Impact of Age on Plasma Inflammatory Biomarkers in the 6 Months Following Mild Traumatic Brain Injury

The gut-brain axis in traumatic brain Injury: Literature review

Traumatic brain injury (TBI) leads to significant alterations in gut microbiota, which play a crucial role in the mechanisms of injury and recovery. Following TBI, the gut-brain axis (GBA, a complex network involving neuronal, hormonal, and immune pathways) becomes disrupted. This disruption results in dysbiosis (imbalance in gut microbiota), neuroinflammation, and cognitive difficulties. This article briefly updates the link between TBI and GBA and the management of patients with TBI in hospital settings. A comprehensive understanding of the involvement of gut microbiota in regulating metabolic and immune functions will drive significant advancements in the treatment and rehabilitation of individuals affected by TBI.

High-dimensional proteomic analysis for pathophysiological classification of traumatic brain injury

Pathophysiology and outcomes after traumatic brain injury (TBI) are complex and heterogeneous. Current classifications are uninformative about pathophysiology. Proteomic approaches with fluid-based biomarkers are ideal for exploring complex disease mechanisms, because they enable sensitive assessment of an expansive range of processes potentially relevant to TBI pathophysiology. We used novel high-dimensional, multiplex proteomic assays to assess altered plasma protein expression in acute TBI. We analysed samples from 88 participants from the BIO-AX-TBI cohort [n = 38 moderate-severe TBI (Mayo Criteria), n = 22 non-TBI trauma and n = 28 non-injured controls] on two platforms: Alamar NULISA™ CNS Diseases and OLINK® Target 96 Inflammation. Patient participants were enrolled after hospital admission, and samples were taken at a single time point ≤10 days post-injury. Participants also had neurofilament light, GFAP, total tau, UCH-L1 (all Simoa®) and S100B (Millipore) data. The Alamar panel assesses 120 proteins, most of which were previously unexplored in TBI, plus proteins with known TBI specificity, such as GFAP. A subset (n = 29 TBI and n = 24 non-injured controls) also had subacute (10 days to 6 weeks post-injury) 3 T MRI measures of lesion volume and white matter injury (fractional anisotropy). Differential expression analysis identified 16 proteins with TBI-specific significantly different plasma expression. These were neuronal markers (calbindin 2, UCH-L1 and visinin-like protein 1), astroglial markers (S100B and GFAP), neurodegenerative disease proteins (total tau, pTau231, PSEN1, amyloid-beta-42 and 14-3-3γ), inflammatory cytokines (IL16, CCL2 and ficolin 2) and cell signalling- (SFRP1), cell metabolism- (MDH1) and autophagy-related (sequestome 1) proteins. Acute plasma levels of UCH-L1, PSEN1, total tau and pTau231 were correlated with subacute lesion volume. Sequestome 1 was positively correlated with white matter fractional anisotropy, whereas CCL2 was inversely correlated. Neuronal, astroglial, tau and neurodegenerative proteins were correlated with each other, IL16, MDH1 and sequestome 1. Exploratory clustering (k means) by acute protein expression identified three TBI subgroups that differed in injury patterns, but not in age or outcome. One TBI cluster had significantly lower white matter fractional anisotropy than control-predominant clusters but had significantly lower lesion subacute lesion volumes than another TBI cluster. Proteins that overlapped on two platforms had excellent (r > 0.8) correlations between values. We identified TBI-specific changes in acute plasma levels of proteins involved in neurodegenerative disease, inflammatory and cellular processes. These changes were related to patterns of injury, thus demonstrating that processes previously studied only in animal models are also relevant in human TBI pathophysiology. Our study highlights how proteomic approaches might improve classification and understanding of TBI pathophysiology, with implications for prognostication and treatment development.

Unveiling the predictive power of biomarkers in traumatic brain injury: A narrative review focused on clinical outcomes

Traumatic brain injury (TBI) has long-term consequences, including neurodegenerative disease risk. Current diagnostic tools are limited in detecting subtle brain damage. This review explores emerging biomarkers for TBI, including those related to neuronal injury, inflammation, EVs, and ncRNAs, evaluating their potential to predict clinical outcomes like mortality, recovery, and cognitive impairment. It addresses challenges and opportunities for implementing biomarkers in clinical practice, aiming to improve TBI diagnosis, prognosis, and treatment.

An exploratory study on the association between blood-based biomarkers and subacute neurometabolic changes following mild traumatic brain injury

BACKGROUND AND OBJECTIVES

Blood-based biomarkers and advanced neuroimaging modalities such as magnetic resonance spectroscopy (MRS) or diffusion tensor imaging (DTI) have enhanced our understanding of the pathophysiology of mild traumatic brain injury (mTBI). However, there is limited published data on how blood biomarkers relate to neuroimaging biomarkers post-mTBI.

METHODS

To investigate this, 30 patients with mTBI and 21 healthy controls were enrolled. Data was collected at two timepoints postinjury: acute, < 24 h, (blood) and subacute, four-to-six weeks, (blood and imaging). Interleukin (IL) 6 and 10 (inflammation), free thiols (systemic oxidative stress) and neurofilament light (NF-L) (axonal injury) were quantified in plasma. The neurometabolites total N-acetyl aspartate (tNAA) (neuronal energetics), Myo-Inositol (Ins) and total Choline (tCh) (inflammation) and, Glutathione (GSH, oxidative stress) were quantified using MRS.

RESULTS

Concentrations of IL-6 and IL-10 were significantly elevated in the acute phase post-mTBI, while NF-L was elevated only in the subacute phase. Total NAA was lowered in patients with mTBI, although this difference was only nominally significant (uncorrected P < 0.05). Within the patient group, acute IL-6 and subacute tNAA levels were negatively associated (r =  - 0.46, uncorrected-P = 0.01), albeit not at a threshold corrected for multiple testing (corrected-P = 0.17). When age was added as a covariate a significant increase in correlation magnitude was observed (ρ =  - 0.54, corrected-P = 0.03).

CONCLUSION

This study demonstrates potential associations between the intensity of the inflammatory response in the acute phase post-mTBI and neurometabolic perturbations in the subacute phase. Future studies should assess the longitudinal dynamics of blood-based and imaging biomarkers after injury.

Transfusion futility thresholds and mortality in geriatric trauma: Does frailty matter?

BACKGROUND

Data on massive transfusion (MT) in geriatric trauma patients is lacking. This study aims to determine geriatric transfusion futility thresholds (TT) and TT variations based on frailty.

METHODS

Patients from 2013 to 2018 TQIP database receiving MT were stratified by age and frailty. TTs and outcomes were compared between geriatric and younger adults and among geriatric adults based on frailty status.

RESULTS

The TT was lower for geriatric than younger adults (34 vs 39 units; p ​= ​0.03). There was no difference in TT between the non-frail, frail, and severely frail geriatric adults (37, 30 and 25 units, respectively, p ​> ​0.05). Geriatric adults had higher mortality than younger adults (63.1% vs 45.8%, p < 0.01). Non-frail geriatric adults had the highest mortality (69.4% vs 56.5% vs 56.2%, p < 0.01).

CONCLUSIONS

Geriatric patients have a lower TT than younger adults, irrespective of frailty. This may help improve outcomes and optimize MT utilization.

A Systematic Review and Meta-Analysis of the Inflammatory Biomarkers in Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) accounts for most TBI cases, the leading cause of morbidity and mortality worldwide. Despite its high incidence, mTBI pathophysiology remains largely unknown. Recent studies have shown that the inflammatory response is activated early after mTBI and can persist for several weeks or months. However, limited evidence on the utility of inflammatory biomarkers as predictors of clinical outcomes in mTBI has been previously provided. Thus, this systematic review and meta-analysis aims to provide an overview of the current knowledge on the role of inflammation in the pathogenesis of mTBI and the potential of some inflammatory biomolecules as biomarkers of mTBI. In this regard, eight studies comprising 1184 individuals were selected. Thus, it was shown that the increase in IL-6, TNF-α, and IL-1β plasma levels could be implicated in the development of early post-concussion symptoms. On the other hand, the persistence of the increased plasmatic concentrations of IL-10 and IL-8 for as long as six months following the brain injury event could suggest chronic inflammation leading to neuroinflammation and late or persistent symptoms. In this context, our findings showed that inflammatory biomarkers could be relevant in diagnosing or predicting recovery or long-term outcomes of mTBI.

Inflammation biomarkers IL‑6 and IL‑10 may improve the diagnostic and prognostic accuracy of currently authorized traumatic brain injury tools

Traumatic brain injury (TBI) is currently one of the leading causes of mortality and disability worldwide. At present, no reliable inflammatory or specific molecular neurobiomarker exists in any of the standard models proposed for TBI classification or prognostication. Therefore, the present study was designed to assess the value of a group of inflammatory mediators for evaluating acute TBI, in combination with clinical, laboratory and radiological indices and prognostic clinical scales. In the present single-centre, prospective observational study, 109 adult patients with TBI, 20 adult healthy controls and a pilot group of 17 paediatric patients with TBI from a Neurosurgical Department and two intensive care units of University General Hospital of Heraklion, Greece were recruited. Blood measurements using the ELISA method, of cytokines IL-6, IL-8 and IL-10, ubiquitin C-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein, were performed. Compared with those in healthy control individuals, elevated IL-6 and IL-10 but reduced levels of IL-8 were found on day 1 in adult patients with TBI. In terms of TBI severity classifications, higher levels of IL-6 (P=0.001) and IL-10 (P=0.009) on day 1 in the adult group were found to be associated with more severe TBI according to widely used clinical and functional scales. Moreover, elevated IL-6 and IL-10 in adults were found to be associated with more serious brain imaging findings (rs<0.442; P<0.007). Subsequent multivariate logistic regression analysis in adults revealed that early-measured (day 1) IL-6 [odds ratio (OR)=0.987; P=0.025] and UCH-L1 (OR=0.993; P=0.032) are significant independent predictors of an unfavourable outcome. In conclusion, results from the present study suggest that inflammatory molecular biomarkers may prove to be valuable diagnostic and prognostic tools for TBI.

Inflammatory cytokines associated with mild traumatic brain injury and clinical outcomes: a systematic review and meta-analysis

Mild traumatic brain injuries (mTBIs) trigger a neuroinflammatory response, which leads to perturbations in the levels of inflammatory cytokines, resulting in a distinctive profile. A systematic review and meta-analysis were conducted to synthesize data related to levels of inflammatory cytokines in patients with mTBI. The electronic databases EMBASE, MEDLINE, and PUBMED were searched from January 2014 to December 12, 2021. A total of 5,138 articles were screened using a systematic approach based on the PRISMA and R-AMSTAR guidelines. Of these articles, 174 were selected for full-text review and 26 were included in the final analysis. The results of this study demonstrate that within 24 hours, patients with mTBI have significantly higher levels of Interleukin-6 (IL-6), Interleukin-1 Receptor Antagonist (IL-1RA), and Interferon-γ (IFN-γ) in blood, compared to healthy controls in majority of the included studies. Similarly one week following the injury, patients with mTBI have higher circulatory levels of Monocyte Chemoattractant Protein-1/C-C Motif Chemokine Ligand 2 (MCP-1/CCL2), compared to healthy controls in majority of the included studies. The results of the meta-analysis also confirmed these findings by demonstrating significantly elevated blood levels of IL-6, MCP-1/CCL2, and Interleukin-1 beta (IL-1β) in the mTBI population compared to healthy controls (p < 0.0001), particularly in the acute stages (<7 days). Furthermore, it was found that IL-6, Tumor Necrosis Factor-alpha (TNF-α), IL-1RA, IL-10, and MCP-1/CCL2 were associated with poor clinical outcomes following the mTBI. Finally, this research highlights the lack of consensus in the methodology of mTBI studies that measure inflammatory cytokines in the blood, and also provides direction for future mTBI research.

Potential Biomarkers of Impulsivity in Mild Traumatic Brain Injury: A Pilot Study

Very few studies have investigated cognition and impulsivity following mild traumatic brain injury (mTBI) in the general population. Furthermore, the neurobiological mechanisms underlying post-TBI neurobehavioral syndromes are complex and remain to be fully clarified. Herein, we took advantage of machine learning based-modeling to investigate potential biomarkers of mTBI-associated impulsivity. Twenty-one mTBI patients were assessed within one-month post-TBI and their data were compared to 19 healthy controls on measures of impulsivity (Barratt Impulsiveness Scale - BIS), executive functioning, episodic memory, self-report cognitive failures and blood biomarkers of inflammation, vascular and neuronal damage. mTBI patients were significantly more impulsive than controls in BIS total and subscales. Serum levels of sCD40L, Cathepsin D, IL-4, Neuropilin-1, IFN-α2, and Copeptin were associated with impulsivity in mTBI patients. Besides showing that mTBI are associated with impulsivity in non-military people, we unveiled different pathophysiological pathways potentially implicated in mTBI-related impulsivity.

Potential Progression Mechanism and Key Genes in Early Stage of mTBI

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease caused by repetitive mild traumatic brain injury (rmTBI), and the lack of sensitive diagnostic and prognostic biomarkers for rmTBI leads to long-term sequelae after injury. The purpose of this study is to identify key genes of rmTBI and find the potential progression mechanism in early stage of mTBI. We downloaded the gene expression profiles of GSE2871 from Gene Expression Omnibus (GEO) datasets. Differentially expressed genes (DEGs) were screened from the cerebral cortex of rats 24 hours after smTBI, and these DEGs were then subjected to GO enrichment analysis, KEGG pathway analysis, PPI analysis, and hub analysis. Key genes were identified as the most significantly expressed genes and had a higher degree of connectivity from hub genes. By using homemade metal pendulum impact equipment and a multiple regression discriminant equation to assess the severity of rats after injury, smTBI and rmTBI rat models were established in batches, and q-PCR analyses were performed to verify the key genes. The main KEGG pathways were cytokine-cytokine receptor interaction and neuroactive ligand-receptor interaction. SPP1 and C3 were the most significant DEGs, and their connectivity degree was the highest 24 hours after smTBI (logFC > 4; connectivity degree ＞15). The q-PCR analyses were performed 24 hours and 14 days after mTBI. The results showed that SPP1 and C3 were significantly upregulated in smTBI and in rmTBI at 24 hours after injury compared with their levels in sham-injured rats, and the phenomenon persisted 14 days after injury. Notably, 14 days after injury, both of these genes were significantly upregulated in the rmTBI group compared with the smTBI. These pathways and genes identified could help understanding the development in mTBI.

Biomarkers of Neuroinflammation in Traumatic Brain Injury

Traumatic brain injury (TBI) is characterized by neuroinflammation and structural damage leading to symptoms and altered brain function. Biomarkers are useful in understanding neuroinflammation and correlations with TBI sequalae. The purpose of this paper is to identify and discuss biomarkers of neuroinflammation used to study TBI and its sequalae. A systematic review was conducted using PubMed, CINAHL, Embase, and Web of Science. A total of 350 articles met criteria; 70 used biomarkers. PRISMA criteria were used for Quality Assessment. Articles included reviews (n = 17), case-control (n = 25), cross-sectional (n = 25) studies, and randomized controlled trials (n = 3). Twenty-seven biomarkers were identified, including inflammasomes, cytokines, neuropeptides, complement complexes, miRNA and exosomes, and glial cell-specific proteins. Biomarkers aid in predicting morbidity and mortality and advance our understanding of neuroinflammation in TBI. This systematic review advances our understanding of the neuroinflammatory response to better enable nurses and clinicians to provide informed care of TBI patients.

Role of Inflammation in Traumatic Brain Injury-Associated Risk for Neuropsychiatric Disorders: State of the Evidence and Where Do We Go From Here

In the past decade, there has been an increasing awareness that traumatic brain injury (TBI) and concussion substantially increase the risk for developing psychiatric disorders. Even mild TBI increases the risk for depression and anxiety disorders such as posttraumatic stress disorder by two- to threefold, predisposing patients to further functional impairment. This strong epidemiological link supports examination of potential mechanisms driving neuropsychiatric symptom development after TBI. One potential mechanism for increased neuropsychiatric symptoms after TBI is via inflammatory processes, as central nervous system inflammation can last years after initial injury. There is emerging preliminary evidence that TBI patients with posttraumatic stress disorder or depression exhibit increased central and peripheral inflammatory markers compared with TBI patients without these comorbidities. Growing evidence has demonstrated that immune signaling in animals plays an integral role in depressive- and anxiety-like behaviors after severe stress or brain injury. In this review, we will 1) discuss current evidence for chronic inflammation after TBI in the development of neuropsychiatric symptoms, 2) highlight potential microglial activation and cytokine signaling contributions, and 3) discuss potential promise and pitfalls for immune-targeted interventions and biomarker strategies to identify and treat TBI patients with immune-related neuropsychiatric symptoms.

Correlation between Mild Traumatic Brain Injury-Induced Inflammatory Cytokines and Emotional Symptom Traits: A Systematic Review

Both mild traumatic brain injuries (mTBI) and systemic injuries trigger a transient neuroinflammatory response that result in similar clinical outcome. The ensuing physical, cognitive, and emotional symptoms fail to subside in approximately 15–20% of the concussed population. Emotional impairments, particularly depression, anxiety, and post-traumatic stress disorder (PTSD), are commonly associated with poor recovery following mTBI. These emotional impairments also have a significant neuroinflammatory component. We hypothesized that the inflammatory cytokines seen in mTBI patients with emotional symptoms would coincide with those commonly seen in patients with emotional symptoms without mTBI. A systematic review was conducted to identify the most common neuroinflammatory cytokines in the mTBI population with psychological symptoms (depression, anxiety, PTSD). The electronic databases EMBASE, MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), PUBMED, and PSYCINFO were searched from data inception to 31 August 2021. A systematic screening approach was employed from screening to data analysis. A total of 994 articles were screened, 108 were selected for full article review, and 8 were selected for data analysis. The included studies consisted of 875 patients of which 81.3% were male. The mean sample size of patients with at least one mTBI was 73.8 ± 70.3 (range, 9–213), with a mean age of 33.9 ± 4.8 years. The most common cytokines associated with poor psychological outcomes involving PTSD and/or depression in the chronic mTBI population were IL-6, TNFα, IL-10, and CRP.

Blood-based biomarkers of inflammation in mild traumatic brain injury: A systematic review

VISSER, K., M. Koggel, J. Blaauw, H.J.v.d. Horn, B. Jacobs, and J.v.d. Naalt. Blood based biomarkers of inflammation in mild traumatic brain injury: A systematic review. NEUROSCI BIOBEHAV REV XX(X) XXX-XXX, 2021. - Inflammation is an important secondary physiological response to traumatic brain injury (TBI). Most of the current knowledge on this response is derived from research in moderate and severe TBI. In this systematic review we summarize the literature on clinical studies measuring blood based inflammatory markers following mild traumatic brain injury (mTBI) and identify the value of inflammatory markers as biomarkers. Twenty-three studies were included. This review suggests a distinct systemic inflammatory response following mTBI, quantifiable within 6 h up to 12 months post-injury. Interleukin-6 is the most promising biomarker for the clinical diagnosis of brain injury while interleukin-10 is a potential candidate for triaging CT scans. The diagnostic and prognostic utility of inflammatory markers may be more fully appreciated as a component of a panel of biomarkers. However, discrepancies in study design, analysis and reporting make it difficult to draw any definite conclusions. For the same reasons, a meta-analysis was not possible. We provide recommendations to follow standardized methodologies to allow for reproducibility of results in future studies.

Aging with Traumatic Brain Injury: Deleterious Effects of Injury Chronicity Are Most Pronounced in Later Life

Understanding the effects of age on longitudinal traumatic brain injury (TBI) outcomes requires attention to both chronic and evolving TBI effects and age-related changes in health and function. The present study examines the independent and interactive effects of aging and chronicity on functional outcomes after TBI. We leveraged a well-defined cohort of individuals who sustained a moderate/severe TBI and received acute inpatient rehabilitation at specialized centers with high follow up rate as part of their involvement in the TBI Model Systems longitudinal study. We selected individuals at one of two levels of TBI chronicity (either 2 or 10 years post-injury) and used an exact matching procedure to obtain balanced chronicity groups based on age and other characteristics (N = 1993). We found that both older age and greater injury chronicity were related to greater disability, reduced functional independence, and less community participation. There was a significant age by chronicity interaction, indicating that the adverse effects of greater time post-injury were most pronounced among survivors who were age 75 or older. The inflection point at roughly 75 years of age was corroborated by post hoc analyses, dividing the sample by age at 75 years and examining the interaction between age group and chronicity. These findings point to a need for provision of rehabilitation services in the chronic injury period, particularly for those who are over 75 years old. Future work should investigate the underlying mechanisms of this interaction towards the goal of developing interventions and models of care to promote healthy aging with TBI.

Systemic inflammation alters the neuroinflammatory response: a prospective clinical trial in traumatic brain injury

Background

Neuroinflammation following traumatic brain injury (TBI) has been shown to be associated with secondary injury development; however, how systemic inflammatory mediators affect this is not fully understood. The aim of this study was to see how systemic inflammation affects markers of neuroinflammation, if this inflammatory response had a temporal correlation between compartments and how different compartments differ in cytokine composition.

Methods

TBI patients recruited to a previous randomised controlled trial studying the effects of the drug anakinra (Kineret®), a human recombinant interleukin-1 receptor antagonist (rhIL1ra), were used (n = 10 treatment arm, n = 10 control arm). Cytokine concentrations were measured in arterial and jugular venous samples twice a day, as well as in microdialysis-extracted brain extracellular fluid (ECF) following pooling every 6 h. C-reactive protein level (CRP), white blood cell count (WBC), temperature and confirmed systemic clinical infection were used as systemic markers of inflammation. Principal component analyses, linear mixed-effect models, cross-correlations and multiple factor analyses were used.

Results

Jugular and arterial blood held similar cytokine information content, but brain-ECF was markedly different. No clear arterial to jugular gradient could be seen. No substantial delayed temporal associations between blood and brain compartments were detected. The development of a systemic clinical infection resulted in a significant decrease of IL1-ra, G-CSF, PDGF-ABBB, MIP-1b and RANTES (p < 0.05, respectively) in brain-ECF, even if adjusting for injury severity and demographic factors, while an increase in several cytokines could be seen in arterial blood.

Conclusions

Systemic inflammation, and infection in particular, alters cytokine levels with different patterns seen in brain and in blood. Cerebral inflammatory monitoring provides independent information from arterial and jugular samples, which both demonstrate similar information content. These findings could present potential new treatment options in severe TBI patients, but novel prospective trials are warranted to confirm these associations.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02264-2.