YKL-40 expression in traumatic brain injury: an initial analysis

Investigating the Relationship of Serum CD163, YKL40 and VILIP-1 Levels with Autism Severity and Language-cognitive Development in Preschool Children with Autism

Objective

This study aimed to compare serum levels of CD163, YKL-40, and VILIP-1 between children with autism spectrum disorder (ASD) and healthy controls, while also investigating their association with the severity of ASD and language development.

Methods

The study included 40 ASD-diagnosed patients (aged 18-72 months) and 40 age-matched healthy controls. Childhood Autism Rating Scale, Preschool Language Scale-4, and Ankara Development Screening Inventory were administered to children in the ASD group. Serum CD163, YKL-40 and VILIP-1 levels were measured with an enzyme- linked immunosorbent assay kit.

Results

In the ASD group compared to the control group, serum VILIP-1 levels were significantly higher (p = 0.046). No significant differences were observed in mean serum CD163 and YKL-40 levels between patients and controls (p = 0.613, p = 0.769). Interestingly, a positive correlation was observed between CD163 and YKL-40 levels and ASD severity (p < 0.001 for both). Additionally, CD163 and YKL-40 levels showed significant predictive value for ASD severity. While no significant associations were found between CD163 and YKL-40 levels and language development, a negative correlation was observed between VILIP-1 levels and language development (p < 0.001).

Conclusion

Our findings highlight that the levels of CD163 and YKL-40 significantly predicted ASD severity, indicating a potential role of neuroinflammation in the development of ASD.

YKL-40 in serum: a promising biomarker of juvenile SLE and strongly correlated with disease duration

BACKGROUND

The biological function of YKL-40 is not well determined in different inflammatory and autoimmune diseases; however, some data highlighted its possible connection with disease activity.

AIM

We investigated the diagnostic utility of serum YKL-40 in patients with SLE and examined its correlation with disease activity. Additionally, we examined any differences in serum YKL-40 levels between juvenile and adult SLE patients.

METHODS

We included 78 female patients with SLE and 42 controls. The level of YKL-40 in serum was measured by ELISA.

RESULTS

The serum YKL-40 level in SLE patients was significantly higher compared to the control group (9 (3) ng/mL vs. 5.5 (0.1) ng/mL; p < 0.001). YKL-40 showed excellent diagnostic utility with an AUC of 1 (p < 0.001) and a cutoff point of 5.6, providing sensitivity and specificity of 100%. YKL-40 was higher in adolescents and those with a positive family history of SLE (p = 0.01 for both) and positively correlated with disease duration (r = 0.45, p < 0.001). YKL-40 level was significantly higher in patients with photosensitivity, fever, vasculitis, blood disorders, positive anti-dsDNA, and APL ab (p < 0.05 for all). Conversely, patients with skin manifestations had a significantly lower YKL-40 (p = 0.004). In juvenile SLE, the AUC was 0.65 and a p-value of 0.01, and at a cutoff value of (8.7) ng/mL, the sensitivity and specificity were 72% and 60%, respectively.

CONCLUSION

YKL-40 in serum could be a promising biomarker in patients with SLE, especially in adolescent-onset cases. It is independently influenced by disease duration, anemia, thrombocytopenia, positive anti-dsDNA, and APL ab features.

Translatable plasma and CSF biomarkers for use in mouse models of Huntington's disease

Huntington's disease is an inherited neurodegenerative disorder for which a wide range of disease-modifying therapies are in development and the availability of biomarkers to monitor treatment response is essential for the success of clinical trials. Baseline levels of neurofilament light chain in CSF and plasma have been shown to be effective in predicting clinical disease status, subsequent clinical progression and brain atrophy. The identification of further sensitive prognostic fluid biomarkers is an active research area, and total-Tau and YKL-40 levels have been shown to be increased in CSF from Huntington's disease mutation carriers. The use of readouts with clinical utility in the preclinical assessment of potential therapeutics should aid in the translation of new treatments. Here, we set out to determine how the concentrations of these three proteins change in plasma and CSF with disease progression in representative, well-established mouse models of Huntington's disease. Plasma and CSF were collected throughout disease progression from R6/2 transgenic mice with CAG repeats of 200 or 90 codons (R6/2:Q200 and R6/2:Q90), zQ175 knock-in mice and YAC128 transgenic mice, along with their respective wild-type littermates. Neurofilament light chain and total-Tau concentrations were quantified in CSF and plasma using ultrasensitive single-molecule array (Quanterix) assays, and a novel Quanterix assay was developed for breast regression protein 39 (mouse homologue of YKL-40) and used to quantify breast regression protein 39 levels in plasma. CSF levels of neurofilament light chain and plasma levels of neurofilament light chain and breast regression protein 39 increased in wild-type biofluids with age, whereas total-Tau remained constant. Neurofilament light chain and breast regression protein 39 were elevated in the plasma and CSF from Huntington's disease mouse models, as compared with wild-type littermates, at presymptomatic stages, whereas total-Tau was only increased at the latest disease stages analysed. Levels of biomarkers that had been measured in the same CSF or plasma samples taken at the latest stages of disease were correlated. The demonstration that breast regression protein 39 constitutes a robust plasma biomarker in Huntington's disease mouse models supports the further investigation of YKL-40 as a CSF biomarker for Huntington's disease mutation carriers. Neurofilament light chain and Tau are considered markers of neuronal damage, and breast regression protein 39 is a marker of inflammation; the similarities and differences in the levels of these proteins between mouse models may provide future insights into their underlying pathology. These data will facilitate the use of fluid biomarkers in the preclinical assessment of therapeutic agents for Huntington's disease, providing readouts with direct relevance to clinical trials.

Serum YKL-40 as a Predictive Biomarker of Cerebral Amyloid Angiopathy-Related Intracerebral Hemorrhage Recurrence

Background

Neuroinflammation is a major cause of secondary brain injury in intracerebral hemorrhage (ICH). To date, the prognostic value of YKL-40 (chitinase-3-like-1 protein), a biomarker of neuroinflammation, in cerebral amyloid angiopathy-related intracerebral hemorrhage (CAA-ICH) remains undiscovered.

Objective

To evaluate the relationships between serum YKL-40 and CAA-ICH recurrence.

Methods

Clinical and imaging information of 68 first-onset probable CAA-ICH cases and 95 controls were collected at baseline. Serum YKL-40 was measured by Luminex assay. Cox proportional hazards model was used to analyze the associations between YKL-40 level and CAA-ICH recurrence.

Results

Serum YKL-40 level was significantly higher in CAA-ICH cases than healthy controls (median [interquartile range, IQR], 46.1 [19.8, 93.4] versus 24.4 [13.9, 59.0] ng/mL, p = 0.004). Higher level of YKL-40 predicted increased risk of CAA-ICH recurrence adjusted for age, ICH volume and enlarged perivascular space score (ePVS) (above versus below 115.5 ng/ml, adjusted hazard ratios 4.721, 95% confidence intervals 1.829-12.189, p = 0.001) within a median follow-up period of 2.4 years. Adding YKL-40 to a model of only MRI imaging markers including ICH volume and ePVS score improved the discriminatory power (concordance index from 0.707 to 0.772, p = 0.001) and the reclassification power (net reclassification improvement 28.4%; integrated discrimination index 11.0%).

Conclusions

Serum YKL-40 level might be a candidate prognostic biomarker for CAA-ICH recurrence.

Astrocytic Chitinase-3-like protein 1 in neurological diseases: Potential roles and future perspectives

Chitinase-3-like protein 1 (CHI3L1) is a secreted glycoprotein characterized by its ability to regulate multiple biological processes, such as the inflammatory response and gene transcriptional signaling activation. Abnormal CHI3L1 expression has been associated with multiple neurological disorders and serves as a biomarker for the early detection of several neurodegenerative diseases. Aberrant CHI3L1 expression is also reportedly associated with brain tumor migration and metastasis, as well as contributions to immune escape, playing important roles in brain tumor progression. CHI3L1 is synthesized and secreted mainly by reactive astrocytes in the central nervous system. Thus, targeting astrocytic CHI3L1 could be a promising approach for the treatment of neurological diseases, such as traumatic brain injury, ischemic stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, and glioma. Based on current knowledge of CHI3L1, we assume that it acts as a molecule mediating several signaling pathways driving the initiation and progression of neurological disorders. This narrative review is the first to introduce the potential roles of astrocytic CHI3L1 in neurological disorders. We also equally explore astrocytic CHI3L1 mRNA expression under physiological and pathological conditions. Inhibiting CHI3L1 and disrupting its interaction with its receptors through multiple mechanisms of action are briefly discussed. These endeavors highlight the pivotal roles of astrocytic CHI3L1 in neurological disorders and could contribute to the development of effective inhibitors based on the strategy of structure-based drug discovery, which could be an attractive therapeutic approach for neurological disease treatment.

Sex-dependent neuro-deconvolution analysis of Alzheimer's disease brain transcriptomes according to CHI3L1 expression levels

Glial activation and related neuroinflammatory processes play a key role in the aging and progression of Alzheimer's disease (AD). CHI3L1/ YKL40 is a widely investigated chitinase in neurodegenerative diseases and recent studies have shown its involvement in aging and AD. Nevertheless, the biological function of CHI3L1 in AD is still unknown. Here, we collected microarray datasets from the National Center for Biotechnology Information (NCBI) brain samples of not demented healthy controls (NDHC) who died from causes not attributable to neurodegenerative disorders (n = 460), and of deceased patients suffering from Alzheimer's disease (AD) (n = 697). The NDHC and AD patients were stratified according to CHI3L1 expression levels as a cut-off. We identified two groups both males and females, subsequently used for our statistical comparisons: the high CHI3L1 expression group (HCEG) and the low CHI3L1 expression group (LCEG). Comparing HCEG to LCEG, we attained four signatures according to the sex of patients, in order to identify the healthy and AD brain cellular architecture, performing a genomic deconvolution analysis. We used neurological signatures (NS) belonging to six neurological cells populations and nine signatures that included the main physiological neurological processes. We discovered that, in the brains of NDHC the high expression levels of CHI3L1 were associated with astrocyte activation profile, while in AD males and females we showed an inflammatory profile microglia-mediated. The low CHI3L1 brain expression levels in NDHC and AD patients highlighted a neuronal activation profile. Furthermore, using drugs opposing CHI3L1 transcriptomic signatures, we found a specific drug profile for AD males and females characterized by high levels of CHI3L1 composed of fostamatinib, rucaparib, cephaeline, prednisolone, and dinoprostone. Brain levels of CHI3L1 in AD patients represent a biological signature that allows distinguishing between males and females and their likely cellular brain architecture.

Pathogenesis and management of traumatic brain injury (TBI): role of neuroinflammation and anti-inflammatory drugs

Traumatic brain injury (TBI) is an important global health concern that represents a leading cause of death and disability. It occurs due to direct impact or hit on the head caused by factors such as motor vehicles, crushes, and assaults. During the past decade, an abundance of new evidence highlighted the importance of inflammation in the secondary damage response that contributes to neurodegenerative and neurological deficits after TBI. It results in disruption of the blood-brain barrier (BBB) and initiates the release of macrophages, neutrophils, and lymphocytes at the injury site. A growing number of researchers have discovered various signalling pathways associated with the initiation and progression of inflammation. Targeting different signalling pathways (NF-κB, JAK/STAT, MAPKs, PI3K/Akt/mTOR, GSK-3, Nrf2, RhoGTPase, TGF-β1, and NLRP3) helps in the development of novel anti-inflammatory drugs in the management of TBI. Several synthetic and herbal drugs with both anti-inflammatory and neuroprotective potential showed effective results. This review summarizes different signalling pathways, associated pathologies, inflammatory mediators, pharmacological potential, current status, and challenges with anti-inflammatory drugs.

Role of Chitinase 3-like 1 as a Biomarker in Multiple Sclerosis: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES

Multiple sclerosis (MS) is an autoimmune disease confined in the CNS, and its course is frequently subtle and variable. Therefore, predictive biomarkers are needed. In this scenario, we conducted a systematic review and meta-analysis to evaluate the reliability of chitinase 3-like 1 as a biomarker of MS.

METHODS

Research through the main scientific databases (PubMed, Scopus, Web of Science, and Cochrane Library) published from January 2010 to December 2020 was performed using the following keywords: "chitinase 3-like 1 and multiple sclerosis" and "YKL40 and multiple sclerosis." Articles were selected according to the 2020 updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines by 2 authors independently, and data were extracted; 20 of the 90 studies screened were included in the meta-analysis. The main efficacy measure was represented by the standardized mean difference of CSF and blood CHI3L1 levels; Review Manager version 5.4 and R software applications were used for analysis.

RESULTS

Higher levels of CHI3L1 were found in CSF of 673 patients with MS compared with 336 healthy controls (size-weighted mean difference [SMD] 50.88; 95% CI = 44.98-56.79; p < 0.00001) and in 461 patients with MS than 283 patients with clinically isolated syndrome (CIS) (SMD 28.18; 95% CI = 23.59-32.76; p < 0.00001). Mean CSF CHI3L1 levels were significantly higher in 561 converting than 445 nonconverting CIS (SMD 30.6; 95% CI = 28.31-32.93; p < 0.00001). CSF CHI3L1 levels were significantly higher in patients with primary progressive MS (PPMS) than in patients with relapsing-remitting MS (RRMS) (SMD 43.15; 95% CI = 24.41-61.90; p < 0.00001) and in patients with secondary progressive MS (SMD 41.86 with 95% CI = 32.39-51.33; p < 0.00001). CSF CHI3L1 levels in 407 patients with MS during remission phase of disease were significantly higher than those in 395 patients with MS with acute relapse (SMD 10.48; 95% CI = 08.51-12.44; p < 0.00001). The performances of CHI3L1 in blood for differentiating patients with MS from healthy controls were not significant (SMD 0.48; 95% CI = -1.18 to 2.14; p: 0.57).

DISCUSSION

CSF levels of CHI3L1 have a strong correlation with the MS pathologic course, in particular with the mechanism of progression of the disease; it helps to distinguish the PPMS from the RRMS. The potential role of CHI3L1 in serum needs to be further studied in the future.

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.

Proteome-Wide Analysis Using SOMAscan Identifies and Validates Chitinase-3-Like Protein 1 as a Risk and Disease Marker of Delirium Among Older Adults Undergoing Major Elective Surgery

BACKGROUND

Delirium (an acute change in cognition) is a common, morbid, and costly syndrome seen primarily in aging adults. Despite increasing knowledge of its epidemiology, delirium remains a clinical diagnosis with no established biomarkers to guide diagnosis or management. Advances in proteomics now provide opportunities to identify novel markers of risk and disease progression for postoperative delirium and its associated long-term consequences (eg, long-term cognitive decline and Alzheimer's disease [AD]).

METHODS

In a nested matched case-control study (18 delirium/no-delirium pairs) within the Successful Aging after Elective Surgery study (N = 556), we evaluated the association of 1305 plasma proteins preoperatively [PREOP] and on postoperative day 2 [POD2]) with delirium using SOMAscan. Generalized linear models were applied to enzyme-linked immunosorbant assay (ELISA) validation data of one protein across the full cohort. Multi-protein modeling included delirium biomarkers identified in prior work (C-reactive protein, interleukin-6 [IL6]).

RESULTS

We identified chitinase-3-like-protein-1 (CHI3L1/YKL-40) as the sole delirium-associated protein in both a PREOP and a POD2 predictor model, a finding confirmed by ELISA. Multi-protein modeling found high PREOP CHI3L1/YKL-40 and POD2 IL6 increased the risk of delirium (relative risk [95% confidence interval] Quartile [Q]4 vs Q1: 2.4[1.2-5.0] and 2.1[1.1-4.1], respectively).

CONCLUSIONS

Our identification of CHI3L1/YKL-40 in postoperative delirium parallels reports of CHI3L1/YKL-40 and its association with aging, mortality, and age-related conditions including AD onset and progression. This highlights the type 2 innate immune response, involving CHI3L1/YKL-40, as an underlying mechanism of postoperative delirium, a common, morbid, and costly syndrome that threatens the independence of older adults.

Pathophysiology of neurodegenerative diseases: An interplay among axonal transport failure, oxidative stress, and inflammation?

Neurodegenerative diseases (NDs) are heterogeneous neurological disorders characterized by a progressive loss of selected neuronal populations. A significant risk factor for most NDs is aging. Considering the constant increase in life expectancy, NDs represent a global public health burden. Axonal transport (AT) is a central cellular process underlying the generation and maintenance of neuronal architecture and connectivity. Deficits in AT appear to be a common thread for most, if not all, NDs. Neuroinflammation has been notoriously difficult to define in relation to NDs. Inflammation is a complex multifactorial process in the CNS, which varies depending on the disease stage. Several lines of evidence suggest that AT defect, axonopathy and neuroinflammation are tightly interlaced. However, whether these impairments play a causative role in NDs or are merely a downstream effect of neuronal degeneration remains unsettled. We still lack reliable information on the temporal relationship between these pathogenic mechanisms, although several findings suggest that they may occur early during ND pathophysiology. This article will review the latest evidence emerging on whether the interplay between AT perturbations and some aspects of CNS inflammation can participate in ND etiology, analyze their potential as therapeutic targets, and the urge to identify early surrogate biomarkers.

Plasma proteome profiling using tandem mass tag labeling technology reveals potential biomarkers for Parkinson's disease: a preliminary study

PURPOSE

Parkinson's disease (PD) is the second most frequently occurring progressive neurodegenerative disorder. Biomarkers are useful indicators for tracking disease progression, early diagnosis, and intervention of disease progression. We aimed to develop plasma biomarker panel which maybe aid to predict the onset and progression of PD.

EXPERIMENTAL DESIGN

Tandem mass tag (TMT) mass spectrometry was applied using an Orbitrap Lumos mass spectrometer to analyze plasma protein expression in patients diagnosed with PD and healthy controls.

RESULTS

In total, 555 proteins were quantified. Using a cut-off of p < 0.05 and a fold change of >1.2 for the variation in expression, 25 proteins were differentially expressed between the PD and control groups. Sixteen proteins were upregulated and nine were downregulated. Several proteins, including Chitinase-3-like protein 1 (CHI3L1) and thymosin beta-4 (TMSB4X) were implicated in PD pathogenesis.

CONCLUSIONS

The data from the TMT-based proteomic profiling of plasma samples in PD may help advance the understanding of the molecular mechanisms of PD and identify potential novel biomarkers of PD for further characterization.

Clinical and Paraclinical Biomarkers and the Hitches to Assess Conversion to Secondary Progressive Multiple Sclerosis: A Systematic Review

Conversion to secondary progressive (SP) course is the decisive factor for long-term prognosis in relapsing multiple sclerosis (MS), generally considered the clinical equivalent of progressive MS-associated neuroaxonal degeneration. Evidence is accumulating that both inflammation and neurodegeneration are present along a continuum of pathologic processes in all phases of MS. While inflammation is the prominent feature in early stages, its quality changes and relative importance to disease course decreases while neurodegenerative processes prevail with ongoing disease. Consequently, anti-inflammatory disease-modifying therapies successfully used in relapsing MS are ineffective in SPMS, whereas specific treatment for the latter is increasingly a focus of MS research. Therefore, the prevention, but also the (anticipatory) diagnosis of SPMS, is of crucial importance. The problem is that currently SPMS diagnosis is exclusively based on retrospectively assessing the increase of overt physical disability usually over the past 6–12 months. This inevitably results in a delay of diagnosis of up to 3 years resulting in periods of uncertainty and, thus, making early therapy adaptation to prevent SPMS conversion impossible. Hence, there is an urgent need for reliable and objective biomarkers to prospectively predict and define SPMS conversion. Here, we review current evidence on clinical parameters, magnetic resonance imaging and optical coherence tomography measures, and serum and cerebrospinal fluid biomarkers in the context of MS-associated neurodegeneration and SPMS conversion. Ultimately, we discuss the necessity of multimodal approaches in order to approach objective definition and prediction of conversion to SPMS.

Co-Expression Network Analysis of MicroRNAs and Proteins in Severe Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) represents one of the leading causes of mortality and morbidity worldwide, placing an enormous socioeconomic burden on healthcare services and communities around the world. Survivors of TBI can experience complications ranging from temporary neurological and psychosocial problems to long-term, severe disability and neurodegenerative disease. The current lack of therapeutic agents able to mitigate the effects of secondary brain injury highlights the urgent need for novel target discovery. This study comprises two independent systematic reviews, investigating both microRNA (miRNA) and proteomic expression in rat models of severe TBI (sTBI). The results were combined to perform integrated miRNA-protein co-expression analyses with the aim of uncovering the potential roles of miRNAs in sTBI and to ultimately identify new targets for therapy. Thirty-four studies were included in total. Bioinformatic analysis was performed to identify any miRNA–protein associations. Endocytosis and TNF signalling pathways were highlighted as common pathways involving both miRNAs and proteins found to be differentially expressed in rat brain tissue following sTBI, suggesting efforts to find novel therapeutic targets that should be focused here. Further high-quality investigations are required to ascertain the involvement of these pathways and their miRNAs in the pathogenesis of TBI and other CNS diseases and to therefore uncover those targets with the greatest therapeutic potential.

Chitinase-Like Protein Ym2 (Chil4) Regulates Regeneration of the Olfactory Epithelium via Interaction with Inflammation

The adult olfactory epithelium (OE) regenerates sensory neurons and nonsensory supporting cells from resident stem cells after injury. How supporting cells contribute to OE regeneration remains largely unknown. In this study, we elucidated a novel role of Ym2 (also known as Chil4 or Chi3l4), a chitinase-like protein expressed in supporting cells, in regulating regeneration of the injured OE in vivo in both male and female mice and cell proliferation/differentiation in OE colonies in vitro We found that Ym2 expression was enhanced in supporting cells after OE injury. Genetic knockdown of Ym2 in supporting cells attenuated recovery of the injured OE, while Ym2 overexpression by lentiviral infection accelerated OE regeneration. Similarly, Ym2 bidirectionally regulated cell proliferation and differentiation in OE colonies. Furthermore, anti-inflammatory treatment reduced Ym2 expression and delayed OE regeneration in vivo and cell proliferation/differentiation in vitro, which were counteracted by Ym2 overexpression. Collectively, this study revealed a novel role of Ym2 in OE regeneration and cell proliferation/differentiation of OE colonies via interaction with inflammatory responses, providing new clues to the function of supporting cells in these processes.SIGNIFICANCE STATEMENT The mammalian olfactory epithelium (OE) is a unique neural tissue that regenerates sensory neurons and nonsensory supporting cells throughout life and postinjury. How supporting cells contribute to this process is not entirely understood. Here we report that OE injury causes upregulation of a chitinase-like protein, Ym2, in supporting cells, which facilitates OE regeneration. Moreover, anti-inflammatory treatment reduces Ym2 expression and delays OE regeneration, which are counteracted by Ym2 overexpression. This study reveals an important role of supporting cells in OE regeneration and provides a critical link between Ym2 and inflammation in this process.

Plasma Protein Profiling by Proximity Extension Assay Technology Reveals Novel Biomarkers of Traumatic Brain Injury-A Pilot Study

BACKGROUND

Traumatic brain injury (TBI) is a significant public health issue affecting nearly 69 million patients worldwide per year. Reliable diagnostic biomarkers are urgently needed to aid in disease diagnosis and prognosis and to guide patient aftercare. Blood biomarkers represent an attractive modality to quickly, cheaply, and objectively evaluate clinical status. We hypothesize that deep and quantitative plasma proteomic profiling with a novel technology, proximity extension assay, may lead to the discovery of diagnostic and/or prognostic biomarkers of TBI.

METHODS

We used high-throughput proximity extension assays (PEA) to quantify the relative abundance of over 1000 unique proteins in plasma. PEA is a highly sensitive multiplex immunoassay capable of detecting very low-abundance proteins (down to fg/mL) in complex biological matrices. Our patient cohort consisted of severe TBI (sTBI) patients, matched healthy controls, and another non-TBI group that was included in the analysis to validate the specificity of the candidates during the selection process. The obtained protein quantification data was then filtered to identify candidate biomarkers through statistical analysis, literature searches, and comparison to our reference control groups.

RESULTS

Overall, we identified 6 novel candidate TBI biomarkers. Candidates exhibit a significant increase in plasma protein abundance in sTBI when comparing between healthy controls and sTBI patients. Candidates generally had low expression in our reference groups compared with the sTBI group.

CONCLUSIONS

Our preliminary findings represent a starting point for future validation. These biomarkers, either alone or in combination, may have significant clinical utility in aiding in TBI diagnosis, prognosis, and/or management.

Neuroinflammation and Hypothalamo-Pituitary Dysfunction: Focus of Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) has increased over the last years with an important impact on public health. Many preclinical and clinical studies identified multiple and heterogeneous TBI-related pathophysiological mechanisms that are responsible for functional, cognitive, and behavioral alterations. Recent evidence has suggested that post-TBI neuroinflammation is responsible for several long-term clinical consequences, including hypopituitarism. This review aims to summarize current evidence on TBI-induced neuroinflammation and its potential role in determining hypothalamic-pituitary dysfunctions.

Novel fluid biomarkers to differentiate frontotemporal dementia and dementia with Lewy bodies from Alzheimer's disease: A systematic review

RATIONALE

Frontotemporal dementia (FTD) and dementia with Lewy bodies (DLB) are two common forms of neurodegenerative dementia, subsequent to Alzheimer's disease (AD). AD is the only dementia that includes clinically validated cerebrospinal fluid (CSF) biomarkers in the diagnostic criteria. FTD and DLB often overlap with AD in their clinical and pathological features, making it challenging to differentiate between these conditions.

AIM

This systematic review aimed to identify if novel fluid biomarkers are useful in differentiating FTD and DLB from AD. Increasing the certainty of the differentiation between dementia subtypes would be advantageous clinically and in research.

METHODS

PubMed and Scopus were searched for studies that quantified and assessed diagnostic accuracy of novel fluid biomarkers in clinically diagnosed patients with FTD or DLB, in comparison to patients with AD. Meta-analyses were performed on biomarkers that were quantified in 3 studies or more.

RESULTS

The search strategy yielded 614 results, from which, 27 studies were included. When comparing bio-fluid levels in AD and FTD patients, neurofilament light chain (NfL) level was often higher in FTD, whilst brain soluble amyloid precursor protein β (sAPPβ) was higher in patients with AD. When comparing bio-fluid levels in AD and DLB patients, α-synuclein ensued heterogeneous findings, while the noradrenaline metabolite (MHPG) was found to be lower in DLB. Ratios of Aβ42/Aβ38 and Aβ42/Aβ40 were lower in AD than FTD and DLB and offered better diagnostic accuracy than raw amyloid-β (Aβ) concentrations.

CONCLUSIONS

Several promising novel biomarkers were highlighted in this review. Combinations of fluid biomarkers were more often useful than individual biomarkers in distinguishing subtypes of dementia. Considering the heterogeneity in methods and results between the studies, further validation, ideally with longitudinal prospective designs with large sample sizes and unified protocols, are fundamental before conclusions can be finalised.

Frontal cortex chitinase and pentraxin neuroinflammatory alterations during the progression of Alzheimer's disease

BACKGROUND

Chitinase 3-like 1 (CHI3L1), chitinase 3-like 2 (CHI3L2), and neuronal pentraxin II (NPTX2) are inflammatory biomarkers of Alzheimer's disease (AD). Although studies have demonstrated that cerebrospinal fluid levels of these proteins are changed in AD, no studies have undertaken a detailed examination of alterations in protein levels, cellular expression, and interaction with amyloid in the brain during the progression of AD.

METHODS

The study evaluated levels of both CHI3L1 and CHI3L2, NPTX2, ionized calcium-binding adapter molecule 1 (Iba1), complement component 1q (C1q), glial fibrillary acidic protein (GFAP), and CD44, in the frontal cortex of people who died with an antemortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), mild/moderate AD (mAD), and severe AD (sAD) using immunoblot and immunohistochemical techniques.

RESULTS

CHI3L1-immunoreactive (-ir) astrocyte numbers were increased in the frontal cortex and white matter in sAD compared to NCI. On the other hand, increases in GFAP and Iba1-ir cell numbers were observed in MCI compared to NCI but only in white matter. Western blot analyses revealed significantly lower frontal cortex CHI3L2 levels, whereas CD44 levels were increased in sAD. No significant differences for CHI3L1, GFAP, C1q, and NPTX2 protein levels were detected between clinical groups. Strong significant correlations were found between frontal cortex CHI3L1 and Iba1-ir cell numbers in white matter and CHI3L1 and C1q protein levels in the early stages of the disease. C1q and Iba1, CD44 with CHI3L2, and GFAP protein levels were associated during disease progression. CHI3L1 and Iba1 cell numbers in white matter showed a significant associations with episodic memory and perceptual speed.

CONCLUSIONS

White matter CHI3L1 inflammatory response is associated with cognitive impairment early in the onset of AD.

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.

GFAP Mutations in Astrocytes Impair Oligodendrocyte Progenitor Proliferation and Myelination in an hiPSC Model of Alexander Disease

Alexander disease (AxD) is a leukodystrophy that primarily affects astrocytes and is caused by mutations in the astrocytic filament gene GFAP. While astrocytes are thought to have important roles in controlling myelination, AxD animal models do not recapitulate critical myelination phenotypes and it is therefore not clear how AxD astrocytes contribute to leukodystrophy. Here, we show that AxD patient iPSC-derived astrocytes recapitulate key features of AxD pathology such as GFAP aggregation. Moreover, AxD astrocytes inhibit proliferation of human iPSC-derived oligodendrocyte progenitor cells (OPCs) in co-culture and reduce their myelination potential. CRISPR/Cas9-based correction of GFAP mutations reversed these phenotypes. Transcriptomic analyses of AxD astrocytes and postmortem brains identified CHI3L1 as a key mediator of AxD astrocyte-induced inhibition of OPC activity. Thus, this iPSC-based model of AxD not only recapitulates patient phenotypes not observed in animal models, but also reveals mechanisms underlying disease pathology and provides a platform for assessing therapeutic interventions.

Epidemiology of Comorbid Conditions Among Adults 50 Years and Older With Traumatic Brain Injury

OBJECTIVES

Aging individuals with traumatic brain injury (TBI) experience multiple comorbidities that can affect recovery from injury. The objective of this study was to describe the most commonly co-occurring comorbid conditions among adults 50 years and older with TBI.

SETTING

Level I Trauma centers.

PARTICIPANTS

Adults 50 years and older with moderate/severe TBI enrolled in the TBI-Model Systems (TBI-MS) from 2007 to 2014 (n = 2134).

DESIGN

A TBI-MS prospective cohort study.

MAIN MEASURES

International Classification of Disease-9th Revision codes collapsed into 45 comorbidity categories. Comorbidity prevalence estimates and trend analyses were conducted by age strata (50-54, 55-64, 65-74, 75-84, ≥85 years). A dimension reduction method, Treelet Transform, classified clusters of comorbidities that tended to co-occur.

RESULTS

The 3 most commonly occurring comorbid categories were hypertensive disease (52.6/100 persons), other diseases of the respiratory system (51.8/100 persons), and fluid component imbalances (43.7/100 persons). Treelet Transform classified 3 clusters of comorbid codes, broadly classified as (1) acute medical diseases/infections, (2) chronic conditions, and (3) substance abuse disorders.

CONCLUSION

This study provides valuable insight into comorbid conditions that co-occur among adults 50 years and older with TBI and provides a foundation for future studies to explore how specific comorbidities affect TBI recovery.

Roles of chitinase 3-like 1 in the development of cancer, neurodegenerative diseases, and inflammatory diseases

Chitinase 3-like 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly increased by various inflammatory and immunological conditions, including rheumatoid arthritis, multiple sclerosis, Alzheimer's disease, and several cancers. However, its physiological and pathophysiological roles in the development of cancer and neurodegenerative and inflammatory diseases remain unclear. Several studies have reported that CHI3L1 promotes cancer proliferation, inflammatory cytokine production, and microglial activation, and that multiple receptors, such as advanced glycation end product, syndecan-1/αVβ3, and IL-13Rα2, are involved. In addition, the pro-inflammatory action of CHI3L1 may be mediated via the protein kinase B and phosphoinositide-3 signaling pathways and responses to various pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 could contribute to a vast array of inflammatory diseases. In this article, we review recent findings regarding the roles of CHI3L1 and suggest therapeutic approaches targeting CHI3L1 in the development of cancers, neurodegenerative diseases, and inflammatory diseases.

Chitinase-3-like protein 1 levels in bipolar disorder

OBJECTIVES

To evaluate the relationship between the expression level and biologic role of YKL-40 in bipolar disorder (BD).

METHODS

This case-control study was conducted in the Faculty of Medicine, Canakkale Onsekiz Mart University, Canakkale, Turkey in 2015. One hundred and four patients diagnosed as having bipolar disorder (DSM5 criteria), and 96 participants were included as healthy controls in this study. A human YKL-40 enzyme-linked immunosorbent assay (ELISA) kit was used to measure the serum YKL-40 levels. As independent variables, we collected data on C-reactive protein (CRP), demographic variables, and medications. Results: The mean YLK-40 levels for the BD was 2723.5±543.8 pg/ml and control groups was 2132.5±576.3 pg/ml (t=7.42, p less than 0.001). The mean CRP levels for the BD was 0.4±0.6 mg/dl and control groups was 0.4±0.7 mg/dl (t=0.02, p=0.985). The receiver operating characteristics (ROC) analysis revealed an area under the curve (AUC) of YKL-40 in the diagnosis of BD as 0.79 (95% confidence interval [CI]: 0.72-0.85) with a sensitivity of 82.7% and specificity of 68.1% at a cutoff level of 2307.1 pg/ml. The use of antidepressants, antipsychotics, mood modifiers, and the presence of any comorbidity was not related to the YKL-40 levels (p greater than 0.05). Conclusion: With acceptable sensitivity and specificity levels, the YKL-40 can be utilized as a marker in the diagnosis and follow-up of BD.

Increased number of monocytes and plasma levels of MCP-1 and YKL-40 in first-episode psychosis

OBJECTIVE

Accumulating evidence implicates immune activation in the development of schizophrenia. Here, monocyte numbers, monocyte chemoattractant protein-1 (MCP-1) and chitinase-3-like protein 1 (YKL-40) were investigated in plasma and cerebrospinal fluid (CSF) in first-episode psychosis (FEP) patients.

METHOD

CSF and blood were sampled from 42 first-episode psychosis (FEP) patients and 22 healthy controls. The levels of YKL-40 and MCP-1 were measured using electrochemiluminescence assay, and blood monocytes were counted using an XN-9000-hematology analyzer.

RESULTS

We found higher plasma levels of MCP-1 and YKL-40 in FEP patients compared with healthy controls, a condition that was unrelated to antipsychotic and/or anxiolytic medication. This was combined with an increased number of blood monocytes and a borderline significant increase in YKL-40 levels in the CSF of tobacco-free FEP patients. Plasma or CSF chemokines or blood monocytes did not correlate with the severity of symptoms or the level of functioning.

CONCLUSION

These data demonstrate activation of monocytes in FEP and strengthens the idea of an immune dysfunction of psychotic disorders. Further studies are required to perceive a role of YKL-40 and MCP-1 in the initiation and progression of schizophrenia.

YKL40 in sporadic amyotrophic lateral sclerosis: cerebrospinal fluid levels as a prognosis marker of disease progression

Amyotrophic lateral sclerosis (ALS) has variable clinical course and fatal outcome. Since inflammation plays a role in the pathogenesis of ALS, chitinase-3-like protein 1 or YKL40 has been assessed as putative biomarker of disease progression. YKL40 mRNA levels are increased in anterior horn of the spinal cord (P=0.004) in sporadic ALS (sALS) cases when compared with age-matched controls. These correlate with increased mRNA expression of microglial markers AIF1 and CD68 in the spinal cord in sALS (P=0.044 and P=0.000, respectively). YKL40 mRNA and protein expression had a tendency to increase in post-mortem frontal cortex area 8 (P=0.06 and P=0.08, respectively). Yet YKL40 immunoreactivity is restricted to a subpopulation of astrocytes in these regions. YKL40 protein levels, as revealed by enzyme-linked immunosorbent assay (ELISA), are significantly increased in the CSF in sALS (n=86) compared with age-matched controls (n=21) (P=0.045). Higher levels are found in patients with fast progression when compared with patients with slow and normal progression (P=0.008 and P=0.004, respectively), and correlates with ALS-FRS-R slope (P=0.000). Additionally, increased protein levels of neurofilament light chain (NF-L) are also found in sALS (P=0.000); highest values are found in patients with fast progression when compared with cases with slow and normal progression (P=0.005 and P=0.000, respectively), and also correlate with ALS-FRS-R slope (P=0.000). Pearson's correlation test linked positively the increased levels of YKL40 with increased NF-L levels (P=0.013). These data point to YKL40 and NF-L protein levels in the CSF as a good biomarker combination of disease progression in sALS.

Differential regulation of the pro-inflammatory biomarker, YKL-40/CHI3L1, by PTEN/Phosphoinositide 3-kinase and JAK2/STAT3 pathways in glioblastoma

Constitutive activation of the phosphoinositide 3-kinase/AKT signaling pathway is frequently observed in high-grade gliomas with high frequency of losing PTEN tumor suppressor. To identify transcriptomic profiles associated with a hyperactivated PI3K pathway, RNA-sequencing analysis was performed in a glioblastoma cell line stably expressing PTEN. RNA-sequencing revealed enriched transcripts of pro-inflammatory mediators, and among the genes that displayed high differential expression was the secreted glycoprotein YKL-40. Treatment with chemical inhibitors that target the PI3K/AKT pathway elicited differential effects on YKL-40 expression in selected GBM cell lines, indicating that its expression displayed tumor cell-specific variations. This variability appeared to be correlated with the ability to transactivate the immune signaling molecules JAK2 and STAT3. In summary, the differential expression of the immunomodulatory molecule YKL-40 may affect the treatment efficacy of PI3K/AKT-based pathway inhibitors in glioblastoma.

Neurofilament light and tau as blood biomarkers for sports-related concussion

Objective

To compare neurofilament light (NfL) and tau as blood-based biomarkers for acute sports-related concussion (SRC) and determine whether their concentrations at different time points after the injury are associated with prolonged time to return to play (RTP).

Methods

A total of 288 professional hockey players were followed longitudinally from September 1, 2012, to April 30, 2015. Data collection and biomarker analyses were conducted between 2015 and 2017. Associations were tested between blood concentrations of NfL and tau, and RTP time. Serum concentrations of S100B and neuron-specific enolase (NSE) were also measured for comparison.

Results

Of 288 players, 105 sustained an SRC. Of these, 87 underwent blood sampling 1, 12, 36, and 144 hours after SRC and at the RTP time point. Serum NfL concentrations 1, 12, 36, and 144 hours after SRC were related to prolonged RTP time, and could separate players with RTP >10 days from those with RTP ≤10 days (area under the receiver operating characteristic curve [AUROC] 0.82). Also, serum NfL 144 hours after SRC discriminated players who resigned from the game due to persistent postconcussion symptoms (PCS) from those who returned to play (AUROC 0.89). Plasma tau 1 hour after SRC was related to RTP but less strongly than NfL, while S100B and NSE showed no such associations.

Conclusion

Serum NfL outperformed tau, S100B, and NSE as a biomarker for SRC. From a clinical standpoint, serum NfL may be useful to identify individuals at risk of prolonged PCS, and may aid in biomarker-informed decisions with regard to when RTP should be considered.

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.

Chitinase-like proteins as regulators of innate immunity and tissue repair: helpful lessons for asthma?

Chitinases and chitinase-like proteins (CLPs) belong to the glycoside hydrolase family 18 of proteins. Chitinases are expressed in mammals and lower organisms, facilitate chitin degradation, and hence act as host-defence enzymes. Gene duplication and loss-of-function mutations of enzymatically active chitinases have resulted in the expression of a diverse range of CLPs across different species. CLPs are genes that are increasingly associated with inflammation and tissue remodelling not only in mammals but also across distant species. While the focus has remained on understanding the functions and expression patterns of CLPs during disease in humans, studies in mouse and lower organisms have revealed important and overlapping roles of the CLP family during physiology, host defence and pathology. This review will summarise recent insights into the regulatory functions of CLPs on innate immune pathways and discuss how these effects are not only important for host defence and tissue injury/repair after pathogen invasion, but also how they have extensive implications for pathological processes involved in diseases such as asthma.

YKL-40 in the brain and cerebrospinal fluid of neurodegenerative dementias

BACKGROUND

YKL-40 (also known as Chitinase 3-like 1) is a glycoprotein produced by inflammatory, cancer and stem cells. Its physiological role is not completely understood but YKL-40 is elevated in the brain and cerebrospinal fluid (CSF) in several neurological and neurodegenerative diseases associated with inflammatory processes. Yet the precise characterization of YKL-40 in dementia cases is missing.

METHODS

In the present study, we comparatively analysed YKL-40 levels in the brain and CSF samples from neurodegenerative dementias of different aetiologies characterized by the presence of cortical pathology and disease-specific neuroinflammatory signatures.

RESULTS

YKL-40 was normally expressed in fibrillar astrocytes in the white matter. Additionally YKL-40 was highly and widely expressed in reactive protoplasmic cortical and perivascular astrocytes, and fibrillar astrocytes in sporadic Creutzfeldt-Jakob disease (sCJD). Elevated YKL-40 levels were also detected in Alzheimer's disease (AD) but not in dementia with Lewy bodies (DLB). In AD, YKL-40-positive astrocytes were commonly found in clusters, often around β-amyloid plaques, and surrounding vessels with β-amyloid angiopathy; they were also distributed randomly in the cerebral cortex and white matter. YKL-40 overexpression appeared as a pre-clinical event as demonstrated in experimental models of prion diseases and AD pathology. CSF YKL-40 levels were measured in a cohort of 288 individuals, including neurological controls (NC) and patients diagnosed with different types of dementia. Compared to NC, increased YKL-40 levels were detected in sCJD (p < 0.001, AUC = 0.92) and AD (p < 0.001, AUC = 0.77) but not in vascular dementia (VaD) (p > 0.05, AUC = 0.71) or in DLB/Parkinson's disease dementia (PDD) (p > 0.05, AUC = 0.70). Further, two independent patient cohorts were used to validate the increased CSF YKL-40 levels in sCJD. Additionally, increased YKL-40 levels were found in genetic prion diseases associated with the PRNP-D178N (Fatal Familial Insomnia) and PRNP-E200K mutations.

CONCLUSIONS

Our results unequivocally demonstrate that in neurodegenerative dementias, YKL-40 is a disease-specific marker of neuroinflammation showing its highest levels in prion diseases. Therefore, YKL-40 quantification might have a potential for application in the evaluation of therapeutic intervention in dementias with a neuroinflammatory component.

Serum YKL-40, a prognostic marker in patients with large-artery atherosclerotic stroke

BACKGROUND AND PURPOSE

Inflammation comprises important aspects of large-artery atherosclerosis (LAA) stroke pathophysiology. YKL-40 is a new and emerging biomarker that is associated with both acute and chronic inflammations. Elevated serum concentrations of YKL-40 have been reported in patients with atherosclerosis and other cardiovascular diseases. This study investigates whether serum YKL-40 concentrations on admission can predict 3-month clinical outcomes after LAA stroke.

METHODS

We recruited control patients (n=85) and those with LAA stroke (n=141) according to the TOAST classification system. The modified Rankin scale at 3 months after stroke was used to evaluate the prognosis. The prognostic accuracy was assessed by the receiver operating characteristic curve.

RESULTS

Serum YKL-40 level was significantly higher for LAA patients than for controls (P<.001). Patients with poor outcomes (n=36) had significantly increased serum YKL-40 concentrations on admission (P=.01). High YKL-40 levels predicted poor functional outcome (OR=6.47, P=.02). Moreover, the combination of YKL-40 level and the NIHSS score could improve the prognostic accuracy of the NIHSS in predicting functional outcome (combined areas under the curve, 0.87; 95% CI, 0.80-0.94; P<.001).

CONCLUSIONS

The level of serum YKL-40 is a significant and independent biomarker to predict the clinical outcome of LAA stroke.

YKL-40 (Chitinase 3-like I) is expressed in a subset of astrocytes in Alzheimer's disease and other tauopathies

BACKGROUND

The innate immune system is known to be involved early in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative disorders. The inflammatory response in the central nervous system can be measured postmortem or through a series of inflammatory mediator surrogates. YKL-40 (also named Chitinase-3-like I) has been frequently investigated in body fluids as a surrogate marker of neuroinflammation in AD and other neurological disorders. However, the expression pattern of YKL-40 in the human brain with neurodegenerative pathology remains poorly investigated. Our aim was to study the cellular expression pattern of YKL-40 in the brain of patients with clinical and neuropathological criteria for AD (n = 11); three non-AD tauopathies: Pick's disease (PiD; n = 8), corticobasal degeneration (CBD; n = 8) and progressive supranuclear palsy (PSP; n = 9) and a group of neurologically healthy controls (n = 6).

METHODS

Semiquantitative neuropathological evaluation and quantitative confocal triple immunofluorescence studies were performed. An in-house algorithm was used to detect and quantify pathology burden of random regions of interest on a full tissue-section scan. Kruskal-Wallis and Dunn's multiple comparison tests were performed for colocalization and quantification analyses.

RESULTS

We found that brain YKL-40 immunoreactivity was observed in a subset of astrocytes in all four diseases and in controls. There was a strong colocalization between YKL-40 and the astroglial marker GFAP but not with neuronal nor microglial markers. Intriguingly, YKL-40-positive astrocytes were tau-negative in PSP, CBD and PiD. The number of YKL-40-positive astrocytes was increased in tauopathies compared with that in controls. A positive correlation was found between YKL-40 and tau immunoreactivities.

CONCLUSIONS

This study confirms that YKL-40 is expressed by a subset of astrocytes in AD and other tauopathies. YKL-40 expression is elevated in several neurodegenerative conditions and correlates with tau pathology.

Astroglial activation and altered amyloid metabolism in human repetitive concussion

OBJECTIVE

To determine whether postconcussion syndrome (PCS) due to repetitive concussive traumatic brain injury (rcTBI) is associated with CSF biomarker evidence of astroglial activation, amyloid deposition, and blood-brain barrier (BBB) impairment.

METHODS

A total of 47 participants (28 professional athletes with PCS and 19 controls) were assessed with lumbar puncture (median 1.5 years, range 0.25-12 years after last concussion), standard MRI of the brain, and Rivermead Post-Concussion Symptoms Questionnaire (RPQ). The main outcome measures were CSF concentrations of astroglial activation markers (glial fibrillary acidic protein [GFAP] and YKL-40), markers reflecting amyloid precursor protein metabolism (Aβ38, Aβ40, Aβ42, sAPPα, and sAPPβ), and BBB function (CSF:serum albumin ratio).

RESULTS

Nine of the 28 athletes returned to play within a year, while 19 had persistent PCS >1 year. Athletes with PCS >1 year had higher RPQ scores and number of concussions than athletes with PCS <1 year. Median concentrations of GFAP and YKL-40 were higher in athletes with PCS >1 year compared with controls, although with an overlap between the groups. YKL-40 correlated with RPQ score and the lifetime number of concussions. Athletes with rcTBI had lower concentrations of Aβ40 and Aβ42 than controls. The CSF:serum albumin ratio was unaltered.

CONCLUSIONS

This study suggests that PCS may be associated with biomarker evidence of astroglial activation and β-amyloid (Aβ) dysmetabolism in the brain. There was no clear evidence of Aβ deposition as Aβ40 and Aβ42 were reduced in parallel. The CSF:serum albumin ratio was unaltered, suggesting that the BBB is largely intact in PCS.

The far-reaching scope of neuroinflammation after traumatic brain injury

The 'silent epidemic' of traumatic brain injury (TBI) has been placed in the spotlight as a result of clinical investigations and popular press coverage of athletes and veterans with single or repetitive head injuries. Neuroinflammation can cause acute secondary injury after TBI, and has been linked to chronic neurodegenerative diseases; however, anti-inflammatory agents have failed to improve TBI outcomes in clinical trials. In this Review, we therefore propose a new framework of targeted immunomodulation after TBI for future exploration. Our framework incorporates factors such as the time from injury, mechanism of injury, and secondary insults in considering potential treatment options. Structuring our discussion around the dynamics of the immune response to TBI - from initial triggers to chronic neuroinflammation - we consider the ability of soluble and cellular inflammatory mediators to promote repair and regeneration versus secondary injury and neurodegeneration. We summarize both animal model and human studies, with clinical data explicitly defined throughout this Review. Recent advances in neuroimmunology and TBI-responsive neuroinflammation are incorporated, including concepts of inflammasomes, mechanisms of microglial polarization, and glymphatic clearance. Moreover, we highlight findings that could offer novel therapeutic targets for translational and clinical research, assimilate evidence from other brain injury models, and identify outstanding questions in the field.

Effect of carotid endarterectomy on brain damage markers

OBJECTIVES

Carotid endarterectomy (CEA) is a recommended treatment in the prevention of ischemic stroke. However, this procedure may cause neurological complications caused by cerebrovascular damage. While YKL-40 is a proinflammatory protein, neurofilament light polypeptide (NEFL) and brain lipid-binding protein (FABP7) are structural components of the brain. The aim of the study was to investigate YKL-40, NEFL, and FABP7 in the serum of patients undergoing CEA.

MATERIALS AND METHODS

The study included 25 participants who underwent CEA due to internal carotid artery stenosis. Blood samples were taken from each patient at three different intervals: prior to the surgery, 12 h after the surgery, and 48 h after the surgery. Serum levels of these brain damage markers were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The study showed that the serum YKL-40 level was significantly increased 48 h after CEA when compared to the level prior to surgery and also when compared to levels 12 h after surgery. There were no statistically significant differences in serum NEFL and FABP7 levels between all three recorded measurements.

CONCLUSIONS

Data from our study showed that CEA affects serum YKL-40 but not NEFL and FABP7 levels. This implicates that YKL-40 may be a valuable serum marker of brain damage after CEA. However, the observed change in serum YKL-40 level in patients after CEA does not necessarily warrant a change in recommendations concerning the use of this treatment in patients with high-grade internal carotid artery stenosis.

High serum YKL-40 level positively correlates with coronary artery disease

AIM

We investigated the predictive value of chitinase-like protein YKL-40 in coronary artery disease (CAD).

PATIENTS

Serum YKL-40 levels in 116 CAD patients and 82 healthy controls were analyzed. Severity of CAD was evaluated using Gensini scores. Spearman's correlation was used to evaluate the correlation between Gensini scores and YKL-40 levels. The predictive value of YKL-40 was determined by receivers operating characteristic curve analysis.

RESULTS

Serum YKL-40 levels were significantly elevated in CAD group as compared with control group. A positive correlation was found between the serum YKL-40 level and Gensini score. The optimum cut-off value of YKL-40 concentration was 127.7 ng/ml for distinguishing CAD patients from healthy controls with a 75.9% sensitivity and 57.3% specificity.

CONCLUSION

A positive correlation exists between YKL-40 levels and CAD, and YKL-40 might be a useful adjunct in the diagnosis of CAD.

Immediate initiation of cART is associated with lower levels of cerebrospinal fluid YKL-40, a marker of microglial activation, in HIV-1 infection

OBJECTIVE

To characterize cerebrospinal fluid (CSF) YKL-40, a unique biomarker that reflects activation of microglial cells, in acute (AHI) and chronic HIV-1 infection (CHI) and to determine the effect of treatment initiation on levels of this marker.

DESIGN

A cross-sectional study of two groups of HIV-infected participants at baseline and follow-up timepoints.

METHODS

AHI (n = 33) and CHI (n = 34) participants underwent CSF and blood sampling before treatment initiation with combination antiretroviral therapy (cART) and at follow-up on cART in a subset of these individuals [6 months in AHI participants (n = 24), 1 year in CHI participants (n = 10)]. Measured parameters were analyzed at each timepoint. Analyses employed Mann-Whitney tests and Spearman correlations.

RESULTS

Baseline median YKL-40 was higher in CHI than AHI (96844 versus 80754 ng/l; P = 0.011). Elevations in the CHI group relative to the AHI group persisted at follow-up despite treatment (87414 versus 66130 ng/l; P = 0.003). In untreated CHI, YKL-40 correlated with neopterin (r = 0.51, P = 0.0025), chemokine (CXC-motif) ligand-10 (r = 0.44, P = 0.011), and neurofilament light chain (r = 0.56, P = 0.0008) in CSF.

CONCLUSIONS

This study is the first to describe the dynamics of CSF YKL-40 in two groups of HIV-infected individuals before and after cART and demonstrates the value of this marker in understanding HIV neuropathogenesis. The results suggest the utility of further exploring the prognostic value of YKL-40, particularly in individuals with early HIV infection or those initiating treatment during CHI.

The Involvement of Pial Microvessels in Leukocyte Invasion after Mild Traumatic Brain Injury

The pathophysiological mechanisms underlying mild traumatic brain injury (mTBI) are not well understood, but likely involve neuroinflammation. Here the controlled cortical impact model of mTBI in rats was used to test this hypothesis. Mild TBI caused a rapid (within 6 h post-mTBI) upregulation of synthesis of TNF-α and IL-1β in the cerebral cortex and hippocampus, followed by an increase in production of neutrophil (CXCL1-3) and monocyte (CCL2) chemoattractants. While astrocytes were not a significant source of CXC chemokines, they highly expressed CCL2. An increase in production of CXC chemokines coincided with the influx of neutrophils into the injured brain. At 6 h post-mTBI, we observed a robust influx of CCL2-expressing neutrophils across pial microvessels into the subarachnoid space (SAS) near the injury site. Mild TBI was not accompanied by any significant influx of neutrophils into the brain parenchyma until 24 h after injury. This was associated with an early induction of expression of intercellular adhesion molecule 1 on the endothelium of the ipsilateral pial, but not intraparenchymal, microvessels. At 6 h post-mTBI, we also observed a robust influx of neutrophils into the ipsilateral cistern of velum interpositum (CVI), a slit-shaped cerebrospinal fluid space located above the 3rd ventricle with highly vascularized pia mater. From SAS and CVI, neutrophils appeared to move along the perivascular spaces to enter the brain parenchyma. The monocyte influx was not observed until 24 h post-mTBI, and these inflammatory cells predominantly entered the ipsilateral SAS and CVI, with a limited invasion of brain parenchyma. These observations indicate that the endothelium of pial microvessels responds to injury differently than that of intraparenchymal microvessels, which may be associated with the lack of astrocytic ensheathment of cerebrovascular endothelium in pial microvessels. These findings also suggest that neuroinflammation represents the potential therapeutic target in mTBI.

Cerebrospinal Fluid Biomarkers of Simian Immunodeficiency Virus Encephalitis : CSF Biomarkers of SIV Encephalitis

Antiretroviral therapy has led to increased survival of HIV-infected patients but also increased prevalence of HIV-associated neurocognitive disorders. We previously identified YKL40 as a potential cerebrospinal fluid (CSF) biomarker of lentiviral central nervous system (CNS) disease in HIV-infected patients and in the macaque model of HIV encephalitis. The aim of this study was to define the specificity and sensitivity along with the predictive value of YKL40 as a biomarker of encephalitis and to assess its relationship to CSF viral load. CSF YKL40 and SIV RNA concentrations were analyzed over the course of infection in 19 SIV-infected pigtailed macaques and statistical analyses were performed to evaluate the relationship to encephalitis. Using these relationships, CSF alterations of 31 neuroimmune markers were studied pre-infection, during acute and asymptomatic infection, at the onset of encephalitis, and at necropsy. YKL40 CSF concentrations above 1122 ng/ml were found to be a specific and sensitive biomarker for the presence of encephalitis and were highly correlated with CSF viral load. Macaques that developed encephalitis had evidence of chronic CNS immune activation during early, asymptomatic, and end stages of infection. At the onset of encephalitis, CSF demonstrated a rise of neuroimmune markers associated with macrophage recruitment, activation and interferon response. CSF YKL40 concentration and viral load are valuable biomarkers to define the onset of encephalitis. Chronic CNS immune activation precedes the development of encephalitis while some responses suggest protection from CNS lentiviral disease.

Longitudinal Measurements of Cerebrospinal Fluid Biomarkers in Parkinson's Disease

OBJECTIVE

The purpose of this study was to investigate whether cerebrospinal fluid (CSF) levels of tau, phosphorylated tau, β-amyloid42 , α-synuclein, neurofilament light, and YKL-40 change over time and if changes correlate with motor progression and/or cognitive decline in patients with PD and controls.

METHODS

We included 63 patients with PD (nondemented) and 21 neurologically healthy controls from the prospective and longitudinal Swedish BioFINDER study, all of whom had clinical assessments and lumbar punctures at baseline and after 2 years.

RESULTS

CSF tau levels correlated strongly with α-synuclein. The levels of CSF α-synuclein, tau, phosphorylated tau, neurofilament light, and YKL-40, but not β-amyloid42 , increased in CSF over 2 years in PD. No changes were seen in the control group. Studying patients with a short disease duration ( ≤ 5 years) and patients with a long disease duration ( > 5 years) separately, α-synuclein and tau only increased in the PD group with long disease duration. In the PD group, an increase in phosphorylated tau over 2 years correlated with faster motor progression and faster cognitive decline. An increase in YKL-40 over 2 years correlated with faster cognitive decline.

CONCLUSION

CSF biomarkers reflecting Lewy body pathology and neurodegeneration (α-synuclein), neuronal degeneration (tau, phosphorylated tau, and neurofilament light), and inflammation (YKL-40) increase significantly over 2 years in PD. CSF levels of α-synuclein and tau correlate and remain stable in the early symptomatic phase of PD but increase in the later phase. We hypothesize that CSF α-synuclein levels might increase as a result of more intense neurodegeneration in PD with long disease duration. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Ultrastructure of Diaschisis Lesions after Traumatic Brain Injury

We used controlled cortical impact in mice to model human traumatic brain injury (TBI). Local injury was accompanied by distal diaschisis lesions that developed within brain regions anatomically connected to the injured cortex. At 7 days after injury, histochemistry documented broadly distributed lesions, particularly in the contralateral cortex and ipsilateral thalamus and striatum. Reactive astrocytosis and microgliosis were noted in multiple neural pathways that also showed silver-stained cell processes and bodies. Wisteria floribunda agglutinin (WFA) staining, a marker of perineuronal nets, was substantially diminished in the ipsilateral, but less so in the contralateral cortex. Contralateral cortical silver positive diaschisis lesions showed loss of both phosphorylated and unphosphorylated neurofilament staining, but overall preservation of microtubule-associated protein (MAP)-2 staining. Thalamic lesions showed substantial loss of MAP-2 and unphosphorylated neurofilaments in addition to moderate loss of phosphorylated neurofilament. One animal demonstrated contralateral cerebellar degeneration at 7 days post-injury. After 21 days, the gliosis had quelled, however persistent silver staining was noted. Using a novel serial section technique, we were able to perform electron microscopy on regions fully characterized at the light microscopy level. Cell bodies and processes that were silver positive at the light microscopy level showed hydropic disintegration consisting of: loss of nuclear heterochromatin; dilated somal and neuritic processes with a paucity of filaments, tubules, and mitochondria; and increased numbers of electron-dense membranous structures. Importantly the cell membrane itself was still intact 3 weeks after injury. Although the full biochemical nature of these lesions remains to be deciphered, the morphological preservation of damaged neurons and processes raises the question of whether this is a reversible process.

Characterisation of the mantle transcriptome and biomineralisation genes in the blunt-gaper clam, Mya truncata

Members of the Myidae family are ecologically and economically important, but there is currently very little molecular data on these species. The present study sequenced and assembled the mantle transcriptome of Mya truncata from the North West coast of Scotland and identified candidate biomineralisation genes. RNA-Seq reads were assembled to create 20,106 contigs in a de novo transciptome, 18.81% of which were assigned putative functions using BLAST sequence similarity searching (cuttoff E-value 1E-10). The most highly expressed genes were compared to the Antarctic clam (Laternula elliptica) and showed that many of the dominant biological functions (muscle contraction, energy production, biomineralisation) in the mantle were conserved. There were however, differences in the constitutive expression of heat shock proteins, which were possibly due to the M. truncata sampling location being at a relatively low latitude, and hence relatively warm, in terms of the global distribution of the species. Phylogenetic analyses of the Tyrosinase proteins from M. truncata showed a gene expansion which was absent in L. elliptica. The tissue distribution expression patterns of putative biomineralisation genes were investigated using quantitative PCR, all genes showed a mantle specific expression pattern supporting their hypothesised role in shell secretion. The present study provides some preliminary insights into how clams from different environments - temperate versus polar - build their shells. In addition, the transcriptome data provides a valuable resource for future comparative studies investigating biomineralisation.

Cerebrospinal fluid neurogranin and YKL-40 as biomarkers of Alzheimer's disease

Objective

Widespread implementation of cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) in clinical settings requires improved accuracy for diagnosis of prodromal disease and for distinguishing AD from non‐AD dementias. Novel and promising CSF biomarkers include neurogranin, a marker of synaptic degeneration, and YKL‐40, a marker of neuroinflammation.

Methods

CSF neurogranin and YKL‐40 were measured in a cohort of 338 individuals including cognitively healthy controls and patients with stable mild cognitive impairment (sMCI), MCI who later developed AD (MCI‐AD), AD dementia, Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), vascular dementia (VaD), and frontotemporal dementia (FTD). The diagnostic accuracy of neurogranin and YKL‐40 were compared with the core AD biomarkers, β‐amyloid (Aβ42 and Aβ40) and tau.

Results

Neurogranin levels were increased in AD and decreased in non‐AD dementia compared with healthy controls. As a result, AD patients showed considerably higher CSF levels of neurogranin than DLB/PDD, VaD and FTD patients. CSF YKL‐40 levels were increased in AD compared with DLB/PDD but not with VaD or FTD. Neither CSF neurogranin nor YKL‐40 levels differed significantly between sMCI patients and MCI‐AD patients. Both biomarkers correlated positively with CSF Aβ40 and tau. CSF neurogranin and YKL‐40 could separate AD dementia from non‐AD dementias (neurogranin, area under the curve [AUC] = 0.761; YKL‐40, AUC = 0.604; Aβ42/neurogranin, AUC = 0.849; Aβ42/YKL‐40, AUC = 0.785), but the diagnostic accuracy was not better compared to CSF Aβ and tau (Aβ42, AUC = 0.755; tau AUC = 0.858; Aβ42/tau, AUC = 0.895; Aβ42/Aβ40, AUC = 0.881). Similar results were obtained when separating sMCI from MCI‐AD cases.

Interpretation

CSF neurogranin and YKL‐40 do not improve the diagnostic accuracy of either prodromal AD or AD dementia when compared to the core CSF AD biomarkers. Nevertheless, the CSF level of neurogranin is selectively increased in AD dementia, whereas YKL‐40 is increased in both AD and FTD suggesting that synaptic degeneration and glial activation may be important in these neurodegenerative conditions.