Differential Expression of Circulating Inflammatory Proteins Following Sport-Related Traumatic Brain Injury

Serum neurofilament light chain, inflammatory markers, and kynurenine metabolites in patients with persistent post-concussion symptoms: A cohort study

BACKGROUND

Concussion leads to persistent post-concussion symptoms (PPCS) in up to one-third of those affected. While previous research has linked the initial trauma to elevated serum levels of neurofilament light chain (NFL), inflammatory markers, and neurotoxic metabolites within the kynurenine pathway, few studies have explored their relevance in PPCS. This study aims to investigate these biomarkers in PPCS patients, elucidating their relevance in the prolonged phase of concussion.

METHODS

Serum samples from 86 PPCS individuals aged 18-30 years, 2-6 months post-trauma were analyzed, with 54 providing follow-up samples after seven months. NFL was measured using single-molecule array (Simoa) technology, 13 inflammatory markers via a Luminex immunoassay, and five kynurenine metabolites using liquid chromatography-mass spectrometry. A control group of 120 healthy anonymous blood donors was recruited for comparison.

RESULTS

No significant NFL differences were found in PPCS participants compared with healthy individuals (p = 0.22). Intriguingly, a subset (9.3%) of PPCS participants initially exhibited abnormally high NFL levels (>9.7 pg/mL), which normalized upon follow-up (p = 0.032). Additionally, serum levels of the inflammatory markers, monocyte chemoattractant protein-1 (MCP-1/CCL2), and eotaxin-1/CCL11 were 25-40% lower than in healthy individuals (p ≤ 0.001). As hypothesized, PPCS participants exhibited a 22% reduction in the ratio of kynurenic acid to quinolinic acid (neuroprotective index) (p < 0.0001), indicating a shift towards the formation of neurotoxic metabolites.

CONCLUSION

NFL may serve as a biomarker to monitor recovery, and future studies should investigate the potential therapeutic benefits of modulating the kynurenine pathway to improve PPCS.

Inflammation and Neurodegeneration in Glaucoma: Isolated Eye Disease or a Part of a Systemic Disorder? - Serum Proteomic Analysis

Introduction

Glaucoma is the most common optic neuropathy and the leading cause of irreversible blindness worldwide, which affects 3.54% of the population aged 40-80 years. Despite numerous published studies, some aspects of glaucoma pathogenesis, serum biomarkers, and their potential link with other diseases remain unclear. Recent articles have proposed that autoimmune, oxidative stress and inflammation may be involved in the pathogenesis of glaucoma.

Methods

We investigated the serum expression of 92 inflammatory and neurotrophic factors in glaucoma patients. The study group consisted of 26 glaucoma patients and 192 healthy subjects based on digital fundography.

Results

Patients with glaucoma had significantly lower serum expression of IL-2Rβ, TWEAK, CX3CL1, CD6, CD5, LAP TGF-beta1, LIF-R, TRAIL, NT-3, and CCL23 and significantly higher expression of IL-22Rα1.

Conclusion

Our results indicate that patients with glaucoma tend to have lower levels of neuroprotective proteins and higher levels of neuroinflammatory proteins, similar to those observed in psychiatric, neurodegenerative and autoimmune diseases, indicating a potential link between these conditions and glaucoma pathogenesis.

Concussion: Beyond the Cascade

Sport concussion affects millions of athletes each year at all levels of sport. Increasing evidence demonstrates clinical and physiological recovery are becoming more divergent definitions, as evidenced by several studies examining blood-based biomarkers of inflammation and imaging studies of the central nervous system (CNS). Recent studies have shown elevated microglial activation in the CNS in active and retired American football players, as well as in active collegiate athletes who were diagnosed with a concussion and returned to sport. These data are supportive of discordance in clinical symptomology and the inflammatory response in the CNS upon symptom resolution. In this review, we will summarize recent advances in the understanding of the inflammatory response associated with sport concussion and broader mild traumatic brain injury, as well as provide an outlook for important research questions to better align clinical and physiological recovery.

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

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

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

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

Multiplex Assessment of Serum Chemokines CCL2, CCL5, CXCL1, CXCL10, and CXCL13 Following Traumatic Brain Injury

Chemokines may promote neuroinflammation following traumatic brain injury (TBI), thereby exacerbating secondary injury. This study was designed to investigate the contributions of chemokines (CCL2, CCL5, CXCL1, CXCL10, and CXCL13) to TBI severity and clinical outcome. Peripheral blood was drawn from 92 TBI patients on admission, and 40 controls were recruited. Serum concentrations of CCL2, CCL5, CXCL1, CXCL10, and CXCL13 on admission were measured by ELISA. Preoperative clinical severity was evaluated using the Glasgow Coma Scale (GCS), and clinical outcome at 90 days post-TBI was evaluated using the Glasgow Outcome Scale (GOS). The associations were evaluated by calculating Spearman's correlation coefficients. A binary logistic regression model was used to identify clinicodemographic factors influencing outcome, and ROC curves were constructed. Serum concentrations of CCL2, CCL5, CXCL1, CXCL10, and CXCL13 were elevated significantly after TBI and negatively correlated with GCS and GOS scores except CCL5. CCL2 may be considered as an independent predictor to predict severity and outcome. Moreover, combination of GCS score, CCL2, and CXCL10 can be a better assessment prognosis of moderate and severe TBI.

Blood biomarkers of secondary outcomes following concussion: A systematic review

Introduction

Blood biomarkers have been identified as an alternative tool for predicting secondary outcomes following concussion. This systematic review aimed to summarize the literature on blood biomarkers of secondary outcomes following concussion in both pediatric and adult cohorts.

Methods

A literature search of Embase, Medline and PubMed was conducted. Two reviewers independently assessed retrieved studies to determine inclusion in systematic review synthesis.

Results

A total of 1771 unique studies were retrieved, 58 of which were included in the final synthesis. S100B, GFAP and tau were identified as being associated with secondary outcomes following concussion. Seventeen percent of studies were performed in a solely pediatric setting.

Conclusions

Validation of biomarkers associated with secondary outcomes following concussion have been largely limited by heterogeneous study cohorts and definitions of concussion and mTBI, presenting a hurdle for translation of these markers into clinical practice. Additionally, there was an underrepresentation of studies which investigated pediatric cohorts. Adult markers are not appropriate for children, therefore pediatric specific markers of secondary outcomes following concussion present the biggest gap in this field.

Biomarkers of Neuroinflammation in Traumatic Brain Injury

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

Increased level of LIGHT/TNFSF14 is associated with survival in aneurysmal subarachnoid hemorrhage

OBJECTIVES

Multiple cytokines have been implicated in aneurysmal subarachnoid hemorrhage (aSAH), but tumor necrosis factor superfamily 14 (LIGHT/TNFSF14) and oncostatin-M (OSM) have not been previously explored.

AIMS OF THE STUDY

The primary objective of this study was to examine the relationship between TNFSF14 and OSM levels and survival. Our secondary goal was to investigate a potential association between these markers and the incidence of delayed cerebral ischemia (DCI).

MATERIALS & METHODS

We consecutively recruited 60 patients with a clinical diagnosis of aSAH. LIGHT/TNFSF14 and OSM serum concentrations were determined by ELISA. The primary endpoint was survival at Day 30, while development of DCI was assessed as secondary outcome.

RESULTS

Patients had significantly higher levels of both markers than the control group (median of LIGHT: 18.1 pg/ml vs. 7 pg/ml; p = 0.01; median of OSM: 10.3 pg/ml vs. 2.8 pg/ml, p < 0.001). Significantly lower serum level of LIGHT/TNFSF14 was found in nonsurviving patients (n = 9) compared with survivors (n = 51; p = 0.011). Based on ROC analysis, serum LIGHT/TNFSF14 with a cutoff value of >7.95 pg/ml predicted 30-day survival with a sensitivity of 71% and specificity of 78% (Area: 0.763; 95% CI: 0.604-0.921, p = 0.013). In addition, it was also a predictor of DCI with a sensitivity of 72.7% and a specificity of 62.5% (AUC: 0.702; 95% CI: 0.555-0.849, p = 0.018). Based on binary logistic regression analysis, LIGHT/TNFSF14 was found to be independently associated with 30-day mortality, but not with DCI.

CONCLUSION

In this cohort, a higher serum level of LIGHT/TNFSF14 was associated with increased survival of patients with aSAH.

Analysis of Cerebrospinal Fluid Extracellular Vesicles by Proximity Extension Assay: A Comparative Study of Four Isolation Kits

There is a lack of reliable biomarkers for disorders of the central nervous system (CNS), and diagnostics still heavily rely on symptoms that are both subjective and difficult to quantify. The cerebrospinal fluid (CSF) is a promising source of biomarkers due to its close connection to the CNS. Extracellular vesicles are actively secreted by cells, and proteomic analysis of CSF extracellular vesicles (EVs) and their molecular composition likely reflects changes in the CNS to a higher extent compared with total CSF, especially in the case of neuroinflammation, which could increase blood–brain barrier permeability and cause an influx of plasma proteins into the CSF. We used proximity extension assay for proteomic analysis due to its high sensitivity. We believe that this methodology could be useful for de novo biomarker discovery for several CNS diseases. We compared four commercially available kits for EV isolation: MagCapture and ExoIntact (based on magnetic beads), EVSecond L70 (size-exclusion chromatography), and exoEasy (membrane affinity). The isolated EVs were characterized by nanoparticle tracking analysis, ELISA (CD63, CD81 and albumin), and proximity extension assay (PEA) using two different panels, each consisting of 92 markers. The exoEasy samples did not pass the built-in quality controls and were excluded from downstream analysis. The number of detectable proteins in the ExoIntact samples was considerably higher (~150% for the cardiovascular III panel and ~320% for the cell regulation panel) compared with other groups. ExoIntact also showed the highest intersample correlation with an average Pearson’s correlation coefficient of 0.991 compared with 0.985 and 0.927 for MagCapture and EVSecond, respectively. The median coefficient of variation was 5%, 8%, and 22% for ExoIntact, MagCapture, and EVSecond, respectively. Comparing total CSF and ExoIntact samples revealed 70 differentially expressed proteins in the cardiovascular III panel and 17 in the cell regulation panel. To our knowledge, this is the first time that CSF EVs were analyzed by PEA. In conclusion, analysis of CSF EVs by PEA is feasible, and different isolation kits give distinct results, with ExoIntact showing the highest number of identified proteins with the lowest variability.