CCL11 is increased in the CNS in chronic traumatic encephalopathy but not in Alzheimer's disease

Diagnostic markers of acute encephalitis syndrome and COVID-associated multisystem inflammatory syndrome in children from Southern India

Acute encephalitis syndrome (AES) in children poses a significant public health challenge in India. This study aims to explore the utility of host inflammatory mediators and neurofilament (NfL) levels in distinguishing etiologies, assessing disease severity, and predicting outcomes in AES. We assessed 12 mediators in serum (n = 58) and 11 in cerebrospinal fluid (CSF) (n = 42) from 62 children with AES due to scrub typhus, viral etiologies, and COVID-associated multisystem inflammatory syndrome (MIS-C) in Southern India. Additionally, NfL levels in serum (n = 20) and CSF (n = 18) were examined. Clinical data, including Glasgow coma scale (GCS) and Liverpool outcome scores, were recorded. Examining serum and CSF markers in the three AES etiology groups revealed notable distinctions, with scrub typhus differing significantly from viral and MIS-C causes. Viral causes had elevated serum CCL11 and CCL2 compared with scrub typhus, while MIS-C cases showed higher HGF levels than scrub typhus. However, CSF analysis showed a distinct pattern with the scrub typhus group exhibiting elevated levels of IL-1RA, IL-1β, and TNF compared with MIS-C, and lower CCL2 levels compared with the viral group. Modeling the characteristic features, we identified that age ≥3 years with serum CCL11 < 180 pg/mL effectively distinguished scrub typhus from other AES causes. Elevated serum CCL11, HGF, and IL-6:IL-10 ratio were associated with poor outcomes (p = 0.038, 0.005, 0.02). Positive CSF and serum NfL correlation, and negative GCS and serum NfL correlation were observed. Median NfL levels were higher in children with abnormal admission GCS and poor outcomes. Measuring immune mediators and brain injury markers in AES provides valuable diagnostic insights, with the potential to facilitate rapid diagnosis and prognosis. The correlation between CSF and serum NfL, along with distinctive serum cytokine profiles across various etiologies, indicates the adequacy of blood samples alone for assessment and monitoring. The association of elevated levels of CCL11, HGF, and an increased IL-6:IL-10 ratio with adverse outcomes suggests promising avenues for therapeutic exploration, warranting further investigation.

Chronic Traumatic Encephalopathy as the Course of Alzheimer's Disease

This editorial investigates chronic traumatic encephalopathy (CTE) as a course of Alzheimer's disease (AD). CTE is a debilitating neurodegenerative disease that is the result of repeated mild traumatic brain injury (TBI). Many epidemiological studies show that experiencing a TBI in early or middle life is associated with an increased risk of dementia later in life. Chronic traumatic encephalopathy (CTE) and Alzheimer's disease (AD) present a series of similar neuropathological features that were investigated in this work like recombinant tau into filaments or the accumulation and aggregation of Aβ protein. However, these two conditions differ from each other in brain-blood barrier damage. The purpose of this review was to evaluate information about CTE and AD from various articles, focusing especially on new therapeutic possibilities for the improvement in cognitive skills.

Longitudinal cytokine and multi-modal health data of an extremely severe ME/CFS patient with HSD reveals insights into immunopathology, and disease severity

Introduction

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) presents substantial challenges in patient care due to its intricate multisystem nature, comorbidities, and global prevalence. The heterogeneity among patient populations, coupled with the absence of FDA-approved diagnostics and therapeutics, further complicates research into disease etiology and patient managment. Integrating longitudinal multi-omics data with clinical, health,textual, pharmaceutical, and nutraceutical data offers a promising avenue to address these complexities, aiding in the identification of underlying causes and providing insights into effective therapeutics and diagnostic strategies.

Methods

This study focused on an exceptionally severe ME/CFS patient with hypermobility spectrum disorder (HSD) during a period of marginal symptom improvements. Longitudinal cytokine profiling was conducted alongside the collection of extensive multi-modal health data to explore the dynamic nature of symptoms, severity, triggers, and modifying factors. Additionally, an updated severity assessment platform and two applications, ME-CFSTrackerApp and LexiTime, were introduced to facilitate real-time symptom tracking and enhance patient-physician/researcher communication, and evaluate response to medical intervention.

Results

Longitudinal cytokine profiling revealed the significance of Th2-type cytokines and highlighted synergistic activities between mast cells and eosinophils, skewing Th1 toward Th2 immune responses in ME/CFS pathogenesis, particularly in cognitive impairment and sensorial intolerance. This suggests a potentially shared underlying mechanism with major ME/CFS comorbidities such as HSD, Mast cell activation syndrome, postural orthostatic tachycardia syndrome (POTS), and small fiber neuropathy. Additionally, the data identified potential roles of BCL6 and TP53 pathways in ME/CFS etiology and emphasized the importance of investigating adverse reactions to medication and supplements and drug interactions in ME/CFS severity and progression.

Discussion

Our study advocates for the integration of longitudinal multi-omics with multi-modal health data and artificial intelligence (AI) techniques to better understand ME/CFS and its major comorbidities. These findings highlight the significance of dysregulated Th2-type cytokines in patient stratification and precision medicine strategies. Additionally, our results suggest exploring the use of low-dose drugs with partial agonist activity as a potential avenue for ME/CFS treatment. This comprehensive approach emphasizes the importance of adopting a patient-centered care approach to improve ME/CFS healthcare management, disease severity assessment, and personalized medicine. Overall, these findings contribute to our understanding of ME/CFS and offer avenues for future research and clinical practice.

Role of Microglia, Decreased Neurogenesis and Oligodendrocyte Depletion in Long COVID-Mediated Brain Impairments

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of a recent worldwide coronavirus disease-2019 (COVID-19) pandemic. SARS-CoV-2 primarily causes an acute respiratory infection but can progress into significant neurological complications in some. Moreover, patients with severe acute COVID-19 could develop debilitating long-term sequela. Long-COVID is characterized by chronic symptoms that persist months after the initial infection. Common complaints are fatigue, myalgias, depression, anxiety, and "brain fog," or cognitive and memory impairments. A recent study demonstrated that a mild COVID-19 respiratory infection could generate elevated proinflammatory cytokines and chemokines in the cerebral spinal fluid. This commentary discusses findings from this study, demonstrating that even a mild respiratory SARS-CoV-2 infection can cause considerable neuroinflammation with microglial and macrophage reactivity. Such changes could also be gleaned by measuring chemokines and cytokines in the circulating blood. Moreover, neuroinflammation caused by mild SARS-CoV-2 infection can also impair hippocampal neurogenesis, deplete oligodendrocytes, and decrease myelinated axons. All these changes likely contribute to cognitive deficits in long-COVID syndrome. Therefore, strategies capable of restraining neuroinflammation, maintaining better hippocampal neurogenesis, and preserving oligodendrocyte lineage differentiation and maturation may prevent or reduce the incidence of long-COVID after SARS-CoV-2 respiratory infection.

Levels of inflammatory cytokines MCP-1, CCL4, and PD-L1 in CSF differentiate idiopathic normal pressure hydrocephalus from neurodegenerative diseases

BACKGROUND

Neuroinflammatory processes have been suggested to play a role in the pathophysiology of neurodegenerative diseases and post-hemorrhagic hydrocephalus, but have rarely been investigated in patients with idiopathic normal pressure hydrocephalus (iNPH). The aim of this study was to investigate whether levels of inflammatory proteins in CSF are different in iNPH compared to healthy controls and patients with selected neurodegenerative disorders, and whether any of these markers can aid in the differential diagnosis of iNPH.

METHODS

Lumbar CSF was collected from 172 patients from a single center and represented iNPH (n = 74), Alzheimer's disease (AD) (n = 21), mild cognitive impairment (MCI) due to AD (n = 21), stable MCI (n = 22), frontotemporal dementia (n = 13), and healthy controls (HC) (n = 21). Levels of 92 inflammatory proteins were analyzed using a proximity extension assay. As a first step, differences between iNPH and HC were investigated, and proteins that differed between iNPH and HC were then compared with those from the other groups. The linear regressions were adjusted for age, sex, and plate number.

RESULTS

Three proteins showed higher (MCP-1, p = 0.0013; CCL4, p = 0.0008; CCL11, p = 0.0022) and one lower (PD-L1, p = 0.0051) levels in patients with iNPH compared to HC. MCP-1 was then found to be higher in iNPH than in all other groups. CCL4 was higher in iNPH than in all other groups, except in MCI due to AD. PD-L1 was lower in iNPH compared to all other groups, except in stable MCI. Levels of CCL11 did not differ between iNPH and the differential diagnoses. In a model based on the four proteins mentioned above, the mean area under the receiver operating characteristic curve used to discriminate between iNPH and the other disorders was 0.91.

CONCLUSIONS

The inflammatory cytokines MCP-1 and CCL4 are present at higher-and PD-L1 at lower-levels in iNPH than in the other investigated diagnoses. These three selected cytokines may have diagnostic potential in the work-up of patients with iNPH.

Repetitive mild traumatic brain injury-induced neurodegeneration and inflammation is attenuated by acetyl-L-carnitine in a preclinical model

Repetitive mild traumatic brain injuries (rmTBI) may contribute to the development of neurodegenerative diseases through secondary injury pathways. Acetyl-L-carnitine (ALC) shows neuroprotection through anti-inflammatory effects and via regulation of neuronal synaptic plasticity by counteracting post-trauma excitotoxicity. This study aimed to investigate mechanisms implicated in the etiology of neurodegeneration in rmTBI mice treated with ALC. Adult male C57BL/6J mice were allocated to sham, rmTBI or ALC + rmTBI groups. 15 rmTBIs were administered across 23 days using a modified weight drop model. Neurological testing and spatial learning and memory assessments via the Morris Water Maze (MWM) were undertaken at 48 h and 3 months. RT-PCR analysis of the cortex and hippocampus was undertaken for MAPT, GFAP, AIF1, GRIA, CCL11, TDP43, and TNF genes. Gene expression in the cortex showed elevated mRNA levels of MAPT, TNF, and GFAP in the rmTBI group that were reduced by ALC treatment. In the hippocampus, mRNA expression was elevated for GRIA1 in the rmTBI group but not the ALC + rmTBI treatment group. ALC treatment showed protective effects against the deficits displayed in neurological testing and MWM assessment observed in the rmTBI group. While brain structures display differential vulnerability to insult as evidenced by location specific postimpact disruption of key genes, this study shows correlative mRNA neurodegeneration and functional impairment that was ameliorated by ALC treatment in several key genes. ALC may mitigate damage inflicted in the various secondary neurodegenerative cascades and contribute to functional protection following rmTBI.

Transcriptomic Analyses of Neurotoxic Astrocytes Derived from Adult Triple Transgenic Alzheimer's Disease Mice

Neurodegenerative diseases such as Alzheimer's disease have been classically studied from a purely neuronocentric point of view. More recent evidences support the notion that other cell populations are involved in disease progression. In this sense, the possible pathogenic role of glial cells like astrocytes is increasingly being recognized. Once faced with tissue damage signals and other stimuli present in disease environments, astrocytes suffer many morphological and functional changes, a process referred as reactive astrogliosis. Studies from murine models and humans suggest that these complex and heterogeneous responses could manifest as disease-specific astrocyte phenotypes. Clear understanding of disease-associated astrocytes is a necessary step to fully disclose neurodegenerative processes, aiding in the design of new therapeutic and diagnostic strategies. In this work, we present the transcriptomics characterization of neurotoxic astrocytic cultures isolated from adult symptomatic animals of the triple transgenic mouse model of Alzheimer's disease (3xTg-AD). According to the observed profile, 3xTg-AD neurotoxic astrocytes show various reactivity features including alteration of the extracellular matrix and release of pro-inflammatory and proliferative factors that could result in harmful effects to neurons. Moreover, these alterations could be a consequence of stress responses at the endoplasmic reticulum and mitochondria as well as of concomitant metabolic adaptations. Present results support the hypothesis that adaptive changes of astrocytic function induced by a stressed microenvironment could later promote harmful astrocyte phenotypes and further accelerate or induce neurodegenerative processes.

Three dimensional evaluation of cerebrovascular density and branching in chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts (RHI) and characterized by perivascular accumulations of hyperphosphorylated tau protein (p-tau) at the depths of the cortical sulci. Studies of living athletes exposed to RHI, including concussive and nonconcussive impacts, have shown increased blood-brain barrier permeability, reduced cerebral blood flow, and alterations in vasoreactivity. Blood-brain barrier abnormalities have also been reported in individuals neuropathologically diagnosed with CTE. To further investigate the three-dimensional microvascular changes in individuals diagnosed with CTE and controls, we used SHIELD tissue processing and passive delipidation to optically clear and label blocks of postmortem human dorsolateral frontal cortex. We used fluorescent confocal microscopy to quantitate vascular branch density and fraction volume. We compared the findings in 41 male brain donors, age at death 31-89 years, mean age 64 years, including 12 donors with low CTE (McKee stage I-II), 13 with high CTE (McKee stage III-IV) to 16 age- and sex-matched non-CTE controls (7 with RHI exposure and 9 with no RHI exposure). The density of vessel branches in the gray matter sulcus was significantly greater in CTE cases than in controls. The ratios of sulcus versus gyrus vessel branch density and fraction volume were also greater in CTE than in controls and significantly above one for the CTE group. Hyperphosphorylated tau pathology density correlated with gray matter sulcus fraction volume. These findings point towards increased vascular coverage and branching in the dorsolateral frontal cortex (DLF) sulci in CTE, that correlates with p-tau pathology.

Vitreous Humor Biomarkers Reflect Pathological Changes in the Brain for Alzheimer's Disease and Chronic Traumatic Encephalopathy

BACKGROUND

Patients with eye disease have an increased risk for developing neurodegenerative disease. Neurodegenerative proteins can be measured in the eye; however, correlations between biomarker levels in eye fluid and neuropathological diagnoses have not been established.

OBJECTIVE

This exploratory, retrospective study examined vitreous humor from 41 postmortem eyes and brain tissue with neuropathological diagnoses of Alzheimer's disease (AD, n = 7), chronic traumatic encephalopathy (CTE, n = 15), both AD + CTE (n = 10), and without significant neuropathology (controls, n = 9).

METHODS

Protein biomarkers i.e., amyloid-β (Aβ 40,42), total tau (tTau), phosphorylated tau (pTau181,231), neurofilament light chain (NfL), and eotaxin-1 were quantitatively measured by immunoassay. Non-parametric tests were used to compare vitreous biomarker levels between groups. Spearman's rank correlation tests were used to correlate biomarker levels in vitreous and cortical tissue. The level of significance was set to α= 0.10.

RESULTS

In pairwise comparisons, tTau levels were significantly increased in AD and CTE groups versus controls (p = 0.08 for both) as well as AD versus AD+CTE group and CTE versus AD+CTE group (p = 0.049 for both). Vitreous NfL levels were significantly increased in low CTE (Stage I/II) versus no CTE (p = 0.096) and in low CTE versus high CTE stage (p = 0.03). Vitreous and cortical tissue levels of pTau 231 (p = 0.02, r = 0.38) and t-Tau (p = 0.04, r = -0.34) were significantly correlated.

CONCLUSION

The postmortem vitreous humor biomarker levels significantly correlate with AD and CTE pathology in corresponding brains, while vitreous NfL was correlated with the CTE staging. This exploratory study indicates that biomarkers in the vitreous humor may serve as a proxy for neuropathological disease.

Dysregulation of miR-155 Expression in Professional Mixed Martial Arts (MMA) Fighters

Psychological and physical stress can induce dysregulation of gene expression via changes in DNA methylation and microRNA (miRNA) expression. Such epigenetic modifications are yet to be investigated in professional Mixed Martial Arts (MMA) fighters subject to highly stressful training involving repetitive head impacts. This study examined differences in DNA methylation and miRNA expression in elite MMA fighters compared to active controls. Global methylation differences between groups were assessed via a LINE-1 assay. At the same time, PCR arrays were used to estimate differential expression in samples of 21 fighters and 15 controls for 192 different miRNAs associated with inflammatory diseases. An Independent-Samples t-Test found no significant difference in LINE-1 methylation between groups. However, an Independent-Samples Mann-Whitney U Test revealed a significant upregulation in the expression of miR-155 in MMA fighter plasma. Since miR-155 has been recognized as an important regulator of neuroinflammation, this dysregulation suggests a possible epigenetic mechanism responsible for chronic inflammation associated with professional-level MMA training. Consistent with other published works, this study highlights the potential of miR-155 not only as a biomarker for monitoring long-term health risks linked to head trauma but also as a target to remediate the impact of chronic neuroinflammation.

Chronic traumatic encephalopathy: Diagnostic updates and advances

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

Neuroimmune proteins can differentiate between tauopathies

BACKGROUND

Tauopathies are a group of neurodegenerative diseases where there is pathologic accumulation of hyperphosphorylated tau protein (ptau). The most common tauopathy is Alzheimer's disease (AD), but chronic traumatic encephalopathy (CTE), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and argyrophilic grain disease (AGD) are significant health risks as well. Currently, it is unclear what specific molecular factors might drive each distinct disease and represent therapeutic targets. Additionally, there is a lack of biomarkers that can differentiate each disease in life. Recent work has suggested that neuroinflammatory changes might be specific among distinct diseases and offers a novel resource for mechanistic targets and biomarker candidates.

METHODS

To better examine each tauopathy, a 71 immune-related protein multiplex ELISA panel was utilized to analyze anterior cingulate grey matter from 127 individuals neuropathologically diagnosed with AD, CTE, PSP, CBD, and AGD. A partial least square regression analysis was carried out to perform unbiased clustering and identify proteins that are distinctly correlated with each tauopathy correcting for age and gender. Receiver operator characteristic and binary logistic regression analyses were then used to examine the ability of each candidate protein to distinguish diseases. Validation in postmortem cerebrospinal fluid (CSF) from 15 AD and 14 CTE cases was performed to determine if candidate proteins could act as possible novel biomarkers.

RESULTS

Five clusters of immune proteins were identified and compared to each tauopathy to determine if clusters were specific to distinct disease. Each cluster was found to correlate with either CTE, AD, PSP, CBD, or AGD. When examining which proteins were the strongest driver of each cluster, it was observed the most distinctive protein for CTE was CCL21, AD was FLT3L, and PSP was IL13. Individual proteins that were specific to CBD and AGD were not observed. CCL21 was observed to be elevated in CTE CSF compared to AD cases (p = 0.02), further validating the use as possible biomarkers. Sub-analyses for male only cases confirmed the results were not skewed by gender differences.

CONCLUSIONS

Overall, these results highlight that different neuroinflammatory responses might underlie unique mechanisms in related neurodegenerative pathologies. Additionally, the use of distinct neuroinflammatory signatures could help differentiate between tauopathies and act as novel biomarker candidate to increase specificity for in-life diagnoses.

Traumatic Brain Injury Biomarkers, Simulations and Kinetics

This paper reviews the predictive capabilities of blood-based biomarkers to quantify traumatic brain injury (TBI). Biomarkers for concussive conditions also known as mild, to moderate and severe TBI identified along with post-traumatic stress disorder (PTSD) and chronic traumatic encephalopathy (CTE) that occur due to repeated blows to the head during one's lifetime. Since the pathways of these biomarkers into the blood are not fully understood whether there is disruption in the blood-brain barrier (BBB) and the time it takes after injury for the expression of the biomarkers to be able to predict the injury effectively, there is a need to understand the protein biomarker structure and other physical properties. The injury events in terms of brain and mechanics are a result of external force with or without the shrapnel, in the wake of a wave result in local tissue damage. Thus, these mechanisms express specific biomarkers kinetics of which reaches half-life within a few hours after injury to few days. Therefore, there is a need to determine the concentration levels that follow injury. Even though current diagnostics linking biomarkers with TBI severity are not fully developed, there is a need to quantify protein structures and their viability after injury. This research was conducted to fully understand the structures of 12 biomarkers by performing molecular dynamics simulations involving atomic movement and energies of forming hydrogen bonds. Molecular dynamics software, NAMD and VMD were used to determine and compare the approximate thermodynamic stabilities of the biomarkers and their bonding energies. Five biomarkers used clinically were S100B, GFAP, UCHL1, NF-L and tau, the kinetics obtained from literature show that the concentration values abruptly change with time after injury. For a given protein length, associated number of hydrogen bonds and bond energy describe a lower bound region where proteins self-dissolve and do not have long enough half-life to be detected in the fluids. However, above this lower bound, involving higher number of bonds and energy, we hypothesize that biomarkers will be viable to disrupt the BBB and stay longer to be modeled for kinetics for diagnosis and therefore may help in the discoveries of new biomarkers.

Evaluating immune response and metabolic related biomarkers pre-allogenic hematopoietic stem cell transplant in acute myeloid leukemia

Although hematopoietic stem cell transplantation (HCT) is the only curative treatment for acute myeloid leukemia (AML), it is associated with significant treatment related morbidity and mortality. There is great need for predictive biomarkers associated with overall survival (OS) and clinical outcomes. We hypothesized that circulating metabolic, inflammatory, and immune molecules have potential as predictive biomarkers for AML patients who receive HCT treatment. This retrospective study was designed with an exploratory approach to comprehensively characterize immune, inflammatory, and metabolomic biomarkers. We identified patients with AML who underwent HCT and had existing baseline plasma samples. Using those samples (n = 34), we studied 65 blood based metabolomic and 61 immune/inflammatory related biomarkers, comparing patients with either long-term OS (≥ 3 years) or short-term OS (OS ≤ 1 years). We also compared the immune/inflammatory response and metabolomic biomarkers in younger vs. older AML patients (≤30 years vs. ≥ 55 years old). In addition, the biomarker profiles were analyzed for their association with clinical outcomes, namely OS, chronic graft versus host disease (cGVHD), acute graft versus host disease (aGVHD), infection and relapse. Several baseline biomarkers were elevated in older versus younger patients, and baseline levels were lower for three markers (IL13, SAA, CRP) in patients with OS ≥ 3 years. We also identified immune/inflammatory response markers associated with aGVHD (IL-9, Eotaxin-3), cGVHD (Flt-1), infection (D-dimer), or relapse (IL-17D, bFGF, Eotaxin-3). Evaluation of metabolic markers demonstrated higher baseline levels of medium- and long-chain acylcarnitines (AC) in older patients, association with aGVHD (lactate, long-chain AC), and cGVHD (medium-chain AC). These differentially expressed profiles merit further evaluation as predictive biomarkers.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain

BACKGROUND

Altered intestinal microbiota composition in later life is associated with inflammaging, declining tissue function, and increased susceptibility to age-associated chronic diseases, including neurodegenerative dementias. Here, we tested the hypothesis that manipulating the intestinal microbiota influences the development of major comorbidities associated with aging and, in particular, inflammation affecting the brain and retina.

METHODS

Using fecal microbiota transplantation, we exchanged the intestinal microbiota of young (3 months), old (18 months), and aged (24 months) mice. Whole metagenomic shotgun sequencing and metabolomics were used to develop a custom analysis workflow, to analyze the changes in gut microbiota composition and metabolic potential. Effects of age and microbiota transfer on the gut barrier, retina, and brain were assessed using protein assays, immunohistology, and behavioral testing.

RESULTS

We show that microbiota composition profiles and key species enriched in young or aged mice are successfully transferred by FMT between young and aged mice and that FMT modulates resulting metabolic pathway profiles. The transfer of aged donor microbiota into young mice accelerates age-associated central nervous system (CNS) inflammation, retinal inflammation, and cytokine signaling and promotes loss of key functional protein in the eye, effects which are coincident with increased intestinal barrier permeability. Conversely, these detrimental effects can be reversed by the transfer of young donor microbiota.

CONCLUSIONS

These findings demonstrate that the aging gut microbiota drives detrimental changes in the gut-brain and gut-retina axes suggesting that microbial modulation may be of therapeutic benefit in preventing inflammation-related tissue decline in later life. Video abstract.

Reduced ccl11/eotaxin mediates the beneficial effects of environmental stimulation on the aged hippocampus

A deterioration in cognitive performance accompanies brain aging, even in the absence of neurodegenerative pathologies. However, the rate of cognitive decline can be slowed down by enhanced cognitive and sensorimotor stimulation protocols, such as environmental enrichment (EE). Understanding how EE exerts its beneficial effects on the aged brain pathophysiology can help in identifying new therapeutic targets. In this regard, the inflammatory chemokine ccl11/eotaxin-1 is a marker of aging with a strong relevance for neurodegenerative processes. Here, we demonstrate that EE in both elderly humans and aged mice decreases circulating levels of ccl11. Interfering, in mice, with the ccl11 decrease induced by EE ablated the beneficial effects on long-term memory retention, hippocampal neurogenesis, activation of local microglia and of ribosomal protein S6. On the other hand, treatment of standard-reared aged mice with an anti-ccl11 antibody resulted in EE-like improvements in spatial memory, hippocampal neurogenesis, and microglial activation. Taken together, our findings point to a decrease in circulating ccl11 concentration as a key mediator of the enhanced hippocampal function resulting from exposure to EE.

Traumatic injury compromises nucleocytoplasmic transport and leads to TDP-43 pathology

Traumatic brain injury (TBI) is a predisposing factor for many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although defects in nucleocytoplasmic transport (NCT) is reported ALS and other neurodegenerative diseases, whether defects in NCT occur in TBI remains unknown. We performed proteomic analysis on Drosophila exposed to repeated TBI and identified resultant alterations in several novel molecular pathways. TBI upregulated nuclear pore complex (NPC) and nucleocytoplasmic transport (NCT) proteins as well as alter nucleoporin stability. Traumatic injury disrupted RanGAP1 and NPC protein distribution in flies and a rat model and led to coaggregation of NPC components and TDP-43. In addition, trauma-mediated NCT defects and lethality are rescued by nuclear export inhibitors. Importantly, genetic upregulation of nucleoporins in vivo and in vitro triggered TDP-43 cytoplasmic mislocalization, aggregation, and altered solubility and reduced motor function and lifespan of animals. We also found NUP62 pathology and elevated NUP62 concentrations in postmortem brain tissues of patients with mild or severe CTE as well as co-localization of NUP62 and TDP-43 in CTE. These findings indicate that TBI leads to NCT defects, which potentially mediate the TDP-43 pathology in CTE.

Repetitive mild traumatic brain injury affects inflammation and excitotoxic mRNA expression at acute and chronic time-points

The cumulative effect of mild traumatic brain injuries (mTBI) can result in chronic neurological damage, however the molecular mechanisms underpinning this detriment require further investigation. A closed head weight drop model that replicates the biomechanics and head acceleration forces of human mTBI was used to provide an exploration of the acute and chronic outcomes following single and repeated impacts. Adult male C57BL/6J mice were randomly assigned into one of four impact groups (control; one, five and 15 impacts) which were delivered over 23 days. Outcomes were assessed 48 hours and 3 months following the final mTBI. Hippocampal spatial learning and memory assessment revealed impaired performance in the 15-impact group compared with control in the acute phase that persisted at chronic measurement. mRNA analyses were performed on brain tissue samples of the cortex and hippocampus using quantitative RT-PCR. Eight genes were assessed, namely MAPT, GFAP, AIF1, GRIA1, CCL11, TARDBP, TNF, and NEFL, with expression changes observed based on location and follow-up duration. The cortex and hippocampus showed vulnerability to insult, displaying upregulation of key excitotoxicity and inflammation genes. Serum samples showed no difference between groups for proteins phosphorylated tau and GFAP. These data suggest that the cumulative effect of the impacts was sufficient to induce mTBI pathophysiology and clinical features. The genes investigated in this study provide opportunity for further investigation of mTBI-related neuropathology and may provide targets in the development of therapies that help mitigate the effects of mTBI.

Chronic Traumatic Encephalopathy: Update on Current Clinical Diagnosis and Management

Chronic traumatic encephalopathy is a disease afflicting individuals exposed to repetitive neurotrauma. Unfortunately, diagnosis is made by postmortem pathologic analysis, and treatment options are primarily symptomatic. In this clinical update, we review clinical and pathologic diagnostic criteria and recommended symptomatic treatments. We also review animal models and recent discoveries from pre-clinical studies. Furthermore, we highlight the recent advances in diagnosis using diffusor tensor imaging, functional magnetic resonance imaging, positron emission tomography, and the fluid biomarkers t-tau, sTREM2, CCL11, NFL, and GFAP. We also provide an update on emerging pharmaceutical treatments, including immunotherapies and those that target tau acetylation, tau phosphorylation, and inflammation. Lastly, we highlight the current literature gaps and guide future directions to further improve clinical diagnosis and management of patients suffering from this condition.

Neuroimaging Biomarkers of Chronic Traumatic Encephalopathy: Targets for the Academic Memory Disorders Clinic

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts, such as those from contact sports. The pathognomonic lesion for CTE is the perivascular accumulation of hyper-phosphorylated tau in neurons and other cell process at the depths of sulci. CTE cannot be diagnosed during life at this time, limiting research on risk factors, mechanisms, epidemiology, and treatment. There is an urgent need for in vivo biomarkers that can accurately detect CTE and differentiate it from other neurological disorders. Neuroimaging is an integral component of the clinical evaluation of neurodegenerative diseases and will likely aid in diagnosing CTE during life. In this qualitative review, we present the current evidence on neuroimaging biomarkers for CTE with a focus on molecular, structural, and functional modalities routinely used as part of a dementia evaluation. Supporting imaging-pathological correlation studies are also presented. We targeted neuroimaging studies of living participants at high risk for CTE (e.g., aging former elite American football players, fighters). We conclude that an optimal tau PET radiotracer with high affinity for the 3R/4R neurofibrillary tangles in CTE has not yet been identified. Amyloid PET scans have tended to be negative. Converging structural and functional imaging evidence together with neuropathological evidence show frontotemporal and medial temporal lobe neurodegeneration, and increased likelihood for a cavum septum pellucidum. The literature offers promising neuroimaging biomarker targets of CTE, but it is limited by cross-sectional studies of small samples where the presence of underlying CTE is unknown. Imaging-pathological correlation studies will be important for the development and validation of neuroimaging biomarkers of CTE.

Examination and characterisation of the effect of amitriptyline therapy for chronic neuropathic pain on neuropeptide and proteomic constituents of human cerebrospinal fluid

INTRODUCTION

Amitriptyline is prescribed to reduce the intensity of chronic neuropathic pain. There is a paucity of validated in vivo evidence in humans regarding amitriptyline's mechanism of action. We examined the effect of amitriptyline therapy on cerebrospinal fluid (CSF) neuropeptides and proteome in patients with chronic neuropathic pain to identify potential mechanisms of action of amitriptyline.

METHODS

Patients with lumbar radicular neuropathic pain were selected for inclusion with clinical and radiological signs and a >50% reduction in pain in response to a selective nerve root block. Baseline (pre-treatment) and 8-week (post-treatment) pain scores with demographics were recorded. CSF samples were taken at baseline (pre-treatment) and 8 weeks after amitriptyline treatment (post-treatment). Proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 9/16 patients experienced a >30% reduction in pain after treatment with amitriptyline and GO analysis demonstrated that the greatest modulatory effect was on immune system processes. KEGG analysis also identified a reduction in PI3K-Akt and MAPK signalling pathways in responders but not in non-responders. There was also a significant decrease in the chemokine eotaxin-1 (p ​= ​0.02) and a significant increase in the neurotrophin VEGF-A (p ​= ​0.04) in responders.

CONCLUSION

The CSF secretome and proteome was modulated in responders to amitriptyline verifying many pre-clinical and in vitro models. The predominant features were immunomodulation with a reduction in pro-inflammatory pathways of neuronal-glia communications and evidence of a neurotrophic effect.

Does a hypoxic injury from a non-fatal overdose lead to an Alzheimer Disease?

Long term consequence of non-fatal overdose in people who use opioids are not well understood. The intermittent exposure to non-fatal overdose leads to a tauopathy that is often accompanied by abrogated neuroprotective response, abnormal amyloid processing and other pathologies. The scope and limitations of available literature are discussed including neuropathologies associated with opioid and overdose exposures, contributing comorbidities and proteinopathies. Contrasting postmortem data of overdose victims with animal models of opioid neuropathologies and hypoxic injury paints a picture distinct from other proteinopathies as well as effects of moderate opioid exposure. Furthermore the reported biochemical changes and potential targets for therapeutic intervention were mapped pointing to underlying imbalance between tau kinases and phosphatases that is characteristic of Alzheimer Disease.

CCL2 is associated with microglia and macrophage recruitment in chronic traumatic encephalopathy

Background

Neuroinflammation has been implicated in the pathogenesis of chronic traumatic encephalopathy (CTE), a progressive neurodegenerative disease association with exposure to repetitive head impacts (RHI) received though playing contact sports such as American football. Past work has implicated early and sustained activation of microglia as a potential driver of tau pathology within the frontal cortex in CTE. However, the RHI induced signals required to recruit microglia to areas of damage and pathology are unknown.

Methods

Postmortem brain tissue was obtained from 261 individuals across multiple brain banks. Comparisons were made using cases with CTE, cases with Alzheimer’s disease (AD), and cases with no neurodegenerative disease and lacked exposure to RHI (controls). Recruitment of Iba1+ cells around the CTE perivascular lesion was compared to non-lesion vessels. TMEM119 staining was used to characterize microglia or macrophage involvement. The potent chemoattractant CCL2 was analyzed using frozen tissue from the dorsolateral frontal cortex (DLFC) and the calcarine cortex. Finally, the amounts of hyperphosphorylated tau (pTau) and Aβ₄₂ were compared to CCL2 levels to examine possible mechanistic pathways.

Results

An increase in Iba1+ cells was found around blood vessels with perivascular tau pathology compared to non-affected vessels in individuals with RHI. TMEM119 staining revealed the majority of the Iba1+ cells were microglia. CCL2 protein levels in the DLFC were found to correlate with greater years of playing American football, the density of Iba1+ cells, the density of CD68+ cells, and increased CTE severity. When comparing across multiple brain regions, CCL2 increases were more pronounced in the DLFC than the calcarine cortex in cases with RHI but not in AD. When examining the individual contribution of pathogenic proteins to CCL2 changes, pTau correlated with CCL2, independent of age at death and Aβ₄₂ in AD and CTE. Although levels of Aβ₄₂ were not correlated with CCL2 in cases with CTE, in males in the AD group, Aβ₄₂ trended toward an inverse relationship with CCL2 suggesting possible gender associations.

Conclusion

Overall, CCL2 is implicated in the pathways recruiting microglia and the development of pTau pathology after exposure to RHI, and may represent a future therapeutic target in CTE.

Systemic inflammation moderates the association of prior concussion with hippocampal volume and episodic memory in high school and collegiate athletes

BACKGROUND

There is a need to determine why prior concussion has been associated with adverse outcomes in some retired and active athletes. We examined whether serum inflammatory markers moderate the associations of prior concussion with hippocampal volumes and neurobehavioral functioning in active high school and collegiate athletes.

METHODS

Athletes (N = 201) completed pre-season clinical testing and serum collection (C-reactive protein [CRP]; Interleukin-6 [IL]-6; IL-1 receptor antagonist [RA]) and in-season neuroimaging. Linear mixed-effects models examined associations of prior concussion with inflammatory markers, self-reported symptoms, neurocognitive function, and hippocampal volumes. Models examined whether inflammatory markers moderated associations of concussion history and hippocampal volume and/or clinical measures.

RESULTS

Concussion history was significantly associated with higher symptom severity, p = 0.012, but not hippocampal volume or inflammatory markers (ps > 0.05). A significant interaction of prior concussion and CRP was observed for hippocampal volume, p = 0.006. Follow-up analyses showed that at high levels of CRP, athletes with two or more prior concussions had smaller hippocampal volume compared to athletes without prior concussion, p = 0.008. There was a significant interaction between prior concussion and levels of IL-1RA on memory scores, p = 0.044, i.e., at low levels of IL-1RA, athletes with two or more concussions had worse memory performance than those without prior concussion (p = 0.014).

CONCLUSION

Findings suggest that certain markers of systemic inflammation moderate the association between prior concussion and hippocampal volume and episodic memory performance. Current findings highlight potential markers for predicting at-risk individuals and identify therapeutic targets for mitigating the long-term adverse consequences of cumulative concussion.

A magnetic resonance spectroscopy investigation in symptomatic former NFL players

The long-term neurologic consequences of exposure to repetitive head impacts (RHI) are not well understood. This study used magnetic resonance spectroscopy (MRS) to examine later-life neurochemistry and its association with RHI and clinical function in former National Football League (NFL) players. The sample included 77 symptomatic former NFL players and 23 asymptomatic individuals without a head trauma history. Participants completed cognitive, behavior, and mood measures. N-acetyl aspartate, glutamate/glutamine, choline, myo-inositol, creatine, and glutathione were measured in the posterior (PCG) and anterior (ACG) cingulate gyrus, and parietal white matter (PWM). A cumulative head impact index (CHII) estimated RHI. In former NFL players, a higher CHII correlated with lower PWM creatine (r = -0.23, p = 0.02). Multivariate mixed-effect models examined neurochemical differences between the former NFL players and asymptomatic individuals without a history of head trauma. PWM N-acetyl aspartate was lower among the former NFL players (mean diff. = 1.02, p = 0.03). Between-group analyses are preliminary as groups were recruited based on symptomatic status. The ACG was the only region associated with clinical function, including positive correlations between glutamate (r = 0.32, p = 0.004), glutathione (r = 0.29, p = 0.02), and myo-inositol (r = 0.26, p = 0.01) with behavioral/mood symptoms. Other positive correlations between ACG neurochemistry and clinical function emerged (i.e., behavioral/mood symptoms, cognition), but the positive directionality was unexpected. All analyses controlled for age, body mass index, and education (for analyses examining clinical function). In this sample of symptomatic former NFL players, there was a direct effect between RHI and reduced cellular energy metabolism (i.e., lower creatine). MRS neurochemicals associated with neuroinflammation also correlated with behavioral/mood symptoms.

Acute Time-Course Changes in CCL11, CCL2, and IL-10 Levels After Controlled Subconcussive Head Impacts: A Pilot Randomized Clinical Trial

OBJECTIVE

To examine changes in plasma levels of CCL11, CCL2, and IL-10 after 10 controlled soccer headers.

SETTING

Laboratory setting.

PARTICIPANTS

Thirty-nine healthy soccer players with at least 3 years of soccer heading experience, between 18 and 26 years old, and enrolled at a large public university.

DESIGN

In this randomized clinical trial using a soccer heading model, participants were randomized into the heading (n = 22) or kicking-control (n = 17) groups to perform 10 headers or kicks.

MAIN MEASURES

Plasma levels of CCL11, CCL2, and IL-10 at preintervention and 0, 2, and 24 hours postintervention.

RESULTS

Mixed-effects regression models did not reveal any significant group differences in changes of plasma CCL11, CCL2, or IL-10 levels from preintervention. Within the heading group, there was a statistically significant time by years of heading experience interaction with 2.0-pg/mL increase in plasma CCL11 each year of prior experience at 24 hours postintervention (P = .001).

CONCLUSION

Findings from this study suggest that 10 soccer headers do not provoke an acute inflammatory response. However, the acute CCL11 response may be influenced by prior exposure to soccer headers, providing a precedent for future field studies that prospectively track head impact exposure and changes in CCL11.

Pathophysiologic Mechanisms of Concussion, Development of Chronic Traumatic Encephalopathy, and Emerging Diagnostics: A Narrative Review

Pathophysiological mechanisms and cascades take place after a mild traumatic brain injury (mTBI) that can cause long-term sequelae, including chronic traumatic encephalopathy in patients with multiple concurrent TBIs. As diagnostic imaging has become more advanced, microanatomical changes present after mTBI may now be more readily visible. In this narrative review, the authors discuss emerging diagnostics and findings in mTBI through advanced imaging, electroencephalograms, neurophysiologic processes, Q2 biochemical markers, and clinical tissue tests in an effort to help osteopathic physicians to understand, diagnose, and manage the pathophysiology behind mTBI, which is increasingly prevalent in the United States.

Repetitive Head Trauma Induces Chronic Traumatic Encephalopathy by Multiple Mechanisms

Exposure to repetitive neurotrauma increases lifetime risk for developing progressive cognitive deficits, neurobehavioral abnormalities, and chronic traumatic encephalopathy (CTE). CTE is a tau protein neurodegenerative disease first identified in boxers and recently described in athletes participating in other contact sports (notably American football, ice hockey, rugby, and wrestling) and in military veterans with blast exposure. Currently, CTE can only be diagnosed by neuropathological examination of the brain after death. The defining diagnostic lesion of CTE consists of patchy perivascular accumulations of hyperphosphorylated tau protein that localize in the sulcal depths of the cerebral cortex. Neuronal abnormalities, axonopathy, neurovascular dysfunction, and neuroinflammation are triggered by repetitive head impacts (RHIs) and likely act as catalysts for CTE pathogenesis and progression. However, the specific mechanisms that link RHI to CTE are unknown. This review will explore two important areas of CTE pathobiology. First, we will review what is known about the biomechanical properties of RHI that initiate CTE-related pathologies. Second, we will provide an overview of key features of CTE neuropathology and how these contribute to abnormal tau hyperphosphorylation, accumulation, and spread.

Systemic Inflammation Persists the First Year after Mild Traumatic Brain Injury: Results from the Prospective Trondheim Mild Traumatic Brain Injury Study

Innate immune activation has been attributed a key role in traumatic brain injury (TBI) and successive morbidity. In mild TBI (mTBI), however, the extent and persistence of innate immune activation are unknown. We determined plasma cytokine level changes over 12 months after an mTBI in hospitalized and non-hospitalized patients compared with community controls; and examined their associations to injury-related and demographic variables at admission. Prospectively, 207 patients presenting to the emergency department (ED) or general practitioner with clinically confirmed mTBI and 82 matched community controls were included. Plasma samples were obtained at admission, after 2 weeks, 3 months, and 12 months. Cytokine levels were analysed with a 27-plex beads-based immunoassay. Brain magnetic resonance imaging (MRI) was performed on all participants. Twelve cytokines were reliably detected. Plasma levels of interferon gamma (IFN-γ), interleukin 8 (IL-8), eotaxin, macrophage inflammatory protein-1-beta (MIP-1β), monocyte chemoattractant protein 1 (MCP-1), IL-17A, IL-9, tumor necrosis factor (TNF), and basic fibroblast growth factor (FGF-basic) were significantly increased at all time-points in patients compared with controls, whereas IFN-γ-inducing protein 10 (IP-10), platelet-derived growth factor (PDGF), and IL-1ra were not. IL-17A and FGF-basic showed significant increases in patients from admission to follow-up at 3 months, and remained increased at 12 months compared with admission. Interestingly, MRI findings were negatively associated with four cytokines: eotaxin, MIP-1β, IL-9, and IP-10, whereas age was positively associated with nine cytokines: IL-8, eotaxin, MIP-1β, MCP-1, IL-17A, IL-9, TNF, FGF-basic, and IL-1ra. TNF was also increased in those with presence of other injuries. In conclusion, mTBI activated the innate immune system consistently and this is the first study to show that several inflammatory cytokines remain increased for up to 1 year post-injury.

Blood biomarkers for assessment of mild traumatic brain injury and chronic traumatic encephalopathy

Mild traumatic brain injuries (mTBI) are prevalent and can result in significant debilitation. Current diagnostic methods have implicit limitations, with clinical assessment tools reliant on subjective self-reported symptoms or non-specific clinical observations, and commonly available imaging techniques lacking sufficient sensitivity to detect mTBI. A blood biomarker would provide a readily accessible detector of mTBI to meet the current measurement gap. Suitable options would provide objective and quantifiable information in diagnosing mTBI, in monitoring recovery, and in establishing a prognosis of resultant neurodegenerative disease, such as chronic traumatic encephalopathy (CTE). A biomarker would also assist in progressing research, providing suitable endpoints for testing therapeutic modalities and for further exploring mTBI pathophysiology. This review highlights the most promising blood-based protein candidates that are expressed in the central nervous system (CNS) and released into systemic circulation following mTBI. To date, neurofilament light (NF-L) may be the most suitable candidate for assessing neuronal damage, and glial fibrillary acidic protein (GFAP) for assessing astrocyte activation, although further work is required. Ultimately, the heterogeneity of cells in the brain and each marker's limitations may require a combination of biomarkers, and recent developments in microRNA (miRNA) markers of mTBI show promise and warrant further exploration.

CCL11 Differentially Affects Post-Stroke Brain Injury and Neuroregeneration in Mice Depending on Age

CCL11 has recently been shown to differentially affect cell survival under various pathological conditions including stroke. Indeed, CCL11 promotes neuroregeneration in neonatal stroke mice. The impact of CCL11 on the adult ischemic brain, however, remains elusive. We therefore studied the effect of ectopic CCL11 on both adolescent (six-week) and adult (six-month) C57BL6 mice exposed to stroke. Intraperitoneal application of CCL11 significantly aggravated acute brain injury in adult mice but not in adolescent mice. Likewise, post-stroke neurological recovery after four weeks was significantly impaired in adult mice whilst CCL11 was present. On the contrary, CCL11 stimulated gliogenesis and neurogenesis in adolescent mice. Flow cytometry analysis of blood and brain samples revealed a modification of inflammation by CCL11 at subacute stages of the disease. In adolescent mice, CCL11 enhances microglial cell, B and T lymphocyte migration towards the brain, whereas only the number of B lymphocytes is increased in the adult brain. Finally, the CCL11 inhibitor SB297006 significantly reversed the aforementioned effects. Our study, for the first time, demonstrates CCL11 to be a key player in mediating secondary cell injury under stroke conditions. Interfering with this pathway, as shown for SB297006, might thus be an interesting approach for future stroke treatment paradigms.

Association of White Matter Rarefaction, Arteriolosclerosis, and Tau With Dementia in Chronic Traumatic Encephalopathy

IMPORTANCE

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive head impacts, including those from US football, that presents with cognitive and neuropsychiatric disturbances that can progress to dementia. Pathways to dementia in CTE are unclear and likely involve tau and nontau pathologic conditions.

OBJECTIVE

To investigate the association of white matter rarefaction and cerebrovascular disease with dementia in deceased men older than 40 years who played football and had CTE.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study involves analyses of data from the ongoing Understanding Neurologic Injury and Traumatic Encephalopathy (UNITE) Study, which is conducted via and included brain donors from the Veterans Affairs-Boston University-Concussion Legacy Foundation brain bank between 2008 and 2017. An original sample of 224 men who had played football and were neuropathologically diagnosed with CTE was reduced after exclusion of those younger than 40 years and those missing data.

EXPOSURES

The number of years of football play as a proxy for repetitive head impacts.

MAIN OUTCOMES AND MEASURES

Neuropathological assessment of white matter rarefaction and arteriolosclerosis severity (on a scale of 0-3, where 3 is severe); number of infarcts, microinfarcts, and microbleeds; and phosphorylated tau accumulation determined by CTE stage and semiquantitative rating of dorsolateral frontal cortex (DLFC) neurofibrillary tangles (NFTs) (none or mild vs moderate or severe). Informant-based retrospective clinical interviews determined dementia diagnoses via diagnostic consensus conferences.

RESULTS

A total of 180 men were included. The mean (SD) age of the sample at death was 67.9 (12.7) years. Of 180, 120 [66.7%]) were found to have had dementia prior to death. Moderate to severe white matter rarefaction (84 of 180 [46.6%]) and arteriolosclerosis (85 of 180 [47.2%]) were common; infarcts, microinfarcts, and microbleeds were not. A simultaneous equations regression model controlling for age and race showed that more years of play was associated with more severe white matter rarefaction (β, 0.16 [95% CI, 0.02-0.29]; P = .03) and greater phosphorylated tau accumulation (DLFC NFTs: β, 0.15 [95% CI, 0.004-0.30]; P = .04; CTE stage: β, 0.27 [95% CI, 0.14-0.41]; P < .001). White matter rarefaction (β, 0.16 [95% CI, 0.02-0.29]; P = .03) and DLFC NFTs (β, 0.16 [95% CI, 0.03-0.28]; P = .01) were associated with dementia. Arteriolosclerosis and years of play were not associated, but arteriolosclerosis was independently associated with dementia (β, 0.21 [95% CI, 0.07-0.35]; P = .003).

CONCLUSIONS AND RELEVANCE

Among older men who had played football and had CTE, more years of football play were associated with more severe white matter rarefaction and greater DLFC NFT burden. White matter rarefaction, arteriolosclerosis, and DLFC NFTs were independently associated with dementia. Dementia in CTE is likely a result of neuropathologic changes, including white matter rarefaction and phosphorylated tau, associated with repetitive head impact and pathologic changes not associated with head trauma, such as arteriolosclerosis.

Circulating factors in young blood as potential therapeutic agents for age-related neurodegenerative and neurovascular diseases

Recent animal studies on heterochronic parabiosis (a technique combining the blood circulation of two animals) have revealed that young blood has a powerful rejuvenating effect on brain aging. Circulating factors, especially growth differentiation factor 11 (GDF11) and C-C motif chemokine 11 (CCL11), may play a key role in this effect, which inspires hope for novel approaches to treating age-related cerebral diseases in humans, such as neurodegenerative and neurovascular diseases. Recently, attempts have begun to translate these astonishing and exciting findings from mice to humans and from bench to bedside. However, increasing reports have shown contradictory data, questioning the capacity of these circulating factors to reverse age-related brain dysfunction. In this review, we summarize the current research on the role of young blood, as well as the circulating factors GDF11 and CCL11, in the aging brain and age-related cerebral diseases. We highlight recent controversies, discuss related challenges and provide a future outlook.

Quantitative Proteomic Analysis Reveals Impaired Axonal Guidance Signaling in Human Postmortem Brain Tissues of Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a distinct neurodegenerative disease that associated with repetitive head trauma. CTE is neuropathologically defined by the perivascular accumulation of abnormally phosphorylated tau protein in the depths of the sulci in the cerebral cortices. In advanced CTE, hyperphosphorylated tau protein deposits are found in widespread regions of brain, however the mechanisms of the progressive neurodegeneration in CTE are not fully understood. In order to identify which proteomic signatures are associated with CTE, we prepared RIPA-soluble fractions and performed quantitative proteomic analysis of postmortem brain tissue from individuals neuropathologically diagnosed with CTE. We found that axonal guidance signaling pathwayrelated proteins were most significantly decreased in CTE. Immunohistochemistry and Western blot analysis showed that axonal signaling pathway-related proteins were down regulated in neurons and oligodendrocytes and neuron-specific cytoskeletal proteins such as TUBB3 and CFL1 were reduced in the neuropils and cell body in CTE. Moreover, oligodendrocyte-specific proteins such as MAG and TUBB4 were decreased in the neuropils in both gray matter and white matter in CTE, which correlated with the degree of axonal injury and degeneration. Our findings indicate that deregulation of axonal guidance proteins in neurons and oligodendrocytes is associated with the neuropathology in CTE. Together, altered axonal guidance proteins may be potential pathological markers for CTE.

Pituitary pathology in traumatic brain injury: a review

PURPOSE

Traumatic brain injury most commonly affects young adults under the age of 35 and frequently results in reduced quality of life, disability, and death. In long-term survivors, hypopituitarism is a common complication.

RESULTS

Pituitary dysfunction occurs in approximately 20-40% of patients diagnosed with moderate and severe traumatic brain injury giving rise to growth hormone deficiency, hypogonadism, hypothyroidism, hypocortisolism, and central diabetes insipidus. Varying degrees of hypopituitarism have been identified in patients during both the acute and chronic phase. Anterior pituitary hormone deficiency has been shown to cause morbidity and increase mortality in TBI patients, already encumbered by other complications. Hypopituitarism after childhood traumatic brain injury may cause treatable morbidity in those survivors. Prospective studies indicate that the incidence rate of hypopituitarism may be ten-fold higher than assumed; factors altering reports include case definition, geographic location, variable hospital coding, and lost notes. While the precise pathophysiology of post traumatic hypopituitarism has not yet been elucidated, it has been hypothesized that, apart from the primary mechanical event, secondary insults such as hypotension, hypoxia, increased intracranial pressure, as well as changes in cerebral flow and metabolism may contribute to hypothalamic-pituitary damage. A number of mechanisms have been proposed to clarify the causes of primary mechanical events giving rise to ischemic adenohypophysial infarction and the ensuing development of hypopituitarism.

CONCLUSION

Future research should focus more on experimental and clinical studies to elucidate the exact mechanisms behind post-traumatic pituitary damage. The use of preventive medical measures to limit possible damage in the pituitary gland and hypothalamic pituitary axis in order to maintain or re-establish near normal physiologic functions are crucial to minimize the effects of TBI.

Variation in TMEM106B in chronic traumatic encephalopathy

The genetic basis of chronic traumatic encephalopathy (CTE) is poorly understood. Variation in transmembrane protein 106B (TMEM106B) has been associated with enhanced neuroinflammation during aging and with TDP-43-related neurodegenerative disease, and rs3173615, a missense coding SNP in TMEM106B, has been implicated as a functional variant in these processes. Neuroinflammation and TDP-43 pathology are prominent features in CTE. The purpose of this study was to determine whether genetic variation in TMEM106B is associated with CTE risk, pathological features, and ante-mortem dementia. Eighty-six deceased male athletes with a history of participation in American football, informant-reported Caucasian, and a positive postmortem diagnosis of CTE without comorbid neurodegenerative disease were genotyped for rs3173615. The minor allele frequency (MAF = 0.42) in participants with CTE did not differ from previously reported neurologically normal controls (MAF = 0.43). However, in a case-only analysis among CTE cases, the minor allele was associated with reduced phosphorylated tau (ptau) pathology in the dorsolateral frontal cortex (DLFC) (AT8 density, odds ratio [OR] of increasing one quartile = 0.42, 95% confidence interval [CI] 0.22–0.79, p = 0.008), reduced neuroinflammation in the DLFC (CD68 density, OR of increasing one quartile = 0.53, 95% CI 0.29–0.98, p = 0.043), and increased synaptic protein density (β = 0.306, 95% CI 0.065–0.546, p = 0.014). Among CTE cases, TMEM106B minor allele was also associated with reduced ante-mortem dementia (OR = 0.40, 95% CI 0.16–0.99, p = 0.048), but was not associated with TDP-43 pathology. All case-only models were adjusted for age at death and duration of football play. Taken together, variation in TMEM106B may have a protective effect on CTE-related outcomes.

Cannabis Therapeutics and the Future of Neurology

Neurological therapeutics have been hampered by its inability to advance beyond symptomatic treatment of neurodegenerative disorders into the realm of actual palliation, arrest or reversal of the attendant pathological processes. While cannabis-based medicines have demonstrated safety, efficacy and consistency sufficient for regulatory approval in spasticity in multiple sclerosis (MS), and in Dravet and Lennox-Gastaut Syndromes (LGS), many therapeutic challenges remain. This review will examine the intriguing promise that recent discoveries regarding cannabis-based medicines offer to neurological therapeutics by incorporating the neutral phytocannabinoids tetrahydrocannabinol (THC), cannabidiol (CBD), their acidic precursors, tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), and cannabis terpenoids in the putative treatment of five syndromes, currently labeled recalcitrant to therapeutic success, and wherein improved pharmacological intervention is required: intractable epilepsy, brain tumors, Parkinson disease (PD), Alzheimer disease (AD) and traumatic brain injury (TBI)/chronic traumatic encephalopathy (CTE). Current basic science and clinical investigations support the safety and efficacy of such interventions in treatment of these currently intractable conditions, that in some cases share pathological processes, and the plausibility of interventions that harness endocannabinoid mechanisms, whether mediated via direct activity on CB₁ and CB₂ (tetrahydrocannabinol, THC, caryophyllene), peroxisome proliferator-activated receptor-gamma (PPARγ; THCA), 5-HT_1A (CBD, CBDA) or even nutritional approaches utilizing prebiotics and probiotics. The inherent polypharmaceutical properties of cannabis botanicals offer distinct advantages over the current single-target pharmaceutical model and portend to revolutionize neurological treatment into a new reality of effective interventional and even preventative treatment.

Traumatic Brain Injury, Chronic Traumatic Encephalopathy, and Alzheimer Disease

Traumatic brain injury (TBI) is a major health and economic burden. With increasing aging population, this issue is expected to continue to rise. Neurodegenerative disorders are more common with aging population in general regardless of history of TBI. Recent evidence continues to support a relation between a TBI and neurocognitive decline later in life (such as in athletes and military). This article summarizes the pathologic and clinical effects of TBI (regardless of severity) on the later development of dementia in individuals 65 years or older.

Multi-Center Pre-clinical Consortia to Enhance Translation of Therapies and Biomarkers for Traumatic Brain Injury: Operation Brain Trauma Therapy and Beyond

Current approaches have failed to yield success in the translation of neuroprotective therapies from the pre-clinical to the clinical arena for traumatic brain injury (TBI). Numerous explanations have been put forth in both the pre-clinical and clinical arenas. Operation Brain Trauma Therapy (OBTT), a pre-clinical therapy and biomarker screening consortium has, to date, evaluated 10 therapies and assessed three serum biomarkers in nearly 1,500 animals across three rat models and a micro pig model of TBI. OBTT provides a unique platform to exploit heterogeneity of TBI and execute the research needed to identify effective injury specific therapies toward precision medicine. It also represents one of the first multi-center pre-clinical consortia for TBI, and through its work has yielded insight into the challenges and opportunities of this approach. In this review, important concepts related to consortium infrastructure, modeling, therapy selection, dosing and target engagement, outcomes, analytical approaches, reproducibility, and standardization will be discussed, with a focus on strategies to embellish and improve the chances for future success. We also address issues spanning the continuum of care. Linking the findings of optimized pre-clinical consortia to novel clinical trial designs has great potential to help address the barriers in translation and produce successes in both therapy and biomarker development across the field of TBI and beyond.

Eotaxin, an Endogenous Cognitive Deteriorating Chemokine (ECDC), Is a Major Contributor to Cognitive Decline in Normal People and to Executive, Memory, and Sustained Attention Deficits, Formal Thought Disorders, and Psychopathology in Schizophrenia Patients

Eotaxin is increased in neurodegenerative disorders and schizophrenia, and preclinical studies indicate that eotaxin may induce cognitive deficits. This study aims to examine whether peripheral levels of eotaxin impact cognitive functioning in healthy volunteers and formal thought disorder (FTD) and psychopathology in schizophrenia patients. Serum levels of eotaxin were assayed and cognitive tests were performed on a sample of 40 healthy participants and 80 schizophrenia patients. Among healthy participants, eotaxin levels were significantly associated with episodic/semantic memory, executive functions, Mini Mental State Examination, emotion recognition, and sustained attention. In addition, age-related effects on these cognitive measures were partly mediated by eotaxin. The super-variable "age-eotaxin" predicted a large part of the variance in cognitive functions among healthy participants, and hence, eotaxin may act as an "accelerated brain aging chemokine" (ABAC). In schizophrenia, eotaxin levels had a strong impact on formal thought disorders and psychopathology. In schizophrenia, increased eotaxin strongly impacts memory and sustained attention, which together to a large extent determine FTD. FTD together with memory deficits predicts around 92.5% of the variance in psychopathology. Moreover, the effects of eotaxin are partially mediated by executive functioning, while the effects of male sex on FTD and psychopathology are mediated by eotaxin. In healthy subjects, eotaxin strongly impacts executive functioning and multiple cognitive domains. In schizophrenia, peripheral levels of eotaxin strongly impact both negative symptoms and psychosis (hallucinations and delusions), and these eotaxin effects are mediated by impairments in frontal functioning, memory, sustained attention, and FTD. Eotaxin is an endogenous cognitive deteriorating chemokine (ECDC) and a novel therapeutic target for age-related cognitive decline and schizophrenia as well.

Cerebrospinal fluid tau, Aβ, and sTREM2 in Former National Football League Players: Modeling the relationship between repetitive head impacts, microglial activation, and neurodegeneration

INTRODUCTION

Cerebrospinal fluid (CSF) protein analysis may facilitate detection and elucidate mechanisms of neurological consequences from repetitive head impacts (RHI), such as chronic traumatic encephalopathy. We examined CSF concentrations of total tau (t-tau), phosphorylated tau, and amyloid β_1-42 and their association with RHI in former National Football League (NFL) players. The role of microglial activation (using sTREM2) was examined as a pathogenic mechanism of chronic traumatic encephalopathy.

METHODS

Sixty-eight former NFL players and 21 controls underwent lumbar puncture to quantify t-tau, p-tau₁₈₁, amyloid β_1-42, and sTREM2 in the CSF using immunoassays. The cumulative head impact index estimated RHI.

RESULTS

No between-group differences for CSF analytes emerged. In the former NFL players, the cumulative head impact index predicted higher t-tau concentrations (P = .041), and higher sTREM2 levels were associated with higher t-tau concentrations (P = .009).

DISCUSSION

In this sample of former NFL players, greater RHI and increased microglial activation were associated with higher CSF t-tau concentrations.

Subconcussive trauma

Even impacts that do not immediately elicit symptoms of a concussion can induce changes in neural integrity. Because these so-called "subconcussive" head acceleration events, or head impact exposures, do not elicit identifiable symptoms, athletes continue to participate with unclear consequences. Neuroimaging studies reveal that neurologic changes, including inflammation, are associated with repetitive head impact exposures. Given that brain changes have been observed in athletes following repetitive head impact exposure, it is important to understand better and mitigate against this phenomenon. It is important to transition from the metric of concussion alone to one that includes repetitive head impact exposure, including the development of models that address why brain integrity may be compromised, who is at risk, and how to mitigate the risk of such exposure. Future work can include a health-monitoring framework to effect change and promote athlete safety.

Chronic traumatic encephalopathy: clinical presentation and in vivo diagnosis

Exposure to repetitive head impacts from contact sport participation (e.g., American football, boxing, soccer) is associated with the neurodegenerative disorder known as chronic traumatic encephalopathy (CTE). The neuropathology of CTE is becoming well defined, and diagnostic criteria have been developed and are being refined. The critical next step in this emerging field is the diagnosis of CTE during life. The objective of this chapter is to describe what is currently known about the clinical presentation and in vivo diagnosis of CTE. This chapter reviews studies in which clinical manifestation of CTE was examined through retrospective telephone interviews with informants of individuals whose brains were donated and were diagnosed with CTE through neuropathologic examination. In vivo research examining the long-term neurobehavioral consequences of repetitive head impacts is also reviewed, followed by a comparison of the existing provisional clinical diagnostic criteria for CTE, as well as preliminary research on possible fluid and neuroimaging biomarkers. An illustrative case study of CTE is presented, and the chapter concludes with a discussion of gaps in knowledge and future directions.