Elevated serum ubiquitin carboxy-terminal hydrolase L1 is associated with abnormal blood-brain barrier function after traumatic brain injury

Evaluating the utility of serum NfL, GFAP, UCHL1 and tTAU as estimates of CSF levels and diagnostic instrument in neuroinflammation and multiple sclerosis

BACKGROUND

This study aimed to evaluate the utility of neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase L1 (UCHL1) and total tau (tTAU) serum concentrations as approximation for cerebrospinal fluid (CSF) concentrations of the respective biomarkers in the context of neuroinflammation and multiple sclerosis (MS).

METHODS

NfL, GFAP, UCHL1 and tTAU concentrations in serum and CSF were measured in 183 patients (122 with neuroinflammatory disease and 61 neurological or somatoform disease controls) using the single molecule array HD-1 analyzer (Quanterix, Boston, MA). Spearman's rank correlations were computed between serum and CSF concentrations. In a second step, the effects of age, BMI, gadolinium-enhancing lesions in MRI, integrity of the blood-brain barrier (BBB) and presence of acute relapse were accounted for by computing partial correlations. The analyses were repeated for a subsample consisting of MS phenotype patients only (n = 118). EDSS, MS disease activity and acute relapse were considered as additional covariates. Receiver operating characteristic (ROC) analysis was performed for each serum/CSF biomarker concentration to assess how well the particular biomarker concentration differentiates MS patients from somatoform disease controls. Correlations between serum and CSF levels as well as area under the curve (AUC) values were compared for the different biomarkers using z-test statistics.

RESULTS

Serum concentrations correlated positively with CSF levels for NfL (r = 0.705, p < 0.01) as well as for GFAP (r = 0.259, p < 0.01). Correlation coefficients were significantly higher for NfL than for GFAP (z = 5.492, p < 0.01). We found no significant serum-CSF correlations for UCHL1 or tTAU. After adjusting for covariates, the results remained unchanged. In the analysis focusing only on MS patients, the results were replicated. ROC analysis demonstrated similarly acceptable performance of serum and CSF NfL values in differentiating MS phenotype patients from somatoform disease controls. AUC values were significantly higher for serum and CSF NfL compared to other biomarkers.

CONCLUSION

NfL and GFAP but not UCHL1 or tTAU serum concentrations are associated with CSF levels of the respective biomarker. NfL exhibits more robust correlations between its serum and CSF concentrations as compared to GFAP independently from BBB integrity, clinical and radiological covariates. Both serum and CSF NfL values differentiate between MS and controls.

Predicting Role of GFAP and UCH-L1 biomarkers in Spontaneous Subarachnoid Hemorrhage: a preliminary study to evaluate in the short-term their correlation with severity of bleeding and prognosis

BACKGROUND

Spontaneous non-traumatic subarachnoid hemorrhage (sSAH) is a severe brain vascular accident. Glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) can be theoretically assayed to predict a patient's progression, picturing different aspects of clinical failure after sSAH. The study aims to: a) explore the correlation between sSAH blood volume and biomarkers variation; b) evaluate if these can be predictive of the neurogenic response after sSAH and be prognostic of patient outcome; c) establish eventual threshold levels of biomarkers to define patients' clinical outcome.

METHODS

Blood volumetry at CT scan upon admission, GFAP and UCH-L1 were collected at 24 h, at 72 h, and after 7 days from hemorrhage. Trends and cut-off serum sampling were determined. Clinical outcome was assessed with mRS scale at 14 days.

RESULTS

A strong correlation between GFAP and UCH-L1 and blood diffusion volume in all explored serum intervals related to unfavorable outcome. GFAP and UCH-L1 were very early predictors of unfavorable outcomes at 24 h from sSAH (p = 0.002 and 0.011 respectively). Threshold levels of UCH-L1 apparently revealed a very early, early and late predictor of unfavorable outcomes.

CONCLUSION

GFAP and UCH-L1 represent a potential tool for prompt monitoring and customization of therapies in neurosurgical patients.

The contribution of the meningeal immune interface to neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI) is a major cause of disability and mortality worldwide, particularly among the elderly, yet our mechanistic understanding of what renders the post-traumatic brain vulnerable to poor outcomes, and susceptible to neurological disease, is incomplete. It is well established that dysregulated and sustained immune responses elicit negative consequences after TBI; however, our understanding of the neuroimmune interface that facilitates crosstalk between central and peripheral immune reservoirs is in its infancy. The meninges serve as the interface between the brain and the immune system, facilitating important bi-directional roles in both healthy and disease settings. It has been previously shown that disruption of this system exacerbates neuroinflammation in age-related neurodegenerative disorders such as Alzheimer's disease; however, we have an incomplete understanding of how the meningeal compartment influences immune responses after TBI. In this manuscript, we will offer a detailed overview of the holistic nature of neuroinflammatory responses in TBI, including hallmark features observed across clinical and animal models. We will highlight the structure and function of the meningeal lymphatic system, including its role in immuno-surveillance and immune responses within the meninges and the brain. We will provide a comprehensive update on our current knowledge of meningeal-derived responses across the spectrum of TBI, and identify new avenues for neuroimmune modulation within the neurotrauma field.

Optimizing Concussion Care Seeking: Connecting Care-Seeking Behaviors and Neurophysiological States Through Blood Biomarkers

BACKGROUND

Timely and appropriate medical care after concussion presents a difficult public health problem. Concussion identification and treatment rely heavily on self-report, but more than half of concussions go unreported or are reported after a delay. If incomplete self-report increases exposure to harm, blood biomarkers may objectively indicate this neurobiological dysfunction.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare postconcussion biomarker levels between individuals with different previous concussion diagnosis statuses and care-seeking statuses. It was hypothesized that individuals with undiagnosed concussions and poorer care seeking would show altered biomarker profiles.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Blood samples were collected from 287 military academy cadets and collegiate athletes diagnosed with concussion in the Advanced Research Core of the Concussion Assessment, Research and Education Consortium. The authors extracted each participant's self-reported previous concussion diagnosis status (no history, all diagnosed, ≥1 undiagnosed) and whether they had delayed or immediate symptom onset, symptom reporting, and removal from activity after the incident concussion. The authors compared the following blood biomarkers associated with neural injury between previous concussion diagnosis status groups and care-seeking groups: glial fibrillary acidic protein, ubiquitin c-terminal hydrolase-L1 (UCH-L1), neurofilament light chain (NF-L), and tau protein, captured at baseline, 24 to 48 hours, asymptomatic, and 7 days after unrestricted return to activity using tests of parallel profiles.

RESULTS

The undiagnosed previous concussion group (n = 21) had higher levels of NF-L at 24- to 48-hour and asymptomatic time points relative to all diagnosed (n = 72) or no previous concussion (n = 194) groups. For those with delayed removal from activity (n = 127), UCH-L1 was lower at 7 days after return to activity than that for athletes immediately removed from activity (n = 131). No other biomarker differences were observed.

CONCLUSION

Individuals with previous undiagnosed concussions or delayed removal from activity showed some different biomarker levels after concussion and after clinical recovery, despite a lack of baseline differences. This may indicate that poorer care seeking can create neurobiological differences in the concussed brain.

The Effects of Transcranial Direct Current Stimulation and Exercise on Salivary S100B Protein Indicated Blood-Brain Barrier Permeability: A Pilot Study

OBJECTIVE

This study aimed to assess the effect of transcranial direct current stimulation (tDCS) and exercise on blood-brain barrier (BBB) permeability in humans as assessed through the quantification of the salivary protein biomarker S100B. It was hypothesized that active tDCS would induce a significant increase in salivary S100B concentration when compared with sham stimulation and no stimulation. It also was hypothesized that the increase in salivary S100B concentration would be greater after active tDCS and exercise than after tDCS or exercise alone.

MATERIALS AND METHODS

A total of 13 healthy adults (five male, eight female), ranging in age from 21 to 32 years, underwent three experimental conditions (active tDCS, sham tDCS, inactive control). To assess exercise- and tDCS-induced changes in BBB permeability, S100B in saliva was measured. Saliva samples were taken before tDCS, after tDCS, and immediately after a ramped cycling time-to-exhaustion (TTE) task. Active tDCS involved the application of anodal stimulation over the primary motor cortex for 20 minutes at 2 mA.

RESULTS

S100B concentrations in the control condition did not differ significantly from the active condition (estimate = 0.10, SE = 0.36, t = 0.27, p = 0.79) or the sham condition (estimate = 0.33, SE = 0.36, t = 0.89, p = 0.38). Similarly, S100B concentrations at baseline did not differ significantly from post-intervention (estimate = -0.35, SE = 0.34, t = -1.03, p = 0.31) or post-TTE (estimate = 0.66, SE = 0.34, t = 1.93, p = 0.06).

CONCLUSIONS

This research provides novel insight into the effect of tDCS and exercise on S100B-indicated BBB permeability in humans. Although the effects of tDCS were not significant, increases in salivary S100B after a fatiguing cycling task may indicate exercise-induced changes in BBB permeability.

Stroke-induced damage on the blood-brain barrier

The blood-brain barrier (BBB) is a functional phenotype exhibited by the neurovascular unit (NVU). It is maintained and regulated by the interaction between cellular and non-cellular matrix components of the NVU. The BBB plays a vital role in maintaining the dynamic stability of the intracerebral microenvironment as a barrier layer at the critical interface between the blood and neural tissues. The large contact area (approximately 20 m2/1.3 kg brain) and short diffusion distance between neurons and capillaries allow endothelial cells to dominate the regulatory role. The NVU is a structural component of the BBB. Individual cells and components of the NVU work together to maintain BBB stability. One of the hallmarks of acute ischemic stroke is the disruption of the BBB, including impaired function of the tight junction and other molecules, as well as increased BBB permeability, leading to brain edema and a range of clinical symptoms. This review summarizes the cellular composition of the BBB and describes the protein composition of the barrier functional junction complex and the mechanisms regulating acute ischemic stroke-induced BBB disruption.

Plasma ubiquitin C-terminal hydrolase-L1 (UCH-L1) level as a blood biomarker of neurological damage after allogeneic hematopoietic cell transplantation

Several biofluid-based biomarkers for traumatic brain injury show promise for use in diagnosis and outcome prediction. In contrast, few studies have investigated biomarkers for non-traumatic brain injury. We focused on ubiquitin C-terminal hydrolase-L1 (UCH-L1), which has been proposed as a screening tool for traumatic brain injury, and investigated whether the plasma UCH-L1 level could also be a useful biomarker in patients with non-traumatic brain injury. We measured UCH-L1 in 25 patients who had experienced neurological complications after allogeneic hematopoietic cell transplantation (HCT) and 22 control patients without any complications or graft-versus-host disease. Although UCH-L1 levels before HCT did not differ significantly (P = 0.053), levels after HCT were higher in patients with neurological complications compared with the control group (P < 0.001). At a UCH-L1 cutoff value of 0.072 ng/ml, sensitivity was 68.0% and specificity was 100%. The statistical power of UCH-L1 for neurological complications seemed to be higher than that of CT and comparable to that of MRI. Thus, increased levels of UCH-L1 might reflect the presence of neurological damage even in patients with non-traumatic brain injury. Further large cohort investigations are warranted.

Fluid Biomarkers of Neuro-Glial Injury in Human Status Epilepticus: A Systematic Review

As per the latest ILAE definition, status epilepticus (SE) may lead to long-term irreversible consequences, such as neuronal death, neuronal injury, and alterations in neuronal networks. Consequently, there is growing interest in identifying biomarkers that can demonstrate and quantify the extent of neuronal and glial injury. Despite numerous studies conducted on animal models of status epilepticus, which clearly indicate seizure-induced neuronal and glial injury, as well as signs of atrophy and gliosis, evidence in humans remains limited to case reports and small case series. The implications of identifying such biomarkers in clinical practice are significant, including improved prognostic stratification of patients and the early identification of those at high risk of developing irreversible complications. Moreover, the clinical validation of these biomarkers could be crucial in promoting neuroprotective strategies in addition to antiseizure medications. In this study, we present a systematic review of research on biomarkers of neuro-glial injury in patients with status epilepticus.

COVID-19 as a Risk Factor for Alzheimer's Disease

Severe acute respiratory disease coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic. Although a primarily respiratory disease, recent reports indicate that it also affects the central nervous system (CNS). Over 25% of COVID-19 patients report neurological symptoms such as memory loss, anosmia, hyposmia, confusion, and headaches. The neurological outcomes may be a result of viral entry into the CNS and/or resulting neuroinflammation, both of which underlie an elevated risk for Alzheimer's disease (AD). Herein, we ask: Is COVID-19 a risk factor for AD? To answer, we identify the literature and review mechanisms by which COVID-19-mediated neuroinflammation can contribute to the development of AD, evaluate the effects of acute versus chronic phases of infection, and lastly, discuss potential therapeutics to address the rising rates of COVID-19 neurological sequelae.

A Pathophysiological Approach To Current Biomarkers

Biomarkers are necessary for screening and diagnosing numerous diseases, predicting the prognosis of patients, and following-up treatment and the course of the patient. Everyday new biomarkers are being used in clinics for these purposes. This section will discuss the physiological roles of the various current biomarkers in a healthy person and the pathophysiological mechanisms underlying the release of these biomarkers. This chapter aims to gain a new perspective for evaluating and interpreting the most current biomarkers.

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

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

Comparison of serum neurodegenerative biomarkers among hospitalized COVID-19 patients versus non-COVID subjects with normal cognition, mild cognitive impairment, or Alzheimer's dementia

INTRODUCTION

Neurological complications among hospitalized COVID-19 patients may be associated with elevated neurodegenerative biomarkers.

METHODS

Among hospitalized COVID-19 patients without a history of dementia (N = 251), we compared serum total tau (t-tau), phosphorylated tau-181 (p-tau181), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), ubiquitin carboxy-terminal hydrolase L1 (UCHL1), and amyloid beta (Aβ40,42) between patients with or without encephalopathy, in-hospital death versus survival, and discharge home versus other dispositions. COVID-19 patient biomarker levels were also compared to non-COVID cognitively normal, mild cognitive impairment (MCI), and Alzheimer's disease (AD) dementia controls (N = 161).

RESULTS

Admission t-tau, p-tau181, GFAP, and NfL were significantly elevated in patients with encephalopathy and in those who died in-hospital, while t-tau, GFAP, and NfL were significantly lower in those discharged home. These markers correlated with severity of COVID illness. NfL, GFAP, and UCHL1 were higher in COVID patients than in non-COVID controls with MCI or AD.

DISCUSSION

Neurodegenerative biomarkers were elevated to levels observed in AD dementia and associated with encephalopathy and worse outcomes among hospitalized COVID-19 patients.

The biological significance and clinical utility of emerging blood biomarkers for traumatic brain injury

HUIBREGTSE, M.E, Bazarian, J.J., Shultz, S.R., and Kawata K. The biological significance and clinical utility of emerging blood biomarkers for traumatic brain injury. NEUROSCI BIOBEHAV REV XX (130) 433-447, 2021.- Blood biomarkers can serve as objective measures to gauge traumatic brain injury (TBI) severity, identify patients at risk for adverse outcomes, and predict recovery duration, yet the clinical use of blood biomarkers for TBI is limited to a select few and only to rule out the need for CT scanning. The biomarkers often examined in neurotrauma research are proteomic markers, which can reflect a range of pathological processes such as cellular damage, astrogliosis, or neuroinflammation. However, proteomic blood biomarkers are vulnerable to degradation, resulting in short half-lives. Emerging biomarkers for TBI may reflect the complex genetic and neurometabolic alterations that occur following TBI that are not captured by proteomics, are less vulnerable to degradation, and are comprised of microRNA, extracellular vesicles, and neurometabolites. Therefore, this review aims to summarize our understanding of how biomarkers for brain injury escape the brain parenchymal space and appear in the bloodstream, update recent research findings in several proteomic biomarkers, and characterize biological significance and examine clinical utility of microRNA, extracellular vesicles, and neurometabolites.

Diagnostic Accuracy of Glial Fibrillary Acidic Protein and Ubiquitin Carboxy-Terminal Hydrolase-L1 Serum Concentrations for Differentiating Acute Intracerebral Hemorrhage from Ischemic Stroke

BACKGROUND

Biomarkers indicative of intracerebral hemorrhage (ICH) may help triage acute stroke patients in the pre-hospital phase. We hypothesized that serum concentration of glial fibrillary acidic protein (GFAP) in combination with ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1), measured by a rapid bio-assay, could be used to distinguish ICH from ischemic stroke.

METHODS

This prospective two-center study recruited patients with a clinical diagnosis of acute stroke both in the pre-hospital phase and at hospital admission (within 4 and 6 h after symptom onset, respectively). Blood samples were analyzed for concentrations of GFAP and UCH-L1 using ELISA techniques. The reference standard was the diagnosis of ICH, ischemic stroke, or stroke mimicking condition achieved after clinical workup including brain imaging.

RESULTS

A total of 251 patients were included (mean age [± SD] 72 ± 15 years; 5 ICH, 23 ischemic strokes and 14 stroke mimics in the pre-hospital part; and 59 ICH, 148 ischemic strokes and 2 stroke mimics in the in-hospital part). Mean delay (± SD) from symptom onset to blood withdrawal was 130 ± 79 min for the pre-hospital patients and 136 ± 86 min for the in-hospital patients. Both GFAP and UCH-L1 serum concentrations were higher in patients having ICH as compared to other diagnoses (GFAP: median 330 ng/L [interquartile range 64-7060, range 8-56,100] vs. 27.5 ng/L [14-57.25, 0-781], p < 0.001; UCH-L1: 401 ng/L [265-764, 133-1812] vs. 338 ng/L [213-549.5, 0-2950], p = 0.025). Area-under-the-curve values were 0.866 (95% CI 0.809-0.924, p < 0.001) for GFAP, and 0.590 (0.511-0.670, p = 0.033) for UCH-L1. Regarding overall diagnostic accuracy, UCH-L1 did not add significantly to the performance of GFAP.

CONCLUSIONS

GFAP may differentiate ICH from ischemic stroke and stroke mimics. A point-of-care test to distinguish between ischemic and hemorrhagic strokes might facilitate triage to different treatment pathways or locations, or be used to select patients for trials of ultra-early interventions.

The expression and clinical value of ubiquitin carboxyl-terminal hydrolase L1 in the blood of neonates with hypoxic ischemic encephalopathy

BACKGROUND

Neonatal hypoxic ischemic encephalopathy (HIE) can result in mental retardation due to the associated brain damage. Early identification of brain injury is vital for the prevention and treatment of brain damage in neonates. This study investigated the expression levels of serum ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) in neonates with HIE and its correlation with brain damage.

METHODS

From January 2019 to December 2020, 56 cases of neonatal patients with HIE were selected as the observation group, and 60 cases of healthy newborns delivered in our hospital during the same period were selected as the control group. Blood samples were obtained from neonates and the serum expression of UCH-L1 was detected by enzyme-linked immunosorbent assays (ELISAs). The relationship between UCH-L1 and neonatal prognosis and clinical features was analyzed.

RESULTS

Compared with the healthy control group, the serum levels of UCH-L1 in the observation group was significantly higher (2.28±1.21 vs. 0.81±0.39 ng/mL, P=0.000). Furthermore, at 6 hours after birth, the serum levels of UCH-L1 were significantly higher in neonates with moderate to severe HIE compared to patients with mild HIE (2.92±0.80 and 1.76±0.72 ng/mL, respectively, P=0.000). Pearson correlation analysis showed that the expression levels of UCH-L1 were negatively correlated with the development quotient (DQ), intelligence index (MI), and the Neonatal Behavioral Neurological Assessment (NBNA) score of HIE newborns (P<0.05).

CONCLUSIONS

The level of UCH-L1 protein expression is elevated in the serum of newborns with HIE, and this may have a certain clinical value in predicting the intelligence of children.

Permeability of the Blood-Brain Barrier after Traumatic Brain Injury; Radiological Considerations

Traumatic brain injury (TBI) is a leading cause of death and disability, especially in young persons, and constitutes a major socioeconomic burden worldwide. It is regarded as the leading cause of mortality and morbidity in previously healthy young persons. Most of the mechanisms underpinning the development of secondary brain injury are consequences of disruption of the complex relationship between the cells and proteins constituting the neurovascular unit or a direct result of loss of integrity of the tight junctions (TJ) in the blood-brain barrier (BBB). A number of changes have been described in the BBB after TBI, including loss of TJ proteins, pericyte loss and migration, and altered expressions of water channel proteins at astrocyte end-feet processes. There is a growing research interest in identifying optimal biological and radiological biomarkers of severity of BBB dysfunction and its effects on outcomes after TBI. This review explores the microscopic changes occurring at the neurovascular unit, after TBI, and current radiological adjuncts for its evaluation in pre-clinical and clinical practice.

Pro-inflammatory cytokines, but not brain- and extracellular matrix-derived proteins, are increased in the plasma following electrically induced kindling of seizures

Background

The aim of the study was to evaluate the brain-derived proteins, extracellular matrix-derived protein and cytokines as potential peripheral biomarkers of different susceptibility to seizure development in an animal model of epilepsy evoked by chronic focal electrical stimulation of the brain.

Methods

The plasma levels of IL-1β (interleukin 1β), IL-6 (interleukin 6), UCH-L1 (ubiquitin C-terminal hydrolase 1), MMP-9 (matrix metalloproteinase 9), and GFAP (glial fibrillary acidic protein) were assessed. The peripheral concentrations of the selected proteins were analyzed according to the status of kindling and seizure severity parameters. In our study, increased concentrations of plasma IL-1β and IL-6 were observed in rats subjected to hippocampal kindling compared to sham-operated rats.

Results

Animals that developed tonic–clonic seizures after the last stimulation had higher plasma concentrations of IL-1β and IL-6 than sham-operated rats and rats that did not develop seizure. Elevated levels of IL-1β and IL-6 were observed in rats that presented more severe seizures after the last five stimulations compared to sham-operated animals. A correlation between plasma IL-1β and IL-6 concentrations was also found. On the other hand, the plasma levels of the brain-derived proteins UCH-L1, MMP-9, and GFAP were unaffected by kindling status and seizure severity parameters.

Conclusions

The plasma concentrations of IL-1β and IL-6 may have potential utility as peripheral biomarkers of immune system activation in the course of epilepsy and translational potential for future clinical use. Surprisingly, markers of cell and nerve ending damage (GFAP, UCH-L1 and MMP-9) may have limited utility.

The Stroke-Induced Blood-Brain Barrier Disruption: Current Progress of Inspection Technique, Mechanism, and Therapeutic Target

Stroke is one of the leading causes of mortality and morbidity worldwide. The blood-brain barrier (BBB) is a characteristic structure of microvessel within the brain. Under normal physiological conditions, the BBB plays a role in the prevention of harmful substances entering into the brain parenchyma within the central nervous system. However, stroke stimuli induce the breakdown of BBB leading to the influx of cytotoxic substances, vasogenic brain edema, and hemorrhagic transformation. Therefore, BBB disruption is a major complication, which needs to be addressed in order to improve clinical outcomes in stroke. In this review, we first discuss the structure and function of the BBB. Next, we discuss the progress of the techniques utilized to study BBB breakdown in in-vitro and in-vivo studies, along with biomarkers and imaging techniques in clinical settings. Lastly, we highlight the mechanisms of stroke-induced neuroinflammation and apoptotic process of endothelial cells causing BBB breakdown, and the potential therapeutic targets to protect BBB integrity after stroke. Secondary products arising from stroke-induced tissue damage provide transformation of myeloid cells such as microglia and macrophages to pro-inflammatory phenotype followed by further BBB disruption via neuroinflammation and apoptosis of endothelial cells. In contrast, these myeloid cells are also polarized to anti-inflammatory phenotype, repairing compromised BBB. Therefore, therapeutic strategies to induce anti-inflammatory phenotypes of the myeloid cells may protect BBB in order to improve clinical outcomes of stroke patients.

Current Evidence Regarding Biomarkers Used to Aid Postoperative Delirium Diagnosis in the Field of Cardiac Surgery-Review

Postoperative cognitive disorders after cardiac surgery may manifest as postoperative delirium (POD) or later as postoperative cognitive dysfunction (POCD). The incidence of POD after cardiac surgery ranges from 16% to 73%. In contrast to POD, POCD is usually diagnosed after the discharge from hospital, with an incidence of 30 to 70% of cases, very often noticed only by close relative or friends, decreasing after six (20–30%) and twelve (15–25%) months after surgery. Perioperative cognitive disorders are associated with adverse short- and long-term effects, including increased morbidity and mortality. Due to the complexity of delirium pathomechanisms and the difficulties in the diagnosis, researchers have not yet found a clear answer to the question of which patient will be at a higher risk of developing delirium. The risk for POD and POCD in older patients with numerous comorbidities like hypertension, diabetes, and previous ischemic stroke is relatively high, and the predisposing cognitive profile for both conditions is important. The aim of this narrative review was to identify and describe biomarkers used in the diagnosis of delirium after cardiac surgery by presenting a search through studies regarding this subject, which have been published during the last ten years. The authors discussed brain-derived biomarkers, inflammation-related biomarkers, neurotransmitter-based biomarkers, and others. Work based on inflammation-related biomarkers, which are characterized by the low cost of implementation and the effectiveness of delirium diagnosis, seems to be the closest to the goal of discovering an inexpensive and effective marker. Currently, the use of a panel of tests, and not a single biomarker, brings us closer to the discovery of a test, or rather a set of tests ideal for the diagnosis of delirium after cardiac surgery.

Biomarkers in traumatic brain injury: new concepts

Traumatic brain injury is a multifaceted condition that encompasses a spectrum of injuries: contusions, axonal injuries in specific brain regions, edema, and hemorrhage. Brain injury determines a broad clinical and disability spectrum due to the implication of various cellular pathways, genetic phenotypes, and environmental factors. It is challenging to predict patient outcomes, to appropriately evaluate the patients, to determine a suitable treatment strategy and rehabilitation program, and to communicate with patient relatives. Biomarkers detected from body fluids are potential evaluation tools for traumatic brain injury patients. These may serve as internal indicators of cerebral damage, delivering valuable information about the dynamic cellular, biochemical, and molecular environments. The diagnostic and prognostic value of biomarkers tested both in animal models of traumatic brain injury is still under question, despite a considerable scientific literature. Recent publications emphasize that a more realistic approach involves combining multiple types of biomarkers with other investigative tools (imaging, outcome scales, and genetic polymorphisms). Additionally, there is increasing interest in the use of biomarkers as tools for treatment monitoring and as surrogate outcome variables to facilitate the design of distinct randomized controlled trials. This review highlights the latest available evidence regarding biomarkers in adults after traumatic brain injury and discusses new approaches in the evaluation of this patient group.

Is Salivary S100B a Biomarker of Traumatic Brain Injury? A Pilot Study

Traumatic brain injury (TBI) results in short and long-term disability neurodegeneration. Mild traumatic brain injury (mTBI) represents up to 85% of head injuries; diagnosis and early management is based on computed tomography (CT) or in-hospital observation, which are time- and cost- intensive. CT involves exposure to potentially harmful ionizing radiation and >90% of the scans are negative. Blood-brain barrier (BBB) damage is suspected pathological event post-TBI contributing to long-term sequelae and a reliable and rapid point-of-care test to screen those who can safely forego acute head CT would be of great help in evaluating patients with an acute mTBI. In this pilot study, 15 adult patients with suspected TBI (mean age = 47 years, range 18–79) and 15 control subjects (mean age = 33 years, range 23–53) were enrolled. We found that the average salivary S100B level was 3.9 fold higher than blood S100B, regardless of the presence of pathology. [S100B]_saliva positively correlated with [S100B]_serum (Pearson' coefficient = 0.79; p < 0.01). Salivary S100B levels were as effective in differentiating TBI patients from control subjects as serum levels (Control vs. TBI: p < 0.01; Serum ROC_AUC = 0.94 and Saliva ROC_AUC = 0.75). I These initial results suggest that measuring salivary S100B could represent an alternative to serum S100B in the diagnosis of TBI. Larger and confirmatory trials are needed to define salivary biomarker kinetics in relation to TBI severity and the possible roles of gender, ethnicity and age in influencing salivary S100B levels.

Mechanisms of Blood-Brain Barrier Dysfunction in Traumatic Brain Injury

Traumatic brain injuries (TBIs) account for the majority of injury-related deaths in the United States with roughly two million TBIs occurring annually. Due to the spectrum of severity and heterogeneity in TBIs, investigation into the secondary injury is necessary in order to formulate an effective treatment. A mechanical consequence of trauma involves dysregulation of the blood–brain barrier (BBB) which contributes to secondary injury and exposure of peripheral components to the brain parenchyma. Recent studies have shed light on the mechanisms of BBB breakdown in TBI including novel intracellular signaling and cell–cell interactions within the BBB niche. The current review provides an overview of the BBB, novel detection methods for disruption, and the cellular and molecular mechanisms implicated in regulating its stability following TBI.

The value of cerebrospinal fluid ubiquitin C-terminal hydrolase-L1 protein as a prognostic predictor of neurologic outcome in post-cardiac arrest patients treated with targeted temperature management

AIM

We evaluated the prognostic value of serum- and cerebrospinal fluid (CSF)-ubiquitin carboxyl-terminal esterase L1 protein (UCHL1) measurements in post- post-out of hospital cardiac arrest (OHCA) patients treated with target temperature management (TTM), to predict neurologic outcome.

METHODS

This was a prospective single-centre observational cohort study, conducted from April 2018 to September 2019. Serum- and CSF-UCHL1 were obtained immediately (UCHL1_initial), 24 h (UCHL1₂₄), 48 h (UCHL1₄₈), and 72 h (UCHL1₇₂) after return of spontaneous circulation (ROSC). The area under the receiver operating characteristic curves (AUROC) and Delong method were used to identify cut-off values of serum- and CSF-UCHL1_initial, UCHL1₂₄, UCHL1₄₈, UCHL1₇₂ for predicting neurologic outcomes.

RESULTS

Of 38 patients enrolled, 16 comprised the poor outcome group. The AUROCs for serum- and CSF-UCHL1_initial were 0.71 and 0.93 in predicting poor neurological outcomes, respectively (p = 0.01). The AUROCs for serum- and CSF-UCHL1₂₄ were 0.85 and 0.91 (p = 0.24). The AUROCs for serum- and CSF-UCHL1₄₈ were 0.90 and 0.97 (p = 0.07). The AUROCs for serum- and CSF-UCHL1₇₂ were 0.94 and 0.98 (p = 0.25).

CONCLUSION

Findings of this study demonstrate that CSF-UCHL1 measured immediately, 24, 48, and 72 h after ROSC is a valuable predictor for evaluating neurologic outcomes, whereas serum-UCHL1 measured at 24, 48, and 72 h after ROSC showed a significant performance in the prognostication of poor outcomes in post-OHCA patients treated with TTM.

Influence of Blood-Brain Barrier Integrity on Brain Protein Biomarker Clearance in Severe Traumatic Brain Injury: A Longitudinal Prospective Study

Brain protein biomarker clearance to blood in traumatic brain injury (TBI) is not fully understood. The aim of this study was to analyze the effect that a disrupted blood–brain barrier (BBB) had on biomarker clearance. Seventeen severe TBI patients admitted to Karolinska University Hospital were prospectively included. Cerebrospinal fluid (CSF) and blood concentrations of S100 calcium binding protein B (S100B) and neuron-specific enolase (NSE) were analyzed every 6–12 h for ∼1 week. Blood and CSF albumin were analyzed every 12–24 h, and BBB integrity was assessed using the CSF:blood albumin quotient (Q_A). We found that time-dependent changes in the CSF and blood levels of the two biomarkers were similar, but that the correlation between the biomarkers and Q_A was lower for NSE (ρ = 0.444) than for S100B (ρ = 0.668). Because data were longitudinal, we also conducted cross correlation analyses, which indicated a directional flow and lag-time of biomarkers from CSF to blood. For S100B, this lag-time could be ascribed to BBB integrity, whereas for NSE it could not. Upon inferential modelling, using generalized least square estimation (S100B) or linear mixed models (NSE), Q_A (p = 0.045), time from trauma (p < 0.001), time from trauma² (p = 0.023), and CSF biomarker levels (p = 0.008) were independent predictors of S100B in blood. In contrast, for NSE, only time from trauma was significant (p < 0.001). These findings are novel and important, but must be carefully interpreted because of different characteristics between the two proteins. Nonetheless, we present the first data that indicate that S100B and NSE are cleared differently from the central nervous system, and that both the disrupted BBB and additional alternative pathways, such as the recently described glymphatic system, may play a role. This is of importance both for clinicians aiming to utilize these biomarkers and for the pathophysiological understanding of brain protein clearance, but warrants further examination.

Association of neuronal repair biomarkers with delirium among survivors of critical illness

PURPOSE

Delirium is prevalent but with unclear pathogenesis. Neuronal injury repair pathways may be protective. We hypothesized that higher concentrations of neuronal repair biomarkers would be associated with decreased delirium in critically ill patients.

MATERIALS AND METHODS

We performed a nested study of hospital survivors within a prospective cohort that enrolled patients within 72 h of respiratory failure or shock. We measured plasma concentrations of ubiquitin carboxyl-terminal-esterase-L1 (UCHL1) and brain-derived neurotrophic factor (BDNF) from blood collected at enrollment. Delirium was assessed twice daily using the CAM-ICU. Multivariable regression was used to examine the associations between biomarkers and delirium prevalence/duration, adjusting for covariates and interactions with age and IL-6 plasma concentration.

RESULTS

We included 427 patients with a median age of 59 years (IQR 48-69) and APACHE II score of 25 (IQR 19-30). Higher plasma concentration of UCHL1 on admission was independently associated with lower prevalence of delirium (p = .04) but not associated with duration of delirium (p = .06). BDNF plasma concentration was not associated with prevalence (p = .26) or duration of delirium (p = .36).

CONCLUSIONS

During critical illness, higher UCHL1 plasma concentration is associated with lower prevalence of delirium; BDNF plasma concentration is not associated with delirium. Clinical trial number: NCT00392795; https://clinicaltrials.gov/ct2/show/NCT00392795.

Chitinase-3-Like Protein 1, Serum Amyloid A1, C-Reactive Protein, and Procalcitonin Are Promising Biomarkers for Intracranial Severity Assessment of Traumatic Brain Injury: Relationship with Glasgow Coma Scale and Computed Tomography Volumetry

OBJECTIVE

The volume and location of intracranial hematomas are well-known prognostic factors for traumatic brain injury. The aim of this study was to determine the relationship of serum biomarkers S100β, glial fibrillary acidic protein, neuron-specific enolase, total tau, phosphorylated neurofilament heavy chain, serum amyloid A1 (SAA1), C-reactive protein, procalcitonin (PCT), and chitinase-3-like protein 1 (YKL-40) with traumatic brain injury severity and the amount and location of hemorrhagic traumatic lesions.

METHODS

A prospective observational cohort of 115 patients with a Glasgow Coma Scale (GCS) score of 3-15 were evaluated. Intracranial lesion volume was measured from the semiautomatic segmentation of hematoma on computed tomography using Analyze software. The establishment of possible biomarker cutoff points for intracranial lesion detection was estimated using the Youden Index (J) obtained from the area under the receiver operating characteristic curve.

RESULTS

SAA1, YKL-40, PCT, and S100β showed the most robust association with level of consciousness, both with total GCS and motor score. Biomarkers significantly correlated with volumetric measurements of subdural hematoma, traumatic subarachnoid hemorrhage, intraparenchymal hemorrhage, intraventricular hemorrhage, and total amount of bleeding. The type of intracranial hemorrhage was associated with various release patterns of neurobiochemical markers.

CONCLUSIONS

YKL-40, SAA1, C-reactive protein, and PCT combined with S100β were the most promising biomarkers to determine the presence, location, and extent of traumatic intracranial lesions. Combination of biomarkers further increased the discriminatory capacity for the detection of intracranial bleeding.

Erythropoietin Does Not Alter Serum Profiles of Neuronal and Axonal Biomarkers After Traumatic Brain Injury: Findings From the Australian EPO-TBI Clinical Trial

OBJECTIVE

To determine profiles of serum ubiquitin carboxy-terminal hydrolase L1 and phosphorylated neurofilament heavy-chain, examine whether erythropoietin administration reduce their concentrations, and whether biomarkers discriminate between erythropoietin and placebo treatment groups.

DESIGN

Single-center, prospective observational study.

SETTING

A sub-study of the erythropoietin-traumatic brain injury clinical trial, conducted at the Alfred Hospital, Melbourne, Australia.

PATIENTS

Forty-four patients with moderate-to-severe traumatic brain injury.

INTERVENTIONS

Epoetin alfa 40,000 IU or 1 mL sodium chloride 0.9 as subcutaneous injection within 24 hours of traumatic brain injury.

MEASUREMENTS AND MAIN RESULTS

Ubiquitin carboxy-terminal hydrolase L1, phosphorylated neurofilament heavy-chain, and erythropoietin concentrations were measured in serum by enzyme-linked immunosorbent assay from D0 (within 24 hr of injury, prior to erythropoietin/vehicle administration) to D5. Biomarker concentrations were compared between injury severities, diffuse versus focal traumatic brain injury and erythropoietin or placebo treatment groups. Ubiquitin carboxy-terminal hydrolase L1 peaked at 146.0 ng/mL on D0, significantly decreased to 84.30 ng/mL on D1, and declined thereafter. Phosphorylated neurofilament heavy-chain levels were lowest at D0 and peaked on D5 at 157.9 ng/mL. D0 ubiquitin carboxy-terminal hydrolase L1 concentrations were higher in diffuse traumatic brain injury. Peak phosphorylated neurofilament heavy-chain levels on D3 and D4 correlated with Glasgow Outcome Score-Extended, predicting poor outcome. Erythropoietin did not reduce concentrations of ubiquitin carboxy-terminal hydrolase L1 or phosphorylated neurofilament heavy-chain.

CONCLUSIONS

Serum ubiquitin carboxy-terminal hydrolase L1 and phosphorylated neurofilament heavy-chain increase after traumatic brain injury reflecting early neuronal and progressive axonal injury. Consistent with lack of improved outcome in traumatic brain injury patients treated with erythropoietin, biomarker concentrations and profiles were not affected by erythropoietin. Pharmacokinetics of erythropoietin suggest that the dose given was possibly too low to exert neuroprotection.

The role of UCH-L1, MMP-9, and GFAP as peripheral markers of different susceptibility to seizure development in a preclinical model of epilepsy

In our study, we assessed the potency of the brain-derived proteins ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), matrix metalloproteinase 9 (MMP-9), glial fibrillary acidic protein (GFAP) and the immune activation indicators interleukin 1β (IL-1β) and interleukin 6 (IL-6) as peripheral biomarkers of different susceptibilities to kindling in a preclinical model. We observed increased plasma UCH-L1 levels in kindled vs. control animals. Furthermore, MMP-9 and IL-1β concentrations were the lowest in rats resistant to kindling. In summary, UCH-L1 is an indicator of neuronal loss and BBB disruption after seizure. MMP-9 and IL-1β may indicate resistance to kindling. UCH-L1, MMP-9 and IL-1β may have utility as peripheral biomarkers with translational potency in the clinic.

Changes in Plasma von Willebrand Factor and Cellular Fibronectin in MRI-Defined Traumatic Microvascular Injury

The neuropathology of traumatic brain injury (TB) is diverse, including primary injury to neurons, axons, glial cells, vascular structures, and secondary processes, such as edema and inflammation that vary between individual patients. Traumatic microvascular injury is an important endophenotype of TBI-related injury. We studied patients who sustained a TBI requiring ER evaluation and had an MRI performed within 48 h of injury. We classified patients into 3 groups based on their MRI findings: (1) those that had evidence of traumatic microvascular injury on susceptibility or diffusion weighted MRI sequences without frank hemorrhage [Traumatic Vascular Injury (TVI) group; 20 subjects]. (2) those who had evidence of intraparenchymal, subdural, epidural, or subarachnoid hemorrhage [Traumatic Hemorrhage (TH) group; 26 subjects], and (3) those who had no traumatic injuries detected by MRI [MRI-negative group; 30 subjects]. We then measured plasma protein biomarkers of vascular injury [von Willebrand Factor (vWF) or cellular fibronectin (cFn)] and axonal injury (phosphorylated neurofilament heavy chain; pNF-H). We found that the TVI group was characterized by decreased expression of plasma vWF (p < 0.05 compared to MRI-negative group; p < 0.00001 compared to TH group) ≤48 h after injury. cFN was no different between groups ≤48 h after injury, but was increased in the TVI group compared to the MRI-negative (p < 0.00001) and TH (p < 0.00001) groups when measured >48 h from injury. pNF-H was increased in both the TH and TVI groups compared to the MRI-negative group ≤48 h from injury. When we used the MRI grouping and molecular biomarkers in a model to predict Glasgow Outcome Scale-Extended (GOS-E) score at 30–90 days, we found that inclusion of the imaging data and biomarkers substantially improved the ability to predict a good outcome over clinical information alone. These data indicate that there is a distinct, vascular-predominant endophenotype in a subset of patients who sustain a TBI and that these injuries are characterized by a specific biomarker profile. Further work to will be needed to determine whether these biomarkers can be useful as predictive and pharmacodynamic biomarkers for vascular-directed therapies after TBI.

Early and rapid detection of UCHL1 in the serum of brain-trauma patients: a novel gold nanoparticle-based method for diagnosing the severity of brain injury

The clinical diagnosis of traumatic brain injury (TBI) is based on neurological examination and neuro-imaging tools such as CT scanning and MRI. However, neurological examination at times may be confounded by consumption of alcohol or drugs and neuroimaging facilities may not be available at all centers. Human ubiquitin C-terminal hydrolase (UCHL1) is a well-accepted serum biomarker for severe TBI and can be used to detect the severity of a head injury. A reliable, rapid, cost effective, bedside and easy to perform method for the detection of UCHL1 is a pre-requisite for wide clinical applications of UCHL1 as a TBI biomarker. We developed a rapid detection method for UCHL1 using surface plasmon resonance of gold nanoparticles with a limit of detection (LOD) of 0.5 ng mL-1. It has a sensitivity and specificity of 100% each and meets an analytical precision similar to that of conventional sandwich ELISA but can be performed rapidly. Using this method we successfully detected UCHL1 in a cohort of 66 patients with TBI and were reliably able to distinguish mild TBI from moderate to severe TBI.

The neurobiological effects of repetitive head impacts in collision sports

It is now recognized that repetitive head impacts (RHI) in sport have the potential for long-term neurological impairments. In order to identify targets for intervention and/or pharmacological treatment, it is necessary to characterize the neurobiological mechanisms associated with RHI. This review aims to summarize animal and human studies that specifically address Blood Brain Barrier (BBB) dysfunction, abnormal neuro-metabolic and neuro-inflammatory processes as well as Tau aggregation associated with RHI in collision sports. Additionally, we examine the influence of physical activity and genetics on outcomes of RHI, discuss methodological considerations, and provide suggestions for future directions of this burgeoning area of research.

Association between the simultaneous decrease in the levels of soluble vascular cell adhesion molecule-1 and S100 protein and good neurological outcomes in cardiac arrest survivors

OBJECTIVE

This study aimed to determine whether simultaneous decreases in the serum levels of cell adhesion molecules (intracellular cell adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], and E-selectin) and S100 proteins within the first 24 hours after the return of spontaneous circulation were associated with good neurological outcomes in cardiac arrest survivors.

METHODS

This retrospective observational study was based on prospectively collected data from a single emergency intensive care unit (ICU). Twenty-nine out-of-hospital cardiac arrest survivors who were admitted to the ICU for post-resuscitation care were enrolled. Blood samples were collected at 0 and 24 hours after ICU admission. According to the 6-month cerebral performance category (CPC) scale, the patients were divided into good (CPC 1 and 2, n=12) and poor (CPC 3 to 5, n=17) outcome groups.

RESULTS

No difference was observed between the two groups in terms of the serum levels of ICAM-1, VCAM-1, E-selectin, and S100 at 0 and 24 hours. A simultaneous decrease in the serum levels of VCAM-1 and S100 as well as E-selectin and S100 was associated with good neurological outcomes. When other variables were adjusted, a simultaneous decrease in the serum levels of VCAM-1 and S100 was independently associated with good neurological outcomes (odds ratio, 9.285; 95% confidence interval, 1.073 to 80.318; P=0.043).

CONCLUSION

A simultaneous decrease in the serum levels of soluble VCAM-1 and S100 within the first 24 hours after the return of spontaneous circulation was associated with a good neurological outcome in out-of-hospital cardiac arrest survivors.

Current progress in searching for clinically useful biomarkers of blood-brain barrier damage following cerebral ischemia

Ischemic stroke is a leading cause of death and disability. Fear of intracranial hemorrhage (ICH) has been the primary reason for withholding tissue plasminogen activator (tPA) and thrombectomy, the only two widely accepted treatments for ischemic stroke. Thrombolysis treatment is only allowed in a very narrow time window (within 4.5–6 h). However, so far, other than the time window guideline, there is no reliable indicator available in the clinic to predict ICH before thrombolysis treatment. Recently, extensive research efforts have been devoted to the development of reliable indicators to predict ICH and safely guide the thrombolysis treatment. Accumulating evidence suggests that ischemic brain regions with a compromised blood–brain barrier (BBB) before tPA treatment develop ICH at the later time during thrombolytic reperfusion. Assessing BBB damage before thrombolysis could potentially help predict the risk of ICH after thrombolysis. This article reviews the literature reports on BBB damage biomarkers that have been developed in recent years, including biochemical markers such as BBB structural proteins, circulating brain microvascular endothelial cells, plasma albumin, and brain parenchyma proteins, as well as image markers such as magnetic resonance imaging assessment for BBB damage.

Metals and oxidative potential in urban particulate matter influence systemic inflammatory and neural biomarkers: A controlled exposure study

BACKGROUND

Oxidative stress and inflammation are considered to be important pathways leading to particulate matter (PM)-associated disease. In this exploratory study, we examined the effects of metals and oxidative potential (OP) in urban PM on biomarkers of systemic inflammation, oxidative stress and neural function.

METHODS

Fifty-three healthy non-smoking volunteers (mean age 28 years, twenty-eight females) were exposed to coarse (2.5-10 μm, mean 213 μg/m³), fine (0.15-2.5 μm, 238 μg/m³), and/or ultrafine concentrated ambient PM (<0.3 μm, 136 μg/m³). Exposures lasted 130 min, separated by ≥2 weeks. Metal concentrations and OP (measured by ascorbate and glutathione depletion in synthetic airway fluid) in PM were analyzed. Blood and urine samples were collected pre-exposure, and 1-h and 21-h post exposure for assessment of biomarkers. We used mixed-regression models to analyze associations adjusting for PM size and mass concentration.

RESULTS

Results for metals were expressed as change (%) from daily pre-exposure biomarker levels after exposure to a metal at a level equivalent to the mean concentration. Exposure to various metals (silver, aluminum, barium, copper, iron, potassium, lithium, nickel, tin, and/or vanadium) was significantly associated with increased levels of various blood or urinary biomarkers. For example, the blood inflammatory marker vascular endothelia growth factor (VEGF) increased 5.3% (95% confidence interval: 0.3%, 10.2%) 1-h post exposure to nickel; the traumatic brain injury marker ubiquitin C-terminal hydrolase L1 (UCHL1) increased 11% (1.2%, 21%) and 14% (0.3%, 29%) 1-h and 21-h post exposure to barium, respectively; and the systemic stress marker cortisol increased 1.5% (0%, 2.9%) and 1.5% (0.5%, 2.8%) 1-h and 21-h post exposure to silver, respectively. Urinary DNA oxidation marker 8‑hydroxy‑deoxy‑guanosine increased 14% (6.4%, 21%) 1-h post exposure to copper; urinary neural marker vanillylmandelic acid increased 29% (3%, 54%) 1-h post exposure to aluminum; and urinary cortisol increased 88% (0.9%, 176%) 1-h post exposure to vanadium. Results for OP were expressed as change (%) from daily pre-exposure biomarker levels after exposure to ascorbate-related OP at a level equivalent to the mean concentration, or for exposure to glutathione-related OP at a level above the limit of detection. Exposure to ascorbate- or glutathione-related OP was significantly associated with increased inflammatory and neural biomarkers including interleukin-6, VEGF, UCHL1, and S100 calcium-binding protein B in blood, and malondialdehyde and 8-hydroxy-deoxy-guanosine in urine. For example, UCHL1 increased 9.4% (1.8%, 17%) in blood 21-h post exposure to ascorbate-related OP, while urinary malondialdehyde increased 19% (3.6%, 35%) and 8-hydroxy-deoxy-guanosine increased 24% (2.9%, 48%) 21-h post exposure to ascorbate- and glutathione-related OP, respectively.

CONCLUSION

Our results from this exploratory study suggest that metal constituents and OP in ambient PM may influence biomarker levels associated with systemic inflammation, oxidative stress, perturbations of neural function, and systemic physiological stress.

Temporal response profiles of serum ubiquitin C-terminal hydrolase-L1 and the 145-kDa alpha II-spectrin breakdown product after severe traumatic brain injury in children

OBJECTIVE

Traumatic brain injury (TBI) is the leading cause of acquired disability among children. Brain injury biomarkers may serve as useful diagnostic and prognostic indicators for TBI. Levels of ubiquitin C-terminal hydrolase-L1 (UCH-L1) and the 145-kDa alpha II-spectrin breakdown product (SBDP-145) correlate with outcome in adults after severe TBI. The authors conducted a pilot study of these biomarkers in children after severe TBI to inform future research exploring their utility in this population.

METHODS

The levels of UCH-L1 and SBDP-145 were measured in serum, and UCH-L1 in CSF from pediatric patients after severe TBI over 5 days after injury. Both biomarkers were also measured in age-matched control serum and CSF.

RESULTS

Adequate numbers of samples were obtained in serum, but not CSF, to assess biomarker temporal response profiles. Using patients with samples from all time points, UCH-L1 levels increased rapidly and transiently, peaking at 12 hours after injury. SBDP-145 levels showed a more gradual and sustained response, peaking at 48 hours. The median serum UCH-L1 concentration was greater in patients with TBI than in controls (median [IQR] = 361 [187, 1330] vs 147 [50, 241] pg/ml, respectively; p < 0.001). Receiver operating characteristic (ROC) analysis revealed an AUC of 0.77. Similarly, serum SBDP-145 was greater in children with TBI than in controls (median [IQR] = 172 [124, 257] vs 69 [40, 99] pg/ml, respectively; p < 0.001), with an ROC AUC of 0.85. When only time points of peak levels were used for ROC analysis, the discriminability of each serum biomarker increased (AUC for UCH-L1 at 12 hours = 1.0 and for SBDP-145 at 48 hours = 0.91). Serum and CSF UCH-L1 levels correlated well in patients with TBI (r = 0.70, p < 0.001).

CONCLUSIONS

Findings from this exploratory study reveal robust increases of UCH-L1 and SBDP-145 in serum and UCH-L1 in CSF obtained from children after severe TBI. In addition, important temporal profile differences were found between these biomarkers that can help guide optimal time point selection for future investigations of their potential to characterize injury or predict outcomes after pediatric TBI.

The diagnostic value of serum UCHL-1 and S100-B levels in differentiate epileptic seizures from psychogenic attacks

OBJECTIVE

To assess the value of postictal serum Ubiquitin C-terminal hydrolase (UCHL-1), a neuronal biomarker, and S100-B, a glial biomarker, levels, in differentiate epileptic seizures (ES) form psychogenic attacks.

METHODS

In this analytical cross-sectional study, serum UCHL-1 and S100-B levels were measured within six hours of occurring seizure, in 43 patients with ES, 20 patients with psychogenic non-epileptic seizures (PNES) and 19 healthy individuals by electrochemiluminescence immunoassay.

RESULTS

Both serum UCHL-1 and S100-B levels were significantly higher in patients with ES than PNES (P < 0.05) and controls (P < 0.01). PNES patients had significantly higher serum S100-B levels compared to controls (P < 0.01). There was a significant correlation between the serum UCHL-1 and S100-B levels in patients with ES (r = 0.46, P = 0.002).

CONCLUSIONS

Our study showed that serum UCHL-1 level could be potentially used in differentiate ES from PNES (sensitivity 72%, specificity 59%). Serum S100-B level had lower value compared to UCHL-1 (AUC 0.68 for UCHL-1 v/s 0.59 for S100B). Post-seizure serum UCHL-1 and S100-B levels could be used in future studies to better understand the underlying mechanism of seizures and may offer as an adjunctive diagnostic test in differentiate ES from PNES.

Relationships between markers of neurologic and endothelial injury during critical illness and long-term cognitive impairment and disability

PURPOSE

Neurologic and endothelial injury biomarkers are associated with prolonged delirium during critical illness and may reflect injury pathways that lead to poor long-term outcomes. We hypothesized that blood-brain barrier (BBB), neuronal, and endothelial injury biomarkers measured during critical illness are associated with cognitive impairment and disability after discharge.

METHODS

We enrolled adults with respiratory failure and/or shock and measured plasma concentrations of BBB (S100B), neuronal (UCHL1, BDNF), and endothelial (E-selectin, PAI-1) injury markers within 72 h of ICU admission. At 3 and 12 months post-discharge, we assessed participants' global cognition, executive function, and activities of daily living (ADL). We used multivariable regression to determine whether biomarkers were associated with outcomes after adjusting for relevant demographic and acute illness covariates.

RESULTS

Our study included 419 survivors of critical illness with median age 59 years and APACHE II score 25. Higher S100B was associated with worse global cognition at 3 and 12 months (P = 0.008; P = 0.01). UCHL1 was nonlinearly associated with global cognition at 3 months (P = 0.02). Higher E-selectin was associated with worse global cognition (P = 0.006 at 3 months; P = 0.06 at 12 months). BDNF and PAI-1 were not associated with global cognition. No biomarkers were associated with executive function. Higher S100B (P = 0.05) and E-selectin (P = 0.02) were associated with increased disability in ADLs at 3 months.

CONCLUSIONS

S100B, a marker of BBB and/or astrocyte injury, and E-selectin, an adhesion molecule and marker of endothelial injury, are associated with long-term cognitive impairment after critical illness, findings that may reflect mechanisms of critical illness brain injury.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

The role and diagnostic significance of cellular barriers after concussive head trauma

The onset of concussive head trauma often triggers an intricate sequence of physical consequences and pathophysiological responses. These sequelae can be acute (i.e., hematoma) or chronic (i.e., autoimmune response, neurodegeneration, etc.), and may follow traumas of any severity. A critical factor for prognostication of postconcussion outcome is the pathophysiological response of cellular barriers, which can be measured by several biomarkers of the acute and chronic postinjury phases. We present herein a review on the postconcussion mechanisms of the blood-brain barrier, as well as the diagnostic/prognostic approaches that utilize differential biomarker expression across this boundary. We discuss the role of the blood-saliva cellular barrier as a regulatory filter for brain-derived biomarkers in blood, and its implications for saliva-based diagnostic assays.

Prospective Assessment of Acute Blood Markers of Brain Injury in Sport-Related Concussion

There is a pressing need to identify objective biomarkers for the assessment of sport-related concussion (SRC) to reduce the reliance on clinical judgment for the management of these injuries. The goal of the current study was to prospectively establish the acute effects of SRC on serum levels of S100 calcium-binding protein beta (S100B), glial fibrillary acidic protein (GFAP), and ubiquitin C-terminal hydrolase-L1 (UCH-L1). Collegiate and high school football players were enrolled and provided blood at pre-season. Injured athletes participated in follow-up visits at ∼6 and 24-48 h following documented SRC (n = 32). Uninjured football players participated in similar follow-up visits and served as controls (n = 29). The median time between injury and blood collection was 2 h (6 h visit) and 22.5 h (24-48 h visit) in concussed athletes. Concussed athletes had significantly elevated UCH-L1 levels at the 6 h visit relative to pre-season levels (Z = 2.22, p = 0.03) and levels in control athletes (Z = 3.02, p = 0.003). Concussed athletes also had elevated S100B at 6 h relative to pre-season (Z = 2.07, p = 0.04) and controls (Z = 2.75, p = 0.006). Both markers showed fair discrimination between concussed and control athletes (UCH-L1 area under receiver operating characteristic curve [AUC] [95% CI] = 0.74 [0.61-0.88], S100B AUC = 0.72 [0.58-0.87]). Percent-change of UCH-L1 and S100B at 6 h relative to pre-season also showed fair discrimination (AUC = 0.79 [0.66-0.92] and AUC = 0.77 [0.64-0.90]). GFAP levels did not differ between groups or in concussed athletes relative to pre-season. This study provides prospective evidence of significant increases in serum levels of UCH-L1 and S100B during the early acute period following SRC, and lays the foundation for future studies examining the clinical potential for blood-based biomarkers in the early detection of concussion.

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.

Prognostic utility of neuroinjury biomarkers in post out-of-hospital cardiac arrest (OHCA) patient management

Despite aggressive intervention, patients who survive an out-of-hospital cardiac arrest (OHCA) generally have very poor prognoses, with nationwide survival rates of approximately 10-20%. Approximately 90% of survivors will have moderate to severe neurological injury ranging from moderate cognitive impairment to brain death. Currently, few early prognostic indicators are considered reliable enough to support patients' families and clinicians' in their decisions regarding medical futility. Blood biomarkers of neurological injury after OHCA may be of prognostic value in these cases. When most bodily tissues are oxygen-deprived, cellular metabolism switches from aerobic to anaerobic respiration. Neurons are a notable exception, however, being dependent solely upon aerobic respiration. Thus, after several minutes without circulating oxygen, neurons sustain irreversible damage, and certain measurable biomarkers are released into the circulation. Prior studies have demonstrated value in blood biomarkers in prediction of survival and neurologic impairment after OHCA. We hypothesize that understanding peptide biomarker kinetics in the early return of spontaneous circulation (ROSC) period, especially in the setting of refractory cardiac arrest, may assist clinicians in determining prognosis earlier in acute resuscitation. Specifically, during and after immediate resuscitation and return of ROSC, clinicians and families face a series of important questions regarding patient prognosis, futility of care and allocation of scarce resources such as the early initiation of extracorporeal cardiopulmonary resuscitation (ECPR). The ability to provide early prognostic information in this setting is highly valuable. Currently available, as well as potential biomarkers that could be good candidates in prognostication of neurological outcomes after OHCA or in the setting of refractory cardiac arrest will be reviewed and discussed.

Endothelial Activation and Blood-Brain Barrier Injury as Risk Factors for Delirium in Critically Ill Patients

OBJECTIVES

During critical illness, impaired endothelial vascular reactivity predicts prolonged acute brain dysfunction, but relationships between endothelial activation, blood-brain barrier/neurological injury, and acute brain dysfunction, including delirium, remain unexamined. We tested the hypothesis that elevated plasma markers of endothelial activation and blood-brain barrier/neurological injury are associated with delirium duration during critical illness.

DESIGN

Prospective cohort study.

SETTING

Medical and surgical ICUs in an academic medical center.

PATIENTS

Adults in acute respiratory failure and/or shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We enrolled subjects within 72 hours of organ failure diagnosis in the ICU. We measured plasma concentrations of plasminogen activator inhibitor-1, E-selectin, and angiopoietin-2 as markers of endothelial activation and S100B as a marker of blood-brain barrier/neurological injury in blood collected at enrollment. We assessed patients for delirium and coma twice daily after enrollment using the Confusion Assessment Method for the ICU and the Richmond Agitation-Sedation Scale. Among 134 patients with a median (interquartile) age of 57 years (46-66 yr) and Acute Physiology and Chronic Health Evaluation II of 26 (19-31), delirium occurred in 94 patients (70%) with a median duration of 2 days (0-4 d). Higher plasminogen activator inhibitor-1 (p = 0.002), E-selectin (p = 0.02), and S100B (p < 0.001) concentrations were associated with fewer delirium/coma-free days after adjusting for age, Charlson comorbidity index, modified Sequential Organ Failure Assessment score, and severe sepsis. Similarly, higher plasminogen activator inhibitor-1 (p = 0.007) and S100B (p = 0.01) concentrations were associated with longer delirium duration in survivors. Adjusting for S100B did not alter plasminogen activator inhibitor-1 and E-selectin associations with delirium, suggesting that these associations were not mediated by blood-brain barrier/neurological injury.

CONCLUSIONS

Elevated plasma markers of endothelial activation and blood-brain barrier/neurological injury during critical illness are associated with prolonged delirium after biomarker measurement. Future research is needed to determine whether these processes have pathophysiologic roles in delirium and whether therapies targeted at the endothelium or blood-brain barrier can prevent and/or treat delirium during critical illness.

Influence of exposure to coarse, fine and ultrafine urban particulate matter and their biological constituents on neural biomarkers in a randomized controlled crossover study

BACKGROUND

Epidemiological studies have reported associations between air pollution and neuro-psychological conditions. Biological mechanisms behind these findings are still not clear.

OBJECTIVES

We examined changes in blood and urinary neural biomarkers following exposure to concentrated ambient coarse, fine and ultrafine particles.

METHODS

Fifty healthy non-smoking volunteers, mean age 28years, were exposed to coarse (2.5-10μm, mean 213μg/m³) and fine (0.15-2.5μm, mean 238μg/m³) concentrated ambient particles (CAPs), and filtered ambient and/or medical air. Twenty-five participants were exposed to ultrafine CAP (mean size 59.6nm, range 47.0-69.8nm), mean (136μg/m³) and filtered medical air. Exposures lasted 130min, separated by ≥2weeks, and the biological constituents endotoxin and β-1,3-d-glucan of each particle size fraction were measured. Blood and urine samples were collected pre-exposure, and 1-hour and 21-hour post-exposure to determine neural biomarker levels. Mixed-model regressions assessed associations between exposures and changes in biomarker levels.

RESULTS

Results were expressed as percent change from daily pre-exposure biomarker levels. Exposure to coarse CAP was significantly associated with increased urinary levels of the stress-related biomarkers vanillylmandelic acid (VMA) and cortisol when compared with exposure to filtered medical air [20% (95% confidence interval: 1.0%, 38%) and 64% (0.2%, 127%), respectively] 21hours post-exposure. However exposure to coarse CAP was significantly associated with decreases in blood cortisol [-26.0% (-42.4%, -9.6%) and -22.4% (-43.7%, -1.1%) at 1h and 21h post-exposure, respectively]. Biological molecules present in coarse CAP were significantly associated with blood biomarkers indicative of blood brain barrier integrity. Endotoxin content was significantly associated with increased blood ubiquitin C-terminal hydrolase L1 [UCHL1, 11% (5.3%, 16%) per ln(ng/m³+1)] 1-hour post-exposure, while β-1,3-d-glucan was significantly associated with increased blood S100B [6.3% (3.2%, 9.4%) per ln(ng/m³+1)], as well as UCHL1 [3.1% (0.4%, 5.9%) per ln(ng/m³+1)], one-hour post-exposure. Fine CAP was marginally associated with increased blood UCHL1 when compared with exposure to filtered medical air [17.7% (-1.7%, 37.2%), p=0.07] 21hours post-exposure. Ultrafine CAP was not significantly associated with changes in any blood and urinary neural biomarkers examined.

CONCLUSION

Ambient coarse particulate matter and its biological constituents may influence neural biomarker levels that reflect perturbations of blood-brain barrier integrity and systemic stress response.

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.

Effects of concussion on the blood-brain barrier in humans and rodents

Traumatic brain injury and the long-term consequences of repeated concussions constitute mounting concerns in the United States, with 5.3 million individuals living with a traumatic brain injury-related disability. Attempts to understand mechanisms and possible therapeutic approaches to alleviate the consequences of repeat mild concussions or traumatic brain injury on cerebral vasculature depend on several aspects of the trauma, including: (1) the physical characteristics of trauma or insult that result in damage; (2) the time “window” after trauma in which neuropathological features develop; (3) methods to detect possible breakdown of the blood–brain barrier; and (4) understanding different consequences of a single concussion as compared with multiple concussions. We review the literature to summarize the current understanding of blood–brain barrier and endothelial cell changes post-neurotrauma in concussions and mild traumatic brain injury. Attention is focused on concussion and traumatic brain injury in humans, with a goal of pointing out the gaps in our knowledge and how studies of rodent model systems of concussion may help in filling these gaps. Specifically, we focus on disruptions that concussion causes to the blood–brain barrier and its multifaceted consequences. Importantly, the magnitude of post-concussion blood–brain barrier dysfunction may influence the time course and extent of neuronal recovery; hence, we include in this review comparisons of more severe traumatic brain injury to concussion where appropriate. Finally, we address the important, and still unresolved, issue of how best to detect possible breakdown in the blood–brain barrier following neurotrauma by exploring intravascular tracer injection in animal models to examine leakage into the brain parenchyma.