Dynamics of S100B release into serum and cerebrospinal fluid following acute brain injury

Diagnostic Accuracy of S100B in Predicting Intracranial Abnormalities on CT Imaging Following Mild Traumatic Brain Injury: A Systematic Review and Meta-analysis

Traumatic brain injury (TBI) is a major cause of health loss and disabilities globally, burdening health care systems. Mild TBI is a common cause of emergency department visits. Computed tomography (CT) scans are the mainstay for acute TBI imaging. S100 calcium-binding protein B (S100B) biomarker is promising for predicting intracranial lesions on CTs in mild TBI. A comprehensive search of the literature was conducted on PubMed, Google Scholar, and Cochrane electronic databases to find eligible studies reporting the diagnostic performance of S100B. A meta-analysis was conducted to evaluate the predictive ability of S100B for CT imaging abnormalities. Of 1545 articles, 32 were included in our meta-analysis. At the threshold of 0.1 μg/L, a bivariate model showed a sensitivity of 89% (95% confidence interval [CI] 83-92) with a specificity of 32% (95% CI 26-39). The aggregate analysis containing all cutoffs showed the optimal cutoff of 0.751 μg/L with a sensitivity of 64% (95% CI 32-87) and a specificity of 85% (95% CI 76-92). The optimal diagnostic performance of S100B in patients with Glasgow Coma Scale 14-15 was estimated to be 0.05 μg/L, with a sensitivity of 98% (95% CI 92-99) and a negative predictive value of 99%. These findings indicate that S100B analysis could minimize the need for unnecessary CT scans in individuals with mild TBI. The test's diagnostic accuracy improves when the S100B analysis is done within 3 h of the injury. However, further research is warranted to validate its superiority to other biomarkers before considering it the standard routine for managing mild TBI.

Serum S100β Levels Are Linked with Cognitive Decline and Peripheral Inflammation in Spinocerebellar Ataxia Type 2

Experimental and clinical studies have indicated a potential role of the protein S100β in the pathogenesis and phenotype of neurodegenerative diseases. However, its impact on spinocerebellar ataxia type 2 (SCA2) remains to be elucidated. The objective of the study is to determine the serum levels of S100β in SCA2 and its relationship with molecular, clinical, cognitive, and peripheral inflammatory markers of the disease. Serum concentrations of S100β were measured by enzyme-linked immunosorbent assay in 39 SCA2 subjects and 36 age- and gender-matched controls. Clinical scores of ataxia, non-ataxia symptoms, cognitive dysfunction, and some blood cell count-derived inflammatory indices were assessed. The SCA2 individuals manifested S100β levels similar to the control group, at low nanomolar concentrations. However, the S100β levels were directly associated with a better performance of cognitive evaluation within the SCA2 cohort. Moreover, the S100β levels were inversely correlated with most peripheral inflammatory indices. Indeed, the neutrophil-to-lymphocyte ratio significantly mediated the effect of serum S100β on cognitive performance, even after controlling for the ataxia severity in the causal mediation analysis. Our findings suggested that, within physiologic concentrations, the protein S100β exerts a neuroprotective role against cognitive dysfunction in SCA2, likely via the suppression of pro-inflammatory mechanisms.

Proteomic profile and predictive markers of outcome in patients with subarachnoid hemorrhage

BACKGROUND

The molecular mechanisms underlying development of posthemorrhagic hydrocephalus (PHH) following subarachnoid hemorrhage (SAH) remain incompletely understood. Consequently, treatment strategies tailored towards the individual patient remain limited. This study aimed to identify proteomic cerebrospinal fluid (CSF) biomarkers capable of predicting shunt dependency and functional outcome in patients with SAH in order to improve informed clinical decision making.

METHODS

Ventricular CSF samples were collected twice from 23 patients with SAH who required external ventricular drain (EVD) insertion (12 patients with successful EVD weaning, 11 patients in need of permanent CSF shunting due to development of PHH). The paired CSF samples were collected acutely after ictus and later upon EVD removal. Cisternal CSF samples were collected from 10 healthy control subjects undergoing vascular clipping of an unruptured aneurysm. All CSF samples were subjected to mass spectrometry-based proteomics analysis. Proteomic biomarkers were quantified using area under the curve (AUC) estimates from a receiver operating curve (ROC).

RESULTS

CSF from patients with SAH displayed a distinct proteomic profile in comparison to that of healthy control subjects. The CSF collected acutely after ictus from patients with SAH was moreover distinct from that collected weeks later but appeared similar in the weaned and shunted patient groups. Sixteen unique proteins were identified as potential predictors of shunt dependency, while three proteins were identified as potential predictors of functional outcome assessed six months after ictus with the modified Rankin Scale.

CONCLUSIONS

We here identified several potential proteomic biomarkers in CSF from patients with SAH capable of predicting (i) shunt dependency and thus development of PHH and (ii) the functional outcome assessed six months after ictus. These proteomic biomarkers may have the potential to aid clinical decision making by predicting shunt dependency and functional outcome following SAH.

How S100B crosses brain barriers and why it is considered a peripheral marker of brain injury

S100B is a 21-kDa protein that is produced and secreted by astrocytes and widely used as a marker of brain injury in clinical and experimental studies. The majority of these studies are based on measurements in blood serum, assuming an associated increase in cerebrospinal fluid and a rupture of the blood-brain barrier (BBB). Moreover, extracerebral sources of S100B are often underestimated. Herein, we will review these interpretations and discuss the routes by which S100B, produced by astrocytes, reaches the circulatory system. We discuss the concept of S100B as an alarmin and its dual activity as an inflammatory and neurotrophic molecule. Furthermore, we emphasize the lack of data supporting the idea that S100B acts as a marker of BBB rupture, and the need to include the glymphatic system in the interpretations of serum changes of S100B. The review is also dedicated to valorizing extracerebral sources of S100B, particularly adipocytes. Furthermore, S100B per se may have direct and indirect modulating roles in brain barriers: on the tight junctions that regulate paracellular transport; on the expression of its receptor, RAGE, which is involved in transcellular protein transport; and on aquaporin-4, a key protein in the glymphatic system that is responsible for the clearance of extracellular proteins from the central nervous system. We hope that the data on S100B, discussed here, will be useful and that it will translate into further health benefits in medical practice.

Arundic acid (ONO-2506) downregulates neuroinflammation and astrocyte dysfunction after status epilepticus in young rats induced by Li-pilocarpine

Astrocytes, the most abundant glial cells, have several metabolic functions, including ionic, neurotransmitter and energetic homeostasis for neuronal activity. Reactive astrocytes and their dysfunction have been associated with several brain disorders, including the epileptogenic process. Glial Fibrillary Acidic Protein (GFAP) and S100 calcium-binding protein B (S100B) are astrocyte biomarkers associated with brain injury. We hypothesize that arundic acid (ONO-2506), which is known as an inhibitor of S100B synthesis and secretion, protects the hippocampal tissue from neuroinflammation and astrocyte dysfunction after status epileptics (SE) induction by Li-pilocarpine in young rats. Herein, we investigated the effects of arundic acid treatment, at time points of 6 or 24 h after the induction of SE by Li-pilocarpine, in young rats. In SE animals, arundic acid was able to prevent the damage induced by Li-pilocarpine in the hippocampus, decreasing neuroinflammatory signaling (reducing IL-1β, COX2, TLR4 and RAGE contents), astrogliosis (decreasing GFAP and S100B) and astrocytic dysfunction (recovering levels of GSH, glutamine synthetase and connexin-43). Furthermore, arundic acid improved glucose metabolism and reduced the glutamate excitotoxicity found in epilepsy. Our data reinforce the role of astrocytes in epileptogenesis development and the neuroprotective role of arundic acid, which modulates astrocyte function and neuroinflammation in SE animals.

Diagnostic accuracy of prehospital serum S100B and GFAP in patients with mild traumatic brain injury: a prospective observational multicenter cohort study - "the PreTBI I study"

Background

The biomarker serum S100 calcium-binding protein B (S100B) is used in in-hospital triage of adults with mild traumatic brain injury to rule out intracranial lesions. The biomarker glial fibrillary acidic protein (GFAP) is suggested as a potential diagnostic biomarker for traumatic brain injury. The aim of this study was to investigate the diagnostic accuracy of early prehospital S100B and GFAP measurements to rule out intracranial lesions in adult patients with mild traumatic brain injury.

Methods

Prehospital and in-hospital blood samples were drawn from 566 adult patients with mild traumatic brain injury (Glasgow Coma Scale Score 14–15). The index test was S100B and GFAP concentrations. The reference standard was endpoint adjudication of the traumatic intracranial lesion based on medical records. The primary outcome was prehospital sensitivity of S100B in relation to the traumatic intracranial lesion.

Results

Traumatic intracranial lesions were found in 32/566 (5.6%) patients. The sensitivity of S100B > 0.10 μg/L was 100% (95%CI: 89.1;100.0) in prehospital samples and 100% (95% CI 89.1;100.0) in in-hospital samples. The specificity was 15.4% (95%CI: 12.4;18.7) in prehospital samples and 31.5% (27.5;35.6) in in-hospital samples. GFAP was only detected in less than 2% of cases with the assay used.

Conclusion

Early prehospital and in-hospital S100B levels < 0.10 μg/L safely rules out traumatic intracranial lesions in adult patients with mild traumatic brain injury, but specificity is lower with early prehospital sampling than with in-hospital sampling. The very limited cases with values detectable with our assay do not allow conclusions to be draw regarding the diagnostic accuracy of GFAP.

Trial registration

ClinicalTrials.gov identifier: NCT02867137.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00891-5.

Alarmins (IL-33, sST2, HMGB1, and S100B) as potential biomarkers for schizophrenia

There is growing evidence that immune/inflammatory processes are related to the etiology of schizophrenia. Danger-/damage-associated molecular patterns (DAMPs), also called alarmins, are recognized as inflammatory mediators that play an important role in the development of many infection-induced or sterile inflammatory diseases. The importance of DAMPs particles in various mental disorders is still not clear. Therefore, this study aimed to evaluate serum levels of the most promising alarmins (IL-33, sST2, HMGB1, and S100B), as potent schizophrenia biomarkers. Sixty-eight adult patients with chronic schizophrenia and twenty-nine healthy volunteers were included in this prospective study. Enzyme-linked immunosorbent assay (ELISA) was used to assess the serum concentration of IL-33, sST2, HMGB1, and S100B. We documented that the serum levels of IL-33 (p = 0.006), sST2 (p = 0.02), HMGB1 (p = 0.01), and S100B (p = 0.04) are significantly higher in patients with schizophrenia than in healthy subjects. In male, but not in female, patients with schizophrenia, we found a significant difference in the serum IL-33, sST2, and HMGB1 concentrations as compared to the healthy men. In both male and female patients with schizophrenia, there was no significant difference in the serum concentrations of S100B in comparison to control subjects. In patients with schizophrenia, no significant correlations were noticed neither between any studied alarmins and PANSS scores nor between CDSS scores. Given that all investigated alarmins participate in the course of the neuroinflammatory process, they might be considered as biomarkers of neuroinflammatory process underlying schizophrenia. Based on our observations, it seems that the most useful biological indicator of schizophrenia would be IL-33.

Post-traumatic Headache and Mild Traumatic Brain Injury: Brain Networks and Connectivity

PURPOSE OF REVIEW

Post-traumatic headache (PTH) consequent to mild traumatic brain injury (mTBI) is a complex, multidimensional, chronic neurological disorder. The purpose of this review is to evaluate the current neuroimaging studies on mTBI and PTH with a specific focus on brain networks and connectivity patterns.

RECENT FINDINGS

We present findings on PTH incidence and prevalence, as well as the latest neuroimaging research findings on mTBI and PTH. Additionally, we propose a new strategy in studying PTH following mTBI. The diversity and heterogeneity of pathophysiological mechanisms underlying mild traumatic brain injury pose unique challenges on how we interpret neuroimaging findings in PTH. Evaluating alterations in the intrinsic brain network connectivity patterns using novel imaging and analytical techniques may provide additional insights into PTH disease state and therefore inform effective treatment strategies.

S100B protein level for the detection of clinically significant intracranial haemorrhage in patients with mild traumatic brain injury: a subanalysis of a prospective cohort study

Background

Clinical assessment of patients with mild traumatic brain injury (mTBI) is challenging and overuse of head CT in the ED is a major problem. Several studies have attempted to reduce unnecessary head CTs following a mTBI by identifying new tools aiming to predict intracranial bleeding. Higher levels of S100B protein have been associated with intracranial haemorrhage following a mTBI in previous literature. The main objective of this study is to assess whether plasma S100B protein level is associated with clinically significant brain injury and could be used to reduce the number of head CT post-mTBI.

Methods

Study design: secondary analysis of a prospective multicentre cohort study conducted between 2013 and 2016 in five Canadian EDs. Inclusion criteria: non-hospitalised patients with mTBI with a GCS score of 13–15 in the ED and a blood sample drawn within 24 hours after the injury. Data collected: sociodemographic and clinical data were collected in the ED. S100B protein was analysed using ELISA. All CT scans were reviewed by a radiologist blinded to the biomarker results. Main outcome: the presence of clinically important brain injury.

Results

476 patients were included. Mean age was 41±18 years old and 150 (31.5%) were women. Twenty-four (5.0%) patients had a clinically significant intracranial haemorrhage. Thirteen patients (2.7%) presented a non-clinically significant brain injury. A total of 37 (7.8%) brain injured patients were included in our study. S100B median value (Q1–Q3) was: 0.043 µg/L (0.008–0.080) for patients with clinically important brain injury versus 0.039 µg/L (0.023–0.059) for patients without clinically important brain injury. Sensitivity and specificity of the S100B protein level, if used alone to detect clinically important brain injury, were 16.7% (95% CI 4.7% to 37.4%) and 88.5% (95% CI 85.2% to 91.3%), respectively.

Conclusion

Plasma S100B protein level was not associated with clinically significant intracranial lesion in patients with mTBI.

Prediction of Neurocognitive Outcome after Moderate-Severe Traumatic Brain Injury Using Serum Neuron-Specific Enolase and S100 biomarkers

Seric biomarkers have been tested in a large number of studies on traumatic brain injuries (TBI) patients in order to predict severity, especially related to the short-term outcome. However, TBI patients have a high risk of developing long-term complications such as physical disability, cognitive impairment, psychiatric pathology, epilepsy, and others. The aim of this study was to assess the correlation between protein biomarkers S100 and neuron-specific enolase (NSE) and neurocognitive status at 10- and 90-days post-injury. Both biomarkers were tested in the first 4h and after 72h post-injury in 62 patients with moderate-severe TBI. The patients were evaluated by a series of neurocognitive tests: Early Rehabilitation Barthel Index (ERBI), Glasgow Outcome Scale-Extended (GOSE), The Mini-Mental State Examination (MMSE), Processing Speed Index (PSI), and Stroop Test, at 10 and 90 days post-injury and supplementary by the Hospital Anxiety and Depression Scale at 90 days. For evaluating the whole neurocognitive status instead of every scale separately, we used Structural Equation Modeling (SEM), while for anxiety and depressive symptoms, we used multiple regression analyses. SEM showed that NSE values at 4 hours were significant predictors of the cognitive status at 10 (p=0.034) and 90 days (p= 0.023). Also, there were found significant correlations between NSE at 4h and the anxiety level. This study demonstrated a significant correlation between NSE at 4h and short and medium-term neuropsychological outcomes, which recommends using this biomarker for selecting patients with a higher risk of cognitive dysfunction.

Reliability of serum S100B measurement following mild traumatic brain injury: a comparison of assay measurements from two laboratories

OBJECTIVE

There is enormous research and clinical interest in blood-based biomarkers of mild traumatic brain injury (MTBI) sustained in sports, daily life, or military service. We examined the reliability of a commercially available assay for S100B used on the same samples by two different laboratories separated by 2 years in time.

METHODS AND PROCEDURES

A cohort of 163 adult patients (head CT-scanned, n = 110) with mild head injury were enrolled from the emergency department (ED). All had Glasgow Coma Scale scores of 14 or 15 in the ED (94.4% = 15). The mean time between injury and venous blood sampling was 2.9 h (SD = 1.4; Range = 0.5-6.0 h). Serum S100B was measured at two independent centers using the same high throughput clinical assay (Elecsys S100B®; Roche Diagnostics).

RESULTS

The Spearman correlation between the two assays in the total sample (N = 163) was r = 0.93. A Wilcoxson Signed Ranks test indicated that the median scores for the values differed (Z = 2,082, p < .001, Cohen's d = 0.151, small effect size). The values obtained from the two laboratories were very similar for identifying traumatic intracranial abnormalities (sensitivity = 80.1% versus 85.7%).

CONCLUSIONS

The serum S100B results measured using the same assay in different laboratories yielded highly correlated and clinically similar, but clearly not identical, results.

Increased Cerebrospinal Fluid S100B and NSE Reflect Neuronal and Glial Damage in Parkinson's Disease

Introduction: The diagnosis of Parkinson’s disease (PD) mainly relies on clinical manifestation, but may be difficult to make in very early stages of the disease, especially in pre-motor PD. Thus, there is great interest in finding a biomarker for PD. Among diagnostic biomarkers, the most promising molecules are those which reflect the pathophysiological mechanisms of the disease. Until now, only α-synuclein, a classical CSF Alzheimer’s disease biomarker, and neurofilament light (NFL) chains have turned out to be helpful in differential diagnosis between PD and healthy control subjects.

Aim: To assess whether CSF molecules related to some pathological processes present in PD might be of interest in the diagnosis of PD and whether they correlate with disease severity.

Methods: CSF levels of S100B and neuron-specific enolase (NSE) were measured in 58 PD patients and in 28 healthy control subjects. Correlations were determined between the levels of these CSF molecules and measures of disease severity (Hoehn–Yahr scale and UPDRS part III), as well as disease duration and levodopa dose.

Results: CSF S100B and CSF NSE were both significantly increased in PD subjects vs. healthy controls (p = 0.007 and p = 0.00035, respectively). CSF S100B was significantly positively correlated with measures of disease severity (H-Y score and UPDRS part III), as well as disease duration (p < 0.05). No correlation was found between CSF NSE levels and disease severity or disease duration (p > 0.05). CSF S100B levels alone provided a relatively high discrimination (AUC 0.77) between PD and healthy controls, with 60.7% sensitivity and 88.5% specificity (p < 0.001) at a cut-off value of 123.22 pg/ml. Similarly, CSF NSE levels alone provided a relatively high discrimination (AUC 0.775) between PD and healthy controls, with 78.6% sensitivity and 74.1% specificity at a cut-off value of 51.56 ng/ml (p < 0.001).

Conclusions: Our results show that both CSF S100B and CSF NSE seem to be promising markers of the axonal and glial degeneration present in PD. Additionally CSF S100B may be a promising marker of PD progression.

Significance and Diagnostic Accuracy of Early S100B Serum Concentration after Aneurysmal Subarachnoid Hemorrhage

Background: Early brain injuries (EBI) are one of the most important causes of morbidity and mortality after subarachnoid hemorrhage. At admission, a third of patients are unconscious (spontaneously or sedated) and EBI consequences are not evaluable. To date, it is unclear who will still be comatose (with severe EBI) and who will recover (with less severe EBI) once the aneurysm is treated and sedation withdrawn. The objective of the present study was to determine the diagnostic accuracy of S100B levels at hospital admission to identify patients with severe neurological consequences of EBI. Methods: Patients were consecutively included in this prospective blinded observational study. A motor component of the Glasgow coma score under 6 on day 3 was used to define patients with severe neurological consequences of EBI. Results: A total of 81 patients were included: 25 patients were unconscious at admission, 68 were treated by coiling. On day 3, 12 patients had severe consequences of EBI. A maximal S100B value between admission and day 1 had an area under the receiver operating characteristic curve (AUC) of 86.7% to predict severe EBI consequences. In patients with impaired consciousness at admission, the AUC was 88.2%. Conclusion: Early S100B seems to have a good diagnostic value to predict severe EBI. Before claiming the usefulness of S100B as a surrogate marker of EBI severity to start earlier multimodal monitoring, these results must be confirmed in an independent validation cohort.

The S100B Protein and Partners in Adipocyte Response to Cold Stress and Adaptive Thermogenesis: Facts, Hypotheses, and Perspectives

In mammals, adipose tissue is an active secretory tissue that responds to mild hypothermia and as such is a genuine model to study molecular and cellular adaptive responses to cold-stress. A recent study identified a mammal-specific protein of the endoplasmic reticulum that is strongly induced in the inguinal subcutaneous white adipocyte upon exposure to cold, calsyntenin 3β (CLSTN3β). CLSTN3β regulates sympathetic innervation of thermogenic adipocytes and contributes to adaptive non-shivering thermogenesis. The calcium- and zinc-binding S100B is a downstream effector in the CLSTN3β pathways. We review, here, the literature on the transcriptional regulation of the S100b gene in adipocyte cells. We also rationalize the interactions of the S100B protein with its recognized or hypothesized intracellular (p53, ATAD3A, CYP2E1, AHNAK) and extracellular (Receptor for Advanced Glycation End products (RAGE), RPTPσ) target proteins in the context of adipocyte differentiation and adaptive thermogenesis. We highlight a chaperon-associated function for the intracellular S100B and point to functional synergies between the different intracellular S100B target proteins. A model of non-classical S100B secretion involving AHNAK/S100A10/annexin2-dependent exocytosis by the mean of exosomes is also proposed. Implications for related areas of research are noted and suggestions for future research are offered.

Role of Damage Associated Molecular Pattern Molecules (DAMPs) in Aneurysmal Subarachnoid Hemorrhage (aSAH)

Aneurysmal subarachnoid hemorrhage (aSAH) represents only a small portion of all strokes, but accounts for almost half of the deaths caused by stroke worldwide. Neurosurgical clipping and endovascular coiling can successfully obliterate the bleeding aneurysms, but ensuing complications such as cerebral vasospasm, acute and chronic hydrocephalus, seizures, cortical spreading depression, delayed ischemic neurological deficits, and delayed cerebral ischemia lead to poor clinical outcomes. The mechanisms leading to these complications are complex and poorly understood. Early brain injury resulting from transient global ischemia can release molecules that may be critical to initiate and sustain inflammatory response. Hence, the events during early brain injury can influence the occurrence of delayed brain injury. Since the damage associated molecular pattern molecules (DAMPs) might be the initiators of inflammation in the pathophysiology of aSAH, so the aim of this review is to highlight their role in the context of aSAH from diagnostic, prognostic, therapeutic, and drug therapy monitoring perspectives. DAMPs represent a diverse and a heterogenous group of molecules derived from different compartments of cells upon injury. Here, we have reviewed the most important DAMPs molecules including high mobility group box-1 (HMGB1), S100B, hemoglobin and its derivatives, extracellular matrix components, IL-1α, IL-33, and mitochondrial DNA in the context of aSAH and their role in post-aSAH complications and clinical outcome after aSAH.

Effects of dexamethasone on the Li-pilocarpine model of epilepsy: protection against hippocampal inflammation and astrogliosis

Background

Temporal lobe epilepsy (TLE) is the most common form of partial epilepsy and is accompanied, in one third of cases, by resistance to antiepileptic drugs (AED). Most AED target neuronal activity modulated by ionic channels, and the steroid sensitivity of these channels has supported the use of corticosteroids as adjunctives to AED. Assuming the importance of astrocytes in neuronal activity, we investigated inflammatory and astroglial markers in the hippocampus, a key structure affected in TLE and in the Li-pilocarpine model of epilepsy.

Methods

Initially, hippocampal slices were obtained from sham rats and rats subjected to the Li-pilocarpine model of epilepsy, at 1, 14, and 56 days after status epilepticus (SE), which correspond to the acute, silent, and chronic phases. Dexamethasone was added to the incubation medium to evaluate the secretion of S100B, an astrocyte-derived protein widely used as a marker of brain injury. In the second set of experiments, we evaluated the in vivo effect of dexamethasone, administrated at 2 days after SE, on hippocampal inflammatory (COX-1/2, PGE2, and cytokines) and astroglial parameters: GFAP, S100B, glutamine synthetase (GS) and water (AQP-4), and K⁺ (Kir 4.1) channels.

Results

Basal S100B secretion and S100B secretion in high-K⁺ medium did not differ at 1, 14, and 56 days for the hippocampal slices from epileptic rats, in contrast to sham animal slices, where high-K⁺ medium decreased S100B secretion. Dexamethasone addition to the incubation medium per se induced a decrease in S100B secretion in sham and epileptic rats (1 and 56 days after SE induction). Following in vivo dexamethasone administration, inflammatory improvements were observed, astrogliosis was prevented (based on GFAP and S100B content), and astroglial dysfunction was partially abrogated (based on Kir 4.1 protein and GSH content). The GS decrease was not prevented by dexamethasone, and AQP-4 was not altered in this epileptic model.

Conclusions

Changes in astroglial parameters emphasize the importance of these cells for understanding alterations and mechanisms of epileptic disorders in this model. In vivo dexamethasone administration prevented most of the parameters analyzed, reinforcing the importance of anti-inflammatory steroid therapy in the Li-pilocarpine model and possibly in other epileptic conditions in which neuroinflammation is present.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1109-5) contains supplementary material, which is available to authorized users.

Serial Sampling of Serum Protein Biomarkers for Monitoring Human Traumatic Brain Injury Dynamics: A Systematic Review

BACKGROUND

The proteins S100B, neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), and neurofilament light (NF-L) have been serially sampled in serum of patients suffering from traumatic brain injury (TBI) in order to assess injury severity and tissue fate. We review the current literature of serum level dynamics of these proteins following TBI and used the term "effective half-life" (t1/2) in order to describe the "fall" rate in serum.

MATERIALS AND METHODS

Through searches on EMBASE, Medline, and Scopus, we looked for articles where these proteins had been serially sampled in serum in human TBI. We excluded animal studies, studies with only one presented sample and studies without neuroradiological examinations.

RESULTS

Following screening (10,389 papers), n = 122 papers were included. The proteins S100B (n = 66) and NSE (n = 27) were the two most frequent biomarkers that were serially sampled. For S100B in severe TBI, a majority of studies indicate a t1/2 of about 24 h, even if very early sampling in these patients reveals rapid decreases (1-2 h) though possibly of non-cerebral origin. In contrast, the t1/2 for NSE is comparably longer, ranging from 48 to 72 h in severe TBI cases. The protein GFAP (n = 18) appears to have t1/2 of about 24-48 h in severe TBI. The protein UCH-L1 (n = 9) presents a t1/2 around 7 h in mild TBI and about 10 h in severe. Frequent sampling of these proteins revealed different trajectories with persisting high serum levels, or secondary peaks, in patients with unfavorable outcome or in patients developing secondary detrimental events. Finally, NF-L (n = 2) only increased in the few studies available, suggesting a serum availability of >10 days. To date, automated assays are available for S100B and NSE making them faster and more practical to use.

CONCLUSION

Serial sampling of brain-specific proteins in serum reveals different temporal trajectories that should be acknowledged. Proteins with shorter serum availability, like S100B, may be superior to proteins such as NF-L in detection of secondary harmful events when monitoring patients with TBI.

Phase-Dependent Astroglial Alterations in Li-Pilocarpine-Induced Status Epilepticus in Young Rats

Epilepsy prevalence is high in infancy and in the elderly population. Lithium-pilocarpine is widely used to induce experimental animal models of epilepsy, leading to similar neurochemical and morphological alterations to those observed in temporal lobe epilepsy. As astrocytes have been implicated in epileptic disorders, we hypothesized that specific astroglial changes accompany and contribute to epileptogenesis. Herein, we evaluated time-dependent astroglial alterations in the hippocampus of young (27-day-old) rats at 1, 14 and 56 days after Li-pilocarpine-induced status epilepticus (SE), corresponding to different phases in this model of epilepsy. We determined specific markers of astroglial activation: GFAP, S100B, glutamine synthetase (GS), glutathione (GSH) content, aquaporin-4 (AQP-4) and potassium channel Kir 4.1; as well as epileptic behavioral, inflammatory and neurodegenerative changes. Phase-dependent signs of hippocampal astrogliosis were observed, as demonstrated by increments in GFAP, S100B and GS. Astrocyte dysfunction in the hippocampus was characterized, based on the decrease in GSH content, AQP-4 and Kir 4.1 channels. Degenerating neurons were identified by Fluoro-Jade C staining. We found a clear, early (at SE1) and persistent (at SE56) increase in cerebrospinal fluid (CSF) S100B levels. Additionally, serum S100B was found to decrease soon after SE induction, implicating a rapid-onset increase in the CSF/serum S100B ratio. However, serum S100B increased at SE14, possibly reflecting astroglial activation and/or long-term increase in cerebrovascular permeability. Moreover, we suggest that peripheral S100B levels may represent a useful marker for SE in young rats and for follow up during the chronic phases of this model of epilepsy. Together, results reinforce and extend the idea of astroglial involvement in epileptic disorders.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

Background

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein “biomarker” of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

Results

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

Conclusion

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

BACKGROUND

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein "biomarker" of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

RESULTS

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

CONCLUSION

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

Protein S-100 and neuron-specific enolase serum levels remain unaffected by electroconvulsive therapy in patients with depression

The mechanism of the reversible cognitive deficits that might occur within an electroconvulsive therapy (ECT) treatment has not been clarified in a substantial way yet. Although the data available so far do not point towards a cause due to any structural or diffuse damage, further clarification, especially of the role of S-100 seems to be necessary before robust conclusions can be drawn. Serum levels of protein S-100 and neuron-specific enolase (NSE) were analysed in 19 patients with depression, who received ECT. The sampling was adjusted for the short half-life of protein S-100. Several outcome parameters such as Hamilton Depression Rating Scale and Mini-mental state examination before and after the ECT, response and remission to the treatment were recorded. S-100 and NSE levels at baseline, 30 and 60 min after the third session and after the end of the ECT remained stable. S-100 and NSE levels were neither associated with antidepressant response or remission nor with alterations in the cognitive performance. Although aiming for detecting potential rise in these established brain damage markers, an increase due to ECT was not observed, which is in line with the previous studies concerning the safety of ECT on a cellular basis.

Influence of the blood-CSF-barrier function on S100B in neurodegenerative diseases

OBJECTIVES

S100B was proposed to be a CSF and blood biomarker in a number of neurological diseases. The route of S100B to the CSF and the blood in neurodegenerative diseases is unclear. To assess the impact of the physiological or impaired blood-CSF-barrier (BCSFB) function on S100B concentrations in CSF and serum, we analysed S100B in correlation of the albumin quotient.

MATERIALS AND METHODS

S100Bserum and S100BCSF were quantified in samples from patients with a variety of neurological diseases using an immunoluminometric assay (Sangtec LIA-mat). Measures were analysed for a potential relation to the CSF/serum-albumin quotient (Qalb ), which indicates the BCSFB functionality.

RESULTS

We reasserted increased S100B concentrations in CSF and serum of CJD patients. Elevated S100Bserum correlated with elevated S100BCSF in all diagnoses but with exceptions. Neither S100BCSF nor S100Bserum did correlate with Qalb , even when the BCSFB function was progressively impaired as demonstrated by increased Qalb .

CONCLUSIONS

The lack of correlation between Qalb and S100BCSF is typically seen for proteins which are brain derived. Therefore, we propose that S100B enters the blood with the bulk flow via Pacchioni's granules and along the spinal nerve sheaths.

Neuroprotein dynamics in the cerebrospinal fluid: intraindividual concomitant ventricular and lumbar measurements

OBJECTIVE

The measurement of neuromarker/neuroproteins in the cerebrospinal fluid (CSF) is gaining increased popularity. However, insufficient information is available on the rostrocaudal distribution of neuroproteins in the CSF to guarantee an appropriate interpretation of ventricular versus lumbar concentrations.

METHODS

In 10 patients treated with both an external ventricular and a lumbar CSF drain, we collected concomitant CSF samples. We measured CSF concentrations of the glial S100B protein, the neuron-specific enolase (Cobas e411®; Roche Diagnostics), the leptomeningeal β-trace protein (BN Pro Spec®; Dade Behring/Siemens), and the blood-derived albumin (Immage; Beckman Coulter). Statistical analysis was performed with a paired Wilcoxon signed ranks test.

RESULTS

In patients with a free CSF circulation without any recent neurosurgical procedure, S100B and neuron-specific enolase concentrations did not differ between the ventricular and lumbar CSF while β-trace and albumin levels were significantly higher in the lumbar than in the ventricular CSF (p=0.008 and p=0.005). Following posterior fossa tumor surgery, all proteins accumulate in the lumbar CSF.

CONCLUSION

For brain-derived proteins, we could not confirm a rostrocaudal CSF gradient while lepto-meningeal and blood-derived proteins accumulate in the lumbar CSF. We conclude that for the interpretation of protein CSF concentrations, the source of the sample is of crucial importance.

Brain-derived protein concentrations in the cerebrospinal fluid: contribution of trauma resulting from ventricular drain insertion

In recent years, the measurement of biomarkers following neurotrauma assisted in improving outcome prediction and guiding therapy. The use of neuroproteins as diagnostic parameters requires a detailed knowledge of their dynamics in biological fluids for an appropriate interpretation. S100B is the most widely studied neuromarker, and its concentration in serum and cerebrospinal fluid (CSF) reflects the extent of brain damage. Neuron-specific enolase (NSE) is considered reflecting neuronal damage, while Beta-Trace is a lepto-meningeal protein used to diagnose CSF leakage. In five patients treated with an external ventricular drain (EVD) because of aneurysmal subarachnoid hemorrhage (SAH, n=3) or postinfectious hydrocephalus (n=2), an EVD exchange was performed 8 to 12 days after initial insertion. S100B and NSE were measured with the Cobas e411(®) electrochemiluminescence assay (Roche Diagnostics, Mannheim, Germany) and Beta-Trace with the BN Pro Spec(®) nephelometer (Dade Behring/Siemens, Germany) 1 h before EVD exchange, upon the insertion of the new drain, and 1, 3, 6, 12, 18, 24 and 48 h after EVD exchange. Before EVD exchange, S100B CSF concentrations were within the normal range in all patients (1.48 ± 0.37 μg/L), while NSE CSF concentrations were normal in four of five patients (6.51 ± 2.98 μg/L). Following EVD exchange, S100B and NSE CSF levels peaked significantly at 3 h after insertion of the new drain (S100B 39.02 ± 9.17 μg/L; NSE 54.80 ± 43.34 μg/L). S100B serum levels were slightly increased 6 to 24 h after EVD exchange. Beta-Trace concentrations in the CSF were not altered by EVD insertion. Our data demonstrate that EVD insertion results in a distinct increase of S100B and NSE concentrations in the CSF. Thus, the tampering of brain-derived protein concentrations in the CSF by diagnostic or therapeutic procedures has to be considered in the interpretation of neuromarker levels.

S100b as a prognostic biomarker in outcome prediction for patients with severe traumatic brain injury

As an astrocytic protein specific to the central nervous system, S100b is a potentially useful marker in outcome prediction after traumatic brain injury (TBI). Some studies have questioned the validity of S100b, citing the extracerebral origins of the protein as reducing the specificity of the marker. This study evaluated S100b as a prognostic biomarker in adult subjects with severe TBI (sTBI) by comparing outcomes with S100b temporal profiles generated from both cerebrospinal fluid (CSF) (n = 138 subjects) and serum (n = 80 subjects) samples across a 6-day time course. Long-bone fracture, Injury Severity Score (ISS), and isolated head injury status were variables used to assess extracerebral sources of S100b in serum. After TBI, CSF and serum S100b levels were increased over healthy controls across the first 6 days post-TBI (p ≤ 0.005 and p ≤ 0.031). Though CSF and serum levels were highly correlated during early time points post-TBI, this association diminished over time. Bivariate analysis showed that subjects who had temporal CSF profiles with higher S100b concentrations had higher acute mortality (p < 0.001) and worse Glasgow Outcome Scale (GOS; p = 0.002) and Disability Rating Scale (DRS) scores (p = 0.039) 6 months post-injury. Possibly as a result of extracerebral sources of S100b in serum, as represented by high ISS scores (p = 0.032), temporal serum profiles were associated with acute mortality (p = 0.015). High CSF S100b levels were observed in women (p = 0.022) and older subjects (p = 0.004). Multivariate logistic regression confirmed CSF S100b profiles in predicting GOS and DRS and showed mean and peak serum S100b as acute mortality predictors after sTBI.

Olympic boxing is associated with elevated levels of the neuronal protein tau in plasma

OBJECTIVES

The aim of this study was to investigate if olympic (amateur) boxing is associated with elevation of brain injury biomarkers in peripheral blood compared to controls.

MATERIALS AND METHODS

Thirty olympic boxers competing in at least 47 bouts were compared to 25 controls. Blood was collected from the controls at one occasion and from the boxers within 1-6 days after a bout and after a rest period of at least 14 days. Tau concentration in plasma was determined using a novel single molecule ELISA assay and S-100B, glial fibrillary acidic protein, brain-derived neurotrophic factor and amyloid β 1-42 were determined using standard immunoassays.

RESULTS

None of the boxers had been knocked-out during the bout. Plasma-tau was significantly increased in the boxers after a bout compared to controls (mean ± SD, 2.46 ± 5.10 vs. 0.79 ± 0.961 ng L(-1), p = 0.038). The other brain injury markers did not differ between the groups. Plasma-tau decreased significantly in the boxers after a resting period compared to after a bout (p = 0.030).

CONCLUSIONS

Olympic boxing is associated with elevation of tau in plasma. The repetitive minimal head injury in boxing may lead to axonal injuries that can be diagnosed with a blood test.

S100B is increased in Parkinson's disease and ablation protects against MPTP-induced toxicity through the RAGE and TNF-α pathway

Parkinson’s disease is a neurodegenerative disorder that can, at least partly, be mimicked by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. S100B is a calcium-binding protein expressed in, and secreted by, astrocytes. There is increasing evidence that S100B acts as a cytokine or damage-associated molecular pattern protein not only in inflammatory but also in neurodegenerative diseases. In this study, we show that S100B protein levels were higher in post-mortem substantia nigra of patients with Parkinson’s disease compared with control tissue, and cerebrospinal fluid S100B levels were higher in a large cohort of patients with Parkinson’s disease compared with controls. Correspondingly, mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed upregulated S100B messenger RNA and protein levels. In turn, ablation of S100B resulted in neuroprotection, reduced microgliosis and reduced expression of both the receptor for advanced glycation endproducts and tumour necrosis factor-α. Our results demonstrate a role of S100B in the pathophysiology of Parkinson’s disease. Targeting S100B may emerge as a potential treatment strategy in this disorder.

Clinical significance of serological biomarkers and neuropsychological performances in patients with temporal lobe epilepsy

Background

Temporal lobe epilepsy (TLE) is a common form of focal epilepsy. Serum biomarkers to predict cognitive performance in TLE patients without psychiatric comorbidities and the link with gray matter (GM) atrophy have not been fully explored.

Methods

Thirty-four patients with TLE and 34 sex - and age-matched controls were enrolled for standardized cognitive tests, neuroimaging studies as well as measurements of serum levels of heat shock protein 70 (HSP70), S100ß protein (S100ßP), neuronal specific enolase (NSE), plasma nuclear and mitochondrial DNA levels.

Results

Compared with the controls, the patients with TLE had poorer cognitive performances and higher HSP70 and S100ßP levels (p < 0.01). The patients with higher frequencies of seizures had higher levels of HSP70, NSE and S100ßP (p < 0.01). Serum HSP70 level correlated positively with duration of epilepsy (σ = 0.413, p < 0.01), and inversely with memory scores in the late registration (σ = −0.276, p = 0.01) and early recall score (σ = −0.304, p = 0.007). Compared with the controls, gray matter atrophy in the hippocampal and parahippocampal areas, putamen, thalamus and supplementary motor areas were found in the patient group. The HSP70 levels showed an inverse correlation with hippocampal volume (R square = 0.22, p = 0.007) after controlling for the effect of age.

Conclusions

Our results suggest that serum biomarkers were predictive of higher frequencies of seizures in the TLE group. HSP70 may be considered to be a stress biomarker in patients with TLE in that it correlated inversely with memory scores and hippocampal volume. In addition, the symmetric extratemporal atrophic patterns may be related to damage of neuronal networks and epileptogenesis in TLE.

Serum GFAP levels in optic neuropathies

BACKGROUND

Complement mediated autoimmunity against aquaporin-4 results in astrocytic damage in neuromyelitis optica (NMO). There is evidence for increased CSF glial fibrillary acidic protein (GFAP) and S100B levels in acute NMO. Here we tested whether the CSF finding also holds true for the diagnostic value of serum GFAP and S100B levels in NMO.

METHODS

A multicentre study included 322 patients from London (n=160), Nijmegen (n=95), Pecs (n=44), and Lyon (n=24). Patients were classified into the following diagnostic categories: neurological control patients (n=45), MS optic neuritis (MSON, n=38), isolated optic neuritis (ION, n=11), relapsing isolated optic neuritis (RION, n=48), chronic relapsing isolated optic neuropathy (CRION, n=18), unclassified optic neuritis (UCON, n=39), NMO (n=77) and relapsing remitting multiple sclerosis (RRMS, n=47). Serum GFAP and S100B levels were quantified using ELISA.

RESULTS

Median serum GFAP but not S100B levels were significantly higher (p<0.0001, general linear model) in patients with NMO (4.83 pg/mL) if compared to MSON (1.5 pg/mL, p=0.0001), UCON (1.92 pg/mL, p<0.01), ION (0.0 ng/mL, p<0.05), RION (1.3 pg/mL, p<0.0001) and CRION (2.2 pg/mL, p=0.01). Serum GFAP levels in the control cohort (3.6 pg/mL) were not significantly different to NMO. There was no relationship between serum GFAP levels and any other clinical or demographic parameter. Serum S100B concentrations correlated with the number of relapses in MSON (R=0.83, p=0.005).

CONCLUSION

In contrast to the CSF, neither serum GFAP nor S100B levels were of major diagnostic value for the laboratory supported differential diagnosis between optic neuritis in the context of NMO and other optic neuropathies.

Utility of Serum S100B Protein for Identification of Central Nervous System Involvement in Systemic Lupus Erythematosus

Objective.

To evaluate utility of S100B protein in serum as a marker of central nervous system involvement in systemic lupus erythematosus (SLE).

Methods.

Forty patients with SLE, hospitalized because of central neuropsychiatric (cNP) manifestations (n = 36) and peripheral NP manifestations (pNP, n = 4) were studied. Patients were evaluated at hospitalization and 6 months later, including a serum and cerebrospinal fluid (CSF) sample. As controls, 4 SLE patients with septic meningitis (SLEsm), 13 surgical SLE patients (SLE surgical), 14 patients with nonautoimmune diseases, and 4 patients with primary NP syndromes were included. Serum and CSF S100B protein levels were determined by ELISA.

Results.

At baseline, serum levels of S100B protein did not differ across SLE groups. Using an arbitrary cutoff value, positive S100B levels in serum were observed in 7 (19%), 6 (46%), and 1 patient from the cNPSLE, SLE surgical, and SLEsm groups, respectively. S100B protein levels in cNPSLE and SLE surgical patients were similar. In CSF, S100B protein levels did not differ among SLE groups, except in patients with SLEsm. Paired serum/CSF samples were obtained in 23 patients with cNPSLE at 6 months after the acute event. Overall, levels of S100B protein in serum did not change despite the decrease observed in CSF (p = 0.004). The correlation coefficient of serum and CSF S100B protein levels among all the SLE patients at baseline was poor (r = 0.23).

Conclusion.

Serum levels of S100B protein do not differentiate SLE patients with and those without central neurological manifestations.

The Passage of S100B from Brain to Blood Is Not Specifically Related to the Blood-Brain Barrier Integrity

Following brain injury, S100B is released from damaged astrocytes but also yields repair mechanisms. We measured S100B in the cerebrospinal fluid (CSF) and serum (Cobas e411 electrochemiluminescence assay, Roche) longitudinally in a large cohort of patients treated with a ventricular drainage following traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Statistical analysis was performed with SPSS software applying the Mann-Whitney rank sum test or chi-test where appropriate. S100B in CSF and serum was significantly increased following TBI (n = 71) and SAH (n = 185) for at least one week following injury. High S100B levels in CSF and serum were inconsistent associated with outcome. The passage of S100B from CSF to blood (100^∗serum_S100B/CSF_S100B) was significantly decreased although the albumin quotient suggested an “open” blood-CSF barrier. Events possibly interfering with the BBB did not affect the S100B passage (P = .591). In conclusion, we could not confirm S100B measurements to reliably predict outcome, and a compromised blood-CSF barrier did not affect the passage of S100B from CSF to serum.