be retrieved without any language restrictions. Two reviewers will independently carry out article selection, data collection, and risk of bias evaluation. Any disagreements will be solved by a third reviewer through discussion.

RESULTS

This study will systematically investigate the effectiveness and safety of acupuncture for treating HL after TBI through evaluating HL assessment, hearing threshold, quality of life, and adverse events.

CONCLUSION

The expected findings of this study will provide latest evidence for assessing the effectiveness and safety of acupuncture for HL after TBI.

ETHICS AND DISSEMINATION

This study is supposed to be published in a peer-reviewed journal. No ethical approval is needed because this study will based on the literature analysis, but not the individual patient.

PROSPERO REGISTRATION NUMBER

PROSPERO CRD42019133417.

Neurotransmitter changes after traumatic brain injury: an update for new treatment strategies

Traumatic brain injury (TBI) is a pervasive problem in the United States and worldwide, as the number of diagnosed individuals is increasing yearly and there are no efficacious therapeutic interventions. A large number of patients suffer with cognitive disabilities and psychiatric conditions after TBI, especially anxiety and depression. The constellation of post-injury cognitive and behavioral symptoms suggest permanent effects of injury on neurotransmission. Guided in part by preclinical studies, clinical trials have focused on high-yield pathophysiologic mechanisms, including protein aggregation, inflammation, metabolic disruption, cell generation, physiology, and alterations in neurotransmitter signaling. Despite successful treatment of experimental TBI in animal models, clinical studies based on these findings have failed to translate to humans. The current international effort to reshape TBI research is focusing on redefining the taxonomy and characterization of TBI. In addition, as the next round of clinical trials is pending, there is a pressing need to consider what the field has learned over the past two decades of research, and how we can best capitalize on this knowledge to inform the hypotheses for future innovations. Thus, it is critically important to extend our understanding of the pathophysiology of TBI, particularly to mechanisms that are associated with recovery versus development of chronic symptoms. In this review, we focus on the pathology of neurotransmission after TBI, reflecting on what has been learned from both the preclinical and clinical studies, and we discuss new directions and opportunities for future work.

The potential roles of dopamine in traumatic brain injury: a preclinical and clinical update

Traumatic brain injury (TBI) is one of the leading causes of death and disability, particularly among the young and the elderly. Several therapeutic options have been investigated, including drug interventions or combinational therapies. Although many drugs have shown promising results in the preclinical stage, all have failed in large clinical trials. Targeting the dopamine system is a novel TBI approach that provides benefits to functional outcomes. TBI could damage the dopaminergic system. Alterations in dopamine levels can impact cellular dysfunction and central nervous system (CNS) inflammation. Experimental evidence suggests that dopamine should be considered a first-line treatment to protect cerebral autoregulation and promote cerebral outcomes in TBI. Furthermore, investigation of dopamine-related genetic factors in relation to injury severity could also be of great significance for promoting TBI treatment. Importantly, various clinical lines of evidence have indicated that many dopamine agonists are beneficial when administered following injury in TBI patients. However, side effects of dopamine treatment prevent their use in TBI treatment, and there is a need for ongoing large, prospective, double-blind randomized controlled trials (RCTs) with these medications by the use of standardized criteria and outcomes to fully understand their effectiveness in this patient group. Here, we review the roles of dopamine in TBI and discuss the role that dopaminergic therapies have in neuroprotective strategies.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

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.

Mitoepigenetics and Neurodegenerative Diseases

Mitochondrial impairment and increased oxidative stress are common features in neurodegenerative disorders, leading researchers to speculate that epigenetic changes in the mitochondrial DNA (mitoepigenetics) could contribute to neurodegeneration. The few studies performed so far to address this issue revealed impaired methylation levels of the mitochondrial regulatory region (D-loop region) in both animal models, postmortem brain regions, or circulating blood cells of patients with Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Those studies also revealed that mtDNA D-loop methylation levels are subjected to a dynamic regulation within the progression of the neurodegenerative process, could be affected by certain neurodegenerative disease-causative mutations, and are inversely correlated with the mtDNA copy number. The methylation levels of other mtDNA regions than the D-loop have been scarcely investigated in human specimens from patients with neurodegenerative disorders or in animal models of the disease, and evidence of impaired methylation levels is often limited to a single study, making it difficult to clarify their correlation with mitochondrial dynamics and gene expression levels in these disorders. Overall, the preliminary results of the studies performed so far are encouraging making mitoepigenetics a timely and attractive field of investigation, but additional research is warranted to clarify the connections among epigenetic changes occurring in the mitochondrial genome, mitochondrial DNA dynamics and gene expression, and the neurodegenerative process.

miR-124-3p is a chronic regulator of gene expression after brain injury

Traumatic brain injury (TBI) initiates molecular and cellular pathologies that underlie post-injury morbidities, including hippocampus-related memory decline and epileptogenesis. Non-coding small RNAs are master regulators of gene expression with the potential to affect multiple molecular pathways. To evaluate whether hippocampal gene expression networks are chronically regulated by microRNAs after TBI, we sampled the dentate gyrus of rats with severe TBI induced by lateral fluid-percussion injury 3 months earlier. Ingenuity pathway analysis revealed 30 upregulated miR-124-3p targets, suggesting that miR-124-3p is downregulated post-TBI (z-score = - 5.146, p < 0.05). Droplet digital polymerase chain reaction (ddPCR) and in situ hybridization confirmed the chronic downregulation of miR-124-3p (p < 0.05). Quantitative PCR analysis of two targets, Plp2 and Stat3, indicated that their upregulation correlated with the miR-124-3p downregulation (r = - 0.647, p < 0.05; r = - 0.629, p < 0.05, respectively). Immunohistochemical staining of STAT3 confirmed the increased protein expression. STRING analysis showed that 9 of the 30 miR-124-3p targets belonged to a STAT3 network. Reactome analysis and data mining connected the targets especially to inflammation and signal transduction. L1000CDS2 software revealed drugs (e.g., importazole, trichostatin A, and IKK-16) that could reverse the observed molecular changes. The translational value of our data was emphasized by in situ hybridization showing chronic post-traumatic downregulation of miR-124-3p in the dentate gyrus of TBI patients. Analysis of another brain injury model, status epilepticus, highlighted the fact that chronic downregulation of miR-124 is a common phenomenon after brain injury. Together, our findings indicate that miR-124-3p is a chronic modulator of molecular networks relevant to post-injury hippocampal pathologies in experimental models and in humans.

Engineering advanced neural tissue constructs to mitigate acute cerebral inflammation after brain transplantation in rats

Stroke, traumatic brain injuries, and other similar conditions often lead to significant loss of functional brain tissue and associated disruption of neuronal signaling. A common strategy for replacing lost neurons is the injection of dissociated neural stem cells or differentiated neurons. However, this method is unlikely to be suitable for replacing large brain cavities, and the resulting distribution of neurons may lack the necessary architecture to support appropriate brain function. Engineered neural tissues may be a viable alternative. Cell death is a prominent concern in neuronal grafting studies, a problem that could be magnified with the transplantation of engineered neural tissues. Here, we examined the effect of one contributor to cell death, acute cerebral inflammation, on neuronal survival after the transplantation of bioengineered constructs based on silk scaffolds. We found evidence of a high degree of inflammation and poor neuronal survival after introducing engineered constructs into the motor cortex of rats. Integrating a corticosteroid (methylprednisolone) into the constructs resulted in significantly improved neuron survival during the acute phase of inflammation. The improved construct survival was associated with decreased markers of inflammation and an anti-inflammatory state of the immune system due to the steroid treatment.

Measuring Histone Deacetylase Inhibition in the Brain

Histone deacetylases (HDACs) represent a family of enzymes that are targets for epigenetic modulation of genomic activity and may be beneficial in the treatment of many diseases, including cancer and central nervous system disorders. In animal models, HDAC inhibitors have neuroprotective, antiepileptogenic, and antidepressant effects. Assaying HDAC activity provides a robust method for identifying HDAC inhibitors and for assessing their effects under various physiological conditions or after pathological insults. In this unit, a simple and sensitive assay for measuring HDAC activity is described. HDAC activity in tissue lysates can be assessed fluorometrically using a Boc-Lys(Ac) HDAC activity kit. HDACs catalyze the deacetylation of the substrate Boc-Lys(Ac)-AMC. Addition of a trypsin-containing developer converts the deacetylated product to a quantifiable fluorophore that can be used both as a screening method to identify putative HDAC inhibitors and to assess the effects of these inhibitors on tissue and animal epigenetic-modulated phenotypes. © 2018 by John Wiley & Sons, Inc.

Impact of Traumatic Brain Injury on Dopaminergic Transmission

Brain trauma is often associated with severe morbidity and is a major public health concern. Even when injury is mild and no obvious anatomic disruption is seen, many individuals suffer disabling neuropsychological impairments such as memory loss, mood dysfunction, substance abuse, and adjustment disorder. These changes may be related to subtle disruption of neural circuits as well as functional changes at the neurotransmitter level. In particular, there is considerable evidence that dopamine (DA) physiology in the nigrostriatal and mesocorticolimbic pathways might be impaired after traumatic brain injury (TBI). Alterations in DA levels can lead to oxidative stress and cellular dysfunction, and DA plays an important role in central nervous system inflammation. Therapeutic targeting of DA pathways may offer benefits for both neuronal survival and functional outcome after TBI. The purpose of this review is to discuss the role of DA pathology in acute TBI and the potential impact of therapies that target these systems for the treatment of TBI.

Different resuscitation strategies and novel pharmacologic treatment with valproic acid in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death in young adults, and effective treatment strategies have the potential to save many lives. TBI results in coagulopathy, endothelial dysfunction, inflammation, cell death, and impaired epigenetic homeostasis, ultimately leading to morbidity and/or mortality. Commonly used resuscitation fluids such as crystalloids or colloids have several disadvantages and might even be harmful when administered in large quantities. There is a need for next-generation treatment strategies (especially in the prehospital setting) that minimize cellular damage, improve survival, and enhance neurological recovery. Pharmacologic treatment with histone deacetylase inhibitors, such as valproic acid, has shown promising results in animal studies of TBI and may therefore be an excellent example of next-generation therapy. This review briefly describes traditional resuscitation strategies for TBI combined with hemorrhagic shock and describes preclinical studies on valproic acid as a new pharmacologic agent in the treatment of TBI. It finally discusses limitations and future directions on the use of histone deacetylase inhibitors for the treatment of TBI.

Biomarkers in traumatic brain injury (TBI): a review

Biomarkers can be broadly defined as qualitative or quantitative measurements that convey information on the physiopathological state of a subject at a certain time point or disease state. Biomarkers can indicate health, pathology, or response to treatment, including unwanted side effects. When used as outcomes in clinical trials, biomarkers act as surrogates or substitutes for clinically meaningful endpoints. Biomarkers of disease can be diagnostic (the identification of the nature and cause of a condition) or prognostic (predicting the likelihood of a person's survival or outcome of a disease). In addition, genetic biomarkers can be used to quantify the risk of developing a certain disease. In the specific case of traumatic brain injury, surrogate blood biomarkers of imaging can improve the standard of care and reduce the costs of diagnosis. In addition, a prognostic role for biomarkers has been suggested in the case of post-traumatic epilepsy. Given the extensive literature on clinical biomarkers, we will focus herein on biomarkers which are present in peripheral body fluids such as saliva and blood. In particular, blood biomarkers, such as glial fibrillary acidic protein and salivary/blood S100B, will be discussed together with the use of nucleic acids (eg, DNA) collected from peripheral cells.