GFAP and S100B: What You Always Wanted to Know and Never Dared to Ask

Exploratory randomised trial of tranexamic acid to decrease postoperative delirium in adults undergoing lumbar fusion-a trial stopped early

Background

Postoperative delirium may be mediated by systemic inflammation and neuroinflammation. By inhibiting the proinflammatory actions of plasmin, tranexamic acid (TXA) may decrease postoperative delirium. To explore this hypothesis, we modified an ongoing randomised trial of TXA on blood loss, adding measures of delirium, cognition, systemic inflammation, and astrocyte activation.

Methods

Adults undergoing elective posterior lumbar fusion randomly received intraoperative i.v. TXA (n=43: 10 mg kg-1 loading dose, 2 mg kg-1 h-1 infusion) or placebo (n=40). Blood was collected before surgery and 24 h after surgery (n=32) for biomarkers (cytokines and S100B). Participants had twice daily delirium assessments (n=65). Participants underwent four measures of cognitive function before surgery and during post-discharge follow-up.

Results

Postoperative blood loss was ∼38% less in the TXA group compared with the placebo group with medians of 128 and 207 ml level-1, respectively, P=0.013. Total blood loss in the TXA and placebo groups did not differ with medians of 305 and 333 ml level-1, respectively, P=0.472. Delirium incidence in the TXA group (7/32=22%) was not significantly less than in the placebo group (11/33=33%); P=0.408, effect size =-0.258 (95% confidence interval -0.744 to 0.229).

Conclusions

A potential 33% relative decrease in postoperative delirium incidence justifies an adequately powered clinical trial to determine if intraoperative TXA decreases delirium in adults undergoing lumbar fusion.

Clinical trial registration

NCT04272606.

Neuroinflammatory fluid biomarkers in patients with Alzheimer's disease: a systematic literature review

INTRODUCTION

Neuroinflammation is associated with both early and late stages of the pathophysiology of Alzheimer's disease (AD). Fluid biomarkers are gaining significance in clinical practice for diagnosis in presymptomatic stages, monitoring, and disease prognosis. This systematic literature review (SLR) aimed to identify fluid biomarkers for neuroinflammation related to clinical stages across the AD continuum and examined long-term outcomes associated with changes in biomarkers.

METHODS

The SLR was conducted per the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We used PubMed®, Embase®, and Cochrane Collaboration databases to search for articles in English (between 2012 and 2022) on AD or mild cognitive impairment due to AD, using "neuroinflammation" or other "immune" search strings. Two independent reviewers screened titles and examined data from full-text articles for the SLR.

RESULTS

After the initial screening, 54 studies were prioritized for data extraction based upon their relevance to the SLR research questions. Nine studies for YKL-40, seven studies for sTREM2, and 11 studies for GFAP examined the relationship between the neuroinflammatory biomarkers and the clinical stage of the disease. Nine longitudinal studies further explored the association of fluid biomarkers with long-term clinical outcomes of disease. Cerebrospinal fluid (CSF) levels of YKL-40 were elevated in patients with AD dementia, while CSF sTREM2 levels were more strongly associated with preclinical and early symptomatic stages of AD. Plasma GFAP levels remained consistently elevated both in patients with AD dementia and individuals in preclinical stages with β-amyloid pathology. Longitudinal changes in plasma GFAP appeared to be predictive of cognitive decline in patients over time.

DISCUSSION

Neuroinflammatory biomarkers are associated with AD progression. More longitudinal studies in the preclinical and MCI stages of AD are needed to validate fluid biomarkers for diagnosis, disease monitoring, and prognosis in clinical practice.

Prognostic Value of Blood-Based Protein Biomarkers in Traumatic Brain Injury: A Living Systematic Review and Meta-Analysis

Circulating biomarkers might improve the prediction of outcomes in patients with traumatic brain injury (TBI) beyond current approaches. Robust and up-to-date evidence is required to support their clinical utility and integration into medical practice to guide decision-making. Our objective was to critically appraise the existing evidence for six core blood-based TBI biomarkers (S100 calcium-binding protein B, glial fibrillary acidic protein [GFAP], neuron-specific enolase, ubiquitin C-terminal hydrolase-L1 [UCH-L1], tau and neurofilament proteins), in predicting outcome after TBI. Electronic databases, including Medline and Embase, were searched for articles published from their inception to October 2023. Studies were included if they evaluated the accuracy of blood biomarker concentrations at hospital presentation for outcome prediction in adult patients with TBI. Outcomes assessed were mortality, Glasgow Outcome Scale (GOS)/GOS extended (GOS-E), or the Rivermead Post-Concussion Symptoms Questionnaire (RPQ). Study selection, data extraction, and quality assessment using the modified Quality Assessment of Prognostic Accuracy Studies tool were performed by two authors independently, with disagreements being resolved through discussion or arbitration. If appropriate, a meta-analysis was conducted by calculating the weighted summary area under the curve (AUC) and using a bivariate regression model. Of 12,792 retrieved records, 32 articles, including 7481 patients with TBI, were selected as relevant. Two biomarkers showed strong associations with in-hospital and 6-month mortality: GFAP (unadjusted pooled AUC 0.81 [95% confidence interval [CI] 0.75-0.87] and 0.82 [0.80-0.85], respectively) and UCH-L1 (0.80 [0.74-0.85] and 0.83 [0.77-0.88]). Their addition to models that included established risk factors consistently improved the predictive value, though models and performance varied substantially across studies. In four studies measuring both markers, UCH-L1 outperformed GFAP in improving risk stratification when added to established prediction models. At ∼1.5 ng/mL (five studies), the summary sensitivity of GFAP for predicting mortality was 78% (95% CI 67-85%), and the summary specificity was 79% (95% CI 64-89%). The other assessed biomarkers had fair to good performance in mortality prediction with unclear added benefits. Neurofilament light (NfL) (three studies) demonstrated the strongest association in predicting a 6-month poor outcome (GOS-E ≤4; GOS ≤3) (unadjusted pooled AUC 0.81 [95% CI 0.75-0.87]), whereas the other assessed biomarkers had a fair performance with unclear or irrelevant added value. All core biomarkers had only marginal or no association with incomplete recovery and post-concussion symptoms/syndrome, as assessed by RPQ. Serious problems were found in the design and analysis of many of the studies. We conclude that admission measurements of core blood TBI biomarkers, in particular GFAP and UCH-L1, are strongly associated with mortality. There remains little evidence that any of these markers are ready for clinical implementation for prognostic purposes. Future work focused on the intended use and applying unbiased rigorous analysis methods is necessary to demonstrate that the biomarker test results are "prognostically actionable."

Volume Loss in the Mammillary Bodies, Fornix, and Other Papez Circuit Structures in Fighters with Traumatic Encephalopathy Syndrome

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder that can only be diagnosed on autopsy. Traumatic encephalopathy syndrome (TES) is a proposed diagnostic framework for the clinical syndrome of CTE that is based on patient history and clinical examination. Given that mammillary body and fornix volume loss has been demonstrated in CTE and is measurable on MRI, this study aims to investigate the relationship between TES status and in vivo mammillary body and fornix volumes to support the role of these structures as imaging biomarkers for TES. Additionally, associations with other structures of the Papez circuit and relevant cognitive tests were explored. This observational cohort study used data from a subset of fighters and control participants in the Professional Athletes Brain Health Study (PABHS). The relationship was examined between clinical groups (controls, TES-negative fighters, and TES-positive fighters) and automated measurements of mammillary body and fornix size. Manual measurements were also performed to confirm the automated results and demonstrate clinical relevance. Associations were assessed between mammillary body/fornix size, cognitive scores, and volumes of other structures including components of the Papez circuit. The sample consisted of 177 individuals (61 controls, 46 TES-positive fighters, and 70 TES-negative fighters). Automated measurements of mammillary body volumes were on average ∼7.6 mm3 (15%) smaller in TES-positive fighters than in TES-negative fighters and controls (p < 0.001 for both). Automated measurements of fornix volumes were on average 110.5 mm3 (24%) smaller in TES-positive fighters than in TES-negative fighters and 156.5 mm3 (29%) smaller in TES-positive fighters than in controls (p < 0.001 for both). Similar findings were observed with manual measurements. Decreased mammillary body and fornix size were associated with lower volumes in the other components of the Papez circuit/associated structures (p < 0.01 for all) and worse psychomotor (p = 0.001 for both) and memory (p < 0.001 for both) scores. This decrease in mammillary body and fornix size among TES-positive fighters suggests that increased exposure to repetitive head impacts damages these structures, and that imaging assessment of the mammillary bodies and fornix is a feasible biomarker to support the diagnosis of TES.

Association of blood biomarkers for neural injury with recent, frequent exposure to partnered sexual strangulation in young adult women

BACKGROUND

"Choking" or partnered strangulation is an emerging and popular sexual behavior that is more often experienced by young women, yet the neurobiological consequences of partnered sexual strangulation remain unclear.

AIM

The aim of the present study was to assess differences in 5 brain-injury blood biomarkers in young adult women who frequently engaged in sexual strangulation.

METHODS

Young adult women were recruited from a large Midwestern university and assigned to groups based on sexual strangulation experience: (1) at least 4 instances of being strangled by a partner during sexual activities in the past 30 days or (2) no prior experience being strangled by a sexual partner. Choking/strangulation history during partnered sexual activities was assessed using a self-report questionnaire. Blood samples were collected via venipuncture. Data from 32 female participants (median 21.5 years old [IQR 20-24]) were available for analysis: 15 with a history of recent, frequent partnered strangulation exposure and 17 without any history of partnered sexual strangulation.

OUTCOMES

Serum levels of 5 blood biomarkers for brain injury were measured using sandwich enzyme-linked immunosorbent assay (S100B) and single-molecule array digital immunoassay (neurofilament light, tau, ubiquitin C-terminal hydrolase L1, and glial fibrillary acidic protein).

RESULTS

Group differences for the 5 biomarkers were examined using 1-way multivariate analysis of covariance, adjusting for age and alcohol use. We observed a significant multivariate effect of group, Pillai's trace = 0.485, F(5, 24) = 4.235, P = .007, η2 = 0.47. Univariate results indicated that female college students who were recently, frequently strangled during partnered sexual activities exhibited elevated S100B levels compared to their peers who had never engaged in this partnered sexual behavior, F(1,28) = 11.165, P = .002, η2 = 0.29.

CLINICAL IMPLICATIONS

Engaging in this partnered sexual behavior may elicit neuroinflammation, with unknown long-term consequences for brain health.

STRENGTHS AND LIMITATIONS

Strengths include the recruitment of a novel population, as this investigation was the first of its kind to examine neurobiological correlates of repetitive exposure to partnered sexual strangulation. Another strength is the panel of 5 blood biomarkers that were assessed, providing information from multiple cell types and pathophysiological processes. Limitations were the relatively small sample size and the cross-sectional design, which prevents causal inference.

CONCLUSION

Young adult women with a history of recent, frequent experience being strangled by a sexual partner exhibited higher serum S100B, an astrocyte-enriched protein, compared to their biomarkers, meriting future work to determine a causal mechanism between partnered sexual strangulation and neuroinflammatory processes.

Sensory driven neurophysiological mechanisms of concussion: a parsimonious and falsifiable theory

Every time a person sustains a blow to the head, they receive multiple atypical sensory inputs, often including pain. These directly stimulate the central nervous system. Yet, sensory input as a causal agent of neurophysiological dysfunction and post-concussion symptoms has never been explored. A new theory is proposed of sensory driven neurophysiological mechanisms of concussion (i) which are causally linked to the momentary blow to the head, (ii) whose time courses and other properties correspond to those observed to date for acute, sub-acute, and chronic symptoms, and (iii) which give rise to testable questions with experimentally measurable consequences. The primary assertion of the theory is that trauma induced excitation of key brain regions including the salience network (SN) and locus coeruleus (LC) can produce persistent dysfunctional alterations in the stable patterns of network excitability on which symptom-free neurological function depends. This mechanism is in play with any physical trauma, with or without a blow to the head. That is because atypical, painful, and otherwise high intensity sensory stimuli excite the SN and thence the LC, inducing plasticity widely in the brain. Many of those sensory stimuli may persist through the recovery period and while the brain is plastic, enable one or another network to learn altered and potentially dysfunctional patterns of network excitability. The secondary assertion of the theory is that with a blow to the head, convergence of high-intensity sensory stimuli within the brainstem and midbrain can cause neurophysiological coupling between brainstem nuclei which normally function independently, i.e. brainstem crosstalk (BCT). It is BCT which causes the signs and symptoms specific to head trauma, e.g., loss of consciousness, and oculomotor and vestibular dysfunction. The theory's reliance on sensory input emphasizes the importance of putative mechanisms whose initiating cause is known to have been present for every head trauma. This is in contrast to the century-long focus on mechanisms whose initiating cause, brain injury, is undetectable by clinical exam, neuroimaging, and bioassay in fully 60% of all head trauma, i.e., 70-75% of all mild TBI. As formulated and described, the theory is readily testable and falsifiable.

Potential Correlation Between Molecular Biomarkers and Oxidative Stress in Traumatic Brain Injury

Diagnosing traumatic brain injury (TBI) remains challenging due to an incomplete understanding of its neuropathological mechanisms. TBI is recognised as a complex condition involving both primary and secondary injuries. Although oxidative stress is a non-specific molecular phenomenon observed in various neuropathological conditions, it plays a crucial role in brain injury response and recovery. Due to these aspects, we aimed to evaluate the interaction between some known TBI molecular biomarkers and oxidative stress in providing evidence for its possible relevance in clinical diagnosis and outcome prediction. We found that while many of the currently validated molecular biomarkers interact with oxidative pathways, their patterns of variation could assist the diagnosis, prognosis, and outcomes prediction in TBI cases.

Exploiting blood-based biomarkers to align preclinical models with human traumatic brain injury

Rodent models are important research tools for studying the pathophysiology of traumatic brain injury (TBI) and developing new therapeutic interventions for this devastating neurological disorder. However, the failure rate for the translation of drugs from animal testing to human treatments for TBI is 100%. While there are several potential explanations for this, previous clinical trials have relied on extrapolation from preclinical studies for critical design considerations, including drug dose optimization, post-injury drug treatment initiation and duration. Incorporating clinically relevant biomarkers in preclinical studies may provide an opportunity to calibrate preclinical models to identical (or similar) measurements in humans, link to human TBI biomechanics and pathophysiology, and guide therapeutic decisions. To support this translational goal, we conducted a systematic literature review of preclinical TBI studies in rodents measuring blood levels of clinically used GFAP, UCH-L1, NfL, total-Tau (t-Tau) or phosphorylated-Tau (p-Tau) published in PubMed/EMBASE up to 10 April 2024. Although many factors influence clinical TBI outcomes, many of those cannot routinely be assessed in rodent studies (e.g. intracranial pressure monitoring). Thus we focused on blood biomarkers' temporal trajectories and discuss our findings in the context of the latest clinical TBI biomarker data. Of 805 original preclinical studies, 74 met the inclusion criteria, with a median quality score of 5 (25th-75th percentiles: 4-7) on the CAMARADES checklist. GFAP was measured in 43 studies, UCH-L1 in 21, NfL in 20, t-Tau in 19 and p-Tau in seven. Data from rodent models indicate that all biomarkers exhibited injury severity-dependent elevations with distinct temporal profiles. GFAP and UCH-L1 peaked within the first day after TBI (30- and 4-fold increases, respectively, in moderate-to-severe TBI versus sham), with the highest levels observed in the contusion TBI model. NfL peaked within days (18-fold increase) and remained elevated up to 6 months post-injury. GFAP and NfL show a pharmacodynamic response in 64.7% and 60%, respectively, of studies evaluating neuroprotective therapies in preclinical models. However, GFAP's rapid decline post-injury may limit its utility for understanding the response to new therapeutics beyond the hyperacute phase after experimental TBI. Furthermore, as in humans, subacute NfL levels inform on chronic white matter loss after TBI. t-Tau and p-Tau levels increased over weeks after TBI (up to 6- and 16-fold, respectively); however, their relationship with underlying neurodegeneration has yet to be addressed. Further investigation into biomarker levels in the subacute and chronic phases after TBI will be needed to fully understand the pathomechanisms underpinning blood biomarkers' trajectories and select the most suitable experimental model to optimally relate preclinical mechanistic studies to clinical observations in humans. This new approach could accelerate the translation of neuroprotective treatments from laboratory experiments to real-world clinical practices.

Changes in molecular biomarkers of neurotoxicity in newborns following prenatal exposure to organophosphate compounds

The rising incidence of neurodevelopmental disorders has been associated with early-life exposure to environmental factors, particularly neurotoxicants like organophosphate compounds (OPCs), which can impact brain development and function. This study examined the relationship between prenatal exposure to OPCs and molecular biomarkers of neurotoxicity in cord blood from 398 mother-child pairs in the GENEIDA birth cohort (Southeastern Spain). Urine samples were collected in the first and third trimesters and analysed for metabolites of organophosphate pesticides (dialkylphosphates, DAPs) and flame retardants (OPFRs) using LC-MS/MS. Six neurotoxicity biomarkers-brain-derived neurotrophic factor (BDNF), neurogranin (Ng), ubiquitin C-terminal hydrolase L1 (UCHL1), neurofilament heavy chain (NFH), glial fibrillary acidic protein (GFAP), and S100 calcium-binding protein B (S100B)-were measured in cord blood via multiplex analysis using Luminex xMAP technology. The results showed that higher levels of DAP metabolites in maternal urine, particularly those with dimethyl groups, were associated with increased GFAP levels in cord blood. OPFR metabolites correlated with elevated GFAP and UCHL1 levels. Sex-specific effects were observed: OPFR levels were linked to higher GFAP in boys, while higher DAP metabolites, particularly those with diethyl groups, were associated with elevated BDNF in girls. Additionally, higher levels of diphenyl phosphate, an OPFR metabolite, were linked to increased S100B in boys. These findings suggest sexually dimorphic effects of prenatal OPC exposure. These findings provide preliminary evidence of developmental neurotoxicity and suggest potential biomarkers in cord blood for early detection of neurodevelopmental deficits. Further studies, including neurobehavioral evaluations and brain imaging, are needed to better understand these molecular effects.

Donepezil Reverses Alcohol-Induced Changes in Hippocampal Neurogenic and Glial Responses Following Adolescent Intermittent Ethanol Exposure Into Adulthood in Female Rats

Adolescent intermittent ethanol (AIE) exposure leads to persisting increases in glial markers and significantly decreases the neurogenic niche in the dentate gyrus of the hippocampus. Our previous study indicated that donepezil (DZ), a cholinesterase inhibitor, can reverse the AIE effect of decreased doublecortin (DCX), a neurogenic marker, and increased cleaved caspase 3, a marker of apoptosis, in the dentate gyrus of male rats. However, to date, no studies have assessed the effects of DZ on AIE effects in females. The purpose of this study was to determine whether DZ can reverse neuroimmune, neurogenic, and neuronal death effects in adulthood after AIE in female rats. Adolescent female rats were given 14 doses of ethanol (5 g/kg) over 24 days by intragastric gavage. Seventeen days later, DZ (2.5 mg/kg, 1.88 mL/kg, i.g., in water) was then administered daily for 4 days prior to sacrifice. Immunohistochemical techniques were utilized to determine the effects of DZ on AIE-induced changes in neurogenesis, cell death, glial, and neuroimmune markers. As expected, AIE decreased the neurogenic markers DCX, SOX2, and Ki-67 in the dentate gyrus and also caused an increase in the glial markers GFAP and Iba-1 in the hippocampus. The effects of AIE on neurogenic and glial markers were reversed by DZ treatment, but the reversal of AIE effects on glial markers was regionally specific within the hippocampus. Overall, these findings indicate that systemic DZ in adult female rats ameliorates the effects of AIE on neurogenesis, neuronal cell death, neuroimmune markers, and glial activation markers. Future studies will determine if DZ alters hippocampally driven behaviors, as well as the mechanisms underlying donepezil's effects.

Diagnostic performance of S100B assay for intracranial hemorrhage detection in patients with mild traumatic brain injury under antiplatelet or anticoagulant therapy

The sampling of S100B protein has been proposed as a screening tool to identify patients with a low risk of post-traumatic intracranial hemorrhage. Its performance for patients on antiplatelet agents or anticoagulants is still debatable. This exploratory study evaluates the diagnostic accuracy of S100B concentrations, measured within 3 h of head trauma, to rule out intracranial hemorrhage in adults on antiplatelet or anticoagulant therapy. This prospective study enrolled adult patients presenting for head trauma within the last 3 h and under antiplatelets or anticoagulants. We hypothesized that a S100B concentration under 0,100 µg.L-1 rule out intracranial hemorrhage with a negative predictive value over 0,99. Sensitivity, specificity, positive predictive value and negative predictive value were analyzed. From June 2020 to January 2023, 155 patients were included. 119 patients had a S100B level at 0,100 µg.L-1 or over. 8 had an intracranial hemorrhage. The sensitivity of S100B was 1 (95%CI 0,68-1), specificity was 0,25 (95%CI 0,18 - 0,32), positive predictive value was 0,07 (95%CI 0.03-0.13), negative predictive value was 1 (95%CI 0,90 - 1). This study suggests that when performed in a 3-hour period after mild head trauma, S100B measurement is an accurate screening tool to rule out intracranial hemorrhage in patients treated with antiplatelet agents or anticoagulants.

Serum GFAP and UCH-L1 for the identification of clinically important traumatic brain injury in children in France: a diagnostic accuracy substudy

BACKGROUND

Many children with mild traumatic brain injury (mTBI), defined by a Glasgow Coma Scale (GCS) score between 13 and 15, undergo hospitalisation or cranial CT (CCT) scans despite the absence of clinically important traumatic brain injury (ciTBI; ie, hospitalisation >2 days associated with intracranial lesions on CCT, neurosurgical intervention, intensive care admission, or death). Clinical algorithms have reduced CCT scans and hospitalisations by 10%. We aimed to established age-appropriate reference values for GFAP and UCH-L1 and evaluate their diagnostic test performance in identifying ciTBI in children.

METHODS

This study was a diagnostic test accuracy substudy within the PROS100B stepped wedge cluster randomised trial that included children aged 16 years or younger, clinically managed within 3 h of mTBI, with a GCS score of 15 requiring hospitalisation or CCT scan according to French Pediatric Society guidelines (equivalent to the intermediate risk group of the PECARN algorithm). Enrolment for PROS100B occurred from Nov 1, 2016, to Oct 31, 2021, at 11 hospital emergency departments in France. Stored blood samples collected from March 1, 2015, to Oct 31, 2015, from children aged 16 years or younger who were outpatients for allergic conditions unrelated to mTBI and free of neurological disease were used as a control group to calculate reference values of GFAP and UCH-L1 across four age groups (<6 months, 6 months to <2 years, 2 years to <4 years, and 4 years to <16 years). The diagnostic test performance of GFAP and UCH-L1, both above the reference range to identify ciTBI, was evaluated in the children with mTBI. GFAP and UCH-L1 were measured with the Alinity analyser (Abbott, Chicago, IL, USA).

FINDINGS

Reference values were calculated from GFAP and UCH-L1 measured in samples from 718 control children (378 [53%] boys and 340 [47%] girls). 531 children (334 [63%] boys and 197 [37%] girls) aged 0-16 years with mTBI were included. By applying our reference values for GFAP and UCH-L1 across four age groups the biomarker combination (both biomarkers above reference ranges) had a sensitivity of 100% (95% CI 69-100), a negative predictive value of 100% (99-100), a specificity of 67% (63-71), a positive likelihood ratio of 3·01 (2·67-3·40), a negative likelihood ratio of 0, and an area under the curve of 0·83 (0·81-0·85) in identifying ciTBI.

INTERPRETATION

Serum GFAP and UCH-L1 identify ciTBI in children with 100% sensitivity and 67% specificity, which could potentially reduce unnecessary CCT scans and hospitalisations in children with mTBI if implemented.

FUNDING

French Ministry of Health.

Circulating Brain-Reactive Autoantibody Profiles in Military Breachers Exposed to Repetitive Occupational Blast

Military breachers are routinely exposed to repetitive low-level blast overpressure, placing them at elevated risk for long-term neurological sequelae. Mounting evidence suggests that circulating brain-reactive autoantibodies, generated following CNS injury, may serve as both biomarkers of cumulative damage and drivers of secondary neuroinflammation. In this study, we compared circulating autoantibody profiles in military breachers (n = 18) with extensive blast exposure against unexposed military controls (n = 19). Using high-sensitivity immunoassays, we quantified IgG and IgM autoantibodies targeting glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), and pituitary (PIT) antigens. Breachers exhibited significantly elevated levels of anti-GFAP IgG (p < 0.001) and anti-PIT IgG (p < 0.001) compared to controls, while anti-MBP autoantibody levels remained unchanged. No significant differences were observed for any IgM autoantibody measurements. These patterns suggest that repetitive blast exposure induces a chronic, adaptive immune response rather than a short-lived acute phase. The elevated IgG autoantibodies highlight the vulnerability of astrocytes, myelin, and the hypothalamic-pituitary axis to ongoing immune-mediated injury following repeated blast insults, likely reflecting sustained blood-brain barrier disruption and neuroinflammatory processes. Our findings underscore the potential of CNS-targeted IgG autoantibodies as biomarkers of cumulative brain injury and immune dysregulation in blast-exposed populations. Further research is warranted to validate these markers in larger, more diverse cohorts, and to explore their utility in guiding interventions aimed at mitigating neuroinflammation, neuroendocrine dysfunction, and long-term neurodegenerative risks in military personnel and similarly exposed groups.

Brain white matter damage biomarkers

White matter (WM), constituting nearly half of the human brain's mass, is pivotal for the rapid transmission of neural signals across different brain regions, significantly influencing cognitive processes like learning, memory, and problem-solving. The integrity of WM is essential for brain function, and its damage, which can occur due to conditions such as multiple sclerosis (MS), stroke, and traumatic brain injury, results in severe neurological deficits and cognitive decline. The primary objective of this book chapter is to discuss the clinical significance of fluid biomarkers in assessing WM damage within the central nervous system (CNS). It explores the biological underpinnings and pathological changes in WM due to various neurological conditions and details how alterations can be detected and quantified through fluid biomarkers. By examining biomarkers like Myelin Basic Protein (MBP), Neurofilament light chain (NFL), and others, the chapter highlights their role in enhancing diagnostic precision, monitoring disease progression, and guiding therapeutic interventions, thus providing crucial insights into maintaining WM integrity and preventing cognitive and physical disabilities.

S100B protein as a biomarker and predictor in traumatic brain injury

OBJECTIVES

To determine the prognostic potential of S100B protein in patients with craniocerebral injury, correlation between S100B protein and time, selected internal diseases, body habitus, polytrauma, and season.

METHODS

We examined the levels of S100B protein in 124 patients with traumatic brain injury (TBI).

RESULTS

The S100B protein level 72 h after injury and changes over 72 h afterwards are statistically significant for prediction of a good clinical condition 1 month after injury. The highest sensitivity (81.4%) and specificity (83.3%) for the S100B protein value after 72 h was obtained for a cut-off value of 0.114. For the change after 72 h, that is a decrease in S100B value, the optimal cut-off is 0.730, where the sum of specificity (76.3%) and sensitivity (54.2%) is the highest, or a decrease by 0.526 at the cut-off value, where sensitivity (62.5%) and specificity (62.9%) are more balanced. The S100B values were the highest at baseline; S100B value taken 72 h after trauma negatively correlated with GCS upon discharge or transfer (r=-0.517, P<0.0001). We found no relationship between S100B protein and hypertension, diabetes mellitus, BMI, or season when the trauma occurred. Changes in values and a higher level of S100B protein were demonstrated in polytraumas with a median of 1.070 (0.042; 8.780) μg/L compared to isolated TBI with a median of 0.421 (0.042; 11.230) μg/L.

CONCLUSION

S100B protein level with specimen collection 72 h after trauma can be used as a complementary marker of patient prognosis.

Neuroprotective effect of vitamin B12 supplementation on cognitive functions and neuronal morphology at different time intervals after traumatic brain injury in male Swiss albino mice

Traumatic brain injury is a highly irreversible process that consists of primary as well as secondary injury which develops and progresses over months to years, leading to cognitive dysfunctions. Vitamin B12 received considerable interest due to its potential therapeutic properties. The pathways of vitamin B12 are closely related to neuronal survival but its effects on the pathophysiology of injury with respect to cognition is a relatively unexplored area of research. In this study, we investigated, the effect of vitamin B12 and its involvement in neuroprotection on TBI-induced pathophysiology in male Swiss albino mice. Our findings suggested that vitamin B12 supplementation improves TBI-mediated neurological impairments, spatial and recognition memory, and anxiety-like behavior. Furthermore, the oxidative stress was reduced by declined homocysteine level with vitamin B12 supplementation validating declined expression of astrocytes and TBI biomarkers. The studies on neuronal morphology revealed that vitamin B12 supplementation increases the dendritic arborization and density of mushroom and filopodia-shaped spines and further increases the expression of synaptic plasticity-related genes and proteins. Taken together, our findings reveal that, supplementation of vitamin B12 restored the TBI-induced downregulation of dendritic arborization, and spine density which ultimately increases synaptic plasticity, cell survival, and recovery of cognitive dysfunctions.

Exploratory Randomised Trial of Tranexamic Acid to Decrease Postoperative Delirium in Adults Undergoing Lumbar Fusion: A trial stopped early

Background

Postoperative delirium may be mediated by perioperative systemic- and neuro-inflammation. By inhibiting the pro-inflammatory actions of plasmin, tranexamic acid (TXA) may decrease postoperative delirium. To explore this hypothesis, we modified an ongoing randomised trial of TXA, adding measures of postoperative delirium, cognitive function, systemic cytokines, and astrocyte activation.

Methods

Adults undergoing elective posterior lumbar fusion randomly received intraoperative intravenous TXA (n=43: 10 mg kg-1 loading dose, 2 mg kg-1 h-1 infusion) or Placebo (n=40). Blood was collected pre- and at 24 h post-operatively (n=32) for biomarkers of systemic inflammation (cytokines) and astrocyte activation (S100B). Participants had twice daily delirium assessments using the 3-minute diagnostic interview for Confusion Assessment Method (n=65). Participants underwent 4 measures of cognitive function preoperatively and during post-discharge follow-up.

Results

Delirium incidence in the TXA group (7/32=22%) was not significantly less than in the Placebo group (11/33=33%); P=0.408, absolute difference=11%, relative difference=33%, effect size = -0.258 (95% CI -0.744 to 0.229). In the Placebo group (n=16), delirium severity was associated with the number of instrumented vertebral levels (P=0.001) and with postoperative interleukin -8 and -10 concentrations (P=0.00008 and P=0.005, respectively) and these associations were not significantly modified by TXA. In the Placebo group, delirium severity was associated with S100B concentration (P=0.0009) and the strength of the association was decreased by TXA (P=0.002).

Conclusions

A potential 33% relative decrease in postoperative delirium incidence justifies an adequately powered clinical trial to determine if intraoperative TXA decreases delirium in adults undergoing lumbar fusion.

Intimate Partner Violence-Related Brain Injury: Unmasking and Addressing the Gaps

Intimate partner violence (IPV) is a significant, global public health concern. Women, individuals with historically underrepresented identities, and disabilities are at high risk for IPV and tend to experience severe injuries. There has been growing concern about the risk of exposure to IPV-related head trauma, resulting in IPV-related brain injury (IPV-BI), and its health consequences. Past work suggests that a significant proportion of women exposed to IPV experience IPV-BI, likely representing a distinct phenotype compared with BI of other etiologies. An IPV-BI often co-occurs with psychological trauma and mental health complaints, leading to unique issues related to identifying, prognosticating, and managing IPV-BI outcomes. The goal of this review is to identify important gaps in research and clinical practice in IPV-BI and suggest potential solutions to address them. We summarize IPV research in five key priority areas: (1) unique considerations for IPV-BI study design; (2) understanding non-fatal strangulation as a form of BI; (3) identifying objective biomarkers of IPV-BI; (4) consideration of the chronicity, cumulative and late effects of IPV-BI; and (5) BI as a risk factor for IPV engagement. Our review concludes with a call to action to help investigators develop ecologically valid research studies addressing the identified clinical-research knowledge gaps and strategies to improve care in individuals exposed to IPV-BI. By reducing the current gaps and answering these calls to action, we will approach IPV-BI in a trauma-informed manner, ultimately improving outcomes and quality of life for those impacted by IPV-BI.

Confounding factors of the expression of mTBI biomarkers, S100B, GFAP and UCH-L1 in an aging population

OBJECTIVES

To evaluate some confounding factors that influence the concentrations of S100 calcium binding protein B (S100B), glial fibrillary acidic protein (GFAP), and ubiquitin carboxyl-terminal hydrolase L-1 (UCH-L1) in older individuals. Indeed, recent guidelines have proposed the combined use of S100B and the "GFAP-UCH-L1" mTBI test to rule out mild traumatic brain injuries (mTBI). As older adults are the most at risk of mTBI, it is particularly important to understand the confounding factors of those mTBI rule-out biomarkers in aging population.

METHODS

The protein S100B and the "GFAP and UCH-L1" mTBI test were measured using Liaison XL (Diasorin) and Alinity I (Abbott), respectively, in 330 and 341 individuals with non-suspected mTBI from the SarcoPhAge cohort.

RESULTS

S100B, GFAP and UCH-L1 were all significantly correlated with renal function whereas alcohol consumption, Geriatric Depression Score (GDS), smoking habits and anticoagulant intake were not associated with any of these three biomarkers. Body mass index (BMI) and age were associated with GFAP and UCH-L1 expression while sex and mini-mental state examination (MMSE) were only associated with GFAP. According to the manufacturer's cut-offs for mTBI rule-out, only 5.5 % of participants were positive for S100B whereas 66.9 % were positive for the "GFAP-UCH-L1" mTBI test. All positive "GFAP-UCH-L1" mTBI tests were GFAP+/UCH-L1-. Among individuals with cystatin C>1.55 mg/L, 25 % were positive for S100B while 90 % were positive for the mTBI test.

CONCLUSIONS

Our data show that confounding factors have different impacts on the positivity rate of the "GFAP-UCH-L1" mTBI test compared to S100B.

Consensus paper on the assessment of adult patients with traumatic brain injury with Glasgow Coma Scale 13-15 at the emergency department: A multidisciplinary overview

Traumatic brain injury (TBI) is a common reason for presenting to emergency departments (EDs). The assessment of these patients is frequently hampered by various confounders, and diagnostics is still often based on nonspecific clinical signs. Throughout Europe, there is wide variation in clinical practices, including the follow-up of those discharged from the ED. The objective is to present a practical recommendation for the assessment of adult patients with an acute TBI, focusing on milder cases not requiring in-hospital care. The aim is to advise on and harmonize practices for European settings. A multiprofessional expert panel, giving consensus recommendations based on recent scientific literature and clinical practices, is employed. The focus is on patients with a preserved consciousness (Glasgow Coma Scale 13-15) not requiring in-hospital care after ED assessment. The main results of this paper contain practical, clinically usable recommendations for acute clinical assessment, decision-making on acute head computerized tomography (CT), use of biomarkers, discharge options, and needs for follow-up, as well as a discussion of the main features and risk factors for prolonged recovery. In conclusion, this consensus paper provides a practical stepwise approach for the clinical assessment of patients with an acute TBI at the ED. Recommendations are given for the performance of acute head CT, use of brain biomarkers and disposition after ED care including careful patient information and organization of follow-up for those discharged.

GFAP as Astrocyte-Derived Extracellular Vesicle Cargo in Acute Ischemic Stroke Patients-A Pilot Study

The utility of serum glial fibrillary acidic protein (GFAP) in acute ischemic stroke (AIS) has been extensively studied in recent years. Here, we aimed to assess its potential role as a cargo protein of extracellular vesicles (EVs) secreted by astrocytes (ADEVs) in response to brain ischemia. Plasma samples from eighteen AIS patients at 24 h (D1), 7 days (D7), and one month (M1) post-symptoms onset, and nine age, sex, and cardiovascular risk factor-matched healthy controls were obtained to isolate EVs using the Exoquick ULTRA EV kit. Subsets of presumed ADEVs were identified further by the expression of the glutamate aspartate transporter (GLAST) as a specific marker of astrocytes with the Basic Exo-Flow Capture kit. Western blotting has tested the presence of GFAP in ADEV cargo. Post-stroke ADEV GFAP levels were elevated at D1 and D7 but not M1 compared to controls (p = 0.007, p = 0.019, and p = 0.344, respectively). Significant differences were highlighted in ADEV GFAP content at the three time points studied (n = 12, p = 0.027) and between D1 and M1 (z = 2.65, p = 0.023). A positive correlation was observed between the modified Rankin Scale (mRS) at D7 and ADEV GFAP at D1 (r = 0.58, p = 0.010) and D7 (r = 0.57, p = 0.013), respectively. ADEV GFAP may dynamically reflect changes during the first month post-ischemia. Profiling ADEVs from peripheral blood could provide a new way to assess the central nervous system pathology.

In Vivo Intracerebral Administration of α-Ketoisocaproic Acid to Neonate Rats Disrupts Brain Redox Homeostasis and Promotes Neuronal Death, Glial Reactivity, and Myelination Injury

Maple syrup urine disease (MSUD) is caused by severe deficiency of branched-chain α-keto acid dehydrogenase complex activity, resulting in tissue accumulation of branched-chain α-keto acids and amino acids, particularly α-ketoisocaproic acid (KIC) and leucine. Affected patients regularly manifest with acute episodes of encephalopathy including seizures, coma, and potentially fatal brain edema during the newborn period. The present work investigated the ex vivo effects of a single intracerebroventricular injection of KIC to neonate rats on redox homeostasis and neurochemical markers of neuronal viability (neuronal nuclear protein (NeuN)), astrogliosis (glial fibrillary acidic protein (GFAP)), and myelination (myelin basic protein (MBP) and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase)) in the cerebral cortex and striatum. KIC significantly disturbed redox homeostasis in these brain structures 6 h after injection, as observed by increased 2',7'-dichlorofluorescein oxidation (reactive oxygen species generation), malondialdehyde levels (lipid oxidative damage), and carbonyl formation (protein oxidative damage), besides impairing the antioxidant defenses (diminished levels of reduced glutathione and altered glutathione peroxidase, glutathione reductase, and superoxide dismutase activities) in both cerebral structures. Noteworthy, the antioxidants N-acetylcysteine and melatonin attenuated or normalized most of the KIC-induced effects on redox homeostasis. Furthermore, a reduction of NeuN, MBP, and CNPase, and an increase of GFAP levels were observed at postnatal day 15, suggesting neuronal loss, myelination injury, and astrocyte reactivity, respectively. Our data indicate that disruption of redox homeostasis, associated with neural damage caused by acute intracerebral accumulation of KIC in the neonatal period may contribute to the neuropathology characteristic of MSUD patients.

Predictive value of S100B and brain derived neurotrophic factor for radiofrequency treatment of lumbar disc prolapse

BACKGROUND

This work aimed to analyze serum S100B levels and brain-derived neurotrophic factor (BDNF) in patients with lumbar disc prolapse to test their predictive values concerning the therapeutic efficacy of pulsed radiofrequency.

METHODS

This prospective interventional study was carried out on 50 patients candidates for radiofrequency for treating symptomatic lumbar disc prolapse. Pain severity and functional disability were assessed using the Numeric Rating Scale (NRS) and Functional rating index (FRI) before as well as two weeks, 1, 3, and 6 months after the radiofrequency. Quantitative assessment of serum S100B level and BDNF was done for all the included patients one day before radiofrequency.

RESULTS

The scores of NRS and FRI were significantly improved at two weeks, 1, 3, and 6 months following radiofrequency (P-value < 0.001 in all comparisons). Statistically significant positive correlations were found between duration of pain, NRS, and S100B serum level before radiofrequency, and both NRS (P-value = 0.001, 0.035, < 0.001 respectively) and FRI (P-value = < 0.001, 0.009, 0.001 respectively) 6 months following radiofrequency. Whereas there were statistically significant negative correlations between BDNF serum level before radiofrequency and both NRS and FRI 6 months following radiofrequency (P-value = 0.022, 0.041 respectively). NRS and S100B serum levels before radiofrequency were found to be independent predictors of NRS 6 months following radiofrequency (P-value = 0.040. <0.001, respectively).

CONCLUSION

Serum level of S100B is a promising biomarker that can predict functional outcomes after pulsed radiofrequency in patients with lumbar disc prolapse.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Comparison of GFAP and UCH-L1 Measurements Using Two Automated Immunoassays (i-STAT® and Alinity®) for the Management of Patients with Mild Traumatic Brain Injury: Preliminary Results from a French Single-Center Approach

The measurement of blood glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) may assist in the management of mild traumatic brain injury (mTBI). This study aims to compare GFAP and UCH-L1 values measured using a handheld device with those measured using a core laboratory platform. We enrolled 230 mTBI patients at intermediate risk of complications. Following French guidelines, a negative S100B value permits the patient to be discharged without a computed tomography scan. Plasma GFAP and UCH-L1 levels were retrospectively measured using i-STAT® and Alinity® i analyzers in patients managed within 12 h post-trauma. Our analysis indicates a strong correlation of biomarker measurements between the two analyzers. Cohen's kappa coefficients and Lin's concordance coefficients were both ≥0.7, while Spearman's correlation coefficient was 0.94 for GFAP and 0.90 for UCH-L1. Additionally, the diagnostic performance in identifying an intracranial lesion was not significantly different between the two analyzers, with a sensitivity of 100% and specificity of approximately 30%. GFAP and UCH-L1 levels measured using Abbott's i-STAT® and Alinity® i platform assays are highly correlated both analytically and clinically in a cohort of 230 patients managed for mTBI according to French guidelines.

THE NEUROENDOTHELIAL AXIS IN TRAUMATIC BRAIN INJURY: MECHANISMS OF MULTIORGAN DYSFUNCTION, NOVEL THERAPIES, AND FUTURE DIRECTIONS

ABSTRACT

Severe traumatic brain injury (TBI) often initiates a systemic inflammatory response syndrome, which can potentially culminate into multiorgan dysfunction. A central player in this cascade is endotheliopathy, caused by perturbations in homeostatic mechanisms governed by endothelial cells due to injury-induced coagulopathy, heightened sympathoadrenal response, complement activation, and proinflammatory cytokine release. Unique to TBI is the potential disruption of the blood-brain barrier, which may expose neuronal antigens to the peripheral immune system and permit neuroinflammatory mediators to enter systemic circulation, propagating endotheliopathy systemically. This review aims to provide comprehensive insights into the "neuroendothelial axis" underlying endothelial dysfunction after TBI, identify potential diagnostic and prognostic biomarkers, and explore therapeutic strategies targeting these interactions, with the ultimate goal of improving patient outcomes after severe TBI.

Blood biomarkers for traumatic brain injury: A narrative review of current evidence

Introduction

A blood-based biomarker (BBBM) test could help to better stratify patients with traumatic brain injury (TBI), reduce unnecessary imaging, to detect and treat secondary insults, predict outcomes, and monitor treatment effects and quality of care.

Research question

What evidence is available for clinical applications of BBBMs in TBI and how to advance this field?

Material and methods

This narrative review discusses the potential clinical applications of core BBBMs in TBI. A literature search in PubMed, Scopus, and ISI Web of Knowledge focused on articles in English with the words "traumatic brain injury" together with the words "blood biomarkers", "diagnostics", "outcome prediction", "extracranial injury" and "assay method" alone-, or in combination.

Results

Glial fibrillary acidic protein (GFAP) combined with Ubiquitin C-terminal hydrolase-L1(UCH-L1) has received FDA clearance to aid computed tomography (CT)-detection of brain lesions in mild (m) TBI. Application of S100B led to reduction of head CT scans. GFAP may also predict magnetic resonance imaging (MRI) abnormalities in CT-negative cases of TBI. Further, UCH-L1, S100B, Neurofilament light (NF-L), and total tau showed value for predicting mortality or unfavourable outcome. Nevertheless, biomarkers have less role in outcome prediction in mTBI. S100B could serve as a tool in the multimodality monitoring of patients in the neurointensive care unit.

Discussion and conclusion

Largescale systematic studies are required to explore the kinetics of BBBMs and their use in multiple clinical groups. Assay development/cross validation should advance the generalizability of those results which implicated GFAP, S100B and NF-L as most promising biomarkers in the diagnostics of TBI.

Evaluation of brain injury in goats naturally infected with Coenurus cerebralis; brain specific biomarkers, acute inflammation, and DNA oxidation

This investigate goals are to establish the utility of brain-specific biomarkers (GFAP and S100B) in vivo and to assess the brain damage in C. cerebralis-infected goats using histopathological and immunopathological methods. The animal material of the study consisted of 10 healthy and 20 Coenurus cerebralis infected female hair goats. Serum GFAP and S100B concentrations were measured to determine brain damage. Serum S100B (p < 0.037), GFAP (p < 0.012), urea (p < 0.045), GGT (p < 0.001) and ALT (p < 0.001) concentrations in the C.cerebralis group were significantly higher than the control group. There was no significant difference between the C.cerebralis group and the control group for hsTnI (p > 0.078), creatinine (p > 0.099) and CK-MB (p > 0.725). In the histopathological examination, pressure atrophy and related inflammatory changes were observed due to mechanical damage of the parasite. Immunohistochemical examinations revealed that the parasite stimulated inflammation with the expression of TNF-α and caused DNA damage with the expression of 8-OHdG. As a result, when the data collected for this study are assessed as a whole, it is thought that the use of brainspecific GFAP and S100B biomarkers may be beneficial in determining brain damage in naturally infected hair goats with C.cerebralis. Changes in the levels of brain-specific biomarkers contribute significantly to determining the prognosis of the disease in vivo. Measurement of GFAP and S100B concentrations from serum offers an important alternative to the CSF method.

Human in vivo evidence of reduced astrocyte activation and neuroinflammation in patients with treatment-resistant depression following electroconvulsive therapy

AIM

The current study aimed to investigate the neuroinflammatory hypothesis of depression and the potential anti-inflammatory effect of electroconvulsive therapy (ECT) in vivo, utilizing astrocyte-derived extracellular vesicles (ADEVs) isolated from plasma.

METHODS

A total of 40 patients with treatment-resistant depression (TRD) and 35 matched healthy controls were recruited at baseline, and 34 patients with TRD completed the post-ECT visits. Blood samples were collected at baseline and post-ECT. Plasma ADEVs were isolated and confirmed, and the concentrations of two astrocyte markers (glial fibrillary acidic protein [GFAP] and S100β), an extracellular vesicle marker cluster of differentiation 81 (CD81), and nine inflammatory markers in ADEVs were measured as main analyses. In addition, correlation analysis was conducted between clinical features and ADEV protein levels as exploratory analysis.

RESULTS

At baseline, the TRD group exhibited significantly higher levels of two astrocyte markers GFAP and S100β, as well as CD81 compared with the healthy controls. Inflammatory markers interferon γ (IFN-γ), interleukin (IL) 1β, IL-4, IL-6, tumor necrosis factor α, IL-10, and IL-17A were also significantly higher in the TRD group. After ECT, there was a significant reduction in the levels of GFAP, S100β, and CD81, along with a significant decrease in the levels of IFN-γ and IL-4. Furthermore, higher levels of GFAP, S100β, CD81, and inflammatory cytokines were associated with more severe depressive symptoms and poorer cognitive function.

CONCLUSION

This study provides direct insight supporting the astrocyte activation and neuroinflammatory hypothesis of depression using ADEVs. ECT may exert an anti-inflammatory effect through inhibition of such activation of astrocytes.

Clinical complications after a traumatic brain injury and its relation with brain biomarkers

We aimed to find out which are the most frequent complications for patients who suffer a traumatic brain injury (TBI) and its relation with brain biomarker levels. We conducted a hospital cohort study with patients who attended the Hospital Emergency Department between 1 June 2018 and 31 December 2020. Different variables were collected such as biomarkers levels after 6 h and 12 h of TBI (S100, NSE, UCHL1 and GFAP), clinical and sociodemographic variables, complementary tests, and complications 48 h and 7 days after TBI. Qualitative variables were analysed with Pearson's chi-square test, and quantitative variables with the Mann-Whitney U test. A multivariate logistic regression model for the existence of complications one week after discharge was performed to assess the discriminatory capacity of the clinical variables. A total of 51 controls and 540 patients were included in this study. In the TBI group, the mean age was 83 years, and 53.9% of the patients were male. Complications at seven days were associated with the severity of TBI (p < 0.05) and the number of platelets (p = 0.016). All biomarkers except GFAP showed significant differences in their distribution of values according to gender, with significantly higher values of the three biomarkers for women with respect to men. Patients with complications presented significantly higher S100 values (p < 0.05). The patient's baseline status, the severity of the TBI and the S100 levels can be very important elements in determining whether a patient may develop complications in the few hours after TBI.

Astroglial Alterations in the Hippocampus of Rats Submitted to a Single Trans-Cranial Direct Current Stimulation Trial

Evidence indicates that transcranial direct current stimulation (tDCS) provides therapeutic benefits in different situations, such as epilepsy, depression, inflammatory and neuropathic pain. Despite the increasing use of tDCS, its cellular and molecular basis remains unknown. Astrocytes display a close functional and structural relationship with neurons and have been identified as mediators of neuroprotection in tDCS. Considering the importance of hippocampal glutamatergic neurotransmission in nociceptive pathways, we decided to investigate short-term changes in the hippocampal astrocytes of rats subjected to tDCS, evaluating specific cellular markers (GFAP and S100B), as well as markers of astroglial activity; glutamate uptake, glutamine synthesis by glutamine synthetase (GS) and glutathione content. Data clearly show that a single session of tDCS increases the pain threshold elicited by mechanical and thermal stimuli, as evaluated by von Frey and hot plate tests, respectively. These changes involve inflammatory and astroglial neurochemical changes in the hippocampus, based on specific changes in cell markers, such as S100B and GS. Alterations in S100B were also observed in the cerebrospinal fluid of tDCS animals and, most importantly, specific functional changes (increased glutamate uptake and increased GS activity) were detected in hippocampal astrocytes. These findings contribute to a better understanding of tDCS as a therapeutic strategy for nervous disorders and reinforce the importance of astrocytes as therapeutic targets.

Neurobiomarker and body temperature responses to recreational marathon running

OBJECTIVES

To assess how biomarkers indicating central nervous system insult (neurobiomarkers) vary in peripheral blood with exertional-heat stress from prolonged endurance exercise.

DESIGN

Observational study of changes in neuron specific enolase (NSE), S100 calcium-binding protein B (S100β), Glial Fibrillary Acid Protein (GFAP) and Ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) at Brighton Marathon 2022.

METHODS

In 38 marathoners with in-race core temperature (Tc) monitoring, exposure (High, Intermediate or Low) was classified by cumulative hyperthermia - calculated as area under curve of Time × Tc > 38 °C - and also by running duration (finishing time). Blood was sampled for neurobiomarkers, cortisol and fluid-regulatory stress surrogates, including copeptin and creatinine (at rested baseline; within 30 min of finishing; and at 24 h).

RESULTS

Finishing in 236 ± 40 min, runners showed stable GFAP and UCH-L1 across the marathon and next-day. Significant (P < 0.05) increases from baseline were shown post-marathon and at 24 h for S100β (8.52 [3.65, 22.95] vs 39.0 [26.48, 52.33] vs 80.3 [49.1, 99.7] ng·L-1) and post-marathon only for NSE (3.73 [3.30, 4.32] vs 4.85 [4.45, 5.80] μg·L-1, P < 0.0001). Whilst differential response to hyperthermia was observed for cortisol, copeptin and creatinine, neurobiomarker responses did not vary. Post-marathon, only NSE differed by exercise duration (High vs Low, 5.81 ± 1.77 vs. 4.69 ± 0.73 μg·L-1, adjusted P = 0.0358).

CONCLUSIONS

Successful marathon performance did not associate with evidence for substantial neuronal insult. To account for variation in neurobiomarkers with prolonged endurance exercise, factors additional to hyperthermia, such as exercise duration and intensity, should be further investigated.

Cerebrospinal Fluid and Serum Biomarker Insights in Aneurysmal Subarachnoid Haemorrhage: Navigating the Brain-Heart Interrelationship for Improved Patient Outcomes

The pathophysiological mechanisms underlying severe cardiac dysfunction after aneurysmal subarachnoid haemorrhage (aSAH) remain poorly understood. In the present study, we focused on two categories of contributing factors describing the brain-heart relationship. The first group includes brain-specific cerebrospinal fluid (CSF) and serum biomarkers, as well as cardiac-specific biomarkers. The secondary category encompasses parameters associated with cerebral autoregulation and the autonomic nervous system. A group of 15 aSAH patients were included in the analysis. Severe cardiac complications were diagnosed in seven (47%) of patients. In the whole population, a significant correlation was observed between CSF S100 calcium-binding protein B (S100B) and brain natriuretic peptide (BNP) (rS = 0.62; p = 0.040). Additionally, we identified a significant correlation between CSF neuron-specific enolase (NSE) with cardiac troponin I (rS = 0.57; p = 0.025) and BNP (rS = 0.66; p = 0.029), as well as between CSF tau protein and BNP (rS = 0.78; p = 0.039). Patients experiencing severe cardiac complications exhibited notably higher levels of serum tau protein at day 1 (0.21 ± 0.23 [ng/mL]) compared to those without severe cardiac complications (0.03 ± 0.04 [ng/mL]); p = 0.009. Impaired cerebral autoregulation was noted in patients both with and without severe cardiac complications. Elevated serum NSE at day 1 was related to impaired cerebral autoregulation (rS = 0.90; p = 0.037). On the first day, a substantial, reciprocal correlation between heart rate variability low-to-high frequency ratio (HRV LF/HF) and both GFAP (rS = -0.83; p = 0.004) and S100B (rS = -0.83; p = 0.004) was observed. Cardiac and brain-specific biomarkers hold the potential to assist clinicians in providing timely insights into cardiac complications, and therefore they contribute to the prognosis of outcomes.

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.

The S100B Protein: A Multifaceted Pathogenic Factor More Than a Biomarker

S100B is a calcium-binding protein mainly concentrated in astrocytes in the nervous system. Its levels in biological fluids are recognized as a reliable biomarker of active neural distress, and more recently, mounting evidence points to S100B as a Damage-Associated Molecular Pattern molecule, which, at high concentration, triggers tissue reactions to damage. S100B levels and/or distribution in the nervous tissue of patients and/or experimental models of different neural disorders, for which the protein is used as a biomarker, are directly related to the progress of the disease. In addition, in experimental models of diseases such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, multiple sclerosis, traumatic and vascular acute neural injury, epilepsy, and inflammatory bowel disease, alteration of S100B levels correlates with the occurrence of clinical and/or toxic parameters. In general, overexpression/administration of S100B worsens the clinical presentation, whereas deletion/inactivation of the protein contributes to the amelioration of the symptoms. Thus, the S100B protein may be proposed as a common pathogenic factor in different disorders, sharing different symptoms and etiologies but appearing to share some common pathogenic processes reasonably attributable to neuroinflammation.

Proteomics Analysis of R-Ras Deficiency in Oxygen Induced Retinopathy

Small GTPase R-Ras regulates vascular permeability in angiogenesis. In the eye, abnormal angiogenesis and hyperpermeability are the leading causes of vision loss in several ischemic retinal diseases such as proliferative diabetic retinopathy (PDR), retinal vein occlusion (RVO), and retinopathy of prematurity (ROP). Oxygen-induced retinopathy (OIR) is the most widely used experimental model for these ischemic retinopathies. To shed more light on how the R-Ras regulates vascular permeability in pathological angiogenesis, we performed a comprehensive (>2900 proteins) characterization of OIR in R-Ras knockout (KO) and wild-type (WT) mice by sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics. OIR and age-matched normoxic control retinas were collected at P13, P17, and P42 from R-Ras KO and WT mice and were subjected to SWATH-MS and data analysis. The most significant difference between the R-Ras KO and WT retinas was an accumulation of plasma proteins. The pathological vascular hyperpermeability during OIR in the R-Ras KO retina took place very early, P13. This led to simultaneous hypoxic cell injury/death (ferroptosis), glycolytic metabolism as well compensatory mechanisms to counter the pathological leakage from angiogenic blood vessels in the OIR retina of R-Ras deficient mice.

L-2-Hydroxyglutaric Acid Administration to Neonatal Rats Elicits Marked Neurochemical Alterations and Long-Term Neurobehavioral Disabilities Mediated by Oxidative Stress

L-2-Hydroxyglutaric aciduria (L-2-HGA) is an inherited neurometabolic disorder caused by deficient activity of L-2-hydroxyglutarate dehydrogenase. L-2-Hydroxyglutaric acid (L-2-HG) accumulation in the brain and biological fluids is the biochemical hallmark of this disease. Patients present exclusively neurological symptoms and brain abnormalities, particularly in the cerebral cortex, basal ganglia, and cerebellum. Since the pathogenesis of this disorder is still poorly established, we investigated the short-lived effects of an intracerebroventricular injection of L-2-HG to neonatal rats on redox homeostasis in the cerebellum, which is mostly affected in this disorder. We also determined immunohistochemical landmarks of neuronal viability (NeuN), astrogliosis (S100B and GFAP), microglia activation (Iba1), and myelination (MBP and CNPase) in the cerebral cortex and striatum following L-2-HG administration. Finally, the neuromotor development and cognitive abilities were examined. L-2-HG elicited oxidative stress in the cerebellum 6 h after its injection, which was verified by increased reactive oxygen species production, lipid oxidative damage, and altered antioxidant defenses (decreased concentrations of reduced glutathione and increased glutathione peroxidase and superoxide dismutase activities). L-2-HG also decreased the content of NeuN, MBP, and CNPase, and increased S100B, GFAP, and Iba1 in the cerebral cortex and striatum at postnatal days 15 and 75, implying long-standing neuronal loss, demyelination, astrocyte reactivity, and increased inflammatory response, respectively. Finally, L-2-HG administration caused a delay in neuromotor development and a deficit of cognition in adult animals. Importantly, the antioxidant melatonin prevented L-2-HG-induced deleterious neurochemical, immunohistochemical, and behavioral effects, indicating that oxidative stress may be central to the pathogenesis of brain damage in L-2-HGA.

Diagnostic performance of S100B as a rule-out test for intracranial pathology in head-injured patients presenting to the emergency department who meet NICE Head Injury Guideline criteria for CT-head scan

BACKGROUND

Traumatic brain injury is a common ED presentation. CT-head utilisation is escalating, exacerbating resource pressure in the ED. The biomarker S100B could assist clinicians with CT-head decisions by excluding intracranial pathology. Diagnostic performance of S100B was assessed in patients meeting National Institute of Health and Clinical Excellence Head Injury Guideline (NICE HIG) criteria for CT-head within 6 and 24 hours of injury.

METHODS

This multicentre prospective observational study included adult patients presenting to the ED with head injuries between May 2020 and June 2021. Informed consent was obtained from patients meeting NICE HIG CT-head criteria. A venous blood sample was collected and serum was tested for S100B using a Cobas Elecsys-S100 module; >0.1 µg/mL was the threshold used to indicate a positive test. Intracranial pathology reported on CT-head scan by the duty radiologist was used as the reference standard to review diagnostic performance.

RESULTS

This study included 265 patients of whom 35 (13.2%) had positive CT-head findings. Within 6 hours of injury, sensitivity of S100B was 93.8% (95% CI 69.8% to 99.8%) and specificity was 30.8% (22.6% to 40.0%). Negative predictive value (NPV) was 97.3% (95% CI 84.2% to 99.6%) and area under the curve (AUC) was 0.73 (95% CI 0.61 to 0.85; p=0.003). Within 24 hours of injury, sensitivity was 82.9% (95% CI 66.4% to 93.44%) and specificity was 43.0% (95% CI 36.6% to 49.7%). NPV was 94.29% (95% CI 88.7% to 97.2%) and AUC was 0.65 (95% CI 0.56 to 0.74; p=0.046). Theoretically, use of S100B as a rule-out test would have reduced CT-head scans by 27.1% (95% CI 18.9% to 36.8%) within 6 hours and 37.4% (95% CI 32.0% to 47.2%) within 24 hours. The risk of missing a significant injury with this approach would have been 0.75% (95% CI 0.0% to 2.2%) within 6 hours and 2.3% (95% CI 0.5% to 4.1%) within 24 hours.

CONCLUSION

Within 6 hours of injury, S100B performed well as a diagnostic test to exclude significant intracranial pathology in low-risk patients presenting with head injury. In theory, if used in addition to NICE HIGs, CT-head rates could reduce by one-quarter with a potential miss rate of <1%.

Double Blast Wave Primary Effect on Synaptic, Glymphatic, Myelin, Neuronal and Neurovascular Markers

Explosive blasts are associated with neurological consequences as a result of blast waves impact on the brain. Yet, the neuropathologic and molecular consequences due to blast waves vs. blunt-TBI are not fully understood. An explosive-driven blast-generating system was used to reproduce blast wave exposure and examine pathological and molecular changes generated by primary wave effects of blast exposure. We assessed if pre- and post-synaptic (synaptophysin, PSD-95, spinophilin, GAP-43), neuronal (NF-L), glymphatic (LYVE1, podoplanin), myelin (MBP), neurovascular (AQP4, S100β, PDGF) and genomic (DNA polymerase-β, RNA polymerase II) markers could be altered across different brain regions of double blast vs. sham animals. Twelve male rats exposed to two consecutive blasts were compared to 12 control/sham rats. Western blot, ELISA, and immunofluorescence analyses were performed across the frontal cortex, hippocampus, cerebellum, and brainstem. The results showed altered levels of AQP4, S100β, DNA-polymerase-β, PDGF, synaptophysin and PSD-95 in double blast vs. sham animals in most of the examined regions. These data indicate that blast-generated changes are preferentially associated with neurovascular, glymphatic, and DNA repair markers, especially in the brainstem. Moreover, these changes were not accompanied by behavioral changes and corroborate the hypothesis for which an asymptomatic altered status is caused by repeated blast exposures.

Chronic traumatic encephalopathy: Diagnostic updates and advances

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that occurs secondary to repetitive mild traumatic brain injury. Current clinical diagnosis relies on symptomatology and structural imaging findings which often vary widely among those with the disease. The gold standard of diagnosis is post-mortem pathological examination. In this review article, we provide a brief introduction to CTE, current diagnostic workup and the promising research on imaging and fluid biomarker diagnostic techniques. For imaging, we discuss quantitative structural analyses, DTI, fMRI, MRS, SWI and PET CT. For fluid biomarkers, we discuss p-tau, TREM2, CCL11, NfL and GFAP.

Markers of blood-brain barrier disruption increase early and persistently in COVID-19 patients with neurological manifestations

Background

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection is associated with disorders affecting the peripheral and the central nervous system. A high number of patients develop post-COVID-19 syndrome with the persistence of a large spectrum of symptoms, including neurological, beyond 4 weeks after infection. Several potential mechanisms in the acute phase have been hypothesized, including damage of the blood-brain-barrier (BBB). We tested weather markers of BBB damage in association with markers of brain injury and systemic inflammation may help in identifying a blood signature for disease severity and neurological complications.

Methods

Blood biomarkers of BBB disruption (MMP-9, GFAP), neuronal damage (NFL) and systemic inflammation (PPIA, IL-10, TNFα) were measured in two COVID-19 patient cohorts with high disease severity (ICUCovid; n=79) and with neurological complications (NeuroCovid; n=78), and in two control groups free from COVID-19 history, healthy subjects (n=20) and patients with amyotrophic lateral sclerosis (ALS; n=51). Samples from COVID-19 patients were collected during the first and the second wave of COVID-19 pandemic in Lombardy, Italy. Evaluations were done at acute and chronic phases of the COVID-19 infection.

Results

Blood biomarkers of BBB disruption and neuronal damage are high in COVID-19 patients with levels similar to or higher than ALS. NeuroCovid patients display lower levels of the cytokine storm inducer PPIA but higher levels of MMP-9 than ICUCovid patients. There was evidence of different temporal dynamics in ICUCovid compared to NeuroCovid patients with PPIA and IL-10 showing the highest levels in ICUCovid patients at acute phase. On the contrary, MMP-9 was higher at acute phase in NeuroCovid patients, with a severity dependency in the long-term. We also found a clear severity dependency of NFL and GFAP levels, with deceased patients showing the highest levels.

Discussion

The overall picture points to an increased risk for neurological complications in association with high levels of biomarkers of BBB disruption. Our observations may provide hints for therapeutic approaches mitigating BBB disruption to reduce the neurological damage in the acute phase and potential dysfunction in the long-term.

Short-term biological variation of serum glial fibrillary acidic protein

OBJECTIVES

Serum glial fibrillary acidic protein (GFAP) is an emerging biomarker for intracerebral diseases and is approved for clinical use in traumatic brain injury. GFAP is also being investigated for several other applications, where the GFAP changes are not always outstanding. It is thus essential for the interpretation of GFAP to distinguish clinical relevant changes from natural occurring biological variation. This study aimed at estimating the biological variation of serum GFAP.

METHODS

Apparently healthy subjects (n=33) had blood sampled for three consecutive days. On the second day, blood was also drawn every third hour from 9 AM to 9 PM. Serum GFAP was measured by Single Molecule Array (Simoa™). Components of biological variation were estimated in a linear mixed-effects model.

RESULTS

The overall median GFAP value was 92.5 pg/mL (range 34.4-260.3 pg/mL). The overall within- (CV_I) and between-subject variations (CV_G) were 9.7 and 39.5%. The reference change value was 36.9% for an increase. No day-to-day variation was observed, however semidiurnal variation was observed with increasing GFAP values between 9 AM and 12 PM (p<0.00001) and decreasing from 12 to 9 PM (p<0.001).

CONCLUSIONS

Serum GFAP exhibits a relatively low CV_I but a considerable CV_G and a marked semidiurnal variation. This implies caution on the timing of blood sampling and when interpreting GFAP in relation to reference intervals, especially in conditions where only small GFAP differences are observed.

Blood-based biomarkers and traumatic brain injury-A clinical perspective

Blood-based biomarkers are promising tools to complement clinical variables and imaging findings in the diagnosis, monitoring and outcome prediction of traumatic brain injury (TBI). Several promising biomarker candidates have been found for various clinical questions, but the translation of TBI biomarkers into clinical applications has been negligible. Measured biomarker levels are influenced by patient-related variables such as age, blood-brain barrier integrity and renal and liver function. It is not yet fully understood how biomarkers enter the bloodstream from the interstitial fluid of the brain. In addition, the diagnostic performance of TBI biomarkers is affected by sampling timing and analytical methods. In this focused review, the clinical aspects of glial fibrillary acidic protein, neurofilament light, S100 calcium-binding protein B, tau and ubiquitin C-terminal hydrolase-L1 are examined. Current findings and clinical caveats are addressed.